Image forming apparatus having multiple driving force transmitting drive trains

An image forming apparatus comprising:

• a first image forming portion for forming an image on a photosensitive member with a developer by a developing roller;
• a second image forming portion for forming an image on a photosensitive member with a developer, different in color from the developer in the first image forming portion, by a developing roller;
• a first gear train for transmitting a driving force to at least one of said developing roller and said photosensitive member which are provided in said first image forming portion;
• a second gear train for transmitting a driving force to at least one of said developing roller and said photosensitive member which are provided in said second image forming portion;
• a first developing roller moving mechanism including (i) a first developing roller moving member for moving the developing roller of said first image forming portion between a first contacting position contacting an associated photosensitive member and a first separating position separated from said associated photosensitive member and (ii) first driving force switching means for switching between a first transmission state in which a driving force is transmitted to said first developing roller moving member to move said developing roller of said first image forming portion and a first disconnected state in which the transmission of the driving force is disconnected;
• and
• a second developing roller moving mechanism including (i) a second developing roller moving member for moving said developing roller of said second image forming portion between a second contacting position contacting an associated photosensitive member and a second separating position separated from said associated photosensitive member and (ii) second driving force switching means for switching between a second transmission state in which a driving force is transmitted to said second developing roller moving member to move said developing roller of said second image forming portion and a second disconnected state in which the transmission of the driving force is disconnected,
• wherein the driving force transmitted to said first developing roller moving member in the first transmission state is supplied from said first gear train, and the driving force transmitted to said second developing roller moving member in the second transmission state is supplied from said second gear train.