ACTION FORCE DETECTING UNIT FOR ROTARY MEMBER

An action force detecting unit for a rotary member that detects a force acting on a rotary member such as a rotary shaft and a wheel easily and accurately. The action force detecting unit comprises: a first rotor rotated integrally with a tire; a second rotor rotated relatively to the first rotor; a case fixed to a vehicle body while rotatably supporting the first rotor and the second rotor; a first thrust bearing supporting the first rotor; a second thrust bearing supporting the second rotor; a load translating mechanism transmitting a torque between the first rotor and the second rotor while translating the torque partially into a thrust force; a detector fixed to the case to detect a flexure relating to the thrust force applied to the second thrust bearing; a calculator calculating the force acting on the tire based on the flexure detected by the detector; and a transmitter transmitting a signal in accordance with a torque calculated by the calculator.