JPS641657B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an air-fuel ratio control device that introduces air into a recirculation passage that leads exhaust gas to an intake system in relation to the output of an air-fuel ratio sensor.

[Problems to be Solved by the Invention] In such an air-fuel ratio control device, a problem arises in that the air-fuel ratio at the time of a shift change greatly deviates from the stoichiometric air-fuel ratio to the rich side due to the response delay of the air-fuel ratio sensor. ing.

An object of the present invention is to provide an air-fuel ratio control device that exhibits excellent effects on air-fuel ratio control during shift changes.

[Example] Embodiments of the present invention will be described with reference to the drawings.

In FIG. 1, a carburetor 1 has a throttle valve 2 that is linked to an accelerator pedal in the driver's cab, and is connected to an air cleaner 3 on the upstream side and an intake branch pipe 4 on the downstream side, and is connected to an air-fuel ratio slightly smaller than the stoichiometric air-fuel ratio. Form the spirit. The air-fuel mixture is combusted in the combustion chamber of the engine body, and exhaust gas is guided through the exhaust pipe 5. An exhaust gas recirculation (EGR) passage 9 connects the exhaust pipe 5 and the intake branch pipe 4, and has a flow cross-sectional area controlled by an EGR valve 10. The EGR valve 10 includes a pressure chamber 12 and an atmospheric chamber 13 separated from each other by a diaphragm 11, a spring 14 that presses the diaphragm 11 toward the atmospheric chamber 13, a valve body 15 coupled to the diaphragm 11, and an exhaust system from the valve body 15. It has a constant pressure chamber 16 provided on the side. Ports 19 and 20 are provided at positions downstream of the throttle valve 2 when the throttle valve 2 reaches a predetermined opening degree or more, and the port 19 is connected to the pressure chamber 12 of the EGR valve 10 via a passage 21.
The pressure regulating valve 25 is connected to the port 2 connected to the passage 21.
6. Chambers 28 and 29 separated from each other by the diaphragm 27, a spring 30 that presses the diaphragm 27 toward the chamber 29, and a valve body 31 that is attached to the diaphragm 27 and opens and closes the port 26. Chamber 28 is connected to the atmosphere and port 20, and chamber 29 is connected to constant pressure chamber 16. An orifice 31 is provided in the passage 21 between the pressure regulating valve 25 and the port 19. The air introduction valve 35 is connected to a port 36 connected to the atmosphere, a port 37 connected to the EGR passage 9, a negative pressure chamber 39 defined by a diaphragm 38, a spring 40 that presses the diaphragm 38, and the diaphragm 38. A reed valve 42 is provided between the valve seat of the valve body 41 and the port 37. Negative pressure chamber 39 is connected to port 4 of intake pipe 4 via passage 45.
6. The electromagnetic on-off valve 47 is connected to the passage 45
The port 49 on the negative pressure chamber 39 side is selectively connected to the port 50 on the port 46 side or the atmospheric port 51 by an electric signal from the electronic control unit 48. An air-fuel ratio sensor 54 that detects the oxygen concentration in exhaust gas is attached to the exhaust pipe 5, and its output is sent to the electronic control section 48.

The above configuration is the same as the conventional device, and its operation will be briefly explained as follows: Port 19 of the carburetor 1
is maintained at negative pressure in the intake pipe when the engine load is greater than a predetermined value, and as a result, the EGR valve 10
Passage 9 is opened to allow exhaust gas to be recirculated to the intake system. The pressure regulating valve 25 prevents fluctuations in the recirculation rate due to pulsations in exhaust gas pressure. When the air-fuel ratio deviates to the rich side, the solenoid valve 47 supplies intake pipe negative pressure to the negative pressure chamber 39 of the air introduction valve 35, and this causes air to flow through the EGR passage 9 to the intake branch pipe 4 and It is introduced into the exhaust pipe 5. Further, when the air-fuel ratio deviates to the lean side, atmospheric pressure is supplied from the atmospheric port 51 of the solenoid valve 47 to the negative pressure chamber 39 of the air introduction valve 35, the valve body 41 closes the valve seat 42, and the air introduction valve 35
The introduction of air into the intake branch pipe 4 and the exhaust pipe 5 via the intake pipe is prevented.

