Perforation device and sheet post-processing device provided therewith

A perforation device comprising:

• a shaft;
• a perforation motor that rotates the shaft;
• an eccentric cam fitted to the shaft;
• a perforation portion having a perforation blade that perforates a sheet, the perforation portion reciprocating the perforation blade in directions toward and away from the sheet as the eccentric cam rotates;
• a rotation speed detecting portion that senses a rotation speed of the shaft;
• a home position detecting portion that detects whether the perforation blade is at a home position away from the sheet;
• and
• a controller that controls driving of the perforation motor,
• wherein
• the perforation portion includes
• at least one first perforation portion that performs first perforation on the sheet with a first perforation blade and
• at least one second perforation portion that performs second perforation on the sheet with a second perforation blade,
• the first and second perforation portion being disposed at positions away from each other in an axial direction with respect to the shaft,
• the eccentric cam includes
• at least a first cam that reciprocates the first perforation blade in the first perforation portion and
• at least a second cam that reciprocates the second perforation blade in the second perforation portion,
• the first and second cams being disposed at positions facing the first perforation portion and the second perforation portions respectively,
• the second cam being disposed with a delay n phase of 180° from the first cam with respect to a first rotation direction of the shaft,
• the controller performs
• a first perforation processing to perform the first perforation with the first perforation portion by rotating the shaft through 180°,
• a second perforation processing to perform the first perforation with the first perforation portion and the second perforation with the second perforation portion in sequence, and
• braking control to brake the perforation motor such that the first and second perforation blades stop at the home position,
• the controller detects with the rotation speed detecting portion the rotation speed of the shaft after the first perforation blade penetrates the sheet during the first perforation, and
• based on the rotation speed detected by the rotation speed detecting portion, the controller determines timing of starting the braking control in the second perforation and performs the braking control,
• in a case where a stop position of the perforation blade when the perforation motor is stopped is deviated from the home position, the controller rotates the perforation motor in the first rotation direction, or in a second rotation direction opposite from the first rotation direction at a lower speed than during perforation so as to move the perforation blade to the home position, wherein
• the home position detecting portion detects whether a rotation angle of the first cam or the second cam is a reference angle, and
• the home position is a range of position in which the perforation blade is located as the shaft is rotated in the first or second rotation direction after the home position detecting portion detects the first or second cam being at the reference angle until a number of the pulse signal outputs from the rotation speed detecting portion reaches a predefined positioning pulse count,
• when in the braking control, the perforation motor is stopped before the perforation blade reaches the home position, the controller rotates the perforation motor in the first or second rotation direction so that, after the first or second cam reaches the reference angle, when the first or second cams rotated by the number of positioning pulses, the controller stops the perforation motor, and
• when in the braking control, the perforation motor is stopped after the perforation blade passes the home position, the controller rotates the perforation motor in an opposite direction by a number of excess pulses by which, after the first or second cam reached the reference angle, the output of the rotation speed detecting portion is beyond the positioning pulse count.