JP2010038147A - Engine exhaust emission control system - Google Patents

Abstract

The present invention provides a technique for suitably performing regeneration control of an exhaust purification device when an engine is stopped.
An EV travel mode includes an LPL-EGR passage 44, an LPL-EGR valve 45, and a second throttle valve 22 that connect an exhaust passage 43 and an intake passage 42 downstream of the exhaust purification device 41. , The LPL-EGR valve 45 is opened, the second throttle valve 22 is closed, and the engine 1 is low-speed motored by the MG 1 so that the high-temperature exhaust gas flowing out from the exhaust gas purification device 41 is supplied to the LPL-EGR passage. 44, regeneration control of the catalyst in the exhaust purification device 41 is performed while circulating in a circulation path including the intake passage 42, the exhaust passage 43, and the exhaust purification device 41. The catalyst temperature can be kept high. In filter regeneration, air can be continuously introduced. In the NOx reduction control, the amount of fuel added due to the rich spike can be reduced.
[Selection] Figure 3

Description

  The present invention relates to an engine exhaust purification system.

  In a diesel hybrid vehicle, as a technique for performing regeneration control of a particulate filter (hereinafter referred to as a filter) during EV travel in which the engine is stopped, temperature increase control of the filter is performed by burning the engine at a low temperature before EV travel is started. Thus, a technique for facilitating the PM oxidation reaction in the filter after the start of EV traveling is known (see Patent Document 1). In this technique, when oxygen necessary for the PM oxidation reaction during EV traveling proceeds, air is supplied to the filter by motoring the engine.

In a diesel hybrid vehicle, as a technology for executing reduction control of the NOx storage reduction catalyst (hereinafter referred to as NOx catalyst) during EV travel when the engine is stopped, a rich spike is generated while the motor assist turbo is driven forward / reversely during EV travel. There has been known a technique in which a reduction atmosphere is created in a NOx catalyst and the progress of the NOx reduction reaction is promoted (see Patent Document 2).
JP 2005-194485 A JP 2006-194170 A Japanese Patent Application Laid-Open No. 11-229973 JP 2004-278465 A JP 2007-198277 A JP 2006-112347 A JP 2006-200362 A JP 2001-73743 A Japanese Patent No. 3905515 JP-A-5-332124

  In the technique described in Patent Document 1, if air is supplied to the filter by motoring the engine, the temperature of the filter may decrease. Therefore, it is difficult to continuously supply air to the filter by continuous engine motoring in order to keep the temperature of the filter at a high temperature necessary for the PM oxidation reaction to proceed appropriately. For this reason, since the oxidation reaction of PM suitably proceeds, sufficient oxygen cannot be supplied to the filter, and there is a problem that the regeneration speed of the filter is slow.

  The technique described in Patent Document 2 has a problem that the power consumption of the motor-assisted turbo is large when the motor-assisted turbo is repeatedly rotated forward and reverse, which may lead to deterioration in fuel consumption.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a technique that can suitably execute the regeneration control of the exhaust purification device in a state where the engine is stopped.

In order to achieve the above object, an exhaust purification system for an engine of the present invention comprises:
An exhaust purification device disposed in the exhaust passage of the engine;
Regeneration control means for performing regeneration control for recovering the exhaust purification capacity of the exhaust purification device;
Exhaust circulation means for circulating at least part of the exhaust gas flowing out from the exhaust purification device in a circulation path including the exhaust purification device;
With
When performing the regeneration control when the fuel supply to the engine is stopped, the regeneration control means executes the regeneration control while circulating the exhaust gas by the exhaust circulation means.

  Here, “when the fuel supply to the engine is stopped” includes not only the state where the engine has stopped due to the fuel cut but also the state where the engine is rotating due to some external energy other than the combustion energy of the fuel. Shall be included.

  During the regeneration control, the gas flowing out from the exhaust purification device becomes high temperature. According to the present invention, since this high-temperature gas is circulated in the circulation path including the exhaust purification device by the exhaust circulation means, it is possible to create a state in which the high-temperature gas continues to flow into the exhaust purification device. Therefore, even when the regeneration control is performed when the fuel supply to the engine is stopped, the temperature of the exhaust purification device can be suppressed from decreasing, and the regeneration control of the exhaust purification device can be suitably executed.

The exhaust gas circulation path in the present invention is, for example, in the configuration of the present invention described above
By providing an EGR passage that connects the exhaust passage downstream of the exhaust purification device and the intake passage of the engine,
At least a part of the exhaust gas flowing out from the exhaust purification device flows into the exhaust purification device via the exhaust passage downstream of the exhaust purification device, the EGR passage, the intake passage, the engine, and the exhaust passage upstream of the exhaust purification device. It can be configured as a configured circulation path.

In this case, in order to circulate the exhaust gas flowing out from the exhaust emission control device when the engine is stopped in this circulation path, for example, in the configuration of the present invention described above,
The engine;
A power source other than the engine, capable of outputting a driving force to a driving shaft, and capable of outputting a driving force for rotating the engine without depending on fuel combustion energy;
Applied to a hybrid system that outputs a required driving force to the driving shaft by at least one of
The hybrid system can operate in an EV traveling mode in which fuel supply to the engine is stopped and a required driving force is output to the driving shaft only by the power source,
An EGR valve that adjusts the amount of exhaust flowing in the EGR passage;
A throttle valve for adjusting the amount of air flowing into the intake passage upstream from the connection point of the EGR passage;
With
The exhaust circulation means includes
The opening of the EGR valve is changed to an opening on the open side compared with the case where the exhaust gas is not circulated, and the opening of the throttle valve is opened on the closed side than when the exhaust gas is not circulated. Change in degrees
The engine may be rotated by the power source.

Alternatively, in order to circulate the exhaust gas flowing out from the exhaust emission control device when the engine is stopped in the circulation path, for example, in the configuration of the present invention,
The engine;
A power source other than the engine, and a first power source capable of outputting a driving force to at least the driving shaft;
A power source other than the engine, at least a second power source capable of outputting a driving force for rotating the engine without depending on fuel combustion energy;
Applied to a hybrid system that outputs a required driving force to the driving shaft by at least one of
The hybrid system can operate in an EV traveling mode in which fuel supply to the engine is stopped and a required driving force is output to the driving shaft only by the first power source,
An EGR valve that adjusts the amount of exhaust flowing in the EGR passage;
A throttle valve for adjusting the amount of air flowing into the intake passage upstream from the connection point of the EGR passage;
With
The exhaust circulation means includes
The opening of the EGR valve is changed to an opening on the open side compared with the case where the exhaust gas is not circulated, and the opening of the throttle valve is opened on the closed side than when the exhaust gas is not circulated. Change in degrees
The engine may be rotated by the second power source.

  By doing so, even in the EV traveling mode in which the engine is stopped, the high-temperature exhaust gas flowing out from the exhaust purification device under regeneration control can be circulated in the circulation path. Furthermore, since the throttle valve is changed to the opening on the closing side, the amount of low temperature fresh air flowing into the circulation path can be reduced. As a result, the temperature of the gas circulating in the circulation path can be more reliably maintained at a high temperature.

  Therefore, when the regeneration control unit executes the regeneration control when the engine is stopped in the EV traveling mode, the regeneration control unit executes the regeneration control of the exhaust purification device while circulating the exhaust gas by the exhaust circulation unit configured as described above. Thus, the temperature of the exhaust emission control device when the regeneration control is executed can be maintained at a high temperature. As a result, it is possible to suitably execute the regeneration control even when the engine is stopped.

  In the above configuration, the exhaust circulation means may fully open the EGR valve and / or fully close the throttle valve. By doing so, it is possible to increase the circulation amount of the hot exhaust gas flowing out from the exhaust purification device and / or further reduce the circulation amount of the low temperature fresh air flowing into the intake passage.

  In the above configuration, when the hybrid system has a power source capable of outputting power to the drive shaft and the engine as a non-engine power source, the non-engine power source is connected to the drive shaft in the EV traveling mode. The remaining surplus power that has output the required driving force to be output can be applied to the power for motoring the engine. Such a non-engine power source can be configured, for example, as a motor that can output power to the drive shaft and the engine and can switch the output destination of the power to the drive shaft and / or the engine.

  In the above configuration, the hybrid system includes a first power source capable of outputting power to the drive shaft and a second power source capable of outputting power to the engine as non-engine power sources. In this case, such a non-engine power source includes, for example, at least a first motor that can output power to the engine and at least a second motor that can output power to the drive shaft. be able to.

As described above, in a configuration in which exhaust is circulated in the circulation path by rotating a stopped engine by a non-engine power source of the hybrid system,
Equipped with a variable valve timing device that can change the exhaust valve timing of the engine
When the regeneration control is executed when the engine is stopped in the EV traveling mode, the regeneration control means circulates the exhaust by the exhaust circulation means (exhaust circulation performed by rotating the engine by a non-engine power source) and a variable valve. The opening timing of the exhaust valve may be advanced by the timing device as compared with the case where the exhaust gas is not circulated.

  In this way, the in-cylinder gas that has been compressed and heated to a high temperature in the cylinder is discharged from the cylinder to the exhaust passage before the temperature drops due to expansion in the expansion stroke or cooling by the engine cooling water. can do. Therefore, since the temperature drop of the gas circulating in the circulation path can be more reliably suppressed, the temperature of the exhaust emission control device when executing the regeneration control can be more reliably maintained at a high temperature.

Further, in a configuration in which exhaust gas is circulated in the circulation path by rotating a stopped engine by a non-engine power source,
A turbocharger having a compressor provided in the intake passage and a turbine provided in the exhaust passage;
When the turbocharger is a variable capacity turbocharger having a nozzle vane having a variable opening in the turbine and capable of changing the supercharging efficiency of the turbocharger by changing the opening of the nozzle vane.
When performing regeneration control when the engine is stopped in the EV traveling mode, the regeneration control means circulates the exhaust gas by the exhaust circulation means (exhaust gas circulation performed by rotating the engine by a non-engine power source), and the nozzle vane The opening may be changed to an opening on the opening side rather than when the exhaust gas is not circulated.

  By doing so, the amount of energy converted into the rotational energy of the turbine out of the thermal energy of the exhaust flowing into the turbine is reduced, so that a decrease in the temperature of the exhaust after passing through the turbine can be suppressed. Therefore, since the temperature drop of the gas flowing into the exhaust purification apparatus can be more reliably suppressed, the temperature of the exhaust purification apparatus when executing the regeneration control can be more reliably maintained at a high temperature.

In the present invention, when the fuel supply to the engine is stopped, the exhaust gas flowing out from the exhaust purification device is circulated in the circulation path including the exhaust purification device.
A turbocharger comprising: a compressor provided in an intake passage of the engine; a turbine provided in the exhaust passage; and a turbo-assist power source capable of rotating the turbine without depending on the energy of exhaust. ,
An EGR passage connecting an exhaust passage downstream of the exhaust purification device and an intake passage of the engine;
An EGR valve that adjusts the amount of exhaust flowing in the EGR passage;
A throttle valve for adjusting the amount of air flowing into the intake passage upstream from the connection point of the EGR passage;
Valve control means for controlling opening and closing of the intake valve and exhaust valve of the engine;
With
The exhaust circulation means
The opening of the EGR valve is changed to an opening on the open side compared with the case where the exhaust gas is not circulated, and the opening of the throttle valve is opened on the closed side than when the exhaust gas is not circulated. Change in degrees
The valve control unit may control the intake valve and the exhaust valve to be in an open state, and the turbine may be rotationally driven by the turbo assist power source.

  In this case, when the fuel supply to the engine is stopped, the engine is not rotated by the non-engine power source, so that the engine stops, but the intake valve and the exhaust valve are both opened by the valve control means (that is, Because the engine stops when the intake valve and the exhaust valve are opened and closed so that the valve opening period of the intake valve overlaps the valve opening period of the exhaust valve), the engine cylinders are free of gas. It will be in a state where it can be distributed. Therefore, according to the above, the exhaust gas flowing out from the turbine that is rotationally driven by the turbo assist power source flows into the turbine through the exhaust passage, the exhaust purification device, the EGR passage, the intake passage, the engine cylinder, and the exhaust passage. Thus, a circulation path can be configured. Therefore, even when the engine rotation is stopped, the high-temperature exhaust gas flowing out from the exhaust emission control device under regeneration control can be circulated in this circulation path. Furthermore, since the throttle valve is changed to the opening on the closing side, the amount of low temperature fresh air flowing into the circulation path can be reduced. As a result, the temperature of the gas circulating in the circulation path can be more reliably maintained at a high temperature.

  Therefore, when the regeneration control unit executes the regeneration control when the engine is stopped, the regeneration control unit performs the regeneration control of the exhaust gas purification device while performing the exhaust gas circulation by the exhaust circulation unit configured as described above. The temperature of the exhaust emission control device at the time of execution can be maintained at a high temperature. As a result, it is possible to suitably execute the regeneration control even when the engine is stopped.

  In the above configuration, the exhaust circulation means may fully open the EGR valve and / or fully close the throttle valve. By doing so, it is possible to increase the circulation amount of the hot exhaust gas flowing out from the exhaust purification device and / or further reduce the circulation amount of the low temperature fresh air flowing into the intake passage.

  Further, the energy required for rotationally driving the turbine by the turbo assist power source is less than the energy required for rotating the engine by the non-engine power source described above. This is because in order to rotate the engine, it is necessary to move the piston-type movable member having a large friction. Therefore, if the exhaust gas is circulated by rotating the turbine with a turbo-assist power source, the fuel efficiency can be improved.

When exhaust circulation is performed by rotationally driving a turbine with a turbo assist power source, valve control is performed so that both the intake valve and the exhaust valve of the engine are opened when the engine stops rotating as described above. Instead of a configuration with means,
A second EGR passage connecting the exhaust passage upstream of the exhaust purification device and the intake passage;
A second EGR valve that adjusts the amount of exhaust flowing in the second EGR passage;
With
The exhaust circulation means includes
The opening of the EGR valve is changed to an opening on the open side compared with the case where the exhaust gas is not circulated, and the opening of the throttle valve is opened on the closed side than when the exhaust gas is not circulated. Change in degrees
The second EGR valve may be opened and the turbine may be rotationally driven by a turbo assist power source.

In this case, the exhaust gas flowing out from the turbine rotated by the turbo assist power source is circulated so as to flow into the turbine through the exhaust passage, the exhaust purification device, the EGR passage, the intake passage, the second EGR passage, and the exhaust passage. A route can be configured. In other words, the second EGR passage functions as an EGR device that causes a part of the exhaust from the engine to flow into the intake passage when the engine is operating, and when the exhaust is circulated by the turbo assist power source when the engine is stopped, the intake passage It functions as a device that causes the gas inside to flow into the exhaust passage without going through the engine.

  Therefore, even if the engine stops rotating with the intake valve and / or the exhaust valve closed, and the gas cannot flow freely through the engine cylinder, it flows out of the exhaust purification device under regeneration control. The hot exhaust gas that circulates can be circulated in this circulation path. Furthermore, since the throttle valve is changed to the opening on the closing side, the amount of low temperature fresh air flowing into the circulation path can be reduced. As a result, the temperature of the gas circulating in the circulation path can be more reliably maintained at a high temperature.

  Accordingly, when the regeneration control unit executes the regeneration control when the engine stops, the regeneration control unit performs regeneration control by performing regeneration control of the exhaust purification device while circulating the exhaust gas by the exhaust circulation unit configured as described above. The temperature of the exhaust emission control device at the time of control execution can be maintained at a reduced temperature. As a result, it is possible to suitably execute the regeneration control even when the engine is stopped.

  In the above configuration, the exhaust circulation means may fully open the EGR valve and / or fully close the throttle valve. By doing so, it is possible to increase the circulation amount of the hot exhaust gas flowing out from the exhaust purification device and / or further reduce the circulation amount of the low temperature fresh air flowing into the intake passage.

  When the exhaust circulation unit is configured to circulate the exhaust gas by rotationally driving the turbine with a turbo assist power source, the regeneration control unit of the present invention performs the regeneration control when the engine is stopped in the EV traveling mode of the hybrid system described above. When performing the above, regeneration control of the exhaust purification device can be performed while exhausting by the exhaust circulation means.

  In this case, even in a situation where it is difficult to circulate the exhaust gas when the fuel supply to the engine is stopped due to engine rotation by the non-engine power source due to restrictions due to the state of charge of the battery, etc. It is possible to suitably execute the reproduction control.

  When the exhaust circulation means is configured to circulate the exhaust gas by rotating the turbine with a turbo assist power source, the regeneration control means of the present invention is a so-called eco-run vehicle, that is, automatically in a predetermined engine stop condition. In the vehicle provided with the engine automatic stop start control means for automatically stopping the engine and automatically restarting the stopped engine under a predetermined engine start condition, the exhaust circulation means when the engine is stopped under the engine stop condition It is also possible to execute regeneration control of the exhaust purification device while performing exhaust according to the above.

  In this case, even in a non-hybrid vehicle that does not have a power source for operating the engine with external force when the engine is stopped, it is possible to suitably execute the regeneration control of the exhaust purification device when the engine is stopped.

The present invention
The exhaust purification device has a filter that collects particulate matter in the exhaust,
The regeneration control means is applied to an engine exhaust purification system configured to execute filter regeneration control for recovering the exhaust purification ability of the filter by oxidizing and removing particulate matter collected by the filter as regeneration control. can do.

In this case, when executing the filter regeneration control when the engine is stopped, the regeneration control means executes the filter regeneration control while circulating the high-temperature exhaust gas flowing out from the filter in the circulation path including the filter. It can suppress that the temperature of a filter falls inside. Therefore, it is possible to suitably execute the filter regeneration control when the engine is stopped.

  When the present invention is applied to filter regeneration control when the engine is stopped, the amount of exhaust gas circulated in the circulation path including the filter by the internal exhaust gas circulation means of the exhaust gas flowing out from the filter according to the temperature of the filter, and / or The amount of air flowing into the intake passage of the engine may be adjusted.

  This makes it possible to reduce the amount of exhaust gas circulating in the filter circulation path or to reduce the amount of fresh air flowing into the intake passage when it can be determined that the filter temperature is higher than a certain allowable upper limit temperature. Since the temperature of the filter can be lowered by increasing the amount, it is possible to suppress the filter from being excessively heated and damaged in the filter regeneration control.

  Further, the amount of air flowing into the engine intake passage may be adjusted according to the oxygen concentration of the exhaust gas flowing into the filter.

  In this way, when it can be determined that sufficient oxygen is not supplied to the filter so that the oxidation reaction of the particulate matter collected in the filter can proceed appropriately, the amount of fresh air flowing into the intake passage is reduced. By increasing it, oxygen can be supplied to the filter. Thereby, it can suppress that filter reproduction | regeneration control becomes unable to be performed suitably because of oxygen shortage.

  At this time, if the amount of air flowing into the intake passage is adjusted so that the minimum necessary oxygen can be supplied in order to suitably execute the filter regeneration control, excess air flows into the intake passage. Thus, it is possible to suppress a decrease in the temperature of the gas circulating in the circulation path.

  When the present invention is applied to filter regeneration control, an EGR passage, an EGR valve, and a throttle valve are provided. When the engine is stopped in the EV traveling mode, the EGR valve is changed to an opening on the open side, and the throttle valve is When the filter regeneration control is executed while circulating the exhaust gas flowing out from the filter by changing the opening to the closing side and rotating the engine with a non-engine power source, depending on the temperature of the filter Further, at least one of the opening degree of the EGR valve, the opening degree of the throttle valve, and the engine speed when the engine is rotated by a non-engine power source may be adjusted.

  In this way, when it can be determined that the temperature of the filter is higher than a certain allowable upper limit temperature, the opening of the EGR valve is changed to the closed side, or the opening of the throttle valve is changed to the open side. By increasing the rotational speed of the engine rotation by the non-engine power source, the temperature rise of the filter can be suppressed, so that the filter can be prevented from being damaged due to excessive temperature rise in the filter regeneration control. .

