Developing device and image forming apparatus and process cartridge incorporating same

An image forming apparatus comprising:

• a latent image bearer to bear an electrostatic latent image thereon;
• a charging device to charge a surface of the latent image bearer;
• and
• a developing device including:
• a developer bearer to carry, by rotation, developer including toner and magnetic carrier to a development range facing the latent image bearer, the developer bearer including:
• a magnetic field generator having multiple magnetic poles, and
• a cylindrical developing sleeve to rotate and bear developer on an outer circumferential surface thereof with magnetic force of the magnetic field generator disposed inside the developing sleeve;
• and
• a first voltage application device to apply, to the developer bearer, development voltage including an AC component having a frequency of 2.0 kHz or lower, the AC component in which a duty ratio of a component having a polarity opposite a toner normal charge polarity is within a range from 4% to 20%.