JPH09256916A - Exhaust gas recirculation valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify stroke adjustment for an exhaust gas recirculation valve. SOLUTION: An exhaust gas recirculation valve is provided with a seat valve 2 opening and closing according to the advance and retreat of a valve shaft 16 and an actuator advancing and retreating the valve shaft 16. The valve shaft is energized by a spring 22 and is projected to the actuator side. The actuator is provided with a housing 24, sleeve piston 26 and a center piston 30 capable of relative motion of a given value, and the center piston 30 is energized in the direction of the valve shaft 16 by a spring 54. A seat member 60 is provided between the tip of the valve shaft and the abutting face of the center piston. The projection amount L10 from the end face 6a of a housing as a unit of the seat valve and the distance L20 between the end face 6a of a housing 6 as a unit of the actuator and abutting face of the center piston are measured. From the actual value and the set stroke L1 , the thickness of the seat member is calculated using the flowing equation: L20 -L10 +L1 .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention returns a part of exhaust gas of a diesel engine to the intake side, mixes it with fresh air, and sucks it into the engine to lower the combustion temperature.
The present invention relates to an exhaust gas recirculation system for suppressing the generation of Ox, and particularly to a valve for this exhaust gas recirculation system.

[0002]

2. Description of the Related Art Diesel engines are widely used in various vehicles such as passenger cars and small trucks to large trucks and buses due to their high thermal efficiency, excellent durability, reliability and economy. However, NOx (nitrogen oxides) and PM (particulate matter) emitted from diesel engines are regarded as the main pollutants in air pollution, and emission regulations are gradually tightened. Therefore, while making use of the excellent characteristics of the diesel engine,
The reduction of x has become an important issue.

In order to reduce NOx emitted from the diesel engine as described above, an exhaust gas recirculation (commonly called EGR) system for recirculating exhaust gas is already known. In this exhaust gas recirculation system, a part of the exhaust gas is returned to the intake side, mixed with fresh air, and sucked into the engine to reduce the O ₂ concentration, thereby slowing combustion,
NOx is suppressed by reducing the combustion temperature.

FIG. 3 is a diagram showing a general structure of the exhaust gas recirculation system, in which the exhaust circulation pipe 1 is provided between the intake pipe 102 and the exhaust pipe 104 of the diesel engine 100.
06, a valve 108 for exhaust gas recirculation is provided in the exhaust circulation pipe 106 to control the recirculation amount of exhaust gas to the intake side, and an intake throttle valve 110 is provided in the intake pipe 102. By controlling the amount of fresh air to be sucked, the diesel engine 100 can be set to an optimum mixing ratio according to the engine speed and the engine load.
Is to be supplied to The exhaust gas recirculation valve 108 and the intake throttle valve 110 are each controlled to open and close by an electromagnetic valve 112.

FIG. 4 shows an example of a conventional exhaust gas recirculation valve 108 used in the exhaust gas recirculation system. The exhaust gas recirculation valve 108 circulates exhaust gas to the intake side. The seat valve 2 that opens and closes the passage and the valve actuator 4 that opens and closes the seat valve 2 are integrated. The seat valve 2 and the valve actuator 4 will be described with reference to FIGS. 4 and 5. An exhaust gas circulation passage 8 is formed in the housing 6 of the seat valve 2, and an inlet side 8a of the circulation passage 8 is circulated to the exhaust pipe 104 of the diesel engine 100 through the exhaust circulation pipe 106 and then circulated. The outlet side 8 b of the passage 8 is connected to the intake pipe 102 of the diesel engine 100 via the exhaust circulation pipe 106.

An annular valve seat 10 is formed on the inner surface of the circulation passage 8 in a plane orthogonal to the axial direction of the seat valve 2 (left and right direction in FIG. 4). A through hole 12 that opens into the circulation passage 8 is formed in the shaft core of the valve housing 6. The through hole 12 has a small diameter portion 12a that opens to the circulation passage 8 and a large diameter portion 12b that opens to the end surface 6a of the valve housing 6 on the actuator 4 side. One end 14
a is press-fitted. The guide sleeve 14 has the other end 14
b extends into the large diameter portion 12b, and the valve shaft 16 is slidably fitted in the guide sleeve 14.

A valve body 18 is provided at an end of the valve shaft 16 on the side of the circulation passage 8. The valve body 18 slides in the axial direction, so that the valve body 18 is moved to the valve seat 1 by the sliding operation.
It is designed to be seated at 0 or separated. An annular spring seat 20 is fixed near the end of the valve shaft 16 opposite to the valve body 18, and the annular spring seat 20 and the flange 14c formed on the outer circumference of the guide sleeve 14 are fixed.
A first spring 22 is elastically mounted between and to constantly bias the valve shaft 16 in a direction in which the valve element 18 is seated on the valve seat 10 (rightward in FIG. 4). The front end 16 a of the valve shaft 16 has an end surface 6 of the valve housing 6.
a (the end surface on the side where the actuator 4 to be described later is attached) is projected, and the tip end 16a is pressed by the actuator 4 to move the valve body 18 to open and close the seat valve 2.

On the other hand, the valve actuator 4 for opening and closing the seat valve 2 has a substantially cup-shaped actuator housing 24, a sleeve piston 26 slidably fitted inside the actuator housing 24, and An annular piston 28 slidably fitted between an outer peripheral surface of the sleeve piston 26 and an inner peripheral surface of the actuator housing 24, and a center piston 3 slidably accommodated inside the sleeve piston 24.
0.

As shown in FIG. 5, the actuator housing 24 slidably supports one end 26f side of the sleeve piston 26 on the inner surface on the opening side (left side in FIG. 5), and also the actuator housing 24. An annular body 32 that partitions the inside of the is fixed via a snap ring 31. Also, the actuator housing 24
The inner peripheral surface on the bottom 24a side (right side in FIG. 5) of the small diameter hole 24b
And the sleeve piston 26 has a bottom 26
The outer peripheral surface of the large diameter portion 26b formed on the a side is the small diameter hole 2
It slides on the inner surface of 4b. A seal member 34 is fitted on the inner peripheral surface of the annular body 32 on which one end 26f side of the sleeve piston 26 slides, and on the outer peripheral surface of the annular body 32 mounted on the inner surface of the actuator housing 24. An O-ring 36 is fitted to keep the inside of the actuator housing 24 airtight. A seal member 38 is also fitted to the outer peripheral surface of the large diameter portion 26b of the sleeve piston 26 that slides on the inner surface of the small diameter hole 24b of the actuator housing 24 to maintain airtightness.

An annular piston 28 is provided in a space defined by the inner peripheral surface of the actuator housing 24, the annular member 32 and the outer peripheral surface of the sleeve piston 26, and the inner peripheral surface of the actuator housing 24 and the sleeve piston 26.
Is slidably fitted to the outer peripheral surface of the. On the inner peripheral surface and the outer peripheral surface of the annular piston 28, sealing members 40,
41 is fitted to keep the airtightness, and
It is divided into two chambers 42 and 43. The second portion is provided between the annular body 32 and the annular piston 28, which are attached to the inner surface of the actuator housing 24 via the snap ring 31.
The spring 44 of the
Is always urged toward the step portion 24d between the small diameter hole 24b and the large diameter hole 24c of the actuator housing 24.

A circular concave portion 26c is formed on the inner surface side of the bottom portion 26a of the sleeve piston 26, and a plate 46 having a circular hole 46a at the center is formed on the snap ring 48 on the inner surface of the other end portion 26f. Is installed through. A center piston 30 is slidably housed inside the sleeve piston 26. One end 30a (right end in FIG. 5) of the center piston 30 has a small diameter shaft-like shape, and this small diameter shaft-like portion 30a is a recess 26c formed in the bottom portion 26a of the sleeve piston 26.
It can be fitted inside. Also, the center piston 3
The other end 30b of 0 has a tubular shape, and the outer peripheral surface of the tubular portion 30b slides on the inner peripheral surface of the sleeve piston 26. A seal member 50 is fitted to the outer peripheral surface of the tubular portion 30b of the center piston 30 to maintain airtightness, and the shaft-shaped portion 30a of the center piston 30 is provided.
A sealed chamber 52 is formed between the outer peripheral surface of the sleeve and the inner peripheral surface of the sleeve piston 26. A third spring 54 having a weaker spring force than the first spring 22 is arranged in the chamber 52 to constantly urge the center piston 30 toward the plate 46 side, that is, the seat valve 2 side. However, the sleeve piston 26 is biased in the opposite direction.

