| 摘要 |
The present invention provides a toner concentration control device which can measure the concentration of toner stably in an extended period of time without influenced by the shape of a developer stirring mixer rib and mounting position of a toner concentration detecting censer, with a result the stagnation or adhesion of toner in the proximity of the toner concentration detecting censer is eliminated, by so composing a toner concentration control device having a toner concentration censer for detecting magnetically the concentration of toner mounted facing a developer stirring mixer in a developing vessel, so that a waveform detection means which detects the output of the toner concentration censer for at least over one cycle before a toner supply means is activated, and an about-minimum value judging means which judges the minimum value or its vicinity detected by the waveform detection means are provided, and an about-minimum detection means is activated on the basis of the value judged as minimum or its vicinity by the about-minimum value judging means.
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