JPH11324822A - Exhaust gas reflux control valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely actuate a valve shaft to the maximum stroke even in the case that deposits are built up and solidified on the valve shaft of an exhaust gas reflux control valve. SOLUTION: A baffle 21 is mounted on the EGR gas flow side of a bearing member 20 supporting a valve shaft 18, and in this baffle 21, a slide ring 23 is slidably fitted around the valve shaft 18, and this slide ring 23 is brought into contact with the periphery of the valve shaft penetrating opening 25 of the baffle 21 by a spring 24. In operation of the normal stroke of the valve shaft 18, deposits stuck on the peripheral surface of the valve shaft 18 are scraped away by the slide ring 23. When the valve shaft 18 is operated at the maximum stroke, deposits built up and solidified on the lower side of a normal scraping away range A are collided with the slide ring 23, therefore the valve shaft 18 can be operated to the maximum stroke while pushing up the slide ring 23 in the direction of the bearing member 20 to the spring 24.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas recirculation control valve for controlling an exhaust gas recirculation amount of an internal combustion engine.

[0002]

2. Description of the Related Art Generally, an exhaust gas recirculation control valve (EGR)
In the valve, the valve shaft supporting the valve body is exposed to the flow of the exhaust gas recirculation gas (EGR gas), so that carbon particles, gum components, and the like in the EGR gas adhere to the outer peripheral surface of the valve shaft. Deposit) may hinder smooth sliding of the valve shaft with respect to the bearing member supporting the valve shaft.

Therefore, as shown in Japanese Utility Model Publication No. 60-32368 (see FIG. 5), a cylindrical member is provided on the EGR gas flow side (lower surface side) of the bearing member 1 so as to cover the sliding surface of the valve shaft 2. Attach baffle 3 and
Inside, the cylindrical adhesion preventing member 4 is slidably fitted to the sliding surface of the valve shaft 2, and the adhesion preventing member 4 is brought into close contact with the end surface of the bearing member 1 by the spring 5,
The deposit is prevented from adhering to the sliding surface of the valve shaft 2 in the baffle 3.

[0004]

In the structure disclosed in the above publication, the portion of the valve shaft 2 exposed from the adhesion preventing member 4 is exposed to the EGR gas, so that the deposit adheres. Therefore, the deposit on the outer peripheral surface of the valve shaft 2 is scraped off by the adhesion preventing member 4 as the valve shaft 2 slides.

[0005] In EGR control during normal operation, the valve shaft 2 is often operated with a stroke of about 70% of the maximum stroke (hereinafter referred to as "normal stroke").
For this reason, as shown in FIG. 5A, the deposit is scraped and solidified just outside the range where the deposit is scraped off by the normal stroke (hereinafter, referred to as “normal scraping range”). In this state, when the valve shaft 2 is operated at the maximum stroke to fully open the EGR valve,
On the way, as shown in FIG. 5 (b), the deposit outside the normal scraping range hits the adhesion preventing member 4 supported by the bearing member 1. At the time of contact with the member 4, the movement of the valve shaft 2 is stopped, the valve shaft 2 cannot be operated up to the maximum stroke, and a problem occurs that the exhaust gas recirculation amount cannot be controlled to the target value. .

[0006] The present invention has been made in view of such circumstances, and an object of the present invention is to provide an exhaust system that can reliably operate a valve shaft up to a maximum stroke even when deposits are solidified on the valve shaft. It is to provide a gas recirculation control valve.

[0007]

To achieve the above object, an exhaust gas recirculation control valve according to the first aspect of the present invention comprises a baffle disposed on an exhaust gas recirculation gas flow side of a bearing member. An annular scraping member for scraping off the adhered material on the surface is arranged, the scraping member is slidably fitted to the valve shaft, and the scraping member is biased in a direction away from the bearing member by biasing means. Thus, a predetermined interval is maintained between the scraping member and the bearing member.

In this case, since the valve shaft frequently slides with respect to the scraping member within the normal stroke range of the valve shaft, the valve shaft is held in a fixed position by the urging means. The deposit attached to the outer peripheral surface is scraped off by the scraping member. As a result, the deposit is scraped and solidified just outside the range where the deposit is scraped off by the normal stroke (usually the scraping range). In the present invention, the scraping member can slide in the axial direction. Therefore, when the deposit accumulated on the valve shaft strikes the scraping member when the valve shaft is operated to the maximum stroke, the valve shaft pushes the scraping member against the urging force of the urging means. It operates up to the maximum stroke while pushing and moving to the bearing member side. Thus, even when deposits are solidified on the valve shaft, the valve shaft can be reliably operated up to the maximum stroke.

