JP2016080103A - Radial foil bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radial foil bearing suppressing warpage of a top foil at both side end parts of a bearing, and preventing local abrasion of the top foil.SOLUTION: A radial foil bearing is externally inserted into a rotational shaft and supports the rotational shaft. The radial foil bearing includes a cylindrical top foil arranged oppositely to the rotational shaft, a back foil arranged to radial outside of the top foil, and a cylindrical bearing housing storing the top foil and the back foil in an internally inserted state. A thickness of a foil containing the top foil arranged between the back foil and the rotational shaft is made thinner at both side parts in a long direction of the rotational shaft than at a central part thereof.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a radial foil bearing.

  Conventionally, as a bearing for a high-speed rotating body, a radial bearing used by being extrapolated to a rotating shaft is known. As such a radial bearing, a thin plate-like top foil that forms a bearing surface, a back foil that elastically supports the top foil, a cylindrical bearing housing that houses the top foil and the back foil, Radial foil bearings with are well known. As a back foil of the radial foil bearing, a bump foil obtained by forming a thin plate into a corrugated plate is mainly used.

In such a radial foil bearing, in order to prevent the top foil and the bump foil from falling off from the bearing housing, one end portion (stop end portion) of the radial foil bearing is usually directly attached to the bearing housing by spot welding or a spacer is attached. It is indirectly fixed through.
In some foil bearings, an intermediate foil is inserted between the top foil and the back foil for the purpose of “improving the damping effect due to friction between the foils” and “reinforcing the rigidity of the top foil”. Similarly to the top foil, this intermediate foil is also arranged so as to go around the bearing housing, and one end thereof is fixed to the bearing housing by welding.

  Furthermore, as a radial foil bearing having such an intermediate foil, for example, in Patent Document 1, the structure of the conventional radial foil bearing is improved, and good performance as designed for the load capacity and dynamic characteristics of the bearing is obtained. What has been proposed is proposed.

JP 2014-37857 A

By the way, the pressure of the fluid lubrication film formed on the bearing surface of the radial foil bearing is high in the bearing center when viewed in the longitudinal section in the bearing length direction, that is, in the longitudinal section cut along the central axis of the bearing. It is low at the edge. This is because the pressure of the fluid lubricating film is substantially the same as the ambient pressure (for example, atmospheric pressure) at both end portions in the bearing length direction. For this reason, when the top foil is viewed in the longitudinal section in the longitudinal direction of the bearing, the center portion of the bearing is deformed so as to be concave, and the both end portions warp to the side approaching the rotating shaft.
However, since the thickness of the fluid lubrication film is as thin as about 10 μm, if the top foil warps at the bearing end, the contact between the top foil and the rotating shaft is likely to occur, and the contact location is localized. May wear out.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a radial foil bearing that suppresses warping of the top foil at both ends of the bearing and prevents local wear of the top foil. There is to do.

  A radial foil bearing of the present invention is a radial foil bearing that is externally attached to a rotating shaft to support the rotating shaft, and has a cylindrical top foil that is disposed to face the rotating shaft, and a diameter of the top foil. A back foil disposed on the outer side in the direction, and a cylindrical bearing housing that accommodates the top foil and the back foil in an inserted state, and is disposed between the back foil and the rotating shaft. The thickness of the foil including the top foil is characterized in that it is formed thinner than the central portion at both side portions in the length direction of the rotating shaft.

When the rotating shaft rotates, the center portion of the top foil sinks to the bump foil side due to the pressure of the fluid lubricating film as described above, and both end portions tend to warp to the rotating shaft side.
However, in the radial foil bearing of the present invention, the thickness of the foil including the top foil disposed between the back foil and the rotating shaft is thinner than the central portion on both sides in the length direction of the rotating shaft. Since it is formed, a gap is formed between the top foil and the back foil at both side portions. Therefore, until this gap is eliminated, no force is generated to push back both end portions of the top foil toward the rotating shaft, and warping of the both end portions of the top foil does not occur. Therefore, the thickness of the fluid lubricating film is suppressed from becoming extremely thin at both end portions of the top foil, and the both end portions of the top foil are maintained in a non-contact state with the rotating shaft even under high load.

Further, in the radial foil bearing, an intermediate foil is disposed between the top foil and the back foil, and both end portions of the intermediate foil are located inside from both end portions of the top foil. Is preferred.
With this configuration, the intermediate foil reliably forms a gap between the top foil and the back foil on both sides in the longitudinal direction of the rotating shaft, and thus prevents warping of both ends of the top foil. Is done.

Further, in the radial foil bearing, a plurality of intermediate foils are arranged between the top foil and the back foil, and at least one of the intermediate foils has both side ends of the top foil. It is preferable that each is located inside the both ends.
With such a configuration, a gap is surely formed on both sides in the longitudinal direction of the rotating shaft between the top foil and the back foil by at least one of the intermediate foils arranged in a stacked manner. Therefore, warping of the both end portions of the top foil is prevented.

In the radial foil bearing, it is preferable that both side portions of the top foil are formed thinner than the central portion.
With such a configuration, the surface on the back foil side of the top foil is particularly thinned to form a thin wall, so that it is ensured on both sides in the longitudinal direction of the rotating shaft between the top foil and the back foil. A gap is formed, and thus warping of both end portions of the top foil is prevented.

  According to the radial foil bearing of the present invention, the thickness of the foil including the top foil disposed between the back foil and the rotating shaft is formed to be thinner than the central portion at both side portions in the length direction of the rotating shaft. Therefore, it is possible to reduce the difference in the thickness of the fluid lubricating film between the central portion and both sides, and therefore, the thickness of the fluid lubricating film becomes extremely thin at both end portions of the top foil. It can suppress and can maintain the non-contact state of the both ends of a top foil and a rotating shaft also at the time of high load. Therefore, it is possible to apply a high load to the bearing by suppressing wear on both side end portions of the top foil, and therefore it is possible to use the bearing at a high load.

