JP2005155407A - Control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine capable of increasing operability by avoiding the occurrence of the fluctuation of torque since an excellent combustion state can be secured in a cylinder injection internal combustion engine. <P>SOLUTION: This control device 1 of the cylinder injection internal combustion engine 3 comprises an ECU 2. According to an engine rotational speed NE, the ECU 2 performs the switching of a combustion mode (steps 85, 87, 92, 151), determines whether or not the absolute value of an opening deviation DTHDS or the absolute value of a rotation deviation DNEDS is larger than a specified value (steps 2, 4), and when the absolute value of the opening deviation DTHDS or the absolute value of the rotation deviation DNEDS is larger than the specified value (steps 104 and 105 are NO) in the case that the combustion mode is a uniform combustion mode, prohibits the switching to the stratified combustion mode (step 107). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a control device for an in-cylinder injection internal combustion engine that is operated by switching a combustion mode between a uniform combustion mode for uniformly burning an air-fuel mixture and a stratified combustion mode for stratified combustion.

  Conventionally, what was described in patent document 1 is known as a control apparatus of an internal combustion engine. This internal combustion engine is an in-cylinder injection type in which fuel is directly injected into a cylinder, and is operated by switching a combustion mode between a uniform combustion mode in which the air-fuel mixture is uniformly combusted and a stratified combustion mode in which stratified combustion is performed.

  In this control device, when the combustion mode is the stratified combustion mode, the misfire frequency is calculated based on the fluctuation amount of the engine speed, and when the misfire frequency reaches a predetermined value during a predetermined period, the air-fuel ratio is rich. And the combustion mode is switched to the uniform combustion mode. Further, after the switching, when the execution time of the uniform combustion mode reaches a predetermined time, the combustion mode is switched again to the stratified combustion mode. The reason why the combustion mode is switched in this way is as follows. That is, generally, in a cylinder injection internal combustion engine, in the stratified combustion mode, the throttle valve opening TH is controlled to be almost fully open, and the air-fuel ratio is controlled to the extremely lean side. When the fuel injection amount changes suddenly due to a sudden load fluctuation caused by an operation or the like, the combustion state tends to deteriorate. On the other hand, in the uniform combustion mode, the throttle valve opening TH is controlled to a smaller value than in the stratified combustion mode, and the air-fuel ratio is controlled to the rich side. In comparison, since the degree of freedom of fuel injection control and intake air amount control is greater, a more stable combustion state can be ensured even when such a sudden load fluctuation occurs. For the above reasons, the combustion mode is switched as described above.

JP-A-9-303189

  According to the conventional control device for an internal combustion engine, even when the combustion mode is switched from the stratified combustion mode to the uniform combustion mode due to the deterioration of the combustion state, when the uniform combustion mode is executed for a predetermined time, the combustion mode Is switched to the stratified combustion mode again. Therefore, during the stratified combustion mode after switching, if a sudden load fluctuation occurs due to the accelerator pedal operation as described above, the combustion state may worsen again and a misfire may occur. Will occur and drivability will be reduced.

  The present invention has been made to solve the above-described problems, and in a direct injection internal combustion engine, it is possible to ensure a good combustion state, thereby avoiding torque fluctuations and improving drivability. It is an object of the present invention to provide a control device for an internal combustion engine capable of performing the above.

  In order to achieve the above object, the invention according to claim 1 is directed to an in-cylinder injection type internal combustion engine 3 that is operated by switching the combustion mode between a uniform combustion mode for uniformly burning an air-fuel mixture and a stratified combustion mode for stratified combustion. And a load parameter detecting means (ECU 2, crank angle sensor 22, throttle valve opening sensor 25) for detecting load parameters (engine speed NE, throttle valve opening TH) representing the load of the internal combustion engine 3. ), Combustion mode switching means (ECU2, steps 73, 85, 87, 92, 151) for switching the combustion mode according to the detected load parameter, and whether the load parameter is in a predetermined fluctuation state The determination means (ECU 2, steps 2 and 4) for determining whether or not the combustion mode is in the uniform combustion mode, the load parameter is determined by the determination means. When it is determined that the motor is in a predetermined fluctuation state (when the determination result of steps 104 and 105 is NO), switching prohibiting means (ECU2) for prohibiting switching to the stratified combustion mode by the combustion mode switching means Steps 85, 87, 92, 107, 151).

  According to the control device for an internal combustion engine, when the combustion mode is the uniform combustion mode, switching to the stratified combustion mode is prohibited when the load parameter representing the load of the internal combustion engine is in a predetermined fluctuation state. Therefore, by setting this predetermined fluctuation state appropriately, a sudden fluctuation state of the load of the internal combustion engine occurs, which is estimated to cause deterioration of the combustion state when the combustion mode is switched to the stratified combustion mode. Unlike the conventional case, the combustion mode is not switched to the stratified combustion mode, and the uniform combustion mode is maintained in which the degree of freedom of fuel injection control and intake air amount control is greater. As a result, even when a sudden fluctuation state of the load of the internal combustion engine is occurring, a better combustion state than the conventional one can be ensured, whereby the occurrence of torque fluctuation can be avoided and the drivability can be improved. .

  According to a second aspect of the present invention, in the control device 1 for the internal combustion engine 3 according to the first aspect, the load parameter is the engine speed NE of the internal combustion engine 3, and the determination means is a variation amount of the engine speed NE ( When the absolute value of rotation deviation | DNEDS |) is equal to or greater than a predetermined value (first and second decrease side threshold values DNEDSDC1, DNEDSDC2, first and second increase side threshold values DNEDSAC1, DNEDSAC2) It is characterized by determining that it exists in.

  According to the control apparatus for an internal combustion engine, when the fluctuation amount of the engine speed is equal to or greater than a predetermined value during the uniform combustion mode, that is, when the combustion mode is switched to the stratified combustion mode due to a large load fluctuation state, When it is estimated that the state will be deteriorated, the combustion mode is maintained in the uniform combustion mode without being switched to the stratified combustion mode. As a result, a better combustion state than before can be obtained more reliably.

  According to a third aspect of the present invention, in the control device 1 for the internal combustion engine 3 according to the first or second aspect, the load parameter is the opening degree of the throttle valve 13a of the internal combustion engine 3, and the determination means is the throttle valve 13a. A variation amount of the opening TH (absolute value of opening deviation | DTHDS |) is a predetermined value (first and second valve closing side threshold values DTHDSCL1, DTHDSCL2, first and second valve opening side threshold values DTHDSOP1, DTHDSOP2). When it is above, it is characterized in that it is determined to be in a predetermined fluctuation state.

  According to the control device for an internal combustion engine, when the variation amount of the throttle valve opening is equal to or greater than a predetermined value during the uniform combustion mode, that is, when the variation state of the load is large, the combustion mode is switched to the stratified combustion mode. When it is estimated that the combustion state is deteriorated, the combustion mode is maintained in the uniform combustion mode without being switched to the stratified combustion mode. As a result, a better combustion state than before can be obtained more reliably.

1 is a diagram illustrating a schematic configuration of a control device according to an embodiment of the present invention and an internal combustion engine to which the control device is applied. It is a flowchart which shows the process which determines the opening state of a throttle valve, and the fluctuation state of an engine speed. It is a flowchart which shows the calculation process of opening degree deviation DTHDS. It is a flowchart which shows the setting process of TH fluctuation flag F_DTHDS. It is a flowchart which shows the calculation process of rotation deviation DNEDS. It is a flowchart which shows the setting process of NE fluctuation | variation flag F_DNEDS. It is a flowchart which shows the main routine of a fuel-injection control process. It is a flowchart which shows a part of setting process of the stratified combustion permission flag F_DISCOK. It is a flowchart which shows the continuation of FIG. It is a flowchart which shows the setting process of the stratified combustion area flag F_DISCAREA. It is a flowchart which shows the setting process of the driving | running state flag F_DSDRCND. It is a flowchart which shows the setting process of delay flag F_TDSCND0. It is a flowchart which shows a fuel-injection process. It is a flowchart which shows the setting process of 2 times injection flag F_DBINJ. It is a figure which shows an example of the map used for calculation of request | requirement torque PMCMD.

  Hereinafter, an internal combustion engine control apparatus according to an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the control device 1 includes an ECU 2. As will be described later, the ECU 2 changes the throttle valve opening and engine speed fluctuation state of an internal combustion engine (hereinafter referred to as “engine”) 3. A determination process, a fuel injection control process, and the like are performed.

  The engine 3 is an in-line 4-cylinder (only one shown) gasoline engine mounted on a vehicle (not shown), and a combustion chamber 3c is formed between a piston 3a and a cylinder head 3b of each cylinder. A recess 3d is formed at the center of the upper surface of the piston 3a. Further, a fuel injection valve (hereinafter referred to as “injector”) 4 and a spark plug 5 are attached to the cylinder head 3b so as to face the combustion chamber 3c, and fuel is directly injected into the combustion chamber 3c. That is, the engine 3 is a cylinder injection type.

