An image forming apparatus is described. An image forming apparatus may include an image forming apparatus body and a tandem type photosensitive unit slidable with respect to the body, wherein the unit includes: a frame; a plurality of photosensitive bodies; a plurality of developer cartridges, including developer carriers, detachably mountable on the frame; and a pressing portion provided on the frame for pressing each of the cartridges so that the developer carrier thereof is directed toward the corresponding photosensitive body, each of the cartridges is pivoted to be movable to an imaging position pressed by the pressing portion and a detached position released from the pressing by the pressing portion, and the body is provided with an abutting portion abutting the cartridge located on the detached position thereby pivoting the cartridge and moving the same to the imaging position when the unit is mounted on the body.

An image forming apparatus has a main casing including an opening provided at an upper portion of the main casing, a process cartridge attachable to the main casing through the opening, and a top cover movable between an open position where the top cover opens the opening and a close position where the top cover closes the opening. The process cartridge includes a photosensitive drum and a memory provided with a first electrical contact. The top cover supports an LED head configured to emit light to expose the photosensitive drum, and a second electrical contact electrically connected to the first electrical contact in a state where the process cartridge is attached to the main casing and in a state where the top cover is positioned at the close position.

An image forming apparatus has an image forming unit configured to form an image on a sheet, a first frame having a plate-like shape and made of metal, the first frame being configured to support the image forming unit, a second frame arranged on an opposite side, with respect to the first frame, of the first frame with sandwiching the image forming unit therebetween, the second frame having a plate-like shape and made of resin, the second frame being configured to support the image forming unit in association with the first frame, a third frame bridging between the first frame and the second frame, a sheet supplying unit being secured to the third frame, and a contacting part formed to each of the first frame and the second frame, contact parts formed to the third frame being configured to contact the first and second frames, respectively.

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 lens unit includes a first lens array including a plurality of first lens elements. The first lens array satisfies D.sub.10.25.Math.P.sub.1 where P.sub.1 is a pitch in a first direction between optical axes of adjacent ones of the first lens elements, and D.sub.1 is a displacement amount that is an absolute value of a difference between a first length W.sub.E1 from a center position of the first lens array to an end position of the first lens array in the first direction at a first temperature, and a second length W.sub.E2 from the center position of the first lens array to the end position of the first lens array at a second temperature higher than the first temperature by 30 C.

A fixing device for thermally fixing a toner image on a sheet includes a heat unit, a pressure unit, and a nip member. One of the heat unit and the pressure unit includes an endless belt having a width in a widthwise direction and a restriction member configured to be abutted against the endless belt. The endless belt includes a base layer having an outer peripheral surface and a pair of widthwise end faces in the widthwise direction, the base layer defining an inner space, and an elastic layer formed on the outer peripheral surface and having a thickness and a pair of widthwise end surfaces in the widthwise direction. One of the end faces and a corresponding one of the end surfaces provides a maximum distance therebetween in the widthwise direction smaller than the thickness of the elastic layer.

An image formation apparatus that includes: first to third image formation units provided in this order in a traveling direction of a transfer target medium; a detector configured to detect first to third correction patterns formed on the transfer target medium by the first to third image formation units, respectively; and a control unit programed to control image misregistration correction based on a result of detection by the detector. The control unit causes the first and third image formation units to form the first and third correction patterns on the transfer target medium, respectively. When an amount of image misregistration between the first correction pattern and the third correction pattern is less than a predetermined value, the control unit neither causes the second image formation unit to form the second correction pattern, nor executes the image misregistration correction.

A developer container includes a memory device with a first marker; and a main body with a second marker, the main body being configured to accommodate a developer. The memory device is attached to the main body such that both the first marker and the second marker are visually recognized.

A development device includes a developer bearing member and a magnet which is fixed inside of the developer bearing member. The magnet includes a first magnetic pole for developing a latent image, a second magnetic pole adjacent to the first magnetic pole and being an opposite pole to the first magnetic pole, and a third magnetic pole adjacent to both the first and second magnetic poles and having an opposite pole to the first magnetic pole. A developer regulation portion is disposed such that when a maximum peak amount of a magnetic flux density of the first magnetic pole in a normal direction of the developer bearing member is defined as positive, the magnetic flux density of the first magnetic pole becomes positive in an entire region from a downstream side of the regulating member in a rotary direction of the developer bearing member and through a developing area.

In a cartridge, a developing roller is configured to rotate around a first rotational axis extending in a predetermined direction and to carry developer thereon, the developing roller having a first end and a second end apart from each other in the predetermined direction, a from-first-to-second direction being defined along the predetermined direction as being directed from the first end to the second end. A developing electrode is formed of a conductive material and is configured to be electrically connected to the developing roller, the developing electrode including a main part and a protruding portion protruding from the main part in the from-first-to-second direction. A detection body is formed of an insulating material and is rotatably supported by the protruding portion, the detection body including a first opening that exposes part of the protruding portion and a covering portion covering part of the protruding portion.