JPH05291027A - Magnet roll and manufacturing method thereof - Google Patents

Abstract

PURPOSE:To manufacture the title magnet roll having a substantially effective length and a wide range of magnetic flux density distribution in the longitudinal direction, the magnet roll being used in developing devices such as an electrophotography and a printer. CONSTITUTION:The magnetic flux density distribution (A) in the longitudinal direction of a main body magnet 1 molded by magnetic field oriented extruding step is added by the magnetic flux density distribution (B) of a shaft 2 magnetized in a length shorter than that of the main body magnet 1 to relieve the edge effect and to increase the substantially effective length.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnet roll used for a developing device or a cleaning device of an electronic copying machine, a printer, etc., which has been remarkably miniaturized in recent years, and more specifically, it requires a uniform magnetic flux density distribution in the longitudinal direction. And a manufacturing method thereof.

[0002]

2. Description of the Related Art Since resin-bonded magnets have a lower content of magnetic material than sintered magnets, magnetic particles having anisotropy are orientated in a specific direction in order to obtain high magnetic characteristics. There is. Normally, the particles are oriented so that the entire magnet is magnetized in one direction, but in the manufacture of an integrated multi-pole magnet, a polar anisotropic orientation method (a plurality of magnetic field generation poles are used to obtain a surface magnetic flux density as high as possible). In many cases, a method of orienting magnetic particles in the direction of the magnetic flux lines emitted by the die or die to have a plurality of magnetic poles on the circumferential surface of the magnet is used. Especially when it is long like a magnet roll, it is known that as a forming means, magnetic field oriented extrusion with high productivity because it is easy to obtain a uniform magnetic flux density distribution in the longitudinal direction is generally cylindrical. It was common to insert a shaft into a magnet formed into a shape.

[0003]

However, in the conventional magnet roll, the concentration of the magnetic flux occurs at the end of the magnet due to the edge effect, which causes the phenomenon that the magnetic field strength at the end of the magnet roll rises. The area in which a uniform magnetic flux density distribution can be secured in the longitudinal direction becomes narrower, and it becomes necessary to make the magnet portion longer than the developing area, which causes a problem that the miniaturization of the device is impaired.

A method of devising a magnetizing yoke to alleviate such an edge effect has been considered (Japanese Patent Laid-Open No. 2-194606), but this method is optimized because the structure of the yoke tip is not flat. There was a problem that it was difficult.

The present invention solves the above-mentioned problems of the prior art. By suppressing the edge effect at the end without using a complicated magnetizing yoke, the magnetic characteristics in the longitudinal direction are uniform and the magnet having a wide developing area is provided. It is intended to provide rolls.

[0006]

In order to achieve the above object, the magnet roll of the present invention has a main body magnet made of a material in which a ferromagnetic powder having magnetic anisotropy is dispersed and mixed in a resin. It has a structure in which a shaft having a surface magnetic charge is inserted in a short range.

[0007]

According to this structure, the magnetic flux density distribution in each portion in the longitudinal direction of the magnet roll appears as the sum of the magnetic flux density distribution of the main body magnet and the magnetic flux density distribution of the shaft. That is, only the area where the surface magnetic charge is applied to the shaft is raised, and the edge effect at the end is substantially alleviated. This makes it possible to reduce the difference between the main body magnet length and the actual effective length.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the principle of the present invention will be described with reference to the drawings. FIG. 1 shows a magnetic roll according to the present invention and a magnetic flux density distribution regarding the magnet roll, and FIGS. 2D and 2E show magnetic flux density distributions of a magnet roll as a comparative example. In each figure, 1 is a main body magnet and 2 is a shaft. In the magnet roll of the present invention shown in FIG. 1, a magnet shaft is used as a shaft, and this magnet shaft is a portion which is given a surface magnetic charge only in a range shorter than the length of the main body magnet 1 and is positioned at both ends of the main body magnet. Has no surface magnetic charge. On the other hand, Fig. 2
The magnet roll of the comparative example shown in (d) is a case where a magnet shaft whose magnetizing range is substantially matched with the length of the main body magnet is used, and the magnet roll of the comparative example shown in FIG. This is the case of using a non-magnetized iron shaft that has been conventionally used as the shaft.

In FIG. 1, (a) shows the magnetic flux density distribution in the longitudinal direction of the main body magnet, (b) shows the magnetic flux density distribution in the longitudinal direction of the magnet shaft, and (c) shows the main body magnet through the magnet shaft. It is a magnetic flux density distribution of the magnet roll of the present invention example constructed and installed.

As shown in (a), the magnetic flux density distribution in the longitudinal direction of the main body magnet formed as usual has a high end due to its edge effect. When a magnet shaft having a magnetic flux density distribution as shown in (b) is inserted there by magnetizing within a range shorter than the main body magnet length, only the central part of the magnetic flux density distribution as shown in (c) is inserted. The area where the magnetic flux density distribution is uniform is expanded and the developable area as a magnet roll is expanded compared to when the main body magnet alone is used. As described above, according to the present invention, since the substantial effective range of the main body magnet is widened, the length of the main body magnet can be made shorter than that of the conventional one when the developable region having the required length is obtained.

Hereinafter, the present invention will be further described based on Examples.
Although described in detail, the present invention is not limited thereto. Examples of the magnetic powder of the bond magnet material used for the main body magnet to which the present invention is applied include hexagonal ferrite, SmCo-based alloys, NdFeB-based alloys, SmFeN-based alloys, and the like. Hexagonal ferrite is particularly preferable because it is inexpensive. These magnetic powders have improved moldability,
Appropriate surface treatment for rust prevention is the same as in the usual method for producing a resin-bonded magnet.

The binder resin is not particularly limited, and a typical binder is a mixture of polyvinyl chloride and polyvinyl acetate homo- or copolymer, chlorinated polyethylene, and a suitable plasticizer.

Although the main body magnet to which the present invention is applied has a substantially cylindrical cross-sectional shape, a cut surface or a groove for positioning or the like is provided on the outer peripheral surface and / or the inner peripheral surface alone or together. May be.

In order to give a predetermined magnetic pole to the outer surface of the main body magnet, either of "polar anisotropic magnetic field oriented extrusion" and "method of multi-pole magnetizing after extruding in a non-magnetic field" can be selected.
The former is preferable because a magnet roll having high magnetic properties can be obtained. However, the latter, which is easy to implement, may be selected as long as the desired surface magnetic flux density can be secured. When a particularly thin magnet roll is required, it is recommended to apply the latter method by using magnetic powder having a high saturation magnetization such as an ultra-quenched NdFeB-based magnetic material. Also, a method of magnetizing a desired number of poles after performing the polar anisotropic magnetic field extrusion can be selected.

As the magnet material used for the shaft, the same bond magnet material as that used for the main body magnet can be used. The content of magnetic powder depends on the required magnetic properties, type of magnetic powder,
Although it is determined in consideration of strength and moldability when formed into a shaft, 30 to 70% by volume is desirable. Any plastic can be used as long as the mixture with the magnetic powder exhibits sufficient strength, and various polyamide resins (so-called nylon), polyethylene terephthalate, polyester, acrylic resin, polyphenylene sulfide (PPS),
Examples thereof include polyimide, liquid crystal polymer and bakelite. A filler may be filled to increase the strength.
It goes without saying that other additives for improving moldability and stabilizers for preventing deterioration of the resin are appropriately added. Injection molding and extrusion molding can be used to manufacture long bonded magnets for shafts using these magnetic materials and plastics. Whether or not magnetic field orientation is performed during molding and the number of magnetic poles to be applied may be determined by the required performance of the magnet roll. In particular, if the shaft is diametrically penetratively magnetized through two poles, the magnetic field from it will travel farther than the field of a multi-pole magnetized magnet. Therefore, a large increase in surface magnetic flux density can be expected by adjusting the relative arrangement of the magnet roll and the magnetizing direction of the main body magnet.

In order to magnetize the molded shaft without a magnetic field, a permanent magnet, an electromagnet, or a magnetizer having an appropriate excitation source may be used.

The shape of the cross section of the shaft can be appropriately selected from a round shape and a square shape, but for the purpose of positioning and the like, the cut surface, the groove and the projection may be provided individually or together. Whatever shape is selected, both ends of the shaft must be constructed so that they can be attached to the rotary support (including other components).

Further, the entire shaft does not have to be a magnetic material such as a bonded magnet material, and a magnetic material such as SS41 material may be used except for a range where surface magnetic charge is required. In some cases a non-magnetic material such as aluminum is preferred.
The method of applying a surface magnetic charge to a predetermined range of the shaft is to magnetize only a predetermined range of the shaft molded from the magnetic material, or to provide a cut surface or a groove in the predetermined range of the shaft, and to place the magnetic material here. Is filled and the relevant portion is magnetized. The range in which the surface magnetic charge is applied to the magnet shaft depends on the size of the main body magnet, but is 10 to 1
1 to 6mmφ magnet from the end of the main body magnet
The inside of 5 mm is preferable.

