JP7048454B2 - Thrust foil bearing - Google Patents

Description

The present invention relates to a thrust foil bearing.

Bearings that support the spindles of turbomachines such as gas turbines and turbochargers are required to withstand harsh environments such as high temperature and high speed rotation. Foil bearings are attracting attention as bearings suitable for use under such harsh conditions. The foil bearing has a bearing surface made of a thin film (leaf) having low flexibility against bending, and is formed in the bearing gap formed between the shaft and the bearing surface of the leaf when the shaft rotates. A fluid film (for example, an air film) is formed to non-contactly support the shaft. According to this foil bearing, the bearing surface is formed of leaves to allow the bearing surface to bend, and the bearing surface deforms following the displacement and thermal expansion of the shaft, so the shaft is stable even under harsh conditions. It has the advantage that it can be supported by bearings.

This foil bearing is roughly classified into a radial foil bearing that supports a load in the radial direction and a thrust foil bearing that supports a load in the thrust direction. Of these, as the thrust foil bearing, the one described in Patent Document 1 below is known. The configuration of this thrust foil bearing is shown in FIGS. 20 and 21. 20 is a plan view of the bearing surface viewed from the axial direction, and FIG. 21 is an enlarged plan view of one leaf.

As shown in FIGS. 20 and 21, in the thrust foil bearing, leaves 100 are arranged at a plurality of positions in the rotation direction R, and a top foil portion 102 having a bearing surface S1 is formed in a region including a front end 101 of each leaf. At the same time, the back foil portion 104 arranged behind the top foil portion 102 of the adjacent leaf is formed in the region including the rear end 103.

The outer diameter edge portion 105 and the inner diameter edge portion 106 of each leaf 100 constituting this thrust foil bearing are both formed by an arc centered on the axis O (paragraph 0027 of Patent Document 1).

Japanese Unexamined Patent Publication No. 2017-82913

22 (a) and 22 (b) are cross-sectional views of the thrust foil bearing shown in FIG. 20. As shown in FIGS. 22 (a) and 22 (b), in the thrust foil bearing, the leaves 100 are laminated, but the same number of leaves are laminated on the outer diameter side and the inner diameter side having different peripheral lengths Lo and Li. Therefore, the leaves are densely laminated on the inner diameter side (FIG. 22 (b)) as compared with the outer diameter side (FIG. 22 (a)). Therefore, the bearing rigidity increases on the inner diameter side of the bearing surface. When the bearing rigidity is increased in this way, the followability of the leaf to the shaft is lowered, and the shaft and the leaf frequently come into contact with each other, especially on the inner diameter side. Therefore, in the conventional thrust doyle bearing, there is a problem that wear progresses locally on the inner diameter side (particularly, the inner diameter edge portion) of the bearing surface.

Therefore, an object of the present invention is to provide a thrust foil bearing capable of preventing local wear of the bearing surface.

In order to solve the above problems, in the present invention, a bearing surface is formed by arranging a plurality of leaves in the circumferential direction, and each leaf is a thrust provided with a front end located on the leading side in the rotational direction and an inner diameter edge portion. The foil bearing is characterized in that each leaf is provided with a retracted portion in which the distance from the axial center is larger than the distance from the axial center of the inner diameter end of the front end at the inner diameter edge portion of each leaf excluding the inner diameter end of the front end. It is something to do.

Each leaf may be provided with a top foil portion that forms a bearing surface and a back foil portion that supports the top foil portions of adjacent leaves. In this case, the retracting portion may be provided on the top foil portion or the back foil portion. When the retracting portion is provided in the back foil portion, it is preferable that the space directly below the inner diameter edge portion of the top foil portion is a space without foil in the entire region of the retracting portion. In addition, a retracting portion can be provided on both the top foil portion and the back foil portion.

Further, the retracted portion can be provided in the entire area of the inner diameter edge portion of the top foil portion except the front end of each leaf. Further, it can be provided in the entire area of the inner diameter edge portion of the back foil portion except the front end of each leaf.

According to the present invention, local wear of the bearing surface can be prevented.

It is a figure which shows the structure of a gas turbine conceptually. It is sectional drawing which shows the support structure of the rotor in the said gas turbine. It is sectional drawing of the foil bearing unit incorporated in the said support structure. It is a top view when the thrust foil bearing is seen from the bearing surface side. It is a top view which shows the leaf of a thrust foil bearing. It is a figure which developed the X-ray cross section in FIG. It is a top view of the foil member which connected a plurality of leaves. It is a top view of the foil member which connected a plurality of leaves. It is a top view which shows the leaf of a foil member enlarged. It is a top view which shows the state which two foil members were temporarily assembled. It is a top view which shows the state which the two temporarily assembled foil members are arranged on the holder body of a foil holder. It is a top view which shows the state which attached the fixing member to the holder body of FIG. It is a top view and a partially enlarged view of the thrust foil bearing which concerns on 1st Embodiment. FIG. 3 is an enlarged plan view showing the leaf in the first embodiment. It is a top view and a partially enlarged view of the thrust foil bearing which concerns on the 2nd Embodiment. FIG. 3 is an enlarged plan view showing the leaf in the second embodiment. It is a top view and a partially enlarged view of the thrust foil bearing which concerns on 3rd Embodiment. FIG. 3 is an enlarged plan view showing the leaf in the third embodiment. It is a top view which shows the modification of the leaf in 1st to 3rd Embodiment. It is a top view which shows the conventional thrust foil bearing. It is a top view which shows the leaf of the conventional thrust foil bearing in an enlarged manner. It is sectional drawing which shows schematic the sectional shape of a thrust bearing.

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

FIG. 1 conceptually shows the configuration of a gas turbine, which is a type of turbomachine. This gas turbine mainly includes a turbine 1 and a compressor 2 having blade rows formed therein, 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 rotary shaft 6 extending in the horizontal direction, and the rotary shaft 6 and the turbine 1 and the compressor 2 form an integrally rotatable rotor. ..

The 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 a high-temperature, high-pressure gas. The rotational force of the turbine 1 is transmitted to the generator 3 via the rotating 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 has 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 completed heat exchange in the regenerator 5 is discharged as exhaust gas after passing through the exhaust heat recovery device 9.

FIG. 2 shows a foil bearing unit 10 that supports the rotary shaft 6 of the rotor in the gas turbine. The foil bearing unit 10 includes a rotary shaft 6, a rotary member 20 fixed to the rotary shaft 6, a radial foil bearing 30, a first thrust foil bearing 40, and a second thrust foil bearing 50. The shaft member 11 is composed of the rotating shaft 6 and the rotating member 20 that rotate integrally. The radial foil bearing 30 supports the shaft member 11 in the radial direction, and the first thrust foil bearing 40 and the second thrust foil bearing 50 support the shaft member 11 in both thrust directions.

As shown in FIG. 3, the rotating member 20 includes a sleeve portion 21 and a disk-shaped flange portion 22 protruding from the sleeve portion 21 to an outer diameter. The flange portion 22 is formed of, for example, a carbon fiber reinforced composite material, and the sleeve portion 21 is formed of, for example, a carbon sintered material.

Hereinafter, the configuration of the first thrust foil bearing 40 will be described.

[Basic configuration of thrust foil bearing]
As shown in FIG. 3, the first thrust foil bearing 40 supports the flange portion 22 of the shaft member 11 (rotating member 20) from one side in the axial direction, and as shown in FIGS. 3 and 4, the foil is used. A holder 41 and a plurality of leaves 42 attached to the foil holder 41 so as to form a band in the circumferential direction are provided. The foil holder 41 has a disk-shaped holder main body 41a having a hole in the axial center, and an annular fixing member 41b provided at the outer diameter end of the end surface 41a1 of the holder main body 41a. By sandwiching each leaf 42 from both sides in the axial direction between the holder main body 41a and the fixing member 41b, each leaf 42 is held by the foil holder 41.

As shown in FIG. 4, the leaves 42 are arranged at a plurality of locations in the rotation direction R (circumferential direction) at equal pitches. FIG. 5 shows only one leaf 42 out of a plurality of leaves 42 arranged in the rotation direction R, and omits the illustration of the other leaves. As shown in FIG. 5, each leaf 42 has a main body portion 42a constituting a top foil portion Tf and a back foil portion Bf, which will be described later, and an extending portion 42b extending from the main body portion 42a to the outer diameter side (indicated by cross-hatching). And are prepared in one piece.

The main body portion 42a of the leaf 42 has a front end 421 located at the end on the rotation direction R side, a rear end 422 located at the end on the opposite rotation direction side, and an inner diameter edge portion 423 connected to both side ends of the front end 421. It has an outer diameter edge portion 424. The front end 421 and the rear end 422 have a so-called herringbone shape, the front end 421 is formed in a convex shape in which the region between both ends thereof protrudes toward the R side in the rotation direction, and the rear end 422 has both ends thereof. It is formed in a concave shape with a recess in the space between them on the R side in the rotation direction. The front end 421 and the rear end 422 have tops 421a, 422a in a substantially central region in the radial direction. By forming the front end 421 and the rear end 422 in a herringbone shape in this way, it is possible to obtain an action of drawing a fluid (for example, air) into the radial center region of the thrust bearing gap during the rotation of the shaft member 11, and the thrust can be obtained. It is possible to increase the load capacity of the foil bearing. In this embodiment, the case where the contour shapes of both tops 421a and 422a are arcuate is illustrated.

The extending portion 42b is formed so as to extend in an inclined direction with respect to the radial direction by retracting the outer diameter side in the counter-rotation direction from the outer diameter end of the main body portion 42a. As shown in FIG. 4, the extending portions 42b arranged in the rotation direction R are arranged on the same plane of the holder main body 41a through the gap in the rotation direction R without overlapping each other. The fixing member 41b is arranged on each extending portion 42b arranged on the holder main body 41a, and the outer diameter portion (shown by cross-hatching in FIG. 5) of the extending portion 42b of each leaf 42 is formed on the holder main body 41a and the fixing member 41b. Each leaf 42 is fixed to the foil holder 41 by sandwiching the members 41a and 41b with a bolt or the like and tightening and fixing them.

FIG. 6 is a cross-sectional view taken along the line XX in FIG. As shown in FIG. 6, each leaf 42 of the first thrust foil bearing 40 is partially overlapped on the end surface 41a1 of the holder body 41a in the rotation direction R while shifting the phase by half a pitch of each leaf 42. Have been placed. The region on the front side in the rotation direction including the front end 421 of each leaf 42 constitutes a top foil portion Tf that rides on the adjacent leaf 42. Further, the region on the anti-rotation direction side including the rear end 422 of each leaf 42 constitutes a back foil portion Bf that elastically supports the top foil portion Tf behind the top foil portion Tf of the adjacent leaf 42. On the surface of the top foil portion Tf of each leaf 42, a thrust bearing surface S facing one end surface 22a of the flange portion 22 is formed.

The thrust foil bearing 40 described above can be manufactured by the following procedure.

First, as shown in FIGS. 7 and 8, two foil members 60 having the same shape are manufactured (in FIGS. 8, 10 to 12 for easy understanding, one foil member 60 is provided with scattered points. (Shown with). In each foil member 60, a plurality of leaves 42 and an annular connecting portion 61 connecting the outer diameter ends thereof are integrally formed by press working on the foil material, wire cutting, or the like. Each foil member 60 is provided with leaves 42, which are half of the leaves 42 incorporated in the thrust foil bearing 40, at equal intervals along the rotation direction R. The main body portion 42a of the adjacent leaf 42 is divided by the notch 62, and a space 63 is formed by punching between the extending portions 42b of the adjacent leaf 42. The extending portion 42b of each leaf 42 is held by the connecting portion 61 via the joining portion 61a. The circumferential dimension L1 of the joint portion 61a is smaller than the circumferential dimension L2 of the outer diameter end of the extending portion 42b of each leaf 42.

FIG. 9 is an enlarged view of two adjacent leaves 42 of each foil member 60. As shown in FIG. 9, a gap C is formed between the front end 421 of each leaf 42 in the foil member 60 and the rear end 422 of the adjacent leaf. The width of this gap C is large near the top 421a and small on both sides of the top 421a. This gap C is formed, for example, by increasing the width of the rotation direction R of the notch 62 that divides the adjacent leaves 42 when forming each foil member 60.

