Stator, electric motor, compressor, and refrigeration cycle device

Abstract

In the present invention, a stator core has an annular core back, N teeth (N being an integer equal to or greater than 2), and N slots. The outer periphery of the core back has, in a plane orthogonal to the central axis, two first linear parts, two second linear parts, and an arc part extending in an arc shape between the first linear parts and the second linear parts in the circumferential direction. The two first linear parts face each other across the central axis, and the two second linear parts face each other across the central axis. The circumferential-direction central part of each first linear part is positioned on the tooth center line of one of the teeth. The circumferential-direction central part of each second linear part is positioned on the slot center line of one of the slots. A first-linear-part recess that is recessed inward in the radial direction is formed on at least one central part of the two first linear parts. An arc-part recess that is recessed inward in the radial direction is formed in the arc part. In a plane orthogonal to the central axis, the area A1 of the first-linear-part recess and the area A2 of the arc-part recess satisfy A1 < A2.

Description

Stator, electric motor, compressor and refrigeration cycle device

[0001] The present disclosure relates to a stator, an electric motor, a compressor, and a refrigeration cycle device.

[0002] The compressor includes a compression mechanism, an electric motor that drives the compression mechanism, and a sealed container that houses these components. During compression, a refrigerant and refrigeration oil that lubricates the compression mechanism circulate within the sealed container. The stator core of the electric motor has a notch on the outer periphery that serves as a flow path for the refrigeration oil (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2006-230054 (for example, see paragraph 0037 and FIG. 11)

[0004] To improve the reliability of the compressor, it is necessary to improve the circulation of the refrigeration oil (i.e., oil return) within the sealed container and prevent the refrigeration oil from leaking into the refrigerant circuit. To achieve this, a wider refrigeration oil flow path is desirable. However, if the notch on the outer periphery of the stator core is made larger, the magnetic path of the stator core becomes narrower, which may lead to a decrease in motor efficiency.

[0005] The present disclosure aims to improve the oil return property and leakage prevention performance of refrigeration oil while suppressing a decrease in motor efficiency.

[0006] The stator of the present disclosure includes a stator core and a coil wound around the stator core. The stator core includes an annular core back centered on a central axis, N teeth (N is an integer greater than or equal to 2) extending radially inward from the core back about the central axis, and N slots formed between each pair of adjacent teeth among the N teeth. The outer periphery of the core back includes, in a plane perpendicular to the central axis, two first linear portions that both extend linearly, two second linear portions that both extend linearly, and an arc portion that extends in an arc between one of the two first linear portions and one of the two second linear portions in the circumferential direction about the central axis. The two first linear portions face each other across the central axis, and the two second linear portions face each other across the central axis. The circumferential center of each first straight line portion is located on a tooth centerline, which is a radial line passing through the circumferential center of one of the N teeth. The circumferential center of each second straight line portion is located on a slot centerline, which is a radial line passing through the circumferential center of one of the N slots. A first straight line portion depression recessed radially inward is formed in the center of at least one of the two first straight line portions. An arc portion depression recessed radially inward is formed in the arc portion. In a plane perpendicular to the central axis, the area A1 of the first straight line portion depression and the area A2 of the arc portion depression satisfy A1 < A2.

[0007] In the present disclosure, the stator core is provided with a first linear portion and a second linear portion, as well as a first linear portion recess and an arc portion recess, thereby ensuring a sufficient flow path for refrigeration oil in a compressor, etc. Furthermore, because the area A1 of the first linear portion recess and the area A2 of the arc portion recess satisfy A1 < A2, it is possible to prevent the magnetic path from being locally narrowed within the stator core. In other words, it is possible to improve the oil return and leakage prevention performance of refrigeration oil while suppressing a decrease in motor efficiency.

[0008] 1. A cross-sectional view showing an electric motor of embodiment 1. A cross-sectional view showing a rotor of embodiment 1. A plan view showing a stator of embodiment 1. A perspective view showing an electric motor of embodiment 1. A plan view showing a stator core of embodiment 1. A schematic view for explaining a first straight portion, a second straight portion, and an arc portion of the stator core of embodiment 1. Schematic views (A), (B), and (C) for explaining the areas of the first straight portion recess, the arc portion recess, and the second straight portion recess of embodiment 1. A view for explaining the distance between two first straight portions and the distance between two second straight portions of embodiment 1. A view for explaining the distance from the arc portion recess to the first straight portion and the distance from the arc portion recess to the second straight portion of embodiment 1. Schematic views (A) and (B) showing an example of a deformed state of the stator core. A view for explaining the position of a crimped portion in the stator core of embodiment 1. A view showing a stator core of a modified example of embodiment 1. A view showing a compressor of embodiment 2. FIG. 10 is a diagram showing a refrigeration cycle device according to a third embodiment.

[0009] Embodiment 1. <Configuration of Electric Motor> Fig. 1 is a plan view showing an electric motor 3 according to embodiment 1. The electric motor 3 according to embodiment 1 has an annular stator 1 and a rotatable rotor 5 provided inside the stator 1. An air gap of 0.25 to 1.0 mm is provided between the stator 1 and the rotor 5.

[0010] Hereinafter, the direction of the central axis Ax, which is the center of rotation of the rotor 5, will be referred to as the "axial direction." The circumferential direction centered on the central axis Ax will be referred to as the "circumferential direction." The radial direction centered on the central axis Ax will be referred to as the "radial direction."

[0011] <Configuration of the rotor> Fig. 2 is a cross-sectional view showing the rotor 5. As shown in Fig. 2, the rotor 5 has a rotor core 50 and permanent magnets 55 attached to the rotor core 50. The rotor core 50 is made by laminating electromagnetic steel sheets in the axial direction and fixing them together by caulking, rivets, or the like. The thickness of the electromagnetic steel sheets is 0.1 to 1.0 mm, and is 0.35 mm, for example.

[0012] The rotor core 50 has a cylindrical shape centered on the central axis Ax. A shaft 90 of the compressor 8 (FIG. 13) is press-fitted into a central hole 50a of the rotor core 50. The central axis of the shaft 90 coincides with the above-mentioned central axis Ax.

[0013] The rotor core 50 has a plurality of magnet insertion holes 51 along its outer periphery. Here, six magnet insertion holes 51 are arranged at equal intervals in the circumferential direction. One permanent magnet 55 is arranged in each magnet insertion hole 51.

[0014] One permanent magnet 55 constitutes one magnetic pole. Since there are six permanent magnets 55, the rotor 5 has six poles. However, the number of poles of the rotor 5 is not limited to six, as long as it is two or more. Furthermore, two or more permanent magnets 55 may be placed in one magnet insertion hole 51.

[0015] The circumferential center of each magnet insertion hole 51 is the pole center P. A radial line passing through the pole center P is defined as the magnetic pole center line. The magnetic pole center line is the d-axis of the rotor 5. The space between adjacent magnet insertion holes 51 is defined as an inter-pole portion M.

[0016] The permanent magnet 55 is a flat plate-shaped member having a width in the circumferential direction and a thickness in the radial direction. The permanent magnet 55 is magnetized in its thickness direction, i.e., in the radial direction. The permanent magnet 55 is a neodymium rare earth magnet containing neodymium (Nd), iron (Fe), and boron (B). However, it may also be a samarium-cobalt magnet containing samarium (Sm) and cobalt (Co), or a ferrite magnet. The permanent magnet 55 is a sintered magnet made by sintering magnetic powder, but it may also be a bonded magnet made by mixing magnetic powder with resin.

[0017] A flux barrier 52 is formed at each of the circumferential ends of the magnet insertion hole 51. The flux barrier 52 is a hole that extends radially from the circumferential end of the magnet insertion hole 51 toward the outer periphery of the rotor core 50. The flux barrier 52 acts to suppress leakage flux between adjacent magnetic poles.

[0018] Radially long slits 53 are formed on the radially outer side of the magnet insertion holes 51. Here, four slits 53 are formed symmetrically with respect to the magnetic pole center line. In addition, circumferentially long side slits 54 are formed adjacent to the pole center P side of the flux barrier 52. However, the number and arrangement of the slits 53 are arbitrary. In addition, the rotor core 50 does not necessarily have to have the slits 53 and the side slits 54.

[0019] The crimped portions 59 that integrally fasten the electromagnetic steel sheets that make up the rotor core 50 are formed on radial straight lines that pass through the inter-pole portions M. The arrangement of the crimped portions 59 is not limited to the arrangement described here.

[0020] A through hole 56 is formed radially inward of the magnet insertion hole 51. Furthermore, a through hole 57 is formed radially inward of the crimped portion 59, and a through hole 58 is formed radially outward of the crimped portion 59. Each of the through holes 56, 57, and 58 extends from one axial end to the other end of the rotor core 50.

[0021] The through holes 56, 57, and 58 are used as flow paths for the refrigerant and refrigeration oil of the compressor 8 (FIG. 13). Any of the through holes 56, 57, and 58 may be used as a rivet hole. The arrangement of the through holes 56, 57, and 58 is not limited to the arrangement described here.

[0022] 1, the stator 1 has an annular stator core 10 centered on a central axis Ax, and a coil 30 wound around the stator core 10. The stator core 10 is made by stacking a plurality of electromagnetic steel plates in the axial direction and fixing them together by caulking or the like. The thickness of the electromagnetic steel plates is 0.1 to 1.0 mm, and is, for example, 0.35 mm.

[0023] Fig. 3 is a plan view showing the stator core 10. The stator core 10 has an annular core back 13 and N teeth 14 extending radially inward from the core back 13, where N is an integer equal to or greater than 2. The outer periphery of the core back 13 is fitted into the inner circumferential surface of a cylindrical shell 81 (Fig. 13). The shell 81 is part of the compressor 8 (Fig. 13) and is made of a magnetic material.

[0024] The teeth 14 are formed at equal intervals in the circumferential direction. A tooth tip 14e with a wide circumferential width is formed at the radially inner tip of each tooth 14. The tooth tip 14e of each tooth 14 faces the rotor 5 (FIG. 2). A coil 30 is wound around the teeth 14 in a distributed winding manner. The number of teeth 14 (N) is 18 in this example, but may be any number equal to or greater than two.

[0025] A slot 15 is formed between adjacent teeth 14. The number of slots 15 is the same as the number (N) of teeth 14, which is 18 in this example. A coil 30 is housed in the slot 15.

[0026] In a plane perpendicular to the central axis Ax, a radial line passing through the circumferential center of each tooth 14 is referred to as a tooth center line T. The tooth center line T is an imaginary line and includes not only the center line within the tooth 14 but also its extension.

[0027] Similarly, in a plane perpendicular to the central axis Ax, a radial line passing through the circumferential center of each slot 15 is referred to as a slot center line S. The slot center line S is an imaginary line and includes not only the center line within the slot 15 but also its extension.

[0028] Fig. 4 is a perspective view showing the electric motor 3. As shown in Fig. 4, the stator 1 has a first-phase coil 31, a second-phase coil 32, and a third-phase coil 33. For example, the first phase is U-phase, the second phase is V-phase, and the third phase is W-phase, but the combination is not limited to this. When it is not necessary to distinguish between the coils 31, 32, and 33, they will be referred to as coil 30.

[0029] Each of the coils 31, 32, and 33 has a conductor made of aluminum or copper and an insulating coating covering the conductor. The coil 31 is located at the outermost position in the radial direction, and the coil 33 is located at the innermost position in the radial direction. The coil 32 is located radially outside the coil 31 and radially inside the coil 33.

[0030] 3n coils 30 are wound around the stator core 10 for each phase, where n is an integer equal to or greater than 1. More specifically, 3n coils 31, 3n coils 32, and 3n coils 33 are wound around the stator core 10.

[0031] 4, n=1. Therefore, three coils 31, three coils 32, and three coils 33 are wound around the stator core 10. The three coils 31 are connected in series with each other, the three coils 32 are connected in series with each other, and the three coils 33 are connected in series with each other.

[0032] Three coils 31 are arranged at 120-degree intervals in the circumferential direction. Each coil 31 is wound at a pitch of three slots. Each coil 31 has a coil end 31 a extending along the end face of the stator core 10 and a coil side 31 b inserted into a slot 15.

[0033] Similarly, three coils 32 are arranged at 120-degree intervals in the circumferential direction. Each coil 32 is wound at a pitch of three slots. Each coil 32 has a coil end 32 a extending along the end face of the stator core 10 and a coil side 32 b inserted into a slot 15.

[0034] Similarly, three coils 33 are arranged at 120-degree intervals in the circumferential direction. Each coil 33 is wound at a pitch of three slots. Each coil 33 has a coil end 33 a extending along the end face of the stator core 10 and a coil side 33 b inserted into a slot 15.

