JPH0126418Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a mold for forming a magnetically anisotropic resin magnet.

2. Description of the Related Art When molding a magnetically anisotropic resin magnet, a mold as shown in FIGS. 3 and 4, or 5 and 6 is conventionally used.

In the former method, a coil 2 made of copper wire wound around a yoke manufactured to the desired orientation is placed inside a core 1 made of a ferromagnetic material, and a large current is passed through the coil 2 to fill a cavity 3 with resin magnet molding material 4. It is oriented before it solidifies. A ring 5 made of a non-magnetic material is attached to the outer periphery of the core 1, and since the cavity 3 on the outer periphery of the resin magnet to be molded is made of a non-magnetic material, the magnetic flux flows as shown by the arrows in Fig. 3. , a predetermined orientation is performed.

However, with the above molding die, (1) a large current (5 to 50 A) cannot be continuously passed through the copper wire, and the magnetomotive force for orienting the magnets is insufficient;

(2) Because the coil is placed inside the mold, it is not possible to produce a large number of molded resin magnets compared to a normal radial orientation mold as explained in Figures 5 and 6, resulting in lower cost performance. bad.

(3) Space is required to wind the coil (copper wire), and molded products with small diameters often lack the number of turns of copper wire, so resin magnet molded products often lack magnetic performance.

Next, the mold shown in FIGS. 5 and 6 has a core 1 and a cavity 3 made of a ferromagnetic material, and a core 1
The magnetic flux flowing through the magnet flows into the cavity 3 through the filled resin magnet molding material 4 (arrows indicate the flow of magnetic flux), thereby radially orienting the molded product.
Members 6 and 7 are made of non-magnetic material and guide the flow of magnetic flux. 8 is an ejection pin of the molded product.

With this mold, when obtaining a molded product in which the outer surface area of the resin magnet is larger than the cross-sectional area of the core 1 (high L/D molded product), the core part becomes magnetically saturated and the magnet on the outer surface is damaged. Since the magnetomotive force for orientation is insufficient, there is a problem of poor magnetic properties.

For example, in FIG. 7, if the inner radius of the resin magnet ⁹ is _r1 , the outer radius is _r2 , and the height is l, then L/D= _2πr2l / _πr12 = _2r2l / _r12 ^. It will be done.

When r ₁ = 6.5 mm, r ₂ = 10 mm, and l = 16 mm, L/D = 2 x 10 x 16/6.5 ² ≒ 7.6.

If the core part is saturated at 18000G, the outer surface of the resin magnet 9 will have a magnetomotive force of 18000/7.6≒2400Oe, and the magnetic field required for orientation (iHc x 2 to 3),
In other words, it will be insufficient for 5000 to 7500 Oe.

Problems to be Solved by the Invention As mentioned above, conventional molding dies lack sufficient magnetomotive force during molding, resulting in the problem that the magnetic properties of resin magnet molded products are insufficient. /D
It is an object of the present invention to provide a molding die which can obtain a molded product with high magnetic properties even in the case of a radially oriented molded product, and which can also mold a large number of pieces.

Means for Solving the Problems In order to achieve the above object, the present invention employs the following structure of a molding die.

That is, in a mold made of a ferromagnetic material, the material of the mold cavity around the outer periphery of the resin magnet to be molded is replaced with a non-magnetic material at regular intervals.
It is characterized in that its specifications match the magnetic direction in which the molded resin magnet is magnetized in a subsequent process.

Effects According to the present invention, when the magnetic flux passing through the mold core made of ferromagnetic material flows toward the cavity side through the resin magnet molding material filled in the cavity, it can be concentrated in the ferromagnetic material portion. That is,
In the outer peripheral portion of the resin magnet where the cavity is molded, magnetic flux is concentrated in the ferromagnetic material portion between the non-magnetic material portion whose material has been replaced and the adjacent portion, and the magnetomotive force of this portion can be increased. Therefore, by matching the specifications with the magnetic direction during magnetization in the subsequent process, a resin magnet with excellent magnetic properties can be obtained.

Embodiment Next, an embodiment of the present invention will be described with reference to FIGS. 1 and 2.

In a molding die consisting of a core 1 made of a ferromagnetic material and a cavity 3, the cavity material around the resin magnet molding material 4 that is filled into the cavity 3 and molded is partially replaced with a non-magnetic material at equal intervals. did. The nonmagnetic material portions 10 are arranged at ten equally spaced locations around the filled resin magnet molding material 4, and the area ratio with the ferromagnetic material portions therebetween is 1:1.

The magnetic flux passing through the core 1 flows into the cavity 3 through the filled resin magnet molding material 4, but it is concentrated in the ferromagnetic material part between the non-magnetic material parts 10, and the magnetomotive force is Figures 5 and 6
(Fig.) is twice as large.

A resin magnet having the dimensions illustrated in FIG. 7 was molded using the mold described above, and the average value of the surface Br after magnetization with 10 outer circumferential poles was ±950G. On the other hand, Figures 5 and 6
A resin magnet of the same dimensions as above, molded using the mold shown in the figure, was similarly magnetized with 10 poles on the outer circumference, and then the surface Br
The average value of is ±850G, and the present invention was able to improve the characteristics by 12%.

Effects of the Invention As described above, the present invention can obtain high magnetic properties even in a high L/D radially oriented resin magnet, and the mold structure does not have a built-in coil, as shown in Fig. 5. The radial orientation specifications are almost the same as the conventional one shown in FIG. 6, and the practical value is extremely great in that it is also possible to produce multiple pieces.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of the main part showing an embodiment of the present invention, Fig. 2 is a longitudinal cross-sectional view of the main part, Fig. 3 is a cross-sectional view of the main part of a conventional molding die, and Fig. 4 is a cross-sectional view of the main part of the same. A vertical cross-sectional view, FIG. 5 is a cross-sectional view of the main part of another conventional molding die, and FIG.
The figure is a longitudinal sectional view of the same essential part, and FIG. 7 is a perspective view of the resin magnet to be molded. 1 is a core, 3 is a cavity, 4 is a resin magnet molding material, and 10 is a non-magnetic material section.

Claims (1)

[Scope of utility model registration request] In a mold made of ferromagnetic material, the material of the mold cavity around the outer periphery of the resin magnet to be molded is replaced with a non-magnetic material at regular intervals, and the specifications are adjusted to match the molded resin magnet in a later process. A mold for forming a magnetically anisotropic resin magnet, characterized in that the mold matches the magnetic direction when magnetized.