Thrust foil bearing

Abstract

To provide a thrust foil bearing capable of suppressing unnecessary contact with a rotor.SOLUTION: A thrust foil bearing comprises: a base plate 10 having the insertion hole for a shaft, and including an annular step part 15 surrounding the insertion hole; a fixing member 40 attached to the step part 15; and a top foil 20 arranged on the base plate 10. The top foil 20 includes a plurality of top foil pieces 21 arranged around the insertion hole, connected to each other on an outer peripheral side, and attached to the base plate 10, each top foil piece 21 including a tab part 26 extending from the top foil piece to the step part 15 and pressed against the step part 15 by the fixing member 40.SELECTED DRAWING: Figure 6B

Description

Technical Field

[0001] The present disclosure relates to a thrust foil bearing.

Background Art

[0002] A thrust foil bearing is a type of fluid bearing. The thrust foil bearing supports a rotating body in a non-contact manner by forming a fluid film between the rotating body. The rotating body moves finely in the axial direction of the rotating body due to vibration, impact, etc.

[0003] Regardless of such fine movement of the rotating body, the thrust foil bearing needs to maintain the formation of the fluid film. Therefore, the thrust foil bearing includes a metal thin plate inclined with respect to the rotating body. The metal thin plate 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 path for increasing the internal pressure of the fluid film. Patent Document 1 discloses a thrust foil bearing including a plurality of top foil pieces as the above-described metal thin plate 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

Summary of the Invention

Problems to be Solved by the Invention

[0005] While the rotation speed of the rotating body is low, a fluid film is not formed, and the rotating body contacts the top foil piece. Further, even when the rotation speed of the rotating body is high and a fluid film is formed, when a large axial impact is received, the rotating body temporarily contacts the top foil piece. That is, the top foil piece is basically easy to wear due to the operating characteristics of the thrust foil bearing.

[0006] The present disclosure has been made in view of the above circumstances, and an object thereof is to provide a thrust foil bearing capable of suppressing unnecessary contact with a rotating body.

Means for Solving the Problems

[0007] A thrust foil bearing according to an aspect of the present disclosure includes a base plate provided with an insertion hole for a shaft and including an annular stepped portion surrounding the insertion hole, a fixing member attached to the stepped portion, and a top foil disposed on the base plate. The top foil includes a plurality of top foil pieces disposed around the insertion hole and connected to each other on the outer peripheral side thereof and attached to the base plate. Each of the top foil pieces includes a tab portion extending from the top foil piece to the stepped portion and pressed against the stepped portion by the fixing member.

[0008] The stepped portion may be connected to the inner peripheral surface of the insertion hole. The fixing member may be formed in an annular shape having the same shape as the stepped portion. The fixing member may be a nut that can be screwed onto a threaded component passing through the stepped portion and the tab portion.

Advantages 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

Figure 2

Figure 3A

Figure 3B

Figure 4A

Figure 4B

Figure 5A

Figure 5B

Figure 5C

Figure 6A

Figure 6B

Figure 6C

Figure 7

MODE FOR CARRYING OUT THE INVENTION

[0011] Hereinafter, some embodiments of the present disclosure will be described. In the drawings, the same reference numerals are given to the common parts, and the overlapping explanations are omitted. For convenience of explanation, the axial direction Z, the circumferential direction CD, the rotation direction TD, and the radial direction RD are defined.

[0012] The axial direction Z is the extending direction of the rotation center axis 8 (see FIG. 1). The rotation center axis 8 is, for example, the center axis of the shaft 2 or the thrust collar 4 which is a rotating body, and is a reference axis for determining the positions of the respective components in the thrust foil bearing 5 according to the present embodiment. The circumferential direction CD is the 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. Further, the radial direction RD is a direction extending on a plane orthogonal to the rotation center axis 8 starting from the rotation center axis 8.

[0013] First, the outline 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. 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 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 houses these components.

[0014] The shaft 2 is rotatably supported by the radial foil bearing 6. The impeller 3 is attached to an 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, the impeller 3, and the thrust collar 4 rotate integrally about the rotation center axis 8.

