JP2020159452A - Foil bearing - Google Patents

Abstract

To devise the relation between respective foils of a foil bearing, to improve stability of support by damping the vibration of a shaft member and improve a load capacity by reducing a bearing clearance.SOLUTION: A foil bearing 20 comprises a shaft member 11 that rotates on one side in a circumferential direction, and a plurality of foils 22 attached to a foil holder 21. Each foil 22 has top foil parts 1tf, 2tf, 3tf, and back foil parts 1bf, 2bf, 3bf supporting the top foil parts from behind. The back foil part 1bf of each foil 22 is arranged behind the top foil parts 2tf and 3tf of two or more foils 22 which are sequentially adjacent to each other on the other side in the circumferential direction.SELECTED DRAWING: Figure 7

Description

The present invention relates to a foil bearing in which a plurality of foils are arranged side by side in the circumferential direction, a foil bearing unit, and a turbomachine.

As is well known, 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 conditions. A foil bearing supports a load by forming a bearing surface with a thin film (foil) having low rigidity and flexibility with respect to bending and allowing the bearing surface to bend. When the shaft member rotates, a fluid film (for example, an air film) is formed between the outer peripheral surface of the shaft member and the bearing surface of the foil, and the shaft member is non-contact supported.

For example, Patent Documents 1 and 2 below disclose a specific structure of a foil bearing (thrust foil bearing) 50 as shown in FIGS. 13 and 14. The foil bearing 50 supports a thrust collar 52 provided on a shaft member 51 that rotates on one side in the circumferential direction (arrow E direction) in the thrust direction. A plurality of foils 54 are attached side by side in the circumferential direction to the end surface 53a of the foil holder 53 facing the end surface 52a of the thrust collar 52. As shown in FIG. 15, one end of each foil 54 in the circumferential direction (hereinafter, front end 54x) is a free end, and the region including the front end 54x of each foil 54 is a top foil portion having a radial bearing surface K. It functions as 54tf. On the other hand, the region including the other end of each foil 54 in the circumferential direction (hereinafter referred to as the rear end 54y) is the back foil portion 54bf that supports the top foil portion 54tf of the foil 54 adjacent to the other side in the circumferential direction from behind. Functions as.

Further, each document also discloses a specific structure of the foil bearing (radial foil bearing) 60 as shown in FIG. The foil bearing 60 supports a shaft member 61 that rotates on one side in the circumferential direction (arrow F direction) in the radial direction. A plurality of foils 64 are attached side by side in the circumferential direction on the inner peripheral surface 62a of the foil holder 62 into which the shaft member 61 is inserted on the inner peripheral side. Similarly to the above, the plurality of foils 64 also have a region that functions as the top foil portion 64tf and a region that functions as the back foil portion 64bf.

Japanese Unexamined Patent Publication No. 2015-132309 Japanese Unexamined Patent Publication No. 2015-113928

By the way, in each of the two types of foil bearings 50 and 60 disclosed in Patent Documents 1 and 2, as can be seen from FIGS. 15 and 16, the back foil portions 54bf and 64bf of one foil 54 and 64 are , The top foil portions 54tf, 64tf of one foil 54, 64 adjacent to the other side in the circumferential direction are supported from behind.

In this type of foil bearing, when the shaft member rotates, adjacent foils slide with each other, and the vibration of the shaft member is damped by the Coulomb friction caused by these sliding. However, as described above, if the back foil portion of one foil has a structure that supports the top foil portion of one foil from behind, the sliding of each foil may be insufficient. Therefore, the ability to attenuate the vibration of the shaft member is limited, and the stability of the support of the shaft member by the foil bearing may be impaired.

Moreover, if each foil has the above structure, it is difficult to reduce the bearing gap. Therefore, the ability to absorb the shape collapse of the foil holder, thrust collar, etc., which are members affected by the bearing gap, is limited, and it becomes difficult to further improve the load capacity.

The technical problem to be solved by the present invention is to improve the stability of the support by the vibration damping of the shaft member and to improve the load capacity by reducing the bearing gap by devising the relationship between the foils of the foil bearing. It is to plan.

