JPH10331708A - Controller for internal combustion engine of direct injection-ignition type - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve controllability by providing a means of selecting any one of uniform combustion and stratified combustion, a means of setting a corresponding fuel injection method to each type of combustion for every cylinder according to the selected result, and a means of setting a corresponding ignition timing to the fuel injection method for every cylinder. SOLUTION: Fuel injected is ignited by an ignition plug 7 for uniform combustion or stratified combustion according to an ignition signal from a control unit 20. The selection of uniform combustion or stratified combustion is made by the use of a map specifying a basic target equivalence ratio with an engine speed and a target engine torque used as a parameter of engine operation condition. According to the result of selection, a combustion injection method is set in correspondence with a combustion method in order for every cylinder. At the time of setting an injection timing for each cylinder, the ignition timing is set according to the combustion injection method for every cylinder. Accordingly, the ignition timing is made in conformity with the requirement of the fuel injection method for every cylinder, resulting in a remarkable improvement in controllability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a control device for a direct injection spark ignition type internal combustion engine.

[0002]

2. Description of the Related Art In recent years, a direct-injection spark ignition type internal combustion engine has attracted attention. In this type, a combustion method is switched according to engine operating conditions, that is, by injecting fuel in an intake stroke to perform combustion. Homogeneous combustion is performed by diffusing fuel into the room to form a homogeneous mixture, and stratified combustion is performed by forming a stratified mixture around the spark plug by injecting fuel in the compression stroke. Switching control is generally performed (see Japanese Patent Application Laid-Open No. S59-37236).

[0003]

However, when either the homogeneous combustion or the stratified combustion is selected according to the operating conditions, the fuel injection timing of the homogeneous combustion is temporal in switching from the stratified combustion to the homogeneous combustion. It is necessary to set earlier than the fuel injection timing of stratified combustion. Therefore, for example, in a cylinder that performs stratified combustion continuously even after the selection of homogeneous combustion,
In addition to the fuel injection amount and the fuel injection timing, especially the ignition timing does not match the stratified combustion, and the ignition timing for homogeneous combustion is set. Then, there is a possibility that the emission may be deteriorated or the drivability may be reduced due to incomplete combustion or misfire.

[0004] Therefore, when switching the combustion mode, it is required to be able to correctly switch between the fuel injection control and the ignition timing control for each cylinder. In addition, when the fuel injection amount for homogeneous combustion and the fuel injection amount for stratified combustion, and the ignition timing for homogeneous combustion and the ignition timing for stratified combustion are always separately calculated, the calculation load increases and Then, the job may not be able to complete.

The present invention has been made in view of the above-mentioned conventional problems, and makes it possible to set the ignition timing in accordance with the fuel injection system of each cylinder at the time of a request for switching between homogeneous combustion and stratified combustion, thereby improving controllability. The purpose is to.

[0006]

According to the present invention, a fuel injection valve for directly injecting fuel into a combustion chamber of an engine is provided, and fuel is injected during an intake stroke according to engine operating conditions. As shown in FIG. 1, in a control device for a direct injection spark ignition type internal combustion engine that controls switching between homogeneous combustion performed by causing the fuel to be injected and stratified combustion performed by injecting fuel in a compression stroke, as shown in FIG. A combustion method determining means for determining whether to select combustion or stratified combustion; and a cylinder-specific fuel injection method for sequentially setting a fuel injection method corresponding to the combustion method for each cylinder according to the determination result of the combustion method. A setting means and cylinder-specific ignition timing setting means for setting an ignition timing according to a fuel injection method for each cylinder when setting the ignition timing for each cylinder are provided.

In the invention according to claim 2, the cylinder-by-cylinder ignition timing setting means sets the ignition timing for each cylinder from execution / non-execution of the fuel injection for homogeneous combustion in each cylinder to uniformity at the time of execution. The ignition timing for combustion and the ignition timing for stratified combustion are set when not performed. In the invention according to claim 3, the cylinder-by-cylinder fuel injection method setting means sets the injection timing for homogenous combustion for each cylinder, and sets the injection timing for stratified combustion for each cylinder. Stratification injection timing setting means separately, at the injection timing for homogeneous combustion of each cylinder, according to the determination result of the combustion method, to set execution / non-execution of fuel injection for homogeneous combustion,
At the injection timing for stratified combustion of each cylinder, execution / non-execution of fuel injection for stratified combustion is set from execution / non-execution of fuel injection for homogeneous combustion immediately before. .

[0010] In the invention according to claim 4, the cylinder-specific fuel injection method setting means includes a homogenous injection amount calculating means for calculating an injection amount for homogeneous combustion, and a stratified injection amount for calculating an injection amount for stratified combustion. It is characterized by having a quantity calculation means separately. In the invention according to claim 5, after the determination of the request to switch to the homogeneous combustion, the injection amount for stratified combustion calculated last by the injection amount calculation device for stratification is held, and the injection amount for homogenization is calculated by the injection amount calculation device for homogenization. Only the injection amount for combustion is newly calculated, and after determining the request to switch to stratified combustion, the injection amount for homogeneous combustion last calculated by the injection amount calculation device for homogenization is held, and the injection amount for stratification is held. An injection amount calculation switching unit for newly calculating only the injection amount for stratified combustion by the calculation unit is provided.

