JP4577656B2 - Control device for an internal combustion engine with a supercharger - Google Patents

Description

  The present invention relates to a control device for a supercharged internal combustion engine in which a supercharger is mounted on an internal combustion engine whose combustion mode is switched between lean combustion and stoichiometric or rich combustion in response to a combustion mode switching request.

  In recent years, in an internal combustion engine mounted on a vehicle, an exhaust turbine supercharger (so-called turbocharger) is added to a lean combustion internal combustion engine (lean burn engine or in-cylinder injection engine) in order to achieve both fuel saving and high output. Some are equipped with chargers. The general configuration of this exhaust turbine supercharger is to connect an exhaust turbine provided in an exhaust passage of an internal combustion engine and a compressor provided in an intake passage, and to rotate the exhaust turbine with the kinetic energy of exhaust gas. The compressor is driven to rotate to supercharge the intake air.

  Such a lean combustion internal combustion engine with a supercharger is generally operated by lean combustion in the middle and low load regions, and switched to stoichiometric (theoretical air-fuel ratio) or rich combustion in the high load region.

  Further, during lean combustion in which an air-fuel mixture containing excess oxygen is burned, the amount of NOx generated is greater than during stoichiometric combustion, and therefore, an NOx occlusion reduction type catalyst (hereinafter simply referred to as “NOx catalyst”) as an exhaust gas purification catalyst. Is often used. This NOx catalyst has a characteristic of storing NOx in exhaust gas when the air-fuel ratio of the exhaust gas is lean, and reducing and purifying stored NOx when the air-fuel ratio of the exhaust gas becomes rich and purging (release). have. From this characteristic, in order to maintain the NOx purification performance of the NOx catalyst, the stored NOx of the NOx catalyst is purged by switching to rich combustion intermittently during the lean combustion operation (Patent Document 1: Japanese Patent Application Laid-Open No. 2002-2002). No. 13429).

  A brake booster that increases the braking force of the brake uses an intake pipe negative pressure generated downstream of the throttle valve as a drive source, but the throttle opening is greatly opened during lean combustion operation, so the brake booster The intake pipe negative pressure to be introduced to the engine cannot be sufficiently secured, and the braking boosting effect of the brake booster is reduced. Therefore, in order to maintain the braking boost effect of the brake booster, the intake pipe negative pressure to be introduced into the brake booster is controlled by switching to the rich combustion temporarily during lean combustion operation and controlling the throttle opening to the closed side. The brake negative pressure control to be secured is executed (see Patent Document 2: Japanese Patent Application Laid-Open No. 2004-245108).

  As described above, in the lean combustion type internal combustion engine, the lean combustion is switched to the stoichiometric or rich combustion when the load is high, the NOx purge is executed, the brake negative pressure is secured, etc., but the lean combustion is changed to the stoichiometric or rich combustion. When switching to instantaneously, the engine torque rises rapidly and a torque shock occurs.

  As a countermeasure against this, in Patent Document 3 (Japanese Patent No. 3633312), when switching from lean combustion to rich combustion, the combustion mode is gradually switched, and the ignition timing is retarded together to increase the engine torque. It suppresses to prevent torque shock.

  However, gradually switching from lean combustion to rich combustion delays switching to rich combustion, so drivability deteriorates when the required torque suddenly increases or suddenly accelerates, or the start of NOx purge is delayed. There is a problem that the discharge amount increases or the brake negative pressure is delayed.

  Further, it is conceivable to apply the combustion mode switching technique of Patent Document 3 to a lean combustion internal combustion engine with a supercharger. In this case, as means for suppressing an increase in engine torque at the time of switching to rich combustion, If the ignition timing retard is used together, the exhaust gas temperature rises due to the ignition timing retard, and the energy of the exhaust gas that rotationally drives the exhaust turbine increases. As a result, the rotational speed of the exhaust turbine increases. As a result, the boost pressure increases, and the increase in engine torque cannot be sufficiently suppressed.

On the other hand, Patent Document 4 (Japanese Patent Laid-Open No. 2002-364212) is a lean combustion internal combustion engine with a supercharger provided with a waste gate valve for opening and closing an exhaust bypass passage for bypassing the exhaust turbine of the supercharger. Is described. This patent document 4 discloses a waste gate valve for the purpose of securing the amount of HC supplied to the NOx catalyst when the NOx purge of the NOx catalyst is executed by temporarily switching to rich combustion during the lean combustion operation. Is open.
JP 2002-13429 A (first page, etc.) JP 2004-245108 A (first page, etc.) Japanese Patent No. 3633312 (Page 5, etc.) Japanese Patent Laid-Open No. 2002-36412 (first page, etc.)

  In the above-mentioned Patent Document 4, the reason why the waste gate valve is opened when the NOx purge is performed is that the rich gas is agitated in the exhaust turbine when the NOx purge is performed, and the HC component supplied to the NOx catalyst is reduced. As a means for preventing this, it is described that the waste gate valve is opened to ensure the amount of HC supplied to the NOx catalyst. However, according to the research result of the present inventor, the phenomenon that the rich gas is agitated in the exhaust turbine and reburned does not occur when the NOx purge is performed. Moreover, the technique of Patent Document 4 is a means for opening the waste gate valve for the purpose of securing the amount of HC supplied to the NOx catalyst at the time of executing the NOx purge, and means for suppressing an increase in engine torque at the time of executing the NOx purge. Is not described at all. Therefore, the technique of Patent Document 4 has no technical idea of preventing torque shock at the time of executing NOx purge (when the combustion mode is switched).

  The present invention has been made in consideration of these circumstances, and therefore, the purpose of the internal combustion engine with a supercharger is to prevent a torque shock when switching the combustion mode from lean combustion to stoichiometric or rich combustion, An object of the present invention is to provide a control device for an internal combustion engine with a supercharger capable of promptly switching to stoichiometric or rich combustion.

In order to achieve the above object, an invention according to claim 1 includes a supercharger that supercharges intake air by driving a compressor provided in an intake passage by an exhaust turbine provided in an exhaust passage of an internal combustion engine; A supercharger comprising a waste gate valve for opening and closing an exhaust bypass passage for bypassing the exhaust turbine, and combustion mode switching means for switching the combustion mode of the internal combustion engine to lean combustion, stoichiometric or rich combustion in response to a combustion mode switching request The internal combustion engine control apparatus includes a torque increase suppression unit that suppresses a torque increase of the internal combustion engine when the combustion mode switching unit switches from lean combustion to stoichiometric or rich combustion, and the torque increase suppression unit includes the combustion mode switching unit. When the switching means switches from lean combustion to stoichiometric or rich combustion, the ignition timing is delayed. It is characterized in that opening the waste gate valve to the opening set in accordance with the retard amount of the ignition timing as well as.

In this configuration, when switching from lean combustion to stoichiometric or rich combustion, the ignition timing is retarded, so the temperature of the exhaust gas rises. However, the waste gate valve is set according to the amount of retardation of the ignition timing. to open up, the flow rate of the exhaust gas where the exhaust gas flow bypassing the exhaust turbine passes through the exhaust turbine increases is reduced. Thereby, while suppressing the increase of the supercharging pressure due to the retard of the ignition timing, it is possible to prevent the torque shock by suppressing the torque increase at the time of switching the combustion mode with a good response by the retard of the ignition timing. In addition, since it is not necessary to gradually switch the combustion mode, it is possible to quickly switch from lean combustion to stoichiometric or rich combustion, which improves drivability when the required torque is increased or accelerated. it can.

Further, when the present invention is applied to an internal combustion engine with a supercharger provided with an air bypass valve that opens and closes an intake bypass passage that bypasses the upstream side and the downstream side of the compressor, When switching to stoichiometric or rich combustion, the ignition timing may be retarded and the air bypass valve may be opened to an opening set in accordance with the retard amount of the ignition timing . In this configuration, when switching from lean combustion to stoichiometric or rich combustion, the air bypass valve is opened to the opening set in accordance with the retard amount of the ignition timing together with the retard of the ignition timing. While suppressing the increase of the supercharging pressure by opening the air bypass valve, torque shock can be prevented by retarding the ignition timing, and switching from lean combustion to stoichiometric or rich combustion can be performed quickly.

Further, when the present invention is applied to an internal combustion engine with a supercharger having both a waste gate valve and an air bypass valve, the ignition timing is changed when switching from lean combustion to stoichiometric or rich combustion as in claim 3. Both the waste gate valve and air bypass valve may be opened to the opening set according to the ignition timing retard amount, or one of them is set according to the ignition timing retard amount. You may open to the opening degree .

In the invention according to claims 1 to 3 described above, by paying attention to the temperature rise amount thus boost pressure rise amount of the exhaust gas in accordance with the retard amount of the ignition timing is changed, the retard amount of the point fire timing In order to set the opening of the waste gate valve and / or air bypass valve accordingly, when switching from lean combustion to stoichiometric or rich combustion, the supercharging pressure is lowered too much by opening the waste gate valve or air bypass valve. The supercharging pressure can be quickly increased after the lean combustion recovery, and the fuel saving performance due to the supercharging effect can be enhanced.

Further, as in claim 4, the conditions for switching from lean combustion to stoichiometric or rich combustion are (1) when it is necessary to purge NOx occluded in the NOx catalyst, and (2) ensure the negative pressure of the brake booster When necessary, (3) During acceleration, (4) When the torque required by the driver shifts to the stoichiometric or rich combustion region, (5) At least one when the temperature of the NOx catalyst rises above a predetermined temperature Good. Here, when the temperature of the NOx catalyst increases, the NOx storage capacity of the NOx catalyst decreases and the purification rate of the exhaust gas decreases. Therefore, when the temperature of the NOx catalyst rises above a predetermined temperature at which the NOx storage capacity cannot be secured. By switching from lean combustion to stoichiometric combustion, the exhaust gas can be purified by the three-way catalyst function of the NOx catalyst while reducing the amount of NOx produced.

