Fusing apparatus having an induction heated fuser roller

Abstract

A fusing apparatus for heating and permanently fusing toner powder images onto an image carrying sheet. The fusing apparatus includes a pressure roller; a closed loop magnetic flux carrying member positioned adjacent the pressure roller and including a first side and a second side opposite the first side. The first side is located between the pressure roller and the second side. The fusing apparatus also includes an electrically conductive wire wound about the second side forming a primary transformer coil having N1 number of turns. The primary transformer coil is connectable to an AC power supply source for inductively transferring AC electric energy to the first side. Importantly, the fusing apparatus includes a rotatable fuser roller forming a fusing nip with the pressure roller. The rotatable fuser roller has an electrically conductive layer and a rigid non-conductive core in the form of a ceramic tube underlying the conductive layer. The rotatable fuser roller is mounted around the first side of the closed loop magnetic flux carrying member and forms a secondary transformer coil inductively coupled to the primary transformer coil, and the conductive layer is inductively heated by power dissipated by current induced therein when the primary transformer coil is connected to the AC power supply source.