Patent ID: 6356847
Filing Date: 2002-03-12
Classification: G01L

Abstract:
A method for determining the torque exerted on a body of revolution capable of being driven rotatably about an axis of rotation, in particular on a bottom bracket bearing shaft of a bicycle, with a first and a second measurement generators which are arranged on the body of revolution at an axial distance or a radial distance from one another and which consist of rings radially surrounding the body of revolution and composed of fields having an alternately different signal behavior, the number of fields of two rings being identical, with a first measurement transducer assigned to the first measurement generator and with a second measurement transducer assigned to the second measurement generator, said measurement traducers both supplying output signals, from which first and second square-wave signals are formed, the average torque being determined from the distances between edges of the first and second square-wave signals over one complete revolution of the body of revolution, wherein the fields having an alternately different signal behavior form uninterrupted rings (7, 8), wherein, over one or more complete revolutions of a nonloaded torque-free body of revolution (2), the edge distances Tml between specific edges of the first square-wave signals (11) and the distances &agr;ml of specific edges of the second square-wave signals (12) from specific edges of the first square-wave signals (11) are in each case summed up and the torque-free ratio&bgr;ml=(&agr;ml1+&agr;ml2+ . . . &agr;min)/(Tml1+Tml2+ . . . Tmin)=&Sgr;&agr;min/&Sgr;Tmin is formed, wherein, over one or more complete revolutions of the body of revolution (2) loaded with the torque to be determined, the edge distances Tm between specific edges of the first square-wave signals (11) and the distances &agr;m of specific edges of the second square-wave signals (12) from specific edges of the first square-wave signal (12) are in each case summed up and the applied-torque ratio&bgr;m=(&agr;ml1+&agr;ml2+ . . . &agr;mn)/(Tml1+Tml2+ . . . Tmn)=&Sgr;&agr;mn/&Sgr;Tmn is formed, wherein the work W on the body of revolution (2) to which torque M is applied is determined from the equationW=âˆ«02&pgr;Md&phgr;={overscore (M)}Â·2&pgr;&ap;(&bgr;mâˆ’&bgr;ml)Â·k, k being a calibration constant and &phgr; being the angle of rotation of the body of revolution (2), and wherein the average torque M exerted on the body of revolution (2) is determined from the equation{overscore (M)}=W/2&pgr;&ap;(&bgr;mâˆ’&bgr;ml)Â·k/2&pgr;.