Rotating electric machine

Abstract

A rotor core (21) has: magnet slots (22) into which N layers (N is a natural number) of magnets (22) are inserted; and flux barriers (24) disposed so as to extend in the magnet slots (22). On the outer peripheral part of the rotor core (21), n types (n is an integer of 2 or more) of a plurality of rotor outer peripheral grooves (50, 60) are disposed at positions symmetrical with respect to the d-axis. The plurality of rotor outer peripheral grooves (50, 60) include a q-axis rotor outer peripheral groove (60) having a groove bottom part at a position overlapping the q-axis. The plurality of rotor outer peripheral grooves (50, 60) are configured such that combinations thereof in which the the groove bottom parts become deeper from the d-axis toward the q-axis are present.

Description

Rotating electrical machine

[0001] The present disclosure relates to a rotating electrical machine.

[0002] As a rotating electrical machine for electric vehicles, hybrid vehicle applications, etc., an embedded magnet type motor is adopted. Along with being small-sized, high-output, and high-efficiency, there are also high requirements for quietness, and it is important to have low torque ripple and low vibration. In order to suppress torque ripple and vibration, it is effective to change the magnetic flux density distribution in the air gap and reduce the harmonic magnetic flux, and generally, grooves are arranged on the outer periphery of the rotor. On the other hand, the demand for further lower torque ripple is increasing, and a rotor structure that can further suppress torque ripple and vibration is required. (For example, refer to Patent Document 1)

[0003] Japanese Patent Application Laid-Open No. 2008-278553

[0004] In Patent Document 1, a structure is proposed in which a bridge for holding the centrifugal force is formed by the grooves on the outer periphery of the rotor, and torque ripple can be suppressed while relaxing the stress. However, as described above, since the demand for further lower torque ripple is increasing, a rotor structure that can further suppress torque ripple and vibration is required.

[0005] The present disclosure discloses a technology for solving the above problems, and an object thereof is to provide a rotating electrical machine having a rotor structure that can further suppress torque ripple and vibration.

[0006] The rotating electric machine of the present disclosure comprises a stator having a stator core having an annular yoke portion and a plurality of teeth projecting radially from the yoke portion, and armature windings wound in a plurality of winding slots formed between the teeth, and a rotor having a rotor core and magnets disposed within the rotor core, wherein the rotor core has magnet slots for inserting N layers (N is a natural number) of the magnets, and flux barriers extending and disposed in the magnet slots, and on the outer periphery of the rotor core, a plurality of rotor outer periphery grooves of n types (n is an integer of 2 or more) are arranged at positions symmetrical with respect to the d axis, the plurality of rotor outer periphery grooves include q-axis rotor outer periphery grooves having the bottom of the groove at a position overlapping with the q axis, and the plurality of rotor outer periphery grooves are configured such that there exist combinations in which the depth of the bottom of the groove increases as you move from the d axis toward the q axis.

[0007] The rotating electric machine of this disclosure provides a rotating electric machine having a rotor structure that can further suppress torque ripple and vibration.

[0008] This is a cross-sectional view showing the overall configuration of the rotating electric machine according to Embodiment 1. This is a diagram showing a part of the axial cross-section of the rotating electric machine according to Comparative Example 1. This is a diagram showing a part of the axial cross-section of the rotating electric machine according to Embodiment 1. Figures 4A, 4B, 4C, and 4D are enlarged views showing the outer peripheral groove of the first rotor of the rotating electric machine according to Embodiment 1. This is an enlarged view of the outer peripheral portion of the rotor of the rotating electric machine according to Embodiment 1. This is a diagram showing the torque ripple waveforms of the rotating electric machine according to Comparative Example 1 and Embodiment 1. This is an axial cross-sectional view divided into six sections in the circumferential direction for a 6-pole 54-slot distributed winding motor, which is a modified example 1 of the rotating electric machine according to Embodiment 1. This is an axial cross-sectional view of a double V-shaped embedded magnet rotor, which is a modified example 2 of the rotating electric machine according to Embodiment 1. This is an axial cross-sectional view of a triple V-shaped embedded magnet rotor, which is a modified example 3 of the rotating electric machine according to Embodiment 1. This is an axial cross-sectional view of a single I-shaped embedded magnet rotor, which is a modified example 4 of the rotating electric machine according to Embodiment 1. This is an axial cross-sectional view of the rotor, which is a modified example 5 of the rotating electric machine according to Embodiment 1. This is an axial cross-sectional view of the rotor, which is a modified example 6 of the rotating electric machine according to Embodiment 1. This is an enlarged view showing the outer peripheral portion of the rotor of the rotating electric machine according to Embodiment 2. This is an enlarged view showing the outer circumference of a rotor, which is a modified example of the rotating electric machine according to Embodiment 2. This is an enlarged view showing the outer circumference of a rotor, which is a modified example of the rotating electric machine according to Embodiment 3. This is a diagram showing a part of the axial cross-section of the rotating electric machine according to Comparative Example 2. This is a diagram showing a part of the axial cross-section of the rotating electric machine according to Embodiment 4. This is an enlarged view of the outer circumference of the rotor of the rotating electric machine according to Embodiment 4. This is a diagram showing the torque ripple waveforms of the rotating electric machines according to Comparative Example 2 and Embodiment 4. This is an enlarged view of the outer circumference of a rotor, which is a modified example of the rotating electric machine according to

[0009] Embodiment 1. Figure 1 is a cross-sectional view showing the overall configuration of a rotating electric machine according to Embodiment 1, and is a cross-sectional view of a plane parallel to the axial direction of the rotating electric machine. As shown in Figure 1, the rotating electric machine 100 has a cylindrical housing 1, and holds a stator 10 inside the housing 1. The stator 10 comprises a stator core 13 and armature windings (hereinafter referred to as coils) 14. A rotor 20 is arranged inside the stator 10, and the shaft 7 and rotor 20 are rotatably mounted via bearings 6 fitted to the housing 1.

[0010] Before describing the features of the rotating electric machine according to Embodiment 1, we will first explain the general structure of a rotating electric machine based on the cross-sectional view of the rotating electric machine according to Comparative Example 1 in Figure 2.

[0011] Figure 2 shows a cross-sectional view of a rotating electric machine as Comparative Example 1, which is a partial cross-sectional view obtained by dividing the axial cross-section of the rotating electric machine into eight sections in the circumferential direction. As shown in Figure 2, the stator 10 has a stator core 13 having an annular yoke portion 11 and a plurality of teeth 12 protruding radially inward from the yoke portion 11, and coils 14 are wound in winding slots formed between the teeth 12. The stator core 13 is constructed by stacking a plurality of electromagnetic steel sheets in the axial direction of the rotating electric machine in order to reduce iron loss generated in the stator core 13. The coils 14 are wound as fully distributed windings to improve the winding coefficient and increase the torque and output of the rotating electric machine, and in the example of Figure 2, they are housed in 48 winding slots. In the rotating electric machine of Comparative Example 1 shown in Figure 2, and the rotating electric machines of the embodiments described in Figure 3 and later, we will describe a rotating electric machine with fully wound windings in order to improve the winding coefficient and achieve high torque and high output, but similar effects can be obtained even if short-section windings are applied to reduce torque ripple.

