JP7643269B2 - Rotor - Google Patents

Description

The present invention relates to motors (drive motors, generators, etc.) for electric vehicles, and in particular to rotors for permanent magnet motors with multiple layers of permanent magnets.

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 motor costs, making it an issue to reduce the amount of magnets used. In cases where existing equipment is being reused, it is possible to reduce the amount of magnets used while keeping equipment modification costs down by changing only the rotor shape.

Conventionally, rotors for use in rotating electrical machines have been proposed, for example, as described in Patent Document 1.

Patent No. 6737354

In Patent Document 1, the stress was reduced by devising a center bridge shape, and torque was improved (reduced amount of magnets used) through magnet dimensions and arrangement, but there was no mention of the bridge on the outer periphery of the rotor, and there was a problem of extra mold costs being incurred because magnets of different dimensions were used.

The present invention aims to solve the above problems, and its purpose is to provide a rotor that can reduce the amount of magnets used.

Therefore, in the rotor of claim 1 , a straight line connecting the rotor axis and the center of any main magnetic pole that generates magnet torque is defined as the d-axis of a 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 recesses extending outward at each of the four corners;
a plurality of third layer side magnet grooves, which are 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, and each of which has a recess extending outward at each of its four corners;
a first layer side magnet group including two magnets that are fitted into the first layer side magnet groove and are 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,
This rotor has a radius of curvature of the recess formed at the q-axis side end of the third layer side magnet groove 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.

The rotor of claim 2 is the rotor of claim 1 , in which the magnets are arranged so that d1 < d2 < d3, where the distance between two adjacent magnets across the d axis in the first layer side magnet group is d1, the distance between two adjacent magnets across the d axis in the second layer side magnet group is d2, and the distance between two adjacent magnets across the d axis in the third layer side magnet group is d3.

In the rotor of claim 3 , a straight line connecting the axis of the rotor and the center of any main magnetic pole that generates magnet torque is defined as a d-axis of a dq coordinate system, and an axis perpendicular to the d-axis in terms of an electrical angle is defined as a q-axis of the dq coordinate system,
a plurality of first layer side magnet grooves arranged in a line symmetrical manner around 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 recesses extending outward at each of the four corners;
a plurality of third layer side magnet grooves, which are 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, and each of which has a recess extending outward at each of its four corners;
a first layer side magnet group including two magnets that are fitted into the first layer side magnet groove and are 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 on the second layer side magnet group 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 on the third layer side magnet group 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',
The values are set so as to satisfy 0<g1<f1, f1'<g2<f2, f2'<g3<f3, and (f3+f3')/2≦g4≦f3'.

The rotor of claim 4 is the rotor of claim 3 , in which the magnets are arranged so that d1 < d2 < d3, where the distance between two adjacent magnets across the d axis in the first layer side magnet group is d1, the distance between two adjacent magnets across the d axis in the second layer side magnet group is d2, and the distance between two adjacent magnets across the d axis in the third layer side magnet group is d3.

The rotor of claim 5 is the rotor of claim 1 or 2 , wherein 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.

According to the inventions of claims 1 to 5 , the reluctance torque can be effectively utilized and the magnet torque ratio can be reduced, thereby reducing the amount of magnets used. By increasing the reluctance torque ratio, it is possible to achieve high torque and high speed rotation while suppressing induced voltage, thereby enabling the motor to have high output.

In addition, because all magnets are oriented to concentrate 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.

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

In addition, the two magnets in the first layer magnet group, the four magnets in the second layer magnet group, and the six magnets in the third layer magnet group distribute the eddy current paths, reducing magnet loss.

Furthermore, since all the magnets are of the same size, only one magnet mold is required, thereby reducing costs.
In addition , the corners of the flux barriers formed between the magnets fitted into each magnet groove on the first layer, second layer, and third layer and the recesses are arranged on concentric circles centered on point A, which smooths the flow of q-axis magnetic flux and improves reluctance torque.

Furthermore , 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.
Furthermore, according to the second and fourth aspects of the invention , the magnetic flux of the magnets in all layers, from the first layer to the third layer, can be effectively utilized.
Furthermore, according to the invention , the first to fourth rotor core outer peripheral grooves are provided, so that the shoulder portion of the gap magnetic flux density distribution waveform is suppressed, and the harmonic components can be reduced.

