| 摘要 |
PROBLEM TO BE SOLVED: To always maintain formed image quality in a stable state regardless of environmental change. SOLUTION: An image by a test patch image is formed in order to keep the image quality constant. By detecting the density of the test patch image, one of image forming conditions being a density control means in an image forming device, for example, the developing bias voltage of a developing device is controlled according to the detected result. Then, a humidity sensor detecting the environmental change, that means, humidity is arranged in the device. When the change of the humidity is detected by the humidity sensor (S51), the reference value of toner mixing ratio in the developer of the developing device is changed and corrected (S52→S54 or S53→S55). When the change of the density by the test patch image is not detected and the developing bias voltage is not corrected, the toner mixing ratio is maintained in a former state and it is not changed and corrected. Thus, since the toner mixing ratio is prevented from being unnecessarily changed according to the change of the humidity, the stable image quality is maintained. |
