Heat roller

Abstract

A heat roller having a cylindrical sheet-like heating element having a resistance member embedded in an insulating member. The sheet-like heating element is arranged between an inner tube and an outer tube. The outer tube is formed so as to be longer than the inner tube for reducing non-uniformity in heat of the heat roller. Further, a thermal expansion coefficient of a material of the outer tube is greater than that of a material of the inner tube. Moreover, a triple-tube heat roller is provided.

1 . A heat roller comprising a cylindrical sheet-like heating element having a resistance member embedded in an insulating member, an inner tube that comes in intimate contact with an inner surface of the sheet-like heating element and an outer tube that comes in intimate contact with an outer surface of the sheet-like heating element, wherein the outer tube is longer than the inner tube.  
     
     
         2 . A heat roller comprising a cylindrical sheet-like heating element having a resistance member embedded in an insulating member, an inner tube that comes in intimate contact with an inner surface of the sheet-like heating element and an outer tube that comes in intimate contact with an outer surface of the sheet-like heating element, wherein a thermal expansion coefficient of a material of the inner tube is greater than a thermal expansion coefficient of a material of the outer tube.  
     
     
         3 . A heat roller comprising a first cylindrical sheet-like heating element having a resistance member embedded in an insulating member, a first tube that comes in intimate contact with an inner surface of the first sheet-like heating element, a second tube that comes in intimate contact with an outer surface of the first sheet-like heating element, a second cylindrical sheet-like heating element that comes in intimate contact with an outer surface of the second tube, and a third tube that comes in intimate contact with an outer surface of the second sheet-like heating element.  
     
     
         4 . A heat roller comprising a cylindrical sheet-like heating element having a resistance member embedded in an insulating member, an inner tube that comes in intimate contact with an inner surface of the sheet-like heating element, an outer tube that comes in intimate contact with an outer surface of the sheet-like heating element and a heat-resistant filler layer provided at least between the inner tube and the sheet-like heating element or between the sheet-like heating element and the outer tube.  
     
     
         5 . A heat roller comprising a cylindrical sheet-like heating element having a resistance member embedded in an insulating member, an inner tube that comes in intimate contact with an inner surface of the sheet-like heating element, an outer tube that comes in intimate contact with an outer surface of the sheet-like heating element and an outer layer disposed at an outer surface of the outer tube.