FORM 2
THE PATENTS ACT, 1970 (39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
PERMANENT MAGNET ROTATING ELECTRIC MACHINE;
MITSUBISHI ELECTRIC CORPORATION, A CORPORATION ORGANISED AND EXISTING UNDER THE LAWS OF JAPAN, WHOSE ADDRESS IS 7-3, MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 1008310, JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

DESCRIPTION
Field
[0001] The present invention relates to a permanent magnet type rotary electric machine that includes a rotor equipped with permanent magnets arranged on its outer circumferential surface.
Background
[0002] A rotary electric machine (for example, see Patent Literature 1) has been previously disclosed. This rotary electric machine includes a rotor that is formed in a cylindrical shape including an outer circumferential surface and an inner circumferential surface and includes field magnets for supplying a field magnetic flux; an inner circumferential side stator that faces the rotor from the inner circumferential surface side and has an armature winding theraaround; and an outer circumferential side stator that faces the rotor from the outer circumferential surface side and has an armature winding therearound. The ratio between the number of pole pairs of the inner circumferential side stator and the number of pole pairs of the outer circumferential side stator and the ratio between the magnitude of the field magnetic flux interlinked with the armature winding of the outer circumferential side stator and the magnitude of the field magnetic flux interlinked with the armature winding of the inner circumferential side stator are selected to be equal to each other.
[0003] Further, there is disclosed (for example, see Patent Literature 2) a hollow actuator that includes a

hollow shaft that includes a flange portion at the counter-load side end; a cylindrical frame that has a counter-load side end to which the flange portion is detachably fixed; a motor that includes a stator fixed to the frame and a cup-shaped rotor disposed inside the stator and formed with an opening on the load side; a reducer that includes a wave generator coupled to the rotor, a flexible spline, and a circular spline; a position detector for angle detection that includes a magnetic sensor disposed on a side closer to the hollow shaft and a magnet disposed on a side closer to the opening of the rotor and facing the magnetic sensor; a low speed bearing that is disposed between the frame and the output side of the reducer; and an output flange that is disposed on the output side of the reducer and is configured to operate at a low speed. The rotor is cantilevered only by the high speed bearing on the load side of the motor, the wave generator coupled to the rotor is bearing-mounted on the rotational support of the outer ring of the high speed bearing disposed on the output flange, the inner ring of the low speed bearing is attached using the output flange as a housing, a hollow portion penetrating the actuator through its center is constituted by the hollow shaft and the output flange, and the position detector is disposed on the counter-load side of the motor.
Citation List Patent Literature [0004]
Patent Literature 1: Japanese Patent Application Laid-open No. 2007-166798
Patent Literature 2: Japanese Patent No. 4650719
Summary

Technical Problem
[0005] According to the conventional technology described in the above-mentioned Patent Literature 1, in order to maintain a magnetic path and thereby improve the torque output, a structure is provided such that it includes a magnetic body having a considerable thickness on the inner circumferential side of the rotor. Consequently, there is a problem in that the weight (inertia) of the rotor increases and this requires the output torque to be partly used for acceleration of this inertia, which reduces the acceleration and deceleration performance and its efficiency.
[0006] Further, according to the conventional technology described in the above-mentioned Patent Literature 2, there is a problem in that the brake portion and the motor portion are arranged side by side in the axial direction and thereby the total length of the motor becomes larger. [0007] The present invention has been made in view of the above, and an object of the present invention is to provide a permanent magnet type rotary electric machine that achieves both a reduction in inertia and an improvement in torque in order to improve the acceleration performance and that has a compact structure equipped with a brake that does not increase the total length.
Solution to Problem
[0008] In order to solve the above problems and achieve the object, an aspect of the present invention is a permanent magnet type rotary electric machine including: a housing that includes a cylindrical frame, a load-side bracket fixed to one end of the frame, and a counter-load-side bracket fixed to another end of the frame, an outer ring of a bearing being fitted in a circular recess formed

in the load-side bracket; a stator that is formed in a cylindrical shape by stacking silicon steel plates, that includes a plurality of teeth on an inner circumferential portion, and that is fitted in the frame of the housing, the teeth having windings wound therearound; a rotor that includes a thin-walled cylindrical portion made of a structural steel and having an outer circumferential portion with a plurality of permanent magnets fixed thereon at regular intervals, a stepped circular disk portion connected to one end of the thin-walled cylindrical portion, and a shaft fixed to a center of the stepped circular disk portion, a stepped portion of the stepped circular disk portion being fitted in an inner ring of the bearing, the rotor being rotatably cantilevered by the load-side bracket of the housing; and a back yoke that is formed in a circular columnar shape by stacking silicon steel plates and is inserted inside the thin-walled cylindrical portion of the rotor with a minute air gap interposed therebetween, the back yoke being cantilevered by the counter-lcad-side bracket of the housing.
Advantageous Effects of Invention
[0009] A permanent magnet type rotary electric machine according to the present invention provides an effect capable of achieving both a reduction in inertia and an improvement in torque in order to improve the acceleration performance and of being equipped with a brake that does not increase the total length.
Brief Description of Drawings
[0010] FIG. 1 is a transverse sectional view illustrating a first embodiment of a permanent magnet type rotary electric machine according to the present invention.

FIG. 2 is a longitudinal sectional view illustrating the permanent magnet type rotary electric machine according to the first embodiment.
FIG. 3 is a longitudinal sectional view illustrating a second embodiment of a permanent magnet type rotary electric machine according to the present invention.
FIG. 4 is a longitudinal sectional view illustrating the permanent magnet type rotary electric machine according to the second embodiment at a phase different from that of FIG. 3.
Description of Embodiments
[0011] Exemplary embodiments of a permanent magnet type
rotary electric machine according to the present invention
will be explained below in detail with reference to the
accompanying drawings. The present invention is not
limited to the following embodiments.
[0012] First embodiment.
FIG. 1 is a transverse sectional view illustrating a first embodiment of a permanent magnet type rotary electric machine according to the present invention. FIG. 2 is a longitudinal sectional view illustrating the permanent magnet type rotary electric machine according to the first embodiment. As illustrated in FIGS. 1 and 2, a permanent magnet type rotary electric machine 91 according to the first embodiment includes a housing 40, which includes a cylindrical frame 41; a load-side bracket 42 fixed to one end of the frame 41; and a counter-load-side bracket 43 fixed to the other end of the frame 41. The outer ring of a bearing 44 is fitted in the circular recess formed at the center of the load-side bracket 42. The bearing 44 is a cross-roller bearing. [0013] Further, the permanent magnet type rotary

electric machine 91 includes a stator 20 that is formed in a cylindrical shape and is fitted in the frame 41 of the housing 40. The stator 20 is provided with a plurality of teeth 22 and a plurality of slots 23 (the number of each of which is twelve in the case of the permanent magnet type rotary electric machine 91 according to the first embodiment) on the inner circumferential portion, and the teeth 22 have windings 24 wound therearound. [0014] Further, the permanent magnet type rotary electric machine 91 includes a rotor 30, which includes a thin-walled cylindrical portion 31 having an outer circumferential portion with a plurality of (eight in the case of the permanent magnet type rotary electric machine 91 according to the first embodiment) permanent magnets 34 fixed thereon at regular intervals; a stepped circular disk portion 32 connected to one end of the thin-walled cylindrical portion 31; and a shaft 33 fixed to the center of the stepped circular disk portion 32. The stepped portion of the stepped circular disk portion 32 is fitted in the inner ring of the bearing 44, so that the rotor 30 is rotatably cantilevered by the load-side bracket 42 of the housing 40. The distal ends of the teeth 22 of the stator 20 face the magnetic pole ends of the permanent magnets 34 of the rotor 30 with an air gap interposed therebetween.
[0015] Further, the permanent magnet type rotary electric machine -91 includes a back yoke 50, which is formed in a circular columnar shape and is inserted inside the thin-walled cylindrical portion 31 of the rotor 30 with a minute air gap interposed therebetween. The back yoke 50 is fixed to a support pedestal 43a of the counter-load-side bracket 43 of the housing 40 by a plurality of bolts 43b such that it is cantilevered by the support pedestal 43a.

Inside the back yoke 50, a hall sensor 52 for detecting the rotational position of the rotor 30 is embedded. [0016] Each of the iron core of the stator 20 and the back yoke 50 is prepared by stacking a number of silicon steel plates to reduce the iron loss. In the rotor 30, the thin-walled cylindrical portion 31, the stepped circular disk portion 32, and the shaft 33 are made of a structural steel to ensure the strength. The radial direction thickness of the thin-walled cylindrical portion 32 is set to be not more than 1/4 of the circumferential direction width of each of the permanent magnets 34, thereby providing a structure such that the magnetic fluxes generated from the permanent magnets 34 and the windings 24 pass into the back yoke 50.
[0017] As described above, in the permanent magnet type rotary electric machine 91 according to the first embodiment, the iron core.of the rotor 30 (i.e., the thin-walled cylindrical portion 31) is made thin, thereby improving the acceleration and deceleration performance of the rotor 30; and a magnetic path for allowing the magnetic fluxes to flow in the back yoke 50 is formed, thereby improving the torque output. Further, the back yoke 50 is formed from, a stack of silicon steel plates, thereby reducing the iron loss and thus improving the efficiency. [0018] Second embodiment.
FIG. 3 is a longitudinal sectional view illustrating a second embodiment of a permanent magnet type rotary electric machine according to the present invention. FIG. 4 is a longitudinal sectional view illustrating the permanent magnet type rotary electric machine according to the second embodiment at a phase different from that of FIG. 3. As illustrated in FIGS. 3 and 4, a permanent magnet type rotary electric machine 92 according to the second

embodiment is similar to the permanent magnet type rotary electric machine 91 of the first embodiment, in terms of the housing 40, the stator 20, and the rotor 30; therefore, detail description thereof will be omitted, and a back yoke 60 having a characteristic configuration will be described. [0019] The back yoke 60 according to the second embodiment is formed in a circular columnar shape by stacking a number of silicon steel plates, and is inserted inside the thin-walled cylindrical portion 31 of the rotor 30 with a minute air gap interposed therebetween. The back yoke 60 is connected to the counter-load-side bracket 43 of the housing 40 by a plurality of coil springs 61. As illustrated in FIG. 4, a plurality of axial direction holes 67 are formed in the counter-load side of the back yoke 60, and a plurality of support rods 66 are fixed to the counter-load-side bracket 43 and are slidably fitted in the axial direction holes 67. The support rods 66 constitute a linear slide mechanism for the back yoke 60. The back yoke 60 is cantilevered by the linear slide mechanism (i.e., the support rods 66) such that the back yoke 60 can be displaced in the axial direction but cannot be rotated about the axis.
[0020] The back yoke 60 can be displaced in the axial direction inside the thin-walled cylindrical portion 31 by expansion and contraction of the coil springs 61, but, in the usual state, it is pressed against the load-side end surface of the rotor 30 by the expansion force of the compressed coil springs 61. Inside the back yoke 60, the hall sensor 52 for detecting the rotational position of the rotor 30 is embedded.
[0021] A circular recess is formed in the counter-load side of the back yoke 60, and a brake coil 63 is embedded in the recess in a state where it is wound inside a field

62. An armature 64 facing the brake coil 63 is attached to the center of the counter-load-side bracket 43.
[0022] When the brake is not released (i.e., when the brake coil 63 is not excited), the load-side end surface of the back yoke 60 is pressed against the load-side end surface of the rotor 30 by the expansion force of the coil springs 61; therefore, the rotor 30 cannot rotate by a frictional force. When the brake is released (i.e., when the brake coil 63 is excited), the field 62 is attracted to the armature 64 by the magnetic attraction force of the brake coil 63, thereby displacing the back yoke 60 toward the counter-load side and allowing the rotor 30 to freely rotate. If the field 62 is made of a pressed powder magnetic core or the like, it becomes possible to reduce the leakage flux that deteriorates the motor characteristics, without being affected by the magnetic fluxes generated from the permanent magnets 34 and the windings 24.
[0023] As described above, in the permanent magnet type rotary electric machine 92 according to the second embodiment, the field 62 and the brake coil 63 that constitute an electromagnetic brake are embedded inside the back yoke 60, thereby enabling a reduction in the total length of the permanent magnet type rotary electric machine 92.
[0024] It should be noted that, if the shaft 33 is rotated by an externally applied force, each of the permanent magnet type rotary electric machine 91 according to the first embodiment and the permanent magnet type rotary electric machine 92 according to the second embodiment can obtain electric power from the windings 24 and thus can be used as a generator.

Reference Signs List
[0025] 20 stator, 22 teeth, 23 slot, 24 winding, 30 rotor, 31 thin-walled cylindrical portion, 32 stepped circular disk portion, 33 shaft, 34 permanent magnet, 40 housing, 41 frame, 42 load-side bracket, 43 anti-load-side bracket, 43a support pedestal, 43b bolt, 44 bearing, 50 back yoke, 52 hall sensor, 60 back yoke, 61 coil spring, 62 field, 63 brake coil, 64 armature, 66 support rod (linear slide mechanism), 67 axial direction hole, 91, 92 permanent magnet type rotary electric machine.

We Claim :
1. A permanent magnet type rotary electric machine comprising:
a housing that includes a cylindrical frame, a load-side bracket fixed to one end of the frame, and a counter-load-side bracket fixed to another end of the frame, an outer ring of a bearing being fitted in a circular recess formed in the load-side bracket;
a stator that is formed in a cylindrical shape by stacking silicon steel plates, that includes a plurality of teeth on an inner circumferential portion, and that is fitted in the frame of the housing, the teeth having windings wound therearound;
a rotor that includes a thin-walled cylindrical portion made of a structural steel and having an outer circumferential portion with a plurality of permanent magnets fixed thereon at regular intervals, a stepped circular disk portion connected to one end of the thin-walled cylindrical portion, and a shaft fixed to a center of the stepped circular disk portion, a stepped portion of the stepped circular disk portion being fitted in an inner ring of the bearing, the rotor being rotatably cantilevered by the load-side bracket of the housing; and
a back yoke that is formed in a circular columnar shape by stacking silicon steel plates and is inserted inside the thin-walled cylindrical portion of the rotor with a minute air gap interposed therebetween, the back yoke being cantilevered by the counter-load-side bracket of the housing.
2. The permanent magnet type rotary electric machine according to claim 1, further comprising:
a linear slide mechanism that is disposed on the

counter-load-side bracket of the housing and cantilevers the back yoke such that the back yoke is displaceable in an axial direction and is not rotatable about an axis;
a spring that is disposed on the counter-load-side bracket of the housing and that presses the back yoke against the load-side bracket;
a field and a brake coil embedded in a counter-load side of the back yoke; and
an armature fixed to the counter-load-side bracket of the housing.
3. The permanent magnet type rotary electric machine according to claim 2, wherein the field is made of a pressed powder magnetic core.
4. The permanent magnet type rotary electric machine according to claim 1, wherein the permanent magnet type rotary electric machine is used as a generator.