JPS59143171A - Production of magnetic roll - Google Patents

Abstract

PURPOSE:To obtain a roll having excellent magnetic characteristics by forming plural types of pieces having magnetization facilitating axes set in a specific direction respectively when the resin magnet part of a magnetic roll for development of an electrostatic/photographic developing device is extruded and fixing these pieces to a shaft after combining them. CONSTITUTION:A magnetic field generating coil 15 is provided to a nonmagnetic die 16 of a single-screw extruder. The magnetic powder and binder resin are kneaded and extruded to form extruded pieces having extruded section forms 11 and 12 are corresponding to a shaft 14 of a magnetic roll. These pieces are continuously demagnetized and then cut into a prescribed length respectively, and the piece sections 17 and 18 are fixed to a roll shaft 20 with an adhesive so that a magnetic path can be easily formed. Then the piece is cut in a prescribed size through its outer circumference and end face and magnetized by a magnetizing coil 22 and via a magnetizing yoke 19. Thus a magnetic roll 21 is obtained. This ensures the high magnetic characteristics with large surface magnetic flux density and small variance width of magnetic flux in both directions toward the outer circumference and shaft.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing a developing magnetic roll in a dry developing system of an electrostatographic developing device such as a copying machine and a facsimile machine.

Conventional Structures and Problems Magnetic rolls have conventionally been manufactured by powder metallurgy as sintered products using ferrite powder, but they have had many drawbacks in the manufacturing process as described below.

Since ferrite powder is manufactured by pressure molding, it is difficult to make long pieces with a long length compared to the diameter, and it also shrinks greatly during firing, the shrinkage rate varies, and dimensional accuracy is difficult to achieve. When the body is fired in a firing furnace, it is affected by gravity, and the magnet after sintering tends to warp or strain, and is extremely susceptible to chipping until it is fired. In addition, sintered products are hard and
It has the disadvantage that it is brittle and cannot be processed in a large amount during cutting and grinding for dimensioning, resulting in poor productivity.

Furthermore, electrostatic photographic processing equipment has become smaller in recent years.

In order to reduce weight, magnetic rolls using resin magnets or com-based resin magnets have come into use.

The manufacturing method for this magnet roll is to blend the magnetic material (ferrite powder containing barium, strontium, etc.) and binder resin in a Henschel type mixer, then knead them under heating in a Banbury mixer or roll. After that, a sheet-shaped resin magnet is obtained through sheeting rolls and sheeting, and the resin magnet sheet is wrapped around a rod-shaped shaft and laminated to obtain the specified dimensional accuracy. Magnetic rolls were manufactured by molding and cutting the end faces. This is easier to work with than baked crystal.

Although this is a very effective method for producing magnetine rolls from the standpoint of productivity, it only yields products with moderate magnetic properties. Alternatively, since it is necessary to further improve productivity, there is a need for a magnetic roll with high magnetic properties and high productivity, and a method for manufacturing the same.

OBJECTS OF THE INVENTION In view of the above-mentioned conventional drawbacks, the present invention provides a magnetic roll with excellent magnetic properties and a method for manufacturing the same.

Structure of the Invention The present invention involves aligning the axis of easy magnetization of ferrite powder in a specific direction using an extruder, and continuously extruding pieces of resin magnets to attach them to a shaft in a manner that facilitates the formation of a specific magnetic path. This is extremely advantageous for improving magnetic properties and productivity.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described based on FIGS. 1 to 5.

Example 1 In a 30φ single screw extruder, the material (magnetic powder blending ratio: 90% by weight) was added to each piece having the cross-sectional shape shown in Fig. 1 for applying the magnetic field shown in Fig. 2. Apply a magnetic field in the die (10,○○O Gauss)
After continuous demagnetization, each piece is cut to a predetermined length and attached to the shaft with adhesive to easily form a magnetic path, as shown in Figure 4. 7
) The end face and outer periphery were cut to a predetermined size, and magnetized using a magnetizing yoke shown in FIG. 5 to obtain a magnetic roll.

The surface magnetic properties and productivity of this magnetic roll are shown in Table 1, and it was found that the magnetic roll had high magnetic properties that could be used sufficiently as a magnetic roll, and the productivity was also high.

Example 2 In Example 1, each piece to which a magnetic field was applied was extruded, and thereafter a magnetic roll was obtained in the same manner as in Example 1.

The surface magnetic properties and productivity of this magnetic roll are shown in Table 1. Although the surface magnetic properties were lower than those of Example 1, it was sufficient as a medium magnetic force type magnetic roll. It had usable characteristics.

Comparative Example 1 A magnetic roll having the same dimensions as in Example 1.2 was made using the sheeting method shown in the conventional example, and the results of its surface magnetic properties and productivity are shown in Table 1.

Although the surface magnetic properties (d) were equivalent to those of Example 2, the productivity was much lower.

This example (d) is just one example of many experiments,
Perhaps there was a slight difference in magnetic properties due to processing conditions (extrusion temperature, extrusion speed, etc.), but Example 1 showed higher values overall than Example 2.

Effects of the Invention In this way, the present invention can be obtained by extrusion molding a piece,
It is possible to obtain a magnetic roll by fixing each piece to a shaft, which improves productivity much higher than the conventional method of manufacturing magnetic rolls, and at the same time magnetizes in a specific direction obtained by extrusion by applying a magnetic field. A magnetic roll having high magnetic properties can be obtained by configuring the pieces facing the easy axis in a manner suitable for forming the magnetic path of the magnetic roll.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing an example of the method of the present invention, Fig. 2 is a sectional view of an extruder, Fig. 3 is a front view of a die for applying a magnetic field, a magnetic field generating yoke, and a yoke, and Fig. 4 is a concept of forming a magnetic path. FIG. 5 is a perspective view of the magnetizing yoke. 1...Photosensitive drum, 2...Charging device, 3
...Exposure, 4...Magnetic Rollpe 5
...Developing device, 6...Transfer device, 7...
- Supply paper, 8... Static eliminator, 9... Magnetic roll, 10... Cleaning device, 11.
12...-Extruded piece cross section, 13...-Extruded piece, 14...-Shaft, 15...-Coil,
16...Die (non-magnetic material), 17゜18...
Extruded piece cross section, 19... Magnetizing yoke, 20
...shaft, 21 ...magnetic roll,
22... Magnetizing coil. Name of agent: Patent attorney Toshio Nakao and 1 other person 1st
Figure 2 Figure 4 Figure ef 20

Claims (2)

[Claims] (1) A magnetic roll that is made up of multiple pieces obtained by extruding the resin magnet part of the magnetic roll using an extruder and orienting the axis of easy magnetization in a specific direction during extrusion, and fixing these pieces to the shaft. manufacturing method. (2) The method for manufacturing a magnetic roll according to claim 1, wherein the ferrite powder is extruded in such a way that the axis of easy magnetization of the ferrite powder is oriented in a specific direction inside an extruder die.