It is a mimetic diagram showing an example of a turbo machine to which a radial foil bearing concerning the present invention is applied. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows schematic structure of 1st Embodiment of the radial foil bearing which concerns on this invention, (a) is a side view of a radial foil bearing, (b) is a figure which shows the principal part of the internal peripheral surface of a bearing housing. . (A) is an exploded perspective view of a main part of the radial foil bearing shown in FIG. 2, (b) is a plan view showing a state in which a fixing tool is fitted in the through groove, and (c) is a fixing tool in the through groove. It is a longitudinal cross-sectional view which shows the state fitted. (A) is a principal part exploded perspective view of the radial foil bearing shown in FIG. 2, (b) is the sectional view on the AA line of FIG. 2 (a). (A) is the side view which shows the main part of Fig.2 (a) planarized typically, (b) is the BB arrow directional view of (a). (A) is a development view of the top foil, and (b) is a development side view of the top foil. It is a principal part enlarged side view of a radial foil bearing. (A) is a development view of one intermediate foil, (b) is a side view of one intermediate foil, (c) is a development view of the other intermediate foil, and (d) is a side view of the other intermediate foil. (A) is a longitudinal cross-sectional view of the bearing length direction for demonstrating the pressure distribution of a fluid lubricating film, (b) is a longitudinal cross-sectional view of 1st Embodiment of a radial foil bearing. It is a side view of 2nd Embodiment of the radial foil bearing which concerns on this invention. (A) is a developed view of the top foil, (b) is a developed side view of the long side of the top foil, and (c) is a developed side view of the short side of the top foil.

  Hereinafter, a radial foil bearing of the present invention will be described in detail with reference to the drawings. In the following drawings, the scale of each member is appropriately changed in order to make each member a recognizable size.

  FIG. 1 is a side view showing an example of a turbo machine to which a radial foil bearing of the present invention is applied. In FIG. 1, reference numeral 1 denotes a rotary shaft, 2 denotes an impeller provided at a tip portion of the rotary shaft, and 3 denotes a main shaft. It is a radial foil bearing which concerns on invention. Although only one radial foil bearing is shown in FIG. 1, normally, two radial foil bearings are provided in the axial direction of the rotating shaft 1 to constitute a support structure for the rotating shaft 1. . Accordingly, it is assumed that two radial foil bearings 3 are also provided in the present embodiment.

A thrust collar 4 is fixed to the rotary shaft 1 on the side where the impeller 2 is formed, and a thrust bearing 5 is disposed on each side of the thrust collar 4 so as to face the thrust collar 4. ing.
The impeller 2 is disposed in the housing 6 on the stationary side, and has a tip clearance 7 between the impeller 2 and the housing 6.
A radial foil bearing 3 is externally attached to the rotary shaft 1 on the center side of the thrust collar 4.

“First Embodiment”
FIGS. 2A and 2B are views showing a first embodiment of a radial foil bearing applied to the turbomachine having such a configuration. The radial foil bearing 3 according to the first embodiment is a cylindrical member that is externally attached to the rotating shaft 1 and supports the rotating shaft 1 as shown in FIG. A cylindrical top foil 10, two (a plurality) of intermediate foils 11 a and 11 b disposed on the radially outer side of the top foil 10, and a back disposed on the radially outer side of the intermediate foil 11 b. A foil 12 and a bearing housing 13 disposed on the radially outer side of the back foil 12 are provided.

  The bearing housing 13 is a metal cylindrical body that constitutes the outermost part of the radial foil bearing 3, and the back foil 12, the intermediate foil 11 b, the intermediate foil 11 a, and the top foil 10 are arranged inside from the outside (rotating shaft 1 Toward the side) in this order. In the bearing housing 13, a through groove 14 is formed on the inner peripheral surface thereof along the axial direction of the bearing housing 13. As shown in FIG. 2 (b), which shows the main part of the inner peripheral surface of the bearing housing 13, the inner peripheral surface of the bearing housing 13 is continuously extended from one end to the other end in the axial direction of the bearing housing 13. A through groove 14 is formed. The through groove 14 has the same length as the bearing housing 13 and has an opening width of about 0.4 mm to 0.6 mm and a depth of about 1.5 mm to 2.5 mm.

  Further, locking grooves 15 are formed at both ends of the through groove 14 so as to communicate with the through groove 14. As shown in FIG. 3A, which is an exploded perspective view of the main part of the radial foil bearing 3, the locking groove 15 is formed by cutting out both side surfaces of the bearing housing 13. Are formed continuously from the outer peripheral edge to the inner peripheral edge along the thickness direction. In the present embodiment, the width of the locking groove 15 is sufficiently wider than the width of the through groove 14 in order to ensure that the locking groove 15 communicates with the through groove 14.

  The through groove 14 is formed with a locking recess 16 on each of its inner side surfaces. These locking recesses 16 are groove-shaped ones that are formed along the length direction of the through-groove 14, and in the present embodiment, the U-shaped cross section having a maximum depth of about 0.2 to 0.3 mm. It is formed in a shape (semi-arc shape). Further, these locking recesses 16 are formed at a depth position within 1 mm from the opening side of the through groove 14, for example, from the inner peripheral surface of the bearing housing 13. Thereby, the latching recessed part 16 can latch the front-end | tip part of the convex part of the top foil 10, the intermediate foil 11a, and the intermediate foil 11b so that it may mention later.

