Sheet feeding device and image forming apparatus

Abstract

Provided is a sheet feeding device and an image forming apparatus capable of performing sheet feeding by electrostatic adsorption at a low noise with a simple configuration. An adsorbing member 400 is arranged to be rotatable in synchronization with rotation of one driving roller (rotary member) 401 , and while the driving roller 401 is performing one rotation, the adsorbing member 400 adsorbs and feeds a sheet from a standby position, and then the adsorbing member 400 returns to the standby position again.

1 . A sheet feeding device, comprising:
 a loading unit that loads a sheet;   a rotary member arranged above the loading unit;   an adsorbing member that is arranged to be movable in synchronization with rotation of the rotary member and electrically adsorbs the sheet loaded on the loading unit;   a driving unit that rotates the rotary member; and   a control unit that controls the driving unit,   wherein the control unit causes the sheet loaded on the loading unit to be adsorbed on the adsorbing member by increasing a downward looseness amount of the adsorbing member, and then feeds the sheet adsorbed on the adsorbing member while reducing the downward looseness amount of the adsorbing member, and   the control unit performs one rotation of the rotary member to move the adsorbing member from a standby position, causes the sheet to be adsorbed and fed, and then moves the adsorbing member to the standby position.   
     
     
         2 . The sheet feeding device according to  claim 1 ,
 wherein the adsorbing member is supported by the rotary member in a loose state.   
     
     
         3 . The sheet feeding device according to  claim 1 ,
 wherein the adsorbing member is an endless member, and a part of the adsorbing member is fixed to the rotary member.   
     
     
         4 . The sheet feeding device according to  claim 1 ,
 wherein the adsorbing member is supported by the rotary member through an elastic member attached to a circumferential surface of the rotary member.   
     
     
         5 . The sheet feeding device according to  claim 1 ,
 wherein the adsorbing member is an open-ended member, fixed to a fixing member whose both ends are attached to the rotary member, and supported by the rotary member while forming a circular arc shape.   
     
     
         6 . The sheet feeding device according to  claim 1 , further comprising,
 a power source for applying a voltage to the adsorbing member and providing adsorption force of adsorbing the sheet by static electricity.   
     
     
         7 . The sheet feeding device according to  claim 6 ,
 wherein two electrodes are arranged in the adsorbing member, and the power source includes a first power source that applies a positive voltage to one of the two electrodes and a second power source that applies a negative voltage to the other of the two electrodes.   
     
     
         8 . The sheet feeding device according to  claim 6 , further comprising,
 a voltage applying member that is arranged between the adsorbing member and the power source, abuts the adsorbing member before the adsorbing member comes into contact with the sheet, and applies a voltage from the power source to the adsorbing member.   
     
     
         9 . The sheet feeding device according to  claim 8 ,
 wherein the power source is an alternating current (AC) power source.   
     
     
         10 . The sheet feeding device according to  claim 1 ,
 wherein a magnitude of the adsorption force by the static electricity by which the adsorbing member eliminates looseness is set to a magnitude by which the sheet is separated from the adsorbing member due to stiffness of the sheet.   
     
     
         11 . The sheet feeding device according to  claim 1 ,
 wherein the adsorbing member has flexibility and is arranged to be movable to a standby position at which the adsorbing member is away from the sheet loaded on the loading unit, an adsorption position at which the sheet loaded on the loading unit is adsorbed, a separation position at which the adsorbed sheet is moved upward and separated from a lower sheet, and a separation position at which the adsorbed sheet is separated from the adsorbing member.   
     
     
         12 . An image forming apparatus, comprising:
 an image forming portion that forms an image on a sheet;   a loading unit that loads a sheet;   a rotary member arranged above the loading unit;   an adsorbing member that is arranged to be movable in synchronization with rotation of the rotary member and electrically adsorbs the sheet loaded on the loading unit;   a driving unit that rotates the rotary member; and   a control unit that controls the driving unit,   wherein the control unit causes the sheet loaded on the loading unit to be adsorbed on the adsorbing member by increasing a downward looseness amount of the adsorbing member, and then feeds the sheet adsorbed on the adsorbing member while reducing the downward looseness amount of the adsorbing member, and   the control unit performs one rotation of the rotary member to move the adsorbing member from a standby position, causes the sheet to be adsorbed and fed, and then moves the adsorbing member to the standby position.