JP2013053645A - Thrust foil bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the pressure of a fluid film caused in a bearing clearance, and increase the load capacity by a foil bearing.SOLUTION: Projections (rectification members 34) or grooves 35 long and large in the circumferential direction are formed on thrust bearing surfaces 33 of foil members (leaves 30). When a shaft 6 rotates, the fluid flowing through the bearing clearance collides with the rectification members 34 or the grooves 35, and thereby the fluid flowing through the bearing clearance is made to flow along the circumferential direction.

Description

  The present invention relates to a thrust foil bearing that supports a rotating member in a thrust direction with a thrust bearing surface formed on a thin film foil member and a fluid film generated in a thrust bearing gap formed on the thrust bearing surface.

  The shafts of gas turbines and superchargers (such as turbochargers) are driven to rotate at high speed. Further, the turbine blade attached to the shaft is exposed to high temperature. For this reason, bearings that support these shafts are required to withstand harsh environments such as high temperature and high speed rotation. An oil-lubricated rolling bearing or an oil dynamic pressure bearing may be used as a bearing for this type of application. However, when lubrication with a liquid such as lubricating oil is difficult, when it is difficult to separately provide an auxiliary machine for the lubricating oil circulation system from the viewpoint of energy efficiency, or when resistance due to liquid shear becomes a problem, etc. Below, the use of bearings with oil is restricted. Therefore, an air dynamic pressure bearing has attracted attention as a bearing suitable for use under the above conditions.

  As an air dynamic pressure bearing, one in which both the rotating side and the fixed side bearing surfaces are made of a rigid body is generally used. However, in this type of air dynamic pressure bearing, if the bearing clearance formed between the rotating and stationary bearing surfaces is insufficiently controlled, a self-excited shaft called a whirl when the stability limit is exceeded. It is easy to cause a whirling. Therefore, gap management according to the rotation speed used is important. However, since the width of the bearing gap fluctuates under the influence of thermal expansion in an environment where the temperature changes rapidly, such as a gas turbine or a supercharger, accurate gap management becomes extremely difficult.

  Foil bearings are known as bearings that can easily manage clearances even in environments with large temperature changes. In the foil bearing, a bearing surface is constituted by a thin film (foil) having low rigidity with respect to bending, and the load is supported by allowing the bearing surface to bend. In the foil bearing, an appropriate bearing gap is formed according to operating conditions such as the rotational speed and load of the shaft and the ambient temperature due to the flexibility of the foil. For this reason, a foil bearing has the characteristic that it is excellent in stability, and it can be used at high speed compared with a general air dynamic pressure bearing. In addition, in general dynamic pressure bearings, it is necessary to always maintain a bearing gap of about several μm. Therefore, it is difficult to strictly manage the gap considering tolerances during manufacturing and thermal expansion when temperature changes are severe. It is. On the other hand, in the case of a foil bearing, it is sufficient to manage the bearing gap of about several tens of μm, and there is an advantage that its manufacture and gap management are easy.

  Further, since the reaction force in the thrust direction of the air flow generated by the high-speed rotation of the turbine is applied to the shaft of the gas turbine or the supercharger, it is necessary to support the shaft not only in the radial direction but also in the thrust direction. For example, Patent Documents 1 to 3 show a thrust foil bearing that supports a rotating shaft in a thrust direction.

JP 61-36725 A Japanese Utility Model Publication No. 61-38321 Japanese Unexamined Patent Publication No. 63-195212

  However, in the thrust foil bearing, as the rotating member rotates, the fluid in the thrust bearing gap tends to flow out to the outer diameter side due to centrifugal force, so the amount of fluid in the thrust bearing gap decreases and the fluid film pressure decreases. There is a fear.

  Therefore, an object of the present invention is to increase the pressure of a fluid film generated in a thrust bearing gap and increase the load capacity of the thrust foil bearing.

  The present invention made to achieve the above object includes a fixed member, a rotating member, and a foil member disposed between the fixing member and the rotating member, and a thrust bearing surface provided on the foil member is used for the thrust. A thrust foil bearing that forms a bearing gap and supports a rotating member in a thrust direction with a fluid film generated in the thrust bearing gap, and a long projection or groove in the circumferential direction is separated from the thrust bearing surface in the radial direction. It is characterized by being formed at a plurality of locations.

