Electrophotography – Diagnostics – Consumable
Reexamination Certificate
2000-02-18
2002-01-08
Pendegrass, Joan (Department: 2852)
Electrophotography
Diagnostics
Consumable
C399S254000
Reexamination Certificate
active
06337956
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a developing device, a process cartridge including the developing device, and an image forming device including the developing device.
Normally, conventional image forming devices include a toner holding chamber or a toner container where toners are contained therein and a developing chamber where a developing roller is provided. An opening is formed at a boundary between the toner holding chamber and the developing chamber, so that the toners are transferred through the opening into the developing chamber. The conventional image forming devices are configured to detect the remaining amount or toner in a developing unit, and once the remaining amount has reached a predetermined value of less, urge the user to replenish the toner. There are many different ways to detect the amount of remaining toner. In one exemplary method, light transmission windows are provided in the toner holding chamber of a developing unit. A light emitting element and a light receiving element are provided, one in confrontation with each of the light transmission windows. The amount of remaining toner in the toner holding chamber is detected by emitting light from the light emitting element so that the light passes through both the light transmission windows. The amount of remaining toner will correspond to the amount of light received by the light receiving element.
However, with this method, it becomes impossible to accurately detect the amount of remaining toner when toner clings to the light transmission windows. Therefore, a cleaning member for cleaning the light transmission window is provided in the toner holding chamber. The cleaning member is configured to slide across and clean the light transmission window while rotating integrally with a toner agitation/transfer member. The toner agitation/transfer member is provided in the toner holding chamber, in order to agitate and transport the toner in the toner holding chamber.
The devices disclosed in Japanese Patent-Application Publication (Kokai) No. HEI-7-56431 or Japanese Patent-Application Publication (Kokai) No. HEI-9-34238 measure the time from when the cleaning member cleans the light transmission window to when the light path is blocked by toner that falls from the toner agitation/transfer member. However, as described in Japanese Patent-Application Publication (Kokai) No. HEI-7-56431, the fluidity of toner changes with changes in environmental conditions and with the length of use. Consequently, the toner falls from the toner agitation/transfer member at various timings, depending on the fluidity of the toner, so that it is impossible to stably detect the remaining amount of toner.
The length of time from when the light transmission windows are wiped until the light transmission windows are covered by toner depends on the amount of toner that drops from the agitator (after the agitator passes by the opening), and on the amount of the toner that billows up into a cloud-like condition in the chamber. However, these amounts will change with changes in the fluidity of the toner. Therefore, the amount of remaining toner can only be detected with extreme instability and inaccuracy.
Also, conventional image forming devices have a problem in that the toner is not always evenly distributed through the toner chamber. For example, when a laser beam printer is transported or when a developing cartridge is taken out and inserted into the laser beam printer for replacement, the toner tends to collect in one end of the toner chamber, so that it is impossible to accurately detect the remaining amount of the remaining toner. Also, when the opening from the toner chamber into the developing chamber is narrower than the developing chamber itself, or when narrow width sheets, such as envelops or postcards, are consecutively printed in large numbers, then toner is consumed unevenly from the toner chamber. The toner will be distributed unevenly in the toner chamber as a result. For this reason, it is difficult to properly detect how much toner remains in the toner chamber.
When a sheet-shaped member is provided to rotate in the toner chamber to agitate the toner, the ends of the sheet-shaped member can slidingly contact against the light transmission windows provided at both end walls of the toner chamber. In such a situation, the sheet shaped member damages the surface of the light transmission windows so that detection of remaining amount of toner cannot be properly performed.
To prevent damage to the light transmission windows, the sheet shape member can be formed shorter than the length of the toner chamber, so that the ends of the sheet shaped member are separated from the walls of the toner chamber. However, with this configuration, toner can accumulate in the space between the side walls of the toner chamber and the ends of the sheet shaped member, so that it is impossible to prevent uneven distribution of toner in certain areas of the toner chamber.
Some image forming device include a screw member to agitate the toner in the toner chamber. The screw member positively transports toner in the toner chamber along the lengthwise direction of the toner chamber. With this configuration, it is difficult to uniformly distribute the toner on both upstream and downstream sides of the transport direction along the screw member. As a result, deviation in the toner accumulation may occur.
In another aspect, when using the developing system that uses non-magnetic single-component toner, the toner must be scraped between a layer thickness regulating member and the developing roller in order to uniformly charge the toner. In conventional devices, the layer thickness regulating blade is usually made from stainless steel and the like in order to reduce production costs. Where the layer thickness regulating blade abuts against the developing roller, the layer thickness regulating blade applies a large pressure onto external additive of the toner. This can force the external additive to become embedded into the base particle of the toner, thereby reducing the fluidity of the toner. When such toner with reduced fluidity is returned from the developing chamber to the toner holding chamber with circulation of toner between toner developing chamber and the toner holding chamber, the time required after the toner with reduced fluidity is agitated by the agitator until the toner settles on the floor of the toner holding chamber may fluctuate depending on how long the toner has been used. This makes it difficult to stably detect the amount of remaining toner. When the amount of the toner with reduced fluidity in the toner holding chamber increases, the toner can become unevenly distributed in the toner holding chamber so that reliable and accurate remaining toner detection cannot be performed.
In still another aspect, the conventional image forming devices need to reliably agitate toner throughout the entire toner holding chamber by provision of a toner agitation/transfer member. The toner agitation/transfer member is disposed to slide against the inner floor surface of the toner holding chamber, with its tip in a bent condition. Also, the toner agitation/transfer member is formed to a width sufficient to substantially contact both walls at lengthwise ends of the toner chamber.
However, when the agitation/transfer member contacts both side surfaces of the toner holding chamber while rotating, the light transmission windows will be scraped off by the agitation/transfer member, in addition to being cleaned off by the cleaning member. Accordingly, the agitation/transfer member removes toner from the light transmission windows at a timing that matches the rotation cycle of the agitation/transfer member, so that light will sometimes, depending on the amount of friction, pass through the light transmission windows at this unwanted timing. Because light passes through the light transmission windows in an unstable manner, improper detection of remaining toner may occur.
Further, in the conventional developing devices, componen
Deguchi Hideaki
Hattori Yoshiteru
Ishii Masahiro
Sato Shougo
Brother Kogyo Kabushiki Kaisha
Oliff & Berridg,e PLC
Pendegrass Joan
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