Sheet stacking apparatus and image forming system

Abstract

A sheet stacking apparatus includes a conveyance unit configured to convey a sheet, a stacking unit on which the sheet conveyed by the conveyance unit is stacked, the stacking unit being configured to be lowered as an amount of the sheets stacked on the stacking unit increases, an abutment portion on which a leading edge of the sheet conveyed by the conveyance unit abuts, an urging unit configured to urge a leading edge portion, of the sheet, abutting on the abutment portion toward the stacking unit, and a control unit configured to adjust an urging force of the urging unit according to sheet information of the sheet conveyed toward the abutment portion.

What is claimed is: 
     
         1 . A sheet stacking apparatus comprising:
 a conveyance unit configured to convey a sheet;   a stacking unit on which the sheet conveyed by the conveyance unit is stacked, the stacking unit being configured to be lowered as an amount of the sheets stacked on the stacking unit increases;   an abutment portion on which a leading edge of the sheet conveyed by the conveyance unit abuts;   an urging unit configured to urge a leading edge portion, of the sheet, abutting on the abutment portion toward the stacking unit; and   a control unit configured to adjust an urging force of the urging unit according to sheet information of the sheet conveyed toward the abutment portion.   
     
     
         2 . The sheet stacking apparatus according to  claim 1 , wherein the sheet information includes information regarding a thickness of the sheet, and
 the control unit is configured to adjust the urging force of the urging unit to a first urging force in a case where the sheet conveyed toward the abutment portion has a first thickness, and to adjust the urging force of the urging unit to a second urging force larger than the first urging force in a case where the sheet conveyed toward the abutment portion has a second thickness larger than the first thickness.   
     
     
         3 . The sheet stacking apparatus according to  claim 1 , wherein the sheet information includes information regarding a stiffness of the sheet, and
 the control unit is configured to adjust the urging force of the urging unit to a first urging force in a case where the sheet conveyed toward the abutment portion has a first stiffness, and to adjust the urging force of the urging unit to a second urging force larger than the first urging force in a case where the sheet conveyed toward the abutment portion has a second stiffness higher than the first stiffness.   
     
     
         4 . The sheet stacking apparatus according to  claim 1 , wherein the sheet information includes information regarding a grammage of the sheet, and
 the control unit is configured to adjust the urging force of the urging unit to a first urging force in a case where the sheet conveyed toward the abutment portion has a first grammage, and to adjust the urging force of the urging unit to a second urging force larger than the first urging force in a case where the sheet conveyed toward the abutment portion has a second grammage larger than the first grammage.   
     
     
         5 . The sheet stacking apparatus according to  claim 1 , wherein the urging unit includes a first member, a second member that is disposed to face the first member and contacts with the sheet, and an urging member disposed between the first member and the second member. 
     
     
         6 . The sheet stacking apparatus according to  claim 5 , further comprising a first driving unit configured to lift and lower the first member,
 wherein the control unit is configured to adjust the urging force of the urging unit by adjusting a position of the first member by the first driving unit.   
     
     
         7 . The sheet stacking apparatus according to  claim 6 , further comprising:
 a second driving unit configured to lift and lower the stacking unit; and   a detection unit configured to detect that a position of an upper surface of a sheet bundle stacked on the stacking unit is a set position,   wherein the control unit is configured to control the second driving unit such that the position of the upper surface of the sheet bundle stacked on the stacking unit becomes the set position.   
     
     
         8 . The sheet stacking apparatus according to  claim 7 , wherein the set position is constant regardless of the sheet information. 
     
     
         9 . The sheet stacking apparatus according to  claim 6 , further comprising an alignment rotary member configured to rotate while contacting with the sheet stacked on the stacking unit to move the sheet toward the abutment portion and align the sheet,
 wherein the first driving unit is configured to lift and lower the alignment rotary member together with the first member.   
     
     
         10 . The sheet stacking apparatus according to  claim 6 , further comprising:
 an alignment rotary member configured to rotate while contacting with the sheet stacked on the stacking unit to move the sheet toward the abutment portion and align the sheet; and   a third driving unit configured to change a pressing force of the alignment rotary member with respect to the sheet stacked on the stacking unit.   
     
     
         11 . The sheet stacking apparatus according to  claim 1 , further comprising:
 a second driving unit configured to lift and lower the stacking unit; and   a detection unit configured to detect a position of an upper surface of a sheet bundle stacked on the stacking unit,   wherein the control unit is configured to control the second driving unit based on a detection result of the detection unit such that the stacking unit is lowered as the amount of the sheets stacked on the stacking unit increases.   
     
     
         12 . The sheet stacking apparatus according to  claim 1 , further comprising an alignment rotary member configured to rotate while contacting with the sheet stacked on the stacking unit to move the sheet toward the abutment portion and align the sheet. 
     
     
         13 . The sheet stacking apparatus according to  claim 12 , wherein the alignment rotary member is elastically deformed by coming into contact with an upper surface of the sheet stacked on the stacking unit, and
 an elastic deformation amount of the alignment rotary member is adjusted according to the sheet information.   
     
     
         14 . The sheet stacking apparatus according to  claim 12 , wherein a region where the alignment rotary member comes into contact with an upper surface of the sheet stacked on the stacking unit and a region where the urging unit comes into contact with the sheet overlap each other in a sheet conveyance direction. 
     
     
         15 . The sheet stacking apparatus according to  claim 12 , wherein the urging unit includes a first member, a second member that is disposed to face the first member and contacts with the sheet, and an urging member disposed between the first member and the second member,
 the sheet stacking apparatus further comprises:
 a first driving unit configured to lift and lower the first member; and 
 a roller configured to support the alignment rotary member, 
   the alignment rotary member is elastically deformed by coming into contact with an upper surface of the sheet stacked on the stacking unit, and   the control unit is configured to adjust the urging force of the urging unit and adjust an elastic deformation amount of the alignment rotary member by adjusting a position of the first member by the first driving unit.   
     
     
         16 . The sheet stacking apparatus according to  claim 1 , further comprising a second driving unit configured to lift and lower the stacking unit,
 wherein the control unit is configured to adjust the urging force of the urging unit by adjusting a position of an upper surface of a sheet bundle stacked on the stacking unit by the second driving unit.   
     
     
         17 . The sheet stacking apparatus according to  claim 16 , further comprising a detection unit configured to detect that the position of the upper surface of the sheet bundle stacked on the stacking unit is a set position,
 wherein the control unit is configured to   (i) change the set position according to the sheet information and   (ii) control the second driving unit such that the position of the upper surface of the sheet bundle stacked on the stacking unit becomes the set position.   
     
     
         18 . The sheet stacking apparatus according to  claim 1 , further comprising:
 a transfer rotary member disposed above the stacking unit;   a gripping unit attached to the transfer rotary member and configured to transfer the sheet in a sheet conveyance direction in a state of gripping the leading edge of the sheet fed from the conveyance unit in the sheet conveyance direction; and   an abutment surface configured to come into contact with the leading edge of the sheet to separate the leading edge of the sheet from the gripping unit.   
     
     
         19 . An image forming system comprising:
 an image forming apparatus configured to form an image on a sheet; and   the sheet stacking apparatus according to  claim 1 , the sheet stacking apparatus being configured to stack the sheet on which the image is formed by the image forming apparatus.