WO2015141357A1

WO2015141357A1 - Foil bearing, turbo machine, and foil holder

Info

Publication number: WO2015141357A1
Application number: PCT/JP2015/054321
Authority: WO
Inventors: 藤原　宏樹
Original assignee: Ntn株式会社; 藤原　宏樹
Priority date: 2014-03-17
Filing date: 2015-02-17
Publication date: 2015-09-24
Also published as: JP6324774B2; JP2015175473A

Abstract

This foil bearing (10) comprises: a plurality of foils (12) having a bearing surface; and a foil holder (11) forming a cylindrical shape and having a plurality of grooves (11c) on the inner circumferential surface thereof. A circumferential direction end section (protruding section (12d)) of each foil (12) is inserted into the grooves (11c) in the foil holder (11). On the outer circumferential surface of this foil holder (11), a large diameter section (11a) and a small diameter section (11b) are alternately provided in the circumferential direction and the grooves (11c) are provided inside the circumferential direction area of the large diameter section (11a).

Description

Foil bearing, turbomachine, and foil holder

The present invention relates to a foil bearing, and more particularly to a foil bearing that supports a radial load of a main shaft provided in a turbo machine such as a gas turbine.

The main shaft of a turbo machine such as a gas turbine or a turbocharger rotates at an ultra high speed, and the turbine blade connected to the main shaft is in a high temperature environment. The main shaft is often supported by an oil-lubricated rolling bearing or an oil dynamic bearing, but it is difficult to use oil (for example, when lubrication with oil is difficult or resistance due to shearing of oil becomes a problem) In this case, an air dynamic pressure bearing that supports the shaft in a non-contact manner so as to be relatively rotatable by the dynamic pressure action of the air film is used.

In air dynamic pressure bearings, it is important to manage the bearing clearance according to the rotational speed used, and if the stability limit is exceeded, whirling called whirl occurs. For this reason, it is impossible to operate at a predetermined rotational speed unless the bearing gap is set strictly. However, in the case of a general air dynamic pressure bearing in which the bearing and the shaft are made of a rigid body, in order to set the bearing clearance with high accuracy, it is necessary to manufacture each member with high accuracy, resulting in high cost. . In particular, in an air dynamic pressure bearing used in an environment where the temperature changes rapidly, such as a gas turbine or a turbocharger, it is extremely difficult to manage the bearing clearance due to the influence of thermal expansion of each member.

Therefore, foil bearings are attracting attention as bearings suitable for use under the above conditions. A foil bearing is configured to support a load by forming a bearing surface with a thin film (foil) having low rigidity with respect to bending, and allowing deflection of the bearing surface (for example, the following patent document). 1 to 3). When the shaft rotates, a fluid film (for example, an air film) is formed between the outer peripheral surface of the shaft and the bearing surface of the foil, and the shaft is supported in a non-contact manner. In the case of foil bearings, the flexibility of the foil automatically forms an appropriate bearing gap according to the operating conditions such as shaft rotation speed, load, and ambient temperature. It can be used at a higher speed than a pressure bearing.

JP 2002-364463 A JP 2003-262222 A JP 2009-299748 A

The present applicant has proposed a foil bearing 200 as shown in FIG. 11 in Japanese Patent Application No. 2013-256843. In the foil bearing 200, a plurality of axial grooves 212 are provided on the inner peripheral surface 211 of the foil holder 210, and the ends of the foils 220 are inserted into the axial grooves 212, so that the foils 220 are connected to the inner surfaces of the foil holders 210. It is attached to the peripheral surface 211. In this document, the foil holder 210 including the axial groove 212 is formed of sintered metal.

In the foil bearing 200, the outer peripheral surface of the foil holder 210 is a cylindrical surface. In this case, since the foil holder 210 has the thinnest circumferential region (groove formation region) in which the axial groove 212 is formed, the outer diameter dimension is set so that the required strength can be obtained in this groove formation region. The For this reason, regions other than the groove forming region of the foil holder 210 are thicker than the groove forming region. The foil bearing supports the shaft with the pressure of the fluid (usually air) in the radial bearing gap between the bearing surface provided on the foil and the outer peripheral surface of the shaft, and the support load is relatively small. The strength required for the holder 210 is also relatively small. For this reason, the area other than the groove forming area of the foil holder 210 is thicker than necessary in terms of strength, leading to an increase in weight as a product and an increase in the amount of shaped material used.

