Vorrichtung zum Ermitteln eines restlichen Tonerpegels

摘要

The present invention provides a developing device of an electrophotographic recording system for developing an electrostatic latent image formed on a photosensitive drum. The developing device includes a hopper which stores toner and a developing roller which develops the electrostatic latent image formed on the photosensitive drum using the toner stored in the hopper. On one side of the hopper at a predetermined height from its bottom, a light-emitting element for emitting light is positioned. A toner detecting device detects the existence or non-existence of toner by using a light-receiving element positioned on the interior of the hopper which outputs signals corresponding to the existence or non-existence of toner in the hopper in response to the amount of the light received from the light-emitting element. An agitator conveys the toner to the developing roller and simultaneously cleans a light-emitting side of the light-emitting element and a light-receiving side of the light-receiving element in synchronism with a conveyance period of the toner. A signal transmitting device transmits signals from the light-receiving element to a CPU which compares the number of signals with a predetermined value, thereby determining a level of the toner.