JP5340809B2 - Magnet for motor and motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor superior in starting torque performance and electromagnetic shield performance. <P>SOLUTION: The motor 10 includes a field magnet 11 comprising an anisotropic pole magnet, a frame 15 comprising a magnetic material arranged on the outer circumferential face 11a side of the field magnet 11, a core 17 arranged on the inner circumferential face 11b side of the field magnet 11, and a shaft 24 rotatably supporting the field magnet 11 and frame 15. A plurality of ribs 13 extended from the upper end 12c to the lower end 12d and arranged in symmetry of rotation with each other are formed on the outer circumference face 12a of the ring body 12 of the field magnet 11. Thus, a space 16 with a fixed thickness is formed between the field magnet 11 and frame 15. Furthermore, the plurality of ribs 13 are formed integrally with the ring body 12 at a position of the outer circumferential face 11a opposite to the center of the magnetic pole formed on the inner circumferential face 11b side of the field magnet 11, using the same material as that of the ring body 12 of the field magnet 11. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a motor magnet composed of a polar anisotropic ring magnet, and a motor using the motor magnet.

  Polar anisotropy ring magnets with magnetic poles appearing on either the inner or outer peripheral surface and magnetized in an arc shape generally have a large magnetic flux density and a sinusoidal magnetic flux density distribution. It is often used for DC motors. (For example, refer to Patent Document 1).

  When a polar anisotropic ring magnet is applied to a motor, a frame (back yoke) disposed on the outer peripheral side of the polar anisotropic ring magnet is formed using a nonmagnetic material instead of a magnetic material, thereby It has been clarified by the inventor's examination that the starting torque is improved. This is because the magnetic flux flowing from the polar anisotropic ring magnet to the frame can be suppressed, and the content is described in Patent Document 2 (Japanese Patent Application No. 2009-0778016; unpublished at the time of this application). .

  As a reference example (not a known example), a DC motor 50 described in Patent Document 2 will be described with reference to FIG. The DC motor 50 is an outer rotor type brushless DC motor, and includes a field magnet 51 made of a polar anisotropic ring magnet magnetized in the circumferential direction and a field magnet 51 made of a non-magnetic material. A substantially cylindrical frame (housing) 52 that is tightly held on the inner peripheral surface, an iron core 53 that functions as an armature with a predetermined interval inside the field magnet 51, and a base that is arranged at the center of the iron core 53. And a shaft 60 fixed to (not shown).

  The iron core 53 is formed by laminating a plurality of silicon steel plates, and includes nine salient poles 55 that project radially from the annular yoke portion 54, and nine slots 59 that are gaps between adjacent salient poles, have. One salient pole 55 includes a salient pole arm portion 56 extending in the radial direction and a tooth portion 57 at the tip thereof. An exciting coil 58 is wound around the salient pole arm portion 56.

  Here, when the inner diameter (diameter) of the field magnet 51 is D, the thickness in the radial direction is T, and the number of magnetic poles is P, a relational expression of 0.09 <T / (πD / 2P) <0.75. By forming the field magnet 51 within a range that satisfies the above conditions, it is possible to obtain performance that achieves both a high starting torque and a low cogging torque as compared with the case where a frame made of a magnetic material is employed.

JP 2006-238536 A

  As described above, combining a polar anisotropic ring magnet and a frame made of a non-magnetic material and improving the performance as a motor by making the polar anisotropic ring magnet into a shape that satisfies the above relational expression. Can do.

  However, in order to construct a motor having excellent electromagnetic shielding performance, a case in which a frame made of a magnetic material must be used is also assumed. In order to improve the electromagnetic shielding performance of the motor described as a reference example, it is conceivable to separately arrange a frame made of a magnetic material on the outer peripheral surface side of the frame made of a nonmagnetic material. However, in this case, since two types of frames are required, there arises a problem that the weight and cost of the entire motor increase.