  When the present invention is applied to filter regeneration control, an EGR passage, an EGR valve, a throttle valve, and a turbocharger having a turbo assist power source are provided. When the engine is stopped, the EGR valve is opened to the opening side. If the engine is configured to change the throttle valve to the opening on the closed side and rotate the turbine with a turbo-assist power source to execute the filter regeneration control while circulating the exhaust gas flowing out from the filter Depending on the temperature of the filter, at least one of the opening degree of the EGR valve, the opening degree of the throttle valve, and the rotational speed of the turbine when the turbine is rotationally driven by the turbo assist power source may be adjusted.

  In this way, when it can be determined that the temperature of the filter is higher than a certain allowable upper limit temperature, the opening of the EGR valve is changed to the closed side, or the opening of the throttle valve is changed to the open side. By increasing the rotational speed of the turbine by the turbo assist power source, it is possible to suppress an increase in the temperature of the filter, and thus it is possible to suppress the filter from being excessively heated and damaged in the filter regeneration control.

  Further, the opening degree of the throttle valve may be adjusted according to the oxygen concentration of the exhaust gas flowing into the filter.

  In this way, when it can be determined that sufficient oxygen is not supplied to the filter so that the oxidation reaction of the particulate matter collected by the filter can proceed appropriately, the opening of the throttle valve is changed to the open side. By doing so, more air can be supplied to the filter. Thereby, it can suppress that filter reproduction | regeneration control becomes unable to be performed suitably because of oxygen shortage.

  At this time, if the opening degree of the throttle valve is adjusted so that the minimum necessary oxygen can be supplied so that the filter regeneration control can be suitably executed, excess air flows into the intake passage and the circulation route It can also be suppressed that the temperature of the gas circulating inside is lowered.

The present invention
The exhaust purification device has a NOx catalyst that stores NOx in exhaust in an oxygen-excess atmosphere, releases the stored NOx in a reducing atmosphere, and reduces the released NOx in the presence of a reducing agent,
The regeneration control means, as regeneration control, releases the NOx occluded in the NOx catalyst by supplying a reducing agent to the NOx catalyst and adjusting the ambient atmosphere of the NOx catalyst to the reducing atmosphere, and the reducing agent The present invention can be applied to an engine exhaust gas purification system configured to execute NOx reduction control for reducing released NOx.

  In this case, when executing the NOx reduction control when the engine is stopped, the regeneration control means executes the NOx reduction control while circulating the high-temperature exhaust gas flowing out from the NOx catalyst in the circulation path including the NOx catalyst. It can suppress that the temperature of a NOx catalyst falls during control execution. Therefore, it is possible to suitably execute NOx reduction control when the engine is stopped.

  Further, in this case, since the exhaust gas flowing out from the NOx catalyst flows into the NOx catalyst again, the supply amount of the reducing agent necessary for making the ambient atmosphere of the NOx catalyst a reducing atmosphere can be reduced. Therefore, fuel consumption can be improved particularly when fuel is used as the reducing agent.

  When the present invention is applied to NOx reduction control, an EGR passage, an EGR valve, and a throttle valve are provided. When the engine is stopped in the EV traveling mode, the EGR valve is changed to an opening on the open side, and the throttle valve is By changing the opening to the closing side and rotating the engine with a non-engine power source, the NOx reduction control can be executed while circulating the exhaust gas flowing out from the NOx catalyst.

In addition, when the present invention is applied to NOx reduction control, an EGR passage, an EGR valve, a throttle valve, and a turbocharger having a turbo assist power source are provided. When the engine is stopped, the EGR valve is opened on the open side. The throttle valve is changed to the opening degree on the closing side, and the turbine is rotationally driven by a turbo assist power source so that NOx reduction control is executed while circulating the exhaust gas flowing out from the NOx catalyst. You can also

  In this case, since the throttle valve is closed, the amount of fresh air flowing into the gas circulating in the circulation path including the NOx catalyst is reduced, so that the ambient atmosphere of the NOx catalyst can be reduced with a smaller amount of reducing agent added. Can be made into a reducing atmosphere necessary for execution of NOx reduction control.

Here, in the present invention, when an engine start condition for starting the engine and performing a load operation is satisfied while the engine is stopped,
The engine is operated in a cranking mode in which the engine is cranked and the number of revolutions of the engine is increased by performing fuel injection adapted to the cranking,
Consider a case in which engine start control means is provided for shifting to a load operation mode in which the engine is loaded when the engine speed reaches a predetermined reference speed in the cranking mode.

  In the present invention, as described above, the regeneration control of the exhaust purification device is executed while at least part of the exhaust gas flowing out from the exhaust purification device circulates in the circulation path including the exhaust purification device while the engine is stopped. can do. Even if the exhaust circulation is stopped when the conditions for restarting the engine are satisfied in such a state, the gas circulated in the circulation path for a while after the exhaust circulation is stopped. Will continue to be inhaled into the engine.

  When the EGR rate of the gas that circulates in the circulation path when the engine is stopped is higher than the target EGR rate that is suitable for engine cranking and load operation, the gas circulated in the circulation path is sucked into the engine. During this time, the fuel supplied to the engine by the fuel injection does not burn properly, and there is a possibility that poor combustion such as misfire may occur. In this case, a large amount of unburned fuel components may flow into the exhaust purification device and cause deterioration or breakage of the exhaust purification device.

  Therefore, in the present invention, when the engine start condition is satisfied when the regeneration control unit performs the regeneration control while circulating the exhaust gas by the exhaust circulation unit while the engine is stopped, The engine start control means starts the engine operation in the cranking mode after stopping the exhaust gas circulation by the exhaust circulation means, and starts fuel injection suitable for cranking in the cranking mode. May be delayed for a predetermined period from the start of engine operation in the cranking mode.

  In the above “predetermined period” for delaying the start of fuel injection in the cranking mode, even if fuel is injected into the engine, there is a risk that the fuel does not burn properly and a combustion failure such as misfire may occur. It is a period that can be judged. According to the above configuration, the gas having an EGR rate that is excessively higher than the target EGR rate suitable for the cranking is circulated in the circulation path by the exhaust circulation means, and still remains after the operation in the cranking mode is started. Fuel injection is not executed during a period in which it is possible to determine that the circulating gas is being sucked into the engine.

  Therefore, even when a gas with an extremely low oxygen concentration is circulated in the circulation path by the exhaust circulation means when the engine is stopped, a combustion failure such as misfire may occur in the cranking mode after the engine start condition is established. Can be suppressed.

  In the present invention, when the present invention is applied to an engine exhaust purification system that has a filter as an exhaust purification device and executes filter regeneration control as regeneration control, the oxidation reaction of particulate matter in the filter can proceed suitably Since the amount of air flowing into the intake passage can be adjusted so that a certain amount of oxygen is supplied, the oxygen concentration of the gas circulating in the circulation path can be excessively reduced by the exhaust circulation means when the engine is stopped. The nature is low.

  On the other hand, when the present invention is applied to an exhaust purification system of an engine that has a NOx catalyst as an exhaust purification device and performs NOx reduction control as regeneration control, a circulation path is used to make the ambient atmosphere of the NOx catalyst a reducing atmosphere. Since the supply of air to the inside may be restricted, there is a possibility that the oxygen concentration of the gas circulated in the circulation path by the exhaust circulation means when the engine is stopped is extremely low. Therefore, performing the control for delaying the start of fuel injection in the cranking mode as described above is particularly suitable when the present invention is applied to the NOx reduction control when the engine is stopped.

  In the present invention, an EGR passage, an EGR valve, and a throttle valve are provided. When the engine is stopped, the EGR valve is changed to the opening on the open side, the throttle valve is changed to the opening on the closing side, and the non-engine power When exhaust gas is circulated by engine rotation by a power source or turbine drive by a turbo assist power source, the EGR valve is closed and the throttle valve is opened when the engine start condition is satisfied. Turbine drive by rotation or turbo assist power source is stopped. Then, cranking of the engine is started, but fuel injection is not yet performed at that time, and no-injection cranking is continued until the predetermined period elapses. Then, fuel injection is started when a predetermined period has elapsed, and the engine speed is increased to a speed at which the engine can be shifted to the load operation mode by cranking and combustion energy of fuel. In this way, even when the engine start condition is satisfied when the regeneration control of the exhaust purification device is being executed while the exhaust gas is circulated while the engine is stopped, the cranking mode at the time of engine start is maintained. It is possible to suppress the occurrence of fuel combustion failure.

Here, an oxygen concentration acquisition means for acquiring the oxygen concentration of the gas sucked into the engine is provided,
The engine start control means may determine a period for delaying the start of fuel injection in the cranking mode based on the oxygen concentration acquired by the oxygen concentration acquisition means.

  As a result, when it is detected that the oxygen concentration of the gas sucked into the engine has become a leaner oxygen concentration than the predetermined reference oxygen concentration at which the fuel can be combusted satisfactorily, fuel injection can be resumed. . The reference oxygen concentration can be obtained in advance. Thereby, fuel injection can be restarted at an optimal timing while monitoring the oxygen concentration of the engine intake gas in real time.

  Further, the engine start control means is configured such that, of the exhaust that is circulated in the circulation path by the exhaust circulation means when the engine is stopped, the exhaust that exists in the intake passage when the engine restart condition is satisfied is A period for delaying the start of fuel injection in the cranking mode may be determined based on the time required for scavenging.

  The time required for the circulating gas (hereinafter referred to as residual gas) existing in the intake passage to be scavenged from the intake passage when the engine restart condition is satisfied depends on the engine cranking speed and the intake passage volume. Etc. can be obtained based on the above. At the time when the engine restart condition is satisfied, the amount of air flowing into the intake passage and the amount of exhaust flowing into the intake passage from the EGR passage are adjusted to an optimum amount for starting the engine. Therefore, after the residual gas is scavenged, the optimum gas for starting the engine is sucked into the engine, and by restarting fuel injection at that time, the injected fuel can be burned well.

As described above, when delaying the start of fuel injection in the cranking mode, the cranking is performed in the state of no fuel injection until it is determined that the gas sucked into the engine has become a gas that can be combusted appropriately. Is done. By the way, in some cases, it is determined that the gas sucked into the engine has become a gas in which the injected fuel can be combusted appropriately, and the engine speed is set to the load operation mode before the delay in starting the fuel injection is released. It is conceivable that the reference rotational speed to be shifted to is reached.

  In such a case, in the present invention, the fuel injection is started and the operation mode is shifted to the load operation mode. In the load operation mode, the target EGR rate is corrected based on the oxygen concentration of the gas sucked into the engine. May be.

  By doing so, the engine can be shifted to the load operation mode without delay when the engine speed reaches the reference speed. At this time, if the oxygen concentration of the gas sucked into the engine is lower than expected, the target EGR rate can be corrected to a value lower than normal. Thus, even when the gas sucked into the engine in the cranking mode has shifted to the load operation mode before satisfying the condition for canceling the delay of the start of fuel injection, that is, the load Even when a gas having a lower oxygen concentration than that assumed in the operation mode is sucked into the engine, the occurrence of defective combustion can be suppressed.

The engine exhaust gas purification system of the present invention comprises:
An exhaust purification device disposed in the exhaust passage of the engine;
Regeneration control means for performing regeneration control for recovering the exhaust purification capacity of the exhaust purification device;
Exhaust circulation means for circulating at least part of the exhaust gas flowing out from the exhaust purification device in a circulation path including the exhaust purification device;
With
In the basic configuration of the present invention, when the regeneration control unit executes the regeneration control when stopping fuel supply to the engine, the regeneration control unit performs the regeneration control while circulating the exhaust gas by the exhaust circulation unit.
A power source capable of outputting a driving force for rotating the engine without depending on fuel combustion energy;
A communication passage connecting the exhaust passage downstream of the exhaust purification device and the intake passage;
A switching valve for opening and closing the communication path;
A throttle valve provided in the intake passage upstream of the connection location of the communication passage;
With
The exhaust circulation means includes
Change the switching valve to an opening on the opening side than when the exhaust gas is not circulated,
The opening of the throttle valve is changed to an opening on the closing side than when the exhaust gas is not circulated,
By rotating the engine by the power source,
Circulating the exhaust,
The regeneration control means may execute the regeneration control while circulating the exhaust gas by the exhaust circulation means when the regeneration control is performed when the fuel supply to the engine is stopped.

According to the engine exhaust purification system configured as described above, the engine is rotated by the power source even when the fuel supply to the engine is stopped. Then, when the switching valve is opened, the high-temperature exhaust gas flowing out from the exhaust emission control device that is performing the regeneration control flows into the communication path, flows into the intake path through the communication path, and is rotated by the power source. The exhaust flows in the circulation path including the exhaust purification device, which is sucked into the exhaust passage, discharged into the exhaust passage, and flows into the exhaust purification device again. Furthermore, the amount of low-temperature fresh air flowing into the circulation path can be reduced by closing the throttle valve. As a result, when the regeneration control is executed when the fuel supply to the engine is stopped, the temperature of the exhaust emission control device can be maintained at a high temperature. As a result, it is possible to suitably execute the regeneration control of the exhaust purification device when the fuel supply to the engine is stopped.

  Further, if this communication path is configured as a path separate from the path that is normally used as the EGR path, there is no need to provide a cooling device such as an EGR cooler in the middle of the communication path. Therefore, the gas circulating through the circulation path can be more reliably maintained at a high temperature. Further, since it is not necessary to provide a passage for bypassing the EGR cooler, a flow passage passing through the bypass passage, and a flow passage passing through the EGR cooler, the complexity and cost of the device are eliminated. There is also an effect that the increase can be suppressed.

  In the above configuration, as a driving force for rotating the engine without depending on the combustion energy of the fuel, a motor generator of a hybrid system can be exemplified. Specifically, when the present invention is applied to a hybrid system that includes an engine and a motor generator as a drive source and is configured to be able to output a drive force to a drive shaft by at least one of the engine and the motor generator, When the fuel supply to the engine is stopped in the EV traveling mode in which the required driving force is output only by the power of the motor generator, the engine is non-injection motored by the surplus power of the remaining motor generator that has output the required driving force. Therefore, a gas flow can be generated in the circulation path in the EV traveling mode. In addition, the hybrid system is configured with an engine, a first motor generator (MG1) that outputs power for engine motoring, and a second motor generator (MG2) that outputs power to the drive shaft as drive sources. The thing of the structure provided may be sufficient. In this case, in the EV traveling mode in which the required driving force is output only by MG2, the engine can be motored by MG1 to generate a gas flow in the above-described circulation path. As a hybrid system to which the present invention is applied, the power of the engine and the motor generator may be transmitted to the drive shaft by a power split and integration device such as a planetary gear mechanism, or the engine and the motor generator may be integrated. The power of the motor generator may be configured to be output to the engine and the drive shaft.

In the above configuration,
An intercooler is provided in the intake passage,
The connection location of the communication passage in the intake passage may be downstream of the intercooler.

  By doing so, since the intercooler is not included in the gas circulation path described above, the gas circulating in the circulation path can be more reliably maintained at a high temperature. Also, compared to the case where the circulation path is configured so that the gas flowing out from the exhaust gas purification apparatus flows into the intake passage upstream of the intercooler, a passage for bypassing the intercooler is provided, Since there is no need to provide a device for switching between a passage that bypasses the cooler and a flow path that passes through the intercooler, there is an effect that the complexity and cost increase of the device can be suppressed.

In the above configuration,
The connection location of the communication passage in the intake passage may be an intake manifold of the engine.

  In this way, the length of the gas circulation path described above can be shortened, so that the gas circulating in the circulation path can be more reliably maintained at a high temperature.

In the above configuration,
An exhaust throttle valve is provided on the downstream side of the connection portion of the communication passage in the exhaust passage,
The exhaust circulation means may change the opening of the exhaust throttle valve to a closing side opening when the exhaust circulation is not performed when the exhaust circulation is not performed.

  By doing so, the gas flowing out from the exhaust purification device is more reliably circulated in the circulation path, so that the gas in the circulation path can be more reliably maintained at a high temperature.

In the above configuration,
The regeneration control means, when performing the regeneration control while circulating the exhaust gas by the exhaust circulation means, when oxygen supply is required for execution of the regeneration control, when oxygen supply is not required In comparison, the opening of the throttle valve may be changed to the open side.

  For example, when performing regeneration processing of a PM filter as an exhaust purification device, it is necessary to supply oxygen necessary for the oxidation reaction of PM. Therefore, the oxygen necessary for the oxidation reaction of PM can be supplied, and the temperature of the gas circulating in the circulation path including the PM filter is maintained at a high temperature so that the regeneration process of the PM filter can be suitably continued. Change the throttle valve opening to the open side so that you can. By doing so, it is possible to prevent the PM regeneration process from being unable to continue due to insufficient oxygen.

  As described above, when the regeneration control of the exhaust purification device is executed while circulating the gas in the circulation path when the fuel supply to the engine is stopped, the high-temperature gas is circulated in the circulation path. The circulating gas is also drawn into the engine. Moreover, since the throttle valve is controlled to the closed side, the pressure of the gas circulating in this circulation path is low. Further, as the regeneration control, when the NOx reduction process of the NOx storage reduction catalyst is performed, the air-fuel ratio of the gas circulating in the circulation path is less than the stoichiometric ratio. As described above, according to the present invention, when the regeneration control of the exhaust purification device is executed while circulating the gas in the circulation path when the fuel supply to the engine is stopped, the gas sucked into the engine is burned into the fuel. May not be in a suitable state.

  Therefore, when the regeneration control of the exhaust purification device is executed while circulating the gas in the circulation path when the fuel supply to the engine is stopped in this way, the fuel supply to the engine is immediately performed when the engine start condition is satisfied. Even if the operation is started, the air-fuel ratio, pressure, and temperature of the intake air do not satisfy the conditions for satisfactory combustion, and there is a possibility of causing a combustion failure such as misfire.

Therefore, in the above configuration,
When the fuel supply to the engine is stopped, an engine start condition for starting the engine and performing a load operation is established when the regeneration control unit performs the regeneration control while circulating the exhaust gas by the exhaust circulation unit. In this case, the opening of the throttle valve is changed to an opening more open than before the engine start condition is satisfied, the switching valve is closed, cranking of the engine is started, You may make it further provide the engine starting control means which starts the fuel supply to the said engine and starts the load operation of the said engine after progress for a predetermined period from the start of cranking.

  According to such an engine start control means, cranking is performed in a state in which the throttle valve is opened without supplying fuel to the engine for a predetermined period after the engine start condition is established. When fresh air is introduced into the intake passage during this predetermined period, the air-fuel ratio of the intake air of the engine becomes lean, the pressure of the intake air rises, and the temperature of the intake air changes. Therefore, it is possible to realize good combustion by starting the fuel supply to the engine after a lapse of a predetermined period.

This predetermined period is determined based on the time required for the air-fuel ratio, pressure, and temperature of the intake air to satisfy the conditions that allow good combustion. The predetermined period may be obtained in advance through experiments or the like.

In particular, it is important for the fuel combustibility in the engine that the air-fuel ratio of the intake air becomes an air-fuel ratio suitable for combustion. Therefore, in the above configuration,
Air-fuel ratio acquisition means for acquiring the air-fuel ratio of the intake air of the engine,
When the condition that the air-fuel ratio acquired by the air-fuel ratio acquisition unit is leaner than a predetermined reference air-fuel ratio is satisfied, the engine start control unit starts fuel supply to the engine and loads the engine You may make it start a driving | operation.

  By doing so, fuel supply is not started at least until the air-fuel ratio having a great influence on the combustion possibility becomes a value suitable for combustion, so that it is possible to suitably ensure the combustion stability at the time of engine start. It becomes.

In the above configuration,
Intake pressure acquisition means for acquiring the pressure of the intake air of the engine;
Intake air temperature acquisition means for acquiring the intake air temperature of the engine;
Further comprising
The engine start control means has a condition that the intake pressure acquired by the intake pressure acquisition means is higher than a predetermined reference pressure, and the intake air temperature acquired by the intake air temperature acquisition means is lower than a predetermined reference temperature. When at least one of the above conditions is further established, fuel supply to the engine may be started to start load operation of the engine.

  Thus, if the fuel supply start timing is set while monitoring the parameter that affects the possibility of combustion, it is possible to more reliably suppress the occurrence of combustion failure at the time of engine start.

