WO2018016268A1

WO2018016268A1 - Foil bearing

Info

Publication number: WO2018016268A1
Application number: PCT/JP2017/023304
Authority: WO
Inventors: 真人吉野; 藤原　宏樹
Original assignee: Ntn株式会社
Priority date: 2016-07-20
Filing date: 2017-06-23
Publication date: 2018-01-25
Also published as: JP6800637B2; JP2018013162A

Abstract

A foil bearing (1) is provided with: a top foil section (21) having a bearing surface (X); a first back foil section (22) for supporting the top foil section (21) from behind; and a base surface (B) for supporting the first back foil section (22) from behind, and the foil bearing (1) supports without contact a shaft (2) by fluid pressure occurring in the bearing gap (C) between the shaft (2) and the bearing surface (X), which rotate relative to each other. A recess (B1) is provided in the base surface (B). The upstream region (S1) of the first back foil section (22) is capable of fitting in the recess (B1) in the base surface (B). The foil bearing (1) has a restriction section (A)(second back foil section (23)) for restricting the fitting of the downstream region (S2) of the first back foil section (22) into the recess (B1).

Description

Foil bearing

The present invention relates to a foil bearing.

A foil bearing is a flexible metal thin plate (foil) that forms a bearing surface. When the foil bends, the bearing clearance varies depending on operating conditions such as shaft rotation speed, load, and ambient temperature. It has the feature of being automatically adjusted to an appropriate width.

For example, the following Patent Document 1 discloses a foil bearing called a bump type as an example of a thrust foil bearing that supports a thrust load. As shown in FIG. 18, the foil bearing is provided with a top foil 114, a corrugated back foil 112 (bump foil) elastically supporting the top foil 114 from the back, a top foil 114 and a back foil 112. And a base plate 110. When the shaft rotates, a wedge-shaped bearing gap C is formed between the bearing surface 114a of the top foil 114 and the thrust collar 115, with the gap width decreasing toward the downstream side. The fluid in the bearing gap C is pushed into the small gap C2 from the large gap C1 of the bearing gap C, thereby increasing the fluid pressure and supporting the thrust collar 115 in a non-contact manner.

Japanese Utility Model Publication No. 61-36725

However, the above foil bearing is expensive because it is necessary to form a corrugated back foil. In particular, in the above-described foil bearing, since the height of the back foil 112 gradually increases toward the downstream side in order to form the wedge-shaped bearing gap C, the design of the back foil 112 becomes complicated.

Therefore, an object of the present invention is to provide a foil bearing that forms a wedge-shaped bearing gap at a low cost.

In order to solve the above problems, the present invention provides a top foil part having a bearing surface, a first back foil part for supporting the top foil part from the back, and a base for supporting the first back foil part from the back. In the foil bearing for supporting the shaft in a non-contact manner by a fluid pressure generated in a bearing gap between the relatively rotating shaft and the bearing surface, a recess is provided in the base surface, and the first back foil portion And a restricting portion for restricting fitting of the downstream region of the first back foil portion into the recess.

The “downstream side” refers to the downstream side in the fluid flow direction with respect to the top foil during relative rotation of the shaft, and the opposite side is referred to as the “upstream side”.

In the above foil bearing, when the fluid pressure in the bearing gap increases with relative rotation of the shaft, the top foil portion and the first back foil portion are pushed into the base surface side. At this time, since the upstream region of the first back foil portion can be fitted into the recess of the base surface, the upstream region of the top foil portion supported in this region is easily pushed into the base surface side ( That is, the rigidity against the fluid pressure generated in the bearing gap is small). On the other hand, the downstream region of the first back foil portion is restricted from being fitted into the concave portion of the base surface by the restricting portion. Therefore, the downstream region of the top foil portion supported in this region is the upstream region. It is harder to be pushed into the base surface than that (that is, the rigidity against the fluid pressure generated in the bearing gap is large). As a result, due to the fluid pressure in the bearing gap, the upstream region of the top foil portion is pushed closer to the base surface side than the downstream region, and the top foil portion curves toward the shaft side as it goes downstream, and the top foil portion A wedge-shaped bearing gap is formed between the bearing surface and the shaft. As described above, according to the present invention, a wedge-shaped bearing gap can be formed without providing a corrugated backfoil whose height increases toward the downstream side as shown in Patent Document 1 above. Can do.

In the above foil bearing, for example, a second back foil portion that functions as the restricting portion can be disposed between the base surface and the downstream region of the first back foil portion. In this case, since the first back foil part is separated from the base surface by the amount of the intervening second back foil part, the step between the upstream area and the downstream area of the top foil part becomes large, and the wedge-shaped bearing gap Is easily formed.

The foil bearing preferably includes a foil member integrally including the top foil portion, the first back foil portion, and the second back foil portion. In this case, compared with the case where each foil part is formed separately, a processing man-hour and an assembly man-hour are reduced, and a manufacturing cost can be reduced.

In the foil bearing described above, a non-contact that does not contact the top foil portion in an intermediate portion of the first back foil portion in a direction orthogonal to the relative rotation direction of the shaft (hereinafter referred to as “rotation orthogonal direction”). It is preferable to provide a part. In this case, since the non-contact part of the first back foil part is arranged behind the intermediate part in the rotation orthogonal direction of the top foil part, it is not contact-supported by the first back foil part. Therefore, when the fluid pressure in the bearing gap is increased, a concave portion that is recessed toward the base surface side rather than both sides thereof is formed in the intermediate portion in the rotation orthogonal direction of the top foil portion. As a result, the fluid flowing in the bearing gap is collected in the concave portion in the intermediate portion in the rotation orthogonal direction of the top foil portion, and the fluid pressure in the bearing gap is further increased.

Specifically, for example, a pair of side portions that are separated from the first back foil portion in a direction orthogonal to the relative rotation direction of the shaft, and a connecting portion that connects downstream end portions of the pair of side portions, And a hole as the non-contact portion can be formed in a region surrounded by the pair of side portions and the connecting portion. In this case, a region adjacent to the downstream side of the concave portion of the top foil portion is supported from behind by the connecting portion of the first back foil portion, and therefore, the region closer to the shaft than the concave portion (bearing) A weir is provided on the side that narrows the gap. This weir makes it difficult for the fluid collected in the concave portion to escape downstream, so that the pressure in the bearing gap is further increased.

In the above foil bearing, for example, the base surface can be formed by a foil holder and a base foil attached to the foil holder, and the concave portion of the base surface can be formed by a hole provided in the base foil. . Thereby, a recessed part can be easily formed compared with the case where a recessed part is directly processed into a foil holder, for example.

As described above, according to the present invention, a foil bearing that forms a wedge-shaped bearing gap can be obtained at low cost.

It is sectional drawing of the foil bearing (thrust foil bearing) which concerns on one Embodiment of this invention. It is the top view which notched a part of the said foil bearing. It is a top view which expands and shows the notched part of FIG. It is a top view of a foil member. It is a top view of a base foil. It is a perspective view which shows a mode that a some foil member is temporarily assembled. It is the top view which looked at the temporary assembly of the several foil member from the bearing surface side. It is the top view which looked at the said temporary assembly from the opposite side to the bearing surface. It is a side view of the said temporary assembly. It is a perspective view which shows a mode that the said temporary assembly is mounted on a base foil. It is sectional drawing of the said foil bearing. FIG. 12 is a cross-sectional view taken along a line UU in FIG. 11. FIG. 12 is a cross-sectional view taken along line VV in FIG. 11. It is sectional drawing in the WW line of FIG. It is a top view of the foil member concerning other embodiments. It is a top view of the base foil which concerns on other embodiment. It is sectional drawing of the foil bearing which concerns on other embodiment. FIG. 16 is a cross-sectional view taken along line YY in FIG. FIG. 16 is a cross-sectional view taken along the line ZZ in FIG. 15. It is sectional drawing of the foil bearing (radial foil bearing) which concerns on other embodiment. It is sectional drawing of the conventional foil bearing.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the foil bearing 1 according to the first embodiment of the present invention is an air film formed between a disc-shaped thrust collar 3 provided on the shaft 2, and the shaft 2 extends in the thrust direction. It is a thrust foil bearing to support. The foil bearing 1 includes a disc-shaped foil holder 10, a plurality of foil members 20, and a base foil 30 disposed between the foil holder 10 and the plurality of foil members 20. As shown in FIG. 2, a plurality of (eight in the illustrated example) foil members 20 are arranged in the rotational direction of the shaft 2 (the circumferential direction of the foil holder 10, see arrow R). The plurality of foil members 20 and the base foil 30 are attached to the foil holder 10.