From the above circumstances, the problem to be solved by the present invention is to reduce the weight and reduce the amount of shaped material used for the foil holder in which the groove for attaching the foil is formed on the inner peripheral surface.

In order to solve the above-mentioned problems, the present invention comprises a plurality of foils having bearing surfaces, and a foil holder having a cylindrical shape and having a plurality of grooves on the inner peripheral surface, and the circumferential ends of the respective foils are provided. A foil bearing inserted into a groove of the foil holder, wherein a large diameter portion and a small diameter portion are alternately provided in a circumferential direction on the outer peripheral surface of the foil holder, and the circumferential direction region of the large diameter portion A foil bearing having a groove is provided.

Thus, by providing a large diameter portion on the outer peripheral surface of the foil holder and providing a groove in a circumferential region of the large diameter portion, the thickness of the foil holder in the groove forming portion is ensured and the necessary strength is obtained. be able to. On the other hand, by providing a small-diameter portion in the circumferential region other than the groove forming portion on the outer peripheral surface of the foil holder, the thickness in this region is reduced, so the weight of the foil holder and the amount of shaped material used can be reduced. Reduction is achieved.

If the large-diameter portion and the small-diameter portion of the outer peripheral surface of the foil holder, and the inner peripheral surface of the foil holder and the groove bottom surfaces of the plurality of grooves are all coaxial cylindrical surfaces, the thickness of the foil holder in the radial direction is reduced. The thickness can be made substantially uniform over the entire circumference. In this case, the foil holder can be made of, for example, a metal plate that has been subjected to drawing.

If the foil inserted in the groove of the foil holder moves in the axial direction, the foil may come off the foil holder. Therefore, if at least one end in the axial direction of the plurality of grooves of the foil holder is provided with a locking portion that engages with the end of the foil inserted into the groove in the axial direction, it is possible to prevent the foil from being detached from the foil holder. .

The above foil bearing can be incorporated into a turbo machine having a housing that holds the foil bearing on the inner periphery. In this case, the large diameter portion of the outer peripheral surface of the foil holder is fixed to the inner peripheral surface of the housing, and a gap is formed between the small diameter portion of the outer peripheral surface of the foil holder and the inner peripheral surface of the housing. Is preferred. In this way, by forming a gap between the housing and the foil holder, it is possible to suppress heat transfer between them and suppress an increase in the temperature of the foil bearing. In particular, if this gap is used as a cooling medium passage, the foil bearing can be efficiently cooled.

As described above, according to the foil bearing of the present invention, by providing a large-diameter portion and a small-diameter portion on the outer peripheral surface of the foil holder, and by providing a groove for attaching the foil in the circumferential region of the large-diameter portion, It is possible to reduce the weight of the foil holder and reduce the amount of shaped material used.

It is a figure which shows notionally the structure of a gas turbine. It is sectional drawing which shows the support structure of the rotor in the said gas turbine. It is sectional drawing of the direction orthogonal to the axial direction of the foil bearing which concerns on one Embodiment of this invention integrated in the said support structure. It is sectional drawing of the axial direction of the foil holder of the said foil bearing. It is a perspective view of the foil holder. It is an expanded sectional view of the foil bearing of FIG. It is sectional drawing which shows the shaping | molding method of the said foil holder. It is a perspective view of the foil of the said foil bearing. It is a perspective view in the state where three foils were temporarily assembled. It is sectional drawing of the axial direction of the foil holder of the foil bearing which concerns on other embodiment. It is a perspective view which shows the manufacturing method of the foil holder of FIG. 1 is a cross-sectional view of a foil bearing described in a previous application by the applicant.

Fig. 1 conceptually shows the configuration of a gas turbine that is a type of turbomachine. This gas turbine mainly includes a turbine 1 and a compressor 2 that form blade cascades, 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 main shaft 6 that extends in the horizontal direction, and the main 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. Fuel is mixed with this compressed air and burned, and the turbine 1 is rotated by high-temperature and high-pressure gas. The rotational force of the turbine 1 is transmitted to the generator 3 via the main 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. The gas that has been subjected to heat exchange in the regenerator 5 is discharged as exhaust gas after passing through the exhaust heat recovery device 9.

