阅读说明：本技术 径向箔轴承 (Radial foil bearing ) 是由 大森直陆 于 2018-06-27 设计创作，主要内容包括：径向箔轴承(3)具备：具有插通孔(12a)的轴承壳体(12)；收纳于插通孔的顶部箔(9)；以及安装于插通孔延伸的轴向上的轴承壳体的端面的盖体(50、50A、50B),顶部箔以两端向轴承壳体侧被引出且交叉的状态卷成圆筒状,盖体与顶部箔的两端、以及安装于轴承壳体且与顶部箔卡合的卡合部件(16、16C)的至少任一方在轴向上对置。(A radial foil bearing (3) is provided with: a bearing housing (12) having an insertion hole (12 a); a top foil (9) received in the through hole; and a cover body (50, 50A, 50B) mounted on the end face of the bearing housing extending in the axial direction of the insertion hole, wherein the top foil is rolled into a cylindrical shape with both ends drawn out toward the bearing housing and intersecting, and the cover body is axially opposed to at least one of both ends of the top foil and engagement members (16, 16C) mounted on the bearing housing and engaged with the top foil.)

1. A radial foil bearing is characterized by comprising:

a bearing housing having an insertion hole;

a top foil received in the insertion hole; and

a cover body attached to an end surface of the bearing housing in an axial direction in which the insertion hole extends,

the top foil is rolled into a cylindrical shape with both ends thereof drawn out toward the bearing housing side and crossed,

the cover body is opposed to at least one of both ends of the top foil and an engaging member attached to the bearing housing and engaged with the top foil in the axial direction.

2. Radial foil bearing according to claim 1,

a through-groove extending in the axial direction from an end surface of the bearing housing is formed in the insertion hole,

both ends of the top foil are received in the through grooves,

the cover covers at least a part of an open end of the through-groove formed in an end surface of the bearing housing.

3. Radial foil bearing according to claim 2,

the engaging member is accommodated in the through groove.

4. Radial foil bearing according to claim 3,

the surface of the engaging member facing the bottom surface of the through groove is flat.

5. Radial foil bearing according to claim 3 or 4,

the engaging member has a chamfered portion facing a corner of the side surface and the bottom surface of the through groove.

6. Radial foil bearing according to claim 5,

the corner of the through groove has a curved surface smoothly connecting the side surface and the bottom surface.

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

the cover body is riveted to the bearing housing.

8. Radial foil bearing according to claim 7,

the cover body has:

a circular ring portion facing an end surface of the bearing housing; and

and a caulking portion extending from an outer edge of the annular portion and facing an outer peripheral surface of the bearing housing located radially outside the insertion hole.

Technical Field

The present disclosure relates to radial foil bearings.

The present application claims priority based on application No. 2017-124796, filed in japan on 27.6.2017, the contents of which are incorporated herein by reference.

Background

Conventionally, as a bearing for a high-speed rotating body, a radial foil bearing used to surround a rotating shaft is known. As such a radial foil bearing, there is known a radial foil bearing having: a thin plate-like top foil forming a bearing surface; a back foil elastically supporting the top foil; and a cylindrical case that houses the top foil and the back foil. As the back foil of the radial foil bearing, for example, a corrugated foil formed by forming a thin plate is used.

In such a radial foil bearing, in order to prevent the top foil from coming off the bearing housing, in patent document 1, a through groove is formed in the inner peripheral surface of the bearing housing, and a fastener is fitted into the through groove to form a plurality of engaging grooves. The top foil has a structure in which a metal foil having a first uneven portion and a second uneven portion at both ends is rolled into a cylindrical shape. The plurality of protrusions (both ends) drawn out toward the bearing housing side at both ends of the top foil are engaged with the plurality of engaging grooves, and the top foil is prevented from falling off from the bearing housing.

Further, the following patent documents 2 to 4 also disclose a radial foil bearing.

Disclosure of Invention

Problems to be solved by the invention

However, in the above-described conventional technique, in order to assemble the top foil to the bearing housing, both ends of the top foil must be engaged with the engagement grooves of the fixture fitted into the bearing housing in a state where both ends of the top foil intersect. To achieve this, it is necessary to round the top foil in a conical shape so as to be smaller than the inner diameter of the insertion hole of the bearing housing and to be inserted into the insertion hole of the bearing housing in the axial direction. As described above, conventionally, the skill and time of the operator are required to assemble the top foil to the bearing housing.

The present disclosure has been made in view of the above problems, and an object of the present disclosure is to improve workability in assembling a top foil to a bearing housing.

Means for solving the problems

In order to solve the above problem, a radial foil bearing according to one aspect of the present disclosure includes: a bearing housing having an insertion hole; a top foil received in the insertion hole; and a cover attached to an end surface of the bearing housing in an axial direction in which the insertion hole extends, wherein the top foil is wound into a cylindrical shape with both ends thereof drawn out toward the bearing housing and intersecting each other, and at least one of the cover, both ends of the top foil, and an engaging member attached to the bearing housing and engaged with the top foil faces in the axial direction.

In the radial foil bearing according to the one aspect of the present disclosure, it is preferable that a through groove extending in the axial direction from an end surface of the bearing housing is formed in the insertion hole, both ends of the top foil are accommodated in the through groove, and the cover covers at least a part of an open end of the through groove formed in the end surface of the bearing housing.

In the radial foil bearing according to the one aspect of the present disclosure, it is preferable that the engaging member is housed in the through groove.

In the radial foil bearing according to the above aspect of the present disclosure, a surface of the engaging member facing a bottom surface of the through groove is preferably flat.

In the radial foil bearing according to the above aspect of the present disclosure, it is preferable that the engaging member has a chamfered portion facing a corner portion of the side surface and the bottom surface of the through groove.

