JPH0452952B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a magnet roll for magnetic brush development used in electrophotographic copying machines and facsimile receivers.

Structure of the conventional example and its problems As shown in Fig. 1, the conventional magnet roll for magnetic brush development consists of integrally molding ferrite particles into a cylindrical shape around a shaft 1, going through a sintering process, and then polishing the outer periphery. Sintered ferrite magnet 2
, and was rotatably incorporated into the cylindrical sleeve 3.

Further, as shown in FIG. 2, a sintered ferrite magnet 4 obtained by polishing and magnetizing a sintered anisotropic magnet into a square prism is radially attached to the outer periphery of the shaft 5. It was configured to be rotatably incorporated within a cylindrical sleeve 6.

However, since both magnet rolls for magnetic brush development require a sintering process, the shrinkage rates of the sintered ferrite magnets 2 and 4 differ partially depending on the sintering conditions, making it difficult to obtain uniform dimensions. It was hot. Further, polishing is required as a post-process, but the sintered ferrite magnets 2 and 4 are brittle and easily damaged, which is a significant disadvantage in terms of yield. Furthermore, in the case of the magnetic brush developing magnet roll shown in Fig. 1, it is very heavy because it is an integral type with a specific gravity of 5.0 to 5.2, and in the magnetic brush developing magnet roll shown in Fig. 2, there is a limit to the shape of the sintered ferrite magnet 4. It was impossible to obtain a compact one due to the limited outer diameter.

In order to improve these drawbacks, magnetic brush developing magnet rolls using resin magnets based on resin or rubber as the magnetic material have come into use.

The method for manufacturing a resin magnet-based magnetic brush developing magnet roll is to mix a magnetic material (for example, ferrite powder containing barium, strontium, or lead, etc.) and a binder resin in a mixer, and then heat it using a Banbury mixer or roll. After kneading, the magnetic material is mechanically oriented while being sheeted with a sheeting roll to obtain a resin magnet sheet, which is then wrapped around a shaft and pressure-formed using a press or the like, or the mechanically oriented resin magnet sheet is A method is to pressure-form multiple magnetic pole pieces with a fan-shaped cross section by stacking them, and then fix the multiple pieces to the shaft using adhesive.Furthermore, a magnetic field is applied externally using an injection molding method or a pressure molding method. A heated plastic magnet composition is placed in a mold, molded into a predetermined piece shape, cooled with the easy magnetization axes of the magnetic powder aligned, and then taken out and attached to the shaft using adhesive. Several methods have been proposed for fixing it. However, all of these methods are batch-type production methods that use adhesives, and are therefore inferior in productivity.

OBJECT OF THE INVENTION The present invention eliminates the above-mentioned conventional drawbacks and improves the magnetic properties, particularly the axis (length) of each magnetic pole.
The present invention provides a method for producing a magnetic brush developing magnet roll with good productivity, which produces a magnetic brush developing magnet roll with uniform and excellent directional characteristics.

Structure of the Invention In order to achieve the above object, the method of manufacturing a magnet roll for magnetic brush development of the present invention includes integrating a cylindrical composite magnet material having at least one end diameter smaller than the center diameter around the shaft. After that, there is a step of heating and raising the temperature, and a step of arranging oriented magnetic poles around the cylindrical magnet member, pressurizing both ends of the magnet member in a cylindrical space larger than the diameter of the central part of the cylindrical magnet member, and forming the magnet in a magnetic field. The method includes the step of rotatably incorporating the formed material into a cylindrical sleeve.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described based on the drawings of FIGS. 3 to 9.

