Electrophotography – Image formation – Development
Reexamination Certificate
2000-06-22
2002-02-05
Chen, Sophia S. (Department: 2852)
Electrophotography
Image formation
Development
C399S357000
Reexamination Certificate
active
06345166
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a developer scraping member for scraping developer from a developer carrying member, and a developing apparatus equipped with such developer scraping member.
2. Related Background Art
In the image forming apparatus such as a copying apparatus, a printer or a facsimile apparatus, there has conventionally been executed visualization of a latent image, formed on an image bearing body such as an electrophotographic photosensitive member or an electrostatic recording dielectric member, as a toner image by development with a developing portion.
As one of such developing portions, there have been proposed and commercialized various types of dry one-component developing portion. However any of these types has been associated with a difficulty in forming a thin layer of non-magnetic toner (non-magnetic one-component toner), which is the non-magnetic one-component developer, on the developer carrying member.
Nevertheless, in order to meet the currently desired improvements in the resolution and definition of the image, the development of the method for forming a thin toner layer and of the apparatus therefor is essential, and certain measures have therefore been proposed.
For example, the Japanese Patent Application Laid-Open No. 54-4303 discloses a method of abutting a metal or rubber elastic blade with a developing roller constituting a developer carrying member and causing the toner to pass between and to be regulated by the elastic blade and the developing roller thereby forming a thin layer of the toner on the developing roller and providing the toner with sufficient triboelectricity by the friction in the abutting portion.
In such method, if the non-magnetic toner is regulated by the elastic blade, there is required a separate toner feeding member for feeding the toner onto the developing roller. This is because the non-magnetic toner cannot be fed by magnetic force, though the magnetic toner can be fed onto the developing roller by the magnetic force of a magnet provided inside the developing roller.
In a developing portion disclosed in the Japanese Patent Application Laid-Open No. 58-116559, as shown in
FIG. 8
, in a developing container
102
containing non-magnetic one-component toner
106
, a fur-brush-like roller (brush roller)
115
contacting a developing roller
103
is provided at an upstream position with respect to an elastic blade
104
in the rotating direction of the developing roller
130
in order to scrape off the residual toner not consumed in the image development but remaining on the developing roller
103
and to feed new toner
106
onto the developing roller
103
.
It is thus rendered possible to satisfactorily form a thin layer of the non-magnetic toner
106
on the developing roller
103
and to satisfactorily develop the electrostatic latent image on a photosensitive drum
101
, whereby a solid black image of a high density and a large area can be faithfully reproduced in the development to obtain a satisfactory image.
However, the above-described brush roller
115
is formed by planting fibers of nylon or rayon on a metal core, and, in a prolonged repeated use of the developing portion, the fibers become detached from the roller and clogged between the elastic blade and the developing roller, thereby generating a white line (streak) in such clogged portion, or the fibers are turned down on the roller to result in defective contact between the brush roller and the developing roller whereby the solid black image cannot be reproduced sufficiently because of deficient feeding and scraping of the toner.
Therefore, it is proposed to form the toner feeding member by an elastic roller with a foamed structure, composed of an open cell foamed member such as polyurethane foam of a relatively low hardness and to contact such roller with a low pressure to the developing roller, whereby the feeding of the toner onto the developing roller and the scraping of the residual toner therefrom are rendered possible by suitable surface irregularity (asperity) of the foamed member.
In such developing portion, however, since the elastic roller is composed of an open cell foamed member, the toner particles enter and gradually clog the cells of the elastic roller when the developing operation is repeated many times, particularly in case the toner of a small particle size is used under a high humidity environment or the toner is substantially spherical. When the toner clogging spreads over the entire foamed member of the elastic roller, it becomes harder to result in an excessively large contact pressure of the elastic roller on the developing roller, eventually leading to an increased driving torque of the developing roller and the elastic roller or unevenness in the coating and scraping of the toner by the elastic roller on the developing roller, whereby uneven coating is developed on the developing roller in the undesirable level.
In order to prevent the drawbacks resulting from such clogging with toner of the interior of the elastic roller, there can be conceived the following measures: (1) providing the surface of the elastic roller with a skin layer for preventing toner clogging; (2) constituting the elastic roller with a closed cell foamed member; and (3) using an open cell foamed member of a high density with as small cells as possible. These measures, however, result in the following drawbacks.
In the measure (1), when the skin layer of the elastic roller is maintained in contact with and rubs the surface of the developing roller, the skin layer has an excessively strong function of rubbing in the toner onto the developing roller, resulting in the fusion of the toner onto the developing roller or physical change of the toner, thereby causing deterioration of the toner and an increase in the fog level when the developing operation is repeated many times. Even if the surface of the skin layer is made appropriately coarse, it is locally harder than the surface of the foamed member, thus applying a locally high pressure on the toner and the developing roller, so that similar drawbacks cannot be avoided.
Also as the skin layer is formed very thin, it may be abraded or scraped off by the friction with the developing roller, whereby the toner particles still intrude the cells of the foamed member and there cannot be assured the stability in the prolonged use.
In the measure (2), the elastic roller can satisfactory execute coating and scraping of the toner on the developing roller as in the open cell foamed member, but the closed cell foamed member has a higher hardness and a higher repulse elasticity in comparison with the open cell foamed member so that the hardness of the elastic roller becomes excessively high. For this reason, if the elastic roller is so positioned as to be stably and securely contacted with the developing roller, the contact (abutting) pressure of the elastic roller becomes excessively high on the toner and the developing roller, resulting in various drawbacks such as an increased driving torque of the developing roller and the elastic roller and an increased fog level derived from the change of physical property (deterioration) of the toner after a prolonged use.
Such drawbacks may be avoided by reducing the hardness of the closed cell foamed member as far as possible, but, in such case, the foamed member inevitably contains a large amount of an oily component which oozes out and sticks to the developing roller and the toner when the elastic roller is left in contact with the developing roller and the toner over a prolonged period under a high temperature environment, whereby the toner is fused and sticks to the developing roller. With such fusion of the toner on the developing roller, the toner newly fed thereto is rubbed with the fused toner on the developing roller, whereby the appropriate triboelectricity cannot be obtained and a fog is undesirably generated by the deficient charging of the toner.
In the measure (3), in comparison with the open cell foamed member o
Nonomura Makoto
Ohzeki Yukihiro
Sakaizawa Katsuhiro
Sekiguchi Manami
No associations
LandOfFree
Developer scraping member and developing 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 Developer scraping member and developing apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Developer scraping member and developing apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2947791