JP2017172764A - Foil bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a supporting force and prevent immersion of foreign materials into a bearing clearance at a foil bearing having tapered bearing clearance.SOLUTION: A foil bearing 10 comprises an inner member 11 having a tapered outer peripheral surface 11a; an outer member 12 having a side part 12a with a tapered inner peripheral surface 12a1 and a seal part 12b extending from one end part in an axial direction of the side part 12a toward an inner diameter; a foil 13 fixed to the tapered inner peripheral surface 12a1 of the outer member 12; and seal spaces S1, S2 arranged between an end surface 11b of the inner member 11 and an end surface 12b1 of the seal part 12b, and the inner member 11 is supported in a relative rotatable manner by fluid pressure in the tapered bearing clearances G1, G2 between the foil 13 and the tapered outer peripheral surface 11a of the inner member 11. The end surface 11b of the inner member 11 is provided with a pump 15 for pushing fluid in the seal spaces S1, S2 toward the outer diameter side as the inner member 11 is relatively rotated.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a foil bearing.

  For example, a turbocharger bearing mounted on an automobile engine or the like is used under severe conditions of high temperature and high speed. As such a bearing, for example, a slide ball bearing or a hybrid ball bearing using a ceramic ball is used, and cooling is performed by supplying engine oil to the bearing. By supplying the engine oil to the bearing in this way, (1) an oil path is required, (2) the amount of engine oil is increased, (3) the engine oil is exposed to high temperature, and the deterioration proceeds (4). Problems such as engine oil mixing into the exhaust and smoke.

  Accordingly, attention has been paid to an air dynamic pressure bearing that does not use oil as a lubricant as a bearing that is used under the high temperature and high speed conditions as described above. In the case of an air dynamic pressure bearing, if the bearing clearance is not sufficiently managed, swinging is likely to occur. Therefore, it is important to manage the clearance according to the rotational speed used. However, in an environment such as a turbocharger or a gas turbine where the temperature changes drastically, the width of the bearing gap fluctuates due to the effect of thermal expansion, so that accurate gap management is extremely difficult.

  A foil bearing is known as an air dynamic pressure bearing that can easily manage a gap even in an environment with a large temperature change. In the foil bearing, a bearing surface is constituted by a thin film (foil) having flexibility, and the load is supported by allowing the bearing surface to bend. As the foil bends, an appropriate bearing gap is formed in accordance with operating conditions such as the rotational speed and load of the shaft and the ambient temperature, so that the stability is excellent.

  When the main shaft of the turbocharger is supported by a foil bearing as described above, a radial foil bearing that supports the main shaft in the radial direction and a thrust foil bearing that supports the main shaft in the thrust direction are usually provided (for example, the following patents) Reference 1). In this case, since the number of parts increases, it may be difficult to arrange in a limited space such as the inside of the turbocharger.

  For example, Patent Document 2 below discloses a foil bearing in which a tapered surface is provided on the inner peripheral surface of the outer member and the outer peripheral surface of the inner member (shaft), and a foil is attached to the tapered surface of the outer member. Yes. In this case, a tapered bearing gap is formed between the bearing surface of the foil and the tapered surface of the inner member, and the inner member is rotatably supported by the fluid pressure in the bearing gap. Since the foil bearing can support the inner member in the radial direction and the thrust direction, the number of parts is reduced, and the foil bearing can be arranged in a narrow space.

Japanese Patent Laying-Open No. 2015-183568 JP 2013-32797 A

  However, in the foil bearing shown in Patent Document 2, when the inner member and the outer member rotate relative to each other, the fluid in the bearing gap is easily discharged from the large diameter side by centrifugal force. For this reason, the fluid pressure in the bearing gap is unlikely to increase, and there is a possibility that sufficient support force cannot be obtained. Further, if foreign matter floating around the foil bearing enters the bearing gap, there is a risk of hindering rotation.

  The problem to be solved by the present invention is to increase the supporting force and to prevent foreign matter from entering the bearing gap in a foil bearing having a tapered bearing gap.

  In order to solve the above-mentioned problems, the present invention is directed to an inner member having a tapered outer peripheral surface having a large diameter on one side in the axial direction, and a tapered outer peripheral surface of the inner member. An outer member having a side portion having a tapered inner peripheral surface having a large diameter, a seal portion extending in an inner diameter direction from an end portion on one axial side of the side portion, and a tapered inner periphery of the outer member A foil attached to a surface or a tapered outer peripheral surface of the inner member, and a seal space provided between one end surface in the axial direction of the inner member and an end surface of the seal portion, the foil A foil bearing that supports the inner member in a relatively rotatable manner with a fluid pressure in a tapered bearing gap that faces the inner member, and is provided on one end surface in the axial direction of the inner member or on the end surface of the seal portion. With the relative rotation of the member, the fluid in the seal space is transferred to the outer diameter side. Pump pushed to provide a foil bearing provided.

