Fixing device having fixing belt heated with radiant heat from heat generating portion and image forming apparatus including same

A fixing device comprising:

• a fixing belt that is endless shaped and circularly movable at a speed substantially equal to a recording medium conveying speed;
• a heater that is disposed inside the fixing belt, that has a heat generating portion in which a filler gas and a filament are sealed and a seal portion that seals each end of the heat generating portion, and that heats the fixing belt with radiant heat from the heat generating portion;
• a holding member that is disposed inside the fixing belt and slides against an inner circumferential surface of the fixing belt;
• a pressure member that is pressed with a predetermined pressure against the holding member with the fixing belt therebetween such that a fixing nip is formed between the fixing belt and the pressure member;
• and
• an end-portion excessive temperature increase prevention member that is attached to each end portions of the heater, that blocks transfer of radiant heat toward each end portion of the fixing belt in a widthwise direction of the fixing belt, and that has a first opening portion formed in such part thereof as faces the seal portion of the heater,
• a recording medium being passed through the fixing nip portion to fix an unfixed toner image carried on the recording medium,
• wherein
• at the each end portion of the fixing belt in the widthwise direction thereof, an end portion ring that prevents the fixing belt from meandering, and an end portion cap that rotatably supports the end portion ring are disposed outside the end-portion excessive temperature increase prevention member in the widthwise direction of the fixing belt, and
• the first opening portion forms a gap between the end portion cap and the end-portion excessive temperature increase prevention member.