JP2008163884A - Control device for internal combustion engine - Google Patents

Abstract

The present invention relates to a control device for an internal combustion engine, and an object thereof is to uniformly diffuse fuel added to exhaust gas even during idling or light load.
A diesel engine includes a turbocharger capable of assisting rotation by an electric motor and a fuel addition valve for adding fuel to exhaust gas. When the fuel is added by the fuel addition valve 52 at the time of idling or light load of the diesel engine 2, the electric motor 14d is operated to increase the turbo rotation speed. Thereby, in the turbine 14b, the exhaust gas containing the added fuel is sufficiently stirred, and the added fuel is uniformly diffused in the exhaust gas. Prior to the start of fuel injection from the fuel addition valve 52, the operation of the electric motor 14d is started.
[Selection] Figure 1

Description

  The present invention relates to a control device for an internal combustion engine.

  Japanese Patent Application Laid-Open No. 2001-55946 discloses that when a NOx absorbent (NOx catalyst) provided in an exhaust passage is refreshed, that is, when NOx absorbed in the NOx absorbent is reduced and discharged, A control device for a diesel engine that increases the fuel injection amount from a fuel injection valve that injects fuel is disclosed. In this device, when the NOx absorbent is refreshed, as a measure for preventing an increase in smoke due to an increase in fuel injection amount, combustion is performed by reducing the nozzle cross-sectional area of the variable nozzle turbocharger and increasing the supercharging pressure. The intake charge amount of the chamber is increased.

JP 2001-55946 A JP 2004-176675 A

  The above conventional technique is considered to be a technique premised on reducing and purifying NOx of the NOx catalyst at the time of medium load operation or high load operation in which supercharging by the turbocharger sufficiently acts. In order to perform NOx reduction purification, it is necessary to make the exhaust air-fuel ratio rich below the stoichiometric air-fuel ratio. Therefore, the amount of fuel necessary to perform NOx reduction purification increases as the amount of exhaust gas increases. That is, reducing and purifying NOx during medium and high load operation with a large amount of exhaust gas causes deterioration of fuel consumption. For this reason, from the viewpoint of improving fuel efficiency, it is desirable to perform NOx reduction purification during light load operation or idling operation with a small amount of exhaust gas. Further, depending on the running conditions of the vehicle, such as when driving in urban areas where there are many stops and gos, there may be a case where NOx reduction purification must be performed during light load operation or idle operation.

  However, the exhaust gas temperature is low during light load operation and idle operation. In addition, since HC and CO in the exhaust gas are small, the amount of heat generated when they react (combust) with the NOx catalyst is also small. For this reason, there is a problem that the temperature of the NOx catalyst usually becomes lower than the activation temperature at which NOx can be reduced and purified during light load operation or idle operation.

  As a method for increasing the temperature of the NOx catalyst at the time of light load operation or idle operation to the activation temperature or higher, a method of adding fuel to the exhaust gas can be considered. However, when fuel is added to the exhaust gas during light load operation or idle operation, the added fuel is difficult to diffuse because the exhaust gas temperature is low and the exhaust gas flow is weak. For this reason, the added fuel flows into the NOx catalyst in a state where it is unevenly distributed in the exhaust gas. As a result, problems such as fuel clogging are likely to occur at the end face of the NOx catalyst (cells or inlets of the filter constituting the NOx catalyst).

  The present invention has been made to solve the above-described problems, and controls an internal combustion engine capable of uniformly diffusing fuel added to exhaust gas even during idling or light load. An object is to provide an apparatus.

In order to achieve the above object, a first invention is a control device for an internal combustion engine,
Fuel addition means for adding fuel to the exhaust gas of the internal combustion engine;
Agitation means for agitating exhaust gas in an exhaust passage downstream of the fuel addition means when fuel is added by the fuel addition means at idle or light load;
It is characterized by providing.

The second invention is the first invention, wherein
The larger the amount of fuel added by the fuel adding means, the stronger the stirring by the stirring means.

The third invention is the first or second invention, wherein
Prior to the timing when the fuel adding means starts to add fuel, the agitation means starts to operate.

Moreover, 4th invention is set in 3rd invention,
The larger the amount of fuel added by the fuel addition means, the earlier the operation start timing of the agitation means is made earlier than the fuel addition start timing of the fuel addition means.

According to a fifth invention, in any one of the first to fourth inventions,
It further comprises exhaust throttling means for performing exhaust throttling during idling or light load.

According to a sixth invention, in any one of the first to fifth inventions,
The internal combustion engine has a supercharger with an electric motor,
The stirring means stirs the exhaust gas by forcibly increasing the rotational speed of the supercharger by the electric motor.

The seventh invention is the sixth invention, wherein
A hybrid system that drives the vehicle using both the output of the internal combustion engine and the output of another prime mover;
In order to suppress a change in driving force transmitted to the vehicle when the output of the internal combustion engine is increased by increasing the supercharging pressure while the motor is operated to stir the exhaust gas while the vehicle is running A driving force change suppressing means for controlling the hybrid system;
Is further provided.

  According to the first invention, when fuel is added to the exhaust gas at the time of idling or light load, the exhaust gas containing the added fuel can be forcibly stirred by the stirring means. By this stirring, the added fuel can be uniformly diffused in the exhaust gas. For this reason, even when the fuel is added to the exhaust gas at the time of idling or light load, it is possible to reliably prevent the adverse effect such as clogging of the added fuel on the end face of the exhaust purification device. it can. Therefore, it is possible to perform NOx reduction purification (rich spike) or the like of the exhaust purification device even during idling or light load. According to the first aspect of the invention, since processing such as NOx reduction purification can be performed at idling or light load with a small amount of exhaust gas, fuel required for the processing can be saved, and excellent fuel consumption performance can be obtained. be able to. Furthermore, according to the first invention, the exhaust gas can flow into the exhaust purification device in a state where the added fuel is uniformly diffused, so that the fuel can be reacted uniformly in the exhaust purification device, The reaction can be promoted. For this reason, the effect of treatments such as NOx reduction purification can be enhanced.

  According to the second invention, as the amount of fuel added to the exhaust gas is larger, the stirring by the stirring means can be strengthened. For this reason, necessary and sufficient stirring can be performed according to the amount of fuel added. Therefore, even when the amount of fuel added is large, the added fuel can be sufficiently diffused and made uniform in the exhaust gas, and the above effect can be obtained with certainty.

  According to the third invention, the operation of the stirring means can be started prior to the start of fuel addition to the exhaust gas. Thereby, it is possible to more reliably prevent the fuel from being insufficiently stirred due to the delay in the operation of the stirring means. For this reason, the added fuel can be diffused more uniformly in the exhaust gas.

  According to the fourth invention, the greater the amount of fuel added to the exhaust gas, the earlier the operation start timing of the stirring means can be made earlier than the fuel addition start timing of the fuel addition means. Thereby, even when the amount of fuel added is large, it is possible to more reliably prevent the fuel from being insufficiently stirred due to the delay in the operation of the stirring means. For this reason, the added fuel can be diffused more uniformly in the exhaust gas.

  According to the fifth aspect of the present invention, exhaust throttling can be performed when fuel is added to the exhaust gas during idling or light load. As a result, the exhaust temperature can be increased by increasing the exhaust resistance, so that evaporation of the added fuel is promoted. Therefore, the added fuel can be diffused more uniformly in the exhaust gas. Moreover, the temperature rise of the exhaust gas purification device can be further promoted, and the processing can be completed in a short time.

  According to the sixth aspect of the invention, the exhaust gas can be agitated using the supercharger with electric motor provided in the internal combustion engine. That is, the exhaust gas can be agitated by forcibly increasing the rotation speed of the supercharger with the electric motor. As a result, a sufficient effect can be obtained, and it is not necessary to separately provide a mechanism for stirring the exhaust gas, so that the cost can be reduced.

  According to the seventh invention, in the hybrid system that drives the vehicle using both the output of the internal combustion engine and the output of another prime mover, the supercharger with an electric motor is used to stir the exhaust gas while the vehicle is running. When the output of the internal combustion engine increases due to the increase of the supercharging pressure due to the operation of this motor, the output of the other prime mover can be reduced so that the driving force transmitted to the vehicle does not change. For this reason, when the supercharger with an electric motor is forcibly driven in order to stir the exhaust gas, it is possible to reliably suppress a change in the driving force of the vehicle, so that good drivability is obtained.

Embodiment 1 FIG.
[Description of system configuration]
FIG. 1 is a diagram for explaining a system configuration according to the first embodiment of the present invention. The system shown in FIG. 1 includes a diesel engine 2. It is assumed that the diesel engine 2 is mounted on a vehicle (automobile). The illustrated diesel engine 2 is an in-line four-cylinder type, but in the present invention, the number of cylinders and the cylinder arrangement are not limited thereto.

  Each cylinder of the diesel engine 2 is provided with an in-cylinder injector 32 for directly injecting fuel into the combustion chamber. The in-cylinder injector 32 of each cylinder is connected to a common rail 34. That is, the diesel engine 2 is a common rail type diesel engine. Fuel stored in a fuel tank (not shown) is pumped up by a supply pump 36, compressed to a predetermined fuel pressure, and supplied to the common rail 34. Although not shown in the drawing, the supply pump 36 includes a low-pressure pump and a high-pressure pump.

  The diesel engine 2 includes an exhaust manifold 6 and an exhaust passage 10 connected to the exhaust manifold 6. The exhaust gas discharged from each cylinder of the diesel engine 2 is collected in the exhaust manifold 6 and discharged to the exhaust passage 10 via the exhaust manifold 6. An exhaust purification device 30 is provided in the middle of the exhaust passage 10. In the exhaust purification device 30, for example, a NOx storage reduction catalyst, a DPF (Diesel Particulate Filter) that collects PM (Particulate Matter), or a DPNR (Diesel Particulate-NOx-Reduction) that combines both functions. system).

  Further, the diesel engine 2 is provided with an intake manifold 4 and an intake passage 8 connected to the intake manifold 4. Air is taken into the intake passage 8 from the atmosphere and is distributed into each cylinder via the intake manifold 4. An air cleaner 12 is attached to the inlet of the intake passage 8. An air flow meter 76 that outputs a signal corresponding to the flow rate of air sucked into the intake passage 8 is provided in the vicinity of the downstream side of the air cleaner 12. An intake throttle valve 22 is provided upstream of the intake manifold 4.

