JPS5922075A - Cleaning device - Google Patents

Abstract

PURPOSE:To prevent fogging due to toner sticking to a nonpicture part, by arranging attracting means between a developing device and a corona discharger for transfer opposite to a photoreceptor. CONSTITUTION:The magnetic attracting means 10 has conductive magnetic pieces 12 and 13 fixed to the magnetic poles N and S of a magnet 11, and the tips of those magnetic pieces 12 and 13 are extended until they face the photoreceptor 1; and the space part between the magnetic pieces 12 and 13 serves as a bank for carriers. Thus, the magnetic attracting means 10 is provided and when a toner image part sticking to the picture part of an electrostatic latent image on the photoreceptor 1 faces the magnet 11, carriers 15 are attracted to the magnetic attracting means 10 together with toner to be removed from the toner image part.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic copying machine, particularly an electrophotographic copying machine that develops an electrostatic latent image formed on a photoreceptor using a developer consisting of a carrier and a toner. The present invention relates to a device in which fog is removed using a cleaning device that removes carrier that has arrived together with toner.

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 applying colored pigment toner in the developing section, and this toner image is transferred to 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 an electrophotographic copying machine such as the one described above, a carrier is used to apply charges of opposite polarity to the charge of the electrostatic latent image to the toner and cause the toner to adhere by applying an electrostatic attraction force. A developer consisting of magnetic powder and toner is used. In other words, the toner is charged in a dominant manner opposite to the electrostatic latent image using frictional charging between the toner and the carrier. Here, when the above-mentioned developer is used, not only the toner but also the gear may adhere 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 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 reduces the suction force of the toner onto the paper due to the action of the corona discharge device. It becomes insufficient and toner transfer is not performed. Since the carrier is generally a conductor, the charge on the paper due to the corona discharge escapes through the carrier, which may cause an attraction force for the toner to not be generated and the toner to not be transferred.

In addition, the developer consisting of toner and carrier is stirred in the developing device, so that the toner is triboelectrified to one polarity and the carrier is triboelectrically charged to the other polarity. It is equipped with a developing roll consisting of a magnetic roller etc. that transports developer to a developing area facing the body, and uses a magnetic brush of the developing roll to electrostatically apply charged toner to an electrostatic latent image on a photoreceptor. It is adsorbed and developed. Here, in order to prevent toner from adhering to the non-image area (white background area of the original) other than the electrostatic latent image corresponding to the image of the original, the developing roll is used to remove toner from the photoreceptor. A bias voltage of the same polarity as the potential is applied. The potential of the bias voltage applied to the developing roll has a polarity opposite to that of the toner. Therefore, by applying a bias voltage, the toner is attracted only to the image area of the electrostatic latent image on the photoreceptor, and the toner is not attracted to the non-image area because the force that holds it toward the developing roll is stronger. If the toner is held with sufficient charge in the device, toner will not adhere to non-image areas, but if there is weakly charged toner that does not hold sufficient charge, toner will not adhere to non-image areas. O where adhesion occurs
However, if sufficient charge is not retained, this weakly charged toner will be attracted to the developing roll by the carrier and the bias voltage L', and will be transferred to the non-image area where the potential is lower than that of the image area. Also, the developer is transported on the developing roll so that it collides with the photosensitive surface, and the toner adhering to the carrier is blown to the photosensitive surface due to centrifugal force. At this time, if the toner is weakly charged, even if you try to hold it back with a bias voltage, it will be facilitated by the centrifugal force mentioned above and will be easily transferred to the photosensitive surface. If it is toner, it will be held back by an attractive force such as a bias voltage, and will not be transferred to the low potential area of the non-image area.In order to prevent the transfer of toner to the non-image area mentioned above, a voltage is applied to the developing roll. Although it is possible to increase the bias voltage, this also inhibits the adhesion of toner to the image area of the electrostatic latent image, resulting in poor development.

In view of the above-mentioned drawbacks, the present invention provides a cleaning device that removes the carrier attached to the photosensitive surface in order to transfer the toner well in the transfer process. This cleaning device is characterized by removing

The present invention uses the above-mentioned cleaning device to remove fog caused by toner adhering to the non-image area of the photoreceptor.

In other words, the purpose is to remove toner from the area.

The cleaning device of the present invention will be explained in detail below with reference to the drawings.

FIG. 1 is a diagram schematically showing the copying process in the electrophotographic copying machine of this invention. A cleaning device for removing carrier attached to a photoreceptor will be described with reference to FIG. In the figure, 1 is a drum-shaped photoreceptor that rotates in the direction of the arrow, 2 is a corona discharger that uniformly charges the surface of the photoreceptor to a specific polarity (for example, O), 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 photoreceptor 1 as a toner image; 5 is a sheet feeder that electrostatically transfers the image of the conveying roller 6 to the toner image; A corona discharger 9 for transferring paper 8 in close contact with the photoreceptor 1
This is a separation roller that separates the image from the photoreceptor 1 and conveys it to the next fixing section. After the transfer process, the photoreceptor 1 is prepared for the next image formation through a cleaning process for eliminating static electricity and removing residual toner after transfer.

Further, the developing device 4 rotates a developing roll 41, and magnetically attracts magnetic 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 electrification, etc., and as the developing roll 410 rotates, the toner is transferred to the developing area facing the photoreceptor 1 on which the electrostatic latent image is formed. The electrostatic latent image is attracted by the action of electrostatic attraction, and a toner image is formed. The developing roll 41 is constructed of a cylindrical sleeve made of a conductive, non-magnetic material, and a magneto roller magnetized so that the outer circumferential poles thereof are sequentially different. The developer is adsorbed onto the sleeve by rotation relative to the sleeve, conveyed to the developing area, and returned into the developing device 4. In fact, a bias voltage having the same potential as the non-image area of the photoreceptor 1 and having substantially the same potential is applied to the sleeve constituting the developing roll.

