JPH04325747A - Air-fuel ratio control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To reduce vibration transmitted to passengers due to switching action so as to improve riding comfort by lengthening the cycle of switching action between fixed duty control and feedback duty control by a hysteretic characteristic so as to reduce the increase/decrease frequency of engine speed. CONSTITUTION:An air-fuel ratio control device 4 for an internal combustion engine controls an air-fuel ratio by switching either to the fixed duty control or feedback duty control of an idle speed control solenoid valve 14 according to the feedback starting water temperature preset to the water temperature of an engine 2. This air-fuel ratio control device 4 is provided with a control part 16 for controlling in such a way as to reduce the fluctuation of engine speed caused by switching action between the fixed duty control and the feedback duty control by adding hysteresis to the feedback starting water temperature.

Description

[Detailed description of the invention]

0001

FIELD OF INDUSTRIAL APPLICATION This invention relates to an air-fuel ratio control device for an internal combustion engine, and in particular, controls either fixed duty control or feedback duty control of a solenoid valve for controlling an idle speed control (ISC) depending on the feedback start water temperature. The present invention relates to an air-fuel ratio control device for an internal combustion engine that controls the air-fuel ratio by adjusting the bypass air amount through idle speed control (ISC) control.

0002

[Prior Art] As an air-fuel ratio control device, an idle speed control (ISC) control solenoid valve installed in a bypass passage that bypasses an intake throttle valve is electrically opened and closed by idle speed control (ISC) control. There is a device that controls the amount of bypass air passing through the bypass passage to control the air-fuel ratio to the internal combustion engine, and controls the rotational speed of the internal combustion engine when the engine is idling.

Idle Speed Control (IS)
C) The control includes the idle speed control (ISC) to adjust the engine speed to correspond to the engine water temperature.
) The control solenoid valve is driven to perform feedback duty (F/BDuty) control or fixed duty (Duty) control of the engine speed.

[0004] This feedback duty (F/BD
For example, when the condition that the idle switch is on and the condition that the engine speed is less than the target engine speed are satisfied, the control is performed such that when the conditions that the idle switch is on and the conditions that the engine speed is less than the target engine speed are satisfied, the condition that the idle switch is turned on and the delay time is satisfied. Select one of the conditions. The condition is satisfied when one of these conditions, the condition that the vehicle speed is less than the control start vehicle speed, and the condition that the engine speed is less than the control start engine speed, and the feedback duty (F/ BDuty) control is started.

[0005] Also, feedback duty (F/B
Duty) control is not established, the IS of the control valve is
The C duty value is maintained at a fixed value, and the fixed duty (D
uty) control.

Furthermore, as an air-fuel ratio control device for an internal combustion engine, there is one disclosed in Japanese Patent Laid-Open No. 1-280651. The air-fuel ratio control device disclosed in this publication inputs a detection signal from a water temperature sensor when starting the engine to preset the starting water temperature for feedback control, and also provides feedback from open control when the engine water temperature reaches the starting water temperature. By providing a control unit that controls the air-fuel ratio for transition to control, a drop in engine speed and engine stalling are prevented when transitioning from open control to feedback control.

[0007]

By the way, in the conventional air-fuel ratio control device for an internal combustion engine, for example, the air flow rate is adjusted according to the wax change due to the engine water temperature during cold start, that is, the wax air amount is adjusted, and the idle speed The engine speed during warm-up is controlled by two adjustment measures: air flow rate adjustment using a control (ISC) control solenoid valve (see FIG. 4).

[0008] Idle speed control (ISC) control also uses preset feedback (F
/B) When the engine water temperature reaches the start water temperature, the fixed duty (Du) of the idle speed control (ISC) control is set as the feedback (F/B) start temperature.
ty) control to feedback duty (F/BDu
ty) control, and depending on the engine water temperature conditions, the idle speed control (ISC)
) controls the function.

However, in the above-mentioned control measures, when the heater blower inside the vehicle is used to warm up the engine during winter start-up, the idle speed control (ISC) is activated as shown in FIG. Feedback duty (F/BDuty) control is started, and the engine speed NE is temporarily lowered to the idle (ID) speed.

[0010] As the amount of heat radiated by the heater blower becomes larger than the amount of heat radiated by the internal combustion engine, the engine water temperature decreases, and this engine water temperature becomes less than the feedback (F/B) start water temperature, and the feedback duty (F/B) is reduced. B
This allows switching from fixed duty (duty) control to fixed duty (duty) control.

