| 摘要 |
PURPOSE:To maintain always the specified toner concn. of a developer by setting at least either of the conditions for determining the control value or control set value of a toner concn. control means at the values different with respect to plural line speed ratios. CONSTITUTION:The line speed ratio of both or either developing device of the developing device 6 or 7 with respect to a photosensitive drum is switchable to two kinds; 3.5 and 4.5. The switching is executed by a selection key which is provided to the operating part 21 of the image forming device and is operated by an operator's hand. The selected mode signal is sent to a CPU 16 and the driving speed of a developing driving means 22 is switched according to the information. The conditions for determining the control value or the set value of the control value is switched according to the information on the line speed when the mode for detecting the density of the toner pattern image to be executed once at every 10 times of image formation at the time of the image formation. The specified concn. of the toner in the developer is maintained by changing the line speed ratio of the sleeve in such a manner even in case of changing the developing capacity. The always stable reproduced images are thus obtd. |