[0012] The rotor 20 consists of a rotor core 21 having an outer circumference shape with the same curvature as the rotor outer diameter, and a substantially rectangular magnet 22. The rotor core 21 is constructed by stacking multiple electromagnetic steel sheets in the axial direction of the rotating electric machine in order to reduce iron loss generated in the rotor core 21. The rotor core 21 has magnet slots 23 for inserting and holding the magnets 22, and flux barriers 24 arranged to extend to both ends of the magnet slots 23. The magnet slots 23 are formed in pairs symmetrically with respect to the d-axis, and the pair of magnet slots 23 are configured in a V-shape such that the distance between them decreases as they move toward the inner circumference of the rotor. In Figure 2, the magnet slots 23 are arranged in only one layer in the radial direction of the rotor. In the following description, the rotor structure in Figure 2 will be referred to as a single-layer V-shaped embedded magnet rotor.

[0013] The inside of the flux barrier 24 is filled with air or a non-magnetic material such as resin. Each magnet 22 is roughly rectangular in shape, with its corners beveled, and is housed in a magnet slot 23. Each magnet 22 is magnetized parallel to the direction parallel to the shorter side of the roughly rectangular magnet 22 (arrow M1 in Figure 2), forming one magnetic pole. The entire rotating electric machine is configured to form eight magnetic poles. In this case, each magnet 22 may be divided in the direction of the longer side in Figure 2, or in the axial direction, in order to reduce eddy current losses during motor drive. In this way, the rotating electric machine shown in Figure 2 is configured as an 8-pole, 48-slot distributed winding motor equipped with a single V-shaped embedded magnet rotor.

[0014] (Structure of Embodiment 1) Next, the structural features of the rotating electric machine according to Embodiment 1 will be explained with reference to Figure 3. Figure 3 shows a partial axial cross-sectional view of the rotating electric machine according to Embodiment 1, divided into eight sections in the circumferential direction. The basic configuration is the same as that of Figure 2, which is described as Comparative Example 1. However, in the rotating electric machine of Embodiment 1 shown in Figure 3, the first rotor outer peripheral groove 50 and the q-axis rotor outer peripheral groove 60 are arranged on the outer periphery of the rotor core 21, with the d-axis as the axis of symmetry. The q-axis rotor outer peripheral groove 60 is arranged on the q-axis, as will be described later. In order to arrange the q-axis rotor outer peripheral groove 60, a part 24a on the outer periphery side of the flux barrier 24 is moved to the inner periphery side so that the radial thickness of the bridge 25, which is the part between the outer periphery of the flux barrier 24 and the outer periphery of the rotor core 21, does not change. At this time, the radial thickness of the bridge 25 is ensured to be at least twice the thickness of the electromagnetic steel sheet that constitutes the rotor core 21. In this way, an 8-pole, 48-slot distributed winding motor is constructed, equipped with a single V-shaped embedded magnet rotor having a groove on the outer circumference of the first rotor and a groove on the outer circumference of the q-axis rotor. Furthermore, the number of phases of the alternating current supplied to the armature winding (coil) is three.

[0015] Figures 4A, 4B, 4C, and 4D show enlarged views of the first rotor outer circumferential groove of the rotor core of the rotating electric machine according to Embodiment 1. Here, the features of the rotor outer circumferential groove in this embodiment will be described. In Figure 4A, the first rotor outer circumferential groove 50 is located on the outer circumference of the rotor core 21, which has a rotor outer circumferential shape with the same curvature as the outer diameter of the rotor 20. Starting from the bent portion 50a, it begins to recess from the outer circumference side to the inner circumference side of the rotor, passes through the intermediate portion 50b, which is the part between the bent portion 50a and the bottom portion 50c, and reaches the bottom portion 50c, forming a recess on the outer circumference of the rotor core 21. The bottom portion 50c of the first rotor outer circumferential groove 50 is configured to be concentric with the outer circumference of the rotor. Although the first rotor outer circumferential groove 50 was described in Figure 4A, the q-axis rotor outer circumferential groove 60 has a similar shape, although the groove depth is different from that of the first rotor outer circumferential groove 50.

[0016] In Figure 4A, the bent portion 50a is shown as an example of an unchamfered corner, but as in the first rotor outer circumference groove 50 in Figure 4B, as long as the inward curve begins from the bent portion 50a, the corner may be smoothly connected by rounding 50d or the like from the viewpoint of press die life, safety, and strength of the electromagnetic steel sheet.

[0017] Figure 4A illustrates a case where the bottom of the first rotor outer circumferential groove 50 is concentric with the outer circumference of the rotor 20. However, any continuous identical shape is acceptable, and it may be a straight bottom 50c1 as shown in the first rotor outer circumferential groove 50 in Figure 4C, or an arc-shaped groove 50c2 that is convex toward the inner circumference as shown in the first rotor outer circumferential groove 50 in Figure 4D. However, in the case of a circular groove 50c2, the position of the groove bottom used to compare the relative depths of each groove, which is assumed to be desirable in this embodiment, should be the deepest part of the circular groove, that is, the position where the distance from the outer circumferential surface of the rotor is maximum.

[0018] Figures 4A to 4D illustrate the outer circumferential groove of the first rotor, but the same principles can be applied to the outer circumferential grooves of the second and third rotors, which will be described later.

[0019] Figure 5 shows an enlarged view of the outer circumference of the rotor of the rotating electric machine according to Embodiment 1. As shown in Figure 5, the flux barrier 24 is composed of an inner-circumferential flux barrier 24A that extends toward the inner circumference of the d-axis and an outer-circumferential flux barrier 24B that extends toward the outer circumference of the q-axis. The outer circumference of the outer-circumferential flux barrier 24B is shaped such that the bridge thickness increases toward the q-axis, starting from the minimum bridge portion 25a where the radial thickness of the bridge 25 is minimized. The first rotor outer circumference groove 50 and the q-axis rotor outer circumference groove 60 are arranged symmetrically with respect to the d-axis, as shown in Figure 3. The first rotor outer circumference groove 50 is located on the d-axis side within the range of the magnetic pole arc angle θp, which is the angle formed by the rotation center O of the rotor 20 and the bent portion 24c on the d-axis side of the outer-circumferential flux barrier 24B, and the depth of the groove from the outer circumference of the rotor 20 is d1.

[0020] Here, in Figure 5, the q-axis magnetic path angle is defined as θq_path, which is the angle formed by the q-axis and the straight line connecting the rotation center O of the rotor 20 and the end of the non-magnetic part that is closest to the q-axis (in this embodiment, the q-axis side end 24d of the outer peripheral flux barrier 24B). The q-axis groove angle is defined as θq, which is the angle formed by the q-axis and the straight line connecting the rotation center O of the rotor 20 and the d-axis side end of the q-axis rotor outer peripheral groove 60. Furthermore, the bridge minimum part angle is defined as θb, which is the angle formed by the q-axis and the straight line connecting the rotation center O and the bridge minimum part 25a. As shown in Figure 18, which will be described later, the q-axis rotor outer peripheral groove 60 has a symmetrical shape with respect to the q-axis, and the q-axis groove angle θq is configured such that θq_path < θq < θb in relation to the q-axis magnetic path angle θq_path and the bridge minimum part angle θb, and the depth of the groove from the outer circumference of the rotor 20 is d2. Furthermore, the depths of the outer grooves 50 of the first rotor and 60 of the outer grooves 60 of the q-axis rotor are in the relationship d1 < d2. In Figure 5, the configuration is such that θq_path < θq < θb, but by satisfying the relationship θq ≥ θq_path, the effect of torque ripple reduction can be enhanced. Also, by satisfying the relationship θb ≥ θq, the stress on the bridge, which is most affected by centrifugal force, can be alleviated.

