JPS6365820B2 - - 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.

This type of device is equipped with a rotation sensor that detects the rotational speed of the engine, and a bypass air passage that opens into the intake passage downstream of the throttle valve and supplies auxiliary air. An actuator is provided, and the actuator is actuated via an idle speed control circuit in accordance with the output of the rotation sensor, and the amount of auxiliary air is reduced when the idle speed exceeds a set value. An engine idle speed control device has been proposed that increases the engine speed when the engine speed falls below a set value, and performs feedback control to bring the engine idle speed approximately to the set value (for example, Japanese Patent Laid-Open No. (Refer to Publication No. 117825, 1983).

In the above device, in order to expand the controllable range of the engine speed, it is necessary to increase the maximum flow rate of the auxiliary air supplied by the auxiliary air flow rate control actuator. There is a problem in that the accuracy deteriorates and the amount of auxiliary air supplied from the bypass air passage cannot be precisely controlled, resulting in poor engine stability.

This invention was made in view of the above problem, and includes a rotation sensor that detects the rotation speed of an engine,
An engine idle speed control device comprising an actuator that controls an auxiliary air amount in a bypass air passage opened downstream of a throttle valve in an intake passage, and a circuit that controls the actuator in accordance with an output of the rotation sensor, A first actuator and a second actuator are arranged in parallel in the bypass air passage, and the opening degree of the first actuator is controlled by a control amount according to the output of the rotation sensor, and the second actuator is controlled to open the first actuator. This invention provides an engine idle speed control device characterized in that it is configured to close when the engine speed is below a certain value close to fully open, and to open when it reaches a certain value.

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. The carburetor 3 is provided with a float chamber 3a, a main fuel passage 3c having a main nozzle 3b, a slow fuel passage 3f having an idle port 3d and 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 4, 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. The above main auxiliary air bleed 9,
The slow auxiliary air bleed 10 is provided with actuators 14 and 15 for air-fuel ratio control, which are constituted by electromagnetic valves that open and close communication ports 9a and 10a with the atmosphere, respectively. The fuel flow rate is controlled by increasing or decreasing.

Reference numeral 16 denotes a bypass air passage that opens downstream of the carburetor throttle valve 3g of the intake passage 2, and the upstream side of the bypass air passage 16 is branched to form a first bypass air passage 17 and a second bypass air passage 18 arranged in parallel. There is.
The first and second bypass air passages 17, 18
A first actuator 19 and a second actuator 20 are interposed for auxiliary air control, which are constituted by electromagnetic valves that open and close communication ports 17a and 18a with the atmosphere, respectively.

The engine 1 is provided with a rotation sensor 21 for detecting its rotation speed, and the rotation sensor 21 and the first
Solenoid 19 of second actuator 19, 20
Idle rotation speed control circuit 2 between a and 20a.
2 are provided. The idle rotation speed control circuit 2
2, only the first actuator 19 is controlled according to the output of the rotation sensor 21 while the fluctuation in the engine speed is small, and the first actuator 1
9, the amount of auxiliary air is controlled by adjusting the opening degree, and when the rotational fluctuation becomes large and the first actuator is fully open or below a certain value near the fully open position, the first actuator operates to close, and when it reaches a certain value, it operates to open; The control of the second actuator 20 is added to the control of the first actuator 19, and both actuators 19 and 20 control the amount of auxiliary air. That is, when the rotation speed of the engine 1 decreases, first, the first actuator 19
The amount of auxiliary air is increased by the opening operation of the first actuator 19, and when the first actuator 19 reaches full open or near full open,
Next, the second actuator 20 operates to open the second
Auxiliary air is also supplied from the actuator 20, and conversely, when the engine speed increases, when the second actuator 20 is operating to open, the second actuator 20 is first operated to close, and then the first actuator 19 is operated to close. The amount of auxiliary air is reduced by reducing the opening of the engine 1, thereby controlling the rotational speed of the engine 1 to approximately the set value.