  The injector 4 is disposed in the center of the top wall of the combustion chamber 3c, and is connected to the high-pressure pump 4a via the fuel pipe 4b. The fuel is boosted to a high pressure from a fuel tank (not shown) by the high-pressure pump 4 a and then supplied to the injector 4 in a state of being regulated by a regulator (not shown). The fuel is supplied to the piston 3 a via the injector 4. Injected toward the recess 3d. As a result, the fuel collides with the upper surface of the piston 3a including the recess 3d to form a fuel jet. In particular, during stratified combustion, which will be described later, most of the fuel injected by the injector 4 collides with the recess 3d to form a fuel jet.

  On the other hand, a fuel pressure sensor 20 is attached to a portion of the fuel pipe 4b near the injector 4. The fuel pressure sensor 20 detects the fuel pressure PF of the fuel injected by the injector 4 and outputs a detection signal to the ECU 2. Further, a fuel temperature sensor 21 is connected to the ECU 2. The fuel temperature sensor 21 detects the fuel temperature TF and outputs a detection signal to the ECU 2. The injector 4 is connected to the ECU 2, and the fuel injection time and the fuel injection timing (the valve opening timing and the valve closing timing), which are the valve opening time, are controlled by a drive signal from the ECU 2. Since the fuel injection time of the injector 4 corresponds to the amount of fuel injected into the cylinder, that is, the fuel injection amount, the fuel injection time of the injector 4 is hereinafter referred to as fuel injection amount.

  The spark plug 5 is also connected to the ECU 2 and discharged when a high voltage is applied from the ECU 2 at a timing corresponding to the ignition timing, thereby burning the air-fuel mixture in the combustion chamber 3c.

  Further, the engine 3 is of the DOHC type and includes an intake camshaft 6 and an exhaust camshaft 7. These intake and exhaust camshafts 6 and 7 have an intake cam 6a and an exhaust cam 7a for opening and closing the intake valve 8 and the exhaust valve 9, respectively. The intake and exhaust camshafts 6 and 7 are connected to the crankshaft 3e via a timing belt (not shown), and rotate once every two rotations according to the rotation of the crankshaft 3e. A cam phase variable mechanism (hereinafter referred to as “VTC”) 10 is provided at one end of the intake camshaft 6.

  The VTC 10 operates by being supplied with hydraulic pressure, and advances or retards the opening / closing timing of the intake valve 8 by advancing or retarding the phase of the intake cam 6a with respect to the crankshaft 3e steplessly. Thus, by increasing or decreasing the valve overlap between the intake valve 8 and the exhaust valve 9, the internal EGR amount is increased or decreased, and the charging efficiency is changed. Further, a VTC electromagnetic control valve 10a is connected to the VTC 10. The VTC electromagnetic control valve 10a is driven by a drive signal from the ECU 2, and supplies hydraulic pressure from a lubrication hydraulic pump (not shown) of the engine 3 to the VTC 10 according to the duty ratio of the drive signal. As a result, the VTC 10 advances or retards the cam phase of the intake cam 6a.

  Further, although not shown, each of the intake cam 6a and the exhaust cam 7a includes a low-speed cam and a high-speed cam having a cam nose higher than that of the low-speed cam. The engine 3 is provided with a plurality of valve timing switching mechanisms (hereinafter referred to as “VTEC (registered trademark)”) 11. Each VTEC 11 switches the intake cam 6a and the exhaust cam 7a between a low speed cam and a high speed cam, thereby changing the valve timing of the intake valve 8 and the exhaust valve 9 to a low speed valve timing (hereinafter referred to as “LO.VT”) and a high speed valve. Switching between timings (hereinafter referred to as “HI.VT”). In this case, LO. Compared with VT, HI. In the case of VT, the opening period of the intake valve 8 and the exhaust valve 9 and the valve overlap between both become longer, and the valve lift amount is also increased, so that the charging efficiency is improved. Similarly to the VTC 10, the VTEC 11 also operates by being supplied with hydraulic pressure via the VTEC electromagnetic control valve 11a by the ECU 2, and executes the switching operation.

  On the other hand, a magnet rotor 22a is attached to the crankshaft 3e. The magnet rotor 22a and the MRE pickup 22b constitute a crank angle sensor 22. The crank angle sensor 22 outputs a CRK signal and a TDC signal, which are pulse signals, as the crankshaft 3e rotates.

  One pulse of the CRK signal is output every predetermined crank angle (for example, 30 °). The ECU 2 obtains the engine speed (hereinafter referred to as “engine speed”) NE of the engine 3 based on the CRK signal. The TDC signal is a signal indicating that the piston 3a of each cylinder is at a predetermined crank angle position near the TDC (top dead center) at the start of the intake stroke, and in this example of the 4-cylinder type, every crank angle of 180 °. One pulse is output.

  A water temperature sensor 23 is attached to the main body of the engine 3. The water temperature sensor 23 is composed of a thermistor, detects an engine water temperature TW that is the temperature of the cooling water circulating in the main body of the engine 3, and outputs a detection signal to the ECU 2.

  The intake pipe 12 of the engine 3 is provided with an air flow sensor 24, a throttle valve mechanism 13, a throttle valve opening sensor 25, an intake pipe absolute pressure sensor 26, and the like in order from the upstream side.

  The air flow sensor 24 is constituted by a hot-wire air flow meter, and outputs a detection signal representing an intake air amount (hereinafter referred to as “TH passage intake air amount”) GTH passing through a throttle valve 13a described later to the ECU 2.

  The throttle valve mechanism 13 includes a throttle valve 13a and an actuator 13b that opens and closes the throttle valve 13a. The throttle valve 13a is rotatably provided in the middle of the intake pipe 12, and changes the TH passing intake air amount GTH by changing the opening degree associated with the rotation. The actuator 13b is a combination of a motor connected to the ECU 2 and a gear mechanism (both not shown). The actuator 13b is driven by a drive signal from the ECU 2, thereby opening the throttle valve 13a (hereinafter referred to as "throttle valve"). TH) is changed.

  Further, the throttle valve opening sensor 25 is composed of, for example, a potentiometer, detects the throttle valve opening TH, and outputs a detection signal to the ECU 2. On the other hand, the intake pipe absolute pressure sensor 26 is composed of a semiconductor pressure sensor or the like, detects an intake pipe absolute pressure PBA, which is an absolute pressure in the intake pipe 12, and outputs a detection signal to the ECU 2. Further, the intake pipe 12 is provided with an intake air temperature sensor 27. The intake air temperature sensor 27 is composed of a thermistor, detects the intake air temperature TA in the intake pipe 12, and outputs a detection signal to the ECU 2.

  An EGR pipe 15 is connected between the intake pipe 12 downstream of the throttle valve mechanism 13 and the exhaust pipe 14 upstream of the catalyst device 17. The EGR pipe 15 recirculates the exhaust gas of the engine 3 to the intake side, and performs an EGR operation for reducing NOx in the exhaust gas by lowering the combustion temperature in the combustion chamber 3c. An EGR control valve 16 is attached to the EGR pipe 15.

  The EGR control valve 16 is a linear electromagnetic valve, and its valve lift varies linearly in response to a drive signal from the ECU 2, thereby opening and closing the EGR pipe 15. The ECU 2 controls the EGR amount by controlling the valve lift amount of the EGR control valve 16 according to the operating state of the engine 3.

The exhaust pipe 14 is provided with a catalyst device 17. The catalyst device 17 is a combination of a NOx catalyst and a three-way catalyst. This NOx catalyst is not shown, but an iridium catalyst (a sintered body of silicon carbide whisker powder carrying iridium and silica) is formed on a honeycomb structure. The surface of the material is coated, and a perovskite-type double oxide (LaCoO ₃ powder and silica fired body) is further coated thereon. The catalyst device 17 purifies NOx in the exhaust gas during the operation in the stratified combustion mode and the lean burn operation, which will be described later, by the reducing action by the NOx catalyst, and other than the lean burn operation by the redox action of the three-way catalyst. The CO, HC and NOx in the exhaust gas during operation are purified.

  Further, a LAF sensor 28 and an oxygen concentration sensor (not shown) are provided on the upstream side and the downstream side of the exhaust pipe 14 from the catalyst device 17, respectively. The LAF sensor 28 is composed of zirconia and a platinum electrode, and linearly detects the oxygen concentration in the exhaust gas in a wide air-fuel ratio A / F range from the rich region richer than the theoretical air-fuel ratio to the extreme lean region. Then, a detection signal representing it is output to the ECU 2. The ECU 2 calculates a detected air-fuel ratio KACT representing the air-fuel ratio in the exhaust gas based on the detection signal of the LAF sensor 28. The detected air-fuel ratio KACT is specifically calculated as an equivalence ratio. The O2 sensor outputs a detection signal indicating the oxygen concentration in the exhaust gas to the ECU 2.

