Sheet stacking device and image forming apparatus including the same

Abstract

A sheet stacking device includes a sheet stacking section, pairs of ejection rollers, an airflow generator, and an airflow guide. The airflow guide has a center exhaust port and paired side exhaust ports. An airflow is blown out from the center exhaust port toward a central part of the lower surface of the sheet in a sheet width direction perpendicular to a conveyance direction of the sheet. Airflows are blown out from the respective paired side exhaust ports toward respective sides of the lower surface of the sheet. An amount of the airflow blown out from the center exhaust port is larger than those of the airflows blown out from the respective paired side exhaust ports.

What is claimed is: 
     
         1 . A sheet stacking device comprising:
 a sheet stacking section on which a sheet is stacked;   pairs of ejection rollers that eject the sheet toward the sheet stacking section;   an airflow generator configured to generate airflows; and   an airflow guide configured to guide the airflows toward a lower surface of the sheet ejected from the pairs of ejection rollers toward the sheet stacking section, wherein   the airflow guide has:
 a center exhaust port that is located below the pairs of ejection rollers and from which an airflow generated by the airflow generating section is blown out toward a central part of the lower surface of the sheet in a sheet width direction perpendicular to a conveyance direction of the sheet; and 
 paired side exhaust ports that are located on respective opposite sides of the center exhaust port in the sheet width direction and from which airflows generated by the airflow generator are blown out toward respective sides of the lower surface, and 
   an amount of the airflow blown out from the center exhaust port is larger than those of the airflows blown out from the respective paired side exhaust ports.   
     
     
         2 . The sheet stacking device according to  claim 1 , wherein
 the center exhaust port and the paired side exhaust ports are directed such that a first blowing angle made by the conveyance direction and a blowing direction of the airflow blown out from the center exhaust port is larger than a second blowing angle made by the conveyance direction and a blowing direction of the airflow blown out from each of the paired side exhaust ports.   
     
     
         3 . The sheet stacking device according to  claim 2 , wherein
 the sheet stacking section has an inclined surface ascending downstream in the conveyance direction, and   the paired side exhaust ports are directed such that the second blowing angle is larger than a third blowing angle made by the conveyance direction and the inclined surface of the sheet stacking section.   
     
     
         4 . The sheet stacking device according to  claim 1 , wherein
 the airflow generator starts blowing the airflows before a leading edge of the sheet passes through the pairs of ejection rollers and stops blowing the airflows before the trailing edge of the sheet passes through the pairs of ejection rollers.   
     
     
         5 . The sheet stacking device according to  claim 1 , wherein
 the airflow generator includes a first airflow generator and a second airflow generator,   the airflow guide includes a first duct and a second duct,   the first duct divides an airflow generated by the first airflow generator and guides respective divided airflows to the center exhaust port and one of the paired side exhaust ports, and   the second duct divides an airflow generated by the second airflow generator and guides respective divided airflows to the center exhaust port and the other of the paired side exhaust ports.   
     
     
         6 . The sheet stacking device according to  claim 1 , wherein
 the pairs of ejection rollers includes:
 a plurality of lower ejection rollers spaced from one another in the sheet width direction; and 
 a plurality of upper ejection rollers each disposed opposite to a corresponding one of the lower ejection rollers, 
   the lower ejection rollers include:
 paired inside rollers disposed in a central part of the sheet stacking device in the sheet width direction and spaced from each other; and 
 paired outside rollers disposed adjacently outside of the respective inside rollers in the sheet width direction, 
   the center exhaust port is located blow a region where the paired inside rollers are located, and   the paired side exhaust ports are located below the respective paired outside rollers.   
     
     
         7 . The sheet stacking device according to  claim 6 , wherein
 the paired side exhaust ports each have an outside edge in the sheet width direction that is substantially aligned in the sheet width direction with an outside edge of a corresponding one of the paired outside rollers in the sheet width direction, and   the paired side exhaust ports each have an inside edge in the sheet width direction that is located inside in the sheet width direction from an inside edge of a corresponding one of the paired outside rollers in the sheet width direction.   
     
     
         8 . The sheet stacking device according to  claim 6 , wherein
 the airflows generated by the airflow generator are blown out from the respective paired side exhaust ports toward regions of the lower surface of the sheet that are being located downstream of the respective pairs of ejection rollers in the conveyance direction.   
     
     
         9 . An image forming apparatus comprising:
 the sheet stacking device according to  claim 1 ; and   an image forming section configured to form an image on the sheet.