JP7593433B2 - Electric motor - Google Patents

Description

The present invention relates to an electric motor.

A known electric motor has an embedded magnet type rotor in which permanent magnets are embedded inside the rotor core. This type of electric motor has a rotor in which multiple magnetic poles are formed on the outer periphery of the permanent magnet and arranged along the circumferential direction, and a stator with multiple teeth and an annular yoke portion arranged on the outer periphery of the rotor.

Related technology includes an electric motor that reduces torque ripple by changing the size of the air gap between the outer circumferential surface of the rotor core and the inner circumferential surface of the teeth in the circumferential direction of the rotating rotor, thereby bringing the magnetic flux density distribution in the air gap along the circumferential direction closer to a sine wave (Patent Document 1).

JP 2021-90351 A

Here, in an electric motor in which the ratio of the number of poles, which is the number of permanent magnets (the number of magnetic poles), to the number of teeth, which is the number of windings around which the windings are wound, is 2:3, an average of three teeth will face the rotor within the range of one pole pair (hereinafter also referred to as a "pole pair"), which is a set of a north pole magnetic pole and a south pole magnetic pole adjacent to each other in the circumferential direction of the rotor. As an example, when three teeth face the range of one pole pair (when the central tooth of the three teeth aligned in the circumferential direction of the rotor is located on the q-axis, which is the straight line connecting the center between the circumferentially adjacent magnetic poles and the center of rotation of the rotor), a magnetic path circulating between the stator and the rotor is formed, attention will be paid to the central tooth of the three teeth aligned in the circumferential direction of the rotor. In this case, two types of magnetic paths are generated: one that passes through the inner end (flange) of the teeth from the N-pole magnetic pole to the S-pole magnetic pole without passing through the yoke of the stator, and the other that passes through the N-pole magnetic pole, crosses the teeth in the radial direction of the rotor, passes through the yoke, and then passes through the adjacent teeth to the S-pole magnetic pole. When two types of magnetic paths are formed in the central teeth in this way, the magnetic flux passing through the central teeth cannot be distributed symmetrically with respect to the q-axis. In other words, in a motor with a ratio of the number of poles to the number of teeth of 2:3, the magnetic flux density distribution passing between the N-pole permanent magnet and the teeth adjacent to the N-pole permanent magnet and the magnetic flux density distribution passing between the S-pole permanent magnet and the teeth adjacent to the S-pole permanent magnet are not symmetric with respect to the q-axis in the N-pole permanent magnet and S-pole permanent magnet that form one pole pair.

Therefore, in a three-phase concentrated winding motor in which the ratio of the number of poles to the number of teeth is 2:3, in other words the ratio of the number of pole pairs (hereinafter also referred to as the "pole pair number") to the number of teeth is 1:3, it is difficult to make the magnetic flux density distribution in the gap between the rotor and the stator in the circumferential direction of the rotating rotor approach a sine wave. One of the reasons for this is, for example, that the shape of the range of the magnetic poles on the outer circumferential surface of the rotor core is symmetrical with respect to the d-axis, which is the straight line connecting the center of the magnetic poles and the center of rotation of the rotor.

The disclosed technology has been developed in consideration of the above, and aims to provide an electric motor that can make the magnetic flux density distribution in the gap between the rotor and the stator in the circumferential direction of the rotating rotor closer to a sine wave.

One aspect of an electric motor disclosed in the present application is an electric motor comprising: a rotor having a rotor core in which a permanent magnet is embedded and in which a plurality of magnetic pole portions are provided along a circumferential direction; and a stator having a plurality of teeth portions arranged on the outer periphery of the rotor, the number of pole pairs of the magnetic pole portions being m, the number of the plurality of teeth portions being 3m, the rotor core having non-magnetic portions extending continuously from each of both ends in the circumferential direction of the permanent magnet, and in a plane perpendicular to the rotation centerline of the rotor, when the outer periphery of the rotor core in a range forming one pole pair, which is one pole pair, is taken as one pole pair outer periphery surface, so that the shape of the outer periphery of the rotor core is point symmetrical with respect to the rotation center of the rotor, the shape of the one pole pair outer periphery surface is repeated m times in the circumferential direction, and in the plane, each magnetic pole portion is located between the rotation center and one of the non-magnetic portions. The rotor core has a magnetic pole outer peripheral surface formed on the outer peripheral surface between a first boundary line passing through the outer peripheral end in the radial direction of the rotor core and a second boundary line passing through the center of rotation and the outer peripheral end in the radial direction of the other non-magnetic portion, and in the plane, a straight line connecting the center of the magnetic pole portion in the circumferential direction and the center of rotation is defined as a d-axis, and a straight line connecting the center between adjacent magnetic pole portions in the circumferential direction and the center of rotation is defined as a q-axis, and each pole pair has an N-pole magnetic pole portion and an S-pole magnetic pole portion arranged on either side of the q-axis, and when either the N-pole magnetic pole portion or the S-pole magnetic pole portion is virtually rotated 360/(2 m) [degrees] around the center of rotation in the plane and overlapped with the other magnetic pole portion of the N-pole magnetic pole portion or the S-pole magnetic pole portion, the magnetic pole outer peripheral surface of the N-pole magnetic pole portion and the magnetic pole outer peripheral surface of the S-pole magnetic pole portion are formed in shapes that do not coincide with each other. In the plane, the magnetic pole outer peripheral surface of the N-pole magnetic pole part is formed in an asymmetric shape with respect to the N-pole d-axis which is the d-axis of the N-pole magnetic pole part, and the magnetic pole outer peripheral surface of the S-pole magnetic pole part is formed in an asymmetric shape with respect to the S-pole d-axis which is the d-axis of the S-pole magnetic pole part, and the magnetic pole outer peripheral surface of the N-pole magnetic pole part has an N-pole front side outer peripheral surface located on the front side of the N-pole d-axis in the rotation direction of the rotor, and an N-pole rear side outer peripheral surface located on the rear side of the N-pole d-axis in the rotation direction. When the N-pole magnetic pole part is virtually folded back along the N-pole d-axis in the plane and the N-pole front side outer peripheral surface is overlapped with the N-pole rear side outer peripheral surface, the N-pole front side outer peripheral surface has an arc-shaped small-diameter outer peripheral surface located inside the N-pole rear side outer peripheral surface in the radial direction and along the N-pole front outer peripheral surface.

According to one aspect of the electric motor disclosed in this application, the magnetic flux density distribution in the gap between the rotor and the stator in the circumferential direction of the rotating rotor can be made to approximate a sine wave.

FIG. 1 is a plan view showing an electric motor according to an embodiment of the present invention. FIG. 2 is a plan view showing a rotor in the embodiment. FIG. 3 is a plan view for explaining a main portion of a rotor core of a rotor in the embodiment. FIG. 4 is an enlarged view showing one pole pair of the rotor core in the embodiment. FIG. 5 is a schematic diagram showing the outer circumferential surface of each magnetic pole portion of the rotor core in the embodiment. FIG. 6 is a schematic diagram for explaining the shape of the outer circumferential surface of the magnetic pole of the rotor core in the embodiment. FIG. 7 is a plan view for explaining a main portion of a rotor core of a comparative example. FIG. 8 is a plan view showing the distribution of magnetic flux in a rotor of a comparative example. FIG. 9 is a diagram showing the magnetic flux density distribution in the circumferential direction of the rotor in the air gap of an electric motor equipped with a rotor of a comparative example. FIG. 10 is a plan view showing the distribution of magnetic flux in the rotor of the embodiment. FIG. 11 is a diagram showing the magnetic flux density distribution in the circumferential direction of the rotor of the embodiment. FIG. 12 is a diagram showing a comparison of vibrations occurring in the electric motor between the embodiment and the comparative example. FIG. 13 is a diagram showing a comparison between the embodiment and the comparative example with respect to noise generated around the electric motor. FIG. 14 is a plan view for explaining a main portion of a rotor core in a reference example. FIG. 15 is a diagram showing the magnetic flux density distribution in the circumferential direction of the rotor of the reference example. FIG. 16 is a plan view showing a main portion of a rotor core according to a modified example.

Below, examples of the electric motor disclosed in this application are described in detail with reference to the drawings. Note that the electric motor disclosed in this application is not limited to the following examples.

(Motor configuration)
Fig. 1 is a plan view showing an electric motor in the embodiment. Fig. 2 is a plan view showing a rotor in the embodiment. As shown in Fig. 1 and Fig. 2, an electric motor 1 in the embodiment is a three-phase motor with six poles and nine slots and a concentrated winding type. The electric motor 1 includes a rotor 21 and a stator 22 arranged on the outer periphery of the rotor 21.

The rotor 21 has a cylindrical rotor core 23 formed by stacking multiple metal plates made of soft magnetic material such as silicon steel, and the multiple metal plates are integrated, for example, by crimping. The shaft 3 serving as a rotating shaft is inserted into the central axis of the rotor core 23, and the shaft 3 and the rotor 21 are fixed. In addition, the rotor core 23 has multiple long hole-shaped refrigerant gas passages 9 that penetrate in the axial direction of the rotor core 23 (axial direction of the shaft 3), and the multiple refrigerant gas passages 9 are arranged at intervals around the axis of the shaft 3. The main parts of the rotor core 23 in the embodiment will be described later.

The stator 22 is formed in a generally cylindrical shape and is arranged to surround the outer periphery of the rotor 21. The stator 22 is fixed, for example, inside a compression vessel of a compressor (not shown). As shown in FIG. 1, the stator 22 includes a stator core 24, an upper insulator 25, a lower insulator (not shown), and a plurality of windings 46.

As shown in FIG. 2, the stator core 24 is arranged with a predetermined gap (air gap) between it and the outer peripheral surface 27 of the rotor core 23. The stator core 24 has nine teeth 32 extending from an annular yoke portion 31 toward the inside in the radial direction of the rotor core 23, which are formed at equal intervals of 40 degrees (mechanical angle) in the circumferential direction of the stator core 24. Each tooth 32 has a flange portion 33 that protrudes from a tip located on the inner peripheral side of the stator core 24 to both sides in the circumferential direction of the stator core 24. Each tooth 32 is formed in the same shape. As shown in FIG. 1, each tooth 32 has a winding portion 45 in which each winding 46 is wound in a concentrated winding. The windings 46 include three U-phase windings 46-U1 to 46-U3, three V-phase windings 46-V1 to 46-V3, and three W-phase windings 46-W1 to 46-W3. In the stator 22, the neutral wires drawn from each winding section 45 and bundled together are covered with an insulating tube and inserted into the gaps between adjacent winding sections 45 in the circumferential direction of the stator 22 (the direction of rotation of the rotor 21) (see FIG. 1). The upper insulator 25 is fixed to the upper end of the stator core 24. The lower insulator is fixed to the lower end of the stator core 24. The upper insulator 25 and the lower insulator are insulating members that insulate the stator core 24 from the windings 46.

As shown in FIG. 2, the rotor core 23 of the electric motor 1 of the embodiment has a plurality of magnet embedding holes 12a, 12b, 12c, 12d, 12e, and 12f (hereinafter also referred to as magnet embedding holes 12) in which permanent magnets 13a, 13b, 13c, 13d, 13e, and 13f (hereinafter also referred to as permanent magnets 13) are embedded. In the rotor core 23, six slit-shaped magnet embedding holes 12 are formed so as to form each side of a regular hexagon centered on the shaft 3. Each magnet embedding hole 12 is arranged at a predetermined interval in the circumferential direction of the rotor core 23. A plate-shaped permanent magnet 13 is embedded in the magnet embedding hole 12. Note that end plates are attached to both axial end faces of the rotor core 23 to prevent the permanent magnets 13 from falling out, but the end plates are omitted from the illustration in order to explain the main parts of the rotor core 23. This end plate is fixed to the rotor core 23 by a rivet 8 that passes through a rivet hole 7 in the rotor core 23.

