An imaging system comprises a stirring-conveyance member to supply developer to a developing roller. The stirring-conveyance member includes a spiral structure to convey the developer and a reverse spiral structure disposed downstream the spiral structure in a conveying direction of the developer. The reverse spiral structure has a maximum outer diameter at an upstream end in the conveying direction and a minimum outer diameter at a downstream end in the conveying direction. The minimum outer diameter is approximately ⅗ or less, of the maximum outer diameter.

An image forming apparatus includes a development device, a toner storage part, a drive unit, a control unit, and an image carrying member. The development device includes a development casing, a developer carrying member, a first stirring transport member, a second stirring transport member, a discharge impeller, and a reverse transport impeller. The development casing includes a first partition wall, a communication part, a developer replenishment port, and a developer discharge part. The first stirring transport member includes a first rotation shaft and a first transport impeller. The second stirring transport member includes a second rotation shaft and a second transport impeller. The control unit can perform a developer discharge mode, in which the first rotation shaft and the second rotation shaft are rotated reversely during a non image formation period, so that the developer around the reverse transport impeller is discharged through the developer discharge part.

A developing device includes: a first transport member and a second transport member that are disposed in a first transport path and a second transport path provided at an upper side and a lower side in a gravitational direction and that transport a developer. The developing device also includes an ejecting path that is provided in the first transport path disposed at the upper side in the gravitational direction and that ejects an excess developer. The developing device includes a reverse helical section that is disposed in front of a support that supports the second transport member. The reverse helical section helically extends in a reverse direction relative to a helical section provided for circulating the developer, the developer being transported to the ejecting path by the reverse helical section.

A developing apparatus including: a first chamber including a first conveyance member conveying developer in a first direction; a second chamber including a second conveyance member having a conveyance portion conveying the developer in a second direction opposite to the first direction and a return conveyance portion provided downstream of the conveyance portion in the second direction to convey the developer in the first direction; a first partition wall provided between the first chamber and the second chamber to form a first communication portion and a second communication portion to form a circulation route; and a bearing member configured to rotatably support the second conveyance member and including: a discharge port provided downstream of the return conveyance portion; and a second partition wall extending from the bearing member in the first direction to cover a portion of the return conveyance portion confronting the first communication portion.

A developing device includes a developing container, a detecting unit including a base portion and a detecting portion, a feeding path, a feeding screw, and a recessed portion provided on a side wall of the developing container. The recessed portion is disposed so as to project toward the feeding screw in the feeding path. The side wall includes a projected region projected toward the screw portion in the feeding path by the recessed portion and a region other than the projected region. The feeding screw includes a first screw portion opposing the projected region and a second screw portion opposing the region other than the projected region. The first screw portion includes a rotation shaft which includes a portion having a shaft diameter smaller than a shaft diameter of a rotation shaft of the second screw portion.

A conveyance mechanism which includes a rotation shaft extending in a direction along a first direction connecting first and second discharge ports that is rotatable with a rotation axis extending in the first direction. Wherein, a first rotation conveyance unit is disposed on the rotation shaft, and is rotatable together with the rotation shaft, conveys developer toward the first discharge port, and a second rotation conveyance unit is disposed on the rotation shaft, and is rotatable together with the rotation shaft, conveys developer toward the second discharge port. The second rotation conveyance unit is configured to provide a larger amount of conveyance than the first rotation conveyance unit.

A developing device includes a developer carrying member for carrying and feeding a developer, first and second chambers for circulating the developer, and a partition wall. A first feeding member feeds the developer in the first chamber in a first feeding direction, and a second feeding member feeds the developer in the second chamber. The second feeding member includes a shaft, a first helical portion for feeding the developer in a second feeding direction, and a second helical portion for feeding the developer in the first feeding direction. The second helical portion is provided on the shaft and provided downstream of the first helical portion via a region where no helical portion is provided. A rib is provided on a first inner surface of the second chamber, with the rib disposed opposite the region where no helical portion is provided and extending upwardly in a vertical direction.

A developing apparatus capable of suppressing an excessive discharge of developer from a developer discharge hole is disclosed. A first opening part through which developer is carried from a first case part to a second case part, and a developer discharge hole through which the developer is discharged are provided to the first case part. A first carrying member includes a counter blade between the first opening part and the developer discharge hole. The counter blade carries the developer in an opposite direction to a carrying direction of a first carrying blade of the first carrying member. A gap is prepared between an upper part of the counter blade and the first case part. A cross-sectional area of a discharge path for the developer from the counter blade to the developer discharge hole changes according to a progress of the developer along the discharge path.

An image forming apparatus includes a development device, a toner storage part, a drive unit, a control unit, and an image carrying member. The development device includes a development casing, a developer carrying member, a first stirring transport member, a second stirring transport member, a discharge impeller, and a reverse transport impeller. The development casing includes a first partition wall, a communication part, a developer replenishment port, and a developer discharge part. The first stirring transport member includes a first rotation shaft and a first transport impeller. The second stirring transport member includes a second rotation shaft and a second transport impeller. The control unit can perform a developer discharge mode, in which the first rotation shaft and the second rotation shaft are rotated reversely during a non image formation period, so that the developer around the reverse transport impeller is discharged through the developer discharge part.

A developing device has a developer container, first and second stirring members, and a developer carrying member. The developer container has a plurality of transport chambers including first and second transport chambers, a communication portion through which the first and second transport chambers mutually communicate in opposite end parts thereof in their longitudinal direction, a developer supply port, and a developer discharge port arranged in a downstream-side end part of the second transport chamber. The second stirring member has a second transport blade, a regulating portion formed on the downstream side of the second transport blade, a discharge blade formed on the downstream side of the regulating portion and discharging developer through the developer discharge port, and a disk formed at a position facing the downstream-side communication portion on the upstream side of the regulating portion and radially protruding over the entire circumference of a rotary shaft.