  In this way, by providing the circumferentially long protrusions or grooves on the thrust bearing surface at a plurality of locations separated in the radial direction, fluid that tends to flow out from the thrust bearing gap to the outer diameter side by centrifugal force Or it hits a groove and flows along the circumferential direction (rectification effect). As a result, the fluid flowing out from the thrust bearing gap to the outer diameter side by centrifugal force can be reduced, and the pressure of the fluid film generated in the thrust bearing gap can be increased. Note that the shape that is “long in the circumferential direction” means that the circumferential dimension is longer than the radial dimension, and is not limited to an arc shape parallel to the circumferential direction, but is long in the circumferential direction. A rectangle (see FIG. 5) and a triangle (see FIG. 7).

  For example, a rectifying member can be fixed to the bearing surface of the foil member, and the above-described protrusion can be formed by the rectifying member. In this case, the rectifying effect is further enhanced by bringing the rectifying member as close as possible to the end surface of the mating member as long as the rectifying member and the end surface of the mating material facing the rectifying member through the thrust bearing gap do not contact each other.

  On the other hand, since the groove can be easily formed on the foil member by pressing or the like, the manufacturing cost can be reduced as compared with the case where the rectifying member is fixed. The rectifying effect can be enhanced by gradually narrowing the groove width of the groove toward the rotation direction leading side or increasing the groove depth of the groove toward the rotation direction leading side.

  The above configuration can be applied to, for example, a leaf-type thrust foil bearing in which the foil member has a plurality of leaves with one circumferential end as a free end. In this case, the foil member includes, for example, a foil having a circumferential end and a free end, and a plurality of leaves provided with thrust bearing surfaces and a connecting portion that connects the plurality of leaves. be able to. Moreover, a foil member can also be constituted by combining a plurality of such foils.

  In a foil bearing, a fluid film is formed between the thrust bearing surface of the foil member and the surface facing the foil bearing during high-speed operation, and these surfaces are in a non-contact state. It becomes difficult to form a fluid film having a surface roughness greater than that of the thrust bearing surface of the foil member and the surface facing the thrust bearing surface. Therefore, there is a possibility that the rotating member and the fixing member come into contact with each other with the foil member interposed therebetween, and the surface of the foil member may be damaged. For this reason, it is preferable to provide a film on the thrust bearing surface of the foil member to prevent damage.

  In addition, sliding of minute displacement occurs between the foils constituting the foil member or between the foil and the surface to which the foil is fixed, due to load fluctuation or vibration. For this reason, it is preferable to provide a coating on the surface opposite to the thrust bearing surface of the foil constituting the foil member to prevent damage due to sliding.

  Since the foil bearing is often used in a place where it is difficult to lubricate with a liquid, a DLC film, a titanium aluminum nitride film, or a molybdenum disulfide film can be used for the coating as described above. DLC films and titanium aluminum nitride films are hard, have a low coefficient of friction, and are excellent in strength. On the other hand, since the molybdenum disulfide film can be sprayed by spraying or the like, a film can be easily formed.

  The thrust foil bearing as described above can be suitably used for supporting a rotor of a gas turbine or a supercharger.

  As described above, according to the present invention, the fluid flow in the thrust bearing gap is rectified in the circumferential direction, thereby increasing the fluid film pressure generated in the thrust bearing gap and increasing the load capacity of the thrust foil bearing. it can.

It is a figure which shows a micro gas turbine notionally. It is sectional drawing which shows the support structure of the rotor of the said micro gas turbine. It is sectional drawing of the radial foil bearing integrated in the said rotor support structure. It is a side view of the thrust foil bearing which concerns on the embodiment of this invention integrated in the said rotor support structure. It is a perspective view of the bearing member of the said thrust foil bearing. It is a top view of the leaf of the said thrust foil bearing. It is a top view of the leaf of the thrust foil bearing which concerns on other embodiment. It is sectional drawing of the bearing member of the thrust foil bearing of FIG. It is a perspective view which shows typically the bearing member of the thrust foil bearing of FIG. It is a top view of the bearing member of the thrust foil bearing which concerns on other embodiment. It is a top view of the bearing member of the thrust foil bearing which concerns on other embodiment. It is a perspective view of the bearing member of the thrust foil bearing which concerns on other embodiment. It is a top view of the foil of the thrust foil bearing of FIG. (A)-(c) is a perspective view which shows a mode that two foils of the thrust foil bearing of FIG. 12 are assembled | attached. It is a top view of the leaf of the thrust foil bearing which concerns on other embodiment. It is a top view of the leaf of the thrust foil bearing which concerns on other embodiment. It is a figure which shows a supercharger notionally.