The exhaust passage 4 is provided with an exhaust sensor 23 composed of an O ₂ sensor for detecting exhaust gas components upstream of the catalyst device 5, and the exhaust sensor 23 and each solenoid of each air-fuel ratio control actuator 14, 15 are connected to each other. An air-fuel ratio control circuit 24 for controlling the fuel flow rate is provided between the fuel pumps 14a and 15a. Through the circuit 24, when the engine 1 is idling, the one actuator 1 is activated according to the output of the exhaust sensor 23.
5, and when the air-fuel ratio of the air-fuel mixture supplied to the engine 1 is richer than the stoichiometric air-fuel ratio, the amount of bleed air of the slow auxiliary air bleed 10 is increased,
When the air-fuel ratio of the air-fuel mixture supplied to the engine 1 is thinner than the stoichiometric air-fuel ratio, the amount of bleed air of the slow auxiliary air bleed 10 is reduced, and the air-fuel ratio during idling operation is controlled to approximately the stoichiometric air-fuel ratio. ing. Also, during medium-high load operation of the engine 1, the other actuator 14 is operated to increase the amount of bleed air in the main auxiliary air bleed 9 when the air-fuel ratio of the air-fuel mixture supplied to the engine 1 is richer than the stoichiometric air-fuel ratio. On the other hand, if the air-fuel ratio of the air-fuel mixture supplied to the engine 1 is thinner than the stoichiometric air-fuel ratio, the amount of bleed air in the main auxiliary air bleed 9 is reduced, and the air-fuel ratio of the air-fuel mixture supplied to the engine 1 is reduced during medium-load or high-load operation. The fuel ratio is controlled to approximately the stoichiometric air-fuel ratio.

Next, in FIG. 2, the idle speed control circuit 22 and air-fuel ratio control circuit 24 will be described in detail.

The air-fuel ratio control circuit 24 includes a buffer circuit _A1 that buffers the output of the exhaust sensor 23 shown in FIG. 4A,
A comparator circuit _B1 outputs an output as _shown in FIG _. Integrating circuit C 1 that integrates the output from B ₁ and outputs the integral signal shown in Figure 4 C, _and the output from comparator circuit B ₁ and the integrating circuit
It is triggered by receiving a trigger signal from an adding circuit D ₁ which adds the outputs from C ₁ and outputs an output as shown in FIG. 4D, and a trigger signal generating circuit H ₁ .
A duty ratio control circuit E ₁ whose pulse width changes according to the output from the adder circuit D 1 and which outputs a pulse signal having a duty ratio as shown in _FIG .
and an actuator drive circuit _F1 that drives the air-fuel ratio control actuator 15 by the output from the duty ratio control circuit _E1 .

On the other hand, the idle speed control circuit 22 includes a waveform shaping circuit _I1 that shapes the waveform of an intermittent signal synchronized with the engine speed from the rotation sensor 21, and an output from the waveform shaping circuit _I1 proportional to the engine speed. As shown in Fig. 4, the output voltage is F-
The difference between the output of the V conversion circuit J ₁ and the output of the F-V conversion circuit J ₁ and the output of the set voltage generation circuit P ₁ that generates the set voltage corresponding to the set value of the engine's idle speed is shown in Figure 4. Comparator circuit K ₁ outputs the output as shown, and the output from comparator circuit K ₁ is integrated,
Integrating circuit that outputs the output shown in Figure 4
A pulse signal that is triggered in response to a trigger signal from L ₁ and trigger signal generation circuit H ₁ , whose pulse width changes according to the output from integration circuit L ₁ , and has a duty ratio as shown in FIG. a duty ratio control circuit _M1 that outputs
a first actuator drive circuit N ₁ that drives 9 by the output from the duty ratio control circuit M ₁ ;
Instead of detecting that the duty ratio output from the duty ratio control circuit _M1 is close to 100%, the output from the integrating circuit _L1 is detected, and the output voltage is shown by the dashed line in Figure 4. When the voltage falls below a certain level, _the duty ratio control circuit _Q1 outputs a detection output as shown in FIG. It is composed of a second actuator drive circuit _R1 . still,
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 Figure 5, and the duty ratio (t/T x 100) is 0%. This is a state in which the actuator is fully closed, and 100% indicates a state in which the actuator is fully open.

As mentioned above, the opening degree of the first actuator 19 is controlled in the range of 0% to 100% according to the duty ratio via the first actuator drive circuit _N1 in accordance with the duty ratio output from the duty ratio control circuit _M1 . While being adjusted, the second actuator 2
0 is opened and closed by turning fully open or fully closed.

Each of the circuits _A1 to _R1 of the air-fuel ratio control circuit 24 and the idle speed control circuit 21 has a circuit configuration as shown in FIG.

In the device having the above configuration, when the idle speed of the engine becomes lower than the set value, in the idle speed control circuit 22, the output voltage from the F-V conversion circuit J ₁ becomes lower than the set voltage, and the output voltage from the comparison circuit K ₁ becomes lower than the set voltage.
A high level signal is output from the integrator circuit due to the change of this signal from low level to high level.
An output that decreases over time is output from L ₁ , and the duty ratio control circuit M ₁
An output whose duty ratio increases as time passes is output, increasing the duty ratio of the first actuator 19, increasing the amount of auxiliary air with precision as time passes, and increasing the engine speed to the set value. It works as expected. When the rotational speed decreases, the degree of decrease is large and the output from the integration circuit _L1 is large.If the duty ratio output from the duty ratio control circuit _M1 exceeds 100% or a constant value near 100%, that is, the 1 Even though the actuator 19 is close to fully open, if it is necessary to further increase the amount of auxiliary air in order to increase the engine speed to the set value, the duty ratio detection circuit Q ₁ outputs a detection signal and The second actuator 20 is driven by the second actuator drive circuit _R1 .
is turned on and fully opened, further increasing the amount of auxiliary air and promoting a rise in engine speed.