  In this foil bearing, as the inner member and the outer member rotate relative to each other, the fluid in the tapered bearing gap is pushed out to the large diameter side (one axial side) by centrifugal force. At this time, the end on the large diameter side of the bearing gap communicates with the outer diameter end of the seal space, so that the fluid in the seal space is pushed to the outer diameter side by the pump with the relative rotation of the inner member. Thus, the fluid in the tapered bearing gap is pushed in from the large diameter side. Thereby, the fluid is prevented from flowing out from the large diameter side of the bearing gap, and the fluid pressure in the bearing gap is increased. Further, by pushing the fluid into the outer diameter side of the seal space, the fluid pressure in the seal space is always positive, so that it is difficult for foreign matter to enter from the outside.

  In order to solve the above problems, the present invention provides an inner member having a pair of tapered outer peripheral surfaces arranged such that end portions on the small diameter side face each other in the axial direction, and a pair of tapers of the inner member. A pair of tapered inner peripheral surfaces arranged so that the end portions on the small diameter side face each other in the axial direction, and the end portions on both sides in the axial direction of the side portions toward the inner diameter. An outer member having a pair of extending seal portions, a pair of tapered inner peripheral surfaces of the outer member or a foil attached to a pair of tapered outer peripheral surfaces of the inner member, and the axial direction of the inner member A pair of seal spaces provided between both end surfaces and the end surfaces of the pair of seal portions, and the inner member can be relatively rotated by fluid pressure in a pair of tapered bearing gaps facing the foil. A foil bearing for supporting the inner member in the axial direction On both end surfaces or end faces of the pair of sealing portions, to provide a foil bearing pump to push the outer diameter side it is provided with fluid in the inner in the pair of sealing space with the relative rotation of the members.

  In this foil bearing as well, as in the above foil bearing, the fluid in the seal space is pushed to the outer diameter side by the pump with the relative rotation of the inner member, so that the fluid in the tapered bearing gap has a larger diameter. Since it is pushed in from the side, the fluid pressure in the bearing gap can be increased, and the inside of the seal space can always be set to a positive pressure to prevent entry of foreign matter. Further, since the pair of tapered bearing gaps are arranged so that the ends on the small diameter side face each other in the axial direction, the inner member can be supported in both thrust directions with respect to the outer member.

  In the foil bearing, the fluid in the pair of seal spaces is pushed into the space between the pair of seal spaces from both sides in the axial direction by being pushed toward the outer diameter side by the pump. At this time, if the space communicating with the pair of seal spaces is closed except for both ends in the axial direction, the pressure in this space tends to increase, so that the fluid pressure in each bearing gap is further increased.

  As the above-described pump, for example, convex portions or concave portions extending radially or spirally can be provided.

  As described above, according to the present invention, the supporting force can be increased by increasing the fluid pressure in the tapered bearing gap. Further, by always setting the seal space to a positive pressure, it is possible to prevent foreign matter from entering the bearing gap.

It is sectional drawing of the turbomachine which has the foil bearing which concerns on one Embodiment of this invention. It is a front view of the inner member of the foil bearing. It is a front view of the inward member which concerns on other embodiment. It is sectional drawing of the axial direction of the said foil bearing. It is sectional drawing of the turbomachine which has the foil bearing which concerns on other embodiment. It is sectional drawing of the turbomachine which has the foil bearing which concerns on other embodiment. It is sectional drawing of the axis orthogonal direction of the foil bearing which concerns on other embodiment. It is sectional drawing of the axis orthogonal direction of the foil bearing which concerns on other embodiment. It is a perspective view of the foil of the foil bearing of FIG. It is a perspective view which shows the state which combined the foil of FIG.

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

  FIG. 1 conceptually shows a turbo machine used as, for example, a gas turbine or a turbocharger. The turbomachine includes a turbine 1 and a compressor 2 having blade rows, a shaft 3 to which the turbine 1 and the compressor 2 are fixed, and a foil bearing 10 that rotatably supports the shaft 3. In the illustrated example, a foil bearing 10 is provided between the turbine 1 and the compressor 2. The configuration of the turbo machine is not limited to this. For example, the turbine 1 and the compressor 2 may be adjacent to each other, and the foil bearings 10 may be provided on one axial side or both axial sides thereof.

  The foil bearing 10 includes an inner member 11, an outer member 12, and a foil 13.

