JP2017227240A - Foil bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a foil bearing capable of arbitrarily changing rigidity of a bearing surface of a foil at each bearing surface.SOLUTION: A foil bearing 10 includes a top foil part Tf including a bearing surface X opposite to a shaft 6 to be supported, and a back foil part Bf elastically supporting the top foil part Tf at the back of the top foil part Tf; and is configured to support the shaft 6 that relatively rotates in a non-contact manner, with a fluid film generated in a bearing gap C between the shaft 6 and the bearing surface X. The back foil part Bf comprises a net-like body 20 in which a plurality of warp materials 21 and weft materials 22 intersect with each other and are regularly arranged and formed.SELECTED DRAWING: Figure 9

Description

  The present invention relates to a foil bearing.

  A foil bearing is known as a bearing that can easily manage the gap width of a bearing gap even in an environment in which a whirl is not easily generated and a temperature change is large. A foil bearing consists of a thin metal plate (foil) that has low rigidity against bending and supports the load by allowing the bearing surface to bend. It is characterized by being automatically adjusted to an appropriate width according to conditions and the like. For example, Patent Document 1 below discloses a foil bearing called a bump type as an example of a radial foil bearing that supports a radial load.

JP2013-87789A

  The foil bearing described in Patent Document 1 includes a cylindrical top foil, a back foil (bump foil) that elastically supports the top foil, and a bearing holder to which the top foil and the back foil are attached. In this bump type foil bearing, since the back foil is elastically deformed when the top foil receives a load, the top foil is allowed to bend.

  Incidentally, the back foil of the bump type foil bearing has a corrugated form in which convex portions 200 extending in the axial direction (arrow direction) are arranged in the circumferential direction as shown in FIG. The back foil formed of such a single plate material is deformed so as to push and spread each convex portion 200 at the time of elastic deformation, but the deformation resistance at that time is large, and the back foil is generally high. It becomes rigid. For this reason, the flexibility of the top foil tends to be insufficient. When the flexibility of the top foil is insufficient, the function of automatically adjusting the bearing gap is impaired, and problems such as easy contact between the shaft and the top foil are caused.

  Then, an object of this invention is to provide the foil bearing which improved the softness | flexibility of the top foil part.

  In order to solve the above problems, the present invention includes a top foil portion having a bearing surface facing a shaft to be supported, and a back foil portion that elastically supports the top foil portion behind the top foil portion. In a foil bearing that supports a relatively rotating shaft in a non-contact manner with a fluid film generated in a bearing gap between the shaft and the bearing surface, the back foil portion intersects a plurality of wires and is regularly arranged It consists of the net-like body formed by being formed.

  In such a configuration, due to the fluid pressure generated in the bearing gap during the operation of the bearing, a compressive force acts in the action direction of the fluid pressure (radial direction in the radial bearing, axial direction in the thrust bearing) via the top foil portion. . And with respect to this fluid pressure, a rigidity difference can be produced in each part in a back foil by comprising a back foil part with the net-like body which made the wire cross | intersect.

  Specifically, the back foil portion has a high rigidity at a portion where the wire and the wire intersect, and the back foil portion has a low rigidity around the high rigidity portion (a portion adjacent to the crossing portion of each wire). When the back foil portion receives fluid pressure, the low rigidity portion elastically deforms, so that the compressive force generated by the fluid pressure can be absorbed.

  The high-rigidity part can move relative to each direction in which the low-rigidity part is provided by elastic deformation of the low-rigidity part. By providing the low-rigidity portion around the high-rigidity portion, the relative movement of the high-rigidity portion in each direction can be allowed, so that the flexibility of the back foil portion can be increased.

  Further, in such a configuration, it is possible to cause a difference in rigidity by crossing wires at an arbitrary position of the back foil part, and a combination of the high rigidity part and the low rigidity part formed in the periphery thereof is combined with the back foil part. It can be distributed throughout. For this reason, the back foil portion can be elastically deformed in accordance with the fluid pressure received by each portion, and the entire bearing surface can be provided with a spring property.

  The mesh body can be formed by crossing a plurality of warps and wefts arranged in two orthogonal directions. Thereby, the compressive force can be absorbed by elastic deformation of the low rigidity portion of the warp material and the weft material, and the warp material and the weft material can be in sliding contact with each other to absorb the vibration from the shaft.

  The net-like body can be formed by partially changing the density of the arranged wires or by using different materials or different thicknesses. Thereby, bearing characteristics, such as the rigidity of a back foil part, can be changed partially, and the support rigidity of the axis | shaft as the whole foil bearing can be adjusted easily.

