JP3252633B2 - Exhaust gas recirculation system 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 improvement in an exhaust gas recirculation (hereinafter, also referred to as EGR) device for an internal combustion engine, and more particularly to an EGR device.
The present invention relates to an improvement in GR amount control and, more particularly, to a technique for controlling an opening degree of an EGR amount control valve.

[0002]

2. Description of the Related Art Conventionally, exhaust gas discharged from an internal combustion engine
Reduce nitrogen oxides (NOx) contained in
There is a strong need to prevent the spread of dye. by the way,
During combustion in the engine combustion chamber, the NOx becomes empty at high temperatures.
Nitrogen (N_Two) And oxygen (O _Two) Reacts with
And the amount increases as the combustion temperature increases
Therefore, it is necessary to suppress the reaction by lowering the combustion temperature.
These are one effective means for reducing NOx.

Therefore, as a device for reducing the combustion temperature, a part of the exhaust gas discharged from the engine is recirculated to the engine intake system and guided into the combustion chamber, and the exhaust gas having a large heat capacity contained in the guided exhaust gas. Various exhaust gas recirculation devices have been proposed in which the combustion temperature is reduced through carbon (CO ₂ ) or the like. In such a device, effective NOx reduction and engine operability maintenance (exhaust gas recirculation amount (hereinafter, also referred to as "EGR amount") becomes excessive when combustion becomes excessive, combustion becomes excessively inactive and adversely affects operability. ) And
It is necessary to precisely control the exhaust gas recirculation amount to the target exhaust gas recirculation amount. For example, in the related art, the exhaust gas recirculation amount is controlled as follows.

That is, in the device disclosed in Japanese Patent Application Laid-Open No. 60-1368 (first conventional example), as shown in FIG.
A negative pressure operation type EGR amount control valve 112 is interposed in the R passage 113, and the negative pressure chamber 112 A communicates with the intake throttle valve 105 upstream of the intake passage 103, and also has an orifice 116 for introducing air. It communicates with the duty solenoid 115. By changing the drive duty ratio of the solenoid 115, the pressure in the negative pressure chamber 112A is
As it can be set variably from approximately atmospheric pressure to engine intake negative pressure,
Thus, the opening degree of the EGR amount control valve 112 can be precisely and finely controlled so that the target EGR amount according to the operating state or the like is obtained.

[0005] As another example (second conventional example), as shown in FIG.
A GR amount control valve 121 is interposed, and the negative pressure chamber 122 communicates with a vacuum pump (not shown) via a vacuum valve 123 and a negative pressure passage 125 for an EGR amount control valve which communicates with the atmosphere via an air valve 124. They are communicating.

[0006] By opening and closing the vacuum valve 123 and the air valve 124, the EG
By adjusting the negative pressure of the R amount control valve 121 introduced into the negative pressure chamber 122, the opening degree of the EGR amount control valve 121, that is, the EGR amount is adjusted. An opening / closing valve type solenoid 127 for controlling the throttle pressure of the vacuum chamber (negative pressure of the intake air) is interposed in a passage 126 communicating with the vacuum pump. Vacuum negative pressure is introduced into the negative pressure chamber 129 of 128, and the intake throttle valve 130 provided in the intake passage 129 is closed, thereby increasing the negative pressure of the intake air and meeting the demand for a large amount of EGR. It has become. In other words, the EG can be varied over a wide range by the combination of the three valves.
It is possible to adjust the R amount.

The technique of combining the vacuum negative pressure and the intake throttle valve is applied to a diesel engine or the like that does not have a throttle valve, cannot make the difference between the exhaust pressure and the intake pressure so large, and has difficulty in obtaining a sufficient exhaust gas recirculation amount. This is a particularly effective technique.

[0008]

By the way, in the first conventional example, fine control of the EGR amount is possible, but the control width of the EGR amount is relatively narrow (the pressure in the negative pressure chamber 112A is substantially increased). (The pressure can be changed only from the atmospheric pressure to the engine intake negative pressure).
Although the amount can be adjusted, fine control is somewhat difficult (because of opening / closing combination instead of opening control). However, the first conventional example and the second conventional example are combined as shown in FIG.
With the configuration shown in (1), it is possible to achieve both the fine EGR amount control and the securing of the control width of the EGR amount. That is, EGR
The atmospheric pressure is introduced into the negative pressure chamber 5C of the quantity control valve 5 through the atmosphere-side orifice 7A, while the vacuum pressure is introduced through the negative-pressure orifice 7B and the duty control valve 8, and the driving duty of the duty control valve 8 is reduced. By the adjustment, the negative pressure guided to the negative pressure chamber 5C of the EGR amount control valve 5 can be finely adjusted from the atmospheric pressure to the vicinity of the vacuum negative pressure of the vacuum pump. Further, the opening / closing combination of the first solenoid valve 12 for switching the communication to the vacuum pressure or the atmosphere and the second solenoid valve 13 for switching the communication to the vacuum pressure or the atmosphere causes the negative pressure chamber 10C of the actuator 10 to be operated under the negative pressure.
A predetermined negative pressure can be introduced into the intake passage 2 so that the amount of closing of the intake throttle valve 9 provided in the intake passage 2 can be adjusted. The adjustment can be more extensive.

However, such an apparatus has the following problems. That is, for example, the duty ratio of the duty control valve 8 is minutely changed and finely adjusted.
When controlling the GR amount, the atmosphere-side orifice 7A is used so that the EGR amount does not suddenly change and adversely affect the engine operability and the exhaust performance.
The ratio ρ (= Da ² / Dv ² ) of the opening area (Da ² ) to the opening area (Dv ² ) of the negative pressure side orifice 7B is increased, and the EGR amount with respect to the drive duty change of the duty control valve 8 is increased. When the rate of change of the opening degree of the control valve is reduced, and if the ratio ρ of the orifice area is reduced by a predetermined value or more, a sufficient vacuum negative pressure cannot be conducted to the negative pressure chamber 5C, and as shown in FIG. EGR amount control valve 5
The required lift cannot be obtained, and the required EGR amount may not be obtained. That is, it has been extremely difficult to achieve both stability of the EGR amount control and securing of the required EGR amount.

