JP6654081B2 - Foil bearing - Google Patents

Description

  The invention relates to a foil bearing.

  Foil bearings have been known as bearings in which whirling hardly occurs and in which the gap width of the bearing gap can be easily controlled even in an environment with a large temperature change. The foil bearing has a bearing surface made of a thin metal plate (foil) having a low rigidity against bending and having flexibility, and supports a load by allowing the deflection of the bearing surface. It has the feature that it is 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.

JP 2013-87789 A

The foil bearing described in Patent Document 1 has a cylindrical top foil, a back foil (bump foil) for elastically supporting the top foil, and a bearing holder to which the top foil and the back foil are attached. In this bump type foil bearing, the back foil is elastically deformed when the load is applied to the top foil, so that the top foil is allowed to bend.

By the way, the back foil of the bump type foil bearing has a corrugated shape in which convex portions 200 extending in the axial direction (arrow direction) are arranged in the circumferential direction as shown in FIG. When the back foil is elastically deformed, each of the projections 200 is deformed so as to push it apart. However, the deformation resistance at that time is large, and the back foil has high rigidity as a whole, so that the flexibility of the top foil is insufficient. Tend to. If the flexibility of the top foil is insufficient, the function of automatically adjusting the clearance between the bearings is impaired, and problems such as easy contact between the shaft and the top foil are caused.

  Therefore, an object of the present invention is to provide a foil bearing in which the flexibility of the top foil is increased.

  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 elastically supporting 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 a bearing surface, the back foil portion has a flat middle portion, and a front side and a back side of the middle portion. A plurality of protruding portions are provided, and a stiffening portion for enhancing the stiffness of the opposing region is provided between the facing region of the bearing surface of the top foil portion facing the protruding portion and the protruding portion. It is characterized by the following.

  In such a configuration, due to the fluid pressure generated in the bearing gap during the operation of the bearing, a compressive force acts on the back foil via the top foil in the direction of action of the fluid pressure (radial direction in a radial bearing, axial direction in a thrust bearing). By providing the back foil with a flat middle portion and a plurality of protrusions protruding on the front side and the back side of the middle portion, the middle portion becomes a portion of the back foil having low rigidity against a compressive force. Therefore, when a compressive force is applied to the back foil, the intermediate portion deforms and absorbs the compressive force. Therefore, the rigidity of the entire back foil is reduced as compared with the back foil portion of the existing bump type foil bearing that does not have such a flat portion. This makes it possible to increase the flexibility of the top foil.

In such a configuration, the protruding portion of the back foil portion is a portion having higher rigidity than the intermediate portion. Therefore, even when the projecting portion comes into contact with the top foil portion under the action of the compressive force, the projecting portion does not deform, and the top foil portion deforms in a convex shape so as to follow the top of the projecting portion. In this case, in the opposing region of the bearing surface facing the protruding portion, the top foil portion is not allowed to be elastically deformed, so that the top foil portion easily comes into contact with the shaft, and the top foil portion may be unevenly worn. There is.

On the other hand, if a stiffening portion for enhancing the stiffness of the facing region is provided between the facing region of the bearing surface of the top foil portion facing the projecting portion and the projecting portion, a compressive force was applied. Also in this case, the deformation of the facing area of the bearing surface is suppressed. Therefore, the top foil portion is allowed to be elastically deformed in the facing region. Therefore, the entire bearing surface easily deforms following the displacement of the shaft, and uneven wear of the top foil portion due to contact with the shaft can be prevented.

The stiffening may be formed by an intermediate foil disposed between the protrusion and the top foil.

In this case, if a hole is provided in a portion of the intermediate foil that faces the middle portion of the back foil, a region other than the facing region of the bearing surface is easily elastically deformed, so that the flexibility of the entire bearing surface is ensured. Can be.

The rigidity enhancing portion may be formed by making the top foil thicker than the other portions in the facing region.

  As described above, according to the present invention, it is possible to enhance the flexibility of the entire bearing surface including the region facing the protrusion of the back foil portion. As a result, the function of automatically adjusting the bearing clearance is favorably exhibited, so that the contact between the shaft and the top foil portion can be reliably prevented, and the load capacity of the foil bearing can be increased.

FIG. 2 is a diagram illustrating a schematic configuration of a rotor support structure of the micro gas turbine. It is sectional drawing of the foil bearing concerning this invention. It is a top view of a foil. It is the top view which looked at the two connected foils from the back side. It is a perspective view which shows the state which assembled three foils temporarily. It is a perspective view which shows a mode that a 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 an uneven | corrugated foil part. FIG. 9 is a sectional view taken along line AA in FIG. 8. FIG. 3 is an expanded view showing an enlarged cross section of the foil bearing shown in FIG. 2. It is a top view of an uneven | corrugated foil part. It is a top view of an uneven | corrugated foil part. It is a top view of the foil which has an uneven foil part. FIG. 4 is an expanded view of a cross section of the foil bearing shown in FIG. 3. It is sectional drawing of the BB line in FIG. It is sectional drawing which shows other embodiment of the uneven | corrugated foil part. It is a perspective view showing other embodiments of an uneven foil part. It is sectional drawing which expands and shows a top foil part and a 1st protrusion part. FIG. 4 is a perspective view showing an embodiment using an intermediate foil. It is sectional drawing which expands and shows a top foil part and a 1st protrusion part. It is sectional drawing which expands and shows a top foil part and a 1st protrusion part. FIG. 3 is a cross-sectional view showing a leaf-type radial foil bearing. It is sectional drawing which shows a bump type radial foil bearing. It is a perspective view showing a leaf type thrust foil bearing. FIG. 25 is a sectional view taken along line DD in FIG. 24. It is a perspective view which shows the back foil of a bump type foil bearing.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 conceptually illustrates an example of a rotor support structure in a micro gas turbine. In this support structure, the radial bearing 10 is disposed around the shaft 6, and the thrust bearings 30 are disposed on both axial sides of the flange 6 b provided on the shaft 6. The shaft 6 is rotatably supported in both the radial direction and the thrust direction by the radial bearing 10 and the thrust bearing 30. In this support structure, a region between the turbine 1 and the compressor 2 has a high-temperature atmosphere because it is adjacent to the turbine 1 rotated by a high-temperature and high-pressure gas. In addition, the shaft 6 rotates at a rotation speed of tens of thousands of rpm or more. Therefore, air bearings, especially foil bearings, are suitable as the bearings 10 and 30 used in this support structure.

  As an example of a foil bearing suitable for the radial bearing 10 for a micro gas turbine described above, 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. 2, the multi-arc radial foil bearing 10 includes a foil holder 11 having a cylindrical inner peripheral surface 11 a, and a plurality of radially extending shafts 6 on the inner peripheral surface 11 a of the foil holder 11. And a foil 12 arranged at the location. The illustrated foil bearing 10 illustrates a case where the foils 12 are arranged at three locations on the inner peripheral surface 11a. The shaft 6 is inserted on the inner diameter side of each foil 12.

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

  The foil material constituting each foil 12 is formed by processing a strip-shaped foil having a good spring property and good workability, for example, a metal foil or a copper alloy having a thickness of about 20 μm to 200 μm into a predetermined shape by press working or the like. It is formed by things. 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 rust-preventing effect of oil cannot be expected. It is easy to occur. In addition, brass may cause a pre-crack due to processing strain (the tendency increases as the content of Zn in brass increases). Therefore, it is preferable to use stainless steel or bronze as the band-like foil.

  As shown in FIG. 3, the foil 12 has a first area 12a on the rotation direction R side of the shaft 6 and a second area 12b on the opposite rotation direction side.

  The first region 12a includes a plurality of top foil portions Tf forming the bearing surface X and a plurality of directions N (hereinafter, simply referred to as “orthogonal directions N”) along the surface of the top foil portions Tf and orthogonal to the rotation direction R. And protruding portions 12a2 that are provided at the locations and extend in the directions protruding toward the rotation direction R, respectively. In the present embodiment, the case where the protrusions 12a2 are formed at three places in the orthogonal direction is illustrated. At the base end of each protrusion 12a2, a minute cut 12a3 is provided extending from the foil edge in the anti-rotational direction.

