JPS61144808A - Manufacture of resin magnet - Google Patents

Abstract

PURPOSE:To obtain a resin magnet having no cracks and distortion by a method wherein two kinds of metal molds are used when a cylindrical multipolar resin magnet is formed, a multipolar magnet is formed around the shaft inserted into the shaft inserting hole of the metal molds maintaining a distance, then the molded article is transferred to another metal mold, and a multipolar magnet similar to the above is formed between the multipolar magnets. CONSTITUTION:Resin injecting holes 1c and multipolar magnets 3-5 to be used for generation of magnetic field, which are positioned on the outer circumference are provided on the cavity 1b of the first metal mold 1 whereon a plurality of short cylin drical cavities 1b are provided maintaining an equal interval with shaft inserting holes 1a. The shaft 2 of resin magnet is inserted into an inserting hole 1, the magnetic powder such as magnetite and the like and the resin such as polyimide are poured into each cavity 1b, and a molded article 6 wherein said magnets are formed maintaining intervals is obtained. Then, said molded article 6 is transferred to the second metal mold 7 wherein cavities 7b are provided between magnets, magnetic powder and resin are poured into the cavities in the same manner as above, and a cylindrical multipolar magnet, wherein the two resin magnets formed as above are formed in one body, is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a resin magnet, particularly a cylindrical multipolar resin magnet.

[Conventional technology]

Cylindrical multipolar magnets are used as developing rolls in dry type copying machines, and conventionally sintered magnets have been used as magnets for this purpose.

In recent years, so-called resin magnets in which magnetic powder is dispersed in resin have been developed as magnets, and the resin magnets are also being used in the developing rolls of the dry copying machines.

However, manufacturing cylindrical multipolar magnets using resin magnets requires a lot of effort and time, and there are many problems such as high costs. In particular, when the cylindrical multipolar magnet is injection molded all at once, there is a problem in that cracks occur or the outer peripheral surface becomes distorted, resulting in non-uniform magnetic properties.

Furthermore, a shaft is essential for the developing roll of a dry type copying machine, but the above-mentioned tendency becomes noticeable when the shaft is injection molded as one unit, so it is impossible to manufacture the shaft and magnet as one unit. It was said to be.

Therefore, when injection molding a developing roll for a dry type copying machine, a molded product with a temporary shaft is first manufactured, and then the temporary shaft is removed from the molded product, and the part from which the temporary shaft has been removed is The method used was to fit and glue the regular shafts together.

[Problems to be Solved by the Invention] The present invention has been made from the viewpoint of ridges, and its purpose is to replace a cylindrical multipolar magnet with a resin magnet at low cost and in a short time. The purpose of this invention is to provide a method for manufacturing a developing roll of a dry type copying machine, and in particular, even when the developing roll of a dry copying machine is injection molded, even if the shaft and magnet are integrally molded without providing a temporary shaft, cracks may occur or distortions may occur on the outer peripheral surface. It is an object of the present invention to provide a method for manufacturing a resin magnet that does not cause magnetic properties to become non-uniform.

[Means for solving problems]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a first cavity having a shaft insertion hole in the center, and a plurality of cavities, preferably short cylindrical cavities, coaxial with the central axis and separated from each other by an appropriate distance in the axial direction. a step of inserting a shaft into the center of the mold, and injecting resin mixed with fine magnetic powder into each of the plurality of cavities, and a step of taking out the molded product from the first mold;
A step of housing the molded product in a second mold that is different from the first mold, and injecting resin mixed with fine magnetic powder into the cavity of the second mold; This is achieved by manufacturing the molded product through a step of taking it out from a molded product and a step of magnetizing the entire molded product into a multipolar shape.

Note that when injecting the resin mixed with magnetic fine powder into each of the plurality of cavity parts, it is desirable to perform the injection under magnetic field orientation.

[For production]

By manufacturing as described above, a cylindrical multipolar magnet can be manufactured using a resin magnet at low cost and in a short time. In particular, a temporary shaft is provided even when manufacturing a developing roll of a dry type copying machine by injection molding. It becomes possible to manufacture the shaft and the magnet integrally from the beginning without any trouble.

Hereinafter, the details of the present invention will be specifically explained with reference to the drawings.

FIGS. 1 to 4 are explanatory diagrams showing the manufacturing process of a resin magnet according to the present invention.

1 to 4, 1 has a shaft insertion hole 1 in the center.
a, 1a, a plurality of short cylindrical cavities 1 coaxial with the central axis and separated from each other by an appropriate distance in the axial direction.
b, a first mold having 1b, IC1lc is a resin injection hole formed in the first mold 1, and 2 is a resin injection hole formed in the first mold 1.
The shafts inserted into the shaft insertion holes 1a and 1a, 3.4 and 5 are multipolar electromagnets that apply a desired magnetic field to the cavity portions 1b and 1b, and 6 is the molding formed by the first mold 1. 7 is a second mold for filling the space of the molded product 6 with resin for molding; 7a, 7a is a shaft insertion hole formed in the center of the second mold 7; 7b; , 7b is the cavity part of the second mold 7, 7C17C is the cavity part of the second mold 7, and 7C17C is the cavity part of the second mold 7.
The resin injection holes 8 and 9 formed in the mold 7 are the same as those in the second mold.
A multipolar electromagnet 10 that applies a desired magnetic field to the cavity portions 7b, 7b of the mold 7 is a molded product formed by the second mold 7.

In the center of the first mold 1, there are shaft insertion holes 1a, 1a.
is formed, and a plurality of short cylindrical cavities 1b, 1b are formed coaxially with this central axis and separated from each other by appropriate distances in the axial direction. Further, multipolar electromagnets 3.4 and 5 are arranged on the outer periphery of the cavity portions 1b, 1b of the first mold 1 to apply a desired magnetic field to the cavity portions 1b, 1b.

