JPS6055690B2 - Engine idle speed control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an idle speed control device that maintains the idle speed of an engine having a carburetor at a set value.

As a device of this type, the present applicant has provided a rotation sensor that detects the engine rotation speed, and a first sensor that opens and closes the bypass passage on and off in a bypass passage that opens into the intake passage downstream of the carburetor throttle valve. A solenoid valve is provided, and the on/off time ratio of the first solenoid valve (
Hereinafter, it will be referred to as duty ratio.

), the first solenoid valve is actuated via a first control circuit that changes the amount of auxiliary air in the bypass air passage when the idle rotation speed exceeds a set value (for example, 650 μm), while reducing the amount of auxiliary air in the bypass air passage. Feedback control is performed so that the idle speed of the engine is approximately equal to the set value by increasing the idle speed when it falls below the set value, and an exhaust sensor and a catalyst device are installed in the engine exhaust system. , and a second solenoid valve that opens and closes the auxiliary air bleed in an on/off manner is interposed in the auxiliary air bleed connected to the slow system fuel passage of the carburetor, and the bypass air passage is emptied by the amount of auxiliary air. The second solenoid valve is actuated via a second control circuit that changes the on/off time ratio of the second solenoid valve according to the output of the exhaust sensor in response to fluctuations in the fuel ratio, and the amount of bleed air of the auxiliary air bleed is vaporized. The fuel flow rate 5 in the slow system fuel passage is controlled by controlling the fuel flow rate 5 in the slow system fuel passage by increasing the amount when the air-fuel mixture produced by the device is richer than the stoichiometric air-fuel ratio, and decreasing it when the air-fuel mixture is thinner than the stoichiometric air-fuel ratio, A system has already been proposed in which the air-fuel ratio of the air-fuel mixture is feedback-controlled to approximately the stoichiometric air-fuel ratio, thereby effectively controlling the idle rotation of the engine (Japanese Patent Application No. 1986-10).
9832).

In the above device, when the range of change in the air-fuel ratio by the first control circuit on the rotation sensor side is larger than the range in which the air-fuel ratio is controlled by the second control circuit on the exhaust sensor side, the entire range of control by the first control circuit cannot reach the stoichiometric air-fuel ratio.
In order to achieve the stoichiometric air-fuel ratio over the entire range of control by the first control circuit, it is necessary to make the control range of the air-fuel ratio by the second control circuit equal to or greater than the range of change in the air-fuel ratio by the first control circuit, If the range of change in the air-fuel ratio of the first and second control circuits is made equal, the rate of change in the air-fuel ratio with respect to the duty ratio will also be the same. However, even if the range of change in the duty ratio is the same, the second control circuit operates with a certain time delay compared to the first control circuit, and the time for stabilization will continue to slide and be delayed. A problem arises in which control by the stable first control circuit becomes unstable. This invention aims to solve the above-mentioned problems, and the range of change in the duty ratio of the first control circuit and the second control circuit is the same, and the amount of change in the duty ratio of the second control circuit is set to be the same as that of the duty ratio of the first control circuit. An engine that is larger than the control circuit and whose stabilization timing is the same even if the control operation of the second control circuit is delayed than the control operation of the first control circuit, thereby improving stability during idling operation, etc. An idle speed control device is provided.

Hereinafter, the present invention will be explained in detail with reference to embodiments shown in the drawings.

In FIG. 1, 1 is an engine, 2 is an intake passage that supplies air-fuel mixture to the engine 1, and 3 is a carburetor. ] Ru.

The carburetor 3 is provided with a main fuel passage 3C having a float chamber 3a, a main nozzle 3b, an idle boat 3d, a slow fuel passage 3f having a slow port 3e, and a carburetor throttle valve 3g. 4 is an exhaust passage connected to the engine 1, 5 is a catalyst device interposed in the exhaust passage J, and 6 is a choke valve provided upstream of the carburetor bench lily 3h.

