JPH1136950A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sufficient output at full valve opening in an area (high load area near full valve opening) where a target air-fuel ratio is made richer than storichiometric mixture ratio in order to increase output. SOLUTION: When a target torque of an engine is set (101), a required basic fuel oil amount is calculated based on the target torque (105), and a target cylinder air volume is calculated from the required basic fuel amount and a target air-fuel ratio, at that time, the target air-fuel ratio treated by a limiter so that it does not become richer than stroichiometic mixture ratio is used as the target air-fuel ratio (103, 104, 106). Also, based on the calculated target cylinder air volume, a target throttle opening is calculated (107), and an electrically controlled throttle valve 4 is controlled. On the other hand, when the target fuel injection amount is calculated from an actual cylinder air volume and target air-fuel ratio by detecting the actual cylinder air volume using an air flowmeter 13 (108), a fuel injection nozzle 5 is controlled based on the calculated target fuel injection amount and using, as the target air-fuel ratio, a value obtained before limiter treatment (103, 109).

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 the engine and a fuel injection amount 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, a required basic fuel amount is calculated based on the target torque of the engine, a target air amount is calculated from the required basic fuel amount and a target air-fuel ratio according to the engine operating conditions, and the target air amount is calculated based on the target air amount. Controls the amount of air supplied.
Further, the actual air amount actually supplied to the engine is detected, the target fuel injection amount is calculated from the actual air amount and the target air-fuel ratio, and the fuel injection amount to the engine is controlled based on the target fuel injection amount.

However, in this torque demand control, the air amount is reduced in a region where the target air-fuel ratio is made richer than the stoichiometric air-fuel ratio, that is, in a high load region near the full opening of the throttle valve in order to improve the output. In some cases, a full-open output cannot be obtained, and improvement in this respect has been demanded. The present invention, in view of such a situation, in order to improve the output, in a region where the target air-fuel ratio is made richer than the stoichiometric air-fuel ratio,
It is intended to obtain a sufficient full-open output.

[0006]

Therefore, in the invention according to claim 1, means for controlling the internal combustion engine is provided by providing means as shown in FIG. Referring to FIG. 1, target air-fuel ratio equivalent value setting means for setting a target air-fuel ratio equivalent value based on engine operating conditions, required basic fuel amount calculating means for calculating a required basic fuel amount of the engine, and required basic fuel amount Target air amount calculating means for calculating a target air amount based on the target air-fuel ratio and an air amount control means for controlling an air amount supplied to the engine based on the target air amount. Actual air amount detecting means for detecting an air amount, target fuel injection amount calculating means for calculating a target fuel injection amount from the actual air amount and a target air-fuel ratio equivalent value, and fuel injection to the engine based on the target fuel injection amount And a fuel injection amount control means for controlling the amount.

[0007] Of the target air-fuel ratio equivalent value input to the target air amount calculating means and the target air-fuel ratio equivalent value input to the target fuel injection amount calculating means, the target air amount input to the target air amount calculating means is selected. Target air-fuel ratio equivalent value limiting means for limiting the fuel ratio equivalent value so as not to be richer than a predetermined value is provided. Therefore, when calculating the target air amount from the required basic fuel amount and the target air-fuel ratio equivalent value, the target air-fuel ratio equivalent value is limited by using a value limited so as not to be richer than a predetermined value. In a region where the fuel ratio is made richer than the stoichiometric air-fuel ratio, the target air amount is increased to obtain a sufficient full-open output.

On the other hand, when calculating the target fuel injection amount from the actual air amount and the target air-fuel ratio equivalent value, the original target air-fuel ratio is achieved by using the value before the limit as the target air-fuel ratio equivalent value. I do. In the invention according to claim 2, the predetermined value is:
It is characterized by a value corresponding to a stoichiometric air-fuel ratio.

In the invention according to claim 3, the target air-fuel ratio is used as the target air-fuel ratio equivalent value, and the target air-fuel ratio equivalent value limiting means limits the target air-fuel ratio so as not to be less than a predetermined value. It is characterized by the following. In the invention according to claim 4, a target equivalence ratio represented by a stoichiometric air-fuel ratio / a target air-fuel ratio is used as the target air-fuel ratio equivalent value, and the target air-fuel ratio equivalent value limiting means determines that the target equivalence ratio exceeds a predetermined value. It is characterized in that it is not restricted.

[0010] In the invention according to claim 5, the excess air ratio is used as the target air-fuel ratio equivalent value, and the target air-fuel ratio equivalent value limiting means limits the excess air ratio so as not to be less than a predetermined value. It is characterized by the following. In the invention according to claim 6, the air amount control means has a target throttle opening degree calculating means for calculating a target throttle opening degree based on a target air amount, and the electronically controlled throttle is set to the target throttle opening degree. It is characterized by driving a valve.

The invention according to claim 7 is characterized in that the fuel injection amount control means drives a fuel injection valve of a direct injection spark ignition type internal combustion engine based on a target fuel injection amount. In the invention according to claim 8, there is provided combustion mode setting means for switching the combustion mode to homogeneous combustion or stratified combustion based on engine operating conditions, and the target air-fuel ratio equivalent value setting section comprises:
It is characterized in that a target air-fuel ratio equivalent value is set for each combustion method based on engine operating conditions.

According to a ninth aspect of the present invention, there is provided a target torque setting means for setting a target torque of the engine, wherein the required basic fuel amount calculating means calculates a required basic fuel amount based on the target torque. (See FIG. 1).

[0013]

According to the first aspect of the invention, when calculating the target air amount from the required basic fuel amount and the target air-fuel ratio equivalent value, the target air-fuel ratio equivalent value does not become richer than a predetermined value. By using such a limited value, the target air amount can be increased to obtain a sufficient full-open output in a region where the target air-fuel ratio is made richer than the stoichiometric air-fuel ratio, while the actual air amount is increased. When calculating the target fuel injection amount from the target air-fuel ratio and the target air-fuel ratio equivalent value, the original target air-fuel ratio can be achieved by using the value before restriction as the target air-fuel ratio equivalent value.

According to the second aspect of the present invention, by setting the predetermined value to a value corresponding to the stoichiometric air-fuel ratio, a sufficient full-open output can be ensured in a region where the target air-fuel ratio is made richer than the stoichiometric air-fuel ratio. Obtainable. According to the third aspect of the invention, control can be performed using the target air-fuel ratio as it is as the target air-fuel ratio equivalent value.

According to the fourth aspect of the present invention, the control can be performed by using the target equivalence ratio as the target air-fuel ratio equivalent value. According to the invention according to claim 5, control can be performed using the excess air ratio as the target air-fuel ratio equivalent value.
According to the invention according to claim 6, highly accurate air amount control can be performed by using the electronically controlled throttle valve for air amount control.

According to the seventh aspect of the invention, by applying the invention to a direct-injection spark ignition type internal combustion engine, high-response torque control becomes possible. According to the invention according to claim 8, by setting the target air-fuel ratio based on the engine operating condition for each combustion method, it is possible to cope with the switching control of the combustion method. According to the ninth aspect, the target torque of the engine can be set and realized.

[0017]

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,
Air is suctioned from the air cleaner 2 by the intake passage 3 under the control of the electronically controlled throttle valve 4.

The opening of the electronically controlled throttle valve 4 is controlled by a step motor or the like which operates according to a signal from the control unit 10. 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 in response to an injection pulse signal output in the intake stroke or the compression stroke from the control unit 10 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. On the basis of an ignition signal from the control unit 10, the fuel is ignited by the ignition plug 6 and burns (homogeneous combustion or stratified combustion).

Exhaust gas from the engine 1 is exhausted from an exhaust passage 7, and an exhaust purification catalyst 8 is interposed in the exhaust passage 7. The control unit 10 includes a CPU, a ROM, an R
A microcomputer including an AM, an A / D converter, an input / output interface, and the like is provided, and signals are input from various sensors.

As the various sensors, there are provided crank angle sensors 11 and 12 for detecting the rotation of the crankshaft of the engine 1 or the rotation of the camshaft. These crank angle sensors 11 and 12 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 13 for detecting an intake air flow rate Qa upstream of the throttle valve 4 in the intake passage 3,
Accelerator sensor 14 for detecting accelerator opening (accelerator pedal depression amount) ACC, opening TV of throttle valve 4
A throttle sensor 15 for detecting O (including an idle switch that is turned on when the throttle valve 4 is fully closed), a water temperature sensor 16 for detecting the cooling water temperature Tw of the engine 1, and a rich / lean exhaust air-fuel ratio in the exhaust passage 7. An O ₂ sensor 17 for outputting a signal corresponding to the above is provided.

