Fixing device and image forming apparatus having the same

摘要

A fixing device 5 includes a belt drive assist mechanism 70 configured to rotationally drive a fixing belt 26. The belt drive assist mechanism 70 is in contact with an inner surface of the fixing belt 26 and an outer diameter of an outer circumferential surface 71a is smaller than an inner diameter of the fixing belt 26 when the fixing belt 26 is in a circular shape. In addition, the belt drive assist mechanism 70 includes a cylindrical rotation member 71 and a pressing roller 72. The cylindrical rotation member 71 is rotationally driven by a motor 79. The pressing roller 72 is in pressure contact with the cylindrical rotation member 71 while interposing the fixing belt 26 therebetween and rotates following rotation of the fixing belt 26 rotationally driven by the cylindrical rotation member 71 or the pressure applying roller 19.

主权项

1. A fixing device comprising:
an endless fixing belt heated by a heating part; a pressing member disposed on a side of an inner surface of the fixing belt, the inner surface configured to slide along an outer surface of the pressing member; a pressure applying roller configured to press the pressing member to form a fixing nip at which the fixing belt is interposed and rotationally driven; and a belt drive assist mechanism disposed outside a nip region of the fixing nip and configured to rotationally drive the fixing belt, wherein the heating part comprises: a coil bent like a loop in an axial direction of the fixing belt and configured to generate a magnetic flux to inductively heat the fixing belt; and a magnetic core disposed adjacent to the coil and configured to guide the magnetic flux to a layer of the fixing belt which is induced to generate heat, wherein the belt drive assist mechanism comprises: a cylindrical rotation member configured to be rotationally driven by a drive source; a pressing roller; and a rotation detector configured to detect whether the fixing belt is rotating by detecting rotation of the pressing roller,
wherein the cylindrical rotation member is configured to be in contact with the inner surface of the fixing belt and to have an outer circumferential surface, a diameter of which is smaller than an inner diameter of the fixing belt for a case where the fixing belt is in a circular shape,wherein the pressing roller is configured to be in pressure contact with the cylindrical rotation member while interposing the fixing belt therebetween and to rotate following rotation of the fixing belt that is driven by the cylindrical rotation member or the pressure applying roller, and
wherein the rotation detector comprises:a detected part including a plurality of slits disposed circumferentially on a side surface of the pressing roller and configured to rotate in unison with the pressing roller; anda light detecting sensor configured to emit light from a light emitting part to the detected part and to receive light reflected off the detected part by a light receiving part.