Electrophotography – Diagnostics – Consumable
Reexamination Certificate
2002-12-20
2004-03-09
Ngo, Hoang (Department: 2852)
Electrophotography
Diagnostics
Consumable
C399S024000, C399S025000
Reexamination Certificate
active
06704524
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a method of detecting the life time of an image bearing member used in an image forming apparatus for forming an electrostatic latent image in an image bearing member by, for example, an electrophotographic system or an electrostatic recording system and visualizing the electrostatic latent image with a developer, to an image forming apparatus using the above method, and further, to a cartridge detachably attachable to the image forming apparatus.
Here, the image forming apparatus with the electrophotographic system include, for example, an electrophotographic copier, an electrophotographic printer (for example, an LED printer and a laser beam printer), and an electrophotographic facsimile.
The cartridge detachably attachable to the main body of the electrophotographic image forming apparatus includes a cartridge having at least one of an electrophotographic photosensitive member, charging means for charging the electrophotographic photosensitive member, developing means for supplying a developer to the electrophotographic photosensitive member and cleaning means for cleaning the electrophotographic photosensitive member. In particular, a process cartridge is a cartridge in which at least one of the charging means, the developing means and the cleaning means, and the electrophotographic photosensitive member are integrally made into the cartridge, and the cartridge is made detachably attachable to the main body of the electrophotographic image forming apparatus, or a cartridge in which at least the developing means and the electrophotographic photosensitive member are integrally made into the cartridge and the cartridge is detachably attachable to the main body of the electrophotographic image forming apparatus.
2. Related Background Art
Conventionally, in an image forming apparatus of an electrophotographic system such as an electrophotographic copier or a laser beam printer, an electrophotographic photosensitive member as an image bearing member is uniformly electrified by using charging means, and thereafter, the surface is irradiated with light corresponding to image information to form a latent image. Then, a developer is supplied to the latent image using developing means to visualize the latent image, and after the visualized image is transferred to a recording medium, the image is fixed in a fixing apparatus to obtain an image on the recording medium. Further, the electrophotographic photosensitive member after the transfer is cleaned with cleaning means.
In such an image forming apparatus, in order to attain simpleness and easiness of exchange and maintenance of expendable supplies such as the electrophotographic photosensitive member and the developer, there is a process-cartridge system in which an electrophotographic photosensitive member, developing means as process means acting on the electrophotographic photosensitive member, charging means, cleaning means, and further, a container for a developer and a container for a waste developer are integrally made into a process cartridge, and the cartridge is detachably attachable to the main body of the image forming apparatus.
According to the cartridge system, a user can conduct maintenance of the apparatus without a serviceman. Images can be formed again by exchanging a cartridge by the user when the developer has run out or when the photosensitive member drum has expired, for example. As described above, the cartridge system can remarkably improve operability of the apparatus, and thus, is widely used in the electrophotographic image forming apparatuses.
In the image forming apparatus of the cartridge system, for example, it is necessary that the user exchange the cartridge at an appropriate time by notifying the user that the expendable supplies such as the electrophotographic photosensitive member and the developer have expired or that they are approaching the end of their life.
Conventionally, as a method of detecting the life of an electrophotographic photosensitive member having, for example, a cylindrical shape, that is, a photosensitive member drum:
(1) there is a method of detecting the end of the life of a photosensitive member drum by integrating the number of sheets of image formation. In the simplest method, in the case where the size of the sheets of the recording medium, on which an image is formed, differs, for example, between A4 size and A3 size, the sheets of the recording medium are counted as the same. However, in this method, the precision of detecting the end of the life of the photosensitive member drum is not satisfactory. Further, with only integration of the number of sheets of image formation, the rotation time of the photosensitive member drum per one sheet of the recording medium differs depending on how many sheets are used for image formation per one job, that is, how many sheets of the recording medium are used for continuous image formation from the start of the image forming operation. Thus, the life of the photosensitive member drum varies in accordance with the rotation time, which is described later. Therefore, in this method, the precision of detecting the end of the life of the photosensitive member drum is not satisfactory.
Moreover, (2) as described in Japanese Patent Application Laid-open No. 4-51259 as prior art, there is a method of detecting a charge amount of a photosensitive drum with a surface potential sensor. In accordance with this method, in actuality, a reduction of charge potential of the photosensitive member drum or a reduction of latent image contrast can be directly detected with the surface potential sensor. Thus, in comparison with the method (1) described above, end of life detection with satisfactory precision is possible, which reflects the state of an output image. However, in order to implement the above method, the surface potential sensor, an electric circuit for processing the output, and the like are needed, and thus, the cost increases. Further, with respect to a longitudinal direction of the photosensitive member drum, only the information on the photosensitive member drum corresponding to the sensor position is data needed to make a decision. Thus, the detection ability to detect a partial defect is weak, and this method is plagued by the variations in the surface potential sensor and instability of change with time and the like. Therefore, this method is not necessarily a method of constantly detecting the end of the life of the photosensitive member drum with accuracy.
Furthermore, (3) as a method of improving detection accuracy of the end of the life of the photosensitive member drum while solving the problem of the above method (1), there is disclosed, in Japanese Patent Application Laid-open No. 5-188674, a method of integrating the rpm of the photosensitive member drum instead of integrating the number of sheets of image formation. Based on the same principle, there is a method of integrating the rotation time of the photosensitive member drum. In any of these methods, since, with respect to one image formation operation, as the size of the recording medium becomes larger, the rpm (rotation time) increases while as the size of the recording medium becomes smaller, the rpm (rotation time) decreases, in accordance with the size of the recording medium, and the detection error of the end of the life of the photosensitive member drum due to the size difference of the recording medium becomes smaller in comparison with the case of integrating the number of sheets on which image formation occurs. Further, the rpm (rotation time) of the photosensitive member drum is directly integrated irrespective of the number of sheets used for image formation per one job, and thus, the precision of the end of life detection is relatively satisfactory.
As a method which is developed on the basis of the above method (3), there is disclosed, in Japanese Patent Application Laid-open No. 4-98265, a method in which the rpm of the photosensitive member drum at the time
Ishii Yasuyuki
Matsuguma Minoru
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Ngo Hoang
LandOfFree
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