JPH1122506A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine capable of maintaining the air-fuel ratio at the target value, controlling the engine torque at the target value, and controlling the engine torque with good accuracy when the target air-fuel ratio is changed in the internal combustion engine. SOLUTION: When the target air-fuel ratio is changed, the target equivalence ratio tDML (the first target equivalence ratio) is divided by the first combustion efficiency ITAF1 for correction to obtain the second target equivalence ratio tDML', the second target equivalence ratio tDML' is phase-lag-corrected in response to the cylinder filling lag of the intake air quantity to obtain the third target equivalence ratio tDML", the third target equivalence ratio tDML" is multiplied by the second combustion efficiency ITAF2 for correction to obtain the fourth target equivalence ratio tDML"', and fuel is fed according to the fourth target equivalence ratio tDML"'.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an internal combustion engine, and more particularly, to a technique for improving torque control accuracy.

[0002]

2. Description of the Related Art A conventional torque control device for an internal combustion engine is disclosed, for example, in Japanese Patent Application Laid-Open No. Sho 62-110536. This torque control device is configured to directly search for a target throttle valve opening from a target engine torque and an engine rotation speed.

[0003] This is because a predetermined air-fuel ratio (for example, a stoichiometric air-fuel ratio) is set as a premise, and cannot be applied to an engine that variably controls the air-fuel ratio in accordance with the operating state. That is, in order to change the air-fuel ratio while maintaining the same engine operation performance, that is, the same engine speed and engine torque, it is necessary to change both the throttle valve opening and the fuel supply amount. When the fuel ratio is lean,
The required intake air amount increases compared to the case of the stoichiometric air-fuel ratio,
Although the required fuel supply is reduced, conventional devices cannot cope with this.

The following can be considered as a method of solving such a problem. That is, in response to the purpose of controlling the target air-fuel ratio and the target torque of the engine at the same time, the reference target air amount and the target equivalent ratio at the time of the stoichiometric air-fuel ratio are obtained from the accelerator opening and the engine rotation speed. The target air amount corresponding to the target air-fuel ratio is obtained, the target throttle valve opening is obtained, and the throttle valve is driven by the throttle valve opening control device, while the basic fuel injection is obtained from the engine speed and the actual intake air amount. The fuel injection valve is driven with the fuel injection pulse width obtained by correcting the pulse width with the target equivalent ratio and the invalid pulse width.

[0005] In this case, the amount of fuel required to generate the same engine torque is substantially constant irrespective of the air-fuel ratio, but the fuel consumption rate is improved during lean operation and the required fuel amount increases as the air-fuel ratio increases. Therefore, by calculating the target throttle valve opening in accordance with the second target intake air amount obtained by multiplying the target intake air amount by the fuel efficiency correction coefficient, it is possible to improve the fuel efficiency ratio with lean operation. Correction must be made accordingly.

[0006]

Incidentally, there is a difference in the torque generated between stratified combustion in which the fuel concentration distribution in the combustion chamber is heterogeneous and homogeneous combustion in which the fuel concentration distribution in the combustion chamber is homogeneous even at the same air-fuel ratio (see FIG. 1). 10). Therefore, in the above-described technology, when the target air-fuel ratio changes over two combustion patterns such as stratified combustion to homogeneous combustion, and homogeneous combustion to stratified combustion, the generated torque is accurately adjusted to the target torque. Can not control.

In view of the above problems, the present invention can control the engine torque to the target value while maintaining the air-fuel ratio at the target value, and more precisely when the target air-fuel ratio changes. An object of the present invention is to provide a control device for an internal combustion engine that can control engine torque.

[0008]

Therefore, according to the first aspect of the present invention, as shown in FIG. 1, throttle valve driving means for driving a throttle valve interposed in an intake system of an engine, and fuel for the engine are provided. Fuel supply means, accelerator operation amount detection means for detecting an accelerator operation amount, engine rotation speed detection means for detecting an engine rotation speed, intake air amount detection means for detecting an intake air amount to the engine, Target equivalent ratio calculating means for calculating a target equivalent ratio corresponding to a reference air-fuel ratio / a target air-fuel ratio based on the detected accelerator operation amount and the detected engine speed; First combustion efficiency calculating means for calculating a first combustion efficiency in response to the first combustion efficiency;
Second combustion efficiency calculating means for calculating a second combustion efficiency according to stratified combustion and homogeneous combustion of the engine; and correcting the target equivalent ratio by dividing the target equivalent ratio by the first combustion efficiency. First
Target equivalent ratio correcting means, second target equivalent ratio correcting means for performing a phase lag correction process on the target equivalent ratio corrected by the first target equivalent ratio correcting means, and the second target equivalent ratio correcting means Multiplying the target equivalence ratio corrected by the above with the second combustion efficiency to correct the target equivalence ratio, and a target intake calculating a target intake air amount corresponding to the target air-fuel ratio. Air amount calculation means, target throttle valve opening degree calculation means for calculating a target throttle valve opening degree based on the target intake air amount and the engine rotation speed, and a target throttle valve opening degree calculation means based on the detected intake air amount and the engine rotation speed. Calculating the basic fuel supply amount corresponding to the reference air-fuel ratio, and correcting the basic fuel supply amount based on the target equivalence ratio corrected by the third target equivalence ratio correction means to calculate the fuel supply amount. Fuel supply amount calculating means; Throttle valve opening control means for controlling the throttle valve driving means so that the throttle valve opening becomes the calculated target throttle valve opening, and the fuel supply amount becomes the calculated fuel supply amount. And a fuel supply amount control means for controlling the fuel supply means.

