Stator, electric motor, compressor, and refrigeration cycle device

Abstract

This stator is used in an electric motor mounted on a compressor. A refrigerant used in the compressor is: a single refrigerant of any of R1234yf, R1234ze(E), R32, and R290, or a mixed refrigerant containing at least one thereof; a single refrigerant of R1132(E), or a mixed refrigerant containing this single refrigerant; or a mixed refrigerant containing at least one of R444A, R444B, R445A, R446A, R447A, R447B, R452B, R454A, R454B, R454C, R455A, R457A, R459A, and R459B. The distance Di from the central axis to the inner periphery of the stator core, the distance Do from the central axis to the outer periphery of the stator core, the distance Ds from the central axis to a position close to the most outer periphery of the slot, and a pressure ratio PA [%] that is the ratio of the saturation pressure of the refrigerant to the saturation pressure of R32 satisfy the relationship of 0.0042 PA 2 +0.0061 PA +17.44 [%] ≤ (Ds-Di) / (Do-Di) × 100 ≤ 56.7 [%].

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] There is a demand for refrigerants with low GWP (global warming potential) as compressor refrigerants. Examples of low GWP refrigerants include HFO refrigerants and HC refrigerants. These refrigerants are characterized by low operating pressure, which reduces the torque required for electric motors.

[0003] In order to obtain the same compressor capacity when using a refrigerant with a low operating pressure as when using a refrigerant with a high operating pressure, it is necessary to operate the electric motor at a high rotation speed. That is, when using a refrigerant with a low operating pressure, it is necessary to operate the electric motor at a low torque and a high rotation speed.

[0004] Conventionally, techniques have been developed for reducing losses in electric motors by optimizing the shape and dimensions of a stator core (for example, see Patent Document 1).

[0005] JP 2019-30056 A (see abstract)

[0006] However, no technology has been developed to improve the efficiency of an electric motor when a refrigerant with a low operating pressure is used and the electric motor is driven at a low torque and a high rotation rate.

[0007] The present disclosure has been made to solve the above-mentioned problems, and aims to improve the efficiency of an electric motor when a refrigerant with a low operating pressure is used and the electric motor is driven at a low torque and a high rotation speed.

[0008] A stator according to the present disclosure is a stator for an electric motor mounted in a compressor, comprising: a stator core formed in an annular shape centered on a central axis and having slots formed from the inner periphery toward the outer periphery; and coils wound in distributed winding on the stator core and housed in the slots, wherein the refrigerant used in the compressor is any one of R1234yf, R1234ze(E), R32, and R290, or a mixed refrigerant containing at least one of these; R1132(E) alone or a mixed refrigerant containing R1132(E), or a mixed refrigerant containing at least one of R444A, R444B, R445A, R446A, R447A, R447B, R452B, R454A, R454B, R454C, R455A, R457A, R459A, and R459B; and wherein a distance Di from the central axis to the inner periphery of the stator core and a distance L from the central axis to the inner periphery of the stator core are set to be equal to or larger than a distance L from the central axis to the inner periphery of the stator core. Distance Do from the central axis to the outer periphery of the stator core, Distance Ds from the central axis to the position closest to the outer periphery of the slot, Pressure ratio P which is the ratio of the saturation pressure of the refrigerant to the saturation pressure of R32 Ａ [%] and 0.0042P Ａ ２ +0.0061P Ａ +17.44[%]≦(Ds−Di) / (Do−Di)×100≦56.7[%] is satisfied.

[0009] According to the present disclosure, the distances Di, Do, and Ds of the stator core and the pressure ratio P of the saturation pressure of the refrigerant Ａ By satisfying the above relationship, it is possible to improve the efficiency of the electric motor when a refrigerant with a low operating pressure is used and the electric motor is driven at a low torque and a high rotation speed.

[0010] 7 is a cross-sectional view showing an electric motor according to a first embodiment; FIG. 8 is a cross-sectional view showing a portion of an electric motor according to a first embodiment; FIG. 9 is a diagram showing two configuration examples of an electric motor according to a first embodiment; FIG. 10 is a cross-sectional view showing a compressor according to a first embodiment; FIG. 11 is a diagram showing a refrigeration cycle device according to a first embodiment; FIG. 12 is a graph showing a relationship between (Ds-Di) / (Do-Di) and electric motor efficiency when refrigerants 1 to 9 are used; FIG. 13 is a graph showing an enlarged view of a portion of the graph of FIG. 6; FIG. 14 is a graph showing the curves for refrigerant 1 and refrigerant 2 extracted from FIG. 7; FIG. 15 is a graph showing the curves for refrigerant 1 and 9 extracted from FIG. 7; FIG. 16 is a graph showing a favorable range of electric motor efficiency when refrigerants 1 to 9 are used; FIG. 17 is a graph showing the relationship between the operating pressure ratio and the lower limit of (Ds-Di) / (Do-Di); FIG. 18 is a graph showing the relationship between the shortest distance Dc from the slot to the notch and the torque ripple rate.

[0011] Embodiment 1. <Configuration of electric motor> Fig. 1 is a cross-sectional view showing an electric motor 3 according to embodiment 1. Fig. 2 is a cross-sectional view showing a part of the electric motor 3. The electric motor 3 according to embodiment 1 is a permanent magnet built-in type electric motor, and is mounted in a compressor 8 (Fig. 4) of a refrigeration cycle device and used together with a refrigerant.

[0012] The electric motor 3 has a rotor 5 and a stator 1 provided to surround the rotor 5. An air gap of, for example, 0.1 mm to 1.5 mm is formed between the stator 1 and the rotor 5. The stator 1 is incorporated inside a cylindrical shell 81 of the compressor 8 (FIG. 5).

[0013] Hereinafter, the direction of the central axis Ax, which is the central axis of rotation of the rotor 5, will be referred to as the "axial direction." The radial direction centered on the central axis Ax will be referred to as the "radial direction." The circumferential direction centered on the central axis Ax will be referred to as the "circumferential direction."

[0014] 1, the rotor 5 has an annular rotor core 50 centered on a central axis Ax, and permanent magnets 55 embedded in the rotor core 50. The rotor core 50 is formed by stacking laminated elements in the axial direction and fixing them together by caulking or the like. The laminated elements are made of electromagnetic steel sheets or amorphous foil.

[0015] When the lamination elements are electromagnetic steel sheets, the thickness is, for example, 0.1 mm to 1.0 mm, and here, 0.35 mm. When the lamination elements are amorphous foils, the thickness is, for example, 20 μm to 50 μm.

