Rotating Electric Machine

Abstract

To provide a rotary electric machine capable of reducing sixth-order harmonic torque ripple by suppressing a decrease of average torque.SOLUTION: A plurality of permanent magnets 122 of a rotary electric machine 100 is magnetized in the same direction along a radial direction of a rotor 20. The rotor 20 includes a plurality of salient pole parts 126 positioned between the adjacent permanent magnets 122. A length (width A) of the salient pole part 126 in a circumferential direction of the rotor 20 is longer than a length (width C) of a tooth 116 in the circumferential direction of the rotor 20. A distance Gs between the salient pole part 126 and the tooth 116 in the radial direction of the rotor 20 is longer than a distance G between the permanent magnet 122 and the tooth 116 in the radial direction of the rotor 20.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a rotating electric machine. [Background technology]

[0002] An example of a conventional rotating electric machine is a brushless motor described in Patent Document 1. The brushless motor described in Patent Document 1 is used as a pressure source for an electric brake system. This brushless motor includes a stator having a coil wound around a plurality of teeth arranged in the circumferential direction, and a rotor facing the stator. The rotor has magnet pole portions having magnets in the circumferential direction of the rotor core, and an iron core portion arranged between the magnet pole portions. The iron core portion functions as the other magnetic pole.

[0003] In a consequent-pole rotor structure such as the brushless motor described in Patent Document 1, there is a magnetic path where the magnetic flux originating from the magnets interlinks with the salient poles provided between the magnets. The stator and rotor of the motor face each other across a gap. When the change in permeance at the middle of this gap is viewed in the circumferential direction, the permeance is high at the points corresponding to the salient poles.

[0004] When the permeance increases at the points corresponding to the salient poles, harmonic voltages of even-order components are generated in the induced electromotive force of the motor. As a result, third-order integer multiple harmonic torque ripple is output, which does not occur in surface permanent magnet rotor structures. In particular, sixth-order integer multiple harmonic torque ripple is a component that tends to dominate the total torque ripple among the harmonic components contained in the torque ripple of the load torque. Therefore, in order to suppress motor vibration noise, it is necessary to reduce the sixth-order integer multiple harmonic torque ripple.

[0005] A method for reducing torque ripple in a consequent pole rotor structure is described in, for example, Patent Document 2. In a motor employing the consequent pole structure described in Patent Document 2, the ratio B / A of the gap distance A on the magnet side to the gap distance B on the salient pole side of the rotor gap relative to the stator is set to 1 [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2019-126138 A [Patent Document 2] JP 2011-83119 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the motor described in Patent Document 2, the magnetic resistance of the gap of the salient pole increases, so that although the torque ripple can be reduced, the average torque also decreases at the same time. In order to suppress the reduction in the average torque, for example, it is necessary to increase the winding current and increase the magnetomotive force of the stator. However, this leads to an increase in the size of the motor.

[0008] In consideration of the above problems, an object of the present invention is to provide a rotating electric machine capable of suppressing a decrease in average torque and reducing sixth-order harmonic torque ripple. [Means for solving the problem]

[0009] ​In order to solve the above problems and achieve the object of the present invention, a rotating electric machine includes an annular rotor having a plurality of permanent magnets and rotating about a rotation axis, and an annular stator having a plurality of teeth facing the plurality of permanent magnets via gaps in the radial direction of the rotor. The plurality of permanent magnets are magnetized in the same direction along the radial direction of the rotor. The rotor has a plurality of salient pole portions located between adjacent permanent magnets. The length of the salient pole portions along the circumferential direction of the rotor is longer than the length of the teeth along the circumferential direction of the rotor. In addition, the distance between the salient pole portions and the teeth along the radial direction of the rotor is longer than the distance between the permanent magnets and the teeth along the radial direction of the rotor. The salient pole portion has a recess on a surface facing the gap. The length of the recess along the circumferential direction of the rotor is set within a range of ±20% of the length of the tooth along the circumferential direction of the rotor. Effect of the Invention

[0010] According to the rotating electric machine having the above configuration, it is possible to suppress a decrease in average torque and reduce sixth-order harmonic torque ripple. Problems, configurations and effects other than those described above will become apparent from the following description of the embodiments. [Brief description of the drawings]

