A target value for a gap between a developer bearing member supported by a developing frame member and a regulating blade that is fixed to the developing frame member is determined based on input information about a local maximum peak value of magnetic flux density of a predetermined magnetic pole which is located closest to the regulating blade when the regulating blade is fixed to the developing frame member among a plurality of magnetic poles included in a magnet fixedly located inside the developer bearing member and configured to generate a magnetic field for causing a developer to be borne by the developer bearing member.

A developing device includes a developing container, a developing roller, a supplying roller, a first magnet including a first magnetic pole, a second magnet including second to fourth magnetic poles, and a regulating member. A maximum magnetic flux density of the second magnetic pole is larger in absolute value than a maximum magnetic flux density of the third magnetic pole in a normal direction to the supplying roller, and a maximum magnetic flux density of the third magnetic pole is larger in absolute value than a maximum magnetic flux density of the fourth magnetic pole in the normal direction. With respect to a rotational direction of the supplying roller, an angle between maximum magnetic flux density positions of the second and third magnetic poles is smaller than an angle between maximum magnetic flux density positions of the third and fourth magnetic poles by 10 degrees or more.

A developing device includes a developing container, a developing roller, a supplying roller, a first magnet including a first magnetic pole, a second magnet including second to fourth magnetic poles, and a regulating member. A maximum magnetic flux density of the second magnetic pole is larger in absolute value than a maximum magnetic flux density of the third magnetic pole in a normal direction to the supplying roller, and a maximum magnetic flux density of the third magnetic pole is larger in absolute value than a maximum magnetic flux density of the fourth magnetic pole in the normal direction. With respect to a rotational direction of the supplying roller, an angle between maximum magnetic flux density positions of the second and third magnetic poles is smaller than an angle between maximum magnetic flux density positions of the third and fourth magnetic poles by 10 degrees or more.

An image forming apparatus in which when toner remaining on a development roller in an area from a developer nip to a regulating blade disposed upstream of a rotation direction of the development roller during a stoppage of the image forming apparatus passes through the developer nip, a bias is applied so that the toner is drawn to the development roller, and a relative speed difference between the photosensitive drum and the development roller is created so as to be larger than the that during an image forming operation.

A device for removing toner attached to a transfer roller in an image forming apparatus is disclosed. The device includes a bar brush to contact an outer circumferential surface of the transfer roller, where the bar brush extends along a part of a longitudinal length of the transfer roller. The device includes an elongated cleaning member to contact the outer circumferential surface of the transfer roller, where the elongated cleaning member extends along the longitudinal length, entirely, of the transfer roller.

A developing device includes a case, a developer holder, a suction duct and a carrier catcher. The case accommodates a developer containing a toner and a carrier. The developer holder is disposed so as to face an image holder disposed outside the case and supplies the developer to the image holder. The suction duct sucks and collects a scattered toner floating in a space around the developer holder. The carrier catcher is formed in a vertical direction and disposed on a lower surface of a path of the suction duct.

A developing device includes a case, a developer holder, a suction duct and a carrier catcher. The case accommodates a developer containing a toner and a carrier. The developer holder is disposed so as to face an image holder disposed outside the case and supplies the developer to the image holder. The suction duct sucks and collects a scattered toner floating in a space around the developer holder. The carrier catcher is formed in a vertical direction and disposed on a lower surface of a path of the suction duct.

A toner conveyance device includes a housing and a conveyance member. The conveyance member includes a conveyance shaft and a conveyance blade. The conveyance blade includes a first blade part, a second blade part and a third blade part. The first blade part is formed along a predetermined spiral direction. The second blade part is connected to the first blade part on a downstream side of the first blade part in a conveyance direction and extends along the conveyance direction. The third blade part is connected to the second blade part on a downstream side of the second blade part in the conveyance direction and formed along a spiral direction opposite to the spiral direction of the first blade part. A boundary between the first blade part and the second blade part is contained within a range of a toner discharge port in the conveyance direction.

A toner conveyance device includes a housing and a conveyance member. The conveyance member includes a conveyance shaft and a conveyance blade. The conveyance blade includes a first blade part, a second blade part and a third blade part. The first blade part is formed along a predetermined spiral direction. The second blade part is connected to the first blade part on a downstream side of the first blade part in a conveyance direction and extends along the conveyance direction. The third blade part is connected to the second blade part on a downstream side of the second blade part in the conveyance direction and formed along a spiral direction opposite to the spiral direction of the first blade part. A boundary between the first blade part and the second blade part is contained within a range of a toner discharge port in the conveyance direction.

A developer conveyance device includes a downward conveyance path in which a developer falls under gravity, a transverse conveyance path communicating with a lower end of the downward conveyance path and extending in a transverse direction intersecting with the downward conveyance path, a transport screw disposed in the transverse conveyance path, and a floating member. The transport screw is configured to rotate in a predetermined direction to transport the developer in the transverse direction. The floating member is configured to contact the transport screw rotating in the predetermined direction to float in the downward conveyance path.