  Furthermore, the diesel engine 2 is provided with a turbocharger (MAT: Motor Assist Turbocharger) 14. The turbocharger 14 is of a variable nozzle type and has an electric assist mechanism. That is, the turbocharger 14 includes a compressor 14a, a turbine 14b, a variable nozzle 14c, and a motor 14d for forced drive.

  The compressor 14 a is disposed in the intake passage 8 from the air flow meter 76 to the intake throttle valve 22. The turbine 14 b is provided in the middle of the exhaust passage 10 from the exhaust manifold 6 to the exhaust purification device 30. The compressor 14a and the turbine 14b are connected by a connecting shaft and rotate together.

  The variable nozzle 14c can be opened and closed. When the opening degree of the variable nozzle 14c is reduced, the inlet area of the turbine 14b is reduced, so that the flow rate of the exhaust gas blown to the turbine 14b is increased. As a result, the rotational speed of the turbocharger 14 (hereinafter referred to as “MAT rotational speed”) increases, and the supercharging pressure increases. Conversely, when the opening of the variable nozzle 14c is increased, the inlet area of the turbine 14b is increased, so that the flow rate of the exhaust gas blown to the turbine 14b is decreased. As a result, the MAT rotation speed decreases and the supercharging pressure decreases.

  An electric motor 14d is disposed between the compressor 14a and the turbine 14b. The connecting shaft between the compressor 14a and the turbine 14b is also a rotor of the electric motor 14d. That is, the compressor 14a and the turbine 14b and the rotor of the electric motor 14d rotate as a unit. With such a configuration, when the motor 14d is operated, the compressor 14a and the turbine 14b can be forcibly driven regardless of the exhaust energy recovered by the turbine 14b.

  A rotation speed sensor 16 for detecting the rotation speed of the electric motor 14d is incorporated in the electric motor 14d. As described above, the electric motor 14d rotates integrally with the compressor 14a and the turbine 14b. For this reason, the rotation speed detected by the rotation speed sensor 16 is equal to the MAT rotation speed.

  An intercooler 17 is provided between the compressor 14a and the intake manifold 4 for cooling the intake air whose temperature has increased due to compression by the compressor 14a. A supercharging pressure sensor (intake pressure sensor) 74 that detects a supercharging pressure (intake pressure) is disposed downstream of the intercooler 17.

  One end of a bypass pipe 50 is connected to the intake passage 8 extending from the compressor 14a to the intercooler 17. A switching valve 18 for switching the air flow path is disposed at the connection portion. The other end of the bypass pipe 50 is connected to the upstream side of the compressor 14 a in the intake passage 8. By operating the switching valve 18 to open the inlet of the bypass pipe 50, a part of the air compressed by the compressor 14a is returned again to the inlet side of the compressor 14a. When the turbocharger 14 is in an operating state in which a surge is likely to occur, the surge can be prevented by returning a part of the air exiting the compressor 14 a to the inlet side of the compressor 14 a through the bypass pipe 50.

  One end of an EGR pipe 24 is connected to the intake passage 8 extending from the intake throttle valve 22 to the intake manifold 4. The other end of the EGR pipe 24 is connected to the exhaust manifold 6. In the present system, a part of the exhaust gas can be introduced into the intake passage 8 through the EGR pipe 24. The exhaust gas introduced into the intake passage 8 through the EGR pipe 24 is hereinafter referred to as “EGR gas”. An EGR cooler 26 for cooling the EGR gas is provided in the middle of the EGR pipe 24. An EGR valve 28 for controlling the amount of EGR gas (EGR amount) is provided downstream of the EGR cooler 26 in the EGR pipe 24. By introducing EGR gas having a high specific heat and a small amount of oxygen in comparison with air into the intake passage 8, the combustion temperature in the cylinder can be lowered and the amount of NOx produced can be reduced.

  The exhaust manifold 6 is provided with a fuel addition valve (fuel addition injector) 52. By injecting fuel from the fuel addition valve 52, the fuel can be added to the exhaust gas. The installation position of the fuel addition valve 52 is not limited to the exhaust manifold 6, and fuel is added to the exhaust port of one of the cylinders or in the middle of the exhaust passage 10 between the exhaust manifold 6 and the turbine 14 b. A valve 52 may be installed.

  An exhaust throttle valve 54 is installed in the middle of the exhaust passage 10 between the turbine 14 b and the exhaust purification device 30.

  The system of this embodiment further includes a motor controller 60 and an ECU (Electronic Control Unit) 70. The motor controller 60 controls the energization state of the electric motor 14d based on a command from the ECU 70. The ECU 70 is a control device that comprehensively controls the entire system. In addition to the motor controller 60, various actuators such as the in-cylinder injector 32, the intake throttle valve 22, the EGR valve 28, the variable nozzle 14 c, the switching valve 18, and the exhaust throttle valve 54 are connected to the output side of the ECU 70. On the input side, various sensors such as a vehicle speed sensor 56, an accelerator position sensor 72, a crank angle sensor 78 and the like are connected in addition to the s rotation speed sensor 16, the air flow meter 76, and the supercharging pressure sensor 74 described above. The accelerator position sensor 72 is a sensor that detects the amount of depression (accelerator opening) of an accelerator pedal (not shown). The crank angle sensor 78 is a sensor that outputs a signal corresponding to the rotation angle of the crankshaft. According to the output of the crank angle sensor 78, the engine speed NE [rpm] or the like can be detected. In addition to these devices and sensors, a plurality of devices and sensors are connected to the ECU 70, but the description thereof is omitted here. The ECU 70 drives each device according to a predetermined control program based on the output of each sensor.