The invention according to claim 2 is characterized in that the target intake air amount calculating means calculates a target intake air amount corresponding to a target air-fuel ratio based on a target engine torque and an engine speed. . The invention according to claim 3 is characterized in that the target engine torque is calculated based on an accelerator operation amount and an engine rotation speed or by an external command.

According to a fourth aspect of the present invention, there is provided a fuel cell system comprising a reference target intake air amount calculating means for calculating a reference target intake air amount corresponding to a reference air-fuel ratio. The intake air amount is corrected to calculate a target intake air amount corresponding to the target air-fuel ratio.

According to a fifth aspect of the present invention, the reference target intake air amount calculating means calculates a reference target intake air amount corresponding to the reference air-fuel ratio based on the detected accelerator operation amount and the detected engine speed. The target intake air amount calculation means calculates the target intake air amount corresponding to the target air-fuel ratio by dividing the reference target intake air amount by the target equivalent ratio calculated by the target equivalent ratio calculation means. And

According to a sixth aspect of the present invention, the first combustion efficiency and the second combustion efficiency are calculated by switching between a value for stratified combustion and a value for homogeneous combustion at different timings. Features. The invention according to claim 7 is characterized in that the first
Is calculated by switching between a value for stratified combustion and a value for homogeneous combustion based on a switching command timing between stratified combustion and homogeneous combustion.

According to an eighth aspect of the present invention, the second combustion efficiency is calculated by switching between a value for stratified combustion and a value for homogeneous combustion based on the actual switching timing between stratified combustion and homogeneous combustion. It is characterized by being performed. According to a ninth aspect of the present invention, the actual switching timing between the stratified combustion and the homogeneous combustion is set based on the switching command timing between the stratified combustion and the homogeneous combustion and the target equivalent ratio corrected by the third target equivalent ratio correcting means. It is characterized by being performed.

According to a tenth aspect of the present invention, the first combustion efficiency is calculated using at least the target equivalence ratio calculated by the target equivalence ratio calculation means as a parameter. The invention according to claim 11 is characterized in that the second combustion efficiency is calculated using at least the target equivalence ratio corrected by the second target equivalence ratio correction means as a parameter.

According to a twelfth aspect of the present invention, the exhaust gas recirculation rate is added as the parameter. According to a thirteenth aspect of the present invention, in the internal combustion engine, the fuel injection valve directly injects fuel into a combustion chamber formed between the piston crown surface, the inner peripheral surface of the cylinder bore, and the lower surface of the cylinder head. It is a direct injection type spark ignition internal combustion engine that performs ignition.

According to a fourteenth aspect of the present invention, the intake air amount and the fuel supply amount are controlled so as to obtain a target engine torque and a target air-fuel ratio according to the operating state of the engine. The target equivalent ratio corresponding to the reference air-fuel ratio / the target air-fuel ratio is divided by the first combustion efficiency, and corrected by a phase delay between the target throttle valve opening and the actual throttle valve opening,
In addition, the calculation is performed by correcting the basic fuel supply amount based on the target equivalent ratio obtained by multiplying the second combustion efficiency.

The operation of the present invention will be described. In the invention according to claim 1, a target throttle valve opening is calculated based on a target intake air amount and an engine rotation speed corresponding to a target air-fuel ratio, and based on the detected intake air amount and an engine rotation speed. The calculated basic fuel supply amount is corrected based on the target equivalence ratio, and the fuel supply amount is calculated.

The throttle valve driving means is controlled so that the throttle valve opening becomes the calculated target throttle valve opening, and the fuel supply is performed so that the fuel supply amount becomes the calculated fuel supply amount. Means are controlled. Therefore, the intake air amount and the fuel supply amount by controlling the throttle valve opening are controlled to the respective target values, and the required target engine torque is obtained while maintaining the target air-fuel ratio and satisfying the exhaust purification performance and the like. Therefore, good driving performance can be secured.

When the target air-fuel ratio changes, a correction is made to divide the target equivalent ratio (first target equivalent ratio) by the first combustion efficiency to obtain a second target equivalent ratio. The second target equivalence ratio is corrected by a phase delay so as to correspond to the cylinder charging delay of the intake air amount, to obtain a third target equivalence ratio. Further, the third target equivalence ratio is changed to the second combustion efficiency. Is corrected to obtain a fourth target equivalence ratio, and fuel is supplied according to the fourth target equivalence ratio.

Accordingly, it is possible to prevent the occurrence of disturbance in the actual engine torque during the change of the air-fuel ratio, and to control the engine torque with high accuracy. Moreover, even when the target air-fuel ratio changes over two combustion patterns such as stratified combustion to homogeneous combustion and homogeneous combustion to stratified combustion, the torque step can be eliminated, and the generated torque is accurately controlled to the target torque. be able to.

