JP4024667B2 - Control device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control apparatus for an in-cylinder internal combustion engine that operates by switching a combustion mode between a stratified combustion mode and a uniform combustion mode and controls a fuel injection amount based on a calculated required fuel amount.
[0002]
[Prior art]
Conventionally, what was disclosed by patent document 1, for example is known as this kind of control apparatus. In this control apparatus, when the combustion mode of the internal combustion engine mounted on the vehicle is switched from the stratified combustion mode to the uniform combustion mode, stratified combustion is continuously performed for some of the plurality of cylinders. Then, the fuel injection amount of some of the cylinders is calculated as follows. That is, the ratio between the previous final fuel injection amount, the current value of the torque correction amount set based on the rotational speed of the internal combustion engine and the previous value, and the ratio between the current value of the basic fuel injection amount and the previous value. And a value obtained by multiplying the two and the other are calculated as the final fuel injection amount. More specifically, the torque correction amount is set as a value that is increased or decreased by a fixed amount according to the increase or decrease between the previous value and the current value of the rotational speed of the internal combustion engine. The basic fuel injection amount is set as a weighted average value of the previous value and the current fuel injection amount calculated based on the intake air amount and the rotational speed of the internal combustion engine. By calculating the fuel injection amount as described above, the fuel injection amount is controlled and the calculation load of the control device is reduced while reflecting changes in the rotational speed of the internal combustion engine and the intake air amount. .
[0003]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 11-50895 (page 5, column 1 to page 8, column 2 and FIGS. 3 to 12)
[0004]
[Problems to be solved by the invention]
However, the conventional control device described above has the following problems. That is, in the fuel injection amount calculation method described above, when the combustion mode is switched, the previous fuel injection amount is used as a base, the ratio between the previous value and the current value of the torque correction amount, and the previous value of the basic fuel injection amount. A value obtained by multiplying the ratio between the current value and the current value is calculated as the fuel injection amount. As described above, since the torque correction amount is only a value that is increased or decreased by a certain amount in accordance with the increase or decrease in the rotational speed of the internal combustion engine, the ratio between the previous value and the current value is the value of the rotational speed of the internal combustion engine. Does not correctly reflect changes in internal combustion engine torque due to changes. The basic fuel injection amount is a weighted average of the previous value and the current value of the basic fuel injection amount set according to the intake air amount and the rotational speed of the internal combustion engine, that is, a smoothed value. Therefore, the ratio between the previous value and the current value also does not correctly reflect the change in torque based on the intake air amount and the rotational speed of the internal combustion engine. Therefore, the output torque of the internal combustion engine obtained by the fuel injection amount calculated based on these parameters does not coincide with the required torque, and as a result, drivability (driability) is reduced.
[0005]
The present invention has been made to solve such a problem, and when the combustion mode is switched, the output torque of the internal combustion engine can be made to coincide well with the required torque, thereby improving drivability. An object of the present invention is to provide a control device for an internal combustion engine.
[0006]
[Means for Solving the Problems]
In order to achieve this object, the invention according to claim 1 is operated by switching the combustion mode between the stratified combustion mode in which the air-fuel mixture is stratified combustion and the uniform combustion mode in which uniform combustion is performed, and the calculated required fuel amount (implementation). A control device 1 for a direct injection internal combustion engine 3 that controls a fuel injection amount on the basis of a required fuel injection time TCYLBS in the embodiment (hereinafter the same in this section), and detects an operating state of the internal combustion engine 3 Required fuel amount calculation for calculating the required fuel amount according to the operating state detecting means (ECU 2, crank angle sensor 22, intake pipe absolute pressure sensor 23, accelerator opening sensor 27) and the detected operating state of the internal combustion engine 3. The request torque for calculating the required torque PMCMDREG of the internal combustion engine 3 in accordance with the means (ECU 2, step 6 in FIG. 3) and the detected operating state of the internal combustion engine 3. Combustion mode determining means (ECU2, FIG. 3) and combustion mode determining means (ECU2, FIG. 2) for determining the combustion mode as one of the stratified combustion mode and the uniform combustion mode according to the calculated required torque PMCMDREG. ) And a storage means (ECU2, FIG. 6) for storing the required fuel amount (requested fuel injection time TCYLLTIN immediately before switching) and the required torque (requested torque PMTCYLIN immediately before switching) calculated immediately before the combustion mode is switched by the combustion mode determining means. Steps 39 and 41), a counter (ECU 2, step 56 in FIG. 7, step 59 in FIG. 8) for measuring the elapsed time from the switching of the combustion mode, and supply for the amount of fuel supplied to the internal combustion engine 3 Combustion efficiency (combustion efficiency parameter) representing the ratio of the output of the internal combustion engine 3 generated by the combustion of the generated fuel KLMTCYH, KLMTCYSD, the KLMTCYLD), combustion efficiency estimation means for estimating, depending on the timed elapsed time from the time of switching the combustion mode (after switching elapsed time N_TCYLLT) (ECU2, step 74B of FIG. 9, 74C, 79, FIG. 10, step 95 of FIG. 12, FIG. 14, step 100 in FIG. 13, step 102 and 103 in FIG. 12, step 108 in FIG. 13, step 120 of FIG. 16, FIG. 17, step 130 of FIG. 18, FIG. 19) and When the combustion mode is switched, the stored required fuel amount and required torque, the calculated current required torque PMCMDREG, and the estimated current combustion efficiency are used as the required fuel amount at the time of switching. Required fuel amount calculation means (ECU2, FIG. 2) at the time of switching for calculating (limit value TCYLLT) Step 80 and 82, characterized in that it comprises steps 109 and 111 in FIG. 13, step 121, 123 in FIG. 16, step 131, 133 in FIG. 18, Step 8) in FIG. 3, a.
[0007]
In this internal combustion engine control device, the required torque is calculated according to the operating state of the internal combustion engine, the combustion mode is determined to be the stratified combustion mode or the uniform combustion mode according to the required torque, and the required fuel amount in each combustion mode Is calculated according to the operating state of the internal combustion engine, and the fuel injection amount is controlled based on the calculated required fuel amount. Further, when the combustion mode is switched, the required fuel amount at switching is calculated as the required fuel amount. This is due to the following reason. That is, in general, in the stratified combustion mode, the intake air amount is very large and combustion is performed at an extremely lean air-fuel ratio, while in the uniform combustion mode, the intake air amount is smaller than that in the stratified combustion mode and a richer air-fuel ratio. Combustion takes place. For this reason, when the combustion mode is switched, the intake air amount does not change immediately, but with a response delay, it takes time to converge to a value suitable for the switched combustion mode. In such a situation, when the required fuel amount is calculated according to the operation state such as the intake air amount when switching the combustion mode, the required fuel amount fluctuates rapidly, and as a result, the output torque of the internal combustion engine This is because it becomes difficult to match the required torque. Further, according to the present invention, the required fuel amount at the time of switching is calculated according to the required fuel amount and required torque calculated immediately before this switching, the current required torque, and the current combustion efficiency. Thus, since the required fuel amount at the time of switching is calculated according to the current required torque, it is possible to set the value as a good reflection of the actual required torque at that time without abrupt fluctuations. it can. Further, since the required fuel amount at the time of switching is calculated based on the required fuel amount and the required torque immediately before the switching, it is possible to smoothly shift the combustion mode without causing a sharp step in the torque before and after the switching. it can. Further, in the stratified combustion mode and the uniform combustion mode, the combustion efficiency changes so as to be different from each other with respect to the torque, whereas according to the above-described configuration, the required fuel amount at the time of switching is calculated according to the current combustion efficiency. Therefore, this can be set to an appropriate value according to the actual combustion efficiency at that time. As described above, at the time of switching the combustion mode, the output torque of the internal combustion engine can be made to agree well with the required torque, thereby improving drivability.
