Technical Field
[0001] The present invention relates to a rotor for a rotary
electric machine.
Background Art
[0002] Among rotors for a rotary electric machine, there is
given a rotor including a non-magnetic ring configured to retain
permanent magnets mounted on a periphery of the rotor.
[0003] For example, in Patent Literature 1, there is disclosed
a rotor including at least a rotor core, a plurality of magnets,
and a non-magnetic ring. The plurality of magnets are fixed to an
outer periphery of the rotor core so as to be arrayed in a
circumferential direction. The non-magnetic ring is provided so
as to surround the plurality of magnets from outside.
[0004] Further, in Patent Literature 2, there is disclosed a
step-skew configuration, in which upper and lower stages of a rotor
are shifted by a predetermined angle in a circumferential direction
so as to reduce cogging torque and torque ripples.
Citation List
Patent Literature
[0005] [PTL 1] JP 2009-106065 A

[PTL 2] JP 2011-55706 A
Summary of Invention Technical Problem
[0006] In the case of the step-skew configuration of the rotor as disclosed in Patent Literature 2, when the non-magnetic ring is brought into contact with the permanent magnets as in the configuration disclosed in Patent Literature 1, a difference in circumferential length of the non-magnetic ring becomes significant between the vicinity of a step-skew boundary and the other portion, and hence an excessive load is generated in the non-magnetic ring. As a result, the non-magnetic ring may be buckled or damaged. Further, when the non-magnetic ring to be used is formed such that both sides of the step skew have the maximum diameter in order to avoid the buckling or damage, press contact between the non-magnetic ring and the magnets may become insufficient in turn. [0007] The present invention has been made in view of the above, and has an object to provide a rotor for a rotary electric machine, which is capable of avoiding increase in distortion amount of a non-magnetic ring in the vicinity of a step-skew boundary, thereby being capable of avoiding buckling or damage.
Solution to Problem
[0008] In order to achieve the above-mentioned object,
according to one embodiment of the present invention, there is

provided a rotor having a plurality of magnetic poles and a step-skew structure with two or more stages, the rotor including a rotor core including: a plurality of protrusions formed on at least a step-skew boundary side; and a tubular non-magnetic ring mounted on outer peripheries of the plurality of magnetic poles so as to cover the step-skew boundary, the non-magnetic ring including a plurality of inner diameter bulging portions, each of the plurality of magnetic poles and each of the plurality of protrusions being brought into abutment against the corresponding inner diameter bulging portions.
Advantageous Effects of Invention
[0009] According to the present invention, it is possible to avoid the increase in distortion amount of the non-magnetic ring in the vicinity of the step-skew boundary, thereby being capable of avoiding the buckling or the damage.
Brief Description of Drawings
[0010] FIG. 1 is a perspective view of a rotor for a rotary electric machine (before a non-magnetic ring is mounted) according to a first embodiment of the present invention.
FIG. 2 is a plan view of the rotor for a rotary electric machine (before the non-magnetic ring is mounted) according to the first embodiment of the present invention.
FIG. 3 is a perspective view of the rotor for a rotary electric machine according to the first embodiment of the present invention.

FIG. 4 is a plan view of the rotor for a rotary electric machine according to the first embodiment of the present invention.
FIG. 5 is an enlarged view of the part V of FIG. 4.
FIG. 6 is a graph for showing the amounts of distortion caused in non-magnetic rings having respective polygonal shapes at step-skew angles of 5°, 8°, and 10°.
FIG. 7 is a perspective view of a core having a square shape at the step-skew angle of 10°.
FIG. 8 is a view for illustrating the core having a square shape and the non-magnetic ring at the step-skew angle of 10°.
FIG. 9 is a perspective view of a rotor for a rotary electric machine (before a non-magnetic ring is mounted) according to a second embodiment of the present invention.
FIG. 10 is aplanviewof the rotor for a rotary electric machine according to the second embodiment of the present invention.
Description of Embodiments
[0011] Now, embodiments of the present invention are described with reference to the accompanying drawings. Note that, in the drawings, the same reference symbols represent the same or corresponding parts. [0012] First Embodiment
FIG. 1 and FIG. 2 are a perspective view and a plan view of a rotor for a rotary electric machine according to a first embodiment of the present invention before a non-magnetic ring is mounted,

respectively. FIG. 3 is a perspective view of the rotor for a rotary electric machine according to the first embodiment. FIG. 4 is a top view of the rotor for a rotary electric machine according to the first embodiment. FIG. 5 is an enlarged view of the part V of FIG. 4.
[0013] As illustrated in FIG. 1 to FIG. 5, a rotor 1 includes a rotor first stage portion 2 and a rotor second stage portion 3. The rotor first stage portion 2 and the rotor second stage portion 3 are arrayed in an extending direction of a rotor shaft 4. Further, the rotor first stage portion 2 and the rotor second stage portion 3 have the same configuration except that the rotor first stage portion 2 and the rotor second stage portion 3 are shifted by a step-skew angle of 10° in a circumferential direction (rotational direction).
[0014] The rotor first stage portion 2 includes a rotor core 21 and a plurality of permanent magnets (magnetic poles) 22. The rotor core 21 is formed by laminating a plurality of magnetic steel sheets (made of a magnetic material) each having a plurality of protrusions 211 arranged at regular intervals in the circumferential direction. Each of the plurality of permanent magnets 22 is bonded between a corresponding pair of protrusions 211, and is arranged out of contact with the pair of protrusions 211. [0015] The rotor second stage portion 3 is formed in the same manner as the rotor first stage portion 2. The rotor second stage portion 3 includes a rotor core 31 and a plurality of permanent

magnets (magnetic poles) 32. The rotor core 31 is formed by laminating a plurality of magnetic steel sheets (made of a magnetic material) each having a plurality of protrusions 311 arranged at regular intervals in the circumferential direction. Each of the plurality of permanent magnets 32 is bonded between a corresponding pair of protrusions 311, and is arranged out of contact with the pair of protrusions 311.
[0016] The plurality of permanent magnets and the plurality of protrusions are arranged at eguiangular pitches in the circumferential direction. In the first embodiment that is an example of the present invention, there is exemplified a case where the number of stages is two and the number of magnetic poles is eight. Thus, in each of the rotor first stage portion 2 and the rotor second stage portion 3, eight permanent magnets 22 or 32 and eight protrusions 211 or 311 are provided.
[0017 ] The rotor core of the present invention has the plurality of protrusions at least on a boundary 6 side . In the first embodiment that is an example, each of the protrusions 211 and 311 extends continuously over the total length of a corresponding one of the rotor first stage portion 2 and the rotor second stage portion 3 in a rotation axis direction. In other words, each of the permanent magnets 22 and 32 extends continuously over the total length of a corresponding one of the rotor first stage portion 2 and the rotor second stage portion 3 in the rotation axis direction, and the length of each of the protrusions 211 and 311 (length in the rotation axis

direction) is equal to the length of each of the permanent magnets 22 and 32 (length in the rotation axis direction) . Further, in plan view, the outer peripheral surface of each of the protrusions 211 and 311 is formed into an arc shape that is curved so as to bulge radially outward.
[0018] Further, in each of the rotor first stage portion 2 and the rotor second stage portion 3, when a radial distance from an axial center of the rotor shaft 4 (rotation center of the rotor) to the outermost portion of each of the protrusions 211 and 311 of the rotor cores 21 and 31 is represented by LI, a curvature radius of each of the protrusions 211 and 311 is represented by Rl, a radial distance from the axial center of the rotor shaft 4 (rotation center of the rotor) to the outermost portion of each of the magnetic poles (permanent magnets 22 and 32) is represented by L2, and a curvature radius of each of the magnetic poles (permanent magnets 22 and 32) is represented by R2, the respective portions concerned are formed so as to satisfy relationships of distance LI^distance L2 and curvature radius Rl^curvature radius R2 .
[0019] Further, the rotor 1 includes a non-magnetic ring 5. The non-magnetic ring 5 is a tubular member made of a non-magnetic material (for example, stainless steel) to have a substantially regular hexadecagonal shape in plan view (when viewed along the extending direction of the rotor shaft 4).
[0020] The non-magnetic ring 5 is mounted so as to cover outer peripheries of the eight permanent magnets 22 and the eight permanent

