Gas bearing device

Abstract

A gas bearing device according to one aspect of the present disclosure comprises: a housing which has therein a housing space that houses a rotary shaft and in which a groove portion extending along the axial direction of the rotary shaft is formed in an inner peripheral surface that defines the housing space; a top foil which is provided in an annular gap formed between the inner peripheral surface and the rotary shaft and which has one end portion in the circumferential direction of the rotary shaft inserted in the groove portion; and a backup foil which is provided in the annular gap on the outer side of the top foil so as to surround the top foil, which is configured to elastically support the top foil, and which has one end portion in the circumferential direction of the rotary shaft inserted in the groove portion such that the one end portion is positioned on one side in the groove portion with respect to the one end portion of the top foil. The groove portion includes a pair of side wall surfaces which are disposed so as to face each other and which include one side wall surface positioned on the one side in the groove portion and the other side wall surface positioned on the other side in the groove portion. The gas bearing device further comprises a pressing force application means disposed in the groove portion and configured to press each of the one end portions of the top foil and the backup foil against the other side wall surface.

Description

Technical Field

[0001] The present disclosure relates to a gas bearing device.

Background Art

[0002] In rotating machines such as electric compressors, a gas bearing, which is a type of oil-free bearing, may be employed to avoid contamination of compressed air due to, for example, mixing of lubricating oil into the compressed air. Since a gas bearing forms a gas film between a rotating shaft and a bearing surface to support the rotating shaft, its bearing load capacity is lower than that of an oil bearing. Therefore, it is necessary to generate gas film pressure as efficiently as possible between the rotating shaft and the bearing. For this purpose, the bearing surface is formed of a thin plate (top foil) that can be deformed following the gas film pressure, and the back surface of the top foil is elastically supported by a plate-shaped backup foil. Further, in order to fix the positions of the top foil and the backup foil in the axial direction of the rotating shaft, fixing components such as snap rings are used, but in this case, there is a problem that the assemblability deteriorates.

[0003] Patent Documents 1 and 2 each describe a gas bearing. In the gas bearing described in Patent Document 1, as a method for fixing the axial positions of the top foil and the backup foil in the axial direction of the rotating shaft, after inserting one end portions of the top foil and the backup foil into a groove formed on the inner surface of a housing surrounding the rotating shaft, a spacer is press-fitted into the groove. In the gas bearing described in Patent Document 2, a method of press-fitting the end portions of the top foil and the backup foil into a groove formed on the inner surface of a housing surrounding the rotating shaft is employed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the fixing means disclosed in Patent Document 1 requires precise finishing of the dimensions of the groove portion and the spacer in accordance with the plate thickness dimensions of the top foil and the backup foil, and there is a problem that these processes are troublesome. Further, the fixing method disclosed in Patent Document 2 also requires precise finishing of the dimensions of the groove portion formed in the housing in accordance with the plate thickness dimensions of the foil member, and there is a problem that the processing of the groove portion is troublesome.

[0006] In view of the above circumstances, an object of the present invention is to enable a foil member constituting a gas bearing to be securely fixed to a housing by simple means.

Means for Solving the Problems

[0007] To achieve the above object, an aspect of a gas bearing device according to the present disclosure is a housing having an accommodation space inside which a rotating shaft is accommodated, the housing having a groove portion formed along the axial direction of the rotating shaft on an inner peripheral surface defining the accommodation space, a top foil provided in an annular gap formed between the inner peripheral surface and the rotating shaft, one end portion in the circumferential direction of the rotating shaft being inserted into the groove portion, and a backup foil provided outside the top foil in the annular gap so as to surround the top foil and configured to elastically support the top foil, one end portion in the circumferential direction of the backup foil being inserted into the groove portion so as to be located on one side in the groove portion with respect to one end portion of the top foil, and the groove portion including a pair of side wall surfaces arranged to face each other, the pair of side wall surfaces including one side wall surface located on one side in the groove portion and the other side wall surface located on the other side in the groove portion, and further including pressing force applying means arranged in the groove portion and configured to press each of the one end portions of the top foil and the backup foil against the other side wall surface.

[0008] Another aspect of the gas bearing device according to the present disclosure is a housing having an accommodation space inside which a rotating shaft is accommodated, the housing having a groove portion formed along the axial direction of the rotating shaft on an inner peripheral surface defining the accommodation space, a top foil provided in an annular gap formed between the inner peripheral surface and the rotating shaft, one end portion of the top foil in the circumferential direction of the rotating shaft being inserted into the groove portion, and a backup foil provided so as to surround the top foil outside the top foil in the annular gap and configured to elastically support the top foil, one end portion of the backup foil in the circumferential direction being inserted into the groove portion so as to be located on one side in the groove portion with respect to one end portion of the top foil, wherein the groove portion includes a wavy groove portion extending in a wavy shape along the axial direction.

[0009] Still another aspect of the gas bearing device according to the present disclosure is a housing having an accommodation space inside which a rotating shaft is accommodated, the housing having a groove portion formed along the axial direction of the rotating shaft on an inner peripheral surface defining the accommodation space, a top foil provided in an annular gap formed between the inner peripheral surface and the rotating shaft, one end portion of the top foil in the circumferential direction of the rotating shaft being inserted into the groove portion, and a plate-shaped backup foil provided so as to surround the top foil outside the top foil in the annular gap and configured to elastically support the top foil, one end portion of the backup foil in the circumferential direction being inserted into the groove portion so as to be located on one side in the groove portion with respect to one end portion of the top foil, wherein the groove portion includes an inclined groove portion in which the distance from the center line of the rotating shaft decreases from one side in the axial direction to the other side, and each of the one end portions of the top foil and the backup foil includes an inclined groove portion in which the distance from the center line of the rotating shaft decreases from one side in the axial direction to the other side, and at least a part of the tip of the inclined portion is arranged in the inclined groove portion so as to contact the bottom surface of the inclined groove portion.

Advantages of the Invention

[0010] According to one aspect of the gas bearing device according to the present disclosure, the frictional force between the wall surface forming the groove portion formed on the inner peripheral surface of the housing provided around the rotating shaft and each end portion of the top foil and the backup foil inserted into the groove portion can be increased, whereby the axial movement of the top foil and the backup foil can be prevented.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0012] Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in these embodiments or shown in the drawings are not intended to limit the scope of the present invention thereto, but are merely illustrative examples. For example, expressions representing relative or absolute arrangements such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric", or "coaxial" not only strictly represent such arrangements, but also represent states with tolerances or relative displacements with angles or distances that can achieve the same function. For example, expressions representing a state where things such as "identical", "equal", and "homogeneous" are equal not only strictly represent an equal state, but also represent states with tolerances or differences that can achieve the same function. For example, expressions representing shapes such as a square shape or a cylindrical shape not only represent shapes such as a square shape or a cylindrical shape in a geometrically strict sense, but also represent shapes including concave and convex portions, chamfered portions, etc. within a range where the same effect can be obtained. On the other hand, expressions such as "comprising", "having", "including", or "possessing" one component are not exclusive expressions that exclude the existence of other components.