[0035] The coils 31, 32, and 33 are arranged so that two of the coil ends overlap in the radial direction. The coil 32 extends from the outer circumferential side of the coil 33 to the inner circumferential side of the coil 31. Because of this arrangement, one coil side is inserted into each of the slots 15 of the stator core 10.

[0036] As described above, the electric motor 3 of the first embodiment has 6 poles, 18 slots, and a slot pitch of 3. Therefore, the winding factor kw is 1.

[0037] A centrifugal separator 60 is attached to one axial end of the shaft 90. The centrifugal separator 60 has a disk portion 61 fixed to the end of the shaft 90 via a fixed shaft 63, and a blade portion 62 fixed to the underside of the disk portion 61 (see FIG. 13). The centrifugal separator 60 is also called an oil separator.

[0038] Centrifugal separator 60 is disposed radially inward of coil ends 31 a, 32 a, 33 a of coils 31, 32, 33 of stator 1. Centrifugal separator 60 discharges refrigerating machine oil with a higher specific gravity radially outward from the refrigerant and refrigerating machine oil that have passed through through holes 56, 57, 58 ( FIG. 2 ) of rotor 5. The refrigerating machine oil discharged from centrifuge 60 passes through gaps between stator core 10 and coil ends 31 a, 32 a, 33 a toward the outer periphery of stator core 10.

[0039] <Outer peripheral shape of stator core 10> Figure 5 is a diagram for explaining the outer peripheral shape of the stator core 10. The outer periphery of the core back 13 of the stator core 10 has a shape in which a circle (referred to as a reference circle) C1 centered on the central axis Ax is cut out by a first linear portion 11A and a second linear portion 11B. Both the first linear portion 11A and the second linear portion 11B are surfaces parallel to the central axis Ax.

[0040] That is, the outer periphery of the core back 13 has, in a plane perpendicular to the central axis Ax, a first linear portion 11A extending linearly, a second linear portion 11B extending linearly, and an arc portion 12 extending arc-like. As shown in the perspective view of Fig. 4, the first linear portion 11A and the second linear portion 11B are both flat portions, and the arc portion 12 is an arc surface portion.

[0041] The arc portion 12 is fitted to the inner peripheral surface of a shell 81 ( FIG. 13 ) of the compressor 8. A flow path for refrigeration oil is formed between the first straight portion 11A and the shell 81. A flow path for refrigeration oil is also formed between the second straight portion 11B and the shell 81. The first straight portion 11A and the second straight portion 11B are also collectively referred to as straight portions 11.

[0042] Fig. 6 is a schematic diagram for explaining the straight portions 11A, 11B and the arc portion 12 of the stator core 10. In Fig. 6, a first straight portion recess 21A, a second straight portion recess 21B, and an arc portion recess 22 (Fig. 5), which will be described later, are omitted.

[0043] As shown in FIG. 6, the outer periphery of the stator core 10 is made up of two first linear portions 11A, two second linear portions 11B, and four arcuate portions 12.

[0044] The two first linear portions 11A are formed to face each other across the central axis Ax. More specifically, the two first linear portions 11A are formed symmetrically with respect to each other with respect to the central axis Ax. The circumferential center of each first linear portion 11A is located on the tooth center line T of one of the teeth 14.

[0045] The two second straight portions 11B are formed to face each other across the central axis Ax. More specifically, the two second straight portions 11B are formed symmetrically with respect to each other with respect to the central axis Ax. The circumferential center of each second straight portion 11B is located on the slot center line S of one of the slots 15.

[0046] The circumferential center of the second straight portion 11B is located at a position 90 degrees from the circumferential center of the first straight portion 11A with respect to the central axis Ax. Therefore, the outer periphery of the stator core 10 fits within a rectangular area. This shape is advantageous in terms of improving the yield when punching electromagnetic steel sheets.

[0047] The arcuate portions 12 are formed in the circumferential direction between the first linear portion 11A and the second linear portion 11B. Here, four arcuate portions 12 are formed.

[0048] To clarify the positions of the straight line portions 11A, 11B and the arc portion 12, points P1 to P8 are defined on the outer periphery of the stator core 10 in the clockwise direction in FIG.

[0049] One first straight line portion 11A has two ends at points P1 and P2, and the other first straight line portion 11A has two ends at points P5 and P6. Similarly, one second straight line portion 11B has two ends at points P3 and P4, and the other second straight line portion 11B has two ends at points P7 and P8.

[0050] Furthermore, the ends of the first arc portion 12 are points P2 and P3, the ends of the second arc portion 12 are points P4 and P5, the ends of the third arc portion 12 are points P6 and P7, and the ends of the fourth arc portion 12 are points P8 and P1.

[0051] Here, we will explain the case where the outer periphery of the stator core 10 has two first straight portions 11A, two second straight portions 11B, and four arc portions 12, but the numbers of the first straight portions 11A, second straight portions 11B, and arc portions 12 are not limited to these numbers.

[0052] 5, a first linear portion recess 21A recessed radially inward is formed at the circumferential center of the first linear portion 11A. The first linear portion recess 21A is located on the tooth center line T.

[0053] A second linear portion recess 21B is formed at the circumferential center of the second linear portion 11B, recessed radially inward. The second linear portion recess 21B is located on the slot center line S.

[0054] An arc portion recess 22 recessed radially inward is formed in the arc portion 12. The arc portion recess 22 is located on the tooth center line T. The arc portion recess 22 is also located between the first straight portion 11A and the second straight portion 11B in the circumferential direction.

[0055] The first linear portion recess 21A, the second linear portion recess 21B, and the arc portion recess 22 are all formed from one end to the other end in the axial direction of the stator core 10, and form a flow path for refrigeration oil.

[0056] In the first embodiment, a sufficient flow path for refrigerating machine oil is ensured by providing the first straight portion 11A and the second straight portion 11B in the stator core 10, as well as the first straight portion recess 21A and the arc portion recess 22. This improves the oil return property (i.e., circulation property) of the refrigerant in the compressor 8 (FIG. 13), and can suppress outflow of refrigerating machine oil into the refrigerant circuit of the refrigeration cycle device 400 (FIG. 14).

