JP2006152870A - Exhaust emission control system of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To oxidize and remove PM accumulated on a filter, while inhibiting degradation of exhaust gas emission and fuel-economy in an exhaust emission control system of an internal combustion engine provided with the filter in the exhaust gas passage of the engine for collecting PM in the exhaust gas. <P>SOLUTION: In the exhaust emission control system, a catalyst having the function of oxidation is placed in the exhaust gas passage upstream of the filter, or it is carried on the filter. The filter is regenerated by supplying unburned fuel to the catalyst. If the adhesion of unburned fuel on the passage reaches at least a specified amount in the filter-regeneration control, an exhaust gas temperature-raising control is started so at to raise the temperature of exhaust gas by raising the engine load. Thereafter, the exhaust gas temperature-raising control is stopped in the timing when the amount of adhesion of unburned fuel on the passage, which increases again upon stop of the exhaust gas temperature-raising control, becomes at most the specified amount of adhesion when the filter regeneration control is stopped. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an exhaust gas purification system for an internal combustion engine provided with a particulate filter that is provided in an exhaust passage of the internal combustion engine and collects particulate matter in the exhaust gas.

  In an exhaust gas purification system for an internal combustion engine provided with a particulate filter (hereinafter simply referred to as a filter) that is provided in an exhaust passage of the internal combustion engine and collects particulate matter (hereinafter referred to as PM) in the exhaust gas, By raising the temperature to the target temperature, filter regeneration control for oxidizing and removing PM accumulated on the filter is performed.

Further, in an exhaust gas purification system for an internal combustion engine provided with a filter that is provided in an exhaust passage of the internal combustion engine and collects PM in exhaust gas, when the idling operation state is continued for a predetermined time or longer, the exhaust flow rate is controlled by an exhaust throttle valve. A technique is known in which the temperature of the exhaust gas flowing into the filter is raised by narrowing down (see, for example, Patent Document 1).
JP 2003-286887 A JP 2004-132224 A JP 2003-269147 A JP 2000-8840 A

  In an exhaust gas purification system for an internal combustion engine that is provided in an exhaust passage of the internal combustion engine and includes a filter that collects PM in exhaust gas, the exhaust purification system of the internal combustion engine is provided in the exhaust passage upstream of the filter or is carried by the filter. Some of them further include a catalyst having an oxidation function.

  In the filter regeneration control in such an exhaust purification system, when the catalyst is in an active state, unburned fuel is supplied to the catalyst from the upstream side of the catalyst, and oxidation generated by oxidizing the unburned fuel with the catalyst. The temperature of the filter may be controlled to the target temperature by heat.

  At this time, since unburned fuel is supplied from the upstream side of the catalyst, a part of the unburned fuel may adhere to the inner wall surface of the exhaust passage upstream of the catalyst. If the amount of unburned fuel attached increases excessively, the amount of white smoke discharged into the atmosphere increases excessively, which may lead to deterioration of exhaust emissions.

  Therefore, in the filter regeneration control, there is a case where exhaust temperature raising control is performed in which unburnt fuel is supplied to the catalyst and the exhaust gas is heated by raising the engine load of the internal combustion engine. In this case, since the unburned fuel is supplied to the catalyst in a state where the exhaust gas is heated, the evaporation of the unburned fuel is promoted, and the amount of unburned fuel attached to the inner wall surface of the exhaust passage is reduced.

  However, since such exhaust temperature raising control is executed by increasing the engine load of the internal combustion engine, there is a risk that fuel consumption will be deteriorated.

  The present invention has been made in view of the above problems, and in an exhaust gas purification system for an internal combustion engine provided with a filter provided in an exhaust passage of the internal combustion engine to collect PM in exhaust gas, exhaust emission and deterioration in fuel consumption are achieved. It is an object of the present invention to provide a technique capable of oxidizing and removing PM deposited on a filter while suppressing the above.

  The present invention relates to a filter that is provided in an exhaust passage of an internal combustion engine and collects particulate matter in exhaust gas, and an oxidation device that is provided in an exhaust passage upstream of the filter or that is supported by the filter. A catalyst having a function is provided, and filter regeneration control is executed by supplying unburned fuel to the catalyst. Then, during the execution of the filter regeneration control, when the amount of unburned fuel attached to the inner wall surface of the exhaust passage upstream of the catalyst (hereinafter referred to as the amount of unburned fuel passage attached) becomes equal to or greater than the specified amount of deposit, Execution of the exhaust gas temperature raising control for raising the temperature of the exhaust gas by increasing the engine load of the internal combustion engine is started, thereby reducing the amount of unburned fuel passage adhesion. After that, when the exhaust gas temperature raising control is stopped, the exhaust gas temperature raising control is stopped at a timing when the unburned fuel passage adhesion amount that increases again becomes equal to or less than the prescribed adhesion amount when the filter regeneration control 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 for collecting particulate matter in the exhaust;
A catalyst having an oxidation function, provided in the exhaust passage on the upstream side of the particulate filter, or carried on the particulate filter;
Particulate matter accumulation amount detection means for detecting the accumulation amount of particulate matter in the particulate filter;
Unburned fuel supply means for supplying unburned fuel to the catalyst from the upstream side of the catalyst;
When the temperature of the catalyst is equal to or higher than the activation temperature, unburned fuel is supplied to the catalyst by the unburned fuel supply means, and the particulate filter is generated by oxidation heat generated when the unburned fuel is oxidized by the catalyst. A filter regeneration control execution means for performing a filter regeneration control for oxidizing and removing particulate matter deposited on the particulate filter,
After the execution of the filter regeneration control is started by the filter regeneration control execution means, the filter regeneration control is performed when the particulate matter accumulation amount detected by the particulate matter accumulation amount detection means becomes equal to or less than the target PM accumulation amount. A filter regeneration control stop means for stopping;
An unburned fuel passage adhering amount detection means for detecting an unburned fuel passage adhering amount that is an adhering amount of unburned fuel on the inner wall surface of the exhaust passage upstream of the catalyst during the execution of the filter regeneration control;
When the unburned fuel passage adhering amount detected by the unburned fuel adhering amount detection means exceeds a predetermined adhering amount, exhaust temperature increase control is performed to raise the exhaust temperature by increasing the engine load of the internal combustion engine. Exhaust temperature raising control execution means for starting execution and thereby reducing the amount of unburned fuel passage adhesion,
Exhaust gas that stops the exhaust gas temperature increase control by the exhaust gas temperature increase control unit after the exhaust gas temperature increase control execution unit starts executing the exhaust gas temperature increase control and before the filter regeneration control stop unit stops the filter regeneration control. Temperature rise control stop means,
The exhaust gas temperature increase control stop means is configured such that when the exhaust gas temperature increase control is stopped, the unburned fuel passage adhesion amount increases again when the filter regeneration control is stopped by the filter regeneration control stop means. The exhaust gas temperature raising control is stopped at the following timing.

