| 摘要 |
<p>PROBLEM TO BE SOLVED: To prevent an unstable transmission action of driving torque or braking torque due to a fluctuation in an effective magnetic flux according to magnetic flux leakage, in a non-excitation-operated electromagnetic coupling device designed to operate on a magnetic flux from a permanent magnet and terminate the operation by canceling the magnetic flux from the permanent magnet by excitation of a coil, wherein exposure of the permanent magnet results in leakage of the magnetic flux from the permanent magnet through a magnetic wall of equipment subjected to the transmission action of driving torque or braking torque, and thus a reduction in the effective magnetic flux contributing to the transmission action of driving torque or braking torque. SOLUTION: As the permanent magnet constituting the non-excitation-operated electromagnetic coupling device, a ringed permanent magnet 32 is used, whose parallel faces are magnetized in opposite polarities. One pole face is joined to the inside of an annular portion 24c of a boss 24, and the other pole face is joined to the side of a pole rotor 33. An outer circumferential edge of the pole rotor 33 is opposed via a gap G3 to an inner circumference of a projecting portion 31a of a shell 31 fixed to an outer circumference of a coil bobbin 28. The permanent magnet is thus protected against external exposure.</p> |
