JP2018150971A - Foil bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a foil bearing that can stably increase friction force generated at a slide surface while suppressing deformation on the processing.SOLUTION: A foil bearing 10 includes: a foil 12 having a bearing surface X; and a foil holder 11 for supporting the foil 12, where the foil 12 is elastically deformable and sliding between the foil 12 and other members except for a shaft 13 to be supported is permitted. An uneven surface formed by chemical conversion treatment is provided at any one or both surfaces generating sliding of a surface of the foil 12 and surfaces of other members.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a foil bearing.

  As a bearing for supporting a shaft of a turbo machine such as a gas turbine or a turbocharger, a foil bearing has attracted attention. In the foil bearing, a bearing surface is constituted by a thin film (foil) having low rigidity with respect to bending, and the load is supported by allowing the bearing surface to bend. When the shaft rotates, a fluid film (for example, an air film) is formed between the outer peripheral surface of the shaft and the bearing surface of the foil, and the shaft is supported in a non-contact manner. In this case, the flexibility of the foil automatically forms an appropriate bearing gap according to the operating conditions such as the rotational speed, load and ambient temperature of the shaft. It can be used at high speed.

  As the above-mentioned foil bearing, the top foil is elastically supported by cutting and raising provided in the back foil (Patent Document 1), and the bearing foil is elastically supported by an elastic body knitted in a net shape ( Patent Document 2), and a back foil provided with a support portion that contacts the inner surface of the outer ring and does not move in the circumferential direction, and an elastic portion that is elastically bent by the surface pressure from the top foil (Patent Document 3), etc. It is known. Patent Documents 4 and 5 show so-called multi-arc type foil bearings in which a plurality of foils are arranged side by side in the circumferential direction, and both circumferential ends of each foil are attached to an outer member.

  In such a foil bearing, when the shaft rotates, the foils, or the foil and the foil holder holding the foil slide. Since the vibration during shaft rotation can be attenuated by the frictional force generated by the sliding, it is important to control the frictional force in order to support the shaft that rotates stably.

  For example, in the foil bearing of Patent Document 6, the friction coefficient of the sliding surface is increased by coating the surface of the surface other than the bearing surface of the foil or the surface of the stationary holding member holding the foil with a metal coating with copper. Increases vibration damping effect.

JP 2002-364463 A JP 2003-262222 A JP 2009-299748 A JP 2009-216239 A JP 2006-57828 A Japanese Patent No. 4287208

  When a metal film layer is formed on the surface of the foil as in Patent Document 6, the foil is likely to be hot during film formation, and the foil bearing is not heated and deforms, so that the foil bearing cannot perform a desired function. .

  Further, the friction force can be controlled by physically increasing the surface roughness of the foil, such as polishing using shot blasting or emery paper. However, when the surface roughness of the foil is increased by physical processing, the variation in surface roughness increases depending on the location and the vibration damping force is not stable, and residual stress is generated in the foil due to processing. There is a problem that deforms.

  Under such circumstances, an object of the present invention is to provide a foil bearing capable of stably increasing the frictional force generated on the sliding surface while suppressing deformation during processing.

  In order to solve the above problems, the present invention includes a foil having a bearing surface, a foil holder that supports the foil, the foil is elastically deformable, and other members excluding the foil and the shaft to be supported. In the foil bearing allowed to slide, an uneven surface formed by chemical conversion treatment is provided on one or both of the surfaces of the foil and the other member that cause the sliding. It is characterized by.

  The foil bearing of the present invention forms an uneven surface on the sliding surface by chemical conversion treatment, and increases the frictional force generated by sliding. In this case, as compared with the case where the uneven surface is formed by a physical method, there is less variation in the roughness of the sliding surface, and the vibration damping effect of the shaft can be stably enhanced. Moreover, since it is not necessary to apply an external force at the time of formation of an uneven surface, there is no possibility of causing deformation of the foil and other members. Further, since the uneven surface can be formed by the treatment at a low temperature, deformation due to heating does not occur.

  As said foil bearing, an uneven surface can be formed in the surface of a chemical conversion film. The uneven surface provided on the chemical conversion film can increase the frictional force generated on the sliding surface.

  As said foil bearing, an uneven surface can form in one or both surfaces by forming an unevenness | corrugation in the interface between a chemical conversion film and a base material, and then removing a chemical conversion film. As a result, an uneven surface can be formed on the base material itself, so that compared with the case where the coefficient of friction is increased by the coating formed on the surface of the base material, the vibration damping force is reduced due to peeling of the coating or the coating is used over time. There is no need to worry about deterioration of the film, and there is no need to perform quality control of the coating to prevent them. Also, covering the foil surface with a coating does not adversely affect the flexibility of the foil.

  As said foil bearing, multiple foil can be provided and another member can be made into either of several foil. By forming an uneven surface on the surface of the foil, the frictional force generated on the sliding surface of the foil can be increased.

  Other members can be used as the foil holder as the foil bearing. Thereby, the frictional force generated on the sliding surface of the foil holder can be increased.

  As described above, in the present invention, it is possible to perform processing at a low temperature without applying an external force when forming the uneven surface, so that the surface roughness does not occur during the processing without causing deformation of the foil or other members. A uniform uneven surface can be formed. Therefore, the foil bearing can stably exhibit the vibration damping effect of the shaft.

It is a schematic block diagram of the foil bearing which concerns on embodiment of this invention. It is a top view which shows foil. It is a top view explaining connection of two foils. It is a perspective view explaining connection of three foils. It is a perspective view explaining a mode that a foil is attached to a foil holder. It is sectional drawing explaining a mode that foil is hold | maintained at a foil holder. It is a figure explaining the uneven | corrugated surface of the foil which concerns on embodiment of this invention. In another embodiment of this invention, it is a figure explaining the process in which an uneven surface is formed in foil. It is an enlarged view of an uneven surface in a different embodiment.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

  As shown in FIG. 1, the foil bearing 10 includes a foil holder 11 having a cylindrical inner peripheral surface 11a and three foils 12 attached to the inner peripheral surface 11a. The foil bearing 10 is a so-called multi-arc type foil bearing in which three foils 12 are arranged in the circumferential direction on the inner peripheral surface 11a. A shaft 13 is inserted into the foil bearing 10 inside the foil 12 on the inner peripheral surface 11a side. The foil bearing 10 and the shaft 13 constitute a foil bearing device 14. The foil bearing 10 supports the shaft 13 in a relatively rotatable manner with a fluid film formed between a bearing surface X (described later) of the foil 12 and the shaft 13.

  The foil holder 11 is formed of a metal (for example, a steel material) such as a sintered metal or a melted material. In the inner peripheral surface 11a, axial grooves 11b serving as holding portions are formed at a plurality of locations (three locations in the illustrated example) separated in the circumferential direction.

  The foil 12 is formed of a strip-like foil having a thickness of about 20 μm to 200 μm made of a metal having high spring properties and good workability, such as a steel material or a copper alloy. In an air dynamic pressure bearing using air as a fluid film as in the present embodiment, since no lubricating oil exists in the atmosphere, the antirust effect by the oil cannot be expected. Typical examples of steel materials and copper alloys include carbon steel and brass, but general carbon steel is susceptible to corrosion due to rust, and brass may cause cracks due to processing strain (in brass) This tendency increases as the Zn content increases.) Therefore, it is preferable to use a stainless steel or bronze foil as the belt-like foil.

  As shown in FIG. 2, the foil 12 has a first region 12 a and a second region 12 b that are arranged in the circumferential direction of the foil holder 11.

  The first region 12a includes a top foil portion 12a1 having a bearing surface, and an insertion portion 12a2 protruding at one end in the circumferential direction at the upper end, the center, and the lower end in the axial direction. A minute circumferential notch 12a3 is provided at a position close to the insertion portion 12a2.

  The second region 12b is provided with a protruding portion 12b1 as an under-foil portion, which is three protruding portions whose axial width is gradually narrowed toward the other end in the circumferential direction. The protrusions 12b1 are provided at the upper end, the center, and the lower end in the axial direction, respectively, and a notch 12b2 formed in a substantially arc shape is provided between the protrusions 12b1. In addition, the cutout portion 12b2 may have a substantially V shape in which a straight line is bent at the center of each protruding portion 12b1.

  As shown in FIG. 1, in the foil bearing 10, the top foil portion 12 a 1 is disposed on the shaft 13 side, and the inner peripheral surface thereof forms a bearing surface X. And underfoil part 12b1 is arranged at the foil holder 11 side, and gives elasticity to top foil part 12a1 by overlapping with top foil part 12a1 of other foil 12 adjacent.