  Here, the target temperature is a temperature at which PM deposited on the filter can be oxidized and removed and the deterioration of the filter is suppressed. In the filter regeneration control according to the present invention, the temperature of the filter is controlled to the target temperature by controlling the amount of unburned fuel supplied to the catalyst.

  Further, after the execution of the filter regeneration control is started, the filter regeneration control is stopped when the PM accumulation amount in the filter becomes equal to or less than the target PM accumulation amount. Here, the target PM accumulation amount may be a predetermined value and may be a PM accumulation amount that can be determined to have a sufficiently small influence on the operating state of the internal combustion engine.

  In the present invention, the unburned fuel passage adhesion amount is detected during the execution of the filter regeneration control. Then, when the unburned fuel passage adhesion amount becomes equal to or greater than the prescribed adhesion amount, execution of the exhaust gas temperature raising control for raising the temperature of the exhaust gas by starting the engine load of the internal combustion engine is started. Here, the specified adhesion amount may be a predetermined value, and may be an amount in which the amount of white smoke discharged into the atmosphere is equal to or less than the upper limit value of the allowable amount. When the exhaust gas temperature raising control is executed, the evaporation of unburned fuel in the exhaust passage is promoted, so that the amount of unburned fuel passage attached decreases.

  This exhaust temperature raising control is stopped before the filter regeneration control is stopped. Therefore, when the exhaust gas temperature raising control is stopped, the unburned fuel passage adhesion amount increases again until the filter regeneration control is stopped.

  In the present invention, the exhaust gas temperature raising control is stopped at a timing when the unburned fuel passage adhesion amount when the filter regeneration control is stopped becomes equal to or less than the specified adhesion amount. That is, after the exhaust gas temperature raising control is stopped, the unburned fuel passage adhesion amount that is increased again until the filter regeneration control is stopped is reduced while the exhaust gas temperature raising control is being executed. The exhaust gas temperature raising control is stopped at the following timing.

  Thus, by executing the filter regeneration control, the amount of unburned fuel passage adhering to the inner wall surface of the exhaust passage can be suppressed to a specified amount or less, and the execution time of the exhaust gas temperature raising control is made as short as possible. Time can be kept down.

  Therefore, according to the present invention, in an exhaust gas purification system for an internal combustion engine provided with a filter that is provided in an exhaust passage of the internal combustion engine and collects PM in the exhaust gas, accumulation on the filter is suppressed while suppressing deterioration of exhaust emission and fuel consumption. The oxidized PM can be oxidized and removed.

  In the present invention, it is preferable to stop the exhaust gas temperature raising control at the timing when the unburned fuel passage adhesion amount when the filter regeneration control is stopped becomes the specified adhesion amount. That is, after the exhaust gas temperature raising control is stopped, the unburned fuel passage adhesion amount that is increased again until the filter regeneration control is stopped is reduced while the exhaust gas temperature raising control is being executed. It is preferable to stop the exhaust gas temperature raising control at the same timing. According to this, the execution time of the exhaust gas temperature raising control can be suppressed to a shorter time, and as a result, fuel consumption deterioration can be further suppressed.

  In the present invention, the filter that estimates the remaining filter regeneration time that is the time from when the exhaust gas temperature raising control execution unit starts executing the exhaust gas temperature raising control to the time point when the filter regeneration control stopping unit stops the filter regeneration control. Regeneration remaining time estimation means and unburned fuel passage adhesion amount reduction amount estimation for estimating the reduction amount of unburned fuel passage adhesion amount from the start time of exhaust temperature raising control when exhaust temperature raising control is being executed And the unburned fuel in the same amount as the unburned fuel passage adhering amount decrease estimated by the unburned fuel passage adhering amount decrease amount estimating means are stopped by the exhaust temperature raising control stopping means. In this case, an unburned fuel reattachment time estimating means for estimating an unburned fuel reattachment time which is a time taken to adhere again to the inner wall surface of the exhaust passage upstream of the catalyst may be further provided.

  In this case, after execution of the exhaust gas temperature raising control is started by the exhaust gas temperature raising control execution means, the sum of the exhaust gas temperature raising control execution time and the unburned fuel reattachment time coincides with the remaining filter regeneration time. At this point, the exhaust gas temperature raising control stop means may stop the exhaust gas temperature raising control.

As described above, in the present invention, when the exhaust gas temperature raising control is executed during the execution of the filter regeneration control, the unburned fuel passage adhesion amount decreases. After that, when the exhaust gas temperature raising control is stopped, unburned fuel starts to adhere again to the inner wall surface of the exhaust passage upstream of the catalyst, so that the unburned fuel passage adhesion amount increases again.

  Therefore, in the above control, when the exhaust gas temperature raising control is being executed, the reduction amount of the unburned fuel passage adhesion amount from the start time of the exhaust gas temperature raising control execution is estimated, and further, based on the reduction amount. The unburned fuel reattachment time after stopping the exhaust gas temperature raising control is estimated. Here, after the start of the exhaust gas temperature raising control, the decrease amount of the unburned fuel passage adhesion amount increases with the passage of time, and accordingly, the unburned fuel reattachment time also becomes longer.

  Then, when the elapsed time from the start of the exhaust gas temperature raising control, that is, the sum of the exhaust gas temperature raising control execution time and the estimated unburned fuel reattachment time matches the remaining filter regeneration time, The temperature rise control is stopped. That is, the exhaust gas temperature increase control is stopped at a timing such that the time when the unburned fuel reattachment time has elapsed after the exhaust gas temperature increase control stops coincides with the time point when the filter regeneration control is stopped by the filter regeneration control stop means. Is done.

