JPS6355356A - Exhaust gas recirculation controller for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve the response, when an exhaust gas recirculation control valve is feedback controlled through an O2 sensor such that a target exhaust gas recirculation rate corresponding to an operating condition of engine is obtained, by varying the proportional constant and the integration constant of the feedback control system according to an intake air pressure and rotation. CONSTITUTION:An EGR control circuit 14 reads out a target exhaust gas recirculation rate from a data map corresponding to detection values from an intake pressure detector 10 and an engine rotation sensor 8, and feedback controls the opening of an EGR control valve 12 through a control negative pressure generator 16 based on a detection value of an O2 sensor 18 disposed in the downstream of an EGR path 11 for an intake tube 2. The EGR control circuit 14 reads out the proportional constant and the integration constant of the feedback control system from a data map according to an intake pressure and rotation so as to calculate a feedback control signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an exhaust gas recirculation control device for an internal combustion engine, which controls the amount of exhaust gas recirculated in an internal combustion engine.

[Conventional technology]

It is well known that so-called exhaust gas recirculation, in which a part of the exhaust gas is introduced into the intake side of the engine, is carried out in order to reduce nitrogen nitride, which is a harmful M component in the exhaust gas of an internal combustion engine. be.

The flow rate of recirculated exhaust gas affects engine performance, fuel efficiency, etc. in addition to reducing nitrogen oxides, so it is desirable that the flow rate of recirculated exhaust gas be controlled with precision according to the operating conditions of the engine. .

FIG. 6 is a configuration explanatory diagram showing a conventional exhaust gas recirculation (hereinafter abbreviated as EGR) control device as disclosed in, for example, Japanese Unexamined Patent Publication No. 55-93950. In FIG. 6, 1 is an engine body, 2 is an intake pipe of the engine, and 3 is an exhaust pipe. A fuel supply device 4 is disposed in the intake pipe 2.

Further, a throttle valve 5 is arranged near a connecting portion between the intake pipe 2 and the intake duct 6. An air cleaner 7 is arranged at the entrance of the intake duct 60.

An intake negative pressure introduction passage 9 communicates with the intake pipe 2 . The intake pressure in the intake pipe 2 is detected by an intake pressure detector 10 through this 9 ft intake negative pressure introduction passage.

The output of the intake pressure detector 10, the opening degree detector 13 of the EGR control valve 12, and the output of the engine rotation speed detector 8 are sent to an EGR control circuit 14.

The EGR control valve 12 is connected to the EGR passage 1□1. The EGR passage 11 communicates the exhaust pipe 3 and the intake pipe 2.

A controlled negative pressure generator 16 is controlled by the output of the EGR control circuit 14. This control negative pressure generator 16 generates the actuator negative pressure by regulating the pressure of the actuator negative pressure using the intake negative pressure and the X atmospheric pressure in order to control the opening/closing degree of the EGR control valve 12.

Next, the operation will be explained. Engine speed and engine intake pressure, which are quantities that indicate the operating state of the engine, are detected by an engine speed detector 8 and an intake pressure detector 10, respectively, and are input to an EGR control circuit 14.

The amount of EGR flowing through the EGR passage 11 is determined by the opening degree corresponding to the target EGR rate stored in the EGR%iJ control circuit 14 according to the engine operating state quantities detected by the engine speed detector 8 and the intake pressure detector 10. The output value of the detector 13 and the EG
The output negative pressure of the control negative pressure generator 16 is introduced into the intake negative pressure by the output signal of the EGR control circuit 14 so that the comparison deviation with the celestially measured output value of the opening detector 13 linked with the R control valve 12 becomes zero. Due to the pressure in passage 9 and atmospheric pressure introduction passage 15 E) ==
It is determined by controlling the opening degree of the EGR control valve 12.

That is, the opening degree of the EGR control valve 12 is detected by the opening 7 degree detector 1.
By performing feedback control using the output of 3,
Nine EGR amounts are obtained depending on the operating condition of the engine.

[Problem that the invention seeks to solve]

In conventional EGR control devices, when used for a long time,
A large amount of carbon contained in the exhaust gas adheres to the EGR control valve 12, which causes the initial exhaust gas flow rate to change depending on the degree of opening and closing of the control valve, making accurate control impossible.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems, and to provide an exhaust gas recirculation control device f for an internal combustion engine that enables highly accurate exhaust gas recirculation control that does not change over time.
It is about providing.

[Means for solving problems]

The exhaust gas recirculation control device for an internal combustion engine according to the present invention inputs the output of an oxygen sensor installed in an intake pipe to detect the oxygen concentration in the intake air of the engine mixed with exhaust gas. It is a good idea to install EGR control means to control the flow rate.

