JPH01216065A - Controller for recirculation of exhaust gas in internal combustion engine - Google Patents

Abstract

PURPOSE:To perform a control at a high precision without change by time by comparing an EGR rate based on an oxygen density in intake air detected by an oxygen sensor with a desired EGR rate based on operating conditions of an internal combustion engine and controlling an EGR control valve corresponding to the deviation by the result of this comparison. CONSTITUTION:An EGR control valve 12 is provided in an EGR passage 11 connecting an intake air tube 2 and an exhaust tube 3 of an engine 1. The EGR control valve 12 is controlled to open and close by an EGR control circuit 14 through a control negative pressure generator 16 based on detection signals from an engine revolution number detector 8, an intake air pressure detector 10 and an opening detector 13 for the EGR control valve 12. In this case, a detection signal is also inputted to the EGR control circuit 14 from an oxygen sensor 18, etc., provided in a downstream suction tube 2 at an open part 17 of the EGR passage 11. An EGR rate corresponding to oxygen density detected by the oxygen sensor 18 is compared with a desired EGR rate, and the EGR control valve 12 is controlled corresponding to the deviation by the result of this comparison.

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.

(Prior Art) 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 oxides, which are harmful components in the exhaust gas of an internal combustion engine. That's right.

Since the flow rate of recirculated exhaust gas affects engine performance, fuel efficiency, etc. in addition to the reduction of nitrogen oxides, it is desirable that the flow rate of recirculated exhaust gas be controlled accurately according to the operating state 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 bag N4 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 part of this intake duct 6,
An air cleaner 7 is arranged.

An intake negative pressure introduction passage 9 communicates with the intake pipe 2 . Through this intake negative pressure introduction passage 9, the intake pressure in the intake pipe 2 is detected by an intake pressure detector IO.

The output of this intake pressure detector 10, EGRIII? 11 Output of opening degree detector 13 of valve 12, engine rotation speed detector 8
The output is sent to the EGR control circuit 14.

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

Negative pressure generator controlled by the output of the EGR control circuit 14! It is designed to control 6. 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 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 EGR control circuits 1 and 4.

The amount of EGR flowing through the EGR passage 11 is determined by the amount of EGR stored in the EGRWIm circuit 14 according to the engine operating state quantities detected by the engine speed detector 8 and the intake pressure detector 10.
It is controlled by the output signal of the EGR control circuit 14 so that the comparison deviation between the output value of the opening detector 13 corresponding to the GR rate and the measured output value of the opening detector 13 linked to the EGR control valve 12 becomes zero. The output negative pressure of the negative pressure generator 16 is regulated by the pressure of the intake negative pressure introduction passage 9 and the atmospheric pressure introduction passage 15, and
It is determined by controlling the opening degree of the GR@I control valve 12.

That is, the opening degree of the EGR control valve 12 is detected by the opening degree detector 13.
By applying feedback control using the output of
To obtain an ECR amount according to the operating state of the engine.

[Problem to be solved by the invention]

In the conventional E G Rill 41 device, when used for a long time, a large amount of carbon contained in the exhaust gas adheres to the EGR control valve 12, and the initial exhaust gas flow rate corresponding to the opening/closing degree of the control valve is reduced. There was a problem that this caused the problem that accurate control could no longer be performed.

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. .

[Means to solve the problem]

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. EGR control means for controlling the flow rate is provided.

[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 EGR rate calculated from the oxygen concentration detected by the oxygen sensor and the engine operating state are determined in advance. Compare the target ECR rate to be set, input these comparative deviations to the proportional amplifier circuit and the integral circuit, multiply the sum signal of the output signals of both circuits by an amount related to the amount of air intake by the engine, and calculate the result. The EGR amount is controlled by calculating the target opening degree of the EGRfI control valve from the multiplication result and the signal related to the intake air pressure, and servo-controlling the □ valve so that the target opening degree is achieved.

Therefore, 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 of exhaust gas can be controlled with excellent responsiveness to changes in the operating conditions 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. 6 are given the same reference numerals, and the parts that are different from those in FIG. 6 will be mainly described.

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. Each sensor generates a sensor output proportional to the oxygen concentration.

