Permanent magnet type rotating electric mechanism

Abstract

A permanent magnet type rotating electrical mechanism comprising: a stator (20) having stator windings (3) wound on a plurality of tooth sections (2a) formed on a stator core (2); and a rotor (30) having permanent magnets (5) embedded between a plurality of magnetic poles formed along a circumferential direction of a rotor core (4), the rotor (30) being rotatable integrally with a shaft (6), the rotor core (4) has a low permeability region (4a, 4b) which has a lower permeability than the material of the rotor core (4), between an outer circumference of each magnetic pole and a side surface of each permanent magnet (5), the low permeability region (4a, 4b) is formed asymmetrically with respect to a geometric center in the circumferential direction of each magnetic pole, so that a magnetic center (A) of the magnetic pole is shifted to one side with respect to the geometric center (B), and the rotor cores (4) are arranged inverted with respect to one another so that a relative position in the circumferential direction of the low permeability regions (4a, 4b) differs with respect to the permanent magnets (5), where, in the case where Z is a number of slots of the stator (Z is a natural number), P is the number of magnetic poles of the rotor (P is a natural number), m is a number of phases, and a number q of slots per pole per phase is represented as q = Z / (mx P), an electrical angle by which the magnetic center is shifted with respect to the geometric center of each magnetic pole when q satisfies (2 / 5) ≤ q < (1 / 2) is set to 15 degrees or greater, and when q satisfies (1 / 2) ≤ q, is set to 30 degrees or greater.

Description

Technical field

[0001] The present invention relates to an internal permanent magnet (IPM) type rotating electric mechanism having permanent magnets embedded in a rotor. State of the art

[0002] In rotating electrical mechanisms such as industrial or automotive motors, high torque, low cogging torque, a wide operating range, and the like must be realized. As a technical method for meeting such requirements, for example, a rotor for a rotating electrical mechanism is disclosed, which includes a rotor having permanent magnets embedded near its outer periphery and having air gaps formed on the outer peripheral side with respect to the permanent magnets such that the position in the circumferential direction of the air gaps differs depending on a position in the axial direction. Since the air gaps are located at different positions in the circumferential direction, the respective cogging torques cancel each other, and thus cogging torque is suppressed (see, for example, Patent Document 1).

[0003] Another rotating electric mechanism is disclosed which has a plurality of rotor cores each having a permanent magnet insertion hole asymmetric in the circumferential direction and having openings symmetrical to each other in the circumferential direction at both ends of the insertion hole, wherein the plurality of rotor cores are alternately inverted and integrally fixed in the axial direction to form a single rotor core (see, for example, Patent Document 2).

[0004] Patent Document 3 describes a permanent magnet dynamoelectric machine including a stator in which the armature winding of the concentrated winding is mounted so as to surround the teeth in a plurality of slots formed in a stator core, and a rotor having permanent magnets arranged in a plurality of permanent magnet insertion holes in the rotor core is rotatably supported by a rotating shaft via a gap on the inner circumference of the stator. The permanent magnet insertion holes provided on the rotor stator are positioned at the same positions in its axial direction when the magnetic flux axis of the permanent magnets is defined as a d-axis and the axis deviating at an electrical angle of 90° from the d-axis is defined as a q-axis. A plurality of magnetic pole slots are provided on the magnetic pole core above the permanent magnet insertion holes.A magnetic pole core is manufactured in which the gap length on the q-axis side is larger than the gap length on the d-axis side to collect the magnetic flux of the permanent magnets. The circular parts of the magnetic pole cores are arranged asymmetrically around the center of the d-axis, a plurality of gap surfaces are provided on the peripheral surface of the magnetic pole core, and the positions of the magnetic pole cores are shifted in a V-shape in their axial direction.

[0005] Patent Document 4 shows an electric machine including a stator and a rotor disposed adjacent to the stator and configured to rotate relative to the stator. The rotor includes a plurality of laminations having an outer diameter and stacked in a stacking direction. Each lamination includes a plurality of nonlinear slots disposed within the outer diameter. Each nonlinear slot includes an inner portion disposed a first distance from the outer diameter and two end portions disposed a second distance from the outer diameter. The second distance is smaller than the first distance. The rotor also includes a plurality of permanent magnets. Each magnet is disposed in one of the nonlinear slots. Quotation listPatent documents Patent Document 1: JP 2005- 176 424 A (page 5, Fig. 5 and Fig. 6) Patent Document 2: JP 2000-134 841 A (pages 3 and 4, Fig. 2 to Fig. 4) Patent Document 3: JP 2008 - 29 095 A Patent specification 4: US 2008 / 0 224 558 A1 Summary of the inventionProblems to be solved by the invention

[0006] In the conventional structure shown in Patent Document 1 above, air gaps are provided in a rotor core portion to reduce cogging torque. However, such air gaps provided near a rotor surface have little effect on reducing q-axis inductance resulting from q-axis magnetic flux. Therefore, there is a problem that inductance increases compared to an SPM motor with a surface magnet structure, and an operating range is reduced due to a power supply voltage constraint.

[0007] Similarly, in the structure shown in Patent Document 2, the shapes of both ends of the permanent magnet insertion hole in the axial direction are changed to reduce cogging torque and torque ripple. However, the q-axis inductance resulting from the q-axis magnetic flux is hardly reduced. Therefore, especially in the case of an IPM motor whose inductance is larger than that of an SPM motor, there is still a problem that the operating range is reduced.

