JPH0697014B2 - Exhaust gas recirculation control device for internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an exhaust gas recirculation control device for an engine, which controls an exhaust gas recirculation amount of an internal combustion engine.

[Conventional technology]

It is well known that so-called exhaust gas recirculation is carried out to introduce a part of the exhaust gas into the intake side of the engine in order to reduce nitrogen oxides which are harmful components in the exhaust gas of the internal combustion engine.

The recirculated exhaust gas flow rate affects not only the reduction of nitrogen oxides but also the engine performance, fuel consumption, etc. Therefore, it is desirable that the recirculated exhaust gas flow rate be accurately controlled according to the operating state of the engine.

FIG. 6 is a structural explanatory view showing a conventional exhaust gas recirculation (hereinafter abbreviated as EGR) control device as shown in, for example, JP-A-55-93950. In FIG. 6, 1 is an engine body, 2 is an engine intake pipe, and 3 is an exhaust pipe.

A fuel supply device 4 is arranged in the intake pipe 2, and a throttle valve 5 is arranged in the vicinity of a connecting portion between the intake pipe 2 and the intake duct 6. At the entrance of this intake duct 6,
An air cleaner 7 is arranged.

An intake negative pressure introduction passage 9 communicates with the intake pipe 2. The intake pressure of the intake pipe 2 is detected by the intake pressure detector 10 through the intake negative pressure introducing passage 9.

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

The EGR control valve 12 is provided in the EGR passage 11, and the EGR passage 11 connects the exhaust pipe 3 and the intake pipe 2.

The output of the EGR control circuit 14 controls the control negative pressure generator 16. This control negative pressure generator 16 generates an actuator negative pressure by controlling the intake negative pressure and the atmospheric pressure to control the opening / closing degree of the EGR control valve 12.

Next, the operation will be described. The engine speed and the engine intake pressure, which are quantities indicating the operating state of the engine, are detected by the engine speed detector 8 and the intake pressure detector 10, respectively, and input to the EGR control circuit 14.

The EGR amount flowing through the EGR passage 11 depends on the engine operating state amount detected by the engine speed detector 8 and the intake pressure detector 10.
The output value of the opening detector 13 corresponding to the target EGR rate stored in the EGR control circuit 14 and the opening detector 1 linked with the EGR control valve 12
The output negative pressure of the control negative pressure generator 16 is controlled by the output signal of the EGR control circuit 14 so that the comparison deviation with the measured output value of 3 becomes zero.
It is determined by adjusting the pressure in the intake negative pressure introducing passage 9 and the atmospheric pressure introducing passage 15 and controlling the opening of the EGR control valve 12.

That is, the opening degree of the EGR control valve 12 is feedback-controlled by using the output of the opening degree detector 13 to obtain the EGR amount according to the operating state of the engine.

[Problems to be solved by the invention]

With the conventional EGR control device, EGR
A large amount of carbon or the like contained in the exhaust gas adheres to the control valve 12, and the initial exhaust gas flow rate changes corresponding to the degree of opening / closing of the control valve, which causes a problem that accurate control cannot be performed.

An object of the present invention is to solve the above-mentioned conventional problems, and it is an object of the present invention to provide an exhaust gas recirculation control device for an internal combustion engine, which enables highly accurate exhaust gas recirculation control without aging. .

[Means for solving problems]

The exhaust gas recirculation control device for an internal combustion engine according to the present invention includes a calculation amount corresponding to the target exhaust gas recirculation rate and the oxygen concentration sensor so that the target exhaust gas recirculation rate is predetermined according to the operating state of the engine. In an exhaust gas recirculation control control device for an internal combustion engine that controls the opening degree of the exhaust gas recirculation control valve based on the deviation from the output signal of, a proportional amplification circuit that proportionally amplifies the deviation, and an integral that performs integral processing of the deviation. And a control circuit that opens and closes the exhaust gas recirculation control valve in response to an addition signal of the output signals of the proportional amplification circuit and the integration circuit, and is a reciprocal of the proportional amplification degree of the proportional amplification circuit. And the reciprocal of the integration time of the integration circuit is changed according to the product of the intake air pressure of the engine and the rotational speed.

[Work]

According to the exhaust gas recirculation control device for an internal combustion engine of the present invention, the oxygen sensor detects the oxygen concentration in the intake air, and the target oxygen concentration preset according to the oxygen concentration detected by the oxygen sensor and the operating state of the engine is detected. In the control circuit that opens and closes the exhaust gas recirculation control valve in response to the added signal of the output signals of both circuits to compare the The proportional amplification degree of the proportional amplification circuit and the reciprocal of the integration time of the integration circuit change according to the product of the intake air pressure of the engine and the rotation speed. Therefore, in this device, the recirculation amount of the exhaust gas is controlled by the oxygen concentration which is proportional to the mixing ratio of the exhaust gas, and moreover, the recirculation amount is controlled responsively and stably regardless of the operating state of the engine.

