Rotating electric machine with embedded permanent magnets

Abstract

Rotating electric machine with embedded permanent magnets, comprising the following: a ring-shaped stator (1; 1A); and a rotor (10, 10A, 10B, 30, 30A, 30B) which is arranged coaxially inside the stator (1; 1A) with an air gap arranged between them, characterized by the fact that: The rotor (10, 10A, 10B, 30, 30A, 30B) includes: a rotor core (12, 12A, 12B) which has an outer shape in which several arcuate curved surfaces (13) which are convex radially outwards are arranged circumferentially, and in which magnet receiving openings (15, 15A) are formed axially through an inner radial side of each of the arcuate curved surfaces (13); a rotating shaft (11) which is inserted in a central axial position of the rotor core (12, 12A, 12B) and holds the rotor core; and Permanent magnets (16, 16A), each manufactured as a rod-shaped body in which a radially outer side of a cross-section perpendicular to a longitudinal direction is a circular arc convex radially outward, and in which two circumferential side faces are flat surfaces parallel to a plane containing a magnet pole center, the permanent magnets each being received in the magnet receiving openings (15, 15A); R1 > R2 > R3 is satisfied, wherein R1 is a radius of curvature of a cylindrical surface (14) that touches the circularly curved surfaces (13) that are arranged circumferentially, R2 is a radius of curvature of the circularly curved surfaces (13), and R3 is a radius of curvature of a top surface of the permanent magnets (16, 16A); the magnet receiving openings (15, 15A) comprise air gap sections (17) in which radially outer sections of two circumferential side sections are extended circumferentially outwards; Surfaces parallel to a plane containing the magnet pole center, which are touching the two circumferential side surfaces of the permanent magnets (16, 16A), are arranged on radially inner sections of the two circumferential side sections of the magnet receiving openings (15, 15A); B1 < B2 is satisfied, wherein B1 is a thickness of a core section of the rotor core (12, 12A, 12B) between the circularly curved surfaces (13) and the magnet receiving openings (15, 15A) in the magnet pole center, and B2 is a thickness of a circumferential end section of the core section; and a distance (Lb) between circumferentially adjacent air gap sections (17) and a distance (Ln) between circumferentially adjacent surfaces from the surfaces that are parallel to the plane containing the magnet pole center, which the two circumferential side surfaces of the permanent magnets (16, 16A) touch, are equal, wherein the permanent magnets (16) are formed with a cross-sectional shape perpendicular to a longitudinal direction, wherein a radially outer side is a circular arc that is convex radially outwards, and a radially inner side is a circular arc that is convex radially outwards, wherein R1 > R4 > R2 > R3 is satisfied, where R4 is a radius of curvature of a bottom surface of the permanent magnets.

Description

Technical area

[0001] The present invention relates to a permanent magnet embedded rotating electrical machine comprising a rotor in which permanent magnets are embedded in a rotor core. State of the art

[0002] In rotating electrical machines, such as industrial and automotive motors, there is a need for reducing the size, increasing the speed, and expanding the operating speed range. Various permanent magnet embedded rotating electrical machines, including a motor in which permanent magnets are embedded in a rotor core, have been proposed as rotating electrical machines to meet these needs (see, for example, Patent Documents 1 and 2). Citation listPatent literature Patent Document 1: Japanese Patent Application Laid-Open No. JP 2001-178037 A (Patent Gazette) Patent Document 2: Japanese Patent Laid-Open No. JP H05-304 737 A (Patent Gazette) Summary of the inventionProblem to be solved by the invention

[0003] Because the outer peripheral surface of a rotor core in a conventional permanent magnet embedded electric machine disclosed in Patent Document 1 is a cylindrical surface, many harmonics are present in the magnetomotive force waveforms generated by the rotor. One problem is the occurrence of cogging torque and torque ripples. Because the outer peripheral surface of the rotor core is a cylindrical surface, the core portion of the rotor core exposed to q-axis magnetic flux is in close proximity to the stator, increasing q-axis inductance. Therefore, voltage saturation is more likely to occur during high-speed rotation. Another problem is that the operating range cannot be expanded.Furthermore, because the inner shapes of magnet receiving holes and the outer shapes of the magnets are similar, the inner shapes of the magnet receiving holes are larger than the outer shapes of the magnets from the perspective of dimensional tolerances. Another problem was that gaps are more likely to occur between radially inner end portions of two circumferential side portions of the magnets, and the magnet receiving holes in particular. Furthermore, because the two circumferential side portions of the permanent magnets are flat surfaces inclined with respect to a magnetic pole center, the thicknesses of the two circumferential side portions of the permanent magnets parallel to the magnetic pole center are thinner. As a result, the operating points of the two side portions of the permanent magnets are lower than the operating point of a central portion of the permanent magnets. Another problem was that demagnetization of the magnets is more likely to occur.

[0004] In a conventional permanent magnet embedded rotating electric machine according to Patent Document 2, an outer peripheral surface of the rotor core forming magnetic poles is designed into a shape in which two ellipses perpendicular to each other are superimposed to reduce harmonics present in the magnetomotive force waveform generated by the rotor. However, in the conventional permanent magnet embedded rotating electric machine according to Patent Document 2, because the inner shapes of magnet receiving holes and the outer shapes of the magnets are also similar, there has also been a problem in that gaps are more likely to occur between radially inner end portions at two circumferential side portions of the magnets and the magnet receiving holes.Furthermore, because the two circumferential side sections of the permanent magnets are flat surfaces inclined relative to the magnetic pole center, the thicknesses of the two circumferential side sections of the permanent magnets parallel to the magnetic pole center are thinner. As a result, the operating points of the two side sections of the permanent magnets are lower than the operating point of a central section of the permanent magnets, and one problem was that demagnetization of the magnets is more likely to occur.

[0005] Rotating electrical machines are known from JP 2012-257 433 A and JP 2002-27 690 A, which comprise an annular stator and a rotor arranged coaxially inside the stator with an air gap therebetween, with permanent magnets embedded therein. The rotor has a rotor core with an outer shape in which several outwardly convex curved surfaces are arranged circumferentially. JP 2 543 165 Y2 shows another rotor.

[0006] The present invention aims to solve the above problems, and an object of the present invention is to provide a permanent magnet embedded rotating electric machine that can reduce cogging torque and torque ripples, expand an operating range, fix magnets without providing gaps in a rotor core, and also suppress demagnetization of the magnets. Means of solving the problem

[0007] A permanent magnet embedded rotating electric machine according to the present invention comprises: an annular stator; and a rotor coaxially disposed inside the stator with an air gap therebetween. The rotor comprises: a rotor core having an outer shape in which a plurality of circular arc-shaped curved surfaces that are convex radially outward are circumferentially arranged, and in which magnet receiving holes are formed axially through an inner radial side of each of the circular arc-shaped curved surfaces; a rotating shaft inserted at a central axial position of the rotor core and supporting the rotor core; and permanent magnets each formed as a rod-shaped body in which a radially outer side of a cross section perpendicular to a longitudinal direction is a circular arc that is convex radially outward, and in which two circumferential side surfaces are flat surfaces parallel to a plane.which contains a magnetic pole center, wherein the permanent magnets are each accommodated in the magnet receiving openings. R1 > R2 > R3 is satisfied, where R1 is a radius of curvature of a cylindrical surface contacting the circumferentially arranged circular-arc curved surfaces, R2 is a radius of curvature of the circular-arc curved surfaces, and R3 is a radius of curvature of an upper surface of the permanent magnets. The magnet receiving openings comprise air gap portions formed by circumferentially expanding radially outer portions of two circumferential side portions outward. Surfaces parallel to a plane containing the magnetic pole center, which contact the two circumferential side surfaces of the permanent magnets, are arranged at radially inner portions of the two circumferential side portions of the magnet receiving openings. B1 < B2 is satisfied.where B1 is a thickness of a core portion of the rotor core between the circular arc-shaped curved surfaces and the magnet receiving openings in the magnetic pole center, and B2 is a thickness of a circumferential end portion of the core portion, and a distance between circumferentially adjacent air gap portions and a minimum distance between circumferentially adjacent surfaces of the surfaces parallel to the plane containing the magnetic pole center that contact the two circumferential side surfaces of the permanent magnets are equal. Effects of the invention

