Multi-Pole Magnetic Encoders for Active Speed-Measurement Systems 1999-01-3402
Automotive wheel speed sensors have generally been based on principles of magnetic field sensing. “Active” sensors, as Hall and Magneto-Resistive, overcome some drawbacks of the previous systems. However, recent conceptual advancements, focusing on the tone-wheel, have proved significant for system performance. The tone-wheel is replaced in fully active systems by a precise ring of steel, bonded to magnetized rubber, where multiple poles are produced in the circumference. The ring serves as an encoder for magnetic sensors, eliminating the need for a large, strong permanent magnet on the sensor - thus significantly reducing size. Active sensor and encoder allow detectable speeds down to zero, improved accuracy, and significantly larger air-gaps and allowable tolerances. These properties, in turn, provide major advantages in manufacture and assembly costs. Usage of elastomeric compounds provides excellent mechanical, dynamic and environmental behavior. Furthermore, many speed-sensing systems are integrated at shaft-ends or in the vicinity of bearings, where seals are required. Elastomeric encoder technology allows combination of multiple functions, as sealing, into a single component - thereby reducing the number of parts.
Affiliated:
Freudenberg-NOK General Partnership, Freudenberg Dichtungs- und Schwingungstechnik
Pages: 8
Event:
Annual Brake Colloquium And Engineering Display
ISSN:
0148-7191
e-ISSN:
2688-3627
Also in:
Sensors and Transducers, Second Edition-PT-105, Proceedings of the 1999 Brake Colloquium-P-349, SAE 1999 Transactions - Journal of Passenger Cars-V108-6
Related Topics:
Identification numbers
Magnetic materials
Sensors and actuators
Elastomers
Seals and gaskets
Assembling
Bearings
Steel
SAE MOBILUS
Subscribers can view annotate, and download all of SAE's content.
Learn More »