JPH05248428A - Gas bearng device - Google Patents

Abstract

PURPOSE:To facilitate control of clearance even at high temperature by forming a radial shaft part, a thrust shaft part, a radial bearing part, and a thrust bearing part by ceramics, and integrating both bearing parts with each other to be elastically supported by a housing. CONSTITUTION:A shaft 10 and a bearing 30 are formed by ceramics of the same quality to keep the bearing clearance constant with the same thermal expansion from the ordinary temperature to high temperature during steady operation. Since the ceramics has a coefficient of thermal expansion about one-fifth as large as that of metal, thermal deformation of the shaft 10 is small so as to keep small and delicate bearing clearance. Furthermore, the ceramic members can exhibit low friction therebetween, little abrasion and good characteristics for solid lubrication from the stop state until the shaft 10 is floated by high speed rotation. A radial bearing part 32 of the bearing 30 and a thrust bearing part 34 are integrated with each other to be elastically supported by the radial bearing part 32, so that it is possible to prevent breakage due to a difference in thermal deformation between the radial bearing part 32 and a metal housing 8, and strong tension is damped by friction so as to stabilize the rotation.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a gas bearing device.

[0002]

2. Description of the Related Art A bearing that floats from a bearing during rotation and supports it via a gas film is known as a so-called gas bearing. Unlike a bearing that supports the shaft through an ordinary oil film, the gas bearing does not have the problem of oil loss or heat deterioration of the oil, so it can be used for bearings at high temperature parts, such as bearings of gas turbines and turbochargers. It is being studied (for example, Japanese Utility Model Publication No. 2-107819).

[0003]

However, since the gas bearing forms a very thin gas film between the shafts to float the shaft, it is important to manage the clearance between the shaft and the bearing. In particular, when applied to a high temperature part, even if the clearance is optimally set at a low temperature, the clearance changes at a high temperature, which makes it difficult to manage the clearance. For example, the above-mentioned actual Kaihei 2-107
Japanese Patent No. 819 discloses that the shaft is made of metal and the bearing is made of ceramic. However, since the coefficient of thermal expansion of metal is larger than that of ceramic, there arises a problem that the clearance becomes small at high temperature. .

When the gas bearing device has not only the radial bearing portion but also the thrust bearing portion, it is difficult to maintain good clearances of both bearing portions at the same time.

Further, until the shaft floats from the bearing, the shaft is in direct contact with and slides on the bearing, so that wear or the like becomes a problem. In order to reduce wear, it is effective to apply plating or surface hardening treatment to the surface of the shaft or bearing. However, when the temperature becomes high, there is a problem that the plating layer or the surface-hardened layer peels off due to the difference in coefficient of thermal expansion between the plating layer or the surface-hardened layer and the uncured portion inside the layer, and the sliding surface becomes rough.

It is an object of the present invention to provide a gas bearing device in which the clearance can be easily controlled and the sliding surface is not roughened even at high temperatures.

[0007]

According to the present invention, the above object is achieved by the following gas bearing device. That is, it has a shaft, a bearing and a housing, the shaft has a radial shaft part that receives a radial load and a thrust shaft part that receives a thrust load, and the bearing has a radial bearing part that receives the radial load and a thrust bearing that receives the thrust load. And a radial shaft portion, a thrust shaft portion, a radial bearing portion, a thrust bearing portion is formed of ceramics,
A gas bearing device in which the radial bearing portion and the thrust bearing portion are integrated and the bearing is elastically supported from the housing.

[0008]

In the above gas bearing device, since both the shaft and the bearing are made of ceramic, the coefficient of thermal expansion of ceramic is smaller than the coefficient of thermal expansion of metal. Is easy to manage. The ceramic bearing is elastically supported by the metal housing to prevent damage to the ceramic bearing due to the difference in the coefficient of thermal expansion between the ceramic and the metal, but when this radial support causes the radial bearing part and the thrust bearing part to move separately. It becomes difficult to manage the clearance of each part. However, in the present invention, since the radial bearing portion and the thrust bearing portion of the bearing are integrated with each other, even if they move, they move in synchronization with each other, and clearance management becomes easy.

With respect to the sliding surface between the shaft and the bearing, since both the shaft and the bearing are made of ceramic, there is no problem of surface peeling and they are resistant to high temperatures, so that the sliding surface is not roughened.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of a gas bearing device according to the present invention will be described below with reference to the drawings. 1 to 4 are turbochargers (superchargers) mounted on vehicles, etc.
1 shows a bearing device according to a first embodiment of the present invention, which is applied to In FIG. 1, a turbine wheel 2 driven by high-temperature exhaust gas and an impeller 4 of a compressor that compresses low-temperature air and supplies the compressed air to an engine are connected via a shaft 10 so as to rotate integrally with each other. Has been done. The shaft 10 is rotatably supported by a bearing 30 via a gas film. The shaft 10 and the bearing 30 have a structure capable of supporting both radial load and thrust load. The bearing 30 is elastically supported by a metal housing 8 via a spring (for example, a leaf spring) 6.

The shaft 10 has a shaft portion 12 to which a radial load is applied.
And a thrust shaft portion 14 to which a thrust load is applied. Of the shaft 10, the radial shaft portion 12 and the thrust shaft portion 14 are
Composed of ceramic.

More specifically, the shaft 10 is made of a ceramic radial shaft 12 which is integrally manufactured or joined to the turbine wheel 2 made of ceramic or metal, and a metallic shaft which is integrated with the impeller 4. It has an impeller shaft portion 16 and a ceramic plate-shaped thrust shaft portion 14 attached to the impeller shaft portion 16. The radial shaft portion 12 is hollow so as to suppress heat conduction from the turbine wheel 2. The impeller shaft portion 16 is joined to the radial shaft portion 12 by, for example, brazing. The thrust shaft portion 14 is fastened to the impeller shaft portion 16 together with the impeller 4 and the nut.

On the outer peripheral portion of the radial shaft portion 12 of the shaft 10,
As shown in FIG. 3, when the shaft 10 rotates, gas is drawn from the outside in the axial direction to the inside in the axial direction and sent to the bank 18 in the center.
Alternatively, grooves 20 for generating dynamic pressure, which form a gas film having a high pressure in the vicinity thereof, are formed on both sides of the bank 18.

Further, as shown in FIG. 4, on both side surfaces of the thrust shaft portion 14, when the shaft 10 rotates, gas is entrained from the outer peripheral side to the inner peripheral side, and the gas having high pressure is fed to the inner peripheral portion. Grooves 22 for forming movement are formed to form a film.

On the other hand, the bearing 30 has a radial bearing portion 32 which receives a radial load and a thrust bearing portion 34 which receives a thrust load. When the thrust load is applied in both left and right directions in FIG. 1, another thrust load receiving member 36 is provided.

The radial bearing portion 32, the thrust bearing portion 34, and the thrust load receiving member 36 are made of ceramics. Further, the radial bearing portion 32 and the thrust bearing portion 34 are integrated with each other. The thrust load receiving member 36 is attached to the cylindrical extending portion 38 that extends in the axial direction from the outer peripheral portion of the thrust bearing portion 34 by the snap ring 4.
It is fixed by 0.

The radial bearing portion 32 is located on the outer peripheral side of the radial shaft portion 12 of the shaft 10, and when the shaft 10 rotates, the groove 20 causes a gas having a high pressure between the radial shaft portion 12 and the radial bearing portion 32. The film is formed, and the shaft 10 floats from the radial bearing portion 32 and becomes rotatable.

Further, the thrust bearing portion 34 and the thrust load bearing member 36 are positioned on both sides of the thrust shaft portion 14 of the shaft 10 in the axial direction, and when the shaft 10 rotates, both sides of the thrust shaft portion 14 are moved by the groove 22. A gas film having a high pressure is formed on the shaft 10, so that the shaft 10 is axially separated from the thrust bearing portion 34 and is rotatable.

In order to facilitate the supply of gas to the groove 20 of the radial shaft portion 12, a communication passage 42 is formed in the housing 8 near the end of the bearing 30 on the turbine wheel 2 side, and the radial bearing portion is formed. Communication passages 44 and 46 are formed in the shaft portion 10 near the end of the compressor impeller 4 on the side of the compressor impeller 4, and a communication hole 48 is formed in the radial bearing portion 32 in the shaft portion 10 near the central portion of the radial bearing portion 32. A communication hole 50 is formed.

Further, in order to smoothly supply the gas to the groove 22 of the thrust shaft portion 14, a communication hole 52 is provided in the housing 8 near the outer peripheral end of the thrust shaft portion 14, and a thrust bearing cylindrical extension portion 38. A communication hole 54 is formed in each.

Further, labyrinth packings 56 and 58 are provided in the vicinity of both axial ends of the housing 8 in order to minimize leakage of engine exhaust gas and intake gas.

As shown in FIG. 2, the ceramic bearing 30 includes a metal housing 8 and a spring 6.
It is elastically supported by. The spring 6 is composed of, for example, four leaf springs arranged side by side in the circumferential direction, and both circumferential ends of each leaf spring come into contact with the housing 8 so that the bearing 30 is supported at the central portion of each leaf spring. There is. The difference in thermal expansion between the ceramic and the metal is escaped by the elastic deformation of the leaf spring.

Next, the operation of the first embodiment will be described. In the turbocharger, the turbine wheel 2 is driven by the exhaust gas, and the intake air is compressed by the impeller 4 and supercharged. The heat of the high-temperature exhaust gas is transmitted, so that the temperature of the gas bearing device becomes high.

When the shaft 10 rotates, dynamic pressure is generated by the groove 20, and the radial shaft portion 12 floats above the radial bearing portion 32 and rotates without lubrication. Dynamic pressure is also generated by the groove 22, and the thrust shaft portion 14 separates from the thrust bearing portion 34 and the thrust load receiving member 36, and rotates without lubrication while enduring the thrust load. In this case, the gas film of the gas bearing is thinner than the oil film of a normal journal bearing using oil as a lubricant, and it is required to control the bearing clearance with high accuracy.

By making the shaft 10 and the bearing 30 ceramic, three advantages are obtained. First, the shaft 10
Since the bearing 30 and the bearing 30 are made of the same ceramic, the same thermal expansion is caused, and the bearing clearance, which requires elaborate management, is kept substantially constant from room temperature to a high temperature (about 150 ° C.) in steady operation. Second, the coefficient of thermal expansion of ceramic is about ⅕ of that of metal, and the change in bearing clearance is small. Further, the shaft 10 is less thermally deformed and is less likely to bend, the straightness is not deteriorated, and the delicate bearing clearance can be maintained. Thirdly, the ceramics have little wear when they come into contact with each other, and exhibit good characteristics with low friction and little wear even with respect to solid lubrication from the time of stopping until the shaft 10 floats at high speed.

Further, the radial bearing portion 32 of the bearing 30.
Since the thrust bearing portion 34 and the thrust bearing portion 34 are integrally formed and elastically supported by the radial bearing portion 32, the following actions and advantages can be obtained.
First, since the radial bearing portion 32 is made of ceramic and the housing 8 is made of metal, there is a difference in thermal deformation. If elastic support is not provided, the deformation of the metal may deform the shellac portion and destroy it. Secondly, the strong vibration force due to the imbalance during rotation can be attenuated by the friction between the spring 6 and the inner peripheral surface of the housing 8 to stabilize the rotation. Thirdly, even when the elastic support portion of the sleeve of the radial bearing portion 32 is tilted by some external force, the thrust bearing portion 34 is also tilted because it is integral, and the radial shaft portion 12 and the thrust shaft portion 14 of the shaft 10 are also the same. Since it is tilted to, the clearance of the delicately managed thrust surface is maintained and there is no point hit.

Since no oil is used, there is a concern that the temperature of the housing 8 will rise.
Water cooling does not cause any problems. Reference numeral 60 is a water jacket for water cooling the housing.

FIG. 5 shows a gas bearing device according to the second embodiment of the present invention. The structure of the second embodiment different from that of the first embodiment is the structure of the shaft, and the other parts are the same as those of the first embodiment. Therefore, the corresponding parts are designated by the same reference numerals as those of the first embodiment and the description thereof is omitted. Only the different points will be described below.

As shown in FIG. 5, in the second embodiment, the shaft 100 comprises a ceramic portion 110 and a metal portion 102. The ceramic part 110 is hollow, and the metal part 102 is inserted through the ceramic part 110. Ceramic part 11
0 has a radial shaft portion 112 to which a radial load is applied and a thrust shaft portion 114 to which a thrust load is applied. The radial shaft portion 112 and the thrust shaft portion 114 are integrated. Therefore, the radial shaft portion 112 and the thrust shaft portion 11
The degree of orthogonality of 4 is accurately obtained, and uneven bearing contact due to poor squareness is eliminated.

The turbine wheel 2 and the shaft 100 are separate bodies, and compared with the case where the turbine wheel and the shaft are made of an integral ceramic body, each member is downsized and the manufacture is facilitated. As a result, the defective rate during molding is reduced. Further, the bending moment generated in the turbine wheel 2 is not applied to the ceramic part 110. The turbine wheel 2 and the metal portion 102 of the shaft 100 are joined by adhesion.

The ceramic part 110 includes a metal part 102,
The ceramic sleeve 110 is fitted in a metal sleeve 104 provided at the axial end of the metal portion 102, and the movement of the ceramic portion 110 in the radial direction is restricted. A leaf spring 106 is interposed between the metal sleeve 104 and the ceramic portion 110 in the axial direction, and the leaf spring 106 restricts the movement of the ceramic portion 110 in the axial direction by a pressing force. Further, due to the pressing force of the leaf spring 106, the ceramic portion 110 does not idle even if the metal portion 102 extends. In addition, the leaf spring 10
The pressure of 6 absorbs the difference in axial thermal expansion between the ceramic part 110 and the metal part 102.

The operation of the second embodiment is similar to that of the first embodiment, and the ceramic portion 110 of the shaft 100 is also provided.
In the above, since the radial shaft portion 112 and the thrust shaft portion 114 are integrated, there is an effect that straightness is obtained and the bearing clearance is finely maintained.

[0033]

According to the present invention, since the radial shaft portion, the thrust shaft portion, the radial bearing portion, and the thrust bearing portion are made of ceramic, the bearing clearance can be finely changed with a small clearance change regardless of the temperature change. It can be maintained and a good sliding surface can be maintained with good durability. Also, since the bearing is elastically supported by the housing and the radial bearing part and thrust bearing part are integrated, the ceramic bearing can be supported on the housing without being damaged due to the difference in thermal expansion between the metal and the radial bearing part and the thrust bearing. Since the parts move in synchronization, it is easy to manage the bearing clearance.

[Brief description of drawings]

FIG. 1 is a sectional view of a gas bearing device according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

3 is a partial side view of a radial shaft portion of the gas bearing device of FIG.

4 is a front view of a thrust shaft portion of the gas bearing device of FIG. 1. FIG.

FIG. 5 is a sectional view of a gas bearing device according to a second embodiment of the present invention.

[Explanation of symbols]

 2 Turbine wheel 4 Impeller 6 Spring 8 Housing 10 Shaft 12 Radial shaft part 14 Thrust shaft part 30 Bearing 32 Radial bearing part 34 Thrust bearing part 36 Thrust load bearing member 100 Shaft 102 Metal part 110 Ceramic part 112 Radial shaft part 114 Thrust shaft part

Claims (1)

[Claims] 1. A shaft, a bearing, and a housing, wherein the shaft has a radial shaft part to which a radial load is applied and a thrust shaft part to which a thrust load is applied, and the bearing has a radial bearing part and a thrust load which receive a radial load. A thrust bearing portion for receiving, the radial shaft portion, the thrust shaft portion, the radial bearing portion, the thrust bearing portion is formed from ceramic, the radial bearing portion and the thrust bearing portion are integrated, the bearing from the housing A gas bearing device, which is elastically supported.