Thrust foil bearing

Abstract

To provide a thrust foil bearing that can suppress unnecessary contact with a rotor.SOLUTION: A thrust foil bearing 5 includes: a baseplate 10 provided with a through hole 12 for a shaft 2; and a top foil 20 including a plurality of top foil pieces 21 disposed around the through hole 12 and connected to one another on the outer peripheral side thereof and disposed to the baseplate 10. The top foil pieces 21 are fitted to the baseplate 10 on both outer peripheral side and inner peripheral side thereof.SELECTED DRAWING: Figure 2

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. A thrust foil bearing supports a rotating body without contact by forming a fluid film between the bearing and the rotating body. The rotating body moves finely in the axial direction of the rotating body due to vibration, shock, etc.

[0003] Regardless of such minute movements of the rotating body, the thrust foil bearing needs to maintain the formation of a fluid film. For this reason, the thrust foil bearing is provided with a metal sheet inclined relative to the rotating body. The metal sheet is provided so as to be flexible in the axial direction, forms a fluid film together with the rotating body, and forms a wedge-shaped flow passage for increasing the internal pressure of the fluid film. Patent Document 1 discloses a thrust foil bearing that includes a plurality of top foil pieces as the above-mentioned metal sheet, and a plurality of back foil pieces that elastically support the plurality of top foil pieces. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-037975 A Summary of the Invention [Problem to be solved by the invention]

[0005] When the rotation speed of the rotor is low, no fluid film is formed and the rotor comes into contact with the top foil piece. Even when the rotation speed of the rotor is high and a fluid film is formed, the rotor temporarily comes into contact with the top foil piece if it receives a large axial impact. In other words, the top foil piece is basically prone to wear due to the operational characteristics of the thrust foil bearing.

[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 embodiment of the present disclosure comprises a base plate having a shaft insertion hole, and a top foil arranged on the base plate, the top foil including a plurality of top foil pieces arranged around the insertion hole and connected to each other on their outer circumferential sides, the plurality of top foil pieces being attached to the base plate on their outer circumferential sides and inner circumferential sides.

[0008] Each of the top foil pieces may include a locking portion provided on its inner periphery, protruding toward the base plate, and locking to the base plate. The locking portion may be provided on a side edge portion extending from the inner periphery side of each of the top foil pieces toward the outer periphery side. The locking portion may be provided on a peripheral portion located on the inner periphery side of each of the top foil pieces. A tip of the locking portion may be folded as a return portion. The locking portion may protrude while being inclined toward the top foil piece on which the locking portion is provided. Effect of the Invention

[0009] According to the present disclosure, it is possible to provide a thrust foil bearing capable of suppressing unnecessary contact with a rotating body. [Brief description 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. [Diagram 2] FIG. 2 is a side view of an example of a thrust foil bearing according to the present embodiment. [Figure 3A] FIG. 2 is a front view of a base plate according to a first example of the present embodiment. [Figure 3B] 3B is a diagram of the groove of the base plate shown in FIG. 3A as viewed from the radially inner side. FIG. [Figure 4A] FIG. 2 is a front view of a back foil according to a first example of the present embodiment. [Figure 4B] FIG. 2 is a front view of a back foil piece according to a first example of the present embodiment. [Figure 4C] 11 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. FIG. [Figure 5A] FIG. 2 is a front view of a top foil according to a first example of the present embodiment. [Figure 5B] FIG. 2 is a perspective view of a top foil piece according to a first example of the present embodiment. [Figure 5C] 5C is an enlarged view of a portion of the top foil piece shown in FIG. 5B when viewed from a radial direction. [Figure 6A] FIG. 11 is a perspective view of a top foil piece according to a second example of the present embodiment. [Figure 6B] 6B is an enlarged view of a portion of the top foil piece shown in FIG. 6A as viewed from a radial direction. FIG. [Figure 7A] FIG. 11 is a front view of a base plate according to a second example of the present embodiment. [Figure 7B] 7B is a cross-sectional view of the groove portion shown in FIG. 7A when viewed from the circumferential direction. [Figure 8] 13 is a view showing a locking portion and a groove portion according to a third example of the present embodiment as viewed from a radial direction. FIG. [Figure 9] 13 is a cross-sectional view of a locking portion and a groove portion according to a fourth example of the present embodiment, as viewed from the circumferential direction. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, several embodiments of the present disclosure will be described. In addition, the same reference numerals are given to common parts in each drawing, 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 are defined.

[0012] The axial direction Z is the extension direction of the central rotation axis 8 (see FIG. 1). The central rotation 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 central rotation axis 8. The rotation direction TD is the rotation direction of the shaft 2 and coincides with one direction of the circumferential direction CD. The radial direction RD is a direction that starts from the central rotation axis 8 and extends on a plane perpendicular to the central rotation axis 8.

[0013] First, an overview of a thrust foil bearing 5 according to this embodiment will be described. Fig. 1 is a side view of an example of a turbo machine 1 to which the thrust foil bearing 5 according to this embodiment is applied. Fig. 2 is a side view of an example of the thrust foil bearing 5 according to this embodiment. As shown in Fig. 1, the turbo machine 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 accommodated in the housing 7 with a gap formed between the impeller 3 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] 2, each thrust foil bearing 5 includes a base plate 10, a top foil 20, and a back foil 30. The top foil 20 is disposed on the base plate 10 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. Both the top foil 20 and the back foil 30 are attached to the base plate 10.

[0017] The top foil 20 includes a plurality of top foil pieces 21 (see FIG. 5A) that are arranged around the insertion hole 12 and are connected to each other on the outer periphery side. The back foil 30 includes a plurality of back foil pieces 31 (see FIG. 4A) that are arranged around the insertion hole 12. The back foil pieces 31 are provided between the top foil piece 21 and the base plate 10, and elastically support the top foil piece 21.

[0018] When the thrust collar 4 is stopped 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 inside the flow 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 passage 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 so that the top foil piece 21 does not deflect excessively. This maintains an appropriate gap between the top foil piece 21 and the thrust collar 4, and makes it possible to maintain non-contact support of the thrust collar 4.

[0021] Next, each configuration of the thrust foil bearing 5 according to this embodiment will be described. FIG. 3A is a front view of the base plate 10 according to a first example of this embodiment. FIG. 3B is a view of the groove portion 15 of the base plate 10 shown in FIG. 3A as viewed from the radial inside (i.e., from the position of the rotation center axis 8). The base plate 10 is a metal flat plate perpendicular to the rotation center axis 8. The base plate 10 has a thickness (e.g., 5 to 8 mm) that is equal to or greater than the length of the locking portion 26 (see FIG. 3B) of the top foil piece 21 along the axial direction Z. The outer shape of the base plate 10 is, for example, a circle as shown in FIG. 3A. However, the outer shape of the base plate 10 is not limited to a circle, and may be, for example, a rectangle.

[0022] 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 axis of rotation 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. 5A) are placed.

[0023] As shown in Fig. 3A, a plurality of grooves (slits) 15 are provided around the insertion hole 12 in the base plate 10. The plurality of grooves 15 are provided at equal intervals in the circumferential direction CD in accordance with the positions of the top foil pieces 21 (see Fig. 3B) of the top foil 20. The number of grooves 15 is equal to the number of top foil pieces 21. For example, when the number of top foil pieces 21 is six, the number of grooves 15 is also six, and the grooves 15 are provided at angular intervals of 60° in the circumferential direction CD around the rotation central axis 8.

[0024] The width of the groove 15 along the circumferential direction CD is set to a value that allows the locking portion 26 to be inserted into the groove 15. The width of the locking portion 26 after insertion may be greater than the width of the groove 15. In this case, the locking portion 26 is locked in the groove 15 by elastically deforming the locking portion 26 and inserting it into the groove 15. The groove 15 extends from the inner circumferential surface 12a toward the outer circumferential side of the base plate 10 by a length equal to or greater than the width of the locking portion 26. The extension direction of the groove 15 is parallel to the side edge portion 21d of the top foil piece 21 placed on the flat surface 11. The locking portion 26 of the top foil piece 21 is inserted into the groove 15. Therefore, the depth of the groove 15 along the axial direction Z is greater than the length of the locking portion 26 (see FIG. 5B) along the axial direction Z. For example, the groove 15 may penetrate the base plate 10 in the axial direction Z.

[0025] 3B, the groove 15 is formed by inner surfaces 15a and 15b facing each other in the circumferential direction CD. With respect to the internal space of the groove 15 as a reference, the inner surface 15a is located in front of the rotation direction TD, and the inner surface 15b is located in the rear of the rotation direction TD. The inner surface 15a extends parallel to the side edge portion 21d of the top foil piece 21.

