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Magnetoresistive Step Motor Flux Sensors

IP.com Disclosure Number: IPCOM000038849D
Original Publication Date: 1987-Mar-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 66K

Publishing Venue

IBM

Related People

Hammer, R: AUTHOR [+3]

Abstract

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.

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Magnetoresistive Step Motor Flux Sensors

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. In those permanent magnet stepper motors having two rotor sections relatively displaced a half tooth on a common shaft, a pair of MR sensors can be placed on opposite ends of the same stator pole, as in Fig. 3. The outputs of MR 9 and MR 10 have a phase difference of 180o between them and are affixed to the side of stator pole 11 beneath flux concentrators 12 and
13. The MR devices can also be mounted on different poles but should provide phase variances 180o to maximize the signal difference. The resistance change of an MR is significantly influenced by the energizing coil on the pole and the direction of current flow. MR...