Patent ID: 8233828

Claim:
A developing apparatus including a developer mixing container in which a developer circulation path along which developer including toner and carrier are mixed and circulated is formed, and a developer holding member to hold the developer mixed on the developer circulation path, the developer mixing container comprising: a first rotation member to supply the developer to the developer holding member and comprising a rotation shaft extending in the same direction as a rotation shaft direction of the developer holding member, a mixing and transfer member having a spiral wing shape on a corresponding rotation shaft to mix and transfer the developer to any one of a lengthwise direction of the rotation shaft, and a circulation auxiliary member having a spiral wing shape formed in a section on a corresponding rotation shaft to transfer the developer to a center portion of the rotation shaft from a downstream side in a developer transfer direction; a second rotation member comprising a rotation shaft extending in the same direction as a rotation shaft direction of the first rotation member and parallel to the first rotation member, a mixing and transfer member having a spiral wing shape on a corresponding rotation shaft to transfer the developer in a direction opposite to the developer transfer direction by the first rotation member, and a circulation auxiliary member having a spiral wing shape formed in a section on a corresponding rotation shaft to transfer the developer to a center portion of the rotation shaft from a downstream side in the developer transfer direction; two end portion partition walls extending from an inner wall of the developer mixing container along the circulation auxiliary member between the first and second rotation members; and a center partition wall formed in a section along the mixing and transfer member at a position separated from the end portion partitions wall between the first and second rotation members, wherein a spiral pitch of the circulation auxiliary member is in a range of about ¼-½ of an outer diameter of the circulation auxiliary member, wherein a section in which the circulation auxiliary member is formed is in a range of about 1.5-3 of the spiral pitch of the circulation auxiliary member, wherein a connection portion through which the developer is circulated is formed as the end portion partition walls and the center partition wall are separated from each other by about 1-1.5 times of the spiral pitch of the mixing and transfer member, and wherein the mixing and transfer member formed on each of the first and second rotation members extends to the downstream side in the developer transfer direction farther than at least a center portion of each of the first and second connection portions.