After manufacturing the two foil members 60, one foil member 60 and the other foil member 60 are overlapped with each other as shown in FIG. At this time, the two foil members 60 are staggered by half the pitch of the leaves 42, and the leading portion of each leaf 42 (main body portion 42a) of one foil member 60 in the rotation direction R is inserted through the notch 62. The other foil member 60 is arranged on the leaf 42 (main body portion 42a) on the side opposite to the rotation direction.

After that, the two foil members 60 temporarily assembled as described above are arranged on the end face 41a1 (see FIG. 3) of the holder main body 41a as shown in FIG. At this time, the outer diameter end of the extending portion 42b of each leaf 42 is arranged along the outer diameter end of the end surface 41a1 of the holder main body 41a. Further, the connecting portion 61 of the foil member 60 is arranged on the outer diameter side of the holder main body 41a. In this state, as shown in FIG. 11, the fixing member 41b is arranged on the foil member 60 on the holder body 41a, and the holder body 41a and the fixing member 41b are fixed by bolts or the like (not shown). As a result, each leaf 42 is fixed to the leaf holder 41, and the intermediate manufacturing body 80 of the foil bearing is completed.

After that, the joint portion 61a protruding toward the outer diameter side of the holder main body 41a and the fixing member 41b is cut, and the connecting portion 61 is separated from each leaf 42. As a result, the thrust foil bearing 40 shown in FIG. 4 is completed. In addition to separating the connecting portion 61 from each leaf 42 in this way, the connecting portion 61 may be left as it is without being separated. That is, the intermediate product 80 can also be used as the first thrust foil bearing 40. In this case, it is preferable to make the outer diameter dimension of the holder body 41a and the fixing member 41b larger than the outer diameter dimension of the connecting portion 61 so that the connecting portion 61 does not protrude to the outer diameter side of the foil holder 41. ..

The second thrust foil bearing 50 shown in FIG. 3 supports the flange portion 22 of the rotating member 20 from the other side in the axial direction, and includes a foil holder 51 and a plurality of leaves 52 fixed to the foil holder 51. .. The foil holder 51 has a disk-shaped holder main body 51a having a hole in the axial center, and a fixing member 51b arranged at the outer diameter end of the end surface 51a1 of the holder main body 51a. Since the configuration and assembly procedure of the second thrust bearing 50 are the same as those of the first thrust bearing 40, the description thereof will be omitted.

The leaves 42 and 52 described above are formed of a metal having a high springiness and good workability, for example, a leaf material having a thickness of about 20 μm to 200 μm made of a steel material or a copper alloy. As the leaf material, it is preferable to use a material made of stainless steel or bronze.

In the first thrust foil bearing 40 (including the second thrust foil bearing 50) shown in FIG. 4, as shown in FIG. 6, the top foil portion Tf of each leaf 42 has a notch 62 between adjacent leaves 42 (FIG. 7 and FIG. Since it rides on the back foil portion Bf of each leaf 42 via (see FIG. 8), the top foil portion Tf is in an inclined and standing state. Therefore, as the shaft member 11 rotates in one direction, a wedge space is formed between the radial bearing surface S2 of each leaf 42 and the end surface of the shaft member 11 (the end surface 22a of the flange portion 22 of the rotating member 20). The shaft member 11 is non-contactly supported in the thrust direction by the fluid dynamic pressure generated in the wedge space.

At this time, due to the flexibility of the leaves 42 and 52, the bearing surfaces S2 and S3 of the leaves 42 and 52 are arbitrarily deformed according to the operating conditions such as the load, the rotation speed of the shaft member 11, and the ambient temperature. , The thrust bearing clearance is automatically adjusted to an appropriate width according to the operating conditions. Therefore, even under harsh conditions such as high temperature and high-speed rotation, the thrust bearing clearance can be managed to the optimum width, and the shaft member 11 can be stably supported.

Further, by providing the gap C between the adjacent leaves of the foil member 60, as shown in FIG. 6, the spring effect of the leaf 42 at the intermediate position sandwiched between the closest front end 421 and the rear end 422 can be obtained. Increase. As a result, the rigidity of the front end 421 of the leaf 42 can be reduced, and the followability of the front end 421 to the end surface 22a of the flange portion 22 can be improved.

