JP2002174240A - Hydrostatic gas bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the slot clearance 23 less prone to be affected by a temperature change by uniformly manufacturing the desired slot clearance 23 in a peripheral direction in a slot throttle hydrostatic gas bearing. SOLUTION: In the manufacturing of the slot clearance 23 of the slot throttle hydrostatic gas bearing, only one of a plurality of bearing sleeve members 11 and 12 is fixed to a housing 2, clearance 3 is provided between the other bearing sleeve member 12 and the housing 2, and end faces of the plurality of bearing sleeve members 11 and 12 are joined and fixed. As a result, the size of the slot clearance 23 is determined by only a level difference dimension of the end faces of the bearing sleeve members 11 and 12 and flatness of both the end faces without being affected by a squareness error of outside diameter surfaces and the end faces of the bearing sleeve members 11 and 12, the desired slot clearance 23 can be uniformly manufactured in the peripheral direction and the slot clearance 23 is not affected by heat expansion of the housing 2 due to a temperature rise. Working cost can be reduced because the squareness of the end faces of the bearing sleeve members 11 and 12 are not required to be finished with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention mainly relates to precision machining,
The present invention relates to a high-precision air bearing or a static pressure gas bearing incorporated in an air slide used for precision inspection or the like.

[0002]

2. Description of the Related Art Conventionally, in a throttle type of a static pressure gas bearing, a self-contained throttle in which a throttle is operated by a plurality of small diameter holes (hereinafter referred to as "supply holes"), and a load is provided by providing a pocket or a groove in the supply holes. There are a composite restrictor that improves the performance, a porous restrictor that operates the restrictor by the fluid resistance of a porous material having air permeability, and the like.

One of these throttle types is a slot throttle. FIG. 7 shows a basic structure of a hydrostatic gas journal bearing having a slot throttle.

In this static pressure gas journal bearing, a bearing sleeve member 11 having a step on an end face is fixed to a housing 2 by shrink fitting or the like in a state where the end faces of the bearing sleeve member 12 are in contact with each other. This is a structure in which a slot gap 23 of several μm to several tens μm is formed between the member 11 and the bearing sleeve member 12. Then, the compressed gas is supplied to the air supply passage 21 and the compressed gas is supplied to the bearing sleeve member 1.
1 through a circumferential groove 22 provided therein and then a slot clearance 2
At 3, the diaphragm is guided to the bearing gap 5 to support the main shaft 1 in a non-contact manner. The bearing sleeve members 11 and 12
Is made of a brittle material with excellent sliding properties, such as graphite and ceramics, to prevent slot clogging due to burrs during finishing of the bearing surface, and to prevent the bearing surface from contacting the shaft due to overload etc. In this case, the durability can be increased.

However, the slot throttle static pressure gas bearing having the above-described structure has the advantages of a higher load capacity and higher rotational accuracy than self-generated throttles and orifice throttles, but there have been few examples of practical use as a product up to now. . This is because slot throttle bearings have a problem that it is difficult to accurately produce a slot gap, and that the bearing performance tends to change due to the bearing temperature as compared with other throttle types.

That is, conventionally, as described above, the slot gap is formed by fixing the bearing sleeve members 11 and 12 having steps on the end surfaces to the housing 2. Therefore, the bearing sleeve member 1
As shown in FIG. 8, in order to fix the outer diameter surfaces of 1 and 12,
When the perpendicularity of the end faces to the outer diameter surfaces of the bearing sleeve members 11 and 12 is poor, it is difficult to uniformly produce a slot gap having a desired size in the circumferential direction. When the linear expansion coefficient of the housing 2 is larger than that of the bearing sleeve members 11 and 12, for example, when the housing 2 is stainless steel and the bearing sleeve members 11 and 12 are graphite, the linear expansion coefficient of stainless steel is generally 11 ×. 10 ^-6 to 18 × 10
^-6 [/ ° C], and the linear expansion coefficient of graphite is 3 × 10 ^{-6 to} 7 × 10
^-6 [/ ° C.], the housing 2 expands more in the axial direction than the bearing sleeve members 11 and 12 due to the temperature rise, and the slot clearance becomes larger. When the size of the slot gap is several μm, the bearing performance changes greatly due to the change in the slot gap due to thermal expansion.

[0007]

SUMMARY OF THE INVENTION Therefore, the present invention
It is an object of the present invention to make it possible to uniformly produce a desired slot gap in a circumferential direction in a slot throttle static pressure gas bearing, and to obtain a slot gap which is hardly affected by a temperature change.

[0008]

In order to solve the above problems, according to the present invention, the bearing sleeve member forming the slot clearance is not fixed by the housing, but one of the bearing sleeve members forming the slot clearance. Only the bearing sleeve is fixed to the housing, the other bearing sleeve member is provided with a clearance between the housing and the other bearing sleeve member, and is fixed to the end face of the one bearing sleeve member.

When the bearing sleeve member is made of a brittle material such as graphite and bolts are used for fixing the bearing sleeve members to each other, a metal is arranged on a surface where the bolt and the brittle material are in contact with each other to form the bearing sleeve member. I fixed it. Thereby, the bearing sleeve member can be protected from damage, and a sufficient fastening force by the bolt can be obtained.

[0010] By adopting the above configuration, the slot clearance is not affected by the squareness error between the outer diameter surface and the end surface of the bearing sleeve member, and only the step size of the end surface of the bearing sleeve member and the flatness of both end surfaces are used. The size is determined. Further, by providing a gap between the bearing sleeve member and the housing, the thermal expansion of the housing made of a material having a large linear expansion coefficient does not affect the slot gap, and the slot gap does not change even when the temperature changes. Further, when the bearing sleeve member is a brittle material, a metal is arranged on a surface where the bolt and the bearing sleeve member are in contact with each other when the bearing sleeve member is fixed by the bolt, so that the bearing sleeve member is protected from damage and the bolt is used. A sufficient fastening force can be obtained.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a hydrostatic gas bearing according to the present invention will be described below.

FIG. 1 shows an example in which the present invention is applied to a single-row air-pressure gas journal bearing having a slot restriction, and is configured as follows.

A bearing sleeve member 11 having a step on one end face is fixed to the housing 2 by shrink fitting, press fitting or bonding. Bearing sleeve member 12
Are fixed to the bearing sleeve member 11 with the bolts 4 in a state where the end surface thereof is aligned with the end surface of the bearing sleeve member 11 on which the step is provided, and the bearing sleeve assembly 15 is formed. A slot gap 23 is formed by a step provided on the end surface of the bearing sleeve member 11.

A gap 3 is provided between the outer diameter surface of the bearing sleeve member 12 and the housing 2, and the bearing sleeve assembly 15 is fixed to the housing 2 only at the outer diameter surface of the bearing sleeve member 11. Have been. The compressed gas guided from the external compressed gas supply source (not shown) to the air supply passage 21 passes through the circumferential groove 22 and is throttled by the slot gap 23.
The main shaft 1 is supplied to the bearing gap 5 and supported in a non-contact manner.

With the above configuration, the slot gap 23 is
The bearing sleeve members 11 and 12 are formed uniformly in the circumferential direction irrespective of the perpendicularity between the outer diameter surfaces and the end surfaces of the bearing sleeve members 11 and 12, so that good bearing performance can be obtained. Further, since the thermal expansion of the housing due to the temperature rise does not act between the bearing sleeve members 11 and 12, the slot gap is kept constant irrespective of the temperature change, and the bearing performance is not affected by the temperature change.

If a brittle material having excellent sliding properties such as graphite or ceramics is used for the bearing surface, the durability in the case where the shaft and the bearing come into contact with each other due to overload or the like is excellent. Clogging can be prevented.

Next, FIG. 2 shows the bearing sleeve members 11, 1
2 shows a hydrostatic gas journal bearing using a material having a larger elastic coefficient than the bearing sleeve members 11 and 12 as a reinforcing material when using a brittle material having a small elastic coefficient such as graphite.

In the embodiment shown in FIG. 2, bearing sleeve members 11 and 12 made of a brittle material such as graphite are used.
Are fixed to the reinforcing members 13 and 14 by shrink fitting or press fitting. The bearing sleeve members 11, 12 fixed to the reinforcing members 13, 14 are fixed by bolts 4 at the end surfaces of the reinforcing members 13, 14.

In the embodiment shown in FIG. 2, the bearing surface is made of a brittle material such as graphite. When the bearing sleeve member is made only of a brittle material such as graphite, the pressure of the compressed gas deforms the bearing sleeve members 11 and 12. In the case of the slot throttle, the rate of change of the slot gap due to the deformation of the bearing sleeve member is not negligible, and it is necessary to suppress the deformation of the bearing sleeve members 11 and 12 in order to obtain stable bearing performance. As in the embodiment of FIG. 2, by using a material having a larger elastic modulus than the brittle material used for the bearing sleeve members 11 and 12 as the reinforcing members 13 and 14, deformation of the bearing sleeve member due to the pressure of the compressed gas is suppressed. It becomes a structure that can be. Also,
By making the reinforcing material the same as the brittle material or a material having a large coefficient of linear expansion having an intermediate linear expansion coefficient between the housing and the brittle material, it is possible to suppress a change in the size of the slot gap due to a temperature change. . As such a reinforcing material, a low thermal expansion cast iron, an invar alloy, or the like can be considered.

FIG. 3 shows an example in which the present invention is applied to a two-row air-supply journal static pressure gas bearing having a slot restriction, and is configured as follows.

The bearing sleeve member 11 having a step on both end surfaces is fixed to the housing 2 by shrink fitting, press-fitting or bonding. The two bearing sleeve members 12 are fixed to the both end surfaces of the bearing sleeve member 11 with the bolts 4 in a state where the two bearing sleeve members 12 are aligned with each other.
5. Due to the steps provided on both end faces of the bearing sleeve member 11, a slot gap 23 is formed between both end faces of the bearing sleeve member 11 and the end faces of the two bearing sleeve members 12, and the bearing sleeve assembly 15 is provided with two rows of slot gaps 23. Having.

A gap 3 is provided between the outer diameter surface of each of the two bearing sleeve members 12 and the housing 2, and the bearing sleeve assembly 15 is provided only on the outer diameter surface of the bearing sleeve member 11 with respect to the housing. Fixed.

In the embodiment shown in FIG. 3, the slot clearance 23 has a uniform bearing in the circumferential direction as in the case of single-row air supply, regardless of the perpendicularity between the outer diameter surfaces and the end surfaces of the bearing sleeve members 11 and 12. Performance can be obtained. Further, the thermal expansion of the housing due to the temperature rise is caused by the bearing sleeve members 11
Since there is no action between them, the slot clearance is kept constant irrespective of the temperature change, and the bearing performance is not affected by the temperature change.

In the embodiment shown in FIG.
Thus, the three bearing sleeve members 11 and 12 are integrally fixed to form the bearing sleeve assembly 15. However, the bearing sleeve member 12 may be fixed to the bearing sleeve member 11 by bolts one by one.

FIG. 4 shows an embodiment in which the bearing sleeve members 11, 12 are formed of a brittle material, and the bearing sleeve members 11, 12 are fixed with bolts.

In this embodiment, the bearing sleeve members 11 and 12 made of a brittle material such as graphite are fixed by bolts 4 through metal rings 31 and 32. This is because, when the bearing sleeve members 11 and 12 are formed of a brittle material such as graphite, when the bearing sleeve members 11 and 12 are directly subjected to internal thread processing, there is a high possibility that the bearing sleeve members 11 and 12 will be damaged by the bolt 4. This is because a sufficient fastening force by the bolt 4 cannot be obtained. Further, the bearing sleeve member 1 is driven by the axial force of the bolt 4.
The reasons 1 and 12 are that local deformation occurs at a position in contact with the bolt 4, and it becomes impossible to obtain a uniform slot clearance 23 in the circumferential direction.

As shown in FIG. 4, metal rings 31 and 32 are arranged on the surfaces of the bolts 4 and the bearing sleeve members 11 and 12 using a brittle material.
12, the bearing sleeve members 11, 1
A sufficient fastening force by the bolt 4 can be obtained without damaging the bolt 2. Further, local deformation due to the tightening of the bolt 4 can be avoided, and a uniform slot gap 23 can be formed in the circumferential direction.

FIG. 5 shows an example in which the present invention is applied to a hydrostatic gas thrust bearing having a slot throttle, and is configured as follows.

Bearing sleeve member 1 having a step on the inner diameter side
Reference numeral 1 denotes a bearing sleeve assembly 15 which is fixed to the bearing sleeve member 12 by shrink fitting or the like in a state where the inner diameter surface is aligned with the outer diameter surface of the bearing sleeve member 12.

The bearing sleeve assembly 15 includes the housing 2
The bearing sleeve member 12 is fixed by shrink-fitting, press-fitting, bonding or bolting. Due to a step provided on the inner diameter surface of the bearing sleeve member 11, a slot clearance 23 is formed between the bearing sleeve member 11 and the bearing sleeve member 12.
Is formed. A gap 3 is provided between the bearing sleeve member 11 and the housing 2, and the bearing sleeve assembly 15 is fixed to the housing 2 only at the end face or the outer diameter surface of the bearing sleeve member 12.

The compressed gas introduced from an external compressed gas supply source (not shown) to an air supply passage (not shown) passes through a circumferential groove 22 and is throttled by a slot clearance 23, and then supplied to the bearing clearance 5 to be supplied to the main shaft. 1 is supported in a non-contact manner. Since the thermal expansion of the housing 2 due to the temperature rise does not act between the bearing sleeve members 11 and 12, the slot gap is kept constant irrespective of the temperature change, and the bearing performance is not affected by the temperature change.

If a brittle material having excellent sliding characteristics such as graphite or ceramics is used for the bearing surface, the durability in the case where the shaft and the bearing come into contact due to overload or the like is excellent, and the slot is formed by burrs during finishing. Clogging can be prevented.

Next, FIG. 6 shows the bearing sleeve members 11, 1
2, when a brittle material is used, the bearing sleeve member 11,
This is an example of a hydrostatic gas thrust bearing in which a material having a larger elastic modulus than 12 is used as the reinforcing members 13 and 14.

The bearing sleeve members 11 and 12 made of a brittle material such as graphite are fixed to the reinforcing members 13 and 14 by shrink fitting or press fitting. When the bearing sleeve members 11, 12 are made only of a brittle material such as graphite, the bearing sleeve members 11, 12 are deformed by the pressure of the compressed gas.
In the case of slot drawing, the bearing sleeve members 11, 12
The rate of change of the slot gap 23 due to the deformation is not negligible, and it is necessary to suppress the deformation of the bearing sleeve members 11 and 12 in order to obtain stable bearing performance.

As shown in FIG. 6, the bearing sleeve members 11, 1
By using a material having a larger elastic modulus than the brittle material used in 2 as the reinforcing members 13 and 14, the structure in which the deformation of the bearing sleeve members 11 and 12 due to the pressure of the compressed gas can be suppressed. In addition, by making the reinforcing members 13 and 14 the same as the brittle material or a material having a large coefficient of linear expansion between the housing 2 and the brittle material,
A change in the size of the slot gap 23 due to a temperature change can be suppressed.

[0036]

As described above, according to the present invention, only one of a plurality of bearing sleeve members is fixed to a housing in manufacturing a slot clearance of a slot throttle static pressure gas bearing, which has been difficult in the past. A gap is provided between the other bearing sleeve member and the housing, and the end surfaces of the plurality of bearing sleeve members are fixed together so that the bearing is not affected by the squareness error between the outer diameter surface and the end surface of the bearing sleeve member. The size of the slot gap is determined only by the step size of the end face of the sleeve member and the flatness of both end faces, so that a desired slot gap can be manufactured uniformly in the circumferential direction. Further, by providing a gap between the bearing sleeve member and the housing, a slot gap that is stable against a temperature change can be obtained without the thermal expansion of the housing due to a rise in temperature affecting the slot gap. Further, since it is not necessary to finish the squareness of the end surface of the bearing sleeve member with high accuracy, there is an effect that the processing cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view showing a first embodiment of the present invention.

FIG. 2 is a partial sectional view showing a second embodiment of the present invention.

FIG. 3 is a partial cross-sectional view showing a third embodiment of the present invention.

FIG. 4 is a partial sectional view showing a fourth embodiment of the present invention.

FIG. 5 is a partial sectional view showing a fifth embodiment of the present invention.

FIG. 6 is a partial cross-sectional view showing a sixth embodiment of the present invention.

FIG. 7 is a partial sectional view showing a conventional slot throttle static pressure gas bearing.

FIG. 8 is a partial sectional view showing a problem of a conventional structure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main shaft 2 Housing 3 Clearance 4 Bolt 5 Bearing clearance 11, 12 Bearing sleeve member 13, 14 Reinforcement material 15 Bearing sleeve assembly 21 Air supply passage 22 Circular groove 23 Slot clearance 31, 32 Ring

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3C048 BC01 CC07 DD12 DD13 EE01 3J102 AA02 BA03 BA17 CA16 CA17 EA02 EA06 EA14 EA15 EA17 FA01 GA07

Claims (7)

[Claims] 1. A slot throttle hydrostatic gas bearing wherein end surfaces of a plurality of bearing sleeve members are aligned and fixed, and a slot is formed in a journal bearing surface by a step provided on an end surface of the bearing sleeve member. Characterized in that only one of them is fixed to the housing, the other bearing sleeve member is fixed to the bearing sleeve member fixed to the housing, and a gap is provided between the slot and the housing. Pressurized gas bearing. 2. A static throttle pressure in which a plurality of bearing sleeve members have their inner and outer diameter surfaces fixed together and form a slot in a thrust bearing surface by a step provided on the inner or outer diameter surface of the bearing sleeve member. In the gas bearing, only one of the plurality of bearing sleeve members is fixed to the housing, the other bearing sleeve members are fixed to the bearing sleeve member fixed to the housing, and a gap is formed between the bearing sleeve member and the housing. A slot throttle static pressure gas bearing characterized by being provided. 3. The slot throttle static pressure gas bearing according to claim 1, wherein at least a bearing surface of the bearing sleeve member is made of a brittle material. 4. The gas throttle bearing according to claim 3, wherein a material having a larger elastic modulus than the brittle material is provided on a side of the bearing sleeve member opposite to the brittle material bearing surface. 5. The slot throttle static pressure according to claim 4, wherein the material having a large elastic coefficient has a thermal expansion coefficient equal to or larger than that of the brittle material and smaller than a thermal expansion coefficient of the housing. Gas bearing. 6. The gas throttle bearing of claim 1, wherein a plurality of bearing sleeve members are bolted together. 7. The slot throttle static pressure gas bearing according to claim 6, wherein a plurality of bearing sleeve members are fastened via a metal ring provided with a female screw and a bolt seat surface.