[Operation of Embodiment 1]
The air-fuel ratio of the exhaust gas of the diesel engine 2 is usually much leaner than the stoichiometric air-fuel ratio. In this state, according to the system of the present embodiment, NOx in the exhaust gas can be suppressed by storing NOx in the exhaust gas in the exhaust purification device 30. In the system of the present embodiment, control for reducing and purifying NOx stored in the exhaust purification device 30 (hereinafter referred to as “rich spike control”) is performed periodically (intermittently).

In the rich spike control, by injecting fuel from the fuel addition valve 52, the air-fuel ratio of the exhaust gas flowing into the exhaust purification device 30 is made equal to or lower than the stoichiometric air-fuel ratio. Thus, unburned fuel in the exhaust gas becomes a reducing agent, the NOx stored in the exhaust purification device 30 can be reduced and purified to N _2. In order for the exhaust purification device 30 to efficiently reduce and purify NOx, a certain high temperature is required. This temperature is hereinafter referred to as “catalytic activity temperature”.

  Consider a case where a vehicle stops when traveling in an urban area. When the driver turns off the accelerator to decelerate the vehicle, fuel injection from the in-cylinder injector 32 is stopped. For this reason, since air flows through the exhaust passage 10, the exhaust purification device 30 is rapidly cooled. And if a vehicle stops, the diesel engine 2 will be in an idle driving | running state. In the idle operation state, the amount of fuel injected from the in-cylinder injector 32 is small, so the exhaust gas temperature is low. Further, since HC and CO in the exhaust gas are also small, the amount of heat generated by the reaction (combustion) of them in the exhaust purification device 30 is small. Due to these influences, during the idling operation, the temperature of the exhaust purification device 30 is usually lower than the catalyst activation temperature, so that there is a problem that rich spike control cannot be performed.

  As a method of setting the temperature of the exhaust purification device 30 to the catalyst activation temperature or higher during idle operation, a method of adding fuel to the exhaust gas by the fuel addition valve 52 and burning the added fuel in the exhaust purification device 30 is conceivable. .

  However, in the idle operation state, since the turbo rotation speed is low, the exhaust gas to which fuel is added is not sufficiently stirred by the turbine 14b. For this reason, when fuel is added to the exhaust gas in the idle operation state, the added fuel does not diffuse uniformly into the exhaust gas and flows into the exhaust purification device 30 in a non-uniform state. As a result, there is a problem that fuel is clogged at the end face of the exhaust purification device 30 (the cell or the inlet of the filter constituting the exhaust purification device 30).

  Therefore, in the present embodiment, when fuel is injected from the fuel addition valve 52 during idle operation, the MAT rotation speed is forcibly increased by operating the electric motor 14d. As a result, the exhaust gas to which fuel is added can be sufficiently agitated by the turbine 14b, and the fuel can be uniformly diffused into the exhaust gas. As a result, fuel clogging to the end face of the exhaust purification device 30 can be reliably prevented.

  Furthermore, in this embodiment, when fuel is injected from the fuel addition valve 52 during idle operation, the flow of the exhaust gas is reduced by reducing the opening of the exhaust throttle valve 54. Thereby, exhaust gas temperature can be raised. For this reason, since the fuel added to the exhaust gas is likely to evaporate, the fuel clogging to the end face of the exhaust purification device 30 can be prevented more reliably. Further, since the temperature of the exhaust purification device 30 can be further increased, the purification efficiency at the time of rich spike can also be increased.

[Specific Processing in Embodiment 1]
FIG. 2 is a flowchart of a routine executed by the ECU 70 in the present embodiment in order to realize the above function. According to the routine shown in FIG. 2, first, the engine speed NE detected by the crank angle sensor 78, the accelerator opening ACCP detected by the accelerator position sensor 72, and the vehicle speed SPD detected by the vehicle speed sensor 56. Each value is acquired (step 100).

  Next, the fuel injection amount QFIN to be injected from the in-cylinder injector 32 is calculated based on the engine speed NE and the accelerator opening ACCP (step 102). Subsequently, based on the engine speed NE and the fuel injection amount QFIN, a required value α of the opening degree of the exhaust throttle valve 54 (hereinafter referred to as “exhaust throttle opening degree”) PLUEX is calculated (step 104). Here, the smaller the fuel injection amount QFIN (load) and the lower the engine speed NE, the smaller the required value α of the exhaust throttle opening PLUEX is calculated.

  Incidentally, the ECU 70 estimates the NOx occlusion amount of the exhaust purification device 30 by a known process executed by another subroutine (not shown). In step 106, the amount of fuel to be injected from the fuel addition valve 52, that is, the required value β of the fuel addition amount QADNOX is calculated based on the estimated NOx storage amount GNOXRD.

  Subsequent to the process of step 106, based on the required value β of the fuel addition amount QADNOX, the rotational speed of the electric motor 14d, that is, the required value γ of the MAT rotational speed EMATREV is calculated (step 108). FIG. 3 is a diagram showing the relationship between the fuel addition amount QADNOX and the MAT rotation speed EMATREV. As shown in the figure, in step 108, the required value γ of the MAT speed EMATREV is set higher as the required value β of the fuel addition amount QADNOX is larger.

