JPH1162658A - Control device for internal combustion engine - Google Patents

Abstract

(57) [Problem] To improve the accuracy of torque control in consideration of pump loss. SOLUTION: A driver request torque tTE0 is calculated based on an accelerator opening APS and an engine speed NE (1).
01). The target equivalent ratio tDML is calculated (102), and the pump loss torque TPL of the engine is calculated based on this (103). The target torque TTC is calculated by adding the pump loss torque TPL to the driver required torque tTE0 (104). A reference target intake air amount TTP is calculated based on the target torque TTC and the engine speed NE (105),
This is divided by the target equivalent ratio tDML to calculate a target intake air amount TTP '(106). Then, the throttle opening is controlled by the electronically controlled throttle valve 4 based on this.

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 for controlling an amount of air supplied to an engine to achieve a target torque of the engine.

[0002]

2. Description of the Related Art A conventional control device for an internal combustion engine is disclosed, for example, in Japanese Patent Application Laid-Open No. Sho 62-110536. In this system, the target throttle opening for air amount control is directly searched from the target torque and the engine speed. However, this method requires operating at a predetermined air-fuel ratio (for example, a stoichiometric air-fuel ratio). Therefore, it cannot be applied to an engine that variably controls the air-fuel ratio according to the operating state.

[0003] In order to change the air-fuel ratio while maintaining the same engine operation performance (torque and rotation speed), it is necessary to change both the air amount (throttle opening) and the fuel injection amount.

[0004]

In view of the above prior art, the following control has been proposed as so-called torque demand control (see Japanese Patent Application No. 8-36902).
In this torque demand control, the target target air ratio tTP and the target equivalent ratio (at the time of the stoichiometric air-fuel ratio) are obtained from the accelerator opening APS and the engine speed NE in order to control the target torque and the target air-fuel ratio of the engine at the same time. = Theoretical air-fuel ratio /
(Target air-fuel ratio) tDML, a target air amount tTP '= tTP / tDML corresponding to the target equivalence ratio is calculated therefrom, and a fuel consumption rate correction tT corresponding to the target equivalence ratio is performed.
P ", the target throttle opening is obtained, and the drive of the electronically controlled throttle valve is controlled, while the basic fuel injection amount TP obtained from the actual intake air flow rate Q and the engine speed NE is converted to the target equivalent ratio t.
The driving of the fuel injection valve is controlled based on the fuel injection amount TI obtained by correction with DML or the like.

As described above, in this torque demand control, the fuel consumption rate is corrected in accordance with the target equivalence ratio for the fuel injection amount, and the required fuel amount is reduced in accordance with the leaning of the air-fuel ratio. The torque is controlled to the target value. On the other hand, the air-fuel ratio is controlled to the target value by performing the fuel efficiency correction according to the target equivalent ratio also on the target air amount. In general, the improvement in fuel efficiency due to lean air-fuel ratio is largely due to a decrease in pump loss and a decrease in cooling loss due to a decrease in combustion temperature, and the pump loss depends on the pressure in the intake pipe.

However, in the above technique, the fuel efficiency correction in accordance with the target equivalent ratio is performed by multiplying the target air amount.
There is a problem that the correction rate is uniform and does not match the actual phenomenon. The present invention has been made in view of the above circumstances, and has as its object to improve the drivability and fuel efficiency by improving the accuracy of torque control.

[0007]

Therefore, according to the first aspect of the present invention, as shown in FIG. 1, a driver required torque (engine torque equilibrium value) is calculated based on the accelerator opening and the engine speed. A driver required torque calculating means, a pump loss torque calculating means for calculating a torque corresponding to a pump loss of the engine, a target torque calculating means for calculating a target torque by adding a torque corresponding to the pump loss to the driver required torque; Control of the internal combustion engine by providing target intake air amount calculating means for calculating a target intake air amount based on the engine speed, and throttle opening control means for controlling a throttle opening degree based on the target intake air amount; Configure the device.

In the invention according to claim 2, the target intake air amount calculating means calculates a target intake air amount by dividing a reference target intake air amount based on a target torque and an engine speed by a target equivalent ratio. Characterized in that: Claim 3
According to the invention, the pump loss torque calculating means calculates a torque corresponding to a pump loss based on a target equivalent ratio.