[0011] [Figure 1] 1 is an overall configuration diagram of a rotating electric machine according to a first embodiment of the present invention; [Diagram 2] 1 is a cross-sectional view of a rotating electric machine according to a first embodiment of the present invention, cut along a plane perpendicular to a rotation axis. [Diagram 3] 1 is a partially enlarged view of a rotating electric machine according to a first embodiment of the present invention. [Figure 4] 1 is a schematic diagram showing a path of magnetic flux in a rotating electric machine according to a first embodiment of the present invention; [Diagram 5] 4 is a distribution graph showing magnetic flux density distribution in an air gap in the rotating electric machine according to the first embodiment of the present invention and in a conventional rotating electric machine. [Figure 6] 4 is a graph comparing harmonic torque ripples in the rotating electric machine according to the first embodiment of the present invention and a conventional rotating electric machine. [Figure 7] 5 is a cross-sectional view of a rotating electric machine according to a second embodiment of the present invention, taken along a plane perpendicular to the rotation axis. FIG. [Figure 8]FIG. 6 is a partial enlarged view of a rotating electric machine according to a second embodiment of the present invention. [Figure 9] FIG. 6 is a schematic diagram showing paths of magnetic flux in a rotating electric machine according to a second embodiment of the present invention. [Figure 10] 4 is a distribution graph showing magnetic flux density distribution in an air gap in the rotating electric machines according to the first and second embodiments of the present invention and in a conventional rotating electric machine. [Figure 11] 4 is a graph comparing harmonic torque ripples in the rotating electric machines according to the first and second embodiments of the present invention and a conventional rotating electric machine. [Figure 12] 11 is a cross-sectional view of a rotating electric machine according to a third embodiment of the present invention, taken along a plane perpendicular to the rotation axis. FIG. [Figure 13] FIG. 11 is a partial enlarged view of a rotating electric machine according to a third embodiment of the present invention. [Figure 14] 10 is a graph showing harmonic torque ripples in a rotating electric machine according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] 1. First embodiment Hereinafter, a rotating electric machine according to a first embodiment of the present invention will be described. Note that the same reference numerals are used to designate the same components in each drawing.

[0013] [Rotary Electric Machines] First, the configuration of a rotating electric machine according to a first embodiment will be described with reference to FIGS. 1 and 2. FIG. Fig. 1 is an overall configuration diagram of a rotating electric machine according to a first embodiment of the present invention, Fig. 2 is a cross-sectional view of the rotating electric machine according to the first embodiment, cut along a plane perpendicular to the rotation axis.

[0014] 1 is a cross-sectional view of a rotating electric machine cut along a plane parallel to the rotating shaft. The rotating electric machine 100 according to the first embodiment is an outer rotor permanent magnet synchronous motor with a consequent pole type rotor structure. The rotating electric machine 100 has 12 coils and 10 magnetic poles.

[0015] As shown in FIG. 1, the rotating electric machine 100 includes an annular stator (staple) 10, an annular rotor 20 rotatably supported radially outside the stator 10, a rotor case 6 covering the rotor 20, and a shaft 4 fixed to the rotor case 6.

[0016] The rotor case 6 does not necessarily need to cover the entire rotor 20. The rotor case 6 is configured as a component that connects the shaft 4 and the rotor 20. Various methods can be used to fix the rotor 20 to the rotor case 6. The rotor 20 faces the stator 10 across a gap 102 in the radial direction of the rotor 20. The rotor 20 rotates about the rotation axis of the shaft 4.

[0017] Hereinafter, the side closer to the rotation axis of the shaft 4 will be referred to as the "inner circumference side," and the side farther from the rotation axis of the shaft 4 will be referred to as the "outer circumference side." Additionally, the direction of a straight line perpendicular to the rotation axis of the shaft 4 will be referred to as the "radial direction," and the rotation direction of the shaft 4 will be referred to as the "circumferential direction."

[0018] As shown in FIG. 2, the rotor 20 has a circular rotor yoke 120 made of a magnetic material, a plurality of salient pole portions 126 protruding radially inward of the rotor yoke 120, and a plurality of permanent magnets 122 fixed to the inner surface of the rotor yoke 120.

[0019] The permanent magnets 122 and the salient poles 126 are arranged alternately in the circumferential direction. The magnetization direction of the permanent magnets 122 is the same as the radial direction. The N poles of the permanent magnets 122 all face the radially inner side. That is, the permanent magnets 122 are magnetized in the same radial direction.

[0020] There are five each of the permanent magnets 122 and the salient pole portions 126. Therefore, the permanent magnets 122 and the salient pole portions 126 form five pole pairs, that is, ten magnetic poles.

[0021] In this embodiment, the multiple permanent magnets 122 are attached to the inner peripheral surface of the rotor yoke 120. However, the method of fixing the permanent magnets according to the present invention is not limited to attachment, and for example, a method may be adopted in which grooves into which the multiple permanent magnets are respectively fitted are provided on the inner peripheral surface of the rotor yoke, and the permanent magnets are fitted into these grooves. Also, a method may be adopted in which the multiple permanent magnets are covered with a magnetic body so as to be integrated with the rotor yoke.

