Thrust foil bearing

Abstract

To provide a thrust foil bearing that can suppress unnecessary contact with a rotating body.SOLUTION: A thrust foil bearing 5 comprises: a base plate 10 provided with an insertion hole 12 for a shaft 2; and a top foil 20 that includes a plurality of top foil pieces 21 arranged around the insertion hole 12, and a support portion (outer ring 22) supporting each top foil piece 21 from the outer periphery thereof. Each top foil piece 21 includes a tab 26 extending toward its inner peripheral side, and the support portion (outer ring 22) is attached to the base plate 10, in which the tab 26 is attached to the base plate 10 by a fastening member (rivet 40) inserted into a through hole 15 formed in the base plate 10.SELECTED DRAWING: Figure 5C

Description

[Technical Field]

[0001] The present disclosure relates to thrust foil bearings. [Background technology]

[0002] A thrust foil bearing is a type of fluid bearing. It supports a rotating body without contact by forming a fluid film between the bearing and the rotating body. The rotating body moves slightly in the axial direction of the rotating body due to vibration, shock, etc.

[0003] Regardless of such minute movements of the rotating body, thrust foil bearings must maintain the formation of a fluid film. To this end, thrust foil bearings are equipped with thin metal plates inclined relative to the rotating body. The thin metal plates are provided so as to be flexible in the axial direction, and form a fluid film together with the rotating body, forming wedge-shaped flow passages to increase the internal pressure of the fluid film. Patent Document 1 discloses a thrust foil bearing equipped with multiple top foil pieces as the above-mentioned thin metal plates and multiple back foil pieces that elastically support the multiple top foil pieces. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2020-037975 Summary of the Invention [Problem to be solved by the invention]

[0005] Each back foil piece is fixed to the base plate by spot welding or via an outer ring that supports the back foil piece. In the former case, the number of parts and manufacturing steps tends to increase. On the other hand, in the latter case, the inner peripheral portion tends to lift up and come into contact with the rotating body.

[0006] The present disclosure has been made in consideration of the above-mentioned circumstances, and aims to provide a thrust foil bearing that can suppress unnecessary contact with a rotating body. [Means for solving the problem]

[0007] A thrust foil bearing according to one aspect of the present disclosure comprises a base plate having a shaft insertion hole, a plurality of top foil pieces arranged around the insertion hole, and a top foil including a support portion that supports each of the top foil pieces from its outer periphery, each of the top foil pieces including a tab extending to its inner periphery, the support portion being attached to the base plate, and the tab being attached to the base plate by a fastening member inserted into a through hole formed in the base plate.

[0008] The base plate may have a recess in which the tab is placed. The recess may be formed in an annular shape centered on the center of the insertion hole. The fastening member may be a rivet. The through hole may be formed as a counterbore hole in which an end of the fastening member is received. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to provide a thrust foil bearing that can suppress unnecessary contact with a rotating body. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a side view of an example of a turbomachine to which a thrust foil bearing according to an embodiment of the present disclosure is applied. [Figure 2] FIG. 1 is a side view of an example of a thrust foil bearing according to an embodiment of the present invention. [Figure 3] FIG. 1 is a front view of an example of a thrust foil bearing according to an embodiment of the present invention. [Figure 4A] FIG. 2 is a front view of the base plate according to the embodiment. [Figure 4B]4B is a cross-sectional view of the through-hole of the base plate shown in FIG. 4A and its surroundings when viewed from the radially inner side. [Figure 5A] FIG. 2 is a front view of the back foil according to the embodiment. [Figure 5B] FIG. 2 is a front view of the back foil piece according to the embodiment. [Figure 5C] FIG. 10 is a side view showing a state in which the back foil piece is attached to the base plate together with the top foil piece. [Figure 6A] FIG. 2 is a front view of the top foil according to the embodiment. [Figure 6B] FIG. 2 is a perspective view of a top foil piece according to the embodiment. [Figure 7A] FIG. 10 is a front view of a base plate according to a first modified example of the embodiment. [Figure 7B] 7B is a cross-sectional view of the recess shown in FIG. 7A when viewed from the circumferential direction. FIG. [Figure 7C] FIG. 10 is a front view of a base plate according to a second modified example of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, several embodiments of the present disclosure will be described. Note that common parts in each drawing are given the same reference numerals, and duplicated explanations will be omitted. For convenience of explanation, the axial direction Z, the circumferential direction CD, the rotational direction TD, and the radial direction RD will be defined.

