Electrophotography – Control of electrophotography process
Reexamination Certificate
2000-01-21
2001-11-06
Brase, Sandra (Department: 2852)
Electrophotography
Control of electrophotography process
Reexamination Certificate
active
06314251
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a copying machine, a printer and other image forming apparatuses which use an electrophotographic system or an electrostatic recording system, particularly to an image forming apparatus which is provided with a plurality of image forming sections and which can form an image in a plurality of colors.
2. Related Background Art
In recent years, as an electrophotographic apparatus, a color image forming apparatus of a tandem system has been developed which has image bearing members (photosensitive members) and developing units for four colors and which forms a color image by overlapping four-color images on a sheet with one path. The apparatus has a merit suitable for performing color recording at a high speed.
Even in this system, image formation can also be performed with a single color, and in this case an image forming process of a color with which no image is formed is stopped. However, since the photosensitive member lightly contacts a belt for conveying a sheet or a resin sheet as a transfer material, the photosensitive member is usually rotated not to be damaged.
On the other hand, the miniaturization of the image forming apparatus has been advanced, but even when each of the charging, exposing, developing, transferring, fixing, and cleaning processes is reduced in size, there is a limitation. Moreover, after the transferring process, the transfer residual toner remaining on the surface of the photosensitive member is cleaned by a cleaner and collected (recovered) as waste toner, but it is preferable not to generate this waste toner.
To solve the problem, a cleanerless image forming apparatus has been proposed in which developing and cleaning are performed by a developing unit at the same time. This simultaneous developing and cleaning (cleaning simultaneous with developing) method comprises recovering the transfer residual toner on the photosensitive member by a fog removing bias into the developing unit during developing in the subsequent processes. According to this method, since the transfer residual toner can be used in the subsequent processes, the waste toner can be eliminated, and the trouble of maintenance can be saved. Furthermore, advantages are also large in a spatial respect, and the image forming apparatus can remarkably be miniaturized.
When this cleaner system is employed in the image forming apparatus of the tandem system, a new problem has arisen.
Specifically, during the monochromatic mode in the tandem system, or when originals with images of single color and a plurality of colors are mixed and loaded, the sheet as the transfer material or a second image bearing member contacts each color photosensitive member, and the photosensitive member of the color with which no image is formed has to be simultaneously rotated. Moreover, particularly when the image forming section of the color with which the image is to be formed is not disposed first in order of passage of the transfer material, a transfer bias for adsorbing the transfer material to a conveying belt has to be applied in the image forming section of the color with which no image is formed. In this case, while toner is still unconsumed, the photosensitive member surface is influenced by paper dust or electric discharge by transfer. Therefore, a smeared image is remarkably generated.
When a cleaning blade is disposed, the surface of the photosensitive member is abraded with the toner or an externally added material by the abutment pressure of the blade. In the cleanerless system, however, there is a problem of the smeared image (smudging) during the full-color image formation subsequent to the monochromatic mode.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an image forming apparatus in which a cleanerless system is employed in each of a plurality of image forming sections.
Another object of the present invention is to provide an image forming apparatus in which both a monochromatic mode and a full-color mode can be realized.
A further object of the present invention is to provide an image forming apparatus in which no smeared image is generated.
A still further object of the present invention is to provide an image forming apparatus, which comprises first image forming means provided with a rotating first image bearing member for bearing a toner image; second image forming means provided with a rotating second image bearing member for bearing a toner image; and transferring means for overlapping the toner images of the first image bearing member and the second image bearing member onto a member to be transferred (transfer member), or transferring one of the toner images to the transfer member. Each of the first and second image forming means contacts the surfaces of the first and second image bearing members from which no transfer residual toner is removed, and comprises a rotating charging member for contacting the image bearing members, and a developing unit for developing an electrostatic image on the image bearing member. The image forming apparatus further comprises rotation controlling means for controlling the rotation of the charging member and the image bearing member. The rotation controlling means rotates the second image bearing member and the charging member of the second image forming means during image formation only with the first image forming means.
Further objects of the present invention will be apparent in the following description.
REFERENCES:
patent: 5386286 (1995-01-01), Kinouchi et al.
patent: 5693441 (1997-12-01), Gibson et al.
patent: 5819138 (1998-10-01), Hashizume
patent: 5890038 (1999-03-01), Ohsawa et al.
patent: 5895146 (1999-04-01), Waki et al.
patent: 6006055 (1999-12-01), Furuya
patent: 6029033 (2000-02-01), Kawasaki
patent: 6077635 (2000-06-01), Okado et al.
patent: 0 886 187 A2 (1998-12-01), None
Fukushima Satoru
Gomi Fumiteru
Hashimoto Kouichi
Kimura Yoichi
Komiya Yoshiyuki
Brase Sandra
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Ngo Hoang
LandOfFree
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 apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Image forming apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2601927