[0022] The material of the permanent magnet 122 may be a magnetic material such as a ferrite-based, neodymium-based, or samarium-cobalt-based material. As shown in Fig. 2, the cross section of the permanent magnet 122 cut in a plane perpendicular to the rotation axis is tile-shaped. However, the cross section of the permanent magnet 122 cut in a plane perpendicular to the rotation axis may be flat. In addition, the permanent magnet per magnetic pole may be formed by arranging multiple magnets with the same magnetization direction in the axial direction or circumferential direction of the shaft 4.

[0023] The stator 10 has a substantially cylindrical stator yoke 110 made of a magnetic material, a plurality of teeth 116 protruding in the radial direction from the outer peripheral surface of the stator yoke 110, and an armature winding 112 wound around the teeth 116. Twelve teeth 116 are provided. The teeth 116 are arranged at equal intervals in the circumferential direction. In addition, there are provided twelve slots 104, which are spaces between adjacent teeth 116, the same number as the number of teeth 116. In other words, the rotating electric machine 100 is a motor with twelve slots and ten magnetic poles.

[0024] The multiple teeth 116 face the multiple permanent magnets 122 and the multiple salient pole portions 126 of the rotor 20 via the gap 102. The teeth 116 have a body portion 116a that is continuous with the stator yoke 110, and a flange portion 116b that is provided on the gap 102 side of the body portion 116a. The flange portion 116b is formed in a substantially elliptical shape that protrudes in the circumferential direction.

[0025] Slots 104, which are spaces between adjacent teeth 116, are formed in a semi-closed shape by flanges 116b of teeth 116. Note that the slots according to the present invention may be formed as open slots in which no flanges are provided on the teeth.

[0026] The armature windings 112 are 12 in number, the same as the number of teeth 116. The armature windings 112 form a coil of any shape. For example, the armature windings 112 are made of one or more copper wires in which an electrical conductor mainly composed of copper is coated with an insulating coating (e.g., enamel, engineering plastic, etc.). The armature windings 112 have conductors 112A and 112B that are respectively disposed in the slots 104. Electric currents are passed through the conductors 112A and 112B in opposite directions in the rotation axis direction when the rotating electric machine 100 is driven.

[0027] Between the armature winding 112 and the teeth 116, an intervening material such as a tape of a non-flammable material or a resin bobbin may be provided, thereby enhancing insulation. Also, the stator according to the present invention may be one in which the armature winding is fixed to the teeth by impregnation with varnish, resin, or the like.

[0028] The magnetic material constituting the rotor yoke 120 and the stator yoke 110 is a laminate in which magnetic steel plates and an electrical insulator are laminated. This makes it possible to reduce eddy current loss. Note that the rotor yoke and the stator yoke according to the present invention may be made of an integrated (bulk) magnetic material. This makes it possible to reduce material costs and processing costs.

[0029] [Relationship between permanent magnets, salient poles, and teeth] Next, the relationship between the permanent magnet 122, the salient pole portion 126, and the teeth 116 will be described with reference to FIG. FIG. 3 is a partially enlarged view of the periphery of the salient pole portion 126 in the rotating electric machine 100. As shown in FIG.

[0030] 3, the circumferential length of salient pole portion 126 is defined as width A. Furthermore, the circumferential length of tooth 116 is defined as width C. Width A is the circumferential length of salient pole portion 126 converted into an electrical angle. Width C is the width of body portion 116a of tooth 116 extended to the position facing gap 102 and converted into an electrical angle.

[0031] Although the teeth 116 in this embodiment are parallel teeth, the width C is defined similarly even in the case of trapezoidal teeth. The width A of the salient pole portion 126 is wider than the width C of the teeth 116 (A>C).

[0032] Further, the radial distance between the outer peripheral surface of the tooth 116 and the inner peripheral surface of the permanent magnet 122 is defined as distance G. The radial distance between the outer peripheral surface of the tooth 116 and the inner peripheral surface of the salient pole portion 126 is defined as distance Gs. In this embodiment, distance Gs is set to be longer than distance G (Gs>G).

[0033] The width A in this embodiment is set to 170 degrees in electrical angle. However, the electrical angle of the width A according to the present invention may be designed to be between 180 degrees and 150 degrees (360 degrees×P / 2 / S, where S is the number of slots and P is the number of magnetic poles). In a combination of 12 slots and 10 magnetic poles, the maximum width C of the teeth 116 is 150 degrees in electrical angle. In reality, the width C of the teeth 116 is smaller than 150 degrees in electrical angle because a space is required to arrange the armature winding 112. Therefore, the width A of the salient pole portion 126, which is larger than the width C of the teeth 116, is set to 150 degrees or more in electrical angle. In this embodiment, the distance Gs is set to twice the distance G (Gs=2G). However, the distance Gs may be larger than twice the distance G (Gs>2G).

[0034] [Path of magnetic flux] Next, the path of magnetic flux originating from the magnets in the rotating electrical machine 100 will be described with reference to FIG. FIG. 4 is a schematic diagram showing the path of magnetic flux in the rotating electric machine 100. As shown in FIG.