[0026] The inner surface 15a has a step 16. The step 16 is provided to engage the return portion 26a of the engagement portion 26. The length of the step 16 along the circumferential direction CD is preferably longer than the length of the return portion 26a along the same direction. In this case, excessive biasing by the return portion 26a against the inner surface 15a can be avoided, and unnecessary distortion of the entire engagement portion 26 can be suppressed. The step 16 may be provided on the inner surface 15b. In this case, the return portion 26a is formed by bending the tip of the engagement portion 26 toward the inner surface 15b. The return portion 26a may be attached in contact with the step 16, or the return portion 26a may be attached between the steps 16 with a slight play.

[0027] Fig. 4A is a front view of the back foil 30 according to the first example of the present embodiment. Fig. 4B is a front view of the back foil piece 31 according to the first example of the present embodiment. Fig. 4C is a side view showing a state in which the back foil piece 31 is attached to the base plate 10 together with the top foil piece 21.

[0028] The back foil 30 is formed of a flexible thin metal plate. As shown in Fig. 4A, 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 of the back foil pieces 31. The back foil pieces 31 are arranged at intervals in the circumferential direction CD. The number of the 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 axis of rotation 8.

[0029] 4A, the back foil piece 31 has a generally sector-shaped outer shape with a circular arc cut out at the top side when viewed from the axial direction Z. Also, 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] 4A and 4B, the back foil piece 31 has an inner peripheral edge 31a, an outer peripheral edge 31b, and side edges 31c and 31d that are spaced apart in the circumferential direction CD and extend in the radial direction RD. The side edge 31d is located on the rear side of the back foil piece 31 in the rotation direction TD and extends from one end of the peripheral edge 31a to one end of the peripheral edge 31b. On the other hand, the side edge 31c is located on the front side of the back foil piece 31 in the rotation direction TD and extends from the other end of the peripheral edge 31a to the outer ring 32. The portion surrounded by the peripheral edges 31a and 31b and the side edges 31c and 31d forms the above-mentioned approximately sector-shaped outer shape.

[0031] The back foil piece 31 also includes a bump portion 34 and a band portion 35. As 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] As shown in Figures 4B and 4C, the bump portion 34 is a flexible corrugated plate including peaks 34a and valleys 34b arranged alternately in the circumferential direction CD or in the tangential direction thereof. 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 are portions that 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] Among the multiple peaks 34a, the peak 34c is located at the front end in the rotation direction TD. The peak 34c extends in the radial direction RD. The other peaks 34a also extend parallel to the peak 34c. As shown in FIG. 4C, the height of the peaks 34a along the axial direction Z is higher as they are positioned further forward in the rotation direction TD. Due to this increase in height, the top foil piece 21 covering the back foil piece 31 is inclined with respect 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 rotation direction TD. Due to this inclination of the top foil piece 21, a wedge-shaped flow path 9 (see FIG. 2) is formed between the top foil piece 21 and the thrust collar 4.

[0034] 4B, 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 portion 34a according to each position in the radial direction RD.

[0035] As shown in Fig. 4A, the outer ring 32 surrounds a group of a plurality of back foil pieces 31 arranged in the circumferential direction CD while being spaced apart from the plurality of 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 a plurality of through holes 33 through which bolts 51 are inserted. The positions of the respective through holes 33 correspond to the positions of the through holes 13 (see Fig. 3A) formed in the base plate 10.

[0036] FIG. 5A is a front view of the top foil 20 according to the first example of this embodiment. The top foil 20 is formed of a flexible thin metal plate. As shown in FIG. 5A, the top foil 20 includes a plurality of top foil pieces 21 arranged around the insertion hole 12, and an outer ring 22 supporting 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 the top foil pieces 21 is the same as the number of the back foil pieces 31, for example, six pieces. In this case, the top foil pieces 21 are arranged at angular intervals of 60° around the rotation central axis 8.

