FR2814199A1 - System for controlling the combustion of an IC engine having Exhaust gas recirculation (EGR) - Google Patents

Abstract

The control unit includes an arrangement for modifying the lag time period corresponding to the functioning state of the Electronic Control unit (16) for fixing the quantity of control corresponding to the torque reduction control during the period of switching between the two combustion states. The control unit is for an IC engine (10) having an exhaust gas recirculating unit EGR (14) between the exhaust (13) and an inlet (12), regulating the switching between a stratified charge mode and an uniform combustion mode by regulating the degree of opening of the EGR valve (20), in such a manner as to control the torque reduction of the IC engine.

Description

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METHOD AND DEVICE FOR CONTROLLING A MOTOR
INTERNAL COMBUSTION
The present invention relates to a method and a device for controlling an internal combustion engine in which the quantity of EGR recirculation gas (initials of exhaust gas recirculation, i.e. exhaust gas recirculation). ) is set by controlling the degree of opening of an EGR recirculation valve and the combustion mode is switched between stratified charge combustion and uniform combustion.

 Internal combustion engines are conventionally known which operate by switching the combustion mode between stratified charge combustion and uniform combustion and which are for example of the type of internal combustion engines with spark ignition and direct injection or the like .

 When such a combustion engine operates in the stratified charge combustion mode, combustion is carried out by injecting fuel during the last period of the compression stroke of the internal combustion engine, so as to form a mixture of fuels fuel rich only around a spark plug in a combustion chamber. During the uniform combustion mode, combustion is achieved by injecting fuel during the intake stroke of the combustion engine, so as to form a uniform mixture layer within the entire combustion chamber. Basically, during stratified charge combustion mode, the output power of the engine is controlled by controlling the amount of fuel injected. The control quantities relating to the injection system, the ignition system and the like, such as the quantity of fuel injected, the ignition timing, etc., are fixed in correspondence with the actuation quantity of a accelerator. On the contrary, during the uniform combustion mode, the output power of the engine is mainly regulated by controlling the degree of opening of a throttle valve.

 The control quantities mentioned above and relating to the injection system, the ignition system and the like, are fixed in correspondence with the quantity of air supplied to the combustion chamber (quantity of intake air).

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 In internal combustion engines in which the combustion mode is switched as described above, the quantity of EGR gas recirculated from the exhaust system to the intake system is regulated via the control d '' an EGR recirculation valve provided in an EGR recirculation passage which connects the exhaust system and the intake system. A large amount of EGR recirculation gas is recirculated to the intake system during the stratified charge combustion mode, in order to improve (decrease) the emission of nuts, reduce combustion noise, etc.

 However, if the EGR recirculation gases introduced during the stratified charge combustion mode remain in significant quantity in the exhaust system or the combustion chamber during or after switching from the stratified charge combustion mode to the uniform combustion mode, combustion can become unstable and misfires can occur, which degrades the road handling of the vehicle.

 In this type of internal combustion engine, therefore, in the event of a request to switch from the stratified charge combustion mode to the uniform combustion mode, the degree of opening of the EGR recirculation valve is modified to the required degree d opening, so as to sufficiently reduce the amount of recirculation gas recirculated to the intake system, as described in, for example, Japanese patent application released for public inspection JP-A-11-287143. After a predetermined delay period has elapsed after changing the degree of opening of the EGR recirculation valve, the control mode of the ignition system or injection system is switched to a control mode designed for uniform combustion. Consequently, the combustion mode is switched after the EGR recirculation gases remaining in the intake system or the combustion chamber have been completely discharged. This can significantly prevent the degradation of handling.

 In addition, at the moment of switching from the stratified charge combustion mode to the uniform combustion mode, in this type of internal combustion engine, the amount of control concerning the intake system (degree of opening of the throttle valve gas) is also changed from a requested value for stratified charge combustion to a requested value for uniform combustion. The control is designed in such a way that the requested value for the degree of opening of the throttle valve is fixed at a value closer to the closed side during the uniform combustion mode than during the stratified charge combustion mode, provided that the amount of throttle operation remains the same. Consequently, when the combustion mode is switched from stratified charge combustion to

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 uniform combustion, the requested value of the throttle valve opening degree is changed to a value on the closed side.

 However, in the intake system, there is a delay in response such as a delay in closing the throttle valve, a delay in air (the time the air moves from the throttle valve to the chamber combustion), etc. Consequently, immediately after the quantity of control concerning the intake system has been changed from the value requested for combustion with stratified charge to the value requested for uniform combustion, the quantity of intake air is still greater than the quantity actually requested, due to the response time in the admission system. Consequently, there is a risk that when the control mode of the injection system and the ignition system is switched to the control mode set for uniform combustion, the control quantities of the injection system and the ignition system ignition are fixed in correspondence with the quantity of intake air (air flow) then present, which is still greater than the quantity requested, so that the engine torque can temporarily increase and that a slip of torque by tiers can occur.

