Fixing apparatus for fixing toner onto a sheet

Abstract

A fixing apparatus according to an embodiment includes: a first roller; a second roller that forms a nip between the second roller and the first roller and presses a sheet passing through the nip against the first roller; a heater that heats at least one of the first roller and the second roller, a heating range of the heater being greater than a maximum printing width of a predetermined maximum sheet width, and a heat-uniformizing member that distributes heat of the heater along a longitudinal direction thereof, an effective length of the heat-uniformizing member in the longitudinal direction being the same as, or greater than, the predetermined maximum sheet width.

What is claimed is: 
     
       1. A fixing apparatus comprising:
 a first roller; 
 a second roller that forms a nip between the second roller and the first roller and presses a sheet passing through the nip against the first roller; 
 a heater that heats at least one of the first roller and the second roller, the heater including a magnetic core and a coil for heating the first roller, wherein a the heating range of the heater extends along a longitudinal width of the coil and which is greater than a maximum printing width of a predetermined maximum sheet width, and a longitudinal width of the magnetic core is greater than the maximum printing width, and 
 a heat-uniformizing member that distributes heat of the heater along a longitudinal direction thereof of the heat-uniformizing member, wherein an effective length of the heat-uniformizing member in the longitudinal direction is the same as, or greater than, the predetermined maximum sheet width, and is the same as, or greater than, a sum of a width of a first region and a width of a second region in a sheet width direction, the first region being a region where heat is lost by the sheet at the nip and the second region being a region where heat is not lost by the sheet at the nip. 
 
     
     
       2. The fixing apparatus according to  claim 1 , wherein,
 the longitudinal width of the coil is less than the sum of the width of the first region and the width of the second region in the sheet width direction. 
 
     
     
       3. The fixing apparatus according to  claim 1 , wherein,
 the heater is a halogen lamp and is configured to heat the second roller.   
     
     
       4. The fixing apparatus according to claim 1, further comprising:
 a third roller, and   a continuous belt extending over the third roller and over a first one of the first and second rollers, wherein the continuous belt contacts the second one of the first and second rollers at the nip.   
     
     
       5. The fixing apparatus according to claim 4, wherein the third roller is hollow, and the heat-uniformizing member is located within the third roller. 
     
     
       6. The fixing apparatus according to claim 4, wherein the third roller comprises opposed end portions at opposed ends of a middle portion thereof, and the diameter of the opposed end portions is smaller than the diameter of the middle portion. 
     
     
       7. A fixing apparatus comprising:
 a first rotary member;   a second rotary member that forms a nip between the second rotary member and the first rotary member and presses a sheet passing through the nip against the first rotary member;   an energy source configured to heat at least one of the first rotary member and the second rotary member, wherein a heating range of the energy source extends in a width direction of the energy source and is greater in width than a maximum printing width of a predetermined maximum sheet width, and   a heat-uniformizing member that distributes heat of the energy source along a longitudinal direction of the heat-uniformizing member, wherein an effective length of the heat-uniformizing member in the longitudinal direction is the same as, or greater than, the predetermined maximum sheet width, and is the same as, or greater than a sum of a width of a first region and a width of a second region in a sheet width direction, the first region being a region where heat is lost by the sheet at the nip and the second region being a region where heat is not lost by the sheet at the nip.   
     
     
       8. The fixing apparatus of claim 7, wherein the energy source includes a magnetic core and a coil for heating the first rotary member. 
     
     
       9. The fixing apparatus according to claim 8, wherein the width of the magnetic core is greater than the maximum printing width. 
     
     
       10. The fixing apparatus of claim 7, further comprising:
 a third rotary member; and   a continuous belt extending over the third rotary member and over a first one of the first and second rotary members, wherein the continuous belt contacts the second one of the first and second rotary members at the nip.   
     
     
       11. The fixing apparatus of claim 10, wherein the third rotary member is hollow and includes the heat-uniformizing member therein. 
     
     
       12. The fixing apparatus of claim 10, wherein the continuous belt comprises a conductive layer contacting the third rotary member.