[0012] The axial direction Z is the extension direction of the rotation center axis 8 (see Figure 1). The rotation center axis 8 is, for example, the central axis of the rotating body, the shaft 2 or the thrust collar 4, and is a reference axis for determining the position of each component in the thrust foil bearing 5 according to this embodiment. The circumferential direction CD is a circumferential direction centered on the rotation center axis 8. The rotation direction TD is the rotation direction of the shaft 2 and coincides with one direction of the circumferential direction CD. Furthermore, the radial direction RD is a direction that starts at the rotation center axis 8 and extends on a plane perpendicular to the rotation center axis 8.

[0013] First, an overview of the thrust foil bearing 5 according to this embodiment will be described. Fig. 1 is a side view of an example of a turbomachine 1 to which the thrust foil bearing 5 according to this embodiment is applied. As shown in Fig. 1, the turbomachine 1 includes a shaft 2, an impeller 3, a thrust collar 4, a pair of thrust foil bearings 5, 5, a radial foil bearing 6, and a housing 7 that accommodates these.

[0014] The shaft 2 is rotatably supported by a radial foil bearing 6. The impeller 3 is attached to the end of the shaft 2 and is housed in the housing 7 with a gap formed between it and the housing 7. The thrust collar 4 is a disk having a predetermined thickness in the axial direction Z, and is fixed to the shaft 2. Therefore, the shaft 2, impeller 3, and thrust collar 4 rotate integrally about the central rotation axis 8.

[0015] The thrust collar 4 is sandwiched between a pair of thrust foil bearings 5, 5. This limits the range of movement of the thrust collar 4 along the axial direction Z. The pair of thrust foil bearings 5, 5 are fixed to the housing 7 by bolts 51 with a tubular sleeve (spacer) 50 sandwiched between them.

[0016] FIG. 2 is a side view of an example of a thrust foil bearing 5 according to this embodiment. FIG. 3 is a front view of an example of a thrust foil bearing 5 according to this embodiment. FIG. 3 shows a top foil 20 with a portion thereof omitted. As shown in these figures, the thrust foil bearing 5 includes a base plate 10, a top foil 20, and a back foil 30. The top foil 20 is disposed so as to face the thrust collar 4, and the back foil 30 is disposed between the top foil 20 and the base plate 10. The top foil 20 and the back foil 30 are both attached to the base plate 10.

[0017] The top foil 20 includes a plurality of top foil pieces 21 arranged around the insertion hole 12. The back foil 30 includes a plurality of back foil pieces 31 arranged around the insertion hole 12. The top foil pieces 21 cover the back foil pieces 31. The back foil pieces 31 are provided between the top foil pieces 21 and the base plate 10, and elastically support the top foil pieces 21.

[0018] When the thrust collar 4 is stopped from rotating, it is placed in a state where it can come into contact with the top foil piece 21. When the thrust collar 4 starts to rotate, it rotates while intermittently or continuously rubbing against the top foil piece 21. At this time, the rotation of the thrust collar 4 causes fluid to flow into the wedge-shaped flow passage 9 formed between them, and the pressure within the passage increases.

[0019] As the rotational speed of the thrust collar 4 increases and the pressure further increases, the top foil 20 bends toward the back foil 30 and moves away from the thrust collar 4. As a result, a continuous fluid film is formed in the circumferential direction CD between the thrust collar 4 and the top foil piece 21, and the thrust collar 4 begins to rotate without contacting the top foil piece 21.