The foil bearing (thrust foil bearing) according to the present invention, which was devised to solve the above problems, includes a foil holder provided on a shaft member that rotates on one side in the circumferential direction and a foil holder that faces the thrust collar in the axial direction, and the foil. It is provided with a plurality of foils mounted side by side in the circumferential direction on the axial end face of the holder, and the end on one side in the circumferential direction of each foil is a free end, and includes the end on one side in the circumferential direction of each foil. A back foil in which a region constitutes a top foil portion having a thrust bearing surface, and a region including an end portion on the other side in the circumferential direction of each foil supports the top foil portion of the foil adjacent to the other side in the circumferential direction from behind. The back foil portion of each foil constitutes a portion, and is characterized in that the back foil portion of each foil is arranged behind the top foil portion of two or more foils sequentially adjacent to each other on the other side in the circumferential direction. Here, the above "two or more" means that two or more and less than the total number are required, but two or more and three or less. Alternatively, it is preferable that the number of sheets is 2 or more and 4 or less, or 2 or more and 5 or less (the same applies to the following "2 or more").

Further, the foil bearing (radial foil bearing) according to the present invention, which was devised to solve the above problems, includes a foil holder in which a shaft member rotating on one side in the circumferential direction is inserted on the inner peripheral side, and the foil holder. It is provided with a plurality of foils mounted side by side in the circumferential direction on the inner peripheral surface, the end on one side in the circumferential direction of each foil is a free end, and the area including the end on one side in the circumferential direction of each foil is formed. A top foil portion having a radial bearing surface is formed, and a region including an end portion on the other side in the circumferential direction constitutes a back foil portion that supports the top foil portion of the foil adjacent to the other side in the circumferential direction from behind. It is characterized in that the backfoil portion of each foil is arranged behind the top foil portion of two or more foils sequentially adjacent to the other side in the circumferential direction.

As described above, in the foil bearing according to the present invention, the back foil portion of one foil in each foil is the top foil portion of two or more foils sequentially adjacent to the other side in the circumferential direction of the one foil. Placed behind. Therefore, three or more foils are overlapped with each other, and when the shaft member is rotated, there are many sliding points between the foils. Therefore, the ability to attenuate the vibration of the shaft member due to the Coulomb friction caused by sliding between the foils is enhanced, and the stability of the support of the shaft member by the foil bearing is improved. Moreover, the bearing gap can be reduced by overlapping three or more foils. Therefore, it becomes easy to absorb the shape deformation of the foil holder, the thrust collar, etc., which are members affected by the bearing gap, and the load capacity can be improved.

In the above configuration, a plurality of foils are mounted side by side at equal pitches in the circumferential direction, and the circumferential length of each foil from one end in the circumferential direction to the other end in the circumferential direction is the mounting pitch of each foil. It may be more than twice the circumferential length of.

In this way, the circumferential length of each foil can be significantly increased in relation to the mounting pitch of each foil, and the degree of freedom of sliding between the foils is increased. Therefore, when the shaft member rotates, the foils are more likely to rub against each other, and the ability to attenuate the vibration of the shaft member due to the Coulomb friction is further improved, and the stability of the support of the shaft member by the foil bearing is further improved. It is planned.

The present invention may provide a foil bearing unit including the foil bearing and the shaft member as a second aspect.

In this way, the foil bearing and the shaft member (rotating member) can be handled integrally, so that assembly work, transfer work, and the like can be easily performed.

The present invention may provide, as a third aspect, a turbomachinery including a rotor including the foil bearing and the shaft member as components.

In this way, the rotor of the turbomachinery can be suitably rotatably supported by the foil bearings.

According to the foil bearing according to the present invention, by devising the relationship between the foils, the stability of the support due to the vibration damping of the shaft member is improved and the load capacity is improved by reducing the bearing gap. Can be planned.

It is the schematic 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 front view which looked at the first thrust foil bearing from the thrust collar side. It is a front view which shows the foil of the 1st thrust foil bearing. It is a front view which looked at the main part of the 1st thrust foil bearing from the thrust collar side. It is sectional drawing which shows the main part of the 1st thrust foil bearing developed. It is a front view which looked at the 2nd thrust foil bearing from the thrust collar side. It is sectional drawing which saw the radial foil bearing from one side in the axial direction. It is a front view which shows the foil of a radial foil bearing. It is a figure which shows the main part of a radial foil bearing developed. It is sectional drawing which looked at the main part of the radial foil bearing from one side in the axial direction. It is sectional drawing which shows the conventional thrust foil bearing. It is a front view which looked at the conventional thrust foil bearing from the thrust collar side. It is sectional drawing which shows the main part of the conventional thrust foil bearing developed. It is sectional drawing which looked at the conventional radial foil bearing from one side in the axial direction.

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 turbo machine. The main components of this gas turbine are 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 rotating shaft 6 extending in the horizontal direction, and the rotating shaft 6 and the turbine 1 and the compressor 2 form an integrally rotatable rotor. ..

In this gas turbine, 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 rotating shaft 6 of the rotor in the gas turbine. The foil bearing unit 10 includes a rotating shaft 6, a shaft member 11 through which the rotating shaft 6 is inserted and fixed, a first thrust foil bearing 20, a second thrust foil bearing 30, and a radial foil bearing 40. The first thrust foil bearing 20 and the second thrust foil bearing 30 support the shaft member 11 in both thrust directions, and the radial foil bearing 40 supports the shaft member 11 in the radial direction. The rotating shaft 6 rotates integrally with the shaft member 11. The shaft member 11 includes a sleeve portion 11s and a disk-shaped flange portion 11f protruding from the sleeve portion 11s to the outer diameter side. The sleeve portion 11s is formed of, for example, a carbon sintered material, and the flange portion 11f is formed of, for example, a carbon fiber reinforced composite material.

Hereinafter, the configuration of the first thrust foil bearing 20 will be described.

As shown in FIG. 3, the first thrust foil bearing 20 supports the flange portion 11f of the shaft member 11 from one side in the axial direction. Here, since the flange portion 11f of the shaft member 11 corresponds to the thrust collar, the flange portion 11f is referred to as the thrust collar 11 in the following description.

The first thrust foil bearing 20 includes a foil holder 21 and a plurality of foils 22 attached to the foil holder 21 so as to form a band in the circumferential direction. The foil 22 is also referred to as a leaf. The foil holder 21 includes a tubular portion 21s and a disk-shaped flange portion 21f protruding from the tubular portion 21s to the outer diameter side. Here, since the first thrust foil bearing 20 is attached only to the flange portion 21f of the foil holder 21, the flange portion 21f is referred to as the foil holder 21 in the following description.

FIG. 4 is a front view of the first thrust foil bearing 20 shown in FIG. 3 as viewed from the thrust collar 11 side. As shown in FIGS. 3 and 4, the end surface 21a of the foil holder 21 is axially opposed to the end surface 11a of the thrust collar 11. An annular fixing member 23 is attached to the outer diameter side end portion of the end surface 21a of the foil holder 21. Each foil 22 is fixed to the end surface 21a of the foil holder 21 by being sandwiched between the foil holder 21 and the fixing member 23 from both sides in the axial direction. As a mounting mode of each foil 22, a plurality of foils 22 (14 in FIG. 4) are mounted side by side at equal pitches in the circumferential direction on the end surface 21a of the foil holder 21. The shaft member 11 (thrust collar 11) rotates toward one side in the circumferential direction indicated by the arrow A.

The foil 22 is 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, for example, a steel material or a copper alloy. As the material of the foil 22, it is preferable to use a material made of stainless steel or bronze.

FIG. 5 shows only one foil 22 out of a plurality of foils 22, and the other foils are not shown. As shown in the figure, the foil 22 is formed by integrally forming a main body portion 22a and an extending portion 22b (indicated by cross-hatching) extending from the main body portion 22a to the outer diameter side. The extending portion 22b of the foil 22 is fixed to the outer diameter side end portion of the end surface 21a of the foil holder 21 by the fixing member 23. The extending portions 22b of all the foils 22 may be connected all around in the circumferential direction. Here, since the extending portion 22b of the foil 22 does not perform a bearing action and only the main body portion 22a of the foil 22 substantially performs a bearing action, the main body portion 22a is referred to as a foil 22 in the following description.

