Patent ID: 6098468
Filing Date: 2000-08-08
Classification: G01L

Abstract:
A torque measuring device comprising a shaft member having a central axis and a generally circular cross section centered at the central axis to be applied with a torque to be measured around the central axis, and first and second magnetic field measuring means, the shaft member having an integral annular outer circumferential portion made of a ferromagnetic material, wherein the shaft member includes a first annular axial portion of the integral ferromagnetic annular outer circumferential portion that axially terminates with a first end face substantially perpendicular to the central axis of the shaft member and is magnetized to bear magnetic fluxes circumferentially circulating therealong, a second axial portion of the integral ferromagnetic annular outer circumferential portion that axially terminates with a second end face substantially perpendicular to the central axis of the shaft member and is magnetized to bear magnetic fluxes circumferentially circulating therealong, the second annular axial portion being proportionally less stressed by the torque applied to the shaft member than said first annular axial portion, the first magnetic field measuring means measuring magnetic fluxes generated to traverse the first end face of the first annular axial portion by the shaft member being applied with a torque to be measured therethrough, and the second magnetic field measuring means for measuring magnetic fluxes generated to traverse the second end face of the second annular axial portion by the shaft member being applied with the torque to be measured therethrough, so as to measure the torque applied to the shaft member based upon an inverse magnetostriction with a cancellation of an influence of a hysteresis in the inverse magnetostriction of the ferromagnetic material on the result of measurement by a compensation of the measurement by the first magnetic field measuring means with the measurement by the second magnetic field measuring means.