JP2002285918A - Exhaust gas control valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent sticking of shaft due to clogging of particles or the like contained in exhaust gas between a sliding face of the shaft, to which a valve element is mounted and a sliding face of a bushing supporting the shaft, in an exhaust gas control valve used for an ECR apparatus of an internal combustion engine. SOLUTION: A valve element 9 of opening-out valve type opening/closing a valve seat opening 8 from the outside is attached to one end of the shaft 10; the bushing 11 slidably supports the shaft 10 in the axial direction; if the exhaust gas passing at a time of opening the valve on a part of a surface of the shaft 10 projecting from and entering into the bushing 11 and the fine particles included in the exhaust gas is deposited on the part, the shaft 10 is likely to stick, because the deposit is caught between the sliding faces. As a countermeasure, a relief groove 31, projecting from the busing 11 and entering into the busing, is formed in the part of the surface of the shaft 10 projecting from and entering into the bushing and around the part to form the deposit, so that a clearance remains formed in between the shaft 10 and the busing 11 prevents the sticking of the shaft.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an exhaust gas control valve used for an exhaust gas recirculation device (EGR device) in an internal combustion engine.

[0002]

2. Description of the Related Art An exhaust gas control valve used in an EGR device of an internal combustion engine is provided for controlling the opening and closing of an EGR passage through which exhaust gas containing fine particles such as combustion residues and carbon flows. When fine particles adhere to the surface of the shaft with the valve attached to form a deposit,
The deposit is caught in the minute gap between the shaft and the cylindrical sliding surface of the bushing (bearing) that slidably supports the shaft, so that the shaft is fixed to the sliding surface of the bushing ( Due to the sticking, the exhaust gas control valve may not be able to open and close smoothly depending on the actuator including the diaphragm or the like.

In order to solve this problem, Japanese Utility Model Application Laid-open No.
In the exhaust gas control valve described in Japanese Patent No. 11181, as a so-called "inner opening valve", a part of a shaft having a valve body attached to one end and capable of opening and closing the inside of a valve seat opening is provided. A first cylindrical body attached to the bushing so as to cover the base and extending toward one end of the shaft; a base fixed to the valve body and extending toward the other end of the shaft to form a portion of the shaft; And a second cylindrical body that covers the first cylinder when at least the valve body is at the valve-open position.
The cylindrical body of the second cylindrical body enters the inside of the second cylindrical body, so that those cylindrical bodies partially overlap,
By covering the periphery of the shaft with the two cylinders in the valve-open state, it is possible to prevent particulates and the like in the exhaust gas from adhering to the surface of the shaft.

[0004]

However, for example, when the exhaust gas control valve is configured as a so-called "opening valve" for the purpose of making it difficult to close the valve seat opening, that is, the valve body is In an exhaust gas control valve in which a shaft opens and closes a valve seat opening outside the valve seat opening, a turbocharger such as a turbocharger is attached to the internal combustion engine, as is often seen recently. In the case or when the pressure of the exhaust gas becomes high, the shaft of the exhaust gas control valve is
Even if it is covered by two overlapping cylinders, a small amount of exhaust gas penetrates into the interior of the cylinder through the gap between the two cylinders due to the high pressure of the exhaust gas. As a result, fine particles and the like in the exhaust gas may adhere to the surface of the shaft, and may stick the bushing to the shaft after a long use period.

[0005] The present invention addresses the problem of sticking of the shaft and bushing due to deposits, which is particularly likely to occur in the exhaust valve of the open-open type, and is used for a long time at a high exhaust gas pressure. However, an object of the present invention is to provide an improved exhaust gas control valve which does not cause the shaft to stick.

[0006]

SUMMARY OF THE INVENTION The present invention provides an exhaust gas control valve according to claim 1 as a means for solving the above-mentioned problems in the prior art.

In the exhaust gas control valve of the present invention, a portion of the shaft which may come into contact with the exhaust gas and goes into and out of the bushing, and a portion of the shaft up to a predetermined distance on both axial sides thereof. , An annular deposit relief groove is formed on the outer periphery of the shaft. Therefore, even if the fine particles and the like contained in the exhaust gas adhere to and accumulate in the annular deposit relief groove, the fine particle deposition layer (deposit)
A gap is formed between the surface of the deposit and the sliding surface of the bushing until the thickness of the bushing fills the depth of the deposit escape groove.

