| 摘要 |
PURPOSE:To prevent image density from decreasing or becoming irregular even if paper has surface unevenness by providing a smoothness quantity detection sensor for the recording paper at part of a recording paper conveyance path, and controlling a developing bias energizing means according to the sensor output. CONSTITUTION:A record player type smoothness quantity detecting device 31 consisting of a detection probe and a moving coil or smoothness quantity detecting device 32 consisting of a reflection type photoelectric sensor detects the quantity of the irregularity of the recording paper, converts the quantity into an electric signal, and sends the signal to a control part 33, which sends a control command for a bias voltage or transfer current to a high voltage power source 34 to control the high voltage power source 34. Namely, the control part compares the signal with a reference value indicating an uneven quantity at which a transfer defect begins to be caused and increases the bias voltage when the reference value is exceeded to increase the supply amount of toner. When the quantity is smaller than the reference value, the bias voltage is controlled to a constant value to make the supply amount of toner constant. Consequently, the image density neither decreases nor becomes irregular owing to the unevenness of the paper. |
