Patent ID: 9733592
Date: 2017-08-15
CPC Classifications: G03G

Claim:
1. A developing device configured to develop an electrostatic latent image formed on an image supporting member with a developer containing toner and carrier, to be resupplied with a developer in proportion to toner consumption and to discharge a used developer, the developing device comprising: a first circulation tank configured to discharge a part of the developer through an outlet while conveying the developer; a second circulation tank divided from the first circulation tank by a partition wall, the second circulation tank configured to convey the developer conveyed thereto from the first circulation tank through a first opening in the partition wall and the developer resupplied thereto through a resupply port to the first circulation tank through a second opening in the partition wall such that the first circulation tank and the second circulation tank form a circulation pathway; a first screw provided in the first circulation tank so as to convey the developer; and a second screw provided in the second circulation tank so as to convey the developer, wherein: the first screw has a first vane in a first portion upstream from the first opening with respect to a conveying direction of the first screw, the first vane exerting a force in the conveying direction on the developer; the first screw has no vanes in a second portion near the first opening; the first screw has a second vane in a third portion adjacently downstream from the second portion with respect to the conveying direction, the second vane exerting a force in a direction opposite to the conveying direction on the developer; the outlet is located at a point of the first circulation tank, downstream from the second vane with respect to the conveying direction; a portion of the first circulation tank downstream from the second vane with respect to the conveying direction is not connected to the second circulation tank in a direction perpendicular to the conveying direction; the first opening extends from a point overlapping with a downstream end of the first vane with respect to the conveying direction to a downstream end of the second vane with respect to the conveying direction, such that all of the second vane overlaps with the first opening; and the first screw receives the developer which is returned from the second circulation tank to the first circulation tank through the second portion, and conveys the received developer toward the outlet.