Fixing apparatus

Abstract

A fixing apparatus for fixing an image on a record sheet . .comprises.!. .Iadd.includes .Iaddend.a fixing roller in which a heater is disposed, a pressing roller urged against the fixing roller, heat pipes extending in either one of the fixing and pressing rollers in a longitudinal direction thereof, and a temperature detection/control device for detecting . .to control.!. .Iadd.and controlling .Iaddend.a temperature of the fixing roller. In a typical embodiment, the heat pipes are disposed in the fixing roller to extend both through . .an imaging portion.!. .Iadd.a sheet passage area.Iaddend., through which a record sheet passes, and through a . .non-imaging portion.!. .Iadd.sheet non-passage area.Iaddend., through which no record sheet passes and the temperature detection/control device has a temperature detection device for detecting a temperature of the fixing roller in contact with the . .non-imaging portion.!. .Iadd.sheet non-passage area.Iaddend.. The temperature detection/control device is provided with a temperature regulating device for interrupting electricity to the heater when the fixing roller exceeds a predetermined temperature. In another embodiment, at least one of .Iadd.the .Iaddend.heat pipes is provided in the fixing roller in parallel with an axis of the fixing roller, and a core of the fixing roller is produced by extrusion.

What is claimed is: 
     
       1. A fixing apparatus for fixing an image on a record sheet, comprising: a tubular fixing roller;   a pressing roller urged against said fixing roller;   a heater received in said fixing roller for heating said fixing roller;   at least one heat pipe embedded in said fixing roller so as to extend in a longitudinal direction of said fixing roller for improving a thermal conductivity; and   temperature detection/control means for detecting a temperature of said fixing roller and controlling said heater so as to adjust said temperature of said fixing roller based on said detected temperature. .; `said fixing roller having an imaging portion at a center thereof and having non-imaging portions at both ends thereof, and.!..Iadd., .Iaddend.said .Iadd.at least one .Iaddend.heat pipe being disposed in said fixing roller so as to extend.Iadd., at least at one end thereof, over a sheet passage area and a sheet non-passage area on said fixing roller, .Iaddend.. .through said imaging portion and said non-imaging portions,.!. said temperature detection/control means . .comprising temperature detection means for detecting said temperature of said fixing roller at said non-imaging portion, said temperature detection/control means comprising temperature regulating means for interrupting electricity to said heater when said fixing roller exceeds a predetermined temperature, said temperature detecting means and said temperature regulating means being in contact with said fixing roller at different positions which are offset in the longitudinal direction of said fixing roller.!. .Iadd.being arranged in said sheet non-passage area in which said at least one heat pipe is disposed.Iaddend..   
     
     
       2. A fixing apparatus according to claim 1, wherein said .Iadd.at least one .Iaddend.heat pipe is at least three in number, and at least one of said heat pipes is in parallel with . .the.!. .Iadd.a .Iaddend.longitudinal axis of said fixing roller. . . 
     
     
       3.  A fixing apparatus according to claim 1, wherein said heat pipe is embedded in a core of said fixing roller, and said core of said fixing roller is produced by extrusion..!. 
     
     
       4. A fixing apparatus . .according to claim 1, wherein.!. .Iadd.for fixing an image on a record sheet, comprising: a tubular fixing roller;   a pressing roller urged against said fixing roller;   a heater received in said fixing roller for heating said fixing roller;   at least one heat pipe embedded in said fixing roller so as to extend in a longitudinal direction of said fixing roller for improving a thermal conductivity; and   temperature detection/control means for detecting a temperature of said fixing roller and controlling said heater so as to adjust said temperature of said fixing roller based on said detected temperature,   said at least one heat pipe being disposed in said fixing roller so as to extend, at least at one end thereof, over a sheet passage area and a sheet non-passage area on said fixing roller, .Iaddend.   both ends of said fixing roller . .are.!. .Iadd.being .Iaddend.made of a material having a low thermal conductivity.   
     
     
       5. A fixing apparatus according to claim 1, wherein said pipe is shorter in the longitudinal direction of said fixing roller than . .a.!. .Iadd.the .Iaddend.sheet passage area of said fixing roller. 
     
     
       6. A fixing apparatus according to claim 1, wherein a heating portion of said heater is shorter in . .a.!. .Iadd.the .Iaddend.longitudinal direction of said fixing roller than . .a.!. .Iadd.the .Iaddend.sheet passage area of said fixing roller. 
     
     
       7. A fixing apparatus according to claim . .6.!. .Iadd.15.Iaddend., wherein said heating portion of said heater is shorter than said heat pipe. 
     
     
       8. A fixing apparatus according to claim 1, wherein said .Iadd.at least one .Iaddend.heat pipe is at least three in number, and at least one of said heat pipes is embedded in an elastic layer of said pressing roller. 
     
     
       9. A fixing apparatus according to claim 2, wherein all of said heat pipes are provided in parallel with the longitudinal axis of said fixing roller. 
     
     
       10. A fixing apparatus according to claim 2, wherein one of said heat pipes is in parallel with said longitudinal axis of said fixing roller, and the others of said heat pipes are oblique with respect to said longitudinal axis of said fixing roller. 
     
     
       11. A fixing apparatus according to claim 8, wherein said heat pipes are supported by support means outside said elastic layer. 
     
     
       12. A fixing apparatus for fixing an image on a record sheet, comprising: a tubular fixing roller;   a pressing roller urged against said fixing roller;   a heater received in said fixing roller for heating said fixing roller;   . .at least one heat pipe embedded in a core of said pressing roller so as to extend in a longitudinal direction of said pressing roller for improving a thermal conductivity, at least a portion of said heat pipe being in an elastic layer of said pressing roller,.!..Iadd.; .Iaddend.and   temperature detection/control means for detecting a temperature of said fixing roller and controlling said heater so as to adjust said temperature of said fixing roller based on said detected temperature. .;.!..Iadd., .Iaddend.`said fixing roller having . .an imaging portion at a center thereof and having non-imaging portions at both ends thereof, and said heat pipe being disposed in said pressing roller so as to extend through said imaging portion and said non-imaging portions, said temperature detection/control means comprising temperature detection means for detecting said temperature of said fixing roller at said non-imaging portion, said temperature detection/control means comprising temperature regulating means for interrupting electricity to said heater when said fixing roller exceeds a predetermined temperature, said temperature detecting means and said temperature regulating means being in contact with said fixing roller at different positions which are offset in the longitudinal direction of said fixing roller.!. .Iadd.a sheet passage area and a sheet non-passage area thereon, said fixing apparatus further comprising at least one heat pipe held on a core of said pressing roller so as to extend in a longitudinal direction of said pressing roller for improving a thermal conductivity, at least a portion of said at least one heat pipe being in an elastic layer of said pressing roller, and said at least one heat pipe being disposed in said pressing roller so as to extend over said sheet passage area and said sheet non-passage area.Iaddend..   
     
     
       13. A fixing apparatus . .according to claim 12, wherein.!. .Iadd.for fixing an image on a record sheet, comprising: a tubular fixing roller;   a pressing roller urged against said fixing roller;   a heater received in said fixing roller for heating said fixing roller; and   temperature detection/control means for detecting a temperature of said fixing roller and controlling said heater so as to adjust said temperature of said fixing roller based on said detected temperature,   said fixing roller having a sheet passage area and a sheet non-passage area thereon,   said fixing apparatus further comprising at least one heat pipe held on a core of said pressing roller so as to extend in a longitudinal direction of said pressing roller for improving a thermal conductivity, at least a portion of said at least one heat pipe being in an elastic layer of said pressing roller, and said at least one heat pipe being disposed in said pressing roller so as to extend over said sheet passage area and said sheet non-passage area, .Iaddend.   said .Iadd.at least one .Iaddend.heat pipe . .is.!. .Iadd.being .Iaddend.formed in an integral with said core. .Iadd.14. A fixing apparatus for fixing an image on a record sheet, comprising:   a tubular fixing roller;   a pressing roller urged against said fixing roller;   a heater received in said fixing roller for heating said fixing roller; and   at least one heat pipe embedded in said fixing roller so as to extend in a longitudinal direction of said fixing roller for improving a thermal conductivity,   said at least one heat pipe being disposed in said fixing roller so as to extend, at least at one end thereof, over a sheet passage area and a sheet non-passage area for a small size sheet on said fixing roller and within a sheet passage area for a maximum size sheet on the fixing roller. .Iaddend..Iadd.15. A fixing apparatus for fixing an image on a record sheet, comprising:   a tubular fixing roller;   a pressing roller urged against said fixing roller;   a heater received in said fixing roller for heating said fixing roller; and   at least one heat pipe embedded in said fixing roller so as to extend in a longitudinal direction of said fixing roller for improving a thermal conductivity,   wherein a heating portion of said heater extends within a sheet passage area for a maximum size sheet on the fixing roller. .Iaddend..Iadd.16. A fixing apparatus according to claim 1, wherein said temperature detection/control means comprises temperature detection means for detecting said temperature of said fixing roller at said sheet non-passage area and temperature regulating means for interrupting electricity to said heater when said fixing roller exceeds a predetermined temperature, said temperature detection means and said temperature regulating means are arranged in different portions which are offset in the longitudinal direction of said fixing roller. .Iaddend..Iadd.17. A fixing apparatus according to claim 14, wherein a heating portion of said heater is shorter than said heat pipe. .Iaddend..Iadd.18. A fixing roller for fixing an image on a record sheet, comprising:   a tubular roller body; and   at least one heat pipe embedded in said roller body so as to extend in a longitudinal direction of said roller body for improving a thermal conductivity,   said at least one heat pipe being disposed in said roller body so as to extend, at least at one end thereof, over a sheet passage area and a sheet non-passage area on said roller body, thereby to allow an arrangement of a temperature detection/control means within said sheet non-passage area. .Iaddend..Iadd.19. A fixing roller for fixing an image on a record sheet, comprising:   a tubular roller body; and   at least one heat pipe embedded in said roller body so as to extend in a longitudinal direction of said roller body for improving thermal conductivity,   said at least one heat pipe being disposed in said roller body so as to extend, at least at one end thereof, over a sheet passage area and a sheet non-passage area on said roller body,   both ends of said roller body being made of a material having a low thermal conductivity. .Iaddend..Iadd.20. A fixing roller for fixing an image on a record sheet, comprising:   a tubular roller body; and   at least one heat pipe embedded in said roller body so as to extend in a longitudinal direction of said roller body for improving a thermal conductivity,   said at least one heat pipe being disposed in said roller body so as to extend, at least at one end thereof, over a sheet passage area and a sheet non-passage area for a small size sheet on said roller body and within a sheet passage area for a maximum size sheet on the roller body. .Iaddend..Iadd.21. A fixing roller for fixing an image on a record sheet, comprising:   a tubular roller body;   a heater received in said roller body for heating said roller body; and   at least one heat pipe embedded in said roller body so as to extend in a longitudinal direction of said roller body for improving a thermal conductivity,   wherein a heating portion of said heater extends within a sheet passage area for a maximum size sheet on the roller body. .Iaddend.