JPS6130139B2 - - 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 provided with a rotation sensor that detects the rotational speed of the engine, and a first actuator that opens and closes the bypass air passage that opens into the intake passage downstream of the carburetor throttle valve. The first actuator is actuated via the first circuit for controlling the amount of auxiliary air in accordance with the output of the rotation sensor, and the amount of auxiliary air is decreased when the number of idle revolutions exceeds a set value. Feedback control is performed so that the idle speed of the engine is approximately equal to the set value by increasing the number of revolutions when it falls below the set value.
An exhaust sensor and a catalyst device are installed in the exhaust system of the engine, and a second actuator for opening and closing the auxiliary air bleed is interposed in the auxiliary air bleed provided in the slow system fuel passage of the carburetor. The second actuator is actuated via a second circuit for air-fuel ratio control that controls the fuel flow rate according to the output, and the bleed air amount of the auxiliary air bleed is controlled so that the air-fuel mixture generated by the carburetor is lower than the stoichiometric air-fuel ratio. The fuel flow rate in the slow system fuel passage is controlled by increasing the amount when the air-fuel mixture is rich and decreasing it when the air-fuel mixture is leaner than the stoichiometric air-fuel ratio.
A system has 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.

In the above device, when the engine is idling,
In order to improve transient response when the engine speed suddenly increases or decreases,
It is better to increase the control signals (for example, integral constant and/or proportionality constant) output from the first and second circuits, but if the control signals are increased, engine vibration will increase when the rotational speed fluctuation is small. , there is a problem of poor stability.

This invention aims to solve the above-mentioned problem, and uses a rotation sensor to detect a sudden change in the engine speed when it is idling, exceeding an upper limit value higher than a set value, or exceeding a lower limit value lower than a set value. At the same time, a correction circuit is provided to correct the auxiliary air amount control of the first circuit for auxiliary air amount control and the slow system fuel flow control of the second circuit for air-fuel ratio control to improve the transient response when the rotation speed changes rapidly. An object of the present invention is to provide a mild rotational speed control device for an engine that improves engine rotational speed and reduces engine vibration caused by a control signal when rotational speed fluctuations are small.

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 includes a main auxiliary air bleed actuator 14 for air-fuel ratio control, which is composed of electromagnetic valves that open and close communication ports 9a and 10a with the atmosphere, respectively, and a second actuator as a slow auxiliary air bleed actuator. 15
has been established. The actuators 14 and 15 open and close the passages on and off, and by increasing and decreasing the amount of bleed air, the fuel flow rate is conversely decreased and increased. At idle, the air-fuel ratio of the intake air-fuel mixture in the intake passage becomes the stoichiometric air-fuel ratio. control to achieve the target air-fuel ratio).

Reference numeral 16 denotes a bypass air passage that opens into the intake passage 2 downstream of the carburetor throttle valve 3g, and the bypass air passage 16 has an auxiliary air amount control valve configured with a solenoid valve that opens and closes the communication port 16a with the atmosphere. A first actuator 17 is provided. The first actuator 17 opens and closes the passage on and off, increases and decreases the amount of auxiliary air, and controls the idle rotation speed.

The engine 1 is provided with a rotation sensor 18 for detecting its rotation speed, and a first circuit 19 as an auxiliary air amount control circuit is provided between the rotation sensor 18 and the solenoid 17a of the first actuator 17. actuating the first actuator 17 in response to the output of the rotation sensor 18 via the first circuit 19;
When the idle speed of the engine 1 is lower than the set value, the amount of auxiliary air in the bypass air passage 16 is increased, while when the idle speed of the engine 1 is higher than the set value, the amount of auxiliary air in the bypass air passage 16 is decreased. Therefore, the rotation speed of the engine 1 during idling is controlled so as to reach the target rotation speed.

