JP6629042B2 - Foil bearing - Google Patents

Description

  The invention relates to a foil bearing.

  The main shaft of a turbomachine (for example, a gas turbine or a turbocharger) rotates at high speed in a high-temperature environment. Further, in a turbomachine, it may be difficult to separately provide an auxiliary device for oil circulation from the viewpoint of energy efficiency, and the shear resistance of the lubricating oil may be a hindrance to high-speed rotation of the main shaft. Therefore, as a bearing for supporting the main shaft of the turbomachine, an air dynamic pressure bearing using air as a pressure generating fluid is often used instead of a rolling bearing or a dynamic pressure bearing using lubricating oil.

  As the air dynamic pressure bearing, a bearing in which both a rotating-side bearing surface and a stationary-side bearing surface are formed of a rigid body is generally used. However, in this type of air dynamic pressure bearing, if the gap width of the bearing gap formed between the two bearing surfaces is insufficiently controlled, a self-excited shaft called a whirl when the stability limit is exceeded is reached. Whirling easily occurs. Therefore, in general air dynamic pressure bearings, it is necessary to control the width of the bearing gap with high accuracy in order to stably exhibit the bearing performance. However, in an environment having a large temperature change, such as a turbomachine, the gap width of the bearing gap tends to fluctuate due to the influence of thermal expansion, and thus it is difficult to exhibit the bearing performance stably.

  Foil bearings are 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 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 Literature 1 below discloses an example of a radial foil bearing that supports a radial load.

JP-A-2005-52345

The foil bearing described in Patent Literature 1 has a plurality of foils arranged in a rotation direction, and each foil is provided with a top foil portion having a bearing surface and an elastically deformable underfoil portion. The underfoil portion is arranged behind a top foil portion of another foil, and one end in the circumferential direction is constituted by a free end movable in the circumferential direction.

One of the factors that affect the bearing performance of this type of foil bearing is the spring stiffness of the underfoil portion. The spring stiffness should be designed to be the optimal size at each part of the underfoil part. However, conventionally, since the underfoil part is formed of a single foil material, the spring stiffness at each part of the underfoil part is increased. Is difficult to optimize, and this point is an obstacle in improving the bearing performance of the foil bearing.

  Accordingly, an object of the present invention is to increase the degree of freedom in designing the spring stiffness of the underfoil portion.

  In order to solve the above problems, the present invention has a foil disposed at a plurality of locations in a relative rotation direction between a shaft to be supported, and each foil has a top foil portion provided with a bearing surface; An elastically deformable underfoil portion disposed behind the foil portion, wherein a circumferential end of the underfoil portion has a free end movable in a circumferential direction; Characterized in that a plurality of foil materials are formed one on top of another.

If the underfoil section has a multilayer structure (multilayer underfoil section) in which a plurality of foil materials are stacked, the spring stiffness can be adjusted with each foil material, so the spring stiffness of the entire underfoil section is optimized. It becomes easy to make it. Specifically, the spring stiffness of the underfoil portion is optimized by changing the shape of the plurality of foil materials constituting the multilayer underfoil portion or by changing the material or thickness of the plurality of foil materials. be able to.

Further, with such a configuration, it is possible to allow micro sliding between a plurality of foil members constituting the under foil portion. Therefore, the effect of absorbing the vibration generated in the rotating member can be enhanced.

  If the plurality of foil members constituting the underfoil portion have different lengths in the circumferential direction, it is easy to provide a difference in spring stiffness in the circumferential direction of the underfoil portion. For this reason, it is possible to increase the wedge angle in the wedge space, thereby increasing the pressure of the fluid film to stabilize the rotation-side member and to quickly shift to a steady rotation of the rotation-side member.

  If the plurality of foil members constituting the underfoil portion have different widths in a direction along the bearing surface and in a direction orthogonal to the circumferential direction, the thickness of the foil in the thickness direction of the foil at both ends of the underfoil portion in the aforementioned direction is increased. It is possible to reduce the spring stiffness at both ends by removing the portion area. This facilitates deformation of the top foil portions facing the both ends, so that, for example, even when the rotating member swings conically, it is possible to prevent the shaft and the foil from coming into contact with each other.

