JPH10123839A - Magnet roll - Google Patents

Abstract

PROBLEM TO BE SOLVED: To raise the magnetic flux density of a specific magnetic pole without causing an increase in cost by fixing a unidirectionally oriented auxiliary magnet over the almost whole length in the magnet main body shaft direction, to a part in the peripheral direction of the pole anisotropically oriented main body magnet. SOLUTION: In this magnetic roll, in order to raise the magnetic flux density of a specific magnetic pole of the pole anisltropically oriented main body magnet 2, the unidirectionally oriented auxiliary magnet 7 is fixed in a groove disposed on the magnetic pole forming position of the pole anisotropically oriented main body magnet 2, so as to let its magnetized direction matching with the magnetized direction of the reinforcing magnetic pole. In such a manner, the magnetic field on the section that the unidirectionally oriented auxiliary magnet 7 is fitted, becomes to the vector composite magnetic field of the magnetic field by the main body magnet 2 and the magnetic field by the auxiliary magnet 7, the asymmetry and the flux density of the magnetic field pattern can be raised. In order to further raise the magnetic field pattern, it is preferable that the auxiliary magnet 7 is deeply buried in the deep part reaching close to the metallic shaft 3.

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 magnetic cylinder incorporated in a copying machine, a facsimile, a laser printer or the like.

[0002]

2. Description of the Related Art Magnetic cylinders are used in developing devices and cleaning devices incorporated in electrophotographic copying machines, facsimile machines and laser printers. As shown in FIGS. 6 and 7, the magnetic cylinder 51 has a structure in which a magnet roll 54 configured by penetrating a shaft 53 through a cylindrical columnar magnet 52 is rotatably supported in a cylindrical sleeve 55. Also recently developed ones include:
In some cases, the surface of the magnet roll 54 is used as a developer transport surface without the cylindrical sleeve 55.

As the magnet roll 54, there are a type formed by sticking rod-shaped sintered magnet pieces in the circumferential direction, and a type formed by forming a cylindrical or cylindrical resin magnet using a resin containing magnetic powder. The latter is becoming mainstream because of its excellent mass productivity, arbitrary shape, and low production cost.

Incidentally, a magnet roll made of a resin magnet has a lower magnetic force than a sintered magnet because it contains a resin component.
For this reason, at the time of magnet roll production, after magnetic field orientation molding is performed and magnetic powder is anisotropically oriented for each pole,
Re-magnetization (hereinafter referred to as extremely anisotropic orientation) has been performed.

[0005]

The magnet roll oriented extremely anisotropically can exert a higher magnetic force than a magnet roll oriented isotropically, but still has a lower magnetic force than a sintered magnet. In particular, in the case of using a soft resin such as a vinyl chloride-based resin or a rubber-based material as the binder, the amount of the magnetic powder to be mixed is limited due to the moldability, and the resulting magnetic force is insufficient. In addition, the magnetic poles provided on the magnet roll are classified into a developing pole, a transport pole, a regulating pole, a collecting pole, and the like.
The magnetic field patterns of these magnetic poles need to be asymmetrical as necessary. However, in the case of a magnet roll oriented in a very anisotropic manner, the magnetic field pattern of each magnetic pole becomes symmetric as shown in FIG. There was a problem that could not meet the demands. Due to these circumstances, in a conventional magnet roll with anisotropic orientation, toner fogging occurs in a one-component magnetic toner, and carrier fogging occurs in a two-component developer,
This has led to a decrease in image quality. Such a problem can be solved by combining only unidirectionally-oriented sintered magnet pieces or resin magnet pieces, but there is a problem in that the method using only the magnet pieces alone is expensive.

SUMMARY OF THE INVENTION The present invention has been made in view of the above situation, and can increase the magnetic flux density of a specific magnetic pole without increasing the cost, and can asymmetrically change the magnetic field pattern of the specific magnetic pole without increasing the cost. It is an object of the present invention to provide a magnet roll capable of forming a shaped magnetic field pattern.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an auxiliary anisotropic magnet which is oriented unidirectionally over a part of the circumferential direction of a main magnet which is extremely anisotropically oriented over substantially the entire axial length of the main magnet. The feature is that the magnet is fixed. The auxiliary magnet is a resin magnet containing rare earth
It is a sintered magnet or the like, and is appropriately selected depending on required characteristics.

When it is desired to strengthen the specific magnetic field, the magnetization direction of the auxiliary magnet is made to substantially match the magnetization direction of the corresponding portion of the main body magnet to which the auxiliary magnet is fixed.

When it is desired to form a magnetic field pattern of a specific magnetic pole into an asymmetric magnetic field pattern, the magnetization direction of the auxiliary magnet is made different from the magnetization direction of a corresponding portion of the main body magnet to which the auxiliary magnet is fixed, or the auxiliary magnet is magnetized. Is fixed to a position biased to one side of the symmetric magnetic field.

[0010]

The magnetic field at the place where the auxiliary magnet oriented in one direction is attached becomes a vector composite magnetic field of the magnetic field generated by the main body magnet and the magnetic field generated by the auxiliary magnet, which can make the magnetic field pattern asymmetric and increase the magnetic flux density.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will now be described with reference to the illustrated embodiments. FIG. 1 shows a magnetic cylinder 1 incorporating a magnet roll 4 of the present invention. In this figure, 3 is a metal shaft, and 5 is a sleeve made of a non-magnetic metal such as aluminum. In this embodiment, in order to increase the magnetic flux density of a specific magnetic pole of the main magnet 2 which is extremely anisotropically oriented, the auxiliary magnet 7 which is unidirectionally oriented as shown by a white arrow in the drawing is provided with a main anisotropically oriented main body. The magnet 2 is fixed to a groove provided at a position where the magnetic pole is formed, in such a manner that the magnetization direction of the magnet is substantially coincident with the magnetization direction of the magnetic pole for enhancing the magnetization direction.

