Position sensor with hall probe

Details Position sensor with hall probe Position sensor with hall probe

2001-06-13

2003-06-03

Lefkowitz, Edward (Department: 2862)

Electricity: measuring and testing

Magnetic

Displacement

C324S207240, C324S251000, C074S4710XY

Reexamination Certificate

active

06573709

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the domain of metrology, and more precisely to the domain of position sensors without contact with Hall probes.
2. Discussion of the Background Art
Hall probe sensors are known, which make it possible to determine the linear or angular position of a permanent magnet in relation to a stator structure.
The French patent FR2670286 is also known, relating to a magnetic sensor of position and speed with a Hall probe enabling acquisition of position or speed in a single dimension.
The European patent EP800055 describes a linear and angular position sensor. This sensor does not describe two gaps, and delivers analog signals which are difficult to use because they are non-linear, and low-level. Such sensors have two paths which are not independent.
SUMMARY OF THE INVENTION
Other patents such as the U.S. Pat. No. 4,639,667 or W09716736 describe sensors operating according to principles which do not permit delivery of linear and independent signals, representative of the position in two dimensions.
The aim of the invention is to propose a sensor making it possible to measure a position in space, according to two independent degrees of freedom.
To this effect, the invention concerns in its most general meaning a position sensor comprising at least one stator structure defining a secondary gap wherein is housed at least one Hall probe, and a mobile magnet in a main gap, characterised in that the stator structure is composed of stator parts defining at least one first secondary gap wherein is housed at least one main Hall probe, delivering a signal which is a function of the displacement of the mobile magnet relative to a first degree of freedom, and at least one second secondary gap wherein is housed at least one second Hall probe delivering a signal which is a function of the displacement of the mobile magnet relative to a second degree of freedom.
Preferably, the secondary gaps are formed of two pairs of secondary gaps. Each pair of secondary gaps contains two Hall probes arranged on either side of the intersection of the first pair of secondary gaps with the second pair of secondary gaps, and means for summation of the electric signals provided by the Hall probes placed in a same gap, to deliver a resulting signal closely proportional to the position of the magnet according t o the degree of freedom corresponding to each of the pairs of Hall probes.
Advantageously, the stator structure is composed of 4 poles in a magnetically soft material defining between them two pairs of secondary gaps crossing each other at a median point and in that the main gap is plane.
According to a first variant, the stator poles are constituted of 4 rectangular parts integral with a non-magnetic base and placed facing a support assembly and together defining two pairs of perpendicular secondary gaps.
According to a preferred embodiment, the L/E relation between the thickness L of the magnet and the thickness E of the gap is comprised between 1 and 2.
According to a second preferred embodiment, the dimensions of the secondary gaps are C
1
+E and C
2
+E, where C
1
and C
2
define the path of the mobile magnet according to the two directions of the secondary gaps.
According to a second embodiment variant, the magnet is in the shape of a half-tube and is mobile according to a first degree of freedom in axial translation and according to a second degree of freedom in axial rotation relative to a stator structure formed of 4 stator poles in the shape of half-rings, and in that it comprises a first pair of Hall probes placed in a first pair of secondary gaps in the median transversal plane of the stator structure, for measuring the position according to the first degree of freedom, and a second pair of Hall probes placed in a second longitudinal secondary gap constituted by longitudinal slits separating the stator half-rings.
According to a third embodiment variant, the magnet is in the shape of a half-tube and is mobile according to a first degree of freedom in axial translation and according to a second degree of freedom in axial rotation relative to a cylindrical stator structure formed of 4 stator poles in the shape of half-cylinders, and in that it comprises a first pair of Hall probes placed in a first pair of secondary gaps in the median transversal plane of the stator structure, for measuring the position according to the first degree of freedom, and a second pair of Hall probes placed in a second longitudinal secondary gap in the longitudinal median plane separating the stator half-cylinders.
According to a preferred embodiment, the longitudinal edges of the stator half-cylinders are chamfered.
According to a fourth embodiment of the invention, the sensor according to the invention is characterised in that the magnet is spherical or hemispherical in shape and is mobile in spherical rotation relative to a stator structure in the shape of a spherical cap formed of 4 stator poles in the shape of a cap sector, and in that it comprises a first pair of Hall probes placed in a first pair of secondary gaps in a first median plane of the stator structure, for measuring the position according to the first degree of freedom, and a second pair of Hall probes placed in a second longitudinal secondary gap in a second median plane.
According to a fifth embodiment variant, the sensor is characterised in that the magnet is of a spherical o r hemispherical shape and is mobile in spherical rotation relative to a stator structure formed of 4 stator poles with internal spherical shape located around the equator of the magnet, and in that it comprises a first pair of Hall probes placed in a first pair of secondary gaps in a first median plane of the stator structure, for measuring the position according to the first degree of freedom, and a second pair of Hall probes placed in a second longitudinal secondary gap in a second median plane.
Preferably, the main gap is spherical in shape.
In a sixth embodiment variant, the sensor is characterised in that the magnet is spherical or hemispherical in shape and is mobile in spherical rotation around a stator structure of spherical shape formed of 4 stator poles in the shape of a quarter of a sphere, and in that it comprises a first pair of Hall probes placed in a first pair of secondary gaps in a first median plane of the stator structure, for measuring the position according to the first degree of freedom, and a second pair of Hall probes placed in a second longitudinal secondary gap in a second median plane.


REFERENCES:
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patent: 0 611 951 (1994-08-01), None
patent: 0 798 541 (1997-10-01), None
patent: 0 800 055 (1997-10-01), None
patent: 2 670 286 (1992-06-01), None
patent: 2 691 534 (1993-11-01), None
patent: WO 97/16736 (1997-05-01), None

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