Conveying screw and image forming apparatus

An conveying screw which conveys powder while rotating around an axis, the conveying screw comprising:

• a conveying blade provided spirally along a conveyance direction of the powder;
• and
• a pair of supporting portions provided only at both end portions of the conveying blade in the conveyance direction and not provided in a section of the conveying blade, wherein
• the conveying blade is formed by alternately arranging a plurality of semicircular blade plates on one side and the other side across a rotational center, and connecting the blade plate on one side and the blade plate on the other side which are adjacent to the conveyance direction,
• the blade plate on one side and the blade plate on the other side which are adjacent to the conveyance direction constitute a plurality of pairs of blade plates having reversed inclinations with respect to the conveyance direction,
• a part of the plurality of pairs of blade plates constitutes a large-diameter blade part having a larger outer diameter than the other part of the pairs of blade plates,
• the blade plate on one side and the blade plate on the other side have central conveying portions which convey the powder around the rotational center, and
• a blade surface of the central conveying portion is formed in a recessed shape in a cross-sectional view.