A developing device includes a developer container, a developer carrier, and first and second members for stirring/conveying. The developer container includes a first partition wall between first and second chambers, a communication portion through which those chambers communicate at opposite ends of the first partition wall, a developer supply port, and a developer discharge portion. The first member stirs and conveys developer in the first chamber in a first direction. The second member stirs and conveys developer in the second chamber in a second direction and includes a regulating portion and a discharging blade. The developer container includes a second partition wall between the first chamber and the regulating portion. The gap from the upper end of the second partition wall to the inner surface of the developer container is larger than the gap thereto from the upper ends of a first helical blade and the regulating portion.

An example operation method of an image forming apparatus includes obtaining, through a sensor in the image forming apparatus, toner data corresponding to an amount of toner remaining in a developing apparatus, obtaining, based on the toner data in every predetermined period, a linear prediction model predicting the amount of toner remaining in the developing apparatus according to a time at which the toner is supplied to the developing apparatus, predicting, based on the linear prediction model, an expected supply time required for the amount of toner remaining in the developing apparatus to reach a target level, and controlling an operation of supplying the toner to the developing apparatus according to a result of comparing the expected supply time with a predetermined reference supply time.

A toner cartridge includes a hollow body having an inner space in which toner is received and a toner discharge portion through which the toner is discharged, a plunger accommodated in the inner space to be movable in a longitudinal direction along the inner space and configured to push the toner through the toner discharge portion to outside of the body, a first hook provided on the body, and a second hook. The second hook has a shape complementary to a shape of the first hook, is provided on the plunger, and is elastically coupled to the first hook when the plunger reaches a bottom dead position.

An image forming apparatus includes a toner container, a toner conveyance portion, a container attachment portion, and a biasing mechanism. The toner container has a toner outflow port at a tip portion thereof. The toner conveyance portion is provided in the toner container and conveys toner in the toner container toward the toner outflow port. The container attachment portion supports the toner container. The biasing mechanism applies a biasing force to change the toner container from a horizontal attitude to an inclined attitude in accordance with a toner conveyance operation of the toner conveyance portion. When the toner container is in the inclined attitude, the toner outflow port faces diagonally downward.

A toner cartridge comprises a toner container which contains toner, a driving member which rotationally drives a conveying member, an agitating member which agitates a toner in the toner container while being rotated, a driven member which rotates in association with the driving member which is for rotationally driving the agitating member, and a rotational body which rotates according to rotation of the driven member, has a plurality of slits in rotational circumference for identifying a type of the toner cartridge, and has 1/K or more of the slits when a ratio of a rotational speed R1 (rad/s) of the driving member and a rotational speed R2 (rad/s) of the driven member is K=R2/R1.

In one embodiment, a toner container comprises a toner container body in which toner is stored, a cover portion configured to cover the toner container body, and a projection. The projection is provided in the vicinity of a rear end portion in a longitudinal direction of the cover portion or a longitudinal direction of the toner container body, and projecting toward a rear side of the toner container.

A powder container includes a container body, a spiral projection, and a convex portion. The container body stores powder and is rotatable around an axis of the container body. The spiral projection is inside the container body. The convex portion includes a flat surface portion and protrudes inward from an inner wall surface of the container body. A virtual plane including the flat surface portion passes through the axis.

A first contact portion provided on a first shutter member that opens and closes a receiving port for receiving a developer from a cartridge and a second contact portion provided on the cartridge are configured to contact each other in an attachment and detachment direction of the cartridge so that the first shutter member is in a position at which the receiving port is opened. The first shutter member is urged by a first urging member so that a contacting state between the first contact portion and the second contact portion is maintained until a second shutter member that opens and closes a supplying port of the cartridge closes the supplying port when the cartridge is discharged from the apparatus body.

An example method of operating an image forming apparatus includes measuring a toner concentration supplied to a developing apparatus through a toner concentration sensor provided in the developing apparatus as a supply mode for supplying toner to the developing apparatus in the image forming apparatus is executed, increasing a driving speed of the developing apparatus when it is determined that the toner concentration has not reached a target toner concentration, measuring the toner concentration in the developing apparatus through the toner concentration sensor as the supply mode is executed in a state where the driving speed of the developing apparatus is increased, and determining an operating state of the image forming apparatus based on a remaining amount of toner when it is determined that the toner concentration has not reached the target toner concentration in the state where the driving speed of the developing apparatus is increased.

A cartridge mountable in an apparatus main body of an image forming apparatus, the cartridge includes a development roller, a frame member including a development chamber, a developer containing chamber, and a first opening portion, the developer containing chamber including an inner wall and a second opening portion, a stirring member including a stirring shaft and a sheet, and a conveyance member driven in such a manner that the developer is replenished into the developer containing chamber through the second opening portion, wherein the sheet is rotated in contact with the inner wall in such a manner that, after the sheet is elastically deformed by contact with a portion of the inner wall, at least a part of the elastic deformation is restored, and wherein the conveyance member is being driven at a timing when the sheet passes through the front side.