| 摘要 |
PURPOSE:To prevent the misdetection of a toner concentration and the dropping of detecting sensitivity by providing a shielding device blocking the infiltration of floating toner on the detecting surface of a toner concentration sensor disposed opposite to the periphery of a photosensitive body. CONSTITUTION:When a toner image 13 on the periphery of the photosensitive body 1 reaches a position opposite to the toner concentration sensor 10, a solenoid 4 is energized with a toner concentration detection commanding signal, and a wire 6 is pulled in by the sucking of a plunger 5. Then, a shutter 8 which covers the detecting surface of the sensor 10 till that time is turned slantingly upward by almost 90 deg. through the use of a shaft 12 as the rotary center so as to be shown by the arrow, and the toner concentration of the toner image 13 is detected via the exposed detecting surface of the toner concentration detecting sensor 10. Further, a plunger 4 is de-energized after defect on is finished, and the plunger 5 is restored to an initial position. The shutter 8 is reset to the initial position by the action of a spring 9 to cover the detecting surface, and the sticking of the floating toner, etc., is prevented. Thus, the misdetection of the toner concentration is prevented. |
