Electrophotography – Image formation – Transfer
Reexamination Certificate
2001-04-17
2003-02-18
Braun, Fred L (Department: 2852)
Electrophotography
Image formation
Transfer
C399S302000, C399S350000
Reexamination Certificate
active
06522856
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an image forming apparatus using the electrophotographic process such as a copier, a printer or a facsimile apparatus, and particularly to cleaning means for a transfer material or developer image bearing and conveying member in the image forming apparatus.
2. Related Background Art
In recent years, compound machines having all of output terminals such as a copier, a printer and a facsimile apparatus have come to be widely accepted in the market. Image forming apparatuses using the electrophotographic process have been widely accepted as such output terminals coping with the network, but the limited number of sheets for which the main body continues to operate normally without maintenance, i.e., the so-called duty cycle, has been mentioned as a great problem. The greatest rate controlling of the duty cycle is the life of an image bearing member, and from the viewpoint of ecology, it has become a great task to eliminate waste, that is, the decrease expendables, to extend the lives of the expendable, improve reliability, etc.
Also, the digitization of conventional analog apparatuses has been advanced, and it has also become a task to make the cost of the main body equivalent to or less than that of the analog apparatus. Further, black-and-white machines have been in the mainstream not only in conventional copiers and printers, but in offices as well, the full coloration of originals or output files is increasing rapidly. Accordingly, not only the digital machines equivalent to black-and-white printers, reducing the cost of the main body and running cost has become a task. For this reason, there has been desired a technique which can epoch-makingly reduce TCO (total cost of owners, i.e., total necessary cost as viewed from the user).
In such a situation, in recent years, the mainstream has been occupied by a color image forming apparatus which is provided with a plurality of photo-sensitive drums and a transfer belt for bearing and conveying a recording material, and sequentially superimposes and transfers toner images of different colors formed on the respective photosensitive drums to the recording material borne on the transfer belt to thereby obtain a color image, i.e., a so-called four-station tandem type color image forming apparatus.
Also, in the above-described image forming apparatus, various adhering materials (such as toners scattering from the photosensitive drums, toners transferred from the photosensitive drums during jam or at the time between a sheet and a sheet, and mold releasing oil adhering to the recording material during the toner image fixation on a first surface when image formation is effected on a second surface of the recording material) adhere onto the transfer belt as a recording material bearing member and therefore, it has been proposed to provide as cleaning means a counter blade system, a fur brush system, an oil cleaner roller for removing the mold releasing oil, an oil cleaner web or the like. There has also been proposed a toner manufactured by the polymerizing method having oil internally added which need not use such mold releasing oil.
An example of such image forming apparatus in which a recording material such as paper is attracted to and conveyed by a transfer belt (endless belt) as a recording material bearing member and image formation is effected will now be described briefly with reference to
FIG. 6
of the accompanying drawings.
The image forming apparatus is provided with a photosensitive drum
205
therein, and a toner image is formed on the photosensitive drum
205
. A transfer belt
206
as a recording material bearing member is installed adjacent to the photosensitive drum
205
, and the toner image formed on the photosensitive drum
205
is transferred onto a recording material P borne on and conveyed by the transfer belt
206
. The recording material P to which the toner image has been transferred has the toner image thereon fixed by heating and pressurizing in a fixing device
209
, whereafter it is discharged out of the apparatus as a recorded image.
An exposure lamp
201
, a photosensitive drum charger
202
, an exposure device
203
, a developing device
204
, a transfer charger
207
and a cleaner
208
are provided around the photosensitive drum
205
, and although not shown, a light source device and a polygon mirror are further installed in the upper portion of the apparatus.
A laser beam emitted from the light source device is scanned by the rotating polygon mirror, and the scanned beam is deflected by a reflecting mirror, and is condensed on the generatrix of the photosensitive drum
205
by an f&THgr; lens and the photosensitive drum
205
is exposed to the light, whereby a latent image conforming to an image signal is formed on the photosensitive drum
205
.
The developing device
204
is filled with a predetermined amount of toner by a toner supplying device, not shown. The developing device
204
develops the latent image on the photosensitive drum
205
and visualizes it as a toner image.
The recording material P is contained in a recording material cassette, not shown, and is supplied therefrom to the transfer belt
206
via a plurality of conveying rollers and registration rollers
213
, and is sequentially fed to a transfer position opposed to the photosensitive drum
205
by the conveyance by the transfer belt
206
.
The transfer belt
206
is formed of a material comprising a dielectric material resin sheet such as a polycarbonate resin sheet, a polyethylene terephthalate resin sheet (PET resin), a polyvinylidene fluoride resin sheet, a polyurethane resin sheet, a polyamide resin sheet or a polyimide resin sheet having a resin filler such as carbon black dispersed therein, and having its volume resistivity adjusted to the order of 10
7
-10
15
&OHgr;cm, and use is made of a belt having its opposite end portions superposed upon each other and joined together, and made into an endless shape, or a belt having no seam (seamless).
This transfer belt
206
is rotated by a driving roller
211
and when it reaches a predetermined speed, the recording material P is fed out from the registration rollers
213
to the transfer belt
206
, and the recording material P is conveyed toward the transfer position. At the same time, an image writing signal becomes ON, and with it as the reference, image formation is effected on the photosensitive drum
205
at predetermined timing. Then, at the transfer position under the photosensitive drum
205
, the transfer charger
207
imparts an electric field or charges, whereby the toner image formed on the photosensitive drum
205
is transferred to the recording material P. The recording material P, when fed out from the registration rollers
213
onto the transfer belt
206
, is immediately nipped with the transfer belt
206
by and between an attracting charger
214
and an attracting charger opposite roller
215
, and an electric field or charges are induced by the attracting charger
214
, whereby the recording material P is electrostatically held on and conveyed by the transfer belt
206
.
As the transfer charger
207
, use is made of a non-contact charger such as a corona discharger, or a contact charger using a charging member such as a charging roller, a charging brush or a charging blade. The non-contact charger suffers from the problem that ozone is created, and the problem that charging is done through the air and therefore such charger is weak to the environmental fluctuations of temperature and humidity and images are not formed stably. On the other hand, the contact charger has the merit that ozone is not created and the charger is strong to the environmental fluctuations of temperature and humidity.
Next, the recording material P to which the toner image has been transferred has its charges eliminated in the downstream portion of the transfer belt
206
with respect to the direction of conveyance by a separating charger
216
and has its electrostatic attraction attenuated, whereby it l
Braun Fred L
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
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