JPS6146198Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to an engine idle speed control device, and in particular focuses on the fact that the operating range of the actuator for controlling the idle speed is different from the operating range of the actuator for controlling the main system fuel flow rate. The structure is such that one actuator is shared and used separately for idle and non-idle to perform the above two types of control, thereby simplifying the structure and reducing costs.

Specifically, the engine idle speed control device according to the invention includes a rotation speed sensor for detecting the engine speed and an idle speed control circuit connected to the rotation speed sensor, and an exhaust system equipped with a catalyst device. An exhaust sensor is provided at the exhaust sensor, and an air-fuel ratio control circuit connected to the exhaust sensor is provided, and a bypass air passage opening into the intake passage downstream of the throttle valve and the upstream side of the main auxiliary air bleed communicating with the main air bleed are merged into a merging area. A solenoid valve that closes the communication port on the main air bleed side when idling and closes the communication port on the bypass air passage side when not idling is installed, and is provided upstream of the on-off valve to control the intake air amount. The first actuator is connected to the idle rotation speed control circuit when idling, and is connected to the air-fuel ratio control circuit when not idling, and when idling, the first actuator is connected to the idle rotation speed control circuit according to the output of the rotation sensor. 1
The actuator is operated to control the amount of bypass air so that the idle rotation speed is approximately the set value, while the first actuator is operated in accordance with the output of the exhaust sensor to control the fuel flow rate in the main system fuel passage when the engine is not idling. A second actuator is provided to control the air-fuel ratio to be the stoichiometric air-fuel ratio and to control the amount of air bleed in the slow system fuel passage, and the second actuator is connected to the air-fuel ratio control circuit to control the output of the exhaust sensor. This feature is characterized in that it is activated according to the situation.

This invention will be explained in detail below 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, 3 is a carburetor, and 4 is a carburetor.
is an exhaust passage, and the carburetor 3 is provided with a float chamber 9, a main system fuel passage 5 having a main nozzle 5a, a slow system fuel passage 6 having an idle port 6a and a slow port 6b, and a carburetor throttle valve 7. On the other hand, a catalyst device 8 is interposed in the exhaust passage 3. In the main system fuel passage 5, a main air bleed 10 is provided between the float chamber 9 and the main nozzle 5a, and in the slow system fuel passage 6,
A slow air bleed 11 is provided between the float chamber 9 and the idle port 6a and slow port 6b. Further, a main auxiliary air bleed 12 is provided within the main air bleed in order to indirectly control the fuel flow rate in the main system fuel passage 5, and a main auxiliary air bleed 12 is provided in the slow air bleed 11 to indirectly control the fuel flow rate in the slow system fuel passage 5. A slow auxiliary air bleed 13 is provided.

14 is a bypass air passage that opens into the intake passage 2 downstream of the carburetor throttle valve 7, and the main auxiliary air bleed 12 is connected upstream of the bypass air passage 14.
The bypass air passage side communication port 15a and the main auxiliary air bleed side communication port 15b are alternately opened and closed to connect the upstream side communication port 15c.
A solenoid-type on-off valve 15 is interposed. The merging passage 16 communicating with the upstream communication port 15c has a first solenoid valve that opens and closes a communication port 17 with the atmosphere at a set frequency.
An actuator 18 is provided. Further, upstream of the slow auxiliary air bleed 13, a second actuator 20 is provided, which is a solenoid valve that opens and closes a communication port 19 with the atmosphere at a set frequency.

On the other hand, the engine 1 is provided with a rotation sensor 21 that detects its rotation speed, and an idle rotation speed control circuit 22 that controls the idle rotation speed to approximately a set value according to the output of the rotation sensor 21 is connected to the first actuator 18. It is connected to the solenoid 18a.
Further, the exhaust passage 3 is provided with an exhaust sensor 23 for detecting the component concentration of the exhaust gas upstream of the catalyst device 8, and air-fuel ratio control is performed to control the air-fuel ratio to approximately the stoichiometric air-fuel ratio according to the output of the exhaust sensor 23. A circuit 24 is connected to each solenoid 18a, 20a of the first actuator 18 and second actuator 20.

Solenoid 18 of the first actuator 18
A, the idle speed control circuit 22, and the air-fuel ratio control circuit 24 are connected to one of them and disconnected from the other by means of a changeover switch 26. The changeover switch 26 is controlled by an idle switch 27, and the changeover switch 26 has a normally closed contact 26a on the side of the air-fuel ratio control circuit 24,
It is composed of a contact plate 26b, a normally open contact 26d on the side of the idle speed control circuit 22, and an electromagnetic coil 26e, and the coil 26e is connected to an idle switch 27 that is turned on during idle.

