Image forming apparatus and developing device

An image forming apparatus for developing an electrostatic latent image on an image carrier with use of a two-component developer including carriers and toner, the image forming apparatus comprising:

• a developing device having (i) a conveyance path in which the two-component developer is conveyed and (ii) an outlet from which the two-component developer is partially discharged while the two-component developer is conveyed;
• a hopper to which (i) a first cartridge containing a first developer including carriers and (ii) a second cartridge containing a second developer including toner and not carriers are attachable, and operable, when the first cartridge is attached thereto, to supply the first developer to the developing device, and when the second cartridge is attached thereto, to supply the second developer to the developing device;
• and
• a switching part operable, when the first developer is supplied, to switch the developing device to a first state by opening the outlet, the first state being a state in which the two-component developer is partially discharged from the outlet, and when the second developer is supplied, to switch the developing device to a second state by closing the outlet, the second state being a state in which the two-component developer is not discharged from the outlet, wherein
• the conveyance path is a circulation conveyance path in which the two-component developer is circularly conveyed, and includes:
• a first conveyance path that is linear and in which the two-component developer is conveyed in a first conveyance direction;
• a second conveyance path that is arranged parallel to the first conveyance path, and in which the two-component developer is conveyed in a second conveyance direction opposite the first conveyance direction;
• a first communication path for communicating a first portion of the first conveyance path located downstream in the first conveyance direction, with a first portion of the second conveyance path located upstream in the second conveyance direction;
• a second communication path for communicating a second portion of the second conveyance path located downstream in the second conveyance direction, with a second portion of the first conveyance path located upstream in the first developer conveyance path;
• and
• a third communication path for communicating a third portion of the first conveyance path with a third portion of the second conveyance path, the third portion of the first conveyance path located more upstream in the first conveyance direction than the first portion thereof, the third portion of the second conveyance path located more downstream in the second conveyance direction than the first portion thereof,
• the outlet is arranged in any of the following portions:
• (i) a portion of the first conveyance path located more downstream in the first conveyance direction than the third portion of the first conveyance path;
• (ii) the first communication path;
• and (iii) a portion of the second conveyance path located more upstream in the second conveyance direction than the third portion of the second conveyance path, and
• the switching part closes the third communication path when opening the outlet, and opens the third communication path when closing the outlet.