JPH04245608A - Magnetic field orientation molding press - Google Patents

Abstract

PURPOSE:To improve surface magnetic field even for a sintered magnet, by decreasing the area of the magnetic field applying surface of one magnetic pole of a main pole or an opposite pole which are arranged so as to face each other via a cavity, as compared with the other pole. CONSTITUTION:While synthetic resin magnet material introduced in a cavity 1 is in a softened state, a magnetic field is applied. Magnetic lines of force permeate said material so as to converge in the central lower part in the cavity 1. Magnetic powder in the magnetic material converges, along the direction of the magnetic lines of force, in the central part of the lower part of the cavity. As to the shapes of a main pole 3 and an opposite pole 4, the area of one magnetic field applying surface is made narrower than the other. Thereby magnetic field is made to converge above the central part of an action surface of a magnet, and the magnetic flux after magnetization can be concentrated, so that the surface magnetic field on the action surface of a magnet can be remarkably increased.

Description

[0001] [Industrial Application Field] This invention relates to a magnetic field orientation molding machine for manufacturing anisotropic magnets, and in particular, it can be used to effectively control the orientation direction of magnetic particles in synthetic resin magnets or sintered magnets. The objective is to improve the surface magnetic field on the working surface of the magnet after magnetization by controlling the magnetic field. [0002] As magnets for health appliances, rare earth or ferrite sintered magnets or plastic magnets have so far been used. Among the above magnets, those with particularly strong surface magnetic fields are rare-earth sintered magnets, followed by rare-earth plastic magnets.Compared to these, ferrite-based sintered magnets have somewhat better performance, and ferrite-based plastic magnets have considerably inferior performance, and each has been used differently depending on its purpose. In other words, expensive rare earth magnets have been used for high-grade applications, and low-cost ferrite magnets have been used for low-grade applications, but in any case, the direction of the magnetic field lines in the magnetically oriented molds used to manufacture them is the thickness direction, so Since the orientation direction of magnetic particles is also in the thickness direction,
Magnetic properties were determined by the quality of the raw materials used. As described above, plastic magnets have the advantage that they can be easily molded into complex shapes, are lightweight, and can be molded in one piece, but compared to sintered magnets, the surface magnetic field of the magnet is lower and the attraction force is lower. I was left with problems in my weak areas. SUMMARY OF THE INVENTION It is an object of the present invention to not only advantageously solve the above-mentioned problems of plastic magnets, but also to improve the surface magnetic field of sintered magnets, which are generally considered to have good magnetic properties. Our goal is to propose a magnetic field orientation molding machine that can achieve further improvements in performance. [Means for Solving the Problems] That is, the present invention provides a magnetic field orientation molding machine that applies a magnetic field to a magnetic material introduced into a cavity of a molding die and orients magnetic particles in the material in a predetermined direction. In this magnetic field orientation molding machine, the area of the magnetic field application surface of either the main pole or the counter pole, which are arranged facing each other with the cavity in between, is reduced compared to that of the other magnetic pole. The magnetic field orientation molding machine of the present invention is particularly suitable for use in producing synthetic resin magnets and sintered magnets. For example, when manufacturing synthetic resin magnets, any conventionally known magnetic powder such as ferrite magnetic powder or rare earth magnetic powder can be used, and the particle shape has an average particle size of about 1.5 μm and a compressed density of 3. .20 or more is preferred. Furthermore, as for the synthetic resin, any conventionally known synthetic resin can be used, and representative examples thereof are as follows. Polyamide-based synthetic resins such as polyamide-6 and polyamide-12. Polyvinyl chloride, vinyl chloride vinyl acetate copolymer, polymethyl methacrylate, polystyrene,
Single or copolymerized vinyl-based synthetic resins such as polyethylene and polypropylene. Synthetic resins such as polyurethane, silicone, polycarbonate, PBT, PET, polyetheretherketone, chlorinated polyethylene and Hypalon. Rubbers such as propylene, neoprene, styrene butadiene and acrylonitrile butadiene. Epoxy resin. Phenolic synthetic resin. Furthermore, the blending ratio of magnetic powder and synthetic resin as a binder is magnetic powder: 90
On the other hand, synthetic resin: desirably about 10. In addition, it goes without saying that conventionally used plasticizers, antioxidants, surface treatment agents, and the like can be used in appropriate amounts depending on the purpose. On the other hand, any conventionally known sintered magnet is suitable. [0008] According to the present invention, the surface magnetic field is improved by modifying the magnetic circuit of the molding die and controlling the orientation direction of magnetic particles in the magnet material. Specifically, by reducing the area of the magnetic field application surface of either the main pole or the counter pole, which are arranged to face each other across the cavity, compared to the other, the lines of magnetic force inside the mold cavity can be reduced. It focuses it in a predetermined direction. In this way, the orientation direction of the magnetic particles of the magnetic material charged into the cavity can be aligned in the direction of the lines of magnetic force, that is, it can be focused above the center of the working surface of the magnet, so that the magnetic flux after magnetization can be narrowed down. As a result, a significant improvement in the surface magnetic field at the working surface of the magnet is realized. FIG. 1 schematically shows a preferred example of a magnetic field orientation molding machine equipped with an injection mold according to the present invention. In the figure, number 1 is a cavity provided in a die 2, 3 is a main pole, and 4 is a counter pole. (auxiliary pole), and in this example, the area of the magnetic field application surface of the counter electrode 4 is reduced compared to that of the main pole 3, while the cavity 1 has an inverted truncated conical shape. Further, 5 is a fixed plate, 6 is a tie bar, 7 is a movable plate, and 8 is an excitation coil, and the direction of the lines of magnetic force is indicated by an arrow in the figure. Note that 9 is a nozzle touch, 10 is a sprue runner, 11 is an ejection pin, and 12 is an ejection plate. In the figure, a ferromagnetic material is used for the main pole 3, counter electrode 4, fixed plate 5, tie bar 6, movable plate 7, ejector pin 11 and ejector plate 12, while a non-magnetic material is used for the die 2. It will be done. Here, as the ferromagnetic material, carbon steel such as S55C, S50C, S40C, SKD1
1. Die steel such as SKD61, other pamendur,
Although pure iron or the like can be used, it is more advantageous to perform surface hardening treatment to improve wear resistance. On the other hand, non-magnetic materials include stainless steel, copper beryllium alloy, high manganese steel,
Bronze, brass, non-magnetic super steel N-7, etc. are advantageously suitable, and it is also advantageous to subject these to surface hardening treatment if necessary to improve wear resistance. Now, in the place shown in FIG. 1, when a magnetic field is applied to the synthetic resin magnet material introduced into the cavity 1 by injection molding while it is in a softened state, the lines of magnetic force are The magnetic particles in the magnet material are oriented along the direction of the lines of magnetic force so as to be focused at the center below the cavity. Here, the shape of the main pole and the counter electrode is such that the area of one magnetic field application surface is smaller than the area of the other magnetic field application surface. For example, when the area of the counter electrode is made narrower than the area of the main pole, Variations as shown in FIGS. 2a and 2b are possible. Furthermore, in the above example, the case where the cavity shape is an inverted truncated cone was mainly explained, but the cavity shape is not limited to this case, and the cavity shape is also a conical shape in which the area of the main pole and the area of the opposite pole are reversed. Including the trapezoid, Figure 3 (a
), (b) and (c), such as polygonal truncated pyramids and quadrangular truncated pyramids, and hemispherical truncated pyramids, as shown in (d) and (e) of the same figure. It may be a cylinder or a rectangular parallelepiped, and the point is that the direction of the magnetic lines of force within the cavity may be focused on either the upper or lower surface of the cavity. However, the slope slope of the cavity is
It is particularly preferred that the direction be equal to the direction of the magnetic lines of force occurring within the cavity. This is because, if the slope gradient is as described above, magnetic leakage from the magnet slope will be minimized in the case of a magnetic product, and the surface magnetic field on the working surface can be maximized. Although we have explained the case where an injection molding mold is mainly used as the mold, if the necessary parts of the magnetic circuit mold are changed for other molding purposes, a compression molding mold as shown in Fig. 4, or even a compression molding mold as shown in FIG. Needless to say, an extrusion mold can be used. In addition, in the place shown in FIG. 4, number 13 is the molding machine frame (magnetic material) that also serves as the yoke of the magnetic circuit, 14 is the upper punch plate bush (magnetic material), 15 is the upper punch plate (magnetic material), and 16 is the molding machine frame (magnetic material). Die control cylinder, 17 is upper punch (magnetic material),
18 is a lower punch (magnetic material), 19 is a die (non-magnetic material),
20 is a die plate (non-magnetic material), 21 is an upper coil, 2
2 is a lower coil, and 23 is a molded body. EXAMPLE Using a magnetic field orientation molding machine equipped with the injection mold shown in FIG. 1, a truncated cone-shaped synthetic resin magnet having the dimensions shown in FIG. 5 was molded under the following conditions. The orientation direction of the magnetic particles of the synthetic resin magnet is as indicated by the arrow in the figure. Raw materials/magnetic powder: Ferrite magnetic powder (magnetoplumbite strontium ferrite with average particle size of 1.5 μm/Synthetic resin: Polyamide 12/Plasticizer: TTS (isopropyl triisostearoyl titanate) Plamag combination/Magnetic powder: 66 vol%/Polyamide 12 : 33 vol% ・TTS: 1 vol% Molding conditions ・Magnetic field in cavity: 1 to 1.4 × 104 Oe
・Mold temperature: 100 ℃ ・Injection cylinder temperature: 300 ℃ ・Injection pressure: 1.5 ton/c
m2 Basic magnetic circuit 1-1, 1-2 and 1-3 (compatible examples) and 1-4 (comparative example) shown in Figure 6 [0017] Table 1 shows the results of investigating the surface magnetic field of the obtained magnetic products. show. [Table 1] [0019] As is clear from the same table, by using the magnetic field orientation molding machine according to the present invention to focus the magnetic powder in the synthetic resin magnet above the magnet working surface, the magnetic particles on the working surface are The surface magnetic field can be significantly improved. [0020] In the above embodiments, the case where a synthetic resin magnet is manufactured using a magnetic field orientation molding machine equipped with an injection molding mold has been mainly explained. Using a magnetic field orientation molding machine, synthetic resin magnets and even green for sintered magnets can also be produced in the same manner. [0021] Thus, according to the present invention, the magnetic particles in the magnet material can be effectively oriented in a predetermined direction, and the surface magnetic field on the working surface of the permanent magnet after magnetization can be increased more than before. It can be improved significantly.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a magnetic field orientation molding machine equipped with an injection mold according to the present invention.

