| 摘要 |
PURPOSE:To reduce the amount of consumption of toner by providing a means for switching from the conditions of image formation in high-density image formation mode to the conditions of image formation in low-density image formation mode and vise versa by means of the adjustment of potential by electrification and exposure. CONSTITUTION:A voltage is applied to an electrifying charger 12 from a voltage power source 29, and a photosensitive drum is electrified by corona discharge. A development bias voltage is applied to each of the development bias electrodes 15 and 16 of a developing device from a high voltage power source 30. An exposure lamp 31 is turned on by the output voltage of a power source voltage 32. A control part 33 outputs control signals to the voltage power sources 29, 30 and 32 according to the type of the image of an original in response to an input signal from a high image density switch 34 or low image density switch 35 so that potential by electrification of the photosensitive drum, the bias voltages of the development bias electrodes 15 and 16 and the exposure of the exposure lamp 31 obtain their optimum values required for the conditions of the formation of a high or low density image. |