The center piston 30 is housed in the sleeve piston 26 and can be axially stroked by L ₁ (see FIG. 5) between the recess 26c and the plate 46. The large diameter portion 26b (right end in FIG. 5) of the sleeve piston 26 that slides in the small diameter portion 24b of the actuator housing 24 is the small diameter portion 24.
It is shorter than the axial length of b by L _2, and the sleeve piston 26 is movable in the axial direction by L ₂ when the annular piston 28 is stopped at the step portion 24d of the actuator housing 24. Has become. further,
The annular piston 28 is movable in the axial direction by L ₃ from the position where it is pressed by the second spring 44 and abuts against the step portion 24d of the actuator housing 24 to the position where it contacts the annular body 32.

The inside of the chamber 42 between the annular body 32 and the annular piston 28 mounted on the opening side of the actuator housing 24 is connected to an air supply source via a first electromagnetic valve (not shown), Air can be supplied to and discharged from the chamber 42 by the operation of the first solenoid valve. On the outer wall of the sleeve piston 26, the sleeve piston 26
Is formed with a passage hole 26d penetrating the inside and the outside thereof, and the chamber 52 between the inner peripheral surface of the sleeve piston 26 and the outer peripheral surface of the shaft-shaped portion 30a of the center piston 30 forms a space between the annular body 32 and the annular piston 28. It is in constant communication with the room 42.
Therefore, when air is introduced into the chamber 42 via the first solenoid valve, the air is also introduced into the chamber 52 inside the sleeve piston 26 via the passage hole 26d. In addition,
The chamber 43 between the annular piston 28 and the stepped portion 24d of the actuator housing 24 is connected to the outside through the through hole 24e so that the annular piston 28 can move.

Further, air can be introduced into the chamber 56 between the bottom portion 24a of the actuator housing 24 and the bottom portion 26a of the sleeve piston 26 through another solenoid valve (second solenoid valve). By introducing air into the chamber 56, the sleeve piston 26 can be moved to the seat valve 2 side.

The actuator 4 is constructed by assembling the actuator housing 24, the sleeve piston 26, the annular piston 28, the center piston 30 and the like into an integral structure.
Is fixed to the end surface 6a of the housing 6 of the seat valve 2. An annular convex portion 6b is formed on the end surface 6a of the seat valve 6.
The annular projection 6b is fitted in the opening of the actuator housing 24 to position the seat valve 2 and the actuator 4. in this way,
When the seat valve 2 and the actuator 4 are assembled, the tip 16a of the valve shaft 16 protruding from the end surface 6a of the housing 6 of the seat valve 2 penetrates the plate 46 attached to the inner surface of the sleeve piston 26, It is inserted into the hole 30c of the tubular portion 30b of the center piston 30. Since the first spring 22 for biasing the valve shaft 16 is set to have a stronger spring force than the third spring 54 between the center piston 30 and the sleeve piston 26, when the valve shaft 16 is inserted, the center piston 30 is pushed up toward the bottom portion 26a of the sleeve piston 26, and the tip of the shaft-shaped portion 30a abuts the bottom surface of the recess 26c of the sleeve piston 26.

[0016]

When the exhaust gas recirculation valve is not in operation, the chambers 42, 52 and 56 are opened to the atmosphere with both the first and second solenoid valves off. The sleeve piston 26 is pushed by the third spring 54 and abuts on the inner surface of the bottom portion 24 a of the actuator housing 24. Further, the valve shaft 16 causes the actuator 4 to move by the first spring 22.
When the valve body 18 is urged to the side, the valve body 18 is seated on the valve seat 10 to close the exhaust gas circulation passage 8, and the tip 16a of the valve body 18 abuts against the end surface of the cylindrical portion 30b of the center piston 30 in the hole 30c. The sleeve piston 26 is pushed up toward the bottom 26a. If the axial dimensions of the sleeve piston 26 and the center piston 30 of the actuator 4 and the respective parts of the valve shaft 16 of the seat valve 2 are accurate, the valve shaft 18 is seated on the valve seat 10 and the valve shaft 16 The tip of the shaft portion 30a of the center piston 30 pushed up by the sleeve piston 2
The bottom surface of the concave portion 26c of No. 6 is abutted.

However, each of the parts 26, 30, 1
There is a possibility that the dimensions of 6 will vary, and if these axial dimensions have variations on the plus side, the tip 16a of the valve shaft 16 will be located at the center piston 30.
When the center piston 30 hits the sleeve piston 26, the valve element 18 does not sit on the valve seat 10 and the valve remains open.

On the contrary, the parts 26, 30, 16
If there is a variation in the axial dimension of the negative side, the tip of the shaft portion 30a of the center piston 30 pushed up by the tip of the valve shaft 16 with the valve closed,
In some cases, the sleeve piston 26 did not come into contact with the sleeve piston 26, and there was a gap between the sleeve piston 26 and the sleeve piston 26. As described above, when the center piston 30 does not come into contact with the sleeve piston 26 during the non-operation and there is a gap, the center piston 3
Since 0 is displaced from the set position toward the seat valve 2, the stroke amount of the center piston 30 becomes smaller than L ₁ when the valve is opened, and the valve opening amount is insufficient. . In particular, in the structure of the conventional exhaust gas recirculation valve, the stroke amounts L ₂ and L ₃ are determined only by the valve actuator 4 side, but L ₁ is the actuator 4 and the valve shaft 1 on the seat valve 2 side.
Therefore, there is a large possibility that variations will occur. Further, the exhaust gas recirculation valve is designed to gradually increase the valve opening amount by switching the operation of the solenoid valve, and the valve opening amount L ₁ of the first stage is set small, so that the stroke However, there is a drawback in that the variation in the value greatly affects the flow rate.

As described above, when the stroke amount of the center piston 30 varies due to the variation in the axial dimension of each of the parts 26, 30, and 16, it is necessary to adjust this. This is dealt with by changing the thickness of the plate 46 attached to the inner surface and restricting the moving end of the center piston 30. However, in this adjustment, it was necessary to assemble the entire exhaust gas recirculation valve once, measure the position, and then disassemble and install the plate 46 having an optimum thickness.
Such adjustment is time-consuming and tedious.

Further, the conventional exhaust gas recirculation valve is
Since the valve shaft 16 is made of steel and the center piston 30 is made of aluminum for weight reduction, the tip 16a of the valve shaft 16 should be brought into direct contact with the bottom surface of the tubular portion 30b of the center piston 30 as described above. In the configuration described above, there is also a problem that the valve lift amount changes due to wear of the aluminum center piston 30 after the durability test.

The present invention has been made in order to eliminate the above-mentioned drawbacks, and provides an exhaust gas recirculation valve capable of extremely easily adjusting the valve lift amount during assembly without disassembling the actuator. That is the purpose. It is another object of the present invention to provide an exhaust gas recirculation valve capable of preventing the valve lift amount from changing after a durability test.

[0022]

An exhaust gas recirculation valve according to the present invention opens and closes a seat valve that opens and closes a circulation passage for exhaust gas and a valve body of the seat valve to advance and retract. The seat valve is provided with a valve actuator, and the seat valve is advanced and retracted by a valve seat formed in a circulation passage of exhaust gas provided in the valve housing and a valve shaft movably supported in the valve housing. The valve actuator includes a valve body and a spring that biases the valve shaft to seat the valve body on a valve seat. The valve actuator is slidably held in the actuator housing and an actuator housing fixed to the valve housing. Sleeve piston and a center pistol held inside the sleeve piston so that they can move relative to each other by a predetermined amount. A spring having a weaker spring force than the spring that is disposed between the center piston and the sleeve piston to urge the center piston in a direction to press the valve shaft and to urge the sleeve piston in the opposite direction. When the seat valve is not in operation, the valve shaft biased by the spring pushes up the center piston, and the sleeve piston is brought into contact with the actuator housing by the spring having a weak spring force. Further, a seat member is arranged between the valve shaft and the center piston, and the stroke amount of the center piston with respect to the sleeve piston is adjusted by appropriately selecting the thickness of the seat member. is there.

