Post-processing apparatus and image formation system capable of post-processing sheet conveyed from image forming apparatus

A post-processing apparatus mounted to an image forming apparatus and capable of subjecting a sheet to post-processing, the post-processing apparatus comprising:

• a blade capable of being pressed into the sheet to form a fold line in the sheet;
• a transfer mechanism that moves the blade toward and away from the sheet;
• a sheet folding roller pair that conveys the sheet with the fold line formed therein by the blade by pinching the sheet at a nip between the sheet folding roller pair;
• a motor that rotatively drives the sheet folding roller pair;
• a drive control device that controls drive of the motor;
• and
• a control device that is formed of a control circuit including a processor and controls the transfer mechanism and the drive control device,
• wherein at a time when the control device controls the transfer mechanism to withdraw the blade, which has been pressed into the sheet and the nip by the transfer mechanism, from the nip, the control device controls the drive control device to stop the motor, wherein
• the drive control device controls the drive of the motor by PLL control and PWM control, and
• for at least a period of time from when the control device drives the transfer mechanism to allow the blade to start pressing into the sheet to when the control device drives the transfer mechanism to allow the blade to end the pressing, the drive control device controls the drive of the motor without performing the PLL control and fixes a duty ratio of the PWM control at 100%.