JP2017009112A - Hydrostatic pressure gas bearing device and guide roller for filamentous member using hydrostatic pressure gas bearing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydrostatic pressure gas bearing device having a simple configuration and durable against a high load in a thrust direction during high speed rotation.SOLUTION: This invention relates to a hydrostatic gas bearing for supporting a load in a thrust direction by discharging compressed gas discharged from discharging holes 3 to the outside from thrust bearing clearances 9a, 9b through a radial bearing clearance 6. Enlarging distances of first thrust bearing clearances 91a, 91b more than distances 92a, 92b of second bearing clearances enables damage of members or inferior rotation of rollers and further stopped rotation of rollers due to seizure to be prevented by eliminating the clogged state instantly with reaction force of the compression gas filled in the first thrust bearing clearances even if the thrust bearing clearance is clogged.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a hydrostatic gas bearing that stably supports a guide roller that guides a high-speed rotating filament or the like in a non-contact manner.

  The static pressure gas bearing rotates a member that rotates in a non-contact manner by providing a fluid film between the rotating member and a member that supports the rotating member. It is used as a bearing. Patent Documents 1 and 2 disclose that a compressed gas discharged from a gap between a radial rotating member of a static pressure gas bearing and a member supporting the same (hereinafter referred to as a radial bearing gap) is a rotating member of the static pressure gas bearing in the thrust direction. There is disclosed a static pressure gas bearing having a structure in which a thrust direction is supported by gas exhausted from a gap (hereinafter referred to as a thrust bearing gap) between the member and a member supporting the same. This static pressure gas bearing has a simple and compact structure without the need for providing a thrust bearing surface for ejecting compressed gas or an exhaust groove other than a thrust bearing gap for exhausting compressed gas.

  However, in the static pressure gas bearings disclosed in Patent Documents 1 and 2, since the radial bearing gap is filled with compressed gas, the radial direction rigidity is high, but the thrust direction is from the radial bearing gap. Since the discharged compressed gas is supported by the gas exhausted toward the atmosphere, the rigidity is low. For this reason, when a large load is applied in the thrust direction, or when the contact around the axial center of the rotating member in the thrust direction becomes large under high speed rotation, one of the thrust bearing gaps at both ends of the rotating member may be blocked. There is. As a result, gas is no longer exhausted from the closed thrust bearing gap, and the pressure of the gas exhausted from the thrust bearing gap on the opposite side cannot push back the thrust bearing gap in the direction in which the gap is generated. Due to the contact between the rotating member that forms the gap and the counterpart member, the roller may not rotate due to damage or defective rotation of the parts, and further due to seizure.

  Patent Document 1 discloses a porous throttle type static pressure gas bearing that discharges compressed gas from a porous layer to a radial bearing gap.

  Patent Document 2 discloses a configuration in which the width of the thrust bearing gap is gradually expanded or reduced from the shaft body toward the opening on the atmosphere side of the gap depending on the shape of the member that forms the thrust bearing gap. In addition, even if the thrust bearing gap is closed, the members forming the thrust bearing gap are not in contact with each other but are in point or line contact, and thus a hydrostatic gas bearing is disclosed that minimizes the reduction in rotational speed and uneven rotation of the roller. ing.

JP 2013-68307 A JP 2000-72330 A

  However, the hydrostatic gas bearing disclosed in Patent Document 1 does not consider any method for dealing with the above-described problem of the blockage of the thrust bearing gap.

  In the hydrostatic gas bearing disclosed in Patent Document 2, since the members forming the thrust bearing gaps are in point or line contact, a large load is applied locally at the point of contact or the line part, and each member is remarkably different. It will be damaged and the life of the member will be shortened. In addition, since there is no constant equal spacing between the thrust bearing gaps, rotation is likely to be unbalanced, and a stable flow rate is not exhausted from the thrust bearing gaps. It does not rotate stably and cannot guide the filamentous body stably.

  The present invention solves these problems, maintains a simple structure, and stably rotates even when a large load is applied during high-speed rotation or in the thrust direction. Provide a static pressure gas bearing to prevent.

The first invention of the present application that achieves the above object is characterized in that a rotating body whose inner surface adjacent to the outer periphery of the shaft portion is cylindrical and rotates in the direction around the shaft center is rotated by the fluid film interposed between the radial bearing gap and the thrust bearing gap. The radial bearing gap and the thrust bearing gap are exhausted from the thrust bearing gap through the radial bearing gap, and the fluid discharged from the air discharge holes provided on the outer peripheral surface of the shaft portion is supported in a non-contact manner. A hydrostatic gas bearing device for forming the fluid film therein,
The thrust bearing gap includes a first thrust bearing gap that communicates with the radial bearing gap, and a second thrust bearing gap that communicates with the first thrust bearing gap and extends away from the shaft portion;
An interval of the thrust bearing gap is larger than the second thrust bearing gap portion continuously or intermittently around the shaft portion in the first thrust bearing gap portion, and is constant in the second thrust bearing gap portion. It is.

  In the first invention, as an achievement means for forming a thrust bearing gap, it is preferable that a concave portion is provided in a portion of the surface of the rotating body that forms the thrust bearing gap corresponding to the first thrust bearing gap. .

In the first invention, as the achievement means for forming the thrust bearing gap, the shaft portion includes the stepped portion that forms the thrust bearing gap together with the rotating body and has an outer diameter larger than the outer diameter of the shaft portion. Provided,
It is preferable that a concave portion is provided in a portion of the surface of the stepped portion that forms the thrust bearing gap, corresponding to the first thrust bearing gap.

  In the first invention, the rotating body is preferably a yarn guide roller.

In addition, the second invention of the present application that achieves the above object is characterized in that the shaft portion inserted and rotated in the hollow portion of the housing having a cylindrical hollow portion is formed by the fluid film interposed in the radial bearing gap and the thrust bearing gap. By supporting the unit in a non-contact manner and exhausting the fluid discharged from the air discharge hole provided in the inner peripheral surface of the hollow portion of the housing from the thrust bearing gap through the radial bearing gap, the radial bearing gap and the A hydrostatic gas bearing device for forming the fluid film in a thrust bearing gap,
The thrust bearing gap includes a first thrust bearing gap that communicates with the radial bearing gap, and a second thrust bearing gap that communicates with the first thrust bearing gap and extends away from the shaft portion;
An interval of the thrust bearing gap is larger than the second thrust bearing gap portion continuously or intermittently around the shaft portion in the first thrust bearing gap portion, and is constant in the second thrust bearing gap portion. It is.

  In the second invention, it is preferable that a concave portion is provided in a portion corresponding to the first thrust bearing gap on the surface of the housing forming the thrust bearing gap as an achievement means for forming the thrust bearing gap.

In the second invention, as an achievement means for forming a thrust bearing gap, the shaft portion is provided with a stepped portion that forms the thrust bearing gap together with the housing and has an outer diameter larger than the outer diameter of the shaft portion. And
It is preferable that a concave portion is provided in a portion of the surface of the stepped portion that forms the thrust bearing gap, corresponding to the first thrust bearing gap.

  In the second invention, it is preferable that the shaft portion is a yarn guide roller.

  According to the present invention, in the static pressure gas bearing, when a large load is applied in the thrust direction, or when the high-speed rotation is performed, the contact in the thrust direction with respect to the axis of the rotating member is increased, and either one of the thrust bearing gaps is Even in the case of the blockage, by making the interval between the first thrust bearing gaps larger than the interval between the second thrust bearing gaps, the reaction force of the compressed gas filled in the first thrust bearing gap causes the thrust bearing gap By eliminating the blockage instantly, it is possible to prevent damage to the member, poor rotation of the roller, and further stop of rotation of the roller due to printing. Furthermore, by setting the second thrust bearing gap to a substantially constant interval, there is little fluctuation in the exhaust flow rate and pressure due to the exhaust from the thrust bearing gap during rotation, and stable rotation can be obtained.

1A and 1B are an external view and an exploded view, respectively, of a hydrostatic gas bearing according to a first embodiment of the present invention, and FIGS. 1C and 1D are longitudinal sectional schematic views. 2A, 2B and 2C are cross-sectional views showing examples of the shapes of the recesses 10a and 10b of the present invention. FIGS. 3A and 3B are front views showing an example of the circumferential shape of the recesses 10a and 10b of the present invention. 4A, 4B and 4C are longitudinal sectional views showing other shapes of the hydrostatic gas bearing of the first embodiment of the present invention. 5A and 5B are longitudinal sectional views of the static pressure gas bearing of the second embodiment of the present invention. 6 (A) and 6 (B) are longitudinal sectional views showing conventional static pressure gas bearings.

  First, the configuration of the static pressure gas bearing device of the first embodiment of the present invention will be described with reference to FIG. (A) and (B) are external views and exploded views, and (C) and (D) are longitudinal sectional views. Reference numeral 1 denotes a rotating roller, 2 denotes a shaft portion. A fluid film is formed between the shaft portion 2 and the roller 1, and a discharge hole 3 for discharging compressed air for supporting the roller 1 with the fluid film is formed. Has been. As for the discharge holes 3, as shown in FIG. 1C, not only a plurality of holes arranged radially on the circumference of the shaft portion are arranged in one or more rows in the rotation axis direction. 2 may be a porous material discharged from a porous layer made of sintered, carbon, ceramic, or the like provided on the outer peripheral surface of 2. Compressed air is supplied from the discharge hole 3 through the air supply path 4 from the supply hole 4 communicating with the discharge hole 3.

  The roller 1 is processed so that the inner diameter of the inner surface of the roller 1 is larger than the outer diameter of the shaft portion 2 by a predetermined dimension so that a radial bearing gap 6 is formed between the roller 1 and the shaft portion 2. Further, the shaft portion 2 has step surfaces 8a and 8b which are larger than the outer diameter of the shaft portion 2 and form thrust bearing gaps 9a and 9b between the end surfaces 7a and 7b of the roller 1. The radial bearing gap 6 and the thrust bearing gaps 9a and 9b communicate with each other, and the compressed gas discharged from the discharge hole 3 is exhausted from the thrust bearing gaps 9a and 9b to the outside through the radial bearing gap 6. It has become. With this configuration, the radial load is supported by the air film formed in the radial bearing gap 6, and the thrust load is supported by the gas air film exhausted to the outside from the thrust bearing gaps 9a and 9b. Is done.

  Here, in the thrust bearing gaps 9a and 9b formed by the end faces 7a and 7b of the roller 1 and the stepped surfaces 8a and 8b of the shaft portion 2, the thrust bearing gaps 91a and 91b at the boundary portions communicating with the radial bearing gap 6 are changed to the first. If the thrust bearing gaps 92a and 92b that communicate with the first thrust bearing gap and the first thrust bearing gaps 91a and 91b and extend away from the shaft portion 2 are the second thrust bearing gaps, the first thrust bearing gap 91a , 91b is provided with recesses 10a, 10b on the end face of the roller 1 at a portion corresponding to the first thrust bearing gaps 91a, 91b so that the gap between the second thrust bearing gaps 92a, 92b is larger. is there. The distance between the second thrust bearing gaps 92a and 92b is set to be substantially constant from the boundary portion communicating with the first thrust bearing gaps 91a and 91b.

  Here, in order to show the superiority with a prior art, the problem of the conventional static pressure gas bearing is demonstrated using FIG.

  In the prior art, as shown in FIG. 6 (A), the thrust bearing gaps 9a, 9b are all uniformly spaced from the communicating portion of the radial bearing gap 6 toward the exhaust side, and the first embodiment of the present invention. The distance between the thrust bearing gaps 9a and 9b in the form of the thrust bearing gap at the portion communicating with the radial bearing gap 6 is larger than the distance between the thrust bearing gaps communicating with the thrust bearing gap and extending away from the shaft portion 2. It is not the structure of providing a recessed part so that it may become.

  For this reason, when a large load is applied to one of the rotating rollers 1 in the thrust direction, or when the rotation of the roller 1 in the thrust direction with respect to the axial center of the roller 1 increases during high-speed rotation, the compression from the radial bearing gap 6 occurs. In either one of the thrust bearing gaps 9a and 9b supported by the air exhaust pressure, for example, in FIG. 6B, if the thrust bearing gap 9a is closed, gas is exhausted from the closed thrust bearing gap 9a. It will not be done. Furthermore, due to the pressure of the gas exhausted from the other thrust bearing gap 9b, a force is applied unilaterally to the closed thrust bearing gap 9a, and a force to push back in the direction of generating the closed thrust bearing gap 9a is exerted. Therefore, the contact between the rotating roller end surface 7a forming the thrust bearing gap 9a and the shaft step surface 8a is not eliminated, and the roller end surface 7a and the shaft step surface 8a are not only damaged. Rotation failure occurred, and in the worst case, the roller 1 sometimes stopped rotating due to seizure.

  As described in the first embodiment shown in FIG. 1, the configuration of the static pressure gas bearing of the present invention is the distance between the first thrust bearing gaps 91 a and 91 b at the boundary communicating with the radial bearing gap 6. The recesses 10a are formed on the end surface of the roller 1 so as to be larger than the interval between the second thrust bearing gaps 92a and 92b, which is in communication with the first thrust bearing gap and extends in a direction away from the shaft portion 2 and is substantially constant. 10b is provided.

  With the above-described configuration, even when one of the thrust bearing gaps 9a and 9b, for example, as shown in FIG. 1D, is closed, the end face 7a of the roller 1 that forms the first thrust bearing gap 91a. The force F that pushes back the roller 1 acts in a direction opposite to the direction in which the compressed gas filled in the concave portion 10a closes the thrust bearing gap 9a, that is, the direction in which the thrust bearing gap 9a is generated, and the thrust bearing gap 9a is closed. Can be resolved instantly. Therefore, it is possible to prevent damage to the member, rotation failure of the roller, and stop of rotation of the roller due to printing.

  Since the second thrust bearing gaps 92a and 92b are substantially constant, the flow rate of the exhaust gas from the thrust bearing gaps 9a and 9b and the pressure fluctuation due to the exhaust are small during the rotation of the roller 1, and the roller 1 Can rotate stably.

  Here, the distance between the recesses 10a and 10b and the shaft step surfaces 8a and 8b that are the first thrust bearing gaps shown in FIG. 1 need not be constant. That is, the shape of the recesses 10a and 10b does not have to be rectangular as shown in FIG. 2A, for example, but is round as shown in FIG. 2B with rounded and arched corners. Or a triangular cross section as shown in FIG. 2C, etc., as long as it communicates with the radial bearing gap 6 and is larger than the second thrust bearing gaps 92a and 92b. In addition, in FIG. 3, the roller end surfaces 7a and 7b are formed in such a manner that the recesses 10a and 10b, which are the first thrust gaps, are continuous on the circumference with respect to the roller end surfaces 7a and 7b as shown in FIG. Alternatively, it may be formed by a plurality of recesses intermittently on the circumference as shown in FIG. In the case of forming with a plurality of recesses in FIG. 3B, it is possible to stabilize the rotation balance of the roller 1 when all the recesses have the same shape and are evenly spaced on the circumference.

  Further, the concave portion configured as the first thrust bearing gap is provided not only on the end surfaces 7a and 7b of the roller 1 as shown in FIG. 1C, but also on the end surface of the roller 1 as shown in FIG. 4A. The recesses 10a and 10b may be formed only on one of the end surfaces 7a and 7b of the roller 1 or the shaft step surfaces 8a and 8b. In addition, the first thrust bearing gaps 91a and 91b are larger than the second thrust gaps 92a and 92b, such as being formed on both the roller end surfaces 7a and 7b and the shaft step surfaces 8a and 8b. Any configuration may be used.

  Since the second thrust bearing gaps 92a and 92b need only have a substantially constant interval in order to stably rotate as described above, the axial direction as shown in FIG. In addition to a vertical one, the cross section may extend in the exhaust direction in the shape of a letter C or a reverse letter C as shown in FIGS. 4 (B) and 4 (C). Alternatively, it may have a shape that extends in the exhaust direction while the cross section is curved.

  Next, the configuration of the static pressure gas bearing device of the second embodiment of the present invention will be described with reference to FIG.

  The static pressure gas bearing device of the first embodiment is configured such that the rotating roller 1 is supported by a fluid film by the compressed gas discharged from the discharge hole 3 of the shaft portion 2. The rotary shaft 11 is inserted into a housing 12 having a cylindrical hollow portion, and the radial bearing gap 6 and the thrust bearing gap are compressed by compressed gas discharged from the discharge hole 3 formed in the inner surface of the housing 12. The rotating shaft 11 supported by the fluid film interposed between 9a and 9b rotates. That is, the hydrostatic gas bearing according to the first embodiment except that the compressed air is supplied from the discharge hole 3 through the air passage 5 from the supply hole 4 communicating with the discharge hole 3 and the rotating shaft 11 rotates. Similarly to the device, the thrust bearing gap 9a communicates with the first thrust bearing gaps 91a and 91b communicating with the radial bearing gap 6 and the first thrust bearing gaps 91a and 91b, and away from the rotary shaft 11. The first thrust bearing gaps 92a and 92b extend, and the first thrust bearing gaps 91a and 91b have a gap larger than the gap between the second thrust bearing gaps 92a and 92b. Concave portions 10a and 10b are provided at the end surfaces of the rotary shaft step surfaces 17a and 17b corresponding to 91a and 91b. The distance between the second thrust bearing gaps 92a and 92b is set to be substantially constant from the boundary portion communicating with the first thrust bearing gaps 91a and 91b.

  As in the first embodiment, the concave portions 10a and 10b do not have to have a rectangular cross section as shown in FIG. 2A, but are rounded and arched at the corner as shown in FIG. As long as it is in communication with the radial bearing gap 6 and is larger than the second thrust bearing gaps 92a and 92b, for example, a round cross section applied or a triangular cross section as shown in FIG. Further, as shown in FIGS. 3A and 3B, the recesses 10a and 10b, which are the first thrust gaps, may be continuously formed on the circumference with respect to the rotary shaft step surfaces 17a and 17b. Alternatively, it may be formed intermittently with a plurality of recesses. In addition, when it forms with a several recessed part of 3 (B), the shape of all the recessed parts is equal, and the rotation balance of a roller can be stabilized when it is equidistantly spaced on the circumference.

  Further, the recesses 10a and 10b configured as the first thrust bearing gaps are not only provided on the step surfaces 17a and 17b of the rotating shaft 11 as shown in FIG. 5B, but also as shown in FIG. 5B. May be formed on the housing end surfaces 18a and 18b opposite to the rotation shaft step surfaces 17a and 17b, and the recess is formed only on one of the rotation shaft step surfaces 17a and 17b or the housing end surfaces 18a and 18b. In addition, the first thrust bearing gaps 91a and 91b are more than the second thrust bearing gaps 92a and 92b, such as formed on both surfaces of the rotary shaft step surfaces 17a and 17b and the housing end surfaces 18a and 18b. What is necessary is just the structure which becomes large.

  The second thrust bearing gaps 92a and 92b are not limited to being perpendicular to the axial direction in order to stably rotate as described above. As shown in the first embodiment, the cross section may be shaped like a letter C or an inverted letter C and extend in the exhaust direction. Alternatively, it may have a shape that extends in the exhaust direction while the cross section is curved.

Example 1
In a synthetic fiber production facility, a guide roller as shown in FIG. 1 for guiding a yarn traveling at 3,000 m / min or more was produced. The dimensions of each part are as follows.
-Shaft part 2: The outer diameter is 22 mm, the axial length is 20 mm, and the outer diameter of the shaft step surfaces 8 a and 8 b is 30 mm, which is equivalent to the outer diameter of the roller 1. The outer peripheral surface of the shaft portion 2 was a sintered layer made of stainless steel porous having a thickness of 2 mm.
Roller 1: outer diameter 30 mm, inner diameter 22.04 mm, axial length of outer peripheral surface 19.92 mm. The first thrust bearing gaps 91a and 91b were formed by cutting grooves with an outer diameter of 24 mm and a depth of 1 mm from the innermost layer on the roller end faces 7a and 7b. The material was made of an aluminum alloy, and the outer peripheral surface was subjected to a hard chrome plating process in order to prevent wear due to abrasion with the yarn.

  The shaft portion 2 and the roller 1 are combined to make the radial bearing gap 6 20 μm and the second thrust bearing gaps 92 a, 92 b 40 μm.

  The roller end surfaces 7a and 7b and the shaft stepped surfaces 8a and 8b have a perpendicularity of 0.01 mm based on the JIS method with respect to the axial center of the shaft portion 2 having a cylindricity of 0.005 mm based on the JIS method. Based on the average surface roughness Ra of 0.2 to 0.4 μm, the second thrust bearing gaps 92a and 92b are substantially constant.

  In this guide roller, compressed air generated from a pneumatic pump (not shown) is introduced from the air supply hole 4 and discharged from the air passage 5 through the sintered layer made of a substantially porous material. The thrust bearing gaps 91a and 91b and the second thrust bearing gaps 92a and 92b are discharged to the atmosphere.

  When the yarn was run on the roller 1 of the guide roller at a high speed under the conditions that the compressed air pressure was 0.4 MPa and the flow rate of the compressed air discharged from the porous layer was 2 to 5 liters / minute, Even at 000 rpm, it was able to rotate stably without causing self-excited vibration or rotation failure.

(Comparative Example 1)
In the guide roller of Example 1, a guide roller having the same form as Example 1 was manufactured except that the first thrust bearing gaps 91a and 91b were not formed. In the same manner as in Example 1, the yarn was run on the roller 1 of the guide roller under the conditions that the compressed air pressure was 0.4 MPa and the flow rate of the compressed air released from the porous layer was 2 to 5 liters / minute. However, rotation failure occurred due to contact between the roller end surface and the shaft step surface at 35,000 rotations / minute, and rotation stopped.

  The present invention can be applied to a guide roller that guides a linear body that travels at a high speed, such as a yarn path guide in a high-speed yarn manufacturing process, but the application range is not limited thereto.

1 Roller (Rotating body)
2 Shaft portion 3 Discharge hole 4 Air supply hole 5 Air passage 6 Radial bearing gap 7a, 7b Roller end face 8a, 8b Shaft step surface 9a, 9b Thrust bearing gap 91a, 91b First thrust bearing gap 92a, 92b Second Thrust bearing gap 10a, 10b Recess 11 Rotating shaft 12 Housing 17a, 17b Rotating shaft step surface 18a, 18b Housing end surface

Claims (8)

A rotating body whose inner surface adjacent to the outer periphery of the shaft portion is cylindrical and rotates in the direction around the shaft center is supported in a non-contact manner with the shaft portion by a fluid film interposed in a radial bearing gap and a thrust bearing gap. A hydrostatic gas bearing that forms the fluid film in the radial bearing gap and the thrust bearing gap by exhausting the fluid discharged from the air discharge hole provided on the outer peripheral surface through the radial bearing gap from the thrust bearing gap. A device,
The thrust bearing gap includes a first thrust bearing gap that communicates with the radial bearing gap, and a second thrust bearing gap that communicates with the first thrust bearing gap and extends away from the shaft portion;
An interval of the thrust bearing gap is larger than the second thrust bearing gap portion continuously or intermittently around the shaft portion in the first thrust bearing gap portion, and is constant in the second thrust bearing gap portion. A static pressure gas bearing device.   2. The hydrostatic gas bearing device according to claim 1, wherein a concave portion is provided in a portion of the surface of the rotating body that forms the thrust bearing gap corresponding to the first thrust bearing gap. The shaft portion is provided with a step portion that forms the thrust bearing gap together with the rotating body and has an outer diameter larger than the outer diameter of the shaft portion,
3. The hydrostatic gas bearing device according to claim 1, wherein a concave portion is provided in a portion of the surface of the stepped portion that forms the thrust bearing gap corresponding to the first thrust bearing gap.   The hydrostatic gas bearing device according to claim 1, wherein the rotating body is a filament-shaped guide roller. A shaft portion that is inserted into the hollow portion of the housing having a cylindrical hollow portion and rotates is supported in a non-contact manner with the housing by a fluid film interposed in a radial bearing gap and a thrust bearing gap. A static pressure gas that forms the fluid film in the radial bearing gap and the thrust bearing gap by exhausting the fluid discharged from the air discharge hole provided in the inner peripheral surface through the radial bearing gap from the thrust bearing gap. A bearing device,
The thrust bearing gap includes a first thrust bearing gap that communicates with the radial bearing gap, and a second thrust bearing gap that communicates with the first thrust bearing gap and extends away from the shaft portion;
An interval of the thrust bearing gap is larger than the second thrust bearing gap portion continuously or intermittently around the shaft portion in the first thrust bearing gap portion, and is constant in the second thrust bearing gap portion. A static pressure gas bearing device.   The hydrostatic gas bearing device according to claim 5, wherein a concave portion is provided in a portion of the surface of the housing that forms the thrust bearing gap corresponding to the first thrust bearing gap. The shaft portion is provided with a step portion that forms the thrust bearing gap together with the housing and has an outer diameter larger than the outer diameter of the shaft portion,
The hydrostatic gas bearing device according to claim 5 or 6, wherein a concave portion is provided in a portion of the surface of the stepped portion that forms the thrust bearing gap corresponding to the first thrust bearing gap.   The static pressure gas bearing device according to claim 5, wherein the shaft portion is a filament-shaped guide roller.

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