| 摘要 |
PURPOSE:To measure a toner level without any influence of an alternating magnetic field produced by the rotation of a magnet roll by arranging a couple of channel-shaped magnetic cores of transformers at equal intervals to the magnet roll while the bottom plate of a toner container which has a step part is interposed. CONSTITUTION:When the oscillation output of an oscillator 11 is applied to primary coils L1a and L1b in order to decide on the toner level of a developing device, output signals corresponding to the coupling degrees of their magnetic circuits are induced at secondary coils L2a and L2b. The differential output between those secondary coils is phase-detected by a phase detector 12 to detect the toner level, and the coupling degree of the magnetic circuit of a comparison- side transformer 17b is adjusted by a magnetic adjusting plate 21 previously; and the cores 15a and 15b of transformers 17a and 17b are at the same distance from the magnet roll 3, so the decision on the toner level is made stably without any influence of the alternating magnetic field produced by the rotation of the magnet roll 3. |
