JPS60160346A - Yoke material manufacturing method - Google Patents

Abstract

PURPOSE:To reduce eddy-current loss increasing electric resistance by injection- molding a thermoplastic resin composition combined with iron powder of 75- 95wt% with 100 mesh or less grain size. CONSTITUTION:First, thermoplastic resin is combined and mixed well with iron powder with 100 mesh or less grain size to prepare a resin composition containing the iron powder of 75-95wt%. The resin composition is injection-molded and yoke material is produced. Thus, the yoke material with lower eddy-current generated by higher electric resistance can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a yoke material, particularly a method for manufacturing a yoke material for a small motor.

Recently, with the development of computers, various types of equipment for so-called office automation and factory automation have been developed. The motors used in the driving parts of these devices have also become significantly smaller with the advent of high-performance magnets such as rare earth magnets. However, in a motor, losses due to eddy currents generated in the yoke portion that guides Fi and magnetic flux often become an obstacle when downsizing the motor. The yoke material is usually manufactured by laminating silicon steel plates, but its productivity is low because it is processed such as providing grooves at appropriate locations to increase its electrical resistance. There is also a method of manufacturing a yoke material by sintering iron powder, but since it is semi-sintered to provide high electrical resistance, it is brittle and has poor workability.

Generally, the torque (T) of a motor is expressed by the following equation, and in order to obtain a large torque, it is necessary to introduce a high magnetic flux density to the yoke.

On the other hand, the eddy current loss (We) generated in the yoke is expressed by: The larger the electrical resistance, the smaller the eddy current loss. Therefore, the characteristics required for the yoke are to increase electrical resistance and reduce eddy current losses due to high magnetic flux density to obtain the necessary torque.

The present invention uses iron powder with a particle size of 100 mesh or less from 7S to 9
The present invention provides a method for manufacturing a yoke material that satisfies the above-mentioned characteristics by injection molding a thermoplastic resin composition containing S (weight).

To explain the present invention in more detail, in the present invention, first, iron powder having a particle size of less than IOO mesh is added to a thermoplastic resin and mixed well to prepare a resin composition containing 73-93 (by weight) of iron powder. do. The thermoplastic resin is appropriately selected from among commonly used thermoplastic resins such as polyamide, polycarbonate, polyacetal, and polyolefin, taking into account the heat resistance required for the yoke, the melt flowability of the iron powder compound, and other properties. be able to.

It is necessary to use iron powder having a particle size of /θO mesh (JIS sieve) or less. When the particle size of the iron powder is larger than the ioθ mesh, the eddy current generated in the yoke increases. Preferably, iron powder with a particle size of 50 mesh or more is used. As for the iron powder, it is preferable to use a flat iron powder rather than a spherical iron powder because a higher magnetic flux density can be obtained. The amount of iron powder mixed is preferably as large as possible from the viewpoint of obtaining a high magnetic flux density, and if it is less than 75% (by weight), it is difficult to obtain the magnetic flux density necessary for a yoke of a small motor.

However, if more than 95 (weight) q6 of iron powder is blended, injection molding will be hindered.

In addition, in addition to the above-mentioned resin and iron powder, the resin composition may contain various auxiliary agents used in ordinary injection molding, such as lubricants and plasticizers, to improve moldability. good.

Injection molding of the resin composition is carried out by a conventional method.

It can also be integrally molded with other parts if desired.

According to the method of the present invention, it is possible to manufacture a yoke material with high dimensional accuracy without the need for post-processing, resulting in high productivity, and the obtained yoke material has a higher productivity than those made of silicon steel plate or sintered iron.
It has a large electrical resistance and generates small eddy currents, so it is particularly useful for high-speed motors.

EXAMPLES The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to the following Examples unless it exceeds the gist thereof.

Example Nylon-6 and granular iron powder having a particle size of less than θθ mesh were blended in a weight ratio of is:gs, and mixed in a kneader at 27
The mixture was kneaded and pelletized at 0°C. This was supplied to an injection molding machine, and injected at 270°C and a pressure of 30% to 9/cfI.
A disk of p×3t was manufactured.

4- This disk was installed as a yoke of a disk type flat motor, and its characteristics were measured. The results are shown in Table 1.

For comparison, Table 1 shows one measurement result of the characteristics of an ordinary steel plate and a sintered iron powder yaw of the same shape.

Table l* Efficiency (%) -<J';=〒4〒o)''X/θ
As is clear from Table 1, the yoke material obtained by the method of the present invention has higher efficiency than the iron plate yoke material commonly used in flat motors.

In addition, it has almost the same efficiency as the iron powder sintered yoke, but it is superior in that it has high productivity, can be formed into any shape, and is easy to process.

Patent applicant: Mitsubishi Chemical Industries, Ltd. Representative Patent Attorney Hase - 1 other person -Mar

Claims (1)

[Claims] (1) Iron powder with a particle size of 75 to 95 (
A method for producing a yoke material for a small motor, which comprises injection molding a thermoplastic resin composition containing weight) qb. (21) The manufacturing method according to claim 1, characterized in that a composition comprising iron powder having a particle size of 2SO mesh or less is injection molded.