Sheet carrying device

Abstract

A sheet carrying device includes: a sheet carrying unit having a first sheet carrying unit and a second sheet carrying unit, at least one of which has a sheet carrying force changing along a direction orthogonal to a traveling direction of a sheet, the first sheet carrying unit carrying the sheet in the traveling direction, the second sheet carrying unit carrying the sheet in the traveling direction together with the first sheet carrying unit; and a control unit which controls the carrying by the first sheet carrying unit and the carrying by the second sheet carrying unit on the basis of a result of detection from a detection unit which detects an inclination of the sheet that is traveling.

1 . A sheet carrying device comprising:
 a sheet carrying unit having a first sheet carrying unit and a second sheet carrying unit, at least one of which has a sheet carrying force changing along a direction orthogonal to a traveling direction of a sheet, the first sheet carrying unit carrying the sheet in the traveling direction, the second sheet carrying unit carrying the sheet in the traveling direction together with the first sheet carrying unit; and   a control unit which controls the carrying by the first sheet carrying unit and the carrying by the second sheet carrying unit on the basis of a result of detection from a detection unit which detects an inclination of the sheet that is traveling.   
     
     
         2 . The device according to  claim 1 , wherein the change in the sheet carrying force is a change in coefficient of friction to the sheet. 
     
     
         3 . The device according to  claim 2 , wherein as the change in the coefficient of friction of at least one of the first sheet carrying unit and the second sheet carrying unit, the coefficient of friction becomes smaller on a side close to a center in the traveling direction of the sheet. 
     
     
         4 . The device according to  claim 2 , wherein the first sheet carrying unit has a first rotating body which supports plural rollers along a first shaft, and a second rotating body which has a different coefficient of friction from the first rotating body, supports plural rollers along a second shaft and nips the sheet together with the first rotating body, and
 the second sheet carrying unit has a third rotating body which supports plural rollers along a third shaft, and a fourth rotating body which has a different coefficient of friction from the third rotating body, supports plural rollers along a fourth shaft and nips the sheet together with the third rotating body.   
     
     
         5 . The device according to  claim 4 , wherein one having a larger coefficient of friction, of the first rotating body and the second rotating body, has a contact surface to the sheet made of a rubber material, and one having a smaller coefficient of friction has a contact surface to the sheet made of a metal material or resin material, and
 one having a larger coefficient of friction, of the third rotating body and the fourth rotating body, has a contact surface to the sheet made of a rubber material, and one having a smaller coefficient of friction has a contact surface to the sheet made of a metal material or resin material.   
     
     
         6 . The device according to  claim 4 , wherein in the rotating body having a larger coefficient of friction, of the first rotating body and the second rotating body, all the rollers rotate integrally with the shaft, and in the rotating body having a smaller coefficient of friction, a part of the rollers rotates integrally with the shaft and the remaining roller is free with respect to the shaft, and
 in the rotating body having a larger coefficient of friction, of the third rotating body and the fourth rotating body, all the rollers rotate integrally with the shaft, and in the rotating body having a smaller coefficient of friction, a part of the rollers rotates integrally with the shaft and the remaining roller is free with respect to the shaft.   
     
     
         7 . The device according to  claim 6 , wherein at least in one of the first sheet carrying unit and the second sheet carrying unit having the changing coefficient of friction to the sheet, the roller that is free with respect to the shaft is located on the side close to the center in the traveling direction of the sheet. 
     
     
         8 . The device according to  claim 3 , wherein the first sheet carrying unit and the second sheet carrying unit are symmetrical about the center in the traveling direction of the sheet, and
 both the first sheet carrying unit and the second sheet carrying unit have the coefficient of friction changing along the direction orthogonal to the traveling direction of the sheet, and as the change in the coefficient of friction, the coefficient of friction becomes smaller on the side close to the center of the traveling direction of the sheet.   
     
     
         9 . The device according to  claim 8 , wherein the first sheet carrying unit has a first rotating body which supports plural rollers along a first shaft, and a second rotating body which has a different coefficient of friction from the first rotating body, supports plural rollers along a second shaft and nips the sheet together with the first rotating body, and
 the second sheet carrying unit has a third rotating body which supports plural rollers along a third shaft, and a fourth rotating body which has a different coefficient of friction from the third rotating body, supports plural rollers along a fourth shaft and nips the sheet together with the third rotating body.   
     
     
         10 . The device according to  claim 8 , wherein one having a larger coefficient of friction, of the first rotating body and the second rotating body, has a contact surface to the sheet made of a rubber material, and one having a smaller coefficient of friction has a contact surface to the sheet made of a metal material or resin material, and
 one having a larger coefficient of friction, of the third rotating body and the fourth rotating body, has a contact surface to the sheet made of a rubber material, and one having a smaller coefficient of friction has a contact surface to the sheet made of a metal material or resin material.   
     
     
         11 . The device according to  claim 8 , wherein in the rotating body having a larger coefficient of friction, of the first rotating body and the second rotating body, all the rollers rotate integrally with the shaft, and in the rotating body having a smaller coefficient of friction, a part of the rollers rotates integrally with the shaft and the remaining roller is free with respect to the shaft, and
 in the rotating body having a larger coefficient of friction, of the third rotating body and the fourth rotating body, all the rollers rotate integrally with the shaft, and in the rotating body having a smaller coefficient of friction, a part of the rollers rotates integrally with the shaft and the remaining roller is free with respect to the shaft.   
     
     
         12 . The device according to  claim 11 , wherein the roller that is free with respect to the shaft in the first sheet carrying unit and the second sheet carrying unit is located on the side close to the center in the traveling direction of the sheet. 
     
     
         13 . The device according to  claim 9 , wherein the control unit controls a first driving unit which rotates the first shaft and the second shaft, and a second driving unit which rotates the third shaft and the fourth shaft. 
     
     
         14 . A sheet carrying device comprising:
 a first sheet carrying unit which nips a sheet between a first rotating body and a second rotating body having a different coefficient of friction from the first rotating body and thus carries the sheet in a traveling direction;   a second sheet carrying unit which nips the sheet between a third rotating body and a fourth rotating body having a different coefficient of friction from the third rotating body and thus carries the sheet in the traveling direction together with the first sheet carrying unit; and   a control unit which controls the carrying by the first sheet carrying unit and the carrying by the second sheet carrying unit on the basis of a result of detection from a detection unit which detects an inclination of the sheet that is traveling.   
     
     
         15 . The device according to  claim 14 , wherein the first rotating body has plural rollers along a first shaft orthogonal to the traveling direction of the sheet, and the second rotating body has plural counter-rollers along a second shaft, the plural counter-rollers facing the plural rollers along the first shaft, and
 the third rotating body has plural rollers along a third shaft orthogonal to the traveling direction of the sheet, and the fourth rotating body has plural counter-rollers along a fourth shaft, the plural counter-rollers facing the plural rollers along the third shaft.   
     
     
         16 . The device according to  claim 15 , wherein in the rotating body having a larger coefficient of friction, of the first rotating body and the second rotating body, all the rollers rotate integrally with the shaft, and in the rotating body having a smaller coefficient of friction, a part of the rollers rotates integrally with the shaft and the remaining roller is free with respect to the shaft, and
 in the rotating body having a larger coefficient of friction, of the third rotating body and the fourth rotating body, all the rollers rotate integrally with the shaft, and in the rotating body having a smaller coefficient of friction, a part of the rollers rotates integrally with the shaft and the remaining roller is free with respect to the shaft.   
     
     
         17 . The device according to  claim 16 , wherein the roller that is free with respect to the shaft in the first sheet carrying unit and the second sheet carrying unit is located on the side close to the center in the traveling direction of the sheet. 
     
     
         18 . An image forming apparatus comprising:
 an image forming unit which forms a toner image on an image carrier;   a sheet carrying device including a sheet carrying unit having a first sheet carrying unit and a second sheet carrying unit, at least one of which has a coefficient of friction changing along a direction orthogonal to a traveling direction of a sheet, the first sheet carrying unit carrying the sheet in the traveling direction, the second sheet carrying unit carrying the sheet in the traveling direction together with the first sheet carrying unit, and a control unit which controls the carrying by the first sheet carrying unit and the carrying by the second sheet carrying unit on the basis of a result of detection from a detection unit which detects an inclination of the sheet that is traveling; and   a transfer unit which transfers the toner image from the image carrier to the sheet carried by the sheet carrying device.   
     
     
         19 . The apparatus according to  claim 18 , wherein as the change in the coefficient of friction of at least one of the first sheet carrying unit and the second sheet carrying unit, the coefficient of friction becomes smaller on a side close to a center in the traveling direction of the sheet. 
     
     
         20 . The apparatus according to  claim 19 , wherein the first sheet carrying unit and the second sheet carrying unit are symmetrical about the center in the traveling direction of the sheet,
 the first sheet carrying unit has a first rotating body which supports plural rollers along a first shaft, and a second rotating body which has a different coefficient of friction from the first rotating body, supports plural rollers along a second shaft and nips the sheet together with the first rotating body, and in the rotating body having a larger coefficient of friction, of the first rotating body and the second rotating body, all the rollers rotate integrally with the shaft, and in the rotating body having a smaller coefficient of friction, a part of the rollers rotates integrally with the shaft and the remaining roller located on the side close to the center is free with respect to the shaft, and   the second sheet carrying unit has a third rotating body which supports plural rollers along a third shaft, and a fourth rotating body which has a different coefficient of friction from the third rotating body, supports plural rollers along a fourth shaft and nips the sheet together with the third rotating body, and in the rotating body having a larger coefficient of friction, of the third rotating body and the fourth rotating body, all the rollers rotate integrally with the shaft, and in the rotating body having a smaller coefficient of friction, a part of the rollers rotates integrally with the shaft and the remaining roller located on the side close to the center is free with respect to the shaft.