A charging device includes a first charging unit and a second charging unit. The first charging unit electrostatically charges a surface of an image bearing member that comes into contact with a medium onto which an image is to be ultimately transferred. The first charging unit is disposed in correspondence with an entire region of the image bearing member in a first scanning direction. The second charging unit is disposed in an overlapping region where a non-passing region of a small-width medium and a passing region of a maximum-usable-width medium overlap when viewed in the first scanning direction. The small-width medium has a width smaller than a maximum usable width of the maximum-usable-width medium. The second charging unit electrostatically charges the overlapping region.

A method of electro-photographic printing includes applying a background voltage to a photo imaging plate using a charge roller that moves relative to the photo imaging plate, and varying the applied background voltage as the roller moves relative to the photo imaging plate, wherein the background voltage is varied in a region of the photo imaging plate where no ink is to be transferred.

According to one embodiment, a charger charges a surface of an image carrier by discharge in a wide-angle. A charging bias voltage application section applies a charging bias voltage to the charger. An exposing device forms an electrostatic latent image in a charged image carrier. A toner carrier causes toner to adhere to the electrostatic latent image formed in the image carrier. A developing bias voltage application section applies the developing bias voltage to the toner carrier. In addition, the developing bias voltage application section changes the charging bias voltage in one step and changes the developing bias voltage applied to the toner carrier in multiple steps.

A cartridge includes a photosensitive member, a roller including a core metal shaft and a coating layer, roller supporting portions, and a regulating portion for regulating a position of the roller with respect to a longitudinal direction of the roller. The roller supporting portions are provided so as to support one end portion and the other end potion of the core metal shaft, respectively, with respect to a direction of a rotational axis of the roller. The roller is further provided with cylindrical holes disposed at respective ends of the core metal shaft with respect to the direction of the rotational axis and extending in the direction of the rotational axis with the rotational axis as a center. The roller is supported by the roller supporting portions at inner peripheral surfaces of the holes.

According to one embodiment, a charger charges a surface of an image carrier by discharge in a wide-angle. A charging bias voltage application section applies a charging bias voltage to the charger. An exposing device forms an electrostatic latent image in a charged image carrier. A toner carrier causes toner to adhere to the electrostatic latent image formed in the image carrier. A developing bias voltage application section applies the developing bias voltage to the toner carrier. In addition, the developing bias voltage application section changes the charging bias voltage in one step and changes the developing bias voltage applied to the toner carrier in multiple steps.

An image forming apparatus includes: a first photoconductor and a second photoconductor; an image carrier onto which a toner image formed on the first photoconductor and a toner image formed on the second photoconductor are transferred; and a controller that, when the toner image formed on the first photoconductor is transferred onto the image carrier, rotates the second photoconductor while keeping the second photoconductor spaced apart from the image carrier.

At least one partial measurement region is set in the longitudinal direction in a printable region of a photosensitive drum. After the photosensitive drum has been charged to a constant potential with a charging roller, different potentials are set in the partial measurement region and a region excluding the partial measurement region with a laser scanner, partial discharge information of the partial measurement region is detected by a discharge information detection unit, and a bias voltage in image formation that is applied to the charging roller is corrected on the basis of the value of the partial discharge information.

An image forming apparatus includes: a photosensitive member; a charger that charges a surface of the photosensitive member; an exposure device that forms a latent image; and a developing device that applies toner to the latent image, wherein the photosensitive member is incorporated in a detachable photosensitive member unit, and the developing device is incorporated in a detachable developing unit, the image forming apparatus including: an optimization controller that performs optimization of a charging bias of the charger and a developing bias of the developing device; and a replacement determiner that determines which of the photosensitive member unit and the developing unit is to be replaced when an optimized developing bias is out of a predetermined allowable range, wherein the replacement determiner determines that the developing unit is to be replaced, and determines that the photosensitive member unit is to be replaced.

An image forming apparatus includes: a photosensitive member; a charger that charges a surface of the photosensitive member; an exposure device that forms a latent image; and a developing device that applies toner to the latent image, wherein the photosensitive member is incorporated in a detachable photosensitive member unit, and the developing device is incorporated in a detachable developing unit, the image forming apparatus including: an optimization controller that performs optimization of a charging bias of the charger and a developing bias of the developing device; and a replacement determiner that determines which of the photosensitive member unit and the developing unit is to be replaced when an optimized developing bias is out of a predetermined allowable range, wherein the replacement determiner determines that the developing unit is to be replaced, and determines that the photosensitive member unit is to be replaced.

A method of electro-photographic printing comprises applying a background voltage to a photo imaging plate using a charge roller that moves relative to the photo imaging plate, and varying the applied background voltage as the roller moves relative to the photo imaging plate, wherein the background voltage is varied in a region of the photo imaging plate where no ink is to be transferred.