Electricity: measuring and testing – Magnetic – Displacement
Reexamination Certificate
1998-11-06
2001-05-15
Snow, Walter E. (Department: 2862)
Electricity: measuring and testing
Magnetic
Displacement
C324S207200
Reexamination Certificate
active
06232771
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a measuring device for contactless capture or determination of an angle of rotation or of a linear motion.
2. Prior Art
From French Patent Disclosure FR 90 15 223, a measuring device is known in which a stator and a rotor are moved relative to one another. Between the stator and the rotor, each of which comprises magnetically conductive material, there is a small air gap. In the rotor, a first annular permanent magnet which is radially polarized is disposed over a length of 180°. In the remaining region of the stator, also encompassing 180°, there is a second annular permanent magnet with opposite polarization. The stator also has two diametrically opposed air gaps. In at least one of these air gaps, there is a Hall sensor. In the rotary motion of the rotor relative to the stator, the intensity of the magnetic field passing through the Hall sensor varies. The linear measurement range of the measurement signal thus generated is limited, however, to a magnitude of approximately±75°. Moreover, this linear measurement range has a change of sign. It is possible to correct this in a complicated and expensive way in an ensuing electrical circuit.
It is also known, for measuring linear motions, to displace permanent magnets relative to a magnet-field-sensitive element. In this respect it is also known to carry the flux of the permanent magnet with the aid of magnetically conductive parts.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved measuring device for contactless determination of an angle of rotation or linear motion that does not suffer from the above-described disadvantage.
According to the invention a measuring device for contactless determination of a rotation angle of a rotor relative to a multi-part stator made from a magnetically conductive material comprises at least one magnet-field-sensitive element and at least one segment of at least one ring magnet arranged in the rotor;
wherein a first air gap is located between the stator and the rotor and at least one second air gap is formed in the stator; the at least one magnet-field-sensitive element is located in the at least one second air gap; the stator comprises stator parts; at least one of the stator parts has a magnetically conductive connection with remaining stator parts and at least one other of the parts has no magnetically conductive connection with remaining stator parts, so that the ring magnet has a magnetic flux split up so as to produce at least one first partial flux which flows through the at least one magnet-field-sensitive element.
The measuring device according to the invention for contactless capture of an angle of rotation or of a linear motion has the advantage over the prior art that a linear measurement range without a change of sign in the measurement voltage is possible. The linear measurement range is greater than 90° and in particular and above all greater than 110°. The linear measurement range free of a change of sign is possible in both directions of rotation of the measuring device, that is, in both the positive and the negative direction of rotation. Depending on how the magnet-field-sensitive element is embodied, a positive or negative output voltage is possible over the linear measurement range.
It is possible with simple engineering provisions to generate an asymmetrical course of the field lines and thus to make the linear measurement range free of a change of sign. This increases the measurement range. The actual measurement angle can be determined individually by the size of the segments.
REFERENCES:
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Bielert Friedrich
Herden Werner
Klotzbuecher Thomas
Marx Klaus
Reichl Asta
Robert & Bosch GmbH
Snow Walter E.
Striker Michael J.
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