Sheet conveying device, image forming apparatus, and sheet conveying method

Abstract

According to one embodiment, a sheet conveying device includes a paper feeding roller, a separating roller, a double-feed detection section, a double-feed determining section, a torque limiter, a driving section, and a driving force-input control section. The paper feeding roller conveys a sheet. The separating roller separates sheets doubly fed to a nip between the separating roller and the paper feeding roller. The double-feed detection section detects conveyance state of the sheets to the nip and outputs a detection signal. The double-feed determining section determines, on the basis of the detection signal, whether sheets conveyed to the nip are doubly fed. If only one sheet is conveyed to the nip, the torque limiter allows the separating roller to be driven to rotate following the paper feeding roller. The driving section inputs driving force to the separating roller via the torque limiter. If the double-feed determining section determines that the sheets are doubly fed, the driving force-input control section causes the driving section to input the driving force to the torque limiter and, if the double-feed determining section determines that the sheets are not doubly fed, the driving force-input control section stops the input of the driving force to the torque limiter by the driving section.

1 . A sheet conveying device comprising:
 a paper feeding roller configured to convey a sheet;   a separating roller configured to separate sheets doubly fed to a nip between the separating roller and the paper feeding roller;   a double-feed detection section configured to detect conveyance state of the sheets to the nip and output a detection signal;   a double-feed determining section configured to determine, on the basis of the detection signal, whether sheets conveyed to the nip are doubly fed;   a torque limiter configured to allow, if only one sheet is conveyed to the nip, the separating roller to be driven to rotate following the paper feeding roller;   a driving section configured to input driving force to the separating roller via the torque limiter; and   a driving force-input control section configured to cause, if the double-feed determining section determines that the sheets are doubly fed, the driving section to input the driving force to the torque limiter and stop, if the double-feed determining section determines that the sheets are not doubly fed, the input of the driving force to the torque limiter by the driving section.   
     
     
         2 . The device according to  claim 1 , wherein the driving section includes:
 a driving force input section configured to input driving force to the torque limiter; and   a clutch provided between the driving force input section and the torque limiter and configured to connect or disconnect transmission of driving force from the driving force input section to the torque limiter under control by the driving force-input control section.   
     
     
         3 . The device according to  claim 2 , wherein
 the torque limiter and the clutch are provided on a same shaft, and   the shaft is different from a shaft of the separating roller.   
     
     
         4 . The device according to  claim 2 , further comprising:
 a conveying roller configured to convey the sheet that finishes passing through the nip in the sheet conveying direction;   a driving system configured to drive the conveying roller; and   a transmitting section configured to transmit the driving force from the driving system to the clutch.   
     
     
         5 . The device according to  claim 1 , wherein a point of detection by the double-feed detection section is further downstream in a sheet conveying direction than the nip. 
     
     
         6 . The device according to  claim 1 , wherein the driving section inputs, to the separating roller, driving force in a direction opposite to a direction of the driven rotation. 
     
     
         7 . An image forming apparatus comprising:
 a paper feeding roller configured to convey a sheet;   a separating roller configured to separate sheets doubly fed to a nip between the separating roller and the paper feeding roller;   a double-feed detection section configured to detect conveyance state of the sheets to the nip and output a detection signal;   a double-feed determining section configured to determine, on the basis of the detection signal, whether sheets conveyed to the nip are doubly fed;   a torque limiter configured to allow, if only one sheet is conveyed to the nip, the separating roller to be driven to rotate following the paper feeding roller;   a driving section configured to input driving force to the separating roller via the torque limiter;   a driving force-input control section configured to cause, if the double-feed determining section determines that the sheets are doubly fed, the driving section to input the driving force to the torque limiter and stop, if the double-feed determining section determines that the sheets are not doubly fed, the input of the driving force to the torque limiter by the driving section; and   an image forming section configured to form an image on a sheet that finishes passing through the nip.   
     
     
         8 . The apparatus according to  claim 7 , wherein the driving section includes:
 a driving force input section configured to input driving force to the torque limiter; and   a clutch provided between the driving force input section and the torque limiter and configured to connect or disconnect transmission of driving force from the driving force input section to the torque limiter under control by the driving force-input control section.   
     
     
         9 . The apparatus according to  claim 8 , further comprising:
 a conveying roller configured to convey the sheet that finishes passing through the nip to the image forming section side;   a driving system configured to drive the conveying roller; and   a transmitting section configured to transmit the driving force from the driving system to the clutch.   
     
     
         10 . The apparatus according to  claim 8 , wherein
 the torque limiter and the clutch are provided on a same shaft, and   the shaft is different from a shaft of the separating roller.   
     
     
         11 . The apparatus according to  claim 10 , wherein the torque limiter is integral with a gear which meshes with a gear provided in the shaft of the separating roller. 
     
     
         12 . The apparatus according to  claim 7 , wherein a point of detection by the double-feed detection section is further downstream in a sheet conveying direction than the nip. 
     
     
         13 . The apparatus according to  claim 7 , wherein the driving section inputs, to the separating roller, driving force in a direction opposite to a direction of the driven rotation. 
     
     
         14 . A sheet conveying method by an image forming apparatus including: a paper feeding roller configured to convey a sheet; a separating roller configured to separate sheets doubly fed to a nip between the separating roller and the paper feeding roller; a double-feed detection section configured to detect conveyance state of sheets to the nip and output a detection signal; a torque limiter configured to allow, if only one sheet is conveyed to the nip, the separating roller to be driven to rotate following the paper feeding roller; and a driving section configured to input driving force to the separating roller via the torque limiter,
 the sheet conveying method comprising: 
 determining, on the basis of the detection signal, whether sheets conveyed to the nip are doubly fed; and 
 causing, if it is determined that the sheets are doubly fed, the driving section to input the driving force to the torque limiter and stopping, if it is determined that the sheets are not doubly fed, the input of the driving force to the torque limiter by the driving section. 
 
     
     
         15 . The method according to  claim 14 , wherein the driving section includes:
 a driving force input section configured to input driving force to the torque limiter; and   a clutch provided between the driving force input section and the torque limiter and configured to connect or disconnect transmission of driving force from the driving force input section to the torque limiter, and   the method further comprises connecting or disconnecting the clutch on the basis of a result of determination concerning whether sheets are doubly fed.   
     
     
         16 . The method according to  claim 15 , wherein the image forming apparatus further includes:
 a conveying roller configured to convey a sheet that finishes passing through the nip to an image forming section side;   a driving system configured to drive the conveying roller; and   a transmitting section configured to transmit the driving force from the driving system to the clutch.   
     
     
         17 . The method according to  claim 15 , wherein
 the torque limiter and the clutch are provided on a same shaft, and   the shaft is different from a shaft of the separating roller.   
     
     
         18 . The method according to  claim 17 , wherein the torque limiter is integral with a gear which meshes with a gear provided in the shaft of the separating roller. 
     
     
         19 . The method according to  claim 14 , wherein a point of detection by the double-feed detection section is further downstream in a sheet conveying direction than the nip. 
     
     
         20 . The method according to  claim 14 , wherein the driving section inputs, to the separating roller, driving force in a direction opposite to a direction of the driven rotation.