Electricity: measuring and testing – Magnetic – Displacement
Patent
1992-03-16
1994-04-05
Strecker, Gerard R.
Electricity: measuring and testing
Magnetic
Displacement
32420725, 336 45, G01B 730, G01D 520, H01F 2102
Patent
active
053008820
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a position sensor for determining the angular position of a rotating shaft comprising a field coil for generating a time-variant magnetic field, at least one sensor coil arranged inside the field coil and a rotatable member arranged for modulating the magnetic flux passing through the sensor coil in accordance with its angular position.
BACKGROUND OF THE INVENTION
Sensors of this type are known in the art. The angular position of a shaft is determined from the signal obtained at the terminals of the sensor coil or coils. However, in the known devices, the amplitude of the variation of the signal as a function of the angular variation of the shaft is relatively small and the precision of the measure is often insufficient.
SUMMARY OF THE INVENTION
The position sensor according to the invention comprises a field coil for generating a time-variant magnetic field, a magnetically conductive housing structure supporting the field coil, at least one sensor coil arranged inside the field coil and supported by the housing structure, and a rotatable member supported for rotation inside the housing structure. The rotatable member is coupled with said rotating shaft and arranged for modulating the magnetic flux passing inside the sensor coil in accordance with its angular position. Each sensor coil comprises a winding and a magnetically permeable core with a flat polar part extending outside said winding so as to face the rotatable member. At least one portion of said housing structure coupled with said field coil is arranged to face the rotatable member on the opposite side from said polar part. The arrangement is such that the air-gaps existing between said polar part and said rotatable member on the one hand, and said portion of said housing structure and the rotatable member on the other hand, are located substantially within the field coil.
It is an object of the present invention to provide a position sensor of the type mentioned at the beginning, which has a simple, economic and compact structure and which produces a position signal of a relatively high amplitude and of very good precision.
The features and the advantages of the present invention will be better understood in the light of the following description relating to one example of embodiment of the sensor according to the invention, illustrated by the attached drawing figures.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an axial section of a position sensor according to the invention, and
FIGS. 2(a) to 2(f) are a simplified representation illustrating the operation of the sensor through different positions of the rotatable member.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The sensor of FIG. 1 comprises a housing composed of a supporting plate 11 and a closing member 12 made of a magnetically permeable material. A part of plastic material 13 is arranged inside this housing and constitutes, in particular, a coil body 14 and a bearing part 15 in which the end of a rotatable shaft 1 is lodged. The shaft 1 is integral with a rotatable member comprising a disc-shaped support 4 and a part 5 such as a ferrite tablet in the present example.
The coil body 14 is used as a support for the winding 2 of a cylindrical field coil which extends over practically the whole height of the closing member 12. On the supporting plate 11, four sensing coils are arranged in a symmetrical way, each being constituted by a winding 3, a coil body 16 and a core 6. Each core 6 is provided with a polar part 7 extending above coil 3 so as to conduct the magnetic flux generated by the field coil winding 2. Two of these sensing coils are shown in axial section in FIG. 1.
In the present example, the polar parts 7 have a circular shape and the ferrite tablet 5 is also substantially of circular cylindrical shape. The support 4 is preferably made of an electrically conductive material, for example of aluminum. The closing member 12 comprises a part 8 which is arranged opposite the rotatable member and which forms with the same
REFERENCES:
patent: 3742340 (1973-06-01), Kiedrowski
patent: 4507638 (1985-03-01), Brosh
patent: 4755751 (1988-07-01), Ray
Baumer Electric A.G.
Strecker Gerard R.
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