Furthermore, by setting the depth of the second to fourth rotor core outer peripheral grooves, the amount of magnetic flux suppression gradually increases from the d-axis to the q-axis, making it possible to more effectively suppress harmonics in the waveform.
Furthermore, according to the invention of claim 5 , the magnets of the first layer side magnet group can bring 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.

FIG. 2 is a partially enlarged view of a rotor core according to an embodiment of the present invention. 4A is an enlarged view of a main portion illustrating point A on the d axis in one embodiment of the present invention, and FIG. 4B is an enlarged view of a main portion illustrating point A on the d axis in another embodiment of the present invention. FIG. 2 is an explanatory diagram showing the angular position of a flux barrier in one embodiment of the present invention. FIG. 4 is an explanatory diagram showing the position of a rotor core outer peripheral groove in one embodiment of the present invention. FIG. 11 is an explanatory diagram showing a recess formed in a first layer side magnet groove in another embodiment of the present invention. 4A is a waveform diagram of the gap magnetic flux density when there is no outer peripheral groove in the rotor core, and FIG. 4B is a waveform diagram of the gap magnetic flux density when there is an outer peripheral groove in the rotor core.

The following describes an embodiment of the present invention 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 rotor 1 of a permanent magnet motor, which is one embodiment of the present invention. In this figure, only one main pole of rotor 1 is shown, and the other main poles have the same configuration as the main pole, so they are not shown.

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 number of stator slots 52 to which stator coils 51 are attached, which are arranged at equal intervals along the outer circumference of the rotor 1.

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

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 electrical angle is the q-axis (auxiliary magnetic pole portion 3) of the dq coordinate system. Figs. 1 and 2(a) show the range from one d-axis to the q-axis that is adjacent to that d-axis in the circumferential direction.

In FIG. 2(a), point A is set on the d-axis, on the outer periphery side of the iron core 10 of the rotor 1 in a radial cross-sectional view. The iron core 10 is arranged along three concentric circles of different radii with point A as the center, and multiple magnet grooves are arranged in which magnets are fitted, with each of the four corners having a recess that flares outward.

That is, in the portion of the iron core 10 along the first concentric circle of the first radius centered on point A, the magnet grooves 11A and 12A constituting the first layer side magnet groove are arranged at a distance from each other and symmetrically about the d axis, and recesses 11a-11d and 12a-12d that extend outward are formed at each of the four corners of the magnet grooves 11A and 12A.

Two magnets 11 and 12, which form the first layer magnet group, are fitted into the magnet grooves 11A and 12A, respectively, with the center lines extending from the centers of the magnets oriented to converge at point A.

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

Four magnets 21 to 24 are fitted into the magnet grooves 21A, 22A, 23A, and 24A as the second layer magnet group, with the center lines extending from the centers of the magnets oriented to converge at point A.

In the portion of the iron core 10 along the third concentric circle of a third radius longer than the second radius, centered on point A, the magnet grooves 31A, 32A, 33A, 34A, 35A, and 36A constituting the third layer side magnet groove are arranged at intervals and in line symmetry with the d axis as the center, and the outwardly expanding recesses 31a, 31b, 31e, 32f, 32g, 32h, 33i, 33j, 33c, 33d, 34c, 34d, 34j, 34i, 35h, 35g, 35f, 36e, 36a, and 36b are formed at the four corners of the magnet grooves 31A, 32A, 33A, 34A, 35A, and 36A, respectively.

Six magnets 31 to 36 are fitted into magnet grooves 31A, 32A, 33A, 34A, 35A, and 36A as the third layer magnet group, with the center lines extending from the centers of the magnets oriented to converge on point A.

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

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

In the second layer magnet group, when magnets 21 to 24 are arranged one by one in magnet grooves 21A to 24A, gaps are formed between each of the recesses 21a, 21b, 21e, 22f, 22g, 22c, 22d, 23c, 23d, 23g, 24f, 24e, 24a, and 24b and magnets 21 to 24, acting as flux barriers (non-magnetic regions).

