JP2013044394A - Thrust foil bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase load capacity of a thrust foil bearing where a thrust bearing gap is formed with a thrust bearing surface formed on thin-film-like foil to support a rotary member in a thrust direction by a fluid film produced in the thrust bearing gap.SOLUTION: Magnets 23, 24 are mounted to a rotary member (flange part 40) and a fixed member (thrust member 21), respectively, and support force is assisted in a thrust direction between the rotary member and the fixed member by repulsive force in the thrust direction generated between the magnets 23, 24.

Description

  The present invention relates to a thrust foil bearing in which a thrust bearing gap is formed by a thrust bearing surface provided in a thin film foil, and a rotating member is supported in a thrust direction by a fluid film generated in the thrust bearing gap.

  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 it is difficult to lubricate with a liquid such as lubricating oil, 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 shearing of the liquid becomes a problem, etc. Under certain conditions, the use of oil bearings is limited. 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 produce the touch around. 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.

  Also, in gas turbines and turbochargers, an airflow in the thrust direction is generated by the high-speed rotation of the rotor of the turbine or compressor, and the reaction force of this airflow is applied to the shaft, so the shaft is not only in the radial direction but also in the thrust direction. Need to support. For example, Patent Documents 1 to 3 show a leaf-type thrust foil bearing as a kind of thrust foil bearing that supports a rotating member in the thrust direction. This thrust foil bearing is provided with a plurality of leaves at a plurality of locations in the circumferential direction of the end face of the fixing member, one end in the circumferential direction of each leaf is a free end, and the other end in the circumferential direction of each leaf is fixed. Fixed to the end face of the member. When the rotating member rotates, a wedge-shaped thrust bearing gap is formed between the bearing surface of each leaf and the end surface of the rotating member opposite to the bearing surface, and the rotating member is supported in a non-contact manner in the thrust direction by the fluid film of the thrust bearing gap. Is done.

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

  However, with only the fluid film in the thrust bearing gap as described above, when a large load is applied in the thrust direction, the load capacity is insufficient, the stability of the rotating member is reduced, or the contact between the rotating member and the fixed member is reduced. May be invited. In particular, thrust bearings used in gas turbines and turbochargers are strongly required to improve the load capacity in the thrust direction because a large thrust load is applied to the shaft as the rotor (blade) rotates at a high speed. .

  Therefore, an object of the present invention is to increase the load capacity of a thrust foil bearing.

  In order to achieve the above object, the present invention includes a fixing member, a rotating member, and a foil member that is disposed between an end surface of the rotating member and an end surface of the fixing member and has a thrust bearing surface. A thrust foil bearing that forms a thrust bearing gap on the thrust bearing surface and supports the rotating member in the thrust direction with a fluid film generated in the thrust bearing gap. The magnet is attached to the fixed member and the rotating member, respectively. And a thrust foil bearing arranged so that repulsive forces in the thrust direction act on each other.

  In this way, by attaching a magnet to the fixed member and the rotating member so that a repulsive force in the thrust direction works, the supporting force in the thrust direction due to the pressure of the fluid film generated in the thrust bearing gap is assisted by the repulsive force generated between the magnets. And the load capacity of the thrust foil bearing is increased.

  By the way, in a general dynamic pressure bearing in which the bearing surfaces of both the rotating member and the fixed member are formed of a rigid body, the thrust bearing clearance is always a very small value of about several μm as described above. When magnets are provided on the member, the distance between the magnets becomes very close, and a relatively large repulsive force acts between the magnets. For this reason, for example, when the pressure of the fluid film in the bearing gap is not sufficiently increased, for example, immediately after start-up or during low rotation immediately before stop, the rotating member is inclined with respect to the fixed member due to the repulsive force between the magnets. Stability may be reduced. On the other hand, in the foil bearing, as described above, the thrust bearing gap can be set to a relatively large value. Therefore, the magnets provided on the fixed member and the rotating member are arranged relatively apart from each other, and A situation in which the repulsive force generated is suppressed and the rotating member tilts can be prevented. When the rotational speed of the rotating member increases and a large thrust load is applied to the rotating member and the thrust bearing gap decreases, the distance between the magnets decreases and the repulsive force between them increases, thereby supporting the thrust direction. Power is increased. At this time, even if the repulsive force generated between the magnets increases, the pressure of the fluid film in the bearing gap (particularly the radial bearing gap) is sufficiently increased due to the high-speed rotation, so that it is possible to prevent the rotating member from being inclined. As described above, in the above thrust foil bearing, when the rotational speed of the rotating member is low, the repulsive force generated between the magnets is small, and it is possible to prevent the rotating member from being tilted due to the repulsive force. The repulsive force generated between them is increased, and the supporting force in the thrust direction is increased.