Further, as in claim 5 , when switching from lean combustion to stoichiometric or rich combustion, if the driver requests acceleration exceeding a predetermined acceleration, the waste gate valve and / or the air bypass valve should not be opened. You may make it do. If it does in this way, when the driver | operator has requested | required rapid acceleration, a boost pressure can be raised effectively and acceleration can be improved.

By the way, while the torque suppression effect due to the retarded operation of the ignition timing appears almost without time delay, the effect of the opening operation of the waste gate valve and the air bypass valve is caused by the decrease of the supercharging pressure (decrease in the rotational speed of the exhaust turbine) There is a time delay before it appears. In consideration of this point, as in claim 6, when switching to the stoichiometric or rich combustion from the lean combustion, thereby previously have waste gate valve and / or the air bypass valve after opening the predetermined delay ignition The timing may be retarded. In this way, the retarding operation of the ignition timing can be delayed and executed by the time delay until the influence of the opening operation of the waste gate valve or the air bypass valve appears. The boost pressure reduction effect due to the opening operation of the waste gate valve or the air bypass valve can be generated in fully synchronized with each other, and the torque shock prevention effect can be enhanced.

Further, as described in claim 7 , when returning from stoichiometric or rich combustion to lean combustion, the opening degree of the waste gate valve and / or the air bypass valve may be immediately switched to the control value at the time of lean combustion. In short, since there is a response delay (turbo lag) from when the waste gate valve or air bypass valve is closed until the boost pressure rises, the opening of the waste gate valve or air bypass valve is set immediately after lean combustion. By switching to the control value, it is possible to quickly increase the supercharging pressure after returning to lean combustion, and it is possible to improve the fuel saving performance due to the supercharging effect.

  Hereinafter, several embodiments in which the best mode for carrying out the present invention is applied to a lean burn engine with a supercharger will be described.

A first embodiment of the present invention will be described with reference to FIGS.
First, a schematic configuration of the entire engine control system will be described with reference to FIG. An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 (intake passage) of the lean burn engine 11 that is a lean combustion type internal combustion engine, and an air flow meter 14 for detecting the intake air amount is provided downstream of the air cleaner 13. Is provided. On the downstream side of the air flow meter 14, a throttle valve 15 whose opening is adjusted by a DC motor or the like and a throttle opening sensor 16 for detecting the throttle opening are provided.

  Further, a surge tank 17 is provided on the downstream side of the throttle valve 15. The surge tank 17 is provided with an intake manifold 19 for introducing air into each cylinder of the engine 11, and a fuel injection valve 20 for injecting fuel is attached in the vicinity of the intake port of the intake manifold 19 of each cylinder. . A spark plug 21 is attached to each cylinder of the engine 11 for each cylinder, and the air-fuel mixture in the cylinder is ignited by spark discharge of each spark plug 21.

  On the other hand, in the exhaust pipe 22 (exhaust passage) of the engine 11, a three-way catalyst 23 for purifying CO, HC, NOx and the like in exhaust gas and a NOx occlusion reduction type catalyst (hereinafter simply referred to as “NOx catalyst”) 40 are connected in series. The air-fuel ratio sensor 24 for detecting the air-fuel ratio of the exhaust gas is provided on the upstream side of the three-way catalyst 23 located on the upstream side.

  Further, the engine 11 is equipped with an exhaust turbine supercharger 25. In the supercharger 25, an exhaust turbine 26 is disposed between the air-fuel ratio sensor 24 and the three-way catalyst 23 in the exhaust pipe 22, and between the air flow meter 14 and the throttle valve 15 in the intake pipe 12. In addition, a compressor 27 is arranged. In the supercharger 25, an exhaust turbine 26 and a compressor 27 are connected, and the exhaust turbine 26 is rotationally driven by the kinetic energy of exhaust gas, whereby the compressor 27 is rotationally driven to supercharge intake air. Yes.

  Further, the intake pipe 12 is provided with an intake bypass passage 28 that bypasses the compressor 27, and an air bypass valve (hereinafter referred to as “ABV”) 29 that opens and closes the intake bypass passage 28 in the middle of the intake bypass passage 28. Is provided. The opening degree of the ABV 29 is controlled by controlling the ABV vacuum switching valve (hereinafter referred to as “ABV VSV”) 30. An intercooler (hereinafter referred to as “IC”) 31 for cooling the intake air pressurized by the compressor 27 of the supercharger 25 is provided between the compressor 27 and the throttle valve 15 in the intake pipe 12. It has been.