Next, the present invention will be described in detail based on specific examples. (Example 1) Magnetic field oriented extrusion was performed using pellets composed of the compound of (Table 1), and the outer diameter was 16 mm, the inner diameter was 6.05 mm, and the length was 2.
A cylindrical body magnet having a diameter of 20 mm and a magnetic pole number of 4 was obtained.

[Table 1] Next, Strontium ferrite “OP7” manufactured by Nippon Benisha
1 "of 90% by weight and nylon 12 as a binder was used to make a pellet of a bonded magnet compound, which was injection-molded under a non-magnetic field to obtain a round bar having a diameter of 6 mm and a length of 250 mm. This is an electromagnet with a length of 212 m at the center.
Apply a uniform magnetic field of 15 kOe in the radial direction to the range of m
The pole was magnetized to obtain a magnet shaft. After applying an adhesive to the hollow portion of the main body magnet obtained above, this magnet shaft was inserted. The measured magnetic flux density distribution in the longitudinal direction of the obtained magnet roll is shown in FIG. The measurement was performed at a position 9.5 mm from the center of rotation. The developable range obtained therefrom is shown in (Table 2). Further, the portion corresponding to this developable range is shown as a substantially effective range of the magnet roll.

Comparative Example 1 The magnetic flux density distribution in the longitudinal direction of the magnet roll obtained by the same operation as in Example 1 except that the magnetizing range of the magnet shaft was set to 220 mm, which is equal to the length of the main body magnet. The measurement is shown in FIG. The developable range obtained therefrom is shown in (Table 2),
The range on the magnet roll corresponding to this developable range is shown as a substantially effective range.

Comparative Example 2 The magnetic flux density distribution in the longitudinal direction of the magnet roll obtained in the same manner as in Example 1 except that a non-magnetized iron shaft was used was measured.
It is (e). The developable range obtained therefrom is also shown (Table 2), and the range on the magnet roll corresponding to this developable range is shown as a substantially effective range.

[Table 2] As is clear from (Table 2), the magnet roll of this example has a wider range having a uniform magnetic flux density distribution than the comparative examples 1 and 2. As described above, according to the present invention, it is possible to obtain a magnet roll having a uniform magnetic flux density distribution in the longitudinal direction and having a substantially wide effective range.

[0022]

As described above, according to the present invention, in a magnet roll using a magnet shaft in which a magnet material is used for a part or all of the shaft, the length for applying the surface magnetic charge of the magnet shaft is set to be larger than that of the main body magnet. By shortening the length, it is possible to obtain a magnet roll in which the edge effect is alleviated and the effective developing range is substantially wide. As a result, not only the characteristics in the longitudinal direction of the magnet roll become uniform, but also the actual length of the magnet body can be shortened, and the embedded device can be downsized.

[Brief description of drawings]

FIG. 1 shows an external appearance of a magnet roll according to the present invention and a magnetic flux density distribution in a longitudinal direction of a main magnet and a magnet shaft that compose the present magnet roll, the magnetic roll, and (a) shows a magnetic flux density distribution of the main magnet, (B) is the magnetic flux density distribution of the magnet shaft, and (C) is the magnetic flux density distribution of the magnet roll constructed by assembling the main body magnet and the magnet shaft.

FIG. 2 shows the appearance of a magnet roll of a comparative example and the magnetic flux density distribution in the longitudinal direction of the magnet roll of each comparative example,
(D) shows the magnetic flux density distribution of Comparative Example 1, and (e) shows the magnetic flux density distribution of Comparative Example 2.

[Explanation of symbols]

 1 Main body magnet 2 Shaft

Claims (2)

[Claims] 1. A main body magnet made of a material in which a ferromagnetic powder having magnetic anisotropy is dispersed and mixed in a resin, and a shaft to which a surface magnetic charge is applied within a range shorter than the magnet length. And a magnet roll. 2. A long multipole cylindrical resin-bonded magnet extruded in a magnetic field is used as a magnet main body, and a shaft made of a magnetic material is provided in a hollow portion of the magnet main body so that a surface magnetic charge is provided in a range shorter than the main magnet length. A method for manufacturing a magnet roll, which is characterized by inserting after applying.