Patent ID: 7526224

Claim:
A developing device including: a casing formed with an elongated opening and having a wall portion along one end edge extending in a longitudinal direction of the opening; a developing agent carrier member for carrying a developing agent on a circumferential surface, disposed so as to expose one portion of the circumferential surface from the opening and provided rotatably about an axis extending in the longitudinal direction; a layer-thickness regulating member for restricting a layer thickness of the developing agent carried on the circumferential surface, formed in a thin plate shape extending in the longitudinal direction and having one distal end portion on one end side in a direction orthogonal to the longitudinal direction for pressing the circumferential surface of the developing agent carrier member; a holding member for holding a proximal end portion on the opposite side of the distal end portion of the layer-thickness regulating member, disposed in an opposed relation to the wall portion; a first seal member for sealing between the wall portion and the holding member, which extends in the longitudinal direction, each of whose both end portions in the longitudinal direction is sandwiched between the wall portion and the holding member and between the wall portion and the layer-thickness regulating member, and in which a central portion between the both end portions is sandwiched at least between the wall portion and the holding member; an oil filler for filling the gap, disposed in a gap formed among the layer-thickness regulating member, the holding member and each of the both end portions of the first seal member; and a second seal member provided partially in a region inward in the longitudinal direction with respect to the oil filler on a opposed surface of the layer-thickness regulating member to the first seal member with at least a portion thereof disposed in a state of being sandwiched between the layer-thickness regulating member and the first seal member.