阅读说明：本技术 径向箔轴承 (Radial foil bearing ) 是由 大森直陆 于 2020-02-07 设计创作，主要内容包括：本公开的径向箔轴承(3)具备：具有插通孔(12a)的轴承壳(12)、在插通孔的内侧配置的顶部箔(9)、以及在顶部箔与轴承壳之间夹设的箔构造体(10、11),箔构造体具有带折回突起部(10c),该带折回突起部朝向插通孔的径向的外侧弯曲并且朝向径向的内侧折返,带折回突起部与嵌合槽(15)嵌合,该嵌合槽(15)形成于插通孔延伸的轴向上的轴承壳的端面。(A radial foil bearing (3) is provided with: the bearing housing (12) having an insertion hole (12a), a top foil (9) disposed inside the insertion hole, and foil structures (10, 11) interposed between the top foil and the bearing housing, wherein the foil structure has a band-folded protrusion (10c) that is bent toward the outside in the radial direction of the insertion hole and folded back toward the inside in the radial direction, the band-folded protrusion is fitted into a fitting groove (15), and the fitting groove (15) is formed in the end face of the bearing housing in the axial direction in which the insertion hole extends.)

1. A radial foil bearing is characterized by comprising:

A bearing housing having an insertion hole;

a top foil disposed inside the insertion hole; and

a foil structure interposed between the top foil and the bearing housing,

the foil structure has a band folded-back projection portion that is bent outward in the radial direction of the insertion hole and folded back inward in the radial direction,

the belt folded-back projecting portion is fitted into a fitting groove formed in an end surface of the bearing housing in an axial direction in which the insertion hole extends.

2. Radial foil bearing according to claim 1,

the foil structure has the band-folded projections at the end edges on both sides in the axial direction.

3. Radial foil bearing according to claim 2,

the foil structure has a hole portion between the folded-back projecting portions formed at the end edges on both sides in the axial direction.

4. Radial foil bearing according to any one of claims 1 to 3,

the foil structure is formed of a plurality of foil pieces arranged in the circumferential direction of the insertion hole,

the foil pieces adjacent in the circumferential direction are each provided with the band folded-back projecting portion, and the band folded-back projecting portions adjacent in the circumferential direction are arranged in one of the fitting grooves in a state of being opposed to each other.

5. Radial foil bearing according to any one of claims 1 to 4,

the foil structure is provided with:

a back-up foil disposed along an inner circumferential surface of the insertion hole; and

an intermediate foil supported by the backing foil and contiguous with the top foil,

the intermediate foil has the folded-back projections,

a cutout through which the folded-back projection passes is formed in the back-up foil.

6. Radial foil bearing according to any one of claims 1 to 4,

the foil structure is provided with:

a back-up foil disposed along an inner circumferential surface of the insertion hole; and

an intermediate foil supported by the backing foil and contiguous with the top foil,

the backing foil having the folded-back projections,

a second folded-back projection portion is formed on the intermediate foil, and the second folded-back projection portion is fitted in a space inside the folded-back projection portion of the back support foil.

7. Radial foil bearing according to claim 5 or 6,

a hole portion is formed in the intermediate foil, and a projecting piece is provided that projects from an opening end of the hole portion in the circumferential direction toward a central portion of the hole portion in the circumferential direction toward the back-up foil side.

Technical Field

The present disclosure relates to a radial foil bearing.

The present application claims priority based on patent application No. 2019-.

Background

Conventionally, as a bearing for a high-speed rotating body, a radial bearing used by being externally inserted to a rotating shaft is known. As such a radial bearing, a radial foil bearing is known which includes: the bearing includes a thin plate-shaped top foil forming a bearing surface, a back-up foil elastically supporting the top foil, and a cylindrical bearing housing accommodating the top foil and the back-up foil. As a back-up foil of a radial foil bearing, a corrugated foil formed by forming a thin plate into a corrugated plate shape is mainly used.

In the radial foil bearing described in patent document 1, in order to suppress the back-up foil from coming off the bearing housing, engaging notches extending from the inner peripheral edge toward the outer peripheral edge of the bearing housing are formed in both side surfaces of the bearing housing, and engaging protruding pieces that engage with the engaging notches are provided in both side end portions of the back-up foil on one side in the circumferential direction of the bearing housing.

Documents of the prior art

Patent document

Patent document 1 Japanese laid-open patent publication No. 2013-87789

Disclosure of Invention

Problems to be solved by the invention

In such a radial foil bearing, energy can be dissipated by friction of the foil (friction between foils, friction between the foil and the bearing housing) or the like, so that variation in film thickness of the fluid lubricating film is attenuated, shaft vibration (self-excited vibration) of the rotating shaft can be suppressed, and the shaft vibration can be easily reduced.

The present disclosure aims to improve the above-described damping effect by friction of the foil.

Means for solving the problems

A radial foil bearing according to an aspect of the present disclosure includes: a bearing housing having an insertion hole; a top foil disposed inside the insertion hole; and a foil structure interposed between the top foil and the bearing shell, the foil structure having a folded-back projection bent outward in a radial direction of the insertion hole and folded back inward in the radial direction, the folded-back projection being fitted into a fitting groove formed in an end surface of the bearing shell in an axial direction in which the insertion hole extends.

In the radial foil bearing according to the above-described aspect, the foil structure may have the folded-back projecting portions at the end edges on both sides in the axial direction.

In the radial foil bearing according to the above-described aspect, the foil structure may have a hole portion between the folded-back projecting portions formed at the end edges on both sides in the axial direction.

In the radial foil bearing according to the above-described aspect, the foil structure may be formed by a plurality of foil pieces arranged in the circumferential direction of the insertion hole, the tape folded-back protrusions may be provided on the respective foil pieces adjacent in the circumferential direction, and the tape folded-back protrusions adjacent in the circumferential direction may be arranged in one of the fitting grooves so as to face each other.

In the radial foil bearing according to the above aspect, the foil structure may include: a back-up foil disposed along an inner circumferential surface of the insertion hole; and an intermediate foil supported by the back-up foil and in contact with the top foil, the intermediate foil having the folded-back projection, the back-up foil having a notch formed therein through which the folded-back projection passes.

In the radial foil bearing according to the above aspect, the foil structure may include: a back-up foil disposed along an inner circumferential surface of the insertion hole; and an intermediate foil supported by the back-up foil and in contact with the top foil, the back-up foil having the band-folded-back projection, the intermediate foil having a second band-folded-back projection formed therein, the second band-folded-back projection being fitted in a space inside the band-folded-back projection of the back-up foil.

In the radial foil bearing according to the above-described aspect, a hole may be formed in the intermediate foil, and a protruding piece may be provided so as to protrude toward the back foil side from an opening end of the hole in the circumferential direction toward a central portion of the hole in the circumferential direction.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present disclosure, the attenuation effect achieved by friction of the foil can be improved.

Drawings

Fig. 1 is a side view showing an example of a turbocharger machine to which the radial foil bearing of the present disclosure is applied.

Fig. 2 is a front view showing a radial foil bearing according to a first embodiment of the present disclosure.

Fig. 3A is an expanded top view of the top foil of the first embodiment of the present disclosure.

Fig. 3B is an expanded front view of the top foil of the first embodiment of the present disclosure.

Fig. 4 is an enlarged perspective view of a main portion of a radial foil bearing according to a first embodiment of the present disclosure.

Fig. 5 is an expanded top view of an intermediate foil according to a first embodiment of the present disclosure.

Fig. 6 is a front view in which a main portion of the radial foil bearing of the first embodiment of the present disclosure is flattened and viewed from the axial direction.

Fig. 7 is a plan view of a main portion of the radial foil bearing according to the first embodiment of the present disclosure, as viewed from the radial direction, being flattened.

Fig. 8 is a plan view of a radial foil bearing according to a modification of the first embodiment of the present disclosure, as seen from the radial direction, with a main portion thereof flattened.

Fig. 9 is a front view of a radial foil bearing according to a modification of the first embodiment of the present disclosure, as seen from the axial direction, with a main portion thereof flattened.

Fig. 10 is a plan view of a radial foil bearing according to a modification of the first embodiment of the present disclosure, as seen from the radial direction, with a main portion thereof flattened.

Fig. 11 is a front view of a radial foil bearing according to a modification of the first embodiment of the present disclosure, as seen from the axial direction, with a main portion thereof flattened.

Fig. 12 is a front view showing a radial foil bearing according to a second embodiment of the present disclosure.

Fig. 13 is an enlarged perspective view of a main portion of a radial foil bearing according to a second embodiment of the present disclosure.

Fig. 14 is a front view in which a main portion of a radial foil bearing according to a second embodiment of the present disclosure is flattened and viewed from the axial direction.

Fig. 15 is a plan view of a main portion of a radial foil bearing according to a second embodiment of the present disclosure, as viewed from the radial direction, being flattened.

Fig. 16 is a plan view of a radial foil bearing according to a modification of the second embodiment of the present disclosure, as seen from the radial direction, with a main portion thereof flattened.

Fig. 17 is a front view of a radial foil bearing according to a modification of the second embodiment of the present disclosure, as seen from the axial direction, with a main portion thereof flattened.

Fig. 18 is a plan view of a radial foil bearing according to a modification of the second embodiment of the present disclosure, as seen from the radial direction, with a main portion thereof flattened.