[0037] As shown in FIG. 5A, the top foil piece 21 has a substantially sector-shaped outer shape with a top side cut out by a circular arc when viewed from the axial direction Z. The top foil piece 21 has an inner peripheral edge portion 21a, an outer peripheral edge portion 21b, and side edges 21c and 21d extending in the radial direction RD at an interval in the circumferential direction CD. The side edge portion 21c is located on the front side of the top foil piece 21 in the rotation direction TD and extends from one end of the peripheral edge portion 21a to one end of the peripheral edge portion 21b. On the other hand, the side edge portion 21d is located on the rear side of the top foil piece 21 in the rotation direction TD and extends from the other end of the peripheral edge portion 21a to the outer ring 22. The portion surrounded by the peripheral edges 21a and 21b and the side edges 21c and 21d forms the above-mentioned substantially sector-shaped outer shape. The peripheral edge portion 21a of each top foil piece 21 forms a through hole 27 centered on the central rotation axis 8 and having a diameter equal to or larger than the inner diameter of the insertion hole 12. Therefore, the peripheral edge portion 21a faces the shaft 2 with a gap therebetween.

[0038] The top foil 20 is formed with a slit 28 for forming the top foil piece 21. The slit 28 extends from the through hole 27 in the approximately radial direction RD so as to form one side edge portion 21c and the other side edge portion 21d of the top foil pieces 21, 21 adjacent to each other in the circumferential direction CD. The slit 28 further extends rearward in the rotation direction TD so as to form the peripheral edge portion 21b and the inner peripheral edge 22a of the outer ring 22. That is, the portion of the slit 28 extending in the approximately radial direction RD is constituted by the one side edge portion 21c and the other side edge portion 21d of the top foil pieces 21, 21 adjacent to each other in the circumferential direction CD. The portion of the slit 28 extending in the circumferential direction CD is constituted by the peripheral edge portion 21b of the top foil piece 21 and the inner peripheral edge 22a of the outer ring 22 located radially outward therefrom.

[0039] The top foil piece 21 includes a pad portion 24 and a band portion 25. As described later, the pad portion 24 is a portion that forms a wedge-shaped flow path 9. On the other hand, the band portion 25 is a portion that is located behind the pad portion 24 in the rotation direction TD, is connected to the pad portion 24, 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 width of the band portion 25 in the circumferential direction CD is smaller than each width of the outer ring 22 and the outer circumferential side of the top foil piece 21. In other words, the band portion 25 includes a constricted portion 25a that is connected to the outer ring 22.

[0040] The belt portion 25 faces the flat surface 11 of the base plate 10 and is capable of contacting the flat surface 11. However, the belt portion 25 is not fixed or fastened to the flat surface 11 by welding or screwing. In other words, the belt portion 25 (side edge portion 21c) is placed in a state in which it can be separated in the axial direction Z.

[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 a portion 21e (see FIG. 5B) of the pad portion 24 that is connected to the band portion 25 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 peaks 34a of the back foil piece 31 (see FIG. 4C). As a result, the pad portion 24 is inclined at an angle according to the arrangement and height of the peaks 34a. Due to this inclination of the pad portion 24, a wedge-shaped flow passage 9 is formed between the top foil 20 and the thrust collar 4.

[0043] 5B, part 21e of pad portion 24 that connects to band portion 25 may have an inclination angle larger than the inclination angle determined by contact with peaks 34a. By providing part 21e, the height of pad portion 24 can be adjusted, and pad portion 24 can be made to substantially coincide with an imaginary inclined plane that connects the tops of peaks 34a.

[0044] As shown in Fig. 5A, the outer ring 22 surrounds a group of the top foil pieces 21 arranged in the circumferential direction CD while being spaced apart from the multiple 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. That is, the multiple top foil pieces 21 are connected to one another via the outer ring 22. In this way, the outer ring 22 supports the top foil pieces 21. The outer ring 22 is formed with multiple through holes 23 through which bolts 51 are inserted. The position of each through hole 23 corresponds to the position of the through hole 13 (see Fig. 3A) 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. Then, 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 fixes 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, and the top foil 20 is prevented from falling off the base plate 10. In addition, at least the outer periphery side portion of the top foil piece 21 can be prevented from being excessively separated from the base plate 10.

[0047] Fig. 5B is a perspective view of the top foil piece 21 according to a first example of this embodiment. Fig. 5C is an enlarged view of a part of the top foil piece 21 shown in Fig. 5B when viewed from the radial direction RD. The top foil piece 21 according to this embodiment is attached to the base plate 10 also at its inner periphery side. For example, as shown in Fig. 5B, the top foil piece 21 includes a locking portion 26 provided on its inner periphery side. The locking portion 26 protrudes toward the base plate 10 and locks onto the base plate 10.