In this case, the scraping member may be brought into contact with the peripheral portion of the valve shaft insertion opening of the baffle by the urging means. By doing so, within the normal stroke range, the gap between the valve shaft insertion port of the baffle and the valve shaft can be closed with a scraping member, and the inflow of exhaust gas recirculation gas into the baffle can be prevented, The deposit can be prevented from being attached to the sliding surface of the valve shaft in the baffle.

However, in the present invention, the valve shaft insertion opening of the baffle may not be closed by the scraping member. Even in this case, if the gap between the valve shaft insertion opening of the baffle and the valve shaft is set small, Deposits on the sliding surface of the valve shaft in the baffle can be reduced.

In this case, a small amount of deposit adheres to the sliding surface of the valve shaft in the baffle, and this deposit is scraped off at the end face of the bearing member when the valve shaft is operated. However, if the distance between the bearing member and the scraping member is too wide, any one of the bearing member and the scraping member is located between the normal scraping range of the bearing member during the normal stroke and the normal scraping range of the scraping member. In addition, there is an area that is not scraped off, and deposits are deposited and solidified in this area. If the deposit becomes too large, when the valve shaft is operated to the maximum stroke, the deposit may abut on the end face of the bearing member on the way, and smooth sliding of the valve shaft may be hindered.

Therefore, the distance between the scraping member and the bearing member held by the urging means may be set smaller than the normal stroke of the valve shaft. In this way, the normal scraping range by the bearing member,
The normal scraping range by the scraping member overlaps. As a result, there is no area in the baffle where the deposit attached to the valve shaft remains without being scraped off,
The operation reliability of the valve shaft can be improved.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment (1) of the present invention will be described below with reference to FIGS. First, the configuration of the EGR valve (exhaust gas recirculation control valve) 11 will be described. As shown in FIG. 3, a lower part of the valve housing 12 of the EGR valve 11 includes:
An EGR gas introduction port 13 connected to an EGR pipe (not shown) is formed.
, An annular valve seat 14 is attached. EGR gas (exhaust gas recirculation gas) introduced from the EGR gas introduction port 13 flows from the EGR gas outflow port 15 through an EGR pipe (not shown) and is introduced into an intake pipe (not shown).

A stepping motor 16 is mounted on the upper portion of the valve housing 12 as an actuator. A female thread of a connecting member 32 is screwed into a screw portion 31 formed below the rotating shaft 17 of the stepping motor 16, and the upper end of the valve shaft 18 is connected to the connecting member 32 via a plate 33. In this case, the forward / reverse rotation of the rotation shaft 17 of the stepping motor 16 is converted into a vertical movement of the connecting member 32 by the screw portion 31,
The valve shaft 18 moves up and down integrally with the connecting member 32. At the lower end of the valve shaft 18, a valve body 19 that comes into contact with and separates from the valve seat 14 is fixed.

An intermediate portion of the valve shaft 18 is slidably supported by a bearing member 20 fixed to the valve housing 12. EGR gas flow side (lower surface side) of this bearing member 20
A flanged bottomed cylindrical baffle 21 is mounted on the valve shaft 18 so as to cover a portion of the valve shaft 18 near the bearing member 20.

As shown in FIG. 1, a slide ring 23 serving as a scraping member is slidably fitted to the valve shaft 18 in the baffle 21.
Thereby, the deposit on the outer peripheral surface of the valve shaft 18 can be scraped off. A spring 24 (biasing means) such as a coil spring is mounted between the slide ring 23 and the bearing member 20.
This slide ring 23 is urged away from
Are kept in contact with the peripheral portion of the valve shaft insertion port 25 of the baffle 21. Thereby, the baffle 21
The gap between the valve shaft insertion port 25 and the valve shaft 18 is closed by the slide ring 23.

In this case, the distance between the slide ring 23 and the bearing member 20 is set to be smaller than the normal stroke of the valve shaft 18. Here, the normal stroke is a stroke frequently driven by the EGR control during the normal operation, and is, for example, about 70% of the maximum stroke. Further, the movable amount of the slide ring 23 (the maximum compression amount of the spring 24) is set to be larger than the difference between the maximum stroke and the normal stroke.