[0035] The dashed curve 160 shown in Fig. 4 is the magnetic flux originating from the permanent magnet 122. In addition, the dashed line 150 indicates the middle part of the distance G. As shown in Fig. 4, the magnetic flux originating from each permanent magnet 122 passes through two adjacent teeth 116 of the stator 10, passes through the air gap 102, and returns to each permanent magnet 122 from the adjacent salient pole portion 126.

[0036] For this reason, a magnetic pole (a south pole relative to a north pole magnet) is generated in the salient pole portion 126 in the opposite direction to the adjacent permanent magnet 122. This results in a magnetic pole pair similar to that obtained when a permanent magnet of the opposite pole is disposed in place of the salient pole portion 126. As a result, a rotating electric machine (motor) can be rotated by current flow similar to that of a general surface permanent magnet synchronous motor.

[0037] In this embodiment, the height of the salient pole portion 126 is made lower than the height of the permanent magnet 122, and the distance Gs is made longer than the distance G (Gs>G) (see FIG. 3). This widens the gap between the salient pole portion 126 and the tooth 116. As a result, the magnetic resistance of the salient pole portion 126 in the magnetic flux path increases overall, and the amount of magnetic flux linkage decreases. Also, in this embodiment, the width A of the salient pole portion 126 is larger than the width C of the tooth 116. This makes it possible to reduce magnetic flux leakage in the salient pole portion 126.

[0038] [Magnetic flux density] Next, the magnetic flux densities of the rotating electric machine of this embodiment and a conventional rotating electric machine will be described with reference to FIG. FIG. 5 is a distribution graph showing the magnetic flux density distribution in the air gap in the rotating electric machine 100 and a conventional rotating electric machine.

[0039] As described above, in the rotating electric machine 100 of this embodiment, the distance Gs is longer than the distance G (see FIG. 3). On the other hand, in a conventional consequent-pole type motor (rotating electric machine), the distance Gs and the distance G are set to be the same (Gs=G).

[0040] Fig. 5 is a distribution graph showing the magnitude of the radial magnetic flux density at the middle of the distance G (dashed line 150 in Fig. 4) when the electrical angle of the rotation angle is θ and the middle point in the circumferential direction between the permanent magnet 122 and the salient pole portion 126 is 0 degrees. As shown in Fig. 5, the magnetic flux density distribution of the conventional rotating electric machine is distorted due to the influence of the permeance of the stator, but is distributed in an approximately sinusoidal shape.

[0041] The range of the salient pole portion 126 is from 0 degrees to 180 degrees as shown in FIG. 5. In the rotating electric machine 100 of this embodiment, the distance Gs is longer than the distance G, so that the magnetic flux density level of the salient pole portion 126 is simply lowered compared to the conventional rotating electric machine. As for the frequency components, the first, second, third, and fifth frequency components are reduced. For example, the first frequency component is reduced by expanding the gap 102, and the second and higher frequency components are determined by the combination of the number of slots and the number of magnetic poles. In this embodiment, the width A of the salient pole portion 126 is made larger than the width C of the teeth 116. Therefore, it is possible to suppress the reduction in the average torque caused by the reduction in the magnetic flux density distribution.

[0042] The sixth-order component of the harmonic torque ripple is considered to be generated by the interaction between the two magnetic poles of the permanent magnets 122 on the rotor 20 side and the teeth 116 on the stator 10 side, which are an integer multiple of three. Therefore, by distorting the magnetic flux density distribution of the salient pole portion 126, which is a virtual magnetic pole (reducing the fundamental wave of the magnetic flux density distribution), it is possible to obtain the effect of reducing the magnitude of the harmonic torque ripple. In particular, the sixth-order torque ripple is caused by the fifth-order and seventh-order components of the magnetic flux and voltage harmonics, and therefore it is important to reduce the fifth-order and seventh-order components of the magnetic flux and voltage harmonics.

[0043] [Harmonic torque ripple] Next, the torque ripple of the rotating electric machine of the first embodiment and a conventional rotating electric machine will be described with reference to FIG. FIG. 6 is a graph comparing harmonic torque ripples in the rotating electric machine 100 and a conventional rotating electric machine.

[0044] Fig. 6 shows the analysis results of the harmonic components of the torque when a three-phase sinusoidal current is applied to the armature winding 112 so that the average torque is approximately the same. Here, the torque ripple is normalized by the ratio of each harmonic component to the average torque and is shown as a percentage. As shown in Fig. 6, the rotating electric machine 100 of this embodiment can reduce the sixth-order harmonic torque ripple more than the conventional rotating electric machine. Therefore, it is possible to suppress the decrease in the average torque and reduce the sixth-order harmonic torque ripple.

