| 摘要 |
PROBLEM TO BE SOLVED: To prevent the sticking of toner to a sensor surface of an optical sensor disposed opposite to a photoreceptor. SOLUTION: The optical sensor 53 is mounted in a tubular easing 1 with a rectangular section which is disposed in an axial direction of a photoreceptor drum 51 and a weir member 2 which interrupts the communication in the easing 1 is mounted on one side of the optical sensor 53. A cover member 3 in which an opening part 3a is formed in the position which is on the wall of the casing and opposed to the sensor surface 53a is attached. The opening part 3a is made to be such a size as to cause no interruption of the transmission and reception of light between the sensor surface 53a and the surface of photoreceptor drum 51. A space which separates the photoreceptor and is opposed to the sensor surface 53a is formed. When air is blown into the casing 1, the air in the space is flown out of the opening part 3a toward the photoreceptor drum 51. Thereby, inflow of toner into the prescribed space is prevented, which makes it possible to prevent the sticking of toner to the sensor surface 3a. |
