A positional relationship between a photosensitive drum and an intermediate transfer belt during a period from the start of the driving of the photosensitive drum to the start of image formation, or during a period of the end of the image formation to the stop of the driving of the photosensitive drum enters a separating state in a case where the image formation is executed when the process speed is a first speed, and enters a contacting state in a case where the image formation is executed when the process speed is a second speed.

An image forming apparatus includes a charging roller and a developing voltage application portion. The charging roller is in contact with a rotating image carrier to charge the image carrier. The developing voltage application portion applies a developing bias voltage including an AC component to a developing roller in a developing portion, when the image carrier is in a rotation state with no image. The rotation state with no image indicates a state in which the charged image carrier rotates with no electrostatic latent image being formed thereon. The developing portion supplies toner containing an external additive to the image carrier.

An image forming apparatus of the present disclosure includes a plurality of image forming portions, an intermediate transfer unit, a secondary transfer member, a belt cleaning device, and a control portion. The intermediate transfer unit includes an intermediate transfer belt, a plurality of primary transfer members, a drive roller, a tension roller, and a contacting/separating mechanism. The belt cleaning device includes a cleaning member which faces the tension roller with the intermediate transfer belt therebetween. In a withdrawal mode, the cleaning member is moved by pressing force of the tension roller further into a housing from an opening portion as compared with in a printing mode. The control portion is capable of executing, while image formation is not being performed, a transfer toner collection mode in which the intermediate transfer belt and the belt cleaning device are driven in the withdrawal mode.

An image forming apparatus includes an image bearing member, a developing member, a controller configured to carry out switching control between a first state in which the developing member is caused to act on the image bearing member and a second state in which the developing member is not caused to act on the image bearing member, a transfer member, and a detector configured to read density information of the recording material. The controller detects a fog density on the basis of a difference in density information between a fog non-occurrence region of a non-image region of the recording material in the second state and a fog occurable region of the non-image region of the recording material in the first state.

An image forming apparatus includes: an image forming unit configured to perform image formation in a first mode, in which image formation is performed by a plurality of image forming stations, or a second mode, in which image formation is performed by a predetermined image forming station among the plurality of image forming stations; and a controller configured to: control the image forming unit to perform a preparation operation in accordance with color mode information; set a restricted operation state in which the controller prohibits the image formation in the first mode and permits the image formation in the second mode when any one image forming station, except for the predetermined image forming station, is incapable of performing image formation; and prevent the image forming unit from performing the preparation operation when the first mode is set as the color mode information and the restricted operation state is set.

An image forming apparatus includes an image bearing member, a developing member, a controller configured to carry out switching control between a first state in which the developing member is caused to act on the image bearing member and a second state in which the developing member is not caused to act on the image bearing member, a transfer member, and a detector configured to read density information of the recording material. The controller detects a fog density on the basis of a difference in density information between a fog non-occurrence region of a non-image region of the recording material in the second state and a fog occurable region of the non-image region of the recording material in the first state.

An image forming apparatus includes an image bearing member, a developing member, a controller configured to carry out switching control between a first state in which the developing member is caused to act on the image bearing member and a second state in which the developing member is not caused to act on the image bearing member, a transfer member, and a detector configured to read density information of the recording material. The controller detects a fog density on the basis of a difference in density information between a fog non-occurrence region of a non-image region of the recording material in the second state and a fog occurable region of the non-image region of the recording material in the first state.

An image forming apparatus includes a motor, an image formation-transfer section, a switching mechanism, a fixing section, and a controller. The motor generates driving force. The image formation-transfer section state-changes between a first contact state and a first separate state by the driving force. The switching mechanism transmits and cuts off the driving force to the image formation-transfer section. The fixing section includes first and second rotating members, and state-changes between a second contact state and a second separate state by the driving force. The controller controls the motor and the switching mechanism and thereby causes part or all of a first period, in which the fixing section state-changes from the second separate state to the second contact state, and part or all of a second period, in which the image formation-transfer section state-changes from the first separate state to the first contact state, to overlap each other.

An image forming apparatus includes an main body, a processing unit, and a pressing member. The main body includes a transfer belt wound around a plurality of rollers. The processing unit can be inserted into and removed from the main body. The processing unit includes a drum that faces the transfer belt in a state of being inserted into the main body. The processing unit forms an image on the surface of the drum. The pressing member is provided on the main body and includes a contacted portion and a contacting portion. The contacted portion comes into contact with the processing unit when the processing unit is inserted into and removed from the main body. The contacting portion comes contact with the transfer belt due to contact with the processing unit to push the transfer belt in a direction away from the processing unit.

An image forming apparatus that has a transfer device that includes an intermediate transfer belt that is tensioned by a plurality of support rollers, a secondary transfer roller that faces one of the support rollers via the intermediate transfer belt, a cam that adjust a pressing force that presses the intermediate transfer belt by the secondary transfer roller, a motor that drives the cam, and a conveyor that conveys a recording medium to a transfer nip formed between the intermediate transfer belt and the secondary transfer roller is provided with a controller that controls an operation of the motor. The controller executes first control of operating the motor with a constant torque and stopping the motor when a rotation angular speed of the motor is less than or equal to a first threshold and second control of operating the motor at a predetermined timing to adjust a transfer nip amount.