JPS638916Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a static eliminator using DC corona discharge in an electrophotographic device, etc. In particular, the photoreceptor has no sensitivity to the polarity of the static-eliminating corona, and both ends of the photoreceptor are static-eliminating. In an electrophotographic device equipped with a photoreceptor that may accumulate excessive charges due to corona, the problem of carrier adhesion is solved by making the effective width of the static elimination corona narrower than the effective width of the charging corona or transfer corona. The present invention provides a static eliminator.

Various types of electrophotographic devices are known, but in general, a drum-shaped or belt-shaped photoreceptor rotates and moves while charging, exposing, and
Various processes such as development, transfer, and fixing proceed to complete the recorded image on the recording paper. When such one recording cycle is completed, the photoreceptor proceeds to a charge removal and cleaning step in preparation for the next recording cycle, and residual charges and toner are removed. If this static elimination and cleaning process is incomplete, a problem arises in that the image quality in the next recording cycle is degraded.

BACKGROUND ART Conventionally, as static eliminators used in electrophotographic apparatuses, an AC static eliminator system, an optical static neutralization system, and the like are known.

In these static elimination methods, the effective width of static elimination is generally set wider than the effective width of charging and transfer corona.

FIG. 1 is a plan view showing charge distribution widths on a photoreceptor during various steps in an electrophotographic apparatus using a conventional AC static elimination method. In the drawing, PC is the photoreceptor,
A indicates the effective width of the charging corona, B1 and B2 indicate the effective width of erase, C indicates the effective width of transfer corona, D indicates the effective width of AC charge removal, and arrow S indicates the moving direction of photoreceptor PC, the densely shaded area. indicates the area to which the developing toner is attached, and the sparsely shaded area indicates the area to which the residual toner is attached.

In the case of Fig. 1, a negative charge is applied to the photoconductor PC by a charged corona, and after erasing both ends B1 and B2, exposure is performed to form an electrostatic latent image on the original, etc. I'm letting you do it. The image is then developed with toner, and then proceeded to various steps of transfer, static elimination, and cleaning.

In this case, in the conventional static eliminator, the effective width D of static elimination is set to be wider than the effective width A of the charged corona to which charges to be erased are applied and the effective width C of the transfer corona. .

In such an AC static elimination method, there is a limit to the cleaning efficiency of residual toner in the next step.

Therefore, recently, a static eliminator using direct current corona discharge has been proposed for the purpose of improving cleaning efficiency by controlling toner polarity during cleaning.

Even in this static elimination device using DC corona discharge, the effective width of the conventional static elimination corona is set wider than the effective width A of the charging corona and the effective width C of the transfer corona, similar to the effective width D of AC static elimination in Fig. 1. ing.

Therefore, excessive charges due to the static elimination corona are attached to both ends of the photoreceptor PC. In this case, if the photoreceptor PC is sensitive to the polarity of the static elimination corona, this problem can be easily solved by using a method such as using optical static elimination together.

However, when the photoreceptor PC has no sensitivity to the polarity of the static elimination corona, the excess charge given by the static elimination corona gradually accumulates.
That is, regions strongly charged with the polarity of the neutralizing corona occur at both ends of the photoreceptor PC, causing problems such as carrier adhesion.

Therefore, the static eliminator of this invention solves these inconveniences in conventional static eliminators that use DC corona discharge, and even in photoreceptors that are not sensitive to the polarity of the static eliminator, there is no excess charge caused by the static eliminator on both ends of the photoreceptor. The purpose is to prevent carrier adhesion from occurring by preventing the accumulation of excessive charges.

The main purpose of the DC corona static elimination method is to control toner polarity during cleaning. Therefore,
The static eliminator of this invention is characterized in that the effective width of the static neutralizing corona is set narrower than the effective widths of the charging corona and the transfer corona. In the narrowest case, the width is set to be approximately equal to the maximum width of the latent image.

FIG. 2 is a plan view showing an example of the charge distribution width on the photoreceptor during various steps in an electrophotographic apparatus equipped with the static eliminator of this invention. The symbols and the like in the drawings are the same as those in FIG. 1, and E indicates the effective width of the DC corona discharge of this invention, and F indicates the effective width of the optical static elimination.

In the case of this Fig. 2, the effective width E of the static elimination corona is
is set to be approximately equal to the maximum width of the latent image. Note that since the latent image is formed with a negative charge, a positive charge is applied as a charge-eliminating corona.

In this way, when the effective width E of the static eliminating corona is made narrower than the effective width A of the charging corona and the effective width C of the transfer corona, the photoconductor PC
At both ends, there are parts that receive only the charging and transfer corona and do not receive the neutralizing corona. However, in this case, the photoreceptor PC has sensitivity to charging and polarity of the transfer corona. Therefore, this problem can be easily solved by using a combination of charge removal corona and optical charge removal, or by providing an erase lamp for erasing the excess charge.

In particular, if the erase lamp is provided in the erase section between the charging corona and the developing device, it is possible to erase the electric charges in unnecessary portions, and it becomes possible to effectively prevent unnecessary toner from adhering. As a result, since no toner exists in a portion that is outside the effective width E of the static eliminating corona and is not exposed to the static eliminating corona, toner whose polarity is not controlled does not enter the cleaning section.

As explained in detail above, in the static eliminator of this invention, in the static eliminator using DC corona discharge, the effective opening width of the static eliminator corona device is set narrower than the effective opening width of the charging or transfer corona device, so that the static eliminator This prevents the charge-eliminating corona from being applied to both ends of the photoreceptor, which is insensitive to the polarity of the photoreceptor, thereby eliminating the risk of carrier adhesion.

Since the charge or transfer corona generated at both ends of the photoreceptor is removed by means such as optical charge removal or a charge eraser lamp, toner does not adhere to the photoreceptor.

Moreover, like the conventional DC corona static eliminator,
It is also possible to control toner polarity, and many excellent practical effects such as improved cleaning efficiency are achieved.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing the charge distribution width on the photoreceptor in various steps in an electrophotographic apparatus using a conventional AC static elimination method, and FIG. 2 is a plan view showing the photoreceptor in various steps in an electrophotographic apparatus equipped with the static elimination device of this invention. It is a top view which shows an example of the electric charge distribution width above. In the drawing, PC is the photoreceptor, A is the effective width of charging corona, B1 and B2 are the effective width of erase, C is the effective width of transfer corona, D is the effective width of AC static elimination, and E
indicates the effective width of the DC corona discharge of this invention, F indicates the effective width of optical static elimination, arrow S indicates the moving direction of the photoreceptor,
Densely shaded areas indicate areas to which developing toner is attached, and sparsely shaded areas indicate areas to which residual toner is attached.

Claims (1)

[Claims for Utility Model Registration] 1. A photoreceptor, a charging device that performs corona charging on the photoreceptor surface, an exposure device that forms a latent image on the photoreceptor surface, and a latent image formed on the photoreceptor surface. a developing device for developing with toner, a transfer device for transferring the toner image developed by the developing device onto recording paper, a fixing device for fixing the toner image transferred on the recording paper onto the recording paper, and a fixing device for fixing the toner image transferred on the recording paper onto the recording paper; a charge eliminating corona device that removes residual toner on the photosensitive surface of the body by direct current corona discharge; and a cleaning device that cleans the residual toner on the photosensitive surface of the photoreceptor; In an electrophotographic apparatus equipped with a photoconductor that has no sensitivity to the electrostatic discharge corona and in which excessive charges are accumulated at both ends of the photoconductor due to the static elimination corona, the effective aperture width of the static elimination corona device is determined by the charging or transfer corona device. A static eliminator characterized by setting the effective aperture width narrower than the effective aperture width of the static eliminator. 2. The static eliminator according to claim 1, wherein the effective aperture width of the static eliminator corona device is approximately equal to the maximum latent image width. 3. The static eliminator according to claim 1 of the above-mentioned utility model registration, characterized in that a light irradiation means is provided before, after, or at the same position as the static eliminator corona device. 4. Claim 1 of the above-mentioned utility model registration, characterized in that a charge erasing lamp is provided between the charging corona device and the developing device to erase the charge in a portion other than the effective opening width of the static eliminating corona device. The static eliminator described.