An image forming apparatus includes a photosensitive drum, first and second charging members, a development member, and first and second charging voltage applying units. The photosensitive drum includes a surface layer constituting a surface of the photosensitive drum. The second charging voltage applying unit applies a second charging voltage to the second charging member. The surface layer of the photosensitive drum has a volume resistivity of 1.0?109 ohm centimeters (?.Math.cm) or more and 1.0?1014 ?.Math.cm or less. The second charging voltage applying unit applies the second charging voltage such that a second potential difference formed between the second charging member and the surface of the photosensitive drum charged by the first charging member is equal to or higher than a discharge starting voltage.

In one example, a method for calibrating a position of a charge roller is described. The method may include a processor positioning a first end of a charge roller to a first plurality of index positions, determining a capacitance between the charge roller and a photoconductor imaging plate at each of the first plurality of index positions, determining a first index position of the first plurality of index positions with a greatest change in capacitance, and calibrating a position of the charge roller based upon the first index position.

An image forming apparatus includes at least one photoconductor unit including a charging roller and a photoconductor. A charging bias obtained by superimposing an AC voltage on a DC voltage is applied to the charging roller. The photoconductor is disposed opposite the charging roller across a gap. An electrostatic latent image is formed on the photoconductor based on image data. The image forming apparatus further includes a high-voltage power supply to generate an output feedback voltage, a control unit as circuitry to control the high-voltage power supply based on the output feedback voltage and refer to first data to calculate the gap value corresponding to the voltage indicated by the output feedback voltage. The first data indicates a relation between the voltage indicated by the output feedback voltage and a gap value indicating a size of the gap.

In one example, a device includes a flexible roller and an actuator to flex the roller while it is rotating to change the gap between the roller and a surface opposite the roller.

In one example, a method for calibrating a position of a charge roller is described. The method may include a processor positioning a first end of a charge roller to a first plurality of index positions, determining a capacitance between the charge roller and a photoconductor imaging plate at each of the first plurality of index positions, determining a first index position of the first plurality of index positions with a greatest change in capacitance, and calibrating a position of the charge roller based upon the first index position.

An image forming apparatus includes a plurality of image forming portions, an intermediate transfer belt, a primary transfer member, a secondary transfer roller, a counter roller, and a charge eliminating device. The counter roller is pressed against the secondary transfer roller via an intermediate transfer belt to thereby form a secondary transfer nip portion. The charge eliminating device includes a charge eliminating needle that is disposed with an end part thereof pointing to a downstream side in a conveyance direction of the recording medium, and that is grounded, and a charge eliminating needle protection cover that has a guide surface that is opposed to the recording medium having passed through the secondary transfer nip portion, and that maintains a constant interval between the recording medium and the charge eliminating needle, and eliminates residual charge on the recording medium having passed through the secondary transfer nip portion.

A cartridge includes a first maintaining member and a second maintaining member, each disposed on respective end portions of a charging roller in an axial direction of the charging roller and configured to maintain a position of the charging roller at a first position, and a first moving portion and a second moving portion, each disposed on respective end portions of an image bearing member in an axial direction of the image bearing member and configured to respectively abut on and move the first and second maintaining members according to rotation of the image bearing member so as to move the charging roller from the first position to the second position. When the image bearing member is rotated in which the charging roller is in the first position, the first moving portion abuts on the first maintaining member, and then the second moving portion abuts on the second maintaining member.

In examples provided herein, a roller damper comprises a damper body element having mass and having a shape to fit an interior of a tubular roller element. The roller element is associated with a natural frequency. The roller damper also comprises an elastomer support member coupled to the damper body element. The mass of the damper body element and the elastomer support member are selected based on the natural frequency of the tubular roller element.

In one example, a method for calibrating a position of a charge roller is described. The method may include a processor positioning a first end of a charge roller to a first plurality of index positions, determining a capacitance between the charge roller and a photoconductor imaging plate at each of the first plurality of index positions, determining a first index position of the first plurality of index positions with a greatest change in capacitance, and calibrating a position of the charge roller based upon the first index position.

A process cartridge includes an electrophotographic photosensitive member and a gap retaining member, where the electrophotographic photosensitive member includes a first region having an undercoat layer, a charge generating layer, and a charge transporting layer on a support in this order and a second region having an undercoat layer and a charge transporting layer on a support in this order, the undercoat layer contains a metal oxide particle and any one of an urethane resin, an amino resin, and a polyamide resin as a binder resin, and the charge transporting layer contains a charge transporting substance and at least one selected from the group consisting of a polycarbonate resin and a polyester resin, and where the gap retaining member comes into contact with a surface of the second region of the electrophotographic photosensitive member.