Performance enhancement of closed-ended magnetic circuits by selective

Abstract

A closed-ended linear voice-coil actuator in which the effects of armature reaction are significantly reduced. The actuator includes a housing formed from longitudinal field plates and end plates which are connected together. A cylindrical or rectangular core of ferromagnetic material is mounted inside the housing with its ends connected to the end plates. Permanent magnets mounted on the field plates are used to produce a transverse magnetic field. A coil of wire is wound around a coil bobbin. The coil of wire and coil bobbin are disposed around the core and are free to move along its length. A coil mounting bracket is mounted to the coil winding to allow the user of the voice-coil actuator to attach a load. A hole is drilled through the core, thereby removing some of the ferromagnetic material of which the core is composed. By placing the hole at the center of the core where the magnetic field due to the permanent magnets is minimal, the field produced by those magnets remains substantially the same. However, the secondary magnetic field produced by the interaction between a current flowing through the coil and the ferromagnetic core is reduced, thereby lessening the effects of armature reaction. In addition, because the physical rigidity of the core is maintained, the structural strength of the device is not compromised.