JPH07168447A - Magnet roll and its production - Google Patents

Abstract

PURPOSE:To obtain an inexpensive magnet roll large in joining strength by forming a shaft supporting a cylindrical isotropic ferrite magnet having an outer circumference worked to a prescribed outside diameter of a thermoplastic resin. CONSTITUTION:The resin made shaft 2a is molded by injection molding method so that the thermoplastic resin (ABS resin with 10% glass fiber or an engineering plastic such as polystyrene resin) melted by heating penetrates a permanent magnet member 1 previously set in a metallic mold. As a result, since joining and fixing work using an adhesive is made unnecessary at the time of integrating the hollow cylindrical permanent magnet member 1 with the resin made shaft 2a and further centerless cylinder grinding machining can be adopted in place of cylinder grinding using the shaft as a reference center at the time of cylinder grinding the outer surface of the permanent magnet member 1, the cost is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention, for example, in electrophotography and electrostatic recording, develops by adsorbing and transporting a magnetic developer from a developer tank to a developing area, or magnetic properties remaining on the surface of an image carrier. The present invention relates to a magnet roll used for adsorbing and removing a developer and a method for manufacturing the magnet roll.

[0002]

2. Description of the Related Art Conventionally, a magnet roll used as a developing roll or a cleaning roll in electrophotography, electrostatic recording and the like has a structure as shown in FIGS. 6 (a) and 6 (b). In FIG. 6 (a), reference numeral 1 denotes a permanent magnet member, which is integrally molded into a hollow cylindrical shape from a sintered powder magnet material such as hard ferrite, and a metal shaft 2 having both ends reduced in diameter at the center is coaxial. And is fixed to the substrate via the adhesive layer 3. A magnet roll is obtained by providing a plurality of magnetic poles (not shown) extending in the axial direction on the outer peripheral surface of the permanent magnet member 1. This magnet roll can be used as it is as a developing roll or the like. Further, flanges 6 and 6a are rotatably mounted on both ends of a metal shaft 2 which supports the permanent magnet member 1 through bearings 7 and a sleeve 8 formed in a hollow cylindrical shape is fitted to the flange. By doing so, the magnet roll with sleeve shown in FIG. 6B is assembled. The flange and the sleeve are made of a non-magnetic material such as aluminum alloy or stainless steel. In the above magnet roll, the diameter (D) of the permanent magnet member 1
Is 15 to 60 mm, and the length (L) is 200 to 350 mm.
In many cases ≧ 3D, but a relatively large outer diameter (D ≧ 1
In the case of the permanent magnet member 1 having 8 mm), the structure shown in FIG. 6 is generally used. The above configuration {Fig. 6 (b)}
By the relative rotation between the permanent magnet member 1 and the sleeve (for example, the permanent magnet member 1 is fixed and the flange is rotated), a magnetic developer (for example, a one-component magnetic toner) is attached to the outer peripheral surface of the sleeve. , Or a two-component developer consisting of toner and carrier) is adsorbed to form a magnetic brush, and a predetermined developing operation is performed.

[0003]

When the hollow-cylindrical permanent magnet member 1 having the above structure and the metal shaft 2 are integrated, for example, a sintered powder magnet material (hard ferrite powder or the like) and PVA (polyvinyl). Alcohol) and other binders are kneaded together to form a hollow cylindrical material by isostatic pressing, for example, and then a sintered body is formed through the sintering means, and a foaming adhesive is applied to the outer peripheral surface. Insert the coated metal shaft 2 into the hollow hole of the sintered body, and 100 ~ 200 ℃
Generally, it is heated and fixed. However,
In many cases, the adhesive is not evenly filled in the gap between the permanent magnet member 1 and the metal shaft 2, and there is a problem in that the bonding strength is insufficient or the bonding strength varies. In addition, since excess adhesive often sticks out to the protruding portion of the metal shaft 2 or the end surface of the permanent magnet member 1,
It is necessary to remove and clean this excess adhesive. Therefore, the bonding work is complicated, and the bonding work requires a lot of time and man-hours. Further, in order to ensure the coaxiality between the permanent magnet member 1 and the metal shaft 2, it is necessary to cylindrically grind the outer peripheral surface of the permanent magnet member 1 after the metal shaft 2 is joined. In this case, cylindrical grinding is performed on the basis of the metal shaft 2. However, since the diameter of the metal shaft 2 is relatively small (6 to 10 mm), the grinding amount per unit time can be increased. Therefore, continuous processing is difficult. In addition, the material of the permanent magnet member 1 is usually 1.5
Since the grinding allowance of about 2 mm is provided, there is a problem that a great amount of time and man-hours are required for the grinding process, and the manufacturing cost is increased. On the other hand, in recent years developing devices, the demands for high reliability and cost reduction have become more and more strict, and the above magnet rolls are no exception, and improvements for higher reliability and cost reduction are desired. An object of the present invention is to solve the problems existing in the above-mentioned conventional techniques, and to provide a magnet roll which has a large bonding strength and can be manufactured at low cost. Another object of the present invention is to provide a manufacturing method capable of obtaining a magnet roll capable of cost reduction.

[0004]

In order to achieve the above object, a first aspect of the present invention uses a thermoplastic resin for a shaft that supports a cylindrical isotropic ferrite magnet whose outer periphery is processed to have a predetermined outer diameter. The technical means of forming was adopted.
In the first invention, in a magnet roll in which a shaft of a cylindrical isotropic ferrite magnet whose outer circumference is processed to have a predetermined outer diameter is formed of a thermoplastic resin, a metal collar may be press-fitted into a bearing portion. . According to the first aspect of the invention, in a magnet roll in which a shaft of a cylindrical isotropic ferrite magnet whose outer circumference is processed to have a predetermined outer diameter is formed of a thermoplastic resin, a short metal shaft is press-fitted into a bearing portion Good. A second aspect of the present invention employs a technical means of arranging the ferrite magnet in a mold and forming a resin shaft by injection molding a melt containing a thermoplastic resin inside the ferrite magnet. did.

