| 摘要 |
PURPOSE:To prevent a couple of rollers from being pressed strongly against each other for a long period, and deforming and straining permanently, and also prevent a defect in fixation performance and the generation of an abnormal noise by increasing or decreasing the distance between the shafts of the couple of rollers according to the heat states of the fixing roller couple and controlling the press-contacting state of the fixing roller couple. CONSTITUTION:When a copying machine is powered on and a halogen heater in a fixing roller 20 is fed with electricity, the surface temperature of the fixing roller 20 rises and the temperature of a pressure roller 21 also rises, so that the silicone rubber of the pressure roller 21 expands with temperature. When a stand-by state continues for a certain time after a wait-up state, a shape memory alloy element 30 which receives heat from the fixing roller 20 through a heat pipe 34 attains to a specific temperature and contracts, so the position of a piston 32 is lowered. The position of a stay 28 is lowered correspondingly and the pressure between the rollers 20 and 21 is reduced. Consequently, invariably proper pressure is maintained, and excessive pressure and the resulting deformation of the roller couple are prevented. |