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

[0016] As shown in FIG. 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. 6A) that are arranged around the insertion hole 12 and are connected to each other on the outer peripheral side thereof. The back foil 30 includes a plurality of back foil pieces 31 (see FIG. 5A) that are arranged around the insertion hole 12. The back foil piece 31 is provided between the top foil piece 21 and the base plate 10 and elastically supports the top foil piece 21.

[0018] When the rotation of the thrust collar 4 stops, the thrust collar 4 is placed in a state where it can contact the top foil piece 21. When the thrust collar 4 starts to rotate, the thrust collar 4 rotates while intermittently or continuously rubbing against the top foil piece 21. At this time, due to the rotation of the thrust collar 4, fluid flows into the wedge-shaped flow path 9 formed between the two, and the pressure in the flow path rises.

[0019] When the rotation speed of the thrust collar 4 increases and the pressure further rises, the top foil 20 deflects toward the back foil 30 and moves away from the thrust collar 4. As a result, a fluid film continuous in the circumferential direction CD is formed between the thrust collar 4 and the top foil piece 21, and the thrust collar 4 starts to rotate non-contactly with respect to 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 pressure after the fluctuation. The back foil piece 31 supports the top foil piece 21 so that the top foil piece 21 does not deflect excessively. Thereby, an appropriate interval between the top foil piece 21 and the thrust collar 4 can be maintained, and the thrust collar 4 can be maintained to be supported non-contactly.

[0021] Next, each component of the thrust foil bearing 5 according to the present embodiment will be described. FIG. 3A is a front view of the base plate 10 according to the present embodiment. FIG. 3B is a cross-sectional view of the stepped portion 15 when viewed from the circumferential direction CD according to the present embodiment. The base plate 10 is a flat metal plate orthogonal to the rotation center axis 8. The outer shape of the base plate 10 when viewed from the axial direction Z is, for example, circular as shown in FIG. 3A. However, the outer shape of the base plate 10 is not limited to circular, and may be, for example, rectangular.

[0022] The base plate 10 has a flat surface 11 facing the thrust collar 4. An insertion hole 12 through which the shaft 2 is inserted is formed in the flat surface 11. The insertion hole 12 penetrates the base plate 10 in the axial direction Z about the rotation center axis 8. Further, 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 the outer peripheral region 14 of the flat surface 11. Note that the outer peripheral region 14 is a region where the outer ring 32 of the back foil 30 and the outer ring 22 of the top foil 20 (see FIG. 6A) are placed.

[0023] As shown in FIG. 3A, the base plate 10 includes a stepped portion 15 surrounding the insertion hole 12. The stepped portion 15 is formed in an annular shape about the rotation center axis 8 and is recessed from the flat surface 11 along the axial direction Z in a direction away from the thrust collar 4. A fixing member 40 (see FIG. 4A) described later is attached to the stepped portion 15.

[0024] As shown in FIG. 3B, the stepped portion 15 has an annular surface 15a and an inner peripheral surface 15b. The annular surface 15a is an annular surface facing the fixing member 40 in the axial direction Z. That is, the annular surface 15a extends radially outward from the inner peripheral surface 12a of the insertion hole 12 and extends in the circumferential direction CD about the rotation center axis 8. That is, the stepped portion 15 shown in FIG. 3B is connected to the inner peripheral surface 12a of the insertion hole 12. On the other hand, the inner peripheral surface 15b is a cylindrical surface facing the fixing member 40 in the radial direction RD. That is, the inner peripheral surface 15b extends in the axial direction Z from the outer edge of the annular surface 15a to the inner edge of the flat surface 11 and extends in the circumferential direction CD about the rotation center axis 8.

[0025] The depth D1 of the stepped portion 15 along the axial direction Z is set to a value such that the fixing member 40 (see FIG. 4A) attached to the stepped portion 15 does not physically interfere with the thrust collar 4. For example, the depth D1 is set to a value equal to or greater than the thickness T1 of the fixing member 40 along the axial direction Z. The width W1 of the stepped portion 15 along the radial direction RD is set to a value such that the fixing member 40 attached to the stepped portion 15 does not physically interfere with the shaft 2. For example, the width W1 is set to a value equal to or greater than the width W2 of the fixing member 40 along the radial direction RD.

