JP7538436B2 - Thrust foil bearing, compressor, and refrigeration device - Google Patents

Description

The present disclosure relates to a thrust foil bearing, a compressor, and a refrigeration device.

Conventionally, thrust foil bearings have been known as bearings for high-speed rotating bodies. Patent Document 1 discloses a thrust foil bearing that is arranged opposite a thrust collar (thrust disk) provided on a rotating shaft.

The thrust foil bearing in Patent Document 1 has a bearing surface formed from a flexible metal thin plate (foil) so that it can absorb the movement of the rotating shaft (axial displacement and tilt of the thrust collar) caused by vibration and shock. The thrust foil bearing has a foil structure below the bearing surface that flexibly supports the bearing surface.

In the thrust foil bearing of Patent Document 1, multiple top foil pieces and multiple back foil pieces are arranged in a circumferential direction, overlapping each other. The top foil pieces are supported by the back foil pieces. As the thrust collar rotates, a lubricating fluid is introduced between the top foil pieces and the thrust collar. This lubricating fluid forms a wedge-shaped fluid lubricating film between the top foil pieces and the thrust collar, and the load capacity of the thrust foil bearing is exerted.

International Publication No. WO 2020/171021

In the thrust foil bearing described in Patent Document 1, the top foil piece and the back foil piece are each fixed to the base plate to prevent them from falling off the base plate. Specifically, the top foil piece has a fixing margin at the edge on the rear side in the rotation direction of the rotating shaft, and the fixing margin is fixed to the base plate. The back foil piece has a fixing margin at the edge on the front side in the rotation direction of the rotating shaft, and the fixing margin is fixed to the base plate.

In the thrust foil bearing of Patent Document 1, a gap is formed between the fixing margin of the top foil piece and the fixing margin of the back foil piece adjacent to the top foil piece so that they do not interfere with each other. In addition, a gap of a certain size is formed between the fixing margins to ensure a working space for fixing the fixing margins.

In this way, thrust foil bearings, which require a gap between the two fixed supports, have no choice but to reduce the area of the bearing surface that functions as a bearing, and there are cases in which the load capacity of the thrust foil bearing is not fully achieved.

The objective of this disclosure is to improve the load capacity of thrust foil bearings.

The first aspect is a thrust foil bearing arranged to face a thrust disk (36) provided on a rotating shaft (35), and includes a top foil (80) arranged to face the thrust disk (36), a back foil (70) arranged on the opposite side of the top foil (80) to the thrust disk (36), and an annular base plate (60) arranged on the opposite side of the back foil (70) to the top foil (80) and supporting the back foil (70).

The back foil (70) has a plurality of back foil pieces (71) arranged along the circumferential direction of the base plate (60). The back foil piece (71) includes a support portion (72) that supports the top foil (80), a first fixed portion (73) that is formed continuously with the support portion (72) on the front side of the support portion (72) in the rotation direction of the rotating shaft (35) and is fixed to the base plate (60), a first end edge (75) that is the end edge on the front side of the first fixed portion (73) in the rotation direction, and a first boundary line (74) that is formed at the boundary between the support portion (72) and the first fixed portion (73).

The top foil (80) has a plurality of top foil pieces (81) arranged to overlap the plurality of back foil pieces (71). The top foil piece (81) includes a main body portion (82) supported by the support portion (72), a second fixing portion (85) formed on the rear side of the main body portion (82) in the rotation direction and continuous with the main body portion (82) and fixed to the base plate (60), a second end edge (87) which is the end edge on the rear side of the second fixing portion (85) in the rotation direction, and a second boundary line (86) formed at the boundary between the main body portion (82) and the second fixing portion (85).

The first end edge (75) has a predetermined angle with respect to the first boundary line (74), and the second end edge (87) has a predetermined angle with respect to the second boundary line (86). The first fixing margin (73) of the back foil piece (71) is fixed to the base plate (60) in a mutually overlapping state with the second fixing margin (85) of the top foil piece (81) supported by another back foil piece (71) positioned adjacent to the back foil piece (71).

In the first embodiment, the first fixing margin (73) of the back foil piece (71) and the second fixing margin (85) of the top foil piece (81) supported by another back foil piece (71) adjacent to the back foil piece (71) are fixed to the base plate (60) in an overlapping state. This makes it possible to reduce the area of the thrust foil bearing that does not function as a bearing surface. This makes it possible to increase the area that functions as a bearing surface, thereby improving the load capacity of the thrust foil bearing.

In addition, in the first embodiment, the first end side (75) has a predetermined angle with respect to the first boundary line (74), or the second end side (87) has a predetermined angle with respect to the second boundary line (86). Therefore, when the first fixing space (73) and the second fixing space (85) adjacent to the first fixing space (73) are overlapped and fixed to each other, the distance between the first boundary line (74) and the second boundary line (86) can be made wide. This makes it easier to fix the first fixing space (73) and the second fixing space (85) to the base plate.

In the second embodiment, when the first end edge (75) of the back foil piece (71) has a predetermined angle with respect to the first boundary line (74) in the first embodiment, the first end edge (75) of the back foil piece (71) is arranged along the second boundary line (86) of the top foil piece (81) supported by another back foil piece (71) located adjacent to the back foil piece (71).

In the second embodiment, the first end edge (75) of the back foil piece (71) is arranged along the second boundary line (86) of the top foil piece (81) supported by another back foil piece (71) adjacent to the back foil piece (71). This makes it easy to position the first fixing space (73) and the second fixing space (85) adjacent to the first fixing space (73) when they are overlapped and fixed. This improves the efficiency of the fixing work of the back foil piece (71) and the top foil piece (81).

In the third aspect, when the second end edge (87) of the top foil piece (81) has a predetermined angle with respect to the second boundary line (86) in the first aspect, the second end edge (87) of the top foil piece (81) is arranged along the first boundary line (74) of the back foil piece (71) supporting another top foil piece (81) located adjacent to the top foil piece (81).

In the third embodiment, the second end edge (87) of the top foil piece (81) is arranged along the first boundary line (74) of the back foil piece (71) that supports another top foil piece (81) adjacent to the top foil piece (81). This makes it easy to position the first fixing space (73) and the second fixing space (85) adjacent to the first fixing space (73) when they are overlapped and fixed. This improves the efficiency of the fixing work of the back foil piece (71) and the top foil piece (81).

In the fourth aspect, in any one of the first to third aspects, the second fixing margin (85) of the top foil piece (81) is fixed to the base plate (60) via the first fixing margin (73) of the back foil piece (71) that supports another top foil piece (81) located adjacent to the top foil piece (81).

