Patent ID: 9727003
Date: 2017-08-08
CPC Classifications: G03G

Claim:
1. An image forming apparatus for printing an image on a medium being fed therethrough, comprising: an image carrier; a charging section disposed in proximity to the image carrier; a power supply applying a first charged voltage to the charging section during a predetermined process and also applying a plurality of second charged voltages sequentially to the charging section in obtaining a predetermined peak-to-peak voltage value, wherein the first charged voltage includes an alternating-current voltage having the predetermined peak-to-peak voltage value, each of the second charged voltages includes an alternating-current voltage, and the alternating-current voltage of the second charged voltage has a peak-to-peak voltage value varying between a forward discharge range where a charge transfer occurs only from the charging section to the image carrier and a back discharge range where a bidirectional charge transfer occurs between the image carrier and the charging section; a current sensing section sensing a value of an alternating-current running through the charging section upon application of each of the second charged voltages; and a control section deriving a first approximation function and a second approximation function on the basis of the alternating-current values sensed by the current sensing section and setting a peak-to-peak voltage value as the predetermined peak-to-peak voltage through a difference function representing a difference value between the derived first approximation function and the derived second approximation function, wherein the first approximation function and the second approximation function represent alternating-current values relative to peak-to-peak voltage values in the forward discharge range and the back discharge range, and the peak-to-peak voltage value being set as the predetermined peak-to-peak voltage is a value for which an amount of change of the difference value per unit peak-to-peak voltage in the difference function takes a predetermined value, wherein the predetermined value is constant regardless of the number of printed pages.