Patent ID: 8682216

Claim:
A developing cartridge comprising: a developing roller main body; a developing roller shaft having first and second end portions, which is arranged along a central axis line of the developing roller main body, and which protrudes from both end portions of the developing roller main body along the central axis line, wherein the developing roller shaft comprises: a D-cut part, which has a D-shaped section having a circumferential surface of the D-shaped section partially notched at the first end portion; and a small diameter part, which is located at a side of the first end portion further outward from the D-cut part in the axis line direction, and which has the cylindrical shape having an outer diameter smaller than an outer diameter of a second end portion opposite to the first end portion; a developing gear that is fixed to the D-cut part of the developing roller shaft; and a gear cover, which is configured to cover the developing gear from outward in the axis line direction, and which comprises a cylindrical part through which the small diameter part of the developing roller shaft is inserted.