Abstract: In a heating roller for fixing which is constituted such that a heating resistor 3 is provided onto an inner circumferential surface 1a of a cylinder 1 with an insulating layer 2 lying therebetween and a cleavage layer 6 is provided onto an outer circumferential surface, electrical insulating properties of the insulating layer 2 are maintained satisfactorily for a long time. A maximum height (Rmax) of surface roughness of the inner circumferential surface 1a of the cylinder 1 is in the range of 0.8 of 50 &mgr;m. A resistance value in the heating roller for fixing is partially adjusted easily. In a heating roller for fixing having a heating resistor 103 on a surface of a cylinder 101 with an insulating layer 102 lying therebetween, the heating resistor 103 is divided into a plurality of zones in an axial direction of the cylinder 101, and slots for adjusting resistance are formed in each zone.

Abstract: In a heating roller for fixing which is constituted such that a heating resistor 3 is provided onto an inner circumferential surface 1a of a cylinder 1 with an insulating layer 2 lying therebetween and a cleavage layer 6 is provided onto an outer circumferential surface, electrical insulating properties of the insulating layer 2 are maintained satisfactorily for a long time.A maximum height (Rmax) of surface roughness of the inner circumferential surface 1a of the cylinder 1 is in the range of 0.8 to 50 .mu.m.A resistance value in the heating roller for fixing is partially adjusted easily.In a heating roller for fixing having a heater resistor 103 on a surface of a cylinder 101 with an insulating layer 102 lying therebetween, the heating resistor 103 is divided into a plurality of zones in an axial direction of the cylinder 101, and slots for adjusting resistance are formed in each zone.

Abstract: A ceramic valve assembly is housed in a recess formed in a metal pipe and is supported via gaskets by the metal pipes. Each gasket has a larger coefficient of linear expansion than that of the metal pipe. A clearance generated due to the thermal expansion difference between the metal pipe and the ceramic housing is absorbed by the large thermal expansion of the gasket so that no play is generated between the ceramic valve assembly and the metal pipe and the sealing force is maintained. Each gasket has beads constructed of spring material. An excessively large load does not act on the ceramic assembly because the beads are deformed to absorb the load.

Abstract: A ceramic heater having a ceramic substrate, a heat-generating resistor disposed in the interior of the ceramic substrate or on the surface of the ceramic substrate and terminals connected to both the ends of the heat-generating resistor, wherein the ceramic substrate is composed of a sintered body of a nitride of an element selected from the group consisting of silicon and aluminum and the heat-generating resistor is composed of a ceramic layer containing titanium nitride (TiN) or tungsten carbide (WC).