Torque limiter

Claim 1

A torque limiter comprising: a cup-shaped cylinder having a radially extending bottom wall at one axial end thereof and an annular wall extending axially from said bottom wall such that said cylinder is open at the other axial end thereof, said cylinder being formed of a magnetic material; a radially extending end plate coaxially and fixedly fitted in said open of said cylinder; an axially extending rotary shaft coaxially and rotatably supported in bearings fitted in said bottom wall of said cylinder and said end plate, respectively; two radially extending disk-shaped rotors formed of a magnetic material and coaxially secured to said rotary shaft with a space therebetween; a radially extending disk-shaped permanent magnet magnetized in a direction parallel to the axis of said rotary shaft and coaxially secured to said rotary shaft between and contiguously to said two rotors; a radially extending annular core formed of a magnetic material and coaxially and fixedly fitted in said open end of said cylinder contiguously to an axial inner end surface of said end plate; magnetic powder filled in an axially extending gap between said annular core and one of said rotors facing said annular core, said magnetic powder being magnetically held in a magnetic flux path which extends axially between said annular core and said one of said rotors; sealing members disposed between an axial inner end surface of said end plate and one of said rotors and between said bottom wall of said cylinder and the other rotor, respectively, to prevent the entrance of said magnetic powder into said bearings; and a spacer disposed between one of said sealing members facing said bottom wall of said cylinder and said other one of said rotors facing said bottom wall of said cylinder.