JPS6213502B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an engine idle control device that maintains an air-fuel ratio and an idle rotational speed at set values during idle operation of an engine having a carburetor.

This type of device includes an exhaust sensor and a catalyst device installed in the engine exhaust system, and a first actuator that opens and closes the auxiliary air bleed provided in the slow system fuel passage of the carburetor. , actuating the first actuator via the air-fuel ratio signal circuit in response to the output of the exhaust sensor to feedback-control the air-fuel ratio of the intake air-fuel mixture to approximately the stoichiometric air-fuel ratio, and detecting the rotational speed of the engine. In addition to providing a rotation sensor to
A second actuator for opening and closing the bypass air passage that opens into the intake passage downstream of the carburetor throttle valve is interposed, and the second actuator is actuated via an idle rotation speed control circuit in accordance with the output of the rotation sensor. A system has been proposed in which the amount of bypass air is controlled and feedback control is performed so that the idle speed of the engine is approximately equal to the set value, so that the idle operation of the engine is well controlled.

In the above device, the amount of bypass air is controlled according to the output of the rotation sensor that detects the engine speed, so if the engine speed suddenly decreases, the amount of bypass air is immediately increased, reducing transient response. Good, but since the fuel flow rate is controlled according to the output of the exhaust sensor installed in the exhaust system, the detection operation by the exhaust sensor lags behind the detection operation by the rotation sensor mentioned above, and the increase in fuel flow rate is delayed and transient response is poor. . As described above, since there is a time difference between the increases in the amount of bypass air and the fuel flow rate, the air-fuel ratio transiently becomes significantly over-lean, which deteriorates the purification rate of the catalyst and the stability of idling operation.

The present invention aims to solve the above-mentioned problem, and provides a pressure compensation device that reduces the pressure upstream of the first actuator of the auxiliary air bleed when a signal related to a sudden change in engine load during idling is detected. The engine is characterized in that the air introduced into the auxiliary air bleed is reduced to increase the fuel flow rate, thereby improving the transient response of air-fuel ratio control when the rotational speed suddenly decreases. The present invention provides an idle control device.

Furthermore, the present invention provides, as the pressure correction device, a communication passage that communicates the auxiliary air bleed upstream of the first actuator with the bypass air passage upstream of the second actuator, so that the The negative pressure change caused by the increase in the number correction air amount is applied to the auxiliary air bleed for air-fuel ratio control, and the amount of air introduced into the auxiliary air bleed is rapidly reduced to rapidly increase the fuel flow rate in the slow system fuel passage. Therefore, it is an object of the present invention to provide an engine idle control device which is characterized in that it reduces the large droop in the air-fuel ratio.

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

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 an exhaust passage. Reference numeral 5 designates a slow system fuel passage provided in the carburetor 3, a slow air bleed 6 is provided in the slow system fuel passage 5, and a slow auxiliary air bleed 7, one end of which is open to the atmosphere, is provided in the slow system fuel passage 5. The ends are connected. 8 is the above auxiliary air bleed 7
The first actuator is a solenoid valve that opens and closes the air bleed 7 provided in the air bleed 7. Reference numeral 9 is a bypass air passage whose one end is open to the intake passage 2 downstream of the carburetor throttle valve 10 and the other end is open to the atmosphere. Reference numeral 11 is a solenoid valve that opens and closes the passage 7, which is interposed in the bypass air passage 9. This is the second actuator.
the second actuator 11 of the bypass air passage 9;
The upstream side and the upstream side of the first actuator 8 of the auxiliary air bleed 7 communicate with each other via a communication passage 12 that constitutes a pressure correction device. The communication path 1
2 is provided with a throttle 13, and throttles 14 and 15 are provided near the atmosphere-opening ends of the auxiliary air bleed 7 and the bypass air passage 9, respectively. still,
The bypass air passage 9 has a larger diameter than the auxiliary air bleed 7.

A catalyst device 16 is provided in the exhaust passage 4, and an exhaust sensor 17 for detecting components of exhaust gas is provided upstream of the catalyst device 16, and the exhaust sensor 17 and the solenoid 8 of the first actuator 8
a is connected via an air-fuel ratio control device 18.
The air-fuel ratio control device 18 controls the first actuator 8 having the configuration shown in FIG. The amount of air in the auxiliary air bleed 7 is increased by increasing the opening time per unit time of the valve body 8b that periodically opens and closes the auxiliary air bleed 7, while the air-fuel ratio of the air-fuel mixture supplied to the engine 1 is reduced to stoichiometric air. If it is thinner than the fuel ratio, the first
The opening time of the actuator 18 is reduced to reduce the amount of air in the auxiliary air bleed 7 to increase the slow system fuel flow rate, thereby controlling the air-fuel ratio of the air-fuel mixture supplied to the engine 1 to approximate the stoichiometric air-fuel ratio. ing.

On the other hand, the engine 1 is provided with a rotation sensor 19 for detecting its rotation speed, and the rotation sensor 19 is connected to the solenoid 11a of the second actuator 11 via an idle rotation speed control device 20. The idle rotation speed control device 20 controls the second actuator 11 according to the detection signal of the rotation sensor 19.
A valve body 11b that periodically opens and closes the bypass passage 9 of
is activated, and when the engine speed is lower than the set value, the opening time of the valve body 11b is increased to increase the amount of bypass air supplied from the bypass air passage 9 to the intake passage 2, while the engine speed is lower than the set value. When the value is higher than the value, the opening time of the valve body 11b is shortened and the amount of bypass air is reduced, thereby controlling the engine speed at idle to be close to the set value.