As is conventionally known, the carburetor 3 is provided with a main air bleed 7 in the main fuel passage 3c and a slow air bleed 8 in the slow fuel passage 3f.

9 is a main auxiliary air bleed installed in parallel with the main air bleed 7 in the main system fuel passage 3c, and 10 is a slow auxiliary air bleed installed in parallel with the slow air bleed 8 in the slow system fuel passage 3f. Above main auxiliary air bleed 9
The slow auxiliary air bleed 10 is provided with a main auxiliary air bleed solenoid valve 14 and a second slow auxiliary air bleed solenoid valve 15 that open and close communication ports 9a and 10a with the atmosphere, respectively. The electromagnetic valves 14 and 15 open and close passages on and off, and by increasing and decreasing the amount of bleed air, the fuel flow rate is conversely decreased and the air-fuel ratio is controlled. )1
A bypass air passage 6 opens into the intake passage 2 downstream of the carburetor throttle valve 3g, and the bypass air passage 16 is provided with a first electromagnetic valve 17 that opens and closes a communication port 16a with the atmosphere.

The first solenoid valve 17 opens and closes the passage on and off, increases and decreases the amount of auxiliary air, and controls the idle speed. The engine 1 is provided with a rotation sensor 18 for detecting its rotation speed, and between the rotation sensor 18 and the solenoid 17a of the first electromagnetic valve 17, the rotation speed of the first electromagnetic valve 17 is adjusted according to the output of the rotation sensor 18. The first to control the on/off time ratio
A control circuit 19 is provided.

When the rotation speed of the engine 1 is lower than a set value, the first control circuit 19 increases the duty ratio of the first solenoid valve 17 and increases the opening time of the first solenoid valve 17 to increase the amount of auxiliary air. When the rotation speed of the engine 1 is higher than the set value, the duty ratio is decreased to shorten the opening time of the first solenoid valve 17, and the amount of auxiliary air is reduced, so that the idle speed of the engine 1 is almost the set value. I try to control it.
The exhaust passage 4 is provided upstream of the catalyst device 8 with an exhaust sensor 20 composed of an 02 sensor that detects components of exhaust gas, and the exhaust sensor 20 and a main auxiliary air bleed solenoid valve 1 are connected to a slow auxiliary air bleed. A second control circuit 21 is provided between the solenoids 14a and 15a of the second solenoid valve 15 for controlling the on/off time ratio of the solenoid valves 14 and 15 in accordance with the output of the exhaust sensor 20.

When the air-fuel ratio of the air-fuel mixture supplied to the engine 1 is richer than the stoichiometric air-fuel ratio, the second control circuit 21 increases the duty ratio of the solenoid valve 14 and the second solenoid valve 15 to increase the amount of bleed air. , while reducing the fuel flow rate, if the air-fuel ratio of the air-fuel mixture supplied to the engine 1 is thinner than the stoichiometric air-fuel ratio, reducing the duty ratio of the solenoid valve 14 and the second solenoid valve 15 to reduce the amount of bleed air; Increase the fuel flow rate, thus
The air-fuel ratio is controlled to the stoichiometric air-fuel ratio. Next, the first control circuit 19 and the second control circuit 21 will be described in detail with reference to FIG. 2 and subsequent figures.

The second control circuit 21 includes a buffer circuit A1 that buffers the output of the exhaust sensor 20 shown in FIG.
A comparator circuit B1 outputs an output as shown at the beginning of Figure 4 as a deviation between the output of the output and a set voltage generating circuit G1 that generates a set voltage corresponding to the stoichiometric air-fuel ratio, and the output from the comparator circuit B1 is integrated. It is triggered by receiving the trigger signal from the second integrating circuit C1 which outputs the output as shown in FIG. , a duty ratio control circuit E1 that outputs a pulse signal having a duty ratio as shown by the solid line in FIG. It is composed of F1. On the other hand, the first control circuit 19 includes a waveform shaping circuit 11 that shapes the waveform of an intermittent signal synchronized with the engine rotational speed from the rotation sensor 18, and an output from the waveform shaping circuit 11 as a voltage proportional to the engine rotational speed. The output of the F-■ conversion circuit J1 outputs as shown in FIG. a comparator circuit K1 that outputs an output as shown in FIG. 4 as a deviation from the comparator circuit K1; a first integrating circuit L1 that integrates the output from the comparator circuit K1 and outputs an output as shown in FIG. 4; Duty ratio control that is triggered by receiving a trigger signal from the trigger signal generation circuit H1, whose pulse width changes according to the output from the integration circuit L1, and outputs a pulse signal having a duty ratio as shown in FIG. circuit M
1, and a solenoid valve drive circuit N1 that drives the first solenoid valve 17 by the output from the duty ratio control circuit M1.