Is the output of this oxygen sensor 18 EGRIIJ? ! 1 circuit 1
I am trying to send it on 4th. 19 is an intake flow rate sensor 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 specifically explained with reference to FIGS. 2 to 5.

Fig. 2 is a relational diagram showing the target EGR rate E determined corresponding to the operating state of the engine stored in the EGR control circuit 14, and Fig. 3 is a relationship diagram showing the EGR rate E and the oxygen concentration C in intake air.
4 is a flow characteristic diagram of the EGR IIJ control valve, FIG. 5(a) is a diagram showing an example of the relationship between the opening degree of the EGR control valve 12 and the EGR rate E, and FIG. ) is a diagram illustrating an example of how the EGR rate E changes depending on the engine intake flow rate QA even if the EGR IIj control valve 12 is opened 12 times.

When the engine 1 is started, the engine rotation speed NE and engine intake pressure P, which indicate the operating state of the engine, are detected by the engine rotation speed detector 8 and the intake pressure detector lO,
It is input to the R control circuit 14. The EGR control circuit 14 is R
It is an electronic circuit consisting of a microcomputer that has internal OM, RAM, etc., and an interface circuit for input/output around the microcomputer.

In this EGRM1 circuit 14, as shown in FIG. 2, a target EGR rate E1 corresponding to the rotational speed Nff1 and intake pressure P is stored, and depending on the rotational speed Nff1 and the intake pressure Pm, For example, the target EGR rate El□ is selected.

On the other hand, the oxygen concentration of the air mixed with EGR gas in the intake pipe 2 is calculated from the output I of the oxygen sensor 18. The EGR rate E corresponding to this calculated oxygen concentration CO1 is the third
Calculated according to the figure. This calculated EGR rate E is compared with the target EGR rate El, and the deviation of these comparisons is expressed as E
The intake flow rate sensor 19 is added to the sum signal of the output signals of both the zero circuits that are input to the proportional amplifier circuit and the integral circuit in the GR @ control circuit 14.
Multiply the intake flow rate Q detected by , and get the required EGR flow rate Q.
. get. From this required EGR flow rate Q and intake pressure Pl, the target opening degree of the 80881M valve is calculated according to FIG. 4, which shows the flow rate characteristics of the EGR control valve 12. The EGR amount is controlled by servo-controlling the valve to achieve this target opening degree.

Incidentally, the operating state of the engine constantly fluctuates in relation to the opening/closing degree of the throttle valve 5 and the output load of the engine.

As shown in FIG. 5(a), the relationship between the opening degree of the EGRI control valve 12 and the EGR rate E is approximately proportional to the opening degree of the EGR I control valve 12 when the engine operating condition is constant. However, if the intake flow rate QA among the quantities that indicate the engine operating condition changes, the EGR rate E shown in Fig. 5 (b) changes.
As shown in , the EGR rate E changes even though the opening degree of the EGR 11 vs. the valve 12 is constant. This is because the EGR rate is defined by the following equation, and the EGR rate is inversely proportional to the intake air flow rate Q.

On the other hand, in the device of the present invention, the sum signal of the output signals of the proportional amplifier circuit and the integral circuit is multiplied by the intake air flow rate Q, and the multiplication result is used as the required EGR flow rate Q.

This required EGR flow rate Q. Based on EcR
Since the opening degree of the sm valve 12 is calculated, it is not affected by the intake flow rate QA.If the intake flow rate IQ^ is not multiplied, when the intake flow rate Q suddenly decreases, the EGR amount will be relatively The oxygen sensor 18 detects this as a decrease in oxygen concentration with a certain delay, and the signal is input to the EGR control circuit 1li14, which starts closing the EGR@control valve 12, causing temporarily excessive EGR. In contrast, in the device of the present invention, the sum signal of the output signals of the proportional amplifier circuit and the integral circuit is multiplied by the intake flow rate Q, and the multiplication result is used as the required EGR flow rate Q. Since the opening degree of the EGR valve 12 is calculated based on this required EGR flow rate Q, when the intake flow rate QA suddenly decreases, the required EGR flow rate Q is calculated without waiting for the oxygen sensor 18 to detect a decrease in oxygen concentration. E
GR flow rate Q. Since the EGRI1m valve 12 is closed, the EGR flow rate does not become excessive even temporarily.

