IMAGE FORMING APPARATUS

To solve the problem in which: sub-scanning color shift caused by extension/contraction of an intermediate transfer belt after a scanner unit enters a constant temperature state after completion of a print job cannot be corrected through thermal shift; the sub-scanning color shift can be addressed by providing a mechanism that directly detects the extension/contraction of the belt, but it leads to complexity and an increase in size of the apparatus.SOLUTION: In a print job executed after a job in which the temperature in the apparatus exceeds a constant value and at a constant time interval or longer, the image forming apparatus predicts the amount of sub-scanning color shift caused by extension/contraction of a belt from a difference in one cycle of the belt between the end of the previous job and the current time, and performs correction of a writing position.SELECTED DRAWING: Figure 7 【課題】プリントジョブ終了後のスキャナユニットが定温状態となった後の中間転写ベルトの伸縮による副走査色ずれは、サーマルシフトによって補正することができない。ベルトの伸縮を直接検知する機構を設けることで対策可能であるが装置の複雑化、大型化を招く。【解決手段】機内温度が一定値を超えたジョブ後、かつ一定以上の時間間隔を空けて実施されるプリントジョブの際には、前回ジョブ終了時と現在のベルト1周周期との差分からベルトの伸縮による副走査色ずれ量を予測し、書き出し位置の補正を行う【選択図】 図７