Patent attributes
A development apparatus is provided that can quickly form high quality printing material by steadily supplying developer charged and thinned to a uniform thickness and can also prevent the decrease in the quality of the printing material in a case where the developer carrier and developer supply unit are operated quickly. The toner supply roller is constructed in a manner using the elastic material with a hardness of HAF [degree] set to 20≦HAF≦80 measured by an Asker F-type and disposed in a manner such that the amount of push δ, defined as the amount pushed by the contact between the developer supply unit and the developer carrier, is 0.5 [mm] or below. In addition, toner supply bias voltage VS [V] applied to the toner supply roller has a frequency f [Hz] of 500≦f≦5000, and, with VSH and VSL as the peak values of the AC voltage component, fulfill the condition of 1≦|VSH−VD|/|VD−VSL≦5.
