Patent ID: 9733594
Date: 2017-08-15
CPC Classifications: G03G

Claim:
1. A developing device comprising: a developing container configured to accommodate a developer containing toner and carrier particles; a cylindrical developing sleeve rotatable while carrying the developer in said developing container; a magnet provided in said developing sleeve and configured to generate a magnetic force for holding the developer; and a plurality of grooves provided at a developer carrying surface of said developing sleeve and formed along a direction crossing a circumferential direction of said developing sleeve, wherein in a cross-section perpendicular to a rotational axis of said developing sleeve, each of said grooves is formed by a flat bottom portion contacting the carrier particle and a pair of side surface portions provided in both sides of said flat bottom portion with respect to the circumferential direction of said developing sleeve and satisfies the following relationships: where r is a volume-average particle size of the carrier particles, w is a length of the flat bottom portion measured in the cross-section perpendicular to the rotational axis of said developing sleeve, L is a width between said side surface portions at the surface of said developing sleeve in the cross-section perpendicular to the rotational axis of said developing sleeve, and s is a depth of each of said grooves.