 In this type of internal combustion engine, therefore, a correction of the ignition timing delay is carried out immediately after the control mode of the ignition system and the intake system has been switched from the control mode designed for uniform combustion, as described in, for example, Japanese patent applications released for public inspection JP-A-10-68375 and 11-107815. The correction of the ignition timing delay cancels the increased amount of runoff corresponding to the response time of the intake system, so as to substantially avoid the appearance of torque slip by steps and to reduce the degradation of road holding.

 However, although setting a delay time period and correcting the ignition timing delay described above may prevent the occurrence of torque fluctuation and the deterioration of handling related When switching from combustion mode from stratified charge combustion to uniform combustion, there are problems discussed below which cannot be ignored.

 In fact, if a delay time period is set as mentioned above, the stratified charge combustion mode continues with a reduced amount of EGR recirculating gas during the delay time period, so that the emission of NOx degrades and the combustion noise increases. Therefore, it is desirable that the delay period be reduced as much as possible. However, if a sufficient delay time is not ensured, the occurrence of an ignition failure will be inevitable. As a result, it is difficult to remove the degrada-

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tion concernant l'émission des NOx et l'augmentation du bruit de combustion et d'assurer en même temps une bonne tenue de route.

regarding the emission of NOx and the increase in combustion noise and at the same time ensuring good handling.

 It has been proposed that the delay time period be reduced in an operating state where the torque fluctuation of the combustion engine is not likely to lead to degradation of the road holding. For example, during sudden acceleration, the reduction in torque caused by an ignition failure is less likely to lead to degraded handling when the vehicle is not subjected to sudden acceleration, because it is the brutal acceleration itself which causes a shock. Consequently, in such a state, it is possible to shorten the delay time period so as to reduce the degradation concerning the emission of NOx and the increase in combustion noise, without degrading the road holding.

 However, even in the state mentioned above, there is an upper limit of the permissible amplitude of the torque fluctuation which does not degrade the handling, and therefore there is also a limit to the reduction of the delay time period.

 Correspondingly, an object of the present invention is to provide a control device and a method for controlling an internal combustion engine which are capable of further improving (reducing) the emission of NOx and reducing noise combustion without degrading the road holding at the time of switching the combustion mode from stratified charge combustion to uniform combustion.

 To this end, the invention according to a first aspect relates to an internal combustion engine control device, which is applied to an internal combustion engine in which the quantity of EGR exhaust gas recirculated from a system exhaust to an intake system, is adjusted by controlling the degree of opening of an EGR recirculation valve provided in an EGR recirculation passage of the exhaust gas connecting the exhaust system and the intake system and which, when switching the combustion mode from a stratified charge combustion mode to a uniform combustion mode, switches a control mode of an injection system and an ignition system a control mode set for the stratified charge combustion mode to a control mode set for the uniform combustion mode after the expiration of a predetermined period of delay time after switching the degree of open re of the EGR recirculation valve to a requested degree of opening fixed for switching from the stratified charge combustion mode to the uniform combustion mode, and which performs a torque reduction control consisting in reducing the torque of the internal combustion engine right after

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 that the control mode has been switched, the control device being characterized in that it comprises: - modification means for modifying the delay time period corresponding to the operating state; and fixing means for fixing the amount of control relating to the torque reduction control in correspondence with the delay time period modified by the modification means.

 Corresponding to this structure, when the combustion mode is to be switched from stratified charge combustion to uniform combustion, the control mode of the injection system and the ignition system is switched from the control mode set for combustion with stratified charge in the control mode fixed for uniform combustion after the expiration of a predetermined delay time period following the modification of the degree of opening of the EGR opening valve. Consequently, the control mode of the injection system and the ignition system is switched to the control mode for uniform combustion after the effect of the existing EGR recirculation gases has been substantially reduced. As a result, the torque drop caused by the occurrence of an ignition failure is reduced.

In addition, immediately after switching the control mode of the injection system and the ignition system, the torque reduction control to reduce the torque of the internal combustion engine is performed. As a result, the increase in torque caused by the delay in the intake system is reduced.

 Furthermore, in this structure the delay time period is changed in correspondence to the operating state, and the amount of control relating to the torque reduction control is set in correspondence to the modified delay time period. As a result, it becomes possible to adjust the torque through the torque reduction control, as the type of torque reduction caused by ignition failures is changed by changing the delay time period. As a result, it becomes possible to more preferably suppress the torque reduction caused by an ignition failure. Thus, it becomes possible to allow a greater reduction in torque, while avoiding degradation of the road holding. Consequently, a further reduction in the delay time period accompanied by the reduction in torque caused by ignition failures can be achieved without degrading the handling. As a result, it becomes possible to reduce the degradation of the NOx emission and the increase in combustion noise while ensuring good handling.

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 In the device described above, the torque reduction control can reduce the torque by a correction of the ignition timing delay of the internal combustion engine, and the fixing means can fix the amount of timing delay correction d 'ignition related to the torque reduction control, corresponding to the delay time period modified by the modification means.

 According to this structure, the torque reduction control is carried out by means of the ignition timing delay correction and the amount of delay correction is fixed in correspondence with the delay time period. As a result, it becomes possible to control the torque more easily and more appropriately.

 According to another embodiment of the invention, the fixing means fix the amount of delay correction so as to cause a torque fluctuation which substantially eliminates the torque fluctuation caused by the modification of the delay time period. The fixing means can fix the amount of delay correction in correspondence with the degree of reduction of the delay time period, and with the required load and the rotational speed of the internal combustion engine.

 According to yet another embodiment of the invention, the modification means reduce the delay time period if the internal combustion engine is in an operating state for which a fluctuation in torque caused by an ignition failure does not risk not lead to degraded handling.

The fixing means fixes the amount of delay correction so as to cause an increase in torque when the delay time period is reduced.

 According to yet another embodiment, the operating state constitutes at least one state in which a vehicle accelerates violently, a state in which the load of the internal combustion engine is high and a state in which a lock-up or lock-up clutch is not completely locked. The internal combustion engine is preferably an internal combustion engine of the spark ignition and direct injection type.

 A second aspect of the invention relates to an internal combustion engine control method which is applied to an internal combustion engine in which a quantity of EGR recirculation gas recirculated from an exhaust system to an intake system , is adjusted by controlling the degree of opening of an EGR recirculation valve provided in an EGR recirculation passage connecting an exhaust system to an intake system and which, when the combustion mode is to be switched from a combustion mode with stratified charge to a uniform combustion mode, switches a system control mode

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 injection and ignition system from a control mode set for the stratified charge combustion mode to a control mode set for the uniform combustion mode, after the expiration of a period of time of predetermined delay after switching the opening degree of the EGR recirculation valve to a requested opening degree fixed for switching from the stratified charge combustion mode to the uniform combustion mode, and which achieves a reduction in torque reduction control the torque of the internal combustion engine immediately after the control mode has been switched. The control method comprises the steps of: modifying the delay time period in correspondence with the operating state and fixing the amount of control relating to the torque reduction control in correspondence with the modified delay time period .

- la figure 2 est un ordinogramme illustrant une procédure de traitement pour la commutation du mode de combustion ; - la figure 3 est un ordinogramme illustrant une procédure de traitement pour la commutation du mode de combustion ; - les figures 4A à 4G sont des diagrammes temporels indiquant des modes de contrôle pendant la commutation du mode de combustion ; et - les figures 5A à 5C sont des diagrammes schématiques indiquant en fonction du temps la transition du couple pendant la commutation du mode de combustion. Other objects, characteristics and advantages of the invention will appear better on reading the following description of preferred embodiments given without limitation and with reference to the appended drawing, in which identical numbers are used to present identical elements , and in which: - Figure 1 is a schematic representation of the general structure of an embodiment of the invention;

- Figure 2 is a flowchart illustrating a processing procedure for switching the combustion mode; - Figure 3 is a flowchart illustrating a processing procedure for switching the combustion mode; - Figures 4A to 4G are time diagrams indicating control modes during switching of the combustion mode; and - Figures 5A to 5C are schematic diagrams indicating as a function of time the transition of the torque during the switching of the combustion mode.

 We will now describe a preferred embodiment of the invention, with reference to the accompanying drawings.

 As shown in Figure 1, in an internal combustion engine 10 formed as an internal combustion engine of the spark ignition type and direct injection, installed on a vehicle, a combustion chamber 11 is connected to an intake passage 12 and an exhaust passage 13. The intake passage 12 for supplying air to the combustion chamber 11 is provided with a throttle valve or throttle valve 15 for adjusting the quantity of air supplied to the combustion chamber II (the intake quantity GA). The degree of opening of the throttle valve 15 (degree of opening of the throttle valve TA) is regulated by the control control of a throttle motor 15a carried out by an electronic control unit (ECU) 16 which performs various checks of the engine. combustion 10. An intake pressure sensor 17 for measuring the pressure inside the intake passage

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 12 (intake pressure PM) is provided downstream of the throttle valve 15 of the intake passage 12. The ECU unit 16 determines the quantity of intake air GA from the measurement results supplied by the intake pressure sensor 17.

 Is provided in the combustion chamber 11 an injector 18 which injects fuel directly into the combustion chamber 11 and a spark plug 19 which ignites the fuel injected by a discharge of sparks. The injector 18 and the spark plug 19 are actuated and controlled by one of the ECUs 16. Consequently, the controls of the injection system and of the ignition system of the combustion engine 10, such as the controls of the instant of fuel injection and the duration of fuel injection, control of the ignition instant, etc. are produced by the ECU 16 unit.

 The exhaust passage 13 is provided with a sensor 13a of the air-fuel ratio for measuring the oxygen concentration in the exhaust gases discharged from the combustion chamber 11. From the result of the measurement by the sensor 13a of the air-fuel sensor, the ECU unit 16 measures the air-fuel ratio of the mixture present in the combustion chamber 11 (the weight ratio of the fuel relative to the air in the mixture).

 An EGR recirculation passage 14 connects the exhaust passage 13 of the engine 10 to part of the intake passage 12 to the valve of the throttle valve 15.

Part of the exhaust gas discharged from the combustion chamber
11 is recirculated into the intake passage 12 via the EGR recirculation passage 14. The EGR recirculation passage 14 is provided with an EGR recirculation valve 20. The degree of opening of the EGR recirculation valve 20 is controlled by the ECU 16, so as to adjust the amount of exhaust gas recirculated in the exhaust passage 12 (recirculating gas or EGR gas), which constitutes the amount of EGR recirculating.

ECU 16 receives output signals from intake pressure sensor
17 and various other sensors and the like, for example, an NE sensor 21 for measuring the speed of rotation of the engine 10 (NE), an accelerator sensor 22 for measuring the amount of actuation of an accelerator pedal ( not shown), in fact, the amount of ECU accelerator actuation, etc. As a result, unity
ECU 16 is able to capture the operating conditions of the combustion engine 10 and the vehicle. In accordance with the operating conditions of the combustion chamber 11 and of the vehicle, entered as described above, the unit
ECU 16 actuates and controls the throttle valve 15, the injector 18, the spark plug 19, the EGR recirculation valve 20, etc., thereby carrying out various checks of the combustion engine 10.

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 As a control member, the ECU unit 16 performs the control of the switching of the combustion mode in the combustion engine 10, between "stratified charge combustion" and "uniform combustion" in correspondence with the operating state of the combustion engine 10 as entered from the actuation quantity of the ACCP accelerator, the rotation speed of the engine NE, etc.

 During the uniform combustion mode, combustion is carried out with a layer of mixture uniformly dispersed in the combustion chamber 11, by fixing the instant of fuel injection at a moment of the intake stroke.

During this mode, the ECU unit 16 fixes a requested value of the quantity of fuel injected from the injector 18, in fact the requested quantity of fuel injection Q in correspondence with the quantity of intake air GA supplied in the combustion chamber 11, so that the air-fuel ratio becomes equal to a predetermined target air-fuel ratio. The quantity of intake air GA is repeated in correspondence with the degree of opening of the throttle valve 15 (degree of throttle opening) TA. Consequently, during the uniform combustion mode, the output power of the combustion engine 10 is regulated by controlling the degree of opening of the throttle valve 15.

 During the stratified charge combustion mode, combustion is carried out with a layer of a fuel mixture which is relatively rich in fuel and which is partially formed only around the spark plug 19, fixing the instant of injection of fuel at an instant which is situated in a later period of the compression stroke which immediately precedes ignition. Consequently, during the stratified charge combustion mode, combustion can be carried out with an air-fuel ratio which is relatively low in fuel and which passes the limit of uniform combustion. During stratified charge combustion, the output power of the combustion engine 10 is regulated by controlling the quantity of fuel injected. The requested quantity of fuel injection Q is fixed in correspondence with the load KL which is determined by the amount of actuation of the accelerator ACCP, the load of the air conditioner, the electrical load, etc.

 We will now describe the switching of the combustion mode from combustion with stratified charge to uniform combustion, in the reaction mode carried out as described above.

 For switching the combustion mode from stratified charge combustion to uniform combustion in this embodiment, the degree of opening of the EGR recirculation valve 20 is first of all changed to a required degree of opening which is requested at the time of switching the combustion mode

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 (in this case, the "fully closed degree"), as is the case with an internal combustion engine control device described above.

 After the expiration of a predetermined delay period following the change in the degree of opening of the EGR recirculation valve 20, the control mode of the injection system and of the ignition system is switched from the control mode. designed for stratified charge combustion to a control mode designed for uniform combustion.

 Further, in this embodiment, after the control mode of the injection system and the ignition system has been switched from the control mode for stratified charge combustion to the control mode for uniform combustion, a control torque reduction to reduce the torque of the internal combustion engine is achieved by a correction of the ignition time delay.

 Setting a delay time period substantially avoids the reduction in torque caused by an ignition failure, and controlling torque reduction by correcting the delay in the ignition time substantially avoids the increase in torque caused by a delay in the intake system, as described above. As a result, torque fluctuations can be avoided while switching the combustion mode.

 The degree of effect of torque fluctuations on handling varies according to the operating state. In a specific state, we can consider as admissible a certain amplitude of the torque reduction caused by an ignition failure. In this embodiment, however, the delay time period is changed in correspondence with the operating state. If the operating state is such that the torque fluctuation caused by an ignition failure is not likely to lead to degraded handling, the delay time period is made shorter than if the operating state is different. Thus, by shortening the delay time period so as to effect the switching of the combustion mode during a period situated further forward while avoiding the degradation of the road holding, the degradation (increase) concerning the emission NOx and increased combustion noise are reduced.

 In addition to the above described mode of switching from the combustion mode from the stratified charge combustion to the uniform combustion, the amount of delay correction A relating to the ignition timing delay correction is fixed in correspondence with the period of delay time modified in correspondence with the operating state. As a result, switching the combustion mode can be performed more preferably.

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 The specific controls concerning the switching of the combustion mode from combustion with stratified charge to uniform combustion carried out by the control device of the internal combustion engine in this embodiment will be described in detail with reference to FIGS. 2 to 5 .

 Figures 2 and 3 illustrate an ECU control procedure 16 relating to switching the combustion mode from stratified charge combustion to uniform combustion. FIGS. 4A to 4G indicate the types of control carried out at the moment of switching the combustion mode.

 As shown in FIG. 4A, at the time point t0, when a demand for switching from stratified charge combustion to uniform combustion arises, the ECU 16 first calculates the reference delay time periods Tdnl, Tdn2 from the instantaneous engine rotation speed NE and the instantaneous requested load KL of the engine 10 (step 10 in FIG. 2).

 The reference delay time periods Tdnl, Tdn2 are delay time periods which are fixed in the state where the torque fluctuation is not likely to lead to degraded handling, as mentioned above. The reference delay time periods Tdnl, Tdn2 are sufficiently long periods of time, so that the remaining EGR recirculation gas decreases to a level which eliminates the risk of ignition failure after the degree of opening of the EGR 20 recirculation valve has been modified. The reference delay time period Tdnl thus fixed is a delay time period from the modification of the degree of opening of the EGR recirculation valve 20 until the switching of the control mode of the intake system to a control mode designed for uniform combustion. The reference delay time period Tdn2 is a delay time period from the modification of the control mode of the intake system to the modification of the control mode of the ignition system and of the injection system towards the control mode for uniform combustion.

 Following step 20, the ECU 16 determines whether the operating state relating to the shortening of the delay time period has been established. In fact, the ECU unit 16 determines whether the present operating state is a state in which the fluctuation in torque is unlikely to lead to degraded handling, and consequently if a certain reduction in torque caused by a shortened delay time period is permissible.

 Examples of the operating states which satisfy the above mentioned condition are set out below.

 During sudden accelerations, the fluctuation of torque is not likely to lead to degraded handling due to the presence of a shock

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 acceleration as mentioned above. During high load operation, too, the torque fluctuation is unlikely to cause degraded handling if the torque fluctuation is moderate, since the combustion engine 10 produces greater noise and vibration.

 In a vehicle in which an automatic transmission is equipped with a lockup or shift clutch, the above mentioned condition is satisfied when the lockup clutch is not in a fully locked state. In such a vehicle, when the lockup clutch is fully locked, the input side and the output side of the automatic transmission are mechanically connected, so that power can be directly transferred between the engine crankshaft and the vehicle transmission axle, without interposition of the torque converter oil. Consequently, during the fully locked state, the torque fluctuations of the combustion engine 10 are transmitted directly to the axle, the engine of the vehicle, and consequently, the torque fluctuations risk leading to degraded road holding of the vehicle. Consequently, when the lock-up or lock-up clutch is not in the fully locked state, i.e. when the linkage of the lock-up clutch is completely removed or when the lock-up clutch does not 'is connected only partially (in a sliding state), the rotation of the combustion engine 10 is transferred to the axle via the torque converter oil. Consequently, when the lock-up clutch is not fully locked, the torque fluctuation is less likely to lead to degraded handling than when the lock-up clutch is fully locked.

 In correspondence with the results of the determination, the ECU 16 modifies the subsequent processing. We will first describe a treatment carried out when the operating state mentioned above is not satisfied ("NO" in step 20), that is to say when the operating state n 'is not a state where the torque fluctuation is not likely to lead to degraded handling.

