JPH0391215A - Manufacture of anisotropic magnet - Google Patents

Abstract

PURPOSE:To safely and economically obtain an anisotropic magnet having excellent magnetic characteristic and stable quality by generating it from a coil for an electromagnet, inducing a magnetic flux in a yoke directed in a mold opening/closing direction, repulsing it in a cavity for forming a molded form, and inducing in a yoke not directed in the mold opening/closing direction. CONSTITUTION:Mixture of magnetic powder, strontium ferrite surface-treated with aminosilane, 6-nylon is kneaded by a biaxial extruder, and granulated as a molding material to be injection molded. The material is injection molded in a cavity 4 of a mold which is composed at the molded form contact face of the cavity of a nonmagnetic material 12 and in which yokes of ferromagnetic material are installed at positions 13, 14, 15, 16 of poles of the outer periphery of the molded form as a predetermined magnet. In this case, before the injected material is charged in the cavity of the mold, an external magnetic field is generated by conducting a coil. Here, a distance between the centers of the cavities is 2.5 to 20 times the outer diameter of the molded form.

Description

[Detailed Description of the Invention] [Scope of Industrial Application] The present invention relates to permanent magnets used in stepping motors of office automation equipment, home appliances, automobiles, etc., developing rolls and cleaning rolls of printers and copiers, etc. The present invention relates to a method for producing an anisotropic magnet in which a permanent magnet is formed by injection or compression molding from a mixture mainly composed of ferromagnetic powder and a polymer compound.

[Conventional technology]

The conventional manufacturing method of anisotropic magnets is described in Japanese Patent Publication No. 56504.
There is a manufacturing method typified by Publication No. 5, but in this method, the coil is installed in the mold, so the mold structure is complicated, resulting in problems in terms of cost, production time, repairs, and poor electrical insulation of the coil. There were safety issues during molded product manufacturing. As another method, JP-A-56-69805 and JP-A-6
There is a manufacturing method typified by Publication No. 0-10610,
In this method, the permanent magnet inserted into the mold is expensive and extremely brittle, so it is easy to crack and chip due to processing and magnetization of the magnet, installation in the mold, molding pressure, etc., and repair of the mold is difficult. It was difficult. Furthermore, there is a method as disclosed in Japanese Patent Application Laid-Open No. 60-10277 in which a permanent magnet and a coil are installed, but this method also has the same problem as described above.

These methods may not be able to satisfy the required magnetic properties depending on the outer diameter and number of poles of the magnet. That is, when the magnetization width of the l pole is 2.5 cm or less, it is extremely difficult to manufacture a mold using the above method.

[Problem to be solved by the invention]

The object of the present invention is to solve the above-mentioned problems,
The present invention provides a safe, economical method for producing anisotropic magnets with excellent magnetic properties and stable quality.

As a result of various studies on the orientation method of anisotropic magnets, the present invention has been developed to achieve an alignment method that can be used in the mold opening/closing direction without arranging magnetic field generating coils or permanent magnets in the mold, regardless of the pole width of the magnet. We discovered that by installing electromagnets to generate magnetic fields that reciprocate only in the same mold, it is possible to obtain a magnet with stable magnetic properties between the cavities even if multiple cavities are placed in the same mold, which led to the present invention. be.

[Means to solve the problem]

The present invention relates to the outer periphery of a molded rod obtained by injection or compression molding a mixture mainly composed of ferromagnetic powder and a polymer compound in a mold having a cylindrical shape or a plurality of cylindrical molding spaces in the presence of a magnetic field. In a method for manufacturing an anisotropic magnet in which a surface is magnetized in the same direction as the anisotropic direction, yokes are installed around the molding space at positions corresponding to the magnetic pole portions, and the magnetic field is applied to the opening and closing of the mold. Magnetic flux is generated from two electromagnetic coils installed in the mold mounting part in the direction, and is guided to the yoke oriented in the mold opening/closing direction, and is repelled by the cavity part that forms each molded product, which is not in the mold opening/closing direction. The present invention relates to a method for manufacturing an anisotropic magnet characterized by using a mold that constitutes a magnetic circuit to be guided to a yoke, and furthermore, the distance between the centers of each cavity forming the molded rod is within the range of the outside of the molded product. The present invention relates to a method for manufacturing an anisotropic magnet characterized by using molds that are separated by 2.5 times or more and 20 times or less the diameter.

The ferromagnetic powder used in the present invention has an average particle size of 500
It refers to ferrites represented by strontium and barium, rare earths represented by samarium-cobalt, neodymium-iron-boron, etc. with a size of 1 micron or more.

Polymer compounds include thermosetting resins such as epoxy and phenol, nylon-6, -12, -66, -46, -11
, olefins such as polyethylene and polypropylene,
Thermoplastic resins such as vinyl chloride, polyurethane, polyester, or copolymers thereof.

Furthermore, as a third substance in the mixture of the ferromagnetic material and the polymer compound, a lubricant such as surface treatment silane of magnetic powder, titanate compound, stearic acid, or low molecular weight polyethylene, etc.
It is possible to include glass fibers, curcum, inorganic fillers such as calcium carbonate, and the like.

The mixture includes a mixture containing a ferromagnetic powder, a polymer compound, and, if necessary, the aforementioned third substance, or a mixture that is melted and kneaded at a temperature higher than the melting point of the polymer compound and processed into granules.

The weight content of the ferromagnetic powder in the mixture is desirably 15 percent or more and 98 percent or less, and particularly in the case of injection molding, 95 percent or less is optimal in consideration of fluidity within the mold.

[For production]

The technical contents of the present invention will be explained according to the drawings.