  Here, in order to form the through groove 14 and the locking recess 16, wire cut electric discharge machining is preferably used. That is, when a continuous groove is formed from one end to the other end in the axial direction of the bearing housing 13 such as the through groove 14 or the groove-shaped locking recess 16, the outer shape of the cross-sectional shape is formed by wire-cut electric discharge machining. By moving the wire so that it can be traced, each groove can be formed easily and accurately. In particular, in this embodiment, the through groove 14 and the locking recesses 16 on both side surfaces thereof can be easily formed by a series of processes. In addition, the processing cost of the locking recess 16 can be kept sufficiently low.

  Moreover, since the groove | channel which continues from the outer peripheral surface side of the bearing housing 13 also to the inner peripheral surface side is formed also about the latching groove | channel 15, the process cost can be suppressed low enough by employ | adopting wire cut electric discharge machining. However, since the locking groove 15 does not particularly require the processing accuracy, it is possible to employ a cutting process using an end mill.

  A fixing tool 17 is fitted and locked in the through groove 14 and the locking groove 15. The fixture 17 is shown in FIG. 3A, FIG. 3B which is a plan view of the through groove 14 and the fixture 17, and FIG. 3C which is a longitudinal sectional view of the through groove 14 and the fixture 17. As described above, a rod-like (quadrangular columnar) base portion 18 that is fitted in and accommodated in the through groove 14, and a pair of folding pieces 19 that are formed at both ends of the base portion 18 and are engaged with the engagement groove 15. It has a piece 19 and two partition pieces 20 which are formed at the center of the base 18 and protrude on the opposite side of the bent piece 19.

  The base 18 is formed to have a height of about 0.5 to 1.5 mm, and is formed so that the upper surface (surface on the partition piece 20 side) sinks about 1 mm from the opening of the through groove 14. The bent piece 19 is formed to have a length substantially equal to the distance between the bottom surface of the through groove 14 and the outer peripheral surface of the bearing housing 13, thereby contacting the locking groove 15 with a sufficient area and bearing. It does not protrude from the outer peripheral surface of the housing 13.

  Here, a restricting portion is formed by the bent piece 19, the bent piece 19, and the locking groove 15 and the locking groove 15 provided in communication with the through groove 14. That is, the pair of bent pieces 19 and the bent pieces 19 are respectively engaged with the engaging grooves 15 provided at both ends of the through groove 14, and thus the pair of bent pieces 19 and the bent pieces 19 are used as the bearing housing 13. As a result, the fixture 17 is restricted from moving in the length direction of the through groove 14 (in the axial direction of the bearing housing 13), and does not substantially move except for the clearance.

  As shown in FIGS. 3B and 3C, the partition piece 20 is formed at two positions that divide the base portion 18 into approximately three equal parts and thus divide the through groove 14 into almost three equal parts. It is formed to the same level as the opening position of the through groove 14 or to protrude slightly from the through groove 14. For example, it may project about half the height of the back foil 12. The partition groove 20 divides the through groove 14 into three substantially in the length direction thereof, so that three engagement grooves 21 are formed in the through groove 14 by the fixing tool 17.

That is, the three engaging grooves 21 can be easily formed by fitting the fixing member 17 into the locking groove 15 and the through groove 14 from the inner peripheral surface side of the bearing housing 13 and locking them. These engaging grooves 21 have a depth of about 1 mm, and the locking recesses 16 are opened on both inner side surfaces thereof.
The fixture 17 can be formed, for example, by wire-cutting a metal plate made of stainless steel having a thickness of about 3 to 4 mm.

  Further, as shown in FIGS. 2 (a) and 4 (a), a holding groove 22 is formed on the inner peripheral surface of the bearing housing 13 between both end surfaces, that is, between both side surfaces along the axial direction. Yes. The holding groove 22 has a width that is sufficiently narrow, for example, 1 mm or less, preferably 0.5 mm or less, corresponding to the width (thickness) of the restrictor 30 described later. The holding groove 22 having such a width can be satisfactorily formed by, for example, wire cut electric discharge machining. Further, the holding groove 22 is formed with a depth sufficiently shallower than the thickness of the bearing housing 13.

  In the present embodiment, as shown in FIG. 2A, such holding grooves 22 are respectively formed at positions where the inner peripheral surface of the bearing housing 13 is substantially divided into three in the circumferential direction. Further, the through groove 14 is disposed between two holding grooves 22 of the three holding grooves 22 and the holding grooves 22.

  4A and 4B, the bearing housing 13 communicates with the holding groove 22 at the central portion in the length direction of the holding groove 22, that is, at the central portion in the axial direction of the bearing housing 13. As shown in FIGS. A locking hole 23 is formed. The locking hole 23 is formed by a through hole penetrating from the inner peripheral surface of the bearing housing 13 to the outer peripheral surface. The locking hole 23 formed of the through hole has a circular or oval opening shape, and is formed by drilling with a drill or the like from the outer peripheral surface of the bearing housing 13 toward the inner peripheral surface.

  By forming the hole 23 by drilling or the like in this way, the inner diameter of the locking hole 23 corresponding to the width direction of the holding groove 22 is larger than the width of the holding groove 22 described above. However, the inner diameter of the locking hole 23 corresponding to the length direction of the holding groove 22 is the width of the locking projection 32 described later (the long side direction of the rod-shaped portion 31 described later) as shown in FIG. Accordingly, the movement of the restricting tool 30 in the axial direction is restricted by engaging the engaging protrusion 32 in the engaging hole 23.

  A restricting tool 30 is locked to the holding groove 22 communicating with the locking hole 23. As shown in FIGS. 4 (a) and 4 (b), the restricting tool 30 includes a thin plate-like (quadrangular columnar) rod-like portion 31 embedded in the holding groove 22, and a latch formed on one side of the rod-like portion 31. It is formed to have a convex portion 32 and a pair of engaging convex portions 33 and engaging convex portions 33 formed on the other side surface of the rod-shaped portion 31, that is, the side surface opposite to the one side surface. .

