| 摘要 |
PURPOSE:To reduce the fitting space of a sensor and to improve its precision by using a thin plate type sheet coil as the coil of a transformer and thus making the sensor thin. CONSTITUTION:When the oscilation output of an oscillator 5 is applied to primary coils L1a and L1b, output signals corresponding to the specific degree of coupling of a magnetic circuit with toner in a copying machine are generated at secondary coils L2a and L2b. The differential output between the secondary coils L2a and L2b is phase-detected 6 and inputted to a voltage comparator 7. The comparator 7 outputs signals indicating whether the toner level is higher than specified or not and whether the toner density is high or not according to the phase detection output. This sensor for toner uses thin plate type sheet coils as the respective coils used in the transformer, so its thickness is reduced. The space of fitting to the copying machine, etc., is small and the sheet coils are formed by photoetching a thin steel plate stuck on an insulating film, so the conductivity never decreases owing to the drawing of winding when a thin wire is wound, so that the precise sensor is obtained. |