In the invention according to claim 6, the cylinder-specific ignition timing setting means includes a homogenization ignition timing calculation means for calculating an ignition timing for homogeneous combustion, and a stratification ignition timing for calculating an ignition timing for stratified combustion. It is characterized by having a calculation means separately. In the invention according to claim 7, after determining the request to switch to homogeneous combustion, the ignition timing for stratified combustion last calculated by the ignition timing calculation means for stratification is held, and the ignition timing for homogenization is calculated by the ignition timing calculation means for homogenization. Only the ignition timing for combustion is newly calculated, and after determining the request to switch to stratified combustion, the ignition timing for homogeneous combustion last calculated by the ignition timing calculation means for homogenization is held, and the ignition timing for stratification is held. An ignition timing calculation switching means for newly calculating only the stratified combustion ignition timing by the calculation means is provided.

[0010] In the invention according to claim 8, the ignition timing calculating means for homogenization is based on a parameter of an engine operating state.
According to a predetermined MBT (optimum ignition timing) calculation formula, MB
The ignition timing corresponding to T is calculated. The invention according to claim 9 is characterized in that the stratification ignition timing calculation means searches the ignition timing by referring to a predetermined map based on the parameters of the engine operating state.

[0011]

According to the first aspect of the present invention, the fuel injection system corresponding to the combustion system is sequentially set for each cylinder in accordance with the determination result of the combustion system, and the ignition timing is set for each cylinder. Since the ignition timing is set for each cylinder in accordance with the fuel injection method for each cylinder, the ignition timing matches the requirement of the fuel injection method for each cylinder, and controllability is greatly improved.

According to the second aspect of the present invention, when the ignition timing for each cylinder is set, the execution of the fuel injection for homogeneous combustion in each cylinder is changed from the execution / non-execution to the ignition timing for the homogeneous combustion in execution. Since the ignition timing for stratified combustion is set at the time of execution,
It is possible to reliably make the ignition timing correspond to the switching of the fuel injection method. According to the invention according to claim 3, the injection timing for homogeneous combustion and the injection timing for stratified combustion are separately set for each cylinder, and the determination result of the combustion method is determined by the injection timing for homogeneous combustion for each cylinder. The execution / non-execution of the fuel injection for the homogeneous combustion is set according to the above, and at the injection timing for the stratified combustion in each cylinder, the execution / non-execution of the fuel injection for the immediately preceding homogeneous combustion is performed, and Is set, execution can be quickly performed, and double injection can be avoided.

According to the fourth aspect of the present invention, since the injection amount calculating means for homogenization and the injection amount calculating means for stratification are separately provided, it is possible to calculate the optimum injection amount for each.
According to the fifth aspect of the present invention, only one of the injection amount for the homogeneous combustion and the injection amount for the stratified combustion is calculated by the switching means of the injection amount calculation in accordance with the determination result of the combustion method. Can be reduced. On the other hand, for the cylinders in which fuel injection is performed by the previous method after the determination of the switching of the combustion method, since the determination is performed using the last calculated value held,
It does not impair controllability.

According to the invention of claim 6, since the ignition timing calculating means for homogenization and the ignition timing calculating means for stratification are separately provided, it is possible to calculate the ignition timing in an optimum manner for each. According to the seventh aspect of the present invention, only one of the ignition timing for homogeneous combustion and the ignition timing for stratified combustion is calculated by the switching means for calculating the ignition timing in accordance with the determination result of the combustion method. Can be reduced. On the other hand, after the determination of the switching of the combustion method, the controllability is not degraded for the cylinders in which ignition is performed by the previous method because the last calculated value held is used.

According to the eighth aspect of the present invention, when calculating the ignition timing for homogeneous combustion, by using the MBT equation, it is possible to reduce the experimental man-hours and the adaptation period and the memory capacity. According to the ninth aspect of the present invention, in calculating the ignition timing for stratified charge combustion, the erroneous control caused by the incompatibility of the MBT formula in the stratified charge combustion is obtained by using a map instead of the MBT formula. It is possible to avoid this and reduce the calculation load.

[0016]

Embodiments of the present invention will be described below. FIG. 2 is a system diagram of an internal combustion engine showing an embodiment. First, this will be described. Air is sucked into the combustion chamber of each cylinder of the internal combustion engine 1 mounted on the vehicle from the air cleaner 2 through the intake passage 3 under the control of the electronically controlled throttle valve 4. In addition, the swirl control valve 5
Is provided, and the flow of air sucked into the combustion chamber can be controlled by controlling the port cross-sectional area.

An electromagnetic fuel injection valve (injector) 6 is provided so as to directly inject fuel (gasoline) into the combustion chamber. The fuel injection valve 6 is energized by a solenoid by an injection pulse signal output in an intake stroke or a compression stroke from a control unit 20, which will be described later, in synchronization with the rotation of the engine, opens the valve, and supplies fuel adjusted to a predetermined pressure. It is designed to inject. The injected fuel diffuses into the combustion chamber in the case of the intake stroke injection to form a homogeneous mixture, and in the case of the compression stroke injection, forms a layered mixture intensively around the spark plug 7. Based on an ignition signal from a control unit 20, which will be described later, the fuel is ignited by the ignition plug 7 and burns (homogeneous combustion or stratified combustion).

Exhaust gas from the engine 1 is exhausted from an exhaust passage 8, and an exhaust purification catalyst 9 is interposed in the exhaust passage 8. Further, a part of the exhaust gas is supplied to the EG through the electronically controlled EGR valve 10.
The air is returned to the intake passage 3 downstream of the throttle valve 4 (intake manifold) by the R passage 11. The control unit 20 includes a microcomputer including a CPU, a ROM, a RAM, an A / D converter, an input / output interface, and the like, receives input signals from various sensors,
Based on this, arithmetic processing is performed to control the operations of the fuel injection valve 6, the ignition plug 7, and the like.

