Charging system, process cartridge and image forming apparatus

摘要

An image forming apparatus has an image bearing member; and a charging member forming a nip with the image bearing member to charge the image bearing member. Conductive particles are provided in the nip and a time factor alpha represented by a following equation satisfies a condition alpha>15:in which rho (Omega) represents a surface resistivity of said image bearing member; Cd (F/mm<2>) represents an electrostatic capacitance of the image bearing member; D (mm) represents a diameter of the conductive particle; Nc (particle/mm<2>) represents a density of the conductive particles present on the charging member; Vc (mm/sec) represents a surface moving speed of the charging member; Vd (mm/sec) represents a surface moving speed of the image bearing member; k=Vc/Vd; and W (mm) represents a width of the nip in the moving direction of the image bearing member.