[0021] Figure 6 shows the torque ripple waveforms of the rotating electric machine of Comparative Example 1 shown in Figure 2 and the rotating electric machine of Embodiment 1 shown in Figure 3. It can be seen that by changing the structure of the rotating electric machine of Embodiment 1 to the structure of Comparative Example 1 shown in Figure 2, the torque ripple can be reduced, and the peak value of the torque ripple can be reduced from 10.2% to 3.0%.

[0022] The appropriate position, length, and depth of the first rotor outer circumferential groove 50 and the q-axis rotor outer circumferential groove 60 in Figure 3 are determined by exploring and using electromagnetic structure analysis and structural analysis, taking into account the strength of the rotor structure, in order to fully achieve the effect of reducing torque ripple. The structures of the first rotor outer circumferential groove, the second rotor outer circumferential groove, the third rotor outer circumferential groove, and the q-axis rotor outer circumferential groove, as described in the following embodiments, are determined in the same manner.

[0023] (Modification of Embodiment 1) Figure 7 shows modification 1 of the rotating electric machine according to Embodiment 1, and shows an axial section cross-sectional view of the rotating electric machine divided into six parts in the circumferential direction when it is a 6-pole 54-slot distributed winding motor. The rotating electric machine shown in Figure 7 is a modification of the 8-pole 48-slot distributed winding motor in Figure 3 to a 6-pole 54-slot distributed winding motor. The configuration of the rotating electric machine shown in Figure 7 is the same as the configuration described in Figures 3 to 6.

[0024] Figure 8 shows a modified example 2 of the rotating electric machine according to Embodiment 1, and shows an axial cross-sectional view in which the rotating electric machine is divided into eight sections in the circumferential direction. In Figure 8, the magnet slots 23A and 23B are arranged in two layers in the rotor radial direction. That is, the magnet slots 23A and 23B are each formed in pairs at symmetrical positions with respect to the d-axis, and the pair of magnet slots 23A and 23B are configured to be V-shaped such that the distance between them decreases as they move toward the inner circumference of the rotor. A pair of magnets 22A are housed in the pair of magnet slots 23A, and a pair of magnets 22B are housed in the pair of magnet slots 23B. Here, the rotating electric machine shown in Figure 8 is called a rotating electric machine equipped with a double V-shaped embedded magnet rotor. The rotating electric machine shown in Figure 8 is equipped with a first rotor outer circumferential groove 50-1 and a second rotor outer circumferential groove 50-2 in addition to the q-axis rotor outer circumferential groove 60 of the rotating electric machine shown in Figure 3. The outer circumferential groove 50-1 of the first rotor is positioned on the d-axis side of the magnetic pole arc angle θp1 of the first layer magnet 22A, and the outer circumferential groove 50-2 of the second rotor is positioned on the d-axis side of the magnetic pole arc angle θp2 of the second layer magnet 22B. The outer circumferential groove 60 of the q-axis rotor has the same characteristics as the outer circumferential groove 60 of the q-axis rotor in Figure 3. Furthermore, if the groove depths of the outer circumferential groove 50-1 of the first rotor, the outer circumferential groove 50-2 of the second rotor, and the outer circumferential groove 60 of the q-axis rotor are d1, d2, and dq, then d1 < d2 < dq. The other configurations are the same as those of the rotating electric machine in Figure 3.

[0025] Figure 9 shows a third modified example of the rotating electric machine according to Embodiment 1, and shows an axial cross-sectional view in which the rotating electric machine is divided into eight sections in the circumferential direction. In Figure 9, the magnet slots 23A, 23B, and 23C are arranged in three layers in the rotor radial direction. That is, the magnet slots 23A, 23B, and 23C are each formed in pairs at symmetrical positions with respect to the d-axis, and the pairs of magnet slots 23A, 23B, and 23C are configured to be V-shaped such that the distance between them decreases as they move toward the inner circumference of the rotor. A pair of magnets 22A are housed in the pair of magnet slots 23A, a pair of magnets 22B are housed in the pair of magnet slots 23B, and a pair of magnets 22C are housed in the pair of magnet slots 23C. Here, the rotating electric machine shown in Figure 9 is called a rotating electric machine equipped with a triple V-shaped embedded magnet rotor. The rotating electric machine shown in Figure 9 is modified from the rotating electric machine shown in Figure 3 by adding a first rotor outer circumferential groove 50-1, a second rotor outer circumferential groove 50-2, and a third rotor outer circumferential groove 50-3 in addition to the q-axis rotor outer circumferential groove 60. The first rotor outer circumferential groove 50-1 is positioned on the d-axis side of the magnetic pole arc angle θp1 of the first layer magnet 22A, the second rotor outer circumferential groove 50-2 is positioned on the d-axis side of the magnetic pole arc angle θp2 of the second layer magnet 22B, and the third rotor outer circumferential groove 50-3 is positioned on the d-axis side of the magnetic pole arc angle θp3 of the third layer magnet 22C. The q-axis rotor outer circumferential groove 60 has the same characteristics as the q-axis rotor outer circumferential groove 60 in Figure 3. Furthermore, if the groove depths of the outer circumferential grooves 50-1, 50-2, 50-3, and 60 of the first rotor, d1, d2, d3, and dq are denoted as d1, d2, d3, and dq, respectively, then d1 < d2 < d3 < dq. The other configurations are the same as those of the rotating electric machine shown in Figure 3.

[0026] Figure 10 shows a modified example 4 of the rotating electric machine according to Embodiment 1, and shows an axial cross-sectional view in which the rotating electric machine is divided into eight sections in the circumferential direction. As shown in Figure 10, the magnet slot 23D housing the magnet 22D is configured in an I-shape so as to be approximately perpendicular to the d-axis. In other words, the rotating electric machine shown in Figure 10 is a modification of the configuration in Figure 3, with a single I-shaped embedded magnet rotor, while the other configurations are the same as those in Figure 3.

[0027] Figure 11 shows a modified example 5 of the rotating electric machine according to Embodiment 1, and shows an axial cross-sectional view in which the rotating electric machine is divided into eight sections in the circumferential direction. In Figure 11, the second rotor outer circumferential groove 70 is positioned between the first rotor outer circumferential groove 50 and the q-axis rotor outer circumferential groove 60 in the circumferential direction, and the groove depths of the first rotor outer circumferential groove 50, the second rotor outer circumferential groove 70, and the q-axis rotor outer circumferential groove 60 are configured such that d2 < d1 < dq, where d1, d2, and dq are the groove depths, respectively. In other words, the rotating electric machine shown in Figure 11 is a modified version of the configuration in Figure 3 in which the rotor outer circumferential grooves are changed to three types and arranged so that the groove depths are d2 < d1 < dq, while the other configurations are the same as those in Figure 3. In Figure 11, there are two combinations such that the depth of the groove bottom increases from the d-axis towards the q-axis: the first rotor outer circumferential groove 50 and the q-axis rotor outer circumferential groove 60, and the second rotor outer circumferential groove 70 and the q-axis rotor outer circumferential groove 60.

