Method and system of introducing media into a media path with minimal positional error

Abstract

A system and method of controlling the movement of a media sheet along a media path to correspond to the timing of a toner image on an intermediate transfer mechanism. A controller controls the timing and sends a pick command to move a media sheet from a pick tray into the media pathway at a time that the media can move at a process speed and intercept the toner image. The controller adjusts the speed of individual rollers within the media path to correct the timing of the media sheet to account for any timing inaccuracies. By the time the media sheet exits the media path and enters a media/image alignment region of the media pathway, the amount of positional error is reduced or eliminated.

What is claimed is:  
     
         1 . A method of adjusting a speed of a media sheet moving along a media path region of a pathway within an image forming apparatus to intercept a toner image at a transfer point, the method comprising the steps of: 
 a. determining a positional error of the media sheet moving along the media path region;    b. determining at least one correction speed that is different than a process speed;    c. moving the media sheet along the section of the media path at the correction speed and reducing the positional error; and    d. moving the media sheet at a speed substantially the same as a process speed along a remaining portion of the media path region.    
     
     
         2 . The method of  claim 1 , wherein moving the media sheet along the section of the media path at the correction speed eliminates the positional error.  
     
     
         3 . The method of  claim 1 , wherein the step of determining the positional error of the media sheet moving along the media path region occurs at least when the media sheet is introduced into the media path region from a pick tray.  
     
     
         4 . The method of  claim 1 , wherein the correction speed cannot exceed a maximum speed.  
     
     
         5 . The method of  claim 1 , wherein the correction speed cannot be less than a minimum speed.  
     
     
         6 . The method of  claim 1 , further including the step of moving the media sheet along the media path region at the process speed prior to determining the positional error.  
     
     
         7 . The method of  claim 1 , wherein the section of the media path is about 110 to 140 millimeters.  
     
     
         8 . The method of  claim 1  further comprising repeatedly determining a positional error and a correction speed based on a current determined position of the media sheet.  
     
     
         9 . The method of  claim 1  further comprising controlling a pair of rollers with a single motor, said rollers moving the media sheet.  
     
     
         10 . A method of adjusting a speed of a media sheet moving along a media path region of a pathway within an image forming apparatus to intercept a toner image at a transfer point, the method comprising the steps of: 
 a. introducing the media sheet into the media path region;    b. sensing the position of the media sheet along the media path;    c. determining a positional error of the media sheet;    d. contacting the media sheet with a transport mechanism to control the speed of the media sheet along a media path section;    e. rotating the transport mechanism to move the media sheet at at least one correction speed;    f. at a downstream end of the media path section, rotating the transport mechanism to move the media sheet at a process speed that is different than the correction speed; and    g. contacting the media sheet with a downstream transport mechanism that is rotating to move the media sheet at a speed that is substantially the same as the process speed.    
     
     
         11 . The method of  claim 10 , wherein the step of determining a positional error comprises determining a difference between an image distance and a media sheet distance.  
     
     
         12 . The method of  claim 10 , wherein the at least one correction speed is a difference between the process speed and a difference between an image position and a media position multiplied by a proportional gain constant.  
     
     
         13 . The method of  claim 10 , wherein the positional error results from the step of introducing the media sheet into the media path region.  
     
     
         14 . The method of  claim 10  further comprising repeatedly determining a position of the media sheet and recalculating the at least one correction speed based in part on said repeated determinations.  
     
     
         15 . A method of timing a media sheet to intercept a toner image at a transfer point comprising the steps of: 
 a. receiving a request to print an image;    b. placing a toner image on a transfer mechanism;    c. moving a media sheet from a pick tray into a media path;    d. sensing a media distance of the media sheet relative to the transfer point and an image distance of the toner image relative to the transfer point;    e. determining a positional error of the media sheet based on the media distance and the image distance;    f. determining at least one correction speed based on the difference between the image distance and the media distance multiplied by a proportional gain constant;    g. moving the media sheet along a first section of the media path at the at least one correction speed by contacting the media sheet with a first roller;    h. moving the media sheet along a second section of the media path at a speed substantially the same as a process speed by contacting the media sheet with a second roller, the process speed being different than the correction speed; and    i. moving the media sheet along a media/image alignment region and intercepting the toner image at the transfer point.    
     
     
         16 . The method of  claim 15 , wherein the request to print the image is received by a main controller.  
     
     
         17 . The method of  claim 16 , wherein the step of determining the positional error of the media sheet is performed by a tray controller.  
     
     
         18 . The method of  claim 17 , wherein the step of moving the media sheet along a first section of the media path is performed by the tray controller.  
     
     
         19 . The method of  claim 15  further comprising periodically recalculating the correction speed based on concurrently determined media sheet position and image position.  
     
     
         20 . A method of synchronizing the arrival of a media sheet and a toner image at a transfer point comprising the steps of: 
 a. moving the toner image along a transfer belt at a speed to arrive at the transfer point at a predetermined time;    b. moving a plurality of rollers positioned along a media path at a process speed;    c. placing a media sheet within the media path a distance away from the transfer point to arrive at the transfer point at the predetermined time when moving at the process speed;    d. determining a positional error of the media sheet at a point along the media path;    e. changing the speed of one of the plurality of rollers from the process speed to at least one correction speed and moving the media sheet through a section of the media path controlled by the one roller;    f. after the sheet has moved through the section of the media path controlled by the one roller, moving the sheet at a speed substantially the same as the process speed; and    g. transferring the sheet to a media/image alignment region.    
     
     
         21 . The method of  claim 20 , wherein moving the media sheet at the at least one correction speed through the section of the media path controlled by the one roller reduces the positional error.  
     
     
         22 . The method of  claim 20 , wherein the correction speed is limited to a maximum speed at which the one of the plurality of rollers can operate.  
     
     
         23 . The method of  claim 20 , wherein the correction speed is limited to a maximum speed at which the one of the plurality of rollers can operate.  
     
     
         24 . The method of  claim 20  further comprising recalculating said correction speed based on a later determined positional error of said media sheet.  
     
     
         25 . A method of moving a media sheet through a media path of an image forming apparatus comprising the steps of: 
 a. controlling movement of the media sheet along a first section of the media path with a first roller;    b. controlling the movement of the media sheet along a second section of the media path with a second roller;    c. rotating both the first roller and the second roller at a process speed;    d. detecting a positional error as the media sheet enters the first section of the media path and changing the first roller from the process speed to a correction speed; and    e. after the media sheet has traveled along the first section of the media path, moving the first roller and the second roller at the process speed and moving the media sheet from the first section to the second section.    
     
     
         26 . The method of  claim 25 , prior to the media sheet reaching a downstream end of the first section, changing the speed of the first roller from the correction speed to a speed substantially the same as the process speed.  
     
     
         27 . The method of  claim 25  further comprising periodically recalculating a positional error of the media sheet and recalculating said correction speed based on the recalculated positional error.  
     
     
         28 . A method of controlling an image forming apparatus, comprising: 
 a. controlling a pair of rollers in a media path with a single motor;    b. correcting positional error of a media sheet with one or more rollers in the media path; and    c. determining if the media sheet has passed a downstream roller of the pair of rollers before correcting for positional error in a subsequent media sheet.