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

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

  FIG. 2 shows a support structure of the rotor, in particular, a support structure of the shaft 6 in the axial direction between the turbine 1 and the compressor 2. Since this region is adjacent to the turbine 1 rotated by high-temperature and high-pressure gas, an air dynamic pressure bearing, particularly a foil bearing is preferably used here. Specifically, the rotor is rotatably supported by a radial foil bearing 10 that supports the shaft 6 in the radial direction and a thrust foil bearing 20 that supports the flange portion 40 provided on the shaft 6 in both thrust directions. .

  As shown in FIG. 3, the radial foil bearing 10 is fixed to the casing 42, and is fixed to the cylindrical outer member 11 with the shaft 6 inserted into the inner periphery, and the inner peripheral surface 11 a of the outer member 11, It consists of a plurality of leaves 12 arranged side by side in the circumferential direction.

  The leaf 12 is formed of a strip-like foil having a thickness of about 20 μm to 200 μm made of a metal having a high spring property and good workability, such as a steel material or a copper alloy. In an air dynamic pressure bearing using air as a fluid film as in the present embodiment, since no lubricating oil exists in the atmosphere, the antirust effect by the oil cannot be expected. Typical examples of steel materials and copper alloys include carbon steel and brass, but general carbon steel is susceptible to corrosion due to rust, and brass may cause cracks due to processing strain (in brass) This tendency increases as the Zn content increases.) Therefore, it is preferable to use a stainless steel or bronze foil as the belt-like foil.

  In each leaf 12, one end 12 a in the circumferential direction (the leading side of the rotation direction of the shaft 6 (see the arrow)) is a free end, and the other end 12 b in the circumferential direction is fixed to the outer member 11. The fixed end 12 b of the leaf 12 is fitted and fixed to an axial groove 11 b formed on the inner peripheral surface 11 a of the outer member 11. A partial region on the free end 12 a side of the leaf 12 is arranged so as to overlap with the other leaf 12 in the radial direction. The surfaces on the inner diameter side of the plurality of leaves 12 constitute a radial bearing surface 12 c having a smooth curved surface without holes or steps, and between the radial bearing surface 12 c of each leaf 12 and the outer peripheral surface 6 a of the shaft 6. A wedge-shaped radial bearing gap R having a narrow radial width toward one circumferential direction is formed.

  As shown in FIG. 4, the thrust foil bearing 20 has a disc-like shape fixed to a flange portion 40 (rotating member, see FIG. 2) provided to protrude from the outer peripheral surface 6 a of the shaft 6 to the outer diameter, and a casing 42. A thrust member 21 (fixing member, see FIG. 5), and a foil member disposed between the flange portion 40 and the thrust member 21 are provided. In the present embodiment, bearing members 20a are provided on both axial sides of the flange portion 40 (see FIG. 2), and the bearing member 20a includes a disc-shaped thrust member 21 (fixing member) and a thrust as shown in FIG. It is comprised with the foil member fixed to the end surface 21a of the member 21. FIG. In the illustrated example, the foil member is composed of a plurality of leaves 30 fixed to the end surface 21a of the thrust member 21 in a state of being arranged at equal intervals in the circumferential direction.

  The leaf 30 is made of a single metal foil having the same material and thickness as the leaf 12 described above, and forms a fan shape along the circumferential direction of the thrust member 21. One end of the leaf 30 in the circumferential direction (the leading side in the rotational direction of the shaft 6, the left side in the figure) is a free end 31, and the other end in the circumferential direction is a fixed end 32 fixed to the thrust member 21. The Of each leaf 30, a curved thrust bearing surface 33 is provided on the surface opposite to the thrust member 21. The curved thrust bearing surface 33 projects from the flange portion 40 side. The thrust bearing surface 33 has a smooth curved surface with no holes or steps. The spring 30a schematically represents the spring property of the leaf 30 and is not actually provided.

