Patent ID: 7469117

Claim:
An image forming apparatus comprising: a rotating member provided with a plurality of attach/detach sections, to and from each of which a developing unit having an element that is capable of performing communication can be attached and detached, where the element has an IC chip and a developing-unit-side antenna; and an antenna for wirelessly communicating, at a plurality of rotation angles of said rotating member, with the elements of the developing units attached respectively to said attach/detach sections; wherein, when R is an outermost diameter of a path traced by said developing units and r is an outermost diameter of a path traced by said elements when said rotating member is rotated with said developing units attached to said attach/detach sections, then a relationship R>r is satisfied, wherein each of said elements is provided on a lateral surface of said developing unit, said lateral surface intersecting with an axial direction of rotation of said rotating member when said developing unit is attached to said attach/detach section, wherein, when said developing unit is attached to said attach/detach section, said antenna is positioned more outward than said element in the axial direction of rotation of said rotating member, wherein, when R is an outermost diameter of a path traced by said developing units and r is an outermost diameter of a path traced by said elements when said rotating member is rotated with said developing units attached to said attach/detach sections, then a relationship R/2>r is satisfied, and wherein, when L is a distance from a center of said rotating member to a position of the outermost side of said antenna in a radial direction of rotation of said rotating member, then a relationship R/2>L is satisfied.