  Further, an atmospheric pressure sensor 29, an accelerator opening sensor 30, a shift position sensor 31, and a vehicle speed sensor 32 are connected to the ECU 2. The atmospheric pressure sensor 29 is constituted by a semiconductor pressure sensor, detects the atmospheric pressure PA, and outputs a detection signal to the ECU 2. The accelerator opening sensor 30 detects an accelerator opening AP, which is an operation amount of an accelerator pedal (not shown), and outputs a detection signal to the ECU 2. The ECU 2 controls the throttle valve opening TH according to the accelerator opening AP and the like.

  On the other hand, the shift position sensor 31 and the vehicle speed sensor 32 respectively detect a shift position POSI and a vehicle speed VP of an automatic transmission (hereinafter referred to as “AT”) (not shown), and output detection signals to the ECU 2.

  On the other hand, the ECU 2 is constituted by a microcomputer including a CPU 2a, a RAM 2b, a ROM 2c, and the like. The ECU 2 executes various arithmetic processes based on the control programs stored in the ROM 2c according to the detection signals of the various sensors 20 to 32 described above.

  Specifically, as will be described later, the fluctuation state of the engine speed NE (load parameter) and the throttle valve opening TH (load parameter) is determined. Further, the operating state of the engine 3 is determined from the various detection signals, and based on the determination result, the combustion mode (combustion mode) of the engine 3 is changed to the stratified combustion mode at the time of extremely low load operation, and at the time of the extremely low load operation. During the operation other than the above, the mode is switched to the uniform combustion mode, and the double injection combustion mode is executed in principle during the combustion transition mode in which one of the uniform combustion mode and the stratified combustion mode is shifted to the other. Further, by controlling the final fuel injection amount TOUT and the fuel injection timing of the injector 4 according to the combustion mode, the fuel injection control process including the air-fuel ratio feedback control process is executed and the ignition timing IG of the spark plug 5 is controlled. To do.

  In the stratified combustion mode, fuel is injected from the injector 4 into the combustion chamber 3c during the compression stroke, and a fuel jet is formed by causing most of the injected fuel to collide with the recess 3d. An air-fuel mixture is generated by this fuel jet and the flow of the inflow air from the intake pipe 12, and the piston 3a is located near the top dead center of the compression stroke, so that the air-fuel mixture is brought close to the spark plug 5. While being unevenly distributed, combustion is performed at an air-fuel ratio A / F (for example, 27 to 60) that is extremely leaner than the theoretical air-fuel ratio. Further, in the stratified combustion mode, the throttle valve opening TH is controlled to be almost fully open.

  Further, in the uniform combustion mode, fuel is injected into the combustion chamber 3c during the intake stroke, and the air-fuel mixture generated by the fuel jet and the air flow is uniformly dispersed in the combustion chamber 3c. Uniform combustion is performed with a rich air-fuel ratio A / F (for example, 12 to 22).

  Further, in the two-injection combustion mode, fuel is injected twice at intervals during one combustion cycle, and combustion is performed at a richer air-fuel ratio A / F (for example, 12 to 22) than in the stratified combustion mode. In this case, the two fuel injections are executed during the intake stroke and the compression stroke.

  In the present embodiment, the ECU 2 constitutes load parameter detection means, combustion mode switching means, determination means, and switching prohibition means.

  Next, referring to FIG. 2, a process executed by the ECU 2 for determining the fluctuation state of the throttle valve opening TH and the engine speed NE will be described. This process is interrupted at a predetermined cycle (for example, 10 msec) according to the setting of the program timer.

  In this process, first, an opening degree deviation DTHDS is calculated in a step (abbreviated as “S1” in the figure. The same applies hereinafter). Specifically, the opening deviation DTHDS is calculated as shown in FIG. That is, first, in step 5, it is determined whether or not the value CTHSMPL of the down-count type sampling counter is “0”. If the determination result is NO and CTHSMPL ≠ 0, the process proceeds to step 9 where the sampling counter value CTHSMPL is decremented by 1, and the process is terminated.

  On the other hand, when the determination result in step 5 is YES and CTHSMPL = 0, the process proceeds to step 6 and the value CTHSMPL of the sampling counter is set to a predetermined value CTTHSMPL (for example, value 10). Next, in step 7, m (for example, 5) buffer values THBUFF stored in the RAM 2b are updated.

  These buffer values THBUFF represent the sampling values of the throttle valve opening TH sampled in m loops before the previous time in synchronization with the execution of this processing. In the update processing, each buffer value THBUFF represents each sampling value in the RAM 2b. The value is set as an old value for one control cycle. For example, the throttle valve opening TH sampled this time is set as the current value THBUFF (n) of the buffer value, the current value THBUFF (n) is set as the previous value THBUFF (n−1), and the previous value THBUFF (n -1) is set as the last time value THBUFF (n-2).

  Next, the routine proceeds to step 8, where the deviation between the current value THBUFF (n) of the buffer value and the value THBUFF (nm) before m times is set as the opening degree deviation DTHDS. Thereafter, this process is terminated.

  Returning to FIG. 2, after the opening degree deviation DTHDS is calculated in step 1 as described above, the process proceeds to step 2 to execute the setting process of the TH fluctuation flag F_DTHDS. This TH fluctuation flag F_DTHDS indicates whether or not the fluctuation amount of the throttle valve opening TH is large, in other words, whether or not the throttle valve opening TH is in a stable state. Specifically, FIG. It is set as shown in

  That is, first, in step 10, it is determined whether or not the accelerator opening flag F_APOPEN is “1”. The accelerator opening flag F_APOPEN is set to “1” when the accelerator opening AP is greater than or equal to a predetermined value, that is, when the accelerator pedal is operated, and is set to “0” otherwise.

  If the determination result in step 10 is YES and the accelerator pedal is operated, the process proceeds to step 11 to determine whether or not the opening degree deviation DTHDS calculated in step 1 is less than or equal to 0. When the determination result is YES, that is, when the throttle valve opening TH changes to the valve closing side or does not change, the routine proceeds to step 12 where the absolute value of the opening deviation | DTHDS | Is determined to be smaller than a predetermined first valve closing side threshold value DTHDSCL1 (predetermined value, for example, 2 °).

  When the determination result is NO, it is determined that the throttle valve opening TH has a large fluctuation amount and is in an unstable state, and the routine proceeds to step 16 where the timer value TDTHDS of the down-counting TH determination delay timer is set to a predetermined value. Set to the first delay value TDTHDS1 (eg, value 20).

  Next, the routine proceeds to step 17 where the TH fluctuation flag F_DTHDS is set to “1” in order to indicate that the throttle valve opening TH is in an unstable state, and then this processing is terminated.

  On the other hand, if the determination result in step 12 is YES and | DTHDS | <DTHDSCL1, it is determined in step 13 whether the timer value TDTHDS of the delay timer for TH determination is 0 or not. If the determination result is NO, it is determined that the throttle valve opening TH is not yet stable, and after executing step 17, the present process is terminated.

  On the other hand, when the determination result in step 13 is YES and the state in which the variation amount of the throttle valve opening TH is small continues for a predetermined time (a time corresponding to the first delay value TDTHDS1) or more, the throttle valve opening TH is stabilized. Assuming that the state is in the state, the process proceeds to step 14, and the TH fluctuation flag F_DTHDS is set to “0” to indicate this, and then the present process is terminated.

  On the other hand, if the determination result in step 11 is NO and the throttle valve opening TH changes to the valve opening side, the process proceeds to step 15 where the absolute value | DTHDS | of the opening deviation is the predetermined first valve opening side. It is determined whether or not it is smaller than a threshold value DTHDSOP1 (predetermined value).

  The first valve opening side threshold value DTHDSOP1 is set to a value (for example, 0.7 °) smaller than the first valve closing side threshold value DTHDSCL1 described above. This is because when the throttle valve opening TH changes to the valve opening side, that is, when the engine load changes to the increase side, the throttle valve opening TH changes to the valve closing side and the engine load decreases. This is because a more stable combustion state is ensured by setting the execution region of the stratified combustion mode to be narrower and setting the execution region of the uniform combustion mode to be wider than when performing the same.

  When the determination result in step 15 is NO, it is assumed that the throttle valve opening TH has a large fluctuation amount and is in an unstable state, and as described above, after executing steps 16 and 17, this process is terminated.

  On the other hand, if the determination result in step 15 is YES and | DTHDS | <DTHDSOP1, the process proceeds to step 13 described above to determine whether the timer value TDTHDS of the TH determination delay timer is 0 or not. If the determination result is NO, it is determined that the throttle valve opening TH is not yet stable, and the TH variation flag F_DTHDS is set to “1” in step 17 described above, and then this process is terminated. On the other hand, when the determination result in step 13 is YES, assuming that the throttle valve opening TH is in a stable state, in step 14 described above, the TH fluctuation flag F_DTHDS is set to “0”, and then this process ends.