[0026] A plurality of through holes 17 are formed in the annular surface 15a. The through holes 17 are provided at locations other than the location where the tab portion 26 (see FIGS. 6A and 6B) of the top foil piece 21 is placed on the annular surface 15a. The through holes 17 penetrate the base plate 10 along the axial direction Z. A screwing component 45 (see FIG. 6B) is inserted into the through holes 17 from the back surface 16 side of the base plate 10. The screwing component 45 is a member having a shaft portion with a thread groove formed at least on the outer peripheral surface, and is, for example, a male screw or a bolt. The screwing component 45 inserted into the through hole 17 is screwed into the screw hole 41 of the fixing member 40.

[0027] The number of the through holes 17 is arbitrary as long as the fixing member 40 can appropriately press the tab portion 26 against the stepped portion 15 (in other words, the fixing member 40 and the stepped portion 15 can appropriately sandwich the tab portion 26 therebetween) so that the displacement of the tab portion 26 does not occur. For example, as shown in FIG. 3A, six through holes 17 are provided in the circumferential direction CD at an angular interval of 60°.

[0028] FIG. 4A is a front view of the fixing member 40 according to the present embodiment. FIG. 4B is a cross-sectional view of the fixing member 40 when viewed from the circumferential direction CD. As shown in FIG. 4A, the fixing member 40 is formed in an annular shape similar to the stepped portion 15. The inner diameter of the fixing member 40 is larger than the diameter (outer diameter) of the shaft 2. For example, the inner diameter of the fixing member 40 is equal to the diameter (inner diameter) of the insertion hole 12 of the base plate 10. Further, the outer diameter of the fixing member 40 is set to a value equal to or less than the diameter (inner diameter) of the inner peripheral surface 15b of the stepped portion 15. Note that the term "annular" includes not only a seamless circular ring as in the present embodiment but also a case where there is a cut in a part of the circular ring. Further, it includes a shape in which the inner and outer circumferences are not perfect circles and bulge or sink radially RD from the circle partially. Since the fixing member 40 is annular, in the present embodiment, each tab portion 26 extending from each top foil 20 toward the stepped portion 15 can be collectively sandwiched between the fixing member 40 and the stepped portion 15.

[0029] As shown in FIG. 4B, the cross-section of the fixing member 40 has a rectangular cross-sectional shape similar to the cross-sectional shape of the stepped portion 15. And, as shown in FIG. 4B, a screw hole 41 is formed in the fixing member 40 at a position corresponding to the through hole 17. The shaft portion of the screwing component 45 is screwed into this screw hole 41.

[0030] The thickness T1 of the fixing member 40 along the axial direction Z is set to a value that does not physically interfere with the thrust collar 4 in a state where the fixing member 40 is attached to the stepped portion 15. For example, the thickness T1 is set to a value equal to or less than the depth D1 of the stepped portion 15 along the axial direction Z. The width W2 of the fixing member 40 along the radial direction RD is set to a value that does not physically interfere with the shaft 2 in a state where the fixing member 40 is attached to the stepped portion 15. For example, the width W1 is set to a value equal to or less than the width W1 of the stepped portion 15 along the radial direction RD.

[0031] The fixing member 40 is installed on the stepped portion 15 and fixed to the stepped portion 15 by screwing with a screwing component 45 (see FIG. 6B). The fixing member 40 fixed to the stepped portion 15 collectively presses a plurality of tab portions 26 placed on the annular surface 15a toward the annular surface 15a. In other words, the fixing member 40, together with the stepped portion 15, collectively sandwiches a plurality of tab portions 26 located therebetween.

[0032] FIG. 5A is a front view of the back foil 30 according to the present embodiment. FIG. 5B is a front view of the back foil piece 31 according to the present embodiment. FIG. 5C is a side view showing a state where the back foil piece 31 is attached to the base plate 10 together with the top foil piece 21.