  Therefore, according to such control, the exhaust gas temperature raising control can be stopped at the timing when the unburned fuel passage adhesion amount when the filter regeneration control is stopped becomes the specified adhesion amount.

  In the present invention, the filter regeneration remaining time estimation means is based on the PM accumulation amount in the filter at the start of execution of the exhaust gas temperature increase control, and the PM removal rate from the filter immediately before the start of the exhaust gas temperature increase control. The remaining filter regeneration time may be estimated.

  That is, assuming that the PM removal rate from the start of exhaust gas temperature raising control to the stop point of filter regeneration control is equivalent to the PM removal rate immediately before the start of exhaust gas temperature raising control, The remaining filter regeneration time can be estimated based on the PM accumulation amount at the start of execution of temperature control and the PM removal speed immediately before the start of execution of exhaust temperature increase control.

  Here, the PM removal rate is the amount of PM removed from the filter per unit time.

  Further, in the present invention, the unburned fuel passage adhesion amount decrease amount estimation means is configured to start exhaust gas temperature increase control from the start of execution based on the exhaust temperature in the exhaust passage upstream of the catalyst during execution of the exhaust gas temperature increase control. The amount of decrease in the unburned fuel passage adhesion amount may be estimated.

  Further, in the present invention, when further provided with an inner wall surface temperature detecting means for detecting the inner wall surface temperature of the exhaust passage upstream of the catalyst (hereinafter simply referred to as exhaust passage inner wall surface temperature), the unburned fuel reattachment time. The estimation means includes a reduction amount of the unburned fuel passage adhesion amount estimated by the unburned fuel passage adhesion amount reduction amount estimation means, and an exhaust temperature increase control detected by the inner wall surface temperature detection means at the start of execution of the exhaust gas temperature raising control. The unburned fuel reattachment time may be estimated based on the exhaust passage inner wall surface temperature.

  That is, by assuming that the exhaust passage inner wall surface temperature after stopping the exhaust temperature raising control is equal to the exhaust passage inner wall temperature at the start of execution of the exhaust temperature raising control, the unburned fuel passage adhesion amount decrease estimation means Based on the estimated decrease amount of the unburned fuel passage adhesion amount and the exhaust passage inner wall surface temperature at the start of execution of the exhaust temperature raising control, the unburned fuel reattachment time after stopping the exhaust temperature raising control is estimated. I can do it.

  It should be noted that during execution of the exhaust gas temperature raising control, the PM removal rate may be higher than immediately before the start of the exhaust gas temperature raising control. Therefore, when the filter regeneration remaining time is estimated based on the PM removal rate immediately before the start of the exhaust gas temperature raising control, the actual filter regeneration remaining time may be shorter than the estimated filter regeneration remaining time.

  However, when the actual remaining filter regeneration time is shorter than the estimated remaining filter regeneration time, the unburned fuel passage adhesion amount when the filter regeneration control is stopped is smaller than the prescribed adhesion amount. Therefore, even in the above case, it is unlikely that exhaust emissions will deteriorate.

  In addition, since the exhaust passage inner wall surface temperature rises when exhaust temperature raising control is executed, the exhaust passage inner wall surface temperature after stopping the exhaust temperature raising control is higher than the exhaust passage inner wall surface temperature at the start of exhaust temperature raising control. May be expensive. Therefore, when the unburned fuel reattachment time is estimated based on the exhaust passage inner wall surface temperature at the start of execution of the exhaust gas temperature raising control, the actual unburned fuel reattachment time is the estimated unburned fuel reattachment time. There is a possibility that it is longer.

  However, when the actual unburned fuel reattachment time is longer than the estimated unburned fuel reattachment time, the unburned fuel passage attachment amount when the filter regeneration control is stopped is smaller than the prescribed attachment amount. Therefore, even in the above case, it is unlikely that exhaust emissions will deteriorate.

  In the present invention, when the exhaust throttle valve provided in the exhaust passage downstream of the filter is further provided, the exhaust temperature increase control execution means executes the exhaust temperature increase control by closing the exhaust throttle valve. Alternatively, the exhaust gas temperature raising control stop means may stop the exhaust gas temperature raising control by opening the exhaust throttle valve.

  Here, the closed state of the exhaust throttle valve means that the flow rate of the exhaust is throttled by controlling the exhaust throttle valve in the valve closing direction. Further, opening the exhaust throttle valve means that the exhaust throttle valve has a larger opening than when the exhaust throttle valve is closed, and includes a case where the exhaust throttle valve is fully opened. .

  When the exhaust throttle valve is closed, the engine load of the internal combustion engine increases, and the exhaust temperature increases. On the other hand, when the exhaust throttle valve is opened, the engine load of the internal combustion engine is lower than when the exhaust throttle valve is closed, so that the exhaust temperature is also lowered. That is, when the exhaust throttle valve is opened, the exhaust gas temperature raising control executed by closing the exhaust throttle valve is stopped.

  In the present invention, when it further comprises auxiliary equipment required load control means for controlling the required load of the auxiliary machine driven by the internal combustion engine, the exhaust gas temperature raising control execution means is requested by the auxiliary equipment required load control means. The exhaust temperature raising control may be executed by increasing the load, and the exhaust temperature raising control stopping means stops the exhaust temperature raising control by lowering the required load of the auxiliary equipment by the auxiliary equipment required load control means. May be.

  When the required load of the auxiliary machine is increased, the engine load of the internal combustion engine is increased, so that the exhaust temperature is increased. On the other hand, when the required load of the auxiliary machine is reduced, the engine load of the internal combustion engine is lower than when the required load of the auxiliary machine is increased, and the exhaust temperature is also lowered. That is, when the required load on the auxiliary machine is reduced, the exhaust gas temperature raising control executed by increasing the required load on the auxiliary machine is stopped.