[0028] Figure 12 shows a modified example 6 of the rotating electric machine according to Embodiment 1, and shows an axial cross-sectional view in which the rotating electric machine is divided into eight sections in the circumferential direction. In Figure 12, the second rotor outer circumferential groove 70 is positioned between the first rotor outer circumferential groove 50 and the q-axis rotor outer circumferential groove 60 in the circumferential direction, and the groove depths of the first rotor outer circumferential groove 50, the second rotor outer circumferential groove 70, and the q-axis rotor outer circumferential groove 60 are d1, d2, and dq, respectively, such that dq < d1 < d2. In other words, the rotating electric machine shown in Figure 12 is a modified version of Embodiment 1 in which the rotor outer circumferential grooves are changed to three types and arranged so that the groove depths are dq < d1 < d2, while the other configurations are the same as in Figure 3. In Figure 12, there is one combination of the first rotor outer circumferential groove 50 and the second rotor outer circumferential groove 70 such that the depth of the groove bottom increases as you move from the d-axis to the q-axis.

[0029] (Explanation of the effects of Embodiment 1) In this embodiment (Figure 3), the stator has an annular yoke portion and a stator core having a plurality of teeth protruding radially from the yoke portion, and armature windings wound in a plurality of winding slots formed between the teeth, and the rotor has a rotor core and magnets disposed within the rotor core, the rotor core has magnet slots for inserting the N-layer (N is a natural number) magnets, and flux barriers extending and disposed in the magnet slots, the outer circumference of the rotor core has n types (n is an integer of 2 or more) of rotor outer circumferential grooves arranged at positions symmetrical with respect to the d axis, the plurality of rotor outer circumferential grooves include q-axis rotor outer circumferential grooves having the bottom of the groove at a position overlapping with the q axis, and the plurality of rotor outer circumferential grooves are configured such that there exist combinations in which the depth of the bottom of the groove increases from the d axis toward the q axis, so that by arranging multiple types of rotor outer circumferential grooves, the magnetic flux density distribution in the air gap can be changed and torque ripple can be reduced. Furthermore, by positioning the q-axis rotor outer circumferential groove in a location that overlaps with the q-axis, the portion of the rotor core overlapping with the q-axis has high rigidity, thus reducing torque ripple while mitigating stress on the rotor. Moreover, by configuring multiple types of rotor outer circumferential grooves to exist in combinations such that the depth of the groove bottom increases from the d-axis towards the q-axis, it is possible to suppress harmonic flux components more effectively while mitigating stress on the rotor and reducing torque ripple. Also, even when the number of pole slots differs as shown in Figure 7, or when the magnet arrangement structure, the number of magnet layers, and the number of types of rotor outer circumferential grooves differ as shown in Figures 8 to 12, the aforementioned characteristics are present, and similar effects are achieved. Furthermore, as shown in Figure 11, since the rotor outer circumferential groove depths are d2 < d1 < dq, and rotor outer circumferential grooves with the relationships d1 < dq and d2 < dq exist, similar effects are achieved. Furthermore, as shown in Figure 12, even when the rotor outer circumferential groove depths are dq < d1 < d2, rotor outer circumferential grooves with the relationship d1 < d2 exist, and similar effects are achieved.

[0030] Furthermore, in this embodiment (Figure 3), the rotor core is configured such that the depth of the bottom of each rotor outer groove increases sequentially from the d-axis to the q-axis. Since the groove depth increases from the d-axis to the q-axis in all rotor outer grooves, the effects of torque ripple reduction and stress relaxation can be enhanced. Also, even when the number of pole slots differs as shown in Figure 7, or when the magnet arrangement structure, the number of magnet layers, and the number of types of rotor outer grooves differ as shown in Figures 8 to 12, the above-mentioned features are retained, and similar effects are achieved.

[0031] Furthermore, in this embodiment (Figure 3), if the q-axis groove angle is θq, the q-axis magnetic path angle is θq_path, and the minimum bridge angle is θb, the configuration is such that θq_path < θq < θb, satisfying the relationship θq ≥ θq_path (Claim 3), thus enhancing the torque ripple reduction effect. Also, since the relationship θb ≥ θq is satisfied (Claim 4), the stress on the bridge, which is most affected by centrifugal force, can be alleviated. Moreover, even when the number of pole slots differs as shown in Figure 7, or when the magnet arrangement structure, the number of magnet layers, and the number of types of rotor outer circumference grooves differ as shown in Figures 8 to 12, the above-mentioned features are retained, and similar effects are achieved.

[0032] Furthermore, in this embodiment (Figure 3), the shape of the bottom surface of the q-axis rotor outer circumferential groove is configured to be concentric with the outer circumference of the rotor core, thereby maintaining high rigidity of the entire rotor. Also, as shown in Figure 7, even when the number of pole slots is different, or as shown in Figures 8 to 12, even when the magnet arrangement structure, the number of magnet layers, and the number of types of rotor outer circumferential grooves are different, the aforementioned features are retained, and similar effects are achieved.

[0033] Furthermore, in this embodiment (Figure 3), since all of the multiple rotor outer circumferential grooves are configured to be concentric with the outer circumference of the rotor core, the overall rigidity of the rotor can be maintained more effectively. Also, as shown in Figure 7, even when the number of pole slots is different, or as shown in Figures 8 to 12, even when the magnet arrangement structure, the number of magnet layers, and the number of types of rotor outer circumferential grooves are different, the above-mentioned features are retained, and similar effects are achieved.

[0034] Furthermore, in this embodiment (Figure 3), in the rotor core, each rotor outer circumferential groove among the plurality of rotor outer circumferential grooves that are adjacent in the circumferential direction is individually arranged on either side of the curved surface that constitutes the outer circumference of the rotor core. Therefore, the torque reduction effect is achieved while minimizing the torque reduction compared to a rotor structure without rotor outer circumferential grooves. Also, as shown in Figure 7, even when the number of pole slots is different, or as shown in Figures 8 to 12, even when the magnet arrangement structure, the number of magnet layers, and the number of types of rotor outer circumferential grooves are different, the above-mentioned features are retained, and similar effects are achieved.

[0035] Furthermore, in this embodiment (Figure 3), if the number of magnet layers is N (where N is a natural number) and the number of types of rotor outer grooves is n (where n is an integer of 2 or more), then N=1, n=2, and the configuration satisfies n=N+1. This minimizes the number of rotor outer grooves to be arranged, improves the maintainability of the rotor core press die, and reduces manufacturing costs. Also, as shown in Figure 7, even when the number of pole slots is different, or as shown in Figures 8 to 10, even when the magnet arrangement structure, the number of magnet layers, and the number of types of rotor outer grooves are different, the aforementioned features are retained, and similar effects are achieved.

