Torque sensor having dual, helically-wound detection coils
A torque sensor for being attached around a magnetostrictive rotating shaft includes a bobbin that is provided coaxially with the rotating shaft, wherein the bobbin includes a resin, a hollow cylindrical shape, and first inclined grooves and second inclined grooves formed on an outer peripheral surface thereof, wherein the first inclined grooves are inclined at a predetermined angle relative to an axial direction, and wherein the second inclined grooves are inclined at a predetermined angle relative to the axial direction in an opposite direction of the first inclined grooves, a first detection coil including an insulated wire wound around the bobbin along the first inclined grooves, a second detection coil including the insulated wire wound around the bobbin along the second inclined grooves, and a measurement portion that detects a inductance variation of the first and second detection coils so as to measure a torque applied to the rotating shaft.
1. A torque sensor for being attached around a magnetostrictive rotating shaft, comprising:
a bobbin that is provided coaxially with and at a distance from the rotating shaft, wherein the bobbin comprises a resin, a hollow cylindrical shape, and a plurality of first inclined grooves and a plurality of second inclined grooves formed on an outer peripheral surface thereof, wherein the first inclined grooves are inclined at a predetermined angle relative to an axial direction, and wherein the second inclined grooves are inclined at a predetermined angle relative to the axial direction in an opposite direction of the first inclined grooves;
a first detection coil comprising an insulated wire wound around the bobbin within the first inclined grooves;
a second detection coil comprising the insulated wire wound around the bobbin within the second inclined grooves; and
a measurement portion that detects a inductance variation of the first and second detection coils so as to measure a torque applied to the rotating shaft,
wherein windings of the first detection coil overlap windings of the second detection coil.
2. The torque sensor according to claim 1 , wherein the first inclined grooves are inclined at +45 degrees relative to the axial direction, and wherein the second inclined grooves are inclined at −45 degrees relative to the axial direction.
3. The torque sensor according to claim 1 , further comprising a magnetic ring comprising a hollow cylindrical magnetic material around the bobbin.
4. The torque sensor according to claim 1 , wherein the bobbin comprises a polyphthalamide resin, a polyether ether ketone resin or a polyphenylene sulfide resin.
5. The torque sensor according to claim 1 , further comprising locking walls provided between the first inclined grooves and the second inclined grooves at both axial edges of the bobbin.
6. The torque sensor according to claim 5 , wherein the locking walls include lateral notches for receiving the windings of one of the first and second detection coils.
7. The torque sensor according to claim 1 , wherein windings of the first and second detection coils traverse both a complete length of the bobbin and part of a circumference of the bobbin.
8. The torque sensor according to claim 1 , wherein each winding of the first and second detection coils traverses both a complete length of the bobbin and part of a circumference of the bobbin.
9. The torque sensor according to claim 1 , wherein the predetermined angle of the second inclined grooves is the negative of the predetermined angle of the first inclined grooves relative to the axial direction.
10. The torque sensor according to claim 8 , wherein the predetermined angle of the first inclined grooves relative to the axial direction is between about 30° and 60°.