JPS6355355A - Exhaust gas recirculation controller for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve the response, when 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 a proportional constant and an integration constant of the feedback control system according to an intake air flow. CONSTITUTION:An EGR control circuit 14 reads out a target exhaust gas recirculation rate from a data map corresponding to detection values of 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 increases the proportional constant and the integration constant of the feedback control system as the intake air flow increases based on a detection value of an intake air flow sensor 19 so as to calculate a feedback control signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] 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.

[Conventional technology]

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 in order 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 recirculated exhaust gas has an impact on engine performance, fuel efficiency, etc., so it is desirable that the flow rate of recirculated exhaust gas be precisely controlled according to the operating conditions of the engine. .

FIG. 6 is a configuration diagram showing a conventional exhaust gas recirculation (hereinafter abbreviated as EGR) control device disclosed in, for example, Japanese Patent Laid-Open 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, and a throttle valve 5 is disposed near the connection 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 in the intake pipe 2 is detected by an intake pressure detector 10 through this intake negative pressure introduction passage 9.

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 speed detector 8 are sent to an EGR control circuit 14.

The EGR control valve 12 is provided in the EGR passage 11,
This 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. The control negative pressure generator 16 generates the actuator negative pressure by adjusting the pressure of the intake negative pressure and the atmospheric pressure in order to control the degree of opening and closing of the EGR control valve 12.

Next, the operation will be explained. Engine rotation speed and engine intake pressure, which indicate the operating state of the engine, are detected by an engine rotation 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 target EGR stored in the EGR control circuit 14 according to the engine operating state quantities detected by the engine rotation speed detector 8 and the intake pressure detector 10.
The output signal of the EGR control circuit 14 is used to control the negative The output negative pressure of the pressure generator 16 is regulated by the pressure of the intake negative pressure introduction passage 9 and the atmospheric pressure introduction passage 15, and the EGR
It is determined by controlling the opening degree of the control valve 12.

That is, the opening degree of the EGR control valve 12 is detected by the opening degree detector 13.
Feedback control using the output of: (15,
To obtain an EGR amount according to the operating state of an 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.

An object of the present invention is to provide an exhaust gas recirculation control device for an internal combustion engine that enables highly accurate exhaust gas recirculation control that does not change over time. .

[Flat membrane to solve 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. This is an EGR control device that controls the flow rate.

[For production]

According to the exhaust gas recirculation control device for an internal combustion engine of the present invention, the oxygen concentration in the intake air is detected by the oxygen sensor, and the target oxygen 711 is preset according to the oxygen concentration detected by the oxygen sensor and the operating state of the engine. A control circuit that inputs these comparative deviations into a proportional amplifier circuit and an integral circuit, and opens and closes the exhaust gas recirculation control valve in order to reduce the comparative deviation to zero in response to the sum signal of the output signals of both circuits. In this case, the proportional amplification degree of the proportional amplification circuit and the integration time of the integration circuit change depending on the intake air flow rate 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 system 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 a configuration 1 of an embodiment of the present invention. In FIG. 1, parts that are the same as those in FIG. 6 are given the same reference numerals, and the parts that are different from FIG. 6 will be mainly described.

Fig. 1 f: As is clear from a comparison with Fig. 6, in Fig. 1, the parts indicated by numerals 1 to 16 are the same as in Fig. 6;
The parts indicated by the reference numeral 17 and after are newly provided in FIG. 1, and are the parts that characterize 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 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 the following sensor output in proportion to oxygen degree.

The output of this oxygen sensor 18 is sent to the EGR control circuit 14. Reference numeral 19 denotes an intake flow rate sensor 19 provided between the air cleaner 7 and the intake duct 6. The other configurations are the same as in FIG. 6.

Next, the operation of the above embodiment will be explained in detail with reference to FIGS. 2 to 5. FIG. 2 is a diagram showing the relationship between the EGR rate and the oxygen temperature Cδ2 in the intake air, and FIG. 3 is a diagram showing the relationship between the EGR rate and the oxygen temperature Cδ2 in the intake air, and FIG. FIG. 4(a) is a diagram showing the relationship between the opening degree of the EGIR control valve 12 and the EGR rate, and FIG. 4(b) is a diagram showing the relationship between the opening degree of the EGIR control valve 12 and the EGR rate.
FIG. 5 (a) is a diagram showing how the EGR rate K changes depending on tQ even if the opening degree of the EGR control valve 120 is constant.
) and FIG. 5(b) are diagrams showing the integral time Txt of the proportional amplifier circuit and the integral circuit, respectively, which are determined corresponding to the engine intake flow rate Q stored in the EGR control circuit 14. be.

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 Ko corresponding to the rotational speed Ng and intake pressure pB is stored. EGR rate KOi is selected.

Target oxygen concentration Cσ2 corresponding to this target EGR rate KOi
1 is calculated according to FIG.

