Provided is a developing device having 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. The transport members transport a developer so as to cause the developer to circulate between the first transport path and the second transport path. A partition wall that separates the first transport path and the second transport path from each other and has an opening including an open-close member that opens and closes the opening.

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 device body in which the first transport path and the second transport path are formed; and a developer discharging structure that discharges excess developer discharged from the first transport path to outside through the second transport path or through a space between an end portion of the second transport path and the developing device body.

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 development-region passing body that passes a development region while holding a developer; a first transport path in which the developer to be supplied to the development-region passing body is transported at least in a first transport direction; a second transport path in which the developer to be sent to the first transport path is transported at least in a second transport direction; a first connection portion through which a portion of the first transport path positioned short of a first-transport-direction-downstream end of the first transport path and a portion of the second transport path positioned short of a second transport-direction-upstream end of the second transport path are connected to one another; and a first transport member having a rotating shaft on which a helical first forward-transport blade is provided, the helical first forward-transport blade rotating to forward-transport the developer in the first transport direction in the first transport path. The first transport member has a helical reverse-transport blade that reverse-transports the developer in a reverse direction reverse to the first transport direction, the reverse-transport blade is provided on at least a portion of part of the rotating shaft adjacent to the first connection portion, and a reverse-direction-downstream end of the reverse-transport blade reaches at least a first-transport-direction-upstream end of the first connection portion.

A developer accommodating device includes a frame extending in a longitudinal direction thereof and an opening portion provided on the frame. The frame includes a guide portion to mount the developer accommodating device on a developing unit along a mounting direction crossing the longitudinal direction, a first portion including first and second chambers arranged in parallel in a first direction crossing the longitudinal direction, and a second portion communicating with the first and second chambers with respect to the longitudinal direction and a volume thereof is larger than that of the first portion. The first chamber, in which the opening portion is formed, does not directly communicate with the second chamber with respect to the first direction but communicates with the second chamber via the second portion. As seen in the longitudinal direction, a cross sectional area of the second chamber is equal to or larger than that of the first chamber.

An example method of operating an image forming apparatus includes measuring a toner concentration supplied to a developing apparatus and increasing a driving speed of the developing apparatus based on the toner concentration not reaching a target toner concentration. The toner concentration is measured in a state where the driving speed of the developing apparatus is increased, and, based on the toner concentration not reaching the target toner concentration based on the driving speed of the developing apparatus being increased, an operating state of the image forming apparatus is determined based on a remaining amount of toner.

A powder container case includes a first member, a second member, a main joint, and an additional joint. The first member and the second member are joined to form an edge portion of a case opening. The main joint is disposed between the first member and the second member, and has an end portion at the edge portion of the case opening. The additional joint is disposed adjacent to the end portion of the main joint.

A developing apparatus includes: a developer tank that contains a developer; and conveyance members that convey the developer while agitating the developer. The conveyance members include a first screw and a second screw. The developer tank includes: a first storage chamber in which the first screw is provided; a second storage chamber in which the second screw is provided; a partition that separates the first storage chamber from the second storage chamber; and a flow area that opens the partition to flow the developer between the first storage chamber and the second storage chamber; a developer detection sensor that detects an amount of the developer thereof; a discharge port that discharges the developer; and a discharge guide that guides the developer to the discharge port. The developer detection sensor detects that the developer tank is full according to the amount of the developer.

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. The developing device includes a developing device body in which the first transport path and the second transport path are formed. The developing device also includes a developer discharging structure that discharges excess developer discharged from the first transport path to outside through the second transport path or through a space between an end portion of the second transport path and the developing device body.

A developing device including a first transport path in which the developer to be supplied to the development-region passing body is transported at least in a first transport direction; a second transport path in which the developer to be sent to the first transport path is transported at least in a second transport direction; and a first connection portion through which a portion of the first transport path positioned short of a first-transport-direction-downstream end of the first transport path and a portion of the second transport path positioned short of a second transport-direction-upstream end of the second transport path are connected to one another. A first transport member in the first transport path has a helical reverse-transport blade that reverse-transports the developer in a reverse direction reverse to the first transport provided adjacent to the first connection portion.