A developing device includes a developer carrying member for carrying a developer; a circulation path along which the developer is circulated; a carrier supplying portion; a discharge opening, provided in the circulation path, through which a portion of the developer is to be overflowed and discharged; and a feeding member comprising a rotation shaft and a blade portion including a helical portion. An outer diameter of the blade portion formed in a first region including at least a portion opposing the discharge opening is smaller than that in a second region adjacent to the first region with respect to a rotation shaft direction. A smaller average angle formed between the rotation shaft and a developer feeding surface of the blade portion in the first region is smaller than that in the second region.

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 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 includes a developer container that accommodates an electrostatic image developer including toner containing a toner particle and a zinc stearate particle, a ratio (D.sub.T/D.sub.S) of a volume-average particle size (D.sub.T) of the toner particle to a volume-average particle size (D.sub.S) of the zinc stearate particle being about 1.9 or more; a developer carrier that supplies the toner to an image carrier; a supply conveyor that supplies the electrostatic image developer while conveying the electrostatic image developer; a mixing conveyor that conveys the electrostatic image developer while mixing the electrostatic image developer; and a partition disposed between the supply conveyor and the mixing conveyor. The electrostatic image developer is moved from the supply conveyor to the mixing conveyor through a first passage and is moved from the mixing conveyor to the supply conveyor through a second passage.

A replenishment conveyance screw portion is provided in a replenishment conveyance path and configured to convey the replenishment developer in a third direction. The replenishment conveyance screw portion includes a first blade portion, a second blade portion, and, a third blade portion. The third blade portion is continuously formed in a region between a terminal end of the first blade portion with respect to the third direction and a starting end of the second blade portion with respect to the third direction, the region being displaced in a circumferential direction of the replenishment conveyance screw portion from the terminal end of the first blade portion and the starting end of the second blade portion.

A developing device includes a developer bearer and a stirring conveyor. The stirring conveyor includes a first conveying chamber including a conveying member and a second conveying chamber to receive the developer from an end of the first conveying chamber. The conveying member includes a forward winding blade, a reverse winding blade, and a shaft portion on which the forward winding blade and the reverse winding blade are mounted with a space therebetween. A circumferential phase of the conveying member at a start position of the reverse winding blade is different from a circumferential phase of the conveying member at an end position of the forward winding blade. The conveying member is disposed in the first conveying chamber so that the space is opposite a portion at which the second conveying chamber receives the developer from the end of the first conveying chamber.

A developing device includes: a case in which a hollow transporting path is formed; a transporting member configured to transport a developer in the transporting path; a support portion fixed to an end portion of the case by a fastening member to support the transporting member at an end portion of the transporting path; and a cooling unit fixed by being sandwiched between the support portion and the case.

A developing device includes a first transport member and a second transport member that are respectively disposed in a first transport path and a second transport path arranged in a vertical direction and that transport developer so as to circulate the developer between the first transport path and the second transport path; a developing member that is disposed to face the first transport path and that receives the developer from the first transport path; and a third transport member that is disposed in a third transport path through which the developer that has not been used by the developing member is collected and transported to the second transport path. A central shaft of the second transport member is disposed farther in a vertically upward direction than is a central shaft of the third transport member.

A developing device includes a first transport member and a second transport member that are respectively disposed in a first transport path and a second transport path arranged in a vertical direction and that transport developer so as to circulate the developer between the first transport path and the second transport path; a developing member that is disposed to face the first transport path and that receives the developer from the first transport path; and a driving device that operates such that a relative speed ratio between a rotational speed of the developing member and a rotational speed of the second transport member is changeable.