JPS6123378B2 - - 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.

Conventionally, when the engine is idling, the amount of air-fuel mixture supplied to the engine is controlled by controlling the opening of the carburetor throttle valve according to the output of a rotation sensor that detects the engine rotation speed. It is often the case that the idle speed of the engine is maintained at a set value regardless of various conditions surrounding the engine, such as changes in the load on the engine, changes in atmospheric pressure, variations in engine mass production, or the degree of engine lapping. Are known.

However, with conventional devices, the engine speed fluctuates widely with respect to the opening degree of the carburetor throttle valve, so in order to keep the engine idle speed at the set value, the carburetor It was difficult to put this into practical use because it was necessary to precisely control the opening of the throttle valve.

In addition, since this conventional device only controls the amount of air-fuel mixture supplied to the engine, it is difficult to create a three-way atmosphere in the catalyst device installed in the engine exhaust system. There was a problem in that even the catalyst device could not effectively purify CO, HC, and NOx in the exhaust gas.

Furthermore, conventionally, the air-fuel ratio of the air-fuel mixture supplied to the engine is controlled to approximately the stoichiometric air-fuel ratio according to the output of an exhaust sensor that detects exhaust gas components. It is well known that the atmosphere is a ternary atmosphere and the catalyst device is used to purify CO, HC and NOx in exhaust gas.

However, this conventional device only controls the air-fuel ratio of the air-fuel mixture supplied to the engine when the engine is idling, and the engine idling speed may vary depending on the various conditions surrounding the engine as described above. There is a fear that this may change and cause the engine to stop.

In addition, since conventional devices control the amount of air-fuel mixture supplied to the engine, the air-fuel ratio control characteristics by auxiliary air bleed do not have uniform characteristics with respect to the air amount, but due to fluctuations in the air amount. The drawback was that the air-fuel ratio was off.

Accordingly, the present invention aims to maintain the idle speed of the engine at a set value regardless of various conditions surrounding the engine by controlling the amount of air-fuel mixture supplied to the engine and the air-fuel ratio of the air-fuel mixture during idling operation of the engine. in the exhaust gas.
It aims to effectively purify CO, HC and NOx.

That is, the present invention controls the amount of auxiliary air supplied to the intake passage downstream of the carburetor throttle valve in accordance with the output of a rotation sensor that detects the rotational speed of the engine, and also controls the amount of auxiliary air supplied to the intake passage downstream of the carburetor throttle valve. This system controls the amount of air bleed in accordance with the output of an exhaust sensor that detects the concentration of components in exhaust gas, thereby controlling the amount of air-fuel mixture supplied to the engine and the air-fuel ratio of the air-fuel mixture. Therefore, the engine idle speed control device according to the present invention is provided with a rotation sensor that detects the engine speed, and has an idle speed control device as a first actuator in a bypass air passage that opens into the intake passage downstream of the throttle valve. A number control actuator is interposed, and the idle rotation speed control actuator is actuated via an idle rotation speed control circuit as a first circuit in accordance with the output of the rotation sensor to control the amount of auxiliary air in the bypass air passage. At the same time, an exhaust sensor and a catalyst device are installed in the engine's exhaust system, and an auxiliary air bleed installed in the slow system fuel passage of the carburetor is installed. An air-fuel ratio control actuator as a second actuator is provided, and the air-fuel ratio control actuator is actuated via an air-fuel ratio control circuit as a second circuit in accordance with the output of the exhaust sensor to bleed the auxiliary air bleed. By controlling the amount of air, the flow rate of fuel passing through the slow system fuel passage is controlled, and the air-fuel ratio of the air-fuel mixture is feedback-controlled to approximately the stoichiometric air-fuel ratio.

Therefore, by combining the above two control means, the present invention has made it possible to control the same air-fuel ratio change with the same control amount at all times, without making the control characteristics of the auxiliary air bleed dependent on the air amount. It is something.