In the fourth embodiment, the back foil piece (71) and the top foil piece (81) are arranged and fixed to the base plate (60) in the order of the first fixed portion (73) and the second fixed portion (85). This is the same arrangement order as the base plate, the back foil, and the top foil, which are components of the thrust foil bearing. This makes it easier to assemble the thrust foil bearing (27).

The fifth aspect is any one of the first to fourth aspects, in which the support portion (72) of the back foil piece (71) is formed with alternating peaks (76) and valleys (77) when viewed from the radial direction of the rotating shaft (35).

In the fifth embodiment, the support portion (72) has alternating peaks (76) and valleys (77), so that the support portion (72) can elastically support the top foil piece (81).

The sixth aspect is the fifth aspect, in which the height of the peak portion (76) increases toward the front in the direction of rotation.

In the sixth embodiment, the height of the ridge portion (76) increases toward the front in the direction of rotation. This allows a wedge-shaped gap to be formed between the thrust disk (36) and the top foil piece (81).

In the seventh aspect, in the fifth aspect, the base plate (60) supports the support portion (72) of the back foil piece (71) and includes an inclined surface (62) that inclines so as to move away from the thrust disk (36) as it moves toward the rear side in the direction of rotation.

In the seventh embodiment, the base plate (60) has an inclined surface (62). This allows a wedge-shaped gap to be formed between the thrust disk (36) and the top foil piece (81).

The eighth aspect is a compressor including the rotating shaft (35) having the thrust disk (36) and a thrust foil bearing (27) of any one of the first to seventh aspects.

In the eighth aspect, a compressor having a thrust foil bearing (27) with improved load capacity can be provided.

The ninth aspect is a refrigeration system including the compressor (20) of the eighth aspect and a refrigerant circuit (1a) through which the refrigerant compressed by the compressor (20) flows.

In the ninth aspect, a refrigeration system can be provided that includes a thrust foil bearing (27) with improved load capacity.

FIG. 1 is a schematic configuration diagram of a refrigeration device according to a first embodiment. FIG. 2 is a schematic vertical cross-sectional view showing the overall configuration of the turbo compressor. FIG. 3 is a side view showing a thrust foil bearing of the present disclosure. FIG. 4 is a plan view showing a thrust foil bearing of the present disclosure. FIG. 5 is a plan view of the back foil piece according to the first embodiment. FIG. 6 is a plan view of the top foil piece according to the first embodiment. FIG. 7 is an explanatory diagram showing how the back foil piece and the top foil piece according to the first embodiment are fixed. FIG. 8 is a side view of FIG. FIG. 9 is a diagram corresponding to FIG. 8 according to a modified example of the first embodiment. FIG. 10 is a diagram corresponding to FIG. 5 according to the second embodiment. FIG. 11 is a diagram corresponding to FIG. 6 according to the second embodiment. FIG. 12 is a diagram corresponding to FIG. 7 according to the second embodiment. FIG. 13 is a diagram corresponding to FIG. 8 according to the second embodiment. FIG. 14 is a diagram corresponding to FIG. 9 according to the second embodiment. FIG. 15 is a diagram corresponding to FIG. 7 according to the third embodiment. FIG. 16 is a diagram corresponding to FIG. 8 according to the third embodiment. FIG. 17 is a diagram corresponding to FIG. 9 according to the third embodiment.

Embodiments of the present disclosure will be described in detail below with reference to the drawings. Note that the present disclosure is not limited to the embodiments shown below, and various modifications are possible without departing from the technical spirit of the present disclosure. Each drawing is intended to conceptually explain the present disclosure, and therefore dimensions, ratios, or numbers may be exaggerated or simplified as necessary for ease of understanding.

First Embodiment
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A thrust foil bearing according to a first embodiment will be described with reference to the drawings. A thrust foil bearing (27) according to the present disclosure is applied to, for example, a turbo compressor (20) of a refrigeration system (1).

(1) Overview of the Refrigeration System The refrigeration system (1) shown in Fig. 1 includes a turbo compressor (hereinafter also referred to as a compressor) (20) and a refrigerant circuit (1a) through which refrigerant compressed by the compressor (20) flows. The refrigerant circuit (1a) is filled with refrigerant. The refrigerant circuit (1a) includes a compressor (20), a radiator (2), a pressure reduction mechanism (3), and an evaporator (4). The pressure reduction mechanism (3) is an expansion valve. The refrigerant circuit (1a) performs a vapor compression refrigeration cycle.

In the refrigeration cycle, the refrigerant compressed by the compressor (20) dissipates heat to the air in the radiator (2). The refrigerant that has dissipated heat is depressurized by the pressure reduction mechanism (3) and evaporates in the evaporator (4). The evaporated refrigerant is sucked into the compressor (20).

The refrigeration system (1) is an air conditioner. The air conditioner may be a cooling only unit, a heating only unit, or an air conditioner that switches between cooling and heating. In this case, the air conditioner has a switching mechanism (e.g., a four-way switching valve) that switches the circulation direction of the refrigerant. The refrigeration system (1) may be a water heater, a chiller unit, a cooling device that cools the air inside the storage unit, etc. The cooling device cools the air inside a refrigerator, a freezer, a container, etc. The expansion mechanism is composed of an electronic expansion valve, a temperature-sensitive expansion valve, an expander, or a capillary tube.

(2) Overview of Compressor The compressor (20) will be described with reference to Fig. 2. The compressor (20) of this embodiment is a single-stage compressor having one compression mechanism (50). The compressor (20) has a casing (21), a motor (30), a rotating shaft (35), and a compression mechanism (50). The casing (21) houses the motor (30), the rotating shaft (35), and the compression mechanism (50). The compressor (20) has bearings that support the rotating shaft (35). The bearings include a radial bearing (26) and a thrust foil bearing (27).

(2-1) Casing The casing (21) has a body portion (22), a first closing portion (23), and a second closing portion (24). The body portion (22) is formed in a cylindrical shape that is open at both axial ends. The first closing portion (23) closes the open portion at one axial end of the body portion (22). The first closing portion (23) includes a housing (25) located in the center thereof. The second closing portion (24) closes the open portion at the other axial end of the body portion (22).

(2-2) Motor The motor (30) has a stator (31) and a rotor (32). The stator (31) is formed in a cylindrical shape. The stator (31) is fixed to the inner circumferential surface of the body (22) of the casing (21). The rotor (32) is provided inside the stator (31). The operation frequency (rotation speed) of the motor (30) is adjusted by an inverter device. In other words, the compressor (20) is an inverter type whose rotation speed is variable. Therefore, the rotation speed of the motor (30) varies between a relatively low rotation speed and a relatively high rotation speed.

