JP2000145777A - Gas bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a gas bearing suitable to use in a vacuum and to enable easy and precise manufacturing by forming it independent of a casing and providing a bearing functional part separably attached to the casing. SOLUTION: In a gas bearing 10, a stepped part 18c of an attaching hole 18 is connected to a stepped part 14c of a bearing functional part 14 by a screw 22, the bearing functional part 14 is separably attached to a casing 12, and an O-ring 26 is arranged in a hole 24 of the stepped part 14c. The bearing functional part 14 is provided with a porous pad 28 in the hole 14d, the porous pad 28 is provided with an air supplying hole 30, the pad 28 is flush with or slightly projected from the inner surface of the bearing functional part 14, and a clearance C between the inner surface of the pad 28 and the front surface of a guide shaft 16 is made to a suitable value by the screw 22. When the bearing 10 is used in a vacuum, high-pressure air allowed to flow through the bearing 10 is discharged to the atmosphere by an exhaust means 34 without leaking into a vacuum. Therefore, machining of the bearing functional part is facilitated, and manufacturing is facilitated when the gas bearing is used together with a long bearing or a round shaft.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a gas bearing, and more particularly to a gas bearing suitable for use in a gas bearing slider. The invention also relates to a gas bearing suitable for being used as a radial bearing.

[0002]

2. Description of the Related Art A gas bearing slider is used for a stage for controlling the position of an article such as a semiconductor wafer. The gas bearing slider includes a guide shaft and a slider that moves along the guide shaft, and the slider is an air bearing formed to act on the guide shaft with air therebetween.

Conventionally, a quadrangular gas bearing slider has been used. This quadrangular gas bearing slider comprises a quadrangular gas bearing corresponding to a quadrangular guide shaft. This type is commercially available. The bearing portion is formed by processing four plates and then assembling them. On the other hand, the radial bearing is formed in a round shape,
It is usually machined as one piece.

[0004]

In recent years, attempts have been made to use gas bearing sliders in vacuum. The gas bearing functions by supplying high-pressure air, and when used in the atmosphere, the high-pressure air passing through the gas bearing can be released to the atmosphere. However, when the gas bearing is used in a vacuum, the high-pressure air that has passed through the gas bearing must be discharged to the atmosphere using an exhaust device without being discharged to the vacuum.

For this reason, there are the following requirements for a gas bearing slider used in a vacuum. From the viewpoint of reducing the amount of high-pressure air leakage, a round shape is better as the bearing shape. The bearing section needs to include a bearing function section and a differential exhaust section, and the length of the gas bearing slider becomes longer. In response to this requirement, if a round-shaped air bearing is used, it is difficult to machine the inner surface of the casing of the air bearing, and it is difficult to form the bearing function part as an integral cylinder because the bearing function part is located at the center of the casing. Occurs. Further, in order to provide the exhaust function, the bearing gap may be about 5 μm instead of about 10 μm in the past, and the clearance adjustment of the gap and the processing accuracy of the bearing function part become more strict.

It is an object of the present invention to provide a gas bearing which is also suitable for use in vacuum and which can be manufactured more easily and precisely.

[0007]

According to the present invention, there is provided a gas bearing comprising a casing, and a bearing function portion formed separately from the casing and detachably attached to the casing. Things. This air bearing is separately manufactured into a casing and a bearing function part, and then the two are assembled. Thus, the processing of the bearing function section can be performed not independently of the processing of the casing, but not as the processing of the inside of the casing. Therefore,
Processing of the bearing function part becomes easy, and a very precise gas bearing can be obtained. Even when a round casing is used, the processing of the bearing function portion can be easily performed. Irrespective of the shape of the casing, fine adjustment of the bearing gap can be performed relatively easily, so that a gas bearing having more desired performance can be obtained. It is also relatively easy to make small bearings that do not allow tools to be placed inside the casing.

The following configuration can be adopted in addition to the above configuration. The bearing function part is mounted on the casing so as to be position-adjustable so that the bearing clearance can be adjusted. The bearing function section includes a plurality of support portions attached to the casing, bearing members supported by the support portions, and air supply means for supplying high-pressure air to the bearing members.

[0009]

FIG. 1 is a perspective view showing a gas bearing according to a first embodiment of the present invention. FIG. 2 is a sectional view of the gas bearing of FIG. The gas bearing 10 is formed separately from the casing 12 and the casing 12.
2 and a bearing function part 14 detachably attached to the bearing function part 14. Reference numeral 16 denotes a guide shaft having a round cross-sectional shape. The casing 12 is formed as a hollow cylinder having a round cross-sectional shape, and has four mounting holes 18 on the circumference at an intermediate portion in the axial direction. The bearing function part 14 is attached to the casing 12 at the attachment hole 18. Each bearing function part 14 has a high-pressure air supply port 20.

[0010] As shown in FIG.
Has a large hole 18a on the inner surface side, a small hole 18b on the outer surface, and a step 18c between the large hole 18a and the small hole 18b. The bearing function part 14 is a member having an arc shape, an outer surface thereof is an arc surface coinciding with the outer surface of the casing 12, and an inner surface thereof is an arc surface slightly projecting inward from the inner surface of the casing 12. The outer peripheral surface of the bearing function part 14 is a large hole part 18a of the mounting hole 18.
And a large wall portion 14a and a small wall portion 14b corresponding to the small hole portion 18a. The step portion 14c corresponding to the step portion 18c of the mounting hole 18 has a large wall portion 14a and a small wall portion 14b.
Is formed between Therefore, the bearing function part 14 fits almost exactly into the mounting hole 18.

A screw 22 connects the step 18c of the mounting hole 18 and the step 14c of the bearing function part 14, so that the bearing function part 14 is detachably attached to the casing 12. Further, an O-ring 26 is disposed in a hole 24 provided in the step portion 14c of the bearing function portion 14. The diameter of the O-ring 26 is greater than the depth of the hole 24 so that when the screw 22 is tightened, the O-ring 26 is significantly deformed. The O-ring 26 thus has a spring action and generates a reaction force against the tightening of the screw 22.

The bearing function part 14 has a porous pad 28 disposed in a hole 14d formed on the inner surface of the bearing function part 14.
And an air supply hole 30 for supplying high-pressure air to the porous pad 28. The high-pressure air supply port 20 is located at an outer end of the air supply hole 30 and is connected to, for example, a high-pressure air supply tube 32. The porous pad 28 is bonded to the wall surface of the hole 14d of the bearing function unit 14. Porous pad 28
Are arranged so as to be flush with the inner surface of the bearing function part 14 or slightly protrude from the inner surface of the bearing function part 14.

The porous pad 28 is important as a bearing member of the gas bearing, and the inner surface of the porous pad 28 and the guide shaft 1
6 must be managed so that the gap C between the surface 6 and the surface 6 has a small appropriate value. For example, the gap C is 5 to 10 μm.
m is preferable. For this reason, in the present invention,
The bearing gap is adjustable. That is, the O-ring 26 has a spring action and urges the bearing function part 14 inward in the radial direction of the casing 12. When the screw 22 is tightened, the bearing function part 14 moves outward in the radial direction of the casing 12, and the gap C between the inner surface of the porous pad 28 and the surface of the guide shaft 16 can be set to an appropriate value. ing.

In the embodiment, the spring action of the O-ring 26 is used, but another elastic member such as rubber or a spring may be disposed between the bearing function portion 14 and the casing 12. In addition, a metal plate (shim) may be inserted between the bearing function unit 14 and the casing 12, and the gap C may be adjusted. Further, the porous pad 28 can be replaced with another member used as a bearing member of the gas bearing, for example, a member having a groove or an orifice.

Further, when the gas bearing 10 is used in a vacuum, the casing 12 is provided with an exhaust means 34 so that the high-pressure air passing through the gas bearing 10 does not leak into the vacuum.
Release to atmosphere. When the gas bearing 10 is used as a gas bearing slider described later,
Casing 12 is provided with means for attaching members to be attached thereto.

With such a structure, the air bearing 1
Numeral 0 is not integrated, and can be manufactured in an environment where the bearing function unit 14 can be easily processed. The assembly of the bearing function unit 14 is performed as follows. First, the porous pad 28 is attached to the bearing function unit 14, the bearing function unit 14 is arranged inside the casing 12, the screw 22 is tightened, and the bearing function unit 14 is attached to the casing 12. At this time, the inner surface of the porous pad 28 of the bearing function unit 14 is positioned to be the same as or outer than the inner surface of the casing 12. Then, after inserting the guide shaft 16 into the air bearing 10, a predetermined gap C is formed with respect to the surface of the guide shaft 16 while adjusting the tightening amount of the screw 22.

As described above, the bearing function part 14 is connected to the casing 1.
2 has an advantage that the bearing function unit 14 does not move toward the guide shaft from the adjusted position. However, there is a restriction on the size that the bearing function part 14 enters the casing 12 during assembly. Although the embodiment has described the air bearing suitable for the guide shaft 16 having a round shape, the present invention can of course be applied to a guide shaft 16 having another shape, for example, a square guide shaft 16. There is no size restriction.

FIG. 3 is a sectional view showing a gas bearing according to a second embodiment of the present invention. The air bearing 10 of this embodiment is basically similar to the embodiment of FIGS. 1 and 2 are denoted by the same reference numerals, and a detailed description thereof will be omitted. This embodiment differs from the embodiments of FIGS. 1 and 2 in that
That is, the bearing function part 14 is assembled from the outside of the casing 12. That is, the mounting hole 18 of the casing 12 includes a small hole 18h on the inner surface, a large hole 18i on the outer surface, a small hole 18h, and a large hole 1h.
8i. Bearing function part 14
Are the small wall 14h, the large wall 14i, and the small wall 1
4h and a large step portion 14i between the large wall portion 14i. The bearing function part 14 fits almost exactly into the mounting hole 18.

FIG. 4 is a sectional view showing a gas bearing according to a fourth embodiment of the present invention. In this embodiment, the air bearing 10
Has a casing consisting of three casing parts 12a, 12b, 12c. Three casing parts 12
a, 12b and 12c are connected to each other by a screw type or an adhesive type. The bearing function part 14 is a central casing part 1.
2b.

The central casing portion 12b is formed in a shape divided into two by a diameter surface of a cylinder.
4 are arranged. The bearing function part 14 is also formed in the form divided into two by the cylindrical diameter surface similarly to the center casing part 12b, and is respectively attached to the divided part of the center casing part 12b. A porous pad 28 is attached to each bearing function part 14.
Further, the high-pressure air supply port 20 is connected to the central casing portion 1.
2b, the high-pressure air supply port 20 communicates with an air supply hole (not shown) provided in each bearing function unit 14.

As described above, the present invention can be applied to a case where the casing is not an integral body. At this time, the casing portion 12b of the bearing function portion 14 may be manufactured as an integral body, but in FIG. 4, the casing portion 12b is divided into halves to facilitate adjustment of the gap. This configuration is advantageous when the length of the bearing portion is increased by adding the exhaust means. FIG. 5 is a perspective view showing an example in which the air bearing 10 of FIG. 1 is used as the air bearing slider 50, for example. Air bearing slider 50
Arranges two air bearings 10 in parallel, and two air bearings 1
The carrier 52 is attached to the casing 12 of the “0”.
The two guide shafts 16 are fixed, and the carrier 52 is movable along the two guide shafts 16 together with the two casings 12. At this time, the air supplied between the porous pad 28 of the bearing function part 14 inside the air bearing 10 and the guide shaft 16 acts as a bearing fluid. Therefore, even when the air bearing 10 is the air bearing slider 50 used together with the round guide shaft 16, a so-called detent is not required. The air bearing slider 50 can be used, for example, in the manufacture of semiconductors. Further, the air bearing 10 can be used not as such an air bearing slider 50 but as a radial bearing.

[0022]

As described above, according to the present invention,
Processing of the bearing function part becomes easy. In particular, when used with a long air bearing or a round-shaped shaft, its manufacture is easy.

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional view of the gas bearing of FIG.

FIG. 3 is a sectional view illustrating a gas bearing according to a second embodiment of the present invention.

FIG. 4 is a perspective view illustrating a gas bearing according to a third embodiment of the present invention.

FIG. 5 is a perspective view showing an example in which the air bearing of FIG. 1 is used as an air bearing slider.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Gas bearing 12 ... Casing 14 ... Bearing function part 16 ... Guide shaft 18 ... Mounting hole 20 ... High pressure air supply port 22 ... Screw 26 ... O-ring 28 ... Porous pad 30 ... Air supply hole

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ichiro Honjo 4-1-1, Kamidadanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fujitsu Limited (72) Inventor Kazushi Ishida 1-32 Asahi-cho, Nerima-ku, Tokyo No. 1 In Advantest Co., Ltd. (72) Inventor Akiyoshi Tsuda 1-32-1 Asahimachi, Nerima-ku, Tokyo F-term in Intranet Advantest Co., Ltd. 3J102 AA02 BA08 CA16 EA02 EA07 EA18 GA01 GA19

Claims (3)

[Claims] 1. A gas bearing, comprising: a casing; and a bearing function portion formed separately from the casing and detachably attached to the casing. 2. The gas bearing according to claim 1, wherein said bearing function part is mounted on said casing so as to be position-adjustable so that a bearing clearance can be adjusted. 3. The bearing function unit includes a plurality of support portions attached to the casing, a bearing member supported by each of the support portions, and air supply means for supplying high-pressure air to the bearing members. The gas bearing according to claim 1, wherein: