| 摘要 |
PURPOSE:To detect whether an abnormal reduction in toner concentration is temporary or caused by the abnormality of replenishment by starting replenishing toner when a detection voltage becomes lower than a first reference voltage and detecting whether or not the detection voltage exceeds a second comparison voltage in a prescribed time and reaches a control voltage within a second prescribed time. CONSTITUTION:A memory 21 holds the first reference voltage appearing when a toner concentration sensor 11 and electrical controls such as an IC are at a low toner concentration level at which a fogging phenomenon occurs. When the detection voltage from the toner concentration sensor 11 becomes lower than the first reference voltage, the toner replenishing means 5 starts replenishing toner. Then, a comparing means detects whether or not the detection voltage from the toner concentration sensor exceeds the second reference voltage higher than a control voltage in the first prescribed time and reaches the control voltage in the second prescribed time. Consequently, toner concentration is detected to generate the signal controlling to the reference value, and in the case of abnormal reduction of the toner concentration, whether the abnormality is caused by a temporarily concentration reduction or the abnormal replenishment of the toner replenishing system is detected. |
