JP2019060396A - Foil bearing - Google Patents

Abstract

To enhance the durability of a foil bearing.SOLUTION: A foil bearing 1 includes a flexible thin plate (foil 20), and supports a shaft 2 with a fluid film generated in a bearing clearance C between a bearing surface X provided in the foil 20 and the shaft 2. The foil 20 includes a composite layer in which a metal part (metal sheet 20a) and a resin part 20b alternately emerge in a direction parallel to the bearing surface X.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a foil bearing.

  The main shaft of a turbomachine such as a gas turbine or turbocharger rotates at a very high speed, and the turbine blades are in a high temperature environment. When it is difficult to use a lubricating oil to support the rotation of the main shaft of such a turbomachine, an air dynamic bearing may be used.

  For example, in the case of a general air dynamic bearing in which both bearing surfaces which rotate relative to each other are rigid, management of the width of the bearing gap according to the rotational speed used is important, and the width of the bearing gap is the stability limit When it exceeds, the whirling called a whirl arises. However, in an air dynamic pressure bearing consisting of a general rigid bearing surface, the bearing clearance needs to be set to about 1/1000 of the diameter of the shaft. For example, if the diameter of the shaft is about several mm, the bearing clearance is several It is set to about μm. For this reason, manufacture of each member and width control of a bearing crevice in a severe environment of temperature change become very difficult.

  On the other hand, a bearing called a foil bearing constitutes a bearing surface with a thin plate (foil) having low rigidity and flexibility for bending, and supports a load while allowing deflection of the foil. During rotation of the shaft, a film of air is formed between the shaft and the foil, and the shaft is supported in a noncontact manner via the air film. In foil bearings, the flexibility of the foil automatically creates a bearing gap of the appropriate width according to operating conditions such as the rotational speed of the shaft, load, and ambient temperature, so the width of the bearing gap is relatively large. It can be set to Specifically, for example, if the diameter of the shaft is about several mm, the width of the bearing gap can be set to about several tens of μm, and this is compared with an air dynamic pressure bearing consisting of a general rigid bearing surface. Thus, the manufacture of each member and the management of the width of the bearing gap become easy.

  At the time of low speed rotation such as immediately after the start of rotation or immediately before stop of the shaft in the foil bearing, the fluid pressure in the bearing gap is not sufficiently increased, so the foil and the shaft contact / slide. Accordingly, since the foil and the shaft repeatedly contact and slide each time the shaft is started and stopped, the bearing surface and the shaft adhere to each other, which may result in an increase in friction torque and eventually breakage of the bearing surface.

  For example, in Patent Document 1 below, by providing a film excellent in lubricity such as molybdenum disulfide, graphite, fluorocarbon resin, etc. on the surface of the foil, the slidability with the shaft is enhanced to suppress the wear of the bearing surface. ing.

Japanese Patent Application Publication No. 2003-56561

  However, even if the above-mentioned coating is provided on the surface (bearing surface) of the foil, if the coating is worn away by sliding with the shaft, the base material (metal) of the foil is exposed on the bearing surface and slides on the shaft Do. In this case, the slidability of the bearing surface is greatly reduced, and the bearing surface may be damaged prematurely.

  Then, an object of the present invention is to raise the endurance of a foil bearing.

  In order to solve the above problems, the present invention is a foil bearing comprising a flexible thin plate and supporting the shaft with a fluid film generated in a bearing gap between the bearing surface provided on the thin plate and the shaft. The thin plate provides a foil bearing comprising a composite layer in which metal parts and resin parts alternate in a direction parallel to the bearing surface.

  As described above, the thin plate has the composite layer in which the metal portion and the resin portion alternately appear in the direction parallel to the bearing surface, so that the bearing surface of the thin plate (or the surface exposed to the bearing surface when the wear progresses) In addition, both the metal part and the resin part of the composite layer are exposed. Thus, not only the metal part but also the resin part slides on the shaft at low speed rotation of the shaft, so that the slidability between the thin plate and the shaft is enhanced.

  For example, if the bearing surface is formed in the composite layer, the metal portion and the resin portion of the composite layer are exposed to the bearing surface, so that the shaft may slide on both the metal portion and the resin portion from the initial use of the foil bearing. it can.

