| 摘要 |
PURPOSE: To set the bias voltage or current impressed on a transfer roller to be in a proper range regardless an environment and to prevent a defective image by controlling the bias level in accordance with humidity and temperature. CONSTITUTION: A temperature detection means and a humidity detection means are provided in a photoreceptor drum, and when resistance variation of a transfer roller is of one digit or more in the case of humidity variation from 20% to 80%, the bias voltage or current is controlled to a specified value by detecting the temperature and humidity of the use environment of the transfer roller and controlling a bias impression means according to the results of the detection. The figure shows a setting range for a set value and a proper transfer area of transfer current (μA) in accordance with the environmental change of the transfer roller when a constant current source is employed for the power supply of the transfer. Here, the proper transfer area means a proper area common to the individual colors of Y, M, C, K, R, G and B for paper and envelope of 161b-361b. |
