Rotor

Abstract

To provide a rotor capable of reducing usage of magnets.SOLUTION: A straight line connecting an axial center of a core 10 of a rotor 1 with a center of any main magnetic pole is defined as d axis, and a point A is set closer to an outer periphery than the core 10 on the d axis. First layer side magnet grooves 11A and 12A are provided in a portion of the core 10 along a first concentric circle, with the point A defined as a center, of a first radius and second layer side magnet grooves 21A-24A are provided in a portion of the core 10 along a second concentric circle of a second radius longer than the first radius. Third layer side magnet grooves 31A-36A are provided in a portion of the core 10 along a third concentric circle of a third radius longer than the second radius, magnets 11 and 12 are fitted to the first layer side magnet grooves 11A and 12A, and magnets 21-24 are fitted to the second layer side magnet grooves 21A-24A. Magnets 31-36 are fitted to the third layer side magnet grooves 31A-36A and the magnets 11, 12, 21-24 and 31-36 are disposed in a direction in which center lines extending from respective centers are concentrated in the point A.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a motor (drive motor, generator, etc.) for an electric vehicle, and more particularly to a rotor for a permanent magnet motor having multiple layers of permanent magnets. [Background technology]

[0002] Permanent magnet motors are widely used in electric vehicle motors to improve output density. However, magnets that use rare earths are expensive and account for the majority of the motor cost, so reducing the amount of magnets used is an issue. When reusing existing equipment, it is possible to reduce the amount of magnets used while suppressing equipment modification costs by changing only the rotor shape.

[0003] 2. Description of the Related Art Conventionally, a rotor provided in a rotating electric machine has been proposed, for example, as described in Patent Document 1. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6737354 Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Document 1, the stress is reduced by improving the shape of the center bridge, and torque is improved (reduced amount of magnets used) through the magnet dimensions and arrangement, but there is no mention of the bridge on the outer periphery of the rotor, and there was a problem of extra mold costs being incurred due to the use of magnets of different dimensions.

[0006] The present invention is intended to solve the above-mentioned problems, and has an object to provide a rotor that can reduce the amount of magnets used. [Means for solving the problem]

[0007] Therefore, claim 1In the rotor of the above, the straight line connecting the rotor shaft center and the center of any main magnetic pole that generates magnet torque is defined as the d-axis of the dq coordinate system, and the axis perpendicular to the d-axis in terms of electrical angle is defined as the q-axis of the dq coordinate system, a plurality of first layer side magnet grooves arranged symmetrically about the d axis at a portion of the rotor core along a first concentric circle of a first radius among a plurality of concentric circles centered on a point A set on the outer periphery side of the rotor core in a radial cross section, the plurality of first layer side magnet grooves having recesses extending outward at each of the four corners; a plurality of second layer side magnet grooves that are arranged symmetrically about the d-axis at a portion of the rotor core along a second concentric circle having a second radius longer than the first radius among the plurality of concentric circles, the plurality of second layer side magnet grooves having recesses extending outward at each of the four corners; a plurality of third layer side magnet grooves arranged in a line symmetrical manner about the d axis at a portion of the rotor core along a third concentric circle having a third radius longer than the second radius among the plurality of concentric circles, the third layer side magnet grooves having recesses extending outward at each of the four corners; a first layer side magnet group including two magnets that fit into the first layer side magnet groove and are arranged such that center lines extending from the centers of the magnets converge on point A; a second layer side magnet group consisting of four magnets fitted into the second layer side magnet groove and having the same dimensions as the magnets of the first layer side magnet group, the center lines extending from the centers of the magnets being oriented to converge at point A; a third layer side magnet group, which is fitted into the third layer side magnet groove and is composed of six magnets having the same dimensions as the magnets of the first layer side magnet group and the second layer side magnet group, and is arranged so that the center lines extending from the centers of the magnets converge at point A; Equipped with a corner of the first layer side magnet groove on the outer periphery side of the rotor core is disposed on the first concentric circle, a corner of the second layer side magnet groove on the outer periphery side of the rotor core is disposed on the second concentric circle, and a corner of the third layer side magnet groove on the outer periphery side of the rotor core is disposed on the third concentric circle, the radius of curvature of the d-axis side corner of the recess formed at the q-axis side end of the second layer side magnet groove is set to be larger than the radius of curvature of the q-axis side corner, In the recess formed at the q-axis side end of the third-layer side magnet groove, the radius of curvature of the q-axis side corner is set to be larger than the radius of curvature of the d-axis side corner. The rotor is such that the radius of curvature of the recess formed at the q-axis side end of the third-layer side magnet groove is set to be larger than the radius of curvature of the recess formed at the q-axis side end of the second-layer side magnet groove.

[0008] Claim 2 The rotor is Claim 1 In the rotor, when the distance between two adjacent magnets of the first-layer side magnet group via the d-axis is d1, the distance between two adjacent magnets of the second-layer side magnet group via the d-axis is d2, and the distance between two adjacent magnets of the third-layer side magnet group via the d-axis is d3, the respective magnets are arranged such that d1 < d2 < d3.

[0009] Claim 3 In the rotor, a straight line connecting the axis center of the rotor and the center of any main pole that generates magnetic torque is defined as the d-axis of the d-q axis coordinate, and an axis orthogonal to the d-axis at an electrical angle is defined as the q-axis of the d-q axis coordinate. Among the plurality of concentric circles centered on point A set on the outer peripheral side of the rotor core in a radial cross-sectional view for each of the d-axes, a plurality of first-layer side magnet grooves are arranged symmetrically spaced apart with respect to the d-axis along the first concentric circle with the first radius, and recesses that spread outward are formed at respective four corners. Among the plurality of concentric circles, a plurality of second-layer side magnet grooves are arranged symmetrically spaced apart with respect to the d-axis along the second concentric circle with the second radius longer than the first radius, and recesses that spread outward are formed at respective four corners in a portion of the rotor core along the second concentric circle. Among the plurality of concentric circles, a plurality of third-layer side magnet grooves are arranged symmetrically spaced apart with respect to the d-axis along the third concentric circle with the third radius longer than the second radius, and recesses that spread outward are formed at respective four corners in a portion of the rotor core along the third concentric circle. A first-layer side magnet group composed of two magnets fitted into the first-layer side magnet grooves, and arranged such that center lines extended from respective centers converge at point A. a second layer side magnet group consisting of four magnets fitted into the second layer side magnet groove and having the same dimensions as the magnets of the first layer side magnet group, the center lines extending from the centers of the magnets being oriented to converge at point A; a third layer side magnet group, which is fitted into the third layer side magnet groove and is composed of six magnets having the same dimensions as the magnets of the first layer side magnet group and the second layer side magnet group, and is arranged so that the center lines extending from the centers of the magnets converge at point A; a first rotor core outer peripheral groove provided on an outer peripheral end surface of the rotor core near a recess formed at a q-axis side end of the first layer side magnet groove; a second rotor core outer peripheral groove provided on an outer peripheral end surface of the rotor core between a recess formed at a q-axis side end of the first layer side magnet groove and a recess formed at a q-axis side end of the second layer side magnet groove; a third rotor core outer peripheral groove provided on an outer peripheral end surface of the rotor core between a recess formed at a q-axis side end of the second layer side magnet groove and a recess formed at a q-axis side end of the third layer side magnet groove; a fourth rotor core outer peripheral groove provided on an outer peripheral end surface of the rotor core near a recess formed at a q-axis side end of the third layer side magnet groove; Equipped with The depths of the second to fourth rotor core outer peripheral grooves are set so that the depth of the second rotor core outer peripheral groove is equal to or less than the depth of the third rotor core outer peripheral groove. The depth of the fourth rotor core outer peripheral groove is set so that the depth of the second rotor core outer peripheral groove is equal to or less than the depth of the third rotor core outer peripheral groove. The distance from the d-axis to the outer peripheral groove of the first rotor core is g1, the distance from the d-axis to the outer peripheral groove of the second rotor core is g2, the distance from the d-axis to the outer peripheral groove of the third rotor core is g3, and the distance from the d-axis to the outer peripheral groove of the fourth rotor core is g4, The angle formed by the end of the magnet on the d-axis side closest to the outer circumferential end of the rotor core of the first layer side magnet group and the d-axis is defined as f1, the angle formed by the end on the d-axis side and the outer circumferential side of the rotor core of the magnet on the d-axis side closest to the outer circumferential end of the rotor core of the second layer side magnet group and the d-axis is defined as f2, and the angle formed by the end on the d-axis side and the outer circumferential side of the magnet on the d-axis side closest to the outer circumferential end of the rotor core of the third layer side magnet group and the d-axis is defined as f3, Let the angle formed between the q - axis side end and the d - axis in the recess formed at the q - axis side end of the first - layer side magnet groove be f1’, the angle formed between the q - axis side end and the d - axis in the recess formed at the q - axis side end of the second - layer side magnet groove be f2’, and the angle formed between the q - axis side end and the d - axis in the recess formed at the q - axis side end of the third - layer side magnet groove be f3’. It is set such that 0 < g1 < f1, f1’ < g2 < f2, f2’ < g3 < f3, and (f3 + f3’) / 2 ≤ g4 ≤ f3’.

[0010] Claim 4 The rotor of Claim 3 In the rotor, when the distance between two adjacent magnets of the first - layer side magnet group via the d - axis is d1, the distance between two adjacent magnets of the second - layer side magnet group via the d - axis is d2, and the distance between two adjacent magnets of the third - layer side magnet group via the d - axis is d3, the magnets are arranged such that d1 < d2 < d3.

[0011] Claim 5 The rotor of Claim 1 or 2 In the rotor, the recess formed at the q - axis side end of the first - layer side magnet groove has a shape that extends from the q - axis side end of the first - layer side magnet groove along the outer circumference of the rotor core toward the d - axis side and is configured to penetrate the rotor core in the axial direction.

