Development gap control unit null of development

摘要

PURPOSE:To prevent a picture from uneven density, deterioration in picture quality, etc. by controlling a developing gap between a photosensitive drum and a developing roll. CONSTITUTION:A displacement detecting means 42 for always detecting the displacement of the photosensitive drum 10 in its radius direction is formed. The means 42 is constituted of a contact 44 which is always in contact with the peripheral end part of the drum 10 e.g. on the upper side of the roll 16 and a distortion gauge 46 of which one end is adhered to the contact 44 and the other end is fixed on a body frame 50 of a copying machine and the contact 44 is energized so as to be always pronght into contact with the surface of the drum 10. An eccentric cam 58 is also rotated by the rotation of a stepping motor 54 to move a housing 14 by the quantity corresponding to a compensating signal outputted from a comparator 60. Consequently, the developing gap between the drum 10 and the roll 16 can be controlled always within an optimum range.