  The back foil portion can be formed by laminating a plurality of nets. Thereby, sliding between the laminated nets can be allowed, and the vibration of the shaft can be more easily absorbed. In addition, by changing the configuration of each mesh member, it is easy to adjust the rigidity and springiness of the entire back foil portion.

  It is preferable that the back foil portion has a convex portion protruding toward the bearing surface, and the convex portions are arranged in a staggered manner with respect to the rotation direction of the shaft. At the position of the convex portion, the back foil portion is highly rigid and difficult to deform, and the fluid film formed between the shaft and the shaft becomes high pressure, and the fluid is difficult to escape in the rotational direction of the shaft. For this reason, by arranging the convex portions in a staggered manner with respect to the rotational direction of the shaft, the fluid flowing through the bearing gap flows while branching in multiple directions so as to avoid the convex portions, and the flow is complicated. Turn into. Thereby, it becomes difficult for the fluid to escape in the bearing gap, and a constant air film can be maintained.

  According to the present invention, flexibility can be imparted to the entire bearing surface. Thereby, since the automatic adjustment function of the bearing gap is satisfactorily exhibited, it is possible to reliably prevent contact between the shaft and the top foil portion.

It is a figure which shows notionally the structure of a micro gas turbine. It is a figure which shows schematic structure of the rotor support structure of a micro gas turbine. It is sectional drawing of the foil bearing concerning this invention. It is a top view of foil. It is the top view which looked at two foils connected from the back side. It is a perspective view showing the state where three foils were temporarily assembled. It is a perspective view which shows a mode that the temporary assembly of foil is attached to a foil holder. It is sectional drawing which expands and shows the foil overlap part of a foil bearing. It is a perspective view of the back foil part formed of a net-like body. It is a top view of a net-like body. It is a top view of the foil of the present invention. It is sectional drawing of a mesh-like body, (a) A figure is the A1-A1 sectional view taken on the line in FIG. 9, (b) The figure is A2-A2 sectional view taken on the line in FIG. It is the schematic which shows arrangement | positioning of the highly rigid part and low rigid part in a net-like body. It is a top view which shows the modification of a back foil part. It is sectional drawing which shows the modification of a back foil part. It is a top view which shows the modification of a back foil part. It is a top view which shows the modification of a back foil part. It is a schematic diagram which shows the flow of the air in a bearing clearance, (a) A figure is a foil bearing of this invention, (b) A figure is a figure which shows the foil bearing using the conventional plate-shaped back foil. It is sectional drawing which shows a leaf type radial foil bearing. It is sectional drawing which shows a bump type radial foil bearing. It is a perspective view which shows a leaf type thrust foil bearing. FIG. 22 is a cross-sectional view taken along line A2-A2 in FIG. It is a perspective view which shows the back foil of a bump type foil bearing.

  FIG. 1 conceptually shows a configuration of a gas turbine device called a micro gas turbine as an example of a turbo machine. The gas turbine apparatus includes a turbine 1 having a blade row, a compressor 2, a generator 3, a combustor 4, and a regenerator 5 as main components. The turbine 1 and the compressor 2 are attached to a shaft 6 extending in the horizontal direction and constitute a rotor on the rotating side together with the shaft 6. One axial end of the shaft 6 is connected to the generator 3. When this micro gas turbine is operated, air is sucked from the air inlet 7, and the sucked air is compressed by the compressor 2 and heated by the regenerator 5 and then sent to the combustor 4. The combustor 4 mixes fuel with compressed and heated air and burns the fuel to generate high-temperature and high-pressure gas, and the turbine 1 is rotated by the gas. When the turbine 1 rotates, the rotational force is transmitted to the generator 3 via the shaft 6, and the generator 3 is rotationally driven. The electric power generated by rotating the generator 3 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 conceptually shows an example of a rotor support structure in the micro gas turbine shown in FIG. In this support structure, the radial bearing 10 is disposed around the shaft 6, and the thrust bearings 30 are disposed on both sides in the axial direction of the flange portion 6 b provided on the shaft 6. The shaft 6 is supported by the radial bearing 10 and the thrust bearing 30 so as to be rotatable in both the radial direction and the thrust direction. In this support structure, the region between the turbine 1 and the compressor 2 becomes a high temperature atmosphere because it is adjacent to the turbine 1 rotated by high temperature and high pressure gas. In addition, the shaft 6 rotates at a rotational speed of tens of thousands rpm or more. Therefore, as the bearings 10 and 30 used in this support structure, an air dynamic pressure bearing, particularly a foil bearing is suitable.

