JPH0681716A - Air-fuel ratio controller for internal combustion engine - Google Patents

Abstract

(57) [Summary] (Correction) [Purpose] The opening of the air bleed control valve of the carburetor is properly adjusted during idle operation and acceleration operation when the carburetor throttle valve of the internal combustion engine is opened from the idle opening. Can be changed to a specific opening degree, leaning of the air-fuel ratio can be avoided and stall of the engine speed can be prevented, or enrichment of the air-fuel ratio can be prevented and exhaust harmful components can be reduced. Get the device. [Structure] When the engine speed when the carburetor throttle valve is opened from the idle opening is less than the set speed, the opening of the air bleed control valve is temporarily changed to the second specific opening, and then the exhaust sensor Feedback control is performed to change the air-fuel ratio to the target value by changing the opening degree by the predetermined opening degree based on the detection signal, and when the engine speed is equal to or higher than the set speed, the opening degree of the air bleed control valve is set lower than the second specific opening degree. A control means is provided for performing a feedback control so that the air-fuel ratio becomes a target value by once changing to a large first specific opening and then changing by a predetermined opening based on the detection signal of the exhaust sensor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air-fuel ratio control system for an internal combustion engine, and more particularly to an air-fuel ratio control due to a delay in feedback control during idle operation when a carburetor throttle valve of the internal combustion engine is opened from an idle opening. Leaning can be avoided, stall of the engine speed can be prevented, and enrichment of the air-fuel ratio during acceleration operation when the carburetor throttle valve of the internal combustion engine is opened from the idle opening can be prevented. The present invention relates to an air-fuel ratio control device for an internal combustion engine, which can achieve good reduction of exhaust harmful components.

[0002]

2. Description of the Related Art Some internal combustion engines mounted on vehicles are equipped with an air-fuel ratio control device as a countermeasure for reducing exhaust harmful components and improving fuel consumption rate. The air-fuel ratio control device
The oxygen concentration in the exhaust gas is detected by the O2 sensor, which is an exhaust sensor provided in the exhaust passage, and the air amount and fuel amount in the fuel system are adjusted based on the detection signal of the O2 sensor to perform feedback control so that the air-fuel ratio becomes the target value. In addition, we are trying to reduce harmful exhaust components and improve fuel consumption rate.

An example of such an air-fuel ratio control device is disclosed in Japanese Patent Application Laid-Open No. 2-188654. The air-fuel ratio control device disclosed in this publication opens the air bleed control valve that controls the air bleed amount of the carburetor based on the detection signal of the exhaust sensor when the carburetor throttle valve of the internal combustion engine is at the idle opening position. Control at the time of opening the carburetor throttle valve immediately when the carburetor throttle valve returns to the idle opening degree by providing an idle feedback control means for controlling the air-fuel ratio to a target value by changing the degree at a low speed. To the control by the idle feedback control means, and a switching means for setting the average value of the idle control positions of the air bleed control valve as the control start position is provided.

[0004]

In the conventional air-fuel ratio control system for an internal combustion engine, the opening of the air bleed control valve of the carburetor of the internal combustion engine is changed by a predetermined opening based on the detection signal of the exhaust sensor. There is one that performs feedback control so that the air-fuel ratio becomes a target value.

This air-fuel ratio control system accelerates from the idle operation state of the carburetor throttle valve to the start operation or from the operating state of the carburetor throttle valve at the idle opening or less (idle switch is ON). If the opening degree of the air bleed control valve is controlled by the detection signal from the O2 sensor at the time of shifting to the operation, there is a problem that control is delayed.

[0006] In response to such a problem, the air-fuel ratio control device is turned on when the carburetor throttle valve is below the idle opening degree, and is off when the carburetor throttle valve is opened to an opening degree larger than the idle opening degree. An idle switch is provided to detect the transition to the acceleration operation state when this idle switch is turned from ON to OFF, and the opening of the air bleed control valve is set to a specific opening (for example, STHA-1). After skipping and once changing the air-fuel ratio to correct the air-fuel ratio, the air-fuel ratio is feedback-controlled so that the air-fuel ratio becomes the target value by changing the opening degree by a predetermined opening based on the detection signal of the O2 sensor.

That is, the air-fuel ratio control device temporarily changes the opening of the air bleed control valve to a specific opening (STHA-1) when the carburetor throttle valve is opened from the idle opening, and then the O2 Feedback control is performed such that the air-fuel ratio becomes a target value by changing the opening degree by a predetermined amount based on the detection signal of the sensor.