  As shown in FIG. 6, a plurality of notch portions 31 a and a land portion 31 b continuous with the thrust bearing surface 33 are provided at the free end 31 of each leaf 30, in the extending direction of the free end 31 (in this embodiment, In the radial direction). In the illustrated example, by forming the free ends 31 in a zigzag shape, triangular cut portions 31a and land portions 31b are alternately formed.

  The thrust bearing surface 33 of each leaf 30 is provided with a plurality of circumferentially long projections at a plurality of locations separated in the radial direction. In the present embodiment, the rectifying member 34 is fixed to the surface of the leaf 30, and the rectifying member 34 forms a protrusion. The rectifying member 34 is formed of, for example, an elongated rectangular metal plate, and is fixed to the surface of the leaf 30 by an appropriate method such as adhesion, welding, or welding. The rectifying member 34 is arranged approximately along the circumferential direction. In the illustrated example, the rectifying member 34 is arranged on a straight line parallel to the tangential direction of the circumference at any point in the longitudinal direction of the rectifying member 34 (for example, the central portion in the longitudinal direction). The The rectifying member 34 is provided on the large gap portion T2 side of the thrust bearing gap T. In the illustrated example, the rectifying member 34 is provided on the rear side in the rotational direction from the circumferential center of each leaf 30. The flow regulating members 34 are arranged side by side at equal intervals in the radial direction. The rectifying member 34 is not limited to a linear shape, and may be formed in an arc shape parallel to the circumferential direction. Further, the protrusion provided on the thrust bearing surface 33 is not limited to the above, and may be formed on the leaf 30 by plastic working (for example, press molding), for example. In this case, if a hole penetrating the leaf 30 is formed, the fluid in the thrust bearing gap T falls out of the hole and the pressure is reduced. Therefore, it is necessary to form a protrusion so that the through hole is not formed in the leaf 30. is there.

  When the shaft 6 rotates in one circumferential direction, between the radial bearing surface 12c of each leaf 12 of the radial foil bearing 10 and the outer peripheral surface 6a of the shaft 6, a wedge shape with a radial width narrowing toward the circumferential direction one side. The radial bearing gap R is formed (see FIG. 3). The fluid film (air film) generated in the radial bearing gap R supports the shaft 6 in a non-contact manner in the radial direction. At the same time, between the end surfaces 41 on both axial sides of the flange portion 40 of the thrust foil bearing 20 and the thrust bearing surfaces 33 of the foil members (leafs 30) provided on both axial sides, the circumferential direction is one. A thrust bearing gap T having a narrower axial width is formed (see FIG. 4). The shaft 6 is supported in a non-contact manner in both thrust directions by a fluid film (air film) generated in the thrust bearing gap T. Note that the actual radial bearing gap R and thrust bearing gap T are as small as several tens of μm, but the widths are exaggerated in FIGS.

  At this time, as indicated by an arrow A in FIG. 4, the fluid in the small gap portion T1 of the thrust bearing gap T flows to the back side (downward in the drawing) of the leaf 30 through the notch portion 31a. As a result, the fluid in the entire large gap portion T2 dynamically flows and the amount of fluid flowing from the large gap portion T2 into the next small gap portion T1 increases, so the pressure generated in the small gap portion T1 is increased to increase the thrust direction. The load capacity can be increased.

