Thrust foil bearing

Abstract

The present application provides a thrust foil bearing (3) having a base plate (30) having a through hole (30a) for a shaft (1) to pass through, and a support surface (30b) extending in a direction orthogonal to the axial direction of the through hole, a step member (50) placed on the support surface and formed separately from the base plate, and a back foil (20) extending in the circumferential direction of the through hole, and a portion thereof supported by the support surface, and another portion adjacent to the portion in the circumferential direction supported by the step member.

Description

TECHNICAL FIELD

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

[0002] This application claims priority based on Japanese Patent Application No. 2020-159534 filed on September 24, 2020, and the contents thereof are incorporated herein. BACKGROUND

[0003] In the past, as a bearing for a high-speed rotating body, a thrust foil bearing in which a thrust ring provided to a rotating shaft is disposed in opposition has been known (for example, refer to Patent Literature 1 described below). The thrust foil bearing is formed of a foil (a thin plate of metal) whose bearing surface is soft, so as to be able to absorb the movement (axial displacement and inclination of the thrust ring) of the rotating shaft due to vibration and impact, and has a foil structure for softly supporting the bearing surface below the bearing surface.

[0004] In the thrust foil bearing, there is a way in which a plurality of top foils and back foils are arranged in the circumferential direction. The top foils are supported to the back foils, and by the rotation of the thrust ring, a lubricating fluid is introduced between the top foils and the thrust ring. This lubricating fluid forms a wedge-shaped fluid lubrication film between the top foils and the thrust ring, and the load capacity of the thrust foil bearing is exerted.

[0005] PRIOR ART DOCUMENTS

[0006] PATENT LITERATURE

[0007] Patent Literature 1: Japanese Patent No. 6065917 SUMMARY

[0008] PROBLEMS TO BE SOLVED BY THE INVENTION

[0009] However, in the above-described prior art, in order to form a wedge-shaped gap between the top foils and the thrust ring, a back foil of a constant height is provided to an inclined surface formed in the base plate. It is considered that such an inclined surface is formed by cutting processing or the like, but if a certain degree of processing accuracy is not ensured, it is sometimes difficult to form the required fluid lubrication film.

[0010] The present disclosure was completed in view of the above-described circumstances, and aims to improve the load capacity of a thrust foil bearing.

[0011] SOLUTION TO THE PROBLEM

[0012] In order to solve the above-described problem, a thrust foil bearing of one embodiment of the present disclosure has a base plate having a through-hole into which a shaft is inserted and a support surface that expands in a direction orthogonal to the axial direction of the through-hole, a step member that is placed on the support surface and formed separately from the base plate, and a back foil that extends in the circumferential direction of the through-hole and is supported by the support surface at a portion thereof and supported by the step member at another portion adjacent to the portion in the circumferential direction.

[0013] In addition, in the above-described one embodiment of the present disclosure, the step member can also be formed in a step shape.

[0014] In addition, in the above-described one embodiment of the present disclosure, the step member can also be formed by overlapping a plurality of spacers.

[0015] In addition, in the above-described one embodiment of the present disclosure, the plurality of spacers can also include spacers having different thicknesses.

[0016] In addition, in the above-described one embodiment of the present disclosure, the plurality of spacers can also include spacers having different offsets of end surfaces.

[0017] In addition, in the above-described one embodiment of the present disclosure, the plurality of spacers can also include spacers that do not directly support the back foil.

[0018] In addition, in the above-described one embodiment of the present disclosure, a ring member can also be installed to the base plate, and the step member is sandwiched between the base plate and the ring member.

[0019] Inventive Effects

[0020] According to the present disclosure, it is possible to improve the load capacity of a thrust foil bearing. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a side view showing an example of a turbomachinery to which a thrust foil bearing of the present disclosure is applied.

[0022] Figure 2 is a side view showing a thrust foil bearing of the present disclosure.

[0023] Figure 3 is a plan view showing a thrust foil bearing of the first embodiment of the present disclosure.

[0024] Figure 4 is Figure 3 the arrow A-A cross-sectional view shown.

[0025] Figure 5 is a cross-sectional view showing a main part of a thrust foil bearing of the second embodiment of the present disclosure.