In the present invention, when both the auxiliary required load control means and the exhaust throttle valve provided in the exhaust passage downstream of the filter are provided, the exhaust throttle valve is closed during the filter regeneration control. It is good also as a state. In this case, after the filter regeneration control is executed and the filter temperature becomes equal to or higher than the target temperature, the auxiliary equipment required load control means reduces the required load of the auxiliary equipment until the exhaust temperature raising control is executed. Reduce. Also in this case, the exhaust gas temperature raising control performed during the execution of the filter regeneration control is executed by increasing the required load of the auxiliary machine, and is stopped by reducing the required load of the auxiliary machine.

  According to such control, the internal combustion engine is made by closing the exhaust throttle valve except when the exhaust gas temperature raising control is executed after the filter temperature becomes equal to or higher than the target temperature during the filter control. An increase in the engine load of the engine is suppressed by reducing the required load of the auxiliary machine. Therefore, deterioration of fuel consumption can be suppressed.

  According to the present invention, in an exhaust gas purification system for an internal combustion engine having a filter that is provided in an exhaust passage of the internal combustion engine and collects PM in the exhaust gas, the PM deposited on the filter while suppressing deterioration of exhaust emission and fuel consumption. Can be oxidized and removed.

  Embodiments of an exhaust gas purification system for an internal combustion engine according to the present invention will be described below with reference to the drawings.

<Schematic configuration of internal combustion engine and intake / exhaust system thereof>
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine and its intake / exhaust system according to the present embodiment. The internal combustion engine 1 is a diesel engine for driving a vehicle having four cylinders 2. A piston 3 is slidably provided in the cylinder 2 of the internal combustion engine 1. An intake port 4 and an exhaust port 5 are connected to the combustion chamber in the upper part of the cylinder 2. The openings of the intake port 4 and the exhaust port 5 to the combustion chamber are opened and closed by an intake valve 6 and an exhaust valve 7, respectively. The intake port 4 and the exhaust port 5 are connected to an intake passage 8 and an exhaust passage 9, respectively. The cylinder 2 is provided with a fuel injection valve 10 that directly injects fuel into the cylinder 2.

  The exhaust passage 9 is provided with a filter 11 that collects PM in the exhaust, and an oxidation catalyst 12 is provided upstream of the filter 11. In this embodiment, the oxidation catalyst 12 may be carried by the filter 11 instead of being provided in the exhaust passage 9 upstream from the filter 11. Moreover, the catalyst provided in the position of the oxidation catalyst 12 should just have an oxidation function, for example, a storage reduction type NOx catalyst etc. may be sufficient.

  An exhaust throttle valve 15 that controls the exhaust flow rate is provided in the exhaust passage 9 downstream of the filter 11.

  An upstream exhaust temperature sensor 13 that outputs an electrical signal corresponding to the exhaust temperature in the exhaust passage 9 is provided in the exhaust passage 9 upstream of the oxidation catalyst 12. A downstream exhaust temperature sensor 14 that outputs an electrical signal corresponding to the exhaust temperature in the exhaust passage 9 is provided in the exhaust passage 9 downstream from the oxidation catalyst 12 and upstream from the filter 11. Further, the exhaust passage 9 includes a pressure in the exhaust passage 9 downstream from the oxidation catalyst 12 and upstream from the filter 11 and a pressure in the exhaust passage 9 downstream from the filter 11 and upstream from the exhaust throttle valve 15. A differential pressure sensor 16 for detecting the difference is provided.

  The internal combustion engine 1 configured as described above is provided with an ECU 20 for controlling the internal combustion engine 1. Various sensors such as an upstream exhaust temperature sensor 13, a downstream exhaust temperature sensor 14, and a differential pressure sensor 16 are electrically connected to the ECU 20. Output signals from various sensors are input to the ECU 20. Then, the ECU 20 estimates the temperature of the oxidation catalyst 12 based on the output value of the upstream side exhaust temperature sensor 13 and / or the downstream side exhaust temperature sensor 14. Further, the ECU 20 estimates the PM accumulation amount in the filter 11 based on the output value of the differential pressure sensor 16.

  Further, the fuel injection valve 10 and the exhaust throttle valve 15 are electrically connected to the ECU 20, and these are controlled by the ECU 20. Further, an alternator 17 having the internal combustion engine 1 as a driving force is electrically connected to the ECU 20, and a required load of the alternator 17 is controlled by the ECU 20. In this embodiment, the auxiliary machine according to the present invention includes the alternator 17.

<Filter regeneration control>
Next, filter regeneration control according to the present embodiment will be described. In this embodiment, when the PM accumulation amount in the filter 11 becomes equal to or more than the specified PM accumulation amount Qpm1, the filter 11 is heated to the target temperature Tft in order to oxidize and remove the PM accumulated on the filter 11. The filter regeneration control to be executed is started.

  Here, the specified PM accumulation amount Qpm1 is a predetermined amount that is smaller than an amount in which the pressure in the exhaust passage 9 upstream of the filter 11 may increase excessively. The target temperature Tft is a temperature at which PM deposited on the filter 11 can be oxidized and removed and the deterioration of the filter 11 is suppressed. This target temperature Tft is determined in advance by experiments or the like.

  In the filter regeneration control according to the present embodiment, first, exhaust gas temperature raising control is executed to raise the temperature of the exhaust gas exhausted from the internal combustion engine 1 in order to raise the temperature of the oxidation catalyst 12 to the lower limit value Tact of the activation temperature. Is done.

  The exhaust gas temperature raising control is performed by closing the exhaust throttle valve 15 and reducing the flow rate of the exhaust gas. When the flow rate of the exhaust is throttled by the exhaust throttle valve 15, the engine load of the internal combustion engine 1 increases, so that the temperature of the exhaust is raised. As the exhaust gas temperature rises, the temperature of the oxidation catalyst 12 also rises.

  When the temperature of the oxidation catalyst 12 becomes equal to or higher than the lower limit value Tact of the activation temperature, supply of unburned fuel to the oxidation catalyst 12 is started by executing post fuel injection in the internal combustion engine 1.

  The post fuel injection is performed by executing the auxiliary fuel injection from the fuel injection valve 10 at a timing later than the main fuel injection in the combustion cycle of the internal combustion engine 1 and at a non-ignition timing. Here, the ignition timing is a timing when most of the injected fuel does not ignite when fuel is injected into the cylinder 2 from the fuel injection valve 10.