[0033] The back foil 30 is formed of a flexible thin metal plate. 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 that supports 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 an angular interval of 60° about the rotation center axis 8.

[0034] As shown in FIG. 5A, the back foil piece 31 has a substantially fan-shaped outer shape with the top side cut out in an arc when viewed from the axial direction Z. Also, the outer shape of the back foil piece 31 when viewed from the axial direction Z matches or is 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.

[0035] As shown in FIGS. 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 extend in a substantially radial direction RD at intervals in the circumferential direction CD. The side edge portion 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 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 rotation direction TD and extends from the other end of the peripheral edge portion 31a to the outer ring 32. The portion surrounded by the peripheral edge portions 31a and 31b and the side edge portions 31c and 31d forms the above-described substantially fan-shaped outer shape.

[0036] Further, the back foil piece 31 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 rotational direction TD, is connected to the bump portion 34, and supports the bump portion 34. The band portion 35 extends radially outward so as to form a side edge portion 31c and is connected to the outer ring 32. The bump portion 34 is cantilevered and supported by the band portion 35. In the present embodiment, the bump portion 34 is arranged at a position that does not overlap the stepped portion 15 in the axial direction.

[0037] As shown in FIGS. 5B and 5C, the bump portion 34 is a flexible corrugated plate including peak portions 34a and valley portions 34b that are alternately arranged in the circumferential direction CD or its tangential direction. The peak portion 34a is a portion that protrudes so as to be able to contact the pad portion 24 of the top foil piece 21. The valley portion 34b is a portion that connects the peak portions 34a, 34a on both sides in the arrangement direction and is provided so as to be able to contact the flat surface 11 of the base plate 10. When the peak portion 34a is pressed toward the base plate 10, the peak portion 34a elastically deforms in the arrangement direction of the peak portion 34a and the valley portion 34b while supporting the pad portion 24. On the other hand, the valley portion 34b contacts the flat surface 11 and supports the peak portion 34a.

[0038] Among the plurality of peak portions 34a, the peak portion 34c is located most forward in the rotational direction TD. The peak portion 34c extends substantially in the radial direction RD. The other peak portions 34a also extend parallel to the peak portion 34c. Further, as shown in FIG. 5C, the height of the peak portion 34a along the axial direction Z is higher for those located forward in the rotational direction TD. Due to such an 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 such that the distance from the flat surface 11 increases (in other words, the distance from the thrust collar 4 decreases) as it goes forward in the rotational 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.

[0039] As shown in FIG. 5B, a plurality of slits 36 may be formed in the bump portion 34. The plurality of slits 36 have different radii of curvature from each other around the rotation center axis 8 and extend from the boundary between the bump portion 34 and the belt portion 35 to the side edge portion 31d. That is, the plurality of slits 36 divide the bump portion 34 into a plurality of arc-shaped pieces arranged in the radial direction RD. By forming the slits 36, flexibility can be imparted to the mountain portion 34a according to each position in the radial direction RD.

[0040] As shown in FIG. 5A, the outer ring 32 surrounds a group of a plurality of back foil pieces 31 arranged in the circumferential direction CD with a predetermined interval in the radial direction RD with respect to the plurality of back foil pieces 31. The outer ring 32 supports the back foil pieces 31 via the belt portion 35. A plurality of through holes 33 through which bolts 51 are inserted are formed in the outer ring 32. 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.

[0041] FIG. 6A is a front view of the top foil 20 according to the present 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 that supports each top foil piece 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 an angular interval of 60° around the rotation center axis 8.

[0042] As shown in FIG. 6A, the top foil piece 21 has a substantially fan-shaped outer shape with an arc-notch at the top side 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 edge portions 21c, 21d that extend in the radial direction RD at intervals 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. On the other hand, 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 portion surrounded by the peripheral edge portions 21a, 21b and the side edge portions 21c, 21d forms the above-described substantially fan-shaped outer shape. The peripheral edge portion 21a of each top foil piece 21 forms a through-hole 27 having a diameter equal to or larger than the inner diameter of the insertion hole 12 with the rotation center axis 8 as the center. Therefore, the peripheral edge portion 21a faces the shaft 2 with a gap therebetween.

