| 摘要 |
PURPOSE:To prevent the precision of toner density detection from lowering, by providing an inductance type toner-density detecting circuit with a humidity detecting circuit and by varying the reference value of a discriminating circuit in accordance with humidity. CONSTITUTION:A detection signal from an inductance type toner-density detecting circuit 2 is supplied to a discriminating circut 18. On the other hand, a detection signal from a humidity circuit 30 which detects ambient relative humidity is supplied to a control circuit 50. When the humidity is below a prescribed value, e.g., 30%, the control circuit 50 increases the reference discrimination value Vr of the discriminating circuit 18 by a prescribed value. When the humidity is above a prescribed value, e.g., 80%, the reference value Vr of the discriminating circuit 18 is decreased by a prescribed value. Thus, an increase or decrease in the detection output of the density detecting circuit 2 at low or high humidity is compensated. For this purpose, the reference value of the discriminating circuit is varied in accordance with the humidity to prevent the precision of toner density detection from lowering. |