  Also, as the shaft 6 rotates, the fluid in the thrust bearing gap T tends to flow out to the outer diameter by centrifugal force. When this fluid collides with the rectifying member 34 provided on the surface of the leaf 30, the fluid flows in the circumferential direction (see arrow B in FIG. 6). By this rectifying effect, the amount of fluid flowing out from the thrust bearing gap T toward the outer diameter side can be reduced, and the amount of fluid flowing into the small gap portion T1 can be increased to increase the pressure. In addition, since the centrifugal force applied to the fluid in the thrust bearing gap T increases toward the outer diameter side, the projection (rectifying member 34) that is long in the circumferential direction is at least on the outer diameter side (in the radial direction center portion) of the thrust bearing surface 33. It is preferably provided on the outer diameter side. In the illustrated example, protrusions are provided at equal intervals over the entire radial direction of the thrust bearing surface 33. Further, in this embodiment, the notch 31a is formed in the free end 31 of the leaf 30, and the fluid in the thrust bearing gap T flows to the back side of the leaf 30 through the notch 31a. The fluid in the tank is easily disturbed. Therefore, the rectifying effect by providing the protrusions (rectifying member 34) on the leaf 30 is particularly effective.

  At this time, due to the flexibility of the leaf 12 of the radial foil bearing 10 and the leaf 30 of the thrust foil bearing 20, the bearing surfaces 12 c and 33 of each leaf 12, 30 cause the load, the rotational speed of the shaft 6, and the ambient temperature. Therefore, the radial bearing gap R and the thrust bearing gap T are automatically adjusted to appropriate widths according to the operating conditions. Therefore, the radial bearing gap R and the thrust bearing gap T can be managed to the optimum width even under severe conditions such as high temperature and high speed rotation, and the shaft 6 can be stably supported.

  In the foil bearings 10, 20, the radial bearing surface 12 c of the leaf 12, the thrust bearing surface 33 of the leaf 30, and the outer peripheral surface 6 a of the shaft 6 are thicker than the surface roughness just before the shaft 6 is stopped or immediately after starting. It becomes difficult to form an air film. Therefore, metal contact is generated between the radial bearing surface 12 c and the outer peripheral surface 6 a of the shaft 6 and between the thrust bearing surface 33 and the flange portion 40. In order to reduce the frictional force due to the metal contact and prevent damage to the leaves 12 and 30 and reduce the torque, it is desirable to form a coating that reduces the friction on the radial bearing surface 12c and the thrust bearing surface 33. . As this type of coating, for example, a DLC film, a titanium aluminum nitride film, or a molybdenum disulfide film can be used. The DLC film, titanium or aluminum nitride film can be formed by CVD or PVD, and the molybdenum disulfide film can be easily formed by spraying. In particular, since the DLC film and the titanium aluminum nitride film are hard, by forming a film with them, the wear resistance of the radial bearing surface 12c and the thrust bearing surface 33 can be improved, and the bearing life is increased. be able to. The coating as described above is formed on the outer peripheral surface 6a of the shaft 6 and the end surface 41 of the flange portion 40 opposed to these surfaces instead of or in addition to the radial bearing surface 12c and the thrust bearing surface 33. It may be formed.

  During the operation of the bearing, the back surface of the leaf 12 (surface opposite to the radial bearing surface 12c) and the inner peripheral surface 11a of the outer member 11, or the back surface of the leaf 30 (surface opposite to the thrust bearing surface 33). ) And the end surface 21 a of the thrust member 21, so that the sliding portion, that is, the rear surfaces of the leaves 12 and 30, the inner peripheral surface 11 a of the outer member 11 in contact with this, and the thrust member 21 Abrasion resistance may be improved by forming the above-mentioned film on one or both of the end faces 21a. In order to improve the vibration damping action, it may be more convenient that a certain amount of frictional force exists in the sliding portion. Therefore, the low friction property is not required for the coating of this portion. Therefore, it is preferable to use a DLC film, titanium, or an aluminum nitride film as the coating of this portion.

  The present invention is not limited to the above embodiment. In the following description, portions having the same functions as those of the above-described embodiment are denoted by the same reference numerals, and redundant description is omitted.

  For example, in the above-described embodiment, the case where the protrusions (rectifying members 34) are provided on the surface of the leaf 30 is shown. However, the present invention is not limited to this. For example, as shown in FIGS. A long groove 35 may be formed in the direction. The groove 35 is formed on the surface of the leaf 30 by plastic working (for example, press molding). The groove 35 is formed so as not to penetrate the leaf 30 (see FIG. 8). Further, in the illustrated example, the groove width (diameter width) of the groove 35 is gradually narrowed toward the rotation direction leading side (free end 31 side) (see FIG. 7). Further, the groove depth of the groove 35 gradually increases toward the leading side in the rotational direction (see FIG. 8). That is, as shown in FIG. 9, the groove 35 has a wide groove width and a shallow groove depth on the fluid inlet side (the fixed end 32 side of the leaf 30), and the fluid outlet side (the free end of the leaf 30). On the end 31 side, the groove width is narrow and the groove depth is deep. In FIG. 9, for simplification of the drawing, the arc-shaped leaf 30 is shown in a rectangular shape in plan view, and the free end 31 of the leaf 30 is shown in a straight line.

