JP4036202B2 - Engine torque control device - Google Patents

Description

The present invention relates to an engine torque control device, and more specifically , a torque control device configured to control an intake air amount and a fuel supply amount of an engine based on a target engine torque and a target equivalence ratio according to an operating state of the engine. About.

As a conventional engine torque control device, for example, there is one disclosed in Patent Document 1.
In this system, the target throttle valve opening is obtained from the target engine torque and the engine speed, and the throttle actuator is controlled based on the target throttle valve opening.
Japanese Patent Laid-Open No. 62-110536

  However, in the conventional engine torque control device, the target throttle valve opening is directly searched from the target engine torque and the engine rotational speed. This is a constant equivalence ratio (for example, stoichiometric air-fuel ratio). Therefore, there is a problem that it cannot be applied as it is to an engine in which the equivalence ratio is variably controlled according to the operating state.

  Further, in recent years, a fuel injection valve that directly injects fuel into the combustion chamber of the engine is provided, and the homogeneous combustion performed by injecting fuel in the intake stroke and the stratified combustion performed by injecting fuel in the compression stroke A spark-ignition direct injection engine has been developed that can be switched according to the engine, but in such an engine, the generated torque differs at the same equivalence ratio at the time of homogeneous combustion and stratified combustion. Only by changing the air amount control value, the target engine torque cannot be obtained with high accuracy, and there is a problem that a torque step is produced when switching between homogeneous combustion and stratified combustion.

  The present invention has been made in view of the above problems. In the spark ignition direct injection engine in which the combustion state is switched along with the change of the target equivalent ratio, the target equivalent ratio and the combustion state are changed / switched. Another object of the present invention is to provide a torque control device that can control the target engine torque with high accuracy and to avoid the occurrence of a torque step when switching between homogeneous combustion and stratified combustion.

Therefore, according to the first aspect of the present invention, the target engine torque and the target equivalent ratio are calculated according to the accelerator operation amount and the engine speed, and the target intake air amount is calculated based on the target engine torque and the target equivalent ratio. The target engine torque is calculated even when switching between homogeneous combustion and stratified combustion in response to the difference in generated torque due to the difference in combustion efficiency due to homogeneous combustion and stratified combustion even if the equivalent ratio is the same. Thus, a combustion efficiency correction value is set according to the homogeneous equivalence combustion and stratified combustion and the target equivalence ratio, and the target intake air amount is corrected with the combustion efficiency correction value. The engine intake air amount is controlled based on the target intake air amount corrected with the combustion efficiency correction value, and the fuel supply amount to the engine is controlled based on the target equivalence ratio and the engine intake air amount. To do.

According to such a configuration, the target intake air quantity is calculated based on the accelerator operation amount and the engine target engine torque is calculated in accordance with the rotational speed and the target equivalent ratio, even with the same equivalent ratio homogeneous combustion, stratified In order to obtain the target engine torque regardless of whether the combustion is homogeneous combustion or stratified combustion in response to the difference in generated torque due to the difference in combustion efficiency due to combustion, The target intake air amount is corrected based on the combustion efficiency correction value set according to the target equivalence ratio, and the actual intake air amount is controlled based on the corrected target intake air amount. The control of the intake air amount according to the target intake air amount is performed, for example, by obtaining a target throttle valve opening corresponding to the target intake air amount and controlling the throttle actuator based on the target throttle valve opening.

On the other hand, the fuel supply to the engine is controlled based on the target equivalence ratio and the intake air amount of the engine.

In the invention according to claim 2, the correction means stores in advance two for homogeneous combustion and one for stratified combustion as a table of combustion efficiency correction values according to a target equivalence ratio, and of these two tables, The target intake air amount is corrected based on the combustion efficiency correction value retrieved from the table corresponding to the combustion state at that time.

According to such a configuration, in the configuration in which the target intake air amount is corrected based on the difference in combustion efficiency depending on the target equivalence ratio, two tables for homogeneous combustion and stratified combustion are stored in advance as tables storing the combustion efficiency correction values. Even when the target equivalence ratio is the same, different combustion efficiency correction values are obtained depending on the table to be referred to, and the target intake air amount is corrected.

