| 摘要 |
PURPOSE:To prevent a developer from scattering to the outside of a developing unit, by forming a filter by a double structure body, and also, specifying a gap size between the edge part of a casing aperture of the developing unit and the outside surface part of a developer carrying body, against the thickness of a developer layer on the developer carrying body. CONSTITUTION:When the pressure of the inside of a developing tank becomes high, an air flow in a casing 1 passes through a filter 10 from a pressure releasing hole 8 and flows out to the outside, and developer particles are decreased as to its flow velocity by the first filter with large meshes and caught or repulsed as to its considerable number, and subsequently, caught or repulsed entirely by the second filter 12 with small meshes. In this case, when a gap size between the aperture edge part 17 of the casing 1, and the outside surface part of a developing sleeve 2 is set so as to satisfy delta-DG<1.5mm against the thickness DG of developer layer 18, the air flow circulates in the casing 1, and does not flow out to the outside, therefore, a developer is shut up in the casing 1. |