SUMMARY OF THE INVENTION The present invention has been made in view of such a conventional problem, and has been developed to maintain the stability of the EGR amount control and to reduce the required EGR amount.
It is an object of the present invention to provide an exhaust gas recirculation device for an internal combustion engine that can achieve both high quantity and high accuracy. Also,
It is also an object of the present invention to make the device practical.

[0011]

Therefore, an exhaust gas recirculation system for an internal combustion engine according to the first aspect of the present invention has, as shown in FIG. 1, an exhaust gas recirculation passage for recirculating a part of exhaust gas to an engine intake system. An exhaust gas recirculation amount control valve for controlling an exhaust gas recirculation amount passing through the exhaust gas recirculation passage, wherein the control valve duty ratio varies.
Opening rate change rate and control with large opening change rate with respect to amount of gasification
The change in the opening degree with respect to the change in the valve duty ratio is small.
And the rate of change of the second opening is changeable.
The first maximum opening, which is the maximum opening when the conversion rate is selected ,
An exhaust gas recirculation amount control valve configured to be larger than a second maximum opening which is a maximum opening when the second opening change rate is selected, and a target exhaust gas recirculation amount according to engine operating conditions are obtained. Target opening degree setting means for setting a target opening degree of the exhaust gas recirculation amount control valve, and the first opening degree change when the set target opening degree is larger than the second maximum opening degree.
Select the rate, if the set target opening degree is smaller than said second maximum opening is configured to include a and opening change ratio selection means for selecting the second opening change rate.

According to a second aspect of the present invention, an opening degree of the exhaust gas recirculation amount control valve is controlled by applying a combined pressure obtained by synthesizing at least two pressures to a valve body of the exhaust gas recirculation amount control valve. In this case, the rate of change in the degree of opening is changed by changing the degree of synthesis of the synthesized pressure.
According to a third aspect of the present invention, the synthetic pressure is adjusted by controlling a communication time ratio of at least two pressures, while a synthesis degree of the synthetic pressure is changed by changing a communication area ratio of the at least two pressures. Thus, the change rate of the opening degree of the exhaust gas recirculation amount control valve is changed.

According to a fourth aspect of the present invention, there is provided an exhaust gas recirculation passage for recirculating a part of the exhaust gas to the engine intake system, and is guided to the negative pressure chamber.
Exhaust gas recirculation amount passing through the exhaust gas recirculation passage according to the negative pressure
And exhaust gas recirculation control valve for controlling, in the negative pressure chamber is one end
And the other end branches into two branches
The side passage communicates with the atmosphere while the other negative pressure side passage is under negative pressure.
An EGR amount control negative pressure passage communicating with the pressure source;
To control the opening / closing of the suction side passage in duty.
Depending on the duty control valve and the negative pressure guided to the negative pressure chamber.
An intake throttle valve that controls the intake negative pressure of the engine intake system and one end
The other end side communicates with the negative pressure chamber and the negative pressure side passage
A throttle valve operating negative pressure passage that joins and communicates with the negative pressure source;
The throttle valve operating negative pressure is disposed in the throttle valve operating negative pressure passage.
OFF side that guides the atmosphere into the passage and inside the negative pressure passage for throttle valve operation
1st switch to switch to ON side to cut off the introduction of air
A magnetic valve , and the throttle valve operation on the negative pressure source side with respect to the first electromagnetic valve.
A throttle valve on the intake throttle valve side disposed in a working negative pressure passage;
The OFF side for communicating the working negative pressure passage with the atmosphere and the intake throttle
The throttle valve operating negative pressure passage on the valve side is connected to the throttle on the negative pressure source side.
No. for switching between ON and communicating with the valve operating negative pressure passage
2 configured to include a solenoid valve, the.

[0014]

According to the first aspect of the present invention having the above configuration,
An opening change rate of the exhaust gas recirculation amount control valve is selected according to a target opening degree of the exhaust gas recirculation amount control valve. As a result, the target opening of the exhaust gas recirculation control valve can be achieved while maintaining the opening degree change rate (control response) as low as possible. In other words, the control stability of the exhaust gas recirculation amount control (the smaller the change rate of the opening is, the better the stability) is maintained as high as possible, and the exhaust gas recirculation amount can be finely controlled and the required exhaust gas recirculation amount is secured. Can be.

According to the second aspect of the invention, the rate of change in the opening degree of the exhaust gas recirculation control valve is changed by changing the degree of pressure synthesis of the combined pressure. The rate of change of the opening degree of the exhaust gas recirculation amount control valve can be changed by a relatively simple configuration in which the volume ratio of the fluid and the magnitude of the pressure itself of each fluid forming the combined pressure are changed.

According to a third aspect of the present invention, the combined pressure is obtained by further embodying the second aspect of the invention.
While adjusting by controlling the communication time ratio of at least two pressures (for example, adjusting by changing the duty ratio of a duty control valve interposed in one passage),
The degree of synthesis of the synthesized pressure is changed by changing the communication area ratio of the at least two pressures (for example, the orifice opening area) to change the opening degree change rate of the exhaust gas recirculation amount control valve.

According to a fourth aspect of the present invention, the intake system of the engine is provided with an intake throttle valve that operates by using a pressure combined with the combined pressure, and the exhaust gas recirculation amount control is performed by changing the opening degree of the intake throttle valve. Even if the valves have the same opening, the exhaust gas recirculation amount can be changed, so that the control width of the exhaust gas recirculation amount control can be expanded and the finer control accuracy can be improved. wherein by utilizing the change in pressure synthesis degree of synthesis pressure due to the operation, with the construction of changing the opening degree change rate of the exhaust gas recirculation control valve to change the pressure synthesis degree of separately said synthesis pressure Therefore, it is not necessary to provide a means for performing the above operation, so that the configuration can be simplified.