  At the rear end 12d (the end on the side opposite to the rotation direction) of the second region 12b, two cutouts 12b2 that are recessed in the rotation direction R and are separated from each other in the orthogonal direction N are formed. The width of each notch 12b2 in the orthogonal direction N gradually decreases in 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 may be formed in a substantially V-shape with a sharp top. Projections 12b1 projecting in the anti-rotation direction are formed on both sides of each notch 12b2 in the orthogonal direction N.

  At the boundary between the first region 12a and the second region 12b, and at a plurality of positions (the same number as the protrusions 12a2) in the orthogonal direction N, the slit-shaped insertion holes into which the protrusions 12a2 of the adjacent foil 12 are inserted. 12c1 is provided. Of these, the insertion ports 12c1 at both ends extend linearly in the orthogonal direction N and open at both ends of the foil 12, respectively. The center insertion opening 12c1 is formed by a linear cutout portion extending along the orthogonal direction N, and a wide cutout portion extending from the cutout portion in the anti-rotational direction and having a circular arc-shaped tip. Become.

  As shown in FIG. 4, each of the protrusions 12a2 of one foil 12 is inserted into the insertion opening 12c1 of the adjacent foil 12, so that the two foils 12 can be connected. In the figure, one of the two foils 12 after the combination is colored gray.

  Then, as shown in FIG. 5, by connecting the three foils 12 circumferentially by the same joining method as in FIG. 4, each foil 12 can be brought into a temporarily assembled state. As shown in FIG. 6, the foil bearing 10 is assembled by inserting the temporary assembly into a tubular shape in the direction of arrow B2 on the inner periphery of the foil holder 11 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 protrusions 12 a 2 of each foil 12 are formed in the axial groove 11 b ( (See FIG. 7) from one side in the axial direction. As described above, the three foils 12 are mounted on 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. 7, when each foil 12 is attached to the foil holder 11, two adjacent foils 12 cross each other. On the rotation direction R side from the intersection, the convex portion 12a2 of one foil 12 goes behind the other foil 12 via 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 anti-rotational direction side of the intersection, 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 so that the back foil portion Bf Is configured. The end on the anti-rotation direction side of the back foil portion Bf is a free end, and the position of the end fluctuates in the circumferential direction (rotation direction and anti-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 circumferentially engaged with another foil 12 (the one foil) at the intersection.

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

In the foil bearing 10, one end (projection 12 a 2) of each foil 12 on the rotation direction R side is attached to the foil holder 11, and the region on the opposite rotation direction side is engaged with the other foil 12 in the circumferential direction. is there. As a result, the adjacent foils 12 abut against each other in the circumferential direction, so that the top foil portion Tf of each foil 12 protrudes toward the foil holder 11 and has a shape along the inner peripheral surface 11 a of the foil holder 11. Bend. The movement of each foil 12 in the rotation direction R side is regulated because the convex portion 12a2 of each foil 12 abuts on the axial groove 11b, but the movement of each foil 12 in the non-rotation direction side is not restricted. Each foil 12 is movable in the anti-rotational direction including the free end of the back foil portion Bf.

  As shown in FIG. 7, since the axial groove 11 b is provided at a slight angle θ1 with respect to the tangential direction of the inner peripheral surface of the foil holder 11, the vicinity of the convex portion 12 a 2 inserted in the axial groove 11 is provided. Then, the top foil portion Tf tries to bend in a 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). The top foil portion Tf rises in a direction inclined away from the inner peripheral surface 11a of the foil holder 11 by riding on the back foil portion 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. The top foil portion Tf is elastically supported by the elastically deformable back foil portion Bf.

  During rotation of the shaft 6 in one direction, the air film generated in the wedge space has a high pressure, so that the shaft 6 receives a levitation force. Therefore, as shown in FIG. 2, 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 without contact with the foil 12. You. Due to the elastic deformation of the top foil portion Tf, the width of the radial bearing gap C is automatically adjusted to an appropriate width according to the operating conditions and the like, so that the rotation of the shaft 6 is stably supported. In FIG. 2, the width of the radial bearing gap C is exaggerated for ease of understanding (the same applies to FIGS. 14, 22, 23, and 25).

  During rotation of the shaft 6, the fluid pressure causes the top foil portion Tf to be pressed against the back foil portion Bf and elastically deformed. Therefore, the top foil portion Tf riding on the back foil portion Bf has a width in the width direction of the bearing gap C. Is formed. As shown in FIG. 4, when a 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 herringbone-shaped step (see the arrow), fluid pressure generating portions are formed at two places in the orthogonal direction N in the bearing gap C. Is done. 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. 3, 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. When deforming, the deformation is performed smoothly.

  In the foil bearing 10 described above, the back foil portion Bf of each foil 12 is formed by the uneven foil 20 shown in FIGS. The uneven foil 20 includes a plurality of first protrusions 21 protruding on the front side (for example, the bearing surface X side) of the back foil portion Bf, and a plurality of second protrusions 22 protruding on the back side (for example, the side opposite to the bearing surface X). And a flat intermediate portion 23 for connecting the protruding portions 21 and 22 integrally. The first projecting portion 21 projects from the intermediate portion 23 toward the front side, and the second projecting portion 22 projects from the intermediate portion 23 toward the back side. The first projecting portion 21 and the second projecting portion 22 have their entire periphery connected to the intermediate portion 23.

  FIG. 10 shows an enlarged cross section of the uneven foil 20. As shown in FIG. 10, the first projecting portion 21, the second projecting portion 22, and the intermediate portion 23 have a uniform thickness. Each of the first protrusion 21 and the second protrusion 22 is formed in a substantially hemispherical shape. Since the inside of the first protrusion 21 and the second protrusion 22 is hollow, when the foil 12 is viewed from one side of the front and back, for example, from the front, the region where the second protrusion 22 exists is a recess. .

The uneven foil 20 is formed by pressing a foil material. For example, as shown in FIG. 3, when forming a top foil portion Tf and a back foil portion Bf on each foil 12, as shown in FIG. By forming the one protruding portion 21 (shown by a white circle), the second protruding portion 22 (shown by a hatched circle), and the intermediate portion 23, the uneven foil 20 and a smooth surface having no such unevenness are formed. A foil 12 integrally having the top foil portion Tf is obtained (the cut-out portion 12b2 shown in FIG. 3 is omitted from the foil 12 in FIG. 11). Note that the arrangement pattern of the first protrusion 21 and the second protrusion 22 shown in FIG. 11 is merely an example, and an arbitrary arrangement pattern different from that in FIG. 11 can be employed as needed.

The three foils 12 are assembled in the same procedure as in FIGS. 4 to 6 to form an assembly, and by attaching this assembly to the foil holder 11, each back foil portion Bf (shown by a dotted pattern) as shown in FIG. The radial foil bearing 10 formed of the uneven foil 20 is completed. As shown in FIG. 10, in this state, the first protruding portion 21 of the back foil portion Bf contacts the top foil portion Tf, and the second protruding portion 22 of the back foil portion Bf contacts the inner peripheral surface 11a of the foil holder 11. Contact.

During the rotation of the shaft 6, as shown in FIG. 10, the top foil portion Tf receives the compressive force P due to the air pressure generated in the bearing gap C, so that the back foil portion Bf receives the compressive force via the top foil portion Tf. A load acts in the same direction. Since the intermediate portion 23 has a thin plate shape extending in a direction orthogonal to the direction of the compressive force P, the intermediate portion 23 has a low rigidity to the compressive force in the back foil portion Bf. Therefore, when a compressive force is applied to the back foil portion Bf, the intermediate portion 23 is first deformed and absorbs the compressive force as shown by a two-dot chain line in FIG. Therefore, the rigidity of the entire back foil portion Bf can be reduced as compared with the back foil portion (see FIG. 23) of the existing bump type foil bearing that does not have such a flat portion. Thereby, the flexibility of the bearing surface X is enhanced, so that the bearing surface X easily deforms following the displacement of the shaft 6 and the like, and it is possible to reliably prevent the contact between the shaft 6 and the top foil portion Tf. .

In addition, as is apparent from FIG. 11, the protruding portions 21 and 22 are dispersedly arranged on the entire back foil portion Bf. Specifically, the contact portions between the protruding portions 21 and 22 and the top foil portion Tf and the foil holder 11 are formed not in a continuous band shape in a certain direction but in a dot shape. That is, the contact portion is formed intermittently in at least two orthogonal directions (for example, the rotation direction R and the orthogonal direction N) along the bearing surface X, and more preferably in all directions along the bearing surface X. Therefore, when the back foil portion Bf is deformed, it is possible to allow relative movement even between adjacent same-type protrusion portions (projection portions having the same protruding direction from the intermediate portion 23), thereby reducing the rigidity of the back foil portion Bf. It can be even lower. Incidentally, in the back foil portion of the existing bump type foil bearing, since the convex portion extends in the axial direction (the orthogonal direction N), it is possible to allow such relative movement between the axial portions of the convex portion. Can not.

By the way, the optimum value of the rigidity required for the bearing surface X is considered to be different for each part of the bearing surface X. Therefore, if only the entire bearing surface X is made flexible, the rigidity of the bearing surface X may be insufficient at some parts, and the bearing performance may be reduced.

On the other hand, in the uneven foil 20, as shown in FIG. 12, if the distribution density of the first protrusion 21 and the second protrusion 22 is changed, the rigidity of the bearing surface X can be partially controlled. . For example, if a region where the first protrusions 21 and the second protrusions 22 are densely distributed is provided in the back foil portion Bf, the support span S between the adjacent protrusions 21 and 22 (see FIG. 10) becomes smaller, so that The rigidity of the region can be increased. Conversely, if an area is provided in which the distribution of the projections 21 and 22 is sparsely distributed, the rigidity of the area can be reduced. Therefore, it is possible to control the rigidity of each part of the back foil part Bf, and hence the rigidity of each part of the bearing surface X.

Hereinafter, a specific example in which the rigidity of the bearing surface X is controlled will be described with reference to FIG.
FIG. 13 shows that the high-density region H (shown by cross-hatching) in which the first projecting portions 21 and the second projecting portions 22 are densely distributed is formed in the back foil portion Bf of the foil 12 in a band shape and an elliptical shape. Things. At this time, the protrusions 21 and 22 are densely distributed toward the rotation direction R side of the high-density region H, and the protrusions 21 and 22 are densely distributed from both ends in the orthogonal direction N toward the center. In other regions of the second region 12b, low-density regions L (shown by hatching) in which the protruding portions 21 and 22 are distributed more sparsely than the high-density regions H are formed.

While the shaft 6 is rotating, a wedge space is formed between the top foil portion Tf and the shaft 6 at the foil overlapping portion W as shown in FIG. At this time, by forming the protruding portions 21 and 22 in the back foil portion Bf with the density pattern shown in FIG. 13, the region forming the wedge space of the top foil portion Tf receives a difference in rigidity of the back foil portion Bf. Thus, as shown in FIG. 15, a concave portion 24 is formed in which the central portion in the orthogonal direction N is concave. On both sides of the concave portion 24 in the orthogonal direction N, the top foil portion Tf has high rigidity and is not easily deformed, so that air in the wedge space hardly escapes in the orthogonal direction N. Further, the wedge space becomes higher in pressure in the direction of rotation R, but the rigidity of the top foil portion Tf becomes maximum near the highest pressure portion of the wedge space due to the difference in rigidity of the back foil portion Bf. Is difficult to escape. Therefore, by forming the protruding portions 21 and 22 in the back foil portion Bf in the density pattern shown in FIG. 13, the efficiency of forming the air film in the wedge space can be improved, and the contact between the shaft 6 and the foil 12 can be ensured. This can be prevented.

In the existing multi-arc foil bearing, as shown in FIG. 3, by providing a notch 12b1 at the rear end 12b of the second region 12b to be the back foil portion Bf, a portion corresponding to the concave portion is formed in the wedge space. However, if a difference in rigidity is provided in the back foil portion Bf as described above, such a notch 12b1 may not be formed in the rear end 12d of the second region 12b (see FIG. 11). It becomes possible to form the concave portion 24 in the form. Of course, after providing the notch 12b1 at the rear end 12d of the foil 12, the density difference between the protrusions 21 and 22 as described above may be provided in the second region 12b.