[0048] The locking portion 26 is a small strip-shaped piece that protrudes from the inner peripheral portion of the side edge portion 21d toward the base plate 10. The locking portion 26 has a predetermined width from the inner peripheral side to the outer peripheral side of the top foil 20. The width of the locking portion 26 is arbitrary as long as the desired mechanical strength is obtained, and is set to a value of, for example, about 1 / 5 of the length of the side edge portion 21d.

[0049] As shown in Fig. 5B, the locking portion 26 is located at the innermost side of the side edge portion 21d. However, the position of the locking portion 26 may be shifted toward the outer periphery side from the position shown in Fig. 5B. In other words, the position of the locking portion 26 is arbitrary as long as it can prevent the inner periphery side portion of the top foil piece 21 from being inadvertently rolled up.

[0050] As shown in FIG. 5C, the tip of the locking portion 26 is formed as a turned portion 26a. The turned portion 26a is formed by bending the tip of the locking portion 26. In this embodiment, the angle of bending is an acute angle. That is, in this embodiment, the portion from the bend toward the tip side of the locking portion 26 extends toward the mounting surface side of the base plate 10. In particular, in this embodiment, the tip of the locking portion 26 extends toward the mounting surface side of the base plate 10. Here, the mounting surface of the base plate 10 is the surface of the base plate on which the top foil piece 21 is arranged. The tip may be bent forward in the rotation direction TD or backward in the rotation direction TD. In the former case, the tip is bent toward the band portion 25, for example, as shown in FIG. 5C.

[0051] The locking portion 26 is inserted into a groove portion 15 formed in the base plate 10. Meanwhile, a step 16 is formed on an inner surface 15a of the groove portion 15 facing the return portion 26a. Therefore, when the locking portion 26 is inserted into the groove portion 15, the return portion 26a gets caught on this step 16, and the locking portion 26 is locked in the groove portion 15. This prevents the locking portion 26 from coming off the groove portion 15, and prevents the inner peripheral portion of the top foil piece 21 from being excessively separated from the base plate 10.

[0052] The inventor of the present disclosure has studied a case where the top foil 20 does not include the locking portion 26 and is fixed to the base plate 10 only by the outer ring 22 that connects the multiple top foil pieces 21. The results of this study have revealed that wear is likely to occur in the inner peripheral portion of the top foil piece 21. The presumed cause is as follows. That is, the rotation speed of the thrust collar 4 is slower as it approaches the rotation center axis 8. Therefore, the internal pressure of the flow path 9 generated when the thrust collar 4 rotates is likely to be lower as it approaches the rotation center axis 8. On the other hand, if there is a shortage of pressure or vibration, the inner peripheral portion of the top foil piece 21 (pad portion 24) is likely to be excessively separated from the base plate 10. In other words, if the pressing force of the fluid against the inner peripheral portion is insufficient, the portion is likely to come into contact with the thrust collar 4. In this case, it is considered that unnecessary wear of the portion progresses and the performance as a bearing is deteriorated.

[0053] In contrast, the top foil piece 21 of this embodiment is attached to the base plate 10 at its inner periphery by engaging the top foil piece 21 itself (for example, the engaging portion 26 in the groove portion 15). Therefore, the inner periphery portion of the top foil piece 21 (pad portion 24) does not become excessively separated from the base plate 10, and unnecessary wear of that 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.

[0054] Fig. 6A is a perspective view of a top foil piece 21 according to a second example of this embodiment. Fig. 6B is an enlarged view of a part of the top foil piece 21 shown in Fig. 6A when viewed from the radial direction. As shown in Fig. 6A, the position of the locking portion 26 in the second example is different from that in the first example. That is, in the top foil piece 21 according to the second example, the locking portion 26 is provided on the peripheral portion 21a located on the inner circumferential side of the top foil piece 21.

[0055] When the top foil 20 placed on the base plate 10 is viewed from the axial direction Z, if the peripheral edge portion 21a overlaps with the inner peripheral surface 12a of the insertion hole 12, i.e., if the peripheral edge portion 21a and the inner peripheral surface 12a are located on the same circle, the locking portion 26 protrudes from a portion of the peripheral edge portion 21a that is included in the band portion 25 toward the base plate 10. That is, the locking portion 26 extends in the axial direction Z along the inner peripheral surface 12a of the insertion hole 12.