Advantages of the Invention

[0012] The invention of claims 1 to 5 According to the present invention, reluctance torque can be effectively utilized, and since the ratio of magnet torque decreases, the amount of magnet used can be reduced. By increasing the ratio of reluctance torque, it is possible to increase the torque and the rotational speed while suppressing the induced voltage, and the motor can be made to have a higher output.

[0013] Also, since all the magnets are oriented to concentrate at point A, the magnet flux can be concentrated at one point, the induced voltage waveform and the gap magnetic flux density distribution waveform approach a sine wave, the iron loss is reduced, and the efficiency can be increased.

[0014] By making the magnetic flux waveform sinusoidal, the harmonic components of the magnetic flux waveform are reduced, and torque ripple can also be reduced.

[0015] In addition, the two magnets in the first layer side magnet group, the four magnets in the second layer side magnet group, and the six magnets in the third layer side magnet group distribute the eddy current paths, thereby reducing magnetic loss.

[0016] Furthermore, since all the magnets are of the same size, only one magnet mold is required, thereby reducing costs. Also Since the corners of the flux barriers formed between the magnets fitted into each magnet groove on the first, second and third layer and the recesses are arranged on concentric circles centred on point A, the flow of q-axis magnetic flux is smoother and reluctance torque is improved.

[0017] moreover Since the radius of curvature is larger on only one of the d-axis side and the q-axis side of the flux barrier, it is possible to disperse stress due to centrifugal force while ensuring the length of the bridge between each recess. Also, claims 2 and 4 According to this invention, the magnetic flux of the magnets in all of the first to third layers can be effectively utilized. Furthermore, claim 3 According to the invention, since the first to fourth rotor core outer peripheral grooves are provided, the shoulder portion of the gap magnetic flux density distribution waveform is suppressed, and the harmonic components can be reduced.

[0018] Also, By setting the depths of the second to fourth rotor core outer peripheral grooves, the magnetic flux suppression amount gradually increases from the d-axis to the q-axis, making it possible to more effectively suppress harmonics in the waveform. And claim 5 According to the invention, the magnets of the first layer side magnet group can make the change in magnetic flux density generated on the outer peripheral surface of the rotor core, particularly the magnetic flux density distribution at both circumferential ends of the main pole, closer to a sine wave. [Brief description of the drawings]

[0019] [Figure 1] FIG. 2 is a partially enlarged view of a rotor core according to an embodiment of the present invention. [Diagram 2]1A is an enlarged view of a main portion illustrating point A on the d axis in one embodiment of the present invention, and FIG. 1B is an enlarged view of a main portion illustrating point A on the d axis in another embodiment of the present invention. [Diagram 3] FIG. 2 is an explanatory diagram showing the angular position of a flux barrier in one embodiment of the present invention. [Figure 4] FIG. 4 is an explanatory diagram showing the position of a rotor core outer peripheral groove in one embodiment of the present invention. [Diagram 5] FIG. 11 is an explanatory diagram showing a recess formed in a first layer side magnet groove in another embodiment of the present invention. [Figure 6] 1A is a waveform diagram of the gap magnetic flux density when there is no outer peripheral groove in the rotor core, and FIG. 1B is a waveform diagram of the gap magnetic flux density when there is an outer peripheral groove in the rotor core. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiment. Figures 1 and 2(a) show a cross-sectional structure perpendicular to the axial direction of a rotor 1 of a permanent magnet motor according to one embodiment of the present invention. In this figure, only one main pole of the rotor 1 is shown, and the other main poles have the same configuration as the main pole and are therefore not shown.

[0021] The permanent magnet motor includes a rotor 1 and a stator 5 (not shown in FIG. 2(a)) that is coaxially arranged around the rotor 1. The stator 5 has a plurality of stator slots 52 to which stator coils 51 are attached, which are formed and arranged at equal intervals along the outer periphery of the rotor 1.

[0022] The iron core 10 (rotor iron core) of the rotor 1 is a substantially cylindrical member formed, for example, by laminating silicon steel plates. The motor shaft 2 is fitted into the axial core of the iron core 10, and the motor shaft 2 is rotatably supported by bearings (not shown).

[0023] The dashed straight line d in Fig. 2(a) that connects the axis of the rotor 1 (motor shaft 2) and the center of the main pole that generates the magnet torque is the d-axis of the dq coordinate system, and the q in Fig. 2(a) that is perpendicular to this d-axis in terms of electrical angle is the q-axis (auxiliary magnetic pole portion 3) of the dq coordinate system. In Fig. 1 and Fig. 2(a), the range from one d-axis to the q-axis that is adjacent to that d-axis in the circumferential direction is shown.

[0024] 2(a), point A is set on the d-axis, on the outer periphery side of iron core 10 of rotor 1 in a radial cross section. At portions of iron core 10 along three concentric circles of different radii centered on point A, multiple magnet grooves into which magnets are fitted are arranged, with recesses at each of the four corners extending outward.

