Electrophotography – Control of electrophotography process – Responsive to number of copies or passage of time
Reexamination Certificate
2000-12-28
2002-01-15
Chen, Sophia S (Department: 2852)
Electrophotography
Control of electrophotography process
Responsive to number of copies or passage of time
C399S274000, C399S284000
Reexamination Certificate
active
06339686
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a developer unit for use in an image forming apparatus such as a copier, printer, facsimile machine, etc., for performing image forming based on the electrophotographic process, in particular is directed to removal of the toner stuck on the toner layer metering blade in a developer unit using a mono-component developer.
(2) Description of the Prior Art
The developer unit for a mono-component developer that contains no carrier, not only has a simple configuration and hence can be made compact because of absence of carrier particles but also offers the advantages of low cost and easy maintenance. In particular, since a non-magnetic mono-component toner that does not contain magnetic toner, does not use a magnetic roller, it is possible to provide an inexpensive, compact, developer unit creating clear images. Further, since the toner does not contain any magnetic material, toner of this type is suitable to be utilized for color imaging. When classifying mono-component developer units based on their developing methods, there have been two known methods, one for the contact developing system for performing development by being in contact with the photoreceptor, and the other for the non-contact developing system for performing development by being not in contact with the photoreceptor.
Generally, in a mono-component developing method in which either the toner is magnetic or non-magnetic, and either the system is in the contact type or non-contact type, a thin layer of the electrified mono-component toner is formed on a developer support, and this thin layer is conveyed with the rotation of the developer support to the developing position where the toner opposes the photoreceptor with a latent image formed thereon, whereby the latent image on the photoreceptor is made into a visible (developed) image. In this case, in order to obtain high quality images, the way that a stable thin toner layer, uniformly charged, and with a uniform thickness is formed on the developer support is very important.
Typically, electrification and formation of the thin toner layer on the developer support are performed using a toner layer metering blade which is pressed against the developer support with a predetermined pressure. Charging and formation of the thin toner layer may be beneficial in the initial stage of use, but toner may stick to the toner layer metering blade after a long period of use, failing to form a preferable toner layer, causing image degradation. Actually, continuous abutment of the toner layer metering blade against the developer support at the predetermined pressure will cause the toner to adhere (stick) to the blade surface within the abutment nip between the toner layer metering blade and the developer support and therearound, due to frictional heat, the pressure and/or environmental factors such as the temperature in the machine and the like.
Such buildups are slight and formed as a thin film at their initial stage, posing no problem in image forming, but will grow as the machine is used, soon presenting adverse effects in the image.
Actually, the stuck buildups deteriorate toner electrification performance by the toner layer metering blade, and clog the toner inflow opening between the blade and the developer support, forming physical irregularities on the surface in contact with the developer support, which causes widespread or local reduction in thickness of the toner layer or excessive toner passing (increase in toner layer thickness), making it impossible to form a uniform and even toner layer. As this result, light print, local white lines, and local black streaks (when monochrome) and the like arise on the image.
In order to solve this problem, some methods of cleaning the stuck toner on the toner layer metering blade have been proposed. For example, Japanese Patent Application Laid-Open Hei 7 No.163440 discloses a stuck toner removal member which is slidable between the developer support and the toner layer metering blade and removes stuck toner as it slides. This publication further discloses another configuration wherein the toner layer metering blade is configured so as to slide up and down along the developer support and sliding the toner layer metering blade up and down removes the stuck buildups.
Japanese Patent Application Laid-Open Hei 5 No.127509 discloses another configuration wherein with the toner layer metering blade fixed to a movement driver, the movement driver is actuated so as to vary the abutment position between the toner layer metering blade and the developer roller, thus preventing toner from sticking to the toner layer metering blade.
As in Japanese Patent Application Laid-Open Hei 7 No.163440, inserting and sliding a removal member between the developer support and the toner layer metering blade abrades the toner layer metering blade surface as well as the developer support and may damage the both.
In general, the toner layer metering blade is pressed against the developer support with a linear pressure of some tens of gf/cm to some hundreds of gf/cm, depending on the configuration. It is not so easy to slide the inserted removal member between the toner layer metering blade and the developer support without damaging them. In the configuration of the above disclosure, the edges of the removal member are finished with precision, needing a high cost. Further, in order to avoid damage, it is necessary to slide the removal member without its being scratched as it moves and move it straightly keeping its face angle constant.
That is, the method described in the above publication, makes it possible to remove stuck buildups from the toner layer metering blade, but are liable to damage the developer support surface as well as the toner layer metering blade and also causes a cost increase. By any means, moving the removal member whilst keeping it in contact with both elements may cause a certain amount of damage.
Further, in the case of Japanese Patent Application Laid-Open Hei 5 No.127509, a movement driver means to which fixing the toner layer metering blade is fixed is additionally needed, leading to a sharp cost increase because of the necessity of the controller means for this movement driver means and needing extra space for setting it. Therefore, application of this method to existing apparatus is limited. In accordance with the method disclosed in the configuration of the above publication, since the toner layer metering blade is moved rubbing the developer roller when the abutment position between the toner layer metering blade and the developer roller shifts, it is not preferred because there is a risk of damaging both the developer roller and the toner layer metering blade.
SUMMARY OF THE INVENTION
In order to solve the above problems, the present inventors hereof have studied intensively and found that instead of using the technique of inserting a cleaning element between the developer support and the toner layer metering blade, adoption of a configuration in which a cleaning element is arranged on the backside of the toner layer metering blade, i.e., the side opposite to the surface in contact with the developer support so that the cleaning element can frictionally move relative to the toner layer metering blade will lower the risk that the cleaning element might cause damage, as it rubs, to the toner layer metering blade surface and the developer support surface on which the metering blade abuts, and will remove the stuck toner on the toner layer metering blade as well as preventing the occurrence of stuck buildups.
At the toner layer metering blade, if the toner stops moving at the same place, the same mass of toner continues to be stressed, soon becomes transmuted, forming stuck buildup. Even in such cases, the stationary toner residing around the blade edge can be removed and eliminated by rubbing of the cleaning element around the blade edge from the backside of the blade, instead of rubbing the blade from the developer support side.
Thus, it is poss
Inoue Atsushi
Kido Eiichi
Kobayashi Mikie
Masuda Jitsuo
Ohgoshi Toshihide
Chen Sophia S
Ngo Hoang
Sharp Kabushiki Kaisha
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