Magnetoelastic torque sensor utilizing FeGa system magnetostriction material

Non-contact torque sensor by using magnetostrictive alloy ring of polycrystalline FeGa (Galfenol) system was developed. For engineering sensor applications for automobile etc., it becomes necessary to increase the strength much more than that of the present binary FeGa alloy. Therefore, in the present paper, at first, ternary FeGaAl alloy with an additional C element was fabricated and then the magnetic property and mechanical property of that alloy were investigated. (Fe-13.6 Ga-6 Al)-1.5C [at.%] sample showed the value of 50 ppm of maximum magnetostriction and value of 667 MPa of fracture stress which seem applicable as a torque sensor material. The torque sensor system was assembled using this alloy ring on the twisted shaft of non-ferromagnetic material and the output magnetic field was measured by ten adjacent Hall-sensor. The output voltage showed the almost linear relationship against applied torque and the sensitivity was 47.5 mOe/N·m, which seems a promising data for the proposed torque sensing system.