The end portion on one side of the foil 22 in the circumferential direction (hereinafter, front end 22x) and the end portion on the other side in the circumferential direction (hereinafter, rear end 22y) both have a herringbone shape. Specifically, the front end 22x has a pair of inclined portions 22xa inclined from both ends in the axial direction toward the central side in the axial direction toward one side in the circumferential direction. Between the pair of inclined portions 22xa, a substantially arc-shaped top portion 22xb that smoothly connects them is provided. The rear end 22y has a pair of inclined portions 22ya inclined from both ends in the axial direction toward the central side in the axial direction toward one side in the circumferential direction. Between the pair of inclined portions 22ya, a substantially arc-shaped top portion 22yb that smoothly connects them is provided.

FIG. 6 illustrates only three foils 22 for convenience of explanation. Further, among these three foils 22, the foil 22 located at one end in the circumferential direction is referred to as the first foil 221 and the two foils 22 sequentially adjacent to the other side in the circumferential direction of the first foil 221 are designated. , The second foil 222 and the third foil 223. As shown in the figure, the rear end 221y of the first foil 221 is located on the other side in the circumferential direction from the front end 222x of the second foil 222 and the front end 223x of the third foil 223. Therefore, the rear end 221y of the first foil 221 and the rear end 222y of the second foil 222 are located in the entire region of the third foil 223 from the front end 223x to the rear end 223y of the third foil 223. Such a positional relationship is similarly established for all the foils 22 arranged over the entire circumference in the circumferential direction.

FIG. 7 is a view obtained by developing a curved cross section cut along the arc D shown by a virtual line in FIG. 6 into a flat cross section, and is viewed from the outer diameter side. As shown in the figure, the region 1tf from the front end 221x of the first foil 221 to the front end 222x position of the second foil 222 constitutes a top foil portion having a thrust bearing surface S of the first foil 221. The region 1bf from the rear end 221y of the first foil 221 to the front end 222x position of the second foil 222 constitutes the back foil portion of the first foil 221. Further, the region 2tf from the front end 222x of the second foil 222 to the front end 223x position of the third foil 223 constitutes a top foil portion having a thrust bearing surface S of the second foil 222. The region 2bf from the rear end 222y of the second foil 222 to the front end 223x position of the third foil 223 constitutes the back foil portion of the second foil 222. Similarly, the region 3tf including the front end 223x of the third foil 223 constitutes a top foil portion having a thrust bearing surface S of the third foil 223.

In this case, the back foil portion 1bf of the first foil 221 includes the top foil portion 2tf of the second foil 222 and supports a region longer than the top foil portion 2tf from behind (foil holder 21 side). The back foil portion 2bf of the second foil 222 includes the top foil portion 3tf of the third foil 223 and supports a region longer than the top foil portion 3tf from behind.

Therefore, the back foil portion 1bf of the first foil 221 is arranged behind the top foil portion 2tf of the second foil 222 and the top foil portion 3tf of the third foil 223. In other words, the back foil portion 1bf of the first foil 221 is arranged behind the top foil portions 2tf and 3tf of the second and third foils 222 and 223 which are sequentially adjacent to each other in the axial direction. In this embodiment, the circumferential length L of each foil 22 is set to be three times the circumferential length P of the mounting pitch of each foil 22. Therefore, each foil 22 has a three-layer structure over the entire circumference in the circumferential direction. In this case, the circumferential length L of each foil 22 may be more than twice the circumferential length P of the mounting pitch of each foil 22. Therefore, the back foil portion 1bf of the first foil 221 may be arranged behind a part region of the third foil 223. The circumferential length L of each foil 22 is preferably 3 times or less, 4 times or less, 5 times or less, or 6 times or less of the circumferential length P of the mounting pitch of each foil 22. Therefore, three or more foils 22 are overlapped over the entire circumference in the circumferential direction.