[0057] The first linear recess 21A has a triangular shape in a plane perpendicular to the central axis Ax, with the apex on the inner periphery. However, the shape of the first linear recess 21A is not limited to a triangular shape and may be, for example, rectangular or semicircular. The same applies to the shapes of the second linear recess 21B and the arcuate recess 22.

[0058] In the example shown in FIG. 5, one of the two first linear portion recesses 21A (indicated by the symbol 21A in FIG. 5) １ The shape of one of the first linear portion recesses 21A is different from the other, and may be rectangular, for example. However, the shapes of the two first linear portion recesses 21A may be the same.

[0059] 7A is a schematic diagram illustrating the area of ​​the first linear portion recess 21A. As shown in FIG. 7A, the first linear portion recess 21A has a length H1 in the circumferential direction and a depth D1 in the radial direction.

[0060] The first linear portion recess 21A has an area A1 in a plane perpendicular to the central axis Ax. The area A1 is the area of ​​a region surrounded by the reference line C2 that defines the first linear portion 11A and the inner edge of the first linear portion recess 21A in the plane perpendicular to the central axis Ax.

[0061] Fig. 7(B) is a schematic diagram for explaining the area of ​​the arc-shaped recess 22. As shown in Fig. 7(B), the arc-shaped recess 22 has a length H2 in the circumferential direction and a depth D2 in the radial direction.

[0062] The arc-portion recess 22 has an area A2 in a plane perpendicular to the central axis Ax. The area A2 is the area of ​​a region surrounded by the reference circle C1 that defines the arc portion 12 and the inner edge of the arc-portion recess 22 in the plane perpendicular to the central axis Ax.

[0063] 7C is a schematic diagram illustrating the area of ​​the second linear portion recess 21B. As shown in FIG. 7C, the second linear portion recess 21B has a length H3 in the circumferential direction and a depth D3 in the radial direction.

[0064] The second linear portion recess 21B has an area A3 in a plane perpendicular to the central axis Ax, which is the area of ​​a region surrounded by a reference line C3 that defines the second linear portion 11B and the inner edge of the second linear portion recess 21B in the plane perpendicular to the central axis Ax.

[0065] The area A1 of the first linear recess 21A (FIG. 7A) and the area A2 of the arcuate recess 22 (FIG. 7B) satisfy A1<A2.

[0066] Since the first straight portion 11A is located radially inward of the arc portion 12, if the above areas A1 and A2 are equal (i.e., A1 = A2), the shortest distance M1 ( FIG. 7A ) from the first straight portion recess 21A to the slot 15 may be too short, resulting in localized narrowing of the magnetic path within the stator core 10.

[0067] Therefore, in this first embodiment, the areas A1 and A2 are set to satisfy A1 < A2, so that the shortest distance M1 from the slot 15 to the first linear portion recess 21A is not too short, thereby preventing the magnetic path within the stator core 10 from being locally narrowed.

[0068] For the same reason, it is desirable that the radial depth D1 (Figure 7(A)) of the first straight portion recess 21A and the radial depth D2 (Figure 7(B)) of the arc portion recess 22 satisfy the relationship D1 < D2.

[0069] As long as the above areas A1 and A2 satisfy A1 < A2, either the circumferential length H1 of the first straight portion recess 21A (Figure 7(A)) or the circumferential length H2 of the arc portion recess 22 (Figure 7(B)) may be longer.

[0070] Furthermore, it is desirable that the area A1 of the first linear portion recess 21A (FIG. 7A) and the area A3 of the second linear portion recess 21B (FIG. 7C) satisfy the relationship A3<A1.

[0071] Since the second straight portion recess 21B is located on the slot center line S, if the above areas A1 and A3 are equal (i.e., A1 = A3), the shortest distance M3 (FIG. 7C) from the second straight portion recess 21B to the slot 15 may be too short.

[0072] In contrast, if the areas A1 and A3 satisfy A3<A1, the shortest distance M3 from the second linear portion recess 21B to the slot 15 will not be too short, and the magnetic path within the stator core 10 will not be locally narrowed.

[0073] For the same reason, it is desirable that the depth D1 of the first linear portion recess 21A (FIG. 7A) and the depth D3 of the second linear portion recess 21B (FIG. 7C) satisfy the relationship D3<D1.

[0074] As long as the above areas A1 and A3 satisfy A3 < A1, either the circumferential length H1 of the first straight portion recess 21A (FIG. 7A) or the circumferential length H3 of the second straight portion 11B (FIG. 7B) may be longer.

[0075] 8 is a diagram illustrating the distance L1 between the two first straight portions 11A and the distance L2 between the two second straight portions 11B of the stator core 10. As described above, the two first straight portions 11A face each other across the central axis Ax. The two second straight portions 11B also face each other across the central axis Ax.

[0076] This shape in which the two first straight portions 11A face each other across the central axis Ax and the two second straight portions 11B face each other across the central axis Ax is advantageous in reducing imbalances in the flow of magnetic flux within the stator core 10 and improving magnetic balance.

[0077] The distance L1 between the two first straight line portions 11A and the distance L2 between the two second straight line portions 11B satisfy L1<L2.

[0078] The first straight portion recess 21A is located on the tooth center line T, while the second straight portion recess 21B is located on the slot center line S. Therefore, when the distances L1 and L2 are equal (i.e., L1 = L2), the shortest distance between the second straight portion recess 21B and the slot 15 becomes shorter, and the magnetic path of the stator core 10 becomes locally narrower.

[0079] Therefore, in the first embodiment, the distances L1 and L2 are set to satisfy L1 < L2 so that the shortest distance between the second linear portion recess 21B and the slot 15 is not too short. This makes it possible to prevent the magnetic path in the stator core 10 from being locally narrowed.

[0080] Next, the position of the arc portion recess 22 in the arc portion 12 will be described. Fig. 9 is a diagram for explaining the distance E1 from the arc portion recess 22 to the first linear portion 11A and the distance E2 from the arc portion recess 22 to the second linear portion 11B.

[0081] 9 , distance E1 is the distance from end F1 of arc-portion recess 22 on the first straight portion 11A side to point P2, which is the boundary between first straight portion 11A and arc portion 12. Distance E2 is the distance from end F2 of arc-portion recess 22 on the second straight portion 11B side to point P3, which is the boundary between second straight portion 11B and arc portion 12.

[0082] In the first embodiment, the distance E1 from the arc portion recess 22 to the first linear portion 11A and the distance E2 from the arc portion recess 22 to the second linear portion 11B satisfy E1<E2. In other words, the arc portion recess 22 is formed at a position closer to the first linear portion 11A than the circumferential center of the arc portion 12. The effect of E1<E2 is as follows.