  When the post fuel injection is performed, the fuel injected by the post fuel injection and discharged from the internal combustion engine 1 in an unburned state (unburned fuel) is supplied to the oxidation catalyst 12. Then, the temperature of the filter 11 is raised by oxidation heat generated when the unburned fuel supplied to the oxidation catalyst 12 is oxidized by the oxidation catalyst 12.

  In this embodiment, when the temperature of the filter 11 becomes equal to or higher than the target temperature Tft after the start of post fuel injection, the exhaust throttle valve 15 is fully opened and the exhaust gas temperature raising control is stopped. During the execution of the subsequent filter regeneration control, the temperature of the filter 11 is controlled to the target temperature Tft by controlling the fuel injection amount by post fuel injection (hereinafter simply referred to as post fuel injection amount).

  In this embodiment, after the start of the filter regeneration control, the filter regeneration control is stopped by stopping the post fuel injection when the PM accumulation amount in the filter 11 becomes equal to or less than the target PM accumulation amount Dpmt. Is done.

<Exhaust temperature rise control during post fuel injection>
In the filter regeneration control according to the present embodiment, when the temperature of the filter 11 becomes equal to or higher than the target temperature Tft, the exhaust gas temperature raising control is stopped, so that unburned fuel evaporates in the exhaust passage 9 upstream of the oxidation catalyst 12. It becomes difficult to be promoted. Therefore, a part of the unburned fuel easily adheres to the inner wall surface of the exhaust passage 9 upstream of the oxidation catalyst 12. If the amount of unburned fuel attached increases excessively, the amount of white smoke discharged into the atmosphere increases excessively, and exhaust emissions may deteriorate.

  Therefore, in the present embodiment, the exhaust throttle valve 15 is set for a certain period during the post fuel injection in order to reduce the amount of unburned fuel passage adhering to the inner wall surface of the exhaust passage 9 upstream of the oxidation catalyst 12. Exhaust temperature raising control is executed by closing the valve.

  Here, the execution start timing and stop timing of the exhaust gas temperature raising control during execution of the post fuel injection according to the present embodiment will be described with reference to FIG. FIG. 2 shows the inner wall surface temperature of the exhaust passage 9 upstream of the oxidation catalyst 12 after the post fuel injection is executed and the temperature of the filter 11 reaches the target temperature Tft in the filter regeneration control (hereinafter simply referred to as the exhaust passage). 5 is a time chart showing changes in PM accumulation amount, unburned fuel passage adhesion amount, and opening degree of the exhaust throttle valve 15 in the filter 12. In the time chart shown in FIG. 2, each horizontal axis represents time t.

  As described above, in the present embodiment, in the filter regeneration control, when the post fuel injection is executed and the temperature of the filter 11 reaches the target temperature Tft, the exhaust throttle valve 15 is fully opened, and the exhaust gas temperature raising control is stopped. The Therefore, after the temperature of the filter 11 reaches the target temperature Tft, the temperature of the exhaust gas flowing in the exhaust passage 9 upstream of the oxidation catalyst 12 decreases, and accordingly, the exhaust passage inner wall surface temperature is shown in FIG. Thus, it gradually decreases with the passage of time. In this embodiment, the exhaust passage inner wall surface temperature is calculated by the ECU 20 based on the output value of the upstream side exhaust temperature sensor 13, the heat capacity of the exhaust passage 9, and the like.

  Further, as shown in FIG. 2, after the temperature of the filter 11 reaches the target temperature Tft, the PM accumulation amount gradually decreases and the unburned fuel passage adhesion amount gradually increases with time. In this embodiment, when the unburned fuel passage adhesion amount becomes equal to or greater than the prescribed adhesion amount Qf1 (time shown by (a) in FIG. 2), the ECU 20 closes the exhaust throttle valve 15 and raises the exhaust gas. Start execution of temperature control. The unburned fuel passage adhesion amount up to the specified adhesion amount Qf1 or more is calculated by the ECU 20 based on the integrated value of the post fuel injection amount, the exhaust passage inner wall surface temperature, and the like.

  When the exhaust temperature raising control is executed, the exhaust passage inner wall surface temperature gradually increases as shown in FIG. And since evaporation of unburned fuel adhering to the inner wall surface of the exhaust passage 9 is promoted, the amount of unburned fuel passage attached gradually decreases as shown in FIG.

  Here, when the exhaust throttle valve 15 is closed, the ECU 20 starts from this point in time when the PM accumulation amount in the filter 11 becomes the target PM accumulation amount Dpmt and the filter regeneration control is stopped (see FIG. 2). The remaining filter regeneration time t1, which is the time until (time indicated by (c)), is estimated.

  Here, the PM removal speed from the time when execution of the exhaust gas temperature raising control is started, that is, from the time when the exhaust throttle valve 15 is closed to the time when the filter regeneration control is stopped is expressed as the exhaust throttle valve. It is assumed that the removal rate of PM from the filter 11 immediately before the valve 15 is closed is equal to that. Then, the ECU 10 is based on the PM accumulation amount in the filter 11 when the exhaust throttle valve 15 is closed, and the PM removal rate from the filter 11 just before the exhaust throttle valve 15 is closed. The remaining filter regeneration time t1 is estimated.

  After the exhaust throttle valve 15 is closed, the ECU 20 estimates a reduction amount ΔQf of the unburned fuel passage adhesion amount from the time when the exhaust throttle valve 15 is closed every specified time. The unburned fuel passage adhesion amount reduction amount ΔQf is estimated based on the exhaust temperature in the exhaust passage 9 upstream of the oxidation catalyst 12 after the exhaust throttle valve 15 is closed. The specified time here is a predetermined time and is preferably as short as possible.

  Further, the ECU 20 oxidizes the unburned fuel in the same amount as the estimated decrease amount ΔQf of the unburned fuel passage adhesion amount when the exhaust temperature raising control is stopped by the exhaust throttle valve 15 being fully opened. An unburned fuel reattachment time t2, which is the time taken to attach again to the inner wall surface of the exhaust passage 9 upstream of the catalyst 12, is estimated.