According to such a configuration, when the shaft member 11 (thrust collar 11) rotates toward one side in the circumferential direction indicated by the arrow A, between the thrust bearing surface S of each foil 22 and the end surface 11a of the thrust collar 11. The pressure of the fluid (for example, air) in the thrust bearing gap T formed is increased. Due to this increased fluid pressure, the thrust collar 11 is in a non-contact support state in one direction in the thrust direction. In this state, since three or more foils 22 are overlapped with each other, the number of sliding points between the foils 22 due to the rotation of the thrust collar 11 increases. Therefore, the ability to attenuate the vibration of the shaft member 11 due to the Coulomb friction caused by sliding between the foils 22 is enhanced, and the stability of the support of the shaft member 11 by the first thrust foil bearing 20 is improved. Moreover, since the circumferential length L of each foil 22 exceeds twice the circumferential length P of the mounting pitch of each foil 22, the circumferential length L of each foil 22 can be significantly lengthened. Therefore, the degree of freedom of sliding between the foils 22 is increased, and the foils 22 are more likely to rub against each other when the shaft member 11 is rotated. As a result, the ability to attenuate the vibration of the shaft member 11 due to the Coulomb friction is further enhanced, and the stability of the support of the shaft member 11 by the first thrust foil bearing 20 is further improved. Moreover, since the three or more foils 22 are overlapped with each other, the thrust bearing gap T can be reduced. Therefore, it becomes easy to absorb the shape collapse of the foil holder 21 and the thrust collar 11 forming the thrust bearing gap T, and the load capacity can be improved.

Next, the configuration of the second thrust foil bearing 30 will be described.

As shown in FIG. 3, the second thrust foil bearing 30 supports the thrust collar 11 (11f) from the other side in the axial direction, and is a foil holder 31 and a plurality of foils 32 fixed to the foil holder 31. And. The foil holder 31 has a disk shape with a through hole formed in the axis. A fixing member 33 for fixing each foil 32 is attached to the outer diameter end portion of the end surface 31a of the foil holder 31. The end face 11b on the other side in the axial direction of the thrust collar 11 (11f) is an element for forming a thrust bearing gap. The thickness and material of the foil 32 are the same as those of the foil 22 of the first thrust foil bearing 20 described above.

FIG. 8 is a front view of the second thrust foil bearing 30 as viewed from the thrust collar 11 side. Since the shaft member 11 (thrust collar 11) rotates in the arrow B direction shown in the figure, the end portion (front end 32x) on one side in the circumferential direction of each foil 32 is the end portion on the arrow B direction side of each foil 32. Corresponds to. The configuration and overlapping state of each foil 32 of the second thrust foil bearing 30 are the same as the configuration and overlapping state of each foil 22 of the first thrust foil bearing 20 already described with reference to FIGS. 5, 6 and 7. is there. Further, the action and effect of the second thrust foil bearing 30 is substantially the same as that of the first thrust foil bearing 20. Therefore, those description will be omitted here.

Next, the configuration of the radial foil bearing 40 will be described.

As shown in FIG. 3, the radial foil bearing 40 supports only the sleeve portion 11s of the sleeve portion 11s and the flange portion 11f of the shaft member 11 in the radial direction. Therefore, in the following description, the sleeve portion 11s is referred to as a shaft member 11.

The radial foil bearing 40 includes a plurality of foils 42 attached so as to form a band on the inner peripheral side of the foil holder 21. The foil holder 21 includes a tubular portion 21s and a flange portion 21f, and the radial foil bearing 40 is attached only to the inner peripheral side of the tubular portion 21s. Therefore, in the following description, the tubular portion 21s is referred to as a foil holder 21.

As shown in FIG. 9, the radial foil bearing 40 includes a plurality of foils (8 in the illustrated example) mounted side by side on the inner peripheral surface 21a of the foil holder 21 at equal pitches in the circumferential direction. The thickness and material of the foil 42 are the same as those of the foil 22 of the first thrust foil bearing 20 described above. The shaft member 11 inserted into the inner peripheral side of the foil holder 21 rotates in one side in the circumferential direction indicated by the arrow C.

As shown in FIG. 10, each foil 42 integrally has a main body portion 42a and an extending portion 42b projecting from one side of the main body portion 42a in the axial direction (upper side in the drawing). The extending portion 42b of each foil 42 is fixed to the inner peripheral surface 21b of the foil holder 21 by an appropriate means such as welding. Here, since the extending portion 42b of the foil 42 does not perform a bearing action and only the main body portion 42a of the foil 42 substantially performs a bearing action, the main body portion 42a is referred to as a foil 42 in the following description.

Both the end portion on one side in the circumferential direction (hereinafter, front end 42x) and the end portion on the other side in the circumferential direction (hereinafter, rear end 42y) of the foil 42 have a herringbone shape. Specifically, the front end 42x has a pair of inclined portions 42xa inclined from both ends in the axial direction toward the central side in the axial direction toward one side in the circumferential direction. Between the pair of inclined portions 42xa, a substantially arc-shaped top portion 42xb that smoothly connects them is provided. The rear end 42y has a pair of inclined portions 42ya inclined from both ends in the axial direction toward the central side in the axial direction toward one side in the circumferential direction. Between the pair of inclined portions 42ya, a substantially arc-shaped top portion 42yb that smoothly connects them is provided.

FIG. 11 is a plan view of the arc-shaped radial foil bearing 40 shown in FIG. 10 developed in a plane and viewed from the inner diameter side. Further, FIG. 11 shows only three foils 42 for convenience of explanation. Hereinafter, among these three foils 42, the foil 42 located at the end on one side in the circumferential direction (the side in the direction of arrow C) is referred to as the first foil 421, and the other side in the circumferential direction of the first foil 421 (arrow C). Two foils 42 that are sequentially adjacent to each other (on the opposite side of the direction) will be described as a second foil 422 and a third foil 423. As shown in the figure, the rear end 421y of the first foil 421 is located on the other side in the circumferential direction from the front end 422x of the second foil 422 and the front end 423x of the third foil 423. Therefore, the rear end 421y of the first foil 421 and the rear end 422y of the second foil 422 are located in the entire region of the third foil 423 from the front end 423x to the rear end 423y of the third foil 423. Such a positional relationship is similarly established for all the foils 42 arranged over the entire circumference in the circumferential direction.

FIG. 12 is an enlarged view of a main part of FIG. 9, and for convenience of explanation, only three foils 42 are shown. As shown in the figure, the region 1tfo from the front end 421x of the first foil 421 to the front end 422x position of the second foil 422 constitutes a top foil portion having a radial bearing surface R of the first foil 421. The region 1bfo from the rear end 421y of the first foil 421 to the front end 422x position of the second foil 422 constitutes the back foil portion of the first foil 421. Further, the region 2tfo from the front end 422x of the second foil 422 to the front end 423x position of the third foil 423 constitutes a top foil portion having a radial bearing surface R of the second foil 422. The region 2bfo from the rear end 422y of the second foil 422 to the front end 423x position of the third foil 423 constitutes the back foil portion of the second foil 422. Similarly, the region 3tfo including the front end 423x of the third foil 423 constitutes a top foil portion having a radial bearing surface R of the third foil 423.

In this case, the back foil portion 1bfo of the first foil 421 includes the top foil portion 2tfo of the second foil 422 and supports a region longer than the top foil portion 2tfo from behind (foil holder 21 side). The back foil portion 2bfo of the second foil 422 includes the top foil portion 3tfo of the third foil 423 and supports a region longer than the top foil portion 3tfo from behind.

Therefore, the back foil portion 1bfo of the first foil 421 is arranged behind the top foil portion 2tfo of the second foil 422 and the top foil portion 3tfo of the third foil 423. In other words, the back foil portion 1bfo of the first foil 421 is arranged behind the top foil portions 2tfo and 3tfo of the second and third foils 422 and 423 which are sequentially adjacent to each other in the axial direction. In this embodiment, the circumferential length L1 of each foil 42 is set to be three times the circumferential length P1 of the mounting pitch of each foil 42. Therefore, each foil 42 has a three-layer structure over the entire circumference in the circumferential direction. In this case, the circumferential length L1 of each foil 42 may exceed twice the circumferential length P1 of the mounting pitch of each foil 42. Therefore, the backfoil portion 1bfo of the first foil 421 may be arranged behind a part region of the third foil 423. The circumferential length L1 of each foil 42 is preferably 3 times or less, 4 times or less, 5 times or less, or 6 times or less of the circumferential length P1 of the mounting pitch of each foil 42. Therefore, three or more foils 42 are overlapped over the entire circumference in the circumferential direction.

