Electrophotography – Image formation – Photoconductive member
Reexamination Certificate
1999-06-01
2001-02-13
Grimley, Arthur T. (Department: 2852)
Electrophotography
Image formation
Photoconductive member
C074S4120TA, C399S116000, C399S117000
Reexamination Certificate
active
06188857
ABSTRACT:
FIELD OF THE INVENTION
The present invention refers to an image forming apparatus such as a copying machine, a printer, etc., provided with a photoreceptor unit with an internal gear. The present invention also refers to a photoreceptor unit with an internal gear for a copying machine, a printer or other image forming apparatuses. The present invention further refers to an internal gear unit for such photoreceptor unit with an internal gear.
BACKGROUND OF THE INVENTION
There are known image forming apparatuses such as copying machines, etc., provided with a cylindrical photoreceptor drum
101
as shown in FIG.
22
. In such image forming apparatuses, the surface of the photoreceptor drum
101
is charged by a main charger
102
, and the photoreceptor drum
101
is exposed by projecting thereon a light beam from an exposure unit
103
, and the resulting electrostatic latent image is developed by a developing unit
104
, and is transferred to a sheet by a transfer charger
105
. Thereafter, the charge on the surface of the photoreceptor drum
101
is removed by a cleaning blade (not shown) of a cleaning unit
106
, and the developed image is permanently affixed onto the sheet by a fusing unit
107
(not shown). In the described image forming process, the photoreceptor drum
101
is driven by a drive unit so as to rotate in one direction.
In Japanese Unexamined Patent Publication No. 120265/1983 (Tokukaisho 58-120265) and Japanese Unexamined Utility Model Application No. 155863/1986 (Jitsukaisho 61-155863, there is shown a drive unit wherein the photoreceptor drum
101
provided with an internal gear is rotated by a drive gear having a small diameter in engagement with the internal gear (for simplicity, the term internal gear system is used herein) as an example of the drive system for the photoreceptor drum
101
. The described arrangement is superior to the arrangement where the photoreceptor drum
101
is provided with an external gear in engagement with the drive gear in the following points. That is, as a greater number of teeth of the drive gear and the driven gear (internal gear) are in engagement with one another, unstable driving condition affected by the drive pitch of the gear is less likely to occur. Additionally, as the drive gear, etc., can be formed in the inside of the photoreceptor drum
101
, the drive device can be made compact, and thus the miniaturization of the image forming apparatus can be achieved.
In the described arrangement, however, various process elements such as a main charger
102
, an exposure unit
103
, a developing unit
104
, a transfer charger
105
, a cleaning unit
106
, etc., are provided along the circumference of the cylindrical photoreceptor drum
101
, and among these process elements, the developing unit
104
and the cleaning blade of the cleaning unit
106
in tight contact with the photoreceptor drum
101
respectively apply contact pressure onto the photoreceptor drum
1
. Therefore, the photoreceptor drum
101
is deformed to some extent which causes a displacement or decentering of the axis. On the other hand, as a greater number of teeth of the drive gear and the driven gear (internal gear) are in engagement with one another as described earlier, depending on the relative position between the process elements in tight contact with the photoreceptor drum
101
and the drive gear, the distortion in torque may occur, thereby presenting the problem that a smooth rotary motion of the internal gear, i.e., the photoreceptor drum
101
by the drive gear cannot be ensured. Such unstable rotary motion of the photoreceptor drum
101
, if occurred, would cause a default image. Japanese Unexamined Patent Publication No. 120265/1983 (Tokukaisho 58-120265) and Japanese Unexamined Utility Model Application No. 155863/1986 (Jitsukaisho 61-155863) fail to provide the solution to such problem.
There are known photoreceptor units through Japanese Unexamined Utility Model Application No. 155863/1986 (Jitsukaisho 61-155863) and Japanese Unexamined Patent Publication No. 120265/1983 (Tokukaisho 58-120265). In Japanese Unexamined Utility Model Application No. 155863/1986 (Jitsukaisho 61-155863), there is shown a photoreceptor unit having arrangements illustrated in FIG.
