JPS5926369Y2 - Electrostatic recording magnet roll - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an electrostatic recording magnet roll used in electrophotographic copying machines, facsimile machines, printers, etc.

In the conventionally commonly used magnetic brush development method, when developing photosensitive paper having an electrostatic latent image that has gone through the process of charging and exposure, a magnet roll having multiple magnetic poles on its surface is rotated. The electrostatic latent image is developed by rubbing it with a brush-like developer attached to the roll surface, but there are the following problems.

First, the adsorption state of the developer to the magnetic roll surface is different between the magnetic poles and between the magnetic poles, and between the magnetic poles, the developer is laid down in the circumferential direction along the lines of magnetic force. Uneven development density occurs at a corresponding period.

Furthermore, if the magnetic attraction force of the magnet roll is weak, when using a two-part developer, fine particles of iron powder called carrier are likely to be adsorbed onto the photosensitive paper, resulting in the so-called fogging phenomenon. When rotating at high speed, the centrifugal force tends to cause the carrier to be shaken off the surface of the magnet roll, making the developed copy unclear.

Therefore, the permanent magnets used in magnet rolls are required to be strong, and in recent years in particular, magnet rolls with a surface magnetic flux density of 1400 Gauss or more on non-magnetic snows are often required; This has been extremely difficult with conventionally known magnet rolls in terms of circuit design or manufacturing.

An object of the present invention is to provide an electrostatic recording magnet roll having a high magnetic force, particularly a surface magnetic flux density of 1400 Gauss or more on the non-magnetic sleeve of the main pole.

The electrostatic recording magnet roll of the present invention has a yoke made of a ferromagnetic material fixed to a part of the shaft, a permanent magnet body serving as a main magnetic pole fixed to the outer periphery of the yoke, and a main magnetic body on both sides of the permanent magnet body. A permanent magnet with a polarity opposite to the magnetic pole is fixed so that the permanent magnet spans both the shaft and the yoke, and the magnetic flux of the main pole on the surface of a non-magnetic sleeve provided on the outer periphery of the permanent magnet. It is characterized by a density of 1400 Gauss or more.

The details of the magnet roll of the present invention will be explained with reference to drawings showing embodiments.

FIG. 1 is a cross-sectional view of the magnet roll of the present invention, and FIG. 2 is a cross-sectional view taken along line AA in FIG.

1a to 1e are permanent magnets such as anisotropic ferrite magnets, which are fixed to the outer periphery of the shaft 2.

NS indicates the magnetic pole of the permanent magnet.

Both ends of the shaft 2 are reduced in diameter and provided with bearing portions 2a and 2b.

A yoke 3 made of a ferromagnetic material such as iron is fixed to a part of the shaft 2.

Among the permanent magnets described above, the permanent magnet 1a serving as the main magnetic pole is fixed to the shaft 2 via the yoke 3.

On both sides of the permanent magnet 1a are permanent magnets 1b with opposite polarity to the main magnetic pole.
and 1C are fixed across both the yoke 3 and the shaft 2.

Next, reference numeral 4 denotes a cylinder made of non-magnetic material such as aluminum or stainless steel, which is disposed outside the permanent magnet with a slight gap, a side plate 5 is fixed to the end, and a shaft 2 is connected by a bearing 7. It is rotatably attached to the end bearing parts 2a and 2b of.

Reference numeral 6 denotes a rotating shaft, which is provided protrudingly from one side plate 5.

In the magnet roll of the present invention, the permanent magnet 1a is fixed to the outer periphery of the shaft 2 via the yoke 3, so the operating point of the magnet is raised, so the magnetic force of the main pole becomes strong, and an extremely strong magnetic field is applied to the outer periphery. can be generated.

Furthermore, since the permanent magnets 1b and 1C on both sides of the permanent magnet 1a are fixed across both the yoke 3 and the shaft 2, magnetic leakage of the sub-pole can be reduced.

In this case, if the width of permanent magnets 1b and 1C is 11,
It is preferable that the width 12 of the permanent magnets 1b and 1C in contact with the shaft 2 is 10% or less of the width 11 of the permanent magnets 1b and 1C.

This is because if it exceeds 10%, the above-mentioned magnetic leakage increases.

Since the magnet roll of the present invention is configured as described above, it is possible to generate a strong magnetic field on the surface of the cylinder made of non-magnetic material.

In the case of development, if the permanent magnet 1a serving as the main pole is fixed so as to face the photosensitive paper developing section, and the rotating shaft 6 is rotated,
The developer is attracted to the surface of the cylinder 4 and moves together with the cylinder 4.

When it reaches directly above the magnetic pole, a strong magnetic brush is formed by the magnetic field of the permanent magnet as described above, but since the main magnetic pole faces the surface of the photoreceptor that has an electrostatic latent image, the magnetic brush is static. By rubbing the electrostatic latent image, toner in the developer adheres to the electrostatic latent image, and development is performed.

After the development is completed, it moves with the rotation of the cylinder 4, is scraped off by a scraping plate (not shown), and is adsorbed and used again after being replenished with I/ner.

In the present invention, the yoke is not limited to the one shown in the above-described embodiment, and the effect will be the same even if a yoke having a shape as shown in FIGS. 3 and 4 is used.

Note that the symbols in FIGS. 3 and 4 correspond to those in FIG. 1.

Further, instead of the yoke, a magnet for reinforcing magnetic force such as a rare earth magnet, ferrite magnet, or rubber magnet may be provided on the lower surface of the permanent magnet 1a to obtain the same effect.

Furthermore, if the surface of the cylinder made of non-magnetic material is roughened by metallizing, shot blasting, knurling, etc., the friction coefficient of the surface will increase, and the developer conveyance capacity can be increased.

A specific example of the present invention will be shown.

Magnet rolls shown in FIGS. 1 and 2 were manufactured.

The outer diameter d of the shaft 2 is 38 mm, the yoke 3 is made of steel and its height is 7 mm, the permanent magnet is an anisotropic ferrite magnet, and the height x width of each magnet is 14 mm x 20 mm, 1
b-1e is 13 mm x 13 mm, and cylinder 4
The outer diameter is 60 mm and the inner diameter is 58 mm.

The magnetic flux density in the cylindrical direction on the sleeve surface was as shown in FIG. 5, and the main magnetic pole was approximately 1500 G.

As described above, according to the magnet roll of the present invention, the magnetic flux density of the main magnetic pole on the surface of the non-magnetic sleeve can be set to 1400 Gauss or more, and therefore good development is possible.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of the magnet roll of the present invention, and Figure 2 is a cross-sectional view of the magnet roll of the present invention.
3 and 4 are cross-sectional views showing other embodiments of the present invention, and FIG. 5 is a diagram showing the magnetic flux distribution on the sleeve surface of the magnet roll of the present invention. . la, lb, IC, ld: permanent magnet, 2: shaft, 3: yoke.

Claims (1)

[Claims for Utility Model Registration] 1. A yoke made of a ferromagnetic material is fixed to a part of the shaft, a permanent magnet body serving as a main magnetic pole is fixed to the outer periphery of the yoke, and a main magnetic pole and a main magnetic pole are fixed on both sides of the permanent magnet body. A permanent magnet body of opposite polarity is fixed so as to span both the shaft and the yoke, and the magnetic flux density of the main pole on the surface of a non-magnetic sleeve provided on the outer periphery of the permanent magnet body is 1400
An electrostatic recording magnet roll characterized by having a magnetic field of Gauss or higher. 2. The electrostatic recording magnet roll according to claim 1, which is a registered utility model, characterized in that a permanent magnet for strengthening magnetic force is provided on the lower surface of the permanent magnet serving as the main magnetic pole instead of the yoke.