[0018]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In FIG. 2 showing the configuration of the first embodiment, an E which connects an intake passage 2 and an exhaust passage 3 of an engine 1 communicates with each other.
A GR passage 4 is provided. A negative pressure operated EGR amount control valve 5 is interposed in the EGR passage 4. The EGR amount control valve 5 has a valve body 5A
By adjusting the lift amount of the exhaust gas, the exhaust gas recirculation amount (EGR amount) is adjusted.

The valve element 5A is connected to a diaphragm 5B, and the diaphragm 5B separates the valve element 5A from the negative pressure chamber 5C. When the negative pressure in the negative pressure chamber 5C becomes equal to or higher than a predetermined value, the diaphragm 5B
The valve body 5A is moved upward in the figure against D to open the valve body 5A, and the lift amount of the valve body 5A can be adjusted according to the magnitude of the negative pressure in the negative pressure chamber 5C. When the negative pressure is smaller than a predetermined value (when the target EGR amount is 0), the valve is biased by the spring 5D so that the EGR gas cannot pass through the EGR passage 4.

The negative pressure chamber 5C communicates with an EGR amount control negative pressure passage 6, and a negative pressure is introduced into the negative pressure chamber 5C via the EGR amount control negative pressure passage 6. . Said E
The GR amount control negative pressure passage 6 is branched into two branches, and one of the atmosphere side passages 6A communicates with the atmosphere via an atmosphere side orifice 7A. A duty control valve 8 is interposed in the other negative pressure side passage 6B and communicates with a vacuum pump or the like (not shown) (normally, a predetermined vacuum pressure is obtained by a pressure adjusting valve or the like). A negative pressure side orifice 7B is interposed between the duty control valve 8 and the vacuum pump. The duty control valve 8 may be interposed between the negative pressure side orifice 7B and the vacuum pump.

The duty control valve 8 is capable of adjusting the opening degree by changing a valve opening time ratio (duty ratio) when the valve is periodically opened and closed. Is controlled by a drive signal from a control unit 50 composed of Accordingly, in the EGR control, the control unit 50 drives the duty control valve 8 at a duty ratio set in advance according to the operating state (load, engine speed, water temperature, etc.) so as to obtain the target EGR amount. It will be.

That is, when the duty control valve 8 is driven, the vacuum negative pressure is adjusted to a predetermined pressure via the duty control valve 8 and is introduced into the negative pressure passage 6B on the side of the negative pressure chamber 5C. Since the pressure is combined with the atmospheric pressure introduced from the side passage 6A, the combined pressure is guided into the negative pressure chamber 5C. Therefore, the target EG is determined by the combined negative pressure.
The duty ratio of the duty control valve 8 is set so that the R amount is adjusted to the lift amount of the valve body 5A that can obtain the R amount.

In this embodiment, an intake throttle valve 9 is further provided in the intake passage 2 in order to adjust the intake negative pressure which is a control factor of the EGR amount. That is, when the intake throttle valve 9 is closed, the intake negative pressure increases, so that even if the lift amount of the valve body 5A is the same, the engine 1 can cause a large amount of EGR to be sucked, and the EGR amount can be increased. The control width can be extended.

For this reason, in the present embodiment, the intake throttle valve 9 is linked to the rod 10A of the negative pressure actuated actuator 10, and the intake throttle valve 9 is operated by the operation of the actuator 10.
The degree of opening can be adjusted. The rod 10A
Is connected to the diaphragm 10B, and the diaphragm 10B separates the rod 10A side from the negative pressure chamber 10C. When the negative pressure in the negative pressure chamber 10C becomes equal to or higher than a predetermined value, the diaphragm 10B moves rightward in the drawing against the spring 10D to move the rod 10A, and the negative pressure in the negative pressure chamber 10C. The amount of movement of the rod 10A, that is, the opening of the intake throttle 9 can be adjusted in accordance with the size of the intake throttle valve 9. If the negative pressure is smaller than the predetermined value, the spring 1
The movement of the rod 10A in the left-right direction is restricted by 0D, and the intake throttle valve 9 is maintained substantially horizontally in the intake air flow, so that there is no ventilation resistance.

A negative pressure passage 11 for throttle valve operation is connected to the negative pressure chamber 10C. The negative pressure passage 11 for throttle valve operation includes a first solenoid valve 12 and a second solenoid valve 13. And, it communicates with the vacuum pump through. The first solenoid valve 1
2 and the second solenoid valve 13 are connected to the control unit 5
These solenoid valves are turned ON / OFF (open / close) by a drive signal from 0. The solenoid valve communicates the atmosphere with the inside of the throttle valve operating negative pressure passage 11 when ON, and the atmosphere and the throttle valve operating negative pressure when OFF. The communication with the inside of the passage 11 is cut off.

Therefore, when the first solenoid valve 12 is turned off (communicating with the atmosphere side) and the second solenoid valve 13 is turned on (communicating with the vacuum side), the vacuum negative pressure is reduced via the second solenoid valve 13. While being introduced into the operation negative pressure passage 11, the first
Since the atmospheric pressure is introduced from the solenoid valve 12, a combined pressure of the vacuum negative pressure and the atmospheric pressure is introduced into the negative pressure chamber 10C. In this case, since the negative pressure introduced into the negative pressure chamber 10C is relatively small, the throttle valve 9 is opened with a relatively small opening (first opening).

On the other hand, when the first solenoid valve 12 is turned on (communication with the vacuum side) and the second solenoid valve 13 is also turned on (communication with the vacuum side), the vacuum pressure is reduced via the second solenoid valve 13 to operate the throttle valve. Into the negative pressure passage 11 and the first
Since atmospheric pressure is not introduced from the solenoid valve 12, a relatively large vacuum negative pressure is introduced into the negative pressure chamber 10C. In this case, since the negative pressure introduced into the negative pressure chamber 10C increases, the throttle valve 9 is closed at a large angle (second
Opening).

That is, according to this configuration, the first solenoid valve 1
2. By the combination of opening and closing of the second solenoid valve 13, a two-stage valve closing characteristic of the intake throttle valve 9 can be obtained. When the second solenoid valve 13 is OFF, the communication between the vacuum negative pressure and the atmosphere is cut off. By the way, as described above, even if the drive duty ratio of the duty control valve 8 is slightly changed for fine EGR amount control or the like, the EGR amount changes abruptly and the engine operability, exhaust performance, etc. The ratio ρ between the opening area (Da ² ) of the atmosphere-side orifice 7A and the opening area (Dv ² ) of the suction-side orifice 7B does not adversely affect the pressure.
(= Da ² / Dv ² ) to increase the EGR amount control valve 5 with respect to the change in the drive duty ratio of the duty control valve 8.
If the ratio of the orifice area between the atmosphere side and the negative pressure side is reduced by a predetermined value or more when the opening degree change rate (lift amount change rate of the valve element 5A) is reduced, a sufficient negative pressure Although the required lift of the EGR amount control valve 5 cannot be obtained because it cannot be guided to the chamber 5C, in order to solve this, in the present embodiment, the following configuration is added.

That is, as shown in FIG. 2, the EGR amount control negative pressure passage 6 can communicate with the atmosphere other than with the atmosphere via the atmosphere-side orifice 7A of the atmosphere-side passage 6A. The second atmosphere side passage 6C is connected to the EGR amount control negative pressure passage 6. In the passage 6C,
A third solenoid valve 14, which is driven ON / OFF, and a second atmosphere-side orifice 7C are interposed. The third solenoid valve 1
4, the arrangement of the second atmosphere-side orifice 7C may be replaced with the arrangement in FIG.

In such a configuration, when the third solenoid valve 14 is turned on (opened), the second atmosphere side orifice 7C
, The communication between the EGR amount control negative pressure passage 6 and the atmosphere can be established, so that the communication between the EGR amount control negative pressure passage 6 and the atmosphere can be made when the third solenoid valve 14 is ON or OFF. The degree can be changed. That is, the vacuum negative pressure introduced through the duty control valve 8 and the negative pressure orifice 7B, the atmospheric pressure introduced from the atmospheric side orifice 6A, and the atmospheric pressure introduced from the second atmospheric side orifice 6C. There are two different degrees of air communication (that is, the vacuum side and the vacuum side and the atmospheric pressure introduced from the atmosphere side orifice 6A). Of the orifice area of the EGR amount control valve 5 with respect to the change of the drive duty ratio of the duty control valve 8 by the difference of the degree of communication with the atmosphere. Therefore, for example, the stability of the EGR amount control can be improved by increasing ρ (increase the opening area of the atmosphere-side orifice) and decreasing the rate of change of the opening degree of the EGR amount control valve 5. On the other hand, if ρ is reduced (the opening area of the orifice on the atmosphere side is reduced) and priority is given to increasing the negative pressure in the negative pressure chamber 5C, the required opening degree of the EGR amount control valve 5 can be satisfied. Thus, the required EGR amount can be secured.

Here, the EGR control performed by the control unit 50 having the functions of the target opening setting means and the opening change rate selecting means of the present invention as software will be specifically described with reference to the flowchart of FIG. .
First, in step (denoted by S in the figure, the same applies hereinafter) 1, the engine rotation speed Ne is detected based on a pulse signal generated at every predetermined crank angle from a crank angle sensor (not shown) or the like.

In step 2, the engine load Vc1 (which may be the accelerator opening, fuel supply amount, intake air flow rate, etc.) is detected. In step 3, the current operating conditions (Ne and V
TH determined by c1 and water temperature, etc.) is MAP1 shown in FIG.
Of the intake throttle areas TH1 to TH3 in the search is obtained by a search.

Then, the process proceeds to step 4, where TH = TH1
Is determined. If TH = TH1, the process proceeds to step 6, and outputs an ON signal to the first solenoid valve 12. T
If not H = TH1, go to step 5. Step 5
Then, an OFF signal is output to the first solenoid valve 12. In step 7, it is determined whether or not TH = TH2. YE
If S, proceed to step 9 and turn on second solenoid valve 13
Output a signal. If NO, it is determined that TH = TH3, and the routine proceeds to step 8.

In step 8, the second solenoid valve 13 is turned off.
Output a signal. That is, TH1 is the first solenoid valve 12,
By turning on both of the second solenoid valves 13, the maximum (the second
A region in which the intake throttle valve 9 is closed (by opening degree) (If the intake throttle valve 9 is not fully closed, the difference between the intake negative pressure and the exhaust pressure is small, the EGR rate itself is high, and only the EGR amount control valve 5 is used.) Then request E
Region where GR rate [EGR amount / intake air flow rate] cannot be obtained)
TH2 is a region in which only the second solenoid valve 13 is turned on and the intake throttle valve 9 is closed at the aforementioned first opening degree where the valve closing degree is relatively small (the intake throttle valve 9 is not closed to some extent). And the difference between the intake negative pressure and the exhaust pressure is small, and the EGR rate itself is intermediate.
TH3 is the first solenoid valve 1).
2, a region where both the second solenoid valve 13 is turned off and the intake throttle valve 9 is not closed (the difference between the intake negative pressure and the exhaust pressure is originally large, the EGR rate itself is low, and only the EGR amount control valve 5 is used). In the region where the required EGR rate is obtained.

Next, at step 10, the target opening L (the opening at which the target EGR rate is obtained) of the EGR amount control valve 5 set according to the operation state is determined with reference to MAP2 shown in FIG. Ask. In step 11, the target opening L is set as shown in FIG.
It is determined whether or not the opening degree L ₀ shown in FIG. If NO, proceed to step 12; if YES, step 14
Proceed to.

In step 12, NO in step 11
Since (target opening L is opening L is ₀ or less) when it is determined that can be communicated atmospheric side orifice 7A, a second air-side orifice 7C, the securing of the target EGR rate Therefore, an ON (opening) signal is output to the third solenoid valve 14 in order to give priority to the control accuracy of the EGR rate. That is, the second atmosphere side orifice 7C is communicated with the atmosphere and
The target EG is increased by increasing the degree of communication between the GR amount control negative pressure passage 6 and the atmosphere (ρ = “total opening area of the atmosphere-side orifice / total opening area of the negative-pressure orifice”).
The changing speed of the negative pressure in the negative pressure chamber 5C with respect to the change in the opening degree of the duty control valve 8 due to the change in the R rate, in other words, the valve element 5
The target EGR rate can be controlled with high accuracy while suppressing the rapid change of the EGR amount by reducing the moving speed of A.

