Developing unit

摘要

A developing unit of the present invention includes a case which accommodates toner containing pigment, a developing roller, a supply roller having chamfered ends and formed of an elastic member arranged to be pressed against a surface of the developing roller in such a manner as to supply toner to the surface of the developing roller. Moreover, the ratio or open cells in the elastic supply roller is made to be 30% or higher and depth of engagement of the supply roller to the developing roller is made to be 0.4 mm or smaller. Also a first sealing member is disposed on the side ends of the developing roller and supply roller so as to prevent leakage to the outside portion of the case. The side surfaces of the developing roller have a surface roughness of 0.5 mu m or smaller in Rmax. Further, a second sealing member in the form of a film is pressed against a lower surface of the developing roller in order to prevent leakage of toner, wherein a quantity 6 of displacement of the sealing member due to its abutment against the developing roller satisfies 0.1 mm < delta < 0.8 mm, and the thickness t of the second sealing member satisfies 50 mu m < t < 500 mu m. <IMAGE>