FR2795025A1 - VEHICLE INTERNAL COMBUSTION ENGINE CONTROL APPARATUS - Google Patents

Abstract

Control apparatus for a vehicle internal combustion engine (10). The engine (10) is operated by selectively changing a combustion mode between a homogeneous charge combustion mode and a stratified charge combustion mode in accordance with an operating state of the engine. The control apparatus includes: fuel cutoff means (30) for stopping the supply of fuel to the engine (10); torque reduction means (30) for reducing an engine output torque (10) before the fuel supply is stopped by the fuel cutoff means (30). According to the invention, if the combustion mode selected is stratified charge combustion, the torque reduction means (30) reduces the output torque of the engine (10) so that the output torque becomes less than the output torque generated when the engine (10) is operated by the stratified charge combustion mode.

Description

MOTOR CONTROL APPARATUS

VEHICLE INTERNAL COMBUSTION

  The present invention relates to a control apparatus for an internal combustion engine of a vehicle and, more particularly, to a control apparatus applied to an internal combustion engine of a vehicle which is operated by changing the combustion mode between a mode of stratified charge combustion and a homogeneous charge combustion mode according to the state of

engine operation.

  In a vehicle equipped with an internal combustion engine, such as a motor vehicle or the like, the rotation of an engine output shaft is transmitted to the drive wheels of the vehicle via a force transmission mechanism. drive comprising transmission and the like. A vehicle having an automatic transmission as a transmission device of a drive force transmission mechanism is equipped with a fluid transmission device, such as a torque converter or the like, which transmits the rotation from the internal combustion engine to the transmission via a fluid such as oil or the like. The provision of such a fluid transmission device allows the rotation of the motor output shaft, which varies greatly in speed, torque or the like, to be transmitted to the wheel side

  training without constraint or significant problem.

  However, in a fluid transmission device such as a torque converter or the like, a reduction in the efficiency of rotation transmission

  is practically inevitable due to the smooth sliding.

  Consequently, in many drive force transmission mechanisms which are equipped with a fluid transmission device, a lock-up clutch is provided for directly connecting an engine side and a transmission side of the fluid transmission device in a manner mechanical. During a predetermined operating state, the locking clutch is engaged, so that the rotation is directly transmitted by diverting the fluid in the fluid transmission device. Thus, a reduction in transmission efficiency is moderate, and the fuel economy of the

  internal combustion engine is improved.

  However, when switching between a state in engagement and a disengaged state of the locking clutch,

  the state of torque transmission between the engine side and the.

  transmission side of the fluid transmission device changes greatly, so that a switching shock occurs. Consequently, when the lock-up clutch is to be changed between the engaged and disengaged states, a slip command of temporarily establishing a partially engaged state on the engine and transmission sides of the lock-up clutch is made so as to allow a difference in rotation between the motor side and the side

  transmission to a certain extent.

  For example, when the locking clutch is changed from the disengaged state to the engaged state, the clutch is first kept in a sliding state during which the difference in rotational speed between the engine side and the transmission side gradually decreases. After the rotational speeds on both sides have become substantially equal, the lockup clutch is established or controlled in a fully engaged state. Of this

  way, a switching shock is moderate.

  When executing the lock-up clutch slip command, the torque transmission between the engine side and the transmission side of the clutch

  locking can be limited to a certain extent.

  That is, during the slip control, an abrupt change in torque and the transmission of a shock caused by the change in torque can be limited although a certain amount of torque is transmitted. Consequently, the execution of the slip command of the locking clutch reduces the rotational resistance on the engine output shaft, and favorably brakes a fall in the engine rotational speed if a fuel cut command. batch fuel to the engine is run during the slip control. Thus, by executing a deceleration slip command of establishing the lock-up clutch in the slip state during deceleration of the engine, for example, deceleration of the vehicle or the like, it becomes possible to cut the fuel off. more actively so as to

  further improve the engine's fuel economy.

  During the sliding state, however, the mechanical connection of the locking clutch is partially maintained, so that the damping effect of the torque shock of the fluid in the fluid transmission device cannot be fully obtained. Consequently, although the deceleration slip command is being executed, a change in stepping motor torque occurs at the time of starting the fuel cut-off or when returning from the cut-off. fuel cannot be sufficiently absorbed, so a torque shock can be caused by the change in torque

step-by-step engine.

  In order to avoid this danger, an internal combustion engine control device described in Japanese patent application pending examination n ° HEI 10-44832 performs a command consisting in gradually reducing the output torque of the engine by gradually delaying the Ignition timing before starting the fuel cut while executing the deceleration slip command of the locking clutch. By reducing the engine's output torque enough before the fuel cut in this way, the device reduces the step-by-step torque change occurring when starting the fuel cut, thereby reducing

the couple shock.

  Thus, in a characteristic internal combustion engine in which the ignition timing can be relatively freely established, the torque shock occurring at the time of starting the fuel cut can be reduced by gradually delaying the ignition timing before starting the fuel cut-off during the slip clutch deceleration control. However, in internal combustion engines operated on the basis of stratified charge combustion, such as a recently marketed direct injection type engine or the like, the control described above cannot be directly applied for the reasons set out below, so that the torque shock occurring when the fuel cut-off is started cannot be reduced sufficiently. The reasons

are as follows.

  An internal combustion engine of the direct injection type is equipped with an injector capable of injecting the fuel directly into a combustion chamber of the engine. By appropriately changing the timing of fuel injection and the like, the combustion mode of the engine is switched between a combustion mode with homogeneous charge and a combustion mode with stratified charge in accordance with the operating state.

of the motor.

  More specifically, during high load operation of the direct injection type engine, the fuel is injected during the intake stroke so as to form a homogeneous air / fuel mixture in the combustion chamber. During operation at low load, the fuel is injected at a setting during the compression stroke which immediately precedes the ignition setting, so as to form a combustible mixture only around the spark plug. By performing ignition at a timing when the mixture exists only around the spark plug, the engine achieves stratified charge combustion, in which combustion at an air / fuel ratio side

  relatively lean fuel is possible.

  If the deceleration slip control described above of the lockup clutch is applied to a direct injection type engine, the rotational resistance on the engine output shaft decreases during the deceleration slip control. As a result, during the deceleration slip control, the operating state of the engine becomes a low load state, so that stratified charge combustion is performed. However, during the stratified charge combustion mode, since it is necessary to carry out the ignition at a specified setting where a fuel exists only in the vicinity of the spark plug as mentioned above, the setting cannot be freely changed. Consequently, during the stratified charge combustion mode of the direct injection type engine, it is possible to carry out the command to reduce the change in torque step by step when starting the fuel cut by adjusting the torque. on the basis of the timing of the injection, unlike the device described in the patent application pending examination mentioned above. Consequently, during a stratified charge combustion mode, the direct injection type engine needs to reduce the engine output torque by reducing the amount of fuel injected. However, a minimum amount of fuel injected is predetermined due to the limitations relating to the construction of the injector, so that the reduction of a step-by-step change in torque based on the amount reduction adjustment d fuel injection can be obtained

only to a limited extent.

  Thus, in internal combustion engines which perform stratified charge combustion such as direct injection type engines and the like, it is impossible to sufficiently reduce the change in torque step by step before the execution of the fuel cut-off during the deceleration slip control of the locking clutch. As a result, it is difficult to sufficiently reduce the torque shock occurring when the fuel cut-off is started. Recently, vehicles equipped with an internal combustion engine which performs stratified charge combustion, such as a direct injection type engine or the like, and a continuously variable transmission have been marketed. Such a vehicle also comprises a fluid transmission device provided between the engine and the transmission, and a locking clutch for mechanically engaging an engine side and a transmission side of the fluid transmission device. In this vehicle, a locked clutch engagement state can be maintained even in a low speed range since the gear change ratio of the transmission can be continuously adjusted

without change step by step.

