JPS61261648A - Method for controlling air-fuel ratio of engine - Google Patents

Abstract

PURPOSE:To allow smooth start-up of engine by making such arrangement in bleed air control of air fuel ratio that an air bleed control valve may be controlled in accordance with judgement on whether coolant temperature at the time of engine start-up is at an extremely high level or not. CONSTITUTION:An air bleed control valve 25 is installed to control bleed air volume that is supplied from an air inlet 30 through air channels 31, 32 to main system- and slow system-fuel passages 33, 34 based on forward and backward motion of a needle valve 29 driven by a stepper motor 26. Air fuel ratio of mixed air is controlled with the valve 25, which is in turn controlled with ECU59. Namely, when coolant temperature is at extremely high levels, for instance, more than 100 deg.C at the time of engine start detection, the control valve 25 is fully opened, and when the engine has completed explosion feedback control of the air fuel ratio fixed by coolant temperature is effected. In the case of start-up at the temperature other than extremely high one, the control valve 25 is completely closed, and after complete explosion of the engine similar feedback control is enforced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of controlling an actuator for controlling an air-fuel ratio of air-fuel mixture supplied to an engine, particularly at the time of starting the engine.

(Prior art) Conventionally, air-fuel ratio control at the time of engine starting was performed using
As described in Publication No. 7-20529, a pulse motor is used as the actuator of the air-fuel ratio control valve, and the air-fuel ratio control valve is driven to a position determined by referring to the engine cooling water temperature, etc. when starting the engine. Then, the air-fuel ratio control valve is held at the specified position until the feedback control condition is satisfied, but in this case, the valve position of the air-fuel ratio control valve is adjusted so that the air-fuel ratio of the air-fuel mixture supplied after the engine starts is correct. In order to drive and set the air-fuel ratio control valve to the correct position,
Although the engine runs well during warm-up after starting, the air-fuel ratio at the time of starting is lean, making it difficult to start the engine, and when starting at a high temperature, the air-fuel mixture may be too rich. Even when starting is difficult, the air-fuel ratio control valve is set at a valve position that allows the engine to operate smoothly after starting, so the air-fuel mixture does not get out of the rich state and the engine runs smoothly. The drawback was that it became increasingly difficult to start.

(Problems to be Solved by the Invention) The object of the present invention is to start the engine cleanly even when the engine temperature is extremely high or other times, and to improve engine operation after starting.

(Means for Solving the Problems) As shown in FIG. 1, the present invention provides a bleed air source by driving an actuator of an air bleed control valve based on signals from various sensors corresponding to the state before starting the engine. When controlling the air-fuel ratio of the air-fuel mixture, in step S01, whether or not it is the time to start the engine is detected, for example, based on the rotational speed of the starter motor.
In step 2, it is determined whether the engine cooling water temperature is extremely high, for example, 100°C or higher, and if it is extremely high, step 8 is performed.
In step S03, the actuator of the air bleed control valve is driven to fully open the air bleed control valve, and at the time of complete explosion after the engine has started, in step S04, the actuator of the air bleed control valve is activated to adjust the temperature of the engine cooling water and the temperature of the engine. Feedback control is performed in response to the air-fuel ratio of the air-fuel mixture determined by the machine state, etc., and if the engine cooling water temperature at the time of engine start start detection is other than the extremely high temperature, the actuator of the air bleed control valve is driven in step SO5. The air bleed control valve is fully opened, and at step S04, when the engine is fully detonated after starting, the actuator of the air bleed control valve is adjusted to correspond to the air-fuel ratio of the air-fuel mixture determined by the engine cooling water temperature, engine warm-up state, etc. A method for controlling an air-fuel ratio of an engine using feedback control.

(Embodiment) Next, the configuration of an embodiment of the present invention will be described with reference to FIG.

A throttle valve 4 that opens in response to the amount of depression of the accelerator pedal is attached to an intake passage 3 that supplies fuel from the carburetor 2 to the engine, and is biased in the valve closing direction by a spring (not shown). In the valve closed position, the operation lever 6 fixed to the shaft 5 of the throttle valve 4 is operated by the actuator 7, and in this case, reversible operation is possible.
A touch head 12 at the tip of an actuator 7 rotates a threaded rod 10 in forward and backward directions via a motor 8 and a gear train 9 to move back and forth an output shaft 11 fitted with a screw to the threaded rod 10 whose movement in the circumferential direction is restricted. The contact of the operating lever 6 with the touch head 12 is determined by the contact of the touch head 12, and the final gear 14 is slightly retracted along with the output shaft 11 against the biasing force of the spring 13, and the idle switch 15 is turned on. output shaft 1
The stroke end of 1 is detected when the dog 16 on the output shaft 11 comes into contact with the lever 18 of the limit switch 17.