  On the other hand, when the thin plate covers the surface of the composite layer and has the resin surface layer on which the bearing surface is formed, the shaft slides only with the resin surface layer in the initial use of the foil bearing, thus exhibiting excellent slidability Do. Then, when the resin surface layer is worn by the sliding with the shaft, the shaft can be made to slide on both the metal portion and the resin portion by exposing the metal portion and the resin portion of the composite layer to the bearing surface.

  The composite layer of the thin plate can be formed of, for example, a metal fiber reinforced resin. As metal fiber reinforced resin, what disperse | distributed metal fiber to resin, and what impregnated resin with the sheet | seat which woven metal fiber can be used.

  Moreover, the composite layer of a thin plate can be formed by the metal sheet as a metal part, and the resin part which entrapped into many micro recessed parts formed in the surface of the metal sheet.

  As described above, according to the present invention, a reduction in the slidability between the thin plate and the shaft due to the wear of the bearing surface is suppressed, and the friction and wear characteristics of the bearing surface are stabilized over a long period of time. Bearing can be obtained.

It is a sectional view of a foil bearing concerning an embodiment of the present invention. It is a top view of foil. Figure 3 is a cross-sectional view of the foil of Figure 2; It is the top view which looked at two connected foils from the back side. It is a perspective view which shows the state which temporarily assembled three sheets of foil. It is a perspective view which shows a mode that the temporary assembly of a foil is attached to a foil holder. It is an expanded sectional view of the foil bearing of FIG. FIG. 6 is a cross-sectional view of a foil according to another embodiment. It is a perspective view of the metal sheet which comprises the foil concerning further another embodiment. 10 is a cross-sectional view of a foil having the metal sheet of FIG. (A)-(D) are top views which show the example of the through-hole provided in the metal sheet of FIG. It is sectional drawing which shows the state which the surface layer of the resin part of the foil of FIG. 10 worn away. It is a sectional view showing a leaf type radial foil bearing. It is sectional drawing which shows the radial foil bearing of bump type | mold. It is a perspective view showing a leaf type thrust foil bearing. It is the DD sectional view taken on the line in FIG.

  Hereinafter, embodiments of the present invention will be described based on the drawings.

  As shown in FIG. 1, the foil bearing 1 according to the present embodiment is disposed at a plurality of locations in the circumferential direction on the foil holder 10 having a cylindrical inner circumferential surface 11 and the inner circumferential surface 11 of the foil holder 10. And the foil 20 as a flexible thin plate. The foil bearing 1 of the example of illustration illustrates the case where the foil 20 is arrange | positioned in three places of the internal peripheral surface 11. As shown in FIG. Further, in the illustrated example, the entire circumferential direction of the inner peripheral surface 11 of the foil holder 10 is covered with the foil 20, and the shaft 2 is inserted in the inner periphery thereof. In the following, the forward side of the rotational direction of the shaft 2 (see arrow R in FIG. 1), that is, the downstream side of the fluid flow direction with respect to the foil 20 at the time of rotation of the shaft 2 is referred to as "downstream side" Say "upstream".

  The foil holder 10 can be formed of a metal such as a sintered metal or a molten material, and is formed of, for example, a steel material. At a plurality of locations (the same number as the number of foils) spaced in the circumferential direction on the inner circumferential surface 11 of the foil holder 10, axial grooves 11a serving as attachment portions for the respective foils 20 are formed.

  The foil 20 comprises a composite layer having a metal part and a resin part, and in the present embodiment, the entire foil 20 is composed of a composite layer. The metal portion is preferably formed of a material having high springiness, and is formed of, for example, an iron-based material (iron or iron alloy) such as stainless steel, or a copper-based material such as bronze (copper or copper alloy). The resin portion is preferably formed of a material having a self-lubricating property, for example, polyetheretherketone (PEEK), polytetrafluoroethylene (PTFE), polyacetal (POM), etc. alone or two or more of them. It is formed of a combined material. If necessary, a solid lubricant such as graphite may be added to the material of the resin part.

