| 摘要 |
PURPOSE:To realize the detection of toner density with high accuracy, by providing an electromagnetic transducer at the area near the developer which is held by a magnetic field of a magnetic brush. CONSTITUTION:A detecting element 10 uses a semiconductor magnetic resistance element, a Hall element, etc. Such element 10 is put into an area close to a developer 3 which is held by a magnetic field of a conveying magnetic roll 4. When the toner density reduces, the carrier, i.e., a magnetic material increases. Thus the magnetic flux is concentrated at the area close to a sleeve 14 of the roll 4. As a result, the quantity of the magnetic flux affecting the element 10 is reduced. In this case, the element 10 is held in a contactless state to the developer 3 and set at the position close to the developer 3. Accordingly the resistance value of the element 10 varies to ensure the detection for the change of toner density. |
