SA E TECHNICAL PAPER SERIES Speed Sensor Integration in Wheel Bearing Hub Units Steven F. Brown SKF - USA Christian Rigaux SKF - France Reprinted from P-242 - Sensors and Actuators 1991 The Engineering Society =For Advancing Mobility and Sea Air and Space, International Congress and Exposition Detroit, Michigan February 25 -March 1,1991 400 COMMONWEALTH DRIVE, WARRENDALE, PA 15096-0001 U.S.A. Downloaded from SAE International by University of Edinburgh, Sunday, August 26, 2018The piyars lnduded ln Ihb durn are abslraded and Indexed in the SAE Oobal M@iy Database. No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior written permission of the publisher. ISSN 0148-71 91 Copyright 1991 Society of Automotive Engineers, Inc. Positions and opinions advanced in this paper are those of the author(s) and not necessarily those of SAE. The author is solely responsible for the content of the paper. A process is available by which discussions will be printed with the paper if it is published in SAE Transactions. For permission to publish this paper in full or in part, contact the SAE Publications Division. Persons wishing to submit papers to be considered for presentation or publication through SAE should send the manuscript or a 300 word abstract of a proposed manuscript to: Secretary, Engineering Activity Board, SAE. Printed in U.S.A. Downloaded from SAE International by University of Edinburgh, Sunday, August 26, 2018Speed Sensor Integration in Wheel Bearing Hub Units Steven F. Brown SKF - USA Christian Rigaux SKF - France ABSTRACT Advancements in vehicle wheel speed sensing technology present automotive engineers with unique design opportunities. Both the integration of speed sensors into wheel bearing hub units and the introduction of new speed sensor technologies will be discussed. INTRODUCTION Since 1938, when the first wheel bearing hub unit was introduced, hub units have incorporated an increasing number of functions. Today's hub unit is a sealed, pre- greased, preset unit, which may also transmit driveline torque, provide mounting for the brake rotor and wheel, and serve as a suspension structural member. Due to the location and mechanical precision of hub units, they are also a natural location for the monitoring of vehicle wheel speed. Currently used vehicle wheel speed sensors have several problems, including cost, assembly, and signal quality. By integrating the wheel speed sensors with hub bearing units (HBU), these problems can be solved. In addition, alternative sensor technologies which expand the capabilities of wheel speed sensors will be presented. CURRENT CONFIGURATION OF WHEEL SPEED SENSORS Most wheel speed sensors today are used solely to provide wheel speed information to the anti-lock braking (ABS) system. The ABS system computer processes this information and determines if the brake fluid pressure to any one wheel should be modulated to prevent wheel lock-up. Downloaded from SAE International by University of Edinburgh, Sunday, August 26, 2018In a conventional arrangement, an inductive sensor is mounted on the knuckle or the axle housing. The sensor uses a tone wheel, or impulse ring, which is mounted on a rotating member. For driven wheels, the rotating member is usually the outboard constant velocity joint or the axle shaft. See Figure 1. required at the vehicle assembly plant. Sensor and impulse ring are exposed to possible damage from the outside environment. High system cost and relatively low reliability. Figure 1 Conventional driven wheel speed sensor arrangement. For nondriven wheels, the impulse ring is usually mounted on the inboard side of the hub, as shown in Figure 2. These types of arrangements have several inherent problems: . Tolerances on sensor location and impulse ring diameter must be closely held to maintain the required ai