JP3374507B2 - Exhaust gas recirculation control device for internal combustion engine - Google Patents

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).

Further, in this case, there is one in which an ON-OFF solenoid valve that can open the passage leading to the control negative pressure chamber of the exhaust gas recirculation valve to the atmosphere is provided.

In this device, when the actual opening of the exhaust gas recirculation valve does not match the target valve opening even after a lapse of a predetermined period (at the time of failure), the ON-OFF solenoid valve is opened to open the exhaust gas recirculation valve. Forced to close. Further, when the vehicle is suddenly accelerated, the ON-OFF solenoid valve is opened and the exhaust gas recirculation valve is closed so that the exhaust gas recirculation is quickly cut off (see Japanese Patent Publication No. 63-9103).

[0007]

However, in the exhaust gas recirculation device for controlling the control negative pressure for setting the opening degree of the exhaust gas recirculation valve by the duty driving of the negative pressure control solenoid valve as described above, Negative pressure control when the valve is closed When the control duty ratio of the solenoid valve is such that the negative pressure is smaller than the negative pressure at which the exhaust gas recirculation valve closes, negative pressure control is performed when the exhaust gas recirculation valve is requested to open. Due to the control delay of the duty ratio until the predetermined negative pressure of the solenoid valve is obtained, the closing of the exhaust gas recirculation valve is delayed.

Further, in the case where an ON-OFF solenoid valve that can open the passage leading to the control negative pressure chamber of the exhaust gas recirculation valve to the atmosphere is provided, when the exhaust gas recirculation valve is closed by opening to the atmosphere, negative pressure control is performed. Since the actual opening degree of the exhaust gas recirculation valve becomes 0 regardless of the solenoid valve, at this time the control duty ratio of the negative pressure control solenoid valve is the duty ratio at which the exhaust gas recirculation valve opens to a negative pressure. At the same time as blocking the release to the atmosphere
The exhaust gas recirculation valve opens.

These are not only variations and changes with time of the negative pressure control solenoid valve and exhaust gas recirculation valve, but also variations and changes with time of the orifices provided in the negative pressure passage, the dilution passage, and the negative pressure in the case of a diesel engine. This is because the proper duty ratio changes due to variations and deterioration of the pump and the like.

Therefore, there is a problem that exhaust gas recirculation cannot be controlled with high precision and exhaust emission deteriorates. In particular, in the case of a diesel engine, it is necessary to properly set the exhaust gas recirculation amount for each operating condition in order to achieve both exhaust emission, drivability, and fuel efficiency. It could be significantly worse.

An object of the present invention is to solve such a problem by learning and controlling the duty ratio of the negative pressure control solenoid valve when the exhaust gas recirculation valve is closed.

[0012]

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. Of the exhaust gas recirculation valve 4, 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 to the control negative pressure chamber of the exhaust gas recirculation valve 4 with the atmosphere. In an exhaust gas recirculation system for an internal combustion engine, which comprises a control means 9 for duty-controlling the negative pressure control solenoid valve 8 based on the target opening degree and the actual opening degree, the target opening degree of the exhaust gas recirculation valve 4 is 0 and the actual opening degree is Under the condition of 0, the duty ratio of the negative pressure control solenoid valve 8 is increased or decreased to open the exhaust gas recirculation valve 4. A predetermined amount smaller duty ratio than the duty ratio to start providing a learning means 10 for learning as the control value for the opening 0. And the negative pressure control solenoid valve 8
The negative pressure passage connected to the control negative pressure chamber of the exhaust gas recirculation valve 4 to the atmosphere.
The control means is provided with an ON-OFF solenoid valve that can be opened.
9 is a condition under which the exhaust gas recirculation valve 4 is forcibly closed and is ON-O.
At the same time when the negative pressure passage is opened to the atmosphere through the FF solenoid valve
In addition, the negative pressure is controlled by the duty ratio of the learning value of the learning means 10.
The solenoid valve 8 is controlled.

