RADIAL FOIL BEARING FOR SUPPORTING A SHAFT

Abstract

A radial foil bearing for supporting a shaft includes a sleeve-like bearing housing with an inner circumference and at least three foil packs distributed over the inner circumference and covering a portion of the inner circumference. Each of the at least three foil packs has an elastic corrugated foil resting against the inner circumference and a top foil. The elastic corrugated foil includes axially opposite side edges running in a circumferential direction and a narrowed portion disposed on at least one of the axially opposite side edges to reduce an axial width and a radial spring rigidity of the elastic corrugated foil at the narrowed portion. The top foil has an underside resting on the elastic corrugated foil and a top side forming a bearing surface for the shaft.

Claims

1. A radial foil bearing for supporting a shaft, comprising a sleeve-like bearing housing having at least three foil packs distributed over the inner circumference of the bearing housing, each covering a portion of the inner circumference of the bearing housing, each consisting of an elastic corrugated foil resting against the inner circumference of the bearing housing and a top foil, of which the underside rests on the corrugated foil and the top side forms a bearing surface for the shaft, wherein the corrugated foils have at least one narrowed portion locally at their side edges running in the circumferential direction, which reduces their axial width, with which the radial spring rigidity of the corrugated foils can be reduced in the region of their side edges.

2. The radial foil bearing according to claim 1, wherein narrowed portions are arranged at both side edges of the corrugated foils and both narrowed portions are designed in the form of circular sections and symmetrical to one another with the same depths and the same lengths.

3. The radial foil bearing according to claim 1, wherein narrowed portions are arranged at both side edges of the corrugated foils and both narrowed portions are designed in the form of circular sections and unsymmetrical to one another with different depths and equal or unequal lengths.

4. The radial foil bearing according to claim 1, wherein narrowed portions are arranged at both side edges of the corrugated foils and both narrowed portions are designed to be unsymmetrical in the circumferential direction with the same depths and the same lengths.

5. The radial foil bearing of claim 1, wherein the narrowed portions at both side edges of the corrugated foils extend in the circumferential direction from the first corrugation crest to the last corrugation crest of each corrugated foil.

6. The radial foil bearing of claim 1, wherein the narrowed portions at both side edges of the corrugated foils extend in the circumferential direction only from the second corrugation crest to the penultimate corrugation crest of each corrugated foil.

7. The radial foil bearing of claim 1, wherein the depth of the narrowed portion is dimensioned such that the width of the corrugated foil between the lowest points of both narrowed portions is between 75% and 95% of the axial width of the corrugated foils at their end edges.

8. A radial foil bearing for supporting a shaft, comprising: a sleeve-like bearing housing comprising an inner circumference; and at least three foil packs distributed over the inner circumference and covering a portion of the inner circumference, each of the at least three foil packs comprising: an elastic corrugated foil resting against the inner circumference, the elastic corrugated foil comprising: axially opposite side edges running in a circumferential direction; and a narrowed portion disposed on at least one of the axially opposite side edges to reduce an axial width and a radial spring rigidity of the elastic corrugated foil at the narrowed portion; and a top foil comprising: an underside resting on the elastic corrugated foil; and a top side forming a bearing surface for the shaft.

9. The radial foil bearing of claim 8 wherein: each elastic corrugated foil comprises a narrowed portion disposed on each axially opposite side edge; and the narrowed portions are symmetric circular sections having a same depth and a same length.

10. The radial foil bearing of claim 8 wherein: each elastic corrugated foil comprises a narrowed portion disposed on each axially opposite side edge; and the narrowed portions are unsymmetric circular sections having different depths.

11. The radial foil bearing of claim 8 wherein: each elastic corrugated foil comprises a narrowed portion disposed on each axially opposite side edge; and the narrowed portions are unsymmetrical in the circumferential direction with same depths and same lengths.

12. The radial foil bearing of claim 8 wherein: each elastic corrugated foil comprises a narrowed portion disposed on each axially opposite side edge; each elastic corrugated foil comprises a plurality of corrugation crests; and the narrowed portions extend circumferentially from a first corrugation crest of the plurality of corrugation crests to a last corrugation crest of the plurality of corrugation crests.

13. The radial foil bearing of claim 8 wherein: each elastic corrugated foil comprises a narrowed portion disposed on each axially opposite side edge; each elastic corrugated foil comprises a plurality of corrugation crests; and the narrowed portions extend circumferentially from a second corrugation crest of the plurality of corrugation crests to a penultimate corrugation crest of plurality of corrugation crests.

14. The radial foil bearing of claim 8 wherein: each elastic corrugated foil comprises a narrowed portion disposed on each axially opposite side edge; and the narrowed portions comprise respective depths dimensioned such that an axial width of each of the elastic corrugated foils between lowest points of the narrowed portions is between 75% and 95% of an axial width at an end of the axially opposite side edges.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] An example embodiment of the radial foil bearing designed according to the present disclosure is explained in more detail below with reference to the accompanying drawings. In the figures:

[0015] FIG. 1 shows a side view of a radial foil bearing designed according to the present disclosure carrying a shaft;

[0016] FIG. 2 shows a perspective view of the radial foil bearing designed according to the present disclosure with a partially broken top foil;

[0017] FIG. 3 shows two versions of a corrugated foil of the radial foil bearing according to the present disclosure with symmetrical narrowing;

[0018] FIG. 4 shows two versions of a corrugated foil of the radial foil bearing according to the present disclosure with unsymmetrical narrowing;

[0019] FIG. 5 shows two versions of a corrugated foil of the radial foil bearing according to the present disclosure with shortened narrowing;

[0020] FIG. 6 shows an embodiment of a corrugated foil of the radial foil bearing according to the present disclosure with narrowing that is unsymmetrical in the circumferential direction.