Note that the duty ratio is expressed as a percentage of the time t during which the solenoid valve is energized per unit time T.
As shown in the figure, duty ratio (t/T×100)
0% means that the solenoid valve is fully closed, and 100%
indicates a state in which the solenoid valve is fully involved. Each of the circuits A1 to P1 constituting the first control circuit 19 and the second control circuit 21 has a circuit configuration as shown in FIG.
The first integrator circuit L1 of the first control circuit 19 and the second integrator circuit C1 of the second control circuit 21 are connected to the register R'' of the first integrator circuit L1, the capacitor C'', and the register of the second integrator circuit C. R'' and the capacitor C'''' are set so that the time constants C'' and R'' of the first integrating circuit L1 are larger than the time constants C'' and R'' of the second integrating circuit C1, Therefore, as shown in FIG. Amount of change in ratio c (amount of change in the on/off time ratio of the second solenoid valve with respect to time, ×...×...× in the figure)
) is larger than the variable ratio b of the duty conversion on the first control circuit 19 side (the amount of change in the on/off time ratio of the first solenoid valve with respect to time, 0...O...O in the figure), That is, the gradient is made large, and the range of change in the duty ratio is kept the same.

In this way, by changing the amount of change in the duty ratio, the same conventional cases (a×-×-× and BO-0-0
), when an operating time delay "゜s" occurs on the second control circuit 21 side, when the first control circuit 19 side is stable (t
1), the second control circuit 21 side was not stable, but the duty ratio change amount of the second control circuit 21 was increased (c×...×...× in the figure), 1st
When the control circuit 19 side becomes stable (t1), the second control circuit 2
The first side will also become stable. Therefore, the first control circuit 19
The control of the air-fuel ratio by the second control circuit 21 is not disturbed by the control by the second control circuit 21, and the control during idling can be performed quickly and stably. Since the range of change in the air-fuel ratio by the circuit 21 is made the same, the stoichiometric air-fuel ratio can be maintained over the entire range of control by the first control circuit 19. Next, the operation of the above device as a whole will be explained. When the idle speed of the engine becomes lower than the set value, the first control circuit 19 side
The output voltage from conversion circuit J1 becomes lower than the set voltage,
A high-level signal is output from the comparator circuit K1, and as this signal changes from low level to high level, an output that decreases over time is output from the integrator circuit K1, and in response to this output, the duty ratio control circuit An output whose duty ratio increases with the passage of time is output from M1, and the first
The duty ratio of the electromagnetic valve 17 is increased, and the amount of corrected air in the bypass air passage 16 is increased over time, thereby increasing the engine speed to a set value.

Due to the increase in the amount of corrected air, the air-fuel ratio of the air-fuel mixture supplied to the engine 1 becomes leaner than the stoichiometric air-fuel ratio, and the output voltage from the exhaust sensor 20 decreases.