(2-3) Rotating Shaft The rotating shaft (35) is fixed to the axis of the rotor (32). The rotating shaft (35) is driven to rotate by the motor (30). The rotating shaft (35) extends along the axial direction of the casing (21).

The rotating shaft (35) has a thrust disk (36). The thrust disk (36) is formed on the rotating shaft (35) near the compression mechanism (50). The thrust disk (36) is an enlarged portion of the rotating shaft (35). The thrust disk (36) is sandwiched between a pair of thrust foil bearings (27) described below.

(2-4) Radial Bearing The radial bearing (26) supports a load acting in the radial direction of the rotating shaft (35) (radial load), among the loads acting on the rotating shaft (35). The compressor (20) of the present embodiment has two radial bearings (26). The number and positions of the radial bearings (26) are merely an example.

One radial bearing (26) is disposed near one end of the rotating shaft (35). The other radial bearing (26) is disposed near the other end of the rotating shaft (35). Each radial bearing (26) is fixed to the body (22) of the casing (21) via a bearing support (28). Each radial bearing (26) rotatably supports the rotating shaft (35).

(2-5) Thrust Foil Bearing The thrust foil bearing (27) supports a load acting in the axial direction of the rotating shaft (35) (thrust load), among the loads acting on the rotating shaft (35). The compressor (20) of the present embodiment has two thrust foil bearings (27). The number and positions of the thrust foil bearings (27) are merely an example.

The thrust foil bearing (27) is located near one end of the rotating shaft (35) (near the compression mechanism (50)). The thrust foil bearing (27) is fixed to the center of a bearing support (28) that is arranged near one end of the rotating shaft (35). The thrust foil bearing (27) restricts axial movement of the rotating shaft (35).

(2-6) Compression Mechanism The compression mechanism (50) is a centrifugal compression mechanism that imparts kinetic energy to a fluid by the centrifugal force of an impeller (51) and converts the kinetic energy into pressure. The compression mechanism (50) includes a housing (25) and an impeller (51). The impeller (51) has a plurality of blades. In the compression mechanism (50), a compression chamber (52) is formed between the housing (25) and the impeller (51). The housing (25) is formed with a suction passage (53) that sends a fluid (refrigerant) to the compression chamber (52).

(3) Details of the Thrust Foil Bearing The thrust foil bearing (27) will be described in detail with reference to FIGS.

As shown in FIG. 3, the two thrust foil bearings (27) are provided on either side of the thrust disk (36). In other words, the compressor (20) has a pair of thrust foil bearings (27). Each of the thrust foil bearings (27) has the same configuration. Each thrust foil bearing (27) is disposed opposite the thrust disk (36).

The thrust foil bearing (27) has a top foil (80), a back foil (70), and a base plate (60). The top foil (80) is disposed facing the thrust disk (36). The back foil (70) is disposed on the side of the top foil (80) opposite the thrust disk (36). The base plate (60) is disposed on the side of the back foil (70) opposite the top foil (80).

The back foil (70) is composed of a plurality of back foil pieces (71). The top foil (80) is composed of a plurality of top foil pieces (81). In this embodiment, the same number of back foil pieces (71) and top foil pieces (81) are provided. One back foil piece (71) is provided corresponding to one top foil piece (81). Note that the same number of top foil pieces (81) and back foil pieces (71) do not have to be provided.

A cylindrical bearing spacer (40) shown by the two-dot chain line in FIG. 3 is sandwiched between the base plates (60) of each of the pair of thrust foil bearings (27). These base plates (60) are connected via the bearing spacer (40) by fastening bolts (41).

As shown in FIG. 4, a plurality of (three in this embodiment) through holes (42) for inserting the fastening bolts (41) are formed on the outer periphery of the base plate (60). One of the base plates (60) connected in this manner abuts against the bearing support (28) by being tightened by the fastening bolts (41).

In the following description, unless otherwise specified, the term "axial direction" refers to the direction of the axis of the rotating shaft (35), the term "radial direction" refers to the direction perpendicular to the axis of the rotating shaft (35), and the term "circumferential direction" refers to the circumferential direction based on the axis of the rotating shaft (35). The term "radial inner side" refers to the side closer to the axis of the rotating shaft (35), and the term "radial outer side" refers to the side farther from the axis of the rotating shaft (35). The term "rotation direction" refers to the direction of rotation of the rotating shaft (35) indicated by arrow Q in FIG. 4.

3, the base plate (60) constitutes the outermost portion in the axial direction of the thrust foil bearing (27). In other words, the base plate (60) is disposed at a position in each thrust foil bearing (27) that is farthest from the thrust disk (36) in the axial direction.

The base plate (60) is made of metal and is a plate-like member having a thickness of about several mm. As shown in FIG. 4, the base plate (60) is annular. In this embodiment, the surface of the base plate (60) is flat and has no steps.

A plurality of support regions (61) are formed on the surface of the base plate (60) facing the thrust disk (36). The support regions (61) are portions for supporting the back foil piece (71) and the top foil piece (81) corresponding to the back foil piece (71). The top foil piece (81) is supported by the back foil piece (71), and the back foil piece (71) is supported by the support region (61) of the base plate (60). In other words, the top foil piece (81) is supported by the support region (61) of the base plate (60) via the back foil piece (71). In this embodiment, the base plate (60) is formed with six support regions (61) that are equally divided in the circumferential direction. All of the support regions (61) in this embodiment are formed on a single flat surface.

(3-2) Back Foil The back foil (70) elastically supports the top foil (80). The back foil (70) is supported by the base plate (60). The back foil (70) of this embodiment is a bump foil formed by pressing a thin plate into a corrugated shape.

As shown in FIG. 4, the back foil (70) has six back foil pieces (71) arranged along the circumferential direction of the base plate (60). The number of back foil pieces (71) is merely an example. Each back foil piece (71) is arranged on each support area (61) of the base plate (60).

The back foil piece (71) is a thin metal plate (foil) having a thickness of several tens of micrometers to several hundreds of micrometers. The back foil piece (71) has a support portion (72), a first fixed margin (73), a first boundary line (74), and a first end edge (75).

The support portion (72) is a portion that supports the top foil piece (81). As shown in FIG. 5, the support portion (72) is formed in a substantially trapezoidal shape with the apex side of the sector cut out and the inner peripheral side and the outer peripheral side each having an arc shape.

As shown in FIG. 8, the support portion (72) has a plurality of peaks (76) and a plurality of valleys (77). In other words, the support portion (72) is formed in a corrugated shape when viewed from the radial direction of the rotating shaft (35). Specifically, in the support portion (72), the valleys (77) and the peaks (76) are formed in an alternating series in a normal direction (hereinafter referred to as the first direction) perpendicular to the end edge of one circumferential side (the front side in the rotation direction Q) of the support portion (72). This first direction is also referred to as a direction perpendicular to the ridge line of the peaks (76). Here, the one side in the first direction refers to the right side in FIG. 5, and the other side in the first direction refers to the left side in FIG. 5. Note that the "circumferential direction" and the "first direction" are different directions.

As shown in FIG. 8, the valley portion (77) is a flat surface. The valley portion (77) faces the base plate (60). The valley portion (77) can abut against the base plate (60). The peak portion (76) is formed in an arch shape that connects adjacent valley portions (77).

In this embodiment, the valleys (77) and the peaks (76) are formed at approximately the same pitch. As shown in FIG. 8, the height of the peaks (76) (the difference in height between the valleys (77) and the peaks (76)) increases in sequence toward the front side in the rotation direction Q of the rotating shaft (35). In this embodiment, the support portion (72) is configured with peaks (76) on one circumferential side (the front side in the rotation direction Q) and with valleys (77) on the other circumferential side (the rear side in the rotation direction Q).

The first fixed portion (73) is a portion that is fixed to the base plate (60). As shown in FIG. 5, the first fixed portion (73) is formed on one circumferential end side of the support portion (72) (in this embodiment, the front side in the rotation direction Q). The first fixed portion (73) is formed continuously with the support portion (72).

The first fixed portion (73) is formed in a flat band shape extending in the radial direction. In other words, the first fixed portion (73) is a portion that extends from one end side of the support portion (72) in the circumferential direction further to one side in the circumferential direction. The first fixed portion (73) is configured as a flat surface that is flush with the valley portion (77).

The end edge on the other circumferential side of the support portion (72) (in this embodiment, the rear side in the direction of rotation Q) is a free end that is not fixed to the base plate (60).

The first boundary line (74) is formed at the boundary between the support portion (72) and the first fixed space (73). Specifically, the first boundary line (74) is an end edge on one circumferential side of the support portion (72) and an end edge on the other circumferential side of the first fixed space (73). The first boundary line (74) extends in the radial direction.

The first end edge (75) is the end edge on one circumferential side (the front side in the rotation direction Q) of the first fixed portion (73) and is also the end edge on one circumferential side (the front side in the rotation direction Q) of the back foil piece (71).

The first end edge (75) of the back foil piece (71) forms a predetermined angle with respect to the first boundary line (74) toward the front side in the rotation direction Q. The first end edge (75) and the first boundary line (74) are not arranged parallel to each other. Therefore, the width (circumferential length) of the first fixing margin (73) formed between the first end edge (75) and the first boundary line (74) gradually increases from the radial inner end toward the radial outer end.

As shown in FIG. 5, the support portion (72) has a plurality of slits (78) (two in this embodiment) that extend circumferentially from the other circumferential side to the one circumferential side. The slits (78) are formed in an arc shape. The slits (78) extend to the peak portion (76) adjacent to the first fixing space (73).

The support portion (72) is radially divided into a plurality of divided regions (79) (three in this embodiment) by the plurality of slits (78). Each of the three divided regions (79) is displaceable in the first direction.

(3-3) Top Foil The top foil (80) acts as a bearing surface during operation of the thrust foil bearing (27). The top foil (80) is supported by the back foil (70).

As shown in FIG. 4, the top foil (80) has six top foil pieces (81) arranged along the circumferential direction. The number of top foil pieces (81) is merely an example, and each top foil piece (81) is arranged overlapping the corresponding back foil piece (71).

The top foil piece (81) is a thin metal plate (foil) having a thickness of several tens of micrometers to several hundreds of micrometers. The top foil piece (81) has a main body portion (82), a second fixing margin (85), a second boundary line (86), and a second end edge (87).

The main body portion (82) is a portion that is supported by the corresponding back foil piece (71). As shown in FIG. 6, the main body portion (82) is formed in a substantially trapezoidal shape with the apex side of the sector cut out and the inner peripheral side and the outer peripheral side each having an arc shape. The main body portion (82) has a supported portion (83) and a raised portion (84).

As shown in FIG. 8, the supported portion (83) is supported by the supporting portion (72) of the corresponding back foil piece (71). The supported portion (83) is arranged so as to rest on the top of the peak portion (76) of the supporting portion (72). The supported portion (83) is inclined at an initial inclination angle toward one circumferential side (the front side in the direction of rotation Q) so as to approach the thrust disk (36) (upward in FIG. 8). Here, the initial inclination angle refers to the inclination angle of the top foil piece (81) relative to the base plate (60) when the load applied to the thrust foil bearing (27) is zero. The supported portion (83) is provided at an incline relative to the supporting region (61) of the base plate (60).

The raised portion (84) is a portion that connects the supported portion (83) and the second fixed portion (85) and adjusts the size of the gap formed between the supported portion (83) and the thrust disk (36). The raised portion (84) is formed on the end edge on the other circumferential side (rear side in the rotation direction Q) of the supported portion (83). The raised portion (84) extends in the radial direction and is formed in a band shape. The raised portion (84) is formed in a stepped shape. In detail, the raised portion (84) has a first bent portion (84a) and a second bent portion (84b).

The first bent portion (84a) is a portion located on the other circumferential side of the rising portion (84). The first bent portion (84a) is bent toward the side opposite the surface of the rising portion (84) that faces the base plate (60). The second bent portion (84b) is a bent portion located on one circumferential side of the rising portion (84). The second bent portion (84b) is bent toward the surface of the rising portion (84) that faces the base plate (60). Both the first bent portion (84a) and the second bent portion (84b) are bent at an obtuse angle with respect to the base plate (60).

The second fixed portion (85) is a portion that is fixed to the base plate (60). In detail, as shown in FIG. 8, the second fixed portion (85) is fixed to the base plate (60) via the first fixed portion (73) of the adjacent back foil piece (71) on the other circumferential side.

As shown in FIG. 6, the second fixing space (85) is formed on the end edge on the other circumferential side (rear side in the rotation direction Q) of the main body portion (82). In detail, the second fixing space (85) is formed on the end edge on the other circumferential side of the raised portion (84). The second fixing space (85) is formed continuously with the main body portion (82).

