Developing agent circulation system and image forming apparatus using same

A development agent circulation unit, comprising:

• a development unit configured to develop a latent image on an image carrier using a developing agent;
• an agitation unit, disposed separately from the development unit, configured to agitate developing agent recovered from the development unit;
• and
• a rotary feeder configured to receive the developing agent from the agitation unit and to discharge the developing agent in predetermined discrete amounts, a gas stream under a given pressure transporting discharged developing agent from the rotary feeder to the development unit,
• the rotary feeder including a rotor and a stator and configured to have a clearance “t” between an external diameter of the rotor and an internal diameter of the stator, the rotor and the stator regulating gas leakage from the gas stream through the clearance “t” by sealing with developing agent interposed between the rotor and the stator,
• the clearance “t” satisfying a relation “t<D” where D denotes a developing agent particle diameter,
• toner particle diameter dt of a toner particle of the developing agent, and a carrier particle diameter dc of a carrier particle of the developing agent satisfying a relation D=dc+2dt.

An image forming apparatus, comprising:

• a development unit configured to develop a latent image on an image carrier using a developing agent;
• an agitation unit, disposed separately from the development unit, configured to agitate developing agent recovered from the development unit;
• and
• a rotary feeder configured to receive the developing agent from the agitation unit and to discharge the developing agent in predetermined discrete amounts, a gas stream under a given pressure transporting discharged developing agent from the rotary feeder to the development unit,
• the rotary feeder including a rotor and a stator and configured to have a clearance “t” between an external diameter of the rotor and an internal diameter of the stator, the rotor and the stator regulating gas leakage from the gas stream through the clearance “t” by sealing with developing agent interposed between the rotor and the stator,
• the clearance “t” satisfying a relation “t<2D” where D denotes a developing agent particle diameter,
• a toner particle diameter dt of a toner particle of the developing agent and a carrier particle diameter dc of the developing agent satisfying a relation D=dc+2dt.