JP4591165B2 - Exhaust gas purification system for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust gas purification system for an internal combustion engine, and more particularly to an exhaust gas purification system for an internal combustion engine that includes a particulate filter that collects particulate matter in the exhaust gas.

  In an exhaust gas purification system for an internal combustion engine equipped with a particulate filter (hereinafter simply referred to as a filter) that collects particulate matter (hereinafter referred to as PM) in exhaust gas, the filter is heated to increase the temperature of the filter. Filter regeneration control is performed to oxidize and remove the collected PM.

  Further, in the exhaust gas purification system for an internal combustion engine provided with such a filter, when further provided with an automatic idling stop device that automatically stops idling when a predetermined condition is satisfied, the predetermined condition is satisfied. In addition, there is known a technique for prohibiting automatic idling by an automatic idling stop device when filter regeneration control is being executed (see, for example, Patent Document 1).

  Further, in an internal combustion engine equipped with a NOx adsorption catalyst that adsorbs NOx when the air-fuel ratio of the exhaust is lean and reduces the adsorbed NOx when the air-fuel ratio of the exhaust is rich, the air-fuel ratio of the exhaust is made stoichiometric or rich. Thus, a technology for prohibiting the idling stop of the internal combustion engine is known during the sulfur poisoning release process for releasing the sulfur poisoning of the NOx adsorption catalyst (see, for example, Patent Document 2).

JP 2003-278575 A JP 2004-278465 A JP 2004-263578 A

  In an exhaust gas purification system for an internal combustion engine provided with a filter, when the operation state of the internal combustion engine shifts to an idle operation state during execution of the filter regeneration control, the temperature of the exhaust gas exhausted from the internal combustion engine decreases, and thus the trapped air is collected. It may be difficult to raise the temperature of the filter to a temperature at which PM can be oxidized. Further, when the operation state of the internal combustion engine shifts to the idle operation state, the flow rate of the exhaust gas decreases, so that the amount of oxygen supplied to the filter may decrease. These may make it difficult to oxidize PM in the filter, that is, it may be difficult to remove PM from the filter. Conversely, when the operating state of the internal combustion engine shifts to the idle operating state and the flow rate of the exhaust gas decreases, the amount of heat removed from the filter by the exhaust gas (hereinafter referred to as the amount of heat removed) decreases. There is also a risk of temperature rise.

  The present invention has been made in view of the above problems, and in an exhaust gas purification system for an internal combustion engine equipped with a filter, PM can be more efficiently removed from the filter while suppressing excessive temperature rise of the filter. It is an object to provide a possible technology.

  The present invention stops the execution of the filter regeneration control and the internal combustion engine if the idle transition condition, which is the condition for shifting the operation state of the internal combustion engine to the idle operation, is satisfied when the filter regeneration control is being performed. The operation is stopped.

More specifically, the exhaust gas purification system for an internal combustion engine according to the present invention is:
A particulate filter provided in an exhaust passage of the internal combustion engine and collecting particulate matter in the exhaust;
Regeneration control execution means for performing filter regeneration control for oxidizing and removing particulate matter collected by the particulate filter by raising the temperature of the particulate filter;
Automatic stop means for automatically stopping the operation of the internal combustion engine,
When filter regeneration control is being executed by the regeneration control execution means, if an idle transition condition that is a condition for shifting the operation state of the internal combustion engine to idle operation is satisfied, execution of the filter regeneration control is stopped, The operation of the internal combustion engine is automatically stopped by the automatic stop means.

  When the operating state of the internal combustion engine shifts to idle operation, the temperature of the exhaust discharged from the internal combustion engine decreases. Further, since the flow rate of the exhaust gas flowing into the filter is lowered, the amount of heat taken away by the exhaust gas is reduced.

  However, in the present invention, when the idle transition condition is satisfied while the filter regeneration control is being executed, the execution of the filter regeneration control is stopped and the operation of the internal combustion engine is automatically stopped. Thereby, the inflow of exhaust gas to the filter is suppressed. That is, the exhaust gas whose temperature has decreased due to the operation state of the internal combustion engine shifting to the idle operation is suppressed from flowing into the filter. Therefore, it is possible to suppress the temperature drop of the filter until the internal combustion engine is restarted. Thereby, after the internal combustion engine is restarted, the temperature of the filter can be raised more quickly to a temperature at which the collected PM can be oxidized. That is, the filter regeneration control can be restarted more quickly. Further, when the inflow of exhaust gas to the filter is suppressed, the supply of oxygen to the filter is suppressed. Therefore, rapid oxidation of PM in the filter can be suppressed, and thus excessive temperature rise of the filter can be suppressed.

  Therefore, according to the present invention, it is possible to more efficiently remove PM from the filter while suppressing excessive temperature rise of the filter.

  In the present invention, the NOx storage reduction catalyst (hereinafter simply referred to as NOx catalyst) provided in the exhaust passage or carried by the filter, and the ambient atmosphere of the NOx catalyst by reducing the air-fuel ratio of the exhaust. An internal combustion engine is operated by a reduction control execution means for executing an oxide reduction control for reducing and releasing the oxide held in the NOx catalyst, and an automatic stop means when an idle transition condition is satisfied. It may further comprise idle stop control execution means for executing idle stop control for automatically stopping. In this case, if the idle shift condition is satisfied when the reduction control is executed by the reduction control execution means, the operation stop of the internal combustion engine by the automatic stop means is prohibited and the operation state of the internal combustion engine is shifted to the idle operation. Further, the execution of the reduction control by the reduction control execution means may be continued.

  The NOx catalyst is a catalyst that retains NOx in the exhaust when the ambient atmosphere is an oxidizing atmosphere, and reduces and releases the retained NOx when the ambient atmosphere is a reducing atmosphere. This NOx catalyst retains SOx in the exhaust gas when the ambient atmosphere is an oxidizing atmosphere, and reduces and releases the retained SOx when the ambient atmosphere is a reducing atmosphere, like NOx. The oxidizing atmosphere is a state where the air-fuel ratio is relatively high, and the reducing atmosphere is a state where the air-fuel ratio is relatively low and a reducing agent is present. Further, when reducing SOx from the NOx catalyst, the temperature of the NOx catalyst needs to be higher than when NOx is reduced.

In the above configuration, when the oxide such as NOx or SOx held in the NOx catalyst is reduced / released, the oxide reduction control is executed by the reduction control execution means. Here, when the operating state of the internal combustion engine shifts to the idle operation, the flow rate of the exhaust gas decreases, so the amount of oxygen supplied to the filter decreases. That is, the amount of oxygen supplied to the NOx catalyst is also reduced. Therefore, it becomes easy to reduce the air-fuel ratio around the NOx catalyst. That is, when the operating state of the internal combustion engine is an idle operation, the atmosphere around the NOx catalyst can be more easily changed to a reducing atmosphere.

  Therefore, in the above configuration, when the idle transition condition is satisfied when the internal combustion engine is in a normal operation state, the idle stop control is executed by the idle stop control execution means, that is, the internal stop engine is automatically operated by the automatic stop means. However, if the idle transition condition is satisfied when the oxide reduction control is being executed, the operation of the internal combustion engine by the automatic stop means is prohibited. Then, the operation state of the internal combustion engine is shifted to the idle operation and the execution of the reduction control is continued.

  Thereby, the oxide held by the NOx catalyst can be reduced and released more efficiently.

  In the present invention, the catalyst having an oxidation function may be provided in the exhaust passage on the upstream side of the filter or may be carried on the filter. Further, it may further comprise a catalyst temperature increase control execution means for executing catalyst temperature increase control for increasing the temperature of the exhaust gas by raising the temperature of the catalyst.

  When the catalyst having an oxidation function is provided as described above, the regeneration control execution means raises the temperature of the filter by supplying a reducing agent to the catalyst that is at or above the activation temperature when executing the filter regeneration control. Let When a reducing agent is supplied to a catalyst having an activation temperature or higher, the reducing agent is oxidized in the catalyst, thereby generating oxidation heat. The temperature of the filter can be increased by this oxidation heat.