Therefore, in the second control circuit 21, the comparator circuit 8 outputs a low level signal, and due to the change of this signal from high level to low level, the integrating circuit C1 outputs an output that decreases over time. In response to the output from the integrating circuit C1, the duty ratio control circuit E1 first jumps the duty ratio by a set value when the output signal to the comparison circuit changes from high level to low level, and then increases the duty ratio as time passes. An output whose ratio decreases is output, which reduces the duty ratio of the second electromagnetic valve 15, reduces the amount of bleed air of the slow auxiliary air bleed 10 over time, and is supplied through the slow system fuel passage 3f. By increasing the fuel flow rate, the air-fuel ratio of the air-fuel mixture is controlled to approximately the stoichiometric air-fuel ratio. Conversely, when the engine speed becomes higher than the set value, the output voltage from the F-V conversion circuit J1 becomes higher than the set voltage, and the duty ratio of the first solenoid valve 17 is decreased.
It operates to reduce the correction air amount over time and lower the engine's idle speed to the set value.

When the air-fuel ratio of the air-fuel mixture supplied to the engine 1 becomes richer than the stoichiometric air-fuel ratio due to the decrease in the corrected air amount,
The output voltage from the exhaust sensor 20 increases, and the second solenoid valve 1
Duty of 5. The air-fuel ratio is increased to control the air-fuel ratio of the air-fuel mixture to approximately the stoichiometric air-fuel ratio. In the above control operation, as described above, the amount of change in the on/off time ratio of the second solenoid valve in the second control circuit 21 with respect to time is determined by the first control circuit 21.
9, the control by the second control circuit 21 can be stabilized without causing a delay in the first control circuit 19, and the idle speed of the engine can be stabilized at the set value quickly. can be controlled.

As is clear from the above description, according to the engine idle speed control device according to the present invention, the first solenoid valve opens and closes the bypass passage, and the second solenoid valve opens and closes the auxiliary air bleed of the slow system fuel passage. Since the amount of change in the on/off time ratio with respect to time is greater on the second solenoid valve side where the control operation is delayed in time, the control operation of the first solenoid valve and the second solenoid valve is almost simultaneous. It is stabilized, and thus instability can be eliminated by the control operation of the first solenoid valve or the second solenoid valve.

Therefore, the engine speed during idling can be quickly maintained at the set speed, which has the advantage of improving drivability.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a schematic configuration of an engine idle speed control device according to the present invention, and FIG.
and a block diagram of the second control circuit, Figure 3 is the circuit diagram of Figure 2, Figure 4 is the output diagram of each circuit, Figure 4 is the output diagram of each circuit, Diagram explaining duty ratio, No. 6
The figure is a diagram comparing the amount of change in duty ratio of the first and second control circuits. 1...Engine, 2...Intake passage, 3
... Carburizer, 4... Exhaust passage, 3c.
...Main system fuel passage, 3f...Slow system fuel passage, 3g...Carburizer throttle valve, 5...
...Catalyst device, 9...Main auxiliary air bleed, 10...Slow auxiliary air bleed, 15...
...Second solenoid valve, 16...Bypass air passage, 17...First solenoid valve, 18...Rotation sensor, 19......No. 1 control circuit, 20...
...Exhaust sensor, 21...Second control circuit.

Claims (1)

[Claims] 1. A rotation sensor that detects the engine rotation speed, a first electromagnetic valve that opens and closes on and off in a bypass passage that opens downstream of the carburetor throttle valve, and an output of the rotation sensor. a first control circuit that controls the on/off time ratio of the first electromagnetic valve according to the timing, an exhaust sensor provided in the exhaust system of the engine equipped with the catalyst device, and an auxiliary circuit connected to the slow system fuel passage of the carburetor. The second part is installed in the air bleed and opens and closes on and off.
A second solenoid valve that controls the on/off time ratio of the solenoid valve and the second solenoid valve according to the output of the exhaust sensor, and that the amount of change in the time ratio with respect to time is greater than the amount of change in the first control circuit.
An engine idle speed control device comprising: a control circuit; 2. The first control circuit and the second control circuit described above each include a first integration circuit and a second integration circuit that determine the amount of change in the time ratio with respect to time, and the time constant of the first integration circuit is changed to a second integration circuit.
An engine idle speed control device according to claim 1, characterized in that the time constant is set larger than the time constant of the integrating circuit.