JPH0518243B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a permanent magnet having radial anisotropy manufactured by an injection molding method and a method for manufacturing the same.

The purpose of the present invention is to increase the magnetic field generated by the magnetic poles and make the magnetization waveform a sine wave, thereby reducing the cost of radial magnets.
The purpose is to improve performance.

In recent years, products such as information equipment and VTRs have grown rapidly,
Stepping motors and servo motors have come to be widely used as such motors. or,
There is a strong demand for these products to be smaller and lighter.
Naturally, motors are also required to be small, lightweight, and high-output. A radially anisotropic magnet (a magnet having radial anisotropy from the inner circumference to the outer circumference) as shown in FIG. 1 was developed to meet this demand. 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,
In most cases, as shown in FIG. 3, the magnetization waveform becomes a sharp trapezoid of N and S, which causes coking of the motor.

As an improvement plan, as shown in Fig. 4, if a concave is made between the poles and the convex part is magnetized as shown in Fig. 5,
The inner periphery of the magnet has a magnetization waveform close to a sine wave, as shown in FIG. 6, which is known to be a countermeasure against coking in the motor.

However, in the past, the concave part on the inner circumference shown in Figure 4 was cut using a processing machine such as an end mill, which resulted in poor dimensional accuracy due to deformation of the magnet, wear of the cutting tool, and poor positional accuracy of the machine. The cost was extremely high, mass production 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 1 FIG. 7 is a sketch of a 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 performed on part B while being energized, a radially anisotropic magnet as shown in FIG. 8 could be easily obtained. This was done with an outer diameter of 34 mm, an inner diameter of 30 mm, a height of 4.5 mm, and an inner diameter recess depth of 1 mm, low carbon steel was used for part A, and injection molding was performed with both ferrite and rare earth-cobalt magnets.

Embodiment 2 FIG. 9 is a cross-sectional view of a mold, in which a beryllium copper alloy chip, which is a non-magnetic material, is brazed to the C portion 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 tends to pass through the D part in FIG. 10, which has a smaller gap.
Magnetic flux is concentrated in the E section and is exerted in the D section. On the other hand, the anisotropy of the magnet injection molded in the D section is concentrated toward the inner circumference rather than in the complete radial direction, resulting in higher performance than conventional radial magnets that are machined. Become. 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.

Embodiment 3 FIG. 11 shows an example in which unevenness is formed on the outer circumference. Magnetic flux concentrates on the outer circumference of the F section, and the molded magnet also becomes stronger at the F section outer circumference.

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.
High precision was also achieved at the same time.

Note that the present invention is effective regardless of the mold material, the type of magnet, and the number of poles (number of projections and depressions).

As described above, in the present invention, by making the thickness of the portion with a low degree of orientation thinner than the thickness of the portion with a high degree of orientation, molding is possible at low cost, and since the direction of orientation is random, it is virtually unnecessary. Since the magnetic path through which the magnetic flux passes through a portion with a certain low degree of orientation is eliminated, it has the remarkable effect of improving the magnetic flux distribution.

[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 recess. FIG. 5 is an explanatory diagram of the magnet subjected to 8-pole magnetization. FIG. 6 shows the inner circumferential magnetization waveform of the magnet shown in FIG. FIG. 7 is a sketch of the mold of the present invention. Figure 8 is a sketch of the 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.

Claims (1)

[Claims] 1 Apply a non-uniform orientation magnetic field in the radial direction,
A permanent magnet comprising a portion with a low degree of orientation and a portion with a high degree of orientation, wherein the thickness of the portion with the low degree of orientation is made thinner than the thickness of the portion with the high degree of orientation.