Electrophotography – Image formation – Photoconductive member
Reexamination Certificate
2000-08-03
2001-10-09
Brase, Sandra (Department: 2852)
Electrophotography
Image formation
Photoconductive member
C399S117000
Reexamination Certificate
active
06301458
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus adapted for use as, for example, an electrophotographic color copying machine of the tandem type.
An electrophotographic color copying machine of the tandem type comprises a plurality of image forming sections that are arranged in the direction of paper transportation. Each image forming section includes a photoconductor drum and a developing unit, which are integrally unitized to form a process unit.
A plurality of drive motors are arranged on the back surface side in the body of the copying machine. A drum shaft of each photoconductor drum is releasably connected for rotation to a drive shaft of its corresponding drive motor.
Toner images of different colors are formed individually on the photoconductor drums of the process unit. The toner images of the individual colors on the drums are transferred successively to the surface of paper that is transported by means of a transfer belt, whereupon a color image is formed on the paper.
The process unit requires maintenance operation after the formation of every tens of thousands of images. Accordingly, the process unit is designed so that it can be loaded into or unloaded from the copying machine body. In starting the maintenance operation, therefore, the process unit can be drawn out of the machine body.
When the process unit is inserted into the color copying machine, the respective drum shafts of its photoconductor drums are connected individually to the respective drive shafts of the drive motors. This connection should be reliable.
The rotation of the drive motors is subject to unevenness or vibration. If the uneven or vibratory rotation is transmitted to the drum shafts of the photoconductor drums through the drive shafts, the resulting images are blurred and lowered in quality.
As is described in Jpn. Pat. Appln. KOKAI Publications Nos. 2-130562, 2-225862, 2-287577, and 3-80264, therefore, arrangements are conventionally used such that a drum shaft and a drive shaft are connected to each other by means of a non-coaxial spur or helical gear train.
Although the drum shaft and the drive shaft can be securely connected to each other in the conventional arrangements, however, the non-coaxial gear train is used for the connection, so that backlash is entailed. Infinitesimal vibration is generated even in helical gears in which impact is dispersed between their teeth. This vibration is transmitted to the photoconductor drums, thereby exerting a bad influence upon the image quality.
In order to solve this problem, a novel arrangement has been developed in which a drum shaft and a drive shaft are coaxially connected to each other by means of a coupling.
In the case of this coupling system, however, the drum shaft cannot be inserted into the coupling if there is relative dislocation between the drum shaft and the drive shaft. In the case of the tandem type, in particular, a plurality of drum shafts are designed to be inserted individually into a plurality of couplings, so that smooth insertion is difficult.
If the drum shaft of a photoconductor drum is inserted into the coupling by force, moreover, images are subject to dimensional unevenness or blur, and excessive load acts on the bearing of the drum shaft. Thus, the bearing is deteriorated, so that satisfactory image quality cannot be ensured.
BRIEF SUMMARY OF THE INVENTION
The present invention has been contrived in consideration of these circumstances, and its object is to provide an image forming apparatus designed so that a shaft of an image carrying body can be securely inserted into a coupling with ease to ensure good image quality.
An image forming apparatus according to the present invention comprises: an image carrying body rotatable around a shaft; image forming means for forming an image on the image carrying body; developing means for supplying a developing agent to the image formed by the image forming means, thereby forming a developing agent image; transfer means for transferring the developing agent image formed by the developing means to a transfer medium; drive means having a drive shaft mounted with a coupling into which the distal end portion of the shaft of the image carrying body is inserted such that the drive shaft and the shaft of the image carrying body are coaxially connected to each other by means of the coupling; and an elastically deformable portion formed on the shaft of the image carrying body and/or the coupling and adapted to be elastically deformed in a direction such that the deformable portion contracts or expands when the shaft of the image carrying body is inserted into the coupling.
Another image forming apparatus according to the invention comprises: a plurality of image forming sections including a plurality of image carrying bodies rotatable around a shaft each, a plurality of image forming means for forming images individually on the image carrying bodies, and a plurality of developing means for supplying developing agents of different colors to the images formed by the image forming means, thereby forming developing agent images, the image carrying bodies and the developing means being integrally unitized to form a process unit; transfer means for successively transferring the developing agent images formed by the image forming sections to a transfer medium; a plurality of drive means each having a drive shaft mounted with a coupling into which the distal end portion of the shaft of each image carrying body is inserted such that the drive shaft and the shaft of the image carrying body are coaxially connected to each other by means of the coupling; and elastically deformable portions formed individually on the respective shafts of the image carrying bodies and/or the couplings and adapted to be elastically deformed in a direction such that the deformable portions contract or expand when the respective shafts of the image carrying bodies are inserted individually into the couplings.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
REFERENCES:
patent: 5132728 (1992-07-01), Suzaki et al.
patent: 5579093 (1996-11-01), Wagner et al.
patent: 5740500 (1998-04-01), Hashimoto
patent: 5745825 (1998-04-01), Okawa et al.
patent: 5774767 (1998-06-01), Shibata et al.
patent: 6055399 (2000-04-01), Omura
patent: 2-130562 (1990-05-01), None
patent: 2-225862 (1990-09-01), None
patent: 2-287577 (1990-11-01), None
patent: 3-80264 (1991-04-01), None
Mori Tokihiko
Tanaka Toshiaki
Brase Sandra
Foley & Lardner
Toshiba Tec Kabushiki Kaisha
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