[0020] When the pressure in the flow path 9 fluctuates due to the thrust force of the thrust collar 4, the deflection of the top foil piece 21 changes according to the fluctuating pressure. The back foil piece 31 supports the top foil piece 21 to prevent the top foil piece 21 from deflecting excessively. This maintains an appropriate gap between the top foil piece 21 and the thrust collar 4, and enables the thrust collar 4 to be supported without contact.

[0021] Next, each component of the thrust foil bearing 5 according to this embodiment will be described. Fig. 4A is a front view of the base plate 10 according to this embodiment. Fig. 4B is a cross-sectional view of the through hole 15 of the base plate 10 shown in Fig. 4A and its surroundings when viewed from the radially inner side (i.e., from the position of the rotation center axis 8). For ease of explanation, Fig. 4B also shows the rivet 40 and the tab 26 of the top foil piece 21.

[0022] The base plate 10 is a flat metal plate that is perpendicular to the central axis of rotation 8. The thickness of the base plate 10 is arbitrary. The outer shape of the base plate 10 is, for example, a circle as shown in FIG. 4A. However, the outer shape of the base plate 10 is not limited to a circle and may be, for example, a rectangle.

[0023] The base plate 10 has a flat surface 11 facing the thrust collar 4. An insertion hole 12 is formed in the flat surface 11, through which the shaft 2 is inserted. The insertion hole 12 passes through the base plate 10 in the axial direction Z, centered on the central rotation axis 8. Furthermore, a plurality of through holes 13 are formed in the flat surface 11. Bolts 51 are inserted into these through holes 13. Each through hole 13 is formed in an outer peripheral region 14 of the flat surface 11. The outer peripheral region 14 is an area on which the outer ring 32 of the back foil 30 and the outer ring 22 of the top foil 20 (see FIG. 6A) are placed.

[0024] As shown in FIG. 4A , a plurality of through holes 15 are provided around the insertion hole 12 in the base plate 10. The through holes 15 are provided at equal intervals in the circumferential direction CD to align with the positions of the mounting holes 27 (see FIG. 6A ) formed in the tab 26. Therefore, the number of through holes 15 is equal to the number of top foil pieces 21. For example, if the number of top foil pieces 21 is six, the number of through holes 15 is also six, and the through holes 15 are provided in the circumferential direction CD at angular intervals of 60° around the rotation central axis 8. A shank 42 of a rivet 40 serving as a fastening member is inserted into the through hole 15. Note that the fastening member is not limited to the rivet 40 shown in FIG. 4B . For example, the fastening member may be a screw (not shown) and a nut (not shown). In this case, the screw is inserted into the through hole 15 so that its head is positioned on the flat surface 11 side.

[0025] As shown in FIG. 4B , the through hole 15 extends in the axial direction Z and penetrates the base plate 10. The through hole 15 is, for example, a countersunk hole as shown in FIG. 4B . In this case, the through hole 15 is composed of a small diameter portion 15a and a large diameter portion 15b that communicate with each other. The small diameter portion 15a opens to the flat surface 11. The small diameter portion 15a has an inner diameter that is larger than the diameter of the shank 42 of the rivet 40 and smaller than the head 41 of the rivet 40. On the other hand, the large diameter portion 15b opens to the surface opposite the flat surface 11. The large diameter portion 15b has an inner diameter that is larger than the inner diameter of the small diameter portion 15a and that allows plastic deformation of the tip 42a of the shank 42 at the large diameter portion 15b.

[0026] The tip 42a of the shank 42 is enlarged by plastic deformation due to impact or the like. If the through hole 15 is a countersunk hole, the enlarged tip 42a fits within the large diameter portion 15b. This prevents the rivet 40 from interfering with a member located on the opposite side of the flat surface 11. However, if it is acceptable for the plastically deformed tip 42a to be exposed from the opposite side of the flat surface 11, the inner diameter of the through hole 15 may be constant.

[0027] Fig. 5A is a front view of the back foil 30 according to this embodiment. Fig. 5B is a front view of the back foil piece 31 according to this embodiment. Fig. 5C is a side view showing the back foil piece 31 attached to the base plate 10 together with the top foil piece 21.

[0028] The back foil 30 is formed of a flexible metal sheet. As shown in Fig. 5A, the back foil 30 includes a plurality of back foil pieces 31 arranged around the insertion hole 12 and an outer ring 32 supporting each back foil piece 31. The back foil pieces 31 are arranged at intervals in the circumferential direction CD. The number of back foil pieces 31 is, for example, six. In this case, the back foil pieces 31 are arranged at angular intervals of 60° around the central rotation axis 8.

[0029] 5A, the back foil piece 31 has a generally fan-shaped outer shape with an arc-shaped notch at the top side when viewed from the axial direction Z. The outer shape of the back foil piece 31 when viewed from the axial direction Z is the same as or slightly smaller than the outer shape of the top foil piece 21. In either case, when the top foil 20 and the back foil 30 are attached to the base plate 10, the back foil piece 31 is covered by the top foil piece 21.

[0030] 5A and 5B, the back foil piece 31 has an inner peripheral edge portion 31a, an outer peripheral edge portion 31b, and side edge portions 31c and 31d that are spaced apart in the circumferential direction CD and extend substantially in the radial direction RD. The side edge portion 31d is located on the rear side of the back foil piece 31 in the rotational direction TD and extends from one end of the peripheral edge portion 31a to one end of the peripheral edge portion 31b. On the other hand, the side edge portion 31c is located on the front side of the back foil piece 31 in the rotational direction TD and extends from the other end of the peripheral edge portion 31a to the outer ring 32. The area surrounded by the peripheral edges 31a and 31b and the side edges 31c and 31d forms the above-mentioned substantially fan-shaped outer shape.

[0031] The back foil piece 31 also includes a bump portion 34 and a band portion 35. As will be described later, the bump portion 34 is a portion having a corrugated cross-sectional shape. On the other hand, the band portion 35 is located in front of the bump portion 34 in the rotation direction TD, and is connected to and supports the bump portion 34. The band portion 35 extends radially outward to form a side edge portion 31c, and is connected to the outer ring 32. The bump portion 34 is cantilevered by the band portion 35.

[0032] 5B and 5C, the bump portion 34 is a flexible corrugated plate including peaks 34a and valleys 34b arranged alternately in the circumferential direction CD or a tangential direction thereto. The peaks 34a are portions that protrude toward the pad portion 24 of the top foil piece 21 so as to be able to come into contact with the pad portion 24. The valleys 34b connect the peaks 34a, 34a on both sides in the arrangement direction and are provided so as to be able to come into contact with the flat surface 11 of the base plate 10. When the peaks 34a are pressed toward the base plate 10, the peaks 34a elastically deform in the arrangement direction of the peaks 34a and valleys 34b while supporting the pad portion 24. Meanwhile, the valleys 34b come into contact with the flat surface 11 and support the peaks 34a.

[0033] Of the multiple peaks 34a, peak 34c is located furthest forward in the rotational direction TD. Peak 34c extends substantially in the radial direction RD. The other peaks 34a also extend parallel to peak 34c. As shown in FIG. 5C , the height of the peaks 34a along the axial direction Z increases as they are positioned further forward in the rotational direction TD. Due to this increase in height, the top foil piece 21 is inclined relative to the flat surface 11 of the base plate 10 so that the distance between the top foil piece 21 and the flat surface 11 increases (in other words, the distance between the top foil piece 21 and the thrust collar 4 decreases) as it moves forward in the rotational direction TD. This inclination of the top foil piece 21 forms a wedge-shaped flow path 9 (see FIG. 2 ) between the top foil piece 21 and the thrust collar 4.