Here, the control unit 10
Performs predetermined arithmetic processing by a built-in microcomputer while inputting signals from the various sensors, 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, The ignition timing of the ignition plug 6 is controlled. Next, basic arithmetic processing contents (torque demand control) will be described with reference to the control block diagram of FIG.

The target torque setting means 101 obtains the driver required torque from the accelerator opening ACC and the engine speed Ne by referring to a map in which the driver required torque is determined in accordance with the obtained values. The target torque tTe is set by adding the idle speed control.
The combustion method setting means 102 includes a plurality of maps each of which determines the combustion method using the engine speed Ne and the target torque tTe as parameters of the engine operation conditions for each water temperature Tw, and, based on the selected map, according to the actual engine operation conditions. The combustion method is set to either homogeneous combustion or stratified combustion.

According to the setting of the combustion system, when switching to homogeneous combustion, the fuel injection timing is set to the intake stroke, and when switching to stratified combustion, the fuel injection timing is set to the compression stroke. The target air-fuel ratio equivalent value setting means 103 refers to a map for each combustion method, and calculates a target air-fuel ratio tAFR, a target air-fuel ratio tAFR, as a target air-fuel ratio equivalent value from the engine speed Ne and the target torque tTe.
The target equivalent ratio tφ or the target excess air ratio tλ is set.

The homogeneous combustion is divided into a stoichiometric region, a lean region, and a rich region (a high load region near full open) according to engine operating conditions, and a target air-fuel ratio t in the stoichiometric region.
AFR = the stoichiometric air-fuel ratio (hereinafter referred to as “stoichiometric” or “stoichiometric air-fuel ratio”, here, 14.6), whereas the target air-fuel ratio tAFR = about 20 to 30 in the lean region and the target air-fuel ratio in the rich region. The fuel ratio tAFR is about 12 to 14. In the case of stratified combustion, the target air-fuel ratio tAFR = 3
It is about 0 to 40.

The target equivalence ratio tφ is represented by the stoichiometric air-fuel ratio / the target air-fuel ratio, and tφ = 14.6 / tAFR. The target excess air ratio tλ is the reciprocal of the target equivalent ratio tφ,
tλ = tAFR / 14.6. The target air-fuel ratio equivalent value limiting unit 104 limits the target air-fuel ratio equivalent value (limiter processing) so that the target air-fuel ratio equivalent value does not become richer than a predetermined value corresponding to the stoichiometric air-fuel ratio.

Specifically, when the target air-fuel ratio tAFR is used as the target air-fuel ratio equivalent value, the larger of the target air-fuel ratio tAFR and the stoichiometric air-fuel ratio 14.6 is calculated by the following equation. The air-fuel ratio is tAFR '. tAFR ′ = MAX (tAFR, 14.6) (1-1). When the target equivalent ratio tφ is used as the target air-fuel ratio equivalent value, the smaller of the target equivalent ratio tφ and the stoichiometric equivalent ratio 1 is set as the post-limiter target equivalent ratio tφ ′ as in the following equation.

Tφ ′ = MIN (tφ, 1) (1-2). When the target excess air ratio tλ is used as the target air-fuel ratio equivalent value, the larger one of the target excess air ratio tλ and the stoichiometric excess air ratio 1 is determined by the following equation. '. tλ ′ = MAX (tλ, 1) (1-3).

The required basic fuel amount calculating means 105 calculates the required basic fuel amount tQf from the target torque tTe and the engine speed Ne by referring to a map which determines the required basic fuel amount tQf in accordance with these. Further, since the combustion efficiency differs between the homogeneous combustion and the stratified combustion, the necessary basic fuel amount tQf is corrected according to these. The target air amount calculating means (target cylinder air amount calculating means) 106 includes a required basic fuel amount tQf and a target air-fuel ratio equivalent value after limiter processing (target air-fuel ratio tAFR ', target equivalent ratio tφ' or target excess air ratio tλ '). Then, the target air amount (here, referred to as the target cylinder air amount) tQcyl is calculated by one of the following equations. The target air-fuel ratio equivalent value used here is a value after the limiter processing.

