Electrophotography – Control of electrophotography process – Responsive to copy media characteristic
Reexamination Certificate
2002-05-17
2004-05-04
Chen, Sophia S. (Department: 2852)
Electrophotography
Control of electrophotography process
Responsive to copy media characteristic
C073S105000, C073S661000
Reexamination Certificate
active
06731886
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an image forming apparatus such as a printer, a copying machine, an ink jet printer, a thermal head printer, a dot impact printer, or a facsimile apparatus of the electrophotographic type or a compound apparatus of these, and particularly to a surface, surface roughness, surface smoothness, or surfaceness discriminating device for discriminating the surfaces of recording materials applicable to these.
2. Description of Related Art
Various kinds of image forming apparatuses heretofore known are generally apparatuses for forming an image on a sheet-like recording material such as plain paper, a postcard, cardboard, an envelope or a plastic thin sheet for OHP, and in an apparatus such as a printer, a copying machine or a facsimile apparatus using the electrophotographic process as a typical example thereof, a toner is used as a developer and a toner image is formed on the recording material by electrostatic image forming means, whereafter the recording material is heated and pressurized by fixing means to thereby fusion-bond the toner image on the recording material and accomplish image formation.
Also, apparatuses such as a printer, a copying machine and a facsimile apparatus using the ink jet process which are other apparatuses use ink as a developer, and form an image on a recording material by image forming means for discharging the ink at a high speed from a recording head constructed by the use of a number of nozzles having minute orifices by the utilization of mechanical or thermal reaction.
Apparatuses such as a printer, a copying machine and a facsimile apparatus using the heat transfer process use an ink ribbon as a developer, and form an image on a recording material by image forming means for thermally transferring ink from the ink ribbon by the use of a thermal head.
By the way, these apparatuses have been improved in recent years and contrivances for a higher quality of image and a higher processing speed have come to be realized by various means and at the same time, a measure for reduced costs has also been contrived and lower prices have been advanced and the apparatuses have come to spread widely.
However, the kinds of recording materials used in these image forming apparatuses are various from plain paper to high-class paper subjected to special surface treatment for use as an envelope and a resin sheet for OHP. Further, these recording materials have come to be used all over the world with the spread of the apparatuses and therefore, it has become necessary to cope with any recording materials used in various parts of the world so as to be capable of forming good images, and particularly the roughness of the surfaces of recording materials with greatly affects the image forming conditions is a very important factor.
For example, in an apparatus adopting the electrophotographic process, when the surface of the recording material used is smooth (hereinafter referred to as smooth paper) and when the surface of the recording material used is rough (hereinafter referred to as rough paper), the heating efficiency of transmitting heat from a heat source to the paper surface in a fixing portion differs in accordance with the heat resistance difference due to the difference in surface roughness, and if the rough paper is fixed at a fixing temperature proper for the smooth paper, insufficient fixing will result and therefore, for the rough paper, it is necessary to fix at a higher temperature. Thus, in the apparatuses as they are, the temperature which can fix the rough paper is used as the fixing temperature and the smooth paper remains fixed always at an excessive temperature and further, for rougher paper, a still higher fixing temperature is necessary and therefore, when such paper is used, there has been provided a selecting mode for making a user change the setting of the fixing temperature.
As a specific example of these, the basic construction of a printer adopting the electrophotographic process is shown in
FIG. 3A
of the accompanying drawings.
FIG. 3A
is a cross-sectional view of the essential portions of a conventional printer, and in the printer, the surface of a photosensitive drum
102
is uniformly charged to a predetermined polarity by a charging roller
101
, whereafter charges are eliminated from only that area of the photosensitive drum
102
which has been exposed by exposing means
103
such as a laser to thereby form a latent image on the photosensitive drum
102
. The latent image is developed and visualized as toner image by the use of a toner
105
in a developing device
104
. That is, the toner
105
in the developing device
104
is triboelectrically charged to the same polarity as the charged surface of the photosensitive drum
102
between a developing blade
104
a
and a developing sleeve
104
b
, and a DC bias and an AC bias are superimposed and applied in a developing gap portion wherein the photosensitive drum
102
and the developing sleeve
104
b
are opposed to each other, and the toner
105
is caused to selectively adhere to the latent image forming portion of the photosensitive drum
102
while being floated and vibrated by the action of an electric field, whereafter the toner
105
is carried to a transfer nip portion formed between a transferring roller
110
and the photosensitive drum
102
by the rotation of the photosensitive drum
102
.
On the other hand, a recording material
107
such as paper on which an image is to be recorded has its leading edge portion fed from a recording material containing box
107
′ to a pair of vertically conveying rollers
106
′ by a pair of feed rollers
107
″, and thereafter it is conveyed to a pair of ante-transfer conveying rollers
106
by the pair of vertically conveying rollers
106
′, and is further conveyed to the transfer nip portion along a transfer guide plate
109
at a prescribed angle of entry by the ante-transfer conveying rollers
106
. During the time when the recording material
107
is conveying from the ante-transfer conveying rollers
106
to the transfer nip portion, the surface of the recording material
107
may be charged by the frictional contact thereof with various members with which the recording material
107
contacts until it is conveyed to this area and therefore, a charge eliminating brush
108
for eliminating such unnecessary charges which may become a factor disturbing the image when electrostatic recording is effected is provided so as to contact with the back side of the recording material
107
being conveyed, and is grounded.
In order to electrostatically attract the toner
105
on the photosensitive drum
102
to the recording material
107
side in a transferring portion, a high voltage opposite in polarity to the toner
105
is applied to a transferring roller
110
on the back of the recording material
107
, whereby the toner
105
is electrostatically attracted to the back of the recording material
107
and the toner image is transferred to the recording material
107
and also, the back side of the recording material
107
is charged to a polarity opposite to that of the toner
105
, and transferring charges for continuing to hold the transferred toner
105
are imparted to the back side of the recording material
107
.
Lastly, the recording material
107
to which the toner image has been transferred is conveyed to a fixing device
112
comprised of a heating rotary member
113
and a pressure roller
114
forming a nip portion therewith, and is heated and pressurized while being controlled to a constant temperature by constant temperature control means
116
provided on the heating rotary member
113
side so as to maintain a fixing temperature preset in the nip portion, whereby the toner image is fixed.
Adhering substances such as the toner differing in polarity remain slightly on the surface of the photosensitive drum
102
after the toner image has been transferred therefrom and therefore, the adhering substances on the surface of the
Canon Kabushiki Kaisha
Chen Sophia S.
Fitzpatrick ,Cella, Harper & Scinto
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