 In this case, the ECU 16 sets the reference delay time periods Tdnl, Tdn2 as delay time periods Tdl, Td2 which are actually used (step 36) and performs a processing relating to the switching of the mode combustion.

 In fact, as shown in FIG. 4B, at time point t0, when the request for mode switching is made, the set opening degree of the EGR recirculation valve 20 is changed to a requested opening degree ( a completely closed state in this case) (step 40). Then, at time point t2, when the reference delay time period Tondi fixed at the delay time period Tdl has elapsed ("YES" in step 50), the system control mode

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 Intake is switched to the control mode designed for uniform combustion, as indicated by the dashed line at one point in Figure 4C. Consequently, the degree of opening TA of the throttle valve 15, at the temporary point t2 is modified towards a requested degree of opening for uniform combustion (step 60) as indicated by the dashed line at a point in the figure. 4D. After the degree of opening of the throttle valves has been modified as described above, the quantity of intake air GA is modified with a certain delay, and remains above the quantity required for uniform combustion, and in fact, remains in an excess amount, as indicated by the dashed line at a point in Figure 4E.

 After this, at time point t4, when the reference delay time period Tdn2 set to the delay time period Td2 has elapsed following time point t2 ("YES" in step 70), the mode the ignition system and injection system control switches to the control mode designed for uniform combustion (step 80), as indicated by the dashed line at a point in Figure 4F. Simultaneously with mode switching, the amount of stall delay correction A is set as indicated by the dashed line at a point in Figure 4G, and torque reduction control is achieved through the correction delay ignition timing (step 110).

 The amount of stall delay correction A in this case is determined from the rotational speed of the NE of the engine and the requested load KL of the combustion engine 10 (step 105). The amount of timing delay correction A is fixed so as to reduce the torque by an amount corresponding to the excess of the amount of intake air GA. More specifically, the amount of setting delay correction A is fixed as described above for a predetermined duration following the time point t4. After this, the amount of stall delay correction A is gradually brought to "0" regardless of changes in the amount of intake air GA.

 After the torque reduction control via the ignition timing delay correction has ended, the degree of opening of the EGR recirculation valve 20 is changed to the required degree of opening for the uniform combustion (step 120), thereby completing the switching of the combustion mode.

 Thus, when the operating state is not a state in which the torque fluctuation is not likely to lead to degraded handling, the delay time period is fixed at a duration which is sufficiently long to the remaining EGR recirculation gas decreases to a level that will not cause ignition failure. In this case, the amount of timing delay correction A is fixed so as to reduce the torque by an amount corresponding to the excess of the amount of air.

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 GA intake caused by delay in the intake system. Thus, the ignition timing is corrected in the direction of the delay. As a result, the torque fluctuation during switching the combustion mode is substantially suppressed as shown in Figure 5A.

 On the contrary, if the predetermined operating state mentioned above is satisfied ("YES" in step 20), that is to say if the operating state is a state in which the torque fluctuation does not risk of leading to degraded handling, the following process is carried out.

 In fact, the ECU 16 determines the reference delay time periods Tdnl, Tdn2 (step 10 in FIG. 2), and further determines delay time periods Tdsl, Tds2 (step 30). Next, the ECU 16 sets the delay time periods thus determined Tdsl, Tds2, as being delay time periods Tdl, Td2 which are actually used for the processing (step 33), and performs the subsequent processing.

 The time periods Tdsl, Tds2 are determined by taking into account the low risk of torque fluctuation leading to degraded handling, in addition to the rotation speed NE of the combustion engine and to the requested load KL of the combustion engine 10. The time periods Tdsl, Tds2 thus determined are fixed shorter than the reference time periods Tdnl, Tdn2. In this case, therefore, the switching of the combustion mode is carried out without waiting for the expiration of a delay time period during which the effect of the remaining EGR recirculation gas can be sufficiently reduced. As a result, a slight drop in torque due to ignition failure occurs.

 In this case, consequently, at the time point t0 where the mode switching request is made, the degree of setpoint opening of the EGR recirculation valve 20 is fixed in the completely closed state, which is the required degree d aperture set for mode switching (step 40). As indicated in solid lines in FIG. 4C, at the time point tl where the time period Tdsl has elapsed, the control mode of the intake system is switched to the uniform combustion control mode. In addition, at time point t0, the degree of opening TA of the throttle valve is fixed to the degree of opening required for uniform combustion (step 60) as indicated by a solid line in FIG. 4E.

 At time point t3, the time period Tds2 fixed as the delay time period Td2 has elapsed by following time point tl, the control mode of the ignition system and of the injection system is switched to the mode control for uniform combustion (step 80), as indicated by a solid line in Figure 4F. At the same time, the torque reduction control by means of the ignition instant delay correction is carried out in use.

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 sant the fixed amount of timing delay correction A (step 110), as indicated by a solid line in FIG. 4G.

 It will be noted here that the amount of correction A of stall delay is determined by taking into account the degree of reduction P of the delay time period in addition to the rotation speed NE of the combustion engine and to the requested load KL of the combustion engine 10 (step 100). The degree of reduction P is determined as being the ratio of the sum of the time periods Tdsl, Tds2 fixed as periods of delay time to the sum of the reference delay time periods Tdnl, Tdn2. The amount of stall delay correction A set by taking the degree of reduction P as indicated by the solid line in Figure 4G is less than the normal amount of stall delay correction A determined from only the rotation speed of the combustion engine NE and of the requested load KL, as indicated by the dashed line in FIG. 4G. In fact, thanks to the torque reduction control by means of the ignition timing delay correction in this case, a sufficient torque reduction corresponding to the excess of the quantity of intake air GA n ' is not performed, but the torque is increased.

 Then, after the torque reduction control via the ignition timing delay correction is completed, the degree of opening of the EGR recirculation valve 20 is changed to the requested degree of opening of the uniform combustion (step 120), thus completing the switching of the combustion mode.

 As described above, the delay time periods Tdl, Td2 are changed in correspondence with the operating state in this embodiment.

If the delay time periods Tdl, Td2 are changed, the amount of EGR recirculation gas remaining during the switching of combustion mode is changed, and the type of torque reduction caused by the effect of EGR recirculation gas remaining is also changed. In this embodiment, the amount of combustion A of stall delay is set in correspondence with the degree of reduction P of the delay time period which is determined by the delay time periods Tdl, Td2, modified as described below. -above. As a result, the ignition timing delay correction can be performed so that the torque is appropriately adjusted in correspondence with the torque reduction caused by the ignition failure.

 If a torque reduction occurs which is due to an ignition failure caused by the modification of the delay time periods Tdl, Td2, it is also possible to prevent the torque reduction caused by an ignition failure, which leads to degraded road holding, for example

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 setting the amount of timing delay correction A so that an increase in torque of an appropriate magnitude will occur immediately after the above-mentioned reduction in torque, as shown in Figure 5B. This measure is effective because the torque fluctuations in the positive and negative directions cancel each other out during the transfer of power from the combustion engine 10 to the axle. Thus, even if a greater reduction in torque occurs as indicated in FIG. 5B, the degradation of road holding can be avoided, by setting an amount of correction A of stall delay such that a greater increase in torque occurs. produces and corresponds to the torque reduction.

 Thus, if the amount of setting delay correction A is fixed in correspondence with the delay time periods Tdl, Td2 (in this case, the degree of reduction P determined by periods of delay time), it becomes possible to perform an appropriate torque control in correspondence with the torque reduction which varies depending on the setting of the delay time periods. By means of this torque control, it becomes possible to allow greater torque reduction to be achieved while appropriately preventing degradation of the road holding. As a result, it becomes possible to further reduce the delay time period.

 From the embodiment described above, the following advantages are obtained.

 In this embodiment, when the combustion mode is switched from stratified charge combustion to uniform combustion, the delay time periods Tdl, Td2, from the modification of the degree of opening of the EGR recirculation valve 20, towards the switching of the control mode of the ignition system and of the injection system is modified in correspondence with the operating state. Then, the amount of stall delay correction A is set in correspondence with the delay time periods Tdl, Td2 modified as described above, and the torque reduction control via the stall delay correction Ignition is carried out immediately after switching the control mode of the injection system and the ignition system. Consequently, it becomes possible to adjust the torque appropriately, when the type of torque reduction caused by the ignition failures is changed by modifying the delay time periods Tdl, Td2. Thus, it becomes possible to more preferably suppress the reduction in torque caused by an ignition failure. Thus, it becomes possible to allow a greater reduction in torque while avoiding degradation of the road holding. Consequently, a further reduction in the delay time periods Tdl, Td2 accompanied by a reduction in torque caused by the ignition failure can be obtained without degradation.

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tion de la tenue de route. En conséquence, il devient possible de réduire la dégradation (augmentation) des émissions de NOx et l'augmentation du bruit de combustion tout en assurant une bonne tenue de route.

handling. As a result, it becomes possible to reduce the degradation (increase) of NOx emissions and the increase in combustion noise while ensuring good handling.

 The foregoing embodiment can be modified as follows.

 Although in the foregoing embodiment, the amount of stall delay correction A is set using the degree of reduction P of the delay time period, the amount of stall delay correction A can also be set to from the values of the delay time periods. In addition, the amount of stall delay correction A can be set from any parameter, such that the value of the parameter is changed in direct correspondence with the delay time period. Similar to the above embodiment, these modifications make it possible to carry out an appropriate torque control in correspondence with the type of torque reduction modified with the delay time period. Thus, the modifications obtain substantially the same advantages as those obtained by the preceding embodiment.