The various sensors include a crank angle sensor 21 for detecting rotation of a crankshaft or a camshaft of the engine 1,
22 are provided. These crank angle sensors 2
1, 22 are 720 ° crank angle, where n is the number of cylinders.
/ N, outputs a reference pulse signal REF at a predetermined crank angle position (for example, 110 ° before compression top dead center) and outputs a unit pulse signal POS every 1 to 2 °. From the REF cycle etc., the engine speed N
e can be calculated. Further, in particular, the camshaft sensor 22 outputs a cylinder discrimination signal PHASE corresponding to a specific cylinder at a predetermined crank angle position at every crank angle 720 °, thereby enabling cylinder discrimination.

In addition, an air flow meter 23 for detecting an intake air flow rate Qa upstream of the throttle valve 4 in the intake passage 3,
Accelerator sensor 24 for detecting the amount of accelerator pedal depression (accelerator opening) ACC, opening TV of throttle valve 4
A throttle sensor 25 for detecting O (including an idle switch which is turned on when the throttle valve 4 is fully closed), a water temperature sensor 26 for detecting the cooling water temperature Tw of the engine 1, and a rich / lean exhaust air-fuel ratio in the exhaust passage 8. An O ₂ sensor 27 that outputs a signal corresponding to the vehicle speed, a vehicle speed sensor 28 that detects a vehicle speed VSP, and the like are provided.

Next, fuel injection control and ignition control performed by the control unit 20 will be described with reference to FIGS.
This will be described with reference to the flowchart of FIG. Figure 3 shows the fuel injection amount
This is an injection timing calculation routine, which is executed as a 10 ms job. Step 1 (referred to as S1 in the figure; the same applies hereinafter)
Then, it is determined whether the request is a homogeneous combustion request or a stratified combustion request.

Here, whether to perform homogeneous combustion or stratified combustion is determined as follows. First, a plurality of maps each defining the basic target equivalent ratio TFBYA0 using the engine speed Ne and the target engine torque tTe as parameters of the engine operating state are provided for each condition such as the water temperature Tw and the time after starting, and are selected from these conditions. The basic target equivalent ratio TFBYA0 is set according to the parameters of the actual engine operating state from the map thus obtained. Note that the target engine torque tTe is a target driving force tTd set based on the accelerator opening ACC and the vehicle speed VSP.
Is determined in consideration of the gear ratio and the torque ratio.

Next, the basic target equivalence ratio TFBYA0 obtained from the map is corrected by the combustion efficiency and the like, and a first-order delay corresponding to the amount of air taken into the cylinder from the throttle chamber is given to calculate the actual fuel injection amount. To obtain the target equivalent ratio TFBYA used in the above. Target equivalent ratio TF
BYA is also called a target fuel-air correction coefficient, and the target air-fuel ratio is represented by t
If it is AF, it is represented by 14.6 / tAF.

When the target equivalent ratio TFBYA crosses the threshold value for determining the switching of the combustion mode, a request for switching the combustion mode (a request for switching to homogeneous combustion or a request for switching to stratified combustion) is generated. Judgment based on request (FIG. 9
And FIG. 10). Step 2 for homogeneous combustion request
Then, the target equivalent ratio TFBYA for homogeneous combustion is calculated, and using this, the homogeneous injection amount CTIH is calculated by the following equation.

CTIH = Tp × TFBYA × α + Ts Here, Tp is a basic fuel injection amount corresponding to stoichiometry, and Tp
= K × Qa / Ne (K is a constant). α is O ₂
This is an air-fuel ratio feedback correction coefficient based on the sensor signal, and is clamped to = 1 during lean operation. Ts is an invalid injection time correction amount depending on the battery voltage.

Then, in step 3, a homogeneous injection amount TISETHn = CTIH for control is set for the cylinder before the intake stroke injection timing in the case of homogeneous combustion. Then, in step 4, the cylinder-specific homogenous request flag F for the cylinder is set.
Set HDMDn to 1. For stratified combustion requests,
In step 5, the target equivalent ratio TFBYA for stratified combustion is calculated, and using this, the stratified injection amount CTIS is calculated by the following equation.

CTIS = Tp × TFBYA × α + Ts The final formula is the same as in the case of homogeneous combustion. However, since the map used in the process of obtaining the target equivalent ratio TFBYA is different, it is calculated separately. In the case of stratified charge combustion, the air-fuel ratio feedback correction coefficient α is always clamped to = 1. Then, in step 6, the stratified injection amount TI for control with respect to the cylinder before the intake stroke injection timing in the case of homogeneous combustion.
Set as SETSn = CTIS.

In step 7, the cylinder-specific homogenity request flag FHDMDn of the cylinder is set to 0. After these,
Proceed to steps 8 and 9. In step 8, from the map (see FIG. 11) in which the injection timing TITMH for homogenization is determined during the intake stroke using the fuel injection amount (homogeneous injection amount CTIH) and the engine speed Ne as parameters of the engine operation state, see FIG. The timing TITMH is searched.

In step 9, the fuel injection amount (stratification injection amount CTIS) and the engine speed Ne are used as parameters of the engine operating state, and the stratification injection timing TITMS is determined during the compression stroke (see FIG. 11). Injection timing TI for stratification
The TMS is searched, and this routine ends. As described above, when a homogeneous combustion request is made, only the homogeneous injection amount CTIH is calculated, and the stratified injection amount CTIS is not calculated. Conversely, when a stratified combustion request is made, only the stratified injection amount CTIH is calculated. By not calculating the homogenous injection amount CTIH, the calculation load can be reduced.