Due to the increase in the amount of auxiliary 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 23 decreases. Therefore, in the air-fuel ratio control circuit 24, the comparison circuit
A low level signal is output from B ₁ , and as this signal changes from high level to low level, an output that decreases over time is output from integration circuit C ₁ , and the output from integration circuit C ₁ and the comparison circuit
The outputs from B ₁ are added in addition circuit D ₁ , and according to the output from addition circuit D ₁ , duty ratio control circuit E ₁ first changes the output signal of comparator circuit B ₁ from high level to low level. When changing, the duty ratio is jumped by a set value, and then an output is output that reduces the duty ratio as time passes, and the duty ratio of the air-fuel ratio control actuator 15 is decreased to reduce the amount of bleed air as time passes. The air-fuel ratio of the air-fuel mixture is controlled to approximately the stoichiometric air-fuel ratio by increasing the flow rate of heating material supplied through the slow system fuel passage 3f.

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 value, the duty ratio output from the duty ratio control circuit _M1 decreases, and the first actuator The opening degree of 19 is small or closed, and it operates to reduce the amount of auxiliary air and lower the idle speed of the engine to the set value. At that time, the duty ratio of the first actuator 19 is 100% or 100%.
From the state where the second actuator 20 is operating at a constant value or higher in the vicinity, the first actuator 19
When the duty ratio decreases, the second actuator 20 first operates to close, and then the opening degree of the first actuator 19 decreases, sequentially reducing the amount of auxiliary air. When the air-fuel ratio becomes richer than the stoichiometric air-fuel ratio in response to the decrease in the amount of auxiliary air, the output voltage from the exhaust sensor 23 increases rapidly, increasing the duty ratio of the air-fuel ratio control actuator 15, and causing bleeding over time. The amount of air is increased to control the air-fuel ratio of the mixture to approximately the stoichiometric air-fuel ratio.

Note that the present invention is not limited to the above-mentioned embodiments, but includes providing two or more bypass air passages in parallel, interposing an actuator in each bypass air passage, and controlling each actuator to open sequentially. The controllable range of flow rate can be expanded.

As is clear from the above explanation, according to the engine idle speed control device according to the present invention,
Two actuators, a first actuator and a second actuator, are arranged in parallel in the bypass air passage,
While the rotation speed is close to the set value and its fluctuation is small, and the amount of auxiliary air flow to be controlled is small, the opening degree of the first actuator is controlled by a control amount according to the output of the rotation sensor, and the second actuator is operated to close. While improving the control accuracy of the auxiliary air flow rate and increasing the stability of the engine, the rotation speed fluctuation is large and the auxiliary air flow rate to be controlled increases, and when the opening degree of the first actuator reaches a constant value near full open, The second actuator also opens, which has the advantage of expanding the controllable range of the auxiliary air flow rate, that is, the controllable rotational speed range.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of an engine idle speed control device according to the present invention, FIG. 2 is a block diagram of the circuit of FIG. 1, and FIG. 3 is a specific circuit diagram of FIG. 2. 4 are output diagrams of each circuit in FIG. 2, and FIG. 5 is an output diagram of the duty ratio of FIG. 2. 1... Engine, 2... Intake passage, 3... Carburetor, 3g... Carburetor throttle valve, 4... Exhaust passage, 16
... Bypass air passage, 19 ... First actuator, 20 ... Second actuator, 21 ... Rotation sensor, 22 ... Idle rotation speed control circuit.

Claims (1)

[Claims] 1. A rotation sensor that detects the engine rotation speed;
An engine idle speed control device comprising an actuator that controls an auxiliary air amount in a bypass air passage opened downstream of a throttle valve in an intake passage, and a circuit that controls the actuator in accordance with an output of the rotation sensor, A first actuator and a second actuator are arranged in parallel in the bypass air passage, and the opening degree of the first actuator is controlled by a control variable having at least integral characteristics according to the difference between the target rotation speed and the output of the rotation sensor. In addition, the second actuator is configured to close when the opening of the first actuator is below a certain value near full open, and to open when the opening reaches the certain value. Rotation speed control device.