The effect of the exhaust gas control valve of the present invention is remarkable when the exhaust gas control valve is constituted as a so-called external opening valve in which the valve body opens and closes the valve from the outside of the valve seat opening where the shaft has passed through the valve seat opening. Become. That is, in the case of the outward opening valve, a portion of the shaft that goes out of the bushing (exhaust gas flow path) when the valve is opened is exposed to the exhaust gas, and the deposit adheres to that portion. When the valve is closed, the portion enters the inside of the bushing, so that the deposit is easily bitten between the surface of the portion of the shaft and the sliding surface of the bushing. If a deposit escape groove is formed in that portion according to the present invention, fine particles and the like in the exhaust gas accumulate in the deposit escape groove to form a deposit, so that between the surface of the deposit and the sliding surface of the bushing. As a result of the formation of the gap, the sticking of the shaft can be avoided even with the outward opening valve.

In the exhaust gas control valve according to the present invention, a stepping motor is used as an actuator, and the combination with a screw mechanism for converting the forward / reverse rotation into a reciprocating motion in the axial direction of the shaft. However, an accurate valve body driving mechanism can be obtained. Therefore, a large control force is exerted as compared with a diaphragm actuator or the like, and an appropriate exhaust gas flow rate is generated by an accurate valve opening.

The first and second sleeves partially overlapping each other as in the prior art can be configured to close the space surrounding the portion of the shaft that enters and exits the bushing. . As a result, the amount of the fine particles adhering in the deposit relief groove formed on the shaft is reduced and it becomes difficult to deposit the fine particles, so that the depth of the deposit relief groove can be reduced.

The depth of the deposit relief groove formed on the surface of the shaft is, for example, 300,000 km in terms of the traveling distance of the vehicle.
During the lifetime of a sufficiently long exhaust gas control valve, the thickness of a deposit formed by depositing and depositing fine particles and the like contained in the exhaust gas on the shaft surface is measured,
If the thickness is determined by multiplying the thickness by a predetermined safety factor, an appropriate depth can be easily determined.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of a specific embodiment of an exhaust gas control valve according to the present invention will be described with reference to the accompanying drawings. Figure 1
1 shows an overall vertical cross section of an exhaust gas control valve 1 as an embodiment of the present invention. Reference numeral 2 denotes a valve housing, which has an exhaust gas inlet 3 and an outlet 4 as openings.
Since the exhaust gas control valve 1 is used in an EGR device of an internal combustion engine, the inlet 3 is connected to an exhaust passage of the internal combustion engine by a conduit (not shown), and the outlet 4 is also connected to an intake passage. An inlet chamber 5 and an outlet chamber 6 are formed inside the housing 2 as independent spaces, and each communicates with the inlet 3 or the outlet 4. A nozzle 7 made of stainless steel or the like is provided as a partition member between the inlet chamber 5 and the outlet chamber 6. A valve seat opening 8 is formed in the nozzle 7.

The exhaust gas control valve 1 in the illustrated embodiment is a so-called "opening valve", and a stainless steel valve body 9 capable of closing a valve seat opening 8 from the inlet chamber 5 side is also made of stainless steel. It is attached to one end (lower end) of a cylindrical rod-shaped shaft 10 gently penetrating the center of the seat opening 8. The shaft 10 is supported by a cylindrical sliding surface of a bushing (bearing) 11 made of carbon (graphite) attached to the housing 2 so as to be able to move in the axial direction together with the valve body 9.

In substantially the same manner as in the prior art described above, the base end is attached to the bushing 11 side and extends toward one end (lower end) of the shaft 10 so that a stainless steel covering a part of the shaft 10 is formed. First sleeve 12
And a portion having a larger diameter than that of the
A second sleeve 13 that is attached to the valve body 9 at one end and extends toward the other end (upper end) to cover a part of the shaft 10 is provided. The first sleeve 12 and the second sleeve 13 are configured to cover the surface of the shaft 10 by partially overlapping the first sleeve 12 and the second sleeve 13 even when the valve is fully lowered and the valve seat opening 8 is fully opened. .

An oil seal 14 made of fluoro rubber is provided at a portion after the shaft 10 has penetrated the bushing 11 upward from the outlet chamber 6 side, and is provided at the other end (upper end) of the shaft 10 extending further upward. Is mounted with a plate 15 formed by drawing a galvanized steel plate into a deep dish shape. A compression spring 17 made of stainless steel is mounted between the peripheral portion of the plate 15 and the seal retainer 16 fitted to the housing 2, and the valve body 9 is always closed through the plate 15 and the shaft 10. It is urging toward.