  Next, it is determined whether or not an idle determination flag existbl indicating whether or not the diesel engine 2 is in an idle operation state is ON (step 110). Whether or not the diesel engine 2 is in the idling state is determined by another routine based on the accelerator opening ACCP, the vehicle speed SPD, and the like. In step 110, when the idle determination flag existbl is OFF, that is, when the diesel engine 2 is not in the idling operation state, the processing after step 100 is executed again.

  On the other hand, if the idle determination flag existsbl is ON in step 110, that is, if the diesel engine 2 is in the idle operation state, first, the ECU command value of the exhaust throttle opening PLUEX is calculated in step 104. The requested value α is set (step 112). As a result, the exhaust throttle valve 54 operates in accordance with a command from the ECU 70 so as to reduce its opening. As a result, the flow of exhaust gas is restricted, and the exhaust gas temperature can be raised.

  Subsequently, it is determined whether or not the MAT operation flag exmat indicating whether or not the operation of the electric motor 14d is permitted (step 114). If the MAT operation flag exmat is ON, the ECU command value for the MAT rotation speed EMATREV is set to the required value γ calculated in step 108 (step 116). Thereby, the drive of the electric motor 14d is started and the MAT rotation speed is controlled to be the required value γ.

  Next, it is determined whether or not the fuel addition permission flag exnoxrd is ON (step 118). If the fuel addition permission flag exnoxrd is ON, the ECU command value for the fuel addition amount QADNOX is set to the required value β calculated in step 106 (step 120). As a result, fuel injection from the fuel addition valve 52 is started, and an amount of fuel corresponding to the required value β is added to the exhaust gas.

  As described above, according to the present embodiment, when fuel is added to the exhaust gas from the fuel addition valve 52 during idle operation, the MAT rotational speed is forcibly increased by operating the motor 14d. Can do. As a result, the exhaust gas containing the added fuel can be sufficiently stirred in the turbine 14b, and the added fuel can be uniformly diffused in the exhaust gas. Therefore, it is possible to reliably prevent the added fuel in the exhaust gas from clogging the end face of the exhaust purification device 30.

  For this reason, in the present embodiment, even during idling, the fuel for raising the temperature of the exhaust purification device 30 to the catalyst activation temperature and the NOx occluded in the exhaust purification device 30 are reduced and purified. The fuel can be added to the exhaust gas. That is, even during idle operation, rich spike control can be executed. By executing the rich spike control during idle operation, it is possible to reliably ensure the execution opportunity of the rich spike control even when traveling in an urban area or during traffic congestion. Further, since rich spike control is executed during idle operation with a small amount of exhaust gas, the amount of fuel required to make the exhaust air-fuel ratio rich can be reduced. Therefore, the deterioration of the fuel consumption accompanying execution of the rich spike is suppressed, and the fuel consumption can be improved.

  Further, since the exhaust gas can flow into the exhaust purification device 30 in a state where the added fuel is evenly diffused, the fuel can be reacted evenly in the exhaust purification device 30 and the reaction can be promoted. it can. Therefore, the temperature of the exhaust purification device 30 can be raised efficiently, and the stored NOx can be purified with high efficiency.

  Further, in the present embodiment, the control is performed so that the MAT rotation speed EMATREV increases as the fuel addition amount QADNOX increases. Therefore, when the fuel addition amount QADNOX is large, the stirring of the exhaust gas in the turbine 14b can be strengthened. For this reason, even when the fuel addition amount QADNOX is large, the added fuel can be sufficiently diffused and made uniform in the exhaust gas, and the above-described effects can be reliably obtained.

  In the present embodiment, the fuel is described as being added to the exhaust gas during idle operation. However, the present invention can also be applied to the case where fuel is added to the exhaust gas during a light load.

  In this embodiment, the case where fuel is added to the exhaust gas for the purpose of reducing and purifying NOx stored in the exhaust purification device 30 has been described as an example. However, the present invention is not limited to this. Absent. That is, the present invention aims to recover sulfur poisoning of the exhaust purification device 30 (S regeneration), or to incinerate and remove PM collected by the exhaust purification device 30 (PM regeneration) in the exhaust gas. The present invention can also be applied when fuel is added.

  In the present embodiment, the fuel addition valve 52 is used to add fuel to the exhaust gas. However, the present invention is not limited to this. That is, the present invention is also applicable to the case where fuel is added to the exhaust gas by performing so-called post injection, in which fuel is additionally injected from the in-cylinder injector 32 after combustion in the cylinder is completed. is there.

  Further, in the present embodiment, the exhaust gas is stirred in the turbine 14b by driving the electric motor 14d to increase the rotational speed of the turbocharger 14, but the present invention is limited to this. is not. That is, in the present invention, a stirring mechanism for stirring the exhaust gas may be provided separately from the supercharger, and the exhaust gas may be stirred using the stirring mechanism.

  In the present embodiment, the exhaust throttle is reduced by reducing the opening of the exhaust throttle valve 54 during idle operation. However, in the present invention, the opening of the variable nozzle 14c of the turbocharger 14 is reduced. By doing so, exhaust throttling may be performed. In the present invention, exhaust throttling during idling may not be performed.

  Moreover, although this embodiment demonstrated the case where this invention was applied to the control apparatus of the diesel engine 2, this invention is applicable also to the control apparatus of spark ignition internal combustion engines, such as a gasoline engine.

  In the first embodiment described above, the turbocharger is provided with the fuel addition valve 52 as the “fuel addition means” in the first invention and the exhaust throttle valve 54 as the “exhaust throttle means” in the fifth invention. The machine 14 corresponds to the “supercharger with electric motor” in the sixth aspect of the invention, and the electric motor 14d corresponds to the “electric motor” in the sixth aspect of the invention. Further, the “stirring means” in the first and sixth inventions is realized by the ECU 70 forcibly increasing the rotational speed of the turbocharger 14 by the electric motor 14d.

Embodiment 2. FIG.
Next, the second embodiment of the present invention will be described with reference to FIG. 4 and FIG. 5. The description will focus on the differences from the first embodiment described above, and the same matters will be described. Simplify or omit.

[Features of Embodiment 2]
FIG. 4 is a timing chart showing an operation signal of the fuel addition valve 52 and an operation signal of the electric motor 14d (MAT) when fuel is injected from the fuel addition valve 52 during the idling operation in the present embodiment. As shown in FIG. 4, in this embodiment, the operation signal of the electric motor 14d is turned on prior to the timing when the operation signal of the fuel addition valve 52 is turned on. Thereby, before the fuel injection from the fuel addition valve 52 is started, the rotational speed of the electric motor 14d, that is, the rotational speed of the turbine 14b can be made sufficiently high in advance. Therefore, the exhaust gas can be sufficiently stirred immediately after the start of fuel injection from the fuel addition valve 52. For this reason, the fuel added to the exhaust gas can be made more uniform.

[Specific Processing in Second Embodiment]
FIG. 5 is a flowchart of a routine executed by the ECU 70 in the present embodiment in order to realize the above function. In FIG. 5, the same steps as those shown in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  The routine shown in FIG. 5 is the same as the routine shown in FIG. 2 except that step 108 is replaced with step 122 and step 124 is added between steps 118 and 120.

  In step 122 of the routine shown in FIG. 5, first, as in step 108 of the routine shown in FIG. 2, the required value γ of the MAT rotation speed EMATREV is calculated based on the required value β of the fuel addition amount QADNOX. Further, the required value t of the fuel addition delay time MATPRE [seconds] is calculated based on the required value β of the fuel addition amount QADNOX. The fuel addition delay time MATPRE is the difference between the timing at which the operation of the electric motor 14d is started and the timing at which fuel injection is started from the fuel addition valve 52, as shown in FIG. In the present embodiment, the required value t of the fuel addition delay time MATPRE is set to a longer time as the required value β of the fuel addition amount QADNOX is larger.

  In the routine shown in FIG. 5, when it is recognized in step 118 that the fuel addition permission flag exnoxrd is ON, the required value t of the fuel addition delay time MATPRE calculated in step 122 has elapsed. After waiting for this (step 124), fuel injection from the fuel addition valve 52 is started (step 120).

  As described above, according to the present embodiment, before the fuel injection from the fuel addition valve 52 is started, the rotational speed of the turbine 14b can be made sufficiently high in advance. Therefore, the exhaust gas containing the added fuel can be sufficiently stirred immediately after the start of fuel injection from the fuel addition valve 52. For this reason, the fuel added to the exhaust gas can be made more uniform.

  Further, according to the routine processing shown in FIG. 5, the fuel addition delay time MATPRE can be lengthened as the fuel addition amount QADNOX increases. That is, as the fuel addition amount QADNOX increases, the operation of the electric motor 14d can be started at an earlier timing than the fuel injection start timing from the fuel addition valve 52. For this reason, as the fuel addition amount QADNOX increases, the rotational speed of the turbine 14b at the fuel addition start time can be increased. Therefore, even when the fuel addition amount QADNOX is large, the added fuel can be reliably diffused into the exhaust gas and can be made sufficiently uniform.

Embodiment 3 FIG.
Next, the third embodiment of the present invention will be described with reference to FIG. 6 to FIG. 10. The description will focus on differences from the above-described embodiment, and the description of the same matters will be simplified. Or omit.

  FIG. 6 is a diagram for explaining a system configuration according to the third embodiment of the present invention. The system shown in FIG. 6 is a hybrid system that drives the drive shaft 82 of the vehicle by combining the output of the diesel engine 2 and the output of the motor (electric motor) 80. This hybrid system further includes a motor 80, a power distribution and integration mechanism 84, a generator 86, an inverter 88, and a battery 90 in addition to the system shown in FIG.

  The power distribution and integration mechanism 84 is composed of a planetary gear mechanism. The sun gear of the power distribution and integration mechanism 84 is connected to the generator 86. The planetary carrier of the power distribution and integration mechanism 84 is connected to the crankshaft of the diesel engine 2. The ring gear of the power distribution and integration mechanism 84 is connected to the motor 80 and is also connected to the drive shaft 82 of the vehicle via the transfer 92.

  The power distribution and integration mechanism 84 can bisect the power of the diesel engine 2 and transmit it to the generator 86 and the drive shaft 82. The power distribution and integration mechanism 84 can integrate the power of the diesel engine 2 and the power of the motor 80 and transmit the power to the drive shaft 82.