The second fixed portion (85) is formed in a flat band shape extending in the radial direction. In other words, the second fixed portion (85) is a portion that extends further in the other circumferential direction from the end edge on the other circumferential side of the main body portion (82).

The end edge on one circumferential side (the front side in the direction of rotation Q) of the main body (82) is a free end that is not fixed to the base plate (60).

The second boundary line (86) is formed at the boundary between the main body portion (82) and the second fixed space (85). Specifically, the second boundary line (86) is the other circumferential end edge of the raised portion (84) of the main body portion (82) and is the one circumferential end edge of the second fixed space (85). The second boundary line (86) extends in the radial direction.

The second end edge (87) is the end edge on the other circumferential side (rear side in the rotation direction Q) of the second fixed space (85). In this embodiment, the second end edge (87) is the end edge on the other circumferential side (front side in the rotation direction Q) of the top foil piece (81). The second end edge (87) is generally parallel to the second boundary line (86). Therefore, the width (circumferential length) of the second fixed space (85) formed between the second end edge (87) and the second boundary line (86) is generally the same from the radial inner end to the radial outer end.

7 and 8, the first fixing margin (73) of the back foil piece (71) is fixed to the base plate (60) in a state where the first fixing margin (73) of the back foil piece (71) overlaps with the second fixing margin (85) of the top foil piece (81) supported by another back foil piece (71) adjacent to the back foil piece (71) on one circumferential side of the back foil piece (71). In other words, the second fixing margin (85) of the top foil piece (81) is fixed to the base plate (60) via the first fixing margin (73) of the back foil piece (71) adjacent to the top foil piece (81) on the other circumferential side.

In this manner, the first fixed margin (73) of the back foil piece (71) and the second fixed margin (85) of the top foil piece (81) adjacent to the back foil piece (71) are fixed to the base plate (60) in an overlapping state. This makes it possible to reduce the area of the thrust foil bearing (27) that does not function as a bearing surface (the fixed margins of the back foil piece (71) and the top foil piece (81)). As a result, the area of the area of the thrust foil bearing (27) that functions as a bearing surface can be increased, thereby improving the load capacity of the thrust foil bearing (27).

In addition, since the first end side (75) of the back foil piece (71) has a predetermined angle toward the front side in the rotational direction Q with respect to the first boundary line (74), the distance between the first boundary line (74) and the second boundary line (86) can be made wider when the first fixing space (73) and the second fixing space (85) adjacent to the first fixing space (73) are overlapped and fixed. This makes it easier to fix the top foil piece (81) and the back foil piece (71) to the base plate (60).

The area (90) where the first fixed length (73) and the second fixed length (85) overlap (hereinafter referred to as the fixed area) is determined by the second fixed length (85) of the top foil piece (81) that is located at the top of the thrust foil bearing (27). Therefore, as shown in FIG. 7, the width of the fixed area (90) in this embodiment is formed to be approximately the same from the radial inner end to the radial outer end.

In this embodiment, the first fixing portion (73) and the second fixing portion (85) are fixed to the base plate (60) by spot welding. As shown in FIG. 7, a plurality of fixing portions (welded portions in this embodiment) (91) are formed in a row in the radial direction in the fixing region (90). Note that the back foil piece (71) and the top foil piece (81) may be fixed to the base plate (60) by a means other than spot welding. For example, the back foil piece (71) and the top foil piece (81) may be fixed to the base plate (60) by a means such as caulking, riveting, or screwing.

When the top foil piece (81) and the back foil piece (71) are fixed, as shown in FIG. 8, the first end edge (75) of the back foil piece (71) is arranged along the second boundary line (86) of the top foil piece (81) supported by another back foil piece (71) located adjacent to the back foil piece (71). In other words, the first end edge (75) of the back foil piece (71) is arranged parallel to the second boundary line (86) of the adjacent top foil piece (81).

As a result, when fixing the top foil piece (81) and the back foil piece (71) to the base plate (60), the top foil piece (81) can be positioned by overlapping it with the first end edge (75) of the back foil piece (71) as a positioning mark. Specifically, the top foil piece (81) is positioned so that the first end edge (75) of the back foil piece (71) and the second boundary line (86) of the top foil piece (81) overlap. This eliminates the need to provide a positioning mark on the back foil piece (71), and makes it easier to position the top foil piece (81). This improves the efficiency of the fixing work of the top foil piece (81) and the back foil piece (71).

(4) Operation of the Compressor Next, the operation of the compressor (20) will be described.

When power is supplied to the motor (30), the rotor (32) of the motor (30) rotates. This causes the rotating shaft (35) and the impeller to rotate. As the impeller (51) rotates, refrigerant is sucked from the suction passage (53) into the compression chamber (52) and compressed. The compressed and high-pressure refrigerant is discharged from the compression chamber (52) to the outside via a discharge passage (not shown).

(5) Function of the Thrust Foil Bearing Next, the function of the thrust foil bearing (27) will be described.

As shown in FIG. 2, the thrust foil bearings (27) are provided on both sides of the thrust disk (36). This makes it possible to suppress movement of the rotating shaft (35) on both sides in the thrust direction.

When the rotating shaft (35) rotates in this state and the thrust disk (36) starts to rotate, the thrust disk (36) and the top foil piece (81) rub against each other, forcing the surrounding fluid into the wedge-shaped space formed between them. When the thrust disk (36) reaches a certain rotational speed, a fluid lubrication film is formed between them. The pressure of this fluid lubrication film presses the top foil piece (81) against the back foil piece (71), and the thrust disk (36) leaves contact with the top foil piece (81) and begins to rotate without contact.

(6) Features (6-1)
Here, the thrust foil bearing (27) is provided with a plurality of pairs (hereinafter referred to as pads) each of which is a top foil piece (81) and a back foil piece (71) supporting the top foil piece (81). In a conventional thrust foil bearing (27), a fixing margin for the top foil piece (81) and a fixing margin for the back foil piece (71) are arranged in the space between one pad and another pad adjacent to the pad, and each is directly fixed to the base plate (60).

In such a conventional thrust foil bearing (27), a gap is required between adjacent pads that is the sum of the width of the fixing margin of the top foil piece (81), the width of the fixing margin of the back foil piece (71), and the tolerance width required for assembly. In the conventional thrust foil bearing (27), an area that does not function as a bearing surface as described above must be provided between the pads. As a result, the area that functions as a bearing surface cannot be sufficiently secured, and the load capacity of the thrust foil bearing is not fully exerted.

