Electrophotography – Diagnostics – Consumable
Reexamination Certificate
2000-02-22
2001-11-27
Brase, Sandra (Department: 2852)
Electrophotography
Diagnostics
Consumable
C399S053000
Reexamination Certificate
active
06324354
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming process and an image forming apparatus, having a toner carrier which faces an electrostatic latent image carrier and carries toner to the developing zone thereon, and provided with a refresh means which refreshes the toner on the toner carrier when image transfer to a recording medium is not done or when the apparatus is in a state of not transferring image.
2. Description of the Related Art
Generally, by repetition of image forming with a developing apparatus which uses uni-component developer, toner of small grain size sticks to the surf ace of the toner carrier attracted by mirror-image force caused by high electrification thereof, the stuck toner hinders another toner from being charged by frictional contact with the surface of the toner carrier, and toner may be carried as far as the latent image on the electrostatic latent image carrier without being charged uniformly on the toner carrier.
This may cause problems such as light density of image and “fog”.
The phenomenon like this is furthered in a case where the image to be formed is of low print rate, because toner particles are liable to remain on the toner carrier (developing sleeve), for small quantity of toner jumps from the toner carrier to the electrostatic latent image zone on the image carrier (photoreceptor drum), effecting reduction in print density and “fog”.
It is possible, in these cases, to alleviate the phenomenon by letting the toner jump in quantity from the developing sleeve to the photoreceptor drum by performing image forming of high print rate image pattern such as black solid fills and transferring the toner to the recording medium to consume the toner on the developing sleeve; however, in a case where black solid fills print is not done after the apparatus is left standing without consuming the toner for an extended period, the toner particles, affected by humidity and others, adheres to the surface of the developing sleeve and may not be able to be recovered. The phenomenon is liable to occur especially under high humidity conditions.
Heretofore, studies on the shape of surface and material of the toner carrier have been carried on, improvements have been made to make enough use of the capabilities of charging toner; however, in some cases toner is charged excessively and the phenomenon described above is easy to occur.
In the developing zone, toner reciprocates between the electrostatic latent image and the toner carrier by applying an AC bias.
Accordingly, by applying a higher AC bias when developing is not executed than when development is executed, the toner is removed from the toner carrier and allowed to jump to the electrostatic latent image.
Therefore, in cases where the print rate is low, that is, the number of dots of the image is small, deterioration in transferred image is prevented by applying an alternating electric field to the toner carrier to consume the toner thereon after the formation of the image, by which the surface of the toner carrier is refreshed.
However, there are drawbacks that the effect is not expected unless applying period of the alternating electric field is long, because, after the apparatus is left standing over an extended period of time, the toner is removed in consecutive order from the surface layer, and a lot of the toner is consumed, which means it is not efficient and economical.
Further, in some cases, as the alternating electric field is applied to the toner carrier and the electrostatic latent image zone when refresh is performed, the reverse-charged toner in the a developing device attaches to the transfer part and pollute the reverse side of the printing sheet. In high humidity condition the reverse-charged toner may be mixed in the positive-charged toner, which raises the like problem as mentioned above.
SUMMARY OF THE INVENTION
An object of the present invention is, in light of such problems as mentioned above, to provide a process and an apparatus, which eliminate image defectiveness such as reductions in image density, fog, and pollution of the reverse side of the printing sheet, by making it possible that the grain size distribution of toner particles on the toner carrier does not vary even after an extended period of use of the apparatus, by enabling a thin, uniform layer of toner to be formed on the toner carrier by removing the residual toner thereon through performing refresh as necessary.
Another object of the present invention is to provide a process and an apparatus for forming image, which solve the problem of image deterioration while minimizing consumption of the toner.
The present invention provides a process and an apparatus for forming image, in which a toner carrier which faces an electrostatic latent image carrier and carries toner to the developing zone thereon is provided; and refresh of the toner on the toner carrier is performed when image transfer to a recording medium is not done, that is, after transfer of the toner image on the electrostatic latent image carrier to the recording medium is finished.
The present invention provides an image forming process, in an image forming apparatus having atoner carrier which faces an electrostatic latent image carrier and carries toner to the developing zone thereon, having a refresh process in which an alternating electric field for refresh is applied between said electrostatic latent image carrier and said toner carrier to it refresh the surface of said toner carrier by carrying the toner on said toner carrier to said electrostatic latent image carrier side when the image is not transferred to a recording medium, wherein said refresh process is performed in a case where print rate of image falls short of proper print rate.
To effectuate the refresh process, an image forming apparatus according to the present invention is provided with a toner carrier which faces an electrostatic latent image carrier and carries toner to the developing zone thereon, and refresh of the toner on the toner carrier is performed when image transfer to a recording medium is not executed, wherein a print rate processing means which processes numerically the print rate corresponding to image pattern; and a refresh means which applies an alternating electric field for refresh between the electrostatic latent image carrier and the toner carrier to carry the toner thereon to the electrostatic latent image carrier side when the print rate falls short of the proper print rate; are provided.
After repetition of image forming by the electrostatic latent image carrier and the toner carrier, the amount of toner which remains on the toner carrier is large when the print rate falls short of proper print rate, as the toner which jumps from the toner carrier to the electrostatic latent image carrier is smaller in quantity than when the print rate is higher. When left standing in this state, the toner particles adhere to the surface of the toner carrier and may not be recovered.
The surface of the toner carrier is cleaned; by providing a print rate processing means which processes numerically the print rate corresponding to the image pattern, and a refresh means which applies an alternating electric field between the electrostatic latent image carrier and the toner carrier to carry the toner thereon to the electrostatic latent image carrier side when the print rate falls short of a proper print rate; by obtaining, counting the number of dots for forming the electrostatic latent image corresponding to the actual image pattern, print rate defined as the ratio of the counted number of dots to that required for forming a black solid fills image; and through refresh by the refresh means which allows the toner on the toner carrier to jump to the electrostatic latent image carrier, after transfer of the toner image on the electrostatic latent image carrier to the recording medium is finished, when the print rate falls short of proper print rate. The toner attached to the surface of the electrostatic latent image carrier can be
Ochiai Eiji
Tode Hiroyoshi
Yamada Masayoshi
Brase Sandra
Kyocera Corporation
Schulte Roth & Zabel
LandOfFree
Image forming process and an image forming apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Image forming process and an image forming apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Image forming process and an image forming apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2571424