[0013] FIG. 1 is a front view cross-sectional view showing a gas bearing device 10A according to an embodiment, and FIG. 2 is a side view cross-sectional view taken along line A - A of FIG. 1. FIG. 3 is an enlarged front view cross-sectional view of a part of FIG. 1, and FIG. 4 is a front view cross-sectional view corresponding to FIG. 3 according to another embodiment of the pressing force applying means 20.

[0014] In FIGS. 1 and 2, the gas bearing device 10A includes a housing 12 having an accommodation space Sc inside which a rotating shaft 100 is accommodated. The rotating shaft 100 is a rotating shaft 100 provided in a rotating machine (for example, an electric compressor, a supercharger, etc.). When accommodated in the accommodation space Sc, it rotates in the direction of arrow a about the central axis O. The inner peripheral surface 12a of the housing 12 is arranged to face the outer peripheral surface of the rotating shaft 100 and defines the accommodation space Sc inside. A groove portion 14 extending along the axial direction (hereinafter, also simply referred to as the "axial direction") of the rotating shaft 100 is formed in a part of the circumferential direction (hereinafter, also simply referred to as the "circumferential direction") of the rotating shaft 100 on the inner peripheral surface 12a. In FIG. 1, the axial direction of the rotation axis 100 is a direction perpendicular to the plane of the paper on which FIG. 1 is shown. As shown in FIG. 2, the central axis O extends in the axial direction of the rotation axis 100.

[0015] An annular gap Sr formed between the housing 12 and the rotation axis 100 housed in the accommodation space Sc is provided with a top foil 16 and a backup foil 18. The top foil 16 is configured in a thin plate shape and is provided so as to surround the rotation axis 100 in the inner region of the annular gap Sr. One end portion 16a of the top foil 16 in the circumferential direction of the rotation axis 100 is inserted into a groove portion 14 extending along the axial direction. The top foil 16 shown in FIG. 1 is formed in a cylindrical shape in accordance with the shape of the outer peripheral surface of the rotation axis 100 having a circular cross section, and forms a smooth inner peripheral surface and outer peripheral surface without unevenness.

[0016] The backup foil 18 is configured in a thin plate shape and is provided outside the top foil 16 in the radial direction of the rotation axis 100 (hereinafter, also simply referred to as the "radial direction") in the annular gap Sr. That is, it is provided so as to surround the top foil 16 and is configured to elastically support the top foil 16. And, similar to the top foil 16, one end portion 18a in the circumferential direction is inserted into the groove portion 14.

[0017] The backup foil 18 shown in FIG. 1 is bent so that unevenness repeats along the circumferential direction of the rotation axis 100. Each unevenness extends along the axial direction and bends so as to advance and retreat in the radial direction of the rotation axis 100 to form valleys. For example, these valleys are formed in a wavy shape like a sine curve, but are not necessarily limited to an arc shape like a sine curve. For example, they may be rectangular unevenness, or unevenness like a parabola. The peak portions 19a of the unevenness formed in this way contact the back surface of the top foil 16, and the valley portions 19b contact the inner peripheral surface 12a of the housing 12 to elastically support the top foil 16.

[0018] Since the backup foil 18 has such a concavo-convex shape, it can be deformed under the pressure of the gas film formed between the rotating shaft 100 and the top foil 16, whereby the top foil 16 can be elastically supported. Therefore, a gas film is retained between the rotating shaft 100 and the top foil 16, and the rotating shaft 100 is lubricated and supported by the gas film.

[0019] As shown in FIGS. 3 and 4, one end portion 16a in the circumferential direction of the top foil 16 and one end portion 18a in the circumferential direction of the backup foil 18 are inserted into the groove portion 14 and fixed inside the groove portion 14 by the pressing force applying means 20 described later. Thereby, axial movement of the top foil 16 and the backup foil 18 is prevented. In the embodiment shown in FIG. 1, the other end portion 16b of the top foil 16 and the other end portion 18b of the backup foil 18 on the side opposite to the one end portions 16a and 18a are free ends. Therefore, the top foil 16 and the backup foil 18 can be freely deformed under the pressure of the gas film formed between the rotating shaft 100 and the top foil 16.

[0020] As shown in FIGS. 3 and 4, the groove portion 14 has a pair of side wall surfaces 14a and 14b arranged to face each other. These pair of side wall surfaces include one side wall surface 14a located on one side and the other side wall surface 14b located on the other side. Here, the "one side" refers to the direction (arrow b direction) toward the one side wall surface 14a in FIGS. 3 and 4, and the "other side" refers to the direction (arrow c direction) toward the other side wall surface 14b. That is, the "one side" refers to the side away from the side where the other end portions 16b and 18b of the top foil 16 and the backup foil 18 wound around the periphery of the rotating shaft 100 from the groove portion 14 are present, and the "other side" refers to the side closer to the other end portions 16b and 18b compared to the "one side". In addition, in the embodiment illustrated in FIG. 1, the rotating shaft 100 rotates in the arrow a direction, but in FIGS. 3 and 4, it rotates from one side toward the other side (in the arrow c direction).

[0021] Inside the groove portion 14, one end portion 18a of the backup foil 18 is arranged on one side with respect to one end portion 16a of the top foil 16, that is, on the side closer to one side wall surface 14a. In the embodiment shown in FIGS. 3 and 4, the one end portion 18a is arranged at a position closer to the one side wall surface 14a with respect to the one end portion 16a such that the opposing surfaces of the two overlap each other.

[0022] As shown in FIGS. 3 and 4, the groove portion 14 is provided with pressing force applying means 20 for applying a pressing force for pressing the one end portions 16a and 18a toward the other side wall surface 14b.

[0023] According to the embodiment shown in FIGS. 3 and 4, since the groove portion 14 is provided with the pressing force applying means 20, each of the one end portion 16a of the top foil 16 and the one end portion 18a of the backup foil 18 inserted into the groove portion 14 is pressed against the other side wall surface 14b by receiving a pressing force from the pressing force applying means 20. As a result, the frictional force acting between the one end portion 16a of the top foil 16 and the one end portion 18a of the backup foil 18 and the frictional force acting between the one end portion 16a of the top foil 16 and the other side wall surface 14b increase, so that the one end portion 16a of the top foil 16 and the one end portion 18a of the backup foil 18 are stably fixed inside the groove portion 14. Therefore, it is possible to prevent the top foil 16 and the backup foil 18 from moving in the axial direction of the rotation shaft 100. In addition, in the present embodiment, unlike the fixing means described in Patent Document 1 or 2, it is not necessary to precisely process the dimensions of the spacer and the groove portion according to the plate thickness of the top foil and the backup foil.

