JPS60249660A - Exhaust-gas recirculation controller for engine - Google Patents

Abstract

PURPOSE:To permit the recirculation control with high accuracy free from the change through years by controlling the opening and closing degree of one exhaust-gas recirculation control valve so that the output signal of an oxygen sensor for detecting the concentration of the oxygen in the inhaled air of an engine becomes equal to the previously set prescribed value. CONSTITUTION:An intake air which flows into a suction pipe 2 from a throttle valve 3 is mixed with the recirculation exhaust gas introduced from a pipe 9' and the fuel supplied from a fuel feeding apparatus 6 and introduced into an engine 1. The recirculation exhaust gas passes through a pipe 9 from an exhaust pipe 7, and the flow rate is controlled by the first and the second control valves 8 and 16. The concentration of the oxygen in the intake air is detected by a sensor 4, and the output signal is input into an electronic controller 18. The electronic controller 18 reads the recirculation rate previously set according to each operation state of the engine 1 coresponding to each output signal of a pressure detector 5 and a revolution speed detector 17, and a control valve 16 is controlled on the basis of the comparison deviation between the recirculation rate and the detected recirculation rate according to the output of the sensor 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an engine exhaust gas recirculation control device that controls the amount of exhaust gas recirculation in an internal combustion engine.

[Prior art]

It is well known that exhaust gas recirculation, in which a portion of the exhaust gas is introduced into the intake side of the engine, is carried out to reduce nitrogen oxides, which are harmful components in the exhaust gas of an internal combustion engine. In addition to reducing nitrogen oxides, the flow rate of the recirculated exhaust gas affects engine performance, fuel efficiency, etc., so it is desirable that the flow rate of the recirculated exhaust gas be precisely controlled according to the engine operating conditions. . By the way, if the exhaust gas recirculation control valve that controls the exhaust gas flow rate is used for a long time, a large amount of carbon contained in the exhaust gas will adhere to it, and the initial exhaust gas flow rate will change depending on the degree of opening and closing of the control valve, making it less accurate. There was a problem that it could not be controlled.

[Summary of the invention]

This invention provides an oxygen sensor that detects the oxygen concentration in the intake air of an engine mixed with exhaust gas, and utilizes the fact that the oxygen concentration is proportional to the mixing rate of the exhaust gas, and uses the output signal of the oxygen sensor to detect the oxygen concentration. The second exhaust gas is configured to perform feedback control of the amount of the recirculated exhaust gas to enable highly accurate recirculation control without aging, and to bypass the first exhaust gas recirculation control valve. By feedback-controlling the recirculation control valve, the second valve is opened and closed in response to the output signal of the oxygen sensor.
The second exhaust gas recirculation control valve is made small and inexpensive, and further, even if the second exhaust gas recirculation control valve fails, it will not have a significant adverse effect on engine operation.

[Embodiments of the invention]

An embodiment of this invention will be described below. FIG. 1 is a block diagram showing an embodiment of the present invention.

In the figure, (2) is the engine, (2) is the engine's intake pipe, (3) is the throttle valve, and (4) is the oxygen sensor that detects the oxygen concentration in the intake air flowing inside the intake pipe (2). For example, it is composed of a solid electrolyte oxygen pump type oxygen concentration measuring device proposed in Japanese Patent Application Laid-Open No. 56-180649, etc., and generates an output at a level proportional to the oxygen concentration.This oxygen concentration measuring device also has an activation temperature. (5) a pressure detector for detecting the pressure inside the intake pipe (2); (6) a fuel supply device disposed in the intake pipe (2); 7) is an exhaust pipe of the engine (1), (8) is a first exhaust gas recirculation control valve, and pipes (9) and (9) communicate the exhaust pipe (7) with the intake pipe (2). ′
) is located between. The control valve (8) is composed of a diaphragm aQ, a valve member a fixed to the diaphragm (IQ), a spring (2), a case σ, and a main body α. The valve member συ is opened and closed by the pressure (negative pressure) in the intake pipe (2) acting on the pipe (9) to control the amount of recirculated exhaust gas flowing from the pipe (9) to the pipe (9'). Near α is a second exhaust gas recirculation control valve that is configured with a solenoid valve or the like and can be electrically controlled to open and close, and the recirculated exhaust gas flows bypassing the exhaust gas recirculation control valve (8) in @1 above. The amount of recirculated exhaust gas introduced into the intake pipe (2) is controlled by the first and second exhaust gas recirculation control valves (8).