[0016] A center hole 50b is formed in the radial center of the rotor core 50. A shaft 90, which is a rotating shaft, is fixed in the center hole 50b of the rotor core 50 by shrink fitting, press fitting, or the like.

[0017] A plurality of magnet insertion holes 51 are formed along the outer periphery 50a of the rotor core 50. One permanent magnet 55 is inserted into each magnet insertion hole 51. One magnet insertion hole 51 corresponds to one magnetic pole. Because the rotor core 50 has six magnet insertion holes 51, the rotor 5 has six poles. However, the number of poles of the rotor 5 is not limited to six, and may be two or more.

[0018] The permanent magnets 55 are flat, have a thickness in the radial direction, and a width in the direction perpendicular to the thickness. The permanent magnets 55 are magnetized in the thickness direction. The circumferential center of the magnet insertion holes 51 corresponds to the pole center. An inter-pole portion is formed between adjacent magnet insertion holes 51. The permanent magnets 55 inserted into adjacent magnet insertion holes 51 have opposite magnetization directions.

[0019] Although one permanent magnet 55 is inserted into each magnet insertion hole 51 in this example, two or more permanent magnets 55 may be inserted into each magnet insertion hole 51. Furthermore, although the magnet insertion holes 51 extend linearly in a plane perpendicular to the axial direction, they may also extend in a V-shape, for example.

[0020] The permanent magnet 55 is a rare earth magnet. More specifically, it is a neodymium magnet containing neodymium (Nd), boron (B), and iron (Fe), or a samarium-cobalt magnet containing samarium (Sm) and cobalt (Co). The permanent magnet 55 is not limited to a rare earth magnet, and may also be a ferrite magnet. Furthermore, the permanent magnet 55 may also be a sintered magnet or a bonded magnet.

[0021] If the permanent magnet 55 is a rare earth magnet, the residual magnetic flux density (Br) is preferably 1.2 T to 1.6 T. If the residual magnetic flux density of the permanent magnet 55 is within this range, it is possible to generate the output of the electric motor 3 required to compress the refrigerant in the compressor 8. If the permanent magnet 55 is a ferrite magnet, the residual magnetic flux density (Br) is preferably 0.35 T to 0.5 T, and it is desirable to use the permanent magnet 55 with a longer axial length than in the case of a rare earth magnet.

[0022] 2, the magnet insertion hole 51 has flux barriers 52, which are gaps, at both circumferential ends thereof. A thin-walled portion is formed between the flux barrier 52 and the outer periphery 50a of the rotor core 50. The radial width of the thin-walled portion is set to be the same as the thickness of the laminated element.

[0023] A side slit 53 is formed on the polar center side of the flux barrier 52 in the rotor core 50. The side slit 53 extends in the circumferential direction along the outer periphery 50a of the rotor core 50. However, the rotor core 50 does not necessarily have to have the side slit 53 formed therein.

[0024] A plurality of radially long slits 54 are formed on the outer periphery of each magnet insertion hole 51 in rotor core 50. Each slit 54 functions to make the magnetic flux distribution on outer periphery 50a of rotor core 50 closer to a sine wave. Here, four slits 54 are formed symmetrically with respect to the pole center, but the number and arrangement of slits 54 are optional. Also, rotor core 50 does not necessarily have to have slits 54 formed therein.

[0025] In the rotor core 50, through holes 56, 57, and 58 are formed radially inward of each magnet insertion hole 51. The through holes 56, 57, and 58 form a refrigerant flow path that allows refrigerant to pass through in the axial direction. The circumferential position of the through hole 56 coincides with the pole center, and the circumferential positions of the through holes 57 and 58 coincide with the inter-pole portions. The through hole 56 has an extension portion 56a that extends toward the magnet insertion hole 51. The through holes 57 and 58 are arranged side by side in the radial direction. However, the positions of the through holes 56, 57, and 58 are not limited to these positions.

[0026] 1, the stator 1 has a stator core 10 and a coil 20 wound around the stator core 10. An insulating portion (not shown) is provided between the stator core 10 and the coil 20. The insulating portion is an insulator that is a resin molded body or an insulating film.

[0027] The stator core 10 is made by stacking lamination elements in the axial direction and fixing them together by caulking or the like. The lamination elements are electromagnetic steel sheets or amorphous foil. When the lamination elements are electromagnetic steel sheets, the thickness is, for example, 0.1 mm to 0.5 mm, and here it is 0.35 mm. When the lamination elements are amorphous foil, the thickness is, for example, 20 μm to 50 μm.

[0028] The stator core 10 has an annular yoke 11 centered on a central axis Ax, and N (N is an integer of 2 or more) teeth 12 extending radially inward from the yoke 11. The outer periphery of the yoke 11 is fixed to the inner periphery of a cylindrical shell 81 ( FIG. 4 ) of the compressor 8 by shrink fitting or welding.

[0029] The teeth 12 are formed at regular intervals in the circumferential direction. The number N of the teeth 12 is 18 here, but may be any number equal to or greater than 2. The teeth 12 have tooth tips 12a that face the rotor 5. The tooth tips 12a are wider than the other portions of the teeth 12.

[0030] Slots 13 for accommodating coils 20 are formed between adjacent teeth 12 in the stator core 10. The slots 13 are formed from the inner periphery of the stator core 10 toward the outer periphery.

[0031] 2, the slot 13 has a slot opening 13a that opens to the inner periphery of the stator core 10. The slot opening 13a is located between the tooth tips 12a of the two teeth 12. The slot 13 has a bottom 13b that faces the outer periphery of the stator core 10. The bottom 13b has a curved shape that is convex toward the outer periphery of the stator core 10, but is not limited to a curved shape.

[0032] The coils 20 are wound in a distributed manner around the teeth 12 of the stator core 10 and are housed in the slots 13. The coils 20 are made of aluminum wire or copper wire.

[0033] M (M is an integer of 2 or more) notches 15 are formed on the outer periphery of the yoke 11. The notches 15 are formed, for example, radially outward from the teeth 12. A flow path is formed between the notches 15 and the shell 81, allowing the refrigerant to flow in the axial direction. The notches 15 are also referred to as a flow path portion.

[0034] The notches 15 are formed in a V-shape on a plane perpendicular to the central axis Ax. However, the shape of the notches 15 is not limited to a V-shape, and they may be U-shaped or flat. The number M of the notches 15 is the same as the number N of the teeth 12 (here, 18), but does not necessarily have to be the same.