On the other hand, the injection timing TITMH for homogeneity and the injection timing TITMS for stratification are always calculated at the same time so that the switching can be performed smoothly. FIG. 4 shows an injection timing setting routine.
REF job, that is, the reference pulse signal REF
It is executed in synchronization with the occurrence of

In step 11, the injection timing for homogenization TIT
Read MH. In step 12, based on the read latest homogenous injection timing TITMH, a reference pulse signal REF up to the intake stroke injection timing for homogeneous combustion is provided for each cylinder.
And the reference pulse signal RE immediately before
The waiting number (angle) ANGTMHn of the unit pulse signal POS from F to the injection timing is calculated and set in the respective subtraction counters.

In step 13, the stratification injection timing TIT
Read MS. In step 14, based on the read latest stratified injection timing TITMS, a reference pulse signal REF up to the compression stroke injection timing for stratified combustion is provided for each cylinder.
INJOFSn and the immediately preceding reference pulse signal RE
The waiting number (angle) ANGTMSn of the unit pulse signal POS from F to the injection timing is calculated, set in the respective subtraction counters, and the present routine ends.

As described above, the homogenous injection timing TITMH and the stratified injection timing TITMS are not only always calculated at the same time, but can be switched smoothly by setting both of them. . still,
The respective decrement counters of INJOFHn and INJOFSn then count and subtract the reference pulse signal REF. The decrement counters of ANGTMHn and ANGTMSn decrement the unit pulse signal POS after the corresponding decrements of INJOFHn and INJOFSn become zero. Is counted and subtracted.

FIG. 5 shows a fuel injection control routine.
The job is executed as an S job, that is, in synchronization with the generation of the unit pulse signal POS. In step 21, it is determined whether or not the subtraction counter of ANGTMHn for detecting the injection timing for homogenization has become 0. In the case of YES, the process proceeds to step 22. In step 22, it is determined whether or not the cylinder-specific homogeneity request flag FHDMDn = 1 for the corresponding cylinder.
If HDMDn = 1, the process proceeds to step 23 to execute fuel injection for homogeneous combustion.

In step 23, the homogenous injection amount TISETHn of the cylinder is read and set. Then, at step 24, TISETHn is added to the fuel injection valve of that cylinder.
The fuel injection is performed by outputting an injection pulse signal having a pulse width corresponding to. Then, at step 25, the homogeneous injection execution flag FHINJEXn is set to 1. In the determination at step 22, the cylinder-specific homogenity request flag FHDMDn = 0
In other words, in the case of a stratification request, the routine proceeds to step 26 without performing the homogeneous injection, and proceeds to the homogeneous injection execution flag FH.
Set INJEXn to 0.

On the other hand, at step 27, it is determined whether or not the subtraction counter of ANGTMSn for detecting the injection timing for stratification has become 0. In the case of YES, the routine proceeds to step 28.
In step 28, it is determined whether or not the homogeneous injection execution flag FHINJEXn = 1 is set for the corresponding cylinder.
In the case of NJEXn = 1, fuel injection for homogeneous combustion has been performed, so that this routine ends without performing stratified injection to avoid double injection.

If FHINJEXn = 0, the process proceeds to step 29 to execute fuel injection for stratified combustion.
In step 29, the stratified injection amount TISET of the cylinder is set.
Read Sn and set. And step 30
Then, an injection pulse signal having a pulse width corresponding to TISETSn is output to the fuel injection valve of that cylinder, fuel injection is performed, and this routine ends.

As described above, both the injection timing for homogenization and the injection timing for stratification are set for each cylinder, and the injection timing for homogenization of each cylinder (ANGTMHn = 0) is set according to the determination result of the combustion system. , Cylinder homogenous requirement (FHDMDn =
Only in the case of 1), the fuel injection for the homogeneous combustion is executed. At the stratified injection timing (ANGTMSn = 0) of each cylinder, the fuel injection for the homogeneous combustion is executed from the immediately preceding execution / non-execution to the non-execution ( Only when FHINJEXn = 0), fuel injection for stratified combustion is executed.

Step 1 in FIG. 3 corresponds to the combustion mode determination means. Steps 2 to 9 in FIG. 3, steps 11 to 14 in FIG. 4, and steps 21 to 30 in FIG. It corresponds to an injection method setting means. In particular, steps 8 and 11 in FIG. 3 and steps 11 and 12 in FIG. 4 correspond to the homogenous injection timing setting means, and steps 9 and 13 and 14 in FIG. It corresponds to setting means. Step 2 in FIG. 3 corresponds to the injection amount calculating means for homogeneity, step 5 in FIG. 3 corresponds to the injection amount calculating means for stratification, and step 1 in FIG. It corresponds to switching means.

FIG. 6 shows an ignition timing calculation routine.
This is executed as an ms job. In step 31, it is determined whether the request is a homogeneous combustion request or a stratified combustion request. If the request is for homogeneous combustion, the process proceeds to steps 32 and 33 to calculate the ignition timing ADVH for homogenization. Specifically, in step 32,
According to the MBT calculation subroutine of FIG.
An MBT calculation value (MBTCAL) is calculated using the T calculation formula, and in step 33, the ignition timing for homogenization ADVH = MBT
Set to CAL.