In the EGR valve 11 configured as described above,
When the valve shaft 18 is at the lower limit position (closed position), the valve body 19 is seated on the valve seat 15 and the EGR gas introduction port 1
3 is closed. When the stepping motor 16 is rotated to move the valve shaft 18 upward, the valve body 1
9 is separated upward from the valve seat 15, and the EGR gas introduction port 13 is opened. As a result, the EGR gas recirculated through the EGR pipe flows from the EGR gas introduction port 13 through the EGR valve 11 to the intake pipe (not shown) from the EGR gas outflow port 15.

During the operation of the EGR valve 11, the valve shaft 18 is exposed to the flow of the EGR gas introduced into the EGR valve 11, so that the carbon particles and the gum component in the EGR gas cause the outer peripheral surface of the valve shaft 18 to move. Deposits adhere. When a large amount of deposit adheres to a portion of the outer peripheral surface of the valve shaft 18 that slides on the bearing member 20 (hereinafter referred to as a “sliding surface”), the valve shaft 18
May be hindered from sliding smoothly.

As a countermeasure against this, in this embodiment (1),
A baffle 21 covers a portion of the valve shaft 18 near the EGR gas flow side of the bearing member 20, and a slide ring 23 closes a gap between the valve shaft insertion port 25 of the baffle 21 and the valve shaft 18. The flow of EGR gas into the baffle 21 is prevented, and the deposit on the sliding surface of the valve shaft 18 in the baffle 21 is prevented.

Even in this case, outside the baffle 21,
The deposit adheres to the outer peripheral surface of the valve shaft 18, but the deposit adhered to the outer peripheral surface of the valve shaft 18 is scraped off by the slide ring 23 when the valve shaft 18 makes a stroke.

In the EGR control during the normal operation, the valve is often operated at a stroke (normal stroke) of, for example, about 70% of the maximum stroke, and the valve shaft 18 frequently contacts the slide ring 23 within the normal stroke range. Since the slide ring 23 slides, the deposit attached to the outer peripheral surface of the valve shaft 18 is scraped off by the slide ring 23 while the slide ring 23 is pressed against the peripheral edge of the valve shaft insertion port 25 of the baffle 21. As a result, as shown in FIG. 1A, the deposit is scraped and solidified just below the range A in which the deposit is scraped off by the slide ring 23 in the normal stroke (hereinafter, referred to as “normal scraping range”) A. It is easy to be in a state where it was done.

Accordingly, when the valve shaft 18 is operated at the maximum stroke and the EGR valve 11 is fully opened, the deposit solidified just below the scraping range A normally hits the slide ring 23 during the normal operation. In the embodiment (1), since the slide ring 23 can slide toward the bearing member 20 by the compression displacement of the spring 24 that biases the slide ring 23, when the deposit hits the slide ring 23, FIG. 2), the valve shaft 18 operates to the maximum stroke while moving the slide ring 23 toward the bearing member 20 against the spring force of the spring 24. Thus, even when the deposit is solidified on the valve shaft 18, the valve shaft 18 can be reliably operated up to the maximum stroke, and the EGR amount (exhaust gas recirculation amount) can be accurately controlled.

When the valve shaft 18 is operated up to the maximum stroke, the slide ring 23 is separated from the valve shaft insertion port 25 of the baffle 21, so that the valve shaft insertion port 25
A small amount of EGR gas enters the baffle 21 from the gap between the valve shaft 18 and the
A small amount of deposit adheres to the sliding surface of the valve shaft, and such a small amount of deposit is generated when the valve shaft 18 is operated.
It is scraped off at the end face of the bearing member 20.

However, the bearing member 20 and the slide ring 2
3 is too wide, the normal scraping range B by the bearing member 20 during the normal stroke and the slide ring 23
Between the normal scraping range A and the bearing member 20 and the slide ring 23, a deposit is deposited and solidified in this region. If the deposit becomes too large, when the valve shaft 18 is operated up to the maximum stroke, the deposit may abut on the end face of the bearing member 20 on the way, and smooth sliding of the valve shaft 18 may be hindered.

As a countermeasure against this, in this embodiment (1),
Since the distance between the slide ring 23 held by the spring 24 and the bearing member 20 is set smaller than the normal stroke of the valve shaft 18, the normal scraping range B by the bearing member 20 and the normal scraping range by the slide ring 23. The range A overlaps. As a result, there is no area in the baffle 21 where the deposit attached to the valve shaft 18 remains without being scraped off, and the valve shaft 18 can be more reliably operated up to the maximum stroke.
The sliding reliability of the valve shaft 18 can be further improved.

However, according to the present invention, the distance between the bearing member 20 and the slide ring 23 does not necessarily have to be set smaller than the normal stroke of the valve shaft 18. 2
If the gap between the valve shaft 5 and the valve shaft 18 is set to be small, the adhesion of the deposit to the sliding surface of the valve shaft 18 in the baffle 21 can be reduced, and the sliding reliability of the valve shaft 18 can be secured.

Further, in the above embodiment (1), the slide ring 23 is brought into contact with the peripheral portion of the valve shaft insertion opening 25 of the baffle 21 by the spring 24, but the embodiment of the present invention shown in FIG. In 2), a spring 28 (biasing means) is provided between the slide ring 27 (scraping member) and the bearing member 20, and the slide ring 2
7 in the direction away from the bearing member 20 and the slide ring 27 and the valve shaft insertion opening 25 of the baffle 21.
An auxiliary spring 29 is provided between the bearing member 20 and the peripheral edge of the bearing member 20 so that the slide ring 27 can be moved in any direction of the bearing member 20 and the valve shaft insertion port 25. Also in this case, the distance between the slide ring 27 held by the springs 28 and 29 and the bearing member 20 is set smaller than the normal stroke of the valve shaft 18 and the movable amount of the slide ring 27 (maximum compression of the spring 28). Is set to be larger than the difference between the maximum stroke and the normal stroke.

In this embodiment (2), the valve shaft insertion port 25 of the baffle 21 is not closed by the slide ring 27. However, if the gap between the valve shaft insertion port 25 of the baffle 21 and the valve shaft 18 is set small. Thus, it is possible to reduce the adhesion of the deposit to the sliding surface of the valve shaft 18 in the baffle 21, and to secure the sliding reliability of the valve shaft 18.

In each of the embodiments (1) and (2),
Although coil-type springs 24 and 28 are used as urging means for urging the slide rings 23 and 27, other types of springs or elastic bodies may be used. Also,
As the actuator for driving the valve shaft 18, a linear solenoid, a negative pressure actuator, or the like may be used instead of the stepping motor 16.

In addition, the present invention can be implemented with various changes without departing from the gist, such as by appropriately changing the shape of the baffle and the slide ring, and by integrally forming the baffle with the valve housing 12. Needless to say.

[Brief description of the drawings]

FIG. 1 is an enlarged longitudinal sectional view of a main part of an EGR valve according to an embodiment (1) of the present invention, in which FIG. 1A shows a state where a valve shaft is at a lower limit position, and FIG. Diagram showing the state of operation up to the stroke

FIG. 2 is an exploded perspective view of a main part.

FIG. 3 is a longitudinal sectional view of an EGR valve.

FIG. 4 is an enlarged longitudinal sectional view of a main part of an EGR valve showing an embodiment (2) of the present invention.

FIG. 5 is an enlarged vertical sectional view of a main part of a conventional EGR valve,
(A) is a diagram showing a state in which the valve shaft is at the lower limit position,
(B) is a diagram showing a state in which the valve shaft has been operated up to the normal stroke.

[Explanation of symbols]

11: EGR valve (exhaust gas recirculation control valve), 13: EGR
Gas introduction port, 14: valve seat, 15: EGR gas outflow port, 16: stepping motor (actuator),
18: valve shaft, 19: valve body, 20: bearing member, 21
... baffle, 22 ... buffer chamber, 23 ... slide ring (scraping member), 24 ... spring (biasing means), 2
5: Valve shaft insertion port, 27: Slide ring (screw-off member), 28: Spring (biasing means), 29: Auxiliary spring.

Claims (3)

[Claims] 1. An exhaust gas recirculation control valve in which a valve shaft provided with a valve element is slidably supported by a bearing member, and a drive stroke of the valve shaft is adjusted by an actuator to adjust an exhaust gas recirculation amount. A baffle provided on the exhaust gas recirculation gas flow side of the bearing member to cover a portion of the valve shaft near the bearing member; and a baffle located in the baffle and sliding on the valve shaft. An annular scraping member that is freely fitted and scrapes off a deposit on the outer peripheral surface of the valve shaft; and an annular scraping member that urges the scraping member in a direction away from the bearing member. An exhaust gas recirculation control valve, comprising an urging means for maintaining a predetermined interval therebetween. 2. The exhaust gas recirculation control valve according to claim 1, wherein said biasing means causes said scraping member to abut on a peripheral portion of a valve shaft insertion opening of said baffle. 3. An apparatus according to claim 1, wherein an interval between said scraping member held by said urging means and said bearing member is set smaller than a normal driving stroke of said valve shaft. 3. The exhaust gas recirculation control valve according to item 1.