[0035] On the outer periphery of the yoke 11, a contact portion 16 that contacts the shell 81 is formed between the circumferentially adjacent notches 15. The contact portion 16 is an arc-shaped surface centered on the central axis Ax.

[0036] 2, the distance from the central axis Ax to the inner periphery of the stator core 10 (i.e., the tips 12a of the teeth 12) is defined as a distance Di. The distance Di corresponds to half the inner diameter of the stator core 10.

[0037] The distance from the central axis Ax to the outer periphery of the stator core 10 (i.e., the abutment portion 16) is defined as a distance Do. The distance Do corresponds to half the outer diameter of the stator core 10.

[0038] The distance from the central axis Ax to the outermost position of the slot 13 (i.e., the bottom 13b) is defined as a distance Ds. The distance Ds corresponds to the longest distance from the central axis Ax to the slot 13. The shortest distance from the slot 13 to the notch 15 is defined as a distance Dc.

[0039] In this embodiment, a parameter (Ds-Di) / (Do-Di)×100 is used as a parameter reflecting the ratio of the cross-sectional area of ​​the slot 13 to the cross-sectional area of ​​the stator core 10. The cross-sectional area refers to the cross-sectional area in a plane perpendicular to the central axis Ax.

[0040] 3A and 3B are diagrams showing two configuration examples of the electric motor 3 with different values ​​of (Ds-Di) / (Do-Di)×100. In FIG. 3A, (Ds-Di) / (Do-Di)×100=45.5%. In FIG. 3B, (Ds-Di) / (Do-Di)×100=56.7%.

[0041] In the configuration example shown in Fig. 3(A), the cross-sectional area of ​​the slot 13 is smaller than in the configuration example shown in Fig. 3(B). If the number of turns of the coil 20 wound around the tooth 12 is the same, the smaller the cross-sectional area of ​​the slot 13, the smaller the cross-sectional area of ​​the coil 20 must be. Therefore, in the configuration example shown in Fig. 3(A), the resistance of the coil 20 is higher than in the configuration example shown in Fig. 3(B), and therefore the copper loss is larger.

[0042] On the other hand, magnetic flux emitted from the permanent magnets 55 of the rotor 5 flows into the tooth tips 12a of the teeth 12, circulates around the slots 13, and returns to the permanent magnets 55. The length of the magnetic path F1 around the slots 13 in Fig. 3(A) is shorter than the length of the magnetic path F2 around the slots 13 in Fig. 3(B). Therefore, the configuration example shown in Fig. 3(A) has smaller iron loss in the stator core 10 than the configuration example shown in Fig. 3(B).

[0043] <Configuration of Compressor> Next, the compressor 8 of the first embodiment will be described. Fig. 4 is a cross-sectional view showing the compressor 8. The compressor 8 is, for example, a rotary compressor. However, the compressor 8 is not limited to a rotary compressor and may be, for example, a scroll compressor.

[0044] The compressor 8 includes a sealed container 80 , a compression mechanism 9 disposed within the sealed container 80 , an electric motor 3 that drives the compression mechanism 9 , and a shaft 90 that connects the electric motor 3 and the compression mechanism 9 .

[0045] The sealed container 80 is formed of a magnetic or non-magnetic material such as a steel plate, and houses the electric motor 3 and the compression mechanism 9. The sealed container 80 has a shell 81 which is a lower shell, and an upper shell 82. A glass terminal 83 for supplying power to the electric motor 3 from outside the compressor 8 and a discharge pipe 85 for discharging the refrigerant to outside the compressor 8 are attached to the upper shell 82.

[0046] 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 inside 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.

[0047] 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.

[0048] 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.

[0049] An oil reservoir 80a is provided at the bottom of the shell 81 of the sealed container 80, in which refrigeration oil is stored to lubricate 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. 4 ) formed in multiple locations on the shaft 90.

[0050] The stator 1 of the electric motor 3 is fixed to the inside of the shell 81 by shrink fitting or welding. Electric power is supplied to the coil 20 of the stator 1 through lead wires 84 from glass terminals 83 attached to the upper shell 82.

[0051] As described above, the rotor 5 of the electric motor 3 is fixed to the shaft 90. The centrifuge 86 is attached to the shaft 90 so as to face the upper end surface of the rotor 5. The centrifuge 86 is a member in which a plurality of blades are arranged in the circumferential direction on a disk, and serves to separate the refrigerant from the refrigeration oil.

[0052] An accumulator 87 that stores refrigerant gas is attached to the shell 81. Refrigerant flows into the accumulator 87 from a refrigeration cycle device 100 (FIG. 5). 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.

[0053] 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.

[0054] 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.

[0055] Meanwhile, refrigeration oil stored in oil reservoir 80a 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.

[0056] The refrigerant and refrigeration oil that have passed through the through holes 56, 57, and 58 of the rotor 5 collide with the centrifugal separator 86. Since the refrigeration oil has a higher specific gravity than the refrigerant, the refrigeration oil is discharged by the centrifugal separator 86 radially outward.

[0057] Therefore, the refrigerant rises further inside the sealed container 80, is discharged from the discharge pipe 85, and is sent to the refrigerant circuit of the refrigeration cycle device 100 (FIG. 5). On the other hand, the refrigeration oil discharged from the centrifugal separator 86 collides with the inner surface of the shell 81, flows into the flow path between the notch 15 of the stator core 10 and the shell 81, and flows downward through the flow path to return to the compression mechanism 9 or the oil reservoir 80a.

[0058] The ability to separate refrigerating machine oil from the refrigerant and return it to the compression mechanism 9 or the oil reservoir 80a is called oil returnability. Good oil returnability prevents refrigerating machine oil from being discharged together with the refrigerant from the discharge pipe 85, thereby preventing refrigerating machine oil from entering the refrigerant circuit of the refrigeration cycle device 100 and preventing a shortage of refrigerating machine oil for lubricating the compression mechanism 9.

[0059] <Refrigeration cycle device> Next, a refrigeration cycle device 100 having the compressor 8 shown in Fig. 4 will be described. Fig. 5 is a diagram showing the refrigeration cycle device 100. The refrigeration cycle device 100 is, for example, an air conditioner, but is not limited thereto and may be, for example, a refrigerator.

[0060] 5 includes a compressor 101 that compresses a refrigerant, a condenser 102 that condenses the refrigerant, a pressure reducing device 103 that reduces the pressure of the refrigerant, and an evaporator 104 that evaporates the refrigerant. The compressor 101, the condenser 102, and the pressure reducing device 103 are provided in an outdoor unit 110, and the evaporator 104 is provided in an indoor unit 120.

[0061] The compressor 101, the condenser 102, the pressure reducing device 103, and the evaporator 104 are connected by a refrigerant pipe 407 to form a refrigerant circuit. The compressor 101 is configured as the compressor 8 shown in Fig. 4. The refrigeration cycle apparatus 100 also includes an outdoor fan 105 facing the condenser 102 and an indoor fan 106 facing the evaporator 104.

[0062] The refrigeration cycle apparatus 100 operates as follows: The compressor 101 compresses the refrigerant and discharges it as a high-temperature, high-pressure refrigerant gas. The condenser 102 exchanges heat between the refrigerant discharged from the compressor 101 and outdoor air sent by the outdoor air blower 105, condenses the refrigerant, and sends it out as a liquid refrigerant. The pressure reducing device 103 expands the liquid refrigerant sent out from the condenser 102 and sends it out as a low-temperature, low-pressure liquid refrigerant.

[0063] The evaporator 104 exchanges heat between the low-temperature, low-pressure liquid refrigerant sent from the pressure reducing device 103 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 104 is supplied into the room by the indoor fan 106.

[0064] <Refrigerant> Next, a description will be given of the refrigerant used in the compressor 8. In order to prevent global warming, the compressor 8 uses a refrigerant with a GWP of 1500 or less. Hereinafter, the types of refrigerant will be described using refrigerant numbers beginning with "R" as defined in the international standard ISO 817.

[0065] (1) First, R1234yf, R1234ze(E), R32, or R290 can be used as a single refrigerant. Also, a mixed refrigerant made by mixing two or more of R1234yf, R1234ze(E), R32, and R290 can be used. Also, a mixed refrigerant made by mixing one or more of R1234yf, R1234ze(E), R32, and R290 with another refrigerant can be used.

[0066] (2) Alternatively, a single refrigerant such as R1132(E) or a mixed refrigerant containing R1132(E) may be used.

[0067] (3) It is also possible to use a mixed refrigerant selected from R444A, R444B, R445A, R446A, R447A, R447B, R452B, R454A, R454B, R454C, R455A, R457A, R459A, and R459B, or a mixed refrigerant containing at least one of these.

[0068] The refrigerants listed in (1) to (3) are characterized by their operating pressures being equal to or lower than the operating pressure of R32 (difluoromethane). The operating pressure of a refrigerant is the same as the saturation pressure of the refrigerant and is a value specific to the refrigerant.

[0069] When a refrigerant with a low operating pressure is used, the torque required of the electric motor 3 is low, and therefore the electric motor 3 is driven with a low torque.

[0070] On the other hand, in order to obtain a compression capacity similar to that of a refrigerant with a high operating pressure, it is necessary to increase the compression volume (i.e., throttle volume) of the cylinders 91, 92 or to increase the drive frequency of the compressor 8.

[0071] In order to increase the compression volume of the cylinders 91, 92, the compressor 8 must be made larger, which increases manufacturing costs. Therefore, in this embodiment, the compression capacity is increased by increasing the drive frequency of the compressor 8. Therefore, the electric motor 3 is driven at a low torque and a high rotation speed.

[0072] When the electric motor 3 is driven at a low torque and a high rotation speed, iron loss becomes more dominant than copper loss in the electric motor 3. Therefore, reducing iron loss is an issue to be addressed in order to improve the efficiency of the electric motor.

[0073] Furthermore, when the electric motor 3 is driven at a high rotation speed, an increase in the amount of refrigerant and refrigeration oil passing through the through holes 56, 57, and 58 of the rotor core 50 (referred to as the amount of suction) occurs. When the amount of suction increases, some of the refrigeration oil may not be separated by the centrifugal separator 86 and may be discharged from the discharge pipe 85 to the outside of the compressor 8. In other words, the oil return property may be reduced.

[0074] Therefore, in this embodiment, in the electric motor 3 that is driven at a low torque and a high rotation speed, the cross-sectional area of ​​the slots 13 in the stator core 10 is reduced to suppress iron loss.

[0075] 3A, when the cross-sectional area of ​​the slot 13 is reduced, the cross-sectional area of ​​the coil 20 housed in the slot 13 also becomes smaller, resulting in an increase in copper loss. On the other hand, the magnetic path of the magnetic flux that emerges from the permanent magnet 55 and flows around the slot 13 becomes shorter, resulting in a decrease in iron loss. This allows the loss balance in the electric motor 3 to move closer to a state where iron loss is dominant, and where iron loss and copper loss are balanced.

[0076] Furthermore, by reducing the cross-sectional area of ​​the slot 13, the cross-sectional area of ​​the flow passage between the notch 15 and the shell 81 can be increased, improving the oil return property. This prevents a decrease in the oil return property that accompanies an increase in the rotation speed of the electric motor 3.

[0077] The torque generated by the electric motor 3 includes magnet torque and reluctance torque. The magnet torque is generated when the magnetic flux of the permanent magnet 55 interlinks with the coil 20. The reluctance torque is generated according to the difference between the reluctance Ld in the d-axis direction passing through the pole center of the rotor 5 and the reluctance Lq in the q-axis direction passing through the inter-pole portion.

[0078] The magnet torque is proportional to the current value of the current flowing through the coil 20, whereas the reluctance torque is proportional to the square of the current value of the current flowing through the coil 20. In this embodiment, the electric motor 3 is driven at low torque and high rotation speed, so the current value of the current flowing through the coil 20 is small, and therefore the magnet torque is larger than the reluctance torque.

[0079] <Parameter Representing Slot Cross-Sectional Area> (Ds-Di) / (Do-Di)×100 is used as a parameter reflecting the ratio of the cross-sectional area of ​​the slot 13 to the cross-sectional area of ​​the stator core 10. As described above, the distance Do is the distance from the central axis Ax to the outer periphery of the stator core 10. The distance Di is the distance from the central axis Ax to the inner periphery of the stator core 10. The distance Ds is the distance from the central axis Ax to the bottom 13b of the slot 13.

[0080] Here, the torque and rotation speed of the motor 3 were set according to the type of refrigerant, and the relationship between the value of (Ds - Di) / (Do - Di) x 100 and the motor efficiency was determined by analysis. In the analysis, the distances Do and Di were both fixed values, and the values ​​of the above parameters were changed by varying the distance Ds. Note that the distance Dc changes depending on the distance Ds.

