Electrophotography – Having particular structure – Modular or displaceable
Reexamination Certificate
2002-07-03
2004-03-16
Chen, Sophia S. (Department: 2852)
Electrophotography
Having particular structure
Modular or displaceable
C399S112000, C399S113000, C399S299000, C399S302000
Reexamination Certificate
active
06708011
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to a system for forming color images, and more particularly to a tandem type color image formation system wherein a plurality of photosensitive members are designed in a single cartridge unit form for detachment/attachment purposes, thereby improving the integrity of maintenance.
Generally, toner image formation means for electro-photography comprises a photosensitive member acting as an image carrier having a photosensitive layer on its outer surface, charger means for uniformly charging the outer surface of the photosensitive member, exposure means for subjecting the outer surface of that member uniformly charged by the charger means to selective exposure to form an electrostatic latent image and developing means for imparting toner that is a developing agent to the electrostatic latent image formed by the exposure means to make a visible (toner) image.
The tandem system for forming color images known in the art are broken down into two types, one called the intermediate transfer belt type wherein a plurality of (e.g., four) such toner image formation means as mentioned above are provided with respect to an intermediate transfer belt (that is one example of the transfer belt) and toner images formed by these monochromatic toner image formation means on photosensitive members are successively transferred on the intermediate transfer belt so that the toner images of different colors (e.g., yellow, cyan, magenta and black) are superposed on the intermediate transfer belt, thereby obtaining a full-color image thereon, and another called the delivery belt type wherein a recording medium (e.g., a recording sheet) is carried and delivered onto a recording medium carrier belt (that is another example of the transfer belt) and toner images formed by a plurality of different monochromatic image formation means are successively transferred on the recording medium, so that the toner images of different colors are superposed on the recording medium, thereby obtaining a full-color image thereon.
For instance, one such conventional tandem image formation system is disclosed in JP-A 62-141574. This system is constructed of a plurality of joinable units, each comprising a plurality of developing and other processing means, so that the joined units are attachable to or detachable from the system proper. The system is economically advantageous because the units are individually designed as being attachable or detachable, so that a dead cartridge(s) alone can be replaced by new one.
JP-A 03-238467 describes an image formation system wherein a plurality of process units, each comprising developing means and an image carrier, are supported on one single support plate. All the process units are removed from the system at a time, and so the integrity of maintenance of the system is improved.
JP-A 09-160471 shows that process units except one for black are integrated together for easy replacement, so that the frequency of replacement of a process portion can be reduced, making control of consumable parts easy.
JP-A 09-304994 shows that a plurality of image carriers are integrally supported. In the examples, such image carriers inclusive of developing means are integrated together, so that the precision of positions of the image carriers in the system proper can be improved, resulting in elimination of color misalignments, improvements in the integrity of maintenance, and no risk of anything wrong upon insertion of the image cartridges.
JP-A 11-174772 shows that a support member is provided to locate both ends of each image formation member at a given position, thereby minimizing position misalignments of each image formation member.
In general image formation systems wherein toner is imparted from developing means to electrostatic latent images on image carriers to render the latent images visible, the service life of the image carriers differs largely from that of the developing means. Especially in the case of an image formation system using a mono-component developing agent, it is necessary to engage a control blade with a developing roller under high loads, thereby controlling the thickness of a developing agent thin layer on the developing roller. Then, the developing roller and control blade wear away due to friction between both, inevitably resulting in their service life becoming shorter than that of the image carriers. Thus, a problem with a conventional system wherein image carriers and developing means are replaced at the same time is that running costs increase because the service life of the system is governed by the developing means and so there is a need of replacing the image carriers even when they are still of avail. In particular, recently developed image carriers are being shifted to the “cleaner-less” type wherein the service life of image carriers is increased because of the absence of any material that wears off the image carriers. There is thus an especially large difference in service life between the image carriers and developing means, leading to growing demands for replacement of only the developing means.
In the tandem type comprising a plurality of image carriers, the precision of color matching is largely depending on the position and shape of the image carriers. When the image carriers are replaced, color matching operation is needed after replacement, because it is difficult to keep the position and shape of the image carriers in perfect alignment between before and after replacement. Referring here to the aforesaid prior art wherein the image carriers are replaced along with the developing means, frequent color matching operations are needed, resulting in a problem that the efficiency of operation becomes low.
In a tandem system for the formation of images, the precision of color matching is largely dependent on the positions of the image carriers on which latent images are to be written. In the aforesaid prior art, write means are mounted on the system proper, and when the image carriers are replaced, there are displacements of latent images written on the image carriers, which give rise to color misalignments and cause image quality to deteriorate.
Furthermore in the tandem for forming images, the precision of color matching is considerably dependent on the precision of transfer positions on the image carriers. In the aforesaid prior art, when the image carriers are replaced, there are displacements of toner images transferred from the image carriers onto a transfer member (an intermediate transfer belt or recording medium), resulting in color misalignments and deterioration of image quality.
SUMMARY OF THE INVENTION
In view of such problems with the prior art as mentioned above, an object of the present invention is to provide a tandem system for the formation of color images wherein a plurality of image carriers are integrated into a single cartridge and developing means for each image carrier is designed to be detachable from or attachable to the cartridge, thereby improving the integrity of maintenance and cutting back on running costs.
Another object of the present invention is to provide a tandem system for the formation of color images wherein a plurality of image carriers and write means are integrated into a single cartridge and developing means for each image carrier is designed to be detachable from or attachable to the cartridge, thereby improving the integrity of maintenance, cutting back on running costs, and reducing color misalignments.
Yet another object of the present invention is to provide a tandem system for the formation of color images wherein a plurality of image carriers and an intermediate transfer belt are integrated into a single cartridge and developing means for each image carrier is designed to be detachable from or attachable to the cartridge, thereby improving the integrity of maintenance, cutting back on running costs, and improving the precision of transfer positions to reduce color misalignments.
A further object of the present invention is to provide a tandem
Abe Nobumasa
Nomura Yujiro
Yoda Kaneo
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