JP2007228762A - Protective structure of ring magnet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the quality performance of a ring magnet by enhancing the radial crushing strength of the ring magnet to become hard to be broken and eliminating the surface coating. <P>SOLUTION: The rotor section 14 has a ring magnet 15 at the outer circumferential portion, and a tubular or tapelike cover film 19 is applied fixedly to the ring magnet 15 by heat shrinkage, heat welding or adhesion. The cover film 19 is composed of a nonmagnetic substance, i.e. synthetic resin, and when the cover film 19 is applied fixedly to the ring magnet 15 over the entire outer circumferential surface by imparting a uniform pressure, the ring magnet 15 is protected against breakage or damage. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a protective structure for a ring-shaped magnet, and more particularly to a protective structure for a ring-shaped magnet that is integrally fixed to the outer periphery of a motor shaft.

  Conventionally, this kind of ring-shaped magnet will be described with reference to FIG. The ring-shaped magnet 1 constitutes a rotor part 3 together with a motor shaft 2 and the like, and the rotor part 3 is rotatably arranged on the inner surface side of a stator yoke part (not shown). The ring-shaped magnet 1 is formed in a cylindrical shape having a predetermined thickness. The material of the ring-shaped magnet 1 is a ferrite magnet, a rare earth magnet, an alnico magnet, etc., depending on the type and application of the motor. Magnetic materials are used.

In a permanent magnet type stepping motor including a rotor portion including a rotor shaft and a stator yoke portion having a plurality of comb-shaped pole portions provided coaxially with the rotor portion, the rotor shaft is press-fitted. A ring member having a ring magnet fixed to the connecting member is known (see, for example, Patent Document 1).
JP-A-8-88965

  Since the conventional ring-shaped magnet is made of a highly brittle magnetic material, it has a drawback that its crushing strength is weak and it is easily broken. In particular, when a ring-shaped magnet is magnetized, there is a drawback that minute cracks are likely to occur, and the cracks gradually grow to cause cracks or breakage in the ring-shaped magnet.

  In addition, rare earth magnets, for example, ring magnets made of neodymium-based magnetic materials, need to be coated on the surface from the viewpoint of rust prevention. During this coating process, bubbles are generated in the ring magnet itself. Therefore, there is a problem that the magnet quality is not stable due to the bubbles.

  Therefore, there is a technical problem to be solved in order to increase the crushing strength of the ring-shaped magnet to make it difficult to break, and to stabilize the magnet quality by eliminating the coating process, and the present invention solves this problem. The purpose is to do.

  The present invention has been proposed in order to achieve the above object, and the invention according to claim 1 is a ring-shaped magnet integrally fixed to the outer peripheral portion of the motor shaft, and is synthesized with the outer peripheral surface of the ring-shaped magnet. Provided is a ring-shaped magnet protection structure in which a cover film made of a non-magnetic material such as resin is attached and fixed.

  According to this configuration, since the cover film made of synthetic resin or the like is adhered and fixed to the outer peripheral surface of the ring-shaped magnet, the ring-shaped magnet is reinforced by the cover film, and the crushing strength of the ring-shaped magnet is reduced. Increase.

  The invention according to claim 2 provides the ring-shaped magnet protection structure according to claim 1, wherein the cover film is fixed to the outer peripheral surface of the ring-shaped magnet by heat welding or adhesion.

  According to this configuration, since the cover film is integrally fixed to the outer peripheral surface of the ring-shaped magnet by heat welding or adhesion, the fixing force of the cover film to the magnet is increased.

  According to a third aspect of the present invention, the cover film is formed in a cylindrical shape, and the cover film is fixed by being thermally contracted over the outer peripheral surface of the ring-shaped magnet. Provide magnet protection structure.

  According to this configuration, when a cylindrical cover film is placed on the outer periphery of the ring-shaped magnet and the cover film is thermally contracted, the inner diameter of the cover film is uniformly reduced toward the center of the ring-shaped magnet. For this reason, the contact | adhesion power with respect to the ring-shaped magnet outer peripheral surface of this cover film becomes uniform in the circumferential direction.

  The invention according to claim 4 is the ring according to claim 1, wherein the cover film is formed in a tape shape with a single-sided adhesive, and the cover film is wound and fixed around the outer peripheral surface of the ring-shaped magnet. A protective structure for a magnet.

  According to this configuration, as the cover film, a single-sided adhesive tape formed of a synthetic resin such as vinyl chloride can be used. By winding the tape around the ring-shaped magnet, the cover film is attached to the outer peripheral surface of the ring-shaped magnet. Worn.

  In the invention according to claim 1, since the ring-shaped magnet is reinforced by the cover film and the crushing strength of the ring-shaped magnet increases, the crack-resistant performance of the ring-shaped magnet increases, and the ring-shaped magnet has a problem such as cracking Can be prevented in advance.

  Moreover, since the cover film has a rust preventive action on the outer peripheral surface of the ring-shaped magnet, it is not necessary to apply a surface coating to the ring-shaped magnet, and the quality performance is further improved as compared with the conventional case.

  In the invention according to claim 2, since the cover film is firmly attached and fixed to the ring-shaped magnet, in addition to the effect of the invention according to claim 1, the crushing strength of the ring-shaped magnet is further increased. Therefore, even if the ring-shaped magnet is broken, it is possible to reliably prevent the fragments of the ring-shaped magnet from scattering.

  In the invention according to claim 3, since the cover film adheres to the outer peripheral surface of the ring-shaped magnet with uniform pressure in the circumferential direction, in addition to the effect of the invention according to claim 1, the ring magnet has a circular shape. The required crushing strength is evenly obtained in the circumferential direction, and the crack resistance performance of the ring magnet is further improved.

  In the invention according to claim 4, since the adhesive tape-like cover film can be fixed only by being wound around the outer peripheral surface of the ring-shaped magnet, in addition to the effect of the invention according to claim 1, the cover film to the ring-shaped magnet is provided. Can be fixed easily, quickly and reliably. Moreover, as the cover film, a thin tape-like one can be used, and a ring-shaped magnet having a high crushing strength can be mass-produced at low cost.

The present invention is fixed to the outer periphery of the motor shaft integrally for the purpose of increasing the crushing strength of the ring-shaped magnet, making it difficult to break, making the coating process unnecessary, and improving the quality performance of the ring-shaped magnet. In the ring-shaped magnet, this is achieved by attaching and fixing a cover film made of a non-magnetic material such as synthetic resin on the outer peripheral surface of the ring-shaped magnet.

  A preferred embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a cross-sectional view showing a main part of a permanent magnet type stepping motor M according to this embodiment. In the figure, reference numeral 10 denotes a motor case, and a stator yoke portion 11 is fixed inside the motor case 10. The stator yoke portion 11 has a yoke 12, and an excitation coil 13 for driving is wound around the yoke 12. A rotor portion 14 is rotatably disposed on the inner surface side of the stator yoke portion 11.

  The rotor portion 14 includes a ring-shaped (cylindrical or annular) magnet 15 constituting an outer peripheral portion thereof, and a pair of steel plate bushes 16 and 16 fixed to inner surfaces of both upper and lower ends of the ring-shaped magnet 15; And a motor shaft 17 that is press-fitted and fixed through the center of the bushes 16. The motor shaft 17 is rotatably attached to the motor case 10 via bearings 18 and 18.

  The ring-shaped magnet 15 has N poles and S poles alternately magnetized in the circumferential direction. Thus, as the material of the ring-shaped magnet 15, for example, a magnetic material such as a ferrite magnet, a rare earth (Nd—Fe—B) bonded magnet, or an alnico magnet can be used. The ring-shaped magnet 15 is covered with a cover film 19, and the cover film 19 is formed of a synthetic resin such as vinyl chloride which is a non-magnetic material (electrical insulator).

  Thus, the axial length of the cover film 19 is set to be equal to or slightly longer than the axial length of the ring-shaped magnet 15. When the axial length of the cover film 19 is longer than the ring-shaped magnet 15 by a dimension L, the portion corresponding to the dimension L of the cover film 19 is the inner peripheral edge of the end of the ring-shaped magnet 15. The inner peripheral edge portion of the end portion of the ring-shaped magnet 15 can also be covered and protected by the cover film 19 by forming a U-shape on the side.

  The cover film 19 is attached to the entire outer peripheral surface of the ring-shaped magnet 15 by fixing means described later. The cover film 19 is attached and fixed so that a constant pressure acts from the outer peripheral surface of the ring-shaped magnet 15 toward the center in the inner diameter direction. In this case, the pressure toward the center of the ring-shaped magnet 15 acts equally in the circumferential direction of the outer surface of the ring-shaped magnet 15.

  When the cover film 19 is externally fixed to the ring-shaped magnet 15, various fixing methods can be adopted. For example, a cylindrical cover film 19 having an inner diameter slightly larger than the outer diameter of the ring-shaped magnet 15 is used. The cylindrical cover film 19 is placed on the outer side of the ring-shaped magnet 15, and the cover film 19 is heated and contracted as it is. Thus, when the diameter dimension of the cover film 19 is reduced, the inner surface of the cover film 19 is tightly fixed to the outer peripheral surface of the ring-shaped magnet 15. In this case, uniform pressure acts on the entire outer peripheral surface of the ring-shaped magnet 15 by the cover film 19.