The grooves are formed at the same time as the main body magnet 2 is formed by injection molding or extrusion molding, or formed by post-processing a cylindrical molded product produced by a conventional method. Is optional. The auxiliary magnet 7 is fixed to the main body magnet 2 using an adhesive. However, if the auxiliary magnet 7 has a dovetail shape as shown in the figure, the adhesive is not necessarily required. Can be. The main magnet 2 which is extremely anisotropically oriented is manufactured by injection molding or extrusion molding of a resin containing magnetic powder. As the binder, any of a soft resin such as vinyl chloride and rubber, and a hard resin such as nylon may be used. When a hard resin is used, a portion corresponding to the shaft may be integrally formed of the hard resin without using a metal shaft. There is no limitation on the number of poles of the main magnet 2 which is extremely anisotropically oriented. The pole to which the auxiliary magnet 7 oriented in one direction is fixed is a specific pole requiring a high magnetic flux density, for example, a developing pole.

By fixing the unidirectionally oriented auxiliary magnet 7 to the main magnet 2 which is extremely anisotropically arranged, the magnetic flux density of a specific magnetic pole can be increased.
In order to further increase the magnetic flux density, it is preferable that the embedded depth of the auxiliary magnet 7 reaches a deep portion near the shaft 3. Normally, the magnet roll is magnetized by applying a magnetic field from the outer peripheral surface side, so in a deep portion near the shaft (near the center of the magnet), the magnetic powder is hardly oriented, and this is the surface of the conventional resin magnet. It was one of the causes of low magnetic force. As shown in FIG. 2, when the unidirectionally oriented auxiliary magnet 7 is arranged to a deep portion near the shaft, the unidirectionally oriented magnetic powder of the auxiliary magnet 7 exists near the shaft. The magnetic flux density increases. In addition, body magnet 2
When the auxiliary magnet 7 having higher characteristics is used, the embedding depth can be reduced.

FIG. 3 shows an auxiliary magnet 7a which is oriented in one direction to make the magnetic field pattern of a specific magnetic pole asymmetric.
Is fixed to a groove provided at a magnetic pole forming position of the main magnet 2 which is extremely anisotropically oriented so as to have an angle with a magnetization direction of a magnetic pole whose magnetization direction is to be asymmetric. Although not shown, the magnetic field pattern may be made asymmetric by disposing the auxiliary magnet 7a which is unidirectionally oriented to one of the symmetric magnetic fields without changing the magnetization direction.

The shape of the unidirectionally oriented auxiliary magnet is appropriately selected according to the magnetic field pattern to be obtained and the magnetic flux density to be reinforced. For example, FIG.
(B) Various types can be adopted as shown in (c).

Further, as shown in FIG. 5, an auxiliary magnet 7e integrated with the shaft may be formed.

[0017]

According to the magnet roll of the present invention, the auxiliary magnet, which is unidirectionally oriented, is fixed to the main body magnet over substantially the entire length in the axial direction of the main magnet in a part of the circumferential direction of the extremely anisotropically oriented main body magnet. Therefore, it is possible to obtain a magnet roll with an increased magnetic flux density of a specific magnetic pole or a magnet roll with an asymmetric magnetic field pattern of a specific magnetic pole without significantly increasing the cost as compared with a magnet roll made of a resin magnet. It can contribute to higher image quality.

[Brief description of the drawings]

FIG. 1 is a cross-sectional explanatory view showing a structure and a magnetic field pattern of a magnetic cylinder incorporating a magnet roll having an increased magnetic flux density of a specific magnetic pole according to a first embodiment of the present invention.

FIG. 2 is an enlarged explanatory view of a main part in the embodiment.

FIG. 3 is a cross-sectional explanatory view showing a structure and a magnetic field pattern of a magnetic cylinder incorporating a magnet roll in which a magnetic field pattern of a specific magnetic pole is unpaired according to a second embodiment of the present invention.

FIG. 4 is an explanatory view showing a modification of an auxiliary magnet oriented in one direction.

5 is a sectional view of a magnetic cylinder according to a third embodiment of the present invention, which incorporates a magnet roll in which a unidirectionally oriented auxiliary magnet is integrated with a shaft. FIG.

FIG. 6 is an explanatory sectional view in the axial direction of a magnetic cylinder incorporating a conventional magnet roll.

FIG. 7 is a radial cross-sectional view of the magnetic cylinder.

FIG. 8 is an explanatory sectional view showing a structure and a magnetic field pattern of a magnetic cylinder incorporating a conventional magnet roll.

[Explanation of symbols]

Reference Signs List 51 magnetic cylinder 52 columnar magnet 53 shaft 54 magnet roll 55 cylindrical sleeve 2 main body magnet 3 metal shaft 4 magnet roll 5 sleeve 7 auxiliary magnet 7a, 7b, 7c auxiliary magnet

Claims (1)

[Claims] 1. A magnet roll comprising: an auxiliary magnet oriented in one direction fixed to a part of a circumferentially oriented main magnet in a circumferential direction of the main magnet in substantially an entire length of the main magnet.