[0026] Figure 6 is an explanatory diagram explaining the load capacity of a thrust foil bearing of the second embodiment of the present disclosure.

[0027] Figure 7 is a cross-sectional view showing a main part of a thrust foil bearing of the third embodiment of the present disclosure.

[0028] Figure 8This is a cross-sectional view showing the main part of a thrust foil bearing of a modified embodiment of the present disclosure. Detailed Implementation

[0029] The thrust foil bearing of this disclosure will now be described with reference to the accompanying drawings.

[0030] Figure 1 This is a side view showing an example of a turbomachinery using the thrust foil bearing disclosed herein.

[0031] exist Figure 1 In the diagram, symbol 1 represents a rotating shaft (shaft), symbol 2 represents an impeller located at the front end of the rotating shaft, and symbol 3 represents the thrust foil bearing of this disclosure.

[0032] A circular thrust ring 4 is mounted on the rotating shaft 1. The thrust ring 4 is held between a pair of thrust foil bearings 3. The impeller 2 is disposed within a housing 5, which is the stationary side, with a tip clearance 6 between it and the housing 5. The rotating shaft 1 is supported by radial foil bearings 7.

[0033] Figure 2 This is a side view showing the thrust foil bearing 3 of this disclosure.

[0034] like Figure 2 As shown, a pair of thrust foil bearings 3 are arranged on both sides, sandwiching a thrust ring 4. Both pairs of thrust foil bearings 3 have the same structure. Each thrust foil bearing 3 includes a top foil 10, a back foil 20, and a base plate 30.

[0035] Clamped between the base plates 30 of each of the pair of thrust foil bearings 3 Figure 2 The cylindrical bearing spacer 40 (annular component) is shown by the double-dotted line. Furthermore, these base plates 30 are connected via the bearing spacer 40 by fastening bolts 41. Through holes 42 for inserting the fastening bolts 41 are formed on the outer periphery of the base plate 30. Additionally, one of the thus connected base plates 30 abuts against the housing 5 by tightening the fastening bolts 41.

[0036] Additionally, the portion of housing 5 that abuts against thrust foil bearing 3 is... Figure 1 The middle part is omitted.

[0037] (First Implementation)

[0038] Figure 3 This is a top view showing the thrust foil bearing 3 according to the first embodiment of this disclosure. Figure 4 yes Figure 3 The arrow AA is shown in the cross-sectional view.

[0039] like Figure 3 As shown, the base plate 30 has an insertion hole 30a for the rotating shaft 1 to be inserted.

[0040] Further, in the following description, the positional relationship of each component is sometimes described with the insertion hole 30a as a reference. Specifically, the "axial direction" refers to the direction in which the insertion hole 30a extends (the direction in which the rotating shaft 1 is inserted, the direction in which the rotating shaft 1 extends). Further, the "radial direction" refers to the radial direction of the insertion hole 30a. Further, the "circumferential direction" refers to the circumferential direction along the inner circumferential surface of the insertion hole 30a. Alternatively, it can also be said that the "radial direction" and the "circumferential direction" are observed from the center of the rotating shaft 1 that is inserted into the insertion hole 30a.

[0041] Further, the "radial direction" can also be said to be the direction that intersects the central axis of the insertion hole 30a when viewed in the direction of the central axis of the insertion hole 30a. The "circumferential direction" can also be said to be the direction around the central axis of the insertion hole 30a.

[0042] The bottom plate 30 constitutes the outermost portion (the side away from the thrust ring) of the axial thrust foil bearing 3. The insertion hole 30a is formed in the bottom plate 30. That is, the bottom plate 30 of the present disclosure is a circular plate-shaped component in which the insertion hole 30a is formed. However, the bottom plate 30 can also be a component other than a circular plate shape (for example, a rectangular plate shape), as long as it has the insertion hole 30a. Further, the insertion hole 30a does not necessarily have to be a strict cylindrical shape.