Since the bearing surface S of each leaf 42 and the end surface 22a of the flange portion 22 slide in contact with each other during low-speed rotation immediately before the shaft member 11 is stopped or immediately after the start, a DLC film or titanium is applied to either or both of them. A low friction film such as an aluminum nitride film, a tungsten disulfide film, or a molybdenum disulfide film may be formed. Further, when the shaft member 11 is rotated, the vibration of the shaft member 11 can be suppressed by the minute sliding between each leaf 42 and each foil holder 41. In order to adjust the frictional force due to the minute sliding, a low friction coating as described above may be formed on either or both of the leaf 42 and each foil holder 41.

[Characteristic configuration of the present invention]
The characteristic configuration of the present invention will be described with the thrust foil bearing 40 described above as a basic structure.

In the thrust foil bearing 40 shown in FIG. 4, both the inner diameter edge portion 423 and the outer diameter edge portion 424 of each leaf 41 are formed by an arc centered on the axis. In such a configuration, as already described, the leaf densities on the inner diameter side and the outer diameter side are different, and the leaf density on the inner diameter side is larger than that on the outer diameter side, so that the bearing rigidity of the inner diameter edge portion 423 is increased. It gets higher. Therefore, the inner diameter edge portion 423 and its vicinity tend to come into contact with the end surface 22a of the flange portion 22, and there is a problem that the inner diameter edge portion 423 of each leaf 42 is particularly locally worn.

In response to this problem, in the present invention, as shown in FIGS. 13 to 18, the inner diameter edge portion 423 of each leaf 42 passes through the inner diameter end of the front end 421 and is on the outer diameter side of the circle centered on the axis O. A retracted portion 425 is provided.

Hereinafter, the first to third embodiments of such a configuration will be described with reference to FIGS. 13 to 18. Note that FIGS. 13, 15, and 17 are plan views of the bearing surface S of the thrust foil bearing 40 as viewed from the axial direction. In these drawings, the area sandwiched between the holder body 41a and the fixing member 41b shown in FIG. 4 is not shown. Further, FIGS. 14, 16 and 18 are plan views showing one leaf 42 in an enlarged manner. In FIGS. 14, 16 and 18, the front end 421'of adjacent leaves (hereinafter referred to as "adjacent leaves") in the assembled state of the thrust foil bearing 40 is shown by a broken line.

The first embodiment will be described with reference to FIGS. 13 and 14 .
In the first embodiment, the retracting portion 425 is provided only in the portion forming the top foil portion Tf of each leaf 42 (the region sandwiched between the front end 421 and the front end 421'of the adjacent leaf). Therefore, the distance r2 from the axis O of the retracting portion 425 provided on each leaf 42 is larger than the distance r1 (radial dimension of the inner diameter end) from the axis O of the inner diameter end of the front end 421 of the leaf 42. (R2> r1). No receding portion is provided in the portion of each leaf 42 forming the backfoil portion Bf (the region sandwiched between the rear end 422 and the front end 421'of the adjacent leaf). Therefore, the contour of the inner diameter edge portion 423 of the portion forming the back foil portion Bf of each leaf 42 is an arc forming a circle passing through the inner diameter end of the front end 421 centered on the axis O.

In order to maximize the formation range of the retracted portion 425 in the rotation direction R, the end portion (referred to as "end point") of the retracted portion 425 opposite to the rotation direction R coincides with the inner diameter end of the front end 421'of the adjacent leaf. To be provided. It is also possible to extend the end point of the retracted portion 425 further to the side opposite to the rotation direction R, and arrange the end point of the retracted portion 425 at the portion that becomes the backfoil portion Bf. On the other hand, the end portion (referred to as "starting point") on the rotation direction R side of the retracting portion 425 is brought as close as possible to the inner diameter end of the front end 421 of the leaf 42. That is, the retracting portion 425 is provided in the region of the inner diameter edge portion 423 of the leaf 42 excluding the inner diameter end of the front end 421. When the start end of the retracting portion 425 reaches the outer diameter side of the front end 421 of the leaf 42, the shape of the front end 421 changes on the inner diameter side, which affects the fluid drawing action of the front end 421 formed in a herringbone shape. To give.