  The composite layer constituting the foil 20 is formed of, for example, a metal fiber reinforced resin. The metal reinforced fiber resin is formed of metal fibers as the metal part and a resin part holding the metal fibers. In the present embodiment, a metal fiber reinforced resin is formed of a metal sheet 20a (see FIG. 2) formed by weaving metal fibers and a resin portion 20b impregnated in the metal sheet 20a. As shown in FIG. 3, the resin portion 20 b is intruding between the metal fibers 20 a 1 constituting the metal sheet 20 a. Thus, in the metal fiber reinforced resin (composite layer) constituting the foil 20, the metal portions (metal fibers 20a1) and the resin portions 20b are alternately arranged in a direction parallel to the bearing surface X (for example, the left and right direction in FIG. 3). appear. In the illustrated example, the bearing surface X is formed on the metal fiber reinforced resin as the composite layer. That is, on the bearing surface X of the foil 20, both the metal fiber 20a1 and the resin portion 20b are exposed. In the foil 20, the rigidity of the foil 20 can be controlled by the thickness of the metal fiber 20a1, the blending amount, the material, the orientation of the fiber, and the like.

  As shown in FIG. 2, the foil 20 includes a top foil portion 21 forming the bearing surface X, an insertion portion 22 provided on the downstream side (the left side of FIG. 2) of the top foil portion 21, and a top foil portion 21. And a back foil portion 23 provided on the upstream side (right side in FIG. 2) of

  The top foil portion 21 has a rectangular shape, and the bearing surface X is provided over the entire surface. The insertion portion 22 extends along the surface of the top foil portion 21 in a direction projecting downstream from the top foil portion 21. In the illustrated example, the insertion portion 22 is at a plurality of locations (for example, in the axial direction in the case of a radial foil bearing; in the vertical direction in FIG. 2) in the direction perpendicular to the rotation direction R of the shaft 2 in the direction along the bearing surface X Provided at three locations. At the downstream end of the top foil portion 21, in the vicinity of each insertion portion 22, a minute notch 21 a extending upstream from the edge of the top foil portion 21 is provided.

  The upstream end of the back foil portion 23 is formed with two notches 23 a that are axially separated and recessed toward the downstream side. The axial dimension of each notch 23a is gradually reduced toward the downstream side. In this embodiment, although the case where the whole notch 23a was formed in circular arc shape is illustrated, each notch 23a can also be formed in the substantially V shape which made the top part pointed shape. On the axial direction both sides of each notch portion 23a, projecting portions 23b that respectively protrude upstream are formed.

  A slit-like insertion in which the insertion portions 22 of the adjacent foils 20 are inserted at a plurality of axial locations (the same number as the insertion portions 22) at the boundary between the top foil portion 21 and the back foil portion 23 A mouth 24 is provided. Among them, the insertion ports 24 at both ends extend linearly along the axial direction and open at both ends of the foil 20 respectively. The central insertion slot 24 comprises a straight notch extending in the axial direction, and a wide notch extending upstream from the notch and having an arc-shaped tip at the tip.

  As shown in FIG. 4, the two foils 20 can be connected by inserting the insertion parts 22 of one foil 20 into the insertion holes 24 of the adjacent foils 20 respectively. In the drawing, one of the two combined foils 20 is given a gray color.

  And as shown in FIG. 5, the three foils 20 can be temporarily assembled in a cylindrical shape by circumferentially connecting the three foils 20 in the same manner as in FIG. The foil bearing 1 is assembled by inserting this temporary assembly into the inner periphery of the foil holder 10 in the direction of the arrow B2 in a state of being rounded into a cylindrical shape as shown in FIG. Specifically, while inserting the temporary assembly of three foils 20 into the inner periphery of the foil holder 10, the axial groove 11a is opened in one end face of the foil holder 10 with the insertion portion 22 of each foil 20. Insert from the one side in the axial direction. Thus, the three foils 20 are attached to the inner circumferential surface 11 of the foil holder 10 in the circumferential direction.

  As shown in FIG. 7, in a state in which each foil 20 is attached to the foil holder 10, two adjacent foils 20 cross each other. On the downstream side of this intersection, the insertion portion 22 of one foil 20 is behind the top foil portion 21 of the other foil 20 that constitutes the bearing surface X via the insertion port 24 of the other foil 20. And inserted into the axial groove 11 a of the foil holder 10. Upstream from the intersection, the back foil portion 23 of the other foil 20 is disposed behind the top foil portion 21 of one of the foils 20 that constitutes the bearing surface X. The upstream end of the back foil portion 23 is a free end, and the position of the end varies in the circumferential direction according to the elastic deformation of the foil 20.