  As described above, when the regeneration control execution means is for raising the temperature of the filter by supplying a reducing agent to the catalyst, the internal combustion engine is stopped after the operation of the internal combustion engine is stopped by the automatic stop means. When the temperature of the catalyst is equal to or higher than the activation temperature when restarted, the supply of the reducing agent to the catalyst may be started by the regeneration control execution means simultaneously with the restart of the internal combustion engine. In this case, since the reducing agent is oxidized in the catalyst and the temperature of the filter is raised, the execution of the filter regeneration control is started again. That is, the filter regeneration control can be restarted more quickly after the internal combustion engine is restarted.

  On the other hand, if the temperature of the catalyst is lower than the activation temperature when the internal combustion engine is restarted after the operation of the internal combustion engine is stopped by the automatic stop means as described above, the internal combustion engine is restarted. At the same time, even if the supply of the reducing agent to the catalyst by the regeneration control execution means is started, the reducing agent is not oxidized in the catalyst, so the temperature of the filter does not increase. Therefore, in this case, the catalyst temperature increase control may be started by the temperature increase control execution means simultaneously with the restart of the internal combustion engine. Then, when the catalyst temperature rises to the activation temperature or higher by the catalyst temperature increase control, supply of the reducing agent to the catalyst by the regeneration control execution means may be started.

  According to the present invention, in an exhaust gas purification system for an internal combustion engine equipped with a filter, PM can be more efficiently removed from the filter while suppressing excessive temperature rise of the filter.

Hereinafter, specific embodiments of an exhaust gas purification system for an internal combustion engine according to the present invention will be described with reference to the drawings.

<Schematic configuration of exhaust system of internal combustion engine>
Here, a case where the present invention is applied to a diesel engine for driving a vehicle will be described as an example. FIG. 1 is a diagram showing a schematic configuration of an exhaust system of an internal combustion engine according to the present embodiment.

  The internal combustion engine 1 is a diesel engine for driving a vehicle. An intake passage 4 and an exhaust passage 2 are connected to the internal combustion engine 1. The exhaust passage 2 is provided with a filter 3 that collects PM contained in the exhaust. This filter 3 carries a NOx catalyst. An oxidation catalyst 6 is provided in the exhaust passage 2 upstream of the filter 3. A fuel addition valve 5 is provided in the exhaust passage 2 upstream of the oxidation catalyst 6 to add fuel as a reducing agent into the exhaust.

  An upstream temperature sensor 7 for outputting an electrical signal corresponding to the exhaust temperature and a downstream temperature are provided in the exhaust passage 2 downstream from the oxidation catalyst 6 and upstream from the filter 3 and the exhaust passage 2 downstream from the filter 3. Each sensor 8 is provided. An air-fuel ratio sensor 11 that outputs an electrical signal corresponding to the air-fuel ratio of the exhaust gas is provided in the exhaust passage 2 downstream of the oxidation catalyst 6 and upstream of the filter 3. Further, the exhaust passage 2 is provided with a differential pressure sensor 9 that outputs an electrical signal corresponding to the pressure difference in the exhaust passage 2 before and after the filter 3.

  The internal combustion engine 1 configured as described above is provided with an electronic control unit (ECU) 10 for controlling the internal combustion engine 1. The ECU 10 is a unit that controls the operation state of the internal combustion engine 1 in accordance with the operation conditions of the internal combustion engine 1 and the request of the driver. The ECU 10 is electrically connected to an upstream temperature sensor 7 and a downstream temperature sensor 8, an air-fuel ratio sensor 11, a differential pressure sensor 9, and an accelerator opening sensor 12 that outputs an electric signal corresponding to the accelerator opening. ing. These output signals are input to the ECU 10.

  Then, the ECU 10 estimates the temperature of the oxidation catalyst 6 based on the output value of the upstream temperature sensor 7 and estimates the temperature of the filter 3 based on the output value of the downstream temperature sensor 8. Further, the amount of PM trapped in the filter 3 is estimated from the output value of the differential pressure sensor 9. Further, the ECU 10 is electrically connected to the fuel injection valve and the fuel addition valve 5 of the internal combustion engine 1 and can control them.

