Sheet Feeding Device and Image Forming Device

Abstract

A sheet feeding device includes: a sheet stacking unit that stacks a bundle of sheets; a pick-up roller that is enabled to move up and down and sends a sheet of the bundle of sheets toward downstream side in a carrying direction; a pair of rollers that is arranged at downstream side in the carrying direction, and when multiple sheets are sent out by the pick-up roller, that separates the first sheet from the second sheet or later; a separation member that is arranged between the pick-up roller and the pair of rollers and that is in contact with a leading end of the sheet and limits the number of the sheet carried to the pair of rollers; and a hardware processor that determines a height position of the pick-up roller corresponding to a type of the sheet and sets the pick-up roller to be at the determined height position.

What is claimed is: 
     
         1 . A sheet feeding device, comprising:
 a sheet stacking unit that is enabled to be lifted and lowered while a bundle of sheets is stacked;   a pick-up roller that is in contact with a top surface of the bundle of sheets and is enabled to move up and down in accordance with the lifting and lowering movement of the sheet stacking unit, and that sends a sheet of the bundle of sheets toward downstream side in a carrying direction;   a pair of rollers that is arranged at downstream side in the carrying direction of the pick-up roller, and when multiple sheets are sent out by the pick-up roller, that separates the first sheet from the second sheet or later and feeds the first sheet toward downstream side in the carrying direction, and restricts a movement of the second sheet or later;   a separation member that is arranged between the pick-up roller and the pair of rollers and that is in contact with a leading end of the sheet that is sent out by the pick-up roller and limits the number of the sheet carried to the pair of rollers; and   a hardware processor that determines a height position of the pick-up roller corresponding to a type of the sheet stacked on the sheet stacking unit and lifts and drives the sheet stacking unit to set the pick-up roller to be at the determined height position.   
     
     
         2 . The sheet feeding device according to  claim 1 , wherein
 the hardware processor determines the type of the sheet based on a rigidity or a basis weight of the sheet.   
     
     
         3 . The sheet feeding device according to  claim 1 , wherein
 the hardware processor determines the height position of the pick-up roller to be higher than the height position for a thin paper or a plain paper when the sheet stacked on the sheet stacking unit is a thick paper.   
     
     
         4 . The sheet feeding device according to  claim 1 , further comprising:
 a pressing unit that presses the pick-up roller to the bundle of sheets stacked on the sheet stacking unit.   
     
     
         5 . The sheet feeding device according to  claim 1 , wherein
 the separation member includes an inclined guide unit, the height of which is gradually elevated from upstream side to downstream side of a sheet carrying path between the pick-up roller and the pair of rollers, and   the hardware processor further:
 determines the height position of the pick-up roller to be the first position which is lower than an upper end of the guide unit when the sheet stacked on the sheet stacking unit is the thin paper or the plain paper; and 
 determines the height position of the pick-up roller to be the second position which is higher than the first position and near the upper end position of the guide unit when the sheet stacked on the sheet stacking unit is the thick paper. 
   
     
     
         6 . The sheet feeding device according to  claim 5  further comprising:
 a pressing unit that presses the pick-up roller to the bundle of sheets stacked on the sheet stacking unit, wherein 
 the pressing unit generates a larger pressing force when the pick-up roller is at the second position compared to the pressing force generated when the pick-up roller is at the first position. 
 
     
     
         7 . The sheet feeding device according to  claim 6 , wherein
 the pressing unit does not press the pick-up roller when the pick-up roller is at the first position, and presses the pick-up roller when the pick-up roller is at the second position.   
     
     
         8 . The sheet feeding device according to  claim 4 , wherein
 the pressing unit increases the pressing force nonlinearly as the height position of the pick-up roller becomes higher.   
     
     
         9 . The sheet feeding device according to  claim 4 , wherein
 the pressing unit is formed from a coil spring.   
     
     
         10 . The sheet feeding device according to  claim 1 , wherein
 the sheet stacking unit has an inclined surface, the height position of which becomes higher from a leading end position to a rear end position of the sheet.   
     
     
         11 . An image forming device that includes the sheet feeding device according to  claim 1 .