In the exhaust gas recirculation valve having the above structure, since the valve shaft pushes up the center piston via the seat member, there is variation in the size of the valve shaft, and the valve shaft is longer than the standard size. In this case, the stroke amount of the center piston can be made equal to the set value by thinning the seat member by that amount, so that the problem that the valve does not close when it is not operated does not occur. On the contrary, when the dimension of the valve shaft is shorter than the reference dimension, the required stroke amount can be secured by increasing the thickness of the seat member accordingly.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments shown in the drawings. FIG. 1 is a vertical cross-sectional view of an exhaust gas recirculation valve according to an embodiment of the present invention. Since the basic structure is the same as the conventional one shown in FIGS. 4 and 5, the same parts are not shown. The same reference numerals are given and the description thereof is omitted.
In this embodiment, between the center piston 30 of the actuator 4 and the tip 16a of the valve shaft 16 inserted into the tubular portion 30b of the center piston 30,
A disc-shaped sheet member 60 is interposed. In this seat member 60, the end surface of the sleeve piston 26 (the right end surface in FIG. 1) contacts the bottom portion 24a of the actuator housing 24, and the tip of the shaft-shaped portion 30a of the center piston 30 contacts the bottom surface of the recess 26c of the sleeve piston 26. In contact with each other and the tip 16a of the valve shaft 16 is in contact with the center piston 30 through the seat member 60,
The valve body 18 of the seat valve 2 is seated on the valve seat 10,
The thickness is set so that the exhaust gas circulation passage 8 is closed. Therefore, the valve shaft 16 of the present embodiment is shorter than the valve shaft 16 of the conventional configuration by the thickness of the seat member 60. Further, as the material of the sheet member 60, a highly durable steel material is used in order to avoid a positional change due to wear.

The seat member 60 is prepared in advance to have a plurality of different thicknesses, and has an optimum thickness for obtaining a predetermined valve lift amount when the seat valve 2 and the actuator 4 are assembled. Is selected and inserted between the center piston 30 and the tip 16a of the valve shaft 16. The procedure for selecting the optimum seat member 60 will be described. The seat valve 2 alone (a state in which only the seat valve 2 side is assembled into a sub-assembly).
And the end surface 6a of the housing 6 on the actuator 4 side.
And the distance L ₁₀ from the tip surface of the valve shaft 16 is measured.

On the other hand, the actuator 4 is also a single body (only the actuator 4 is assembled into a sub-assembly).
Then, the seat valve 2 side end surface 24f of the actuator housing 24 and the cylindrical portion 30 of the center piston 30 are
Measure the distance L ₂₀ to the bottom of b. Note that FIG.
Then, since the actuator 4 and the seat valve 2 are assembled, the center piston 30 is pushed toward the bottom portion 26a side of the sleeve piston 26 by bending the third spring 54, but when the distance L ₂₀ is measured. Is performed by the actuator 4 alone, the center piston 3
0 is pushed by the third spring 54 and the plate 46
Is in contact with In this state, the distance L ₂₀ is measured. In this case, by turning on the first solenoid valve, air is introduced into the chamber 52 between the shaft-shaped portion 30a of the center piston 30 and the inner surface of the sleeve piston 26 via the chamber 42 and the passage hole 26d, The center piston 30 may be forcibly pressed against the plate 46, as in the operation.

