Patent ID: 7477863
Filing Date: 2009-01-13
Classification: G03G

Abstract:
1. A color image forming apparatus comprising: a first image forming portion having a first charger unit which charges a first image bearing member, a first exposure unit which forms a first electrostatic latent image on the first image bearing member, and a first developing unit which houses first toner and forms the first toner image corresponding to the first electrostatic latent image on the first image bearing member while collecting residual toner remaining on the first image bearing member; a second image forming portion having a second charger unit which charges a second image bearing member, a second exposure unit which forms a second electrostatic latent image on the second image bearing member, and a second developing unit which houses second toner and forms the second toner image corresponding to the second electrostatic latent image on the second image bearing member while collecting residual toner remaining on the second image bearing member; a third image forming portion having a third charger unit which charges a third image bearing member, a third exposure unit which forms a third electrostatic latent image on the third image bearing member, and a third developing unit which houses third toner and forms the third toner image corresponding to the third electrostatic latent image on the third image bearing member while collecting residual toner remaining on the third image bearing member; a fourth image forming portion having a fourth charger unit which charges a fourth image bearing member, a fourth exposure unit which forms a fourth electrostatic latent image on the fourth image bearing member, and a fourth developing unit which houses fourth toner and forms the fourth toner image corresponding to the fourth electrostatic latent image on the fourth image bearing member while collecting residual toner remaining on the fourth image bearing member; an intermediate transfer member which carries the first, second, third, and fourth color toner images thereon; a first transfer member which transfers the first, second, third, and fourth color toner images in order on the intermediate transfer member, the first transfer member comprising individual transfer members which respectively transfer the first, second, third, and fourth color toner images in order on the intermediate transfer member; a second transfer member which transfers the first, second, third, and fourth color toner images on the intermediate transfer member onto the image recording medium; and a control portion which, when transfer of the toner image from the intermediate transfer member to the image recording medium is completed, controls to return the residual toner remaining on the intermediate transfer member to the first image bearing member, wherein the first image forming portion is set at most upstream along the moving direction of the intermediate transfer member and the second, third, and fourth image forming portions are downstream of the first image forming portion along the moving direction of the intermediate transfer member, the first image forming portion houses the black toner as the first toner in a predetermined quantity which is larger than the quantity of the second toner in the second developing unit, the third toner in the third developing unit, and the fourth toner in the fourth developing unit, and the first developing unit ejects at least a part of the black toner in the first developing unit as waste toner.