A second aspect of the invention is the control means 9 of the first aspect of the invention.
Is a case where acceleration of a predetermined amount or more is detected, a target opening degree of the exhaust gas recirculation valve 4 is 0, or a deviation between the target opening degree of the exhaust gas recirculation valve 4 and the actual opening degree is a predetermined value or more. When the condition is satisfied, it is considered that the condition is that the exhaust gas recirculation valve 4 is forcibly closed.
Eggplant

A third invention is an ON-OFF of the first invention.
After the negative pressure passage is opened to the atmosphere by the solenoid valve and the actual opening degree of the exhaust gas recirculation valve 4 becomes 0, the opening of the atmosphere in the negative pressure passage is shut off by the ON-OFF solenoid valve and the exhaust gas recirculation is performed at that time. When the target opening degree of the valve 4 is 0, the learning means 10 executes learning.

In a fourth aspect of the present invention, the learning in the first and third aspects is executed after the engine is operated for a predetermined period or after the battery is restored.

[0016]

In the first aspect of the invention, the learning is started when the target opening degree of the exhaust gas recirculation valve is 0 and the actual opening degree is 0. That is, the duty ratio of the negative pressure control solenoid valve is increased or decreased to change the control negative pressure introduced to the exhaust gas recirculation valve, thereby determining the duty ratio when the exhaust gas recirculation valve starts opening, and A duty ratio smaller than the duty ratio by a predetermined amount is learned.
Then, through the ON-OFF solenoid valve, the negative pressure control solenoid valve
Control the exhaust recirculation valve to the atmosphere through the negative pressure passage connected to the negative pressure chamber.
Exhaust recirculation valve forcibly opened regardless of negative pressure control solenoid valve
When the valve is closed, the negative pressure control solenoid valve is controlled with the learning value.
By doing so, when the ON-OFF solenoid valve is returned, exhaust gas recirculation
Prevent valve opening.

[0017] In the second invention, when the Tokoro constant over acceleration is detected, if the target opening degree of the exhaust gas recirculation valve is zero, the deviation between the target opening and the actual opening of the EGR valve is equal to or higher than a predetermined value If either of the above conditions is met, the ON-OFF solenoid valve is used to
It can be closed forcibly exhaust gas recirculation valve Te.

In the third invention, the ON-OF of the first invention is used.
The exhaust gas recirculation valve is forcibly closed by the F solenoid valve, and thereafter, when the target opening degree of the exhaust gas recirculation valve is 0, learning is performed to accurately learn the duty ratio of 0 opening. Be seen.

In the third invention, the ON-OF of the second invention is used.
The exhaust gas recirculation valve is forcibly closed by the F solenoid valve, and thereafter, when the target opening degree of the exhaust gas recirculation valve is 0, learning is performed to accurately learn the duty ratio of 0 opening. Be seen.

In the fourth invention, the learning in the first and third inventions is periodically executed every time the engine is operated for a predetermined period, or when the battery is replaced and the system is restored. It

[0021]

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

In FIG. 2, 20 is an engine, 21 is an intake passage, 22 is an exhaust passage, and 23 is an exhaust gas recirculation passage that connects 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.

The negative pressure of the vacuum pump 28 driven by the engine 20 is introduced into the control negative pressure chamber 27 through the negative pressure source passage 29 and the negative pressure passage 30.
A negative pressure control solenoid valve 31 is provided between 9 and 30.

A vacuum pump 28 is provided in the negative pressure source passage 29.
An orifice 32 for setting the negative pressure from V to a constant pressure is provided, and the negative pressure passage 30 is connected to a dilution passage 34 which is opened to the atmosphere via an orifice 33.

The negative pressure introduced through the negative pressure source passage 29 is
It is diluted with the atmosphere introduced from the dilution passage 34 according to the valve opening time ratio (duty ratio) of the negative pressure control solenoid valve 31,
It is guided to the control negative pressure chamber 27 of the EGR valve 24 via the negative pressure passage 30.

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.

The negative pressure passage 30 is provided with an ON-OFF solenoid valve 35 branching from the negative pressure passage 30. When the ON-OFF solenoid valve 35 is opened (ON), the negative pressure passage 30 is directly exposed to the atmosphere. It will be released.

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

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 cooling water temperature is provided, and these signals are also input to the control unit 37.

Each of the sensors 36 and 3 is controlled by the control unit 37 which is composed of a microcomputer.
The negative pressure control solenoid valves 31, O based on the signals from 8 to 40.
The N-OFF control solenoid valve 35 is controlled, the EGR valve 24 is controlled, that is, the exhaust gas recirculation control (EGR control) is performed, and the learning control of the opening degree of the EGR valve 24 is performed.

