Sheet feeding apparatus and image forming apparatus equipped with it

A sheet feeding apparatus comprising:

• a sheet stacking tray for supporting sheets;
• a sheet feeding roller for feeding the sheets supported by said sheet stacking tray;
• a separation roller, provided to be in pressure contact with said sheet feeding roller, for separating the sheets between said sheet feeding roller by being supplied with a separation force in a direction reverse to a sheet feeding direction by a driving source;
• a separation roller shaft which is rotated by being transmitted a driving of said driving source;
• an idling angle securing member disposed between said separation roller and said separation roller shaft, for setting a clearance for permitting a relative rotation within a constant angle range between said separation roller and said separation roller shaft;
• and
• a spring biasing said separation roller in a rotation direction reverse to the sheet feeding direction within the constant angle range;
• wherein a separation force to be supplied to said separation roller by said spring at a time of idling of said separation roller by said idling angle securing member is set to be smaller than a separation force of said separation roller by a driving force from the driving source.

An image forming apparatus comprising:

• sheet supporting means for supporting sheets;
• sheet feeding means for feeding the sheets supported by said sheet supporting means;
• separating means for separating the sheets between said sheet feeding means;
• separation force giving means for supplying a separation force to said separating means in a direction reverse to a sheet feeding direction;
• separation force switching means for being switched between a connection state for supplying the separation force to said separating means by said separation force giving means and a cut-off state in which the separation force is not supplied to said separating means;
• and
• image forming means for forming an image on a sheet separated and fed by said sheet feeding means and said separating means;
• wherein said separation force switching means is switched into the cut-off state at a time of a beginning of the feeding and is switched into the connection state when said sheet feeding means has fed the sheets for a predetermined distance from the beginning of the feeding, and a separation force supplied to said separating means in a state such that said separation force switching means is switched into the cut-off state is set to be smaller than a separation force in a state such that said separation force switching means is switched into the connection state.

An image forming apparatus comprising:

• a sheet stacking tray for supporting sheets;
• a sheet feeding roller for feeding the sheets supported by said sheet stacking tray;
• a separation roller provided to be in pressure contact with said sheet feeding roller, for separating the sheets between said sheet feeding roller by being fed with a separation force in a direction reverse to a sheet feeding direction by a driving source;
• a separation roller shaft which is rotated by being transmitted a driving of said driving source;
• an idling angle securing member disposed between said separation roller and said separation roller shaft, for setting a clearance for permitting a relative rotation within a constant angle range between said separation roller and said separation roller shaft;
• a spring biasing said separation roller in a rotation direction reverse to the sheet feeding direction within the constant angle range;
• and
• image forming means for forming an image on a sheet separated and fed by said sheet feeding roller and said separation roller;
• wherein a separation force to be supplied to said separation roller by said spring at a time of idling of said separation roller by said idling angle securing member is set to be smaller than a separation force of said separation roller by a driving force from the driving source.