[For production]

According to the exhaust gas recirculation control device for an internal combustion engine of the present invention, an oxygen sensor detects the oxygen concentration in intake air, and a target oxygen concentration is preset according to the oxygen concentration detected by the oxygen sensor and the operating state of the engine. In the control circuit, the comparison deviation is input to the proportional amplifier circuit and the integration circuit, and the exhaust gas recirculation control valve is opened and closed in response to the sum signal of the output signals of both circuits to make the comparison deviation zero. , the proportional amplification degree of the proportional amplification circuit and the integration time of the integration circuit change depending on the intake air pressure and rotation speed of the engine. Therefore, in this device, the amount of recirculation of exhaust gas is controlled by the oxygen concentration that is proportional to the mixing rate of exhaust gas, and the amount of recirculation is controlled stably and with good responsiveness regardless of the operating state of the engine.

〔Example〕

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the exhaust gas recirculation control device for an internal combustion engine according to the present invention will be described in more detail with reference to preferred embodiments shown in the accompanying drawings.

FIG. 1 is a diagram showing the configuration of an embodiment of the present invention. In FIG. 1, parts that are the same as those in FIG. I will explain.

As is clear from comparing FIG. 1 with FIG. 6, in FIG. 1, the parts indicated by numerals 1 to 16 are the same as in FIG. This is a newly provided part and is a feature of this invention.

That is, 17 is an opening of the EGR passage 11 to the intake pipe 2, and 18 is an oxygen sensor provided in the intake pipe 2 downstream of this opening 17. This oxygen sensor 18 detects the oxygen concentration in the intake air flowing through the intake pipe 2, and this oxygen sensor 18 is a solid electrolyte oxygen pump type oxygen sensor proposed in, for example, Japanese Patent Laid-Open No. 58-153155. Like a sensor, it generates a sensor output proportional to oxygen concentration.

The output of this oxygen sensor 18 is sent to the EGR control circuit 14. The other configurations are the same as in FIG. 6.

Next, the operation of the embodiment will be specifically explained with reference to FIGS. 2 to 5. Figure 2 is a diagram showing the relationship between the EGR rate and the cumulative Q degree C62 during intake, and Figure 3 is a diagram showing the relationship between the EGR rate and the cumulative Q degree C62 during intake.
A diagram showing a target EGR rate Kok determined corresponding to the operating state of the engine stored in the GR control circuit 14,
FIG. 4(a) is a diagram showing the relationship between the opening degree of the EGR control valve 12 and the EGR rate. EGR
Figures 5(a) and 5(6), which show how the rate K changes, correspond to the engine intake pressure PB and engine speed N stored in the EGR control circuit 14, respectively. FIG. 3 is a diagram showing a determined proportional amplification degree KP of a proportional amplifier circuit and an integration time TIe of an integral circuit.

When the engine body 1 is started, the engine rotation speed NE and the engine intake pressure P, which indicate the operating state of the engine body 1, are
B is detected by the engine speed detector 8 and the intake pressure detector 10, and is input to the EGR control circuit 14.

In this EGR control circuit 14, as shown in FIG. 3, a target EGR rate K corresponding to the rotational speed Ng and intake pressure PB is
0 is stored, and a target EGR rate KOi, for example, is selected according to the rotational speed NE and the intake pressure pBO value.

Target oxygen concentration Cδ2 corresponding to this target EGR rate KOi
I is calculated according to FIG.

On the other hand, the oxygen concentration of the air mixed with EGR gas in the intake pipe 2 is calculated from the output IP of the oxygen sensor 18. This calculated oxygen concentration CO2 and the target oxygen concentration Cδ21
and inputs the comparison deviation to the proportional amplification circuit and the integration circuit in the EGR control circuit 14. The sum signal of the output signals of both circuits corresponds to the opening degree of the EGR control valve 12, and the EGR control circuit 14 controls the control negative so that the opening degree of the EGR control valve 12 matches the correspondence relationship with the addition signal. A signal is output to the pressure generator 16. Control negative pressure generator 16 is EG
The υ output negative pressure is regulated by the output of the R control circuit 14 using the pressure of the intake negative pressure introduction passage 9 and the atmospheric pressure introduction passage 15, and the E
The opening degree t of the GR control valve 12 is driven and controlled, and the EGR gas amount is adjusted to eliminate the comparative deviation. It is constantly changing in relation to

The relationship between the opening degree of the EGR control valve 12 and the EGR rate of 0 is as shown in FIG.
The R rate KO is obtained, but if, for example, the rotational speed NE among the quantities indicating the operating state of the engine changes, the EGR rate K changes as the opening degree of the EGR control valve 12 becomes constant, as shown in FIG. 5(b). Nevertheless, it changes. This indicates that the characteristics of the engine to be controlled change depending on the operating state. Proportional amplification degree KP of the amplifier circuit (!: Integration time T of the integration circuit
When I is set, the fifth
As shown in Figure 1), the EGR rate changes greatly with respect to changes in the opening degree of the EGR control valve 12, so it tends to become unstable.