Fig. 19 is a front view of a radial foil bearing according to a modification of the second embodiment of the present disclosure, as seen from the axial direction, with a main portion thereof flattened.

Fig. 20 is a plan view of a main portion of a radial foil bearing according to a third embodiment of the present disclosure, as viewed from the radial direction, being flattened.

Fig. 21 is a sectional view in an arrow a-a direction of a main portion shown in fig. 20.

Fig. 22 is a plan view of a radial foil bearing according to a modification of the third embodiment of the present disclosure, as seen from the radial direction, with a main portion thereof flattened.

Fig. 23 is a sectional view in an arrow B-B direction of a main portion shown in fig. 22.

Fig. 24 is a plan view of a main portion of a radial foil bearing according to a fourth embodiment of the present disclosure, as viewed from the radial direction, being flattened.

Fig. 25A is a front view of a bearing housing of a fourth embodiment of the present disclosure.

Fig. 25B is an arrow C-C sectional view of a bearing shell according to a fourth embodiment of the present disclosure.

Detailed Description

The radial foil bearing of the present disclosure is described in detail below with reference to the accompanying drawings.

Fig. 1 is a side view showing an example of a turbocharger machine to which the radial foil bearing of the present disclosure is applied.

In fig. 1, reference numeral 1 denotes a rotary shaft (main shaft), reference numeral 2 denotes an impeller provided at a tip on one axial side of the rotary shaft, and reference numeral 3 denotes a radial foil bearing of the present disclosure. Further, although only one radial foil bearing is omitted in fig. 1, two radial foil bearings are generally provided in the axial direction of the rotating shaft 1. Thus, also in the present disclosure two radial foil bearings 3 are provided.

A radial foil bearing 3 is inserted onto the rotating shaft 1. That is, the rotary shaft 1 is inserted through the radial foil bearing 3. A thrust collar 4 is provided between the impeller 2 of the rotary shaft 1 and the radial foil bearing 3. Thrust bearings 5 are disposed on both sides of the thrust ring 4 in the axial direction. That is, the rotary shaft 1 is inserted through the thrust bearing 5. The impeller 2 is disposed in a casing 6 as a stationary side, and a tip clearance 7 is provided between the impeller 2 and the casing 6.

(first embodiment)

Fig. 2 is a front view showing a radial foil bearing 3 according to a first embodiment of the present disclosure.

The radial foil bearing 3 is inserted around the rotating shaft 1 and supports the rotating shaft 1. The radial foil bearing 3 includes: top foil 9, intermediate foil 10 (foil structure), back-up foil 11 (foil structure), and bearing shell 12. The bearing housing 12 has an insertion hole 12a through which the rotary shaft 1 is inserted.

In the following description, the positional relationship of the respective members may be described with reference to the insertion hole 12 a. Specifically, "axial" means: the insertion hole 12a extends in a direction (a direction in which the rotary shaft 1 is inserted). In addition, "radial" means: the insertion hole 12a is radial. In addition, "circumferential" means: along the circumferential direction of the inner circumferential surface of the insertion hole 12 a.

The bearing housing 12 is a cylindrical member constituting the outermost portion of the radial foil bearing 3 in the radial direction. The bearing housing 12 is formed with an insertion hole 12 a. In the insertion hole 12a are accommodated: a backing foil 11, an intermediate foil 10, a top foil 9. Specifically, the back foil 11 is supported by the inner peripheral surface of the insertion hole 12a, the intermediate foil 10 is supported by the back foil 11, and the top foil 9 is supported by the intermediate foil 10. That is, the intermediate foil 10 and the back-up foil 11 are foil structures interposed between the top foil 9 and the bearing housing 12. The bearing housing 12 of the present disclosure is a cylindrical member having an insertion hole 12 a. However, as long as the insertion hole 12a is provided, the bearing housing 12 may be a member having a shape other than a cylindrical shape (for example, a prismatic shape).

Fig. 3A is an expanded top view of the top foil 9 of the first embodiment of the present disclosure, and fig. 3B is an expanded front view of the top foil 9.

As shown in fig. 3A, the top foil 9 is a rectangular metal foil having a long side in the circumferential direction and a short side in the axial direction. As shown in fig. 2, the top foil 9 is wound in a cylindrical shape and disposed so as to face the circumferential surface of the rotating shaft 1.

As shown in fig. 3A, a first uneven portion 23A is formed on one short side (end portion; first end) in the longitudinal direction of the top foil 9, and the first uneven portion 23A is configured to have: one convex portion 21a protruding to one side in the longitudinal direction, and two concave portions 22a formed on both sides in the short-side direction of the convex portion 21 a. That is, one short side in the longitudinal direction of the top foil 9 includes: one convex portion 21a protruding to one side in the longitudinal direction, and a step extending and connecting to both sides in the short-side direction of the convex portion 21 a.

Further, the top foil 9 has a second uneven portion 23b formed on the other short side (the short side (end portion; second end) on the other side in the longitudinal direction) opposite to the one short side, and the second uneven portion 23b includes: two convex portions 21b distant in the short-side direction, and one concave portion 22b located between the two convex portions 21 b. Alternatively, the top foil 9 includes, on the other short side in the longitudinal direction: a recess 22b recessed toward one side in the longitudinal direction, and steps located on both sides of the recess 22b in the short-side direction.

The concave portion 22b of the second concave-convex portion 23b is formed corresponding to the convex portion 21a of the first concave-convex portion 23 a. The concave portion 22a of the first concave-convex portion 23a is formed to correspond to the convex portion 21b of the second concave-convex portion 23 b. That is, the minimum distance in the lateral direction of the concave portion 22b is larger than the maximum width in the lateral direction of the convex portion 21 a. In the present disclosure, the interval in the longitudinal direction of the concave portion 22b and the length in the longitudinal direction of the convex portion 21a are constant.

The concave portion 22b of the second concave-convex portion 23b is formed such that the convex portion 21a passes through the concave portion 22b when the top foil 9 is rolled into a cylindrical shape so that the first concave-convex portion 23a overlaps with the second concave-convex portion 23 b. Similarly, the concave portions 22a of the first concave-convex portion 23a are formed such that the convex portions 21b pass through the concave portions 22a when the top foil 9 is rolled into a cylindrical shape. That is, a portion (convex portion 21a) of the top foil 9 extending from the first end (one short side) to one side in the circumferential direction and a portion (convex portion 21b) extending from the second end (the other short side) to the other side in the circumferential direction intersect in the axial direction.

As shown in fig. 2, the convex portions 21a and 21b (both ends of the top foil 9) passing through the concave portions 22b and 22a are drawn out toward the bearing housing 12, respectively. That is, if the top foil 9 disposed on the inner peripheral side of the insertion hole 12a is viewed from the axial direction, the convex portion 21a and the convex portion 21b intersect. In addition, the convex portion 21a of the top foil 9 is located between the two convex portions 21b in the axial direction. A through groove 13 into which the protruding portions 21a, 21b are inserted is formed in the inner peripheral surface of the insertion hole 12a of the bearing housing 12. The through groove 13 is formed from one end surface 12b to the other end surface 12b in the axial direction of the bearing housing 12.

As shown in fig. 3B, thin portions 24 that are thinner (thin) than the central portion therebetween are formed on the side (one short side) of the top foil 9 on which the first concave-convex portions 23a are formed and the side (the other short side) on which the second concave-convex portions 23B are formed. As shown in fig. 2, the outer peripheral surface (the surface on the bearing housing 12 side) of the thin portion 24 is recessed from the outer peripheral surface of the central portion and is thin.

As shown in fig. 2, the circumferential length L of the thin portion 24 is a length corresponding to the distance from the through groove 13 to the peak portion 11c at one end of the back-up foil 11. In the present disclosure, the top foil 9 disposed on the bearing housing 12 has a step on the outer circumferential surface side and is thin via the step. The thin portions 24 extend from both ends of the top foil 9 in the circumferential direction to positions in the circumferential direction beyond the nearest ridge portions 11 c.

The back-up foil 11 is arranged between the bearing shell 12 and the intermediate foil 10. The back support foil 11 is a foil (thin plate) that elastically supports the intermediate foil 10 and the top foil 9. Examples of the back-support foil 11 include bump foils, spring foils described in japanese patent laid-open nos. 2006-57652 and 2004-270904, and back-support foils described in japanese patent laid-open nos. 2009-299748. In the present embodiment, a bump foil is used as the back-up foil 11.

The backing foil 11 of the present disclosure is composed of three (a plurality of) backing foil pieces 11a arranged along the inner peripheral surface of the insertion hole 12 a. The back support foil piece 11a is a foil (thin plate) having a corrugated shape in the circumferential direction. The three back support foil pieces 11a are bent into a substantially cylindrical shape as a whole when viewed from the axial direction. The back support foil piece 11a is disposed along the inner circumferential surface of the insertion hole 12 a. In the present disclosure, the three back support foil pieces 11a are all formed in the same shape and size. Therefore, the back-support foil piece 11a is disposed so as to substantially divide the inner peripheral surface of the insertion hole 12a into three parts along the circumferential direction.

