HP M5025 Service Manual - Page 160

Fuser/delivery block The fuser/delivery block is structured into two blocks: the fusing block, which fuses toner onto the media, and the delivery block, which delivers the fused media to the face-down bin. The fuser/delivery block operates as follows: 1. Media is fed to the fuser unit from the pickup feed block. The paper warp is adjusted here by the loop control. Different motors are used so the feed speed in the fuser unit differs from the feed speed in the pickup/feed block. Loop control prevents an image or paper transport defect by keeping within the specified paper warp before entering the fuser unit. 2. When the face-down bin becomes full, the delivery tray paper full sensor (SR1) detects the condition. When the DC controller determines that the face-down bin is full, it notifies the formatter. Loop control Loop control prevents image and paper transport defects by keeping within the specified paper warp between the transfer charging roller in the pickup/feed block and the fuser pressure roller. The feed speeds of the fuser pressure roller and the transfer charging roller are not the same, resulting in these problems when media is fed to the fuser unit: ● When the rotational speed of the fuser pressure roller is slower than that of the transfer charging roller, the paper warp is increased. This can cause an image defect or a paper crease. ● When the rotational speed of the fuser pressure roller is slower than that of the transfer charging roller, the paper warp is decreased and image misregistration in the sub-scanning direction occurs. To resolve these problems, the DC controller maintains the paper warp at a specified amount by monitoring the paper loop sensor (SR4) and changing the rotational speed of the fuser pressure roller according to the SR4 output signals. Figure 4-26 Loop control mechanism 130 Chapter 4 Theory of operation ENWW