  In this foil bearing 1, the downstream end (insert 22) of each foil 20 is attached to the foil holder 10, and the top foil 21 of each foil 20 is circumferentially aligned with the top foil 21 of the other foil 20. In the engaged state. As a result, the adjacent foils 20 are in a state where they are mutually thrust in the circumferential direction, so the top foil portion 21 of each foil 20 projects to the outer diameter side and curves in a shape along the inner circumferential surface 11 of the foil holder 10 Do. The downstream movement of each foil 20 is restricted as the inset 22 of each foil 20 abuts against the axial groove 11a, but the upstream movement of each foil 20 is not restricted. Thus, each foil 20 can be slightly slid (reciprocated) in the circumferential direction with respect to the inner circumferential surface 11 of the foil holder 10.

  As shown in FIG. 7, since the axial groove 11 a is provided slightly inclined at an angle θ 1 with respect to the tangential direction of the inner circumferential surface 11 of the foil holder 10, the insertion portion 22 inserted into the axial groove 11 a In the vicinity of the top foil portion 21, the top foil portion 21 tries to be curved so as to be convex toward the inner diameter side. In addition, when the top foil portion 21 rides on the back foil portion 23, the top foil portion 21 is inclined to the downstream side away from the inner circumferential surface 11 of the foil holder 10. Thus, a weir space is formed between the bearing surface X of the top foil portion 21 and the outer peripheral surface of the shaft 2. Further, the top foil portion 21 can be elastically displaced in the radial direction by the elastic force of the curved portion convex to the inner diameter side and the elastic force of the portion which rides on the back foil portion 23.

  During rotation of the shaft 2, the fluid film (air film in the present embodiment) generated in the weir space is at a high pressure, so that the shaft 2 receives the levitation force. Therefore, as shown in FIG. 1, an annular radial bearing gap C is formed between the bearing surface X of each foil 20 and the shaft 2, and the shaft 2 is rotatably supported without contact with the foil 20. Ru. The elastic deformation of the top foil portion 21 automatically adjusts the clearance width of the radial bearing clearance C to an appropriate width according to the operating conditions and the like, so that the rotation of the shaft 2 is stably supported. In FIG. 1, the width of the radial bearing gap C is exaggerated for ease of understanding.

  During rotation of the shaft 2, the top foil portion 21 is pressed against the back foil portion 23 and elastically deformed by the fluid pressure of the bearing gap C, so the top foil portion 21 riding on the back foil portion 23 has a bearing clearance A step in the width direction of C is formed. As shown in FIG. 4, when the notch 23a is provided at the upstream end of the back foil 23 of each foil 20, this step becomes a herringbone shape corresponding to the shape of the notch 23a. . Since the fluid flowing along the top foil portion 21 flows along the above-mentioned herringbone-shaped step (see the arrow in FIG. 4), pressure generation of fluid occurs at two axially spaced locations in the bearing gap C. A part is formed. This makes it possible to support the moment load while enhancing the floating effect of the shaft 2. In the present embodiment, as shown in FIG. 2, the top foil portion 21 is formed with a notch in the back foil portion 23 because a minute notch 21 a is formed in the top foil portion 21 to reduce the rigidity of the top foil portion 21. The deformation is performed smoothly also when deformed along the portion 23a.

  During low speed rotation, such as immediately after start of the shaft 2 or immediately before stop, the fluid pressure in the bearing gap C is insufficient, so the bearing surface X of the foil 20 and the outer peripheral surface of the shaft 2 contact and slide. At this time, as shown in FIG. 3, since both the metal portion (metal sheet 20 a) and the resin portion 20 b are exposed on the bearing surface X of the foil 20, the shaft 2 is not only the metal portion but also the resin portion 20 b. Also slide. As a result, the sliding property of the bearing surface X is enhanced by the resin portion 20b, and the strength of the bearing surface X is enhanced by the metal portion, so that the excellent friction and wear characteristics of the bearing surface X can be maintained for a long time. it can. In particular, by forming the resin portion 20 b of a self-lubricating resin, the self-lubricating resin is supplied to the sliding portion between the shaft 2 and the bearing surface X, so that the slidability can be further enhanced.