  Said magnet can be arrange | positioned along the circumferential direction (circumferential direction around the rotating shaft center of a rotating member), for example. In this case, the magnet can be easily attached to the fixed member or the rotating member if the magnet is formed in a ring shape continuous over the entire circumference. On the other hand, if the above-mentioned magnet is composed of a plurality of magnets spaced apart from each other in the circumferential direction, the diameter of the entire magnet can be freely set, so that the degree of design freedom is increased. Moreover, in this case, since each magnet can be made into an arbitrary shape, the cost can be reduced by using an off-the-shelf magnet.

  As described above, when the magnets are arranged along the circumferential direction, if the outer diameter of the magnet attached to the rotating member is different from the outer diameter of the magnet attached to the fixed member, the inner diameter side of one magnet The other magnet is arranged, and the radial stability of the rotating member can be increased. That is, for example, as shown in FIG. 13A, when ring-shaped magnets 101 and 102 having the same diameter are opposed to each other in the thrust direction, the magnets 101 and 102 are slightly in the radial direction as shown in FIG. In the case of deviation, the repulsive force generated between the two magnets 101 and 102 acts in a direction to increase the radial deviation (see the white arrow in the figure). On the other hand, as shown in FIG. 14A, when ring-shaped magnets 103 and 104 having different outer diameters are arranged concentrically and the magnet 103 is arranged on the inner diameter side of the magnet 104, as indicated by an arrow in the figure. In addition, the repulsive force generated between the magnets 103 and 104 acts in the direction of urging the small-diameter magnet 103 toward the inner diameter. Therefore, even if the small-diameter magnet 103 is slightly displaced in the radial direction with respect to the large-diameter magnet 104 as shown in FIG. The magnet 103 can be biased toward the axial center of the large-diameter magnet 104. Thereby, the radial displacement of the magnets 103 and 104 is corrected, and the radial stability of the rotating member is improved.

  For example, in the case of a thrust foil bearing used in a high temperature environment such as a gas turbine or a supercharger, it is preferable to use a samarium cobalt magnet that exhibits good characteristics even in a high temperature environment.

  For example, the foil member includes a foil having one end in the circumferential direction as a free end, and a plurality of leaves provided with thrust bearing surfaces and a connecting portion that connects the plurality of leaves. Can do. 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 load capacity of the thrust foil bearing can be increased by the repulsive force generated between the magnets.

It is a figure which shows a micro gas turbine notionally. It is sectional drawing which shows the rotor support structure of the said micro gas turbine. It is sectional drawing of the radial foil bearing integrated in the said rotor support structure. It is sectional drawing of the thrust foil bearing based on one Embodiment of this invention integrated in the said rotor support structure. (A) is sectional drawing of the thrust member in the XX line of FIG. 4, (b) is sectional drawing of the flange part in the YY line of FIG. It is a perspective view of the component of the said thrust foil bearing. It is sectional drawing of the said thrust foil bearing. It is a top view of the foil which comprises the said thrust foil bearing. (A)-(c) is a perspective view which shows a mode that two foils are assembled | attached. (A) is sectional drawing of the thrust member which concerns on other embodiment, (b) is sectional drawing of the flange part which concerns on other embodiment. It is sectional drawing of the thrust foil bearing which concerns on other embodiment. It is a figure which shows a supercharger notionally. (A) is the top view and sectional drawing which show the state which has arrange | positioned the magnet of the same diameter concentrically, (b) is the top view and sectional drawing which show the case where the magnet of (a) figure is shifted to radial direction. . (A) is the top view and sectional drawing which show the state which has arrange | positioned the magnet from which an outer diameter differs concentrically, (b) is the top view and sectional drawing which show the case where the magnet of (a) figure is shifted to radial direction. is there.