  On the other hand, when the determination result of step 10 is NO and the accelerator pedal is not operated, the process proceeds to step 18 to determine whether or not the opening degree deviation DTHDS is 0 or less. If the determination result is YES, that is, if the throttle valve opening TH has changed to the valve closing side or has not changed, the routine proceeds to step 19 where the absolute value of the opening deviation | DTHDS | It is determined whether or not the valve side threshold value DTHDSCL2 is smaller. The second valve closing side threshold value DTHDSCL2 is set to a value (for example, 0.5 °) smaller than the first valve closing side threshold value DTHDSCL1 described above. This is because when the accelerator pedal is not operated, it is estimated that the engine is idling, so the amount of variation in the throttle valve opening TH is smaller than that in the normal operation where the accelerator pedal is operated. This is because the stratified combustion mode is executed when the fluctuation of the engine load is smaller, thereby ensuring a more stable combustion state.

  When the determination result is NO, it is determined that the throttle valve opening TH has a large fluctuation amount and is in an unstable state, the process proceeds to step 23, and the timer value TDTHDS of the TH determination delay timer described above is set to a predetermined second value. The delay value TDTHDS2 is set. The second delay value TDTHDS2 is set to a value (for example, value 80) larger than the first delay value TDTHDS described above. This is because when the accelerator pedal is not operated, it is presumed that the engine is idling, so the engine load fluctuation is smaller than in the normal operation where the accelerator pedal is operated. This is because the transition to the stratified combustion mode is prohibited until the uniform combustion mode is continued.

  Next, the routine proceeds to step 24, where the TH fluctuation flag F_DTHDS is set to “1” in order to indicate that the throttle valve opening TH is in an unstable state, and then this processing is terminated.

  On the other hand, if the determination result in step 19 is YES and | DTHDS | <DTHDSCL2, it is determined in step 20 whether or not the timer value TDTHDS of the TH determination delay timer is zero. If the determination result is NO, it is determined that the throttle valve opening TH is not yet stable, and after executing step 24, the present process is terminated.

  On the other hand, when the determination result in step 20 is YES and the state in which the variation amount of the throttle valve opening TH is small continues for a predetermined time (a time corresponding to the second delay value TDTHDS2) or more, the throttle valve opening TH is stabilized. Assuming that the state is in the state, the process proceeds to step 21, and the TH fluctuation flag F_DTHDS is set to “0” to represent it, and then this process is terminated.

  On the other hand, when the determination result of step 18 is NO and the throttle valve opening TH changes to the valve opening side, the routine proceeds to step 22 where the absolute value | DTHDS | of the opening deviation is set to the predetermined second valve opening side. It is determined whether or not the threshold value DTHDSOP2 is smaller. The second valve opening side threshold value DTHDSOP2 (predetermined value) is set to a value (for example, 0.1 °) smaller than the first valve opening side threshold value DTHDSOP1. As described above, when the throttle valve opening TH changes to the valve opening side and the engine load changes to the increase side, the throttle valve opening TH changes to the valve closing side and the engine load decreases. This is because a more stable combustion state can be ensured by setting the execution region of the stratified combustion mode to be narrower and setting the execution region of the uniform combustion mode to be wider than when performing the same.

  When the determination result in step 22 is NO, it is assumed that the throttle valve opening TH has a large fluctuation amount and is in an unstable state, and as described above, after executing steps 23 and 24, the present process is terminated.

  On the other hand, if the determination result in step 22 is YES and | DTHDS | <DTHDSOP2, the process proceeds to step 20 described above to determine whether or not the timer value TDTHDS of the TH determination delay timer is zero. If the determination result is NO, it is determined that the throttle valve opening TH is not yet stable, and the TH variation flag F_DTHDS is set to “1” in step 24 described above, and then the present process is terminated. On the other hand, when the determination result in step 20 is YES, assuming that the throttle valve opening TH is in a stable state, the TH variation flag F_DTHDS is set to “0” in step 21 described above, and then this process is terminated.

  Returning to FIG. 2, after setting the TH fluctuation flag F_DTHDS in step 2 as described above, the process proceeds to step 3 to calculate the rotation deviation DNEDS. Specifically, this rotational deviation DNEDS is calculated as shown in FIG.

  That is, in step 30, it is determined whether or not the value CNESMPL of the down-count type sampling counter is “0”. If the result of this determination is NO and CNESMPL ≠ 0, the routine proceeds to step 34 where the sampling counter value CNESMPL is decremented by 1, and then this processing is terminated.

  On the other hand, if the decision result in the step 30 is YES and CNESMPL = 0, the process proceeds to a step 31 where the value CNESMPL of the sampling counter is set to a predetermined value CTNESMPL (for example, value 10). Next, in step 32, m (for example, 5) buffer values NEBUFF stored in the RAM 2b are updated.

  These buffer values NEBUFF represent the sampling values of the engine speed NE sampled in the m loops before the previous time in synchronization with the execution of this processing, and in the update processing, the respective values in the RAM 2b. Is set as an old value for one control cycle. For example, the engine speed NE sampled this time is set as the current value NEBUFF (n) of the buffer value, the current value NEBUFF (n) is set as the previous value NEBUFF (n−1), and the previous value NEBUFF (n− 1) is set as the last time value NEBUFF (n-2).

  Next, the routine proceeds to step 33, where the difference between the current value NEBUFF (n) of the buffer value and the value NEBUFF (nm) before m times is set as the rotational deviation DNEDS. Thereafter, this process is terminated.

  Returning to FIG. 2, after calculating the rotation deviation DNEDS as described above in step 3, the process proceeds to step 4, where the NE variation flag F_DNEDS is set. This NE fluctuation flag F_DNEDS indicates whether or not the fluctuation amount of the engine speed NE is large, in other words, whether or not the engine speed NE is in a stable state. Specifically, FIG. 6 shows. Is set as follows.

  First, in step 40, it is determined whether or not the NP shift position flag F_ATNP is “1”. The NP shift position flag F_ATNP is set to “1” when the current AT shift position POSI is the N range or the P range, and is set to “0” otherwise.

  If the determination result is NO and the current AT shift position POSI is in a range other than the N range and the P range, for example, the D range, the process proceeds to step 41 to determine whether or not the vehicle speed VP is equal to or lower than the predetermined vehicle speed VDNEDS. To do. The predetermined vehicle speed VDNEDS is used to determine whether or not the vehicle is traveling at a high speed, and is set to a value having a predetermined width with hysteresis.

  If the determination result in step 41 is NO and the vehicle is traveling at high speed, the process proceeds to step 42 to determine whether or not the rotational deviation DNEDS calculated in step 3 is less than or equal to zero. If the determination result is YES, that is, if the engine speed NE has changed to the decreasing side or has not changed, the routine proceeds to step 43, where the absolute value of rotation deviation | DNEDS | It is determined whether or not the value is smaller than a predetermined first decrease side threshold value DNEDSDC1 (predetermined value, for example, 200 rpm).

  When the determination result is NO, it is determined that the engine speed NE has a large fluctuation amount and is in an unstable state, the process proceeds to step 47, and the timer value TDNEDS of the down-count type NE determination delay timer is set to a predetermined first value. One delay value TDNEDS1 (for example, value 20) is set.

  Next, the routine proceeds to step 48, where the NE fluctuation flag F_DNEDS is set to “1” in order to indicate that the engine speed NE is in an unstable state, and then this processing is terminated.

  On the other hand, if the determination result in step 43 is YES and | DNEDS | <DNEDSDC1, it is determined in step 44 whether or not the timer value TDNEDS of the NE determination delay timer is zero. If the determination result is NO, it is determined that the engine speed NE is not yet stable, and after executing step 48, the present process is terminated.

  On the other hand, when the determination result in step 44 is YES and the state where the fluctuation amount of the engine speed NE is small continues for a predetermined time (a time corresponding to the first delay value TDNEDS1) or longer, the engine speed NE is in a stable state. In step 45, the NE fluctuation flag F_DNEDS is set to “0” to indicate this, and then the present process is terminated.

  On the other hand, if the determination result in step 42 is NO and the engine speed NE has changed to the increasing side, the routine proceeds to step 46 where the absolute value | DNEDS | of the rotational deviation is a predetermined first increasing threshold DNEDSAC1 ( It is determined whether it is smaller than a predetermined value.

  The first increase side threshold value DNEDSAC1 is set to a value (for example, 50 rpm) smaller than the first decrease side threshold value DNEDSDC1. This is because when the engine speed NE changes to the increase side, that is, when the engine load changes to the increase side, the engine speed NE changes to the decrease side and the engine load decreases. This is because a more stable combustion state is ensured by setting the execution region of the stratified combustion mode to be narrower and setting the execution region of the uniform combustion mode to be wider.

  When the determination result in step 46 is NO, it is assumed that the engine speed NE has a large fluctuation amount and is in an unstable state, and as described above, after executing steps 47 and 48, the present process is terminated. On the other hand, if the determination result in step 46 is YES and | DNEDS | <DNEDSAC1, the process proceeds to step 44 described above, and it is determined whether or not the timer value TDNEDS of the NE determination delay timer is zero.

  If the determination result is NO, assuming that the engine speed NE is not yet stable, the NE variation flag F_DNEDS is set to “1” in step 48 described above, and then the present process is terminated. On the other hand, when the determination result in step 44 is YES, assuming that the engine speed NE is in a stable state, the NE variation flag F_DNEDS is set to “0” in step 45 described above, and then this process is terminated.

