| 摘要 |
PURPOSE:To prevent the correspondent relation between the magnetic permeability of a developer and a toner density from changing even if the developer is deteriorated and to prevent the degradation in the output of a toner density sensor by providing the developer and toner density sensor which are respectively specific. CONSTITUTION:This device has the developer 11 having a toner of >=0.8 Wadell' s operational sphericity and the toner density sensor 12 having a fluororesin on its surface in order to detect the toner density by measuring the magnetic permeability of the developer 11. The Wadell's operational sphericity is expressed by the diameter of the min. circle circumscribing the projected image of the diameter/particle of the circle equal to the projected area of the particle. There is no change in the sticking state of the toner and the toner density is stably maintained if the toner having the surface approximate to a sphere is used from the beginning. Since the density sensor 12 has the fluororesin on the surface of the outside frame, the sticking of the toner to the sensor surface is prevented. |