In the radial foil bearing according to the above aspect of the present disclosure, it is preferable that a corner of the through groove has a curved surface smoothly connecting the side surface and the bottom surface.

In the radial foil bearing according to the above aspect of the present disclosure, it is preferable that the cover is attached to the bearing housing by caulking.

In the radial foil bearing according to the above aspect of the present disclosure, it is preferable that the cover includes: a circular ring portion facing an end surface of the bearing housing; and a caulking portion extending from an outer edge of the annular portion and facing an outer peripheral surface of the bearing housing located radially outside the insertion hole.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present disclosure, the workability of assembling the top foil to the bearing housing can be improved.

Drawings

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

Fig. 2 is a front view showing a radial foil bearing of the present disclosure.

Fig. 3 is a front view showing a state in which a cover is attached to the radial foil bearing of the present disclosure.

Fig. 4 is a perspective view showing a mounting structure of the back foil and the intermediate foil to the bearing housing according to the present disclosure.

Fig. 5 is a schematic view of flattening the mounting structure of the back foil and the intermediate foil of the present disclosure with respect to the bearing housing, fig. 5(a) is a plan view, and fig. 5(b) is a front view.

Fig. 6 is a schematic diagram of the top foil of the present disclosure after being unfolded, fig. 6(a) is a plan view, and fig. 6(b) is a front view.

Fig. 7 is a schematic view of a main portion in the through groove of the bearing housing of the present disclosure, fig. 7(a) is an exploded perspective view, fig. 7(b) is a plan view, and fig. 7(c) is a sectional view as viewed along line a-a.

Fig. 8 is a sectional view taken along line B-B of fig. 7.

Fig. 9 is a diagram for explaining a manufacturing process of the engaging member in the present disclosure.

Fig. 10 is a front view showing a radial foil bearing according to a modification of the present disclosure.

Fig. 11 is a bottom view showing a radial foil bearing according to a modification of the present disclosure.

Fig. 12 is a front view showing the cover before being mounted on the bearing housing of fig. 11.

Fig. 13 is a schematic view of a main portion in a through groove of a radial foil bearing in one modification of the present disclosure, fig. 13(a) is an exploded perspective view, fig. 13(b) is a plan view, and fig. 13(C) is a cross-sectional view as viewed along line C-C.

Detailed Description

Hereinafter, the radial foil bearing of the present disclosure will be described in detail with reference to the drawings.

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

In fig. 1, reference numeral 1 denotes a rotary shaft, reference numeral 2 denotes an impeller provided at the tip of one side in the axial direction of the rotary shaft, and reference numeral 3 denotes a radial foil bearing according to the present disclosure. Although only one radial foil bearing is omitted in fig. 1, two radial foil bearings are usually provided in the axial direction of the rotating shaft 1. Thus, also in the present disclosure two radial foil bearings 3 are provided.

The radial foil bearing 3 is provided so as to surround 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 rotating shaft 1 and the radial foil bearing 3. Thrust bearings 5 are disposed (inserted) on both axial sides of the thrust ring 4. The impeller 2 is disposed in a casing 6 on a stationary side, and a tip clearance 7 is provided between the impeller and the casing 6.

Fig. 2 is a front view showing the radial foil bearing 3 of the present disclosure. Fig. 3 is a front view showing a state in which a cover 50 is attached to the radial foil bearing 3 of the present disclosure.

The radial foil bearing 3 is provided so as to surround the rotating shaft 1, and is a bearing for supporting the rotating shaft 1. The radial foil bearing 3 includes a top foil 9, an intermediate foil 10, a back foil 11, and a bearing housing 12. The bearing housing 12 has an insertion hole 12a through which the rotary shaft 1 is inserted. The bearing housing 12 formed with the insertion hole 12a of the present disclosure is cylindrical.

In the following description, the positional relationship of the respective members may be described with reference to the insertion hole 12 a. Specifically, "axial direction" refers to a direction in which the insertion hole 12a extends (a direction in which the rotary shaft 1 is inserted). The "radial direction" refers to a radial direction of the insertion hole 12a (i.e., a direction perpendicular to the central axis of the insertion hole 12a (see reference symbol O in fig. 2, 3, and 10)). The "circumferential direction" refers to a circumferential direction along the inner circumferential surface of the insertion hole 12a (i.e., a direction of the insertion hole 12a around the central axis).

The bearing housing 12 is a cylindrical member constituting the outermost portion of the radial foil bearing 3 in the radial direction. The back foil 11, the intermediate foil 10, and the top foil 9 are accommodated in the insertion hole 12a of the bearing housing 12. 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. The bearing housing 12 of the present disclosure is a cylindrical member having an insertion hole 12 a. However, if the insertion hole 12a is provided, the bearing housing 12 may be a member other than a cylindrical member (for example, a prismatic member).

The back foil 11 is disposed on the inner circumferential surface of the insertion hole 12a of the bearing housing 12. The back foil 11 is a foil (thin plate) that elastically supports the intermediate foil 10 and the top foil 9. Examples of the back foil 11 include a bump foil, a spring foil described in japanese patent application laid-open No. 2006-57652 or 2004-270904, and a back foil described in japanese patent application laid-open No. 2009-299748. In the present disclosure, a bump foil is used as the back foil 11.

The back foil 11 of the present disclosure is composed of three (a plurality of) back foil pieces 11a arranged along the inner peripheral surface of the insertion hole 12 a. The foil (thin plate) of the back foil piece 11a has a corrugated shape in the circumferential direction. The three back foil pieces 11a are bent into a substantially cylindrical shape as a whole when viewed in the axial direction. That is, the back foil piece 11a is supported on the inner circumferential surface of the insertion hole 12 a. In the present disclosure, the three back foil pieces 11a are all formed in the same shape and size. Therefore, the back foil pieces 11a are arranged so as to approximately trisect the inner circumferential surface of the insertion hole 12a in the circumferential direction.

The back foil piece 11a is formed with ridges 11c protruding radially inward and valleys 11b protruding radially outward as viewed from the ridges 11c alternately in the circumferential direction. The valley portion 11b has a flat portion facing the bearing housing 12, and the flat portion can abut against the inner peripheral surface of the insertion hole 12 a. The ridge 11c can abut against the intermediate foil 10 (intermediate foil piece 10 a). In this way, the back foil piece 11a elastically supports the top foil 9 from the ridge 11c via the intermediate foil piece 10 a. In addition, both circumferential ends of the back foil piece 11a become valleys 11 b.

The intermediate foil 10 is arranged between the top foil 9 and the back foil 11. The intermediate foil 10 of the present disclosure is composed of three intermediate foil pieces 10a arranged along the inner peripheral surface of the insertion hole 12 a. The intermediate foil 10a is formed in a developed shape having a substantially rectangular shape. The three intermediate foil pieces 10a are bent into a substantially cylindrical shape as a whole when viewed in 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 pieces 10a are arranged so as to approximately trisect the inner circumferential surface of the insertion hole 12a in the circumferential direction. Further, the intermediate foil piece 10a of the present disclosure is separated from the adjacent intermediate foil pieces 10a at a circumferential position between the tops of the circumferentially adjacent mountain portions 11c and at a separation position of the circumferentially adjacent back foil pieces 11 a. That is, the intermediate foil piece 10a is not separated at a position facing the top of the peak portion 11c of the back foil piece 11 a.

Further, a plurality of first engagement grooves 25 extending radially outward from the inner peripheral edge (inner peripheral surface) of the insertion hole 12a are formed on both end surfaces 12b of the bearing housing 12 in the axial direction. That is, the end surface 12b of the bearing housing 12 includes a recess extending to the inner peripheral surface of the bearing housing 12. The first engagement grooves 25 of the present disclosure are formed at positions that approximately trisect the end surface 12b of the bearing housing 12 in the circumferential direction. The engaging pins 30 for attaching the back foil 11 and the intermediate foil 10 to the bearing housing 12 are engaged with the first engaging grooves 25.

The first engagement groove 25 of the present embodiment is formed from the inner peripheral edge (inner peripheral surface) of the insertion hole 12a to the outer peripheral edge (outer peripheral surface) of the bearing housing 12, but the present disclosure is not limited thereto. For example, the first engagement groove may be formed from the inner peripheral edge (inner peripheral surface) of the insertion hole 12a to an intermediate position in the thickness direction (radial direction) of the plate member constituting the bearing housing 12. That is, the first engagement groove may not reach the outer peripheral edge of the bearing housing 12.

Fig. 4 is a perspective view showing a mounting structure of the back foil 11 and the intermediate foil 10 to the bearing housing 12 according to the present disclosure. Fig. 5 is a schematic view of flattening the mounting structure of the back foil 11 and the intermediate foil 10 of the present disclosure with respect to the bearing housing 12, fig. 4(a) is a plan view, and fig. 4(b) is a front view.

As shown in fig. 4 and 5(a), the back foil piece 11a has notches 26 at both axial end edges. These notches 26 are formed in the valleys 11b of the back foil piece 11 a.

The cutout 26 is formed at a circumferential position between both circumferential ends of the back foil piece 11a (a central position of the back foil piece 11a in the circumferential direction in the present disclosure). That is, the back foil piece 11a has recesses in the axial direction at the circumferential positions on both axial edges. As shown in fig. 4, the notch 26 is disposed at a position corresponding to the first engagement groove 25 of the bearing housing 12, that is, at a position overlapping the first engagement groove 25. In other words, the notch 26 is disposed at the same position as the first engagement groove 25 in the axial direction and the circumferential direction. The width (circumferential width) of the notch 26 is formed smaller than the width (circumferential width) of the first engagement groove 25. That is, both circumferential ends of the cutout 26 are located at circumferential positions between both circumferential ends of the first engaging groove 25.

As shown in fig. 5(a), the outer shape of the intermediate foil 10a has a size substantially equal to the outer shape of the back foil 11 a. As shown in fig. 5(b), the intermediate foil piece 10a has a flat surface portion 10b contacting the top of the peak portion 11c of the back foil 11, and a recessed portion 10c recessed (protruding) radially outward from the flat surface portion 10 b. I.e. the recess 10c is remote from the top foil 9. As shown in fig. 5(a), the recess 10c is formed at a circumferential position between the circumferential ends of the intermediate foil 10a (in the present disclosure, the central position of the intermediate foil 10a in the circumferential direction).

The recess 10c of the present disclosure has a bottom portion that is positioned radially outward of the planar portion 10b and is flat in the circumferential direction, and tapered portions that are positioned at both circumferential ends of the bottom portion and extend radially inward toward the planar portion 10 b. The interval between the pair of tapered portions increases from the radially outer side toward the radially inner side. As shown in fig. 4, the width of the bottom of the recesses 10c in the circumferential direction is longer than the width of the flat portions of the valleys 11b of the back foil 11a in the circumferential direction. Further, in the case where the mountain portions 11c and the valley portions 11b are each formed periodically with one peak, the width in the circumferential direction of the valley portion 11b in the present disclosure is a smaller interval of the intervals in the circumferential direction of the mountain portions 11c and the valley portions 11b of the back foil piece 11a than the radial position at the middle of the radial positions of the peaks of the mountain portions 11c and the peak portions of the valley portions 11 b.

As shown in fig. 4, the intermediate foil 10a has notches 27 (second notches) at both axial end edges. These notches 27 are formed in the recesses 10c of the intermediate foil 10 a. The notch 27 is formed at a circumferential position between both circumferential ends of the intermediate foil 10a (a central position of the intermediate foil 10a in the circumferential direction in the present disclosure). That is, the intermediate foil 10a has recesses in the axial direction at the circumferential positions on both axial end edges.

