US Patent 7917076 Toner conveying device and image forming apparatus

A toner conveying device includes a pipe body (conveying pipe) having an inside diameter thereof that is modified in a pipe-axis direction and a screw member coaxially located in the pipe body for feeding the toner. The screw member includes a screw shaft that rotates about an axis and a spiral fin that is spirally formed around an outer circumferential surface of the screw shaft. The distance between an outer circumferential surface of the spiral fin and an inner circumferential surface of the pipe body is constant in the longitudinal direction of the pipe body.