Patent ID: 7734220

Claim:
A velocity correction device attached removably to an image forming apparatus including a rotor, a motor for driving the rotor, a motor control unit for controlling an operation of the motor, and a velocity command memory for storing velocity command data and supplying the motor control unit with a command signal based on the velocity command data, wherein the image forming apparatus does not include a velocity measuring unit for correcting a rotational velocity of the rotor, the velocity correction device comprising: a velocity measuring unit for measuring a rotational velocity or a peripheral velocity of the rotor of the image forming apparatus; an arithmetic unit; and an interface unit for supplying the velocity command data to the velocity command memory of the image forming apparatus; wherein: the velocity correction device is attached to the image forming apparatus in a manufacturing process of the image forming apparatus or in a replacement process of a unit in which the rotor is mounted so that the rotational velocity or the peripheral velocity of the rotor is measurable by the velocity measuring unit of the velocity correction device; the interface unit of the velocity correction device is connected to the velocity command memory of the image forming apparatus; the velocity measuring unit measures the rotational velocity or the peripheral velocity of the rotor when the motor is rotating at a reference rotational velocity which is a fixed velocity; the arithmetic unit compares the measured velocity with a no-velocity-fluctuation velocity of the rotor calculated by the reference rotational velocity of the motor, extracts a velocity fluctuation component of the rotor, and generates the velocity command data to cancel the extracted velocity fluctuation component; the velocity command data generated by the arithmetic unit are transmitted to the velocity command memory through the interface unit and stored in the velocity command memory, and the velocity correction device is removed from the image forming apparatus after storing the velocity command data.