  By engaging the other end of the underfoil portion in the circumferential direction with another foil in the circumferential direction, it is possible to hold the underfoil portion with another foil and prevent the underfoil portion from falling off. This engagement can be performed by crossing another foil at the boundary between the top foil and the underfoil of each foil. The intersection of the foils can be performed, for example, by inserting the other foil into a slit provided in one foil.

  As described above, according to the present invention, the degree of freedom in designing the spring stiffness of the underfoil portion can be increased. Therefore, it is easy to design a foil bearing suitable for various uses.

FIG. 1 is a diagram illustrating a schematic configuration of a micro gas turbine. 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 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 a 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 sectional drawing which expands and shows the foil overlap part of a foil bearing. It is a top view of the foil material of a front side. It is a top view of the foil material of the back side. It is an expanded sectional view showing a foil overlapping part typically (immediately after rotation start of a shaft). It is an expanded sectional view showing typically a foil overlap part (during the steady rotation of a shaft). It is a top view of the foil material of a front side. It is a top view of the foil material of the back side. It is sectional drawing in the direction N orthogonal to the rotation direction of a foil overlap part. It is an expanded sectional view of an important section of a foil holder.

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

  FIG. 1 conceptually shows a configuration of a gas turbine device called a micro gas turbine as an example of a turbo machine. This gas turbine device includes a turbine 1 having a cascade, 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 together with the shaft 6, constitute a rotating rotor. One end of the shaft 6 in the axial direction is connected to the generator 3. When the micro gas turbine is operated, air is sucked from the inlet 7, and the sucked air is compressed by the compressor 2 and heated by the regenerator 5 before being sent to the combustor 4. The combustor 4 generates a high-temperature and high-pressure gas by mixing fuel with the compressed and heated air and burning the fuel, thereby rotating the turbine 1. When the turbine 1 rotates, the rotational force is transmitted to the generator 3 via the shaft 6, and the generator 3 is driven to rotate. Electric power generated by rotating the generator 3 is output via the inverter 8. Since the gas after rotating the turbine 1 has a relatively high temperature, the gas is sent to the regenerator 5 to exchange heat with the compressed air before combustion, thereby regenerating the heat of the gas after combustion. Use. The gas that has completed the 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 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.

  In the present invention, a so-called multi-arc type foil bearing is used as the foil bearing suitable for the radial bearing 10 for the micro gas turbine. Hereinafter, the basic configuration of this multi-arc foil bearing will be described with reference to FIGS. In addition, as described later, the present invention is characterized in that each foil 12 of the foil bearing is formed of a plurality of foil materials that are superimposed on each other. In FIG. 8), for ease of understanding, description will be made on the assumption that each foil 12 is formed of one foil material.

[Basic configuration of multi-arc foil bearing]
As shown in FIG. 3, a 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. 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 20-200 μm-thick metal foil or a copper alloy into a predetermined shape by press working or the like. It is formed by. Typical examples of steel materials and copper alloys include carbon steel and brass.General carbon steel has no lubricating oil in its atmosphere and cannot be expected to have the rust-preventive effect of oil. It is easy to occur. In addition, brass may cause a pre-crack due to processing strain (the more the content of Zn in brass, the stronger this tendency). Therefore, it is preferable to use stainless steel or bronze as the band-like foil.

  As shown in FIG. 4, 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 anti-rotation direction side.

  The first region 12a includes a plurality of top foil portions 12a1 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 12a1 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 anti-rotation direction side) of the second region 12b, two notches 12b2 that are recessed in the rotation direction R and are separated in the orthogonal direction N are formed. The width dimension 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 can also 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 the 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 port 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. The first area 12a and the second area 12b are connected by the area 12c3 between the insertion ports 12c1.

  As shown in FIG. 5, 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 drawing, one of the two foils 12 after the combination is colored gray.

