An image forming apparatus configured to form images on a first surface and a second surface of a sheet includes an apparatus body, an image forming unit, a feed tray, and a return unit configured to return the sheet having an image formed on the first surface of the sheet toward the image forming unit. The return unit includes a first guide, a second guide, and an adjuster. The first guide is detachably attached to the second guide and includes a first roller and a positioned portion. The second guide is positioned in the apparatus body and includes a second roller facing the first roller, and a positioning portion configured to contact the positioned portion of the first guide, thereby positioning the first guide relative to the second guide. The adjuster is configured to adjust an orientation of the second guide relative to the apparatus body.

A misattachment prevention device for an image forming unit includes multiple developer containing parts that contain individual color developers, and process parts each of which is capable to be engaged with any of the developer containing parts, and forms the image forming unit for an individual color by having one of the developer containing parts engaged, wherein (c) each of the process parts is provided with an intermediate locking member guide part in a place opposing the one of the developer containing parts, and (d) the intermediate locking member guide part is provided with an intermediate locking member that is locked with a locking part formed on the one of the individual developer containing parts, protruded from the intermediate locking member guide part to a side of an apparatus main body, and locked with a locked part formed on the apparatus main body.

A controller calculates a first time period T1 and a second time period T2. The first time period T1 is defined as a time period required for conveying the end portion of the sheet, which is conveyed in a first conveyance direction E, disposed on the upstream side in the first conveyance direction E up to a reversal position A3. The second time period T2 is defined as a time period required for conveying an end portion of the reversed sheet disposed on an upstream side in a second conveyance direction R from the reversal position A3 to a branching point A1.

An image forming apparatus, including a photosensitive drum, an exposure head, a base frame, and a spring, is provided. The exposure head includes light emitters, a lens array, and a head frame, and is movable between an exposable position and a retracted position. The base frame supports the photosensitive drum and includes a reference face. The reference face is configured to define a position of the exposure head with regard to a sub-scanning direction, which is orthogonal to a direction of an optical axis of the light from the light emitters and to a direction of a rotation axis of the photosensitive drum, by being contacted by the head frame of the exposure head when the exposure head is at the exposable position. The spring is arranged in the head frame and presses the head frame toward the reference face.

An exposure unit includes a light-emitting element array and a lens array. The light-emitting element array includes a plurality of light-emitting elements that are disposed in a first direction and each emit a light beam. The lens array faces the light-emitting element array in a second direction that is orthogonal to the first direction, and focuses the light beams emitted from the respective light-emitting elements. The following expression [3] is satisfied. A symmetric property, determined from the following expression [1], of a light amount distribution in the first direction of at least one of the light beams focused by the lens array satisfies the following expression [2].
S=|(HLHR)/(XE/2)|[1]
0S0.65[2]
LoLB[3]

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.

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 moving-member detecting device includes an image acquiring unit and a speed calculating unit. The image acquiring unit includes a light source configured to emit a light beam to a detecting position of a moving member; an area sensor configured to acquire image data of a one- or two-dimensional image; and an area-sensor control unit configured to acquire the image data. The image acquiring unit is configured to acquire pieces of image data of the moving member at first and second positions, respectively, in a moving direction of the moving member so as to acquire the piece of position image data for the second position when the moving member is at the second position after acquiring the piece of image data for the first position. The speed calculating unit is configured to calculate a moving speed of the moving member from the pieces of image data.

An image forming apparatus comprising: an exposing unit including: a first light source comprising a first light emitter and a first light receiver including a first electric output responsive to a received light quantity of the first light emitter; a second light source comprising a second light emitter and a second light receiver including a second electric output responsive to a received light quantity of the second light emitter; and a first light-source driver electrically connected to the first light source and the second light source. The first light-source driver includes: a first output terminal electrically connected to the first light emitter; a second output terminal electrically connected to the second light emitter; and an input terminal electrically connected to both the first electric output and the second electric output.

An image forming apparatus includes a body casing, a drum unit movable between an inside position and an outside position, and a waste toner storage unit. The drum unit includes a photosensitive drum, a cleaning unit configured to remove toner remaining on a surface of the photosensitive drum, a conveying unit including a conveying member to convey the toner in a moving direction of the drum unit, and a conveying tube that can accommodate the conveying member and having a discharging outlet through which the toner is discharged to the waste toner storage unit. Moreover, the conveying tube includes a first conveying tube extending in the moving direction and accommodating the conveying member, and a second conveying tube connectable to the first conveying tube and extending in a direction intersecting with a direction in which the first conveying tube extends.