  On the other hand, the exhaust pipe 22 is provided with an exhaust bypass passage 32 that bypasses the exhaust turbine 26, and a waste gate valve (hereinafter referred to as “WGV”) that opens and closes the exhaust bypass passage 32 in the middle of the exhaust bypass passage 32. 33 is provided. The WGV 33 is configured such that the opening degree of the WGV 33 is controlled by controlling a diaphragm type actuator 35 by controlling a WGV vacuum switching valve (hereinafter referred to as “WGV VSV”) 34.

  A cooling water temperature sensor 36 that detects the cooling water temperature and a crank angle sensor 37 that outputs a pulse signal each time the crankshaft of the engine 11 rotates a predetermined crank angle are attached to the cylinder block of the engine 11. Based on the output signal of the crank angle sensor 37, the crank angle and the engine speed are detected.

  Outputs of these various sensors are input to an engine control circuit (hereinafter referred to as “ECU”) 38. The ECU 38 is mainly composed of a microcomputer, and executes the routines shown in FIGS. 2 to 4 stored in a built-in ROM (storage medium) to thereby control the fuel injection valve 20 according to the engine operating state. The fuel injection amount, the ignition timing of the spark plug 21, and the throttle opening (intake air amount) are controlled, and the combustion mode of the engine 11 is set to lean combustion and stoichiometric according to the engine operating region (for example, required torque and engine speed Ne). Or it functions as a combustion mode switching means for switching to rich combustion.

Further, the ECU 38 switches the combustion mode of the engine 11 from lean combustion to stoichiometric or rich combustion when any one of the following conditions (1) to (5) is satisfied.
(1) When the NOx stored in the NOx catalyst 40 needs to be purged (when a NOx purge request is generated)
(2) When it is necessary to secure the negative pressure of a brake booster (not shown) (when a request to ensure brake negative pressure occurs)
(3) During acceleration
(4) When the temperature of the NOx catalyst 40 rises above a predetermined temperature at which NOx storage capacity cannot be secured
(5) When the required torque requested by the driver shifts to the stoichiometric or rich combustion region

  Further, the ECU 38 functions as a torque increase suppression unit that suppresses an increase in engine torque (torque shock) when switching from lean combustion to stoichiometric or rich combustion, and delays the ignition timing when switching from lean combustion to stoichiometric or rich combustion. In addition, both the WGV 33 and the ABV 29 (or either one) are opened to a preset opening (fully opened or predetermined opening).

  At this time, the ignition timing may be retarded simultaneously with the opening of the WGV 33 and / or the ABV 29. However, in the first embodiment, the effect of the opening operation of the WGV 33 and the ABV 29 is caused by a decrease in the supercharging pressure (exhaust gas). Taking into account the time delay until it appears as a decrease in the rotational speed of the turbine 26), ignition is performed with a delay corresponding to the time delay in which the effect of the opening operation appears after the WGV 33 and / or ABV 29 is opened first. I am trying to retard the time. Compared with the time delay of WGV33 and ABV29, the time delay until the influence of the retarding operation of the ignition timing appears as engine torque suppression or exhaust gas temperature rise is very small and almost negligible.

  The combustion mode switching control according to the first embodiment described above is executed by the ECU 38 according to the routines shown in FIGS. The processing contents of these routines will be described below.

[Engine control main routine]
The engine control main routine of FIG. 2 is executed at a predetermined cycle during engine operation. When the main routine is started, first, in step 100, the required torque is calculated based on the accelerator opening, the engine speed, and the like. After this, the routine proceeds to step 200, the combustion mode determination routine of FIG. 3 is executed to determine the combustion mode, and then the routine proceeds to step 300, where the combustion mode switching control routine of FIG. For example, the combustion mode switching control is executed, and the air system control routine, the fuel system control routine, and the ignition system control routine (not shown) are executed in the next steps 400 to 600 to control the air system, the fuel system, and the ignition system. The parameter is controlled with a target value corresponding to the combustion mode.

[Combustion mode decision routine]
The combustion mode determination routine of FIG. 3 is a subroutine executed in step 200 of the engine control main routine of FIG. When this routine is started, first, in step 201, a required combustion mode determination map is searched, and lean combustion and stoichiometric combustion (or rich combustion) are performed in accordance with the current engine operating state (for example, engine speed Ne and required torque). One of these is selected as the required combustion mode. In this required combustion mode determination map, lean combustion is selected with priority given to fuel saving in the low / medium rotation and low / medium torque ranges, while stoichiometric combustion (or priority is given to engine output in the high rotation and high torque ranges). Rich combustion) is selected.