  Accordingly, the present invention has been made in view of such circumstances, and a motor excellent in electromagnetic shielding performance while maintaining a high starting torque and a low cogging torque without increasing the weight and cost, and its An object of the present invention is to provide a motor magnet suitable for realizing such a motor.

  In order to solve the above problems, the motor magnet of the present invention is a motor magnet that forms a part of the motor in combination with a frame made of a magnetic material, and is a substantially ring-shaped polar anisotropic magnet. And a ring-shaped ring body portion having a plurality of magnetic poles along the circumferential direction on the inner peripheral surface side, and a plurality of ribs formed on the outer peripheral surface side of the ring main body portion. .

  In this case, it is preferable that each of the ribs is integrally formed using the same material as that of the ring main body.

  Moreover, it is preferable that each of the ribs is formed at a position facing the plurality of magnetic poles of the ring main body.

  Moreover, it is preferable that each of the ribs is formed continuously from one open end side of the ring main body portion to the other open end side.

  Further, it is preferable that a gate is provided at a portion corresponding to one end portion of at least one rib and formed by injection molding.

  Further, when the inner diameter of the ring body portion is represented by D, the thickness in the radial direction is represented by T, and the number of magnetic poles is represented by P, the ring body portion satisfies 0.09 <T / (πD / 2P) <0.75. It is preferable to be configured to satisfy the relational expression.

  The motor of the present invention includes the motor magnet and a frame formed of a magnetic material and disposed on the outer peripheral surface side of the motor magnet.

  In this case, the motor magnet and the frame may be integrally formed.

  According to this invention, the magnet for motors is comprised from the ring-shaped ring main-body part which consists of a polar anisotropic magnet, and the rib formed in the outer peripheral surface. For this reason, in a state where the frame is disposed on the outer peripheral surface side of the motor magnet, a gap having a thickness corresponding to the radial thickness of the rib is formed between the outer peripheral surface of the ring main body and the frame. . That is, many areas of the outer peripheral surface of the motor magnet are covered with a nonmagnetic material (air). Thereby, the starting torque of a motor can be improved similarly to the reference example mentioned above. Further, the interior of the motor (such as a motor magnet or iron core) is covered with a magnetic material (frame). Thereby, the electromagnetic shielding performance of the motor can be improved.

  Further, when each of the ribs is formed at a position facing the plurality of magnetic pole centers of the ring main body, the magnetic flux generated from the motor magnet can be increased, and the starting torque of the motor can be further improved.

It is a cross-sectional view for demonstrating the structure of the motor which concerns on embodiment of this invention. It is a perspective view of the magnet for motors integrated in the motor. It is a graph which shows the relationship between rib height / air gap and starting torque. It is a plane conceptual diagram for demonstrating the structure of the motor as a reference example.

  Hereinafter, as an example of a preferred embodiment of the present invention, a motor 10 will be described with reference to the drawings.

  As shown in FIG. 1, the motor 10 includes a field magnet (motor magnet) 11 having a substantially ring shape, a frame 15 arranged coaxially so as to cover the outer peripheral surface 11 a of the field magnet 11, and a field An iron core 17 that functions as an armature and is arranged on the inner peripheral surface 11b side of the magnet magnet 11, and a shaft 24 that is located at the center of the iron core 17 and rotatably supports the field magnet 11 and the frame 15. It is equipped with.

  Among these, since the iron core 17 and the shaft 24 have the same configuration as the above-described reference example, each component of the iron core 17 (the annular yoke portion 18, the salient pole 19, the salient pole arm portion 20, the tooth portion 21, The description including the slot 22 and the excitation coil (not shown) will be omitted as appropriate, and the field magnet 11 and the frame 15 will be mainly described below.

  In this embodiment, the field magnet 11 is a polar anisotropic ring magnet made of a kneaded product of magnetic powder (for example, Sm-Fe-N powder) and binder resin (for example, nylon 6) and formed by an injection molding method. It is. As shown in FIG. 2, the field magnet 11 is formed on a ring-shaped ring main body 12 and an outer peripheral surface 12 a (circular surface) of the ring main body 12. A plurality of (in this embodiment, twelve) ribs 13 having a circular arc cross section continuously extending from the open end (12c) toward the lower end (the other open end) 12d.

  Further, the field magnet 11 has a magnetic pole center (N pole and S pole) on the side of the inner peripheral surface 11b (the inner peripheral surface 12b of the ring main body 12) that is a circumferential surface, etc. Multiple magnetic poles (12 poles in this embodiment) are magnetized at intervals. Magnetization is performed in parallel with the central axis (symmetric axis) from the upper end 12c to the lower end 12d. And the some rib 13 is each formed in the position of the outer peripheral surface 11a (12a) facing the some magnetic pole center which appears on the inner peripheral surface 11b (12b) side.

  Since the field magnet 11 is formed by the injection molding method as described above, the plurality of ribs 13 are formed integrally with the ring body 12 using the same material as the ring body 12. And at least a part of the gate mark 14 formed by injection molding on the plane (end part) on the upper end 12c side of the four ribs 13 arranged at the 90-degree rotationally symmetrical position among the twelve ribs 13 Is present. The gate mark 14 may be appropriately removed by grinding or the like.

  On the other hand, the frame 15 is formed in a ring shape using a magnetic material (in this embodiment, iron). The frame 15 is arranged on the outer peripheral surface 11 a side of the field magnet 11, and the inner peripheral surface 15 a (circumferential surface) of the frame 15 is in contact with the top portion 13 a that is the outermost portion of the rib 13. It is formed to a certain inner diameter. That is, the inner radius of the frame 15 is substantially matched with the virtual radius of the field magnet 11 at the top portion 13 a of the rib 13 (the distance between the central axis of the field magnet 11 and the top portion 13 a of the rib 13). The frame 15 is not limited to a ring shape, and may be a cup shape formed by integrating a ring and a base (not shown), for example.

  In a state where the frame 15 is arranged on the outer peripheral surface 11a side of the field magnet 11, the outer peripheral surface 11a of the field magnet 11 (the outer peripheral surface 12a of the ring main body 12) and the frame except for the region where each of the ribs 13 exists. A gap 16 having a constant radial thickness is formed between the inner peripheral surface 15a of the fifteen. In the present embodiment, the gap 16 is divided into 12 equal parts in the circumferential direction.

  Next, the effect of the motor 10 configured as described above will be described.

  The field magnet 11 is made of a polar anisotropic magnet, and a plurality of ribs 13 protruding outward in the radial direction are formed on the outer peripheral surface 12a of the ring-shaped ring main body 12 constituting the field magnet 11. A ring-shaped frame 15 made of a magnetic material is disposed on the outer peripheral surface 11 a side of the field magnet 11 so as to cover the entire outer peripheral surface 11 a of the field magnet 11. Therefore, a gap 16 having a thickness corresponding to the radial thickness (height) of the rib 13 is formed between the outer peripheral surface 12 a of the ring main body 12 and the inner peripheral surface 15 a of the frame 15. That is, many areas of the outer peripheral surface 12a of the ring main body portion 12 made of a polar anisotropic magnet are covered with a nonmagnetic material (air) having a constant thickness.

  For this reason, compared with the prior art (a configuration in which a frame made of a magnetic material is closely arranged without providing a gap on the outer peripheral surface side of the field magnet), the field magnet 11 is removed from the frame without increasing the weight and cost. The magnetic flux flowing through 15 can be suppressed. Thereby, the starting torque of the motor 10 can be improved.

  In particular, when the field magnet 11 has a predetermined shape mentioned in the reference example (when the inner diameter of the ring body 12 of the field magnet 11 is D, the thickness in the radial direction is T, and the number of magnetic poles is P9, 0.09 In the case of <T / (πD / 2P) <a shape satisfying the relational expression of 0.75), it is possible to obtain performance that achieves both high starting torque and low cogging torque.

  The interior of the motor 10 (field magnet 11, iron core 17, etc.) is covered with a magnetic material that forms the frame 15. Thereby, the electromagnetic shielding performance of the motor 10 can be improved.

  Further, both ends of the plurality of ribs 13 are formed flush with the upper end 12c and the lower end 12d of the ring body 12 respectively. For this reason, the radial thickness (thickness) of the field magnet 11 at the portion where the rib 13 is formed increases. As a result, a large space for arranging the gate can be secured when the field magnet 11 is formed by the injection molding method. As a result, the field magnet 11 can be easily manufactured and the moldability is improved.

  Next, the influence of the ribs 13 of the field magnet 11 on the improvement of the starting torque of the motor will be specifically described based on examples.

  First, FIG. 3 shows the result of examining the relationship between the height (radial thickness) of the rib 13, that is, the radial thickness of the air gap 16, and the starting torque of the motor. In FIG. 3, the height of the rib 13 is normalized by dividing by the air gap L. Here, the air gap L is the shortest distance between the inner peripheral surface 11 b of the field magnet 11 (the inner peripheral surface 12 b of the ring main body 12) and the tooth portion 21 of the iron core 17. As shown in FIG. 1, the tooth portion 21 of the present embodiment is formed such that the distance from the inner peripheral surface 11 a of the field magnet 11 increases as the distal end surface moves away from the center in the circumferential direction. . Therefore, the air gap L is a radial distance between the symmetrical central portion of the tooth portion 21 of the iron core 17 and the inner peripheral surface 11 b of the field magnet 11. The ring body 12 of the field magnet 11 has an inner diameter D of 80 mm, a radial thickness T of 2 mm, and a number of magnetic poles P of 12.

  FIG. 3 shows that the starting torque increases as the height of the rib 13 is increased and the thickness of the gap 16 in the radial direction is increased. However, if the “rib height / air gap” is greater than about 1, the starting torque tends to be constant (saturated). Therefore, when the height of the rib 13 is set so that the “rib height / air gap” is 1 or more, a stable high starting torque can be obtained. The case where “rib height / air gap” is 0 (zero) corresponds to the prior art.

  Next, the result of examining the relationship between the position where the rib in the ring body of the field magnet is formed and the starting torque of the motor will be described. In the above-described embodiment and example, the rib is provided at a position on the outer peripheral surface side facing the magnetic pole center of the ring main body. On the other hand, when the rib is provided at a position on the outer peripheral surface facing the gap between the magnetic poles of the ring main body portion (intermediate portion of the adjacent magnetic pole center), the starting torque is larger than in the conventional technique, It was confirmed that the starting torque was reduced by about 15% as compared with the case where the ribs were provided in the case. From this result, it can be seen that it is preferable to provide the rib at a position facing the magnetic pole center of the ring main body portion from the viewpoint of increasing the starting torque.

  The reason why the starting torque is improved by providing the rib at a position facing the center of the magnetic pole rather than between the magnetic poles of the ring main body is considered as follows. That is, when a ring-shaped magnet is magnetized with polar anisotropy, the magnetization vector is generally directed radially in the magnet near the magnetic pole center. In general, when the magnetization vector faces in the radial direction, the influence of the demagnetizing field increases due to the small size (substantial thickness in the direction in which the magnetization vector faces). Therefore, when the thickness in the vicinity of the magnetic pole center is increased by providing the rib, the influence of the demagnetizing field can be reduced, and as a result, the magnetic flux generated from the ring main body can be increased.