The engine exhaust gas purification system of the present invention comprises:
An exhaust purification device disposed in the exhaust passage of the engine;
Regeneration control means for performing regeneration control for recovering the exhaust purification capacity of the exhaust purification device;
Exhaust circulation means for circulating at least part of the exhaust gas flowing out from the exhaust purification device in a circulation path including the exhaust purification device;
With
In the basic configuration of the present invention, when the regeneration control unit executes the regeneration control when stopping fuel supply to the engine, the regeneration control unit performs the regeneration control while circulating the exhaust gas by the exhaust circulation unit.
A communication passage connecting the exhaust passage downstream of the exhaust purification device and the exhaust passage upstream of the exhaust purification device;
A power source for generating a gas flow from the exhaust passage downstream of the exhaust purification device to the exhaust passage upstream of the exhaust purification device in the communication passage;
A switching valve for opening and closing the communication path;
An exhaust throttle valve provided on the downstream side of the connecting portion of the communication passage in the exhaust passage downstream of the exhaust purification device;
A throttle valve provided in the intake passage;
With
The exhaust circulation means includes
Change the opening of the switching valve to an opening on the opening side than when the exhaust gas is not circulated,
The opening of the exhaust throttle valve is changed to an opening on the closing side than when the exhaust gas is not circulated,
Change the opening of the throttle valve to the opening on the closed side than when the exhaust gas is not circulated,
The exhaust gas is circulated by generating the gas flow in the communication path by the power source,
The regeneration control means may execute the regeneration control while circulating the exhaust gas by the exhaust circulation means when the regeneration control is performed when the fuel supply to the engine is stopped.

  According to the engine exhaust purification system configured as described above, when the fuel supply to the engine is stopped, the gas flowing out from the exhaust purification device flows into the communication passage, flows into the exhaust passage upstream of the exhaust purification device, A gas flow in the circulation path that flows into the exhaust purification device again occurs. Furthermore, the amount of low-temperature fresh air flowing into the circulation path is reduced by closing the throttle valve. Furthermore, if the circulation path is configured to guide the gas from the immediately downstream side of the exhaust purification apparatus to the upstream side of the exhaust purification apparatus, the length of the circulation path can be made as short as possible. Among the heat of the gas circulating through the heat, the heat lost from the piping wall surface of the circulation path can be reduced. As a result, the temperature of the circulating gas can be more reliably maintained at a high temperature, and the temperature of the exhaust emission control device can be maintained at a high temperature when regeneration control is executed when fuel supply to the engine is stopped. Therefore, it is possible to suitably execute the regeneration control of the exhaust purification device when the fuel supply to the engine is stopped.

  In the above configuration, as a power source for generating the circulation of the gas in the circulation path, a pump for causing the gas in the communication path to flow from the exhaust passage side downstream of the exhaust purification device to the exhaust passage side upstream of the exhaust purification device Can be used.

  Using this pump as a power source, a gas flow can be generated in the circulation path including the exhaust purification device. The energy required to drive this pump can be reduced compared to the energy required to motor the engine by the motor or to rotate the motor-assisted turbocharger by the motor. The power consumption required to generate the flow can be reduced.

In the above configuration,
Reducing agent supply means for supplying a reducing agent into the communication passage on the exhaust passage side downstream of the exhaust purification device from the pump;
When the regeneration control unit executes the regeneration control while the exhaust gas circulation unit circulates the exhaust gas, when the regenerative control requires a supply of a reducing agent, the reducing agent supply unit performs the communication path. You may make it supply a reducing agent in the gas which flows.

  As a result, the reducing agent can be supplied into the gas circulating in the circulation path, and since the reducing agent is supplied upstream of the pump, the reducing agent is well mixed with the circulating gas by the pump. It is possible to supply the reducing agent in a high state to the exhaust gas purification device. Thereby, the reactivity of the reducing agent in the exhaust purification device can be improved, and the exhaust purification rate of the exhaust purification device can be maintained well.

In the above configuration,
The power source is configured to be able to generate a gas flow in the exhaust passage from the upstream side to the exhaust purification device side from the connection point of the communication passage in the exhaust passage upstream of the exhaust purification device,
An EGR passage connecting an exhaust passage upstream of the exhaust purification device and an intake passage downstream of the throttle valve;
An EGR valve provided in the EGR passage;
With
When the regeneration control means executes the regeneration control while circulating the exhaust gas by the exhaust circulation means, when supply of oxygen is required for the execution of the regeneration control,
The opening of the throttle valve is changed to the open side rather than when oxygen supply is not required,
The opening of the EGR valve is changed to the open side rather than when oxygen supply is not required,
The gas flow may be generated in an exhaust passage upstream of the exhaust purification device by the power source.

  As a result, the air in the intake passage flows from the intake passage side to the exhaust passage side through the EGR passage, flows into the exhaust passage, and flows into the circulation path including the exhaust purification device described above. Thereby, oxygen can be supplied into the gas circulating in the circulation path. Thereby, when performing the regeneration process of PM filter as regeneration control, it can control that the oxidation reaction of PM does not advance by lack of oxygen. This oxygen supply amount can be adjusted by changing the opening of the EGR valve. At this time, the opening degree of the switching valve of the communication path may be changed to the closed side.

In order to supply the air in the intake passage into the gas circulating in the circulation path,
The power source is configured to be able to generate a gas flow in the exhaust passage from the upstream side to the exhaust purification device side from the connection point of the communication passage in the exhaust passage upstream of the exhaust purification device,
Valve control means for controlling opening and closing of the intake valve and exhaust valve of the engine;
With
When the regeneration control means executes the regeneration control while circulating the exhaust gas by the exhaust circulation means, when supply of oxygen is required for the execution of the regeneration control,
The opening of the throttle valve is changed to the open side rather than when oxygen supply is not required,
The valve control means controls the intake valve and the exhaust valve of the engine to be in an open state,
The gas flow may be generated in an exhaust passage upstream of the exhaust purification device by the power source.

  In this case, since both the intake valve and the exhaust valve are opened and overlapped, the air in the intake passage passes through the cylinder and flows into the exhaust passage, and enters the circulation path including the exhaust purification device described above. Inflow. Thereby, oxygen can be supplied into the gas circulating in the circulation path.

  As described above, the air in the intake passage flows into the exhaust passage via the EGR passage or the cylinder in the valve overlap state, and the gas in the communication passage is exhausted from the exhaust passage downstream of the exhaust purification device to the upstream of the exhaust purification device. The power source that can flow to the passage side is provided at the connection portion of the communication passage in the exhaust passage upstream of the exhaust purification device, the exhaust passage upstream from the connection portion, and the communication upstream from the connection portion. A pump that allows gas to flow from the passage to the exhaust purification device side can be used.

  According to the present invention, it is possible to suitably execute the regeneration control of the exhaust purification device when the engine is stopped.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram showing a schematic configuration of a hybrid system to which an engine exhaust purification system according to the present invention is applied.

  This hybrid system has an engine 1, a first motor generator (hereinafter referred to as “MG1”), and a second motor generator (hereinafter referred to as “MG2”) as power sources. The power of the engine 1 is distributed and output to the MG 1 and the output unit 4 by the power split mechanism 3. The power split mechanism 3 is configured by a known planetary gear mechanism. The power of MG2 is output to the output unit 4. The power of the engine 1 and the MG 2 output to the output unit 4 is transmitted to the drive wheels 40 as a driving force for driving the drive wheels 40 of the vehicle on which the hybrid system is mounted via the transmission unit 8. The transmission unit 8 has a known configuration such as a drive shaft or a differential gear.

  MG1 is a synchronous motor generator that functions as a motor or a generator.

  MG1 can operate as a motor by electric power supplied from battery 25 and / or electric power generated by MG2 when operated as a generator. The power of MG 1 when operated as a motor is output to the output shaft (crankshaft) of engine 1 as a driving force for motoring engine 1 via power split mechanism 3.

  Here, motoring the engine 1 means that the engine 1 is mechanically rotationally driven by an external force without depending on the internal combustion energy due to fuel combustion. In the hybrid system of the present embodiment, the engine 1 can be motored by the power of the MG1, so that the fuel injection is not performed in the engine 1 or the injection amount necessary for the engine 1 to rotate independently is less than The engine 1 can be operated even in a state where a small amount of fuel is injected.

  MG1 is driven by the power of engine 1 distributed to MG1 via power split mechanism 3, and can operate as a generator. The electric power generated by MG1 when operating as a generator is consumed as electric power for charging battery 25 and / or electric power for operating MG2 as a motor.

  MG2 is also a synchronous motor generator that functions as a motor or a generator.

  MG2 can operate as a motor by the electric power supplied from battery 25 and / or the electric power generated by MG1 when operated as a generator. The power of the MG 2 when operating as a motor is transmitted to the driving wheel 40 as a driving force for driving the driving wheel 40 via the output unit 4.

  The MG 2 is driven by the kinetic energy of the drive wheel 40 transmitted via the transmission unit 8 and the output unit 4 and can operate as a generator. The electric power generated by MG2 when operating as a generator is consumed as electric power for charging battery 25 and / or electric power for operating MG1 as a motor. In this case, regenerative power generation is performed by the kinetic energy of the drive wheels 40, and a braking force is applied to the drive wheels 40.

  The inverter 24 converts DC power supplied from the battery 25 into AC power and supplies it to MG1 and MG2, and also converts AC power supplied from MG1 and MG2 into DC power when operating as a generator. The battery 25 is supplied.

The engine 1 is a diesel engine. FIG. 2 shows a schematic configuration of the intake / exhaust system and the control system of the engine 1.

  The engine 1 is a four-cylinder engine, and each cylinder 49 is provided with a common rail injector 29 that directly injects fuel into the combustion chamber of the engine 1. An intake passage 42 that supplies air and EGR gas to be described later to the combustion chamber is connected to the engine 1 via the intake manifold 17. Further, an exhaust passage 43 for discharging burned gas in the combustion chamber is connected to the engine 1 via an exhaust manifold 18.

  Each cylinder 49 communicates with the intake manifold 17 via an intake port (not shown) and also communicates with the exhaust manifold 18 via an exhaust port (not shown). Each cylinder 49 is provided with an unillustrated intake valve that opens and closes an intake port and an unillustrated exhaust valve that opens and closes an exhaust port. The engine 1 of this embodiment is provided with a variable valve timing mechanism (VVT) 46 that can variably control the opening and closing timings of the intake and exhaust valves.

  An HPL-EGR passage that guides part of the exhaust discharged from the exhaust manifold 18 to the exhaust passage 43 into the intake passage 42 near the connection portion with the intake manifold 17 is provided in the intake passage 42 in the vicinity of the connection portion with the intake manifold 17. 15 is connected. The intake passage 42 upstream of the connection location of the HPL-EGR passage 15 is provided with a first throttle valve 9 that adjusts the amount of gas flowing in the intake passage 42. An intercooler 2 is provided in the intake passage 42 upstream of the first throttle valve 9.

  The intake passage 42 on the upstream side and downstream side of the intercooler 2 communicates with the intercooler bypass passage 10 that bypasses the intercooler 2. An intercooler bypass valve 20 that opens and closes the intercooler bypass passage 10 is provided in the middle of the intercooler bypass passage 10.

  The intake passage 42 upstream of the intercooler 2 is provided with the compressor 11 of the turbocharger 13. Connected to the intake passage 42 upstream of the compressor 11 is an LPL-EGR passage 44 that guides part of the exhaust gas flowing out from an exhaust purification device 41 described later into the intake passage 42 upstream of the compressor 11. The intake passage 42 upstream of the connection point of the LPL-EGR passage 44 is provided with a second throttle valve 22 that adjusts the amount of gas flowing in the intake passage 42. An intake passage 42 upstream of the second throttle valve 22 is provided with an air flow meter 7 that measures the flow rate of air flowing into the intake passage 42.

  An HPL-EGR passage 15 is connected to the exhaust passage 43 in the vicinity of the connection location with the exhaust manifold 18. A turbine 12 of the turbocharger 13 is provided in the exhaust passage 43 on the downstream side of the connection place of the HPL-EGR passage 15.

  The turbocharger 13 is a variable capacity turbocharger provided with a nozzle 12 having a variable opening in the turbine 12 and capable of changing the supercharging efficiency of the turbocharger 13 by changing the opening of the nozzle vane 5. Further, the turbocharger 13 includes a turbo assist motor 21 that can rotationally drive the turbine 12 without depending on exhaust energy. The turbine 12 is rotated by the turbo assist motor 21 to rotate the turbine 12 even in a situation where there is no exhaust flow, and thereby the gas flowing from the upstream exhaust passage 42 to the downstream exhaust passage 42 of the turbine 12. Can produce a flow of.

The exhaust passage 43 on the downstream side of the turbine 12 is provided with a first A / F sensor 50 that measures the air-fuel ratio of the exhaust. The exhaust passage 43 downstream of the first A / F sensor 50 is provided with a fuel addition valve 19 that adds fuel to the exhaust. An exhaust gas purification device 41 is provided in the exhaust passage 43 on the downstream side of the fuel addition valve 19. The exhaust emission control device 41 includes an oxidation catalyst and a filter that is disposed downstream of the oxidation catalyst and collects particulate matter in the exhaust gas.

  A differential pressure sensor 47 that measures the differential pressure between the upstream side and the downstream side of the exhaust purification device 41 is provided. In the exhaust passage 43 on the downstream side of the exhaust purification device 41, an exhaust temperature sensor 37 that measures the temperature of the exhaust gas that flows out from the exhaust purification device 41, and a second A / F that measures the air-fuel ratio of the exhaust gas that flows out from the exhaust purification device 41. An F sensor 38 is provided. An LPL-EGR passage 44 is connected to the exhaust passage 43 downstream of the exhaust temperature sensor 37 and the second A / F sensor 38. An exhaust throttle valve 6 that adjusts the flow rate of the exhaust gas flowing through the exhaust passage 43 is provided in the exhaust passage 43 on the downstream side of the connection point of the LPL-EGR passage 44.

  The exhaust passage 43 upstream from the turbine 12 and the intake passage 42 downstream from the compressor 11 are connected by the HPL-EGR passage 15, and a part of the exhaust flowing through the exhaust passage 43 upstream from the turbine 12. Can flow into the intake passage 42 downstream of the compressor 11 as HPL-EGR gas through the HPL-EGR passage 15. An HPL-EGR cooler 16 for cooling the HPL-EGR gas is provided in the middle of the HPL-EGR passage 15. The HPL-EGR passage 15 on the upstream side and the downstream side of the HPL-EGR cooler 16 communicates with each other by an HPL-EGR cooler bypass passage 36. An HPL-EGR cooler bypass valve 23 that opens and closes the HPL-EGR cooler bypass passage 36 is provided in the middle of the HPL-EGR cooler bypass passage 36. An HPL-EGR valve 14 that adjusts the amount of HPL-EGR gas is provided in the HPL-EGR passage 15 on the intake passage 42 side of the HPL-EGR cooler 16.

  The exhaust passage 43 on the downstream side of the exhaust purification device 41 and the intake passage 42 between the second throttle valve 22 and the compressor 11 are communicated with each other by an LPL-EGR passage 44. Can flow into the intake passage 42 as LPL-EGR gas through the LPL-EGR passage 44. An LPL-EGR cooler 33 that cools the LPL-EGR gas is provided in the middle of the LPL-EGR passage 44. The LPL-EGR passage 44 on the upstream side and the downstream side of the LPL-EGR cooler 33 communicates with each other via the LPL-EGR cooler bypass passage 35. An LPL-EGR cooler bypass valve 34 that opens and closes the LPL-EGR cooler bypass passage 35 is provided in the middle of the LPL-EGR cooler bypass passage 35. An LPL-EGR valve 45 that adjusts the amount of LPL-EGR gas is provided in the LPL-EGR passage 44 closer to the intake passage 42 than the LPL-EGR cooler 33.

  The engine 1 includes a water temperature sensor 48 that measures the cooling water temperature of the engine 1, a crank angle sensor 30 that measures the rotation angle of the crankshaft of the engine 1, an accelerator opening sensor 27 that measures the depression amount of the accelerator pedal 52, and a hybrid system. Is provided with a vehicle speed sensor 28 for measuring the vehicle speed of the vehicle on which is mounted.

  The control system of this hybrid system will be described with reference to FIGS.

  This hybrid system includes an ECU 26 that is a computer unit that controls the operation of the entire hybrid system. The ECU 26 is an electronic control computer having a known configuration such as a CPU, a ROM, and a RAM.

The ECU 26 includes a differential pressure sensor 47, a vehicle speed sensor 28, a water temperature sensor 48, a crank angle sensor 30, an air flow meter 7, an accelerator opening sensor 27, an exhaust temperature sensor 37, a first A / F sensor 50, and a second A / F sensor 38. An SOC sensor 51 for acquiring the state of charge of the battery 25, an MG1 rotational speed sensor 31 for measuring the rotational speed of MG1, an MG2 rotational speed sensor 32 for measuring the rotational speed of MG2, and other state quantities of the hybrid system and the vehicle. A sensor device to be measured is connected, and information on the state quantity measured by each sensor is input to the ECU 26.

  The ECU 26 includes a VVT 46, a fuel addition valve 19, an injector 29, a first throttle valve 9, a second throttle valve 22, an LPL-EGR valve 45, an HPL-EGR valve 14, an exhaust throttle valve 6, a nozzle vane 5, and a turbo assist. The motor 21, the intercooler bypass valve 20, the HPL-EGR cooler bypass valve 23, the LPL-EGR cooler bypass valve 34, the inverter 24, and other actuators that drive various devices of the hybrid system and the vehicle are connected. Based on information input from the sensor, a control signal for driving and controlling the operation of each device is output.

  The ECU 26 calculates the current engine load, the engine speed, and the required torque based on the accelerator opening information input from the accelerator opening sensor 27 and the crank angle information input from the crank angle sensor 30, and the SOC sensor The required torque of the engine 1 is calculated according to the charging state information of the battery 25 from 51 and the required power of auxiliary equipment such as an air conditioner. Based on the calculated required torque, the fuel injection amount and the intake air amount from the injector 29 are controlled. The target value of the fuel injection amount from the injector 29 is determined based on the map from the engine load and the engine speed obtained based on the information from each sensor as described above. Further, the smoke limit injection amount determined so that the smoke generation amount does not exceed the allowable upper limit is determined based on the map from the engine speed and the intake air amount. A final fuel injection command value is determined so that the target value of the fuel injection amount does not exceed the smoke limit injection amount, and a command signal is sent to the injector 29.

  The ECU 26 controls the operation of the engine 1, MG1, and MG2 based on the information regarding the driving state of the vehicle, the charging state of the battery 25, and the request from the driver, which are grasped based on the input from each sensor.

  For example, in a low-speed driving state immediately after the vehicle starts to travel, the engine 1 is stopped, MG2 is powered as a motor, and a driving force for vehicle traveling is output using only the power of MG2. Such a travel mode is referred to as an EV travel mode.

  When the vehicle speed increases and reaches a predetermined speed or load, the engine 1 is cranked by the MG 1 and the fuel injection by the injector 29 is started to start the engine 1, and the engine 1 and the MG 2 are used together to drive the vehicle. The driving force is output. In this case, a part of the output of the engine 1 is distributed to the MG 1 by the power split mechanism 3, the MG 2 is operated as a motor by the electric power generated by the MG 1, and the engine 1 is assisted by the power of the MG 2.

  Further, when the amount of charge of the battery 25 is reduced to a predetermined reference level or less based on information from the SOC sensor 51, the output exceeds the output required for the engine 1 to output the driving force for traveling the vehicle. The power is output to the engine 1, and the MG 1 is operated as a generator by the surplus power of the engine 1 to charge the battery 25.

  When the braking is requested, the rotational energy of the drive wheel 40 is transmitted to MG2, and MG2 is operated as a generator to perform braking by regenerative power generation.

The ECU 26 calculates the required operation state of the motor / power generation of MG1 / MG2, the required output rotation speed and the required output torque of MG1 and MG2 according to the operation state, and outputs a command for independently controlling MG1 and MG2 to the inverter 24. To do. Inverter 24 generates a three-phase alternating current to be supplied to MG1 and MG2 from a direct current voltage supplied from battery 25 in accordance with a command from ECU 26.