Furthermore, the elapsed time from the switching of the combustion mode is measured by the counter, and the combustion efficiency is estimated according to the elapsed time.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a schematic configuration of an internal combustion engine control device 1 of the present invention and an internal combustion engine (hereinafter referred to as “engine”) 3 to which the control device 1 is applied. In addition, the control device 1 includes an ECU 2.
[0009]
The engine 3 is an in-line four-cylinder (only one cylinder is shown) type gasoline engine for vehicles (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. The cylinder head 3b is provided with an intake pipe 4 and an exhaust pipe 5, respectively, and a fuel injection valve (hereinafter referred to as "injector") 6 and a spark plug 7 are attached so as to face the combustion chamber 3c. . That is, the engine 3 is of a direct injection type in which fuel is directly injected into the combustion chamber 3c by the injector 6.
[0010]
The injector 6 is disposed at the center of the top wall of the combustion chamber 3c, and is connected to the fuel pump 6b via the fuel pipe 6a. The fuel is boosted to a high pressure by a fuel pump 6b from a fuel tank (not shown), and then supplied to the injector 6 in a state of being regulated by a regulator (not shown). The fuel is injected from the injector 6 toward the concave portion 3d side of the piston 3a, and collides with the upper surface of the piston 3a including the concave portion 3d to form a fuel jet. In particular, during stratified combustion, which will be described later, most of the fuel injected from the injector 6 collides with the recess 3d to form a fuel jet.
[0011]
A brake booster 9 is connected to the intake pipe 4 via a branch pipe 8, and the brake booster 9 is constituted by a circular rubber diaphragm or the like. The brake booster 9 is supplied with a negative pressure generated by closing a throttle valve 10 provided in the intake pipe 4. The brake pedal operated by the driver is supplied by the negative pressure in the supplied brake booster 9. 11 pedal depression force is amplified. The branch pipe 8 is provided with a negative pressure sensor 21, which detects the negative pressure in the brake booster 9 and outputs a detection signal to the ECU 2.
[0012]
An electric motor 10a is connected to the throttle valve 10, and the electric motor 10a is connected to the ECU 2. The ECU 2 controls the intake air amount of the engine 3 by controlling the opening degree of the throttle valve 10 via the electric motor 10 a according to the operating state of the engine 3.
[0013]
The crankshaft 3e of the engine 3 is provided with a crank angle sensor 22 (operating state detection means). The crank angle sensor 22 includes a magnet rotor 22a and an MRE pickup 22b. The crank angle sensor 22 outputs a CRK signal and a TDC signal, which are pulse signals, as the crankshaft 3e rotates.
[0014]
The CRK signal is output every predetermined crank angle (for example, 30 °). The ECU 2 obtains the rotational speed NE (hereinafter referred to as “engine rotational 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 °. Is output. The engine 3 is provided with a cylinder discrimination sensor (not shown), and this cylinder discrimination sensor sends a cylinder discrimination signal, which is a pulse signal for discriminating the cylinder, to the ECU 2. The ECU 2 determines the crank angle position for each cylinder based on the cylinder determination signal, the CRK signal, and the TDC signal.
[0015]
On the other hand, an intake pipe absolute pressure sensor 23 (operating state detection means) is disposed downstream of the throttle valve 10 in the intake pipe 4. The intake pipe absolute pressure sensor 23 detects an intake pipe absolute pressure PBA, which is an absolute pressure in the intake pipe 4, and sends a detection signal to the ECU 2.
[0016]
Further, an EGR pipe 12 is connected between the intake pipe 4 downstream of the throttle valve 10 and the exhaust pipe 5 upstream of the catalyst device (not shown). The EGR pipe 12 recirculates the exhaust gas of the engine 3 to the intake side, and executes an EGR operation for reducing NOx in the exhaust gas by lowering the combustion temperature in the combustion chamber 3c.
[0017]
An EGR control valve 13 is attached to the EGR pipe 12. The EGR control valve 13 is connected to a rotor of a stepping motor (not shown) via a spring (not shown), and the operation of this stepping motor is controlled by a drive signal from the ECU 2 to thereby perform EGR control. The EGR pipe 12 is opened and closed by changing the valve lift amount LACT of the valve 13. The valve lift amount LACT is detected by the valve lift amount sensor 24, and the detection signal is sent to the ECU 2.
[0018]
The ECU 2 calculates the target valve lift amount LCMD of the EGR control valve 13 according to the operating state of the engine 3 and controls the EGR control valve 13 so that the actual valve lift amount LACT becomes the target valve lift amount LCMD. , Controlling the EGR rate.
[0019]
A LAF sensor 25 is disposed upstream of the catalyst device in the exhaust pipe 5. The LAF sensor 25 linearly detects the oxygen concentration in the exhaust gas in a wide range of air-fuel ratio A / F from the rich region richer than the theoretical air-fuel ratio to the extremely lean region, and outputs proportional to the oxygen concentration. Send KACT to ECU2.
[0020]
A detection signal indicating the temperature (hereinafter referred to as “engine water temperature”) TW of the cooling water circulating in the main body of the engine 3 is sent from the water temperature sensor 26 to the ECU 2 from the accelerator opening sensor 27 (operating state detection means). Detection signals representing the opening (hereinafter referred to as “accelerator opening”) AP of a pedal (not shown) are output.
[0021]
The ECU 2 is composed of a microcomputer including an I / O interface, CPU, RAM, ROM, and the like. The detection signals from the various sensors 21 to 27 described above are A / D converted by the I / O interface and then input to the CPU. In accordance with these detection signals, the CPU executes a fuel cut (hereinafter referred to as “F / C”) of the engine 3 according to a control program stored in the ROM and calculates the required torque PMCMDREG as described later. Further, the CPU determines the combustion mode of the engine 3 according to the required torque PMCMDREG, and controls the fuel injection time of the injector 6 and the ignition timing of the spark plug 7 according to the determined combustion mode. This fuel injection time is controlled based on a required fuel injection time TCYLBS (required fuel amount) calculated as described later. In the present embodiment, the ECU 2 constitutes an operating state detecting means, a required fuel amount calculating means, a required torque calculating means, a combustion mode determining means, a storage means, a counter, a combustion efficiency estimating means, and a switching required fuel amount calculating means. Has been.
[0022]
The combustion mode is determined and switched to the stratified combustion mode at the time of extremely low load operation such as idle operation and to the uniform combustion mode at the time of operation other than the extremely low load operation. In addition, the double injection mode is executed when the combustion mode is shifted.
[0023]
In the stratified combustion mode, fuel is injected from the injector 6 into the combustion chamber 3c during the compression stroke, and most of the injected fuel collides with the recess 3d to form a fuel jet. An air-fuel mixture is generated by the fuel jet and the flow of the inflow air from the intake pipe 4, and the piston 3a is located near the top dead center of the compression stroke. Stratified combustion is performed while being unevenly distributed in the vicinity. In addition, the air-fuel ratio A / F in the stratified combustion mode is controlled to a value (for example, 27 to 60) that is extremely leaner than the stoichiometric air-fuel ratio by controlling the throttle valve 10 to be in a fully open state.