[0043] The top foil 20 is formed with a slit 28 for forming the top foil piece 21. The slit 28 extends substantially in the radial direction RD from the through-hole 27 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 rotational 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 that extends substantially in the radial direction RD is constituted by 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. Also, the portion of the slit 28 that extends 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 outside thereof.

[0044] The top foil piece 21 includes a pad portion 24 and a band portion 25. As will be described later, the pad portion 24 is a portion that forms the wedge-shaped flow path 9. On the other hand, the band portion 25 is located behind the pad portion 24 in the rotational direction TD, and is a portion that connects to and supports the pad portion 24. The band portion 25 extends radially outward so as to form a side edge portion 21d, and connects to the outer ring 22. The width of the band portion 25 along the circumferential direction CD is smaller than the widths of the outer ring 22 and the outer peripheral side of the top foil piece 21. That is, the band portion 25 includes a constricted portion 25a that connects to the outer ring 22.

[0045] The band portion 25 faces the flat surface 11 of the base plate 10 and can contact the flat surface 11. However, the band portion 25 is not fixed or fastened to the flat surface 11 by welding or screwing. That is, the band portion 25 (side edge portion 21c) is placed in a state where it can be separated in the axial direction Z.

[0046] 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. That is, the side edge portion 21c is provided as a free end of the pad portion 24, and a portion 21e (see FIG. 6B) of the pad portion 24 that connects to the band portion 25 is provided as a fixed end of the pad portion 24. The portion 21e gradually separates from the flat surface 11 of the base plate 10 as it goes from the band portion 25 toward the pad portion 24 along the rotational direction TD. Therefore, the portion 21e forms a stepped structure that connects the band portion 25 and the pad portion 24. In other words, the pad portion 24 is connected to the band portion 25 via the bent portion 21e.

[0047] The pad portion 24 covers the corresponding back foil piece 31. The pad portion 24 contacts the top of the peak portion 34a of the back foil piece 31 (see FIG. 5C). As a result, the pad portion 24 inclines at an angle corresponding to the arrangement and height of the peak portion 34a. Due to the inclination of the pad portion 24, a wedge-shaped flow path 9 is formed between the top foil 20 and the thrust collar 4.

[0048] As shown in FIG. 6B, among the pad portions 24, the portion 21e connecting to the belt portion 25 may have an inclination angle larger than the inclination angle determined by the contact with the peak portion 34a. By providing this portion 21e, the height of the pad portion 24 can be adjusted, and the pad portion 24 can be made to substantially coincide with a virtual inclined surface connecting the tops of the respective peak portions 34a.

[0049] As shown in FIG. 6A, the outer ring 22 surrounds a group of top foil pieces 21 arranged in the circumferential direction CD while being spaced apart from the plurality of top foil pieces 21 by a predetermined interval in the radial direction RD. As described above, the belt portion 25 of the top foil piece 21 is connected to the outer ring 22. That is, the plurality of top foil pieces 21 are connected to each other via the outer ring 22. Thereby, 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. 3A) formed in the base plate 10.

[0050] The outer ring 22 is placed on the base plate 10 together with the outer ring 32 of the back foil 30. At this time, the through hole 23 of the outer ring 22 and the through hole 33 of the outer ring 32 are aligned with the through hole 13 of the base plate 10. Thereafter, the bolt 51 is screwed into the housing 7 through the through holes 13, 23, and 33.

[0051] For example, in the case of the form shown in FIG. 2, by tightening the bolt 51, 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. By this pressing, the top foil 20 and the back foil 30 are fixed to the base plate 10. That is, the top foil pieces 21 are attached to the base plate 10 via the outer ring 22 on the outer peripheral side thereof. Thereby, the top foil 20 is prevented from falling off the base plate 10. Also, at least the portion on the outer peripheral side of the top foil piece 21 can be prevented from excessively separating from the base plate 10.