  Then, as shown in FIG. 6, by connecting the three foils 12 circumferentially by the same joining method as in FIG. 5, each foil 12 can be brought into a temporarily assembled state. As shown in FIG. 7, the foil bearing 10 is assembled by forming the temporary assembly into a tubular shape and inserting it into the inner periphery of the foil holder 11 in the direction of arrow B <b> 2. 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 grooves 11 b ( (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 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 12a1 of the other foil 12 forms the bearing surface X. On the anti-rotation direction side of the intersection, the top foil portion 12a1 of one foil 12 constitutes the bearing surface X, and the second region 12b of the other foil goes behind one foil 12 to form the underfoil portion. Constitute. The end of the underfoil portion 12b on the anti-rotation direction side 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 underfoil portion 12b. The end of the under foil 12b 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 12a1 and the under foil portion 12b 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 this 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 a region on the opposite rotation direction side is engaged with another 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 12a1 of each foil 12 protrudes toward the foil holder 11 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 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 underfoil portion 12b.

  As shown in FIG. 8, 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 12a1 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). Further, the top foil portion 12a1 rises in a state of being inclined in a direction away from the inner peripheral surface 11a of the foil holder 11 by riding on the under foil portion 12b. Therefore, a wedge space is formed between the bearing surface X of the top foil portion 12a1 and the outer peripheral surface of the shaft 6. In addition, the top foil portion 12a1 is supported by the elastically deformable underfoil portion 12b, so that the top foil portion 12a1 can be deformed by following the displacement of the shaft 6, thermal expansion and the like.

  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, 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. Due to the elastic deformation of the top foil portion 12a1, the width of the radial bearing gap 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 width of the radial bearing gap C is exaggerated for easy understanding (the same applies to FIG. 9).

  In the present embodiment, as shown in FIG. 5, a notch 12b2 is provided at the rear end 12d of the second region 12b of each foil 12. During rotation of the shaft 6, the fluid pressure causes the top foil portion 12a1 of the foil overlapping portion W to be pressed and elastically deformed by the under foil portion 12b, so that the top foil 12a1 riding on the under foil portion 12b has a bearing gap. A step in the width direction of C is formed. This step has a shape corresponding to the herringbone shape of the notch 12b2. Since the fluid flowing along the top foil portion 12a1 flows along the step (see the arrow), fluid pressure generating portions are formed in the bearing gap C at two places in the orthogonal direction N. 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 12a1 to reduce the rigidity of the top foil portion 12a1, the top foil portion 12a1 extends along the notch portion 12b2. When deforming, the deformation is performed smoothly.

[Characteristic configuration of the present invention]
According to the present invention, in the above-described multi-arc foil bearing, as shown in FIG. 9, a plurality of (two in the present embodiment) foil materials 121 and 122 are stacked to form each foil 12 in a multilayer structure. The point is a characteristic configuration.

FIG. 10 is a plan view of the foil material 121 on the front side (the side facing the bearing gap C) of the two foil materials 121 and 122, and the plane of the foil material 122 on the back side (the side away from the bearing gap C). The figure is shown in FIG. As shown in FIGS. 10 and 11, each of the foil members 121 and 122 has a first region 12a having a top foil portion 12a1 and a convex portion 12a2, and an under foil portion as in the foil 12 shown in FIG. A second area 12b and an insertion port 12c1 located at a boundary between the first area 12a and the second area 12b are formed.

In the two foil members 121 and 122 shown in FIGS. 10 and 11, the insertion port 12c1 and a region on the rotation direction R side of the insertion port 12c1 are formed in the same shape. Therefore, when the two foil members 121 and 122 are overlapped with the position of the insertion port 12c1 matched, the first regions 12a of both foil members 121 and 122 completely overlap without one protruding from the other. State.

On the other hand, the underfoil portions 12b of the two foil members 121 and 122 have different shapes by making the lengths in the rotation direction R different. 9 to 11 show an example in which the length of the underfoil portion 12b of the front foil material 121 is shorter than the length of the underfoil portion 12b of the rear foil material 122.

