Patent ID: 8649708
Filing Date: 2014-02-11
Classification: G03G

Abstract:
1. A developing apparatus comprising: a developer container that is partitioned into a plurality of convey chambers which include a first convey chamber and a second convey chamber having a U shape in section which are disposed in parallel with each other, and that stores a two-component developer which includes a carrier and a toner; a first stir member that stirs and conveys the developer in the first convey chamber in a rotational axis direction; a second stir member that is composed of a rotational shaft and a spiral blade formed on an outer circumference of the rotational shaft, stirs and conveys the developer in the second convey chamber in a direction opposite to the first stir member; a developer carry body that is rotatably supported in the developer container and carries on a surface thereof the developer in the second convey chamber; a communication portion that connects the first convey chamber and the second convey chamber to each other at both end portions in a longitudinal direction thereof; a developer supply opening that is arranged to supply the developer into the developer container; a developer discharge opening which is formed at an end portion in a downstream side of the second convey chamber and from which a surplus developer is discharged; a restriction portion that is disposed in a downstream of the communication portion with respect to the second stir member to oppose the developer discharge opening in a developer convey direction, and places a restriction on movement of the developer to the developer discharge opening; a sensor disposition portion that is a portion which is formed in an upstream of the second convey chamber with respect to the restriction portion in the developer convey direction, and where a toner concentration sensor for detecting a toner concentration in the developer is disposed, wherein across a predetermined width in the developer convey direction including a detection surface of the toner concentration sensor, a distance between curved surface portions on both sides of a U-shaped inner wall surface and the second stir member is wider than another portion of the second stir chamber, wherein in the sensor disposition position, a distance between a bottom surface and the second stir member is equal to a distance at another portion of the second convey chamber, and a radius of curvature of the curved surface portion is smaller than a radius of curvature of another portion of the second convey chamber.