  The inner member 11 is fixed to the outer periphery of the shaft 3. The inner member 11 has a pair of tapered outer peripheral surfaces 11a. The pair of tapered outer peripheral surfaces 11a are arranged so that the ends on the small diameter side face each other in the axial direction. In the illustrated example, the ends on the small diameter side of the pair of tapered outer peripheral surfaces 11a are directly connected to each other. The inner member 11 is divided at a boundary (a central portion in the axial direction) between the pair of tapered outer peripheral surfaces 11a.

  The outer member 12 is fixed to a housing (not shown). The outer member 12 has a cylindrical side portion 12a and a pair of seal portions 12b provided on both sides in the axial direction of the side portion 12a.

  The side portion 12a is provided with a pair of tapered inner peripheral surfaces 12a1. The pair of tapered inner peripheral surfaces 12a1 are arranged so that the ends on the small diameter side face each other in the axial direction. In the illustrated example, the ends on the small diameter side of the pair of tapered inner peripheral surfaces 12a1 are directly connected to each other. Each tapered inner peripheral surface 12a1 is parallel to each tapered outer peripheral surface 11a of the inner member 11, and faces each other in the normal direction. The side portion 12a is divided at the boundary (axial center portion) between the pair of tapered inner peripheral surfaces 12a1. In addition, you may form the side part 12a integrally.

  The seal part 12b is provided on both sides in the axial direction of the side part 12a. Each seal portion 12b has a disk shape extending in the inner diameter direction from the axially outer end of the side portion 12a. The inner peripheral surface 12b1 of each seal portion 12b faces the outer peripheral surface of the shaft 3 in the radial direction. The end surface 12b2 of each seal portion 12b faces the end surface 11b of the inner member 11 in the axial direction, and a pair of seal spaces S1, S2 are formed between them. The seal spaces S1, S2 are connected to the end portions on the large diameter side of the bearing gaps G1, G2. The axial width of the seal spaces S1, S2 is larger than the width of the bearing gaps G1, G2 (the width in the normal direction of the bearing surface). The seal portion 12b may be formed integrally with the side portion 12a.

  Any one of the surfaces (end surface 12b2 of the seal portion 12b and end surface 11b of the inner member 11) facing each other through the seal spaces S1 and S2 is provided in the seal spaces S1 and S2 as the inner member 11 rotates. A pump 15 for pushing the fluid to the outer diameter side is provided. The pump 15 is preferably provided on the rotation side member, and in this embodiment, the pump 15 is provided on both axial end surfaces 11b of the inner member 11. The pump 15 includes, for example, a radially extending convex portion or concave portion (see FIG. 2), or a spiral extending convex portion or concave portion (see FIG. 3). In addition, the arrow of FIG. 3 shows the rotation direction of the inner member 11.

  The foil 13 is attached to the pair of tapered inner peripheral surfaces 12 a 1 of the outer member 12. As shown in FIG. 4, the foil 13 of the present embodiment includes a metal top foil 13 a and a metal back foil 13 b that elastically supports the top foil 13 a from the back. The top foil 13a is composed of a single taper foil, and a smooth tapered bearing surface is provided on the inner peripheral surface. The back foil 13b is composed of a single foil having a taper shape as a whole, and is disposed between the top foil 13a and the tapered inner peripheral surface 12a1 of the outer member 12. The back foil 13b can be elastically compressed in the radial direction. The back foil 13b in the illustrated example has a bent portion 13b1 protruding toward the outer diameter from a plurality of locations in the circumferential direction. One end in the circumferential direction of the top foil 13 a and the back foil 13 b is fixed to the tapered inner peripheral surface 12 a 1 of the outer member 12.

  The top foil 13a and the back foil 13b are formed of a thin film foil made of a metal having high spring properties 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. Accordingly, the top foil 13a and the back foil 13b are preferably formed of stainless steel or bronze.

  When the shaft 3 and the inner member 11 are rotated, the tapered bearing gaps G1 and G2 are formed between the bearing surface of the top foil 13a of each foil 13 of the foil bearing 10 and the pair of tapered outer peripheral surfaces 11a of the inner member 11. Is formed, and the shaft 3 and the inner member 11 are supported in a non-contact manner in the radial direction and the thrust direction by the fluid film generated in the bearing gaps G1 and G2 (see FIG. 1). In particular, when the shaft 3 is rotated in a horizontal state as in the present embodiment, the inner member 11 is decentered downward by its own weight with respect to the outer member 12 and the foil 13, so that one of them in the circumferential direction is between them. The wedge-shaped bearing gaps G1 and G2 narrowed toward the end are formed. Then, as the inner member 11 rotates, the fluid in the wedge-shaped bearing gaps G1 and G2 is pushed toward the narrow side, whereby the pressure of the fluid film is increased. Note that the actual widths of the bearing gaps G1 and G2 are as small as several tens of μm, but in FIG. 1, the widths are exaggerated.

  At this time, due to the flexibility of the top foil 13a and the back foil 13b, the bearing surface of the top foil 13a is arbitrarily deformed according to the operating conditions such as the load, the rotational speed of the shaft 3, and the ambient temperature. G1 and G2 are automatically adjusted to an appropriate width according to the operating conditions. Therefore, the bearing gaps G1 and G2 can be managed to the optimum width even under severe conditions such as high temperature and high speed rotation, and the shaft 3 can be stably supported.

  When the inward member 11 rotates, the fluid in the tapered bearing gaps G1 and G2 tends to move to the larger diameter side (axially outer side) by centrifugal force. In the present embodiment, the outer diameter ends of the bearing gaps G1 and G2 communicate with the seal spaces S1 and S2, respectively, and the fluid in the seal spaces S1 and S2 is inward as the inner member 11 rotates. It is pushed into the outer diameter side by a pump 15 provided on the end surface 11 b of the member 11. Thereby, since the fluid in each bearing gap G1, G2 is pushed in from the large diameter side (axial direction outer side), the situation where the fluid in the bearing gap G1, G2 flows out from the large diameter side is prevented, and the bearing gap G1, The fluid pressure in G2 is likely to increase.

  In particular, in this embodiment, the space (the space including the bearing gaps G1 and G2) communicating with the seal spaces S1 and S2 is closed except for both ends in the axial direction. In the illustrated example, the end portions on the small diameter side of the bearing gaps G1 and G2 are directly connected to each other. In this case, when the inner member 11 rotates, the fluid in the seal spaces S1, S2 is pushed into the closed space from both sides in the axial direction by the pump 15 provided in the inner member 11. As a result, the fluid pressure in the bearing gaps G1 and G2 can be further increased.

  Incidentally, at the time of low-speed rotation immediately before the shaft 3 is stopped or immediately after starting, the bearing surface of the top foil 13a of each foil 13 and the tapered outer peripheral surface 11a of the inner member 11 are in contact with each other. A low friction coating such as a DLC film, a titanium aluminum nitride film, a tungsten disulfide film, or a molybdenum disulfide film may be formed on both of them. Further, in order to adjust the frictional force caused by the minute sliding between the foil 13 and the tapered inner peripheral surface 12a1 of the outer member 12, a low friction coating as described above is applied to either or both of them. It may be formed.

  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.

  In said embodiment, although the case where the edge parts by the side of the small diameter of bearing gap G1, G2 were connected was shown, it is not restricted to this. For example, in the embodiment shown in FIG. 5, a pair of foil bearings 20 obtained by dividing the foil bearing 10 are arranged apart from each other in the axial direction. In this case, the bearing rigidity with respect to the moment load is increased.

  However, in the foil bearing 20 of FIG. 5, the small-diameter-side ends of the bearing gaps G1 and G2 open into a large space (non-closed space), so that the fluid pressure in the bearing gaps G1 and G2 may escape from the opening. is there. Therefore, from the viewpoint of increasing the fluid pressure in each of the bearing gaps G1 and G2, it is preferable to close the space communicating with the seal spaces S1 and S2 except for both axial ends as in the foil bearing 10 of FIG. . In this case, as shown in FIG. 1, in addition to directly connecting the end portions on the small diameter side of the bearing gaps G1 and G2, a space having a small volume may be provided between the bearing gaps G1 and G2. For example, the foil bearing 30 shown in FIG. 6 includes a cylindrical surface 11c that connects the small diameter ends of the pair of tapered outer peripheral surfaces 11a of the inner member 11, and a pair of tapered inner peripheral surfaces 12a1 of the outer member 12. It has a cylindrical surface 12a2 that connects the small diameter ends. In this case, the radial width of the space between the cylindrical surfaces 11c and 12a2 is equal to the radial dimension of the bearing gaps G1 and G2.

  Further, only one of the foil bearings 20 shown in FIG. 5 may be used. In this case, it is preferable to arrange so that the seal portion 12b is arranged on the turbine 1 side where foreign matter is likely to be generated.

  In the above-described embodiment, the case where the foil 13 is configured by the top foil 13a and the back foil 13b has been described, but the present invention is not limited thereto. For example, in the embodiment shown in FIG. 7, a plurality of leaf-type foils 17 are arranged in the circumferential direction on the tapered inner peripheral surface 12 a 1 of the outer member 12. Each foil 17 has a downstream end 17 a as a free end, and an upstream end 17 b fixed to the outer member 12. Between each foil 17 and the tapered outer peripheral surface 11a of the inner member 11, bearing gaps G1 and G2 are formed.

  Further, in the embodiment shown in FIG. 8, the insertion portion 18a provided at the downstream end of each foil 18 is inserted into the groove 12a2 provided in the tapered inner peripheral surface 12a1 of the outer member 12, An underfoil portion 18 b provided at the upstream end of the foil 18 is disposed between the adjacent foil 18 and the tapered inner peripheral surface 12 a 1 of the outer member 12. As shown in FIG. 9, an insertion port 18 c is provided near the upstream end of the foil 18. As shown in FIG. 10, the plurality of foils 18 are integrated by inserting the insertion portion 18a of each foil 18 into the insertion port 18c of the adjacent foil. 9 and 10 show a state in which the substantially rectangular foils 18 are assembled in a cylindrical shape for the sake of convenience, but in actuality, each foil 18 has a substantially sector shape, and these are assembled in a tapered shape. It is done.

  Moreover, although the case where the outer member 12 was made into the fixed side and the inner member 11 was made into the rotation side was shown in the above embodiment, it is not restricted to this, For example, the outer member 12 is made into the rotation side, the inner member 11 is made It may be the fixed side. Alternatively, both the outer member 12 and the inner member 11 may be rotated and relatively rotated.

  Moreover, although the case where the foil 13 was attached to the outer member 12 was shown in the above embodiment, you may attach the foil 13 to the taper-shaped outer peripheral surface 11a of the inner member 11 not only in this. However, if the foil 13 is attached to the rotation-side member, the foil 13 may be damaged by centrifugal force. Therefore, the foil 13 is preferably attached to the fixed-side member.

  Moreover, although the case where the foil bearing 10 which concerns on this invention was applied to the gas turbine was shown in the above embodiment, it is not restricted to this, For example, turbochargers (supercharger), vehicle bearings, such as a motor vehicle, or industry The foil bearing according to the present invention can be used as a bearing for 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 Shaft 10 Foil bearing 11 Inner member 11a Tapered outer peripheral surface 12 Outer member 12a1 Tapered inner peripheral surface 12b Seal part 13 Foil 13a Top foil 13b Back foil 15 Pump G1, G2 Bearing clearance S1, S2 Seal space

Claims (5)

An inner member having a tapered outer peripheral surface having a large diameter on one side in the axial direction, and a side having a tapered inner peripheral surface facing the tapered outer peripheral surface of the inner member and having a large diameter on one side in the axial direction And an outer member having a seal portion extending in an inner diameter direction from an end portion on one side in the axial direction of the side portion, and a tapered inner peripheral surface of the outer member or a tapered outer peripheral surface of the inner member. An attached foil, and a seal space provided between one end face in the axial direction of the inner member and the end face of the seal portion, and a fluid pressure in a tapered bearing gap facing the foil. A foil bearing that supports the inner member in a relatively rotatable manner,
A foil bearing provided with a pump for pushing the fluid in the seal space to the outer diameter side with relative rotation of the inner member on one end surface in the axial direction of the inner member or the end surface of the seal portion. An inner member having a pair of tapered outer peripheral surfaces arranged so that the end portions on the small diameter side face each other in the axial direction, and the pair of tapered outer peripheral surfaces of the inner member are opposed to each other, and the end portions on the small diameter side are shafts An outer member having a pair of tapered inner peripheral surfaces disposed so as to face each other in a direction, a pair of seal portions extending in an inner diameter direction from end portions on both sides in the axial direction of the side portions, and the outer member A pair of tapered inner peripheral surfaces of the inner member or a foil attached to the pair of tapered outer peripheral surfaces of the inner member, and the axially opposite end surfaces of the inner member and the end surfaces of the pair of seal portions A foil bearing that supports the inner member in a relatively rotatable manner with fluid pressure in a pair of tapered bearing gaps facing the foil.
A foil bearing provided with pumps that push the fluid in the pair of seal spaces to the outer diameter side with relative rotation of the inner member on both axial end surfaces of the inner member or the end surfaces of the pair of seal portions. .   The foil bearing according to claim 2, wherein a space communicating with the pair of seal spaces is closed except for both ends in the axial direction.   The foil bearing according to any one of claims 1 to 3, wherein the pump is a convex portion or a concave portion extending radially.   The foil bearing according to any one of claims 1 to 3, wherein the pump is a convex portion or a concave portion extending in a spiral shape.

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