In the above description, the first protrusion 21 and the second protrusion 22 of the back foil portion Bf are all the same size. However, one or both of the front side and the back side of the back foil portion Bf may have another size. It is also possible to form a projection having a size different from that of the projection. FIG. 16 shows an example thereof, in which a large projection 21a and a small projection 21b are provided as the first projection 21 on the front side, and a large projection 22a and a small projection 22b are provided as the second projection 22 on the back side. Things. The projecting amounts from the intermediate portion 23 are different between the large projecting portions 21a and 22a and the small projecting portions 21b and 22b.

In the back foil portion Bf shown in FIG. 16, when the compressive force (compressive load in the width direction of the bearing gap C) applied thereto is gradually increased, the large projecting portions 21a and 22a are deformed after the intermediate portion 23 is deformed. Finally, the small protrusions 21b and 22b are deformed. Therefore, when the compressive load is small, the amount of deformation of the back foil portion Bf with respect to the increase in the load increases, and when the compressive load is large, the amount of deformation of the back foil portion Bf with respect to the increase in the load decreases. That is, non-linearity can be given to the spring characteristic of the back foil portion Bf.

As described above, when the spring characteristic of the back foil portion Bf has nonlinearity, the top foil portion Tf is easily deformed when the compressive load is low, so that the pressure of the air film is low (just after the rotation of the shaft 6 starts or stops. Even immediately before), a wedge space is easily formed. On the other hand, when the compressive load is high, the top foil portion Tf is less likely to be deformed. Therefore, even when the pressure of the air film is high (steady rotation of the shaft 6), the deformation of the top foil portion Bf is suppressed, and the top foil portion Tf is not deformed. Air leakage can be prevented. Therefore, the shaft 6 can be stably supported irrespective of low-speed rotation and high-speed rotation.

FIG. 17 shows that the rigidity of the intermediate portion 23 is reduced by providing a large number of openings 26 in the intermediate portion 23 of the back foil portion Bf shown in FIG. Thereby, the intermediate portion 23 becomes more flexible, so that the rigidity of the back foil portion Bf can be further reduced, and the degree of freedom of deformation of the top foil portion Tf can be improved. In the embodiment shown in FIG. 17, the intermediate portion 23 extends radially from each of the protrusions 21 and 22, and each intermediate portion 23 is connected to the adjacent protrusions 21 and 22. In this case, it is possible to control the rigidity of the intermediate portion 23 and the rigidity of the back foil portion Bf by adjusting the area and the number of the opening portions 26 to change the distribution state of the opening portions 26.

Means for changing the spring characteristics of the back foil portion Bf described above, namely, changing the distribution density of the protrusions 21 and 22 (FIG. 12), changing the size of the protrusions 21 and 22 (FIG. 16), and opening The spring characteristics of each part of the backfoil portion Bf can be optimized by selecting any one of the changes in the distribution state 26 (FIG. 17) or appropriately combining two or more means. Thereby, each part of the bearing surface X can be set to an optimal rigidity in terms of the bearing function, and the degree of freedom in bearing design is dramatically increased. Although the protrusions 21 and 22 are illustrated as being hemispherical (arc-shaped in cross section), the shapes of the protrusions 21 and 22 are arbitrary, and for example, the cross section may be polygonal. By changing the shape (cross-sectional shape) of the protruding portions 21 and 22 in this manner, the rigidity and spring characteristics of the back foil portion Bf can be changed.

[Characteristic configuration of the present invention]
Next, a characteristic configuration of the present invention will be described.
In the configuration in which the uneven foil 20 is used for the back foil portion Bf, the rigidity of the protruding portions 21 and 22 with respect to the compressive force P is greater than that of the flat portion 23, so that the top foil portion Tf is pressed against the back foil portion Bf by the compressive force P. Also at this time, as shown in FIG. 18, the first protrusion 21 in contact with the top foil portion Tf is hardly deformed. Therefore, the top foil portion Tf is deformed so as to follow the top of the first projecting portion 21, and has a small radius of curvature in a region X <b> 1 of the bearing surface X facing the first projecting portion 21 (hereinafter, referred to as “facing region”). A projection is formed. In this state, since the elastic deformation of the top foil portion Tf in the facing region X1 is restricted, the facing region X1 of the bearing surface X easily slides on the shaft 6, and the top foil portion Tf may be unevenly worn. .