  As an example of the foil bearing suitable for the radial bearing 10 for the micro gas turbine, a so-called multi-arc type is used. Hereinafter, a basic configuration of the multi-arc foil bearing will be described with reference to FIGS.

[Basic configuration of multi-arc foil bearing]
As shown in FIG. 3, the multi-arc radial foil bearing 10 includes a foil holder 11 having a cylindrical inner peripheral surface 11 a, and a plurality of rotational directions of the shaft 6 on the inner peripheral surface 11 a of the foil holder 11. And a foil 12 disposed at a location. The foil bearing 10 of the example of illustration has illustrated the case where the foil 12 is arrange | positioned in three places of the internal peripheral surface 11a. A shaft 6 is inserted on the inner diameter side of each foil 12.

  The foil holder 11 can be formed of metal (for example, steel material) such as sintered metal or melted material. On the inner peripheral surface 11 a of the foil holder 11, axial grooves 11 b serving as attachment portions of the foils 12 are formed at a plurality of locations (the same number as the number of foils) separated in the rotation direction R.

  The foil material constituting each foil 12 is processed into a predetermined shape by press working or the like, which is made of a metal having a high spring property and good workability, for example, a steel foil or a copper alloy having a thickness of about 20 μm to 200 μm. Is formed. Typical examples of steel materials and copper alloys include carbon steel and brass. However, in general carbon steel, there is no lubricating oil in the atmosphere and the antirust effect by oil cannot be expected. It tends to occur. Further, brass may cause cracks due to processing strain (this tendency becomes stronger as the Zn content in brass increases). Therefore, it is preferable to use a stainless steel or bronze foil as the belt-like foil.

  As shown in FIG. 4, the foil 12 has a first region 12 a on the rotation direction R side of the shaft 6 and a second region 12 b on the counter rotation direction side.

  The first region 12a includes a top foil portion Tf that forms the bearing surface X, and a plurality of directions N (hereinafter simply referred to as “orthogonal directions N”) that are along the surface of the top foil portion Tf and orthogonal to the rotation direction R. And a convex portion 12a2 extending in a direction protruding to the rotation direction R side. In this embodiment, the case where the convex part 12a2 is formed in the three places of the said orthogonal direction is illustrated. A minute notch 12a3 extending in the counter-rotating direction from the foil edge is provided at the base end of each convex portion 12a2.

  At the rear end 12d (end on the counter-rotation direction side) of the second region 12b, two notches 12b2 that are spaced apart in the orthogonal direction N and are recessed toward the rotation direction R are formed. The width dimension in the orthogonal direction N of each notch 12b2 is gradually reduced toward the rotation direction R. In the present embodiment, the case where the entire cutout portion 12b2 is formed in an arc shape is illustrated, but each cutout portion 12b2 can also be formed in a substantially V shape with the top portion being pointed. Protruding portions 12b1 that protrude in the counter-rotating direction are formed on both sides of each cutout portion 12b2 in the orthogonal direction N.

  A slit-like insertion port into which the convex portions 12a2 of the adjacent foils 12 are inserted at a boundary portion between the first region 12a and the second region 12b and at a plurality of locations in the orthogonal direction N (the same number as the convex portions 12a2). 12c1 is provided. Among these, the insertion ports 12 c 1 at both ends extend linearly in the orthogonal direction N and open at both ends of the foil 12. The central insertion port 12c1 includes a linear cutout portion extending along the orthogonal direction N, and a wide cutout portion extending from the cutout portion in the counter-rotating direction and having a circular arc at the tip. Become.

  As shown in FIG. 5, the two foils 12 can be connected by inserting each convex portion 12 a 2 of one foil 12 into the insertion port 12 c 1 of the adjacent foil 12. In the figure, one of the two foils 12 after the combination is given a gray color.

  And as shown in FIG. 6, each foil 12 can be made into the state of a temporary assembly by connecting the three foils 12 in the circumferential shape with the joint method similar to FIG. 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 convex portion 12 a 2 of each foil 12 is opened in the axial groove 11 b (opened on one end face of the foil holder 11. (See FIG. 7) from one side in the axial direction. As described above, 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 rotation direction R.