This carburetor 2 has a main cut NI for cutting the fuel supply to the main nozzle 20 formed in the small bench lily 19 of the intake passage 3 at the main jet 21 position.
valve 22, a slow cut solenoid valve 24 for cutting fuel supply to the slow boat 23 formed near the throttle valve 4 in the intake passage 3, and an air bleed control O- for adjusting bleed air for the main and slow systems.
In this case, by rotating the nut body 27 forward and backward through the stepper motor 26 of the electric actuator and moving the needle valve 29 back and forth together with the threaded rod 28 whose movement in the circumferential direction is regulated, the air hole 30 is opened. An air bleed control valve 25 adjusts the amount of bleed air supplied from the air passages 31, 32 to the main system and slow fund fuel passages 33, 34, and controls the amount of fuel supplied to the engine during engine startup, acceleration, etc. In this case, the auxiliary fuel pump 35 sucks fuel from the float chamber 40 of the carburetor 2 by reciprocating the piston 39 through the plunger 38 due to the on/off operation of the solenoid coil 36 and the biasing force of the spring 37. After the fuel is sucked into the cylinder chamber 42 through the side check valve 41, it is supplied to the intake passage 3 from the discharge side check valve 43 through the auxiliary nozzle 45 formed above the large venturi 44, respectively. is installed.

In the carburetor 2 configured in this way, the DC motor 8 of the actuator 7, each switch 15, 17, each fuel cut solenoid valve 22, 24, the stepper motor 26 of the air bleed control valve 25, and the auxiliary The solenoid coil 36 of the fuel pump 35, the throttle opening sensor 46 attached to the carburetor 2 and generating an output corresponding to the opening degree of the throttle valve 4, the water temperature sensor 47 attached to the water jacket of the engine, and the ignition An engine rotation speed sensor 48 such as a coil, a vehicle speed sensor 49 that generates an output corresponding to the speed of the vehicle,
The 02 sensor 50 is installed in the exhaust passage and generates an output corresponding to the oxygen concentration, the clutch/neutral detection sensor 51 changes the output when the clutch is off and in the neutral state, and the side lamp generates an output when the side lamp is on. A switch 52, an economy/diagnosis lamp 53 that lights up during economy and diagnosis, an air conditioner switch 54, a starter switch 55, an ignition key switch 56, and an alternator control circuit 5.
7 are connected to an electric control circuit 59 for engine control, commonly known as an ECU, in which power supply from a battery 58 is controlled on and off by an ignition key switch 56.

Next, FIG. 3 shows a specific example of the electric control circuit 59, in which the microcomputer CPU, which is controlled according to the program in the storage circuit ROM, receives the engine rotational speed from the engine rotational speed sensor 48 via the waveform shaper 60. In addition to inputting a pulse signal with a frequency corresponding to the frequency, an analog signal corresponding to the engine cooling water temperature from the water temperature sensor 47, an analog signal corresponding to the opening degree of the throttle valve 4 from the throttle opening sensor 46, and an analog signal corresponding to the opening degree of the throttle valve 4 from the 02 sensor 50 are input. The analog signals corresponding to the oxygen concentration from
On/off signals from the clutch/neutral detection switch 51, air conditioner switch 54, pulse output vehicle speed sensor 49, ignition key switch 56, starter switch 55, and side lamp switch 52 are input via the input port 3. , and each drive circuit 6 is connected to the output port 4 of the microcomputer CPU.
5 to 69, the DC motor 8 of the actuator 7, the solenoid coil 36 of the auxiliary fuel pump 35, the main cut solenoid valve 22, the slow cut solenoid valve 24, and the alternator control circuit 57 are connected, as well as the output port door. 0 is connected to the stepper motor 26 of the air bleed control valve 25 via a drive circuit 71.

Next, the operation of this embodiment will be explained.

In an engine control device configured in this way, in particular an engine control device for an electronically controlled chokeless carburetor, the air-fuel ratio of the air-fuel mixture supplied to the engine, especially at the time of starting the engine, is controlled according to the flowchart shown in FIG. Ru.