In the first embodiment, in the region where the retracted portion 425 is formed, the leaf closest to the end surface 22a of the flange portion 22 is the backfoil portion Bf of the leaf adjacent to the rotation direction R side. As a result, in the inner diameter edge portion 423, which tends to have high rigidity, the distance between the leaf 42 and the end surface 22a of the flange portion 22 becomes large, so that it becomes difficult for the leaf 42 and the end surface 22a of the flange portion 22 to come into contact with each other. That is, the high-rigidity portion of the top foil portion Tf is less likely to come into contact with the end surface 22a of the flange portion 22. Therefore, local wear of the bearing surface S can be prevented.

Next, a second embodiment will be described with reference to FIGS. 15 and 16 .
In this second embodiment, of the inner diameter edge portion 423 of each leaf 42, a retracting portion 425 is provided on both a portion forming the top foil portion Tf and a portion forming the back foil portion Bf. The distances r2 and r3 from the axial center O of the two retracting portions 425 provided in the portion constituting the top foil portion Tf and the portion constituting the back foil portion Bf are the axial centers of the inner diameter ends of the front end 421 of the leaf 42. The distance from O is greater than r1 (r2> r1, r3> r1). In the assembled state of the thrust foil bearing shown in FIG. 15 , the retracted portion 425 of the top foil portion Tf is located at a position overlapping the retracted portion 425 provided in the back foil portion Bf of the adjacent leaf.

Even in such a configuration, similarly to the first embodiment shown in FIGS. 13 and 14 , the highly rigid portion (inner diameter edge portion 423 and its periphery) of the top foil portion Tf of each leaf 42 comes into contact with the end surface 22a of the flange portion 22. It becomes difficult to do. Therefore, local wear of the bearing surface S can be prevented. In particular, in this embodiment, the contact between the end surface 22a of the flange portion 22 and the backfoil portion Bf can be prevented in the region where the retracting portion 425 is provided, so that the effect of suppressing local wear is further enhanced.

Next, a third embodiment will be described with reference to FIGS. 17 and 18 .
In the third embodiment, of the inner diameter edge portion 423 of each leaf 42, the retracting portion 425 is provided only in the portion forming the backfoil portion Bf. The distance r3 from the axial center O of the retracting portion 425 provided in the portion forming the back foil portion Bf is larger than the distance r1 from the axial center O of the inner diameter end of the front end 421 of the leaf 42 (r3> r1). .. The recessed portion 425 is not provided in the portion forming the top foil portion Tf. Therefore, the contour of the inner diameter edge portion 423 of the top foil portion Tf is an arc forming a circle passing through the inner diameter end of the front end 421 centered on the axis O.

In such a configuration, since the space is directly below the inner diameter edge portion 423 of the top foil portion Tf, the spring force that supports the top foil portion Tf is low. Therefore, the inner diameter edge portion 423 of the top foil portion Tf is easily elastically deformed, and the followability of the inner diameter edge portion 423 of the top foil portion Tf to the end surface 22a of the flange portion 22 is increased. This makes it possible to prevent local wear of the top foil portion Tf due to contact with the end surface 22a of the flange portion 22.

In the first embodiment and the second embodiment described above, as shown in FIGS. 14 and 16 , a circle centered on the axis O between the start point of the retracting portion 425 and the inner diameter end of the front end 421. Although the arc-shaped inner diameter edge portion 423 is formed, as shown in FIGS. 19A and 19B, the starting point of the retracting portion 425 may be aligned with the inner diameter end of the front end 421.

Further, in the third embodiment, as shown in FIG. 18 , an arc-shaped inner diameter edge portion 423 centered on the axis O is provided between the start point of the retracting portion 425 and the inner diameter end of the front end 421'of the adjacent leaf. Although formed, as shown in FIG. 19 (c), the starting point of the retracted portion 425 may coincide with the inner diameter end of the front end 421'of the adjacent leaf.

