Patent ID: 8498560

Claim:
A fixing device for heating and melting a toner image to fix the toner image onto a recording medium, comprising: two roller members that form a nip portion in which the recording medium is pressed by a pressure device and transported thereof; and a drive gear that engages with a shaft portion of one of the two roller members and transmits driving force to one of the two roller members, wherein the drive gear includes a key that protrudes toward a rotational center and is integrally formed with the drive gear as a single unit at an inner diameter portion of the drive gear, a gap is provided in a co-axial direction between an inner diameter portion of the drive gear and an outer diameter portion of the shaft portion, when a rotation velocity of the two roller members is normal, transmission of driving force from the drive gear to the shaft portion is rotationally driven via contacting and engaging at most one side in a rotational direction; and when a rotation velocity of one of the two roller members increases, transmission of the driving force from the drive gear to the shaft portion is suspended and the drive gear slides freely on the shaft portion.