JP2001012469A - Static pressure fluid bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remarkably improve the exhausting efficiency and to allow a static pressure fluid bearing to sufficiently operate even with double exhaust channels and under the ultra high vacuum environment of above a predetermined value, by inclining an inner wall of at least an air supplying channel with respect to one of guide surfaces at a specific angle. SOLUTION: The compressed fluid supplied to a clearance T between a first guide surface 2 and a second guide surface 4 is recovered by a suction pump by means of double exhaust channels 7, 8 formed around an air supply hole 6 to prevent the fluid from leaking from the clearance T. As an inner wall of the exhaust channel 7 positioned at least inside is inclined to the second guide surface 4 at an angle a of 40-65 degrees, most of fluid is recovered by the exhaust channel 7, and the remained fluid is recovered by an outside exhaust channel 8, which remarkably reduces the fluid amount leaking from the clearance T. A static pressure fluid bearing can be operated without impairing a vacuum degree even under the ultra high vacuum environment of over 1×10-5 Torr.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of spraying a compressed fluid between two members to form a hydrostatic fluid layer, and recovering the compressed fluid supplied between the two members to leak the fluid to the outside. The present invention relates to a hydrostatic bearing used for rotary motion and linear motion that can be driven without any problem, and in particular, a vacuum-compatible static pressure that can be used in a vacuum, especially in an ultra-high vacuum of 1 × 10 ⁻⁵ Torr or more. It is suitable as a fluid bearing.

[0002]

2. Description of the Related Art Conventionally, hydrostatic bearings have been used as means for performing smooth rotational movement and linear movement. The hydrostatic fluid bearing supports the movable member on the fixed member by static pressure by ejecting a compressed fluid into a minute gap between the fixed member and the movable member to form a hydrostatic fluid layer. Since the two members do not directly contact each other, the frictional resistance is extremely small, and the movable member can be smoothly rotated or linearly moved.

In order to support the movable member on the fixed member by static pressure, it is necessary to leak the compressed fluid supplied between the two members to the outside, but cannot be used as it is in a vacuum atmosphere. The applicant of the present application is, for example, as shown in FIG.
A hydrostatic bearing as shown in FIG. 1B has been proposed (see Japanese Patent Publication No. 8-1215).

This hydrostatic bearing has a support plate 23 at both ends.
24, the outer wall of which is the first columnar body.
A first member 21 serving as a guide surface 22, and a cylindrical body surrounding the first member 21, the inner wall of which is a second guide surface 32
The second guide surface 32 has a pocket 33 and an air supply hole 3 which communicates with the pocket 33 and ejects a compressed fluid such as air toward the first guide surface 22.
4, the compressed gas is ejected from the air supply hole 34 and diffused by the pocket 33 so that the first guide surface 22
A static pressure fluid layer is formed in a small gap S between the second member 31
Is supported on the first member 21 by static pressure. Further, between the second member 31 and each of the support plates 23 and 24, an outer envelope 25, 26 made of, for example, neoprene rubber or the like having a contractive property so as to cover the outer periphery of the first member 21 is hermetically sealed. Exhaust holes 2 attached to each support plate 23, 24 to allow fluid leaking from the gap S between the first member 21 and the second member 31
The vacuum environment is maintained by releasing the gas from outside the vacuum atmosphere from 3a and 24a.

[0005] Then, in order to move the second member 31,
The nut 43 screwed to the screw shaft 42 installed in parallel with the first member 21 is connected to the second member 31, and the motor 44 rotates the screw shaft 42 to move the nut 43 in the axial direction. The two members 31 are moved along the first member 21.

As means for moving the second member 31, besides driving the motor 44 via the ball screw 41, motor driving via a belt or direct driving of the second member 31 by an air cylinder or a linear motor. That was also done.