<Filter regeneration control>
Here, the filter regeneration control according to the present embodiment will be described. In this embodiment, when the amount of collected PM in the filter 3 is equal to or greater than the specified amount of collection, execution of filter regeneration control is started to oxidize and remove the PM collected by the filter.

  Here, the specified trapped amount is a PM that can be determined that if the operating state of the internal combustion engine 1 is a normal operating state, the possibility that the filter 3 will overheat due to heat generated when the PM is oxidized is low. The value is equal to or less than the upper limit value of the deposition amount, and is a value determined in advance by experiments or the like.

In the filter regeneration control according to the present embodiment, when the NOx catalyst (hereinafter simply referred to as NOx catalyst) carried on the oxidation catalyst 6 and / or the filter 3 is at an activation temperature or higher, the fuel addition valve 5 is exhausting the exhaust gas. By adding the fuel to the fuel, the fuel is supplied to the oxidation catalyst 6 and / or the NOx catalyst. This fuel is oxidized by the oxidation catalyst 6 and / or the NOx catalyst, and the temperature of the filter 3 is raised by the oxidation heat generated at this time. Then, by controlling the amount of fuel added from the fuel addition valve 5, the temperature of the filter 3 is raised to the target filter temperature, thereby oxidizing and removing the PM collected by the filter 3. The target filter temperature is a temperature at which PM collected by the filter 3 can be oxidized and removed, and deterioration of the filter 3 can be suppressed.

<Control when idle transition condition is satisfied during filter regeneration control>
Next, in the present embodiment, a control routine when an idle transition condition, which is a condition for shifting the operation state of the internal combustion engine 1 to the idle operation, is established during the execution of the filter regeneration control will be described based on the flowchart shown in FIG. To do. This routine is a routine that is executed at regular intervals while the ECU 10 is ON, and is stored in the ECU 10 in advance.

  In this routine, first, in S101, the ECU 10 determines whether or not an idle transition condition is satisfied based on an output value of the accelerator opening sensor 12 or the like. Here, the idle transition condition can be exemplified when the vehicle on which the internal combustion engine 1 is mounted is decelerated or stopped. When an affirmative determination is made in S101, the ECU 10 proceeds to S102, and when a negative determination is made, the ECU 10 once ends the execution of this routine.

  The ECU 10 having proceeded to S102 determines whether or not the filter regeneration control is being executed. If an affirmative determination is made in S102, the ECU 10 proceeds to S103, and if a negative determination is made, the ECU 10 proceeds to S105.

  The ECU 10 having advanced to S103 stops the filter regeneration control by stopping the fuel addition into the exhaust gas by the fuel addition valve 5.

  Next, the ECU 10 proceeds to S104 and stops the operation of the internal combustion engine 1. Thereafter, the ECU 10 once terminates execution of this routine.

  On the other hand, the ECU 10 having advanced to S105 shifts the operation state of the internal combustion engine 1 to the idle operation. Thereafter, the ECU 10 once terminates execution of this routine.

  When the operating state of the internal combustion engine 1 shifts to idle operation, the temperature of the exhaust discharged from the internal combustion engine 1 decreases. Moreover, since the flow rate of the exhaust gas flowing into the filter 3 decreases, the amount of heat taken away by the exhaust gas decreases.

  However, according to the control routine, if the idle transition condition is satisfied when the filter regeneration control is being executed, the execution of the filter regeneration control is stopped and the operation of the internal combustion engine 1 is automatically stopped. . Thereby, the inflow of the exhaust gas to the filter 3 is suppressed (the exhaust gas flow rate can be made substantially zero). That is, the exhaust gas whose temperature has decreased due to the operation state of the internal combustion engine 1 shifting to the idle operation is suppressed from flowing into the filter 3. Therefore, the temperature drop of the filter 3 can be suppressed until the internal combustion engine 1 is restarted. Thereby, after the internal combustion engine 1 is restarted, the temperature of the filter 3 can be raised more rapidly to a temperature at which the collected PM can be oxidized. That is, the filter regeneration control can be restarted more quickly. Further, when the inflow of exhaust gas to the filter 3 is suppressed, the supply of oxygen to the filter 3 is suppressed. Therefore, rapid oxidation of PM in the filter 3 is suppressed, and thus excessive temperature rise of the filter 3 can be suppressed.