The molding material is plasticized and melted in the injection cylinder 1 shown in Fig. 1, and filled into the cavity 4.4'' of the mold 3 through the nozzle 2. Due to the magnetic flux induced into the cavity through the yoke 7.7'' in the mold by an externally applied magnetic field generated from 6.6'', the magnetic flux is aligned approximately perpendicular to this magnetic flux.

At this time, the magnetic circuit in this manufacturing method consists of a ferromagnetic pole piece 9, 9'' installed inside the coil 6.6', a yoke 7.7'' in the mold, and a yoke 8.7'' in the mold. 8", a yoke 10.10' installed outside the mold, and a tie bar 1111° of the injection molding machine connected to a pole piece 9.9" installed inside the coil.

Furthermore, the coils are wired so that the generated magnetic field is repelled by the mold cavity.

The cavity inside the mold has a structure as shown in FIG. The contact surface of the molded product in the cavity part is made of a non-magnetic material 12, and the position of the magnetic pole on the outer periphery of the molded product is 13.14.15.
．． A ferromagnetic yoke is installed at 16. Furthermore, the thickness of the non-magnetic portion between the yoke tip 17 and the inner surface of the cavity is adjusted and determined depending on the strength of the magnetic pole at that position.

In the mold structure shown in Fig. 3, in which a plurality of cavities are installed in a direction perpendicular to the axis of the molded product, magnetic fluxes of the same polarity are induced to face each other in the yoke 18 installed between the cavities. Therefore, when the distance between the centers of the cavities is small, the repulsive force within the yoke is strong, and the position of the magnetic pole at this yoke position deviates from the yoke position, and the magnetic force decreases, making it impossible to produce a molded product with desired magnetic properties. I can't get it.

The characteristics of the magnet according to the present invention are shown in FIG. 4 (A), and the case where the distance between the cavities is inappropriate is shown in FIG. 4 (B).

Here, the distance between the centers of each cavity is suitably 2.5 times or more and 20 times or less the outer diameter of the molded product.

If it is less than 2.5 times, the magnetic properties of the magnetic poles between the cavities will be poor, and if it is more than 20 times, the outer shape of the mold will become large, causing problems in terms of economic efficiency.

〔Example〕

A mixture consisting of 100 parts by weight of strontium ferrite with an average particle size of 1ξ croms and 14 parts by weight of 6-nylon with an average molecular weight of 10,000, which was surface-treated with 1 part by weight of Amofusilan per 100 parts by weight of magnetic powder, was passed through a twin-screw extruder. using 260
The mixture was kneaded and granulated at a temperature of °C to obtain a molding material for injection bottom molding.

Using this molding material in the mold shown in Figure 3,
A magnet having the specifications of the molded product shown in the figure is obtained by injection molding into a cavity with a diameter of 14ξ mm, a length of 230 mm, and magnetized with four poles on the outer circumferential surface. At this time, an external magnetic field is generated by energizing the coil before the injected molding material is filled into the mold cavity. If the molded product requires further deburring or secondary processing such as cutting, it may be demagnetized after cooling, or it may be taken out without demagnetization, and if it is subjected to secondary processing after demagnetization, it may be further oriented. A predetermined magnet is created by magnetizing the magnet again at that position. The obtained magnet has extremely uniform magnetic properties also in the length direction, as shown in FIG. It has been recognized that this is an economical method with a simple structure and high productivity in mass production compared to the conventional methods described above.

〔Effect of the invention〕

According to the method of the present invention, it is possible to obtain an anisotropic magnet with uniform magnetic properties in the length direction from a mold with an extremely simple structure, and it is also possible to obtain an anisotropic magnet with uniform magnetic properties in the length direction. This eliminates difficulties such as manufacturing costs caused by structural complexity, difficulty in maintenance and management, concerns about safety, difficulty in modifying molds, and difficulty in adapting to small magnetic pole widths, making it possible to improve industrial performance. This is suitable as a method for manufacturing anisotropic magnets.

The magnet produced by the method of the present invention is used in OA equipment, home appliances, stepping motors of automobiles, etc., developing rolls and cleaning rolls of printers and copiers, and the like.

[Brief explanation of drawings]

Figure 1 is a typical overall structural diagram of the method for manufacturing an anisotropic magnet of the present invention, and Figure 2 is an enlarged view of the cavity part, which is the main part of Figure 1, and the arrow in the figure is from the coil. Indicates the guiding direction of the generated lines of magnetic force. FIG. 3 is a structural diagram of a mold showing one embodiment of the apparatus according to the present invention, and FIG. 4 shows the magnetic characteristics of the outer periphery of a molded product in a conventional embodiment. FIGS. 5 and 6 are graphs showing the characteristics of an embodiment of a magnet used in a mag roll of a copying machine.

Claims (2)

[Claims] (1) The outer periphery of a molded body obtained by injection or compression molding of a mixture mainly composed of ferromagnetic powder and a polymer compound in a mold having a cylindrical shape or multiple cylindrical molding spaces in the presence of a magnetic field. In a method for manufacturing an anisotropic magnet in which a surface is magnetized in the same direction as the anisotropic direction, yokes are installed around the molding space at positions corresponding to the magnetic pole portions, and the magnetic field is applied to the opening and closing of the mold. Magnetic flux is generated from two electromagnetic coils installed in the mold mounting part in the direction, and is guided to the yoke oriented in the mold opening/closing direction, and is repelled by the cavity part that forms each molded product, which is not in the mold opening/closing direction. A method for producing an anisotropic magnet, characterized by using a mold that constitutes a magnetic circuit that guides the yoke. (2) An anisotropic magnet characterized in that a mold is used in which the distance between the centers of the cavities forming the molded body is 2.5 times or more and 20 times or less the outer diameter of the molded product. Production method.