Patent ID: 7421233

Claim:
A developing device, comprising: a housing for holding toner, a conveying screw arranged in the housing, and including a rotary shaft and a blade provided on the rotary shaft for conveying the toner from one end of the rotary shaft toward the other end thereof by the rotation of the rotary shaft, and a developing roller provided in the housing in a state where a part of the developing roller being exposed from the housing, and rotatable to obtain the toner conveyed by the conveying screw, wherein a toner pressing force of the blade differs depending on the angle of rotation of the rotary shaft and wherein the blade includes larger blade portions for pressing the toner in a conveying direction and smaller blade portions having a smaller pressing force than the larger blade portions, and wherein the blade has a spiral shape continuous from a position near the one end of the rotary shaft to a position near the other end thereof, the spiral shared blade defining larger blade portions having a larger diameter and smaller blade portions having a smaller diameter than the larger blade portions with the rotary shaft as a center, the smaller blade portions being configured so that a substantially plane surface is defined by connecting a plurality of adjacent smaller blade portions and extends parallel to the rotary shaft from a position near the one end of the rotary shaft to a position near the other end thereof.