In the device configured as described above, first, when the idle speed of the engine becomes lower than the set value, the second actuator 11 is actuated via the idle speed control device 20 in response to a detection signal from the rotation sensor 19, and the intake passage 2 The rotational speed correction air supplied to the engine increases, raising the engine speed to the set value. At the same time, due to an increase in the amount of intake air supplied to the engine 1, the air-fuel ratio of the mixture supplied to the engine 1 becomes thinner than the stoichiometric air-fuel ratio, and the air-fuel ratio control device The first actuator 8 is actuated via 18;
The amount of air in the auxiliary air bleed 7 is decreased, the slow system fuel flow rate is increased, and the air-fuel ratio of the air-fuel mixture is controlled to the stoichiometric air-fuel ratio.

On the other hand, when the engine speed suddenly decreases during idling, the rotation sensor 20 detects this sudden change in the engine load during idling, and the second actuator 11 operates according to the detection signal from the rotation sensor 20. To quickly increase the opening time per unit time and rapidly increase the amount of rotation correction air. Therefore, the amount of rotating supplementary air sucked into the bypass air passage 9 increases rapidly, and a large negative pressure acts on the auxiliary air bleed 7 through the communication passage 12, causing the auxiliary air bleed 7 to pass through the first actuator 8. slow air bleed 6
The amount of air introduced into the tank suddenly decreases. Therefore, due to the detection delay of the exhaust sensor 17, the operation of the first actuator 8 is delayed, and even if the opening time per unit time remains before the rapid increase in rotation correction air, the amount of air for air-fuel ratio control is controlled by the communication path 12. The amount of fuel in the slow system fuel passage 5 rapidly increases due to the negative pressure. Therefore, even if there is a sudden change in the engine load during idling, the air-fuel ratio can be controlled to the stoichiometric air-fuel ratio with good responsiveness.

When the idle speed of the engine becomes higher than the set value, conversely, the second
The actuator 11 reduces the amount of bypass air to approximate the rotation speed to the set value, and the first actuator 8 increases the amount of air bleed in response to the detection signal of the exhaust sensor 17 to reduce the fuel flow rate of the slow system fuel passage 5. The air-fuel ratio is reduced to approximate the stoichiometric air-fuel ratio.

The present invention is not limited to the above-mentioned embodiment, and as shown in FIG. The end of the merging passage 21 may be opened to the atmosphere through the throttle 22, and depending on the bypass air amount (rotation speed correction air amount) controlled by the second actuator 11, the air upstream of the first actuator Any other suitable structure may be used as long as the structure is such that negative pressure acts on the bleed to change the amount of air bleed (when the amount of bypass air is large, the amount of air bleed is made small). In addition, as a pressure correction means in the pressure correction device, the bypass air amount controlled by the first actuator is not used, and when the engine speed suddenly decreases or when the engine speed decreases due to a load applied to the engine. If the pressure upstream of the first actuator of the auxiliary air bleed is reduced at the same time as the load is applied,
Other suitable means may be employed.

As is clear from the above explanation, according to the engine idle control output according to the present invention, when the engine speed suddenly decreases and a sudden change in engine load occurs when the engine is idling, the engine speed is corrected. A pressure correction device using air or the like lowers the pressure upstream of the first actuator for controlling the air-fuel ratio of the auxiliary air bleed, so even if the control operation of the first actuator is delayed, the air is introduced into the air bleed from the first actuator. The amount of air decreases rapidly, the transient response of air-fuel ratio control improves, and the air-fuel ratio is quickly controlled to the stoichiometric air-fuel ratio. In addition, when the engine speed changes rapidly, the pressure correction device performs correction control, so the rate of change of the control signal output from the air-fuel ratio control device does not need to be large, and is optimal when the speed fluctuation is small. To output the signal,
Engine vibration caused by control signals can be prevented and stability during idling operation can be improved. In addition, since the air-fuel ratio can be quickly controlled to the stoichiometric air-fuel ratio regardless of the magnitude of fluctuations in engine speed, it also has the advantage of improving the purification rate of the catalyst.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing one embodiment of the apparatus according to the present invention, FIG. 2 is an explanatory diagram of first and second actuators, and FIG. 3 is a schematic configuration diagram showing another embodiment. 1... Engine, 2... Intake passage, 3... Carburetor, 4... Exhaust passage, 5... Slow system fuel passage,
6...Air bleed, 7...Auxiliary air bleed,
8...First actuator, 9...Bypass air passage, 11...Second actuator, 12...Communication passage, 13...Aperture, 16...Catalyst device, 17...
...Exhaust sensor, 18...Air-fuel ratio control device, 19...
... Rotation sensor, 20... Idle rotation speed control device.

Claims (1)

[Scope of Claims] 1. An exhaust sensor provided in the exhaust system of an engine equipped with a catalyst device, a first actuator provided in an auxiliary air bleed that supplies air to a slow system fuel passage of a carburetor, and an intake mixture in an intake passage. an air-fuel ratio control device that controls the amount of air in the auxiliary air bleed with a first actuator according to the output of the exhaust sensor so that the air-fuel ratio of the air is approximately the stoichiometric air-fuel ratio; and a rotation sensor that detects the rotational speed of the engine. , a second actuator installed in the bypass air passage that supplies auxiliary air downstream of the carburetor throttle valve; and a second actuator installed in the bypass air passage that supplies auxiliary air to the downstream side of the carburetor throttle valve; In an engine idle control device having a rotation speed control device for controlling the amount of auxiliary air bleed upstream of the first actuator and the bypass air by a second actuator, the An idle control device for an engine, characterized in that a communication passage is provided that communicates the passage with an upstream side of a second actuator.