[0008] According to the present invention, the rotor core is formed with an outer shape constructed by circumferentially arranging a plurality of circular-arc curved surfaces 13 that are convex radially outward. Thus, harmonics present in the magnetomotive force waveform generated by the rotor are reduced, which can prevent the generation of cogging torque and torque ripples. Because the portions of the rotor core exposed to q-axis magnetic flux are separated from the stator, q-axis inductance is reduced. Thus, voltage saturation is less likely to occur during high-speed rotation, allowing the operating range to be expanded.

[0009] Because R1 > R2 > R3 is satisfied, where R1 is the radius of curvature of a cylindrical surface, R2 is the radius of curvature of the circular arc-shaped curved surfaces, and R3 is the radius of curvature of the top surface of the permanent magnets, the thicknesses of the core sections of the rotor core on a radially outer side of the permanent magnets gradually increase with increasing distance from the magnetic pole centers. Thus, the core sections radially outside the permanent magnets at the magnetic pole centers are easily magnetically saturated, which reduces the amount of magnetic flux leakage in the magnetic flux of the magnets, thereby achieving increased performance.In addition, because the amount of magnetic flux reaching the air gap from the permanent magnets gradually decreases with increasing distance from the magnetic pole centers, the harmonic magnetic flux density component in the air gap magnetic flux density component is reduced, which can prevent the generation of cogging torque and torque ripples.

[0010] Because the magnet receiving holes have air gap portions formed by circumferentially expanding the radially outer portions of two circumferential side portions, irregularities in the permanent magnets are accommodated by the air gap portions when the permanent magnets are housed in the magnet receiving holes. In addition, surfaces parallel to the two circumferential side surfaces of the permanent magnets and to the radial direction, formed on the radially inner portions of the two circumferential side portions of the magnet receiving holes, contact the two circumferential side surfaces of the permanent magnets. The permanent magnets can thus be fixed to the rotor core without providing gaps.

[0011] Because B2 > B1 is satisfied, where B1 is the thickness of a core portion of the rotor core between the circular-arc curved surfaces and the magnet accommodating holes at a magnetic pole center, and B2 is the thickness of a peripheral end portion of the core portion, q-axis magnetic flux is less likely to flow through the core portion. Thus, q-axis inductance in the rotor is reduced, allowing the operating range to be expanded.

[0012] Because the two circumferential side portions of the permanent magnets are formed as flat surfaces inclined with respect to the magnetic pole centers, the thickness of the two circumferential side portions of the permanent magnets increases in a direction parallel to the magnetic pole centers, thereby raising the operating points of the two side portions of the permanent magnets and preventing demagnetization of the permanent magnets. Furthermore, because the thickness in the areas of the rotor core located radially outside the permanent magnets gradually increases from a circumferential center portion toward the two side portions, magnetic flux from the stator is less likely to pass through the two side portions of the permanent magnets, preventing demagnetization of the permanent magnets. Short description of the drawings Fig. 1 is a cross-sectional view showing a permanent magnet embedded rotating electric machine according to Embodiment 1 of the present invention; Fig. 2 is a partial enlargement showing a vicinity of a permanent magnet of a rotor in the permanent magnet-embedded rotating electric machine according to Embodiment 1 of the present invention; Fig. 3 is a schematic diagram explaining a flow of a q-axis magnetic flux in a rotor of the permanent magnet embedded rotating electric machine according to Embodiment 1 of the present invention; Fig. 4 is a cross-sectional view showing a rotor in an exemplary rotary electric machine with embedded permanent magnets; Fig. 5 is a partial enlargement showing a vicinity of a permanent magnet of a rotor core in the exemplary permanent magnet embedded rotating electric machine; Fig. 6 is a schematic diagram explaining a q-axis magnetic flux pattern in the rotor of the exemplary permanent magnet embedded rotating electric machine; Fig. 7 is a schematic diagram showing q-axis magnetic flux paths in the rotor of the permanent magnet embedded rotating electric machine according to Embodiment 1 of the present invention; Fig. 8 is a cross-sectional view showing the permanent magnet in the permanent magnet-embedded rotating electric machine according to Embodiment 1 of the present invention; Fig. 9 is a partial enlargement showing a vicinity of a magnet insertion hole of a rotor core in the permanent magnet embedded rotating electric machine according to Embodiment 1 of the present invention; Fig. 10 is a diagram showing a magnitude of a cogging torque when an outer peripheral surface shape of the rotor core is modified in the permanent magnet embedded rotating electric machine according to Embodiment 1 of the present invention; Fig. 11 is an end plan view showing a rotor core in a permanent magnet embedded rotary electric machine according to Embodiment 2 of the present invention; Fig. 12 is a partial enlargement showing a vicinity of a permanent magnet of a rotor in the permanent magnet-embedded rotating electric machine according to Embodiment 2 of the present invention; Fig. 13 is an end plan view showing a rotor core in a permanent magnet embedded rotary electric machine according to Embodiment 3 of the present invention; Fig. 14 is a cross-sectional view showing the rotor core in the permanent magnet embedded rotary electric machine according to Embodiment 3 of the present invention; Fig. 15 is a partial enlargement showing a vicinity of a permanent magnet of a rotor in the permanent magnet-embedded rotating electric machine according to Embodiment 3 of the present invention; Fig. 16 is a diagram explaining a pattern of leakage magnetic flux in the rotor of the permanent magnet embedded rotating electric machine according to Embodiment 3 of the present invention; Fig. 17 is a partial enlargement showing the vicinity of the permanent magnet of the rotor in the permanent magnet-embedded rotating electric machine according to Embodiment 3 of the present invention; Fig. 18 is a cross-sectional view showing a permanent magnet embedded rotating electric machine according to Embodiment 4 of the present invention; Fig. 19 is an oblique projection showing a rotor core in the permanent magnet embedded rotary electric machine according to Embodiment 4 of the present invention; Fig. 20 is a diagram showing a relationship between torque ripples and a step offset angle in the permanent magnet embedded rotating electric machine according to Embodiment 4 of the present invention; Fig. 21 is a side plan view showing a rotor core in a permanent magnet embedded rotary electric machine according to Embodiment 5 of the present invention; Fig. 22 is a side plan view showing a rotor core in a permanent magnet embedded rotary electric machine according to Embodiment 6 of the present invention; and Fig. 23 is a partial enlargement showing a vicinity of a permanent magnet of a rotor in a permanent magnet-embedded rotating electric machine according to Embodiment 7 of the present invention. Description of the embodiments

[0013] Preferred embodiments of a permanent magnet embedded rotating electric machine according to the present invention will now be described with reference to the drawings. Embodiment 1