The invention according to claim 4 is characterized in that the pump loss torque calculating means calculates a torque corresponding to a pump loss based on a target equivalent ratio and a target EGR rate. The invention according to claim 5 is characterized in that the pump loss torque calculating means calculates a torque corresponding to a pump loss based on a parameter related to an intake pipe pressure (boost).

According to a sixth aspect of the present invention, the parameter relating to the intake pipe pressure is a total gas amount in the cylinder.

[0011]

According to the first aspect of the present invention, a torque corresponding to a pump loss of the engine is added to a driver request torque based on the accelerator opening and the engine speed, and this is set as a target torque. The throttle opening is controlled by calculating the target intake air amount based on the engine speed and the engine speed, so that the accuracy of torque control can be improved in consideration of pump loss, and fuel efficiency can be improved without impairing drivability. . Further, the calculation of the fuel efficiency correction in the prior art can be omitted.

According to the second aspect of the present invention, the target intake air amount is calculated by dividing the reference target intake air amount based on the target torque and the engine speed by the target equivalent ratio.
The target intake air amount can be set accurately. According to the third aspect of the present invention, since the pump loss changes depending on the target equivalence ratio, by calculating based on this, the torque corresponding to the pump loss can be easily and accurately obtained.

According to the fourth aspect of the present invention, since the pump loss varies not only with the target equivalent ratio but also with the target EGR rate, a torque corresponding to the pump loss can be more accurately obtained by calculating based on these. Can be. According to the fifth aspect of the present invention, since the pump loss depends on a parameter related to the intake pipe pressure, a torque corresponding to the pump loss can be accurately obtained by calculating based on the parameter.

According to the sixth aspect of the invention, the total gas amount in the cylinder is calculated as a parameter related to the pressure in the intake pipe, and the torque corresponding to the pump loss can be obtained extremely accurately based on the calculated total gas amount in the cylinder.

[0015]

Embodiments of the present invention will be described below. FIG. 2 is a system diagram of a direct injection spark ignition type internal combustion engine showing an embodiment. First, this will be described. In the combustion chamber of each cylinder of the engine 1 mounted on the vehicle,
Under the control of an electronically controlled throttle valve 4 as a throttle opening control means from an air cleaner 2 through an intake passage 3,
Air is inhaled.

The opening of the electronically controlled throttle valve 4 is controlled by a step motor or the like operated by a signal from the control unit 11. An electromagnetic fuel injection valve (injector) 5 is provided so as to directly inject fuel (gasoline) into the combustion chamber. The fuel injection valve 5 is energized by a solenoid by an injection pulse signal output in the intake stroke or the compression stroke from the control unit 11 in synchronization with the engine rotation, opens the valve, and injects fuel adjusted to a predetermined pressure. It has become. 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 stratified mixture around the ignition plug 6. Based on the ignition signal from the control unit 11, the fuel is ignited by the ignition plug 6 to perform combustion (homogeneous combustion or stratified combustion).

Exhaust gas from the engine 1 is discharged from an exhaust passage 7, and an exhaust purification catalyst 8 is interposed in the exhaust passage 7. In addition, a part of the exhaust gas is transmitted through an electronically controlled EGR valve 9 controlled by a signal from the control unit 11 to the EGR.
The air is returned to the intake passage 3 downstream of the throttle valve 4 (intake pipe) by the passage 10. The control unit 11 has a CP
A microcomputer including a U, a ROM, a RAM, an A / D converter, an input / output interface, and the like is provided, and signals are input from various sensors.

As the various sensors, crank angle sensors 12 and 13 for detecting the rotation of the crankshaft or the rotation of the camshaft of the engine 1 are provided. These crank angle sensors 12 and 13 have a crank angle of 72 when the number of cylinders is n.
The reference pulse signal REF is output at a predetermined crank angle position every 0 ° / n, and the unit pulse signal POS is output every 1 to 2 °. NE can be calculated.

In addition, an air flow meter 14 for detecting an intake air flow rate Q upstream of the throttle valve 4 in the intake passage 3, an accelerator sensor 15 for detecting an accelerator opening (accelerator pedal depression amount) APS, and an opening of the throttle valve 4 TVO
Sensor 16 (including an idle switch that is turned on when the throttle valve 4 is fully closed) for detecting the engine 1
Temperature sensor 17 for detecting the cooling water temperature Tw of the exhaust passage 7
An O ₂ sensor 18 for outputting a signal corresponding to the rich / lean exhaust air-fuel ratio is provided.