  At this time, the ECU 20 determines the exhaust passage inner wall surface temperature after the exhaust throttle valve 15 is fully opened, and the exhaust passage inner wall surface temperature at the time when the exhaust temperature raising control is started by closing the exhaust throttle valve 15. The unburned fuel reattachment time t2 is estimated on the assumption that it is equivalent to Tp1. That is, after the exhaust throttle valve 15 is closed, the ECU 20 performs the unburned fuel reattachment time t2 based on the decrease ΔQf of the unburned fuel passage adhering amount and the exhaust passage inner wall surface temperature Tp1 every specified time. Is estimated.

  Here, since the decrease amount ΔQf of the unburned fuel passage adhering amount increases with the lapse of time after the start of the exhaust gas temperature raising control, the unburned fuel reattachment time t2 also increases accordingly.

  Then, the ECU 20 determines that the elapsed time from when the exhaust throttle valve 15 is closed, that is, the sum of the exhaust temperature raising control execution time t3 and the unburned fuel reattachment time t2 is the remaining filter regeneration time t1. At the time (time shown by (b) in FIG. 2), the exhaust throttle valve 15 is fully opened, and the exhaust gas temperature raising control is stopped.

  When the exhaust gas temperature raising control is stopped by fully opening the exhaust throttle valve 15, as shown in FIG. 2, the PM accumulation amount in the filter 11 becomes the target PM accumulation amount Dpmt, and the filter regeneration control is stopped. In the meantime, the exhaust passage inner wall surface temperature decreases again, and the amount of unburned fuel increases again.

  If the estimated filter regeneration remaining time t1 and the unburned fuel reattachment time t2 estimated as described above are equivalent to the actual filter regeneration remaining time t1 and the unburned fuel reattachment time t2, respectively, By stopping the exhaust gas temperature raising control with the exhaust throttle valve 15 fully opened at such timing, the unburned fuel adhesion amount when the filter regeneration control is stopped becomes the specified adhesion amount Qf1.

  However, in this embodiment, as described above, the PM removal speed from the time when the exhaust throttle valve 15 is closed to the time when the filter regeneration control is stopped is the same as the exhaust throttle valve 15 is closed. Assuming that the removal rate of PM from the filter 11 immediately before starting the exhaust gas temperature raising control is equivalent, the remaining filter regeneration time t1 is estimated. However, since the exhaust gas temperature becomes higher during execution of the exhaust gas temperature raising control, the PM removal speed may be higher than immediately before the exhaust throttle valve 15 is closed as shown in FIG. In this case, if the filter regeneration remaining time t1 is estimated based on the PM removal speed immediately before the exhaust throttle valve 15 is closed, the actual filter regeneration remaining time t1 is larger than the estimated filter regeneration remaining time t1. Shorter.

In this embodiment, as described above, the exhaust passage inner wall surface temperature after the exhaust throttle valve 15 is fully opened is set to the time when the exhaust temperature increase control is started by setting the exhaust throttle valve 15 to the closed state. Assuming that the exhaust passage inner wall surface temperature is equal to Tp1, the unburned fuel reattachment time t2 is estimated. However, since the exhaust passage inner wall surface temperature rises when the exhaust temperature raising control is executed, as shown in FIG. 2, the exhaust passage inner wall surface temperature after the exhaust temperature raising control is stopped is the same as that at the start of the exhaust temperature raising control. The exhaust passage inner wall surface temperature Tp1 may be higher. In this case, if the unburned fuel reattachment time t2 is estimated based on the exhaust passage inner wall surface temperature Tp1 at the time when the exhaust gas temperature raising control is started, the actual unburned fuel reattachment time t2 becomes the estimated unburned fuel reattachment time t2. It becomes longer than the adhesion time t2.

  Thus, when the actual filter regeneration remaining time t1 is shorter than the estimated filter regeneration remaining time t1, and / or the actual unburned fuel reattachment time t2 is the estimated unburned fuel reattachment time. When longer than t2, if the exhaust temperature raising control is stopped with the exhaust throttle valve 15 fully opened at the timing as described above, the unburned fuel adhesion amount when the filter regeneration control is stopped is smaller than the specified adhesion amount Qf1. Amount.

  That is, according to the present embodiment, the unburned fuel adhesion amount when the filter regeneration control is stopped is equal to or less than the specified adhesion amount Qf1.

<Control routine for filter regeneration control>
Hereinafter, the control routine of the filter regeneration control according to the present embodiment will be described based on the flowchart shown in FIG. This routine is stored in advance in the ECU 20 and is executed at specified time intervals during the operation of the internal combustion engine 1.

  In this routine, first, in S101, the ECU 20 determines whether or not the PM accumulation amount in the filter 11 is equal to or greater than the specified PM accumulation amount Qpm1. If an affirmative determination is made in S101, the ECU 20 proceeds to S102, and if a negative determination is made, the ECU 20 once ends the execution of this routine.

  In S102, the ECU 20 performs the exhaust gas temperature raising control by closing the exhaust throttle valve 15.

  Next, the ECU 20 proceeds to S103 and determines whether or not the temperature of the oxidation catalyst 12 is equal to or higher than the lower limit value Tact of the activation temperature. If an affirmative determination is made in S103, the ECU 20 proceeds to S104, and if a negative determination is made, the ECU 20 repeats S103.

  In S <b> 104, the ECU 20 performs post fuel injection in the internal combustion engine 1.

  Next, the ECU 20 proceeds to S105 and determines whether or not the temperature of the filter 11 has become equal to or higher than the target temperature Tft. If an affirmative determination is made in S105, the ECU 20 proceeds to S106, and if a negative determination is made, the ECU 20 repeats S105.

  In S106, the ECU 20 stops the exhaust gas temperature raising control by opening the exhaust throttle valve 15 fully.

  Next, the ECU 20 proceeds to S107, and determines whether or not the unburned fuel passage adhesion amount is equal to or greater than the specified adhesion amount Qf1. If an affirmative determination is made in S107, the ECU 20 proceeds to S110, and if a negative determination is made, the ECU 20 proceeds to S108.

