Position sensor with compensated magnetic poles
AssigneeElectricfil Automotive
InventorBertrand Legrand
Life of this patent
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Abstract
The object of the invention relates to an encoder for a rotary position sensor, including a multipolar magnetic ring driven into rotation around its axis, and provided at its circumference with magnetic poles of a given sign, alternately positioned with magnetic poles of an opposite sign, so as to form at least one series of pairs of magnetic poles with a determined period, each magnetic pole of a given sign having a width Ii and a magnetic polarisation value Mi whereas each magnetic pole of opposite sign has a width Ii+1 different from width Ii and a magnetic polarisation value Mi+1, characterized in that the polarization of the magnetic poles is such that Mi×Ii=Mi+1×I+1.
Claims13
1- An encoder for a rotary position sensor, including a multipolar magnetic ring driven into rotation around its axis (x), and provided on its circumference with magnetic poles of a given sign (Pi) alternately positioned with magnetic poles of an opposite sign (Pi+1) so as to form at least one series of at least one pair of magnetic poles with a determined period (Ti), each magnetic pole (Pi) of a given sign having a width Ii and a magnetic polarization value Mi whereas each magnetic pole of opposite sign (Pi+1) has a width Ii+1 different from width Ii and a magnetic polarization value Mi+1, characterized in that the polarization of the magnetic poles (Pi, Pi+1) is such that Mi×Ii=Mi+1×Ii+1.
2- The encoder according to claim 1, characterized in that it includes as magnetic poles (Pi, Pi+1), regular magnetic poles of a given sign (P1) and regular magnetic poles of an opposite sign (P2) so as to form a series of pairs of regular magnetic poles with a determined period (T1), each regular magnetic pole (P1) of a given sign having a width I1 and a magnetic polarization value M1 so that each regular magnetic pole of opposite sign (P2) has a width I2 different from width I1 and a magnetic polarization value M2, such that M1×I1=M2×I2.
3- The encoder according to claim 1, characterized in that it includes as magnetic poles (Pi, Pi+1), at least one magnetic singularity formed by at least one irregular magnetic pole of a given sign (P3) having a width I3 and a magnetic polarization value M3 and by an irregular magnetic pole of opposite sign (P4) having a width I4 different from width I3 and a magnetic polarization value M4, so as to form a series of at least one pair of irregular magnetic poles with a determined period (T2), the polarization of the irregular magnetic poles (P3, P4) being such that:
- M3×I3=M4×I4.
4- The encoder according to claim 2, characterized in that it includes as magnetic poles (Pi, Pi+1), at least one magnetic singularity formed by at least one irregular magnetic pole of a given sign (P3) having a width I3 and a magnetic polarization value M3 and by an irregular magnetic pole of opposite sign (P4) having a width I4 substantially equal to width I3 and a magnetic polarization value M4, so as to form a series of at least one pair of irregular magnetic poles with a determined period (T2), the polarization of the irregular magnetic poles (P3, P4) being such that:
- M3×I3=M4×I4.
5- The encoder according to claim 3, characterized in that it includes as magnetic poles (Pi, Pi+1), regular magnetic poles of a given sign (P1) and regular magnetic poles of an opposite sign (P2) so as to form a series of pairs of regular magnetic poles with a determined period (T1), each regular magnetic pole (P1) of a given sign having a width I1 and a magnetic polarization value M1 whereas each regular magnetic pole of opposite sign (P2) has a width I2 substantially equal to width I1, and a magnetic polarization value M2, such that M1×I1=M2×I2.
6- The encoder according to claim 3, characterized in that the regular (P1, P2) and irregular (P3, P4) magnetic poles are such that:
- M1×I1=M2×I2=M3×I3=M4×I4.
7- The encoder according to claim 6, characterized in that the regular magnetic pole (P1) is of the same sign as the irregular magnetic pole (P3), whereas the regular magnetic pole (P2) and the irregular magnetic pole (P4) are of the same sign, opposite to the sign of the poles (P1, P3).
8- The encoder according to claim 6, characterized in that the regular (P1, P2) and irregular (P3, P4) magnetic poles are such that I1+I2=I3+I4, so that the period (T1) of the regular magnetic poles is equal to the period (T2) of the irregular magnetic poles.
9- The encoder according to claim 7, characterized in that the width I1 of the regular magnetic pole (P1) is equal to the width I4 of the irregular magnetic pole (P4) whereas the width I2 of the magnetic pole (P2) is equal to the width I3 of the irregular magnetic pole (P3) so that the cyclic ratios for the regular and irregular magnetic poles are complementary.
10- A rotary position sensor characterized in that it includes an encoder according to claim 1, the multipolar magnetic ring of which moves past at least one detector cell (3).
11- The rotary position sensor according to claim 10, characterized in that the encoder is blocked in rotation on a shaft of an engine of a motor vehicle.
12- The rotary position sensor according to claim 10, characterized in that the detector cell (3) is a mono-component detector cell.
13- The sensor according to claim 12, characterized in that the detector cell (3) is a Hall effect cell, a differential Hall effect cell, a Hall effect cell with flux concentrator, a magneto-resistive cell or a giant magneto-resistive cell.