  As shown in FIG. 8, when the foils 12 are attached to the foil holder 11, the two adjacent foils 12 cross each other. On the rotation direction R side with respect to the intersecting portion, the convex portion 12a2 of one foil 12 wraps behind the other foil 12 through the insertion port 12c1 of the other foil 12, and the axial groove 11b of the foil holder 11 Has been inserted. The top foil portion Tf of the other foil 12 constitutes the bearing surface X. On the counter-rotation direction side of the intersecting portion, the top foil portion Tf of one foil 12 constitutes the bearing surface X, and the second region 12b of the other foil wraps behind the one foil 12 and backfoil portion Bf. Configure. The end of the back foil portion Bf on the side opposite to the rotation direction is a free end, and the position of the end varies in the circumferential direction (rotation direction and counter rotation direction) according to the elastic deformation of the back foil portion Bf. The end of the back foil portion Bf on the rotation direction R side is in a state of being engaged with another foil 12 (the one foil) in the circumferential direction at the intersection.

  A foil overlap portion W in which the foils overlap each other is formed at the portion where the top foil portion Tf and the back foil portion Bf overlap. The foil overlapped portion W is formed at a plurality of locations in the rotation direction R (the same number as the foil 12 and three locations in the present embodiment).

  In this foil bearing 10, one end (convex portion 12 a 2) on the rotation direction R side of each foil 12 is attached to the foil holder 11, and the region on the counter-rotation direction side is engaged with another foil 12 in the circumferential direction. is there. As a result, the adjacent foils 12 are in a state of sticking to each other in the circumferential direction, so that the top foil portion Tf of each foil 12 projects to the foil holder 11 side, and has a shape along the inner peripheral surface 11a of the foil holder 11. Bend. The movement of each foil 12 in the rotation direction R side is restricted because the convex portion 12a2 of each foil 12 hits the axial groove 11b, but the movement of each foil 12 in the counter rotation direction side is not restricted, Each foil 12 is movable in the counter-rotating direction including the free end of the back foil portion Bf.

  As shown in FIG. 8, since the axial groove 11b is provided with a slight inclination by an angle θ1 with respect to the tangential direction of the inner peripheral surface of the foil holder 11, the vicinity of the convex portion 12a2 inserted into the axial groove 11 Then, the top foil portion Tf tends to bend in the direction opposite to the bending direction of the entire foil 12 (the bending direction of the inner peripheral surface 11a of the foil holder 11). Moreover, the top foil part Tf rises in the state inclined in the direction away from the inner peripheral surface 11a of the foil holder 11 by riding on the back foil part Bf. Therefore, a wedge space is formed between the bearing surface X of the top foil portion Tf and the outer peripheral surface of the shaft 6. Further, the top foil portion Tf is elastically supported by the elastically deformable back foil portion Bf.

  While the shaft 6 rotates in one direction, the air film (fluid film) generated in the wedge space has a high pressure, so that the shaft 6 receives a lifting force. Therefore, an annular radial bearing gap C is formed between the bearing surface X of each foil 12 and the shaft 6, and the shaft 6 is rotatably supported in a non-contact state with respect to the foil 12. Due to the elastic deformation of the top foil portion Tf, the clearance width of the radial bearing clearance C is automatically adjusted to an appropriate width according to operating conditions and the like, so that the rotation of the shaft 6 is stably supported. In FIG. 3, the radial width of the radial bearing gap C is exaggerated for easy understanding (FIG. 22 is the same).

  While the shaft 6 is rotating, the top foil portion Tf is pressed against the back foil portion Bf by the fluid pressure and elastically deforms. Therefore, the top foil portion Tf riding on the back foil portion Bf has a width direction of the bearing gap C. Are formed. As shown in FIG. 5, when the notch 12b2 is provided at the rear end 12d of the second region 12b of each foil 12, this step has a herringbone shape corresponding to the shape of the notch 12b2. Since the fluid flowing along the top foil portion Tf flows along the steps (see arrows), fluid pressure generating portions are formed at two locations in the orthogonal direction N of the bearing gap C. This makes it possible to support the moment load while enhancing the floating effect of the shaft 6. In the present embodiment, as shown in FIG. 4, since the notch 12a3 is formed in the top foil portion Tf to reduce the rigidity of the top foil portion Tf, the top foil portion Tf extends along the notch portion 12b2. Even when deforming, the deformation is performed smoothly.

[Characteristic configuration of the present invention]
As for the foil bearing 10 of this embodiment, the back foil part Bf of each foil 12 is comprised by the net-like body 20 shown in FIG. The net-like body 20 is formed by regularly arranging a plurality of warps 21 and a plurality of wefts 22 which are metal wires, and intersecting each other. As shown in FIG. 10, the region partitioned by the warp material 21 and the weft material 22 constitutes a square hole-shaped window portion 23 penetrating the front and back. As the warp material 21 and the weft member 22, a resin wire can be used in addition to a metal wire.

