Sheet feeding device, sheet feeding unit and image forming apparatus connected with the sheet feeding unit with a controlled floating air blowing mechanism

A sheet feeding unit comprising:

• (a) at least one sheet tray which stores sheets;
• (b) a sheet stacking table that rises and falls in a sheet stacking direction, on which a plurality of sheets are stacked on at least the one sheet tray;
• (c) a sucking and conveying mechanism having a sucking surface, which sucks the sheets stacked on the sheet stacking table from an upper surface of the sheets, sucks an uppermost sheet to be sucked on the suction surface, and conveys the uppermost sheet sucked on the suction surface onto a sheet conveyance path;
• (d) a floating air blowing mechanism which blows floating air against the sheets from a side surface of the stacked sheets when the sheet is fed from the sheet stacking table;
• (e) a sheet position detecting sensor which detects an upper surface position in a vertical direction of the sheets stacked, and detects a floating state of the sheets floated by the floating air;
• and
• (f) a controller which judges the floating state of the sheets detected by the sheet position detection sensor in a predetermined finite floating state detecting period in connection with a blowing of the floating air, and controls an air volume of floating air blown from the floating air blowing mechanism based on the floating state of the sheets,
• wherein the sheet position detecting sensor detects the floating state of the sheets based on a number of turning on-and-off operations thereof in the predetermined finite floating state detecting period;
• wherein there is at least one off and one on operation thereof in the predetermined finite floating state detecting period.

An image forming apparatus comprising:

• (a) an image forming section which forms an image on a sheet;
• (b) a sheet feeding device which feeds the sheet onto the image forming section;
• and
• (c) a controller which controls the sheet feeding device to feed the sheet onto the image forming section, and controls the image forming section to form the image,
• wherein the image feeding device comprises:
• (1) a sheet stacking table that rises and falls in a sheet stacking direction, on which a plurality of sheets are stacked;
• (2) a sucking and conveying mechanism having a suction surface, which sucks the sheets stacked on the sheet stacking table from an upper surface of the sheets, sucks an uppermost sheet to be sucked on the suction surface, and conveys the uppermost sheet sucked on the suction surface onto a sheet conveyance path;
• (3) a floating air blowing mechanism which blows floating air against the sheets from a side surface of the stacked sheets when the sheet is fed from the sheet stacking table;
• and
• (4) a sheet position detecting sensor which detects an upper surface position in a vertical direction of the sheets stacked, and detects a floating state of the sheets floated by the floating air,
• wherein the controller judges the floating state of the sheets detected by the sheet position detection sensor in a predetermined finite floating state detecting period in connection with a blowing of the floating air, and controls an air volume of floating air blown from the floating air blowing mechanism based on the floating state of the sheets,
• wherein the sheet position detecting sensor detects the floating state of the sheets based on a number of turning on-and-off operations thereof in the predetermined finite floating state detecting period;
• wherein there is at least one off and one on operation thereof in the predetermined finite floating state detecting period.

A sheet feeding device comprising:

• (a) a sheet stacking table that rises and falls in a sheet stacking direction, on which a plurality of sheets are stacked;
• (b) a conveyer which conveys an uppermost sheet on the suction surface onto a sheet conveyance path;
• (c) a floating air generator which generates floating air against the sheets from a side surface of the stacked sheets when the sheet is fed from the sheet stacking table;
• (d) a sheet position detecting sensor which detects an upper surface position in a vertical direction of the sheets stacked, and detects a floating state of the sheets floated by the floating air;
• and
• (e) a controller which judges the floating state of the sheets detected by the sheet position detection sensor in a predetermined finite floating state detecting period in connection with a blowing of the floating air, and controls an air volume of floating air generated by the floating air generator based on the floating state of the sheets,
• wherein the sheet position detecting sensor detects the floating state of the sheets based on a number of turning on-and-off operations thereof in the predetermined finite floating state detecting period;
• wherein there is at least one off and one on operation thereof in the predetermined finite floating state detecting period.