  On the other hand, when the determination result of either step 40 or 41 is YES, that is, when the shift position POSI is in the N range or P range, or when traveling at a low speed or stopping, the routine proceeds to step 49 where the rotational deviation DNEDS is It is determined whether or not the value is 0 or less. When the determination result is YES and the engine speed NE has changed to the decreasing side or has not changed, the routine proceeds to step 50 where the absolute value | DNEDS | of the rotational deviation is a predetermined second decreasing threshold DNEDSDC2. It is determined whether or not it is smaller.

  The second decrease side threshold value DNEDSDC2 (predetermined value) is set to a value (for example, 20 rpm) smaller than the first decrease side threshold value DNEDSDC1 described above. This is because when the shift position POSI is in the N range or the P range, it is estimated that the engine is idling. For example, compared with the case where the shift position POSI is in the D range, the fluctuation amount of the engine speed NE is smaller and the engine load This is because the stratified combustion mode is executed when the fluctuation of the engine is smaller, thereby ensuring a more stable combustion state.

  When the determination result in step 50 is NO, the engine speed NE is large in fluctuation and is in an unstable state, the process proceeds to step 54, and the timer value TDNEDS of the NE determination delay timer described above is set to a predetermined first value. 2 Set to the delay value TDNEDS2.

  The second delay value TDNEDS2 is set to a value (for example, value 80) larger than the first delay value TDNEDS described above. This is presumed that when the shift position POSI is in the N range or P range, or when traveling at a low speed or when the vehicle is stopped, it is estimated that the vehicle is close to idle operation. This is because the transition to the stratified combustion mode is prohibited and the uniform combustion mode is continued until a stable operation state is achieved in which the fluctuation of the engine load is smaller than in the case.

  Next, the routine proceeds to step 55, where the NE fluctuation flag F_DNEDS is set to “1” to indicate that the engine speed NE is in an unstable state, and then this processing is terminated.

  On the other hand, if the determination result in step 50 is YES and | DNEDS | <DNEDSDC2, it is determined in step 51 whether or not the timer value TDNEDS of the NE determination delay timer is 0. If the determination result is NO, it is determined that the engine speed NE is not yet stable, and after executing step 55, the present process is terminated.

  On the other hand, when the determination result in step 51 is YES and the state where the fluctuation amount of the engine speed NE is small continues for a predetermined time (a time corresponding to the second delay value TDNEDS2) or longer, the engine speed NE is in a stable state. If there is, the process proceeds to step 52, and the NE fluctuation flag F_DNEDS is set to “0” to indicate this, and then this process is terminated.

  On the other hand, if the determination result in step 49 is NO and the engine speed NE has changed to the increasing side, the routine proceeds to step 53, where the absolute value | DNEDS | of the rotation deviation is greater than the predetermined second increasing side threshold value DNEDSAC2. Determine whether it is small. The second increase side threshold value DNEDSAC2 (predetermined value) is set to a value (for example, 5 rpm) smaller than the first increase side threshold value DNEDSAC1 described above. As described above, when the engine speed NE changes to the increasing side and the engine load changes to the increasing side, the engine speed NE changes to the decreasing side and the engine load decreases. This is because a more stable combustion state is ensured by setting the execution region of the stratified combustion mode to be narrower and setting the execution region of the uniform combustion mode to be wider.

  When the determination result in step 53 is NO, it is assumed that the engine speed NE has a large fluctuation amount and is in an unstable state, and as described above, after executing steps 54 and 55, this process is terminated.

  On the other hand, if the determination result in step 53 is YES and | DNEDS | <DNEDSAC2, the process proceeds to step 51 described above to determine whether or not the timer value TDNEDS of the NE determination delay timer is 0. If the determination result is NO, assuming that the engine speed NE is not yet stable, the NE variation flag F_DNEDS is set to “1” in step 55 described above, and then the present process is terminated. On the other hand, when the determination result in step 51 is YES, assuming that the engine speed NE is in a stable state, the NE variation flag F_DNEDS is set to “0” in step 52 described above, and then this process is terminated.

  Returning to FIG. 2, after the NE fluctuation flag F_DNEDS is set in step 4 as described above, the present process is terminated.

  Next, the fuel injection control process will be described with reference to FIG. This process is interrupted in synchronization with the input of the TDC signal. In this process, first, in step 59, the required torque PMCMD is calculated by searching the map shown in FIG. 15 according to the engine speed NE and the accelerator pedal opening AP. In this map, the required torque PMCMD is set to a larger value as the engine speed NE is higher or the accelerator pedal opening AP is larger. This is because the engine load becomes larger as the engine speed NE is higher or the accelerator pedal opening AP is larger, and this is to cope with it. The required torque PMCMD is calculated as a value corresponding to the combustion pressure at the time of air-fuel mixture combustion. Next, in step 60, a stratified combustion permission flag F_DISCOK setting process is executed. Details of this processing will be described later.

  Next, in step 61, various correction coefficients are calculated. Each of these various correction factors is calculated by searching various tables or maps (none of which are shown) according to various parameters (for example, intake air temperature TA, atmospheric pressure PA, engine water temperature TW, etc.). .

  Next, in steps 62 and 63, a target air-fuel ratio KCMD1ST for intake stroke injection and a target air-fuel ratio KCMD2ND for compression stroke injection are calculated. The former is used during the uniform combustion mode, the latter is used during the stratified combustion mode, and one of KCMD1ST and KCMD2ND is used as appropriate in the combustion transition mode. Further, the target air-fuel ratios KCMD1ST and KCMD2ND for intake stroke injection and compression stroke injection are calculated according to the engine speed NE and the required torque PMCMD.

  In step 64 following step 63, the air-fuel ratio F / B correction coefficient KAF is calculated. The air-fuel ratio F / B correction coefficient KAF is calculated according to the combustion mode. Specifically, the air-fuel ratio F / B correction coefficient KAF is determined according to the detected air-fuel ratio KACT, the target air-fuel ratio KCMD1ST for intake stroke injection, or the like. It is calculated by a predetermined feedback control algorithm according to the fuel ratio KACT and the target air-fuel ratio KCMD2ND for compression stroke injection.

  Next, in steps 65 and 66, a basic fuel injection amount TIM1ST for intake stroke injection and a basic fuel injection amount TIM2ND for compression stroke injection are calculated. Specifically, the actual intake air amount GCYL (the amount of air estimated to be actually taken into the cylinder) is calculated based on the TH passing intake air amount GTH and the intake pipe absolute pressure PBA. Then, by searching a table (not shown) according to the actual intake air amount GCYL, a basic fuel injection amount table value is calculated, and by correcting the table value, a basic fuel injection for intake stroke injection is performed. The quantity TIM1ST is calculated. Similarly, a basic fuel injection amount TIM2ND for compression stroke injection is also calculated.

  Next, the routine proceeds to step 67, where the required fuel injection amount TCYL is calculated. Specifically, the required fuel injection amount TCYL is calculated as follows. First, in an operating state in which the uniform combustion mode is to be executed, various correction coefficients calculated in steps 61, 62, 64, and 65, a target air-fuel ratio KCMD1ST for intake stroke injection, an air-fuel ratio F / B correction coefficient KAF, and Based on the basic fuel injection amount TIM1ST for intake stroke injection, the required fuel injection amount TCYL is calculated. In the operating state in which the stratified combustion mode is to be executed, various correction coefficients calculated in steps 61, 63, 64, and 66, an air-fuel ratio F / B correction coefficient KAF, a target air-fuel ratio KCMD2ND for compression stroke injection, The required fuel injection amount TCYL is calculated based on the basic fuel injection amount TIM2ND for compression stroke injection.

  Further, in the combustion transition mode when shifting from one of the uniform combustion mode and the stratified combustion mode to the other, the required fuel injection amount TCYL calculated as described above is set from the start of the execution until the intake air amount becomes stable. By performing the limit processing, the final required fuel injection amount TCYL is calculated. Further, after the intake air amount is stabilized, the required fuel injection amount TCYL is calculated without executing the limit processing. In this combustion transition mode, the limit execution flag F_TCYLLMT is set to “1” to indicate that the required fuel injection amount TCYL has been subjected to limit processing, and is set to “0” otherwise. .

  Next, the final fuel injection amount TOUT is calculated by correcting the calculated required fuel injection amount TCYL according to the fuel pressure PF and the fuel temperature TF (step 68). Next, the process proceeds to step 69, and as will be described later, after executing the fuel injection process, this process is terminated.

  Next, the above-described stratified combustion permission flag F_DISCOK setting process will be described with reference to FIGS. In this process, as described below, the values of various flags including the stratified combustion permission flag F_DISCOK are set.

