Patent attributes
The present invention provides a developing apparatus and an image forming apparatus which are capable of outputting stable images with no surface staining and toner scattering even when an image forming process is repeated over a long time period, or even when image formation is performed after special use conditions in which little toner is consumed have continued over a long time period. An area in which a relationship of 0.6<Vlocal/Vaverage<0.9, where Vaverage is an average flow speed of a developer during one circuit of a developing container and Vlocal is a local flow speed of the developer as it moves through the developing container, is satisfied exists in the developing container, and a negatively charged toner maintains a relationship of μ0 (t)≧μ1 (t) between an electrostatic charge distribution peak position μ0 (t) of toner in an external force imparting developer and an electrostatic charge distribution peak position μ1 (t) of a replenishing toner, this relationship being measured in a deteriorated toner testing method.
