Patent ID: 6140813
Filing Date: 2000-10-31
Classification: G01P

Abstract:
A magnetic object motion sensor comprising:a pair of magnetoelectric transducer elements disposed opposite a magnetic material protrusion of a rotating magnetic object;a magnet for generating bias magnetic flux toward said pair of magnetoelectric transducer elements;unbalanced biasing means for producing imbalance in the magnetic field detection sensitivity between said pair of magnetoelectric transducer elements;a differential amplifier for amplifying in a differential fashion the electric signals output by said pair of magnetoelectric transducer elements;a waveform shaping circuit for converting the differential signal output by said differential amplifier to a pulse signal corresponding to the edges of said magnetic material protrusion;wherein said pair of magnetoelectric transducer elements are disposed in such a manner that one element is a predetermined distance apart from the other in the direction of motion of said rotating magnetic object to enable said pair of magnetoelectric transducer elements to detect a change in magnetic flux caused by the motion of said magnetic material protrusion;the detection sensitivity of the magnetoelectric transducer element that said magnetic material protrusion passes over first is set lower by said unbalanced biasing means than the detection sensitivity of the other magnetoelectric transducer element by setting an angle of inclination .alpha. between said magnet and said pair of transducer elements in a range between five and sixty degrees, andsaid unbalanced bias producing means produces a difference in the amplitude of the magnetic flux density between that applied to one element of said pair of magnetoelectric transducer elements and that applied to the other element so that the difference in the electric signal level corresponding to said difference in the amplitude of the magnetic flux density becomes greater than the hysteresis of said waveform shaping circuit and so that a rapid change in magnetic flux density is produced and said differential signal changes abruptly when said magnetic material protrusion passes over said transducer elements.