IMAGE FORMING DEVICE HAVING MOVABLE DEVELOPING DEVICE WITH DEVELOPER DENSITY DETECTOR

摘要

PURPOSE:To attain isolation from the outside, to correct variation in characteristics of a detecting element, and to perform stable, high-precision detection by allowing a developer density detecting means provided at the bottom part of a developing device to contact a developer at a development position and detect its density except at the development position. CONSTITUTION:Detection parts 65a and 65b are provided on the wall surface of the detection chamber 61 of the developer density detector 6 formed at the bottom wall 13 of the developing device 8 and a lamp 66 and a photodetector 67 are arranged opposite. When the developing device reaches the development position, a developer D enters the detection chamber 61 and the developing device rotates on developing operation to enter an inverted state at a position 8c. Then, the developer comes out of the chamber 61 and the detector 67 detects the density of toner sticking on a transparent wall 65. Then, the changes with the lapse of time in characteristics of the lamp and detector are compensated by comparison with a standard transmission density part 68. Therefore, the detection part 6 is shielded from the outside and the characteristic variation of the detecting element is also corrected externally, so that the density is detected accurately and stably with high density by the simple structure.