[0014] Fig. 1 is a cross-sectional view showing a permanent magnet embedded electric rotating machine according to Embodiment 1 of the present invention, Fig. 2 is a partial enlargement showing a vicinity of a permanent magnet of a rotor in the permanent magnet-embedded rotating electric machine according to Embodiment 1 of the present invention, Fig. 3 is a schematic diagram explaining a q-axis magnetic flux pattern in a rotor of the permanent magnet embedded rotary electric machine according to Embodiment 1 of the present invention, Fig. 4 is a cross-sectional view showing a rotor in an exemplary rotary electric machine with embedded permanent magnets, Fig. 5 is a partial enlargement showing a vicinity of a permanent magnet of a rotor core in the exemplary permanent magnet embedded rotating electric machine, Fig. 6 is a schematic diagram explaining a q-axis magnetic flux pattern in the rotor of the exemplary permanent magnet embedded rotating electric machine, Fig. 7 is a schematic diagram showing q-axis magnetic flux paths in the rotor of the permanent magnet embedded rotary electric machine according to Embodiment 1 of the present invention, Fig. Fig. 8 is a cross section showing the permanent magnet in the permanent magnet embedded rotating electric machine according to Embodiment 1 of the present invention, and Fig. 9 is a partial enlargement showing a vicinity of a magnet insertion hole of a rotor core in the permanent magnet embedded rotating electric machine according to Embodiment 1 of the present invention.

[0015] In Fig. 1 comprises a rotating electrical machine 100 with embedded permanent magnets: an annular stator 1; and a rotor 10 arranged coaxially and rotatably inside the stator 1 with an air gap 9 therebetween.

[0016] The stator 1 includes a stator core 2, which is made by stacking and integrating electromagnetic steel sheets, and is formed such that teeth 2b each protrude radially inward from an inner wall surface of an annular rear yoke 2a at a uniform angular pitch circumferentially. In this case, thirty slots 2c formed by the rear yoke 2a and adjacent teeth 2b are circumferentially arranged. Furthermore, although not shown, distributed winding stator windings are attached to the stator core 2.

[0017] The rotor 10 includes: a rotor core 12 made by stacking and integrating electromagnetic steel sheets, and having an outer shape in which a plurality of circular arc-shaped curved surfaces 13 are circumferentially arranged at a uniform angular pitch; a rotary shaft 11 inserted and fixed at a central axial position of the rotor core 12; and permanent magnets 16 embedded in an outer peripheral side of the rotor core.

[0018] As in Fig. As shown in Figure 2, the rotor core 12 is configured such that ten protruding portions having a radius of curvature R2, formed by the circular-arc curved surfaces 13, are circumferentially arranged at a uniform angular pitch. The ten circumferentially arranged circular curved surfaces 13 contact a cylindrical surface 14 having a radius of curvature R1. Magnet receiving holes 15 are formed axially through the rotor core 12 on an inner radial side of each of the circular-arc curved surfaces 13.

[0019] As in the Fig. 2 and Fig. As shown in Fig. 8, the permanent magnets 16 are formed as rod-shaped bodies having a length approximately equal to an axial length of the rotor core 12, and having a cross-sectional shape perpendicular to a longitudinal direction formed into a circular arc shape surrounded by a top surface that is convex radially outward having a radius of curvature R3, a bottom surface that is convex radially outward having a radius of curvature R4, and a pair of flanking sides formed by parallel straight lines. The permanent magnets 16 are received and fixed in the respective magnet receiving holes 15, and are circumferentially arranged such that polarities of faces (top surfaces) on outer peripheral sides of the permanent magnets 16 are alternately lined up as a north (N)-going pole, a south (S)-going pole, an N pole, an S pole, etc.Furthermore, Wm is a distance between the pair of flanking sides of the permanent magnets 16, that is, a circumferential width.

[0020] As in the Fig. 2 and Fig. As shown in Fig. 9, the magnet receiving holes 15 are formed with an opening shape similar to an outer shape of the permanent magnets 16, except that they have air gap portions 17 formed by circumferentially expanding radially outer portions of two circumferential side portions outward. Furthermore, Ws is a distance between magnet locking portions 18 (described below), that is, a circumferential width.

[0021] Here, in the cross section perpendicular to a central axis of the rotary shaft 11, the radius of curvature R1 of the cylindrical surface 14 is larger than the radius of curvature R4 of the lower surfaces of the permanent magnets 16, which is larger than the radius of curvature R2 of the circular-arc curved surfaces 13, which is larger than the radius of curvature R3 of the upper surfaces of the permanent magnets 16. In addition, radii of curvature of the upper surface and the lower surface of the inner wall surfaces of the magnet receiving openings 15 approximately correspond to the radius of curvature R3 of the upper surfaces of the permanent magnets 16 and the radius of curvature R4 of the lower surfaces of the permanent magnets 16, respectively. The circular-arc curved surfaces 13, the opening shapes of the magnet receiving openings 15, and the outer shapes of the permanent magnets 16 each have a mirror symmetry having a plane passing through the central axis of the rotary shaft 11 and a circumferential center of the circularly curved surfaces 13 as a plane of symmetry.This plane of symmetry is a magnetic pole center.

[0022] The core sections of the rotor core 12 on a radially outer side of the permanent magnets 16 constitute bridge sections 20. These bridge sections 20 are formed such that their thickness increases circumferentially with increasing distance from the magnetic pole centers. The thickness at the magnetic pole center of the bridge sections 20 is B1, and the thickness of the circumferential end sections is B2 (> B1).

[0023] Interpole centers are planes passing through the center axis of the rotating shaft 11 and the centers between circumferentially adjacent magnet receiving openings 15 (permanent magnets 16). The opposite wall surfaces of the air gap portions 17 of the circumferentially adjacent magnet receiving openings 15 are parallel to the interpole centers. Radially inner portions of the two circumferential side portions of the magnet receiving openings 15, i.e., the radially inner portions of the air gap portions 17, are wall surfaces parallel to the magnet pole centers and form magnet locking portions 18. Lb is a distance between circumferentially adjacent air gap portions 17, and Ln is a distance between the circumferentially adjacent magnet locking portions 18.

[0024] The thus constructed permanent magnet embedded rotating electric machine 100 operates as a ten-pole, thirty-slot rotating electric machine.

[0025] According to Embodiment 1, the outer peripheral surface of the rotor core 12 is configured such that ten circular-arc curved surfaces 13, each with a radius of curvature R2, are circumferentially arranged at a uniform angular pitch. Thus, compared to Patent Document 1, which uses a rotor with a perfectly circular outer shape, the harmonics present in the magnetomotive force waveform generated by the rotor 10 are reduced, thereby preventing the generation of cogging torque and torque ripples. Because the portions of the rotor core 12 subject to q-axis magnetic flux are separated from the stator 1, the q-axis inductance is reduced. Thus, voltage saturation is less likely to occur during high-speed rotation, allowing the operating range to be expanded.

[0026] Because the opening shape of the magnet accommodating holes 15 is formed in a shape similar to that of the permanent magnets 16, except for having air gap portions 17 formed by circumferentially expanding radially outer portions of two circumferential side surfaces outward, dimensional irregularities in the permanent magnets 16 are absorbed by the air gap portions 17 when the permanent magnets 16 are accommodated in the magnet accommodating holes 15. The magnet locking portions 18 formed by the radially inner sides of the two circumferential side portions of the magnet accommodating holes 15 contact the two circumferential side surfaces of the permanent magnets 16 in parallel in a radial direction, whereby the permanent magnets 16 can be fixed without causing gaps in the rotor core 12.By fixing the permanent magnets 16 in this way without creating gaps in the rotor core 12, the magnet positions are no longer irregular. This makes it possible to prevent cogging torque and torque ripples that occur due to irregularities in the magnet position.

[0027] Because the two circumferential side portions of the permanent magnets 16 are flat surfaces parallel to the magnetic pole centers, the operating points of the two side portions of the permanent magnets 16 are higher because the magnet thicknesses of the two side portions of the permanent magnets 16 are thicker in the direction parallel to the magnetic pole centers, thereby preventing demagnetization of the permanent magnets 16.

[0028] Because the air gap portions 17 are integrally formed on the two circumferential side portions of the magnet receiving openings 15, the width LB of the interpole core portions is narrower. Thus, magnetic leakage flux in the magnetic flux of the magnets due to magnetic saturation of the respective core portions is reduced, thereby improving performance.

[0029] Now, a rotating electrical machine using a rotor core 12 having an outer peripheral surface formed by arranging ten circular arc-shaped curved surfaces 13 having a radius of curvature R2 circumferentially at a uniform angular pitch (R1 > R2 > R3) and a rotating electrical machine using a rotor core having a perfect circle as its outer shape (R1 = R2 > R3) were manufactured, and the cogging torque was measured, the results of which are shown in Fig. 10 are shown. Fig. Figure 10 is a diagram showing a magnitude of the cogging torque when an outer peripheral surface shape of the rotor core is modified in the permanent magnet embedded electric machine according to Embodiment 1 of the present invention. Furthermore, the rotor core, which has a perfect circle as its outer shape, is constructed in a manner similar to the rotor core 12, except that it has a cylindrical surface contacting the circular arc-shaped curved surfaces 13 of the rotor core 12 as its outer peripheral surface. Furthermore, in Fig. 10 shows the magnitude of the cogging torque of the rotating electrical machine using a rotor core with a perfect circle as an outer shape (R1 = R2 > R3) when the magnitude of the cogging torque of the rotating electrical machine using the rotor core 12 (R1 > R2 > R3) is one.

[0030] Out of Fig. 10, it was confirmed that the cogging torque when a rotor core 12 is used which has an outer peripheral surface formed by arranging circular arc-shaped curved surfaces 13 with a radius of curvature R2 circumferentially at a uniform angular pitch is significantly reduced compared to when a rotating electrical machine in which a rotor core with a perfect circle as an outer shape (R1 = R2 > R3) is used was manufactured and the cogging torque was measured, the results of which are shown in Fig. 10. This cogging torque reducing effect may be due to the fact that the harmonics present in the magnetomotive force waveform generated by the motor are reduced when a rotor core 12 having an outer peripheral surface formed by circumferentially arranging circular-arc curved surfaces 13 with a radius of curvature R2 at a uniform angular pitch is used, compared to when a rotor core having a perfect circle as its outer shape is used.

[0031] Next, effects due to the fact that the radius of curvature R3 of the outer peripheral surfaces of the permanent magnets 16 is smaller than the radius of curvature R2 of the circular arc-shaped curved surfaces 13 will be explained in contrast to a comparative example.

[0032] As in the Fig. 4 and Fig. 5, a rotor 110 in a comparative permanent magnet-embedded rotating electric machine is constructed in a manner similar to the rotor 10 in the present permanent magnet-embedded rotating electric machine 100, except that the radius of curvature R1 of the cylindrical surface 14 of the rotor core 112 is larger than the radius of curvature R2 of the circular arc-shaped curved surfaces 13, which is equal to the radius of curvature R3 of the top surfaces of the permanent magnets 16 in a cross section perpendicular to a center axis of the rotating shaft 11. Because the radius of curvature R2 of the circular arc-shaped curved surfaces 13 in the comparative rotor 110 is equal to the radius of curvature R3 of the top surfaces of the permanent magnets 16, the thickness of the bridge portions 20 is uniform.In other words, the thickness B1 at the magnetic pole centers of the bridge sections 20 and the thickness B2 at the two circumferential end portions of the bridge sections 20 are the same.

[0033] In the comparative rotor 110, the mechanical strength of the bridge sections 20 is reduced when the thickness B2 of the two end portions of the bridge sections 20 is reduced, and there is a possibility that the bridge sections 20 may be damaged due to centrifugal forces acting on the permanent magnets 16 during high-speed rotation. The q-axis magnetic flux generated by the stator winding enters the two circumferential end portions of the bridge sections 20. Because the thickness B2 of the two end portions of the bridge sections 20 is thinner, the q-axis magnetic flux passes through the bridge sections 20 and flows through the permanent magnets 16 on a radially inner side, as shown by the arrows in Fig. 6. Here, the q-axis magnetic flux flows through the permanent magnets 16 in a direction opposite to the magnetization alignment direction, and the permanent magnets 16 are subjected to a demagnetizing field, which promotes demagnetization of the permanent magnets 16.

[0034] Furthermore, in the comparative rotor 110, the mechanical strength of the bridge sections 20 could be increased and demagnetization of the permanent magnets 16 by the q-axis magnetic flux could be prevented by increasing the thickness B2 at the two end portions of the bridge sections 20. However, increasing the thickness B2 at the two end portions of the bridge sections 20 would increase the thickness B1 of the bridge sections 20 at the magnetic pole centers, which would increase the magnetic flux leakage in the magnetic flux of the magnets. Thus, increases in torque due to the magnetic flux generated by the permanent magnets 16 would be prevented, reducing the performance.

[0035] Because the radius of curvature R3 of the outer peripheral surface of the permanent magnets 16 is smaller than the radius of curvature R2 of the circular arc-shaped curved surfaces 13 in the rotor 110 of the present permanent magnet-embedded rotating electrical machine 100, the thickness B1 of the bridge portions 20 at the magnetic pole centers is made thinner than the thickness B2 at the two circumferential end portions. Thus, because magnetic leakage flux in the magnetic flux of the magnets is reduced by magnetic saturation at the magnetic pole centers of the bridge portions 20, torque due to the magnetic flux generated by the permanent magnets 16 is increased, thereby improving performance. Furthermore, because the thickness B2 at the two circumferential end portions of the bridge portions 20 can be increased, the mechanical strength of the bridge portions 20 is high, thereby increasing resistance to centrifugal force.In addition, the thickness of the bridge sections 20 increases circumferentially with increasing distance from the magnetic pole centers. Thus, the amount of magnetic flux escaping from the permanent magnets 16 and reaching the air gap 9 decreases from the magnetic pole centers to the interpole sides. The harmonic magnetic flux density component in the air gap magnetic flux density component is thereby reduced, reducing cogging torque and torque ripples.

[0036] Because the thickness B2 is increased at the two circumferential end portions of the bridge portions 20, the q-axis magnetic flux generated by the stator winding flows radially inward from the two circumferential end portions of the bridge portions 20 through intermediate pole core portions as shown by arrows in Fig. 3. Thus, the demagnetizing field acting on the permanent magnets 16 due to the q-axis magnetic flux flowing through the permanent magnets 16 is reduced, thereby preventing demagnetization of the permanent magnets 16.

[0037] Because the radius of curvature R4 of the bottom surface of the permanent magnets 16 is larger than the radius of curvature R3 of the top surface of the permanent magnets 16, the magnet volume decreases with increasing distance from the magnet pole centers. Thus, the amount of magnetic flux escaping from the permanent magnets 16 and reaching the air gap 9 decreases from the magnet pole centers to the sides. The harmonic magnetic flux density component in the air gap magnetic flux density component is thereby reduced, which reduces cogging torque and torque ripple.

