Abstract A heat roll for electrophotography of a surface heating type having a heating resistor is arranged such that a bonding layer, an insulating layer, a resistance layer, and a surface insulating layer are consecutively provided on an outer surface of a hollow cylindrical core, and a bearing member for fitting with a bearing is fitted at each opposite end of the heat roll. A pipe or a round bar formed of aluminum, an aluminum alloy, copper, a copper alloy, or the like which has a greater coefficient of thermal conductivity than that of mild steel is disposed inside the core to permit a uniform distribution of the temperature. In addition, a gap of 0.2 mm or more is provided between the inner surface of the core and an outer peripheral surface of the member formed of the high-temperature conductive material. As a result, effects that are attributable to a difference in the coefficients of thermal conductivity can be alleviated, and a temperature rise of the heat roll up to a predetermined temperature can be accelerated.
A heat roll for electrophotography of a surface-heating type having a heating resistor on an outer surface of a hollow cylindrical core made of mild steel, said heat roll comprising a high-temperature conductive material which is formed into the shape of a pipe or a round bar and has a greater coefficient of thermal conductance than that of mild steel, said high-temperature conductive material being inserted in said core.
Claim 2
Dependent Claim
69 words
A heat roll for electrophotography of a surface-heating type having a heating resistor on an outer surface of a hollow cylindrical core made of mild steel, said heat roll comprising a high-temperature conductive material which is formed into the shape of a pipe or a round bar and has a greater coefficient of thermal conductance than that of mild steel, said high-temperature conductive material being inserted in said core.
Claim 3
Dependent Claim
22 words
The heat roll for electrophotography according to claim 1, wherein said high-temperature conductive material is formed of aluminum of an aluminum alloy.
Claim 4
Dependent Claim
42 words
The heat roll for electrophotography according to claim 1, wherein the outside diameter of said pipe or said round bar formed of said high-temperature conductive material is smaller than the inside diameter of said core, and a diametrical difference is provided therebetween.
Claim 5
Dependent Claim
18 words
The heat roll for electrophotography according to claim 3, wherein said diametrical difference is 0.2 mm or more.
Claim 6
Dependent Claim
22 words
The heat roll for electrophotography according to claim 4, wherein the outside diameter of said heat roll is 20 mm or less.
Claim 7
Dependent Claim
64 words
The heat roll for electrophotography as in claim 3 wherein said diametrical difference is set in relation to the relative thermal conductivities of said core and said high-temperature conductive material such that the inner surface of said core and the outer surface of said high-temperature conductive material are brought into contact with each other when the heat roll is raised to an elevated temperature.