According to a third aspect of the present invention, the correction means corrects the combustion efficiency correction value corresponding to the target equivalence ratio with different gains for homogeneous combustion and stratified combustion, and based on the corrected combustion efficiency correction value. The target intake air amount is corrected. According to this configuration, the same combustion efficiency correction value is set according to the target equivalence ratio regardless of the combustion state, but the combustion efficiency correction value according to the target equivalence ratio is set to a gain that is different between homogeneous combustion and stratified combustion. In order to correct the target intake air amount, the target intake air amount is corrected with a combustion efficiency correction value that differs depending on whether the combustion is substantially homogeneous combustion or stratified combustion. .

According to a fourth aspect of the invention, the target intake air amount is calculated based on the target engine torque corrected based on the pumping loss torque corresponding to the target equivalent ratio. According to this configuration, different pumping loss torques are added to the target engine torque according to the target equivalence ratio, and the target intake air amount is calculated based on the target engine torque to which the pumping loss torque is added.

According to the first aspect of the present invention, the target intake air amount corresponding to the target engine torque and the target equivalence ratio is set to cope with the variable control of the target equivalence ratio, and even with the same equivalence ratio, homogeneous combustion, stratification Corresponding to the difference in generated torque due to the difference in combustion efficiency due to combustion, in order to obtain the target engine torque even if switching between homogenous combustion and stratified combustion is performed, separate the homogeneous combustion and stratified combustion from the target equivalent Since the target intake air amount is corrected based on the combustion efficiency correction value set in accordance with the ratio, the target intake air amount corresponding to the difference in combustion efficiency between homogeneous combustion and stratified combustion can be set. There is an effect that it is possible to avoid the occurrence of a torque step due to switching between combustion and stratified combustion.

According to the second aspect of the present invention, the target equivalent ratio is obtained by retrieving the combustion efficiency correction value for dealing with the difference in combustion efficiency due to the difference in target equivalent ratio from different tables for stratified combustion and homogeneous combustion. In addition, there is an effect that the target intake air amount can be accurately corrected in accordance with the combustion efficiency corresponding to the difference between stratification and homogeneous combustion.

According to the third aspect of the invention, the target equivalent ratio is corrected by correcting the combustion efficiency correction value for dealing with the difference in combustion efficiency due to the difference in target equivalent ratio with a gain different between stratified combustion and homogeneous combustion. In addition, there is an effect that the correction of the target intake air amount for coping with the difference between stratification and homogeneous combustion can be easily executed. According to the fourth aspect of the invention, the target intake air amount is calculated based on the target engine torque to which different pumping loss torques are added according to the target equivalence ratio, so that the target engine torque requested by the driver can be accurately obtained. There is an effect that it is obtained.

Embodiments of the present invention will be described below.
FIG. 1 is a system configuration diagram of an engine in the embodiment.
In FIG. 1 , an accelerator opening sensor 1 serving as an accelerator operation amount detection means detects an accelerator operation amount APS corresponding to an accelerator pedal depression amount by the driver as an engine load (engine torque) desired by the driver.

  The crank angle sensor 2 as an engine rotation speed detection means outputs a position signal POS for each unit crank angle and a reference signal REF for each stroke phase difference between cylinders, and measures the number of occurrences of the position signal POS per unit time. The engine speed NE can be detected by measuring the generation period of the reference signal REF.

The air flow meter 3 detects an intake air amount (intake air amount per unit time = intake air flow rate) Q of the engine 4.
The water temperature sensor 5 detects the cooling water temperature TW of the engine 4.
The engine 4 is provided with an electromagnetic fuel injection valve 6 that is driven to open by an injection pulse signal and directly injects fuel into the combustion chamber, and an ignition plug 7 that is attached to the combustion chamber and performs ignition. The intake passage 8 is provided with a throttle valve 9, and a throttle valve control device 10 for controlling the throttle valve 9 to a target throttle opening by driving the throttle valve 9 with a throttle actuator such as a motor.

  Detection signals from the various sensors are input to a control unit 11 having a built-in microcomputer, and the control unit 11 detects the throttle valve control device 10 according to an operating state detected based on signals from the various sensors. The opening of the throttle valve 9 is controlled via the valve, the fuel injection valve 6 is driven to control the fuel supply amount (air-fuel ratio), the ignition timing is set, and the spark plug 7 is ignited at the ignition timing. Take control.

