Noise-Reduction Technology for Density Unevenness in Electrophotographic Process

Abstract

This paper introduces a noise-reduction technology for density unevenness caused by resistance unevenness of the charge roller in the electrophotographic (EP) process. Generally, active noise control (ANC) is known to reduce noise in real time. With this technology, the control signal is applied to the noise source in the same physical quantity and antiphase signal of the noise source. To reduce density unevenness by applying this technology for the EP process, it is necessary to move the rotators, such as photoconductors and development rollers, to cancel the fluctuation in the developing gap; however, the moments of inertia of the rotators are too large to respond sufficiently. Against such a situation, we previously developed a control method based on ANC to reduce noise (image density unevenness) in the EP process by applying the control input of different physical quantities from the noise source. With this method, the developing electric field is controlled using the modulation of the developing bias voltage and charging bias voltage instead of making an adjustment in the distance of the developing gap. In this study, we applied our previous method to the periodic fluctuation in the charging process and developed a noise-reduction method that reduces the periodic image density unevenness caused by the resistance unevenness of the charge roller. With this proposed technology, the surface voltage on the photoconductor is measured by surface voltage sensor without forming toner patterns, the control table is calculated from the detected uneven surface voltage, and the periodic fluctuation is reduced by modulation of the charging bias voltage in real time based on the rotation of the charge roller. The experiments we conducted confirmed that our proposed method improves periodic density uniformity caused by the resistance unevenness of the charge roller effectively.