  Further, the ECU 26 performs so-called eco-run control for the engine 1. That is, the engine 1 is automatically stopped when a predetermined engine stop condition is satisfied, for example, when the vehicle stops due to a signal waiting at an intersection or the like, and then, for example, when the brake pedal is released or the clutch is Control is performed to automatically start the engine 1 when a predetermined engine start condition such as when the engine is depressed is satisfied. By executing such eco-run control, fuel efficiency and emissions are improved.

  Next, filter regeneration control, which is a feature of this embodiment, will be described.

  Since the pressure loss in the filter increases as the amount of particulate matter collected in the filter of the exhaust purification device 41 increases, if it is determined that the amount of particulate matter collected in the filter exceeds a predetermined reference amount, Filter regeneration control is performed in which the temperature of the filter is raised to the ignition temperature of the particulate matter, and the particulate matter is oxidized and removed from the filter.

  Filter regeneration control during operation of the engine 1 is performed by increasing the load on the engine 1. When the load on the engine 1 is increased, the temperature of the exhaust gas from the engine 1 increases, so that the temperature of the filter rises and the particulate matter collected by the filter is oxidized. Other known control methods may be used for filter regeneration control during operation of the engine 1.

  Further, the present embodiment is characterized in that the filter regeneration control is executed even when the engine 1 is stopped. In the present embodiment, when the engine 1 is stopped refers to a case where the hybrid system is operating in the EV traveling mode or a case where the engine 1 is automatically stopped by the eco-run control. The filter regeneration control executed when the engine 1 is stopped will be described with reference to FIG. FIG. 3 is a flowchart showing a filter regeneration control routine performed when the engine 1 is stopped. This routine is repeatedly executed during the operation of the hybrid system.

  In step S101, the ECU 26 determines whether or not the engine 1 is in a stopped state. In the present embodiment, when the hybrid system is operating in the EV travel mode, or when the engine 1 is automatically stopped by the eco-run control, it is determined that the engine 1 is in a stopped state. If it is determined in step S101 that the engine 1 is in a stopped state (Yes), the ECU 26 proceeds to step S102. If it is determined in step S101 that the engine 1 is not stopped (No), the ECU 26 once exits this routine.

In step S102, the ECU 26 determines whether an execution condition for the filter regeneration control is satisfied. In the present embodiment, as described above, when it is determined that the collected amount of particulate matter in the filter exceeds the reference amount, it is determined that the condition for executing the filter regeneration control is satisfied. In this embodiment, the collected amount of particulate matter in the filter is determined based on the measured value by the differential pressure sensor 47. That is, the pressure loss in the filter is calculated based on the measurement value by the differential pressure sensor 47, and when the calculated pressure loss is larger than a predetermined reference pressure loss, the collected amount of particulate matter in the filter is the reference value. It is determined that the amount has been exceeded. If it is determined in step S102 that the filter regeneration control execution condition is satisfied (Yes), the ECU 26 proceeds to step S103. If it is determined that the filter regeneration control execution condition is not satisfied (No), the ECU
26 once exits this routine.

  In step S <b> 103, the ECU 26 performs filter temperature increase control. In this embodiment, the engine 1 is motored by the MG 1 and fuel is added to the exhaust passage 43 by the fuel addition valve 19. At this time, the second throttle valve 22 and the first throttle valve 9 are opened. As a result, the air taken into the intake passage 42 passes through the engine 1 without being combusted, is discharged to the exhaust passage 43, and flows through the exhaust passage 43 together with the fuel added by the fuel addition valve 19, thereby purifying the exhaust gas. Flows into the device 41. Then, oxygen in the air reacts with the added fuel in the oxidation catalyst disposed in the front stage of the filter of the exhaust gas purification device 41, and the subsequent stage filter is heated by the reaction heat.

  In step S104, the ECU 26 acquires the temperature of the filter. In this embodiment, the temperature of the exhaust gas flowing out from the exhaust gas purification device 41 is measured by the exhaust gas temperature sensor 37, and the temperature of the filter is estimated based on this measured value.

  In step S105, the ECU 26 determines whether the temperature increase of the filter has been completed. In this embodiment, when the temperature of the filter acquired in step S104 is equal to or higher than a predetermined reference temperature, it is determined that the temperature increase of the filter has been completed. Here, the reference temperature is determined based on the temperature of the filter necessary for the particulate matter oxidation reaction to proceed in the filter (for example, 600 ° C.). If it is determined in step S105 that the temperature raising of the filter has been completed (Yes), the ECU 26 proceeds to step S106. If it is determined in step S105 that the temperature rise of the filter has not been completed (No), the ECU 26 returns to step S104.

  In step S106, the ECU 26 executes exhaust gas circulation control. Here, the exhaust gas circulation control means control for circulating at least a part of the exhaust gas flowing out from the filter in the circulation path including the filter. In this embodiment, specifically, the second throttle valve 22 is closed, the LPL-EGR valve 45 is opened, the first throttle valve 9 is opened, the HPL-EGR valve 14 is closed, The intercooler bypass valve 20 is opened, the LPL-EGR cooler bypass valve 34 is opened, the valve opening / closing control for closing the exhaust throttle valve 6 is executed, and the engine 1 is motored by MG1.

  Thereby, the gas flowing out from the filter flows into the intake passage 42 through the LPL-EGR passage 44 and is sucked into the engine 1 motored by the MG1. Here, since the fuel supply to the engine 1 is stopped, the intake air drawn into the engine 1 is discharged into the exhaust passage 43 as it is without burning. Exhaust gas discharged to the exhaust passage 43 flows into the filter through the turbine 12. As described above, by executing the exhaust gas circulation control, the gas flowing out from the filter circulates in the circulation path including the filter. Here, since the temperature of the filter has been raised, and the oxidation reaction of the particulate matter collected by the filter has started, high-temperature gas has flowed out of the filter. Since this high-temperature gas circulates in the circulation path and flows into the filter again, the temperature of the filter can be kept high.

  In step S107, the ECU 26 uses the VVT 46 to advance the closing timing of the exhaust valve of the engine 1 and sets the opening timing of the exhaust valve at a timing immediately after top dead center. As a result, the gas in the cylinder 49 that has been compressed in the compression stroke and has reached a high temperature is discharged into the exhaust passage 43 before the temperature drops due to cooling with the cooling water of the engine 1 or expansion in the expansion stroke. Thereby, the temperature of the gas which circulates in the circulation path and flows into the filter can be more reliably maintained at a high temperature. Therefore, the temperature of the filter during execution of the filter regeneration control can be more reliably maintained at a high temperature.

  In step S108, the ECU 26 acquires the oxygen concentration of the exhaust gas flowing into the filter. In the present embodiment, the air-fuel ratio of the exhaust is measured by the second A / F sensor 38, and the oxygen concentration of the exhaust flowing into the filter is estimated based on this measured value.

  In step S109, the ECU 26 determines whether or not the oxygen concentration of the exhaust gas flowing into the filter is insufficient with respect to the oxygen concentration necessary for the oxidation reaction of the particulate matter collected by the filter to proceed appropriately. judge. In this embodiment, when the oxygen concentration of the exhaust gas flowing into the filter acquired in step S108 is less than a predetermined reference oxygen concentration, it is determined that the oxygen concentration of the exhaust gas flowing into the filter is insufficient. Here, the reference oxygen concentration is determined based on the oxygen concentration of the filter inflow gas necessary for the oxidation reaction of the particulate matter to proceed in the filter. If it is determined in step S109 that the oxygen concentration of the filter inflow gas is insufficient (Yes), the ECU 26 proceeds to step S110. When it is determined in step S109 that the oxygen concentration of the filter inflow gas is not insufficient (No), the ECU 26 once exits this routine.

  In step S110, the ECU 26 determines whether the temperature of the filter is equal to or higher than the reference temperature. As described above, the reference temperature is determined in advance based on the temperature necessary for the particulate matter oxidation reaction to proceed in the filter. If it is determined in step S110 that the temperature of the filter is equal to or higher than the reference temperature (Yes), the ECU 26 proceeds to step S111. If it is determined in step S110 that the filter temperature is not equal to or higher than the reference temperature (No), the ECU 26 once exits this routine.

  In step S111, the ECU 26 executes control for increasing the oxygen concentration of the gas circulating in the circulation path including the filter. In this embodiment, the opening degree of the second throttle valve 22 is changed to the opening side opening degree. By doing so, the amount of fresh air flowing into the above-described circulation path increases, so that the oxygen concentration of the gas circulating in the circulation path and flowing into the filter can be increased. The ECU 26 that has executed Step S111 returns to Step S108.

  By executing the filter regeneration control routine described above, when performing the filter regeneration control when the engine is stopped, the high-temperature gas flowing out from the filter is circulated in the circulation path including the filter. Can be suppressed. Since the opening of the second throttle valve 22 is controlled so that the temperature of the filter is maintained at a high temperature and oxygen necessary for the particulate matter oxidation reaction in the filter can be supplied. Filter regeneration control can be executed while continuously introducing fresh air into the gas circulating in the circulation path.

  Conventionally, when performing filter regeneration control while performing engine motoring with MG1 when the engine is stopped, if fresh air is introduced to supply oxygen necessary for the oxidation reaction of particulate matter to the filter, low temperature fresh air is introduced. The temperature of the filter will decrease, so if the temperature of the filter decreases, the introduction of fresh air will be stopped, the temperature of the filter will be raised again, and the introduction of fresh air will start again. It was difficult to introduce new air continuously. Therefore, there has been a problem that the regeneration speed of the filter (the speed at which the particulate matter is oxidized and removed from the filter) is slow.

  In this respect, in the case of the present embodiment, as described above, even if fresh air is continuously introduced, the high-temperature gas discharged from the filter circulates in the circulation path including the filter, so the temperature of the filter decreases. Can be suppressed. Therefore, oxygen can be continuously supplied to the filter, and the regeneration speed of the filter can be increased.

  In order to achieve such an effect peculiar to the present embodiment, at least, when the filter regeneration control is executed while the engine 1 is stopped, the exhaust gas flowing out from the filter can be circulated, and It is sufficient if the opening degree of the second throttle valve 22 can be adjusted so that oxygen necessary for filter regeneration control can be supplied to the filter while suppressing the temperature drop of the filter.

  Therefore, the components related to HPL-EGR (HPL-EGR passage 15, HPL-EGR valve 14, HPL-EGR cooler 16, HPL-EGR cooler bypass passage 36, HPL-EGR cooler bypass valve 23, first throttle valve 9) Is not necessarily required. Further, the turbocharger 13 does not need to be a motor assist turbocharger or a variable capacity turbocharger. Further, it is sufficient to have MG1 capable of motoring engine 1 as a power source for circulating the exhaust gas flowing out from the filter in the circulation path including the filter when engine 1 is stopped, and the eco-run control can be executed. It does not have to be a secure system. If the engine motoring power source corresponding to MG1 is provided, the configuration of the hybrid system is not limited to the configuration exemplified in this embodiment.

  Further, the intercooler bypass passage 10 is provided to open the intercooler bypass valve 20 during filter regeneration control, or the LPL-EGR cooler bypass passage 35 is provided to open the LPL-EGR cooler bypass valve 34 during filter regeneration control. In other words, the advancement of the opening timing of the exhaust valve by the VVT 46 has the effect of maintaining the temperature of the gas flowing into the filter at a high temperature when the engine is stopped. Although it can be further enhanced, it is not an essential requirement for achieving the effects of the present embodiment.

  In addition, in order to determine the execution condition of the filter regeneration control, an example is shown in which the collected amount of particulate matter in the filter is estimated based on the measured value by the differential pressure sensor 47. You may determine the execution conditions of reproduction | regeneration control. In addition, as an example of the filter temperature raising control, a method of adding fuel into the exhaust gas from the fuel addition valve 19 and causing the oxidation-reduction reaction with the oxidation catalyst in the upstream stage of the filter has been exemplified. Also good. Further, the case where the determination as to whether or not oxygen for the filter regeneration control is insufficient is illustrated based on the measurement value of the second A / F sensor 38 that measures the air-fuel ratio of the exhaust gas flowing out from the filter. Various other known methods can be used as a method for determining oxygen shortage. Further, in this embodiment, an example of performing estimation based on the measurement result of the temperature of the exhaust gas flowing out from the filter in order to acquire the temperature of the filter has been described. However, there are various other known methods for acquiring the filter temperature. Can be used.

  In the present embodiment, the second throttle valve 22 corresponds to the throttle valve in the present invention. The LPL-EGR valve 45 corresponds to the EGR valve in the present invention. The LPL-EGR passage 44 corresponds to the EGR passage in the present invention. MG1 corresponds to a power source other than the engine (also referred to as a non-engine power source) in the present invention, particularly “second power source”. MG2 corresponds to a power source other than the engine in the present invention (also referred to as a non-engine power source), particularly “first power source”. In step S106, the second throttle valve 22 is closed, the LPL-EGR valve 45 is opened, and the ECU 26 that controls the MG 1 to motor the engine 1 corresponds to the exhaust circulation means in the present invention. The VVT 46 corresponds to the variable valve timing device in the present invention. The ECU 26 that executes Steps S103 to S105 and Steps S107 to S111 corresponds to the regeneration control means in the present invention.

Next, a second embodiment of the present invention will be described. In this embodiment, in the hybrid system described in the first embodiment, when the filter regeneration control is executed while the exhaust gas is circulated in the circulation path including the filter while the engine 1 is stopped, the temperature of the filter is excessively increased. Control for suppressing is performed. In the present embodiment, components that are substantially the same as those in the first embodiment are denoted by the same names and reference numerals as those in the first embodiment, and detailed description thereof is omitted.

  In this embodiment, filter regeneration control that is executed when the engine 1 is stopped will be described with reference to FIG. FIG. 4 is a flowchart showing a routine of filter regeneration control performed when the engine 1 is stopped. This routine is repeatedly executed during the operation of the hybrid system.

  Steps S101 to S107 are the same as the control described in the first embodiment based on FIG. In the present embodiment, the ECU 26 that has executed step S107 proceeds to step S208.

  In step S208, the ECU 26 acquires the temperature of the filter. In step S208, as described in step S104 of the first embodiment, the exhaust temperature sensor 37 measures the temperature of the exhaust gas flowing out from the exhaust purification device 41, and estimates the filter temperature based on this measured value. get.

  In step S209, the ECU 26 determines whether or not there is a possibility that the temperature of the filter is excessively increased. In the present embodiment, when the temperature of the filter acquired in step S208 exceeds a predetermined upper limit temperature, it is determined that there is a possibility that the temperature of the filter is excessively increased. Here, the upper limit temperature is a filter temperature at which it can be determined that the possibility that the filter will be excessively heated and damaged when the temperature of the filter further increases, and is determined in advance by experiments or the like (eg, 700 ° C.). If it is determined in S209 that there is a risk that the filter will overheat (Yes), the ECU 26 proceeds to step S210. If it is determined in step S209 that there is no risk that the filter will overheat (No), the ECU 26 once exits this routine.

  In step S210, the ECU 26 executes control for reducing the temperature of the gas circulating in the circulation path including the filter. In the present embodiment, the opening degree of the second throttle valve 22 is changed to the open side, the opening degree of the LPL-EGR valve 45 is changed to the closing side, and the motoring rotational speed of the engine 1 by MG1 is increased. When the second throttle valve 22 is changed to the open side, low temperature fresh air flows into the circulation path, and the temperature of the gas in the circulation path decreases. Further, when the LPL-EGR valve 45 is changed to the closed side, high-temperature exhaust gas from the filter flowing into the circulation path is reduced, so that the temperature of the gas in the circulation path is lowered. Further, since the amount of gas passing through the filter is increased by increasing the motoring rotational speed of the engine 1 by the MG1, the temperature of the filter can be lowered by removing heat by the passing gas. After executing step S210, the ECU 26 returns to step S208.

  As described in the first embodiment, in this embodiment, when the filter regeneration control is executed when the engine 1 is stopped, the high-temperature gas flowing out from the filter is circulated in the circulation path including the filter. There is an effect that a decrease in temperature can be suppressed. Because of this effect, in some cases, the temperature of the filter may become too high. In this respect, according to the present embodiment, when the temperature of the filter exceeds the upper limit temperature, control is performed to lower the gas temperature in the circulation path or the temperature of the filter. Can be suppressed.

  In this embodiment, in order to lower the temperature of the gas in the circulation path in step S210, the second throttle valve 22 is opened, the LPL-EGR valve 45 is closed, and the engine motoring rotational speed by MG1 is set. However, it may be configured to execute at least one of them. Even in such a case, the effect of lowering the temperature of the gas in the circulation path can be achieved.

  In this embodiment, the ECU 26 that executes Steps S103 to S105, Step S107, and Steps S208 to S210 corresponds to the regeneration control means in the present invention.

  Next, a third embodiment of the present invention will be described. In this embodiment, when the filter regeneration control is executed when the engine 1 is stopped, the turbine 12 is rotated by the turbo assist motor 21 to circulate the exhaust gas in the circulation path including the filter. This is different from the first or second embodiment in which the exhaust gas is circulated in the circulation path by motoring the engine 1 with the MG 1 when the engine is stopped. In the present embodiment, components that are substantially the same as those in the first or second embodiment are denoted by the same names and symbols as those in the first or second embodiment, and detailed description thereof is omitted.

  In this embodiment, filter regeneration control that is executed when the engine 1 is stopped will be described with reference to FIG. FIG. 5 is a flowchart showing a routine of filter regeneration control performed when the engine 1 is stopped. This routine is repeatedly executed during the operation of the hybrid system.

  Steps S101 to S105 are the same as the control described in the first embodiment based on FIG. In the present embodiment, the ECU 26 that has executed Step S105 proceeds to Step S306.

  In step S306, the ECU 26 executes exhaust gas circulation control. In the exhaust gas circulation control in this embodiment, the second throttle valve 22 is closed, the LPL-EGR valve 45 is opened, the first throttle valve 9 is opened, the HPL-EGR valve 14 is closed, Valve control that opens the cooler bypass valve 20, opens the LPL-EGR cooler bypass valve 34, closes the exhaust throttle valve 6, and stops both the intake valve and the exhaust valve of the engine 1 in the open state by the VVT 46 And the turbine 12 is rotationally driven by the turbo assist motor 21.

  Since both the intake valve and the exhaust valve of the engine 1 are fixed in the open state by the VVT 46, even when the engine 1 is stopped, the intake air flowing into the intake manifold 17 passes through the cylinder 49 and passes through the exhaust manifold 18. Flows out. Thereby, the gas flowing out from the filter flows into the intake passage 42 through the LPL-EGR passage 44, flows out into the exhaust passage 43 through the intake manifold 17, the cylinder 49, and the exhaust manifold 18, and is discharged by the turbo assist motor 21. It is sent out to the exhaust purification device 41 side by the turbine 12 driven to rotate, and flows into the filter again. As described above, by executing the exhaust gas circulation control, the gas flowing out from the filter circulates in the circulation path including the filter. As described in the first embodiment, since the temperature of the filter has been increased at this time, and the oxidation reaction of the particulate matter collected by the filter has started, high temperature gas flows out from the filter. Yes. Since this high-temperature gas circulates in the circulation path and flows into the filter again, the temperature of the filter can be kept high.

  In the present embodiment, the ECU 26 that has executed Step S306 executes Steps S208 to S209 described in Embodiment 2 with reference to FIG. That is, the temperature of the filter is acquired, and it is determined whether or not there is a possibility that the filter is excessively heated. If it is determined in step S209 that there is a risk that the filter will overheat (Yes), the ECU 26 proceeds to step S310. If it is determined in step S209 that there is no risk that the filter will overheat (No), the ECU 26 once exits this routine.

  In step S310, the ECU 26 executes control to reduce the temperature of the gas circulating in the circulation path including the filter. In this embodiment, the opening degree of the second throttle valve 22 is changed to the open side, the opening degree of the LPL-EGR valve 45 is changed to the closing side, and the rotational speed of the turbine 12 by the turbo assist motor 21 is increased. The effect of lowering the gas temperature in the circulation path by changing the second throttle valve 22 to the open side and changing the LPL-EGR valve 45 to the close side is as described in the second embodiment. By increasing the rotational speed of the turbine 12 by the turbo assist motor 21, the amount of gas passing through the filter is increased, so that the temperature of the filter can be lowered by carrying away heat by the passing gas. After executing step S310, the ECU 26 returns to step S208.

