An image forming apparatus includes a rotatable image bearing member to bear an electrostatic latent image, a developing container to accommodate developer including toner and to allow new developer to be replenished by a developer replenishing container, and a developer bearing member to develop the electrostatic latent image into a toner image by using the developer in the developing container. A transfer roller transfers the toner image born on the image bearing member onto the recording material, and a controller notifies replenishment information for prompting replenishing the developing container with the new developer by the developer replenishing container. The controller notifies the replenishment information in a state in which an index correlated with a ratio of an amount of paper dust mixed in the developer in the developing container to an amount of the developer in the developing container has not exceeded a preset threshold value of the index.

An image forming apparatus includes a photosensitive drum, a development roller configured to supply developer to the photosensitive drum, a transfer roller configured to transfer a developer image formed on the photosensitive drum to a recording material, and a cleaning roller being in contact with the photosensitive drum, configured to clean a part of the recording material adhered to the photosensitive drum, wherein the diameter of the transfer roller is greater than the diameter of the development roller and the diameter of the cleaning roller is greater than the diameter of the development roller.

A sheet conveyance apparatus includes a conveyance portion including a rotary member, and a counter member, a first contact member, a second contact member, and a contacting and separating mechanism. The contacting and separating mechanism causes the second contact member to separate from the surface of a rotary member of a conveyance portion when the rotary member rotates in the first direction, and causes the second contact member to abut against the surface of the rotary member when the rotary member rotates in a second direction opposite to the first direction.

An image forming apparatus includes a rotatable image bearing member configured to bear an electrostatic latent image, a developing container configured to accommodate developer comprising toner, a developing member configured to develop the electrostatic latent image born on the image bearing member into a toner image by using the developer in the developing container, a transfer member configured to transfer the toner image born on the image bearing member onto the recording material, and a notification portion configured to notify replenishment information for prompting replenishing the developing container with the developer. The notification portion is configured to notify the replenishment information in a state in which an index correlated with a ratio of an amount of paper dust mixed in the developer in the developing container to an amount of the developer in the developing container has not exceeded a preset threshold value of the index.

An image forming apparatus includes a photosensitive member, a charging member, an exposing device, a developing device, a transfer member, a brush, a voltage applying portion, and a control portion controlling a surface potential of the photosensitive member at the brush contacting position. When a value of subtracting a value of the surface potential of the photosensitive member in the brush contacting position from a value of the brush voltage is defined as a contacting position potential difference, the control portion controls the surface potential of the photosensitive member in the brush contacting position so that the contacting position potential difference is changed from a first potential difference to a second potential difference in a predetermined direction which is either one of an increasing direction or a decreasing direction, and then the contacting position potential difference is changed from the second potential difference to a third potential difference in the predetermined direction.

A sheet conveyance apparatus includes a conveyance portion including a rotary member, and a counter member, a first contact member, a second contact member, and a contacting and separating mechanism. The contacting and separating mechanism causes the second contact member to separate from the surface of a rotary member of a conveyance portion when the rotary member rotates in the first direction, and causes the second contact member to abut against the surface of the rotary member when the rotary member rotates in a second direction opposite to the first direction.

A paper dust collecting member removes and collects paper dust attached to a conveying roller, and is attachable along the attaching direction parallel to the axial direction of the conveying roller via an opening portion provided in a side plate of an apparatus main body. The paper dust collecting member has a removing member and a holding member. The removing member removes paper dust attached to the conveying roller. The holding member holds the removing member. The holding member includes a protrusion portion which is disposed, on its distal end portion side, along a side surface of the removing member and which protrudes in the thickness direction of the removing member beyond a contact surface of the removing member.

A paper dust collecting member removes and collects paper dust attached to a conveying roller, and is attachable along the attaching direction parallel to the axial direction of the conveying roller via an opening portion provided in a side plate of an apparatus main body. The paper dust collecting member has a removing member and a holding member. The removing member removes paper dust attached to the conveying roller. The holding member holds the removing member. The holding member includes a protrusion portion which is disposed, on its distal end portion side, along a side surface of the removing member and which protrudes in the thickness direction of the removing member beyond a contact surface of the removing member.

An image forming apparatus includes a paper dust collecting unit which collects, by application of a voltage, paper dust attached to a sheet, an optical detection unit provided on a downstream side of the paper dust collecting unit in a sheet conveyance direction, which irradiates the sheet with light and receives light via the sheet, a guide member which comes into contact with the sheet to be conveyed to guide the sheet, at least one of light directed toward the sheet from the optical detection unit and light directed toward the optical detection unit from the sheet passing through the guide member, and a control unit which switches a polarity of the voltage to be applied to the paper dust collecting unit and causes the sheet charged through the paper dust collecting unit to be conveyed to the guide member.

Provided is an inexpensive image forming apparatus capable of monitoring the generating state of various powders. The image forming apparatus includes a minute-particle-measuring device, a toner-particles-detecting air duct, a paper-dust-detecting air duct, and blower fans. The minute-particle-measuring device detects the concentration of minute particles in air. The toner-particle-detecting air duct is an air duct leading from the image forming unit to the minute-particle-measuring device. The paper-dust-detecting air duct is an air duct leading from the paper-conveying path to the minute-particle-measuring device. The blower fans are respectively provided in the toner-particle-detecting air duct and the paper-dust-detecting air duct, and generate airflow that flows toward the minute-particle-measuring device side. The blower fans in the toner-particle-detecting air duct and in the paper-dust-detecting air duct are switched.