Electrophotography – Diagnostics – Consumable
Reexamination Certificate
2002-12-09
2004-08-31
Royer, William J. (Department: 2852)
Electrophotography
Diagnostics
Consumable
C399S045000, C399S396000
Reexamination Certificate
active
06785479
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to an image forming apparatus of an electrophotographic type or an electrostatic recording type. More particularly, the invention is suitably applicable to an image forming apparatus in which a cartridge, i.e., a process cartridge or a developing unit in the form of a cartridge, can be detachably mounted on the main body of the image forming apparatus, and which has a developer remaining amount detecting member for successively detecting the remaining amount of a developer in a developer container.
Applicable electrophotographic type image forming apparatuses include an electrophotographic copying machine, an electrophotographic printer (such as an LED printer or a laser beam printer), an electrophotographic facsimile machine, and an electrophotographic wordprocessor. The term “a cartridge detachably attached to the main body of an electrophotographic image forming apparatus” as used herein means a cartridge formed from at least one of an electrophotographic photosensitive member, charging means which charges an electrophotographic photosensitive member, a developing member which supplies a developer to an electrophotographic photosensitive member, and cleaning means which cleans an electrophotographic photosensitive member, which is then made easily detachable from the main body of the electrophotographic image forming apparatus. In particular, the process cartridge is a cartridge composed of at least one of charging means serving as process means acting on an electrophotographic photosensitive member and the electrophotographic photosensitive member are integrally formed into a cartridge, and is made detachable from the main body of the electrophotographic image forming apparatus.
2. Description of the Related Art
In a conventional image forming apparatus, such as a copying machine or a laser beam printer of the electrophotographic type, an electrostatic latent image is formed by irradiating light (laser beam or the like) in accordance with image information onto an electrophotographic photosensitive member (hereinafter simply referred to as a “photosensitive member”). The thus formed electrostatic latent image is made visible into a developer image (toner image) by supplying a developer (toner) as a recording material to the latent image by developing means, and an image is formed on a recording medium, such as recording paper from the photosensitive member.
A developer container serving as a developer containing vessel is connected to the developing means, where developer is consumed by forming an image. The developer container, the photosensitive member and the charging means are often formed integrally as a process cartridge detachably mounted on the main body of the image forming apparatus (hereinafter simply referred to as the “apparatus main body”). When the developer is exhausted, for example, the user can form again an image by replacing this process cartridge. This is a developing unit having the developing means and the developer container formed into a cartridge detachably mounted individually on the apparatus main body. In particular, according to the process cartridge process, it is possible to apply the developer, and at the same time, replace other supplies, such as the photosensitive member, by replacing the process cartridge relative to the apparatus main body, thereby permitting a remarkable improvement of maintainability of the apparatus.
For example, for the purpose of knowing from time to time the remaining amount of the developer usable for forming an image in the process cartridge, a process cartridge or an apparatus main body having a developer remaining amount detecting member capable of successively detecting the developer remaining amount level is becoming more popular.
Available means for achieving detection of the developer remaining amount level include a method of measuring the amount of developer through a change in capacitance by means of a capacitor-type bipolar electrode (conductive section), and a method of measuring the amount of developer from a difference between the amount of transmitted light and the amount of received light, produced by emitting light into the developer container.
A detecting method based on a so-called plate antenna, in which a capacitor-type bipolar electrode is arranged, will now be described as an example of the developer remaining amount detecting member. The plate antenna has a pair of electrodes (conductive section) arranged substantially in parallel with each other spaced apart by a prescribed distance. This electrode pair is arranged, for example, in or outside the process cartridge so as to cover the toner in the developer container. That is, this is based on the fact that the capacitance varies with the amount of developer between the electrode pair. This makes it possible to establish a correlation between the amount of developer in the developer container and the capacitance between the electrode pair. It is therefore possible to know at any time the remaining amount level of developer in the developer container by measuring the capacitance by means of the plate antenna. The capacitance of the plate antenna from the current value is generated in one of the electrode pair by impressing an AC bias onto the other.
However, the above-mentioned conventional detecting method of the developer remaining amount level, i.e., the method of measuring the amount of developer from a change in capacitance between two electrode poles may sometimes cause the following problems.
In the conventional method, the capacitance varies with the area of the plate antenna provided in the developer container covered by the developer. A developer remaining amount level is calculated in response to this change, and the result of calculation is notified to the user.
For more recent image forming apparatuses, however, the frequency of use of a laser beam printer is only increasing, and the print volume is also increasing. Furthermore, there is a demand for increasing the printing speed of the apparatus main body (hereinafter referred to as a “throughput”) for improving usability and reducing the output time.
Measures taken so far for increasing the throughput include replacement of the driving motor by one with a higher rotating speed, and reduction of the distance between two recording sheets conveyed when continuously outputting images, known as the paper distance.
Because an increase in the absolute amount of heat results from rotation and fixing along with an increase in throughput, temperature increase and similar problems tend to occur. In order to obtain a high-quality output image, it is necessary to increase the fixing temperature. Particularly, when conveying a small-sized recording medium with a narrow width, such as an envelope and a postcard (hereinafter referred to as the “paper feed”), an abnormal temperature is observed at portions not feeding the paper.
An increasing number of apparatuses have now diversified throughput to cope with higher-accuracy printing (high-resolution image), including provision of a plurality of modes, such as a half-speed mode or high-accuracy printing mode at a very low speed.
The increase in throughput also has an effect on the state of the developer in the developer container. An example is the calculation of the developer in the developer container caused by a stirring unit. When the rotating speed of the driving motor is increased so as to increase the throughput, rotation of the stirring unit provided in the developer container also increases. As a result, the developer in the developer container is actively stirred.
The increase in throughput leads to a considerably reduced acquired data by the developer remaining amount detecting member relative to the image output to a recording sheet. If data are processed for detecting the remaining amount level of the developer with the thus reduced acquired data, the influence of developer circulation in the developer container section caused by stirring
Hibi Takashi
Matsumoto Hideki
Naito Norihito
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