Patent ID: 7228090

Claim:
An image forming apparatus for forming an image attached with a removable process unit, the image forming apparatus comprising: a first driving force transmitting member for receiving rotary driving force to a process unit; and an intermediate driving force transmitting member for receiving rotary driving force from the first driving force transmitting member, the intermediate driving force transmitting member being arranged between the first driving force transmitting member and a process unit, wherein either the first driving force transmitting member or the intermediate driving force transmitting member has a concave section and the other driving force transmitting member has an end section located in the concave section, where a minimum diameter of the concave section is less than a diameter of the end section which is less than a maximum diameter of the concave section, the end section has three edge sections at its side section, contact members of which hardness is higher than the edge sections of the end section are arranged at portions on an inner surface of the concave section to make contact with the edge sections of the end section, the concave section has contact sections to be in contact with the edge sections at side section, number of the contact sections is three or a multiple of three, the edge sections and the contact sections have different twisting angles, and rotary driving force is transmitted from the intermediate driving force transmitting member to a process unit.