Patent ID: 8670698

Claim:
A development device using a developing agent comprising a toner and a carrier, the development device comprising: a development roller that attaches the developing agent to a circumference surface of the development roller and transfers the developing agent to a development region in which the development roller faces a photo receptor; and a regulation portion to regulate an amount of the developing agent transferred to the development region, wherein the regulation portion comprises first, second, and third regulation portions sequentially disposed in the stated order in an opposite direction to a rotational direction of the development roller, the first, second, and third regulation portions are respectively spaced apart from the circumference surface of the development roller by first, second, and third intervals, the second interval is greater than the third interval, and the third interval is narrowed in the rotational direction of the development roller, wherein the first regulation portion forms a first developing agent pressure, the second regulation portion forms a second developing agent pressure that is smaller than the first developing agent pressure, and the third regulation portion forms a third developing agent pressure that is greater than the second developing agent pressure, wherein the second regulation portion forms a circulation space to allow the developing agent blocked by the first regulation portion to be discharged from the regulation portion through the third regulation portion outside the regulation portion, wherein A>B and C>B, where A is an interval between a front end portion of the third regulation portion in the rotational direction of the development roller and the circumference surface of the development roller, B is an interval between a back end portion of the third regulation portion in the rotational direction of the development roller and the circumference surface of the development roller, and C is the second interval, and wherein 2 mm≦A≦8 mm, 0.5 mm≦B≦4 mm, and 1 mm≦C≦7 mm.