[0007]

However, FIG. 9 (a)
The hydrostatic bearing shown in (b) can be used in a vacuum atmosphere only when the degree of vacuum is up to about 10 ⁻³ Torr. Is too large, the outer enclosures 25, 26 expand rapidly and eventually break, resulting in 1 × 10 ⁻³ T
It could not be used in a vacuum environment exceeding orr.

Further, even in a vacuum environment of 1 × 10 ⁻³ Torr or less, the movement of the outer enclosures 25 and 26 which contracts with the movement of the second member 31 becomes a resistance and the second member 31 There is also a problem that the smooth movement performance of the second member 31 is impaired because the movement is hindered.

Therefore, as a hydrostatic bearing which can be used in a vacuum environment without using the outer enclosures 25 and 26 which impede the smooth movement performance of the second member 31, FIG.
(B) has been proposed (JP-A-63-19).
No. 2864).

[0010] The hydrostatic bearing is a cylindrical body,
The first member 51 has an outer wall as a first guide surface 52 and a second member 61 which is a cylindrical body surrounding the first member 51 and has an inner wall as a second guide surface 62. The guide surface 62 has a pocket 63 formed at the center thereof along the circumferential direction, an air supply hole 64 communicating with the pocket 63 and ejecting a compressed fluid toward the first guide surface 52, and the pocket 63. Triple exhaust grooves 65, 66, 67 formed on each side of the exhaust groove along the circumferential direction;
5, 66, 67 respectively, and has suction holes 68, 69, 70 for forcibly exhausting gas leaking from a small gap R between the first guide surface 52 and the second guide surface 62. Was. The inner walls of the exhaust grooves 65, 66, and 67 were formed perpendicular to the second guide surface 62, respectively.

Each of the suction holes 68, 69, 70 is designed to be vacuum-suctioned by a suction pump (not shown) via hoses 71, 72, 73, and the air supply holes 64 are provided.
The compressed fluid is supplied from a compression pump (not shown) via a hose 74.

In order to operate the hydrostatic bearing, compressed gas is ejected from the air supply hole 64 of the second member 61 and diffused in the pocket 63, thereby forming a small gap R with the first guide surface 52. A static pressure fluid layer is formed on the first member 51, and the second member 61 is supported on the first member 51 by static pressure.
The fluid leaking from the minute gap R between the guide surface 52 and the second guide surface 62 is supplied to the first exhaust groove 65, the second exhaust groove 66,
By forcibly exhausting the gas sequentially through the third exhaust groove 67, the fluid is prevented from leaking to the outside (in vacuum), and the vacuum environment is maintained.

However, the hydrostatic bearing shown in FIGS. 10A and 10B can be operated without lowering the degree of vacuum at most on the order of 10 ^-4 Torr to 10 ^-5 T.
Torr level, and 10 ^-6 Torr exceeding 1 × 10 ^-5 Torr recently required in semiconductor manufacturing processes and the like.
It could not be used in a table or an ultra-high vacuum environment.

Further, in the hydrostatic bearing shown in FIGS. 10A and 10B, a first guide surface 52 and a second guide surface are provided after securing a static pressure region necessary for maintaining the bearing rigidity. 6
In order to prevent the gas from leaking from the small gap R and maintain the operable vacuum environment, at least both low-, medium-, and high-vacuum It requires two exhaust grooves 65, 66, 67, making it difficult to reduce the size of the second member 61 while maintaining the rigidity of the bearing. Since 72 and 73 are required,
The number of parts is large, the structure is complicated, and the hoses 74, 75, 76 connected to the suction pumps 71, 72, 73 are further provided.
When the second member 61 moves linearly on the first member 51, the hoses 74, 7 associated with the movement are increased.
There is also a risk that the bending of 5, 76 may cause resistance and hinder the smooth linear movement of the second member 61.

[0015]

In view of the above-mentioned problems, the present inventor has reduced the number of exhaust grooves and has reduced the number of exhaust grooves to 1 × 1 even with double exhaust grooves.
After extensive research on hydrostatic bearings capable of operating in an ultra-high vacuum environment of 0 ^-5 Torr or higher,
At least the inner wall of the exhaust groove close to the air supply hole is inclined at an angle so as to spread outward from the opening, so that the exhaust efficiency from the exhaust groove can be remarkably improved. It has been found that it can operate sufficiently even in an ultra-high vacuum environment of 1 × 10 ⁻⁵ Torr or more,
The present invention has been reached.

That is, the hydrostatic bearing of the present invention comprises a first member having a first guide surface, and a second member having a second guide surface opposed to the first guide surface with a gap provided therebetween. The first guide surface or the second guide surface has an air supply hole for ejecting a compressed fluid into the gap to form a hydrostatic fluid layer, and is engraved around the air supply hole to collect the compressed fluid. A double exhaust groove is provided, and at least an inner wall of the exhaust groove located inside is inclined outward in a range of 40 to 65 degrees with respect to the first guide surface or the second guide surface. I do.

[0017]

Embodiments of the present invention will be described below.

FIG. 1 is a perspective view showing an example of a hydrostatic bearing of the present invention, FIG. 2 is a cross-sectional view showing only a main part taken along line XX of FIG. 1, and FIG. 3 is a view showing only a second member of FIG. It is the perspective view which fractured | shown one part.

This hydrostatic bearing has a support plate 13 at both ends.
14 is a columnar body, the outer wall of which is the first
A first member 1 serving as a guide surface 2 and a second member 3 which is a tubular body surrounding the first member 1 and has an inner wall serving as a second guide surface 4 are provided. Is pocket 5
And an air supply hole 6 which communicates with the pocket 5 and ejects a compressed fluid such as air toward the first guide surface 2.
A static fluid layer is formed in a small gap T with the first guide surface 2 by spraying a compressed fluid from the first member 5 and diffusing the compressed fluid by the pocket 5, and the second member 3 is statically supported on the first member 1. It has become.

The second guide surface 4 is provided with a double engraving formed around the pocket 5 (or the air supply hole 6) for recovering the compressed fluid injected into the gap T with the first guide surface 2. An exhaust hole 7, 8 is provided, and the inner wall of the exhaust hole 7 located inside, that is, the exhaust groove 7 close to the air supply hole 6, is disposed outside from the opening at an angle α of 40 to 65 degrees with respect to the second guide surface 4. And the inner wall of the exhaust groove 8 located outside, that is, the exhaust groove 8 farther from the air supply hole 6, is inclined toward the second guide surface 4.
Are formed perpendicular to.

The inside of the second member 3 is provided with an air supply passage 21 communicating with the air supply hole 6 formed in each of the second guide surfaces 4.
And suction passages 22 and 23 communicating with the exhaust grooves 7 and 8 formed in the second guide surfaces 4. The air supply passage 21 is connected to the compression pump 10 via a hose 24 and the suction passages 2.
2, 23 are suction pumps 11 through hoses 25, 26,
12 respectively.

The hydrostatic bearing includes a first member 1
The screw shaft 17 of the ball screw 16 is installed in parallel with
A nut 18 screwed to the screw shaft 17 is connected to the second member 3 via a connecting member 19, and a motor 20 is connected to one end of the screw shaft 17.

In FIG. 1, the driving means by the motor 20 via the ball screw 16 is shown as the means for moving the second member 3, but the motor driving via the belt or the second
The member 3 may be directly driven by an air cylinder or a linear motor.

In order to move the second member 3 using this hydrostatic bearing, first, a compressed fluid such as air is jetted from the air supply hole 6 toward the first guide surface 2. At this time,
The compressed fluid is diffused by the pockets 5, and a static pressure fluid layer is formed in the gap T between the first guide surface 2 and the second member 3.
It is supported on the member 1 by static pressure. By moving the nut 18 in the axial direction while rotating the screw shaft 17 by the motor 20, the second member 3 is not in contact with the first member 1, so that there is no sliding resistance between them. , Second
The member 3 can be moved smoothly along the first member 1.

The compressed fluid supplied to the gap T between the first guide surface 2 and the second guide surface 4 is supplied to the suction pump 14 by the double exhaust grooves 7 and 8 formed around the air supply hole 6. Fifteen
According to the present invention, at least the inner wall of the exhaust groove 7 located on the inner side is prevented from leaking through the gap T between the first guide surface 2 and the second guide surface 4. Angle α of 40 ° to 65 ° with respect to 2 guide surface 4
, The most part of the fluid is collected by the exhaust groove 7, and the remaining fluid is collected by the outer exhaust groove 8, so that the fluid can be removed from the gap T between the first guide surface 2 and the second guide surface 4. Since the amount of leaking fluid can be extremely reduced, it can be operated without reducing the degree of vacuum even in an ultra-high vacuum environment exceeding 1 × 10 ⁻⁵ Torr.

Moreover, the first guide surface 2 and the second guide surface 4
The recovery of the fluid ejected into the gap T between the second member 3 and the second member 3 can be achieved by the double exhaust grooves 7 and 8 as compared with a conventional hydrostatic bearing having triple exhaust grooves. And the weight of the second member 3 can be reduced, so that the amount of compressed fluid ejected from the air supply holes 6 to support the second member 3 under static pressure can be reduced, which is economical.

In addition, since the two exhaust grooves 7, 8 are used, only two suction pumps 11, 12 are required, so that the structure can be simplified and the suction passage 22 communicating with each of the exhaust grooves 7, 8 can be obtained. , 23 and the suction pumps 11, 12 can be reduced to two hoses 25, 26, respectively.
The resistance due to the bending of the hoses 25 and 26 accompanying the movement of the member 3 can be reduced, and the smooth movement of the second member 3 can be prevented from being hindered.

By the way, in order to obtain such an effect, as described above, at least the inner wall of the exhaust hole 7 located inside of the double exhaust grooves 7 and 8 is It is important to incline so as to extend outward from the opening at an angle α of 40 to 65 degrees.

That is, in order to efficiently collect the compressed fluid jetted into the gap T between the first guide surface 2 and the second guide surface 4, it is better to make the inner wall of the exhaust groove 7 as inclined as possible. However, if the angle α with respect to the second guide surface 4 is less than 40 degrees, it is not possible to increase the fluid recovery efficiency even if the angle is further inclined, and moreover, compared with a conventional hydrostatic fluid bearing having a triple exhaust groove. On the other hand, if the angle α with respect to the second guide surface 4 exceeds 65 degrees, the efficiency of fluid recovery is poor, and the double exhaust grooves 7 and 8 cannot be used. This is because the amount of fluid leaking from the gap T becomes too large, so that it cannot be operated without lowering the degree of vacuum in an ultra-high vacuum environment exceeding 1 × 10 ⁻⁵ Torr. Preferably, the second guide surface 4 is inclined so as to spread outward from the opening at an angle α of 40 to 45 degrees.

In order to increase the efficiency of fluid recovery by the exhaust grooves 7, 8, the groove width L of the inner
Is twice or more the groove width N of the exhaust groove 8 located on the outside, and the interval M between the exhaust grooves 7 and 8 is equal to or greater than the groove width N of the exhaust groove 8 located on the outside. Preferably, it is longer. When the groove width L of the exhaust groove 7 located on the inner side is less than twice the groove width N of the exhaust groove 8 located on the outer side, the amount of fluid that can be collected in the exhaust groove 7 is small because the groove width L is small. If the distance M between the exhaust groove 7 and the exhaust groove 8 is smaller than the groove width N of the exhaust groove 8 located on the outside, the distance M between the two is too short. This is because the flow rate of the fluid passing through the gap is large, the amount of fluid flowing into the exhaust groove 8 is increased, and the efficiency of fluid recovery by the double exhaust grooves 7 and 8 is reduced.

In FIG. 2, the exhaust grooves 7 near the air supply holes 6 are shown.
The example in which only the inner wall of the outer exhaust groove 8 is inclined is shown.
May be inclined under the same conditions as the exhaust groove 7, so that the fluid can be collected more efficiently.

In this embodiment, the first member 1 is the second member.
Although the hydrostatic bearing has a structure in which the second member 3 is linearly moved in a state where the second member 3 is supported on the first member 1 by static pressure, the first member 1 is not necessarily surrounded by the second member 3. It is not necessary that the present invention is applicable to a hydrostatic bearing in which a compressed fluid is jetted into a gap between a first plate-shaped member and a second plate-shaped member to support the hydrostatic pressure. Needless to say.

Further, the present invention is not limited to a hydrostatic bearing that linearly moves. The static member having a structure in which a first member is surrounded by a second member and the first member rotates in the second member. Needless to say, the present invention can be applied to a pressure fluid bearing, and the same effect can be obtained.

[0034]

(Embodiment 1) Here, in order to confirm the efficiency of fluid recovery by the hydrostatic fluid bearing of the present invention and the conventional hydrostatic fluid bearing, as shown in FIG. Flat plate 4
A member 41 provided with a double exhaust groove 44, 45 on a guide surface 42 opposite to a member 0 is provided at an interval of 5 μm, and a member 40, as shown in FIG. Triple exhaust grooves 49, 50, 51 are provided on the opposed guide surface 47.
Are provided at intervals of 5 μm, and the vacuum vessel 5 of the experimental apparatus shown in FIG. 5 is prepared.
In FIG. 4, when the compressed air is blown into the gap between the flat plate 40 and each of the members 41 and 46, the double exhaust groove 4 shown in FIG.
4, 45 and the triple exhaust grooves 49, 50, shown in FIG.
The efficiency of air recovery by 51 was confirmed by examining the degree of decrease in the degree of vacuum in the vacuum vessel 52.

In FIGS. 4A and 4B, reference numerals 43,
Numeral 48 denotes each member 4 for ejecting compressed air to the flat plate 40.
These are the air supply holes provided in the first and second air intakes 46. FIG. 5 is FIG.
3A shows a state in which the flat plate 40 and the member 41 are set in the vacuum vessel 52, and three sides of the gap between the flat plate 40 and the member 41 are closed by the sealing members 53, 54, and 85 and remain. Only one side is open. Here, 56 is an exhaust pump for evacuating the vacuum vessel 52, 57 is a vacuum gauge for measuring pressure fluctuation in the vacuum vessel 52, and 58 is a member 4
A hose for supplying compressed air to the first air supply hole 43,
9 and 60 are hoses for sending air collected from the exhaust grooves 44 and 45 of each member 41 to a suction pump (not shown).

In FIG. 4A, the width of the exhaust groove 44 close to the air supply hole 43 is 20 mm, the width of the outer exhaust groove 45 is 10 mm, and the interval between the exhaust grooves 44, 45 is 10 mm.
Further, the inner wall of the exhaust groove 44 is inclined outward from the opening at an angle β of 45 degrees with respect to the guide surface 42, and the inner wall of the exhaust groove 45 is formed perpendicular to the guide surface 42, as shown in FIG. In b), the groove width of the exhaust groove 49 near the air supply hole 48 is 10 mm, the groove width of the next exhaust groove 50 is 10 mm, the groove width of the outer exhaust groove 51 is 10 mm, and the exhaust grooves 49, 50, and 5 are provided.
1 is 10 mm, and each exhaust groove 49, 50, 5
Each of the inner walls was formed perpendicular to the guide surface 47.

In order to confirm the efficiency of air recovery using this experimental apparatus, the air in the vacuum vessel 52 is evacuated by the exhaust pump 56 to a degree of vacuum of 5 × 10 ⁻⁶ Torr, and then each member 41 ( Air is collected by the exhaust grooves 44, 45 (49, 50, 51) in a state where compressed air of 2 liter / min is jetted from the air supply hole 43 (48) of the 46) to the plane 40, and the vacuum gauge at that time is collected. The degree of vacuum of 57 was confirmed.

As a result, FIG. 4B shows the exhaust grooves 49 and 5.
Since the inner walls 0, 85 are formed perpendicular to the guide surface 47, the efficiency of air recovery is poor, and
The degree of vacuum in the vacuum vessel 52 has been reduced to the order of 10 ^-5 Torr due to a large amount of air leaking from the gap between the member 46 and the gap.

On the other hand, FIG. 4A shows a double exhaust because the inner wall of the exhaust groove 44 is inclined outward from the opening at an angle β of 45 ° with respect to the guide surface 42. Even though the grooves 44 and 45 are provided, the flat plate 4
Since the amount of air leaking from the gap between the zero and the member 41 is extremely small, the degree of vacuum in the vacuum vessel 52 is 1 × 10 ⁻⁵ Torr.
r and could be used even under ultra-high vacuum.

Therefore, in the structure of FIG. 4A, the inner wall of the exhaust groove 44 is set at 30 °, 45 ° with respect to the guide surface 42,
The air recovery efficiency was measured under the same conditions except for inclining at an angle β of 65 degrees and 75 degrees.

The results are as shown in FIG.

As a result, when the angle β exceeds 45 degrees, the degree of vacuum in the vacuum vessel 52 gradually decreases, and when the angle β exceeds 65 degrees, it falls below 1 × 10 ⁻⁵ Torr and is maintained at a level of 10 ⁻⁶ Torr. Is no longer possible. However, if the angle β is smaller than 40 degrees, the member 41 becomes large, which is not preferable.

Therefore, of the double exhaust grooves 44 and 45,
By inclining the inner wall of the exhaust groove 44 near the air supply hole 43 so as to spread outward from the opening at an angle β of 40 to 65 degrees with respect to the guide surface 42, the double exhaust groove 44, 4 is formed.
5, a high air recovery efficiency can be obtained, and 1 × 10 ⁻⁵ Torr
It turns out that the degree of vacuum of r or more can be maintained.

(Embodiment 2) Next, in the structure of FIG. 4A, the same conditions as in Embodiment 1 are applied to the air recovery efficiency when the width of the exhaust groove 44 near the air supply hole 43 is changed. Was measured. In the experiment, the inclination angle β of the inner wall of the exhaust groove 44 was 45 degrees, the interval between the exhaust grooves 44, 45 was 10 mm, and the groove width of the exhaust groove 45 was 10 mm.

The results are as shown in FIG.

As a result, by setting the groove width of the exhaust groove 44 close to the air supply hole 43 to be at least twice the groove width of the other exhaust groove 45, the efficiency of recovering air is increased, and the vacuum in the vacuum vessel 52 is increased. The degree could be 1 × 10 ⁻⁵ Torr or more.

As a result, it is found that the width of the exhaust groove 44 close to the air supply hole 43 should be at least twice the width of the other exhaust groove 45.

(Embodiment 3) Further, in the structure shown in FIG. 4A, the air recovery efficiency when the interval between the exhaust grooves 44 and 45 is changed is measured under the same conditions as in Embodiment 1. Was.

In the experiment, the inclination angle β of the inner wall of the exhaust groove 44 was 45 degrees, the groove width of the exhaust groove 44 was 20 mm, and the groove width of the exhaust groove 45 was 10 mm.

The results are as shown in FIG.

As a result, the degree of vacuum in the vacuum vessel 52 is set to 1 × 10 ⁻⁵ Torr or more by setting the interval between the exhaust grooves 44 and 45 to be equal to or longer than the groove width of the outer exhaust groove 45. I was able to.

As a result, it is understood that the interval between the exhaust grooves 74 and 45 should be equal to or greater than the width of the outer exhaust groove 45.

[0053]

As described above, according to the hydrostatic bearing of the present invention, the first member having the first guide surface and the second guide surface facing the first guide surface with a gap provided therebetween are provided. And a second member having an air supply hole formed on the first guide surface or the second guide surface to eject a compressed fluid into the gap to form a hydrostatic fluid layer, and engraved around the air supply hole. And a double exhaust groove for recovering the compressed fluid, wherein at least the inner wall of the exhaust groove located at the inner side is formed in a range of 40 to 65 degrees with respect to the first guide surface or the second guide surface. Of the fluid ejected into the gap between the first guide surface and the second guide surface even in the double exhaust groove, the first exhaust surface and the second guide surface are inclined. The amount of fluid leaking to the outside from the gap with the surface can be extremely reduced Because, 1 × can also be operated without reducing the degree of vacuum under ultra-high vacuum environment of 10 ^-5 Torr or more.

Further, since the fluid can be recovered by the double exhaust grooves, the member having the air supply hole can be reduced in size as compared with the conventional hydrostatic fluid bearing having the triple exhaust grooves. At the same time, since the weight can be reduced, the amount of compressed fluid ejected from the air supply hole can be reduced, which is economical.

Further, since only two suction pumps are required for recovering the gas, the structure can be simplified, and the number of hoses connecting the suction holes and the suction pumps communicating with the respective exhaust grooves can be reduced to two. Therefore, when the member provided with the exhaust groove moves, the resistance due to the bending of the hose can be reduced, and the smooth movement of the hydrostatic bearing can be maintained.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of a hydrostatic bearing according to the present invention.

FIG. 2 is a cross-sectional view showing only a main part along line XX in FIG.

FIG. 3 is a partially broken perspective view showing only a second member in FIG. 1;

FIG. 4A is a cross-sectional view illustrating a member having a double exhaust groove in an experiment, and FIG. 4B is a cross-sectional view illustrating a member having three types of exhaust grooves in an experiment.

FIG. 5 is a schematic view showing an experimental apparatus.

FIG. 6 is a graph showing a relationship between an inclination angle of an inner wall of an exhaust groove close to an air supply hole and a degree of vacuum in a vacuum vessel.

FIG. 7 is a graph showing a relationship between a groove width of an exhaust groove close to an air supply hole and a degree of vacuum in a vacuum vessel.

FIG. 8 is a graph showing a relationship between an interval between double exhaust grooves and a degree of vacuum in a vacuum vessel.

9A is a perspective view showing an example of a conventional hydrostatic bearing, and FIG. 9B is a sectional view taken along line YY in FIG. 9A.

10A is a perspective view showing another example of the conventional hydrostatic bearing, and FIG. 10B is a sectional view taken along line ZZ of FIG. 10A.

[Explanation of symbols]

1: First member 2: First guide surface 3: Second member 4:
Second guide surface 5: Pocket 6: Air supply hole 7, 8: Exhaust groove 10: Compression pump 1
1, 12: suction pump 13, 14: support member 16: ball screw 17: screw shaft 18: nut 19: connecting member 20: motor L, N: groove width of exhaust groove T: gap between first member and second member M: Spacing between double exhaust grooves α: Incline angle of the exhaust groove inner wall with respect to a plane perpendicular to the guide surface

Claims (1)

[Claims] A first member having a first guide surface; and a second member having a second guide surface opposed to the first guide surface with a gap provided between the first member and the second member.
The guide surface includes an air supply hole for ejecting a compressed fluid into the gap to form a static pressure fluid layer, and a double exhaust groove formed around the air supply hole to collect the compressed fluid, and A hydrostatic bearing wherein at least an inner wall of an exhaust groove located inside is inclined at an angle of 40 to 65 degrees outward with respect to the first guide surface or the second guide surface.