  On the other hand, between the magnetic poles of the ring body, the magnetization vector is generally oriented in the circumferential direction. When the magnetization vector is oriented in the circumferential direction, which has a larger dimension than the radial direction, the influence of the demagnetizing field is small. Therefore, even if the thickness near the magnetic poles is increased by providing the ribs, the effect of increasing the magnetic field generated from the ring main body is small. For this reason, it is considered that providing the rib near the center of the magnetic pole increases the magnetic flux generated from the ring main body and improves the starting torque of the motor more than providing the rib between the magnetic poles.

  From the above, the rib 13 of the field magnet 11 functions as a spacer for forming the air gap 16 between the field magnet 11 and the frame 15 and increases the magnetic flux by reducing the influence of the demagnetizing field. It became clear that

  The preferred embodiments of the present invention have been described above. However, the embodiments are not limited to the above, and various modifications can be made without departing from the gist of the present invention.

  For example, the field magnet 11 and the frame 15 may be integrally formed. In this case, a reduction in manufacturing cost can be expected, and it is advantageous for promoting the thinning of the field magnet 11.

  Moreover, in the said embodiment, although the cross-sectional shape of the rib 13 was made into circular arc shape, it is not limited to this. For example, a rectangular shape may be used instead of the arc shape.

  Moreover, in the said embodiment, although the rib 13 was set as the structure extended continuously from the upper end 12c of the ring main-body part 12 to the lower end 12d, it is not limited to this. When only the function of the rib as a spacer is required, for example, the rib may be discretely formed on each of the upper end 12c side and the lower end 12d side.

  Moreover, in the said embodiment, although the rib 13 is integrally formed with the ring main-body part 12 using the same material as the ring main-body part 12, it is not limited to this. When only the function of the rib as a spacer is required, the rib may be formed of a nonmagnetic material, and may not be integrally formed with the ring body 12. (For example, it may be fixed using an adhesive.)

  Further, the field magnet 11 (ring main body portion 12) may be formed by a method other than the injection molding method or may not be a bonded magnet.

10 Motor 11 Field Magnet (Motor Magnet)
11a outer peripheral surface 11b inner peripheral surface 12 ring main body 12a outer peripheral surface 12b inner peripheral surface 12c upper end 12d lower end 13 rib 13a top 14 gate mark 15 frame 15a inner peripheral surface 16 gap 17 iron core 18 annular yoke 19 salient pole 20 salient pole Arm 21 Teeth 22 Slot 24 Shaft

Claims (9)

A motor magnet that constitutes a part of a motor in combination with a frame made of a magnetic material,
It consists of a substantially ring-shaped polar anisotropic magnet,
A ring-shaped ring body portion having a plurality of magnetic poles along the circumferential direction on the inner peripheral surface side;
And a plurality of ribs formed on the outer peripheral surface side of the ring main body.   The motor magnet according to claim 1, wherein each of the ribs is integrally formed using the same material as the ring main body.   The motor magnet according to claim 2, wherein each of the ribs is formed at a position facing the plurality of magnetic poles of the ring main body.   4. The motor magnet according to claim 2, wherein each of the ribs is formed continuously from one open end side of the ring body portion to the other open end side. 5.   The motor magnet according to claim 4, wherein a gate is provided at a portion corresponding to one end of at least one rib and formed by injection molding.   When the inner diameter of the ring body is represented by D, the thickness in the radial direction is represented by T, and the number of magnetic poles is represented by P, the relation that the ring body is 0.09 <T / (πD / 2P) <0.75 The motor magnet according to claim 1, wherein the magnet is configured to satisfy the following. A magnet for a motor according to any one of claims 1 to 6,
And a frame that is disposed on an outer peripheral surface side of the motor magnet and is formed of a magnetic material. The radial thickness of each of the ribs is set to be equal to or more than the shortest distance between the inner peripheral surface of the motor magnet and the iron core tooth portion disposed on the inner peripheral surface side of the motor magnet. The motor according to claim 7. The motor according to claim 7 or 8 , wherein the motor magnet and the frame are integrally formed.

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