[0024]
In the uniform combustion mode, the 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. . Further, the air-fuel ratio A / F in the uniform combustion mode is controlled to a richer value (for example, 12 to 22) than in the stratified combustion mode by controlling the throttle valve 10 to an opening smaller than that in the stratified combustion mode. . Further, the target valve lift amount LCMD in the uniform combustion mode is set to a value smaller than that in the stratified combustion mode.
[0025]
Further, in the double injection mode, fuel is injected twice at intervals in one cycle, and combustion is performed at a richer air-fuel ratio A / F (for example, 12 to 22) than in the stratified combustion mode. The two fuel injections in this case are executed once each during the intake stroke and the compression stroke. The two-time injection mode is executed for the following reason. That is, between the stratified combustion mode and the uniform combustion mode, the target values of the intake air amount and the EGR rate are greatly different as described above, and when the combustion mode is switched, the actual intake air amount and the EGR rate are changed after the switching. This is because it takes time to converge to a value suitable for the mode, and during that time, fuel injection is divided into two to prevent misfire and to suppress the torque step.
[0026]
The determination of the combustion mode is performed based on the map shown in FIG. 2, and the value of the combustion mode monitor ST_EMOD indicating the combustion mode is set accordingly. More specifically, in the map, in the stratified combustion region where both the required torque PMCMDREG and the engine speed NE are low, the stratified combustion mode is determined, and the combustion mode monitor ST_EMOD is set to “2”. In the lean combustion region in the uniform combustion region where the required torque PMCMDREG and the engine speed NE are higher than those in the stratified combustion region, the lean combustion mode is determined, and the combustion mode monitor ST_EMOD is set to “1”. Further, in the stoichiometric combustion region in the uniform combustion region where the required torque PMCMDREG and the engine speed NE are higher than the lean combustion region, the stoichiometric combustion mode is determined, and the combustion mode monitor ST_EMOD is set to “0”. The stoichiometric combustion region in this map includes a rich combustion region in which the air-fuel mixture is burned at an air-fuel ratio A / F that is richer than the stoichiometric air-fuel ratio in addition to a region in which the air-fuel mixture is burned mainly at the stoichiometric air-fuel ratio. In the following, this is called stoichiometric combustion including rich combustion.
[0027]
Hereinafter, the process for calculating the required fuel injection time TCYLBS will be described with reference to the flowchart of FIG. This process is interrupted in synchronization with the input of the TDC signal. First, in step 1, the required torque PMCMDREG is calculated by searching a map (not shown) according to the engine speed NE and the accelerator pedal opening AP.
[0028]
Next, the required fuel injection time TCYLBS at that time is set as the previous value TCYLBS1 (step 2), and the target air-fuel ratio KCMD is calculated (step 3). This target air-fuel ratio KCMD is calculated as a value obtained by multiplying the basic target air-fuel ratio KBS by the water temperature correction coefficient KTW. The basic target air-fuel ratio KBS is based on the engine speed NE and the required torque PMCMDREG, and the water temperature correction coefficient KTW is searched on the respective maps (not shown) based on the engine water temperature TW and the intake pipe absolute pressure PBA. Each is required.
[0029]
Next, it is determined whether or not the start mode flag F_STMOD is “1” (step 4). If the answer is YES and the engine 3 is starting, the required fuel injection time TCYLBS is set to a value obtained by multiplying the basic fuel injection time TIM by the target air-fuel ratio KCMD calculated in step 3 (step 5). End this program. The basic fuel injection time TIM is obtained by searching a map (not shown) based on the engine speed NE and the intake pipe absolute pressure PBA.
[0030]
When the answer to step 4 is NO and the engine 3 has been started, the normal-time required fuel injection is performed using the target air-fuel ratio KCMD and the basic fuel injection time TIM calculated in steps 3 and 5, respectively. Time TCYLTMP is calculated by the following equation (1) (step 6).
TCYLTMP = TIM, KCMD, KEGR, KAF, KAST, KLS (1)
Here, KEGR is an EGR correction coefficient for compensating a change in the intake air amount due to a change in the EGR rate, and is set according to the target valve lift amount LCMD, the actual valve lift amount LACT, and the intake pipe absolute pressure PBA. The KAF is a feedback correction coefficient for feedback control of the air-fuel ratio of the air-fuel mixture so that the output KACT of the LAF sensor 25 converges to the target air-fuel ratio KCMD, and is estimated from the output KACT of the LAF sensor 25 by the observer. It is set according to the actual air-fuel ratio for each cylinder and the target air-fuel ratio KCMD. Further, KAST is a start time correction coefficient for performing fuel injection amount increase correction when the engine 3 is started. KLS is a leaning correction coefficient for deceleration for suppressing the richness of the air-fuel ratio during deceleration.
[0031]
Next, a switching limit process is executed (step 7). In the switching limit process, the switching required fuel injection time TCYLLMT is calculated as described later. Next, the calculated required fuel injection time TCYLLMT at the time of switching is set as the required fuel injection time TCYLBS (step 8), the current required torque PMCMDREG is set as its previous value PMCMDREG1 (step 9), and this program is terminated. To do.
[0032]
FIG. 4 is a flowchart showing a subroutine of limit processing at the time of switching executed in step 7 of FIG. In this process, the limit value TCYLLT (required fuel amount at switching) for limiting the normal time required fuel injection time TCYLTMP set as described above is calculated for each combustion mode switching pattern. That is, as described above, the intake air amount and the EGR rate to be set differ greatly between the stratified combustion mode and the uniform combustion mode, and there is a response delay between them, so that the intake pipe absolute pressure PBA depends on the difference. The normal-time required fuel injection time TCYLTMP increases at the time of switching from the stratified combustion mode to the uniform combustion mode, and tends to decrease at the time of the reverse switching. In order to limit the fuel injection time TCYLTMP, a limit value TCYLLT is calculated. For this reason, the limit value TCYLLT is set so as to limit the normal-time required fuel injection time TCYLTMP to the decreasing side when switching to the uniform combustion mode and to the increasing side when switching to the opposite stratified combustion mode.
[0033]
First, in steps 10 and 11, it is determined whether or not the previous value F_FCZ of the F / C execution flag is “1” and whether or not the current value F_FC is “0”. The F / C execution flag F_FC is set to “1” when the F / C is being executed.
[0034]
If both of these answers are YES and the current loop is immediately after the end of F / C, the value CTCYL of the delay counter is set to a predetermined value #CTCYLD (for example, 28 TDC) (step 12), and step 13 to be described later. Proceed to
[0035]
On the other hand, if any of the answers to Steps 10 and 11 is NO and the current loop is not immediately after the end of F / C, it is determined whether or not the value CTCYL of the delay counter is 0 (Step 14). When the answer is NO, the value CTCYL of the delay counter is decremented (step 15), and then the process proceeds to step 13. If the answer to step 14 is YES, the process proceeds to step 13 as it is.
[0036]
In step 13, it is determined whether or not the delay counter value CTCYL is zero. If the answer is NO, that is, if the time corresponding to the predetermined value #CTCYLD has not elapsed since the end of F / C, the calculation of the limit value TCYLLT is prohibited, and the normal time required fuel injection time TCYLTMP is requested at the time of switching. The fuel injection time TCYLLMT is set (step 16), and this program ends. As described above, the calculation of the limit value TCYLLT is prohibited for the following reason. That is, the limit value TCYLLT, as will be described later, is obtained by calculating the previous required fuel injection time TCYLBS1, the combustion efficiency parameter KLMTCYH, KLMTCYSD or KLMTCYLD (combustion efficiency), and the ratio between the current value PMCMDREG and the previous value PMCMDREG1 of the required torque. Since the values are set to be multiplied by each other, the value is calculated as 0 at the end of the F / C in which the previous required fuel injection time TCYLBS1 is 0 and thereafter, and cannot be set appropriately. is there.
[0037]
On the other hand, if the answer to step 13 is YES and CTCYL = 0, that is, if the time corresponding to the predetermined value #CTCYLD has elapsed since the end of the F / C, a parameter for calculating the limit value TCYLLT is set. The limit value calculation parameter setting process is executed (step 17), the limit value calculation process is executed (step 18), and the program is terminated.
[0038]
5 and 6 are flowcharts showing a subroutine of limit value calculation parameter setting processing executed in step 17 of FIG. First, in steps 20 and 21, it is determined whether or not the previous value ST_EMOD1 of the above-described combustion mode monitor ST_EMOD is “2” and whether or not the current combustion mode monitor ST_EMOD is “0”. If both of these answers are YES and the current loop is immediately after the combustion mode is switched from the stratified combustion mode to the stoichiometric combustion mode, the switching status EMOD_STS is set to “1” (step 22).
[0039]
Next, in steps 23 and 24, it is determined whether or not the negative pressure request flag F_PBM is “1” and whether or not the accelerator pedal fully closed flag F_APIDLE is “0”. The negative pressure request flag F_PBM is set to “1” because there is a negative pressure request when it is determined that sufficient negative pressure is not secured in the brake booster 9 and this negative pressure should be increased. Is. Further, when the negative pressure request flag F_PBM is set to “1”, the combustion mode is prohibited from being set to the stratified combustion mode or the lean combustion mode, and is forcedly set to the stoichiometric combustion mode. Further, the accelerator pedal fully closed flag F_APIDLE is set to “0” when the accelerator pedal is fully closed, that is, not depressed.
[0040]
When both of the answers to Steps 23 and 24 are NO, that is, when there is no negative pressure request and the accelerator pedal is depressed, the limit time NTCYL is set to the first predetermined time (number of times) #NTCYLDSS (for example, equivalent to 500 msec). On the other hand, if any of these answers is YES, the limit time NTCYL is set to a second predetermined time #NTCYLDS (e.g., equivalent to 1000 msec) (step 26). This limit time NTCYL is defined as a count execution time of a limit time counter TCYLT10MS (described later) that counts the limit execution period based on the limit value TCYLLT for each combustion mode switching pattern. The limit value TCYLLT is calculated. The second predetermined time #NTCYLDS is set longer than the first predetermined time #NTCYLDSS for the following reason. That is, when there is a negative pressure request, the volume of the brake booster 9 increases by a volume corresponding to the negative pressure, so that it takes time for the intake pipe absolute pressure PBA to stabilize. This is to extend the execution period of the limit. In the case of an extremely low load operation state where the accelerator pedal is not depressed, the actual intake air amount after the switching becomes a value suitable after the switching because the switching is performed in a state where the required torque PMCMDREG is not increasing. This takes time to extend the limit execution period.
[0041]
On the other hand, when any of the answers to Steps 20 and 21 is NO, in Steps 27 and 28, whether or not the previous value ST_EMOD1 of the combustion mode monitor is “2” and the current combustion mode monitor ST_EMOD is “1”. Or not. If both of these answers are YES and the combustion mode is immediately after switching from the stratified combustion mode to the lean combustion mode, the switching status EMOD_STS is set to “2” (step 29), and the limit time NTCYL is set to the third time. It is set to a predetermined time #NTCYLDL (for example, equivalent to 400 msec) (step 30).
[0042]
When either of the answers to Steps 27 and 28 is NO, in Steps 31 and 32, whether or not the previous value ST_EMOD1 of the combustion mode monitor is “0” and the current combustion mode monitor ST_EMOD is “2”. Respectively. If both of these answers are YES and the combustion mode is immediately after switching from the stoichiometric combustion mode to the stratified combustion mode, the switching status EMOD_STS is set to “3” (step 33), and the limit time NTCYL is set to the fourth time. It is set to a predetermined time #NTCYLSD (e.g., equivalent to 600 msec) (step 34).
[0043]
When any of the answers to Steps 31 and 32 is NO, in Steps 35 and 36, whether or not the previous value ST_EMOD1 of the combustion mode monitor is “1”, and the current combustion mode monitor ST_EMOD is “2”. Respectively. If both of these answers are YES and the combustion mode is immediately after switching from the lean combustion mode to the stratified combustion mode, the switching status EMOD_STS is set to “4” (step 37), and the limit time NTCYL is set to the fifth time. It is set to a predetermined time #NTCYLLD (for example, equivalent to 600 msec) (step 38). The first predetermined time #NTCYLDSS and the third to fifth predetermined times #NTCYLDL, #NTCYLSD and #NTCYLLD are equal to those in the stratified combustion mode as described above with the target valve lift amount LCMD of the EGR control valve 13 as described above. Considering the fact that the value is greatly different between the combustion modes and the responsiveness of the EGR control valve 13, it is necessary to ensure that the actual valve lift amount LACT reaches a value suitable for the combustion mode after switching. Each time is set. In the above example, the fourth and fifth predetermined times #NTCYLSD and #NTCYLLD when the combustion mode is switched to the stratified combustion mode are the first and third predetermined times # used when switching the stratified combustion mode. The time is set longer than NTCYLDSS and #NTCYLDL. This is because when the EGR control valve 13 is closed, a reaction force to the closing side by the spring further acts on the valve body of the EGR control valve 13 in addition to the driving force to the closing side by the stepping motor. This is because the time required for closing the valve body is shorter than the valve opening time. As described above, during the response delay of the EGR control valve 13 at the time of switching the combustion mode, the limit based on the limit value TCYLLT can be reliably executed.
[0044]
In step 39 following step 25, 26, 30, 34 or 38, the previous value TCYLBS1 of the required fuel injection time is set as the required fuel injection time TCYLLTIN immediately before switching (the required fuel amount calculated immediately before the combustion mode is switched). To do. Next, it is determined whether or not the previous value PMCMDREG1 of the requested torque PMCMDREG is smaller than a predetermined upper limit value #PMTCCYLMIN (for example, 1.2 kgf / cm ² ) (step 40).
[0045]
When the answer is YES, the previous value PMCMDREG1 of the requested torque is set as the requested torque PMTCYLIN immediately before switching (the requested torque calculated immediately before the combustion mode is switched) (step 41), and one of the four switching patterns Immediately after switching of the combustion mode by, the parameter setting completion flag F_TCYLIN is set to “1” to indicate that the parameter setting for calculating the limit value TCYLLT has been completed (step 42). Exit the program. When the answer to step 40 is NO and PMCMDREG1 ≧ # PMTCCYLMIN, the predetermined upper limit value #PMTCCYLMIN is set as the torque immediately before switching PMTCYLIN (step 43), and the above step 42 is executed and the program is terminated. .
[0046]
On the other hand, if any of the answers to Steps 35 and 36 is NO and it is not immediately after switching of any of the combustion modes according to the four switching patterns, the parameter setting completion flag F_TCYLIN is set to “0” (Step 44), It is determined whether or not the limit permission flag F_TCYLLT is “0” (step 45). If the answer is NO and the limit value TCYLLT is being executed, the program is terminated. If the answer is YES, the switching status EMOD_STS is reset to “0” (step 46), and the program is executed. finish.
[0047]
7 and 8 are flowcharts showing a subroutine of limit value calculation processing executed in step 18 of FIG. First, in steps 50 and 51, it is determined whether or not the required torque PMCMDREG and its previous value PMCMDREG1 are larger than 0. If any of these answers is NO, torque is not required for the engine 3, and therefore the limit permission flag F_TCYLLT is set to “0” on the assumption that the calculation of the limit value TCYLLT is not performed (step 52). The required fuel injection time TCYLTMP during normal time is set as the required fuel injection time TCYLLMT during switching (step 53), and this program ends.
[0048]
On the other hand, when both of the answers to Steps 50 and 51 are YES, it is determined whether or not the parameter setting completion flag F_TCYLIN described above is “1” (Step 54). When the answer is YES, that is, when the current loop is immediately after the switching of the combustion mode by any of the four switching patterns, the limit permission flag F_TCYLLT is set to “1” (step 55) and the up-count type The limit time counter value TCYLT10MS is set to 0 (step 56), and the process proceeds to step 57. This limit time counter TCYLT10MS is incremented every predetermined time (for example, 10 msec). Instead of such a time timer, a counter that is incremented every time the TDC signal is output may be used.
[0049]
On the other hand, if the answer to step 54 is NO and the current loop is not immediately after switching of the combustion mode, the above steps 55 and 56 are skipped and the process proceeds to step 57.
[0050]
In this step 57, it is determined whether or not the limit permission flag F_TCYLLT is “1”. When the answer is YES, it is determined whether or not the limit time counter value TCYLT10MS is smaller than the limit time NTCYL set in the step 25, 26, 30, 34 or 38 (step 58).
[0051]
If the answer is YES and the time corresponding to the limit time NTCYL has not elapsed after switching of the combustion mode, the limit time counter value TCYLT10MS at that time is set as the post-switching elapsed time N_TCYLLT (step 59). Next, at step 60, it is determined whether or not the switching status EMOD_STS is “1”. If the answer is YES and the current combustion mode switching is from the stratified combustion mode to the stoichiometric combustion mode, a limit value TCYLLT for switching from the stratified to stoichiometric combustion mode is calculated (step 61). Similarly, in steps 62 and 63, it is determined whether or not the switching status EMOD_STS is “2” and “3”, respectively, and when the answer of step 62 is YES, the answer of step 63 is YES, and NO, respectively. Then, limit values TCYLLT for switching from stratified to lean combustion mode, stoichiometric to stratified combustion mode, and lean to stratified combustion mode are calculated (steps 64 to 66), and the program is terminated.
[0052]
On the other hand, if the answer to step 58 is NO and the time corresponding to the limit time NTCYL has elapsed after switching to the combustion mode, it is determined that the limit execution period based on the limit value TCYLLT has ended, and the steps after step 52 are executed. The permission flag F_TCYLLT is set to “0”, the normal time required fuel injection time TCYLTMP is set as the required fuel injection time TCYLLMT at the time of switching, and this program ends.
[0053]
In addition, after the execution period of the limit by the limit value TCYLLT is completed in this way, the answer to the step 57 becomes NO by the execution of the step 52. In this case, the step 52 and the subsequent steps are executed. Exit this program.
[0054]
FIG. 9 is a flowchart showing a subroutine of a calculation process of limit value TCYLLT for switching from the stratified to stoichiometric combustion mode executed in step 61 of FIG. First, in step 70, it is determined whether or not the required torque PMCMDREG is larger than a predetermined upper limit torque #PMTCCYLLG. If the answer is YES and the required torque PMCMDREG is very large, the required torque region outside flag F_TCYH is set to “1” (step 71), and the combustion efficiency parameter KLMTCYH is set to a predetermined value #CALIB (step 72). The predetermined value #CALIB is set to a value larger than the combustion efficiency parameter KLMTCYH when calculated as described later.
[0055]
On the other hand, when the answer to step 70 is NO and the required torque PMCMDREG ≦ the upper limit torque #PMTCYLLG, it is determined whether or not the required torque region outside flag F_TCYH is “1” (step 73). When this answer is YES, the step 72 is executed. Thus, even if the required torque PMCMDREG once becomes larger than the upper limit torque #PMTCCYLLG and then becomes smaller than the upper limit torque #PMTCCYLLG, the combustion efficiency parameter KLMTCYH is set to the predetermined value #CALIB as long as the combustion mode is not switched. Maintained.
[0056]
If the answer to step 73 is NO and the required torque PMCMDREG has never exceeded the upper limit torque #PMTCCYLLG since the switching of the combustion mode, whether or not the negative pressure request flag F_PBM is “1” in steps 74 and 74A And whether the accelerator pedal fully closed flag F_APIDLE is “0” or not. If none of these answers is NO, that is, there is no negative pressure request to increase the negative pressure in the brake booster 9 and the accelerator pedal is depressed, the post-switching progress set in step 59 of FIG. Based on the time N_TCYLLT, the value obtained by searching the KLMTCYHBDSN table for the negative pressure non-request shown by the solid line in FIG. 10 is set as the combustion efficiency coefficient KLMTCYHBDS (step 74B). This table value KLMTCYHBDSN is set to increase gradually as the post-switching elapsed time N_TCYLLT is large, that is, as the elapsed time from switching the combustion mode is long, and at the first predetermined time T1 (for example, 600 msec), The predetermined value KDS1 (for example, 0.8) is set, and after the first predetermined time T1 is exceeded, the maximum value KDSMAX (for example, 4.0) larger than the predetermined value KDS1 is set.
[0057]
If the answer to any of steps 74 and 74A is YES, the value obtained by searching the KLMTCYHBDSY table for the negative pressure request shown by the broken line in FIG. 10 is calculated based on the post-switching elapsed time N_TCYLLT, similar to step 74B. The efficiency coefficient KLMTCYHBDS is set (step 74C). The table value KLMTCYHBDSY for negative pressure request is set to a high value as a whole compared with the above-described table value KLMTCCYHBDSN for negative pressure non-request and exceeds the first predetermined time T1. It continues to increase until time T1b (for example, 1100 msec), that is, the increase period is set longer, and is set to the maximum value KDSMAX after the predetermined time T1b.
[0058]
Next, a value obtained by subtracting the request torque PMTCYLIN immediately before switching set in step 41 or 43 of FIG. 6 from the request torque PMCMDREG is calculated as a torque deviation dpmetmp (step 75). Is also larger (step 76). If the answer is YES and the requested torque PMCMDREG is greater than the requested torque PMTCYLIN immediately before switching, a correction coefficient kdpmmetmpds is calculated by searching the dpmetmp-kdpmmetmpds table shown in FIG. 11 based on the torque deviation dpmmetmp (step 77). ). In this table, the correction coefficient kdpmetmpds is set to the minimum value kdsmin (for example, 1.0) and the first predetermined value dp1 (for example, 1.2 kgf / cm ² ) when the torque deviation dpmetmp is equal to or less than the first predetermined value dp1. And a second predetermined value dp2 (for example, 2.0 kgf / cm ² ) larger than this, the torque deviation dpmetmp is set so as to increase linearly, and when the torque value exceeds the second predetermined value dp2 The torque deviation dpmetmp is set so as to increase linearly with a smaller inclination as the torque deviation dpmetmp increases.
[0059]
On the other hand, when the answer to step 76 is NO and the required torque PMCMDREG is equal to or less than the request torque PMTCYLIN immediately before switching, the correction coefficient kdpmmetmpds is set to a value 1.0 (step 78). Next, a value obtained by multiplying the combustion efficiency coefficient KLMTCYHBDS calculated in step 74B or 74C by the correction coefficient kdmetmpds set in step 77 or 78 is set as the combustion efficiency parameter KLMTCYH (step 79).
[0060]
In step 80 following step 72 or 79, the required fuel injection time TCYLLTIN immediately before switching set in step 39 of FIG. 6, the combustion efficiency parameter KLMTCYH, the required torque PMCMDREG, and the step 41 or 43 of FIG. The limit value TCYLLT is calculated by the following equation (2) using the torque immediately before switching PMTCYLIN.
TCYLLT = TCYLLTIN (1 + KLMTCYH) PMCMDREG / PMTCYLIN (2)
[0061]
The combustion efficiency represents the ratio of the output of the engine 3 generated by the combustion of the supplied fuel to the amount of fuel supplied to the engine 3. This combustion efficiency tends to be lower in the uniform combustion mode than in the stratified combustion mode in the low load region where the combustion mode is switched. Therefore, when the combustion mode is switched from the former to the latter, the combustion efficiency is the same. The required fuel injection time TCYLBS for outputting torque tends to increase. For this reason, in the above equation (2), a value (1 + KLMTCYH) obtained by adding the combustion efficiency parameter KLMTCYH to the value 1 is set as a value representing the degree of decrease in combustion efficiency with reference to immediately before switching, and multiplied by this. Thereby, the limit value TCYLLT is set to a larger value.
[0062]
Further, as described above, in the table for non-negative pressure request and negative pressure request in FIG. 10, the respective table values KLMTCYHBDSN and KLMTCYHBDSY are gradually increased as the post-switching elapsed time N_TCYLLT increases. Accordingly, the limit value TCYLLT gradually increases accordingly, thereby ensuring the minimum acceleration feeling that should be obtained when the accelerator pedal is depressed slowly. Furthermore, in the table of FIG. 11 described above, when the torque deviation dpmmetmp is larger than the first predetermined value dp1 and the required torque PMCMDREG has increased to some extent from before the switching of the combustion mode, the correction coefficient kdpmmetmpds is equal to the torque deviation dpmmetmp. Since the larger value is set to a larger value, the increase in the combustion efficiency parameter KLMTCYH is corrected and the required fuel injection time TCYLBS is increased and corrected, thereby satisfying the driver's acceleration request.
[0063]
Further, as described above, the combustion efficiency coefficient KLMCYCYBDS when there is a negative pressure request or when the accelerator pedal is not depressed is set to a larger value than when there is no negative pressure request and the accelerator pedal is depressed. The reason is as follows. That is, the negative pressure request is generally detected in an extremely low load operation state where the accelerator pedal is not depressed, and therefore the difference in combustion efficiency between the stratified combustion mode and the stoichiometric combustion mode is more This is to enlarge.
[0064]
Next, it is determined whether or not the normal time required fuel injection time TCYLTMP calculated in step 6 of FIG. 3 is longer than the calculated limit value TCYLLT (step 81). When the answer is YES, the limit value TCYLLT is set as the switching required fuel injection time TCYLLMT (step 82), and the program is terminated.
[0065]
If the answer is NO and TCYLTMP ≦ TCYLLT, the normal time required fuel injection time TCYLTMP is set as the required fuel injection time TCYLLMT at the time of switching (step 83). In addition, since the limit value TCYLLT is in a relationship not less than the normal time required fuel injection time TCYLTMP and the limit by the limit value TCYLLT cannot be performed, the limit permission flag F_TCYLLT is set to “0” in order to end this limit. Set (step 84), and the program ends.
[0066]
In the table of FIG. 10 described above, the maximum value KDSMAX is the limit value TCYLLT calculated as described above, and the post-switching elapsed time N_TCYLLT exceeds the first predetermined time T1 or the predetermined time T1b. The value is set to be surely larger than the normal time required fuel injection time TCYLTMP at the time. Even if a time larger than the first predetermined time T1 or the predetermined time T1b is erroneously input to the limit time NTCYL, the answer to the step 81 is obtained when the first predetermined time T1 or the predetermined time T1b is exceeded. This is because NO is set to NO and the limit based on the limit value TCYLLT is surely terminated.
[0067]
Further, as described above, the increase period of the combustion efficiency coefficient KLMTCYHBDS when there is a negative pressure request or when the accelerator pedal is not depressed is larger than when there is no negative pressure request and the accelerator pedal is depressed. Is set to This is for the same reason as described above in step 26, and is for consistency with this.
[0068]
FIGS. 12 and 13 are flowcharts showing a subroutine of limit value calculation processing at the time of switching from stratified to lean combustion mode, which is executed in step 64 of FIG. This process is almost the same as the process in the case of the stratification → stoichiometric combustion mode in FIG. 9 described above, and in comparison with this, it is determined whether the current combustion mode is the stoichiometric combustion mode or the lean combustion mode. The only difference is that the combustion efficiency parameter KLMTCYH is calculated for each combustion mode.
[0069]
The reason why the combustion efficiency parameter KLMTCYH is calculated for each stoichiometric or lean combustion mode determined in this way is as follows. That is, as apparent from the setting method described above, the switching status EMOD_STS does not change even when switching between the stoichiometric combustion mode and the lean combustion mode, and from the lean combustion mode to the stoichiometric combustion mode. This is because the switching to is performed in an extremely short time, and may be performed during the limit execution period based on the limit value TCYLLT. As shown in FIG. 12, the execution contents of Steps 90 to 93 are the same as Steps 70 to 73 of FIG. 9 described above, and a specific description thereof will be omitted. Therefore, the processing from step 94 following step 93 will be described below.
[0070]
In step 94, it is determined whether or not the combustion mode monitor ST_EMOD is “0”. When this answer is NO and the combustion mode at that time is the lean combustion mode, the N_TCYLLT-KLMTCYHBDL table shown in FIG. 14 is searched based on the post-switching elapsed time N_TCYLLT to thereby obtain the combustion efficiency coefficient KLMTCYHBDL for the lean combustion mode. Is calculated (step 95). In this table, the combustion efficiency coefficient KLMTCYHBDL is set so as to increase gradually as the post-switching elapsed time N_TCYLLT increases, as in the table of FIG. 10 described above, and at a second predetermined time T2 (eg, 500 msec) The value KDL1 (for example, 0.4) is set, and after the second predetermined time T2 is exceeded, the maximum value KDLMAX (for example, 1.0) that is larger than the predetermined value KDL1 is set. In this case, the degree of increase in the combustion efficiency coefficient KLMTCYHBDL is set smaller than that in the case of the table value KLMTCYHBDSN for non-negative pressure in FIG. 10 described above. This is because the lean combustion mode has higher combustion efficiency than the stoichiometric combustion mode.
[0071]
Next, similarly to Steps 75 and 76 in FIG. 9, a torque deviation dpmmetmp between the requested torque PMCMDREG and the requested torque PMTCYLIN immediately before switching is calculated (Step 96), and it is determined whether dpmmetmp> 0 (Step 96). 97). When the answer is YES and the required torque PMCMDREG is larger than the request torque PMTCCYLIN immediately before switching, the correction coefficient kdpmmetmpdl for the lean combustion mode is obtained by searching the dpmetmp-kdmetmpdl table shown in FIG. 15 based on the torque deviation dpmmetmp. Calculate (step 98). In this table, the correction coefficient kdpmetmpdl is set to the minimum value kdlmin (for example, 1.0) and the third predetermined value dp3 when the torque deviation dpmetmp is not more than a third predetermined value dp3 (for example, 1.2 kgf / cm ² ). Is set so as to increase linearly as the torque deviation dpmetmp increases. In this case, the degree of increase of the correction coefficient kdpmetmpdl is set smaller than the correction coefficient kdpmetmpds in the table of FIG. 11 described above. This is because the lean combustion mode has higher combustion efficiency than the stoichiometric combustion mode. On the other hand, if the answer to step 97 is NO, the correction coefficient kdpmetmpdl is set to a value of 1.0 as in step 78 (step 99).
[0072]
In step 100 following step 98 or 99, the combustion efficiency parameter KLMTCYH is set to a value obtained by multiplying the combustion efficiency coefficient KLMTCYHBDL calculated in step 95 by the correction coefficient kdmetmpdl set in step 98 or 99.
[0073]
On the other hand, when the answer to step 94 is YES, since the combustion mode is switched from the lean combustion mode to the stoichiometric combustion mode, steps 101 to 108 are executed in the same manner as steps 74 to 79 described above.
[0074]
Using the combustion efficiency parameter KLMTCYH set in step 100 or 108, the limit value TCYLLT is calculated by the above-described equation (2) in the same manner as in step 80 (step 109). Next, steps 110 to 113 are executed in the same manner as steps 81 to 84 in FIG. 9, and this program is terminated. In the table of FIG. 14 described above, the maximum value KDLMAX is the limit value TCYLLT calculated using the maximum value KDLMAX for the same reason as described above with reference to the table of FIG. The value is set to be surely larger than the normal time required fuel injection time TCYLTMP at the time when T2 is exceeded.
[0075]
FIG. 16 is a flowchart showing a subroutine for calculating the limit value TCYLLT for switching from stoichiometric to stratified combustion mode, which is executed in step 65 of FIG. First, in step 120, a combustion efficiency parameter KLMTCYSD for switching from stoichiometric to stratified combustion mode is calculated by searching an N_TCYLLT-KLMTCYSD table shown in FIG. 17 based on the elapsed time N_TCYLLT after switching. In this table, for the same reason as described above with reference to the tables of FIGS. 10 and 11, the combustion efficiency parameter KLMTCYSD is set to gradually increase as the post-switching elapsed time N_TCYLLT increases, and the third predetermined value is set. The predetermined value KSD1 (for example, 0.4) is set at the time T3 (for example, 800 msec), and the maximum value KSDMAX (for example, 4.0) larger than the predetermined value KSD1 is set after the third predetermined time T3 is exceeded. Yes.
[0076]
Next, at step 121, a limit value TCYLLT is calculated by the following equation (3) using the fuel injection time TCYLLTIN immediately before switching, the combustion efficiency parameter KLMTCYSD, the required torque PMCMDREG, and the required torque PMTCCYLIN immediately before switching.
TCYLLT = TCYLLTIN ・ (1-KLMTCYSD) ・ PMCMDREG / PMTCYLIN ...... (3)
[0077]
In the low load region, the combustion efficiency tends to be higher in the stratified combustion mode than in the uniform combustion mode as described above, and therefore the same torque is output when switching the combustion mode from the former to the latter. Therefore, the required fuel injection time TCYLBS tends to decrease. Therefore, in the above equation (3), unlike the above equation (2), a value (1−KLMTCYSD) obtained by subtracting the combustion efficiency parameter KLMTCYSD from the value 1 is a value representing the degree of increase in combustion efficiency with reference to immediately before switching. And multiplying by this, the limit value TCYLLT is set to a smaller value.
[0078]
Next, it is determined whether or not the normal time required fuel injection time TCYLTMP is smaller than the calculated limit value TCYLLT (step 122). When the answer is YES, the limit value TCYLLT is set as the switching-time required fuel injection time TCYLLMT (step 123), and the program is terminated.
[0079]
When the answer is NO and TCYLTMP ≧ TCYLLT, the normal time required fuel injection time TCYLTMP is set as the required fuel injection time TCYLLMT at the time of switching (step 124). In addition, the limit value TCYLLT is in a relationship less than or equal to the normal required fuel injection time TCYLTMP, and the limit by the limit value TCYLLT cannot be performed, so the limit permission flag F_TCYLLT is set to “0” in order to end this limit. (Step 125), and the program is terminated.
[0080]
In the table of FIG. 17 described above, the maximum value KSDMAX is set such that the limit value TCYLLT becomes a negative value when the post-switching elapsed time N_TCYLLT exceeds the third predetermined time T3, that is, the normal time at this time The limit value TCYLLT is set to a value that is surely smaller than the required fuel injection time TCYLTMP. As in the tables of FIGS. 10 and 14 described above, even if a time larger than the third predetermined time T3 is erroneously input to the limit time NTCYL, when the third predetermined time T3 is exceeded, This is because the answer to step 122 is NO and the limit based on the limit value TCYLLT is surely terminated.
[0081]
FIG. 18 is a flowchart showing a subroutine for calculating the limit value TCYLLT for switching from lean to stratified combustion mode, which is executed in step 66 of FIG. First, in step 130, a combustion efficiency parameter KLMTCYLD for switching from lean to stratified combustion mode is calculated by searching an N_TCYLLT-KLMTCYLD table shown in FIG. 19 based on the post-switching elapsed time N_TCYLLT. In this table, as in the table of FIG. 17 described above, the combustion efficiency parameter KLMTCYLD is set to gradually increase as the post-switching elapsed time N_TCYLLT increases, and at a fourth predetermined time T4 (for example, 800 msec), a predetermined value. KLD1 (for example, 0.3) is set, and after the fourth predetermined time T4 is exceeded, the maximum value KLDMAX (for example, 4.0) larger than the predetermined value KLD1 is set. In this case, the degree of increase in the combustion efficiency parameter KLMTCYLD is set smaller than that in the case of the combustion efficiency parameter KLMTCYSD in the table of FIG. 17, and the predetermined value KLD1 is the predetermined value KSD1 in the table of FIG. Is set smaller than. This is because the lean combustion mode has higher combustion efficiency than the stoichiometric combustion mode.
