Patent ID: 8213833

Claim:
An image forming apparatus, comprising: an image bearer configured to bear an image; a charger configured to charge the image bearer; an irradiator configured to irradiate the image bearer to form an electrostatic latent image thereon; an image developer configured to develop the electrostatic latent image with a developer comprising a toner and a carrier to form a toner image on the image bearer; a transferer configured to transfer the toner image onto a receiving material; a fixer configured to fix the toner image on the receiving material; a developer feeder configured to feed a supplemental developer comprising the toner and the carrier into the image developer; and a developer collector configured to collect the developer in the image developer, wherein the developer feeder includes a cylindrical supplemental developer container configured to contain the supplemental developer, the cylindrical supplemental developer container including a spiral developer guide race on the inner circumferential surface thereof; an air feeder; and a sub-hopper configured to store the supplemental developer, wherein the air feeder is located between the supplemental developer container and the sub-hopper and is configured to feed the supplemental developer to the sub-hopper from the supplemental developer container, and wherein the sub-hopper stirs and feeds the supplemental developer to the image developer, and wherein the carrier has a true specific gravity greater than 4g/cm 3 and includes a core material; and a layer coated on the core material, the layer including a binder resin and non-black or a non-color inorganic particulate material.