According to such a configuration, when the shaft member 11 rotates toward one side in the circumferential direction indicated by the arrow C, a radial formed between the radial bearing surface R of each foil 42 and the outer peripheral surface 11a of the shaft member 11 is formed. The pressure of the fluid (for example, air) in the bearing gap J is increased. The shaft member 11 is in a non-contact support state in the radial direction due to the increased fluid pressure. In this state, since three or more foils 42 are overlapped with each other, the number of sliding points between the foils 42 due to the rotation of the shaft member 11 increases. Therefore, the ability to attenuate the vibration of the shaft member 11 due to the Coulomb friction caused by sliding between the foils 42 is enhanced, and the stability of the support of the shaft member 11 by the radial foil bearing 40 is improved. Moreover, since the circumferential length L1 of each foil 42 exceeds twice the circumferential length P1 of the mounting pitch of each foil 42, the circumferential length L1 of each foil can be significantly lengthened. Therefore, the degree of freedom of sliding between the foils 42 is increased, and the foils 42 are more likely to rub against each other when the shaft member 11 is rotated. As a result, the ability to attenuate the vibration of the shaft member 11 due to the Coulomb friction is further enhanced, and the stability of the support of the shaft member 11 by the radial foil bearing 40 is further improved. Moreover, the radial bearing gap J can be reduced by overlapping the three or more foils 42. Therefore, it becomes easy to absorb the shape deformation of the foil holder 21 and the shaft member 11 forming the radial bearing gap J, and the load capacity can be improved.

The foil bearing according to the present invention can be widely used not only as a turbomachine such as a gas turbine or a supercharger, but also as a bearing for vehicles such as automobiles and a bearing for industrial equipment.

Further, each foil bearing described above is an pneumatic dynamic bearing that uses air as the pressure generating fluid, but the present invention is not limited to this, and other gases can be used as the pressure generating fluid, or water or oil. Liquids such as can also be used.

1 Turbine 1bf, 1bfo, 2bf, 2bfo Backfoil part 1tf, 1tfo, 2tf, 2tfo, 3tf, 3tfo Top foil part 10 Foil bearing unit 11 Shaft member 11 Thrust collar 11a Thrust collar end faces 20, 30 Thrust foil bearings 21, 31 Foil holders 21a, 31a End surface of foil holder 21b Inner peripheral surface of foil holder 22, 32, 42 Foil 22x, 42x One end (front end) of foil in the circumferential direction
The other end (rear end) of the 22y and 42y foils in the circumferential direction.
40 Radial Foil Bearings P, P1 Foil Mounting Pitch S Thrust Bearing Surface T Thrust Bearing Gap R Radial Bearing Surface

Claims (5)

A foil holder provided on a shaft member that rotates on one side in the circumferential direction and a foil holder that is axially opposed to the thrust collar, and a plurality of foils that are arranged side by side in the circumferential direction on the axial end face of the foil holder are provided. One end in the circumferential direction of the foil is a free end, and a region including one end in the circumferential direction of each foil constitutes a top foil portion having a thrust bearing surface, and the other end in the circumferential direction of each foil. A foil bearing in which the region including the end portion constitutes a back foil portion that supports the top foil portion of the foil adjacent to the other side in the circumferential direction from behind.
A foil bearing, wherein the back foil portion of each foil is arranged behind the top foil portion of two or more foils sequentially adjacent to each other on the other side in the circumferential direction. A foil holder in which a shaft member rotating on one side in the circumferential direction is inserted on the inner peripheral side, and a plurality of foils mounted side by side in the circumferential direction on the inner peripheral surface of the foil holder are provided, and one of the circumferential directions of each foil is provided. A region in which a side end is a free end and a region including one end in the circumferential direction of each foil constitutes a top foil portion having a radial bearing surface and includes an end on the other side in the circumferential direction of each foil. Is a foil bearing that constitutes a back foil portion that supports the top foil portion of the foil adjacent to the other side in the circumferential direction from behind.
A foil bearing, wherein the back foil portion of each foil is arranged behind the top foil portion of two or more foils sequentially adjacent to each other on the other side in the circumferential direction. A plurality of foils are mounted side by side at equal pitches in the circumferential direction, and the circumferential length from one end of each foil in the circumferential direction to the other end in the circumferential direction is the circumferential length of the mounting pitch of each foil. The foil bearing according to claim 1 or 2, which is more than twice as large as the above. A foil bearing unit including the foil bearing according to any one of claims 1 to 3 and the shaft member. A turbomachine provided with the foil bearing according to any one of claims 1 to 3 and a rotor having the shaft member as a component.

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