In this way, at idle, the idle switch 27 is turned on, the electromagnetic coil 26e is energized, the contact plate 26b contacts the contact 26d, and the solenoid 18a is connected to the idle speed control circuit 22, while the solenoid 18a and the air-fuel ratio Control circuit 2
4, the idle switch is turned OFF at times other than idling, the electromagnetic coil 26e is de-energized, the connection between the solenoid 18a and the idle speed control circuit 22 is cut off, and the solenoid 18a is used to control the air-fuel ratio. It is connected to the circuit 24. The idle switch 27 is connected to the solenoid 15d of the on-off valve 15 at the junction of the bypass air passage 14 and the main auxiliary air bleed 12, and closes the communication port 15b on the side of the main auxiliary air bleed 12 during idle, but when not idle. The communication port 15a on the side of the bypass air passage 14 is closed.

The idle switch 27 detects, for example, the opening of the carburetor throttle valve 7 or the amount of depression of an accelerator pedal (not shown), and is turned on only when the vehicle is idling.

In the device configured as described above, when the idle switch 27 is turned on during idling operation, the on-off valve 15
As shown in the figure, the communication port 15b on the main auxiliary air bleed 12 side is closed, the communication port 15c on the bypass air passage 14 side is communicated with the first actuator 18, and at the same time, the first actuator 18 is set to the idle speed using the changeover switch 26. It is connected to the control circuit 22, and the first actuator 18 is operated according to the output of the rotation sensor 21. That is, when the engine speed is lower than the set value, the first actuator 18
By increasing the duty ratio of the solenoid valve (i.e., the ratio of open time of the solenoid valve per unit time), the amount of bypass air flowing from the bypass air passage 14 to the intake passage 2 is increased, and the engine speed is increased to approximately the set value. At the same time, the exhaust sensor 23 detects the leanness of the air-fuel ratio of the intake mixture due to the increase in the intake air amount, and the output of the exhaust sensor 23 increases. In response to this, the air-fuel ratio control circuit 24 reduces the duty ratio of the solenoid valve as the second actuator 20 to reduce the bleed air amount of the slow auxiliary air bleed 13, and controls the air-fuel ratio of the air-fuel mixture to approximately the stoichiometric air-fuel ratio. On the other hand, if the engine speed is higher than the set value, the duty ratio of the solenoid valve serving as the first actuator 18 is reduced and the bypass air passage 14 is
By reducing the amount of bypass air to the intake passage 2,
At the same time, the exhaust sensor 23 supplies an amount of intake air commensurate with the amount of air-fuel mixture that is equivalent to lowering the engine speed to approximately the set value, and at the same time detects the enrichment of the air-fuel ratio of the intake air-fuel mixture due to the decrease in the amount of intake air. In response to the output of the exhaust sensor 23, the air-fuel ratio control circuit 24 increases the duty ratio of the solenoid valve as the second actuator 20, increases the amount of bleed air of the slow auxiliary air bleed 13, and adjusts the air-fuel ratio of the mixture. is controlled to approximately the stoichiometric air-fuel ratio. At idle, the amount of air in the main auxiliary air bleed 12 is not controlled, but since fuel is not supplied from the main system fuel passage 5 at idle, there is no need to control it. In this manner, when the engine is idling, the engine speed is controlled in a feedbag manner so that the engine speed is approximately at the set value, and the air-fuel ratio of the intake air-fuel mixture is also controlled in a feedbag manner so that the air-fuel ratio becomes the stoichiometric air-fuel ratio. Therefore, the engine's idle speed can be maintained at the set value regardless of changes in the load applied to the engine 1 during idle, changes in atmospheric pressure, variations in engine mass production, or the degree of lapping progress, so the engine's idle speed can always be maintained at the set value. Since stability can be maintained well and the atmosphere in the catalyst device 8 provided in the exhaust passage 4 of the engine 1 can be made into a three-way atmosphere, the catalyst device 8 can purify CO.HC. and NOx in the exhaust gas. This makes it possible to maintain a good engine emission level at all times.