[0025] That is, in the portion of iron core 10 along the first concentric circle of the first radius centered at point A, magnet grooves 11A, 12A constituting the first layer side magnet groove are arranged spaced apart and symmetrically about the d axis, and recesses 11a-11d, 12a-12d extending outward are formed at each of the four corners of magnet grooves 11A, 12A.

[0026] Two magnets 11, 12 as a first layer side magnet group are fitted in the magnet grooves 11A, 12A, respectively, and are arranged so that the center lines extending from the centers of the magnets converge on point A.

[0027] In a portion of the iron core 10 along a second concentric circle of a second radius longer than the first radius, centered on point A, magnet grooves 21A, 22A, 23A, and 24A constituting the second layer side magnet groove are arranged spaced apart and symmetrically about the d axis, and outwardly extending recesses 21a, 21b, 21e, 22f, 22g, 22c, 22d, 23c, 23d, 23g, 24f, 24e, 24a, and 24b are respectively formed at the four corners of the magnet grooves 21A, 22A, 23A, and 24A.

[0028] Four magnets 21 to 24 as a second layer side magnet group are respectively fitted in the magnet grooves 21A, 22A, 23A, and 24A, and are arranged so that the center lines extending from the centers of the magnets converge on point A.

[0029] In a portion of iron core 10 along a third concentric circle of a third radius longer than the second radius, centered at point A, magnet grooves 31A, 32A, 33A, 34A, 35A, and 36A constituting the third layer side magnet groove are arranged spaced apart and symmetrically about the d axis, and outwardly extending recesses 31a, 31b, 31e, 32f, 32g, 32h, 33i, 33j, 33c, 33d, 34c, 34d, 34j, 34i, 35h, 35g, 35f, 36e, 36a, and 36b are respectively formed in the four corners of magnet grooves 31A, 32A, 33A, 34A, 35A, and 36A.

[0030] Six magnets 31 to 36 as a third layer side magnet group are fitted in magnet grooves 31A, 32A, 33A, 34A, 35A, and 36A, respectively, with center lines extending from the centers of the magnets 31 to 36 oriented to converge at point A.

[0031] The magnets 11, 12, 21 to 24, and 31 to 36 are each configured to have the same dimensions.

[0032] In the first layer side magnet group, when magnets 11 and 12 are arranged one by one in the magnet grooves 11A and 12A, gaps serving as flux barriers (non-magnetic regions) are formed between each of the recesses 11a-11d, 12a-12d and the magnets 11 and 12.

[0033] In the second layer side magnet group, with magnets 21 to 24 arranged one by one in the magnet grooves 21A to 24A, a gap is formed between each of the recesses 21a, 21b, 21e, 22f, 22g, 22c, 22d, 23c, 23d, 23g, 24f, 24e, 24a, 24b and the magnets 21 to 24, respectively, as a flux barrier (non-magnetic region).

[0034] In the third layer side magnet group, with magnets 31 to 36 arranged one by one in the magnet grooves 31A to 36A, a gap is formed between each of the recesses 31a, 31b, 31e, 32f, 32g, 32h, 33i, 33j, 33c, 33d, 34c, 34d, 34j, 34i, 35h, 35g, 35f, 36e, 36a, 36b and the magnets 31 to 36, respectively, such that a gap is formed as a flux barrier (non-magnetic region).

[0035] A center bridge portion 10c is formed between recess 11c and recess 12c, which are closest to the d axis on the first layer side, a center bridge portion 20c is formed between recess 22c and recess 23c, which are closest to the d axis on the second layer side, and a center bridge portion 30c is formed between recess 33c and recess 34c, which are closest to the d axis on the third layer side.

[0036] Furthermore, the magnets arranged on the first layer side to the third layer side are not limited to being all independent magnets as shown in Figures 1 and 2(a), but may be arranged on the second layer side, as shown in Figure 2(b), with magnets 25 and 26 divided into two in a direction perpendicular to the longitudinal direction, and magnets 37 and 38 divided into three in a direction perpendicular to the longitudinal direction, and arranged on the third layer side, with the center lines extending from the centers of magnets 11, 12, 25, 26, 37, and 38 oriented to converge at point A.

[0037] In this case, magnet 25 is fitted into magnet groove 25A, and recesses 25a-25d are formed in the four corners of magnet groove 25A, magnet 26 is fitted into magnet groove 26A, and recesses 26a-26d are formed in the four corners of magnet groove 26A, magnet 37 is fitted into magnet groove 37A, and recesses 37a-37d are formed in the four corners of magnet groove 37A, and magnet 38 is fitted into magnet groove 38A, and recesses 38a-38d are formed in the four corners of magnet groove 38A, and the other parts are configured in the same manner as in Figure 2(a).