[0034] 5B, multiple slits 36 may be formed in the bump portion 34. The multiple slits 36 have different radii of curvature around the central axis of rotation 8 and extend from the boundary between the bump portion 34 and the band portion 35 to the side edge portion 31d. In other words, the multiple slits 36 divide the bump portion 34 into multiple arc-shaped small pieces aligned in the radial direction RD. By forming the slits 36, it is possible to impart flexibility to the peak portions 34a according to their positions in the radial direction RD.

[0035] As shown in Fig. 5A, the outer ring 32 surrounds a group of multiple back foil pieces 31 arranged in the circumferential direction CD while maintaining a predetermined distance between the multiple back foil pieces 31 in the radial direction RD. The outer ring 32 supports the back foil pieces 31 via band portions 35. The outer ring 32 is formed with multiple through holes 33 through which bolts 51 are inserted. The positions of the through holes 33 correspond to the positions of the through holes 13 (see Fig. 4A) formed in the base plate 10.

[0036] FIG. 6A is a front view of the top foil 20 according to this embodiment. FIG. 6B is a perspective view of the top foil piece 21 according to this embodiment. The top foil 20 is formed of a flexible thin metal plate. As shown in FIG. 6A, the top foil 20 includes a plurality of top foil pieces 21 arranged around the insertion hole 12 and an outer ring 22 as a support portion that supports each of the top foil pieces 21. The top foil pieces 21 are arranged at intervals in the circumferential direction CD and cover the corresponding back foil pieces 31. The number of top foil pieces 21 is the same as the number of back foil pieces 31, for example, six. In this case, the top foil pieces 21 are arranged at angular intervals of 60° around the central axis of rotation 8.

[0037] As shown in FIG. 6A , the top foil piece 21 has a generally fan-shaped outer shape with an arc-shaped notch at the top side when viewed from the axial direction Z. The top foil piece 21 has an inner peripheral edge 21a, an outer peripheral edge 21b, and side edge portions 21c and 21d that extend in the radial direction RD and are spaced apart in the circumferential direction CD. The side edge portion 21c is located on the front side of the top foil piece 21 in the rotational direction TD and extends from one end of the peripheral edge portion 21a to one end of the peripheral edge portion 21b. Meanwhile, the side edge portion 21d is located on the rear side of the top foil piece 21 in the rotational direction TD and extends from the other end of the peripheral edge portion 21a to the outer ring 22. The area surrounded by the peripheral edges 21a and 21b and the side edge portions 21c and 21d forms the generally fan-shaped outer shape described above.

[0038] The top foil piece 21 also includes a pad portion 24, a band portion 25, and a tab 26. The band portion 25 is located rearward of the pad portion 24 in the rotation direction TD, and is connected to and supports the pad portion 24. The band portion 25 extends radially outward to form a side edge portion 21d, and is connected to the outer ring 22. The band portion 25 also faces the flat surface 11 of the base plate 10 and is capable of coming into contact with the flat surface 11.

[0039] The tab 26 is a small strip-shaped piece that extends from the peripheral edge portion 21a toward the inner periphery of the top foil piece 21. For example, the tab 26 extends a predetermined length radially inward from the strip portion 25 and is placed on the flat surface 11. This predetermined length is set to a value that prevents the tab 26 from being exposed in the insertion hole 12 when the top foil 20 is placed on the flat surface 11.

[0040] 6B, a mounting hole 27 is formed in the tab 26. The position of the mounting hole 27 corresponds to the position of the through-hole 15 (see FIG. 4A) formed in the base plate 10. The diameter of the mounting hole 27 is larger than the diameter of the shank 42 of the rivet 40 and smaller than the diameter of the head of the rivet 40.