  As shown in FIG. 2, at the boundary between the first region 12 a and the second region 12 b, the insertion ports 12 c 1, 12 c 2, and 12 c 1 into which the insertion portions 12 a 2 of the adjacent foil 12 are inserted are respectively the upper end in the axial direction, the center, Provided at the lower end. The insertion port 12c1 is a rectangular cutout portion and is provided to reach the axial end of the foil 12. The insertion port 12c2 has a rectangular cutout portion provided at the same position in the circumferential direction as the insertion port 12c1, and a rectangular cutout portion that protrudes toward the other end in the circumferential direction and has a circular arc at the tip. It consists of a notch part whose width is narrower than that. Moreover, the connection part 12c3 which connects both is formed in the boundary of the 1st area | region 12a and the 2nd area | region 12b.

  As shown in FIG. 3, the two foils 12 can be connected by inserting the insertion portions 12a2, 12a2, 12a2 of one foil 12 into the insertion ports 12c1, 12c2, 12c1 of the adjacent foils 12. it can. The foil 12 constitutes a foil overlap portion C that overlaps in the radial direction of the shaft 13 in a state where the foil 12 is assembled to a foil bearing 10 described later.

  Then, as shown in FIG. 4, the three foils 12 can be temporarily assembled by connecting the three foils 12 circumferentially by the method. The foil bearing 10 is assembled by making this temporary assembly into a cylindrical shape and inserting it into the inner periphery of the foil holder 11 in the direction of arrow B2, as shown in FIG. Specifically, while inserting the temporary assembly of the three foils 12 into the inner periphery of the foil holder 11, the insertion portion 12 a 2 of each foil 12 is opened in the axial groove 11 b opened on one end surface of the foil holder 11. Insert from one end in the axial direction. Thus, the three foils 12 are attached to the inner peripheral surface 11a of the foil holder 11 in a state of being arranged in the circumferential direction.

  As shown in FIG. 6, in the state where the three foils 12 are assembled to the foil holder 11, the insertion portion 12 a 2 that is one circumferential end of each foil 12 is held in contact with the foil holder 11. In the example of illustration, the insertion part 12a2 of each foil 12 is distribute | arranged to the back (outside diameter side) of the foil 12 adjacent, respectively. Specifically, the insertion portion 12a2 provided at one end in the circumferential direction of each foil 12 has an axial groove on the inner peripheral surface 11a of the foil holder 11 via the insertion port 12c1 (12c2) of the adjacent foil 12. 11b. On the other hand, the projecting portion 12b1 provided at the other circumferential end of each foil 12 is disposed between the top foil portion 12a1 of the adjacent foil 12 and the inner peripheral surface 11a of the foil holder 11, and the top of the adjacent foil 12 is disposed. The foil part 12a1 is supported from behind, and the underfoil part 12b1 is configured. The adjacent foils 12 are engaged with each other in the circumferential direction so as to stick to each other. Thereby, the top foil part 12a1 of each foil 12 protrudes to the outer diameter side, and is curved into a shape along the inner peripheral surface 11a of the foil holder 11.

  Moreover, in this embodiment, as shown in FIG. 3, the notch part 12b2 is provided in the protrusion part 12b1, and the level | step difference along the notch part 12b2 is formed in the top foil part 12a1 which rides on this. As a result, the fluid flowing along the top foil portion 12a1 flows along the above steps and is collected on the center side in the axial direction, so that the pressure improvement effect is enhanced (see the arrow in FIG. 3).

  At this time, by providing the minute notch 12a3 in the vicinity of the insertion portion 12a2 in one circumferential end portion of the top foil portion 12a1, the rigidity of this portion is lowered. Thereby, the top foil part 12a1 can be easily deformed along the notch part 12b2 of the second region 12b arranged behind the top foil part 12a1.

  When the shaft 13 rotates in the direction of arrow B1 in FIG. 1, the fluid film in the radial bearing gap between the inner diameter surface (bearing surface) of the top foil portion 12a1 of each foil 12 of the foil bearing 10 and the outer peripheral surface of the shaft 13 Pressure is increased. Since the region including the circumferential end of the top foil portion 12a1 (the end portion on the rotation direction leading side) rides on the protruding portion 12b1 of the adjacent foil 12, the bearing surface of the shaft 13 faces the rotation direction leading side. Gradually approach the outer surface. As a result, a radial bearing gap gradually narrowing toward the leading side in the rotational direction is formed between the bearing surface of each foil 12 and the outer peripheral surface of the shaft 13, and fluid is pushed into the narrow side of the radial bearing gap. It is. Thereby, the pressure of the fluid film in the radial bearing gap is increased, and the shaft 13 is supported in a non-contact manner in the radial direction by this pressure.

