Electrophotography – Image formation – Development
Reexamination Certificate
2003-03-26
2004-07-27
Chen, Sophia S. (Department: 2852)
Electrophotography
Image formation
Development
C399S071000, C399S082000, C399S302000, C399S343000
Reexamination Certificate
active
06768891
ABSTRACT:
This document claims priority and contains subject matter related to Japanese Patent Applications Nos. JPAP11-166288 filed on Jun. 14, 1999, JPAP11-365318 filed on Dec. 22, 1999 and JPAP2000-114451 filed on Apr. 14, 2000, and the entire contents thereof are herein incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming apparatus such as, a copying machine, a facsimile, a printer, etc., and more particularly to an image forming unit device including a belt-formed member and a belt device in which the belt-formed member drives accurately even when the belt-formed member temporarily separates from some of opposing members.
2. Discussion of the Background
As an image forming apparatus, a tandem multicolor image forming apparatus, that includes an intermediate transfer element supported by a plurality of supporting rollers and a plurality of photoconductive elements as opposing members (image bearing members) arranged side by side in a line opposite to the intermediate transfer element and contacting the intermediate transfer element is known (e.g. in Japanese Utility Model Laid-Open No. 59-192159 and Japanese Patent Laid-Open publication No. 8-160839). In the apparatus, visible images corresponding to respective colors formed on surfaces of respective photoconductive elements are transferred onto the intermediate transfer element one after another while being superimposed with each other (a primary transfer). The visible image thus formed on the intermediate transfer element is then transferred onto a transfer member at one time (a secondary transfer) to form a multicolor image on the transfer member. In those multicolor image forming apparatuses, there are apparatuses configured such that a black and white image forming mode using a single photoconductive element and a multicolor image forming mode superimposing toner images of a plurality of colors with each other using a plurality of photoconductive elements are selectable.
FIG. 27
illustrates a fullcolor electrophotographic copying machine using liquid developer as an example of the above-described tandem multicolor image forming apparatus. In the apparatus, four drum-shaped photoconductive elements
501
Y,
501
M,
501
C and
501
B corresponding to respective colors of yellow Y, magenta M, cyan C and black BK are provided side by side in a line such that the axes of rotation of photoconductive elements are located in parallel and in the same plane. Around respective photoconductive elements
501
Y,
501
M,
501
C and
501
B rotating in a clockwise direction, charging devices, writing systems to form an electrostatic image by irradiation of beam light corresponding to respective colors, developing units with liquid developer for respective colors etc. (not shown) are provided respectively in an order of a liquid electrophotographic printing process. Further, an intermediate transfer belt
505
as an intermediate transfer member is supported by a tension roller
502
, guide rollers
503
and
504
etc. so as to rotate in a counterclockwise direction. The intermediate transfer belt
505
is disposed so as to contact each primary transfer area of photoconductive elements
501
Y,
501
M,
501
C and
501
B. The intermediate transfer belt
505
is pressed by spanning rollers
506
Y,
506
M,
506
C and
506
B so that it windingly contacts respective photoconductive elements. An image on the intermediate transfer belt
505
, which has been formed as a result of transferring images of respective colors (Y, M, C and BK) at the primary transfer areas of respective photoconductive elements
501
Y,
501
M,
501
C and
501
B superimposing one after another, is conveyed to a secondary transfer area where a portion of the intermediate transfer belt
505
spanned between guide rollers
503
and
504
contacts a secondary transfer roller
507
. Then, the image is transferred onto a transfer sheet
508
at the secondary transfer area to form a multicolor image on the transfer sheet
508
. Further, a cleaning device
509
is provided at a place where the intermediate transfer belt
505
is supported by the tension roller
502
.
In the fullcolor electrophotographic copying machine with liquid developer, a color mode can be freely selected from among, for example, a single color mode and a multicolor mode with four colors (a full color mode), two colors or three colors. For example, when a single color mode (black color mode) is selected, a black color image is formed on the transfer sheet
508
using the photoconductive element
501
B, electrophotographic copying process members and the intermediate transfer belt
505
.
When a single color image forming operation is performed in the above-described electrophtographic copying machine having selectable single color and multicolor modes, inconveniences may be caused because the photoconductive elements which are not involved in the image forming operation are located in contact with or in close proximity to the intermediate transfer element.
For example, life times of the photoconductive elements may be decreased because the photoconductive elements are kept in contact with the intermediate transfer element even when the photoconductive elements are not involved in the image forming operation. In the apparatus illustrated in
FIG. 27
, even in the black color mode, photoconductive elements
501
Y,
501
M and
501
C, which are not involved in the image forming operation, are kept in contact with the intermediate transfer belt
505
and are rubbed by it. Therefore the life times of these photoconductive elements may be decreased.
Further, when photoconductive elements which are not involved in the image forming operation are kept in contact with or in close proximity to the intermediate transfer element, developer remaining on the photoconductive elements may be flown by the intermediate transfer element and scattered inside the apparatus. Developer remaining on the photoconductive elements may also adhere to a surface of the intermediate transfer element, which results in unnecessary consumption of developer.
The above-described inconveniences such as the life times of opposing members, such as photoconductive elements being decreased due to unnecessary contact of a belt-formed member, such as the intermediate transfer element, with the opposing members are caused not only in the above-described exemplary construction where a plurality of photoconductive elements are located side by side in a line so as to oppose and contact the belt-formed intermediate transfer element, but also in a construction where a plurality of opposing members are disposed side by side in a line so as to oppose and contact a belt-formed member supported by a plurality of supporting rollers driven while being temporarily separated from part of the plurality of opposing members. The above-described inconveniences are also caused, for example, in a construction where a belt-formed photoconductive element drives while the belt-formed photoconductive element is temporarily separated from part of a plurality of developer bearing members as the plurality of opposing members, or in a construction where a belt-formed transfer sheet conveying member drives while the belt-formed transfer sheet conveying member is temporarily separated from part of a plurality of photoconductive elements as the plurality of opposing members. Further, the above-described scattering of developer and unnecessary consumption of the developer occur not only when the plurality of opposing members are located side by side in a line opposing and contacting the belt-formed member but also when the plurality of opposing members are located side by side in a line opposing the belt-formed member in close proximity.
For example, in Japanese Patent Laid-Open Publication No. 9-146383, an example of an image forming apparatus, configured such that a transfer sheet conveying belt partly moves to separate from three photoconductive elements out of four, is described.
The inventors discovered the f
Aoyama Yuichi
Miyawaki Katsuaki
Obu Makoto
Sasamoto Tetsurou
Suzuki Minoru
Chen Sophia S.
Ricoh & Company, Ltd.
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