A developing device includes a developer bearer, a developer regulator, a developer supply passage, and a stopper. The developer bearer includes a magnetic field generator and is configured to bear a developer containing toner and magnetic carriers and conveys the developer to a developing area by rotation. A stopper is configured to prevent the developer blocked by the developer regulator from moving to a surface of the developer bearer, while securing a supply path for passing the developer in the developer supply passage to the developer bearer between the stopper and an upper end of a side wall of the developer supply passage that is opposite to the developing bearer. A width of the supply path in a direction perpendicular to a direction of a rotation axis of the developer bearer is in a range of 7% or more and less than 10% of a circumference of an outer diameter of the developing bearer.

A toner cartridge includes a first casing, a second casing, an auger screw, and a shutter. The first casing has a first internal space. The second casing has: a second internal space smaller than the first internal space; a first opening allowing toner in the second internal space to be discharged; and a second opening allowing air in the second internal space to be sent to an outside. The auger screw is rotatable about a first rotation axis and configured to convey toner in the first internal space to the second internal space. The shutter is rotatable relative to the second casing about a second rotation axis between a first position in which the shutter closes the first opening and a second position in which the shutter opens the first opening. In a state where the shutter is at the second position, the shutter does not close the second opening.

A powder transport device includes: a rotation shaft rotatably supported in a container chamber that contains powder and plural blade members detachably attached to the rotation shaft, the blade members including spiral blades configured to transport the powder in an axial direction of the rotation shaft in response to the rotation shaft rotating.

A powder container includes a collection port to receive and collect powder from outside; a driven unit that is disposed on one end side in a width direction of the powder container and to which drive is transmitted from outside; a first rotary shaft that rotates by the drive transmitted to the driven unit; a first gear disposed on other end side of the powder container and rotating with the first rotary shaft; a second rotary shaft that is disposed on the other end side, that includes a second gear to which drive is transmitted from the first gear, and that rotates with the second gear; and a driving gear that is disposed on the second rotary shaft in a position between the second gear and a central portion in the width direction of the powder container, and that rotates with the second rotary shaft to transmit drive to outside.

An attachment and detachment structure attaches and detaches a toner container to and from an attachment unit. The toner container includes a container main body, a rotational member and a power transmission body. The rotational member rotates around an axis to agitate the toner contained in the container main body. The power transmission body is provided outside the container main body and rotates around an axis to transmit a rotational force to the rotational member. The attachment unit includes a contact body which comes into contact with the power transmission body on attachment process and detachment process of the toner container to and from the attachment unit and rotates the power transmission body. The power transmission body comes into contact with the contact body on the attachment process of the toner container to the attachment unit, and is rotated around the axis to rotate the rotational member around the axis.

A developing device includes an agitating transport device, a density detecting device, and an attracting device. The agitating transport device has a transport path and transports developer including a magnetic carrier while agitating the developer. The density detecting device detects density of the developer in the transport path of the agitating transport device. The attracting device is provided in the agitating transport device and has magnetic poles of one and another polarities exposed to the transport path facing the density detecting device so as to attract the developer by a magnetic force.

A conveyance screw includes a shaft member, a first blade and a second blade each formed helically on a circumference of the shaft member. The first blade includes a first wide portion and a first narrow portion both located within an area in the axial direction where both of the first blade and the second blade are provided. The first wide portion is protruded radially outward from the shaft member to a first outer diameter. The first narrow portion is formed continuously with the first wide portion in a winding direction of the first blade around the shaft member, and is protruded radially outward from the shaft member to a second outer diameter that is smaller than the first outer diameter.

A feeding screw for feeding a developer includes a rotation shaft, a first blade portion helically formed on an outer peripheral surface of the rotation shaft to feed the developer in one direction, a second blade portion helically formed on the outer peripheral surface to feed the developer in the one direction, and a third blade portion helically formed on the outer peripheral surface to feed the developer in the one direction. The first blade portion and the second blade portion overlap with each other with respect to a rotational axis direction of the feeding screw, the second blade portion and the third blade portion do not overlap with each other with respect to the rotational axis direction, and the third blade portion and the first blade portion overlap with each other with respect to the rotational axis direction.

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.

According to a first aspect of the present invention, a developing apparatus includes a developer container, a conveyance screw, and an inductance sensor. The conveyance screw further comprises a rib, protruding in a radial direction from the shaft portion, provided at a position opposed to the inductance sensor, and a second blade portion provided continuously to an upstream end portion of the rib with respect to the conveyance direction and configured to convey the developer to the conveyance direction by rotation. The second blade portion is formed to extend not more than one-third of a turn from the upstream end portion of the rib downstream in a direction of rotation of the conveyance screw when viewed in an axial direction of the conveyance screw.