A charging device for electrically charging 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, 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, a cleaning member provided on the movable member and configured to clean the discharging wire, and a brush member provided on the movable member and configured to brush the helical groove.

An image forming apparatus includes a belt unit including an endless belt, a supporting unit and a steering unit, and further includes a cleaning unit, a receiving opening and a communicating portion. The communicating portion includes a tube-shaped portion constituted by a bellows-shaped elastic member capable of expansion and contraction with movement of the steering unit.

A rotary-body support structure includes: a rotary body including a rotary shaft and a contact portion spirally wound around the rotary shaft; and bearing parts that rotatably support the rotary body. The amount of engagement of the rotary body with a contact body that is in contact with the contact portion of the rotary body changes when the rotary body moves toward one side in a rotation axis direction.

An image forming apparatus includes a photosensitive drum, a charging roller, a transfer roller, and a control circuit. The control circuit is configured to perform an alternating bias control. During the alternating bias control, the control circuit causes the charging roller and the transfer roller to rotate in accordance with a rotation of the photosensitive drum, and controls the charging roller to alternately turn off and on to a first bias of a predetermined polarity and the transfer roller to alternately turn off and on to a second bias of the predetermined polarity, such that at least a part of a region of the photosensitive drum biased by the first bias is not biased by the second bias, and that at least a part of a region of the photosensitive drum biased by the second bias is not biased by the first bias.

An image forming apparatus includes: a photosensitive drum; a magnetic roller; a transfer belt; a drum cleaning roller for collecting toner on the photosensitive drum and discharging collected toner to the photosensitive drum; a belt cleaner; a waste toner accommodating unit; and a controller configured to perform a printing operation for forming an image on a sheet and a cleaning operation for cleaning the drum cleaning roller. The controller is configured to perform: when performing the printing operation, collecting toner on the photosensitive drum using the drum cleaning roller; and when performing the cleaning operation, discharging the toner on the drum cleaning roller collected in the collecting to the photosensitive drum; transferring the toner on the photosensitive drum onto the transfer belt; and collecting the toner on the transfer belt using the belt cleaner so that the collected toner is accommodated in the waste toner accommodating unit.

An image forming apparatus includes a developing cartridge, a drum cartridge, a casing, a connector, and a controller. The drum cartridge includes a photosensitive drum, a drum cartridge memory, a charger, and a cleaner. The charger is configured to charge the photosensitive drum and including a wire and a grid electrode. The cleaner is configured to clean the wire. The connector is configured to be electrically connected to the drum cartridge memory. Information is writable to the drum memory through the connector. The detection circuit board is configured to detect a state of discharge of the charger. The controller is configured to perform: determining whether or not the state of discharge detected by the detection circuit board is abnormal; and writing, in the drum cartridge memory, information representing occurrence of the abnormal discharge through the connector in a case where occurrence of the abnormal discharge is determined.

An image forming apparatus includes an image holding unit that holds an image that is formed of a developer, the image being intended to be transferred onto a medium, and an image that is not intended to be transferred onto a medium, a transfer unit that transfers the image that is intended to be transferred onto a medium onto a medium, a removing unit that removes the image that is not intended to be transferred onto a medium from the image holding unit, and a forming unit that forms the image that is not intended to be transferred onto a medium onto the image holding unit by using a developer and that has a first forming mode for a first medium and a second forming mode for a second medium that has a transfer sensitivity lower than a transfer sensitivity of the first medium, the forming unit being configured to use a larger amount of the developer in formation of the image that is not intended to be transferred onto a medium in the first forming mode than in the second forming mode.

In an image forming apparatus, in a case in which a second toner image to be transferred to a same recording material as a first toner image is to be transferred is formed on the photosensitive member after the first toner image is formed on the photosensitive member and the first toner image is formed on an area of the photosensitive member including at least a part of a position of the second toner image one cycle before with respect to a movement direction of the surface of the photosensitive member, a control unit changes a value of a transfer current at a time of transferring the first toner image to a transfer-receiving member between a first value and a second value of which an absolute value is greater than an absolute value of the first value, based on image information regarding the second toner image.

A rotary-body support structure includes: a rotary body including a rotary shaft and a contact portion spirally wound around the rotary shaft; and bearing parts that rotatably support the rotary body. The amount of engagement of the rotary body with a contact body that is in contact with the contact portion of the rotary body changes when the rotary body moves toward one side in a rotation axis direction.

A bearing component for rotatably receiving a rotating shaft on an end of a rotating unit includes a component body, an inner protrusion, and one or more outer protrusions. The component body has a recess into which the rotating shaft is rotatably inserted. The inner protrusion protrudes from a wall portion of the recess facing an end surface of the rotating shaft. The inner protrusion receives an axial load by the rotating shaft. The outer protrusions protrude from an outer surface of the component body opposite to the recess. The one or more outer protrusions are in contact with a holding unit. A contact portion between the outer protrusions and the holding unit is offset from a contact portion position between the inner protrusion and the end surface. The contact portion between at least one of the outer protrusions and the holding unit has a non-planar shape.