JPH06109026A - Bearing structure for high temperature - Google Patents

Abstract

PURPOSE:To surely protect a sleeve which is made of ceramics and holds a shaft, from the external force caused by the thermal deformation of a housing. CONSTITUTION:The first recessed part 21 which extends in the peripheral direction is formed on the outer peripheral surface of the first sleeve 20, and the second recessed part 22 which extends in the peripheral direction is formed on the inner peripheral surface of the first sleeve 20, and a thin part 23 is formed on the first sleeve 20 by superposing the edge part of the first recessed part 21 and the edge part of the second recessed part 22, and the first sleeve 20 is elastically deformed in the radial direction. Accordingly, the thermal deformation of a housing 11 can be absorbed by the first sleeve 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high temperature bearing structure using a ceramic sleeve, and more particularly to a high temperature bearing structure for surely protecting a ceramic sleeve from an external force due to thermal deformation of a housing.

[0002]

2. Description of the Related Art An automobile is equipped with a turbocharger as one of means for increasing engine output. The turbocharger controls the opening of the wastegate valve to increase the rotational speed of the exhaust turbine in the low speed range and controls the amount of exhaust gas flowing into the turbine in the high speed range to prevent turbine overrun. ing.

7 and 8 show the vicinity of a wastegate valve in a conventional turbocharger.
In the figure, 1 indicates a turbine housing, and 2 indicates a turbine rotor. The turbine housing 1 is formed with a bypass passage 3 for allowing exhaust gas from the engine to bypass the turbine rotor 2 and flow. A metal wastegate valve 4 is arranged in the bypass passage 3.

The wastegate valve 4 is connected to the shaft 5, and by rotating the shaft 5 around the axis, the wastegate valve 4 is bypassed by the bypass passage 3.
It is designed to open and close. The shaft 5 is rotatably held by a bush 6 provided in the turbine housing 1.

As one of the prior arts regarding the bearing structure of a turbocharger, Japanese Utility Model Laid-Open No. 62-152033 is known. In the bearing device of the present publication, a sleeve having a small thermal expansion coefficient is interposed between the exhaust passage wall and the shaft,
Gaps are formed at positions axially different from each other between the exhaust passage wall and the sleeve and between the sleeve and the shaft.

[0006]

However, the bearing device of the above publication has the following problems. In the bearing device of the above publication, the fitting area between the housing and the sleeve is reduced due to the formation of the gap. When the housing is deformed by heat,
Since the fitting area of the sleeve functions as a pressure receiving area, a large local force acts on the sleeve due to the reduction of the pressure receiving area.

In order to prevent seizure of the sleeve and the shaft, it is desired that the sleeve is made of ceramic. However, when the fitting area between the housing and the sleeve is reduced as described above, the sleeve made of ceramic is used. Excessive force will act on. Since ceramic is brittle against external force, if the sleeve holding the shaft is simply made of ceramic, the sleeve may be damaged by external force due to thermal deformation of the housing, which is a problem in terms of durability and reliability.

In view of the above problems, it is an object of the present invention to provide a high temperature bearing structure capable of reliably protecting a ceramic sleeve holding a shaft from an external force caused by thermal deformation of a housing. And

[0009]

A high temperature bearing structure according to the present invention which meets the above object has a cylindrical first sleeve made of metal fitted in a metallic housing, and an inner side of the first sleeve. A cylindrical second sleeve made of ceramic is fitted to the first sleeve, the shaft is movably inserted into the second sleeve, and the first sleeve extends circumferentially on the outer peripheral surface of the first sleeve.
And a second recess extending in the circumferential direction on the inner peripheral surface of the first sleeve, and the end of the first recess and the end of the second recess are axially formed. Composed of layers.

[0010]

In the high temperature bearing structure thus constructed, the first sleeve is made of metal and the second sleeve is made of ceramic. Since the first recess made of metal is formed so that the first recess and the second recess overlap in the axial direction, a thin portion is locally formed on the first sleeve, and the first recess is formed. The sleeve is elastically deformable in the radial direction.

Therefore, even if the metal housing is thermally deformed due to high temperature, the deformation amount of the housing can be absorbed by the elastic deformation of the first sleeve. Therefore, an excessive force does not act on the second sleeve made of ceramic, and the second sleeve is reliably protected from being broken by an external force.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the high temperature bearing structure according to the present invention will be described below with reference to the drawings.

First Embodiment FIGS. 1 to 3 show a first embodiment of the present invention.
In particular, it shows the case where it is applied to the opening control mechanism of the waste gate valve of the turbocharger. In the figure, 11 indicates a turbine housing of the turbocharger. The turbine housing 11 is made of metal. A turbine rotor 13 is arranged in the exhaust gas passage 12 formed in the turbine housing 11.