  First, in step 70, an air-fuel ratio state flag F_DSAFCND is set. In this step 70, the air-fuel ratio state flag F_DSAFCND is set to “1” when the air-fuel ratio is in a state where the stratified combustion mode can be executed, and is set to “0” otherwise. More specifically, the LAF sensor 28 is activated, the air-fuel ratio feedback control based on the detected air-fuel ratio KACT is executed, and the purge gas concentration is equal to or lower than a predetermined concentration. When established, it is set to “1”, otherwise it is set to “0”.

  Next, at step 71, a process for setting the fuel pressure flag F_DSPFCND is executed. In step 71, the fuel pressure flag F_DSPFCND is set to “1” when the fuel pressure PF indicates a normal value, that is, when the high-pressure pump 4b is operating normally, and to “0” otherwise. Is set.

  Next, the process proceeds to step 72, where the learning completion flag F_IXREFLRN is set. In step 72, the learning completion flag F_IXREFLRN is set to “1” when idle learning in the uniform combustion mode is completed, and is set to “0” otherwise.

  Next, the routine proceeds to step 73, where the stratified combustion zone flag F_DISCAREA is set. This stratified combustion region flag F_DISCAREA indicates whether or not the engine 3 and the vehicle are in an operation region in which the stratified combustion mode can be executed. Specifically, the setting process is executed as shown in FIG. Is done.

  In this process, first, in step 100, a setting process of the operation state flag F_DSDRCND is executed. This operation state flag F_DSDRCND indicates whether or not the engine 3 is in an operation state in which the stratified combustion mode can be executed, and is specifically set as shown in FIG.

  That is, first, in step 110, various threshold values are set. Specifically, the threshold value TWDSL for determining the engine water temperature, the upper and lower limit values NEDSH and NEDSL for determining the engine speed, and the threshold value PADSL for determining the atmospheric pressure are set according to the previous value of the operation state flag F_DSDRCND. One of two predetermined values is selectively set. Further, upper limit value PMCDSH for request torque determination is set to a search value searched from a map (not shown) according to engine speed NE and vehicle speed VP, and lower limit value PMCDSL for request torque determination is set to engine speed NE. Accordingly, the search value searched from a table (not shown) is set. In each of these maps and tables, one of two types is selected according to the previous value of the operation state flag F_DSDRCND.

Next, in steps 111 to 114, it is determined whether or not the following conditions (c1) to (c4) are satisfied. If all four conditions (c1) to (c4) are satisfied, step 115 is performed. Therefore, in order to indicate that the engine 3 is in an operation state in which the stratified combustion mode can be executed, the operation state flag F_DSDRCND is set to “1”.
(C1) TWDSL <TW
(C2) NEDSL ≦ NE ≦ NEDSH
(C3) PADSL <PA
(C4) NEDSL ≦ PMCMD ≦ NEDSH

  On the other hand, when any one of the above four conditions (c1) to (c4) is not established, in order to indicate that the engine 3 is not in an operation state capable of executing the stratified combustion mode in step 116, an operation state flag is set. F_DSDRCND is set to “0”. Thereafter, this process is terminated.

  Returning to FIG. 10, after setting the operation state flag F_DSDRCND as described above in Step 100, the process proceeds to Step 101 to determine whether or not the operation state flag F_DSDRCND is “1”. If the determination result is YES and the operation state is such that the stratified combustion mode can be executed, the process proceeds to step 102 to determine whether or not the learning completion flag F_IXREFLRN described above is “1”.

  When the determination result is YES and the idle learning is completed, the process proceeds to step 104 described later. On the other hand, when the determination result is NO, the process proceeds to step 103, where it is determined whether or not the vehicle speed VP is equal to or higher than a predetermined vehicle speed VPIXREF. The predetermined vehicle speed VPIXREF is used to determine whether or not the vehicle is traveling, and is set to a value (for example, 3 km / h) that allows such determination. When the determination result at step 103 is YES and the vehicle is traveling, the routine proceeds to step 104.

  In step 104 following step 102 or 103, it is determined whether or not the TH fluctuation flag F_DTHDS set in step 2 is “0”. If the determination result is YES and the throttle valve opening TH is in a stable state, the routine proceeds to step 105, where it is determined whether or not the NE fluctuation flag F_DNEDS set in the step 4 is “0”.

  If the determination result is YES and the engine speed NE is in a stable state, the routine proceeds to step 106, where the stratified combustion region flag is displayed to indicate that the engine 3 and the vehicle are in the operation region in which the stratified combustion mode can be executed. After F_DISCAREA is set to “1”, this process ends.

  On the other hand, when the determination result of either step 104 or 105 is NO, that is, when the fluctuation amount of the throttle valve opening TH or the engine speed NE is large and unstable, the routine proceeds to step 107, where the engine 3 or In order to indicate that the vehicle is not in an operation region in which the stratified combustion mode can be executed, the stratified combustion region flag F_DISCAREA is set to “0”. Thereafter, this process is terminated.

  Further, when the determination result in step 103 is NO, that is, when idle learning is not completed and the vehicle is stopped, in step 107, the engine 3 or the vehicle is not in an operation region where the stratified combustion mode can be executed. In order to express this, the stratified combustion zone flag F_DISCAREA is set to “0”, and then the present process is terminated.

  Further, even when the determination result of step 101 is NO, after executing step 107 as described above, the present process is terminated.

  As described above, in the setting process of the stratified combustion zone flag F_DISCAREA, even when the engine 3 is in an operation state in which the stratified combustion mode can be executed (F_DSDRCND = 1), the variation of the throttle valve opening TH or the engine speed NE is changed. When the amount is large and unstable, the stratified combustion zone flag F_DISCAREA is set to “0”.

  Returning to FIG. 8, in step 73, the stratified combustion region flag F_DISCAREA is set as described above, and then the process proceeds to step 74 where the delay flag F_TDSCND0 is set. The delay flag F_TDSCND0 indicates whether or not the delay time determined according to the operating state of the engine 3 has elapsed, and the setting process is specifically executed as shown in FIG. .

  That is, first, in step 120, it is determined whether or not the brake negative pressure control flag F_PBDCSP is “1”. The brake negative pressure control flag F_PBDCSP is set to “1” when the brake negative pressure control is executed, and to “0” when the brake negative pressure control is not executed. This brake negative pressure control is a throttle valve for supplying negative pressure in the intake pipe 12 to the master back in order to recover the negative pressure in the master back (not shown) due to brake operation. The opening degree TH is controlled.

  If the determination result in step 120 is YES and the brake negative pressure control is being executed, the process proceeds to step 121, where the delay time TMDSPBS for negative pressure control is set to a predetermined value TMDSPBSREF. On the other hand, if the determination result in step 120 is NO and the brake negative pressure control is not being executed, the routine proceeds to step 122, where the delay time TMDSPBS for negative pressure control is set to the value 0.

  Next, in step 123 following step 121 or 122, it is determined whether or not the fuel cut flag F_FC is “1”. If the determination result is YES and the fuel cut operation is in progress, the routine proceeds to step 124, where the delay time TMDSAFC for the fuel cut operation is set to a predetermined value TMDSAFCREF. On the other hand, when the determination result of step 123 is NO and the fuel cut operation is not being performed, the routine proceeds to step 125 where the delay time TMDSAFC for fuel cut operation is set to 0.

  Next, in step 126 following step 124 or 125, it is determined whether or not the lift switching flag F_VTEC is “1”. The lift switching flag F_VTEC is set so that the valve timing of the intake valve 8 and the exhaust valve 9 is HI. When set to VT, it is set to “1” and LO. When it is set to VT, it is set to “0”.

  If the determination result in step 126 is YES, the valve timings of the intake valve 8 and the exhaust valve 9 are HI. When it is set to VT, the routine proceeds to step 127, where HI. The delay time TMDSVTEC for VT is set to a predetermined value TMDSVTECREF. On the other hand, if the determination result of step 126 is NO, LO. When it is set to VT, the routine proceeds to step 128, where HI. The delay time TMDSVTEC for VT is set to 0.

  Next, in step 129 following step 127 or 128, the timer value TDSND of the down-count delay timer is set. Specifically, the three delay times TMDSPBS, TMDSAFC, and TMDSVTEC set as described above are compared with the timer value TDSND stored in the RAM 2b (that is, the value decremented after setting in the previous loop). The maximum value among these values is set as the timer value TDSND of the delay timer.

  Next, the routine proceeds to step 130, where it is determined whether or not the timer value TDSND of the delay timer is zero. If the determination result is NO and the delay time has not elapsed, the delay flag F_TDSCND0 is set to “0” in step 131 to indicate that. Thereafter, this process is terminated.

  On the other hand, if the decision result in the step 130 is YES and the delay time has elapsed, the delay flag F_TDSCND0 is set to “1” in a step 132 to indicate that. Thereafter, this process is terminated.

  Returning to FIG. 8, after the delay flag F_TDSCND0 is set as described above in step 74, the process proceeds to step 75 where the value of the stratified combustion permission flag F_DISCOK stored in the RAM 2b is set to the previous value of the stratified combustion permission flag. Set as the value F_DISCOKZ.