The back support foil pieces 11a are formed with: a peak portion 11c projecting radially inward, and a valley portion 11b projecting radially outward from the peak portion 11 c. That is, the backing foil piece 11a (backing foil 11) has irregularities in the radial direction of the insertion hole 12 a. A flat portion of the valley portion 11b facing the insertion hole 12a can abut against the bearing housing 12. The ridge 11c can abut against the intermediate foil 10 (intermediate foil piece 10 a). In this way, the back support foil piece 11a elastically supports the top foil 9 via the intermediate foil piece 10a by the ridge portion 11 c. Further, both ends in the circumferential direction of the back support foil piece 11a are valleys 11 b.

The intermediate foil 10 is arranged between the top foil 9 and the backing foil 11. In the present disclosure, the intermediate foil 10 is composed of three intermediate foil pieces 10a arranged along the inner peripheral surface of the insertion hole 12 a. The three intermediate foil pieces 10a have a substantially rectangular developed shape, and are bent as a whole into a substantially cylindrical shape as shown in fig. 2 when viewed from the axial direction. In the present disclosure, all of the three intermediate foils 10a are formed in the same shape and size. Therefore, the intermediate foil piece 10a is disposed so as to substantially divide the inner peripheral surface of the insertion hole 12a into three parts along the circumferential direction.

The thickness of the intermediate foil 10a is thinner than that of the back foil 11 a. The outer shape of the intermediate foil 10a has a size substantially equal to that of the back foil 11 a. The intermediate foil 10a has: a flat portion 10b contacting the top of the peak portion 11c of the back support foil 11, and a folded-back projecting portion 10c recessed (projecting) radially outward from the flat portion 10 b. That is, the tape folding back projection 10c is distant from the top foil 9. The band folding back protrusion 10c is formed at a circumferential position between both ends of the circumferential direction of the intermediate foil piece 10a (a central position of the intermediate foil piece 10a in the circumferential direction in the present disclosure).

As shown in fig. 2, a pair of fitting grooves 15 extending radially outward from the inner peripheral edge of the insertion hole 12a are formed in the end surfaces 12b on both sides of the bearing housing 12 in the axial direction. In the present disclosure, the pair of fitting grooves 15 are formed at positions that substantially divide the end surface 12b of the bearing housing 12 into three portions along the circumferential direction thereof. The folded-back projecting portion 10c of the intermediate foil piece 10a is fitted in the fitting groove 15. In the figure, a gap is provided between the fitting groove 15 and the belt folding projection 10 c. However, the gap is provided for clearly distinguishing the respective members, and the respective members abut each other in an actual device (the same applies to the following drawings).

In the present disclosure, the through groove 13 is disposed between two of the three fitting grooves 15. One fitting groove 15 is circumferentially opposed to the through groove 13. The fitting groove 15 can be formed by appropriately selecting cutting using an end mill or the like. The fitting groove 15 may not be formed so as to pass through from the inner peripheral edge to the outer peripheral edge of the bearing housing 12.

Fig. 4 is an enlarged perspective view of a main portion of the radial foil bearing 3 of the first embodiment of the present disclosure. Fig. 5 is an expanded top view of the middle foil 10a of the first embodiment of the present disclosure. Fig. 6 is a front view in which a main portion of the radial foil bearing 3 of the first embodiment of the present disclosure is flattened and viewed from the axial direction. Fig. 7 is a plan view in which a main portion of the radial foil bearing 3 of the first embodiment of the present disclosure is flattened and viewed from the radial direction. Further, the intermediate foil 10a on the back foil 11a is not shown on the upper side of the paper of fig. 7 in order to improve the visibility.

As shown in the drawing, notches 16 are formed in both axial edges (both side peripheral edges) of the back foil piece 11 a. The notch 16 is provided at a circumferential position between both ends of the back support foil piece 11a in the circumferential direction (a central portion in the back support foil piece 11a in the direction along the circumferential direction of the bearing shell 12). That is, there is a recess in the axial direction at a circumferential position between both ends of the edge portion of the back support foil piece 11a in the circumferential direction.

As shown in fig. 4 and 7, the slits 16 are formed in the valleys 11b of the back support foil piece 11 a. The notch 16 of the present disclosure is formed such that a region including the trough portion 11b and the root portions of the peak portions 11c and 11c adjacent to each other with the trough portion 11b interposed therebetween (i.e., the portions of the peak portions 11c adjacent to the trough portion 11 b) is notched toward the center portion in the axial direction of the bearing housing 12. That is, the notches 16 are formed across circumferential positions including the trough portions 11 b. The notch 16 is formed in the back-up foil piece 11a at a position corresponding to the fitting groove 15 of the bearing housing 12, that is, at a position overlapping the fitting groove 15. The width of the notch 16 is equal to the width of the fitting groove 15.

As shown in fig. 5, the intermediate foil piece 10a has folded-back projections 10c formed on both axial edges (both side peripheral edges). The band-folded back protrusion 10c is provided at a circumferential position between both ends of the circumferential direction of the intermediate foil piece 10a (a central portion in the intermediate foil piece 10a in the direction along the circumferential direction of the bearing shell 12). That is, the intermediate foil piece 10a has two folded-back projecting portions 10c at positions axially opposed to each other. Alternatively, the intermediate foil piece 10a may have folded-back projecting portions 10c at the end edges on both sides in the axial direction. The intermediate foil piece 10a has a hole 10d between two folded-back projecting portions 10c formed at the end edges on both sides in the axial direction. The hole 10d has a circumferential width greater than or equal to the circumferential width of the folded-back projection 10c and extends in the axial direction. The axial width of the hole 10d is larger than the axial width of the folded-back projection 10 c. That is, the intermediate foil piece 10a has hole portions 10d (slits) extending in the axial direction at circumferential positions between both ends in the circumferential direction. That is, the two flat portions 10b of the intermediate foil piece 10a are divided by the hole portions 10d (slits), and are connected by the two folded-back projecting portions 10c at the both side peripheral edge portions of the intermediate foil piece 10 a.

As shown in fig. 6 and 7, the folded-back projecting portion 10c passes through the notch 16 of the back support foil piece 11a in the radial direction and is fitted into the fitting groove 15 of the bearing housing 12. That is, the folded-back projecting portion 10c is formed at a position corresponding to the notch 16 of the back support foil piece 11a and the fitting groove 15 of the bearing housing 12, that is, at a position overlapping the notch 16 and the fitting groove 15. As shown in fig. 6, the folded-back projecting portion 10c is bent from one planar portion 10b toward the radially outer side of the insertion hole 12a and folded back toward the other planar portion 10b toward the radially inner side, of the two planar portions 10b divided by the hole portion 10 d. Specifically, the belt folding projection 10c is formed in a substantially U shape having: an extended portion (first bent portion) 10c1 extending from the one planar portion 10b toward the radially outer side; a return portion (second inflection portion) 10c3 extending radially inward toward the other planar portion 10 b; and a connecting portion 10c2 connecting the extending portion 10c1 with the return portion 10c 3.

That is, the extending portion (first flexed portion) 10c1 extends radially outward from one planar portion 10b, the returning portion (second flexed portion) 10c3 extends radially outward from the other planar portion 10b, and the connecting portion 10c2 connects radially outer end portions of the extending portion (first flexed portion) 10c1 and the returning portion (second flexed portion) 10c3 to each other.

The extending portion 10c1, the connecting portion 10c2, and the returning portion 10c3 may be provided continuously in the circumferential direction in order from the planar portion 10 b. Although the present disclosure provides the connecting portion 10c2, the extending portion 10c1 and the returning portion 10c3 may be connected to each other in a substantially V shape, for example, without the connecting portion 10c 2.

In the present disclosure, the extended portion 10c1 is bent substantially 90 ° toward the radial outside with respect to the planar portion 10 b. In addition, the connecting portion 10c2 is bent substantially 90 ° toward the radially inner side with respect to the extending portion 10c 1. The return portion 10c3 is bent substantially 90 ° radially inward with respect to the connecting portion 10c2, and is connected to the other flat surface portion 10 b. The folded-back projection 10c is in contact with the fitting groove 15 in an accumulated state. The folded-back projecting portion 10c of the present disclosure is formed by bending a single plate spring (elastic member) substantially in a U-shape. The belt folding projection 10c is fitted into the fitting groove 15 in a slightly contracted state in the circumferential direction. Thus, the band folding back projection 10c is acted with a spring back that opens the extended portion 10c1 and the return portion 10c3 in the circumferential direction. Thereby, a frictional force is generated between the tape folded-back protrusion 10c and the fitting groove 15, and the intermediate foil piece 10a is held by the bearing housing 12.

Next, the operation of the radial foil bearing 3 configured as described above will be described.

In a state where the rotary shaft 1 is stopped, the top foil 9 is biased toward the rotary shaft 1 side by the back support foils 11 (three back support foil pieces 11a) via the intermediate foils 10 (three intermediate foil pieces 10a) and is brought into close contact with the rotary shaft 1. In the present embodiment, since both end portions of the top foil 9 are the thin portions 24, the force (local preload) for fastening the rotary shaft 1 by the thin portions 24 is reduced as compared with the case where the thin portions 24 are not provided.

When the rotary shaft 1 is started in the direction of arrow P in fig. 2, the rotation is started at a low speed first, and then gradually accelerated to rotate at a high speed. Then, as shown by an arrow Q in fig. 2, the surrounding fluid is introduced from one end side of each of the top foil 9, the intermediate foil 10, and the back-up foil 11, and flows between the top foil 9 and the rotating shaft 1. Thereby, a fluid lubrication film is formed between the top foil 9 and the rotary shaft 1.