If the request is for stratified combustion, the routine proceeds to step 34, where the stratified ignition timing ADVS is calculated. Specifically, a stratification ignition timing ADVS is retrieved from a map in which the stratification ignition timing ADVS is determined using the engine speed Ne and the basic fuel injection amount Tp (or the target engine torque tTe) as parameters of the engine operating state. Characteristically, it is set on the more retarded side than the MBT in the case of homogeneous combustion.

As described above, when a request for homogeneous combustion is made, only the ignition timing for homogeneity ADVH is calculated, and the ignition timing for stratification ADVH is calculated.
On the other hand, when stratified combustion is requested, only the stratified ignition timing ADVS is calculated, and the homogeneous ignition timing A is calculated.
By not performing the DVH calculation, the calculation load can be reduced. In addition, in the case of homogeneous combustion, the MBT calculation formula can be applied. However, in the case of stratified combustion, the conditions are greatly different, and applying the MBT calculation formula causes inconvenience.
An appropriate ignition timing can be calculated using a map.

FIG. 7 shows an ignition timing setting routine.
It is executed as an EF job. In step 41, the homogeneous injection execution flag FHINJEXn =
It is determined whether it is 1 or not. Homogeneous injection execution flag FHINJE
If Xn = 1, the fuel injection (intake stroke injection) for homogeneous combustion is being performed, so the routine proceeds to step 42, where the control ignition timing ADV is set to the homogenization ignition timing ADVH.

A homogeneous injection execution flag FHINJEXn = 0
In the case of, fuel injection for stratified combustion (compression stroke injection)
Then, the routine proceeds to step 43, where the control ignition timing ADV is set to the stratification ignition timing ADVS. Thus, the ignition timing is set according to the fuel injection method. Next, at step 44, since the ignition timing ADV is the ignition advance angle [° BTDC] from the compression top dead center, the crank angle from the reference signal REF to the compression top dead center is set to CR.
If SET # (for example, 110 °), the crank angle FADV from the reference signal REF (current time) to the ignition timing is calculated by the following equation.

FADV = CRSET # -ADV Then, at step 45, FADV is set in the subtraction counter, and this routine ends. The FADV decrement counter then counts and decrements the unit pulse signal POS.

FIG. 8 shows an ignition control routine, which is executed as a POS job. In step 51, it is determined whether or not the subtraction counter of the ignition timing detection FADV has become 0. In the case of YES, the process proceeds to step 52. In step 52, an ignition signal is output to the ignition cylinder to cause ignition. The step 31 in FIG. 6 corresponds to the combustion mode determination means, and includes steps 32 to 34 in FIG. 6, steps 41 to 45 in FIG. 7, and steps 51 and 52 in FIG. 41 to 43) correspond to cylinder-specific ignition timing setting means. In particular, steps 32 and 33 in FIG. 6 correspond to the ignition timing calculating means for homogeneity, step 34 in FIG. 6 corresponds to the ignition timing calculating means for stratification, and step 31 in FIG. It corresponds to a switching means of the ignition timing calculation.

Next, the manner of switching the combustion mode will be described with reference to FIGS. This example shows a case of six cylinders, and shows only the cylinders # 1 to # 4 in the ignition order. FIG. 9 shows a case where the mode is switched from stratified combustion to homogeneous combustion. When the target equivalent ratio TFBYA exceeds the threshold value and a request to switch to homogeneous combustion is determined, the cylinder is switched to homogeneous combustion from the # 4 cylinder immediately before the intake stroke injection timing in the case of homogeneous combustion.

That is, when the request for switching to the homogeneous combustion is determined, the homogenous injection amount CTIH is calculated at that time, and
When the calculation is completed, the cylinder-by-cylinder homogeneity request (FHDMD) is started from the # 4 cylinder immediately before the intake stroke injection timing in the case of homogeneous combustion.
n = 1) is set. At this time, in the # 4 cylinder, the injection timing TITMH for homogenization and the injection timing TITMS for stratification are set at the time of generation of the reference pulse signal REF immediately before the # 4 cylinder, and the subtraction counter (ANGTM) for the injection timing for homogenization is set.
Hn) is in the middle of the subtraction, and when the subtraction counter becomes 0, the homogenization request for each cylinder (FHDMDn = 1) is determined, and the homogenization injection is performed.

Thereafter, in the # 4 cylinder, the stratification injection timing TITMS has already been set, and the stratification injection timing subtraction counter (ANGTMSn) also starts subtracting from the immediately preceding reference pulse signal REF. When the counter becomes 0, the homogeneous injection has been executed (FHI
Since NJEXn = 1), stratification injection (double injection) is not performed.

Regarding the ignition control, when a request to switch to homogeneous combustion is determined, the ignition timing ADV for homogenization starts from that point.
H is calculated, and when the reference pulse signal REF immediately before the ignition timing of the # 4 cylinder is generated, the homogeneous injection has been executed (FHINJE
Xn = 1), and since it has been executed, the ignition timing ADV is set to the latest homogeneous ignition timing ADVH, and
Perform ignition control.

On the other hand, for the # 3 cylinder which is the last of the stratified combustion, at the time when the request to switch to the homogeneous combustion is determined,
Because the intake stroke injection timing for homogeneous combustion has passed,
Cylinder homogeneity requirement (FHDMDn = 1) is not set,
Thereafter, a decrementing counter (ANGTM) for the stratification injection timing is used.
When Sn) becomes 0, stratification injection is performed. At this time, the new calculation of the stratification injection amount CTIS has been stopped, and the held final calculation value is used.