[0056] When the top foil 20 placed on the base plate 10 is viewed from the axial direction Z, and the peripheral portion 21a is located radially outward from the inner surface 12a of the insertion hole 12, that is, when the diameter of an imaginary circle including the peripheral portion 21a is larger than the diameter of the insertion hole 12, the engagement portion 26 first extends radially inward along the flat surface 11 from the portion of the peripheral portion 21a that is included in the band portion 25, and then extends in the axial direction Z along the inner surface 12a of the insertion hole 12.

[0057] Similar to the locking portion 26 according to the first example (see FIG. 5C), the tip of the locking portion 26 according to the second example is also formed as a turned portion 26a. As shown in FIG. 6B, the turned portion 26a is formed by bending the tip of the locking portion 26 toward the band portion 25.

[0058] FIG. 7A is a front view of the base plate 10 according to a second example of this embodiment. FIG. 7B is a cross-sectional view of the groove portion 15 shown in FIG. 7A when viewed from the circumferential direction. As shown in these figures, the position of the groove portion 15 in the second example is different from that in the first example. That is, in the second example, the groove portion 15 is formed on the inner circumferential surface 12a of the insertion hole 12. In this case, the groove portion 15 is formed at a position facing the return portion 26a on the inner circumferential surface 12a. The groove portion 15 has a height in the axial direction Z, a width in the circumferential direction CD, and a depth in the radial direction RD that can accommodate the return portion 26a. The groove portion 15 may be dotted in the circumferential direction CD as shown in FIG. 7A, or may be formed in a ring shape centered on the rotation central axis 8.

[0059] Also in the second example, the top foil piece 21 is attached to the base plate 10 at its inner circumferential side by, for example, engaging the engaging portion 26 with the groove portion 15. This makes it possible to suppress the progress of localized wear of the top foil piece 21 as described above, thereby improving the durability of the thrust foil bearing 5. It is also possible to suppress the deterioration of the performance as a bearing.

[0060] 8 is a view of the locking portion 26 and the groove portion 15 according to a third example of this embodiment as viewed from the radial direction RD. The third example is a modified example of the first example. That is, although the positions of the locking portion 26 and the groove portion 15 in the third example are similar to those in the first example, their shapes are different.

[0061] 8, the locking portion 26 according to the third example does not have a turned portion 26a. Instead, the locking portion 26 according to the third example protrudes from a side edge portion 21d of the top foil piece 21 while inclining toward the top foil piece 21 on which the locking portion 26 is provided. However, both of the inner surfaces 15a and 15b are flat surfaces without a step 16.

[0062] The angle θ between the locking portion 26 and the band portion 25 is set to an acute angle at which the locking portion 26 is locked in the groove portion 15. Such a value is, for example, 45° to 60°. However, the angle θ is not limited to the exemplified value. The width of the locking portion 26 approximately along the radial direction RD can be the width described in the first example.

[0063] Meanwhile, groove 15 according to the third example is also inclined with respect to flat surface 11 so that locking portion 26 is locked. That is, inner surfaces 15a, 15b forming groove 15 according to the third example face each other and extend from flat surface 11 toward the inside of base plate 10 in a direction parallel to locking portion 26. Locking portion 26 comes into contact with and is locked to inner surface 15a. Therefore, in a cross section viewed from the radial inside, groove 15 is inclined with respect to flat surface 11 at the same angle θ as the inclination angle of locking portion 26.

[0064] The depth of the groove 15 according to the third example is set to a value capable of accommodating the locking portion 26. As long as this condition is satisfied, the groove 15 may extend from the flat surface 11 to a position inside the base plate 10, or may penetrate the base plate 10. The width of the groove 15 approximately along the radial direction RD can be the same as that described in the first example.

[0065] 9 is a cross-sectional view of the locking portion 26 and the groove portion 15 according to a fourth example of this embodiment, as viewed in the circumferential direction CD. The fourth example is a modified example of the second example. The positions of the locking portion 26 and the groove portion 15 in the fourth example are similar to those in the second example, but the shapes of the locking portion 26 and the groove portion 15 are different.