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

  FIG. 1 conceptually shows the configuration of a gas turbine device called a micro gas turbine. This micro gas turbine mainly includes a turbine 1, a compressor 2, 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 shaft 6 is supported in the radial direction by the radial foil bearing 10, and the flange portion 40 provided on the shaft 6 is supported in both thrust directions by the thrust foil bearing 20 according to the embodiment of the present invention. The

  The radial foil bearing 10 is constituted by, for example, a leaf type foil bearing. In the present embodiment, as shown in FIG. 3, the shaft 6 is inserted into the inner periphery, the cylindrical outer member 11 fixed to the casing 50, and the inner peripheral surface 11 a of the outer member 11 are fixed, It comprises a plurality of leaves 12 arranged at equal intervals 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 12c having a smooth curved surface without holes or steps. Between the radial bearing surface 12c of each leaf 12 and the outer peripheral surface 6a of the shaft 6, a wedge-shaped radial bearing gap R having a radial width narrowed toward one circumferential direction is formed. The actual radial bearing gap R has a very small width of about several tens of μm, but the width is exaggerated in FIG.

  As shown in FIG. 4, the thrust foil bearing 20 includes a flange portion 40 (rotating member) provided so as to protrude from the outer peripheral surface 6 a of the shaft 6 to an outer diameter, and a thrust member 21 (fixed member) fixed to the casing 50. And a foil member 22 disposed between the flange portion 40 and the thrust member 21. In the present embodiment, a pair of thrust members 21 are provided on both axial sides of the flange portion 40, and the foil member 22 is fixed to the end surface 21 a of each thrust member 21. Thrust bearing gaps T are formed between one end surface 41a of the flange portion 40 and the one foil member 22, and between the other end surface 42a of the flange portion 40 and the other foil member 22, respectively.

  Magnets 23 and 24 are attached to the flange portion 40 and the thrust member 21 of the thrust foil bearing 20, respectively. The magnets 23 and 24 are arranged so that a repulsive force in the thrust direction works on each other, that is, the same poles (N poles or S poles) face each other. In the present embodiment, the magnets 23 and 24 are both arranged along the circumferential direction. Specifically, as shown in FIGS. 5A and 5B, the magnets 23 and 24 are continuous over the entire circumference. It forms a ring shape and is arranged concentrically. In the illustrated example, the magnets 23 and 24 have the same shape, and both have a hollow disk shape with a rectangular cross section. As described above, the magnets 23 and 24 form a continuous ring shape on the entire circumference, so that they can be easily attached to the flange portion 40 or the thrust member 21.

  One magnet 23 is fixed to the flange portion 40 and is embedded in the flange portion 40 in the present embodiment. Specifically, as shown in FIG. 4, a pair of flange members 41 and 42 formed by dividing the flange portion 40 at the intermediate portion in the axial direction are provided, and an annular end surface is provided on the opposing end surfaces of the pair of flange members 41 and 42. The ring-shaped magnet 23 is disposed in a space formed by forming the recesses 41b and 42b and facing the recesses 41b and 42b. One magnet 23 may be damaged when rotated at a high speed together with the shaft 6, but by embedding one magnet 23 in the flange portion 40 as described above, it is possible to prevent the damage at the time of high-speed rotation. Note that the means for preventing the magnet 23 from being damaged is not limited to the above, and for example, a case covering the magnet 23 may be attached.

