Electrophotography – Diagnostics – Consumable
Reexamination Certificate
2000-10-27
2003-07-08
Lee, Susan S. Y. (Department: 2852)
Electrophotography
Diagnostics
Consumable
C399S012000, C399S119000
Reexamination Certificate
active
06591070
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming apparatus and a cartridge detachably mountable to such an image forming apparatus and more particularly, it relates to an image forming apparatus capable of detecting a remaining amount of developer and a cartridge detachably mountable to such an image forming apparatus.
Here, an electrophotographic image forming apparatus as an example of the image forming apparatus may be, for example, an electrophotographic copying machine, an electrophotographic printer (for example, LED printer, laser beam printer or the like), an electrophotographic facsimile or the like.
Further, a process cartridge detachably mountable to a main body (assembly) of the image forming apparatus may incorporate therein at least one of an electrophotographic photosensitive member, charging means for charging the electrophotographic photosensitive member, developing means for supplying developer to the electrophotographic photosensitive member and cleaning means for cleaning the electrophotographic photosensitive member. In particular, the process cartridge may incorporate therein at least one of charging means, developing means and cleaning means, and an electrophotographic photosensitive member as a cartridge unit which can be detachably mounted to a main body of the image forming apparatus or may incorporate therein at least an electrophotographic photosensitive member and developing means as a cartridge unit which can be detachably mounted to a main body of the image forming apparatus.
2. Related Background Art
In conventional electrophotographic image forming apparatuses of the electrophotographic type, such as an electrophotographic copying machine, a laser beam printer or the like, a latent image is formed on an electrophotographic photosensitive member by illuminating the photosensitive member with a beam corresponding to image information, and developer (including toner) is supplied to the latent image by using developing means to visualize the latent image as a toner image, which is, in turn, transferred from the photosensitive member onto a recording medium, thereby forming an image on the recording medium. A developer containing container is connected to the developing means so that the developer is consumed by image formation.
In such an image forming apparatus, in order to facilitate exchange and maintenance of consumption parts, such as the electrophotographic photosensitive member and the developer, the electrophotographic photosensitive member and the developing means, charging means and cleaning means as process means acting on the electrophotographic photosensitive member and further a developer containing container and a waste developer container are integrally incorporated as a process cartridge that can be detachably mounted to a main body of the image forming apparatus. According to the process-cartridge system, since maintenance of the apparatus can be performed by the user himself without any expert, operability can be improved considerably. Thus, the process cartridge system has widely been used in the electrophotographic image forming apparatus.
Further, for example, in a color image forming apparatus having a plurality of color developing means, when the consumption degrees of the respective developing means are different, respective color developing cartridges may be formed by integrally incorporating the respective color developing means and corresponding developer containing containers, and such cartridges can detachably be mounted to the image forming apparatus to permit exchange independently.
In such image forming apparatuses of the cartridge type, the user permits the image formation again by exchanging the cartridge when the developer is used up. To this end, in some cases, such an image forming apparatus is provided with means for detecting the fact that the developer is used up and for informing the user of such fact, i.e., a developer amount detecting device.
Regarding the developer amount detecting device, in order to always know the amount of developer to be supplied for image formation remaining within the cartridge, developer remaining amount detecting means capable of detecting the developer remaining amount level are provided on the cartridge or the main body of the image forming apparatus.
Particularly, there is a technique in which the user's convenience is further enhanced not only by informing the user of the fact that the developer is used up but also by successively detecting and informing the user of the amount of the developer. In an image forming apparatus incorporating such a technique, the percentage (with respect to the unused condition) of the developer remaining amount may be calculated and a calculated result be successively communicated to the user, or the “absence of developer” indicating the fact that the developer is decreased to the extent that image formation cannot be effected with a predetermined quality may be determined, thereby warning the user of the fact that the remaining developer is insufficient, before a poor image is generated.
As an example of such developer remaining amount detecting means, there is a plate antenna system. According to this plate antenna system, for example, metal plates constituting electrodes are installed at locations opposed to a developer bearing member of the developing means or at other plural locations, and the fact that capacitances between the metal plates and the developer bearing member and between the metal plates are varied with the amount of developer such as insulation toner is utilized.
That is to say, if gaps between the metal plates and the developer bearing member and between the metal plates are filled with the developer, the capacitances therebetween become greater, and, as the developer is decreased, the air occupying ratio in the gaps is increased, with the result that the capacitances are decreased. Accordingly, by previously seeking a relationship between the capacitances (between the metal plates and the developer bearing member and between the metal plates) and the developer amount, the developer amount level can be detected by measuring the capacitances.
The measurement of the capacitance is effected by measuring electric current flowing to the metal plate from the developer bearing member when AC bias is applied to the developer bearing member. Alternatively, when a plurality of metal plates are provided, by measuring electric current flowing from one of the metal plates to the other metal plate when AC bias is applied to one of the metal plates as electrodes, the capacitance between the metal plates can be measured similarly. In the developer amount detecting device of the plate antenna type, in many cases, during the image formation in which the developing bias is applied to the developer bearing member, the developer amount is detected.
However, as mentioned above, even when the developer remaining amount detecting means capable of detecting the developer remaining amount level is provided, in some cases, the value of the developer remaining amount detected by the developer remaining amount detecting means does not coincide with the amount of the developer actually remaining in the developing device. In this case, the developer remaining amount cannot be detected correctly.
For example, in case of the above-mentioned developer amount detecting device of the plate antenna type, the capacitances between the developer bearing member and the metal plates as electrodes or the capacitances between the metal plates depend upon respective positional relationships. That is to say, even when there is no developer in the developing device, if a distance between both (developer bearing member and metal plate or metal plate and metal plate) is small, the absolute value of the capacitance becomes greater, whereas, if the distance between both is great, the absolute value of the capacitance becomes smaller. Thus, for example, due to tolerance of the metal plates of the developer remainin
Kakeshita Tomomi
Matsumoto Hideki
Shoji Takeo
Takahashi Atsuya
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Lee Susan S. Y.
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