The exhaust passage 4 is provided upstream of the catalyst device 5 with an exhaust sensor 20 composed of an _O2 sensor that detects components of exhaust gas, and the exhaust sensor 20, main auxiliary air bleed actuator 14, and slow auxiliary air bleed are connected to each other. A second circuit 21 serving as an air-fuel ratio control circuit for controlling the fuel flow rate is provided between the solenoids 14a and 15a of the second actuator 15 for use. The second circuit 21 operates the second actuator 15 according to the output of the exhaust sensor 20 when the engine 1 is idling, and slows down when the air-fuel ratio of the air-fuel mixture supplied to the engine 1 is richer than the stoichiometric air-fuel ratio. While increasing the amount of bleed air in the auxiliary air bleed 10, 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 slow auxiliary air bleed 10 is decreased, and therefore, during idling operation. The air-fuel ratio is controlled to approximately the stoichiometric air-fuel ratio. Also, during medium/high load operation of the engine 1, the main auxiliary air bleed actuator 14 is operated, and the engine 1
If the air-fuel ratio of the air-fuel mixture supplied to the engine 1 is richer than the stoichiometric air-fuel ratio, the bleed air amount of the main auxiliary air bleed 9 is increased. Reduce the amount of bleed air of the main auxiliary air bleed 9,
Therefore, the air-fuel ratio during medium and high load operation is controlled to approximately the stoichiometric air-fuel ratio.

The first circuit 19 and the second circuit 20 are activated when the engine speed detected by the rotation sensor 18 suddenly changes and exceeds an upper limit value higher than the set value or exceeds a lower limit value lower than the set value. First circuit 19
The second circuit 2 corrects the auxiliary air flow control of the
A correction signal from a correction circuit 22 that corrects the fuel flow rate control of No. 1 is input. By the correction circuit 22,
When the engine speed suddenly increases and exceeds the upper limit value, which is higher than the set value, the auxiliary air amount control of the first circuit 19 is corrected to suddenly decrease the auxiliary air amount, and the second circuit 19
While the fuel flow control of the circuit 21 is corrected to rapidly reduce the slow system fuel flow rate, when the engine speed suddenly decreases and exceeds the lower limit value lower than the set value, the first circuit 19 is corrected to reduce the auxiliary air flow rate. At the same time, the second circuit 21 is corrected to rapidly increase the fuel flow rate.

Next, the first circuit 19, second circuit 21, and correction circuit 22 will be described in detail.

The second circuit 21 generates a deviation signal between the buffer circuit A ₁ that buffers the output of the exhaust sensor 20 and the output of the buffer circuit A ₁ and the output of the set voltage generation circuit G ₁ that generates a set voltage corresponding to the stoichiometric air-fuel ratio. A comparator circuit B ₁ outputs, an integrator circuit C 1 integrates the output from the comparator circuit B ₁ and outputs an integral signal, and the output from the comparator circuit _{B 1 and} the output from the integrator circuit C ₁ are added together and output. is triggered by the trigger signal from the adder circuit D ₁ and the trigger signal generating circuit H ₁ , and the duty ratio according to the output from the adder circuit D ₁ (as the potential of the addition signal from the adder circuit D ₁ becomes higher) duty ratio control circuit _E1 that outputs a pulse signal having a duty ratio that increases accordingly
and an actuator drive circuit _F1 that drives the second actuator 15 using the output from the duty ratio control circuit _E1 .

On the other hand, the first circuit 19 includes a waveform shaping circuit I1 that shapes the waveform of an intermittent signal synchronized with the engine rotational speed from the rotation sensor 18, and a waveform shaping circuit _I1 that converts the output from the waveform shaping circuit _I1 into a voltage proportional to the engine rotational speed. The deviation output of _{the F-V conversion circuit J 1 which outputs} as A comparator circuit _K1 that outputs an output, an integrator circuit _L1 that integrates the output from the comparator circuit K1 and outputs an integral signal, and an integrator circuit _L1 that is triggered by receiving a trigger signal from the trigger signal generation circuit _{H1 .} The first actuator 17 is connected to a duty ratio control circuit _M1 that outputs a pulse signal having a duty ratio corresponding to the output from the integrator _L1 (a duty ratio that decreases as the potential of the integral signal from the integrating circuit L1 increases). The actuator drive circuit _N1 is driven by the output from the ratio control circuit _M1 .

