| 摘要 |
PURPOSE:To suppress the increase of power consumption and the degradation in characteristic of a photosensitive body and prevent the reduction of the life of an ion current generating means and the variance of an ion current due to humidity change by controlling the driving voltage or frequency of the ion current generating means in accordance with humidity. CONSTITUTION:When formation of an electrostatic charge image of additional information by a writing head 5 is started, a surface potential measuring area 2B is electrified, and a potential sensor 190 measures the electrification potential. A control part 40 compares the output of the sensor 190 with a reference value and controls a power supply circuit 191 on the basis of the deviation to control not only the voltage applied to the electrode of the writing head 5 cut also the bias voltage of a developing device. If the humidity is raised and the resistance value of a humidity sensor 255 is reduced, outputs of differential amplifiers DA3 and DA4 are increased by reception of the reference voltage controlled by a Zener diode ZD1, and the primary-side voltage of a transistor T is increased through a transistor TR1 to raise the high frequency voltage level applied to a drive electrode 31 of the head 5. |