  Thereafter, the process proceeds to step 202, where it is determined whether the required combustion mode is stoichiometric combustion (or rich combustion). If the required combustion mode is stoichiometric combustion (or rich combustion), the process proceeds to step 203, where It is determined whether the actual combustion mode is stoichiometric or rich combustion. If the current actual combustion mode is not stoichiometric or rich combustion, it is necessary to switch the combustion mode. Therefore, the routine proceeds to step 204, the combustion mode switching flag is turned on, and the routine proceeds to step 205 where the stoichiometric or rich combustion is performed. Switch. On the other hand, if the current actual combustion mode is stoichiometric or rich combustion, there is no need to switch the combustion mode, so step 204 is skipped and the routine proceeds to step 205 where the combustion mode is maintained at stoichiometric or rich combustion.

  If it is determined in step 202 that the required combustion mode is not stoichiometric combustion (or rich combustion), the routine proceeds to step 206, and it is determined whether or not a combustion mode switching request to stoichiometric or rich combustion has occurred. The combustion mode switching request to the stoichiometric or rich combustion is generated when any of the following conditions (1) to (4) is satisfied.

(1) When the NOx stored in the NOx catalyst 40 needs to be purged (when a NOx purge request is generated)
(2) When it is necessary to secure the negative pressure of a brake booster (not shown) (when a request to ensure brake negative pressure occurs)
(3) During acceleration
(4) When the temperature of the NOx catalyst 40 rises above a predetermined temperature at which NOx storage capacity cannot be secured

  If it is determined in step 206 that the combustion mode switching request is generated, the processing after step 203 is executed to switch (or maintain) the combustion mode to stoichiometric or rich combustion.

  On the other hand, if it is determined in step 206 that the combustion mode switching request is not generated, the process proceeds to step 207 to determine whether or not the current actual combustion mode is lean combustion. If the current actual combustion mode is not lean combustion, it is necessary to switch the combustion mode. Therefore, the routine proceeds to step 208, the combustion mode switching flag is turned on, and the routine proceeds to step 209 to switch to lean combustion. On the other hand, if the current actual combustion mode is lean combustion, there is no need to switch the combustion mode, so step 208 is skipped and the routine proceeds to step 209, where the combustion mode is maintained at lean combustion.

[Combustion mode switching control routine]
The combustion mode switching control routine of FIG. 4 is a subroutine executed in step 300 of the engine control main routine of FIG. When this routine is started, first, at step 301, it is determined whether or not the combustion mode switching to the stoichiometric or rich combustion is being performed based on whether or not the combustion mode switching flag is ON. Is ON (combustion mode switching to stoichiometric or rich combustion), the routine proceeds to step 311 and the combustion mode switching to stoichiometric or rich combustion is determined depending on whether or not the air-fuel ratio A / F has become richer than the predetermined air-fuel ratio. It is determined whether or not the process has ended. Then, when the air-fuel ratio A / F becomes richer than the predetermined air-fuel ratio, the routine proceeds to step 312, where the combustion mode switching flag is reset to OFF and the combustion mode switching control is terminated.

  On the other hand, if it is determined in step 301 that the combustion mode switching flag is OFF (combustion mode switching is not in progress), the routine proceeds to step 302, where it is determined whether or not the current actual combustion mode is lean combustion. As a result, if it is determined that the current actual combustion mode is rich combustion, the routine proceeds to step 303, where it is determined whether or not there is a request for switching to lean combustion. If there is a request for switching to lean combustion, the routine proceeds to step 304, where a request to close the WGV 33 and ABV 29 is output. Thereby, when switching from stoichiometric or rich combustion to lean combustion, the WGV 33 and the ABV 29 are closed simultaneously with the switching to lean combustion, and the supercharging pressure is quickly increased.

  If it is determined in step 302 that the current actual combustion mode is lean combustion, the process proceeds to step 305, where it is determined whether there is a request for switching to stoichiometric or rich combustion, and switching to stoichiometric or rich combustion is performed. If there is no request, this routine is terminated as it is, and if there is a request for switching to stoichiometric or rich combustion, the routine proceeds to step 306, and a request to open the WGV 33 and ABV 29 is output. Thus, when switching from lean combustion to stoichiometric or rich combustion, the ignition is performed in consideration of the time delay until the effect of the opening operation of the WGV 33 and ABV 29 appears as a decrease in supercharging pressure (decrease in the rotational speed of the exhaust turbine 26). Before retarding the timing, the WGV 33 and the ABV 29 are opened to a preset opening (fully opened or predetermined opening).

  In the next step 307, the delay time counter is incremented to count the delay time from the start of the opening operation of the WGV 33 and the ABV 29. In the next step 308, the delay time counted by the delay time counter is set to the predetermined time K. It is determined whether it has been exceeded. Here, the predetermined time K is set to a time corresponding to a delay time until the effect of the opening operation of the WGV 33 and the ABV 29 appears as a decrease in the supercharging pressure (a decrease in the rotational speed of the exhaust turbine 26). If it is determined in step 308 that the delay time counted by the delay time counter is less than the predetermined time K, this routine is terminated without starting the switching to the stoichiometric or rich combustion, and the lean combustion is continued.

