Rotational angle detection device having two magnetoresistive sensing elements
AssigneeNippon Electric Co., Ltd.
InventorSusumu Ito
Life of this patent
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Abstract
A rotational angle detection device having two magnetoresistive sensing elements positioned at a 45.degree. angle with respect to each other senses the rotary position of a permanent magnet. Sine and cosine waves are applied to first and second bridge circuits respectively incorporating the two sensing elements. The resulting bridge circuit outputs are differentially combined to provide an output whose phase relative to either of the input sine or cosine waves is dependent upon the rotational position of the permanent magnet. The phase difference is detected and the rotational position is calculated therefrom.
Claims21
A rotational angle detection device comprising:
- a permanent magnet rotatable in response to the rotation of a rotary shaft for generating a rotating magnetic field;
- power supplying means for generating sine wave and cosine wave outputs;
- a magnetic field sensor having said sine wave and cosine wave outputs applied thereto and being responsive to the magnetic field of said permanent magnet for generating an altered sine wave output and an altered cosine wave output having phase angles dependent upon the rotational position of said permanent magnet, said magnetic field sensor comprising at least two magnetoresistive sensing elements formed of ferromagnetic material and positioned to form a 45.degree. angle therebetween;
- a voltage difference detector for detecting the difference between said altered sine wave and altered cosine wave outputs;
- a phase difference detector for detecting the phase difference between either of the two outputs of said power supplying means and the output of said voltage difference detector;
- and
- a rotational angle calculator for calculating the rotational angle of said rotary shaft on the basis of the output from said phase difference detector.
Dependencies are inferred from the claim text.