At a step S13, the duty ratio D of the duty control valve 8 at which the target opening L of the EGR amount control valve 5 is obtained is stored in a table TBL1 shown in FIG.
, The duty ratio D is output to the duty control valve 8 and the flow returns (or the present flow ends) in step 16. On the other hand, in step 14, the target opening degree L is larger than the opening degree L _0, E
If the degree of communication between the GR amount control negative pressure passage 6 and the atmosphere is increased to maintain the control accuracy of the EGR rate high, the target EGR rate cannot be secured.
In order to give priority to securing the rate, the third solenoid valve 14 is connected to the third solenoid valve 14 so as to communicate with the atmosphere only through the atmosphere-side orifice 7A.
Outputs FF (valve closing) signal. That is, the communication between the second atmosphere-side orifice 7C and the atmosphere is cut off to reduce the degree of communication between the inside of the EGR amount control negative pressure passage 6 and the atmosphere (ρ = “total opening area of the atmosphere-side orifice / By reducing the total opening area of the negative pressure side orifice), the negative pressure in the EGR amount control negative pressure passage 6 is increased, thereby generating a negative pressure capable of obtaining the required opening degree in the negative pressure chamber 5C. It can be so.

In step 15, the EGR amount control valve 5
The duty ratio D of the duty control valve 8 at which the target opening degree L is obtained is set in the table TBL2 shown in FIG. 4 [(2) in FIG.
Step 1)
At 6, the duty ratio D is output to the duty control valve 8, and the flow ends. As described above, according to the first embodiment, the combined pressure of the vacuum negative pressure and the atmospheric pressure guided into the EGR amount control negative pressure passage 6 via the third solenoid valve 14 and the second atmospheric orifice 7C. Thus, the target degree of opening of the EGR amount control valve can be achieved while maintaining the rate of change of the degree of opening (control responsiveness) as low as possible. That is, fine control of the exhaust gas recirculation amount can be performed while maintaining the control stability of the exhaust gas recirculation amount control as high as possible, and the required exhaust gas recirculation amount can be secured.

In this embodiment, the intake throttle valve 9 is provided.
Although the configuration in which the opening degree is changed depending on the operation region has been described, even if the intake throttle valve 9 is not provided,
The present invention may be applied to any configuration provided that the ratio between the opening area of the atmosphere side orifice and the opening area of the negative pressure side orifice is made variable in accordance with the target EGR rate (ie, the lift amount of the valve element 5A). This has an effect and is within the scope of the present invention (the same applies to the following second and third embodiments).

Next, a second embodiment will be described.

The second embodiment shares the basic concept with the first embodiment, and has a configuration in which the ratio ρ between the opening area of the atmosphere side orifice and the opening area of the negative pressure side orifice is variable, as shown in FIG. (Note that the first solenoid valve 12 and the second solenoid valve 1
2 is also provided in the same manner as in FIG. 2, but not shown here), a bypass passage 15 that bypasses the suction side orifice 7B, a second suction side orifice 7D interposed in the bypass passage 15, and a suction side. And a fourth solenoid valve 16 for making the opening area of the whole orifice variable. The other configuration is the same as that of the first embodiment, and the description is omitted.

The EGR control performed by the control unit 50 according to the second embodiment will be described below with reference to the flowchart of FIG. Steps 1 to 10 in the figure are the same as those in the flowchart of FIG. 3 of the first embodiment, and thus the description thereof will be omitted, and only the steps after step 21 will be described. That is, step 21
In target opening L is, it is determined whether the opening degree L ₀ is larger than that shown in FIG. If NO, proceed to step 22 and proceed to Y
If it is ES, the process proceeds to step 24.

In step 22, the target opening L is set to the opening L _0.
Since it is determined that the following conditions are satisfied, the target EGR rate can be secured by introducing the negative pressure of the vacuum pump from the negative pressure side orifice 7B. In such a case, the priority is given to the control accuracy of the EGR rate. 4 OFF to solenoid valve 16
(Valve closed) signal is output. That is, the negative pressure orifice 7
EG by introducing vacuum negative pressure only from B
The rate of change of the negative pressure in the R amount control negative pressure passage 6 is slowed down (ρ is increased), so that the change in the opening degree of the duty control valve 8 due to the change in the target EGR rate is caused in the negative pressure chamber 5C. In other words, the moving speed of the valve element 5A is reduced so that the target EGR rate can be obtained with high accuracy while suppressing a sudden change in the EGR amount.

Then, in step 23, the duty ratio D of the duty control valve 8 for obtaining the target opening L of the EGR amount control valve 5 is set in the table TBL1 shown in FIG. 1) corresponding to the line), the duty ratio D is output to the duty control valve 8 in step 26, and the flow ends. On the other hand, in step 24, larger target opening L is than the opening degree L _0, the [rho (= "total opening area of all open area / suction orifice of the air-side orifice") control accuracy of the larger to the EGR rate If the target EGR rate is to be maintained at a high level, the target EGR rate cannot be secured. In such a case, it is necessary to reduce the ρ (to increase the opening area of the entire negative pressure side orifice) in order to give priority to securing the target EGR rate. Compression orifice 7
B and the second solenoid valve 16 so as to introduce a negative pressure from the vacuum pump through both the second suction side orifice 7D and the second suction side orifice 7D.
To output an ON (valve open) signal. That is, by connecting the EGR amount operation negative pressure passage 6 and the vacuum pump via the second negative pressure side orifice 7D, a large negative pressure can be introduced into the EGR amount control negative pressure passage 6 (ρ = “ Opening area of atmospheric orifice / opening area of negative pressure orifice "
Is reduced) to increase the negative pressure in the EGR amount control negative pressure passage 6 so that the negative pressure that can obtain the required opening degree in the negative pressure chamber 5C can be generated.