  Accordingly, by maintaining the engaged state of the lockup clutch during a deceleration of engine speed, such as deceleration of the vehicle or the like, it becomes possible to more actively shut off fuel and further improve the engine's fuel economy. Thus, in order to reduce the torque shock relating to the fuel cut made during the engagement state of the locking clutch at the time of an engine speed deceleration, it is necessary to reduce the torque sufficiently

  before starting the fuel cut-off.

  However, in internal combustion engines which perform stratified charge combustion, such as

  direct injection type engines as described above

  above, the operating state of the engine becomes a low load state during deceleration of the vehicle,

  so that stratified charge combustion is achieved.

  As a result, the step-by-step torque change cannot be reduced enough in advance, so that the

  torque shock cannot be reduced enough.

  Consequently, it is an object of the invention to provide a vehicle internal combustion engine control apparatus which effectively reduces a change in stepping motor torque occurring at the time of starting the fuel cut-off in an engine in which the combustion mode is selectively changed between the homogeneous charge combustion mode and the stratified charge combustion mode in accordance with the operating state. This object is achieved by a control device for an internal combustion engine of a vehicle conforming to the

present invention.

  The foregoing and other objects, features and advantages of the present invention will become apparent to

  from the following description of the embodiments

  preferred with reference to the accompanying drawings, in which identical reference numerals are used to represent identical elements and in which: FIG. 1 is a simplified illustration of an overall construction of a first embodiment of the present invention; Figure 2 is a flow diagram illustrating a procedure relating to a deceleration slip control .; Figure 3 is a flowchart illustrating a procedure relating to the determination of switching to either of the combustion modes; Figures 4 (a) to 4 (f) are timing diagrams indicating a control manner according to the first embodiment; Figures 5 (a) to 5 (f) are timing diagrams indicating a control manner according to a second embodiment;

  Figure 6 is a flowchart illustrating a sub-

  torque control program according to a third embodiment; Figs. 7 (a) to 7 (d) are timing diagrams indicating a manner of control according to the third embodiment;

  Figure 8 is a flowchart illustrating a sub-

  fuel cut execution program according to a fourth embodiment; and Figures 9 (a) to 9 (c) are timing diagrams indicating a control mode according to the fourth mode

of achievement.

  Preferred embodiments in which the control apparatus of the invention is applied to an internal combustion engine of a vehicle will be described by

  below with reference to the accompanying drawings.

FIRST EMBODIMENT

  Figure 1 is a simplified illustration of an overall construction of a control apparatus for an internal combustion engine according to a first embodiment of the invention. Referring to Figure 1, a construction of an internal combustion engine 10 to which the control apparatus is applied will be described in

detail.

  The engine 10 to which the control apparatus of the embodiment is applied is an internal combustion engine with direct injection of the spark plug type. As shown in FIG. 1, an injector 14 is provided above a combustion chamber 12 so as to inject the fuel directly into a cylinder 11. A piston 13 is placed in the cylinder 11 to slide therein -and- comes. An upper surface of the piston 13 has a recess 13a. A space defined in the recess 13a

  forms part of the combustion chamber 12.

  A spark plug 15 to ignite the air / fuel mixture is provided above the combustion chamber 12. The timing of the injection of the spark plug 15 to ignite the air / fuel mixture is adjusted by an igniter. 16 which is provided above the

spark plug 15.

  In the engine 10, the combustion mode is switched between a combustion mode with homogeneous charge and a combustion mode with stratified charge according to the state of

engine operation.

  In order to achieve homogeneous charge combustion, the fuel is injected from the injector 14 during the intake stroke of the engine 10. Since the air taken from the combustion chamber 12 is agitated in the combustion chamber 12 in Due to the air intake operation, the fuel injected into the combustion chamber 12 mixes well with the (agitated) air, thereby forming a

homogeneous air / fuel mixture.

  In order to achieve stratified charge combustion, the fuel is injected from the injector 14 at a stall during the compression stroke of the engine 10 which

  immediately precedes ignition of the air / fuel mixture.

  Consequently, the fuel is injected into the cylinder 11 and is blown into the recess 13a of the upper surface of the piston 13, which is moved upwards at the time of the injection of the fuel. As a result, a fuel air / fuel mixture is formed only in the vicinity of the spark plug 15 exposed to the combustion chamber 12. By igniting the air / fuel mixture in this way through the use of the plug ignition 15, good combustion of the air / fuel mixture can be obtained even at a ratio

  air / fuel side considerably lean.

  During high load operation of engine 10, combustion mode is set to combustion mode

  homogeneous load to ensure an engine output.

  During the low load operation, the combustion mode is set to the stratified charge combustion mode to achieve combustion at a considerably lean air / fuel ratio and thereby reduce the loss of cooling, loss of pumping and the like. Thus, in the engine 10, the improvement in fuel economy is continued by switching the combustion mode between the homogeneous charge combustion mode and the stratified charge combustion mode in accordance with

  the operating condition of the engine.

  During stratified charge combustion mode, the ignition timing cannot be freely adjusted, and the reduction in the amount of fuel injected is limited, i.e., a minimum amount of fuel injection is substantially fixed, due to limitations relating to the construction of the injector 14, as mentioned above. Consequently, the degree of freedom to reduce the output torque of the engine 10 becomes less during the stratified charge combustion mode than during the homogeneous charge combustion mode, during which the ignition timing can

  be adjusted relatively freely.

  In the engine 10, the combustion mode of which can be changed between the homogeneous charge combustion mode and the stratified charge combustion mode, an engine output shaft (crankshaft) 17 is connected to a torque converter 20. The torque converter 20 is a kind of fluid transmission device and transmits the rotations between the engine 10 and an automatic transmission 22 via a fluid such as an oil or the like. By transmitting the rotation via the fluid, the torque converter 20 transmits the rotation of the output shaft of the motor 17 which tends to vary greatly in speed, in torque or the like, to the automatic transmission 22 without any constraint or any significant problem. . The torque converter 20 includes a locking clutch 21 which allows the direct rotation transmission which does not use fluid. The locking clutch 21 is driven on the basis of the control of a hydraulic pressure (hydraulic locking engagement pressure) produced by a locking relay valve 23 for directly connecting the output shaft of the engine 17 and the automatic transmission 22 in a mechanical coupling. By appropriately establishing the direct mechanical connection using the lock-up clutch 21, the reduction in transmission efficiency caused by oil slippage occurring in the torque converter 20 is moderate, and the fuel economy of the engine 10 can be improved. In addition to a state (engaged state) in which the output shaft of the engine 17 and the automatic transmission 22 are directly completely connected and a state (disengaged state) in which the direct connection is removed, the locking clutch 21 can also be established in a semi-engaged state (sliding state), that is to say, an intermediate state between the engaged state and the disengaged state. The locking clutch 21 is switched to the sliding state by appropriately limiting the coupling force of the locking clutch 21 based on the adjustment of the hydraulic pressure (hydraulic locking engagement pressure ) of the locking relay valve 23. In the sliding state of the locking clutch 21, the direct mechanical connection between the output shaft of the engine 17 and the automatic transmission 22 is maintained to a certain degree and, when a significant torque change occurs, a difference in rotation between the output shaft of the engine 17 and the automatic transmission 22 is authorized so as to limit the transmission of an impact caused by the

change of torque.

  As is apparent from the description below

  above, the engine 10 is connected to the automatic transmission 22 and to the vehicle drive wheels, via the torque converter 20, which is a kind of fluid transmission device which transmits the rotation via a fluid, and the clutch of lock 21 which allows the direct transmission of the rotation which does not use the fluid contained in the converter

couple 20.

  The motor 10 and the locking clutch 21 are

  controlled by an electronic control unit 30.

  The electronic control unit 30 performs such commands based on the operating states of the vehicle and the engine 10 installed therein which are detected on the basis of the detection results achieved by various sensors provided in various parts of the vehicle and the engine 10 In this embodiment, the various sensors previously mentioned include a throttle opening sensor 31 for detecting the extent of opening of a throttle valve (not shown) which 'adjusts the flow of the inlet air introduced into the engine, a speed sensor 32 for detecting the speed of rotation of the engine output shaft 17, a speed sensor of the engine 33 for detecting the speed of movement of the vehicle (speed of the vehicle), an accelerator operation sensor 34 for detecting the amount of depression of an accelerator pedal 24, and the like. On the basis of the detection results delivered by the various sensors, the electronic control unit 30 controls the operation of the injector 14, of the igniter 16 and the like so as to adjust the setting of the spark plug 15 to igniting the air / fuel mixture (ignition timing), the amount of fuel to be injected from the injector 14, the timing of the fuel injection, and the like. In addition, based on the detection results delivered by the various sensors, the electronic control unit 30 controls the operation of the lock relay valve 23 so as to change the lock clutch 21 from the engaged state. ,

  the disengaged state and the sliding state.

  In this embodiment, a deceleration slip command consisting in establishing the locking clutch 21 in the sliding state is carried out during a deceleration of the motor 10. By performing this command, the rotational resistance on the shaft output of the engine 17 can be reduced so as to avoid an excessive drop in the speed of rotation of the engine while the direct connection between the output shaft of the engine 17 and the automatic transmission 22 is maintained at a certain extent, as is mentioned above. Consequently, it becomes possible to carry out the fuel cut-off more actively, that is to say, in a

  wider engine operating region.

  Figure 2 is a flowchart illustrating a processing procedure performed by the electronic control unit 30 with respect to the determination as to execute the deceleration slip command. The electronic control unit 30 performs this treatment

  periodically during engine operation 10.

  When this procedure is started, the electronic control unit 30 first determines in step S100 whether a condition for executing the deceleration slip command is met. In this embodiment, it is determined that the execution condition is met if all of the following conditions are met. (A) The depressing of the accelerator pedal PA detected by the accelerator operating sensor 34 is at zero (i.e., the accelerator pedal 24 is not

not pressed at all).

  (B) The rotation speed of the ME motor detected by the rotation speed sensor 32 is greater than one

predetermined value K1.

  (C) The vehicle speed SPD detected by the vehicle speed sensor 33 is greater than a value

predetermined K2.

  That is to say that when the accelerator pedal 24 is not actuated at all while the speed of rotation of the engine NE and the speed of the vehicle SPD are greater than certain levels (predetermined values), the control of deceleration slip is achieved in this

embodiment.

  If the execution conditions (A) to (C) are met (YES in step S100), the electronic control unit 30 establishes an execution indicator XSLU (XSLU = 1) in step S110 to produce an instruction to execute the deceleration slip command. Conversely, if any of the conditions (A) to (C) is not met (NO at step S100), the electronic control unit 30 erases the execution indicator XSLU (XSLU = 0) in step S120. After actuation of the execution indicator XSLU in this way, the electronic control unit 30 temporarily terminates the procedure. After this, the electronic control unit 30 outputs an instruction signal to the latch relay valve 23, based on the execution indicator XSLU. If the execution indicator XSLU has been set to execute the deceleration slip control, the electronic control unit 30 controls the drive of the latch relay valve 23 so as to provide a hydraulic engagement pressure clutch which is necessary to establish the locking clutch 21 in the sliding state. As a result, the force of the lockup clutch 21 to connect the output shaft of the engine 17 and the automatic transmission 22 is appropriately adjusted to establish the slip state, in which the output shaft of the engine 17 and automatic transmission 22 are partially directly interconnected to a certain extent. Thus, in this embodiment, the deceleration slip control consisting in establishing the locking clutch 21 in the sliding state during a

  engine 10 is decelerated.

  During the deceleration slip control, the direct connection between the output shaft of the engine 17 and the automatic transmission 22 is maintained at a certain extent, and the transmission of extremely large variations in torque is moderate. As a result, fuel shutdown can be achieved more actively. However, if the fuel cut is carried out during the deceleration slip control, the torque shock caused by a step-by-step change of torque occurring at the start of the fuel cut-off cannot be effectively absorbed by the oil contained in the torque converter 20 since the direct connection between the output shaft of the engine 17 and the automatic transmission 22 obtained by the locking clutch 21 is maintained although it is partially maintained. Consequently, in order to reduce the change in torque step by step, this embodiment performs a torque reduction command so as to reduce the torque of the engine 10 before starting the fuel cut during deceleration (fuel cut of deceleration). In the torque reduction control, the combustion mode of the engine 10 is changed so as to

  reduce torque more effectively.

  Figure 3 is a flowchart illustrating a processing procedure performed by the electronic control unit 30 with respect to the determination as to the change of combustion mode. A combustion mode change command in accordance with this embodiment will be described below with reference to the

figure 3.

  The electronic control unit 30 periodically performs this procedure during operation of the

motor 10.

  First, in step S200, the electronic control unit 30 determines whether the present operating region of the engine 10 is within a region

  preset to perform stratified charge combustion.

  In this embodiment, the region carrying out the stratified charge combustion is set so that the stratified charge combustion is carried out in a region

  operating at low load and low speed.

  If the present operating region of the engine 10 is not in the stratified charge combustion production region (NO in step S200), the electronic control unit 30 establishes, in step S220, a mode of combustion of the engine 10 to obtain an operation of the

  engine based on homogeneous charge combustion.

  Conversely, if the present operating region of the engine 10 is in the stratified charge combustion production region (YES in step S200), the electronic control unit 30 determines in step S210 whether the execution indicator XSLU, activated in the procedure intended to determine whether to carry out the deceleration slip control (steps S110, S120 in FIG. 2), has been established, that is to say, if the deceleration slip command is currently in

course of realization.

  If the execution indicator XSLU has been cleared (NO at step S210), that is to say, if the deceleration slip command is not in progress, the electronic control unit 30 establishes, in step S230, a mode of combustion of the engine 10 to obtain an engine operation on the basis of the combustion at

stratified charge.

  Conversely, if the execution indicator XSLU has been set (YES in step S210), that is to say, if the deceleration slip command is in progress, the unit of electronic control 30 sets the combustion mode of the engine 10 to the homogeneous charge combustion mode in step S200, although the present operating region of the engine 10 is within the region

  for carrying out stratified charge combustion.

  After establishing the combustion mode in this way, the electronic control unit 30 ends

temporarily the procedure.

  In summary, when the deceleration slip control is performed, the electronic control unit 30 of this embodiment establishes the combustion mode in the combustion mode with homogeneous charge without consideration of the present operating state of the engine 10. After 1 establishment of the homogeneous load combustion mode when starting the deceleration slip control, the electronic control unit 30 executes the torque reduction command on the basis of

adjusting the ignition timing.

  Figs. 4 (a) to 4 (f) are timing diagrams indicating a manner of control performed by the control apparatus of the embodiment during deceleration

motor 10.

  When the depressing of the accelerator pedal PA is reduced to zero (FIG. 4 (a)), the engine 10 is decelerated. If the deceleration slip command execution condition (A) is met due to the zero value of depressing the accelerator pedal PA while the other execution conditions (B) and (C) have met, the XSLU execution indicator (figure 4 (c)) is set to execute the drag command of

deceleration.

  When the execution indicator XSLU is set, the electronic control unit 30 controls the driving of the locking relay valve 23 to increase the hydraulic clutch engagement pressure so as to establish the clutch of lock 21 in the sliding state. In this case, the electronic control unit establishes the combustion mode of the engine 10 (FIG. 4 (f)) in the combustion mode with homogeneous charge without worrying about the present operating state. It follows that the engine 10 is actuated in the homogeneous charge combustion mode, during which the torque can be adjusted on the

basis of ignition timing.

