JP3090396B2 - Hydrostatic gas bearing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrostatic gas bearing having an extremely low outflow amount of an extremely small amount of gas flowing out to the surroundings, and to a guide mechanism provided in a measuring device, a processing machine, a positioning device or the like. Available.

[0002]

2. Description of the Related Art Generally, a guide mechanism using a sliding guide, a rolling guide, or a static pressure guide is used as a guide mechanism for various devices requiring positioning, such as a measuring instrument, a processing machine, and a positioning device. Among them, a guide mechanism using a sliding guide or a rolling guide causes problems such as stick-slip, vibration, and elastic deformation. Therefore, when high-precision positioning is required, a guide mechanism using a static pressure guide is often used. . Oil or air is used as a lubricant for the guide mechanism using this static pressure guide. However, when high-precision positioning is required due to factors such as temperature and contamination, a static pressure gas bearing is used. Guide mechanisms are widely used.

Conventionally, as one form of a high-precision or ultra-precision system provided with a guide mechanism using a hydrostatic gas bearing,
A laser interferometer is used as a length measuring system for grasping the amount of displacement of a member that is displaced in accordance with the guidance of the guide mechanism, and the entire system including the laser interferometer and the guide mechanism is covered with a chamber, so that ambient heat and air One that blocks the effect of the flow of air. The installation of such a chamber,
The purpose of the present invention is to remove or suppress the effects of expansion and contraction of components due to temperature fluctuation and air fluctuation on the optical path of the laser interferometer.

[0004]

However, in the above-described system entirely covered by the chamber, the influence of heat and air flow outside the chamber can be cut off. Since there is gas flowing out (all the gas supplied to the bearing surface of the static pressure gas bearing from the outside), there is a problem that the influence of the temperature and flow of the gas flowing out into the chamber cannot be avoided.

An object of the present invention is to provide a hydrostatic gas bearing which can suppress the amount of gas flowing out to the surroundings extremely low.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to achieve the above object by exhausting gas supplied to a bearing surface from an exhaust passage. Specifically, the hydrostatic gas bearing of the present invention has an air supply passage which is opened on a bearing surface and supplies gas to the bearing surface, and which is disposed on an outer peripheral side of the bearing surface and is concavely recessed from the bearing surface. A pocket formed in the pocket, an exhaust path opened in the wall of the pocket and communicating the pocket with the outside, and according to a supply amount of gas supplied from the air supply path,
Negative pressure suction means for suctioning the gas in the pocket from the exhaust path under a negative pressure , wherein the negative pressure suction means comprises:
And a supply-side flow sensor provided in the middle of the exhaust passage.
An exhaust-side flow sensor provided on the way;
Inside and provided downstream of the exhaust-side flow sensor.
A negative pressure generator, the air supply side flow sensor, and the exhaust side flow
So that the flow rate detected by the
And a control device for controlling the pressure generating device.
I do. Here, the negative pressure suction means may be configured to suck the negative pressure from the exhaust path according to the supply amount of the gas so that the gas supplied from the air supply path does not flow out of the static pressure gas bearing. For example, a negative pressure suction unit having a suction amount substantially equal to the supply amount of the gas supplied from the air supply path can be employed.

Here, as a preferable specific example of the negative pressure generating device, a negative pressure ejector provided in the middle of the exhaust passage and downstream of the exhaust side flow sensor, the negative pressure ejector and the negative pressure ejector are provided. One provided with an air passage in the middle of the air supply passage and communicating with the upstream side of the air supply side flow sensor, and a regulator provided in the middle of the air passage and operated by the control device. Can be

The above-described static pressure gas bearing is provided with a pocket
Are arranged continuously on the outer peripheral side of
It is preferable to have an outer peripheral resistance portion arranged. here
The dimensions (size) and arrangement shape of the pocket,
The number and diameter (cross-sectional area) of the airways, and the shape of the peripheral resistance part
The shape, area, etc. are determined by the desired exhaust rate Qr (= discharge flow rate Qex /
Inflow flow rate Qin; see FIGS. 1 and 2 described later).
It may be determined appropriately as described above. For example, increase the number of exhaust passages
Or increase the area of the outer peripheral resistance part.
The resistance of the outer peripheral resistance part is much larger than the resistance of the exhaust path.
The discharge flow rate Qex becomes large,
A low exhaust rate Qr is obtained.

[0009]

[Action] In the present invention, comprising a negative pressure suction means for vacuum sucking the gas in the pocket in accordance with the supply amount of the gas supplied from the air supply passage, the negative pressure suction means supply side
Flow sensor, exhaust side flow sensor, negative pressure generator, and
Since the control device is provided, the amount of gas flowing out of the hydrostatic air bearing can be reduced as much as possible. Therefore, in the case of using a laser interferometer for a high-precision or ultra-precision system equipped with a guide mechanism using a hydrostatic gas bearing, particularly a laser interferometer for a length measurement system, adverse effects on the system due to the temperature and flow of the outflowing gas are avoided. Objective is achieved. In particular,
As described above, if the negative pressure suction means having a suction amount substantially equal to the supply amount of the gas supplied from the air supply passage is employed, the outflow gas can be reduced to zero.

Moreover, the negative pressure suction means described above, the air supply-side flow rate sensor, an exhaust side flow sensor is provided with the negative pressure generating apparatus, and a control unit, air supply flow rate sensor and the detection by the exhaust-side flow rate sensor By controlling the negative pressure generating device with the control device so that the flow rates are substantially equal, it is possible to easily and reliably reduce the outflow of gas to the surroundings to zero. Further, if the above-described hydrostatic gas bearing is provided with an outer peripheral resistance portion continuously disposed on the outer peripheral side of the pocket and substantially on the same surface as the bearing surface, the supply of gas supplied from the air supply passage is provided. Even if there is a temporary difference between the amount of gas and the amount of gas suctioned by the negative pressure by the negative pressure suction means, the outflow of gas is ensured by temporarily regulating the outflow of gas by the outer peripheral resistance portion. Can be prevented.

[0011]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the overall configuration of a hydrostatic gas bearing 10 according to the present embodiment. The hydrostatic gas bearing 10 includes a bearing body 11 having a bearing surface 12 formed on a downward surface in the figure, an air supply passage 20 for supplying gas such as air to the bearing surface 12 from the outside,
A pocket 30 arranged on the outer peripheral side of the bearing surface 12 to collect gas, an exhaust path 40 for discharging gas in the pocket 30 to the outside, an outer peripheral resistance portion 50 arranged on the outer peripheral side of the pocket 30, A negative pressure suction means 60 for performing a negative pressure suction of the gas in the pocket 30 through the exhaust path 40 is provided.

The bearing body 11 is provided with an opposing member 15 provided on the lower side of the bearing body 11 in the drawing so as to face the bearing surface 12.
And a predetermined interval H. Hydrostatic gas bearing 1
Reference numeral 0 denotes a configuration in which the bearing mechanism 11 is configured to move relative to the facing member 15 while maintaining a predetermined interval H while the load W is being applied, thereby forming a guide mechanism. In addition, with respect to the space, either the bearing body 11 or the facing member 15 may be on the fixed side.

FIG. 2 shows an enlarged state and pressure distribution of the bearing main body 11. FIG. 3 shows the bearing body 1.
1 shows a state when viewed from the bearing surface 12 side. 2 and 3, an air supply passage 20 includes an air supply hole 21 formed inside the bearing body 11, an air supply pipe 22 connected to the bearing body 11 so as to communicate with the air supply hole 21, and an air supply hole. Air supply groove 2 formed at a portion where 21 is open to bearing surface 12
3. In the air supply hole 21, a narrowed portion 21 </ b> A having a smaller diameter than the air supply pipe 22 is formed in a portion on the air supply groove 23 side. Air supply groove 23
Is a groove having a cross-sectional shape such as an arc shape, a triangular shape, or a quadrangular shape that is formed so as to be depressed from the bearing surface 12 (see FIG. 2), and is arranged to form a substantially square on the bearing surface 12. (See FIG. 3).

The pocket 30 is a groove having a rectangular cross-sectional shape formed so as to be depressed from the position of the extension surface of the bearing surface 12 (see FIG. 2), and has a substantially square shape on the outer peripheral side of the bearing surface 12. (See FIG. 3). Exhaust path 40
Is formed by an exhaust hole 41 formed inside the bearing main body 11 and opening to the wall surface of the pocket 30, and an exhaust pipe 42 connected to the bearing main body 11 so as to communicate with the exhaust hole 41.

The outer peripheral resistance portion 50 is arranged continuously on the outer peripheral side of the pocket 30 where the gas supplied to the bearing surface 12 flows out, that is, so as to form a substantially square shape without interruption. Further, the surface of the outer peripheral resistance portion 50 is the bearing surface 1.
2 are arranged on substantially the same plane.

Here, an example of the dimensions of each part of the hydrostatic gas bearing 10 is shown in FIG. 2 and FIG.
1 thickness S2 = 20 mm, pocket 30 depth S1 = 5
mm, the width L1 of the air supply groove 23 = 30 mm, the width L2 from the air supply groove 23 to the pocket 30 = 10 mm, the width L3 of the pocket 30 = 5 mm, the width L4 of the outer peripheral resistance portion 50 = 5 mm, and the size of the bearing body 11. L5 = 70 mm and the like. However,
The dimensions of each part are not limited to these numerical values.

Returning to FIG. 1, the air supply path 20 (the air supply pipe 22)
A pressure source 25 for supplying an external gas is provided at the right end in the drawing, and a filter 26 for purifying the inflow gas, A regulator 27 for adjusting the pressure or the flow rate, a pressure gauge 28 for measuring the pressure of the inflow gas, and a supply-side flow sensor 61 for measuring the flow rate of the inflow gas are provided.

In the middle of the exhaust path 40 (exhaust pipe 42), there is provided an exhaust-side flow sensor 62 for measuring the flow rate of gas collected in the pocket 30 and discharged through the exhaust path 40. Further, a negative pressure ejector 71 that ejects gas to generate a negative pressure is provided downstream of the exhaust-side flow sensor 62. The negative pressure ejector 71 and the air supply passage 20
A midway of the (air supply pipe 22) and a position between the filter 26 and the regulator 27 are communicated by a ventilation path 72.

In the middle of the ventilation passage 72, from the upstream side (right side in the figure), a regulator 73 for adjusting the pressure or flow rate of the gas passing through the ventilation passage 72, a pressure gauge 7 for measuring the pressure.
4. An electropneumatic regulator 75 for adjusting the pressure or flow rate of the gas sent to the negative pressure ejector 71 is provided.
The negative pressure ejector 71, the ventilation path 72, the regulator 73, the pressure gauge 74, and the electropneumatic regulator 75 constitute a negative pressure generator 70.

Further, between the supply-side flow sensor 61 and the exhaust-side flow sensor 62 and the electropneumatic regulator 75,
An arithmetic processing unit (CPU) 81 and a power amplifier 82 are provided. The arithmetic processing device 81 and the power amplifier 82 constitute a control device 80 for controlling the negative pressure generating device 70. The control device 80
The detection signals of the supply-side flow sensor 61 and the exhaust-side flow sensor 62 are input to the arithmetic processing unit 81, and the inflow flow rate Qin and the discharge flow rate Qe obtained from these detection signals
The output of the arithmetic processing device 81 calculated based on the value of x is sent to the electropneumatic regulator 75 via the power amplifier 82 to operate the electropneumatic regulator 75, thereby controlling the state of the negative pressure ejector 71. It has become.
Then, the above-described negative pressure generating device 70 and control device 8
0, supply-side flow sensor 61, and exhaust-side flow sensor 6
2 constitutes a negative pressure suction means 60.

In this embodiment, the hydrostatic gas bearing 10 is operated as follows. First, an external gas is supplied by the pressure source 25 through the air supply passage 20 to the air supply groove 23.
From the bearing surface 12. Further, the gas is also sent to the ventilation path 72 branched from the air supply path 20, and the gas is supplied to the negative pressure ejector 71.

Next, as shown in FIG. 2, the gas (inflow flow rate Qin) supplied to the bearing surface 12 passes through the gap between the outer peripheral resistance portion 50 and the facing member 15 and flows out to the periphery (outflow flow rate Qin). Flow rate Qout) and the gas collected in the pocket 30 and discharged to the outside through the exhaust path 40 (discharge flow rate Qe).
x). At this time, the gas in the pocket 30 is vacuum-suctioned by the negative pressure suction means 60 and the outflow flow rate Qo
ut = 0.

That is, the detection signal (inflow flow rate Qin) of the supply-side flow sensor 61 and the detection signal (exhaust flow rate Qex) of the exhaust-side flow sensor 62 are input by the control device 80, and these values become equal (inflow state). Flow rate Qin = discharge flow rate Qex), that is, outflow flow rate Qout = 0.
The state of the negative pressure ejector 71 is controlled by operating the electropneumatic regulator 75 such that The feedback control by the control device 80 is performed by the static pressure gas bearing 10.
The operation is continuously performed during the operation period.

Further, as shown in FIG. 2, the pressure distribution during operation of the static pressure gas bearing 10 is such that the air supply groove 23 of the bearing surface 12 is provided.
The pressure Pr is uniform and high in the portion on the inner peripheral side, and the portion of the bearing surface 12 on the outer peripheral side of the air supply groove 23 gradually decreases from the pressure Pr toward the outer peripheral side. Has become. Further, at the position of the pocket 30, the pressure is reduced to the pressure Pp, and at the position of the outer peripheral resistance portion 50, the pressure gradually decreases from the pressure Pp toward the outer peripheral side to reach the atmospheric pressure Pa. .
Then, vacuum suction of the gas in the pocket 30 by the negative pressure suction means 60 as described above is performed, and the outflow flow rate Qout =
When it is set to 0, the pressure distribution approaches the distribution indicated by the two-dot chain line in FIG.

According to this embodiment, the following effects can be obtained. That is, there is provided negative pressure suction means 60 for suctioning the gas in the pocket under a negative pressure in accordance with the supply amount Qin of the gas supplied from the air supply path 20, and the negative pressure suction means 60 is provided on the air supply side.
Flow rate sensor 61, exhaust side flow rate sensor 62, negative pressure generator
70 and the control device 80, the amount Qout of gas flowing out of the hydrostatic air bearing 10 can be reduced as much as possible. Therefore, in a high-precision or ultra-precision system having a guide mechanism using a static pressure gas bearing, particularly when a laser interferometer is used in a length measuring system, it is possible to avoid adverse effects on the system due to the temperature and flow of outflowing gas.
In particular, as described above, since the negative pressure suction means 60 having a suction amount Qex substantially similar to the supply amount Qin of the gas supplied from the air supply passage 20 is employed, the amount of outflow gas Qout
Can be zero.

Further, negative pressure suction means 60, air supply flow sensor 61, the exhaust side flow rate sensor 62, the negative pressure generating device 70,
And the control device 80, the inflow flow rate Qin and the exhaust flow rate Qe obtained from the detection signals of the air supply side flow sensor 61 and the exhaust side flow sensor 62, respectively.
The controller 80 controls the negative pressure generator 70 so that x becomes equal.
Control the outflow flow rate Qou easily and reliably.
t = 0 can be set. In addition, supply to bearing surface 12
Pocket 30 for discharging the exhausted gas to the outside, and
An exhaust path 40 is provided, and is provided on the outer peripheral side of the pocket 30.
Since the circumferential resistance portion 50 is provided, the flow of gas to the surroundings
Outflow can be further suppressed. And the outer peripheral resistance part
50, the inflow supplied from the air supply passage 20
The flow rate Qin and the exhaust air amount Qo by the negative pressure suction means 60
ut, even if there is a temporary difference,
By temporarily restricting the outflow of gas,
Outflow can be reliably prevented.

It should be noted that the present invention is not limited to the above-described embodiment, but includes other configurations that can achieve the object of the present invention. For example, the following modifications are also included in the present invention. That is, in the above embodiment, the pocket 30
Has a rectangular cross-sectional shape, but is not limited to such a cross-sectional shape, for example, may be a circular arc shape, a triangular shape, a U-shaped cross-sectional shape, in short, What is necessary is just to be formed so that it may be depressed concavely from the position of the extension surface of the bearing surface 12.

In the above embodiment, the pocket 30 is
Although it is arranged so as to form a substantially square shape on the outer peripheral side of the bearing surface 12, the present invention is not limited to such a continuous annular arrangement. For example, as shown in FIG. , 91 or the exhaust hole 4
The one opening may be the pocket 92 as it is, or the pocket 93 may be arranged in multiple layers. The pockets 30 do not need to be arranged in a substantially square shape, and may be arranged in a circular or rectangular shape, for example. In short, the pockets 30 are arranged so as to secure a necessary area of the bearing surface 12. I just need.

Further, the number, diameter, length,
The bending state, the number of times of merging, and the like are arbitrary. However, by increasing the number and diameter of the exhaust passages 40 to increase the overall cross-sectional area of the exhaust passages 40, shortening the length of the exhaust passages 40, reducing the number of bending states and the number of times of confluence, and the like, It is preferable to reduce the resistance of the exhaust path 40, and this makes it easier for gas to flow toward the exhaust path 40, so that the outflow flow rate Qout can be further reduced.

In the above embodiment, the outer peripheral resistance portion 50
Was arranged to form a substantially square on the outer peripheral side of the pocket 30, but is not limited to a substantially square arrangement, and may be, for example, a circle or a rectangle. In short, what is necessary is just to arrange continuously on the outer peripheral side of the pocket 30. Further, in the above embodiment, the surface of the outer peripheral resistance portion 50 has a flat shape. However, as shown in FIG. 5, the outer peripheral resistance portion 50 may be formed as a labyrinth to increase the resistance. Peripheral resistance parts 101 to 103 tapered in part or all
It may be.

Further, the surface of the outer peripheral resistance portion 50 is
It is sufficient if they are arranged on substantially the same plane as 2. That is, it may be arranged completely on the same plane as the bearing surface 12, or may be arranged so as to protrude toward the facing member 15 side or to be recessed in the opposite direction from the position of the bearing surface 12. However, if it is arranged completely on the same plane as the bearing surface 12, machining can be performed easily. The width L4, the area, and the like of the outer peripheral resistance portion 50 are arbitrary. However, it is preferable to increase the resistance of the outer peripheral resistance portion 50 by increasing the width L4, the area, and the like. This makes it easier for the gas to flow toward the exhaust path 40, so that the outflow flow rate Qout is further reduced. It becomes possible.

In the above embodiment, the negative pressure suction means 60 is used.
Had a configuration including a negative pressure generating device 70, a control device 80, a supply-side flow sensor 61, and an exhaust-side flow sensor 62. Of these, the control device 80, the supply-side flow sensor 61, and The exhaust side flow sensor 62 may be omitted, and the negative pressure suction may be performed only by the negative pressure generator 70.
However, it is preferable to provide the controller 80, the supply-side flow sensor 61, and the exhaust-side flow sensor 62, so that the outflow flow rate Qout = 0 can be reliably and easily achieved.

Further, in the above embodiment, the negative pressure generator 7
0 has a configuration including a negative pressure ejector 71, a ventilation path 72, and an electropneumatic regulator 75. However, if the gas in the pocket 30 can be suctioned at a negative pressure, another configuration using a pump or the like can be used. You may.

In the above embodiment, the hydrostatic gas bearing 1
Although 0 is a thrust type static pressure gas bearing for a linear guide surface, the static pressure gas bearing of the present invention may be applied to a radial type static pressure gas bearing.

[0035]

The following experiment was conducted to confirm the effects of the present invention. In the above embodiment (in the case where the negative pressure suction means 60 is installed), the flying height H (μm)
The relationship between the exhaust rate Qr (%), the load capacity W (kgf), and the load control pressure Psuc (MPa) was examined. FIG. 6 shows the results of this experiment. According to FIG. 6, the exhaust rate Qr (= discharge flow rate Qex / inflow flow rate Qin) is 100% with respect to all the values of the flying height H, and the effect of the present invention is remarkably shown. Further, it is shown that the load control pressure Psuc needs to be increased as the load capacity W is smaller and the flying height H is larger. In addition, as a reference, the value of the exhaust rate Qr when the exhaust is performed through the four exhaust paths 40 without providing the negative pressure suction means 60 (see FIG. 7 described later) is indicated by black circles. In the case of the embodiment in which the negative pressure suction means 60 is provided, it is understood that the exhaust rate Qr is high and the exhaust characteristics are excellent as compared with the case where the negative pressure suction means 60 is not provided.

In the case where the exhaust is performed through one or four exhaust paths 40 without providing the negative pressure suction means 60, the exhaust rate Qr (%) and the load capacity W ( kgf), inflow flow rate Qin (liter / mi)
n), the relationship between the outflow flow rate Qout (liter / min) was examined. 7 and 8 show the results of this experiment. According to FIG. 7, even when the number of the exhaust passages 40 is one or four, it is possible to exhaust 95% or more of the inflow flow rate Qin, but it is possible to exhaust completely.
In order to exhaust 100% of the inflow flow rate,
It turns out to be important to use the pulling means 60. When the number of the exhaust passages 40 is one, the exhaust rate Qr is reduced in a region where the flying height H is large as compared with the case where the number of the exhaust passages is four. However, the use region (the flying height H is about 8 to 12 μm) It can be seen that the difference between the exhaust rates Qr is small. FIG.
According to this, the outflow flow rate Qout is constant in a region where the flying height H is small, and particularly when the number of the exhaust passages 40 is four, the flow amount Qout is also constant in the use region. When the flying height H is 10 μm, the inflow flow rate Qin is about 4 Nl /
min (see FIG. 7), the outflow flow rate Qout is about 0.5
It can be seen that it is 1 N liter / min (see FIG. 8).

[0038]

According to the present invention as described, according to the present invention above, comprising a negative pressure suction means for vacuum sucking the gas in the pocket in accordance with the supply amount of the gas supplied from the air supply passage, a negative pressure suction means
Are air supply side flow sensor, exhaust side flow sensor, negative pressure generator
With the arrangement and the control device, the amount of gas flowing out of the hydrostatic air bearing can be reduced as much as possible. Therefore, there is an effect that adverse effects on the high-precision or ultra-precision system due to the temperature and flow of the outflow gas can be avoided.

When negative pressure suction means is provided so as to perform negative pressure suction of the gas in the pocket, the amount of gas flowing out to the surroundings can be further suppressed, and the amount of the gas can be reduced to zero. There is an effect that can be. When the negative pressure suction means is provided with a supply side flow rate sensor, an exhaust side flow rate sensor, a negative pressure generation device, and a control device, the detection by the supply side flow rate sensor and the exhaust side flow rate sensor is performed. By controlling the negative pressure generating device with the control device so that the flow rates are substantially equal, there is an effect that the outflow amount of gas to the surroundings can be easily and reliably set to zero.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing one embodiment of the present invention.

FIG. 2 is an enlarged detailed view of a part of the embodiment.

FIG. 3 is another enlarged detail view of a portion of the embodiment.

FIG. 4 is a schematic configuration diagram showing a modified example of the present invention.

FIG. 5 is a schematic configuration diagram showing another modified example of the present invention.

FIG. 6 is an explanatory diagram of an experimental result of the present invention (in the case of the embodiment provided with the negative pressure suction means).

FIG. 7 is an explanatory diagram of an experimental result of the present invention (when no negative pressure suction means is provided).

FIG. 8 is another explanatory diagram of an experimental result of the present invention (when no negative pressure suction means is provided).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Static pressure gas bearing 12 Bearing surface 20 Supply path 30, 90-93 Pocket 40 Exhaust path 50, 100-103 Outer circumference resistance part 60 Negative pressure suction means 61 Supply side flow sensor 62 Exhaust side flow sensor 70 Negative pressure generator 71 Negative pressure ejector 72 Ventilation path 75 Electropneumatic regulator 80 Control device

Claims (2)

(57) [Claims] An opening is formed in a bearing surface and gas is applied to the bearing surface.
Supply air supply path, and disposed on the outer peripheral side of the bearing surface;
A pocket formed concavely from the bearing surface;
Opened on the wall of the pocket for communication between the pocket and the outside
Exhaust path and supply amount of gas supplied from the air supply path
Depending on the pressure of the gas in the pocket from the exhaust path.
Negative pressure suction means for suctioning, wherein the negative pressure suction means includes an air supply side flow sensor provided in the middle of the air supply path, an exhaust side flow sensor provided in the middle of the exhaust path, The negative pressure generating device provided in the middle of the exhaust path and downstream of the exhaust-side flow sensor, and the negative pressure so that the detection flow rates of the supply-side flow sensor and the exhaust-side flow sensor are substantially equal. A hydrostatic gas bearing, comprising: a control device for controlling a generator. 2. The hydrostatic gas bearing according to claim 1 , further comprising an outer peripheral resistance portion continuously disposed on an outer peripheral side of said pocket and substantially on the same surface as said bearing surface. Features a hydrostatic gas bearing.