  According to the present embodiment, when the temperature of the filter exceeds the upper limit temperature, control is performed to reduce the gas temperature in the circulation path or the temperature of the filter, so that excessive temperature rise of the filter can be suppressed. it can.

  In this embodiment, in step S310, the second throttle valve 22 is opened, the LPL-EGR valve 45 is closed, and the turbo assist motor 21 increases the rotational speed of the turbine 12. Although an example in which the gas temperature in the circulation path is effectively reduced by executing all of the above has been described, the temperature of the gas in the circulation path can be reduced by performing at least one of these. The effect of reducing can be produced.

  Further, in this embodiment, instead of the engine motoring by MG1 in the second embodiment, the rotation of the turbine 12 by the turbo assist motor 21 is used to drive the gas flowing out from the filter when the engine is stopped in the circulation path including the filter. Although the case where it circulates was demonstrated, instead of the engine motoring by MG1 in Example 1, the rotational drive of the turbine 12 by this turbo assist motor 21 can also be used. In this case, the filter regeneration control routine when the engine is stopped executes step S306 of FIG. 5 instead of step S106 in the flowchart of FIG. 3, and after executing step S306, executes step S108 to step S111 of FIG. You can do that. Thus, even in a configuration in which the turbine 12 is rotated by the turbo assist motor 21 to circulate the gas from the filter when the engine is stopped, the oxygen necessary for the filter regeneration control while suppressing the temperature drop of the filter. Can be continuously supplied to the filter, and the regeneration speed of the filter can be improved.

  Further, as in the present embodiment, when the rotational drive of the turbine 12 by the turbo assist motor 21 is used for gas circulation when the engine is stopped, power such as MG1 capable of motoring the engine 1 is used. There is no need to have a source. Therefore, if at least a turbo assist turbocharger is provided, this embodiment can be applied to a non-hybrid vehicle equipped with only an engine as a power source.

  In this embodiment, the ECU 26 that executes steps S103 to S105, steps S208 to S209, and step S310 corresponds to the regeneration control means in the present invention.

Next, a fourth embodiment of the present invention will be described. In the present embodiment, in the configuration of the hybrid system shown in FIG. 2, the exhaust purification device 41 has an NOx storage reduction catalyst. The NOx catalyst stores NOx in exhaust in an oxygen-excess atmosphere, releases the stored NOx in a reducing atmosphere with a reduced oxygen concentration, and reduces the released NOx in the presence of a reducing agent. It is a catalyst that purifies exhaust gas.

  In this embodiment, at least when the hybrid system is operating in an operation mode in which the engine 1 generates power for driving the vehicle, NOx in the exhaust discharged from the engine 1 is stored in the NOx catalyst. Then, when the engine 1 is stopped, the NOx reduction control for releasing and reducing the NOx stored in the NOx catalyst by performing a rich spike by the fuel addition valve 19 is performed. Here, when the engine 1 is stopped refers to a case where the hybrid system is operating in the EV traveling mode or a case where the engine 1 is automatically stopped by the eco-run control. The NOx reduction control executed when the engine 1 is stopped will be described with reference to FIG. FIG. 6 is a flowchart showing a routine of NOx reduction control performed when the engine 1 is stopped. This routine is repeatedly executed during the operation of the hybrid system.

  In step S101, the ECU 26 determines whether or not the engine 1 is in a stopped state. Since the content of this step S101 is the same as the content of step S101 of FIG. 3 demonstrated in Example 1, detailed description is abbreviate | omitted. In this embodiment, the ECU 26 executes step S101 and then proceeds to step S402.

  In step S402, the ECU 26 determines whether an execution condition for NOx reduction control is satisfied. In this embodiment, as described above, basically, NOx is stored in the NOx catalyst during engine operation, and NOx reduction control is executed when the engine is stopped. However, even when the engine is stopped, if the stored amount of NOx in the NOx catalyst is not so large as to require execution of the NOx reduction control, the routine is temporarily exited without executing the NOx reduction control. In this embodiment, the NOx occlusion amount in the NOx catalyst is estimated based on the operation history (fuel consumption, travel distance, and other information) since the previous execution of NOx reduction control. When the estimated NOx occlusion amount exceeds a predetermined reference amount, it is determined that the execution condition for the NOx reduction control is satisfied. If it is determined in step S402 that the execution condition for the NOx reduction control is satisfied (Yes), the ECU 26 proceeds to step S403. If it is determined that the execution condition for the NOx reduction control is not satisfied (No), the ECU 26 once exits this routine.

  In step S403, the ECU 26 performs temperature increase control of the NOx catalyst. The content of the temperature increase control of the NOx catalyst in step S403 is substantially the same as the temperature increase control of the filter in step S103 of FIG. 3 described in the first embodiment. That is, fuel is added to the exhaust gas by the fuel addition valve 19, and the temperature of the NOx catalyst is raised by utilizing the reaction heat between the added fuel and oxygen in the air.

  In step S404, the ECU 26 acquires the temperature of the NOx catalyst. In this embodiment, the exhaust temperature sensor 37 measures the temperature of the exhaust gas flowing out from the exhaust purification device 41, and estimates the temperature of the NOx catalyst based on this measured value. It is good also as a structure provided with the sensor which measures the bed temperature of a NOx catalyst directly.

  In step S405, the ECU 26 determines whether or not the temperature increase of the NOx catalyst has been completed. In the present embodiment, when the temperature of the NOx catalyst acquired in step S404 is equal to or higher than a predetermined reference temperature, it is determined that the temperature increase of the NOx catalyst is completed. Here, the reference temperature is determined based on the temperature of the NOx catalyst necessary for the NOx reduction reaction to proceed in the NOx catalyst (for example, 200 ° C.). If it is determined in step S405 that the temperature increase of the NOx catalyst has been completed (Yes), the ECU 26 proceeds to step S106. Since the content of this step S106 is the same as the content of step S106 of FIG. 3 demonstrated in Example 1, detailed description is abbreviate | omitted. If it is determined in step S405 that the temperature increase of the NOx catalyst has not been completed (No), the ECU 26 returns to step S404.

  When the ECU 26 executes step S106, the gas flowing out from the NOx catalyst flows into the intake passage 42 through the LPL-EGR passage 44 and is taken into the engine 1 motored by the MG1. Here, since the fuel supply to the engine 1 is stopped, the intake air drawn into the engine 1 is discharged into the exhaust passage 43 as it is without burning. The exhaust discharged into the exhaust passage 43 flows into the NOx catalyst through the turbine 12. As described above, by executing the exhaust gas circulation control, the gas flowing out from the NOx catalyst circulates in the circulation path including the NOx catalyst. Therefore, when a rich spike is executed in step S408, which will be described later, and a release reduction reaction of NOx stored in the NOx catalyst is started, the high-temperature gas flowing out from the NOx catalyst circulates in the circulation path and again returns to the NOx. Since it flows into the catalyst, the temperature of the NOx catalyst can be kept high.

  Furthermore, since the second throttle valve 22 is closed, the inflow of fresh air into the circulation path is suppressed. Therefore, the air-fuel ratio of the circulating gas flowing into the NOx catalyst is maintained on the rich side. As a result, the amount of fuel to be added by the rich spike from the fuel addition valve 19 in order to create a reducing atmosphere for the NOx release / reduction reaction to proceed appropriately in the NOx catalyst can be reduced. As a result, it is possible to suppress the fuel addition amount necessary for executing the NOx reduction control, and thus it is possible to suppress the fuel consumption amount related to the NOx reduction control.

  In step S407, the ECU 26 changes the opening degree of the nozzle vane 5 to the open side. As a result, the rotational speed of the turbine 12 of the variable capacity turbocharger 13 decreases. Therefore, the amount of energy converted into the rotational motion of the turbine 12 in the thermal energy of the exhaust gas discharged from the engine 1 is reduced. That is, the temperature drop of the exhaust before and after passing through the turbine 12 can be suppressed. Thereby, the temperature of the gas which circulates in the circulation path and flows into the NOx catalyst can be more reliably maintained at a high temperature. Therefore, the temperature of the NOx catalyst during execution of NOx reduction control can be more reliably maintained at a high temperature.

  In step S408, the ECU 26 performs a rich spike by the fuel addition valve 19 and starts a release / reduction reaction of NOx stored in the NOx catalyst.

  By executing the NOx reduction control routine described above, when the NOx reduction control is executed when the engine is stopped, the high-temperature gas flowing out from the NOx catalyst is circulated in the circulation path including the NOx catalyst. A decrease in temperature can be suppressed. Since a relatively rich gas always flows into the NOx catalyst, the amount of fuel to be added is reduced by a rich spike to make the ambient atmosphere of the NOx catalyst a reducing atmosphere in which NOx reduction control can be suitably performed. can do. Therefore, it is possible to reduce the fuel consumption related to the NOx reduction control.

  In order to achieve such effects peculiar to the present embodiment, it is sufficient that at least the exhaust gas flowing out from the NOx catalyst can be circulated when the NOx reduction control is executed while the engine 1 is stopped. is there. Further, in this embodiment, it is sufficient to have MG1 that can motor the engine 1 as a power source for circulating the exhaust gas flowing out from the NOx catalyst in the circulation path including the NOx catalyst when the engine 1 is stopped. is there. Therefore, components related to HPL-EGR, the turbo assist motor 21 and a system capable of executing eco-run control are not essential. If the engine motoring power source corresponding to MG1 is provided, the configuration of the hybrid system need not be limited to the configuration exemplified in this embodiment.

Also, opening the intercooler bypass valve 20, opening the LPL-EGR cooler bypass valve 34, or opening the nozzle vane 5 causes the NOx catalyst to flow into the NOx catalyst when the engine is stopped. Although the effect of this example of maintaining the temperature of the gas to be maintained at a high temperature can be further enhanced, it is not essential for achieving the effect of this example.

  Further, in the present embodiment, the example in which the determination of whether or not the NOx reduction control is necessary is performed based on the operation history from the previous execution of the NOx reduction control has been described, but the determination method is not limited to this, and a known method The execution ratio of the NOx reduction control can be determined by various methods.

  Next, a fifth embodiment of the present invention will be described. In the present embodiment, when NOx reduction control is executed when the engine 1 is stopped, the turbine 12 is rotationally driven by the turbo assist motor 21 to circulate the exhaust gas in the circulation path including the NOx catalyst. This is different from the fourth embodiment in which the exhaust gas is circulated in the circulation path by motoring the engine 1 with the MG 1 when the engine is stopped. In the present embodiment, components that are substantially the same as those in the fourth embodiment or each of the above-described embodiments are given the same names and symbols as those of the respective embodiments, and detailed description thereof is omitted.

  In this embodiment, the NOx reduction control executed when the engine 1 is stopped will be described with reference to FIG. FIG. 7 is a flowchart showing a routine of NOx reduction control performed when the engine 1 is stopped. This routine is repeatedly executed during the operation of the hybrid system.

  Steps S101 to S405 are equivalent to the control described in the fourth embodiment with reference to FIG. In this embodiment, if it is determined in step S405 that the temperature increase of the NOx catalyst has been completed (Yes), the ECU 26 proceeds to step S506.

  In step S506, the ECU 26 executes exhaust gas circulation control. In the exhaust gas circulation control in this embodiment, the second throttle valve 22 is closed, the LPL-EGR valve 45 is opened, the first throttle valve 9 is opened, the HPL-EGR valve 14 is opened, The cooler bypass valve 20 is opened, the LPL-EGR cooler bypass valve 34 is opened, the HPL-EGR cooler bypass valve 23 is opened, the exhaust throttle valve 6 is closed, and the turbine assist motor 21 is used to close the turbine 12. Is driven to rotate.

  Since the HPL-EGR valve 14 is opened, the intake air in the intake passage 42 flows into the exhaust passage 43 through the HPL-EGR passage 15 even when the engine 1 is stopped. That is, the flow direction of the gas in the HPL-EGR passage 15 is reversed from the case where the HPL-EGR valve 14 is opened during engine operation and normal EGR is performed. Thereby, the gas flowing out from the NOx catalyst flows into the intake passage 42 through the LPL-EGR passage 44, flows into the exhaust passage 43 through the HPL-EGR passage 15, and is rotationally driven by the turbo assist motor 21. It is sent out to the exhaust purification device 41 side by the turbine 12 and flows into the NOx catalyst again. As described above, by executing the exhaust gas circulation control, the gas flowing out from the NOx catalyst is circulated in the circulation path including the NOx catalyst. Therefore, when a rich spike is executed in the subsequent step S408 to start the release reduction reaction of NOx stored in the NOx catalyst, the high-temperature gas flowing out from the NOx catalyst circulates in the circulation path and again returns to the NOx. Since it flows into the catalyst, the temperature of the NOx catalyst can be kept high.

  Further, the second throttle valve 22 is closed to suppress the inflow of fresh air into the circulation path, the air-fuel ratio of the circulation gas flowing into the NOx catalyst is maintained on the rich side, and should be added by a rich spike. As described in the fourth embodiment, the amount of fuel can be reduced.

In the present embodiment, after executing step S506, the ECU 26 proceeds to step S408 and executes a rich spike by the fuel addition valve 19. Since the content of step S408 is the same as that of Example 4, detailed description is abbreviate | omitted.

  By executing the NOx reduction control routine described above, when the NOx reduction control is executed when the engine is stopped, the high-temperature gas flowing out from the NOx catalyst is circulated in the circulation path including the NOx catalyst. A decrease in temperature can be suppressed. Since a relatively rich gas always flows into the NOx catalyst, the amount of fuel to be added is reduced by a rich spike to make the ambient atmosphere of the NOx catalyst a reducing atmosphere in which NOx reduction control can be suitably performed. can do. Therefore, it is possible to reduce the fuel consumption related to the NOx reduction control.

  In the present embodiment, as in the third embodiment, HPL- is used as a power for circulating the exhaust gas by rotating the turbine 12 by the turbo assist motor 21 and as a path for guiding the gas in the intake passage 42 to the exhaust passage 43 when the engine is stopped. Although the example using the EGR passage 15 has been described, the configuration described in the third embodiment may be used in order to guide the gas in the intake passage 42 to the exhaust passage 43 when the engine is stopped. In other words, both the exhaust valve and the intake valve of the engine 1 may be fixed in the open state by the VVT 46, and the gas in the intake manifold 17 may be guided to the exhaust manifold 18 via the cylinder 49. Conversely, in the third embodiment, the gas in the intake passage 42 can be guided to the exhaust passage 43 using the HPL-EGR passage 15 as in the present embodiment.

  Next, a sixth embodiment of the present invention will be described. In this embodiment, when the engine start condition is satisfied when the NOx reduction control is executed while the engine is motored by MG1 and the exhaust gas is circulated while the engine is stopped. In the start-up control, the time for resuming the fuel injection to the engine 1 is delayed. In the present embodiment, components that are substantially the same as those in the fourth embodiment are denoted by the same names and reference numerals as those in the fourth embodiment, and detailed description thereof is omitted.

  Conventionally, when an engine start condition is satisfied while the engine is stopped, fuel injection to the engine is resumed simultaneously with engine cranking. However, in the fourth embodiment, when there is a NOx reduction control request while the engine is stopped, the NOx reduction control is performed while executing the exhaust gas circulation control. At this time, as described in the fourth embodiment, the rich gas flowing out from the NOx catalyst flows out of the exhaust path including the NOx catalyst (in this case, flows out of the exhaust purification device 41, and the LPL-EGR passage 44, the intake passage 42, The air is circulated through the intake manifold 17, the cylinder 49, the exhaust manifold 18, and the exhaust passage 43.

  Accordingly, when the engine start condition is satisfied, the LPL-EGR valve 45 is closed at the same time to stop the exhaust circulation control, and even if the second throttle valve 22 is opened and the introduction of air is started, the intake passage During the period until the rich circulating gas remaining in 42 is scavenged, the engine 1 is not inhaled with enough air to burn fuel. Even if fuel injection is performed during the period required for scavenging the circulating gas, the fuel cannot be combusted suitably, and there is a possibility of misfire.

  If it does so, a large amount of unburned components may be discharged to the exhaust passage 43 and the performance of the exhaust purification device 41 may be deteriorated. That is, as in the fourth embodiment, in the situation where the NOx reduction control is executed while the exhaust circulation control is executed while the engine is stopped, the engine cranking and the fuel injection are started at the same time as the engine start condition is satisfied. It is difficult to suitably burn the fuel.

Therefore, in this embodiment, when the engine start condition is satisfied in the situation where the NOx reduction control is being performed while performing the exhaust gas circulation control when the engine is stopped, the fuel injection is performed with respect to the timing when the engine start condition is satisfied. The restart timing was delayed. Such engine start control in the present embodiment will be described with reference to FIGS. FIG. 8 and FIG. 9 are flowcharts showing the engine start control routine of this embodiment. This routine is repeatedly executed during the operation of the hybrid system.

  In step S601 of FIG. 8, the ECU 26 determines whether or not NOx reduction control is being performed while exhaust circulation control is being performed while the engine is stopped. If it is determined in step S601 that the NOx reduction control while the engine is stopped is being executed (Yes), the ECU 26 proceeds to step S602. When it is determined in step S601 that the NOx reduction control while the engine is stopped is not being executed (No), the ECU 26 temporarily exits this routine.

  In step S602, the ECU 26 determines whether an engine start condition is satisfied. In the present embodiment, when the operation mode of the hybrid system is an operating condition for shifting from the EV traveling mode to a mode in which the engine 1 is loaded, or when a condition for automatically starting the engine 1 by the eco-run control is satisfied. Then, it is determined that the engine start condition is satisfied. If it is determined in step S602 that the engine start condition is satisfied (Yes), the ECU 26 proceeds to step S603. If it is determined in step S602 that the engine start condition is not satisfied (No), the ECU 26 once exits this routine.

  In step S603, the ECU 26 stops the NOx reduction control. In the present embodiment, the execution of rich spike by the fuel addition valve 19 is stopped.

  In step S604, the ECU 26 stops the exhaust gas circulation control. In this embodiment, the second throttle valve 22 is opened, the LPL-EGR valve 45 is closed, the first throttle valve 9 is opened, the HPL-EGR valve 14 is closed, and the exhaust throttle valve 6 is opened. Open the valve. Thereby, the gas flowing out from the NOx catalyst is stopped from flowing into the intake passage 42 through the LPL-EGR passage 44, and fresh air starts to flow into the intake passage 42. Here, the present embodiment is based on the fourth embodiment. In the fourth embodiment, power for circulating the exhaust gas is obtained by motoring the engine 1 with the MG1. Therefore, in order to stop the exhaust circulation control, it is necessary to stop the motoring of the engine 1 by the MG1. However, in the case of the present embodiment, as will be described later, since the engine 1 is motored by the MG1 again for the purpose other than the exhaust circulation control in the subsequent steps after the step S605, the engine by the MG1 is executed in the step S604. The control for stopping the motoring 1 was omitted.

  In step S605, the ECU 26 starts cranking of the engine 1. In this embodiment, the engine 1 is cranked by motoring the engine 1 with the MG1. In the conventional technology, normally, when the engine is started, fuel injection is started simultaneously with the start of cranking of the engine 1. That is, the fuel cut control is canceled simultaneously with the start of cranking. However, in this embodiment, the fuel cut control is not canceled at the same time as the engine cranking start timing in step S605. After executing step S606 and step S607, which will be described later, the fuel cut control is canceled. This is a characteristic point of the present embodiment.

  In step S606, the ECU 26 acquires the oxygen concentration of the intake air of the engine 1. In the present embodiment, the oxygen concentration of the intake air of the engine 1 is estimated based on the measurement value by the first A / F sensor 50.

  In step S607, the ECU 26 determines the possibility of combustion of the injected fuel when fuel is injected into the engine 1. In the present embodiment, it is determined that the injected fuel can be combusted in the engine 1 when the oxygen concentration of the intake air acquired in step S606 is equal to or higher than a predetermined reference concentration. The reference concentration is determined based on the lower limit value of the oxygen concentration that allows the injected fuel to burn. If it is determined in step S607 that the injected fuel can be combusted in the engine 1 (Yes), the ECU 26 proceeds to step S608 in FIG. If it is determined in step S607 that the injected fuel is not combustible in the engine 1 (No), the ECU 26 returns to step S606.

