| 摘要 |
PURPOSE:To miniaturize a device by decreasing a drum diameter and to reduce its cost by setting the drum diameter to B4 size and by providing the idling process of a drum while keeping a copying speed unchanged for a copy of A3 size. CONSTITUTION:A photoreceptor drum 8 and a transfer drum 25 are driven by a gear 38 via gears 8a and 25a, and an optical scanning system is driven with a clutch wheel 39 engaged with a clutch lever 45 provided to the drum 44. For a B4 size sheet S1, the optical system is returned in a no-picture area theta1 via a solenoid 65. For A3 size, however, returning it in the theta1 results in that region (theta1-theta2) is not exposed, so displacement of a pin 51 for releasing a clutch lever delays the disengagement time of a lever 45. As a reuslt, the returning process somewhat overlaps with the next process, so succeeding 2nd rotation is idle. In this case, single rotation is made idle corresponding to the number of separated colors. Thus, the drum diameter is decreased to miniaturize the device. |