In order to move the valve body 9 to the valve-opening position against the urging force of the compression spring 17, the inside of a housing consisting of a mounting seat 19 and a cover 20 fastened to the upper end of the valve housing 2 by bolts 18. Is provided with a step motor 21 as an actuator. The structure of the step motor 21 is well known, and a plurality (for example, four sets) of coils 22 are provided in a fixed field portion. The coil 22 is connected to the terminal 2 from an external control device or the like.
A pulse-like drive current is supplied via the switch 3. The rotation shaft 2 of the step motor 21 is rotated so as to be able to rotate on the extension of the shaft 10 inside the field portion.
4 is pivotally supported by the cover 20 and the mounting seat 19 via bearings 25 and 26. The rotating shaft 24 has a cylindrical shape as a whole and magnetic poles N, S, N,
A rotor 27 composed of a permanent magnet magnetized in many parts is attached so that S,... Appear.

A male screw portion 28 is formed in an extension below the rotary shaft 24, and is formed of a hard synthetic resin (PPS) column fitted to the upper edge of the plate 15 described above. It is screwed with the female screw part 30 formed at 29. Since the rotation of the column 29 itself is prevented by the cross-shaped groove formed in the mounting seat 19 and the guide mechanism engaged with the groove, the male screw 28 rotates together with the rotation shaft 24 of the step motor 21. At times, the column 29 moves only in the vertical direction.

The stepping motor 21 constituting the actuator and the screw mechanism linked therewith have such a structure, so that when a pulse-like driving current flows from the external control device or the like to the coil 22, the rotating shaft 24 is moved to a predetermined position. The rotation is performed by an angle corresponding to the number of pulses input to the coil 22 in the forward or reverse direction in units of a small rotation angle. When the rotation shaft 24 rotates, the screw mechanism operates to rotate the rotation shaft 24 by a direction and a distance corresponding to the rotation direction and the rotation angle.
The column 29 moves up and down. Column 2
As the shaft 10 connected via the plate 15 moves up and down along with the movement of the valve 9, the size of the gap between the valve element 9 and the valve seat opening 8 changes in the valve-open state,
The amount of exhaust gas flowing from the inlet chamber 5 to the outlet chamber 6 can be adjusted. Further, when the valve body 9 contacts the valve seat opening 8 from the outside and takes the valve closing position, the flow of exhaust gas diverted from the exhaust passage of the internal combustion engine and returned to the intake passage is completely shut off, and the EGR amount is reduced. Can be set to zero.

When the exhaust gas control valve 1 is in the open position, the exhaust gas diverted from the exhaust passage of the internal combustion engine passes from the inlet chamber 5 through the gap between the valve seat opening 8 and the valve body 9 to the outlet chamber 6. Since the exhaust gas flows into the outlet chamber 6, the outlet chamber 6 is filled with the exhaust gas.
And the second sleeve 13 partially overlap to close the space around a portion of the shaft 10 that enters and exits the bushing 11, so that the exhaust gas enters the space closed by the sleeves 12 and 13. It is possible to prevent the shaft 10 from coming into contact with the surface of the shaft 10 immediately.

However, when the exhaust gas pressure is high, when the exhaust gas control valve 1 is opened, a small amount of exhaust gas passes through the gap between the two sleeves 12 and 13 and enters the internal space. Since it is almost impossible to completely prevent the exhaust gas from entering, the fine particles and the like contained in the exhaust gas that has entered for a long period of time gradually adhere to the surface of the shaft 10 to form a deposit. In particular, as in the illustrated embodiment,
In the case where the valve body 9 is in the form of an open valve with respect to the valve seat opening 8, if a deposit adheres to a portion of the shaft 10 that comes out of the bushing 11 when the valve is opened, that portion is closed together with the deposit when the valve is closed. 11, the deposit is caught between the surface of the shaft 10 and the sliding surface of the bushing 11, the shaft 10 and the bushing 11 are fixed, and the exhaust gas control valve 1 becomes inoperable. Is likely to be

In order to avoid the possibility of such a trouble, in the illustrated embodiment, as shown in FIG. 2 in an enlarged manner, the shaft 10 is inserted into the bushing 11 when the exhaust gas control valve 1 is opened and closed. Not only the part that goes in and out,
An annular deposit relief groove 31 having a constant depth is formed by turning so as to include portions at predetermined small distances on the upper and lower sides. Thereby, the shaft 1
At 0, a small-diameter portion 32 is formed at a portion that goes into and out of the bushing 11, and at a portion near the portion.