Regarding the ignition control of the # 3 cylinder, when the reference pulse signal REF immediately before the ignition timing of the # 3 cylinder is generated, it is determined whether the homogeneous injection has been executed (FHINJEXn = 1),
Since it has not been executed, the ignition control is performed by setting the ignition timing ADV to the stratification ignition timing ADVS. At this time,
The new calculation of the stratification ignition timing ADVS is stopped, and the held final calculation value is used.

FIG. 10 shows a case where switching from homogeneous combustion to stratified combustion is performed. When the target equivalent ratio TFBYA falls below the threshold,
When a request to switch to stratified combustion is determined, the cylinder is switched to stratified combustion from the # 4 cylinder immediately before the intake stroke injection timing in the case of homogeneous combustion. That is, when a request for switching to stratified combustion is determined, the stratified injection amount CTIS is calculated at that time, and when the calculation is completed, FHDMDn = from the # 4 cylinder immediately before the intake stroke injection timing in the case of homogeneous combustion. 0 (stratification request for each cylinder).

At this time, in the # 4 cylinder, the homogenous injection timing TITMH is generated when the immediately preceding reference pulse signal REF is generated.
And the injection timing for stratification TITMS are set, and the subtraction counter (ANGTMHn) for the injection timing for homogenization is in the process of being subtracted. When the subtraction counter reaches 0, the homogenization request for each cylinder (FHDMDn = 1) is issued. Is determined,
Since FHDMDn = 0 (cylinder-specific stratification requirement), injection for homogenization is not performed.

Thereafter, in the # 4 cylinder, the stratification injection timing TITMS has already been set, and the stratification injection timing subtraction counter (ANGTMSn) also starts subtracting from the immediately preceding reference pulse signal REF. Becomes zero when homogeneous injection has been executed (FHINJE
Xn = 1) is determined, and since it has not been executed, stratification injection is performed.

Regarding the ignition control, when a request to switch to stratified combustion is determined, the stratified ignition timing ADV
S is calculated, and when the reference pulse signal REF is generated immediately before the ignition timing of the # 4 cylinder, the homogeneous injection has been executed (FHINJE
Xn = 1), and since it has not been executed, the ignition timing ADV is set to the latest stratification ignition timing ADVS to perform ignition control.

On the other hand, for the # 3 cylinder at the end of the homogeneous combustion, when the request to switch to the stratified combustion is determined,
Since the injection for homogenization has ended after the intake stroke injection timing in the case of homogeneous combustion, the time when the stratified injection timing subtraction counter (ANGTMSn) becomes 0 after that, the homogenous injection has been executed (FHINJEXn). = 1), no stratification injection is performed.

Regarding the ignition control of the # 3 cylinder, when the reference pulse signal REF is generated immediately before the ignition timing of the # 3 cylinder, it is determined whether or not the homogeneous injection has been executed (FHINJEXn = 1).
Since the execution has been completed, the ignition timing ADV is set to the homogenization ignition timing ADVH, and the ignition control is performed. At this time, the new calculation of the homogeneous ignition timing ADVH has been stopped,
The last operation value held is used.

Finally, the MBT calculation subroutine of FIG. 12 will be described. In addition, this is Japanese Patent Application No. 8-183637.
And Japanese Patent Application No. 8-238784. In step 101, the charging efficiency ITAC is calculated by the following equation using the basic fuel injection amount Tp corresponding to the cylinder intake air amount.

ITAC = Tp / Tp100 (1) where Tp100 is a T corresponding to a filling efficiency of 100%.
This is a fixed fixed value of p. In step 102, using the target equivalence ratio TFBYA, the fuel weight equivalent coefficient FUELG is calculated by the following equation.

FUELG = TFBYA0 / 14.6 (2) For example, at the stoichiometric air-fuel ratio, FUELG = 1.0 / 1
4.6, and a lean air-fuel ratio of 1.0 / 14.
The value is smaller than 6. In step 103, the gas weight in the cylinder (new air weight GAIR and self-residual gas weight G
REG) and the fresh air weight (GAIR) is calculated. Specifically, the filling efficiency I
A predetermined map is searched for and obtained from the TAC and the engine speed Ne.

In step 104, a predetermined table is retrieved from the charging efficiency ITAC, and the unburned gas density basic value D is retrieved.
Ask for ENS. This unburned gas density basic value DENS is I
This value increases as TAC increases. In step 105, a predetermined map is retrieved from the charging efficiency ITAC and the engine speed Ne, and the laminar flame speed basic value FL is searched.
Find ML. The laminar flame velocity is the flame propagation velocity when the gas is stationary, that is, the flame propagation velocity when there is no flow (turbulence). Accordingly, the basic value of the laminar flame speed FLML is equal to ITA under the condition that the engine speed N is constant.
The value increases as C increases, and when the ITAC is constant, the value increases as the engine speed N increases.

In step 106, first, a predetermined table is retrieved from the swirl control valve opening to determine a swirl control valve opening coefficient SCADMP. Next, using the swirl control valve opening coefficient SCADMP, a swirl correction coefficient SCVTF is calculated by the following equation. SCVTF = SCADMP × SCVK + 1.0 (3) where SCVK is a conformity coefficient.

The swirl correction coefficient SCVTF is a value indicating the rate at which the flame speed increases due to increased turbulence when the swirl control valve is fully closed. Since this value is determined by the swirl control valve opening, it is 0 at the fully open position of the swirl control valve and 1 at the fully closed position. At the intermediate opening, the value calculated by linear interpolation is the swirl control valve opening coefficient SCAD.
Used as MP. Further, the adaptation coefficient SCVK is determined for each engine because it differs depending on the shape of the intake port of the engine.