  In step S608 in FIG. 9, the ECU 26 releases the fuel cut control and starts fuel injection into the engine 1.

  In step S609, the ECU 26 acquires the rotational speed of the engine 1.

  In step S610, the ECU 26 determines whether a condition for shifting the engine 1 to the load operation is satisfied. In the present embodiment, when the rotational speed of the engine 1 acquired in step S609 is equal to or higher than a predetermined reference rotational speed, it is determined that the condition for shifting the engine 1 to the load operation is satisfied. If it is determined in step S610 that the condition for shifting the engine 1 to load operation is satisfied (Yes), the ECU 26 proceeds to step S611. If it is determined in step S610 that the condition for shifting the engine 1 to the load operation is not satisfied (No), the ECU 26 returns to step S609.

  In step S611, the ECU 26 causes the engine 1 to perform a load operation.

  When the engine start control described above is executed, the operation mode of the hybrid system, the amount of fuel added by the fuel addition valve 19, the opening of the second throttle valve 22, the opening of the LPL-EGR valve 45, the rotational speed of the engine 1 FIG. 10 shows an example of the time variation of the oxygen concentration of the intake air of the engine 1 and the fuel cut control signal of the engine 1.

  In the example shown in FIG. 10, in the EV traveling mode before time t1, the second throttle valve 22 is closed as shown in FIG. 10 (c), and the LPL-EGR valve 45 is shown in FIG. 10 (d). Exhaust circulation control is executed by opening the valve and performing low-speed engine motoring by MG1 as shown in FIG. Then, as shown in FIG. 10 (b), fuel is added from the fuel addition valve 19, and NOx reduction control of the NOx catalyst is executed. At this time, as shown in FIG. 10 (f), the oxygen concentration in the intake air of the engine 1 is low (a rich air-fuel ratio) because the NOx reduction reaction proceeds favorably.

  When the engine start condition is satisfied at time t1, the engine 1 shifts to the cranking mode as shown in FIG. At the same time, the second throttle valve 22 is opened as shown in FIG. 10C, the LPL-EGR valve 45 is closed as shown in FIG. 10D, and the exhaust circulation control is stopped. Air begins to flow into the intake passage 42. Then, as shown in FIG. 10B, the fuel addition from the fuel addition valve 19 is stopped, and the NOx reduction control is stopped. Further, as shown in FIG. 10 (e), cranking of the engine 1 by the MG 1 is started, and the rotational speed of the engine 1 starts to gradually increase.

However, at this time, as shown in FIG. 10 (f), the oxygen concentration of the intake air of the engine 1 does not rise immediately, and the low oxygen concentration state is maintained for a while. This is because during this period, the rich circulating gas remaining in the intake passage 42 on the downstream side of the connection portion of the LPL-EGR passage 44 is sucked into the engine 1. When all the remaining circulating gas is sucked into the engine 1 and scavenged from the intake passage 42 at time t2, as shown in FIG. 10 (f), oxygen concentration in the intake air of the engine 1 is substantially equal to air. Change to concentration.

  At this timing, the fuel cut signal is canceled and fuel injection into the engine 1 is started as shown in FIG. As a result, the fuel injected from the injector 29 burns well without misfiring, and the rotational speed of the engine 1 further increases due to the combustion energy and cranking by MG1, as shown in FIG. 10 (e). Then, when the engine speed reaches the reference speed (time t3), the engine 1 shifts to the load operation mode as shown in FIG. In the load operation mode, the opening degree of the second throttle valve 22 and the LPL-EGR valve 45 is controlled according to the required load and the rotational speed.

  By executing the engine start control described above, when the engine start condition is satisfied in a situation where the NOx reduction control is being performed while performing the exhaust gas circulation control when the engine is stopped, sufficient air that can burn the fuel is supplied. The fuel cut control is not canceled during the period until the intake air including the intake air is taken into the engine 1, and the rotational speed of the engine 1 is increased only by cranking by the MG1. When it is determined that the amount of air in the gas sucked into the engine 1 has become a sufficient amount that the fuel can be combusted, the fuel cut control is canceled, and both the combustion energy of the fuel and the motoring by the MG1 are performed. As a result, the rotational speed of the engine 1 is increased.

  As a result, fuel injection into the engine 1 is not performed during a period immediately after the engine start condition is satisfied and during which fuel cannot be suitably burned even when fuel is injected, so that misfire can be suppressed. Therefore, it is possible to suppress performance deterioration of the exhaust purification device 41 and deterioration of exhaust emission.

  In the present embodiment, the exhaust circulation control performed when the NOx reduction control is executed when the engine is stopped has been described based on the configuration of the fourth embodiment in which engine motoring is performed by MG1, but the turbine 12 is rotated by the turbo assist motor 21. The engine start control of this embodiment can also be applied to a configuration in which exhaust circulation control is performed by driving. In that case, when stopping the exhaust gas circulation control in step S604, in addition to the above-described valve controls, the rotational drive of the turbine 12 by the turbo assist motor 21 is stopped. In step S605, the engine 1 is cranked. If the configuration includes a hybrid system having a power source for driving the engine corresponding to MG1, the engine 1 may be cranked by the MG1, or if the configuration does not include such a hybrid system, The cranking of the engine 1 may be performed by a cell motor provided in the engine.

  In the present embodiment, the case where the air-fuel ratio of the intake air is estimated based on the measured value of the exhaust air-fuel ratio by the first A / F sensor 50 has been described, but the method of acquiring the air-fuel ratio of the intake air is not limited to this. An A / F sensor or an oxygen sensor may be provided at a position closer to the cylinder 49, and the air-fuel ratio of the intake air may be measured based on the measured value, or the A / F sensor, oxygen may be provided in the intake passage 42 or the intake manifold 17. A sensor such as a sensor or an HC sensor may be provided, and the air-fuel ratio of the intake air may be measured based on the measured values.

  Further, based on the intake system volume from the connection point of the LPL-EGR passage 44 to the cylinder 49 in the intake passage 42, the measured value by the air flow meter 7, the rotational speed of the engine 1, etc., the intake passage of the circulating gas by the exhaust circulation control The time required for scavenging the remaining amount in the intake passage 42 is calculated, and the calculated scavenging time is compared with the elapsed time after the LPL-EGR valve 45 is closed in step S604. Based on the above, the air-fuel ratio of the intake air of the engine 1 or the determination of the combustion possibility of the injected fuel may be performed.

Although this embodiment has been described on the assumption of the fourth embodiment, the engine start control according to the present embodiment performs NOx reduction while executing exhaust gas circulation control while the engine is stopped in a configuration in which the exhaust purification device 41 includes a NOx catalyst. In the case where the control is executed, the present invention can be similarly applied to the case where the exhaust gas purification device 41 includes a filter and the filter regeneration control is executed while the exhaust gas circulation control is executed while the engine is stopped. However, when the filter regeneration control is performed, as described in the first embodiment, for example, the opening degree of the second throttle valve 22 is set so that sufficient oxygen is supplied to the filter so that the oxidation reaction of the particulate matter proceeds appropriately. Since the adjustment is performed, the rich degree of the gas circulating in the circulation path by the exhaust circulation control is small compared to the case of performing the NOx reduction control, that is, a certain amount of oxygen exists in the circulation gas. Therefore, the delay period from the timing when the engine start condition is satisfied to the timing when the fuel cut control is released may be shorter than in the case of NOx reduction control.

  In this embodiment, the ECU 26 that executes the engine start control routine corresponds to the engine start control means in the present invention.

  Next, a seventh embodiment of the present invention will be described. In this embodiment, in the sixth embodiment, after the engine start condition is satisfied, the engine speed reaches the reference speed before the possibility of combustion of the injected fuel when the fuel injection is performed to the engine 1 is affirmed. In this case, the fuel cut control is canceled to restart the fuel injection and shift to the load operation regardless of the determination result of the possibility of combustion. At this time, it is characterized in that good combustion is realized by setting the target EGR rate in the load operation mode to a value lower than the default target value.

  This engine start control in the present embodiment will be described with reference to FIGS. 11 and 12 are flowcharts showing a routine for engine start control according to this embodiment. This routine is repeatedly executed during the operation of the hybrid system.

  Steps S601 to S607 and steps S608 to S611 in FIG. 12 executed when it is determined in step S607 that the injected fuel can be combusted (Yes) are the same as those in the sixth embodiment. Omitted. In this embodiment, if it is not determined in step S607 that the injected fuel can be fueled (No), the ECU 26 proceeds to step S708 in FIG.

  In step S708 of FIG. 12, the ECU 26 acquires the rotational speed of the engine 1.

  In step S709, the ECU 26 determines whether or not a condition for shifting the engine 1 to the load operation is satisfied. In this embodiment, when the rotation speed of the engine 1 acquired in step S708 is equal to or higher than a predetermined reference rotation speed, it is determined that the condition for shifting the engine 1 to the load operation is satisfied. If it is determined in step S709 that the condition for shifting the engine 1 to the load operation is satisfied (Yes), the ECU 26 proceeds to step S710. If it is determined in step S709 that the condition for shifting the engine 1 to the load operation is not satisfied (No), the ECU 26 returns to step S606 in FIG.

  In step S710, the ECU 26 cancels the fuel cut control and starts fuel injection to the engine 1.

In step S711, the ECU 26 corrects the target EGR rate to a value lower than normal, and sets the corrected EGR rate as the final target EGR rate. In this embodiment, the correction amount of the EGR rate is determined according to the oxygen concentration of the intake air of the engine 1 acquired in step S606. After setting the correction target EGR rate in step S711, the ECU 26 proceeds to step S611 and causes the engine 1 to perform a load operation.

  When the engine start control described above is executed, the operation mode of the hybrid system, the amount of fuel added by the fuel addition valve 19, the opening of the second throttle valve 22, the opening of the LPL-EGR valve 45, the rotational speed of the engine 1 FIG. 13 shows an example of changes over time in the oxygen concentration of the intake air of the engine 1, the fuel cut control signal of the engine 1, and the target EGR rate.

  Similar to FIG. 10, until the time t1, in the EV traveling mode, the NOx reduction control is executed while performing the exhaust circulation control by the low speed engine motoring by the MG1. When the engine start condition is satisfied at time t1, the exhaust circulation control and the NOx reduction control are stopped, and cranking of the engine 1 by MG1 is started. At this time, release of the fuel cut signal is delayed. The steps so far are as described in the sixth embodiment.

  Here, as shown in FIG. 13 (e), at time t3 when the engine speed reaches the reference speed by engine cranking by MG1, as shown in FIG. The concentration has not yet reached the reference concentration. Therefore, the fuel cut signal that is to be released on condition that the oxygen concentration in the intake air of the engine 1 has reached the reference concentration satisfies the rotational speed condition that should cause the engine 1 to shift to the load operation. However, it is not canceled.

  In such a situation, in this embodiment, as shown in FIG. 13G, even when the oxygen concentration of the intake air does not reach the reference concentration, the fuel cut signal is canceled and fuel injection is started. As shown to 13 (a), the engine 1 transfers to load operation mode. However, at this time, since the oxygen concentration of the intake air has not yet reached the reference concentration, the target EGR rate is corrected to a value lower than the normal target EGR rate, as shown in FIG. Thereby, it is possible to suppress the injection fuel from causing a combustion failure such as misfire in the load operation.

  In this embodiment, the ECU 26 that executes the engine start control routine corresponds to the engine start control means in the present invention.

  Each of the above-described embodiments is an example for explaining the present invention, and various modifications can be made to the above-described embodiments without departing from the spirit of the present invention, and as much as possible. It can be implemented in combination.

  For example, in each of the above-described embodiments, the power source for circulating the exhaust gas in the circulation path including the filter and the NOx catalyst while the fuel supply to the engine 1 is stopped is not limited to MG1, and the combustion energy of the engine 1 is not limited to MG1. Any power source may be used as long as the power source can rotate without depending on the power source. Further, as a configuration using a motor generator as a power source for circulating exhaust gas, in each of the above-described embodiments, a configuration provided with MG1 separately from MG2 that outputs a driving force for vehicle travel has been described as an example. In this case, MG1 in the embodiment corresponds to the second power source in the present invention, and MG2 corresponds to the first power source.

Further, the MG2 that outputs the driving force for driving the vehicle is configured to motor the engine 1 with the remaining surplus power that outputs the driving force for driving the vehicle, and only the MG2 is provided as a power source other than the engine 1. It can also be configured. In this case, MG2 corresponds to a power source (non-engine power source) other than the engine in the present invention. In this case, the configuration of the hybrid system does not need to be configured to transmit the power of the engine and the motor generator to the drive shaft via the power split mechanism as described in the above embodiments, but various known hybrid systems. For example, a motor that is mounted integrally with the crankshaft of the engine, and that the motor can drive the drive shaft and the engine by connecting / disconnecting a clutch mounted on the drive shaft side. Even if it exists, it is possible to apply this invention.

  Next, an eighth embodiment of the present invention will be described. In the present embodiment, the configuration of the hybrid system is substantially the same as that described in Embodiments 1 to 7 with reference to FIG. FIG. 14 is a diagram showing a schematic configuration of an engine and its intake / exhaust system according to the present embodiment. In FIG. 14, the same names and symbols are used for the same components as those of the engine and the intake / exhaust system described with reference to FIG. .

  As shown in FIG. 14, the exhaust system of the engine 1 of the present embodiment includes a communication passage 54 that connects the exhaust passage 43 on the downstream side of the exhaust purification device 41 and the intake manifold 17. The communication path 54 is provided with a switching valve 53 that opens and closes the communication path 54. The opening / closing operation of the switching valve 53 is controlled by the ECU 26. In the present embodiment, it is assumed that the exhaust purification device 41 has an NOx storage reduction catalyst. In this embodiment, a fuel addition valve 190 is provided in the exhaust manifold 18 instead of the fuel addition valve 19 that adds fuel to the exhaust passage 19.

  In this embodiment, when the NOx reduction control is executed when the fuel supply to the engine 1 is stopped, the exhaust throttle valve 6 is set to the closing side opening, the switching valve 53 is set to the opening side opening, and the first throttle valve 9 is set. Is the opening on the closing side, the opening of the HPL-EGR valve 14 is the opening on the closing side, and the engine 1 is motored by MG1. As a result, the high-temperature exhaust gas flowing out from the NOx catalyst is in a circulation path including the NOx catalyst such as the communication passage 54, the intake manifold 17, the cylinder 49 of the engine 1, the exhaust manifold 18, the exhaust passage 43, the turbine 12, and the exhaust purification device 41. Circulate with.

  Accordingly, when the rich spike is executed and the NOx release reduction reaction stored in the NOx catalyst is started, the high-temperature gas flowing out from the NOx catalyst circulates in the circulation path and flows into the NOx catalyst again. The temperature of the NOx catalyst can be kept high.

  At this time, the opening of the first throttle valve 9 is closed, so that the amount of low temperature fresh air flowing into the circulation path can be reduced. As a result, the temperature drop of the gas in the circulation path can be suppressed, and the air-fuel ratio of the circulation gas passing through the NOx catalyst is maintained rich.

  Therefore, the amount of fuel to be added by the rich spike from the fuel addition valve 190 can be reduced in order to create a reducing atmosphere for the NOx release / reduction reaction to proceed appropriately in the NOx catalyst. As a result, it is possible to suppress the fuel addition amount necessary for executing the NOx reduction control, and thus it is possible to suppress the fuel consumption amount related to the NOx reduction control.

  The NOx reduction control executed when the fuel supply to the engine 1 is stopped in the present embodiment as described above will be described with reference to FIG. FIG. 15 is a flowchart showing a routine of NOx reduction control performed when the engine 1 is stopped. This routine is repeatedly executed during the operation of the hybrid system.

  Steps S101 to S405 are equivalent to the control described in the fourth embodiment with reference to FIG. In this embodiment, when it is determined in step S405 that the temperature increase of the NOx catalyst has been completed (Yes), the ECU 26 proceeds to step S806.

In step S806, the ECU 26 executes exhaust gas circulation control. In the exhaust circulation control in the present embodiment, as described above, the switching valve 53 is opened, the first throttle valve 9 is closed, the HPL-EGR valve 14 is closed, and the exhaust throttle valve 6 is closed. At the same time, the engine 1 is motored by the MG1. As a result, the hot exhaust gas flowing out from the exhaust purification device 41 flows into the communication passage 54, passes through the communication passage 54, flows into the intake manifold 17, and is sucked into the cylinder 49 of the engine 1 that is motored by the MG1. Then, the gas is discharged from the cylinder 49 to the exhaust manifold 18, passes through the exhaust passage 43 and the turbine 12, and flows into the exhaust purification device 41 again.

  As described above, by executing the exhaust gas circulation control, the gas flowing out from the NOx catalyst is circulated in the circulation path including the NOx catalyst. Therefore, when a rich spike is executed in the subsequent step S408 to start the release reduction reaction of NOx stored in the NOx catalyst, the high-temperature gas flowing out from the NOx catalyst circulates in the circulation path and again returns to the NOx. Since it flows into the catalyst, the temperature of the NOx catalyst can be kept high.

  Further, the first throttle valve 9 is closed to suppress the inflow of fresh air into the circulation path, the air-fuel ratio of the circulation gas flowing into the NOx catalyst is maintained on the rich side, and should be added by a rich spike. As described in the fourth embodiment, the amount of fuel can be reduced.

  In this embodiment, after executing step S806, the ECU 26 proceeds to step S807 and executes a rich spike by the fuel addition valve 190. As a result, the NOx stored in the NOx catalyst is released and reduced.

  By executing the NOx reduction control routine described above, when the NOx reduction control is executed when the engine is stopped, the high-temperature gas flowing out from the NOx catalyst is circulated in the circulation path including the NOx catalyst. A decrease in temperature can be suppressed. Since a relatively rich gas always flows into the NOx catalyst, the amount of fuel to be added is reduced by a rich spike to make the ambient atmosphere of the NOx catalyst a reducing atmosphere in which NOx reduction control can be suitably performed. can do. Therefore, it is possible to reduce the fuel consumption related to the NOx reduction control.

  In the case of the present embodiment, since the circulation path including the exhaust purification device 41 does not include the LPL-EGR passage having a long path length, the length of the circulation path can be shortened. Thereby, it can suppress that the heat of the gas which circulates through a circulation path is lost from the wall surface of the piping of a circulation path, and a circulation gas is cooled. Further, the LPL-EGR cooler 33, the HPL-EGR cooler 16, and the intercooler 3 are not included in the circulation path. Therefore, an LPL-EGR cooler bypass passage, an HPL-EGR cooler bypass passage, and an intercooler bypass passage for suppressing cooling of the circulating gas flowing through the circulation path are provided, and a flow path that passes through and bypasses these bypass paths. There is no need to provide a bypass valve for switching between the two. Therefore, there is an effect that the complexity and cost increase of the device and control can be suppressed.

  In this embodiment, the example in which the NOx reduction control is performed while circulating the high-temperature exhaust gas in the circulation path including the exhaust purification device 41 while the fuel supply to the engine 1 is stopped has been described. Can also be applied to the regeneration control of the PM filter. However, when performing regeneration control of the PM filter, it is necessary to supply sufficient oxygen in the gas circulating in the circulation path so that the oxidation reaction of PM deposited on the filter suitably proceeds. Therefore, when performing the regeneration control of the PM filter while performing the exhaust circulation control while the fuel supply to the engine 1 is stopped, the first throttle valve 9 is opened and the fresh air is introduced into the circulation path. It is preferable to do. In this case, an appropriate amount of fresh air is allowed to enter the circulation path so that the oxidation reaction of the PM accumulated on the filter can proceed suitably, and the temperature of the filter is not reduced too much by the low temperature fresh air. The opening degree of the first throttle valve 9 may be adjusted so as to flow in.

In this embodiment, the MG 1 that motors the engine 1 corresponds to “a power source capable of outputting a driving force that rotates the engine without depending on the combustion energy of the fuel” in the present invention. The communication path 54 of the present embodiment corresponds to the communication path in the present invention. The switching valve 53 of the present embodiment corresponds to the switching valve in the present invention. The first throttle valve 9 of this embodiment corresponds to the throttle valve in the present invention. ECU26 which performs step S806 of a present Example is equivalent to the exhaust gas circulation means in this invention. The ECU 26 that executes step S807 of this embodiment corresponds to the regeneration control means in the present invention.

  In this embodiment, the engine start condition for starting the engine 1 is satisfied when the NOx reduction control of the NOx catalyst is executed while circulating the exhaust gas as described in the embodiment 8 while the fuel supply to the engine 1 is stopped. The control in the case of having performed will be described.

  As described in the eighth embodiment, when there is a NOx reduction control request while the fuel supply to the engine 1 is stopped, the NOx reduction control is performed while executing the exhaust gas circulation control. At this time, as described in the eighth embodiment, the rich and high-temperature gas flowing out from the NOx catalyst flows out of the exhaust path including the NOx catalyst (in this case, flows out from the exhaust purification device 41, and the communication passage 54, the intake manifold 17, Circulating through the cylinder 49, the exhaust manifold 18, and the exhaust passage 43).

  Therefore, when the engine start condition is satisfied, the gas sucked into the engine 1 has a stoichiometric or rich air-fuel ratio, is at a high temperature, has a low pressure, and is not in a state suitable for fuel combustion. Therefore, even if fuel supply to the engine 1 is started simultaneously with the establishment of the engine start condition, the fuel cannot be combusted suitably, and there is a possibility that a combustion failure such as misfire may occur.

  Therefore, in this embodiment, when the engine start condition is satisfied when the exhaust gas circulation and NOx reduction control in the circulation path when the engine is stopped as described in the eighth embodiment is performed, the first throttle valve 9 Is changed to the opening on the opening side, and the switching valve 53 is fully closed. Then, the engine 1 is cranked by the MG 1 without performing fuel injection to the engine 1. When the air-fuel ratio of the intake air has become leaner than a predetermined threshold value, the first throttle valve 9 is fully opened and fuel injection into the engine 1 is started to start the engine 1.

  Such engine start control in the embodiment will be described with reference to FIG. FIG. 16 is a flowchart showing a routine for engine start control according to this embodiment. This routine is repeatedly executed during the operation of the hybrid system.

  Steps S601 to S603 are the same as the control described in the sixth embodiment with reference to FIG. In this embodiment, after executing step S603, the ECU 26 proceeds to step S904.

  In step S904, the ECU 26 stops the exhaust gas circulation control. In this embodiment, the switching valve 53 is fully closed, the first throttle valve 9 is changed to the opening degree on the opening side, the HPL-EGR valve 14 is closed, and the exhaust throttle valve 6 is opened. As a result, fresh air flows from the intake passage 42 into the intake manifold 17, and intake air in the intake manifold 17 is suppressed from flowing directly into the exhaust passage 43 through the communication passage 54. As in the sixth embodiment, in this embodiment, the exhaust circulation control is performed by motoring the engine 1 with the MG1, but the motoring of the engine 1 with the MG1 is performed by cranking the engine 1 in the subsequent step S905. In step S904, the motoring of the engine 1 by the MG1 is not stopped.

In step S905, the ECU 26 starts cranking of the engine 1. In this embodiment, the engine 1 is cranked by motoring the engine 1 with the MG1. As a result, fresh air that has flowed into the intake manifold 17 is drawn into the cylinder 49, and the proportion of fresh air in the intake air that is drawn into the cylinder 49 increases.

  In step S906, the ECU 26 acquires the air-fuel ratio of the intake air of the engine 1. In this embodiment, the air-fuel ratio of the intake air is estimated based on the measured value by the first A / F sensor 50.

  In step S907, the ECU 26 determines the possibility of combustion of the injected fuel when fuel is injected into the engine 1. In the present embodiment, when the air-fuel ratio of the intake air acquired in step S906 is an air-fuel ratio leaner than a predetermined threshold, it is determined that the injected fuel can be combusted in the engine 1. This threshold is determined based on the lower limit value of the intake air / fuel ratio at which the injected fuel can be combusted. If it is determined in step S907 that the injected fuel can be combusted in the engine 1 (Yes), the ECU 26 proceeds to step S908. If it is determined in step S907 that the injected fuel is not combustible in the engine 1 (No), the ECU 26 returns to step S906.

  In step S908, the ECU 26 cancels the fuel cut control and starts fuel injection into the engine 1.

  In step S909, the ECU 26 starts the load operation of the engine 1.

  When the engine start control described above is executed, the operation mode of the hybrid system, the opening of the first throttle valve 9, the air-fuel ratio of the intake air, the pressure of the intake air, the temperature of the intake air, and the time change of the fuel cut control signal An example is shown in FIG.

  In the example shown in FIG. 17, in the EV traveling mode before time t1, the first throttle valve 9 is closed as shown in FIG. 17B, and the low speed engine motoring by MG1 is performed, so that the exhaust gas circulation control is performed. Is running. Fuel is added from the fuel addition valve 190, and NOx reduction control of the NOx catalyst is executed. At this time, as shown in FIG. 17C, the air-fuel ratio of the intake air of the engine 1 is rich because the NOx reduction reaction proceeds favorably.

  At time t1, the engine start condition is satisfied. At this time, as shown in FIG. 17C, the air-fuel ratio of the intake air is rich, and the air-fuel ratio condition under which the fuel can be suitably combusted in the engine 1 is satisfied. not filled. Further, as shown in FIG. 17D, the pressure of the intake air is low, and the temperature of the intake air is high as shown in FIG. 17E. In this respect also, the operating conditions under which the fuel is suitably burned in the engine 1 are satisfied. Not satisfied. Therefore, as shown in FIG. 17F, the fuel cut control is not canceled at this time, and fuel is not supplied.

  As shown in FIG. 17A, the engine 1 shifts to the cranking mode. At the same time, as shown in FIG. 17B, the first throttle valve 9 is opened and the switching valve 53 is closed. As a result, exhaust circulation control is stopped and air begins to flow into the cylinder 49 from the intake passage 42. As a result, the air-fuel ratio of the intake air gradually changes to the lean side as shown in FIG. 17C, and the pressure of the intake air gradually increases as shown in FIG. 17D, as shown in FIG. As a result, the temperature of the intake air gradually decreases.

  At time t2, when the air-fuel ratio of the intake air becomes leaner than the threshold as shown in FIG. 17C, the fuel cut control is canceled as shown in FIG. The first throttle valve 9 is opened as shown in FIG. 17 (B), and the engine 1 shifts to the load operation mode as shown in FIG. 17 (A).

  By executing the engine start control described above, when the engine start condition is satisfied in a situation where the NOx reduction control is being performed while performing the exhaust gas circulation control when the engine is stopped, sufficient air that can burn the fuel is supplied. During the period until the intake air including the air is taken into the engine 1, the fuel cut control is not released and the cranking by the MG1 is performed. Then, when it is determined that the air-fuel ratio of the intake air sucked into the engine 1 has become an air-fuel ratio at which the fuel can be combusted, the fuel cut control is canceled, and the fuel supply to the engine 1 is started. Load operation is started.

  Thereby, even when the engine start condition is satisfied when the exhaust gas circulation control and the NOx reduction control are performed while the engine is stopped, it is possible to suppress the occurrence of combustion failure, and the exhaust purification device 41 can be degraded in performance. It becomes possible to suppress the deterioration of exhaust emission.

  In the present embodiment, the example in which the fuel cut control is canceled and the engine 1 is loaded when the condition that the air-fuel ratio of the intake air is leaner than a predetermined threshold is satisfied has been described. This is because, among the air-fuel ratio, pressure, and temperature of the intake air, the air-fuel ratio has the greatest influence on the fuel combustion possibility. Of course, not only the condition that the air-fuel ratio of the intake air has become leaner than the threshold value, but also the condition that the pressure of the intake air has become higher than the predetermined reference pressure, or the temperature of the intake air has become lower than the predetermined reference temperature. The release timing of the fuel cut control may be determined in consideration of whether or not the condition is satisfied. However, as described above, the air-fuel ratio is the most important for the possibility of combustion.Therefore, even if the intake air pressure and the intake air temperature satisfy the reference value, the air-fuel ratio does not satisfy the reference value. It is preferable not to start fuel injection. Although not shown, the intake pressure and the intake air temperature may be measured by providing a pressure sensor or a temperature sensor in the intake passage 42 or the intake manifold 17, or may be estimated from various physical quantities representing the operating state. .

  The ECU 26 that executes steps S602 to S909 of this embodiment corresponds to the engine start control means in the present invention. The ECU 26 and the first A / F sensor 50 that acquire the air-fuel ratio of the intake air of the engine 1 in step S906 of the present embodiment correspond to the air-fuel ratio acquisition means in the present invention. The threshold value that is a comparison target with the measurement of the air-fuel ratio in step S907 of the present embodiment corresponds to the reference air-fuel ratio in the present invention.

  Next, a ninth embodiment of the present invention will be described. In this embodiment, the configuration of the hybrid system is substantially the same as that described in Embodiments 1 to 7 with reference to FIG. FIG. 18 is a diagram showing a schematic configuration of the engine and its intake / exhaust system according to the present embodiment. In FIG. 18, components that are substantially the same as the configurations of the engine and the intake and exhaust systems described in FIGS. 1 to 7 in Embodiments 1 to 7 are denoted by the same names and symbols, and detailed description thereof is omitted. .

  As shown in FIG. 18, the exhaust system of the engine 1 of the present embodiment communicates with an intake passage 43 on the downstream side of the exhaust purification device 41 and an intake passage 43 on the upstream side of the exhaust purification device 41. 56 is provided. The communication path 56 is provided with a switching valve 55 that opens and closes the communication path 56. The opening / closing operation of the switching valve 55 is controlled by the ECU 26. The communication path 56 is provided with a second fuel addition valve 57 that adds fuel to the communication path 56. Execution of fuel addition by the second fuel addition valve 57 is controlled by the ECU 26.

A pump 58 is provided at a connection location of the communication passage 56 in the exhaust passage 43 on the upstream side of the exhaust purification device 41. The pump 58 guides the gas in the communication passage 56 from the exhaust passage 43 side downstream of the exhaust purification device 41 to the exhaust passage 43 side upstream of the exhaust purification device 41 and flows the gas to the exhaust purification device 41 side. 58 has a function of flowing the gas in the exhaust passage 43 upstream from the connection portion 58 to the exhaust purification device 41 side. The operation of the pump 58 is controlled by the ECU 26.

  In the present embodiment, it is assumed that the exhaust purification device 41 has an NOx storage reduction catalyst. In the present embodiment, as in the eighth embodiment, the exhaust manifold 18 is provided with a fuel addition valve 190.

  In this embodiment, when the NOx reduction control is performed in the NOx catalyst of the exhaust purification device 41 when the fuel supply to the engine 1 is stopped, the exhaust throttle valve 6 is closed, the first throttle valve 9 is closed, and the HPL− The EGR valve 14 is closed and the switching valve 55 is opened. Then, the pump 58 is driven to cause the catalyst output gas flowing out from the exhaust purification device 41 to flow into the communication passage 56, to flow the communication passage 56 toward the exhaust passage 43 upstream of the exhaust purification device 41, and again to the exhaust purification device 41. It circulates in the circulation path which flows in. Further, at this time, fuel is added to the gas flowing through the communication passage 56 by the second fuel addition valve 57 to supply a reducing component necessary for NOx reduction control. The fuel added into the communication path 56 by the second fuel addition valve 57 is mixed by the pump 58 and supplied to the exhaust purification device 41 as a highly reactive reducing component.

  The catalyst exit gas circulation path configured as in the present embodiment has a short path length, and can reduce the amount of heat lost by heat dissipation through the piping wall surface or the like in the circulation process. Thereby, the temperature fall of the catalyst outgas which circulates in the circulation path can be suppressed appropriately, and the exhaust gas purification device 41 can be maintained at a high temperature.

  Further, in the configuration of the present embodiment, it is not necessary to motor the engine 1 or rotate the turbine by MAT in order to circulate the catalyst output gas in the circulation path. Therefore, it is possible to suppress the power consumed to circulate the catalyst output gas in the circulation path.

  In this embodiment, the exhaust circulation control and the NOx reduction control that are performed when the fuel supply to the engine 1 is stopped will be described with reference to FIG. FIG. 19 is a flowchart showing a routine for exhaust gas circulation control and NOx reduction control performed when fuel supply to the engine 1 is stopped. This routine is executed by the ECU 26 periodically during operation of the hybrid system.

  Steps S101 to S405 are equivalent to the control described in the fourth embodiment with reference to FIG. In this embodiment, when it is determined in step S405 that the temperature increase of the NOx catalyst has been completed (Yes), the ECU 26 proceeds to step S1006.

In step S1006, the ECU 26 performs exhaust gas circulation control. In this embodiment, the switching valve 56 is opened, the first throttle valve 9 is closed, the HPL-EGR valve 14 is closed, the exhaust throttle valve 6 is closed, and the pump 58 is driven. As a result, as described above, the NOx catalyst outflow gas flowing out from the exhaust purification device 41 is guided to the exhaust passage 43 upstream of the exhaust purification device 41 through the communication passage 56 and flows into the exhaust purification device 41 again. It circulates in the circulation path called. Therefore, when a rich spike is executed in the subsequent step S807 to start the release reduction reaction of NOx stored in the NOx catalyst, the high-temperature gas flowing out from the NOx catalyst circulates in the circulation path and again returns to the NOx. Since it flows into the catalyst, the temperature of the NOx catalyst can be kept high. In addition, by closing the first throttle valve 9, the flow of low-temperature fresh air into the circulation path is suppressed, the air-fuel ratio of the circulating gas flowing into the NOx catalyst is maintained on the rich side, and is added by a rich spike. The amount of fuel to be reduced can be reduced, and the temperature drop of the circulating gas in the circulation path can be suppressed.

  In step S <b> 1007, the ECU 26 adds fuel using the second fuel addition valve 57. As a result, the unburned fuel component is supplied as a reducing agent into the gas circulating in the circulation path. As described above, the added fuel is mixed by the pump 58 and supplied to the NOx catalyst as a good reactive reducing agent, so that the NOx reduction control can be suitably performed.

  By executing the NOx reduction control routine described above, when the NOx reduction control is executed when the engine is stopped, the high-temperature gas flowing out from the NOx catalyst is circulated in the circulation path including the NOx catalyst. A decrease in temperature can be suppressed. Since a relatively rich gas always flows into the NOx catalyst, the amount of fuel to be added is reduced by a rich spike to make the ambient atmosphere of the NOx catalyst a reducing atmosphere in which NOx reduction control can be suitably executed. can do. Therefore, it is possible to reduce the fuel consumption related to the NOx reduction control.

  In the present embodiment, the example in which the NOx reduction control of the NOx catalyst is performed while performing the exhaust circulation control when the fuel supply to the engine 1 is stopped has been described. However, in this embodiment, the filter regeneration is performed when the fuel supply to the engine 1 is stopped. Control can also be performed. In the filter regeneration control, it is necessary to supply a certain amount of oxygen to the filter in order to suitably advance the oxidation reaction of PM deposited on the filter. Therefore, when the present embodiment is applied to the filter regeneration control when the engine is stopped, the first throttle valve 9 and the HPL-EGR are supplied so that oxygen required for performing the filter regeneration control is supplied to the filter. Open the valve 14 to the opening side.

  In the present embodiment, since the pump 58 can cause a gas flow from the exhaust passage 43 upstream of the pump 58 to the exhaust purification device 41 side, the first throttle valve 9 and the HPL-EGR valve 14 are opened. By setting the opening to the side, the air in the intake passage 42 flows from the intake passage 42 into the HPL-EGR passage 15, passes through the HPL-EGR passage 15, and flows into the exhaust passage 43. Is sent to the exhaust purification device 41 side. Thereby, air can be supplied into the gas circulating in the circulation path.

  At this time, the air that suppresses an excessive decrease in the temperature of the gas circulating in the circulation path and can supply oxygen necessary for suitable implementation of the filter regeneration control is introduced into the circulation path. Thus, the opening degree of the HPL-EGR valve 14 and / or the first throttle valve 9 is adjusted. In this way, even when the fuel supply to the engine 1 is stopped, the filter regeneration control can be suitably executed while suppressing the temperature drop of the filter.

  Here, an example in which air in the intake passage 42 is led to the exhaust passage 43 via the HPL-EGR passage 15 in order to introduce air into the circulation path has been described. However, the engine 1 of this embodiment is If it is possible to make the valve overlap state in which both the intake valve and the exhaust valve are opened, the air in the intake passage 42 is exhausted via the cylinder 49 in the valve open valve overlap state. Can also lead to.

The communication path 56 of the present embodiment corresponds to the communication path in the present invention. The pump 58 of the present embodiment corresponds to “a power source that generates a gas flow from the exhaust passage downstream of the exhaust purification device to the exhaust passage upstream of the exhaust purification device in the communication passage” or a pump in the present invention. The switching valve 55 of the present embodiment corresponds to the switching valve in the present invention. The exhaust throttle valve 6 of the present embodiment corresponds to the exhaust throttle valve in the present invention. The first throttle valve 9 of this embodiment corresponds to the throttle valve in the present invention. ECU26 which performs step S1006 of a present Example is equivalent to the exhaust gas circulation means in this invention. The ECU 26 that executes step S1007 of this embodiment corresponds to the regeneration control means in the present invention. The second fuel addition valve 57 of this embodiment corresponds to the reducing agent supply means in the present invention.

It is a figure which shows the control block diagram of the hybrid system in an Example. It is a figure which shows schematic structure of the engine in the Example, its intake-exhaust system, and a control system. 3 is a flowchart illustrating a routine for exhaust gas circulation control and filter regeneration control when the engine is stopped in the first embodiment. 6 is a flowchart illustrating a routine for exhaust gas circulation control and filter regeneration control when the engine is stopped in the second embodiment. 12 is a flowchart illustrating a routine for exhaust gas circulation control and filter regeneration control when the engine is stopped in the third embodiment. 12 is a flowchart illustrating a routine for exhaust gas circulation control and NOx reduction control when the engine is stopped in the fourth embodiment. 10 is a flowchart showing a routine for exhaust gas circulation control and NOx reduction control when the engine is stopped in Embodiment 5. 12 is a flowchart illustrating an engine start control routine in a sixth embodiment. 12 is a flowchart illustrating an engine start control routine in a sixth embodiment. When the engine start control in the sixth embodiment is executed, the operation mode of the hybrid system, the amount of fuel added by the fuel addition valve, the opening of the second throttle valve, the opening of the LPL-EGR valve, the engine speed, the engine speed It is a figure which shows an example of the oxygen concentration of intake air, and the time change of the fuel cut control signal of an engine. 18 is a flowchart illustrating an engine start control routine according to a seventh embodiment. 18 is a flowchart illustrating an engine start control routine according to a seventh embodiment. The hybrid system operation mode, the amount of fuel added by the fuel addition valve, the opening of the second throttle valve, the opening of the LPL-EGR valve, the engine speed, It is a figure which shows an example of the time change of the oxygen concentration of intake air, the fuel cut control signal of an engine, and a target EGR rate. It is a figure which shows schematic structure of the engine which concerns on Example 8, and its intake / exhaust system. 18 is a flowchart illustrating a routine for exhaust gas circulation control and NOx reduction control when the engine is stopped in an eighth embodiment. 10 is a flowchart illustrating an engine start control routine according to a ninth embodiment. Hybrid system operation mode, first throttle valve opening, intake air-fuel ratio, intake air pressure, intake air temperature, and engine fuel cut control signal time when engine start control in the ninth embodiment is executed It is a figure which shows an example of a change. It is a figure which shows schematic structure of the engine which concerns on Example 10, and its intake / exhaust system. FIG. 18 is a flowchart illustrating a routine for exhaust gas circulation control and NOx reduction control when the engine is stopped in Example 10. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Intercooler 3 Power split mechanism 4 Output part 5 Nozzle vane 6 Exhaust throttle valve 7 Air flow meter 8 Transmission part 9 1st throttle valve 10 Intercooler bypass passage 11 Compressor 12 Turbine 13 Turbocharger 14 HPL-EGR valve 15 HPL-EGR Passage 16 HPL-EGR cooler 17 Intake manifold 18 Exhaust manifold 19 Fuel addition valve 20 Intercooler bypass valve 21 Turbo assist motor 22 Second throttle valve 23 HPL-EGR cooler bypass valve 24 Inverter 25 Battery 26 ECU
27 Accelerator opening sensor 28 Vehicle speed sensor 29 Injector 30 Crank angle sensor 31 MG1 rotational speed sensor 32 MG2 rotational speed sensor 33 LPL-EGR cooler 34 LPL-EGR cooler bypass valve 35 LPL-EGR cooler bypass passage 36 HPL-EGR cooler bypass passage 37 exhaust temperature sensor 38 2nd A / F sensor 39 exhaust purification device (NOx catalyst)
40 Drive wheel 41 Exhaust gas purification device (filter)
42 Intake passage 43 Exhaust passage 44 LPL-EGR passage 45 LPL-EGR valve 46 VVT
47 Differential pressure sensor 48 Water temperature sensor 49 Cylinder 50 1st A / F sensor 51 SOC sensor 52 Accelerator pedal 53 Switching valve 54 Communication path 55 Switching valve 56 Communication path 57 Second fuel addition valve 58 Pump 190 Fuel addition valve

