Electricity: measuring and testing – Magnetic – Displacement
Patent
1994-05-20
1996-07-02
Strecker, Gerard R.
Electricity: measuring and testing
Magnetic
Displacement
3242072, 32420724, G01B 714, G01D 514
Patent
active
055325858
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
2. Discussion of the Background
The present invention concerns a position sensor incorporating a magnetism-sensitive probe designed to measure positions along a rectilinear trajectory. German Patent No. 2923644 describes a probe consisting of a ferromagnetic stator composed of two magnetically-insulated components. The stator has a longitudinal orifice forming the air gap, within which a permanent bipolar magnet can travel. The sensor according to prior art further comprises two magnetism-sensitive probes whose signals are transmitted to a differential amplifier.
SUMMARY OF THE INVENTION
The present invention is intended to propose a sensor allowing simplified manufacture and assembly and a high degree of reliability, and which transmits a quasi-linear signal.
To this end, the invention concerns, more particularly, a position sensor incorporating a permanent bipolar magnet mobile within a thin principal air gap delimited by the two ferromagnetic components.
The thickness of the permanent magnet is small in relation to the width of the poles as measured in the direction of travel, so that induction is substantially uniform for a given position along each of the poles of the stator separated by the slot in which the magnetism-sensitive probe is housed. The width of the magnet poles is typically at least six times greater than the thickness L of the magnet as measured in the direction of their magnetization.
The reversible permeability of the magnet approaches 1, and preferably, less than 1.2, in order to produce good response linearity.
The two ferromagnetic components are connected by non-magnetic connection elements. The length of the air gap measured in the direction of travel of the mobile magnet is at least 2(C+E), C being the course of travel of stroke of the magnet and E, the width of the air gap. The length of the magnet is at least equal to (C+E). The course of travel of stroke of the mobile magnet, which is magnetized in the direction of the width of the air gap, (+C/2)+(-C/2) in relation to a secondary air gap perpendicular to the main air gap and containing the magnetism-sensitive probe.
Production of a sensor of this kind is simple and economical, and it allows an advanced degree of miniaturization.
According to a preferred embodiment, the two ferromagnetic components are connected by non-magnetic lateral flanges made, for example, of brass. The ferromagnetic components are advantageously made of a 50/50 iron-nickel alloy.
According to an advantageous variant, the mobile magnet travels inside a fluid-tight tubular part placed between the ferromagnetic components. This variant makes it possible to produce a fluid-tight sensor for use in applications such as sensors designed for jack control valves.
The magnet is advantageously enclosed in a sheath of a material having a low coefficient of friction, such as Teflon.
In an embodiment comprising plane magnets, the width Z of these magnets as measured along the axis perpendicular to the direction of travel and to the direction of magnetization is greater than or equal to 3L, L being the length of the magnet as measured in the direction of its magnetization.
According to a variant embodiment of a fluid-tight linear sensor, the device according to the invention comprises a movable device consisting of a bearing incorporating, in its upper part, a clamp allowing coupling of a connection rod, this bearing having a cavity in which a first ferromagnetic component and a thin magnet are arranged, the second ferromagnetic component being placed adjacent to the outer surface of the bottom of a housing made of a non-magnetic material, the magnetism-sensitive probe being placed within a secondary air gap perpendicular to the direction of travel of the movable device.
According to a specific embodiment permitting a degree of unrestricted rotation of the connection rod, this connection rod comprises two stops and two springs arranged, respectively, between the rear stop and the rear surface of the clamp, and
REFERENCES:
patent: 3194990 (1965-07-01), Kendall
patent: 4338823 (1982-07-01), Iwasaki
patent: 4471304 (1984-09-01), Wolf
patent: 4592249 (1986-06-01), Lehmann et al.
patent: 4793241 (1988-12-01), Mano et al.
patent: 4851772 (1989-07-01), Acht et al.
patent: 4985652 (1991-01-01), Oudet et al.
patent: 5003363 (1991-03-01), Lachmann
patent: 5041785 (1991-08-01), Bogaerts et al.
patent: 5072181 (1991-12-01), Burger
patent: 5136194 (1992-08-01), Oudet et al.
patent: 5231352 (1993-07-01), Huber
patent: 5298825 (1994-03-01), Oudet et al.
patent: 5334893 (1994-08-01), Oudet et al.
patent: 5359288 (1994-10-01), Riggs et al.
Hencke, "Analoge Halbleiter-Hallsensoren", CHIP Plus 5, May 1989, pp. 20-22.
Paret, "Les Capteurs Magneto-resistifs", Electronique Radio Plans, Jul. 1990, pp. 11-17.
Oudet Claude
Prudham Daniel
Moving Magnet Technologies (S.A.)
Strecker Gerard R.
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