The negative pressure switching valve 59 is connected to the port 46 of the intake branch pipe 4.
a port 60 connected to the negative pressure chamber 39 of the air introduction valve 35, a port 61 connected to the negative pressure chamber 39 of the air introduction valve 35, and a chamber 6 separated from each other by a diaphragm 62.
3, 64, orifice 65 and check valve 69 provided in diaphragm 62, and diaphragm 6
2 towards the chamber 63, a valve body 67 connected to the diaphragm 62. room 64
is connected to sensing port 68. The sensing port 68 is located downstream of the throttle valve 2 when the throttle valve 2 is at the idling opening, and is upstream of the throttle valve 2 when the throttle valve 2 is opened from the idling opening.

During a shift change, the accelerator pedal is released and the throttle valve 2 is opened at idling. Therefore, intake pipe negative pressure is supplied from the sensing port 68 to the chamber 64 of the negative pressure switching valve 59, and the diaphragm 62 is bent against the spring 66 due to the pressure difference between the chambers 64 and 63, and the valve body 67 is pressed down. As a result, intake pipe negative pressure is supplied to the chamber 39 of the air introduction valve 35, the valve body 41 is separated from the valve seat, and air is supplied to the intake branch pipe 4 and the exhaust pipe 5. When the idling opening degree continues for a predetermined time or more, the orifice 65 brings the chambers 63 and 64 to the same pressure, and the valve body 67
closes the opening of the valve seat, and air introduction from the air introduction valve 35 to the intake system and the exhaust system is stopped. When the opening of the throttle valve 2 becomes larger than the idling opening, the sensing port 68 becomes upstream of the throttle valve 2, the valve element 67 of the negative pressure switching valve 59 closes the valve seat, and air is no longer introduced from the air introduction valve 35 into the intake system. This prevents the air-fuel ratio from shifting significantly toward the rich side during a shift change.

FIG. 2 is a graph showing the change in air-fuel ratio during a shift change, where the horizontal axis shows time t, the vertical axis shows the air-fuel ratio A/F, and t1, t2, and t3 show the shift change times, respectively. The solid line shows the characteristics of the present invention, and the broken line shows the characteristics of the conventional device. It can be seen that according to the present invention, the air-fuel ratio at the time of a shift change is well controlled without significantly shifting toward the rich side.

FIG. 3 shows another embodiment of the invention. Parts corresponding to those in FIG. 1 are designated with the same reference numerals and explanations are omitted.
Only the different points will be explained. In this embodiment, the negative pressure switching valve is omitted. When the throttle valve 2 is returned to the idling opening degree during a shift change and the sensing port 68 becomes downstream of the throttle valve 2, the negative pressure switch 71 is activated due to the change in negative pressure at the sensing port 68. An electronic control unit 48 including a microprocessor detects the output of the negative pressure switch 71 and detects the output of the air-fuel ratio sensor 54 during a shift change.
The port 49 of the solenoid valve 47 is connected to the port 50 for a predetermined period of time regardless of the output of the solenoid valve 47 . As a result, intake pipe negative pressure is supplied to the negative pressure chamber 39 of the air introduction valve 35, the valve body 41 is separated from its valve seat, and air is introduced into the intake branch pipe 4.

[Effects of the Invention] As described above, according to the present invention, air is supplied to the intake branch pipe through the EGR passage during a shift change, so that the air-fuel ratio is greatly reduced to the rich side due to the response delay of the air-fuel ratio sensor. It is possible to prevent the shift from occurring and maintain a good air-fuel ratio during a shift change.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a graph showing air-fuel ratio changes during a shift change in the present invention, and FIG. 3 is a block diagram of another embodiment of the present invention. 2... Throttle valve, 5... Exhaust pipe, 9... EGR passage, 10... EGR valve, 35... Air introduction valve, 3
9... Negative pressure chamber, 47... Solenoid valve, 48... Electronic control unit, 54... Air-fuel ratio sensor, 59... Negative pressure switching valve, 68... Sensing port, 71... Negative pressure switch.

Claims (1)

[Claims] 1. A recirculation passage that guides exhaust gas to the intake system downstream from the throttle valve, a control valve that controls the flow cross-sectional area of the recirculation passage in relation to the opening degree of the throttle valve, and a negative pressure chamber. an air-fuel ratio controller comprising: an air inlet valve for introducing air into the recirculation passage in relation to the negative pressure of the air-fuel ratio; In the control device,
An air-fuel ratio control device comprising means for detecting that a throttle valve has reached an idling opening degree and supplying negative pressure to a negative pressure chamber of an introduction valve.