[0052] FIG. 6B is a perspective view of the top foil piece 21 according to the present embodiment. FIG. 6C is an enlarged view of a part of the top foil piece 21 shown in FIG. 6B when viewed from the radial direction RD. The top foil piece 21 according to the present embodiment is also held by the base plate 10 on its inner peripheral side. That is, as shown in FIG. 6B, the top foil piece 21 includes a tab portion 26 provided on its inner peripheral side. The tab portion 26 extends from the top foil piece 21 to the stepped portion 15 and is pressed against the stepped portion 15 by the fixing member 40.

[0053] The tab portion 26 of the present embodiment is a strip-shaped small piece that protrudes radially inward from a portion included in the band portion 25 of the peripheral edge portion 21a. The length of the tab portion 26 along the radial direction RD is set to a value that reaches between the fixing member 40 and the annular surface 15a of the stepped portion 15. In other words, the length of the tab portion 26 is set to a value that is pressed against the annular surface 15a of the stepped portion 15 by the fixing member 40 (clamped by the fixing member 40 and the stepped portion 15). The width of the tab portion 26 along the circumferential direction CD is arbitrary as long as the tab portion 26 is properly clamped by the fixing member 40 and the stepped portion 15. The width of the tab portion 26 may be set to a value equal to or less than the width of the band portion 25 along the circumferential direction CD, for example.

[0054] In a state where the fixing member 40 is attached to the stepped portion 15 by the screwing component 45, the tab portion 26 is located between the fixing member 40 and the inner peripheral surface 15b of the stepped portion 15, and between the fixing member 40 and the annular surface 15a of the stepped portion 15. Since the fixing member 40 and the stepped portion 15 have a rectangular cross-sectional shape with respect to the circumferential direction CD, the tab portion 26 has a substantially L-shaped cross-sectional shape between the fixing member 40 and the stepped portion 15 (see FIG. 6C). Note that this substantially L-shaped cross-sectional shape may be formed in advance, or may be formed by attaching the fixing member 40 to the stepped portion 15. That is, in the former case, the tab portion 26 has a substantially L-shaped cross-sectional shape before the fixing member 40 is attached to the stepped portion 15. In the latter case, the tab portion 26 extends on the same plane as the band portion 25 before the fixing member 40 is attached to the stepped portion 15, and is bent by the attachment of the fixing member 40.

[0055] As described above, the tab portion 26 is pressed against the annular surface 15a of the stepped portion 15 by the fixing member 40. As a result, the movement of the tab portion 26 in the radial direction RD is restricted. Also, the movement of the tab portion 26 in the circumferential direction CD is restricted. On the other hand, the top foil piece 21 is attached to the base plate 10 on its outer peripheral side. Therefore, it is possible to prevent the inner peripheral side portion of the top foil piece 21 from being excessively separated from the base plate 10.

[0056] The inventor of the present disclosure examined the case where the top foil 20 does not include the tab portion 26 and is fixed to the base plate 10 only by the outer ring 22 that connects the plurality of top foil pieces 21. According to the result of this examination, it was found that wear is likely to occur in the inner peripheral side portion of the top foil piece 21. The presumed causes are as follows. That is, the rotational 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 tends to be lower as it approaches the rotation center axis 8. On the other hand, if there are circumstances such as insufficient pressure or vibration, the inner peripheral side portion of the top foil piece 21 (pad portion 24) is likely to be excessively separated from the base plate 10. That is, when the pressing force of the fluid against the inner peripheral side portion is insufficient, that portion is likely to come into contact with the thrust collar 4. In this case, it is considered that unnecessary wear of that portion progresses and the performance as a bearing deteriorates.

[0057] On the other hand, in the top foil piece 21 of the present embodiment, since the tab portion 26 is held, it is pressed against the base plate 10 on its inner peripheral side. Therefore, the inner peripheral side portion of the top foil piece 21 (pad portion 24) does not excessively separate from the base plate 10, and it is possible to suppress the progress of unnecessary wear of that portion. That is, the durability of the thrust foil bearing 5 can be improved, and a decrease in the performance as a bearing can also be suppressed.

