An image forming apparatus includes an image bearing member, an exposure device configured to expose the image bearing member to form an electrostatic latent image thereon, and a developing device including a rotatable developing member configured to carry and feed a developer containing toner and a carrier to develop the electrostatic latent image formed on the image bearing member, and a magnet provided non-rotatably and stationarily inside the rotatable developing member including a developing magnetic pole, wherein magnetic chains formed by the carrier, on the rotatable developing member, magnetized by the magnet contact the electrostatic latent image formed on the image bearing member in a developing region of the rotatable developing member, wherein a maximum peak position where a magnetic flux density of the developing magnetic pole is maximum with respect to a normal direction of the rotatable developing member exists within a range of the developing region with respect to a rotational direction of the rotatable developing member, and wherein a ratio of an 80%-value-width which is a width of a portion where the magnetic flux density of the developing magnetic pole with respect to the normal direction of the rotatable developing member is 80% of the maximum of the magnetic flux density of the developing magnetic pole with respect to the normal direction of the rotatable developing member to a half peak width which is a width of a portion where the magnetic flux density of the developing magnetic pole with respect to the normal direction of the rotatable developing member is half of the maximum of the magnetic flux density of the developing magnetic pole with respect to the normal direction of the rotatable developing member is 0.65 or more.

A developer cartridge is described. The developer cartridge detachably mountable on a tandem type photosensitive unit slidable to a drawn-out position and a mounted position with respect to an image forming apparatus body may include a casing; a developer carrier rotatably supported on one end portion of the casing for carrying a developer; a pair of upright portions arranged on another end portion of the casing at an interval from each other in the axial direction of the developer carrier to extend from another end portion of the casing in a detaching direction for the developer cartridge; and an elastically deformable coupling portion extending in the axial direction of the developer carrier for coupling the upright portions with each other.

A semiconductive roller is provided, which has a toner transport amount and a toner charge amount properly controlled, particularly, when being used as a developing roller, and is substantially free from imaging failure such as fogging and background smudging. The semiconductive roller is formed from a semiconductive rubber composition, and has an outer peripheral surface having a surface roughness defined by a roughness profile such that an arithmetic average roughness is not greater than 0.7 μm and a difference Rδc between vertical section levels at two different load length percentages (at a load length percentage Rmr1 of 25% and a load length percentage Rmr2 of 75%) is not greater than 1.2 μm.

A developing device includes a development container, a toner carrier, and a regulation blade. The toner carrier supplies toner contained in the development container to an image carrier in a facing region between the toner carrier and the image carrier. The regulation blade contacts the toner carrier on an upstream side of the facing region in a rotation direction of the toner carrier, and regulates a thickness of a layer of the toner carried on the toner carrier. The regulation blade is formed of a metal material polished in a direction same as a toner moving direction in a contact region between the regulation blade and the toner carrier such that an arithmetic average roughness of a surface of the regulation blade is 0.3 μm or less.

The image forming apparatus includes a main body, a pick-up device to pick up a printing medium, a developing device to develop an image on a side of the printing medium picked up by the pick-up device, a fixing device to fix the image developed on the side of the printing medium, a paper reverse device to guide the printing medium from a transfer direction of the printing medium passing through the fixing device, through a reverse path to the developing device and the fixing device, to develop and fix another image on other side of the printing medium, a discharging device to discharge the printing medium outside the main body, a post-processing device provided in the main body, and a post-processing path selection device rotatable to a first position to guide the printing medium through a discharge path to guide the printing medium passing through the fixing device to the discharging device and a second position to guide the printing medium from the discharge path to a post-processing path branched from the discharge path, to guide the printing medium to the post-processing device.

A binary ink developer (BID) assembly for a liquid electrophotography (LEP) printing device can include a developer roller having an electrically insulating exterior coating that receives ink from an ink supply and transfers the received ink to a photoconductive imaging cylinder in accordance with an electrostatic image on the imaging cylinder. A charge-specified boundary condition can exist at the boundary between the exterior coating and the ink. Electrically conductive ink may not be transferred to the imaging cylinder at background portions of the electrostatic image.

A developer storage level detecting device includes: a main body having a transporting path through which a developer is transported; a developer transporting unit that is disposed to rotate in the transporting path and has a transporting section provided spirally around a rotating shaft; a swingable member that comes in contact with a surface of the developer being transported in the transporting path and swings while following at least a level of the surface of the developer stored; and a detecting unit that detects a swing state of the swingable member, wherein the transporting unit has a non-transporting section without the transporting section, and the swingable member is disposed to swing in the non-transporting section.

A developing device includes a rotatable developing sleeve for carrying a developer including toner and a magnetic carrier and for developing an electrostatic latent image, formed on an image bearing member, in a developing region where the developer contacts the image bearing member; and a magnetic field generating portion provided inside the developing sleeve and having a developing pole provided at a position opposing the image bearing member in order to form the developing region, wherein a ratio of an 80%-value-width of magnetic flux density of the developing pole with respect to a normal direction of the developing sleeve to a half peak width of the magnetic flux density of the developing magnetic pole with respect to the normal direction is 0.65 or more, and with respect to a rotational direction of the developing sleeve, a magnetic force of the developing pole in the normal direction of the developing sleeve in each of neighborhoods of both end portions of the developing region is larger than a magnetic force of the developing pole at a central portion of the developing region.

A developing device includes a rotatable developing sleeve to carry and feed a developer including toner and a carrier toward a developing region, and a magnetic field generating portion provided inside the developing sleeve and having a developing magnetic pole for forming the developing region. The developing magnetic pole is disposed opposite to a closest position of the image bearing member to the developing sleeve. A ratio of an 80%-value-width of magnetic flux density of the developing magnetic pole with respect to a normal direction of the developing sleeve to a half peak width of the magnetic flux density of the developing magnetic pole with respect to the normal direction is 0.65 or more.

When the area of a developing frame member corresponding to the maximum image area of an image bearing member is, in a section perpendicular to a rotational axis of a developing rotary member, divided by a straight line passing through the center of rotation of the developing rotary member and the center of rotation of the image bearing member and a perpendicular line passing through the center of rotation of a first conveying screw with respect to the straight line, a gate portion is provided at a bottom portion of the developing frame member in a divided area of the developing frame member not provided with the attachment portion, and a gate portion is not provided at the bottom portion of the developing frame member in a divided area of the developing frame member provided with the attachment portion.