Development device, process cartridge, and image forming apparatus incorporating same

An image forming apparatus comprising:

• a latent image bearer on which a latent image is formed;
• and
• a development device to develop the latent image formed on the latent image bearer, the development device including:
• a developer container for containing two-component developer;
• a developer bearer to carry by rotation the developer contained in the developer container to a development range facing a latent image bearer;
• a partition dividing at least partly the developer container into an upper compartment and a lower compartment arranged vertically;
• an upper developer conveyance member disposed in the upper compartment to transport the developer inside the upper compartment;
• a lower developer conveyance member disposed in the lower compartment to transport the developer inside the lower compartment;
• a communication portion through which the developer moves from the lower compartment to the upper compartment, the communication portion disposed in a downstream end portion of the lower compartment in a direction in which the lower developer conveyance member transports the developer, and
• a toner concentration detector to detect a concentration of toner in the developer beneath the communication portion inside the lower compartment,

A process cartridge removably installable in an image forming apparatus, the process cartridge comprising:

• a latent image bearer on which a latent image is formed;
• and
• a development device to develop the latent image formed on the latent image bearer,
• the development device including:
• a developer container for containing two-component developer;
• a developer bearer to carry by rotation the developer contained in the developer container to a development range facing a latent image bearer;
• a partition dividing at least partly the developer container into an upper compartment and a lower compartment arranged vertically;
• an upper developer conveyance member disposed in the upper compartment to transport the developer inside the upper compartment;
• a lower developer conveyance member disposed in the lower compartment to transport the developer inside the lower compartment;
• a communication portion through which the developer moves from the lower compartment to the upper compartment, the communication portion disposed in a downstream end portion of the lower compartment in a direction in which the lower developer conveyance member transports the developer, and
• a toner concentration detector to detect a concentration of toner in the developer beneath the communication portion inside the lower compartment.