Electrophotography – Image formation – Development
Reexamination Certificate
2001-03-13
2003-07-15
Beatty, Robert (Department: 2852)
Electrophotography
Image formation
Development
C399S252000
Reexamination Certificate
active
06594462
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a developing apparatus for forming a developer image by adhering developer to an electrostatic image formed on an image bearing body, which is suitable to be used with an image forming apparatus of electrophotographic type such as a copying machine, a printer, a facsimile and the like.
2. Related Background Art
As a developing apparatus used with an image forming apparatus of an electrophotographic type, various developing apparatuses have been proposed. For example, recently, there has been proposed a so-called nonmagnetic one-component DC contact developing system in which developing is effected by urging a semiconductive developing roller or a developing roller having a surface constituted by a dielectric layer against a surface layer of a photosensitive member.
FIG. 10
is a schematic constructural view showing an image forming apparatus (laser beam printer of an electrophotographic type) having a contact type one-component developing apparatus (referred to merely as “developing apparatus” hereinafter) for effecting development by a conventional nonmagnetic one-component DC contact developing system.
The image forming apparatus includes a drum type electrophotographic photosensitive member (referred to as photosensitive drum” hereinafter)
1
as an image bearing body. Around the photosensitive drum
1
, there are disposed a charging roller
2
, a developing apparatus
3
, a transfer roller
4
and a cleaning blade
5
, and an exposing apparatus
6
is disposed between the charging roller
2
and the developing apparatus
3
. Further, a fixing apparatus is disposed at a downstream side of a transfer nip between the photosensitive drum
1
and the transfer roller
4
in a transfer material conveying direction.
The photosensitive drum
1
is for example an organic photosensitive member having negative charging polarity and is constituted by coating a photosensitive layer (not shown) on an aluminium drum substrate (not shown) and is rotated at a predetermined peripheral speed in a direction shown by the arrow (clockwise direction). During the rotation, the drum is negatively charged uniformly with predetermined potential.
The charging roller
2
as charging means is rotatingly contacted with the surface of the photosensitive drum
1
and serves to negatively charge the photosensitive drum
1
with the predetermined potential by charging bias applied to a charging bias power source (not shown).
The developing apparatus
3
is a contact one-component developing apparatus for effecting development with nonmagnetic toner T as one-component developer and includes a developing roller
9
as developer carrying body) opposed to the photosensitive drum
1
at an opening portion of a developing container
8
and is rotatable in a direction shown by the arrow (counterclockwise direction), a rotatable elastic roller
10
urged against the developing roller
9
, a regulating blade
11
having elasticity and abutting against the developing roller
9
, and an agitating member
12
for agitating the toner T in the developing container
8
. The regulating blade
11
abuts against the developing roller
9
at a downstream side of the abut portion between the developing roller
9
and the elastic roller
10
in a rotational direction of the developing roller
9
.
The toner T agitated by the agitating member
12
is supplied to a surface of the developing roller
9
by the rotating elastic roller
10
urged against the developing roller
9
. The toner T supplied to the surface of the developing roller
9
is carried by the rotation of the developing roller
9
and is subjected to charging by friction in the abut portion between the regulating blade
11
and the developing roller
9
and is formed as a thin toner on the surface of the developing roller
9
. The toner in the thin layer is carried by the rotation of the developing roller
9
and is adhered to the electrostatic latent image formed on the photosensitive drum
1
in the abut portion (developing portion) between the photosensitive drum
1
and the developing roller, thereby visualizing the latent image as a toner image. Incidentally, the toner on the developing roller
9
, which did not contribute to the developing is scraped off by the elastic roller
10
.
The transfer roller
4
as transferring means is urged against the surface of the photosensitive drum
1
with predetermined pressure to define a transfer nip therebetween and serves to transfer the toner image formed on the surface of the photosensitive drum
1
onto a transfer material P in the transfer nip between the photosensitive drum
1
and the transfer roller
4
, by the transfer bias applied from the transfer bias power source (not shown).
The cleaning blade
5
serves to remove residual toner remaining on the surface of the photosensitive drum
1
after the transferring.
The exposing apparatus
6
includes a laser driver, a laser diode and a polygon mirror
14
. In the exposing apparatus, a laser beam modulated in correspondence to a time-lapse electrical digital image signal of image information inputted to the laser driver is outputted from the laser diode, and, by scanning the laser beam by the polygon mirror rotating at a high speed and by effecting image exposure L on the surface of the photosensitive drum
1
through an optical lens system
15
, an electrostatic latent image corresponding to the image information is formed.
The fixing apparatus
7
includes a fixing roller
7
a
and a pressing roller
7
b
. In the fixing apparatus, while the transfer material P is being pinched and conveyed in a fixing nip between the fixing roller
7
a
and the pressing roller
7
b
, the toner image transferred to the surface of the transfer material P is thermally fixed onto the transfer material by heat and pressure.
Next, an image forming operation of the image forming apparatus will be explained.
During the image formation, the photosensitive drum
1
is rotated by driving means (not shown) at the predetermined peripheral speed in the direction shown by the arrow and is uniformly charged by the charging roller
2
. The image exposure L is given to the charged surface of the photosensitive drum
1
by the exposing apparatus
6
, thereby forming the electrostatic latent image corresponding to the inputted image information.
By applying developing bias having the same polarity as a charging polarity (negative polarity) of the photosensitive drum
1
to the developing roller
9
of the developing apparatus
3
, in the developing portion, the toner T charged with the same polarity as the charging polarity (negative polarity) of the photosensitive drum
1
is adhered to the electrostatic latent image formed on the photosensitive drum
1
, thereby visualizing the latent image as the toner image. When the toner image on the photosensitive drum
1
reaches the transfer nip between the photosensitive drum
1
and the transfer roller
4
, in synchronism with this, the transfer material P, such as paper supplied by a pick-up roller
16
, is conveyed to the transfer nip through a registration roller pair (not shown).
By applying transfer bias having polarity (positive polarity) opposite to the polarity of the toner to the transfer roller
4
, the toner image on the photosensitive drum
1
is transferred onto the transfer material P conveyed to the transfer nip. The transfer material P to which the toner image was transferred is conveyed to the fixing apparatus
7
, where the transfer material P is heated and pressurized in the fixing nip between the fixing roller
7
a
and the pressing roller
7
b
to thermally fix the toner image to the transfer material. Thereafter, the transfer material is discharged onto a sheet discharge tray
17
. In this way, a series of image forming operations are finished.
On the other hand, after the toner image transferring, residual toner remaining on the surface of the photosensitive drum
1
is removed by the cleaning blade
5
and is collected into a waste toner container
Ishii Yasuyuki
Kakeshita Tomomi
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