Here, the state of fuel supply amount control and throttle opening control by the control unit 11 will be described based on the control block diagram of FIG.
The accelerator operation amount APS and the engine rotational speed NE are input to the engine torque equilibrium value calculation unit A, and an engine torque equilibrium value (target engine torque) tTEO is previously set using the accelerator operation amount APS and the engine rotational speed NE as parameters. An engine torque equilibrium value (target engine torque) tTEO is calculated with reference to the stored map (target engine torque calculating means) .

  The engine torque balance value (target engine torque) tTEO calculated by the engine torque balance value calculation unit A is input to the target intake air amount calculation unit B, and the engine torque balance value (target engine torque) tTEO and the engine speed are preliminarily input. With reference to a map storing the target intake air amount TTPO with NE as a parameter, the target intake air amount TTPO corresponding to the reference equivalence ratio (for example, the theoretical air-fuel ratio) is calculated.

As the target intake air amount TTPO, the intake air amount per intake stroke itself, the basic fuel injection amount (pulse width) corresponding to the intake air amount per intake stroke, and the air flow meter 3 are detected. The amount of intake air per unit time may be used.
The engine torque balance value calculation unit A and the target intake air amount calculation unit B constitute the target intake air amount calculation unit in the present embodiment. The configuration may be such that the part B is integrated and the target intake air amount TTPO is directly calculated from the accelerator operation amount APS and the engine rotational speed NE.

On the other hand, the accelerator operation amount APS and the engine speed NE are also input to the target equivalence ratio calculation unit C, similarly to the engine torque balance value calculation unit A, and the accelerator operation amount APS and the engine rotation speed NE are previously set. The target equivalent ratio tDML is calculated with reference to a map storing the target equivalent ratio tDML as a parameter (target equivalent ratio calculating means) . The target equivalence ratio tDML is calculated using parameters such as the accelerator operation amount APS and the engine rotational speed NE, the cooling water temperature, the time after starting, the vehicle speed, the acceleration, the auxiliary load during idling, and the master back negative pressure. It may be a configuration.

The target equivalent ratio tDML calculated by the target equivalent ratio calculation unit C is input to the combustion efficiency correction rate calculation unit D. In addition to the target equivalent ratio tDML, the combustion efficiency correction factor calculation unit D receives a determination signal indicating which of stratified combustion and homogeneous combustion is selected.
As described above, the engine 4 according to the present embodiment includes the fuel injection valve 6 that directly injects fuel into the combustion chamber. The engine 4 injects fuel in the intake stroke, and injects fuel in the compression stroke. It is configured to be able to switch between stratified combustion capable of combustion at an ultra lean equivalent ratio performed by injection (combustion state switching means), and the target equivalent ratio calculation unit C is premised on switching control between the homogeneous combustion and stratified combustion. The equivalence ratio within the equivalence ratio control range in each combustion state is set. In practice, in the target equivalence ratio calculation unit C, the target equivalence ratio tDML is set and the homogeneous combustion and stratified combustion are performed. Which one to select is determined.

In the combustion efficiency correction rate calculation unit D, two tables, a table for homogeneous combustion and a table for stratified combustion, are stored as the tables storing the combustion efficiency correction rate (combustion efficiency correction value) ITAF in advance according to the target equivalent ratio tDML. The type is stored. This is because even when the equivalence ratio is the same, the generated torque differs depending on the difference in combustion efficiency between stratified combustion and homogeneous combustion, and stratified combustion is performed for the same target equivalent ratio tDML in the switching control between stratified combustion and homogeneous combustion. This is because there are cases where selection is made and homogeneous combustion is selected (see FIG. 8).

Then, one of the two tables is selected from the determination signal of the homogeneous and stratified combustion, and the combustion efficiency correction rate ITAF corresponding to the target equivalent ratio tDML at that time is searched in the selected table.
The combustion efficiency correction factor ITAF is multiplied by the target intake air amount TTPO calculated by the target intake air amount calculation unit B ( correction means ), and the target intake air amount TTP1 obtained by the multiplication correction is Dividing by the target equivalent ratio tDML ( correcting means ), the final target intake air amount TTP2 is set.

