Patent ID: 8676103

Claim:
A fixing device comprising: a tubular belt holder extending in an axial direction thereof; a rotatable, flexible fuser belt looped into a generally cylindrical configuration around the belt holder to rotate in a circumferential direction of the belt holder; a heater disposed adjacent to the belt holder to heat the belt holder to in turn heat the fuser belt through conduction; a fuser pad accommodated in the belt holder inside the loop of the fuser belt, having a central axis thereof extending in the axial direction of the belt holder; and a pressure member disposed opposite the belt holder with the fuser belt interposed between the fuser pad and the pressure member, the pressure member pressing in a load direction against the fuser pad through the fuser belt to form a fixing nip therebetween, through which a recording medium travels in a conveyance direction under heat and pressure; the belt holder including, along a circumferential dimension thereof, an upstream, first circumferential portion at which the belt holder is subjected to heating by the heater upstream from the fixing nip, a downstream, second circumferential portion at which the recording medium separates from the fuser belt downstream from the fixing nip, and a midstream, third circumferential portion disposed upstream from the first circumferential portion and downstream from the second circumferential portion, the first circumferential portion defining a first, arc-shaped cross-section whose outer radius is approximately equal to or smaller than an inner radius of the fuser belt in the generally cylindrical configuration thereof, and whose center is displaced, in the conveyance direction, away from a reference plane containing the central axis of the fuser pad and extending perpendicular to the conveyance direction, the second circumferential portion defining a second, arc-shaped cross-section whose outer radius is dimensioned relative to the radius of the first circumferential portion, and whose center is displaced away from the center of the first circumferential portion toward the fixing nip both in the conveyance direction and in the load direction, wherein a maximum diameter of the belt holder, as defined by a maximum distance between outer surfaces of the first circumferential portion and the second circumferential portion, is larger than an inner diameter of the fuser belt in the generally cylindrical configuration thereof.