JP2019138374A - Foil bearing, foil bearing unit and turbo machine - Google Patents

Abstract

To increase a load capacity of a bearing at a low cost, in the foil bearing.SOLUTION: A foil bearing 10 comprises a cylindrical foil holder 11, and a plurality of foils 13 which are aligned along an internal peripheral face 11a of the foil holder 11. Each foil 13 has a top foil part Tf having a bearing face S opposing an external periphery 6a of a shaft 6 which should be supported, and a back foil part Bf for elastically supporting the to foil part Tf of the adjusting foil 13 from a rear side of the bearing face S, and the shaft 6 is rotatably supported by a fluid film which is formed in a bearing clearance h between the bearing face S of the top foil Tf and the external peripheral face 6a of the shaft 6. The internal peripheral face 11a of the foil holder 11 is formed of a surface of a resin layer 11y.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a foil bearing that rotatably supports a shaft, a foil bearing unit including a foil bearing, and a turbomachine.

  A bearing that supports a main shaft of a turbo machine such as a gas turbine or a turbocharger is required to withstand a severe environment such as high temperature and high speed rotation. As a bearing suitable for use under such conditions, a foil bearing as disclosed in Patent Document 1 has attracted attention.

  The foil bearing disclosed in this document includes a cylindrical foil holder, and a foil having a bearing surface that is disposed along the inner peripheral surface of the foil holder. The foil is a thin film having low flexibility with respect to bending. The foil bearing supports a load while allowing the bearing surface of the foil to bend. When the shaft rotates, a fluid film (for example, an air film) is formed in the bearing gap 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.

  By the way, since the lubricant is a gas, the foil bearing has an advantage that the shaft can be rotated with a lower torque than a dynamic pressure bearing using oil as a lubricant. On the other hand, since the load capacity of the bearing depends on the viscosity of the lubricant, the foil bearing has a disadvantage that the load capacity is smaller than that of the dynamic pressure bearing using oil as a lubricant. Therefore, in order to expand the application range of the foil bearing, it is necessary to further increase the load capacity.

  Here, as conceptually shown in FIG. 8, the magnitude of the load capacity of the hydrodynamic bearing is not only the viscosity of the lubricant, but also the outer peripheral surface 100a of the shaft 100 and the inner diameter of the bearing 200 facing the outer peripheral surface 100a. It also depends on the size of the bearing gap h formed between the peripheral surface 200a. The load capacity increases as the bearing gap h decreases. For this reason, in order to increase the load capacity of the foil bearing, it is effective to make the bearing gap between the outer peripheral surface of the shaft and the bearing surface of the foil as small as possible.

JP2015-113927A

  However, for the following reasons, it is difficult to increase the load capacity even if the bearing gap is simply reduced.

  That is, as exaggeratedly shown in FIG. 9, the outer peripheral surface 100a of the shaft 100 and the inner peripheral surface 200a of the bearing 200 are caused by waviness and protrusions (hereinafter collectively referred to as irregularities) due to the processing accuracy of these members. Say) is unavoidable. Therefore, as the bearing gap becomes smaller, the unevenness of the outer peripheral surface 100a of the shaft 100 and the unevenness of the inner peripheral surface 200a of the bearing 200 come into contact with each other, and it is impossible to increase the load capacity beyond that. It becomes possible. The same applies to the foil bearing, and the foil disposed along the inner peripheral surface is deformed following the unevenness due to the unevenness existing on the inner peripheral surface of the foil holder, resulting in unevenness on the bearing surface. appear. As a result, as the bearing gap becomes smaller, the irregularities on the outer peripheral surface of the shaft and the irregularities on the bearing surface of the foil will eventually come into contact.

  For the purpose of increasing the load capacity of the bearing, it is possible to take measures to suppress irregularities by improving the processing accuracy of the shaft and bearing, but in that case, the manufacturing cost will rise significantly. There is a difficulty to do. Under such circumstances, a technology capable of increasing the load capacity of the bearing at a low cost has been required in the foil bearing.