  The target throttle valve opening calculation unit E is inputted with the engine intake speed NE together with the target intake air amount TTP2, and a map in which the target throttle valve opening TTPS is stored in advance using the target intake air amount TTP2 and the engine rotation speed NE as parameters. , And the target throttle valve opening TTPS corresponding to the target intake air amount TTP2 and the engine rotational speed NE at that time is calculated.

The target throttle valve opening TTPS is input to the throttle valve control device 10, and the target intake air amount TTP2 is obtained by controlling the throttle actuator so as to become the target throttle valve opening TTPS (intake). Air quantity control means).
On the other hand, the actual intake air amount Q detected by the air flow meter 3 and the engine speed NE are input to the basic fuel supply amount calculation unit F, and the basic fuel supply corresponding to the reference equivalence ratio (for example, the theoretical air-fuel ratio) is input. The amount (basic injection pulse width) TP is calculated.

  When an intake pressure sensor is provided instead of the air flow meter 3, the basic fuel supply amount (basic injection pulse width) TP is determined based on the intake pressure detected by the intake pressure sensor and the engine speed NE. It is also possible to calculate the basic fuel supply amount TP based on the throttle valve opening and the engine speed.

In the correction calculation unit G, the basic fuel supply amount (basic injection pulse width) TP is corrected by the target equivalent ratio tDML, the correction amount TS by the battery voltage, etc., and the final fuel supply amount (fuel injection pulse width) TI. Is calculated. The control unit 11 outputs an injection pulse signal having a pulse width corresponding to the fuel supply amount (fuel injection pulse width) TI to the fuel injection valve 6 at an injection timing corresponding to homogeneous combustion and stratified combustion (fuel supply control). Means) .

The flowchart of FIG. 3 shows the control contents shown in the control block diagram of FIG . 2. First, in S1, the target engine torque (engine torque equilibrium value) is determined based on the accelerator operation amount APS and the engine speed NE. ) Calculate tTEO.
In S2, the target equivalence ratio tDML is calculated based on the accelerator operation amount APS and the engine speed NE.

In S3, the target intake air amount TTPO is calculated based on the target engine torque tTEO and the engine speed NE (target intake air amount calculating means).
In S4, it is determined whether or not the stratified combustion state is set. If stratified combustion is being performed, the process proceeds to S5, and the combustion efficiency correction rate ITAF for stratified combustion is calculated. If so, the process proceeds to S6 to calculate the combustion efficiency correction factor ITAF for homogeneous combustion.

In S7, the target intake air amount TTPO is multiplied by the combustion efficiency correction factor ITAF to calculate the target intake air amount TTP1 subjected to the combustion efficiency correction according to the combustion state and the target equivalence ratio tDML ( correction means ). .
In S8, the target intake air amount TTP1 is divided by the target equivalent ratio tDML to calculate a target intake air amount TTP2 corresponding to the target equivalent ratio tDML ( correcting means ).

In S9, the target throttle valve opening TTPS is calculated based on the target intake air amount TTP2 and the engine speed NE, and this is output to the throttle valve control device 10 (intake air amount control means).
In S10, the basic fuel supply amount TP is calculated based on the intake air amount Q, the engine speed NE and the reference equivalence ratio at that time. In S11, the basic fuel supply amount TP is corrected by the target equivalence ratio tDML or the like. The final fuel supply amount TI is calculated. In S12, an injection pulse signal having a pulse width corresponding to the fuel supply amount TI is output to the fuel injection valve 6 at an injection timing corresponding to homogeneous and stratified combustion.

According to the above configuration, even if the equivalence ratio is the same, the target intake air amount is corrected in response to the difference in generated torque between homogeneous combustion and stratified combustion, so a torque step occurs when switching from homogeneous combustion to stratified combustion. Can be avoided.
FIG. 4 is a control block diagram showing the second embodiment. Only the configuration shown below is different from the first embodiment shown in FIG . That is, a pumping loss torque calculator H that calculates a pumping loss torque (pump loss torque) TpI corresponding to the target equivalent ratio tDML calculated by the target equivalent ratio calculator C is provided. The calculated pumping loss torque TpI is added to the engine torque balance value (target engine torque) tTEO calculated by the engine torque balance value calculation unit, and the target intake air amount is calculated based on the target engine torque TTC after the addition correction. The calculation unit B is configured to calculate the target intake air amount TTPO.