Hereinafter, the present invention will be described 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, and this carburetor 3 includes a main system fuel passage 3c having a float chamber 3a and a main nozzle 3b; A slow system fuel passage 3f having an idle port 3d and a slow port 3e and a carburetor throttle valve 3g are provided. 4 is an exhaust passage connected to the engine 1, and 5 is a catalyst device interposed in the exhaust passage 4. Note that 6 is a choke valve provided upstream of the carburetor bench lily 3h. As is conventionally known, the main fuel passage 3c of the carburetor 3 is provided with a main air bleed 7, and the slow fuel passage 3f of the carburetor 3 is provided with a slow air bleed 8. 9
10 is a main auxiliary air bleed installed in parallel with the main air bleed 7 in the main system fuel passage 3c.
is a slow auxiliary air bleed installed in parallel with the slow air bleed 8 in the slow system fuel passage, and each of the auxiliary air bleeds 9 and 10 is composed of a solenoid valve that opens and closes communication ports 9a and 10a with the atmosphere. Main auxiliary air bleed actuators 14 and 15 for air-fuel ratio control are provided. Reference numeral 16 designates a bypass air passage that opens into the intake passage 2 downstream of the carburetor throttle valve 3g, and an actuator 17 for controlling idle rotation speed, which is constituted by a solenoid valve that opens and closes a communication port 16a with the atmosphere in the bypass air passage 16.
will be established. The engine 1 is provided with a rotation sensor 18 for detecting its rotation speed, and an idle rotation speed control circuit 19 as a first circuit is provided between the rotation sensor 18 and the solenoid 17a of the actuator 17. The idle speed control actuator 17 is operated according to the output to increase the amount of air in the bypass air passage 16 when the engine 1 rotation speed is low, while increasing the air amount in the bypass air passage 16 when the engine 1 rotation speed is high. to reduce the The exhaust passage 4 has a catalyst device 5 therein.
An exhaust sensor 20 composed of an O ₂ sensor for detecting components of exhaust gas is provided in front of the exhaust gas sensor 20, and a connection between the exhaust gas sensor 20 and each solenoid 14a, 15a of the main auxiliary air bleed and air-fuel ratio control actuators 14, 15 is provided. An air-fuel ratio control circuit 21 as a second circuit is provided in between, and when the engine 1 is idling, the air-fuel ratio control actuator 15 is operated according to the output of the exhaust sensor 20 to control the engine 1.
If the air-fuel ratio of the mixture supplied to the engine 1 is richer than the stoichiometric air-fuel ratio, the amount of air in the slow auxiliary air bleed 10 is increased, while if the air-fuel ratio of the mixture supplied to the engine 1 is thinner than the stoichiometric air-fuel ratio, In addition to reducing the amount of air in the auxiliary air bleed 13, the actuator 1 for the main auxiliary air bleed, which is inactive during idling operation, is activated during normal rotation of the engine 1.
4, if the air-fuel ratio of the mixture supplied to the engine 1 is richer than the stoichiometric air-fuel ratio, the amount of air in the main auxiliary air bleed 12 is increased, while the air-fuel ratio of the mixture supplied to the engine 1 is increased. If the air-fuel ratio is thinner than the stoichiometric air-fuel ratio, the amount of air in the main auxiliary air bleed 12 is reduced.

Next, according to FIG. 2, the idle speed control circuit 1
9 and the air-fuel ratio control circuit 21 will be explained in detail.

The air-fuel ratio control circuit 21 includes a buffer circuit _A1 that buffers the output of the exhaust sensor 20 shown in FIG. 4A, and a set voltage generation circuit _G1 that generates a set voltage corresponding to the output of the buffer circuit _A1 and the stoichiometric air-fuel ratio. A comparator circuit B ₁ outputs an output as shown in FIG. 4B as the deviation of the output of , and an integrating circuit C ₁ integrates the output from the comparator circuit B ₁ and outputs an output as shown in FIG. 4C. , output from comparator circuit B ₁ and integrator 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.
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 .

The idle speed control circuit 19 also includes a waveform shaping circuit I1 that shapes the waveform of an intermittent signal synchronized with the engine speed from the rotation sensor ₁₈ , and an output from the waveform shaping circuit _I1 proportional to the engine speed. As shown in Fig. 4, the output voltage is F-
Figure 4 shows the deviation 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 idling speed. Comparator circuit K ₁ outputs an output like this, and the output from comparator circuit K ₁ is integrated,
Integrating circuit that outputs the output shown in Figure 4
_L1 and a trigger signal from the trigger signal generation circuit _H1 , the pulse width changes according to the output from the integrating circuit _L1 , and a pulse signal having a duty ratio as shown in Fig. 4 is generated. An actuator drive circuit that drives the output duty ratio control circuit _M1 and the idle rotation speed control actuator 17 by the output from the duty ratio control circuit _M1 .
It consists of N ₁ . Each of the above-mentioned circuits _A1 to _P1 constituting the air-fuel ratio control circuit 21 and the idle speed control circuit 19 has a circuit configuration as shown in FIG. 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, 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.

Next, the operation of the above-mentioned constituent device will be explained.

First, when the idle speed of the engine becomes lower than the set value, the output voltage from the F-V conversion circuit _J1 becomes lower than the set voltage, and the output voltage from the comparator circuit _K1 becomes "1".
A level signal is output, and the change of this signal from the “0” level to the “1” level causes the integration circuit L ₁
outputs an output that decreases over time,
In response to this output, the duty ratio control circuit M ₁ outputs an output whose duty ratio increases with the passage of time, increasing the duty ratio of the idle rotation speed control actuator 17 and increasing the amount of auxiliary air with the passage of time. The engine operates to increase the engine speed to the set value. At the same time,
Since the amount of intake air supplied to the engine 1 is increased, 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 rapidly. circuit B ₁
A “0” level signal is output from the integrator circuit C1, and as this signal changes from the “ ₁ ” level to the “0” level, an output that decreases over time is output from the integrator circuit _C1. The output and the output from the comparator circuit B ₁ are added in the adder circuit D ₁ , and according to the output from the adder circuit D ₁ , the output signal from the comparator circuit B ₁ is first output from the duty ratio control circuit E ₁ from the “1” level. When changing to the "0" level, the duty ratio is jumped by the set value, and then an output is output in which the duty ratio decreases as time passes, reducing the duty ratio of the air-fuel ratio control actuator 15, and causing bleed as time passes. By reducing the amount of air and increasing the flow rate of fuel supplied through the slow system fuel passage 3f, the air-fuel ratio of the air-fuel mixture is controlled to approximately the stoichiometric air-fuel ratio.

Conversely, when the idle speed of the engine becomes higher than the set value, the output voltage from the F-V conversion circuit J ₁ becomes higher than the set voltage, decreasing the duty ratio of the idle speed control actuator 17, and increasing the voltage as time passes. It operates to reduce the amount of auxiliary air and lower the engine's idle speed to the set value.
At the same time, when the amount of intake air supplied to the engine 1 decreases and the air-fuel ratio of the mixture supplied to the engine 1 becomes richer than the stoichiometric air-fuel ratio, the exhaust sensor 2
The output voltage from 0 increases rapidly, increasing the duty ratio of the air-fuel ratio control actuator 15,
The amount of bleed air is increased over time to control the air-fuel ratio of the air-fuel mixture to approximately the stoichiometric air-fuel ratio.

As described above, the idle rotation speed control circuit 19 controls the idle rotation speed control actuator 17 with the output of the rotation sensor 18, and the main auxiliary air bleed actuator 14 and the air-fuel ratio control actuator 15 are controlled with the output of the exhaust sensor 20. By the action of the air-fuel ratio control circuit 21, the duty ratio of the idle speed control actuator 17 and the idle speed control width are controlled as shown in the relationship curve in FIG.
At the same time, the bleed air amount of the slow auxiliary air bleed 10 is adjusted by controlling the duty ratio of the idle speed control actuator 17 and the duty ratio of the air-fuel ratio control actuator 15 as shown in the relationship curve. Then,
As the air-fuel ratio of the air-fuel mixture supplied to the engine 1, a result as shown in the relationship curve between the duty ratio of the idle speed actuator 17 and the air-fuel ratio in FIG. 6 can be obtained.

That is, the engine 1 equipped with the rotation speed control device configured as described above is capable of keeping the air-fuel ratio substantially constant regardless of the duty ratio of the idle rotation speed control actuator 17.

Therefore, the idle speed of the engine 1 can be maintained at the set value, and the air-fuel ratio of the air-fuel mixture supplied to the engine 1 can be made to be approximately the stoichiometric air-fuel ratio, thereby preventing changes in the load on the engine 1. The stability and emission level of the engine can always be maintained at a good level, regardless of changes in atmospheric pressure, variations in engine mass production, or the degree of engine wrapping.

In addition, as a modification of a part of the circuit in FIGS. 2 and 3, the rotation sensor 18' is adapted to take out the voltage generated by the primary ignition coil in the distributor of the ignition system of the engine 1, and
The idle rotation speed control circuit 19' is formed by a waveform shaping circuit _I2 that shapes the waveform of an intermittent signal synchronized with the engine rotational speed from the rotation sensor 18' as shown in FIG. 7A and B, and a waveform shaping circuit _I2 . An F-V conversion circuit _J2 outputs the output as a voltage proportional to the engine speed as shown in Figure 8A, and an F-V conversion circuit.
A setting generation circuit P ₂ that generates a set voltage corresponding to the set value of the output of J ₂ and the idle speed of the engine.
A comparator circuit _K2 outputs an output as shown in _{Figure 8B} as the deviation of the output of
An integrating circuit L ₂ which jumps the integral value by a set amount when the level changes from the "1" level or from the "1" level to the "0" level and outputs an output as shown in FIG _. and the output of the triangular wave generating circuit _Q2 as two inputs, and compare them as shown in FIG. 8 D, and output the pulses shown in FIG. ₈ E, and the idle rotation speed The control actuator 17' may be configured with an actuator drive circuit _N2 that is driven by the output from the duty ratio control circuit _M2 .

Note that the operation of the above-mentioned constituent devices is substantially the same as that shown in FIGS. 2 and 3, and therefore will not be described here.

Further, as another modification of FIG. 2, FIG. 9 shows a case where the outputs of the rotation sensor 18'' and the exhaust sensor 20'' are digitally processed. In addition,
In the embodiment shown in FIG.
The auxiliary air bleed 10 is provided with a needle valve or a butterfly valve, and these valves are controlled using a pulse motor.

In FIG. 9A, the air-fuel ratio control circuit 21'' is
Waveform shaping circuit a, data flip-flop b, exclusive OR circuit c, oscillator d, counter e, data flip-flop f, AND circuit g, AND circuit h, OR circuit i, and gate circuits j, k and a drive circuit l. The first waveform shaping circuit a that shapes the waveform of the output of the exhaust sensor 20''
The output shown in Figure 10 (B) is the T input, and the output shown in Figure 10 (B) from the oscillator d is the D input. 1st of
The output of the exhaust sensor 20'' when the air-fuel ratio of the air-fuel mixture supplied to the engine 1 becomes leaner or richer than the stoichiometric air-fuel ratio is determined by the exclusive OR circuit c that inputs the output shown in Figure 0 C. The counter e and the data flip-flop f are controlled by the output shown in FIG. 10D from the exclusive OR circuit, and the output from the data flip-flop f shown in FIG. The 10th output of oscillator d
AND circuits g and h which gate the pulse shown in Figure H and the pulse shown in Figure 10 G from the counter e which is the frequency-divided pulse of the oscillator d are opened and closed, and the setting is made based on the change in the output of the exhaust sensor 20''. While outputting the pulse of the oscillator d to the OR circuit i for a time,
After the set time elapses, the frequency-divided pulse of the counter e is output to the OR circuit i, and the output of the waveform shaping circuit a opens and closes the gate circuits j and k that gate the output from the OR circuit i shown in FIG. When the air-fuel ratio of air is thinner than the stoichiometric air-fuel ratio, the gate circuit j is opened, the output from the OR circuit i is sent to the pulse motor m via the drive circuit l, and the auxiliary air bleed 13 provided in the slow system fuel passage 3f is bleed. While reducing the amount of air, when the air-fuel ratio of the air-fuel mixture is richer than the stoichiometric air-fuel ratio, the gate circuit k is opened and the output from the OR circuit is sent to the pulse motor m via the drive circuit l, which is installed in the slow system fuel passage 3f. By increasing the amount of bleed air from the auxiliary air bleed 13, the air-fuel ratio of the air-fuel mixture supplied to the engine 1 is controlled to approximately the stoichiometric air-fuel ratio.

In Fig. 9B, idle speed control circuit 1
9″ with waveform shaping circuit n, frequency divider o, and AND circuit p
It consists of a first oscillator q, a counter r, a decoder s, a data flip-flop t, a second oscillator u, a NAND circuit v, an AND circuit w, and a drive circuit x. The output pulse of the frequency divider o to which the Ig pulse of the rotation sensor 18'' is input via the waveform shaping circuit n has a pulse width according to the engine rotation speed. The pulse width is wide as shown in FIG. Counter pulses are input, and in cooperation with decoder s, the number of pulses N corresponding to the set rotation speed during engine idling is counted, and the output shown in Figure 10 is sent to the T input of data flip-flop t. Add.Data flip-flop t is the 10th
When the output shown in the figure is generated, read the state of the output pulse of the frequency divider o applied to the D input. Therefore, when the engine speed is low, the pulse width of the frequency divider o is long, so the Q output of the data flip-flop t is "1" as shown in Figure 10F, and conversely, when the engine speed is high, the pulse width is Since it is narrow, the Q output becomes "0" as shown in FIG. The output of the data flip-flop t opens and closes the gate circuits v and w that gate the pulses of the second oscillator u, and when the engine idle speed is lower than the set value, the gate circuit w is opened and the pulses from the second oscillator u are gated. The output is sent to the pulse motor y via the drive circuit x to increase the opening area of the bypass air passage 16 and increase the amount of auxiliary air. On the other hand, when the idle speed of the engine is higher than the set value, the gate circuit v is opened and the The output from the second oscillator u is sent to the pulse motor y via the drive circuit x, the opening area of the bypass air passage 16 is reduced, the amount of auxiliary air is reduced, and the idle speed of the engine 1 is maintained at the set value. is controlled. Further, the rotation sensor 18 may detect engine rotation using a ring gear, and the idle rotation speed control circuit may increase its set voltage when a load such as a cooler or power steering is applied. In addition, a throttle valve switch may be used to stop the operation of the bypass air actuator or fix the duty ratio at times other than idling, or the bypass air actuator may be fully opened during deceleration to function as an anti-afterburn valve. In addition, during cranking, the bypass air actuator may be closed to cut off the rotation speed control.Furthermore, in order to improve the startability of the rotation speed control range of the idle rotation speed control circuit 19, the bypass air actuator may be closed during cranking. Prevent air from being introduced during normal operation to improve running performance from 400rpm.
The opening of the bypass air passage may be limited to a range of 1000rpm, and the cross-sectional area of the opening of the bypass air passage may be 100rpm as a rotation speed fluctuation range compared to the gap between the intake passage and the throttle valve.
pm or more, it may be set to 1/5 times or more of the gap, or 3 times or less of the gap to provide an anti-afterburn valve function during deceleration, or the bypass air passage 16 may be set to a slow system. The bypass hole may be opened directly below the bypass hole to promote atomization of the introduced fuel.