The notch 27 of the present disclosure is formed by cutting out a part of the bottom of the recess 10c formed between the planar portion 10b and the planar portion 10b toward the central portion of the intermediate foil 10a in the axial direction. The notch 27 is formed at a position corresponding to the first engagement groove 25 of the bearing housing 12 and the notch 26 of the back foil piece 11a, that is, at a position overlapping the first engagement groove 25 and the notch 26 in the circumferential direction. In other words, the notch 27 is disposed at the same position as the first engagement groove 25 and the notch 26 in the axial direction and the circumferential direction. The width (circumferential width) of the notch 27 is smaller than the width (circumferential width) of the first engagement groove 25 and is equal to the width (circumferential width) of the notch 26.

As shown in fig. 4, the engagement pin 30 is attached to the first engagement groove 25 of the bearing housing 12. The engagement pin 30 extends through the notch 26 and the notch 27 on the surface side (radially inward side) of the intermediate foil 10 (intermediate foil piece 10a) to the outside of the formation range of the notch 27 in the circumferential direction. The engagement pin 30 includes: an engaging portion 31 that engages with the first engaging groove 25 of the bearing housing 12; insertion portions 32 through which the slits 26 and 27 are inserted (or fitted); and a return portion 33 opposed to the surface side of the intermediate foil 10 (back foil 11).

The engaging portions 31 abut against the inner surfaces 25a of the first engaging groove 25 at both ends in the circumferential direction. The inner surfaces 25a of the first engagement grooves 25 face each other with a gap therebetween in the circumferential direction and extend in parallel in the radial direction. The engaging portion 31 is formed in a rectangular frame shape that contacts each inner surface 25a of the first engaging groove 25 with a predetermined width in the radial direction. Further, a region which becomes a gap in the circumferential direction exists between a portion where one circumferential side of the engagement portion 31 faces the inner surface 25a and a portion where the other circumferential side of the engagement portion 31 faces the inner surface 25 a. The engaging portion 31 is formed with a circular arc (curved shape) or the like so as to be smoothly separated from the inner surface 25 a. That is, the corner of the rectangular frame of the engaging portion 31 is curved.

The insertion portion 32 extends in parallel from the upper portion of the rectangular frame-shaped engagement portion 31 toward the radially inner side. The two insertion portions 32 are formed by the engagement portions 31 and are separated from each other. The insertion portion 32 and the engagement portion 31 are smoothly connected to each other with a circular arc (curved shape) or the like. The insertion portion 32 is in contact with the intermediate foil piece 10a or the back foil piece 11a in the axial direction.

The returning portions 33 are formed so as to be bent in directions opposite to each other in the circumferential direction from the distal end portions of the insertion portions 32 extending in parallel radially inward. That is, the engagement pin 30 includes a pair of return portions 33 extending in opposite directions in the circumferential direction. The pair of returning portions 33 are housed in the recesses 10c of the intermediate foil 10, and are located radially outward of the opening positions (upper ends, radially inner ends) of the recesses 10c as shown in fig. 5 b.

The engaging pin 30 is in contact with the inner surface 25a of the first engaging groove 25 in an accumulated state. The engaging pin 30 of the present disclosure is formed by bending one plate spring (elastic member) into a substantially C shape (bottle shape). The engaging portion 31 of the engaging pin 30 is engaged with the first engaging groove 25 in a slightly circumferentially tapered state. Accordingly, the engagement portion 31 is subjected to springback to open in the circumferential direction. Thereby, a frictional force is generated between the engaging portion 31 and the inner surface 25a of the first engaging groove 25, and the engaging pin 30 is held by the bearing housing 12. Further, the "stored state" of the present disclosure refers to an elastically compressed state.

Fig. 6 is a schematic view of the top foil 9 of the present disclosure after being unfolded, fig. 6(a) is a plan view, and fig. 6(b) is a front view.

As shown in fig. 6(a), the top foil 9 is a substantially 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 rolled into a cylindrical shape with both ends 9A in the circumferential direction intersecting each other. The top foil 9 is disposed to face the outer circumferential surface of the rotary shaft 1.

As shown in fig. 6(a), a first uneven portion 23a is formed on one of the two end portions 9A of the top foil 9 in the longitudinal direction and on one of the short sides thereof, and the first uneven portion 23a includes one convex portion 21a protruding in one of the longitudinal directions and two concave portions 22a formed on both sides of the convex portion 21a in the short side thereof. That is, one of the long sides of the top foil 9 in the longitudinal direction includes one convex portion 21a protruding in the longitudinal direction and a step extending to both sides of the convex portion 21a in the short side direction.

In addition, a second uneven portion 23b is formed on the other short side (the short side on the other side in the longitudinal direction) of the two end portions 9A of the top foil 9, and the second uneven portion 23b includes two convex portions 21b separated in the short side direction and one concave portion 22b located between the two convex portions 21 b. Alternatively, the top foil 9 includes a concave portion 22b recessed toward the other side in the longitudinal direction and a step portion located on both sides of the concave portion 22b in the short side direction on the short side of the other side in the longitudinal 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 value of the interval in the short side direction of the concave portion 22b is larger than the maximum value of the width in the short side direction of the convex portion 21 a. In the present disclosure, the longitudinal interval (depression depth) of the concave portion 22b and the longitudinal interval (length) of the convex portion 21a are constant in the longitudinal direction.

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 and the second concave-convex portion 23b overlap each other. Similarly, the concave portions 22a of the first concave-convex portion 23a are formed such that, when the top foil 9 is rolled into a cylindrical shape, the convex portions 21b pass through the concave portions 22a, respectively.

