Mag stop clutch with center pole

Abstract

An improved brake/clutch unit for use in a riding lawnmower or another vehicle is provided. The unit includes a rotor assembly disposed radially outwardly of a longitudinally extending input shaft, an armature assembly, and a field shell assembly. The rotor assembly includes a rotor disc disposed radially outwardly of the input shaft. The armature assembly includes an armature axially-spaced from the rotor disc and an output member connected to the armature. The field shell assembly includes a field shell that is fixed against rotation, a pair of permanent magnets, first and second pole pieces having relatively low magnetic reluctance, a third pole piece having a relatively high magnetic reluctance, and a field coil. The field shell includes a radially outwardly extending flange on which all of the pole pieces are disposed. The magnets are disposed between the flange and the first and second pole pieces while the third pole piece is disposed between the first and second pole pieces. The field shell, magnets, first and second pole pieces and armature form a magnetic circuit that draws the armature in a first axial direction into a braked position in engagement with the first and second pole pieces. Upon energizing the field coil, a second magnetic circuit is formed between the field shell, rotor disc, and armature. The second magnetic circuit draws the armature in a second axial direction towards the rotor disc and into a clutch engaged position. In particular, a portion of the armature angularly opposite the magnets engages the rotor disc first and forces the armature to disengage from one of the first and second pole pieces.