〔Example〕

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 a preferred embodiment shown in the accompanying drawings.

FIG. 1 is a diagram showing a configuration of an embodiment of the present invention. In FIG. 1, the same parts as those in FIG. 6 are denoted by the same reference numerals, and the parts different from FIG. 6 will be mainly described. .

As is apparent from a comparison of FIG. 1 with FIG. 6, in FIG. 1, the portions indicated by reference numerals 1 to 16 are the same as those in FIG.
The parts shown after 17 are the parts newly provided by this FIG. 1 and are the features of the present 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 the opening 17. The oxygen sensor 18 detects the oxygen concentration in the intake air flowing through the intake pipe 2.
For example, like the solid electrolyte oxygen pump type oxygen sensor proposed in Japanese Patent Laid-Open No. 58-153155, a sensor output proportional to the oxygen concentration is generated.

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

Next, the operation of the above embodiment will be specifically described with reference to FIGS. Fig. 2 shows the relationship between EGR rate K and oxygen concentration C ₂ in the intake air, and Fig. 3 shows EGR.
The figure which shows the target EGR rate K _O determined corresponding to the operating state of the engine stored in the control circuit 14, FIG. 4 (a)
Is a diagram showing the relationship between the opening of the EGR control valve 12 and the EGR rate K,
FIG. 5B is a diagram showing that the EGR rate K is changed by the engine speed N _{E even} when the opening of the EGR control valve 12 is constant, and FIGS. 5A and 5B. ) Is the proportional amplification degree of the proportional amplification circuit determined corresponding to the engine intake pressure P _B and the engine speed N _E stored in the EGR control circuit 14, respectively.
Is a diagram showing an integration time T _I of K _P and an integration circuit.

When the engine body 1 is started, the engine speed N _E indicating the operating state of the engine body 1 and the intake pressure P of the engine
_B is detected by the engine speed detector 8 and the intake pressure detector 10 and input to the EGR control circuit 14.

The EGR control circuit 14, a third target EGR rate K _O corresponding to the rotational speed N _E intake pressure P _B is stored as shown in FIG., The rotational speed N _E, the intake pressure P _B For example, the target EGR rate K _O i is selected according to the value.

The target oxygen concentration C _2i corresponding to this target EGR rate K _O i is the second
Calculated according to the figure.

On the other hand, the oxygen concentration of the air mixed with the EGR gas in the intake pipe 2 is calculated from the output I _P of the oxygen sensor 18. The calculated oxygen concentration C _O2 is compared with the target oxygen concentration C _2i, and the comparison deviation between them is input to the proportional amplification circuit and the integration circuit in the EGR control circuit 14. The addition signal of the output signals of both circuits corresponds to the opening degree of the EGR control valve 12, and the EGR control circuit
Reference numeral 14 outputs a signal to the control negative pressure generator 16 so that the opening degree of the EGR control valve 12 matches the above-mentioned addition signal. The control negative pressure generator 16 regulates the output negative pressure by the output of the EGR control circuit 14 using the pressures of the intake negative pressure introduction passage 9 and the atmospheric pressure introduction passage 15, and controls the opening of the EGR control valve 12. , The EGR
The amount of gas is adjusted so as to eliminate the comparative deviation, but the operating state of the engine is constantly changing in relation to the opening / closing degree of the throttle valve 5 and the output load of the engine.

The relationship between the opening of the EGR control valve 12 and the EGR rate K _O is shown in Fig. 4 (a).
As shown in, but EGR ratio K _O which is substantially proportional to the opening degree of the EGR control valve 12 when the operating state of the engine is constant is obtained, for example, the rotational speed N _E of the amounts indicating the operating state of the engine
Changes, the EGR rate K as shown in Fig. 4 (b)
Changes even though the opening of the EGR control valve 12 is constant.
This indicates that the characteristics of the engine to be controlled change depending on the operating state.For example, the EGR should be responsive and stable in the high engine speed range.
When the proportional amplification degree K _P of the proportional amplification circuit in the control circuit 14 and the integration time T _I of the integration circuit are set, as shown in FIG. 4 (b), the EGR control valve 12 of the EGR control valve 12 is set in the low engine speed region. Since the EGR rate K changes greatly with respect to the change in opening, it tends to become unstable.

Therefore, in the EGR control circuit 14, as shown in FIGS. 5 (a) and 5 (b), the engine speed N _E and the intake pressure P _B corresponding to the engine operating state are shown. The proportional amplification degree K _P of the proportional amplification circuit and the integration time T _{I of the} integration circuit are stored. For example, the proportional amplification degree K _P i and the integration time are stored according to the values of the rotational speed N _E and the intake pressure P _B. T _I i is selected.