As shown in fig. 2, the convex portions 21a and 21b passing through the concave portions 22b and 22a are drawn out toward the bearing housing 12. Thus, the top foil 9 is wound into a cylindrical shape in a state where the protruding portions 21a and 21b (both ends) are drawn (extended) to the bearing housing 12 side (radially outward) and intersect each other. That is, when 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 each other. 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 continuous from one end surface 12b to the other end surface 12b in the axial direction is formed in the inner peripheral surface of the insertion hole 12a of the bearing housing 12. In the present disclosure, the through groove 13 is disposed between two pairs of the first engagement grooves 25 of the three pairs of the first engagement grooves 25. Further, the pair of first engagement grooves 25 radially face the through groove 13.

Fig. 7 is a schematic view of a main portion in the through groove 13 of the bearing housing 12 of the present disclosure, fig. 7(a) is an exploded perspective view, fig. 7(b) is a plan view, and fig. 7(c) is a sectional view as viewed along the line a-a. Fig. 8 is a sectional view taken along line B-B of fig. 7.

As shown in fig. 7(a) and 7(b), recessed portions 15 are formed in the through groove 13 on the side surfaces that face each other in the circumferential direction. The recessed portion 15 is formed over the entire length of the through groove 13. The cross-sectional shape of the recess 15 is a U-shape (semicircular arc shape). The recessed portion 15 is formed at a position (radially outward) deeper than the opening end of the through groove 13 in the radial direction, that is, the inner peripheral surface (insertion hole 12a) of the bearing housing 12. As shown in fig. 2, the convex portions 21a, 21b passing through the concave portions 22b, 22a are inserted into the concave portion 15.

As shown in fig. 7(a), an engaging member 16 is fitted into the through groove 13. The engaging member 16 is attached to the bearing housing 12 and engages with the top foil 9. As shown in fig. 7a to 7 c, the engaging member 16 has a rod-shaped (quadrangular prism-shaped) base 17 accommodated in the through groove 13, and two partition pieces 19 formed on the base 17. The partition piece 19 protrudes from the base portion 17 toward the inner peripheral side (radially inward). The base 17 is housed over the entire length of the through groove 13. The base 17 is housed in the through groove 13 in a state where its upper surface (the surface on the partition piece 19 side) is slightly depressed from the opening of the through groove 13(a state located radially outward). That is, the radial foil bearing 3 has a step between the inner peripheral surface (the insertion hole 12a) of the bearing housing 12 and the surface facing the inner periphery of the base portion 17, which step faces radially outward when viewed from the inner peripheral surface of the bearing housing 12. Further, a step may be provided between the inner circumferential surface of the bearing housing 12 and the surface of the partition wall piece 19 facing the inner circumference, the step facing the inside in the radial direction when viewed from the inner circumferential surface of the bearing housing 12.

The corner 13c of the through-groove 13 of the present disclosure, which is a connecting portion of the side surface 13a and the bottom surface 13b, has a curved surface smoothly connecting the side surface 13a and the bottom surface 13 b. The surface of the engaging member 16 (the radially outer surface of the base 17) facing the bottom surface 14b of the through groove 13 is flat. As shown in fig. 8, the base 17 has a chamfered portion 17a facing the corner 13c of the side surface 13a and the bottom surface 13b of the through groove 13, and the bottom surface 13b and the base 17 can abut against each other. That is, the center of curvature C1 of the curved surface of the corner portion 13C exists in the space inside the through groove 13. The chamfered portion 17a is formed by rounding the corner of the base portion 17 in a quadrangular prism shape in cross-sectional view. The radius of curvature of the chamfered portion 17a may be equal to or larger than the radius of curvature of the corner portion 13 c. The chamfered portion 17a may be a slope obtained by obliquely cutting off the corner of the quadrangular prism-shaped base portion 17 in a cross-sectional view.

As shown in fig. 7(b) and 7(c), the partition wall pieces 19 are formed at two positions that approximately trisect the base portion 17 in the axial direction. As shown in fig. 7(c), the partition wall pieces 19 have the same height as the opening position of the through grooves 13 or a height to a degree slightly protruding radially inward from the opening position of the through grooves 13. The partition piece 19 has three second engagement grooves 20 formed in the axial direction by approximately trisecting the upper surface of the base 17.

The protruding portions 21a and 21b passing through the recessed portions 22b and 22a are engaged with the three second engaging grooves 20, respectively. As shown in fig. 2, the tip end portion thereof is inserted into the recess 15. The convex portions 21a, 21b are inserted into the concave portion 15, thereby suppressing the movement (rotation) of the top foil 9 in the circumferential direction. As a result, resistance acts on both end portions 9A of the top foil 9 in the circumferential direction.

The top foil 9 is tapered (inclined in the tangential direction of the top foil 9 wound in a cylindrical shape) toward both ends in the circumferential direction, and approaches the insertion hole 12a of the bearing housing 12. That is, the interval between the inner circumferential side surface of the top foil 9 and the center line of the insertion hole 12a is enlarged as going toward both ends in the circumferential direction. In other words, the interval between the top foil 9 and the inner peripheral surface of the insertion hole 12a gradually narrows as it goes to both ends of the top foil 9 in the circumferential direction. Similarly, the top foil 9 approaches the intermediate foil 10 described later in a wedge shape as it goes toward both ends in the circumferential direction. In other words, the interval between the top foil 9 and the intermediate foil 10 gradually narrows as it goes to both ends of the top foil 9 in the circumferential direction. Further, the protrusions 21a and 21b engage with the second engagement groove 20, thereby suppressing the top foil 9 from moving in the axial direction.