However, when the carburetor throttle valve of the internal combustion engine is opened from the idle opening degree, if the opening degree of the air bleed control valve is once changed to a specific opening degree (for example, STHA), after the operation state transition, There is a disadvantage that the opening of the air bleed control valve cannot follow the state where the air-fuel ratio becomes lean, and the engine speed stalls. In order to obtain engine stability during idle operation, this is, for example, in an idle operation range (idle switch: ON, engine speed Ne <1.
This is because the control speed of the air bleed control valve of 500 rpm) is slowed (see Japanese Patent Laid-Open No. 2-188654).

Therefore, the specific opening (STHA) of the air bleed control valve, which is changed when the carburetor throttle valve is opened from the idle opening, is changed to a small specific opening (for example, STH).
By setting A ': STHA>STHA'), it is possible to avoid the stall of the engine speed after the transition to the operating state, but at the time of starting, the air bleed control valve causes a shortage of the air bleed amount and the air-fuel ratio is rich. And CO, which is a harmful component of exhaust gas, increases.

[0010]

In order to eliminate the above-mentioned inconvenience, the present invention changes the opening of the air bleed control valve of the carburetor of the internal combustion engine by a predetermined opening based on the detection signal of the exhaust sensor. Feedback control is performed so that the air-fuel ratio becomes a target value, and when the carburetor throttle valve is opened from the idle opening, the opening of the air bleed control valve is temporarily changed to a specific opening and then the exhaust gas is exhausted. In an air-fuel ratio control device for an internal combustion engine that performs feedback control so that the air-fuel ratio becomes a target value by changing it by a predetermined opening based on a detection signal of a sensor, the engine rotation when the carburetor throttle valve is opened from an idle opening. When the number of rotations is less than the set rotation speed, the opening of the air bleed control valve is temporarily changed to the second specific opening, and then the opening is changed by a predetermined opening based on the detection signal of the exhaust sensor. Feedback control so that the air-fuel ratio reaches a target value, and when the engine speed when the carburetor throttle valve is opened from the idle opening is equal to or higher than the set speed, the opening of the air bleed control valve is adjusted. The second
A control means is provided to perform a feedback control so that the air-fuel ratio becomes a target value by once changing to a first specific opening larger than the specific opening and then changing by a predetermined opening based on a detection signal of the exhaust sensor. Is characterized by.

[0011]

According to the structure of the present invention, the control means causes
When the engine speed when the carburetor throttle valve is opened from the idle opening is less than the set speed, the opening of the air bleed control valve is temporarily changed to the second specific opening, and then the exhaust sensor detects By performing feedback control so that the air-fuel ratio becomes the target value by changing the opening degree by a predetermined amount based on the signal,
When the carburetor throttle valve of the internal combustion engine is opened from the idle opening, the opening of the air bleed control valve of the carburetor during the idle operation when the engine speed is less than the set speed is set to the appropriate second specific opening. Can be changed up to.

Further, when the engine speed when the carburetor throttle valve is opened from the idle opening is equal to or higher than the set speed by the control means, the opening of the air bleed control valve is set to the second opening.
By temporarily changing to a first specific opening that is larger than the specific opening and then changing the opening by a predetermined opening based on the detection signal of the exhaust sensor, feedback control is performed so that the air-fuel ratio becomes a target value. When the carburetor throttle valve is opened from the idle opening degree, the opening degree of the air bleed control valve during the acceleration operation is set to a proper first value larger than the second specific opening degree.
It can be changed to a specific opening.

[0013]

Embodiments of the present invention will be described in detail below with reference to the drawings.

1 and 2 show an embodiment of the present invention. In FIG. 2, 2 is an internal combustion engine, 4 is an intake passage,
6 is an exhaust passage, 8 is an air cleaner, 10 is a carburetor, 12
Is a throttle valve, 14 is an O2 sensor which is an exhaust gas sensor, and 16 is a catalytic converter which incorporates a three-way catalyst (not shown).

The air-fuel ratio control device 18 provided in the internal combustion engine 2 is provided with an air bleed passage 20 which communicates with the air cleaner 8 at one end side and at the other end side with the carburetor 10. In the middle of the air bleed passage 20, an air bleed control valve 22 (Air
bleed Control Valve: ABC
V) is provided. The opening of the air bleed control valve 22 is changed by an actuator 24 that operates in steps.

