| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a developing device of a vertical one-directional circulation system capable of preventing a problem such as overflow-dragging or depletion of toner with a simple configuration resulting in an enhanced image quality. <P>SOLUTION: A developing device 5 includes: a magnetic permeability sensor 70b disposed at the downstream side of a supply screw 53 for supplying a developer to a developing roller 51; and a magnetic permeability sensor 70a disposed at the downstream side of a recovery screw 54. Control means 80 previously stores values of average output voltage for magnetic permeability sensors 70a and 70b in a normal state of the image density in a memory (not shown). When the average output voltage value on the magnetic permeability sensor 70b reduces exceeding the previously stored voltage value, the control means 80 controls to replenish the toner via a toner replenishment port 56 to increase the developer amount in the developing device to ensure the height of the developer to prevent a depletion problem that developer is not supplied to the developing roller 51. <P>COPYRIGHT: (C)2013,JPO&INPIT |