Here, the control unit 11
Performs predetermined arithmetic processing by a built-in microcomputer while inputting signals from the various sensors described above, and performs a throttle opening degree by the electronically controlled throttle valve 4, a fuel injection amount and an injection timing by the fuel injection valve 5, and the like. Control.
Next, with respect to the basic arithmetic processing contents (torque demand control), according to the control block diagram and the flowchart,
explain.

FIG. 3 is a control block diagram of the first embodiment, and FIG. 4 is a flowchart thereof. The driver request torque calculating means 101 calculates the accelerator opening APS and the engine speed NE.
Then, the driver required torque tTE0 is calculated with reference to a map that defines the driver required torque (engine torque equilibrium value) tTE0 in accordance with these. The target equivalence ratio calculation means 102 calculates the target equivalence ratio tDML from the accelerator opening APS and the engine speed NE with reference to a map that defines the target equivalence ratio tDML according to these.

The target equivalence ratio tDML is expressed as 14.6 / target air-fuel ratio, where the stoichiometric air-fuel ratio (stoichiometric air-fuel ratio) is 14.6. At the same time as the determination of the target equivalent ratio tDML, the combustion method (homogeneous combustion or stratified combustion) is determined. Then, in the case of homogeneous combustion, the fuel injection timing is set to the intake stroke, and in the case of stratified combustion, the fuel injection timing is set to the compression stroke.

The pump loss torque calculating means 103 calculates the pump loss torque T based on the target equivalent ratio tDML.
With reference to the table that determines PL, pump loss torque T
Calculate PL. Here, the larger the target equivalent ratio tDML (stoichiometric side or rich side), the larger the pump loss torque TPL, and the smaller the target equivalent ratio tDML (lean side), the smaller the pump loss torque TPL.
This is because, as the air becomes leaner, more air is introduced, so that the negative pressure is reduced and the pump loss is reduced.

The target torque calculating means 104 is constituted by an adder, and adds the pump loss torque TPL to the driver required torque tTE0 to obtain a target torque TTC = tTE0 + T
Calculate PL. The target intake air amount calculation means (reference target intake air amount calculation means) 105 refers to a map in which the reference target intake air amount TTP is determined based on the target torque TTC and the engine speed NE in accordance with the target torque TTC and the engine speed NE. The air amount TTP is calculated. Here, the reference target intake air amount TT
P is equivalent to required basic fuel amount × 14.6.

The target intake air amount calculating means 106 is constituted by a divider, and calculates the reference target intake air amount TTP by a target equivalent ratio t.
Divide by DML to obtain the final target intake air amount TT
Calculate P ′ = TTP / tDML. When the final target intake air amount TTP 'is calculated, the opening of the electronically controlled throttle valve 4 is controlled based on this.

More specifically, based on the target intake air amount TTP 'and the engine speed NE, a target throttle opening tTVO is determined by referring to a map in which the target throttle opening tTVO is determined in accordance with (TTP' × NE). The electronic control throttle valve 4 is calculated so as to step-drive, for example, a step motor by a command signal corresponding to the calculated value, and to control the electronically-controlled throttle valve 4 so that the target throttle opening tTVO is obtained.

On the other hand, the actual intake air flow rate Q controlled by the throttle valve 4 is detected by the air flow meter 14. The basic fuel injection amount calculating means 201 firstly calculates the actual intake air flow rate Q detected by the air flow meter 14,
From the engine speed NE, a basic fuel injection amount (basic injection pulse width) TP corresponding to stoichiometry is calculated by the following equation.

TP = K × Q / NE where K is a constant. The fuel injection amount calculating means 202 multiplies the basic fuel injection amount TP by the target equivalence ratio tDML and adds an invalid injection amount (invalid pulse width) TS as shown in the following equation to obtain a final fuel injection amount. The quantity (injection pulse width) TI is calculated. TI = TP × tDML + TS Actually, various corrections are made, but they are omitted here.

