A rotatable member for use with a rotatable driving member provided in a process cartridge or an electrophotographic image forming apparatus includes a hollow cylindrical rotation shaft engageable with the rotatable driving member. The rotation shaft includes a seam extending from one end to the other end thereof in an axial direction thereof. The rotation shaft includes a transmitting surface engageable with the driving member and configured to receive a driving force for rotating the rotation shaft about the axial direction. The transmitting surface is twisted or inclined with respect to the axial direction.

An image forming apparatus configured to, in a case where a difference between a charging current flowing through a first charging roller and a charging current flowing through a second charging roller is larger a first threshold value, perform first cleaning processing in which a cleaning ability of one cleaner of a first cleaner and a second cleaner, which corresponds to one of the first charging roller and the second charging roller, is lower than a cleaning ability of another cleaner of the first cleaner and the second cleaner, which corresponds to another of the first charging roller and the second charging roller, a charging current flowing through the one charging roller being larger than a charging current flowing through the other charging roller.

An image forming apparatus includes a photosensitive member having a surface having elastic deformation power of 47% or more, a charging roller forming a nip between itself and the photosensitive member, and an image forming portion. When a nip region corresponding to the nip is formed and then an area of independent contact portions between the charging member and a measuring contact member is measured, the following relationship is satisfied: (contact width X)(Contact area ratio )0.1, where a length from a position of one end to a position of the other end of the nip region with respect to a direction perpendicular to a longitudinal direction of the charging roller is the contact width X, and a ratio of a sum of areas of the independent contact portions to an entire area of a measuring region is the contact area ratio .

A charging roller includes a surface layer containing first and second surface particles and satisfying the following:

6.0 (m)Rz18.8 (m), i)

where Rz is a ten-point average roughness (m) of a charging roller surface,

7 (m)d20 (m), ii)

where d is a thickness (m) of the surface layer,

9.8 (m)D115.8 (m) and 2.8 (m)D25.2 (m), iii)

where D1 and D2 are average particle size (m) of the first surface particles, and the second surface particles, respectively,

3.0D1/D25.6, and iv)

0.10M1/(M1+M2)0.32, v)

where M1 is a total weight (mg) of the first surface particles per unit area of the charging roller surface, and M2 is a total weight (mg) of the second surface particles per unit area of the charging roller surface.

An image forming apparatus includes a photosensitive drum, a charging member, a developing member. The controller controls to perform a preparation operation so that rotation of the photosensitive drum is started in contacting the developing member with the photosensitive drum, and charging and developing voltages are changed stepwise respectively so that a potential difference between a surface potential of the photosensitive drum and the developing voltage becomes a predetermined value. The controller controls to change the charging voltage to a voltage of the same polarity as during the image formation and an absolute value thereof lower than a discharge start voltage from a state of not applying the charging voltage, and then so as to change the charging voltage to a plurality of values of the same polarity as during the image formation and the absolute value thereof equal to or greater than the discharge start voltage.

An image forming apparatus includes an image bearing member, a charging member, a charging voltage source, an electrostatic image forming portion, a developing member, a developing voltage source, a transfer portion, a cleaning member, and a controller. The controller effects control so that a peak-to-peak voltage of an AC component of a charging voltage satisfying the following relationship is applied to the charging member to execute a toner supplying operation: 2Vth (V)Vpp1 (V)(2Vth+200) (V), where a discharge start voltage of a DC component of a charging voltage between the image bearing member and the charging member is Vth (V), and the peak-to-peak voltage of the AC component applied during execution of the toner supplying operation is Vpp1 (V). A peak-to-peak voltage of the AC component applied during image formation is larger than the peak-to-peak voltage Vpp1 (V).

An electrophotographic roller includes an electro-conductive shaft core including a metallic layer at its surface, and an elastic layer on the shaft core. When kinetic friction coefficients of an outer peripheral surface of each end portion of the shaft core with respect to polyester resin are measured for one rotation of the shaft core, an average value r of the kinetic friction coefficients is 0.05 to 0.50. When each outer peripheral surface is divided into three equal ranges, defined as a region A1, a region A2, and a region A3, in a peripheral direction of the shaft core, each of the regions has a location where the kinetic friction coefficients fall within a range of 1.5 r to 1.8 r, and a location where the kinetic friction coefficients fall within a range of 0.2 r to 0.5 r.

An image forming apparatus includes a movable photosensitive member, a charging roller, an electrostatic image forming portion, a developing sleeve, a charging voltage source, a charging voltage conducting path, a developing voltage source, a developing voltage conducting path, and a capacitor electrically connected between an output terminal of the charging voltage source and a ground potential or between the charging voltage conducting path and the ground potential. The capacitor satisfies the following relationship: {C1/(C1+C2)}Vpp5 (V), where C1 (pF) is electrostatic capacity formed by the first and second conducting paths, C2 (pF) is electrostatic capacity of the capacitor, and Vpp (V) is a peak-to-peak voltage of the AC component of the developing voltage.

An electrophotographic imaging device includes a charging device, a cleaning device, and a fuser member that each include hydrophobic carbon nanotubes. The use of hydrophobic carbon nanotubes can increases the charging device's, the cleaning device's, and the fuser member's durability, conductivity, and contaminants deposition.

A rotatable member for use with a rotatable driving member provided in a process cartridge or an electrophotographic image forming apparatus includes a hollow cylindrical rotation shaft engageable with the rotatable driving member. The rotation shaft includes a seam extending from one end to the other end thereof in an axial direction thereof. The rotation shaft includes a transmitting surface engageable with the driving member and configured to receive a driving force for rotating the rotation shaft about the axial direction. The transmitting surface is twisted or inclined with respect to the axial direction.