US 4,364,278 AGranted

Assembly for monitoring torsional loading of a drive shaft

AssigneeZahnradfabrik Friedrichshafen AG

InventorsHans-Dieter Horter, Wolfgang Maier, Herbert Seibold

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Abstract

An assembly for monitoring torsional loading of a drive shaft comprises a magnetic-field generator juxtaposed to a cylindrical body of magnetostrictive material rigidly surrounding the shaft, the body being in the form of a thin foil attached to the shaft via a layer of magnetically insulating material, or a sleeve attached to the shaft by at least two spaced brackets or an outer layer of the shaft specially treated to have a homogeneous magnetic permeability in an unstressed state. A pick-up or magnetic-field sensor is juxtaposed to the body or sheath for detecting differential changes in the magnetic permeability thereof, the pick-up advantageously being connected to a demodulator which extracts a signal whose polarity is determined by the direction of loading of the shaft. In order to monitor the rotation rate of the shaft, the foil or sleeve is provided with a longitudinal slot and the demodulator is connected at its output to a low-pass filter and a high-pass filter which extract a torsion-dependent signal and a rotation-rate-dependent signal, respectively.

Claims14

Dependent claims

An assembly for monitoring torsional loading of a drive shaft, said assembly comprising:

a cylindrical body of magnetostrictive material having a high magnetic permeability in an unstressed state of said body, said body being rigid with and substantially surrounding said shaft;
induction means juxtaposed at least in part with an outer surface of said body for generating a magnetic field therein;
insulating means for inhibiting the penetration of magnetic flux lines into said shaft from said body;
pick-up means including an electromagnetic sensor juxtaposed with said body for detecting distortions in said magnetic field due to torsional loading of said shaft and for generating an output signal containing information on the magnitude and direction of torsional loading of said shaft, said output signal including a high-frequency carrier waveform and a low-frequency modulating wveform having a polarity determined by the direction of loading of said shaft;
and
a demodulator operatively connected to said pick-up means for extracting said modulating waveform from said carrier waveform, said body being formed with a slot, whereby said modulating waveform includes a pulsatile component whose frequency is equal to the rotation rate of said shaft.

3 more elements

Dependencies are inferred from the claim text.