With respect to a rotational direction of a rotatable developing member of a developing device, an opposing position where a regulating portion of the developing device is opposed to an outer peripheral surface of the rotatable developing member is between a first maximum position and a position where a magnetic flux density of a regulating pole in a tangential direction relative to the outer peripheral surface of the rotatable developing member is zero. With respect to the rotational direction of the rotatable developing member, the position where the magnetic flux density of the regulating pole in the tangential direction relative to the outer peripheral surface of the rotatable developing member is zero is within a range of ±2° of a midpoint between the first maximum position and a second maximum position or is downstream of the range.

An image forming apparatus includes an image bearing member, a developing apparatus, a driving device, an airflow space portion, a duct, and, a drawing fan. A driving-force transmission member, the driving device and the airflow space portion are disposed on a side on which a developer container faces the image bearing member. The driving-force transmission member, the driving device, the duct and the drawing fan are disposed on one end side of a developing rotary member in a rotation-axis direction of the developing rotary member. The duct is disposed underneath the developer container, formed from the side on which the developer container faces the image bearing member to a side opposite to the side on which the developer container faces the image bearing member. The drawing fan is disposed on the side opposite to the side on which the developer container faces the image bearing member.

A developing device includes a developing rotator configured to rotate through a developing region while carrying a magnetic developer, a supply transport member configured to rotate to transport the developer to be supplied to the developing rotator, a non-magnetic movement assist member arranged between the developing rotator and the supply transport member, and having a slope that receives the developer from the supply transport member and moves the developer to the developing rotator, a first adjusting member having a facing surface that faces, with distances, the slope of the movement assist member and a surface of the developing rotator at a part passing over the movement assist member, and configured to adjust a movement amount of the developer from the movement assist member to the developing rotator and a carrying amount of the developer on the surface of the developing rotator, and a second adjusting member having a distance from the surface of the developing rotator at a part passing over the first adjusting member, and configured to adjust the carrying amount of the developer on the surface of the developing rotator before the developer reaches the developing region. A first minimum distance between the slope of the movement assist member and the facing surface of the first adjusting member, a second minimum distance between the facing surface of the first adjusting member and the surface of the developing rotator, and a third minimum distance between the second adjusting member and the surface of the developing rotator are reduced in descending order.

A developing device includes a developing rotator configured to rotate through a developing region while carrying a magnetic developer, a supply transport member configured to rotate to transport the developer to be supplied to the developing rotator, a non-magnetic movement assist member arranged between the developing rotator and the supply transport member, and having a slope that receives the developer from the supply transport member and moves the developer to the developing rotator, a first adjusting member having a facing surface that faces, with distances, the slope of the movement assist member and a surface of the developing rotator at a part passing over the movement assist member, and configured to adjust a movement amount of the developer from the movement assist member to the developing rotator and a carrying amount of the developer on the surface of the developing rotator, and a second adjusting member having a distance from the surface of the developing rotator at a part passing over the first adjusting member, and configured to adjust the carrying amount of the developer on the surface of the developing rotator before the developer reaches the developing region. A first minimum distance between the slope of the movement assist member and the facing surface of the first adjusting member, a second minimum distance between the facing surface of the first adjusting member and the surface of the developing rotator, and a third minimum distance between the second adjusting member and the surface of the developing rotator are reduced in descending order.

A conduction mechanism includes: a conductive bearing that rotatably supports a rotary shaft; a non-conductive axial positioner that has a cylinder externally fitted to the bearing; and a contact terminal attached to an outer circumferential surface side of the cylinder. The cylinder has a slit, and the contact terminal has an abutment piece that is exposed to an inner circumferential surface side of the cylinder from the slit and abuts an outer circumferential surface of the bearing.

A developing device includes a developing container storing a two-component developer, a developer carrying member, and a regulation member. The developer carrying member includes a developing sleeve, and a magnet having a regulation pole opposite the regulation member and a main pole opposite the image carrying member. The regulation member is arranged downstream of the position at which the vertical magnetic force of the regulation pole is 0 [mT] but upstream of a position at which the vertical and horizontal magnetic forces of the regulation pole are equal. Let the horizontal magnetic force gradient at the position at which the horizontal magnetic force of the main pole is 0 [mT] be A and the horizontal magnetic force gradient at the upstream-side surface of the regulation member along the rotation direction of the developing sleeve be B, then |A|>2.45 and |B|<1.30.

A developing device includes a developing container storing a two-component developer, a developer carrying member, and a regulation member. The developer carrying member includes a developing sleeve, and a magnet having a regulation pole opposite the regulation member and a main pole opposite the image carrying member. The regulation member is arranged downstream of the position at which the vertical magnetic force of the regulation pole is 0 [mT] but upstream of a position at which the vertical and horizontal magnetic forces of the regulation pole are equal. Let the horizontal magnetic force gradient at the position at which the horizontal magnetic force of the main pole is 0 [mT] be A and the horizontal magnetic force gradient at the upstream-side surface of the regulation member along the rotation direction of the developing sleeve be B, then |A|>2.45 and |B|<1.30.

A developing device includes a developing container storing a two-component developer containing a magnetic carrier and a toner, a developer carrying member carrying the developer on its outer circumferential surface, and a regulation member arranged to be opposed at a prescribed distance to the developer carrying member. The developer carrying member includes a developing sleeve on which a magnetic brush is formed, and a magnet secured in the developing sleeve and having a plurality of magnetic poles including a regulation pole opposed to the regulation member and a downstream-side magnetic pole arranged downstream of the regulation pole with respect to the rotation direction of the developing sleeve. The magnet is such that the vertical magnetic force gradient [mT/° ] has a local minimum value near a position at which the vertical magnetic force is 0 [mT] between the downstream-side surface of the regulation member and the downstream-side magnetic pole.

A developing device includes a developer roller that is rotatable about an axis, to carry a developer to a development region; a rectifier member extending in a direction parallel to an axial direction of the developer roller. The rectifier member includes a developer collecting part that is spaced apart by a predetermined distance from a surface of the developer roller, and a rectifying part to guide air from within the developing device via the developer collecting part toward an upstream side of the development region, in a rotational direction of the developer roller.

An image forming apparatus includes an image forming portion including a photosensitive member and a developing portion configured to develop, with toner, an electrostatic latent image formed on the photosensitive member, the image forming portion being configured to form an image on the sheet, a first frame including an upper space supporting the image forming portion and a lower space under the upper space, an accommodating portion configured to accommodate the sheet, a feeding portion configured to feed the sheet accommodated in the accommodating portion, and a supply container configured to contain the toner to be supplied to the developing portion of the image forming portion. The accommodating portion and the feeding portion are provided in the lower space and, alternatively, the supply container is provided in the lower space together with a second frame which is mountable to a lower portion of the first frame.