| 摘要 |
<P>PROBLEM TO BE SOLVED: To prevent such a trouble that no images are output even though an image forming process is performed by correctly detecting a state that a newly installed developing unit stores no developer. <P>SOLUTION: The concentration detection voltage of a toner concentration sensor 57 before the start of the idling drive of a printer 1 is compared with the concentration detection voltage of the toner concentration sensor 57 directly before the stop of the idling drive. In the case there is no difference that exceeds a predetermined range, it is determined that two-component developer is absent in the mixing stir part 52 of the developing unit 5. Before and after the operation of stirring the two-component developer in the developing unit 5, the concentration detection voltage of the toner concentration sensor 57 changes. This fact is used for correctly determining whether two-component developer is present or absent in the developing unit 5. <P>COPYRIGHT: (C)2003,JPO |