  By the way, the foil 12 is held by the foil holder 11 by the insertion portion 12 a 2 being inserted into the axial groove 11 b of the foil holder 11, and is not fixed to the foil holder 11. For this reason, the foil 12 is allowed to change its posture and position with respect to the foil holder 11, and can be elastically deformed in accordance with the fluid pressure fluctuation generated in the bearing gap. For this reason, while the shaft 13 is rotating, the foil 12 and other members slide, and a frictional force is generated between them. Specifically, during the rotation of the shaft 13, the foils 12 or the foil 12 and the foil holder 11 slide to generate a frictional force.

  As shown in FIG. 6, when the shaft 13 rotates in the direction of the arrow B1, the top foil portion 12a1 and the protruding portion 12b1, the top foil portion 12a1 and the protruding portion 12b1, the inner peripheral surface 11a of the foil holder 11, the insertion portion 12a2 and the shaft The inner wall of the directional groove 11b slides, and a frictional force is generated between them. And the effect which attenuates the vibration at the time of rotation of the axis | shaft 13 by the frictional force which generate | occur | produces by this sliding can be acquired. For this reason, in order to stably support the shaft 13 on which the foil bearing 10 rotates, it is important to control the frictional force.

  Therefore, in the present embodiment, by forming an uneven surface on the surface other than the bearing surface of the foil 12 by chemical conversion treatment, the above-described frictional force is increased to enhance the vibration damping effect. Specifically, a chemical conversion treatment can be performed on the outer diameter surface of the top foil portion 12a1, both surfaces of the insertion portion 12a2, and both surfaces of the second region 12b (see FIG. 2). However, an uneven surface may be formed by chemical conversion treatment only on a part of these sliding surfaces, or chemical conversion treatment may be applied to the bearing surface for some reason.

  As a specific method, as shown in FIG. 7, the chemical conversion film 15 having the uneven surface 15 a is formed on the surface of the foil 12 by reacting a treatment agent on the surface of the foil 12 to cause a chemical reaction. . Thereby, the friction coefficient of the sliding surface of the foil 12 is increased, and the vibration damping effect is enhanced. In the present embodiment, the chemical conversion film 15 can be formed by causing a phosphate or oxalate such as iron phosphate, zinc phosphate, or manganese phosphate to act on the surface of the foil 12. Further, a chromate treatment in which chromate is applied to the surface of the foil 12 to form the chemical conversion film 15 or a black dyeing treatment in which a high temperature and high concentration alkaline solution is applied to the surface of the foil 12 to form the chemical conversion film 15 is used. You can also These methods can be appropriately selected according to the material used for the foil 12, the desired foil surface roughness, and the like. As an example, the chemical conversion treatment using zinc phosphate as a treating agent can form a chemical conversion film 15 having a maximum height roughness (Rz) of the uneven surface of 0.5 to 4.0 μm on the surface of the foil 12. . In addition, the maximum height roughness of an uneven surface here is the maximum height roughness defined by JISB0601-2001.

  As a method of forming an uneven surface on the surface of the foil 12, by adopting the method of forming a chemical conversion film on the surface of the foil 12 by chemical conversion treatment as described above, the treatment can be performed at a low temperature. The deformation of the foil 12 due to heating can be suppressed. In addition, since an external force is not applied to the foil 12 as in the case where an uneven surface is physically formed on the surface of the foil 12, no deformation or distortion occurs in the foil 12. Moreover, compared with a physical processing method, it can form with uniform roughness, without producing unevenness of an uneven surface. Therefore, it is possible to manufacture a foil bearing that can hardly support variations in shape and characteristics and can support a shaft that stably rotates at a high speed.

  Furthermore, as a method different from the above-described embodiment, a method of removing the chemical conversion film after forming the surface of the foil 12 on the uneven surface by chemical conversion treatment can be employed. Specifically, first, a chemical conversion treatment is performed on the surface of the foil 12 (see FIG. 8a). By this chemical conversion treatment, a chemical conversion film 15 is formed on the surface of the foil 12, and an unevenness is formed at the interface between the chemical conversion film 15 and the foil 12 (base material) by the action of the treatment agent (see FIG. 8 b). Thereafter, the chemical conversion film 15 is chemically removed from the foil 12 to form the foil 12 having the irregular surface 12d on the surface (see FIG. 8c).

