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DEVELOPER ROLLER BIASING

IP.com Disclosure Number: IPCOM000025375D
Original Publication Date: 1985-Feb-28
Included in the Prior Art Database: 2004-Apr-04
Document File: 2 page(s) / 68K

Publishing Venue

Xerox Disclosure Journal

Abstract

A problem arises in an electrophotographic printing machine when the developer roller encounters voltages in excess of the electrical bias applied thereon. This occurs during cycle up and cycle down when the photoreceptor voltage is stepped up or turned off. The developer has a large effective area and must wait until the photoreceptor voltage transition, during turn off, has cleared the development zone, and must be turned on prior to the step of the photoreceptor voltage entering the development zone. During these transitions, when there is voltage on the development roller and no voltage on the photoreceptor, the critical first voltage can be exceeded. These high positive fields cause excessive development with wrong sign toner particles. This problem may be overcome by a system in which the voltage on the photoreceptor and the voltage on the developer roller ramp at the same time. This minimizes the positive field and yet produces no negative field. The system requires the use of a constant ramp circuit that takes an incoming step in voltage and ramps the power supply to its proper level. In addition, because of the different voltage levels of the photoreceptor and the developer roller, the ramp times are different. In dealing with this problem, it is apparent that the maximum error voltage occurs as the maximum voltage is reached. This requires that the end of each ramp meet. The problem of different ramp durations is solved by calculating the difference in voltage between the photoreceptor and developer roller and adjusting the turn on time of the developer roller ramping voltage. A system of this type permits the use of reclaimed toner particles, allows for higher voltages and minimizes the possibility of positive fields during cycle up and down.

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XEROX DISCLOSURE JOURNAL

DEVELOPER ROLLER BIASING Proposed Thomas A. Hayes, Jr. Classification

US. C1. 118/657 Int. C1. G03g 15/09

A problem arises in an electrophotographic printing machine when the developer roller encounters voltages in excess of the electrical bias applied thereon. This occurs during cycle up and cycle down when the photoreceptor voltage is stepped up or turned off. The developer has a large effective area and must wait until the photoreceptor voltage transition, during turn off, has cleared the development zone, and must be turned on prior to the step of the photoreceptor voltage entering the development zone. During these transitions, when there is voltage on the development roller and no voltage on the photoreceptor, the critical first voltage can be exceeded. These high positive fields cause excessive development with wrong sign toner particles. This problem may be overcome by a system in which the voltage on the photoreceptor and the voltage on the developer roller ramp at the same time. This minimizes the positive field and yet produces no negative field. The system requires the use of a constant ramp circuit that takes an incoming step in voltage and ramps the power supply to its proper level. In addition, because of the different voltage levels of the photoreceptor and the developer roller, the ramp times are different. In dealing with this problem, it is apparent that the maximum error voltage occurs as the maximum voltage is reached...