On the other hand, the oxygen temperature of the air mixed with the BGR 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 C52i
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 sent to the pressure generator 16. Control negative pressure generator 16 is EG
The 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 of the GR control valve 12 is controlled and the EGR gas amount is adjusted to eliminate the comparison deviation, but the engine operating state is determined by the opening/closing degree of the throttle valve 5 and the output load of the carrot. It's always weird 2! ;'J
are doing.

The relationship between the opening degree of the EGR control valve 12 and the EGR rate KO is as shown in FIG.
Although the R rate KO is obtained, if the intake flow rate Q changes among the quantities that indicate the operating state of the engine, the EGR rate K changes even though the opening degree of the EGR control valve 12 is constant, as shown in Fig. 5). It changes without any change.

This shows that the characteristics of the engine, which is the object of control, change depending on the operating condition. For example, the intake air flow fit
E so that the response is good and stable in the large Q region.
When the proportional amplification degree KP of the proportional amplification circuit and the integration time TI of the integral circuit in the GR control circuit 14 are set, in a region where the intake flow rate Q is small, the opening of the EGR control valve 12 is changed as shown in FIG. Since the change in EGR''lr=K with respect to the change in temperature is large, it tends to become unstable.

Therefore, in this EGR♂1] control circuit 14, as shown in FIG.
As shown in a) and FIG. 5 (1)), among the quantities indicating all the engine operating conditions, the proportional amplification degree Kp of the proportional amplification circuit and the integration time TI of the integral circuit corresponding to the intake air flow rate Q are stored. , intake flow rate Q output by the intake flow rate sensor 19
For example, the proportional amplification degree KPi and the integration 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 integration time TIi, 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 integration time TI are based on the intake flow mQ output from the intake flow rate sensor 19.
Although Km was made to correspond to the number of revolutions Ng, the intake air flow rate q calculated from the intake air pressure PB and the intake air temperature T may be changed.

Further, in the above embodiment, 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 does not need to have it. Furthermore, EGR
The control circuit 14 is composed of an electronic circuit including an electric memory circuit, and the internal configuration may be analog type or digital type including an analog-daisymel converter and a micro combinator. But that's fine.

[Effects of the Invention] As explained above, according to the exhaust gas recirculation control device for an internal combustion engine of the present invention, the EGR control circuit is controlled based on the output of the oxygen sensor that detects the oxygen concentration in the intake air mixed with exhaust gas. The oxygen concentration calculated in the above is compared with the oxygen a degree in the intake air, which is determined according to the EGR rate set according to the operating state of the engine, and the comparison deviation is calculated by the proportional amplification circuit in the EGR control circuit, and The EGR control valve that controls the exhaust gas recirculation t introduced into the intake air of the engine is input to the integral circuit so that the opening corresponds to the sum signal of the output signals of both circuits, and the proportional amplification The proportional amplification degree and integration time of the circuit and integral circuit are made to change in accordance with the intake flow rate of the engine, making it possible to control exhaust gas recirculation that does not change over time.Moreover, the responsiveness is maintained regardless of the operating state of the engine. The reflux amount can be well and stably controlled.

[Brief explanation of drawings]

FIG. 1 is a configuration explanatory diagram showing an exhaust gas recirculation control device for an internal combustion engine according to an embodiment of the present invention, and 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 a diagram showing the relationship between the opening degree of the EGR control valve 12 and the EGR rate. The diagram shown in Figure 4) shows that E due to the intake flow rate Q
Figures 5(a) and 5(a) show how the EGR rate K changes even if the opening and opening of the GR control valve 12 is constant.
B) is a diagram showing the proportional amplification degree KP of the proportional amplification circuit and the integration time T of the integral circuit, which are determined corresponding to the engine intake flow rate Q stored in the EGR control circuit. This is a groove bottom explanatory diagram showing an 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... -, E G
R passage, 12...EGR control valve, 14...EGR
Control circuit, 18...Oxygen sensor, 19...Intake flow rate sensor. In addition, the same reference numerals in the drawings indicate the same parts corresponding to 7'c and 2.

Claims (1)

[Claims] It is equipped with an exhaust gas recirculation control valve installed in the exhaust gas recirculation passage that communicates the exhaust system and intake system of the internal combustion engine, and an oxygen concentration sensor installed downstream of the exhaust gas recirculation passage opening in the intake system. The exhaust gas recirculation control valve is operated 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 set in advance in accordance with the state. An exhaust gas recirculation control device for an internal combustion engine that controls the opening degree of an internal combustion engine, comprising a proportional amplification circuit that proportionally amplifies the deviation, and an integration circuit that integrates the deviation, and that output signals from the proportional amplification circuit and the integration circuit. The exhaust gas recirculation control valve is configured to include a control circuit that opens and closes the exhaust gas recirculation control valve in response to an addition signal, and the proportional amplification degree of the proportional amplification circuit and the integration time of the integral circuit change depending on the intake flow rate of the engine. An exhaust gas recirculation control device for an internal combustion engine, characterized in that: