Developer Supply Device and Image Forming Apparatus Having the Same

An image forming apparatus comprising:

• a photoconductive body configured to form a developer image thereon;
• and
• a development agent supply device configured to supply charged development agent to the photoconductive body,
• wherein the development agent supply device comprises:
• a developer carrying body comprising a developer carrying surface that is configured to carry the development agent thereon, formed as a cylindrical circumferential surface parallel to a first direction, and disposed to face the photoconductive body in a first position where the development agent held on the developer carrying surface is supplied to the photoconductive body,
• wherein the developer carrying body is configured to rotate around an axis parallel to the first direction such that the developer carrying surface moves in a second direction perpendicular to the first direction;
• a casing comprising:
• an opening opened toward the photoconductive body;
• and
• a developer storage section configured to store the development agent therein,
• wherein the casing is configured to rotatably support the developer carrying body near the opening;
• a first transfer board housed in the casing so as to face the developer carrying surface in a second position, the second position, where the developer carrying surface faces an inside of the casing, being located upstream relative to the first position in the second direction,
• wherein the first transfer board is configured to transfer the development agent from the developer storage section to the second position with a traveling-wave electric field generated when a multi-phase alternating-current voltage is applied to the first transfer board, such that the development agent is supplied onto the developer carrying surface in the second position, and transfer the development agent in a direction opposite to the second direction in the second position;
• an electrification member disposed to face the developer carrying surface in a third position that is located downstream relative to the second position and upstream relative to the first position in the second direction,
• wherein the electrification member is configured to further charge the development agent supplied onto the developer carrying surface in the third position with an alternating electric field generated between the developer carrying body and the electrification member;
• and
• a second transfer board that is supported by an inner wall surface of the casing so as to face the developer carrying surface in a fourth position that is located downstream relative to the first position and upstream relative to the second position in the second direction,
• wherein the second transfer board is configured to transfer the development agent to the developer storage section in a direction identical to the second direction in the fourth position, with a traveling-wave electric field generated when a multi-phase alternating-current voltage is applied to the second transfer board.