Position detector including a reference position wherein the sensor is saturating the MR sensor for preventing hysteresis and in a bridge circuit
First Claim
1. A position detector comprising:
- a movable body having poles with alternating opposite magnetization polarities at a first magnetization pitch on a surface thereof except at a reference position part which has a second magnetization reference position pitch larger than said first magnetization pitch; and
a transducer, including at least two ferromagnetic thin film stripe elements disposed in a direction of movement of said movable body and connected together in a bridge circuit whose AC output is nearly zero when proximate to said reference position part, facing said movable body for generating an alternating current voltage signal corresponding to an intensity of a magnetic field from said magnetized surface, said transducer being saturated when said magnetic field intensity in said direction of movement of said movable body is above a predetermined level at which hysteresis of said thin film elements does not occur;
wherein an intensity of said magnetic field in said direction of movement of said movable body at said reference position part is above said predetermined level.
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Accused Products
Abstract
A position detector which provides improved reference position detecting precision by stabilizing the output signal from magnetoelectric transducers in a reference position part. A rotor has a magnetized surface alternately provided with different magnetic poles and a reference positional part in which magnetic poles provided on the magnetized surface are partly omitted. A rotational angle sensor has MR elements laid out thereon in opposition to the magnetized surface of the rotor to output the voltage signal VS according to the magnetic field intensity in the magnetized surface due to the rotation of the rotor. A waveform processing circuit and a pulse signal processing signal shape the waveform of the voltage signal from the rotational angle sensor, and also generate the rotational angle pulse signal and a reference position pulse signal according to the waveform reforming signal. The reference positional part is arranged so that the magnetic field intensity therein can be within the saturation magnetic field region of the Mr elements.
58 Citations
25 Claims
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1. A position detector comprising:
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a movable body having poles with alternating opposite magnetization polarities at a first magnetization pitch on a surface thereof except at a reference position part which has a second magnetization reference position pitch larger than said first magnetization pitch; and a transducer, including at least two ferromagnetic thin film stripe elements disposed in a direction of movement of said movable body and connected together in a bridge circuit whose AC output is nearly zero when proximate to said reference position part, facing said movable body for generating an alternating current voltage signal corresponding to an intensity of a magnetic field from said magnetized surface, said transducer being saturated when said magnetic field intensity in said direction of movement of said movable body is above a predetermined level at which hysteresis of said thin film elements does not occur; wherein an intensity of said magnetic field in said direction of movement of said movable body at said reference position part is above said predetermined level.
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2. A position detector comprising:
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a movable body having poles with alternating opposite magnetization polarities at a first magnetization pitch on a surface thereof except at a reference position part which has a second magnetization reference position pitch larger than said first magnetization pitch; and a magnetoresistive transducer facing said movable body for generating a voltage signal corresponding to an intensity of a magnetic field from said magnetized surface, said transducer being saturated when said magnetic field intensity is above a predetermined level; wherein an intensity of said magnetic field at said reference position part is above said predetermined level, and said movable body comprises a rotor having a magnetized circumferential rim as said surface and wherein a magnetic field intensity of a portion of said circumferential surface immediately adjacent to said reference position part is higher than that of other ones of said magnetic poles. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 25)
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13. A position detector comprising:
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a rotor having poles with alternating opposite magnetization polarities at a first magnetization pitch on a circumferential magnetized surface thereof except at a reference position part which has a second magnetization reference position pitch larger than said first magnetization pitch, a degree of magnetization of a portion of said circumferential surface immediately adjacent to said reference position part being higher than that of other ones of said magnetic poles; two ferromagnetic reluctance transducer elements, disposed in a direction of movement of said magnetic surface and facing said rotor, for generating a voltage signal corresponding to an intensity of a magnetic field from said magnetized surface, said transducer elements being saturated when said magnetic field intensity is above a predetermined level at which hysteresis of the transducer elements does not occur, said two transducer elements being connected together in a bridge circuit whose output is zero in the absence of a net magnetic field, wherein an intensity of said magnetic field at said reference position part is above said predetermined level, and said rotor having a magnetized circumferential rim as said circumferential magnetized surface and wherein a magnetic field intensity of a portion of said circumferential surface immediately adjacent to said reference position part is higher than that of other ones of said magnetic poles. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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Specification