As a countermeasure, in the present invention, as shown in FIG. 19, an intermediate foil 40 is interposed between the top foil portion Tf and the back foil portion Bf. The intermediate foil 40 integrally has a plurality of contact portions 41 provided corresponding to the first projecting portions 21 of the back foil portion Bf, and a column portion 42 connecting the adjacent contact portions 21. A hole 43 is formed in a region surrounded by the plurality of pillars 42. The holes 43 are provided at a plurality of positions of the intermediate foil 40, and are located at positions facing the intermediate portion 23 and the second protrusion 22 of the back foil portion Bf.

At the end on the rotation direction R side of the intermediate foil 40, a mounting portion 44 is formed. The attachment part 44 and the main body part 45 which is an aggregate of the contact part 41 and the pillar part 42 are connected via a connection part 46. The main body part 45 of the intermediate foil 40 has a shape and dimensions that cover at least the back foil part Bf of the adjacent foil 12.

The intermediate foil 40 is attached to the foil holder 11 (see FIG. 2) in a state where the intermediate foil 40 overlaps the top foil portion Tf. In this mounting, the convex portion 12a2 of the top foil portion Tf and the mounting portion 44 of the intermediate foil 40 are overlapped, and the stacked convex portion 12a2 and the mounting portion 44 are inserted into the axial groove 11b of the foil holder 11 (see FIG. 7). It is done by that.

In such a configuration, as shown in FIG. 20, the contact portion 41 of the intermediate foil 40 is disposed between the top foil portion Tf and the first protrusion 21 of the back foil portion Bf. When the top foil portion Tf is pressed against the back foil portion Bf by the compressive force P, the contact portion 41 of the intermediate foil 40 comes into contact with the first protrusion 21. At this time, since the contact portion 41 of the intermediate foil 40 suppresses the deformation of the opposing region X1 of the bearing surface X, the opposing region X1 becomes a convex portion having a large radius of curvature, and the bearing surface X becomes smooth as a whole including the opposing region X1. It deforms into a continuous form (a slight gap Y is formed between the top foil portion Tf and the contact portion 41 of the intermediate foil 40). In this state, the contact portion 41 does not adhere to the first protruding portion 21 to be in a point contact or a contact state similar thereto, so that the elastic deformation of the top foil portion Tf in the facing region X1 is allowed. Therefore, it is possible to secure the flexibility of the entire top foil portion Tf and prevent uneven wear of the top foil portion Tf due to contact with the shaft 6. As described above, the contact portion 41 of the intermediate foil 40 functions as a rigidity enhancing portion that enhances the rigidity of the facing area X1 of the bearing surface X that faces the first protrusion 21.

The effect described above is achieved by providing a rigidity enhancing portion that enhances the rigidity of the facing region X1 between the facing region X1 of the bearing surface X and the first projecting portion 21 to suppress the deformation of the facing region X1 of the bearing surface X. This can be achieved by: For example, as shown in FIG. 21, when the contact portion 41 of the intermediate foil 40 is integrated with the top foil portion Tf, that is, without using the intermediate foil 40, the back side of the top foil portion Tf (contact with the first projecting portion 21). ), The deformation of the top foil portion Tf in the facing region X1 is suppressed even when the top foil portion Tf is partially thickened. Therefore, the entire bearing surface X including the facing region X1 can be elastically deformed, and the uneven wear of the top foil portion Tf can be prevented in the same manner as described above. In this embodiment, the thickened portion 41 of the top foil portion Tf functions as a rigidity enhancing portion that enhances the rigidity of the facing region X1. The top foil portion Tf in which the convex rigidity reinforcing portion 41 is formed on the back surface as described above can be manufactured by, for example, a method such as etching.

In the embodiment shown in FIG. 19, even when the intermediate foil 40 is formed in a single plate shape without the holes 43, deformation of the bearing surface X in the facing region X <b> 1 is suppressed and the top by contact with the shaft 6 is suppressed. It is considered that uneven wear of the foil portion Tf can be prevented. On the other hand, in such a configuration, the rigidity of the bearing surface X is enhanced not only in the facing region X1 of the bearing surface X but also in a portion other than the facing region X1 (a portion facing the intermediate portion 23 of the back foil portion Bf), thereby deforming. It becomes difficult to do. Therefore, the flexibility of the entire bearing surface X is reduced, and the automatic adjustment function of the bearing gap may be impaired.