[0041] The pad portion 24 extends in the circumferential direction CD (rotational direction TD) from the band portion 25 to the side edge portion 21c. The pad portion 24 is cantilevered by the band portion 25. In other words, the side edge portion 21c is provided as a free end of the pad portion 24, and the portion 21e of the pad portion 24 that connects to the band portion 25 (see FIG. 6B) is provided as a fixed end of the pad portion 24. The pad portion 24 covers the corresponding back foil piece 31.

[0042] The pad portion 24 comes into contact with the tops of the ridges 34a of the back foil piece 31 (see FIG. 5C). As a result, the pad portion 24 is inclined at an angle according to the arrangement and height of the ridges 34a. This inclination of the pad portion 24 forms a wedge-shaped flow path 9 between the top foil 20 and the thrust collar 4 (see FIG. 2).

[0043] 6B, portion 21e of pad portion 24, which connects to band portion 25, may have an inclination angle greater than the inclination angle determined by contact with peaks 34a. By providing portion 21e, the height of pad portion 24 can be adjusted, and pad portion 24 can be made to approximately coincide with the imaginary inclined plane connecting the tops of peaks 34a. In this embodiment, a bend is present between portion 21e and band portion 25, and between portion 21e and the rest of pad portion 24 excluding portion 21e.

[0044] As shown in Fig. 6A, the outer ring 22 surrounds a group of top foil pieces 21 arranged in the circumferential direction CD while maintaining a predetermined distance between the top foil pieces 21 in the radial direction RD. As described above, the belt portions 25 of the top foil pieces 21 are connected to the outer ring 22. In this way, the outer ring 22 supports the top foil pieces 21. A plurality of through holes 23, through which bolts 51 are inserted, are formed in the outer ring 22. The position of each through hole 23 corresponds to the position of the through hole 13 (see Fig. 4A) formed in the base plate 10.

[0045] The outer ring 22, together with the outer ring 32 of the back foil 30, is placed on the base plate 10. At this time, the through holes 23 of the outer ring 22 and the through holes 33 of the outer ring 32 are aligned with the through holes 13 of the base plate 10. Thereafter, the bolts 51 are screwed into the housing 7 through the through holes 13, 23, and 33.

[0046] 2 , for example, when the bolt 51 is tightened, the sleeve 50 presses the outer ring 22 of the top foil 20 and the outer ring 32 of the back foil 30 toward the base plate 10. This pressing attaches the top foil 20 and the back foil 30 to the base plate 10. In other words, the top foil piece 21 is attached to the base plate 10 via the outer ring 22 on its outer periphery, preventing the top foil 20 from falling off the base plate 10. Furthermore, at least the outer peripheral portion of the top foil piece 21 can be prevented from excessively separating from the base plate 10.

[0047] The outer ring 22 may be divided into a plurality of arcuate portions so as to support only the corresponding top foil pieces 21. In this case, a through hole 23 is formed in each arcuate portion.

[0048] The top foil piece 21 according to this embodiment is also attached to the base plate 10 at its inner circumferential side. That is, as shown in FIG. 4B , the tab 26 of the top foil piece 21 is fixed to the base plate 10 by a rivet 40. Specifically, the shank 42 of the rivet 40 is inserted into the small diameter portion 15a via the attachment hole 27 provided in the tab 26. By inserting the shank 42 into the through-hole 15 from the flat surface 11 side, the tip 42a of the shank 42 is exposed in the large diameter portion 15b. The tip 42a exposed in the large diameter portion 15b is expanded by plastic deformation due to the impact and fits within the large diameter portion 15b. As a result, the tab 26 is clamped between the head 41 of the rivet 40 and the flat surface 11 and attached to the base plate 10.

[0049] The rotation speed of the thrust collar 4 slows as it approaches the central axis of rotation 8. Therefore, the internal pressure in the flow path 9 generated when the thrust collar 4 rotates also tends to decrease as it approaches the central axis of rotation 8. If the inner peripheral portion of the top foil piece 21 (pad portion 24) becomes excessively separated from the base plate 10 due to insufficient pressure or vibration, and the pressing force of the fluid against that portion is insufficient, that portion will likely come into contact with the thrust collar 4, causing unnecessary wear to that portion and reducing bearing performance.