[0005]

With the above construction, when the hollow-cylindrical permanent magnet member and the shaft are integrated with each other, it is not necessary to perform a bonding and fixing work using an adhesive, and the outer surface of the permanent magnet member is cylindrically ground. So, instead of performing cylindrical grinding based on the shaft, centerless cylindrical grinding can be adopted,
Cost reduction can be realized.

[0006]

1 is a sectional view of a magnet roll showing an embodiment of the present invention, and the same parts as those in FIG. 6 are designated by the same reference numerals. The material of the permanent magnet member 1 shown in FIG. 1 is produced by molding a raw material obtained by dry-mixing Ba ferrite particles and a binder such as PVA into a hollow cylindrical shape by isostatic pressing and sintering the same as in the conventional case. On the other hand, in the material of the present invention, the raw material of the permanent magnet member 1 is a hollow cylindrical shape and a long shape which are obtained by extruding a raw material in which Ba ferrite particles are sufficiently mixed with water and alcohol from an extrusion die to obtain a predetermined material. It may be formed by cutting both ends to the length in the axial direction, drying and sintering. Then, the outer peripheral surface of the material of the permanent magnet member is subjected to centerless cylindrical grinding to finish the outer diameter of the permanent magnet member 1 to a predetermined size. There is no problem if the inner diameter side of the permanent magnet member 1 is finished to a rough size, and the outer peripheral side has a grinding allowance of 0.5 mm by centerless cylindrical grinding.
Since it can be reduced to a small extent, processing cost and material cost can be reduced by about 55% as compared with the conventional one. Then, a thermoplastic resin (engineering plastic such as ABS resin or polystyrene resin containing 10% glass fiber) that has been heated and melted is injected into the cavity of the mold by an injection molding method (not shown) using a mold for injection molding. Then, the resin shaft 2a is molded so as to penetrate the permanent magnet member 1 which is set in the mold in advance. It should be noted that by changing the material from the conventional metal shaft to the resin shaft by injection molding of the present invention and by eliminating the step of bonding the shaft and the permanent magnet member, the manufacturing cost is about It can be reduced by 10-20%. 2 is a cross-sectional view of a magnet roll showing another embodiment of the present invention, and the same parts as those in FIG. 6 are designated by the same reference numerals. When it is necessary to apply a bias voltage from the bearing portion of the shaft or impart wear resistance to the bearing portion, as shown in FIG. 2, after injection molding a resin shaft, the metal short shaft 4 is attached to the metal shaft. It is press-fitted into the end of a resin shaft 2a in which a concave hole is formed in a shape matching the cross section of the short shaft made of metal, or the short metal shaft is previously inserted into a mold for injection molding to injection-mold the resin. do it. 3 shows a perspective view of the metal short shaft 4, the permanent magnet member 1 and the resin shaft 2a when the metal short shaft 4 is press-fitted. FIG. 4 shows another embodiment in the case where a bias voltage is applied from the bearing portion of the shaft or abrasion resistance is required,
The same parts as those in FIG. 6 are designated by the same reference numerals. In the magnet roll shown in FIG. 4, since it is not possible to obtain good electrical conduction only with the resin shaft 2a and the abrasion resistance is low, the metal collar 5 (stainless steel or brass etc.) is used as the resin roll. The shaft 2a is press-fitted into both end bearings. In this magnet roll, one of the collars 5 may be omitted.

[0007]

EFFECTS OF THE INVENTION Since the present invention has the structure and operation as described above, the following effects can be obtained. (1) When the outer surface of the permanent magnet member is ground, centerless cylindrical grinding can be adopted, and the number of processing steps and processing time can be reduced, so that the magnet roll can be manufactured at low cost. (2) The step of bonding the permanent magnet member and the shaft can be omitted, and the magnet roll can be manufactured at low cost, and
The reliability of joining and fixing the permanent magnet member and the shaft can be improved.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a part of a magnet roll showing an embodiment of the present invention.

FIG. 2 is a partially omitted vertical sectional view of a magnet roll showing another embodiment of the present invention.

3 is a perspective view of a permanent magnet member and a metallic short shaft in FIG. 2. FIG.

FIG. 4 is a partially omitted vertical sectional view of a magnet roll showing another embodiment of the present invention.

5 is a perspective view of the metal collar in FIG.

FIG. 6 is a partially omitted vertical sectional view showing an example of a conventional magnet roll.

[Explanation of symbols]

1 Permanent Magnet Member, 2 Metal Shaft, 2a Resin Shaft, 3 Adhesive Layer 4 Metal Short Shaft, 5 Metal Collar, 6, 6a
Flange, 7 bearings, 8 sleeves

Claims (4)

[Claims] 1. A cylindrical isotropic ferrite magnet having an outer periphery machined to have a predetermined outer diameter, and a shaft supporting the ferrite magnet, and the shaft is formed of a thermoplastic resin. Magnet roll. 2. The magnet roll according to claim 1, wherein a metal collar is press-fitted into the bearing portion of the shaft. 3. The magnet roll according to claim 1, wherein a metallic short shaft is press-fitted into the bearing portion of the shaft. 4. A cylindrical isotropic ferrite magnet having an outer periphery processed to have a predetermined outer diameter is disposed in a mold, and a melt containing a thermoplastic resin is injection-molded inside the ferrite magnet. By forming a resin shaft for supporting the ferrite magnet by the method.