The film pressure of the fluid lubricant film acts on the top foil 9, and presses the respective ridge portions 11c of the back foil piece 11a via the intermediate foil 10 in contact with the top foil 9. Then, the back foil piece 11a is pressed by the intermediate foil 10, so that the mountain portion 11c thereof is pressed and spread, thereby moving the back foil piece 11a on the bearing housing 12 in the circumferential direction thereof. That is, the back support foil pieces 11a (back support foils 11) elastically support the top foil 9 via the intermediate foil 10, and therefore deform in the circumferential direction when a load is received from the top foil 9, and the top foil 9 and the intermediate foil 10 are supported while allowing the deflection thereof.

As shown in fig. 6, the folded-back projecting portion 10c of the intermediate foil piece 10a is inserted into the notch 16 formed at the axial end edge of the back foil piece 11 a. The belt folded-back protrusion 10c is fitted in a fitting groove 15 formed in the end surface 12b of the bearing housing 12, and the belt folded-back protrusion 10c is inserted into the notch 16, thereby suppressing rotation of the back-up foil piece 11a in the circumferential direction. Therefore, the respective ridge portions 11c of the back support foil piece 11a are deformed (moved) in the circumferential direction with the notches 16 through which the folded-back projecting portions 10c are inserted.

Two belt folding projections 10c are provided at axially opposite positions. The tape folded-back projection 10c is axially opposed to the bearing housing 12 and also axially opposed to the back support foil piece 11 a. That is, the band-folded back protrusions 10c suppress the movement in the axial direction of the intermediate foil 10a relative to the bearing shell 12, and also suppress the movement in the axial direction of the back support foil 11 a. Therefore, the intermediate foil piece 10a and the back foil piece 11a can be suppressed from falling off from the bearing housing 12.

As shown in fig. 5 and 7, the intermediate foil 10a has a hole 10d between the two folded-back projecting portions 10 c. If the hole 10d is not formed, the region of the intermediate foil piece 10a that is axially inward of the two folded-back projections 10c may protrude radially outward by bending similarly to the folded-back projections 10c, and this region may interfere with the back foil piece 11 a. Therefore, the hole 10d is provided between the two folded-back projecting portions 10c, and interference between the intermediate foil piece 10a and the back foil piece 11a can be avoided.

When a load is transmitted from the top foil 9 to the back foil piece 11a, the intermediate foil piece 10a is flexed together with the top foil 9 and the back foil piece 11 a. At this time, "sliding" occurs between the intermediate foil 10a and the top foil 9, the back-up foil 11a, and the bearing housing 12. That is, when pressure fluctuation occurs in the fluid lubrication film due to shaft vibration of the rotating shaft 1, the pressure fluctuation is transmitted to the top foil 9, and the "slip" occurs. This "slip" causes energy dissipation due to friction, and attenuates the film pressure fluctuation, so that the shaft vibration of the rotating shaft 1 can be suppressed.

A fluctuating load (repeated application of load and release of load) caused by shaft vibration of the rotary shaft 1 acts on the back-up foil pieces 11a, and for example, when the load is on the load release side, the back-up foil pieces 11a slightly float from the inner peripheral surface of the insertion hole 12a of the bearing housing 12. At this time, the intermediate foil 10a is lifted together with the back foil 11 a. Here, the folded-back projecting portion 10c of the intermediate foil piece 10a abuts on the fitting groove 15 of the bearing housing 12. Therefore, "sliding" occurs between the belt-folding projection 10c and the fitting groove 15, which causes energy dissipation due to friction and promotes attenuation. Further, the same is true when the load is on the load application side.

As described above, the radial foil bearing 3 includes: the intermediate foil 10 has a folded-back projecting portion 10c, the folded-back projecting portion 10c is bent toward the radial outside of the insertion hole 12a and folded back toward the radial inside, and the folded-back projecting portion 10c is fitted into a fitting groove 15 formed in an end surface 12b of the bearing housing 12 in the axial direction extending through the insertion hole 12 a. With this configuration, the attenuation effect by the friction of the foil can be improved.

The radial foil bearing 3 of the first embodiment may also adopt the structure shown in fig. 8 and 9.

Fig. 8 is a plan view of a radial foil bearing 3 according to a modification of the first embodiment of the present disclosure, as seen from the radial direction, with a main portion thereof flattened. Further, the intermediate foil 10a on the back foil 11a is not shown on the upper side of the paper of fig. 8 in order to improve the visibility. Fig. 9 is a front view of a radial foil bearing 3 according to a modification of the first embodiment of the present disclosure, as seen from the axial direction, with a main portion thereof flattened.

In the back-support foil piece 11a of the radial foil bearing 3 shown in fig. 8, the ridge portions 11c and 11c adjacent to each other across the notch 16 are separated into a first ridge portion 11c1 and a second ridge portion 11c2 by a slit 11d extending in the circumferential direction. Therefore, the first and second mountain portions 11c1 and 11c2 that axially face each other with the slit 11d therebetween can be independently deformed. The slits 11d shown in fig. 8 are formed to valley portions 11b adjacent to the first peak portions 11c 1.

The slits 11d extend from the end of the notch 16 toward the center of the back foil piece 11a in the axial direction to both sides in the circumferential direction. That is, a T-shaped recess is present in the axial direction at a circumferential position between both circumferential ends of the edge portion of the back-support foil piece 11a in the circumferential direction. The first peak 11c1 is axially inward of the slit 11d, and the second peak 11c2 is axially outward of the slit 11 d. The first mountain portion 11c1 is formed with the same pitch width p1 as the other mountain portions 11 c. On the other hand, the second mountain portions 11c2 are formed with a pitch width p2 smaller than the first mountain portions 11c 1. Thus, the circumferential end of the second peak portion 11c2 on the side of the notch 16 is the valley portion 11b and abuts against the insertion hole 12a of the bearing housing 12. As described above, the notch 16 of the present modification is not formed by cutting the root portions of the ridge portions 11c and 11c adjacent to each other with the notch 16 interposed therebetween as in the embodiment shown in fig. 7.

As in the intermediate foil piece 10a of the radial foil bearing 3 shown in fig. 8, a groove portion 10e may be formed in the flat portion 10b so as to protrude radially outward toward the back foil piece 11 a. The groove portion 10e is formed in a substantially V shape as viewed from the axial direction as shown in fig. 9.

The groove 10e is disposed at a circumferential position between the top of any one of the ridge portions 11c of the back foil piece 11a in the wave plate shape and the top of the ridge portion 11c adjacent to the ridge portion 11 c. Further, the second flat surface portion 10b1 divided in the circumferential direction by the groove portion 10e is formed in the flat surface portion 10 b.

Further, the intermediate foil piece 10a may have a projecting piece 10f projecting from the circumferential opening end of the hole portion 10d toward the circumferential central portion of the hole portion 10d toward the back foil piece 11a side (radially outer side). The protruding piece 10f and the groove portion 10e are arranged with one ridge portion 11c interposed therebetween in the circumferential direction. The protruding pieces 10f and the groove portions 10e are formed obliquely so as to contact portions other than the top portions of the ridge portions 11c (side surfaces of the ridge portions 11 c). That is, the side surface of the ridge portion 11c is a curved surface, and the contact surface between the protruding piece 10f and the groove portion 10e, which are in contact with the side surface of the ridge portion 11c, is an inclined surface (flat surface). That is, the side surface of the ridge portion 11c is separated from the other portions by contacting the protruding piece 10f and the groove portion 10e at one point. This makes it easy for energy dissipation to occur due to friction at the contact points between the side surfaces of the ridge portions 11c and the protruding pieces 10f and the groove portions 10 e.

According to the above configuration, in the intermediate foil piece 10a, in addition to the first contact point which comes into contact with the top of the peak portion 11c of the back foil piece 11a being formed on the flat portion 10b and the second flat portion 10b1, the second contact point which comes into contact with a portion other than the top of the peak portion 11c of the back foil piece 11a is formed on the projecting piece 10f and the groove portion 10 e. Therefore, the contact area between the intermediate foil piece 10a and the back foil piece 11a is increased, the damping effect by friction between the intermediate foil piece 10a and the back foil piece 11a is improved, and the stability when supporting the rotating shaft 1 rotating at a high speed can be further improved.

Further, the radial foil bearing 3 according to the first embodiment may also have a structure as shown in fig. 10 and 11.

Fig. 10 is a plan view of a radial foil bearing 3 according to a modification of the first embodiment of the present disclosure, as seen from the radial direction, with a main portion thereof flattened. Further, the intermediate foil 10a on the back foil 11a is not shown on the upper side of the paper of fig. 10 in order to improve the visibility. Fig. 11 is a front view of a radial foil bearing 3 according to a modification of the first embodiment of the present disclosure, as seen from the axial direction, with a main portion thereof flattened.

The intermediate foil piece 10a of the radial foil bearing 3 shown in fig. 10 and 11 is structured such that the intermediate foil piece 10a shown in fig. 8 and 9 is divided into two pieces at the center portion in the circumferential direction. The divided intermediate foil pieces 10a adjacent in the circumferential direction are each provided with a folded-back projection 10c, and the folded-back projections 10c adjacent in the circumferential direction are arranged so as to face each other in one fitting groove 15 (see fig. 11).

