Torque sensor using perpendicularly magnetizing coils

A quick response and robust torque sensor is presented for a carbon-steel shaft on which a pair of magnetostrictive layers were formed and a pair of twin coils were set. A current flows through a twin coil generating a magnetic field perpendicularly applied to the magnetostrictive layer plane, which simultaneously magnetizes the steel shaft in a radial direction (difficult magnetization direction). Linear characteristics for the sensor output and applied torque (-4~4 kgf-m) were obtained using these twin coils magnetized with frequencies up to 600 kHz. A sensitive and reliable magnetostrictive layer of Fe₄₀ Ni₅₆Cr₄ was formed using a low-pressure plasma spray method. Good stability for temperature variation also resulted