JPH0210821Y2 - - 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. 9 (see, for example, Japanese Patent Laid-Open No. 56-35816). In the same figure,
Reference numeral 1 denotes a holder, and the holder 1 is formed into a cylindrical shape, and an elastic member 3 having an end and a corrugated plate shape is provided around the inner surface of a hollow portion 2. A top foil (top foil) having an end and a planar shape is attached to this elastic member 3.
foil), that is, the enclosure 4 is fixed. 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 on the same side are clamped and fixed by a key 6 press-fitted into the inner surface of the holder 1. The outer surface of the holder 1 is held in surface contact with the outer casing 7.

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 deviates from its axis position due to dynamic loads, impact loads, etc. generated by the rotation of the rotating shaft 5, but as shown in FIG. Since the elastic member 3 deforms to a certain extent (lower end in the figure) in response to the deviation of the rotating shaft 5, the region where the thickness of the gas film is uniform becomes wider with respect to the deviation of the rotating shaft 5. Therefore, the effects of the above-mentioned shocks and the like are 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. 11 shows the pressure distribution with respect to the deviation from the axial center 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 region where the gas film thickness is uniform is narrow;
It can be said that it is easily affected by adverse effects such as shock.

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. Become. in general,
In a gas bearing, since the distance between the enclosure 4 and the rotating shaft 5 is very small, 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, causing seizure. I was afraid.

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.

Furthermore, in the past, the ends of the enclosure 4 and the elastic member 3 on the same side were separated and fixed separately, so the elastic member 3 could not maintain its corrugated shape near this end. In other words, the height of the waves becomes uneven, and the enclosure 4 also has to maintain a uniform planar shape, which makes it difficult to form a uniform gas film thickness around the entire circumference of the rotation axis. There was a drawback. Furthermore, the bearing clearance is not uniform in the axial direction (longitudinal direction) in the vicinity of the key 6, resulting in a decrease in bearing performance, and furthermore, as the key 6 protrudes into the cavity 2, the durability of the bearing decreases. There was a drawback of doing so.

[Purpose of invention]

The present invention has been developed in view of the above circumstances, and has a compensating function to keep the gas film thickness constant against thermal expansion of the rotating shaft, and also has an enclosure and an elastic member around the entire circumference of the rotating shaft. The purpose is to provide a gas bearing that can be formed into a substantially uniform shape so that the gas film thickness is uniform over the entire circumference, thereby improving bearing performance and durability. It is.

[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, and the elastic constant is greater than that of the elastic member between the outer surface of the movable body and the inner surface of the cavity. A small compensating elastic member is provided, the ends of the elastic member and the enclosure on the same side are overlapped, and the overlapped end is inserted into a slit drilled from the inner surface to the outer surface of the movable body. By fixing the rotating shaft, the rotating shaft expands thermally, the gas film thickness decreases, and the pressure rises. This increased pressure causes the movable body to move away from the rotating shaft.
In addition to keeping the gas film thickness constant, by overlapping the ends of the enclosure and the elastic member on the same side and inserting them into the slits and fixing them as described above, the enclosure can be fixed even near the fixed end. It is possible to maintain a uniform planar shape of the elastic member and a uniform corrugated plate shape of the elastic member.