That is, the air bleed control valve 25 is based on signals from various sensors corresponding to the state before starting the engine.
When controlling the air-fuel mixture at the time of engine startup and after engine startup to the required air-fuel ratio by controlling the amount of bleed air by υ control of the actuator, in this case, the stepper motor 26, it is determined in step 101 whether or not it is the time to start the engine. For example, it is determined by the on/off state of the starter switch 55 or the engine speed, and before starting the engine, in step 102, it is determined whether the engine cooling water temperature is a specific water temperature that is high enough to make starting difficult, for example, extremely high temperature of 100 degrees Celsius or more. At the same time, when the temperature is extremely high at 100° C. or higher, the stepper motor 26 of the air bleed control valve 25 is driven to fully open the air bleed control valve 25 in step 103, and when the starter switch 55 is turned on, the engine enters air bleed control. Starting is started in a lean air-fuel mixture state with the valve 25 fully open, and the engine is easily started even when restarted at an extremely high temperature of ii oo ℃ or above. After starting the engine, the needle valve 29 position of the air bleed control valve 25 is set to step 104.
As shown in FIG. 5, during warm-up operation after startup, the needle valve 29 is driven and held at a predetermined hold position corresponding to the appropriate air-fuel ratio, and in step 105, the conditions for executing air-fuel ratio feedback, such as water temperature, are set. It is determined whether or not the execution condition that the 02 sensor 50 is activated at 60° C. or higher is satisfied, and in a state where the execution condition is satisfied, the air bleed control valve 25 adjusts the preset economic air-fuel ratio, etc. in step 106. As a result, the air-fuel ratio of the air-fuel mixture supplied to the engine is appropriately set before and after starting the engine. Even in the restart state at an extremely high temperature of 100° C. or higher, the startup and operation are smoothly controlled as shown in FIG.

On the other hand, when it is determined in step 102 that the engine cooling water temperature is relatively easy to start, for example, less than 100° C., the stepper motor 26 of the air bleed control valve 25 is driven in step 107, and the air bleed control valve 25 is fully opened. When the starter switch 55 is turned on, the engine is easily started in a rich air-fuel mixture state with the air bleed control valve 25 fully closed, and this engine start start state is determined in step 101. In step 104, the needle valve 29 position of the bleed control valve 25 is driven and held at a predetermined hold position corresponding to the appropriate air-fuel ratio during warm-up operation after startup, as shown in FIG. In step 105, it is determined whether or not the air-fuel ratio feedback execution condition, for example, the execution condition that the 02 sensor 50 is activated when the water temperature is 60° C. or higher, is satisfied. The bleed control valve 25 is feedback-controlled in accordance with the air-fuel ratio of the air-fuel mixture determined by the engine cooling water temperature and the warm-up state of the engine, or a preset economic air-fuel ratio, etc., and controls the mixture supplied to the engine in this way. As a result, the air-fuel ratio of air is appropriately set before and after starting the engine, so that the engine can be started and operated smoothly as shown in FIG.

(Effects of the Invention) The present invention controls the air-fuel ratio of the air-fuel mixture by controlling the amount of bleed air by driving the actuator of the air bleed control valve based on signals from various sensors corresponding to the state before starting the engine! When performing IJ m, it is detected whether or not it is the time to start the engine, and if the engine cooling water temperature is extremely high when the engine start start is detected, the actuator of the air bleed control valve is driven to fully open the air bleed control valve. When the engine is completely exploded, the actuator of the air bleed control valve is feedback-controlled in accordance with the air-fuel ratio of the air-fuel mixture determined by the engine cooling water temperature and the warm-up state of the engine, and the engine cooling water temperature is When the temperature is other than the extremely high temperature, the actuator of the air bleed control valve is activated to set all air bleed control valves, and when the engine is completely exploded, the actuator of the air bleed control valve is activated to control the engine cooling water temperature, engine warm-up state, etc. The present invention provides a method for controlling an air-fuel ratio of an engine, which performs feed pack control in accordance with the air-fuel ratio of an air-fuel mixture determined by the following.

As a result, the present invention allows the engine to start smoothly even when the engine temperature is extremely high or other times, and
This has the effect of improving engine operation after starting.

[Brief explanation of the drawing]

Fig. 1 is a flowchart clearly showing the configuration of the present invention, Fig. 2 is an explanatory diagram of an embodiment of the invention, Fig. 3 is its electrical control circuit diagram, Fig. 4 is its flowchart, and Figs. FIG. 7 is a diagram showing its operating characteristics. 801~SO5...Step

Claims (1)

[Claims] When controlling the air-fuel ratio of the air-fuel mixture by controlling the amount of bleed air by driving the actuator of the air bleed control valve based on signals from various sensors corresponding to the state before starting the engine, it is detected whether or not it is time to start the engine. When the engine cooling water temperature is extremely high when detecting the start of the engine, the actuator of the air bleed control valve is driven to fully open the air bleed control valve, and when the engine is completely exploded, the actuator of the air bleed control valve is opened to the engine. Feedback control is performed in accordance with the air-fuel ratio of the air-fuel mixture determined by the cooling water temperature and the warm-up state of the engine, and the actuator of the air bleed control valve is operated when the engine cooling water temperature is other than the extremely high temperature at the time of detecting the start of engine start. In addition to fully closing the air bleed control valve, the actuator of the air bleed control valve is fed back in response to the air-fuel ratio of the air-fuel mixture, which is determined by the engine cooling water temperature and engine warm-up state, etc. 1. A method for controlling an air-fuel ratio of an engine.