EMBEDDED MAGNET ROTARY ELECTRIC MACHINE AND METHOD FOR MANUFACTURING EMBEDDED MAGNET ROTOR
USED THEREIN
BACKGROUND OF THE INVENTION [0001]
1. Field of the Invention
The present invention relates to an embedded magnet rotary electric machine in which permanent magnets are embedded inside a rotor core and to a method for manufacturing an embedded magnet rotor that is used therein.
[0002]
2. Description of the Related Art
In conventional embedded magnet rotors, magnet sets are formed by disposing a metal plate on a first surface of a magnet, and also disposing a metal plate on a second surface of the magnet so as to have a tabular rubber elastic body interposed, and the magnets are embedded in a rotor core by compressing the magnet sets in a thickness direction, inserting the magnet sets into slots that are disposed on the rotor core while compressing the rubber elastic bodies, and then press-fitting the magnet sets into the slots (see Patent Literature 1, for example).
CITATION LIST PATENT LITERATURE [0003]
[Patent Literature l] Japanese Patent No. 4351482 (Specification)
SUMMARY OF THE INVENTION
PROBLEM TO BE SOLVED BY THE INVENTION

In conventional embedded magnet rotors, because the tabular rubber elastic bodies are interposed between the magnets and the metal plates, one problem has been that a great deal of force is required to compress the magnet sets in the thickness direction, reducing mass producibility of the rotor, and also giving rise to damage to the magnets, thereby reducing yield. In addition, because the magnet sets are press-fitted into the slots after the rubber elastic bodies are compressed and the magnet sets inserted into the slots of the rotor core, other problems have been that the operation of installing the magnets into the rotor core is complicated, reducing mass producibility of the rotor, and stresses also act on the magnets through the metal plates in the direction of insertion into the slots, giving rise to damage to the magnets, and deformation of the inner wall surfaces of the slots also arises, reducing yield.
[5]
The present invention aims to solve the above problems and an object of the present invention is to provide an embedded magnet rotary electric machine and a method for manufacturing an embedded magnet rotor used therein, that can improve mass producibility of the rotor, and that can increase reliability by interposing a cord-shaped rubbery elastic body such that a longitudinal direction thereof is oriented axially and so as to be stretched longitudinally between a magnet insertion aperture and a permanent magnet that are disposed on a rotor core so as to hold the permanent magnet elastically on the rotor core using a force of recovery of the rubbery elastic body.
MEANS FOR SOLVING THE PROBLEM
[6]

In order to achieve the above object, according to one aspect of the present invention, there is provided an embedded magnet rotary electric machine including: a stator; and a rotor including: a rotor core that is rotatably disposed inside the stator; and a permanent magnet that is inserted into and fixed inside a magnet insertion aperture that is formed so as to pass axially through the rotor core, a cord-shaped rubbery elastic body being interposed between the permanent magnet and the magnet insertion aperture in a longitudinally stretched state so as to extend in an aperture direction of the magnet insertion aperture, and the permanent magnet being held elastically in the rotor core by being pressed against an outer circumferential wall surface of the magnet insertion aperture by a force of recovery that accompanies contraction of the rubbery elastic body.
EFFECTS OF THE INVENTION
[7]
According to the present invention, because cord-shaped rubbery elastic bodies are used, forces that compress the rubbery elastic bodies are reduced. The permanent magnets are pressed against the outer circumferential wall surfaces of the magnet insertion apertures and held elastically in the rotor core simply by allowing the stretched rubbery elastic bodies to contract. Thus, ease of assembly of the permanent magnets is increased, improving mass producibility of the rotor.
Because it is not necessary to press-fit the permanent magnets, and excessive loads do not act on the permanent magnets, occurrence of damage to the permanent magnets is suppressed, increasing yield.
BRIEF DESCRIPTION OF THE DRAWINGS
[8]

•I I
t
Figure 1 is a longitudinal cross section that schematically shows an embedded magnet rotary electric machine according to Embodiment 1 of the present invention;
Figure 2 is a partial cross section that shows an embedded state of a magnet in the embedded magnet rotary electric machine according to Embodiment 1 of the present invention,'
Figures 3A through 3D are process cross sections that explain a method for embedding the magnet into a rotor that is used in the embedded magnet rotary electric machine according to Embodiment 1 of the present invention;
Figure 4 is a table that shows results of high-temperature tests on a rubbery elastic body that is used in the embedded magnet rotary electric machine according to Embodiment 1 of the present invention;
Figure 5 is a lateral cross section that explains a permanent magnet elastic holding mechanism by the rubbery elastic body in the embedded magnet rotary electric machine according to Embodiment 1 of the present invention;
Figure 6 is a lateral cross section that shows a variation of a permanent magnet elastic holding construction by the rubbery elastic body in the embedded magnet rotary electric machine according to Embodiment 1 of the present invention,'
Figure 7 is a lateral cross section that shows another variation of a permanent magnet elastic holding construction by the rubbery elastic body in the embedded magnet rotary electric machine according to Embodiment 1 of the present invention;
Figure 8 is a longitudinal cross section that shows part of an embedded magnet rotary electric machine according to Embodiment 2 of the present invention;