 Although in the foregoing embodiment, the torque reduction control is performed through the ignition timing delay correction, similar torque control can also be performed using other parameters, for example example, by correcting the amount of fuel injected. Such a modification also makes it possible to carry out an appropriate torque control, in correspondence with the torque reduction if the amount of control relating to the torque reduction control is fixed in correspondence with the delay time period. Thus, the modification obtains substantially the same advantages as those obtained by the foregoing embodiment.

 While the invention has been described with reference to what is considered to be the preferred embodiments, it will be understood that the invention is not limited to the embodiments or structures described. On the contrary, the invention is intended to cover the various modifications and equivalent arrangements. In addition, while the various elements of the invention thus described are represented in various combinations and configurations, they are cited by way of examples, other combinations and possibly more numerous configurations, or else a single configuration also corresponds the spirit and scope of the invention.

Claims (10)

 the control device being characterized in that it comprises: modification means (16) for modifying the delay time period corresponding to the operating state; and - fixing means (16) for fixing the quantity of control relating to the torque reduction control in correspondence with the delay time period modified by the modification means.

 CLAIMS 1. An internal combustion engine control device, which is applied to an internal combustion engine (10) in which the amount of EGR exhaust gas recirculated from an exhaust system to a intake system, is adjusted by controlling the degree of opening of an EGR recirculation valve (20) provided in an EGR recirculation passage (14) connecting the exhaust system and the intake system and which, when '' you must switch the combustion mode from a stratified charge combustion mode to a uniform combustion mode, switch a control mode of an injection system and an ignition system of a control mode set for stratified charge combustion mode to a control mode set for uniform combustion mode after the expiration of a predetermined period of delay time after switching the degree of opening of the EGR recirculation valve (20 ) at ad required degree of opening fixed for switching from combustion mode with stratified charge to uniform combustion mode, and which performs a torque reduction control consisting in reducing the torque of the internal combustion engine (10) immediately after the mode of control has been switched,  2. Control device according to claim 1, characterized in that the torque reduction control reduces the torque by means of a correction of the ignition timing delay of the internal combustion engine (10).  3. Control device according to claim 2, characterized in that the fixing means (16) fix the amount of ignition timing delay correction related to the torque reduction control corresponding to the modified delay time period by means of modification.  4. Control device according to claim 3, characterized in that the fixing means (16) fix the amount of delay correction so as to cause a torque fluctuation which substantially suppresses the torque fluctuation caused by the modification of the period delay time. <Desc / Clms Page number 19>  5. Control device according to claim 3 or 4, characterized in that the fixing means (16) fix the amount of delay correction in correspondence with the degree of reduction of the delay time period, and with the load and the required speed of rotation of the internal combustion engine (10).  6. Control device according to any one of claims 1 to 5, characterized in that the modification means (16) reduce the delay time period if the internal combustion engine (10) is in an operating state for which a torque fluctuation caused by an ignition failure does not risk leading to degraded handling.  7. Control device according to claim 6, characterized in that the fixing means (16) fix the amount of delay correction so as to cause an increase in torque when the delay time period is reduced.  8. Control device according to claim 6 or 7, characterized in that the operating state constitutes at least one state in which a vehicle accelerates violently, a state in which the load of the internal combustion engine (10) is high and a state in which a lock-up or bypass clutch is not fully locked.  9. Control device according to any one of claims 1 to 8, characterized in that the internal combustion engine (10) is an internal combustion engine of the spark ignition type and direct injection.  10. A method of controlling an internal combustion engine which is applied to an internal combustion engine (10) in which an amount of EGR exhaust gas recirculated from the exhaust system to an intake system is controlled by controlling the degree of opening of an EGR recirculation valve (20) arranged in an EGR recirculation passage (14) connecting the exhaust system and the intake system, and which, when the mode has to be switched of combustion from a combustion mode with stratified charge at charge to a uniform combustion mode, switches the control mode of an injection system and of an ignition system from a control mode fixed for the mode combustion with stratified charge to a control mode set for the uniform combustion mode after the expiration of a predetermined period of delay time after switching the degree of opening of the EGR recirculation valve (20) to one degree <Desc / Clms Page number 20>  the control method being characterized in that it comprises the steps consisting in: - modifying the delay time period in correspondence with an operating state; and - to set the amount of control relating to the torque reduction control in correspondence with the modified delay time period.

 opening demand fixed for switching from the stratified charge combustion mode to the uniform combustion mode, and which performs a torque reduction control consisting in reducing the torque of the internal combustion engine (10) immediately after the control mode has been switched,