The correction circuit 22 is an upper limit detection circuit that detects a sudden increase in engine speed and outputs an output to the first circuit 19 and the second circuit 21 to correct the duty ratio.
Q ₁ and a lower limit detection circuit R ₁ that detects a sudden decrease in engine speed and outputs an output to the first circuit 19 and second circuit 21 to correct the duty ratio. As shown in FIG. 3, the upper limit detection circuit Q ₁ receives an output voltage proportional to the engine speed from the F-V conversion circuit J ₁ of the first circuit 19 and a high voltage corresponding to an upper limit higher than the set value. When the voltage of the F-V conversion circuit J ₁ becomes higher than the upper limit value, the output (high potential) of the comparison circuit 23 is Duty ratio control circuit E ₁ of second circuit 21
is applied to point (A), increases the duty ratio output from the duty ratio control circuit _E1 , increases the opening degree of the second actuator 15 or fully opens it, increases the amount of bleed air, and decreases the slow system fuel flow rate. At the same time, the output of the comparison circuit 23 is connected to the diode 26
and is applied to point (B) of the duty ratio control circuit _M1 of the first circuit 19 through the resistor 27, which reduces the duty ratio output from the duty ratio control circuit _M1 and reduces the opening degree of the first actuator 17. Or close it to reduce the amount of auxiliary air. The lower limit detection circuit R ₁ is an F-V conversion circuit J ₁ as shown in FIG.
The comparator circuit 28 is configured to compare an output voltage proportional to the engine speed from ₁ to 28 with a low voltage corresponding to a lower limit value lower than the set value. At this time, the output (low potential) of the comparator circuit 28 is connected to the diode 29 and the resistor 30.
The duty ratio control circuit of the second circuit 21 via
Applied to point (a) of E ₁ , reducing the duty ratio,
The second actuator 15 is operated to reduce the amount of bleed air and increase the slow system fuel flow rate, and the output of the comparison circuit 28 is transmitted to the duty ratio control circuit _M1 of the first circuit 19 via the diode 31 and resistor 32. (B) is applied to the point, increases the duty ratio, operates the first actuator 17, and increases the amount of auxiliary air. Note that the duty ratio is expressed as a percentage of the time t in which the solenoid valve is energized per unit time T, and the duty ratio (t/
T×100) of 0% means that the actuator is fully closed, and 100% means that the actuator is fully open.

Next, the operation of the above device will be explained.

First, the idle speed of the engine is set to the first circuit 1.
When the value becomes lower than the set value set in step 9, the first circuit 1
On the 9 side, the output voltage from the F-V conversion circuit J ₁ is lower than the set voltage, and the output voltage from the comparator circuit K ₁ is “high”.
A level signal is output, and as this signal changes from low level to high level, an output that decreases over time is output from the integrating circuit _L1 , and in response to this output, the duty ratio control circuit _M1 outputs an output that decreases over time. At the same time, an output that increases the duty ratio is output, increasing the duty ratio of the first actuator 17, increasing the amount of auxiliary air over time, and operating to raise the engine speed to the set value.

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 20 decreases. Therefore, in the second circuit 21, a low level signal is output from the comparator circuit _B1 , and due to the change of this signal from high level to low level, the integration circuit
C ₁ outputs an output that decreases over time, and the output from this integrating circuit C ₁ and the output from comparator circuit B ₁ are added in addition circuit D ₁ , and according to the output from this addition circuit D ₁ . , the duty ratio control circuit E ₁ first jumps the duty ratio by a set value when the output signal of the comparator circuit B ₁ changes from high level to low level, and then outputs an output whose duty ratio decreases as time passes. , the duty ratio of the second actuator 15 is decreased, the amount of bleed air is decreased over time, and the flow rate of fuel supplied through the slow system fuel passage 3f is increased, so that the air-fuel ratio of the mixture is almost the stoichiometric. The air-fuel ratio is controlled.