23
and FIG.
24
. As shown in these figures, around both ends of a photoreceptor drum
201
, plural rollers
202
are provided for supporting the photoreceptor drum
201
. On the inner circumference of the photoreceptor drum
201
, formed is an internal gear unit
203
, and a rotary motion of the photoreceptor drum
201
is actuated by a drive gear
205
in engagement with an internal gear member
204
of the internal gear unit
203
.
In Japanese Unexamined Patent Publication No. 120265/1983 (Tokukaisho 58-120265), there is shown a photoreceptor unit having an arrangement shown in FIG.
25
. As shown in the figure, an internal gear unit
302
is centrally situated on an inner circumference of a photoreceptor drum
301
. With an internal gear member
303
of the internal gear unit
302
, engaged is a gear
305
for a motor
304
which is formed in the inside of the photoreceptor drum
301
.
The described conventional photoreceptor units have the following drawbacks. That is, the former photoreceptor unit requires a complicated structure for supporting a rotatable photoreceptor drum, and a smooth rotary motion of such photoreceptor drum is difficult to be ensured. On the other hand, the latter photoreceptor unit does not refer to the desirable structure of a support mechanism for the rotatable photoreceptor drum.
To solve the described problem, there has been proposed a photoreceptor unit shown in FIG.
26
. The photoreceptor unit is arranged such that an internal gear unit
403
with an internal gear member
402
is fitted to the end of a photoreceptor drum
401
. A rotary motion of the photoreceptor drum
401
is actuated by a drive system including a drive pinion gear
404
.
The internal gear unit
403
includes a gear support member
405
formed on a face perpendicular to an axis of the photoreceptor drum
401
and a bearing member
406
centrally situated in the gear support member
405
. An end portion
406
a
formed in an axial direction of the bearing member
406
is situated to the inside in an axial direction with respect to an end portion
402
a
of the internal gear member
402
.
In the described arrangement, as the bearing member
406
is formed right below the internal gear member
402
, the foreign substances such as powders generated by the abrasion of the internal gear member
402
, etc., may drop and enter the bearing member
406
, and the frictional resistance of the bearing member
406
increases, which may even damage the bearing member
406
itself. This may result in the problems of unstable rotary motion, shaking and locking of the photoreceptor drum
401
or an increase in load during a rotary motion thereof.
The internal unit
403
shown in
FIG. 26
is arranged such that the length B of the teeth tip portion of the internal gear member
82
(
402
) (see an explanatory view of
FIG. 20
) is selected to be larger than the length A of the teeth bottom portion as shown in FIG.
20
. For this reason, for example, the shrinkage at the portion of the length B delays in the cooling process in the resin manufacturing process. As a result, as shown in
FIG. 27
, the free end side of the internal gear member
402
formed perpendicular to the gear support member
405
may be deformed towards the center of the internal gear unit
403
.
Such deformation occurs by the following mechanism. For example, in the case where a member which includes a thick ridge portion
502
centrally situated on a flat plate
501
is formed by an injection molding as shown in FIG.
28
(
a
), in general, as the hardening process is delayed, the thick ridge portion
502
shrinks and is bent in the direction of an arrow in FIG.
28
(
b
).
The maximum amount of deformation of the internal gear member
402
would be around 50-80 &mgr;m. This may lower the precision of the internal gear member
402
Harada Yoshikazu
Kadowaki Hideaki
Kitabatake Yasuo
Yamanaka Toshio
Yamauchi Yasuji
Grimley Arthur T.
Ngo Hoang
Sharp Kabushiki Kaisha
LandOfFree
Imaging forming apparatus provided with photoreceptor unit... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Imaging forming apparatus provided with photoreceptor unit..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Imaging forming apparatus provided with photoreceptor unit... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2581829