[0043] The bottom plate 30 is formed of, for example, a metal plate having a thickness of several mm or so. The bottom plate 30 has a support surface 30b (flat surface) that extends in a direction orthogonal to the axial direction of the insertion hole 30a. The support surface 30b is disposed in opposition to the thrust ring 4. The top foil 10, the back foil 20, and the step component 50 described later are disposed around the insertion hole 30a (opening) of the support surface 30b. Specifically, the top foil 10 is supported by the back foil 20, and the back foil 20 is supported by the bottom plate 30 and the step component 50. That is, the top foil 10 is also supported by the bottom plate 30 and the step component 50 via the back foil 20.

[0044] In the present disclosure, the top foil 10 and the back foil 20 are each formed of a plurality of (six) top foil pieces 11 and back foil pieces 21. The bottom plate 30 supports the six top foil pieces 11 and back foil pieces 21 at equal intervals in the circumferential direction of the support surface 30b. Further, the number of pieces of the top foil pieces 11 and the back foil pieces 21 is not limited to six, and can be two to five or seven or more.

[0045] The top foil 10 of the present disclosure is formed of six metal thin plates (top foil pieces 11) arranged in the circumferential direction. The top foil piece 11 has an inclined portion 12 that is inclined upward (in the front side of the paper surface in the present disclosure, or in the axial direction from the bottom plate 30 toward the side of the top foil piece 11) from the circumferential one side (the upstream side in the rotating direction of the rotating shaft 1) toward the circumferential other side (the downstream side in the rotating direction of the rotating shaft 1), and a mounting portion 13 that is continuously provided with the circumferential one side of the inclined portion 12 and is mounted to the bottom plate 30. Figure 3

[0046] ​like Figure 3 As shown, the inclined portion 12 is formed into a generally trapezoidal shape by cutting off the apex side of the fan shape and setting the inner and outer peripheral sides as arcs. That is, the inclined portion 12 has: two end edges that are separated in the circumferential direction and extend from the inner peripheral side to the outer peripheral side; an end edge on the inner peripheral side that connects the two end edges on the inner peripheral side; and an end edge on the outer peripheral side that connects the two end edges on the outer peripheral side. The end edge extending from the inner peripheral side to the outer peripheral side of the inclined portion 12 on the other side of the circumference (hereinafter referred to as the end 12a on the other side of the circumference) becomes a free end.

[0047] On the other hand, the end edge extending from the inner circumferential side to the outer circumferential side of the inclined portion 12 is connected to the mounting portion 13 via the bending portion 14. For example... Figure 4 As shown, the curved portion 14 is composed of a first fold and a second fold located on the other side of the first fold in the circumferential direction. The first fold bends toward the back side of the top foil 11 opposite to the bottom plate 30. The second fold bends toward the surface side of the top foil 11 opposite to the bottom plate 30. That is, the curved portion 14 is stepped. In addition, both the first fold and the second fold are obtuse angles.

[0048] In other words, the first bend protrudes toward the base plate 30, and the second bend protrudes toward the side opposite to the base plate 30 (the thrust ring 4 side).

[0049] The inclined portion 12, located on the circumferential side opposite to the curved portion 14, is supported by the support portion 22 of the back foil 21. The inclined portion 12, supported by the support portion 22, is inclined at an initial tilt angle as it gradually moves away from the base plate 30 from one circumferential side towards the other. Here, the initial tilt angle refers to the tilt angle of the top foil 11 (i.e., the inclined portion 12) relative to the base plate 30 when the load is zero. The base plate 30 of this disclosure has a support surface 30b extending in a direction orthogonal to the axial direction, and the inclined portion 12 is inclined relative to this support surface 30b.

[0050] The mounting portion 13 is connected to one circumferential side (first folded side) of the bent portion 14. In this disclosure, the mounting portion 13 is formed as a strip in the radial direction with the same length as the bent portion 14, and is spot-welded to the base plate 30. That is, the welding position is the mounting position of the top foil 11 relative to the base plate 30. In addition, the mounting of the top foil 11 relative to the base plate 30 can also be performed by means of, for example, threaded fastening, in addition to spot welding. Furthermore, the mounting portion 13 and the bent portion 14 do not necessarily need to be of the same length in the radial direction.

