JP2019082195A - Foil bearing, foil bearing unit and turbo machine - Google Patents

Abstract

To provide flexibility to a foil to prevent warpage of a foil, regardless of material of a coat to be formed.SOLUTION: A foil bearing 10 comprises a foil holder 11, and a foil 13 attached to the foil holder 11, and supports a shaft 6 in a relatively rotatable manner. The foil 13 has a slide layer 14 on a bearing surface S supporting the shaft 6. The slide layer 14 comprises a plurality of regions 14a made of a material different from a base material of the foil 13, and divided in a circumferential direction of the foil bearing 10.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a foil bearing, a foil bearing unit, and a turbomachine provided with a foil bearing.

  Foil bearings have attracted attention as bearings for supporting the shaft of turbomachines such as gas turbines and turbochargers. The foil bearing constitutes a bearing surface with a thin film (foil) having flexibility, and supports a load while allowing deflection of the bearing surface (for example, Patent Document 1).

  The above-mentioned foil bearing supports the shaft in a non-contact manner by the fluid (gas) which is mediated between the shaft and the foil, and a contact occurs between the shaft and the foil at the time of start and stop. For this reason, in order to improve the wear resistance and durability of the foil surface, inventions have already been made to apply a coating treatment to form a coating such as DLC, molybdenum disulfide or nickel plating on the bearing surface of the foil (for example, Patent documents 2, 3).

Japanese Patent Publication No. 2008-519662 JP 2003-262222 A JP, 2015-113927, A

  As described above, by forming a film, the wear resistance and durability of the foil can be improved, but on the other hand, depending on the type of film, the rigidity of the foil may be too high. For example, when a hard coating such as DLC is formed on the foil, the flexibility of the foil is impaired and the bearing function is reduced, or in the case of a foil bearing of a type giving a preload as in Patent Document 1, the preload is It becomes excessive and deformation and wear of the foil occur. In addition, there is a problem that residual stress is generated in the film after the coating process, and the residual stress causes the warp of the foil to cause deterioration in the assemblability of the bearing and the bearing function.

  From such a circumstance, in the present invention, regardless of the material to be configured, maintaining the rigidity of the foil at a certain level or less allows the foil to have flexibility and has a sliding layer capable of preventing the foil from warping. The purpose is to realize bearings.

  In order to solve the above problems, the present invention is a foil bearing comprising a foil holder and a foil attached to the foil holder, the foil bearing rotatably supporting an axis, the foil supporting the axis And a sliding layer, the sliding layer being formed of a material different from the base material of the foil, and characterized by a foil bearing comprising a plurality of regions divided in the circumferential direction of the foil bearing.

  By dividing the sliding layer into a plurality of regions in the circumferential direction, it is possible to allow elastic deformation of the base material in the gap between the regions, so that the foil can have flexibility. In addition, by dividing the sliding layer into a plurality of pieces, it is possible to reduce the residual stress generated at the time of forming the sliding layer in each region, so that the foil can be prevented from warping.

  In the present invention, the foil can be provided with a sliding layer to improve the durability and wear resistance of the foil, maintain the flexibility of the foil, and prevent deformation of the foil when forming the sliding layer .

It is a figure which shows the structure of a gas turbine notionally. It is sectional drawing which shows the support structure of the rotor in the said gas turbine. It is sectional drawing of the foil bearing unit integrated in the said support structure. (A) The figure is a perspective view of the foil of a radial foil bearing, and the (b) figure is a perspective view in the state which temporarily assembled three sheets of foil. It is a perspective view of the foil which provided the sliding layer of this embodiment. It is sectional drawing of the foil which provided the sliding layer of this embodiment. It is a figure which shows the mode of elastic deformation of the foil of this embodiment. It is a figure which shows the foil provided with the sliding layer of the structure different from this invention.