In the present embodiment, the first concave-convex portion 23a and the second concave-convex portion 23b are provided on the top foil 9, but the present disclosure is not limited to this configuration. The top foil may be provided with a first concave-convex portion and a second concave-convex portion at both ends in the circumferential direction, the first concave-convex portion may include at least one convex portion and one concave portion, the second concave-convex portion may include at least one convex portion and one concave portion, the convex portion of the first concave-convex portion may pass through the concave portion of the second concave-convex portion, and the convex portion of the second concave-convex portion may pass through the concave portion of the first concave-convex portion in a state where the top foil is rolled into a cylindrical shape so that the first concave-convex portion and the second concave-convex portion overlap each other. In this case, the structures of the through grooves 13 and the engaging members 16 may be appropriately changed according to the number of the convex portions and the concave portions provided in the first concave-convex portion and the second concave-convex portion. The number of convex portions and concave portions provided in the first concave-convex portion and the second concave-convex portion may be increased as compared with the present embodiment. For example, the first concave-convex portion may have two convex portions and three concave portions, and the second concave-convex portion may have three convex portions and two concave portions.

In the through groove 13 of the present embodiment, two recessed portions 15 are provided, but the present disclosure is not limited to this configuration, and other configurations may be used. For example, instead of the recessed portions 15, protruding pieces for locking both circumferential ends of the top foil may be provided at the opening ends of the through grooves 13.

Returning to fig. 6 b, the top foil 9 has a thin portion 24 formed on the side where the first uneven portion 23a is formed (on one short side) and the side where the second uneven portion 23b is formed (on the other short side), the thin portion having a thickness smaller (thinner) than the central portion between the two portions. As shown in fig. 2, the outer peripheral surface (the surface on the bearing housing 12 side) of these thin portions 24 is recessed and made thinner than the outer peripheral surface of the central portion. That is, the outer peripheral side surface of the top foil 9 has a step from the central portion toward the inner peripheral side at both end sides.

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

Returning to fig. 3, the cover 50 is attached to each of the two axial end surfaces 12b of the bearing housing 12. The lid 50 is axially opposed to the engaging members 16 engaged with the both end portions 9A of the top foil 9. The cover 50 of the present disclosure covers at least a part of the open end 13A of the through groove 13 formed in the axial end surface 12b of the bearing housing 12. That is, in the present disclosure, the inner peripheral side of the through groove 13 is exposed from the inner peripheral edge of the cover 50 as viewed from the axial direction. Specifically, the cover 50 covers the through groove 13 radially outward of the recessed portion 15. Thereby, the cover 50 is axially opposed to the base 17 of the engaging member 16 shown in fig. 7 and 8. Alternatively, the lid 50 is disposed so as to overlap at least a part of the base 17 in the axial direction. That is, the cover 50 may axially face at least a part of the engaging member 16.

The cover 50 of the present disclosure is formed in a circular ring plate shape along the circumferential direction of the bearing housing 12. The diameter of the inner periphery of the lid 50 is larger than the diameter of the inner periphery of the bearing housing 12, and the diameter of the outer periphery of the lid 50 is smaller than the diameter of the outer periphery of the bearing housing 12. The lid 50 covers at least a part of the first engaging groove 25 that accommodates the engaging pin 30. That is, the cover 50 of the present disclosure is axially opposed to (overlapped with) the engaging portion 31 of the engaging pin 30. That is, the cover 50 and at least a part of the engaging portion 31 of the engaging pin 30 may be opposed to each other in the axial direction.

The lid 50 is screwed to a screw hole 52 (see fig. 2) formed in the bearing housing 12 in the vicinity of the first engagement groove 25 by a screw 51. The cover 50 of the present disclosure fixes the end surfaces 12b of the bearing housing 12 to positions approximately trisected in the circumferential direction thereof by screws. According to the above configuration, the engagement member 16 can be prevented from coming off the open end 13A of the through-groove 13 in the axial direction. Further, according to the above configuration, the engagement pin 30 can be prevented from coming off from the first engagement groove 25 in the axial direction.

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 pressed against the rotary shaft 1 by the back foil 11 (three back foil pieces 11a) via the intermediate foil 10 (three intermediate foil pieces 10a) to the rotary shaft 1 side. Further, in the present disclosure, since both end portions of the top foil 9 become the thin portions 24, a force (local preload) of fastening the rotary shaft 1 in these thin portions 24 is relaxed as compared with a 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 the rotation is accelerated gradually to rotate at a high speed. Then, as indicated by an arrow Q in fig. 2 and 3, the ambient fluid is introduced from one end side of each of the top foil 9, the intermediate foil 10, and the back 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 lubricating 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, and the ridge portion 11c expands, whereby the back foil piece 11a is moved on the bearing housing 12 in the circumferential direction thereof. That is, the back foil piece 11a (back foil 11) elastically supports す the top foil 9 via the intermediate foil 10, and therefore deforms in the circumferential direction thereof when receiving a load from the top foil 9, allowing the top foil 9 and the intermediate foil 10 to flex and support them.

As shown in fig. 5(b), the back foil piece 11a and the intermediate foil piece 10a have engaging pins 30 inserted through notches 26 and 27 formed at the axial end edges. The engagement pin 30 engages with the first engagement groove 25 of the bearing housing 12, and the engagement pin 30 is inserted through the notch 26 and the notch 27, thereby suppressing the rotation of the back foil piece 11a and the intermediate foil piece 10a in the circumferential direction.

Further, the engagement pin 30 abuts against the back foil piece 11a and the intermediate foil piece 10a, and movement of the back foil piece 11a and the intermediate foil piece 10a in the axial direction is also suppressed. In the engaging pin 30, a returning portion 33 (see fig. 4) is formed on the surface side of the intermediate foil piece 10a (back foil piece 11a) passing through the notch 26 and the notch 27, and the returning portion 33 prevents the back foil piece 11a and the intermediate foil piece 10a from coming off in the radial direction. Therefore, the back foil piece 11a and the intermediate foil piece 10a can be prevented from falling off the bearing housing 12.

