Electrophotography – Control of electrophotography process – Control of cleaning
Reexamination Certificate
2001-09-28
2003-10-07
Chen, Sophia S. (Department: 2852)
Electrophotography
Control of electrophotography process
Control of cleaning
C399S101000, C399S302000
Reexamination Certificate
active
06631249
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming apparatus capable of duplex image formation by performing image formation on one side of a recording material first and then by performing image formation on the back side of the same recording material also by an electrophotographic process.
2. Description of the Related Art
Conventionally various kinds of image forming apparatus commonly including features like the following are proposed. The apparatus are equipped with a plurality of image forming portions adopting an electrophotographic process. Each image forming portion forms a toner image having a different color from each other. The toner images are sequentially superimposed on each other on the same recording material by being transferred to form a color image on the recording material. Furthermore, a color copying machine for performing color high-speed recording was proposed as an image forming apparatus. The machine is equipped with a transfer belt being a recording-material transporting member in a shape of an endless belt, and a plurality of image forming portions arranged in a straight line along the transfer belt.
A brief description of an example of the color copying machine is given on the basis of FIG.
1
. In the machine, a first, a second, a third and a fourth image forming portions Pa, Pb, Pc and Pd are disposed. The image forming portions Pa, Pb, Pc and Pd are equipped with electrophotographic photosensitive drums
3
(
3
a
,
3
b
,
3
c
,
3
d
) being respectively image bearing members for their respective exclusive use, and each color toner image is formed on each photosensitive drum
3
. A transfer belt (recording material transportation member in the shape of a belt)
30
adjoining each photosensitive drum
3
is disposed. Each color toner image formed on each photosensitive drum
3
is superimposed on each other to be transformed on a recording material P to be transported by the transfer belt
30
. After the recording material P, on which each color toner image is transferred, is heated and pressurized by a fixing device
9
, the recording material P is delivered to the outside of the machine as a recording material P bearing a color recorded image.
In such an image forming apparatus, mold releasing oil (also called as “fixing oil”) such as dimethyl silicone oil is reserved in an oil reservoir
53
for the prevention of the adherence of the toner on a recording material to a fixing roller
51
of the fixing device
9
, and the mold releasing oil is coated on the surface of the fixing roller
51
with a coating roller
50
.
Moreover, because toner smear (mainly consisting of untransferred residual toner (called as “fogging toner”) transferred from the photosensitive drums
3
to the transfer belt
30
, and also including paper dust and the like as a part) exist on the transfer belt
30
that has finished transferring, the toner smear is scraped off by the abutting of a cleaning blade
8
a
that is made from an elastic material such as rubber and is fixed on a transfer belt cleaner
8
against the transfer belt
30
, and the scraped toner is collected into the cleaner
8
.
In the configuration shown in
FIG. 1
, the cleaning blade
8
a
is disposed such that the edge surface (a surface parallel to the thickness direction of the blade
8
a
from the abutting portion of the blade
8
a
against the transfer belt
30
) of the blade
8
a
faces toward upward in the gravity direction.
Such a disposition of the cleaning blade
8
a
makes it easy to hold toner on the edge surface of the blade
8
a
, and the holding of the toner makes it possible to realize a stable slidableness at the abutting portion against the transfer belt
30
, and also makes it possible to improve the cleaning performance partly owing to the addition of the polishing effect of the toner.
However, in the case where images are formed on two sides of a recording material in such an image forming apparatus, there is the possibility that toner excessively accumulates on the edge surface of the blade
8
a
to overflow upwards from the cleaner
8
. The overflowed toner adheres to the back side of the recording material to become back side smear, or disperses in the apparatus to smear the inside of the apparatus.
The present inventor's studies reveal the following cause of the accumulation of the toner on the edge surface of the blade
8
a
. That is, after images have been formed on one side of a recording material and then the formed images have been fixed by the fixing device
9
, when the recording material is turned over and borne on the transfer belt
30
again for the image-forming on the back side (second side), the oil, which had been coated on the fixing roller
51
and was adhered to the front side (first side) of the recording material at the time of fixation, adheres to the transfer belt
30
to be carried to the cleaning blade
8
a
. Consequently, when the smear toner on the transfer belt
30
is carried to the blade
8
a
, the toner being powder is mixed with the oil to be clayey. The clayey toner accumulates on the edge surface of the blade
8
a.
Even if the image forming apparatus is one adopting the so-called intermediate transfer process in which toner images on a photosensitive drum is once transferred on an intermediate transfer member and then the images are transferred from the intermediate transfer member to a recording material, the aforesaid problem occurs when the cleaning device having the aforesaid configuration is used.
SUMMARY OF THE INVENTION
One object of the invention is to provide an image forming apparatus capable of preventing the overflow of toner owing to the excessive accumulation of the toner on a cleaning member for a recording material bearing member, intermediate transfer member or a transfer member, and capable of avoiding the troubles of the smearing in a machine, the back side smear of a recording material and the like.
For attaining the foregoing object, a preferable aspect of the invention comprises:
image forming means for forming a toner image;
a recording-material transporting member for bearing and transporting the recording material;
cleaning means equipped with a cleaning blade abutting against a surface of the recording-material transporting member; and
fixing means equipped with a fixing member on which a mold release agent is coated, the apparatus being capable of forming an image on a surface of the recording material, a fixing operation of which has been performed by the fixing means, the surface of the recording material being opposite to a surface thereof on which the toner image is transferred,
wherein:
the cleaning blade is arranged such that a normal line of a surface of the cleaning blade, which is close to an abutting portion against the recording-material transporting member and faces to an upstream side of a transportation direction of the recording-material transporting member against the abutting portion, is substantially directed to a gravity direction; and
the apparatus further comprises control means for controlling the apparatus to transfer a supply toner image, which is to be fed to the cleaning means, formed by the image forming means on the recording-material transporting member directly, and to feed the supply toner image transferred on the recording-material transporting member to the cleaning means by transporting the recording-material transporting member.
Another preferable aspect of the invention comprises:
image forming means for forming a toner image;
an intermediate transfer member for bearing the toner image formed by the image forming means;
transferring means for transferring the toner image borne on the intermediate transfer member onto a recording material;
cleaning means equipped with a cleaning blade abutting against a surface of the intermediate transfer member; and
fixing means equipped with a fixing member on which a mold release agent is coated, the apparatus being capable of forming an image on a surface of the recording material, a fixin
Katsumi Toru
Omata Haruhiko
Suzuki Shinya
Canon Kabushiki Kaisha
Chen Sophia S.
Fitzpatrick ,Cella, Harper & Scinto
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