This is the total amount of exhaust gas flowing near σ. αη is the above machine
A rotation speed detector that detects the rotation speed of the sensor (υ), (G) inputs the output signals of the rotation speed detector ση, the pressure detector (5), and the oxygen sensor (4), and these inputs. It is an electronic control device that drives the second exhaust gas recirculation control valve αQ in response to the information and controls the amount of recirculated exhaust gas introduced into the intake pipe (2) to a desired value.

The operation of the inventive device configured as above will be explained. When the engine (υ) is started, intake air drawn into the engine (1) passes from the atmosphere through an air cleaner (not shown) and flows into the intake pipe (2) from the throttle valve (3).

The fuel is then mixed with recirculated exhaust gas introduced from the pipe (9') and further mixed with fuel injected from the fuel supply device (6), and introduced into the engine. The recirculated exhaust gas introduced from the above pipe (9') is connected to the exhaust pipe (7).
The exhaust gas is then passed through a pipe (9), the flow rate of which is adjusted by the first and second exhaust gas recirculation control valves (+8) and DI, and introduced into the intake pipe (2) from the pipe (9'). Relationship between the oxygen concentration in the intake air mixed with the exhaust gas in the intake pipe (2) and the mixing ratio of the intake air and the recirculated exhaust gas in the intake pipe (2) (exhaust gas recirculation rate) is as shown in Figure 2. Therefore, by detecting the oxygen concentration in the intake air using the oxygen sensor (4), the exhaust gas recirculation rate can be determined. The above oxygen sensor (4) is disclosed in Japanese Patent Application Laid-open No. 56-180.
When using the solid electrolyte oxygen pump-type oxygen partial pressure measuring bag and device proposed in 649 etc., an output signal proportional to the oxygen concentration can be obtained, so as a result, an output signal proportional to the exhaust gas recirculation rate can be obtained. Obtained from the oxygen sensor (4). The output signal from this oxygen sensor (4) is input to an electronic control device. Then, in response to the output signals of the pressure detector (5) and the rotation speed detector Qη, the electronic control unit (to) reads out a recirculation rate preset according to each operating state of the engine f1), and uses this value and The opening/closing degree of the second exhaust gas recirculation control valve α is controlled based on the comparison deviation with the recirculation rate detected by the output of the oxygen sensor (4), and the amount of exhaust gas to be recirculated is adjusted. Control is performed so that the above-mentioned one-bite deviation is eliminated.

In the embodiment shown in FIG. 1, the first exhaust gas recirculation control valve (8) is configured to be opened and closed by the negative pressure generated in the intake pipe of the engine, but the throttle valve (3)
The opening/closing drive may be configured to be driven in conjunction with the opening/closing operation.

〔Effect of the invention〕

As described above, the present invention provides first and second exhaust gas recirculation control valves for controlling the amount of recirculated exhaust gas introduced into the intake air of an engine, and the oxygen concentration in the intake air mixed with the exhaust gas. The second exhaust gas recirculation control valve is controlled to open and close so that the output signal of the oxygen sensor becomes a predetermined value. Even if carbon etc. adhere to the exhaust gas recirculation control valve and the initial exhaust gas amount changes depending on the degree of opening/closing, the above second exhaust gas recirculation control valve compensates for this, resulting in highly accurate recirculation that does not change over time. control has become possible. In addition, since the exhaust gas to be recirculated is divided and controlled between the first and second exhaust gas recirculation control valves, even if either one breaks down, the performance between the rows will not be significantly impaired. .

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention. Second
The figure is a characteristic diagram showing the relationship between the oxygen concentration in the intake pipe and the exhaust gas recirculation rate. In Figure 1, (1) is the engine, (2) is the intake pipe, and (4) is the engine.
) is an oxygen sensor, (7) is an exhaust pipe, (8) is a first exhaust gas recirculation control valve, and 0 o'clock is a second exhaust gas recirculation control valve. Note that the same reference numerals in the figures indicate the same parts. Agent: Masuo Odai, Figure 1] Figure 2, pυ゛ space recirculation rate (≠)

Claims (2)

[Claims] (1) First and second exhaust gas recirculation control valves that control the amount of exhaust gas introduced into the intake air of the engine, and an oxygen sensor that detects the oxygen concentration in the intake air mixed with the exhaust gas. and an exhaust gas recirculation control device for an engine, comprising means for controlling the opening/closing degree of the second exhaust gas recirculation control valve so that the output signal of the oxygen sensor becomes a predetermined value. (2) The exhaust gas recirculation control device for an engine according to claim 1, wherein the first exhaust gas recirculation control valve is driven to open and close by a negative pressure generated in the intake pipe of the engine or by a slot valve.