In step 107, a predetermined table is searched from the water temperature Tw, and the water temperature correction coefficients TWHOS1,
Find WHOS2. In step 108, a predetermined table is retrieved from the target equivalence ratio TFBYA to obtain equivalence ratio correction coefficients RMDHS1 and RMDHS2. In step 109, first, the charging efficiency ITAC and the engine speed Ne
A predetermined map is searched for and the set EGR rate RATE
Find GR. This set EGR rate RATEGR is equal to EG
It is a value defined as R gas flow rate / (new air flow rate + EGR gas flow rate). Next, the set EGR rate RATE
Using the GR, a corrected EGR value EGRC is calculated by the following equation.

EGRC = RATEGR × HK (4) Here, HK is a correction coefficient (constant value), and is adapted for each engine in order to correct a deviation between the actual EGR rate and the set EGR rate. . In step 110, the filling efficiency ITAC,
Corrected EGR value EGRC, fuel weight equivalent coefficient FUELG,
Using the fresh air ratio ITAN, the total gas mass in the cylinder (more precisely, the value per unit cylinder volume) MA
Calculate SSC.

MASSC = ITAC × [1 + EGRC + FUELG + (1-ITAN) / ITAN] (5) In this equation, the second, third, and fourth terms on the right side represent EGR, air-fuel ratio, and self-residual gas, respectively. The effect on the total gas mass in the cylinder is considered.

In step 111, the flame propagation speed FLV is calculated by the following equation using the laminar flame speed basic value FLML, the equivalent ratio correction coefficient RMDHS2, the water temperature correction coefficient TWHOS2, the swirl correction coefficient SCVTF, and the like. FLV = FLML × RMDHS2 × TWHOS2 × (1-A2 × EGR0) + FLMT × SCVTF × A3 (6) where A2: flame speed correction coefficient A3: flame speed correction coefficient EGR0: EGR correction coefficient FLMT: turbulent flame Speed basic value (fixed value).

In this equation, the first term on the right-hand side is the flame speed when there is no swirl, and the second term on the right-hand side is the improvement in the flame speed by swirl. In the first term on the right side, RMDHS
No. 2 considers the effect of the air-fuel ratio (target equivalent ratio TFBYA) on the laminar flame speed, and TWHOS2 considers the effect of the cooling water temperature Tw on the laminar flame speed.

The EGR correction coefficient EGR of the first term on the right side
0 is a value necessary for reducing the flame speed when performing EGR, and is calculated from the set EGR rate and the fresh air rate. The coefficient A2 is a constant value and is suitable for each engine. The turbulent flame velocity basic value FLMT in the second term on the right side is a value (fixed value) determined by performing a fishhook experiment in a fully closed state of the swirl control valve. Therefore, when the swirl control valve is at an intermediate opening that is not at the fully closed position, the swirl correction coefficient SCVTF is used to calculate F
LMT is corrected for weight reduction. The coefficient A3 is a value proportional to the engine speed Ne.

In step 112, using the unburned gas density basic value DENS, the equivalent ratio correction coefficient RMDHS1, and the water temperature correction coefficient TWHOS1, the unburned gas density RO
Calculate U. ROU = DENS × RMDHS1 × TWHOS1 (7) In this equation, TWHOS1 gives the effect of the cooling water temperature Tw on the unburned gas density, and RMDHS1 gives the air-fuel ratio (target equivalent ratio TFBYA) on the unburned gas density. Consider the impact.

As described above, the total gas mass M in the cylinder
After calculating the ASSC, the flame speed FLV, and the unburned gas density ROU, the routine proceeds to step 113. In step 113,
Using these, the MBT operation value MBTCA is calculated by the following equation.
Calculate L [° BTDC]. MBTCAL = [B1 + A1 × MASSC / (ROU × FLV)] × B2-B3 (8) where B1: ignition delay time B2: conversion variable from time to crank angle B3: crank angle correction coefficient for MBTCAL calculation.

A1 = ρ0 × Vcyl, where ρ0 is the standard air density and Vcyl is the stroke volume. Therefore, A1 × M
ASSC is the total air weight in the cylinder. MBT is the ignition timing when the crank angle position at which the in-cylinder pressure at the time of combustion becomes the maximum is set at a predetermined crank angle (10 ° to 15 °) after the compression top dead center. In this case, conventionally, MBT is generally adopted as the basic ignition timing,
While a map of the basic ignition timing using the engine speed and the load as parameters is determined in advance by a suitable experiment, the MBT is quantified by an arithmetic expression here.

In the equation (8), the value obtained by dividing the total gas weight in the cylinder, A1 × MASSC, by the product of the unburned gas density ROU and the flame speed FLV is equal to the flame reaching all the unburned gas in the cylinder. In terms of time (burning time), the unit is logically [ms]. A value obtained by adding the ignition delay time B1 [ms] to the combustion time is converted into a crank angle unit by the conversion variable B2, thereby determining an ignition advance value at which MBT is obtained.

According to this equation, when the flame speed FLV is constant, the time required for combustion becomes longer as the total gas weight in the cylinder increases, so that the value of MBTCAL increases accordingly and the total gas weight in the cylinder increases. When is constant, the time required for combustion decreases as the flame speed FLV increases,
The value of MBTCAL moves accordingly to the retard side. Furthermore, even if the time required for combustion is constant, the crank angle section corresponding to that time varies depending on the rotation speed, and the higher the rotation speed, the more MBTCAL must be set on the advance side. Ne is proportional to Ne. B1,
B3 is a constant value and is suitable for each institution.

