| 摘要 |
PURPOSE:To constitute a device in a narrow place by providing a detecting coil and a reference coil on the same plane and covering the surface of the reference coil in the same side as the detecting surface of the detecting coil with a magnetic material and providing a control magnetic material on the rear side of the reference coil. CONSTITUTION:A detecting primary coil 13 and a reference primary coil 14 are connected in series and are connected to an oscillator 15. Detecting primary and secondary coils 16 are arranged on the same plane, and a detecting surface 17 is formed on them, and both coils are surrounded with a magnetic core member 18, and a voltage corresponding to the density of a toner material 1 flowed to the detecting surface 17 is outputted from the secondary coil 16. Reference primary and secondary coils 14 and 20 are arranged on the same plane as detecting coils 13 and 16, and upper faces of coils 14 and 20 are covered with a magnetic material 22, and a plate-shaped control magnetic material 23 is moved in the direction of an arrow B under coils 14 and 20 to control the toner concn. measuring area. The differential output between coils 16 and 20 is detected with the phase difference of the oscillator 15 by a phase detector 19 and is compared with a preliminarily set toner voltage by a comparator 24, and a toner supply device omitted in the figure is driven through a driving circuit 25 and a driving mechanism 26 by the output of the comparator 24. Thus, the detector is made small-sized. |
