JPH06307449A - Static pressure gas bearing - Google Patents

Abstract

PURPOSE:To damp small vibration rapidly with a simple structure. CONSTITUTION:In a static pressure gas bearing 10 for floating and supporting a motion member 13 for carrying out straight motion or rotation motion by static pressure gas, a static pressure gas bearing 10 is formed so as to form bearing space 16 partitioned between the motion guide surface 12 of a solid member 11 and the bearing surface 14 of the motion member 13 in a small size to extent such that viscous resistance of static pressure as in the bearing space is acted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a static pressure gas for floating and supporting a motion member for linear motion or rotary motion, which is used in a super precision machine tool, a super precision measuring machine, etc. It relates to bearings.

[0002]

2. Description of the Related Art Conventionally, such a static pressure gas bearing is constructed as shown in FIG. 4, for example. In the figure, a static pressure gas bearing 1 has a motion guide surface 3 formed on a fixed member 2.
A moving member 4 that carries out a linear motion or a rotary motion is placed on the top.

A pressure gas is supplied to a bearing gap 7 defined between the motion guide surface 3 and the bearing surface 5 via an air supply pipe 6 provided so as to penetrate the motion member 4, and Thus, the movement member 4 is floated.

The air supply pipe 6 has an air supply groove 6a around its opening. By this, the air supply pipe 6
The pressure gas discharged from the device is dispersed around. In this case, the bearing gap 7 is set to a dimension d1 of, for example, several μm to several tens of μm.

Further, in the static pressure gas bearing 1 thus constructed, in order to improve the rigidity and motion accuracy of the motion member 4,
The movement member 4 is provided on the upper and lower surfaces. As a result, the bearing structure has a so-called two-face constraint. The moving member 4 can move extremely smoothly because there is no friction due to direct contact with the fixed member 2.

[0006]

However, in the static pressure gas bearing 1 having such a structure, a minute vibration generated by a minute fluctuation of the gas pressure is generated in the moving member 4 at rest and during operation. It may happen.

Here, since the moving member 4 is floated by the pressure gas, the minute vibration particularly when the motion is stopped is maintained for a long time. In addition, since small vibrations will be generated even at rest and during movement,
There was a problem that the positioning accuracy and the like deteriorate.

In view of the above points, the present invention has an object to provide a hydrostatic gas bearing which has a simple structure and is capable of rapidly damping minute vibrations.

[0009]

According to the present invention, the above object is to provide a hydrostatic gas bearing for levitating and supporting a motion member performing a linear motion or a rotary motion with a hydrostatic gas. The bearing gap defined between the bearing surface and the motion guide surface on the side of the fixed member is formed so small that the viscous resistance of the static pressure gas in the bearing gap acts. Is achieved by

In the device according to the invention, the bearing gap is preferably selected to be smaller than 20 times the surface roughness of the movement guide surface on the fixed member side and the bearing surface of the movement member.

[0011]

According to the above construction, the bearing clearance is equal to, for example, 2 times the surface roughness of the motion guide surface on the fixed member side and the bearing surface of the motion member.
When the moving member causes a minute vibration because it is smaller than 0 times and is molded, the minute vibration is quickly attenuated by the viscous resistance of the pressure gas in the bearing gap. Become. Moreover, since the bearing gap is small, the bearing load capacity is improved and the rigidity is also improved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to FIGS. It should be noted that the examples described below are suitable specific examples of the present invention, and therefore, various technically preferable limitations are given, but the scope of the present invention particularly limits the present invention in the following description. Unless otherwise stated, the present invention is not limited to these modes.

FIG. 1 shows an embodiment of a hydrostatic gas bearing according to the present invention. In FIG. 1, a static pressure gas bearing 10
On a motion guide surface 12 formed on the fixed member 11 and finished with high precision, a motion member 13 that performs linear motion or rotary motion is placed.

Then, the motion guide surface 12 is provided through an air supply pipe 15 provided so as to penetrate the motion member 13.
The moving member 13 is floated by supplying pressurized gas into the bearing gap 16 defined between the bearing surface 16 of the fixing member 13 and the bearing surface 14 of the fixing member 13.
Here, the air supply pipe 15 has an air supply groove 15a around the opening thereof. As a result, the pressure gas discharged from the air supply pipe 15 is dispersed around.

Further, the static pressure gas bearing 10 thus constructed can be more specifically constructed as shown in FIG. In this example, for example, the fixing member 11 is
The movement member 13 is fixed to the support member 20.
Is fitted on the fixing member 11 so as to surround the fixing member 11.

Here, the fixing member 11 is finished with high accuracy by using four surfaces as guide surfaces. Also, the movement member 1
The inner surfaces of the guide surfaces 3 are the guide surfaces 1 of the fixing member 11, respectively.
The bearing surface facing 2 is similarly finished with high precision. Further, the moving member 13 is provided with the static pressure gas bearings 10 on each of the four inner surfaces thereof, and the air supply pipe 15 of each static pressure gas bearing 10 is opened to the outer surface of the moving member 13.

Further, the movement member 13 has a feed nut 22 attached integrally, and a feed screw 21 schematically shown.
Meshes with. Therefore, when the feed screw 21 is rotationally driven by the motor 23, the movement member 1
3 is smoothly moved along the fixing member 11. At this time, the movement member 13 is the fixed member 1
On the other hand, since there is no friction due to direct contact with No. 1, it can move extremely smoothly.

Here, the static pressure gas bearing 10 according to the present embodiment.
In this case, the bearing gap 16 is selected to be small so that the pressure gas introduced through the air supply pipe 15 has viscous resistance.

For example, in the bearing gap 7, as shown in FIG. 3, the surface roughness d2 and d3 of the motion guide surface 12 of the fixed member 11 and the bearing surface 14 of the motion member 13 are 0.03, respectively.
In the case of .mu.m and 0.08 .mu.m, the maximum value is 0.08 .mu.m, which is 20 times smaller than 1.6 .mu.m.

As a result, the pressure gas present in the bearing gap 16 has viscous resistance.

The static pressure gas bearing 10 of this embodiment is constructed as described above, and since the pressure gas in the bearing gap 16 has a viscous resistance, when the moving member 13 causes a minute vibration. The viscous resistance of the pressure gas acts on the minute vibrations to damp the minute vibrations.

Therefore, for example, even if a minute vibration is generated due to the pressure fluctuation of the pressure gas or the like, this minute vibration is quickly attenuated by the viscous resistance of the pressure gas. Thus, the positioning accuracy and the like are improved.

As described above, in this embodiment, the bearing clearance is smaller than 20 times the surface roughness of the stationary member side motion guide surface and the bearing surface of the motion member. When the member causes minute vibration, the minute vibration is rapidly attenuated by viscous resistance of the pressure gas existing in the bearing gap.

As a result, for example, when the moving member is stationary or moving, minute vibrations caused by pressure fluctuations of the pressure gas are quickly removed, and the motion of the moving member is stabilized. Therefore, when applied to an ultra-precision machine tool, an ultra-precision measuring machine, etc., the machining accuracy and the measurement accuracy are improved. Further, since the bearing gap is small, the bearing load capacity is improved and the rigidity is also improved, so that high rigidity is achieved.

In the above embodiment, the air supply groove 1
The case of a so-called surface-throttled static pressure gas bearing provided with 5a has been described. On the contrary, it is obvious that the present invention can be applied.

[0026]

As described above, according to the present invention, it is possible to provide a hydrostatic gas bearing in which minute vibrations are quickly damped with a simple structure.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a hydrostatic gas bearing according to the present invention.

FIG. 2 is a schematic perspective view showing a configuration example in which the static pressure gas bearing of FIG. 1 is incorporated.

3 is a partially enlarged cross-sectional view of a main part of the hydrostatic gas bearing of FIG.

FIG. 4 is a sectional view showing an example of a conventional static pressure gas bearing.

[Explanation of symbols]

 10 Static Pressure Gas Bearing 11 Fixed Member 12 Motion Guide Surface 13 Motion Member 14 Bearing Surface 15 Air Supply Pipe 16 Bearing Clearance

Claims (2)

[Claims] 1. A hydrostatic gas bearing for levitating and supporting a moving member that performs a linear motion or a rotary motion with a hydrostatic gas, wherein a bearing surface of the moving member and a motion guide surface on the fixed member side. The static pressure gas bearing is characterized in that the bearing gap defined by is formed so small that the viscous resistance of the static pressure gas in the bearing gap acts. 2. The static pressure gas bearing, wherein the bearing gap is smaller than 20 times the surface roughness of the motion guide surface on the fixed member side and the bearing surface of the motion member.