In the third layer magnet group, when magnets 31 to 36 are arranged one by one in magnet grooves 31A to 36A, gaps are formed as flux barriers (non-magnetic regions) between each of the recesses 31a, 31b, 31e, 32f, 32g, 32h, 33i, 33j, 33c, 33d, 34c, 34d, 34j, 34i, 35h, 35g, 35f, 36e, 36a, and 36b and magnets 31 to 36.

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.

In addition, the magnets arranged on the first to third layers do not necessarily have to be all independent magnets as shown in Figures 1 and 2(a), but may be arranged as shown in Figure 2(b) with magnets 25 and 26 divided into two in a direction perpendicular to the longitudinal direction on the second layer side, and magnets 37 and 38 divided into three in a direction perpendicular to the longitudinal direction on the third layer side, with the center lines extending from the centers of magnets 11, 12, 25, 26, 37, and 38 converging on point A.

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 way as in Figure 2(a).

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.

By orienting all magnets to concentrate 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, i.e., the torque ripple, so reducing the harmonic components of the magnetic flux waveform can also reduce the torque ripple.

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 size, only one magnet mold is required, reducing costs. The magnets in each layer may also be further divided horizontally (in the longitudinal direction of the magnet) into two.

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 the magnet 24 on the second layer side near the outer circumferential end 10a of the core 10, the magnet 36 on the third layer side, and the recess 24a and recess 36a in a configuration on one q-axis side from the d-axis.

In FIG. 3, the 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 the 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. The 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 omitted from FIG. 3.

The radius of curvature of the d-axis side corner 24ad in the recess 24a formed at the q-axis side end (the end closer to the outer circumferential end 10a of the core 10) of the second layer side magnet groove is set to be 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 in the recess 36a formed at the q-axis side end (the end closer to the outer circumferential end 10a of the core 10) of the third layer side magnet groove is set to be larger than the radius of curvature of the d-axis side corner 36ad.

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 in FIG. 3.

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 barrier (24a, 36a), the stress caused by centrifugal force can be reduced (dispersed), but if the radius of curvature is increased, the narrowest part of the bridge between recesses 24a and 36a becomes shorter, increasing the leakage flux and leading to a decrease in torque.

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 in the roughly 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.

Since the first layer has low stress due to centrifugal force, there is flexibility in the shape of the flux barrier. Therefore, instead of the recesses 11a, 11b, 12a, and 12b at the q-axis end in FIG. 2, slits 11X and 12X may be used that extend from the q-axis end along the outer periphery (10a) of the core 10 to the d-axis side and penetrate the core 10 in the axial direction, as shown in FIG. 5.

The slits 11X and 12X in FIG. 5 have a much smaller magnetic permeability than the iron core 10, making it very difficult for magnetic flux to pass through, and function as magnetic cutoff sections. This allows the change in magnetic flux density distribution generated on the outer circumferential surface of the rotor 1 by the magnets 11 and 12, particularly the magnetic flux density distribution at both circumferential ends of the main pole, to approach a sine wave.

As shown in FIG. 1, the magnets are arranged so that d1 < d2 < d3 holds when the distance between the two adjacent magnets 11 and 12 on the d axis in the first layer magnet group is d1, the distance between the two adjacent magnets 22 and 23 on the d axis in the second layer magnet group is d2, and the distance between the two adjacent magnets 33 and 34 on the d axis in the third layer magnet group is d3.

If the distance between the magnets is narrower than the layers on the outer diameter side, for example d2>d3, the magnetic flux of the third layer magnet cannot be effectively utilized and torque decreases. By making d1<d2<d3, the magnetic flux of the magnets in all layers can be effectively utilized. The center bridge width may be second layer>third layer (i.e., the width of center bridge 20c>width of center bridge 30c).

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

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 end of the magnet groove 24A on the second layer side.

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 end of the magnet groove 36A on the third layer side.

A fourth rotor core outer peripheral groove 44 is engraved on the outer peripheral end 10a of the core 10 near the recess 36a on the third layer side.

The depth and position of the first to fourth rotor core outer peripheral grooves 41 to 44 and the positional relationship between the magnets 12, 24, 36 and the recesses 12a, 24a, 36a are set as follows:

The depths of the second to fourth rotor core outer circumferential grooves 42 to 44 are set such that the depth of the second rotor core outer circumferential groove 42 is less than or equal to the depth of the third rotor core outer circumferential groove 43 and less than or equal to the depth of the fourth rotor core outer circumferential groove 44.

