JPS60124812A - Manufacture of permanent magnet - Google Patents

Abstract

PURPOSE:To obtain the highly efficient radial magnet of excellent dimensional accuracy at low cost by a method wherein the titled permanent magnet is injection-molded in magnetic field using the mold having a roughened surface. CONSTITUTION:The A-part of a mold is a magnetic substance, and it is designed in such a manner that the magnetic flux when a molding process is performed will be radially emitted from inside to outside. A work is performed on the inner mold and protrusions are provided on the circumference using a wire-cutting machine. The mold is closed, an injection molding work is performed on the B-part under the state of magnetic excitation, and a radial anisotropic magnet is obtained in a simple manner. Low carbon steel is used at the A-part, and an injection-molding is performed using ferrite and rate earth cobalt magnet. The inner circumference of the magnet is formed into the magnetizing waveform which is approximate to a sine wave, thereby enabling to have the cogging measure for a motor.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a permanent magnet having radial anisotropy, which is manufactured by injection molding.

The object of the present invention is to provide either an inner periphery or an outer periphery, or
It is an object of the present invention to manufacture a radial magnet which is not circular but has two or more concave or convex portions at a low cost, has high performance, and has high dimensional accuracy.

In recent years, products such as information equipment and VTRs have grown rapidly, and stepping motors and servo motors have come to be widely used as their motors. In addition, these products have strong demands for miniaturization and @footprinting.1 Inevitably, the motors must also be made smaller and smaller.
A lightweight and high-output device is desired. A radial anisotropic magnet (a magnet with radial anisotropy from the inner circumference to the outer circumference) was developed to meet this demand, as shown in Figure 1.
It is. This magnet is used with multipole magnetization of two or more poles as shown in Figure 2. Compared to conventional isotropic magnets, radial anisotropic magnets have a magnetic performance of 1.5 to 2. It is twice as strong, smaller, lighter, and can greatly contribute to higher output.

However, such magnets are difficult to magnetize, and in most cases the magnetization waveform is a clear trapezoid of N-8, as shown in Figure 3, which causes coking in the motor. .

As an improvement plan, as shown in Figure 4, if a concave is formed between the poles and the convex part is magnetized as shown in Figure 5, the inner circumference of the magnet will have a sine wave as shown in Figure 6. The magnetization waveform was close to , and it was known that this could be used as a countermeasure against coking in the motor.

However, in the past, the four parts of the inner periphery shown in Figure 4 were cut using an end mill, etc., which resulted in poor dimensional alignment due to deformation of the magnet, wear of the cutting tool, and poor positioning of the machine. However, the processing cost was very high, the mass productivity was poor, and it had not yet been put into practical use industrially.

The present invention is intended to solve these drawbacks, and makes it possible to manufacture high-performance radial magnets with good dimensional accuracy at low cost by injection molding in a magnetic field into a mold with projections and depressions.

Examples will be explained below.

Example row 1 FIG. 7 is a sketch of the mold of the present invention. Part A is a magnetic material, and is designed so that the magnetic flux during molding is radially diverged from the inside to the outside. The inner mold is machined using a wire cutting machine to create a convex shape on the normal circumference. When the mold was closed and injection molding was carried out on part B while being energized, a radially anisotropic magnet as shown in FIG. 8 could be simply obtained (8) fiii. This was done with an outer diameter of 34 mm, an inner diameter of 30 mm, a height of 4.5 ml, and an inner diameter recess of 1 depth. I went with both.

Implementation 1''2 Fig. 9 is a cross-sectional view of the mold, in which a beryllium copper alloy chip, which is an external material, is soldered to the 0th part to achieve higher efficiency.

That is, in the non-magnetic material C part, the gap with the outer circumferential magnetic material A becomes large, and the magnetic flux during excitation tries to pass through D Hl (FIG. 10), which has a smaller gap, and the magnetic flux concentrates in the E part. The anisotropy of the magnet injection molded in the D part becomes divergent in the D part.
It becomes concentrated towards the inner circumference, resulting in a more concentrated branching performance than a conventional machined radial magnet. In this experiment, compared to the conventional method, the magnetic flux generated at the inner periphery of the D section after magnetizing the magnet was increased by 6.1% for the rare earth-cobalt magnet.

(4) Implementation 115 In Fig. 11, the unevenness was made on the outer periphery. Magnetic flux concentrates on the outer periphery of the 7th part, and the molded magnet also becomes stronger at the outer periphery of the 1st part.

As described above, according to the present invention, a radial magnet with unevenness can be easily manufactured. Moreover, in this experiment, the variation in dimensions was less than 0.03 mm, and high precision was also achieved at the same time.

In addition, the present invention depends on the mold material, the type of magnet, and the number of poles (number of unevenness).
is valid regardless of

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a conventional radial anisotropic magnet. FIG. 2 is an explanatory diagram of the magnet magnetized with eight poles. FIG. 3 shows the inner circumferential magnetization waveform of the magnet shown in FIG. 2. FIG. 4 is an explanatory diagram of a radial magnet having a gate. FIG. 5 is an explanatory diagram of the magnet subjected to 8-pole magnetization.゛Figure 6 is the inner circumferential magnetization waveform of the magnet in Figure 5. FIG. 7 is a perspective view of the mold of the present invention. FIG. 8 is a sketch of a magnet molded with the mold. FIG. 9 is a cross-sectional view of the mold shown in FIG. 7, with a non-magnetic material placed in the convex portion. FIG. 10 is an explanatory diagram of the generated magnetic flux in FIG. 9. FIG. 11 is a cross-sectional view of a mold with a non-magnetic convex portion on the outer periphery. Applicant Suwa Seikosha Co., Ltd. Patent Attorney Tsutomu Mogami

Claims (1)

[Claims] Manufactured by injection molding using a mold that has two or more concavities or convexities on either the inner or outer circumference, or both, of a permanent magnet that has anisotropy in the radial direction. A method for manufacturing a permanent magnet, characterized by: