JPH07253056A - Exhaust gas recirculation controller of internal combustion engine - Google Patents

Abstract

PURPOSE:To reduce wear of a slide face of a sensor by duty-controlling a negative pressure controlling solenoid valve based on opening degree of an exhaust gas recirculation valve and target opening degree and shutting off a negative pressure passage for the exhaust gas recirculation valve by means of an ON-OFF solenoid valve when opening degree of the exhaust gas recirculation valve almost coincides with the target opening degree. CONSTITUTION:An exhaust gas recirculation valve 4 which operates in accordance with negative pressure is provided on the halfway of an exhaust gas recirculation passage 3, and opening degree of the valve is controlled by negative pressure signals which pass a negative pressure control solenoid valve 8 which dilutes and controls negative pressure from a negative pressure source with atmospheric air. The negative pressure control solenoid valve 8 is controlled by duty signals which are output from a control means 10 in accordance with deviation between target opening degree which is set based on engine operation conditions and actual opening degree by an opening detection means 7. In such a device, an ON-OFF solenoid valve 11 which shuts off negative pressure passage 9 when actual opening degree of the exhaust gas recirculation valve 4 almost coincides with the target opening degree is provided, and when the solenoid valve 11 is shut off, duty ratio of the negative pressure control solenoid valve 8 is corrected and updated by a correction means 12 in accordance with negative pressure fluctuation conditions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas recirculation (EGR) control device for an internal combustion engine.

[0002]

2. Description of the Related Art An engine employs an exhaust gas recirculation device that recirculates a part of exhaust gas to an intake system through an exhaust gas recirculation passage in order to reduce NOx in the exhaust gas.

A negative pressure responsive type (diaphragm type) is used as the exhaust gas recirculation valve provided in the exhaust gas recirculation passage, but in order to accurately control the exhaust gas recirculation amount, the exhaust recirculation valve is opened (lifted). Some have a sensor.

This is because the negative pressure introduced from the negative pressure source to the exhaust gas recirculation valve is such that the opening of the exhaust gas recirculation valve matches the target EGR amount (target valve opening) assigned for each operating condition of the engine. The required exhaust gas recirculation is controlled by controlling the duty of a negative pressure control solenoid valve for diluting the air with the atmosphere (see Japanese Patent Laid-Open No. 64-66459).

[0005]

However, in such exhaust gas recirculation control, the negative pressure control solenoid valve is always duty controlled so that the actual exhaust gas recirculation valve opening coincides with the target valve opening. The negative pressure applied to the control negative pressure chamber (diaphragm chamber) of the exhaust gas recirculation valve is oscillatingly controlled.

Therefore, even when the target valve opening is constant, such as during steady operation, the exhaust gas recirculation valve opening is oscillatingly controlled around a predetermined value. Therefore, the contact recirculation valve provided in the exhaust gas recirculation valve is controlled. There is a risk that the sliding surface of the lift sensor will be worn away and the sensor output will be changed.

The present invention aims to solve such problems.

[0008]

The first aspect of the present invention is provided, as shown in FIG. 1, with an exhaust gas recirculation passage 3 that connects an exhaust passage 1 and an intake passage 2 of an engine, and in the middle of the exhaust gas recirculation passage 3. Negative pressure responsive exhaust gas recirculation valve 4, means 5 for detecting engine operating conditions, means 6 for setting a target opening of the exhaust gas recirculation valve 4 based on the operating conditions, and actual opening of the exhaust gas recirculation valve 4. And a negative pressure control solenoid valve 8 capable of dilution control by duty driving for communicating the negative pressure introduced from the negative pressure source with the atmosphere,
A duty signal is output to the negative pressure passage 9 that guides this control negative pressure to the control negative pressure chamber of the exhaust gas recirculation valve 4 and to the negative pressure control solenoid valve 8 so that the actual opening of the exhaust gas recirculation valve 4 matches the target opening. An exhaust gas recirculation system for an internal combustion engine, comprising:
An ON-OFF solenoid valve 11 that shuts off the negative pressure passage 9 when the actual opening degree of the exhaust gas recirculation valve 4 substantially matches the target opening degree;
A correction unit 12 that corrects and updates the duty ratio of the duty signal output from the control unit 10 to the negative pressure control solenoid valve 8 is provided in accordance with the negative pressure fluctuation condition of the negative pressure source during this interruption.

In a second aspect of the present invention, the negative pressure fluctuation condition is a change in the engine speed for driving the negative pressure source and a use state of a brake using the negative pressure of the negative pressure source.

[0010]

In the first aspect of the invention, the negative pressure control solenoid valve is duty-controlled based on the opening degree of the exhaust gas recirculation valve and the target opening degree to control the negative pressure to the exhaust gas recirculation valve. When the degree substantially matches the target opening degree, the ON-OFF solenoid valve shuts off the negative pressure passage to the exhaust gas recirculation valve. As a result, the exhaust gas recirculation valve is stopped and wear of the sliding surface of the sensor that detects the opening degree of the exhaust gas recirculation valve is reduced.

On the other hand, while the negative pressure passage is shut off, the duty ratio of the negative pressure control solenoid valve is corrected and updated according to the negative pressure fluctuation condition of the negative pressure source. Therefore, when the negative pressure passage is opened by the ON-OFF solenoid valve, the opening degree of the exhaust gas recirculation valve is prevented from changing due to the negative pressure fluctuation of the negative pressure source.

According to a second aspect of the present invention, when the negative pressure source of the first aspect is driven by an engine, and when the negative pressure is used for a brake, a change in the engine speed and a use state of the brake are negative. As a pressure fluctuation condition, the duty ratio of the negative pressure control solenoid valve is accurately corrected.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 2, 20 is a diesel engine, 21 is an intake passage, 22 is an exhaust passage, and 23 is an exhaust gas recirculation passage connecting the exhaust passage 22 to the intake passage 21.

A negative pressure responsive exhaust gas recirculation valve (EGR valve) 24 is provided in the exhaust gas recirculation passage 23.

In the EGR valve 24, the valve body 25 interposed in the passage portion is connected to the diaphragm 26, and the diaphragm 26
It is opened according to the negative pressure introduced into the control negative pressure chamber 27 separated by.

In the control negative pressure chamber 27, the negative pressure of the negative pressure pump 28 driven by the engine 20 is supplied to the negative pressure source passage 29,
Although guided through the negative pressure passage 30, the passages 29, 30
A negative pressure control solenoid valve 31 is provided between the two.

An orifice 32 is provided in the negative pressure source passage 29, and a dilution passage 34 which is open to the atmosphere is connected to the negative pressure passage 30 via an orifice 33.

The negative pressure introduced from the negative pressure pump 28 to the negative pressure control solenoid valve 31 via the negative pressure source passage 29 is supplied from the dilution passage 34 according to the valve opening time ratio (duty ratio) of the negative pressure control solenoid valve 31. The negative pressure passage 30 is diluted with the introduced air.
Through the control negative pressure chamber 27 of the EGR valve 24.

The negative pressure to the control negative pressure chamber 27 is controlled by the duty control of the negative pressure control solenoid valve 31, and the EGR valve 2
The opening degree of 4 is controlled. The characteristic of the control negative pressure obtained by the duty ratio of the negative pressure control solenoid valve 31 is shown in FIG. 3, and the relationship between the control negative pressure and the opening degree of the EGR valve 24 is shown in FIG.

An ON-OFF solenoid valve 35 is provided in the middle of the negative pressure passage 30 (on the side of the control negative pressure chamber 27 from the connection portion of the dilution passage 34). When the ON-OFF solenoid valve 35 is turned ON, a negative pressure is generated. The pressure passage 30 is shut off.

The EGR valve 24 is provided with a contact type lift sensor 36 for detecting the opening (lift), and the signal thereof is input to the control unit 37.

On the other hand, as a sensor for detecting the operating condition of the engine 20, a rotation speed sensor 38 for detecting the rotation speed of the engine, a load sensor 39 for detecting the load of the engine from the fuel injection amount of the engine, the accelerator opening degree, etc. A water temperature sensor 40 for detecting the temperature of the cooling water is provided, and these signals are input to the control unit 37.

When the negative pressure of the negative pressure pump 28 is used for braking the vehicle, a brake sensor 41 for detecting the operation of the brake is provided, and the signal thereof is also input to the control unit 37.

Each of the sensors 36 and 3 is controlled by a control unit 37 composed of a microcomputer.
Based on the signals from 8 to 41, the negative pressure control solenoid valve 31 is controlled, and when the opening degree of the EGR valve 24 substantially matches the target opening degree, E is controlled via the ON-OFF control solenoid valve 35.
Fixed control of the GR valve 24 and correction control of the negative pressure control solenoid valve 31 are performed.

Next, the control contents of the control unit 37 will be described with reference to the flow charts of FIGS.

First, in step 0, the brake operation status is read, in step 1, the engine speed Ne is read, in step 2, the engine load Q, and in step 3, the water temperature Tw.

In step 4, it is judged whether the water temperature Tw is equal to or higher than a predetermined value. If it is lower than the predetermined value, the target EG is determined in step 5.
Set 0 for R valve opening T_VL.

When the water temperature Tw is equal to or higher than the predetermined value, the map value is read from the opening map shown in FIG. 7 based on the engine speed Ne and the engine load Q in step 6 to obtain the target EG.
Set R valve opening T_VL.

In step 7, the output S_VL of the lift sensor 36 of the EGR valve 24 is read, and in step 8, the difference X between the target EGR valve opening T_VL and the lift sensor output S_VL.
Ask for.

At step 9, the target EGR valve opening T_VL
The absolute value of the difference X between the lift sensor output S_VL and the lift sensor output S_VL is compared with a predetermined value. If the absolute value of X is greater than or equal to the predetermined value, step 10 is performed.
And if the absolute value of X is less than the predetermined value, step 14
Proceed to.

In step 10, the ON-OFF solenoid valve 3
An OFF signal is output to 5 (the negative pressure passage 30 is opened). In step 11, a counter described later is reset.

In steps 12 and 13, a PI (proportional integral) constant is set based on the absolute value of the difference X between the target EGR valve opening T_VL and the lift sensor output S_VL, and negative pressure control is performed using the following equation (1). The duty ratio of the solenoid valve 31 is calculated.

Duty ratio = previous Duty ratio + (KP + KI) × X (1) The PI constant KP represents a proportional component, and KI represents an integral component, respectively with respect to the absolute value of X in FIGS. 8 and 9. It is allocated like this.

However, KP takes a value only when the sign of X of the last time and the sign of X of this time are inverted, and is set to 0 otherwise. KI is set to 0 when the sign of X of the previous time and the sign of X of this time are reversed, and takes a value at other times.

The control signal of this duty ratio is output to the negative pressure control solenoid valve 31 in step 24.

That is, the PI control of the duty ratio of the negative pressure control solenoid valve 31 is performed based on the difference between the target opening of the EGR valve 24 and the actual opening to control the negative pressure introduced into the control negative pressure chamber 27. The EGR valve 24 is quickly controlled to the target opening.

On the other hand, if the process proceeds to step 14, that is, EG
When the opening degree of the R valve 24 substantially matches the target opening degree, the target E
The sign of the difference X between the GR valve opening T_VL and the lift sensor output S_VL is determined, and if it is reversed from the previous sign of X in steps 15 and 16, the counter is incremented in step 17.

In step 18, the value of the counter is compared with a predetermined value. If the value of the counter is less than the predetermined value, the previous duty ratio is set to the duty ratio of the negative pressure control solenoid valve 31 in step 23. When the value of the counter exceeds a predetermined value, the ON-OFF solenoid valve 35 is turned ON in step 19.
A signal is output (the negative pressure passage 30 is cut off).

When the ON-OFF electromagnetic valve 35 is turned ON, the negative pressure for maintaining the EGR valve 24 at the target opening degree is confined in the control negative pressure chamber 27 of the EGR valve 24, and the EGR valve 24 is set at the almost target opening degree. In this case, the ON-OFF solenoid valve 35 is turned ON after the opening degree of the EGR valve 24 is reversed a predetermined number of times with the target value sandwiched in between because the ON-OFF solenoid valve 35 is frequently controlled. This is to prevent

[0041] In step 20, read the previous duty ratio, in step 21, determining the negative pressure variation correction value K_ _Duty from the operating condition of the engine rotational speed Ne and the brake.

The negative pressure variation correction value K_ _Duty, as in FIG. 10, a brake operating conditions with respect to the engine rotational speed Ne (O
(N, OFF) The negative pressure level value B_OFF immediately before the ON-OFF solenoid valve 35 is _turned on and the current negative pressure level value B are read from the characteristic line set for each N, OFF, and calculated by the following equation (2). .

[0043] _{K_ Duty = B / B_ OFF ‥‥} (2) determine the negative pressure variation correction value K_ _Duty, when the operation status of the engine rotational speed Ne and brakes are different, the negative pressure obtained by the vacuum pump 28 Is to cope with the change as shown in FIG.

Then, in step 22, step 20
Multiplied by the negative pressure variation correction value K_ _Duty the read duty ratio seeking duty ratio after the correction, and outputs a control signal of the duty ratio in the negative pressure control solenoid valve 31 at step 24.

Due to this structure, the EGR valve 24 is
Negative pressure control solenoid valve 3 for controlling the negative pressure introduced to the control negative pressure chamber 27
When the opening degree of the EGR valve 24 becomes almost the target opening degree by the PI control of the duty ratio of 1, when the opening degree of the EGR valve 24 becomes almost the target opening degree, the negative pressure to the control negative pressure chamber 27 is controlled by the ON-OFF solenoid valve 35. The passage 30 is blocked.

That is, when the EGR valve 24 is controlled to a substantially target opening degree, the negative pressure in the control negative pressure chamber 27 is confined and the EGR valve 24 is stopped in that state.

Therefore, at this time, the EGR valve 24 is not oscillatingly controlled by the duty control of the negative pressure control solenoid valve 31, whereby the wear of the lift sensor 36 of the EGR valve 24 is reduced, and the lift sensor 36 is reduced. Output fluctuations are prevented.

When the target opening changes from this state, the negative pressure passage 30 is opened by the ON-OFF solenoid valve 35, and the duty ratio PI of the negative pressure control solenoid valve 31 is again set.
While the control is performed, while the negative pressure passage 30 is being blocked, the duty of the negative pressure control solenoid valve 31 is determined based on the engine speed immediately before the cutoff, the current operating speed of the brake from the brake operating state, and the brake operating status. The ratio is corrected.

That is, the negative pressure obtained by the negative pressure pump 28 increases as the engine speed increases after the negative pressure passage 30 is shut off, and the negative pressure decreases as the engine speed decreases. OF at the time of cutoff of 30
When the brake in the F state is turned on, the negative pressure pump 28
The negative pressure obtained by means of becomes smaller, and the negative pressure obtained when the brake that was in the ON state is turned off becomes larger,
The duty ratio of the negative pressure control solenoid valve 31 is accurately corrected for this negative pressure fluctuation.

Therefore, the negative pressure in the control negative pressure chamber 27 does not differ from the negative pressure from the negative pressure control solenoid valve 31, and the negative pressure passage 3
When 0 is opened, deterioration of exhaust emission due to a change in the opening degree of the EGR valve 24 is prevented, and the PI control is smoothly shifted.

[0051]

As described above, according to the first aspect of the present invention, the exhaust gas recirculation passage that connects the exhaust passage and the intake passage of the engine, and the negative pressure responsive exhaust gas recirculation valve provided in the middle of the exhaust gas recirculation passage are provided. A means for detecting the operating conditions of the engine, a means for setting the target opening of the exhaust gas recirculation valve based on the operating conditions, a means for detecting the actual opening of the exhaust gas recirculation valve, and a negative pressure source derived from a negative pressure source. A negative pressure control solenoid valve that can perform dilution control by duty drive that communicates pressure with the atmosphere, a negative pressure passage that guides this control negative pressure to the control negative pressure chamber of the exhaust gas recirculation valve, and the actual opening of the exhaust gas recirculation valve is the target. In an exhaust gas recirculation system for an internal combustion engine, comprising: a control unit that outputs a duty signal to a negative pressure control solenoid valve so as to match the opening degree, when the actual opening degree of the exhaust gas recirculation valve substantially matches the target opening degree, a negative An ON-OFF solenoid valve that shuts off the pressure passage and a negative pressure source negative during this shutoff. Since the correction means for correcting and updating the duty ratio of the duty signal output from the control means to the negative pressure control solenoid valve is provided according to the changing condition, wear of the opening detection means of the exhaust gas recirculation valve can be reduced, and The reliability is improved and the opening degree of the exhaust gas recirculation valve is prevented from changing when the negative pressure passage is opened by the ON-OFF solenoid valve,
Exhaust gas recirculation can be properly controlled.

According to the second aspect of the invention, the negative pressure fluctuation condition in the first aspect of the invention is set to the change of the engine speed for driving the negative pressure source and the use state of the brake using the negative pressure of the negative pressure source. The duty ratio of the negative pressure control solenoid valve can be accurately corrected, and high control accuracy can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of the invention.

FIG. 2 is a configuration cross-sectional view of an example.

FIG. 3 is a characteristic diagram showing a relationship between a duty ratio of a negative pressure control solenoid valve and a control negative pressure.

FIG. 4 is a characteristic diagram showing a relationship between a control negative pressure and an opening degree of an EGR valve.

FIG. 5 is a flowchart showing control contents.

FIG. 6 is a flowchart showing control contents.

FIG. 7 is a characteristic diagram showing an opening degree map of an exhaust gas recirculation valve.

FIG. 8 is a characteristic diagram showing proportional data of PI control.

FIG. 9 is a characteristic diagram showing integral data of PI control.

FIG. 10 is a characteristic diagram showing correction data for negative pressure fluctuations.

FIG. 11 is a characteristic diagram of negative pressure of a negative pressure source with respect to engine speed and brake operation.

[Explanation of symbols]

 20 engine 21 intake passage 22 exhaust passage 23 exhaust gas recirculation passage 24 exhaust gas recirculation valve 27 control negative pressure chamber 28 vacuum pump 29 negative pressure source passage 30 negative pressure passage 31 negative pressure control solenoid valve 32 orifice 33 orifice 34 dilution passage 35 ON-OFF Solenoid valve 36 Lift sensor 37 Control unit 38 Rotation speed sensor 39 Load sensor 40 Water temperature sensor 41 Brake sensor

Claims (2)

[Claims] 1. An exhaust gas recirculation passage communicating between an exhaust passage and an intake passage of an engine, a negative pressure responsive exhaust gas recirculation valve provided in the middle of the exhaust gas recirculation passage, and means for detecting engine operating conditions. A means for setting the target opening of the exhaust gas recirculation valve based on operating conditions, a means for detecting the actual opening of the exhaust gas recirculation valve, and a duty-controlled dilution control that connects the negative pressure derived from the negative pressure source to the atmosphere. A possible negative pressure control solenoid valve, a negative pressure passage for guiding this control negative pressure to the control negative pressure chamber of the exhaust gas recirculation valve, and a negative pressure control solenoid valve so that the actual opening of the exhaust gas recirculation valve matches the target opening. In an exhaust gas recirculation system for an internal combustion engine, comprising: a control means for outputting a duty signal to an ON-OF which shuts off the negative pressure passage when the actual opening degree of the exhaust gas recirculation valve substantially matches a target opening degree.
The F solenoid valve and the correction means for correcting and updating the duty ratio of the duty signal output from the control means to the negative pressure control solenoid valve according to the negative pressure fluctuation condition of the negative pressure source during the shutoff are provided. An exhaust gas recirculation control device for an internal combustion engine. 2. The exhaust gas recirculation of an internal combustion engine according to claim 1, wherein the negative pressure variation condition is a change in the rotational speed of an engine that drives a negative pressure source and a use state of a brake that uses the negative pressure of the negative pressure source. Control device.