FIG. 2 is a diagram showing a combination of a main electrode and a counter electrode in the present invention.

FIG. 3 is a diagram showing a preferred shape of a cavity according to the present invention.

FIG. 4 is a schematic diagram of a magnetic field orientation molding machine equipped with a compression molding mold according to the present invention.

FIG. 5 is a diagram showing dimensions and shapes of synthetic resin magnets produced in Examples.

FIG. 6 is a diagram showing a combination of a main electrode and a counter electrode and a cavity shape in an example.

[Explanation of symbols]

1 Cavity 2 Die 3 Main pole 4 Counter electrode (auxiliary electrode) 5 Fixed plate 6 Tie bar 7. Moving board 8 Excitation coil 9 Nozzle touch 10 Sprue runner 11 Eject pin 12　Protrusion plate 13 Molding machine frame 14 Upper punch plate bush 15 Upper punch plate 16 Die control cylinder 17 Upper punch 18 Lower punch 19 Die 20 Die plate 21 Upper coil 22 Lower coil 23 Molded object

Claims (1)

[Claims] 1. A magnetic field orientation molding machine that applies a magnetic field to a magnetic material introduced into a cavity of a molding die to orient magnetic particles in the material in a predetermined direction, the machine comprising: A magnetic field orientation molding machine characterized in that the area of the magnetic field application surface of either the main pole or the counter pole is reduced compared to that of the other magnetic pole.