HP Color LaserJet Enterprise CM4540 Service Manual - Page 87

Primary-transfer-roller engagement and disengagement The sequence of the primary-transfer-roller engagement and disengagement control is as follows: 1. The fuser motor turns on the primary-transfer disengagement solenoid and rotates the primarytransfer-roller disengagement cam. 2. As the cam rotates, the Y/M/C primary-transfer-roller slide plate or the Bk primary-transfer-roller slide plate moves to the right or left, which causes the primary-transfer roller to move up or down. 3. The ITB engages with or separates from the photosensitive drum depending on the movement of the primary-transfer rollers. Depending on the requirements of the print job, the primary-transfer rollers engage with the ITB so it can receive toner from the photosensitive drums. The primary-transfer roller has three engagement states. Table 1-10 Primary-transfer-roller engagement states All rollers disengaged All rollers engaged Black roller engaged The ITB is disengaged from all the four photosensitive drums. This state is the home position for the ITB unit. The ITB is engaged with all four photosensitive drums. The state for full-color printing. The ITB is engaged with only the black photosensitive drum. The state for blackcolor mode printing . The DC controller determines a primary-transfer-roller disengagement failure and notifies the formatter when it does not detect a signal from the primary-transfer disengagement sensor even though the primary-transfer disengagement solenoid is turned on. If the DC controller does not receive the expected signal from the ITB home-position sensor when the primary-transfer-roller engages or disengages, but the primary-transfer-roller disengagement motor is rotating, the DC controller determines that the primary-transfer-disengagement mechanism has failed, and notifies the formatter. The DC controller detects whether the ITB unit is new by monitoring the new ITB unit sensor. The DC controller determines the ITB unit is at end of life and notifies the formatter when a specified number of pages are printed after the ITB unit is replaced. If swapping ITB units between two products for troubleshooting purposes, be sure to return the ITB units to their original products to maintain the correct life count. NOTE: A new ITB has a flag that causes the ITB life counter to be reset. When an ITB is installed in the product, it cannot be removed and used again as a new ITB. The DC controller detects the presence of an ITB unit by monitoring the primary-transfer-roller disengagement sensor. The DC controller turns on the primary-transfer disengagement solenoid for specified times during an initial rotation period when the following events occur: ● The product is turned on. ● The product exits sleep mode. ● The door is closed. ENWW Image-formation system 35