  Each of the motor 80 and the generator 86 is configured as a known synchronous generator motor that can be driven as a generator and can be driven as a motor. In such a hybrid system, the battery 90 can be charged with the electric power generated by the generator 86 via the inverter 88. In addition, the electric energy stored in the battery 90 can be supplied to the motor 80 via the inverter 88 to drive the motor 80. Further, the motor 80 can be driven by supplying the electric power generated by the generator 86 to the motor 80 via the inverter 88.

  In such a hybrid system, the diesel engine 2 does not perform idling operation in principle. Therefore, in the present embodiment, rich spike control is performed during light load operation of the diesel engine 2. At that time, when adding fuel from the fuel addition valve 52 to the exhaust gas, as in the first embodiment, the motor 14d is operated to increase the MAT rotation speed, thereby stirring the exhaust gas and adding fuel. Is controlled to diffuse uniformly. At this time, the supercharging pressure PIM also increases as the MAT speed increases.

  FIG. 7 is a diagram showing the relationship between the supercharging pressure PIM and the engine load (engine torque) ELD [Nm] when the engine speed NE and the fuel injection amount QFIN are constant. As shown in this figure, when the engine speed NE and the fuel injection amount QFIN are constant, the engine load ELD increases as the boost pressure PIM increases.

  FIG. 8 shows a vehicle-side transmission system load (vehicle-side transmission system torque) TLD [Nm], an engine load ELD, and a motor 80 that are transmitted to the vehicle-side driving force transmission system during light load operation of the diesel engine 2. It is a figure which shows the relationship with the load (torque) MLD [Nm]. As shown in this figure, during a light load operation of the diesel engine 2, the engine load ELD and the motor load MLD are added together and transmitted to the drive shaft 82 as a vehicle side transmission system load TLD.

  In FIG. 8, the left bar graph indicates a case where the electric motor 14 d of the turbocharger 14 is not operating, and the left bar graph indicates a case where the electric motor 14 d of the turbocharger 14 is operating. Yes. As described above, the supercharging pressure PIM increases when the electric motor 14d is activated along with the execution of the rich spike control. As a result, the engine load ELD increases as shown by the change from the left bar graph to the right bar graph. In this case, if the motor load MLD remains constant and the engine load ELD increases, the vehicle-side transmission system load TLD increases accordingly. For this reason, excessive torque exceeding the driver's expectation is transmitted to the drive shaft 82, and the driver easily feels uncomfortable.

  Therefore, in this embodiment, as shown in FIG. 8, when the rich spike control is executed, if the engine load ELD increases with the start of the operation of the electric motor 14d, the motor load MLD is decreased to reduce the vehicle side transmission. Control was performed so that the light load TLD was kept constant.

[Specific Processing in Embodiment 3]
FIG. 9 is a flowchart of a routine executed by the ECU 70 in the present embodiment in order to realize the above function. In the present embodiment, it is assumed that the routine shown in FIG. 9 is executed together with the routine shown in FIG. 2 or FIG.

  According to the routine shown in FIG. 9, first, the values of the engine speed NE, the fuel injection amount QFIN, the supercharging pressure PIM, the vehicle side transmission system load TLD, the motor load MLD, and the engine load ELD are acquired (step). 130). The supercharging pressure PIM is detected by a supercharging pressure sensor 74. Further, each value of the vehicle-side transmission system load TLD, the motor load MLD, and the engine load ELD can be detected or estimated by a known method.

Subsequently, it is determined whether or not the MAT operation flag exmat is ON (step 132). When the MAT operation flag exmat is OFF, it can be determined that the motor 14d is not operating. In this case, since it is not necessary to perform the processing after step 134, the processing after step 130 is executed again. On the other hand, when the MAT operation flag exmat is ON, it can be determined that the electric motor 14d is operating. In this case, it is next determined whether or not the engine speed NE and the fuel injection amount QFIN have changed (step 134). Specifically, whether the engine speed NE _{n + 1} and the fuel injection amount QFIN _{n + 1} in the current ECU calculation cycle are the same as the engine speed NE _n and the fuel injection amount QFIN _n in the previous ECU calculation cycle. Whether it is determined.

  If it is determined in step 134 that at least one of the engine speed NE and the fuel injection amount QFIN has changed, it can be determined that the driver intends to accelerate or decelerate the vehicle. In this case, it is not necessary to keep the vehicle-side transmission system load TLD constant. Therefore, in this case, the processing after step 130 is executed again.

On the other hand, if it is determined in step 134 that neither the engine speed NE nor the fuel injection amount QFIN has changed, the motor load MLD is decreased to keep the vehicle-side transmission system load TLD constant. The process is executed (step 136). Specifically, the motor 80 is controlled so that the motor load MLD becomes a value calculated by the following equation.
MLD _{n + 1} = MLD _n −ε × (PIM _{n + 1} −PIM _n ) (1)

In the above equation (1), MLD _{n + 1} and PIM _{n + 1} are respectively the motor load MLD and the supercharging pressure PIM in the current ECU calculation cycle, and MLD _n and PIM _n are respectively the previous ECU calculation. The motor load MLD and the supercharging pressure PIM in the cycle. Further, ε is a supercharging pressure difference correction coefficient. FIG. 10 is a map for determining the supercharging pressure difference correction coefficient ε based on the engine speed NE and the fuel injection amount QFIN. As shown in this figure, the supercharging pressure difference correction coefficient ε is smaller as the engine speed NE is lower and the fuel injection amount QFIN is smaller. Conversely, the engine speed NE is higher and the fuel injection amount QFIN is smaller. The greater the number, the greater the value.