  The locking protrusion 32 is formed and arranged at a position corresponding to the locking hole 23 of the bearing housing 13, that is, at the axial center of the bearing housing 13 (the center in the length direction of the holding groove 22). Further, as described above, the locking protrusion 32 is formed such that the length along the length direction of the holding groove 22 is substantially equal to the inner diameter of the locking hole 23 in the axial direction. Therefore, the locking projection 32 is inserted through the locking hole 23 and locked so as to be almost immovable in the length direction of the holding groove 22. Thereby, the movement of the restricting tool 30 in the axial direction of the bearing housing 13 is restricted.

  Here, the axially central portion of the bearing housing 13 does not mean the axial center position of the bearing housing 13, but excludes both side surfaces (both end surfaces) of the bearing housing 13 and the vicinity thereof. It means the entire central part. Therefore, the locking hole 23 may be formed and arranged at a position deviated to one or the other from the center without being arranged at the center of the bearing housing 13 in the axial direction. In that case, the locking projections 32 of the restricting tool 30 are also formed and arranged so as to be offset from the center in the length direction of the rod-shaped portion 31 corresponding to the locking holes 23.

The engaging projections 33 are formed on both ends of the rod-shaped portion 31 so as to protrude to the opposite side of the locking projection 32.
The restricting tool 30 having such a configuration is embedded in the holding groove 22 in a state where the locking projection 32 is locked in the locking hole 23 of the bearing housing 13 as described above. At that time, the pair of engaging protrusions 33 and the engaging protrusions 33 protrude above the inner peripheral surface of the bearing housing 13 at both ends of the holding groove 22.

  As shown in FIG. 2A, the back foil 12 is formed of a foil (thin plate) and elastically supports the intermediate foil 11b, the intermediate foil 11a, and the top foil 10. Examples of such a back foil 12 include a bump foil, a spring foil described in JP 2006-57652 A, JP 2004-270904 A, and the like, JP 2009-299748 A, and the like. A back foil or the like is used. In the present embodiment, a bump foil is used as the back foil 12. However, it goes without saying that the spring foil or the back foil may be used as the back foil of the present invention.

  In the present embodiment, the back foil 12 (bump foil) is constituted by three (plural) back foil pieces 12a arranged along the circumferential direction of the top foil 10, the intermediate foil 11a, and the intermediate foil 11b. These back foil pieces 12a are formed such that a foil (thin plate) is formed into a corrugated plate shape, and the side surfaces are formed into a substantially arc shape as a whole, and all three are formed in the same shape and size. Therefore, these back foil pieces 12 a are arranged by dividing the inner peripheral surface of the bearing housing 13 into approximately three parts.

  Moreover, although these back foil pieces 12a are arranged with a certain amount of gaps at positions where the through-grooves 14 are sandwiched, other end portions are arranged close to each other at other positions. With such a configuration, the three back foil pieces 12 a are formed in a substantially cylindrical shape as a whole and are arranged along the inner peripheral surface of the bearing housing 13.

  Further, the back foil piece 12a formed in the corrugated plate shape as described above is formed in a circumferential direction of the bearing housing 13 as shown in FIG. A flat valley portion 12b in contact with the bearing housing 13 and a curved peak portion 12c in contact with the intermediate foil 11b are alternately formed. As a result, the back foil piece 12a elastically supports the top foil 10 via the intermediate foil 11b and the intermediate foil 11a, particularly by the crest 12c in contact with the intermediate foil 11b. Further, a fluid passage is formed by the crests 12 c and the troughs 12 b in the axial direction of the radial foil bearing 3.

  Further, as shown in FIG. 5B, which is a view taken along the line B-B of FIG. 5A, these back foil pieces 12a have respective circumferential center portions (along the circumferential direction of the bearing housing 13). Engagement notches 12d are formed in the peripheral edge portions on both sides of the central portion in the direction. The engagement notch 12d is formed in the valley portion 12b of the back foil piece 12a as shown in FIG. 5A, and the valley portion 12b composed of a flat portion formed between the mountain portion 12c and the mountain portion 12c is formed. These are formed by cutting out in a rectangular shape from the peripheral edge to the inside.

  The engagement notch 12d is formed at a position corresponding to the engagement convex portion 33 of the restricting tool 30 provided in the bearing housing 13, that is, a position overlapping with the engagement convex portion 33. The engaging projections 33 are formed to have substantially the same vertical and horizontal width so as to engage with the mating projections 33. Specifically, the lateral width along the circumferential direction of the bearing housing 13 is about 0.2 mm to 0.4 mm, and the vertical width along the axial direction is about 1 mm to 2 mm.

In addition, about formation of the engagement notch 12d, it is preferable to perform foil by an etching process or an electrical discharge process so that a burr | flash does not generate | occur | produce and the distortion by a process does not arise. That is, it is preferable to form the back foil piece 12a by forming the engagement notch 12d in the foil by etching process or electric discharge process and then performing press molding to form the peak part 12c or the valley part 12b.
Under such a configuration, the engagement notch 12d of the back foil piece 12a is engaged with the engagement convex portion 33 of the restricting tool 30 as shown in FIGS. 4 (b) and 5 (a). Yes.

  In this way, the engagement notch 12d of the back foil piece 12a is engaged with the engagement convex portion 33 extending to the upper side of the rod-shaped portion 31, and three back foils are formed on the inner peripheral surface of the bearing housing 13 in this state. Since the piece 12a is arranged, the restricting tool 30 is prevented from falling off from the bearing housing 13 particularly when the rod-like portion 31 is pressed by the back foil piece 12a.

  As shown in FIG. 2 (a), the top foil 10 is wound in a cylindrical shape along the inner surface of the back foil 12 composed of three back foil pieces 12a, and is formed on one end side. 41 a and a convex portion 41 b formed on the other end side are arranged so as to be engaged with the engaging concave portion 16 in the through groove 14 formed in the bearing housing 13, respectively. As shown in FIG. 6A, which is a developed view of the top foil 10, a substantially rectangular metal foil having a long side in the bearing circumferential direction and a short side in the bearing length direction is a side view thereof. It is formed by being wound in a cylindrical shape in the direction of the arrow in FIG. 6B (long side length direction: bearing circumferential direction).

  As shown in FIG. 6A, the top foil 10 has a first uneven portion 43a having one convex portion 41a and two concave portions 42a on one side (short side). And a second uneven portion 43b having two convex portions 41b and one concave portion 42b on the other side (short side) opposite to the one side (short side). Is formed. The concave portion 42b of the second concave-convex portion 43b is formed corresponding to the convex portion 41a of the first concave-convex portion 43a, and the concave portion 42a of the first concave-convex portion 43a corresponds to the convex portion 41b of the second concave-convex portion 43b. Is formed.

  That is, when the top foil 10 is wound in a cylindrical shape so that the first uneven portion 43a and the second uneven portion 43b overlap with each other, the concave portion 42b of the second uneven portion 43b is formed in the concave portion 42b. Is formed to pass through. Similarly, the concave portion 42a of the first uneven portion 43a is formed so that the convex portion 41b passes through the concave portion 42a when the top foil 10 is wound in a cylindrical shape. The convex portions 41 a and the convex portions 41 b are formed so that the width thereof substantially coincides with the length of the engaging groove 21 formed by the through groove 14 and the fixture 17. .

  The concave portion 42b and the convex portion 41a and the convex portion 41b that have passed through the concave portion 42a are pulled out to the bearing housing 13 side as shown in FIG. It can be stopped. In this embodiment, as shown in FIG. 7 which is an enlarged view of the main part of FIG. 2A, the tips of the convex portions 41a and 41b are respectively inserted into the engaging grooves 21 in the through grooves 14. After being engaged, they are further put into the locking recess 16 and locked there. As a result, the top foil 10 is arranged such that its movement in the circumferential direction is restricted and the amount of movement is small.

  In other words, the convex portions 41 a and the convex portions 41 b are disposed so that the distal ends thereof are in contact with the inner surface of the locking recess 16 without the tips of the protruding portions being strongly abutted against the inner surface of the locking recess 16. Therefore, during the steady operation of the rotating shaft 1, the convex portion 41 a and the convex portion 41 b do not receive a large reaction force from the locking concave portion 16 or the engaging groove 21, so that the top foil 10 is not distorted. Further, when an unexpected external force is applied to the radial foil bearing 3 due to the shaft shake of the rotating shaft 1, the top foil 10 does not rotate inside the bearing housing 13, and the bearing housing 13 and the rotating shaft 1 are further rotated. It is designed not to fall out.

  That is, when an unexpected external force is applied, the convex portion 41a and the convex portion 41b are firmly locked to the inner surface of the locking concave portion 16, so that the convex portion 41a and the convex portion 41b are detached from the locking concave portion 16. Further, the top foil 10 is not disengaged from the engagement groove 21. Therefore, the top foil 10 rotates or is excessively deformed, and the convex portions 41a and 41b come out of the concave portions 42b and 42a, so that the top foil 10 Is prevented from falling off from the bearing housing 13.

  Further, the protrusion 41 a and the protrusion 41 b are restricted from moving in the axial direction by the partition piece 20 of the fixture 17 that defines the engagement groove 21. That is, both sides of the convex portion 41a are restricted by the partition piece 20, so that the movement in the axial direction is restricted on the first uneven portion 43a side where the convex portion 41a is formed. In addition, the two convex portions 41b are respectively regulated on the one side by the partition piece 20 and are regulated in opposite directions, so that the second concave and convex portion 43b side on which the two convex portions 41b are formed is also a shaft. Movement in the direction is restricted. Thus, the top foil 10 is prevented from jumping out from the bearing housing 13 because the movement of the bearing housing 13 in the axial direction is restricted.

  Moreover, as shown in FIG.6 (b), the top foil 10 is the side (one side) in which the 1st uneven part 43a was formed, and the side (the other side) in which the 2nd uneven part 43b was formed. In addition, a thin portion 44 that is thinner (thin) than the central portion between them is formed. As shown in FIG. 2A, these thin portions 44 are thinned (thinned) so that the outer peripheral surface (the surface on the bump foil 12 side) is recessed from the outer peripheral surface of the central portion. Is formed.

In order to form the thin portion 44, for example, both end portions of the top foil 10 are controlled to an order of 10 μm by etching to form a desired thickness (thinness). Specifically, when the thickness of the top foil 10 is 100 μm, the thickness of the thin portion 44 is set to about 80 μm. In such an etching process, the stress generated in the top foil 10 is extremely small as compared with the bending process, and therefore the top foil 10 is hardly distorted.
Moreover, the circumferential length L of the thin portion 44 shown in FIG. 6B is equal to one of the through groove 14 and the peak of the end of the bump foil 12 (back foil) as shown in FIG. The length corresponds to the minute.

  Since the thin portions 44 are formed at both ends of the top foil 10 as described above, these both ends (thin portions 44) are easily elastically deformed, and therefore these both ends are curved surfaces constituting the inner peripheral surface of the bearing housing 13. It becomes a curved surface following. As a result, the top foil 10 hardly generates a force (local preload) for tightening the rotating shaft 1 at both ends thereof.

