Chapter 77-24F-7-247.4.10 D-max Control 0014-4592imagePRESS C1 P / imagePRESS C1This D-max control (image density correction control) is executed to control the variation in image density caused by the change in environment, or deteriorationof the photosensitive drum or toner.Activation Timing- At PASCAL control- At every paper intervalControl DescriptionThe DC controller creates patch patterns of each color (Y, M, C, Bk) on the drum at every paper interval. Afterwards, the patch image read sensor (PS3) measuresthe patch patterns to execute toner supply control according to patch density. At this point, the ATR sensor (PS7) reads the sleeve surface of the developing assemblyto measure the T/D ratio. The DC controller evaluates whether to execute toner supply by measuring result of the T/D ratio to determine the developing bias andthe grid bias for each color (Y, M, C, Bk) in order to realize optimal density.Memo:T-7-111 Vt Application Estimate the voltage corresponding the current listed on the environmental table and then apply Vt1 to Vt3 tothe bias roller. Gauge the current at HVT6 and feed back the results to the DC controller.2 Drawing Target It-Vt Curve Measure the current (It) at the voltages Vt1 to Vt3, and draw an It-Vt curve.3 Determining the Cleaning Bias DC controller calculates a target Vt from the target It and then determines the most suitable cleaning bias basedthe target Vt.Condition Cause RemedyThe patch density is light, and thesleeve surface is darkThe toner density developed to the drum is gettinglower due to developing-related reasons,Stop toner supply, and determine the developing bias and thegrid bias in order to obtain optimal density.The patch density is dark, and thesleeve surface is lightThe toner density developed to the drum is gettinghigher due to developing-related reasons,Execute toner supply forcibly, and determine the developingbias and the grid bias in order to obtain optimal density.Target ItVt3Vt2Vt1 VtCurrent (It)Voltage (Vt)
