Toner conveyance device including conveyance screw and image forming apparatus

A toner conveyance device comprising:

• a casing having a cylindrical duct extending in a predetermined conveyance direction, and provided with a toner conveyance path in the duct;
• a screw conveying a toner in the toner conveyance path in a predetermined conveyance direction;
• and
• a downstream side bearing rotatably supporting a downstream side end portion of the screw in the conveyance direction, wherein
• the screw includes:
• a shaft extending in the conveyance direction;
• and
• a spiral fin provided around an outer circumferential face of the shaft,
• the shaft has a downstream side insertion part inserted into the downstream side bearing,
• the downstream side insertion part has an outer diameter larger than an outer diameter of a downstream side end portion of the fin in the conveyance direction,
• the duct has a flange protruded radially outward on a downstream side end portion of the duct in the conveyance direction, and
• the flange covers a gap between the downstream side insertion part and the downstream side bearing from an upstream side in the conveyance direction.