Torque detection device, method of manufacturing torque detection device, and electric power steering system including torque detection device

A method of manufacturing a torque detection device that includes:

• a torsion bar that couples a first shaft member and a second shaft member to each other;
• a permanent magnet that is fixed to the first shaft member, and that forms a magnetic field around the first shaft member;
• a magnetic yoke that is fixed to the second shaft member, that is arranged within the magnetic field formed by the permanent magnet, and that forms a magnetic circuit of which a magnetic flux density changes in response to a change in a position of the magnetic yoke relative to the permanent magnet due to torsion of the torsion bar;
• an annular magnetic flux collecting unit that includes:
• an annular holder formed by resin molding and having a through-hole that passes through the holder in a radial direction;
• a magnetic flux collecting ring that is fitted to an inner periphery of the holder so as not to cover the through-hole and that collects magnetic fluxes from the magnetic yoke;
• and a magnetic shield that is fitted to an outer periphery of the holder so as to cover the through-hole and that reduces influence of an external magnetic field on the magnetic circuit, the magnetic flux collecting unit being arranged so as to surround the magnetic yoke;
• a magnetic sensor that detects magnetic fluxes, which are generated in the magnetic circuit, via the magnetic flux collecting ring;
• and
• a sensor housing that is made of resin supplied onto an outer periphery of the magnetic flux collecting unit, and that is formed so as to be integrated with the magnetic flux collecting unit, the method comprising:
• a magnetic flux collecting unit manufacturing step of assembling the magnetic flux collecting unit;
• and
• a sensor housing forming step of forming the sensor housing by supplying resin onto the outer periphery of the magnetic flux collecting unit after the magnetic flux collecting unit manufacturing step.