Manufacturing method of transfer unit

Abstract

A diameter of middle section of at leas one of rollers, which are spanned by an intermediated transfer substance, is increased in respect to the diameter of end sections thereof by an amount which is determined in accordance with a degree of sub-scanning curvature of an image transferred onto a sheet.

1 . A manufacturing method of a transfer unit to transfer a plurality of toner images transferred from a photo conducive substance onto a sheet, having a endless belt and a plurality of rollers which are spanned by the endless belt, the method comprising:
 determining an increasing amount of a diameter of a middle section of at least one of a plurality of the rollers in respect to end sections thereof, in accordance with a degree of sub-scanning curvature of an image transferred onto the sheet.   
   
   
       2 . The manufacturing method of  claim 1 , wherein the rollers are produced by machining. 
   
   
       3 . The manufacturing method of  claim 1 , wherein the rollers are produced by casting. 
   
   
       4 . The manufacturing method of  claim 1 , wherein the increasing amount of the diameter of the middle section of the roller is determined based on a measurement value of the degree of sub-scanning curvature of the image transferred onto the sheet. 
   
   
       5 . The manufacturing method of  claim 1 , wherein the increasing amount of the diameter of the middle section of the roller is determined based on a measurement value of the degree of sub-scanning curvature of the image transferred onto the sheet measured by an image sensor. 
   
   
       6 . The manufacturing method of  claim 1 , wherein the increasing amount of the diameter of the middle section of the roller is determined by presumption of the degree of sub-scanning curvature in case the image is transferred onto the sheet based on a rigidity calculation of the endless belt and the rollers. 
   
   
       7 . The manufacturing method of  claim 1 , wherein the increasing amount of the diameter of the middle section of the roller is determined by presumption of the degree of sub-scanning curvature in case the image is transferred onto the sheet based on measurement amounts of distortion of the endless belt and the rollers. 
   
   
       8 . The manufacturing method of  claim 1 , wherein the increasing amount of the diameter of the middle section of the roller is determined by presumption of the degree of sub-scanning curvature in case the image is transferred onto the sheet based on a measurement circumferential speed of the endless belt. 
   
   
       9 . The manufacturing method of  claim 1 , wherein the photoconductive substance is in a shape of a drum. 
   
   
       10 . The manufacturing method of  claim 1 , wherein the photoconductive substance is in a shape of a belt. 
   
   
       11 . The manufacturing method of  claim 1 , wherein the end less belt is an intermediate transfer substance on which the toner image developed, by developer is transferred. 
   
   
       12 . The manufacturing method of  claim 1 , wherein the end less belt is a conveyance belt to convey the sheet.