Patent ID: 8693936

Claim:
A fixing device comprising: a tubular heat pipe formed of a sheet of metal bent into a generally cylindrical configuration, with a pair of opposed longitudinal edges thereof spaced apart from each other to define a longitudinal slot therebetween; a rotatable, flexible fuser belt looped for rotation around the heat pipe, with variable clearance between the inner surface of the fuser belt and the outer surface of the heat pipe; a heater disposed within the heat pipe to heat the heat pipe to conduct heat to the fuser belt; an elongated, stationary fuser pad accommodated in the longitudinal slot of the heat pipe inside the loop of the fuser belt; a rotatably driven pressure member disposed parallel to the heat pipe with the fuser belt interposed between the fuser pad and the pressure member, the pressure member pressing against the fuser pad through the fuser belt to form a fixing nip therebetween, through which a recording medium is conveyed under heat and pressure; and a coupling mechanism comprising: a pair of first coupling portions in the fuser pad, one on each longitudinal edge of the fuser pad; and a pair of second coupling portions in the heat pipe, one in each of the pair of opposed longitudinal edges of the bent sheet of metal, the first coupling portion engageable with the second coupling portion to couple together the pair of opposed longitudinal edges to retain the heat pipe in the generally cylindrical configuration, wherein a minimum clearance between the fuser belt and the heat pipe at a normal, room temperature exceeds an amount of deformation of the heat pipe during warm-up, but does not exceed an amount of deformation of the heat pipe upon completion of warm-up.