Electrophotography – Image formation – Development
Reexamination Certificate
2000-12-12
2003-02-18
Chen, Sophia S. (Department: 2852)
Electrophotography
Image formation
Development
C399S277000
Reexamination Certificate
active
06522854
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a developing apparatus used with an image forming apparatus of electrophotographic or electrostatic type such as a copying machine, a printer and the like and adapted to develop a latent image an an image bearing member.
2. Related Background Art
In conventional image forming apparatuses of electrophotographic type, a latent image is formed on a photosensitive drum as an image bearing member by selectively exposing a surface of the photosensitive drum uniformly charged by a charging apparatus by means of an exposing apparatus, and the latent image is visualized with toner as a developer by a developing apparatus to form a toner image, and the toner image is transferred onto a recording medium such as a paper or an OHP sheet, and the toner image is fixed to the recording material with heat and pressure, thereby obtaining an image.
On the other hand, after the toner image is transferred, residual toner remaining on the photosensitive drum is removed by a cleaning apparatus, for preparing for next image formation starting from charging.
Incidentally, in such image forming apparatuses, when the apparatus is used for a long term, replenishing of new toner to the developing apparatus and adjustment, cleaning and exchanging of various process parts including the photosensitive drum are required. It was practically difficult for the users other than experts to perform such maintenance. Thus, in order to solve this problem, there has been proposed a process cartridge in which a toner and process means such as a photosensitive drum, a developing apparatus, charging apparatus and cleaning apparatus are integrally incorporated as a cartridge unit which can detachably be mounted to an image forming apparatus, thereby enhancing maintenance ability, and such a process cartridge is put to practical use.
The developing apparatus included in such a process cartridge comprises a developing apparatus frame for containing toner as developer, a developer carrying member, and a developing blade as a developer regulating member.
The developer carrying member comprises a developing roller as a hollow cylindrical member in which flanges as shaft members are attached to both ends of a hollow cylinder made of conductive and nonmagnetic material such as aluminum, and a magnet roller held within the developing roller. A gear for transmitting a rotational driving force to the developing roller is secured to one of the flanges of the developing roller. The developer carrying member is arranged so that an outer peripheral surface of the developer roller cylinder is opposed to an outer peripheral surface of the photosensitive drum with a predetermined gap (preferably, 0.2 to 0.5 mm) therebetween.
The developing blade has one end secured to the developing apparatus frame and the other or free end urged against the outer peripheral surface of the developing roller cylinder.
The interior of the developing apparatus frame is divided into a toner chamber and a developer supplying chamber, and the toner as developer is contained in the toner chamber, and the developer carrying member and the developing blade are contained in the developer supplying chamber.
The toner in the toner chamber is carried from the toner chamber to the developer supplying chamber by its own weight or by conveying means and is attracted to the vicinity of the developer carrying member by a magnetic force of the magnet roller. During image formation, the developing roller is rotated by the driving force transmitted to the flange gear at its one end. The toner attracted around the outer peripheral surface of the developing roller is carried toward the developing blade as the developing roller is rotated, and regulation of a developer layer thickness and application of tribo-electricity are effected by the developing blade while the toner is being carried toward the photosensitive drum.
As the developer carrying members, there have been proposed a developer carrying member in which, as shown in
FIG. 7
, magnet shafts (first magnet shaft
272
and a second magnet shaft
273
) as shaft portions provided on both ends of a magnetizing portion
271
as a main part of a magnet roller
270
as a magnetic field generating member extend through holes formed in flanges
262
,
263
as shaft members of a developing roller
260
as a hollow cylindrical member and are supported by a developing apparatus frame
246
, and a developer carrying member in which, as shown in
FIGS. 8 and 9
, one (first magnet shaft
172
) of magnet shafts as shaft portions is held within an inner diameter portion of one (first flange
162
) of flanges as shaft members and only the other magnet shaft (second magnet shaft
173
) extends through a through hole formed in the other flange (second flange
163
) and is held by a developing apparatus frame
146
,and these developer carrying members are put to practical use.
Next, the developer carrying members will be fully described.
First of all, the cylinder-shaped developer carrying member
261
in which the shafts at both ends of the magnet roller are held by the developing apparatus frame
246
will be explained with reference to FIG.
7
.
As mentioned above, the developing roller
260
as the hollow cylindrical member which forms a main part of the developer carrying member
261
includes a cylinder portion
261
formed from aluminum, and the first and second flanges
262
,
263
as the shaft members attached to both ends of the cylinder portion
261
and is rotatably held by the first and second flanges
262
,
263
.
A gear
264
as drive transmitting means is secured to the first flange
262
.
The magnet roller
270
as the magnetic field generating means disposed within the developing roller
260
has the magnetizing portion
271
having a plurality of magnetic poles, and the first and second magnet shafts
272
,
273
as the shaft portions provided on both ends of the magnetizing portion.
The first and second magnet shafts
272
,
273
extend through the first and second flanges
262
,
263
of the developing roller
260
, and at least one of the magnet shafts is provided at its tip end area with D-cut shaped rotation preventing means so that the magnet roller
270
is always held at a predetermined angle in a circumferential direction.
If the first and second flanges
262
,
263
of the developing roller
260
are misaligned with the cylinder portion
261
in an axial direction, since the developing roller
260
is shifted by an amount corresponding to the misalignment amount during one revolution thereof, an abutting condition between the developing roller and the developing blade
242
will be changed, with the result that uniformity of the image cannot be maintained. On the other hand, since a temperature within the main body of the apparatus is increased as the apparatus is operated, operating environmental humidity of the developing apparatus is not constant. Thus, in order to maintain the concentricity between the first and second flanges
262
,
263
and the cylinder portion
261
with high accuracy regardless of the environmental temperature, a technique in which at least one of the first and second flanges
262
,
263
is formed from aluminum similar to the cylinder portion
261
and the aluminum flange is press-fitted in the cylinder portion
261
and the first and second flanges
262
,
263
due to difference in thermal expansion caused by the temperature increase is prevented. Incidentally, in this case, the gear
264
is generally secured to the aluminum flange.
Next, the cylinder-shaped developer carrying member
161
in which one (first magnet shaft
172
) of the magnet roller
170
is held within the inner diameter portion of one (first flange
162
) of flanges and the second magnet shaft
173
is held by the developing apparatus frame
146
will be explained with reference to FIG.
8
.
Also in the developing roller
160
shown in
FIGS. 8 and 9
, similar to the developing roller
260
shown in
FIG. 8
, it is preferable t
Canon Kabushiki Kaisha
Chen Sophia S.
Fitzpatrick ,Cella, Harper & Scinto
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