Dynamo-electric motor, air conditioner onto which the dynamo-electric motor is mounted, refrigerator, and on-vehicle device

Abstract

To provide a dynamo-electric motor capable of reducing cogging torque.SOLUTION: A dynamo-electric motor 30 comprises: a rotator 40 that can be rotated as a center of a shaft C; and a cylindrical stator 31 that surrounds the rotator 40. At a center of a peripheral direction of an outer peripheral surface in an auxiliary magnetic pole part 40b of the rotator 40, a convex part 52 is formed by a space between a pair of concave parts 51 that is concaved to a shaft side of both sides of their peripheral direction. Since the concave part 51 is a circular arc shape, the change of a magnetic flux passing through a teeth part 33 when a neighbor of the convex part 52 and the concave part 51 passes the teeth part 33 of the stator 31 in accordance with a rotation of the rotator 40 can be relaxed. Thus, cogging torque of the dynamo-electric motor 30 can be reduced.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an electric motor having a permanent magnet inserted in a rotor, and to an air conditioner, a refrigerator, and an in-vehicle device equipped with the electric motor. [Background technology]

[0002] There are known electric motors for driving compressors installed in air conditioners and refrigerators, in-vehicle devices installed in vehicles, etc., that have a rotor with a permanent magnet housed in a magnet housing hole. This type of electric motor is generally called an embedded permanent magnet electric motor.

[0003] An embedded permanent magnet motor includes a cylindrical stator with multiple teeth protruding on the inner circumference side, and a rotor arranged inside the stator with a space between the tips of the teeth. The rotor has main magnetic poles and auxiliary magnetic poles arranged alternately in the circumferential direction. The circumferential centers of the magnet accommodating holes are located in the main magnetic poles. The circumferential centers of the auxiliary magnetic poles are located between magnet accommodating holes adjacent in the circumferential direction. Such embedded permanent magnet motors rotate the rotor relative to the stator by utilizing both the magnet torque due to the main magnetic poles (permanent magnets) and the reluctance torque due to the salient poles of the auxiliary magnetic poles.

[0004] In addition, in a permanent magnet embedded motor, when the boundary between the main magnetic pole and the auxiliary magnetic pole of the rotor passes through the teeth as the rotor rotates, the magnetic flux passing through the teeth may change suddenly, causing cogging torque. In order to reduce this cogging torque, in Patent Document 1, the outer peripheral surface of the main magnetic pole is formed in an arc shape centered on the rotor axis, and the outer peripheral surface of the auxiliary magnetic pole is positioned on the axis side of a virtual arc surface extending circumferentially from the outer peripheral surface of the main magnetic pole. Furthermore, a trapezoidal convex portion is formed between a pair of concave portions, both sides of which are concave in a trapezoidal shape, at the circumferential center of the auxiliary magnetic pole, thereby reducing the cogging torque of the motor. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2007-159197 A Summary of the Invention [Problem to be solved by the invention]

[0006] Compared to the above Patent Document 1, further reduction in cogging torque is desired.

[0007] The present invention has been made in response to the above-mentioned demands, and has an object to provide an electric motor capable of reducing cogging torque, and an air conditioner, a refrigerator, and an in-vehicle device equipped with the electric motor. [Means for solving the problem]

[0008] In order to achieve this object, the electric motor of the present invention comprises a rotor rotatable around an axis, and a cylindrical stator surrounding the rotor, the stator comprising a cylindrical yoke portion forming an outer periphery of the stator, and a plurality of teeth protruding from the yoke portion towards the axis, a winding is inserted into a slot between adjacent teeth in the circumferential direction, the rotor has a plurality of magnet accommodating holes into which permanent magnets are respectively inserted, the magnet accommodating holes being rotationally symmetrical about the axis, and the motor is rotationally driven by passing current through the windings. In the magnet accommodating hole, auxiliary magnetic pole portions that are formed circumferentially symmetrically with respect to the circumferential center between the multiple magnet accommodating holes and main magnetic pole portions are arranged alternately in the circumferential direction, and in a cross section perpendicular to the axis, the outer peripheral surface of the main magnetic pole portion is formed in an arc shape centered on the axis, the outer peripheral surface of the auxiliary magnetic pole portion is located on the axis side of an imaginary arc surface that is a circumferential extension of the outer peripheral surface of the main magnetic pole portion, and a convex portion is formed in the circumferential center of the outer peripheral surface of the auxiliary magnetic pole portion between a pair of concave portions that are concave in an arc shape toward the axis on both circumferential sides. Effect of the Invention

[0009] According to the electric motor of claim 1, a convex portion is formed in the circumferential center of the outer peripheral surface of the auxiliary magnetic pole portion between a pair of concave portions whose both circumferential sides are concave toward the shaft. Because this concave portion is arc-shaped, when the vicinity of the convex portion and the concave portion pass through the teeth portion as the rotor rotates, the change in the magnetic flux passing through the teeth portion can be made gentler. Therefore, the cogging torque of the electric motor can be reduced.

