Patent ID: 7103298

Claim:
A developing device, comprising: a developing agent carrying member which faces a latent image carrying member and rotates in a direction such that the portion thereof facing said latent image carrying member rotates in the same direction as said latent image carrying member at that position, while carrying on the surface thereof a developing agent containing magnetic particles; a casing which forms a developing agent storing space therein for storing developing agent, and has an opening whereby a portion of the surface of said developing agent carrying member in the direction of rotation of said developing agent carrying member is made to face said latent image carrying member; a developing agent restricting member disposed within said casing, upstream, in the direction of rotation of said developing agent carrying member, of a developing region where said developing agent carrying member and said latent image carrying member face one another, such that a gap is formed between said developing agent restricting member and said developing agent carrying member, so as to restrict the amount of developing agent supplied to said developing region; whereby developing is performed by bringing the developing agent on the surface of said developing agent carrying member with said latent image carrying member at said developing region; magnetic field generating means for generating a magnetic field such that said developing agent is made to form a magnetic brush so as to close off the space between the surface of said developing agent carrying member and the inner wall of said casing at least one time while said developing agent being carried by the surface of said developing agent carrying member is being carried from said gap to said developing region; and a gas exhaust path for exhausting gas, in an upstream space defined by the surface of said developing agent carrying member and the inner wall of said casing upstream in the rotational direction of said developing agent carrying member from said developing region, into the inner space of a device or member employing a structure whereby developing agent existing therein is prevented from scattering within an image formation apparatus, at a position downstream in the rotational direction of said developing agent carrying member from a brush formation position where said developing agent forms a magnetic brush due to said magnetic field generating means.