| 摘要 |
<p>PURPOSE:To always accurately detect the depletion of toner by preventing the malfunction of a toner depletion sensor using a piezo-electric element from being caused. CONSTITUTION:According as the length and the board thickness of the vibrators 42 and 43 of a tuning fork part 41 in the toner depletion sensor 26 being a tuning fork type sensor are changed, the oscillation frequency of the tuning fork part 41 is made different from the natural frequency of a developing device 5. The power (amplitude) of an electrical signal given to the oscillating side piezo-electric element 44 of the vibrator 42 of the tuning fork part 41 is made periodically larger to allow the vibrator 42 to vibrate fiercely, so that the toner is prevented from being stuck to the tuning fork part 41.</p> |