On the other hand, when the throttle valve 7 opens beyond the set opening degree and the idling operation changes to normal operation, the idle switch 27 is turned OFF, and the on-off valve 15 opens the communication port 15b of the main auxiliary air bleed 12 to communicate with the first actuator 18. On the other hand, the communication port 15a of the bypass air passage 14 is closed. Therefore, the supply of bypass air from the bypass air passage 14 to the intake passage 2 is stopped, but during normal rotation of the engine 1, the bypass air passage 1 for idle speed control is stopped.
Supplying bypass air from No. 4 is unnecessary because it impairs drivability. idle switch 27
When turned off, the changeover switch 26 connects the first actuator 18 to the air-fuel ratio control circuit 24.
Therefore, during normal rotation of the engine 1, the amount of bleed air from the main auxiliary air bleed 12, which is inactive during idle rotation, is controlled by the air-fuel ratio control circuit 24 to the first actuator 1 in accordance with the output of the exhaust sensor 23.
When the air-fuel ratio of the air-fuel mixture is richer than the stoichiometric air-fuel ratio, the amount of bleed air is increased, while when the air-fuel ratio of the air-fuel mixture is leaner than the stoichiometric air-fuel ratio, the amount of bleed air is decreased, and the intake air-fuel ratio is Feedbag control is performed to maintain the stoichiometric air-fuel ratio. In this way, the atmosphere in the catalyst device 8 provided in the exhaust passage 4 of the engine 1 can be made into a three-way atmosphere.
It is possible to purify CO.HC and NOx.

In the above embodiment, solenoid valves are used as the first and second actuators, but
It is also possible to use a valve body that is opened and closed by a diaphragm device, and to control the dilution rate of the intake negative pressure acting on the negative pressure chamber of the diaphragm device with the atmosphere using the above-mentioned solenoid valve.

As is clear from the above description, the idle speed control device according to the invention takes advantage of the fact that the control range of the idle speed and the air-fuel ratio control range of the fuel flow rate in the main fuel passage are completely different. Since one actuator is used in common, the number of actuators can be reduced, and the number of auxiliary parts thereof can also be reduced, resulting in a simple structure and a significant cost reduction. In addition, by controlling the idle speed of the engine and the air-fuel ratio of the air-fuel mixture supplied to the engine, it is possible to always obtain a good idle speed of the engine.
Therefore, it has the outstanding advantage of being able to maintain good engine operating stability and emission level.

[Brief explanation of drawings]

The drawing is an explanatory diagram showing a schematic configuration of an engine idle speed control device according to the present invention. 1... Engine, 2... Intake passage, 3... Carburetor, 4... Exhaust passage, 5... Main system fuel passage,
6... Slow system fuel passage, 7... Carburetor throttle valve, 8
...Catalyst device, 12...Main auxiliary air bleed, 13...Slow auxiliary air bleed, 14...
Bypass passage, 15... Opening/closing valve, 18... First actuator, 20... Second actuator, 2
DESCRIPTION OF SYMBOLS 1... Rotation sensor, 22... Idle rotation speed control circuit, 23... Exhaust sensor, 24... Air-fuel ratio control circuit, 26... Changeover switch, 27... Idle switch.

Claims (1)

[Claim for Utility Model Registration] A rotation sensor that detects the engine rotation speed is provided, and the amount of bypass air supplied to the intake passage downstream of the carburetor throttle valve is controlled according to the output of the rotation sensor to keep the engine idling. In addition to feedback controlling the rotation speed to approximately the set value, an exhaust sensor and a catalyst device are installed in the engine's exhaust system, and depending on the output of the exhaust sensor, the amount of air bleed in the slow system fuel passage of the carburetor and the main of the carburetor are controlled. In an engine idle speed control device that controls the fuel flow rate in the system fuel passage to feedback-control the air-fuel ratio of the intake air-fuel mixture to approximately the stoichiometric air-fuel ratio, the bypass air amount and the fuel flow rate in the main system fuel passage are both controlled. A first actuator is provided, and the first actuator is connected to the above-mentioned idle speed control circuit when the engine is idling, and is selectively connected to the above-mentioned air-fuel ratio control circuit when the engine is not idling. The first actuator is operated according to the output of the rotation sensor to control the amount of bypass air, and the first actuator is operated according to the output of the exhaust sensor to control the fuel flow rate in the main system fuel passage when the engine is not idling. On the other hand, an engine characterized in that a second actuator for controlling the amount of air bleed in the slow system fuel passage is provided, and the second actuator is operated by being connected to the air-fuel ratio control circuit connected to the exhaust sensor. idle speed control device.