[0045] 2. Second embodiment Next, a rotating electric machine according to a second embodiment will be described. Note that the same reference numerals are used to designate the same components in each drawing.

[0046] [Rotary Electric Machines] First, the configuration of a rotating electric machine according to the second embodiment will be described with reference to FIGS. Fig. 7 is a cross-sectional view of the rotating electric machine according to the second embodiment cut along a plane perpendicular to the rotation axis, and Fig. 8 is a partially enlarged view of the rotating electric machine according to the second embodiment.

[0047] The rotating electric machine 200 according to the second embodiment has a similar configuration to the rotating electric machine 100 according to the first embodiment (see FIG. 2). The rotating electric machine 200 differs from the rotating electric machine 100 in a salient pole portion 226. Therefore, here, the salient pole portion 226 will be described, and a description of the configuration common to the first embodiment will be omitted.

[0048] 7, a recess 228 is provided in salient pole portion 226 of rotating electric machine 200. Recess 228 is formed as a single arc-shaped depression in the center of the inner circumferential surface of salient pole portion 226. That is, a cross section of recess 228 perpendicular to the rotation axis of shaft 4 is formed in an arc shape.

[0049] The recess of the salient pole portion according to the present invention is not limited to having an arc-shaped cross section perpendicular to the rotation axis of the shaft 4, and may have, for example, a polygonal or V-shaped groove cross section perpendicular to the rotation axis of the shaft 4. Even when the cross section of the recess is a polygonal or V-shaped groove, the same effect as when the cross section of the recess is an arc-shaped cross section can be obtained. This effect will be described later.

[0050] 8, the circumferential length of the salient pole portion 226 is defined as width A. The circumferential length of the recessed portion 228 is defined as width B. The circumferential length of the tooth 116 is defined as width C. Note that widths A and C are converted into electrical angles, and are the same as in the first embodiment. Width B is defined as the circumferential length of the recessed portion 228 converted into an electrical angle.

[0051] Width A of salient pole portion 226 is wider than width C of tooth 116 (A>C). Width A of salient pole portion 226 is also wider than width B of recess 228 (A>B). If width B of recess 228 is made too wide, the magnetic resistance of salient pole portion 126 increases, as described with reference to FIG. 4. Therefore, width B of recess 228 is set within a range of ±20% of width C. Also, the corners on both ends of width A of salient pole portion 226 are cut into an arc shape.

[0052] The radial distance between the outer peripheral surface of the tooth 116 and the inner peripheral surface of the permanent magnet 122 is defined as distance G. The radial distance between the outer peripheral surface of the tooth 116 and a portion of the inner peripheral surface of the salient pole portion 226 other than the recessed portion 228 is equal to distance G. The distance from the deepest point of the recessed portion 228 in the salient pole portion 226 to the outer peripheral surface of the tooth 116 is defined as distance Gs. In other words, distance Gs is the distance from the radially outermost point on the inner peripheral surface of the salient pole portion 226 to the outer peripheral surface of the tooth 116.

[0053] In this embodiment, the distance Gs is set to be longer than the distance G (Gs>G). Specifically, the distance Gs is set to be three times the distance G (Gs=3G). In other words, the depth (radial length) of the recess 228 is twice the distance G.

[0054] [Path of magnetic flux] Next, the path of magnetic flux originating from the magnets in the rotating electric machine 200 will be described with reference to FIG. FIG. 9 is a schematic diagram showing the path of magnetic flux in the rotating electric machine 200. As shown in FIG.

[0055] The dashed curve 160 shown in Fig. 9 is the magnetic flux originating from the permanent magnet 122. Moreover, the dashed line 150 indicates the middle part of the distance G. As shown in Fig. 9, the magnetic flux originating from each permanent magnet 122 passes through two adjacent teeth 116 of the stator 10, and returns to each permanent magnet 122 from the adjacent salient pole portion 226 via the air gap 102. The recess 228 of the salient pole portion 226 has a high magnetic resistance. Therefore, the magnetic flux of the salient pole portion 226 is concentrated near both sides of the recess 228.

[0056] [Magnetic flux density] Next, the magnetic flux density of the rotating electric machines according to the second and first embodiments and a conventional rotating electric machine will be described with reference to FIG. FIG. 10 is a distribution graph showing the magnetic flux density distribution in the air gap in the rotating electric machine 200, the rotating electric machine 100, and a conventional rotating electric machine.

[0057] 10, the magnetic flux density distributions of the conventional rotating electric machine and the rotating electric machine 100 of the first embodiment are substantially sinusoidal. On the other hand, in the magnetic flux density distribution of the rotating electric machine 200 of the second embodiment, the magnetic flux density corresponding to the salient pole portion 226 fluctuates up and down due to the influence of the recessed portion 228, and the peaks of the sine wave are distorted.

