Developing device, image forming unit and color image forming apparatus, both having the developing device

摘要

A developing device used in an image forming apparatus has a developing roller at a lower opening of a toner hopper, and the developing roller contacts a photosensitive drum to form a developing portion therebetween. The hopper stores nonmagnetic toner and is provided with a toner stirring member and a toner feed roller being in press-contact with the developing roller in a lower part of the hopper. A doctor blade contacts a circumferential surface of the developing roller on an upstream side of the developing portion in a rotation direction of the drum. A conductive scooping sheet contacts the circumferential surface of the developing roller on a downstream side of the developing portion. A residual toner not used to develop a latent image on the drum and left on the developing roller is passed under the sheet into the hopper with the rotation of the developing roller. A sheet bias voltage ranging from 0V to -250V is applied to the sheet, so that an attaching force of the residual toner to the developing roller is weakened so that the residual toner can be easily removed by the feed roller.