In addition, in order to calculate the target opening degree of the EGR control valve 12, the required EGR flow rate Q and the intake pressure P are used in accordance with FIG. 4, which shows the EGR III control valve flow rate characteristics.
It is not affected by.

In addition, in the above-described embodiment, the intake flow detected by the intake flow rate sensor 19! Although Q Todoroki was used, the intake flow rate Qa'-CXPix Nt/T calculated from the rotational speed N, intake pressure P1, intake temperature T, and constant C may also be used. The intake pressure P detected by the pressure detector 10 was used, but in addition, the intake pressure P1' calculated from the rotation speed Nt1 intake flow rate Q a % intake temperature T and constant C is calculated as follows:
X N t ) may also be used.

Furthermore, the EGRIIIi11 circuit 14 includes ROM and RAM.
Centering on microcomputers with internal components,
Although this is an electronic circuit composed of an interface circuit for input/output around the electronic circuit, it may be an analog electronic circuit.

〔Effect of the invention〕

As explained above, according to the present invention, the EGR rate is set according to the engine operating state and the EGR rate 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 exhaust gas. The comparison deviation is input to the proportional amplifier circuit and the integral circuit, and the sum signal of the output signals of both circuits is multiplied by an amount related to the amount of air intake by the engine, and the multiplication result is The EGR amount is controlled by calculating the target opening of the EGR II Jfl valve from the signal related to the intake air pressure and the intake air pressure, and controlling the EGR amount by servo-controlling the valve to achieve this target opening. Gas recirculation control becomes possible, and the recirculation amount can be controlled with good responsiveness and stability regardless of the operating state of the engine.

[Brief explanation of the drawing]

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. 2 is a diagram showing a target EGR rate E in the exhaust gas recirculation control device for an internal combustion engine. Fig. 3 is a diagram showing the relationship between the oxygen concentration in the intake air and the EGR rate E in the exhaust gas recirculation control device of the internal combustion engine, Fig. 4 is a flow rate characteristic diagram of the EGR control valve, and Fig. 5 (a) is the EGR @ A diagram showing an example of the relationship between the opening degree of the control valve and the EGR rate E. Figure 5 (b) shows how the BGR rate E changes depending on the intake flow rate Q even if the opening degree of the EGR @ control valve is constant. FIG. 6 is a configuration diagram of a conventional exhaust gas recirculation control device for an internal combustion engine. l...Engine body, 2...Intake pipe, 3...Exhaust pipe, 5...Throttle valve, 8...Engine speed detector, lO...Intake pressure detector, 11... - EGR passage, 12... EGRIIJIII valve, 13... Opening degree detector, 14... EGRi control circuit, 18... Oxygen sensor, 19... Intake flow rate sensor. Note that the same reference numerals in the figures indicate the same or equivalent parts. Agent Masuo Oiwa - LMmlobe) Fig. 2 Fig. 3 EGR function E (%) Fig. 4 Intake function EGR 'L1 Fig. 5 EGRWm valve opening intake function Qa

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 sensor installed downstream of the exhaust gas recirculation passage opening in the intake system. The exhaust gas recirculation control valve is opened based on the deviation between the calculation amount corresponding to the target exhaust gas recirculation rate and the output signal of the oxygen sensor so as to reach a predetermined target exhaust gas recirculation rate corresponding to the state. An exhaust gas recirculation control device for an internal combustion engine that controls the temperature of an internal combustion engine, comprising a proportional amplification circuit that proportionally amplifies the deviation, and an integration circuit that integrates the deviation, and adds output signals of the proportional amplification circuit and the integration circuit. A multiplication circuit that multiplies the signal by an amount related to the intake air amount of the engine, and a target opening degree of the control valve based on the output result of this multiplication circuit and a signal related to the pressure in the intake pipe downstream of the exhaust gas recirculation control valve. 1. An exhaust gas recirculation control device for an internal combustion engine, comprising: a valve opening calculation circuit that calculates the target opening; and a servo circuit that controls opening and closing of an exhaust gas recirculation control valve so that the target opening is achieved.