Density unevenness reduction method and sheet transport mechanism

Abstract

A density unevenness reduction method of a printing apparatus having a sheet transport mechanism which transmits a driving force of a driving device to a roller via a plurality of gears to drive the roller for transporting a sheet, the method includes: assuming one tooth and one turn of each of the gears each to be a simple harmonic oscillation of a single sine wave, and generating a synthesized wave of the sine waves of the gears; and adjusting the module and the number of teeth of each of the gears, thereby dispersing a frequency at which the oscillations of the gears overlap and are amplified in the synthesized wave.

1 . A density unevenness reduction method of a printing apparatus having a sheet transport mechanism which transmits a driving force of a driving device to a roller via a plurality of gears to drive the roller for transporting a sheet, the method comprising:
 assuming one tooth and one turn of each of the gears each to be a simple harmonic oscillation of a single sine wave, and generating a synthesized wave of the sine waves of the gears; and   adjusting the module and the number of teeth of each of the gears, thereby dispersing a frequency at which the oscillations of the gears overlap and are amplified in the synthesized wave.   
     
     
         2 . A sheet transport mechanism comprising:
 a roller used for transporting a sheet;   a driving device for driving the roller; and   a plurality of gears for transmitting a driving force of the driving device to the roller,   wherein, assuming one tooth and one turn of each of the gears each to be a simple harmonic oscillation of a single sine wave, a synthesized wave of the sine waves of the gears is generated; and   the module and the number of teeth of each of the gears are adjusted so as to disperse a frequency at which the oscillations of the gears overlap and are amplified in the synthesized wave and shorten the amplitude of the frequency of the synthesized wave over a long period.   
     
     
         3 . The sheet transport mechanism according to  claim 2 , wherein the roller is a paper feed roller disposed on at least one of the upstream side and the downstream side of a platen roller in a transport direction of the sheet. 
     
     
         4 . The sheet transport mechanism according to  claim 3 ,
 wherein the paper feed roller is configured as a projection roller of which a plurality of projection teeth engaged with the teeth of one of the gears are arranged in parallel with the circumferential direction of the paper feed roller,   assuming one projection tooth and one turn of the paper feed roller each to be a simple harmonic oscillation of a single sine wave, a synthesized wave of the sine waves of the gears and the paper feed roller is generated, and   the size of the paper feed roller and the number of projection teeth are set so as to disperse a frequency at which the oscillations of the gears and the paper feed roller overlap and are amplified in the synthesized wave so as to shorten the amplitude of the frequency of the synthesized wave over a long period.   
     
     
         5 . The sheet transport mechanism according to  claim 2 , wherein the roller is a platen roller.