  After that, when the delay time counted by the delay time counter exceeds the predetermined time K, it is judged as “Yes” in Step 308 and proceeds to Step 309 to close the throttle opening and switch from lean combustion to stoichiometric or rich combustion. At the same time, the ignition timing is retarded simultaneously with switching to the stoichiometric or rich combustion. In the next step 310, the combustion mode switching flag is turned ON to display that the combustion mode switching from lean combustion to stoichiometric or rich combustion is being performed.

  Thereafter, the routine proceeds to step 311 where it is determined whether or not the combustion mode switching to the stoichiometric or rich combustion is completed depending on whether or not the air-fuel ratio A / F has become richer than the predetermined air-fuel ratio. Then, when the air-fuel ratio A / F becomes richer than the predetermined air-fuel ratio, the routine proceeds to step 312, where the combustion mode switching flag is reset to OFF and the combustion mode switching control is terminated.

  An example of the combustion mode switching control of the first embodiment described above will be described with reference to the time chart of FIG. The time chart of FIG. 5 shows a control example when the combustion mode is switched from lean combustion to rich combustion in response to the NOx purge request. At the time t1 when the required combustion mode is switched from lean combustion to rich combustion, the WGV 33 and ABV 29 are immediately opened to a preset opening (fully opened or predetermined opening).

  After the start of the opening operation of the WGV 33 and the ABV 29, a time point t2 corresponding to the delay time until the influence of the opening operation of the WGV 33 and the ABV 29 appears as a decrease in the supercharging pressure (a decrease in the rotational speed of the exhaust turbine 26) has elapsed t2. Thus, the throttle opening is closed to switch from lean combustion to rich combustion, and at the same time as switching to rich combustion, the ignition timing is retarded to suppress an increase in engine torque at the time of switching the combustion mode to prevent torque shock. . The retard amount of the ignition timing is set to a retard amount necessary for suppressing an increase in engine torque when switching the combustion mode within a range in which combustion stability can be ensured.

  Conventionally, even after the combustion mode is switched from lean combustion to rich combustion, the WGV 33 and ABV 29 are maintained in the valve-closed state. Therefore, as a means for suppressing an increase in engine torque when switching to rich combustion, the ignition timing is set. If retarded, the temperature of the exhaust gas rises and the energy of the exhaust gas that rotationally drives the exhaust turbine increases. As a result, the rotational speed of the exhaust turbine 26 rises more than in the first embodiment, and the boost pressure Increases, and the increase in engine torque cannot be sufficiently suppressed.

  In contrast, in the first embodiment, when the combustion mode is switched from lean combustion to rich combustion, the WGV 33 and ABV 29 are opened and the ignition timing is retarded. Is suppressed by the opening operation of the WGV 33 and the ABV 29, and the engine torque increase at the time of switching the combustion mode can be suppressed with good response by retarding the ignition timing, thereby preventing torque shock.

  In the first embodiment, at the time t1 when the required combustion mode is switched from lean combustion to rich combustion, the WGV 33 and the ABV 29 are immediately opened, and then the effect of the opening operation of the WGV 33 and the ABV 29 is caused by a decrease in the supercharging pressure ( Since the ignition timing is retarded at the time t2 when the time K corresponding to the delay time until it appears as a decrease in the rotational speed of the exhaust turbine 26), the torque suppression effect by the retarding operation of the ignition timing and the WGV 33 And the boost pressure lowering effect due to the opening operation of the ABV 29 can be generated in complete synchronization, and the torque shock preventing effect can be enhanced. However, in the present invention, when the combustion mode is switched from lean combustion to rich combustion, the ignition timing may be retarded simultaneously with opening the WGV 33 and ABV 29.

  Thereafter, at the time t3 when the required combustion mode is switched from rich combustion to lean combustion, the throttle opening is opened to switch from rich combustion to lean combustion, the ignition timing is advanced simultaneously with the switching to lean combustion, and Then, the opening degree of WGV33 and ABV29 is closed to the control value at the time of lean combustion. Thereby, when switching to lean combustion, the rotational speed of the exhaust turbine 26 can be quickly increased to quickly increase the supercharging pressure, and the fuel saving performance due to the supercharging effect can be enhanced.

  In the first embodiment, when switching from lean combustion to stoichiometric or rich combustion, the WGV 33 and the ABV 29 are opened to a preset opening (fully opened or predetermined opening), as shown in FIGS. 6 and 7. In the second embodiment of the present invention, when switching from lean combustion to stoichiometric or rich combustion, focusing on the fact that the temperature rise amount of the exhaust gas and thus the boost pressure rise amount changes according to the retard amount of the ignition timing, The WGV 33 and the ABV 29 are opened to an opening set according to the retard amount of the ignition timing.