Specifically, each of the folded-back projecting portions 10c of the intermediate foil pieces 10a adjacent in the circumferential direction includes: extension 10c1, connecting portion 10c2, return portion 10c 3. In the present modification, the returning portion 10c3 does not connect to the flat portion 10b, and constitutes an end portion in the circumferential direction of the intermediate foil piece 10 a. The return portions 10c3 of the intermediate foil pieces 10a adjacent in the circumferential direction abut in the circumferential direction. That is, the intermediate foil piece 10a shown in fig. 10 and 11 is composed of two separate portions arranged in the circumferential direction with the fitting groove 15 interposed therebetween. In addition, the two separated portions each have a flat portion 10b and a folded-back projecting portion 10c extending from the flat portion 10 b. The folded-back projecting portions 10c at the two separated locations are inserted into the fitting grooves 15. In the fitting groove 15, the belt folding projections 10c press against each other. According to the above configuration, the contact portion (the return portion 10c3) with the folded-back protrusion 10c of each of the intermediate foil pieces 10a adjacent in the circumferential direction "slides". Therefore, the damping effect by friction is improved, and the stability when supporting the rotating shaft 1 that rotates at a high speed can be further improved.

(second embodiment)

Next, a second embodiment of the present invention will be explained. In the following description, the same or equivalent structures as those of the above-described embodiments are denoted by the same reference numerals, and the description thereof is simplified or omitted.

Fig. 12 is a front view showing a radial foil bearing 3 according to a second embodiment of the present disclosure. Fig. 13 is an enlarged perspective view of a main portion of a radial foil bearing 3 according to a second embodiment of the present disclosure. Fig. 14 is a front view in which a main portion of the radial foil bearing 3 of the second embodiment of the present disclosure is flattened and viewed from the axial direction. Fig. 15 is a plan view of a main portion of the radial foil bearing 3 according to the second embodiment of the present disclosure, which is flattened and viewed from the radial direction. Further, the intermediate foil 10a on the back foil 11a is not shown on the upper side of the paper of fig. 15 in order to improve the visibility.

As shown in these figures, the radial foil bearing 3 of the second embodiment is different from the first embodiment in that the back support foil piece 11a is also formed with the folded-back projecting portion 11 g.

The folded-back projecting portions 11g of the back support foil piece 11a are recessed (projected) radially outward from the trough portions 11 b. The band folded-back projecting portion 11g is formed at a circumferential position between both ends in the circumferential direction of the back support foil piece 11a (in the present disclosure, a central position of the back support foil piece 11a in the circumferential direction). The folded-back projecting portion 11g of the back support foil piece 11a is fitted in the fitting groove 15 of the bearing housing 12. In the figure, a gap is provided between the fitting groove 15 and the belt folding projection 11 g. However, the gap is provided for clearly distinguishing the respective members, and the respective members are in contact with each other in an actual apparatus.

The back support foil piece 11a has two folded-back projecting portions 11g at axially opposite positions. The back support foil piece 11a has a hole 11h between the two folded-back projecting portions 11g (see fig. 13 and 15). The hole portion 11h has a circumferential width equal to or greater than the circumferential width of the folded-back projecting portion 11g and extends in the axial direction. That is, a hole portion 11h (slit) extending in the axial direction is provided at a circumferential position between both ends of the back support foil piece 11a in the circumferential direction. That is, the back stay foil pieces 11a are divided by the hole portions 11h (slits), and the divided two back stay foil pieces 11a are connected at both side peripheral edge portions by the two folded-back projecting portions 11 g. In the two pieces of the back stay foil piece 11a divided by the hole 11h, the end on the hole 11h side (i.e., the end adjacent to the hole 11 h) is a valley portion 11 b.

As shown in fig. 14, the belt folded-back projecting portion 11g is fitted into the fitting groove 15 of the bearing housing 12. That is, the belt folded-back projecting portion 11g is formed at a position corresponding to the fitting groove 15 of the bearing housing 12, that is, at a position overlapping with the fitting groove 15. As shown in fig. 13, the folded-back projecting portion 11g is bent radially outward from one of the trough portions 11b, and is folded back radially inward toward the other trough portion 11b, of the two trough portions 11b adjacent to each other across the hole portion 11 h. Specifically, the belt folding projection 11g is formed in a substantially U shape as shown in fig. 14, and the U shape has: an extending portion (first inflection portion) 11g1 extending radially outward from one trough portion 11b, a returning portion (second inflection portion) 11g3 extending radially inward toward the other trough portion 11b divided by the band-folded projecting portion 11g, and a connecting portion 11g2 connecting the extending portion 11g1 and the returning portion 11g 3.

That is, the extended portion (first bent portion) 11g1 extends radially outward from one trough portion 11b, the return portion (second bent portion) 11g3 extends radially outward from the other trough portion 11b, and the connecting portion 11g2 connects radially outer end portions of the extended portion (first bent portion) 11g1 and the return portion (second bent portion) 11g3 to each other.

In the present disclosure, the extended portions 11g1 are bent substantially 90 ° toward the radially outer side with respect to the valley portions 11 b. Further, the connecting portion 11g2 is bent substantially 90 ° toward the radially inner side with respect to the extending portion 11g 1. The return portion 11g3 is bent substantially 90 ° radially inward with respect to the connecting portion 11g2, and is connected to the other trough portion 11 b. The folded-back projection 11g is in contact with the fitting groove 15 in an accumulated state. The folded-back projecting portion 11g of the present disclosure is formed by bending a plate spring (elastic member) substantially in a U-shape. The belt folding projection 11g is fitted into the fitting groove 15 in a slightly contracted state in the circumferential direction. This causes the extending portion 11g1 and the returning portion 11g3 to spring back to open in the circumferential direction, acting on the belt folding projection 11 g. Thereby, a frictional force is generated between the tape folded-back protrusion 11g and the fitting groove 15, and the back support foil piece 11a is held by the bearing housing 12.

The band folding projection 10c (second band folding projection) formed on the intermediate foil piece 10a fits into the space inside the band folding projection 11g of the back support foil 11 (the space between the extending portion 11g1 and the returning portion 11g 3). That is, the band folded-back protrusion 10c is formed at a position corresponding to the band folded-back protrusion 11g of the back support foil piece 11a and the fitting groove 15 of the bearing housing 12, that is, at a position overlapping with the band folded-back protrusion 11g and the fitting groove 15. In the figure, a gap is provided between the belt folding projection 10c and the belt folding projection 11 g. However, the gap is provided for clearly distinguishing the respective members, and the respective members are in contact with each other in an actual apparatus.

The belt folding projection 10c is in contact with the inner side of the belt folding projection 11g (the extending portion 11g1 and the returning portion 11g3) in an accumulated state. The belt folding projection 10c is fitted inside the belt folding projection 11g in a slightly contracted state in the circumferential direction. Thus, the band folding back projection 10c is acted with a spring back that opens the extended portion 10c1 and the return portion 10c3 in the circumferential direction. Thereby, a frictional force is generated between the tape folding projection 10c and the tape folding projection 11g, and the intermediate foil piece 10a is held by the back foil piece 11 a.

According to the second embodiment of the above configuration, in addition to the operational effects of the first embodiment, when the top foil 9 receives a fluctuating load due to shaft vibration of the rotary shaft 1 and the intermediate foil piece 10a and the back-up foil piece 11a flex together, not only "sliding" occurs between the belt folded-back protrusion 11g and the fitting groove 15, but also "sliding" occurs between the belt folded-back protrusion 11g and the belt folded-back protrusion 10c, which causes energy dissipation by friction and contributes to attenuation.

According to the radial foil bearing 3 of the second embodiment, the contact area between the intermediate foil piece 10a and the back foil piece 11a can be increased, and the damping effect by friction between the intermediate foil piece 10a and the back foil piece 11a can be further improved.

As shown in fig. 13 and 15, the back stay foil piece 11a has a hole 11h between the two folded-back projecting portions 11 g. If the hole 11h is not formed, the region of the back support foil piece 11a that is axially inward of the two folded-back projections 11g may be bent outward in the radial direction in the same manner as the folded-back projections 11g, and this region may interfere with the bearing housing 12. Therefore, by providing the hole 11h between the two folded-back projecting portions 11g, interference between the back support foil piece 11a and the bearing housing 12 can be avoided.

The radial foil bearing 3 of the second embodiment may also adopt the structure shown in fig. 16 and 17.

Fig. 16 is a plan view of a radial foil bearing 3 according to a modification of the second embodiment of the present disclosure, as seen from the radial direction, with a main portion thereof flattened. Further, the intermediate foil 10a on the back foil 11a is not shown on the upper side of the paper of fig. 16 in order to improve the visibility. Fig. 17 is a front view of a radial foil bearing 3 according to a modification of the second embodiment of the present disclosure, as seen from the axial direction, with a main portion thereof flattened.

In the back-support foil piece 11a of the radial foil bearing 3 shown in fig. 16, slits 11d extending in the circumferential direction are formed in the ridge portions 11c and 11c adjacent to each other across the notch 16, and the flat portion 11i is located axially outward of the slits 11 d.