  In S110, the ECU 20 executes the exhaust gas temperature raising control by closing the exhaust throttle valve 15 in order to promote the evaporation of the unburned fuel in the exhaust passage 9 and reduce the amount of unburned fuel passage adhesion.

Next, the ECU 20 proceeds to S111, and as described above, estimates the remaining filter regeneration time t1 and the unburned fuel reattachment time t2, and the elapsed time from when the exhaust throttle valve 15 is closed in S110. That is, it is determined whether or not the sum of the exhaust gas temperature raising control execution time t3 and the unburned fuel reattachment time t2 matches the filter regeneration remaining time t1. If an affirmative determination is made in S111, the ECU 20 proceeds to S112, and if a negative determination is made, the ECU 20 repeats S111.

  In S112, the ECU 20 stops the exhaust gas temperature raising control by opening the exhaust throttle valve 15 fully. Thereafter, the ECU 20 proceeds to S108.

  In S108, the ECU 20 determines whether or not the PM accumulation amount in the filter 11 is equal to or less than the target PM accumulation amount. If an affirmative determination is made in S108, the ECU 20 proceeds to S109, and if a negative determination is made, the ECU 20 returns to S107.

  In S109, the ECU 20 stops the filter regeneration control by stopping the post fuel injection. Thereafter, the ECU 20 temporarily stops the execution of this routine.

  According to the control routine described above, by executing the filter regeneration control, the amount of unburned fuel passage adhering to the inner wall surface of the exhaust passage 9 can be suppressed to a specified amount of attachment Qf1 or less, and post fuel injection is performed. The execution time t3 of the exhaust gas temperature raising control in the inside can be suppressed as short as possible.

  Therefore, according to the present embodiment, PM deposited on the filter can be oxidized and removed while suppressing deterioration of exhaust emission and fuel consumption.

  In this embodiment, instead of controlling the opening degree of the exhaust throttle valve 15, the exhaust gas temperature raising control may be executed by controlling the required load of the alternator 17.

  In this case, when executing the exhaust gas temperature raising control, the required load of the alternator 17 is increased by the ECU 20, thereby increasing the engine load of the internal combustion engine 1. When stopping the exhaust gas temperature raising control, the required load of the alternator 17 is reduced by the ECU 20, thereby reducing the engine load of the internal combustion engine 1.

  Even in such a case, the execution start timing and stop timing of the exhaust gas temperature raising control are the same as those in the case where the exhaust gas temperature raising control is executed or stopped by the opening degree control of the exhaust throttle valve 15 described above. That is, the required load of the alternator 17 is increased at the same timing as when the exhaust throttle valve 15 is closed, and the required load of the alternator 17 is increased at the same timing as when the exhaust throttle valve 15 is fully opened. Decrease.

  In this embodiment, when the exhaust passage 9 upstream of the oxidation catalyst 12 is further provided with a fuel addition valve for adding fuel into the exhaust, fuel is added from the fuel addition valve instead of post fuel injection. Thus, unburned fuel may be supplied to the oxidation catalyst 12.

<Modification>
Here, a modified example of the filter regeneration control according to the present embodiment will be described with reference to FIG. FIG. 4 is a flowchart showing a control routine of a modified example of the filter regeneration control according to the present embodiment. This flowchart differs from the flowchart shown in FIG. 3 only in that S106, S110, and S112 are replaced with S206, S210, and S212, respectively, and the other steps are the same. Therefore, only S206, S210, and S212 will be described, and descriptions of other steps will be omitted. In addition, this routine is also stored in advance in the ECU 20 and is executed every specified time during the operation of the internal combustion engine 1.

  In this routine, if an affirmative determination is made in S105, the ECU 20 proceeds to S206. In S206, the ECU 20 reduces the required load of the alternator 17. Thereafter, the ECU 20 proceeds to S107.

  If an affirmative determination is made in S107, the ECU 20 proceeds to S210 and increases the required load of the alternator 17. Thereafter, the ECU 20 proceeds to S111.

  If an affirmative determination is made in S111, the ECU 20 proceeds to S212 and reduces the required load of the alternator 17. Thereafter, the ECU 20 proceeds to S108.

  According to the control routine described above, the exhaust throttle valve 15 is maintained in the closed state during execution of the filter regeneration control. When the temperature of the filter 11 becomes equal to or higher than the target temperature Tft after the start of the filter regeneration control, the required load of the alternator 17 is reduced. Thereby, an increase in the engine load of the internal combustion engine 1 due to the exhaust throttle valve 15 being closed is suppressed.

Further, after the required load of the alternator 17 is reduced, the exhaust gas temperature raising control executed to reduce the amount of unburned fuel passage adhesion is executed at the same timing as described above by increasing the required load of the alternator 17. Is done. Further, the exhaust gas temperature raising control is stopped at the same timing as described above by reducing the required load of the alternator 17. Further, after the exhaust gas temperature raising control is stopped until the filter regeneration control is stopped, the increase in the engine load of the internal combustion engine 1 caused by closing the exhaust throttle valve 15 is the required load of the alternator 17. It is suppressed by reducing.

  That is, during the execution of the filter control, after the temperature of the filter 11 becomes equal to or higher than the target temperature Tft, the exhaust throttle valve 15 is closed so that the exhaust throttle valve 15 is closed except when the exhaust temperature raising control is executed. An increase in engine load is suppressed by reducing the required load of the alternator 17. Therefore, deterioration of fuel consumption can be suppressed.

