| 摘要 |
PURPOSE:To reduce carrier deterioration of a developer by using one developer detecting means provided except at a development position, detecting density values of developers in plural developing devices, and operating the developing devices only during density detection except development. CONSTITUTION:When a developing device reaches a detecting means 11, the toner density of a developer is detected. A developing sleeve 20 and screws 22 and 23 for developer circulation and agitation operate firstly as shown by arrows and then the developer T circulates through a path shown by an arrow. When a main pole N1 for development is covered sufficiently with the developer, a detection signal (j) which is reflected light from a light source 16a for density detection is read. Then, the developer on the sleeve is removed by a nap cutting blade 24 and a reflected signal (i) from the sleeve is read at the position of N1 to stop the developing device immediately. Thus, carrier deterioration due to the density detection of the developer is reduced. |