[0058] As for the frequency components related to the rotating electric machine 200, the first and fifth frequency components are reduced, and the third and sixth frequency components are increased. The third and sixth frequency components are offset by the influence of the three-phase AC. Therefore, the rotating electric machine 200 can reduce the fifth frequency component that contributes to the reduction of the sixth torque ripple. That is, in the rotating electric machine 100 of the first embodiment, the harmonics of the magnetic flux density are reduced over a wide range, but in the rotating electric machine 200, since the recess 228 is provided, the harmonics (fifth frequency components) that are the source of the torque ripple can be reduced more selectively. In addition, in this embodiment, the width A of the salient pole portion 226 is made larger than the width C of the tooth 116. Therefore, the reduction in the average torque caused by the reduction in the magnetic flux density distribution can be suppressed.

[0059] [Harmonic torque ripple] Next, the torque ripple of the rotating electric machines according to the second and first embodiments and a conventional rotating electric machine will be described with reference to FIG. FIG. 11 is a graph comparing harmonic torque ripples in the rotating electric machine 200, the rotating electric machine 100, and a conventional rotating electric machine.

[0060] Fig. 11 shows an analysis result of the harmonic components of the torque when a three-phase sinusoidal current is applied to the armature winding 112 so that the average torque is approximately the same. Here, the torque ripple is normalized by the ratio of each harmonic component to the average torque and is shown as a percentage. As shown in Fig. 11, the rotating electric machine 200 of the second embodiment can reduce the 6th and 12th harmonic torque ripple more than the conventional rotating electric machine.

[0061] Furthermore, since the rotating electric machine 200 is provided with the recess 228, it is possible to reduce the sixth and twelfth harmonic torque ripples more than the rotating electric machine 100 of the first embodiment. In particular, the rotating electric machine 100 of the first embodiment was unable to reduce the twelfth harmonic torque ripple, but the rotating electric machine 200 can also reduce the twelfth harmonic torque ripple. Therefore, it is possible to suppress a decrease in the average torque and reduce the sixth-order integer multiple harmonic torque ripple.

[0062] 3. Third embodiment Next, a rotating electric machine according to a third embodiment will be described. Note that the same reference numerals are used to designate the same components in the various drawings.

[0063] [Rotary Electric Machines] First, the configuration of a rotating electric machine according to the third embodiment will be described with reference to FIGS. Fig. 12 is a cross-sectional view of the rotating electric machine according to the third embodiment cut along a plane perpendicular to the rotation axis, and Fig. 13 is a partially enlarged view of the rotating electric machine according to the third embodiment.

[0064] The rotating electric machine 300 according to the third embodiment has a similar configuration to the rotating electric machine 100 according to the first embodiment (see FIG. 2). As shown in FIG. 12, the rotating electric machine 300 has 36 teeth 116, 16 permanent magnets 122, and 16 salient pole portions 326. That is, the rotating electric machine 300 is a motor with 36 slots and 32 magnetic poles.

[0065] The rotating electric machine 300 differs from the rotating electric machine 100 in the number of teeth 116, permanent magnets 122, and salient pole portions 326, and the shape of the salient pole portions 326. Therefore, only the salient pole portions 326 will be described here, and a description of the configuration common to the first embodiment will be omitted.

[0066] 12 and 13, two recesses 328 are provided in salient pole portion 326 of rotary electric machine 300. The two recesses 328 are formed as two arc-shaped depressions on the inner circumferential surface of salient pole portion 326. The two recesses 328 are disposed at positions symmetrical with respect to the center of the inner circumferential surface of salient pole portion 326.

[0067] As shown in FIG. 13, the circumferential length of the salient pole portion 326 is defined as width A. The circumferential length of the recessed portion 328 is defined as width D. The circumferential length of the tooth 116 is defined as width C. Note that widths A, C, and D are converted into electrical angles. Width A of the salient pole portion 326 is wider than width C of the tooth 116 (A>C). Width D of each recessed portion 328 is set to about half width C of the tooth 116 (D=C / 2). Moreover, the corners at both ends of width A of the salient pole portion 326 are cut diagonally.

[0068] The radial distance between the outer peripheral surface of the tooth 116 and the inner peripheral surface of the permanent magnet 122 is defined as distance G. The radial distance between the outer peripheral surface of the tooth 116 and the inner peripheral surface of the salient pole portion 326 is equal to distance G. The distance from the deepest point of the recess 328 in the salient pole portion 326 to the outer peripheral surface of the tooth 116 is defined as distance Gs. In other words, distance Gs is the distance from the radially outermost point on the inner peripheral surface of the salient pole portion 326 to the outer peripheral surface of the tooth 116.

[0069] In this embodiment, the distance Gs is set to be longer than the distance G (Gs>G). The distance Gs is set to be three times the distance G (Gs=3G). In other words, the depth (radial length) of the recess 328 is twice the distance G.

[0070] Generally, in a motor (rotating electric machine) with 36 slots and 16 pole pairs, even-order components are mixed in the magnetic flux and voltage harmonic components. For this reason, a consequent pole type motor with 36 slots and 16 pole pairs generates large third-order integer multiple harmonic torque ripple.

[0071] The rotating electric machine 300 according to the third embodiment has recesses similar to those in the second embodiment, and therefore can reduce sixth-order integer multiple harmonic torque ripples. In addition, by providing two recesses 328 and setting the width D of each recess 328 to half the width C of the tooth 116 and the depth of the recess 328 to twice the distance G, it is possible to reduce third-order integer multiple harmonic torque ripples. Furthermore, in this embodiment, the width A of the salient pole portion 326 is made larger than the width C of the tooth 116. This makes it possible to suppress a decrease in average torque caused by a decrease in magnetic flux density distribution.

[0072] [Harmonic torque ripple] Next, the torque ripple of the rotating electric machine according to the third embodiment will be described with reference to FIG. FIG. 14 is a graph showing harmonic torque ripples in the rotating electrical machine 300. As shown in FIG.

[0073] 14 compares the third embodiment in which two recesses 328 are provided, a salient pole portion 326 in which no recesses are provided, and a salient pole portion 326 in which one recess is provided with a width approximately equal to the width C of the tooth 116. When one recess is provided, the recess is located in the center of the inner peripheral surface of the salient pole portion 326.

[0074] As shown in Fig. 14, the one with one recess can reduce the sixth harmonic torque ripple compared to the one without any recess. However, the one with one recess increases the third and ninth harmonic torque ripple. In contrast, the third embodiment with two recesses 328 can reduce the sixth, ninth and twelfth harmonic torque ripple while suppressing the increase in the third harmonic torque ripple. As a result, the third embodiment with two recesses 328 can reduce the overall harmonic torque ripple.

[0075] 4. Summary As described above, the rotating electric machine 100 according to the first embodiment includes an annular rotor 20 (rotor) having a plurality of permanent magnets 122 and rotating around the rotation axis of the shaft 4, and an annular stator 10 (stator) having a plurality of teeth 116 facing the plurality of permanent magnets 122 via gaps 102 in the radial direction of the rotor 20. The plurality of permanent magnets 122 are magnetized in the same direction along the radial direction of the rotor 20. The rotor 20 has a plurality of salient pole portions 126 located between adjacent permanent magnets 122. The length (width A) of the salient pole portions 126 along the circumferential direction of the rotor 20 is longer than the length (width C) of the teeth 116 along the circumferential direction of the rotor 20. The distance (distance Gs) between the salient pole portions 126 and the teeth 116 along the radial direction of the rotor 20 is longer than the distance (distance G) between the permanent magnets 122 and the teeth 116 along the radial direction of the rotor 20. This distorts the magnetic flux density distribution of the salient pole portion 126, which is a virtual magnetic pole (reducing the fundamental wave of the magnetic flux density distribution), thereby reducing the sixth harmonic torque ripple. Also, the length (width A) of the salient pole portion 126 along the circumferential direction of the rotor 20 is made longer than the length (width C) of the teeth 116 along the circumferential direction of the rotor 20. This makes it possible to suppress a decrease in average torque caused by a decrease in the magnetic flux density distribution.

[0076] Moreover, the salient pole portion 226 according to the second embodiment described above has one recess 228 on the surface (inner peripheral surface) facing the air gap 102. This makes it possible to reduce the sixth-order integer multiple harmonic torque ripple. Moreover, the salient pole portion 326 according to the third embodiment described above has two recesses 328 on the surface (inner peripheral surface) facing the air gap 102. This makes it possible to reduce the overall harmonic torque ripple.

[0077] Moreover, the cross section of the recess 228 in the second embodiment described above, which is perpendicular to the rotation axis of the shaft 4, is formed in an arc shape. Moreover, the recess of the salient pole portion according to the present invention may be a groove having a polygonal or V-shaped cross section perpendicular to the rotation axis of the shaft 4. This makes it possible to easily provide the recess.

[0078] Moreover, the corners that form both ends in the circumferential direction of the rotor 20 (both ends of the width A) of the salient pole portion 326 according to the third embodiment described above are cut obliquely. As a result, when the teeth 116 and the salient pole portion 326 face each other across the gap 102, the overlap between the teeth 116 and the salient pole portion 326 gradually increases compared to when there is a substantially right-angled corner. As a result, the ease with which magnetic flux passes through the salient pole portion 326 gradually increases, and the force with which the teeth 116 are attracted to the salient pole portion 326 gradually increases. Therefore, harmonic torque ripple can be reduced.

[0079] Moreover, the corners of the salient pole portions 226 according to the second embodiment, which form both ends in the circumferential direction of the rotor 20 (both ends of the width A), are cut into an arc shape. This allows the teeth 116 and the salient pole portions 226 to gradually overlap each other more than in the third embodiment. As a result, it is possible to reduce harmonic torque ripple more than in the third embodiment.

[0080] Furthermore, the length (width A) of the salient pole portion 126 according to the first embodiment and the salient pole portion 226 according to the second embodiment described above along the circumferential direction of the rotor 20 is in the range of 180 to 150 electrical degrees. This allows the length (width A) of the salient pole portions 126, 226 along the circumferential direction of the rotor 20 to be longer than the length (width C) of the teeth 116 along the circumferential direction of the rotor 20 in the rotating electric machines 100, 200 having 12 slots and 10 magnetic poles.

[0081] Moreover, the rotor 20 according to the above-described first to third embodiments has P (P is a natural number equal to or greater than 2) magnetic poles. The number of teeth 116 of the stator 10 is S (S is a natural number equal to or greater than 3). The number of slots per pole per phase (S / P / 3) is 0.25 or more and 0.5 or less. This makes it possible to reduce sixth-order integer multiple harmonic torque ripple in a rotating electric machine with fractional slots that improves the output voltage waveform.

[0082] Moreover, the rotor 20 according to the first to third embodiments described above is disposed outside the stator 10. That is, the rotor 20 according to the first to third embodiments is an outer rotor. This allows the salient pole portions to be shaped so as to widen as they move away from the air gap. As a result, magnetic flux can easily pass through portions of the salient pole portions other than the recesses, and a decrease in the magnetic resistance of the salient pole portions can be suppressed.

[0083] On the other hand, when the rotor 20 is an inner rotor arranged outside the stator 10, the salient poles have a shape that narrows as it moves away from the air gap. Therefore, the structure is such that the magnetic flux is less likely to pass through the salient poles than in an outer rotor. As a result, it is more difficult to suppress the decrease in magnetic resistance of the salient poles than in an outer rotor.

[0084] The above describes the embodiment of the rotating electric machine of the present invention, including its functions and effects. However, the rotating electric machine of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the invention described in the claims.

[0085] The above-mentioned embodiments have been described in detail to clearly explain the present invention, and are not necessarily limited to those including all of the configurations described. It is also possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to add, delete, or replace a part of the configuration of each embodiment with another configuration.

[0086] For example, in the above-described third embodiment, the corners at both ends of the width A of the salient pole portion 326 are cut obliquely. However, the corners at both ends of the width A of the salient pole portion 326 may be cut in an arc shape. [Explanation of symbols]

[0087] Reference Signs List 4...shaft, 6...rotor case, 10...stator, 20...rotor, 100, 200, 300...rotating electric machine (motor), 102...air gap, 104...slot, 110...stator yoke, 112...armature winding, 112A, 112B...conductor, 116...teeth, 116a...body portion, 116b...flange portion, 120...rotor yoke, 122...permanent magnet, 126, 226, 326...salient pole portion, 228, 328...recess

Claims

1. A rotating electric machine including an annular rotor having a plurality of permanent magnets and rotating about a rotation axis, and an annular stator having a plurality of teeth facing the plurality of permanent magnets via gaps in a radial direction of the rotor, The plurality of permanent magnets are magnetized in the same radial direction of the rotor, the rotor has a plurality of salient poles located between adjacent permanent magnets, a length of the salient pole portion along a circumferential direction of the rotor is longer than a length of the tooth along the circumferential direction of the rotor, a distance between the salient pole portion and the tooth in a radial direction of the rotor is longer than a distance between the permanent magnet and the tooth in a radial direction of the rotor, The salient pole portion has a recess on a surface facing the gap, The length of the recess along the circumferential direction of the rotor is set within a range of ±20% of the length of the tooth along the circumferential direction of the rotor. Rotating electric motor.

2. The cross section of the recess perpendicular to the rotation axis is formed in an arc shape, a polygonal shape, or a V shape. The rotating electric machine according to claim 1 .

3. The corners of the salient pole portions at both ends in the circumferential direction of the rotor are cut obliquely or in an arc shape. The rotating electric machine according to claim 1 .

4. The length of the salient pole portion along the circumferential direction of the rotor is in the range of 180 to 150 electrical degrees. The rotating electric machine according to any one of claims 1 to 3.

5. The rotor has P magnetic poles (P is a natural number equal to or greater than 2), The number of teeth of the stator is S (S is a natural number equal to or greater than 3), The number of slots per pole per phase is 0.25 or more and 0.5 or less. The rotating electric machine according to any one of claims 1 to 3.

6. The rotor is disposed outside the stator. The rotating electric machine according to any one of claims 1 to 3.

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