JP2017085731A - Motor rotor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotor of a motor which secures driving torque while suppressing noise.SOLUTION: The motor rotor comprises: an iron core rotatably supported around a predetermined axis center; a plurality of permanent magnets arranged on the outer circumference side of the iron core and having alternately different polarities in the circumferential direction facing outwardly; and a cover of magnetic material covering the plurality of permanent magnets together with the iron core. The cover includes: a base portion located at an end portion of the iron core in the direction of the axis center; a first holding portion extending from the base portion in the direction of the axis center and pressing the adjacent end portions of the outer surfaces of the two adjacent permanent magnets out of the plurality of permanent magnets to the iron core side; and a second holding portion extending from the base portion in the direction of the axis center and pressing adjacent end portions of the outer surfaces of the two adjacent permanent magnets out of the plurality of permanent magnets to the iron core side. A center portion of each outer surface of the plurality of permanent magnets in the circumferential direction is exposed from the cover.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a rotor of a motor.

  In order to prevent scattering of a plurality of permanent magnets arranged on the outer peripheral surface of an iron core, a motor rotor provided with a nonmagnetic cover is known. In Patent Document 1, it is proposed to use a magnetic cover instead of a non-magnetic cover in order to approximate the magnetic flux density distribution in the circumferential direction of the rotor to a sine wave.

Japanese Utility Model Publication No. 64-50663

  Such a rotor preferably suppresses noise during rotation, and such noise depends on the cogging torque of the rotor. For example, as in Patent Document 1, it is considered that such a cogging torque is reduced and noise is suppressed by using a magnetic cover.

  However, if all of the outer surfaces of the plurality of permanent magnets are covered with the magnetic cover, there is a possibility that the driving torque cannot be secured.

  Accordingly, an object of the present invention is to provide a rotor of a motor that secures a driving torque while suppressing noise.

  The object is to provide an iron core rotatably supported around a predetermined axis, a plurality of permanent magnets arranged on the outer peripheral side of the iron core and having different polarities facing outward in the circumferential direction, and a plurality together with the iron core. A cover made of a magnetic material that covers the permanent magnet, and a base that is positioned at an end of the iron core in the direction of the axis, and that extends from the base toward the axis. A first pressing portion that presses adjacent ends of outer surfaces of two adjacent permanent magnets of the permanent magnets toward the iron core side, and extends from the base toward the axis, and a plurality of the permanent magnets. A second pressing portion that presses adjacent ends of the outer surfaces of the two adjacent permanent magnets against the iron core, and a central portion in the circumferential direction of each outer surface of the plurality of permanent magnets is By the motor rotor exposed from the cover It can be formed.

  ADVANTAGE OF THE INVENTION According to this invention, the rotor of the motor which ensured the drive torque, suppressing a noise can be provided.

1A and 1B are external views of a rotor of a motor according to this embodiment. FIG. 2 is an external view of a rotor of a comparative example. 3A and 3B are magnetic flux diagrams of the rotors of the present example and the comparative example, respectively. FIG. 4 is a graph showing changes in magnetic flux density when the rotors of the present example and the comparative example are rotated. FIG. 5 is a graph showing the counter electromotive voltage of the rotors of this example and the comparative example. FIG. 6 is a graph showing the cogging torque of the rotors of the present example and the comparative example. FIG. 7 is an external view of a modified rotor.

  1A and 1B are external views of a rotor R of a motor according to this embodiment. The rotor R includes an iron core 10, permanent magnets 30a to 30d, and a cover 50. The iron core 10 has a substantially cylindrical shape with a hole 11 formed in the center. A shaft that rotatably supports the iron core 10 is inserted into the hole 11. The iron core 10 includes an outer peripheral surface 14 and an upper surface 16a and a lower surface 16b in the direction of the axial center in which the hole 11 extends. From the outer peripheral surface 14 of the iron core 10, the protrusions 18 protrude radially outward at equal angular intervals. In FIGS. 1A and 1B, the projection 18 is formed so as to extend in the axial direction, although it is covered with the cover 50. These protrusions 18 are positioned in contact with the side surfaces of the permanent magnets 30a to 30d. Accordingly, the permanent magnets 30a to 30d are spaced at the same distance in the circumferential direction. The permanent magnets 30a to 30d are fixed to the outer peripheral surface 14 with an adhesive.