Here, MB using the basic ignition timing map
In the T control method, a large amount of adaptation experiments are required corresponding to the representative points of the engine speed and the load, whereas in the MBT control method using a unique calculation formula, the MBT control method is performed with few experiments.
The arithmetic expression can be adapted, the development period can be shortened, and the memory of the control unit is reduced, so that the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing a configuration of the present invention.

FIG. 2 is a system diagram of an internal combustion engine showing an embodiment of the present invention.

FIG. 3 is a flowchart of a fuel injection amount / injection timing calculation routine;

FIG. 4 is a flowchart of an injection timing setting routine.

FIG. 5 is a flowchart of a fuel injection control routine.

FIG. 6 is a flowchart of an ignition timing calculation routine.

FIG. 7 is a flowchart of an ignition timing setting routine.

FIG. 8 is a flowchart of an ignition control routine.

FIG. 9 is a diagram showing a state of switching from stratified combustion to homogeneous combustion.

FIG. 10 is a diagram showing a state of switching from homogeneous combustion to stratified combustion.

FIG. 11 shows an injection timing setting map.

FIG. 12 is a flowchart of an MBT calculation subroutine.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 internal combustion engine 3 intake passage 4 electrically controlled throttle valve 5 swirl control valve 6 fuel injection valve 7 spark plug 8 exhaust passage 10 electrically controlled EGR valve 20 control unit 21, 22 crank angle sensor 23 air flow meter 24 accelerator sensor

Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 41/34 F02D 41/34 F 43/00 301 43/00 301B 301J F02P 5/15 F02P 5/15 B

Claims (9)

[Claims] A fuel injection valve for directly injecting fuel into a combustion chamber of an engine, wherein the fuel is injected in an intake stroke in accordance with engine operating conditions, and a fuel is injected in a compression stroke. Method for determining whether to select homogeneous combustion or stratified combustion according to engine operating conditions in a direct injection spark ignition type internal combustion engine that controls switching between stratified combustion and combustion system determination results Means for setting the fuel injection method corresponding to the combustion method for each cylinder in accordance with the cylinder injection method, and setting the ignition timing for each cylinder to ignite according to the fuel injection method for each cylinder. A control device for a direct injection spark ignition type internal combustion engine, comprising: cylinder-specific ignition timing setting means for setting a timing. 2. The ignition timing setting means for each cylinder, when the ignition timing for each cylinder is set, from execution / non-execution of fuel injection for homogeneous combustion in each cylinder to ignition timing for homogeneous combustion in execution. 2. The control device for a direct injection spark ignition type internal combustion engine according to claim 1, wherein an ignition timing for stratified combustion is set when not in execution. 3. The fuel injection method setting means for each cylinder includes a homogeneous injection timing setting means for setting an injection timing for homogeneous combustion for each cylinder, and a stratification injection for setting an injection timing for stratified combustion for each cylinder. And a timing setting means separately, and at the injection timing for homogeneous combustion of each cylinder, execution / non-execution of fuel injection for homogeneous combustion is set in accordance with the determination result of the combustion system, for stratified combustion of each cylinder. At the injection timing, the fuel injection for stratified combustion is executed,
3. The control device for a direct injection spark ignition type internal combustion engine according to claim 1, wherein non-execution is set. 4. The cylinder-specific fuel injection method setting means includes a homogenous injection quantity calculating means for calculating an injection quantity for homogeneous combustion, and a stratified injection quantity calculating means for calculating an injection quantity for stratified combustion. The control device for a direct injection spark ignition type internal combustion engine according to any one of claims 1 to 3, wherein: 5. After determining the request for switching to homogeneous combustion, the injection amount for stratified combustion calculated last by the injection amount calculation device for stratification is held, and the injection amount for homogeneous combustion is calculated by the injection amount calculation device for homogenization. Only the injection amount is newly calculated, and after the determination of the request to switch to stratified combustion is made, the injection amount for homogeneous combustion last calculated by the injection amount calculation device for homogenization is held, and the injection amount calculation device for stratification is held. 5. The control device for a direct injection spark ignition type internal combustion engine according to claim 4, further comprising an injection amount calculation switching means for newly calculating only the injection amount for stratified combustion. 6. The cylinder-specific ignition timing setting means separately comprises a homogenization ignition timing calculation means for calculating ignition timing for homogeneous combustion, and a stratification ignition timing calculation means for calculating ignition timing for stratified combustion. Claim 1 to Claim 5
The control device for a direct injection spark ignition type internal combustion engine according to any one of the above. 7. After determining the request for switching to homogeneous combustion, the ignition timing for stratified combustion last calculated by the ignition timing calculation means for stratification is held, and the ignition timing for homogeneous combustion is calculated by the ignition timing calculation means for homogenization. Only the ignition timing is newly calculated, and after the determination of the request to switch to stratified combustion is made, the ignition timing for homogeneous combustion last calculated by the ignition timing calculation means for homogenization is held, and the ignition timing calculation means for stratification is retained. 7. The control device for a direct injection spark ignition type internal combustion engine according to claim 6, further comprising an ignition timing calculation switching means for newly calculating only the ignition timing for stratified combustion. 8. The ignition timing calculating means for homogenization calculates an ignition timing corresponding to MBT by a predetermined MBT calculation formula based on a parameter of an engine operating state. A control device for a direct injection spark ignition type internal combustion engine according to claim 7. 9. A stratification ignition timing calculating means for retrieving an ignition timing by referring to a predetermined map based on a parameter of an engine operation state. 8. The control device for a direct injection spark ignition type internal combustion engine according to any one of 8.