  When the clutch engagement hydraulic pressure exceeds a predetermined slip criterion hydraulic pressure and, therefore, the lockup clutch 21 is switched to the slip state after the combustion mode has been changed to the shift mode. . combustion under homogeneous load, the electronic control unit 30 gradually delays the ignition timing (Figure 4 (e)) to gradually reduce the torque of the engine 10. Thereafter, when the ignition timing is sufficiently delayed so that the output torque of the engine 10 is reduced to a sufficiently low level (target torque level), the electronic control unit 30 interrupts the supply of fuel to the engine 10, starting

thus the fuel cut.

  Thus, the internal combustion engine control apparatus of the invention, when performing the deceleration slip control, changes the combustion mode to the homogeneously charged combustion mode, which provides a relatively high degree of freedom by adjusting the ignition timing, and consequently provides a relatively high degree of freedom in adjusting the torque, regardless of the operating condition of the engine 10. Consequently, the change in stepping torque occurs at the time of a fuel cut start during deceleration (deceleration fuel cut) can be reduced more effectively, and the appearance of a

  torque shock can be more effectively moderate.

  As is apparent from the description below

  above, during the torque reduction command carried out before starting the deceleration fuel cut-off, the control device of the embodiment vigorously changes the combustion mode of the engine 10 to the combustion mode with homogeneous charge, which allows a more efficient torque reduction, regardless of the engine's current operating condition. As a result, the step-by-step torque change occurring when starting the deceleration fuel cut-off can be more effectively reduced and the occurrence of

  torque at this time may be more effectively moderate.

  It follows that it becomes possible to achieve more actively the deceleration fuel cut while moderating the appearance of a torque shock. As a result, the fuel economy of the engine can be further improved. In addition, since the combustion mode is changed to the combustion mode with homogeneous charge when the deceleration slip command is executed, it becomes possible to start the torque reduction command based on the ignition timing at an earlier stage and start the deceleration fuel cut to a relatively earlier stage. As a result, the deceleration fuel cutoff can be continued for a relatively long time, so

  that fuel economy can be further improved.

  The above-described torque reduction command of the embodiment, i.e., a command in which, if the combustion mode presently selected is the stratified charge combustion mode when the output torque is to be reduced, the combustion mode is switched to the homogeneous charge combustion mode without consideration of the present operating state of the engine 10, so that the output torque is reduced by a delay in the ignition timing, can also be applied to a case where the deceleration fuel is cut off on occasions other than the execution of the deceleration slip command of the locking clutch 21. For example, in a vehicle, such as a vehicle equipped with a transmission continuously variable, in which the fuel cut-off is carried out more actively by maintaining the state of engagement of the locking clutch during a deceleration of the engine, such that during deceleration of the vehicle, the deceleration fuel cut-off is sometimes performed during the execution of the deceleration lock command, during which the engine and the transmission are directly connected. In such a case, the damping effect of the fluid contained in a fluid transmission device (torque converter 20) cannot be obtained so that a torque shock caused by a step-by-step change of torque occurring at the when starting the deceleration fuel cutoff is more likely to be perceived. Consequently, by performing the torque reduction command before the execution of the deceleration fuel cut during the deceleration lock command, the occurrence of a shock of

  torque can also be effectively moderate.

  In addition, if the fuel cut-off during vehicle deceleration is also performed on occasions other than the execution of the deceleration lock command or the deceleration slip control of the lock clutch 21 during engine deceleration , a step-by-step change in torque may occur and, as a result, a certain amount of torque shock may occur, even if the torque shock is reduced by the buffering effect of the fluid by the fluid transmission device (torque converter ). In such a case, too, the appearance of such a torque shock can be moderated by carrying out a command in which if the combustion mode presently selected is the combustion mode with stratified charge before the deceleration fuel cut-off, the combustion mode is switched to homogeneous charge combustion mode regardless of the engine operating state, and in which before deceleration fuel cut, the output torque is reduced by delaying stalling

ignition.

  The execution condition of the drag command

  deceleration in this embodiment is arbitrary.

  That is, the condition is not limited to the previously mentioned conditions (A) to (C), but it is possible to establish appropriate conditions according to the engine and vehicle to which the embodiment

is applied.

  Although the control apparatus of the embodiment of the invention is applied to a vehicle internal combustion engine in which the combustion mode is changed between the homogeneous charge combustion mode and the stratified charge combustion mode in accordance with in the operating state of the engine, the invention is also applicable to internal combustion engines which use ways of changing the combustion mode which are different as described above. In summary, the control device of the invention is applicable to any internal combustion engine in which the combustion mode is changed in accordance with the operating state of the engine and in which a limitation of the reduction of the output torque may occur depending on the combustion mode that was selected when starting the deceleration fuel cut-off. In such applications, the invention more effectively moderates the appearance of a shock

of couple.

  Although in the embodiment, the engine 10 is connected to the automatic transmission 22 via the torque converter 20 comprising the locking clutch 21, the torque converter 20 can be replaced by a different type of fluid transmission device which transmits rotation via the fluid, for example, a simple fluid coupling or

analogues.

  In addition, although in this embodiment, the output shaft of the engine 17 and the automatic transmission 22 are directly mechanically connected by the locking clutch 21 provided in the torque converter 20, the locking device for directly connecting the output shaft of the engine 17 and the automatic transmission 22 while omitting the use of the fluid in the fluid transmission device is not limited to the locking clutch 21 but may be any suitable device whatsoever. That is to say that any other locking mechanism can be used as long as the mechanism allows the connection between the engine and the transmission to be changed among

  the engaged state, the disengaged state and the sliding state.

  Although in the embodiment, the combustion mode is changed when the deceleration slip control is performed, the combustion mode changing the timing can be arbitrarily changed if the combustion mode is appropriately selected for the reduction control of torque, which is performed before a

  starting the deceleration fuel cut-off.

SECOND EMBODIMENT

  A second embodiment of the vehicle internal combustion engine control apparatus of the invention will be described mainly with respect to the features which distinguish the second embodiment.

  realization of the first embodiment.

  Since a torque shock cannot be sufficiently absorbed during the deceleration slip control, as described above, it is desirable that the motor output torque is reduced to reduce the change in torque step by step before a start of the deceleration fuel cut-off during the deceleration slip control. However, it is not only during the deceleration slip control or the deceleration lock control but also on other occasions that the motor output torque undergoes a stepping change and therefore causes a shock of torque when starting the deceleration fuel cut-off. If the effect of torque shock is not negligible on certain occasions, it is desirable that the change in stepping torque is reduced by reducing the output torque of the motor before

  starting the deceleration fuel cut-off.

  However, in an internal combustion engine in which the combustion mode is changed between the homogeneous charge combustion mode and the stratified charge combustion mode in accordance with the operating state of the engine, a sufficient reduction in the output torque engine can become difficult if the combustion mode actually selected is the combustion mode

with stratified charge.

  Even in a situation like the one shown above

  above, the output torque of the engine can be properly reduced by vigorously changing the combustion mode from the stratified charge combustion mode to the homogeneous charge combustion mode regardless of the operating condition of the engine, as is described above in connection with the first mode of

production.

  Even if the combustion mode actually selected is the stratified charge combustion mode and therefore the engine output torque cannot be reduced enough by the above-mentioned measures, the engine output torque can be further reduced by decreasing the number of cylinders in operation of the engine. In this embodiment, therefore, the adjustment of the torque for the deceleration fuel cut during the deceleration slip is achieved by controlling the number of cylinders in operation if the combustion mode actually selected is a mode which allows only one low degree of freedom in reducing the torque of

motor output.