In contrast, in the thrust foil bearing (27) of this embodiment, the first end edge (75) of the back foil piece (71) has a predetermined angle with respect to the first boundary line (74). The first fixing margin (73) of the back foil piece (71) is fixed to the base plate (60) in a state where it overlaps with the second fixing margin (85) of the top foil piece (81) supported by another back foil piece (71) located adjacent to the back foil piece (71).

By fixing the first fixed portion (73) and the second fixed portion (85) to the base plate (60) in an overlapping state, the area of the region that does not function as a bearing surface can be reduced. This increases the area of the region that functions as a bearing surface, thereby improving the load capacity of the thrust foil bearing (27).

Furthermore, in the past, the first fixed portion (73) and the second fixed portion (85) were fixed to the base plate (60) separately. In contrast, in the thrust foil bearing (27) of this embodiment, the first fixed portion (73) and the second fixed portion (85) are fixed to the base plate (60) in an overlapping state. This reduces the number of fixing points by half, thereby reducing the time required for the fixing work and reducing the number of defective products due to failure in the fixing work.

In addition, because the first end side (75) has a predetermined angle with respect to the first boundary line (74), the distance between the first boundary line (74) and the second boundary line (86) can be made wider when the first fixing space (73) and the second fixing space (85) are overlapped and fixed to each other. This makes it possible to secure a working space for fixing the first fixing space (73) and the second fixing space (85) to the base plate (60), making the fixing work easier.

(6-2)
The first end edge (75) of the back foil piece (71) is arranged along the second boundary line (86) of the top foil piece (81) supported by another back foil piece (71) located adjacent to the back foil piece (71).

This makes it easier to position the first fixing portion (73) and the second fixing portion (85) adjacent to the first fixing portion (73) when they are overlapped and fixed together. This improves the efficiency of the fixing operation.

(6-3)
The second fixing portion (85) of the top foil piece (81) is fixed to the base plate (60) via the first fixing portion (73) of the back foil piece (71) that supports another top foil piece (81) located adjacent to the top foil piece (81).

This ensures that the arrangement order of the base plate (60), back foil (70), and top foil (80), which are components of the thrust foil bearing (27), is the same, making it easier to assemble the thrust foil bearing (27).

(6-4)
The support portion (72) of the back foil piece (71) has peaks (76) and valleys (77) alternately formed when viewed in the radial direction of the rotating shaft (35), thereby enabling the back foil piece (71) to elastically support the top foil piece (81).

(6-5)
The height of the ridges (76) of the support portion (72) of the back foil piece (71) increases toward the front in the rotational direction Q. This allows a wedge-shaped gap to be formed between the thrust disk (36) and the top foil piece (81).

(7) Modifications The above embodiment may be modified as follows: In the following description, the differences from the above embodiment will be mainly described.

As shown in FIG. 9, in this modified example, the configuration of the back foil piece (71) and the base plate (60) in the thrust foil bearing (27) of the above embodiment is changed. In the back foil piece (71) of this modified example, the heights of the multiple peaks (76) in the support portion (72) are all formed to be the same height.

In the base plate (60) of this modified example, each support region (61) is formed with an inclined surface (62) and a flat surface (63) that is continuous with the inclined surface (62). The inclined surface (62) is formed on the rear side of the support region (61) in the rotation direction Q. The height of the inclined surface (62) increases along the rotation direction Q. That is, the height of the inclined surface (62) (height in the axial direction of the rotation shaft (35)) increases toward the front side of the rotation direction Q. In other words, the inclined surface (62) inclines so as to move away from the thrust disk (36) toward the rear side of the rotation direction Q.

The flat surface (63) is formed on the front side of the support area (61) in the rotation direction Q. The flat surface (63) is a flat surface that is not inclined in the support area (61). The flat surface (63) is a surface that continues from the highest position (the end on the front side in the rotation direction Q) of the inclined surface (62) to the support area boundary line (64) formed between adjacent support areas (61). The flat surface (63) is a surface that is approximately parallel to the back surface of the base plate (60). The flat surface (63) is formed in a band shape extending in the radial direction.

The surface boundary line (65) between the inclined surface (62) and the flat surface (63) is formed along the radial direction of the base plate (60). The support area boundary line (64) is also formed along the radial direction of the base plate (60).

The height of the inclined surface (62) is gradually decreased in a direction perpendicular to the surface boundary line (65). Therefore, a step is formed in the portion where each support area boundary line (64) is formed (between adjacent support areas (61) on either side of each support area boundary line (64)).

The back foil piece (71) is positioned on the inclined surface (62) and flat surface (63) of the support area (61). This allows a wedge-shaped gap to be formed between the top foil piece (81) and the thrust disk (36).

In the base plate (60) of this modified example, a support area boundary line (64) is formed between adjacent support areas (61). The support area boundary line (64) and the first end edge (75) of the back foil piece (71) are arranged to overlap. In this way, when assembling the thrust foil bearing (27), the first end edge (75) of the back foil piece (71) can be overlapped using the support area boundary line (64) of the base plate (60) as a guide, making it easier to position the back foil piece (71).

In addition, as in the above embodiment, the first end edge (75) of the back foil piece (71) is arranged along the second boundary line (86) of the adjacent top foil piece (81), which facilitates the positioning work when overlapping and fixing the first fixing space (73) and the second fixing space (85). This further improves the efficiency of the fixing work.

Second Embodiment
A thrust foil bearing (27) of embodiment 2 will be described. The thrust foil bearing (27) of this embodiment is obtained by modifying the configurations of the back foil piece (71) and the top foil piece (81) in the thrust foil bearing (27) of embodiment 1. Here, the thrust foil bearing (27) of this embodiment will be described with respect to differences from embodiment 1.

10, the first end side (75) of the back foil piece (71) of the present embodiment is generally parallel to the first boundary line (74). Therefore, the width (circumferential length) of the first fixing margin (73) formed between the first end side (75) and the first boundary line (74) is generally constant from the inner end to the outer end in the radial direction.

As shown in FIG. 11, the second end edge (87) of the top foil piece (81) of this embodiment has a predetermined angle with respect to the second boundary line (86) on the rear side in the rotational direction Q. The second end edge (87) and the second boundary line (86) are not arranged parallel to each other. Therefore, the width (circumferential length) of the second fixing margin (85) formed between the second end edge (87) and the second boundary line (86) gradually increases from the inner end toward the outer end in the radial direction.

As shown in Figures 12 and 13, the first fixing margin (73) of the back foil piece (71) is fixed to the base plate (60) in an overlapping state with the second fixing margin (85) of the top foil piece (81) supported by another back foil piece (71) adjacent to the back foil piece (71) on one circumferential side of the back foil piece (71).