[0082]
Next, a limit value TCYLLT is calculated by the following equation (4) using the required fuel injection time TCYLLTIN immediately before switching, the combustion efficiency parameter KLMTCYLD, the required torque PMCMDREG, and the required torque PMTCCYLIN immediately before switching (step 131).
TCYLLT = TCYLLTIN ・ (1-KLMTCYLD) ・ PMCMDREG / PMTCYLIN …… （4）
In the above equation (4), as in the above equation (3), a value obtained by subtracting the combustion efficiency parameter KLMTCYLD from the value 1 (1-KLMTCYLD) is a value representing the degree of increase in combustion efficiency with reference to immediately before switching. And multiplying by this, the limit value TCYLLT is set to a smaller value.
[0083]
Next, similarly to steps 122 to 125 in FIG. 16, steps 132 to 135 are executed, and this program is terminated. In the table of FIG. 19 described above, the maximum value KLDMAX is the normal-time required fuel injection time when the limit value TCYLLT calculated using the maximum value KCYDLT exceeds the fourth predetermined time T4 after the switching elapsed time N_TCYLLT. The value is set so as to be surely smaller than TCYLTMP. This is for the same reason as described above for the table of FIG.
[0084]
As described above, according to the present embodiment, when the combustion mode is switched, the limit value TCYLLT is calculated according to the required torque PMCMDREG by the equations (2) to (4). Unlike the normal required fuel injection time TCYLTMP calculated according to the absolute pressure PBA, the actual required torque PMCMDREG at that time can be set as a value that reflects well without abrupt fluctuations. Further, since the limit value TCYLLT is calculated based on the fuel injection time TCYLLTIN immediately before switching and the required torque PMTCYLIN immediately before switching, the transition of the combustion mode can be performed smoothly without causing a steep step in torque before and after switching. it can. Furthermore, since the limit value TCYLLT is calculated according to the combustion efficiency parameters KLMTCYH, KLMTCYSD or KLMTCYLD, it can be set to an appropriate value according to the actual combustion efficiency at that time. As described above, at the time of switching the combustion mode, the output torque of the internal combustion engine can be made to agree well with the required torque, thereby improving drivability.
[0085]
In addition, this invention can be implemented in various aspects, without being limited to embodiment described. For example, in the present embodiment, the present invention is applied to the engine 3 for a vehicle. However, the present invention is not limited thereto, and is applied to an engine for a marine propulsion device such as an outboard motor having a crankshaft arranged in a vertical direction. Also good. In addition, it is possible to appropriately change the detailed configuration within the scope of the gist of the present invention.
[0086]
【The invention's effect】
As described above, according to the control device for an internal combustion engine of the present invention, when the combustion mode is switched, the output torque of the internal combustion engine can be matched well with the required torque, thereby improving drivability. It has the effect of being able to.
[Brief description of the drawings]
FIG. 1 is a schematic configuration of a control device 1 of the present invention and an engine to which the control device 1 is applied.
FIG. 2 is a map used for determining a combustion mode.
FIG. 3 is a flowchart showing a calculation process of a required fuel injection time.
4 is a flowchart showing a subroutine of switching limit processing in step 7 of FIG. 3;
FIG. 5 is a flowchart showing a subroutine of limit value calculation parameter setting processing in step 17 of FIG. 4;
6 is a continuation of the flowchart of FIG.
7 is a flowchart showing a subroutine of limit value calculation processing in step 18 of FIG.
FIG. 8 is a continuation of the flowchart of FIG.
FIG. 9 is a flowchart showing a subroutine for calculating a limit value for switching the combustion mode from the stratified combustion mode to the stoichiometric combustion mode in step 61 of FIG. 8;
FIG. 10 is a diagram showing an example of a table for setting a combustion efficiency coefficient KLMTCYHBDS depending on whether there is a negative pressure request or the like.
FIG. 11 is a diagram illustrating an example of a dpmetmp-kdpmetmpds table used in the processes of FIGS. 9 and 13;
12 is a flowchart showing a subroutine for calculating a limit value for switching the combustion mode from the stratified combustion mode to the lean combustion mode in step 64 of FIG. 8;
FIG. 13 is a continuation of the flowchart of FIG.
14 is a diagram showing an example of an N_TCYLLT-KLMTCYHBDL table used in the processing of FIG.
FIG. 15 is a diagram illustrating an example of a dpmetmp-kdpmetmpdl table used in the processing of FIG. 13;
16 is a flowchart showing a subroutine for calculating a limit value for switching the combustion mode from the stoichiometric combustion mode to the stratified combustion mode in step 65 of FIG. 8;
17 is a diagram illustrating an example of an N_TCYLLT-KLMTCYSD table used in the process of FIG.
18 is a flowchart showing a subroutine for calculating a limit value for switching the combustion mode from the lean combustion mode to the stratified combustion mode in step 66 of FIG.
FIG. 19 is a diagram showing an example of an N_TCYLLT-KLMTCYLD table used in the processing of FIG.
[Explanation of symbols]
1 Control device
2 ECU (operating state detecting means, required fuel amount calculating means, required torque calculating means
Stage, combustion mode determination means, storage means, counter, combustion efficiency estimation
Setting means, means for calculating required fuel amount at switching)
3 Engine
22 Crank angle sensor (operating state detection means)
23 Intake pipe absolute pressure sensor (operating state detection means)
27 Accelerator opening sensor (operating state detection means)
TCYLBS Required fuel injection time (Required fuel amount)
PMCMDREG Required torque TCYLLTIN Requested fuel injection time immediately before switching (calculated just before the combustion mode is switched)
Requested fuel amount)
PMTCYLIN request torque immediately before switching (requested torque calculated immediately before switching combustion mode)
KLMTCYH Combustion efficiency parameter (combustion efficiency)
KLMTCYSD combustion efficiency parameter (combustion efficiency)
KLMTCYLD combustion efficiency parameter (combustion efficiency)
TCYLLT limit value (required fuel amount at switching)
Elapsed time after switching N_TCYLLT (time elapsed since switching of the timed combustion mode)

Claims (1)

An in-cylinder injection type internal combustion engine that operates by switching the combustion mode between a stratified combustion mode for stratified combustion of the air-fuel mixture and a uniform combustion mode for uniform combustion and controls the fuel injection amount based on the calculated required fuel amount A control device of
Operating state detecting means for detecting the operating state of the internal combustion engine;
A required fuel amount calculating means for calculating the required fuel amount according to the detected operating state of the internal combustion engine;
Requested torque calculating means for calculating a required torque of the internal combustion engine according to the detected operating state of the internal combustion engine;
Combustion mode determining means for determining the combustion mode as one of the stratified combustion mode and the uniform combustion mode in accordance with the calculated required torque;
Storage means for storing the required fuel amount and the required torque calculated immediately before the combustion mode is switched by the combustion mode determining means;
A counter for measuring the elapsed time from the switching of the combustion mode;
The combustion efficiency representing the ratio of the output of the internal combustion engine generated by the combustion of the supplied fuel to the amount of fuel supplied to the internal combustion engine is determined according to the elapsed time from the time of switching the measured combustion mode. A combustion efficiency estimating means for estimating;
When the combustion mode is switched, the stored required fuel amount and required torque, the calculated current required torque, and the estimated current combustion efficiency are switched as the required fuel amount. A required fuel amount calculation means at the time of switching for calculating the required fuel amount;
A control device for an internal combustion engine, comprising:

Images