magnets 32 of the rotor first stage portion 2 and the rotor second stage portion 3, outer peripheries of the eight protrusions 211 and the eight protrusions 311 of the rotor first stage portion 2 and the rotor second stage portion 3, and an outer periphery of the boundary 6 between the rotor first stage portion 2 and the rotor second stage portion 3.
[0021] The non-magnetic ring 5 includes sixteen are-shaped inner diameter bulging portions 51 as many as the sum of the number of magnetic poles and the number of protrusions of the rotor core. Thus, the outer shape (outer diameter) of the non-magnetic ring 5 has a substantially regular hexadecagonal loop outline connecting the plurality of inner diameter bulging portions 51 as gentle ridge lines.
[0022] The inner peripheral surfaces (radially inner surfaces) of the inner diameter bulging portions 51 of the non-magnetic ring 5 are held in contact with the outer peripheral surfaces of each of the plurality of magnetic poles (permanent magnets 22 and 32) and each of the plurality of protrusions of the rotor core, to thereby apply a radially-inward urging force to each of the magnetic poles. [0023] Further, when a circumferential length of an imaginary circumscribed circle, which is held in contact with all of the plurality of magnetic poles and the plurality of protrusions of the rotor core, is represented by L3, and an inner circumferential length of the non-magnetic ring 5 is represented by L4, the non-magnetic ring 5 is formed so as to satisfy a relationship of

circumferential length L3 of imaginary circumscribed circle>inner circumferential length L4 of non-magnetic ring.
[002 4] Further, the protrusion of the rotor core protrudes radially outward with respect to a common tangential line C, which is held in contact with a pair of magnetic poles located adjacent to each other across the protrusion.
[0025] Now, general description is made of the configurations of the magnetic poles, the protrusions of the rotor core, and the non-magnetic ring. When the number of poles, namely the number of magnetic poles of the rotor for a rotary electric machine is represented by n, the number of protrusions of the rotor core is n, and the non-magnetic ring is formed to have a regular 2n-sided polygonal shape (regular m-sided polygonal shape). Further, the magnetic poles and the protrusions of the rotor core are arranged at equal pitches. In plan view, an angle 9 between a radial line passing through the axial center of the rotor shaft 4 and through a center portion of the magnetic pole and a radial line passing through the axial center of the rotor shaft 4 and through a center portion of the protrusion is expressed as follows.
e-360°/2n ... (1) [0026] Next, a relationship between the number of sides of the non-magnetic ring and the distortion amount relative to the step-skew angle is described with reference to FIG. 6 and FIG. 7 . [0027] FIG. 6 is a graph for showing the amounts of distortion caused in non-magnetic rings having respective polygonal shapes

at step-skew angles of 5°, 8°, andl0°. As schematically illustrated in FIG. 7 and FIG. 8, when a circumferential length of the rotor core at a portion other than the step-skew boundary is represented by L5, and a circumferential length at the step-skew boundary 6 is represented by L6, a distortion amount y of the non-magnetic ring is expressed by Expression (2).
Y={L6-L5)/L5*100 ... (2)
Further, when a half of the length of each diagonal line of an m-sided polygon is represented by a, an angle between the diagonal lines is represented by 0m, and a step-skew angle is represented by 9', the circumferential lengths L5 and L6 are expressed by Expression (3) and Expression (4 ) , respectively.
L5=mxax{2x(1-cosGm) }" (1/2) ... (3)
L6=mxax{2x(l-cos6' } fAf1/2)+mxax{2*(1-cos(9m-ef)) }A(1/2) . .. (4)
[0028] Then, Expression (2) can be expressed as Expression (5) with use of Expression (3) and Expression (4).
y={{1-cosG')A(1/2)+(1-cos(0m-9'))"(1/2)}/{(l-cos0m)"(1/2) } ... (5)
[0029] FIG. 7 and FIG. 8 are views of an example in a case where the rotor cores are square and the step-skew angle is 20°, namely explanatory views of a case where m=4 , 9m=90° , and 9 '=10° . As shown in FIG. 6, it is understood that Lhe amount of distortion caused in the non-magnetic ring is increased as the number of sides is decreased, and is also increased as the step-skew angle is increased.