  The outer surfaces of the permanent magnets 30a to 30d are magnetized so that different polarities are alternately arranged in the circumferential direction. For example, the outer surfaces and inner surfaces of the permanent magnets 30a and 30c are magnetized to N and S poles, respectively, and the outer surfaces and inner surfaces of the permanent magnets 30b and 30d are magnetized to S and N poles, respectively. Therefore, in this embodiment, the outer surfaces of the permanent magnets 30a to 30d are magnetized to the N pole, the S pole, the N pole, and the S pole, respectively. Each of the permanent magnets 30a to 30d is formed to be curved with a certain curvature so that the outer surface thereof becomes a cylindrical outer peripheral surface as a whole. The inner surfaces of the permanent magnets 30 a to 30 d are fixed to the outer peripheral surface of the iron core 10.

  The cover 50 is attached to prevent the permanent magnets 30a to 30d from being scattered from the iron core 10 while the rotor R is rotating. The cover 50 is a magnetic body made of a magnetic material, and is formed, for example, by pressing a magnetic steel sheet. The cover 50 includes base portions 52a to 52d that partially cover the lower surface 16b of the iron core 10, and pressing portions 53a to 53d that are bent substantially vertically from the base portions 52a to 52d and partially cover the outer surfaces of the permanent magnets 30a to 30d. including. The lower surface 16b of the iron core 10 is an example of an end portion in the axial direction.

  The bases 52a to 52d are horizontal with respect to the axial direction, and are formed substantially radially as a whole. Further, a clearance hole 51 for escaping the shaft inserted into the hole 11 is formed at the center of the base portions 52a to 52d.

  The presser portions 53a to 53d are provided at equiangular intervals around the shaft center and extend in the shaft center direction. The presser portions 53a to 53d are curved with a certain curvature as viewed from the axial direction so as to be partially adhered to the outer surfaces of the permanent magnets 30a to 30d. The axial lengths of the presser portions 53a to 53d are substantially the same as the axial lengths of the iron core 10 and the permanent magnets 30a to 30d. Therefore, the tips of the presser portions 53a to 53d do not cover the upper surface 16a.

  The pressing portion 53a presses the adjacent end portions of the outer surfaces of the adjacent permanent magnets 30a and 30b to the iron core 10 side. Similarly, the pressing portion 53b is formed between the ends of the outer surfaces of the permanent magnets 30b and 30c. The parts are pressed against the iron core 10 side.

  The presser portions 53a to 53d press the permanent magnets 30a to 30d against the iron core 10 side by elastic restoring force. The reason is as follows. The distance between the presser portion 53a and the tip of the presser portion 53c facing the presser portion 53a is slightly smaller than the diameter including the iron core 10 and the permanent magnets 30a to 30d. For this reason, the elastic restoring force of the pressing parts 53a and 53c acts on the permanent magnets 30a to 30d by inserting the iron core 10 with the permanent magnets 30a to 30d bonded between the pressing parts 53a and 53c. The same applies to the presser portions 53b and 53d. The presser portions 53a to 53d are examples of first and second presser portions.

  The cover 50 exposes a central portion in the circumferential direction of each outer surface of the permanent magnets 30a to 30d. In other words, the width, interval, and position in the circumferential direction of the presser portions 53a to 53d are set so as not to cover the circumferential central portion of each outer surface of the permanent magnets 30a to 30d. Accordingly, the central portions of the permanent magnets 30a to 30d are exposed between the presser portions 53d and 53a, between the presser portions 53a and 53b, between the presser portions 53b and 53c, and between the presser portions 53c and 53d, respectively.

  Next, a rotor Rx of a comparative example different from the rotor R of the present embodiment will be described. FIG. 2 is an external view of a rotor Rx of a comparative example different from the rotor R of the present embodiment. In addition, about the same structure, the overlapping description is abbreviate | omitted by attaching | subjecting the same code | symbol. Unlike the cover 50, the cover 50x of the rotor Rx is a non-magnetic material. The peripheral wall 53x of the cover 50x has a cylindrical shape that covers the entire outer surface of the permanent magnets 30a to 30d.

  In the assembly process of the rotor Rx, it is necessary to fix the permanent magnets 30a to 30d to the outer peripheral surface 14 of the iron core 10 with an adhesive, and then press-fit the iron core 10 into the peripheral wall portion 53x of the cover 50x. Here, since the peripheral wall part 53x is cylindrical, it is hard to elastically deform in the circumferential direction and radial direction. For this reason, unless the dimension of the cover 50x in the radial direction, the dimension of the iron core 10 in the radial direction, the thickness of the permanent magnets 30a to 30d, etc. are not accurately formed, the peripheral wall of the iron core 10 to which the permanent magnets 30a to 30d are fixed. It may be difficult to press fit into the portion 53x, or there may be a gap between the inner surface of the peripheral wall portion 53x and the outer surfaces of the permanent magnets 30a to 30d.

  On the other hand, in the rotor R of the present embodiment, the presser portions 53a to 53d are separated from each other, and it is easy to be elastically deformed so that these tip portions are separated. For this reason, even if there is a variation in dimensions as described above, the iron core 10 in which the permanent magnets 30a to 30d are fixed can be easily inserted between the presser portions 53a to 53d by elastically deforming the presser portions 53a to 53d. . Thus, the assembling property of the cover 50 is improved, and the rotor R can be easily assembled.

  Further, as described above, since the presser portions 53a to 53d press the ends of the permanent magnets 30a to 30d, scattering of the permanent magnets 30a to 30d is effectively prevented. Further, since the cover 50x is a non-magnetic material, the cover 50 is a magnetic material, so that the cover 50 can be manufactured at a relatively low cost.

  Next, the difference in magnetic characteristics between the rotor R of the present embodiment and the rotor Rx of the comparative example will be described. 3A is a magnetic flux diagram of the rotor R of the present embodiment, and FIG. 3B is a magnetic flux diagram of the rotor Rx of the comparative example. As shown in FIG. 3A, since the cover 50 of the rotor R is a magnetic body, the magnetic flux lines emitted from one end portion in the circumferential direction of the outer surface of the permanent magnet 30a pass through the presser portion 53a and pass through the permanent magnet 30b. The magnetic flux lines emitted from the other end portion in the circumferential direction of the outer surface of the permanent magnet 30a are directed to the outer surface of the permanent magnet 30d through the pressing portion 53d. Thus, the pressing portion 53a defines a part of the magnetic path between the adjacent permanent magnets 30a and 30b, and the pressing portion 53d defines a part of the magnetic path between the adjacent permanent magnets 30a and 30d. Similarly, a part of the magnetic flux lines coming out from one end portion in the circumferential direction of the outer surface of the permanent magnet 30c pass through the holding portion 53c toward the outer surface of the permanent magnet 30d, and in the circumferential direction of the outer surface of the permanent magnet 30c. Part of the magnetic flux lines coming out from the other end of the wire pass through the presser 53b and go to the outer surface of the permanent magnet 30b.

  As described above, the presser portions 53a to 53d are respectively a part of the magnetic path between the permanent magnets 30a and 30b, a part of the magnetic path between the permanent magnets 30b and 30c, and a magnetic path between the permanent magnets 30c and 30d. And part of the magnetic path between the permanent magnets 30a and 30d. In addition, the magnetic flux line which comes out of a part of outer peripheral surface of the permanent magnets 30a-30d covered with the pressing parts 53a-53d passes the pressing parts 53a-53d.

  Moreover, the center part in the circumferential direction of each outer surface of the permanent magnets 30a to 30d is not covered with the presser parts 53a to 53d but exposed. For this reason, a part of magnetic flux line which comes out of the center part of the outer surface of the permanent magnet 30a goes to the center part of the permanent magnet 30b or 30d without passing any of the pressing parts 53a to 53d. Similarly, a part of the magnetic flux line coming out from the center portion of the outer surface of the permanent magnet 30c goes to the center portion of the permanent magnet 30b or 30d without passing through any of the presser portions 53a to 53d.

  On the other hand, as shown in FIG. 3B, the cover 50x, which is a non-magnetic material, covers all the outer surfaces of the permanent magnets 30a to 30d, and the magnetic flux lines of the permanent magnets 30a to 30d are affected by the cover 50x. It passes through the cover 50x without.

  FIG. 4 is a graph showing changes in magnetic flux density when the rotor R of the present embodiment and the rotor Rx of the comparative example are rotated. Line segments M and Mx indicate the magnetic flux densities of the rotors R and Rx, respectively. The rotor R has a slightly lower magnetic flux density than the rotor Rx. The reason for this is that, as described above, in the rotor R, a part of the magnetic flux lines emitted from the outer surfaces of the permanent magnet 30a and the permanent magnet 30c pass through the presser portions 53a to 53d and the outer surfaces of the permanent magnet 30b and the permanent magnet 30d. This is because it is detected that the magnetic flux density of the rotor R is smaller than that of the rotor Rx.

  FIG. 5 is a graph showing the back electromotive force between the rotor R of the present embodiment and the rotor Rx of the comparative example. The counter electromotive voltage is a voltage generated in the drive coil when the rotors R and Rx are forcibly rotated by an external force in a motor in which the rotors R and Rx are respectively incorporated. Line segments V and Vx indicate back electromotive voltages of the rotors R and Rx, respectively. The rotor R has a back electromotive force curve closer to a sine wave than the rotor Rx.

  FIG. 6 is a graph showing the cogging torque between the rotor R of the present embodiment and the rotor Rx of the comparative example. Line segments T and Tx indicate cogging torques of the rotors R and Rx, respectively. The cogging torque is lower in the rotor R than in the rotor Rx. The reason for this is considered that the magnetic flux density of the rotor R is smaller than that of the rotor Rx. Thus, since the cogging torque of the rotor R is suppressed, noise and vibration during rotation are suppressed compared to the rotor Rx. Moreover, since the cover 50 of the rotor R exposes the center part of each outer surface of the permanent magnets 30a to 30d, the magnetic flux lines flowing through the exposed part contribute to the drive torque. Therefore, the rotor R of this embodiment has a drive torque while suppressing noise.

  Next, a modified example will be described. FIG. 7 is an external view of a modified example of the rotor Ra. In addition, about the same structure, the overlapping description is abbreviate | omitted by attaching | subjecting the same code | symbol. In the rotor Ra, two permanent magnets 30a1 and 30b1 are fixed to the outer peripheral surface 14 of the iron core 10a. Two protrusions 18 for positioning the two permanent magnets 30a1 and 30b1 are provided on the outer peripheral surface 14 of the iron core 10a. Each of the permanent magnets 30a1 and 30b1 has a larger width in the circumferential direction than each of the permanent magnets 30a to 30d described above. The outer surface and inner surface of the permanent magnet 30a1 are magnetized to N and S poles, respectively, and the outer surface and inner surface of the permanent magnet 30b1 are magnetized to S and N poles, respectively. Therefore, the polarities of the outer surfaces of the permanent magnets 30a1 and 30b1 are in the order of N pole and S pole in the circumferential direction.

  The cover 50a has two pressing portions 53a and 53c. The pressing portion 53a presses the outer end portions of the permanent magnets 30a1 and 30b1, that is, one end portion of the permanent magnet 30a1 and one end portion of the permanent magnet 30b1 to the iron core 10a side. The holding portion 53c presses the other end of the permanent magnet 30a1 and the other end of the permanent magnet 30b1 against the iron core 10a. Further, the presser portions 53a and 53c are exposed at the center in the circumferential direction of the outer surfaces of the permanent magnets 30a1 and 30b1. The permanent magnets 30a1 and 30b1 are examples of two adjacent permanent magnets among the plurality of permanent magnets. The presser portions 53a and 53c are examples of first and second presser portions.

  Thus, the same effect as that of the rotor R can be obtained by adopting the cover 50a for the rotor Ra provided with only the two permanent magnets 30a1 and 30b1.

  As described above, the number of pressing portions of the cover is desirably the same as the number of permanent magnets fixed to the iron core. In addition, the number of pressing parts and the number of permanent magnets may be two or more, respectively.

  Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and modifications and changes can be made within the scope of the gist of the present invention described in the claims. Is possible.

R Rotor 10 Iron core 30a-30d Permanent magnet 50 Cover 52a-52c Base 53a-53d Presser

Claims (2)

An iron core supported rotatably around a predetermined axis;
A plurality of permanent magnets arranged on the outer peripheral side of the iron core and having different polarities alternately directed in the circumferential direction,
A magnetic cover that covers the plurality of permanent magnets together with the iron core, and
The cover is
A base located at the end of the iron core in the direction of the axis;
A first pressing portion that extends in the direction of the axial center from the base portion and presses adjacent ends of the outer surfaces of two adjacent permanent magnets of the plurality of permanent magnets toward the iron core;
A second pressing portion that extends in the direction of the axial center from the base portion and presses adjacent ends of the outer surfaces of two adjacent permanent magnets of the plurality of permanent magnets toward the iron core side,
The center part in the circumferential direction of each outer surface of the plurality of permanent magnets is a motor rotor exposed from the cover. The first presser portion presses adjacent ends of the outer surfaces of two adjacent permanent magnets among the plurality of permanent magnets to the iron core side by an elastic restoring force,
2. The motor rotor according to claim 1, wherein the second pressing portion presses adjacent ends of outer surfaces of two adjacent permanent magnets among the plurality of permanent magnets to the iron core side by an elastic restoring force. .

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