  The other magnet 24 is fixed to each of the pair of thrust members 21. In this embodiment, the thrust member 21 is attached to the other end surface 21b (the end surface opposite to the foil member 22). Specifically, an annular recess 21c is formed on the other end surface 21b of the thrust member 21, and a ring-shaped magnet 24 is fitted and fixed to the recess 21c.

  The foil member 22 is attached to the end surface 21a of the hollow disc-shaped thrust member 21 as shown in FIG. The foil member 22 of the present embodiment is configured by combining a plurality of foils, and in the illustrated example, is configured by two metal foils 30 and 30 ′ having the same shape (see FIG. 9). In the foil member 22, leaves 31, 31 'provided on the foils 30, 30' are alternately arranged in the circumferential direction. As shown in FIG. 7, one end 31a, 31a 'in the circumferential direction of each leaf 31, 31' (the rotation direction leading side of the shaft 6, the left side in the figure) is a free end, whereby each leaf 31, 31 'can bend freely. The free ends 31 a and 31 a ′ of the leaves 31 and 31 ′ are arranged at substantially the same circumferential position as the other circumferential ends 31 b ′ and 31 b of the adjacent leaves 31 ′ and 31. Surfaces on the flange portion 40 side (upper surface in the drawing) of the plurality of leaves 31 and 31 ′ constitute arc-shaped thrust bearing surfaces 31 c and 31 c ′ that protrude from the flange portion 40 side (upper side in the drawing). The thrust bearing surfaces 31c and 31c 'are smooth curved surfaces having no holes or steps. Between the thrust bearing surfaces 31c and 31c 'and the end surface 41a of the flange portion 40, a thrust bearing gap T having a narrower axial width toward one circumferential direction is formed. The actual width of the thrust bearing gap T is as small as several tens of μm, but the width is exaggerated in FIG.

  Here, the structure of each foil 30 and 30 'which comprises the foil member 22 is demonstrated. Since the foils 30 and 30 'have exactly the same configuration, only the configuration of one foil 30 will be described, and the description of the other foil 30' will be omitted. Further, in the drawing, “′” is attached to a portion corresponding to one foil 30 in the other foil 30 ′.

The foil 30 has the same material and thickness as the leaf 12 described above, and as shown in FIG. 8, a plurality (four in the illustrated example) of leaves 31 arranged at equal intervals in the circumferential direction, It has the connection part 32 which connects the leaf 31 integrally. The foil 30 has a circular shape, and a circular hole 33 through which the shaft 6 is inserted is provided at the center thereof. In the present embodiment, a plurality of leaves 31 and connecting portions 32 are formed by cutting a single foil 30 by wire cutting or pressing. Specifically, the radial direction of the radial direction of the circular foil 30 extends from the hole 33 toward the outer diameter at a plurality of equally spaced circumferential positions (four positions in the illustrated example) and ends in front of the outer diameter end of the foil 30. A cut 34 is provided. A circumferential cut 35 is provided from the outer diameter end of each cut 34 to the other circumferential side (the rear side in the rotational direction of the shaft 6, counterclockwise in FIG. 7). The circumferential cut 35 extends to the circumferential center of the adjacent radial cut 34 and has a length of 1/8 of the entire circumference in the illustrated example. The width t ₁ of the circumferential cut 35 is larger than the width t ₂ of the radial cut 34 (t ₁ > t ₂ ). By forming the notches 34 in the radial direction and the notches 35 in the circumferential direction, one end 31a in the circumferential direction of each leaf 31 becomes a free end that can freely move up and down in the axial direction. The connecting portion 32 includes an annular portion 32a surrounding the outer periphery of the plurality of leaves 31, and a plurality (four in the illustrated example) of extending portions 32b extending from the annular portion 32a toward the inner diameter. The leaf 31 is continuous with the other circumferential end 31b (shown by a dotted line in FIG. 8).

  Next, a method of forming the foil member 22 by assembling the two foils 30 and 30 'will be described with reference to FIG. The two foils 30 and 30 ′ are made of the same material and shape, but in FIG. 9, one foil 30 ′ is given a dot for easy understanding. Here, the description will be made assuming that the central axis direction of the foils 30 and 30 ′ is the vertical direction.