Then, a shaft 2 made of stainless steel, copper or steel is inserted into the shaft insertion hole 1a, 1a of the first mold 1, and a multipolar electromagnet 3. is inserted into the cavity portion 1b, 1b of the first mold 1. 4 and 5 to apply a desired magnetic field, and at the same time apply magnetite, At least one or two or more types of magnetic fine powder selected from the group consisting of alnico, calcium ferrite, barium ferrite, and samarium cobalt are added to polyamide resin, polyester, polypropylene, synthetic rubber NBR, chlorinated polyethylene, etc. Inject the dispersed resin.

Thus, the short cylindrical cavity portions 1 isolated from each other
The resin mixed with the magnetic fine powder injected into the cavities 1b and 1b is caused by the action of the multipolar electromagnets 3.4 and 5 provided on the outer periphery of the cavity portions 1b and 1b, and the magnetic material in the resin is The fine powder is formed into a highly magnetic resin magnet oriented in a desired direction to match the intended use of the magnet.

The molded product 6, in which resin magnets are formed at regular intervals on the shaft 2, is taken out from the first mold 1, and the outer circumferential surface of the molded product 6 is cleaned of debris, small whiskers, etc. The resin magnet portion is once demagnetized.

Thereafter, the molded product 6 is housed in a second mold 7, and a multipolar electromagnet 8 and 9 applies a desired magnetic field, and at the same time disperses the magnetic fine powder into the cavity portions 7b, 7b in each cavity at once or over an appropriate period of time through the resin injection hole 7C17C formed in the second mold 7. Inject the resin.

The molded body 6 is then injected into the hollow portions 7b, 7b in the cavity, and the resin mixed with the magnetic fine powder is used to form the molded body 6.
A resin magnet is molded in the space.

The portion where the resin magnet is molded is operated by multipolar electromagnets 8 and 9 provided on the outer periphery of the cavity portions 7b and 7b, so that the magnetic fine powder in the resin matches the purpose of use of the magnet. It is made of a highly magnetic resin magnet oriented in a desired direction.

The molded product 10 molded by the second mold 7 is taken out from the second mold 7, and the portion molded into the resin magnet is once demagnetized.1. Thereafter, a resin magnet is molded by magnetizing the entire molded product 10 into a multipolar shape.

〔Example〕

Thus, the cavity portions 1b and 7b of the first and second molds 1.7 are each formed to have an inner diameter of 24 mar and a length of 60 m.
The above manufacturing process is carried out by using the first and second molds 1.7 in which a six-pole coil is incorporated in the outer periphery of molds 1.7 and 7b, and inserting the stainless steel shaft 2 into their shaft insertion holes 1a and 7a. According to the process, a molded product 10 was manufactured in which the longitudinal dimension of the portion to be used as a resin magnet was 300 mm.

After that, when the above molded product 10 was magnetized into a multipolar shape using a 6-pole yoke, the magnetic flux density in the multipole was 1400.
A strong and uniform magnet reaching G was obtained. Additionally, there were no visible whiskers or scratches throughout, and the adhesion of the shaft was strong, so no flaws that would pose a practical problem were found.

〔Effect of the invention〕

Since the present invention has a ridge-like structure, according to the present invention, a cylindrical multipolar magnet can be manufactured using a resin magnet at low cost and in a short time, especially when injection molding a developing roll of a dry type copying machine. Since the shaft and the magnet can be manufactured integrally from the beginning without providing a temporary shaft, it is possible to provide the developing roll at low cost. Furthermore, the method of the present invention has the advantage that a small magnet for orientation during injection is sufficient.

Note that the present invention is not limited to the embodiment on ridges. That is, for example, in this embodiment, when molding is performed within the first and second molds 1.7, molding is performed within a magnetic field,
Although it has been explained that the molded products 6 and 10 are demagnetized once after being taken out from the first and second molds 1.7, it is also possible to mold magnets without relying on magnetic field molding. It is also possible to demagnetize it while it is attached to the second mold 1, 7. In addition, although the cavity in the first mold is shaped like a short cylinder, it can be shaped like a top, concave lens, or dish, or have various irregular cross-sections. The position and number of the elements can be freely changed within the scope of the present invention, and the present invention encompasses all of them.

[Brief explanation of the drawing]

FIGS. 1 to 4 are explanatory diagrams showing the manufacturing process of a resin magnet according to the present invention.

Claims (1)

[Scope of Claims] 1) A method for manufacturing a resin magnet comprising the manufacturing steps described in items a) to e) below. a) Insert the shaft into the center of a first mold having a shaft insertion hole in the center and a plurality of cavities coaxial with the center axis and separated from each other by an appropriate distance in the axial direction, and insert the shaft into the center of the first mold. The process of injecting resin mixed with fine magnetic powder into each cavity. b) A step of taking out the molded product from the first mold. c) A step of housing the molded product in a second mold and injecting resin mixed with fine magnetic powder into the cavity. d) A step of taking out the molded product from the second mold. e) A step of magnetizing the entire molded product into a multipolar shape. 2) When injecting the resin mixed with magnetic fine powder in the first and second molds, a magnetic field was applied to the cavity portion, and the molded products were taken out from the first and second molds. A method for manufacturing a resin magnet according to claim 1, wherein the resin magnet is demagnetized each time. 3) The resin mixed with the above magnetic fine powder is magnetite,
Claim 1 or 1, wherein at least one or two or more magnetic fine powders selected from the group consisting of alnico, calcium ferrite, barium ferrite, and samarium cobalt are dispersed in a thermoplastic resin. 2. A method for producing a resin magnet according to item 2.