| 摘要 |
There is provided a printing device capable of detecting a toner concentration in the developing unit from outside, and according to the detection result, capable of detecting reduction in the usable amount of toner stepwise and issuing an warning. In a printing device 100 of the present invention, the print controller 70 can detect a toner concentration in the developing unit 20 through the toner concentration sensor 30 provided at the outside of the developing unit 20 and can determine whether the toner in the developing unit 20 is out or not using the detection result. This eliminates the conventional need of disposing the toner concentration sensor in a narrow developing unit or the need of disposing the toner remaining amount detection sensor in the toner supply unit. Further, it is possible to detect reduction in the amount of toner every time the toner in the developing unit is out, thereby detecting reduction in the usable amount of toner stepwise and issuing an adequate warning whose level is changed depending on the detection result. Thus, the printing device meets the need for miniaturization and is capable of favorably performing printing operation and maintenance work.
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