During the above-mentioned idling operation, when a large load is applied to the engine 1 by operating the cooler compressor, etc., and the rotation speed rapidly decreases and exceeds the lower limit value of the lower limit detection circuit Q ₁ of the correction circuit 22, the correction circuit 22 The duty ratios of the first circuit 19 and the second circuit 21 are corrected, the auxiliary air amount and the slow system fuel flow rate are rapidly increased, and the engine speed is rapidly increased to the set value. In this way, when the rotation speed decreases, while the degree of decrease is small, it is controlled only by the first circuit 19 and the second circuit 21, but when the rotation speed suddenly decreases, the setting of the lower limit detection circuit _Q1 When the lower limit of the value is exceeded, the correction circuit 22 performs correction control.

Conversely, when the engine speed becomes higher than the set value set in the first circuit 19, the output voltage from the F-V conversion circuit _B1 becomes higher than the set voltage on the first circuit 19 side, and the first actuator 17 It operates to reduce the duty ratio of the engine, reduce the amount of auxiliary air over time, and lower the engine idle speed to the set value. Due to the decrease in the amount of auxiliary air, the second actuator 1 on the second circuit 21 side
The duty ratio of 5 is increased, the amount of bleed air is increased, and the slow system fuel flow rate is decreased to maintain the air-fuel ratio near the stoichiometric air-fuel ratio.

The above-mentioned rotational speed increases rapidly, and the correction circuit 2
When the upper limit value set by the upper limit detection circuit _R1 of No. 2 is exceeded, the correction circuit 22 detects the upper limit value of the first circuit 19.
Then, the duty ratio of the second circuit 21 is corrected, the supplementary air amount and the slow system fuel flow rate are rapidly reduced, the engine speed is quickly lowered to the set value, and the air-fuel ratio is controlled to the stoichiometric air-fuel ratio.

Note that in the above embodiment, a sudden change in the engine speed is detected by exceeding the upper and lower limits set within a certain range with respect to the set value of the engine idling speed. others,
For example, detecting the load acting on the engine,
By detecting the fluctuation rate of the engine speed, a sudden change in the engine speed can also be detected.

Furthermore, in the above embodiment, the slow system fuel flow rate was controlled by changing the amount of bleed air.
The slow system fuel flow rate can also be directly controlled by changing the passage area of the slow system fuel flow passage.

As is clear from the above explanation, according to the engine idle speed control device according to the present invention,
A correction circuit is provided that detects a sudden increase or decrease in engine speed and corrects the auxiliary air amount control in the first circuit, as well as the fuel flow control in the second circuit, so when the engine speed fluctuations are large. It has good transient response and can maintain the idle speed at the set value without time delay, as well as maintain the air-fuel ratio at the stoichiometric air-fuel ratio. Further, when the rotational speed fluctuation is small, the optimum signal is outputted only by the first circuit and the second circuit, so there are advantages such as no engine vibration caused by the control signal.

[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.
This figure is a block diagram showing the configuration of the first circuit, second circuit, and correction circuit shown in FIG. 1, and FIG. 3 is a specific circuit diagram of the correction circuit. 1... Engine, 2... Intake passage, 3... Carburetor, 3f... Slow system fuel passage, 3g... Carburetor throttle valve, 4... Exhaust passage, 5... Catalyst device, 10...
...Slow auxiliary air bleed, 15...Second actuator, 17...First actuator, 18...
... Rotation sensor, 19 ... First circuit, 20 ... Exhaust sensor, 21 ... Second circuit, 22 ... Correction circuit.

Claims (1)

[Claims] 1 A rotation sensor that detects the engine rotation speed,
A first actuator provided in a bypass air passage supplying auxiliary air downstream of the carburetor throttle valve, and controlling the first actuator in accordance with the output of the rotation sensor so that the idle rotation speed of the engine becomes a target rotation speed. A first circuit, an exhaust sensor provided in the exhaust system of the engine equipped with a catalyst device, a second actuator that controls the fuel flow rate in the slow system fuel passage of the carburetor, and a second actuator that controls the air-fuel ratio of the intake air-fuel mixture in the intake passage. and a second circuit for controlling the second actuator according to the output of the exhaust sensor so as to maintain the fuel ratio. A correction circuit is provided that corrects the auxiliary air amount control of the first circuit and the slow system fuel flow control of the second circuit when the sensor detects an upper limit value higher than the set value and a lower limit value lower than the set value. Features an engine idle speed control device.