[0024] In one embodiment, as shown in FIG. 3, the pressing force applying means 20 includes a spring member 20a configured separately from the backup foil 18. The spring member 20a is inserted between the one side wall surface 14a and the one end portion 18a of the backup foil 18 and is arranged along the extending direction (axial direction) of the groove portion 14.

[0025] The spring member 20a applies a pressing force to one end portion 18a of the backup foil 18 and also applies a pressing force to one side wall surface 14a. The one side wall surface 14a to which the pressing force is applied from the spring member 20a applies a reaction force equivalent to the pressing force to the spring member 20a. As a result, the frictional force generated between one end portion 16a of the top foil 16 and one end portion 18a of the backup foil 18 and the frictional force generated between one end portion 16a of the top foil 16 and the other side wall surface 14b increase, so that one end portion 16a of the top foil 16 and one end portion 18a of the backup foil 18 are stably fixed inside the groove portion 14. Therefore, by the simple means of arranging the spring member 20a in the groove portion 14, it is possible to prevent the top foil 16 and the backup foil 18 from moving in the axial direction of the rotation shaft 100.

[0026] In the embodiment illustrated in FIG. 3, the spring member 20a is constituted by a torsion coil spring 22. FIG. 5 is a perspective view showing the torsion coil spring 22 according to one embodiment. The torsion coil spring 22 shown in FIG. 5 is configured by bending a single small-diameter bar into a circular shape to form a coil shape and extending along the direction of the axis AL. Both end portions of the bar have straight portions 22a and 22b that protrude outward from the outer peripheral surface of the coil in the tangential direction and extend linearly. Since the straight portions 22a and 22b have such a shape, when inserted into the groove portion 14, they are surely pressed against one side wall surface 14a or one end portion 18a of the backup foil 18.

[0027] As shown in FIG. 3, the torsion coil spring 22 is inserted between one side wall surface 14a and one end portion 18a of the backup foil 18. Inside the groove portion 14, one of the straight portions 22a and 22b applies a spring force that presses one side (in the direction of arrow b) against one side wall surface 14a, and the other of the straight portions 22a and 22b applies a spring force that presses one end portion 18a of the backup foil 18 to the other side (in the direction of arrow c).

[0028] According to this embodiment, since one of the straight portions 22a and 22b of the torsion coil spring 22 applies a pressing force to one side wall surface 14a, and the other of the straight portions 22a and 22b applies a spring force that presses one end portion 18a of the backup foil 18 to the other side, one end portion 16a of the top foil 16 and one end portion 18a of the backup foil 18 are pressed against the other side wall surface 14b. As a result, the frictional force generated between one end portion 16a of the top foil 16 and one end portion 18a of the backup foil 18, and the frictional force generated between one end portion 16a of the top foil 16 and the other side wall surface 14b increase, so that one end portion 16a of the top foil 16 and one end portion 18a of the backup foil 18 are stably fixed inside the groove portion 14. Therefore, by the simple means of arranging the torsion coil spring 22 in the groove portion 14, the top foil 16 and the backup foil 18 can be prevented from moving in the axial direction.

[0029] FIG. 6 is an enlarged front sectional view of a part of a gas bearing device including a spring member 20a according to another embodiment. In this embodiment, the spring member 20a is composed of a plurality of coil springs 26 inserted between one side wall surface 14a and one end portion 18a of the backup foil 18. Each individual coil spring 26 is inserted in a compressed state in the direction of the axis AL between one side wall surface 14a and one end portion 18a of the backup foil 18 with the axis AL oriented in the circumferential direction. The plurality of coil springs 26 are arranged adjacent to or spaced apart from each other in parallel along the direction (axial direction) in which the groove portion 14 extends. Also in this embodiment, since the coil spring 26 applies a pressing force to one side wall surface 14a and one end portion 18a of the backup foil 18 along the direction of the axis AL, the same operational effects as those of the above embodiment can be obtained.

[0030] In the embodiment shown in FIG. 4, the pressing force applying means 20 includes an extending portion 20b formed integrally with one end portion 18a of the backup foil 18. One end portion of the extending portion 20b is formed integrally with one end portion 18a of the backup foil 18 inside the groove portion 14 and extends from the other side toward the one side.

[0031] The extending portion 20b extends to one side wall surface 14a and contacts the one side wall surface 14a, and is press-fitted into the groove portion 14 in a state of applying a spring force to the one side wall surface 14a. When the extending portion 20b applies a pressing force to the one side wall surface 14a, a reaction force equal to the pressing force is received from the one side wall surface 14a as a reaction. Since this reaction force is transmitted to one end portion 18a of the backup foil 18 through the extending portion 20b, one end portion 16a of the top foil 16 and one end portion 18a of the backup foil 18 are pressed against the other side wall surface 14b. As a result, the frictional force generated between one end portion 16a of the top foil 16 and one end portion 18a of the backup foil 18, and the frictional force generated between one end portion 16a of the top foil 16 and the other side wall surface 14b increase, so that one end portion 16a of the top foil 16 and one end portion 18a of the backup foil 18 are stably fixed inside the groove portion 14. Therefore, by means of the simple means of providing the extending portion 20b in the groove portion 14, the top foil 16 and the backup foil 18 can be prevented from moving in the axial direction.

[0032] In the embodiment illustrated in FIG. 4, the extending portion 20b has a first extending portion 24a and a second extending portion 24b. One end of the first extending portion 24a is integrally formed with one end portion 18a of the backup foil 18, extends from one end portion 18a of the backup foil 18 toward the one side wall surface 14a, and is configured such that the other end reaches the one side wall surface 14a. The second extending portion 24b is integrally formed with the other end of the first extending portion 24a and extends toward the rotation axis 100 side while contacting the one side wall surface 14a.

[0033] In this embodiment, since substantially the entire surface on one side of the second extending portion 24b is arranged to be in contact with the one side wall surface 14a, a sufficient contact area with the one side wall surface 14a can be ensured. Therefore, the pressing force of the extending portion 20b can be reliably applied to the one side wall surface 14a, and the reaction force received from the one side wall surface 14a can be reliably transmitted to the one end portion 16a of the top foil 16 via the one end portion 18a of the backup foil 18. Therefore, the frictional force generated between the one end portion 16a of the top foil 16 and the one end portion 18a of the backup foil 18, and the frictional force generated between the one end portion 16a of the top foil 16 and the other side wall surface 14b can be reliably increased, thereby reliably preventing the top foil 16 and the backup foil 18 from moving in the axial direction.

[0034] Note that the first extending portion 24a and the second extending portion 24b may be provided in the entire axial region of the one end portion 18a extending along the axial direction, or may be provided only partially in the axial direction with respect to the one end portion 18a extending along the axial direction. In the latter case, the first extending portion 24a and the second extending portion 24b may be provided in a comb-like shape.

[0035] According to some embodiments illustrated in FIGS. 3 to 6, the one end portion 16a of the top foil 16 is in direct contact with the other side wall surface 14b and receives the load from the spring member 20a and the extending portion 20b via the one end portion 18a of the backup foil 18. Therefore, the position of the one end portion 16a of the top foil 16 inside the groove portion 14 is not affected by the deformation of the spring member 20a and the extending portion 20b and can be accurately held at a predetermined position.

[0036] Also, in these embodiments, since the rotating shaft 100 rotates from one side to the other side, the rotational force of the rotating shaft 100 is biased to the one end portion 16a of the top foil 16, and the one end portion 16a is pressed against the other side wall surface 14b. As a result, the frictional force between the one end portion 16a of the top foil 16 and the other side wall surface 14b increases, and the top foil 16 can be more stably fixed inside the groove portion 14.

[0037] The groove portion 14 shown in FIGS. 3 and 4 and the like has a rectangular cross-section. The pair of side wall surfaces 14a and 14b are formed as flat surfaces and are formed parallel to each other. In the case of this shape, the pressing force applied by the spring member 20a or the extending portion 20b to one side wall surface 14a and the reaction force applied from the one side wall surface 14a to the spring member 20a or the extending portion 20b are generated substantially perpendicular to the side wall surfaces 14a and 14b, and thus are efficiently transmitted. On the other hand, the pair of side wall surfaces 14a and 14b do not have to be parallel to each other. That is, the side wall surfaces 14a and 14b may be inclined with respect to each other as long as the pressing force of the spring member 20a or the extending portion 20b and the reaction force of the one side wall surface 14a are effectively transmitted to the other side wall surface 14b.

[0038] Further, in the embodiments shown in FIGS. 3 and 4 and the like, the bottom surface 14c of the groove portion 14 has a flat surface. However, the bottom surface 14c does not necessarily have to be a flat surface. Also, the groove portion 14 has a substantially square cross-section. However, it does not have to be square, and may be, for example, rectangular or other shapes.

[0039] In one embodiment, the other side wall surface 14b has a surface roughness with an arithmetic mean roughness Ra of 3 to 50 μm (preferably 5 to 30 μm).

[0040] According to this embodiment, since the surface roughness of the other side wall surface 14b has an arithmetic mean roughness Ra of 3 μm to 50 μm, the frictional force generated between the other side wall surface 14b and one end portion 16a of the top foil 16 pressed against the other side wall surface 14b can be further increased. Therefore, the axial movement of the top foil 16 can be more reliably prevented.

[0041] FIG. 7 shows a gas bearing device 10B according to another embodiment, and is a front view showing the inner peripheral surface 12a of the housing 12. This embodiment is similar to the embodiments shown in FIGS. 1 to 6. The housing 12 is provided around the rotation axis 100, and an annular gap Sr (not shown) is formed between the rotation axis 100 and the housing 12. And, a wavy groove portion 34 extending along the axial direction of the rotation axis 100 is formed on the inner peripheral surface 12a of the housing 12. The wavy groove portion 34 has a wavy groove portion 34 with a shape different from the groove portion 14 according to the embodiments shown in FIGS. 1 to 6. In the annular gap Sr, the top foil 16 is provided so as to surround the rotation axis 100, and one end portion 16a of the top foil 16 in the circumferential direction of the rotation axis 100 is inserted into the wavy groove portion 34. A backup foil 18 is provided outside the top foil 16 in the radial direction so as to surround the top foil 16, and the backup foil 18 elastically supports the top foil 16. One end portion 18a of the backup foil 18 in the circumferential direction is inserted into the inside of the wavy groove portion 34. Note that in FIG. 7, configurations other than the inner peripheral surface 12a of the housing 12 where the wavy groove portion 34 is formed are omitted.

[0042] The wavy groove portion 34 has a pair of side wall surfaces 34a and 34b arranged to face each other. One side wall surface 34a is located on one side (the side in the direction of arrow b) of the wavy groove portion 34, and the other side wall surface 34b is located on the other side (the side in the direction of arrow c) of the wavy groove portion 34. The pair of side wall surfaces 34a and 34b forming the wavy groove portion 34 have a wavy shape in which concavities and convexities are repeated along the axial direction. That is, the side wall surfaces 34a and 34b are periodically concaved and convexed along the axial direction, and curved concavities and convexities that advance and retreat in the circumferential direction of the rotation axis 100 are formed.

[0043] Furthermore, one end portion 18a of the backup foil 18 is inserted into the wavy groove portion 34 so as to be located on one side (the side in the direction of arrow b) inside the wavy groove portion 34 with respect to the one side wall surface 34a and the one end portion 16a of the top foil 16. That is, one end portion 18a of the backup foil 18 is inserted between the one side wall surface 34a and the one end portion 16a of the top foil 16. Also, similar to the embodiment shown in FIG. 1, the rotation axis 100 (not shown) rotates in the other direction (the direction of arrow c).

[0044] According to the present embodiment, since a pair of side wall surfaces 34a and 34b forming the corrugated groove portion 34 have unevenness in the circumferential direction, one end portion 16a of the top foil 16 and one end portion 18a of the backup foil 18 inserted into the corrugated groove portion 34 can be inserted into the corrugated groove portion 34 so as to repeatedly contact a plurality of convex portions 36a and 36b formed on each of the side wall surfaces 34a and 34b, as shown in FIG. 7. Thereby, since the frictional force generated between one end portion 16a of the top foil 16 and one end portion 18a of the backup foil 18 and the side wall surfaces 34a and 34b can be increased, it is possible to effectively prevent the top foil 16 and the backup foil 18 from moving in the axial direction.

[0045] In one embodiment, one end portion 16a of the top foil 16 and one end portion 18a of the backup foil 18 may be bent to have a certain degree of unevenness so as to be insertable into the corrugated groove portion 34 and inserted into the corrugated groove portion 34, or, in a straight shape, the elasticity of one end portion 16a of the top foil 16 and one end portion 18a of the backup foil 18 may be utilized to press-fit them into the corrugated groove portion 34. In the latter case, since one end portion 16a of the top foil 16 and one end portion 18a of the backup foil 18 can be inserted into the corrugated groove portion 34 in a state of being in pressure contact with the convex portions 36a and 36b of the corrugated groove portion 34, the frictional force generated between one end portion 16a of the top foil 16 and one end portion 18a of the backup foil 18 and the convex portions 36a and 36b can be increased. Therefore, the top foil 16 and the backup foil 18 can be stably fixed to the corrugated groove portion 34.

[0046] In any of the above insertion methods, since one end portion 16a of the top foil 16 and one end portion 18a of the backup foil 18 are in contact only with the convex portions 36a and 36b and the entire surfaces are not in contact with the side wall surfaces 34a and 34b, the one end portion 16a of the top foil 16 and the one end portion 18a of the backup foil 18 can be easily inserted into the corrugated groove portion 34, and it is not necessary to precisely process the dimension between the side wall surface 34a and the side wall surface 34b according to the plate thickness dimension of the one end portion 16a of the top foil 16 and the one end portion 18a of the backup foil 18.

[0047] The concave and convex shapes formed on the pair of side wall surfaces 34a and 34b may be formed, for example, in a wave shape (such as a sine curve) having valleys in the circumferential direction, or may be rectangular concave and convex. That is, the convex portions 36a and 36b may be formed of flat surfaces, or may be formed in an arc shape such as a parabola.

[0048] In the present embodiment, at least one of one side wall surface 34a and the other side wall surface 34b of the corrugated groove portion 34 may be configured to have a surface roughness with an arithmetic mean roughness Ra of 3 to 50 μm (preferably 5 to 30 μm). As a result, since the arithmetic mean roughness Ra of the other side wall surface 34b has a surface roughness of 3 μm to 50 μm, the frictional force generated between the other side wall surface 34b and one end portion 16a of the top foil 16 pressed against the other side wall surface 34b can be further increased. Therefore, the axial movement of the top foil 16 and the backup foil 18 can be more reliably prevented.

[0049] FIG. 8 is a front view cross-sectional view along the axial direction showing a gas bearing device 10C according to still another embodiment. Similar to the embodiment shown in FIGS. 1 to 7, in the gas bearing device 10C, the housing 12 is provided around the rotating shaft 100, and an annular gap Sr is formed between the rotating shaft 100 and the housing 12. And, the inner peripheral surface 12a of the housing 12 is provided with an inclined groove portion 44 whose distance from the central axis O of the rotating shaft 100 decreases from one axial side to the other axial side. The bottom surface 44c of the inclined groove portion 44 is inclined so that the distance from the central axis O decreases from one axial side to the other axial side. And, one end portion 16a of the top foil 16 and one end portion 18a of the backup foil 18 are arranged in the inclined groove portion 44 so that the tips thereof are in contact with at least a part of the bottom surface 44c of the inclined groove portion 44, respectively.

[0050] In the annular gap Sr, the top foil 16 is provided so as to surround the rotating shaft 100, and one end portion 16a of the top foil 16 in the circumferential direction of the rotating shaft 100 is inserted into the inclined groove portion 44. Outside the top foil 16 in the radial direction, a backup foil 18 is provided so as to surround the top foil 16, and the backup foil 18 elastically supports the top foil 16. One end portion 18a of the backup foil 18 in the circumferential direction is inserted into the inside of the inclined groove portion 44. In FIG. 8, although one end portion 18a of the backup foil 18 is not shown, the one end portion 18a is arranged in a hidden state having the same height as the one end portion 16a on the back side of the one end portion 16a of the top foil 16. Therefore, in FIG. 8, the reference numerals 18a and 18a1 are shown in parentheses.

[0051] Also, "one axial side" means the direction in which the distance between the bottom surface 44c of the inclined groove portion 44 and the central axis O of the rotating shaft 100 gradually increases (the direction of arrow d in FIG. 8) in FIG. 8, and "the other axial side" means the direction in which the distance between the bottom surface 44c of the inclined groove portion 44 and the central axis O of the rotating shaft 100 gradually decreases (the direction of arrow e in FIG. 8).

[0052] According to the present embodiment, since the tip 16a1 (the radially outermost edge of the one end portion 16a) of the one end portion 16a of the top foil 16 inserted into the inclined groove portion 44 and the tip 18a1 (the radially outermost edge of the one end portion 18a) of the one end portion 18a of the backup foil 18 are in contact with at least a part of the bottom surface 44c of the inclined groove portion 44, a frictional force is generated between them. Due to this frictional force, the axial movement of the top foil 16 and the backup foil 18 is prevented, and they are stably held in the inclined groove portion 44.

[0053] In the embodiment illustrated in FIG. 8, the tips 16a1 and 18a1 of the one end portion 16a of the top foil 16 and the one end portion 18a of the backup foil 18 are also inclined so that the distance from the one side end surface 12b in the direction of the arrow e becomes smaller with respect to the central axis O, similar to the inclined groove portion 44. On the other hand, in another embodiment, the tips 16a1 and 18a1 of the one end portion 16a of the top foil 16 and the one end portion 18a of the backup foil 18 may be parallel to the central axis O in the axial direction.

[0054] Further, in the embodiment illustrated in FIG. 8, the inclination angle θ1 of the bottom surface 44c with respect to the central axis O and the inclination angle θ2 of the one end portion 16a of the top foil 16 and the one end portion 18a of the backup foil 18 with respect to the central axis O are in the relationship of θ2 < θ1. In the region B (the other region in the axial direction) in FIG. 8, the tips 16a1 and 18a1 of the one end portions 16a and 18a are in contact with the bottom surface 44c of the inclined groove portion 44.

[0055] On the other hand, in another embodiment, θ1 = θ2 may be satisfied. When θ1 = θ2, the tips 16a1 and 18a1 of the one end portion 16a of the top foil 16 and the one end portion 18a of the backup foil 18 are in contact with the bottom surface 44c in the entire axial region of the one end portion 16a of the top foil 16 and the one end portion 18a of the backup foil 18. Therefore, the frictional force generated between them further increases. Therefore, the axial movement of the top foil 16 and the backup foil 18 can be surely prevented.

[0056] In the embodiment illustrated in FIG. 8, the bottom surface 44c of the inclined groove portion 44 forms a linear flat surface along the axial direction, but it may be a curved surface that is curved along the axial direction. In the embodiment illustrated in FIG. 8, the bottom surface 44c of the inclined groove portion 44, one end portion 16a of the top foil 16, and one end portion 18a of the backup foil 18 are inclined so that the distance from the central axis O decreases from one side (left side of the paper) to the other side (right side of the paper). However, they may be inclined so that the distance from the central axis O increases from one side (left side of the paper) to the other side (right side of the paper).

[0057] In one embodiment, as shown in FIG. 8, a second housing 50 connected to one axial side of the housing 12 is further provided. The second housing 50 has a shape that protrudes toward the rotation axis 100 side from the housing 12. Each of one end portion 16a of the top foil 16 and one end portion 18a of the backup foil 18 is disposed in the inclined groove portion 44 in a state where a pressing force is applied from one axial side to the other axial side by the second housing 50.

[0058] According to this embodiment, since a pressing force is applied from one axial side to the other axial side by the second housing 50 to each of one end portion 16a of the top foil 16 and one end portion 18a of the backup foil 18 inserted into the inclined groove portion 44, axial movement of the top foil 16 and the backup foil 18 can be more reliably prevented.

[0059] In the above embodiment, the second housing 50 may be provided integrally with the housing 12, or may be provided separately from the housing 12. In the embodiment illustrated in FIG. 8, the tip on the rotation axis 100 side of the second housing 50 extends to a position substantially equivalent to the tip portion on the rotation axis 100 side of the backup foil 18 on the rotation axis 100 side. Thereby, axial movement of the top foil 16 and the backup foil 18 can be reliably prevented.

[0060] Furthermore, in another embodiment, the wavy groove portion 34 of the gas bearing device 10B shown in FIG. 7 is configured to have a bottom surface 44c inclined with respect to the central axis O of the rotating shaft 100 from one axial side to the other side, like the inclined groove portion 44 of the gas bearing device 10C shown in FIG. 8. And one end portion 16a of the top foil 16 and one end portion 18a of the backup foil 18 inserted into the wavy groove portion 34 are arranged in the inclined groove portion 44 such that their tips 16a1 and 18a1 are in contact with the bottom surface 44c of the inclined groove portion 44.

[0061] According to this embodiment, one end portion 16a of the top foil 16 and one end portion 18a of the backup foil 18 come into contact with the convex portions 36a and 36b formed in the wavy groove portion 34 to generate frictional force, and the respective tips 16a1 and 18a1 of one end portion 16a of the top foil 16 and one end portion 18a of the backup foil 18 generate frictional force with the inclined bottom surface 44c. Therefore, since the frictional force generated between the tips 6a1 and 18a1 and the wavy groove portion 34 increases multiplicatively, axial movement of the top foil 16 and the backup foil 18 can be more effectively prevented.

[0062] The content described in each of the above embodiments is understood as follows, for example.

[0063] 1) A gas bearing device according to one aspect includes a housing (12) having an accommodation space (Sc) inside which a rotating shaft (100) is accommodated. The housing (12) has a groove portion (14) formed on an inner peripheral surface (12a) that defines the accommodation space (Sc) and extends along the axial direction of the rotating shaft (100). A top foil (16) is provided in an annular gap (Sc) formed between the inner peripheral surface (12a) and the rotating shaft (100), and one end portion (16a) in the circumferential direction of the rotating shaft (100) is inserted into the groove portion (14). A backup foil is provided outside the top foil (16) in the annular gap (Sr) so as to surround the top foil (16) and is configured to elastically support the top foil (16). One end portion (18a) in the circumferential direction is inserted into the groove portion (14) so as to be located on one side (in the direction of arrow a) in the groove portion (14) with respect to one end portion (16a) of the top foil (16). The backup foil (18) is provided. The groove portion (14) includes a pair of side wall surfaces arranged to face each other, including one side wall surface (14a) located on one side (in the direction of arrow b) in the groove portion (14) and the other side wall surface (14b) located on the other side (in the direction of arrow c) in the groove portion (14). The gas bearing device further includes pressing force applying means (20) arranged in the groove portion (14) and configured to press each of the one end portions (16a, 18a) of the top foil (16) and the backup foil (18) against the other side wall surface (14b).

[0064] According to such a configuration, since the pressing force applying means (20) is provided, one ends (16a, 18a) of the top foil (16) and the backup foil (18) inserted into the groove portion (14) are pressed against the other side wall surface (14b) of the pair of side wall surfaces (16a, 18a) by the pressing force applying means (20). As a result, the frictional force generated between the one ends (16a, 18a) of the top foil (16) and the backup foil (18), and the frictional force generated between the one end (16a) of the top foil (16) and the other side wall surface (14b) increase, so that the top foil (16) and the backup foil (18) can be prevented from moving in the axial direction of the rotation axis (100).

[0065] 2) The gas bearing device according to another aspect is the gas bearing device described in 1), wherein the pressing force applying means (20) is a spring member configured separately from the backup foil (18), and includes a spring member (20a) arranged along the extending direction of the groove portion (14).

[0066] According to such a configuration, the pressing force applying means (20) includes the spring member (20a), and the spring member (20a) generates a spring force for pressing one ends (16a, 18a) of the top foil (16) and the backup foil (18) against the other side wall surface (14b). As a result, the frictional force generated between the one ends (16a, 18a) of the top foil (16) and the backup foil (18), and the frictional force generated between the one end (16a) of the top foil (16) and the other side wall surface (14b) can be increased. Therefore, by a simple means of arranging the spring member (20a) in the groove portion (14), the top foil (16) and the backup foil (18) can be prevented from moving in the axial direction. Further, since the top foil (16) is in direct contact with the other side wall surface (14b) and receives the pressing force of the spring member (20a), the position of the one end (16a) of the top foil (16) is not affected by the deformation of the spring member (20a) and is accurately held at a predetermined position.

[0067] 3) Further, a gas bearing device according to another aspect is the gas bearing device described in 1), wherein the pressing force applying means (20) is an extending portion integrally formed with the backup foil (18) at the one end portion (18a) of the backup foil (18), and includes an extending portion (20b) extending from the other side (in the direction of arrow c) to the one side (in the direction of arrow b) in the groove portion (14).

[0068] According to such a configuration, since the extending portion (20b) abuts against one side wall surface (14a) of the pair of side wall surfaces (14a, 14b) and applies a pressing force to the one side wall surface (14a), conversely, it receives the reaction force of the other side wall surface (14b), and due to this reaction force, the extending portion (20b) can generate a pressing force that presses the one end portions (16a, 18a) of the top foil (16) and the backup foil (18) against the other side wall surface (14b). As a result, the frictional force generated between the one end portions (16a, 18a) of the top foil (16) and the backup foil (18) and the frictional force generated between the one end portion (16a) of the top foil (16) and the other side wall surface (14b) can be increased. Therefore, by forming the extending portion (20b) on the backup foil (18), it is possible to prevent the top foil (16) and the backup foil (18) from moving in the axial direction by a simple means.

[0069] 4) Further, a gas bearing device according to another aspect is the gas bearing device according to any one of 1) to 3), wherein the other side wall surface (14b) has an arithmetic mean roughness Ra of 3 μm or more and 50 μm or less.

[0070] According to such a configuration, since the other side wall surface (14b) has a surface roughness with an arithmetic mean roughness Ra of 3 μm or more and 50 μm or less, the frictional force generated between the one end portion (16a) of the top foil (16) pressed against the other side wall surface (14b) by the pressing force applying means (20) and the other side wall surface (14b) can be further increased. As a result, the axial movement of the top foil (16) can be effectively prevented.

[0071] 5) A gas bearing device according to still another aspect includes a housing (12) having an accommodation space (Sc) inside which a rotating shaft (100) is accommodated. A groove portion (14) extending along the axial direction of the rotating shaft (100) is formed on an inner peripheral surface (12a) that defines the accommodation space (Sc). The housing (12) is provided with a top foil (16) formed in an annular gap (Sr) formed between the inner peripheral surface (12a) and the rotating shaft (100), and one end portion (16a) in the circumferential direction of the rotating shaft (100) is inserted into the groove portion (14). A backup foil is provided outside the top foil (16) in the annular gap (Sr) so as to surround the top foil (16) and is configured to elastically support the top foil (16). One end portion (18a) in the circumferential direction is inserted into the groove portion (14) so as to be located on one side (in the direction of arrow b) in the groove portion (14) with respect to one end portion (16a) of the top foil (16). The groove portion (14) includes a corrugated groove portion (34) extending in a corrugated shape along the axial direction.

[0072] According to such a configuration, since the groove portion (14) includes the corrugated groove portion (34) extending in a corrugated shape along the axial direction, one end portions (16a, 18a) of the top foil (16) and the backup foil (18) inserted into the corrugated groove portion (34) can be arranged inside the corrugated groove portion (34) in a state of being in contact with a plurality of convex portions (36a, 36b) formed on a pair of side wall surfaces (34a, 34b) of the corrugated groove portion (34). Thereby, the frictional force generated between these one end portions (16a, 18a) and the corrugated groove portion (34) can be increased, so that the top foil (16) and the backup foil (18) can be prevented from moving in the axial direction.

[0073] 6) A gas bearing device according to still another aspect is the gas bearing device according to 5), wherein the wavy groove portion (34) is a pair of side wall surfaces arranged to face each other, and includes one side wall surface (34a) located on one side (in the direction of arrow b) in the groove portion (34) and the other side wall surface (34b) located on the other side (in the direction of arrow c) in the groove portion (34). At least one of the one side wall surface (34a) and the other side wall surface (34b) has an arithmetic mean roughness Ra of 3 μm or more and 50 μm or less.

[0074] According to such a configuration, since the other side wall surface (34b) of the pair of side wall surfaces (34a, 34b) forming the wavy groove portion (34) has a surface roughness with an arithmetic mean roughness Ra of 3 μm or more and 50 μm or less, the frictional force generated between one end portion (16a) of the top foil (16) pressed against the other side wall surface (34b) by the pressing force applying means (20) and the other side wall surface (34b) can be further increased. Therefore, the axial movement of the top foil (16) can be more effectively prevented.

[0075] 7) A gas bearing device according to still another aspect is the gas bearing device according to 5) or 6), wherein the groove portion (14) includes an inclined groove portion (44) whose distance from the center line (O) of the rotating shaft (100) decreases from one side (in the direction of arrow d) to the other side (in the direction of arrow e) in the axial direction. The respective one end portions (16a, 18a) of the top foil (16) and the backup foil (18) are arranged in the inclined groove portion (44) such that the respective tips (16a1, 18a1) at the respective one end portions (16a, 18a) are in contact with the bottom surface (44c) of the inclined groove portion (44).

[0076] According to such a configuration, in the inclined groove portion (44), since the tips (16a1, 18a1) of the respective ends (16a, 18a) of the top foil (16) and the backup foil (18) inserted into the inclined groove portion (44) are in contact with the bottom surface (44c) of the inclined groove portion (44), frictional force is generated between them. Therefore, in addition to the frictional force generated between the ends (16a, 18a) of the top foil (16) and the backup foil (18) and the pair of side wall surfaces of the corrugated groove portion (44), the ends (16a, 18a) of the top foil (16) and the backup foil (18) can also generate frictional force with the inclined bottom surface (44c) forming the corrugated groove portion (44). As a result, since the frictional force generated between the ends (16a, 18a) of the top foil (16) and the backup foil (18) and the corrugated groove portion (34) increases multiplicatively, the axial movement of the top foil (16) and the backup foil (18) can be more effectively prevented.

[0077] 8) A gas bearing device according to still another aspect includes a housing (12) having an accommodation space (Sc) inside which a rotating shaft (100) is accommodated. A groove portion (14) extending along the axial direction of the rotating shaft (100) is formed on the inner peripheral surface (12a) that defines the accommodation space (Sc). A top foil (16) is provided in an annular gap (Sr) formed between the inner peripheral surface (12a) and the rotating shaft (100), and one end portion (16a) in the circumferential direction of the rotating shaft (100) is inserted into the groove portion (14). A backup foil is provided outside the top foil (16) in the annular gap (Sr) so as to surround the top foil (16) and is configured to elastically support the top foil (16). One end portion (18a) in the circumferential direction is inserted into the groove portion (14) so as to be located on one side (in the direction of arrow b) in the groove portion (14) with respect to one end portion (16a) of the top foil (16). The groove portion (14) includes an inclined groove portion (44) whose distance from the center line (O) of the rotating shaft (100) decreases from one side (in the direction of arrow d) to the other side (in the direction of arrow e) in the axial direction. The respective one end portions (16a, 18a) of the top foil (16) and the backup foil (18) are arranged in the inclined groove portion (44) such that the respective tips (16a1, 18a1) at the respective one end portions (16a, 18a) are in contact with the bottom surface (44c) of the inclined groove portion (44).

[0078] According to such a configuration, in the inclined groove portion (44), since the tips (16a1, 18a1) of the respective one end portions (16a, 18a) of the top foil (16) and the backup foil (18) are in contact with the bottom surface (44c) of the inclined groove portion (44), a frictional force is generated between them. By this frictional force, axial movement of the top foil (16) and the backup foil (18) can be prevented.

[0079] 9) A gas bearing device according to still another aspect further includes a second housing (50) connected to one side (in the direction of arrow d) in the axial direction with respect to the housing (12) in the gas bearing device described in 8). One end portion (16a, 18a) of each of the top foil (16) and the backup foil (18) is disposed in the inclined groove portion (44) in a state where a pressing force is applied from one side (in the direction of arrow d) to the other side (in the direction of arrow e) in the axial direction by the second housing (50).

[0080] According to such a configuration, a pressing force is applied to one end portion (16a, 18a) of each of the top foil (16) and the backup foil (18) inserted into the inclined groove portion (44) from one side (in the direction of arrow d) to the other side (in the direction of arrow e) in the axial direction by the second housing (50). Therefore, axial movement of the top foil (16) and the backup foil (18) can be reliably prevented.

Explanation of Reference Numerals

[0081] 10A, 10B, 10C Gas bearing device 12 Housing 12a Inner peripheral surface 12b One side end face 12c Other side wall surface 14 Groove portion 14a One side wall surface (pair of side wall surfaces) 14b Other side wall surface (pair of side wall surfaces) 14c Bottom surface 16 Top foil 16a One end portion 16a1 Tip 16b Other end portion 18 Backup foil 18a One end portion 18a1 Tip 18b Other end portion 19a Crest 19b Trough 20 Pressing force applying means 20a Spring member 22 Torsion coil spring Straight portions 22a and 22b Extended portion 20b First extended portion 24a Second extended portion 24b Coil spring 26 Wave-shaped groove portion 34 One side wall surface (pair of side wall surfaces) 34a The other side wall surface (pair of side wall surfaces) 34b Protrusions 36a and 36b Inclined groove portion 44 Bottom surface 44c Second housing 50 Rotating shaft 100 Axis line AL Central axis line O Accommodation space Sc Annular gap Sr Inclination angles θ1 and θ2

Claims

1. A housing having an accommodation space for accommodating a rotating shaft therein, the housing having a groove portion formed on an inner peripheral surface defining the accommodation space and extending along an axial direction of the rotating shaft; A top foil provided in an annular gap formed between the inner peripheral surface and the rotating shaft, with one end portion of the rotating shaft in the circumferential direction being inserted into the groove portion; A backup foil provided outside the top foil in the annular gap so as to surround the top foil and configured to elastically support the top foil, with one end portion in the circumferential direction being inserted into the groove portion so as to be located on one side in the groove portion with respect to one end portion of the top foil. The groove portion includes a pair of side wall surfaces arranged to face each other, including one side wall surface located on one side in the groove portion and the other side wall surface located on the other side in the groove portion. Further comprising pressing force applying means disposed in the groove portion and configured to press each of the one end portions of the top foil and the backup foil against the other side wall surface. The pressing force applying means is a spring member configured separately from the backup foil and includes a spring member arranged along the extending direction of the groove portion. The spring member is a torsion coil spring formed by shaping a single bar into a coil shape, and has a first straight portion extending along the one side wall surface at one end portion of the bar and a second straight portion extending along the other side wall surface at the other end portion of the bar. A gas bearing device.

2. A housing having an accommodation space for accommodating a rotating shaft therein, the housing having a groove portion formed on an inner peripheral surface defining the accommodation space and extending along an axial direction of the rotating shaft; A top foil provided in an annular gap formed between the inner peripheral surface and the rotating shaft, with one end portion of the rotating shaft in the circumferential direction being inserted into the groove portion; A backup foil provided so as to surround the top foil outside the top foil in the annular gap and configured to elastically support the top foil, wherein one end portion in the circumferential direction is inserted into the groove portion so as to be located on one side in the groove portion with respect to one end portion of the top foil, and a backup foil. The groove portion includes a pair of side wall surfaces arranged to face each other, including one side wall surface located on one side in the groove portion and the other side wall surface located on the other side in the groove portion. Further provided with pressing force applying means configured to press each of the one end portions of the top foil and the backup foil against the other side wall surface, which is disposed in the groove portion. The pressing force applying means is a spring member configured separately from the backup foil, and includes a plurality of coil springs arranged in parallel or at intervals along the extending direction of the groove portion. Each of the plurality of coil springs is inserted in a compressed state in the direction of the axis between the one side wall surface and the one end portion of the backup foil with the axis of the coil spring facing the circumferential direction of the rotating shaft. Gas bearing device.

3. A housing having an accommodation space inside which a rotating shaft is accommodated, the housing having a groove portion formed along the axial direction of the rotating shaft on an inner circumferential surface defining the accommodation space. A top foil provided in an annular gap formed between the inner circumferential surface and the rotating shaft, and one end portion in the circumferential direction of the rotating shaft is inserted into the groove portion. A backup foil provided so as to surround the top foil outside the top foil in the annular gap and configured to elastically support the top foil, wherein one end portion in the circumferential direction is inserted into the groove portion so as to be located on one side in the groove portion with respect to one end portion of the top foil, and a backup foil. The groove portion includes a pair of side wall surfaces arranged to face each other, including one side wall surface located on one side in the groove portion and the other side wall surface located on the other side in the groove portion. Further provided with pressing force applying means arranged in the groove portion and configured to press one end portion of each of the top foil and the backup foil against the other side wall surface. The pressing force applying means is an extending portion integrally formed with the backup foil at one end portion of the backup foil, and includes an extending portion extending from the other side to the one side in the groove portion. The extending portion includes a first extending portion integrally formed at one end of the backup foil and extending from the one end of the backup foil toward the one side wall surface, and a second extending portion integrally formed with the other end of the first extending portion and extending toward the rotation axis side while contacting the one side wall surface. Gas bearing device.

4. The other side wall surface has an arithmetic mean roughness Ra of 3 μm or more and 50 μm or less. The gas bearing device according to any one of claims 1 to 3.

5. A housing having an accommodation space inside which a rotating shaft is accommodated, and the housing is formed with a groove portion extending along the axial direction of the rotating shaft on an inner peripheral surface defining the accommodation space. A top foil provided in an annular gap formed between the inner peripheral surface and the rotating shaft, and one end portion in the circumferential direction of the rotating shaft is inserted into the groove portion. A backup foil provided so as to surround the top foil outside the top foil in the annular gap and configured to elastically support the top foil, and one end portion in the circumferential direction is inserted into the groove portion so as to be located on one side in the groove portion with respect to one end portion of the top foil. The groove portion includes a pair of side wall surfaces arranged to face each other, including one side wall surface located on one side of the groove portion and the other side wall surface located on the other side of the groove portion. The groove portion includes a wavy groove portion extending in a wavy shape along the axial direction. Gas bearing device.

6. The wavy groove portion includes a pair of side wall surfaces arranged to face each other, including one side wall surface located on one side of the groove portion and the other side wall surface located on the other side of the groove portion. The gas bearing device according to claim 5, wherein at least one of the one side wall surface and the other side wall surface has an arithmetic mean roughness Ra of 3 μm or more and 50 μm or less.

7. The groove portion includes an inclined groove portion in which the distance from the center line of the rotating shaft decreases from one side to the other side in the axial direction. Each one end portion of the top foil and the backup foil is arranged in the inclined groove portion such that the tip of each one end portion contacts the bottom surface of the inclined groove portion. The gas bearing device according to claim 5 or 6.

8. A housing having an accommodation space inside which a rotating shaft is accommodated, the housing having a groove portion formed along the axial direction of the rotating shaft on an inner peripheral surface defining the accommodation space. A top foil provided in an annular gap formed between the inner peripheral surface and the rotating shaft, with one end portion in the circumferential direction of the rotating shaft inserted into the groove portion. A backup foil provided outside the top foil in the annular gap so as to surround the top foil and configured to elastically support the top foil, with one end portion in the circumferential direction inserted into the groove portion so as to be located on one side in the groove portion with respect to one end portion of the top foil. The groove portion includes an inclined groove portion whose distance from the center line of the rotation axis decreases from one side in the axial direction to the other side. One end of each of the top foil and the backup foil is disposed in the inclined groove portion such that the tip of each at one end contacts the bottom surface of the inclined groove portion. Gas bearing device.

9. It further includes a second housing connected to one side in the axial direction with respect to the housing. One end of each of the top foil and the backup foil is disposed in the inclined groove portion in a state where a pressing force is applied from the one side to the other side in the axial direction by the second housing. The gas bearing device according to claim 8.

Images