  FIG. 1 conceptually shows the configuration of a gas turbine apparatus as an example of a turbomachine. This gas turbine mainly includes a turbine 1 and a compressor 2 forming a cascade, a generator 3, a combustor 4 and a regenerator 5. The turbine 1, the compressor 2, and the generator 3 are provided with a common shaft 6 extending in the horizontal direction, and the shaft 6 and the turbine 1 and the compressor 2 constitute a rotor that can integrally rotate. The air taken in from the air inlet 7 is compressed by the compressor 2, heated by the regenerator 5, and fed to the combustor 4. The compressed air is mixed with fuel and burned, and the turbine 1 is rotated by the high temperature, high pressure gas. The rotational force of the turbine 1 is transmitted to the generator 3 via the shaft 6 to generate electricity as the generator 3 rotates, and this power is output via the inverter 8. Since the gas after rotating the turbine 1 is at a relatively high temperature, this gas is sent to the regenerator 5 to exchange heat with the compressed air before combustion to reheat the heat of the gas after combustion. Use The gas whose heat exchange has been completed by the regenerator 5 is discharged as exhaust gas after passing through the exhaust heat recovery device 9.

  FIG. 2 shows an example of the support structure of the rotor in the gas turbine. In this support structure, the radial bearings 10 are disposed at two places in the axial direction, and the thrust bearings 20, 20 are disposed on both sides in the axial direction of the flange portion 6 b of the shaft 6. The shaft 6 is rotatably supported in the radial direction and in both thrust directions by the radial bearing 10 and the thrust bearing 20.

  In this support structure, the area between the turbine 1 and the compressor 2 is a high temperature atmosphere because it is adjacent to the turbine 1 rotated with a high temperature, high pressure gas. In this high-temperature atmosphere, since a lubricant composed of a lubricant and grease is degraded and evaporated, it is difficult to apply a normal bearing (rolling bearing or the like) using such a lubricant. Therefore, air dynamic bearings, in particular foil bearings, are suitable as the bearings 10, 20 used in this type of support structure.

  Hereinafter, the configuration of the foil bearing 10 compatible with the radial bearing for the gas turbine and the foil bearing unit 30 provided with the foil bearing 10 will be described based on the drawings.

  As shown in FIG. 3, the foil bearing 10 has a cylindrical (cylindrical in the illustrated example) foil holder 11 and a plurality of (three in the illustrated example) foils 13 attached to the inner peripheral surface of the foil holder 11. Have. The plurality of foils 13 are circumferentially arranged on the inner circumferential surface of the foil holder 11. In addition, a foil bearing unit 30 is constituted by the foil bearing 10 and the shaft 6 supported by the foil bearing 10.

  A groove 11 b is formed on the inner circumferential surface 11 a of the foil holder 11. In the present embodiment, grooves 11 b extending in the axial direction are provided at a plurality of locations (three locations in the illustrated example) at equal intervals in the circumferential direction of the foil holder 11. The foil holder 11 is formed of metal and is integrally molded, for example, including the groove 11b. The foil holder 11 of the present embodiment is integrally molded of sintered metal. When the foil bearing 10 is used in a relatively low temperature environment, the foil holder 11 may be molded with resin.

  Each foil 13 is provided with the convex part 13c provided in the circumferential direction end, and the recessed part 13d provided in the circumferential direction other end, as shown to Fig.4 (a). The protrusion 13 c and the recess 13 d of each foil 13 are provided at the same position in the axial direction. As shown in FIG. 4B, by inserting the convex portions 13c of the respective foils 13 into the concave portions 13d of the adjacent foils 13, three foils 13 can be temporarily assembled in a tubular shape. In this case, in the axial direction view shown in FIG. 3, one circumferential end (convex portion 13c) of each foil 13 and the other circumferential end (convex portions 13e on both axial sides of concave portion 13d) of adjacent foils 13 intersect It will be in a state of In this state, both circumferential ends of each foil 13 are held by the foil holder 11. Specifically, the convex portion 13e at the other circumferential end of each foil 13 is inserted into the groove 11b of the foil holder 11, and the convex portion 13c at one circumferential end of each foil 13 is the outer diameter surface 13b of the adjacent foil 13. And the inner peripheral surface 11 a of the foil holder 11. In this case, the movement of the plurality of foils 13 in the forward direction of the rotation is restricted by the projections 13e of the respective foils 13 abutting against the corners of the grooves 11b, but the backward direction of the plurality of foils 13 is restricted. Movement is not regulated. Thereby, the plurality of foils 13 can be moved circumferentially with respect to the foil holder 11.

  The inner diameter surface 13a of each foil 13 functions as a radial bearing surface S (see FIG. 3). In the illustrated example, the multi-arc radial bearing surface S is formed by three foils 13. A member (such as a back foil) for applying an elastic force to the foil 13 is not provided between the inner circumferential surface 11 a of the foil holder 11 and each foil 13, and the outer diameter surface 13 b of the foil 13 and the foil The inner circumferential surface 11 a of the holder 11 is slidable. The protrusion 13 c of each foil 13 is disposed on the outer diameter side of the radial bearing surface S of the adjacent foil 13 and functions as an under-foil portion.

The foil 13 is formed of a strip-like foil having a thickness of about 20 μm to 200 μm made of a metal having high springiness and good workability, such as a steel material or a copper alloy. In the case of an air dynamic pressure bearing using air as a fluid film as in the present embodiment, no lubricating oil exists in the atmosphere, so the antirust effect by the oil can not be expected. Carbon steel and brass can be mentioned as typical examples of steel materials and copper alloys, but corrosion is likely to occur due to rust in general carbon steel, and placing cracks may occur due to working strain in brass (in brass This tendency becomes stronger as the Zn content of Therefore, it is preferable to use stainless steel or bronze as the strip foil.

  In the above configuration, when the shaft 6 rotates in one circumferential direction (the direction of the arrow in FIG. 3), a bearing gap is formed between the radial bearing surface S of the foil 13 of the foil bearing 10 and the outer peripheral surface 6 a of the shaft 6 The shaft 6 is supported in the radial direction by the pressure of the air film generated in the bearing gap.

  At this time, due to the flexibility of the foil 13, the bearing surface S of each foil 13 is arbitrarily deformed according to the operating conditions such as the load, the rotational speed of the shaft 6, and the ambient temperature. Automatically adjusted to the appropriate width according to. Therefore, even under severe conditions such as high temperature and high speed rotation, the bearing gap can be controlled to the optimum width, and the shaft 6 can be supported stably.

  In addition, it is difficult to form an air film having a thickness equal to or greater than the surface roughness on the bearing surface S of each foil 13 and the outer peripheral surface 6a of the shaft 6 at low speed rotation immediately before stopping or starting. Therefore, metal contact is caused between the bearing surface S of each foil 13 and the outer peripheral surface 6 a of the shaft 6 to cause an increase in torque. For this reason, in the present embodiment, a coating for reducing the friction of the surface is formed on the bearing surface S (inner diameter surface 13a) of each foil 13 to prevent abrasion of the surface of the foil 13.

  Specifically, as shown in FIGS. 5 and 6, the bearing surface S of the foil 13 (the sliding layer 14 is provided on the inner diameter surface 13a. The sliding layer 14 is formed of a plurality of circumferentially divided foil bearings. Each coating 14 a is provided so as to extend in the axial direction of the foil 13.

  In the present embodiment, the film 14a is a hard film formed by DLC. However, not limited to this, a soft coating may be used. As another example, a titanium aluminum nitride film or a molybdenum disulfide film can be used.

  By providing the sliding layer 14 on the bearing surface S of the foil 13, the durability and wear resistance of the foil 13 can be improved, and the bearing life can be increased.

  Further, as in the present embodiment, by forming the sliding layer 14 with the coating 14 a divided into a plurality, even if a hard coating is used as the coating 14 a, the flexibility of the foil 13 is impaired. I have not. That is, as shown in the enlarged view of FIG. 6, elastic deformation of the foil 13 which is a base material can be allowed in the gap X between the coating 14a and the coating 14a. For example, as shown in FIG. 7, the foil 13 can be elastically deformed along the outer peripheral surface 6 a of the shaft 6.

  Therefore, according to the configuration of the present embodiment, regardless of the material of the film 14 a constituting the sliding layer 14, elastic deformation of the foil 13 according to operating conditions such as load applied to the foil 13, rotation speed of the shaft 6, and ambient temperature. Can be tolerated. This allows the foil bearing 10 to form an appropriate bearing gap and facilitates the design of the foil bearing 10. Further, since the rigidity of the foil 13 is not excessively increased, it is possible to prevent the preload from being excessive even in a foil bearing configured to apply a preload to the foil 13.

  Furthermore, by the configuration of the sliding layer of the present embodiment, it is possible to suppress the deformation of the foil 13 due to the residual stress of the coating. That is, as in the case of the sliding layer 14 'having a configuration different from that of the present embodiment shown in FIG. The stress causes a large force to be applied to the foil 13 in the direction in which the foil 13 is pulled or compressed. As a result, the foil 13 is deformed, resulting in the deterioration of the assemblability of the foil bearing and the deterioration of the bearing function. On the other hand, when the sliding layer 14 is constituted by a plurality of coatings 14a divided in the circumferential direction as in the configuration of the present embodiment shown in FIG. 6, the force applied from each coating 14a to the foil 13 is By being relatively smaller, it is possible to suppress the warpage of the foil 13 as a whole, and the quality of the bearing is stabilized.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the above-mentioned embodiment, Of course in the range which does not deviate from the summary of this invention, a various change can be added. The shape of the above-mentioned foil bearing is an example, and of course it is not limited to the shape.

  Although the case where the sliding layer of the present invention is applied to the radial file bearing 10 is shown in the above embodiment, the present invention is applied to the bearing surface (surface facing the flange portion 6b) of the thrust foil bearing 20 (see FIG. 2). The sliding layer of the invention may be provided.

  The above embodiment shows the case where the sliding layer is divided into a plurality of regions in the circumferential direction of the foil. In addition to this, it is preferable that the sliding layer be divided into a plurality of regions in the axial direction.

  In addition to providing the sliding layer 14 on the bearing surface S of the foil 13, the outer circumferential surface 6 a of the shaft 6 may be provided with a sliding layer formed of a coating or the like.

  The application object of the foil bearing unit 30 according to the present invention is not limited to the above-described gas turbine, and can be used, for example, as a bearing for supporting a rotor of a supercharger. Further, the foil bearing according to the present invention is not limited to turbo machines such as gas turbines and turbochargers, but it is difficult to lubricate with a liquid such as lubricating oil. It can be widely used as a bearing for vehicles such as automobiles used under the limitation that it is difficult to provide, or resistance by shearing of liquid becomes a problem, and further, a bearing for industrial equipment.

  In addition, each foil bearing described above is an air dynamic bearing using air as a pressure generating fluid, but the invention is not limited to this, it is possible to use other gas as a pressure generating fluid, or water or oil Liquids such as can also be used.

10 foil bearing 11 foil holder 13 foil 14 sliding layer 14a coating (area)
30 foil bearing unit S bearing surface

Claims (3)

A foil bearing comprising a foil holder and a foil attached to the foil holder, the foil bearing rotatably supporting an axis relative to each other,
The foil has a sliding layer on the surface supporting the shaft,
A foil bearing, wherein the sliding layer is made of a material different from a base material of the foil, and is composed of a plurality of circumferentially divided regions of a foil bearing.   A foil bearing unit comprising the foil bearing according to claim 1 and the shaft.   A turbomachine comprising the foil bearing according to claim 1 and the shaft.

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