JPS61230309A - Metallic mold for magnetic field formation - Google Patents

Abstract

PURPOSE:To enable simultaneous anisotropic orientation in both surfaces-- radial and end-- by providing a non-magnetic cavity block forming the upper section of the cavity. CONSTITUTION:Magnetic lines are focused onto a magnetic ring core 16 by a magnetic cavity block 11 after passing a fixed-side template 1. At the same time, part of magnetic lines directly enter the end surface of the cavity block and are flowed along the radial direction of the magnetic cavity block 14 by a non-magnetic, magnetic line prevention section 15 because of contact of the fixed-side cavity block 11 to the external diameter of the movable-side cavity. This time, the magnetic lines go forward straightly at the upper section and are intensely oriented along this direction by a non-magnetic cavity block 9, enabling a simultaneous orientation of the end surface and the radial direction.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention involves injection molding a mixed material of synthetic resin and ferromagnetic powder under the application of a magnetic field, and magnetizing it uniformly in the radial direction and partially in the end face direction. The present invention relates to a molding die suitable for manufacturing a plastic magnet having a ring shape.

[Prior art]

Ring-shaped magnets are often used in rotating machines such as DC motors, generators, hysteresis motors, step parts, and servo motors. In recent years, motors used in floppy disks, ■1, etc. have been equipped with servo functions to improve the accuracy of controlling the number of revolutions. For this purpose, a plane anisotropic magnet is used for rotation detection, and a radial anisotropic magnet is used as a driving magnet. In addition, fan motors and other motors are brushless motors that rotate magnets to eliminate wear on the brushes, and end faces are now used to detect the reversal position of the magnet's poles. There is. Conventionally, magnets with surface anisotropy were attached to the end faces, but in order to make the motor thinner, one magnet has two functions, reducing the number of processes and reducing costs. In order to cope with this tendency, it has been desired to orient the radial and end surfaces at the same time. Conventionally, structures in which only radial orientation is performed are known, for example, in Japanese Patent Application Laid-Open No. 58-151230 and Japanese Patent Application Publication No. 58-7633. Figure 2 is JP-A-58-1
It is a partial sectional view of the molding die described in 51230 gazette. To explain this figure, it is composed of a fixed side template (not shown in the figure) and a fixed side intermediate plate (2) made of magnetic material, and a fixed side intermediate plate (3) having a combination structure of non-magnetic and magnetic materials. It has a combination structure of a fixed side, a non-magnetic material, and a magnetic material.

In Figure 2, the fixed cavity block aυ is in contact with the inner diameter of the cavity (II), so the lines of magnetic force are concentrated on the cavity core (le). At this time, since almost no lines of magnetic force pass through the upper end of the cavity a, the end face It is also possible to extend the fixed cavity block αυ to the outer periphery of the cavity as shown in Fig. The magnetic force at the end face can be made stronger than the structure shown in Figure 2. However, since the movable cavity block a◆ and the fixed cavity block aD are in contact with each other, the lines of magnetic force are Leak,
A large magnetic field is required.

[Purpose of the invention]

The present invention solves the conventional drawbacks, and is made by injection molding a mixed material of synthetic resin and magnetic powder under the application of a magnetic field to create a ring-shaped plastic magnet that is uniformly oriented in the radial direction and the end face direction at the same time. This invention relates to a mold suitable for manufacturing.

[Structure of the invention]

The present invention provides a ring-shaped cavity α in a mold for molding a plastic magnet material mixed with magnetic powder into a ring shape.
1, the diameter of the lower surface in contact with the upper surface of the ring-shaped cavity wall is the same as the outer diameter of the ring-shaped cavity H, and a cylindrical or inverted conical sprue block (υ and the sprue block made of magnetic material) A ring-shaped cavity block (9) made of a non-magnetic material forms a part of the fixed-side intermediate template and the cavity, which is located on the outer periphery of the block αυ and is made of a striped outer periphery α of a non-magnetic material. )
, a cylindrical or conical cavity block α4 made of magnetic material, a cavity outer circumference 0 made of non-magnetic material on the outer periphery of the cavity block I, and a lower surface of the ring-shaped cavity whose center is the same as that of the ring-shaped cavity. The diameter of the upper surface in contact with the ring-shaped cavity is greater than or equal to the outer diameter of the ring-shaped cavity, and the magnetic field line prevention part (1
! This mold for magnetic field forming is characterized by having a movable intermediate mold plate (3) consisting of 9.

The plastic magnetic materials used in the present invention are ferromagnetic powders such as barium ferrite, strontium ferrite, and rare earth metals, olefin resins such as d+7 ethylene, polypropylene, ethylene vinyl acetate copolymer, Surlyn, and pyramid-6, 6-6. Polyamide resin such as ゜12.10, phenylene sulfide (PPS), z
Lysluaone (PS) 1, -1-' IJ ether sulfone (PES), polyether ether ketone (PE
The material is a material kneaded with an engineering plastic such as EK), but the present invention is not limited thereto.

of This invention! One embodiment will be described in detail with reference to the drawings.

FIG. 1 is a sectional view of a two-cavity molding die. The basic structure of this mold is generally a commonly used mold, that is, a so-called 2-plate type mold in the drawings, but when making a multi-point gate, it may be a 3-plate type mold. I don't mind. Figure 1 shows a fixed side template (1) made of magnetic material and a fixed side intermediate template (2) having a combination structure of non-magnetic and magnetic materials.
a fixed side made up of a fixed side, a movable side intermediate template (3) having a combination structure of non-magnetic materials and magnetic materials, and a movable side made up of movable side templates (4, 5, 6) mainly made of magnetic materials. It's getting better. Fixed side template (1) and fixed side intermediate template (
2) is fixed to the fixed plate with the nozzle hole of the injection molding machine,
The movable intermediate template (3) and the movable templates (4, 5, 6) have a two-plate structure that is fixed to the movable plate of the injection molding machine. The sprue (7) is provided on the fixed side as shown in the drawing, and the runner (8) is provided on the surface of the movable side in contact with the fixed side, so that the material flows through one gate on the cavity aQ side of the movable side. It becomes.

The feature of the present invention in this mold lies in the structure of the fixed intermediate mold plate (2) and the movable intermediate mold plate (3). That is, the fixed side intermediate template (2) has a ring-shaped cavity (1 (I
A cavity block I in which the diameter of the lower surface in contact with the upper surface is the same as the outer diameter of the ring-shaped cavity member, the material is a magnetic material, and the shape is cylindrical or inverted conical, and the outer periphery of the cavity block αυ The sprue outer periphery is made of non-magnetic material. In addition, the movable side intermediate template (
3) is made of a magnetic material and has a ring-shaped cavity a,
A ring-shaped cavity block made of a non-magnetic material (
9), in contact with the bottom of the fil cavity block (9),
A cavity block 11, which forms the remaining outer periphery of the cavity a1 and has a cylindrical or conical shape, is located on the outer periphery of the cavity block I and is made of a non-magnetic material. The diameter of the upper surface in contact with the lower surface is larger than the outer diameter of the ring-shaped cavity (1G,
The magnetic force line preventing portion 05 is made of a non-magnetic material and has a cylindrical or inverted conical shape. And, of course, the striped block (11) and the ring-shaped capitei (IG
The center of each of the magnetic force line preventing portions a9 is the same. Next, the usage and effects of the above-mentioned mold will be described.

In FIG. 1, with the mold closed, a coil (not shown) is energized to apply a magnetic field. The magnetic field lines are the fixed side template (
1) When electricity is applied, it is concentrated in the ring core αe of the magnetic material by the cavity block Miko of the magnetic material, and at the same time, since the cavity block I on the fixed side is in contact with the outer diameter of the cavity on the movable side, some lines of magnetic force are drawn from the end surface of the cavity. Directly entering the magnetic field, the lines of magnetic force tend to flow where they flow most easily.

However, since this mold is provided with a magnetic force line preventing portion α9 made of a non-magnetic material, the magnetic force flows in the radial direction of the cavity block I made of a magnetic material. At this time, since there is a cavity block (9) made of a non-magnetic material, the lines of magnetic force travel straight at the upper end and are strongly oriented in this direction. As described above, the plastic magnet material is injected into the mold by the injection molding machine while applying a magnetic field that can simultaneously orient the end face and the radial direction. In this case, the magnetic powder of the plastic magnet is oriented in the direction of the lines of magnetic force by the force of the magnetic field within the ring-shaped cavity α. Next, the magnetic field is removed, the mold is opened, and a ring-shaped plastic magnet that is oriented and magnetized simultaneously in the cooled and solidified end face and in the radial direction can be taken out. If the thickness of the cavity block (9) made of non-magnetic material is too thick, the radial direction becomes weak, and if it is thin, the end face becomes weak. Therefore, it is difficult to achieve this balance, and the magnetic circuit is generally designed and determined according to the application.

〔Effect of the invention〕

By providing a cavity block made of a non-magnetic material that forms the upper part of the cavity, the mold of the present invention eliminates the leakage of magnetic lines of force and at the same time makes the end faces more strongly oriented. The radial surface of the resulting plastic magnet can be used for driving, and the end surface can be used for rotation detection, so both the radial surface and end surface can be made anisotropic at the same time.

〔Example〕

Create molds as shown in Figures 1, 2, and 3, and pour strontium ferrite powder into 88% by weight of amide-12.
Using the filled material, the outer diameter is 391rr1n and the inner diameter is 32m.
, a ring-shaped magnet with a height of 7.5 wm was molded, the end face and inner surface were magnetized with four poles, and the surface magnetic flux density of each was measured. The results are shown in the table below. For the measurement, a Gaussmeter 3251 and a probe 3252-02 manufactured by Yokotsutsu Electric were used.

As described above, by using the mold of the present invention, the end surface can be raised without changing the inner surface.

[Brief explanation of the drawing]

Fig. 1 is a structural sectional view of the magnetic field forming mold of the present invention, Fig. 2 is a partial sectional view of a conventional radial anisotropic mold, and Fig. 3 is a partial sectional view of a partially improved mold. It is a partially sectional view. Patent applicant Sumitomo Bakelite Co., Ltd. Figure 1

Claims (1)

[Claims] In a mold for molding a plastic magnet material mixed with magnetic powder into a ring shape, the center is the same as the ring-shaped cavity, and the diameter of the lower surface in contact with the upper surface of the ring-shaped cavity is the same as the outer diameter of the ring-shaped cavity. A cylindrical or inverted cone-shaped sprue block made of magnetic material, a stationary intermediate template on the outer periphery of the sprue block and made of the sprue outer periphery of non-magnetic material, and forming a part of the cavity, and a sprue block made of non-magnetic material. a ring-shaped cavity block, a cylindrical or conical cavity block made of a magnetic material in contact with the cavity block, a cavity outer periphery made of a non-magnetic material on the outer periphery of the cavity block, and the same center as the ring-shaped cavity; The ring-shaped cavity has a movable-side intermediate template having a diameter of the upper surface in contact with the lower surface of the ring-shaped cavity that is equal to or larger than the outer diameter of the ring-shaped cavity, and is made of a cylindrical or inverted conical magnetic field line prevention part made of a non-magnetic material. A mold for magnetic field forming characterized by the following.