Method and apparatus for supplying toner to a developing device in an

Abstract

A device for replenishing a developing device with a toner is disclosed, which device is for use in electrophotographic image forming equipment such as a copying machine or a printer. The replenishment of the developing device with the toner is executed when the toner concentration in the developer held in the developing device decreases below a prescribed reference concentration. Otherwise, this replenishment is effected supplementarily when the ratio of the dark part to the bright part of the image on a given document to be printed exceeds a prescribed reference value and, at the same time, the equipment is set for a copying mode in which the toner is consumed quickly. This mode consists in causing the copying action to be performed continuously, allowing the copying operation to be performed on copying papers of a size larger than a prescribed reference size, or reproducing an image in a high density. Since the replenishment of the toner is attained under a prescribed condition even when the toner concentration in the developer exceeds a prescribed reference concentration, the image forming equipment is enabled to reproduce an image of high quality on a copying paper even under the condition in which the toner is quickly consumed.