  FIGS. 5 (a) to 5 (f) are timing diagrams indicating the transition from the state of a deceleration slip command according to the second embodiment. The deceleration slip control of this embodiment will be described in detail in

  referring to Figures 5 (a) to 5 (f). In the description which

  follows, the control apparatus of this embodiment for a vehicle internal combustion engine is applied to

  a four-cylinder engine for a vehicle.

  In the second embodiment, the deceleration slip control is performed under the conditions that the depressing of the accelerator pedal PA (figure (a)) is reduced to zero, and that the rotation speed of the engine NE ( Figure 5 (b)) is greater than a predetermined value K1, and the motor speed is greater than a predetermined value K2, as in the

first embodiment.

  This embodiment performs a control such as that described below at the time of the deceleration slip control carried out under the conditions mentioned above, if the combustion mode actually selected is the stratified charge condition, in which the degree of freedom in the reduction in engine output torque is relatively low. At an instant tl, the execution indicator XSLU of deceleration slip (FIG. 5 (c)) is established (ACTIVE) if the conditions for the execution of the command

  deceleration slip come together.

  In response to setting the indicator, the latch relay valve 23 is driven and controlled to increase the hydraulic clutch engagement pressure (Figure 5 (d)) to establish the clutch.

  lock 21 in the sliding state.

  At an instant t2, when the clutch engagement hydraulic pressure reaches a slip criterion hydraulic pressure and the locking clutch 21 enters the slip state, the quantity of fuel injection TAU (FIG. 5 (e)) is gradually reduced to reduce the motor output torque. It should be noted that since the minimum amount of fuel injection that is allowed for the injector 14 is limited as mentioned above, the reduction of torque by this normal torque adjustment process for the mode

  stratified charge combustion is also limited.

  Accordingly, this embodiment achieves torque adjustment by controlling the number of cylinders in operation when the torque adjustment by controlling the amount of fuel injection reaches a limit. That is to say that after an instant t3, when the amount of fuel injection is reduced to the minimum fuel injection amount of the injector 14, the number of cylinders in operation (FIG. 5 (f )) is gradually decreased to reduce the motor output torque. At an instant t4, the number of cylinders in operation is reduced to zero, and the

  deceleration fuel cut has started.

  In the vehicle engine control apparatus of the second embodiment described above, the engine output torque is adjusted by controlling the number of cylinders in operation before the deceleration fuel cut-off if the combustion mode under load laminate was selected. Consequently, a further reduction of the engine output torque is authorized despite the limitation imposed by the minimum fuel injection quantity of the injector 14, so that the appearance. of a torque shock in connection with the execution of the deceleration fuel cut-off may

be effectively moderate.

  In addition, torque adjustment is achieved by controlling the number of cylinders in operation before deceleration fuel cut during deceleration slip control, on which occasion it is difficult for the torque converter to absorb a change. of couple step by step. Consequently, the embodiment is capable of effectively moderating the appearance of a considerable torque shock which would otherwise be in the condition mentioned above. In the second embodiment, when the

  amount of fuel injection is reduced to or at

  below the predetermined amount, a number of cylinders in operation is decreased in order to further reduce the engine output torque before starting the deceleration fuel cut. Since the number of cylinders in operation is decreased after the output torque per cylinder has been sufficiently reduced, the torque changes step by step in response to decreases in the number of cylinders in operation can be reduced. In the embodiment, in particular, since the predetermined quantity previously mentioned is established at the minimum fuel injection quantity of the injector 14, the number of cylinders in operation is reduced after the output torque per cylinder has been reduced to a least allowable limit of the adjustment of the engine output torque obtained by the fuel injection quantity control. Consequently, the step-by-step change in torque is favorably reduced. Thus, the embodiment is capable of more gently reducing the output torque

of the motor.

  The engine output torque reduction command may also be applied in connection with the deceleration fuel cut performed on occasions other than the deceleration slip command. If the torque reduction command is applied to a vehicle engine that performs deceleration fuel shutdown during the deceleration lock command of directly connecting the engine and transmission using a lockup clutch as described above, it becomes possible to effectively control the appearance of a torque shock although the torque shock becomes more likely to be perceived when the engine and the transmission are directly connected. Even on occasions other than the deceleration slip control or the deceleration lock command, the application of the torque reduction command before the reduction of the deceleration fuel cut-off also moderates the appearance of a shock. couple. In the embodiment, the manner of changing the number of cylinders in operation in relation to the deceleration slip control is arbitrary as long as the number of cylinders in operation is controlled so as to appropriately adjust the output torque of the engine. before the cut-off starts

deceleration fuel.

  The adjustment of the engine output torque via the control of the number of operating cylinders relating to the deceleration slip control is not limited to the stratified charge combustion mode, but can also be carried out when

  the homogeneous charge combustion mode is selected.

  In this case, it becomes possible to carry out the adjustment of the engine output torque beyond the adjustment limit based on the ignition timing control.

  during homogeneous charge combustion mode.

THIRD EMBODIMENT

  A third embodiment of the vehicle internal combustion engine control apparatus of the invention will be described mainly in relation to the features which distinguish the third embodiment.

  realization of the first and second embodiments.

  If the stratified charge combustion mode was selected when starting the deceleration fuel cut-off, the adjustment of the engine output torque based on the control of the number of cylinders in operation will achieve an additional torque adjustment. - engine output beyond the adjustment limit which can be reached by a normal torque command based on the fuel injection quantity command, so that the appearance of a torque shock when the cut-off starts

  deceleration fuel can be effectively moderate.

  However, adjustment simply by controlling the number of cylinders in operation achieves only relatively regular stepping changes in the motor output torque, so that a certain amount of stepping torque change caused by a change of the number of cylinders in operation cannot be eliminated. Particularly in an engine with a small number of cylinders, the change in stepping torque tends to increase due to a reduced degree of freedom in controlling the number of cylinders in operation. Consequently, in this embodiment, the amount of fuel injected into the operating cylinders is increased when the number of operating cylinders is changed to adjust the engine output torque before the deceleration fuel cut off. If the amount of fuel injection is increased so that an increase in the engine output torque caused by the increase in the amount of fuel injection significantly offsets a reduction in the engine output torque caused by a decrease in the number of cylinders in operation, the appearance of a change in torque step by step can be prevented or moderate. In addition, by gradually reducing the amount of fuel injection temporarily increased so as to reduce the engine output torque, it becomes possible to make a smooth torque adjustment while favorably avoiding the appearance of a change in torque. not driven by a change in the number of

cylinders in operation.

  Figure 6 is a flowchart illustrating a sub-

  torque control program used in the third embodiment. The engine output torque control performed before starting the deceleration fuel cut-off in this embodiment will be

  described in detail with reference to Figure 6. This sub-

  program is periodically performed by the electronic control unit 30 at predetermined time intervals. The control subroutine will be described below in connection with a case where the number of cylinders in operation is changed from four to two to adjust the output torque of the engine before starting the

  deceleration fuel cut.

  When this routine is started, the electronic control unit 30 first determines in step S300 whether there is a demand for torque adjustment based on the fuel injection amount control before starting the deceleration fuel cut-off. More specifically, it is determined in step S300 whether the operating state of the current engine meets a condition for executing the deceleration fuel cut-off and the stratified charge combustion mode is actually selected. -If the deceleration fuel cut is to be performed during the deceleration slip control, it is determined that the condition for executing the deceleration fuel cut is met, since the deceleration slip control conditions previously mentioned (A) to (C) are met and that the locking clutch 21 (FIG. 1) is in the sliding state,

  as in the first and second embodiments.

  If it is determined that the request to execute the deceleration fuel cutoff is not present (NO in step S300), the electronic control unit 30 performs the processing in step S350 (described below) below) and finish

  then temporarily the subroutine.

  Conversely, if it is determined that the request to execute the deceleration fuel cut is present (YES in step S300), the processing before in step S310. In step S310, the electronic control unit 30 determines whether a required value of the amount of fuel injection per cylinder (required amount of injection QINJ) calculated in accordance with the actually required amount of the engine output torque is less than a minimum value of fuel injection quantity (minimum injection quantity QMIN). The amount of fuel injection required is calculated in a routine separate from the torque control routine and is gradually reduced with time lapses after the deceleration fuel cut performance condition has been met. If it is determined that the amount of fuel injection required is not less than the minimum injection amount (NO at step S310), the process advances to step S350. In step S350, the electronic control unit 30 establishes the calculated value of the quantity of fuel injection required as the final value of the quantity of fuel injection per cylinder in operation (quantity of final injection QFIN ). Thereafter, the electronic control unit 30 temporarily terminates the subroutine. Thus, in this embodiment, the engine output torque is reduced by gradually reducing the amount of fuel injection while keeping the four cylinders in operation until the amount of injection required becomes less than the amount d minimum injection of

the injector 14.

  Conversely, when the required injection quantity becomes less than the minimum injection quantity during the reduction of the engine output torque (YES in step S310), the process advances to step S320. In this case, since an additional reduction of the engine output torque cannot be obtained simply by controlling the amount of fuel injection, the control of the number of cylinders in operation is performed to adjust the engine output torque . In step S320, the

  number of cylinders in operation is set to two.

  In addition, in step S320, a quantity of final injection QFIN corresponding to the number of cylinders in reduced operation is determined as in the following equation: QFIN = QINJ x ([number of cylinders in operation before change] / [number of cylinders in operation after change]) In this step, a final injection quantity is established in such a way that the quantity of fuel injection for each reduced number of cylinders in operation increases so as to prevent a step change. not in the engine output torque when reducing the number of cylinders in operation. In this embodiment, as the number of cylinders

  in operation is reduced from four to two, that is

  say, the number is halved, a quantity of final injection is determined in such a way that the quantity of fuel injection for each number

  reduced cylinders in double operation.

  Subsequently in step S330, the electronic control unit 30 determines whether the quantity of final injection QFIN determined in the form of a quantity of fuel injection for each of the reduced number of cylinders in operation at step S320 is less than the minimum injection quantity QMIN. If the final injection quantity QFIN is not less than the minimum injection quantity QMIN (NO at step S330), the control unit

  electronics 30 temporarily terminates this routine.

  Conversely, when the final injection quantity QFIN determined in the form of a fuel injection quantity for each of the reduced number of cylinders in operation in step S320 becomes less than the minimum injection quantity QMIN (YES at step S330) as the required amount of injection QINJ, which reflects the required amount of engine output torque, is further reduced, the process advances to step S340. In step S340, the electronic control unit 30 starts cutting the deceleration fuel. Thereafter, the unit

  electronic control unit 30 temporarily terminates the

  program. Figs. 7 (a) through 7 (d) show a transition of the control ways in relation to the torque control routine before starting the deceleration fuel cut. The engine output torque control performed before deceleration fuel cut according to this embodiment will be

  described below with reference to Figures 7 (a) to 7 (d).

  At an instant t1, the reduction in the quantity of final injection QFIN is started as the clutch of. lock 21 enters the sliding state. Then, the quantity of fuel injection per cylinder in operation (figure 7 (a)), that is to say, the quantity of final injection QFIN (QFIN = QINJ during time tl or t2), is gradually reduced with

the passage of time.

  At an instant t2, when the quantity of injection required QINJ (QINJ), that is to say, the quantity of fuel injection for each of the four cylinders in operation, becomes less than the minimum quantity of injection QMIN of the injector 14, the number of cylinders in operation is reduced from four to two, as shown in Figure 7 (b). In response to the reduction in the number of cylinders in operation, the amount of injection per cylinder in operation is temporarily increased as shown in Figure 7 (a). Increasing the amount of fuel injection per cylinder in operation prevents step-by-step changes in the total injection amount for all cylinders in operation (Figure 7 (c)) and in the engine output torque ( figure 7 (d)) at the time

  reduction in the number of cylinders in operation.

* After time t2, the amount of injection required continues to be reduced, and the amount of fuel injection per cylinder in operation, i.e., the amount of final injection QFIN, is also gradually reduced with the passage of time, as

  this is shown in Figure 7 (a).

  At an instant t3, when the final injection quantity QFIN becomes less than the minimum injection quantity QMIN of the injector 14, the fuel injection is stopped for all the cylinders, and the deceleration fuel cut-off begins. At this stage, the engine's output torque has been sufficiently reduced by the reductions in the number of cylinders in operation, and as a result, the step-by-step change in torque occurring at the start of the fuel cut-off.

  deceleration is also reduced enough.

  In the vehicle engine control apparatus of the third embodiment described above, the amount of fuel injection per cylinder in operation is increased simultaneously with a reduction in the number of cylinders in operation during the control of the number of cylinders in operation to adjust the engine output torque before starting the deceleration fuel cut-off. Thus, the increase in the engine output torque driven by the increase in the amount of fuel injection substantially offsets the reduction in the engine output torque caused by the reduction in the number of cylinders in operation. Consequently, it becomes possible to effectively moderate the appearance of a step-by-step change in torque when reducing the number of cylinders in operation while reducing the torque shock occurring when the fuel cut starts. deceleration by reducing the engine output torque sufficiently by controlling the number of cylinders in operation. Moderating a step-by-step torque change when reducing the number of cylinders in operation by increasing the amount of fuel injection is particularly effective when applied to an internal combustion engine having a relatively small number of cylinders in which the degree of freedom in controlling the number of cylinders in operation is relatively small and the change in torque step by step when reducing the number of cylinders in operation tends to be large. The torque reduction command described above performed before the deceleration fuel cut, that is to say a command in. which if the combustion mode actually selected is the stratified charge combustion mode, the engine output torque is reduced first by the fuel injection amount control and, when the fuel injection amount QFIN decreases at or below a predetermined quantity (minimum injection quantity QMIN of the injector 14), the number of cylinders in operation is reduced, and in which at the time of a reduction in the number of cylinders in operation, the amount of fuel injection per cylinder in operation is increased, can also be applied to the deceleration fuel cut performed on occasions other than the deceleration slip command, for example, during the deceleration lock command performed during engine deceleration, and the like, as in the first and second embodiments. The torque reduction control described above is particularly effective when applied to the torque reduction control performed before the deceleration fuel is cut off in a condition where a torque shock is relatively easily perceived, for example, during execution of the deceleration lock command or the deceleration slip command performed

  during deceleration of the engine or the like.

  Although in the embodiment, the engine output torque is adjusted by changing the number of cylinders in operation from four to two before the deceleration fuel cut starts, the manner of controlling the number of cylinders in operation in order to adjust the engine output torque is arbitrary as long as the number of cylinders in operation is controlled so as to appropriately adjust the engine output torque before starting

  deceleration fuel cut.

  In addition, in the embodiment, it is also possible to increase the amount of fuel injection per cylinder in operation at the time of a reduction in the number of cylinders in operation without achieving the reduction in the engine output torque on the basis of the fuel injection quantity control before the

  deceleration fuel cut.