[0083] 10A is a schematic diagram showing the deformation state of a stator core 10 that satisfies E1<E2 during shrink fitting. The stator core 10 is fixed to a shell 81 of a compressor 8 or the like by shrink fitting. During shrink fitting, the stator core 10 is inserted inside the shell 81, which has been heated in advance to expand its inner diameter. When the shell 81 cools and shrinks radially inward, the stator core 10 fits inside the shell 81. The amount of shrinkage of the shell 81 is determined by the shrink fitting allowance. The shrink fitting allowance is generally 20 μm to 200 μm, but is assumed to be 200 μm here.

[0084] When the shell 81 contracts in this way, the portions of the shell 81 corresponding to the straight portions 11A and 11B contract significantly, but the portions corresponding to the arc portions 12 contract less due to resistance from the arc portions 12.

[0085] Therefore, the shape of the shell 81 is as shown by the reference numeral 81 in FIG. ｄｅｆ 10A, in order to clearly show the shape of the shell 81, the shell 81 is shown as bulging outward in the radial direction from the stator core 10, but in reality the shell 81 contracts inward in the radial direction and presses against the arc portion 12 of the stator core 10.

[0086] The stator core 10 is deformed radially inward due to the compressive stress from the shell 81. The stator core 10 is particularly susceptible to deformation around the recesses 21A, 21B, and 22.

[0087] The amount of radial inward deformation of the first straight portion recess 21A is Q1, the amount of radial inward deformation of the arc portion recess 22 is Q2, and the amount of radial inward deformation of the second straight portion recess 21B is Q3.

[0088] In the case of the stator core 10 that satisfies E1<E2, the deformation amount Q1 of the first linear portion recess 21A and the deformation amount Q2 of the arc portion recess 22 are both relatively small, and the deformation amount Q3 of the second linear portion 11B is relatively large. The large deformation amount Q3 is due to the relationship L1<L2 described with reference to FIG. 8.

[0089] 10B is a schematic diagram showing the deformation state of a stator core 10E that satisfies E1>E2 during shrink fitting. In the stator core 10E, the arc-portion recesses 22 are formed closer to the second linear portions 11B than the circumferential center of the arc-portion 12. Except for the position of the arc-portion recesses 22, the stator core 10E is configured similarly to the stator core 10.

[0090] As shown in Figure 10(B), in the case of a stator core 10E that satisfies E1 > E2, the deformation amounts Q1 and Q3 of the straight portion recesses 21A and 21B are equivalent to those in Figure 10(A), but the deformation amount Q2 of the arc portion recess 22 is larger than that in Figure 10(A).

[0091] Since the arc recess 22 is located on the center line of the tooth, if the radial inward deformation amount Q2 of the arc recess 22 is large, the gap between the tooth 14 and the rotor 5 (Figure 1) will be narrowed, causing an increase in noise.

[0092] Therefore, as shown in FIG. 10A, a stator core 10 that satisfies E1<E2 is desirable.

[0093] Next, the positions of the crimped portions 18 in the stator core 10 will be described. Fig. 11 is a diagram for explaining the positions of the crimped portions 18 in the stator core 10. The stator core 10 is formed by a laminate of a plurality of electromagnetic steel sheets, and the plurality of electromagnetic steel sheets are fixed at the crimped portions 18.

[0094] When the stator core 10 is fixed to the shell 81 by shrink fitting, the shrink fitting allowance is generally 20 μm to 200 μm, but may exceed this range. If the compressive stress that the stator core 10 receives from the shell 81 is large, deformation of the electromagnetic steel sheets occurs on the axial end faces of the stator core 10. Deformation of the electromagnetic steel sheets may lead to damage to the insulating coating of the coils 30 wound around the teeth 14.

[0095] Both the first linear recess 21A and the arcuate recess 22 are located on the tooth center line T, but the amount of deformation when subjected to compressive stress is greater in the arcuate recess 22 than in the first linear recess 21A. Therefore, it is desirable to provide crimped portions 18 on both circumferential sides of the arcuate recess 22.

[0096] In particular, if the crimped portions 18 are provided between the arcuate recess 22 and the first linear portion 11A, and between the arcuate recess 22 and the second linear portion 11B, the fastening force of the electromagnetic steel sheets can be increased.

[0097] On the other hand, since magnetic flux flows through the stator core 10, forming the crimped portion 18 in a portion where a large amount of magnetic flux flows increases magnetic resistance. For this reason, it is desirable to form the crimped portion 18 as close to the outer periphery of the core back 13 as possible.

[0098] Specifically, it is desirable that the distance R1 from the central axis Ax to the crimped portion 18 and the distance R2 from the central axis Ax to the arcuate recess 22 satisfy R1≧R2.

[0099] Furthermore, since the magnetic flux that flows through the teeth 14 flows into the core back 13 and is divided into two parts flowing in the circumferential direction, the flow of magnetic flux is relatively small on the tooth center line T of the core back 13. For this reason, it is desirable to form the crimped portion 18 on the tooth center line T of the core back 13.

[0100] In this way, by forming the crimped portion 18 so that R1≧R2 is satisfied and on the tooth center line T, it is possible to increase the fastening force of the electromagnetic steel plate while suppressing an increase in magnetic resistance, and to suppress deformation of the stator core 10.

[0101] Although the stator core 10 has 18 slots in this example, the number of slots is not limited to 18 and may be, for example, 24, 36, or the like.

[0102] Further, although an example in which the first straight portion recess 21A is formed in both of the two first straight portions 11A has been described here, it is sufficient that the first straight portion recess 21A is formed in at least one of the first straight portions 11A.

[0103] Similarly, although an example in which second straight portion recesses 21B are formed in both of the two second straight portion 11B has been described here, it is sufficient that second straight portion recesses 21B are formed in at least one second straight portion 11B.

[0104] Similarly, although an example in which the arcuate recesses 22 are formed in all four arcuate portions 12 has been described here, it is sufficient that the arcuate recesses 22 are formed in at least one arcuate portion 12 .