[0008] The present invention has been made to solve the above problems, and an object of the present invention is to provide, in particular, a permanent magnet type rotating electric mechanism in which both a cogging torque and torque ripple are reduced while lowering the q-axis inductance. Solution to the problems

[0009] The object underlying the invention is achieved by a rotating electrical mechanism of the permanent magnet type according to claim 1.

[0010] Advantageous developments of the rotating electric mechanism according to the present invention are specified in the dependent claims 2 to 8. Effects of the invention

[0011] According to the permanent magnet type rotating electric mechanism of the present invention, the rotor core has a low-permeability region having a lower permeability than the material of the rotor core between an outer periphery of each magnetic pole and a side surface of each permanent magnet. The low-permeability region is formed asymmetrically with respect to a geometric center in the circumferential direction of each magnetic pole so that the magnetic center of each magnetic pole is shifted to one side. The rotor cores are arranged upside down with respect to each other so that a relative position in the circumferential direction of the low-permeability regions with respect to the permanent magnets differs. Therefore, q-axis inductance can be reduced thanks to the formation of the low-permeability regions, and a reduction in an operating range due to a power supply voltage constraint can be prevented.In addition, since the relative position in the circumferential direction of the low permeability regions is different, cogging torque and torque ripple phases are shifted, which achieves the same effect as in the case of skewing permanent magnets and can reduce cogging torque and torque ripple. Short description of the drawings Fig. 1 is a sectional view of a permanent magnet type rotating electric mechanism according to Embodiment 1 of the present invention taken along a direction perpendicular to the axial direction. Fig. 2 is a sectional view of a rotor of the permanent magnet type rotating electric mechanism in Fig. 1 along a direction perpendicular to the axial direction. At Fig. 3 are sectional views of a core I and a core II, from which the rotor in Fig. 2. Fig. 4 is a view showing the core I and the core II in Fig. 3, which are combined in the axial direction. Fig. 5 is a sectional view of a rotor of a permanent magnet type rotating electric mechanism taken along a direction perpendicular to the axial direction as a comparative example. Fig. 6 is a waveform diagram of cogging torques in the case that the Fig. 3 and Fig. 5 shown rotor cores can be used. At Fig. 7 are sectional views showing another example of the core I and the core II of the rotor of the permanent magnet type rotating electric mechanism according to Embodiment 1 of the present invention. Fig. 8 is a view of Core I and Core II of Fig. 7, which are combined in the axial direction. Fig. 9 is a sectional view taken along a direction perpendicular to the axial direction, showing still another example of the rotor of the permanent magnet type rotating electric mechanism according to Embodiment 1 of the present invention. Fig. 10 is a sectional view of the rotor in the case where the number of cavities constituting a low permeability region of the rotor core in the first embodiment is changed. Fig. Figure 11 is a diagram showing the relationship between the number of cavities of the low permeability region and the magnitude of a harmonic in the Fig. 10 shows the rotor. Fig. 12 is a sectional view of a rotor of a permanent magnet type rotating electric mechanism according to Embodiment 2 of the present invention taken along a direction perpendicular to the axial direction. Fig. 13 is a diagram showing the relationship between an inductance reduction rate and a depth to which a low permeability region is formed in a region up to a depth L in a radial direction of the Fig. 12 shows the rotor core. Fig. Fig. 14 is a diagram showing the relationship between a depth to which the low permeability region is formed and a difference in an inductance reduction rate calculated from Fig. 13 is calculated. Fig. 15 is a partial sectional view of a rotor of a permanent magnet type rotating electric mechanism according to Embodiment 3 of the present invention taken along a direction perpendicular to the axial direction. Fig. 16 is a diagram showing the relationship between torque ripple and an angle by which a magnetic pole center is shifted in a rotor of a permanent magnet type rotating electric mechanism according to Embodiment 4 of the present invention. Fig. 17 is a diagram for explaining the case where the axial length of the rotor of the permanent magnet type rotating electric mechanism according to Embodiment 4 is changed. Fig. 18 is a diagram showing the relationship between a 6f component of torque ripple and an angle by which a magnetic pole center is shifted in each rotor of Fig. 17 shows. Fig. 19 is a view of a core I and core II combined in the axial direction of a rotor of a permanent magnet type rotating electric mechanism according to Embodiment 5 of the present invention. Description of the embodimentsEmbodiment 1

[0012] Fig. 1 is a sectional view of a permanent magnet type rotating electric mechanism according to Embodiment 1 of the present invention taken along a direction perpendicular to the axial direction of a rotating shaft. Fig. 2 is a sectional view of a rotor showing only a rotor part of Fig. 1 shows. In the Fig. 1 and Fig. 2, the number of teeth of a stator is 12, and the number of magnetic poles of the rotor is 10.

[0013] First, with reference to Fig. 1 describes the summary of the overall structure of the permanent magnet type rotating electric mechanism. A permanent magnet type rotating electric mechanism 10 includes a stator 20 supported by an inner wall of a casing 1 and a rotor 30 inserted through an extremely small gap inside the stator 20.

[0014] The stator 20 has a stator core 2 formed by stacking thin electromagnetic steel sheets having a ring shape, and a stator winding 3 wound around twelve tooth portions 2a formed on the inner peripheral side of the stator core 2 via an insulator.

[0015] On the other hand, the rotor 30 has a rotor core 4 with ten magnetic poles, ten permanent magnets 5 embedded between the magnetic poles of the rotor core 4, and a shaft 6 fixed in the center of the rotor core 4 and having ends supported by bearings (not shown) provided on brackets of the housing 1 so that the shaft 6 is rotatable. The permanent magnets 5 have a rectangular cross-sectional shape whose longitudinal direction is directed in a radial direction and are made of the Fig. 1, starting from the center side to the outer peripheral side of the rotor core 4, are arranged radially and equally along the circumferential direction.

[0016] The rotor core 4 has low-permeability regions 4a and 4b, which have a lower permeability than a material forming the rotor core 4. Their details will be described later.

[0017] When current is applied to the stator winding 3 to form a rotating magnetic field, the rotor 30 rotates around the shaft 6.

[0018] With reference to Fig. 2 the structure of the rotor 30 is described in more detail.

[0019] The rotor core 4 consists of multiple thin electromagnetic steel sheets stacked in the axial direction of the rotor 30.

[0020] The permanent magnets 5 are embedded substantially over the entire axial length of the rotor core 4, and their magnetization directions are as shown in Fig. 2. In order to prevent each permanent magnet 5 from protruding from the rotor core 4 due to centrifugal force during rotation of the rotor 30, a nail portion 4c is provided on the outer peripheral side of the rotor core 4 to lock the permanent magnet 5. Although in Fig. 2, a non-magnetic material may be provided between the nail portion 4c and the permanent magnet 5. The non-magnetic material is provided only on the rotor outer peripheral side of the permanent magnet 5 and also plays a role in dissipating a stress exerted by the nail portion 4c on the permanent magnet 5. The permanent magnet 5 and the rotor core 4 may be fixed by an adhesive or the like to increase their strength.

[0021] In the rotor core 4 of Fig. 2, the magnetic poles are formed individually and then combined with the permanent magnets 5. However, disc-like electromagnetic steel sheets with permanent magnet insertion holes and shaft insertion holes punched therein can also be stacked on top of each other.

[0022] As a feature of the present invention, the rotor core 4 has the low permeability regions 4a and 4b near its outer periphery, which are asymmetric in the circumferential direction at each of the magnetic poles of the rotor core 4.

[0023] At each individual pole, from the direction of Fig. 2, a center line in the radial direction connecting the center of the outer circumferential length of the fan-shaped magnetic pole and the center of the shaft 6, that is, a geometric center line of the magnetic pole, is denoted by A, and a magnetic center line of the magnetic pole is denoted by B. In this case, the low-permeability region 4a and the low-permeability region 4b are formed asymmetrically with respect to the center line A, so that the center line B is shifted from the center line A by a predetermined angle θ. Thus, the magnetic center (hereinafter simply referred to as the magnetic pole center), which is the center of a magnetic flux passing through the magnetic pole portion, is shifted from the center line A. That is, the asymmetric formation of the low-permeability regions 4a and 4b shifts the magnetic pole center from the geometric center to one side in the circumferential direction.

[0024] The low permeability regions 4a and 4b are formed, for example, by several thin cavities that have an arc shape, as in Fig. 2 is shown. In Fig. 2 the arches have different lengths to achieve the asymmetry.

[0025] The displacement direction of the asymmetric low permeability regions 4a and 4b is reversed in the center in the axial direction of the rotor 30, so that the displacement direction is reversed depending on a position in the axial direction of the rotor 30. This is explained with reference to Fig. 3 and Fig. 4 described. Fig. 3 is a sectional view of the rotor core 4 seen from the axial direction. Fig. 4 is a plan view of the rotor core 4 as seen from a direction perpendicular to the axial direction. In Fig. 4 the permanent magnets 5 are not shown.

[0026] In Fig. 3, a kernel I in (a) has the same form as in Fig. 2, and a core II at (b) has the low-permeability region 4a and the low-permeability region 4b reversed in the circumferential direction compared to core I. That is, the relative position of the low-permeability regions 4a and 4b differs in the circumferential direction with respect to the permanent magnets 5 between (a) and (b). In fact, core II is obtained by reversing core I.

[0027] That is, in the manufacture of the rotor, core I and core II are manufactured using the same mold. For example, assuming the surface shown in (a) as a front surface, core I consists of multiple electromagnetic steel sheets superimposed on each other with their front surfaces facing upward, and core II consists of multiple electromagnetic steel sheets superimposed on each other with their back surfaces facing upward. Therefore, since the same mold can be used, manufacturing costs can be reduced.

[0028] In Fig. 3, which are each stacked to the same height, are combined to form the whole such that one half in the axial direction of the rotor 30 corresponds to the block of the core I and the other half to the block of the core II, as shown in Fig. 4 is shown.

[0029] Here, while the geometric centerline of the core is denoted by A and the magnetic centerline of each magnetic pole by B, as in Fig. 2 is shown in Fig. 3 a crossing of the line B and the core outer circumference is designated as point C for core I and as point D for core II. In this case, as in Fig. 4, point C and point D are offset from each other in the axial direction. In addition, in the region of core I, point C continuously appears at the same position in the axial direction, and similarly, in the region of core II, point D continuously appears at the same position in the axial direction.

[0030] Fig. Figure 5 is a sectional view of a rotor of a permanent magnet type rotating electric mechanism, showing a comparative example for explaining the operation and effect of the present invention. The number of magnetic poles of the rotor is 10, as shown in Fig. 2, and low-permeability regions 4d are formed symmetrically in each individual pole of the rotor core 4. That is, the geometric center and the magnetic center of each magnetic pole coincide with each other.