  As an example of the above-described processing method, Chemiblast (registered trademark) processing of Nippon Parkerizing Co., Ltd. can be used. In the chemiblast treatment, an uneven surface is formed on the surface of the foil by the etching action of the treating agent, and then the chemical conversion film formed on the surface of the foil is removed. By this method, the surface roughness of the foil can give a roughness having a maximum height roughness (Rz) of 0.2 to 5.0 μm as an example.

  In FIG. 9, the enlarged view of the uneven | corrugated surface of the foil 12 formed by said chemiblasting is shown. In this embodiment, compared with a normal chemical conversion treatment, a finer and sharper uneven surface can be formed, and the surface area can be increased.

  In the present embodiment, the surface of the foil 12 itself is an uneven surface, and the coefficient of friction can be increased without forming a film on the surface of the foil 12. Therefore, since the thickness of the foil 12 hardly changes due to the formation of the uneven surface, there is no adverse effect such as deterioration of the flexibility of the foil 12 or an increase in the variation in flexibility.

  In addition, unlike the case where a film is formed on the surface of the foil 12, the film does not peel off or the film deteriorates due to the aging of the foil bearing 10, and the state of the film needs to be managed in order to prevent them. Absent.

  Further, as in the above-described embodiment, the foil is not deformed by heating or external force during the process, and the uneven surface can be formed with uniform roughness.

  From the above, it is possible to manufacture a foil bearing that can maintain a constant vibration damping effect of the foil bearing and can support a shaft that rotates stably at a high speed with little trouble in quality control. .

  The embodiment of the present invention has been described above, but the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the gist of the present invention.

  In the above embodiment, the case where the chemical conversion treatment is performed on the sliding surface of the foil is illustrated, but the inner peripheral surface 11a of the foil holder (other member) 11 may be chemical conversion treatment to form an uneven surface. Thereby, the frictional force between the foil and the foil holder can be increased, and the vibration damping effect of the shaft can be enhanced.

  A low friction coating such as PTFE, DLC film, titanium aluminum nitride film, tungsten disulfide film, or molybdenum disulfide film may be formed on the outer peripheral surface of the shaft 13 or the bearing surface X of the foil 12. Thereby, the frictional force generated between the shaft 13 and the foil 12 can be reduced, and the wear of the foil 12 can be reduced.

  Although the case where the radial foil bearing 10 is configured by a multi-arc bearing has been described in the above embodiment, the present invention is not limited thereto, and one end in the circumferential direction of each foil is attached to the inner peripheral surface 11a of the foil holder 11, and A so-called leaf-type radial bearing foil with the other end in the circumferential direction as a free end, or a so-called bump foil-type radial bearing foil with a corrugated back foil arranged on the outer diameter of a cylindrical top foil can be used. Good. Of course, the present invention can be applied to a thrust foil bearing. In this case, similarly to the above-described embodiment, an uneven surface can be formed on a surface other than the bearing surface of the foil.

  Moreover, although the case where the shaft 13 was a rotation side member and the foil holder 11 was a fixed side member was illustrated in the above embodiment, conversely, the shaft 13 is a fixed side member and the foil holder 11 is the rotation side. Even when it is a member, the configuration of FIG. 1 can be applied as it is. However, in this case, since the foil 12 serves as a rotation side member, it is necessary to design the foil 12 in consideration of deformation of the entire foil 12 due to centrifugal force.

DESCRIPTION OF SYMBOLS 10 Foil bearing 11 Foil holder 11a Inner peripheral surface 11b Axial direction groove | channel (holding part)
12 Foil 12a1 Top foil part 12a2 Insertion part 12b1 Protruding part (underfoil part)
12d Uneven surface 13 Shaft 15 Conversion coating 15a Uneven surface X Bearing surface

Claims (5)

In a foil bearing having a foil having a bearing surface and a foil holder for supporting the foil, the foil being elastically deformable, and allowing sliding between the foil and other members excluding the shaft to be supported.
A foil bearing characterized in that an uneven surface formed by chemical conversion treatment is provided on one or both of the surfaces of the foil and the surface of the other member that cause the sliding.   The foil bearing according to claim 1, wherein the uneven surface is formed on a surface of the chemical conversion coating.   The foil bearing according to claim 1, wherein the uneven surface is formed on the one or both surfaces by forming the unevenness at the interface between the chemical conversion film and the base material and then removing the chemical conversion film.   The foil bearing according to any one of claims 1 to 3, comprising a plurality of the foils, wherein the other member is one of the plurality of foils.   The foil bearing according to any one of claims 1 to 4, wherein the other member is a foil holder.

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