TQcyl = tQf × tAFR ′ (2-1) tQcyl = tQf × (14.6 / tφ ′) (2-2) tQcyl = tQf × (14.6 × tλ ′) -(2-3). The expression 2-2 and the expression 2-3 represent tQf × 14.
6 is a target cylinder air amount at the time of stoichiometry. In the equation 2-2, by dividing this by the target equivalent ratio tφ ′,
The target cylinder air amount tQcyl is obtained.
In the equation, the target cylinder air amount tQcyl is obtained by multiplying this by the target excess air ratio tλφ ′.

Further, regarding the calculation flow of the target cylinder air amount tQcyl, the target air-fuel ratio t
FIG. 4 shows the case where the AFR is used, FIG. 5 shows the case where the target equivalent ratio tφ is used, and FIG. 6 shows the case where the target excess air ratio tλ is used.
It is shown in The target throttle opening calculation means 107
From the target cylinder air amount tQcyl and the engine speed Ne,
The target throttle opening tTVO is calculated with reference to a map defining the target throttle opening tTVO in accordance with these.

When the target throttle opening tTVO is calculated, the electronic control throttle valve 4 is controlled so that the step motor is step-driven by a command signal corresponding to the target throttle opening tTVO so that the target throttle opening tTVO is obtained. The target throttle opening calculating means 107, together with the electronically controlled throttle valve 4, corresponds to an air amount control means. On the other hand, the actual intake air flow rate Q controlled by the throttle valve 4 by the air flow meter 13
a is detected.

The actual air amount calculating means (actual cylinder air amount calculating means) 108 divides the actual intake air flow rate Qa detected by the air flow meter 13 by the engine speed Ne, smoothes and delays the actual intake air flow rate Qa. The air amount (here, called the actual cylinder air amount) Qcyl is calculated. The actual cylinder air amount calculating means 108 and the air flow meter 13 correspond to an actual air amount detecting means.

The target fuel injection amount calculating means 109 calculates the actual cylinder air amount Qcyl and the target air-fuel ratio equivalent value (target air-fuel ratio tA).
From FR, the target equivalent ratio tφ, or the target excess air ratio tλ), the target fuel injection amount tQfi is calculated by one of the following equations. The target air-fuel ratio equivalent value used here is a value before the limiter process. tQfi = Qcyl / tAFR (3-1) tQfi = Qcyl × (tφ / 14.6) (3-2) tQfi = Qcyl / (tλ × 14.6) (3-3) ).

The expression 3-2 and the expression 3-3 represent Q
cyl / 14.6 is the stoichiometric target fuel injection amount (basic fuel injection amount Tp). In the equation 3-2, the target fuel injection amount tQfi is obtained by multiplying this by the target equivalent ratio tφ.
In the equation 3-3, the target fuel injection amount tQ is obtained by dividing this by the target excess air ratio tλφ ′.
fi is determined.

The fuel injection amount correcting means 110 performs various corrections on the target fuel injection amount tQfi. When the final target fuel injection amount tQfi is calculated, the fuel injection valve 5 is driven by an injection pulse signal having a pulse width corresponding to tQfi at the fuel injection timing, and the fuel injection is performed so that the target fuel injection amount tQfi is obtained. The valve 5 is controlled. This part corresponds to the fuel injection amount control means.

Regarding the control of the ignition timing by the ignition plug 6, the ignition timing ADV is set and controlled in accordance with the parameters of the engine operating conditions with reference to a map for each combustion system. Next, the operation will be described with reference to the timing chart of FIG.
FIG. 7 shows a case where the target air-fuel ratio tAFR changes from lean to stoichiometric to rich. Even after the target air-fuel ratio tAFR is enriched, the target air-fuel ratio tAFR 'after the limiter processing is maintained at stoichiometric.

Here, when calculating the target cylinder air amount tQcyl by multiplying the required basic fuel amount tQf by the target air-fuel ratio, the target air-fuel ratio after the limiter process, which is limited so as not to be rich, as the target air-fuel ratio. By using tAFR ', after enrichment, the target cylinder air amount tQcyl can be increased as compared with the normal case (indicated by a dotted line), and thereby the torque can be increased by controlling the throttle opening.