[0105] <Effects of the embodiment> As described above, in the stator 1 according to the first embodiment, the stator core 10 has an annular core back 13, N (N is an integer of 2 or greater) teeth 14, and N slots 15. The outer periphery of the core back 13 has, in a plane perpendicular to the central axis Ax, two first straight portions 11A that both extend linearly, two second straight portions 11B that both extend linearly, and an arc portion 12 that extends arc-shaped in the circumferential direction between the first straight portion 11A and the second straight portion 11B. The two first straight portions 11A face each other across the central axis Ax, and the two second straight portions 11B face each other across the central axis Ax. The circumferential center of each first straight portion 11A is located on the tooth center line T of one of the teeth 14, and the circumferential center of each second straight portion 11B is located on the slot center line S of one of the slots 15. A first straight portion recess 21A recessed radially inward is formed in the circumferential center of at least one of the two first straight portions 11A. An arc portion recess 22 recessed radially inward is formed in the arc portion 12. In a plane perpendicular to the central axis Ax, the area A1 of the first straight portion recess 21A and the area A2 of the arc portion recess 22 satisfy A1 < A2.

[0106] In this way, the provision of first straight portion 11A and second straight portion 11B in stator core 10, as well as first straight portion recess 21A and arc portion recess 22, ensures a sufficient flow path for refrigerant oil. Furthermore, by ensuring that area A1 of first straight portion recess 21A and area A2 of arc portion recess 22 satisfy A1 < A2, it is possible to prevent the magnetic path from being locally narrowed within stator core 10. In other words, it is possible to improve the oil return property and outflow prevention performance of refrigerant oil while avoiding a decrease in motor efficiency.

[0107] Furthermore, the coils 30 are wound around the stator core 10 in a distributed winding manner, with 3n coils per phase (n is an integer greater than or equal to 1), and the winding factor is 1, so that the magnetic flux of the permanent magnet 55 can be linked to the coils 30 most efficiently, thereby improving the efficiency of the motor.

[0108] Furthermore, since the stator core 10 has 18 slots 15 (i.e., N = 18), it is possible to realize an electric motor 3 in which the stator core 10 has the first straight portion 11A, the second straight portion 11B, and the arc portion 12 as described above, and in which the winding factor is 1.

[0109] Furthermore, since the distance L1 between the two first straight portions 11A and the distance L2 between the two second straight portions 11B satisfy L1 < L2, the shortest distance between the slot 15 and the straight portions 11A, 11B is prevented from becoming too short, and it is possible to avoid the magnetic path of the stator core 10 from becoming locally narrow.

[0110] Furthermore, since the distance E1 from the arc portion recess 22 to the first straight portion 11A and the distance E2 from the arc portion recess 22 to the second straight portion 11B satisfy E1 < E2, deformation of the stator core 10 can be suppressed in response to the compressive stress that the stator core 10 receives from the shell 81.

[0111] Furthermore, a crimped portion 18 is formed on the stator core 10, and the distance R1 from the central axis Ax to the crimped portion 18 and the distance R2 from the central axis Ax to the arc portion recess 22 satisfy R1 ≧ R2, thereby improving the fastening force of the electromagnetic steel plates of the stator core 10 and suppressing deformation of the stator core 10 due to compressive stress from the shell 81.

[0112] Furthermore, since the crimped portion 18 is disposed on the tooth center line T of one of the teeth 14, the effect of the crimped portion 18 on the flow of magnetic flux within the stator core 10 can be minimized.

[0113] Furthermore, since the circumferential center of the second straight portion 11B is located at a position 90 degrees from the circumferential center of the first straight portion 11A with respect to the central axis Ax, the stator core 10 fits within a rectangular area, improving the yield when punching the electromagnetic steel sheet.

[0114] Furthermore, in a plane perpendicular to the central axis Ax, the area A1 of the first straight portion recess 21A and the area A3 of the second straight portion recess 21B satisfy A3 < A1, so that the shortest distance between the second straight portion recess 21B and the slot 15 is not too short, and it is possible to avoid the magnetic path of the stator core 10 from being locally narrowed.

[0115] 12 is a plan view showing a modified stator core 10A. The modified stator core 10A differs from the stator core 10 of the first embodiment in that each arc portion 12 has two arc portion recesses 22A, 22B.

[0116] In the arc portion 12, the first arc portion recess 22A is formed on the first linear portion 11A side, and the second arc portion recess 22B is formed on the second linear portion 11B side. Both the first arc portion recess 22A and the second arc portion recess 22B are located on the tooth center line T of the corresponding tooth 14.

[0117] 12, the first arc-shaped recess 22A and the second arc-shaped recess 22B have the same area in a plane perpendicular to the central axis Ax, but the areas may be different from each other. It is desirable that the relationship A1<A2 described in the first embodiment be satisfied for both the first arc-shaped recess 22A and the second arc-shaped recess 22B.

[0118] In the modified example of Figure 12, two arc recesses 22A, 22B are formed in each arc portion 12, so the flow path for refrigerant oil can be made larger than in embodiment 1, and oil return properties can be further improved.

[0119] Second Embodiment Next, a compressor 8 according to a second embodiment will be described. Fig. 13 is a cross-sectional view showing the compressor 8. The compressor 8 here is a rotary compressor.

[0120] The compressor 8 includes a sealed container 80, a compression mechanism 9 disposed in the sealed container 80, an electric motor 3 that drives the compression mechanism 9, a shaft 90 that connects the electric motor 3 and the compression mechanism 9, and a centrifuge 60 fixed to the shaft 90. The configuration of the electric motor 3 is as described in the first embodiment.

[0121] The centrifuge 60 is disposed above the rotor 5 of the electric motor 3 and radially inside the coil 30 of the stator 1. The centrifuge 60 has a disk portion 61 fixed to the upper end of the shaft 90 via a fixed shaft 63, and a blade portion 62 fixed to the underside of the disk portion 61.

[0122] The sealed container 80 is a sealed container made of, for example, a steel plate, and covers the electric motor 3 and the compression mechanism 9. The sealed container 80 has a shell 81 and an upper container part 82. Attached to the upper container part 82 are a glass terminal 83 serving as a terminal part for supplying electric power to the electric motor 3 from outside the compressor 8, and a discharge pipe 85 for discharging the refrigerant compressed in the compressor 8 to the outside. The shell 81 houses the electric motor 3 and the compression mechanism 9.

[0123] The compression mechanism 9 has an annular first cylinder 91 and a second cylinder 92 arranged along the shaft 90. The first cylinder 91 and the second cylinder 92 are fixed to the inner periphery of the shell 81. An annular first piston 93 is arranged on the inner periphery of the first cylinder 91, and an annular second piston 94 is arranged on the inner periphery of the second cylinder 92. The first piston 93 and the second piston 94 are rotary pistons that rotate together with the shaft 90.