  Further, since the outer peripheral surface of both end portions of the top foil 10 is thinned so as to be recessed from the outer peripheral surface of the central portion to form the thin portion 44, the back foil 12 that supports the outer peripheral surface side thereof is formed. A gap is formed between one and the other end of the mountain. Thereby, in the thin part 44, the force (local preload) which fastens the rotating shaft 1 is reliably prevented. The circumferential length L of the thin wall portion 44 is a length corresponding to up to about three ridges at the end of the through groove 14 and the bump foil 12 instead of the example shown in FIG. It may be good.

  The intermediate foil 11a and the intermediate foil 11b are arranged between the back foil 12 (bump foil) and the top foil 10 as shown in FIG. 2A, and the intermediate foil 11a is arranged on the top foil 10 side. The foils 11b are arranged and stacked on the back foil 12 side. The intermediate foil 11 a and the intermediate foil 11 b are formed by being wound in a cylindrical shape along the inner surface of the back foil (bump foil) 12, similarly to the top foil 10.

  The intermediate foil 11a is a side view of a substantially rectangular metal foil having a long side in the bearing circumferential direction and a short side in the bearing length direction, as shown in FIG. 8 (b) is formed by being wound in a cylindrical shape in the arrow direction (long side length direction: bearing circumferential direction). In the intermediate foil 11a, the developed planar shape has a short side shorter than the planar shape of the top foil 10 indicated by a two-dot chain line in FIG. That is, in the intermediate foil 11 a, both side ends in the short side direction that is the bearing length direction (the length direction of the rotating shaft 1) are located on the inner side than the both side ends of the top foil 10. In other words, the intermediate foil 11a is formed to have a short length in the short side direction by cutting off both side portions from the planar shape of the top foil 10 respectively.

  In the intermediate foil 11a, the length M1 from which each side portion is cut off as compared with the top foil 10 is about 0.05M or more and 0.3M or less, where M is the length in the short side direction of the top foil 10. . In the intermediate foil 11a, the length M1 is made shorter than the top foil 10 and the back foil 12 (back foil piece 12a), so that the thickness between the back foil 12 and the top foil 10 is reduced. The both side portions in the length direction of the rotating shaft 1 are formed thinner than the central portion.

Further, as described above, the thickness of the intermediate foil 11a is about 30 μm when the thickness of the top foil 10 is 100 μm.
As with the top foil 10, the intermediate foil 11a has a first uneven portion 45a formed on one end side and a second uneven portion 45b formed on the other end side. And the convex part 46a and the convex part 46b in each uneven | corrugated | grooved part are each engaging with the said engaging groove 21 with the convex part 41a and the convex part 41b of the top foil 10, respectively.

  As shown in FIG. 8C, which is a developed view of the intermediate foil 11b, a substantially rectangular metal foil having a long side in the bearing circumferential direction and a short side in the bearing length direction is a side view thereof. 8 (d) is formed by being wound in a cylindrical shape in the direction of the arrow (long side length direction: bearing circumferential direction). The intermediate foil 11b is formed such that the developed planar shape is the same as the planar shape of the top foil 10 indicated by a two-dot chain line in FIG.

Also, the thickness of the intermediate foil 11b is about 30 μm when the thickness of the top foil 10 is 100 μm as described above.
Similarly to the top foil 10, the intermediate foil 11b is also formed with a first uneven portion 47a on one end side and a second uneven portion 47b on the other end side. And the convex part 48a and convex part 48b in each uneven | corrugated | grooved part are each engaged with the said engaging groove 21 with the convex part 41a and convex part 41b of the top foil 10, and the convex part 46a and convex part 46b of the intermediate foil 11a, respectively. ing.

  As described above, the intermediate foil 11a and the intermediate foil 11b are disposed so as to overlap each other between the top foil 10 and the back foil 12, so that the thickness between the back foil 12 and the top foil 10, that is, the intermediate foil 11a. And the total thickness of the intermediate foil 11b is formed thinner on both sides than the central portion in the length direction of the rotating shaft 1. Thereby, the thickness of the foil including the top foil 10 disposed between the back foil 12 and the rotating shaft 1 is formed thinner than the central portion at both side portions in the length direction of the rotating shaft 1.

Next, the operation of the radial foil bearing 3 having such a configuration will be described.
When the rotary shaft 1 is stopped, the top foil 10 is in close contact with the rotary shaft 1 by being urged by the back foil 12 to the rotary shaft 1 side through the intermediate foil 11b and the intermediate foil 11a. In the present embodiment, since both end portions of the top foil 10 are thin portions 44, a force (local preload) for tightening the rotating shaft 1 hardly occurs in the thin portions 44.

  When the rotary shaft 1 is started in the direction of the arrow P in FIG. 2A, it starts rotating at a low speed first, and then gradually accelerates and rotates at a high speed. 2A, one end of the top foil 10, the intermediate foil 11a, and the intermediate foil 11b (the convex portion 41a side, the convex portion 46a side, and the convex portion 48a side) and one end of the back foil 12 are indicated. Ambient fluid is drawn in between the two and flows between the top foil 10 and the rotary shaft 1. Thereby, a fluid lubricating film is formed between the top foil 10 and the rotating shaft 1.

  At that time, in a transient state until the fluid lubrication film is formed, solid friction is generated between the rotary shaft 1 and the top foil 10, and this becomes a resistance at the time of starting. However, as described above, no preload is generated at both ends of the top foil 10, and the top foil 10 on the side into which the surrounding fluid flows is a thin-walled portion 44 that is soft and rotates with the top foil 10. Since the space between the shaft 1 and the shaft 1 is easily opened, a fluid lubricating film is formed at an early stage when the rotating shaft 1 is started. When the top foil 10 is pressed against the back foil 12 by the pressure of the fluid lubricating film, the rotating shaft 1 rotates in a non-contact state with respect to the top foil 10.