In FIGS. 10 and 11, the shape of the foil 12 shown in FIG. 4 is simplified. Specifically, the protrusion 12a2 and the insertion port 12c1 of the first area 12a are arranged at two places in the orthogonal direction N. Also, the notch 12b2 at the rear end 12d of the second region 12b is omitted. Of course, each of the foil members 121 and 122 may be provided with the same number (three) of protrusions 12a2 and insertion ports 12c1 as the foil 12 shown in FIG. A notch 12b2 similar to the foil 12 shown in FIG. 4 may be formed at the rear end 12d of the second region 12b of each of the foil members 121 and 122.

The foil bearing 10 is assembled in a procedure similar to the procedure described with reference to FIGS. At this time, the two foil materials 121 and 122 stacked on each other are handled as one foil 12 shown in FIGS. That is, as shown in FIG. 5, when connecting the foils 12 to each other, the other foil 12 made of the two foils 121 and 122 is inserted into the insertion port 12c1 where the two foils 121 and 122 overlap. Are inserted. When attaching the three foils 12 connected in a circumferential shape to the foil holder 11, the overlapping convex portions 12a2 of the foil materials 121 and 122 are inserted into the axial grooves 11b of the foil holder 11 (FIG. 9).

As a result of the above assembling steps, as shown in FIG. 9, the foil bearing 10 has a multilayer top foil portion 12A1 in which the top foil portions 12a1 of the foil materials 121 and 122 are stacked, and a foil material of another foil 12. A multilayer underfoil portion 12B in which the underfoil portions 121b of 121 and 122 are overlapped is formed. A bearing surface X is formed on the surface of the top foil portion 12a1 on the front side of the multilayer top foil portion 12A1. The multilayer underfoil portion 12B is behind (on the back side of) the multilayer top foil portion 12A1, and elastically supports the multilayer top foil portion 12A1. Each end on the anti-rotation direction side of the multilayer underfoil portion 12B constitutes a free end, and each end on the rotation direction side is in a state of being engaged with the other foil 12 in the circumferential direction. Further, a foil overlapping portion W is formed by overlapping the multilayer top foil portion 12A1 and the multilayer underfoil portion 12B.

The multilayer underfoil portion 12B is formed with a multilayer portion E1 in which the two underfoil portions 12b overlap, and a single layer portion E2 including only one underfoil portion 12b among the two underfoil portions 12b. You. The multilayer portion E1 is located on the rotation direction R side of the single layer portion E2.

FIGS. 12 and 13 schematically show the cross-sectional structure of the foil overlapping portion W when each of the foils 12 described above is attached to the foil holder 11. 12 shows a state immediately after the rotation of the shaft 6 is started, and FIG. 13 shows a state during the steady rotation of the shaft 6.

As shown in FIG. 12, when the shaft 6 starts rotating, the multilayer top foil portion 12A1 receives the air pressure P in the arrow direction generated in the bearing gap C, and the multilayer top foil portion 12A1 expands the width dimension of the bearing gap C (downward in the figure). 13), the multilayer top foil portion 12A1 is pressed against the multilayer underfoil portion 12B as shown in FIG. In a region other than the foil overlapping portion W, the multilayer top foil portion 12A1 is pressed against the inner peripheral surface 11a of the foil holder 11.

In the multilayer underfoil portion 12B, the spring rigidity of the multilayer portion E1 formed by the two foil members 121 and 122 is larger than the spring rigidity of the single layer portion E2 formed by the single foil member 122. . Due to this difference in spring stiffness, during rotation of the shaft 6, as shown in FIG. 13, the multilayer top foil portion 12A1 bends slightly (a small amount of deformation) in a region facing the multilayer portion E1, and the single layer portion E2 (The amount of deformation is large). Therefore, the wedge angle α of the wedge space formed between the bearing surface X of the multilayer top foil portion 12A1 and the outer peripheral surface of the shaft 6 is such that each foil 12 is formed of one foil material (FIG. 8 and the like). Reference)). As the wedge angle α of the wedge space increases, the air pressure generated in each wedge space increases, so that the shaft 3 can be shifted to the steady rotation early, and the stability of the shaft 6 during the steady rotation is enhanced. It becomes possible.

