Patent ID: 8620176

Claim:
A developing device comprising: a developing roller including a roller body portion configured to carry a non-magnetic monocomponent developer on an outer peripheral surface thereof; a casing including: a developer storage unit having a boxed shape and configured to store the developer therein; a roller supporting unit which protrudes in a direction perpendicular to a central axis direction of the developing roller from the developer storage unit and rotatably supports both end portions of the developing roller outside the roller body portion in the central axis direction; and an opening which extends in a longitudinal direction along the central axis direction so as to provide communication between the developer storage unit and the roller supporting unit; and a seal member that is mounted on the casing outside the opening in the central axis direction and faces an end portion of the outer peripheral surface of the roller body portion in the central axis direction, the seal member configured to rub against the end portion of the outer peripheral surface in the central axis direction when the seal member is elastically deformed by being pressed in a radial direction of the roller body portion by the roller body portion, wherein the seal member includes a protruding portion that protrudes along a movement direction of the developing roller at a downstream end portion of the seal member in the movement direction, wherein the casing includes: an outer projection that is provided along the moving direction of the developing roller so as to abut an outer end portion of the seal member in the central axis direction, the outer projection protruding in a position inside of the roller supporting unit in the central axis direction; and an inner projection that is provided along the outer projection so as to abut an inner end portion of the seal member in the central axis direction, the inner projection protruding in a position which is outside the opening in the central axis direction, wherein the protruding portion of the seal member is provided closer to the outer projection than the inner projection, and wherein the inner projection includes: a protruding-side abutting portion that abuts an inner end portion of the protruding portion in the central axis direction; an inner abutting portion that is provided inside the protruding-side abutting portion in the central axis direction, the inner abutting portion provided on an upstream side in the movement direction than the protruding-side abutting portion; and a terminating abutting portion that is provided along the central axis direction so as to connect the protruding-side abutting portion and the inner abutting portion, the terminating abutting portion abutting a downstream end portion, in the movement direction, of a portion of the seal member in which the protruding portion is not provided.