Torque sensor for automotive power steering systems
First Claim
1. A noncontacting, leakage flux torque sensor for an automotive, electrically powered steering assist system comprising:
- an input shaft;
an output shaft;
a ferromagnetic member fixed to both said input shaft and said output shaft so as to transfer torque to said output shaft from said input shaft, said ferromagnetic member having at least one discontinuity;
a lost motion connection means for directly coupling said input shaft to said output shaft so that said input shaft may rotate a predetermined distance with respect to said output shaft before said lost motion connection means engages said output shaft, said lost motion connection means, when engaged, coupling said input and output shafts and thereby shunting additional torque directly from said input shaft to said output shaft;
a primary coil for establishing an induced excitation current in said ferromagnetic member thereby generating a magnetic leakage flux at said discontinuity;
two differentially connected secondary coils for measuring the change in leakage flux at said discontinuity when a torsional stress is applied to said ferromagnetic member to rotate said member less than said predetermined distance; and
amplitude and phase means for deriving the amplitude and phase of the induced current output of said secondary coils.
1 Assignment
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Accused Products
Abstract
A non-contacting, inductively coupled leakage flux torque sensor particularly adapted for automobile power steering systems. The input and output shafts of the system are coupled by a lost motion mechanism. Discontinuities are formed in a ferromagnetic member. The discontinuities may comprise sets of slots or ferromagnetic projections on facing end surfaces of the ferromagnetic member. As a result of torsional stress on the member, the discontinuities change shape and dimension or are displaced, resulting in a change in leakage flux. The change in leakage flux is detected by two differentially connected coils. A modulator-demodulator circuit provides a determination of torque as a function of the changed flux.
33 Citations
13 Claims
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1. A noncontacting, leakage flux torque sensor for an automotive, electrically powered steering assist system comprising:
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an input shaft; an output shaft; a ferromagnetic member fixed to both said input shaft and said output shaft so as to transfer torque to said output shaft from said input shaft, said ferromagnetic member having at least one discontinuity; a lost motion connection means for directly coupling said input shaft to said output shaft so that said input shaft may rotate a predetermined distance with respect to said output shaft before said lost motion connection means engages said output shaft, said lost motion connection means, when engaged, coupling said input and output shafts and thereby shunting additional torque directly from said input shaft to said output shaft; a primary coil for establishing an induced excitation current in said ferromagnetic member thereby generating a magnetic leakage flux at said discontinuity; two differentially connected secondary coils for measuring the change in leakage flux at said discontinuity when a torsional stress is applied to said ferromagnetic member to rotate said member less than said predetermined distance; and amplitude and phase means for deriving the amplitude and phase of the induced current output of said secondary coils. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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Specification