In step 25, the EGR amount control valve 5
The duty ratio D of the duty control valve 8 at which the target opening L is obtained is set in a table TBL2 shown in FIG. 4 ((2) in FIG. 5).
(Corresponding to the line), and in step 26,
The duty ratio D is output to the duty control valve 8, and the flow ends. Thus, according to the second embodiment,
Through the fourth solenoid valve 16 and the second negative pressure side orifice 7D,
Since the degree of synthesis of the combined pressure of the vacuum negative pressure and the atmospheric pressure introduced into the EGR amount control negative pressure passage 6 can be adjusted, the change rate of the opening degree as much as possible (control responsiveness) is thereby achieved.
Is maintained low, and the target opening of the EGR amount control valve can be achieved. That is, fine control of the exhaust gas recirculation amount can be performed while maintaining the control stability of the exhaust gas recirculation amount control as high as possible, and the required exhaust gas recirculation amount can be secured.

Next, a third embodiment will be described.

Although the third embodiment has the same concept as the first and second embodiments, as shown in FIG. 8 (the first solenoid valve 12 and the second solenoid valve 13 are also similar to FIG. 2). Although not shown here, the passage 6B communicating with the vacuum pump is directly connected to the vacuum pump by bypassing the negative pressure side orifice 7B, the duty control valve 8, and the atmosphere side orifice 7B.
A passage 17 communicating with the GR amount control negative pressure passage 6 is provided, and a fifth solenoid valve 18 composed of an ON / OFF valve and a third negative pressure side orifice 7E are interposed in the passage 17. Other configurations are the same as those of the above-described embodiments, and a description thereof will be omitted.

Hereinafter, EGR control performed by the control unit 50 in the third embodiment will be described with reference to the flowchart of FIG. Steps 1 to 10 in the figure are the same as those in the first and second embodiments, so that the description thereof will be omitted, and only the steps after step 31 will be described. That is, in step 31, the target opening L
There, it is determined whether the opening degree L ₀ greater than or not shown in FIG.
If NO, proceed to step 32, and if YES, proceed to step 34.

In step 32, the target opening L is set to the opening L _0.
If the vacuum pressure is introduced from the vacuum side orifice 7B, the target E
Since the GR rate can be secured, in such a case, E
An OFF (closed) signal is output to the fifth solenoid valve 18 in order to give priority to the control accuracy of the GR rate. In other words, the vacuum negative pressure is introduced only from the negative pressure side orifice 7B so that the rate of change of the negative pressure in the EGR amount control negative pressure passage 6 is delayed (ρ is increased), and the target EGR rate is reduced. The target EGR is suppressed while the rising speed of the negative pressure in the negative pressure chamber 5C with respect to the change in the opening degree of the duty control valve 8 due to the change, in other words, the moving speed of the valve element 5A is suppressed to suppress a sudden change in the EGR amount. Be able to control the rate with high precision.

In step 33, the duty ratio D of the duty control valve 8 for obtaining the target opening L of the EGR amount control valve 5 is set in the table TBL1 shown in FIG.
(Corresponding to the line (1) of FIG. 2)], the duty ratio D is output to the duty control valve 8 in step 36, and the flow ends. On the other hand, in step 34, larger target opening L is than the opening degree L _0, wherein [rho (= "open area of the opening area / suction orifice of the air-side orifice")
If the control accuracy of the EGR rate is to be maintained at a high level by increasing the target EGR rate, the target EGR rate cannot be secured. In order to introduce a negative pressure from the vacuum pump through both the suction side orifice 7B and the third suction side orifice 7E, an ON (opening) signal is sent to the fifth solenoid valve 18 in order to increase the opening area of the opening. Output. That is, by connecting the EGR amount operation negative pressure passage 6 and the vacuum pump via the third negative pressure side orifice 7E, a large negative pressure can be introduced into the EGR amount control negative pressure passage 6 (ρ = “ (Opening area of atmospheric side orifice / opening area of negative pressure side orifice))
The negative pressure in the negative pressure passage 6 for controlling the R amount is increased, so that the negative pressure chamber 5
It is possible to generate a negative pressure at which the required opening degree is obtained at C.

In step 35, the EGR amount control valve 5
The duty ratio D of the duty control valve 8 at which the target opening degree L is obtained is set in the table TBL2 shown in FIG. 4 [(2) in FIG.
Equivalent to a line], and in step 36,
The duty ratio D is output to the duty control valve 8, and the flow ends. Thus, according to the second embodiment,
Via the fifth solenoid valve 18 and the third negative pressure side orifice 7E,
Since the degree of synthesis of the combined pressure of the vacuum negative pressure and the atmospheric pressure introduced into the EGR amount control negative pressure passage 6 can be adjusted, the change rate of the opening degree as much as possible (control responsiveness) is thereby achieved.
Is maintained low, and the target opening of the EGR amount control valve can be achieved. That is, fine control of the exhaust gas recirculation amount can be performed while maintaining the control stability of the exhaust gas recirculation amount control as high as possible, and the required exhaust gas recirculation amount can be secured.

Here, a fourth embodiment will be described.

The fourth embodiment differs from the fourth embodiment in that, as shown in FIG. 10, the third solenoid valve 14 and the second atmosphere-side orifice 7C shown in FIG. 2 are not provided. In the fourth embodiment, when the intake throttle valve 9 is in the intermediate closed state (the first opening degree), the rate of change in the opening degree of the EGR amount control valve 5 with respect to the change in the duty ratio of the duty control valve 8 Is set so that the area ratio ρ between the atmosphere-side orifice 7A and the negative-pressure-side orifice 7B is set in advance.

This is because when the ratio ρ of the orifice area is increased, when the intake throttle valve 9 is intermediately closed, the atmosphere is introduced into the vacuum pump side by the ON operation of the second solenoid valve 13. Vacuum negative pressure changes,
Utilizing that the negative pressure in the EGR amount control negative pressure passage 6 is affected, thereby affecting the opening degree characteristics of the EGR amount control valve 5 and decreasing the rate of change of the opening degree of the EGR amount control valve 5 It was done. That is, instead of changing the ratio ρ of the orifice area, the ON / OF of the first solenoid valve 12 and the second solenoid valve 13 is changed.
By changing the negative pressure side positively by using the F operation positively, substantially the same effect as changing the orifice area ratio ρ is provided.