  In addition, although in the embodiment, the condition for reducing the number of cylinders in operation is that the quantity of fuel injection per cylinder in operation is equal to or less than the minimum injection quantity of the injector 14, the condition is not limiting. For example, in the case o during the reduction of the engine output torque before the deceleration fuel cut-off, the torque is reduced first by the fuel injection quantity control, and o when the quantity of fuel injection becomes equal to or less than a predetermined amount, the torque is reduced by controlling the number of cylinders in operation, the change in torque step by step when reducing the number of cylinders in operation can be reduced and the motor output torque can be reduced more regularly. Of course, if the predetermined quantity previously mentioned is established at the minimum injection quantity of the injector 14, the change in torque step by step occurring at the time of a reduction in the number of cylinders in operation can be reduced to a limit which can be achieved by controlling the amount of fuel injection, obtaining

this fact more important advantage.

FOURTH EMBODIMENT

  A fourth embodiment of the vehicle engine control apparatus of the invention will be described mainly with respect to the features which distinguish the fourth embodiment from the first to

third embodiments.

  As mentioned above, during deceleration slip control or deceleration lock control, a torque shock cannot be sufficiently absorbed. Therefore, it is desirable that before the deceleration fuel is cut off during the deceleration slip control or the deceleration lock control, the engine output torque is reduced

  to minimize the change in torque step by step.

  However, if the stratified charge combustion mode was selected on such an occasion, a sufficient output torque reduction may not be achieved in some cases due to the limitations relating to the

construction of the injector.

  However, even in such a situation in an internal combustion engine which performs stratified charge combustion, the output torque can be properly reduced, for example, by controlling the number of cylinders in operation or by vigorously changing the combustion mode to homogeneous charge combustion mode without worrying about the state of

  current engine operation (as described above

  above in conjunction with the first to third embodiments). During the stratified charge combustion mode, it is necessary to precisely control the ignition timing and the fuel injection timing in good association, for example, carrying out the ignition at a timing at which the injected fuel is expected. be in the vicinity of the spark plug. A simple delay in ignition timing, which is achieved during the homogeneous charge combustion mode, degrades the combustion and fails to correctly reduce the output torque during the stratified charge combustion mode, as mentioned above. -above. However, even during the stratified charge combustion mode, if the ignition timing and the injection timing are correctly adjusted in good association with each other, it is possible to correctly reduce the engine output torque by controlling the timing ignition timing and fuel injection timing, while appropriately moderating the degradation of combustion. Consequently, in this embodiment, if stratified charge combustion is selected before deceleration fuel cut-off, the engine output torque is reduced by performing the fuel injection amount control and the timing control d ignition and timing of fuel injection. In addition, in order to moderate the degradation of the combustion caused by the changes in the ignition timing and the injection timing, the output torque is firstly reduced by controlling the quantity of fuel injection and, after the amount of fuel injection decreases to or below a predetermined amount, the output torque is reduced by controlling the ignition timing and the timing of the fuel injection. During the reduction of the output torque based on the ignition timing and fuel injection timing control, the ignition timing and fuel injection timing are delayed while the interval between these are kept constant.

  Figure 8 is a flowchart illustrating a sub-

  deceleration fuel cut execution program, that is to say, a control procedure carried out before execution of the deceleration fuel cut. The processing operations in this subroutine are sequentially executed by the electronic control unit 30, following an instant when a condition for executing the deceleration fuel cut is encountered during a deceleration of the engine. In this embodiment, the condition for executing the deceleration fuel cut-off includes the aforementioned execution conditions (A) to (C). Consequently, after conditions (A) to (C) have been met, the processing of these subroutines is sequentially

executed.

  When this subroutine is started after the conditions for executing the deceleration fuel cut have been met, the electronic control unit 30 first determines in step S400 whether the engine is started in the mode of stratified charge combustion. If the determination is negative, i.e., if the engine is operated in the homogeneous charge combustion mode, the electronic control unit 30 reduces the engine output torque by delaying the ignition timing to step S440 and performs fuel cutoff by stopping the fuel supply in step

  S450, and then ends this cycle of the sub-

  program. Conversely, if the determination in step S400 is affirmative, that is, if the stratified charge combustion mode has been selected, the electronic control unit 30 advances to step S410. In step S410, the electronic control unit 30 determines whether the quantity of fuel injection QFIN is less than or equal to the minimum injection quantity QMIN of

the injector 14.

  If the determination in step S410 is negative, the electronic control unit 30 reduces the amount of fuel injection QFIN by a predetermined amount in step S420, and then returns to step S400. Thus, as long as the combustion mode selected is the stratified charge combustion mode, the engine output torque is reduced by reducing the amount of fuel injection until the amount of fuel injection QFIN becomes equal to or less than the quantity

  minimum injector injection QMIN 14.

  When the fuel injection amount QFIN decreases to or below the minimum injection amount QMIN of the injector 14 (YES at step S410), the process advances to step S430, at which the electronic control unit 30 reduces the engine output torque by controlling the ignition timing and the fuel injection timing. In this embodiment, the electronic control unit 30 delays the ignition timing and fuel injection timing while maintaining a constant interval between the ignition timing and the fuel injection timing (that is, difference in the angle of the crankshaft between them). After the engine output torque is sufficiently reduced by controlling the ignition timing and fuel injection timing, the electronic control unit 30 performs the fuel cut-off by stopping the fuel supply to the engine. step S450, and then ends the present

cycle of the subroutine.

  Figs. 9 (a) to 9 (c) show, as examples, a control manner performed before the execution of the deceleration fuel cut-off during the stratified charge combustion mode. The engine output torque control executed in this embodiment, before the deceleration fuel cut is started, will be described with reference to

Figures 9 (a) to 9 (c).

  If the engine is operated in the stratified charge combustion mode (YES in step S400) when the conditions for performing the deceleration fuel cut are met, the quantity of fuel injection QFIN (figure 9 (a )) is then gradually reduced (steps S400 to S420), so that the motor output torque gradually decreases so

corresponding (figure 9 (c)).

  Then, at an instant t1 when the quantity of fuel injection QFIN is reduced to the minimum injection quantity QMIN of the injector 14 (YES at step S410), it becomes impossible to further reduce the output torque by fuel injection quantity control. In this embodiment, consequently, after the instant t1, the output torque is reduced by controlling the ignition timing and the timing of the fuel injection (step S430). More specifically, the ignition timing and fuel injection timing are delayed while the interval (difference in crankshaft angle) between them is kept constant, as shown in Figure 9 (b ). As a result, further reduction of the output torque beyond the fuel injection quantity control limit

can be obtained.

  Subsequently at an instant t2, when the output torque is sufficiently reduced, the fuel supply is stopped, thereby starting the fuel cut-off

deceleration (step S450).

  In the vehicle engine control apparatus of this embodiment, the engine output torque is reduced by the fuel injection amount control and the ignition timing and injection timing control. fuel before deceleration fuel cut-off, if the current combustion mode is the stratified charge combustion mode. As a result, it becomes possible to obtain a further reduction in the output torque beyond the limit of the fuel injection control even in an engine which performs stratified charge combustion. Thus, an insufficient reduction of the engine output torque before starting the deceleration fuel cut is avoided, that is to say, a step-by-step change of torque occurring at the start of the fuel cut

can be reduced enough.

  In addition, in this embodiment, the engine output torque is reduced by controlling the ignition timing and fuel injection timing after the amount of fuel injection QFIN has become equal to or less at the predetermined amount. As a result, the ignition timing and fuel injection timing are not changed until the amount of fuel injection is sufficiently reduced. Thus, the embodiment considerably reduces the disadvantages, such as the degradation of the combustion efficiency or the like, which are caused by the changes in the ignition timing and / or the timing of the fuel injection during the combustion mode. stratified charge combustion. The disadvantages can be minimized if the predetermined quantity is set at the minimum injection quantity QMIN of the injector 14 and the ignition timing and the fuel injection timing are kept fixed until the torque of output be reduced to the limit that can be reached by

  fuel injection quantity control.