  The present invention is not limited to the above embodiment. Hereinafter, other embodiments of the present invention will be described, but the description of the same points as the above embodiments will be omitted.

  Although said embodiment showed the case where the composite layer (metal fiber reinforced resin) which comprises the foil 20 has the metal sheet 20a which interwovenly formed the metal fiber 20a1, it is not restricted to this. For example, in the embodiment shown in FIG. 8, the metal portion of the composite layer constituting the foil 20 is constituted by the metal fibers 20 a 1 dispersed and held in the resin portion 20 b. The foil 20 is formed, for example, by impregnating a non-woven fabric using metal fibers 20a1 with a resin, or by injection molding using a molten resin containing the metal fibers 20a1.

  Moreover, the composite layer provided on the foil 20 is not limited to the metal fiber reinforced resin. For example, as shown in FIG. 9, a composite layer of the foil 20 is formed by a metal sheet 20c having a large number of microrecesses on the surface and a resin portion 20b (see FIG. 10) which has entered the microrecesses of the metal sheet 20c. be able to. In the present embodiment, the metal sheet 20c has a through hole 20c1 penetrating in the thickness direction as a minute recess. The metal sheet 20c is made of, for example, a punched metal in which a through hole 20c1 is punched and formed. The through holes 20c1 are preferably arranged regularly. The through holes 20c1 are provided at least throughout the area corresponding to the top foil portion 21 and may be provided in one or both of the areas corresponding to the insertion portion 22 and the back foil portion 23. Moreover, the micro recessed part formed in the metal sheet 20c may be a recessed part by which the back side (opposite to a bearing surface) was obstruct | occluded not only a through-hole.

  The foil 20 of this embodiment is provided with the composite layer A which consists of said metal sheet 20c and the resin part 20b with which the through-hole 20c1 of the metal sheet 20c was filled, as shown in FIG. The surface of the composite layer A is covered with a resin surface layer 20d. In the illustrated example, the resin portion 20b inside the through hole 20c1 and the resin surface layer 20d covering the surface of the composite layer A are integrally formed. The resin surface layer 20d is provided at least on the entire area of the top foil portion 21 (that is, the entire area of the bearing surface X), and in the present embodiment, the front side (bearing surface X side) of the foil 20 including the insertion portion 22 and the back foil portion 23. Provided on the entire surface of the In the composite layer A, the metal portions (metal sheet 20c) and the resin portion 20b appear alternately in a direction parallel to the bearing surface X (for example, the left and right direction in FIG. 10). The foil 20 is formed, for example, by injection molding of a resin using the metal sheet 20c as an insert part, or by applying a resin to the surface of the metal sheet 20c.

  In the foil 20, the rigidity of the foil 20 can be adjusted by the thickness of the metal sheet 20c and the resin surface layer 20d, and the size, shape, arrangement pattern, spacing, and the like of the through holes 20c1 of the metal sheet 20c. As the shape of the through hole 20c1 of the metal sheet 20c, for example, a round hole {see FIG. 11 (A)}, a long hole {see FIG. 11 (B)}, a cross shape {see FIG. 11 (C)}, a honeycomb shape { See FIG. 11D) and the like.

  When the resin portion 20b and the resin surface layer 20d are formed by injection molding, a recess may be formed on the bearing surface X of the resin surface layer 20d due to the influence of the molding shrinkage of the resin portion 20b entering the through hole 20c1. It is preferable to set the size, the shape, and the like of the through hole 20c1 so that such a recess is not formed as much as possible. In addition, the resin surface layer 20d integrated with the through hole 20c1 does not easily peel off from the composite layer A due to the resin portion 20b that has entered the through hole 20c1. In order to enhance such an effect, it is preferable to set the size, the shape, and the like of the through hole 20c1 so that the contact area between the metal sheet 20c and the resin portion 20b is wide.

  At the initial stage of use of the foil bearing 1, the entire area of the bearing surface X is formed of the resin surface layer 20 d, and therefore, has excellent slidability. Then, when the resin surface layer 20d is abraded due to the bearing surface X of the foil 20 sliding repeatedly with the shaft 2, the composite layer A is exposed to the bearing surface X as shown in FIG. At this time, since not only the metal sheet 20c but also the resin portion 20b which has entered the through hole 20c1 of the metal sheet 20c is exposed to the bearing surface X which has been worn, deterioration of the sliding property of the bearing surface X is suppressed. In particular, the resin portion 20 b is formed of a self-lubricating resin, whereby the self-lubricating resin continues to be supplied to the sliding portion between the bearing surface X and the shaft 2. This maintains the excellent friction and wear characteristics of the bearing surface X over a long period of time.

