Fusing device and image forming apparatus

摘要

A fuser portion is configured to include a fuser roller, a tension roller, an endless fuser belt stretched over the fuser roller and the tension roller, a heater unit for heating the fuser belt, and a pressure roller pressed to the fuser roller through the fuser belt. The heater unit is so arranged as to be pressed to the fuser belt, while the tension roller has a thermal insulation layer arranged on its outer circumference touching the fuser belt.

主权项

1. A fusing device for fixing an image to a sheet, comprising;
a fuser roller; a tension roller arranged in parallel with the fuser roller; an endless fuser belt stretched over the fuser roller and the tension roller; a heater for heating the fuser belt; and a pressure roller pressed to the fuser roller through the fuser belt for conveying a sheet carrying an image formed with a developer while sandwiching the sheet between the pressure roller and the fuser belt, wherein the heater is arranged to be pressed to the fuser belt, and the tension roller has a thermal insulation member arranged at an outer circumference touching the fuser belt, wherein when the outer diameter of the tension roller is represented by “r” while the outer diameter of the fuser roller is represented by “R”, “r ” and “R” satisfy the relational expression indicated below:
r<=⅔*R.