Electrophotography – Control of electrophotography process – Having temperature or humidity detection
Reexamination Certificate
1999-09-22
2001-05-01
Pendegrass, Joan (Department: 2852)
Electrophotography
Control of electrophotography process
Having temperature or humidity detection
C399S066000, C399S302000
Reexamination Certificate
active
06226465
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an image forming apparatus using the electrophotographic method such as a copying apparatus, a printer or a facsimile apparatus.
2. Related Background Art
Image forming apparatuses according to the earlier technology use various methods such as the electrophotographic method, the thermal transfer method and the ink jet method. Among these, the electrophotographic method is excellent as compared with the other methods in terms of high speed, high quality of image and quietude, and has widely spread in recent years.
A color image forming apparatus using this electrophotographic method is grouped into various methods such as the multi-development method in which color images are superposed on the surface of a photosensitive member, whereafter they are collectively transferred to thereby effect image formation, the multi-transfer method in which the cycle of development-transfer is repetitively effected, and the intermediate transfer method in which developed images of respective colors are once sequentially transferred onto an intermediate transfer member, and thereafter are collectively transferred to a transfer material, among these, particularly the intermediate transfer method is an excellent method for the reasons that there is no possibility of colors being mixed with one another and that application to various media is possible.
FIG. 5
of the accompanying drawings shows an example of the construction of the intermediate transfer belt method which is an intermediate transfer method. In
FIG. 5
, a photosensitive drum
101
is rotated in the direction indicated by the arrow, and around the peripheral surface thereof, there are disposed a plurality of developing devices, i.e., a black developing device
105
, a magenta developing device
106
, a cyan developing device
107
and a yellow developing device
108
, which are designed to be brought into contact with the photosensitive drum
101
by means, not shown, as required.
The photosensitive drum
101
is uniformly charged by a charger
102
, and a latent image is formed thereon by a laser beam
104
with the aid of a laser exposure optical system
103
or the like. Next, this latent image is developed by one of the aforementioned developing devices
105
to
108
, and is sequentially primary-transferred onto an intermediate transfer belt
109
rotated in the direction indicated by the arrow in a primary transfer portion (transfer position). The above-described steps are also successively effected with respect to the other developing devices, and color images of four colors superposed on top of one another are formed on the intermediate transfer belt
109
, whereupon a secondary transfer roller
111
is brought into contact with the intermediate transfer belt with a transfer material
118
interposed therebetween, and the color images are collectively secondary-transferred onto the transfer material
118
.
At the above-described primary transfer step, if the photosensitive drum
101
is, for example, an OPC (organic photoconductor) photosensitive member of the negative polarity, toners of the negative polarity are used when the exposed portion exposed by the laser beam
104
is developed by the developing devices
105
to
108
, and accordingly, a transfer bias of the positive polarity is applied from a bias voltage source
120
to the primary transfer roller
110
, and transfer is effected.
However, when in the primary transfer portion of the above-described image forming apparatus, the peripheral speeds of the photosensitive drum
101
and the intermediate transfer belt
109
are equal to each other, there has been the problem that sufficient transfer efficiency is not obtained and a so-called hollow image (edge effect) is created.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an image forming apparatus which can prevent hollow characters from being created in a toner image transferred from an image bearing member to an intermediate transfer member and also which can stably keep a pressure force with which transfer means presses the intermediate transfer member against the image bearing member to prevent toner from fusing and bonding to the image bearing member or the intermediate transfer member.
In accordance with these objects there is provided an image forming apparatus having a movable image bearing member for bearing a toner image thereon, a movable intermediate transfer member, and transfer means for pressing the intermediate transfer member against the image bearing member at a transfer position at which the image bearing member is in con tact with the intermediate transfer member so that the transfer means transfers the toner image on the image bearing member to the intermediate transfer member, wherein the toner image transferred onto the intermediate transfer member by the transfer means is transferred to a transfer material, wherein a ratio of a moving speed of the intermediate transfer member at the transfer position to a moving speed of the image bearing member at the transfer position is 1.002 to 1.020, and a pressure force with which the transfer means presses the intermediate transfer member against the image bearing member is 10 to 70 g/cm.
In accordance with yet another aspect of the invention, there is provided an image forming apparatus having a movable image bearing member bearing a toner image thereon, a movable intermediate transfer member to which the toner image on the image bearing member is transferred at a transfer position, the toner image on the intermediate transfer member being transferred to a transfer material, detecting means for detecting temperature and humidity in a main body of the apparatus, and control means for controlling a ratio of a moving speed of the intermediate transfer member at the transfer position to a moving speed of the image bearing member at the transfer position based on a result of detection by the detecting means.
The above and other objects, features an advantages of the present invention will become more apparent upon consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 5508789 (1996-04-01), Castelli et al.
patent: 5778291 (1998-07-01), Okubo et al.
patent: 6026269 (2000-02-01), Setoriyama
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Pendegrass Joan
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