  Next, in step 76, it is determined whether or not the stratified failsafe flag F_FSPDISC is “1”. The stratified failsafe flag F_FSPDISC is set to “1” when a malfunction of the device occurs, and is set to “0” otherwise.

  When the determination result in step 76 is YES, it is determined that the stratified combustion mode should not be executed due to a malfunction of the equipment, and the process proceeds to step 84 in FIG. 9 to indicate that the stratified combustion mode cannot be executed. The flag F_DISCCAN is set to “0”. Next, in step 85, the stratified combustion permission flag F_DISCOK is set to “0” in order to indicate that the engine 3 and the vehicle are not in an operation state in which the stratified combustion mode is to be executed.

  On the other hand, when the determination result of step 76 is NO, the process proceeds to step 77 to determine whether or not the start mode flag F_STMOD is “1”. If the determination result is YES and the engine is in the start mode, the timer value TDSST of the down-count type start mode delay timer is set to a predetermined value TMDSST in step 82.

  Thereafter, in step 83, the timer value TDDSLLY of the down-count type stratification start permission delay timer is set to a predetermined value TMDDSLY. Next, as described above, after executing Steps 84 and 85 in FIG. 9, this processing is terminated.

  On the other hand, if the determination result in step 77 is NO and the engine is not in the start mode, the process proceeds to step 78 to determine whether or not the timer value TDSST of the start mode delay timer is “0”. When the determination result is NO, as described above, after executing steps 83 to 85, the present process is terminated. On the other hand, if the determination result in step 78 is YES and the time corresponding to the predetermined value TMDSST has elapsed after the start mode ends, the routine proceeds to step 79 where the air-fuel ratio state flag F_DSAFCND set in step 70 is “1”. It is determined whether or not.

  When the determination result is NO, as described above, after executing steps 83 to 85, the present process is terminated. On the other hand, if the determination result in step 79 is YES and the air-fuel ratio is in a state where the stratified combustion mode can be executed, it is determined in step 80 whether or not the fuel pressure flag F_DSPFCND set in step 71 is “1”. To do.

  When the determination result is NO, as described above, after executing steps 83 to 85, the present process is terminated. On the other hand, if the determination result in step 80 is YES and the high-pressure pump 4b is operating normally, the process proceeds to step 81 to determine whether or not the intake pipe icing flag F_ICEGRJUD is “1”. The intake pipe icing flag F_ICEGRJUD is set to “1” when there is a possibility that icing has occurred in the intake pipe 12 because the intake air temperature TA is extremely low, and is set to “0” otherwise. Is done.

  When the determination result in step 81 is YES and there is a possibility that icing has occurred in the intake pipe 12, as described above, after executing steps 83 to 85, the present process is terminated. On the other hand, if the decision result in the step 81 is NO, the process advances to a step 86 in FIG. 9 to determine whether or not the timer value TDSDLY of the stratification start permission delay timer is 0.

  When this determination result is YES, that is, when the determination result of steps 79 and 80 is YES and the determination result of step 81 is NO, the process proceeds to step 87 when a time corresponding to the predetermined value TMDDSLY has elapsed. Then, it is determined whether or not the stratified combustion zone flag F_DISCAREA set in step 73 is “1”.

  When the determination result is YES and the engine 3 and the vehicle are in the operation region where the stratified combustion mode can be executed, the process proceeds to step 88 to determine whether or not the delay flag F_TDSCND0 set in step 74 is “1”. To do. When the determination result is YES and the delay time determined according to the operating state of the engine 3 has elapsed, the process proceeds to step 89 to determine whether or not the limit execution flag F_TCYLLMT is “1”.

  If the determination result is YES and the required fuel injection amount TCYL in the combustion transition mode is subjected to limit processing, the process proceeds to step 90, and whether the value of the stratified combustion enable flag F_DISCCAN stored in the RAM 2b is “1”. Determine whether or not. When the determination result is YES and the stratified combustion mode can be executed in the previous main loop, the process proceeds to step 91 described later. On the other hand, if the determination result in step 89 is YES and the required fuel injection amount TCYL in the combustion transition mode is not subjected to limit processing, step 90 is skipped and the process proceeds to step 91.

  Next, in step 91 following step 89 or 90, the stratified combustion enable flag F_DISCCAN is set to “1” to indicate that the stratified combustion mode can be executed. Next, in step 92, the stratified combustion permission flag F_DISCOK is set to “1” in order to indicate that the engine 3 and the vehicle are in an operation state in which the stratified combustion mode is to be executed.

  On the other hand, when the determination result of any of steps 87, 88, 90 is NO, as described above, after executing steps 84, 85, the present process is terminated.

  As described above, in the setting process of the stratified combustion permission flag F_DISCOK, when the stratified combustion zone flag F_DISCAREA is “1”, that is, the engine 3 is in an operating state capable of executing the stratified combustion mode, and the throttle valve opening degree When both TH and engine speed NE are in a stable state, stratified combustion permission flag F_DISCOK is set to “1”. On the other hand, when the stratified combustion region flag F_DISCAREA is “0”, that is, when the throttle valve opening TH or the engine speed NE is unstable, the stratified combustion permission flag F_DISCOK is set to “0”. When the stratified combustion permission flag F_DISCOK = 0, execution of the stratified combustion mode is prohibited, and operation in the uniform combustion mode is selected.

  Next, the above-described fuel injection process will be described with reference to FIG. In this process, first, in step 140, a combustion transition mode flag F_DSCMOD setting process is executed.

  The combustion transition mode flag F_DSCMOD indicates whether or not the engine 3 is in an operating state in which the combustion transition mode described above should be executed. The value of the fuel cut flag F_FC described above and the stratified combustion permission flag F_DISCOK described above are displayed. Is set to “1” when the engine 3 is in the operating state in which the combustion transition mode should be executed, and is set to “0” otherwise. In particular, when the previous value and the current value of the stratified combustion permission flag F_DISCOK are equal, the combustion transition mode flag F_DSCMOD is set to “0”. That is, when the value of the stratified combustion permission flag F_DISCOK is unchanged, the combustion transition mode is not executed.

  Next, in step 141, a process for setting the double injection flag F_DBINJ is executed. This double injection flag F_DBINJ indicates whether or not the double injection in one combustion cycle should be executed, and the setting process is specifically executed as shown in FIG.

  That is, first, in step 150, it is determined whether or not the combustion transition mode flag F_DSCMOD set in step 140 is “1”. If the determination result is NO and the engine 3 is in an operating state where the combustion transition mode should not be executed, the routine proceeds to step 151 where it is determined whether or not the stratified combustion permission flag F_DISCOK is “1”.

  When the determination result is YES and the engine 3 and the vehicle are in the operation state in which the stratified combustion mode is to be executed, it is assumed that the fuel should be injected in the compression stroke. The stroke injection flag F_DIHC is set to “0”, and the compression stroke injection flag F_DISC is set to “1”.

  Next, the routine proceeds to step 154, where the double injection flag F_DBINJ is set to “0” to indicate that the double injection should not be executed, and then this processing is terminated.

  On the other hand, when the determination result in step 151 is NO and the engine 3 and the vehicle are in an operation state in which the uniform combustion mode is to be executed, it is assumed that fuel should be injected in the intake stroke. At 156, the intake stroke injection flag F_DIHC is set to “1”, and the compression stroke injection flag F_DISC is set to “0”. Next, as described above, after executing step 154, the present process is terminated.

  On the other hand, if the determination result in step 150 is YES and the engine 3 is in the operating state in which the combustion transition mode should be executed, the process proceeds to step 157 and the final fuel injection amount TOUT calculated in step 68 and the fuel for the compression stroke injection It is determined whether or not the deviation from the amount TIMDSC (TOUT−TIMDSC), that is, the fuel amount for the intake stroke injection is smaller than a predetermined injection possible lower limit value TOUTDIMIN.

  This injectable lower limit value TOUTDIMIN represents the minimum value of the amount of fuel that can be injected by the injector 4. Further, the fuel amount TIMDSC for compression stroke injection is calculated by searching a table (not shown) according to the engine speed NE.

  When the determination result in step 157 is NO, that is, when TOUT−TIMDSC ≧ TOUTDIMIN is satisfied, it is assumed that the two injections should be executed. In order to express this, in steps 163 to 165, the intake stroke injection flag F_DIHC, The compression stroke injection flag F_DISC and the double injection flag F_DBINJ are both set to “1”. Thereafter, this process is terminated.

  On the other hand, if the determination result in step 157 is YES and the amount of fuel to be injected in the intake stroke of the two injections cannot be injected, the routine proceeds to step 158, where it is determined whether or not the stratified combustion permission flag F_DISCOK is “1”. Determine.

  When this determination result is YES, that is, when the combustion mode before starting the combustion transition mode is the uniform combustion mode, it is determined in steps 159 and 160 that the fuel should be injected in the intake stroke, in order to express it. Then, the intake stroke injection flag F_DIHC is set to “1”, and the compression stroke injection flag F_DISC is set to “0”. Next, as described above, after executing step 154, the present process is terminated.

  On the other hand, when the determination result of step 158 is NO, that is, when the combustion mode before starting the combustion transition mode is the stratified combustion mode, it is assumed that the fuel should be injected in the compression stroke. 161 and 162, the intake stroke injection flag F_DIHC is set to “0”, and the compression stroke injection flag F_DISC is set to “1”. Next, as described above, after executing step 154, the present process is terminated.

  Returning to FIG. 13, in step 141, the process for setting the double injection flag F_DBINJ is executed as described above, and then the process proceeds to step 142, where the double injection flag F_DBINJ set in step 141 is “1”. Determine whether or not. When the determination result is YES and the two injections are to be executed, the process proceeds to step 143, and the two injection control is executed. That is, fuel for the intake stroke injection (TOUT-TIMDSC) is injected in the intake stroke, and fuel for the compression stroke injection TIMDSC is injected in the compression stroke. Thereafter, this process is terminated.

  On the other hand, when the determination result of step 142 is NO, the process proceeds to step 144 to determine whether or not the intake stroke injection flag F_DIHC is “1”. If the determination result is YES and fuel should be injected in the intake stroke, the routine proceeds to step 145, and intake stroke injection control is executed. That is, fuel corresponding to the final fuel injection amount TOUT is injected in the intake stroke. Thereafter, this process is terminated.

  On the other hand, when the determination result of step 144 is NO, the process proceeds to step 146 to determine whether or not the compression stroke injection flag F_DISC is “1”. When the determination result is YES and the fuel should be injected in the compression stroke, the process proceeds to step 147, and the compression stroke injection control is executed. That is, the fuel for the final fuel injection amount TOUT is injected in the compression stroke. Thereafter, this process is terminated.

  On the other hand, when the determination result of step 146 is NO and the fuel injection should not be executed, that is, when the fuel cut operation is performed, the present process is ended as it is. Thereby, fuel injection is stopped.

  As described above, according to the control device 1 of the present embodiment, in the setting process of the stratified combustion zone flag F_DISCAREA in FIG. = 1, that is, when the fluctuation amount of the engine speed NE or the throttle valve opening TH is large and in an unstable state, the stratified combustion zone flag F_DISCAREA is set to “0” (step 107), thereby The stratified combustion permission flag F_DISCOK is set to “0” (steps 85 and 87). Therefore, when the operation mode up to now is the uniform combustion mode, the stratified combustion permission flag F_DISCOK is held at “0”, thereby prohibiting the transition to the stratified combustion mode (steps 140 and 150). It continues (steps 151 and 155).

  Thus, during the execution of the uniform combustion mode, when the fluctuation amount of the engine speed NE or the throttle valve opening TH is large and in an unstable state, that is, the fluctuation state of the engine load is large, the combustion mode is stratified combustion. When switching to the mode, when it is estimated that the combustion state tends to become unstable, the combustion mode is maintained in the uniform combustion mode without being switched to the stratified combustion mode. As a result, it is possible to ensure a better combustion state than in the past, thereby avoiding torque fluctuations and improving drivability.

  In the setting process of the TH fluctuation flag F_DTHDS, the threshold value DTHDSOP1 (or DTHDSOP2) used when the throttle valve opening TH is changed to the valve opening side is changed so that the throttle valve opening TH is changed to the valve closing side. Is set to a value smaller than the threshold value DTHDSCL1 (or DTHDSCL2) used during the operation (DTHDSOP1 <DTHDSCL1, DTHDSOP2 <DTHDSCL2). Thus, when the throttle valve opening TH changes to the valve opening side and the engine load changes to the increase side, the throttle valve opening TH changes to the valve closing side and the engine load decreases. As compared with, since the execution region of the stratified combustion mode is set narrower and the execution region of the uniform combustion mode is set wider, a more stable combustion state can be ensured.

  Further, the threshold value DTHDSOP2 (or DTHDSCL2) used when the accelerator opening flag F_APOPEN = 0 is set to a value smaller than the threshold value DTHDSOP1 (or DTHDSCL1) used when F_APOPEN = 1. , DTHDSCL2 <DTHDSCL1). In addition, the second delay value TDTHDS2 used when F_APOPEN = 0 is set to a value larger than the first delay value TDTHDS used when F_APOPEN = 1. As described above, when it is estimated that the accelerator pedal is not operated and the engine is idling, stratification is performed until a stable driving state is achieved in which the fluctuation of the engine load is smaller than in the case of other driving. Since the transition to the combustion mode is prohibited and the uniform combustion mode is continued, a more stable combustion state can be ensured.

  Further, in the setting process of the NE fluctuation flag F_DNEDS, the threshold value DNEDSAC1 (or DNEDSAC2) used when the engine speed NE changes to the increase side is set when the engine speed NE changes to the decrease side. It is set to a value smaller than the threshold value DNEDSDC1 (or DNEDSDC2) to be used (DNEDSAC1 <DNEDSDC1, DNEDSAC2 <DNEDSDC2). Thus, when the engine speed NE changes to the increasing side and the engine load changes to the increasing side, the engine speed NE decreases and the stratified combustion mode is compared to when the engine load decreases. Is set to be narrower and the execution range of the uniform combustion mode is set to be wider, so that a more stable combustion state can be ensured.

  Further, the threshold value DNEDSAC2 (or DNEDSDC2) used when the shift position POSI is in the N range or P range, or when traveling at a low speed or when the vehicle is stopped, is used when the shift position POSI is outside the N or P range or during high speed traveling. It is set to a value smaller than the threshold DNEDSAC1 (or DNEDSDC1) used sometimes (DNEDSAC2 <DNEDSAC1, DNEDSDC2 <DNEDSDC1). In addition to this, the second delay value TDNEDS2 is set to a value larger than the first delay value TDNEDS. As described above, when it is estimated that the shift position POSI is in the N range or the P range, or is running at a low speed or is stopped, and the engine is idling, the engine load is compared with that in other driving. Since the shift to the stratified combustion mode is prohibited and the uniform combustion mode is continued until a stable operation state in which the fluctuation of the engine is smaller, a more stable combustion state can be ensured.

  The embodiment is an example in which the fluctuation amount of the engine speed NE and the throttle valve opening TH is used as the fluctuation amount of the load parameter. However, the fluctuation amount of the load parameter is not limited to this, and the load of the internal combustion engine 3 is not limited thereto. The amount of change in the load parameter that represents For example, a fluctuation amount of the accelerator opening AP may be used. Further, as a mechanism for controlling the intake air amount, a valve operating mechanism for driving the intake valve 8 and the exhaust valve 9 of the engine 3 continuously controls the lift and open / close timing of both valves 8 and 9 according to the control signal from the ECU 2. When it is configured so as to be freely changed, the fluctuation amount of the control signal value from the ECU 2 to the valve operating mechanism may be used as the fluctuation amount of the load parameter.

Explanation of symbols

1 Control device
2 ECU (load parameter detection means, combustion mode switching means, determination means, switching prohibition means)
3 Internal combustion engine
13a Throttle valve
22 Crank angle sensor (load parameter detection means)
25 Throttle valve opening sensor (load parameter detection means)
NE Engine speed (load parameter)
| DNEDS | Absolute value of rotational deviation (variation in engine speed)
DNEDSDC1 First decreasing threshold (predetermined value)
DNEDSDC2 Second decreasing threshold (predetermined value)
DNEDSAC1 first increase side threshold value (predetermined value)
DNEDSAC2 second increase side threshold value (predetermined value)
TH Opening of throttle valve (load parameter)
| DTHDS | Absolute value of the deviation of the opening (variation of the opening of the throttle valve)
DTHDSCL1 First valve closing threshold (predetermined value)
DTHDSCL2 Second valve closing threshold (predetermined value)
DTHDSOP1 First valve opening side threshold value (predetermined value)
DTHDSOP2 Second valve opening threshold (predetermined value)

Claims (3)

A control device for an in-cylinder injection internal combustion engine operated by switching a combustion mode between a uniform combustion mode for uniformly burning an air-fuel mixture and a stratified combustion mode for stratified combustion,
Load parameter detecting means for detecting a load parameter representing the load of the internal combustion engine;
Combustion mode switching means for performing switching of the combustion mode according to the detected load parameter;
Determining means for determining whether or not the load parameter is in a predetermined fluctuation state;
When the combustion mode is the uniform combustion mode and the determination means determines that the load parameter is in the predetermined fluctuation state, the combustion mode switching means prohibits switching to the stratified combustion mode. Switching prohibition means to
A control device for an internal combustion engine, comprising: The load parameter is an engine speed of the internal combustion engine,
2. The control device for an internal combustion engine according to claim 1, wherein the determination unit determines that the engine is in the predetermined fluctuation state when a fluctuation amount of the engine speed is equal to or greater than a predetermined value. The load parameter is an opening of a throttle valve of the internal combustion engine,
3. The control device for an internal combustion engine according to claim 1, wherein the determination unit determines that the predetermined fluctuation state exists when a variation amount of the opening degree of the throttle valve is equal to or greater than a predetermined value. .

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