JPS58184980A - Electrophotographic copying machine - Google Patents

Abstract

PURPOSE:To eliminate the disturbance of a toner image due to a removed carrier, by arranging a magnetic attracting means between a developing part and a transfer part to remove the magnetic carrier which is stuck together with the toner to the surface of the latent image of a photoreceptor and transferring the toner well in the transfer process. CONSTITUTION:A magnetic attracting means 10 is arranged between a developing device 4 and a corona discharger 5 for transfer so as to face a photoreceptor 1. By providing the magnetic attracting means 10 in this manner, a carrier 18 is attracted to the magnetic attracting means 10 together with the toner and is removed from a toner image part stuck to the latent image on the photoreceptor 1 when this toner image part faces the magnet 10. That is, though the toner as well as the carrier may be stuck to the electrostatic latent image part simultaneously in the developing part, the stuck carrier 18 receives the magnetic attraction and is attracted to the magnetic attracting means 10 when it faces the magnetic attracting means 10. At this time, the toner does not receive the action of the magnetic attraction and is not attracted to the magnetic attracting means 10 because it is not a magnetic material. Thus, the image is transferred well without omission of image.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic copying machine, particularly one in which an electrostatic latent image formed on a photoreceptor is visualized using a developer consisting of toner and a magnetic carrier. The present invention relates to an electrophotographic copying machine that can successfully transfer toner images onto paper.

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 by adhering a colored pigment toner in a developing section, 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. . 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 electrophotographic copying machine as described above, a carrier is used to apply an electric charge to the toner with a polarity opposite to that of the electrostatic latent image and apply an electrostatic attraction force to cause the toner to adhere. A developer consisting of magnetic iron powder and toner is used. In other words, 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, resulting in image omissions (white spots) and the like. In other words, the part facing the carrier appears white.

The reason for this is that the carrier diameter is very large compared to the toner diameter, so during the transfer process, the paper is closely attached to the photoreceptor surface, and a gap is created by one carrier, which causes the toner to be transferred to the paper by the action of the corona discharge device. The suction power is insufficient and toner transfer is not performed. and,
Since the carrier is generally a conductor, the charge charged on the paper by the corona discharge device escapes through the carrier, which may cause toner transfer resulting in toner attraction.

SUMMARY OF THE INVENTION In view of the above-mentioned drawbacks, the present invention provides an electrophotographic copying machine that can transfer toner well in a transfer process. That is, the present invention is an electrophotographic copying machine characterized in that, in order to transfer the toner well, the carrier attached together with the toner is removed before the transfer process.

Here, as a means for removing the carrier, a means for magnetically attracting the carrier made of iron powder or the like, such as a magnet, may be provided, but the removed carrier may come into contact with the toner image and disturb the toner image. is possible. Another object of the present invention is to prevent the toner image from being disturbed due to the removal of the carrier.

The electrophotographic copying machine of the present invention will be explained 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 drum-shaped photoreceptor that rotates in the direction of the arrow; 2 is a discharger that uniformly charges the surface of the photoreceptor to a specific polarity of 1"; and 3 is an optical system (not shown) that charges the original image. 4 is a developing device that visualizes the electrostatic latent image formed on the photoconductor 1 as a toner image; 5 is a paper feeder that guides the paper along conveyance rollers 6 and guides 7; A corona discharger 9 transfers the paper 8 to the toner image onto 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.

Further, the developing device 4 rotates a developing roll 41, and magnetically attracts iron powder, which is a magnetic carrier, onto the surface of the developing roll 41. A large amount of toner is attached to this carrier due to frictional charging, etc., and as the developing roll 41 rotates, the toner is transported to the developing area facing the photoreceptor 1 on which the electrostatic latent image is formed. Electrostatic latent image 1
A toner image is formed by being attracted by the action of electrostatic attraction force.

In the present invention, in the structure as described above, a magnetic attraction means IO is disposed between the developing device 4 and the corona discharger 5 for transfer so as to face the photoreceptor 1.
O is a magnetic piece 1 on each of the N and S magnetic poles of the magnet 11.
2 and 13 are fixed to each other, and the tips of the magnetic pieces 12 and 13 are extended to a position facing the photoreceptor 1. Magnetic piece 12I of magnetic adsorption means 10! :1B constitutes a carrier pool 14 when carrier attached to the photoreceptor 1 is removed, which will be described later. The tips of the magnetic pieces 12 and 13 facing the photoreceptor 1 are disposed so as to face the entire width of the photoreceptor 1 in the axial direction.

