Abstract: An image forming apparatus includes a photosensitive member, a transfer unit having a transfer belt, a primary transfer roller, a secondary transfer inner roller below the primary transfer roller in a vertical direction, and a stretching roller, a secondary transfer outer roller, a support unit, and an air duct provided in the transfer unit. The secondary transfer outer roller faces the secondary transfer inner roller via the transfer belt and forms a nip portion for secondarily transferring a toner image on the transfer belt to a sheet. The air duct is located downstream of the nip portion in a sheet conveyance direction and below a portion of the transfer belt stretched between the secondary transfer inner roller and the stretching roller in the vertical direction. The air duct includes an air intake port and moves with the transfer unit with movement of the transfer unit from the support unit.

Abstract: An image forming apparatus includes an image forming unit configured to form a toner image on an image bearing member, a first unit including an intermediate transfer belt on which the toner image is transferred from the image bearing member and a first roller disposed in contact with an inner surface of the intermediate transfer belt to stretch the intermediate transfer belt, the first unit being drawable from a main body of the image forming apparatus, a second unit including a second roller configured to form, with the first roller, a transfer nip portion in which the toner image is transferred from the intermediate transfer belt to a recording material, the second unit being drawable from the main body, and a high-voltage circuit board disposed in the second unit and configured to apply a voltage to the first roller.

Abstract: An image forming apparatus includes an image forming unit and a belt conveyance apparatus. The belt conveyance apparatus includes a transfer belt, a tension roller, a movement mechanism, and a drive unit. A toner image on an image bearing member is transferred to the transfer belt in tension from the tension roller. The movement mechanism moves the tension roller to apply tension to, and release tension from, the transfer belt. The drive unit is disposed in a width direction and drives the transfer belt. The movement mechanism includes an attachment portion disposed on a side opposite the drive unit in the width direction and to which a handle member that operates the movement mechanism is detachably attached. The movement mechanism is configured such that the belt conveyance apparatus is attached to an image forming apparatus body in a state in which the handle member is detached from the attachment portion.

Abstract: A rotation center of a secondary transfer inner roller located at a first position is located downstream of a rotation center of a secondary transfer outer roller in a movement direction of an intermediate transfer belt tensioned by the secondary transfer inner roller and an idler roller. The rotation center of the secondary transfer inner roller located at a second position coincides in position with the rotation center of the secondary transfer outer roller, or is located upstream of the rotation center of the secondary transfer outer roller in the movement direction of the intermediate transfer belt tensioned by the secondary transfer inner roller and the idler roller.

Abstract: An image forming apparatus includes an image forming unit and a belt conveyance apparatus. The belt conveyance apparatus includes a transfer belt, a tension roller, a movement mechanism, and a drive unit. A toner image on an image bearing member is transferred to the transfer belt in tension from the tension roller. The movement mechanism moves the tension roller to apply tension to, and release tension from, the transfer belt. The drive unit is disposed in a width direction and drives the transfer belt. The movement mechanism includes an attachment portion disposed on a side opposite the drive unit in the width direction and to which a handle member that operates the movement mechanism is detachably attached. The movement mechanism is configured such that the belt conveyance apparatus is attached to an image forming apparatus body in a state in which the handle member is detached from the attachment portion.

Abstract: An image forming apparatus includes an intermediate transfer belt, a plurality of rollers including an inner roller and where the intermediate transfer belt is stretched, an outer roller provided at a position facing the inner roller with the intermediate transfer belt in between, and an arm member. The intermediate transfer belt receives transfer of a toner image. The outer roller forms a transfer nip to transfer the toner image from the intermediate transfer belt to a recording medium. The arm member rotatably supports both end parts of the inner roller. When the inner roller is positioned at a first rotating position, the transfer nip is formed at a first position in an outer roller circumferential direction, and when the inner roller is positioned at a second rotating position, the transfer nip is formed at a second position different from the first transfer nip position in the outer roller circumferential direction.