In the invention according to claim 2, a target intake air amount corresponding to a target air-fuel ratio is calculated based on the target engine torque and the engine speed. In this case, in the invention according to claim 3, the target engine torque is calculated based on the accelerator operation amount and the engine rotation speed or by an external command. In the invention according to claim 4, when obtaining the target intake air amount for obtaining the target engine torque at the target air-fuel ratio, a reference target intake air amount for obtaining the target engine torque once at the reference air-fuel ratio is calculated. As a result of correcting the target intake air amount, the amount of data required for calculation can be reduced.

In this case, in the invention according to claim 5,
A reference target intake air amount corresponding to the reference air-fuel ratio is calculated based on the detected accelerator operation amount and the detected engine speed, and the reference target intake air amount is divided by the target equivalent ratio to obtain a target air-fuel ratio. Is calculated. In the invention according to claims 6 to 8, the first combustion efficiency is based on a switching command timing between stratified combustion and homogeneous combustion, and the second combustion efficiency is based on an actual switching timing between stratified combustion and homogeneous combustion. Are switched to a value for stratified combustion and a value for homogenous combustion, and as a result, the first combustion efficiency and the second combustion efficiency are different at different timings. Value.

In this case, in the invention according to claim 9,
The actual switching timing between the stratified combustion and the homogeneous combustion is set based on the switching command timing between the stratified combustion and the homogeneous combustion and the target equivalent ratio corrected by the third target equivalent ratio correcting means. In the invention according to claims 10 to 12, the first combustion efficiency is at least the target equivalence ratio and the exhaust gas recirculation rate calculated by the target equivalence ratio calculation means, and the second combustion efficiency is at least the second target efficiency. The target equivalence ratio and the exhaust gas recirculation rate corrected by the equivalence ratio correction means are respectively calculated using the parameters.

According to a thirteenth aspect of the present invention, the fuel is directly injected into the combustion chamber formed between the piston crown surface, the inner peripheral surface of the cylinder bore, and the lower surface of the cylinder head by the fuel injection valve, and the fuel is sparked by the spark plug. Ignite.
In the invention according to claim 14, the intake air amount and the fuel supply amount by controlling the throttle valve opening are controlled to respective target values, and the target air-fuel ratio is maintained while satisfying the exhaust purification performance and the like. A good target engine torque is obtained, and good driving performance can be secured.

Further, when the target air-fuel ratio changes, it is possible to prevent the occurrence of disturbance of the actual engine torque during the change of the air-fuel ratio and to control the engine torque with high accuracy. 2 from homogeneous combustion to stratified combustion
Even when the target air-fuel ratio changes over two combustion patterns, the torque step can be eliminated, and the generated torque can be accurately controlled to the target torque.

[0026]

According to the first and fourteenth aspects of the present invention,
By controlling the throttle valve opening, the intake air amount and the fuel supply amount can be controlled to their respective target values, and the required target engine torque is obtained while maintaining the target air-fuel ratio and satisfying the exhaust purification performance, etc. As well as ensuring good driving performance, the engine torque can be controlled accurately even when the target air-fuel ratio changes. In particular, two combustion patterns, from stratified combustion to homogeneous combustion and from homogeneous combustion to stratified combustion, can be obtained. Even when the target air-fuel ratio changes over the range, the torque step can be eliminated, and the generated torque can be accurately controlled to the target torque.

According to the second aspect of the present invention, the target intake air amount corresponding to the target air-fuel ratio can be easily calculated based on the target engine torque and the engine speed. In particular, claim 3
According to the present invention, the target engine torque can be easily calculated based on the accelerator operation amount and the engine rotation speed or by an external command. According to the fourth aspect of the present invention, when calculating the target intake air amount, the amount of data required for the calculation can be reduced.

In particular, according to the invention of claim 5, the target intake air amount corresponding to the target air-fuel ratio can be easily calculated from the reference target intake air amount and the target equivalence ratio. Claim 6-
According to the invention of claim 8, the first combustion efficiency is based on the switching command timing between stratified combustion and homogeneous combustion, and the second combustion efficiency is based on the actual switching timing between stratified combustion and homogeneous combustion. The first combustion efficiency and the second combustion efficiency are switched to a value for stratified combustion and a value for homogeneous combustion, respectively, at different timings, for example, by being calculated by switching between a value for combustion and a value for homogeneous combustion. As a result of the switching, even when the target air-fuel ratio changes over two combustion patterns such as from homogeneous combustion to stratified combustion, the torque step can be effectively eliminated.

In this case, according to the ninth aspect of the present invention,
The actual switching timing between stratified combustion and homogeneous combustion can be easily set based on the switching command timing between stratified combustion and homogeneous combustion and the target equivalent ratio corrected by the third target equivalent ratio correcting means. According to the tenth to twelfth aspects of the present invention, the first combustion efficiency and the second combustion efficiency are respectively set using the target equivalence ratio and the exhaust gas recirculation rate corrected by at least the second target equivalence ratio correction means as parameters. The calculation can be performed, and the generated torque can be more accurately controlled to the target torque.

According to the thirteenth aspect, the torque controllability of the direct injection type spark ignition internal combustion engine can be improved.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the attached drawings. FIG. 2 is a system diagram of a direct injection type spark ignition internal combustion engine as one embodiment of the internal combustion engine according to the present invention. In this figure, a combustion chamber 1 of each cylinder is formed between a cylinder head 2 and a piston 3. On the cylinder head 2 side, an ignition plug 4 is arranged at the center, and an intake port 6 communicating with an intake passage 5 and an exhaust port 8 communicating with an exhaust passage 7 are formed so as to surround the ignition plug 4. 9 and an exhaust valve 10 are provided.

A fuel injection valve (injector) 11 as a fuel supply means is provided for each cylinder so as to directly inject fuel into the combustion chamber 1, and the fuel is supplied from a fuel gallery common to all cylinders. You. Such a fuel injection valve 11 is
An electromagnetic fuel injection valve which is energized by an injection pulse signal from the control unit 12 to open, and is deenergized and closed by controlling the fuel injection amount (fuel supply amount) by the pulse width of the injection pulse signal. Is done.

The control unit 12 includes an engine rotation speed signal from a crank angle sensor 13, an accelerator opening signal from an accelerator sensor 14, and an air flow provided in the intake passage 5 for controlling a fuel injection amount and the like. Meter 1
5, a cooling water temperature signal from a water temperature sensor 17 mounted on the cylinder block 16, an oxygen concentration signal from an oxygen sensor (O ₂ sensor) 18 provided in the exhaust passage 7, and the like. ing.

Here, the accelerator sensor 14 as the accelerator operation amount detecting means detects the depression amount of the accelerator pedal depressed by the driver as an engine load (engine torque) desired by the driver. The crank angle sensor 13 as an engine rotation speed detecting means generates a position signal for each unit crank angle and a reference signal for each cylinder stroke phase difference, and measures the number of position signals generated per unit time, or By measuring the reference signal generation cycle, the engine speed can be detected.

The air flow meter 15 as the intake air amount detecting means detects the intake air amount to the engine (the intake air amount per unit time). A throttle valve 19 is interposed in the intake passage 5, and a throttle actuator 20 is provided as throttle valve opening drive means capable of electronically controlling the opening of the throttle valve 19.

The control unit 12 controls a throttle valve 19 via a throttle actuator 20 in accordance with an operation state detected based on signals from the sensors.
As described above, the fuel injection valve 11 is driven to control the fuel injection amount, the ignition timing is set, and the ignition plug 4 is ignited at the ignition timing.

FIG. 3 shows a functional configuration of an embodiment of the present invention. The reference target intake air amount calculation unit A constituting the reference target intake air amount calculation means includes an accelerator operation amount APS.
And the engine speed Ne are input, and a target engine torque corresponding to the operating state determined by the input value is set as a value corresponding to an intake air amount obtained at a stoichiometric air-fuel ratio as a reference air-fuel ratio. tTP is calculated.

Specifically, data of the reference target intake air amount tTP obtained experimentally in advance is used as the accelerator operation amount APS.
And the engine speed Ne are stored in a map using the parameters as parameters, and the map is searched for. As the reference target intake air amount tTP, in addition to the basic fuel injection amount (pulse width) corresponding to the intake air amount for each intake stroke, 1
The intake air amount itself for each intake stroke may be used.

The target equivalent ratio calculating section B constituting the target equivalent ratio calculating means includes an accelerator operation amount APS and an engine speed N.
e is input, and a target equivalence ratio tDML (first target equivalence ratio described later) is calculated in accordance with a target air-fuel ratio corresponding to the driving state. This target equivalent ratio tDML is basically calculated as reference air-fuel ratio (stoichiometric air-fuel ratio) / target air-fuel ratio, but this value may be corrected by the cooling water temperature Tw.

In a target intake air amount calculating section C as a target intake air amount calculating means, the reference target intake air amount tTP is calculated.
Is divided by the target equivalent ratio tDML to calculate a target intake air amount tTP 'corresponding to the target air-fuel ratio. The target intake air amount tTP 'corresponding to the target air-fuel ratio is an intake air amount determined so as to obtain the target engine torque at the target air-fuel ratio.

The target intake air amount tTP 'and the engine speed Ne are input to a target throttle valve opening calculating section D as a target throttle valve opening calculating means, and the target throttle valve opening tTPS is calculated. . The target throttle valve opening tTPS is such that the target intake air amount tTP 'can be obtained. The signal of the target throttle valve opening tTPS is input to the throttle actuator 20 via the throttle valve opening control unit H, whereby the throttle actuator 20
9 is driven to reach the target throttle valve opening tTPS.

Next, the fuel supply amount will be described. The basic fuel supply amount calculation unit E1 constituting the fuel supply amount calculation means
The fuel supply amount is calculated by the correction calculation unit E2.
An intake air amount Q per unit time detected by the air flow meter 3 and the engine rotation speed Ne are input to the basic fuel supply amount calculation unit E1, and based on these, one intake air at a stoichiometric air-fuel ratio (reference air-fuel ratio) is obtained. The basic fuel injection pulse width TP corresponding to the intake air amount per stroke is calculated.

The correction calculation unit E2 determines whether the basic fuel injection pulse width TP has a target equivalence ratio tDML "" (fourth described later).
), And calculates the effective fuel injection pulse width TE, adds the invalid pulse width TS corresponding to the battery voltage to the effective fuel injection pulse width TE, and calculates the final fuel injection pulse width TI. I do. Then, the fuel injection pulse width T
An injection pulse signal having I is output to the fuel injection valve 11 via the fuel supply control unit I, and the fuel injection valve 11 is driven to inject and supply a fuel amount corresponding to the target air-fuel ratio to the engine.

On the other hand, the target equivalence ratio tDML (first target equivalence ratio) calculated by the target equivalence ratio calculator B is corrected by dividing it by the first combustion efficiency ITAF1, and the second target equivalence ratio tDML is performed. 'And a second target equivalence ratio tDML' corrected by the first target equivalence ratio correction unit G1 as first target equivalence ratio correction means for obtaining '
Is corrected to a phase delay corresponding to the cylinder charging delay of the intake air amount or the like to obtain a third target equivalent ratio tDML ″.
A second target equivalence ratio corrector G2 as a target equivalence ratio corrector and a third target equivalence ratio tDML "corrected by the second target equivalence ratio corrector G2 have a second combustion efficiency IT.
Correction by multiplying by AF2 is performed to obtain the fourth target equivalent ratio tDM.
L "" as the third target equivalent ratio correction means for obtaining L "".
And a target equivalence ratio correction unit G3.

Here, the second target equivalent ratio correction unit G2
Performs a phase lag correction process on the second target equivalence ratio tDML '. This delays the change in the intake air amount due to a delay in the operation of the throttle valve, a delay in filling the cylinder with the intake air amount, and the like. In contrast, the amount of fuel supplied can follow the change in the target equivalence ratio with almost no delay, so the actual equivalence ratio is delayed with respect to the change in the target equivalence ratio, and the phase delay is corrected to match this delay. It is.

The first combustion efficiency ITAF1 and the second combustion efficiency ITAF2 are switched and set between a combustion efficiency for stratified combustion and a combustion efficiency for homogeneous combustion based on different timings. In the present embodiment, the first
Is switched between a value for stratified combustion and a value for homogeneous combustion based on the switching command timing between stratified combustion and homogeneous combustion, and is set to the second combustion efficiency ITAF1.
AF2 is switched and set between a value for stratified combustion and a value for homogeneous combustion based on the actual switching timing of stratified combustion and homogeneous combustion.

That is, as shown in FIG. 4, a combustion switching command section K1 as a combustion switching command section and a first combustion efficiency calculating section J1 as a first combustion efficiency calculating section are provided. The first combustion efficiency computing unit J1 switches the first combustion efficiency ITAF1 between a value for stratified combustion and a value for homogeneous combustion based on the combustion switching command flag FSTR from Is calculated based on the target equivalent ratio tDML calculated by the target equivalent ratio calculating unit B.

A combustion switching section K2 as combustion switching means
And a second combustion efficiency calculating section J2 as second combustion efficiency calculating means, and based on the combustion switching flag FSTRr from the combustion switching section K2, a second combustion efficiency calculating section J2 is provided.
Switches the second combustion efficiency ITAF2 between a value for stratified combustion and a value for homogeneous combustion, and outputs the second combustion efficiency ITAF2.
2 is calculated based on the target equivalence ratio (third target equivalence ratio tDML ″) corrected by the second target equivalence ratio correction unit G2.

FIGS. 5A and 5B show the first combustion efficiency I.
TAF1 is calculated using the target equivalence ratio tDML as a parameter, and the second combustion efficiency ITAF2 is calculated using the target equivalence ratio tDM.
FIG. 4 is a functional configuration diagram when a calculation is performed using L ″ as a parameter, and a first combustion efficiency calculation unit J1 calculates a target equivalent ratio tDM.
A map in which the first combustion efficiency ITAF1 is assigned to L, stratified combustion, and homogeneous combustion is provided, and the first combustion efficiency ITAF1 is searched from the map.

The second combustion efficiency calculation section J2 provides a map in which the target equivalence ratio tDML ″ and the second combustion efficiency ITAF2 for stratified combustion and homogeneous combustion are assigned, and the second combustion efficiency ITAF2 is calculated from the map. To search for. Here, in the combustion switching section K2, the actual switching timing between stratified combustion and homogeneous combustion is determined by the switching command timing between stratified combustion and homogeneous combustion and the corrected target equivalent ratio (fourth target equivalent ratio t).
DML "'').

The function of the combustion switching section K2 will be described with reference to the flowchart of FIG. Step 1 (in the figure, S
Abbreviated as 1. In the following, the determination is made on the previous combustion state. That is, it is determined whether the combustion switching flag FSTRr is 1 (stratified combustion), and the combustion switching flag FS
If TRr is 1 (stratified combustion), the process proceeds to step 2, and if the combustion switching flag FSTRr is not 1 (stratified combustion), that is, if the combustion is homogeneous, step 3 is performed.
Proceed to.