When the final fuel injection amount TI is calculated,
This is set in a register for controlling the fuel injection amount. Thereby, at the fuel injection timing, the fuel injection valve 5 is driven by the injection pulse signal having the pulse width corresponding to TI,
Inject fuel. As described above, the pump loss torque of the engine is added to the driver request torque based on the accelerator opening and the engine speed, and this is set as the target torque, and the target intake air is calculated based on the target torque and the engine speed. By calculating the amount and controlling the throttle opening, the accuracy of torque control can be improved in consideration of pump loss.

Further, in the first embodiment, since the pump loss changes depending on the target equivalent ratio tDML, the pump loss torque TPL can be easily and accurately obtained by calculating based on this. FIG. 5 is a control block diagram of the second embodiment, and FIG. 6 is a flowchart thereof. The second embodiment differs from the first embodiment only in the method of calculating the pump loss torque, and therefore, only that part will be described. Further, since the fuel injection amount control is the same, it is omitted from the flowchart.

The target equivalence ratio calculating means 102 calculates the target equivalence ratio tDML from the accelerator opening APS and the engine speed NE with reference to a map in which the target equivalence ratio tDML is determined according to these. The target EGR rate calculation means 111
To use for controlling the electronically controlled throttle valve 9, the target E is determined from the accelerator opening APS and the engine speed NE in accordance with these.
Referring to a map in which the GR rate tEGR is determined, the target EGR
Calculate the rate tEGR.

The pump loss torque calculating means 112 calculates the pump loss torque TPL from the target equivalence ratio tDML and the target EGR rate tEGR with reference to a map that determines the pump loss torque TPL according to these. Here, the pump loss torque TPL increases as the target equivalent ratio tDML increases (stoichiometric side or rich side), and the pump loss torque TPL decreases as the target equivalent ratio tDML decreases (lean side).
PL is calculated small. This is because, as the air becomes leaner, more air is introduced, so that the negative pressure is reduced and the pump loss is reduced.

Further, as the target EGR rate tEGR is larger,
The pump loss torque has a small TPL and a target EGR rate tE
The smaller the GR rate, the larger the pump loss torque TPL is calculated. This is because the increase in the EGR rate reduces the negative pressure and reduces the pump loss. In the third embodiment, since the pump loss changes not only according to the target equivalent ratio tDML but also the target EGR rate tEGR, the pump loss torque TPL can be more accurately obtained by calculating based on these.

FIG. 7 is a control block diagram of the third embodiment, and FIG. 8 is a flowchart thereof. This third embodiment also
Since only the method of calculating the pump loss torque is different from that of the first embodiment, only that part will be described.
The basic intake air amount calculating means 121 calculates the basic intake air amount TTP0 from the driver required torque tTE0 and the engine speed NE with reference to a map that defines the basic intake air amount TTP0 according to these.

The target equivalence ratio calculation means 102 calculates the target equivalence ratio tDML from the accelerator opening APS and the engine speed NE with reference to a map that defines the target equivalence ratio tDML in accordance with these. The target EGR rate calculation means 111
To use for controlling the electronically controlled throttle valve 9, the target E is determined from the accelerator opening APS and the engine speed NE in accordance with these.
Referring to a map in which the GR rate tEGR is determined, the target EGR
Calculate the rate tEGR.

The adding means 122 obtains 1 + tEGR.
The dividing means (tDML correcting means) 123 outputs the target equivalent ratio t
DML is divided by 1 + tEGR to obtain a corrected target equivalent ratio tDML ′ = tDML / (1 + tEGR). The dividing means (TTPGAS calculating means) 124 calculates the corrected target equivalent ratio tDML ′ = tDML by subtracting the basic intake air amount TTP0.
/ (1 + tEGR), and calculates a cylinder total gas amount equivalent value TTPGAS = TTP0 / tDML 'as a parameter related to the intake pipe pressure (boost).

The pump loss torque calculation means 125 refers to a table in which the pump loss torque TPL is determined from the cylinder total gas amount equivalent value TTPGAS, and
The pump loss torque TPL is calculated. Here, as the value TTPGAS corresponding to the total gas amount in the cylinder is larger, the pump loss torque TPL is calculated to be smaller.

