Developing device, process cartridge, and image forming apparatus

A developing device comprising:

• a developer bearer;
• a first conveying screw disposed in a first conveyance path and facing the developer bearer, the first conveying screw to convey developer from one end of the first conveyance path to another end of the first conveyance path in a first direction along an axial direction of the first conveying screw;
• a partition;
• and
• a second conveying screw disposed in a second conveyance path and facing the first conveying screw via the partition, the second conveying screw to convey the developer from one end of the second conveyance path to another end of the second conveyance path in a second direction opposite to the first direction along an axial direction of the second conveying screw,
• wherein the partition has:
• a first communication port communicating the one end of the first conveyance path and the another end of the second conveyance path;
• and
• a second communication port communicating the another end of the first conveyance path and the one end of the second conveyance path,
• the first conveying screw includes:
• a first shaft;
• a first screw portion wound around the first shaft;
• a first portion having a first shaft diameter, the first portion ranged from one end of the first conveying screw, corresponding to the one end of the first conveyance path, to a position away from the first communication port toward a center of the first conveying screw by a first predetermined distance in the axial direction of the first conveying screw;
• and
• a first adjacent portion adjacent to the first portion, the first adjacent portion having a second shaft diameter larger than the first shaft diameter;
• and
• the second conveying screw includes:
• a second shaft;
• a second screw portion wound around the second shaft;
• a second portion having a third shaft diameter, the second portion ranged from another end of the second conveying screw, corresponding to the another end of the second conveyance path, to a position away from the first communication port toward a center of the second conveying screw by a second predetermined distance in the axial direction of the second conveying screw;
• and
• a second adjacent portion adjacent to the second portion, the second adjacent portion having a fourth shaft diameter smaller than the third shaft diameter.