[0038] Since the induced voltage of a PM motor is proportional to the rotation speed, the maximum motor rotation speed is limited to a range where the induced voltage does not exceed the inverter's withstand voltage. The structures in Figures 1 and 2 make effective use of reluctance torque, and since the magnet torque ratio is lower, the amount of magnets used can be reduced. By increasing the reluctance torque ratio, it is possible to achieve higher torque and higher rotation speeds while suppressing the induced voltage, resulting in higher motor output.

[0039] By orienting all magnets so that they are concentrated at point A, the magnetic flux can be concentrated at one point, and the induced voltage waveform and gap magnetic flux density distribution waveform become closer to a sine wave, reducing iron loss and improving efficiency. Note that since the induced voltage is the product of the no-load interlinkage magnetic flux and the rotor angular speed, making the induced voltage waveform sinusoidal leads to making the magnetic flux waveform sinusoidal. In addition, the time average of torque is the product of the interlinkage magnetic flux and the current, and the product of the harmonic components of the interlinkage magnetic flux and the current is the harmonic components of the torque waveform, in other words, the torque ripple, so reducing the harmonic components of the magnetic flux waveform can also reduce the torque ripple.

[0040] Multi-layered inner diameter magnets (magnets arranged on the axial side of the iron core 10) are greatly affected by slot harmonic magnetic flux and tend to increase eddy current loss, but because the second layer is divided into two and the third layer into three, the eddy current paths are dispersed and magnetic loss can be suppressed. Furthermore, because all the magnets are the same dimensions, only one magnet mold is required, reducing costs. The magnets in each layer can also be further divided horizontally (in the longitudinal direction of the magnet) into two.

[0041] Next, the angular position of the flux barrier formed between the recess and the magnet will be explained with reference to Figure 3. Figure 3 shows the flux barrier (24a, 36a) formed between magnet 24 on the second layer side close to outer peripheral end 10a of iron core 10, magnet 36 on the third layer side, and recess 24a, recess 36a in a configuration on one q-axis side from the d-axis.

[0042] In Fig. 3, corners 20 of the second-layer magnet groove on the outer periphery of the rotor core are arranged on a second concentric circle centered on point A, and corners 30 of the third-layer magnet groove on the outer periphery of the rotor core are arranged on a third concentric circle centered on point A. Corners of the first-layer magnet groove on the outer periphery of the rotor core are arranged on a first concentric circle centered on point A, but are not shown in Fig. 3.

[0043] The radius of curvature of the d-axis side corner 24ad of the recess 24a formed at the q-axis side end (the end closer to the outer peripheral end 10a of the iron core 10) of the second layer side magnet groove is set larger than the radius of curvature of the q-axis side corner 24aq, and the radius of curvature of the q-axis side corner 36aq of the recess 36a formed at the q-axis side end (the end closer to the outer peripheral end 10a of the iron core 10) of the third layer side magnet groove is set larger than the radius of curvature of the d-axis side corner 36ad.

[0044] The radius of curvature of the recess 36a on the third layer side is set to be larger than the radius of curvature of the recess 24a on the second layer side. The configuration on the other side of the q axis from the d axis is the same as that in FIG.

[0045] As shown in Figure 3, by arranging the corners of the magnet groove on a concentric circle centered on point A, the flow of the q-axis magnetic flux becomes smoother (the q-axis reactance Lq becomes larger) and the reluctance torque improves. By increasing the radius of curvature of the corners of the flux barriers (24a, 36a), the stress due to centrifugal force can be reduced (dispersed), but increasing the radius of curvature shortens the narrowest part of the bridge between recesses 24a and 36a by that amount, increasing leakage flux and leading to a decrease in torque.

[0046] Since stress is concentrated on the d-axis side in the second layer and on the q-axis side in the third layer, by increasing the radius of curvature on only one side of each as shown in Figure 3, the stress is dispersed while maintaining the bridge length. The greater the mass carried by the bridge, the greater the stress generated in the bridge due to centrifugal force. In other words, the greater the mass of the magnets and iron cores present in the approximately sector-shaped section consisting of the magnet grooves and rotor outer diameter of each layer, the greater the generated stress. Therefore, since the magnitude of the generated stress is second layer < third layer, the radius of curvature should also be second layer < third layer.

[0047] The first layer has a low generated stress due to centrifugal force, so there is a degree of freedom in the shape of the flux barrier. Thus, instead of the recesses 11a, 11b, 12a, and 12b at the q-axis side end in FIG. 2, for example, as shown in FIG. 5, it may be in a shape extending from the end at the q-axis side along the outer periphery (10a) of the core 10 toward the d-axis side, and the slit portions 11X and 12X formed by penetrating the core 10 in the axial direction may be used.

[0048] The slit portions 11X and 12X in FIG. 5 have a very low magnetic permeability compared to the core 10, making it extremely difficult for magnetic flux to pass through, and they function as magnetic blocking portions. As a result, it is possible to approximate the change in the magnetic flux density distribution generated on the outer peripheral surface of the rotor 1 by the magnets 11 and 12, particularly the magnetic flux density distribution at both end portions in the circumferential direction of the main magnetic poles, to a sine wave.

[0049] Also, as shown in FIG. 1, when the distance between two adjacent magnets 11 and 12 of the first layer side magnet group via the d-axis is d1, the distance between two adjacent magnets 22 and 23 of the second layer side magnet group via the d-axis is d2, and the distance between two adjacent magnets 33 and 34 of the third layer side magnet group via the d-axis is d3, they are arranged such that d1 < d2 < d3.

[0050] If the distance between the magnets is narrower than that of the outer diameter side layer, for example, when d2 > d3, the magnetic flux of the magnets in the third layer cannot be effectively utilized and the torque decreases. By setting d1 < d2 < d3, the magnetic flux of the magnets in all layers can be effectively utilized. Incidentally, the center bridge width may be such that the second layer > the third layer (that is, the width of the center bridge 20c > the width of the center bridge 30c may also be acceptable).

[0051] Next, an embodiment in which a groove is provided at the outer peripheral end 10a of the core 10 will be described with reference to FIG. 4. FIG. 4 shows the configuration on one q-axis side from the d-axis. A first rotor core outer peripheral groove 41 is engraved on the outer peripheral end 10a of the core 10 near the recess 12a formed at the q-axis side end of the magnet groove 12A on the first layer side.

[0052] A second rotor core outer peripheral groove 42 is engraved on the outer peripheral end 10a of the core 10 between the recess 12a on the first layer side and the recess 24a formed at the q-axis side end of the magnet groove 24A on the second layer side.

[0053] A third rotor core outer peripheral groove 43 is engraved on the outer peripheral end 10a of the core 10 between the recess 24a on the second layer side and the recess 36a formed at the q-axis side end of the magnet groove 36A on the third layer side.

[0054] A fourth rotor core outer circumferential groove 44 is formed in the outer circumferential end 10a of the core 10 near the recess 36a on the third layer side.

[0055] The depths and positions of the first to fourth rotor core outer peripheral grooves 41 to 44 and the positional relationships between the magnets 12, 24, 36 and the recesses 12a, 24a, 36a are set as follows.

[0056] The depths of the second to fourth rotor core outer peripheral grooves 42 to 44 are set so that the depth of the second rotor core outer peripheral groove 42≦the depth of the third rotor core outer peripheral groove 43≦the depth of the fourth rotor core outer peripheral groove 44.

[0057] The distance from the d-axis to the first rotor core outer peripheral groove 41 is g1, the distance from the d-axis to the second rotor core outer peripheral groove 42 is g2, the distance from the d-axis to the third rotor core outer peripheral groove 43 is g3, and the distance from the d-axis to the fourth rotor core outer peripheral groove 44 is g4.

[0058] The angle formed by the end of magnet 12 in the first layer side magnet group on the d-axis side closest to outer peripheral end 10a of iron core 10 and the d-axis is defined as f1, the angle formed by the end of magnet 24 in the second layer side magnet group on the d-axis side and on the outer peripheral side of iron core 10 closest to outer peripheral end 10a of iron core 10 and the d-axis is defined as f2, and the angle formed by the end of magnet 36 in the third layer side magnet group on the d-axis side and on the outer peripheral side of iron core 10 closest to outer peripheral end 10a of iron core 10 and the d-axis is defined as f3.

[0059] Let the angle formed by the q-axis side corner 12aq and the d-axis in the recess 12a on the first layer side be f1', the angle formed by the q-axis side corner 24aq and the d-axis in the recess 24a on the second layer side be f2', and the angle formed by the end on the q-axis side and the d-axis in the recess 36b on the third layer side be f3'.

[0060] And it is set such that 0 < g1 < f1, f1' < g2 < f2, f2' < g3 < f3, and (f3 + f3') / 2 ≤ g4 ≤ f3'.

[0061] In addition, the depth and position of the outer peripheral grooves 41 to 44 of the rotor core on the other q-axis side from the d-axis, and the positional relationship between the magnets 11, 21, 31 and the recesses 11a, 21a, 31a, 31b are set in the same manner as in FIG. 4.

[0062] By forming the outer peripheral grooves 41 to 44 of the rotor core as shown in FIG. 4, the shoulder portion of the gap magnetic flux density distribution waveform can be suppressed, and the harmonic components can be reduced. By setting the depth of the outer peripheral grooves of the rotor core such that the depth of the second outer peripheral groove 42 of the rotor core ≤ the depth of the third outer peripheral groove 43 of the rotor core ≤ the depth of the fourth outer peripheral groove 44 of the rotor core, the magnetic flux suppression amount gradually increases from the d-axis to the q-axis, so the harmonics of the waveform can be more effectively suppressed.

[0063] If there is an outer peripheral groove of the rotor core on the q-axis side rather than the angle f3' formed by the end on the q-axis side and the d-axis in the recess 36b on the third layer side, the torque reduction is large. Therefore, the distance g4 from the d-axis to the fourth outer peripheral groove 44 of the rotor core is preferably f3 < g4 ≤ f3' shown in FIG. 4.

[0064] At this time, if the fourth outer peripheral groove 44 of the rotor core is too close to f3, the bridge thickness becomes small and the strength decreases. Therefore, the fourth outer peripheral groove 44 of the rotor core is on the q-axis side rather than the intermediate position between f3 and f3' in FIG. 4 and is at a position equal to or on the d-axis side of f3', that is, (f3 + f3') / 2 ≤ g4 ≤ f3', so that stress reduction due to centrifugal force can be achieved simultaneously.

[0065] The depth of the first rotor core outer peripheral groove 41 may be greater than or equal to the depth of the second rotor core outer peripheral groove 42, and the first rotor core outer peripheral groove 41 may be replaced with slit portions 11X, 12X protruding toward the d-axis side described in Fig. 5. If the second rotor core outer peripheral groove 42 to the fourth rotor core outer peripheral groove 44 were to be the slit portions, a large decrease in Lq (q-axis side reactance) would occur, resulting in a decrease in torque, and therefore the outer peripheral grooves (42 to 44) are preferable.

[0066] FIG. 6 shows the gap magnetic flux density waveform, where (a) shows the case where the peripheral grooves (41 to 44) as in FIG. 4 are not provided, and (b) shows the case where the peripheral grooves 41 to 44 in FIG. 4 are provided.

[0067] According to FIG. 6, it can be seen that when rotor core outer peripheral grooves 41 to 44 are provided, the total harmonic rate is reduced from 15% to 10%. [Explanation of symbols]

[0068] 1...Rotor 2...Motor shaft 3…Auxiliary magnetic pole part 5...Stator 10...Iron core 10a...Outer periphery of rotor core 10c, 20c, 30c…Center bridge section 11, 12, 21-26, 31-38...Magnets 11A, 12A, 21A~26A, 31A~38A...Magnet groove 11a to 11d, 12a to 12d, 21a, 21b, 21e, 22f, 22g, 22c, 22d, 23c, 23d, 23g, 24f, 24e, 24a, 24b, 25a to 25d, 26a to 26d, 31a, 31b, 31e, 32f, 32g, 32h, 33i, 33j, 33c, 33d, 34c, 34d, 34j, 34i, 35h, 35g, 35f, 36e, 36a, 36b, 37a to 37d, 38a to 38d...concave 11X, 12X...Slit section 41~44...Rotor core outer circumferential groove 51...Stator coil 52…Status slot

Claims

1. A straight line connecting the rotor axis and the center of any main pole that generates magnet torque is defined as the d-axis of the dq coordinate system, and an axis perpendicular to the d-axis in terms of electrical angle is defined as the q-axis of the dq coordinate system, a plurality of first layer side magnet grooves arranged in a line symmetrical manner about the d axis at a portion of the rotor core along a first concentric circle of a first radius among a plurality of concentric circles centered on a point A set on the outer periphery side of the rotor core in a radial cross section, the plurality of first layer side magnet grooves having recesses extending outward at each of the four corners; a plurality of second layer side magnet grooves arranged in a line symmetrical manner about the d-axis at a portion of the rotor core along a second concentric circle having a second radius longer than the first radius among the plurality of concentric circles, the plurality of second layer side magnet grooves having outwardly expanding recesses at each of the four corners; a plurality of third layer side magnet grooves arranged in a line symmetrical manner about the d-axis at a portion of the rotor core along a third concentric circle having a third radius longer than the second radius among the plurality of concentric circles, the third layer side magnet grooves having recesses extending outward at each of the four corners; a first layer side magnet group, which is two magnets fitted into the first layer side magnet groove and is arranged such that center lines extending from the centers of the magnets converge on the point A; a second layer side magnet group, which is fitted into the second layer side magnet groove and has the same dimensions as each magnet of the first layer side magnet group, and is arranged such that center lines extending from the centers of the magnets converge at point A; a third layer side magnet group, which is fitted into the third layer side magnet groove and is composed of six magnets having the same dimensions as the magnets of the first layer side magnet group and the second layer side magnet group, and which is arranged so that the center lines extending from the centers of the magnets converge at point A; Equipped with a corner of the first layer side magnet groove on the outer periphery side of the rotor core is disposed on the first concentric circle, a corner of the second layer side magnet groove on the outer periphery side of the rotor core is disposed on the second concentric circle, and a corner of the third layer side magnet groove on the outer periphery side of the rotor core is disposed on the third concentric circle, a radius of curvature of a d-axis side corner of a recess formed at a q-axis side end of the second layer side magnet groove is set to be larger than a radius of curvature of a q-axis side corner, a radius of curvature of a q-axis side corner of a recess formed at a q-axis side end of the third layer side magnet groove is set to be larger than a radius of curvature of a d-axis side corner of the recess, A rotor characterized in that the radius of curvature of the recess formed at the q-axis side end of the third layer side magnet groove is set to be larger than the radius of curvature of the recess formed at the q-axis side end of the second layer side magnet groove.