This makes it possible to reduce the area of the thrust foil bearing (27) that does not function as a bearing surface (the fixing margin of the back foil piece (71) and the top foil piece (81)). As a result, the area of the area of the thrust foil bearing (27) that functions as a bearing surface can be increased, thereby improving the load capacity of the thrust foil bearing (27).

In addition, since the second end side (87) of the top foil piece (81) has a predetermined angle with respect to the second boundary line (86) on the rear side in the rotational direction Q, the distance between the first boundary line (74) and the second boundary line (86) can be made wider when the first fixing space (73) and the second fixing space (85) adjacent to the first fixing space (73) are overlapped and fixed. This makes it easier to fix the top foil piece (81) and the back foil piece (71) to the base plate (60). As shown in FIG. 12, the width of the fixing region (90) in this embodiment is formed to gradually increase from the radial inner end to the radial outer end.

When the top foil piece (81) and the back foil piece (71) are fixed, as shown in FIG. 13, the second end edge (87) of the top foil piece (81) is arranged along the first boundary line (74) of the back foil piece (71) supporting the other top foil piece (81) located next to the top foil piece (81). In other words, the second end edge (87) of the top foil piece (81) is arranged parallel to the first boundary line (74) of the adjacent back foil piece (71).

As a result, when fixing the top foil piece (81) and the back foil piece (71) to the base plate (60), the top foil piece (81) can be positioned by overlapping it using the first boundary line (74) of the back foil piece (71) as a positioning mark. Specifically, the top foil piece (81) is positioned so that the first boundary line (74) of the back foil piece (71) and the second end edge (87) of the top foil piece (81) overlap. This eliminates the need to provide a positioning mark on the back foil piece (71), and makes it easier to position the top foil piece (81). This improves the efficiency of the work of fixing the top foil piece (81) and the back foil piece (71).

(2) Modifications The above embodiment may be modified as follows: In the following description, the differences from the above embodiment will be mainly described.

As shown in FIG. 14, in this modification, the configuration of the back foil piece (71) and the base plate (60) of the thrust foil bearing (27) of the above embodiment is modified in the same way as in the modification of the first embodiment. In the back foil piece (71) of this modification, the heights of the multiple peaks (76) in the support portion (72) are all the same. In the base plate (60) of this modification, each support region (61) is formed with an inclined surface (62) and a flat surface (63) that is continuous with the inclined surface (62). The configurations of the inclined surface (62) and the flat surface (63) are the same as in the modification of the first embodiment.

In this modified example, as in the second embodiment, the second end edge (87) of the top foil piece (81) is arranged along the first boundary line (74) of the adjacent back foil piece (71), which facilitates the positioning work when overlapping and fixing the first fixing space (73) and the second fixing space (85). This further improves the efficiency of the fixing work.

Third Embodiment
A thrust foil bearing (27) of embodiment 3 will be described. The thrust foil bearing (27) of this embodiment is obtained by modifying the configurations of the back foil piece (71) and the top foil piece (81) in the thrust foil bearing (27) of embodiment 1. Here, the thrust foil bearing (27) of this embodiment will be described with respect to differences from embodiment 1.

(1) Back Foil Piece and Top Foil Piece The back foil piece (71) of this modified example has the same configuration as the back foil piece (71) of the first embodiment. Specifically, the first end side (75) of the back foil piece (71) has a predetermined angle with respect to the first boundary line (74) on the front side in the rotation direction Q. The first end side (75) and the first boundary line (74) are not arranged in parallel. Therefore, the width (circumferential length) of the first fixing margin (73) formed between the first end side (75) and the first boundary line (74) gradually increases from the inner end toward the outer end in the radial direction. Specifically, the first fixing margin (73) of the present embodiment is formed in a sector shape with a small central angle.

The top foil piece (81) of this modified example has the same configuration as the top foil piece (81) of the second embodiment. Specifically, the second end side (87) of the top foil piece (81) has a predetermined angle with respect to the second boundary line (86) on the rear side of the rotation direction Q. The second end side (87) and the second boundary line (86) are not arranged parallel to each other. Therefore, the width (circumferential length) of the second fixing space (85) formed between the second end side (87) and the second boundary line (86) gradually increases from the inner end toward the outer end in the radial direction. Specifically, the second fixing space (85) of this embodiment is formed in a sector shape with a small central angle.

As shown in Figures 15 and 16, the first fixing margin (73) of the back foil piece (71) is fixed to the base plate (60) in an overlapping state with the second fixing margin (85) of the top foil piece (81) supported by another back foil piece (71) adjacent to the back foil piece (71) on one circumferential side of the back foil piece (71).

In this embodiment, the first fixed space (73) and the second fixed space (85) each gradually widen from the inner end toward the outer end in the radial direction. Therefore, the fixed area (90) where the first fixed space (73) and the second fixed space (85) overlap is formed in a sector shape. The fixed area (90) in this embodiment has the smallest area when the first fixed space (73) and the second fixed space (85) are overlapped and fixed to the base plate (60). In other words, in this embodiment, the gap between adjacent pads can be made the narrowest. As a result, in this embodiment, the area that does not function as a bearing surface can be minimized. As a result, the area of the area that functions as a bearing surface can be made larger, and the load capacity of the thrust foil bearing can be further improved.

In addition, in this embodiment, since the fixing region (90) is formed in a narrow sector shape with a small central angle, the fixing portion (91) is provided only on the radially outer side of the fixing region (90). In other words, the fixing portion (91) is not provided on the radially inner side of the fixing region (90). This reduces the number of steps required to form the fixing portion (91).

Furthermore, as shown in FIG. 16, in this embodiment, the first end edge (75) of the back foil piece (71) is disposed along the second boundary line (86) of the adjacent top foil piece (81), and the second end edge (87) of the top foil piece (81) is disposed along the first boundary line (74) of the adjacent back foil piece (71). This makes it easier to position the first fixing space (73) and the second fixing space (85) when they are overlapped and fixed to the base plate (60). This improves the efficiency of the fixing work.

(2) Modifications The above embodiment may be modified as follows: In the following description, the differences from the above embodiment will be mainly described.

As shown in FIG. 17, in this modification, the configuration of the back foil piece (71) and the base plate (60) of the thrust foil bearing (27) of the above embodiment is modified in the same way as in the modification of the first embodiment. In the back foil piece (71) of this modification, the heights of the multiple peaks (76) in the support portion (72) are all the same. In the base plate (60) of this modification, each support region (61) is formed with an inclined surface (62) and a flat surface (63) that is continuous with the inclined surface (62). The configurations of the inclined surface (62) and the flat surface (63) are the same as in the modification of the first embodiment.