The operation of the intake throttle valve 9 is fully open when EGR is not performed, the intermediate valve is closed (first opening degree) when the EGR amount is small, and the maximum valve is closed when the EGR amount is large. (Second opening), and the setting accuracy of the EGR amount is maximized by using the intermediate closing valve having a small opening degree change rate of the EGR amount control valve 5 as much as possible.

Here, the EGR control performed by the control unit 50 in the fourth embodiment will be described with reference to the flowchart of FIG. In step 41, the engine rotation speed Ne is determined based on a pulse signal generated at every predetermined crank angle from a crank angle sensor (not shown) or the like.
Is detected. In step 42, the engine load Vc1 (may be accelerator opening, fuel supply amount, intake air flow rate, etc.)
Is detected.

In step 43, the current operating condition (Ne
TH is determined by Mc shown in FIG.
Which of the intake throttle regions TH1 to TH3 in AP1 'corresponds is obtained by a search. In step 44, a target opening L (an opening at which a target EGR rate is obtained) of the EGR amount control valve 5 set according to the operating state is determined with reference to MAP2 'shown in FIG.

At step 45, it is determined whether or not TH = TH3. If not TH = TH3, step 4
The program proceeds to step S6, where an ON (opening) signal is output to the second solenoid valve 13. If TH = TH3, the process proceeds to step 47. In step 47, since the EGR is cut off, the first solenoid valve 12 and the second solenoid valve 13 are turned off (closed) in order to fully open the intake throttle valve 9 (to prevent airflow resistance).
Output a signal.

Then, in step 48, the duty ratio is set to 0 (non-EGR), and after proceeding to step 52, the present flow is terminated. On the other hand, after sending an ON (opening) signal to the second solenoid valve 13 in step 46, it is determined in step 49 whether or not TH = TH2. TH
If not = TH2, then TH = TH1, so in step 50, an ON (opening) signal is output to the first solenoid valve 12, and the intake throttle valve 9 is set to the maximum value so that the intake negative pressure can be maximized. The opening degree (ie, the second opening degree). In this case, since the communication with the atmosphere is cut off, the negative pressure in the negative pressure passage 6 for controlling the EGR amount also becomes maximum, and the area ratio ρ of the orifice becomes substantially a small value. Priority can be given to securing the lift amount of the valve 5. Therefore, it is possible to obtain a maximum lift L _3.

Then, the process proceeds to a step 51, wherein the EGR
Duty control valve 8 for obtaining target opening L of quantity control valve 5
In the table TBL2 ′ shown in FIG.
[Equivalent to the β line in FIG. 13] is obtained by retrieval, and in step 52, the duty ratio D is output to the duty control valve 8, and the flow ends. On the other hand, in step 49,
If it is determined that TH = TH2, step 5
Proceed to 3 and output an OFF (valve closing) signal to the first solenoid valve 12, and proceed to step 54. In this case, since there is some communication with the atmosphere, the negative pressure in the negative pressure passage 6 for controlling EGR amount also decreases, and the area ratio ρ of the orifice becomes a substantially large value. Cannot be obtained, but EGR for the change in the opening degree of the duty control valve 8
The rate of change of the opening of the quantity control valve 5 can be reduced.

In step 54, the EGR amount control valve 5
The duty ratio D of the duty control valve 8 at which the target opening L is obtained from the table TBL1 ′ (corresponding to the α line in FIG. 13) shown in FIG.
Then, the duty ratio D is output to the duty control valve 8,
This flow ends. As described above, according to this embodiment, as in the first to third embodiments, the EGR amount control valve 5 such as the third solenoid valve 14, the fourth solenoid valve 1, and the fifth solenoid valve 18 is used.
Without having a solenoid valve to change the opening characteristics of the
The opening degree characteristic of the EGR amount control valve 5 is improved by positively utilizing the change in the operating negative pressure in the operating state of the intake throttle valve 9, that is, in the ON / OFF state of the first solenoid valve 12 and the second solenoid valve 13. Can be changed. Therefore, the cost can be reduced as compared with the first to third embodiments.

In the fourth embodiment, the change rate of the opening degree of the EGR amount control valve 5 is changed by utilizing the change of the vacuum negative pressure caused by the operation of the intake throttle valve 9. 9 may not be provided, and in such a case, the vacuum negative pressure may be changed by another device. For example, the vacuum pressure is changed by changing the set pressure of an adjustment valve that adjusts the vacuum negative pressure, or by interposing an electromagnetic valve in a passage communicating with the vacuum negative pressure and switching the electromagnetic valve on and off. You may make it do.

In each of the above embodiments, the case where the EGR amount control valve 5 and the intake throttle valve 9 are operated by using the vacuum negative pressure is described. However, the present invention is not limited to this. Alternatively, the EGR amount control valve 5 and the intake throttle valve 9 may be operated by a composite pressure of a plurality of pressures such as compressed air, atmosphere, and vacuum negative pressure. In this case, the rate of change in the degree of opening of the EGR amount control valve 5 can be changed by changing the degree of pressure synthesis of each fluid (communication area ratio of each fluid, the pressure itself of each fluid, etc.). .

[0064]

As described above, according to the first aspect of the present invention, according to the target opening degree of the exhaust gas recirculation amount control valve,
Since the change rate of the opening degree of the exhaust gas recirculation control valve is selected, the control stability of the exhaust gas recirculation control (the smaller the rate of change of the opening degree is, the better the stability) is maintained as high as possible. The recirculation amount can be controlled, and the required exhaust gas recirculation amount can be secured.

According to the second and third aspects of the present invention, the rate of change in the opening degree of the exhaust gas recirculation amount control valve is changed by changing the degree of pressure synthesis of the synthesized pressure. By changing the volume ratio of each fluid forming the pressure and the magnitude of the pressure itself of each fluid forming the combined pressure, the opening change rate of the exhaust gas recirculation amount control valve can be changed. .