[0010] According to the electric motor of claim 2, in addition to the effects of the electric motor of claim 1, the following effects are achieved. In a cross section perpendicular to the axis, the convex portion is formed by a curve that is connected to the arc-shaped concave portion via an inflection point. This makes it possible to make the change in the magnetic flux passing through the teeth more gradual when the vicinity of the convex portion and the concave portion pass through the teeth as the rotor rotates. This makes it possible to further reduce the cogging torque of the electric motor.

[0011] The electric motor of claim 3 has the following effect in addition to the effect of the electric motor of claim 1. The range of angle θ1 at which the main magnetic pole parts continue around the axis is 52° to 70° when the number of poles, which is the number of main magnetic pole parts, is 4, 14° to 38° when the number of poles is 6, 4° to 20° when the number of poles is 8, 2.5° to 13° when the number of poles is 10, and 0.1° to 7° when the number of poles is 12. Within these ranges, the cogging torque of the electric motor can be sufficiently reduced compared to when the outer circumferential surfaces of the main magnetic pole parts and the auxiliary magnetic pole parts in a cross section perpendicular to the axis are substantially perfect circles that continue all around.

[0012] According to the electric motor of claim 4, in addition to the effects of the electric motor of claim 1, the following effect is achieved. The recess is formed by cutting out an arc of radius R centered on a point on an imaginary arc surface extending in the circumferential direction from the outer circumferential surface of the main pole part. This radius R is 0.4 mm to 0.8 mm. This makes it possible to further reduce the cogging torque of the electric motor.

[0013] According to the electric motor of claim 5, in addition to the effects of the electric motor of claim 1, the following effects are achieved. The outer peripheral surface of the auxiliary magnetic pole portion has a slope portion connecting the recess and the main magnetic pole portion. The slope portion is formed by a straight line that gradually moves away from an imaginary straight line connecting the circumferential ends of adjacent main magnetic pole portions in a cross section perpendicular to the axis, toward the recess, in a radially outward direction. This makes it possible to make the change in the magnetic flux passing through the teeth gentler when the position passing through the teeth changes from the main magnetic pole portion to the recess, or from the recess to the main magnetic pole portion, as the rotor rotates. As a result, the cogging torque of the electric motor can be further reduced.

[0014] The electric motor of claim 6 achieves the following effect in addition to the effect achieved by the electric motor of claim 1. In a cross section perpendicular to the axis, a plurality of magnet accommodating holes (permanent magnets) are arranged on each side of a regular polygon. In other words, the magnet accommodating holes are linear. This makes it easier to reduce the manufacturing cost of the electric motor compared to cases where the magnet accommodating holes are V-shaped or arc-shaped.

[0015] An air conditioner according to a seventh aspect, a refrigerator according to an eighth aspect, and an in-vehicle device according to a ninth aspect are each equipped with the electric motor according to any one of the first to sixth aspects, and exert the effects exerted by the electric motor. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1A is a block diagram showing an air conditioner equipped with an electric motor according to an embodiment, and FIG. 1B is a cross-sectional view showing a part of the air conditioner. [Diagram 2] 2 is a cross-sectional view of the electric motor taken along line II-II in FIG. [Diagram 3] FIG. 2 is a partially enlarged cross-sectional view of a rotor of an electric motor. [Figure 4] 4 is a partially enlarged cross-sectional view of the rotor, showing an enlarged portion IV of FIG. 3. [Diagram 5] 11 is a graph showing the change in the angle θ1 of the main magnetic pole portion and the cogging torque when the number of poles is 4, 6, and 8. [Figure 6]11 is a graph showing the change in the angle θ1 of the main magnetic pole portion and the cogging torque when the number of poles is 10 and 12. [Figure 7] 1 is a graph showing the change in radius R of the recess and cogging torque for each outer diameter of the rotor. [Figure 8] FIG. 1(a) is a block diagram that shows a schematic diagram of a vehicle equipped with an electric motor, and FIG. 1(b) is a block diagram that shows a schematic diagram of a refrigerator equipped with an electric motor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, preferred embodiments will be described with reference to the accompanying drawings. Fig. 1(a) is a block diagram showing an air conditioner 10 equipped with an electric motor 30 according to one embodiment. Fig. 1(b) is a cross-sectional view showing a compressor 11, which is a part of the air conditioner 10. Fig. 2 is a cross-sectional view of the electric motor 30 taken along line II-II in Fig. 1(b). In Fig. 1(b), hatching of a part of the compressor 11 (such as the stator 31 and the rotor 40) is omitted in order to simplify the drawing.

[0018] As shown in Fig. 1(a) and Fig. 1(b), an air conditioner 10 is a device for blowing cool air generated by a compressor 11 into a room or the like. The compressor 11 mainly includes a compression mechanism 20, an electric motor 30, and an accumulator 12. The compression mechanism 20 and the electric motor 30 are disposed in a sealed container 13. A suction pipe 15 and a discharge pipe 16 that communicate between the inside and outside of the sealed container 13 are provided in the sealed container 13.

[0019] The accumulator 12 separates the cooling medium (e.g., cooling gas) from the lubricating oil. The cooling medium separated in the accumulator 12 returns to the compression mechanism 20 via the suction pipe 15. The lubricating oil separated in the accumulator 12 returns to the lubricating oil reservoir 17 in the sealed container 13.

[0020] The compression mechanism 20 includes a cylinder 21 and an eccentric rotor 23 driven by an electric motor 30 via a rotating shaft 22. The rotating shaft 22 is a rod-shaped member that rotates around an axis C that is the axial center of the rotating shaft 22. The compression mechanism 20 compresses the cooling medium sucked from the suction pipe 15 inside the cylinder 21 as the eccentric rotor 23 rotates around the axis C. In the following description, the axial direction of the axis C is simply referred to as the "axial direction", the direction perpendicular to the axis C is referred to as the "radial direction", and the direction around the axis C is referred to as the "circumferential direction".

[0021] The cooling medium compressed by the compression mechanism 20 passes through grooves, holes, gaps, etc. formed in various parts of the motor 30, and is discharged from the discharge pipe 16. In the compressor 11 of this embodiment, a mixture of the cooling medium and the lubricating oil is discharged from the discharge pipe 16.

[0022] The electric motor 30 includes a cylindrical stator 31 fixed to the sealed container 13, and a cylindrical rotor 40 disposed on the inner circumferential side of the stator 31. The rotor 40 surrounds the axis C, and the stator 31 surrounds the rotor 40. The stator 31 and the rotor 40 are formed by stacking a plurality of thin, plate-shaped electromagnetic steel sheets in the axial direction.

[0023] 2, the stator 31 includes a cylindrical yoke portion 32 that forms the outer periphery of the stator 31, and a plurality of teeth portions 33 that protrude from the inner periphery of the yoke portion 32 toward the axis C. The teeth portions 33 have the same shape and are arranged at equal intervals in the circumferential direction.

[0024] Teeth portion 33 has tip surface 33a facing the outer circumferential surface of rotor 40, and teeth end portion 33b extending tip surface 33a in the circumferential direction. Teeth end portion 33b is a portion of teeth portion 33 on the tip surface 33a side that protrudes in the circumferential direction.

[0025] A plurality of slots 34 are formed between the teeth portions 33 adjacent to each other in the circumferential direction. In this embodiment, the number of teeth portions 33 and slots 34 is 12, but this may be changed as appropriate. A concentrated winding type winding 35 is inserted into the slots 34. The winding 35 is not limited to the concentrated winding type, and may be a distributed winding type winding.

[0026] In addition, the concentrated winding method can accommodate the winding 35 in the slot 34 more efficiently than the distributed winding method. Also, the concentrated winding method can reduce the amount of the winding 35 protruding from the slot 34. When the amount of the winding 35 protruding from the slot 34 is small, the copper loss of the winding 35 is reduced. Furthermore, in the concentrated winding method, the circumferential length of the tooth ends 33b is longer than in the distributed winding method. For this reason, the tooth ends 33b are more likely to become magnetically saturated than in the distributed winding method.

[0027] In the distributed winding method, the number of teeth 33 of the stator 31 facing one pole of the rotor 40 is greater than in the concentrated winding method. Therefore, the magnetic flux flowing from the teeth 33 to the rotor 40 or from the rotor 40 to the teeth 33 is dispersed, and the magnetic flux is less likely to concentrate at the teeth end 33b. Therefore, in the distributed winding method, the difference in magnetic flux density at the teeth end 33b is smaller than in the concentrated winding method, and vibration noise during operation can be reduced. In addition, in the distributed winding method, the concentration of magnetic flux at the teeth end 33b is suppressed, so there is no need to consider local demagnetization of the permanent magnet 44 of the rotor 40. This allows the thickness of the permanent magnet 44 in the magnetization direction to be thinner, and the amount of permanent magnets used can be reduced.

[0028] 1(b) and 2, the rotor 40 is configured to be rotatable about an axis C relative to the stator 31. The rotor 40 is driven to rotate by passing current through the windings 35. Between the outer circumferential surface of the rotor 40 and the tip surfaces 33a of the teeth portions 33 of the stator 31, a gap of a predetermined range is set.

[0029] The rotor 40 has a rotating shaft hole 41, a magnet accommodating hole 42, and a pin hole 43 formed therethrough in the axial direction. The rotating shaft hole 41 is a hole centered on the axis C. The rotating shaft 22 is inserted into the rotating shaft hole 41 and fixed by press fitting, shrink fitting, or the like.

[0030] The magnet accommodating holes 42 are located near the outer circumferential surface of the rotor 40, and eight of them are provided rotationally symmetrically around the axis C. The eight magnet accommodating holes 42 are disposed on each side of a regular octagon. That is, the magnet accommodating holes 42 are formed linearly in a cross section perpendicular to the axis C (as viewed in the axial direction).

[0031] Permanent magnets 44 such as ferrite magnets or rare earth magnets are inserted into each of the eight magnet accommodating holes 42 and fixed by clearance fit or the like. The permanent magnets 44 have substantially the same shape as the magnet accommodating holes 42 and are plate-like with the plate thickness direction being in the radial direction. This makes it easier to manufacture the permanent magnets 44 and reduces the manufacturing costs of the motor 30 compared to when the magnet accommodating holes 42 (permanent magnets 44) are V-shaped or arc-shaped.

[0032] Furthermore, with the permanent magnet 44 inserted into the magnet accommodating hole 42, gaps are formed on both circumferential sides of the permanent magnet 44. This makes it possible to prevent magnetic flux from leaking in the circumferential direction from the permanent magnet 44. The gaps may be filled with a non-magnetic material such as resin.

[0033] The pin holes 43 are located between the rotating shaft hole 41 and the magnet accommodating holes 42, and four of them are provided at equal intervals in the circumferential direction. End plates 45 are placed on both axial ends of the rotor 40 to close both ends of the magnet accommodating holes 42. The end plates 45 are fixed to the rotor 40 by pins 46 that pass through the end plates 45 and are inserted into the pin holes 43. In addition, balance weights 47 placed on the end plates 45 are also fixed to the rotor 40 by the pins 46.

[0034] Next, the rotor 40 will be described in more detail with reference to Figures 3 and 4. Figure 3 is a partially enlarged cross-sectional view of the rotor 40. Figure 4 is a partially enlarged cross-sectional view of the rotor 40, enlarging part IV in Figure 3. In Figures 3 and 4, hatching of the rotor 40 is omitted in order to simplify the drawings. Similarly to Figure 2, the cross sections in Figures 3 and 4 are cross sections perpendicular to the axis C. In the following description using Figures 3 and 4, unless otherwise specified, the shapes of each part of the rotor 40 in the cross section perpendicular to the axis C will be described.

[0035] As shown in FIG. 3, the rotor 40 has main magnetic poles 40a and auxiliary magnetic poles 40b arranged alternately in the circumferential direction. In the rotor 40, the range of angle θ1 around the axis C shown in FIG. 3 is the main magnetic poles 40a, and the range of angle θ2 around the axis C is the auxiliary magnetic poles 40b. The number of main magnetic poles 40a and the number of auxiliary magnetic poles 40b are the same, and this number is called the pole number N. In this embodiment, the pole number N is 8 poles, and the rotor 40 is formed with 8 (= pole number N) rotational symmetry around the axis C, except for the pin hole 43. In addition, the angles θ1, θ2, and the pole number N have a relationship of θ1+θ2=360° / N. That is, if the pole number N is 8 poles and the angle θ1 is 15°, the angle θ2 is 30°.

[0036] An imaginary straight line that extends radially from the axis C and passes through the centers of the magnet accommodating holes 42 that are adjacent in the circumferential direction is defined as an auxiliary center line A. The circumferential center of the auxiliary magnetic pole portion 40b is located on the auxiliary center line A. The auxiliary magnetic pole portion 40b is formed circumferentially symmetrical with respect to the auxiliary center line A.

[0037] The main magnetic pole portion 40a is located at the circumferential center of the magnet accommodating hole 42. The main magnetic pole portions 40a adjacent to each other in the circumferential direction are magnetized so that the permanent magnets 44 accommodated in the respective magnet accommodating holes 42 have different polarities. That is, the magnetic poles on the outer periphery of the permanent magnets 44 are arranged such that N poles and S poles are alternately arranged in the circumferential direction.

[0038] The electric motor 30 including such a rotor 40 uses both the magnet torque due to the main magnetic pole portion 40a (permanent magnet 44) and the reluctance torque due to the salient pole of the auxiliary magnetic pole portion 40b (between the permanent magnets 44) to rotate the rotor 40 relative to the stator 31. However, as this rotation occurs, when the boundary between the main magnetic pole portion 40a and the auxiliary magnetic pole portion 40b passes through the teeth portion 33 of the stator 31, the magnetic flux passing through the teeth portion 33 may suddenly change, generating a cogging torque.

[0039] The outer peripheral surface of the main magnetic pole portion 40a is formed in an arc shape centered on the axis C. The outer peripheral surface of the auxiliary magnetic pole portion 40b is located on the axis C side with respect to an imaginary arc surface B that is a circumferential extension of the outer peripheral surface of the main magnetic pole portion 40a. This allows the change in magnetic flux passing through the teeth portion 33 to be gradual when the rotor 40 rotates, and the cogging torque of the electric motor 30 to be reduced.

[0040] 3 and 4, a protrusion 52 is formed between a pair of recesses 51 that are recessed toward the axis C on both circumferential sides of the outer circumferential surface of the auxiliary magnetic pole portion 40b in the circumferential center (on the auxiliary center line A). The recesses 51 and the protrusions 52 are also formed circumferentially symmetrical with respect to the auxiliary center line A. The recesses 51 are located radially outward from the circumferential ends of the magnet accommodating holes 42.

[0041] Such recesses 51 and protrusions 52 can prevent the magnetic flux of the permanent magnets 44 in the magnet accommodating holes 42 from being short-circuited through the teeth 33 of the stator 31. As a result, the cogging torque of the electric motor 30, which is generated by a short-circuit of the magnetic flux, can be reduced.

[0042] Furthermore, because the recesses 51 are formed in an arc shape, when the vicinity of the recesses 51 and the protrusions 52 pass through the teeth 33 as the rotor 40 rotates, the change in the magnetic flux passing through the teeth 33 can be made gentler. As a result, the cogging torque of the motor 30 can be further reduced.

[0043] The recess 51 is formed by cutting out an arc D of radius R centered on a point on the arc surface B. With such a recess 51, when the vicinity of the recess 51 and the protrusion 52 passes through the teeth 33, the change in the magnetic flux passing through the teeth 33 can be made more gradual. As a result, the cogging torque of the electric motor 30 can be further reduced.

[0044] The protrusions 52 are formed by curves that smoothly connect with the arc-shaped recesses 51 via inflection points, i.e., by curves that protrude outward in the radial direction. This makes it possible to make the change in the magnetic flux passing through the teeth 33 more gradual when the vicinity of the recesses 51 and the protrusions 52 passes through the teeth 33 as the rotor 40 rotates. As a result, the cogging torque of the motor 30 can be further reduced.

[0045] The outer peripheral surface of the auxiliary magnetic pole portion 40b includes a slope portion 54 that connects the recess 51 and the main magnetic pole portion 40a. The slope portion 54 is formed by a straight line that gradually moves away from the imaginary straight line E that connects the circumferential ends of the adjacent main magnetic pole portions 40a toward the recess 51 in the radial direction. This makes it possible to make the change in the magnetic flux passing through the teeth portion 33 gentler when the position passing through the teeth portion 33 changes from the main magnetic pole portion 40a to the recess 51 or from the recess 51 to the main magnetic pole portion 40a as the rotor 40 rotates. As a result, the cogging torque of the electric motor 30 can be further reduced.

[0046] Next, the relationship between the angle θ1 of the main magnetic pole portion 40a of the electric motor 30 and the cogging torque for each number of poles N will be described with reference to Fig. 5(a) to Fig. 6(b). The change in the cogging torque of the electric motor 30 when the angle θ1 of the main magnetic pole portion 40a is changed for each number of poles N is analyzed, and the graphs of the analysis results are shown by solid lines in Fig. 5(a) to Fig. 6(b), respectively. In each graph, the vertical axis represents the cogging torque, and the horizontal axis represents the angle θ1 of the main magnetic pole portion 40a.

[0047] Figure 5(a) shows a graph when the number of poles N is 4. Figure 5(b) shows a graph when it is 6 poles, Figure 5(c) shows a graph when it is 8 poles, Figure 6(a) shows a graph when it is 10 poles, and Figure 6(b) shows a graph when it is 12 poles.

[0048] The electric motor 30 used in the analysis for the eight-pole case is the one described in Fig. 1(b) to Fig. 4, and further detailed dimensions are shown below. The eight-pole electric motor 30 has 12 slots 34, an outer diameter of the stator 31 of 96 mm, and an inner diameter of the stator 31 of 62.3 mm. The width (circumferential dimension) of the teeth portion 33 excluding the teeth end portions 33b is 7.8 mm. The width of the opening between the teeth portions 33 (teeth end portions 33b) adjacent in the circumferential direction is 3.2 mm. The gap between the tip end surfaces 33a of the teeth portion 33 of the stator 31 and the outer circumferential surface of the rotor 40 is 0.4 mm to 0.8 mm in the radial direction. The axial dimension of the stator 31 is 42 mm.

[0049] The outer diameter of the rotor 40 (twice the radius from the axis C to the main magnetic pole portion 40a) is 61.5 mm. The inner diameter of the rotor 40 (diameter of the rotating shaft hole 41) is 19.5 mm. The axial dimension of the rotor 40 is 42 mm. The radius R of the arc D of the recess 51 is 0.2 mm. The radius of curvature of the protrusion 52 is 0.2 mm.

[0050] The stator 31 and the rotor 40 are laminated with 35A300 electromagnetic steel sheets as specified in JIS C2552:2014. The electromagnetic steel sheets have a thickness of 0.35 mm, an iron loss W15 / 50 of 3.0 W / kg, and an iron loss W15 / 60 of 3.74 W / kg. The permanent magnet 44 has a residual magnetic flux density Br of 1.3 to 1.5 T and a coercive force Hcj of 21 kOe or more at 20°C.

[0051] It has been confirmed that analysis results with the same tendency as the graph in FIG. 5(c) can be obtained even if the above numerical values ​​and specifications are appropriately changed within the range in which the 8-pole motor 30 is driven appropriately.

[0052] Only the changes made to the 8-pole motor 30 described above in the motors 30 used in the analysis of the 4, 6, 10, and 12 poles will be described. In the 4, 6, 10, and 12-pole motors 30, the same number of magnets as the number of poles N are arranged in a regular N-sided polygon (for example, a regular square in the case of 4 poles). Furthermore, the number of slots 34, the width of the teeth 33, the width of the openings between the teeth 33, and the specifications of the windings 35 are set so that the motor 30 operates appropriately according to the number of poles N. It should be noted that when there are multiple values ​​or specifications for the motor 30 to operate appropriately, it has been confirmed that analysis results with similar tendencies can be obtained with any combination of values ​​or specifications.

[0053] 5(a) to 6(b) show graphs of analysis results of a comparative example Ce, which is a comparative example for the above-mentioned electric motor 30, in which the outer peripheral surface of the rotor 40 (main magnetic pole portion 40a and auxiliary magnetic pole portion 40b) in a cross section perpendicular to the axis C is a substantially perfect circle that is continuous all around, for each number of poles N. The cogging torque of this comparative example Ce is constant with respect to the angle θ1. Furthermore, in FIG. 5(a) to FIG. 6(b), the median M between the minimum value of the cogging torque of the above-mentioned electric motor 30 and the cogging torque of the comparative example is shown by a dashed line for each number of poles N.

[0054] 5(a), the cogging torque of the four-pole motor 30 is substantially the same as (slightly lower than) that of the comparative example Ce when the angle θ1 is smaller than 50° or larger than 75°, and is lower than that of the comparative example Ce when the angle is between 50° and 75°. Therefore, in the four-pole motor, it is preferable to set the angle θ1 to 50° to 75° in order to reduce the cogging torque.

[0055] Furthermore, the cogging torque of the four-pole motor 30 is equal to or less than the median M when the angle θ1 is between 52° and 70°, and is close to the minimum when the angle θ1 is between 55° and 68°. Therefore, in order to reduce the cogging torque, with four poles, it is more preferable that the angle θ1 be between 52° and 70°, and even more preferably between 55° and 68°.

[0056] 5(b), the cogging torque of the six-pole electric motor 30 is lower than that of the comparative example Ce when the angle θ1 is between 10° and 40°, is below the median value M when the angle is between 14° and 38°, and is close to the minimum value when the angle is between 16° and 36°. Therefore, with six poles, in order to reduce the cogging torque, the angle θ1 is preferably set to 10° to 40°, more preferably to 14° to 38°, and even more preferably to 16° to 36°.

[0057] 5(c), the cogging torque of the eight-pole electric motor 30 is lower than that of comparative example Ce when the angle θ1 is between 2.5° and 22°, is below the median value M when the angle is between 4° and 20°, and is close to the minimum value when the angle is between 6° and 17°. Therefore, with eight poles, in order to reduce the cogging torque, the angle θ1 is preferably set to 2.5° to 22°, more preferably to 4° to 20°, and even more preferably to 6° to 17°.

[0058] 6(a), the cogging torque of the 10-pole motor 30 is lower than that of comparative example Ce when the angle θ1 is 0.5° to 17°, is below the median value M when the angle is 2.5° to 13°, and is close to the minimum value when the angle is 3° to 11°. Therefore, with 10 poles, in order to reduce the cogging torque, the angle θ1 is preferably set to 0.5° to 17°, more preferably to 2.5° to 13°, and even more preferably to 3° to 11°.

[0059] 6(b), the cogging torque of the 12-pole motor 30 is lower than that of comparative example Ce when the angle θ1 is 0.1° to 12°, is below the median value M when the angle is 0.1° to 7°, and is close to the minimum value when the angle is 0.5° to 3°. Therefore, with 12 poles, in order to reduce the cogging torque, the angle θ1 is preferably set to 0.1° to 12°, more preferably to 0.1° to 7°, and even more preferably to 0.5° to 3°.

[0060] These results are because, for each pole number N, when the angle θ1 is smaller than the minimum value, the saliency of the main magnetic pole portion 40a becomes too strong, making it difficult to reduce the cogging torque of the motor 30. Also, for each pole number N, when the angle θ1 is greater than the maximum value, the outer circumferential surface of the rotor 40 approaches a substantially perfect circle as a whole, making it difficult to reduce the cogging torque of the motor 30.

[0061] Next, with reference to Figures 7(a) to 7(d), the relationship between the radius R of the arc D of the recess 51 of the electric motor 30 and the cogging torque for each outer diameter of the rotor 40 (twice the radius from the axis C to the main magnetic pole portion 40a). The change in the cogging torque of the electric motor 30 when the radius R of the recess 51 is changed for each outer diameter of the rotor 40 is analyzed, and the graphs of the analysis results are shown by solid lines in Figures 7(a) to 7(d), respectively. In each graph, the vertical axis represents the cogging torque, and the horizontal axis represents the radius R of the recess 51.

[0062] Fig. 7(a) shows a graph in the case where the outer diameter of the rotor 40 is 50 mm, Fig. 7(b) shows a graph in the case where the outer diameter is 61.5 mm, Fig. 7(c) shows a graph in the case where the outer diameter is 70 mm, and Fig. 7(d) shows a graph in the case where the outer diameter is 80 mm.

[0063] The electric motor 30 used in the analysis for the 61.5 mm case has the same configuration as the 8-pole electric motor 30 used in the analysis of the graph in Fig. 5(c), except that the angle θ1 is fixed at 2.5° and the radius R is varied. The electric motors 30 used in the analysis for the 50, 70, and 80 mm cases have the same configuration as the electric motor 30 for the 61.5 mm case, except that the stator 31 is enlarged or reduced overall so that the size of the gap between the tip surface 33a of the teeth portion 33 of the stator 31 and the outer circumferential surface of the rotor 40 does not change.

[0064] 7(a) to 7(d) show graphs with dashed lines the analysis results of Comparative Example Ce in which the outer peripheral surface of rotor 40 in a cross section perpendicular to axis C is made to be a nearly perfect circle that is continuous all around for each outer diameter of rotor 40 for the above-mentioned electric motor 30. In Comparative Example Ce, since recess 51 is not present, the value of the cogging torque with respect to radius R of recess 51 is constant.

[0065] 7(a) to 7(d), the cogging torque of the electric motor 30 is sufficiently reduced compared to Comparative Example Ce when the radius R of the recess 51 is 0.4 mm to 0.8 mm, regardless of the outer diameter of the rotor 40. Also, as the radius R becomes smaller than 0.4 mm or larger than 0.8 mm, the reduction rate of the cogging torque of the electric motor 30 compared to Comparative Example Ce becomes lower, but the torque is still reduced.

[0066] This is because if the radius R is smaller than 0.4 mm, the outer circumferential surface of the rotor 40 becomes nearly a perfect circle overall, making it difficult to reduce the cogging torque of the motor 30. Also, if the radius R is larger than 0.8 mm, the salient pole of the auxiliary magnetic pole portion 40b becomes too strong, making it difficult to reduce the cogging torque of the motor 30.

[0067] It has been confirmed that even if the dimensions and specifications of each part of the electric motor 30 are appropriately changed within a range in which the electric motor 30 operates appropriately, analysis results with trends similar to those shown in Figures 7(a) to 7(d) can be obtained, so long as the center point of the radius R of the recess 51 is located on the arcuate surface B. As a result of the above, if the radius R of the recess 51 is 0.4 mm to 0.8 mm, the cogging torque of the electric motor 30 can be further reduced.

[0068] The present invention has been described above based on an embodiment, but the present invention is not limited to the above embodiment, and it can be easily inferred that various improvements and modifications are possible within the scope of the present invention without departing from the spirit of the present invention.

[0069] For example, the electric motor 30 is mounted on the indoor air conditioner 10 in the above description, but the present invention is not limited to this. As shown in Fig. 8(a), the electric motor 30 may be mounted on an air conditioner 61 for blowing cool air into the interior of a vehicle 60. This air conditioner 61 generates cool air with a compressor 11 mainly including the electric motor 30 and an accumulator 12, similar to the air conditioner 10 described in the above embodiment. This air conditioner 61 may include a receiver for storing the compressed cooling medium together with the accumulator 12 or instead of the accumulator 12.

[0070] Furthermore, the electric motor 30 may be installed in an in-vehicle device other than the air conditioner 61 among the in-vehicle devices installed in the vehicle 60. Examples of the in-vehicle devices other than the air conditioner 61 include power windows, wipers, and power seats.

[0071] As shown in Fig. 8(b), the electric motor 30 may be mounted on the refrigerator 70. The refrigerator 70 generates cold air using a compressor 11 mainly including the electric motor 30 and an accumulator 12, similar to the air conditioner 10 described in the above embodiment, and cools the interior of the refrigerator with the cold air.

[0072] In the above embodiment, the rotor 40 has a single-phase structure in which the permanent magnets 44 are arranged in only one layer in the radial direction in the main magnetic pole portion 40a of the rotor 40, but this is not limited thereto. For example, the permanent magnets 44 may be arranged in multiple layers in the radial direction to form a rotor 40 with a multi-layer structure.

[0073] Furthermore, the permanent magnets 44 (magnet accommodating holes 42) are not limited to being arranged on each side of a regular polygon in a cross section perpendicular to the axis C and each being formed linearly. The arrangement and shape of the permanent magnets 44 (magnet accommodating holes 42) may be V-shaped or arc-shaped, for example.

[0074] In the above embodiment, the slope portion 54 is a straight line in a cross section perpendicular to the axis C, but is not limited thereto. The slope portion 54 may be a curved line that gradually moves away from the imaginary straight line E toward the recessed portion 51 in a cross section perpendicular to the axis C. In particular, it is preferable that the curved lines of the slope portions 54 adjacent to each other on both sides of the circumferential direction of the protruding portion 52 are formed symmetrically in the circumferential direction with respect to the auxiliary center line A, and are formed by arcs having different centers. In this case, the change in the magnetic flux passing through the teeth portion 33 accompanying the rotation of the rotor 40 can be made gentle between the main magnetic pole portion 40a and the recessed portion 51. As a result, the cogging torque of the electric motor 30 can be further reduced. [Explanation of symbols]

[0075] 10 Air conditioner 30 Electric motor 31 Stator 32 York 33 Teeth 34 Slots 35 windings 40 Rotor 40a Main magnetic pole part 40b Auxiliary magnetic pole part 42 Magnet receiving hole 44 Permanent Magnets 51 Recess 52 Convex 54 Slope section 61 Air conditioner (vehicle equipment) 70 Refrigerator

Claims

1. An electric motor including a rotor rotatable around an axis and a cylindrical stator surrounding the rotor, The stator includes a cylindrical yoke portion that forms an outer circumferential portion of the stator, and a plurality of teeth portions that protrude from the yoke portion toward the axis, and a winding is inserted into a slot between the teeth portions that are adjacent to each other in a circumferential direction, The rotor has a plurality of magnet accommodating holes, into which permanent magnets are respectively inserted, which are provided rotationally symmetrically around the axis, and is rotationally driven by passing current through the windings. In the rotor, auxiliary magnetic pole portions which are formed circumferentially symmetrically about a circumferential center between the plurality of magnet accommodating holes, and main magnetic pole portions are alternately arranged in the circumferential direction, In a cross section perpendicular to the axis, an outer peripheral surface of the main magnetic pole portion is formed in an arc shape centered on the axis, and an outer peripheral surface of the auxiliary magnetic pole portion is located on the axis side with respect to a virtual arc surface extending in a circumferential direction from the outer peripheral surface of the main magnetic pole portion, an electric motor, characterized in that a convex portion is formed at the circumferential center of the outer circumferential surface of the auxiliary magnetic pole portion, between a pair of concave portions that are recessed in an arc shape toward the shaft on both circumferential sides.

2. 2. The electric motor according to claim 1, wherein the convex portion is formed by a curve that is connected to the arc-shaped concave portion via an inflection point in a cross section perpendicular to the shaft.

3. The electric motor according to claim 1, characterized in that the range of angle θ1 at which the main magnetic pole portions continue around the axis is 52° to 70° when the number of poles, which is the number of the main magnetic pole portions, is 4 poles, 14° to 38° when the number of poles is 6 poles, 4° to 20° when the number of poles is 8 poles, 2.5° to 13° when the number of poles is 10 poles, and 0.1° to 7° when the number of poles is 12 poles.

4. the recess is formed by cutting out an arc having a radius R centered on a point on the arc surface, 2. The electric motor according to claim 1, wherein the radius R is 0.4 mm to 0.8 mm.

5. an outer circumferential surface of the auxiliary magnetic pole portion includes a slope portion connecting the recess and the main magnetic pole portion; 2. The electric motor according to claim 1, wherein the slope portion is formed by a straight line that, in a cross section perpendicular to the axis, gradually moves radially outward from an imaginary line connecting circumferential ends of adjacent main pole portions as the slope portion approaches the recess.

6. 2. The electric motor according to claim 1, wherein a plurality of said magnet accommodating holes are arranged on each side of a regular polygon in a cross section perpendicular to said axis.

7. An air conditioner having the electric motor according to any one of claims 1 to 6 mounted thereon.

8. A refrigerator equipped with the electric motor according to any one of claims 1 to 6.

9. 7. An on-vehicle device having the electric motor according to claim 1 mounted thereon.

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