In the present invention, a magnetic adsorption means 10 is placed between a developing device 4 and a corona discharger 5 for transfer, facing the photoreceptor 1, in a device having a configuration like a secondary chain. The adsorption means 10 fixes conductive magnetic pieces 12 and 13 to the N and S magnetic poles of the Macneso T. The magnetic piece of the magnetic adsorption means 10]2
The space formed between and 13 is created by removing the galley attached to the photoreceptor 1 and removing the gear stagnation part 14 at the time of ζ. '! 'j has been completed. h4 facing the photoreceptor 1
The tip of the magnetic 12° 13 is attached to the photoreceptor 1 as shown in FIG.
The entire length of the IJ in the axial direction is opposite to each other. 1, magnetic pieces 12 and 13 are fixed to the magnetic throat 11 with adhesive, for example.

By providing the magnetic adsorption means 10 as described above, the photoreceptor 1
When the toner image portion adhering to the image area of the electrostatic latent image faces the magnet 11, the carrier 15 is attracted to the magnetic attracting means 10 together with the toner as shown in FIG. 2, and is removed from the l.toner image area. Ru.

In other words, the gear and the toner may adhere to the electrostatic latent image portion at the same time in the developing section. When the attached carrier 15 faces the magnetic attraction means 10, it receives the magnetic attraction force and is attracted to the magnetic attraction means 10. The carrier attached to the photoreceptor 1 is mostly attracted to the magnetic piece 12 in front.

The amount of carrier 15 removed by the magnetic piece 12 gradually increases as copying is repeated, and some of the carrier is pushed into the reservoir 14 of the gear rear. The magnetic adsorption means 10 for removing the adhering carrier 15 applies a bias voltage 7 (L) having the same polarity as the bias voltage applied to the sleeve of the developing roll 41 as shown in FIG.
A pressure 16 is applied. In this way, the magnetic attraction means 10 attracts the carrier 15 with the magnetic piece 12, and forms a spike of the carrier 15 on that part by a magnetic plan equivalent to that of the developing roll 41. Therefore, a gear 15 based on a magnetic plan is in sliding contact with the rotating photoreceptor 1 at the tip of the magnetic piece 12, and a bias voltage 16 having a polarity opposite to that of the charged toner is applied to the magnetic attraction means 10. , the toner adhering to the non-image area of the photoreceptor 1 becomes the magnetic piece 1.
It is attracted to the carrier 15 side on the second side, and fog can be removed. Toner adsorbed to the non-image area of the photoreceptor is attracted to the photoreceptor with much weaker force than the image area.
It is easily removed by the magnetic attraction means 10. The bias voltage applied to the magnetic attraction means 10 can be sufficiently effective if it is equal to the bias voltage of the developing area. This is because the developer is conveyed on the sleeve in the developing section, so the toner adhering to the gear rear is about to be thrown outward, and this is encouraged, especially in the strong band.
lf l・ner has metastasized to the non-image area. For this reason,
There is no movement of the developer, especially the carrier, in the magnetic adsorption means 10.
No force is applied to cause the toner to fly outward, and the toner and the like that fly out in the developing section are attracted by the bias voltage of the magnetic attraction means 10 and removed.

Here, at the initial stage, there is almost no carrier 15 attracted to the magnetic piece 12 of the magnetic attraction means 1o, and the capri toner adhering to the non-image area of the photoreceptor 1 cannot be removed. Therefore, it is sufficient to adsorb carrier to the magnetic piece 12 in advance to the extent that it comes into sliding contact with the photoreceptor 1.

It is clear that the magnetic attraction means 1o of the present invention is not limited to that shown in FIGS. 1 and 2, but may also be implemented with a structure such as the developing roll 41. In this case, it is desirable that the developer transport speed be slower than that of the developing section.

As explained above, according to the gear rear cleaning device after development of the present invention, since the magnetic adsorption means is disposed between the development section and the transfer section, the magnetic adsorption means attached to the latent image surface of the photoreceptor together with the toner can be removed. The carrier can be removed and toner can be transferred well in the transfer process.

Further, the magnetic attraction means has a bias ri having a polarity opposite to that of the toner.
Since lh-= is applied, the toner attached to the non-image area of the photoreceptor can be removed from the carrier etc. removed by the magnetic attraction means, and the copy quality can be improved.

Furthermore, if the developing and cleaning device adopts a method that collects and reuses toner after transfer, it is possible to reuse weakly charged toner that tends to land on non-image areas of the photoreceptor where performance has deteriorated. This makes it possible to maintain the performance of the developer and to minimize the need for replacement due to developer deterioration.

[Brief explanation of drawings]

FIG. 1 is a diagram schematically showing the copying process of an electrophotographic copying machine using the IJ=ing device of the present invention, and FIG. 2 is a sectional view showing details of the magnetic attraction means of the present invention.

Claims (1)

[Claims] 1. Form an electrostatic latent image on the photoconductor by charging and exposing means, and apply toner to the electrostatic latent image using a developing means using a developer consisting of a magnetic carrier and toner. In the electrophotographic copying machine, the electrophotographic copying machine includes magnetic adsorption means that faces the photoreceptor and magnetically attracts the carrier on the photoreceptor between the development means and the transfer step of transferring the toner image on the photoreceptor. A cleaning device is provided in which a carrier is removed by the cleaning device, and a bias voltage having a polarity opposite to the charge charged on the toner is applied to the self-magnetic attraction means.