According to the process of step 136, the motor side transmission system load TLD is kept constant by absorbing the increase in the engine load ELD accompanying the increase in supercharging pressure (PIM _{n + 1} −PIM _n ). The load MLD can be accurately controlled.

Following the processing of step 136, it is determined whether or not the vehicle-side transmission system load TLD is kept constant (step 138). That is, the vehicle-side transmission system load TLD _{n + 1} in the current ECU calculation cycle, whether the same as the vehicle-side transmission system load TLD _n in the preceding ECU calculation cycle is determined. As a result, when it is recognized that the vehicle-side transmission system load TLD is kept constant, the control of this routine is ended.

  As described above, according to the present embodiment, when the motor 14d is operated for the purpose of stirring and uniformly diffusing the fuel added to the exhaust gas, the supercharging pressure PIM increases. An increase in engine torque can be absorbed by decreasing the torque of the motor 80. For this reason, the vehicle-side transmission system load TLD can be kept constant, and an increase in the vehicle-side transmission system load TLD unintended by the driver can be reliably prevented. Therefore, it is surely avoided that the driver feels uncomfortable, and good drivability is obtained.

  In this embodiment, as described above, the increase in engine torque is absorbed by decreasing the torque of the motor 80, but the present invention is not limited to this. For example, in the present invention, the increase in engine torque is absorbed by increasing the amount of power generated by the generator 86 and the amount of charge to the battery 90, and the vehicle side transmission system load TLD is controlled to be kept constant. good.

  In the third embodiment described above, the motor 80 corresponds to “another prime mover” in the seventh invention. Further, the “driving force change suppressing means” according to the seventh aspect of the present invention is implemented by the ECU 70 executing the routine shown in FIG.

It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a figure which shows the relationship between fuel addition amount and MAT rotation speed. It is a timing chart showing the operation signal of a fuel addition valve, and the operation signal of an electric motor in Embodiment 2 of the present invention. It is a flowchart of the routine performed in Embodiment 2 of this invention. It is a figure for demonstrating the system configuration | structure of Embodiment 3 of this invention. It is a figure which shows the relationship between a supercharging pressure and an engine load. It is a figure which shows the relationship between a vehicle side transmission system load, an engine load, and a motor load. It is a flowchart of the routine performed in Embodiment 3 of the present invention. 3 is a map for determining a supercharging pressure difference correction coefficient based on an engine speed and a fuel injection amount.

Explanation of symbols

2 Diesel Engine 4 Intake Manifold 6 Exhaust Manifold 8 Intake Passage 10 Exhaust Passage 12 Air Cleaner 14 Turbo Supercharger 14a Compressor 14b Turbine 14c Variable Nozzle 14d Electric Motor 16 Speed Sensor 17 Intercooler 18 Switching Valve 22 Intake Throttle Valve 24 EGR Pipe 26 EGR Cooler 28 EGR valve 30 Exhaust gas purification device 32 In-cylinder injector 34 Common rail 36 Supply pump 50 Bypass pipe 52 Fuel addition valve 54 Exhaust throttle valve 70 ECU
74 Supercharging pressure sensor 76 Air flow meter 78 Crank angle sensor 80 Motor 82 Drive shaft 84 Power distribution and integration mechanism 86 Generator

Claims (7)

Fuel addition means for adding fuel to the exhaust gas of the internal combustion engine;
Agitation means for agitating exhaust gas in an exhaust passage downstream of the fuel addition means when fuel is added by the fuel addition means at idle or light load;
A control device for an internal combustion engine, comprising:   2. The control apparatus for an internal combustion engine according to claim 1, wherein as the amount of fuel added by the fuel adding means increases, the stirring by the stirring means is strengthened.   The control device for an internal combustion engine according to claim 1 or 2, wherein the operation of the agitation means is started prior to the timing when the fuel addition means starts to add fuel.   4. The control of an internal combustion engine according to claim 3, wherein the greater the amount of fuel added by the fuel addition means, the earlier the operation start timing of the stirring means is made relative to the fuel addition start timing of the fuel addition means. apparatus.   The control apparatus for an internal combustion engine according to any one of claims 1 to 4, further comprising exhaust throttle means for performing exhaust throttle at idle or light load. The internal combustion engine has a supercharger with an electric motor,
The internal combustion engine control according to any one of claims 1 to 5, wherein the agitating means agitates the exhaust gas by forcibly increasing the rotational speed of the supercharger by the electric motor. apparatus. A hybrid system that drives the vehicle using both the output of the internal combustion engine and the output of another prime mover;
In order to suppress a change in driving force transmitted to the vehicle when the output of the internal combustion engine is increased by increasing the supercharging pressure while the electric motor is operated to stir the exhaust gas while the vehicle is running Driving force change suppression means for controlling the hybrid system;
The control apparatus for an internal combustion engine according to claim 6, further comprising:

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