Asymmetric Charging Roller Axis for Uniform Nip Width

The patent positions the central axis of the photosensitive drum at a location that does not overlap with the central axis line passing through the charging roller and cleaning roller. This asymmetric arrangement ensures that the biasing force is distributed more uniformly along the charging roller shaft, preventing distortion and maintaining consistent nip width across the roller width while still applying sufficient charging pressure.

By positioning the photosensitive drum's central axis non-coincident with the charging roller's central axis line, the patent creates an asymmetric configuration that distributes the contact force more evenly across the roller shaft. This prevents the shaft distortion that would otherwise cause variations in distance and electric potential, ensuring reliable and consistent charging across the entire drum surface.

The patent deliberately adopts an asymmetric configuration where the central axis of the photosensitive drum does not overlap with the central axis line of the charging roller. While this increases structural complexity slightly, it effectively distributes the mechanical load and prevents shaft distortion, thereby achieving uniform charging across the drum surface.

The asymmetric positioning of the photosensitive drum relative to the charging roller creates a more favorable load distribution pattern. This prevents the shaft from distorting under contact pressure, thereby maintaining consistent nip width across the roller width while still ensuring adequate contact pressure for effective charging.