In addition, in the foil overlapping portion W, since the multilayer top foil portion 12A1 rides on the plurality of underfoil portions 12B having two foil thicknesses, the step formed in the multilayer top foil portion 12A1 ( The step in the width direction of the bearing gap C) increases. From this point as well, the wedge angle α of the wedge space can be increased, and the above effect can be further remarkable.

In FIGS. 12 and 13, for ease of understanding, the deformation modes of the foil members 121 and 122 and the gaps formed between the foil members 121 and 122 are illustrated as simplified as possible. Therefore, in the actual foil bearing 10, each of the foil members 121 and 122 is not always deformed in the mode shown in FIGS. 12 and 13, and between the foil members 121 and 122 in the mode shown in FIGS. 12 and 13. The gap is not always formed.

In the above description, of the two foil materials 121 and 122 constituting the multilayer underfoil portion 12B, the length of the underfoil portion 12b of the front foil material 121 is made longer than that of the underfoil portion 12b of the rear foil material 122. Although the case where the length is shortened is illustrated, conversely, even when the length of the underfoil portion 12b on the front side is made longer than the length of the underfoil portion 12b on the back side, the circumference of the multilayer underfoil portion 12B is similarly formed as described above. A difference in spring stiffness can be formed in the direction, and the same effect as described above can be obtained.

14 and 15 show that the underfoil portions 12b are formed in different shapes by making the width dimensions of the underfoil portions 12b of the two foil materials 121, 122 in the orthogonal direction N different. In the present embodiment, the width L2 of the underfoil portion 12b of the foil material 122 on the back side is smaller than the width L1 of the underfoil portion 12b of the foil material 121 on the front side (L2 <L1).

With such a configuration, as shown in FIG. 16, in the foil overlapping portion W, both ends of the multilayer underfoil portion 12B in the orthogonal direction N are partially removed in the thickness direction. In this case, since the spring stiffness at both ends of the multilayer underfoil portion 12B decreases, both ends of the multilayer top foil portion 12A1 in the orthogonal direction N are deformed following the displacement of the shaft 6 as compared with the central portion thereof. Easier to do. For this reason, even when the shaft 6 and the bearing surface X may be in contact with each other, such as when the shaft 6 is used for conical swinging, such edge contact can be prevented. When the shaft 6 and the bearing surface X come into contact with the edge, the contact surface pressure is increased, so that the foil 12 and the shaft 6 are liable to be worn, but the configuration shown in FIG. Can be.

FIG. 16 illustrates a case where the width dimension of the underfoil portion 12b of the back foil material 122 of the multilayer underfoil portion 12B is reduced. However, contrary to FIG. The same effect can be obtained even when the width of the foil 12b is smaller than that of the underfoil 12b on the back side. The same effect can be obtained by removing the thickness of a part of the thickness of both ends of the multilayer top foil portion 12A1 in addition to removing the thickness in the thickness direction of the two ends of the multilayer underfoil portion 12B. Can be obtained. For example, in the top foil part 12a1 of the foil material 122 on the back side of the multilayer top foil part 12A1, even if the width dimension is smaller than the width dimension of the top foil part 12a1 of the foil material 121 on the front side, the same as above. The effect can be obtained.

In FIGS. 14 and 15, similarly to the embodiment shown in FIG. 9, the circumferential length of the underfoil portion 12 b of the rear foil material 122 is set to the circumferential length of the underfoil portion 12 b of the front foil material 121. Although it is larger than the length, the length relationship between the two may be reversed, or both may be the same length.

As described above, in the present invention, the underfoil portion of the foil bearing 10 is constituted by the multilayer underfoil portion 12B in which a plurality of foil materials 121 and 122 are stacked. In this case, by making the spring stiffness of each of the foil members 121 and 122 different, the spring stiffness of each portion can be optimized in the entire multilayer underfoil portion 12B. Therefore, the degree of freedom in designing the underfoil portion is increased, and the design of the foil bearing adapted to the use conditions is facilitated. Specifically, as shown in FIG. 10, FIG. 11, FIG. 14, and FIG. 15, the under foil portion 12b of each of the foil members 121 and 122 is formed in a different shape so that the spring material can be rotated in the rotation direction R or the orthogonal direction N. A difference in rigidity can be provided. In addition, the same effect can be obtained by configuring the multilayer underfoil portion 12B with foil materials 121 and 122 having different materials and thicknesses (irrespective of whether the shapes are the same or different).

