Torque detection device and sensor module

A sensor module mounted on a wall member constituting a casing in an electric power steering apparatus to constitute a torque detection device in the electric power steering apparatus together with a multipolar magnet disposed coaxially with a torsion bar that coaxially couples a first shaft and a second shaft together on a rotation center axis, the multipolar magnet being housed inside the wall member, a first magnetic circuit part disposed on one side of the multipolar magnet in an axial direction parallel to the rotation center axis, and a second magnetic circuit part disposed on the other side of the multipolar magnet in the axial direction, the sensor module comprising:

• a plurality of magnetic sensors disposed between the first magnetic circuit part and the second magnetic circuit part so as to output an electric signal corresponding to a magnetic flux density in a magnetic circuit formed by the first magnetic circuit part and the second magnetic circuit part, the plurality of magnetic sensors being arranged in an arrangement direction included in a plane intersecting the axial direction;
• a circuit board module including the plurality of magnetic sensors mounted on the circuit board module and facing the magnetic circuit on one end side in a width direction, the width direction being included in the plane and intersecting the arrangement direction;
• and
• a sensor housing coupled to one end side in the arrangement direction of the circuit board module so as to support the circuit board module on the one end side in the arrangement direction of the circuit board module, wherein
• the circuit board module has a waterproof structure that covers a plurality of circuit elements including the plurality of magnetic sensors and a circuit board on which the plurality of circuit elements are mounted with a waterproof covering member,
• a waterproof seal member is disposed on a coupling part between the sensor housing and the circuit board module,
• the waterproof seal member is formed in a ring-like shape, and
• the waterproof seal member is formed in such a manner that an outer diameter in the axial direction is smaller than a dimension in the axial direction of an end face of the sensor housing from which the circuit board module projects.

A sensor module mounted on a wall member constituting a casing in an electric power steering apparatus to constitute a torque detection device in the electric power steering apparatus together with a multipolar magnet disposed coaxially with a torsion bar that coaxially couples a first shaft and a second shaft together on a rotation center axis, the multipolar magnet being housed inside the wall member, a first magnetic circuit part disposed on one side of the multipolar magnet in an axial direction parallel to the rotation center axis, and a second magnetic circuit part disposed on the other side of the multipolar magnet in the axial direction, the sensor module comprising:

• a magnetic sensor disposed between the first magnetic circuit part and the second magnetic circuit part so as to output an electric signal corresponding to a magnetic flux density in a magnetic circuit formed by the first magnetic circuit part and the second magnetic circuit part;
• a circuit board module projecting in a projecting direction included in a plane intersecting the axial direction, the circuit board module including the magnetic sensor mounted on the circuit board module and facing the magnetic circuit on one end side in a width direction, the width direction being included in the plane and intersecting the projecting direction;
• and
• a sensor housing coupled to one end side in the projecting direction of the circuit board module so as to support the circuit board module on the one end side in the projecting direction of the circuit board module, wherein
• the circuit board module has a waterproof structure that covers a plurality of circuit elements including the magnetic sensor and a circuit board on which the plurality of circuit elements are mounted with a waterproof covering member,
• a waterproof seal member is disposed on a coupling part between the sensor housing and the circuit board module,
• the waterproof seal member is formed in a ring-like shape, and
• the waterproof seal member is formed in such a manner that an outer diameter in the axial direction is smaller than a dimension in the axial direction of an end face of the sensor housing from which the circuit board module projects.

A torque detection device configured to output an electric signal corresponding to a torsional torque generated in a torsion bar that coaxially couples a first shaft and a second shaft together on a rotation center axis, the torsional torque being caused by relative rotation between the first shaft and the second shaft about the rotation center axis, the torque detection device comprising:

• a first magnetic circuit part disposed on one side of a multipolar magnet in an axial direction parallel to the rotation center axis, the multipolar magnet being configured in such a manner that magnetic poles are alternately inverted in a circumferential direction surrounding the rotation center axis and being disposed coaxially with the torsion bar so as to rotate about the rotation center axis along with the relative rotation;
• a second magnetic circuit part disposed on the other side of the multipolar magnet in the axial direction;
• one or more magnetic sensors disposed between the first magnetic circuit part and the second magnetic circuit part so as to output an electric signal corresponding to a magnetic flux density in a magnetic circuit formed by the first magnetic circuit part and the second magnetic circuit part;
• and
• a circuit board module projecting in a projecting direction included in a plane intersecting the axial direction, the circuit board module including the magnetic sensors mounted on the circuit board module and facing the magnetic circuit, wherein
• the circuit board module has a waterproof structure that covers a plurality of circuit elements including the magnetic sensors and a circuit board on which the plurality of circuit elements are mounted with a waterproof covering member, wherein
• a sensor housing is coupled to one end side in the projecting direction of the circuit board module so as to support the circuit board module on the one end side in the projecting direction of the circuit board module,
• a coupling part between the sensor housing and the circuit board module has a waterproof seal structure,
• an O-ring is attached so as to surround the coupling part between the sensor housing and the circuit board module, and
• the O-ring is pressed in a ring radial direction intersecting the projecting direction between the coupling part and the wall member to liquid-tightly join the sensor housing to the wall member.