Sheet detecting apparatus and image forming apparatus

A sheet detecting apparatus which detects a sheet conveyed by a conveying portion which conveys the sheet, the sheet detecting apparatus comprising:

• a sheet detecting member including a plurality of abutment surfaces against which the leading edge of the sheet conveyed by the conveying portion abuts, the plurality of abutment surfaces being formed in a peripheral direction of the sheet detecting member, the sheet detecting member being pressed by the conveyed sheet to rotate;
• a sensor which generates a signal based on a position of the sheet detecting member;
• and
• an urging portion which positions one of the plurality of abutment surfaces of the sheet detecting member in a waiting position in which the leading edge of the sheet conveyed by the conveying portion abuts against the one of the plurality of abutment surfaces,
• wherein the urging portion comprises:
• a first rotary member connected to a rotary shaft of the sheet detecting member;
• a second rotary member connected to the first rotary member so as to rotate, when the first rotary member rotates, at a speed ratio of the second rotary member to the first rotary member, wherein the speed ratio is the same number as a number of the plurality of abutment surfaces;
• and
• an urging spring which provides the sheet detecting member with an urging force for positioning the one of the plurality of abutment surfaces in the waiting position, the urging spring being connected to the second rotary member in such a manner that, when a rotation of the first rotary member along with a rotation of the sheet detecting member is transmitted to the second rotary member to rotate the second rotary member by a predetermined angle, a state in which the urging spring exerts an urging force for positioning the one of the plurality of abutment surfaces to the waiting position is changed to a state in which the urging spring exerts an urging force for positioning, in the waiting position, another one of the plurality of abutment surfaces against which a succeeding sheet abuts.