[0051] On the other hand, the back foil 20 is formed of six thin metal sheets (back foil sheets 21) arranged circumferentially. The back foil sheet 21 has a support portion 22 that supports the inclined portion 12 of the top foil sheet 11. For example... Figure 4As shown, the support portion 22 is a foil (wave foil) with alternating peaks 22a and valleys 22b. The support portion 22 elastically supports the inclined portion 12 of the top foil 11.

[0052] Furthermore, as the support part 22, for example, corrugated foil, spring foil described in Japanese Patent Application Publication No. 2006-57652, Japanese Patent Application Publication No. 2004-270904, and back foil described in Japanese Patent Application Publication No. 2009-299748 can be used. The spring foil described in Japanese Patent Application Publication No. 2006-57652, Japanese Patent Application Publication No. 2004-270904, and back foil described in Japanese Patent Application Publication No. 2009-299748 are foils used for radial bearings, but if they are unfolded into a planar shape to form a circular plate, they become foils (support part 22) for thrust foil bearing 3.

[0053] The support portion 22 of this disclosure is formed of corrugated foil. Figure 3 In the top view shown, the support portion 22 is formed to be slightly smaller than the inclined portion 12 of the top foil 11. Therefore, the support portion 22 is covered by the inclined portion 12. The support portion 22, like the inclined portion 12, is formed into a generally trapezoidal shape with the apex side of the fan shape cut off, and the inner and outer peripheral sides respectively set as arcs. That is, the support portion 22 has: two end edges that are separated in the circumferential direction and extend from the inner peripheral side to the outer peripheral side; an inner peripheral end edge that connects the two end edges on the inner peripheral side; and an outer peripheral end edge that connects the two end edges on the outer peripheral side.

[0054] A parallel portion (hereinafter referred to as back foil end 21a) is formed on the end edge extending from the inner circumferential side to the outer circumferential side of the support portion 22 (hereinafter referred to as the end edge extending from the inner circumferential side to the outer circumferential side of the other circumferential side of the support portion 22) that extends parallel to the end edge extending from the inner circumferential side to the outer circumferential side of the support portion 22 (hereinafter referred to as the end edge extending from the inner circumferential side to the outer circumferential side of the support portion 22). On the support portion 22, in a first direction from the back foil end 21a toward the end edge extending from the other circumferential side of the support portion 22, that is, in the normal direction orthogonal to the end edge extending from the back foil end 21a to the other circumferential side of the support portion 22 (also referred to as the direction orthogonal to the ridge line of the peak portion 22a), the valley portion 22b and the peak portion 22a are alternately connected.

[0055] like Figure 4 As shown, the valley portion 22b has a flat surface and faces the base plate 30 and the step member 50. The peak portion 22a is an arched portion connecting adjacent valley portions 22b. The back foil sheet 21 is supported by the base plate 30 and the step member 50. Therefore, the valley portion 22b can abut against the base plate 30 and the step member 50. The two ends of the support portion 22, namely the back foil end 21a and the other circumferential end of the support portion 22 (hereinafter referred to as the mounting portion 21b), are each formed from the valley portion 22b.

[0056] In the present disclosure, the valley portions 22b and the peak portions 22a are formed at substantially equal intervals, respectively. In addition, the peak portions 22a are formed at a constant height. The mounting portions 21b are spot-welded (spot-welded joints) with respect to the step member 50. That is, the welding positions become the mounting positions of the back foil 21 in the circumferential direction. That is, in the present disclosure, the mounting positions of the back foil 21 are the valley portions 22b (mounting portions 21b) of the end portions on the other side (right side in the paper surface) in the first direction. Figure 4

[0057] In addition, the valley portions 22b (back foil end portions 21a) of the end portions on the one side (left side in the paper surface) in the first direction of the back foil 21 are free ends. That is, when a load acts on the back foil 21, the back foil end portions 21a can move toward the one side in the first direction. In addition, with respect to the mounting of the back foil 21 with respect to the step member 50, in addition to spot welding, for example, it can be performed by screw fastening or the like. Figure 4

[0058] The step member 50 is formed separately from the bottom plate 30 and placed on the support surface 30b. The step member 50 has: a step support portion 51 that supports the back foil 21 (back foil 20) from the middle of the circumferential direction; an extension portion 52 that is provided continuously with the other side in the circumferential direction of the step support portion 51 and extends to the radially outer side; and a clamped portion 53 that is provided continuously with the extension portion 52 at a position radially outward of the step support portion 51 and extends to the one side in the circumferential direction. Figure 3

[0059] The extension portion 52 is connected to the radially outer side of the other side in the circumferential direction of the step support portion 51. This extension portion 52 is formed in a band shape that extends to the radially outer side and is connected to the clamped portion 53.