As shown in FIG. 7, in this embodiment, the fuel injection amount T
The corrected target equivalence ratio tDML '= tDML / (1 + t) which is the output of the dividing means 123 is obtained by dividing the target equivalence ratio used in the calculation of I.
As EGR), the fuel injection amount TI is calculated by the following equation. TI = TP × tDML ′ + TS In the third embodiment, since the pump loss depends on the total gas amount in the cylinder, which is a parameter related to the pressure in the intake pipe, a value TTPGAS equivalent to the total gas amount in the cylinder is calculated. By calculating based on this, the pump loss torque TPL can be accurately captured.

FIG. 9 is a control block diagram of the fourth embodiment, and FIG. 10 is a flowchart thereof. The fourth embodiment also differs from the first embodiment only in the method of calculating the pump loss torque, and therefore only the portion will be described. The target equivalent ratio calculating means 102 calculates the accelerator opening APS
From the engine speed NE and the target equivalent ratio t in accordance with these.
Referring to the map defining DML, target equivalent ratio tDML
Is calculated.

Since the target EGR rate calculating means 111 is used for controlling the electronically controlled throttle valve 9, the target EGR rate t is calculated based on the accelerator opening APS and the engine speed NE.
Referring to a map in which EGR is determined, target EGR rate tEG
Calculate R. The multiplication means 131 calculates the target EGR rate tEG
R is multiplied by the target intake air amount TTP ′ to calculate a target EGR amount TTPGR = tEGR × TTP ′.

Multiplication means (TTPGAS calculation means) 132
Is the target EGR amount TTPEG
R is added, and as a parameter related to the intake pipe pressure (boost), a cylinder total gas amount equivalent value TTPGA
S = TTP '+ TTPEGR is calculated. Z- ¹ means 13
Numeral 3 is provided to use the previous value TTGAS corresponding to the total gas amount in the cylinder in the calculation in order to avoid a loop calculation.

The pump loss torque calculation means 125 calculates the pump loss torque TPL from the previous value TTPGAS corresponding to the total gas amount in the cylinder with reference to a table in which the pump loss torque TPL is determined accordingly. Here, as the value TTPGAS corresponding to the total gas amount in the cylinder is larger, the pump loss torque TPL is calculated to be smaller.

In the fourth embodiment, as in the third embodiment, the pump loss depends on the total gas amount in the cylinder, which is a parameter related to the pressure in the intake pipe. By calculating and calculating based on this, the pump loss torque TPL can be accurately captured.

[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 control block diagram of the first embodiment.

FIG. 4 is a flowchart of the first embodiment.

FIG. 5 is a control block diagram of a second embodiment.

FIG. 6 is a flowchart of the second embodiment.

FIG. 7 is a control block diagram of a third embodiment.

FIG. 8 is a flowchart of the third embodiment.

FIG. 9 is a control block diagram of a fourth embodiment.

FIG. 10 is a flowchart of the fourth embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 internal combustion engine 4 electrically controlled throttle valve 5 fuel injection valve 6 spark plug 9 electrically controlled EGR valve 11 control unit 12, 13 crank angle sensor 14 air flow meter 15 accelerator sensor

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 45/00 364 F02D 45/00 364A

Claims (6)

[Claims] 1. A driver required torque calculating means for calculating a driver required torque based on an accelerator opening and an engine speed, a pump loss torque calculating means for calculating a torque corresponding to a pump loss of an engine, and a pump loss calculated by a driver required torque. A target torque calculating means for calculating a target torque by adding a substantial torque; a target intake air amount calculating means for calculating a target intake air amount based on the target torque and the engine speed; And a throttle opening control means for controlling the throttle opening. 2. The target intake air amount calculating means calculates a target intake air amount by dividing a reference target intake air amount based on a target torque and an engine speed by a target equivalent ratio. The control device for an internal combustion engine according to claim 1, wherein 3. The control device for an internal combustion engine according to claim 1, wherein said pump loss torque calculating means calculates a torque corresponding to a pump loss based on a target equivalence ratio. 4. The internal combustion engine according to claim 1, wherein said pump loss torque calculating means calculates a torque corresponding to a pump loss based on a target equivalence ratio and a target EGR rate. Control device. 5. The internal combustion engine according to claim 1, wherein said pump loss torque calculating means calculates a torque corresponding to a pump loss based on a parameter related to an intake pipe pressure. Control device. 6. The control device for an internal combustion engine according to claim 5, wherein the parameter related to the pressure in the intake pipe is a total gas amount in the cylinder.