2. A rotor as described in claim 1, characterized in that when the distance between two adjacent magnets in the first layer side magnet group across the d axis is d1, the distance between two adjacent magnets in the second layer side magnet group across the d axis is d2, and the distance between two adjacent magnets in the third layer side magnet group across the d axis is d3, the magnets are arranged so that d1 < d2 < d3.

3. A straight line connecting the rotor axis and the center of any main pole that generates magnet torque is defined as the d-axis of the dq coordinate system, and an axis perpendicular to the d-axis in terms of electrical angle is defined as the q-axis of the dq coordinate system, a plurality of first layer side magnet grooves arranged in a line symmetrical manner about the d axis at a portion of the rotor core along a first concentric circle of a first radius among a plurality of concentric circles centered on a point A set on the outer periphery side of the rotor core in a radial cross section, the plurality of first layer side magnet grooves having recesses extending outward at each of the four corners; a plurality of second layer side magnet grooves arranged in a line symmetrical manner about the d-axis at a portion of the rotor core along a second concentric circle having a second radius longer than the first radius among the plurality of concentric circles, the plurality of second layer side magnet grooves having outwardly expanding recesses at each of the four corners; a plurality of third layer side magnet grooves arranged in a line symmetrical manner about the d-axis at a portion of the rotor core along a third concentric circle having a third radius longer than the second radius among the plurality of concentric circles, the third layer side magnet grooves having recesses extending outward at each of the four corners; a first layer side magnet group, which is two magnets fitted into the first layer side magnet groove and is arranged such that center lines extending from the centers of the magnets converge on the point A; a second layer side magnet group, which is fitted into the second layer side magnet groove and has the same dimensions as each magnet of the first layer side magnet group, and is arranged such that center lines extending from the centers of the magnets converge at point A; a third layer side magnet group, which is fitted into the third layer side magnet groove and is composed of six magnets having the same dimensions as the magnets of the first layer side magnet group and the second layer side magnet group, and which is arranged so that the center lines extending from the centers of the magnets converge at point A; a first rotor core outer peripheral groove provided on an outer peripheral end surface of the rotor core near a recess formed at a q-axis side end of the first layer side magnet groove; a second rotor core outer peripheral groove provided on an outer peripheral end surface of the rotor core between a recess formed at a q-axis side end of the first layer side magnet groove and a recess formed at a q-axis side end of the second layer side magnet groove; a third rotor core outer peripheral groove provided on an outer peripheral end surface of the rotor core between a recess formed at a q-axis side end of the second layer side magnet groove and a recess formed at a q-axis side end of the third layer side magnet groove; a fourth rotor core outer peripheral groove provided on an outer peripheral end surface of the rotor core near a recess formed at a q-axis side end of the third layer side magnet groove; Equipped with the depths of the second to fourth rotor core outer peripheral grooves are set such that: the depth of the second rotor core outer peripheral groove≦the depth of the third rotor core outer peripheral groove≦the depth of the fourth rotor core outer peripheral groove; The distance from the d-axis to the outer peripheral groove of the first rotor core is g1, the distance from the d-axis to the outer peripheral groove of the second rotor core is g2, the distance from the d-axis to the outer peripheral groove of the third rotor core is g3, and the distance from the d-axis to the outer peripheral groove of the fourth rotor core is g4, The angle formed by the end of the magnet on the d-axis side closest to the outer circumferential end of the rotor core of the first layer side magnet group and the d-axis is defined as f1, the angle formed by the end of the magnet on the d-axis side and the outer circumferential side of the rotor core of the magnet closest to the outer circumferential end of the rotor core of the second layer side magnet group and the d-axis is defined as f2, and the angle formed by the end of the magnet on the d-axis side and the outer circumferential side of the rotor core of the magnet closest to the outer circumferential end of the rotor core of the third layer side magnet group and the d-axis is defined as f3, the angle between the q-axis side end of the recess formed at the q-axis side end of the first layer side magnet groove and the d-axis is f1', the angle between the q-axis side end of the recess formed at the q-axis side end of the second layer side magnet groove and the d-axis is f2', and the angle between the q-axis side end of the recess formed at the q-axis side end of the third layer side magnet groove and the d-axis is f3', A rotor characterized in that g4 and f3' are set so as to satisfy 0<g1<f1, f1'<g2<f2, f2'<g3<f3, and (f3+f3') / 2≦g4≦f3'.

4. A rotor as described in claim 3, characterized in that when the distance between two adjacent magnets in the first layer side magnet group across the d axis is d1, the distance between two adjacent magnets in the second layer side magnet group across the d axis is d2, and the distance between two adjacent magnets in the third layer side magnet group across the d axis is d3, the magnets are arranged so that d1 < d2 < d3.

5. A rotor as described in claim 1 or 2, characterized in that the recess formed at the q-axis side end of the first layer side magnet groove has a shape extending from the q-axis side end of the first layer side magnet groove along the outer periphery of the rotor core to the d-axis side, and is configured to penetrate the rotor core in the axial direction.

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