[0066] As shown in FIG. 9, the locking portion 26 according to the fourth example does not have a return portion 26a. Instead, the locking portion 26 according to the fourth example inclines toward the top foil piece 21 (band portion 25) on which the locking portion 26 is provided, and protrudes from a portion of the peripheral portion 21a of the top foil piece 21 that is included in the band portion 25. The angle θ formed by the locking portion 26 and the band portion 25 is set to an acute angle at which the locking portion 26 is locked in the groove portion 15. Such a value is, for example, 45° to 60°. However, the angle θ is not limited to the exemplified value. The width of the locking portion 26 along the approximately radial direction RD can be the width described in the first example.

[0067] On the other hand, the groove portion 15 according to the fourth example is formed at a position facing the locking portion 26 on the inner circumferential surface 12a of the insertion hole 12. The groove portion 15 extends in the axial direction Z from an edge portion 12b of the inner circumferential surface 12a that is connected to the flat surface 11. It has a width in the circumferential direction CD and a length in the axial direction Z that can accommodate the locking portion 26. However, the depth of the groove portion 15 along the radial direction RD increases the farther it is from the flat surface 11. In other words, the bottom surface 15c of the groove portion 15 is inclined with respect to the flat surface 11 so that the locking portion 26 contacts and is locked to the bottom surface 15c. Moreover, the bottom surface 15c of the groove portion 15 is inclined with respect to the flat surface 11 at the same angle θ as the inclination angle of the locking portion 26.

[0068] The length of the groove 15 along the axial direction Z is set to a value capable of accommodating the locking portion 26. As long as this condition is satisfied, the length of the groove 15 may be equal to the thickness of the base plate 10 or may be shorter than the thickness of the base plate 10.

[0069] The top foil piece 21 according to each example of this embodiment is attached to the base plate 10 via an outer ring 22 that supports the top foil piece 21 on its outer periphery. Also, the top foil piece 21 is attached to the base plate 10 on its inner periphery by the structure of the top foil piece 21 itself (e.g., the locking portion 26). That is, unlike this embodiment, a welding process or attachment parts such as screws are not essential when attaching the top foil piece to the base plate. (Note that this description does not exclude the use of a welding process or attachment parts such as screws.) Also, because the inner periphery side of the top foil piece 21 is attached to the base plate, unnecessary contact with the rotating body can be suppressed.

[0070] Furthermore, in the third and fourth examples, the locking portion 26 and the groove portion 15 are inclined at the same angle, and the locking portion 26 is locked while contacting the inner surface 15a or the bottom surface of the groove portion 15. Therefore, the manufacturing process for forming the return portion 26a can be omitted. Regarding the groove portion 15, the process for forming a step on the inner surface 15a (15b) can also be omitted.

[0071] The present disclosure is not limited to the above-described embodiment, but is defined by the claims, and includes all modifications within the meaning and scope equivalent to the claims. [Explanation of symbols]

[0072] Reference Signs List 1... turbomachine, 2... shaft, 3... impeller, 4... thrust collar, 5... thrust foil bearing, 6... radial foil bearing, 7... housing, 8... central rotating shaft, 9... flow path, 10... base plate, 11... flat surface, 12... insertion hole, 13... through hole, 15... groove portion (slit), 16... step, 20... top foil, 21... top foil piece, 22... outer ring, 23... through hole, 24... pad portion, 25... band portion, 26... engagement portion, 26a... return portion, 28... slit, 30... back foil, 31... back foil piece, 32... outer ring, 33... through hole, 34... bump portion, 35... band portion, 36... slit

Claims

1. A base plate having a shaft insertion hole; a top foil including a plurality of top foil pieces arranged around the insertion hole and connected to each other on an outer circumferential side thereof, the top foil being arranged on the base plate; Equipped with The plurality of top foil pieces are attached to the base plate at their outer and inner periphery sides. Thrust foil bearing.

2. Each of the top foil pieces includes a locking portion that is provided on an inner periphery thereof, protrudes toward the base plate, and is locked to the base plate.

2. A thrust foil bearing according to claim 1.

3. The locking portion is provided on a side edge portion extending from an inner periphery side to an outer periphery side of each of the top foil pieces.

3. A thrust foil bearing according to claim 2.

4. The locking portion is provided on a peripheral portion located on an inner peripheral side of each of the top foil pieces.

3. A thrust foil bearing according to claim 2.

5. The tip of the locking portion is bent as a return portion.

5. A thrust foil bearing according to claim 3 or 4.

6. The locking portion protrudes while being inclined toward the top foil piece on which the locking portion is provided.

5. A thrust foil bearing according to claim 3 or 4.

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