The figure which shows schematic structure of the internal combustion engine which concerns on the Example of this invention, and its intake / exhaust system. In the filter regeneration control, the exhaust passage inner wall surface temperature after the post fuel injection is executed and the filter temperature reaches the target temperature, the PM accumulation amount in the filter, the unburned fuel passage adhesion amount, and the exhaust throttle valve opening. Time chart showing the change in degrees. The flowchart which shows the control routine of the filter reproduction | regeneration control which concerns on the Example of this invention. The flowchart which shows the control routine of the filter reproduction | regeneration control which concerns on the modification of the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Cylinder 9 ... Exhaust passage 10 ... Fuel injection valve 11 ... Particulate filter 12 ... Oxidation catalyst 13 ... Upstream exhaust temperature sensor 14 ... Downstream exhaust temperature sensor 15 .... Exhaust throttle valve 16 .... Differential pressure sensor 17 ... Alternator 20 ... ECU

Claims (6)

A particulate filter provided in an exhaust passage of the internal combustion engine for collecting particulate matter in the exhaust;
A catalyst having an oxidation function, provided in the exhaust passage on the upstream side of the particulate filter, or carried on the particulate filter;
Particulate matter accumulation amount detection means for detecting the accumulation amount of particulate matter in the particulate filter;
Unburned fuel supply means for supplying unburned fuel to the catalyst from the upstream side of the catalyst;
When the temperature of the catalyst is equal to or higher than the activation temperature, unburned fuel is supplied to the catalyst by the unburned fuel supply means, and the particulate filter is generated by oxidation heat generated when the unburned fuel is oxidized by the catalyst. A filter regeneration control execution means for performing a filter regeneration control for oxidizing and removing particulate matter deposited on the particulate filter,
After the execution of the filter regeneration control is started by the filter regeneration control execution means, the filter regeneration control is performed when the particulate matter accumulation amount detected by the particulate matter accumulation amount detection means becomes equal to or less than the target PM accumulation amount. A filter regeneration control stop means for stopping;
An unburned fuel passage adhering amount detection means for detecting an unburned fuel passage adhering amount that is an adhering amount of unburned fuel on the inner wall surface of the exhaust passage upstream of the catalyst during the execution of the filter regeneration control;
When the unburned fuel passage adhering amount detected by the unburned fuel adhering amount detection means exceeds a predetermined adhering amount, exhaust temperature increase control is performed to raise the exhaust temperature by increasing the engine load of the internal combustion engine. Exhaust temperature raising control execution means for starting execution and thereby reducing the amount of unburned fuel passage adhesion,
Exhaust gas that stops the exhaust gas temperature increase control by the exhaust gas temperature increase control unit after the exhaust gas temperature increase control execution unit starts executing the exhaust gas temperature increase control and before the filter regeneration control stop unit stops the filter regeneration control. Temperature rise control stop means,
The exhaust gas temperature increase control stop means is configured such that when the exhaust gas temperature increase control is stopped, the unburned fuel passage adhesion amount increases again when the filter regeneration control is stopped by the filter regeneration control stop means. An exhaust gas purification system for an internal combustion engine, wherein the exhaust gas temperature raising control is stopped at the following timing. The remaining filter regeneration that estimates the remaining filter regeneration time, which is the time from when the exhaust gas warming control execution means is started to when the filter regeneration control stop means stops the filter regeneration control. Time estimation means;
An unburned fuel passage adhesion amount decrease amount estimation means for estimating a decrease amount of the unburned fuel passage adhesion amount from the start of execution of the exhaust temperature increase control when the exhaust temperature increase control is being executed;
When the exhaust gas temperature increase control is stopped by the exhaust temperature increase control stop means for the same amount of unburned fuel passage decrease amount estimated by the unburned fuel path adhesion amount decrease amount estimation means And an unburned fuel reattachment time estimating means for estimating an unburned fuel reattachment time which is a time taken to reattach to the inner wall surface of the exhaust passage upstream of the catalyst.
After the execution of the exhaust gas temperature raising control is started by the exhaust gas temperature raising control execution means, the execution time of the exhaust gas temperature raising control, and the unburned fuel reattachment time estimated by the unburned fuel reattachment time estimating means, 2. The exhaust gas temperature increase control stop unit stops the exhaust gas temperature increase control when the sum of the values coincides with the filter regeneration remaining time estimated by the filter regeneration remaining time estimation unit. An exhaust purification system for an internal combustion engine. An inner wall surface temperature detecting means for detecting an inner wall surface temperature of the exhaust passage upstream of the catalyst;
The filter regeneration remaining time estimation means includes the amount of particulate matter accumulated in the particulate filter at the start of execution of exhaust gas temperature raising control, and the particulate form from the particulate filter immediately before the start of exhaust gas temperature raising control. Estimate the remaining filter regeneration time based on the material removal rate,
The unburned fuel passage adhering amount reduction amount estimation means is configured to perform unburned fuel from the start of execution of exhaust gas temperature increase control based on the exhaust temperature in the exhaust passage upstream from the catalyst during execution of exhaust gas temperature increase control. Estimate the amount of fuel passage adhesion reduction,
The unburned fuel reattachment time estimating means detects the unburned fuel passage adhesion amount reduction amount estimated by the unburned fuel passage adhesion amount reduction amount estimation means, and the inner wall surface temperature detection means detects the exhaust gas. 3. The exhaust gas purification of an internal combustion engine according to claim 2, wherein an unburned fuel reattachment time is estimated based on an inner wall surface temperature of the exhaust passage upstream of the catalyst at the start of execution of temperature rise control. system. An exhaust throttle valve provided in an exhaust passage downstream of the particulate filter;
The exhaust gas temperature raising control execution means executes the exhaust gas temperature raising control by closing the exhaust throttle valve,
The exhaust gas purification control system for an internal combustion engine according to any one of claims 1 to 3, wherein the exhaust gas temperature increase control stop means stops the exhaust gas temperature increase control by opening the exhaust throttle valve. . An auxiliary machine required load control means for controlling the required load of the auxiliary machine driven by the internal combustion engine,
The exhaust temperature raising control execution means executes the exhaust temperature raising control by increasing the required load of the auxiliary machine by the auxiliary machine required load control means,
4. The exhaust gas temperature raising control stop means stops the exhaust gas temperature raising control by lowering the required load of the auxiliary machine by the auxiliary machine required load control means. 5. Exhaust gas purification system for internal combustion engines. An exhaust throttle valve provided in an exhaust passage downstream of the particulate filter;
During the execution of the filter regeneration control by the filter regeneration control execution means, the exhaust throttle valve is closed,
After the temperature of the particulate filter becomes equal to or higher than the target temperature by executing the filter regeneration control, the auxiliary machine request is required until the exhaust gas temperature raising control is executed by the exhaust gas temperature raising control execution means. 6. The exhaust gas purification system for an internal combustion engine according to claim 5, wherein a required load of the auxiliary machine is reduced by a load control means.

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