| 摘要 |
PURPOSE:To detect an amount of toner remaining in a developing unit stably with high sensitivity, by grasping a toner amount attached to a vibrator provided with the wall surface of a toner hopper as change of vibrator displacement. CONSTITUTION:Piezoelectric vibrator 2 is formed by applying electrodes to both sides of a thin ceramic disc. When the toner is out of contact to the disc, frequency- admittance characteristics as shown in a full line are exhibited, but when in contact, large difference in admittance appears as shown in short dashes. Each constant of a vibrator circuit, transistors, etc. are set so as to run vibtator 2 when out of contact and not to work vibrator 2 when in contact by use of the above difference, permitting toner dificiency warning to be given to an operator by detecting vibration of vibrator 2 and flickering a light emitting diode. |