FIG. 2 shows an example of a rotor support structure in the gas turbine. In this support structure, radial bearings 10 are disposed at two axial positions, and

thrust bearings

20, 20 are disposed on both axial sides of the flange portion 6 b provided on the main shaft 6. The radial bearing 10 and the thrust bearing 20 support the main shaft 6 so as to be rotatable in the radial direction and in both thrust directions.

In this support structure, the region between the turbine 1 and the compressor 2 is adjacent to the turbine 1 that is rotated by high-temperature and high-pressure gas, and therefore has a high-temperature atmosphere. In this high temperature atmosphere, the lubricant composed of lubricating oil, grease and the like is altered and evaporated, so it is difficult to apply a normal bearing (such as a rolling bearing) using these lubricants. Therefore, as the

bearings

10 and 20 used in this type of support structure, an air dynamic pressure bearing, particularly a foil bearing is suitable.

Hereinafter, the configuration of the foil bearing 10 that is suitable for the radial bearing for the gas turbine will be described with reference to the drawings.

As shown in FIG. 3, the foil bearing 10 includes a tubular (cylindrical in the illustrated example) foil holder 11, and a plurality (three in the illustrated example) of foils 12 attached to the inner peripheral surface of the foil holder 11. Have

The outer peripheral surface of the foil holder 11 is provided with large diameter portions 11a and small diameter portions 11b alternately in the circumferential direction. In the example of illustration, the large diameter part 11a and the small diameter part 11b are each formed in three places at equal pitches. Between the large-diameter portion 11a and the small-diameter portion 11b, there is provided a stepped surface that extends in the radial direction between these circumferential end portions and extends along the axial direction.

A plurality of grooves 11 c are formed on the inner peripheral surface of the foil holder 11. In the present embodiment, grooves 11c extending along the axial direction are provided at a plurality of locations (three locations in the illustrated example) at equal intervals in the circumferential direction of the foil holder 11. A region between the circumferential directions of the plurality of grooves 11c is a cylindrical surface 11d. The circumferential end of each foil 12 is inserted into the groove 11c. As shown in FIGS. 4 and 5, a locking portion 11e is provided at one axial end of each groove 11c. The inner peripheral surface of the locking portion 11e is a cylindrical surface having the same diameter that is continuous with the cylindrical surface 11d. The other axial end of each groove 11c is open to the end face of the foil holder 11. The extending direction of the groove 11c is set according to the shape of the foil 12, and for example, the groove 11c may be extended in a direction inclined with respect to the axial direction.

The groove 11c is provided in a circumferential region of the large diameter portion 11a on the outer peripheral surface. As shown in FIG. 6, each groove 11 c is provided with a groove bottom surface 11 c 1 having a diameter larger than that of the cylindrical surface 11 d, and a side surface 11 c 2 that is continuous with both ends of the groove bottom surface 11 c 1 in the circumferential direction and the cylindrical surface 11 d. A circumferential end (convex portion 12d) of the foil 12 abuts against a corner portion 11c3 provided at the boundary between the groove bottom surface 11c1 and one side surface 11c2.

As described above, by providing the groove 11c in the circumferential region of the large-diameter portion 11a on the outer peripheral surface of the foil holder 11, it is possible to ensure the thickness of the foil holder 11 in the radial direction in the region where the groove 11c is formed. it can. Further, by providing the small-diameter portion 11b in a region other than the region where the groove 11c is formed in the outer peripheral surface of the foil holder 11, the thickness of the foil holder 11 is reduced, the weight of the foil bearing 10 is reduced, and the shape material is used. The amount is reduced. In the illustrated example, the large-diameter portion 11a and the small-diameter portion 11b on the outer peripheral surface of the foil holder 11, and the cylindrical surface 11d and the groove bottom surface 11c1 on the inner peripheral surface are all coaxial cylindrical surfaces. Thereby, the thickness of the foil holder 11 can be made substantially uniform over the entire circumference. In particular, the thickness difference of the large diameter portion 11a and the groove bottom surface 11c1 of the groove 11c and the diameter difference of the small diameter portion 11b and the cylindrical surface 11d are made the same, thereby making the thickness of the foil holder 11 uniform. Can do.

As described above, by making the thickness of the foil holder 11 uniform, the foil holder 11 can be constituted by a metal plate that has been subjected to drawing processing. Specifically, as shown in FIG. 7, the metal plate W is formed into a bottomed cylindrical shape by drawing the flat metal plate W (see the left figure) with a press molding machine (see the center figure). ). The formed metal plate W is provided with a cylindrical portion W1, a flange portion W2 provided at one axial end of the cylindrical portion W1, and a bottom portion W3 that closes an opening at the other axial end of the cylindrical portion W1. A large diameter portion 11a and a small diameter portion 11b are formed on the outer peripheral surface of the cylindrical portion W1, and a groove 11c and a cylindrical surface 11d are formed on the inner peripheral surface of the cylindrical portion W1. Then, the foil holder 11 is completed by removing the flange part W2 and bottom part W3 of the bottomed cylindrical metal plate W by cutting (see the right figure). At this time, a part of the bottom portion W3 remains as a locking portion 11e that closes one axial end of the groove 11c.

The foil 12 is formed by pressing a metal 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 this embodiment, since there is no lubricating oil in the atmosphere, it is preferable to use a stainless steel or bronze metal foil.

The foil 12 is arranged on the inner peripheral surface of the foil holder 11 in the circumferential direction. As shown in FIG. 8A, each foil 12 includes a convex portion 12a provided at one end in the circumferential direction, a concave portion 12b provided at the other circumferential end, and a main body portion provided between these circumferential directions. 12c. As shown in FIG. 8B, the three foils 12 can be temporarily assembled into a cylindrical shape by fitting the convex portions 12 a of each foil 12 into the concave portions 12 b of the adjacent foils 12. In this case, when viewed in the axial direction shown in FIG. 3, one end in the circumferential direction (convex portion 12a) of each foil 12 and the other end in the circumferential direction of the adjacent foil 12 (convex portions 12d on both sides in the axial direction of the concave portion 12b) intersect. It will be in the state.

This temporary assembly is inserted into the inner periphery of the foil holder 11 in a state where the three foils 12 are temporarily assembled in a cylindrical shape. Specifically, while inserting the temporary assembly of the three foils 12 into the inner periphery of the foil holder 11, the convex portions 12d provided on both axial sides of the concave portions 12b at the other circumferential ends of the foils 12, It inserts in the groove | channel 11c of the foil holder 11 from an axial direction one end side (opening side). And if the convex part 12d of the circumferential direction other end of each foil 12 contact | abuts to the latching | locking part 11e of the groove | channel 11c of the foil holder 11, insertion will be completed. At this time, the convex portion 12a at one circumferential end of each foil 12 is disposed between the outer diameter surface of the adjacent foil 12 and the cylindrical surface 11d of the inner peripheral surface of the foil holder 11 (see FIG. 6). Moreover, the convex part 12d of the circumferential direction other end of each foil 12 is only inserted in the groove | channel 11c of the foil holder 11, and can be freely moved inside the groove | channel 11c. As described above, both ends in the circumferential direction of each foil 12 are held on the inner peripheral surface of the foil holder 11. At this time, the other end of the one foil 12 (both ends in the axial direction of the concave portion 12b) and one end of the other foil 12 (the root portion of the convex portion 12a) are engaged with each other in a circumferential direction so as to stick to each other. Thereby, the main-body part 12c of each foil 12 protrudes on the outer diameter side, and curves in the shape along the inner peripheral surface (cylindrical surface 11d) of the foil holder 11.

The inner peripheral surface of the main body 12c of each foil 12 functions as a bearing surface. In the present embodiment, as shown in FIG. 3, a multi-arc bearing surface is formed by three foils 12. The outer diameter surface of each foil 12 and the inner peripheral surface (groove 11c and cylindrical surface 11d) of the foil holder 11 are slidable. The convex part 12a of the circumferential direction one end of each foil 12 functions as an underfoil part which supports the main-body part 12c of the adjacent foil 12 from an outer diameter side.

The foil bearing 10 having the above configuration is assembled to the gas turbine by fixing the outer peripheral surface of the foil holder 11 to the inner peripheral surface 31 of the housing 30 of the gas turbine (see FIG. 3). In the present embodiment, the large-diameter portion 11a on the outer peripheral surface of the foil holder 11 and the cylindrical inner peripheral surface 31 of the housing 30 are fixed by press-fitting, welding, or the like. At this time, by providing the large-diameter portion 11a and the small-diameter portion 11b on the outer peripheral surface of the foil holder 11, the following advantages can be obtained in the fixing portion with the housing 30. For example, as shown in FIG. 3, when the inner peripheral surface 31 of the housing 30 is a cylindrical surface, a gap P is formed between the small diameter portion 11 b on the outer peripheral surface of the foil holder 11 and the inner peripheral surface 31 of the housing 30. The If the cooling medium supply part (illustration omitted) which supplies a cooling medium (for example, air) positively is provided in this clearance gap P, and the clearance gap P is made into a cooling-medium channel | path, the foil bearing 10 can be cooled efficiently. . Or although illustration is abbreviate | omitted, a convex part is provided in the internal peripheral surface 31 of the housing 30, and this convex part and the step part of the large diameter part 11a and the small diameter part 11b of the outer peripheral surface of the foil holder 11 are circumferential. If engaged, the foil holder 11 can be prevented from rotating.

The main shaft 6 is inserted into the inner periphery of the foil bearing 10 fixed to the housing 30. At this time, it is preferable to insert the main shaft 6 from one end side in the axial direction of the foil bearing 10 (opening side of the groove 11c). In this case, the foil 12 tends to move to the other end side in the axial direction due to friction with the main shaft 6, but the convex portion 12 d at the other circumferential end of each foil 12 is engaged with the engaging portion 11 e of the groove 11 c of the foil holder 11. As a result, the axial movement of each foil 12 relative to the foil holder 11 is restricted. Thereby, the situation where the foil 12 remove | deviates from the foil holder 11 at the time of the assembly of a turbomachine can be prevented.

When the main shaft 6 rotates in the direction of the arrow in FIG. 3, the pressure of the air film in the radial bearing gap between the inner peripheral surface (bearing surface) of the main body portion 12 c of each foil 12 of the foil bearing 10 and the outer peripheral surface 6 a of the main shaft 6. The foil 12 is pushed to the outer diameter side. At this time, the main body portion 12c of each foil 12 rides on the underfoil portion (convex portion 12a) of the adjacent foil, so that this portion is curved. Further, in the present embodiment, each foil 12 is pushed to the front side in the rotation direction due to friction with the fluid (air) flowing along with the rotation of the main shaft 6, and as shown in FIG. 6, the groove 11 c of the foil holder 11. The foil 12 bends against the corner 11c3. The shape of the foil 12 is maintained at a position where the elastic force of the curved portion of the foil 12 and the pressure of the air film formed in the radial bearing gap are balanced. Thus, a radial bearing gap gradually narrowing toward the rotation direction leading side is formed between the bearing surface of each foil 12 and the outer peripheral surface 6a of the main shaft 6, and air is pushed into the narrow side of the radial bearing gap. It is. As a result, the pressure of the air film in the radial bearing gap is increased, and the main shaft 6 is supported in a non-contact manner in the radial direction by this pressure.

At this time, due to the flexibility of the foil 12, the bearing surface of each foil 12 is arbitrarily deformed according to the operating conditions such as the load, the rotational speed of the spindle 6, the ambient temperature, etc. It is automatically adjusted to the appropriate width. Therefore, even under severe conditions such as high temperature and high speed rotation, the radial bearing gap can be managed to the optimum width, and the main shaft 6 can be stably supported. Further, while the main shaft 6 is rotating, the foil 12 is pressed against the foil holder 11 due to the influence of the air film formed in the radial bearing gap, and accordingly, a slight sliding occurs between the two. The vibration of the main shaft 6 can be attenuated by the frictional energy generated by the minute sliding.

Note that the bearing surface of each foil 12 and the outer peripheral surface of the main shaft 6 are in sliding contact with each other at the time of low-speed rotation immediately before the main shaft 6 is stopped or immediately after starting. A low friction coating such as a ride film, a tungsten disulfide film, or a molybdenum disulfide film may be formed. Moreover, in order to adjust the frictional force caused by the minute sliding between the foil 12 and the foil holder 11, the above-described low friction coating may be formed on one or both of them.

The present invention is not limited to the above embodiment. For example, in the above-described embodiment, the case where the locking portion 11e is provided at one end in the axial direction of the groove 11c of the foil holder 11 is shown, but not limited to this, as shown in FIG. Further, an end portion (convex portion 12d) of the foil 12 inserted into the groove 11c may be provided with an engaging portion that can be engaged in the axial direction. In this case, since the foil holder 11 including the engaging portions 11e at both ends of the groove 11c cannot be formed by drawing, the foil holder 11 is formed by cutting, for example. Alternatively, as shown in FIG. 10, the locking portion 11e at one end in the axial direction of the groove 11c is formed by drawing, and a protruding portion 11f protruding in the axial direction from the end surface of the foil holder 11 is formed. The locking portion 11e at the other end in the axial direction may be provided by bending 11f in the direction of the arrow in the figure. In addition, when the latching | locking part is especially unnecessary, the latching | locking part 11e may be abbreviate | omitted and the axial direction both sides of the groove | channel 11c may be opened to the end surface of the foil holder 11. FIG.

The application object of the foil bearing according to the present invention is not limited to the gas turbine described above, and can be used as a bearing for supporting a rotor of a turbocharger (supercharger), for example. The foil bearing according to the present invention is not limited to turbomachines such as gas turbines and turbochargers, but can be widely used as vehicle bearings and industrial equipment bearings in which the use of oil is restricted.

Each of the foil bearings described above is an air dynamic pressure bearing that uses air as a pressure generating fluid. However, the present invention is not limited to this, and other gases can be used as the pressure generating fluid, or water or oil can be used. A liquid such as can also be used.

1 Turbine 6 Main shaft 10 Foil bearing 11 Foil holder 11a Large diameter portion 11b Small diameter portion 11c Groove 11e Locking portion 12 Foil 20 Thrust bearing 30 Housing P Clearance

Claims

A foil bearing comprising a plurality of foils having a bearing surface and a foil holder having a cylindrical shape and having a plurality of grooves on an inner peripheral surface thereof, and a circumferential end portion of each foil is inserted into the groove of the foil holder. There,
A foil bearing in which a large diameter portion and a small diameter portion are alternately provided in a circumferential direction on the outer peripheral surface of the foil holder, and the groove is provided in a circumferential region of the large diameter portion.
The foil bearing according to claim 1, wherein the large-diameter portion and the small-diameter portion of the outer peripheral surface of the foil holder, and the inner peripheral surface of the foil holder and the groove bottom surfaces of the plurality of grooves are all coaxial cylindrical surfaces.
The foil bearing according to claim 1 or 2, wherein the foil holder is made of a drawn metal plate.
The foil according to any one of claims 1 to 3, wherein at least one end in the axial direction of the plurality of grooves of the foil holder is provided with a locking portion that engages with an end of the foil inserted into the groove in the axial direction. bearing.
A foil bearing according to any one of claims 1 to 4 and a housing that holds the foil bearing on an inner periphery thereof, and a large-diameter portion of an outer peripheral surface of the foil holder is fixed to the inner peripheral surface of the housing. A turbomachine in which a gap is formed between the small diameter portion of the outer peripheral surface of the foil holder and the inner peripheral surface of the housing.
The turbomachine according to claim 5, wherein the gap is a cooling medium passage.
A foil holder having a cylindrical shape and having a plurality of foils attached to the inner peripheral surface thereof,
It has a plurality of grooves into which the end portions of the respective foils are inserted, and has a large diameter portion and a small diameter portion alternately in the circumferential direction on the outer peripheral surface, and the groove is provided in a circumferential region of the large diameter portion. Foil holder.