JPH0210817Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of application of the invention] The invention uses a high-temperature rotating shaft that rotates at high speed to
This invention relates to a hydrodynamic gas bearing that is rotatably supported in a suspended state by a film of gas such as nitrogen or helium.

[Background of the idea]

First, a conventional example will be explained based on FIG. 8 (see, for example, Japanese Patent Laid-Open No. 56-35816). In the figure, reference numeral 1 denotes a holder, and the holder 1 is formed into a cylindrical shape, and a corrugated elastic member 3 is circumferentially attached to the inner surface of a cavity 2. A top foil or enclosure 4 is fixed to the elastic member 3. The enclosure 4 surrounds the entire circumference of the rotating shaft 5 while being spaced apart from the rotating shaft 5. One end of the enclosure 4 and the elastic member 3 are clamped and fixed by a key 6 fixed to the inner surface of the holder 1. The outer surface of the holder 1 is connected to the outer casing 7.
is held in surface contact with.

Next, the operation will be explained. When the rotating shaft 5 rotates,
The surrounding gas is drawn into the minute gap between the outer surface of the rotating shaft 5 and the enclosure 4 due to its viscosity, and pressure is generated by a so-called wedge film action, and the rotating shaft 5 is made rotatable by the gas film based on the pressure. Supported. The pressure of this gas film is determined by the distance between the rotating shaft 5 and the enclosure 4, that is, the thickness of the gas film.

In the case of a gas bearing having an elastic member 3, the rotating shaft 5
The rotating shaft 5 is deviated from the axis position due to the dynamic load, impact load, etc. caused by the rotation of the 9th axis.
As shown in the figure, since the elastic member 3 deforms to a certain extent in response to the deflection of the rotating shaft 5 (see the lower end of the figure), the thickness of the gas film changes with respect to the deflection of the rotating shaft 5. Therefore, the influence of the above-mentioned impact etc. is relaxed and absorbed, resulting in a gas bearing with a large load capacity. During normal operation, the bearing can operate with a large gas film thickness, making it a highly reliable bearing. For reference, FIG. 10 shows the pressure distribution with respect to the deviation from the axis position of the rotating shaft 5 in a type of gas bearing that does not have the elastic member 3. As can be seen from the figure, the area where the gas film thickness is uniform is narrow and is likely to be adversely affected by impacts and the like.

As mentioned above, by providing the elastic member 3,
Although it is a highly reliable gas bearing that is not susceptible to adverse effects such as impacts acting on the rotating shaft 5,
Conventionally, no consideration was given to thermal expansion of the rotating shaft 5. That is, when using a gas bearing in a high temperature field, the heat of the turbine is transferred to the rotating shaft 5, and as a result, the rotating shaft 5 thermally expands, and the gap between the enclosure 4 and the rotating shaft 5 becomes smaller. . In general, in a gas bearing, the distance between the enclosure 4 and the rotating shaft 5 is very small, so a gas film is not formed when the rotating shaft 5 rotates, and the rotating shaft 5 and the enclosure 4 come into direct solid contact, resulting in seizure. There was a risk of this happening.

As other conventional examples, fluid bearings described in Japanese Patent Publication No. 55-17851 and Japanese Patent Application Laid-open No. 55-166525 have been provided, but these also do not take into account the thermal expansion of the rotating shaft. It has the same drawbacks as the conventional example described above.

[Purpose of invention]

The present invention was devised in view of the above circumstances, and it is an object of the present invention to provide a gas bearing having a compensating function to maintain a constant gas film thickness against thermal expansion of a rotating shaft.

[Summary of the idea]

A feature of the present invention is that a movable body is disposed in a part between the inner surface of the cavity of the holder and the elastic member, the elastic member is fixed at an appropriate position on the inner surface of the movable body, and the movable body is By disposing a compensating elastic member having a smaller elastic constant than the elastic member between the outer surface and the inner surface of the cavity, when the rotating shaft thermally expands, the gas film thickness decreases, and the pressure increases, This increased pressure causes the movable body to move in a direction away from the rotating shaft, thereby keeping the gas film thickness constant.

[Example of idea]

Hereinafter, the present invention will be explained in detail based on the embodiments shown in the drawings. FIG. 1 is a sectional view of a gas bearing according to the present invention, and FIG. 2 is a sectional view of a main part showing the actual usage state. In the figure, reference numeral 8 indicates a movable body, and the movable body 8 has a substantially crescent-shaped cross section and is disposed in a part between the inner surface of the cavity 2 of the holder 1 and the elastic member 3. One end 10 of the elastic member 3 is welded and fixed to the inner arcuate surface 9 of the movable body 8. Further, a corrugated plate-shaped compensating elastic member 12 is disposed between the outer arcuate surface 11 of the movable body 8 and the inner surface of the cavity 2, with a part thereof being welded and fixed to the inner surface of the cavity 2. The compensating elastic member 12 is set to have a smaller elastic constant than the elastic member 3. The inner surface of the cavity 2 has two inner surfaces 13, 1 with different curvatures.
4. That is, the curvature of the inner surface 13 is greater than that of the inner surface 14. The inner surface 14 is formed within a range of an arcuate angle of 120 degrees, and the seats 15, 15, . . . of the elastic member 3 are in contact with a portion of the inner surface 14. Further, the curvature of the inner circular arc surface 9 of the movable body 8 is formed to be slightly larger than the curvature of the inner surface 14, so that even when the movable body 8 moves outward, an appropriate bearing gap is created over the entire circumference of the bearing. It is formed.
In FIG. 2, 16 indicates a turbine.

Next, the action will be explained. The rotating shaft 5 thermally expands due to heat transfer from the turbine 16, and when the gap with the enclosure 4, that is, the gas film thickness becomes smaller, the pressure increases. Then, the enclosure 4 receives a force in the direction of expansion, and this force presses the movable body 8 in a direction away from the rotating shaft 5. At this time, since the elastic constant of the compensating elastic member 12 is set smaller than that of the elastic member 3,
The compensating elastic member 12 is deformed. Thereby, the thermal expansion of the rotating shaft 5 is compensated for by the movement of the movable body 8, and the gas film thickness is kept constant.

FIG. 3 is a sectional view showing another embodiment of the present invention, in which the shape of the compensating elastic member 12 is not a corrugated plate shape as in the previous embodiment, but a plane bent shape.
Other configurations and operations are similar to those of the previous embodiment, so the same parts are denoted by the same reference numerals and explanations will be omitted.

FIG. 4 is also a cross-sectional view showing another embodiment of the present invention, in which the holder 1 has a multi-point contact structure with the outer casing 7, and non-contact parts 17, 18, which form gaps between the holder 1 and the casing 7, 19. Reference numerals 20, 21, and 22 indicate contacts constituting the multi-point contact structure. The contacts 20, 21, 22 are divided into at least three equal parts in the circumferential direction to prevent rattling.
Create a contact structure with points or more. Figures 5 and 6 are
FIG. 5 is a perspective view of a main part showing different embodiments of the contact 20. In FIG.
In FIG. 6, projections 20c and 20d are formed by protruding inward from both ends of the holder 1 in the width direction. Both the holder 1 and the casing 7
This structure is designed to increase the size of the non-contact area.
The rest of the configuration is similar to that of the previous embodiment, so the same parts are given the same reference numerals and the explanation will be omitted. Operationally, the heat transfer from the turbine 16 is through the non-contact part 1, which is the air gap.
7, 18, and 19, the heat transfer to the gas bearing is significantly reduced, and thermal deterioration of the gas bearing can be prevented. Moreover, the elastic member 3,
Deterioration of the spring characteristics of the spring 12 and thermal deformation and oxidation of the enclosure 4 and the elastic member 3 can be prevented.

FIG. 7 is a sectional view showing another embodiment of the present invention. In the embodiment shown in FIG. 4, the shape of the compensating elastic member 12 is the same as that in the embodiment shown in FIG. 3. Since the other configurations and functions are the same as those of the previous embodiment, the same parts are denoted by the same reference numerals and the explanation thereof will be omitted.

[Effect of idea]

According to the present invention, a movable body is provided which has a compensating function of moving in a direction to cancel out the thermal expansion of the rotating shaft, so that the gas film thickness is always kept constant even when the thermal expansion occurs. dripping Therefore, even if the gas bearing is used in a high-temperature field, there is less risk of damage due to seizure or the like as in conventional gas bearings, resulting in a highly reliable gas bearing.

[Brief explanation of drawings]

Figure 1 is a sectional view of the gas bearing according to the present invention, Figure 2 is a cross-sectional view of the gas bearing according to the present invention;
Figure 2 is a sectional view of the main part showing the actual usage state, Figure 2 is a sectional view of the main part showing the actual usage state, Figures 3 and 4 are sectional views showing other different embodiments of the invention, 5 and 6 are perspective views of main parts showing different embodiments of the embodiment shown in FIG. 4,
Fig. 7 is also a sectional view showing another embodiment of the present invention, Fig. 8 is a sectional view showing a conventional example, and Fig. 9 is a pressure distribution of the gas film with respect to deviation from the axis of the rotating shaft in the conventional example. FIG. 10 is a reference diagram of pressure distribution. DESCRIPTION OF SYMBOLS 1... Holder, 2... Cavity part, 3... Elastic member, 4... Enclosure, 5... Rotating shaft, 7... Casing, 8... Movable body, 9... Inner circular arc surface, 11...
...outer circular arc surface, 12...compensating elastic member, 17,
18, 19...Non-contact part.

Claims (1)

[Claims for Utility Model Registration] (1) In a gas bearing in which a holder having a cylindrical cavity is provided with an enclosure that surrounds the rotating shaft at a distance via an elastic member on the inner surface of the cavity, the inner surface of the cavity A movable body is disposed in a part between the movable body and the elastic member, and the elastic member is fixed at an appropriate position on the inner surface of the movable body, and between the outer surface of the movable body and the inner surface of the cavity. A gas bearing characterized in that a compensating elastic member having a smaller elastic constant than the elastic member is disposed at the elastic member. (2) The gas bearing according to claim 1, wherein the holder and the outer casing have a multi-point contact structure, and a non-contact portion is provided between the holder and the casing.