Patent ID: 8824932

Claim:
A development device to develop a latent image formed on a latent image carrier with two-component developer consisting essentially of toner and carrier, the development device comprising: a casing; a developer container housed in the casing, for containing the developer; a hollow, cylindrical nonmagnetic developer carrier rotatably disposed within the casing, to transport the developer while rotating, the developer carrier exposed partly through an opening of the casing and facing the latent image carrier in a development area; a magnetic field generator disposed inside the developer carrier, having multiple magnetic poles including an attraction pole to attract the developer from the developer container to the developer carrier, a developer conveyance pole to keep the developer on the developer carrier downstream from the development area in a direction in which the developer carrier rotates to a developer release portion, and a release pole to separate the developer from the developer carrier and to return the developer to the developer container; a developer agitator disposed in the developer container, to agitate the developer while transporting the developer in an axial direction of the developer carrier; and a developer regulator housed in the casing, to adjust a layer thickness of the developer carried on the developer carrier, wherein a predetermined gap is kept between an outer circumferential surface of the developer carrier at a position inside which the developer conveyance pole is disposed and an inner wall of the casing at a portion downstream from the opening formed in the casing and upstream from the developer release portion in the direction in which the developer carrier rotates, multiple recesses are formed in the outer circumferential surface of the developer carrier at intervals, and a pitch between adjacent recesses in a circumferential direction of the developer carrier is shorter than half a width of a magnetic flux density of the developer conveyance pole in a direction perpendicular to an axial direction of the developer carrier, wherein the development device is removably installable in an image forming apparatus in a direction parallel to the axial direction of the developer carrier, and wherein each of the multiple recesses formed in the outer circumferential surface of the developer carrier is oval-shaped and is positioned with its long axis oblique to the axial direction of the developer carrier, and in the direction in which the development device is installable in the image forming apparatus, a back end portion of the recess is positioned upstream in the direction in which the developer carrier rotates and a front end portion of the recess is positioned downstream in the direction in which the developer carrier rotates.