  At this time, the pressure of the fluid lubrication film is high in the bearing center when viewed in the longitudinal section in the bearing length direction shown in FIG. 9A, that is, in the longitudinal section cut along the central axis of the bearing. It is low at the edge. This is because the pressure of the fluid lubricating film is substantially the same as the ambient pressure (for example, atmospheric pressure) at both end portions in the bearing length direction. For this reason, as shown by a two-dot chain line in FIG. 9A, the center portion of the top foil 10 sinks toward the back foil 12 and tends to warp to the side closer to the rotating shaft at both end portions. .

  However, in the present embodiment, as shown in FIG. 8A, the intermediate foil 11a has a shape in which both sides are cut off from the planar shape of the top foil 10 and the length in the short side direction is shortened. As shown in FIG. 9B, the thickness of the foil including the top foil 10 disposed between the back foil 12 and the rotating shaft 1 has both side portions in the length direction (bearing length direction) of the rotating shaft 1. In FIG. 2, it is formed thinner than the central portion. Accordingly, a gap S is generated between the top foil 10 and the back foil 12 at the both side portions, and until the gap S disappears, there is no force to push back both end portions of the top foil 10 toward the rotating shaft 1 side. 10 does not warp at both ends.

  Further, even if both end portions of the top foil 10 are pushed into the back foil 12 and the gap S disappears, the spring reaction force by the back foil 12 is weakened by the gap S compared to the center portion. As a result, both side ends of the top foil 10 are difficult to get up. Thereby, it is suppressed that the thickness of the fluid lubricating film becomes extremely thin at both end portions of the top foil 10, and both end portions of the top foil are maintained in a non-contact state with the rotating shaft even under high load. .

  In such a radial foil bearing 3, the thickness of the foil including the top foil 10 disposed between the back foil 12 and the rotating shaft 1 is set at the center on both sides in the length direction of the rotating shaft 1. Therefore, the difference in film thickness of the fluid lubrication film between the central part and both side parts can be reduced. Therefore, the thickness of the fluid lubrication film at the both end parts of the top foil 10 can be reduced. Is suppressed from becoming extremely thin, and the non-contact state between the both end portions of the top foil 10 and the rotary shaft 1 can be maintained even during a high load. Therefore, it is possible to apply a high load to the bearing by suppressing wear on both side end portions of the top foil 10, and therefore it is possible to use the bearing at a high load.

  Further, as shown in FIG. 9 (b), two (plural) intermediate foils 11a and 11b are arranged between the top foil 10 and the back foil 12, and one intermediate foil 11a is disposed on both sides thereof. Since the end is located inside the both side ends of the top foil 10, the gap S can be surely formed between the top foil 10 and the back foil 12 on both sides in the length direction of the rotating shaft 1. Therefore, it is possible to satisfactorily prevent warping of both side end portions of the top foil 10.

  Further, since both side ends of the intermediate foil 11a positioned on the top foil 10 side are positioned inside the both side ends of the top foil 10, the intermediate foil 11a is also formed as an intermediate foil 11b with respect to the top foil 10. On the other hand, stress concentration is less likely to occur due to the surface contact, and therefore the designed bearing performance can be exhibited without adversely affecting the load capacity of the bearing.

  Further, since the intermediate foil 11a and the intermediate foil 11b are provided between the top foil 10 and the back foil 12, when the shaft 1 vibrates during rotation, the associated film pressure fluctuations are caused by the top foil 10. It is transmitted to the back foil 12 through the intermediate foil 11a and the intermediate foil 11b. At this time, the top foil 10 is caused to be slightly bent (varied according to the load) due to the load fluctuation, and thereby, between the top foil 10 and the intermediate foil 11a, between the intermediate foil 11a and the intermediate foil 11b, Furthermore, “slip” occurs between the intermediate foil 11 b and the back foil 12. This "slip" causes energy dissipation due to friction and attenuates membrane pressure fluctuations. That is, an attenuation effect is obtained. Therefore, the axial vibration can be suppressed by the damping effect, and the axial vibration can be easily settled. Furthermore, the rigidity of the top foil 10 can be reinforced by the intermediate foil 11a and the intermediate foil 11b. Therefore, the dynamic characteristics (rigidity and damping) of the radial foil bearing 3 can be sufficiently enhanced.

In the first embodiment, two intermediate foils are used, and one of the intermediate foils 11a is formed such that both side ends thereof are located inside the both side ends of the top foil 10, respectively. Both foils may be formed such that both side edges are located inside the both side edges of the top foil 10.
Further, without using two intermediate foils, only one or three or more layers may be used. When only one intermediate foil is used, the both sides of the intermediate foil are naturally formed so as to be located inside the both sides of the top foil 10. When three or more intermediate foils are used in an overlapping manner, at least one of the intermediate foils is formed such that both side ends thereof are located inside the both side ends of the top foil 10.

  Further, as shown in FIGS. 8A and 8C, the intermediate foil is formed in a rectangular shape by cutting off the short side without forming an uneven portion on both sides (short side). May be. In that case, the intermediate foil is arranged without engaging with the engaging groove 21. However, since the intermediate foil is sandwiched between the back foil 12 and the top foil 10 and held by friction, the bearing housing can be used even when an axial displacement occurs between the intermediate foil and the bearing housing 13. Jumping out of 13 is prevented.