[0060] The clamped portion 53 is formed in a substantially trapezoidal shape in which the apex side of a sector is cut off and the inner circumferential side and the outer circumferential side are respectively provided in a circular arc shape. That is, the clamped portion 53 has: two end edges that are separated in the circumferential direction and extend from the inner circumferential side to the outer circumferential side; an end edge on the inner circumferential side that connects the two end edges on the inner circumferential side; and an end edge on the outer circumferential side that connects the two end edges on the outer circumferential side.

[0061] A slit 54 is formed between the clamped portion 53 and the step support portion 51. The slit 54 divides the step member 50 into an inner side region and an outer side region in the radial direction. The slit 54 extends in the circumferential direction from the end edge on the one side of the step member 50 toward the end edge on the other side. Here, as shown in the drawing, the region on the outer side of the slit 54 is provided to extend to the radial position at which the bearing spacer 40 is disposed. That is, the clamped portion 53 is clamped in the axial direction between the bottom plate 30 and the bearing spacer 40. Figure 3

[0062] ​​​​The clamped portion 53 is formed with a through-hole 55 through which the fastening bolt 41 for mounting the bearing spacer 40 to the bottom plate 30 is inserted. The through-hole 55 of the clamped portion 53 overlaps the through-hole 42 of the bottom plate 30 in the axial direction. The through-hole 55 of the clamped portion 53 is disposed near the connection position of the extended portion 52. As shown in Figure 3 The radial dimension of the clamped portion 53 can be the same as the radial dimension from the inner circumferential surface to the outer circumferential surface of the bearing spacer 40, so that the bearing spacer 40 can be brought into contact with the substantially entire body. In addition, the clamped portion 53 can have a circumference of about 60° (about 1 / 6 of the entire circumference) of the entire circumference 360° of the bearing spacer 40. Thus, the six stepped members 50 (clamped portions 53) are clamped by the substantially entire circumference of the bearing spacer 40.

[0063] As shown in Figure 4 The stepped member 50 is formed by overlapping a plurality of spacers 60 (thin plates made of metal). The plurality of spacers 60 are each formed in a plate shape having a constant thickness. The plurality of spacers 60 are overlapped in the stepped support portion 51 with the end surface 61 of the circumferential one side shifted toward the circumferential other side as the step increases. That is, the end surface 61 of the second layer of spacers 60 is shifted toward the circumferential other side by a constant distance with respect to the end surface 61 of the first layer of spacers 60. The same applies to the end surface 61 of the third layer and subsequent layers of spacers 60. In addition, the end surfaces of the portions other than the stepped support portion 51 (the extended portion 52 and the clamped portion 53 described above) of the plurality of spacers 60 are aligned.

[0064] That is, the end surfaces of the portions other than the stepped support portion 51 (the extended portion 52 and the clamped portion 53 described above) of the plurality of spacers 60 are aligned in the position in the direction along the support surface 30b.

[0065] The shift amount P of the end surfaces 61 of the overlapped spacers 60 (for example, the first layer of spacers 60 and the second layer of spacers 60) is constant. The shift amount P is the same as the pitch of the peak portions 22a and the valley portions 22b of the backing foil 21. In addition, the plurality of spacers 60 are the same number as the peak portions 22a. In addition, the plurality of spacers 60 are one less than the number of the valley portions 22b. The plurality of spacers 60 (the stepped support portion 51) support the valley portions 22b other than the valley portion 22b located on the circumferential one side. That is, the valley portion 22b (part) located on the circumferential one side is supported by the support surface 30b of the bottom plate 30, and the other valley portions 22b (remaining part) are each supported by each layer of the stepped support portion 51.

[0066] Next, the effects of the thrust foil bearing 3 configured by such a structure will be described.