  First, two foils 30 and 30 ′ shown in FIG. 9A are arranged one above the other as shown in FIG. 9B, and the lower side of the radial foil 34 is cut from the upper side of the foil 30. Insert the free end 31a 'of the leaf 31' of the foil 30 '. As a result, the free end 31 a ′ of the leaf 31 ′ of the lower foil 30 ′ is disposed above the connecting portion 32 (extending portion 32 b) of the upper foil 30. Then, by rotating the two foils 30, 30 ′ relatively, as shown in FIG. 9C, the free end 31 a ′ of the leaf 31 ′ of the lower foil 30 ′ becomes the upper foil 30. It reaches above the end portion 31b of the leaf 31. As described above, the foil member 22 in which the leaf 31 of the upper foil 30 and the leaf 31 ′ of the lower foil 30 ′ are alternately arranged in the circumferential direction is obtained.

  The foil member 22 in which the two foils 30 and 30 'are integrated as described above is fixed to the end surface 21a of the thrust member 21 (see FIG. 6). The fixing means is not particularly limited, and is fixed by, for example, adhesion or welding. For example, in a state where two foils 30 and 30 ′ are overlapped, a plurality of circumferential portions of the annular portions 32 a and 32 a ′ of the coupling portions 32 and 32 ′ are fixed to the thrust member 21 by welding two at a time. The thrust member 21 to which the foil member 22 is attached in this manner is fixed to the casing 50, and the foil member 22 and the flange portion 40 are opposed to each other in the thrust direction, whereby the thrust foil bearing 20 is completed (see FIG. 4).

  When the shaft 6 rotates in one circumferential direction, a fluid film is generated in the radial bearing gap R between the radial bearing surface 12 c of the leaf 12 of the radial foil bearing 10 and the outer peripheral surface 6 a of the shaft 6. Is supported in a non-contact manner in the radial direction (see FIG. 3). At the same time, the thrust bearing gap T between the thrust bearing surfaces of the pair of foil members 22 of the thrust foil bearing 20 (the bearing surfaces 31c and 31c ′ of the leaves 31 and 31 ′) and the end surfaces 41a and 42a of the flange portion 40 is formed. A fluid film is generated, and the shaft 6 is supported in a non-contact manner in both thrust directions by this fluid film (see FIG. 4). At this time, due to the flexibility of the leaf 12 of the radial foil bearing 10 and the leaves 31, 31 'of the thrust foil bearing 20, the bearing surfaces 12c, 31c, 31c' of the leaves 12, 31, 31 ' 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.

  Further, the thrust force in the thrust direction of the shaft 6 is further enhanced by the repulsive force in the thrust direction of the magnets 23 and 24 provided on the thrust foil bearing 20. That is, the repulsive force between the magnets 23 and 24 urges the flange portion 40 and the thrust member 21 in the direction away from each other in the thrust direction, and assists the thrust bearing gap T in the thrust direction by the fluid film. In particular, when a large load in the thrust direction is applied to the shaft 6 due to the high-speed rotation of the turbine 1 and the thrust bearing gap T becomes small, the distance between the magnets 23 and 24 approaches, so the repulsive force acting between them increases. . Thereby, it can avoid that the flange part 40 contacts the foil member 22 and the thrust member 21 itself. When the repulsive force between the magnets 23 and 24 is increased, the force acting on the flange portion 40 is increased, the flange portion 40 is inclined with respect to the thrust member 21, and the thrust bearing gap T becomes nonuniform in the circumferential direction. However, since the shaft 6 rotates at a high speed, the pressure of the fluid film in the radial bearing gap R increases and the moment rigidity of the shaft 6 increases, so that such a problem can be prevented.

  In the foil bearings 10 and 20, the radial bearing surface 12 c of the leaf 12 and the thrust bearing surfaces 31 c and 31 c ′ of the leaves 31 and 31 ′ and the outer peripheral surface 6 a and It becomes difficult to form an air film having a thickness equal to or greater than the surface roughness on the end surface 41 of the flange portion 40. 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 surfaces 31 c and 31 c ′ and the flange portion 40. In order to reduce the frictional force caused by the metal contact at this time, and to reduce the damage and torque of the leaves 12, 31, 31 ′, the radial bearing surface 12c and the thrust bearing surfaces 31c, 31c ′ are coated with a low friction surface. It is desirable to form. 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 surfaces 31c and 31c ′ can be improved, and the bearing life is increased. Can be increased. The coating as described above is formed on the outer peripheral surface 6a of the shaft 6 and the flange portion 40 facing the surfaces instead of or in addition to the radial bearing surface 12c and the thrust bearing surfaces 31c and 31c ′. You may form in an end surface.

  During the operation of the bearing, between 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, and the back surfaces of the leaves 31, 31 ′ (thrust bearing surfaces 31c, 31c). Micro-sliding also occurs between the surface opposite to ') and the end surface 21a of the thrust member 21. For this reason, one or both of the sliding portions of these surfaces, that is, the rear surfaces of the leaves 12, 31, 31 ′ and the inner peripheral surface 11 a of the outer member 11 and the end surface 21 a of the thrust member 21 in contact therewith A film may be formed. 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 embodiment, the case where the magnets 23 and 24 are both formed in a ring shape continuous over the entire circumference is shown. However, the present invention is not limited to this, and one or both of the magnets 23 and 24 are arranged in the circumferential direction. You may comprise by the some magnet arrange | positioned spaced apart. For example, in the example shown in FIG. 10, both of the magnets 23 and 24 are configured by a plurality of magnets 23a and 24a arranged at a plurality of locations (eight locations in the illustrated example) at equal intervals in the circumferential direction. The plurality of magnets 23 a and 24 a are fixed to the end surface 21 b of the thrust member 21 and the end surface of the flange member 41, respectively. In this case, the diameter of the whole magnets 23 and 24 can be freely changed only by changing the arrangement of the magnets 23a and 24a. For example, in the illustrated example, the outer diameter D1 of the magnet 23 and the outer diameter D2 of the magnet 24 are arranged to be equal to each other. However, the present invention is not limited to this, and each magnet 24a constituting the magnet 24 is placed on the outer diameter side from the drawing. It is possible to arrange the magnet 24 so that the outer diameter D2 of the magnet 24 is larger than the outer diameter D1 of the magnet 23. Further, the individual magnets 23a and 24a do not need to have a special shape, and for example, rectangular (rectangular) magnets 23a and 24a as in the illustrated example can be used. Thus, if the shape of the magnets 23a and 24a is simple, an inexpensive off-the-shelf magnet can be used, so that the manufacturing cost can be reduced.

  Moreover, although said embodiment showed the case where the ring-shaped magnets 23 and 24 of the same shape were attached to the flange part 40 and the thrust member 21, it is not restricted to this. For example, in the embodiment shown in FIG. 11, the outer diameter of the magnet 23 attached to the flange portion 40 is different from the outer diameter of the magnet 24 attached to the thrust member 21, and these are arranged concentrically. Specifically, the outer diameter of the magnet 24 is larger than the outer diameter of the magnet 23, and the small-diameter magnet 23 is arranged on the inner diameter side of the large-diameter magnet 24. The magnets 23 and 24 may be formed in a ring shape that is continuous over the entire circumference (see FIG. 5), or may be composed of a plurality of magnets that are spaced apart in the circumferential direction (see FIG. 10). In this case, since the small-diameter magnet 23 can be urged toward the inner diameter side by the radial component of the repulsive force generated between the two magnets 23 and 24, the radial displacement of both the magnets 23 and 24, and hence the flange portion It is possible to correct the radial displacement between the thrust member 21 and the thrust member 21 and stabilize the support of the flange portion 40 by the magnets 23 and 24.