J. >
Figure 9 is a lateral cross section that shows part of an embedded magnet rotary electric machine according to Embodiment 3 of the present invention;
Figure 10 is a lateral cross section that shows part of an embedded magnet rotary electric machine according to Embodiment 4 of the present invention;
Figure 11 is a cross section that shows part of an embedded magnet rotary electric machine according to Embodiment 5 of the present invention;
Figure 12 is a side elevation that shows a rubbery elastic body that is used in an embedded magnet rotary electric machine according to Embodiment 6 of the present invention," and
Figure 13 is a longitudinal cross section that shows part of a rotor core that is used in an embedded magnet rotary electric machine according to Embodiment 7 of the present invention.
DESCRIPTION OF EMBODIMENTS
[9]
Preferred embodiments of an embedded magnet rotary electric machine according to the present invention will now be explained using the drawings.
[10] Embodiment 1
Figure 1 is a longitudinal cross section that schematically shows an embedded magnet rotary electric machine according to Embodiment 1 of the present invention, Figure 2 is a partial cross section that shows an embedded state of a magnet in the embedded magnet rotary electric machine according to Embodiment 1 of the present invention, Figures 3A through 3D are process cross sections that explain a method for embedding

the magnet into a rotor that is used in the embedded magnet rotary electric machine according to Embodiment 1 of the present invention, Figure 4 is a table that shows results of high-temperature tests on a rubbery elastic body that is used in the embedded magnet rotary electric machine according to Embodiment 1 of the present invention, Figure 5 is a lateral cross section that explains a permanent magnet elastic holding mechanism by the rubbery elastic body in the embedded magnet rotary electric machine according to Embodiment 1 of the present invention, Figure 6 is a lateral cross section that shows a variation of a permanent magnet elastic holding construction by the rubbery elastic body in the embedded magnet rotary electric machine according to Embodiment 1 of the present invention, and Figure 7 is a lateral cross section that shows another variation of a permanent magnet elastic holding construction by the rubbery elastic body in the embedded magnet rotary electric machine according to Embodiment 1 of the present invention. Moreover, the rubbery elastic body in a free state is represented by a broken line in Figure 2. A "longitudinal cross section" is a cross section that includes a central axis of a shaft, and a "lateral cross section" is a cross section that is perpendicular to the central axis of the shaft.
[0011]
In Figure 1, an embedded magnet electric motor 1 that functions as an embedded magnet rotary electric machine includes: a shaft 8 that is rotatably supported by a frame (not shown); a rotor 5 that is fixed to the shaft 8 and that is rotatably disposed inside the frame; and a stator 2 that has: an annular stator core 3; and a stator coil 4 that is mounted onto the stator core 3, the stator core 3 being held by the frame, and the stator 2 being disposed so as to surround the rotor 5 so as to have a predetermined gap interposed.
[0012]

The rotor 5 includes: a rotor core 6 that is formed by laminating and integrating electromagnetic steel plates that have been punched into predetermined shapes, for example,' the shaft 8, which is press-fitted into and fixed to a shaft insertion aperture 7 that is formed so as to pass through a central axial position of the rotor core 6! permanent magnets 10 that are inserted into magnet insertion apertures 9 that are each formed so as to pass through the rotor core 6, and that are arranged concyclically at a uniform angular pitch; and rubbery elastic bodies 11 that hold the permanent magnets 10 elastically in the rotor core 6.
[13]
The magnet insertion apertures 9 are formed so as to have an aperture shape that has a rectangular cross-sectional shape perpendicular to the central axis of the shaft 8. The permanent magnets 10 are formed into strip shapes that have a rectangular cross-sectional shape that can be inserted loosely into the magnet insertion apertures 9, and that have a length that is approximately equal to an axial length of the rotor core 6. Rubbery elastic body housing grooves 12 are formed on circumferentially central positions of inner circumferential wall surfaces (bottom surfaces) of the magnet insertion apertures 9 so as to extend from a first end to a second end in an axial direction of the shaft 8 so as to have a semi-elliptical cross-sectional shape (a groove shape) perpendicular to a groove direction, and so as to have the groove direction oriented in the axial direction of the shaft 8. The rubbery elastic bodies 11 are formed so as to have cord shapes that have a circular cross-sectional shape perpendicular to a longitudinal direction. The rubbery elastic bodies 11 are interposed between the permanent magnets 10 and the rubbery elastic body housing grooves 12 so as to be housed inside the rubbery elastic body housing grooves 12 in a longitudinally stretched state.


The cross-sectional shape of the rubbery elastic bodies 11 perpendicular to the longitudinal direction in the longitudinally stretched state is narrower than the cross-sectional shape thereof in a free state (a state free from external forces). Thus, the length of the rubbery elastic bodies 11 that are interposed between the permanent magnets 10 and the rubbery elastic body housing grooves 12 tries to contract (recover) to the length of the free state, and the cross-sectional shape perpendicular to the longitudinal direction tries to expand (recover) to the cross-sectional shape of the free state. This cross-sectional shape-recovering force from the rubbery elastic bodies 11 acts so as to press the permanent magnets 10 against outer circumferential wall surfaces (upper surfaces) of the magnet insertion apertures 9. As shown in Figure 2, the rubbery elastic bodies 11 are elastically deformed, and are interposed between the permanent magnets 10 and the rubbery elastic body housing grooves 12 in a state in which a predetermined force of recovery remains. The permanent magnets 10 are thereby held elastically in the rotor core 6 by the force of recovery of the rubbery elastic bodies 11.
[15]
Moreover, the rubbery elastic bodies 11 are squashed by the permanent magnets 10 and the rubbery elastic body housing grooves 12, and are elastically deformed into approximately elliptical cross sections that expand outward in a groove width direction of the rubbery elastic body housing grooves 12 from a circular cross section. As shown in Figure 2, the rubbery elastic body housing grooves 12 have gaps at outer circumferential surfaces of the portions of the rubbery elastic bodies 11 that expand outward in the groove width direction of the rubbery elastic body housing grooves 12.
[16]

A method for assembling the permanent magnets 10 in the rotor core 6 will now be explained based on Figure 3.
[17]
First, a rubbery elastic body 11 is passed through a magnet insertion aperture 9, and the rubbery elastic body 11 is stretched by gripping two end portions thereof and pulling longitudinally. The rubbery elastic body 11 is positioned inside a rubbery elastic body housing groove 12 in the stretched state as shown in Figure 3A. Next, a permanent magnet 10 is inserted into the magnet insertion aperture 9 as shown in Figure 3B. After the permanent magnet 10 is housed completely inside the magnet insertion aperture 9, pulling force on the rubbery elastic body 11 is loosened as shown in Figure 3C. The length of the rubbery elastic body 11 thereby shrinks gradually. The rubbery elastic body 11 recovers such that the cross-sectional shape perpendicular to the longitudinal direction thereof gradually assumes its initial state, and pushes the permanent magnet 10 upward. When the permanent magnet 10 contacts the upper surface of the magnet insertion aperture 9, the rubbery elastic body 11 recovers by a predetermined amount so as to expand outward in the groove width direction, and then stops recovering. Thus, when gripping of the two end portions of the rubbery elastic body 11 is released, the permanent magnet 10 is held elastically on the rotor core 6 by being pressed against the upper surface of the magnet insertion aperture 9 by the force of recovery of the rubbery elastic body 11 in a direction that is perpendicular to the longitudinal direction, as shown in Figure 3D.
[18]
Moreover, the rubbery elastic body 11 is allowed to recover gradually by relaxing the pulling force on the rubbery elastic body 11 after the permanent magnet 10 is housed completely inside the magnet insertion aperture 9, but the rubbery elastic body 11 may also be allowed to recover

by releasing gripping of the rubbery elastic body 11 after the permanent magnet 10 is housed completely inside the magnet insertion aperture 9.
[19]
According to Embodiment 1, cord-shaped rubbery elastic bodies 11 are passed through magnet insertion apertures 9 that are formed so as to pass axially through a rotor core 6, the rubbery elastic bodies 11 are stretched longitudinally and positioned on bottom surface sides of the magnet insertion apertures 9, permanent magnets 10 are inserted into the magnet insertion apertures 9, and then the rubbery elastic bodies 11 are allowed to recover by releasing the stretching force to hold the permanent magnets 10 elastically in the rotor core 6.
[20]
Thus, permanent magnets 10 can be mounted into the rotor core 6 easily, enabling mass producibility of a rotor 5 to be increased.
[0021]
Stresses also do not act on the permanent magnets 10 as the permanent magnets 10 are inserted into the magnet insertion apertures 9. Because the forces that stretch the rubbery elastic bodies 11 are released when the permanent magnets 10 are housed in the magnet insertion apertures 9, stresses act on the permanent magnets 10 mainly in the thickness directions of the permanent magnets 10, and stresses in the aperture directions of the magnet insertion apertures 9 do not act on the permanent magnets 10. Consequently, the occurrence of damage to the permanent magnets 10 as the permanent magnets 10 are mounted into the rotor core 6 can be significantly reduced, enabling yield to be increased.
[0022]
In addition, because stresses in the aperture directions of the magnet insertion apertures 9 do not act on the inner wall surfaces of the magnet insertion apertures 9 as the permanent magnets 10 are inserted

into the magnet insertion apertures 9, or as the forces that stretch the rubbery elastic bodies 11 are released, the occurrence of situations such as the inner wall surfaces of the magnet insertion apertures 9 being deformed is avoided, enabling yield to be increased.
[23]
The rubbery elastic body housing grooves 12 are formed on circumferentially central positions of bottom surfaces of the magnet insertion apertures 9 such that groove directions are oriented in an axial direction of the shaft 8 so as to extend from a first end to a second end in the axial direction of the shaft 8. Thus, setting of the rubbery elastic bodies 11 inside the magnet insertion apertures 9 is facilitated, improving assembly of the permanent magnets 10 into the rotor core 6. Circumferential misalignment of the rubbery elastic bodies 11 inside the magnet insertion apertures 9 is also prevented, increasing stability of the elastic holding of the permanent magnets 10.
[24]
The rubbery elastic body housing grooves 12 are formed so as to have groove shapes that have gaps at outer circumferential surfaces of portions of the rubbery elastic bodies 11 that are interposed between the permanent magnets 10 and the rubbery elastic body housing grooves 12 that expand outward in the groove width direction of the rubbery elastic body housing grooves 12. Thus, because compressive loads do not act on the rubbery elastic bodies 11 from the groove width direction of the rubbery elastic body housing grooves 12, the occurrence of loss of resilience in the rubbery elastic bodies 11 can be prevented. The rubbery elastic bodies 11 can thereby stably hold the permanent magnets 10 elastically for a long time.

Two end portions of the rubbery elastic bodies 11 protrude from end surfaces of the rotor core 6. Thus, by gripping the two protruding end portions of the rubbery elastic bodies 11 and stretching the rubbery elastic bodies 11, the load that elastically holds the permanent magnets 10 can be removed, and the permanent magnets 10 extracted. The permanent magnets 10 can thereby be extracted easily without being damaged, enabling recycling of the permanent magnets 10.
[0026]
Now, rotors 5 were prepared in which compression ratios ((compressed thickness/free-state thickness) x 100) (%) of rubbery elastic bodies 11 that were installed in magnet insertion apertures 9 were varied, the rubbery elastic bodies 11 were extracted after high-temperature testing (150 degrees Celsius for 120 hours), and the recovered state of the rubbery elastic bodies 11 was observed, the results being shown in Figure 4. Moreover, the permanent magnets 10 were prepared using neodymium magnets (epoxy-coated), and the rubbery elastic bodies 11 were prepared using Fluoro Rubber FR-27 (manufactured by Tigers Polymer Corporation).
[0027]
Function to hold the permanent magnets 10 elastically after high-temperature testing was retained in rubbery elastic bodies 11 that were installed in the magnet insertion apertures 9 at compression ratios of 65 percent and 70 percent, respectively. When the rubbery elastic bodies 11 were removed from the magnet insertion apertures 9, the rubbery elastic bodies 11 each recovered to their free-state thickness.
Function to hold the permanent magnets 10 elastically was reduced slightly after high-temperature testing in rubbery elastic bodies 11 that were installed in the magnet insertion apertures 9 at a compression ratio of 60 percent. When the rubbery elastic bodies 11 were removed from the

magnet insertion apertures 9, the rubbery elastic bodies 11 recovered to a thickness that was 80 percent of their free-state thickness.
[0028]
Function to hold the permanent magnets 10 elastically was reduced significantly after high-temperature testing in rubbery elastic bodies 11 that were installed in the magnet insertion apertures 9 at a compression ratio of 55 percent. When the rubbery elastic bodies 11 were removed from the magnet insertion apertures 9, the rubbery elastic bodies 11 only recovered to a thickness that was 60 percent of their free-state thickness.
Function to hold the permanent magnets 10 elastically after high-temperature testing was lost in rubbery elastic bodies 11 that were installed in the magnet insertion apertures 9 at compression ratios of 50 percent and 40 percent, respectively. When the rubbery elastic bodies 11 were removed from the magnet insertion apertures 9, the rubbery elastic bodies 11 had deformed plastically to 50 percent and 40 percent, respectively, of their free-state thickness. In other words, the extracted rubbery elastic bodies 11 did not recover at all.
[29]
It can thus be seen that if the thickness of the rubbery elastic bodies 11 is compressed to less than or equal to 60 percent of the free-state thickness, loss of resilience arises, and the permanent magnets 10 cannot be held elastically for a long time. Thus, from Figure 4, considering loss of resilience in the rubbery elastic bodies 11, it is preferable that the compression ratio of the rubbery elastic bodies 11 that are installed in the magnet insertion apertures 9 be made greater than 60 percent.

Next, the elastic holding of the permanent magnets 10 by the rubbery elastic bodies 11 will be explained based on Figure 5.
[31]

< ,
As shown in Figure 5, a normal component of reaction N acts on the permanent magnets 10 from the rubbery elastic bodies 11 that are installed in the magnet insertion apertures 9. If the embedded magnet electric motor 1 is used as an automotive electric motor, inertial force I acts on the permanent magnets 10 during rapid acceleration and during vibration. At the same time, static frictional force F acts on the permanent magnets 10 in a reverse direction to the inertial force I. Thus, a condition for the permanent magnets 10 to be held by the rotor core 6 during operation of the embedded magnet electric motor 1 is that the static frictional force F on the permanent magnets must be greater than the inertial force I on the permanent magnets during rapid acceleration and during vibration.
[32]
Thus, the compression ratio of the rubbery elastic bodies 11 must be set so as to satisfy the condition that the static frictional force F on the permanent magnets be greater than the inertial force I of the permanent magnets during rapid acceleration and during vibration based on the operating conditions of the automobile, the configuration of the rotor 5, and the materials of the respective members, as described below.
[33]
The inertial force I due to rapid acceleration can be found from maximum angular acceleration of the rotor 5 multiplied by the radius of the magnet position in the rotor 5 multiplied by the magnet weight. The inertial force I due to vibration can be found from vibration acceleration multiplied by the magnet weight. Here, if the maximum angular acceleration of the rotor 5 is 5770 rad/s2, the radius of the positions of installation of the permanent magnets 10 is 57 mm, the weight of the permanent magnets 10 is 16 g, and the vibration is 30 G, then the inertial force I due to rapid acceleration is 5.26 N, and the inertial force I due to vibration is 4.70 N.

Consequently, it is necessary to make the static frictional force F on the permanent magnets 10 greater than 9.96 N (= 5.26 N + 4.70 N).
[34]
The static frictional force F on the permanent magnets 10 can be found from the normal component of reaction N received from the rubbery elastic bodies 11 in the compressed state multiplied by a coefficient of static friction. When the compression ratios of rubbery elastic bodies 11 that were installed in magnet insertion apertures 9 were set to 80 percent, 70 percent, and 60 percent, measured normal components of reaction N were 13.3 N, 21.3 N, and 18.0 N, respectively. Because the coefficient of static friction between the rubbery elastic bodies 11 and the permanent magnets 10 is 0.7, and the coefficient of static friction between the rotor core 6 and the permanent magnets 10 is 0.1, the total coefficient of static friction is 0.8. Thus, the static frictional forces F on the permanent magnets 10 when the compression ratio of the rubbery elastic bodies 11 is 80 percent, 70 percent, and 60 percent, are 10.6 N, 17.0 N, and 14.4 N, respectively.
[35]
From the above, it is preferable to make the compression ratio of the rubbery elastic bodies 11 that are installed in the magnet insertion apertures 9 less than or equal to 80 percent in order to hold the permanent magnets 10 elastically in the rotor core 6.
Here, the normal component of reaction N when the compression ratio of the rubbery elastic bodies 11 that were installed in the magnet insertion apertures 9 was set to 60 percent was less than the normal component of reaction N when the compression ratio of the rubbery elastic bodies 11 that were installed in the magnet insertion apertures 9 was set to 70 percent. From this it can be inferred that the rubbery elastic bodies 11 that were set to a compression ratio of 60 percent reached a plastically deforming region.

Moreover, in Embodiment 1 above, the cross-sectional shape of the rubbery elastic bodies 11 is circular, and the groove cross-sectional shape of the rubbery elastic body housing grooves 12 is semi-elliptical, but the cross-sectional shape of the rubbery elastic bodies and the groove cross-sectional shape of the rubbery elastic body housing grooves are not limited to these shapes. As shown in Figure 6, for example, the cross-sectional shape of the rubbery elastic bodies 11 may also be made circular, and a groove cross-sectional shape of rubbery elastic body housing grooves 12A made rectangular. As shown in Figure 7, a cross-sectional shape of rubbery elastic bodies 11A may also be made rectangular, and the groove cross-sectional shape of the rubbery elastic body housing grooves 12A made rectangular. In addition, from the viewpoint of suppressing the occurrence of loss of resilience in the rubbery elastic bodies 11 or 11A, it is preferable that the rubbery elastic body housing grooves 12 or 12A have gaps at outer circumferential surfaces of portions of the rubbery elastic bodies 11 and 11A that expand outward in the groove width direction of the rubbery elastic body housing grooves 12 when interposed between the permanent magnets 10 and the rubbery elastic body housing grooves 12 or 12A. Moreover, in Figures 6 and 7, the rubbery elastic bodies 11 and 11A in a free state are indicated by broken lines.
[37] Embodiment 2
Figure 8 is a longitudinal cross section that shows part of an embedded magnet rotary electric machine according to Embodiment 2 of the present invention.
[38]
In Figure 8, end plates 13 are prepared into ring-shaped flat plates using a nonmagnetic metal such as aluminum, and recess portions 14 that

' I I
house end portions of the rubbery elastic bodies 11 are formed on first surfaces of the end plates 13 at a uniform angular pitch so as to face respective magnet insertion apertures 9. End plates 13 that are prepared in this manner are fixed to two axial ends of a rotor core 6 by screws, etc., (not shown) so as to house end portions of the rubbery elastic bodies 11 inside the recess portions 14.
Moreover, the rest of the configuration is configured in a similar manner to Embodiment 1 above.
[39]
. According to Embodiment 2, because end portions of the rubbery elastic bodies 11 that protrude from end surfaces of the rotor core 6 are covered by the end plates 13, the end portions of the rubbery elastic bodies 11 can be preemptively prevented from stretching due to centrifugal forces and interfering with other members during rotation of the rotor 5A.
It is also not necessary to cut the end portions of the rubbery elastic bodies 11 that protrude from the end surfaces of the rotor core 6, suppressing decreases in mass producibility of the rotor 5A.
[40] Embodiment 3
Figure 9 is a lateral cross section that shows part of an embedded magnet rotary electric machine according to Embodiment 3 of the present invention.

In Figure 9, rubbery elastic body housing grooves 12 are respectively formed so as to form two rows circumferentially on positions that are symmetrical about a circumferential center of a bottom surface of a magnet insertion aperture 9 so as to extend from a first end to a second end in an axial direction of a shaft 8, and so as to have" groove directions oriented in the axial direction of the shaft 8. Two rubbery elastic bodies

11 are respectively interposed between a permanent magnet 10 and each of the rubbery elastic body housing grooves 12 so as to be housed inside the rubbery elastic body housing grooves 12 in longitudinally stretched states.
Moreover, the rest of the configuration is configured in a similar manner to Embodiment 1 above.
[42]
According to Embodiment 3, because the two rubbery elastic bodies 11 are interposed between the permanent magnets 10 and the rubbery elastic body housing grooves 12 in longitudinally stretched states so as to form two rows circumferentially, elastic holding of the permanent magnets 10 is stabilized.
[43]
Moreover, in Embodiment 3 above, the rubbery elastic body housing grooves 12 are formed at positions that are symmetrical about the circumferential centers of the bottom surfaces of the magnet insertion apertures 9, but it is not absolutely necessary for the two rubbery elastic body housing grooves 12 to be formed at positions that are symmetrical about the circumferential centers of the bottom surfaces of the magnet insertion apertures 9, provided that they are formed so as to be positioned on two circumferential sides of the bottom surfaces of the magnet insertion apertures 9.
In Embodiment 3 above, two rubbery elastic body housing grooves are formed on the bottom surfaces of the magnet insertion apertures 9, but the number of rubbery elastic body housing grooves may also be three or more.
[44] Embodiment 4

Figure 10 is a lateral cross section that shows part of an embedded magnet rotary electric machine according to Embodiment 4 of the present invention.
[45]
In Figure 10, lower portion corner portions at two width direction ends of a permanent magnet 10A are eased over an entire longitudinal region. Rubbery elastic bodies 11 are respectively interposed between the eased portions 15 and lower portion corner portions at two circumferential ends of a magnet insertion aperture 9 in longitudinally stretched states.
Moreover, the rest of the configuration is configured in a similar manner to Embodiment 1 above.
[46]
In Embodiment 4, because the rubbery elastic bodies 11 are respectively interposed between the eased portions 15 and the lower portion corner portions at the two circumferential ends of the magnet insertion apertures 9 in longitudinally stretched states, the forces of recovery of the rubbery elastic bodies 11 that try to contract act on the eased portions 15. Thus, pinching forces act on the permanent magnets 10A from two circumferential sides in addition to the forces that press radially outward on the permanent magnets 10A.
[47]
Consequently, according to Embodiment 4, radial and circumferential movements of the permanent magnets 10A can be restricted.
Because rubbery elastic body housing grooves can be omitted, preparation of the rotor core 6 is facilitated.
[48] Embodiment 5

Figure 11 is a cross section that shows part of an embedded magnet rotary electric machine according to Embodiment 5 of the present invention. Moreover, Figure 11 is a figure in which a cross section in which a permanent magnet that is inserted into a magnet insertion aperture is sectioned in a plane that is parallel to a bottom surface of the magnet insertion aperture is viewed from radially outside.
[49]
In Figure 11, a single rubbery elastic body 11 is interposed between a permanent magnet 10 and rubbery elastic body housing grooves 12 in a longitudinally stretched state so as to be housed inside a first rubbery elastic body housing groove 12, be returned at an axially outer end of the rotor core 6, and be housed inside a remaining rubbery elastic body housing groove 12.
Moreover, the rest of the configuration is configured in a similar manner to Embodiment 3 above.
[50]
In Embodiment 5, because single rubbery elastic bodies 11 are also interposed between the permanent magnets 10 and the rubbery elastic body housing grooves 12 in a longitudinally stretched state so as to be returned at an axially outer end of the rotor core 6 to form two rows circumferentially, similar effects to those in Embodiment 3 above are exhibited.
According to Embodiment 5, because single rubbery elastic bodies 11 are returned axially outside the rotor core 6 and are arranged in two rows in a circumferential direction, the number of parts can be reduced.
Embodiment 6

Figure 12 is a side elevation that shows a rubbery elastic body that is used in an embedded magnet rotary electric machine according to Embodiment 6 of the present invention.
[52]
In Figure 12, a rubbery elastic body 11B is formed so as to have a circular cross-sectional shape, and such that its diameter (thickness) becomes gradually smaller (thinner) from a longitudinally central portion toward end portions. A longitudinal end portion thickness h2 of the rubbery elastic body 11B is thinner than a longitudinally central thickness hi, and is thicker than a thickness of the rubbery elastic body 11B when interposed between a permanent magnet 10 and a rubbery elastic body housing groove 12.
Moreover, the rest of the configuration is configured in a similar manner to Embodiment 1 above.
[53]
In Embodiment 6, the rubbery elastic bodies 11B are formed such that their thicknesses become gradually thinner from a longitudinally central portion toward end portions. Thus, when rubbery elastic bodies 11B that are disposed inside rubbery elastic body housing grooves 12 in a stretched state are allowed to contract, the rubbery elastic bodies 11B recover, and contact the permanent magnets 10 at central portions in the groove directions of the rubbery elastic body housing grooves 12. The positions of the rubbery elastic bodies 11B that contact the permanent magnets 10 then proceed from the central portions toward the end portions in the groove directions of the rubbery elastic body housing grooves 12.
[54]
Consequently, because the rubbery elastic bodies 11B contact the permanent magnets 10 over an entire longitudinal region without leaving gaps, elastic holding of the permanent magnets 10 is stabilized.

m
[55] Embodiment 7
Figure 13 is a longitudinal cross section that shows part of a rotor core that is used in an embedded magnet rotary electric machine according to Embodiment 7 of the present invention.
[56]
In Figure 13, a rubbery elastic body housing groove 12B is formed so as to have a semi-elliptical groove cross-sectional shape, and such that its groove depth becomes gradually deeper from a central portion in a groove direction toward end portions.
Moreover, the rest of the configuration is configured in a similar manner to Embodiment 1 above.
[57]
In Embodiment 7, because the rubbery elastic bodies 11 are formed so as to have longitudinally uniform cross-sectional shapes, when the rubbery elastic bodies 11 that are disposed inside rubbery elastic body housing grooves 12B in a stretched state are allowed to contract, the rubbery elastic bodies 11 recover, and contact the permanent magnets 10 at central portions in the groove directions of the rubbery elastic body housing grooves 12B. The positions of the rubbery elastic bodies 11 that contact the permanent magnets 10 then proceed from the central portions toward the end portions in the groove directions of the rubbery elastic body housing grooves 12B.
[58]
Consequently, the rubbery elastic bodies 11 contact the permanent magnets 10 over an entire longitudinal region without leaving gaps, stabilizing elastic holding of the permanent magnets 10.
[59]

<
Moreover, in each of the above embodiments, explanations are given for embedded magnet electric motors, but the present invention is not limited to embedded magnet electric motors, and similar effects are also exhibited if the present invention is applied to embedded magnet rotary electric machines such as embedded magnet alternators, or embedded magnet generator-motors.
In each of the above embodiments, the end portions of the rubbery elastic bodies protrude from the end surfaces of the rotor core, but end portions of rubbery elastic bodies may also be flush with the end surfaces of the rotor core or positioned inside the magnet insertion apertures.
[0060]
In each of the above embodiments, the permanent magnets are prepared into strip shapes that have rectangular cross sections, but the cross-sectional shapes of the permanent magnets are not limited to rectangular shapes. For example, the permanent magnets may also be prepared into strip shapes that have circular arc-shaped cross sections that have circular arcs as inner circumferences and outer circumferences. In that case, the magnet insertion apertures should be made to have circular arc-shaped aperture shapes that are slightly larger than the cross-sectional shapes of the permanent magnets.
[0061]
In each of the above embodiments, single permanent magnets are inserted into the magnet insertion apertures, but the number of permanent magnets that are inserted into the magnet insertion apertures is not limited to one. For example, a plurality of permanent magnets may also be inserted into the magnet insertion apertures so as to line up in a single row in an aperture direction, or a plurality of permanent magnets may also be inserted into the magnet insertion apertures so as to line up in a single row in a width direction.

WE CLAIM:
1. An embedded magnet rotary electric machine comprising: a stator (2); and
a rotor (5, 5A) comprising:
a rotor core (6) that is rotatably disposed inside said stator (2); and
a permanent magnet (10, 10A) that is inserted into and fixed inside a magnet insertion aperture (9) that is formed so as to pass axially through said rotor core (6), characterized in that:
a cord-shaped rubbery elastic body (11, 11A, 11B) is interposed between said permanent magnet (10, 10A) and said magnet insertion aperture (9) in a longitudinally stretched state so as to extend in an aperture direction of said magnet insertion aperture (9); and
said permanent magnet (10, 10A) is held elastically in said rotor core (6) by being pressed against an outer circumferential wall surface of said magnet insertion aperture (9) by a force of recovery that accompanies contraction of said rubbery elastic body (11, 11 A, 11B).
2. An embedded magnet rotary electric machine according to Claim 1, wherein two end portions of said rubbery elastic body protrude (11, 11 A, 11B) from said rotor core (6) at two axial ends.
3. An embedded magnet rotary electric machine according to Claim 2, further comprising end plates (13) that are mounted to said two axial ends of said rotor core (6), said two end portions of said rubbery elastic body (11, 11A, 11B) being housed inside recess portions (14) that are formed on surfaces of said end plates (13) that face said rotor core (6).

4. An embedded magnet rotary electric machine according to any one of Claims 1 through 3, wherein:
a rubbery elastic body housing groove (12, 12A, 12B) is formed on a bottom surface of said magnet insertion aperture (9) so as to have a groove direction oriented in an axial direction and so as to extend from a first axial end to a second axial end; and
said rubbery elastic body (11, 11A, 11B) is housed inside said rubbery elastic body housing groove (12, 12A,12B).
5. An embedded magnet rotary electric machine according to Claim 4, wherein:
two of said rubbery elastic body housing grooves (12, 12A, 12B) are formed on said bottom surface of said magnet insertion aperture (9) so as to line up in two rows in a circumferential direction; and
said rubbery elastic body (11, 11 A, 11B) is housed in each of said rubbery elastic body housing grooves (12, 12A, 12B) so as to be arranged in two rows in said circumferential direction.
6. An embedded magnet rotary electric machine according to either of Claims 4 or 5, wherein said rubbery elastic body housing groove (12, 12A, 12B) is formed so as to have a groove shape that has a gap at an outer circumferential surface of a portion of said rubbery elastic body (11, 11A, 11B) that expands outward in a groove width direction of said rubbery elastic body housing groove.
7. An embedded magnet rotary electric machine according to any one of Claims 1 through 3, wherein:

said permanent magnet (10A) has eased portions (15) that are formed over an entire longitudinal region on lower portion corner portions on two width direction sides; and
said rubbery elastic body (11, 11A, 11B) is interposed between each of said eased portions (15) of said permanent magnet (10a) and lower portion corner portions on two circumferential sides of said magnet insertion aperture (9) so as to be arranged in two rows in said circumferential direction.
8. An embedded magnet rotary electric machine according to any one of Claims 5 through 7, wherein:
said rubbery elastic body (11, 11A, 11B) that is arranged in two rows in said circumferential direction is constituted by a single rubbery elastic body that is returned axially outside said rotor core (6).
9. An embedded magnet rotary electric machine according to any one of Claims 1 through 8, wherein said rubbery elastic body (11, 11A, 11B) is interposed between said permanent magnet (10, 10A) and said magnet insertion aperture (9) so as to have a thickness that is greater than 60 percent of a thickness of said rubbery elastic body in a free state.
10. An embedded magnet rotary electric machine according to any one of Claims 1 through 9, wherein said rubbery elastic body (11B) is configured such that a free-state thickness becomes gradually thinner from a longitudinally central portion toward an end portion.
11. An embedded magnet rotary electric machine according to any one of Claims 4 through 6, wherein said rubbery elastic body housing groove

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(12B) is configured such that a groove depth becomes gradually deeper from a central portion in said groove direction toward an end portion.
12. A method for manufacturing an embedded magnet rotor (5, 5A) that has a permanent magnet (10, 10A) that is inserted into and fixed inside a magnet insertion aperture (9) that is formed so as to pass astially through a rotor core (6),
said method for manufacturing said embedded magnet rotor (5, 5A) being characterized in comprising steps of
passing a cord-shaped rubbery elastic body (11, 11A, 11B) through said magnet insertion aperture (9) and stretching said rubbery elastic body longitudinally;
inserting said permanent magnet (10, 10A) into said magnet insertion aperture (9) through which said longitudinally stretched rubbery elastic body (11, 11A, 11B) is inserted; and
allowing said longitudinally stretched rubbery elastic body (11, 11A, 11B) to contract longitudinally to generate a force of recovery in said rubbery elastic body that presses said permanent magnet (10, 10A) against a wall surface of said magnet insertion aperture (9) to hold said permanent magnet elastically.