  Therefore, according to the present embodiment, PM can be more efficiently removed from the filter 3 while suppressing an excessive temperature rise of the filter 3.

In the filter regeneration control according to the present embodiment, the fuel is supplied to the oxidation catalyst 6 and / or the NOx catalyst by adding fuel into the exhaust gas by the fuel addition valve 5, but in the internal combustion engine 1 after the main fuel injection. The fuel may be supplied to the oxidation catalyst 6 and / or the NOx catalyst by executing the auxiliary fuel injection at this time.

  Further, instead of supplying fuel to the oxidation catalyst 6 and / or the NOx catalyst, an exhaust throttle valve is provided in the exhaust passage 2 to reduce the exhaust flow rate or to delay the injection timing of the main fuel injection in the internal combustion engine 1. The exhaust gas temperature may be raised by making it horn, and thereby the filter 3 may be raised to the target filter temperature.

<Filter regeneration control when the internal combustion engine is restarted>
Next, in the present embodiment, the control routine for restarting the internal combustion engine 1 after stopping the operation of the internal combustion engine 1 that the idle transition condition is satisfied during the execution of the filter regeneration control is shown in the flowchart shown in FIG. Based on Similarly to the above, this routine is also a routine that is executed at regular intervals while the ECU 10 is ON, and is stored in the ECU 10 in advance.

  In this routine, the ECU 10 first determines in S201 whether or not the operation of the internal combustion engine 1 has been automatically stopped during the execution of the filter regeneration control. If an affirmative determination is made in S201, the ECU 10 proceeds to S202, and if a negative determination is made, the ECU 10 once ends the execution of this routine.

  The ECU 10 having proceeded to S202 determines whether or not an engine restart condition for restarting the internal combustion engine 1 is satisfied based on an output value of the accelerator opening sensor 12 or the like. Here, examples of the engine restart condition include a case where there is a request for acceleration of a vehicle on which the internal combustion engine 1 is mounted. If an affirmative determination is made in S202, the ECU 10 proceeds to S203, and if a negative determination is made, the ECU 10 repeats S202.

  The ECU 10 that has advanced to S203 executes the restart of the internal combustion engine 1.

  Next, the ECU 10 proceeds to S204, and determines whether or not the temperature Tcco of the oxidation catalyst 6 and / or the temperature of the filter 3, that is, the temperature Tnsr of the NOx catalyst is equal to or higher than the activation temperature T0. If an affirmative determination is made in S204, the ECU 10 proceeds to S205, and if a negative determination is made, the ECU 10 proceeds to S206.

  In S205, the ECU 10 starts fuel addition by the fuel addition valve 5. That is, execution of filter regeneration control by supplying fuel to the oxidation catalyst 6 and / or the NOx catalyst is resumed. Thereby, the filter regeneration control can be restarted more promptly after the internal combustion engine 1 is restarted. Thereafter, the ECU 10 once terminates execution of this routine.

  On the other hand, in S206, the ECU 10 starts execution of the exhaust gas temperature raising control for increasing the temperature of the exhaust gas discharged from the internal combustion engine 1. Here, as the exhaust gas temperature raising control, control for delaying the execution timing of the main fuel injection in the internal combustion engine 1 can be exemplified. Thereafter, the ECU 10 returns to S204.

<Schematic configuration of exhaust system of internal combustion engine>
Since the schematic configuration of the exhaust system of the internal combustion engine according to the present embodiment is the same as that of the first embodiment, the description thereof is omitted.

<Idle stop control of internal combustion engine>
In the present embodiment, a so-called economy running system is employed, and when the idle transition condition is satisfied, the ECU 10 executes idle stop control in which the internal combustion engine 1 is automatically stopped. Here, the idle transition condition is the same as the idle transition condition according to the first embodiment described above. When the engine restart condition for restarting the internal combustion engine 1 is satisfied after the idle stop control is executed, the internal combustion engine 1 is automatically restarted. Here, the engine restart condition is the same as the engine restart condition according to the first embodiment described above.

<NOx reduction control>
Here, the NOx reduction control according to the present embodiment will be described. In this embodiment, every time the integrated amount of fuel injection by main fuel injection in the internal combustion engine 1 becomes the specified integrated amount, execution of NOx reduction control is started to reduce and release NOx held in the NOx catalyst. Is done.

  Here, the prescribed integrated amount is a value that is smaller than a value that can be determined that the amount of NOx retained in the NOx catalyst is an amount that excessively reduces the exhaust purification capacity of the NOx catalyst, and is determined in advance by experiments or the like. Value.

  In the NOx reduction control according to the present embodiment, the atmosphere around the NOx catalyst is made the reducing atmosphere by adding fuel into the exhaust gas by the fuel addition valve 5. That is, the air-fuel ratio of the exhaust gas flowing into the filter 3 is lowered to the target air-fuel ratio at which NOx held in the NOx catalyst can be reduced, and the fuel is caused to flow into the filter 3. Thereby, NOx held in the NOx catalyst is reduced and released.

<Control when idle transition condition is satisfied during NOx reduction control>
Next, in the present embodiment, a control routine when the idle transition condition is satisfied during the execution of the NOx reduction control will be described based on the flowchart shown in FIG. This routine is a routine that is executed at regular intervals while the ECU 10 is ON, and is stored in the ECU 10 in advance.

  In this routine, the ECU 10 first determines in S301 whether or not an idle transition condition is established based on an output value of the accelerator opening sensor 12 or the like. When an affirmative determination is made in S301, the ECU 10 proceeds to S302, and when a negative determination is made, the ECU 10 once ends the execution of this routine.

  The ECU 10 having proceeded to S302 determines whether or not the NOx reduction control is being executed. If an affirmative determination is made in S302, the ECU 10 proceeds to S303, and if a negative determination is made, the ECU 10 proceeds to S305.

  The ECU 10 having proceeded to S303 prohibits the execution of the idle stop control. That is, the operation stop of the internal combustion engine 1 is prohibited.

  Next, the ECU 10 proceeds to S304, shifts the operation state of the internal combustion engine 1 to the idle operation, and continues the execution of the NOx reduction control. Thereafter, the ECU 10 once terminates execution of this routine.

  On the other hand, the ECU 20 that has proceeded to S305 executes idle stop control. That is, the operation of the internal combustion engine 1 is automatically stopped. Thereafter, the ECU 10 once terminates execution of this routine.

In this embodiment, when the operation state of the internal combustion engine 1 is a normal operation state, that is, when the NOx reduction control is not executed, the idle stop control is executed by the ECU 10 when the idle transition condition is satisfied. . However, when the operating state of the internal combustion engine 1 shifts to the idle operation, the flow rate of the exhaust gas decreases, so the amount of oxygen supplied to the filter 3 decreases. That is, the amount of oxygen supplied to the NOx catalyst is also reduced. Therefore, it becomes easy to reduce the air-fuel ratio around the NOx catalyst. That is, when the operating state of the internal combustion engine 1 is an idle operation, the atmosphere around the NOx catalyst can be more easily changed to a reducing atmosphere.

  Therefore, in the present embodiment, by executing the control routine, if the idle transition condition is satisfied when the NOx reduction control is being performed, the operation stop of the internal combustion engine 1 is prohibited. Then, the operation state of the internal combustion engine 1 is shifted to the idle operation, and the execution of the NOx reduction control is continued.

  Therefore, according to the present embodiment, NOx retained in the NOx catalyst can be reduced and released more efficiently.

  In this embodiment, the case where the idle transition condition is satisfied during the execution of the NOx reduction control has been described. However, the idle transition condition is satisfied during the execution of the SOx reduction control for reducing and releasing SOx held in the NOx catalyst. The same control may be performed also in such a case.

  That is, in the SOx reduction control, the atmosphere around the NOx catalyst needs to be a reducing atmosphere. Therefore, when the idle transition condition is satisfied during the execution of the SOx reduction control, the execution of the idle stop control is prohibited. Then, the operation state of the internal combustion engine 1 is shifted to the idle operation, and the execution of the SOx reduction control is continued.

  According to such control, SOx held in the NOx catalyst can be reduced and released more efficiently.