  An object of the present invention is to increase the load capacity of a bearing at a low cost in a foil bearing.

  The present invention made to solve the above problems comprises a cylindrical foil holder and a plurality of foils arranged side by side along the inner peripheral surface of the foil holder, and each foil has a shaft to be supported. A top foil portion having a bearing surface facing the outer peripheral surface, and a back foil portion for elastically supporting the top foil portion of the adjacent foil from the back side of the bearing surface, the bearing surface of the top foil portion and the outer peripheral surface of the shaft A foil bearing that rotatably supports the shaft with a fluid film formed in a bearing gap between the foil holder and the inner peripheral surface of the foil holder is composed of a surface of an elastic material included in the foil holder It is characterized by.

  In the foil bearing of the present invention, the inner peripheral surface of the foil holder is constituted by the surface of an elastic material included in the foil holder. As a result, when the shaft is decentered and the bearing gap is reduced, the inner surface of the foil holder and the foil (top foil portion) disposed along the inner surface are accompanied by fluctuations in the pressure distribution of the fluid film. Both bearing surfaces can be elastically deformed so as to follow the unevenness of the outer peripheral surface of the shaft. As a result, the bearing clearance between the outer peripheral surface of the shaft and the bearing surface of the foil can be reduced by an amount corresponding to the deformation of the bearing surface of the foil, and the load capacity of the bearing can be increased. Moreover, in the foil bearing of this invention, when increasing load capacity, the inner peripheral surface of a foil holder should just be comprised with the surface of the elastic material contained in the foil holder. For this reason, for the purpose of increasing the load capacity, for example, it is possible to avoid a significant increase in cost such as improving the processing accuracy of the inner peripheral surface of the foil holder. From the above, according to the foil bearing of the present invention, the load capacity of the bearing can be increased at low cost.

  In said foil bearing, the foil holder may use the cylindrical body which consists of sintered metals as a base material, and the elastic material may be fixed along the internal peripheral surface of a cylindrical body.

  In this way, the cylindrical body made of sintered metal is used as the base material of the foil holder, so that the dimensional accuracy of the inner peripheral surface of the foil holder constituted by the surface of the elastic material can be improved. Further, the elastic material can be firmly fixed to the inner peripheral surface of the cylindrical body by the anchor effect using the voids contained in the sintered metal.

  In said foil bearing, at least one of the outer peripheral surface of a foil holder and the axial direction end surface of a foil holder may be comprised by the surface of the sintered metal.

  In this way, when the foil bearing is incorporated into a turbo machine or the like, an advantage in incorporation can be obtained. That is, there are advantages such as avoiding the occurrence of defects due to creep when using press-fit for assembling, and improving the fastening strength between the foil bearing and the turbo machine.

  In the foil bearing described above, the thickness of the elastic material along the axial diameter direction may be within a range of 0.01 mm to 5 mm.

  If the thickness of the elastic material along the axial diameter direction is 0.01 mm or more, it is suitable for elastically deforming the inner peripheral surface of the foil holder so as to follow the unevenness of the outer peripheral surface of the shaft when the shaft is eccentric. Become. Furthermore, if the thickness along the axial direction of the elastic material is 5 mm or less, it is suitable for improving the shape accuracy of the inner peripheral surface of the foil holder formed by the surface of the elastic material. From the above, if the thickness along the axial direction of the elastic material is within the range of 0.01 mm to 5 mm, the shape accuracy of the inner peripheral surface is also suitably deformed while suitably elastically deforming the inner peripheral surface of the foil holder. It becomes possible to raise.

  In the above foil bearing, the foil and the elastic material may be integrally formed.

  In this way, it is not necessary to provide a portion for holding the foil in the foil holder. For this reason, the cost for providing the said site | part becomes unnecessary, and it becomes possible to achieve further cost reduction.

  If the above-described foil bearing and shaft are unitized as a foil bearing unit, they can be handled as a unit and can be easily assembled to a turbo machine or the like.

  The above foil bearing can be suitably applied to a turbomachine.

  According to the present invention, in a foil bearing, the load capacity of the bearing can be increased at low cost.

It is a figure which shows notionally the structure of a gas turbine. It is sectional drawing which shows the support structure of the rotor with which the gas turbine was equipped. It is sectional drawing which shows the foil bearing unit integrated in the support structure. (A) is a perspective view of the foil of a radial foil bearing, (b) is a perspective view of the state which temporarily assembled three foils. It is sectional drawing for demonstrating the effect | action of a foil bearing notionally. It is sectional drawing for demonstrating the effect | action of a foil bearing notionally. It is sectional drawing which shows the modification of a foil bearing unit. It is sectional drawing for demonstrating the subject in the past notionally. It is sectional drawing for demonstrating the subject in the past notionally.

  FIG. 1 conceptually shows the configuration of a gas turbine that is an example of a turbomachine. This gas turbine includes a turbine 1 and a compressor 2 that form blade rows, a generator 3, a combustor 4, and a regenerator 5 as main components. The turbine 1, the compressor 2, and the generator 3 are provided with a common shaft 6 that extends in the horizontal direction, and the shaft 6 and the turbine 1 and the compressor 2 constitute a rotor that can rotate integrally. . Air sucked from the intake port 7 is compressed by the compressor 2, heated by the regenerator 5, and then sent to the combustor 4. Fuel is mixed with this compressed air and burned, and the turbine 1 is rotated by high-temperature and high-pressure gas. The rotation of the turbine 1 is transmitted to the generator 3 via the shaft 6, and the generator 3 rotates to generate power, and this electric power is output via the inverter 8. Since the gas after rotating the turbine 1 is at a relatively high temperature, the heat of the gas after combustion is regenerated by sending this gas to the regenerator 5 and exchanging heat with the compressed air before combustion. Use. The gas that has been subjected to heat exchange in the regenerator 5 is discharged as exhaust gas after passing through the exhaust heat recovery device 9.

  FIG. 2 shows an example of a support structure for the rotor provided in the gas turbine. In this support structure, radial bearings 10 are arranged at two locations with an interval in the axial direction, and thrust bearings 20 are arranged on both sides in the axial direction with the flange portion 6b of the shaft 6 interposed therebetween. The shaft 6 is rotatably supported by the radial bearing 10 and the thrust bearing 20.

  In this support structure, the region located between the turbine 1 and the compressor 2 is adjacent to the turbine 1 that is rotated by the high-temperature and high-pressure gas, and thus has a high-temperature atmosphere. Under this high temperature atmosphere, the lubricant composed of lubricating oil, grease and the like is altered or evaporated, and it is difficult to apply a normal bearing (such as a rolling bearing) using these lubricants. Therefore, as the bearings 10 and 20 used in this type of support structure, an air dynamic pressure bearing, particularly a foil bearing is suitable.

  Hereinafter, the structure of the foil bearing 10 suitable for said gas turbine and the foil bearing unit 30 provided with the foil bearing 10 is demonstrated based on drawing.

  As shown in FIG. 3, the foil bearing 10 includes a tubular (cylindrical in the illustrated example) foil holder 11 and a plurality (three in the illustrated example) of foils 13 held by the foil holder 11. . The plurality of foils 13 are arranged in the circumferential direction along the inner peripheral surface 11 a of the foil holder 11. The foil bearing unit 30 is configured by the foil bearing 10 and the shaft 6 supported by the foil bearing 10.

  The foil holder 11 includes a cylindrical body 11x made of sintered metal as a base material, and a resin layer 11y as an elastic material fixed along the inner peripheral surface 11xa of the cylindrical body 11x. The sintered metal that forms the cylindrical body 11x includes pores. The resin layer 11y is firmly fixed to the inner peripheral surface 11xa of the cylindrical body 11x by the anchor effect using the holes.

  The inner peripheral surface 11a of the foil holder 11 is constituted by the surface of the resin layer 11y. On the other hand, the outer peripheral surface 11c of the foil holder 11 is composed of a surface of a sintered metal forming the cylindrical body 11x. Since the outer peripheral surface 11c is formed of a sintered metal surface in this way, when the foil bearing 10 is incorporated into the gas turbine using press-fitting, it is possible to avoid occurrence of problems due to creep. Advantages such as improved fastening strength can be obtained.

  The resin layer 11y may be formed by adhering a sheet made of a resin rolled into a cylindrical shape to the inner peripheral surface 11xa of the cylindrical body 11x, or insert-molded to the cylindrical body 11x. You may form by. This resin layer 11y has an elastic coefficient such that it can be elastically deformed along the axial direction in accordance with fluctuations in the pressure distribution of the fluid film formed in the bearing gap. The elastic modulus of the resin layer 11y is smaller than that of the sintered metal. The thickness along the axial diameter direction of the resin layer 11y is preferably within a range of 0.01 mm to 5 mm. Within this range, as will be described in detail later, when the shaft 6 is decentered, the inner peripheral surface 11a of the foil holder 11 can be suitably elastically deformed, and the shape accuracy of the inner peripheral surface 11a can be increased. Is possible. As the resin forming the resin layer 11y, for example, PEEK (polyether ether ketone), PAI (polyamideimide), or the like can be employed. However, the present invention is not limited to this, and another resin may be adopted depending on the use conditions in consideration of heat resistance and wear resistance.

  A groove 11b is formed on the inner peripheral surface 11xa of the cylindrical body 11x. In the present embodiment, the grooves 11b are arranged at a plurality of locations (three locations in the illustrated example) at regular intervals along the circumferential direction of the inner peripheral surface 11xa. Each groove 11b extends along the axial direction. As described above, the cylindrical body 11x is made of a sintered metal, and is integrally molded including the groove 11b, for example. In addition, when the foil bearing 10 is used in a relatively low temperature environment, the cylindrical body 11x may be molded with a resin. That is, the entire foil holder 11 may be made of resin.

  As shown to Fig.4 (a), each foil 13 is provided with the convex part 13c provided in the circumferential direction one end, and the recessed part 13d provided in the circumferential direction other end. The convex portion 13c and the concave portion 13d of each foil 13 are provided at the same position in the axial direction. As shown in FIG. 4B, the three foils 13 can be temporarily assembled into a cylindrical shape by fitting the convex portions 13 c of the respective foils 13 into the concave portions 13 d of the adjacent foils 13. In this case, as shown in FIG. 3, when viewed from the axial direction, one end in the circumferential direction (convex portion 13c) of each foil 13 and the other circumferential end of the adjacent foil 13 (on both sides in the axial direction across the concave portion 13d). The formed protrusion 13e) intersects. In this state, each foil 13 is held by the foil holder 11. Specifically, the protrusion 13e at the other circumferential end of each foil 13 is inserted into the groove 11b of the foil holder 11, and the protrusion 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 toward the front side in the rotational direction is restricted by the convex portions 13e of the foils 13 striking the corners of the grooves 11b. On the other hand, the movement to the back side of the rotation direction of the plurality of foils 13 is not restricted. Accordingly, the plurality of foils 13 can be moved in the circumferential direction with respect to the foil holder 11.

  In each foil 13, a portion where the inner diameter surface 13 a is exposed to the inner peripheral side from the adjacent foil 13 is provided with a radial bearing surface S (hereinafter simply referred to as a bearing surface S) facing the outer peripheral surface 6 a of the shaft 6. It functions as a foil part Tf (see FIG. 3). In the illustrated example, a multi-arc bearing surface S is formed by three foils 13. No member (such as a bump foil) is provided between the inner peripheral surface 11a of the foil holder 11 and the outer diameter surface 13b of each foil 13 for elastically supporting each foil 13 from the outer diameter surface 13b side. The outer diameter surface 13b of the foil 13 and the inner peripheral surface 11a of the foil holder 11 are slidable. The convex portion 13c of each foil 13 is a back foil portion that elastically supports the top foil portion Tf of the adjacent foil 13 from the back side (outer diameter surface 13b side) of the bearing surface S in place of the elastic support member. Functions as Bf.

  The foil 13 is formed as a strip-like foil having a thickness of about 20 μm to 200 μm made of a metal (for example, a steel material or a copper alloy) that is rich in spring properties and has good workability. In the air dynamic pressure bearing using air as a fluid film like the foil bearing 10 of 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.) For this reason, it is preferable to use stainless steel or bronze as the strip-like foil.

  In the above configuration, when the shaft 6 rotates in one circumferential direction (the arrow direction in FIG. 3), the bearing gap h (FIG. 6) is formed between the bearing surface S of the top foil portion Tf and the outer peripheral surface 6a of the shaft 6. And the shaft 6 is supported in the radial direction (axial diameter direction) by the pressure of the air film formed in the bearing gap h.

  At this time, due to the flexibility of the foil 13, the bearing surface S of the top foil portion Tf is arbitrarily deformed according to the operating conditions such as the load, the rotational speed of the shaft 6, the ambient temperature, etc. It is automatically adjusted to an appropriate size according to the operating conditions. Therefore, the bearing gap can be managed to an optimum size even under severe conditions such as high temperature and high speed rotation, and the shaft 6 can be stably supported.

  Further, in the foil bearing 10 of the present embodiment, the inner peripheral surface 11a of the foil holder 11 is configured by the surface of the resin layer 11y that is an elastic material, so that the following effects can be obtained. Hereinafter, the operation will be described with reference to FIGS. In both figures, of the shaft 6 and the foil bearing 10, the unevenness on the shaft 6 side (unevenness such as undulations and protrusions existing on the outer peripheral surface 6a of the shaft 6) is omitted, and the unevenness on the foil bearing 10 side is omitted. Only shown. Further, in both figures, the unevenness is exaggerated from the actual one.

  First, for comparison with the foil bearing 10 of the present embodiment, as shown in FIG. 5, the inner peripheral surface 11a of the foil holder 11 is virtually constituted by the inner peripheral surface 11xa of the cylindrical body 11x. explain.

  In this case, the foil 13 located on the inner peripheral surface 11xa is deformed following the unevenness due to the unevenness inevitably existing on the inner peripheral surface 11xa of the cylindrical body 11x, and as a result, the bearing surface S has unevenness. appear. When the shaft 6 is eccentric and the bearing gap h becomes smaller, the size of the bearing gap h when the unevenness (not shown) of the outer peripheral surface 6a of the shaft 6 and the unevenness of the bearing surface S come into contact with each other. It becomes the minimum value of the gap h. Since the inner peripheral surface 11xa is not substantially deformed even if the pressure distribution of the fluid film fluctuates due to the magnitude of the elastic coefficient of the sintered metal forming the cylindrical body 11x, the bearing is caused by the unevenness of the inner peripheral surface 11xa. It is unavoidable that irregularities appear on the surface S.

  Next, as shown in FIG. 6, the case where the inner peripheral surface 11a of the foil holder 11 is constituted by the surface of the resin layer 11y will be described as in this embodiment.

  In this case, when the shaft 6 is decentered and the bearing gap h becomes smaller, the foil 13 (top) located on the inner peripheral surface 11a and the inner peripheral surface 11a of the foil holder 11 accompanies fluctuations in the pressure distribution of the fluid film. The bearing surface S of the foil portion Tf) can be elastically deformed so as to follow the unevenness (not shown) of the outer peripheral surface 6a of the shaft 6. Therefore, the bearing gap h between the outer peripheral surface 6a of the shaft 6 and the bearing surface S of the foil 13 can be reduced by the amount of deformation of the bearing surface S of the foil 13, and the load capacity can be increased. it can.

  Moreover, in the foil bearing 10 of this embodiment, when increasing load capacity, the inner peripheral surface 11a of the foil holder 11 should just be comprised with the surface of the resin layer 11y. For this reason, for the purpose of increasing the load capacity, for example, it is possible to avoid processing that causes a significant increase in cost, such as improving the processing accuracy of the inner peripheral surface 11xa of the cylindrical body 11x and suppressing unevenness.