In this modified example, as in the third embodiment, the first end edge (75) of the back foil piece (71) is arranged along the second boundary line (86) of the adjacent top foil piece (81), and the second end edge (87) of the top foil piece (81) is arranged along the first boundary line (74) of the adjacent back foil piece (71). This makes it easier to position the first fixing space (73) and the second fixing space (85) when they are overlapped and fixed to the base plate (60). This improves the efficiency of the fixing work.

Other Embodiments
The above embodiment may be configured as follows.

The back foil (70) in each of the above embodiments may be something other than a corrugated bump foil. Specifically, it may be a spring foil such as that disclosed in JP 2004-270904 A, or a back foil as disclosed in JP 2009-299748 A or JP 2017-180685 A. The back foils described in the above publications are foils used in radial bearings, but by developing them into a flat surface and forming them into an annular plate shape, they can be applied to foils used in thrust foil bearings.

Although the embodiments and modifications have been described above, it will be understood that various modifications of form and details are possible without departing from the spirit and scope of the claims. Furthermore, elements of the above embodiments, modifications, and other embodiments may be combined or substituted as appropriate.

The descriptions "first," "second," "third," etc. mentioned above are used to distinguish the words to which these descriptions are attached, and do not limit the number or order of the words.

As described above, the present disclosure is useful for thrust foil bearings, compressors, and refrigeration systems.

1 Refrigeration equipment
1a Refrigerant circuit
20 Turbo compressor (compressor)
27 Thrust foil bearing
35 Rotational Axis
36 Thrust disc
60 Base Plate
62 Inclined Surface
70 Back Foil
71 Back foil piece
72 Support
73 First Fixed Fee
74 First Boundary
75 First edge
76 Yamabe
77 Valley
80 Top Foil
81 Top foil piece
82 Main body
85 Second fixed charge
86 Second Boundary
87 Second edge

Claims (9)

A thrust foil bearing disposed opposite a thrust disk (36) provided on a rotating shaft (35),
a top foil (80) disposed opposite the thrust disk (36);
a back foil (70) disposed on the opposite side of the top foil (80) from the thrust disk (36);
a base plate (60) having an annular shape, the base plate (60) being disposed on the opposite side of the back foil (70) to the top foil (80) and supporting the back foil (70),
The back foil (70) has a plurality of back foil pieces (71) arranged along the circumferential direction of the base plate (60),
The back foil piece (71) is
a support portion (72) that supports the top foil (80);
a first fixed space (73) formed contiguous with the support portion (72) on a front side of the support portion (72) in the rotation direction of the rotating shaft (35) and fixed to the base plate (60);
a first end edge (75) which is an end edge on a front side in the rotation direction of the first fixed width (73);
a first boundary line (74) formed at a boundary between the support portion (72) and the first fixed space (73),
The top foil (80) has a plurality of top foil pieces (81) arranged to overlap the plurality of back foil pieces (71),
The top foil piece (81) is
a main body portion (82) supported by the support portion (72);
a second fixing space (85) formed contiguous with the main body portion (82) on a rear side in the rotational direction of the main body portion (82) and fixed to the base plate (60);
a second end edge (87) which is a rear end edge of the second fixed width (85) in the rotation direction;
a second boundary line (86) formed at a boundary between the main body portion (82) and the second fixing space (85),
The main body portion (82) includes a supported portion (83) supported by the supporting portion (72) of the back foil piece (71), and a rising portion (84) connecting the supported portion (83) and the second fixed space (85),
the first end side (75) has a predetermined angle with respect to the first boundary line (74), and the second end side (87) has a predetermined angle with respect to the second boundary line (86);
the predetermined angle is an angle such that a width of the fixing margin (73, 85) formed between the end side (75, 87) and the boundary line (74, 86) corresponding to the end side (75, 87) gradually increases from the radial inner end toward the radial outer end of the rotating shaft (35),
the first fixing margin (73) of the back foil piece (71) is fixed to the base plate (60) in a state where the first fixing margin (73) and the second fixing margin (85) of the top foil piece (81) supported by another back foil piece (71) positioned adjacent to the back foil piece (71) are overlapped with each other;
A fixing region (90), which is a region where the first fixing space (73) and the second fixing space (85) overlap, is formed in a sector shape,
The fixing region (90) is formed with a fixing portion (91) for fixing the first fixing space (73) and the second fixing space (85),
The fixing portion (91) is formed only on the radially outer side of the fixing region (90),
The width in the rotational direction at the radially inner end of the fixing region (90) is smaller than the width in the rotational direction of the rising portion (84).
Thrust foil bearing. 2. The thrust foil bearing according to claim 1, wherein when the first end edge (75) has a predetermined angle with respect to the first boundary line (74), the first end edge (75) of the back foil piece (71) is arranged along the second boundary line (86) of the top foil piece (81) supported by another back foil piece (71) located adjacent to the back foil piece (71). 2. The thrust foil bearing according to claim 1, wherein when the second end edge (87) has a predetermined angle with respect to the second boundary line (86), the second end edge (87) of the top foil piece (81) is arranged along the first boundary line (74) of the back foil piece (71) supporting another top foil piece (81) located adjacent to the top foil piece (81). 4. A thrust foil bearing as described in any one of claims 1 to 3, wherein the second fixing margin (85) of the top foil piece (81) is fixed to the base plate (60) via the first fixing margin (73) of the back foil piece (71) supporting another top foil piece (81) located adjacent to the top foil piece (81). 4. The thrust foil bearing according to claim 1, wherein the support portion (72) of the back foil piece (71) has alternating peaks (76) and valleys (77) when viewed in the radial direction of the rotating shaft (35). The thrust foil bearing according to claim 5 , wherein the height of the ridge portion (76) increases toward the front side in the direction of rotation. 6. The thrust foil bearing according to claim 5, wherein the base plate (60) supports the support portion (72) of the back foil piece (71) and includes an inclined surface (62) that inclines so as to move away from the thrust disk (36) toward the rear side in the direction of rotation. the rotating shaft (35) having the thrust disk (36);
A compressor comprising a thrust foil bearing (27) according to any one of claims 1 to 3. A compressor (20) according to claim 8;
The refrigeration system comprises a refrigerant circuit (1a) through which the refrigerant compressed by the compressor (20) flows.