As shown in FIG. 2, a portion of the photoreceptor 1, for example, the rear end of the photoreceptor 1, is placed close to a rear end presser 15 on which the photoreceptor 1 is fixed, so as to conduct electricity. sex drum 1
A convex portion 17 is formed on the entire length of the convex portion 1 in the axial direction.
A convex portion is formed on the surface of the photoreceptor 1 facing the photoreceptor 7. Although the convex portion 17 is formed on the drum 16 which is a supporting material for the photoreceptor 1, it may be provided directly on the photoreceptor 1. Also, the convex part 1
The drum 16 is preferably made of a non-magnetic material.
The convex portion 17 may be formed integrally with the drum as long as it is made of aluminum or the like. It is preferable that the convex portion 17 be provided in a non-image forming area of the photoreceptor 1.

By providing the magnetic adsorption means 10 as described above, the photoreceptor 1
When the toner image portion adhering to the latent image faces the magnet 10, the toner is transferred to the carrier 18 as shown in FIG.
is attracted by the magnetic attraction means 10 and removed from the toner image area. In other words, carrier may adhere to the electrostatic latent image area together with the toner in the developing section. When the attached carrier 18 faces the magnetic attraction means 10, it receives the magnetic attraction force and is attracted to the magnetic attraction means 10. At this time,
Since the toner is not a magnetic substance, it is not affected by the magnetic attraction force and is not attracted to the magnetic attraction means IO. After the carrier attached to the photoconductor 1 is removed together with the toner by the magnetic adsorption means 1O, the toner image on the photoconductor 1 is placed opposite the corona discharger 5, and the paper ``8'' is appropriately fed.
), the image is transferred well without any image omission.

To explain in more detail how the carrier is removed by the magnetic adsorption means 10, most of the carrier attached to the photoreceptor 1 is removed at the tip of the magnetic piece 12 located upstream. It is attached near the tip of this magnetic piece 12. The carrier 18 attached to the tip moves to the reservoir 14 and gradually accumulates therein. A large amount of carrier accumulates near the tip of the magnetic piece 12, comes into contact with the toner image on the photoreceptor, and tends to disturb the toner image. However, the carrier accumulated near the tip of the magnetic piece 12 comes into contact with the protrusion 17 provided at the rear end of the photoreceptor 1 and enters the reservoir 14 before reaching an amount that would disturb the toner image. pressed into place. In other words, the removed carrier is transferred to the convex portion 17.
, and is attracted to the lower side wall of the magnetic piece 12 by the magnetic force of the magnet 11 . Also, some of the carriers come into contact with the convex portion 7, are blown away, and are attracted to the magnetic piece 13 on the downstream side. The carriers attached to the magnetic pieces 13 on the downstream side are also pushed into the reservoir 14 at the entry section 17, and the carriers 18 gradually accumulate in the reservoir 14 as shown in FIG.

As explained above, according to the electrophotographic copying machine of the present invention, since the magnetic adsorption means is disposed between the developing section and the transfer section, the magnetic carrier attached to the latent image surface of the photoreceptor along with the toner is removed. Therefore, the toner can be transferred well in the transfer process.

Here, the magnetic adsorption means forms a carrier pool and pushes the carrier removed by a convex part provided on a part of the photoconductor into the pool, so the removed carrier is used to form a toner image. There will be no disturbance.

[Brief explanation of drawings]

FIG. 1 is a diagram schematically showing the copying process of the electrophotographic copying machine according to the present invention, and FIGS. 2 and 3 are side sectional views of the magnetic attraction means for explaining carrier removal by the magnetic attraction means according to the present invention. be. l: Photoreceptor, 2: Corona discharger, 3: Exposure section, 4: Developing device, 41: Developing roll, 5: Corona discharger (for transfer)
, 8; paper, 10; magnetic adsorption means, 11; magnet,
+2. t: (; Magnetic piece, 14; Reservoir, 17; Convex part. Daijoto Patent attorney Aihiko Fukushi (and 2 others) 461

Claims (1)

[Claims] 1. After forming an electrostatic latent image on a photoconductor by a charging and exposing means and visualizing the electrostatic latent image as a toner image by a developing means using a developer consisting of a carrier and a toner, the toner image is In an electrophotographic copying machine of a type that transfers onto paper, an adsorption means for magnetically attracting magnetic carriers attached to the photoreceptor is provided between the developing means and the toner image transfer step, facing the photoreceptor. The adsorption means is a magnet,
The magnetic piece is fixed to both ends of the magnet and extends to a position where the tip thereof faces the photoreceptor, and a carrier reservoir is formed between the magnetic pieces, and one is disposed on a part of the photoreceptor. An electrophotographic copying machine is provided with a protrusion for forcibly moving carriers attracted to a loading means to a reservoir.