Image forming apparatus and detachably mountable developer cartridge

An image forming apparatus comprising:

• an apparatus main body;
• a driving-force generating portion disposed in the apparatus main body and generating a driving force;
• a developer cartridge configured to be detachably mounted in the apparatus main body, the developer cartridge comprising:
• a drive member configured to be driven by the driving force and to move in a moving direction when the developer cartridge is mounted in the apparatus main body;
• a moving portion provided on the drive member and configured to move together with the drive member in the moving direction past a predetermined detection position at least a first time;
• and
• an interfering portion disposed downstream of the predetermined detection position with respect to the moving direction, thereby interfering with the moving portion and preventing the moving portion from passing the predetermined detection position a second time;
• a detecting portion that detects passage of the moving portion at the predetermined detection position;
• and
• an information determining portion that determines information on the developer cartridge based on detection results of the detecting portion.