O 2 sensor 1 for detecting oxygen concentration in exhaust gas
4 and the actuator 24 that operates the air bleed control valve 22 are connected to a control unit 26 that is a control unit.
The control unit 26 includes an idle switch 28 that is turned on when the throttle valve 12 of the carburetor 10 is turned on at an idle opening or less and is turned off when the throttle valve 12 is opened from this idle opening to a larger opening than the idle opening, and a throttle valve. A fully open switch 30 that is turned on at the fully open opening and is turned off when the open opening is closed to a smaller opening than the fully open opening, and an ignition coil 32 that outputs an ignition signal are connected. There is.

Further, the control section 26 is provided with a fuel cutoff valve 3 which is closed to cut off the fuel during deceleration operation of the internal combustion engine 2.
4 for detecting different temperature states of the internal combustion engine 2
The water temperature switch 36 and the second water temperature switch 38 are connected.

The air-fuel ratio control device 18 causes the control unit 26 to change the opening degree of the air bleed control valve 22 of the carburetor 10 by a predetermined opening degree by the actuator 24 based on the detection signal of the O2 sensor 14, and to change the Feedback control is performed so that the fuel ratio becomes the target value. Further, the air-fuel ratio control device 18 causes the control unit 26 to temporarily change the opening degree of the air bleed control valve 22 to a specific opening degree when the throttle valve 12 of the carburetor 10 is opened from the idle opening degree. Based on the detection signal from the O2 sensor 14, the feedback control is performed so that the air-fuel ratio becomes the target value by changing the opening degree by a predetermined opening degree.

In such an air-fuel ratio control device 18,
The control unit 26 sets the engine rotation speed Ne when the throttle valve 12 of the carburetor 10 is opened from the idle opening degree to the set rotation speed N.
If it is less than eα, the opening of the air bleed control valve 22 is skipped to the second specific opening (STHA-2) and changed once, and then the opening is changed by a predetermined opening based on the detection signal of the O2 sensor 14. Feedback control is performed so that the air-fuel ratio becomes the target value.

Further, the control unit 26 controls the opening degree of the air bleed control valve 22 when the engine speed Ne when the throttle valve 12 of the carburetor 10 is opened from the idle opening degree is equal to or higher than the set rotation speed Neα. To a first specific opening (STHA-1) which is larger than the second specific opening (STHA-2) and is changed once, and then is changed by a predetermined opening based on the detection signal of the O2 sensor 14. Feedback control is performed so that the air-fuel ratio reaches the target value.

That is, when the throttle valve 12 of the carburetor 10 is opened from the idle opening degree and the idle switch 28 is turned from ON to OFF, the control unit 26 determines that the engine speed Ne is less than the set speed Neα. Air bleed control valve 2
The second opening is temporarily changed to the second specific opening (STHA-2).

Further, the control unit 26 controls the idle switch 2
When the engine speed Ne is equal to or higher than the set speed Neα when 8 is turned from ON to OFF, the air bleed control valve 22
The opening degree is changed to the first specific opening degree (STHA-1). The second specific opening (STHA-2) is smaller than the first specific opening (STHA-1) (STHA-2 <S
It is set to THA-1).

The set rotational speed Neα for skipping the opening of the air bleed control valve 22 is Neβ <Neα <N.
It is set to eγ. Neβ turns the idle switch 28 from ON to OFF when the throttle pedal is depressed.
However, it is the highest speed among them. Further, Neγ is the air bleed control valve 2
2 is the maximum rotation speed (for example, 1500 rpm) that is controlled (the control speed is slow) in the idling operation range for engine stability during idling operation.

Next, the operation will be described.

The air-fuel ratio control device 18 controls as shown in FIG. The control unit 26 starts control (step 1
00), the idle switch 28 turns from ON to OFF
It is determined whether or not (step 102).

When the throttle valve 12 of the carburetor 10 is not opened from the idle opening degree and the determination (step 102) is NO, the opening degree of the air bleed control valve 22 of the carburetor 10 is set to the O2 sensor 14. Based on the detection signal, the actuator 24 changes the opening degree by a predetermined degree to perform feedback control (step 110) so that the air-fuel ratio becomes the target value, and then returns (step 112).

When the throttle valve 12 of the carburetor 10 is opened from the idle opening degree and the judgment (step 102) is YES, it is judged whether the engine speed Ne is equal to or higher than the set speed Neα (step). 104)

When the engine speed Ne is less than the set speed Neα and the determination (step 104) is NO, the opening of the air bleed control valve 22 is set to the second specific opening (STHA-
Up to step 2), the temperature is changed once by step 106, and the actuator 24 changes the opening degree by a predetermined opening based on the detection signal of the O2 sensor 14 so that the air-fuel ratio becomes the target value. Step 112) is performed.