[0067] As shown in Figure 2 The thrust foil bearing 3 is disposed on both sides sandwiching the thrust ring 4. Therefore, it is possible to suppress the movement of the rotating shaft 1 in the direction of the thrust force.

[0068] In this state, as the rotating shaft 1 rotates and the thrust ring 4 begins to rotate, the thrust ring 4 rubs against the top foil 11, and the surrounding fluid is forced into the wedge-shaped space formed between them. Furthermore, when the thrust ring 4 reaches a constant rotational speed, a fluid lubricating film forms between them. Through the pressure of this fluid lubricating film, the top foil 11 is pressed towards the back foil 21, and the thrust ring 4 disengages from contact with the top foil 11, rotating in a non-contact manner.

[0069] Here, as Figure 4 As shown, a portion of the back foil 21 is supported by the support surface 30b, and the remaining portion is supported by the stepped member 50 from the midpoint of the circumferential direction. The support surface 30b is a flat surface that extends in a direction orthogonal to the axial direction of the through hole 30a. The stepped member 50 is placed on the support surface 30b and is formed into a stepped shape that increases in height as it moves toward the other side of the circumference. That is, in this embodiment, the stepped member 50 has multiple surfaces that are substantially parallel to the support surface 30b and have different heights. Since the stepped member 50 is separate from the base plate 30, high-precision machining is possible, and a high-precision simulated inclined surface can be formed on the support surface 30b. As a result, the back foil 21 can be given an appropriate inclination, and a good fluid lubrication film can be formed between the thrust ring 4 and the top foil 11.

[0070] Therefore, according to the first embodiment described above, the load capacity of the thrust foil bearing 3 can be improved by adopting the following structure, which includes: a base plate 30 having an insertion hole 30a for the rotating shaft 1 to pass through, and a support surface 30b extending in a direction orthogonal to the axial direction of the insertion hole 30a; a stepped member 50, which is placed on the support surface 30b and is separately formed from the base plate 30; and a back foil 20, which extends in the circumferential direction of the insertion hole 30a, and is partially supported by the support surface 30b, with the remaining portion supported by the stepped member 50 from the middle of the circumferential direction.

[0071] In other words, such as Figure 4 As shown, a portion of the back foil 21 is supported by the support surface 30b, and other portions adjacent to this portion in the circumferential direction are supported by the stepped member 50. The back foil 21 may also have portions that are neither supported by the support surface 30b nor by the stepped member 50.

[0072] Furthermore, in the first embodiment, since the step member 50 is formed in a step shape, it is possible to form a high-precision simulated inclined surface with a simple shape.

[0073] Furthermore, in the first embodiment, the stepped member 50 is formed by overlapping multiple gaskets 60. The gaskets 60 can be mass-produced with high precision through etching, precision stamping, and other processes.

[0074] In addition, in the first embodiment, such asFigure 3 As shown, a bearing spacer 40 is mounted on the base plate 30, and the stepped component 50 is clamped between the base plate 30 and the bearing spacer 40. Thus, the stepped component 50 can be clamped using the bearing spacer 40, which ensures space for a pair of thrust foil bearings 3 on the base plate 30. Furthermore, by clamping the stepped component 50, movement of the stepped component 50 from its fixed position is prevented.

[0075] (Second Implementation)

[0076] Next, a second embodiment of this disclosure will be described. In the following description, structures that are the same as or equivalent to those in the above embodiments will be marked with the same reference numerals, and their descriptions will be simplified or omitted.

[0077] Figure 5 This is a cross-sectional view showing the main parts of the thrust foil bearing 3 according to the second embodiment of this disclosure. Additionally, Figure 5 With the above Figure 3 The arrow AA shown corresponds to the sectional view.

[0078] like Figure 5 As shown, the second embodiment differs from the above embodiment in that the step component 50 (a plurality of gaskets 60) includes gaskets 60 of different thicknesses.

[0079] Specifically, the first layer gasket 60 is formed with a thickness t1. The second layer gasket 60 is formed with a thickness t2 greater than t1. The third layer gasket 60 is formed with a thickness t3 less than t2. The fourth layer gasket 60 is formed with a thickness t4 less than t3. The fifth layer gasket 60 is formed with a thickness t5 slightly less than t4.

[0080] That is, the second layer of gasket 60 has the greatest thickness, and as the thickness increases from the second layer of gasket 60 towards one axial side ( Figure 5 On the upper side of the paper, on the 4th side of the thrust ring) and on the other side ( Figure 5 The thickness of the pad 60 decreases as it moves away from the lower side of the paper surface (the side of the base plate 30). The back foil 21 is supported by a plurality of pads 60 (stepped support portions 51) of such thickness. The top foil 11 supported by the back foil 21 has a curved inclined portion 12A that protrudes axially to one side. The inclined portion 12A is curved in such a way that the inclination relative to the support surface 30b (in other words, the thrust ring 4) gradually decreases as it moves toward the other side in the circumferential direction.

[0081] Figure 6 This is an explanatory diagram illustrating the load capacity of the thrust foil bearing 3 according to the second embodiment of this disclosure. Figure 6 In the chart shown, the horizontal axis x represents the circumferential position, and the vertical axis P(x) represents the pressure of the fluid lubrication film, i.e., the load capacity of the thrust foil bearing 3.

[0082] like Figure 6 As shown, in the second embodiment, since the top foil 11 has a curved inclined portion 12A, the pressure of the fluid lubricating film increases by an amount corresponding to the area where the mesh is applied, compared to the inclined portion 12 of the inclined surface (a surface with a single inclined angle) in the first embodiment.

[0083] That is, according to this second embodiment, such as Figure 5 As shown, by making the thicknesses of the multiple shims 60 different, the load capacity of the thrust foil bearing 3 can be improved.

[0084] (Third Implementation)

[0085] Next, a third embodiment of this disclosure will be described. In the following description, structures that are the same as or equivalent to those in the above embodiments will be marked with the same reference numerals, and their descriptions will be simplified or omitted.

[0086] Figure 7 This is a cross-sectional view showing the main parts of the thrust foil bearing 3 according to the third embodiment of this disclosure. Additionally, Figure 7 With the above Figure 3 The arrow AA shown corresponds to the sectional view.

[0087] like Figure 7 As shown, the third embodiment differs from the above embodiments in that the stepped component 50 (a plurality of gaskets 60) includes gaskets 60 with different offsets of their end faces 61. Furthermore, the thickness of the plurality of gaskets 60 is constant, but may also be different.

[0088] Specifically, the second layer gasket 60 overlaps with the first layer gasket 60 at an offset of P1 relative to its end face 61. Furthermore, the third layer gasket 60 overlaps with the second layer gasket 60 at an offset of P2 relative to its end face 61, which is smaller than the offset P1. Additionally, the fourth layer gasket 60 overlaps with the third layer gasket 60 at an offset of P3 relative to its end face 61, which is larger than the offset P2. Finally, the fifth layer gasket 60 overlaps with the fourth layer gasket 60 at an offset of P4 relative to its end face 61, which is larger than the offset P3.

[0089] That is, the offset P2 of the third layer gasket 60 is the smallest (the support area of ​​the second layer gasket 60 is the smallest), and as the offset from the second layer gasket 60 towards one side axially ( Figure 5 (on the paper side) and the other side ( Figure 5 The support area of ​​the pad 60 increases as the paper surface moves away from the lower side. The back foil 21 is supported by a plurality of such pads 60 (stepped support portions 51). The top foil 11 supported by the back foil 21 forms a curved inclined portion 12B that protrudes axially to one side. Thus, similar to the second embodiment, the load capacity of the thrust foil bearing 3 can be improved.

[0090] The above-mentioned support area refers to the area of the region exposed to the back foil 20 side in each gasket 60.

[0091] In addition, in the third embodiment, the gasket 60 of the second layer does not directly support the valley portion 22b of the back foil 21, and the gasket 60 of the fourth layer supports two valley portions 22b. Thereby, it is also possible to form the shape of the inclined portion 12B of the top foil 11 as a curved surface of a cubic function, instead of a simple curved surface of a quadratic function. In Figure 7 In the example shown, the circumferential other side of the inclined portion 12B is curved in a manner that is warped toward the one side in the axial direction. Thereby, it is possible to improve the load capacity of the circumferential other side of the top foil 11.

