Sheet conveyance device and determination method

Abstract

According to one embodiment, a sheet conveyance device includes a plurality of conveyance rollers, a sheet sensor, and a control unit. The conveyance rollers convey a sheet on a conveyance path. The sheet sensor is provided at least at a first position and a second position on the conveyance path for the sheet and senses passage of a front end of the sheet and passage of a rear end of the sheet. The control unit determines double sheet feed based on a first time as time from passage of a front end of a first sheet through the first position to passage of the front end of the first sheet through the second position, a second time as time from sensing of the passage of the front end of the first sheet by a sheet sensor to sensing of passage of a rear end of the first sheet by the sheet sensor, a third time as time from passage through the first position of a front end of a second sheet conveyed by the conveyance roller after the first sheet to passage of the front end through the second position, and a fourth time as time from sensing of the passage of the front end of the second sheet by a sheet sensor to sensing of passage of a rear end of the second sheet by the sheet sensor.

What is claimed is: 
     
         1 . A sheet conveyance device, comprising:
 a plurality of conveyance rollers that convey a sheet on a conveyance path;   a sheet sensor provided at least at a first position and a second position on the conveyance path for the sheet that senses passage of a front end of the sheet and passage of a rear end of the sheet; and   a controller configured to determine an occurrence of double sheet feed based on a first time as time from passage of a front end of a first sheet through the first position to passage of the front end of the first sheet through the second position, a second time as time from sensing the passage of the front end of the first sheet by the sheet sensor to sensing passage of a rear end of the first sheet by the sheet sensor, a third time as time from passage through the first position of a front end of a second sheet conveyed by the conveyance roller after the first sheet to passage of the front end through the second position, and a fourth time as time from sensing of the passage of the front end of the second sheet by the sheet sensor to sensing of passage of a rear end of the second sheet by the sheet sensor.   
     
     
         2 . The sheet conveyance device according to  claim 1 , wherein the controller determines that double sheet feed occurs in a case where a first condition indicating that the first time and the third time are equal in length to each other is satisfied. 
     
     
         3 . The sheet conveyance device according to  claim 2 , wherein the controller determines that double sheet feed occurs in a case where the first condition is satisfied and a second condition indicating that the fourth time is longer than the second time is satisfied. 
     
     
         4 . The sheet conveyance device according to  claim 1 , wherein, in a case where it is determined that double sheet feed occurs, the controller performs output indicating the occurrence. 
     
     
         5 . The sheet conveyance device according to  claim 1 , further comprising an image forming component configured to form an image on the sheet. 
     
     
         6 . The sheet conveyance device according to  claim 5 , further comprising a registration roller pausing the front end of the sheet before the image forming component forms the image. 
     
     
         7 . The sheet conveyance device according to  claim 6 , wherein, on the conveyance path for the sheet, a plurality of sheet sensors are provided upstream of the registration roller in a conveyance direction of the sheet. 
     
     
         8 . The sheet conveyance device according to  claim 7 , wherein the registration roller is at a position other than between the first position and the second position on the conveyance path for the sheet. 
     
     
         9 . The sheet conveyance device according to  claim 1 , comprising a sheet accommodating portion accommodating the sheet,
 wherein the plurality of conveyance rollers convey the sheet accommodated in the sheet accommodating portion.   
     
     
         10 . The sheet conveyance device according to  claim 9 , comprising a pickup roller taking the sheet out of the sheet accommodating portion,
 wherein the plurality of conveyance rollers convey the sheet taken out of the sheet accommodating portion by the pickup roller.   
     
     
         11 . A determination method performed by a sheet conveyance device including a plurality of conveyance rollers conveying a sheet on a conveyance path and a sheet sensor provided at least at a first position and a second position on the conveyance path for the sheet and sensing passage of a front end of the sheet and passage of a rear end of the sheet, comprising:
 measuring a first time as time from passage of a front end of a first sheet through the first position to passage of the front end of the first sheet through the second position;   measuring a second time as time from sensing of the passage of the front end of the first sheet by a sheet sensor to sensing of passage of a rear end of the first sheet by the sheet sensor;   measuring a third time as time from passage through the first position of a front end of a second sheet conveyed by the conveyance roller after the first sheet to passage of the front end through the second position;   measuring a fourth time as time from sensing of the passage of the front end of the second sheet by a sheet sensor to sensing of passage of a rear end of the second sheet by the sheet sensor are acquired; and   determining an occurrence of double sheet feed based on the first time, the second time, the third time, and the fourth time.   
     
     
         12 . The determination method according to  claim 11 , further comprising determining that double sheet feed occurs in a case where a first condition indicating that the first time and the third time are equal in length to each other is satisfied. 
     
     
         13 . The determination method according to  claim 12 , further comprising determining that double sheet feed occurs in a case where the first condition is satisfied and a second condition indicating that the fourth time is longer than the second time is satisfied. 
     
     
         14 . The determination method according to  claim 11 , in a case where it is determined that double sheet feed occurs, further comprising performing output indicating the occurrence. 
     
     
         15 . The determination method according to  claim 11 , further comprising forming an image on the sheet. 
     
     
         16 . The determination method according to  claim 15 , further comprising pausing the front end of the sheet with a registration roller before forming the image. 
     
     
         17 . The determination method according to  claim 11 , further comprising conveying the sheet accommodated in the sheet accommodating portion with a plurality of conveyance rollers. 
     
     
         18 . The determination method according to  claim 17 , further comprising conveying the sheet taken out of the sheet accommodating portion by a pickup roller. 
     
     
         19 . An image forming apparatus, comprising:
 an image forming component; and   a sheet conveyance device, comprising:
 a plurality of conveyance rollers that convey a sheet on a conveyance path; 
 a sheet sensor provided at least at a first position and a second position on the conveyance path for the sheet that senses passage of a front end of the sheet and passage of a rear end of the sheet; and 
 a controller configured to determine an occurrence of double sheet feed based on a first time as time from passage of a front end of a first sheet through the first position to passage of the front end of the first sheet through the second position, a second time as time from sensing the passage of the front end of the first sheet by the sheet sensor to sensing passage of a rear end of the first sheet by the sheet sensor, a third time as time from passage through the first position of a front end of a second sheet conveyed by the conveyance roller after the first sheet to passage of the front end through the second position, and a fourth time as time from sensing of the passage of the front end of the second sheet by the sheet sensor to sensing of passage of a rear end of the second sheet by the sheet sensor. 
   
     
     
         20 . The image forming apparatus according to  claim 19 , wherein the controller determines
 that double sheet feed occurs in a case where a first condition indicating that the first time and the third time are equal in length to each other is satisfied; or   that double sheet feed occurs in a case where the first condition is satisfied and a second condition indicating that the fourth time is longer than the second time is satisfied.