| 摘要 |
PURPOSE:To detect a toner density accurately by bringing a detecting part of a detecting member, which is arranged to face closely a nonmagnetic sleeve, into contact with the layer of a developer which is carried along the nonmagnetic sleeve. CONSTITUTION:Near a developing gap D, an electrostatic latent image formed on a drum 1 by rubbing the surface of the photosensitive drum 1 with a magnetic brush formed with developer 2 is developed. The developer 3 after passage of the developing gap D is scraped off from a nonmagnetic sleeve 2 by a repelling magnetic field and is recovered in a developer tank 3 when the developer reaches the part where the same poles face each other. The recovered developer 2 is agitated and mixed togehter with a toner 2a, which is discharged from a toner tank 10, by an impeller 9 and is attracted onto the nonmagnetic sleeve 2 and is used for development. When the developer 2 reaches a position near a pole S1 after passing the developing gap D, the toner density of the developer is detected by a toner density detecting member 8 which is brought into contact with the developer layer in this position, and an external signal is outputted in accordance with the detected toner density, and the rotation of a toner supply roll 13 is controlled by a driving means. |