  The net-like body 20 is formed by weaving the weft 22 against the linear warp 21 while raising and lowering it. Each linear warp 21 is at the same level (see FIG. 12 a), and wefts 22 pass alternately above and below the warp 21.

  In the net-like body 20, convex portions 22 a and 22 b that protrude to the front and back sides of the net-like body 20 are formed at portions where the weft material 22 is raised and sinked. A protruding portion 22a protruding to the top foil portion Tf side (front side) is formed at the floating portion of the weft material 22, and a protruding portion 22b protruding to the foil holder 11 side (back side) is formed at the sinking portion.

  As shown in FIG. 4, when the top foil portion Tf and the back foil portion Bf are formed by a single foil 12, as shown in FIG. 11, the circumferential end of the mesh body 20 and the thin plate-like top foil portion Tf. The foil 12 can be formed by connecting the parts by a method such as welding.

  By attaching the back foil portion Bf of the foil 12 formed in this way to the foil holder 11 in the same procedure as in FIGS. 5 to 7, as shown in FIG. 3, each back foil portion Bf (shown in a dotted pattern) The radial foil bearing 10 formed of the mesh body 20 is completed.

  12A is a cross-sectional view taken along the line A1-A1 in FIG. 9, and FIG. 12B is a cross-sectional view taken along the line A2-A2 in FIG. 9, each showing a cross section of the foil bearing 10. The convex portion 22a on the front side of the back foil portion Bf contacts the top foil portion Tf, and the convex portion 22b on the back side of the back foil portion Bf contacts the inner peripheral surface 11a of the foil holder 11.

  While the shaft 6 is rotating, the top foil portion Tf receives the pressure P due to the air pressure generated in the bearing gap C. Therefore, the compression force in the pressure P direction acts on the back foil portion Bf via the top foil portion Tf. At this time, in the weft member 22 constituting the back foil portion Bf, the region 22c (see FIG. 12A) between the protrusions 22a and 22b, and the warp member 21 of the weft member 22 of the warp member 22 A region 21c (see FIG. 12B) sandwiched between the regions is a portion having low rigidity with respect to the compressive force P. Therefore, when the compression force P is applied to the back foil portion Bf, these low-rigidity portions 21c and 22c are elastically deformed as indicated by two-dot chain lines shown in FIGS. 12 (a) and 12 (b), respectively. Thus, the compressive force P is absorbed.

  On the other hand, at the position of the convex portion 22 a, the weft member 22 is supported by the warp member 21 from the direction opposite to the direction of the compression force P, and this portion is a portion having higher rigidity than the other portions of the weft member 22. For this reason, in the position of the top foil part Tf corresponding to the convex part 22a, the air film formed in the bearing gap C becomes a high pressure, and it becomes difficult for air to escape.

  As shown in FIG. 13, in the mesh body 20, the convex portion 22 a (portion indicated by a black circle in FIG. 13) that is a highly rigid portion is in two orthogonal directions (rotational direction R and orthogonal direction N) along the bearing surface X. Low rigidity parts 21c and 22c are provided so as to surround the four sides of the convex part 22a, sandwiched between the low rigidity parts 21c and 22c (parts indicated by white circles in FIG. 13) from both sides. The low-rigidity portions 21c and 22c are elastically deformed by receiving the compressive force P, so that the high-rigidity portion 22a can be relatively moved in the arrow N direction and the R-direction, thereby reducing the rigidity of the back foil portion. it can.

  Further, the warp member 21 and the weft member 22 constituting the mesh body 20 are not fixed to each other by a method such as welding, and the warp member 21 extends in the direction of arrow N in FIG. Reference numerals 22 are provided so as to be relatively movable in the direction of arrow R in FIG. Accordingly, the relative movement of the respective wires in accordance with the compressive force P received by the back foil portion Bf allows a slight sliding between the warp material 21 and the weft material 22. By this sliding, the vibration that the back foil portion Bf receives due to the rotation of the shaft 6 can be absorbed, and the foil bearing 10 can stably support the rotation of the shaft 6.

  By the way, it is considered that the optimum value of rigidity required for the bearing surface X is different in each part of the bearing surface X. For this reason, in order to obtain the optimum bearing rigidity that matches the shaft 6, the rigidity of the foil bearing 10 is partially increased or decreased, so that the rigidity of each part of the bearing surface X is appropriately adjusted. It is necessary to.