When a fluid lubricating film is formed between the top foil 9 and the rotary shaft 1, the rotary shaft 1 and the top foil are in a non-contact state. During the transition period to this non-contact state, solid friction occurs between the rotating shaft 1 and the top foil 9. At this time, the coating applied to the surface of the top foil 9 suppresses abrasion with the rotating shaft 1. Thus, solid friction is generated between the rotating shaft 1 and the top foil 9, and the top foil 9 is to rotate in the circumferential direction together with the rotating shaft 1. However, both ends of the top foil 9 are inserted into the recesses 15 of the through-grooves 13 and therefore do not rotate in the circumferential direction.

The movement of the top foil 9 in the axial direction is suppressed by the lid 50 attached to the end face 12b of the bearing housing 12. The lid 50 is axially opposed to the engaging member 16 engaged with the top foil 9. Therefore, even if the engaging member 16 is moved in the axial direction, the engaging member 16 is caught by the inner peripheral edge portion (or the surface on the inner side in the axial direction) of the lid body 50, and the top foil 9 is prevented from coming off in the axial direction. That is, the top foil 9 of the present disclosure is disposed so as to overlap the partition wall piece 19 of the engaging member 16 in the axial direction. Further, since the rotation shaft 1 is inserted into the top foil 9 wound in a cylindrical shape, the top foil 9 does not fall off radially inward. Therefore, the top foil 9 can be suppressed from falling off the bearing housing 12.

As described above, the present disclosure includes: a bearing housing 12 having an insertion hole 12 a; a top foil 9 received in the insertion hole 12 a; and a lid body 50 attached to an end surface 12b of the bearing housing 12 extending in the axial direction of the insertion hole 12a, wherein the top foil 9 is wound into a cylindrical shape with both ends drawn out toward the bearing housing 12 side and intersecting each other, and the lid body 50 is attached to the bearing housing 12 and faces the engaging member 16 engaged with the top foil 9 in the axial direction, and thus the top foil 9 can be prevented from falling off the bearing housing 12.

As shown in fig. 7, a through groove 13 extending in the axial direction is formed in the bearing housing 12. The top foil 9 is rolled into a cylindrical shape, and is inserted in the axial direction along the through groove 13 in a state where both end portions 9A thereof are engaged with the second engagement grooves 20 of the engagement member 16. Unlike the engagement member of the related art described above (japanese patent application laid-open nos. 2013-217425), the engagement member 16 does not include a pair of leg portions for engaging with the bearing housing 12. Therefore, the engaging member 16 can be inserted straight into the through groove 13 in the extending direction in a state of being engaged with the top foil 9.

According to the above configuration, it is not necessary to attach the engaging member 16 to the bearing housing 12 prior to insertion of the top foil 9 as in the conventional art. Therefore, for example, it is not necessary to round the top foil 9 into a conical shape and insert the top foil 9 into the bearing housing 12 in the axial direction in a state of being formed into a circle smaller than the inner diameter of the insertion hole 12 a. Therefore, in the assembly work of the top foil 9, the skill of the operator is not required, the assembly time is shortened, and as a result, the assembly cost is reduced. In addition, the coating of the top foil 9 prevents damage to the coating due to friction between the two ends of the top foil 9 when the top foil 9 is assembled, and thus inhibits wear from progressing therefrom and reducing the bearing life.

Further, by allowing the engaging member 16 to be inserted straight into the through groove 13, the shape of the through groove 13 can be simplified as shown in fig. 8. That is, the corner portion 13c of the through groove 13 has a curved surface smoothly connecting the side surface 13a and the bottom surface 13 b. This curved surface corresponds to a tool fillet of the cutting through groove 13. In the prior art, in order to suppress the floating of the engaging member 16 due to the curved surface, the corner portion 13c is cut deeper than the bottom surface 13 b. However, if the engaging member 16 is made straight as disclosed in the present disclosure, the chamfered portion 17a is more easily formed than an engaging member having leg portions as in the above-described conventional technique (japanese patent application laid-open No. 2013-217425). This eliminates the need to deeply cut the corner portion 13c, and can reduce the processing cost of the through groove 13.

Fig. 9 is a diagram for explaining a manufacturing process of the engaging member 16 in the present disclosure.

The engaging member 16 can be manufactured through the steps shown in fig. 9(a) to 9(d), for example. First, as shown in fig. 9(a), an elongated plate material 60 of the engaging member 16 is cut. Next, as shown in fig. 9(b), a plurality of partition pieces 19 are cut from the plate material 60. Next, as shown in fig. 9(c), a chamfered portion 17a is formed in the longitudinal direction of the base portion 17 on the opposite side of the partition wall piece 19. Finally, the base portion 17 is cut every two partition pieces 19 in the longitudinal direction, whereby the engaging member 16 can be manufactured. Thus, the chamfered portion 17a is easily formed by preventing the leg portion from protruding to the side opposite to the partition wall piece 19 as in the above-described conventional technique (japanese patent laid-open publication No. 2013-217425). Therefore, the manufacturing cost of the engaging member 16 can be reduced.

While one embodiment of the present disclosure has been described above with reference to the drawings, the present disclosure is not limited to the above embodiment. The various shapes, combinations, and the like of the respective constituent members shown in the above-described embodiments are examples, and various modifications can be made based on design requirements and the like without departing from the scope of the present disclosure.

For example, the present disclosure can employ modifications as shown in fig. 10 to 13. In the following description, the same or equivalent components as those in the above-described embodiments are denoted by the same reference numerals, and the description thereof is simplified or omitted.

Fig. 10 is a front view of a radial foil bearing 3A according to a modification of the present disclosure.

The lid 50A shown in fig. 10 is axially opposed to both the ends of the top foil 9 and the engaging members 16 engaged with the ends. That is, the inner diameter of the lid 50A is substantially equal to the inner diameter of the bearing housing 12. The cover 50A covers substantially all of the open ends 13A of the through grooves 13 forming the end surfaces 12b of the bearing housing 12. According to this configuration, when the engaging member 16 is hooked on the inner end edge of the lid body 50A, both ends of the top foil 9 are also hooked on the inner end edge of the lid body 50A, and therefore, the movement of the top foil 9 in the axial direction can be reliably suppressed.

