A charging device for electrically charging a rotatable image bearing member includes a corona charger including a discharging wire, a rotatable rotation shaft provided along the discharging wire and provided with a helical groove on an outer peripheral surface thereof, a motor configured to rotate the rotation shaft, and a movable member including a projected portion engaging with the helical groove and mounted on the rotation shaft so as to be movable along the rotation shaft with rotation of the rotation shaft. In addition, a cleaning member is provided on the movable member to clean the discharging wire, and a brush member is provided on the movable member and configured to brush the helical groove.

A cleaning roller comprises a shaft including a rotational axis extending in an axial direction and an elastic layer covering the shaft. The elastic layer includes a base covering the shaft and a first helical protrusion protruding from the base and having a first helical ridge.

A cleaning roller includes a shaft and an elastic body. The shaft extends in an axial direction where a center axis of the shaft extends. The shaft defines a radial direction and has a circumferential surface. The elastic body is helically wound about the shaft and defines a helical direction. The elastic body has a widthwise dimension in a widthwise direction orthogonal to the helical direction and to the radial direction. The elastic body has a base end portion extending in the helical direction and a distal end portion extending in the helical direction. The base end portion is in contact with the circumferential surface and fixed thereto. The distal end portion has a sharp edge and is positioned farthest from the circumferential surface in the radial direction. The widthwise dimension is gradually reduced from the base end portion to the distal end portion in the radial direction.

An electrifier cleaning mechanism includes a cleaning member which makes contact with part of a long discharge member, a ball screw arranged in parallel with a longitudinal direction of the discharge member and rotatably supported, a drive source which rotates the ball screw in both of forward and reverse directions, a holding member which holds the cleaning member and has a screw hole in which a screw part of the ball screw is screwed, and rotation of which in a circumferential direction of the ball screw is regulated, and a pressing member which presses the holding member from a first end side of the discharge member toward a second end side thereof in the longitudinal direction.

An image carrier unit includes an image carrier, a charging device including a charging member, a cleaning member, a pair of bearing members rotatably supporting the charging member and the cleaning member, a biasing member biasing the bearing members in an approaching direction to the image carrier, and a charging housing holding the charging member and the cleaning member, and a pair of separation members. The bearing members each include a first bearing portion supporting a first rotary shaft of the charging member, a second bearing portion supporting a second rotary shaft of the cleaning member, and an engaged portion. The first bearing portion has an elongated hole shape having a greater inner diameter in an approach/separation direction. The separation members are each inserted between the charging housing and the engaged portion, thus causing the bearing members to move in such a direction as to separate from the image carrier.

An image forming apparatus includes a photosensitive member, a charging member for charging the photosensitive member, a cleaning member that comes into contact with the charging member and moves relative to the charging member to clean the charging member, an opening/closing member for exposing an inside of the apparatus, and a driving mechanism that moves the charging member and the cleaning member relative to each other in association with opening/closing of the opening/closing member.

An image forming apparatus includes a photosensitive member, a charging member, electrostatic image forming portion, a developing member, a transfer member, a transfer voltage source, a brush member, a brush voltage source, and a controller capable of executing a cleaning operation. The controller carries out control so that the cleaning operation includes a first operation in which a potential difference is formed between the transfer member and the photosensitive member so that toner charged to a normal charge polarity is moved from the transfer member toward the photosensitive member, and a second operation in which a potential difference is formed between the brush member and the photosensitive member so that the toner charged to the normal charge polarity is moved from the photosensitive member toward the brush member.

A process unit includes: a photosensitive drum on a surface of which a toner image is formed; a charging roller being pressed against the photosensitive drum so as to charge the photosensitive drum; a cleaning roller being pressed against the charging roller so as to clean the charging roller; and at least one biasing member biasing the charging roller or the cleaning roller. A central axis of the photosensitive drum is located at a position not overlapping with a central axis line passing through a central axis of the charging roller and a central axis of the cleaning roller. A biasing direction of the at least one biasing member is on a same line as the central axis line.

A photosensitive member unit includes a photosensitive member, a charging roller, a charging roller bearing member, a gear, a separation member having an engagement portion, a guide portion, and a frame to support the photosensitive member. The guide portion guides the charging roller bearing member urged by a urging member to separate the charging roller from the photosensitive member in a state where the engagement portion and the gear are engaged with each other and guides the charging roller bearing member urged by the urging member so that the charging roller comes into contact with the photosensitive member in a state where the engagement portion and the gear are not engaged. A distance between the urged charging roller bearing member and the frame is less than a length in which the engagement portion and the gear are engaged in the state where the engagement portion and the gear are engaged.

An image carrier unit includes an image carrier including a cylindrical main body portion and a pair of flange portions attached to both ends of the main body portion, a first cleaning member that rotates in contact under a prescribed pressure with an outer circumferential surface of the main body portion, a unit frame that rotatably supports the image carrier and the first cleaning member, and an image carrier protective cover that includes a cover main body extending in an axial direction of the image carrier and a side surface portion that is disposed on one end side of the cover main body. On the side surface portion, an image carrier holding portion is formed that performs positioning of the image carrier with respect to the unit frame and releases a pressure contact state between the image carrier and the first cleaning member.