International Business Machines Corporation

Robert C Brannan

Robert F Pryor

Michael R Headrick

Harvey R Markham

Ben A Nilsson

Robert J Fogoros

Ainis Krumins

The temperature of a hot roll xerographic fuser is controlled by a control system which compares a command set point temperature to the fuser's actual temperature and energizes a fuser heater accordingly. A cold start of the fuser is distinguished from a warm start, and the command set point temperature is magnitude-programmed accordingly.

Hot roll fuser temperature control

An electrophotographic copier having a toner concentration control apparatus which periodically effects a toner-patch test cycle during which the optical density of toner deposited on a photoconductor test area is measured, as by light reflectance. A time period of copier non-use, exceeding a preset time period, or a copier on/off operation, referred to as critical events, results in a transient mode of copier operation which includes reduction of photoconductor charge magnitude during the next subsequent use, independent of the extent of the prior copier use history. During such subsequent use, the toner-patch test cycle is operable to effect closed-loop control of changing the photoconductor's charge magnitude back to its nominal working value. More specifically, so long as the results of a toner-patch test cycle indicate an acceptable toner density, the photoconductor charge magnitude is maintained at a lower than working level. As the results of the toner-patch test cycle periodically indicate lower than acceptable toner density, as by a high light reflectance off the test patch, the photconductor's charge magnitude is periodically increased until finally the working charge magnitude is reached. The results of the toner-patch test cycle are operable to add toner to the copier's developer only when the photoconductor's charge magnitude has been increased to at or near the working magnitude.

Charge density control for an electrostatic copier

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Longmont, CO, United States of America

Robert C Brannan