The slits 11d extend from both axial ends of the hole 11h of the back foil piece 11a to both circumferential sides. That is, H-shaped holes are formed in the circumferential direction between the circumferential ends of the back support foil piece 11a in the axial direction. The flat portion 11i is located axially outward of the slit 11 d. In addition, as shown in fig. 17, the flat portion 11i extends in the circumferential direction at the same radial position as the top of the peak portion 11 c. That is, the flat portion 11i of the back foil piece 11a is in surface contact with the radially outer surface of the flat portion 10b of the intermediate foil piece 10a, and energy dissipation by friction on the contact surface is likely to occur. Further, a belt-folded projection 11g is continuously provided at the circumferential end of the flat portion 11 i.

According to the above configuration, the contact portion that contacts the flat portion 10b of the intermediate foil piece 10a can be formed not only on the top portion of the ridge portion 11c of the back foil piece 11a but also on the flat portion 11 i. Therefore, the contact area between the intermediate foil piece 10a and the back foil piece 11a is increased, the damping effect by friction between the intermediate foil piece 10a and the back foil piece 11a is improved, and the stability when supporting the rotating shaft 1 rotating at a high speed can be further improved.

Further, the radial foil bearing 3 according to the second embodiment may also have the structure shown in fig. 18 and 19.

Fig. 18 is a plan view of a radial foil bearing 3 according to a modification of the second embodiment of the present disclosure, as seen from the radial direction, with a main portion thereof flattened. Further, the intermediate foil 10a on the back foil 11a is not shown on the upper side of the paper of fig. 18 in order to improve the visibility. Fig. 19 is a front view of a radial foil bearing 3 according to a modification of the second embodiment of the present disclosure, as seen from the axial direction, with a main portion thereof flattened.

The back-support foil piece 11a of the radial foil bearing 3 shown in fig. 18 and 19 is divided into two pieces at the center in the circumferential direction of the back-support foil piece 11 a. The divided back stay foil pieces 11a adjacent in the circumferential direction are each provided with a folded-back protrusion 11g, and the folded-back protrusions 11g adjacent in the circumferential direction are arranged so as to face each other in one fitting groove 15 (see fig. 19).

Specifically, each of the folded-back projecting portions 11g of the back support foil pieces 11a adjacent in the circumferential direction has: extension 11g1, connecting portion 11g2, return portion 11g 3. In the present modification, the returning portion 11g3 does not connect to the trough portion 11b, and constitutes a circumferential end portion of the back-support foil piece 11 a. The return portions 11g3 of the circumferentially adjacent back foil pieces 11a abut in the circumferential direction. The intermediate foil piece 10a is also configured such that the intermediate foil piece 10a is divided into two pieces at the center portion in the circumferential direction, and each of the folded-back protrusions 10c is fitted into a space inside the folded-back protrusion 11g of the back foil piece 11 a. In addition, two separated portions of the intermediate foil 10a arranged in the circumferential direction do not contact each other. According to the above configuration, the contact portion (the returning portion 11g3) of the folded projecting portion 11g of each of the back foil pieces 11a adjacent in the circumferential direction "slides", and the contact portion between the folded projecting portion 11g and the folded projecting portion 10c fitted inside the folded projecting portion "slides". Therefore, the damping effect by friction is improved, and the stability when supporting the rotating shaft 1 that rotates at a high speed can be further improved.

(third embodiment)

Next, a third embodiment of the present invention will be explained. In the following description, the same or equivalent structures as those of the above-described embodiments are denoted by the same reference numerals, and the description thereof is simplified or omitted.

Fig. 20 is a plan view of a main portion of the radial foil bearing 3 according to the third embodiment of the present disclosure, which is flattened and viewed from the radial direction. Fig. 21 is a sectional view in an arrow a-a direction of a main portion shown in fig. 20.

The third embodiment is different from the first and second embodiments in that a branch piece 40 (protruding portion) branched from a planar portion 10b is provided in an intermediate foil 10 (intermediate foil piece 10 a). That is, a portion protruding radially outward is provided to extend from the radially outer surface of the intermediate foil piece 10 a.

As shown in fig. 20, the branch piece 40 has a slit 41 formed in the flat surface portion 10b, and a portion surrounded by the slit 41 is extended (cut) so as to protrude outward in the radial direction. In the present disclosure, the slit 41 is formed by two cuts parallel to the circumferential direction and a cut parallel to the axial direction connecting the ends of the two cuts. The rectangular branch piece 40 surrounded by the slit 41 obliquely projects outward in the radial direction. That is, the branch piece 40 extends from an end portion (hereinafter also referred to as a slit end portion) of the two cuts parallel to the circumferential direction, which is not connected to the cut parallel to the axial direction. The branch piece 40 is separated from an end (slit end) not connected to the cut parallel to the axial direction in the circumferential direction and separated from the end toward the outer side in the radial direction. That is, the branch piece 40 is separated in the circumferential direction from an end (slit end) not connected to the cut parallel to the axial direction and monotonically increases in radial position outward in the radial direction. The branch piece 40 protrudes toward the back foil piece 11a at a circumferential position between the top of at least one of the ridge portions 11c and the top of the ridge portion 11c adjacent to the ridge portion 11c in the wave plate shape of the back foil piece 11 a.

As shown in fig. 21, the branch pieces 40 are provided in pairs so as to sandwich the ridge portions 11c of the back support foil piece 11 a. That is, the slits 41 are formed on both sides of the position corresponding to the mountain portion 11c of the back support foil piece 11a, and the group of the branch pieces 40 cut from these slits 41 extend so as to be apart from each other. That is, two cuts parallel to the circumferential direction, which are separated in the circumferential direction, are provided so as to overlap with the circumferential position of one of the ridge portions 11c, respectively. That is, two sets of two cuts parallel to the circumferential direction are provided with respect to one of the mountain portions 11c, the two sets being distant from each other in the circumferential direction and being arranged so as to overlap with the circumferential position of the one of the mountain portions 11 c. And, the cut parallel to the axial direction extends from the end portion on the side away from each other of the two cuts parallel to the circumferential direction. With this configuration, the two branch pieces 40 are configured to sandwich one peak portion 11c, and to have both circumferential ends projecting radially outward and a space therebetween located radially inward. The two branch pieces 40 (one set of branch pieces) provided so as to sandwich the mountain portion 11c of the back foil piece 11a in the circumferential direction are in contact with the mountain portion 11c of the back foil piece 11a from both sides in the circumferential direction. In the present disclosure, as shown in fig. 20, two rows of slits 41 are provided in the planar portion 10b, and four branch pieces 40 are in contact with one peak portion 11 c. The slits 41 (the branch pieces 40) may be arranged in a single row, or may be arranged in three or more rows.

In addition, in the flat surface portion 10b of the intermediate foil 10, a branching position 43 at which the branching piece 40 branches is provided between the top of a first peak portion 11c (left peak portion 11c shown in fig. 21) and the top of a second peak portion 11c (right peak portion 11c shown in fig. 21) of the back foil 11 adjacent in the circumferential direction. The flat portion 10b is a portion located on a flat surface obtained by drawing a substantially circular closed curve that surrounds the intermediate foil 10 in the circumferential direction without including the branch piece 40 in the axial direction of the intermediate foil 10. In the present disclosure, the planar portion 10b is provided with a first branch position 43 (a left branch position 43 shown in fig. 21) between the top of the first peak portion 11c and the top of the second peak portion 11c, and a second branch position 43 (a right branch position 43 shown in fig. 21) at a position different from the first branch position 43. That is, two branch pieces 40 are formed between the top of the first ridge portion 11c and the top of the second ridge portion 11c of the back-up foil 11 adjacent in the circumferential direction. Alternatively, it can be said that there are two branch positions 43 in the circumferential direction between the valley portions 11b adjacent in the circumferential direction. In the radial foil bearing 3 of the present disclosure, the intermediate foil 10a and the back-up foil 11a are radially separated from each other at the radial position of the branch position 43 in a state where the inserted rotary shaft 1 is not rotated.

At circumferential both sides (side surfaces 11c3) of the top of the peak 11c, a pair of branch pieces 40 that open in directions away from each other are connected to each other. That is, in the intermediate foil piece 10a, in addition to the contact point P1 where the flat portion 10b contacts the top of the ridge portion 11c of the back foil piece 11a, a contact point P3 where the branch piece 40 contacts a portion (the side surface 11c3) other than the top of the ridge portion 11c of the back foil piece 11a is formed.

Here, in a state where the inserted rotation shaft 1 is not rotated, there is a possibility that a contact point is not formed between the two contact points P3 sandwiching the top portion of the mountain portion 11 c. At this time, the inserted rotation shaft 1 rotates, and a contact point P1 is generated between two contact points P3 that sandwich the top of the mountain portion 11 c. Further, the radially outer surface of the branch piece 40 extends from the top of the peak 11c toward the valley 11b adjacent to the peak 11c beyond the contact point P3. However, the radially outer surface of the branch piece 40 does not reach the radial position of the valley portion 11b adjacent to the peak portion 11 c.

The side surface 11c3 of the peak 11c is a curved surface, and the branch piece 40 in contact with the side surface 11c3 is a flat surface. That is, since the side surface 11c3 of the peak 11c and the branch piece 40 contact each other at the point of the contact point P3 and are separated from each other, the "slip" at the contact point P3 is likely to occur.