On the other hand, when calculating the target fuel injection amount tQfi by dividing the actual cylinder air amount Qcyl by the target air-fuel ratio, the target air-fuel ratio tc before the limiter process is used as the target air-fuel ratio.
By using the AFR, the original target air-fuel ratio tAFR is achieved.

[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 showing arithmetic processing contents.

FIG. 4 is a flowchart of a first embodiment of calculating a target cylinder air amount;

FIG. 5 is a flowchart of a second embodiment of a target cylinder air amount calculation.

FIG. 6 is a flowchart of a third embodiment of calculating a target cylinder air amount;

FIG. 7 is a timing chart showing the operation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Internal combustion engine 4 Electric throttle valve 5 Fuel injection valve 6 Spark plug 10 Control unit 11, 12 Crank angle sensor 13 Air flow meter 14 Accelerator opening sensor

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 45/00366 F02D 45 / 00366F

Claims (9)

[Claims] 1. A target air-fuel ratio equivalent value setting means for setting a target air-fuel ratio equivalent value based on engine operating conditions; a required basic fuel amount calculating means for calculating a required basic fuel amount of the engine; Target air amount calculation means for calculating a target air amount from a target air-fuel ratio equivalent value; air amount control means for controlling an air amount supplied to the engine based on the target air amount; actual air actually supplied to the engine An actual air amount detecting means for detecting an amount, a target fuel injection amount calculating means for calculating a target fuel injection amount from the actual air amount and a target air-fuel ratio equivalent value, and a fuel injection amount to the engine based on the target fuel injection amount. And a fuel injection amount control means for controlling the target air-fuel ratio value input to the target air amount calculation means and the target air-fuel ratio value input to the target fuel injection amount calculation means. Of the above The target air-fuel ratio equivalent value input to the target air amount calculating means, a predetermined value the control apparatus for an internal combustion engine, characterized in that a target air-fuel ratio corresponding value limiting means for limiting so as not to richer than the. 2. The control device for an internal combustion engine according to claim 1, wherein said predetermined value is a value corresponding to a stoichiometric air-fuel ratio. 3. A target air-fuel ratio value is used as a target air-fuel ratio equivalent value, and said target air-fuel ratio equivalent value limiting means limits the target air-fuel ratio so as not to be less than a predetermined value. The control device for an internal combustion engine according to claim 1 or 2. 4. A target equivalent ratio represented by a stoichiometric air-fuel ratio / a target air-fuel ratio is used as a target air-fuel ratio equivalent value, and said target air-fuel ratio equivalent value limiting means prevents the target equivalent ratio from exceeding a predetermined value. 3. The control device for an internal combustion engine according to claim 1, wherein the control device is restricted. 5. The method according to claim 1, wherein an excess air ratio is used as the target air-fuel ratio equivalent value, and said target air-fuel ratio equivalent value limiting means limits the excess air ratio so as not to be less than a predetermined value. The control device for an internal combustion engine according to claim 1 or 2. 6. The air amount control means includes target throttle opening degree calculating means for calculating a target throttle opening degree based on a target air amount, and drives the electronically controlled throttle valve so as to attain the target throttle opening degree. The control device for an internal combustion engine according to any one of claims 1 to 5, wherein the control device is configured to: 7. The fuel injection amount control means for driving a fuel injection valve of a direct-injection spark ignition type internal combustion engine based on a target fuel injection amount.
The control device for an internal combustion engine according to any one of the above. 8. A combustion mode setting means for switching a combustion mode to a homogeneous combustion or a stratified combustion based on an engine operation condition, wherein said target air-fuel ratio equivalent value setting means sets a target air-fuel ratio for each combustion mode based on an engine operation condition. 8. The control device for an internal combustion engine according to claim 7, wherein a value corresponding to a fuel ratio is set. 9. The apparatus according to claim 1, further comprising target torque setting means for setting a target torque of the engine, wherein said required basic fuel amount calculating means calculates a required basic fuel amount based on the target torque. A control device for an internal combustion engine according to any one of claims 1 to 8.