  Thus, by forming the circumferentially long groove 35 in the leaf 30, the fluid flowing through the thrust bearing gap T enters the inside of the groove 35 with the rotation of the shaft 6 and hits the side wall of the groove 35. As a result, the fluid flows along the circumferential direction (see arrow C in FIG. 7). In particular, since the groove 35 in the illustrated example has a wide groove width on the fluid inlet side and a shallow groove depth, the fluid easily enters. Further, the directivity of the fluid flowing out from the tip of the groove 35 can be enhanced by gradually narrowing the groove width of the groove 35 toward the end portion on the leading side in the rotation direction.

  The shape of the groove 35 is not limited to the above, and for example, the groove depth of the groove 35 may be constant or the groove width may be constant (not shown). Further, the groove 35 may have a rectangular shape that is long in the circumferential direction or an arc shape that is parallel to the circumferential direction.

  Moreover, although the case where the free end 31 of the leaf 30 extended along the radial direction was shown in said embodiment, it is not restricted to this. For example, as shown in FIGS. 10 and 11, the outer diameter end of the free end 31 of the leaf 30 may be inclined toward the rotation direction leading side of the shaft 6 toward the inner diameter side. Thereby, as the shaft 6 rotates, air on the outer diameter side of the thrust foil bearing 20 is sent to the inner diameter side along the leaf 30 (see the dotted arrow in FIG. 10), so that a large amount of air enters the thrust bearing gap T. And the pressure in the thrust bearing gap T is further increased. Specifically, for example, as shown in FIG. 10, the free ends 31 of the leaves 30 can be arranged in a pump-in type spiral shape. Alternatively, as shown in FIG. 11, the free end 31 of the leaf 30 may have a herringbone shape. Here, the herringbone shape means a substantially V shape in which the outer diameter end and the inner diameter end of the free end 31 are inclined toward the rotation direction leading side of the shaft 6 toward the radial center.

  In the above-described embodiment, a case where a plurality of leaves are separately formed has been described. However, the present invention is not limited to this. For example, a plurality of leaves may be formed on a single foil. For example, in the embodiment shown in FIG. 12, the foil member 50 is configured by combining two foils 60, 60 ′ having a plurality of leaves 61, 61 ′, and the foil member 50 is fixed to the thrust member 21.

  Here, the configuration of the foils 60 and 60 'will be described. Since the foils 60 and 60 'have exactly the same configuration, only the configuration of one foil 60 will be described, and the description of the other foil 60' will be omitted (in FIGS. 12 and 14, the other foil 60 ' Of these, a portion corresponding to one of the foils 60 is indicated with “′”).

  The foil 60 has a circular shape, and a circular hole 63 through which the shaft 6 is inserted is provided at the center thereof. In the present embodiment, a plurality of (four in the illustrated example) leaves arranged at equal intervals in the circumferential direction by making a substantially L-shaped cut into one foil 60 by wire cutting or pressing. 61 and a connecting part 62 are formed. Specifically, the circular foil 60 extends in a zigzag shape from the hole 63 toward the outer diameter at a plurality of equally spaced circumferential positions (four in the illustrated example), and ends in front of the outer diameter end of the foil 60. A radial cut 64 is provided. A circumferential notch 65 extends from the outer diameter end of each notch 64 to the other circumferential direction (the rear side in the rotational direction of the shaft 6, the counterclockwise direction in FIG. 13). By forming the radial notch 64 and the circumferential notch 65 in the foil 60, a plurality of leaves 61 in which one end 61a in the circumferential direction is freely movable up and down in the axial direction are connected to each other. The connecting portion 62 to be formed can be formed integrally. The connecting portion 62 includes an annular portion 62a surrounding the outer periphery of the plurality of leaves 61, and a plurality (four in the illustrated example) of extending portions 62b extending from the annular portion 62a toward the inner diameter. The leaf 30 is continuous with the other circumferential end 62 (shown by a dotted line in FIG. 13). In the example of illustration, the extension part 62b of the connection part 62 and the leaf 61 are the same lengths in the circumferential direction, and these are provided alternately in the circumferential direction. The free end 61a of the leaf 61 is formed in a zigzag shape having a plurality of cutout portions 61a1 and land portions 61a2. The leaf 61 is formed with a plurality of protrusions or grooves 66 that are long in the circumferential direction and spaced apart in the radial direction.