[0036] Furthermore, in this embodiment (Figure 3), if S is the number of winding slots in the stator, t is the number of phases of the AC current supplied to the armature winding, and p is the number of magnetic poles in the rotor, then if M is the integer obtained by rounding up S / t / p to the nearest whole number, then S = 48, t = 3, p = 8, and M = 2, satisfying N ≤ M. Here, M represents the number of slots per pole per phase. The number of slots per pole per phase M affects the smoothness of the rotating magnetic field generated by the motor, and is therefore determined considering iron loss, torque ripple, manufacturing cost, etc. If the number of slots per pole per phase M is large relative to the number of magnet layers, the magnetic flux of adjacent stator teeth may short-circuit through the rotor core, increasing the magnetic flux density of the teeth and increasing the iron loss generated in the stator, which can worsen motor efficiency. In this embodiment, since N ≤ M is satisfied, it is possible to prevent the magnetic flux of adjacent stator teeth from short-circuiting and increasing the iron loss generated in the stator. As a result, the configuration suppresses motor losses, improves motor efficiency, and reduces torque ripple. Furthermore, even when the number of pole slots differs as shown in Figure 7, or when the magnet arrangement structure, the number of magnet layers, and the number of types of rotor outer grooves differ as shown in Figures 8, 10, 11, and 12, the same effect is achieved if the aforementioned features are present.

[0037] Furthermore, in this embodiment (Figure 3), in the rotor, the magnet slots housing the magnets are formed in pairs symmetrically with respect to the d-axis, and the pair of magnet slots are configured in a V-shape such that the distance between them decreases as they move toward the inner circumference. This allows for the placement of more magnets in the rotor, thereby improving the magnet torque. In addition, by placing more non-magnetic areas inside the rotor, the reluctance torque can also be improved, enabling high torque over a wide operating range. Moreover, similar effects are achieved even when the number of pole slots differs, as shown in Figure 7, or when the number of magnet layers and the number of types of grooves on the outer circumference of the rotor differ, as shown in Figures 8 and 9.

[0038] Furthermore, in a modified example of this embodiment (Figure 10), the magnet slots housing the magnets in the rotor are configured in an I-shape so as to be substantially perpendicular to the d-axis. This reduces the number of magnets, simplifies the structure, and reduces the number of parts, thus effectively lowering costs. When used as a motor for electric vehicles, hybrid vehicles, etc., increasing the magnetic pole arc angle and arranging more magnets in order to achieve high torque and high output increases the magnetomotive force harmonics, which in turn increases torque ripple and vibration. However, by applying the structure of this embodiment, it is possible to achieve cost reduction, low torque ripple, and low vibration simultaneously.

[0039] Furthermore, in this embodiment (Figure 3), the rotor is configured such that the number of magnet layers N (where N is a natural number) is N=1. Since the number of magnet layers is 1, the number of parts can be minimized, and manufacturing costs can be reduced. In motors with N≧2, the number of parts and manufacturing processes increase, resulting in higher costs, but magnetomotive force harmonics can be reduced by devising the magnet arrangement. On the other hand, if a motor with N=1 is adopted to minimize the number of parts and achieve cost reduction, magnetomotive force harmonics become larger, leading to increased torque ripple or vibration. Therefore, by applying the structure of this embodiment, even with a motor with N=1, low torque ripple and low vibration can be achieved, and cost reduction can also be attained. Moreover, even if the number of pole slots is different, as shown in Figure 7, or the structure of the magnet arrangement is different, as shown in Figure 10, the same effects can be obtained if the above-mentioned features are present.

[0040] Embodiment 2. (Description of the structure of Embodiment 2) The basic configuration of the rotating electric machine according to Embodiment 2 is the same as that of Embodiment 1, so only the different parts of the rotor outer circumference groove will be described. Figure 13 shows an enlarged view of the outer circumference of the rotor of the rotating electric machine according to Embodiment 2. As shown in Figure 13, the outer circumference of the rotor core 21 has a first rotor outer circumference groove 50, a second rotor outer circumference groove 70, and a q-axis rotor outer circumference groove 60, all of which are concentric grooves that are concentric with the outer circumference of the rotor core 21, and are configured such that d1 < d2 < dq, where their respective depths are d1, d2, and d3. The second rotor outer circumference groove 70 and the q-axis rotor outer circumference groove 60 are connected, and only the first rotor outer circumference groove 50 is individually positioned on the d-axis side of the magnet pole arc angle, sandwiching the curved surface that constitutes the outer circumference of the rotor core 21 from the other rotor outer circumference grooves. Furthermore, although not shown in the diagram, if the q-axis magnetic path angle θq_path, the q-axis groove angle θq, and the bridge minimum angle θb are defined in the same positions as in Embodiment 1, the outer circumferential groove 60 of the q-axis rotor has a symmetrical shape with respect to the q-axis and is configured such that θq_path < θq < θb.

[0041] Figure 14 shows a modified example of the rotating electric machine according to Embodiment 2, and displays an enlarged view of the outer circumference of the rotor when all rotor outer circumference grooves are connected. As shown in Figure 14, this modified example has a first rotor outer circumference groove 50 and a q-axis rotor outer circumference groove 60 on the outer circumference of the rotor core 21, and the first rotor outer circumference groove 50 and the q-axis rotor outer circumference groove 60 are concentric grooves that are concentric with the outer circumference of the rotor core 21. The first rotor outer circumference groove 50 and the q-axis rotor outer circumference groove 60 have depths d1 and dq, respectively, and are configured such that d1 < dq. Furthermore, the first rotor outer circumference groove 50 and the q-axis rotor outer circumference groove 60 are connected, and there are no individually arranged rotor outer circumference grooves. In addition, similar to the q-axis rotor outer circumference groove 60 in Figure 13, it is configured such that θq_path < θq < θb.

[0042] (Description of the Effects of Embodiment 2) In this embodiment, the description of the effects achieved by the same structure as in Embodiment 1 is omitted. In this specification, the treatment as another groove constituting a plurality of rotor outer peripheral grooves is not limited to the case where the grooves are discretely arranged at circumferential positions where it is clear that they are different grooves. For rotor outer peripheral grooves having a bottom with a certain depth within a certain range, such as the configuration of Embodiment 2 described above and its modifications, they are treated as another groove.

[0043] In this embodiment (FIG. 13), in the rotor core, among the plurality of rotor outer peripheral grooves, those adjacent to each other in the circumferential direction are configured to be connected. Therefore, the stress concentration acting on the groove ends of the rotor outer peripheral grooves can be alleviated. Also, as shown in FIGS. 7 to 11, even when the pole slots, the structure of the magnet arrangement, the number of magnet layers, and the number of types of rotor outer peripheral grooves and the groove depth are different, if they have the above-mentioned characteristics, the same effects can be achieved.

[0044] Also, in a modification of this embodiment (FIG. 14), in the rotor core, among the plurality of rotor outer peripheral grooves, those adjacent to each other in the circumferential direction are configured to be all connected. Therefore, while alleviating the stress concentration acting on the groove ends of the rotor outer peripheral grooves, the number of pressing operations during rotor core manufacturing can be reduced, and the manufacturing cost can be lowered. Also, as shown in FIGS. 7 to 11, even when the pole slots, the structure of the magnet arrangement, the number of magnet layers, and the number of types of rotor outer peripheral grooves are different, if they have the above-mentioned characteristics, the same effects can be achieved.