The second specific opening (STHA-2) is smaller than the first specific opening (STHA-1) (STHA-2).
<STHA-1). As a result, when the throttle valve 12 of the carburetor 10 of the internal combustion engine 2 is opened from the idle opening degree, the air bleed control valve 22 of the carburetor 10 of the carburetor 10 during idle operation in which the engine speed Ne is less than the set speed Neα is set. The opening is the first specific opening (STHA
-1) An appropriate second specific opening (STHA-
It can be changed up to 2). Therefore, it is possible to prevent the air-fuel ratio from becoming lean due to the delay of the feedback control, and it is possible to prevent the engine speed from stalling.

When the engine speed Ne is equal to or higher than the set speed Neα and the determination (step 104) is YES, the opening of the air bleed control valve 22 is set to the first specific opening (STHA).
-2) is changed once by step (step 108), and the actuator 24 is changed by a predetermined opening degree based on the detection signal of the O2 sensor 14 to perform feedback control (step 110) so that the air-fuel ratio becomes the target value, and the return is performed. (Step 112).

This first specific opening (STHA-1) is larger than the second specific opening (STHA-2) (STHA-2).
<STHA-1). As a result, the air bleed control valve 2 during acceleration operation when the throttle valve 12 of the carburetor 10 of the internal combustion engine 2 is opened from the idle opening degree.
The second opening can be changed to an appropriate first specific opening (STHA-1) larger than the second specific opening (STHA-2). Therefore, it is possible to prevent the air-fuel ratio from becoming rich during acceleration operation, and it is possible to achieve a good reduction of exhaust harmful components.

[0032]

As described above, according to the present invention, when the carburetor throttle valve of the internal combustion engine is opened from the idle opening degree,
It is possible to change the opening degree of the air bleed control valve of the carburetor to an appropriate second specific opening degree that is smaller than the first specific opening degree during the idle operation in which the engine speed is less than the set rotational speed. Therefore, it is possible to prevent the air-fuel ratio from becoming lean due to the delay of the feedback control, and it is possible to prevent the engine speed from stalling.

Further, when the carburetor throttle valve of the internal combustion engine is opened from the idle opening, the opening of the air bleed control valve during the acceleration operation is set to a proper first specified value which is larger than the second specified opening. The opening can be changed. For this reason,
It is possible to prevent enrichment of the air-fuel ratio during acceleration operation, and to achieve good reduction of exhaust harmful components.

[Brief description of drawings]

FIG. 1 is a flowchart of control of an air-fuel ratio control device showing an embodiment of the present invention.

FIG. 2 is a block diagram of an air-fuel ratio control device.

[Explanation of symbols]

 2 Internal combustion engine 4 Intake passage 6 Exhaust passage 8 Air cleaner 10 Vaporizer 12 Throttle valve 14 O2 sensor 16 Catalytic converter 18 Air-fuel ratio control device 20 Air bleed passage 22 Air bleed control valve 24 Actuator 26 Control unit 28 Idle switch 30 Full open switch 32 Ignition Coil 34 Fuel cutoff valve 36 First water temperature switch 38 Second water temperature switch

Claims (1)

[Claims] 1. An carburetor of an internal combustion engine is feedback-controlled so that an air-fuel ratio reaches a target value by changing the opening of the air bleed control valve by a predetermined opening based on a detection signal of an exhaust sensor, and the carburetor throttle is also provided. When the valve is opened from the idle opening, the opening of the air bleed control valve is once changed to a specific opening, and then the air-fuel ratio is changed to a target value by changing the opening by a predetermined opening based on the detection signal of the exhaust sensor. In an air-fuel ratio control device for an internal combustion engine that performs feedback control so that when the engine speed when the carburetor throttle valve is opened from an idle opening is less than a set speed, the opening of the air bleed control valve is 2 Once the air-fuel ratio is changed to a specific value, the air-fuel ratio is changed to a target value by feedback control so that the air-fuel ratio becomes a target value. A first specific opening that makes the opening of the air bleed control valve larger than the second specific opening when the engine speed when the carburetor throttle valve is opened from the idle opening is equal to or higher than the set speed. The air-fuel ratio control device for an internal combustion engine is provided with a control means for performing feedback control so that the air-fuel ratio becomes a target value by changing the opening degree by a predetermined opening degree based on the detection signal of the exhaust sensor.