An image forming apparatus includes an attaching and detaching unit, an attached and detached section, and a pressing member. The attaching and detaching unit includes a developing device including a developer bearer to develop a latent image on a latent image bearer and is detachably attached to the attached and detached section. The attached and detached section includes the latent image bearer, a main reference portion, and a sub-reference portion. The main reference portion contacts a main reference part of the attaching and detaching unit. The sub-reference portion contacts a sub-reference part of the attaching and detaching unit. The pressing member presses the attaching and detaching unit to generate a biasing force biasing the developer bearer toward the latent image bearer and a rotational moment toward the sub-reference portion of the attached and detached section around the main reference part with respect to the attaching and detaching unit.

A transfer device includes: a transfer drum that has a groove-like recess extending in an axial direction in an outer circumferential portion thereof, rotates about an axis thereof, and comes into contact with a medium being transported at a portion thereof on an upstream side of the recess in a rotation direction; a nip member, the nip member and the transfer drum forming therebetween a nip part where the medium is nipped; an application member that applies a voltage to the nip part where the medium is nipped, so that an image is transferred to the medium; and a contact mechanism that causes the nip member to come into contact only with a portion on the upstream side of the recess in the transfer drum in the rotation direction at a transfer-start time when the transfer of the image to the medium starts.

In an image formation device, a driven gear is coupled to a far end portion in a unit inserting and withdrawing direction of a rotary fixing member or a rotary pressure member of a fixing unit. A driving gear is provided in a far end portion of a fixing unit housing part and engages with the driven gear when the fixing unit is housed in the fixing unit housing part. The driving gear and the driven gear are formed so that a transmission force transmitted from the driving gear to the driven gear in a mutual engagement position has a component so directed as to horizontally press the fixing unit against columns making a pair. The fixing unit as housed in the fixing unit housing part is pressed by the transmission force against the columns and positioned in a direction orthogonal to the unit inserting and withdrawing direction.

A fixing device is configured to fix a toner image to a sheet by heat and includes: a heating rotator; a pressurizing roller contacting with the heating rotator; a heater configured to heat the heating rotator such that the heat is transferred to the sheet passing through a contact portion between the heating rotator and the pressurizing roller; a plurality of separation claws configured to separate the sheet from the heating rotator such that the sheet passing through the contact portion is not caught in the heating rotator, the separation claws being provided opposite to the heating rotator; and an adjustor configured to adjust positions of the separation claws relative to the heating rotator such that distances between the separation claws and the heating rotator are equal to each other.

There is provided a guide incorporated in a fixing device including a belt configured to circularly move in a moving direction. The guide includes: a guide portion elongated in a longitudinal direction orthogonal to the moving direction; a first gate mark; and a second gate mark arranged spaced apart from the first gate mark in the longitudinal direction. The guide portion includes a resin and a plurality of elongated-shaped fillers dispersed in the resin. The guide portion has a guide surface configured to guide movement of the belt in the moving direction, a peripheral surface of the belt being configured to contact the guide surface.

An image forming apparatus includes a recording sheet storage unit for storing recording sheets substantially in an upright position, an image forming unit which forms an image on a recording sheet conveyed from the recording sheet storage unit, and a recording sheet receiving unit for storing the recording sheet conveyed from the image forming unit substantially in an upright position. In this image forming apparatus, a paper conveyance passage for conveying the recording sheet extends upward from a lower portion of the recording sheet storage unit toward the recording sheet receiving unit. The image forming unit positioned on the paper conveyance passage comprises a fixing device and a developer unit at least including a developer carrier, and the fixing device is arranged above the developer unit.

A branch frame has a first guide surface and a second guide surface. In a state where a first cover is located at an open position, at least part of the first cover is located in a space through which a fixing device passes when the fixing device is detached from a mount portion, and the fixing device is unattachable to and undetachable from the mount portion through a first opening. In a state where the branch frame is attached to a main housing, at least part of the branch frame is located in the space, and the fixing device is unattachable to and undetachable from the mount portion through the first opening. In a state where the first cover and the branch frame are detached from the main housing, the fixing device is attachable to and detachable from the mount portion through the first opening.

A fixing device includes: a first heater including a first glass tube, a first heating body, and a first lead portion; a second heater including a second glass tube, a second heating body, and a second lead portion; a frame including first and second fixing surfaces; and a first terminal member including a first connection portion and a first fixed portion; and a second terminal member including a second connection portion and a second fixed portion. The first and second heaters are elongated in an elongated direction and arrayed in a first array direction. The first and second lead portions are fixed to the first and second connection portions, respectively. The first and second fixed portions are fixed to the first and second fixing surfaces, respectively, and arrayed in a second array direction. The first array direction is inclined relative to the second array direction when viewed in the elongated direction.

A first protrusion is provided between an operation lever and a lock lever. The operation lever is for moving a pressure roller. The lock lever is provided for a sheet guide member for guiding a sheet that has passed through a fixing unit downstream in the sheet conveyance direction. The lock lever is for locking the sheet guide member at a position where the sheet guide member is engaged with a housing. The first protrusion protrudes from the sheet guide member toward an exterior cover. The first protrusion is provided with a second protrusion on the lock lever side of the first protrusion.

A fixing device includes a first rotatable member with a heater, a second rotatable member contacting the first rotatable member and forming a fixing nip, a pressing unit pressing the first rotatable member to the second rotatable member in a pressing direction, a pair of side boards disposed with a space in the widthwise direction, and first, second and third stays supporting the pair of side boards. The first stay is provided upstream of a center of the fixing nip in the pressing direction and upstream of the center in a feeding direction of a recording material. The second stay is provided upstream of the center in the pressing direction and downstream of the center in the feeding direction. The third stay is provided downstream of the center in the pressing direction and at least one of upstream and downstream of the center in the feeding direction.