Sheet transport apparatus and image reading apparatus

A sheet transport apparatus for transporting a sheet to a processing section having a processing position to process the sheet, comprising:

• at least one transport roller for transporting a sheet to the processing section at a predetermined velocity;
• a driving motor for driving the at least one transport roller;
• and
• a driving transmission mechanism for transferring driving of the driving motor to the transport roller,
• wherein the driving transmission mechanism comprises
• a rotary shaft for supporting the transport roller,
• a transmission rotary member having a circular fit hole,
• a holder member with a press-fit hole formed therein, the press-fit hole having a curved part and a flat part, and
• a coupling mechanism for coupling the holder member and the transmission rotary member,
• wherein the rotary shaft comprises
• a fitting part having a circular cross section at one end side on the rotary shaft to be fitted into the circular fit hole of the transmission rotary member, and
• a press-fit part having a curved part and a flat part press-fitted with the press-fit hole of the holder member, and
• wherein the coupling mechanism comprises
• a convex portion formed on a side of the transmission rotary member, and
• a concave portion formed on a side of the holder member press-fitted with the convex portion of the transmission rotary member.