JPH04266615A - Static pressure porous gas bearing - Google Patents

Abstract

PURPOSE:To provide a static pressure porous gas bearing having a higher thrust load capacity by providing such a constitution as never releasing a pressure generated in a pocket part by an eccentric load outside. CONSTITUTION:In a static pressure porous gas bearing in which a gas is blown out through a porous member 4 mounted on one bearing member 1, at least either of one bearing surface 4b and the other bearing surface 3a opposed thereto through a bearing space 7 has a plurality of pockets 10 in the circumferential direction, and land members 11, 12 are present between the adjacent pockets and between the pocket 10 and the atmosphere, respectively. Since a high pressure generated in the pocket is prevented by the land parts and never released outside, a resisting pressure is independently kept in the pocket when an eccentric load acts on the pocket.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvements in hydrostatic porous gas bearings suitable for use in main shafts, rotary tables, etc. of precision machines, ultra-precision machines, etc.

0002

2. Description of the Related Art A conventional hydrostatic porous gas bearing of this type is proposed in, for example, Japanese Utility Model Application No. 1-75624. A typical example is one in which a cylindrical rotating member is rotatably supported in a non-contact manner inside a fixed housing. It has a department. A short cylindrical porous material is fixed to the inner peripheral surface of the housing that faces the radial bearing surface that is the receiving surface of the rotating member, and the cylindrical inner peripheral surface forms a radial bearing surface. The end surface facing the flange-like flange forms a thrust bearing surface. Therefore, on the thrust bearing surface, which is the inner surface of the flange-like collar that faces the thrust bearing surface, a pocket with a depth similar to that of the gap in the exhaust part of the gas in the bearing clearance to the atmosphere is formed. ing. This pocket functions as a pressure reservoir for compressed air ejected from the porous material into the bearing gap, thereby greatly improving the thrust load resistance of the bearing.

0003

[Problems to be Solved by the Invention] However, although the conventional hydrostatic porous gas bearing described above exhibits a high thrust load capacity when an axial thrust load is applied to the center of the rotating shaft, There is a problem in that if the load is radially off the center of the rotating shaft and applied as an eccentric load, or if a moment load is applied, a satisfactory load capacity increasing effect cannot be obtained.

In other words, as shown in FIG. 3, the pocket P, which serves as a pressure reservoir provided on the thrust receiving surface S, is continuous in a circular ring shape. When a load is applied, the thrust bearing clearance near point A narrows and the fluid pressure at that point increases, trying to support the load, but the high pressure generated at point A creates resistance to fluid flow. small pocket P
This is because the pressure escapes in the circumferential direction shown by the arrows A and B, making it impossible to obtain a high enough pressure to counter the applied eccentric load.

Generally, the thrust load applied to a gas bearing is rarely applied to the center of rotation, and in most cases it is an eccentric load. Therefore, when designing gas bearings,
Although emphasis must be placed on load capacity against eccentric loads, in conventional hydrostatic porous gas bearings, the effect of providing pockets as described above is insufficient against eccentric loads, and a higher thrust load capacity is required. What is desired is a hydrostatic porous gas bearing having a high static pressure.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a hydrostatic porous gas bearing having a higher thrust load capacity by preventing the pressure generated in the pocket portion due to an eccentric load from escaping.

[0007]

[Means for Solving the Problems] The present invention provides that one bearing surface of a porous member attached to one bearing member faces the other bearing surface provided on the other bearing member via a bearing clearance,
In the hydrostatic porous gas bearing in which gas is ejected from the one bearing surface, at least one of the one bearing surface and the other bearing surface has a plurality of pockets in the circumferential direction, and adjacent pockets A land portion is present between the pocket and the atmosphere, respectively.

[0008]

[Operation] Fluid flow resistance is extremely large in the land portion. The high pressure generated in each pocket is blocked by the lands between adjacent pockets and the lands between the pockets and the atmosphere, and does not escape to other areas. Therefore, when an eccentric load acts on a certain pocket, a counterpressure is independently maintained only within that pocket.

[0009]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal cross-sectional view of an embodiment of the hydrostatic porous gas bearing of the present invention, in which a rotating member 2, which is the other bearing member, is rotatably mounted inside a fixed housing 1, which is one bearing member. is supported by At both axial ends of the cylindrical portion of the rotating member 2, outwardly flanged collar portions 3, 3 are fixed. At least one of the flanges 3 is removably screwed in consideration of the attachment of the rotating member 2 to the housing 1.

Two short cylindrical porous members 4, 4 are fixed to the inner peripheral surface of the housing 1 at a slight distance in the axial direction. Further, the housing 1 is provided with air supply holes 5, 5 extending from its outer peripheral surface to the outer peripheral surfaces of the porous members 4, 4, and compressed air is sent to the porous members 4, 4 through the air supply holes 5, 5. It has a structure. The inner peripheral surface 4a of each porous member 4 is a radial bearing surface, and faces the outer peripheral surface 2a of the rotating member 2, which is a radial bearing surface, with a radial bearing clearance 6, 6 in between. Further, the annular outer surface 4b of each porous member 4 is a thrust bearing surface. On the other hand, the inner surface 3a of each collar 3 of the rotating member 2 is a thrust bearing surface, and the thrust bearing surface (4) is one of the bearing surfaces.
b) faces the other thrust bearing surface (3a) with a thrust bearing clearance 7 in between.

In the case of this embodiment, the annular thrust bearing surface (3a), which is the other thrust bearing surface, has a plurality of pockets 10 in the circumferential direction, with radial lands between adjacent pockets. It is partitioned by a section 11 (see FIG. 2). Furthermore, an annular outer land portion 12 exists between the pocket 10 and the atmosphere, that is, on the outer circumference side of the pocket, and an annular inner land portion 13 exists on the inner circumference side of the pocket. Each land portion 11, 12, 13 is continuous on the same plane. On the other hand, the pockets 10 are independent from each other, forming fan-shaped recesses whose depth d is approximately the same as the width w of the gap 8 of the gas discharge section.

Next, the operation will be described. When compressed air is supplied from the air supply hole 5 of the housing 1, the compressed air passes through the porous member 4 and is uniformly ejected from the inner peripheral surface 4a (radial bearing surface) and outer surface 4b (thrust bearing surface). As a result, a high pressure air layer is formed in the radial bearing gaps 6, 6 and the thrust bearing gaps 7, 7, and the rotating member 2 is floated and supported on the housing 1 without contacting it. The ejected compressed air continuously flows out into the atmosphere from the gap 8 in the gas discharge part, but each pocket 10 on the thrust bearing surface (3a) becomes a pressure reservoir, and the air pressure increases, causing the static pressure porous gas bearing to Increase thrust load capacity. Also,
When an eccentric load is applied to the outer surface 3b of the flange 3 of the rotating member 2, the flange 3 is pushed and tilted inward, and the thrust bearing clearance 7 is partially narrowed, causing the flange 3 to be closer to the location where the eccentric load is applied. The pressure in the pocket 10 in the position increases. Even if the air in this pocket 10 with high pressure tries to flow out into the adjacent pocket 10 with lower pressure or into the atmosphere, the thrust bearing clearance 7 of the surrounding radial land portion 11 and outer peripheral land portion 12 is narrow. , the outflow is suppressed due to the large flow resistance. That is, in the pocket 10 where the pressure is increased, the pressure is maintained within the pocket 10 without escaping in the circumferential direction or radial direction as in conventional continuous pockets. Therefore, sufficient load capacity can be obtained even against eccentric loads.

In this embodiment, since the pressure in the radial bearing gaps 6, 6 is kept high, the inner peripheral land portion 13
Even if there is no land portion 11, the adjacent pockets 10, 10 separated by the land portion 11 do not communicate with each other. However, in the case where the radial bearing clearances 6, 6 are not provided and the inner circumferential portion of the pocket 10 is configured to communicate with the atmosphere, the inner circumferential land portion 13 is used to maintain the pressure within the pocket 10 at a high level. is necessary.

Furthermore, the land portion 11 is not necessarily radial, and the outer peripheral land portion 12 is not necessarily circular. Further, in the above embodiment, the pocket 10 was provided on the inner surface 3a (thrust receiving surface) of the collar 3, which is the rotating side member of the hydrostatic porous gas bearing. It may be formed on the outer surface 4b (thrust bearing surface), or it may be formed on both the thrust bearing surface and the thrust bearing surface.

[0015]

As explained above, in the hydrostatic porous gas bearing of the present invention, at least one of the one bearing surface and the other bearing surface has a plurality of pockets in the circumferential direction. Assuming that there is a land between the pockets, and that there is also a land between the pocket and the atmosphere, the high pressure generated in one pocket will be blocked by these lands and will not escape to other areas. did. Therefore, when an eccentric load is applied to a certain pocket, counter pressure is maintained independently only within the pocket, resulting in a hydrostatic porous structure with a high thrust load capacity that can sufficiently handle the eccentric load. A gas bearing can be provided.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an embodiment of the present invention.

FIG. 2 is a front view of the other bearing surface in FIG. 1;

FIG. 3 is a front view of a conventional thrust bearing surface (the other bearing surface).

[Explanation of symbols]

1 Housing (one bearing member) 2 Rotating member (other bearing member) 3a Thrust bearing surface (
Other bearing surface) 4 Porous member 4b Thrust bearing surface (one bearing surface) 7 Bearing clearance (thrust) 10 Pocket

Claims (1)

[Claims] Claim 1: One bearing surface of a porous member attached to one bearing member faces another bearing surface provided on the other bearing member via a bearing clearance, and gas is ejected from the one bearing surface. In the hydrostatic porous gas bearing, at least one of the one bearing surface and the other bearing surface has a plurality of pockets in the circumferential direction, and a land portion is provided between the adjacent pockets, A hydrostatic porous gas bearing characterized in that a land portion exists between the pocket and the atmosphere.