Electrophotography – Cleaning of imaging surface – Plural diverse
Reexamination Certificate
2003-02-05
2004-11-09
Royer, William J. (Department: 2852)
Electrophotography
Cleaning of imaging surface
Plural diverse
C399S356000, C399S358000
Reexamination Certificate
active
06816700
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cleaning apparatus for removing a developer on an image bearing member, a copying machine provided with this cleaning apparatus, and an image forming apparatus such as a printer.
2. Related Background Art
Conventionally, as an image forming apparatus of this type, there has generally been used an image forming apparatus for sticking toner to an electrostatic latent image electrostatically formed on a surface of a photosensitive member as an image bearing member to form a toner image, and electrostatically transferring this toner image to a transferring material (sheet, transparent film or the like).
In such an image forming apparatus, toner remaining (residual toner) on the photosensitive member without being transferred to the transferring material in transferring must be sufficiently removed each time in order to form a next image (image formation). As its cleaning means, means for pressing a cleaning blade made of an elastic material such as urethane rubber into contact with the surface of the photosensitive member to remove the residual toner has been put into wide practical use.
However, from the viewpoint of prolonging a life of a high-speed machine, in the image forming apparatus using an a-Si (amorphous silicon) photosensitive member, it is necessary to remove not only the residual toner but also various foreign objects such as deposited organic materials or corona products caused by presence of high-pressure members in the apparatus which may cause deterioration of image quality if stuck to the photosensitive member. These foreign objects cannot be removed completely only by the cleaning blade.
Therefore, in the case of the image forming apparatus using the a-Si photosensitive member and one component magnetic toner, integrally with the cleaning blade, a magnet roller may be arranged as removal assisting means in the vicinity thereof. That is, there has been used a method for removing various foreign objects in a slide-rubbing manner by using toner magnetism, collected toner and a magnetic brush formed on the magnet roller. The magnetic brush is uniformly formed by a toner coating amount regulating member.
Further, a constitution is employed where the toner coating amount regulating member and an end scraper are separately disposed and, through a gap between the two members, toner scratched off by the toner coating amount regulating member and the end scraper is smoothly sent to a waste toner carrying portion.
In addition to the foreign object removing operation, the aforementioned method has various advantages, such as prevention of so-called “blade tearing-off” which easily occurs when there is no toner at all on the surface of the photosensitive member by using the magnetic brush to supply toner little by little, and facilitation of toner removal by the blade by applying a mechanical force to the toner electrostatically stuck to the surface of photosensitive member to reduce a sticking force of the toner to the photosensitive member. The method has been effective to a certain extent in the image forming apparatus which uses only one component magnetic toner in order to obtain a black and white image.
Now, color toner in a multicolor image forming apparatus of two colors or more is usually prepared by mixing dyes or pigments in a transparent resin to make clear a color of a copy image, and it is often nonmagnetic toner. In the case of a constitution using only nonmagnetic toner including black toner, the residual toner is often removed by the aforementioned cleaning blade.
However, since control of toner concentration is not necessary for the one component magnetic toner, and a developing apparatus can be constituted to be simpler compared with two components, there have been seen examples of using it as black toner. In the case of such a constitution, if the cleaning apparatus having the magnet roller is applied, the color toner is not adsorbed by the magnet roller, which makes it impossible to prevent problems in a cleaning function.
A constitution which removes the magnet roller and depends only on the cleaning blade in order to coordinate the cleaning operation with the nonmagnetic toner is not advisable because of the aforementioned advantages of the magnet roller and a probably largest frequency of obtaining a black image.
That is, it is desired that cleaning of the nonmagnetic toner is carried out without losing the effects provided by the magnet roller in the cleaning of the magnetic toner.
Thus, when the nonmagnetic toner is actually collected in the cleaning apparatus comprising the magnet roller, first, the nonmagnetic toner is stuck to the magnetic toner on the magnet roller by the application of an electrostatic adsorbing force or van der Waals force to be removed. However, after supplying of the nonmagnetic toner to a certain extent, the toner is freed without being captured any more, and leaked to the outside. As a result, the toner may be scattered or stuck in a gap between the magnet roller to damage the cleaning function, or rubbed by the blade to be fused on the photosensitive member.
That is, while the magnetic brush formed around the magnet roller has a capturing function of nonmagnetic toner of a given amount or lower, further supplying of the nonmagnetic toner causes sudden deterioration of the capturing function.
Therefore, as one countermeasure, a method has been employed which prevents the deterioration of the cleaning function by supplying the magnetic toner to a cleaner at given intervals in accordance with a frequency of forming color images to reduce a ratio of the nonmagnetic toner.
However, according to the aforementioned conventional technology, the nonmagnetic toner is not completely bound by the magnet roller, and accumulated in a toner receiver below the magnet roller while a cleaning operation is repeated. As a result, a phenomenon called dripping occurs where the nonmagnetic toner is leaked from a toner container.
The toner scratched off by the toner coating amount regulating member is passed on the toner coating amount regulating member and guided to a waste toner carrying path, and then discharged to the outside of the machine by a waste toner carrying screw. However, while the magnetic brush of the magnet roller is rotated from the toner coating amount regulating member to a photosensitive drum, not a little nonmagnetic toner of a weak holding force is freed from the magnetic brush to be accumulated in the toner receiver. If the cleaning operation is repeated, the amount of accumulated toner only increases.
On the other hand, in the case of the magnetic toner, because of the application of a magnetic binding force, the amount of toner freed from the magnetic brush is small. Even if freed, the toner is recollected, and thus the toner accumulated in the toner receiver is never increased beyond a certain amount.
FIGS. 9
,
10
and
11
show cases where toner coating amount regulating members are respectively a roller, a blade and a block. In these drawings, a reference numeral
5
denotes a magnet roller rotated in a direction of an arrow C. Similarly, a reference numeral
5
a
denotes a magnetic brush,
6
a waste toner carrying screw,
7
a cleaning blade,
8
a
a roller (toner coating amount regulating roller),
8
b
a blade (toner coating amount regulating blade),
8
c
a block (toner coating amount regulating block),
15
a photosensitive member (image bearing member, photosensitive drum) rotated in a direction of an arrow A,
25
a cleaning container,
28
a toner receiver,
29
a supporting member (also a wall member for separating the magnetic brush from a first waste toner carrying path),
32
,
33
blades, and
35
the first waste toner carrying path.
In
FIG. 9
, if the toner coating amount regulating member is a roller
8
a
, the roller
8
a
is supported on both side walls of the cleaning container
25
, and there are a blade
32
for scratching off toner scratched off by the roller
8
a
, and a blade
33
for preventing revers
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Royer William J.
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