[0124] A partition plate 97 is provided between the first cylinder 91 and the second cylinder 92. The partition plate 97 is a disk-shaped member with a through-hole in the center. The cylinder chambers of the first cylinder 91 and the second cylinder 92 are provided with vanes (not shown) that divide the cylinder chambers into an intake side and a compression side. The first cylinder 91, the second cylinder 92, and the partition plate 97 are fixed together with bolts 98.

[0125] An upper frame 95 is disposed above the first cylinder 91 so as to close the upper side of the cylinder chamber of the first cylinder 91. A lower frame 96 is disposed below the second cylinder 92 so as to close the lower side of the cylinder chamber of the second cylinder 92. The upper frame 95 and the lower frame 96 support the shaft 90 rotatably.

[0126] An oil reservoir 86 is provided at the bottom of the shell 81 to store refrigeration oil for lubricating the sliding parts of the compression mechanism 9. The refrigeration oil flows up through a hole 90a formed in the shaft 90 in the axial direction, and is supplied to the sliding parts of the compression mechanism 9 from oil supply holes 90b (only one of which is shown in FIG. 13 ) formed in multiple locations on the shaft 90.

[0127] The stator 1 of the electric motor 3 is attached to the inside of the shell 81 by shrink fitting. Electric power is supplied to the coil 30 of the stator 1 through lead wires 84 from glass terminals 83 attached to the upper part 82 of the case. The rotor 5 is fixed to the shaft 90 as described above.

[0128] An accumulator 87 that stores refrigerant gas is attached to the shell 81. The accumulator 87 is attached, for example, to the outside of the shell 81. A pair of suction pipes 88, 89 are attached to the shell 81, and refrigerant gas is supplied from the accumulator 87 to cylinders 91, 92 via the suction pipes 88, 89.

[0129] As the refrigerant, for example, R410A, R407C, or R22 may be used, but from the viewpoint of preventing global warming, it is desirable to use a refrigerant with a low GWP (global warming potential). For example, the following refrigerants can be used as the low GWP refrigerant.

[0130] (1) First, a halogenated hydrocarbon having a carbon-carbon double bond in its composition, such as HFO (Hydro-Fluoro-Orefin)-1234yf (CF ３ CF=CH ２) can be used. The GWP of HFO-1234yf is 4. (2) Alternatively, a hydrocarbon having a carbon-carbon double bond in its composition, such as R1270 (propylene), may be used. The GWP of R1270 is 3, which is lower than that of HFO-1234yf, but its flammability is higher than that of HFO-1234yf. (3) Alternatively, a mixture containing at least one halogenated hydrocarbon having a carbon-carbon double bond in its composition or a hydrocarbon having a carbon-carbon double bond in its composition, such as a mixture of HFO-1234yf and R32, may be used. The above-mentioned HFO-1234yf is a low-pressure refrigerant and therefore tends to cause large pressure loss, which may lead to a decrease in the performance of the refrigeration cycle (especially the evaporator). Therefore, it is practically desirable to use a mixture of HFO-1234yf with R32 or R41, which are higher-pressure refrigerants than HFO-1234yf.

[0131] The basic operation of the compressor 8 is as follows: Refrigerant gas supplied from the accumulator 87 is supplied to each cylinder chamber of the first cylinder 91 and the second cylinder 92 through suction pipes 88 and 89. When the electric motor 3 is driven to rotate the rotor 5, the shaft 90 rotates together with the rotor 5.

[0132] When the shaft 90 rotates, a first piston 93 and a second piston 94 fitted to the shaft 90 rotate eccentrically within the respective cylinder chambers of the cylinders 91 and 92, compressing the refrigerant. The compressed refrigerant is discharged from the cylinders 91 and 92 and flows upward through the through holes 56, 57, and 58 (FIG. 2) of the rotor 5.

[0133] Meanwhile, refrigeration oil stored in oil reservoir 86 at the bottom of compressor 8 flows upward through hole 90a formed in shaft 90 and is supplied through oil supply hole 90b to each sliding part of compression mechanism 9. In addition, some of the refrigeration oil flows upward together with the refrigerant through through holes 56, 57, 58 (FIG. 2) of rotor 5.

[0134] The refrigerant and refrigerating machine oil that have passed through the through holes 56, 57, 58 of the rotor 5 collide with the centrifugal separator 60. Since the refrigerating machine oil has a higher specific gravity than the refrigerant, it is discharged by the centrifugal separator 60 radially outward.

[0135] Therefore, the refrigerant rises further within the shell 81, is discharged from the discharge pipe 85, and is sent to the refrigerant circuit of the refrigeration cycle device 400 (FIG. 14).

[0136] Meanwhile, refrigeration oil discharged from the centrifuge 60 passes through the gap between the stator core 10 and the coil 30, heads radially outward, collides with the inner surface of the shell 81, and flows into the flow passage between the straight portions 11A, 11B (including the straight portion recesses 21A, 21B) of the stator core 10 and the shell 81, and into the flow passage between the arc portion recesses 22 and the shell 81. The refrigeration oil flows downward through the flow passage and returns to the oil reservoir 86.

[0137] The smooth circulation of the refrigerating machine oil within the compressor 8 prevents the refrigerating machine oil from being discharged together with the refrigerant from the discharge pipe 85. This prevents the refrigerating machine oil from being mixed into the refrigerant circuit of the refrigeration cycle device, and also prevents a shortage of refrigerating machine oil for lubricating the compression mechanism 9.

[0138] The compressor 8 of the second embodiment has the electric motor 3 described in the first embodiment, and therefore can improve the oil return property and the outflow prevention performance of the refrigeration oil, thereby preventing the refrigeration oil from being mixed into the refrigerant circuit of the refrigeration cycle device and preventing a shortage of the refrigeration oil for lubricating the compression mechanism 9.

[0139] Furthermore, because the centrifugal separator 60 is disposed radially inside the coil ends 31 a, 32 a, 33 a of the coil 30 of the stator 1, the refrigeration oil discharged from the centrifuge 60 can be directed through the gaps between the stator core 10 and the coil ends 31 a, 32 a, 33 a toward the straight portions 11A, 11B (including the straight portion recesses 21A, 21B) and the arc portion recesses 22. This further improves the oil return property and outflow prevention performance of the refrigeration oil.

