| 摘要 |
PROBLEM TO BE SOLVED: To keep the excellent image quality by controlling the toner supply based on the output of an image density judging means, and judging the degree of degradation of the developer based on the output of a developer density measuring means. SOLUTION: Whether the image density is larger or smaller than the reference value is judged based on the output from a reflection type image density sensor 8. If the image density is smaller than the reference, the toner is supplied. If the image density is larger than the reference value, the control is completed. As for the degradation of the developer, the detected result of a permeability sensor 9 and the copying quantity are red respectively. The read permeability and copying quantity are collated with the table consisting of the standard change data of the developer density and the data of the lower limit value of the developer density. Whether or not the permeability, i.e., the developer density reaches the lower limit value, is judged, and when it reaches the lower limit value, the indication of exchanging the developer is expressed. Otherwise, whether or not the degradation of the developer is earlier is judged from the permeability and the copying quantity. |