Abstract: An image forming apparatus includes an image forming unit configured to form a toner image on an image bearing member, a first unit including an intermediate transfer belt on which the toner image is transferred from the image bearing member and a first roller disposed in contact with an inner surface of the intermediate transfer belt to stretch the intermediate transfer belt, the first unit being drawable from a main body of the image forming apparatus, a second unit including a second roller configured to form, with the first roller, a transfer nip portion in which the toner image is transferred from the intermediate transfer belt to a recording material, the second unit being drawable from the main body, and a high-voltage circuit board disposed in the second unit and configured to apply a voltage to the first roller.

Abstract: A rotation center of a secondary transfer inner roller located at a first position is located downstream of a rotation center of a secondary transfer outer roller in a movement direction of an intermediate transfer belt tensioned by the secondary transfer inner roller and an idler roller. The rotation center of the secondary transfer inner roller located at a second position coincides in position with the rotation center of the secondary transfer outer roller, or is located upstream of the rotation center of the secondary transfer outer roller in the movement direction of the intermediate transfer belt tensioned by the secondary transfer inner roller and the idler roller.

Abstract: In an image forming apparatus, at least a part of a cleaning roller is provided on the same side as an opposed roller with respect to an external common tangent Z of a first roller and a second roller. In a case in which a surface velocity of the driving roller is designated as v1; a surface velocity of the cleaning roller is designated as v2; a radius of the cleaning roller is designated as r; a radius of the opposed roller is designated as s; and a distance between the center of rotation of the cleaning roller and the center of rotation of the opposed roller is designated as x, the cleaning roller is rotated so as to satisfy a relationship: v2/v1<r/(x?s).

Abstract: At least a part of a cleaning roller is provided on the same side as an opposed roller with respect to an external common tangent Z of a first roller and a second roller. In a case in which a surface velocity of the driving roller is designated as v1; a surface velocity of the cleaning roller is designated as v2; a radius of the cleaning roller is designated as r; a radius of the opposed roller is designated as s; and a distance between the center of rotation of the cleaning roller and the center of rotation of the opposed roller is designated as x, the cleaning roller is rotated so as to satisfy a relationship: v2/v1<r/(x?s).

Abstract: An image forming apparatus includes an intermediate transfer belt, a plurality of rollers including an inner roller and where the intermediate transfer belt is stretched, an outer roller provided at a position facing the inner roller with the intermediate transfer belt in between, and an arm member. The intermediate transfer belt receives transfer of a toner image. The outer roller forms a transfer nip to transfer the toner image from the intermediate transfer belt to a recording medium. The arm member rotatably supports both end parts of the inner roller. When the inner roller is positioned at a first rotating position, the transfer nip is formed at a first position in an outer roller circumferential direction, and when the inner roller is positioned at a second rotating position, the transfer nip is formed at a second position different from the first transfer nip position in the outer roller circumferential direction.

Abstract: In an image forming apparatus, an inertia roller having a large moment of inertia is arranged between a secondary transfer section and a primary transfer section, and in the neighborhood of the secondary transfer section. This configuration effectively reduces a velocity variation of an endless intermediate transfer belt that occurs when a printing medium enters the secondary transfer portion. Image defects are thus suppressed.

Abstract: In an image forming apparatus, an inertia roller having a large moment of inertia is arranged between a secondary transfer portion and a primary transfer section, and in the neighborhood of the secondary transfer section. This configuration effectively reduces a velocity variation of an endless intermediate transfer belt that occurs when a printing medium enters the secondary transfer portion. Image defects are thus suppressed.

Abstract: An image forming apparatus includes a control portion that controls a drive speed of a first drive source, so that a speed of a sheet conveyed in a conveyance nip portion is greater than a speed of the sheet conveyed in a transfer nip portion, and a drive speed of a second drive source, so that the speed of the sheet conveyed in the transfer nip portion is greater than a speed of the sheet conveyed in a fixing nip portion. The control portion changes a rotation speed of a pair of conveyance members from a first speed to a second speed greater than the first speed after a first loop amount of the sheet formed between the transfer nip portion and the fixing nip portion becomes greater than a second loop amount of the sheet formed between the transfer nip portion and the conveyance nip portion.