According to the third embodiment of the above configuration, the branch position 43 and the second branch position 43 at which the branch piece 40 branches from the planar portion 10b are provided between the top portion of the first peak portion 11c and the top portion of the second peak portion 11c of the back support foil 11 adjacent in the circumferential direction. As shown in fig. 21, the branch piece 40 is in contact with a portion other than the top of the peak portion 11c of the back support foil 11. Therefore, the intermediate foil 10 and the back-up foil 11 are in contact not only with the planar portion 10b but also with the branch pieces 40 branched from the planar portion 10 b. Therefore, the contact position of the intermediate foil 10 and the back-up foil 11 increases, and the damping effect by friction of the intermediate foil 10 and the back-up foil 11 is improved. That is, two contact points P3 are formed for each peak 11 c.

The branch pieces 40 are provided in pairs so as to sandwich the peak portions 11c of the back-up foil 11. Therefore, even when the back support foil 11 is deformed so as to expand or contract in the circumferential direction, the contact state between the branch piece 40 and the peak portion 11c can be maintained at all times, and the damping effect by the friction between the intermediate foil 10 and the back support foil 11 can be improved.

The radial foil bearing 3 of the third embodiment may also adopt the structure shown in fig. 22 and 23.

Fig. 22 is a plan view of a radial foil bearing 3 according to a modification of the third embodiment of the present disclosure, as seen from the radial direction, with a main portion thereof flattened. Fig. 23 is a sectional view in an arrow direction B-B of a main portion shown in fig. 22.

The intermediate foil 10 shown in fig. 22 and 23 includes a branch sheet 40B having a shape different from that of the branch sheet 40, instead of the branch sheet 40.

As shown in fig. 22, the branch piece 40B has a slit 41B formed in the flat surface portion 10B, and a portion surrounded by the slit 41B is extended so as to protrude radially outward. That is, the branch piece 40B of the present disclosure protrudes radially outward from the flat surface portion 10B in the circumferential direction and extends radially inward beyond the protruding peak. In the present disclosure, the slit 41B is formed in an H shape. The two branch pieces 40B formed by the slits 41B extend in a curved shape so as to protrude outward in the radial direction, and are formed in a wave plate shape. That is, the branch piece 40B extends from the edge of the rectangular cutout at both ends in the circumferential direction toward the other end edge, when viewed in the circumferential direction. The distal ends of the two branch pieces 40B are circumferentially distant from each other.

As shown in fig. 23, the branch pieces 40B are arranged at positions corresponding to the trough portions 11B of the back-support foil piece 11 a. That is, the branch piece 40B extends to the peak portion 11c adjacent to both sides of the trough portion 11B in the circumferential direction, including the radial position of the trough portion 11B. However, the tip of the branch piece 40B is located on the valley portion 11B side with respect to the apex of the peak portion 11 c. Therefore, the branch piece 40B includes one peak 11c and extends to the circumferential position of the adjacent peak 11 c. As shown in fig. 22, the slit 41B has a region in the center thereof where the back foil 11 is exposed when viewed in the radial direction. From this exposed region, a position corresponding to the top of the mountain portion 11c of the back foil piece 11a is exposed. The two branch pieces 40B cut out from the slit 41B are deformed in a curved shape so as to be apart from each other, and as shown in fig. 23, come into contact with the ridge portions 11c, which are disposed on both sides of the ridge portion 11c disposed at a position corresponding to the center portion of the slit 41B. That is, the peak portions 11c sandwiched by the branch pieces 40B from both sides in the circumferential direction and the peak portions 11c not sandwiched by the branch pieces 40B from both sides in the circumferential direction are alternately arranged. In other words, the top of the mountain portion 11c of the back support foil piece 11a and the peak of the branch piece 40B alternate in the circumferential direction. And in other words, the crest of one branch piece 40B exists between the crests of the mountain portions 11c adjacent to the crest of the mountain portion 11 c. In addition, the radial position of the peak is referred to herein as the peak.

In the planar portion 10B, a branch position 43B at which the branch piece 40B branches is provided between the top of the first peak portion 11c and the top of the second peak portion 11c of the back-up foil 11 adjacent in the circumferential direction. That is, one branch piece 40B is formed between the top of the first ridge portion 11c and the top of the second ridge portion 11c of the back-up foil 11 adjacent in the circumferential direction. The branch sheet 40B includes: a distal portion 40B1 that is radially outwardly distal from the planar portion 10B, a proximal portion 40B2 that extends from the distal portion 40B1 and approaches the radially inner side toward the planar portion 10B, and a tip portion 40B3 that extends from the proximal portion 40B2 and extends along the planar portion 10B. The distant portion 40B1 and the near portion 40B2 have smooth curved shapes with the same radius of curvature. The distance portion 40B1 and the approach portion 40B2 may be a combination of a linear shape and a linear shape, or may be a combination of a linear shape and a curved shape.

The side surface 11c3 of the peak 11c is connected to the distant portion 40B1 of the branch piece 40B. That is, in the intermediate foil piece 10a, in addition to the contact point P1 at which the flat surface portion 10B contacts the top portion of the ridge portion 11c of the back foil piece 11a, a contact point P4 is formed at which the separated portion 40B1 of the branch piece 40B contacts a portion (side surface 11c3) other than the top portion of the ridge portion 11c of the back foil piece 11 a. The side surface 11c3 of the peak 11c is a curved surface, and the separated portion 40B1 of the branch piece 40B that is in contact with the side surface 11c3 is a curved surface. The side surface 11c3 and the distant portion 40B1 are curved surfaces that are convex to each other. That is, since the side surface 11c3 of the peak 11c and the separated portion 40B1 of the branch piece 40B contact at the point of the contact point P4 and are separated at other portions, the "slip" at the contact point P4 is likely to occur. That is, in the present disclosure, the contact point P4 is formed by the two branch pieces 40B across the top of one peak portion 11 c. On the other hand, the peak 11c adjacent to the peak 11c does not have a contact point with the branch piece 40B. Further, the length from the contact point P4 of the branch piece 40B to the tip of the branch piece 40B is longer than the length between the branch position 43B of the branch piece 40B and the contact point P4. That is, in the present disclosure, the length from the contact point P4 to the tip of the branch piece 40B is longer than the length from the top of the peak 11c sandwiched by the contact points P4 to the contact point P4.

According to the above configuration, the branch position 43B at which the branch piece 40B branches from the planar portion 10B is provided between the top of the first ridge portion 11c and the top of the second ridge portion 11c of the back support foil 11 adjacent in the circumferential direction. As shown in fig. 23, the branch piece 40B is in contact with a portion other than the top of the peak portion 11c of the back support foil 11. Therefore, the intermediate foil 10 and the back-up foil 11 are in contact with not only the flat portion 10B but also the branch piece 40B branched from the flat portion 10B. Therefore, the contact position of the intermediate foil 10 and the back-up foil 11 increases, and the damping effect by friction of the intermediate foil 10 and the back-up foil 11 is improved.

The branch piece 40B is provided so as to sandwich the peak 11 c. Therefore, the branch piece 40B contacts the peak portion 11c regardless of the deformation of the back-up foil 11 in such a manner as to expand or contract in the circumferential direction. The branching piece 40B has a wave plate shape including: a distant portion 40B1 distant from the planar portion 10B to the radially outer side, and a close portion 40B2 extending from the distant portion 40B1 and approaching to the radially inner side toward the planar portion 10B. When the back support foil 11 is deformed in the circumferential direction, the branch piece 40B is pressed by the ridge portion 11c, and thus, as shown by a symbol S in fig. 23, a lateral slip occurs as in the back support foil 11 (bump foil). At this time, "slipping" may occur between the tip portion 40B3 of the branch piece 40B and the top foil 9, and the damping effect by friction is further improved.

(fourth embodiment)

Next, a fourth embodiment of the present invention will be explained. In the following description, the same or equivalent structures as those of the above-described embodiments are denoted by the same reference numerals, and the description thereof is simplified or omitted.

Fig. 24 is a plan view of a main portion of a radial foil bearing 3 according to a fourth embodiment of the present disclosure, which is flattened and viewed from the radial direction. Further, the intermediate foil 10a on the back foil 11a is not shown on the upper side of the paper of fig. 24 in order to improve the visibility. Fig. 25A is a front view of a bearing housing 12 of a fourth embodiment of the present disclosure, and fig. 25B is a sectional view of the bearing housing 12 in the arrow direction C-C.

As shown in fig. 25A, the bearing housing 12 of the fourth embodiment is provided with a protruding portion 50 that protrudes radially inward (radially inward) from the inner peripheral surface of the insertion hole 12 a. The projection 50 of the present disclosure is integrally formed with the bearing housing 12. The projection 50 may be attached to the bearing housing 12 as a separate member. The protruding portion 50 is formed annularly along the circumferential direction of the inner circumferential surface of the insertion hole 12 a. Specifically, the protruding portion 50 is formed in a C-shape substantially over the entire circumference of the inner circumferential surface of the insertion hole 12a excluding the through groove 13.

As shown in fig. 25B, the projection 50 has: a flat top wall portion 50a that is radially inward (radially reduced) of the inner peripheral surface of the insertion hole 12a and extends in the circumferential direction; and a pair of side wall portions 50b located at both ends of the top wall portion 50a in the axial direction and extending radially outward toward the inner peripheral surface of the insertion hole 12 a. The side wall portion 50b extends perpendicularly with respect to the top wall portion 50 a. The protruding portion 50 includes a top wall portion 50a at an axial position within a range of ± 5% of the axial center position C1 of the insertion hole 12 a.