[0011] Furthermore, when fixed duty (Duty) control starts, the idle speed control duty (ISCDuty) ratio increases, the engine speed increases, and the engine water temperature also increases, causing the engine water temperature to become feedback. (F/B) When the starting water temperature is reached, fixed duty (Duty) control is switched to feedback duty (F/BDuty) control.

As a result, fixed duty (Duty) control and feedback duty (F
/BDuty) control is performed, the engine speed increases or decreases more frequently, and vibrations caused by the switching operation are transmitted to the occupants, worsening ride comfort and being disadvantageous in practical terms. .

[0013]

[Means for Solving the Problems] Therefore, in order to eliminate the above-mentioned disadvantages, the present invention provides a means for adjusting the idle speed by adjusting the feedback start water temperature set in advance to the engine water temperature.
In an air-fuel ratio control device for an internal combustion engine that controls the air-fuel ratio by switching between fixed duty control and feedback duty control of a control solenoid valve, hysteresis is added to the feedback start water temperature to control the fixed duty control and the feedback duty. The present invention is characterized in that it is provided with a control section that performs control to reduce fluctuations in engine rotational speed due to switching operations with the control.

[0014]

[Operation] As described above, the hysteresis added to the feedback start water temperature reduces fluctuations in engine speed caused by switching between fixed duty control and feedback duty control, reduces vibrations caused by switching, and improves riding comfort. is improving.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below in detail with reference to the drawings.

FIGS. 1 to 3 show an embodiment of the present invention. In FIG. 2, 2 is an internal combustion engine, and 4 is an internal combustion engine 2.
This is an air-fuel ratio control device.

This air-fuel ratio control device 4 bypasses the intake throttle valve 8 provided in the intake passage 6 of the internal combustion engine 2, and controls the intake passage 6-1 on the upstream side and the intake passage 6-2 on the downstream side of the intake throttle valve 8. A bypass passage 12 is provided which communicates with the surge tank 10 of. This bypass passage 12 is provided with an idle speed control solenoid valve 14 that is operated according to a duty value.

The solenoid valve 14 performs feedback duty (F/BDuty) control or fixed duty (Duty) control to adjust the amount of bypass intake air passing through the bypass passage 12, thereby controlling the engine speed.

The solenoid valve 14 is provided in the middle of the bypass passage 12 that bypasses the intake throttle valve 8, and is electrically controlled to open and close by idle speed control (ISC) control to control the amount of bypass air passing through the bypass passage 12. The intake air amount to the internal combustion engine 2 is controlled by adjusting the amount of air taken into the internal combustion engine 2, and is connected to the control unit 16.

Further, a cooling water temperature sensor (not shown) for detecting the engine water temperature, which is the cooling water temperature of the internal combustion engine 2, other sensors, and various switch groups are connected to the control unit 16, respectively. .

An injector 18 is provided in the intake passage 6 of the internal combustion engine 2 on the downstream side of the intake throttle valve 8 provided in the intake passage 6 . Fuel injected from the injector 18 is drawn into the combustion chamber 20 together with air and is combusted. After combustion, the exhaust gas produced by combustion is discharged to the outside through the exhaust passage 22.

Further, an air regulator 24 is provided to be connected to a portion upstream of the solenoid valve 14 in the middle of the bypass passage 12, and one end of the air regulator 24 communicates with the intake passage 6 downstream of the intake throttle valve 8. Then, intake pressure is introduced to adjust the air pressure to a predetermined pressure.

The control unit 16 of the air-fuel ratio control device 4 performs fixed duty control when the engine water temperature measured by a cooling water temperature sensor (not shown) is less than a preset feedback (F/B) start water temperature. When the engine water temperature reaches the feedback (F/B) start water temperature, the feedback duty (F/BDuty) is
is under control.

The control section 16 adds hysteresis to the feedback (F/B) start water temperature and performs fixed duty (Duty) control and feedback duty (Duty) control.
It has a configuration that controls to reduce fluctuations in engine speed due to switching operation with F/BDuty) control.

More specifically, as shown in FIG. 3, hysteresis is added to the feedback (F/B) starting water temperature of the control section 16 to set two different set values A and B (A<B).
will be established. Then, the set value A is the hiss temperature, and when the engine water temperature is less than the set value A, the fixed duty (Duty) is changed from the feedback duty (F/BDuty).
Switch to control.

[0026] Furthermore, the set value B can be changed using conventional feedback (
When the engine water temperature reaches the set value B, the fixed duty (Duty) control is switched to the feedback duty (F/B Duty) control, and the hysteresis characteristic as shown in FIG. It is added to.

[0027] Reference numeral 26 is an air cleaner.

Next, the operation will be explained.

When the engine water temperature rises and reaches the set value B, the engine water temperature becomes the feedback (F/B) start water temperature, and fixed duty (Duty) control is switched to feedback duty (F/BDuty) control, and this feedback Duty (F/BDuty)
The solenoid valve 14 is opened and closed under control to control the air-fuel ratio.

[0030] Then, this feedback duty (
F/BDuty) If the engine water temperature drops to less than the set value A, which is smaller than the set value B, the feedback duty (F/BDuty) will be changed from the fixed duty (D
This fixed duty (D
Opening and closing the solenoid valve 14 by Uty) control,
It controls the air-fuel ratio.

Furthermore, when the engine water temperature rises and reaches the set value B again during fixed duty (Duty) control, the fixed duty (Duty) control is switched to feedback duty (F/BDuty) control.

Furthermore, when the engine is cold, air flows as shown by arrow a in FIG. 2, and when the idle speed control solenoid valve 14 is opened, air flows as shown by arrow b in FIG.
As shown in the figure, air flows through it.

[0033] As a result, the cycle of switching operation between fixed duty (Duty) control and feedback duty (F/BDuty) control can be made longer than before due to the hysteresis characteristic, and the frequency of increase or decrease in engine speed can be increased. This is advantageous in practice, since the vibration transmitted to the occupant due to the switching operation can be reduced, and riding comfort can be improved.

Furthermore, since the hysteresis characteristic can be added simply by changing the program in the control section 18, there is no risk of complicating the configuration, making it easy to manufacture, and keeping costs low. It is possible and economically advantageous.

[0035]

As described in detail above, according to the present invention, either the fixed duty control or the feedback duty control of the solenoid valve for controlling the idle speed control is performed according to the feedback start water temperature set in advance to the engine water temperature. In an air-fuel ratio control device for an internal combustion engine that controls the air-fuel ratio by switching the air-fuel ratio, there is provided a control unit that adds hysteresis to the feedback start water temperature to reduce fluctuations in engine speed caused by switching between fixed duty control and feedback duty control. As a result, the cycle of switching operation between fixed duty control and feedback duty control can be lengthened due to hysteresis characteristics, reducing the frequency of increase or decrease in engine speed, and reducing vibrations caused by switching operation transmitted to passengers. This is advantageous in practice because it can reduce the amount of noise and improve riding comfort. In addition, since the hysteresis characteristic can be added by simply changing the program in the control section, there is no risk of complicating the configuration, and manufacturing is easy and costs can be kept low, making it economically viable. It's advantageous.

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram showing hysteresis characteristics according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of an air-fuel ratio control device for an internal combustion engine.

FIG. 3 is a time chart of an air-fuel ratio control device for an internal combustion engine.

[Fig. 4] Adjustment by wax air amount and idle speed control (ISC) showing the prior art of this invention.
) is a time chart of engine speed control during warm-up by adjusting air flow rate using a control solenoid valve.

FIG. 5 is a time chart of an air-fuel ratio control device for an internal combustion engine showing a conventional technique of the present invention.

[Explanation of symbols]

2 Internal combustion engine 4 Air-fuel ratio control device 6 Intake passage 8 Intake throttle valve 12 Bypass passage 14 Idle speed control solenoid valve 16 Control unit 18 Injector 24 Air regulator

Claims (1)

[Claims] Claim 1: An air-fuel ratio of an internal combustion engine in which the air-fuel ratio is controlled by switching between fixed duty control and feedback duty control of a solenoid valve for idle speed control according to a feedback start water temperature set in advance to the engine water temperature. An air conditioner for an internal combustion engine, characterized in that the control device includes a control section that adds hysteresis to the feedback start water temperature to reduce fluctuations in engine speed caused by switching between fixed duty control and feedback duty control. Fuel ratio control device.