Fixing device for electrophotographic apparatus

Abstract

A fixing device to be used in electrophotographic apparatus for providing a clear fixed image with no offset with use of no oil or the least amount of oil, wherein an endless fixing belt provided with a metal body having a release thin film thereon is stretched between a fixing roller having a elastic surface and a heating roller, a pressing roller is arranged to press the surface of the elastic fixing roller upwardly from the lower side thereof through the fixing belt to form a nip portion between the fixing belt and the pressing roller, a guide plate for unfixed image carrying support member is provided underneath the fixing belt, between the heating roller and the nip portion, to form substantially a linear heating path between the guide plate and the fixing belt, and the metal body of the fixing belt has a heat capacity per cm 2 within a range of 0.001 to 0.02 cal/°C.

What is claimed is: 
     
       1. A fixing device for electrophotographic apparatus, comprising: a fixing roller having an elastic surface;   a heating roller for supplying a heat;   an endless fixing belt comprising a metal body and a release thin film formed on a surface thereof, said fixing belt being stretched between the fixing roller and the heating roller, said metal body having a heat capacity per cm 2  in the range of 0.001 to 0.02 cal/°C.   a pressing roller for pressing said fixing roller through the fixing belt, said pressing roller forming a nip portion together with the fixing belt therebetween; and   a guide plate disposed between the heating roller and the nip portion to guide an unfixed image carrying support member to said nip portion, said guide plate forming substantially a linear heating path together with said fixing belt.   
     
     
       2. A fixing device according to claim 1, wherein said metal body is formed by nickel electroforming. 
     
     
       3. A fixing device according to claim 1, wherein said metal body has a thickness of 45 μm. 
     
     
       4. A fixing device according to claim 1, wherein said release thin film is made of a silicone rubber. 
     
     
       5. A fixing device according to claim 1, wherein said release thin film has a thickness within a range of 10 to 200 μm. 
     
     
       6. A fixing device according to claim 1, wherein said release thin film has a thickness within a range of 50 to 100 μm. 
     
     
       7. A fixing device according to claim 1, wherein said fixing belt has a thickness within a range of 0.01 to 0.2 mm. 
     
     
       8. A fixing device according to claim 1, wherein said guide plate is arranged with a clearance within a range of 0.5 to 10 mm relative to the fixing belt. 
     
     
       9. A fixing device according to claim 1, wherein said heating roller is kept at a temperature within a range of 140° to 190° C. 
     
     
       10. A fixing device according to claim 1, wherein said pressing roller is kept at a temperature within a range of 100° to 138° C. at the nip portion. 
     
     
       11. A fixing device according to claim 1, wherein said fixing belt is kept at a temperature within a range of 135° to 185° C. in the heating path.