  In this regard, as in the present embodiment, in the case of the configuration in which the mesh body 20 in which the wires are regularly arranged is the back foil portion Bf, it is easy to change the partial rigidity by changing the configuration of the mesh body 20. Therefore, it is possible to design a foil bearing that matches the required bearing rigidity.

  For example, in the mesh body 20, the warp material 21 and the weft material 22 are arranged at equal intervals in the R direction and the N direction, respectively, but as shown in FIG. 14, the interval at which the warp material 21 and the weft material 22 are arranged. The interval may be changed, for example, by partially increasing. By partially changing the interval between the adjacent wire rods, the density of the wire rod in that portion of the mesh 20 can be adjusted, and the rigidity of the back foil portion Bf can be partially changed. That is, by increasing the density of the wire, it is possible to increase the rigidity of the back foil portion Bf at that portion, or conversely, to decrease the rigidity by decreasing the density of the wire.

  Further, as shown in FIG. 14, by partially increasing the interval between the warp members 21, the support span S (see FIG. 12a) of the convex portions 22a and the convex portions 22b of the weft material 22 can be increased. By increasing the span S and decreasing the circumferential curvature of the weft member 22, the portions of the regions 21c and 22c are easily elastically deformed, and the rigidity of these portions can be further reduced. On the contrary, the rigidity of the back foil portion Bf can be increased by reducing the support span S and increasing the circumferential curvature of the weft member 22. Thus, the rigidity of the back foil portion Bf can be partially adjusted by adjusting the interval between the warps 21.

  Moreover, as shown in FIG. 15, it can also be set as the structure which arrange | positions two or more warps 21 adjacently, and arranges two or more (2 pieces in a figure). By increasing the number of the warp members 21 that support the weft member 22, the support force of the weft member 22 can be increased, the rigidity of the back foil portion Bf in the protrusion portion 22a can be increased, and the protrusions contacting the top foil portion Tf can be increased. The area of the portion 22a can be increased, and the range of the highly rigid portion can be expanded.

  The thicknesses of the warp material 21 and the weft material 22 do not have to be uniform, and some of the warp material 21 and the weft material 22 are thickened to increase the rigidity of the portion, or conversely, the rigidity is reduced by reducing the thickness. And can be easily elastically deformed.

  Further, the warp material 21 and the weft material 22 can be formed of a plurality of different metal materials. The rigidity of the back foil portion Bf can be partially changed, for example, by using a partially rigid wire.

  Further, the arrangement method of the wires constituting the mesh body 20 is not limited to the one shown in FIG. 9 and can be appropriately changed according to the required bearing rigidity and the like. For example, contrary to the embodiment of FIG. 9, the warp material 21 may be wavy, the weft material 22 may be linear, or both the warp material 21 and the weft material 22 may be wavy. Moreover, each wire may be provided to be inclined with respect to the arrow R direction or the arrow N direction, or the wire rods may be arranged so as to intersect in three or more directions.

  As shown in FIG. 16, the mesh body 20 can be formed by arranging the warp material 21 and the weft material 22 in a lattice shape and connecting the intersecting portions by a method such as welding. A region partitioned by the warp material 21 and the weft material 22 constitutes a square hole-shaped window portion 23 penetrating the front and back. The intersecting portion 251 between the wires becomes a portion having high rigidity with respect to the pressure P, and the connecting portion 252 adjacent to the intersecting portions on the four surrounding sides becomes a portion having lower rigidity than the intersecting portion 251. When the back foil portion Bf receives the pressure P, the connecting portion 252 is elastically deformed to absorb the compressive force P generated by the pressure P.

  Furthermore, as shown in FIG. 17, the mesh body 20 can be formed by knitting. That is, the mesh-like body 20 is formed by passing the loop portions 24a of the adjacent wire rods 24 through the plurality of loop portions 24a formed on the wire rod 24 and continuously providing them. The wire 24 constituting the mesh body 20 has the connecting portion 24b that connects the loop portions 24a expand and contract in the arrow R direction (the left and right arrow directions in the figure), so that the loop portion 24a extends in the arrow N direction (up and down in the figure). It can be expanded and contracted in the direction of the arrow). By the expansion and contraction of the wire rod 24, the adjacent wire rods 24 can be brought into sliding contact with each other to absorb the vibration of the shaft 6.

  A backfoil portion Bf may be formed by laminating a plurality of the mesh bodies 20 described above in the direction of application of the pressure P. Thereby, sliding between the laminated mesh bodies 20 can be permitted, and the vibration of the shaft 6 can be more easily absorbed. For this reason, the foil bearing 10 can stably support the rotation of the shaft 6. In addition, by changing the configuration of the individual mesh body 20, it is easy to adjust the rigidity and springiness of the entire backfoil portion Bf. Further, the shaft 6 can be supported from the back side of the top foil portion Tf by the plurality of back foil portions Bf, and the support rigidity of the back foil portion Bf as a whole can be increased.

  In this way, by forming the back foil portion Bf by the mesh body 20 in which the wire materials are regularly arranged, a method of arranging the wire materials in the mesh body 20 and a method of crossing the wire materials (weaving method or knitting method) By changing, the shape of the back foil part Bf can be variously changed. Further, the thickness, material, etc. of the wire can be changed partially. Compared with a foil bearing in which the back foil portion Bf is formed of a plate material as shown in FIGS. 4 and 23, the bearing rigidity of the back foil portion Bf, etc. The degree of freedom in design with respect to the characteristics of the For this reason, the foil bearing which has the optimal bearing rigidity matched with the rigidity calculated | required by each part of a bearing surface is realizable.

  As a net-like body formed by regularly arranging the wire rods of the present invention, as in the case of the back foil portion Bf shown in FIG. 9, the wire rods are arranged at equal intervals over the entire back foil portion Bf. In this case, a part of the regularity of the arrangement of the wires is included, such as when the interval is partially changed, when the thickness of the wire is changed, or when the way of crossing the wires is changed. By regularly arranging the wires in the entire backfoil part Bf or a part thereof, the rigidity and springiness of the backfoil part Bf can be periodically changed. There is an advantage that management of springiness and the like becomes easy.

  Further, like the back foil portion Bf shown in FIG. 4, the mesh body 20 can be formed in a shape in which a notch portion 12 b 2 is provided on the rear end side of the foil 12. Further, by changing the density of the wire, the portion corresponding to the notch portion 12b2 is formed as the high rigidity portion, and the other portion of the back foil portion Bf is formed as the low rigidity portion in the back foil portion Bf of FIG. It is also possible to form a pressure generating portion equivalent to the fluid pressure generating portion and support the moment load while enhancing the floating effect of the shaft 6.

  FIG. 18A is a schematic view of the bearing surface X viewed from the shaft 6 side, and the hatched portion D in the figure corresponds to the portion provided with the convex portion 22a of the back foil portion Bf. The convex portion 22a is a portion where the weft member 22 protrudes toward the shaft 6 and is a portion where the warp member 21 and the weft member 22 intersect. In this portion, since the convex portion 22a is highly rigid and difficult to deform with respect to the pressure P received by the back foil portion Bf, the air film formed in the bearing gap C becomes high pressure, and the air runs along the bearing surface. It becomes difficult to escape in the direction. In the present invention, the high-pressure portion D (convex portion 22a) is arranged in a so-called zigzag pattern with respect to the arrow R direction that is the rotation direction of the shaft 6.

  When the shaft 6 rotates, air flows in the direction of the arrow R in the bearing gap C formed between the shaft 6 and the bearing surface X. At this time, at the position of the high pressure portion D, an air film is formed under high pressure so that the air is difficult to escape, and the air flowing through the bearing gap C is arranged in a staggered manner on the bearing surface X. The low-pressure portion flows while branching in multiple directions (for example, it flows while branching in the direction of the arrow in the figure).

  On the other hand, for example, as shown in FIG. 18B, in the configuration in which the high pressure portion (convex portion) is arranged in parallel with the arrow R direction, the air that has flowed into the bearing gap C due to the rotation of the shaft 6 enters the high pressure portion D. It flows without changing the course in the direction parallel to the arrow R direction without colliding. For this reason, air easily escapes from the bearing gap C, and it becomes difficult to maintain a constant air film in the bearing gap C.

  On the other hand, in the present embodiment, the air flowing through the bearing gap C branches in multiple directions as described above and flows in the direction of the arrow R while repeatedly changing its course, so that it is difficult for air to escape from the bearing gap C. . In addition, since the high pressure portions D are provided in a distributed manner on the entire bearing surface X, air is easily supplied to the entire bearing surface X through the low pressure portions provided between the high pressure portions D. Thus, a constant air film can be formed in the bearing gap C, and the foil bearing 10 can stably support the shaft 6 in a non-contact manner.

  As an example of arranging the high pressure portions (convex portions) D in a staggered manner in the direction of the arrow R, in addition to the arrangement of the mesh body 20 of FIG. 9 shown in FIG. 18A, for example, as shown in FIG. The net-like body 20 which arrange | positions the part D may be sufficient. In this way, by disposing the high pressure portions D adjacent in the direction of the arrow R alternately on both sides in the direction of the arrow N, the air flow in the bearing gap C is complicated, and a constant air film is formed in the bearing gap C. Can be formed.

  In the above description, a so-called multi-arc radial foil bearing has been exemplified as the foil bearing 10, but the form of the foil bearing to which the present invention is applicable is not limited thereto. For example, the present invention can be applied to a so-called leaf-type radial foil bearing 10 shown in FIG. The leaf type foil bearing is configured by arranging a plurality of foils 12 (leafs) in the rotation direction R of the shaft 6 with one end on the rotation direction R side as a free end and the other end on the counter rotation direction side as a fixed end. The region on the rotation direction R side of the foil 12 functions as the top foil portion Tf, and the region on the counter-rotation direction side functions as the back foil portion Bf. In this leaf-type radial foil bearing, the same effect as described above can be obtained by forming the back foil portion Bf (shown as a dotted pattern) of each leaf 12 with the mesh body 20.

  The present invention can also be applied to a so-called bump-type radial foil bearing 10 shown in FIG. In the bump type foil bearing 10, the same effect as described above can be obtained by forming the entire back foil portion Bf with the mesh body 20. In FIG. 20, the back foil portion Bf is continuous over the entire circumference of the inner peripheral surface 11 a of the foil holder 11, but the back foil portion Bf can be divided at one place or a plurality of places in the circumferential direction. In this case, the divided individual elements are formed by the mesh body 20.

  Furthermore, the present invention can also be applied to the thrust foil bearing 30 shown in FIG. FIG. 21 shows a leaf type thrust foil bearing as an example of the thrust foil bearing 30. Also in this thrust foil bearing, as shown in FIG. 22, the same effect as described above can be obtained by forming the back foil portion Bf (indicated by the dotted pattern) of each leaf 12 with the mesh body 20.

  In the above description, the case where the shaft 6 is the rotation side member and the foil holder 11 is the fixed side member is illustrated. On the contrary, the shaft 6 is the fixed side member and the foil holder 11 is the rotation side member. In this case, the present invention can be applied. 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.

  The foil bearing according to the present invention is not limited to the gas turbine described above, and can be used as a foil bearing that supports a rotor of a turbomachine including a supercharger, for example. The foil bearing according to the present invention is not limited to the above examples, and can be widely used as a bearing for a vehicle such as an automobile and further as a bearing for industrial equipment. Further, each foil bearing of the present embodiment is an air dynamic pressure bearing using air as a pressure generating fluid, but is not limited thereto, and other gases can be used as the pressure generating fluid, or water or oil It is also possible to use a liquid such as

6 shafts 10 radial foil bearings 11 foil holders 12 foils 20 nets 21 warps (wires)
22 Weft (wire)
22a Convex part 22b Convex part 30 Thrust foil bearing Tf Top foil part Bf Back foil part C Bearing gap D High pressure part R Rotation direction N Orthogonal direction X Bearing surface

Claims (7)

A bearing gap between the shaft and the bearing surface, comprising a top foil portion having a bearing surface facing the shaft to be supported, and a back foil portion for elastically supporting the top foil portion behind the top foil portion. In the foil bearing that supports the relative rotating shaft in a non-contact manner with the fluid film generated in
The foil bearing is characterized in that the back foil portion is formed of a net-like body formed by crossing a plurality of wires and regularly arranging the wires.   2. The foil bearing according to claim 1, wherein the mesh member is formed by intersecting a warp material and a weft material, which are wire rods arranged in two orthogonal directions.   3. The foil bearing according to claim 1, wherein the mesh body has partially changed the density of the arranged wire. 4.   The foil bearing according to any one of claims 1 to 3, wherein the mesh body is formed of a plurality of wires made of different materials. The foil bearing according to any one of claims 1 to 4, wherein the mesh body is formed of a plurality of wires having different thicknesses.   The foil bearing according to any one of claims 1 to 5, wherein the back foil portion is formed by laminating a plurality of the mesh bodies. The back foil portion has a convex portion protruding to the bearing surface side,
The foil bearing according to any one of claims 1 to 6, wherein the convex portions are arranged in a staggered manner with respect to a rotation direction of the shaft.

Images