  The combustion mode switching control routine of FIG. 6 executed in the second embodiment is obtained by changing the processing of step 306 of the combustion mode switching control routine of FIG. 4 described in the first embodiment to processing of steps 306a and 306b. The process of each step other than this is the same.

  In the combustion mode switching control routine of FIG. 6, when a switching request from lean combustion to stoichiometric or rich combustion is generated, “Yes” is determined in step 305, the process proceeds to step 306 a, and the ignition delay at the time of switching the combustion mode is determined. Read angular amount. Thereafter, the process proceeds to step 306b, and the WGV 33 and ABV 29 opening degrees are set according to the ignition delay amount at the time of switching the combustion mode with reference to the WGV opening / ABV opening setting map using the ignition delay amount as a parameter. To do. The characteristic of this WGV opening / ABV opening setting map is that the opening of the WGV 33 and the ABV 29 is increased as the ignition retard amount is increased, considering that the temperature increase amount of the exhaust gas increases as the ignition retard amount increases. It is set to increase.

  Then, as shown in FIG. 7, at the time t1 when the required combustion mode is switched from lean combustion to rich combustion, the WGV 33 and ABV 29 are immediately released to the opening set in step 306b. The subsequent processing is the same as in the first embodiment.

  According to the second embodiment described above, when switching from lean combustion to stoichiometric or rich combustion, the WGV 33 and ABV 29 are opened to the opening set in accordance with the retard amount of the ignition timing. When switching from stoichiometric to rich combustion, it is possible to avoid a situation where the supercharging pressure is excessively lowered by opening the WGV 33 and ABV 29, and to quickly increase the supercharging pressure after the lean combustion is restored. It is possible to improve the fuel saving performance due to the supercharging effect.

  In the second embodiment of the present invention, when the requested acceleration requested by the driver is larger than the predetermined acceleration Ac by executing the combustion mode switching control routine of FIG. 8, the release of the WGV 33 and ABV 29 is prohibited and the combustion mode is switched. Is switched from lean combustion to rich combustion.

  The combustion mode switching control routine of FIG. 8 is obtained by adding the processing of step 302a between steps 302 and 305 of the combustion mode switching control routine of FIG. 4 described in the first embodiment. The processing of the steps is the same.

  In this routine, when the combustion mode switching flag is OFF and the current actual combustion mode is lean combustion, the routine proceeds to step 302a through step 301 and step 302, and the requested acceleration requested by the driver is the predetermined acceleration. It is determined whether it is larger than Ac. As a result, if it is determined that the required acceleration is equal to or less than the predetermined acceleration Ac, the process proceeds to step 305, and the same processing as in the first embodiment is executed. If it is determined that the required acceleration is greater than the predetermined acceleration Ac, step Steps 309 are skipped over 305-308. As a result, when the requested acceleration requested by the driver is larger than the predetermined acceleration Ac, the opening of the WGV 33 and ABV 29 is prohibited, and the combustion mode is immediately switched from lean combustion to rich combustion. If it does in this way, when the driver | operator has requested | required rapid acceleration, a boost pressure can be raised effectively and acceleration can be improved.

When the requested acceleration requested by the driver is larger than the predetermined acceleration Ac, the opening of the WGV 33 and the ABV 29 may be prohibited, and the retard of the ignition timing may be prohibited.
In each of the first to third embodiments described above, when switching from lean combustion to stoichiometric or rich combustion, both WGV33 and ABV29 are opened, but only one of WGV33 and ABV29 is opened. Also good. Moreover, it is good also as a structure which abbreviate | omitted either WGV33 or ABV29 from the intake / exhaust system.

  In addition, the present invention can be applied to a cylinder injection engine with a supercharger. In this case, when switching from lean combustion (stratified combustion: compression stroke injection) to stoichiometric or rich combustion (homogeneous combustion: intake stroke injection), the WGV 33 and / or ABV 29 are opened as in the first to third embodiments. At the same time, the ignition timing may be retarded.

It is a schematic block diagram of the whole engine control system in Example 1 of this invention. 6 is a flowchart showing a flow of processing of an engine control main routine according to the first embodiment. 3 is a flowchart showing a flow of processing of a combustion mode determination routine according to the first embodiment. 3 is a flowchart showing a process flow of a combustion mode switching control routine according to the first embodiment. 3 is a time chart illustrating a control example of the first embodiment. 6 is a flowchart showing a processing flow of a combustion mode switching control routine according to a second embodiment. 6 is a time chart illustrating a control example of Embodiment 2. 7 is a flowchart showing a flow of processing of a combustion mode switching control routine of Embodiment 3.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Lean burn engine (internal combustion engine), 12 ... Intake pipe (intake passage), 14 ... Air flow meter, 15 ... Throttle valve, 20 ... Fuel injection valve, 21 ... Spark plug, 22 ... Exhaust pipe (exhaust passage), 23 ... three-way catalyst, 24 ... air-fuel ratio sensor, 25 ... supercharger, 26 ... exhaust turbine, 27 ... compressor, 28 ... intake bypass passage, 29 ... ABV (air bypass valve), 31 ... IC (intercooler), 32 ... Exhaust bypass passage, 33 ... WGV (waste gate valve), 38 ... ECU (combustion mode switching means, torque increase suppression means), 40 ... NOx catalyst (NOx occlusion type catalyst)

