Electricity: measuring and testing – Magnetic – Displacement
Reexamination Certificate
1999-03-17
2001-10-02
Metjahic, Safet (Department: 2862)
Electricity: measuring and testing
Magnetic
Displacement
C324S207120, C324S252000
Reexamination Certificate
active
06297628
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the field of magnetically sensitive sensors. The present invention relates particularly to a sensor having a magnetoresistive (MR) bridge array optimized for reading fine pitch ring magnets with high air gap at low gauss levels.
2. Description of the Related Art
MR bridges have been proposed before for sensing ring magnets. For example, see Durable and Multifunctional Magnetic Rotation Sensor for Rotary Encoders, Sei et al., IEEE “Transitions on Magnetics”, Vol. mag-23, No. 5, pages 2185-2187, (September 1987), and Integrated MR Sensors for Automobile, Akiyama et al., IEEE “Transactions on Magnetics”, Vol. 30, No. 6, pages 4617-4619, November 1994.
However, Applicant is unaware of any practical commercial application of MR bridge and ring magnet which has been optimized for sensing at low gauss and high air gap applications for the sensing of fine pitch, 20 to 50 pole pair, ring magnets. This scenario is particularly important for automobile wheel speed sensing which figures prominently in anti-lock brake systems, anti-slip drive systems, power-assists, and other stability systems on modern automobiles.
SUMMARY OF THE INVENTION
The present invention shows an anisotropic magnetoresistive bridge constructed and arranged of parallel, interleaved bridge elements with dimensions optimized to maximize sensitivity of the sensor at large air gap and low gauss signals in an economically producable package. This is accomplished in a preferred embodiment by matching magnet pole dimensions to the spacing between the array halves to yield a positive and negative going waveform from the MR bridge by passage of a single pole over the array. The sensor can then output a square wave, or single pulse duty cycle, for the passage of each pole over the array. The length, width, thickness and spacing of the individual resistive elements, or runners, as well as their number and arrangement is also disclosed.
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M. Sei, M. Sakakihara, and H. Suzuki: “Durable and Multifunctional Magnetic Rotation Sensor for Rotary Encoders”;IEEE Transactions on Magnetics, vol. MAG-23, No. 5; pp. 2185-2187; Sep. 1987.
O. Akiyama and H. Konno, D. Inami, Y. Kuraishi; “Integrated MR Sensors for Automobile”;IEEE Transactions on Magnetics, vol. 30, No. 6; pp. 4617-4619; Nov. 1994.
Uwe Dibbern; “Magnetoresistive Sensors”;Sensors, A Comprehensive Survey, vol. 5 Magnetic Sensors, Chapter 9 Magnetoresistive sensor, pp. 342-378; published in 1989.
Bicking Robert E.
Furlong Greg R.
Holman Perry A.
Stern Ed L.
Abeyta Andrew A.
Honeywell Inc
Metjahic Safet
Norris Roland W.
Zaveri Subhash
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