The distance L ₁₀ between the end surface 6a of the valve housing 6 on the actuator 4 side and the end surface of the valve shaft 16, the end surface 24f of the actuator housing 24 on the seat valve 2 side, and the tubular portion 30b of the center piston 30. The distance L ₂₀ from the bottom surface of the sheet member 60 is measured individually, and then the stroke amount L ₁ of the center piston 30 set in advance is added to the difference between these distances to calculate the thickness of the sheet member 60. When the seat valve 2 and the actuator 4 are assembled (see the first expression below), the seat member 60 having this thickness is inserted into the tubular portion 30b of the center piston 30. The thickness of the sheet member _{60 = L 20 -L 10 + L} 1 ............ (1) formula

As described above, the sleeve piston 26
With the actuator housing 24, the center piston 30 with the sleeve piston 26, and the valve element 18 of the seat valve 2 seated on the valve seat 10, the tip 16a of the valve shaft 16 and the center The end surface of the piston 30 inside the tubular portion 30b is the seat member 6
Since the thickness of the seat member 60 is selected so that the contact is made via 0, an accurate valve lift amount L ₁ can be obtained. Moreover, when assembling the exhaust gas recirculation valve, the valve lift amount can be easily adjusted without disassembling the actuator 4 as in the conventional case.
Further, in this embodiment, since the seat member 60 is made of steel, it is prevented that the valve lift amount changes after the durability test because the valve shaft 16 directly hits the aluminum center piston as in the conventional case. it can.

Here, an example of the operation of the apparatus of this embodiment having the above-mentioned configuration will be described with reference to FIGS. The exhaust gas recirculation valve shown in FIG. 1 is capable of controlling the valve lift amount in four steps. The exhaust gas recirculation valve controls the exhaust gas recirculation amount and the intake throttle valve 110. By combining it with the control of the fresh air amount by, it is possible to obtain the optimum mixing ratio according to the engine speed and the engine load.

First, when the exhaust gas recirculation valve is not operated (during the first stage operation), it is formed between the annular body 32 and the annular piston 28 fixed to the opening side of the actuator housing 24. The first solenoid valve for supplying and exhausting air into and out of the chamber 42 is turned off, and the bottom portion 24a of the actuator housing 24 and the sleeve piston 26 are
The second solenoid valve for supplying and exhausting air to and from the chamber 56 between the bottom portion 26a of the above is also turned off. In this state, both chambers 42, 5
6 and sleeve piston 26 and center piston 30
Since air pressure does not act on any of the chambers 52 between the valve piston 16 and the valve piston 16, the three pistons of the sleeve piston 26, the annular piston 28, and the center piston 30 of the actuator 4 and the valve shaft 16 of the valve seat 2 are all springs 22. , 44, 54 to stop in the non-actuated position shown in FIG. In this state, the valve body 18 integrated with the valve shaft 16 is seated on the valve seat 10 to close the valve, and the exhaust pipe 104 and the intake pipe 102 of the diesel engine 100 are shut off and recirculated to the intake side. The exhaust gas is zero.

During the second stage operation of the exhaust gas recirculation valve, the second solenoid valve for supplying and exhausting air into the chamber 56 between the bottom portion 24a of the actuator housing 24 and the bottom portion 26a of the sleeve piston 26 is turned off. The first solenoid valve for supplying and exhausting air to and from the chamber 42 between the annular body 32 and the annular piston 28 is turned on while keeping the above state. Then, the pressure air introduced into the chamber 42 between the ring-shaped body 32 and the ring-shaped piston 28 passes through the wall surface of the sleeve piston 26 through the passage hole 26.
It is also introduced into the chamber 52 between the sleeve piston 26 and the center piston 30 via d to urge the center piston 30 to the seat valve 2 side.

The center piston 30 is moved by this air pressure to a position where it hits a plate 46 attached to the opening side of the sleeve piston 26. That is,
The center piston 30 strokes toward the seat valve 2 side by L ₁ and pushes the valve shaft 16 to the left in FIG. 1 by the same amount. As a result, the valve body 18 fixed to the valve shaft 16 is separated from the valve seat 10 by L _1, and the exhaust gas circulation passage 8 is communicated with the exhaust gas, and a part of the exhaust gas discharged from the diesel engine 100 is sucked in. Reflux to. At this time, since the second solenoid valve is off,
Air pressure does not act on the sleeve piston 26, and the sleeve piston 26 is stopped by hitting the bottom portion 24 a of the actuator housing 24 by the third spring 54. In addition, the annular piston 28 also has the second spring 4
4 and the air pressure in the chamber 42 are acting,
Has stopped at the position.

During the operation of the third stage, the second solenoid valve is turned on in addition to the first solenoid valve. Then, the sleeve piston 26 moves to the seat valve 2 side by the air pressure introduced into the chamber 56 on the bottom portion 26a side. At this time, the annular piston 28 is pressed against the stepped portion 24d of the actuator housing 24 by the force of the second spring 44 and the air pressure in the chamber 42, similarly to the operation of the second stage. Therefore, the sleeve piston 26 moves by L _{2 to a} position where it abuts on the annular piston 28, and stops. Further, the center piston 30 moves by L _{1 with} respect to the sleeve piston 26 due to the pressure in the chamber 52 between the sleeve piston 26 and the center piston 30. Therefore, the amount of movement of the center piston 30 as a whole is L ₁ + L ₂ , and this amount is the amount of movement of the valve shaft 16
Is moved to separate the valve body 18 from the valve seat 10, and the circulation passage 8 in the valve housing 6 is opened slightly larger than in the second stage.

Further, during the operation of the fourth stage, the second solenoid valve remains on and the first solenoid valve is turned off. When the first solenoid valve is turned off, the annular body 32 and the annular piston 28
The air pressure in the chamber 42 between and and the chamber 52 between the sleeve piston 26 and the center piston 30 is released. At this time, the bottom portion 26a of the sleeve piston 26
Air pressure acts only on the side, so sleeve piston 2
6 presses the center piston 30 to push the seat valve 2
While stroking to the side, the annular piston 28 is also pressed to integrally stroke to the seat valve 2 side. Chamber 5 between center piston 30 and sleeve piston 26
Since the air pressure does not act inside 2, the tip of the shaft-shaped portion 30a of the center piston 30 has a sleeve piston 26
Of the sleeve piston 26. Therefore, the sleeve piston 26 has a large diameter portion 26b in the annular piston 28.
The distance L ₂ until the contact with the annular piston 28
The valve shaft 16 moves by a distance including the distance L ₃ up to the point 2 and the valve shaft 16 also moves by L ₂ + L ₃ via the center piston 30 to open the valve to the maximum extent.

Next, an exhaust gas recirculation valve according to the second embodiment of the present invention will be described with reference to FIG. Since this exhaust gas recirculation valve has the same basic configuration as that of the first embodiment, the same parts are designated by the same reference numerals and description thereof is omitted. In this embodiment, the shaft-shaped portion 3 of the center piston 30 pushed up by the valve shaft 16 in the non-operating state, that is, in the state where the valve body 18 fixed to the valve shaft 16 is seated on the valve seat 10.
A gap 70 is provided between the tip of the groove 0a and the bottom surface of the recess 26c of the sleeve piston 26. in this way,
By positively providing the gap 70 between the sleeve piston 26 and the center piston 30, even if there is a variation in the position of the valve shaft 16, the valve can be surely closed when not operating.

Also in this embodiment, the distance L between the end surface 6a of the valve housing 6 on the actuator 4 side and the tip surface of the valve shaft 16 is the same as in the first embodiment.
₁₀ , the end face 24f of the actuator housing 24 on the seat valve 2 side, and the cylindrical portion 3 of the center piston 30.
After measuring the distance L ₂₀ between the bottom surface of 0b and the bottom surface individually, the stroke amount L ₁ of the center piston 30 set in advance is added to the difference between these distances to determine the thickness of the sheet member 60. Since the seat member 60 having this thickness is arranged between the center piston 30 and the valve shaft 16, the stroke amount L is calculated even if the gap 70 is provided.
There is no variation in ₁ . However, at the time of the operation of the fourth stage in which the sleeve piston 26 strokes together with the annular piston 28, the stroke amount decreases by the amount of the gap 70. However, in this case, the valve opening amount is large, so the fluctuation of the stroke amount is a problem. do not become.