Claims (7)

A turbocharger that drives a compressor provided in an intake passage by an exhaust turbine provided in an exhaust passage of the internal combustion engine to supercharge intake air; and a waste gate valve that opens and closes an exhaust bypass passage that bypasses the exhaust turbine; A control apparatus for an internal combustion engine with a supercharger comprising combustion mode switching means for switching the combustion mode of the internal combustion engine to lean combustion and stoichiometric or rich combustion in response to a combustion mode switching request;
Torque increase suppression means for suppressing an increase in torque of the internal combustion engine when switching from lean combustion to stoichiometric or rich combustion by the combustion mode switching means,
When the combustion mode switching means switches from lean combustion to stoichiometric or rich combustion, the torque increase suppression means retards the ignition timing and opens the waste gate valve according to the retard amount of the ignition timing. A control device for an internal combustion engine with a supercharger, characterized in that it opens to a certain degree . A turbocharger that drives a compressor provided in an intake passage by an exhaust turbine provided in an exhaust passage of the internal combustion engine to supercharge intake air, and an intake bypass passage that bypasses the upstream side and the downstream side of the compressor In a control device for an internal combustion engine with a supercharger comprising an air bypass valve that opens and closes, and a combustion mode switching means that switches a combustion mode of the internal combustion engine to lean combustion and stoichiometric or rich combustion in response to a combustion mode switching request,
A torque increase suppressing means for suppressing an increase in torque of the internal combustion engine when switching from lean combustion to stoichiometric or rich combustion by the combustion mode switching means;
When the combustion mode switching means switches from lean combustion to stoichiometric or rich combustion, the torque increase suppressing means retards the ignition timing and opens the air bypass valve according to the retard amount of the ignition timing. A control device for an internal combustion engine with a supercharger, characterized in that it opens to a certain degree . A turbocharger that drives a compressor provided in an intake passage by an exhaust turbine provided in an exhaust passage of the internal combustion engine to supercharge intake air; and a waste gate valve that opens and closes an exhaust bypass passage that bypasses the exhaust turbine; An air bypass valve for opening and closing an intake bypass passage for bypassing the upstream side and the downstream side of the compressor, and a combustion mode switching means for switching the combustion mode of the internal combustion engine to lean combustion, stoichiometric or rich combustion in response to a combustion mode switching request In a control device for an internal combustion engine with a supercharger comprising:
Torque increase suppression means for suppressing an increase in torque of the internal combustion engine when switching from lean combustion to stoichiometric or rich combustion by the combustion mode switching means,
The torque increase control means, wherein when switching to stoichiometric or rich combustion from the lean combustion by the combustion mode switching means, the retard of the ignition timing the waste gate valve and / or the air bypass valve as well as retarding the ignition timing A control device for an internal combustion engine with a supercharger, wherein the control device opens to a degree of opening set according to the amount . The conditions for switching from lean combustion to stoichiometric or rich combustion by the combustion mode switching means are as follows: (1) When it is necessary to purge NOx occluded in the NOx occlusion-type catalyst provided in the exhaust passage, (2) The brake booster When it is necessary to ensure negative pressure, (3) When accelerating, (4) When the torque required by the driver shifts to the stoichiometric or rich combustion region, (5) The temperature of the NOx occlusion type catalyst is equal to or higher than a predetermined temperature. 4. The control device for an internal combustion engine with a supercharger according to claim 3 , wherein the control device is at least one when the engine is raised. The torque increase suppression means is configured to switch the waste gate valve and / or the air flow when the driver requests acceleration over a predetermined acceleration when the combustion mode switching means switches from lean combustion to stoichiometric or rich combustion. control device for an internal combustion engine with a supercharger according to claim 3 or 4, characterized in that prohibiting the opening of the bypass valve. When the combustion mode switching means switches from lean combustion to stoichiometric or rich combustion, the torque increase suppressing means provides a predetermined delay after first opening the waste gate valve and / or the air bypass valve. The control apparatus for an internal combustion engine with a supercharger according to any one of claims 3 to 5 , wherein the ignition timing is retarded. It said combustion mode switching means, from the stoichiometric or rich combustion when returning to the lean burn, immediately the waste gate valve and / or the claims 3 to 6 switches the opening degree of the air bypass valve control value during lean combustion The control apparatus of the internal combustion engine with a supercharger in any one.

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