Alternatively, a diaphragm device may be used as the actuator to control the intake negative pressure acting on the negative pressure chamber of the diaphragm device.

As described in detail in the above embodiments, the engine idle speed control device according to the present invention includes a rotation sensor that detects the engine speed and a bypass air passage provided in the bypass air passage that supplies auxiliary air downstream of the carburetor throttle valve. an engine comprising: a first actuator; a first circuit for controlling the amount of auxiliary air in the bypass air passage with the first actuator according to the output of the rotation sensor so that the idle speed of the engine is approximately at a set value; and a catalyst device; The exhaust sensor installed in the exhaust system of the carburetor, the second actuator installed in the auxiliary air bleed that supplies air to the slow system fuel passage of the carburetor, and the air-fuel ratio of the intake air-fuel mixture in the intake passage are arranged so that the air-fuel ratio becomes approximately the stoichiometric air-fuel ratio. It has a simple configuration including a second circuit that controls the amount of bleed air of the auxiliary air bleed by the second actuator according to the output of the exhaust sensor. By controlling the air-fuel ratio by a combination of the above-mentioned first circuit and second circuit,
The control characteristics of the auxiliary air bleed do not depend solely on the amount of air, and the same air-fuel ratio changes can always be controlled with the same amount of control, making it possible to always obtain a good engine idle speed. Therefore, it has the outstanding advantage of being able to maintain good engine operating stability and emission level.

[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, FIG. 2 is a block diagram showing the configuration of the rotation speed control circuit and air-fuel ratio control circuit of FIG. 1, and FIG. The figure is a specific circuit diagram of Figure 2, Figure 4 is an output diagram of each circuit in Figure 2, and Figure 5 is a specific circuit diagram of Figure 2.
The figure is an output diagram of the duty ratio of Figure 2, and Figure 6 is a diagram of the relationship between the rotation control width for the duty ratio of the rotation speed control actuator, the duty ratio of the air-fuel ratio control actuator, and the air-fuel ratio by the device of Figure 1, Figures 7A and 7B are a block diagram and a specific circuit diagram respectively showing a modification of the rotation speed control circuit in Figure 2;
Figure 8 is the output diagram of each circuit in Figure 7, Figure 9 A,
B is a block diagram showing another modification of the rotation speed control circuit and air-fuel ratio control circuit shown in FIG. 2, and FIG.
9 is an output diagram of each circuit in FIG. 1... Engine, 2... Intake passage, 3... Carburetor, 3b... Main nozzle, 3c... Main system fuel passage, 3f... Slow system fuel passage, 3g... Carburetor throttle valve, 4... Exhaust passage, 5... Catalyst device, 9
...Main auxiliary air bleed, 10...Slow auxiliary air bleed, 14, 15, 17... Actuator, 16... Bypass air passage, 18, 1
8', 18''... Rotation sensor, 19, 19', 1
9″...Idle speed control circuit, 20, 20″...
...Exhaust sensor, 21,21''...Air-fuel ratio control circuit.

Claims (1)

[Claims] 1 A rotation sensor that detects the engine rotation speed,
A first actuator installed in the bypass air passage that supplies auxiliary air downstream of the carburetor throttle valve, and a first actuator that controls the amount of auxiliary air in the bypass air passage according to the output of the rotation sensor so that the engine idle speed is approximately at the set value. a first circuit controlled by the first actuator, an exhaust sensor provided in the exhaust system of the engine equipped with the catalyst device, and a second circuit provided in the auxiliary air bleed that supplies air to the slow system fuel passage of the carburetor.
an actuator; and a second circuit for controlling the amount of bleed air of the auxiliary air bleed according to the output of the exhaust sensor so that the air-fuel ratio of the intake air-fuel mixture in the intake passage becomes approximately the stoichiometric air-fuel ratio. An engine idle speed control device characterized by: