JP2005287191A - Permanent magnet motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct a deformation of an inside diameter of a stator eccentrically shifted in the axial direction so as to approximate it to a perfect circle, circumferentially uniformize an air gap length between the stator and a rotor in any positions in the axial direction, and reduce a cogging torque. <P>SOLUTION: The permanent magnet motor is provided with a cylindrical frame 1, a stator core 2 fixed to an inner circumference of the frame 1 and having a plurality of teeth radially protruding, and the rotor 4 coaxially disposed within the stator core 2. The frame 1 comprises a structure having a protrusion 3 disposed on its inner circumferential face and approximating the deformation of the inside diameter of the stator core 2 to the perfect circle in any positions in the axial direction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a permanent magnet motor, and more particularly to a permanent magnet motor with reduced cogging torque.

  Currently, servo motors and the like that require high controllability have a problem of torque unevenness called cogging torque. The cogging torque corresponds to a torque fluctuation generated when the rotor coil is rotated by an external force with the stator coil current set to zero. As described above, the cogging torque is a main cause of a decrease in positioning accuracy of the servo motor. Therefore, reducing the cogging torque is an important issue when manufacturing a high-precision motor.

  The stator is fixed in the frame by shrink fitting or the like. However, the stator core may be deformed by the stress of the frame, and the inner diameter shape may be deformed. Due to this deformation, a cogging torque is generated. Therefore, in the smooth armature winding type motor described in Patent Document 1, a groove is provided on the inner peripheral surface of the frame, a protrusion is provided on the outer peripheral surface of the stator, the groove and the protrusion are fitted, and shrink fitting is performed. The groove and the protrusion are coupled to reduce the cogging torque caused by the deformation of the stator core.

JP 2000-245124 A (page 2-3, FIG. 1)

  During the manufacturing process of the motor, the inner diameter of the stator is deformed to a state deviating from a perfect circle. Since the deformation deviated from the perfect circle changes into various shapes in the axial direction, there is a non-uniform state of the gap length between the stator and the rotor at various circumferential positions in the axial direction.

  Conventionally, the deformation of the stator inner diameter deviated from the perfect circle is uniform in the axial direction as in Patent Document 1 above, so even if a measure for preventing the deformation is taken, the effect of reducing the cogging torque is reduced. Is not enough.

  The present invention corrects the deformation of the inner diameter of the stator that deviates from the perfect circle in the axial direction so as to approach the perfect circle, and the gap length between the stator and the rotor is circumferential at any position in the axial direction. The purpose is to reduce the cogging torque so as to be uniform.

A permanent magnet motor according to the present invention includes a cylindrical frame, a stator having a plurality of teeth that are fixed to the inner periphery of the frame and projecting in a radial direction, and the stator is coaxial with the stator. An arranged rotor,
The frame has a protrusion for bringing the deformation of the inner diameter of the stator close to a perfect circle at any position in the axial direction of the inner peripheral surface thereof.

A cylindrical frame; a stator having a plurality of teeth fixed to the inner periphery of the frame and projecting in a radial direction; and a rotor disposed coaxially with the stator inside the stator; With
The frame has a plurality of protrusions on its inner peripheral surface, and the protrusions are arranged with a predetermined pitch shifted in the circumferential direction and the axial direction.

A cylindrical frame; a stator having a plurality of teeth fixed to the inner periphery of the frame and projecting in a radial direction; and a rotor disposed coaxially with the stator inside the stator; With
The frame has a plurality of recesses in the axial direction of the inner peripheral surface thereof, and the recesses are connected to each other and are shifted at a predetermined pitch in the circumferential direction and the axial direction.

  According to the permanent magnet motor according to the present invention, the frame has the protrusions for bringing the deformation of the inner diameter of the stator closer to a perfect circle in the axial direction of the inner peripheral surface thereof, so that the cogging torque can be reduced.

  Further, the frame has a plurality of protrusions on the inner peripheral surface thereof, and the protrusions are arranged at a predetermined pitch in the circumferential direction and the axial direction, so that the cogging torque can be reduced and received from the frame. Since the pressure is reduced only to the protrusions from the entire frame circumferential direction, loss torque (DC component of torque pulsation) can be reduced.

  In addition, the frame has a plurality of holes in the axial direction of the inner peripheral surface thereof, and the holes are connected to each other and are arranged at a predetermined pitch in the circumferential direction and the axial direction. While being able to reduce, loss torque can be reduced.

Embodiment 1 FIG.
FIG. 1 is a front view (a) and a side view (b) showing a first embodiment of a permanent magnet motor according to the present invention. FIG. 2 shows the inner diameter of the stator at three points in the axial direction of the permanent magnet motor. 2A is a position in the vicinity of one axial end face, FIG. 2B is a position in the approximate center in the axial direction, and FIG. 2C is a position in the vicinity of the other axial end face. It is the result measured at the position.

  As shown in FIG. 1, the permanent magnet motor according to the first embodiment includes a cylindrical frame 1, a stator core 2 fixed inside the frame 1, and a stator core inside the stator core 2. 2 and a rotor 4 arranged coaxially.

  The rotor 4 has a ring magnet magnetized to 8 poles (4 pole pairs). The stator core 2 is formed by connecting 12 divided cores 2a having teeth protruding in the inner diameter direction. The split core 2a is formed by stacking core pieces formed by punching thin steel plates with a press or the like. The split cores 2a formed by laminating the core pieces are connected in a straight line to form a linear stator core 2, and a coil is mounted between the slots formed between the teeth of the split core 2a. As shown in the drawing, the stator core 2 is formed into an annular shape by bending at the connecting portion of the split core 2a, and both ends are fixed by welding.

  In this way, the stator core 2 is formed into an annular shape by bending the linear stator core 2 at the connecting portion of the split core 2a, and both ends are fixed by welding, so as shown in FIG. In addition, the inner diameter is not a perfect circle, the split core 2a is inclined, or a portion having a larger inner diameter is formed, and the deformed shape has various shapes in the axial direction. Further, the deformed shape in the axial direction is substantially similar depending on the product row.

  The frame 1 is made of aluminum or iron, and a projection 3 is provided on the inner peripheral surface of the frame 1. The protrusion 3 is provided at a position where the deformation is corrected in the axial direction in accordance with the deformation of the inner diameter of the stator core 2 and the deformation of the stator core 2 by the frame 1 during shrink fitting. For example, in order to correct the deformation of the stator core 2 due to the frame 1 at the time of shrink fitting by pressing down the protrusion 3a for correcting the inclination of the split core 2a or the portion where the inner diameter is increased to bring it closer to a perfect circle. The protrusion 3b is provided at a correction location in the axial direction.

  The stator core 2 is inserted into the frame 1 and fixed by shrink fitting. At this time, in the axial direction, the protrusion 3 presses the divided core 2a in which the protruding portion 3a and the protruding portion 3b are inclined and the divided core 2a in which the inner diameter is increased. By correcting the deformation, the inner diameter shape of the stator core 2 approaches a perfect circle at any axial position.

  In FIG. 1, the protrusion 3 is exaggerated, but its radial thickness is several μm to several tens μm, and the gap between the inner peripheral surface of the frame 1 and the outer peripheral surface of the stator core 2 is There will be almost nothing.

  According to the first embodiment, the gap between the rotor 4 and the stator core 2 is uniform in the circumferential direction at any position in the axial direction, and the cogging torque is reduced.

  Further, this effect can be obtained not only by shrink fitting, but also in the case of press fitting and molding with a resin such as a mold. The protrusion 3 of the frame 1 is preferably formed by welding from the viewpoint of freedom of positioning.

Embodiment 2. FIG.
3 and 4 are a front view (a) and a plan view (b) showing a second embodiment of the permanent magnet motor according to the present invention.

  The thin steel plate used for the split core 2a has magnetic anisotropy. When thin steel plates are laminated, the magnetic characteristics differ depending on the circumferential position of the stator core 2, and this causes cogging torque.

  Usually, in order to reduce the cogging torque resulting from this magnetic anisotropy and to reduce the loss torque, so-called rolling is performed in which core pieces made of thin steel plates are rotated around the axis and stacked.

  In the second embodiment, as shown in FIGS. 3 and 4, a plurality of protrusions 3 are provided on the inner periphery of the frame 1, and the protrusions 3 are arranged at a predetermined pitch in the circumferential direction and the axial direction. In this configuration, stress is applied to the stator core 2 by the projections 3 and remains as residual stress in a portion that cannot be released due to strain, and the magnetic characteristics of this portion deteriorate. Degradation of magnetic properties due to stress is greater than the difference in magnetic properties due to magnetic anisotropy, and the degree of degradation of magnetic properties due to stress in areas where magnetic properties are good Since it becomes larger than the degree of deterioration of the characteristic and becomes almost the same magnetic characteristic, according to this configuration, the magnetic characteristic as viewed in the divided core 2a unit of the stator core 2 can be made uniform. . That is, the same effect as that of turning and stacking can be obtained. In addition, as shown in the figure, the portion where the magnetic properties are deteriorated and the magnetic flux is difficult to pass is shifted by a predetermined pitch in the circumferential direction and the axial direction. Also, since the projections 3 are arranged in a distributed manner, the stator core 2 in the frame 1 can be fixed stably.

  In addition, since no stress is applied to the recesses between the protrusions 3, a portion where the magnetic properties are not deteriorated is formed, and this portion has a reduced magnetic resistance so that the magnetic flux passes as shown by the arrows in the figure. Therefore, loss torque is also reduced.

  According to the second embodiment, the same effect as that of turning and stacking can be obtained, the cogging torque can be reduced, and the loss torque can also be reduced.

  The protrusions 3 are provided corresponding to the respective teeth, and are preferably provided corresponding to the respective teeth in order to make it easier for the magnetic flux to pass in the circumferential direction.

Embodiment 3 FIG.
5 and 6 are a front view (a) and a plan view (b) showing a third embodiment of the permanent magnet motor according to the present invention.

  In the second embodiment, a plurality of protrusions 3 are provided on the inner peripheral surface of the frame 1, and the protrusions 3 are arranged at a predetermined pitch in the circumferential direction and the axial direction. However, as shown in FIGS. In addition, a plurality of recesses 5 are provided on the inner peripheral surface of the frame 1, the recesses 5 are connected to each other, and are arranged at a predetermined pitch in the circumferential direction and the axial direction.

  In the case of the third embodiment, since the recess 5 does not apply stress to the stator core 2, the magnetic characteristics of the portion of the stator core 2 facing the hole 5 are not deteriorated, and the magnetic characteristics of the portion without the recess 5 are deteriorated. To do. The connection part between the recessed parts 5 formed in the step shape becomes a path of magnetic flux, and magnetic flux passes as shown by the arrow of FIG.5 and FIG.6.

  According to the third embodiment, similar to the second embodiment, the same effect as that of the turning and stacking can be obtained, the cogging torque can be reduced, and the loss torque can also be reduced.

  The concave portion 5 is provided corresponding to each tooth, and it is preferable to provide the concave portion 5 corresponding to each tooth in order to make the magnetic flux easily pass in the circumferential direction.

Embodiment 4 FIG.
FIG. 7 is a front view showing Embodiment 4 of the permanent magnet motor according to the present invention. The third embodiment relates to the shape of the protrusion 3 of the first embodiment.

  By making the shape of the protrusion 3 a square, the square corner acts as a wedge with respect to the circumferential surface of the stator core 2, and serves as a detent that prevents the stator core 2 from rotating. The shape of the protrusion 3 is not limited to a quadrangle, and a similar effect can be obtained even when it is a polygon.

  Further, by making the shape of the protrusion 3 round, it becomes point contact with the stator core 2 and the shape of the inner diameter can be changed with a little external pressure, so that the thickness of the frame can be reduced.

  The permanent magnet motor according to the present invention can be applied to servo motors such as machine tools, vehicle motors, elevator motors, and the like, and can reduce cogging torque.

It is the front view (a) and top view (b) which show Embodiment 1 of the permanent magnet motor which concerns on this invention. It is a figure which shows the internal diameter of the stator in the axial direction 3 points | pieces of a permanent magnet motor. It is the front view (a) and top view (b) which show Embodiment 2 of the permanent magnet motor which concerns on this invention. It is the front view (a) and top view (b) which show Embodiment 2 of the permanent magnet motor which concerns on this invention. It is the front view (a) and top view (b) which show Embodiment 3 of the permanent magnet motor which concerns on this invention. It is the front view (a) and top view (b) which show Embodiment 3 of the permanent magnet motor which concerns on this invention. It is a front view which shows Embodiment 4 of the permanent magnet motor which concerns on this invention.

Explanation of symbols

1 frame, 2 stator core, 2a split core, 3 protrusion, 3a, 3b protrusion,
4 Rotor, 5 recesses.

Claims (7)

A cylindrical frame, a stator having a plurality of teeth fixed to the inner periphery of the frame and projecting in a radial direction, and a rotor disposed coaxially with the stator inside the stator. ,
The permanent magnet motor according to any one of the preceding claims, wherein the frame has a protrusion for bringing the deformation of the inner diameter of the stator closer to a perfect circle at any position in the axial direction of the inner peripheral surface thereof. The permanent magnet motor according to claim 1, wherein a cross-sectional shape of the protrusion is a polygon. The permanent magnet motor according to claim 1, wherein a cross-sectional shape of the protrusion is round. A cylindrical frame, a stator having a plurality of teeth fixed to the inner periphery of the frame and projecting in a radial direction, and a rotor disposed coaxially with the stator inside the stator. ,
The frame has a plurality of protrusions on an inner peripheral surface thereof, and the protrusions are arranged at a predetermined pitch in the circumferential direction and the axial direction. The permanent magnet motor according to claim 4, wherein the protrusion is disposed corresponding to the tooth. A cylindrical frame, a stator having a plurality of teeth fixed to the inner periphery of the frame and projecting in a radial direction, and a rotor disposed coaxially with the stator inside the stator. ,
The frame has a plurality of recesses in the axial direction on an inner peripheral surface thereof, the recesses are connected to each other, and are arranged at a predetermined pitch in the circumferential direction and the axial direction. Magnet motor. The permanent magnet motor according to claim 6, wherein the concave portion is arranged corresponding to the tooth.

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