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

The angle between the d-axis and the end of the magnet 12 in the first layer magnet group closest to the outer peripheral end 10a of the iron core 10, is f1; the angle between the d-axis and the end of the magnet 24 in the second layer magnet group closest to the outer peripheral end 10a of the iron core 10, is f2; and the angle between the d-axis and the end of the magnet 36 in the third layer magnet group closest to the outer peripheral end 10a of the iron core 10, is f3.

The angle between the q-axis side corner 12aq and the d-axis in the recess 12a on the first layer side is f1', the angle between the q-axis side corner 24aq and the d-axis in the recess 24a on the second layer side is f2', and the angle between the q-axis side end of the recess 36b on the third layer side is f3'.

These are set so that 0<g1<f1, f1'<g2<f2, f2'<g3<f3, and (f3+f3')/2≦g4≦f3'.

The depth and position of the rotor core outer peripheral grooves 41-44 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 Figure 4.

By carving the rotor core outer circumferential grooves 41 to 44 as shown in Figure 4, the shoulder portion of the gap magnetic flux density distribution waveform is suppressed, and the harmonic components can be reduced. By setting the depth of the rotor core outer circumferential grooves so that the depth of the second rotor core outer circumferential groove 42 is less than or equal to the depth of the third rotor core outer circumferential groove 43 and less than or equal to the depth of the fourth rotor core outer circumferential groove 44, the amount of magnetic flux suppression gradually increases from the d-axis to the q-axis, and the harmonics of the waveform can be suppressed more effectively.

If the rotor core outer circumferential groove is located closer to the q-axis than the angle f3' between the q-axis end of the recess 36b on the third layer side and the d-axis, torque reduction is large, so the distance g4 from the d-axis to the fourth rotor core outer circumferential groove 44 should be f3 < g4 ≦ f3' as shown in Figure 4.

In this case, if the fourth rotor core outer peripheral groove 44 is too close to f3, the bridge thickness will be small and the strength will decrease, so the fourth rotor core outer peripheral groove 44 is located closer to the q-axis than the midpoint between f3 and f3' in Figure 4 and is equal to f3' or closer to the d-axis than f3', that is, (f3 + f3')/2 ≤ g4 ≤ f3', which allows both reduction in centrifugal stress and reduction in stress.

The depth of the first rotor core outer circumferential groove 41 may be greater than or equal to the depth of the second rotor core outer circumferential groove 42, and instead of the first rotor core outer circumferential groove 41, the slit portions 11X and 12X protruding toward the d-axis side described in FIG. 5 may be used. If the second rotor core outer circumferential groove 42 to the fourth rotor core outer circumferential groove 44 were to be the slit portions, the reduction in Lq (q-axis side reactance) would be large, resulting in a decrease in torque, so the outer circumferential grooves (42 to 44) are preferable.

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

Figure 6 shows that when rotor core outer peripheral grooves 41-44 are provided, the total harmonic rate is reduced from 15% to 10%.

Reference Signs List 1: rotor 2: motor shaft 3: auxiliary magnetic pole portion 5: stator 10: core 10a: rotor core outer periphery 10c, 20c, 30c: center bridge portion 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...recessed portion 11X, 12X...slit portion 41 to 44...rotor core outer peripheral groove 51...stator coil 52...stator slot

Claims (5)

A straight line connecting the rotor axis and the center of any main magnetic 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 around 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 recesses extending outward at each of the four corners;
a plurality of third layer side magnet grooves, which are 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, and each of which has a recess extending outward at each of its four corners;
a first layer side magnet group including two magnets that are fitted into the first layer side magnet groove and are 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. 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. A straight line connecting the rotor axis and the center of any main magnetic 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 around 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 recesses extending outward at each of the four corners;
a plurality of third layer side magnet grooves, which are 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, and each of which has a recess extending outward at each of its four corners;
a first layer side magnet group including two magnets that are fitted into the first layer side magnet groove and are 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 on the second layer side magnet group 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 on the third layer side magnet group 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'. 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. 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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