Electrophotography – Image formation – Transfer
Reexamination Certificate
2001-05-24
2002-12-17
Grainger, Quana M. (Department: 2852)
Electrophotography
Image formation
Transfer
C399S313000
Reexamination Certificate
active
06496679
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a pivotally movable abutment mechanism that pivotally moves to abut against an abutted member, and an image forming apparatus such as an electrophotographic copying machine or a printer using the pivotally movable abutment mechanism. In particular, the present invention relates to a mechanism for causing charging means and transferring means to pivotally move to abut and an image formation using the mechanism.
2. Related Background Art
A conventional image forming apparatus will be described with reference to FIG.
12
. An image forming apparatus shown in
FIG. 12
includes four process units. Latent images are formed on photosensitive drums
101
(
101
a,
101
b,
101
c
and
101
d
), which are image bearing members, in the respective process units. The formed latent images are developed, and then toner images are superimposed to be transferred on a transfer material on a transfer material bearing member one after another. A full color image is obtained by heating to fix the toner images by a fixing unit (not shown) in the downstream.
Inside an elliptical shape formed by a transfer belt
102
being a transfer material bearing member, a transfer blade unit is provided which includes transfer blades
103
(
103
a,
103
b,
103
c
and
103
d
) being transfer charging means, which are plate-like contact electrodes, blade holders
104
(
104
a,
104
b,
104
c
and
104
d
) for supporting the transfer blades
103
a
to
103
d,
and pivoting shafts
105
a,
105
b,
105
c
and
105
d
for pivotally supporting the blade holders
104
a
to
104
d.
The transfer belt
102
contacts the photosensitive drums
101
a
to
101
d
being image bearing members, and is supported and biased by the transfer blades
103
a
to
103
d
at each contact point and is applied a transfer voltage.
However, in the above-mentioned conventional example, the pivoting shafts
105
(
105
a,
105
b,
105
c
and
105
d
) being rotational center shafts of the transfer blades
103
and the blade holders
104
are fixed at their respective predetermined positions. Thus, there is a problem in that a distribution of an abutting pressure of the transfer blades
103
in the longitudinal direction of the photosensitive drums
101
becomes even.
For example, a case will be considered in which both ends of the pivoting shafts
105
are not parallel with axes of the photosensitive drums
101
, and rotational centers in the back side of the apparatus are closer to the photosensitive drums
101
than to rotational centers in the front side of the apparatus. In such a case, when the transfer blades
103
rotate about the pivoting shafts
105
, the back sides of the transfer blades
103
abut against the transfer belt
102
first. At this point, the contacting portions are in positions deviated to the downstream side of the transfer belt movement from ideal positions (positions the transfer blades
103
should originally abut against the transfer belt
102
). In addition, the front sides of the transfer blades
103
have not abutted against the transfer belt
102
yet.
When more pressure is applied to the transfer blades
103
, the portions of the transfer blades
103
abutting against the transfer belt
102
start to bent first by the pressurizing power because the transfer blades
103
are formed of a material having flexibility such as a rubber plate member and a brush. With the abutment portions of the transfer blades
103
bending, non-abutment portions more in front than the abutment portions start to abut against the transfer belt
102
. Before long, the back sides of the transfer blades
103
bend significantly, and the pressurizing completes when the portions of the transfer blades
103
on the front sides abut against the transfer belt
102
. At this point, an abutment pressure distribution in the longitudinal direction of the abutment portions of the transfer blades
103
and the transfer belt
102
is high in the back side and low in the front side. This is because the pressurizing power by pressurizing means is lost by the bent of the transfer blades
103
and is not sufficiently transmitted to the front side.
The contacting portions of the transfer blades
103
and the transfer belt
102
are in positions more deviated with the transfer blades
103
bending from the positions at the instance of abutment. The higher the abutment pressure is, this tendency gets stronger, the back sides of the transfer blades
103
where the abutment pressure is high bend more, and the positional deviations increase accordingly.
That is, in the case in which the back sides of the pivoting shafts
105
of the transfer blades
103
positionally deviate in the direction to approach the photosensitive drums
101
(upward) and the front sides positionally deviate in the direction to recede from the photosensitive drums
101
(downward), the abutment pressure distribution is high in the back sides. To the contrary, in the case in which the back sides of the pivoting shafts
105
positionally deviate in the direction to recede from the photosensitive drums
101
(downward) and the front sides positionally deviate in the direction to approach the photosensitive drums
101
(upward), the abutment pressure distribution of the transfer blades
103
and the photosensitive drums
101
is high in the front sides.
In addition, in the case in which the pivoting shafts
105
of the transfer blades
103
positionally deviate in the direction to approach the photosensitive drums
101
(upward), the contacting portions of the transfer blades
103
deviate in the downstream side of the moving direction of the transfer belt
102
. In the case in which the pivoting shafts
105
positionally deviate in the direction to recede from the photosensitive drums
101
(downward), the contacting portions deviate in the upstream side of the moving direction of the transfer belt
102
.
In this way, as the abutment pressure distribution of the transfer blades
103
becomes unequal, the bent amount of the transfer blades
103
also becomes unequal. Thus, the positional deviations of the contacting points of the transfer blades
103
and the transfer belt
102
get larger and increase a deviation amount due to dimensions of parts.
In addition, when the abutment pressure of the transfer blades
103
exceeds a predetermined value, the abutment portions of the photosensitive drums
101
, the transfer blades
103
and the transfer belt
102
are abraded more, which shortens lifetimes of these parts.
In addition, when the abutment pressure of the transfer blades
103
gets lower than a predetermined value, normal transfer cannot be performed and an image defect such as a blank area is generated. In particular, this tendency is evident when an image is transferred on a cardboard or an undulated sheet (e.g., a second side in a two-side recording, left paper at high temperature and high humidity, left paper at low temperature and low humidity, or the like). In addition, a positional deviation of the transfer blades
103
exceeding a predetermined amount can be a cause of an image defect.
Here, in order to hold an abutment pressure distribution of the transfer blades
103
within a predetermined amount, it is necessary to extremely accurately manage a rotational central positions of the transfer blades
103
, which increases costs for parts. In addition, in some cases, an adjustment process is necessary when an apparatus is assembled, which increases production costs of the apparatus.
Further, this is not limited to an abutment of a transfer blade. It is also very important from a perspective of an equal charging performance and a lifetime to cause a charging member to abut equally, for example, in a charging device that charges a charged member by causing the charging member to abut against the charged member along the longitudinal direction.
In this way, in the case of a configuration for pivotally moving an abutment member to cause it to abut against an abutted member along the longitudinal
LandOfFree
Pivotally movable abutment mechanism, charging device and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Pivotally movable abutment mechanism, charging device and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Pivotally movable abutment mechanism, charging device and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2932687