  In addition, in the embodiment, when the output torque is reduced by controlling the ignition timing and fuel injection timing, the ignition timing and fuel injection timing are delayed while the interval between them is kept constant. Since the interval between fuel injection and ignition is kept constant, disadvantages, such as combustion degradation and the like, can be appropriately reduced to a

certain extent.

  The torque reduction control described above of this embodiment is particularly effective when applied to a torque reduction control that is performed before the deceleration fuel is cut in a situation where a torque shock is relatively highly susceptible to be perceived, such as during the deceleration slip command or the deceleration lock command during an engine deceleration. Although in the embodiment, during the reduction of the output torque on the basis of the ignition timing and fuel injection timing control, the ignition timing and the fuel injection timing are delayed while the interval between them is kept constant, the way of changing the ignition timing and fuel injection timing can be changed arbitrarily. However, if the ignition timing and fuel injection timing are appropriately changed during the stratified charge combustion mode, the combustion deteriorates causing various disadvantages such as deterioration in fuel economy and analogues. Accordingly, it is desirable that the ignition timing and the fuel injection timing are appropriately adjusted in good association with each other, for example, delaying the timing while maintaining the constant interval between them as in the embodiment. However, in some cases, for example, a case where the amount of stall delay becomes greater than a certain amount, simply keeping a constant interval between the ignition timing and the fuel injection timing fails to sufficiently moderate combustion degradation, due to correlation with the position of the piston or the like. In such a case, it is desirable that the output torque is reduced by controlling the ignition timing and the injection timing.

  more appropriately.

  In addition, although in the previous embodiment, the reduction in output torque based on the ignition timing control and fuel injection timing is performed after the amount of fuel injection QFIN has become equal to or less than the minimum injection quantity QMIN of the injector 14, this manner of control is not limiting. For example, if the output torque is reduced by performing the fuel injection amount control without performing the ignition timing and fuel injection timing control until the injection amount of QFIN fuel becomes equal to or less than a predetermined amount, the disadvantages of changing the ignition timing and fuel injection timing during stratified charge combustion can be reduced to some extent. If the disadvantages of changing the ignition timing and fuel injection timing during the stratified charge combustion mode are negligible, it is also possible to reduce the output torque by controlling the ignition timing and stalling the fuel injection without waiting for the QFIN fuel injection amount to be reduced to or below the predetermined amount. The above-described engine output torque reduction control performed before the deceleration fuel cut in each of the previous embodiments is also applicable to a torque reduction control that is performed in connection with the fuel cut deceleration in an internal combustion engine installed in a vehicle which is neither equipped with the fluidic transmission device (for example, torque converter 20) for the rotation transmission via the fluid, nor with a locking mechanism (for example , locking clutch 21) to allow a direct rotation transmission which does not use the fluid in the fluidic transmission device. Even in the case of an engine installed in a vehicle which is not equipped - with a locking mechanism (and consequently does not carry out a deceleration slip control or a

  deceleration lock, as described above

  above), a step-by-step change in torque may occur and therefore a certain amount of torque shock may occur when starting the deceleration fuel cut-off. In such an engine, the use of the torque reduction control described above will sufficiently reduce the engine output torque before the deceleration fuel cut-off so as to effectively moderate the appearance of a torque shock even during

  the stratified charge combustion mode.

  Although in the previous embodiments, the adjustment or control of the engine output torque is carried out before the start of the deceleration fuel cut-off during the deceleration slip control, the engine output torque control can also be performed before the start of the deceleration fuel cut-off on occasions other than the deceleration slip control. Although the present invention has been described with reference to what is now considered to be its preferred embodiments, it will be understood that the present invention is not limited to the embodiments or constructions described. On the contrary, the present invention is intended to cover various modifications and equivalent arrangements. In addition, while the various elements of the described invention are shown in various combinations and configurations, which are exemplary, other combinations and configurations, including more, less or only a single embodiment, are also inside. of spirit and

scope of the present invention.

Claims (12)

  1. Control apparatus for a vehicle internal combustion engine (10) comprising a fuel injector (14) which injects fuel directly into a combustion chamber (12), the engine (10) is actuated by selectively changing a mode combustion between a homogeneous charge combustion mode and a stratified charge combustion mode in accordance with an operating state of the engine, the control apparatus comprising: fuel cutoff means (30) for stopping the fuel supply toward the engine (10) when a predetermined condition is encountered during an engine deceleration operation (10); torque reduction means (30) for reducing an engine output torque (10) before the fuel supply is stopped by the fuel cutoff means (30); characterized in that: if the combustion mode selected is stratified charge combustion, the torque reduction means (30) reduces the output torque of the engine (10), by controlling the engine (10) so that the torque output becomes less than an output torque generated when the engine (10) is operated by the stratified charge combustion mode with a minimum amount of fuel injection that the fuel injector (14) is capable of injecting. 2. Control apparatus according to claim 1, characterized in that it further comprises: a fluidic transmission device (20) which transmits the rotation from the motor (10) to a transmission (22) via a fluid; a locking mechanism (21) which allows direct transmission of the rotation from the motor (10) to the transmission (22) while omitting the use of the fluid; and a locking mechanism control means (30) which performs a sliding control of establishing a connection between the motor (10) and the transmission (22) in a sliding state by controlling the mechanism (21) when the engine deceleration operation (10), wherein the torque reduction means (30) reduces the output torque of the engine (10) during the slip control performed by the drive control means locking mechanism (30).   3. Control apparatus according to claim 1, characterized in that it further comprises: a fluidic transmission device (20) which transmits the rotation from the motor (10) to the transmission (22) via a fluid; a locking mechanism (21) which allows direct transmission of the rotation from the motor (10) to the transmission (22) while omitting the use of the fluid; and a locking mechanism control means (30) which performs a locking control in which the motor - (10) and the transmission (22) are directly connected, by controlling the locking mechanism (21), when motor deceleration operation (10), wherein the torque reduction means (30) reduces the output torque of the motor (10) during the latch command executed by the control means of the locking mechanism (30).   4. Control device according to any one of   claims 1 to 3, wherein the means for reducing   couple (30) comprises: combustion mode changing means for vigorously changing the combustion mode to the homogeneous charge combustion mode, if the selected combustion mode is the stratified charge combustion mode; and an ignition timing control means (30) for delay an ignition timing.   5. Control device according to any one of   claims 1 to 3, wherein the means for reducing   torque (30) comprises: means for controlling the quantity of injection. fuel (30) to reduce an amount of fuel injection; and cylinder control means (30) for reducing a   number of cylinders in operation of the engine (10).   6. Control apparatus according to claim 5, characterized in that the cylinder control means (30) reduces the number of cylinders in operation of the engine (10) when the amount of fuel injection becomes   equal to or less than a predetermined amount.   7. Control device according to claim 6, characterized in that the predetermined quantity is the minimum quantity that the fuel injector (14) is able to inject.   8. Control apparatus according to any one of   claims 5 to 7, characterized in that the means for   fuel injection quantity control (30) increases the fuel injection quantity for the cylinders in operation of the engine (10) when the number of   cylinders in operation is reduced.   9. Control unit according to any one of   claims 1 to 3, the torque reduction means (30)   comprising: fuel injection amount control means (30) for reducing a fuel injection amount; and ignition / injection timing control means (30) for delaying ignition timing and timing fuel injection.   10. Control apparatus according to claim 9, characterized in. that the ignition timing / fuel injection control means (30) delays the ignition timing and fuel injection timing when the amount of fuel injection becomes equal to or   less than a predetermined amount.   11. Control unit according to claim 10, characterized in that the predetermined quantity is the minimum quantity that the fuel injector (14) is able to inject.   12. Control apparatus according to any one of   Claims 9 to 11, characterized in that the means for   ignition / injection timing control (30) delays ignition timing and fuel injection timing while maintaining a constant interval between timing   ignition timing and fuel injection.