[0045] Embodiment 3. (Description of the structure of Embodiment 3) The basic configuration of the rotating electric machine according to Embodiment 3 is the same as that of Embodiment 1, so only the different parts of the rotor outer circumferential groove will be described. Figure 15 shows an enlarged view of the outer circumferential part of the rotor of the rotating electric machine according to Embodiment 3. As shown in Figure 15, the outer circumferential part of the rotor core 21 has a first rotor outer circumferential groove 50 and a q-axis rotor outer circumferential groove 60. The first rotor outer circumferential groove 50 is a groove with a depth d1 and a circular cross-section, and the q-axis rotor outer circumferential groove 60 is a concentric groove with a depth d2 that is concentric with the outer circumferential part of the rotor core. The first rotor outer circumferential groove 50 is located on the d-axis side of the magnet pole arc angle. Although not shown, if the q-axis magnetic path angle θq_path, the q-axis groove angle θq, and the bridge minimum part angle θb are defined in the same positions as in Embodiment 1, the q-axis rotor outer circumferential groove 60 has a symmetrical shape with respect to the q-axis, and is configured such that θq_path < θq < θb.

[0046] Figure 16 shows an enlarged view of the outer circumference of a rotor in the case of a double V-shaped embedded magnet rotor, which is a modified example of the rotating electric machine according to Embodiment 3. As shown in Figure 16, this modified example has a first rotor outer circumference groove 50-1, a first rotor outer circumference groove 50-2, and a q-axis rotor outer circumference groove 60. The first rotor outer circumference groove 50-1 and the first rotor outer circumference groove 50-2 are circular grooves in cross-section, and the q-axis rotor outer circumference groove 60 is a concentric groove that is concentric with the outer circumference of the rotor core. The first rotor outer circumference groove 50-1 is located on the d-axis side of the magnetic pole arc angle of the first layer magnet 22A, and the first rotor outer circumference groove 50-2 is located on the d-axis side of the magnetic pole arc angle of the second layer magnet 22B. The q-axis rotor outer circumference groove 60 has the same characteristics as the q-axis rotor outer circumference groove 60 in Figure 15.

[0047] (Description of the Effects of Embodiment 3) In this embodiment, the description of the effects achieved by the same structure as in Embodiment 1 is omitted. In this embodiment (FIG. 15), in the rotor core, since the shape of the bottom surface of the q-axis rotor outer peripheral groove is configured to be concentric with the outer periphery of the rotor core, (Claim 5) even if other grooves other than the q-axis rotor outer peripheral groove are circular cross-section grooves, the bottom surface shape of the q-axis rotor outer peripheral groove is a concentric groove, so the rigidity of the entire rotor can be maintained high. Further, as shown in FIG. 16, even when the number of magnet layers and the number of rotor outer peripheral grooves are different, if the bottom surface shape of the q-axis rotor outer peripheral groove is a concentric groove, the same effect can be achieved. Therefore, even when the magnet arrangement structure, pole slots, number of magnet layers, and number of types of rotor outer peripheral grooves are different as shown in FIGS. 7 to 11, if they have the above-mentioned characteristics, the same effect can be achieved.

[0048] Embodiment 4. (Description of the Structure of Embodiment 4) FIG. 17 shows an axial cross-sectional view divided into 12 in the circumferential direction of a rotating electric machine according to Comparative Example 2. The rotating electric machine according to Comparative Example 2 is composed of a stator 10 and a rotor 20 disposed inside the stator 10 and rotatable, as shown in FIG. 1. As shown in FIG. 17, the stator 10 includes a yoke portion 11 divided in the circumferential direction, a stator core 13 formed by combining 36 stator core segments 13A having teeth 12 protruding in the radial direction in the circumferential direction, and armature windings (coils) 14 wound around winding slots formed between the teeth 12. The stator core 13 is formed by laminating electromagnetic steel sheets in the axial direction in order to reduce iron loss generated in the stator core 13. Further, the coil 14 is wound in a concentrated winding manner in order to lower the coil end and reduce the motor volume.

[0049] The rotor 20 consists of a rotor core 21 having an outer circumference shape with the same curvature as the rotor outer diameter, and a substantially rectangular magnet 22D. The rotor core 21 is constructed by laminating electromagnetic steel sheets in the axial direction to reduce iron loss generated in the rotor core 21. The rotor core 21 has magnet slots 23D for inserting and holding the magnet 22D, and flux barriers 24D arranged to extend from both ends of the magnet slots 23D. The magnet slots 23D are configured so that the magnets 22D are positioned perpendicular to the d-axis, and are arranged in only one layer in the radial direction (single-layer I-shaped embedded magnet rotor). The inside of the flux barriers 24D is filled with air or a non-magnetic material such as resin. The corners of the magnets 22D are chamfered, and they are housed in the magnet slots 23D. They are magnetized in parallel in a direction parallel to the short side of the magnet (arrow M1), and arranged so that 24 magnetic poles are formed in the rotating electric machine as a whole. In this case, the magnet 22D may be divided in the direction of the long side or the axial direction on Figure 17 in order to reduce eddy current losses during motor drive. In this way, a concentrated winding motor with 24 poles and 36 slots equipped with a single I-shaped embedded magnet rotor is constructed.

[0050] Figure 18 shows an axial cross-sectional view of a rotating electric machine according to Embodiment 4, divided into 12 circumferential sections. The basic configuration of the rotating electric machine according to Embodiment 4 is the same as in Figure 17, but a first rotor outer circumferential groove 50 and a q-axis rotor outer circumferential groove 60 are arranged on the outer circumferential part of the rotor core 21. In order to arrange the rotor outer circumferential grooves, the outer circumferential portion of the flux barrier 24D is moved to the inner circumferential side so that the radial thickness of the bridge 25D, which is the part between the flux barrier 24D and the outer circumferential part of the rotor core, does not change. At this time, the radial thickness of the bridge 25D is ensured to be at least twice the thickness of the electromagnetic steel sheet that constitutes the rotor core 21. In this way, a concentrated winding motor with 24 poles and 36 slots is constructed, equipped with a single I-shaped embedded magnet rotor having rotor outer circumferential grooves.

[0051] Figure 19 shows an enlarged view of the outer circumference of the rotor of the rotating electric machine according to Embodiment 4. As shown in Figure 19, the outer circumference of the flux barrier 24D is shaped such that the bridge thickness increases towards the q-axis, starting from the minimum bridge portion where the radial thickness of the bridge 25D is minimized. The first rotor outer circumference groove 50 and the q-axis rotor outer circumference groove 60 are configured to be symmetrical with respect to the d-axis. The first rotor outer circumference groove 50 is located on the outer circumference of the magnetic pole arc angle θp, which is the angle formed by the d-axis, the rotation center O, and the bent portion on the d-axis side of the flux barrier 24D, and the groove depth from the rotor outer circumference is d1. When the q-axis magnetic path angle θq_path, the q-axis groove angle θq, and the minimum bridge portion angle θb are defined in the same positions as in Embodiment 1, the q-axis rotor outer circumference groove 60 is symmetrical with respect to the q-axis and is configured such that θq_path < θq < θb. Furthermore, the depth of the groove 60 on the outer circumference of the q-axis rotor from the outer circumference of the rotor is dq, and the depths of the two rotor outer grooves are in the relationship d1 < dq.

[0052] Figure 20 shows the torque ripple waveforms of the rotating electric machine of Comparative Example 2 and the rotating electric machine according to Embodiment 4. It can be seen that by changing the structure of the rotating electric machine of Embodiment 4 from that of Comparative Example 2, the torque ripple can be reduced, and the peak value of the torque ripple can be reduced from 13.9% to 7.7%.

