Patent ID: 6079818
Filing Date: 2000-06-27
Classification: B41J

Abstract:
An image forming apparatus comprising:a supplying means at least having a developer support carrying one color of developer;an opposing electrode disposed facing the developer support;a control electrode at least comprising:an insulative substrate disposed between the developer support and the opposing electrode;a plurality of gates formed in the insulative substrate for forming passages for the developer;one or more electrode groups provided covering a multiple number of the gates; anda shield electrode having one or more electrode elements each having openings which directly or electrically expose at least part of the gates and the electrode groups with the gates to the developer support;a control means having a control circuit means which is able to apply a predetermined voltage to each electrode on the control electrode in accordance with the image data, wherein the control means controls the passage of the developer through the gates by applying the designated voltage to the corresponding electrodes of the electrode groups so as to form an image on the surface of a recording medium which is being conveyed between the control electrode and the opposing electrode, characterized in that the degree of exposure of an arbitrary one of gates or electrode groups disposed around the gates, to the developer carried on the developer support is controlled by the shield electrode;a detecting means for detecting characteristics of the developer or characteristic values of the developer being carried on the developer support, comparing the detected characteristic values of the developer with predetermined developer characteristics and outputting the detected values, andwherein, based on the detected values, the control means controls the degree of exposure by governing at least one or combination of the positional relationship of the shield electrode relative to the developer support and the electrode group, the relative potential difference of the shield electrode relative to the developer support and the electrode group and the ratio of the exposed portion of the shield electrode to that of the electrode group so as to perform individual control for each gate or identical control for a plurality of gates.