[0037]

As described above, according to the present invention, the seat valve that opens and closes the exhaust gas circulation passage and the valve actuator that opens and closes the passage by moving the valve body of the seat valve forward and backward are provided. The seat valve includes a valve seat formed in a circulation passage for exhaust gas provided in a valve housing, a valve body that is moved forward and backward by a valve shaft that is supported in the valve housing so as to move forward and backward, and a valve. And a spring for biasing the shaft to seat the valve element on the valve seat, wherein the valve actuator includes an actuator housing fixed to the valve housing, and a sleeve piston slidably held in the actuator housing. , The center piston held in the sleeve piston so as to be relatively movable by a predetermined amount, and the center piston And a spring having a weaker spring force than the spring for urging the center piston in a direction to press the valve shaft and urging the sleeve piston in the opposite direction, the spring being disposed between the stone and the sleeve piston. In the exhaust gas recirculation valve in which the valve shaft biased by the spring pushes up the center piston and the sleeve piston abuts the actuator housing by a spring having a weak spring force when the seat valve is not operating, By disposing a seat member between the valve shaft and the center piston, and by appropriately selecting the thickness of the seat member, by adjusting the stroke amount of the center piston with respect to the sleeve piston,
A predetermined stroke amount can be obtained simply by appropriately replacing the seat member interposed between the seat valve and the valve actuator, and the adjustment of the stroke amount is extremely simple.

Further, since the seat member is made of steel and the tip of the valve shaft that moves forward and backward does not directly contact the aluminum center piston, the stroke amount changes due to wear after the durability test. Can be prevented.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of an exhaust gas recirculation valve according to an embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view of an exhaust gas recirculation valve according to a second embodiment of the present invention.

FIG. 3 is a schematic view showing an example of a general exhaust gas recirculation system.

FIG. 4 is a vertical sectional view of a conventional exhaust gas recirculation valve.

FIG. 5 is an enlarged vertical sectional view showing an actuator of a conventional exhaust gas recirculation valve.

[Explanation of symbols]

2 seat valve 4 valve actuator 6 valve housing 8 exhaust gas circulation passage 10 valve seat 16 valve shaft 18 valve body 22 spring 24 actuator housing 26 sleeve piston 30 center piston 54 weak spring force 60 seat member L ₁ stroke amount

Claims (4)

[Claims] 1. A seat valve for opening and closing an exhaust gas circulation passage, and a valve actuator for advancing and retracting a valve body of the seat valve to open and close the passage. The seat valve is provided in a valve housing. Valve seat formed in the exhaust gas circulation passage, a valve body that is moved forward and backward by a valve shaft that is supported in the valve housing so that it can move forward and backward, and a valve body that biases the valve shaft to move the valve seat. The valve actuator has a spring to be seated on the valve housing, and the valve actuator includes an actuator housing fixed to the valve housing, a sleeve piston slidably held in the actuator housing, and a relative movement within the sleeve piston by a predetermined amount. Between the center pistons that are held possible and between these center pistons and the sleeve piston And a spring having a spring force weaker than that of the spring for biasing the center piston in a direction to press the valve shaft and biasing the sleeve piston in the opposite direction. In the exhaust gas recirculation valve in which the valve shaft biased by the spring pushes up the center piston and the sleeve piston is brought into contact with the actuator housing by the spring having a weak spring force, the valve shaft and the center piston are An exhaust gas recirculation valve, wherein a stroke amount of a center piston with respect to a sleeve piston is adjusted by arranging a seat member therebetween and appropriately selecting the thickness of the seat member. 2. The thickness of the seat member is such that the amount of protrusion of the valve shaft from the end face of the valve housing on the actuator side of the seat valve alone is L _10, and the end face of the actuator housing on the seat valve side of the actuator alone. And the distance between the center piston and the surface with which the seat member abuts is L _20, and the set stroke amount of the center piston with respect to the sleeve piston during operation is L ₁ , which is determined by the following equation (1). The exhaust gas recirculation valve according to claim 1, which is characterized in that. L ₂₀ −L ₁₀ + L ₁ ………… (1) Formula 3. The exhaust gas recirculation valve according to claim 1, wherein the seat member is made of steel. 4. A gap is formed between the other end of the center piston pushed up by the valve shaft and the sleeve piston in a state where the valve element is seated on the valve seat. Exhaust gas recirculation valve.