[0050] However, the top foil piece 21 is attached to the base plate 10 on its inner circumferential side by a fastening member such as a rivet 40. Therefore, the inner circumferential portion of the top foil piece 21 (pad portion 24) does not become excessively separated from the base plate 10, and unnecessary wear of this portion can be suppressed. In other words, the durability of the thrust foil bearing 5 can be improved, and a decrease in performance as a bearing can also be suppressed.

[0051] FIG. 7A is a front view of a base plate 10 according to a first modified example of this embodiment. The recess 16 of this embodiment is formed on the surface of the base plate 10 on which the top foil piece 21 is placed, and has a bottom when viewed in the axial direction. FIG. 7B is a cross-sectional view of the recess 16 shown in FIG. 7A as viewed from the circumferential direction. FIG. 7C is a front view of a base plate 10 according to a second modified example of this embodiment. As shown in these figures, the base plate 10 may have a recess 16 on which a tab 26 is placed. The recess 16 is formed at a position on the flat surface 11 corresponding to the position of the tab 26. As shown in FIG. 7B, the tab 26 is bent so as to be in surface contact with the bottom surface 16a of the recess 16. The dimensions of the recess 16 are arbitrary as long as the tab 26 can be in surface contact with the bottom surface 16a of the recess 16. For example, the recess 16 may or may not reach the inner circumferential surface 12a of the insertion hole 12.

[0052] As described above, the head 41 of the rivet 40 rests on the tab 26. Meanwhile, to maintain non-contact support of the thrust collar 4 (see FIG. 2 ) by the thrust foil bearing 5, the head 41 must be lower than the side edge 21c of the top foil piece 21 when viewed in the circumferential direction CD. For this reason, the head 41 tends to be thin. However, if the head 41 is made excessively thin, it will no longer be able to maintain the required mechanical strength. Therefore, the recess 16 is formed in the flat surface 11 to lower the position of the head 41. This allows the mechanical strength of the head 41 to be increased without interfering with the thrust collar 4.

[0053] 7C, the recess 16 may be formed in a ring shape centered on the center of the insertion hole 12. In this case, it is not necessary to form the recess 16 only at each of the predetermined positions spaced apart, and therefore the processing step of the recess 16 can be simplified.

[0054] The present disclosure is not limited to the above-described embodiments, but is defined by the claims, and includes all modifications within the meaning and scope equivalent to the claims. [Explanation of symbols]

[0055] 1. Turbomachinery 2 shafts 3 impeller 4 Thrust Collar 5 Thrust foil bearing 6 Radial foil bearings 7. Housing 8 Rotational axis 9 Flow path 10 Base Plate 12 Insertion hole 15 through holes 20 Top Foil 21 Top foil piece 22 outer ring 26 tabs 30 Back Foil 31 Back foil piece 32 outer ring 40 Rivet (fastening member)

Claims

1. a base plate provided with a shaft insertion hole; a top foil including a plurality of top foil pieces arranged around the insertion hole and support portions that support each of the top foil pieces from an outer periphery thereof; Equipped with Each of the top foil pieces includes a tab extending inwardly therefrom; the support is attached to the base plate; The tab is attached to the base plate by a fastening member inserted into a through hole formed in the base plate. Thrust foil bearing.

2. The base plate has a recess in which the tab is placed.

2. The thrust foil bearing according to claim 1.

3. The recess is formed in an annular shape centered on the center of the insertion hole.

3. A thrust foil bearing according to claim 2.

4. The fastening member is a rivet.

2. The thrust foil bearing according to claim 1.

5. The through hole is formed as a counterbore hole in which the end of the fastening member is received. A thrust foil bearing according to any one of claims 1 to 4.

Images