Patent ID: 8427666

Claim:
An abnormality detecting device for a rotation body, comprising: a rotation body that rotates while coming in contact with a sheet being transported at a predetermined speed; an output unit that outputs a plurality of pulses of a number in proportion to an amount of rotation of the rotation body along with the rotation of the rotation body; an acquisition unit that acquires periodic information in which a position of the rotation body during a single rotation of the rotation body and a period of each of the pulses corresponding to the position are associated with each other, the periodic information being acquired based on the plurality of pulses outputted from the output unit along with the rotation of the rotation body at the predetermined speed; a memory that stores the periodic information acquired by the acquisition unit as reference periodic information; and an abnormality detector that detects an abnormality occurred in at least one of the rotation body and the output unit based on the reference periodic information read from the memory and new periodic information that is acquired after the reference periodic information is acquired.