Sheet transport device, sheet transport control method, and printer

Abstract

According to one aspect of the embodiment, a sheet transport device includes a detecting unit configured to detect skew with respect to a transport direction of a sheet that is supplied, a transport unit configured to transport the sheet using a plurality of transport members disposed on the right and on the left at different intervals from an upstream side toward a downstream side in the transport direction and a control unit configured to cause rotation velocities of transport members on the right among the plurality of transport members to be different from rotation velocities of transport members on the left among the plurality of transport members in accordance with the skew of the sheet detected by the detecting unit.

1 . A sheet transport device comprising:
 a detecting unit configured to detect skew with respect to a transport direction of a sheet that is supplied;   a transport unit configured to transport the sheet using a plurality of transport members disposed on the right and on the left at different intervals from an upstream side toward a downstream side in the transport direction; and   a control unit configured to cause rotation velocities of transport members on the right among the plurality of transport members to be different from rotation velocities of transport members on the left among the plurality of transport members in accordance with the skew of the sheet detected by the detecting unit.   
     
     
         2 . The sheet transport device according to  claim 1 ,
 wherein the detecting unit includes a plurality of sensors disposed in a direction perpendicular to the transport direction, and determines whether or not detection timings of detecting the sheet by the plurality of sensors are the same, and   wherein, when the detection timings are not the same, the control unit executes either or both of decreasing the rotation velocities of the transport members on the side of a sensor that detects the sheet first among the plurality of sensors, and increasing the rotation velocities of the transport members on the side of a sensor that detects the sheet later among the plurality of sensors.   
     
     
         3 . The sheet transport device according to  claim 1 , further comprising:
 a measuring unit configured to measure a detection time difference in the detecting unit, the detection time difference being caused by skew of the sheet that is transported,   wherein the control unit calculates at least one of a skew distance and a skew angle on the basis of the rotation velocities and the detection time difference measured by the measuring unit, and determines a difference in rotation velocity between the transport members on the right and the transport members on the left and a transport period on the basis of one of the skew distance and the skew angle.   
     
     
         4 . The sheet transport device according to  claim 1 ,
 wherein each of the plurality of transport members is constituted by a roller member having a reduced contact area that contacts the sheet.   
     
     
         5 . The sheet transport device according to  claim 1 ,
 wherein the plurality of transport members of the transport unit are disposed in a V-like shape from the upstream side toward the downstream side in the transport direction.   
     
     
         6 . The sheet transport device according to  claim 1 ,
 wherein the control unit controls the plurality of transport members so that the transport members on the right operate simultaneously and the transport members on the left operate simultaneously with respect to the transport direction.   
     
     
         7 . The sheet transport device according to  claim 1 ,
 wherein the transport unit includes a plurality of driving motors for rotating the plurality of transport members, and   wherein the control unit performs rotation control of each of the plurality of driving motors in accordance with the detected skew of the sheet.   
     
     
         8 . The sheet transport device according to  claim 1 ,
 wherein the control unit minimizes a difference in rotation velocity between the transport members on the right and the transport members on the left on the basis of the detected skew.   
     
     
         9 . The sheet transport device according to  claim 2 ,
 wherein the plurality of sensors include a light emitting unit configured to emit light to a measurement point, and a light receiving unit configured to receive the light emitted by the light emitting unit, and   wherein, when the light emitted to the light receiving unit is cut off, the control unit determines that the sheet is detected.   
     
     
         10 . The sheet transport device according to  claim 1 , further comprising:
 a skew monitoring unit configured to monitor skew of the sheet that has passed the transport unit,   wherein, when the skew monitoring unit detects the skew, the transport unit returns the sheet to a transport start position.   
     
     
         11 . A sheet transport control method comprising:
 detecting skew with respect to a transport direction of a sheet that is supplied; and   performing control by causing rotation velocities of transport members on the right among a plurality of transport members to be different from rotation velocities of transport members on the left among the plurality of transport members in accordance with the detected skew of the sheet, the plurality of transport members being disposed on the right and on the left at different intervals from an upstream side toward a downstream side in the transport direction.   
     
     
         12 . The sheet transport control method according to  claim 11 , further comprising:
 determining whether or not detection timings of detecting the sheet by a plurality of sensors are the same, the plurality of sensors being disposed in a direction perpendicular to the transport direction; and   when the detection timings are not the same, executing either or both of decreasing the rotation velocities of the transport members on the side of a sensor that detects the sheet first among the plurality of sensors, and increasing the rotation velocities of the transport members on the side of a sensor that detects the sheet later among the plurality of sensors.   
     
     
         13 . The sheet transport control method according to  claim 11 , further comprising:
 measuring, with a measuring unit, a detection time difference caused by skew of the sheet that is transported;   calculating at least one of a skew distance and a skew angle on the basis of the rotation velocities and the detection time difference; and   determining a difference in rotation velocity between the transport members on the right and the transport members on the left and a transport period on the basis of one of the skew distance and the skew angle.   
     
     
         14 . The sheet transport control method according to  claim 11 , further comprising:
 monitoring skew of the sheet that has been transported; and   when skew is detected in the sheet that has been transported, returning the sheet to a transport start position.   
     
     
         15 . A printer comprising:
 a detecting unit configured to detect skew with respect to a transport direction of a sheet that is taken from a feeding unit;   a transport unit configured to transport the sheet using a plurality of transport members disposed on the right and on the left at different intervals from an upstream side toward a downstream side in the transport direction; and   a control unit configured to cause rotation velocities of transport members on the right among the plurality of transport members to be different from rotation velocities of transport members on the left among the plurality of transport members in accordance with the skew of the sheet detected by the detecting unit.   
     
     
         16 . The printer according to  claim 15 ,
 wherein the detecting unit includes a plurality of sensors disposed in a direction perpendicular to the transport direction, and determines whether or not detection timings of detecting the sheet by the plurality of sensors are the same, and   wherein, when the detection timings are not the same, the control unit executes either or both of decreasing the rotation velocities of the transport members on the side of a sensor that detects the sheet first among the plurality of sensors, and increasing the rotation velocities of the transport members on the side of a sensor that detects the sheet later among the plurality of sensors.   
     
     
         17 . The printer according to  claim 15 , further comprising:
 a measuring unit configured to measure a detection time difference in the detecting unit, the detection time difference being caused by skew of the sheet that is taken,   wherein the control unit calculates at least one of a skew distance and a skew angle on the basis of the rotation velocities and the detection time difference measured by the measuring unit, and determines a difference in rotation velocity between the transport members on the right and the transport members on the left and a transport period on the basis of one of the skew distance and the skew angle.   
     
     
         18 . The printer according to  claim 15 ,
 wherein the plurality of transport members of the transport unit are disposed in a V-like shape from the upstream side toward the downstream side in the transport direction.   
     
     
         19 . The printer according to  claim 15 ,
 wherein the control unit includes a rotation velocity setting table in which minimized differences in rotation velocity between the transport members on the right and the transport members on the left are set on the basis of the detected skew.   
     
     
         20 . The printer according to  claim 15 , further comprising:
 a skew monitoring unit configured to monitor skew of the sheet that has passed the transport unit,   wherein, when the skew monitoring unit detects the skew, the transport unit returns the sheet to a transport start position.