Magnetoresistive Step Motor Flux Sensors
Original Publication Date: 1987-Mar-01
Included in the Prior Art Database: 2005-Feb-01
Stator-mounted magnetoresistors (MRs) in rotary stepper motors enable faster slewing rates and obviate the need of externally mounted shaft encoders to determine motor position or rotational direction. MR sensors in variable numbers may be mounted either parallel to or transversely of stator poles, on the same or different poles, and in permanent magnet or variable reluctance motors. In Fig. 1, MR sensor 1 is placed between silicon iron flux concentrator 2 and silicon iron spacer 3 on the side of a recessed stator tooth 4. Sensor resistance varies approximately 40% between aligned and unaligned rotor teeth 5 during rotation. In Fig. 2, MR sensor 6 is transversely sandwiched between stator laminate 7 and group 8 of shortened laminate sections. This arrangement requires the flux path to pass through MR 6.