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

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

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. 9 on the basis of the engine speed Ne and the engine load Q in step 6 to obtain the target EG.
Set R valve opening T_VL.

At step 7, the target EGR valve opening T_VL
Is determined to be 0. If it is not 0, the process proceeds to step 8, and if it is 0, the process proceeds to step 13.

In step 8, the variation ΔQ of the engine load Q is calculated.

In step 9, the variation ΔQ of the engine load Q is compared with a predetermined value, and if it is smaller than the predetermined value, the process proceeds to step 10, and if it is more than the predetermined value, it is determined that the acceleration is a certain amount or more and the process proceeds to step 13. .

In step 10, the output S_VL of the lift sensor 36 of the EGR valve 24 is read, and in step 11, the difference X with respect to the target EGR valve opening T_VL is obtained.

In step 12, the difference X is set to a predetermined value A
Compared with (negative), if X is greater than the predetermined value A, the process proceeds to step 14, and if X is less than or equal to the predetermined value A, the target E
When it is determined that the EGR valve 24 is too open for the GR valve opening degree, the process proceeds to step 13.

At this time, when the routine proceeds to step 14, since the target EGR valve opening T_VL is not 0, the learning control flag for the duty ratio and the learning start flag, which will be described later, are reset at step 15 and the EGR at steps 17-20. Get into control.

In step 17, the target EGR valve opening T_V
The absolute value of the difference X of the lift sensor output S_VL with respect to L is compared with a predetermined value B, and when the absolute value of X is greater than or equal to the predetermined value B,
In steps 18 and 19, a PI (proportional integral) constant is set based on the absolute value of X, and the negative pressure control solenoid valve 31 is set by the following equation (1).
Find the duty ratio of.

Duty ratio = previous Duty ratio + (KP + KI) × X (1) KP of the PI constant indicates a proportional amount and KI indicates an integral amount, and X is as shown in FIGS. 10 and 11, respectively. Allocated.

However, KP takes a value only when the sign of the previous X and the sign of the present X are inverted, and is set to 0 in other cases. 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.

When the absolute value of X is less than the predetermined value B, the previous duty ratio is set to the negative pressure control solenoid valve 31 in step 20.
The duty ratio of

The control signals of these duty ratios are output to the negative pressure control solenoid valve 31 in step 29.

That is, the actual E with respect to the target EGR valve opening
When the difference in opening of the GR valve 24 is large, PI control with a high control speed is performed, and when the difference is small, the duty ratio is kept constant. As a result, the negative pressure introduced into the control negative pressure chamber 27 of the EGR valve 24 is controlled, and the EGR valve 24 is controlled to the target opening quickly and without hunting.

On the other hand, when the process proceeds from step 7, 9, 12 to step 13, that is, the target EGR valve opening T_VL is 0.
At this time, during the acceleration operation above a certain level, or when the EGR valve 24 is too open with respect to the target EGR valve opening degree, the EGR valve 24 is closed.

This is because the drive signal (open signal) of the ON-OFF solenoid valve 35 is output in step 22, and the EGR valve 24 is opened.
The negative pressure passage 30 communicating with the control negative pressure chamber 27 is opened to the atmosphere, and the EGR valve 24 is forcibly closed.

Next, a learning value L_D which will be described later in step 23.
uty (duty ratio when the negative pressure control solenoid valve 31 is closed)
In step 24, the correction amount K_Vb for the battery voltage Vb is read from the table shown in FIG. 12, and in step 25 these are multiplied to obtain the duty ratio.

The control signal of this duty ratio is output to the negative pressure control solenoid valve 31 in step 29. The correction amount K_Vb for the battery voltage Vb is set in order to prevent the relationship between the duty ratio and the control negative pressure from being deviated by the voltage driving the negative pressure control solenoid valve 31.

In step 13, the lift sensor output S_VL
When = 0 is determined, the process proceeds to step 21 and ON-OFF
A closing signal is output to the solenoid valve 35 to shut off the opening of the negative pressure passage 30 to the atmosphere.

After this interruption, step 14 is entered. At this time, if the target EGR valve opening T_VL is not 0, the learning control flag and the learning start flag are reset in step 15 as described above, and the EGR control of steps 17 to 20 is started.