[0031] In the case where a magnetic flux axis of the rotor core 4 is defined as a d-axis and an axis orthogonal to the d-axis with respect to an electrical angle is defined as a q-axis, a q-axis magnetic flux in a two-dot chain line part is Fig. 5 is shown representatively. The Fig. The low-permeability regions 4d shown in Fig. 5, which are formed in the rotor core 4, block the flow of the q-axis magnetic flux, thereby reducing the q-axis inductance. The same applies to the case where the low-permeability regions 4a and 4b are formed in each pole of the rotor core, such as in the core I and the core II shown in Fig. 3 of the present invention are formed asymmetrically, and the q-axis inductance can be reduced.

[0032] Next, the operation and effect of the present invention will be explained with reference to Fig. 6 described.

[0033] Fig. 6 is a diagram showing waveforms of cogging torques that occur when the rotor of the Fig. 5 and the comparison example shown in Fig. 4 shown rotor 30 of the present invention, which has a Fig. 3 shown combination of the core I and the core II, can be set in rotation in the case in which the number of teeth of the stator 20 as in Fig. 1 shown is 12.

[0034] Waveforms of cogging torques occurring at the core I and core II in the rotor 30 of the present invention have phases shifted from a cogging torque waveform (shown by a thin solid line) in the rotor having the low permeability regions 4d shown in Fig. 5, are formed symmetrically in each pole. That is, a waveform shown by a dashed line occurs in core I, and a waveform shown by a dotted line occurs in core II. As a result, in the rotor 30 of the present invention, which has core I and core II, the waveforms shown in Fig. 4, are combined in the axial direction, both waveforms are synthesized to form a waveform represented by a thick solid line in Fig. 6 shown waveform, and it turns out that a cogging torque compared to the rotor of Fig. 5 is reduced.

[0035] In addition, as described above, since the q-axis inductance can be reduced thanks to the formation of the low permeability regions 4a and 4b in the rotor core 4, a reduction in an operation range due to a power supply voltage constraint condition can be suppressed, and, for example, a rotation speed range in which constant torque operation can be performed can be expanded.

[0036] In Fig. 1, the number of teeth of the stator is 12, and the number of magnetic poles of the rotor is 10. However, the number of teeth of the stator and the number of magnetic poles of the rotor are not limited to those in Fig. 1. The same effect can also be achieved by a rotating electrical mechanism with a different combination of the number of teeth and the number of magnetic poles.

[0037] In the above description, the low-permeability regions in the rotor core are formed by a plurality of arc-shaped cavities. However, the low-permeability regions can also be formed by deformation in the thickness direction to cause magnetic degradation, and their shapes are not particularly limited. However, the low-permeability regions formed by a plurality of arc-shaped cavities between the outer periphery of the magnetic poles and the side surfaces of the permanent magnets can most effectively reduce inductance.

[0038] In the rotor described above, the two low-permeability regions 4a and 4b are formed asymmetrically with respect to the geometric center line A of each magnetic pole, thereby shifting the magnetic center of the magnetic pole to one side with respect to the geometric center. Modifications of this will be described next.

[0039] At Fig. 7 are sectional views taken along a direction perpendicular to the axial direction, showing another example of the core I and the core II of the rotor of the permanent magnet type rotating electric mechanism. Fig. 8 is a view of Core I and Core II shown in Fig. 7, which are combined in the axial direction. A difference to Fig. 3 is that a low permeability region 4e is formed near the outer circumference of the rotor core 4 on only one side in the circumferential direction of each pole of the rotor core 4.

[0040] As in Fig. As shown in Fig. 7, the low-permeability region 4e is formed between the outer periphery of each magnetic pole of the rotor core 4 and a side surface of one of the permanent magnets 5 arranged on both sides of the magnetic pole. The low-permeability region 4e in the core II of (b) is formed on the opposite side in the circumferential direction with respect to that in the core I of (a). Actually, the core II is obtained by inverting the core I. Therefore, the core II can be manufactured by punching with the same die.

[0041] In Fig. 7 shown blocks of the core I and the core II are joined in the axial direction of the rotor core 4 at the center position to be integrated, as in Fig. 8 is shown.

[0042] The same functionality and effect as in Fig. 3 can also be achieved by such a structure. If the low permeability regions of the rotor core 4 are increased, the strength of the rotor core 4 is weakened. However, since the low permeability regions 4e are smaller than in the case of Fig. 3 are formed only on one side, the strength of the entire rotor core 4 is increased, and therefore the rotational speed of the rotor can be increased.

[0043] Fig. 9 is a sectional view taken along a direction perpendicular to the axial direction, showing yet another modification example of the rotor of the permanent magnet type rotating electric mechanism. In the above description, the permanent magnets 5 are arranged radially. In the present example, two permanent magnets 5 are provided for one pole of the rotor core 4. The two permanent magnets 5 are arranged to extend in a V shape from the center side to the outer peripheral side of the rotor core 4. The magnetization directions of the permanent magnets 5 are indicated as N and S in Fig. 9 shown.

[0044] As in the case of Fig. 2 is a center line in the radial direction connecting the center in the outer circumferential direction of the fan-shaped magnetic pole and the center of the shaft 6, that is, a geometric center line of the magnetic pole, denoted by A, and a magnetic center line of the magnetic pole is denoted by B. In this case, the low permeability region 4a and the low permeability region 4b are formed asymmetrically with respect to the center line A, so that the center line B is shifted from the center line A by a predetermined angle θ. Thus, the magnetic pole center is shifted. In addition, as in the case of Fig. 4 the displacement direction in the axial direction of the rotor is reversed in the middle.

[0045] The same operation and effect as above can also be achieved by the rotating electrical mechanism of the permanent magnet type, which is shown in Fig. 9 is removed. In addition, the Fig. 9 can be applied to the embodiments to be described later in addition to Embodiment 1.

[0046] Next, the number of cavities in the case where the low-permeability regions are formed by thin cavities will be described. For example, the low-permeability regions can be changed by changing the length of each cavity, increasing the number of cavities, or changing the area of ​​each cavity. Among these methods, changing the number of the plurality of cavities is effective in terms of harmonic suppression, as described below.

[0047] Fig. 10 is a sectional view of the rotor of the permanent magnet type rotating electric mechanism similar to Fig. 2. In Fig. 10, for example, the number of cavities in one (4f) of the asymmetrically formed low permeability regions is four, and the number of cavities in the other (4g) is two. Fig. Figure 11 is a diagram showing the magnitude of a harmonic that occurs when the rotor of Fig. 10 rotates counterclockwise in the case where the number of cavities in the low-permeability region 4f on a delayed side is changed in the direction of rotation. A harmonic in the case where the number of cavities in the low-permeability region 4f is four is defined as 1.

[0048] Out of Fig. From Figure 11, it can be seen that a harmonic can be further reduced by increasing the number of cavities forming the low-permeability region 4f from four. Reducing a harmonic can reduce torque ripple and iron loss. Thus, increasing the number of cavities is effective in counteracting a harmonic. However, an excessive increase in the number of cavities causes problems in terms of machining and strength. Therefore, it is desirable to determine the number of cavities in light of the size, capacity, usage conditions, etc. of the rotating electrical mechanism.

[0049] As described above, the permanent magnet type rotating electric mechanism of Embodiment 1 includes a stator having stator windings wound on a plurality of tooth portions formed on a stator core; and a rotor having permanent magnets sandwiched between a plurality of magnetic poles formed along a circumferential direction of a rotor core, the rotor being rotatable integrally with a shaft. The rotor core has a low permeability region, which has a lower permeability than the material of the rotor core, between the outer periphery of each magnetic pole and a side surface of each permanent magnet. The low permeability region is formed asymmetrically with respect to the geometric center in the circumferential direction of each magnetic pole, so that the magnetic center of each magnetic pole is shifted to one side with respect to the geometric center.Such rotor cores are arranged upside down with respect to each other so that the relative position of the low-permeability regions in the circumferential direction differs with respect to the permanent magnets. Therefore, in an IPM rotating electric mechanism with an internal magnet structure, which generally has a larger inductance than an SPM rotating electric mechanism with a surface magnet structure, the q-axis inductance can be reduced thanks to the formation of the low-permeability regions, and a reduction in the operating range due to a power supply voltage constraint can be prevented.Since the relative position of the low permeability regions in the circumferential direction is different, cogging torque and torque ripple phases are shifted, which achieves the same effect as in the case of skewing permanent magnets and can reduce cogging torque and torque ripple.

[0050] The permanent magnets are arranged radially from the center to the outer peripheral side of the rotor core. Therefore, low-permeability regions can be effectively provided in a rotating electrical IPM mechanism, and the effect of reducing q-axis inductance is enhanced.

[0051] Two permanent magnets may be provided for one magnetic pole of the rotor core, and the two permanent magnets may be arranged to extend in a V-shape from the center to the outer peripheral side of the rotor core. Thus, the same effect as above can be achieved even in a rotating electric IPM mechanism with permanent magnets arranged in a V-shape.

[0052] Each low-permeability region is formed by a plurality of thin cavities formed between the outer periphery of each magnetic pole of the rotor core and each side surface of the permanent magnets arranged on both sides of the magnetic pole. The number or length of the cavities differs between the right and left with respect to the geometric center of each magnetic pole. Therefore, the low-permeability regions can be easily and effectively formed with a forming die during rotor core manufacturing. Furthermore, a harmonic wave with a magnetic flux waveform generated from the surface of the rotor core can be reduced, and cogging torque and torque ripple can be further reduced.

[0053] Each low-permeability region may be formed by a plurality of cavities formed between the outer periphery of each magnetic pole of the rotor core and a side surface of one of the permanent magnets arranged on both sides of the magnetic pole. In this case, the rigidity of the rotor is increased compared to the case of providing the low-permeability regions on both sides, and therefore the rotational speed can be increased. Embodiment 2

[0054] Fig. 12 is a sectional view of a rotor of a permanent magnet type rotating electric mechanism according to Embodiment 2. The sectional shape of the entire permanent magnet type rotating electric mechanism is the same as that of Embodiment 1 of Fig. 1, so the drawing and its description are omitted. Fig. 13 is a diagram showing the relationship between a depth to which the low permeability region is formed and an inductance reduction rate in the present embodiment. Fig. 14 is a diagram showing the relationship between the depth to which the low permeability region is formed and the difference in inductance reduction rate. The present embodiment refers to the region where the low permeability region is formed in the rotor core 4.

[0055] In Fig. 12, L denotes a depth from the outer peripheral surface of the rotor core 4 to the center side of the shaft.

[0056] Fig. 13 shows the relationship between a depth to which the low permeability regions 4a and 4b are formed and the inductance reduction rate within a region up to the depth L from the outer peripheral surface of the rotor core 4. Here, L = 0 indicates that no low permeability regions 4a and 4b are formed at all.

[0057] Fig. 14 shows a depth to which the low permeability region is formed and a difference in inductance reduction rate based on Fig. 13.

[0058] As in Fig. As shown in Figure 13, from the outer peripheral side to the shaft side in the rotor core 4, the deeper the low-permeability region is formed, the lower the inductance reduction rate. Since a reduction effect is achieved, the deeper the low-permeability region is formed, the more the inductance is reduced. However, if the low-permeability region is formed deeply, the strength of the rotor core 4 is reduced. Therefore, it is necessary to effectively reduce the inductance without increasing the depth of the low-permeability region more than necessary.

[0059] As shown by the relationship between a depth to which the low permeability region is formed and a difference in the inductance reduction rate in Fig. As shown in Figure 14, the inductance can be reduced most effectively at a depth of approximately 1 / 4 L. A position where the difference in the reduction rate is the same as in the case where the low permeability region is formed near the outer periphery is at a depth of approximately 1 / 2 L.

[0060] Based on the above, it is effective that the depth to which the low permeability region is formed is set to within ½ of the depth L from the outer peripheral surface of the rotor toward the center side of the shaft.

[0061] As described above, in the permanent magnet type rotating electric mechanism of Embodiment 2, in the case where L is a depth from the outer circumference of the stator core to the shaft surface, the low permeability region is formed within a range of 1 / 2 L from the outer circumference side. Therefore, while suppressing a reduction in the strength of the rotor core, the low permeability region can be effectively formed, and the same effect as in Embodiment 1 can be achieved. Embodiment 3

[0062] Fig. 15 is a partial sectional view of a rotor of a permanent magnet type rotating electric mechanism according to Embodiment 3. The overall shape of the rotor is the same as that of Embodiment 1 in Fig. 2, so the drawing and description thereof are omitted. The present embodiment specifies the position where the low permeability region is formed in more detail.

[0063] As in Fig. 15 in a cross section perpendicular to the axial direction, a denotes a distance from the outer peripheral surface of the rotor core 4 to ends of the low permeability regions 4a and 4b (hereinafter represented by 4a) which are close to the outer peripheral surface, and b denotes a distance from a side surface of the permanent magnet 5 (a long side of its rectangular sectional shape) to an end of the low permeability region 4a which is close to the side surface.

[0064] Shortening the length a makes it possible to lengthen the low-permeability region 4a, thereby providing an effect of reducing q-axis inductance. However, in the case where the rotor core 4 is manufactured with a die, an electromagnetic steel sheet is usually punched during manufacturing. Therefore, it is necessary to ensure the length so that the electromagnetic steel sheet is prevented from warping during punching.

[0065] Regarding the distortion, in the case where, for example, the rotor core 4 was manufactured with a general electromagnetic steel sheet having a thickness of 0.35 mm, it was found that the length a can be set to 0.2 mm to 0.7 mm depending on the design of the forming die or its accuracy.

[0066] On the other hand, the length b from a side surface of the permanent magnet 5 to the low permeability region 4a corresponds to the area of ​​the permanent magnet 5 in contact with the rotor core 4, and the area is subjected to a force from the permanent magnet 5 when the rotor 30 rotates. In addition, since the nail portion 4c prevents the permanent magnet 5 from dissipating due to centrifugal force, a large force is applied to the nail portion 4c. Therefore, if the length b is short, the strength of the rotor 30 is lowered. Therefore, it is necessary to lengthen the length b to an extent that an inductance reduction effect is not lost.

[0067] In view of the above, it was found that if the length a is set within the above range and the length a and the length b are adjusted so that a < b, a structure can be achieved that can reduce inductance while achieving a desired rotor strength. Furthermore, it was found that if the length b is set to approximately 3 mm or shorter, the inductance reduction effect is hardly lost.

[0068] When the rotor strength is reduced, there is a possibility that the permanent magnets will drift apart due to centrifugal force, and therefore, it is difficult to increase the rotational speed of the rotor. However, by adopting the structure of Embodiment 3, it becomes possible to increase the rotational speed of the rotor without reducing the rotor strength.

[0069] As described above, in the permanent magnet type rotating electric mechanism of Embodiment 3, in the case where a is a distance from the outer peripheral surface of each magnetic pole of the rotor core to an end of each low permeability region close to the outer peripheral surface, and b is a distance from a side surface of each permanent magnet to an end of each low permeability region close to the side surface, a is set to 0.2 mm to 0.7 mm, and b is longer than a but not longer than 3 mm. Therefore, in addition to providing the same effect as in Embodiment 1, it is possible to increase the rotation speed while suppressing a decrease in the rigidity of the rotor due to the formation of the low permeability regions.

[0070] During motor rotation, iron loss of the rotor surface occurs due to changes in the permeability of the slots. To reduce iron loss, reduce flux leakage, and improve performance while maintaining strength, it is preferable to set the length a to 0.2 mm, which is the minimum value, and the length b to approximately 0.35 mm, which is equal to the sheet thickness, taking punching into account. Embodiment 4

[0071] Fig. 16 is a diagram for explaining an effect of reducing a 6f component and a 12f component of torque ripple in a permanent magnet type rotating electric mechanism according to Embodiment 4. The entire structure of the rotating electric mechanism is the same as that of Fig. 1, and the sectional view of the rotor is the same as that of Fig. 2, Fig. 7, Fig. 9, Fig. 10, etc., so the drawings and descriptions thereof are omitted. The present embodiment refers to an electrical angle by which the magnetic center of each magnetic pole is shifted by the formation of the low-permeability regions.

[0072] In a graphical torque ripple display in Fig. Figure 16 is a graph in an ideal state where no magnetic flux leakage occurs in the axial direction or the like. The magnitudes of a 6f component and a 12f component of torque ripple in a state where the magnetic center of each magnetic pole is not shifted are defined as 1. Note that f is an electrical cycle.

[0073] If the number of slots (= number of teeth) of the stator is denoted by Z (Z is a natural number), the number of phases is denoted by m, and the number of poles of the rotor is denoted by P (P is a natural number), a number q of slots per pole per phase is represented as q = Z / (m × P). A magnitude principal component of torque ripple occurring during driving differs depending on the value of q.

[0074] For example, in the case of Fig. For the three-phase rotating electrical mechanism shown in Figure 1, q = 2 / 5, and a torque ripple principal component is a 12f component. When q = 1 / 2 or q = 1, a torque ripple principal component is a 6f component.

[0075] Therefore, in the case where the magnetic center of each magnetic pole is shifted by means of the low permeability regions as in the present invention, if the shift angle is changed in accordance with the value of q, a torque ripple can be further effectively reduced.

[0076] Starting from Fig. 16 Theoretically, in the case that q = 2 / 5, when the magnetic pole center is shifted by an electrical angle of 15 degrees to reduce a 12f component, a torque ripple principal component can be reduced, and in the case that q = ½ or q =1, that is, q ≥ ½, when the magnetic pole center is shifted by an electrical angle of 30 degrees to reduce a 6f component, a torque ripple principal component can be reduced.

[0077] Fig. Figure 16 shows an ideal state. In fact, due to the influence of stray magnetic flux and the like, the displacement angle varies depending on the length of the rotor core. This will be described below.

[0078] Fig. Figure 17 is an axial direction view showing models of rotor cores of rotating electrical mechanisms with different lengths when q = 1 / 2. Each model has a combination of cores reversed to each other at the center position in the axial direction. Although an axial length L of a model in which the rotor diameter and axial length are substantially the same is used as a reference, a total of three models with axial lengths L, 1.5L, and 2L are shown. Fig. Figure 18 shows a 6f torque ripple component obtained in the case where the magnetic pole center in each model of Fig. 17 is postponed.

[0079] In the case where the length of the rotor core of the rotating electrical mechanism differs, the torque ripple cannot be reduced in the same way even if the displacement angle of the magnetic pole center is the same. Fig. 16, the displacement angle of the magnetic pole center that can reduce a 6f torque ripple component the most is 30 degrees in the case of q = ½. However, in fact, as shown in Fig. As shown in Figure 18, the displacement angle is offset, and the displacement amount also varies depending on the axial length. However, in any case, it turns out that torque ripple can be further effectively reduced when the displacement angle is greater than 30 degrees.

[0080] In this respect, the same result is also obtained for a 12f torque ripple component. In the case of q = 2 / 5, the displacement angle of the magnetic pole center is Fig. The ideal state shown in Figure 16 is 15 degrees. When the displacement angle is greater than 15 degrees, torque ripple can be further effectively reduced.

[0081] Based on the above, in the case of q = 2 / 5, when the shift angle of the magnetic pole center is set to be larger than 15 degrees at which a 12f torque ripple component can be reduced most in an ideal state, a torque ripple can be further effectively reduced, and in the case of q ≥ 1 / 2, when the shift angle of the magnetic pole center is set to be more than 30 degrees at which a 6f torque ripple component can be reduced most in an ideal state, a torque ripple can be further effectively reduced.

[0082] However, depending on the actual size or shape of the rotating electrical mechanism, it is desirable to set an upper limit of approximately 50 degrees or less, also in terms of manufacturing.

[0083] As described above, in the permanent magnet type rotating electric mechanism of Embodiment 4, in the case where Z is the number of slots of the stator (Z is a natural number), P is the number of magnetic poles of the rotor (P is a natural number), m is the number of phases, and a number q of slots per pole per phase is represented as q = Z / (mxP), an electrical angle by which the magnetic center is shifted with respect to the geometric center of each magnetic pole is set to 15 degrees or greater when q satisfies (2 / 5) ≤ q < (1 / 2), and to 30 degrees or greater when q satisfies (1 / 2) ≤ q. Thus, by changing the shift angle of the magnetic center of each magnetic pole in accordance with a combination of the number of poles and the number of slots, cogging torque and torque ripple can be further effectively reduced. Embodiment 5

[0084] Fig. Fig. 19 is a plan view of a rotor core of a permanent magnet type rotating electric mechanism according to Embodiment 5 of the present invention, viewed from a direction perpendicular to the axial direction. In the rotor core, the Fig. 3 or Fig. 7 and the core II obtained by turning the core I over.

[0085] If the axial length of the entire rotor core is defined as 1, as in Fig. As shown in Figure 19, a core I block having a length of 1 / 4, a core II block having a length of 1 / 2, and then a core I block having a length of 1 / 4 are joined together in the axial direction to form the assembly. A total axial length of the core I blocks and a total axial length of the core II blocks are equal to each other.