Even if a small amount of exhaust gas enters the internal space through the gap between the sleeves 12 and 13 and the fine particles contained in the exhaust gas adhere to and accumulate on the surface of the shaft 10, Since the deposit escape groove 31 is formed in a portion of the bushing 10 that goes into and out of the bushing 11 and in the vicinity thereof, the fine particles adhere to the surface of the small diameter portion 32 in the deposit escape groove 31. Therefore, for example, by examining the thickness of a deposited layer of fine particles (deposit) while the vehicle travels its useful distance of 300,000 km, it is sufficiently deeper than the thickness. If the deposit relief groove 31 is formed at the problematic part on the shaft 10,
Even if deposits accumulate in the deposit escape groove 31, a sufficiently large gap remains between the surface of the deposit and the sliding surface of the bushing 11, so that the shaft 10 and the bushing 11 cannot be fixed.

When numerical values are specifically exemplified, as shown in FIG. 3, when the diameter of the shaft 10 is 6 mm,
If the diameter of 2 is 5.8 mm, a deposit relief groove 31 having a depth of 0.1 mm is formed. Life of a vehicle equipped with an exhaust gas control valve 1 together with an internal combustion engine (300,000 k
m), the thickness of the deposit varies depending on the environmental conditions of the exhaust gas control valve 1.
Assuming that the thickness is 0 μm, if the deposit relief groove 31 having a depth of 0.1 mm is formed, the safety coefficient becomes a sufficient value of 3 or more. In addition, the deposit relief groove 31 is
Does not need to be formed at a constant depth in the longitudinal direction, and the shape of the bottom surface and the shape of the side surface of the groove can be arbitrarily selected.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of an exhaust gas control valve of the present invention.

FIG. 2 is an enlarged longitudinal sectional view showing a main part of FIG. 1;

FIG. 3 is a longitudinal sectional view illustrating specific dimensions of a main part of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Exhaust gas control valve 8 ... Valve seat opening 9 ... Valve element 10 ... Shaft 11 ... Bushing (bearing) 12 ... 1st sleeve 13 ... 2nd sleeve 21 ... Step motor 22 ... Coil 24 ... Rotating shaft 27 ... Rotation Child 28: Male screw part 30: Female screw part 31: Deposit escape groove 32: Small diameter part

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hideo Endo 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation F-term (reference) 3G062 EC15 3H062 AA02 BB26 CC02 DD11 EE06 HH10

Claims (5)

[Claims] A shaft mounted on one end of a valve body capable of opening and closing a valve seat opening; a bushing for supporting the shaft so as to be slidable in an axial direction thereof; An exhaust gas control valve comprising: an actuator coupled to the other end of the shaft for movement between the valve position and the bushing, the exhaust gas control valve being capable of contacting exhaust gas with the bushing. An exhaust gas control valve, wherein an annular deposit relief groove is formed on the outer periphery of the shaft, extending between a portion that enters and exits and a portion that extends a predetermined distance to both sides in the axial direction of the portion. 2. The valve according to claim 1, wherein the valve element opens and closes the valve seat opening from outside the valve seat opening when viewed from the actuator side, where the shaft has passed through the valve seat opening. An exhaust gas control valve attached to one end of the shaft. 3. The device according to claim 1, wherein the actuator comprises a step motor, and is provided together with a screw mechanism for converting forward and reverse rotation of the step motor into reciprocating motion of the shaft in the axial direction. An exhaust gas control valve. 4. The method according to claim 1, wherein
A first sleeve having a proximal end attached to the bushing side and extending toward one end of the shaft to cover a portion of the shaft that enters and exits the bushing; a first sleeve having a larger diameter than the first sleeve; A second sleeve capable of covering a part of the shaft by having a base end attached to one end of the shaft and extending toward the other end. In any lift position of the body, the first sleeve and the second sleeve are partially overlapped such that they form around the portion of the shaft that enters and exits the bushing. An exhaust gas control valve, wherein the exhaust gas control valve is configured to close a space. 5. The method according to claim 1, wherein
An exhaust gas control valve according to claim 1, wherein a depth of said deposit relief groove is determined based on a thickness of a deposit deposited on a surface of said shaft within a predetermined service life.