  The two foils 60, 60 'are assembled by the method shown in FIG. The two foils 60, 60 'are identical in material and shape, but in FIG. 14, one foil 60' is dotted to facilitate understanding. Here, the description will be made assuming that the central axis direction of the foils 60, 60 'is the vertical direction.

  First, the two foils 60, 60 ′ shown in FIG. 14A are arranged one above the other as shown in FIG. 14B, and from the radial cut 64 of the upper foil 60, Insert the free end 61a 'of the leaf 61' of the foil 60 '. As a result, the free end 61a 'of the leaf 61' of the lower foil 60 'is disposed above the connecting portion 62 (extending portion 62b) of the upper foil 60. Then, by rotating the two foils 60, 60 ′ relatively, as shown in FIG. 14C, the free end 61 a ′ of the leaf 61 ′ of the lower foil 60 ′ becomes the upper foil 60. It reaches above the end 61b of the leaf 61. Thus, the foil member 50 in which the leaves 61 of the upper foil 60 and the leaves 61 'of the lower foil 60' are alternately arranged in the circumferential direction is obtained. At this time, the thrust bearing surfaces 61c and 61c 'provided on the upper surfaces of the leaves 61 and 61' are alternately arranged in the circumferential direction and are arranged without interruption in the circumferential direction. By fixing the foil member 50 to the thrust member 21, the thrust foil bearing 20 shown in FIG. 12 is completed.

  Further, the shape of the free end 31 of the leaf 30 is not limited to the above, and the free end 31 of the leaf 30 may be formed in a corrugated shape, for example, as shown in FIG. Alternatively, as shown in FIG. 16, the free end 31 of the leaf 30 may be provided with a plurality of cuts 31 a at a plurality of locations separated in the radial direction. Further, the shape of the cut 31a and the land portion 31b may be a rectangle (see FIG. 6), a waveform (see FIG. 15), an arc shape (see FIG. 16), a rectangle or a trapezoid (not shown). Further, the free end 31 may be formed in a straight line (not shown).

  In the above embodiment, the case where the foil member is fixed to the fixing member (thrust member 21, outer member 11) is shown, but conversely, the foil member is the rotating member (flange portion 40, shaft 6). ) May be fixed. In this case, a wedge-shaped thrust bearing gap or a radial bearing gap is formed between the bearing surface provided on the foil member and the fixing member. However, in this case, since the foil member rotates at a high speed together with the shaft 6, the foil member may be deformed by centrifugal force. In particular, when the foil member of the thrust foil bearing 20 is rotated, there is a high possibility that the foil member is deformed by centrifugal force. Therefore, it is preferable to fix the foil member to the fixing member from the viewpoint of avoiding deformation of the foil member.

  Moreover, in the above embodiment, although the bearing member 20a was provided in the axial direction both sides of the flange part 40, and the structure which supports the flange part 40 in both thrust directions was shown, it is not restricted to this, One axial direction of the flange part 40 is shown. It is good also as a structure which provides the bearing member 20a only in and supports only to one side of a thrust direction. Such a configuration can be applied to the case where the other support in the thrust direction is unnecessary or the case where the other support in the thrust direction is achieved by another configuration.

  Moreover, although the case where this invention was applied to the leaf type thrust foil bearing was shown in the above embodiment, it is not restricted to this. For example, a bump foil type thrust foil bearing composed of a top foil having a thrust bearing surface and a corrugated back foil disposed between the top foil and the thrust member, or a leaf type and a bump foil type are used in combination. The present invention can also be applied to a thrust foil bearing (with a back foil disposed between a leaf and a thrust member).