A flange 14 is attached to one side surface of the turbine housing 11. A bypass passage 15 that bypasses the turbine rotor 13 is formed on the upstream side of the turbine housing 11. A cylindrical tube 16 made of ceramic is arranged in the bypass passage 15. A seal groove 17 extending in the circumferential direction is formed on the outer peripheral surface of the cylindrical tube 16. A piston ring 18 as a seal ring is attached to the seal groove 17. The piston ring 18 is in close contact with the inner wall surface of the bypass passage 15, and the hollow portion of the cylindrical pipe 16 functions as the bypass passage 15.

The turbine housing 11 is formed with a wall portion 11a extending parallel to the axial direction of the turbine rotor 13. A mounting hole 19 is formed in the wall portion 11 a so as to penetrate the outside of the turbine housing 11 and the bypass passage 15. The mounting hole 19 has a metal first sleeve 20.
Are fitted. The first sleeve 20 is formed in a cylindrical shape. On the outer peripheral surface of the first sleeve 20, as shown in FIG. 1, a first recess 21 extending in the circumferential direction is formed. The first recess 21 extends from the central portion in the axial direction of the first sleeve 20 to the vicinity of the end portion of the first sleeve 20.

The first sleeve 20 is press-fitted into the mounting hole 19 in this embodiment, so that the first sleeve 20 is fixed to the turbine housing 11. Note that the first sleeve 20 and the mounting hole 19 may be fitted with a clearance fit, and the first sleeve 20 may be fixed to the turbine housing 11 by welding.

A second concave portion 22 extending in the circumferential direction is formed on the inner peripheral surface of the first sleeve 20. The second recesses 22 are located at the ends of the first sleeve 20, respectively. The end of the first recess 21 and the end of the second recess 22 overlap in the axial direction of the first sleeve 20. As a result, the thin portion 23 is formed on the first sleeve 20. The thin portion 23 is easily elastically deformed in the radial direction.

A second sleeve 24 made of ceramic is fitted on the inner peripheral surface of the first sleeve 20. The axial center B of the second sleeve 24 is, as shown in FIG.
Is eccentric by a distance S with respect to the axis A of the sleeve 20. The second sleeve 24 extends from the above-described cylindrical tube 16 toward the wall portion 11a. In this embodiment, the cylindrical tube 1
6 and the second sleeve 24 are manufactured by integral molding. The linear expansion coefficient of the second sleeve 24 is about 1/2 to 1/4 that of the first sleeve 20. The shaft 25 is inserted through the inner peripheral surface of the second sleeve 24. The fitting portion between the first sleeve 20 and the second sleeve 24 is brazed.

The axis B of the second sleeve 24 is set to the first
The eccentricity with respect to the axis A of the sleeve 20 of
This is because the diameter of the mounting hole 19 is made as small as possible, which makes it possible to minimize the exhaust gas leakage from the fitting portion between the turbine housing 11 and the first sleeve 20.

A wastegate valve 26 arranged in the cylindrical tube 16 is connected to one end of a shaft 25 inserted through the second sleeve 24. The shaft 25 and wastegate valve 26 are made of ceramic. In this embodiment, the shaft 25 and the waste gate valve 26 are integrated. The shaft 25 may be made of metal.

A lever 27 is attached to the other end of the shaft 25. The lever 27 is connected to a link mechanism (not shown) and can swing around the shaft 25. The swinging motion of the lever 27 is transmitted to the waste gate valve 26 via the shaft 25, and the flow rate of the exhaust gas flowing through the bypass passage is controlled by adjusting the opening degree of the waste gate valve 26.

Next, the operation of the first embodiment will be described. When the engine is started, the exhaust gas passage 12
The exhaust gas flowing through the turbine rotor 13 rotates the turbine rotor 13 to perform supercharging. During operation of the engine, the turbine housing 11 is heated by the exhaust gas flowing through the exhaust gas passage 12, and the turbine housing 11 is thermally deformed.

The external force due to the thermal deformation of the turbine housing 11 acts on the first sleeve 20, but since the first sleeve 20 is elastically deformable in the radial direction by the thin portion 23, the heat of the turbine housing 11 is reduced. The deformation can be absorbed by the elastic deformation of the first sleeve 20 in the radial direction. Therefore, an excessive force does not act on the second sleeve 24 fitted with the first sleeve 20, and the second sleeve 24 made of ceramic is used.
Are reliably protected from external force due to thermal deformation of the turbine housing 11.

Since the waste gate valve 26 and the cylindrical pipe 16 in which the waste gate valve 26 is arranged are both made of ceramic, thermal deformation of the waste gate valve 26 and the cylindrical pipe 16 due to high temperature exhaust gas can be suppressed to a significantly small level. To be Therefore, wastegate valve 2
When the valve 6 is closed, the degree of sealing between the waste gate valve 26 and the seating surface of the cylindrical pipe 16 is improved, and the exhaust gas leak in the bypass passage 15 is suppressed to an extremely small level.

Since the piston ring 18 as a seal ring is mounted on the outer peripheral surface of the cylindrical tube 16,
The thermal deformation of the turbine housing 11 is caused by the piston ring 18
It is possible to absorb the elastic deformation in the radial direction. As a result, the cylindrical tube 16 made of ceramic is also reliably protected from external force due to thermal deformation of the turbine housing 11.

In the present embodiment, the first recess 21 extends from the axial center of the first sleeve 20 to the vicinity of the end of the first sleeve 20, and the second recess 22 forms the first sleeve 2.
However, as shown in FIG. 4, the first recess 21 is disposed at the end of the first sleeve 20, and the second recess 22 is disposed at the end of the first sleeve 20. Even if the structure extends from the central portion in the axial direction to the vicinity of the end portion of the first sleeve 20, the same effect as described above can be obtained.

Second Embodiment FIG. 5 shows a second embodiment of the present invention. The second embodiment differs from the first embodiment only in the shapes of the first sleeve and the second sleeve, and the other portions are the same as the first embodiment.
Since this embodiment is similar to the embodiment, the corresponding parts are denoted by the same reference numerals as those in the first embodiment, and the description of the corresponding parts is omitted. Only different parts will be described. The same applies to other embodiments described later.

Although the axial center A of the first sleeve 20 and the axial center B of the second sleeve 24 are eccentric, the axial center A and the axial center B coincide with each other in this embodiment. Therefore, the thin portion 23 can be formed over the entire circumference of the first sleeve 20, and the first sleeve 20 can be elastically deformed in the radial direction with respect to the external force from all directions.

In the first embodiment, the second sleeve 24 is formed integrally with the cylindrical tube 16, but in the present embodiment, the second sleeve 24 is used alone. Therefore, in this case, not only the wastegate valve 26 of the turbocharger but also the opening / closing mechanism such as a butterfly valve used at high temperature can be applied.

Third Embodiment FIG. 6 shows a third embodiment of the present invention. In both the first and second embodiments, the shaft 25 is rotated, but in this embodiment, the shaft 25 moves in the axial direction. Therefore, the present embodiment can be applied to a poppet valve that moves in the axial direction, such as an intake valve and an exhaust valve of an engine. In this case, the valve stem as a shaft is slidably held by the second sleeve 24. It

[0031]

According to the present invention, the following effects can be obtained.

(1) A second sleeve made of ceramic is fitted inside the first sleeve made of metal, and the shaft is movably inserted into the second sleeve, and the outer peripheral surface of the first sleeve is inserted. A first concave portion extending in the circumferential direction is formed, and a second concave portion extending in the circumferential direction is formed on the inner peripheral surface of the first sleeve, and an end portion of the first concave portion and an end portion of the second concave portion are formed. Since they are overlapped in the axial direction, the thin portion can be formed in the first sleeve, and the first sleeve can be elastically deformed in the radial direction. Therefore, the second sleeve made of ceramic can be surely protected from the external force due to the thermal deformation of the housing, and the durability reliability of the bearing at high temperature can be improved.

(2) Since the second sleeve through which the shaft is inserted is made of ceramic, it is possible to eliminate seizure between the shaft and the second sleeve even if the shaft is made of metal.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view of a main part of a high temperature bearing structure according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view near a turbine housing of a turbocharger adopting the high temperature bearing structure of FIG.

3 is a plan view of FIG. 2 seen from the direction of arrow F. FIG.

FIG. 4 is an enlarged sectional view of an essential part showing a modified example of the high temperature bearing structure of FIG.

FIG. 5 is an enlarged sectional view of an essential part of a high temperature bearing structure according to a second embodiment of the present invention.

FIG. 6 is an enlarged sectional view of a main part of a high temperature bearing structure according to a third embodiment of the present invention.

FIG. 7 is a cross-sectional view showing an example of a conventional high temperature bearing structure.

8 is a side view of FIG. 7 viewed from the direction of arrow G. FIG.

[Explanation of symbols]

 11 Turbine housing as housing 20 1st sleeve 21 1st recessed part 22 2nd recessed part 23 Thin part 24 2nd sleeve 25 Shaft

Claims (1)

[Claims] 1. A cylindrical first sleeve made of metal is fitted into a metallic housing, and a cylindrical second sleeve made of ceramic is fitted inside the first sleeve, A shaft is movably inserted into the second sleeve to form a first recess extending circumferentially on the outer peripheral surface of the first sleeve, and a second recess extending circumferentially on the inner peripheral surface of the first sleeve. Is formed, and the end of the first recess and the end of the second recess are axially overlapped with each other.