Torque detection device, and electric power steering system including the torque detection device

A torque detection device, comprising:

• a first shaft;
• a second shaft;
• a torsion bar that coaxially couples the first shaft and the second shaft to each other;
• a permanent magnet that is attached to an outer periphery of the first shaft;
• a first magnetic yoke that is formed of a strip-shaped soft magnetic plate, that is attached to the second shaft, that is arranged within a magnetic field of the permanent magnet to form a magnetic circuit, that causes flow of magnetic fluxes between the permanent magnet and the first magnetic yoke to change in accordance with a change in rotational position with respect to the permanent magnet, and that has a yoke proximity portion and a yoke distant portion formed by bending the soft magnetic plate, a distance between the yoke proximity portion and the permanent magnet being smaller than a distance between the yoke distant portion and the permanent magnet;
• a second magnetic yoke that is attached to the second shaft, that is arranged within the magnetic field of the permanent magnet to form a magnetic circuit, and that causes flow of magnetic fluxes between the permanent magnet and the second magnetic yoke to change in accordance with a change in rotational position with respect to the permanent magnet;
• and
• a magnetic sensor that outputs a signal based on magnetic fluxes that flow between the first magnetic yoke and the second magnetic yoke.