  Moreover, although the case where the thrust foil bearing 20 which concerns on this invention was applied to the gas turbine was shown in the above embodiment, you may apply not only to this but to a supercharger as shown, for example in FIG. This supercharger is a so-called turbocharger that sends air to the engine 83 and includes a compressor 81 and a turbine 82. The compressor 81 and the turbine 82 are connected by a shaft 6. The shaft 6 is supported by the radial foil bearing 10 and the thrust foil bearing 20 in the radial direction and in both thrust directions. In the illustrated example, the radial foil bearings 10 are provided at two locations separated in the axial direction. Air sucked from an intake port (not shown) is compressed by the compressor 81, mixed with fuel, and supplied to the engine 83. The engine 83 burns compressed air mixed with fuel, and the turbine 82 is rotated by the high-temperature and high-pressure gas exhausted from the engine 83. The rotational force of the turbine 82 at this time is transmitted to the compressor 81 via the shaft 6. The gas after rotating the turbine 82 is discharged to the outside as exhaust gas.

  The foil bearing according to the present invention is not limited to a micro turbine or a supercharger, and it is difficult to lubricate with a liquid such as a lubricating oil. From the viewpoint of energy efficiency, it is difficult to separately provide an auxiliary machine for a lubricating oil circulation system. In addition, it can be widely used as a bearing for a vehicle such as an automobile used under a restriction that resistance due to liquid shear becomes a problem, and further as a bearing for industrial equipment.

  The foil bearing described above can be used not only as an air dynamic pressure bearing using air as a pressure generating fluid but also as an oil dynamic pressure bearing using lubricating oil as a pressure generating fluid.

DESCRIPTION OF SYMBOLS 1 Turbine 2 Compressor 3 Generator 4 Combustor 5 Regenerator 6 Shaft 10 Radial foil bearing 11 Outer member 12 Leaf 12c Radial bearing surface 20 Thrust foil bearing 20a Bearing member 21 Thrust member 30 Leaf (foil member)
33 Thrust bearing surface 34 Rectifying member (protrusion)
35 Groove 40 Flange R Radial bearing clearance T Thrust bearing clearance

Claims (12)

A fluid film formed in a thrust bearing gap, comprising a fixed member, a rotating member, and a foil member disposed between the fixing member and the rotating member, forming a thrust bearing gap on a thrust bearing surface provided in the foil member A thrust foil bearing for supporting the rotating member in the thrust direction,
A thrust foil bearing, wherein a plurality of protrusions or grooves that are long in the circumferential direction are formed on the thrust bearing surface at a plurality of locations separated in the radial direction.   The thrust foil bearing according to claim 1, wherein a rectifying member is fixed to the bearing surface, and the protrusion is configured by the rectifying member.   The thrust foil bearing according to claim 1, wherein the groove width of the groove is gradually narrowed toward the leading side in the rotational direction.   The thrust foil bearing according to claim 1 or 3, wherein the groove depth of the groove is gradually deepened toward the leading side in the rotation direction.   The thrust foil bearing according to any one of claims 1 to 4, wherein the foil member has a plurality of leaves having one circumferential end as a free end.   The thrust according to claim 5, wherein the foil member includes a foil integrally including a plurality of leaves having one end in a circumferential direction as a free end and provided with the thrust bearing surface and a connecting portion connecting the plurality of leaves. Foil bearing.   The thrust foil bearing according to claim 6, wherein the foil member is configured by combining a plurality of the foils.   The thrust foil bearing in any one of Claims 1-7 which provided the film in the thrust bearing surface of the said foil member.   The thrust foil bearing in any one of Claims 1-8 which provided the film in the surface on the opposite side to a thrust bearing surface among the foils which comprise the said foil member.   The thrust foil bearing according to claim 8 or 9, wherein the coating is any one of a DLC film, a titanium aluminum nitride film, and a molybdenum disulfide film.   The thrust foil bearing in any one of Claims 1-10 used for the rotor support of a gas turbine.   The thrust foil bearing in any one of Claims 1-10 used for the rotor support of a supercharger.

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