As described above, the rotor core 23 has six magnetic poles 11, i.e., three N-pole magnetic poles 11N and three S-pole magnetic poles 11S, which are alternately arranged along the circumferential direction of the rotor core 23 by embedding the permanent magnets 13 therein. The N-pole magnetic poles 11N and S-pole magnetic poles 11S (hereinafter also referred to as magnetic poles 11) include the permanent magnets 13 and are the outer peripheral portion of the permanent magnets 13 in the radial direction of the rotor core 23 (the portion between the permanent magnets 13 and the outer peripheral surface 27 of the rotor core 23). In addition, the plate-shaped permanent magnets 13 are arranged in each magnetic pole portion 11 so that the thickness direction of the permanent magnets 13 is aligned with the d-axis D described below.

The electric motor disclosed in the present application has m pole pairs formed by the magnetic pole portions 11 (north pole magnetic pole portion 11N and south pole magnetic pole portion 11S), and 3m teeth portions 32, where m is a natural number. The number of magnetic pole portions 11, i.e., the number of poles, is 2m. As an example, the electric motor 1 of the embodiment has 6 poles, 3 pole pairs, and 9 teeth portions 32.

In addition, in a plane (hereinafter also referred to as an orthogonal plane) perpendicular to the rotation center line passing through the rotation center O of the rotor 21 (rotation center of the rotor core 23), the straight line connecting the center of the magnetic pole portion 11 (the center of the permanent magnet 13) in the circumferential direction of the rotor 21 and the rotation center O is defined as the d-axis D, and the straight line connecting the center between adjacent magnetic pole portions 11 in the circumferential direction of the rotor 21 and the rotation center O is defined as the q-axis Q. The rotation center line passing through the rotation center O coincides with the center line of the shaft 3 along the axial direction of the shaft 3. The rotor core 23 has multiple d-axes D extending radially from the rotation center O at equal intervals in the circumferential direction of the rotor core 23, and multiple q-axes Q extending radially from the rotation center O at equal intervals in the circumferential direction of the rotor core 23.

Figure 3 is a plan view for explaining the main parts of the rotor core 23 of the rotor 21 in the embodiment. As shown in Figures 2 and 3, the rotor core 23 has a plurality of non-magnetic parts 14a to 14f, 15a to 15f (hereinafter referred to as non-magnetic parts 14, 15), a plurality of grooves 16, 17, and a plurality of bridge parts 18 formed between the non-magnetic parts 14, 15 and the grooves 16, 17. Here, of the non-magnetic parts 14, 15 formed on both ends of the magnet embedding hole 12, the first non-magnetic part 14 (14a to 14f) which is one of the non-magnetic parts is located on the front side in the rotation direction R of the rotor 21, and the second non-magnetic part 15 (15a to 15f) which is the other non-magnetic part is located on the rear side in the rotation direction R. Details of the shape of the outer peripheral surface 27 of the rotor core 23 in the circumferential direction of the rotor core 23 will be described later.

The rotor core 23 has non-magnetic parts (flux barriers) 14, 15 that extend radially outward from both ends of the permanent magnet 13 in the circumferential direction of the rotor core 23, i.e., toward the outer peripheral surface 27 of the rotor core 23. The non-magnetic parts 14, 15 are formed as spaces that continue to the magnet embedding holes 12, and prevent the generation of a magnetic path that circulates between the magnetic pole parts 11 via the flange parts 33 of the teeth parts 32 without passing through the yoke parts 31 of the stator 22 between adjacent magnetic pole parts 11. In other words, the rotor core 23 has a through hole that penetrates the rotor core 23 in the axial direction, and the area of the through hole that is filled with the permanent magnet 13 is the magnet embedding hole 12, and the area of the through hole that is not filled with the permanent magnet 13 is the non-magnetic parts 14, 15 that are spaces.

Grooves 16, 17 are formed on the outer peripheral surface 27 of the rotor core 23 between adjacent magnetic pole portions 11 in the circumferential direction of the rotor core 23, with portions of the outer peripheral surface 27 cut out in the radial direction of the rotor core 23 to form recesses along the rotation centerline of the rotor core 23. In other words, the grooves 16, 17 are located between adjacent non-magnetic portions 14, 15 in the circumferential direction of the rotor core 23, and are arranged on the q-axis Q. Details of the inner surface shape of the grooves 16, 17 in the embodiment will be described later.

(Characteristic structure of rotor core)
Next, a description will be given of a characteristic structure of the rotor core 23 in the embodiment. The characteristics of the embodiment include the shape of the outer circumferential surface 27 of the rotor core 23 in the circumferential direction of the rotor core 23.

(Shape of one pole and outer periphery)
As shown in FIGS. 1 to 3, in a plane perpendicular to the rotation centerline of the rotor 21 (the orthogonal plane that is the paper surface of the drawings, hereinafter also referred to as the orthogonal plane), the outer circumferential surface 27 of the rotor core 23 in a range that forms one pole pair is defined as a one-pole pair outer circumferential surface 28. In addition, in the orthogonal plane, the number of pole pairs formed by the magnetic pole portion 11 (a set of the N pole magnetic pole portion 11N and the S pole magnetic pole portion 11S) is defined as m (m is a natural number). In this case, the overall shape of the outer circumferential surface 27 of the rotor core 23 in the orthogonal plane is formed by repeating the shape of one one-pole pair outer circumferential surface 28 m times in the circumferential direction of the rotor core 23. In other words, in the orthogonal plane, each of the m one-pole pair outer circumferential surfaces 28 is formed to be rotationally symmetrical with respect to the rotation center O of the rotor 21. In other words, in an orthogonal plane, the outer peripheral surface 27 of the rotor core 23 is divided into m equal parts in the circumferential direction based on the q-axis Q described later, and each of the m pole-pair outer peripheral surfaces 28 has the same shape. As a result, the path of the magnetic flux formed by the rotor core 23 and the stator core 24 radially opposed to the rotor core 23 is also periodically repeated m times. As a result, the same magnetic flux density distribution is periodically repeated every 360/m [degrees] in mechanical angle and every 360 [degrees] in electrical angle, so that it is possible to suppress an increase in vibration due to an irregular fluctuation in the magnetic flux density distribution during one rotation of the rotor core 23. For example, the outer peripheral surface 27 of the rotor core 23 in the embodiment is formed with the pole-pair outer peripheral surface 28 repeated three times around the entire circumference of the rotor core 23.

Here, in the above-mentioned orthogonal plane, the inner peripheral surfaces of the nonmagnetic parts (first nonmagnetic part 14, second nonmagnetic part 15) are located at the outermost positions in the radial direction of the rotor core 23 as the outer peripheral ends 14E and 15E. Also, a straight line passing through the center of rotation O of the rotor 21 and the outer peripheral end 14E of the first nonmagnetic part 14 in the radial direction of the rotor core 23 is defined as the first boundary line B1. Also, a straight line passing through the center of rotation O of the rotor 21 and the outer peripheral end 15E of the second nonmagnetic part 15 in the radial direction of the rotor core 23 is defined as the second boundary line B2. At this time, the outer peripheral surface 27 of each magnetic pole part 11 of the rotor core 23 has a magnetic pole outer peripheral surface 29 formed in the range between two boundaries (first boundary line B1 and second boundary line B2) that pass through one magnetic pole part 11.

Therefore, the one pole pair outer peripheral surface 28 is a range of one pole pair including, in the circumferential direction of the outer peripheral surface 27 of the rotor core 23, the inner surface of the groove portion located forward in the rotation direction R with respect to the q-axis Q in the groove portion 17, the magnetic pole outer peripheral surface 29 (hereinafter also referred to as the N-pole outer peripheral surface 29N) of the N-pole magnetic pole portion 11N located forward in the rotation direction R with respect to the groove portion 17, one groove portion 16 located forward in the rotation direction R with respect to the N-pole outer peripheral surface 29N, the magnetic pole outer peripheral surface 29 (hereinafter also referred to as the S-pole outer peripheral surface 29S) of the S-pole magnetic pole portion 11S located forward in the rotation direction R with respect to the groove portion 16, and the inner surface of the groove portion located rearward in the rotation direction R with respect to the q-axis Q in the other groove portion 17 located forward in the rotation direction R with respect to the S-pole magnetic pole portion 11S. One magnetic pole outer surface 29 (N-pole outer surface 29N or S-pole outer surface 29S) is the range of the magnetic pole portion 11 that does not include the grooves 16, 17, within the range of the outer surface 27 located between two circumferentially adjacent q axes Q on the outer surface 27. In other words, each magnetic pole outer surface 29 (N-pole outer surface 29N and S-pole outer surface 29S) is a portion formed in the range between two boundary lines (first boundary line B1, second boundary line B2) that pass through one magnetic pole portion 11 in the circumferential direction of the outer surface 27.

Figure 4 is an enlarged view showing one pole pair of the rotor core 23 in the embodiment. As shown in Figures 3 and 4, in the orthogonal plane, the N-pole outer peripheral surface 29N of the N-pole magnetic pole portion 11N and the S-pole outer peripheral surface 29S of the S-pole magnetic pole portion 11S are formed in such a shape that they do not match each other when either the N-pole magnetic pole portion 11N or the S-pole magnetic pole portion 11S is virtually rotated 60 degrees around the rotation center O of the rotor 21 and placed on the other magnetic pole portion of the N-pole magnetic pole portion 11N and the S-pole magnetic pole portion 11S. The magnetic pole portion to be virtually rotated may be either the N-pole magnetic pole portion 11N or the S-pole magnetic pole portion 11S. The direction of rotation around the rotation center O may be either clockwise or counterclockwise. Here, the explanation will be given assuming that the N-pole magnetic pole portion 11N is virtually rotated 60 degrees counterclockwise and placed on the S-pole magnetic pole portion 11S.

In conventional rotor cores (see Figure 7 for a comparative example described later), the shape of the outer circumferential surface of a pole pair, including the outer circumferential surface of each magnetic pole part, between adjacent magnetic pole parts (south pole magnetic pole part and north pole magnetic pole part) is generally symmetrical with respect to the q-axis Q. Therefore, in the north pole permanent magnet and south pole permanent magnet that form one pole pair, the magnetic flux density distribution passing between the north pole permanent magnet and the teeth part adjacent to this north pole permanent magnet, and the magnetic flux density distribution passing between the south pole permanent magnet and the teeth part adjacent to this south pole permanent magnet are not symmetrical with respect to the q-axis Q.

In contrast, in the rotor core 23 in the embodiment, when focusing on one pole-pair outer peripheral surface 28, this pole-pair outer peripheral surface 28 is formed in a different shape with respect to the q-axis Q, so that in the N-pole permanent magnet 13 and the S-pole permanent magnet 13 that form one pole pair, the magnetic flux density distribution passing between the N-pole permanent magnet 13 and the teeth portion 32 adjacent to this N-pole permanent magnet, and the magnetic flux density distribution passing between the S-pole permanent magnet 13 and the teeth portion 32 adjacent to this S-pole permanent magnet 13 can be made to be close to symmetrical with respect to the q-axis Q. Therefore, the magnetic flux density distribution at the position of the air gap formed between the rotor core 23 and the teeth portion 32 in the range of the pole-pair outer peripheral surface 28 (the magnetic flux density [T] in the radial direction at the air gap position measured or analyzed over the circumferential direction) can be made to be close to a sine wave.

For example, in the embodiment, the radius of curvature r of the radius change region A3 (described later) where the distance from the center of rotation O of the rotor 21 to the outer circumferential surface 27 of the rotor core 23 changes is different between the radius change region A3 of the N-pole outer circumferential surface 29N and the radius change region A3 of the S-pole outer circumferential surface 29S. This makes it easy to realize that the pole-pair outer circumferential surfaces 28 have different shapes relative to the q-axis Q.

When one of the N-pole magnetic pole portion 11N and the S-pole magnetic pole portion 11S is overlapped with the other magnetic pole portion 11, the rotation angle of one magnetic pole portion 11 around the rotation center O is 360/(2m) [degrees]. (The number of pole pairs is m.) In the following description, the rotation angle when the magnetic pole portion 11 is virtually rotated around the rotation center O of the rotor 21 is also 360/(2m) [degrees]. For example, in the embodiment, since the number of pole pairs is m=3, when the N-pole magnetic pole portion 11N is virtually rotated around the rotation center O of the rotor 21 and overlapped with the S-pole magnetic pole portion 11S, the rotation angle is 360/6=60 [degrees].

(Shape of the magnetic pole outer surface)
Fig. 5 is a schematic diagram showing the magnetic pole outer peripheral surface 29 of each magnetic pole portion 11 of the rotor core 23 in the embodiment. Fig. 6 is a schematic diagram for explaining the shape of the magnetic pole outer peripheral surface 29 of the rotor core 23 in the embodiment.

As shown in Figures 5 and 6, in the orthogonal plane, the N-pole outer peripheral surface 29N of the N-pole magnetic pole portion 11N is formed in an asymmetric shape with respect to the N-pole d-axis DN, which is the d-axis D of this N-pole magnetic pole portion 11N, and the S-pole outer peripheral surface 29S of the S-pole magnetic pole portion 11S is formed in an asymmetric shape with respect to the S-pole d-axis DS, which is the d-axis of this S-pole magnetic pole portion 11S.

In this way, by devising the shape of the magnetic pole outer peripheral surface 29 formed within the range of each magnetic pole portion 11, it is possible to make the magnetic flux density distribution passing between the N-pole permanent magnet 13 and the teeth portion 32 adjacent to the N-pole permanent magnet 13, and the magnetic flux density distribution passing between the S-pole permanent magnet 13 and the teeth portion 32 adjacent to the S-pole permanent magnet 13, in one pole pair, more symmetrical with respect to the q-axis Q. Therefore, in addition to the effect obtained by devising the shape of the one pole pair outer peripheral surface 28 described above, the magnetic flux density distribution in the gap (air gap) formed between the rotor core 23 and the teeth portion 32 within the range of the one pole pair outer peripheral surface 28 can be made more sine wave.

(Shape of N-pole outer periphery)
Specifically, the N-pole outer peripheral surface 29N of the N-pole magnetic pole portion 11N has an N-pole front outer peripheral surface 29N-F located on the front side of the rotational direction R of the rotor 21 relative to the N-pole d-axis DN, and an N-pole rear outer peripheral surface 29N-R located on the rear side of the rotational direction R relative to the N-pole d-axis DN, as shown in Figure 5.

Figure 6 shows the magnetic pole portion 11 virtually folded back along the d-axis D in the orthogonal plane of the rotor core 23, and the front outer peripheral surface 29-F virtually overlaps with the rear outer peripheral surface 29-R. Here, we will explain the case where the N-pole magnetic pole portion 11N is virtually folded back. As shown in Figure 6, when the N-pole magnetic pole portion 11N is virtually folded back and overlapped along the N-pole d-axis DN in the orthogonal plane of the rotor core 23, the N-pole front outer peripheral surface 29N-F has a small diameter outer peripheral surface 34 located inside the N-pole rear outer peripheral surface 29N-R in the radial direction of the rotor core 23. On the other hand, the N-pole rear outer peripheral surface 29N-R does not have a portion located inside the N-pole front outer peripheral surface 29N-F in the radial direction of the rotor core 23. In other words, the N pole front outer peripheral surface 29N-R only has a portion that overlaps with the N pole rear outer peripheral surface 29N-R (overlapping outer peripheral surface 35) and a portion that is located more inward than the N pole rear outer peripheral surface 29N-R (small diameter outer peripheral surface 34). When viewed from the N pole rear outer peripheral surface 29N-R, the N pole rear outer peripheral surface 29N-R only has a portion that overlaps with the N pole front outer peripheral surface 29N-F (overlapping outer peripheral surface 35) and a portion that is more outward than the N pole front outer peripheral surface 29N-F (large diameter outer peripheral surface 36).

(Shape of S pole outer surface)
Also, similar to the N-pole magnetic pole outer peripheral surface 29N described above, as shown in Figure 5, the S-pole magnetic pole portion 11S's S-pole outer peripheral surface 29S-F has an S-pole front outer peripheral surface 29S-F located on the front side of the rotational direction R of the rotor 21 relative to the S-pole d-axis DS, and an S-pole rear outer peripheral surface 29S-R located on the rear side of the rotational direction R relative to the S-pole d-axis DS.

The case where the S-pole magnetic pole portion 11S is virtually folded back will be described. As shown in FIG. 6, when the S-pole magnetic pole portion 11S is virtually folded back and stacked along the S-pole d-axis DS in the orthogonal plane of the rotor core 23, the S-pole front outer peripheral surface 29S-F has a small diameter outer peripheral surface 34 located inside the S-pole rear outer peripheral surface 29S-R in the radial direction of the rotor core 23. On the other hand, the S-pole rear outer peripheral surface 29S-R does not have a portion located inside the S-pole front outer peripheral surface 29S-F in the radial direction of the rotor core 23. In other words, the S-pole front outer peripheral surface 29S-F only has a portion that overlaps with the S-pole rear outer peripheral surface 29S-R (overlapping outer peripheral surface 35) and a portion located on the inner side of the S-pole rear outer peripheral surface 29S-R (small diameter outer peripheral surface 34). When viewed from the S pole rear outer peripheral surface 29S-R, the S pole rear outer peripheral surface 29S-R only has a portion that overlaps with the S pole front outer peripheral surface 29S-F (overlapping outer peripheral surface 35) and a portion that is located further outboard than the S pole front outer peripheral surface 29S-F (large diameter outer peripheral surface 36).

(Relationship between the outer circumferential surface of the north pole and the outer circumferential surface of the south pole)
Also, as shown in Figures 3 and 4, in an orthogonal plane, the N-pole rear side outer peripheral surface 29N-R and the S-pole rear side outer peripheral surface 29S-R are formed in shapes that do not coincide with each other when the N-pole magnetic pole portion 11N and the S-pole magnetic pole portion 11S are overlapped by virtually rotating the rotor 21 360/(2 m) [degrees] around the rotation center O.

Specifically, when the N-pole rear outer peripheral surface 29N-R is virtually rotated 360/(2 m) [degrees] around the center of rotation O of the rotor 21 in the orthogonal plane of the rotor core 23 and overlapped with the S-pole rear outer peripheral surface 29S-R, the S-pole rear outer peripheral surface 29S-R has a small diameter outer peripheral surface 34 (see FIG. 3) located inside the N-pole rear outer peripheral surface 29N-R in the radial direction of the rotor core 23, and the N-pole rear outer peripheral surface 29N-R does not have a portion located inside the S-pole rear outer peripheral surface 29S-R in the radial direction of the rotor core 23. In other words, the S-pole rear outer peripheral surface 29S-R only has a portion that overlaps with the N-pole rear outer peripheral surface 29N-R (overlapping outer peripheral surface 35) and a portion (small diameter outer peripheral surface 34) located on the inner side of the N-pole rear outer peripheral surface 29N-R. The N pole rear outer peripheral surface 29N-R only has a portion that overlaps with the S pole rear outer peripheral surface 29S-R (overlapping outer peripheral surface 35) and a portion that is located further outward than the S pole rear outer peripheral surface 29S-R (large diameter outer peripheral surface 36).

Alternatively, conversely, when the N-pole rear outer peripheral surface 29N-R is virtually rotated 360/(2 m) [degrees] around the center of rotation O of the rotor 21 in the orthogonal plane of the rotor core 23 and overlapped with the S-pole rear outer peripheral surface 29S-R, the N-pole rear outer peripheral surface 29N-R has a small diameter outer peripheral surface (not shown) located inside the S-pole rear outer peripheral surface 29S-R in the radial direction of the rotor core 23, and the S-pole rear outer peripheral surface 29S-R does not have to have a portion located inside the N-pole rear outer peripheral surface 29N-R in the radial direction of the rotor core 23. In other words, the N-pole rear outer peripheral surface 29N-R may be formed to have a portion overlapping with the S-pole rear outer peripheral surface 29S-R (overlapping outer peripheral surface 35) and a portion located on the inner side of the S-pole rear outer peripheral surface 29S-R (small diameter outer peripheral surface 34). The S pole rear outer peripheral surface 29S-R may be formed to have only a portion that overlaps with the N pole rear outer peripheral surface 29N-R (overlapping outer peripheral surface 35) and a portion that is located further outward than the N pole rear outer peripheral surface 29N-R (large diameter outer peripheral surface 36).

For example, in the embodiment, the radius of curvature r of the radius change area A3 where the distance from the center of rotation O of the rotor 21 to the outer circumferential surface of the rotor core 23 changes is different between the radius change area A3 of the N-pole outer circumferential surface 29N and the radius change area A3 of the S-pole outer circumferential surface 29S. This makes it easy to virtually rotate either the N-pole magnetic pole portion 11N or the S-pole magnetic pole portion 11S by 360/(2 m) [degrees] around the center of rotation O of the rotor 21, and to create shapes that do not match when placed over the other magnetic pole portion of either the N-pole magnetic pole portion 11N or the S-pole magnetic pole portion 11S.

Similarly, in the orthogonal plane of the rotor core 23, the N-pole front outer peripheral surface 29N-F and the S-pole front outer peripheral surface 29S-F are formed in shapes that do not coincide with each other when the rotor 21 is virtually rotated 360/(2 m) [degrees] around the center of rotation O to overlap the N-pole magnetic pole portion 11N and the S-pole magnetic pole portion 11S (see Figure 3).

Specifically, when the N-pole front outer peripheral surface 29N-F is virtually rotated 360/(2 m) degrees around the center of rotation O of the rotor 21 in the orthogonal plane of the rotor core 23 and overlapped with the S-pole front outer peripheral surface 29S-F, the S-pole front outer peripheral surface 29S-F has a small diameter outer peripheral surface 34 (see FIG. 3) located inside the N-pole front outer peripheral surface 29N-F in the radial direction of the rotor core 23, and the N-pole front outer peripheral surface 29N-F does not have a portion located inside the S-pole front outer peripheral surface 29S-F in the radial direction of the rotor core 23. In other words, the S-pole front outer peripheral surface 29S-F only has a portion that overlaps with the N-pole front outer peripheral surface 29N-F (overlapping outer peripheral surface 35) and a portion (small diameter outer peripheral surface 34) located on the inner side of the N-pole front outer peripheral surface 29N-F. The N pole front outer peripheral surface 29N-F only has a portion that overlaps with the S pole front outer peripheral surface 29S-F (overlapping outer peripheral surface 35) and a portion that is located further outboard than the S pole front outer peripheral surface 29S-F (large diameter outer peripheral surface 36).

Alternatively, conversely, when the N-pole front outer peripheral surface 29N-F is virtually rotated 360/(2 m) [degrees] around the rotation center O of the rotor 21 in the orthogonal plane of the rotor core 23 and overlapped with the S-pole front outer peripheral surface 29S-F, the N-pole front outer peripheral surface 29N-F has a small diameter outer peripheral surface (not shown) located inside the S-pole front outer peripheral surface 29S-F in the radial direction of the rotor core 23, and the S-pole front outer peripheral surface 29S-F does not have to have a portion located inside the N-pole front outer peripheral surface 29N-F in the radial direction of the rotor core 23. In other words, the N-pole front outer peripheral surface 29N-F may be formed to have a portion (overlapping outer peripheral surface 35) that overlaps with the S-pole front outer peripheral surface 29S-F and a portion (small diameter outer peripheral surface 34) that is located on the inner side of the S-pole front outer peripheral surface 29S-F. The south pole front outer peripheral surface 29S-F may be formed to have only a portion that overlaps with the north pole front outer peripheral surface 29N-F (overlapping outer peripheral surface 35) and a portion that is located further outward than the north pole front outer peripheral surface 29N-F (large diameter outer peripheral surface 36).

For example, in the embodiment, the radius of curvature r of the radius change area A3 where the distance from the center of rotation O of the rotor 21 to the outer circumferential surface of the rotor core 23 changes is different between the radius change area A3 of the N-pole outer circumferential surface 29N and the radius change area A3 of the S-pole outer circumferential surface 29S. This makes it easy to virtually rotate either the N-pole magnetic pole portion 11N or the S-pole magnetic pole portion 11S by 360/(2 m) [degrees] around the center of rotation O of the rotor 21, and to create shapes that do not match when placed over the other magnetic pole portion of either the N-pole magnetic pole portion 11N or the S-pole magnetic pole portion 11S.

In the orthogonal plane, the magnetic pole outer peripheral surface 29 of the rotor core 23 is formed so that the distance from the center of rotation O of the rotor 21 gradually decreases as it approaches the grooves 16 and 17 from the d-axis D, as shown in FIG. 3.

Specifically, in the orthogonal plane of the rotor core 23, each of the magnetic pole outer peripheral surfaces 29 of the rotor core 23 has a maximum outer diameter L, which is the distance (radius) from the center of rotation O of the rotor 21 at a position on the d-axis D, as shown in FIG. 3. Also, in the orthogonal plane, the N-pole outer peripheral surface 29N of the N-pole magnetic pole portion 11N and the S-pole outer peripheral surface 29S of the S-pole magnetic pole portion 11S have the same distance from the center of rotation O, i.e., the same outer diameter L, at a position on the d-axis D.

The outer peripheral surface 27 of the rotor core 23 has a groove region A1 in which the inner surface 16a of the groove 16 is formed so that the q-axis Q passes through the groove 16, and a groove region A1 in which the inner surface 17a of the groove 17 is formed so that the q-axis Q passes through the groove 17. Here, the groove region A1 is, for example, a region in which, in an orthogonal plane, the angle between a tangent (not shown) tangent to the inner surface 16a (inner surface 17a) of the groove 16 (groove 17) and the q-axis Q on the inside of the groove 16 (groove 17) is 45 degrees or less. In other words, in an orthogonal plane, the radius change region A3 is a region in which the angle between a tangent tangent to one end of the groove 16 (groove 17) and the q-axis Q on the inside of the groove 16 (groove 17) exceeds 45 degrees.

As shown in Figures 3 and 5, the magnetic pole outer peripheral surface 29 has a constant diameter region A2 formed at a position where the d-axis D passes and has a constant distance from the center of rotation O of the rotor 21, and a diameter change region A3 formed between the groove region A1 and the constant diameter region A2 and has a variable distance from the center of rotation O of the rotor 21. The constant diameter region A2 is a maximum radius of curvature region formed with a radius of curvature that is the maximum radius of curvature rm from the center of rotation O. The radius change region A3 is formed with multiple radii of curvature smaller than the maximum radius of curvature rm from the center of rotation O in the constant diameter region A2.

In FIG. 3, the constant diameter region A2 on the side of the N-pole magnetic pole portion 11N is referred to as the constant diameter region An2, the front side of this constant diameter region An2 in the direction of rotation R is referred to as the constant diameter region An2-F, and the rear side of this constant diameter region An2 in the direction of rotation R is referred to as the constant diameter region An2-R. Similarly, the constant diameter region A2 on the side of the S-pole magnetic pole portion 11S is referred to as the constant diameter region As2, the front side of this constant diameter region As2 in the direction of rotation R is referred to as the constant diameter region As2-F, and the rear side of this constant diameter region As2 in the direction of rotation R is referred to as the constant diameter region As2-R.

The multiple radii of curvature forming the radius change region A3 gradually decrease in radius of curvature r as they approach the grooves 16 and 17. For the sake of simplicity, the combination of radii of curvature forming the radius change region A3 of the N-pole front outer peripheral surface 29N-F and the combination of radii of curvature forming the radius change region A3 of the N-pole rear outer peripheral surface 29N-R are assumed to be equal. That is, the first radius of curvature r1-F of the front side radius change region A3-F and the first radius of curvature r1-R of the rear side radius change region A3-R are set as r1-F = r1-R = r1, and the second radius of curvature r2-F of the front side radius change region A3-F and the second radius of curvature r2-R of the rear side radius change region A3-F are set as r2-F = r2-R = r2. As an example, the radius change region A3 has a first region A3-1 formed with a first radius of curvature r1 smaller than the maximum radius of curvature rm, and a second region A3-2 formed with a second radius of curvature r2 smaller than the first radius of curvature r1. In the radius change region A3, the first region A3-1 and the second region A3-2 are formed in this order from the constant diameter region A2 toward the groove region A1. In the first embodiment, the difference between the first radius of curvature r1 and the second radius of curvature r2 is relatively small, so that the first region A3-1 and the second region A3-2 are smoothly continuous. The center Or (Or1, Or2) of each radius of curvature r (r1, r2) is arranged so that it approaches the outer circumferential surface 27 of the rotor core 23 as the radius of curvature becomes smaller. The number of types of the multiple radii of curvature is not limited to two.

In FIG. 3, of the second radius of curvature r2-F of the front radius change region A3-F, the N-pole magnetic pole portion 11N side is the second radius of curvature rn2-F, and the S-pole magnetic pole portion 11S side is the second radius of curvature rs2-F. Similarly, of the second radius of curvature r2-R of the rear radius change region A3-R, the N-pole magnetic pole portion 11N side is the second radius of curvature rn2-R, and the S-pole magnetic pole portion 11S side is the second radius of curvature rs2-R. Note that the first radius of curvature r1 is not shown in FIG. 3.

5, the constant diameter region A2 has a front constant region A2-F located on the front side of the rotation direction R of the rotor 21 with respect to the d-axis D, and a rear constant region A2-R located on the rear side of the rotation direction R with respect to the d-axis D. The circumferential length of the front constant region A2-F is smaller than the circumferential length of the rear constant region A2-R. This makes it easy to obtain a shape in which the air gap formed in the range of the front outer peripheral surface 29-F gradually increases toward the q-axis Q, and the ratio of the air gap formed in the range of the rear outer peripheral surface 29-R gradually increases toward the q-axis Q is smaller than the ratio of the air gap formed in the range of the front outer peripheral surface 29-F gradually increases toward the q-axis Q. In other words, because the front fixed area A2-F is smaller than the rear fixed area A2-R, when the N-pole magnetic pole portion 11N is virtually folded back along the N-pole d-axis DN in each orthogonal plane and the N-pole front outer peripheral surface 29N-F is overlapped with the N-pole rear outer peripheral surface 29N-R, the N-pole front outer peripheral surface 29N-F has a small diameter outer peripheral surface 34 located inside the N-pole rear outer peripheral surface 29N-R in the radial direction of the rotor core 23, and the N-pole rear outer peripheral surface 29N-R does not have a portion located inside the N-pole front outer peripheral surface 29N-F in the radial direction of the rotor core 23.

In the embodiment, as shown in FIG. 5, the front diameter change area A3-F located on the front side of the rotation direction R of the rotor 21 with respect to the d-axis D is larger than the rear diameter change area A3-R located on the rear side of the rotation direction R with respect to the d-axis D. This makes it easy to obtain a shape in which the gaps formed in the range of the front outer peripheral surface 29-F are gradually increased in each magnetic pole outer peripheral surface 29, and the ratio at which the gaps formed in the range of the rear outer peripheral surface 29-R are gradually increased is smaller than that of the front outer peripheral surface 29-F.

For the sake of simplicity, the combination of multiple radii of curvature forming the front diameter change region A3-F of the N-pole front outer peripheral surface 29N-F and the combination of multiple radii of curvature forming the diameter change region A3-R of the N-pole rear outer peripheral surface 29N-R have been described as being equal to each other, but the combinations of multiple radii of curvature of the front diameter change region A3-F and the rear diameter change region A3-R may be different from each other. For example, the first radius of curvature r1-F of the front diameter change region A3-F (As3-F) and the first radius of curvature r1-R of the rear diameter change region A3-R (As3-R) may be different from each other. Similarly, the second radius of curvature r2-F (rs2-F) of the front radius change region A3-F (As3-F) and the second radius of curvature r2-R (rs2-R) of the rear radius change region A3-R (As3-R) may be different from each other.

(Inner surface shape of groove)
3, in an orthogonal plane of the rotor core 23, the shape of the inner surface 16a of the groove portion 16 is formed asymmetrically with respect to the q axis Q. Similarly, the shape of the inner surface 17a of the groove portion 17 is formed asymmetrically with respect to the q axis Q. Furthermore, in the outer peripheral surface 27 of the rotor core 23, the groove portions 16 and the groove portions 17 are alternately arranged along the circumferential direction of the rotor core 23. In the orthogonal plane, the shapes of the inner surfaces 16a of the groove portions 16 and the inner surfaces 17a of the groove portions 17 adjacent to each other in the circumferential direction of the rotor core 23 are different from each other. The shapes of the inner surfaces 16a, 17a of the groove portions 16, 17 are formed as a result of smoothly connecting the inner surfaces 16a, 17a with the diameter change region A3 of the outer peripheral surface 29 of each magnetic pole.

(Shape of non-magnetic part)
The two non-magnetic parts (first non-magnetic part 14, second non-magnetic part 15) of the S-pole magnetic pole part 11S are formed in shapes that are asymmetrical with respect to the S-pole d-axis DS, which is the d-axis of the S-pole magnetic pole part 11S. The two non-magnetic parts (first non-magnetic part 14, second non-magnetic part 15) of the N-pole magnetic pole part 11N are formed in shapes that are asymmetrical with respect to the N-pole d-axis DN, which is the d-axis of the N-pole magnetic pole part 11N. In addition, the two non-magnetic parts 14, 15 of the N-pole magnetic pole part 11N and the two non-magnetic parts 14, 15 of the S-pole magnetic pole part 11S are formed in shapes that do not match with each other when the N-pole magnetic pole part 11N and the S-pole magnetic pole part 11S are overlapped by virtually rotating them 360/(2 m) [degrees] around the rotation center O of the rotor 21.

Specifically, in the orthogonal plane of the rotor core 23, the four nonmagnetic parts 14, 15 of the N-pole magnetic pole part 11N and the S-pole magnetic pole part 11S have different shapes. For example, as shown in FIG. 3, the shapes of the four nonmagnetic parts 14a, 15a, 14b, 15b in the magnetic pole parts 11 (N-pole magnetic pole part 11N and S-pole magnetic pole part 11S) adjacent in the circumferential direction of the rotor core 23 are different from each other. This is because the shapes are different from each other as a result of ensuring that each nonmagnetic part 14, 15 is large and that the mechanical strength of the bridge part 18 is appropriately ensured in accordance with the shape of the magnetic pole outer peripheral surface 29 and the shape of the groove parts 16, 17. Therefore, according to the rotor core 23, it is possible to appropriately adjust the magnetic flux density distribution by the one-pole outer peripheral surface 28 including the magnetic pole outer peripheral surface 29, adjust the magnetic flux flow by the nonmagnetic parts 14, 15, and ensure the mechanical strength of the bridge part 18.

The center of each rivet hole 7 in the rotor core 23 is located on the q-axis Q. Although not shown, each magnetic pole portion 11 of the rotor core 23 is not limited to a structure having two non-magnetic portions 14, 15, and for example, another non-magnetic portion (space portion) may be provided adjacent to each non-magnetic portion 14, 15 on the d-axis D side between the magnet embedment hole 12 and the magnetic pole outer peripheral surface 29 (see FIG. 8 showing a comparative example described later).

(Comparison between Examples and Comparative Examples)
A comparative example to be compared with the above-mentioned embodiment will be described. FIG. 7 is a plan view for explaining a main part of a rotor core of the comparative example. As shown in FIG. 7, the rotor core 101 of the comparative example differs from the embodiment in that a pole pair outer peripheral surface 128 in the range of one pole pair is formed symmetrically with respect to the q-axis Q. The rotor core 101 of the comparative example also differs from the embodiment in that a magnetic pole outer peripheral surface 129 of each magnetic pole portion 11 is formed symmetrically with respect to the d-axis D. Furthermore, the outer peripheral surface 127 of the rotor core 101 of the comparative example differs from the embodiment in the range in which the groove portion 102 is formed and in that a protrusion portion 103 is formed on the q-axis Q in the range of this groove portion 102.

Figure 8 is a plan view showing the distribution of magnetic flux (magnetic flux lines) in a rotor of a comparative example. In Figure 8, the mechanical angle ranges from 0 degrees to 120 degrees with respect to the rotor rotation direction R (counterclockwise). In the experimental model shown in Figure 8, the refrigerant gas passage 9 of the rotor core 101 is omitted. Figure 8 shows a state in which the N pole magnetic pole portion 11N and the S pole magnetic pole portion 11S are arranged in this order with respect to the rotor rotation direction R, and the central tooth portion 32 of the three teeth portions 32 arranged circumferentially of the rotor is located on the q-axis Q at 60 degrees.

As shown in FIG. 8, the circumferential center of the central teeth portion 32 is located on the q-axis Q, but in the central teeth portion 32, a magnetic path is created in which the magnetic flux that flows from the N-pole magnetic pole portion 11N to the central teeth portion 32 flows to the adjacent S-pole magnetic pole portion 11S via the flange portion 33 without passing through the yoke portion 31, and it is clearly evident that the distribution of magnetic flux in this magnetic path is asymmetric with respect to the q-axis Q.

Figure 9 shows the magnetic flux density distribution in the circumferential direction of the rotor in the air gap of an electric motor equipped with a rotor of the comparative example. In Figure 9, the vertical axis shows the radial magnetic flux density [T], and the horizontal axis shows the mechanical angle [degrees] with respect to the circumferential direction of the rotor. In Figure 9, an ideal sine wave is shown by a solid line, and the comparative example is shown by a dashed line. Figure 9 shows the magnetic flux density distribution in the gap (air gap) between one pole pair outer peripheral surface 128 of the rotor core 101 of the comparative example and each tooth portion 32 in the mechanical angle range of 0 [degrees] to 120 [degrees] in Figure 8.

As shown in FIG. 9, the magnetic flux density distribution of the comparative example has a large deviation (distortion) from the ideal sine wave at each position near 0 degrees, 60 degrees, and 120 degrees. Therefore, in the comparative example, the magnetic flux acting on the rotor does not change smoothly, and the vibration force generated in the radial direction of the rotor is likely to be large. In addition, the points at which the magnetic flux density, which is the reference when vector controlling the motor, becomes 0 (zero) [T] appear at 0 degrees, 60 degrees, and 120 degrees in an ideal sine wave, whereas in the motor equipped with the rotor of the comparative example, the points at which the magnetic flux density becomes 0 (zero) [T] appear at mechanical angles that are particularly 3 to 5 degrees away from 0 degrees and 60 degrees. Therefore, in the motor having the rotor of the comparative example, the magnetic flux density distribution in the circumferential direction of the rotor deviates from an ideal sine wave, and in particular, when the number of pole pairs formed by the set of the N-pole magnetic pole portion 11N and the S-pole magnetic pole portion 11S is m, the point where the magnetic flux density becomes 0 [T] appears at a mechanical angle away from an angle that is a multiple of 360/(2m) [degrees] in the circumferential direction of the rotor core 101, and the rotation control of the rotor cannot be optimized. As a result, the electric motor having the rotor of the comparative example cannot sufficiently reduce vibrations generated in the radial direction of the rotor. In addition, near the positions of 40 [degrees] and 80 [degrees], which are the openings between the teeth portions 32 in the circumferential direction of the rotor, the magnetic flux density [T] drops sharply, and as a result, the magnetic flux density distribution deviates significantly from the sine wave.

Figure 10 is a plan view showing the distribution of magnetic flux (magnetic flux lines) in the rotor 21 of the embodiment. In Figure 10, the mechanical angle ranges from 0 degrees to 120 degrees with respect to the rotation direction R of the rotor 21. In the experimental model shown in Figure 10, the refrigerant gas passage 9 of the rotor core 23 is omitted. Figure 10 shows a state in which the U-phase teeth 32U, V-phase teeth 32V, and W-phase teeth 32W are arranged in this order with respect to the rotation direction R of the rotor 21, and the U-phase teeth 32U and V-phase teeth 32V face the N-pole outer peripheral surface 29N of the N-pole magnetic pole portion 11N, and the V-phase teeth 32V and W-phase teeth 32W face the S-pole outer peripheral surface 29S of the S-pole magnetic pole portion 11S. The flow of magnetic flux in the rotor 21 will be described using this state as an example.

As shown in FIG. 10, in this embodiment, for the U-phase teeth 32U, the outer diameter of the rotor core 23 in the vicinity of the q-axis Q (diameter change region A3) of the N-pole rear outer peripheral surface 29N-R of the rotor core 23 is gradually reduced toward the q-axis Q side, and the gap between the N-pole rear outer peripheral surface 29N-R and the flange portion 33 of the U-phase teeth 32U is increased. This increases the magnetic resistance in the vicinity of the q-axis Q of the N-pole rear outer peripheral surface 29N-R, suppresses leakage of magnetic flux from the N-pole rear outer peripheral surface 29N-R, and effectively flows magnetic flux from the N-pole rear outer peripheral surface 29N-R toward the U-phase teeth 32U, making the flow of magnetic flux smoother.

Next, in the embodiment, for the V-phase teeth portion 32V, the ratio at which the outer diameter of the rotor core 23 near the q-axis Q of the N-pole front outer peripheral surface 29N-F of the rotor core 23 decreases toward the q-axis Q is increased compared to the vicinity of the q-axis Q of the N-pole rear outer peripheral surface 29N-R. This adjusts the flow of magnetic flux toward the V-phase teeth portion 32V near the q-axis Q of the N-pole front outer peripheral surface 29N-F, and prevents the magnetic flux flowing from the N-pole front outer peripheral surface 29N-F to the V-phase teeth portion 32V from passing through the yoke portion 31 and via the flange portion 33 of the V-phase teeth portion 32V to the adjacent S-pole magnetic pole portion 11S.

In addition, in the V-phase teeth portion 32V, since there is little magnetic flux flowing from the flange portion 33 of the V-phase teeth portion 32V toward the S-pole magnetic pole portion 11S, the outer diameter of the rotor core 23 near the q-axis Q of the S-pole rear outer peripheral surface 29S-R is made larger than the outer diameter near the q-axis Q of the S-pole front outer peripheral surface 29S-F, and is gradually made smaller.

Next, in the embodiment, for the W-phase teeth 32W, the outer diameter of the rotor core 23 in the vicinity of the q-axis Q of the S-pole front outer peripheral surface 29S-F of the rotor core 23 is gradually reduced toward the q-axis Q side, and the gap between the S-pole front outer peripheral surface 29S-F and the flange 33 of the W-phase teeth 32W is increased. This increases the magnetic resistance of the S-pole front outer peripheral surface 29S-F in the vicinity of the q-axis Q and suppresses leakage of magnetic flux from the flange 33 of the W-phase teeth 32W, effectively allowing magnetic flux to flow from the W-phase teeth 32W toward the S-pole front outer peripheral surface 29S-F, smoothing the flow of magnetic flux toward the permanent magnet 13 of the S-pole magnetic pole 11S.

Compared to the comparative example shown in FIG. 8, the embodiment shown in FIG. 10 has a feature in that in the V-phase teeth portion 32V, which is the central teeth portion 32 of the three teeth portions 32, the distribution of magnetic flux in the magnetic path in which the magnetic flux flows from the N-pole magnetic pole portion 11N to the V-phase teeth portion 32V, without passing through the yoke portion 31, passes through the flange portion 33, and flows to the adjacent S-pole magnetic pole portion 11S, is prevented from becoming asymmetric with respect to the q-axis Q. As a result, the magnetic flux density distribution is brought closer to an ideal sine wave near 60 degrees, where the central teeth portion 32 is located on the q-axis Q (see FIG. 11).

In the embodiment, by forming the pole-pair outer peripheral surface 28 as described above, the magnetic flux density distribution in the air gap between the rotor core 23 and each tooth portion 32 in the range of one pole-pair outer peripheral surface 28 is made to approach a sine wave. In addition, the outer peripheral surface 27 of the rotor core 23 has three pole-pair outer peripheral surfaces 28 formed in rotational symmetry, and the magnetic flux flow is the same in each pole-pair outer peripheral surface 28. Therefore, by optimizing the magnetic flux density distribution in one pole-pair outer peripheral surface 28 as described above, the magnetic flux density distribution in the entire outer peripheral surface 27 of the rotor core 23 can be optimized.

Figure 11 is a diagram showing the magnetic flux density distribution in the circumferential direction of the rotor 21 of the embodiment. In Figure 9, the vertical axis shows the magnetic flux density [T], and the horizontal axis shows the mechanical angle [degrees] with respect to the circumferential direction of the rotor 21. In Figure 11, the sine wave is shown by a solid line, and the embodiment is shown by a dashed line. Figure 11 shows the magnetic flux density distribution at the position of the gap (air gap) between one pole pair outer peripheral surface 28 of the rotor core 23 of the embodiment and each tooth portion 32 for the mechanical angle range of 0 [degrees] to 120 [degrees] in Figure 10.

As shown in FIG. 11, in the embodiment, the magnetic flux density distribution is close to overlapping with an ideal sine wave at each position near 0 degrees, near 60 degrees, and near 120 degrees, and the magnitude of deviation (distortion) from an ideal sine wave is reduced in the magnetic flux density distribution of the embodiment compared to the comparative example shown in FIG. 9. In particular, compared to the comparative example, in the embodiment, the magnetic flux density at the 60 degree position is nearly 0 (zero) [T], similar to the magnetic flux density at the 60 degree position of an ideal sine wave.

In the embodiment, the points at which the magnetic flux density, which is the reference when vector controlling the electric motor 1, is 0 (zero) [T] appear at 0 [degrees], 60 [degrees], and 120 [degrees] in an ideal sine wave, whereas in the magnetic flux density distribution of the embodiment, the points at which the magnetic flux density is 0 (zero) [T] appear almost coincident with 0 [degrees], 60 [degrees], and 120 [degrees]. As a result, when the number of pole pairs formed by the set of the N pole magnetic pole portion 11N and the S pole magnetic pole portion 11S is m, the points at which the magnetic flux density is 0 [T] appear almost coincident with the mechanical angle positions that are multiples of 360/(2m) [degrees] in the circumferential direction of the rotor core 23, so that the rotation control of the rotor 21 can be optimized. In addition, by making the magnetic flux density distribution in the circumferential direction of the rotor 21 approach a sine wave near the mechanical angle where the angle is a multiple of 360/(2 m) [degrees], the magnetic flux acting on the rotor 21 changes smoothly, so that the vibration force generated in the radial direction of the rotor 21 can be reduced. As a result, the electric motor 1 equipped with the rotor 21 of the embodiment can reduce the vibration generated in the radial direction of the rotor 21.

Fig. 12 is a diagram showing a comparison between the vibrations generated in the electric motor in the embodiment and the comparative example. In Fig. 12, the vertical axis indicates acceleration [m/ ^s2 ], and the horizontal axis indicates frequency [Hz]. Fig. 13 is a diagram showing a comparison between the noise generated around the electric motor in the embodiment and the comparative example. In Fig. 13, the vertical axis indicates sound pressure [dB], and the horizontal axis indicates frequency [Hz]. Here, frequency is a value proportional to the rotation speed of the rotor 21. In Figs. 12 and 13, the embodiment is shown in black, and the comparative example is shown in white.

As shown in FIG. 12, the embodiment reduces vibration (acceleration) over the entire frequency range of the electric motor 1 compared to the comparative example. Therefore, as shown in FIG. 13, the embodiment reduces noise over the entire frequency range of the electric motor 1 compared to the comparative example.

(Effects of the embodiment)
As described above, the outer peripheral surface 27 of the rotor core 23 in the electric motor 1 of the embodiment is formed by repeating m times in the circumferential direction of the rotor core 23 so that the shape of one pole pair outer peripheral surface 28 is rotationally symmetrical about the rotation center O of the rotor 21, where the number of pole pairs of the magnetic pole portions 11 is m. Each magnetic pole portion 11 has a magnetic pole outer peripheral surface 29 formed on the outer peripheral surface 27 between a first boundary line B1 passing through the rotation center O and the outer peripheral end of each first non-magnetic portion 14, and a second boundary line B2 passing through the rotation center O and the outer peripheral end of the second non-magnetic portion 15, in an orthogonal plane. In an orthogonal plane, when one of the N-pole magnetic pole portion 11N and the S-pole magnetic pole portion 11S is virtually rotated 360/(2 m) degrees around the rotation center O of the rotor 21 and overlapped with the other of the N-pole magnetic pole portion 11N and the S-pole magnetic pole portion 11S, the N-pole outer peripheral surface 29N of the N-pole magnetic pole portion 11N and the S-pole outer peripheral surface 29S of the S-pole magnetic pole portion 11S are formed in shapes that do not coincide with each other. By forming the magnetic pole outer peripheral surface 29 in such a shape, even in an electric motor in which the ratio of the number of poles, which is the number of permanent magnets 13 (the number of magnetic pole portions 11), to the number of teeth portions 32, which is the number of winding portions 45 around which the windings 46 are wound, is 2:3, when attention is paid to the magnetic path in which the magnetic flux flowing from the N-pole magnetic pole portion 11N to the tooth portion 32 (32V) of the three teeth portions 32 flows to the adjacent S-pole magnetic pole portion 11S via the flange portion 33 without passing through the yoke portion 31, in the central tooth portion 32 (32V) among the three teeth portions 32 as shown in Fig. 10, the magnetic flux distribution is prevented from becoming asymmetric with respect to the q-axis Q. Therefore, the magnetic flux density distribution in the vicinity of 60 degrees where the central tooth portion 32 (32V) is located on the q-axis Q is made to approach an ideal sine wave. As a result, the magnetic flux density distribution in the air gap between the rotor 21 and the stator 22 in the circumferential direction of the rotating rotor 21 can be made to approach a sine wave as shown in FIG. 11. In particular, when the number of pole pairs formed by the set of the N-pole magnetic pole portion 11N and the S-pole magnetic pole portion 11S is m, the point where the magnetic flux density is "0" (zero) [T] appears almost coincident with the position of the mechanical angle which is a multiple of 360/(2m) [degrees] in the circumferential direction of the rotor core 23, so that the rotation control of the rotor 21 can be optimized. In addition, by making the magnetic flux density distribution in the circumferential direction of the rotor 21 approach a sine wave near the mechanical angle which is a multiple of 360/(2m) [degrees], the magnetic flux acting on the rotor 21 changes smoothly, so that the fluctuation of the excitation force generated in the radial direction of the rotor 21 can be suppressed. As a result, according to the embodiment, the vibration of the electric motor 1 can be reduced, and the noise around the electric motor 1 can be reduced.

In addition, the rotor core 23 in the electric motor 1 of the embodiment has a magnetic pole outer peripheral surface 29 having a front outer peripheral surface 29-F located on the front side of the rotation direction R of the rotor 21 with respect to the d-axis D, and a rear outer peripheral surface 29-R located on the rear side of the rotation direction R with respect to the d-axis D. When the magnetic pole portion 11 is virtually folded back along the d-axis D in an orthogonal plane and the front outer peripheral surface 29-F is overlapped with the rear outer peripheral surface 29-R, the front outer peripheral surface 29-F has a small diameter outer peripheral surface 34 located inside the rear outer peripheral surface 29-R in the radial direction of the rotor core 23, and the rear outer peripheral surface 29-R does not have a portion located inside the front outer peripheral surface 29-F in the radial direction of the rotor core 23. This makes it possible to make the magnetic flux density distribution in the air gap between the rotor 21 and the stator 22 in the circumferential direction of the rotating rotor 21 even closer to a sine wave.

The magnetic pole outer peripheral surface 29 of the rotor core 23 in the electric motor 1 of the embodiment has a constant diameter region A2 formed at a position where the d-axis D passes and has a constant distance from the rotation center O of the rotor 21, and a diameter change region A3 formed between the groove region A1 and the constant diameter region A2 and has a variable distance from the rotation center O. The constant diameter region A2 has a front constant region A2-F located on the front side of the rotation direction R of the rotor 21 with respect to the d-axis D, and a rear constant region A2-R located on the rear side of the rotation direction R with respect to the d-axis D. The circumferential length of the front constant region A2-F is smaller than the circumferential length of the rear constant region A2-R. This makes it easy to obtain a shape in which the gaps formed in the range of the front outer peripheral surface 29-F gradually increase in each magnetic pole outer peripheral surface 29, and the ratio of the gaps formed in the range of the rear outer peripheral surface 29-R gradually increases is smaller than that of the front outer peripheral surface 29-F.

In addition, each tooth portion 32 of the stator 22 in the electric motor 1 of the embodiment has a winding portion 45 in which the winding 46 is wound in a concentrated winding manner. The problem of the present invention can be solved in such a concentrated winding type electric motor 1.

The reference example and the modified examples are described below with reference to the drawings. In the reference example and the modified examples, the same components as those in the embodiment are given the same reference numerals as those in the embodiment, and the description thereof is omitted. The reference example differs from the embodiment in that the magnetic pole outer peripheral surface 29 of each magnetic pole portion 11 is formed in the same shape.

(Reference example)
14 is a plan view for explaining the main part of the rotor core in the reference example. As shown in FIG. 14, in the rotor core 51 in the reference example, similar to the embodiment, the magnetic pole outer peripheral surface 29 of each magnetic pole portion 11 has a front outer peripheral surface 29-F located on the front side of the rotation direction R of the rotor 21 with respect to the d-axis D, and a rear outer peripheral surface 29-R located on the rear side of the rotation direction R with respect to the d-axis D. When the magnetic pole portion 11 is virtually folded back along the d-axis D in the orthogonal plane (the paper surface of FIG. 14) and the front outer peripheral surface 29-F is overlapped with the rear outer peripheral surface 29-R, the front outer peripheral surface 29-F has a small diameter outer peripheral surface 34 located inside the rear outer peripheral surface 29-R in the radial direction of the rotor core 51, and the rear outer peripheral surface 29-R does not have a portion located inside the front outer peripheral surface 29-F in the radial direction of the rotor core 51.

In the reference example, the N-pole outer peripheral surface 29N of the N-pole magnetic pole portion 11N and the S-pole outer peripheral surface 29S of the S-pole magnetic pole portion 11S are formed in shapes that match each other when the rotor 21 is virtually rotated 360/(2 m) [degrees] around the rotation center O to overlap the N-pole magnetic pole portion 11N and the S-pole magnetic pole portion 11S in an orthogonal plane. In this respect, the reference example differs from the embodiment. In other words, in the rotor core 51 of the reference example, the magnetic pole outer peripheral surfaces 29 of the N-pole magnetic pole portion 11N and the S-pole magnetic pole portion 11S have the same shape in an orthogonal plane, and the magnetic pole outer peripheral surface 29 of the same shape is repeatedly formed around the entire circumference of the outer peripheral surface 27 of the rotor core 51.

In addition, the magnetic pole outer circumferential surface 29 of the rotor core 51 in the reference example is formed in an asymmetric shape with respect to the d-axis D, as in the embodiment, but differs from the embodiment in that the N-pole outer circumferential surface 29N and the S-pole outer circumferential surface 29S have the same shape. The detailed shape of the magnetic pole outer circumferential surface 29 in the reference example, which is asymmetric with respect to the d-axis D, is similar to that of the magnetic pole outer circumferential surface 29 in the embodiment (see Figures 5 and 6), so a description thereof will be omitted.

(Shape of the groove and non-magnetic portion)
In the reference example, grooves 52 having a common shape in the circumferential direction of the rotor core 51 are formed on the q-axis Q between the magnetic pole portions 11. The shape of the inner surface 52a of the grooves 52 is formed asymmetrically with respect to the q-axis Q. Meanwhile, in each magnetic pole portion 11, the first non-magnetic portions 14 located on the front side in the rotational direction R of the rotor 21 have the same shape. Also, in each magnetic pole portion 11, the second non-magnetic portions 15 located on the rear side in the rotational direction R have the same shape.

In the embodiment, the magnetic flux density distribution in the air gap between the rotor core 23 and each tooth portion 32 in the circumferential direction of the rotor 21 is made to be closer to a sine wave by forming each magnetic pole outer surface 29 in an asymmetric shape with respect to the d-axis D and by forming the pole pair outer surface 28 including the N-pole outer surface 29N, the S-pole outer surface 29S, and the groove portion 16 (groove portion 17) in an asymmetric shape with respect to the q-axis Q. In contrast, in the reference example, the magnetic pole outer surfaces 29 of each magnetic pole portion 11 are formed in the same shape, and each magnetic pole outer surface 29 is formed in an asymmetric shape with respect to the d-axis D, thereby making the magnetic flux density distribution in the air gap between the rotor core 51 and each tooth portion 32 in the circumferential direction of the rotor 21 closer to a sine wave.

Figure 15 is a diagram showing the magnetic flux density distribution in the circumferential direction of the rotor 21 of the reference example. In Figure 15, the vertical axis shows the magnetic flux density [T], and the horizontal axis shows the mechanical angle [degrees] with respect to the circumferential direction of the rotor 21. In Figure 11, an ideal sine wave is shown by a solid line, and a reference example is shown by a dashed line. Figure 15 shows the magnetic flux density distribution in the air gap between the rotor 21 and each tooth portion 32 for a mechanical angle range of 0 degrees to 120 degrees, which is the range of the pole-pair outer peripheral surface 28 in which the two magnetic pole portions 11 and groove portions 52 shown in Figure 14 are formed.

As shown in FIG. 15, in the reference example, similar to the working example, the magnetic flux density is brought close to overlapping with a sine wave at each position near 0 degrees, near 60 degrees, and near 120 degrees, and compared to the comparative example shown in FIG. 9, the magnetic flux density distribution of the working example has a reduced deviation (distortion) from an ideal sine wave. In particular, compared to the comparative example, in the working example, the magnetic flux density is nearly 0 (zero) [T] at a position near 60 degrees, similar to the magnetic flux density at 60 degrees in an ideal sine wave.

(Effects of the Reference Example)
Therefore, in the reference example, as in the embodiment, when the number of pole pairs formed by the set of the N-pole magnetic pole portion 11N and the S-pole magnetic pole portion 11S is m, the point where the magnetic flux density is 0 [T] appears almost coincident with the mechanical angle that is a multiple of 360/(2m) [degrees] in the circumferential direction of the rotor core 51, so that the rotation control of the rotor 21 can be optimized. In addition, since the magnetic flux density distribution in the circumferential direction of the rotor 21 is made to approach an ideal sine wave near the mechanical angle that is a multiple of 360/(2m) [degrees], the magnetic flux acting on the rotor 21 changes smoothly, so that the fluctuation of the excitation force generated in the radial direction of the rotor 21 is suppressed. As a result, the vibration generated in the radial direction of the electric motor 1 equipped with the rotor 21 of the reference example can be reduced, and the noise around the electric motor 1 can be reduced.

In addition, when comparing the reference example shown in FIG. 15 with the embodiment shown in FIG. 11, the magnetic flux density distribution in the air gap between the rotor 21 and each tooth portion 32 in the circumferential direction of the rotor 21 is closer to a sine wave in the embodiment than in the reference example, and the embodiment is preferable in terms of approximating a sine wave.

(Modification)
FIG. 16 is a plan view showing a main part of a rotor core of a modified example. In the rotor core 61 of the modified example, the arrangement of the permanent magnets 13 is different from that of the embodiment. As shown in FIG. 16, in each magnetic pole portion 11, two plate-shaped permanent magnets 13 are arranged in a substantially V-shape so that the thickness direction of each permanent magnet 13 intersects. In each magnetic pole portion 11, two non-magnetic portions 14 and 15 extending from one end of each of the two permanent magnets 13 toward the outer circumferential surface 27 of the rotor core 61 and a non-magnetic portion 19 formed on the d-axis D passing between the other ends of the two permanent magnets 13 are formed. In the modified example, regardless of the arrangement of the permanent magnets 13, the outer circumferential surface 27 of the rotor core 61 is formed in the same manner as in the embodiment, so that the same effect as in the embodiment can be obtained.

REFERENCE SIGNS LIST 1 electric motor 3 shaft 11 magnetic pole portion 11N north pole magnetic pole portion 11S south pole magnetic pole portion 13 permanent magnet 14 (14a to 14f), 15 (15a to 15f), 19 non-magnetic portion 14E, 15E outer circumferential end 16, 17, 52 groove portion 16a, 17a inner surface 21 rotor 22 stator 23 rotor core 24 stator core 27 outer circumferential surface 28 one pole pair outer circumferential surface 29 magnetic pole outer circumferential surface 29-F front outer circumferential surface 29-R rear outer circumferential surface 29N north pole outer circumferential surface (magnetic pole outer circumferential surface)
29N-F N pole front side outer circumferential surface (front side outer circumferential surface)
29N-R N pole rear outer circumferential surface (rear outer circumferential surface)
29S S pole outer circumferential surface (magnetic pole outer circumferential surface)
29S-F S pole front side outer peripheral surface (front side outer peripheral surface)
29S-R S pole rear outer circumferential surface (rear outer circumferential surface)
31 Yoke part 32 Teeth part 34 Small diameter outer circumferential surface 45 Winding part 46 Winding wire A1 Groove area A2 Constant diameter area A2-F Front constant area A2-R Rear constant area A3 Diameter changing area B1 First boundary line B2 Second boundary line O Rotation center D d-axis DN N-pole d-axis DS S-pole d-axis Q q-axis R Rotation direction rm Maximum radius of curvature r1 First radius of curvature (radius of curvature)
r2 Second radius of curvature (radius of curvature)

Claims (21)

An electric motor comprising: a rotor having a rotor core in which permanent magnets are embedded and in which a plurality of magnetic pole portions are provided along a circumferential direction; and a stator having a plurality of teeth portions arranged on an outer circumferential side of the rotor, wherein the number of pole pairs of the magnetic pole portions is m and the number of the plurality of teeth portions is 3m, and the rotor core has non-magnetic portions extending continuously from both ends of the permanent magnet in the circumferential direction,
When an outer circumferential surface of the rotor core in a range that forms one pole pair in a plane perpendicular to a rotation centerline of the rotor is defined as a one pole pair outer circumferential surface, the outer circumferential surface of the rotor core is formed by repeating a shape of the one pole pair outer circumferential surface m times in the circumferential direction so that the shape of the one pole pair outer circumferential surface is rotationally symmetrical with respect to the rotation center of the rotor,
In the plane, each magnetic pole portion has a magnetic pole outer peripheral surface formed on the outer peripheral surface between a first boundary line which is a straight line passing through the center of rotation and an outer peripheral end of one of the non-magnetic portions in the radial direction of the rotor core, and a second boundary line which is a straight line passing through the center of rotation and an outer peripheral end of the other of the non-magnetic portions in the radial direction,
In the plane, a straight line connecting the center of the magnetic pole portion in the circumferential direction and the rotation center is defined as a d-axis, and a straight line connecting the center between adjacent magnetic pole portions in the circumferential direction and the rotation center is defined as a q-axis.
Each pole pair has an N pole portion and an S pole portion disposed on either side of the q axis,
In the plane, when one of the N-pole magnetic pole portion and the S-pole magnetic pole portion is virtually rotated about the rotation center by 360/(2 m) [degrees] and overlapped with the other magnetic pole portion, the magnetic pole outer circumferential surface of the N-pole magnetic pole portion and the magnetic pole outer circumferential surface of the S-pole magnetic pole portion are formed in shapes that do not coincide with each other,
In the plane, the magnetic pole outer peripheral surface of the N-pole magnetic pole portion is formed in an asymmetric shape with respect to an N-pole d-axis, which is the d-axis of the N-pole magnetic pole portion, and the magnetic pole outer peripheral surface of the S-pole magnetic pole portion is formed in an asymmetric shape with respect to an S-pole d-axis, which is the d-axis of the S-pole magnetic pole portion,
the magnetic pole outer peripheral surface of the N-pole magnetic pole portion has an N-pole front outer peripheral surface located on the front side of the rotation direction of the rotor with respect to the N-pole d-axis, and an N-pole rear outer peripheral surface located on the rear side of the rotation direction with respect to the N-pole d-axis,
When the N-pole magnetic pole part is virtually folded back along the N-pole d-axis on the plane and the N-pole front outer peripheral surface is superimposed on the N-pole rear outer peripheral surface,
the N-pole front outer peripheral surface is located radially inward of the N-pole rear outer peripheral surface and has an arc-shaped small-diameter outer peripheral surface that follows the N-pole front outer peripheral surface . An electric motor comprising: a rotor having a rotor core in which permanent magnets are embedded and in which a plurality of magnetic pole portions are provided along a circumferential direction; and a stator having a plurality of teeth portions arranged on an outer circumferential side of the rotor, wherein the number of pole pairs of the magnetic pole portions is m and the number of the plurality of teeth portions is 3m, and the rotor core has non-magnetic portions extending continuously from both ends of the permanent magnet in the circumferential direction,
When an outer circumferential surface of the rotor core in a range that forms one pole pair in a plane perpendicular to a rotation centerline of the rotor is defined as a one pole pair outer circumferential surface, the outer circumferential surface of the rotor core is formed by repeating a shape of the one pole pair outer circumferential surface m times in the circumferential direction so that the shape of the one pole pair outer circumferential surface is rotationally symmetrical with respect to the rotation center of the rotor,
In the plane, each magnetic pole portion has a magnetic pole outer peripheral surface formed on the outer peripheral surface between a first boundary line which is a straight line passing through the center of rotation and an outer peripheral end of one of the non-magnetic portions in the radial direction of the rotor core, and a second boundary line which is a straight line passing through the center of rotation and an outer peripheral end of the other of the non-magnetic portions in the radial direction,
In the plane, a straight line connecting the center of the magnetic pole portion in the circumferential direction and the rotation center is defined as a d-axis, and a straight line connecting the center between adjacent magnetic pole portions in the circumferential direction and the rotation center is defined as a q-axis.
Each pole pair has an N pole portion and an S pole portion disposed on either side of the q axis,
In the plane, when one of the N-pole magnetic pole portion and the S-pole magnetic pole portion is virtually rotated about the rotation center by 360/(2 m) [degrees] and overlapped with the other magnetic pole portion, the magnetic pole outer circumferential surface of the N-pole magnetic pole portion and the magnetic pole outer circumferential surface of the S-pole magnetic pole portion are formed in shapes that do not coincide with each other,
In the plane, the magnetic pole outer peripheral surface of the N-pole magnetic pole portion is formed in an asymmetric shape with respect to an N-pole d-axis, which is the d-axis of the N-pole magnetic pole portion, and the magnetic pole outer peripheral surface of the S-pole magnetic pole portion is formed in an asymmetric shape with respect to an S-pole d-axis, which is the d-axis of the S-pole magnetic pole portion,
The magnetic pole outer peripheral surface of the S pole magnetic pole portion has an S pole front outer peripheral surface located on the front side of the S pole d axis in the rotation direction of the rotor, and an S pole rear outer peripheral surface located on the rear side of the S pole d axis in the rotation direction,
When the S-pole magnetic pole portion is virtually folded back along the S-pole d-axis on the plane and the S-pole front outer peripheral surface is superimposed on the S-pole rear outer peripheral surface,
the south pole front outer peripheral surface is located radially inward of the south pole rear outer peripheral surface and has an arc -shaped small diameter outer peripheral surface that follows the south pole front outer peripheral surface . An electric motor comprising: a rotor having a rotor core in which permanent magnets are embedded and in which a plurality of magnetic pole portions are provided along a circumferential direction; and a stator having a plurality of teeth portions arranged on an outer circumferential side of the rotor, wherein the number of pole pairs of the magnetic pole portions is m and the number of the plurality of teeth portions is 3m, and the rotor core has non-magnetic portions extending continuously from both ends of the permanent magnet in the circumferential direction,
When an outer circumferential surface of the rotor core in a range that forms one pole pair in a plane perpendicular to a rotation centerline of the rotor is defined as a one pole pair outer circumferential surface, the outer circumferential surface of the rotor core is formed by repeating a shape of the one pole pair outer circumferential surface m times in the circumferential direction so that the shape of the one pole pair outer circumferential surface is rotationally symmetrical with respect to the rotation center of the rotor,
In the plane, each magnetic pole portion has a magnetic pole outer peripheral surface formed on the outer peripheral surface between a first boundary line which is a straight line passing through the center of rotation and an outer peripheral end of one of the non-magnetic portions in the radial direction of the rotor core, and a second boundary line which is a straight line passing through the center of rotation and an outer peripheral end of the other of the non-magnetic portions in the radial direction,
In the plane, a straight line connecting the center of the magnetic pole portion in the circumferential direction and the rotation center is defined as a d-axis, and a straight line connecting the center between adjacent magnetic pole portions in the circumferential direction and the rotation center is defined as a q-axis.
Each pole pair has an N pole portion and an S pole portion disposed on either side of the q axis,
In the plane, when one of the N-pole magnetic pole portion and the S-pole magnetic pole portion is virtually rotated about the rotation center by 360/(2 m) [degrees] and overlapped with the other magnetic pole portion, the magnetic pole outer circumferential surface of the N-pole magnetic pole portion and the magnetic pole outer circumferential surface of the S-pole magnetic pole portion are formed in shapes that do not coincide with each other,
In the plane, the magnetic pole outer peripheral surface of the N-pole magnetic pole portion is formed in an asymmetric shape with respect to an N-pole d-axis, which is the d-axis of the N-pole magnetic pole portion, and the magnetic pole outer peripheral surface of the S-pole magnetic pole portion is formed in an asymmetric shape with respect to an S-pole d-axis, which is the d-axis of the S-pole magnetic pole portion,
the magnetic pole outer peripheral surface of the N-pole magnetic pole portion has an N-pole front outer peripheral surface located on the front side of the rotation direction of the rotor with respect to the N-pole d-axis, and an N-pole rear outer peripheral surface located on the rear side of the rotation direction with respect to the N-pole d-axis,
The magnetic pole outer peripheral surface of the S-pole magnetic pole portion has an S-pole front outer peripheral surface located on the front side of the S-pole d axis in the rotation direction of the rotor, and an S-pole rear outer peripheral surface located on the rear side of the S-pole d axis in the rotation direction,
an electric motor in which, when one of the magnetic pole portions is virtually rotated 360/(2 m) degrees around the center of rotation in the plane and placed over the other magnetic pole portion, the N-pole rear side outer peripheral surface and the S-pole rear side outer peripheral surface are formed in shapes that do not coincide with each other . When the N pole rear outer peripheral surface is virtually rotated 360/(2 m) [degrees] around the rotation center on the plane and superimposed on the S pole rear outer peripheral surface,
The S pole rear side outer peripheral surface has a small diameter outer peripheral surface located more inwardly than the N pole rear side outer peripheral surface in the radial direction.
4. The electric motor according to claim 3 . When the N pole rear outer peripheral surface is virtually rotated 360/(2 m) [degrees] around the rotation center on the plane and superimposed on the S pole rear outer peripheral surface,
The N-pole rear side outer peripheral surface has a small diameter outer peripheral surface located more inward than the S-pole rear side outer peripheral surface in the radial direction.
4. The electric motor according to claim 3 . In the plane, when the one magnetic pole portion is virtually rotated around the rotation center by 360/(2 m) [degrees] and overlapped with the other magnetic pole portion, the N-pole front side outer peripheral surface and the S-pole front side outer peripheral surface are formed in shapes that do not coincide with each other.
4. The electric motor according to claim 3 . When the N-pole front outer peripheral surface is virtually rotated 360/(2 m) [degrees] around the rotation center on the plane and superimposed on the S-pole front outer peripheral surface,
The S pole front outer peripheral surface has a small diameter outer peripheral surface located inside the N pole front outer peripheral surface in the radial direction.
4. The electric motor according to claim 3 . When the N-pole front outer peripheral surface is virtually rotated 360/(2 m) [degrees] around the rotation center on the plane and superimposed on the S-pole front outer peripheral surface,
The N-pole front outer peripheral surface has a small diameter outer peripheral surface located inside the S-pole front outer peripheral surface in the radial direction.
4. The electric motor according to claim 3 . An electric motor comprising: a rotor having a rotor core in which permanent magnets are embedded and in which a plurality of magnetic pole portions are provided along a circumferential direction; and a stator having a plurality of teeth portions arranged on an outer circumferential side of the rotor, wherein the number of pole pairs of the magnetic pole portions is m and the number of the plurality of teeth portions is 3m, and the rotor core has non-magnetic portions extending continuously from both ends of the permanent magnet in the circumferential direction,
When an outer circumferential surface of the rotor core in a range that forms one pole pair in a plane perpendicular to a rotation centerline of the rotor is defined as a one pole pair outer circumferential surface, the outer circumferential surface of the rotor core is formed by repeating a shape of the one pole pair outer circumferential surface m times in the circumferential direction so that the shape of the one pole pair outer circumferential surface is rotationally symmetrical with respect to the rotation center of the rotor,
In the plane, each magnetic pole portion has a magnetic pole outer peripheral surface formed on the outer peripheral surface between a first boundary line which is a straight line passing through the center of rotation and an outer peripheral end of one of the non-magnetic portions in the radial direction of the rotor core, and a second boundary line which is a straight line passing through the center of rotation and an outer peripheral end of the other of the non-magnetic portions in the radial direction,
In the plane, a straight line connecting the center of the magnetic pole portion in the circumferential direction and the rotation center is defined as a d-axis, and a straight line connecting the center between adjacent magnetic pole portions in the circumferential direction and the rotation center is defined as a q-axis.
Each pole pair has an N pole portion and an S pole portion disposed on either side of the q axis,
In the plane, when one of the N-pole magnetic pole portion and the S-pole magnetic pole portion is virtually rotated about the rotation center by 360/(2 m) [degrees] and overlapped with the other magnetic pole portion, the magnetic pole outer circumferential surface of the N-pole magnetic pole portion and the magnetic pole outer circumferential surface of the S-pole magnetic pole portion are formed in shapes that do not coincide with each other,
A groove portion is formed in an outer peripheral surface of the rotor core between the magnetic pole portions adjacent in the circumferential direction, the outer peripheral surface being recessed in the radial direction along the rotation center line,
an electric motor, wherein on the plane , the groove portion is formed only between the non-magnetic portions adjacent in the circumferential direction, and an inner surface shape of the groove portion is formed asymmetrically with respect to the q axis. In the plane, the inner surface shapes of the groove portions adjacent to each other in the circumferential direction are different from each other.
10. The electric motor according to claim 9 . In the plane, the distance from the rotation center of the outer circumferential surface of the magnetic pole of the rotor core gradually decreases as the outer circumferential surface approaches the groove from the d axis.
10. The electric motor according to claim 9 . In the plane, the distance from the center of rotation of each of the magnetic pole outer peripheral surfaces of the rotor core is maximized at a position on the d axis,
In the plane, the magnetic pole outer peripheral surface of the N-pole magnetic pole portion and the magnetic pole outer peripheral surface of the S-pole magnetic pole portion are equidistant from the rotation center at a position on the d-axis.
12. The electric motor according to claim 11 . An electric motor comprising: a rotor having a rotor core in which permanent magnets are embedded and in which a plurality of magnetic pole portions are provided along a circumferential direction; and a stator having a plurality of teeth portions arranged on an outer circumferential side of the rotor, wherein the number of pole pairs of the magnetic pole portions is m and the number of the plurality of teeth portions is 3m, and the rotor core has non-magnetic portions extending continuously from both ends of the permanent magnet in the circumferential direction,
When an outer circumferential surface of the rotor core in a range that forms one pole pair in a plane perpendicular to a rotation centerline of the rotor is defined as a one pole pair outer circumferential surface, the outer circumferential surface of the rotor core is formed by repeating a shape of the one pole pair outer circumferential surface m times in the circumferential direction so that the shape of the one pole pair outer circumferential surface is rotationally symmetrical with respect to the rotation center of the rotor,
In the plane, each magnetic pole portion has a magnetic pole outer peripheral surface formed on the outer peripheral surface between a first boundary line which is a straight line passing through the center of rotation and an outer peripheral end of one of the non-magnetic portions in the radial direction of the rotor core, and a second boundary line which is a straight line passing through the center of rotation and an outer peripheral end of the other of the non-magnetic portions in the radial direction,
In the plane, a straight line connecting the center of the magnetic pole portion in the circumferential direction and the rotation center is defined as a d-axis, and a straight line connecting the center between adjacent magnetic pole portions in the circumferential direction and the rotation center is defined as a q-axis.
Each pole pair has an N pole portion and an S pole portion disposed on either side of the q axis,
In the plane, when one of the N-pole magnetic pole portion and the S-pole magnetic pole portion is virtually rotated about the rotation center by 360/(2 m) [degrees] and overlapped with the other magnetic pole portion, the magnetic pole outer circumferential surface of the N-pole magnetic pole portion and the magnetic pole outer circumferential surface of the S-pole magnetic pole portion are formed in shapes that do not coincide with each other,
A groove portion is formed in an outer peripheral surface of the rotor core between the magnetic pole portions adjacent in the circumferential direction, the outer peripheral surface being recessed in the radial direction along the rotation center line,
the outer circumferential surface of the rotor core has a groove region in which the groove is formed such that the q-axis passes through the groove,
the magnetic pole outer circumferential surface has a constant diameter region formed at a position through which the d-axis passes and having a constant distance from the rotation center, and a variable diameter region formed between the groove region and the constant diameter region and having a variable distance from the rotation center,
the radius change region is formed with a plurality of radii of curvature smaller than the radius of curvature from the center of rotation in the constant radius region . The plurality of radii of curvature of the diameter change region are gradually reduced toward the groove portion.
14. The electric motor according to claim 13 . the constant diameter region has a front constant region located on a front side of the d axis in a rotation direction of the rotor, and a rear constant region located on a rear side of the d axis in the rotation direction,
The front constant region has a smaller size in the circumferential direction than the rear constant region.
14. The electric motor according to claim 13 . In each magnetic pole portion, the plate-shaped permanent magnet is arranged such that the thickness direction of the permanent magnet is aligned along the d axis.
2. The electric motor according to claim 1. In each magnetic pole portion, two plate-shaped permanent magnets are arranged such that the thickness directions of the permanent magnets intersect.
2. The electric motor according to claim 1. An electric motor comprising: a rotor having a rotor core in which permanent magnets are embedded and in which a plurality of magnetic pole portions are provided along a circumferential direction; and a stator having a plurality of teeth portions arranged on an outer circumferential side of the rotor, wherein the number of pole pairs of the magnetic pole portions is m and the number of the plurality of teeth portions is 3m, and the rotor core has non-magnetic portions extending continuously from both ends of the permanent magnet in the circumferential direction,
When an outer circumferential surface of the rotor core in a range that forms one pole pair in a plane perpendicular to a rotation centerline of the rotor is defined as a one pole pair outer circumferential surface, the outer circumferential surface of the rotor core is formed by repeating a shape of the one pole pair outer circumferential surface m times in the circumferential direction so that the shape of the one pole pair outer circumferential surface is rotationally symmetrical with respect to the rotation center of the rotor,
In the plane, each magnetic pole portion has a magnetic pole outer peripheral surface formed on the outer peripheral surface between a first boundary line which is a straight line passing through the center of rotation and an outer peripheral end of one of the non-magnetic portions in the radial direction of the rotor core, and a second boundary line which is a straight line passing through the center of rotation and an outer peripheral end of the other of the non-magnetic portions in the radial direction,
In the plane, a straight line connecting the center of the magnetic pole portion in the circumferential direction and the rotation center is defined as a d-axis, and a straight line connecting the center between adjacent magnetic pole portions in the circumferential direction and the rotation center is defined as a q-axis.
Each pole pair has an N pole portion and an S pole portion disposed on either side of the q axis,
In the plane, when one of the N-pole magnetic pole portion and the S-pole magnetic pole portion is virtually rotated about the rotation center by 360/(2 m) [degrees] and overlapped with the other magnetic pole portion, the magnetic pole outer circumferential surface of the N-pole magnetic pole portion and the magnetic pole outer circumferential surface of the S-pole magnetic pole portion are formed in shapes that do not coincide with each other,
In each magnetic pole portion, the plate-shaped permanent magnet is disposed such that the thickness direction of the permanent magnet is aligned along the d axis,
Each magnetic pole portion has two non-magnetic portions extending from both ends of the permanent magnet toward the outer circumferential surface of the rotor core,
the two non-magnetic portions of the S-pole magnetic pole portion are formed in shapes asymmetric with respect to an S-pole d-axis, which is a d-axis of the S-pole magnetic pole portion,
the two non-magnetic portions of the N-pole magnetic pole portion are formed in shapes asymmetric with respect to an N-pole d-axis, which is a d-axis of the N-pole magnetic pole portion;
an electric motor in which, when the two non-magnetic portions of one of the magnetic pole portions are virtually rotated around the center of rotation by 360/(2 m) degrees and overlapped with the two non-magnetic portions of the other magnetic pole portion, the two non-magnetic portions of the N-pole magnetic pole portion and the two non-magnetic portions of the S-pole magnetic pole portion are formed in shapes that do not coincide with each other. In the plane, the four non-magnetic portions of the N-pole magnetic pole portion and the S-pole magnetic pole portion have different shapes from each other.
20. The electric motor of claim 18 . the stator includes a stator core having an annular yoke portion and the plurality of teeth portions extending radially inward from the yoke portion,
The plurality of teeth portions are formed in the same shape.
2. The electric motor according to claim 1. Each tooth portion has a winding portion in which the winding is wound in a concentrated winding manner.
2. The electric motor according to claim 1.

Images