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 can be applied is not limited to this. 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 such that a plurality of foils 12 (leaves) having one end on the rotation direction R side as a free end and the other end on the opposite rotation direction side as a fixed end are arranged in the rotation direction R of the shaft 6. A region on the rotation direction R side of the foil 12 functions as a top foil portion Tf, and a region on the opposite rotation direction side functions as a back foil portion Bf. In this leaf-type radial foil bearing, the back foil portion Bf (shown by a dotted pattern) of each leaf 12 is formed by an uneven foil 20, and an intermediate foil 40 is used as shown in FIG. As shown, by forming the top foil portion Tf partially thick, the same effect as described above can be obtained.

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 entire back foil portion Bf is formed by the uneven foil 20, and an intermediate foil 40 (not shown in FIG. 23) shown in FIG. 20 is used, or a partial foil shown in FIG. By using the thicker top foil portion Tf, the same effect as described above can be obtained. In FIG. 23, the back foil portion Bf is continuous over the entire circumference of the inner peripheral surface 11a of the foil holder 11, but the back foil portion Bf may be divided at one or a plurality of locations in the circumferential direction. In this case, the divided individual elements are formed by the uneven foil 20.

Further, the present invention can be applied to a thrust foil bearing 30 shown in FIG. FIG. 24 shows a leaf-type thrust foil bearing as an example of the thrust foil bearing 30. In this thrust foil bearing as well, as shown in FIG. 25, the back foil portion Bf (shown by a dotted pattern) of each leaf 12 is formed by the uneven foil 20, and further, the intermediate foil 40 shown in FIG. The same effect as described above can be obtained by using a not-shown) or by using a partially thick top foil portion Tf shown in FIG.

In the above description, the case where the shaft 6 is a rotation-side member and the foil holder 11 is a fixed-side member has been exemplified. Conversely, the shaft 6 is a fixed-side member, and the foil holder 11 is a rotation-side member. In this case, the present invention can be applied. However, in this case, since the foil 12 becomes a rotating member, it is necessary to design the foil 12 in consideration of the deformation of the foil 12 as a whole due to centrifugal force.

Further, the foil bearing according to the present invention is not limited to the gas turbine described above, but can be used as a foil bearing for supporting a rotor of a turbomachine such as a turbocharger. Without being limited to the above examples, the foil bearing according to the present invention can be widely used as a bearing for vehicles such as automobiles and a bearing for industrial equipment. 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 to this, and other gases can be used as a pressure generating fluid, or water or oil can be used. It is also possible to use such a liquid.

6 Shaft 10 Foil bearing 11 Foil holder 11a Inner peripheral surface 12 Foil 20 Concavo-convex foil 21 Projection (first projection)
22 Projection (second projection)
23 Intermediate part 40 Intermediate foil 41 Rigidity strengthening part (contact part)
42 Column part 43 Hole C Bearing gap X Bearing surface X1 Opposing area

Claims (4)

Comprising a top foil portion having a bearing surface for the shaft and the counter to be supported, and a back foil portion supporting the top foil portion elastically behind the top foil portion, between said shaft and said bearing surface in fluid film generated in the bearing clearance, the foil bearing for supporting the shaft for relative rotation in a non-contact,
The back foil portion, a flat intermediate portion, and a plurality of protrusions projecting to the front side and back side of the intermediate portion is provided, the protruding portion is formed in a hemispherical shape, of the bearing surface of the top foil portion the facing region facing the protruding portion, between the protrusions, the foil bearing, characterized in that a rigid reinforcing part for reinforcing the rigidity of the facing region. Wherein the rigid reinforcement portion, the foil bearing according to claim 1 formed with an intermediate foil arranged between the projecting portion and the top foil portion. The foil bearing according to claim 2 , wherein a hole is provided in a portion of the intermediate foil that faces the intermediate portion of the back foil portion . Foil bearing according to the rigidity reinforcement unit, to claim 1, the top foil portion in the opposite region is constituted by a thicker than elsewhere.

Images