In step 2, the combustion switching command flag FS
It is determined whether or not TR is 1 (stratified combustion command). If the combustion switching command flag FSTR is 1 (stratified combustion command), the process returns to step 1 because combustion switching is unnecessary. The combustion switching command flag FSTR is 1 (stratified combustion command)
If not, that is, if there is a homogeneous combustion command, the process proceeds to step 4.

In step 4, the fourth target equivalent ratio tDM
It is determined whether or not L '''is equal to or greater than a predetermined value. If it is equal to or greater than the predetermined value, homogeneous combustion is performed, so the routine proceeds to step 5, and the combustion switching flag FSTRr is set to 0 (homogeneous combustion). If the fourth target equivalence ratio tDML "" is less than the predetermined value, the process returns to step 1 with stratified combustion.

On the other hand, in step 3 after it is determined that homogeneous combustion is currently performed, the combustion switching command flag FSTR is set to 0.
(Homogeneous combustion command) is determined, and if the combustion switching command flag FSTR is 0 (homogeneous combustion command), the process returns to step 1 because combustion switching is not performed. If the combustion switching command flag FSTR is not 0 (homogenous combustion command), that is, if there is a stratified combustion command, the process proceeds to step 6.

In step 6, the fourth target equivalent ratio tDM
It is determined whether or not L '''is equal to or less than a predetermined value. If it is equal to or less than the predetermined value, the process proceeds to step 7 because the stratified charge combustion is performed, and the combustion switching flag FSTRr is set to 1 (stratified charge combustion). If the fourth target equivalent ratio tDML "" exceeds the predetermined value, the process returns to step 1 while maintaining homogeneous combustion.

It should be noted that the determination value of the fourth target equivalent ratio tDML "" in steps 4 and 6 may be provided with hysteresis. FIG. 8A is a flowchart showing the function of switching between the combustion efficiency for stratification and the combustion efficiency for homogeneity in the first combustion efficiency calculation section. In step 11, the combustion switching command flag FSTR is set to 1 (stratified combustion command). )
Is determined, the combustion switching command flag FSTR
Is 1 (stratified combustion command), the routine proceeds to step 12, the ITAF1 is set for stratified combustion, and the combustion switching command flag FSTR is not 1 (stratified combustion command), that is, the combustion switching command flag FSTR. Is 0 (homogeneous combustion command)
If, the routine proceeds to step 13, where the ITAF1 is set for homogeneous combustion.

FIG. 8B is a flow chart showing the function of switching between the combustion efficiency for stratification and the combustion efficiency for homogeneity in the second combustion efficiency calculation section. In step 21, based on the result of the flow chart in FIG. And the combustion switching flag FS
It is determined whether TRr is 1 (stratified combustion command),
If the combustion switching flag FSTRr is 1 (stratified combustion command), the routine proceeds to step 22, the ITAF 2 is set for stratified combustion, and the combustion switching flag FSTRr is not 1 (stratified combustion command), that is, combustion switching. If the flag FSTRr is 0 (homogeneous combustion command), the routine proceeds to step 23, where ITAF1 is set for homogeneous combustion.

FIG. 9 shows the combustion switching command flag FS shown in FIG.
TR and target equivalence ratio (tDML, tDML ', tDML ") of combustion switching flag FSTRr, (B), and final and target equivalence ratios of combustion efficiency ITAF1, ITAF2, and (D) in (C) FIG. 9 is a time chart showing the relationship between tDML (the fourth target equivalent ratio tDML ″ ′ in the present invention) and the engine torque of the conventional and the present invention of (E) based on the time change. This shows the lapse of time when the mode switches to combustion.

That is, in (A), the combustion switching command flag FSTR changes from 1 (stratified combustion) to 0 (homogeneous combustion), and after this change, the combustion switching flag FSTRr changes from 1 (stratified combustion) to 0 (stratified combustion). (Homogeneous combustion). Therefore, in (C), the first combustion efficiency ITAF1 is:
The combustion switching command flag FSTR is changed from 1 (stratified combustion) to 0
At the timing of the change of (homogeneous combustion), the value is switched from stratified to homogenous, and the second combustion efficiency ITAF2 is changed when the combustion switching flag FSTRr changes from 1 (stratified combustion) to 0 (homogeneous combustion). The value has been switched from stratified to homogeneous.

As described above, the second combustion efficiency ITAF2 is
As a result of the value switching from stratified to homogeneous, the target equivalent ratio t
DML (first target equivalent ratio) is converted to first combustion efficiency ITAF
The second target equivalent ratio tDML 'obtained by dividing by 1 is further corrected by a third target equivalent ratio tDML''obtained by further correcting the phase delay.
Fourth obtained by multiplying the combustion efficiency ITAF2
The target equivalence ratio tDML "" of the second combustion efficiency ITAF2 from stratification to homogenization is shown in FIG.
Changes sharply and then gradually increases (the difference in combustion efficiency becomes lean at the time of combustion switching).

Such a fourth target equivalent ratio tDM
Due to the change of L "", the portion of the engine torque which has conventionally occurred does not exist as shown in FIG. 9E, and the engine torque is controlled to be flat in the control of the present invention. According to the embodiment of the present invention described above, the intake air amount and the fuel supply amount by controlling the throttle valve opening are
By controlling to the respective target values, it is possible to obtain a required target engine torque and maintain a good driving performance while maintaining the target air-fuel ratio and satisfying the exhaust purification performance and the like.

When the target air-fuel ratio changes, a correction for dividing the target equivalence ratio tDML (first target equivalence ratio) by the first combustion efficiency ITAF1 is performed, and the second target equivalence ratio tAF is calculated.
DML ', and this second target equivalent ratio tDML'
Phase delay correction to obtain a third target equivalent ratio tDML ″,
Further, the third target equivalence ratio tDML "is corrected by multiplying the third target equivalence ratio tDML" by the second combustion efficiency ITAF2 to obtain a fourth target equivalence ratio tDML "". Since the fuel is supplied in accordance with ″ ″, it is possible to prevent the occurrence of disturbance of the actual engine torque during the change of the air-fuel ratio, and to control the engine torque with high accuracy.

Further, even when the target air-fuel ratio changes over two combustion patterns such as stratified combustion to homogeneous combustion and homogeneous combustion to stratified combustion, the torque step can be eliminated as described with reference to FIG. , The generated torque can be accurately controlled to the target torque.

In the above-described embodiment, an example has been described in which the first combustion efficiency is calculated using the target equivalent ratio as a parameter, and the second combustion efficiency is calculated using the target equivalent ratio as a parameter. May be calculated using the target equivalent ratio and the exhaust gas recirculation rate (EGR rate) as parameters, and the second combustion efficiency may be calculated using the target equivalent ratio and the exhaust gas recirculation rate (EGR rate) as parameters.

FIG. 6 is a functional block diagram of this embodiment. The first combustion efficiency calculating section J1 calculates the first combustion efficiency ITAF based on the target equivalent ratio and the EGR rate for each of stratified and homogeneous combustion.
Two maps to which 1 is assigned are provided, each map is switched depending on the combustion state, and the first combustion efficiency ITAF1 is searched from the switched map. In addition, the second combustion efficiency calculation unit K2 provides two maps in which the second combustion efficiency ITAF2 is assigned with the target equivalent ratio and the EGR rate for each of stratified and homogeneous combustion, and maps each map according to the combustion state. Switching, the second combustion efficiency ITAF from the switched map
Search for 2.

In this embodiment, the first combustion efficiency and the second combustion efficiency are calculated using not only the target equivalence ratio but also the exhaust gas recirculation rate (EGR rate) as a parameter. The target torque can be controlled well.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to claims of a control device for an internal combustion engine of the present invention.

FIG. 2 is a system diagram of an embodiment of the control device for the internal combustion engine according to the embodiment;

FIG. 3 is a functional configuration diagram of an embodiment of the present invention.

FIG. 4 is a functional configuration diagram of a combustion efficiency calculation in the embodiment of the present invention;

FIGS. 5A and 5B show first combustion efficiency and second combustion efficiency;
Configuration diagram for calculating the combustion efficiency of a fuel using the target equivalent ratio as a parameter

FIGS. 6A and 6B show first combustion efficiency and second combustion efficiency;
Configuration diagram when the combustion efficiency of the fuel is calculated using the target equivalent ratio and the EGR rate as parameters.

FIG. 7 is a flowchart illustrating a function of a combustion switching unit.

8A and 8B are flowcharts showing a function of switching between combustion efficiency for stratification and combustion efficiency for homogenization.

FIG. 9 is a time chart for explaining control contents of the present invention.

FIG. 10 is a characteristic diagram illustrating a conventional problem.

[Explanation of symbols]

 Reference Signs List 1 combustion chamber 11 fuel injection valve (injector) 12 control unit 13 crank angle sensor 14 accelerator sensor 15 air flow meter 19 throttle valve 20 throttle actuator A reference target intake air amount calculation unit B target equivalent ratio calculation unit C target suction air amount calculation unit D Target throttle valve opening calculator E1 Basic fuel supply amount calculator E2 Correction calculator G1 First target equivalent ratio corrector G2 Second target equivalent ratio corrector G3 Third target equivalent ratio corrector J1 First Combustion efficiency calculation unit J2 Second combustion efficiency calculation unit K1 Combustion switching command unit K2 Combustion switching unit

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 43/00 301 F02D 43/00 301J 301N 45/00 324 45/00 324 (72) Inventor Taiyo Yoshino Kanagawa, Yokohama, Kanagawa 2 Takara-cho, Nissan Motor Co., Ltd.

Claims (14)

[Claims] A throttle valve driving means for driving a throttle valve interposed in an intake system of the engine; a fuel supply means for supplying fuel to the engine; an accelerator operation amount detecting means for detecting an accelerator operation amount; Engine rotation speed detection means for detecting a rotation speed; intake air amount detection means for detecting an intake air amount to the engine; and a reference air / fuel ratio based on the detected accelerator operation amount and the detected engine rotation speed. Target equivalence ratio calculation means for calculating a target equivalence ratio corresponding to a target air-fuel ratio; first combustion efficiency calculation means for calculating a first combustion efficiency according to stratified combustion and homogeneous combustion of the engine; A second combustion efficiency calculating means for calculating a second combustion efficiency according to the combustion and the homogeneous combustion; and a first correcting the target equivalence ratio by dividing the target equivalence ratio by the first combustion efficiency. Target equivalent ratio correction means and A second target equivalent ratio corrector that performs a phase delay correction process on the target equivalent ratio corrected by the first target equivalent ratio corrector; and a target equivalent ratio corrected by the second target equivalent ratio corrector. Third target equivalence ratio correction means for multiplying the second combustion efficiency to correct the target equivalence ratio, target intake air amount calculation means for calculating a target intake air amount corresponding to a target air-fuel ratio, and the target intake Target throttle valve opening calculating means for calculating a target throttle valve opening based on the air amount and the engine speed; and a basic air-fuel ratio corresponding to the reference air-fuel ratio based on the detected intake air amount and the engine speed. A fuel supply amount calculating unit that calculates a fuel supply amount and corrects the basic fuel supply amount based on a target equivalent ratio corrected by the third target equivalent ratio correction unit to calculate a fuel supply amount; Valve opening Throttle valve opening control means for controlling the throttle valve driving means so as to have the calculated target throttle valve opening degree, and so that the fuel supply amount becomes the calculated fuel supply amount.
A control device for an internal combustion engine, comprising: a fuel supply amount control means for controlling the fuel supply means. 2. The internal combustion engine according to claim 1, wherein said target intake air amount calculating means calculates a target intake air amount corresponding to a target air-fuel ratio based on a target engine torque and an engine speed. Engine control device. 3. The control device for an internal combustion engine according to claim 2, wherein said target engine torque is calculated based on an accelerator operation amount and an engine rotation speed or by an external command. 4. A reference target intake air amount calculating means for calculating a reference target intake air amount corresponding to a reference air-fuel ratio, wherein the target intake air amount calculating means corrects the reference target intake air amount. 2. The control device for an internal combustion engine according to claim 1, wherein a target intake air amount corresponding to the target air-fuel ratio is calculated by the calculation. 5. A reference target intake air amount calculating means calculates a reference target intake air amount corresponding to a reference air-fuel ratio based on a detected accelerator operation amount and a detected engine speed. 5. The amount calculating means for calculating a target intake air amount corresponding to a target air-fuel ratio by dividing the reference target intake air amount by a target equivalent ratio calculated by the target equivalent ratio calculating means. Internal combustion engine control device. 6. The first combustion efficiency and the second combustion efficiency are:
The control device for an internal combustion engine according to any one of claims 1 to 5, wherein the calculation is performed by switching between a value for stratified combustion and a value for homogeneous combustion at different timings. 7. The first combustion efficiency is calculated by switching between a value for stratified combustion and a value for homogeneous combustion based on a switching command timing between stratified combustion and homogeneous combustion. A control device for an internal combustion engine according to any one of claims 1 to 6. 8. The method according to claim 1, wherein the second combustion efficiency is calculated by switching between a value for stratified combustion and a value for homogeneous combustion based on an actual switching timing between stratified combustion and homogeneous combustion. The control device for an internal combustion engine according to any one of claims 1 to 7, wherein: 9. An actual switching timing between the stratified combustion and the homogeneous combustion is set based on a switching command timing between the stratified combustion and the homogeneous combustion and a target equivalent ratio corrected by a third target equivalent ratio correcting means. The control device for an internal combustion engine according to claim 8, wherein: 10. The method according to claim 1, wherein the first combustion efficiency is calculated using at least the target equivalence ratio calculated by the target equivalence ratio calculation means as a parameter. Internal combustion engine control device. 11. The method according to claim 1, wherein the second combustion efficiency is calculated using at least a target equivalence ratio corrected by a second target equivalence ratio correction unit as a parameter.
0. The control device for an internal combustion engine according to any one of 0. 12. The control device for an internal combustion engine according to claim 10, wherein an exhaust gas recirculation rate is added as the parameter. 13. The internal combustion engine injects fuel directly into a combustion chamber formed between a piston crown surface, a cylinder bore inner peripheral surface, and a cylinder head lower surface by a fuel injection valve, and performs spark ignition by a spark plug. The control device for an internal combustion engine according to any one of claims 1 to 12, wherein the control device is a direct injection type spark ignition internal combustion engine. 14. An intake air amount and a fuel supply amount are controlled so as to obtain a target engine torque and a target air-fuel ratio according to an operation state of the engine, and the fuel supply amount is determined by a reference air-fuel ratio / a target air-fuel ratio. The target equivalence ratio corresponding to the fuel ratio is divided by the first combustion efficiency, corrected by the phase delay between the target throttle valve opening and the actual throttle valve opening, and multiplied by the second combustion efficiency. A control device for an internal combustion engine, which is calculated by correcting a basic fuel supply amount based on a target equivalence ratio obtained as described above.