Patent ID: 6032012
Filing Date: 2000-02-29
Classification: G03G

Abstract:
A developing apparatus, comprising:a developing hopper which (i) has an opening facing an image carrier on which an electrostatic latent image is formed, and (ii) stores a single-component nonmagnetic toner;a developing roller which (i) is provided in the opening to expose a part of a circumferential surface of the developing roller, (ii) forms a developing portion between the exposed part of the circumferential surface and the image carrier, and (iii) carries the nonmagnetic single-component toner on the circumferential surface thereof to transport the single-component nonmagnetic toner to the developing portion from the hopper and to develop the electrostatic latent image on the image carrier at the developing portion;a doctor blade which (i) contacts the circumferential surface of the developing roller on an upstream side of the developing portion in a rotational direction of the developing roller, and (ii) controls a thickness of the toner carried on the circumferential surface of the developing roller;a toner feed roller which (i) is arranged in the developing hopper, and (ii) presses on the developing roller on an upstream side of the doctor blade in the rotational direction of the developing roller to feed the toner in the hopper to the circumferential surface of the developing roller;a conductive sheet member which (i) contacts the circumferential surface of the developing roller on a downstream side of the developing portion and on an upstream side of the toner feed roller in the rotational direction, (ii) permits a residual toner not used to develop the electrostatic latent image on the image carrier at the developing portion and left on the developing roller to pass into the developing hopper, and (iii) prevents the toner in the developing hopper from leaking out along the circumferential surface of the developing roller on the downstream side of the developing portion and on the upstream side of the toner feed roller in the opening;a developing bias voltage applying device which applies a developing bias voltage to the developing roller, said developing bias voltage having a same polarity as that of a charge characteristic of the toner;a doctor bias voltage applying device which applies a doctor bias voltage to the doctor blade, said doctor bias voltage being larger than the developing bias voltage in the absolute value and having the same polarity as that of the charge characteristic of the toner;a feed bias voltage applying device which applies a feed bias voltage to the toner feed roller, said feed bias voltage being larger than the developing bias voltage in absolute value and having the same polarity as that of the charge characteristic of the toner; anda conductive sheet bias voltage applying device which applies a sheet bias voltage, ranging from 0V to the developing bias voltage, to the conductive sheet member to generate a potential difference between the conductive sheet member and the developing roller, thereby weakening an attachment of the residual toner to the developing roller.