Alignment system for permanent magnet motors

Abstract

A permanent magnet motor for use in such electrically-powered devices as appliances, power tools, and the like includes a longitudinally-split cylindrical ferromagnetic wrapper having an inner diameter normally less in its free state than the outer cross-sectional dimension of a permanent magnet array. During assembly of the motor, the split wrapper is expanded to fit around the magnet array, and then is allowed to contract, to urge the magnet array radially inwardly against cooperating surfaces formed on each of two end caps. This maintains a predetermined orientation or alignment of the magnet array relative to the armature, including, for example, a predetermined air gap between the magnet array and the armature. Accordingly, the conventional requirement for such additional retention mechanisms as spring clips, adhesives, fasteners, and the like, is eliminated. The split wrapper also automatically aligns the respective bore axes of the end caps with respect to each other and with respect to an armature axis, regardless of any pre-existing axial misalignment of the edges defining the split in the wrapper. This automatic alignment enhances the lives of bearings mounted in the end cap bores. Another feature is the use of multi-function, unitary end caps, namely those which not only contain motor element alignment features, but also one or more integral electrical and mechanical connection features.