JPH0582582B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic brush developing device, and particularly to a magnetic brush developing device.
The present invention relates to a magnetic brush developing device suitable for use in multicolor recording devices such as color electrophotographic copying machines and full-color copying machines.

[Prior art]

A multicolor recording device has a plurality of developing devices arranged along the moving path of the image carrier surface, and repeatedly forms an electrostatic latent image or a magnetic latent image on the image carrier surface, and develops it each time with a different developing device. There are the most things. and,
As a developing device, a so-called magnetic brush developing device is often used, which forms a developer layer on a developing sleeve using magnetic force, and develops a latent image by rubbing the developer layer against the surface of an image carrier. In the multicolor recording device described above, the surface of the image carrier on which the latent image is formed passes through a developing device and is developed in the next developing device, or the developed surface passes through the developing device and is developed again. It can be brought to the latent image forming area or to the transfer area. Therefore, when a magnetic brush developing device is used, at least when the latent image surface or the developing surface of the image carrier simply passes through the developing device, the developing device is in a state where no development is performed or a state where no shadow is cast on the previous development, i.e. , it is necessary to maintain a state in which the developer layer on the developing sleeve does not come into contact with the surface of the image carrier.

As a multicolor recording device using a magnetic brush developing device, one of the plurality of developing devices that performs development is brought close to the photosensitive drum, which is an image carrier, so that its abutting roller comes into contact with the photoreceptor drum, which is an image carrier. If you don't have one, there is a copying device that can be separated from the photoreceptor drum.
It is known from USP3854449, and
A cam is provided on the photoreceptor drum side to move a plurality of developing devices toward and away from each other. A copying apparatus in which the magnetic brush is spaced apart from the photosensitive drum is known from US Pat. No. 3,970,042. Such a recording device that moves the developing device has a complicated mechanism for moving it, making the recording device large and expensive, and also has the disadvantage that it is difficult to maintain accuracy during development. .

As a way to bring the magnetic brush into contact or keep it out of contact without moving the developing device, if you want to move the ear cutting plate that regulates the layer thickness of the developer layer on the developing sleeve and perform development, you can use the ear cutting method. The position of the plate is set at the position where the magnetic brush that contacts the surface of the image carrier is formed, and when no development is performed, the position of the cutting board is set at the position where it almost contacts the surface of the developing sleeve.
There are ways to prevent magnetic brushes from forming. Although this method does not increase the size of the recording apparatus, there is a strong possibility that the movement of the ear cutting plate will not be carried out smoothly, and there is a drawback that it is difficult to maintain accuracy during development and non-development.

[Purpose of the invention]

The present invention has been made in order to provide a magnetic brush developing device that eliminates the above-mentioned drawbacks, and a magnetic brush that rubs the surface of an image carrier during development can perform the development without moving the developing device or the cutting plate. The present invention provides a magnetic brush developing device which is formed on a sleeve, is capable of preventing a developer layer on the developing sleeve from coming into contact with an image carrier during non-development, and is suitably used in a multicolor recording device.

[Structure of the invention]

In the present invention, at least during development, the developing sleeve rotates, and a magnet having a plurality of N and S magnetic poles arranged in the circumferential direction is fixed with one magnetic pole facing the developing area.
The layer thickness of the developer layer that moves on the developing sleeve as the developing sleeve rotates is controlled by the cutting plate provided between the N and S magnetic poles that face the developing sleeve surface and are adjacent to each other in the circumferential direction of the magnet. In a magnetic brush developing device, in which a developer layer whose thickness is regulated rubs against the surface of an image carrier in a developing area, a magnetic material is used for the cutting plate, and the rotation of the developing sleeve is continued at the end of development. The magnetic brush developing device is characterized in that it prevents the developer layer from coming into contact with the surface of the image carrier by rotationally displacing the magnet body to a position where one magnetic pole faces the ear cutting plate. Thus, the above purpose is achieved.

〔Example〕

The present invention will be explained below using illustrated examples.

FIG. 1 is a partial sectional view of a recording device showing an example of the developing device of the present invention, and FIG. 2 is a partially enlarged view of FIG. 1 showing a state when development is stopped.

In the figure, reference numeral 1 denotes a drum-shaped image carrier that rotates in the direction of the arrow and on which an electrostatic latent image or a magnetic latent image is formed by a known latent image forming device (not shown), and the formed latent image is The toner image is developed by the developing device 2, and the toner image is transferred and fixed onto a recording sheet or the like by a known transfer device (not shown).

The developing device 2 includes a developing sleeve 3 made of a non-magnetic material such as aluminum or stainless steel that rotates in the direction of the arrow at an opening facing the image carrier 1. A magnet body 4 having N and S magnetic poles 41 to 46 is provided, and a magnet body such as ferrite or magnetic stainless steel is provided opposite to the surface of the developing sleeve 3 on the exit side of the opening through which the developing sleeve 3 rotates in the direction of the arrow. , an ear cutting plate 5 made of a magnetic material such as iron is provided.

When developing the latent image on the image bearing member 1 with this developing device 2, the magnet body 4 is moved to the magnetic pole 4 as shown in FIG.
1 faces the developing area, that is, the position closest to the image carrier 1, and rotates to a position where the N and S magnetic poles 45 and 46 face the ear cutting plate 5. When the developing sleeve 3 rotates in the direction of the arrow in the state shown in FIG. Along with this, a developer layer is formed by passing through the gap between the cutting board 5 and the developing sleeve 3 with approximately the same thickness, and the developer layer is spread onto the developing sleeve 3 by the magnetic force of the magnetic poles 46, 41 to 43. It is held and moves in the same direction as the developing sleeve 3 rotates and returns to the developer reservoir 6, but in the middle of the process, in the developing area, the developer layer stands up due to the magnetic field lines from the magnetic pole 41 and carries the image. The latent image is developed by rubbing the body surface.

When the latent image on the image carrier 1 passes through the development area and development is completed, the magnet body 4 is rotated approximately 20 degrees in the direction of the arrow as shown in FIG. It is brought to a position facing the ear cutting board 5. As a result, a strong magnetic field is formed between the ear cutting plate 5 and the magnetic pole 46 of the magnet body 4, which prevents the developer from moving as the developing sleeve 3 rotates, so that the developer passes through the position of the ear cutting plate 5. There is almost no developer layer on the surface of the developing sleeve 3, or even if there is, it is very thin, and the developer layer on the developing sleeve 3 does not come into contact with the surface of the image carrier 1. In the example shown in FIG. 2, due to the rotational displacement of the magnet body 4, the intermediate portions of the N and S magnetic poles 41 and 42 come to face each other in the developing area, so that in the developing area, the lines of magnetic force are aligned between the developing sleeve 3 and the image carrier. 1, the developer layer on the developing sleeve 3 is more securely prevented from contacting the surface of the image carrier 1. Therefore, even if the latent image surface or the developed surface of the image carrier 1 passes through the developing device 2 from now on, the passing latent image surface will not be developed by the developing device 2, or the developed surface will not be developed by the developing device 2. Nothing will be disturbed.

In the developing device of the present invention described above, even if the developing sleeve 3 continues to rotate even after the end of development, it stops rotating after the developer layer that does not contact the image carrier 1 reaches the developing area. It may also be something that stops. Further, the developer may be a one-component developer using magnetic toner or a two-component developer using toner and a magnetic carrier. The illustrated example shows a developing device using a monocomponent developer supplied with magnetic toner from a toner supply cartridge 7.

〔Effect of the invention〕

As described above, the magnetic brush developing device of the present invention can be used without moving the developing device or the ear cutting plate.
During development, the developer layer on the developing sleeve rubs against the surface of the image carrier, and during non-development, it can be kept in a state where it does not come into contact with the surface of the image carrier. Suitable for use in electrophotographic color printers, electrostatic color printers, etc. However, even when the magnetic brush developing device of the present invention is used in a monochrome recording device, toner consumption can be reduced and the burden on the image carrier cleaning device can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view of a recording device showing an example of the developing device of the present invention, and FIG. 2 is a partially enlarged view of FIG. 1 showing a state when development is stopped. DESCRIPTION OF SYMBOLS 1... Image carrier, 2... Developing device, 3... Developing sleeve, 4... Magnet, 41-46... Magnetic pole, 5... Ear cutting board, 6... Developer reservoir, 7... Toner supply cartridge.

Claims (1)

[Scope of Claims] 1. At least during development, the developing sleeve rotates, and a magnet body having a plurality of N and S magnetic poles arranged in the circumferential direction is fixed with one magnetic pole facing the developing area, and the developing sleeve rotates. The layer thickness of the developer layer that moves on the developing sleeve as it rotates is regulated by a cutting plate provided at a position between N and S magnetic poles adjacent to each other in the circumferential direction of the magnet body, facing the developing sleeve surface. In a magnetic brush developing device in which a developer layer with a regulated layer thickness rubs against the surface of an image carrier in a developing area, a magnetic material is used for the cutting plate, and when development is completed, a magnet is used while the developing sleeve continues to rotate. A magnetic brush developing device characterized in that a developer layer is prevented from coming into contact with an image carrier surface by rotationally displacing a body to a position where one magnetic pole faces a brush cutting plate. 2. The magnetic brush developing device according to claim 1, wherein the rotational displacement of the magnet body at the end of development causes the circumferentially adjacent N and S magnetic poles to face the development area.