Image forming apparatus, sheet conveying method, and program for sheet conveyance

Abstract

A technique in an image forming apparatus in which the front and back sides of a sheet are reversed by using a reversal conveyance path is provided for causing the sheet to wait such that the sheet is not damaged when a unit for conveying the sheet to the reversal conveyance path is pulled out for the purpose of clearing a jam or the like. A roller for conveying the sheet is controlled such that the sheet to be turned back and directed into the reversal conveyance path is caused to wait until the sheet can be conveyed into the reversal conveyance path. As a standby position of the sheet while the sheet is caused to wait, a position is set such that an upstream end portion in the second conveying direction of the sheet to be directed into the reversal conveyance path does not extend for a predetermined length or longer into another conveyance unit adjacent to the intermediate conveyance unit upstream from the intermediate conveyance unit in the second conveying direction.

1 . An image forming apparatus which turns back a sheet from a first conveying direction toward an outside of the apparatus to a second conveying direction toward an inside of a reversal conveyance path to reverse a front side and a back side of the sheet, the apparatus comprising:
 an intermediate conveyance unit which is pulled out of the apparatus;   a retraction unit which is placed downstream from the intermediate conveyance unit in the first conveying direction, into which the sheet to be turned back is conveyed;   a detection unit which detects entering of the sheet into the retraction unit;   a roller which conveys the sheet into the retraction unit; and   a control unit which controls the roller such that the sheet to be turned back is caused to wait at a predetermined position if the detection unit detects the entering of the sheet into the retraction unit.   
     
     
         2 . The image forming apparatus of  claim 1 , wherein the predetermined position is a position such that an upstream end portion in the second conveying direction of the sheet to be turned back does not extend for a predetermined length or longer into the retraction unit. 
     
     
         3 . The image forming apparatus of  claim 2 , wherein the predetermined length is set in a range from more than 0 mm to 20 mm. 
     
     
         4 . The image forming apparatus of  claim 1 , wherein the control unit controls the roller such that the sheet to be turned back is caused to wait at the predetermined position until the sheet can be conveyed into the reversal conveyance path. 
     
     
         5 . The image forming apparatus of  claim 1 , further comprising an output tray in which a sheet discharged from the image forming apparatus is put,
 wherein the retraction unit is placed below the entire output tray or below a portion of the output tray.   
     
     
         6 . The image forming apparatus of  claim 1 , further comprising a sheet length determining section which determines whether the sheet to be turned back is long enough in a sheet conveying direction so as to extend into the retraction unit during the conveyance of the sheet involving the turning back,
 wherein the control unit causes the sheet to wait at the predetermined position only if the sheet length determining section determines that the sheet has such a length as to extend into the retraction unit during the conveyance involving the turning back.   
     
     
         7 . A sheet conveying method in an image forming apparatus which turns back a sheet from a first conveying direction toward an outside of the apparatus to a second conveying direction toward an inside of a reversal conveyance path to reverse a front side and a back side of the sheet, the method comprising:
 conveying the sheet to be turned back into a retraction unit which is placed downstream from an intermediate conveyance unit in the first conveying direction, wherein the intermediate conveyance unit is pulled out of the apparatus;   detecting entering of the sheet into the retraction unit;   conveying the sheet into the retraction unit; and   controlling a roller such that the sheet to be turned back is caused to wait at a predetermined position if the sheet is detected to enter into the retraction unit.   
     
     
         8 . The method of  claim 7 , wherein the predetermined position is a position such that an upstream end portion in the second conveying direction of the sheet to be turned back does not extend for a predetermined length or longer into the retraction unit. 
     
     
         9 . The method of  claim 8 , wherein the predetermined length is set in a range from more than 0 mm to 20 mm. 
     
     
         10 . The method of  claim 7 , wherein the roller is controlled such that the sheet to be turned back is caused to wait at the predetermined position until the sheet can be conveyed into the reversal conveyance path. 
     
     
         11 . The method of  claim 7 , wherein the apparatus includes an output tray in which a sheet discharged from the image forming apparatus is put,
 wherein the retraction unit is placed below the entire output tray or below a portion of the output tray.   
     
     
         12 . The method of  claim 7 , further comprising:
 determining whether the sheet to be turned back is long enough in a sheet conveying direction so as to extend into the retraction unit during the conveyance of the sheet involving the turning back; and   causing the sheet to wait at the predetermined position only if the sheet is determined to have such a length as to extend into the retraction unit during the conveyance involving the turning back.   
     
     
         13 . A non-transitory computer-readable recording medium having recorded therein a sheet conveying program for sheet conveyance in an image forming apparatus which turns back a sheet from a first conveying direction toward an outside of the apparatus to a second conveying direction toward an inside of a reversal conveyance path to reverse a front side and a back side of the sheet, the program comprising instructions which, when executed by a processor of the image forming apparatus, cause the image forming apparatus to perform a sheet conveying method including:
 conveying the sheet to be turned back into a retraction unit which is placed downstream from an intermediate conveyance unit in the first conveying direction, wherein the intermediate conveyance unit is pulled out of the apparatus;   detecting entering of the sheet into the retraction unit;   conveying the sheet into the retraction unit; and   controlling a roller such that the sheet to be turned back is caused to wait at a predetermined position if the sheet is detected to enter into the retraction unit.   
     
     
         14 . The computer-readable recording medium of  claim 13 , wherein the predetermined position is a position such that an upstream end portion in the second conveying direction of the sheet to be turned back does not extend for a predetermined length or longer into the retraction unit. 
     
     
         15 . The computer-readable recording medium of  claim 14 , wherein the predetermined length is set in a range from more than 0 mm to 20 mm. 
     
     
         16 . The computer-readable recording medium of  claim 13 , wherein the roller is controlled such that the sheet to be turned back is caused to wait at the predetermined position until the sheet can be conveyed into the reversal conveyance path. 
     
     
         17 . The computer-readable recording medium of  claim 13 , wherein the apparatus includes an output tray in which a sheet discharged from the image forming apparatus is put,
 wherein the retraction unit is placed below the entire output tray or below a portion of the output tray.   
     
     
         18 . The computer-readable recording medium of  claim 13 , wherein the method further includes:
 determining whether the sheet to be turned back is long enough in a sheet conveying direction so as to extend into the retraction unit during the conveyance of the sheet involving the turning back; and   causing the sheet to wait at the predetermined position only if the sheet is determined to have such a length as to extend into the retraction unit during the conveyance involving the turning back.