[0081] 6 is a graph showing the relationship between the value of (Ds-Di) / (Do-Di)×100 and the motor efficiency when refrigerants 1 to 9 are used. The horizontal axis represents (Ds-Di) / (Do-Di)×100, and the vertical axis represents the motor efficiency. The motor efficiency on the vertical axis is expressed as a percentage (%) of the theoretical value.

[0082] The refrigerant 1 is R32. The operating pressure (i.e., saturation pressure) of the refrigerant 1 is 1.10 MPa at a temperature of 10°C and 3.14 MPa at a temperature of 50°C.

[0083] Refrigerants 2 to 9 have operating pressures lower than R32. When using these refrigerants, the torque is reduced by the amount of the decrease in operating pressure, and the rotation speed is increased, in order to make the capacity of the compressor 8 (i.e., the product of torque and rotation speed) the same as when R32 is used.

[0084] Hereinafter, the ratio of the operating pressure of each refrigerant to the operating pressure of R32 will be referred to as the “operating pressure ratio.” The operating pressure ratio is also referred to as the pressure ratio or the saturation pressure ratio.

[0085] Refrigerant 2 is a refrigerant, such as R452B or R454B, that has an operating pressure ratio of 90% to refrigerant 1. When refrigerant 2 is used, the torque is reduced by 10% and the rotation speed is increased by 10% compared to when refrigerant 1 is used.

[0086] Refrigerant 3 is a refrigerant, such as R446A, whose operating pressure ratio is 80% of that of refrigerant 1. When refrigerant 3 is used, the torque is reduced by 20% and the rotation speed is increased by 20% compared to when refrigerant 1 is used.

[0087] Refrigerant 4 is a refrigerant, such as R454A or R455A, whose operating pressure ratio is 70% of that of refrigerant 1. When refrigerant 4 is used, the torque is reduced by 30% and the rotation speed is increased by 30% compared to when refrigerant 1 is used.

[0088] Refrigerant 5 is a refrigerant, such as R290 or R454C, that has an operating pressure ratio of 60% relative to refrigerant 1. When refrigerant 5 is used, the torque is reduced by 40% and the rotation speed is increased by 40% compared to when refrigerant 1 is used.

[0089] Refrigerant 6 is a refrigerant, such as R457A, whose operating pressure ratio is 50% of that of refrigerant 1. When refrigerant 6 is used, the torque is reduced by 50% and the rotation speed is increased by 50% compared to when refrigerant 1 is used.

[0090] Refrigerant 7 is a refrigerant, such as R1234yf, whose operating pressure ratio is 40% relative to refrigerant 1. When refrigerant 7 is used, the torque is reduced by 60% and the rotation speed is increased by 60% compared to when refrigerant 1 is used.

[0091] Refrigerant 8 is a refrigerant, such as R445A, whose operating pressure ratio is 30% relative to refrigerant 1. When refrigerant 8 is used, the torque is reduced by 70% and the rotation speed is increased by 70% compared to when refrigerant 1 is used.

[0092] Refrigerant 9 is a refrigerant, such as R1234ze(E), whose operating pressure ratio is 20% relative to refrigerant 1. When refrigerant 9 is used, the torque is reduced by 80% and the rotation speed is increased by 80% compared to when refrigerant 1 is used.

[0093] As shown in FIG. 6, when any of Refrigerants 1 to 9 is used, the motor efficiency increases as the value of (Ds-Di) / (Do-Di)×100 increases, and then decreases after peaking.

[0094] Fig. 7 is a graph showing an enlarged portion of the graph in Fig. 6 that includes the peaks of the curves for refrigerants 1 to 9. The horizontal axis represents (Ds - Di) / (Do - Di) x 100, and the vertical axis represents motor efficiency.

[0095] 7, when refrigerant 1 is used, the motor efficiency peaks when (Ds-Di) / (Do-Di)×100 is 56.7%. The lower the operating pressure of the refrigerant, the smaller the value of (Ds-Di) / (Do-Di)×100 when the motor efficiency peaks.

[0096] Fig. 8 is a graph showing the curves for refrigerant 1 and refrigerant 2 extracted from the graph of Fig. 6. The horizontal axis represents (Ds-Di) / (Do-Di) x 100, and the vertical axis represents motor efficiency.

[0097] 8, the motor efficiency when the value of (Ds-Di) / (Do-Di)×100 is 56.7% (i.e., the motor efficiency on the line indicated by the symbol T) is set as the reference value. Note that 56.7% is the value of (Ds-Di) / (Do-Di)×100 when the motor efficiency peaks when refrigerant 1 is used.

[0098] When refrigerant 2 is used, as shown by arrow A, when (Ds-Di) / (Do-Di) x 100 is in the range of 51.6% to 56.7%, the motor efficiency is above the standard value.

[0099] In other words, when refrigerant 2 is used, if (Ds-Di) / (Do-Di) x 100 is in the range of 51.6% to 56.7%, motor efficiency equal to or higher than that achieved when the configuration of motor 3 is the same as when refrigerant 1 is used and motor efficiency is at its peak.

[0100] Fig. 9 is a graph showing the curves for refrigerant 1 and refrigerant 9 extracted from the graph of Fig. 6. The horizontal axis represents (Ds-Di) / (Do-Di) x 100, and the vertical axis represents motor efficiency.

[0101] 9, the motor efficiency when the value of (Ds-Di) / (Do-Di)×100 is 56.7% is taken as the reference value, that is, the motor efficiency on the straight line indicated by the symbol T. When refrigerant 9 is used, as indicated by arrow B, the motor efficiency is equal to or greater than the reference value when (Ds-Di) / (Do-Di)×100 is in the range of 19.3% to 56.7%.

[0102] The same can be said for refrigerants 3 to 9. That is, as shown in Fig. 7, when refrigerant 3 is used, the motor efficiency is equal to or greater than the reference value when (Ds - Di) / (Do - Di) x 100 is in the range of 45.5% to 56.7%.

[0103] Furthermore, when refrigerant 4 is used, the motor efficiency is equal to or greater than the reference value when (Ds-Di) / (Do-Di)×100 is in the range of 38.5% to 56.7%.

[0104] Furthermore, when refrigerant 5 is used, the motor efficiency is equal to or greater than the reference value when (Ds-Di) / (Do-Di)×100 is in the range of 32.8% to 56.7%.

[0105] Furthermore, when refrigerant 6 is used, the motor efficiency is equal to or greater than the reference value when (Ds-Di) / (Do-Di)×100 is in the range of 28.0% to 56.7%.

[0106] Furthermore, when refrigerant 7 is used, the motor efficiency is equal to or greater than the reference value when (Ds-Di) / (Do-Di)×100 is in the range of 24.3% to 56.7%.

[0107] Furthermore, when refrigerant 8 is used, the motor efficiency is equal to or greater than the reference value when (Ds-Di) / (Do-Di)×100 is in the range of 21.5% to 56.7%.

[0108] By appropriately setting (Ds-Di) / (Do-Di) x 100 in this way, it is possible to obtain high motor efficiency using a refrigerant with a low GDP (i.e., a refrigerant with a low operating pressure).Furthermore, for the same motor efficiency, a refrigerant with a lower GWP can be used.

[0109] 10 is a graph showing the ranges where the motor efficiency is equal to or greater than the reference value when each of refrigerants 1 to 9 is used. The horizontal axis represents (Ds - Di) / (Do - Di) x 100, and the vertical axis represents the motor efficiency. Each curve corresponds to refrigerants 1 to 9, and the operating pressure ratios of each refrigerant 1 to 9 are also shown in parentheses.

[0110] 11 is a graph showing the relationship between the operating pressure ratios of refrigerants 2 to 9 and the lower limit of (Ds-Di) / (Do-Di)×100. The horizontal axis represents the operating pressure ratio, and the vertical axis represents the lower limit of (Ds-Di) / (Do-Di)×100.

[0111] As shown in FIG. 11, the larger the operating pressure ratio, the larger the lower limit value of (Ds-Di) / (Do-Di)×100. Ａ The curve in FIG. 11 is expressed as follows: (Ds-Di) / (Do-Di)×100 lower limit = 0.0042P Ａ ２ +0.0061P Ａ It is expressed as +17.44.

[0112] Also, from FIG. 10, the upper limit value of (Ds-Di) / (Do-Di)×100 is 56.7% when refrigerant 1 is used, at which point the motor efficiency reaches its peak.

[0113] From the above results, the operating pressure ratio of the refrigerant P Ａ and the distances Di, Do, and Ds are 0.0042P Ａ ２ +0.0061P Ａ It can be seen that if +17.44 [%] ≦ (Ds ​​− Di) / (Do − Di) × 100 ≦ 56.7 [%] is satisfied, the motor efficiency can be improved even when the motor 3 is driven with a refrigerant having a low operating pressure (and therefore at a low torque and high rotation speed).

[0114] The individual refrigerants can be considered as follows: When using refrigerant 2 (for example, R452B or R454B) with an operating pressure ratio of 90%, the motor efficiency can be improved when 51.6%≦(Ds−Di) / (Do−Di)×100≦56.7% is satisfied.

[0115] When a refrigerant 3 (e.g., R446A) with an operating pressure ratio of 80% is used, motor efficiency can be improved when 45.5%≦(Ds−Di) / (Do−Di)×100≦56.7% is satisfied.

[0116] When a refrigerant 4 (e.g., R454A or R455A) with an operating pressure ratio of 70% is used, motor efficiency can be improved when 38.5%≦(Ds−Di) / (Do−Di)×100≦56.7% is satisfied.

[0117] When a refrigerant 5 (e.g., R290 or R454C) with an operating pressure ratio of 60% is used, motor efficiency can be improved when 32.8%≦(Ds−Di) / (Do−Di)×100≦56.7% is satisfied.

[0118] When a refrigerant 6 (e.g., R457A) with an operating pressure ratio of 50% is used, motor efficiency can be improved when 28.0%≦(Ds−Di) / (Do−Di)×100≦56.7% is satisfied.

[0119] When a refrigerant 7 (e.g., R1234yf) with an operating pressure ratio of 40% is used, motor efficiency can be improved when 24.3%≦(Ds−Di) / (Do−Di)×100≦56.7% is satisfied.

[0120] When a refrigerant 8 (e.g., R445A) with an operating pressure ratio of 30% is used, motor efficiency can be improved when 21.5%≦(Ds−Di) / (Do−Di)×100≦56.7% is satisfied.

[0121] When a refrigerant 9 (e.g., R1234ze(E)) with an operating pressure ratio of 20% is used, the motor efficiency can be improved when 19.3%≦(Ds−Di) / (Do−Di)×100≦56.7% is satisfied.

[0122] Here, refrigerants 1 to 9 have been described as specific examples, but refrigerants other than these may also be used.

[0123] For example, the operating pressure ratio of R1132(E) is 96.0%. The operating pressure ratio of R444A is 35.1%. The operating pressure ratio of R444B is 54.6%. The operating pressure ratio of R447A is 85.0%. The operating pressure ratio of R447B is 87.0%. The operating pressure ratio of R459A is 87.2%. The operating pressure ratio of R459B is 54.8%. These refrigerants have lower operating pressures than Refrigerant 1 (i.e., R32) and a GWP of 1500 or less.

[0124] Furthermore, R1234yf, R1234ze(E), R32, and R290 may be used as a single refrigerant, or two or more of these may be combined to form a mixed refrigerant, or at least one of the above may be combined with another refrigerant to form a mixed refrigerant.

[0125] Similarly, R1132(E) may be used as a single refrigerant or may be combined with other refrigerants to form a mixed refrigerant.

[0126] Furthermore, R444A, R444B, R445A, R446A, R447A, R447B, R452B, R454A, R454B, R454C, R455A, R457A, R459A, and R459B are all mixed refrigerants, but two or more of these may be combined, or at least one of these may be combined with another refrigerant.

[0127] Among the above-mentioned refrigerants, R1234yf, R1234ze(E), and R1132(E) are HFO refrigerants. R29 is an HC refrigerant. Using these HFO or HC refrigerants can further reduce GWP and improve motor efficiency.

[0128] <Distance Dc from Slot 13 to Notch 15> Next, a description will be given of the relationship between the distance Dc from the slot 13 to the notch 15 and the torque ripple rate. As described above, the notch 15 formed on the outer periphery of the stator core 10 forms a flow path for the refrigerant and the refrigeration oil between the notch 15 and the shell 81.

[0129] In stator core 10 of the present embodiment, the small cross-sectional area of ​​slot 13 allows for a large flow passage cross-sectional area between notch 15 and shell 81. By increasing the flow passage cross-sectional area between notch 15 and shell 81, the ability to return refrigeration oil that has passed through through holes 56, 57, and 58 of rotor core 50 to compression mechanism 9 or oil reservoir 80a, i.e., oil return performance, can be improved.

[0130] 12 is a graph showing the relationship between the torque ripple rate and the distance Dc (FIG. 2), which is the shortest distance from the bottom 13b of the slot 13 to the notch 15. The horizontal axis represents the distance Dc, and the vertical axis represents the torque ripple rate.

[0131] The torque ripple rate is the ratio of the difference between the maximum torque and the minimum torque to the time-average torque. The smaller the fluctuation in the rotation speed of the electric motor 3, the more the load fluctuation is suppressed, and therefore the smaller the torque ripple rate.

[0132] The curve C1 shown in FIG. 12 shows the results of an analysis in which the distances Do, Di, and Ds are each set to a constant value so as to satisfy (Ds-Di) / (Do-Di)×100=45.5[%] as shown in FIG. 3(A), and the distance Dc is varied.

[0133] Furthermore, curve C2 shown in FIG. 12 shows the results of an analysis in which the distances Do, Di, and Ds are each set to a constant value so as to satisfy (Ds-Di) / (Do-Di)×100=56.7[%] as shown in FIG. 3(B), and the distance Dc is varied.

[0134] From FIG. 12, in both cases of curves C1 and C2, when the distance Dc is 8.2 mm or more, the torque ripple rate is constant, but when the distance Dc is below 8.2 mm, the torque ripple rate increases.

[0135] This is because, when the distance Dc is less than 8.2 mm, the magnetic path in the stator core 10 becomes locally narrow between the slot 13 and the notch 15, which causes magnetic saturation.

[0136] The difference between the distance Do and the distance Ds, (Do - Ds), corresponds to the distance from the slot 13 to the outer periphery of the stator core 10. Therefore, the maximum value of the distance Dc from the slot 13 to the notch 15 is (Do - Ds). The larger the notch 15, the smaller the value of Dc.

[0137] To improve oil return, it is desirable to have a large flow path cross-sectional area between the notch 15 and the shell 81. Therefore, for example, it is desirable that the distance Dc be equal to or less than (Do - Ds) / 2. In the configuration example of FIG. 3A, Do = 140.1 mm and Ds = 107 mm, so (Do - Ds) / 2 = 16.6 mm. In the configuration example of FIG. 3B, Do = 140.1 mm and Ds = 113.8 mm, so (Do - Ds) / 2 = 13.2 mm.

[0138] From the above, in order to reduce the torque ripple rate and improve oil return performance, it is desirable that the distance Dc from the slot 13 to the notch 15 satisfies 8.2 [mm]≦Dc≦(Do−Ds) / 2.

[0139] <Effects of the embodiment> As described above, the stator 1 of the first embodiment is provided in the electric motor 3 used together with a refrigerant in the compressor 8. The stator 1 is an annular stator core 10 centered on the central axis Ax, and includes the stator core 10 having slots 13 formed from the inner periphery to the outer periphery, and the coils 20 arranged in the slots 13. The refrigerant used may be: (1) a single refrigerant selected from R1234yf, R1234ze(E), R32, and R290, or a mixed refrigerant containing at least one of these; (2) a single refrigerant selected from R1132(E), or a mixed refrigerant containing R1132(E); or (3) a mixed refrigerant selected from R444A, R444B, R445A, R446A, R447A, R447B, R452B, R454A, R454B, R454C, R455A, R457A, R459A, and R459B. In addition, the distance Di from the central axis Ax to the inner periphery of the stator core 10, the distance Do from the central axis Ax to the outer periphery of the stator core 10, the distance Ds from the central axis Ax to the position closest to the outer periphery of the slot 13, and the pressure ratio P Ａ [%] is 0.0042P Ａ ２ +0.0061P Ａ +17.44≦(Ds−Di) / (Do−Di)×100≦56.7 is satisfied.

[0140] Because of this configuration, when the electric motor 3 is used with a refrigerant having a low operating pressure (i.e., a refrigerant having a low GWP) and is driven at a low torque and a high rotation speed, the iron loss and copper loss in the stator 1 can be made nearly equal, and the efficiency of the electric motor can be improved.

[0141] In particular, by using an HFO refrigerant or an HC refrigerant as the refrigerant, it is possible to reduce the GWP and improve the efficiency of the electric motor.

[0142] Furthermore, since the shortest distance Dc from the slot 13 to the notch 15 serving as the flow passage portion is 8.2 mm or more, the torque ripple rate can be reduced, and fluctuations in the rotation speed of the electric motor 3 can be reduced.

[0143] Furthermore, since the shortest distance Dc from the slot 13 to the notch 15 satisfies Dc≦(Do−Ds) / 2, the flow path cross-sectional area between the notch 15 and the shell 81 can be increased, improving oil return performance.

[0144] Furthermore, since the stator core 10 is a laminate of lamination elements, and the lamination elements are electromagnetic steel sheets with a thickness of 0.1 mm to 0.5 mm or amorphous foil with a thickness of 20 μm to 50 μm, it is possible to suppress eddy current loss within the stator core 10. This makes it possible to suppress iron loss that occurs when the rotation speed of the electric motor 3 increases.

[0145] In addition, since the stator core 10 is fixed to the shell 81 of the compressor 8 by shrink fitting or welding, the stator core 10 can be firmly fixed to the shell 81 while forming a flow path for the refrigerant and refrigeration oil between the stator core 10 and the shell 81.

[0146] Furthermore, since the magnet torque is greater than the reluctance torque in the torque generated by the electric motor 3, the electric motor 3 is suitable for driving at low torque and high rotation speed.

[0147] Furthermore, because the permanent magnet 55 is a rare earth magnet with a residual magnetic flux density of 1.2 T to 1.6 T, it is possible to generate the output of the electric motor 3 required for the compressor 8. Alternatively, if the permanent magnet 55 is a ferrite magnet with a residual magnetic flux density of 0.35 T to 0.5 T, it is possible to generate the output of the electric motor 3 required for the compressor 8 by making the axial length of the permanent magnet 55 longer than in the case of a rare earth magnet.

[0148] In addition, since the air gap between the stator core 10 and the rotor core 50 is 0.1 mm to 1.5 mm, the magnetic flux of the permanent magnet 55 can be sufficiently linked to the coil 20, thereby improving the efficiency of the electric motor.

[0149] Although the preferred embodiments have been specifically described above, various improvements and modifications can be made to these embodiments.

[0150] DESCRIPTION OF SYMBOLS 1 stator, 3 electric motor, 5 rotor, 8 compressor, 9 compression mechanism, 10 stator core, 11 yoke, 12 teeth, 12a tooth tip portion, 13 slot, 13a slot opening, 13b bottom portion, 15 notch (flow path portion), 16 abutment portion, 20 coil, 50 rotor core, 51 magnet insertion hole, 52 flux barrier, 53 side slit, 54 slit, 55, 56, 57 through hole, 80 sealed container, 80a oil reservoir portion, 80 sealed container, 81 shell, 85 discharge pipe, 86 centrifuge, 90 shaft, 100 refrigeration cycle device, 101 compressor, 102 condenser, 103 pressure reducing device, 104 evaporator.

Claims

1. A stator for an electric motor mounted on a compressor, comprising: a stator core formed in an annular shape centered on a central axis and having slots formed from the inner circumference to the outer circumference; and a coil wound in distributed winding on the stator core and housed in the slots, wherein the refrigerant used in the compressor is any one of a single refrigerant of R1234yf, R1234ze(E), R32, and R290, or a mixed refrigerant containing at least one of these, a single refrigerant of R1132(E) or a mixed refrigerant containing R1132(E), or a mixed refrigerant containing at least one of R444A, R444B, R445A, R446A, R447A, R447B, R452B, R454A, R454B, R454C, R455A, R457A, R459A, and R459B, and wherein a distance Di from the central axis to the inner circumference of the stator core and a distance Do from the central axis to the outer periphery of the stator core, a distance Ds from the central axis to a position of the slot closest to the outer periphery, and a pressure ratio P which is a ratio of a saturation pressure of the refrigerant to a saturation pressure of R32. Ａ [%] is 0.0042P Ａ ２ +0.0061P Ａ A stator that satisfies +17.44[%]≦(Ds−Di) / (Do−Di)×100≦56.7[%].

2. A stator for an electric motor mounted on a compressor, comprising: a stator core formed in an annular shape centered on a central axis and having slots formed from the inner circumference toward the outer circumference; and a coil wound in distributed winding on the stator core and housed in the slots, wherein the refrigerant used in the compressor is an HFO refrigerant or an HC refrigerant, and wherein: a distance Di from the central axis to the inner circumference of the stator core; a distance Do from the central axis to the outer circumference of the stator core; a distance Ds from the central axis to a position of the slot closest to the outer circumference; and a pressure ratio P which is the ratio of the saturation pressure of the refrigerant to the saturation pressure of R32. Ａ [%] is 0.0042P Ａ ２ +0.0061P Ａ A stator that satisfies +17.44[%]≦(Ds−Di) / (Do−Di)×100≦56.7[%].

3. The stator according to claim 1, wherein the refrigerant is R452B or R454B, and the distances Di, Do and Ds of the stator core satisfy 51.6[%]≦(Ds−Di) / (Do−Di)×100≦56.7[%].

4. The stator according to claim 1, wherein the refrigerant is R446A, and the distances Di, Do and Ds of the stator core satisfy 45.5[%]≦(Ds−Di) / (Do−Di)×100≦56.7[%].

5. The stator according to claim 1, wherein the refrigerant is R454A or R455A, and the distances Di, Do and Ds of the stator core satisfy 38.5[%]≦(Ds-Di) / (Do-Di)×100≦56.7[%].

6. The stator according to claim 1, wherein the refrigerant is R290 or R454C, and the distances Di, Do and Ds of the stator core satisfy 32.8[%]≦(Ds−Di) / (Do−Di)×100≦56.7[%].

7. The stator according to claim 1, wherein the refrigerant is R457A, and the distances Di, Do and Ds of the stator core satisfy 28.0[%]≦(Ds−Di) / (Do−Di)×100≦56.7[%].

8. The stator according to claim 1, wherein the refrigerant is R1234yf, and the distances Di, Do and Ds of the stator core satisfy 24.3[%]≦(Ds−Di) / (Do−Di)×100≦56.7[%].

9. The stator according to claim 1, wherein the refrigerant is R445A, and the distances Di, Do and Ds of the stator core satisfy 21.5[%]≦(Ds−Di) / (Do−Di)×100≦56.7[%].

10. The stator according to claim 1, wherein the refrigerant is R1234ze(E), and the distances Di, Do and Ds of the stator core satisfy 19.3[%]≦(Ds−Di) / (Do−Di)×100≦56.7[%].

11. A stator according to any one of claims 1 to 10, further comprising a flow passage portion on the outer periphery of the stator core for circulating the coolant.

12. The stator according to claim 11, wherein the shortest distance Dc from the slot to the flow passage portion is 8.2 mm or more.

13. The stator according to claim 11 or 12, wherein a shortest distance Dc from the slot to the flow passage portion satisfies Dc≦(Do−Ds) / 2.

14. A stator according to any one of claims 1 to 13, wherein the stator core is constructed by laminating lamination elements, and the lamination elements are electromagnetic steel sheets or amorphous foils.

15. A stator according to claim 14, wherein the laminated elements are electromagnetic steel sheets having a thickness of 0.1 mm or more and 0.5 mm or less, or amorphous foils having a thickness of 20 μm or more and 50 μm or less.

16. A stator according to any one of claims 1 to 15, wherein the stator core is fixed to the shell of the compressor by shrink fitting or welding.

17. An electric motor comprising: a stator according to any one of claims 1 to 16; and a rotor provided inside the stator and rotatable about the central axis.

18. The electric motor according to claim 17, wherein the rotor has a permanent magnet, and among the torques generated by the electric motor, magnet torque is larger than reluctance torque.

19. An electric motor as claimed in claim 17 or 18, wherein the rotor has a permanent magnet, the permanent magnet being a rare earth magnet having a residual magnetic flux density of 1.2 T or more and 1.6 T or less, or a ferrite magnet having a residual magnetic flux density of 0.35 T or more and 0.5 T or less.

20. The electric motor according to any one of claims 17 to 19, wherein the air gap between the stator and the rotor is 0.1 mm or more and 1.5 mm or less.

21. A compressor comprising: an electric motor according to any one of claims 17 to 20; a compression mechanism driven by said electric motor; and a sealed container housing said electric motor and said compression mechanism.

22. A refrigeration cycle device comprising the compressor according to claim 21, a condenser, a pressure reducing device, and an evaporator.

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