Method and apparatus for automatically compensating a degradation of the charge roller voltage in a laser printer
US6122460A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 2, 1999 |
| Grant date | Sep 19, 2000 |
| Priority date | — |
| Expiry date | Dec 2, 2019 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03G2215/021
- WIPO fieldOptics
- WIPO sectorInstruments
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 …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.