  Moreover, although the case where the foil member was fixed to the fixing member (thrust member 21) was shown in the above embodiment, conversely to this, the foil member is fixed to the rotating member (the flange portion 40 of the shaft 6). Also good. In this case, a wedge-shaped thrust bearing gap is formed between the thrust bearing surface provided on the leaf of the foil member and the end surface of the fixing member. However, if the foil member is fixed to the rotating member, the foil member rotates at a high speed, and thus the foil may be deformed by centrifugal force. Therefore, from the viewpoint of avoiding deformation of the foil, it is preferable to attach the foil member to the fixing member.

  In the above embodiment, the thrust member 21 and the foil member 22 are provided on both axial sides of the flange portion 40 and the flange portion 40 is supported in both thrust directions. The thrust member 21 and the foil member 22 may be provided only on one side in the axial direction and supported only on one side in the 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.

  Further, in the above embodiment, the foil member 22 of the thrust foil bearing 20 is configured by combining the foil 30 integrally including the plurality of leaves 31 and the foil 30 ′ integrally including the plurality of leaves 31 ′. Not limited to this. For example, the plurality of leaves may be fixed to the thrust member 21 one by one. Or you may employ | adopt the bump foil type foil member comprised by the top foil which has a thrust bearing surface, and the corrugated back foil arrange | positioned between a top foil 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 63, and includes a compressor 61 and a turbine 62. The compressor 61 and the turbine 62 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 61, mixed with fuel, and supplied to the engine 63. The compressed air mixed with fuel is burned by the engine 63, and the turbine 62 is rotated by the high-temperature and high-pressure gas exhausted from the engine 63. The rotational force of the turbine 62 at this time is transmitted to the compressor 61 via the shaft 6. The gas after rotating the turbine 62 is discharged to the outside as exhaust gas.

  The foil bearing according to the present invention is not limited to a gas 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 20 Thrust foil bearing 21 Thrust member (fixing member)
22 Foil member 23 Magnet 24 Magnet 30 Foil 31 Leaf 31c Thrust bearing surface 40 Flange (rotating member)
41 Flange member R Radial bearing clearance T Thrust bearing clearance

Claims (13)

A thrust member having a thrust bearing surface, the thrust bearing surface forming a thrust bearing gap, and the thrust bearing having a thrust bearing surface, the thrust bearing surface being formed between the fixed member, the rotating member, and the end surface of the rotating member; A thrust foil bearing that supports the rotating member in the thrust direction with a fluid film generated in the gap,
A thrust foil bearing in which a magnet is attached to each of a fixed member and a rotating member, and these magnets are arranged so that a repulsive force acts in the thrust direction.   The thrust foil bearing of Claim 1 which has arrange | positioned the said magnet along the circumferential direction.   The thrust foil bearing according to claim 2, wherein the magnet has a ring shape that is continuous over the entire circumference.   The thrust foil bearing according to claim 2, wherein the magnet includes a plurality of magnets spaced apart in the circumferential direction.   The thrust foil bearing according to any one of claims 2 to 4, wherein an outer diameter of the magnet attached to the rotating member is different from an outer diameter of the magnet attached to the fixed member.   The thrust foil bearing in any one of Claims 1-5 which used the samarium cobalt magnet as the said magnet.   The foil member according to any one of claims 1 to 6, wherein the foil member includes a foil having a circumferential end and a plurality of leaves provided with the thrust bearing surface, and a connecting portion for connecting the plurality of leaves. A thrust foil bearing according to any one of the above.   The thrust foil bearing according to claim 7, wherein the foil member is configured by combining a plurality of the foils.   The thrust foil bearing according to any one of claims 1 to 8, wherein a coating is provided on a thrust bearing surface of the foil member.   The thrust foil bearing in any one of Claims 1-9 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 9 or 10, 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 1-11 used for the rotor support of a gas turbine.   The thrust foil bearing according to any one of claims 1 to 11, which is used for supporting a rotor of a supercharger.

Images