Image forming apparatus with a cam shaft for selectively operating one of a plurality of developing units

摘要

An electrophotographic image forming apparatus is provided that includes a plurality of developing units (4), a cam shaft (120), and a plurality of cams (131) disposed on the cam shaft (120) corresponding to the respective developing units (4). A power transmitting device disposed between the developing units (4) and the cams (131) selectively transmits rotational force from a driving source (10) to the plurality of developing units (4).