[0038] Next, as indicated by the arrows in Fig. 7, the q-axis magnetic flux entered into the rotor core 12 has: a path along which it flows radially through the inter-pole core portion, circumferentially through a core portion on the radially inner side of the permanent magnets 16, and radially outward through the adjacent inter-pole core portion; and a path along which it flows circumferentially through the bridge portions 20.

[0039] The thickness B2 of the two end portions of the bridge portions 20 is determined by structural constraints. Thus, when an identical amount of magnets is used, the thicknesses B2 of the two end portions of the bridge portions 20 of the rotor 10 of the present rotary electric machine 100 with embedded permanent magnets and the rotor 110 of the comparison rotary electric machine with embedded permanent magnets are identical. Because B1 is smaller than B2 in the present rotor 10, the q-axis magnetic flux is less likely to flow through the bridge portions 20 compared to the comparison rotor 110. Therefore, the q-axis inductance in the rotor 10 is lower than in the comparison rotor 110.

[0040] Now, the voltage when the permanent magnet embedded rotating electric machine 100 operates as a motor is expressed by Expression (1). Here, V0 is the voltage, R is a winding resistance of the stator winding, Lp is a q-axis inductance, Ld is a d-axis inductance, Iq is a q-axis electric current, Id is a d-axis electric current, and Φf is a permanent magnet density. formula 1 V0=(R⋅Id−ω⋅Lq⋅Iq)2+(R+Iq+ω(Ld⋅Id+ϕf))2

[0041] From Expression (1), it can be seen that the voltage V0 decreases as Lp decreases. This means that the voltage saturation of the motor is improved. Because the q-axis inductance Lq is reduced as mentioned above, it can be seen that the operating range of the present embedded permanent magnet rotating electric machine 100 can be expanded compared to the comparative embedded permanent magnet rotating electric machine.

[0042] In addition to structural constraints, manufacturing constraints also exist for Ln, B1, and B2. The rotor core 12 is formed by stacking and integrating punched electromagnetic steel sheets. If the sheet thickness of the electromagnetic steel sheets is t, the width of Ln, B1, and B2 that can be produced by punching is greater than or equal to 0.4 xt. Therefore, if there are no structural strength issues, it is ideal to punch the electromagnetic steel sheets so that B1 is equal to 0.4 xt. This can reduce magnetic flux leakage in the magnetic flux of the magnets, thereby increasing the torque due to the magnetic flux of the magnets, and improving performance.

[0043] However, when punching the electromagnetic steel sheets using a punching tool such that B1 is equal to 0.4 × t, it is necessary to punch in multiple steps to prevent the bridge sections 20 from bending. Therefore, the punching tool is larger and the punching processing time is longer, which increases costs. For this reason, it is desirable to set B1 greater than or equal to 1.4 × t to avoid increasing the size of the punching tool and to prevent an increase in punching processing time. From the standpoint of reducing magnetic flux leakage in the magnetic flux of the magnets, it is particularly desirable to set B1 equal to 1.4 × t.

[0044] Next, the opening shape of the magnet receiving holes 15 and the outer shape of the permanent magnets 16 are examined. Designing the circumferential width Wm of the permanent magnets 16 equal to the circumferential width Ws between the magnet locking portions 18 of the magnet receiving holes 15 results in an increased magnet volume. This increases the amount of magnetic flux generated by the permanent magnets 16, which can improve performance.

[0045] When considering dimensional tolerances during manufacturing, it is desirable to set Ws such that Wm + 0.05 mm ≤ Ws ≤ Wm + 0.1 mm is satisfied. In particular, if Ws is set equal to Wm + 0.1 mm, the circumferential width Wm of the permanent magnets 16 can be maximized.

[0046] In addition, if the distance Lb between the opposing air gap portions 17 and the distance Ln between the opposing magnet locking portions 18 are designed to be equal, the circumferential width Wm of the permanent magnets 16 can be maximized while ensuring the mechanical strength of the bridge portions 20, whereby the performance can be improved.

[0047] Moreover, in the above embodiment 1, the stator winding is formed by distributed windings, but the stator winding is not limited to distributed windings, and concentrated windings may also be used.

[0048] In the above embodiment 1, a rotating electrical machine having ten poles and thirty slots was explained, but the number of poles and the number of slots in the rotating electrical machine are not limited to this.

[0049] In the above embodiment 1, the radius of curvature R4 of the bottom surface of the permanent magnets is larger than the radius of curvature R3 of the top surface, but the radius of curvature R4 of the bottom surface of the permanent magnets may be smaller than or equal to the radius of curvature R3 of the top surface. Embodiment 2

[0050] Fig. 11 is an end plan view showing a rotor core in a permanent magnet embedded rotary electric machine according to Embodiment 2 of the present invention, and Fig. 12 is a partial enlargement showing a vicinity of a permanent magnet of a rotor in the permanent magnet-embedded rotating electric machine according to Embodiment 2 of the present invention.

[0051] In the Fig. 11 and Fig. 12, a rotor 10A comprises: a rotor core 12A having an outer shape in which a plurality of circular-arc curved surfaces 13 are circumferentially arranged at a uniform angular pitch, and in which magnet receiving holes 15A are formed on an inner radial side of each of the circular-arc curved surfaces 13; and permanent magnets 16A each inserted and fixed into the magnet receiving holes 15A.

[0052] The permanent magnets 16A are made as rod-shaped bodies having a length approximately equal to an axial length of the rotor core 12, and having a cross-sectional shape perpendicular to a longitudinal direction formed into a semi-cylindrical shape surrounded by a top surface having a radius of curvature R3, a bottom surface formed by a straight line perpendicular to a direction of a radius passing through the circumferential center of the top surface, and a pair of flanking sides formed by straight lines parallel to the direction of the radius passing through the circumferential center of the top surface.

[0053] As in the Fig. 2 and Fig. 9, the magnet receiving holes 15A are formed with an opening shape similar to an outer shape of the permanent magnets 16A, except that it has air gap portions 17 formed by circumferentially expanding radially outer portions of two circumferential side portions outward.

[0054] In addition, the rest of the configuration is formed in a manner similar or identical to that of the above embodiment 1.

[0055] Consequently, in Embodiment 2, similar or identical effects to those of the above Embodiment 1 can also be achieved.

[0056] According to Embodiment 2, since the permanent magnets 16A are formed as rod-shaped bodies having a semi-cylindrical cross section, machining of the permanent magnets 16A is facilitated compared to the permanent magnets 16 in which the upper and lower surfaces are formed into circular arc-shaped curved surfaces, thereby achieving cost reductions.

[0057] Because the undersides of the permanent magnets 16A are formed as flat surfaces perpendicular to the magnetic pole centers, the magnet volume decreases with increasing distance from the magnetic pole centers. Thus, the amount of magnetic flux escaping from the permanent magnets 16A and reaching the air gap 9 decreases from the magnetic pole centers to the interpole sides. The harmonic magnetic flux density component in the air gap magnetic flux density component is thereby reduced, thereby reducing the cogging torque and torque ripples. Embodiment 3

[0058] Fig. 13 is an end plan view showing a rotor core in a permanent magnet embedded rotary electric machine according to Embodiment 3 of the present invention, Fig. 14 is a cross-sectional view showing the rotor core in the permanent magnet embedded rotary electric machine according to Embodiment 3 of the present invention, Fig. 15 is a partial enlargement showing a vicinity of a permanent magnet of a rotor in the permanent magnet-embedded rotating electric machine according to Embodiment 3 of the present invention, Fig. 16 is a diagram explaining a pattern of a magnetic leakage flux in the rotor of the permanent magnet embedded rotary electric machine according to Embodiment 3 of the present invention, and Fig. 17 is a partial enlargement showing the vicinity of the permanent magnet of the rotor in the permanent magnet embedded rotating electric machine according to Embodiment 3 of the present invention.