Here, similarly to the first embodiment shown in FIGS. 2 and 3 , the target intake air amount TTPO is corrected according to the target equivalent ratio tDML and corrected by the combustion efficiency correction factor ITAF. However, since the pumping loss torque TpI is added to the target engine torque tTEO, the correction by the combustion efficiency correction factor ITAF is a correction obtained by subtracting the pumping loss reduction due to lean combustion (for example, a correction such as an increase in thermal efficiency). ).

The flowchart of FIG. 5 shows the control contents shown in the control block diagram of FIG . 4. First, at S21, an engine torque equilibrium value (target engine torque) tTEO is calculated, and at S22, the target equivalent ratio tDML is calculated. Is calculated.
In S23, a pumping loss torque TpI is calculated based on the target equivalent ratio tDML.

In S24, the pumping loss torque TpI is added to the target engine torque tTEO to obtain a corrected target engine torque TTC.
In S25, the target intake air amount TTPO is calculated based on the target engine torque TTC.
In S26, the target intake air amount TTPO is divided by the target equivalent ratio tDML to calculate a target intake air amount TTP1 corresponding to the target equivalent ratio tDML.

In S27, it is determined whether or not stratified combustion is being performed. If stratified combustion is being performed, the process proceeds to S28, and a combustion efficiency correction factor ITAF for stratified combustion is calculated. If so, the process proceeds to S29 to calculate the combustion efficiency correction factor ITAF for homogeneous combustion.
In S30, the target intake air amount TTP2 is calculated by multiplying the target intake air amount TTP1 by the combustion efficiency correction factor ITAF.

In S31, the target throttle valve opening TTPS is calculated based on the target intake air amount TTP2, and the target throttle valve opening TTPS is output to the throttle valve control device 10.
On the other hand, in S41, the basic fuel supply amount TP is calculated, and in the next S42, the basic fuel supply amount TP is corrected with the target equivalent ratio tDML, and the final fuel supply amount TI is calculated. In S43, it is determined whether or not the injection timing is different between stratified combustion and homogeneous combustion, and an injection pulse signal having a pulse width corresponding to the fuel supply amount TI is generated at the injection timing. Output to.

FIG. 6 is a control block diagram showing the third embodiment, and the configuration shown below is different from the first embodiment shown in FIG .
That is, the combustion efficiency correction rate calculation unit D is configured to calculate the combustion efficiency correction rate ITAF only from the target equivalent ratio tDML, while the combustion efficiency correction rate ITAF calculated by the combustion efficiency correction rate calculation unit D is calculated. A stratification / homogeneous gain switching section I is provided for switching the gain Gain to be corrected depending on whether homogeneous combustion or stratified combustion. The stratification / homogeneous gain switching unit I outputs gain = 1 at the time of homogeneous combustion, and outputs a stratification gain at the time of stratified combustion. The combustion efficiency correction factor calculation unit D is adapted to correct the combustion efficiency suitable for homogeneous combustion. The rate ITAF is calculated, and at the time of stratified combustion, the combustion efficiency correction rate ITAF suitable for the homogeneous combustion is corrected by the stratified gain, so that the combustion efficiency correction rate ITAF suitable for stratified combustion is converted.

The flowchart of FIG. 7 shows the control contents shown in the control block diagram of FIG . 6. First, in S51, an engine torque equilibrium value (target engine torque) tTEO is calculated. In S52, the target equivalent ratio tDML is calculated. Is calculated.
In S53, the target intake air amount TTPO is calculated based on the target engine torque tTEO.

In S54, the combustion efficiency correction rate ITAF is calculated based on the target equivalent ratio tDML.
In S55, it is determined whether or not stratified combustion is being performed. If stratified combustion is being performed, the process proceeds to S56 to select a stratified combustion efficiency gain. If not stratified combustion but homogeneous combustion is being performed, the process proceeds to S57. Select the homogeneous combustion efficiency gain.

