JPS5450340A - Detection of toner density in developing agent - Google Patents

Abstract

PURPOSE:To highly accurately detect the toner density in a developing agent by detecting the fluidity of the developing agent falling down from a container with the use of detecting measn. CONSTITUTION:Normally, a first shutter plate 23 covers the head of a hopper 13, and a second shutter plate 24 is retracted from an outlet 14. When in the toner density detecting operation, the first shutter plate 23 is shifted to a position shown in broken lines, and the second shutter plate 24 is shifted to shut off the outlet 14. When the developing agent is stored in the hopper 13 after a preset time lapse, the first and second shutter plates 23 and 24 are returned to their initial positions, and the developing agent in the hopper 13 simultaneously begins falling from the outlet 14 into a cylinder 15. The abrupt change in the frequency oscillated from a coil 16 at that time is detected by a frequency detector 17 so that the fluidity of the falling agent may be detected. A comparator circuit 19 calculates the toner density at the preset time from that fluidity so that the rotations of a toner supply roller 21 may be controlled by means of a drive circuit 22.