Image forming apparatus

Details Image forming apparatus Image forming apparatus

2002-02-11

2003-09-23

Chen, Sophia S. (Department: 2852)

Electrophotography

Image formation

Photoconductive member

C399S302000, C399S308000

Reexamination Certificate

active

06625410

ABSTRACT:

The present disclosure relates to the subject matter contained in Japanese Patent Application No. 2001-287437 filed on Sep. 20, 2001, which is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming apparatus, such as a copying machine and a printer, and more particularly to the improvement over the image forming apparatus for transferring an image formed on a photoreceptor onto a recording medium through an intermediate member.
2. Description of the Related Art
An image forming apparatus according to the related art, which adopts the intermediate transfer type, has been known in which an intermediate transfer belt as an intermediate transfer member is disposed to face a photosensitive drum as a photoreceptor. Toner images containing color components are primarily transferred onto the intermediate transfer belt in successive order. The transferred toner images are transferred, at a time, from the intermediate transfer belt onto a recording medium, e.g., a recording sheet of paper.
In this type of the image forming apparatus, the intermediate transfer belt is usually constructed as a belt unit in which the intermediate transfer belt is wound on a plurality of rolls and circulatively moves in a predetermined travelling direction.
In the belt unit, the intermediate transfer belt moves not straightly while being displacing in an axial direction of tension rolls that is, so-called meandering occurs. The meandering of the intermediate transfer belt is caused by variations in the parallelism among rotary shafts of the tension rolls, variations in the outside diameters of the tension rolls, and a non-uniformity of tensions caused by a variation of the periphery length of the intermediate transfer belt per se.
When the meandering occurs, transfer positions of the toner images, which are transferred onto the intermediate transfer belt in successive order, are displaced from the correct ones. As a result, there is a possibility that such image defects as color mis-registration and hue variation occur in the color image formed on the recording medium, e.g., a recording sheet.
Some measures have been taken for the meandering of the belt. One of the measures is that the end of the belt is abutted against the edge guide to position the belt in place. Another measure is that ribs are formed at the ends of the rear side of the belt to control the meandering motion of the belt. Yet another measure is that belt end positions are detected by position sensors, and the parallelism of a desired tension roll is variably adjusted according to the sensing results.
In those measures, the edge guides and ribs for abutting are provided on both ends of the belt. The position sensors for detecting both end positions of the belt are also provided at both ends of the belt. However, the belt will finally displace by variations of the parallelism and diameters of the tension rolls.
In such circumstances, the reinforcing structure for avoiding the damage of the belt by stress concentration on the butting edge guide, and bonding of the ribs are high in cost. Further, it is disadvantageous in the light of space saving that the belt width is larger than the image forming width.
To cope with this, a technique, which employs a technique for shifting the belt to one side, simplifies the structure, and stabilizes the meandering correcting performance, already has been proposed.
There has been a known technique for shifting the belt to one side in which the diameter of one tension roll is gradually varied in the axial direction to shift the belt to one side (e.g., JP-A-Hei.6-278894) and has been another known technique to incline the parallelism of a desired tension roll.
After or when it is mounted on the apparatus body, due to distortion of the belt unit, although the parallelism of each tension roll of the belt unit is kept, the tension rolls may be slanted in the same direction by the distortion.
Under the circumstances, when the technique for shifting the belt to one side (the technique for gradually varying the diameter of the tension roll or the technique for inclining the parallelism of one tension roll) is employed, depending on the distortion direction of the belt unit, it is feared that the belt is directed to a side which is opposite to the side as intended.
To set the gradual variation of the diameter of the tension roll and the inclination of the parallelism of the tension rolls in consideration with the twist of the belt unit, the variation and inclination must be set large. If the variation and inclination are set too large, this becomes cause of tension wrinkle so that it is feared to have disadvantage in performance of transfer.
Incidentally, such problems does not only arise in the technique for shifting the belt to one side, but also similarly arise in the technique for restricting the meandering of the belt at both side because in many cases, the belt is shifted to any of sides.
Accordingly, the present invention has been made for solving the above problems and provides the following technique: even when a twist occurs in the belt in a state that the parallelism of a tension roll of the belt is kept, the belt may be shifted to one side in a desired direction without causing tension wrinkles and the like in the belt, and hence, the meandering control of the belt is alleviated in load. With this technique, the invention provides an image forming apparatus which can reduce the color mis-registration and can perform good image formation.
SUMMARY OF THE INVENTION
According to the invention, there is provided an image forming apparatus having a photoreceptor, an intermediate transfer member, and a plurality of tension rolls, in which one of the photoreceptor and the intermediate transfer member is formed like a drum, in which the other of the photoreceptor and the intermediate transfer member is formed like a belt, which is wound on the plurality of tension rolls, and in which the following relationship is satisfied:
∑
n
=
3
N
⁢
a
n
<
x
a
n
is the contact lengths between the other and the n tension rolls, respectively and x is contact length between the photoreceptor and the intermediate transfer member.
DESCRIPTION OF THE INVENTION
According to the present invention, as shown in
FIG. 1A
, there is provided an image forming apparatus for transferring an image formed on a photoreceptor
1
onto a recording medium
3
through an intermediate transfer member
2
, in which one of the photoreceptor
1
and the intermediate transfer member
2
is shaped like a drum, while the other is shaped like a belt, which is put on a plurality of tension rolls
4
, and the following relation is satisfied:
a+b+c+ . . . <x
where a, b, c, . . . are contact lengths between the other of the intermediate transfer member
2
and photoreceptor
1
, which are formed in a belt like shape, and each of tension rolls
4
and x is contact length between the intermediate transfer member
2
and the photoreceptor
1
.
It should be understood that the present invention thus technically implemented is applied to a variety of image forming apparatus. It is preferable that the invention is applied to the color image forming apparatus since remarkable technical effects are produced in such applications. However, it should be understood that the invention may be applied to the monochromatic image forming apparatus, as a matter of course.
In relation to a mode of the photoreceptor
1
and the intermediate transfer member
2
, one of them is formed in a drum shape, and the other is formed in a belt shape. A belt-like intermediate transfer member
2
is used for a drum-like photoreceptor
1
(the combination of them is illustrated in FIG.
1
). A drum-like intermediate transfer member
2
is used for a belt-like photoreceptor
1
.
Further, as a measure for the meandering of a belt like member (hereinafter, referred to simply as a belt), in view of simplification of the structure of the apparatus, it is preferable that

Affiliated with

Also associated with

Rating

Image forming apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Image forming apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Image forming apparatus will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3079789