That is, the top wall portion 50a of the protruding portion 50 extends from the axial center position C1 of the insertion hole 12a toward one axial side and the other axial side by a length of 5% of the width of the insertion hole 12a (bearing housing 12) in the axial direction, respectively. That is, when the full width of the insertion hole 12a (bearing housing 12) in the axial direction is D1 and the full width of the top wall portion 50a in the axial direction is D2, D2 is preferably formed in the range of 10% of D1. Further, if D2 is not formed within the range of 10% of D1, no effect is produced.

As shown in fig. 24, the back support foil 11 of the fourth embodiment is configured such that the back support foil 11 of the first embodiment is separated in the axial direction of the insertion hole 12 a. In the back support foil 11 (hereinafter, the first back support foil 11) arranged on one side in the axial direction (upper side in fig. 24) with respect to the protruding portion 50, a notch 16 is formed at an end edge on one side in the axial direction, and a folded-back protruding portion 10c of the intermediate foil 10 is inserted therethrough. No notch 16 is formed at the end edge on the other side in the axial direction of the first back foil 11. The other axial end edge of the first back-up foil 11 is arranged to abut against or leave a slight gap from the side wall 50b of the protruding portion 50 in the axial direction.

Although not shown, a notch 16 is formed in the back support foil 11 (hereinafter, the second back support foil 11) disposed on the other side in the axial direction (lower side in fig. 24) with respect to the protruding portion 50, and the folded-back protruding portion 10c with the intermediate foil 10 is inserted therethrough. No notch 16 is formed at the axial one-side end edge of the second back foil 11. The axial end edge of the second back-up foil 11 is disposed so as to contact or leave a slight gap in the axial direction with respect to the side wall portion 50b of the protruding portion 50.

That is, the back support foil 11 includes four end edges (two end edges of the first back support foil 11 and two end edges of the second back support foil 11) extending in the direction intersecting the axial direction with the protruding portion 50 interposed therebetween. In other words, the backing foil 11 has four end edges when viewed in the axial direction. Notches 16 are formed at the axial end edges of the back-up foil 11 and engage with the intermediate foil 10. On the other hand, the notches 16 are not formed at the end edges of the back-up foil 11 facing the protruding portion 50, that is, at the two end edges located axially inward, and these two end edges are arranged so as to be axially adjacent to or spaced apart from the side wall portion 50b of the protruding portion 50 by a slight gap.

In addition, the intermediate foil 10 of the fourth embodiment is also separated from the protruding portion 50 in the axial direction of the insertion hole 12 a. The intermediate foil 10 (hereinafter, referred to as the first intermediate foil 10) disposed on the other side in the axial direction (lower side in fig. 24) with respect to the protruding portion 50 has a notch 16 formed at the other end edge in the axial direction, the notch being provided with a folded-back protrusion 10c and inserted into the back-up foil 11. The first intermediate foil 10 has no folded-back projection 10c at its axial end. The axial end edge of the first intermediate foil 10 is disposed so as to contact or leave a slight gap in the axial direction with respect to the side wall portion 50b of the protruding portion 50.

Although not shown, the intermediate foil 10 (hereinafter, referred to as the second intermediate foil 10) disposed on one side in the axial direction (upper side in fig. 24) with respect to the protruding portion 50 is formed with a folded-back projecting portion 10c at an end edge on one side in the axial direction and is engaged with the backing foil 11. The second intermediate foil 10 has no folded-back projection 10c at the other axial end. The other axial end edge of the second intermediate foil 10 is disposed so as to contact or leave a slight gap in the axial direction with respect to the side wall portion 50b of the protruding portion 50.

That is, the intermediate foil 10 includes four end edges (two end edges of the first intermediate foil 10 and two end edges of the second intermediate foil 10) extending in the direction intersecting the axial direction with the projecting portion 50 interposed therebetween. In other words, the intermediate foil 10 is provided with four end edges, when seen in the axial direction. The intermediate foil 10 has folded-back projecting portions 10c formed at its axial end edges on both sides and engaged with the back-up foil 11. On the other hand, the folded-back projecting portions 10c are not formed at the end edges of the intermediate foil 10 facing the projecting portion 50, that is, at the two end edges located axially inward, and these two end edges are arranged so as to be axially adjacent to or spaced apart from the side wall portion 50b of the projecting portion 50 by a slight gap.

Further, the top foil 9 is not separated in the axial direction, and is supported by two back-up foils 11 and two intermediate foils 10, respectively, which are separated in the axial direction. A gap is formed between the separated first and second back-up foils 11 and between the first and second intermediate foils 10, and a projection 50 is disposed in the gap. That is, the top foil 9 is supported by the back support foil 11 and the intermediate foil 10 at both sides of the protruding portion 50. I.e. the top wall portion 50a faces the top foil 9 in the radial direction. The top foil 9 is arranged to overlap the protruding portion 50 in the radial direction of the insertion hole 12 a. The top wall portion 50a of the protrusion 50 faces the outer peripheral surface (back surface) of the top foil 9 with a gap in the radial direction of the insertion hole 12 a.

The protruding portion 50 extends from the inner peripheral surface of the insertion hole 12a to a radial position radially outward (radially outward) of the top of the ridge portion 11c of the back up foil 11. That is, the protruding portion 50 does not protrude radially inward (radially inward) with respect to the top of the peak portion 11 c. Therefore, when no load is applied, the top wall portion 50a of the protrusion 50 is separated from the outer peripheral surface of the top foil 9. The protruding portion 50 preferably has a height of 75% or less of the entire height of the ridge portion 11c, for example.

The projecting portion 50 extends to a radial position radially inward (radially inward) of the valley portion 11b of the back-up foil 11. As a result, as shown in fig. 24, a part of the end edge of the back-up foil 11 facing the protruding portion 50 can face the side wall portion 50b, and the back-up foil 11 can be positioned in the axial direction.

According to the fourth embodiment having the above configuration, the same operational effects (improvement of the damping effect by friction) as those of the first to third embodiments can be obtained. Further, when a large external force acts on the supercharger equipped with the radial foil bearing 3, the radial displacement of the rotary shaft 1 can be suppressed. That is, when the bearing load increases due to a strong external force, the back-up foil 11 is pressed down, and the outer diameter side (back side) of the top foil 9 starts to contact the top wall portion 50a of the protrusion 50. In this state, even if the bearing load increases, the increased load is supported by the protruding portion 50, and the radial displacement of the rotary shaft 1 reaches the limit. Therefore, the tip clearance 7 between the impeller 2 and the casing 6 shown in fig. 1 can be maintained, and contact between the impeller 2 and the casing 6 can be avoided.

As shown in fig. 25A, the protrusion 50 includes a top wall 50a at an axial position within a range of ± 5% of the axial center position C1 of the insertion hole 12 a. Therefore, the deflection of the top foil 9 in the vicinity of the center of the insertion hole 12a in the axial direction can be effectively suppressed. That is, the pressure of the fluid lubrication film reaches the peak near the center in the axial direction, and decreases toward both ends in the axial direction. That is, the rate of change in the pressure of the fluid lubrication film increases from the vicinity of the center in the axial direction toward both ends in the axial direction. The support by the top wall portion 50a is preferably in the vicinity of the peak of the fluid lubrication film. In the range of ± 5% with respect to the center position C1 in the axial direction shown in fig. 25B, the support by the top wall portion 50a functions more effectively without a large variation in the peak top pressure of the fluid lubrication film.

Further, as shown in fig. 25A, since the protruding portion 50 of the present disclosure is formed annularly along the circumferential direction of the inner circumferential surface of the insertion hole 12a, the deflection of the top foil 9 near the center of the insertion hole 12a in the axial direction can be suppressed over the entire circumference. As shown in fig. 24, the back support foil 11 (intermediate foil 10) is separated in the axial direction of the insertion hole 12a, and therefore can be disposed on the inner circumferential surface of the insertion hole 12a without interfering with the annularly formed protruding portion 50.

Further, annular covers may be attached to both end surfaces 12b in the axial direction of the bearing housing 12. The lid covers the folded-back projecting portion 10c fitted in the fitting groove 15, and thereby the intermediate foil 10 and the back-up foil 11 can be prevented from coming off from the bearing housing 12 in the axial direction.

The embodiments of the present disclosure have been described above with reference to the drawings, but the present disclosure is not limited to the above embodiments. The shapes, combinations, and the like of the respective constituent members shown in the above embodiments are merely examples, and various modifications can be made in accordance with design requirements and the like within a scope not departing from the spirit of the present disclosure.

For example, the structures of the above embodiments and modifications may be replaced or combined as appropriate.

Industrial applicability of the invention

The present disclosure can be applied to a radial foil bearing.

Description of the symbols

3-radial foil bearings; 9 — top foil; 10-intermediate foil (foil structure); 10 a-intermediate foil; 10c — a belt folding projection (second belt folding projection); 10 d-hole section; 11-backing foil (foil structure); 11 a-a backing foil; 11 g-with folded-back protrusions; 12-a bearing shell; 12 a-an insertion hole; 12b — end face; 15-the engagement groove.