[0053] Figure 21 shows an enlarged view of the outer circumference of the rotor in the case of a single V-shaped embedded magnet rotor, which is a modified example of the rotating electric machine according to Embodiment 4. The rotating electric machine shown in Figure 21 is modified from the single I-shaped embedded magnet rotor of Figure 19 to a single V-shaped embedded magnet rotor, with the first rotor outer circumference groove 50 positioned on the d-axis side of the magnet pole arc angle θp, while the other configurations are the same as in Figure 19.

[0054] Figure 22 shows an enlarged view of the outer circumference of the rotor, which is a modified example of the rotating electric machine according to Embodiment 4, in which the outer circumference groove 50 of the first rotor is an arc-shaped groove and the outer circumference groove 60 of the q-axis rotor is a concentric groove. The rotating electric machine shown in Figure 22 has the configuration of Figure 19 changed to an arc-shaped groove for the outer circumference groove 50 of the first rotor, and is positioned on the d-axis side of the magnet pole arc angle θp, while the other configurations are the same as in Figure 19.

[0055] Figure 23 shows a modified example of the rotating electric machine according to Embodiment 4, which is a single V-shaped rotor. The figure shows an enlarged view of the outer circumference of the rotor when the outer circumference groove 50 of the first rotor is an arc-shaped groove and the outer circumference groove 60 of the q-axis rotor is a concentric groove. The rotating electric machine shown in Figure 23 is the same as the rotating electric machine in Figure 22, but the rotor has been changed to a single V-shaped rotor.

[0056] Figure 24 shows an enlarged view of the outer circumference of the rotor, which is a modified example of the rotating electric machine according to Embodiment 4, when all the rotor outer circumference grooves are connected. The rotating electric machine shown in Figure 24 is the same as in Figure 19, but with adjacent rotor outer circumference grooves of different types, namely the first rotor outer circumference groove 50 and the q-axis rotor outer circumference groove 60, all connected, and the other configurations are the same as in Figure 19.

[0057] (Explanation of the effects of Embodiment 4) In this embodiment (Figure 19), by arranging two types of rotor outer grooves, a first rotor outer groove and a q-axis rotor outer groove, the magnetic flux density distribution in the air gap can be changed, thereby reducing torque ripple. Furthermore, if the depths of the first rotor outer groove and the q-axis rotor outer groove are d1 and d2, then by satisfying the relationship d1 < d2, grooves with greater depth and a higher torque ripple reduction effect can be placed in the part of the rotor core with high rigidity, thus also easing the stress acting on the entire rotor. Moreover, as shown in Figures 21 to 23, even if the structure of the magnet arrangement and the shape of the rotor outer grooves are different, the above-mentioned features are present, and similar effects are achieved. In addition, although not shown, even if the number of pole slots, the number of magnet layers, and the number of rotor outer grooves are different, the above-mentioned features are present, and similar effects are achieved.

[0058] In this embodiment (Figure 19), since the groove depth of all rotor outer circumferential grooves increases from the d-axis to the q-axis, the effects of torque ripple reduction and stress relaxation can be enhanced. Furthermore, as shown in Figures 21 to 23, even if the structure of the magnet arrangement and the shape of the rotor outer circumferential grooves are different, the aforementioned features are present and similar effects are achieved. In addition, although not shown, even if the number of pole slots, the structure of the magnet arrangement, the number of magnet layers, and the number of rotor outer circumferential grooves are different, the aforementioned features are present and similar effects are achieved.

[0059] In this embodiment (Figure 19), the outer groove of the q-axis rotor has a symmetrical shape with respect to the q-axis. If the q-axis magnetic path angle is θq_path, the q-axis groove angle is θq, and the minimum bridge angle is θb, then the configuration satisfies θq_path < θq < θb, thus satisfying the relationship θq ≥ θq_path, which enhances the torque ripple reduction effect. Furthermore, since the relationship θb ≥ θq is also satisfied, the stress on the bridge, which is most affected by centrifugal force, can be alleviated. In addition, as shown in Figures 21 to 23, even if the magnet arrangement structure and the shape of the rotor outer groove differ, the aforementioned features are present, and similar effects are achieved. Although not shown, even if the number of pole slots, the number of magnet layers, and the number of rotor outer grooves differ, similar effects are achieved as long as the aforementioned features are present.

[0060] In this embodiment (Figure 19), the q-axis rotor outer circumferential groove is configured such that the shape of its bottom surface is concentric with the outer circumference of the rotor core, thereby maintaining high rigidity of the entire rotor. Furthermore, as shown in Figures 21 to 22, even if the magnet arrangement structure and the shape of the rotor outer circumferential groove differ, the aforementioned features are retained, and similar effects are achieved. In addition, although not shown, even if the number of pole slots, the number of magnet layers, and the number of rotor outer circumferential grooves differ, the aforementioned features are retained, and similar effects are achieved.

[0061] In this embodiment (Figures 19 and 21), all rotor outer circumferential grooves are configured to be concentric with the outer circumference of the rotor core, thereby more effectively maintaining high rigidity of the entire rotor. Although not shown, even if the number of pole slots, magnet arrangement structure, number of magnet layers, and number of rotor outer circumferential grooves differ, similar effects will be achieved as long as the aforementioned features are present.

[0062] In this embodiment (Figure 19), the rotor outer circumferential grooves are individually arranged, with adjacent grooves in the circumferential direction flanking the curved surface that constitutes the outer circumference of the rotor core. This minimizes torque reduction compared to conventional groove-less structures while achieving a torque ripple reduction effect. Furthermore, as shown in Figures 21, 22, and 23, even if the magnet arrangement structure and the shape of the rotor outer circumferential grooves differ, the aforementioned features are retained, resulting in similar effects. Although not shown, even if the number of pole slots, the number of magnet layers, and the number of rotor outer circumferential grooves differ, the aforementioned features are retained, resulting in similar effects.

[0063] If N is the number of magnet layers and n is the number of types of rotor outer grooves, then in this embodiment (Figure 19), N=1, n=2, and n=N+1 is satisfied. Therefore, the number of rotor outer grooves to be arranged can be minimized, the maintainability of the rotor core press die can be improved, and manufacturing costs can be reduced. Furthermore, as shown in Figures 21 to 23, even if the magnet arrangement structure and the shape of the rotor outer grooves are different, the aforementioned features are present and similar effects can be achieved. In addition, although not shown, even if the number of pole slots, the number of magnet layers, and the number of rotor outer grooves are different, the aforementioned features can be present and similar effects can be achieved.

[0064] Let S be the number of winding slots in the stator, t be the number of phases of the AC current flowing through the armature winding, and p be the number of magnetic poles in the rotor. If M is the integer obtained by rounding up S / t / p, then in this embodiment (Figure 19), S = 48, t = 3, p = 8, and M = 1. Since N ≤ M is satisfied, the magnetic fluxes of adjacent stator teeth do not short-circuit, preventing an increase in iron loss in the stator. This configuration suppresses motor losses, improves motor efficiency, and reduces torque ripple. Furthermore, as shown in Figures 21 to 23, even if the structure of the magnet arrangement and the shape of the rotor outer periphery grooves are different, the above-mentioned characteristics are present, and similar effects are achieved. Although not shown, even if the number of pole slots, the number of magnet layers, and the number of rotor outer periphery grooves are different, the above-mentioned characteristics are present, and similar effects are achieved.