Thus, the ring-shaped magnet 15 covered and fixed by the cylindrical cover film 19 is reinforced by the cover film 19, and the crushing strength of the ring-shaped magnet 15 is remarkably increased. In particular, when the cylindrical cover film 19 is put on the outer periphery of the ring-shaped magnet 15 and thermally contracted, the cover film 19 is deformed by reducing its diameter toward the center of the ring-shaped magnet 15. The magnet 15 is firmly fixed to the outer peripheral surface of the magnet 15 with uniform pressure in the entire circumferential direction.

  In this embodiment, since the cylindrical cover film 19 is heat-shrinked and fixed to the outer peripheral surface of the ring-shaped magnet 15, the required crushing strength is evenly distributed in the circumferential direction of the ring-shaped magnet 15. can get. Thus, the ring-shaped magnet 15 as a whole has an improved crack resistance as compared with the conventional one, and the ring-shaped magnet 15 can be prevented from cracking or breaking. Even if the ring-shaped magnet 15 is damaged, it is possible to reliably prevent the fragments of the ring-shaped magnet 15 from being scattered around.

  Further, since the cover film 19 has the same rust prevention effect as the coating treatment for the ring-shaped magnet 15, even when a neodymium permanent magnet is used as the ring-shaped magnet 15, for example, the ring-shaped magnet 15. It is not necessary to perform a coating treatment for rust prevention on the outer peripheral surface of the steel sheet.

  Further, when the coating process is omitted, the base area of the ring-shaped magnet 15 is widened, so that the magnetic performance of the ring-shaped magnet 15 is improved accordingly. If necessary, the ring-shaped magnet 15 may be coated, but in this case, the coating film can be formed much thinner than the conventional film, so that the magnetic performance of the ring-shaped magnet 15 is improved accordingly.

  Unlike the above fixing method, when the cover film 19 is fixed, the cover film 19 is heat-welded while the cover film 19 is covered on the ring-shaped magnet 15, or the ring-shaped magnet 15 is bonded with an adhesive. The cover film 19 may be integrally adhered and fixed to the entire outer peripheral surface. If comprised in this way, since the fixing force of the cover film 19 with respect to this ring-shaped magnet 15 will become large, the crushing strength of this ring-shaped magnet 15 will increase further.

  Further different from the fixing method described above, when fixing the cover film 19, a tape-shaped cover film 19 with a single-sided adhesive having a circumferential length substantially equal to the circumferential length of the ring-shaped magnet 15 is prepared, and this is attached to the ring shape. The tape-shaped cover film 19 can be adhesively fixed so that a predetermined tension pressure acts on the outer surface of the ring-shaped magnet 15 by being wound around the entire outer peripheral surface of the magnet 15.

  Further, since the tape-like cover film 19 can be adhesively fixed only by being wound around the outer peripheral surface of the ring-shaped magnet 15, the fixing operation of the cover film 19 can be performed easily, quickly and reliably. Further, since a thin synthetic resin tape can be used as the tape-shaped cover film 19, material costs can be reduced, and the ring-shaped magnet 15 excellent in quality performance can be mass-produced at low cost.

  The present invention can be variously modified without departing from the spirit of the present invention, and the present invention naturally extends to the modified one.

The perspective view of a ring-shaped magnet which shows one Example of this invention. The principal part sectional drawing of the motor which concerns on one Example. The perspective view which shows a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Stator yoke part 12 Yoke 13 Excitation coil 14 Rotor part 15 Ring-shaped magnet 16 Bush (connection member)
17 Motor shaft 19 Cover film

Claims (4)

  A ring-shaped magnet that is integrally fixed to the outer peripheral portion of a motor shaft, wherein a cover film made of a non-magnetic material such as a synthetic resin is attached and fixed to the outer peripheral surface of the ring-shaped magnet. Construction.   2. The ring magnet protection structure according to claim 1, wherein the cover film is fixed to the outer peripheral surface of the ring magnet by heat welding or adhesion.   2. The protection of a ring-shaped magnet according to claim 1, wherein the cover film is formed in a cylindrical shape, and the cover film is fixed by being thermally contracted over the outer peripheral surface of the ring-shaped magnet. Construction. 2. The protective structure of a ring-shaped magnet according to claim 1, wherein the cover film is formed in a tape shape with a single-sided adhesive, and the cover film is wound around the outer peripheral surface of the ring-shaped magnet and fixed by adhesion. .

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