IMAGE FORMING APPARATUS

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of always forming a stable good image by increasing the strength of a main body drive output gear in a driving part for a rotary developing device. SOLUTION: When a stepping motor 9 is driven and one developing unit 11Y is moved with rotation toward a developing position 3, an input gear 23 is engaged with an output gear 22, then, the rotation of a driving motor 26 is transmitted to a driving shaft 15Y through a sleeve gear 21, then, a developing sleeve 12Y is rotated so as to develop a latent image formed on a photoreceptor 2. As for the output gear 22 of the driving device and the input gear 23 engaged with the output gear 22, the tooth tips of them are sharpened so that the engagement is facilitated, and in order to increase the durability, they are respectively hardened by using metal sintering material. The hardness difference between the tooth parts of both gears 22 and 23 is made ≥300 and ≤600 as for Vickers hardness. The hardness specifying area is from the outside diameter surface of each gear 22 and 23 to the gear center or from the outside diameter surface to 2.5 modules. COPYRIGHT: (C)2004,JPO