[0065] The rotor shown in this embodiment (Figures 19, 22, and 24) is an I-shaped embedded magnet rotor, which has a small number of magnets, a simple structure, and a reduced number of parts, thus effectively reducing costs. When used as a motor for electric vehicles, hybrid electric vehicles, etc., increasing the magnetic pole arc angle and arranging more magnets in order to increase torque and output will increase the magnetomotive force harmonics, leading to increased torque ripple or vibration. However, by applying the structure of this embodiment, cost reduction and low torque ripple and low vibration can be achieved simultaneously. Furthermore, although not shown, even if the number of pole slots, the number of magnet layers, and the number of grooves on the outer circumference of the rotor are different, the same effect will be achieved if it is an I-shaped embedded magnet rotor.

[0066] In this embodiment (Figure 19), the rotor of the rotating electric machine has a magnet layer count N=1, thus minimizing the number of parts and reducing manufacturing costs. In motors with N≧2, the number of parts and manufacturing processes increase, leading to higher costs, but magnetomotive force harmonics can be reduced by optimizing the magnet arrangement. On the other hand, if a motor with N=1 is adopted to minimize the number of parts and achieve cost reduction, magnetomotive force harmonics increase, resulting in increased torque ripple or vibration. Therefore, by applying the structure of this embodiment, low torque ripple and low vibration can be achieved even with a motor with N=1, and cost reduction can also be achieved. Furthermore, as shown in Figures 21 to 23, even if the magnet arrangement structure and the shape of the rotor outer circumference grooves are different, the aforementioned features are retained, and similar effects are achieved. Although not shown, even if the number of pole slots and the number of rotor outer circumference grooves are different, a single-magnet rotor will still produce similar effects.

[0067] In the rotor outer circumferential groove shown in Figure 24, which is a modified example of this embodiment, stress concentration at the groove ends can be mitigated because adjacent grooves are connected to each other. Furthermore, since all adjacent different grooves are connected, the number of presses during rotor core manufacturing can be reduced while mitigating stress concentration at the groove ends of the rotor outer circumferential grooves, thereby reducing manufacturing costs. Although not shown, similar effects can be achieved even if the pole slot structure, magnet arrangement structure, number of magnet layers, and number of types of rotor outer circumferential grooves are different, as long as they possess the aforementioned features.

[0068] While this disclosure describes various exemplary embodiments and examples, the various features, aspects, and functions described in one or more embodiments are not limited to the application of a particular embodiment, but are applicable individually or in various combinations to the embodiments. Accordingly, countless variations not illustrated are envisioned within the scope of the art disclosed in this specification. For example, these include modifying, adding or omitting at least one component, or extracting at least one component and combining it with a component from another embodiment.

[0069] 10 Stator, 11 Yoke, 12 Teeth, 13 Stator core, 14 Armature winding (coil), 20 Rotor, 21 Rotor core, 22, 22A, 22B, 22C, 22D Magnets, 23, 23A, 23B, 23C, 23D Magnet slots, 24, 24D Flux barrier, 25, 25D Bridge, 50 Outer groove of first rotor, 60 Outer groove of q-axis rotor, 70 Outer groove of second rotor, 100 Rotating electric machine.

Claims

1. A rotating electric machine comprising: a stator having an annular yoke portion and a plurality of teeth projecting radially from the yoke portion, and armature windings wound in a plurality of winding slots formed between the teeth; and a rotor having a rotor core and magnets disposed within the rotor core, wherein the rotor core has magnet slots for inserting N layers (N is a natural number) of the magnets and flux barriers extending and disposed within the magnet slots, and on the outer periphery of the rotor core, a plurality of rotor outer periphery grooves of n types (n is an integer of 2 or more) are arranged at positions symmetrical with respect to the d axis, the plurality of rotor outer periphery grooves include q-axis rotor outer periphery grooves having the bottom of the groove at a position overlapping with the q axis, and the plurality of rotor outer periphery grooves are configured such that there exist combinations in which the depth of the bottom of the groove increases from the d axis toward the q axis.

2. The rotating electric machine according to claim 1, wherein in the rotor core, the depth of the bottom of each rotor outer circumferential groove increases sequentially from the d-axis to the q-axis.

3. The rotating electric machine according to claim 1 or 2, wherein the rotor core is configured such that θq ≥ θq_path, where θq is the angle formed by the q-axis and a straight line connecting the rotation center of the rotor and the end of the non-magnetic portion that is closest to the q-axis, and θq is the angle formed by the q-axis and a straight line connecting the rotation center of the rotor and the end of the outer groove of the q-axis rotor.

4. The rotating electric machine according to claim 3, wherein the rotor core has a bridge formed between the portion of the flux barrier that extends toward the outer circumference of the rotor and the outer circumference of the rotor core, the shape of the bridge such that the radial thickness increases toward the q-axis, and the angle of the minimum part of the bridge, which is the angle formed by the q-axis and the straight line connecting the rotation center of the rotor and the portion of the bridge with the minimum radial thickness, is configured such that θb ≥ θq.

5. The rotating electric machine according to any one of claims 1 to 4, wherein the rotor core is configured such that the shape of the bottom surface of the outer peripheral groove of the q-axis rotor is concentric with the outer circumference of the rotor core.

6. The rotating electric machine according to any one of claims 1 to 5, wherein all of the plurality of rotor outer peripheral grooves are configured to be concentric with the outer circumference of the rotor core.

7. The rotating electric machine according to any one of claims 1 to 6, wherein, in the rotor core, each rotor outer circumferential groove among the plurality of rotor outer circumferential grooves that are adjacent in the circumferential direction are individually arranged on either side of the curved surface that constitutes the outer circumference of the rotor core.

8. The rotating electric machine according to any one of claims 1 to 6, wherein the rotor core is configured such that among the plurality of rotor outer circumferential grooves, there exist rotor outer circumferential grooves that are adjacent to each other in the circumferential direction and are connected.

9. The rotating electric machine according to claim 8, wherein in the rotor core, all of the multiple rotor outer circumferential grooves are configured to be adjacent to each other in the circumferential direction.

10. The rotating electric machine according to any one of claims 1 to 9, wherein the rotor is configured such that n = N + 1, where N is a natural number and n is an integer of 2 or more for the number of layers of the magnets and n is an integer of 2 or more for the number of types of grooves on the outer circumference of the rotor.

11. The rotating electric machine according to claim 10, wherein, when S is the number of winding slots of the stator, t is the number of phases of the alternating current supplied to the armature winding, and p is the number of magnetic poles of the rotor, M is the integer obtained by rounding up S / t / p to the nearest whole number, and the machine is configured such that N ≤ M.

12. The rotating electric machine according to any one of claims 1 to 11, wherein in the rotor, a pair of magnet slots housing the magnets are formed symmetrically with respect to the d-axis, and the pair of magnet slots are configured in a V-shape such that the distance between them decreases as they move toward the inner circumference.

13. The rotating electric machine according to any one of claims 1 to 11, wherein the magnet slots housing the magnets in the rotor are configured in an I-shape so as to be substantially perpendicular to the d-axis.

14. The rotating electric machine according to claim 12 or claim 13, wherein the rotor is configured such that the number of layers N (where N is a natural number) of the magnets is N = 1.

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