[0092] That is, the portion of the circumferential one side of the inclined portion 12B is curved in a manner that is convex toward the one side in the axial direction, and the portion of the circumferential other side of the inclined portion 12B is curved in a manner that is convex toward the other side in the axial direction, and thus, in Figure 7 In this case, the inclined portion 12B is curved in an inverted S shape.

[0093] In addition, the gasket 60 of the second layer does not contact the valley portion 22b of the back foil 21.

[0094] The above, with reference to the drawings, the preferred embodiments of the present disclosure are described, but the present disclosure is not limited to the above-mentioned embodiments. In the above-mentioned embodiments, each shape, combination, etc. of each constituent part shown is one example, and various changes can be made based on design requirements, etc. within the scope of the gist of the present disclosure.

[0095] For example, as in the modification example shown in Figure 8 The step member 50 of this modification example has a plurality of steps 70 that are integrally formed by etching processing or precision press processing, etc., and these plurality of steps 70 form the step support portion 51.

[0096] In addition, for example, in the above-mentioned embodiments, the step member 50 is sandwiched between the bottom plate 30 and the bearing spacer 40, but it is also possible to be fixed to the bottom plate 30 by welding, bolting, etc.

[0097] Industrial applicability

[0098] The present disclosure can be applied to a thrust foil bearing that has a bottom plate and a back foil supported by the bottom plate, and aims to improve the load capacity of the thrust foil bearing.

[0099] Explanation of symbols

[0100] 1 - rotating shaft (spindle); 2 - impeller; 3 - thrust foil bearing; 4 - thrust ring; 5 - housing; 6 - tip clearance; 7 - radial foil bearing; 10 - top foil; 11 - top foil piece; 12 - inclined portion; 12a - end portion; 12A - inclined portion; 12B - inclined portion; 13 - mounting portion; 14 - bent portion; 20 - back foil; 21 - back foil piece; 21a - back foil end portion; 21b - mounting portion; 22 - support portion; 22a - peak portion; 22b - valley portion; 30 - base plate; 30a - insertion hole; 30b - support surface; 40 - bearing spacer; 41 - fastening bolt; 42 - through hole; 50 - step member; 51 - step support portion; 52 - extension portion; 53 - clamped portion; 54 - slit; 55 - through hole; 60 - gasket; 61 - end surface; 70 - step; P - offset amount.

Claims

1. A thrust foil bearing, characterized in that, have: The base plate has an insertion hole for shaft insertion and a support surface extending in a direction orthogonal to the axial direction of the insertion hole; A stepped component, which is placed on the supporting surface and is separately formed from the base plate. The back foil extends circumferentially along the through hole, and is partially supported by the support surface, while other portions adjacent to the partially supported circumferentially are directly supported by the stepped member. The back foil is a wave foil with peaks and valleys. The stepped component has a stepped support portion that supports the valley on its surface.

2. The thrust foil bearing according to claim 1, characterized in that, The stepped component is formed in a stepped shape.

3. The thrust foil bearing according to claim 1 or 2, characterized in that, The stepped component is formed by overlapping multiple pads.

4. The thrust foil bearing according to claim 3, characterized in that, The plurality of gaskets includes gaskets of different thicknesses.

5. The thrust foil bearing according to claim 3, characterized in that, The plurality of gaskets includes gaskets with different end face offsets.

6. The thrust foil bearing according to claim 3, characterized in that, The plurality of gaskets includes gaskets that do not directly support the back foil.

7. The thrust foil bearing according to claim 1 or 2, characterized in that, A ring-shaped component is installed on the base plate. The stepped component is held between the base plate and the annular component.

8. The thrust foil bearing according to claim 1, characterized in that, The step component is made of metal.

9. The thrust foil bearing according to claim 1 or 2, characterized in that, It has a top foil supported by the back foil.

10. The thrust foil bearing according to claim 9, characterized in that, The top foil is bent such that the inclination relative to the support surface gradually decreases as it moves from one part toward the other parts in the circumferential direction.

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