DEVELOPING DEVICE AND IMAGE FORMING APPARATUS INCLUDING THE SAME

• Main Authors: NAKAMURA HITOSHI, HAMAGUCHI MASAYA
• Format: Patent
• Language: English; Japanese
• Published: 01.10.2015
• Subjects: CINEMATOGRAPHY; ELECTROGRAPHY; ELECTROPHOTOGRAPHY; HOLOGRAPHY; MAGNETOGRAPHY; PHOTOGRAPHY; PHYSICS

PROBLEM TO BE SOLVED: To provide a developing device that can give an image with good graininess while suppressing occurrence of base contamination, and an image forming apparatus including the developing device.SOLUTION: A developing device 4 includes a developing roller 42A as a developer carrier that travels and carries a two-component developer comprising a toner and a carrier on its travelling surface and that is disposed to oppose to a photoreceptor 2 as a latent image carrier. The developing device includes a picture quality improving roller 42B as a downstream counter member that is disposed to oppose to the photoreceptor 2 at a downstream side along a surface traveling direction of the photoreceptor 2 with respect to the developing region where the developing roller 42A opposes to the photoreceptor 2, and that travels and carries a two-component developer having sufficiently low toner concentration compared to the two-component developer carried on the surface of the developing roller 42A or carries only a carrier on its travelling surface. The developing device also includes a power supply unit as AC voltage application means to apply a voltage including an AC component such as an alternating voltage to the picture quality improving roller 42B. 【課題】地汚れの発生を抑制しつつ粒状性も良好な画像を得ることができる現像装置及びこれを備えた画像形成装置を提供する。【解決手段】トナーとキャリアとを含む二成分現像剤を表面に担持して表面移動し、潜像担持体である感光体２に対して対向配置される現像剤担持体である現像ローラ４２Ａを有する現像装置４において、現像ローラ４２Ａが感光体２に対向する現像領域に対して感光体２の表面移動方向下流側で感光体２に対向配置され、現像ローラ４２Ａの表面に担持される二成分現像剤に比べてトナー濃度が十分に低い二成分現像剤、または、キャリアのみを担持して表面移動する下流側対向部材である画質改善ローラ４２Ｂを有し、画質改善ローラ４２Ｂに交番電圧等の交流成分を含む電圧を印加する交流電圧印加手段である電源部を備える。【選択図】図１