| 摘要 |
PURPOSE:To exactly detect a toner mixing ratio by a simple constitution, by providing a magnetic material iron core coil having a magnetic path a part of which has been opened, that is to say, an opened magnetic path, on the lower face side of a down stream of a developer flow, and detecting the toner mixing ratio of a developer without obstructing a flow of the developer at all. CONSTITUTION:A detecting coil 9 used for detecting a toner mixing ratio is constituted so as to detect a variation of inductance between terminals 13, by winding a wire 12 round a magnetic material iron core 11 having an opened magnetic path in the direction for contacting with a developer 10. The opened magnetic path of the detecting coil 9 contacts with only a flow of the developer in the direction of its flow, therefore, almost all magnetic fluxes generated by the coil pass through the developer flow, accordingly, sensitivity for detecting the toner mixing ratio is excellent, and also a measuring error due to the influence by the magnetic flux from a magnetic roll 3 and influence of scattering of a developer, etc. is scarcely generated. The magnetic material iron core 11 containing the winding 12 is installed by use of a filler 15 in a case 14 made of a non-magnetic insulator, so that the face contacting with the developer 10 becomes smooth. |