In the configuration of FIG. 7 and FIG. 8, the amount of distortion caused in the non-magnetic ring is about 3.2%.
[0030] In the case of the configuration illustrated in FIG. 1 to FIG. 5, the step-skew angle is 10° and the shape of the deformed non-magnetic ring is a hexadecagonal shape. That is, this case is an example in which m=16, 0m=22.5°, and 6'=10°. Thus, the amount of distortion caused In the non-magnetic ring is about 0.5%. In contrast, in a configuration in a case where the step-skew angle is the same angle of 10° and the rotor core has no protrusion, namely the shape of the deformed non-magnetic ring is an octagonal shape, that is, in a configuration in which m=8, 0m=45°, and 0'=1O°, the amount of distortion caused in the non-magnetic ring is about 1.4%. Thus, in the first embodiment in which the rotor core has the protrusions, the amount of distortion that may be caused in the non-magnetic ring can be reduced by about 60% as compared to the case where the rotor core has no protrusion.
[0031] As described above, in the first embodiment, each of the protrusions is provided between the magnets of the rotor core, and the non-magnetic ring is arranged on the magnets and the protrusions so that both of the magnets and the protrusions of the rotor core are brought into abutment against the non-magnetic ring. Thus, the magnets and the protrusions of the rotor core are brought into abutment against the non-magnetic ring at a larger number of points, thereby being capable of deforming the non-magnetic ring into a polygonal shape having a larger number of sides. Further,

when the non-magnetic ring is deformed into a polygonal shape having a larger number ofsidesas described above, the increase in distortion amount of the non-magnetic ring in the vicinity of the step-skew boundary along with the step skew can be avoided without requiring increase in number of components or increase in distance between the magnets andthestator, thereby being capable of avoiding buckling or damage. [0032] Second Embodiment
Next, referring to FIG. 9 and FIG. 10, a second embodiment of the present invention is described. FIG. 9 is a perspective view of a rotor for a rotary electric machine (before a non-magnetic ring is mounted) according to the second embodiment of the present invention. FIG. 10 is a plan view of the rotor for a rotary electric machine according to the second embodiment of the present invention. Note that, the second embodiment is the same as the above-mentioned first embodiment except for the parts described below. [0033] The second embodiment has a feature in that the protrusions are provided partially in the rotation axis direction of the rotor (at least on the boundary side). FIG. 9 and FIG. 10 are illustrations of an example of such a feature of the second embodiment. As in the first embodiment, a rotor 7 of the second embodiment includes a rotor first stage portion 8 and a rotor second stage portion 9. The rotor first stage portion 8 and the rotor second stage portion 9 are arrayed in the extending direction of the rotor shaft 4. Further, the rotor first stage portion 8 and the rotor

second stage portion 9 have the same configuration except that the rotor first stage portion 8 and the rotor second stage portion 9 are shifted by a step-skew angle of 10° in the circumferential direction (rotational direction).
[0034] The rotor first stage portion 8 includes a rotor core and a plurality of permanent magnets 822. The rotor core of the rotor first stage portion 8 includes a rotor core portion 83 formed of magnetic steel sheets (made of a magnetic material) each having no protrusion, and a rotor core portion 81 made of a non-magnetic material having protrusions 811.
[0035] Similarly, the rotor second stage portion 9 also includes a rotor core and a plurality of permanent magnets 822. The rotor core of the rotor second stage portion 9 also includes a rotor core portion 8 3 formed of magnetic steel sheets (made of a magnetic material) each having no protrusion, and a rotor core portion 81 made of a non-magnetic material having protrusions 811. [0036] The rotor core portion 81 of the rotor first stage portion
8 and the rotor core portion 81 of the rotor second stage portion
9 are positioned in a region on a boundary 10 side between the rotor first stage portion 8 and the rotor second stage portion 9. That is, the protrusions 811 of the rotor first stage portion 8 and the protrusions 811 of the rotor second stage portion 9 are provided only on the boundary 10 side between the rotor first stage portion 8 and the rotor second stage portion 9.
[0037] Further, the side surfaces of the permanent magnets 822

of the rotor first stage portion 8 are held in contact with the
side surfaces of the protrusions 811, and the side surfaces of the
permanent magnets 832 of the rotor second stage portion 9 are also
held in contact with the side surfaces of the protrusions 811.
[0038] According to the above-mentioned rotor for a rotary
electric machine of the second embodiment, the amount of distortion
that may be caused in the non-magnetic ring in the vicinity of the
step-skew boundary can be reduced for the same reason as that of
the first embodiment. In addition, the positions of the permanent
magnets in the circumferential direction can securely be regulated
through the contact of the permanent magnets with the protrusions
of the rotor core. Further, torque reduction that may be caused
by leakage of magnetic fluxes from the permanent magnets can be
avoided through the formation of the rotor core portion having the
protrusions with use of a non-magnetic material.
[0039] Although the details of the present invention are
specifically described above with reference to the preferred
embodiments, it is apparent that persons skilled in the art may
adopt various modifications based on the basic technical concepts
and teachings of the present invention.
Reference Signs List
[0040] 1, 7 rotor, 5 non-magnetic ring, 6, 10 boundary, 21, 31 rotor core, 22, 32, 822, 832 permanent magnet (magnetic pole), 211, 311, 811 protrusion, 51 inner diameter bulging portion, 81

rotor core portion

[Claim 1] Arotor having a plurality ofmagneticpoles and a step-skew structure with two or more stages, the rotor comprising a rotor core comprising:
a plurality of protrusions formed on at least a step-skew boundary side; and
a tubular non-magnetic ring mounted on outer peripheries of the plurality of raagnetic poles so as to cover the step-skew boundary,
the non-magnetic ring comprising a plurality of inner diameter bulging portions,
each of the plurality of magnetic poles and each of the plurality of protrusions being brought into abutment against the corresponding inner diameter bulging portions.
[Claim 2] A rotor according to claim 1, wherein the protrusion of the rotor core protrudes radially outward with respect to a common tangential line, which is held in contact with a pair of the magnetic poles located adjacent to each other across the protrusion.
[Claim 3] A rotor according to claim 1 or 2, wherein, when a radial distance from a rotation center of the rotor to an outermost portion of the protrusion is represented by Ll, and a radial distance from the rotation center of the rotor to an outermost portion of the magnetic pole is represented by L2, a relationship of distance 1,1 ^distance L2 is satisfied.

[Claim 4] A rotor according to any one of claims 1 to 3, wherein a length of each of the protrusions is equal to a length of each of the magnetic poles.
[Claim 5] A rotor according to any one of claims 1 to 3, wherein the protrusions are provided only on the step-skew boundary side.
[Claim 6] A rotor according to any one of claims 1 to 5, wherein, in plan view, an outer peripheral surface of the each of the protrusions is formed into an arc shape that is curved so as to bulge radially outward.
[Claim 7] A rotor according to any one of claims 1 to 6,
wherein the rotor core comprising the protrusions is made of
a magnetic material, and
wherein the each of the protrusions is kept out of contact
with the pair of the magnetic poles located adjacent to each other.
[Claim 8] A rotor according to any one of claims 1 to 6,
wherein a rotor core portion comprising the protrusions is made of a non-magnetic material, and
wherein the each of the protrusions is held in contact with the pair of the magnetic poles located adjacent to each other.

[Claim 9] A rotor according to any one of claims 1 to 8, wherein the plurality of permanent magnets and the plurality of protrusions are arranged at equiangular pitches in a circumferential direction.