Claims (35)

An exhaust purification device disposed in the exhaust passage of the engine;
Regeneration control means for performing regeneration control for recovering the exhaust purification capacity of the exhaust purification device;
Exhaust circulation means for circulating at least part of the exhaust gas flowing out from the exhaust purification device in a circulation path including the exhaust purification device;
With
The engine exhaust purification system according to claim 1, wherein the regeneration control means executes the regeneration control while circulating the exhaust gas by the exhaust circulation means when the regeneration control is executed when the fuel supply to the engine is stopped. In claim 1,
The engine;
A power source other than the engine, capable of outputting a driving force to a driving shaft, and capable of outputting a driving force for rotating the engine without depending on fuel combustion energy;
Applied to a hybrid system that outputs a required driving force to the drive shaft by at least one of
The hybrid system can operate in an EV traveling mode in which fuel supply to the engine is stopped and a required driving force is output to the driving shaft only by the power source,
An EGR passage connecting an exhaust passage downstream of the exhaust purification device and an intake passage of the engine;
An EGR valve that adjusts the amount of exhaust flowing in the EGR passage;
A throttle valve for adjusting the amount of air flowing into the intake passage upstream from the connection point of the EGR passage;
With
The exhaust circulation means includes
The opening of the EGR valve is changed to an opening on the open side compared with the case where the exhaust gas is not circulated, and the opening of the throttle valve is opened on the closed side than when the exhaust gas is not circulated. Change in degrees
By rotating the engine by the power source,
Circulating the exhaust,
The engine exhaust purification system, wherein the regeneration control means executes the regeneration control while circulating the exhaust gas by the exhaust circulation means when the regeneration control is executed when the engine is stopped in the EV traveling mode. . In claim 1,
The engine;
A power source other than the engine, and a first power source capable of outputting a driving force to at least the driving shaft;
A power source other than the engine, at least a second power source capable of outputting a driving force for rotating the engine without depending on fuel combustion energy;
Applied to a hybrid system that outputs a required driving force to the drive shaft by at least one of
The hybrid system can operate in an EV traveling mode in which fuel supply to the engine is stopped and a required driving force is output to the driving shaft only by the first power source,
An EGR passage connecting an exhaust passage downstream of the exhaust purification device and an intake passage of the engine;
An EGR valve that adjusts the amount of exhaust flowing in the EGR passage;
A throttle valve for adjusting the amount of air flowing into the intake passage upstream from the connection point of the EGR passage;
With
The exhaust circulation means includes
The opening of the EGR valve is changed to an opening on the open side compared with the case where the exhaust gas is not circulated, and the opening of the throttle valve is opened on the closed side than when the exhaust gas is not circulated. Change in degrees
By rotating the engine by the second power source,
Circulating the exhaust,
The engine exhaust purification system, wherein the regeneration control means executes the regeneration control while circulating the exhaust gas by the exhaust circulation means when the regeneration control is executed when the engine is stopped in the EV traveling mode. . In claim 2 or 3,
A variable valve timing device capable of changing the exhaust valve timing of the engine;
When performing the regeneration control when the engine is stopped in the EV traveling mode, the regeneration control means circulates the exhaust by the exhaust circulation means, and sets the opening timing of the exhaust valve by the variable valve timing device. An exhaust purification system for an engine, wherein the exhaust angle is advanced more than when exhaust gas is not circulated. In claim 2 or 3,
A turbocharger having a compressor provided in the intake passage and a turbine provided in the exhaust passage;
The turbocharger is a variable capacity turbocharger having a variable-opening nozzle vane in the turbine and capable of changing the supercharging efficiency of the turbocharger by changing the opening of the nozzle vane.
When the regeneration control means executes the regeneration control when the engine is stopped in the EV driving mode, the exhaust circulation is performed by the exhaust circulation means, and the opening degree of the nozzle vane is not performed by the exhaust circulation. The engine exhaust purification system is also characterized by changing the opening to the opening side. In claim 1,
A turbocharger comprising: a compressor provided in an intake passage of the engine; a turbine provided in the exhaust passage; and a turbo-assist power source capable of rotating the turbine without depending on the energy of exhaust. ,
An EGR passage connecting the exhaust passage downstream of the exhaust purification device and the intake passage;
An EGR valve that adjusts the amount of exhaust flowing in the EGR passage;
A throttle valve for adjusting the amount of air flowing into the intake passage upstream from the connection point of the EGR passage;
Valve control means for controlling opening and closing of the intake valve and exhaust valve of the engine;
With
The exhaust circulation means includes
The opening of the EGR valve is changed to an opening on the open side compared with the case where the exhaust gas is not circulated, and the opening of the throttle valve is opened on the closed side than when the exhaust gas is not circulated. Change in degrees
The valve control means controls the intake valve and the exhaust valve to be in an open state, and the turbine is rotated by the turbo assist power source to circulate the exhaust,
When the regeneration control is performed when the engine is stopped, the regeneration control unit performs the regeneration control while circulating the exhaust by the exhaust circulation unit. In claim 1,
A turbocharger comprising: a compressor provided in an intake passage of the engine; a turbine provided in the exhaust passage; and a turbo-assist power source capable of rotating the turbine without depending on the energy of exhaust. ,
An EGR passage connecting the exhaust passage downstream of the exhaust purification device and the intake passage;
An EGR valve that adjusts the amount of exhaust flowing in the EGR passage;
A throttle valve for adjusting the amount of air flowing into the intake passage upstream from the connection point of the EGR passage;
A second EGR passage connecting the exhaust passage upstream of the exhaust purification device and the intake passage;
A second EGR valve that adjusts the amount of exhaust flowing in the second EGR passage;
With
The exhaust circulation means includes
The opening of the EGR valve is changed to an opening on the open side compared with the case where the exhaust gas is not circulated, and the opening of the throttle valve is opened on the closed side than when the exhaust gas is not circulated. Change in degrees
By opening the second EGR valve and rotating the turbine by the turbo assist power source,
Circulating the exhaust,
When the regeneration control is performed when the engine is stopped, the regeneration control unit performs the regeneration control while circulating the exhaust by the exhaust circulation unit. In claim 6 or 7,
The engine;
A power source other than the engine, capable of outputting a driving force to a driving shaft, and capable of outputting a driving force for rotating the engine without depending on fuel combustion energy;
Applied to a hybrid system that outputs a required driving force to the drive shaft by at least one of
The hybrid system can operate in an EV traveling mode in which fuel supply to the engine is stopped and a required driving force is output to the driving shaft only by the power source,
The engine exhaust purification system, wherein the regeneration control means executes the regeneration control while circulating the exhaust gas by the exhaust circulation means when the regeneration control is executed when the engine is stopped in the EV traveling mode. . In claim 6 or 7,
The engine;
A power source other than the engine, and a first power source capable of outputting a driving force to at least the driving shaft;
A power source other than the engine, at least a second power source capable of outputting a driving force for rotating the engine without depending on fuel combustion energy;
Applied to a hybrid system that outputs a required driving force to the drive shaft by at least one of
The hybrid system can operate in an EV traveling mode in which fuel supply to the engine is stopped and a required driving force is output to the driving shaft only by the first power source,
The engine exhaust purification system, wherein the regeneration control means executes the regeneration control while circulating the exhaust gas by the exhaust circulation means when the regeneration control is executed when the engine is stopped in the EV traveling mode. . In claim 6 or 7,
An engine automatic stop start control means for automatically stopping the engine in a predetermined engine stop condition and automatically restarting the stopped engine in a predetermined engine start condition;
When the regeneration control means executes the regeneration control when the engine is stopped under the engine stop condition, the regeneration control system executes the regeneration control while circulating the exhaust gas by the exhaust circulation means. . In any one of Claims 1-10,
The exhaust purification device has a filter that collects particulate matter in the exhaust,
The regeneration control means executes, as the regeneration control, filter regeneration control for recovering the exhaust gas purification ability of the filter by oxidizing and removing particulate matter collected by the filter. Purification system. In any one of Claims 1-10,
The exhaust purification device has a filter that collects particulate matter in the exhaust,
The regeneration control means executes filter regeneration control for recovering the exhaust gas purification ability of the filter by oxidizing and removing particulate matter collected in the filter as the regeneration control,
When the regeneration control means executes the filter regeneration control when the fuel supply to the engine is stopped, the regeneration control means circulates in the circulation path by the exhaust circulation means of the exhaust gas flowing out from the filter according to the temperature of the filter. An exhaust emission control system for an engine, characterized by adjusting an amount of exhaust gas and / or an amount of air flowing into the intake passage of the engine. In any one of Claims 1-10,
The exhaust purification device has a filter that collects particulate matter in the exhaust,
The regeneration control means executes filter regeneration control for recovering the exhaust gas purification ability of the filter by oxidizing and removing particulate matter collected in the filter as the regeneration control,
When performing the filter regeneration control when the fuel supply to the engine is stopped, the regeneration control unit adjusts the amount of air flowing into the intake passage of the engine according to the oxygen concentration of the exhaust flowing into the filter. An exhaust purification system for an engine characterized by that. In any one of Claims 2-5,
The exhaust purification device has a filter that collects particulate matter in the exhaust,
The regeneration control means executes filter regeneration control for recovering the exhaust gas purification ability of the filter by oxidizing and removing particulate matter collected in the filter as the regeneration control,
When the regeneration control means executes the filter regeneration control when the engine is stopped in the EV travel mode, the opening of the EGR valve, the opening of the throttle valve, and other than the engine according to the temperature of the filter An engine exhaust purification system characterized by adjusting at least one of the engine rotational speeds when the engine is rotated by a power source. In any one of Claims 6-10,
The exhaust purification device has a filter that collects particulate matter in the exhaust,
The regeneration control means executes filter regeneration control for recovering the exhaust gas purification ability of the filter by oxidizing and removing particulate matter collected in the filter as the regeneration control,
The regeneration control means, when executing the filter regeneration control when the fuel supply to the engine is stopped, according to the temperature of the filter, the opening degree of the EGR valve, the opening degree of the throttle valve, and the turbo assist An engine exhaust purification system characterized by adjusting at least one of the turbine rotational speeds when the turbine is rotationally driven by a power source. In any one of Claims 2-10,
The exhaust purification device has a filter that collects particulate matter in the exhaust,
The regeneration control means executes filter regeneration control for recovering the exhaust gas purification ability of the filter by oxidizing and removing particulate matter collected in the filter as the regeneration control,
The regeneration control means adjusts the opening of the throttle valve according to the oxygen concentration of the exhaust gas flowing into the filter when the filter regeneration control is executed when the fuel supply to the engine is stopped. Engine exhaust purification system. In any one of Claims 1-10,
The exhaust purification apparatus has a NOx catalyst that stores NOx in exhaust in an oxygen-excess atmosphere, releases the stored NOx in a reducing atmosphere, and reduces the released NOx in the presence of a reducing agent,
As the regeneration control, the regeneration control means releases the NOx occluded in the NOx catalyst by supplying a reducing agent to the NOx catalyst and adjusts the ambient atmosphere of the NOx catalyst to the reducing atmosphere and reduces the NOx catalyst. An exhaust purification system for an engine, characterized in that NOx reduction control for reducing the released NOx by an agent is executed. In any one of Claims 1-17,
When an engine start condition for starting the engine and performing a load operation is satisfied while the engine is stopped,
The engine is operated in a cranking mode in which the engine is cranked and fuel injection adapted to the cranking is performed to increase the rotational speed of the engine,
Engine start control means for shifting to a load operation mode in which the engine is loaded when the engine speed reaches a predetermined reference speed in the cranking mode;
When the engine start condition is satisfied when the regeneration control unit performs the regeneration control while circulating the exhaust gas by the exhaust circulation unit while the engine is stopped, the engine start control unit After stopping the exhaust gas circulation by the exhaust gas circulation means, the engine operation in the cranking mode is started, and in the cranking mode, the start of fuel injection suitable for the cranking is performed. An exhaust purification system for an engine characterized by delaying a predetermined period from the start of engine operation in the mode. In claim 18,
Comprising oxygen concentration acquisition means for acquiring the oxygen concentration of gas sucked into the engine;
The engine start control means determines an interval for delaying the start of fuel injection in the cranking mode based on the oxygen concentration acquired by the oxygen concentration acquisition means. In claim 18,
The engine start control means is required for scavenging the exhaust gas existing in the intake passage at the time when the engine restart condition is satisfied among the exhaust gas circulated by the exhaust circulation means from the intake passage. An engine exhaust purification system characterized in that a period for delaying the start of fuel injection in the cranking mode is determined based on time. In any one of Claims 18-20,
The engine start control means starts fuel injection and loads the engine when the engine speed reaches the reference speed during a period in which the start of fuel injection is delayed in the cranking mode. The engine exhaust gas purification system, wherein the target EGR rate is corrected based on the oxygen concentration of the gas sucked into the engine in the load operation mode. In claim 1,
A power source capable of outputting a driving force for rotating the engine without depending on fuel combustion energy;
A communication passage connecting the exhaust passage downstream of the exhaust purification device and the intake passage;
A switching valve for opening and closing the communication path;
A throttle valve provided in the intake passage upstream of the connection location of the communication passage;
With
The exhaust circulation means includes
Change the switching valve to an opening on the opening side than when the exhaust gas is not circulated,
The opening of the throttle valve is changed to an opening on the closing side than when the exhaust gas is not circulated,
By rotating the engine by the power source,
Circulating the exhaust,
The engine exhaust purification system characterized in that the regeneration control means executes the regeneration control while circulating the exhaust gas by the exhaust circulation means when the regeneration control is executed when fuel supply to the engine is stopped. . In claim 22,
An intercooler is provided in the intake passage,
An exhaust purification system for an engine, wherein a connection portion of the communication passage in the intake passage is downstream of the intercooler. In claim 22 or 23,
The engine exhaust gas purification system, wherein the connection portion of the communication passage in the intake passage is an intake manifold of the engine. In any one of Claims 22-24,
An exhaust throttle valve is provided on the downstream side of the connection portion of the communication passage in the exhaust passage,
The exhaust gas purifying system according to claim 1, wherein when the exhaust gas is circulated, the exhaust throttle valve is changed to an opening closer to the closing side than when the exhaust gas is not circulated. In any one of Claims 22-25,
The regeneration control means, when performing the regeneration control while circulating the exhaust gas by the exhaust circulation means, when oxygen supply is required for execution of the regeneration control, when oxygen supply is not required In comparison, the engine exhaust purification system is characterized in that the opening of the throttle valve is changed to the open side. In any one of Claims 22-26,
When the fuel supply to the engine is stopped, an engine start condition for starting the engine and performing a load operation is established when the regeneration control unit performs the regeneration control while circulating the exhaust gas by the exhaust circulation unit. In this case, the opening of the throttle valve is changed to an opening more open than before the engine start condition is satisfied, the switching valve is closed, cranking of the engine is started, An engine exhaust gas purification system, further comprising engine start control means for starting fuel supply to the engine and starting load operation of the engine after elapse of a predetermined period from the start of cranking. In claim 27,
Air-fuel ratio acquisition means for acquiring the air-fuel ratio of the intake air of the engine,
When the condition that the air-fuel ratio acquired by the air-fuel ratio acquisition unit is leaner than a predetermined reference air-fuel ratio is satisfied, the engine start control unit starts fuel supply to the engine and loads the engine An exhaust purification system for an engine characterized by starting operation. In claim 28,
Intake pressure acquisition means for acquiring the pressure of the intake air of the engine;
Intake air temperature acquisition means for acquiring the intake air temperature of the engine;
Further comprising
The engine start control means has a condition that the intake pressure acquired by the intake pressure acquisition means is higher than a predetermined reference pressure, and the intake air temperature acquired by the intake air temperature acquisition means is lower than a predetermined reference temperature. When at least one of the above conditions is further established, fuel supply to the engine is started and load operation of the engine is started. In claim 1,
A communication passage connecting an exhaust passage downstream of the exhaust purification device and an exhaust passage upstream of the exhaust purification device;
A power source for generating a gas flow from the exhaust passage downstream of the exhaust purification device to the exhaust passage upstream of the exhaust purification device in the communication passage;
A switching valve for opening and closing the communication path;
An exhaust throttle valve provided on the downstream side of a connection point of the communication passage in the exhaust passage downstream of the exhaust purification device;
A throttle valve provided in the intake passage;
With
The exhaust circulation means includes
Change the opening of the switching valve to an opening on the opening side than when the exhaust gas is not circulated,
Change the opening of the exhaust throttle valve to the opening on the closed side than when the exhaust is not circulated,
Change the opening of the throttle valve to the opening on the closed side than when the exhaust gas is not circulated,
The exhaust gas is circulated by generating the gas flow in the communication path by the power source,
The exhaust purification system for an engine, wherein the regeneration control means executes the regeneration control while circulating the exhaust gas by the exhaust circulation means when the regeneration control is executed when fuel supply to the engine is stopped. . In claim 30,
The engine exhaust gas purification system, wherein the power source is a pump that causes the gas in the communication passage to flow from an exhaust passage side downstream of the exhaust purification device to an exhaust passage side upstream of the exhaust purification device. In claim 30 or 31,
Reducing agent supply means for supplying a reducing agent into the communication passage on the exhaust passage side downstream of the exhaust purification device from the pump;
When the regeneration control unit executes the regeneration control while the exhaust gas circulation unit circulates the exhaust gas, when the regenerative control requires a supply of a reducing agent, the reducing agent supply unit performs the communication path. An exhaust purification system for an engine, characterized in that a reducing agent is supplied into the gas flowing through the engine. In any one of Claims 30-32,
The power source is configured to be able to generate a gas flow in the exhaust passage from the upstream side to the exhaust purification device side from the connection point of the communication passage in the exhaust passage upstream of the exhaust purification device,
An EGR passage connecting an exhaust passage upstream of the exhaust purification device and an intake passage downstream of the throttle valve;
An EGR valve provided in the EGR passage;
With
When the regeneration control means executes the regeneration control while circulating the exhaust gas by the exhaust circulation means, when supply of oxygen is required for the execution of the regeneration control,
The opening of the throttle valve is changed to the open side rather than when oxygen supply is not required,
The opening of the EGR valve is changed to the open side rather than when oxygen supply is not required,
An exhaust purification system for an engine, characterized in that the gas flow is generated in an exhaust passage upstream of the exhaust purification device by the power source. In any one of Claims 30-32,
The power source is configured to be able to generate a gas flow in the exhaust passage from the upstream side to the exhaust purification device side from the connection point of the communication passage in the exhaust passage upstream of the exhaust purification device,
Valve control means for controlling opening and closing of the intake valve and exhaust valve of the engine;
With
When the regeneration control means executes the regeneration control while circulating the exhaust gas by the exhaust circulation means, when supply of oxygen is required for the execution of the regeneration control,
The opening of the throttle valve is changed to the open side rather than when oxygen supply is not required,
The valve control means controls the intake valve and the exhaust valve of the engine to be in an open state,
An exhaust purification system for an engine, characterized in that the gas flow is generated in an exhaust passage upstream of the exhaust purification device by the power source. In claim 33 or 34,
The power source is provided at a connection location of the communication passage in an exhaust passage upstream of the exhaust purification device, and is connected to the exhaust purification device from the exhaust passage upstream of the connection location and the communication passage upstream of the connection location. An exhaust gas purification system for an engine characterized by being a pump for flowing gas to the side.

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