In S58, the combustion efficiency correction rate ITAF is corrected according to the gain Gain selected according to the stratification and homogeneous combustion as described above.
In S59, the target intake air amount TTPO is corrected by the corrected combustion efficiency correction factor ITAF ′ to calculate the target intake air amount TTP1.
In S60, the final target intake air amount TTP2 is calculated by dividing the target intake air amount TTP1 by the target equivalent ratio tDML.

In S61, a target throttle valve opening TTPS is calculated based on the engine speed NE and the target intake air amount TTP2, and the target throttle valve opening TTPS is output to the throttle valve control device 10.
In S62, the basic fuel supply amount TP is calculated based on the actual intake air amount Q at that time and the reference equivalent ratio, and in S63, the basic fuel supply amount TP is corrected by the target equivalent ratio tDML or the like. The final fuel supply amount TI is calculated. In S64, an injection pulse signal having a pulse width corresponding to the fuel supply amount TI is output to the fuel injection valve 6 at a predetermined timing.

The system block diagram of the engine in embodiment. The control block diagram which shows 1st Embodiment. The flowchart which shows 1st Embodiment. The control block diagram which shows 2nd Embodiment. The flowchart which shows 2nd Embodiment. The control block diagram which shows 3rd Embodiment. The flowchart which shows 3rd Embodiment. The diagram which shows the difference in the fuel consumption rate by the difference between stratified combustion and homogeneous combustion.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Accelerator operation amount sensor, 2 ... Crank angle sensor, 3 ... Air flow meter, 4 ... Engine, 5 ... Water temperature sensor, 6 ... Fuel injection valve, 9 ... Throttle valve, 10 ... Throttle valve control device, 11 ... Control unit, A ... engine torque equilibrium value calculation unit, B ... target intake air amount calculation unit, C ... target equivalence ratio calculation unit, D ... combustion efficiency correction rate calculation unit, E ... target throttle valve opening calculation unit, F ... basic fuel supply Quantity calculation unit, G ... Correction calculation unit, H ... Pumping loss torque calculation unit, I ... Stratification / homogeneous gain switching unit

Claims (4)

A fuel injection valve that injects fuel directly into the combustion chamber of the engine;
Combustion state switching means for switching control between homogeneous combustion performed by injecting fuel in the intake stroke and stratified combustion performed by injecting fuel in the compression stroke;
An accelerator operation amount detecting means for detecting an accelerator operation amount;
Engine speed detecting means for detecting the engine speed;
Target engine torque calculating means for calculating a target engine torque according to the detected accelerator operation amount and engine rotation speed;
A target equivalent ratio calculating means for calculating a target equivalent ratio in accordance with the detected accelerator operation amount and engine rotational speed;
Target intake air amount calculating means for calculating a target intake air amount based on the target engine torque and the target equivalent ratio;
Even if the equivalence ratio is the same, the target engine torque can be obtained even when switching between homogeneous combustion and stratified combustion is performed in response to the difference in generated torque due to the difference in combustion efficiency between homogeneous combustion and stratified combustion. As described above, the combustion efficiency correction value is set according to the target equivalence ratio and the homogeneous combustion and the stratified combustion that are controlled by the combustion state switching means, and the target intake air amount is corrected by the combustion efficiency correction value. Correction means to
Intake air amount control means for controlling the intake air amount of the engine based on the target intake air amount corrected by the correction means;
Fuel supply control means for controlling the fuel supply amount to the engine based on the target equivalent ratio and the intake air amount of the engine;
An engine torque control device comprising: The correction means stores in advance two for homogeneous combustion and stratified combustion as tables for combustion efficiency correction values according to the target equivalence ratio, and a table corresponding to the current combustion state among these two tables. The engine torque control apparatus according to claim 1, wherein the target intake air amount is corrected based on a combustion efficiency correction value retrieved from the engine. The correction means corrects the combustion efficiency correction value according to the target equivalence ratio with different gains for homogeneous combustion and stratified combustion, and corrects the target intake air amount based on the corrected combustion efficiency correction value. The engine torque control apparatus according to claim 1, wherein The target intake air amount calculation means calculates a target intake air amount based on a target engine torque corrected based on a pumping loss torque corresponding to a target equivalence ratio. The engine torque control device described.

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