JPS6117170A - Carrier removing device - Google Patents

Abstract

PURPOSE:To remove a carrier stuck to a photosensitive body by arranging a magnetic body, for example, an iron piece in lines of the magnetic force of a magnet and magnetizing this iron piece by the magnet. CONSTITUTION:A photosensitive body 1 after development faces an iron plate 10 provided in the part of a doctor 45 on the way of going to a transfer part, and the iron plate 10 is magnetized by a magnet 43 to attract magnetically the carrier to its front end. That is, the carrier on the photosensitive body 1 is attracted magnetically by the magnetic force of the iron plate 10 and is stuck especially to the front end part (facing the photosensitive body 1) of the iron plate 10. The quantity of the carrier stuck to the iron plate 10 is not increased over a certain quantity for long-time copying. Though the carrier stuck to the photosensitive body 1 is attracted to the front end part of the iron plate 10, the carrier is attracted to the side of a sleeve 42 and is recovered when the binding force due to the magnetic force of the iron plate 10 becomes weaker than the magnetic force in a developing position due to the magnet 43.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to an electrophotographic copying machine, for example, and particularly to a system in which an electrostatic latent image formed on a photoreceptor, which is a recording medium, is visualized using a developer consisting of toner and a magnetic carrier. The present invention relates to an apparatus capable of removing carriers adhering to the photoreceptor and successfully transferring a visualized toner image onto paper.

<Prior Art> In an electrophotographic copying machine, the surface of a photoreceptor including a photoconductive layer is first uniformly charged to a specific polarity. By exposing the surface of this charged photoreceptor to a light image of the original, an electrostatic latent image corresponding to the original image is formed. The electrostatic latent image thus formed is visualized in the developing section by adhering colored pigment toner, and this toner image is transferred onto a sheet of paper that is sent as appropriate, for example, by the action of a corona discharge device for transfer. Ru.

The toner image transferred onto the paper is fixed on the paper as the paper is conveyed through the fixing section. The above is the general copying process using electrophotography.

In the developing section of the above electrophotographic copying machine, in order to impart a charge to the toner with a polarity opposite to that of the electrostatic latent image,
A developer consisting of magnetic iron powder called a carrier and toner is used. The toner is charged to a polarity opposite to that of the electrostatic latent image using frictional charging between the toner and the carrier. Here, when the above-mentioned developer is used, not only toner but also carrier may be attached to the electrostatic latent image.

If this carrier adheres, the toner will not be properly transferred to the paper during the transfer process, and image dropouts (white spots) will occur.In other words, the portion facing the carrier will appear white.

The reason for this is that since the carrier diameter is much larger than the toner diameter, the paper does not come into close contact with the photoreceptor surface during the transfer process, and a gap is created by the carrier, which causes the suction force of the toner to the paper due to the action of the corona discharge device. is insufficient and toner transfer is not performed. Since the carrier is generally a conductor, the charge on the paper caused by the corona discharge device escapes through the carrier, causing no toner attraction force and no toner transfer.

Therefore, conventionally, the carrier attached to the photoreceptor is forcibly removed using magnetic means between the developing device and the transfer device. When the amount of carrier magnetically attracted by the magnetic means gradually increases, the removed carrier may rub against the surface of the photoreceptor, thereby disturbing the formed toner image. Therefore, it is necessary to periodically clean the carrier of the magnetic means or replace the magnetic means itself. Moreover, since a space is required to provide the magnetic means, the arrangement position of the image forming means, which is disposed opposite to the periphery of the other photoreceptor, is restricted.

<Object of the Invention> An object of the present invention is to provide a means for removing carrier attached to a photoreceptor.

An object of the present invention is to provide a carrier removing means that eliminates the need for cleaning the carrier.

Still, the present invention aims to remove carriers using existing magnetic means without requiring special magnetic means for removing carriers.

A further object of the present invention is to collect the carrier in the developing device.

<Embodiment> The carrier removing means of the present invention uses a magnetic brush developing method as a developing device, and is a device that uses a magnet of the developing device to remove carrier attached to a photoreceptor. To this end, the configuration is such that a magnetic body, for example, an iron piece, is placed in the magnetic lines of force of the magnet, and the iron piece is magnetized by the magnet to remove carriers attached to the photoreceptor.

The present invention will be described in detail below with reference to the drawings. FIG. 1 is a diagram schematically showing a copying process in an electrophotographic copying machine according to the present invention. In the figure, 1 is a photoreceptor provided on the surface of a conductive drum that is rotated in the direction of the arrow; 2 is a corona discharger that uniformly charges the surface of the photoreceptor to a specific polarity; and 3 is an optical system (not shown) that charges the original image. ), 4 is the photoreceptor 1
A developing device 5 visualizes the electrostatic latent image formed on the toner image as a toner image;
A corona discharger 9 transfers the toner image onto the paper 8 guided along the photoreceptor 1.
This is a separation roller that separates the image and conveys it to the next fixing section.

After the transfer process, the photoreceptor 1 undergoes a static elimination and cleaning process, and is ready for the next image formation.

The developing device 4 is configured by providing a developing roll 41 for developing the electrostatic latent image on the photoreceptor 1 in a developing tank 40 . The developing roll 41 has a magnet 43 provided within a cylindrical sleeve 42 made of a non-magnetic material and formed to correspond to the entire length of the photoreceptor 1 in the width direction. In particular, the magnet 43 is fixed in such a way that the main pole (for example, N pole) faces the developing position facing the photoreceptor 1, and the sleeve 42 is attached to the magnet 43.
is rotated in the direction of the arrow. Therefore, magnet 4
The developer is attracted to the surface of the sleeve 420 by the magnetic force of step 3.
As the sleeve '42 rotates, the developer on its surface is conveyed in the direction of rotation of the sleeve '42 and circulated within the developing area facing the photoreceptor 1 and the developing tank 40. Here, lines of magnetic force are generated between the magnetic poles of the magnet 43 (between the SN poles), and the developer is attracted to the sleeve 42 along these lines of magnetic force. And especially at each pole (for example, N pole),
The developer is formed into a magnetic brush shape, and this developer brush rubs the surface of the photoreceptor 1. As a result, the toner is electrostatically attracted to the electrostatic latent image on the photoreceptor 1 and attached to that portion, thereby performing development.

On the other hand, a doctor 45 that regulates the amount of developer attached to the sleeve 42 is provided in the developer tank 40 on the way the developer moves toward the development area due to the rotation of the sleeve 42 . The doctor 45 is made of a non-magnetic material in order to keep the amount of developer attached always constant without being affected by the magnetic force of the magnet 43. For example, an iron plate 10 made of a magnetic material is provided on the outside of the doctor 45, that is, on the side facing the photoreceptor 1. As shown in FIG. 2, this iron plate 10 is arranged at an angle such that one end thereof is substantially flush with the plane of the doctor 450. Further, the iron plate 10 is provided at a position where the lines of magnetic force between N-8 are concentrated (a position along the lines of magnetic force).

In the above-described configuration, when the photoreceptor 1 passes through the steps of charging and exposure, an electrostatic latent image corresponding to an original image or the like is formed on the photoreceptor 1. When this latent image faces the developing device 4, toner is attached thereto by the action of the developing roll 41, and the latent image is made flexible. At this time, not only toner but also carrier may adhere to the latent image area.

On the way to the transfer section, the photoreceptor 1, which has undergone the above-mentioned development, faces an iron plate 1° provided at the doctor section 45. The iron plate 10 is magnetized by a magnet 43, and the carrier is magnetically attracted to the tip thereof. That is, the carriers on the photoreceptor 1 are magnetically attracted by the magnetic force of the iron plate 1o, and are particularly attached to the tip of the iron plate 1o (the part facing the photoreceptor 1). Here, the carrier attached to the iron plate 10 does not increase by more than a certain amount even during long-time copying. This is because the carrier attached to the photoreceptor 1 is attracted to the tip of the iron plate 10, but if the restraining force due to the magnetic force of the iron plate 10 is smaller than the magnetic force at the developing position due to the magnet 43, the carrier will be attracted to the sleeve 42 side. It is aspirated and collected.

At this time, the outer side of the iron plate 10 (the surface facing the photoreceptor 1)
In this case, the magnetic force is extremely reduced and the carrier is magnetically soldered, and the carriers are not attached to that part but are all attached to the tip of the iron plate 10 and collected. Like this,
The developer carrier adheres to the photoreceptor 1, and after development, the iron plate 1
Since the carrier is adsorbed at zero and collected by the developing roll 41, there is no need to periodically clean the carrier removed from the photoreceptor.

In this embodiment, the iron plate 10 is provided in the doctor section 45, but at least after development, the magnet 4
What is necessary is just to provide it in the position magnetized in 3. Moreover, iron plate 1
0 is more effective if it is provided close to the photoreceptor 1.

Alternatively, an iron plate 10 with a thickness of 1 inch and a width of 10 mm was provided along the entire length facing the photoreceptor 1, but the thickness and width of the iron plate 10 are not so important, and the position of the iron plate 10 is very important. In particular, it is more effective if the iron plate 10 is placed between the N-8 poles and at a position where the lines of magnetic force can be concentrated. In other words, the iron plate 10 may be provided at a position where it can be strongly magnetized. However, as described above, the closer it is to the photoreceptor 1, the more effective it becomes.

Furthermore, by providing the iron plate 10, the composite magnetic field of the magnet 43 changes, which does not affect development much, but the strength and arrangement of each magnetic pole of the magnet 43, the position and shape of the iron plate 10, etc. can be adjusted as appropriate. You can prevent this effect by setting this.

<Effects of the Invention> According to the carrier removal device of the present invention, a magnetic plan development is used as the development device, and the magnetic material magnetized by the magnet of the development device is placed at a position after development and at a position facing the photoreceptor. Because of this arrangement, the magnetic material can magnetically attract and remove carriers attached to the photoreceptor, and the carriers attached to the magnetic material are collected by the developing device by the magnetic force of the magnet. . Thereby, it is not necessary to periodically clean the carrier removed from the photoreceptor, and the work for that purpose can be made unnecessary.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example in which a carrier removing device according to the present invention is provided in a developing section, and FIG. 2 is a sectional view showing details of the carrier removing device.

Claims (1)

[Scope of Claims] 1. A magnetic blank development device that visualizes an electrostatic latent image on a recording medium, and a magnetic blank development device that is magnetized by a magnet of the development device and is positioned after the development is completed and is placed at a position facing the recording medium. A carrier removal device consisting of a magnetic material. 2. The carrier removing device according to claim 1, wherein the magnetic body is provided at a position along the magnetic lines of force of the magnet. 3. Claim 1, characterized in that the magnetic material is provided in a doctor section that regulates the amount of developer attached to the developing device.
2. The carrier removal device according to item 2 or item 2.