[0086] In the Fig. In the structure shown in Figure 4 described in Embodiment 1, the displacement directions of the magnetic centers of the magnetic poles in the core I and core II are different between both axial end sides. Therefore, when a load is applied, a force is applied in a thrust direction, and a bearing or the like may break. In contrast, in the present embodiment, the magnetic centers of the magnetic poles on one axial end side and the other axial end side are aligned at the same position. Therefore, thrust forces cancel each other, so no thrust force occurs.

[0087] In Fig. 19, cores I and II contain two reversals between them. However, they can also contain a larger number of reversals (which should be an even number).

[0088] As described above, in the permanent magnet type rotating electric mechanism of Embodiment 5, the relative position in the circumferential direction of the low permeability regions is reversed depending on a position in the axial direction of the rotor, and the number of reversals is an even number, so that the magnetic centers of the magnetic poles on one axial end side and the other axial end side of the rotor are aligned at the same position. Therefore, thrust forces applied to the shaft of the rotor cancel each other, so that no thrust force occurs. Therefore, power degradation due to thrust force can be suppressed.

[0089] It should be noted that, within the scope of the present invention, the above embodiments may be freely combined with each other, or each of the above embodiments may be modified or abbreviated as appropriate. Description of reference symbols

[0090] 1 housing, 2 stator core, 2a tooth section, 3 stator winding, 4 rotor core, 4a, 4b, 4d, 4e, 4f, 4g low permeability region, 4c nail section, 5 permanent magnet, 6 shaft, 10 rotating electrical mechanism, 20 stator, 30 rotor

Claims

[1] A rotating electric mechanism of the permanent magnet type, comprising: a stator (20) having stator windings (3) wound on a plurality of tooth sections (2a) formed on a stator core (2); and a rotor (30) having permanent magnets (5) embedded between a plurality of magnetic poles formed along a circumferential direction of a rotor core (4), the rotor (30) being rotatable integrally with a shaft (6), the rotor core (4) has a low permeability region (4a, 4b) which has a lower permeability than the material of the rotor core (4), between an outer circumference of each magnetic pole and a side surface of each permanent magnet (5), the low permeability region (4a, 4b) is formed asymmetrically with respect to a geometric center in the circumferential direction of each magnetic pole, so that a magnetic center (A) of the magnetic pole is shifted to one side with respect to the geometric center (B), and the rotor cores (4) are arranged inverted with respect to one another so that a relative position in the circumferential direction of the low permeability regions (4a, 4b) differs with respect to the permanent magnets (5), where, in the case where Z is a number of slots of the stator (Z is a natural number), P is the number of magnetic poles of the rotor (P is a natural number), m is a number of phases, and a number q of slots per pole per phase is represented as q = Z / (mx P), an electrical angle by which the magnetic center is shifted with respect to the geometric center of each magnetic pole when q satisfies (2 / 5) ≤ q < (1 / 2) is set to 15 degrees or greater, and when q satisfies (1 / 2) ≤ q, is set to 30 degrees or greater. [2] A permanent magnet type rotating electric mechanism according to claim 1, wherein the permanent magnets (5) are radially arranged from a center side to an outer peripheral side of the rotor core (4). [3] A permanent magnet type rotating electric mechanism according to claim 1, wherein the permanent magnets (5) are provided in pairs for one pole of the magnetic poles of the rotor core (4), and the two permanent magnets (5) are arranged so that they extend in a V-shape from a center side to an outer peripheral side of the rotor core (4). [4] A permanent magnet type rotating electric mechanism according to claim 2 or 3, wherein the low permeability region (4a, 4b) is formed by a plurality of thin cavities formed between the outer periphery of each magnetic pole of the rotor core (4) and each side surface of the permanent magnets (5) arranged on both sides of the magnetic pole, and a number or a length of the cavities is different between right and left with respect to the geometric center (B) of each magnetic pole. [5] A permanent magnet type rotating electric mechanism according to claim 2 or 3, wherein said low permeability region (4a, 4b) is formed by a plurality of thin cavities formed between the outer periphery of each magnetic pole of said rotor core (4) and a side surface of one of said permanent magnets (5) arranged on both sides of said magnetic pole. [6] A permanent magnet type rotating electric mechanism according to any one of claims 1 to 5, wherein in the case where L is a depth from an outer circumference of the stator core (2) to a surface of the shaft (6), the low permeability region (4a, 4b) is formed within a range of 1 / 2 L from the outer circumference side. [7] A permanent magnet type rotating electric mechanism according to any one of claims 1 to 6, wherein in the case where a is a distance from an outer peripheral surface of each magnetic pole of the rotor core (4) to an end of the low permeability region (4a, 4b) close to the outer peripheral surface, and b is a distance from a side surface of each permanent magnet to an end of the low permeability region close to the side surface, a is set to 0.2 to 0.7 mm and b is longer than a but not longer than 3 mm. [8] A permanent magnet type rotating electric mechanism according to any one of claims 1 to 7, wherein the relative position in the circumferential direction of the low permeability regions (4a, 4b) is reversed depending on a position in an axial direction of the rotor (30), a number of the reversals being an even number, so that the magnetic centers (A) of the magnetic poles on one axial end side and the other axial end side of the rotor (30) are aligned at the same position.

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