Patent ID: 7801466

Claim:
A developing device, comprising: a container that contains developer including toner and carrier, and includes a first opening and a second opening; a developer carrier that is rotatably supported to face an image carrier via the first opening of the container, and carries the developer; a stirring and transferring unit that is located in the container to mix and stir the toner and the carrier, and circulates the developer in the container, the stirring and transferring unit including a rotation shaft and a screw blade extending from the rotation shaft; a replenishing unit that replenishes the container with developer from the second opening; a discharging mechanism that discharges surplus developer out of the container, and is located on a shaft end of the rotation shaft of the stirring and transferring unit, the shaft end of the rotation shaft of the stirring and transferring unit including a collection port to collect the developer in the container, a discharge port positioned outside of the container to discharge the developer that is collected in the rotation shaft, and a hollow portion inside the shaft end and extending from the collection port to the discharge port to transport the developer from the collection port to the discharge port, and the hollow portion is tapered such that a diameter of the hollow portion at the discharge port is larger than a diameter of the hollow portion at the collection port; and a bearing that is disposed between the collection port and the discharge port.