Electrophotography – Diagnostics – Image forming component
Patent
1999-12-02
2000-09-19
Pendegrass, Joan
Electrophotography
Diagnostics
Image forming component
399 43, 399 50, 399176, G03G 1500, G03G 1502
Patent
active
06122460&
ABSTRACT:
An improved electrophotographic printer is provided in which the voltage applied to the charge roller is automatically adjusted to compensate for its changing characteristics over its life span. A high voltage DC power supply includes an output that is connected to the charge roller, and the input side of this high voltage DC power supply is controlled by a microprocessor of the print engine. The print engine controls the output voltage of the high voltage DC power supply by changing the duty cycle of the pulse-width modulated control signal that is supplied to the input of the high voltage DC power supply. A look-up table contains the correct duty cycle for the pulse-width modulated control signal with respect to the number of prints that have been made. The result of the inspection of the look-up table is used by the microprocessor of the print engine to control the correct duty cycle for the pulse-width modulated signal. Over time, the charge roller characteristics begin to change, and after a predetermined number of prints have been made, the pulse-width modulated control signal has its duty cycle increased by a value that is provided in the look-up table. This increase in the duty cycle is performed several times over the operating life of the charge roller, in order to maintain the effective voltage applied to the photoconductive drum to a nominal value.
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Meece Kermit Arnold
Strack Christopher David
Tomson Troy Dustin Smith
Brady John A.
Lexmark International Inc.
Pendegrass Joan
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