According to the fourth aspect of the present invention, the intake system of the engine is provided with an intake throttle valve that operates by using a pressure combined with the combined pressure, and the exhaust gas recirculation amount control is performed by changing the opening degree of the intake throttle valve. Even if the valves have the same opening, the exhaust gas recirculation amount can be changed, so that the control width of the exhaust gas recirculation amount control can be expanded and the finer control accuracy can be improved. wherein by utilizing the change in pressure synthesis degree of synthesis pressure due to the operation, with the construction of changing the opening degree change rate of the exhaust gas recirculation control valve to change the pressure synthesis degree of separately said synthesis pressure Since it is not necessary to provide a means for performing the above, the configuration can be simplified and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of the present invention.

FIG. 2 is an overall configuration diagram of a first embodiment.

FIG. 3 is a flowchart illustrating an EGR control routine of the embodiment.

FIG. 4 is a view for explaining a search map of each control value in the EGR control of the embodiment.

FIG. 5 is a view for explaining a relationship between a duty ratio of the duty control valve and an EGR amount control valve opening degree in the embodiment.

FIG. 6 is an overall configuration diagram of a second embodiment.

FIG. 7 is a flowchart illustrating an EGR control routine of the embodiment.

FIG. 8 is an overall configuration diagram of a third embodiment.

FIG. 9 is a flowchart illustrating an EGR control routine of the embodiment.

FIG. 10 is an overall configuration diagram of a fourth embodiment.

FIG. 11 is a flowchart illustrating an EGR control routine of the embodiment.

FIG. 12 is a view for explaining a search map of each control value in the EGR control of the embodiment.

FIG. 13 is a view for explaining the relationship between the duty ratio of the duty control valve and the EGR amount control valve opening degree in the embodiment.

FIG. 14 is an example of a conventional exhaust gas recirculation device.

FIG. 15 is an example of another conventional exhaust gas recirculation device.

FIG. 16 illustrates a conventional problem.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Intake passage 3 Exhaust passage 4 EGR passage 5 EGR amount control valve 6 EGR amount control negative pressure passage 7A Atmospheric side orifice 7B Negative pressure side orifice 7C Second atmospheric side orifice 7D Second negative pressure side orifice 8 Duty control valve 9 Intake throttle valve 12 First solenoid valve 13 Second solenoid valve 14 Third solenoid valve 16 Fourth solenoid valve 18 Fifth solenoid valve 50 Control unit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F02M 25/07 550 F02M 25/07 570 F02M 25/07 580 F02D 35/00 380

Claims (4)

(57) [Claims] An exhaust gas recirculation passage for recirculating a part of exhaust gas to an engine intake system, and an exhaust gas recirculation amount control valve for controlling an amount of exhaust gas recirculated through the exhaust gas recirculation passage, the amount of change in the control valve duty ratio To
Opening change rate and control valve due to large opening change
The second opening change is small in the opening change with respect to the change in the tee ratio.
And the first opening degree change rate is selected.
The first maximum opening, which is the maximum opening when selected , is the second maximum opening .
An exhaust gas recirculation amount control valve configured to be larger than a second maximum opening degree which is a maximum opening degree when the opening degree change rate is selected, and a target exhaust gas recirculation amount according to engine operating conditions can be obtained. A target opening setting means for setting a target opening of the exhaust gas recirculation amount control valve; and selecting the first opening change rate when the set target opening is larger than the second maximum opening. and, when the set target opening degree is smaller than said second maximum opening, the front
An exhaust gas recirculation device for an internal combustion engine, comprising: an opening change rate selection means for selecting the second opening change rate . 2. The method according to claim 1, wherein a combined pressure obtained by combining at least two pressures is applied to a valve body of the exhaust gas recirculation amount control valve to control an opening degree of the exhaust gas recirculation amount control valve.
2. The exhaust gas recirculation device for an internal combustion engine according to claim 1, wherein an opening degree change rate is changed by changing a pressure synthesis degree of the synthesized pressure. 3. The synthetic pressure is adjusted by controlling a communication time ratio of at least two pressures, and a synthesis degree of the synthetic pressure is changed by changing a communication area ratio of the at least two pressures. 3. The exhaust gas recirculation device for an internal combustion engine according to claim 2, wherein the rate of change of the opening degree of the exhaust gas recirculation amount control valve is changed. 4. An exhaust gas recirculation passage for recirculating a part of exhaust gas to an engine intake system, and passing through the exhaust gas recirculation passage according to a negative pressure guided to a negative pressure chamber.
An exhaust gas recirculation amount control valve for controlling the amount of exhaust gas recirculated, one end of which communicates with the negative pressure chamber and the other end of which is bifurcated.
And one of the atmosphere passages communicates with the atmosphere while the other
EGR amount control negative pressure in which one of the negative pressure side passages communicates with a negative pressure source
A passage, and the opening and closing of the suction-side passage arranged in the suction-side passage.
Duty control valve to control the intake air pressure in the engine intake system according to the negative pressure guided to the negative pressure chamber.
An intake throttle valve to be controlled, one end of which communicates with the negative pressure chamber and the other end of which has the negative pressure;
Negative pressure for throttle valve operation that merges with the side passage and communicates with the negative pressure source
A passage, and the throttle valve operating negative pressure disposed in the throttle valve operating negative pressure passage.
OFF side that guides the atmosphere into the passage and inside the negative pressure passage for throttle valve operation
1st switch to switch to ON side to shut off the introduction of air to the
A magnetic valve , and the throttle valve operating negative pressure on the negative pressure source side with respect to the first solenoid valve.
A negative pressure for operating the throttle valve on the intake throttle valve side which is disposed in a passage;
OFF side for communicating the passage with the atmosphere and before the intake throttle valve side
The throttle valve operating negative pressure passage is connected to the negative pressure source side for the throttle valve operating.
Second solenoid valve for switching between ON side and communication with the negative pressure passage
And an exhaust gas recirculation device for an internal combustion engine.