The foil holder 10 is made of metal or resin. The foil holder 10 has a hollow disk shape having an inner hole 10b into which the shaft 2 is inserted (see FIG. 1). A base foil 30 and a plurality of foil members 20 are attached to one end face 10 a of the foil holder 10. The other end face 10c of the foil holder 10 is fixed to a housing of a facility (for example, a turbo machine such as a gas turbine) in which the foil bearing 1 is incorporated.

The foil member 20 is formed of a metal having high spring properties and good workability, for example, steel or copper alloy. The foil member 20 is formed of a thin metal plate (foil) having a thickness of about 20 μm to 200 μm. In an air dynamic pressure bearing using air as a fluid film as in the present embodiment, since there is no lubricating oil in the atmosphere, the foil member 20 is preferably formed of stainless steel or bronze.

As shown in FIG. 4, the foil member 20 includes a top foil part 21, a first back foil part 22 provided on the downstream side of the top foil part 21, and a second provided on the upstream side of the top foil part 21. A back foil portion 23 is integrally provided. The foil member 20 is formed into a flat plate shape by subjecting the foil to press working (punching) or electric discharge machining.

The top foil portion 21 has a substantially fan shape, and has a smooth bearing surface X with no irregularities on the front side (thrust collar 3 side) surface. In a state where a plurality of foil members 20 are attached to the foil holder 10, the bearing surface X of the top foil portion 21 of each foil member 20 is continuously provided in the circumferential direction and exposed to the surface facing the thrust collar 3. (See FIG. 2).

The first back foil portion 22 extends from the downstream end portion of the top foil portion 21 to the downstream side. The first back foil portion 22 has a substantially fan-shaped outer shape, and its circumferential dimension and radial dimension are slightly smaller than the top foil part 21. The first back foil portion 22 includes a pair of side portions 22a that are spaced apart in the radial direction, a connecting portion 22b that connects downstream end portions of the pair of side portions 22a, and a hole 22c surrounded by these. The hole 22c penetrates the first back foil portion 22 in the thickness direction. The hole 22c functions as a non-contact portion that does not contact the top foil portion 21 (details will be described later).

The second back foil part 23 is provided on the upstream side of the top foil part 21. In the illustrated example, the second back foil portion 23 has a substantially sector shape and is connected to the top foil portion 21 via the connection portion 24. The 2nd back foil part 23 functions as the control part A which controls the fitting to recessed part B1 of the 1st back foil part 22 of the other foil member 20 (it mentions later for details). The radial dimension of the second back foil part 23 is equal to the radial dimension of the top foil part 21. The circumferential dimension of the second back foil portion 23 is smaller than the circumferential dimension of the top foil portion 21 and is, for example, ½ or less. The connecting portion 24 has a smaller radial dimension than the top foil portion 21 and the second back foil portion 23. The connecting portion 24 and the connecting portion (boundary) between the top foil portion 21 and the first back foil portion 22 are provided at different radial positions. In the illustrated example, the connecting portion 24 is provided in the radial region of the hole 22 c of the first back foil portion 22, and in particular, provided in the central portion in the radial direction of the second back foil portion 23.

In addition, the shape of the 1st back foil part 22 and the 2nd back foil part 23 is not restricted above. For example, the radial dimension of the first back foil portion 22 may be equal to that of the top foil portion 21. Further, the radial dimension of the second back foil portion 23 may be smaller than that of the top foil portion 21.

The foil member 20 has a fixing portion for fixing to the foil holder 10. In the present embodiment, an extending portion 21a extending from the upstream end portion of the top foil portion 21 to the outer diameter side, and an extending portion 23a extending from the downstream end portion of the second back foil portion 23 to the outer diameter side, Functions as a fixed part. These extending

portions

21 a and 23 a are fixed to the end surface 10 a of the foil holder 10 together with the base foil 30 by appropriate means such as welding. Since the connection part 24 which connects the top foil part 21 and the 2nd back foil part 23 among the foil members 20 is the most weak, as mentioned above, it adjoins to the circumferential direction both sides of the connection part 24, and a fixing | fixed part ( It is preferable to provide extending

portions

21a, 23a).

If fixing portions are provided on both the outer diameter side and the inner diameter side of the foil member 20, the foil member 20 and the foil holder 10 hardly move relative to each other. There is a possibility that the vibration damping function due to sliding with the holder 10 or the like is not sufficiently exhibited. Therefore, it is preferable to provide the fixing portion only on either the outer diameter side or the inner diameter side of the foil member 20. In particular, in order to avoid interference with the shaft 2, it is preferable to provide a fixing portion only on the outer diameter side of the foil member 20 as in the illustrated example.

The base foil 30 is formed of an annular flat foil, as shown in FIG. A plurality of holes 35 are formed in the base foil 30 at equal intervals in the circumferential direction. The base foil 30 includes, for example, a large-diameter annular portion 31, a small-diameter annular portion 32, a plurality of radial portions 33 that connect these in the radial direction, and a circumferential direction extending in the circumferential direction from the radial center of the radial portion 33. It has the part 34 and the hole 35 divided by these. In the illustrated example, each hole 35 has a substantially U-shape that is substantially the same shape as the first back foil portion 22 of the foil member 20. Specifically, the hole 35 includes a pair of circumferential portions 35a that are separated from each other in the radial direction, and a radial portion 35b that connects downstream ends of the pair of circumferential portions 35a.

The base foil 30 is formed by subjecting a thin metal plate (foil) to press working (punching) or electric discharge machining. In the illustrated example, the small-diameter annular portion 32 is divided into a plurality of portions in the circumferential direction so that the base foil 30 can be easily formed by electric discharge machining. However, the small-diameter annular portion 32 may be continuous over the entire circumference.

The base foil 30 is formed of a foil having the same thickness and the same material as the foil member 20, for example. The thickness and material of the base foil 30 may be different from those of the foil member 20. For example, the base foil 30 may be formed of a foil that is thicker than the foil member 20.

Next, a method for assembling the foil bearing 1 will be described.

First, as shown in FIG. 6, a plurality of foil members 20 are connected. Specifically, the second back foil portion 23 of the foil member 20 adjacent to the downstream side is inserted into the hole 22c of the first back foil portion 22 of each foil member 20 from the front side (bearing surface X side). And as shown in FIG. 7, the upstream end part and downstream end part of the top foil part 21 of the adjacent foil member 20 are distribute | arranged to the substantially same circumferential direction position. Thereby, the temporary assembly M by which the some foil member 20 was connected is formed. 6 to 9, the foil members 20 are shown in different colors (darkness) for easy understanding.

As shown in FIG. 8, the first back foil portion 22 of each foil member 20 constituting the temporary assembly M is disposed behind the top foil portion 21 of the foil member 20 adjacent to the downstream side. The second back foil portion 23 of each foil member 20 is disposed behind the top foil portion 21 of the foil member 20 adjacent to the upstream side. As shown in FIG. 9, the first back of the foil member 20 adjacent to the upstream side is disposed between the top foil portion 21 of each foil member 20 and the second back foil portion 23 of the foil member 20 adjacent to the downstream side. A foil part 22 is arranged. The overlapping portion N where the three foils (the top foil portion 21, the first back foil portion 22, and the second back foil portion 23) overlap is disposed at a position closer to the downstream side of the top foil portion 21. Specifically, the central portion in the circumferential direction of the overlapping portion N is disposed on the downstream side of the central portion in the circumferential direction of the top foil portion 21.

Next, as shown in FIG. 10, the base foil 30 is disposed on the end face 10a of the foil holder 10 (not shown), and the temporary assemblies M of the plurality of foil members 20 are disposed thereon. At this time, the base surface that supports the first back foil portion 22 and the second back foil portion 23 of the foil member 20 from the back by the base foil 30 and the end surface 10a of the foil holder 10 exposed from the hole 35 of the base foil 30. B is formed. In addition, the recess 35 B of the base surface B is formed by the hole 35 provided in the base foil 30. The bottom surface of the recess B <b> 1 is formed by the end surface 10 a of the foil holder 10.

As shown in FIG. 3, at least the upstream region S1 (the entire region in the illustrated example) of the first backfoil portion 22 of each foil member 20 is disposed so as to overlap with the hole 35 (recessed portion B1) of the base foil 30 in the axial direction. The The second back foil portion 23 of each foil member 20 is provided across the large-diameter annular portion 31 and the small-diameter annular portion 32 of the base foil 30 in the radial direction. The second back foil portion 23 of each foil member 20 is provided across the radial direction portion 33 and the circumferential direction portion 34 of the base foil 30 in the circumferential direction. That is, a region including the downstream end portion (radial direction portion 35b) of the hole 35 of the base foil 30 is covered with the second back foil portion 23, and the first back foil portion 22 is located on the upper side (thrust collar 3 side). Arranged. Thereby, the 2nd back foil part 23 functions as the control part A which controls the fitting to the recessed part B1 of the downstream area S2 of the 1st back foil part 22, and the downstream area of the 1st back foil part 22 S2 is always arranged above the base surface B. On the other hand, since no other foil is interposed between the upstream region S1 of the first back foil portion 22 and the base surface B, the upstream region S1 of the first back foil portion 22 has a recess B1 (base foil). 30 holes 35).

And the fixing | fixed part (

extension part

21a, 23a) of each foil member 20 and the large diameter annular part 31 of the base foil 30 are fixed to the end surface 10a of the foil holder 10 by appropriate means, such as welding. Thus, the foil bearing 1 is completed.

As shown in FIG. 11, when the shaft 2 and the thrust collar 3 rotate in one circumferential direction (in the direction of arrow R), the space between the bearing surface X of each top foil portion 21 of the foil bearing 1 and the end surface 3 a of the thrust collar 3. The fluid pressure in the bearing gap C is increased, and each foil member 20 is pressed against the foil holder 10 side (downward in the figure). As a result, in the upstream region of each top foil portion 21 (near the line U-U in FIG. 11), the upstream region S1 of the first back foil portion 22 becomes the base foil 30 as shown in FIG. It fits into the hole 35 (recess B1). Accordingly, the upstream region of the top foil portion 21 supported by the upstream region S1 of the first back foil portion 22 is pushed into the base surface B side (see arrow).

On the other hand, the overlapping region N (VV line, WW line in FIG. 11) that overlaps the downstream region of each top foil part 21, in particular, the first back foil part 22 and the second back foil part 23 in the axial direction. In the vicinity), as shown in FIGS. 12B and 12C, the second back foil portion 23 as the restricting portion A is interposed between the first back foil portion 22 and the base foil 30. For this reason, in this region, even when the fluid pressure in the bearing gap C is increased as the shaft 2 rotates, the first back foil portion 22 does not fit into the hole 35 of the base foil 30, and the base surface always remains. It is arranged on the thrust collar 3 side from B (the upper surface of the base foil 30). Thereby, a level | step difference exists between the upstream area | region S1 fitted in the recessed part B1 of the base surface B among the 1st back foil parts 22, and the downstream area | region S2 distribute | arranged upwards rather than the base surface B. Occurs (see FIG. 11). In particular, in the present embodiment, since the second back foil portion 23 is interposed between the downstream region S2 of the first back foil portion 22 and the base foil 30, the upstream region S1 of the first back foil portion 22 is present. And the downstream area S2 become larger.

Thus, by forming a step in the first back foil portion 22, the top foil portion 21 supported by the first back foil portion 22 is curved following the first back foil portion 22, and the bearing surface X approaches the thrust collar 3 as it goes downstream. As a result, the bearing gap C between the bearing surface X of the top foil portion 21 and the end surface 3a of the thrust collar 3 has a wedge-shaped cross section that becomes narrower toward the downstream side. The air flowing through the bearing gap C is pushed into the small gap portion of the wedge-shaped bearing gap C (near the downstream end of each top foil portion 21), thereby increasing the pressure of the air film in the bearing gap C. With this pressure, the shaft 2 and the thrust collar 3 are supported in a non-contact manner in the thrust direction.

Moreover, in this embodiment, the hole 22c enclosed by a pair of side part 22a and the connection part 22b is formed in the 1st back foil part 22. As shown in FIG. In this case, when the air pressure in the bearing gap C is increased, the vicinity of both ends in the radial direction in the downstream region of the top foil portion 21 is supported by the pair of side portions 22a of the first back foil portion 22 {FIG. (See (B)}, the vicinity of the downstream end is supported by the connecting portion 22b of the first back foil portion 22 (see FIG. 12C). On the other hand, since the hole 22c (non-contact part) of the first back foil part 22 is arranged behind the radial direction intermediate part (radial direction center part in the illustrated example) of the downstream region of the top foil part 21, It is not supported by one back foil part 22. Therefore, a concave portion P is formed in the central portion in the radial direction of the downstream region of the top foil portion 21 so as to be recessed below the base (base surface B side) {shaded region in FIG. 2 and FIG. ) See dotted line}. Thereby, since the air flowing through the bearing gap C is collected in the concave portion P in the central portion in the radial direction in the downstream region of each top foil portion 21, the pressure in the bearing gap C is further increased.

In particular, in the illustrated example, the region adjacent to the downstream side of the concave portion P in the top foil portion 21 is supported by the connecting portion 22b of the first back foil portion 22. A weir Q close to the collar 3 side is provided {see FIG. 2 and FIG. 12 (C)}. This weir Q makes it difficult for the air collected in the recess P to escape downstream, so that the pressure in the bearing gap C is further increased.

Note that the bearing surface X of each top foil portion 21 and the end surface 3a of the thrust collar 3 slide in contact with each other at the time of low-speed rotation immediately before the shaft 2 is stopped or immediately after the shaft 2 is driven. Alternatively, a low friction coating such as a titanium aluminum nitride film, a tungsten disulfide film, or a molybdenum disulfide film may be formed.

Further, during the rotation of the shaft 2, micro sliding occurs between the top foil part 21, the first back foil part 22, the second back foil part 23, the base foil 30, and the end surface 10 a of the foil holder 10. The vibration of the shaft 2 can be attenuated by the frictional energy generated by the minute sliding. In order to adjust the frictional force due to such micro-sliding, a low friction coating as described above may be formed on one or both of the surfaces that slide with each other.

The present invention is not limited to the above embodiment. Hereinafter, although other embodiment of this invention is described, description is abbreviate | omitted about the point which overlaps with said embodiment.

In the embodiment shown in FIG. 13, the foil member 20 does not have the second back foil part, and is constituted only by the top foil part 21 and the first back foil part 22. In the example of illustration, the 1st back foil part 22 is formed in the substantially sector shape which does not have a hole. For example, as shown in FIG. 14, the base foil 30 of this embodiment has holes 35 surrounded by a large-diameter annular portion 31, a small-diameter annular portion 32, and a radial direction portion 33 at a plurality of locations separated in the radial direction. .

14 is fixed to the end face 10a of the foil holder 10, and a plurality of foil members 20 are fixed thereon. At this time, the first back foil portion 22 of the foil member 20 adjacent to the upstream side is disposed behind the top foil portion 21 of each foil member 20. A hole 35 of the base foil 30 is disposed behind the upstream region S1 of the first back foil portion 22 of each foil member 20. A radial direction portion 33 of the base foil 30 is disposed behind the downstream region S2 of the first back foil portion 22 of each foil member 20.

When the shaft 2 rotates and the fluid pressure in the bearing gap C increases, the top foil part 21 and the first back foil part 22 are pushed downward (foil holder 10 side) as shown in FIG. At this time, the upstream region S1 of the first back foil portion 22 is fitted into the recess B1 of the base surface B (the hole 35 of the base foil 30), and the upstream region of the top foil portion 21 supported in this region is It is pushed into the base surface B side {see FIG. 16 (A)}. On the other hand, the downstream region S2 of the first back foil portion 22 is supported from behind by the radial portion 33 of the base foil 30 and therefore does not fit into the recess B1 of the base surface B. That is, the radial direction portion 33 of the base foil 30 functions as a restricting portion A that restricts the fitting of the downstream region S2 of the first back foil portion 22 into the recess B1. Thereby, the downstream region of the top foil portion 21 supported by the downstream region S2 of the first back foil portion 22 is arranged above the base surface B (the thrust collar 3 side) {FIG. 16B reference}. As described above, the top foil portion 21 is curved, and the bearing surface X becomes closer to the end surface 3a of the thrust collar 3 as it goes downstream, so that a wedge-shaped bearing gap C is formed (see FIG. 15).

In the above embodiment, the base surface B is formed by the end surface 10a of the foil holder 10 and the base foil 30, and the recess B1 is formed by the hole 35 of the base foil 30, but it is not limited thereto. For example, the base surface B may be formed only by the end surface 10a of the foil holder 10, and the recess B1 may be directly formed on the end surface 10a (not shown).

Moreover, in the above embodiment, although the top foil part 21, the 1st back foil part 22, and the 2nd back foil part 23 are integrally formed as the foil member 20, you may form these separately. . In this case, you may provide the top foil member which connected and integrated the several top foil part 21. FIG. Similarly, a first back foil member in which a plurality of first back foil portions 22 are connected and integrated, or a second back foil member in which a plurality of second back foil portions 23 are connected and integrated may be provided. .

In the above embodiment, the case where the present invention is applied to a thrust foil bearing has been described. However, the present invention may be applied to a radial foil bearing that supports a shaft in a radial direction. For example, the radial foil bearing 40 shown in FIG. 17 includes a cylindrical foil holder 41 and a plurality of foil members 42 attached to the inner peripheral surface 41a of the foil holder 41 side by side in the circumferential direction. Of each foil member 42, the downstream region functions as the top foil portion 42 a, and the upstream region functions as the first back foil portion 42 b (shown with a dotted pattern). The inner peripheral surface 41a of the foil holder 41 functions as a base surface B, and a plurality of recesses B1 are provided on the inner peripheral surface 41a.

When the fluid pressure in the bearing gap C between the bearing surface X of the top foil portion 42a and the outer peripheral surface of the shaft 2 is increased as the shaft 2 rotates, the upstream region of the first back foil portion 42b becomes a foil holder. The inner peripheral surface 41a (base surface B) 41 is fitted into the recess B1. On the other hand, the downstream region of the first back foil portion 42 b is supported from behind by the inner peripheral surface 41 a of the foil holder 41 and does not fit into the recess B 1 of the foil holder 41. That is, in the inner peripheral surface 41a of the foil holder 41, a region adjacent to the downstream side of the concave portion B1 functions as a regulating portion A that regulates the fitting of the first back foil portion 42b into the concave portion B1 in the downstream region. To do. Thereby, a step is formed in the first back foil portion 42b, the top foil portion 42a is curved following the first back foil portion 42b, and the bearing surface X becomes closer to the outer peripheral surface of the shaft 2 as it goes downstream. Thus, a wedge-shaped bearing gap C is formed.

In the above embodiment, the case where the foil bearing is fixed and the shaft 2 is rotated is shown. However, the present invention is not limited thereto, and the shaft 2 may be fixed and the foil bearing may be rotated. However, if the foil bearing is rotated, the foil may be damaged by centrifugal force. Therefore, it is preferable to fix the foil bearing as in the above embodiment.

In addition, the foil bearings described above can be used, for example, as bearings for main shafts of turbo machines such as gas turbines and turbochargers (superchargers), bearings for vehicles such as automobiles, or bearings for industrial equipment. It is.

Further, the foil bearing described above can be used not only as an air dynamic pressure bearing using air as a pressure generating fluid but also as an oil dynamic pressure bearing using lubricating oil as a pressure generating fluid.

DESCRIPTION OF SYMBOLS 1 Foil bearing 2 Shaft 3 Thrust collar 10 Foil holder 20 Foil member 21 Top foil part 22 First back foil part

22a Side part

22b Connection part 22c Hole (non-contact part)
23 Second back foil portion 24 Connection portion 30 Base foil 35 Hole A Restriction portion B Base surface B1 Recess C of the base surface C Bearing gap S1 Upstream region S2 of the first back foil portion Downstream region X of the first back foil portion Surface P Recess Q in top foil part Weir

Claims

A shaft and a bearing surface having a top foil portion having a bearing surface, a first back foil portion for supporting the top foil portion from the back, and a base surface for supporting the first back foil portion from the back, and the bearing surface In the foil bearing that supports the shaft in a non-contact manner with the fluid pressure generated in the bearing gap between
A recess is provided in the base surface,
A foil bearing having a restricting portion that allows the upstream region of the first back foil portion to be fitted into the concave portion of the base surface and restricts the fitting of the downstream region of the first back foil portion into the concave portion. .
The foil bearing according to claim 1, wherein a second back foil portion functioning as the restricting portion is disposed between the base surface and a downstream region of the first back foil portion.
The foil bearing according to claim 2, comprising a foil member integrally including the top foil portion, the first back foil portion, and the second back foil portion.
The foil according to any one of claims 1 to 3, wherein a non-contact portion that does not contact the top foil portion is provided in an intermediate portion of the first back foil portion in a direction orthogonal to the relative rotation direction of the shaft. bearing.
The first back foil portion has a pair of side portions separated in a direction orthogonal to the relative rotation direction of the shaft, and a connecting portion that connects downstream end portions of the pair of side portions, The foil bearing according to claim 4, wherein a hole as the non-contact portion is formed in a region surrounded by a side portion and the connecting portion.
The base surface is formed of a foil holder and a base foil attached to the foil holder;
The foil bearing according to any one of claims 1 to 5, wherein the recess is formed by a hole provided in the base foil.