Therefore, in this EGR control circuit 14, as shown in FIG.
Among the quantities that indicate the operating state of the engine, as shown in FIG.
is stored, and according to the values of the rotation 12 Ng and the intake pressure PB, for example, proportional amplification [Kpi and integral time T
Ii is selected.

The EGR control circuit 14 changes the outputs of the proportional amplification circuit and the integration circuit from time to time based on the proportional amplification degree KPi and the integral time Tri K, so that the opening degree of the EGR control valve 12 corresponds to the sum signal of both outputs. outputs a signal to the control negative pressure generator 16, and the EGR control valve 12 is driven and controlled.

In the above-mentioned embodiment, the proportional amplification degree KP and the integral time TI were configured to correspond to the rotational speed N and the intake pressure pB, respectively. It may be made to correspond to the product.

Further, in the embodiment described above, the EGR control valve 12 is configured to be driven by negative pressure via the pressure diaphragm, but it may be configured to be driven by an electric motor. Note that the opening degree detector 13 may not be provided. Furthermore, E.G.
The R control circuit 14 is constituted by an electronic circuit including an electric storage circuit, and the internal configuration may be of an analog type or a digital type including an analog-digital converter and a microcomputer.

〔Effect of the invention〕

As explained above, according to the uninvented exhaust gas recirculation control device for an internal combustion engine, the EGR control circuit calculates the oxygen concentration based on the output of the oxygen sensor that detects the oxygen concentration in the intake air mixed with exhaust gas. The oxygen concentration in the intake air is compared with the oxygen concentration in the intake air, which is determined according to the EGR rate set according to the engine operating condition, and the comparison deviation is input to the proportional amplifier circuit and integral circuit in the EGR control circuit. The EGR control valve that controls the amount of exhaust gas recirculated to the intake air of the engine is controlled so that the opening degree corresponds to the addition signal of the output signal of the circuit, and the proportional amplification circuit and the integral circuit are Since the degree and integral time are made to change in accordance with the engine's intake pressure and rotation speed, exhaust gas recirculation control that does not change over time is possible, and is highly responsive and stable regardless of the engine operating state. Reflux t can be controlled.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing an exhaust gas recirculation control device for an internal combustion engine according to an embodiment of the present invention, and Fig. 2 shows the oxygen concentration in intake air and the EGR rate in the exhaust gas recirculation control device for an internal combustion engine. FIG. 3 is a diagram showing the target EGR rate KO in the exhaust gas recirculation control device of the internal combustion engine, and FIG. 4(a) is the relationship between the opening degree of the EGR control valve 12 and the EGR rate. FIG. 4(b) is a diagram showing the engine rotation speed N,
Even if the opening degree of the EGR control valve 12 is constant, the EGR
Figures 5(a) and 5(b), which show how the R rate K changes, correspond to the engine intake pressure PR and engine speed N stored in the EGR control circuit, respectively. FIG. 6 is a diagram showing a determined proportional amplification degree KP of a proportional amplification circuit and an integral time TI' of an integral circuit, and FIG. 6 is an explanatory diagram showing a conventional exhaust gas recirculation control device for an internal combustion engine. DESCRIPTION OF SYMBOLS 1... Engine body, 2... Intake pipe, 3... Exhaust pipe, 5... Throttle valve, 8... Engine speed detector, 10... Intake pressure detector, 11... - EGR passage, 12... EGR control valve, 14... EGR control circuit, 18... oxygen sensor. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (2)

[Claims] (1) An exhaust gas recirculation control valve provided in an exhaust gas recirculation passage that communicates the exhaust system and intake system of the internal combustion engine, and an oxygen concentration sensor provided downstream of the exhaust gas recirculation passage opening in the intake system, The exhaust gas recirculation is performed based on the deviation between the calculation amount corresponding to the target exhaust gas recirculation rate and the output signal of the oxygen concentration sensor so that the target exhaust gas recirculation rate is predetermined in accordance with the operating state of the engine. An exhaust gas recirculation control device for an internal combustion engine that controls the opening degree of a control valve, comprising a proportional amplification circuit that proportionally amplifies the deviation, and an integration circuit that performs integral processing of the deviation, and a combination of the proportional amplification circuit and the integration circuit. The control circuit includes a control circuit that opens and closes the exhaust gas recirculation control valve in response to a sum signal of output signals, and the proportional amplification degree of the proportional amplification circuit and the integration time of the integral circuit are controlled by the intake air pressure and rotation speed of the engine. An exhaust gas recirculation control device for an internal combustion engine, characterized in that the exhaust gas recirculation control device changes according to the (2) A patent claim characterized in that the proportional amplification degree of the proportional amplification circuit and the reciprocal of the integration time of the integration circuit are adapted to change in proportion to the product of the intake air pressure and the rotational speed of the engine. An exhaust gas recirculation control device for an internal combustion engine according to item 1.