In the present embodiment, the underfoil portion of the foil bearing 10 and the top foil portion have a multilayer structure in which a plurality of foil materials 121 and 122 are stacked. Therefore, it is possible to allow micro sliding between the foil members 121 and 122 constituting the multilayer top foil portion 12A1 and the multilayer underfoil portion 12B. As a result, the effect of absorbing the vibration of the shaft 6 is enhanced, so that the unstable behavior of the shaft 6 can be prevented and its rotation can be stably supported.

Incidentally, the axial groove 11b formed in the foil holder 11 is formed substantially in the tangential direction of the inner peripheral surface 11a as shown in FIG. The axial groove 11b can be formed by wire cutting or the like. However, simply reciprocating the wire causes the end of the outlet of the axial groove 11b on the rotation direction R side as shown in FIG. The edge 11c 'is obtained. When the edge 11c 'is formed at the outlet of the axial groove 11b in this manner, when the shaft 6 collides with this portion, the vicinity of the edge 11c' is deformed. There is a risk of lowering. In order to prevent such a problem, as shown in FIG. 9, it is preferable to provide a chamfer 11c at the end of the outlet of the axial groove 11b on the rotation direction R side. The chamfer 11c can be formed, for example, by bending the traveling direction of the wire by 90 ° toward the inner peripheral surface 11a at the end of the return stroke of the wire during wire cutting. Of course, the chamfered portion 11c can be formed by dropping the edge 11c 'by post-processing (cutting or the like) after the formation of the axial groove 11b.

  In the above description, a so-called multi-arc type radial foil bearing is exemplified as the foil bearing 10, but the form of the foil bearing is not limited to this, and an elastically deformable underfoil portion behind the top foil portion is provided. The present invention can be applied to a foil bearing of any form in which one end in the circumferential direction of the underfoil portion is arranged and configured as a free end movable in the circumferential direction. In addition, the present invention can be applied not only to a radial foil bearing that supports a radial load but also to a thrust foil bearing that supports a thrust load, as long as the foil bearing has this configuration.

  Further, 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 is a rotating member, it is necessary to design the foil 12 in consideration of deformation of the foil 12 as a whole due to centrifugal force.

  Furthermore, the foil bearing according to the present invention is not limited to the gas turbine described above, and can be used, for example, as a foil bearing for supporting a rotor of a supercharger. 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 thereto, 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 11b Axial groove (mounting part)
Reference Signs List 12 foil 12a1 top foil part 12A1 multilayer top foil part 12b under foil part 12B multilayer under foil part 12d rear end 121 foil material 122 foil material C bearing gap R rotation direction N direction orthogonal to rotation direction X bearing surface

Claims (5)

It has foils arranged at a plurality of points in the direction of relative rotation between the shaft to be supported, and each foil has a top foil portion provided with a bearing surface and an elastically deformable arranged behind the top foil portion. An under foil portion is provided, wherein one end of the under foil portion in the circumferential direction is a free end movable in the circumferential direction.
A foil bearing , wherein the underfoil portion is formed by stacking a plurality of foil materials, and the plurality of foil materials constituting the underfoil portion have different shapes . The foil bearing according to claim 1, wherein the plurality of foil members constituting the underfoil portion have different lengths in a circumferential direction. The foil bearing according to claim 1, wherein the plurality of foil members constituting the underfoil portion have different widths in a direction orthogonal to a circumferential direction. The foil bearing according to claim 1, wherein the plurality of foil members constituting the underfoil portion are made of different materials or thicknesses. The foil bearing according to any one of claims 1 to 4 , wherein the other end of the underfoil portion in the circumferential direction is engaged with another foil in the circumferential direction.

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