[0059] In the Fig. 13 to 15, a rotor 10B is fixed to a rotating shaft 11 by shrinking or press-fitting, etc., and includes end plates 21 arranged in contact with two axial end surfaces of a rotor core 12. The end plates 21 are formed as annular flat plates having a diameter Rm at which outer peripheral edges thereof are flush with radial positions of intersections between top surfaces and side surfaces of the permanent magnets 16.

[0060] In addition, the rest of the configuration is formed in a manner similar or identical to that of the above embodiment 1.

[0061] In Embodiment 3, since the rotor core 12, the magnet receiving holes 15, and the permanent magnets 16 are formed in a manner similar to or identical to that of the above Embodiment 1, effects similar to those of the above Embodiment 1 can be achieved.

[0062] In Embodiment 3, the end plates 21 are fixed to the rotating shaft 11, with the two axial end surfaces of the rotor core 12 in contact with each other, as viewed from an axial direction, and overlapping at least a portion of the permanent magnets 16. Thus, even when electromagnetic imbalances exist and an axial thrust force acts on the permanent magnets 16, the end plates 21 prevent axial movement of the permanent magnets 16. Consequently, axial detachment of the permanent magnets 16 from the rotor core 12 is reliably prevented.

[0063] Now, from a standpoint of suppressing magnetic flux leakage from the permanent magnets 16, it is desirable to manufacture the end plates 21 using a non-magnetic material. However, when end plates 21 made using a non-magnetic material are fixed to the rotating shaft 11 by shrinking or press-fitting, etc., as the temperature of the rotor 10B increases, there is a possibility that the joined portions between the end plates 21 and the rotating shaft 11 may loosen due to differences in the thermal expansion coefficient between the end plates 21 and the rotating shaft 11, and the end plates 21 may possibly come off.If the assembly tolerance is designed too tightly to prevent loosening of the mating portions between the end plates 21 and the rotary shaft 11, it becomes necessary to increase the shrink-fitting temperature in the shrink-fitting step, and the press-fitting pressure increases in the press-fitting step, resulting in poor machinability. Based on the above, it is desirable that the end plates 21 be manufactured using a magnetic material.

[0064] When the diameter Rm of the end plates 21 made using a magnetic material is equal to the outer diameter of the rotor core 12, the entire end surface of the permanent magnets 16 is in contact with the end plates 21, which increases the magnetic leakage flux. Here, the area of ​​the end surfaces of the permanent magnets 16 that contact the end plates 21 can be reduced by reducing the diameter Rm of the end plates 21. As shown by the arrows in Fig. 16, the magnetic flux emanating from the permanent magnets 16 enters the end plates 21 from portions of the end surfaces of the permanent magnets 16 that contact the end plates 21, flows radially inward through the end plates 21, then enters a core portion of the rotor core 12 on the radially inner side of the permanent magnets 16, and flows through magnetic paths that return to the permanent magnets 16. Because the flow of the magnetic flux from the portions of the end surfaces of the permanent magnets 16 exposed by the end plates 21 to the end plates 21 is thus suppressed, leakage magnetic flux can be suppressed compared to the case where the outer diameter of the end plates 21 is designed to be equal to the outer diameter of the rotor core 12. Therefore, the smaller the area of ​​the end plates 21 that contacts the end surface of the permanent magnets 16, the more the leakage magnetic flux can be reduced.

[0065] Moreover, even if the end plates 21 cover only a part of the permanent magnets 16 when viewed from the axial direction, they are still effective in preventing the axial loosening of the permanent magnets 16. As shown in Fig. 17, it is sufficient to reliably stop the axial loosening of the permanent magnets 16 if the end plates 21, viewed from the axial direction, cover an area that is greater than or equal to half the thickness Hm of the permanent magnets 16 in the magnet pole center.

[0066] Based on the foregoing, from the viewpoints of reducing magnetic flux leakage and preventing axial loosening of the permanent magnets 16, it is desirable to set the outer diameter Rm so that the radial position of the outer peripheral edges of the end plates 21 is greater than or equal to a radial position of a point which is half the thickness Hm of the permanent magnets 16 in the magnetic pole center, and is smaller than or equal to a radial position of an intersection point between the top and side surfaces of the permanent magnets 16. Embodiment 4

[0067] Fig. 18 is a cross-sectional view showing a permanent magnet embedded electric rotating machine according to Embodiment 4 of the present invention, Fig. 19 is an oblique projection showing a rotor core in the permanent magnet embedded rotary electric machine according to Embodiment 4 of the present invention, and Fig. 20 is a diagram showing a relationship between torque ripples and a step offset angle in the permanent magnet embedded rotating electric machine according to Embodiment 4 of the present invention.

[0068] In the Fig. 18 and Fig. 19 comprises a rotating electric machine 101 with embedded permanent magnets: an annular stator 1A; and a rotor 30 arranged coaxially and rotatably inside the stator 1A with an air gap 9 therebetween.

[0069] The stator 1A includes: a stator core 2A, which is made by stacking and integrating electromagnetic steel sheets, and which is formed such that teeth 2b, each protruding from an inner wall surface of an annular rear yoke 2a, are circumferentially arranged at a uniform angular pitch; and a stator winding 3a attached to the stator core 2A. In this case, twelve slots 2c, formed by the rear yoke 2a and adjacent teeth 2b, are circumferentially arranged. The stator winding 3 includes concentrated winding coils 3a, which are formed by winding conductor wires onto each of the teeth 2b.

[0070] The rotor 30 includes: first and second rotor cores 121 and 122 functioning as core segments made by stacking and integrating electromagnetic steel sheets, the first and second rotor cores 121 and 122 having outer shapes in which a plurality of circular-arc curved surfaces 13 are circumferentially arranged at a uniform angular pitch and coaxially in an axial direction; a rotary shaft 11 inserted and fixed into central axial positions of the first and second rotor cores 121 and 122; and permanent magnets 16 embedded in outer peripheral sides of the first and second rotor cores 121 and 122.

[0071] The first and second rotor cores 121 and 122 are each configured such that eight protruding portions with a radius of curvature R2, formed by the circular-arc curved surfaces 13, are circumferentially arranged at a uniform angular pitch. Magnet receiving holes 154 are formed axially through the first and second rotor cores 121 and 122 on an inner radial side of each of the circular-arc curved surfaces 13. Furthermore, the permanent magnets 16 are inserted into and fixed in the magnet receiving holes 15, respectively.

[0072] The first and second rotor cores 121 and 122 are fixed to the rotating shaft 11, which is arranged at the central portions thereof coaxially inserted in the axial direction in contact with each other such that magnetic pole centers are offset in a circumferential direction. Furthermore, the first and second rotor cores 121 and 122 are constructed in a manner similar to or identical to the rotor core 12 in Embodiment 1, except that eight permanent magnets 16 are embedded and the axial thickness is half. Furthermore, a step offset angle is a circumferential angle between the magnetic pole centers of the first and second rotor cores 121 and 122 arranged in the axial direction.

[0073] In general, in rotating electrical machines with embedded permanent magnets, when the stator windings are concentrated windings, harmonics are larger and torque ripples are more likely to be increased than when a stator winding consisting of distributed windings is used.

[0074] Harmonics are particularly large when there are eight poles and twelve slots.

[0075] In this permanent magnet embedded rotating electric machine 101, since the first and second stator cores 121 and 122 are coaxially arranged in the axial direction such that magnetic pole centers are offset in a circumferential direction, that is, a step offset is applied, a shift in the phase of torque ripples generated in the axial direction occurs, whereby the torque ripples can be reduced.

[0076] Theoretically, for eight-pole, twelve-slot motors, 1f is a period in which the motor electrically makes one revolution, and large torque ripples occur in a 6f component. Therefore, the step shift is applied to electrically set a phase difference of 30 degrees. Now, in the case of an eight-pole motor, 30 electrical degrees corresponds to 7.5 mechanical degrees. However, because the permanent magnets 16 are embedded in the first and second rotor cores 121 and 122, a magnetic leakage flux flows axially through core portions of the first and second rotor cores 121 and 122 located on an outer peripheral side of the permanent magnets 16, which makes the phase shift in the torque ripples formed in the axial direction different from the theoretical 30 degrees.

[0077] Now a relationship between the step offset angle (electrical degrees) and torque ripples in Fig. 20 shown.

[0078] Starting from Fig. 20, torque ripples gradually decrease with an increase in the step offset angle from 28 degrees, and the torque ripples are further reduced when the step offset angle is greater than or equal to 30 degrees (mechanical angle: 7.5 degrees). Then, when the step offset angle exceeds 43 degrees, reductions in torque ripples become slow, and when the step offset angle exceeds 48 degrees, there is hardly any reduction in torque ripples.

[0079] Since increasing torque ripples lead to power degradation, from the perspective of reducing torque ripples and preventing power degradation, it is desirable to set the tap angle to greater than or equal to 30 electrical degrees and less than or equal to 48 degrees. A case with eight poles and twelve slots was explained here, but it has also been demonstrated that similar or identical effects can be achieved in three-phase motors where the number of slots per phase per pole in the motor is half or one-quarter. Embodiment 5

[0080] Fig. 21 is a side plan view showing a rotor core in a permanent magnet embedded rotary electric machine according to Embodiment 5 of the present invention.

[0081] In Fig. 21, first and second rotor cores 121 and 122 are coaxially arranged such that magnetic pole centers are offset in a circumferential direction to ensure a gap d in an axial direction.

[0082] In addition, the rest of the configuration is formed in a manner similar or identical to that of the above embodiment 4.

[0083] In the rotor 30 according to the above embodiment 4, since the first and second rotor cores 121 and 122 are arranged to contact each other in the axial direction, leakage magnetic flux flows axially through core portions of the first and second rotor cores 121 and 122 located on an outer peripheral side of the permanent magnets 16, resulting in decreases in performance.

[0084] In the rotor 30A according to Embodiment 5, a gap d is ensured between the first and second rotors 121 and 122 arranged in line in the axial direction. The amount of magnetic leakage flux flowing axially through portions of the first and second rotor cores 121 and 122 located on an outer peripheral side of the permanent magnets 16 is thereby reduced, whereby the step offset angle can be reduced to reduce torque ripples. Performance decreases as the step offset angle is increased. Therefore, according to Embodiment 5, performance can be increased compared to the above-mentioned Embodiment 4.

[0085] Now, it is possible to improve performance by reducing magnetic flux leakage in the magnetic flux of the magnets if the gap d is set to be greater than or equal to the thickness B1 in core portions of the first and second rotor cores 121 and 122 located on an outer peripheral side of the permanent magnets 16, that is, in the magnetic pole centers of the bridge portions 20. Therefore, if t is the layer thickness of the electromagnetic steel sheets, it is desirable to set the gap d so that d ≥ 0.4 xt because the producible B1 is greater than or equal to 0.4 xt. Embodiment 6

[0086] Fig. 22 is a side plan view showing a rotor core in a permanent magnet embedded rotary electric machine according to Embodiment 6 of the present invention.

[0087] In Fig. 22, a rotor core is formed by first to third rotor cores 131, 132, and 133, which function as core segments. The first and third rotor cores 131 and 133 are formed identically. The second rotor core 132 is configured in a manner similar to or identical to that of the first and third rotor cores 131 and 133, except that its axial length is twice that of the first and third rotor cores 131 and 133. The first and third rotor cores 131 and 133 are arranged coaxially in an axial direction at opposite ends of the second rotor core 132 in contact with it. The circumferential positions of the magnetic pole centers of the first and third rotor cores 131 and 133 are aligned, and the magnetic pole centers of the second rotor core 132 are offset in a circumferential direction from the magnetic pole centers of the first and third rotor cores 131 and 133.

[0088] In addition, the rest of the configuration is formed in a manner similar or identical to that of the above embodiment 4.

[0089] In Embodiment 6, the first and third rotor cores 131 and 133 are formed identically, and the circumferential positions of their magnetic pole centers are aligned. Furthermore, the axial length of the first and third rotor cores 131 and 133 is half the axial length of the second rotor core 132. The second rotor core 132 is stepped with respect to the first and third rotor cores 131 and 133. This eliminates a thrust force acting in the axial direction during rotation of the rotor 30B as a result of the step displacement. Consequently, stresses on the bearings of the permanent magnet-embedded rotating electrical machine are reduced, thereby preventing failure in the bearings from occurring. Embodiment 7

[0090] Fig. 23 is a partial enlargement showing a vicinity of a permanent magnet of a rotor in a permanent magnet-embedded rotating electric machine according to Embodiment 7 of the present invention.

[0091] In Fig. 23, a rotor core 12b is formed such that a distance Ln between opposing magnet locking portions 18 is formed larger than a thickness B2 at circumferential end portions of bridge portions 20.

[0092] In addition, the rest of the configuration is formed in a manner similar or identical to that of the above embodiment 1.

[0093] A magnetic flux emanating from a first permanent magnet 16 flows to an adjacent permanent magnet 16 through a magnetic path passing through a core portion of the rotor core 12B on an outer peripheral side between poles, and through a magnetic path passing through an inter-pole core portion of the rotor core 12B, and returns to the first permanent magnet 16. The magnitude of the amount of leakage magnetic flux in the magnetic flux emanating from the permanent magnets 16 is determined by the thickness B2 at the circumferential end portions of the bridge portions 20. Consequently, the amount of leakage magnetic flux does not change even when Ln>B2. As Ln increases, the mechanical strength of the bridge portions 20 also increases to withstand high-speed rotation.

[0094] Because Ln is larger than B2 according to embodiment 7, resistance to centrifugal forces can be increased without increasing the magnetic leakage flux.

[0095] Furthermore, in each of the above embodiments, a single long permanent magnet is accommodated in each of the magnet receiving holes, but a plurality of short permanent magnets may be accommodated in each of the magnet receiving holes in a single row. Explanation of the numbering

[0096] 1, 1A stator; 9 air gap; 10, 10A, 10B, 30, 30A, 30B rotor; 11 rotating shaft; 12, 12A, 12B rotor core; 13 circular arc-shaped curved surface; 14 cylindrical surface; 15, 15A magnet receiving hole; 16, 16A permanent magnet; 17 air gap section; 20 bridge section; 21 end plate; 121 first rotor core (core segment); 122 second rotor core (core segment); 131 first rotor core (core segment); 132 second rotor core (core segment); 133 third rotor core (core segment); d gap.

Claims

[1] Rotating electrical machine with embedded permanent magnets, comprising: an annular stator (1; 1A); and a rotor (10, 10A, 10B, 30, 30A, 30B) arranged coaxially inside the stator (1; 1A) with an air gap arranged therebetween, characterized by , that: the rotor (10, 10A, 10B, 30, 30A, 30B) comprises: a rotor core (12, 12A, 12B) having an outer shape in which a plurality of circular arc-shaped curved surfaces (13) which are convex radially outward are circumferentially arranged, and in which magnet receiving holes (15, 15A) are formed axially extending through an inner radial side of each of the circular arc-shaped curved surfaces (13); a rotary shaft (11) inserted in a central axial position of the rotor core (12, 12A, 12B) and holding the rotor core; and Permanent magnets (16, 16A), each made as a rod-shaped body in which a radially outer side of a cross section perpendicular to a longitudinal direction is a circular arc convex radially outward, and in which two circumferential side surfaces are flat surfaces parallel to a plane containing a magnetic pole center, the permanent magnets being respectively received in the magnet receiving openings (15, 15A); R1 > R2 > R3 is satisfied, wherein R1 is a radius of curvature of a cylindrical surface (14) contacting the circular-arc curved surfaces (13) arranged circumferentially, R2 is a radius of curvature of the circular-arc curved surfaces (13), and R3 is a radius of curvature of an upper surface of the permanent magnets (16, 16A); the magnet receiving openings (15, 15A) comprise air gap sections (17) in which radially outer sections of two circumferential side sections are circumferentially expanded outwards; Surfaces parallel to a plane containing the magnetic pole center, which contact the two circumferential side surfaces of the permanent magnets (16, 16A), are arranged at radially inner portions of the two circumferential side portions of the magnet receiving openings (15, 15A); B1 < B2 is satisfied, wherein B1 is a thickness of a core portion of the rotor core (12, 12A, 12B) between the circular arc-shaped curved surfaces (13) and the magnet receiving openings (15, 15A) in the magnetic pole center, and B2 is a thickness of a peripheral end portion of the core portion; and a distance (Lb) between circumferentially adjacent air gap portions (17) and a distance (Ln) between circumferentially adjacent surfaces of the surfaces parallel to the plane containing the magnetic pole center that touch the two circumferential side surfaces of the permanent magnets (16, 16A) are equal, wherein the permanent magnets (16) are formed with a cross-sectional shape perpendicular to a longitudinal direction, in which a radially outer side is a circular arc which is convex radially outward, and a radially inner side is a circular arc which is convex radially outward, satisfying R1 > R4 > R2 > R3, where R4 is a radius of curvature of a bottom surface of the permanent magnets. [2] The permanent magnet embedded rotating electric machine according to claim 1, wherein Wm + 0.05 mm ≤ Ws ≤ Wm + 0.1 mm is satisfied, where Wm is a circumferential width between radially inner end portions of two circumferential side portions of the permanent magnets (16, 16A), and Ws is a circumferential width between the radially inner end portions of the two circumferential side portions of the magnet receiving holes (15, 15A). [3] The permanent magnet embedded rotating electric machine according to claim 1 or 2, wherein a circumferential thickness of the rotor core (12B) between magnet accommodating holes (15) adjacent to each other in a circumferential direction is thicker than a radial thickness of core portions of the rotor core (12B) on an outer peripheral side of two peripheral side portions of the permanent magnets (16). [4] Rotating electrical machine with embedded permanent magnets, comprising: an annular stator (1; 1A); and a rotor (10, 10A, 10B, 30, 30A, 30B) arranged coaxially inside the stator (1; 1A) with an air gap arranged therebetween, characterized by , that: the rotor (10, 10A, 10B, 30, 30A, 30B) comprises: a rotor core (12, 12A, 12B) having an outer shape in which a plurality of circular arc-shaped curved surfaces (13) which are convex radially outward are circumferentially arranged, and in which magnet receiving holes (15, 15A) are formed axially extending through an inner radial side of each of the circular arc-shaped curved surfaces (13); a rotary shaft (11) inserted in a central axial position of the rotor core (12, 12A, 12B) and holding the rotor core; and Permanent magnets (16, 16A), each made as a rod-shaped body in which a radially outer side of a cross section perpendicular to a longitudinal direction is a circular arc convex radially outward, and in which two circumferential side surfaces are flat surfaces parallel to a plane containing a magnetic pole center, the permanent magnets being respectively received in the magnet receiving openings (15, 15A); R1 > R2 > R3 is satisfied, wherein R1 is a radius of curvature of a cylindrical surface (14) contacting the circular-arc curved surfaces (13) arranged circumferentially, R2 is a radius of curvature of the circular-arc curved surfaces (13), and R3 is a radius of curvature of an upper surface of the permanent magnets (16, 16A); the magnet receiving openings (15, 15A) comprise air gap sections (17) in which radially outer sections of two circumferential side sections are circumferentially expanded outwards; Surfaces parallel to a plane containing the magnetic pole center, which contact the two circumferential side surfaces of the permanent magnets (16, 16A), are arranged at radially inner portions of the two circumferential side portions of the magnet receiving openings (15, 15A); B1 < B2 is satisfied, wherein B1 is a thickness of a core portion of the rotor core (12, 12A, 12B) between the circular arc-shaped curved surfaces (13) and the magnet receiving holes (15, 15A) in the magnetic pole center, and B2 is a thickness of a peripheral end portion of the core portion; End plates (21) are arranged to touch two axial end surfaces of the rotor core (12, 12A, 12B) and, viewed from an axial direction, to cover at least part of the permanent magnets (16, 16A); and a radial position of outer peripheral edges of the end plates (21) is greater than or equal to a radial position of a point that is half a thickness of the permanent magnets (16, 16A) in the magnetic pole center, and is less than or equal to a radial position of an intersection point between the top and side surfaces of the permanent magnets (16, 16A) wherein the permanent magnets (16) are formed with a cross-sectional shape perpendicular to a longitudinal direction, in which a radially outer side is a circular arc which is convex radially outward, and a radially inner side is a circular arc which is convex radially outward, satisfying R1 > R4 > R2 > R3, wherein R4 is a radius of curvature of a bottom surface of the permanent magnets. [5] An embedded permanent magnet rotating electrical machine according to any one of claims 1 to 4, wherein the rotor core is formed such that n core segments (121, 122, 131, 132, 133) are axially arranged, where n is an integer greater than or equal to two, and magnetic pole centers of axially adjacent core segments (121, 122, 131, 132, 133) are offset in a circumferential direction. [6] The permanent magnet embedded rotating electric machine according to claim 5, wherein the permanent magnet embedded rotating electric machine is a three-phase permanent magnet embedded motor, the stator (19, 10A) comprises: an annular rear yoke (2a); teeth (2b) each arranged projecting inwardly from the rear yoke (2a); and a stator winding (3) mounted on slots (2c) formed by the rear yoke (2a) and adjacent teeth (2b); a number of slots (2c) per phase per pole is one half or one quarter; and an offset angle in the circumferential direction between the magnetic pole centers of the axially adjacent core segments (121, 122, 131, 132, 133) is greater than or equal to 30 electrical degrees or less than or equal to 48 electrical degrees. [7] An embedded permanent magnet rotating electrical machine according to claim 5 or claim 6, wherein a gap is disposed between the axially adjacent core segments (121, 122, 131, 132, 133). [8] The permanent magnet embedded rotating electric machine according to claim 7, wherein B1 ≤ d is satisfied, where d is the gap.

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