Abstract: A bearing, for supporting a rotation shaft of a rotatable member, capable of being supported by a supporting portion provided with an engaging hole engageable with the bearing includes positioning projections having contact surfaces and bearing projections having sliding surfaces on which an outer peripheral surface of the rotation shaft slides. The positioning projections project from different positions so that between adjacent positioning projections, an outer peripheral surface of the bearing and the inner wall surface of the engaging hole form a gap therebetween. The bearing projections project from different positions so that between adjacent bearing projections, an inner peripheral surface of the bearing and an outer peripheral surface of the rotation shaft form a gap therebetween. With respect to a circumferential direction of the rotation shaft, the positioning projections and the bearing projections are provided at positions different from each other.

Abstract: There is provided a configuration in which a foreign object is less likely to drop onto a detection surface of a sensor when a protection member moves. The protection member is disposed above the sensor movably between a first position and a second position, and has a detection hole formed to expose a detection surface of the sensor at the first position. The protection member covers the detection surface in a part, in which the detection hole is not formed, at the second position. A protruding wall portion is provided at least at an upstream edge of the detection hole, with respect to a direction in which the protection member moves from the second position to the first position, so as to protrude upward from a top surface of the protection member.

Abstract: An image forming apparatus includes optical sensor units provided opposed to an image bearing member; light blockers provided between the image bearing member and the optical sensor units, respectively, the blockers being movable between locking and exposing positions, respectively; calibration members provided where the light is incident when the blockers are in the blocking positions, respectively, the calibration members calibrating data acquired by the optical sensor units; a movable link connected with the blockers; a switching portion for switching the blockers between the exposing and blocking positions; and a positioning portion for determining the blocking position, the positioning portion being disposed at a position where at least one of the blockers is contacted to the positioning portion when the blockers are switched from the exposing positions to the blocking positions.

Abstract: A bearing, for supporting a rotation shaft of a rotatable member, capable of being supported by a supporting portion provided with an engaging hole engageable with the bearing includes positioning projections having contact surfaces and bearing projections having sliding surfaces on which an outer peripheral surface of the rotation shaft slides. The positioning projections project from different positions so that between adjacent positioning projections, an outer peripheral surface of the bearing and the inner wall surface of the engaging hole form a gap therebetween. The bearing projections project from different positions so that between adjacent bearing projections, an inner peripheral surface of the bearing and an outer peripheral surface of the rotation shaft form a gap therebetween. With respect to a circumferential direction of the rotation shaft, the positioning projections and the bearing projections are provided at positions different from each other.

Abstract: An image forming apparatus includes optical sensor units provided opposed to an image bearing member; light blockers provided between the image bearing member and the optical sensor units, respectively, the blockers being movable between locking and exposing positions, respectively; calibration members provided where the light is incident when the blockers are in the blocking positions, respectively, the calibration members calibrating data acquired by the optical sensor units; a movable link connected with the blockers; a switching portion for switching the blockers between the exposing and blocking positions; and a positioning portion for determining the blocking position, the positioning portion being disposed at a position where at least one of the blockers is contacted to the positioning portion when the blockers are switched from the exposing positions to the blocking positions.

Abstract: An image forming apparatus includes optical sensor units provided opposed to an image bearing member; light blockers provided between the image bearing member and the optical sensor units, respectively, the blockers being movable between locking and exposing positions, respectively; calibration members provided where the light is incident when the blockers are in the blocking positions, respectively, the calibration members calibrating data acquired by the optical sensor units; a movable link connected with the blockers; a switching portion for switching the blockers between the exposing and blocking positions; and a positioning portion for determining the blocking position, the positioning portion being disposed at a position where at least one of the blockers is contacted to the positioning portion when the blockers are switched from the exposing positions to the blocking positions.