  Further, in the present embodiment, when a so-called EGR device that allows a part of the exhaust gas to flow into the intake passage 4 from the exhaust passage 2 is provided, the NOx reduction control or the SOx reduction is performed after the internal combustion engine 1 is shifted to the idle operation. When the execution of the control is continued, more exhaust gas may be caused to flow into the exhaust passage 2 by the EGR device. As a result, the air-fuel ratio of the exhaust can be more easily lowered, and unburned fuel components in the exhaust can be supplied to the oxidation catalyst 6 and the NOx catalyst. As a result, the unburned fuel component in the exhaust is oxidized by the oxidation catalyst 6 and the NOx catalyst, and the temperature reduction of the NOx catalyst can be suppressed by the oxidation heat generated at that time.

The figure which shows schematic structure of the exhaust system of the internal combustion engine which concerns on the Example of this invention. 6 is a flowchart illustrating a control routine when an idle transition condition is satisfied during execution of filter regeneration control in Embodiment 1 of the present invention. 3 is a flowchart illustrating a control routine for restarting the internal combustion engine after stopping the operation of the internal combustion engine during execution of the filter regeneration control in the first embodiment of the present invention. In Example 2 of this invention, the flowchart which shows a control routine when an idle transfer condition is satisfied during execution of NOx reduction control.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Exhaust passage 3 ... Particulate filter 5 ... Fuel addition valve 6 ... Oxidation catalyst 7 ... Upstream temperature sensor 8 ... Downstream temperature sensor 9 ..Differential pressure sensor 10

Claims (3)

A particulate filter provided in an exhaust passage of the internal combustion engine and collecting particulate matter in the exhaust;
Regeneration control execution means for performing filter regeneration control for oxidizing and removing particulate matter collected by the particulate filter by raising the temperature of the particulate filter;
Automatic stop means for automatically stopping the operation of the internal combustion engine,
When filter regeneration control is being executed by the regeneration control execution means, if an idle transition condition that is a condition for shifting the operation state of the internal combustion engine to idle operation is satisfied, execution of the filter regeneration control is stopped, An exhaust purification system for an internal combustion engine, wherein the operation of the internal combustion engine is automatically stopped by the automatic stop means. An NOx storage reduction catalyst provided in the exhaust passage or carried on the particulate filter;
By reducing the air-fuel ratio of the exhaust, the ambient atmosphere of the NOx storage reduction catalyst is made a reducing atmosphere, thereby executing oxide reduction control for reducing and releasing the oxide held in the NOx storage reduction catalyst. Reduction control execution means;
Idle stop control execution means for executing idle stop control for automatically stopping the operation of the internal combustion engine by the automatic stop means when the idle transition condition is satisfied,
If the idle transition condition is satisfied when the reduction control is being executed by the reduction control execution means, the automatic stop means prohibits the operation of the internal combustion engine from being stopped, and the operation state of the internal combustion engine is set to idle operation. 2. The exhaust gas purification system for an internal combustion engine according to claim 1, wherein the reduction control by the reduction control execution means is continued. A catalyst having an oxidation function provided in the exhaust passage upstream of the particulate filter or carried on the particulate filter;
Catalyst temperature increase control execution means for executing catalyst temperature increase control for increasing the temperature of the catalyst by increasing the temperature of the exhaust, and
When the regeneration control execution means executes filter regeneration control, when the particulate filter is heated by supplying a reducing agent to the catalyst that is at an activation temperature or higher,
After the operation of the internal combustion engine is stopped by the automatic stop means, when the internal combustion engine is restarted, if the temperature of the catalyst is equal to or higher than the activation temperature, the regeneration control is performed simultaneously with the restart of the internal combustion engine. The execution means starts supplying the reducing agent to the catalyst,
After the operation of the internal combustion engine is stopped by the automatic stop means, when the temperature of the catalyst is lower than the activation temperature when the internal combustion engine is restarted, the temperature increase is performed simultaneously with the restart of the internal combustion engine. 2. The exhaust gas purification system for an internal combustion engine according to claim 1, wherein the catalyst temperature raising control is started by the control execution means.

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