  Hereinafter, modifications of the foil bearing unit 30 will be described. In the description of the modified example, elements that are substantially the same as those already described in the above embodiment are denoted by the same reference numerals, and redundant description is omitted, and differences from the above embodiment are described. Only explained.

  As shown in FIG. 7, the foil bearing unit 30 of the modified example is different from the foil bearing unit 30 of the above-described embodiment in that the foil 13 and the resin layer 11 y are different in the foil bearing 10 provided therein. It is the point formed integrally and the point from which the groove | channel 11b is excluded from the cylindrical body 11x. In this modification, the foil 13 is made of the same resin as the resin layer 11y. Moreover, in this modification, the foil 13 and the resin layer 11y are united by the site | part corresponded to the convex part 13e in said embodiment being continuous with the resin layer 11y. According to this modification, it is not necessary to provide the foil holder 11 with the groove 11b for holding the foil 13. For this reason, the cost for providing the groove | channel 11b becomes unnecessary, and it becomes possible to achieve further cost reduction.

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

  In the above embodiment, the outer peripheral surface 11c of the foil holder 11 is formed of a sintered metal surface. Instead of or in addition to this, the axial end surface Es of the foil holder 11 (see FIG. 2). ) May be composed of a sintered metal surface. Moreover, in said embodiment, although resin is employ | adopted as an elastic material, the material which can elastically deform the internal peripheral surface 11a of the foil holder 11 may be employ | adopted as an elastic material also except this.

  The application object of the foil bearing unit 30 according to the present invention is not limited to the gas turbine described above, and can be used, for example, as a bearing that supports a rotor of a supercharger. Furthermore, the foil bearing according to the present invention is not limited to a turbo machine such as a gas turbine or a supercharger, but (1) lubrication with a liquid such as a lubricating oil is difficult. (2) Lubricating oil circulation from the viewpoint of energy efficiency As a bearing for vehicles such as automobiles used under restrictions such as (3) resistance due to liquid shear becomes a problem, and also as a bearing for industrial equipment Can be widely used.

  The foil bearing described above is an air dynamic pressure bearing that forms an air film as a fluid film. However, the present invention is not limited to this, and a film made of another gas or liquid may be formed as a fluid film. Good. For this reason, other gas or liquids, such as water and oil, can be used as a lubricant.

6 shaft 6a shaft outer surface 10 foil bearing 11 foil holder 11a foil holder inner surface 11c foil holder outer surface 11x cylindrical body 11xa cylindrical body inner peripheral surface 11y resin layer 13 foil 30 foil bearing unit Es foil holder End face in the axial direction h Bearing clearance S Bearing surface Tf Top foil part Bf Back foil part

Claims (7)

A top foil portion comprising a cylindrical foil holder and a plurality of foils arranged side by side along the inner peripheral surface of the foil holder, each foil having a bearing surface facing the outer peripheral surface of the shaft to be supported And a back foil portion that elastically supports the top foil portion of the adjacent foil from the back side of the bearing surface,
A foil bearing that rotatably supports the shaft with a fluid film formed in a bearing gap between a bearing surface of the top foil portion and an outer peripheral surface of the shaft,
The foil bearing is characterized in that an inner peripheral surface of the foil holder is constituted by a surface of an elastic material included in the foil holder.   2. The foil bearing according to claim 1, wherein the foil holder includes a cylindrical body made of sintered metal as a base material, and the elastic material is fixed along an inner peripheral surface of the cylindrical body. .   The foil bearing according to claim 2, wherein at least one of an outer peripheral surface of the foil holder and an axial end surface of the foil holder is formed of a surface of the sintered metal.   The foil bearing according to any one of claims 1 to 3, wherein a thickness of the elastic material along an axial diameter direction is within a range of 0.01 mm to 5 mm.   The foil bearing according to claim 1, wherein the foil and the elastic material are integrally formed.   The foil bearing unit provided with the foil bearing in any one of Claims 1-5, and the said axis | shaft.   The turbomachine provided with the foil bearing in any one of Claims 1-5, and the said axis | shaft.

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