[0140] Third Embodiment Next, a refrigeration cycle apparatus 400 according to a third embodiment will be described. Fig. 14 is a diagram showing the refrigeration cycle apparatus 400. The refrigeration cycle apparatus 400 is, for example, an air conditioner, but is not limited thereto and may be, for example, a refrigerator.

[0141] 14 includes a compressor 401, a condenser 402 that condenses a refrigerant, a pressure reducing device 403 that reduces the pressure of the refrigerant, and an evaporator 404 that evaporates the refrigerant. The compressor 401, the condenser 402, and the pressure reducing device 403 are provided in an outdoor unit 410, and the evaporator 404 is provided in an indoor unit 420.

[0142] The compressor 401, the condenser 402, the pressure reducing device 403, and the evaporator 404 are connected by refrigerant piping 407 to form a refrigerant circuit. The compressor 401 is configured as the compressor 8 (FIG. 13) described in the second embodiment. The refrigeration cycle apparatus 400 also includes an outdoor fan 405 facing the condenser 402 and an indoor fan 406 facing the evaporator 404.

[0143] The refrigeration cycle apparatus 400 operates as follows: The compressor 401 compresses the refrigerant it draws in and sends it out as high-temperature, high-pressure refrigerant gas. The condenser 402 exchanges heat between the refrigerant sent out from the compressor 401 and outdoor air sent by the outdoor air blower 405, condenses the refrigerant, and sends it out as liquid refrigerant. The pressure reducing device 403 expands the liquid refrigerant sent out from the condenser 402 and sends it out as low-temperature, low-pressure liquid refrigerant.

[0144] The evaporator 404 exchanges heat between the low-temperature, low-pressure liquid refrigerant sent from the pressure reducing device 403 and the indoor air, evaporating the refrigerant and sending it out as refrigerant gas. The air from which heat has been removed by the evaporator 404 is supplied into the room by the indoor fan 406.

[0145] In the refrigeration cycle apparatus 400 of the third embodiment, the compressor 401 is configured as the compressor 8 described in the second embodiment, and therefore, the intrusion of refrigeration oil into the refrigerant circuit is prevented. Therefore, it is possible to prevent a decrease in operating efficiency due to the intrusion of refrigeration oil, and it is possible to improve the operating efficiency of the refrigeration cycle apparatus 400.

[0146] Although the preferred embodiments have been specifically described above, the present disclosure is not limited to the above-described embodiments, and various improvements and modifications can be made.

[0147] DESCRIPTION OF SYMBOLS 1 stator, 5 rotor, 8 compressor, 9 compression mechanism, 10 stator core, 11A first straight portion, 11B second straight portion, 12 arc portion, 13 core back, 14 teeth, 15 slot, 18 crimped portion, 21A first straight portion recess, 21B second straight portion recess, 22 arc portion recess, 30, 31, 32, 33 coil, 50 rotor core, 51 magnet insertion hole, 55 permanent magnet, 56, 57, 58 through hole, 60 centrifuge, 80 sealed container, 81 shell, 82 container upper portion, 86 oil reservoir, 90 shaft, 400 refrigeration cycle device, 401 compressor, 402 condenser, 403 pressure reducing device, 404 evaporator, S slot centerline, T teeth centerline.

Claims

1. Stator core and The coil wrapped around the stator core and It has, The stator core is, An annular core back centered on the central axis, N teeth (where N is an integer of 2 or more) extend radially inward from the core back with respect to the central axis, N slots are formed between two adjacent teeth among the N teeth mentioned above. It has, The outer circumference of the core back has, in a plane perpendicular to the central axis, two first straight sections extending in a straight line, two second straight sections extending in a straight line, and an arc section extending in an arc shape between one of the two first straight sections and one of the two second straight sections in the circumferential direction about the central axis. The two first straight sections face each other across the central axis, and the two second straight sections face each other across the central axis. The circumferential center of each first straight section is located on the tooth centerline, which is a radial straight line passing through the circumferential center of any of the N teeth. The circumferential center of each second straight section is located on the slot centerline, which is a radial straight line passing through the circumferential center of any of the N slots. At least one of the two first straight sections has a first straight section recess formed in its center, which is recessed radially inward. The aforementioned arc portion has an arc recess formed inward in the radial direction. In the plane perpendicular to the central axis, the area A1 of the first straight recess and the area A2 of the arc recess satisfy A1 < A2. The distance L1 between the two first straight sections and the distance L2 between the two second straight sections satisfy L1 < L2. stata.

2. The coil is wound around the stator core in a distributed winding pattern, with 3n coils per phase (where n is an integer greater than or equal to 1), and the winding coefficient is 1. The stator according to claim 1.

3. N is 18. The stator according to claim 1 or 2.

4. The distance E1 from the arc recess to the first straight section and the distance E2 from the arc recess to the second straight section satisfy E1 < E2. The stator according to claim 1 or 2.

5. A crimped portion is formed on the stator core. The distance R1 from the central axis to the crimped portion and the distance R2 from the central axis to the arc recess satisfy R1 ≥ R2. The stator according to claim 1 or 2.

6. A crimped portion is formed on the stator core. The crimped portion is positioned on the center line of one of the N teeth. The stator according to claim 1 or 2.

7. The circumferential center of the second straight section is located at a 90-degree angle from the circumferential center of the first straight section with respect to the central axis. The stator according to claim 1 or 2.

8. At least one of the two second straight sections has a second straight section recess formed in the center, which is recessed radially inward. In the plane perpendicular to the central axis, the area A1 of the first straight recess and the area A3 of the second straight recess satisfy A3 < A1. The stator according to claim 1 or 2.

9. Two or more arc-shaped recesses are formed in the aforementioned arc portion. The stator according to claim 1 or 2.

10. A stator according to claim 1 or 2, A rotor positioned inside the stator and An electric motor equipped with [a specific feature].

11. The electric motor according to claim 10, A compression mechanism driven by the aforementioned electric motor, A shaft connecting the electric motor and the compression mechanism, A centrifugal separator fixed to the aforementioned shaft and A compressor equipped with a compressor.

12. The centrifugal separator is located radially inward of the coil ends of the coils of the stator. The compressor according to claim 11.

13. A compressor according to claim 11, a condenser, a pressure reducing device, and an evaporator are included. Refrigeration cycle device.