[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 the gas bearing according to the present invention, FIGS. 2 and 3 are enlarged plan views of the same main parts, and FIG. 4 is a sectional view of the main parts showing actual usage conditions.
FIG. 5 is an enlarged perspective view of the main part before the enclosure is assembled, and FIG. 6 is an enlarged perspective view of the main part before the elastic member is assembled. 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. A compensating elastic member 12 in the form of a corrugated plate 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. Furthermore, a plurality of protrusions 23 are provided at appropriate intervals on the outer arcuate surface 11 of the movable body 8.
23,... are provided protrudingly. The protrusion 23,2
3, . . . are provided apart from the opposing inner surface 13, and this distance is the maximum amount of movement of the movable body 8. A slit is bored in a substantially central portion of the movable body 8 from an inner arcuate surface 9 to an outer arcuate surface 11. A fixing tongue piece 25 is protruded from the end of the enclosure 4 (FIG. 5), and a fixing tongue piece 26 is also protruded from the end of the elastic member 3 (FIG. 6). These both fixing tongue pieces 25, 26 and both ends are overlapped, and the fixing tongue piece 25,
26 into the slit 24, the enclosure 4 and elastic member 3 are fixed to the movable body 8. By adopting the insertion fixing structure by overlapping the ends in this way, the corrugated plate shape of the elastic member 3 can be formed to the vicinity of the fixed part, and the uniform planar shape of the enclosure 4 can also be formed to the vicinity of the fixed part. can be formed. 27 indicates a recessed portion or a recessed portion. The inner surface of the cavity 2 has two different curvatures.
It is formed by two inner surfaces 13 and 14. 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 seat portions 15, 15,
...is in contact. 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,
The bearing is formed so that there is an appropriate bearing clearance around the entire circumference of the bearing. The holder 1 and the outer casing 7 are in contact with each other through a multi-point contact structure, and non-contact parts 17, 18, and 19 are formed between the holder 1 and the casing 7, which serve as gaps. 20,2
Reference numerals 1 and 22 indicate contacts constituting the multi-point contact structure. The contacts 20, 21, 22 have a contact structure of at least three points equally divided in the circumferential direction to prevent backlash. With this structure, heat transfer from the outside is significantly reduced by the non-contact parts 17, 18, and 19, which are voids, so heat transfer to the gas bearing is significantly reduced and thermal deterioration of the gas bearing can be prevented. can. Further, deterioration of the spring characteristics of the elastic members 3 and 12 and thermal deformation and oxidation of the enclosure 4 and the elastic member 3 can be prevented. In FIG. 4, 16 indicates a turbine.

Next, the effect 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. Furthermore, due to the overlapping insertion and fixing structure of the ends of the elastic member 3 and the enclosure 4, it is possible to maintain the corrugated plate shape and planar shape of the elastic member 3 and the enclosure 4 up to the vicinity of the fixed portion. As a result, the gas film thickness can be formed to be substantially constant over the entire circumference of the rotating shaft.

FIG. 7 is a cross-sectional view showing another embodiment of the present invention, in which the compensating elastic member 12 is formed not in the shape of a corrugated plate but in a bent plane shape, and other configurations and functions are the same as in the previous embodiment. Identical parts are given the same reference numerals and explanations will be omitted.

FIG. 8 is also a sectional view showing another embodiment of the present invention, in which the outer surface of the holder 1 is formed into a uniform cylindrical 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.

[Effect of idea]

According to the present invention, a movable body is provided that 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 constant even when the thermal expansion occurs. It is maintained. 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.

In addition, since the ends of the enclosure and the elastic member on the same side are overlapped and fixed by being inserted into the slit provided in the movable body as described above, the enclosure is uniform evenly near the fixed end. Since it is possible to maintain a flat planar shape and a uniform corrugated shape of the elastic member, the spring stiffness of the elastic member is approximately uniform over the entire circumference of the rotating shaft, and the gas film thickness can be made uniform. This allows the bearing performance to be improved. Furthermore, the reliability and durability of the vicinity of the fixing part can be improved compared to fixing with a conventional key.

[Brief explanation of the drawing]

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;
Figures 3 and 3 are enlarged plan views of the same main parts, respectively.
The figure is a sectional view of the main part showing the actual usage state, FIG. 5 is an enlarged perspective view of the main part in the state before the enclosure is assembled,
FIG. 6 is an enlarged perspective view of the main part of the elastic member before assembly, FIGS. 7 and 8 are sectional views showing different embodiments of the present invention, and FIG. 9 is a sectional view showing a conventional example. , FIG. 10 is an explanatory diagram showing the pressure distribution of the gas film with respect to the deviation from the axial center position of the rotating shaft in the conventional example, and FIG. 11 is a reference explanatory diagram of the 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, 24...slit.

Claims (1)

[Scope of utility model registration request] An elastic member with an end and a corrugated plate shape is provided around the inner surface of the hollow part of a holder having a cylindrical hollow part, and an enclosure body with an end and a planar shape is attached to the elastic member, and the rotation axis is controlled by the enclosure body. In the gas bearing that is separated and enclosed, a movable body is disposed in a part between the inner surface of the cavity and the elastic member, and the elastic member is disposed between the outer surface of the movable body and the inner surface of the cavity. disposing a compensating elastic member having a smaller elastic constant than the member, overlapping the ends of the elastic member and the enclosure on the same side;
A gas bearing characterized in that the overlapping ends are inserted and fixed into a slit bored from the inner surface to the outer surface of the movable body.