Printer

Abstract

A second driven roller that is rotated by following a second driving roller has a larger outer diameter than a first driven roller. A front edge of a recording sheet being lifted up from a first nip contacts the second driven roller, and hence the front edge does not directly hit the first driven roller. The second driven roller rotates at a higher rotational speed than a rotational speed of the first driven roller. The second driven roller gently flips the front edge of the recording sheet which has contacted the second driven roller, and leads the front edge quickly to the first nip. The front edge of the recording sheet is smoothly led to the nip.

1 . A printer comprising:
 a driving roller conveyance mechanism and a driven roller conveyance mechanism both arranged downstream of a print section in a conveying direction of a sheet with a conveyance path interposed between the driving roller conveyance mechanism and the driven roller conveyance mechanism,   wherein the driving roller conveyance mechanism includes   a first driving roller having an outer circumferential surface made of a material having a large friction coefficient, the first driving roller having a shaft center extending in a direction orthogonal to the conveying direction,   a second driving roller having an outer circumferential surface made of a material having a smaller friction coefficient than the outer circumferential surface of the first driving roller, the second driving roller being coaxial with the first driving roller,   a first driving mechanism configured to rotate the first driving roller so that the sheet is conveyed toward a downstream side in the conveying direction, and   a second driving mechanism configured to rotate the second driving roller at a higher rotational speed than a rotational speed of the first driving roller so that the sheet is conveyed toward the downstream side in the conveying direction,   wherein the driven roller conveyance mechanism includes   a rotatable first driven roller being in contact with the first driving roller, the first driven roller having a shaft center extending in the direction orthogonal to the conveying direction,   a rotatable second driven roller being in contact with the second driving roller, the second driven roller having a shaft center extending in the direction orthogonal to the conveying direction, the second driven roller having a larger outer diameter than the first driven roller,   a first urging mechanism urging the first driven roller in a direction in which the first driven roller contacts the first driving roller, and   a second urging mechanism urging the second driven roller in a direction in which the second driven roller contacts the second driving roller, and   wherein the second driven roller is formed of a spur roller having a toothed part on an outer circumferential part of the second driven roller.   
     
     
         2 . The printer according to  claim 1 ,
 wherein the first driving mechanism includes a first drive shaft having a shaft center extending in the direction orthogonal to the conveying direction,   wherein the first driving roller is attached to the first drive shaft so that the first driving roller rotates with the first drive shaft,   wherein the second driving roller is rotatably supported by the first drive shaft,   wherein the second driving mechanism includes   a second drive shaft extending in parallel to the first drive shaft,   a first power transmission mechanism linking the first drive shaft with the second drive shaft, and   a second power transmission mechanism linking the second drive shaft with the second driving roller, and   wherein at least one of the first power transmission mechanism and the second power transmission mechanism rotates the second driving roller at a higher rotational speed than a rotational speed of the first drive shaft.   
     
     
         3 . The printer according to  claim 2 ,
 wherein the second driving roller includes a plurality of second driving rollers provided at an interval in a longitudinal direction of the first drive shaft, and   wherein the second driven roller includes a plurality of second driven rollers corresponding to the plurality of second driving rollers.   
     
     
         4 . The printer according to  claim 2 ,
 wherein the first driving roller includes a plurality of first driving rollers provided at an interval in a longitudinal direction of the first drive shaft,   wherein the second driving roller includes a plurality of second driving rollers provided at a plurality of positions on the first drive shaft not occupied by the first driving rollers, the second driving rollers rotatably supported by the first drive shaft,   wherein the first driven roller includes a plurality of first driven rollers corresponding to the plurality of first driving rollers, and   wherein the second driven roller includes a plurality of second driven rollers corresponding to the plurality of second driving rollers.   
     
     
         5 . The printer according to  claim 2 ,
 wherein the conveyance path has a width orthogonal to the conveying direction,   wherein the second driving roller includes three second driving rollers disposed at the center and both ends in a width direction of the conveyance path,   wherein the first driving roller includes two first driving rollers disposed among the three second driving rollers, at both sides of the center of the conveyance path,   wherein the first driven roller includes a plurality of first driven rollers corresponding to the plurality of first driving rollers, and   wherein the second driven roller includes a plurality of second driven rollers corresponding to the plurality of second driving rollers.   
     
     
         6 . The printer according to any of  claims 1  to  5 , wherein the second urging mechanism provides a smaller urging force for urging the second driven roller in the direction in which the second driven roller contacts the second driving roller than an urging force of the first urging mechanism for urging the first driven roller in the direction in which the first driven roller contacts the first driving roller. 
     
     
         7 . The printer according to any of  claims 1 - 5 ,
 wherein the outer circumferential surface of the first driving roller is made of rubber, and   wherein the outer circumferential surface of the second driving roller is made of synthetic resin having a smaller friction coefficient than the rubber.   
     
     
         8 . The printer according to any of  claims 1 - 5 , wherein the first driven roller is formed of a spur roller having a toothed part on an outer circumferential part of the first driven roller. 
     
     
         9 . The printer according to any of  claims 1 - 5 , wherein the first driving roller has an outer diameter equivalent to the second driving roller.