[0058] FIG. 7 is a diagram showing a modified example of the tab portion 26 and the fixing member 40 according to the present embodiment. As shown in FIG. 7, the through hole 17 may be formed at a location on the annular surface 15a where the tab portion 26 of the top foil piece 21 is placed. In this case, an insertion hole 29 for the screwing component 45 is also formed in the tab portion 26. Therefore, the tab portion 26 is pressed against the stepped portion 15 with the screwing component 45 inserted therethrough.

[0059] Also, as shown in FIG. 7, the fixing member 40 may be a nut that can be individually screwed to each screwing component 45. In this case, each tab portion 26 is individually pressed against the stepped portion 15. The thickness of the nut is set under the same conditions as when the fixing member 40 is formed in an annular shape. Note that the outer shape of the nut is arbitrary and may be hexagonal, square, or other polygonal. Since the nut is an existing component that is widely distributed, the process of forming the fixing member 40 in an annular shape can be omitted, and the cost can be reduced.

[0060] The top foil piece 21 according to each example of the present embodiment is attached to the base plate 10 via an outer ring 22 that supports the top foil piece 21 on its outer peripheral side. Also, the top foil piece 21 is pressed against the base plate 10 by the fixing member 40 on its inner peripheral side. That is, as in the present embodiment, a welding process or mounting components such as screws when attaching the top foil piece to the base plate are not essential. (Note that this description does not exclude the use of a welding process or mounting components such as screws.) Also, since the inner peripheral side of the top foil piece 21 is attached to the base plate, unnecessary contact with the rotating body can be suppressed.

[0061] Note that the stepped portion 15 may be configured as a part of an annular groove portion (not shown) formed in the flat surface 11 concentric with the insertion hole 12. In this case, the groove portion has the annular surface 15a as the bottom surface, and further has an annular inner peripheral surface (not shown) facing the inner peripheral surface 15b in the radial direction RD.

[0062] Note that the present disclosure is not limited to the above-described embodiments, but is shown by the description of the claims, and further includes all changes within the meaning and scope equivalent to the description of the claims.

Description of Reference Numerals

[0063] 1... Turbo machine, 2... Shaft, 3... Impeller, 4... Thrust collar, 5... Thrust foil bearing, 6... Radial foil bearing, 7... Housing, 8... Rotation center axis, 9... Flow path, 10... Base plate, 11... Flat surface, 12... Insertion hole, 12a... Inner peripheral surface, 13... Through hole, 14... Outer peripheral region, 15... Step portion, 15a... Annular surface, 15b... Inner peripheral surface, 16... Rear surface, 17... Through hole, 20... Top foil, 21... Top foil piece, 22... Outer ring, 23... Through hole, 24... Pad portion, 25... Band portion, 26... Tab portion, 27... Through hole, 28... Slit, 29... Insertion hole, 30... Back foil, 31... Back foil piece, 32... Outer ring, 33... Through hole, 34... Bump portion, 35... Band portion, 36... Slit, 40... Fixing member, 41... Screw hole

Claims

1. A base plate provided with an insertion hole for a shaft and including an annular step portion surrounding the insertion hole, A fixing member attached to the step portion, A top foil disposed on the base plate, and comprising: The top foil includes a plurality of top foil pieces disposed around the insertion hole and connected to each other on the outer peripheral side thereof and attached to the base plate, Each of the top foil pieces includes a tab portion that extends from the top foil piece to the step portion and is pressed against the step portion by the fixing member. A thrust foil bearing.

2. The step portion is connected to the inner peripheral surface of the insertion hole. The thrust foil bearing according to claim 1.

3. The fixing member is formed in an annular shape having the same shape as the step portion. The thrust foil bearing according to claim 1.

4. The fixing member is a nut that can be screwed onto a screwing component that penetrates the step portion and the tab portion. The thrust foil bearing according to claim 1.

Images