On the other hand, the target EGR valve opening T_VL is 0
If so, in step 26, the absolute value of the difference X of the lift sensor output S_VL with respect to the target EGR valve opening T_VL is set to a predetermined value C.
When the absolute value of X is smaller than the predetermined value C, the learning control flag is set in step 27 and the learning control of step 28 is started.

The ON-OFF solenoid valve 35 is opened and closed to E
After forcibly closing the GR valve 24, the target EGR valve opening T
The learning start condition is when _VL is 0.

In the learning control, as shown in FIGS. 7 and 8, first, in step 31, the battery voltage Vb, in step 32, the engine speed Ne, and in step 33, the engine speed Ne.
Read the integrated value Sum_Ne of.

In step 34, the learning start flag is checked. If not, it is determined in step 35 whether the Vb flag is 0 or not.

The Vb flag is set to 0 when the battery voltage becomes 0 (battery replacement, etc.). This is to cope with the learning value being cleared when the battery is removed. When the learning start flag is set or reset or the learning value L_Duty is updated after the battery is restored, the Vb flag takes a value other than 0 for the first time.

When the Vb flag is 0, the preset initial value L_Duty is read in step 36, and the learning start flag is set in step 39.

Next, in step 40, the correction amount K_Vb for the battery voltage Vb is read (FIG. 12), and step 4
1 is the initial value L_Duty and the correction amount for the battery voltage Vb
The initial duty ratio is determined by multiplying K_Vb, and the routine proceeds to step 42.

If the Vb flag is not 0, step 3
In step 7, the previous learning value L_Duty is read, and in step 38, the integrated value Sum_Ne of the engine speed Ne is compared with a predetermined value. The learning frequency is set based on the integrated value Sum_Ne.

If the integrated value Sum_Ne has not reached the predetermined value, it is determined that the predetermined period has not elapsed since the previous learning, and the previous learning value L_Duty is determined in steps 48 and 49.
Is multiplied by the correction amount K_Vb for the battery voltage Vb to determine the duty ratio. The duty ratio control signal is output to the negative pressure control solenoid valve 31 in step 29 of FIG.

If the integrated value Sum_Ne is equal to or larger than the predetermined value, it is determined that the predetermined period has elapsed since the previous learning, and the learning start flag is set in step 39.

Next, in step 40, the correction amount K_Vb for the battery voltage Vb is read, and in step 41, the previous learning value L_Duty is corrected by the correction amount K_V for the battery voltage Vb.
Multiply b to determine the duty ratio, and proceed to step 42.

In step 42, it is judged whether or not the current lift sensor output S_VL is 0. If it is 0, step 4
If not 0, go to step 44.

If step 43 is reached, step 44
Before proceeding to the process of (1), a value obtained by adding a predetermined value based on the duty ratio of step 41 is set as a duty ratio, and a control signal of the duty ratio is output to the negative pressure control solenoid valve 31 (step 29 of FIG. 6). , This is repeated until the lift sensor output S_VL does not become 0.

If the routine proceeds to step 43 after the processing of step 44, the duty ratio obtained by adding a predetermined value to the duty ratio of step 44 is set as the duty ratio, and the control signal of the duty ratio is output to the negative pressure control solenoid valve 31 (see FIG. Step 29) of 6).

On the other hand, in the case of proceeding to step 44, before proceeding to the processing of step 43, the duty ratio is obtained by subtracting a predetermined value from the duty ratio of step 41 as a reference.
The control signal of the duty ratio is output to the negative pressure control solenoid valve 31 (step 29 in FIG. 6), and this is repeated until the lift sensor output S_VL becomes zero.

When the routine proceeds to step 44 after the processing of step 43, the duty ratio obtained by subtracting a predetermined value from the duty ratio of step 43 is set as the duty ratio, and the control signal of the duty ratio is output to the negative pressure control solenoid valve 31 (see FIG. Step 29) of 6).

In step 45, the previous lift sensor output
It is determined whether or not S_VL is 0. If it is 0, the learning start flag is reset in step 46, and step 47 is entered. At this time, the battery correction amount K_Vb is removed from the duty ratio after subtraction in step 44. Value
Set as learning value L_Duty.

That is, the duty ratio learning is ON-OF.
After the E solenoid valve 24 is forcibly closed by the F electromagnetic valve 35, it is performed when the target EGR valve opening T_VL is 0, but if the lift sensor output S_VL is 0 at the start, negative pressure control is performed in step 43. The duty ratio of the solenoid valve 31 is increased by a predetermined value. When the EGR valve 24 starts to open due to the increase in the duty ratio, the duty ratio (after battery correction) obtained by subtracting a predetermined value from the duty ratio at that time is learned in step 44.

If the lift sensor output S_VL is not 0 at the start, the duty ratio of the negative pressure control solenoid valve 31 is decreased by a predetermined value in step 44. And EG
When the R valve 24 is closed, the EGR valve 24 starts to open due to the increase of the predetermined value of the duty ratio in step 43, and the duty ratio (after the battery correction) is learned by subtracting the predetermined value from the duty ratio at that time in step 44.

In this way, the duty ratio of the negative pressure control solenoid valve 31 when the EGR valve 24 is closed is learned, and the negative pressure control solenoid valve 31, the EGR valve 24, the negative pressure source passage 29 and the dilution passage 34 are learned. Orifices 32 and 33, negative pressure pump 2
The learned value L_Duty becomes the maximum duty ratio when the EGR valve 24 is fully closed, regardless of variations such as 8 and the like, changes over time, deterioration, and the like.

With such a configuration, when the EGR valve 24 is closed, the negative pressure control solenoid valve 31 is controlled with the duty ratio of the learning value L_Duty, so that the EGR valve is not affected by variations in each part and aging. 24 is surely closed.

In this case, when the target EGR valve opening is 0,
ON-when the EGR valve 24 is excessively opened with respect to the target EGR valve opening degree during acceleration operation above a certain level.
By opening the negative pressure passage 30 to the atmosphere by the OFF solenoid valve 35, the EGR valve 24 is forcibly closed regardless of the negative pressure control solenoid valve 31, but from this forced closing, the negative pressure control is performed with the duty ratio of the learning value L_Duty. ON by controlling the solenoid valve 31
When the opening of the negative pressure passage 30 to the atmosphere is shut off by the -OFF solenoid valve 35, the EGR valve 24 can be reliably closed.

Further, since the learning value L_Duty has the maximum duty ratio when the EGR valve 24 is kept fully closed, the negative pressure to the EGR valve 24 is increased by a slight change in the duty signal when the valve is opened. , Promptly EGR valve 2
4 is opened, and a high valve opening response is obtained.

On the other hand, the learning of the duty ratio is changed to ON-OF.
Since the EGR valve 24 is forcibly closed by the F electromagnetic valve 35 and then the target EGR valve opening is 0, learning can be performed quickly and accurately.

Further, since learning is performed every time a predetermined period of time elapses, such as when the battery is replaced, an accurate learning value can always be obtained and the EGR valve 24 can be closed.

Therefore, the exhaust gas recirculation can be controlled with high precision, and the exhaust emission, drivability and fuel efficiency are improved.

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, Means for detecting the operating conditions of the engine, means for setting the target opening of the exhaust gas recirculation valve based on the operating conditions, means for detecting the actual opening of the exhaust gas recirculation valve, control of the exhaust gas recirculation valve from the negative pressure source Negative pressure control solenoid valve that can control dilution by duty drive that communicates the negative pressure leading to the negative pressure chamber with the atmosphere, and negative pressure control solenoid
Large negative pressure passage from the valve to the control negative pressure chamber of the exhaust gas recirculation valve
An exhaust gas recirculation system for an internal combustion engine, comprising: an ON-OFF solenoid valve that can be opened to the air; and a control unit that duty-controls a negative pressure control solenoid valve based on a target opening and an actual opening of the exhaust gas recirculation valve. The target opening of the recirculation valve is 0 and the actual opening is 0.
Under the condition of (1), learning means is provided to increase / decrease the duty ratio of the negative pressure control solenoid valve and learn a duty ratio smaller than the duty ratio at which the exhaust gas recirculation valve starts opening as a control value of opening 0 as a control value . The control means forces the exhaust gas recirculation valve
The negative pressure passage via the ON-OFF solenoid valve under the condition
Is released to the atmosphere and the learning value of the learning means is
Since the negative pressure control solenoid valve is controlled by the tee ratio , the exhaust recirculation valve can be operated well regardless of variations in the negative pressure control solenoid valve, the exhaust gas recirculation valve, the negative pressure passage, the negative pressure source, etc., changes over time, deterioration, etc. it is possible to obtain the closing control, exhaust emissions performs exhaust gas recirculation control accurately, it is possible to improve drivability, ON-
The exhaust gas recirculation valve opens when the OFF solenoid valve is restored.
You can prevent it .

[0082] The According to the second invention, when the Tokoro constant over acceleration is detected, if the target opening degree of the exhaust gas recirculation valve is zero, the target opening and the actual opening deviation of a predetermined value of the exhaust gas recirculation valve When either of the above cases is established, the negative pressure passage is opened to the atmosphere via the ON-OFF solenoid valve , and the exhaust gas recirculation valve is forcibly forced.
Can be closed .

According to the third invention, after the negative pressure passage is opened to the atmosphere by the ON-OFF solenoid valve in the first invention and the actual opening degree of the exhaust gas recirculation valve becomes 0, the ON-OFF solenoid valve is opened. Thus, the opening of the atmosphere in the negative pressure passage is blocked, and when the target opening degree of the exhaust gas recirculation valve is 0 at that time, the learning means executes the learning, so that the learning can be accurately performed.

According to the fourth invention, the learning is executed after the engine is operated for a predetermined period or after the battery is restored, so that an accurate learning value can always be obtained.

[Brief description of drawings]

FIG. 1 is a partial configuration 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 flowchart showing learning control.

FIG. 8 is a flowchart showing learning control.

FIG. 9 is a characteristic diagram showing an opening degree map of an exhaust gas recirculation valve.

FIG. 10 is a characteristic diagram showing proportional data of PI control.

FIG. 11 is a characteristic diagram showing integral data of PI control.

FIG. 12 is a characteristic diagram showing correction data of a battery.

[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 Revolution sensor 39 Load sensor 40 Water temperature sensor

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Claims (4)

(57) [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 negative pressure from the negative pressure source to the control negative pressure chamber of the exhaust gas recirculation valve as atmospheric pressure. A negative pressure control solenoid valve that enables dilution control by communicating with a duty drive, and connects from the negative pressure control solenoid valve to the control negative pressure chamber of the exhaust gas recirculation valve
An exhaust gas recirculation system for an internal combustion engine, comprising an ON-OFF solenoid valve capable of opening a negative pressure passage to the atmosphere, and control means for duty-controlling a negative pressure control solenoid valve based on a target opening and an actual opening of the exhaust gas recirculation valve. In the condition that the target opening degree of the exhaust gas recirculation valve is 0 and the actual opening degree is 0, the duty ratio of the negative pressure control solenoid valve is increased or decreased to a predetermined amount from the duty ratio at which the exhaust gas recirculation valve starts opening. Learning means for learning a small duty ratio as a control value for opening 0 is provided , and the control means is forcibly closing the exhaust gas recirculation valve,
Open the negative pressure passage to the atmosphere via the ON-OFF solenoid valve.
At the same time, the negative pressure is controlled by the duty ratio of the learning value of the learning means.
An exhaust gas recirculation control device for an internal combustion engine, characterized by controlling a solenoid valve . 2. The control means , when acceleration of a predetermined value or more is detected, and when the target opening degree of the exhaust gas recirculation valve is 0, the deviation between the target opening degree of the exhaust gas recirculation valve and the actual opening degree becomes a predetermined value or more. If either of the above conditions is met , the exhaust gas recirculation valve is forced
The exhaust gas recirculation control device for an internal combustion engine according to claim 1 , which is regarded as a closing condition . 3. After the negative pressure passage is opened to the atmosphere by the ON-OFF solenoid valve and the actual opening of the exhaust gas recirculation valve becomes 0, the opening of the atmosphere in the negative pressure passage is shut off by the ON-OFF solenoid valve. At the same time, the target opening degree of the exhaust gas recirculation valve is 0
If the exhaust gas recirculation control apparatus for an internal combustion engine according to claim 1, the learning means and executes the learning. 4. The exhaust gas recirculation control device for an internal combustion engine according to claim 1, wherein the learning is executed after the engine is operated for a predetermined period or after the battery is restored.