Electrophotography – Diagnostics – Consumable
Reexamination Certificate
2002-06-11
2004-09-14
Lee, Susan (Department: 2852)
Electrophotography
Diagnostics
Consumable
C399S127000
Reexamination Certificate
active
06792218
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to the field of electrophotographic image forming, and more particularly to a method of promoting good image quality by compensating for undesirably low toner consumption.
The quality of printing produced by an electrophotographic printing process is governed by a number of factors, including the choice of the particular electrophotographic printing process used, the alignment of various mechanical components, and the properties of the toner being employed. In turn, factors helping to determine the properties of the toner include the chemical composition of the toner, its particle size, and its process/environmental history. With particular regard to the present invention, it has been noticed that when an electrophotographic printing device is called on to produce output with very low print factor for a prolonged period, the print quality suffers. It has been proposed that one reason for this phenomenon is that the low toner usage that accompanies prolonged low print factor printing results in “conditioning” of the toner, leading to reduced print quality.
Several approaches have been proposed to address this situation. One example is disclosed in U.S. Pat. No. 5,168,293 which addresses this problem by tracking the print factor on a pixel-by-pixel basis between various size print media. When the pixel-by-pixel print factor falls too low, the '293 device forcibly consumes toner to bring the pixel-by-pixel print factor back to at least the desired minimum level. However, this approach's reliance on pixel-by-pixel tracking of toner usage consumes substantial memory and processing power that could be otherwise used within the electrophotographic printing device. Also, the approach relies on a complex computation of available print area for various sized print media, further consuming computational resources. As such, there remains a need for other approaches to compensating for low toner usage.
SUMMARY OF THE INVENTION
The present invention monitors the rate of toner consumption with respect to mechanical activity of the electrophotographic printing device in order to minimize the incidence of “conditioned” toner by triggering an artificial toner consumption operation when the toner consumption rate is too low.
One embodiment of the present invention is a method of controlling an electrophotographic printing assembly that comprises measuring mechanical activity of the printing assembly, monitoring a rate of consumption of toner; and then forcing artificial consumption of toner in response to the rate failing to satisfy a predetermined threshold with respect to the mechanical activity. The artificial toner consumption may be achieved though a dummy print operation where an intentionally un-printed latent image is formed on a photoconductive drum, but the corresponding toner rendering the latent image visable is routed to appropriate waste toner reservoir(s) and the image is not printed on the recording medium (e.g., paper). The dummy print toner may be cleaned from the photoconductive drum without being transferred to an intermediate transfer medium and/or may be cleaned from the intermediate transfer medium, both without transferring the toner to the recording medium.
A controller may time the dummy print operation to correspond to a next normally occurring interdocument gap or may adjust the printing process such that a dedicated dummy print period is inserted between print jobs. Also, the monitoring of printer mechanical activity and rate of toner consumption may be done with respect to the printer as a whole or on a toner cartridge-by-toner cartridge basis, as desired.
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Sato et al., “Electrophotographic Recording Apparatus”, Oct. 1991, JP03233487A (translation), p. 10, lines 2-18.
Carter, Jr. Albert M.
Denton Gary A.
Ravitz Cary
Tungate, Jr. Stanley C.
Twardeck Thomas G.
Brady John A.
Lee Susan
Lexmark International Inc.
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