First, as shown in Fig. 3, a cylindrical composite magnet material 7 made of a composite of 90% by weight of barium ferrite powder, which is a magnetic substance, and 10% by weight of a binder consisting of a polymeric material such as polyamide and a lubricant, etc., is made from SUS or the like. It is integrated around the shaft 8. The type and composition ratio of the magnetic material and binder can be selected arbitrarily depending on the required characteristics, but the magnetic material can also be used as a polymer material such as strontium ferrite, lead ferrite, or rare earth magnetic powder. In addition, resins such as polyethylene and polypropylene are useful, and the magnetic material content is selected within the range of 70 to 90% by weight. The diameter A of at least one end of this cylindrical composite magnet material 7 needs to be smaller than the diameter B of the center.
A method of extruding a cylindrical composite magnet material with a uniform diameter to reduce the diameter by cutting only the rear end, or a split piece where the radius of the end is smaller than that of the center, as shown in Figure 4. There is a method in which the shaft 9 is obtained by injection molding or the like and then integrated with the shaft 8 by fitting or the like. In either case, it is desirable for the shaft 8 to be longer than the cylindrical composite magnet material 7 and to have both ends protruding from the perspective of the next process.

Next, this cylindrical composite magnet material 7 is heated using a high-frequency dielectric heating device or a hot air drying device, and the temperature is raised to about 120° C. to 220° C., where it will plastically deform when pressurized, and then it is heated to about 120° C. to 220° C. A mold 12 having a cylindrical space larger than the central diameter B of the cylindrical composite magnet material 7 in which an oriented magnetic pole 10 is arranged between non-magnetic materials 11 as shown in the figure is chucked at both ends and pressure is applied to both ends. Insert it together with the pressure jig 13. Immediately, the mold 12 was placed in an orientation device consisting of the orientation magnetic pole 10 shown in FIG. After the columnar composite magnet material 7 fills the space of the mold 12 and is maintained in this state for 5 to 30 seconds, the current in the coil 15 is turned off and the mold 12 is taken out from the orientation device and cooled. After the temperature of mold 12 has cooled down to about 100℃ or less, mold 1
Open 2 and take out the cylindrical magnet.

The cylindrical magnet 16 obtained in this way is
As shown in the figure, a magnet roll for magnetic brush development in one embodiment of the present invention can be obtained by rotatably attaching it inside a cylindrical non-magnetic sleeve 17. An example of the longitudinal magnetic properties of the magnetic brush development magnet roll obtained in this way is shown in FIG. 8, and the obtained surface magnetic flux density is high and has excellent linearity.

As a comparative example that more clearly shows the effects of the present invention,
Figure 9 shows the magnetic properties of a magnet roll for magnetic brush development obtained by orienting a cylindrical composite magnet material with the same material composition and uniform end diameter and center diameter in a pressurized magnetic field under the same processing conditions. However, the characteristics of the end portion were poor and the linearity was poor.

Effects of the Invention As described above, according to the present invention, it is possible to integrate a composite magnet material made of a resin magnet on the outer circumferential surface of a shaft without using an adhesive, and moreover, a surface magnetic flux with high and uniform characteristics in the length direction can be achieved. This has the effect of making it possible to obtain a magnet roll for magnetic brush development with excellent density, that is, excellent magnetic properties, and is of great industrial value.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views of a conventional magnetic brush developing magnet roll, and FIG. 3 is a schematic configuration diagram showing a cylindrical composite magnet material in an embodiment of the magnetic brush developing magnet roll of the present invention. Fig. 4 is a perspective view of a divided piece constituting a cylinder, Figs. 5 a and b are a side view and a sectional view showing an embodiment of the mold used in the present invention,
FIG. 6 is a schematic configuration diagram of an embodiment of the orientation device used in the present invention, FIG. 7 is a cross-sectional view of a magnet roll for magnetic brush development according to the manufacturing method of the present invention, and FIG. 8 is a diagram showing the magnetic brush development according to the present invention. FIG. 9 is a characteristic diagram of a magnet roll for magnetic brush development not according to the present invention. 7...Cylindrical composite magnet material, 8...Shaft,
9...Divided piece, 10...Oriented magnetic pole, 11...
... Non-magnetic material, 12 ... Mold, 13 ... Pressure jig,
14...magnetic pole, 15...coil, 16...sleeve.

Claims (1)

[Claims] 1. A cylindrical composite magnet material having at least one end diameter smaller than the center diameter is integrated around the shaft, heated to a high temperature, and oriented magnetic poles are arranged around the shaft. A method of manufacturing a magnet roll for magnetic brush development, characterized in that both ends are pressurized and formed in a magnetic field, and then assembled into a cylindrical sleeve.