“Second Embodiment”
Next, a second embodiment of the radial foil bearing of the present invention will be described. FIG. 10 is a view showing a second embodiment of the radial foil bearing applied to the turbomachine shown in FIG. 1, and reference numeral 50 in FIG. 10 denotes a radial foil bearing. The radial foil bearing 50 is different from the radial foil bearing 3 shown in FIG. 2A in that the shape of the top foil 51 and the intermediate foil are not provided.

  That is, as shown in FIG. 10, the radial foil bearing 50 of the present embodiment is not provided with the intermediate foil 11 a and the intermediate foil 11 b shown in FIG. 2A, and therefore the top foil 51 directly on the back foil 12. Has been placed.

  The top foil 51 has a flat shape developed as shown in FIG. 11 (a), which is the same as the top foil 10 shown in FIG. 6 (a). Accordingly, the first uneven portion 43a and the second foil It has an uneven portion 43b. Further, as shown in FIG. 11B, which is a developed side view of the long side of the top foil 51, the side surface along the circumferential direction of the bearing is also formed in the same manner as the top foil 10.

  However, on the short side of the top foil 51, as shown in FIG. 11C, which is a developed side view thereof, both sides of the top foil 51 (both sides in the length direction of the rotating shaft 1) are reduced in thickness. Thus, the thinned portion 52 is thinner than the central portion. That is, assuming that the thickness of the central portion of the top foil 51 is 100 μm, the surface on the back foil 12 side on both sides thereof is reduced by about 20 μm to 30 μm to be formed to a thickness of about 70 μm to 80 μm. The thinned portion 52 can be formed in the same manner as the thin portion 44, that is, simultaneously with the thin portion 44, for example, by etching.

  Further, the width M2 of the thinned portion 52 in the length direction of the rotating shaft 1 is the same as the length of M1 shown in FIG. That is, when the length in the short side direction (the length direction of the rotating shaft 1) of the top foil 51 is M, the width M2 is set to about 0.05M or more and 0.3M or less. By forming such a reduced thickness portion 52 corresponding to the width M2, the thickness of the foil including the top foil 51 disposed between the back foil 12 and the rotating shaft 1 (in the present embodiment, the top foil 51). Is formed thinner at the both sides in the length direction of the rotary shaft 1 than at the center.

  Even in the radial foil bearing 50 of the present embodiment, the thickness of the foil including the top foil 10 disposed between the back foil 12 and the rotating shaft 1 is set on both sides in the length direction of the rotating shaft 1. Since it is formed thinner than the central portion, the difference in film thickness of the fluid lubricating film between the central portion and both side portions can be reduced, and accordingly, the thickness of the fluid lubricating film at the both end portions of the top foil 10 is reduced. It is possible to suppress the thickness from becoming extremely thin, and to maintain a non-contact state between the both end portions of the top foil 10 and the rotary shaft 1 even at a high load. Therefore, it is possible to apply a high load to the bearing by suppressing wear on both side end portions of the top foil 10, and therefore it is possible to use the bearing at a high load.

In addition, since the thickness on the side of the back foil 12 is reduced on both sides of the top foil 51 to form a thinned portion 52 that is thinner than the central portion, the length of the rotary shaft 1 between the top foil 51 and the back foil 12 is reduced. It is possible to reliably form a gap on both sides in the direction, and thus it is possible to satisfactorily prevent warping of both end portions of the top foil 51.
Further, since the gap can be formed without providing an intermediate foil, the number of parts can be reduced and the cost can be reduced.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention.
For example, in the first embodiment, the intermediate foil 11a has a shape in which both sides are cut off from the planar shape of the top foil 10 and the length in the short side direction is shortened, but instead of cutting off both sides in this way. Then, like the thinned portion of the top foil 51 in the second embodiment, both side portions may be shaved and thinned to form a thin thickness.

  Further, in the second embodiment, the top foil 51 is arranged directly on the back foil 12 without providing the intermediate foil. However, the intermediate foil is arranged between the back foil 12 and the top foil 51, and the foils are arranged between the foils. The damping effect due to “slip” may be enhanced.

Further, the configuration of the through groove 14 for holding the end portions of the top foil 10 (51), the intermediate foil 11a, and the intermediate foil 11b, the configuration of the fixing tool 17, and the regulation tool 30 for fixing the back foil piece 12a. The configuration and the like are not limited to the above embodiment, and various configurations can be collected.
Moreover, in the said embodiment, although the bearing housing was formed in the cylindrical shape, an annular flange may be integrally formed in one side surface or both side surfaces, and the whole may be formed in a substantially cylindrical shape. By forming the flange, it is possible to facilitate attachment to a turbomachine housing or the like.

DESCRIPTION OF SYMBOLS 1 ... Rotary shaft, 3, 50 ... Radial foil bearing 10, 51 ... Top foil, 11a, 11b ... Intermediate foil, 12 ... Back foil (bump foil), 12a ... Back foil piece, 13 ... Bearing housing, 52 ... Reduction Meat part

Claims (4)

A radial foil bearing that is extrapolated to a rotating shaft and supports the rotating shaft,
A cylindrical top foil disposed opposite to the rotating shaft, a back foil disposed radially outside the top foil, and a cylindrical shape that accommodates the top foil and the back foil in an interpolated state. A bearing housing,
The thickness of the foil including the top foil disposed between the back foil and the rotating shaft is formed to be thinner than the central portion at both side portions in the length direction of the rotating shaft. Radial foil bearing.   The intermediate foil is disposed between the top foil and the back foil, and both end portions of the intermediate foil are located inside the both end portions of the top foil. Radial foil bearing.   A plurality of intermediate foils are disposed between the top foil and the back foil, and at least one of the intermediate foils has both side ends positioned on both sides of the top foil. The radial foil bearing according to claim 1, wherein:   The radial foil bearing according to claim 1, wherein both side portions of the top foil are formed thinner than a central portion.

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