Electrophotography – Diagnostics – Consumable
Reexamination Certificate
2001-05-25
2003-01-28
Tran, Hoan (Department: 2852)
Electrophotography
Diagnostics
Consumable
C399S026000, C399S027000
Reexamination Certificate
active
06512896
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming apparatus, such as a printer or an electrophotographic copying machine, and more particularly to an image forming apparatus comprising a detachably mountable process cartridge that includes a main cartridge accommodating a photosensitive body and a toner cartridge for replenishing toner.
2. Description of the Related Art
As has been known, while an image forming apparatus repeats recording operation on recording sheets, toner is used up or a photosensitive drum wears out and deteriorates. When such an inconvenience occurs, it is necessary to replenish toner or replace the photosensitive drum. Also, a cleaning device needs to be replaced when it is filled with waste toner being removed from the surface of the photosensitive drum.
Conventionally, devices such as a photosensitive drum, a cleaning device and so on are normally replaced by a service person. Hence, a user's urgent demand cannot be met, which has been raising a problem that the service is less satisfactory.
For this reason, a process cartridge accommodating a photosensitive drum and peripheral mechanisms of the photosensitive drum has been employed and becoming increasingly popular in recent years. The process cartridge is detachably mounted to the image forming apparatus main body and can be replaced by a user, thereby facilitating the convenience of maintenance and improving serviceability.
One type of the process cartridge is arranged such that a cleaning device or a developing device is accommodated therein together with a photosensitive drum. Another type of the process cartridge is arranged such that at least one of a charging device, a developing device, or a cleaning device is accommodated therein together with a photosensitive drum.
However, because such a process cartridge puts an emphasis on easy maintenance, a large margin is provided concerning the lifetime of a photosensitive drum, a developing device and a cleaning device accommodated in the process cartridge, in order to ensure a reliable operation of the photosensitive drum and other devices until toner cartridge becomes empty. Thus, in this case, when a process cartridge is replaced at the time a toner cartridge has become empty, a still serviceable photosensitive drum and other devices are also removed, which has been resulting in wastes of these components.
Given such a background, there has been proposed a process cartridge arranged so as to be divided into two portions: a main cartridge accommodating a photosensitive drum and other devices, and a toner cartridge filled with toner. In this case, when the toner is used up, only the toner cartridge is to be replaced, and when deterioration occurs in the photosensitive drum or any other devices after using several toner cartridges, both of the toner cartridge and the main cartridge, that is, a whole process cartridge, is to be replaced.
According to such an arrangement, it is necessary to find the end of the service life of the photosensitive drum, with which several toner cartridges have been used. For example, there is a simple method, by which a main cartridge accommodating a photosensitive drum is to be replaced after replacing toner cartridges for a predetermined number of times.
In this method, however, the predetermined time cannot be selected without an assumption of a standard using condition, such as assuming an average print ratio of a document (ratio of printed area to overall area of a document) as approximately 5% in the case of an A4 size document and a print job of a relatively large number of sheets at a time. On the contrary, actual using conditions cannot be uniform and are diverse. A replacement timing of a toner cartridge or a main cartridge can vary depending on situations, and thus the method is not providing an actual replacement timing of the cartridges.
Examples of cases beyond the standard using condition are such as where a document having a relatively high print ratio is frequently recorded, or oppositely, where a document having a relatively low print ratio is recorded, where a continuous printing or intermittent printing operation is carried out, and so on. Thus, the above simple method cannot be the way to find an actual timing of replacement for a toner cartridge or a main cartridge used under these conditions. For example, in cases where a print operation with a low print ratio is performed most of the time, a film on the photosensitive drum accommodated in the main cartridge wares out to cause a poor image quality before the toner in the toner cartridge is used up.
Hence, there is a need for another method to precisely determine the end of the service life of a photosensitive drum accommodated in a main cartridge. For example, introduction of an optical sensor allows direct judgment of the end of the service life of a photosensitive drum. However, this method cannot be the best under the condition using a toner, because the optical sensor cannot be kept clean.
Instead, there has been proposed another method, by which the service life of a photosensitive drum is detected based on the number of recording sheets having undergone a recording operation or a total time of rotation of the photosensitive drum. For example, Japanese Unexamined Patent Publication JP-A 8-185094 (1996) describes an art of judging the end of the service life of the photosensitive drum based on a total number of rotations of the photosensitive drum.
However, the above method of using a total number of rotations of a photosensitive body, either, is not able to flexibly deal with the change in print ratio resulting in a gap with a standard using condition. Thus, the longer the service period of a photosensitive body, the larger becomes a judging error with respect to the service life of the photosensitive body.
Likewise, in cases where the service life of a photosensitive body is judged based on the number of recording sheets having undergone a recording operation, it is not able to flexibly deal with the change in print ratio resulting in a gap with a standard using condition. Thus, it has been impossible to accurately judge an actual replacement timing of the photosensitive body.
As above, none of the conventional methods is taking into consideration a change of printing condition such that goes out of an assumed standard, thereby resulting in a difficulty in accurately determining an actual replacement timing of a main cartridge accommodating a photosensitive body.
SUMMARY OF THE INVENTION
The invention is devised to solve the conventional problems as set forth for example above, and therefore, has an object to provide an image forming apparatus which applies a process cartridge that at least includes a main cartridge accommodating a photosensitive body and a toner cartridge for replenishing toner, and is capable of precisely judging the service life of the photosensitive body and the replacement timing of the main cartridge.
In order to solve the above problems, the invention provides an image forming apparatus comprising a process cartridge detachably mounted thereto, including a main cartridge accommodating a photosensitive body and a toner cartridge for replenishing toner; recording sheets counting means for counting a number of recording sheets having undergone a recording operation during a service period of the main cartridge; total operation time measuring means for measuring an operation time of a photosensitive body during the service period of the main cartridge as a total operation time; toner cartridge related operation time measuring means for measuring an operation time of the photosensitive body during a service period of the toner cartridge as a toner cartridge related operation time; toner replenishing time measuring means for measuring a time of replenishing toner from the toner cartridge as a toner replenishing time; and judging means for judging, based on the number of recording sheets counted by the recording sheets counting means, the total operation time measured
Asanuma Masato
Fujita Syouichi
Naoi Hiroo
Saiko Hideji
Sakita Hirofumi
Birch & Stewart Kolasch & Birch, LLP
Sharp Kabushiki Kaisha
Tran Hoan
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