Developing device and image forming apparatus including the same

An image forming apparatus comprising:

• a photosensitive drum including an outer circumferential surface of which an electrostatic latent image is formed;
• and
• a developing device that develops the electrostatic latent image formed on the photosensitive drum,
• wherein the developing device comprises:
• an agitating and conveying unit that receives a developer formed of carrier and toner, and includes at least one agitating and conveying member to mix and agitate the developer and convey the developer in a developer conveying direction;
• and
• a developing roller that is installed facing a photosensitive drum to receive an electrostatic latent image is formed thereon, and that attaches the developer mixed and agitated by the agitating and conveying unit to an outer circumferential surface of the developing roller and that supplies the developer to the photosensitive drum,
• wherein the agitating and conveying member comprises:
• a support shaft that extends in the developer conveying direction and is rotatably coupled to the developing device;
• a plurality of agitation wings that are disposed on an outer circumferential surface of the support shaft to define a pitch between adjacent agitation wings and to mix and agitate the developer and to convey the developer along the developer conveying direction;
• and
• at least one paddle which protrudes in a radial direction from the support shaft and extends along a direction of the support shaft in the pitch and has an upstream-most end having a first height and a downstream-most end having a second height such that the second height increases from the first height in a non-linear manner.

An agitating and conveying unit to convey developer stored in a developing unit in a conveying direction, comprising:

• a first support shaft extending along the conveying direction;
• a second support shaft disposed adjacent the first support shaft and extending parallel to the first support shaft in the conveying direction;
• a partition disposed between the first and second support shafts to define first and second developer passages between the developing unit and the partition;
• a plurality of first wings disposed on the first shaft each being inclined in a first direction and having a first pitch to define a space between adjacent agitation wings;
• and
• a plurality of second wings disposed on the second shaft each being inclined in a second direction opposite the first direction of the first wings and having a second pitch to define a space between adjacent agitation wings,
• at least one paddle that protrudes in a radial direction from at least one of the first and second support shafts and extends along a direction of the at least one of the first and second support shafts in at least one of the first and second pitch and has an upstream-most end having a first height and a downstream-most end having a second height such that the second height increases from the first height in a non-linear manner.