The outputs of the proportional amplification circuit and the integration circuit are changed instantaneously based on the proportional amplification degree K _P i and the integration time T _I i, so that the opening of the EGR control valve 12 corresponds to the addition signal of both outputs. The EGR control circuit 14 outputs a signal to the control negative pressure generator 16, and the EGR control valve 12 is drive-controlled.

In the above-described embodiment, the proportional amplification degree K _P and the integration time are set based on both the engine speed and the intake pressure by creating a three-dimensional map shown in FIGS. 5 (a) and 5 (b). The selection process of the proportional amplification degree Kpi and the integration time T _I i becomes complicated. Therefore, in order to simplify the selection process, the reciprocal of the proportional amplification degree of the proportional amplification circuit and the reciprocal of the integration time of the integration circuit may correspond to the product of the intake air pressure of the engine and the rotation speed.

Further, in the above-mentioned embodiment, the EGR control valve 12 is configured to be driven by the negative pressure via the pressure diaphragm, but it may be configured to be driven by the electric motor. The opening detector 13 may be omitted. Furthermore, EGR control circuit 1
4 is composed of an electronic circuit including an electric storage circuit, and the internal structure may be an analog type or a digital type including an analog-digital converter and a microcomputer.

〔The invention's effect〕

As described above, according to the exhaust gas recirculation control device for an internal combustion engine of the present invention, oxygen calculated by the EGR control circuit based on the output of the oxygen sensor that detects the oxygen concentration in the intake air mixed with the exhaust gas. The concentration is compared with the oxygen concentration in the intake air determined according to the EGR rate set according to the operating state of the engine, and the comparison deviation is input to the proportional amplification circuit and integration circuit in the EGR control circuit. The EGR control valve that controls the exhaust gas recirculation amount introduced into the intake air of the engine is controlled so that the opening corresponds to the addition signal of the circuit output signal, and the reciprocal of the proportional amplification degree of the proportional amplification circuit and Since the reciprocal of the integration time of the integration circuit is made to correspond to the product of the intake air pressure of the engine and the rotation speed, the process of selecting the proportional amplification degree of the proportional amplification circuit and the integration time of the integration circuit is simplified, and No exhaust gas recirculation control Possible and will, moreover irrespective of the operating state of the engine, it is possible to control the good response and stable recirculation amount.

[Brief description of drawings]

FIG. 1 is a structural explanatory view showing an exhaust gas recirculation control device for an internal combustion engine according to an embodiment of the present invention, and FIG. 2 is a graph showing an oxygen concentration in intake air in the exhaust gas recirculation control device for the internal combustion engine.
FIG. 3 is a diagram showing a relationship of the EGR rate K, FIG. 3 is a diagram showing a target EGR rate K _O in the exhaust gas recirculation control device for the internal combustion engine, FIG.
FIG. 4A shows the relationship between the opening of the EGR control valve 12 and the EGR rate K, and FIG. 4B shows that the opening of the EGR control valve 12 is constant depending on the engine speed N _E. Also shows how the EGR rate K is changed, FIGS. 5 (a) and 5 (b) are respectively the intake pressure P of the engine stored in the EGR control circuit.
_B , a diagram showing the proportional amplification degree K _P of the proportional amplification circuit and the integration time T _I of the integration circuit, which are determined corresponding to the rotational speed N _E , and FIG. 6 shows a conventional exhaust gas recirculation control device for an internal combustion engine. It is a structure explanatory view. 1 ... Engine body, 2 ... Intake pipe, 3 ... Exhaust pipe, 5
...... Slottle valve, 8 ...... Engine speed detector, 10 ...
… Intake pressure detector, 11 …… EGR passage, 12 …… EGR control valve,
14 …… EGR control circuit, 18 …… Oxygen sensor. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (1)

[Claims] 1. An exhaust gas recirculation control valve provided in an exhaust gas recirculation passage communicating an exhaust system and an intake system of an internal combustion engine, and an oxygen concentration sensor provided downstream of an exhaust gas recirculation passage opening of the intake system. The exhaust gas is provided based on a deviation between a calculation amount corresponding to the target exhaust gas recirculation rate and an output signal of the oxygen concentration sensor so that the target exhaust gas recirculation rate is predetermined according to the operating state of the engine. An exhaust gas recirculation control control device for an internal combustion engine, which controls the opening of a gas recirculation control valve, comprises: a proportional amplification circuit for proportionally amplifying the deviation; and an integration circuit for integrating the deviation. A control circuit that opens and closes the exhaust gas recirculation control valve in response to an addition signal of an output signal from the circuit,
The exhaust gas of an internal combustion engine, wherein the reciprocal of the proportional amplification degree of the proportional amplification circuit and the reciprocal of the integration time of the integration circuit change according to the product of the intake air pressure of the engine and the rotational speed. Gas recirculation control device.