In the arrangement of the cover 50A shown in fig. 10, the engaging member 16 may be omitted. That is, even if the engaging member 16 is not provided, both ends of the top foil 9 are hooked on the inner end edge of the lid body 50A, and the top foil 9 can be prevented from coming off the bearing housing 12.

That is, in the above-described embodiment and modification, the covers 50 and 50A and the engaging member 16 face each other in the axial direction, but the present disclosure is not limited thereto. The following structure is also possible: the lid body is axially opposed to both ends of the top foil 9 and not axially opposed to the engaging members regardless of the presence or absence of the engaging members.

Fig. 11 is a bottom view of a radial foil bearing 3B according to a modification of the present disclosure. Fig. 12 is a front view showing the cover 50B before being attached to the bearing housing 12 shown in fig. 11.

The cover 50B shown in fig. 11 is attached to the bearing housing 12 by caulking. Specifically, the cover 50B includes: a circular ring portion 53 (see fig. 12) facing the end surface 12b of the bearing housing 12; and a caulking portion 54 extending from an outer edge of the annular portion 53 and facing the outer peripheral surface 12c of the insertion hole 12a of the bearing housing 12 in the radial direction. In other words, the caulking portion 54 extends from the outer edge of the annular ring portion 53 and faces the outer peripheral surface 12c of the bearing housing 12 located radially outside the insertion hole 12 a.

As shown in fig. 12, a plurality of caulking portions 54 (preferably three or more) are formed along the outer edge of the annular portion 53 at intervals in the circumferential direction. As shown in fig. 11, the caulking portion 54 extends in the axial direction along the outer peripheral surface 12c of the bearing housing 12 and is bent toward the inner peripheral side (radially inward). An annular groove 12c1 extending in the circumferential direction is formed in the outer circumferential surface 12c of the bearing housing 12, and the tip end of the caulking portion 54 is inserted into the annular groove 12c 1. In addition, a positioning groove 12B1 of the cover 50B is formed in the end surface 12B of the bearing housing 12. That is, the axial end face 12B of the bearing housing 12 facing the lid 50B has a step in the axial direction. On the other hand, an insertion portion 55 to be inserted into the positioning groove 12B1 is formed in the annular portion 53 of the lid 50B. The fitting portion 55 is a projection (recess) that is formed by pressing a part of the lid 50B to project (recess), and is fitted into the positioning groove 12B1, thereby suppressing rotation of the lid 50B in the circumferential direction.

According to this configuration, the cover 50B can be attached to the bearing housing 12 by caulking without using the plurality of screws 51. Therefore, the time for the attachment work of the lid 50 is shortened, resulting in a reduction in manufacturing cost.

As shown in fig. 12, a mounting flange 70 is connected to an end surface 12B of the bearing housing 12 to which the lid 50B is not attached. The mounting flange 70 has a plurality of mounting holes 71, and the mounting holes 71 are used to mount the radial foil bearing 3B to a mounting object, not shown. The mounting flange 70 is axially opposed to at least one of both ends of the top foil 9 and the engaging members 16 engaged with the both ends. That is, in this embodiment, the cover 50B is attached to only one end surface 12B of the bearing housing 12.

Fig. 13 is a schematic view of a main portion in the through groove 13C of the radial foil bearing 3C in one modification of the present disclosure, fig. 13(a) is an exploded perspective view, fig. 13(b) is a plan view, and fig. 13(C) is a cross-sectional view taken along line C-C.

The engaging member 16C shown in fig. 13 is formed in an L shape in a plan view (as viewed in a radial direction), and has a protruding portion 18 protruding in a circumferential direction from one side surface of one end portion in the axial direction of the base portion 17. In the through groove 13C, a storage groove 14 having an L shape in a plan view (in a radial direction) for storing the protruding portion 18 is formed. According to this configuration, the protruding portion 18 of the engaging member 16C engages with the receiving groove 14 of the through groove 13C at one end portion in the axial direction. Therefore, the cover 50 may be attached only to the one end surface 12b of the bearing housing 12 on the side where the receiving groove 14 is formed.

The engaging member 16C is not provided with the protruding portion 18, but the base portion 17 is formed to have a tapered shape in the longitudinal direction. The receiving groove 14 is not formed in the through groove 13C, but the through groove 13C itself is formed to be tapered in the axial direction. Thereby, the engaging member 16C is engaged with the through groove 13C in a wedge shape. Even in this case, the cover 50 is attached to only one end surface 12b of the bearing housing 12 on the side where the wedge is loose (the side where the circumferential width of the wedge is wide).

As another modification, for example, the cover 50 may not be annular as long as the engaging pin 30 is used for attaching the back foil 11 and the intermediate foil 10. That is, the cover 50 may be a rectangular or arc-shaped plate that covers at least a part of the open end 13A of the through-groove 13.

In the present disclosure, the embodiment having the intermediate foil 10 is exemplified, but the embodiment without the intermediate foil 10 may be adopted.

Industrial applicability

The present disclosure can be applied to a radial foil bearing supported so as to surround a rotating shaft.

Description of the symbols

3-radial foil bearing, 9-top foil, 9A-both ends, 12-bearing housing, 12 a-insertion hole, 12B-end face, 12C-outer peripheral face, 13-through groove, 13A-open end, 13A-side face, 13B-bottom face, 13C-corner, 16C-engagement member, 17 a-chamfered portion, 21 a-projecting portion (both ends), 21B-projecting portion (both ends), 50A, 50B-lid body, 53-circular ring portion, 54-riveted portion, C1-curvature center.