By aligning the start end of the retracted portion 425 with the inner diameter end of the front end 421, 421'of the leaf 42 in this way, the inner diameter edge portion 423 of the top foil portion Tf has the inner diameter end of the front end 421, 421' of each leaf 42. A recessed portion 425 is formed in all regions except the above (FIGS. 19A and 19B), and the inner diameter edge portion 423 of the backfoil portion Bf is provided with the inner diameter ends of the front ends 421 and 421'of each leaf 42. A receding portion 425 is formed in all areas except (FIG. 19 (c)). From such a configuration, since the area of the retracted portion 425 viewed from the axial direction is expanded, it is possible to prevent local wear of the top foil portion Tf over a wider range.

The application target of the thrust foil bearing described above is not limited to the gas turbine described above, and can be used, for example, as a bearing for supporting the rotor of a supercharger. In addition, the thrust foil bearings described above are not limited to turbo machines such as gas turbines and superchargers, but are auxiliary equipment for lubricating oil circulation systems from the viewpoint of energy efficiency, where lubrication with liquids such as lubricating oil is difficult. It can be widely used as a bearing for vehicles such as automobiles and a bearing for industrial equipment, which is difficult to provide separately or is used under restrictions such as resistance due to liquid shearing becomes a problem.

The thrust foil bearing described above is a pneumatic bearing that uses air as the pressure generating fluid, but is not limited to this, and other gases can be used as the pressure generating fluid, or water or oil. You can also use liquids such as. Further, the case where the shaft member 11 is rotated has been described, but conversely, the thrust foil bearing described above can be adopted when the foil holders 31, 41, 51 side (leaf side) are rotated. ..

11 Shaft member 40 Thrust foil bearing 41 Foil holder 42 Leaf 60 Foil member 61 Connecting part 62 Notch 421 Front end 422 Rear end 423 Inner diameter edge 424 Outer diameter edge 425 Retreat Bf Back foil part C Gap O Axis center R Rotation direction S Bearing surface Tf Top foil part

Claims (5)

In a thrust foil bearing in which a bearing surface is formed by arranging a plurality of leaves in the circumferential direction, and each leaf has a front end located on the leading side in the rotation direction and an inner diameter edge portion.
A retracting portion is provided on each leaf at the inner diameter edge portion excluding the inner diameter end of the front end so that the distance from the axis is larger than the distance from the axis of the inner diameter end of the front end .
Each leaf is provided with a top foil portion that forms the bearing surface and a back foil portion that supports the top foil portion of the adjacent leaf, and the recessed portion is provided in the top foil portion. bearing. In a thrust foil bearing in which a bearing surface is formed by arranging a plurality of leaves in the circumferential direction, and each leaf has a front end located on the leading side in the rotation direction and an inner diameter edge portion.
A retracting portion is provided on each leaf at the inner diameter edge portion excluding the inner diameter end of the front end so that the distance from the axis is larger than the distance from the axis of the inner diameter end of the front end.
Each leaf is provided with a top foil portion that forms the bearing surface and a back foil portion that supports the top foil portion of the adjacent leaf, and the retracted portion is provided in the back foil portion.
A thrust foil bearing characterized in that, in the entire region of the retracted portion, a space directly below the inner diameter edge portion of the top foil portion is a space without foil. In a thrust foil bearing in which a bearing surface is formed by arranging a plurality of leaves in the circumferential direction, and each leaf has a front end located on the leading side in the rotation direction and an inner diameter edge portion.
A retracting portion is provided on each leaf at the inner diameter edge portion excluding the inner diameter end of the front end so that the distance from the axis is larger than the distance from the axis of the inner diameter end of the front end.
Each leaf is provided with a top foil portion that forms the bearing surface and a back foil portion that supports the top foil portion of the adjacent leaf, and the retracted portion is provided on both the top foil portion and the back foil portion. Thrust foil bearings that feature . The thrust foil bearing according to claim 1 or 3, wherein the retracted portion is provided in the entire region of the inner diameter edge portion of the top foil portion except the front end of each leaf. The thrust foil bearing according to claim 2 or 3, wherein the retracted portion is provided in the entire region of the inner diameter edge portion of the back foil portion except the front end of each leaf.

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