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 guide unit holding portion is formed at a position between two struts in a longitudinal direction of a fixing unit. When a main cover portion rotates from an open position to a closed position, a supported portion of a swing guide unit moves from a position where the supported portion is separated from the guide unit holding portion to a position where the supported portion is in contact with the guide unit holding portion. Further, the supported portion slides on the guide unit holding portion. When the supported portion slides on the guide unit holding portion, the swing guide unit is swung upward, and then held at a target position by the guide unit holding portion.

A heating unit urging member urges a first support body of a heating unit toward a second support body of a fixing unit with elastic force. The heating unit urging member brings the first support body into contact with the second support body and brings the second support body into contact with two struts. An interlocking mechanism moves the heating unit along a direction in which the heating unit and the fixing unit are arranged, in conjunction with movement of an operation portion. When the operation portion moves from a first position to a second position, the interlocking mechanism moves the first support body from a reference position where the first support body is in contact with the second support body to a retracted position where the first support body is separated from the second support body.

A fixing device, which is included in an image forming apparatus, includes a heater, a heating target body, a biasing body, a pressure body, a moving body, a drive source, and a drive transmitter. The heating target body is configured to be heated by the heater. The biasing body is configured to apply a biasing force. The pressure body is configured to be pressed by the biasing body toward the heating target body. The moving body is configured to move the pressure body away from the heating target body against the biasing force applied by the biasing body. The drive source is configured to apply a driving force. The drive transmitter is configured to transmit the driving force of the drive source to the moving body and includes a planetary gear device and a worm gear.

An image forming apparatus includes a transfer unit, a fixing unit, a reverse rotary member pair, a first conveyance path, a second conveyance path, an opening and closing member, a first guide member, a second guide member, and a dividing member. The second guide member is supported by the opening and closing member and forms an inserted portion where a case of the fixing unit is inserted and one side of guide surfaces of the second conveyance path. The second guide member forms one side of guide surfaces of the first conveyance path in a state where the opening and closing member is in a closed position. The dividing member, in the state where the opening and closing member is in the closed position, divides a gap formed between the second guide member and the case inserted into the inserted portion from the second conveyance path.

According to one embodiment, a fixing device includes a belt, a heater, and a holder. The holder has a plurality of support portions that contact an end of the first heating region and an end of the second heating region along the direction perpendicular to the transport direction, and a plurality of non-contacting portions that do not contact the end of the first heating region and the end of the second heating region between the plurality of support portions, the end of the second heating region contacts one of the plurality of support portions at a side in the direction perpendicular to the transport direction, and the end of the second heating region faces to one of the plurality of non-contacting portions at the other side in the direction perpendicular to the transport direction.

A fuser includes a pressure roller to rotate and a heating belt to form a fixing nip with the pressure roller. The heating belt comprises at each end of the heating belt a bush to support the heating belt, a fixing flange to rotatably support the bush, and a plurality of springs to elastically connect between the bush and the fixing flange, to rotate the bush about an axis passing through a first surface of the bush and a second surface of the bush opposite to the first surface of the bush.

According to one embodiment, a fixing device includes a belt, a heater, and a holder. The belt is formed into a cylindrical shape, is rotated in a circumferential direction to transport a sheet, and applies heat to the sheet. The heater is arranged on an inner side of the belt and extends in a predetermined longitudinal direction to heat the belt. The holder extends in the longitudinal direction of the heater and holds the heater. The holder includes a support portion and a retraction portion. The support portion comes into contact with the heater and supports the heater. The retraction portion is provided at a position avoiding the support portion in the longitudinal direction of the heater, and includes a smaller contact area with the heater than the contact area between the support portion and the heater or does not come into contact with the heater.

A unit attachment-detachment mechanism includes a unit and a pair of guide rails. The pair of guide rails slidably supports a pair of side faces of the unit. The side faces respectively have formed thereon engagement projections that engage with the guide rails. The pair of guide rails has formed therein at least a pair of inclined portions. The pair of inclined portions is formed asymmetrically with each other in the unit width direction perpendicular to the attachment-detachment direction.

A positioning member is configured to be fixed to a main assembly frame of an image forming apparatus and configured to position a fixing device. The positioning member includes a mounting portion, a first projected portion configured to be inserted into a first hole of the main assembly frame, a second projected portion configured to be inserted into a second hole of the main assembly frame, and a third projected portion configured to be inserted into a third hole of the main assembly frame. The third projected portion includes a snap-off facilitating portion that snaps off in order to permit movement of the positioning member relative to the main assembly frame.