  In the foil 20 shown in FIG. 10, not only the surface on the front side (bearing surface X side, upper side in the figure) of the composite layer A but also the back side of the composite layer A (opposite to the bearing surface X, lower side in the figure) The surface may also be coated with a resin surface layer. Alternatively, in the foil 20 shown in FIG. 10, the resin surface layer 20d may be omitted, and the metal portion (metal sheet 20c) and the resin portion 20b of the composite layer A may be exposed to the bearing surface X from the beginning. Also, the surface of the composite layer made of metal fiber reinforced resin as shown in FIG. 3 and FIG. 8 may be covered with a resin surface layer, and the bearing surface X may be formed on this resin surface layer.

  Although the so-called multi-arc type radial foil bearing is illustrated as the foil bearing 1 in the above embodiment, the form of the foil bearing to which the present invention can be applied is not limited thereto. For example, the present invention can be applied to a so-called leaf type foil bearing 1 shown in FIG. The foil bearing 1 has one end on the downstream side as a free end, and a plurality of foils 20 (leafs) having the other end on the upstream side as a fixed end arranged in the circumferential direction. The downstream region of each foil 20 functions as the top foil portion 21, and the upstream region functions as the back foil portion 23.

  The present invention can also be applied to a so-called bump type foil bearing 1 shown in FIG. In the foil bearing 1, a corrugated back foil portion 23 and a cylindrical top foil portion 21 are separately provided, and the back foil portion 23 is disposed between the top foil portion 21 and the foil holder 10.

  Furthermore, the present invention can be applied not only to radial foil bearings but also to thrust foil bearings that support thrust collars provided on the shaft 2 in the thrust direction. FIG. 15 shows a leaf type thrust foil bearing as an example of the thrust foil bearing 3. As shown in FIG. 16, the downstream region of each foil 20 functions as the top foil portion 21, and the upstream region functions as the back foil portion 23.

  In the above description, the shaft 2 is used as the rotating side member and the foil holder 10 is used as the fixed side member. Conversely, the shaft 2 is used as the fixed side member and the foil holder 10 is used as the rotating side member. The present invention can also be applied to the case where However, in this case, since the foil 20 is a rotating side member, it is necessary to design the foil 20 in consideration of the deformation of the entire foil 20 due to the centrifugal force.

  The foil bearing according to the present invention can be used, for example, as a foil bearing for supporting a rotor of a turbomachine including a gas turbine and a turbocharger. In addition, the foil bearing according to the present invention can be widely used as a bearing for vehicles such as automobiles and a bearing for industrial equipment. In addition, each foil bearing of the present embodiment is an air dynamic bearing using air as a pressure generating fluid, but the invention is not limited to this, and another gas can be used as a pressure generating fluid, or water or oil It is also possible to use liquids such as.

1 foil bearing 2 axis 10 foil holder 20 foil 20a metal sheet 20a1 metal fiber (metal part)
20b resin part 20c metal sheet (metal part)
20c1 through hole 20d resin surface layer 21 top foil portion 22 insertion portion 23 back foil portion C bearing clearance X bearing surface

Claims (5)

A foil bearing comprising a flexible thin plate and supporting the shaft with a fluid film generated in a bearing gap between the bearing surface provided on the thin plate and the shaft,
A foil bearing comprising a composite layer in which the thin plate alternately shows a metal portion and a resin portion in a direction parallel to the bearing surface.   The foil bearing according to claim 1, wherein the bearing surface is formed in the composite layer.   The foil bearing according to claim 1, wherein the thin plate has a resin surface layer covering the surface of the composite layer and the bearing surface is formed.   The foil bearing according to any one of claims 1 to 3, wherein the composite layer is formed of a metal fiber reinforced resin. The said composite layer was formed by the metal sheet as said metal part, and the said resin part which entrapped in many micro recessed parts formed in the surface of the said metal sheet. Foil bearing.

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