DETAILED DESCRIPTION

[0021] FIG. 1 shows a radial foil bearing 1 for supporting a shaft 13. The radial foil bearing has a sleeve-like bearing housing 2 with at least three foil packs 4, 5, 6 distributed over the inner circumference 3 of the bearing housing 2, each of which covers a portion of the inner circumference 3 of the bearing housing 2. As can be seen in FIG. 2, these foil packs 4, 5, 6 each include an elastic corrugated foil 7 resting against the inner circumference 3 of the bearing housing 2 and a top foil 8, of which the underside rests on the corrugated foil 7 and the top side forms a bearing surface for the shaft 13. Arranged on the inner circumference 3 of the bearing housing 2 are six insertion grooves 9, 10, which extend parallel to the axis of rotation of the bearing and protrude obliquely from the inside outwards into the bearing housing 2. The insertion grooves serve to accommodate the end edges 11, 12 which delimit the corrugated foils 7 and the top foils 8, each in the circumferential direction. The end edges are arranged tangentially in the insertion grooves 9, 10 so as to be freely movable.

[0022] Furthermore, it can be seen from FIG. 2 that the corrugated foils 7 have at least one narrowed portion 16, 17 locally at their side edges 14, 15 (ref. FIGS. 3-6) running in the circumferential direction, reducing their axial width B, with which the radial spring rigidity of the corrugated foils 7 can be reduced in the region of their side edges 14, 15. This is intended to ensure that the air pressure caused by the rotation of the shaft 13 is also sufficient at the two side edges of the top foils 8, which are connected to the ambient air pressure, to compress the associated corrugated foils 7 in such a way that the required small distance is created between the top foils 8 and the shaft 13 and there is no longer edge running at these points, which was previously the cause of bearing damage or bearing failures.

[0023] In the first embodiment of a corrugated foil 7 shown in FIG. 3, narrowed portions 16, 17 are arranged at both side edges 14, 15 of the corrugated foils 7 and both narrowed portions 16, 17 are designed in the shape of a segment of a circle and symmetrically to one another, in that they have the same depths TT1, TT2 and the same lengths TL1, TL2. The only difference between the two corrugated foils 7 shown and intended for different radial foil bearings is that the depths TT1, TT2 of the narrowed portions in the corrugated foil 7 shown on the left are greater than in the corrugated foil 7 shown on the right.

[0024] The alternative second embodiment of a corrugated foil 7 shown in FIG. 4 differs from the embodiment shown in FIG. 3 in that the narrowed portions 16, 17 at both side edges 14, 15 of the corrugated foils 7 are also designed in the shape of a segment of a circle but are unsymmetrical to one another. The narrowed portions 16, 17 can be clearly seen to have different depths TT1, TT2 with the same lengths TL1, TL2, the depths TT1, TT2 of the corrugated foil 7 shown on the left also being greater here than in the corrugated foil 7 shown on the right.

[0025] In addition, a third alternative embodiment of a corrugated foil 7 can be seen in FIG. 6. This embodiment includes narrowed portions 16, 17 at both side edges 14, 15 of the corrugated foils 7 that are unsymmetrical in the circumferential direction and have the same depths TT1, TT2 and the same lengths TL1, TL2. In this embodiment, the narrowed portions 16, 17 clearly deviate from the shape of a segment of a circle and instead have a curved or arcuate contour.

[0026] It can also be seen from the drawings that the narrowed portions 16, 17 at both side edges 14, 15 of the corrugated foils 7 extend in the circumferential direction either, as shown in FIGS. 3 and 4, from the first corrugation crest W1 to the last corrugation crest W5 of each corrugated foil 7, or as shown in FIGS. 5 and 6, only from the second corrugation crest W2 to the penultimate corrugation crest W4 of each corrugated foil 7. The selection of these lengths TL1, TL2 of the narrowed portions is dependent on the desired degree of reduction of axial spring rigidity of the corrugated foils 7. In addition, the depths TT1, TT2 of the narrowed portions should be dimensioned in such a way that the width of the corrugated foil 7 between the deepest points of both narrowed portions 16, 17 is between 75% and 95% of the axial width B of the corrugated foils 7 at their end edges 11, 12.

TABLE-US-00001 REFERENCE NUMERALS 1 Radial foil bearing 2 Bearing housing 3 Inner circumference of 2 4 Foil pack 5 Foil pack 6 Foil pack 7 Corrugated foil 8 Top foil 9 Insertion groove 10 Insertion groove 11 End edges of 7 12 End edges of 8 13 Shaft 14 Side edge of 7 15 Side edge of 7 16 Narrowed portion at 14 17 Narrowed portion at 15 B Axial width of 7 TT1 Depth of narrowed portion at 14 TT2 Depth of narrowed portion at 15 TL1 Length of narrowed portion at 14 TL2 Length of narrowed portion at 15 W1 First corrugation crest of 7 W2 Second corrugation crest of 7 W4 Penultimate corrugation crest of 7 W5 Last corrugation crest of 7