| 摘要 |
<p>A variable reluctance sensor (10) for sensing the rotational speed of a target wheel (22) having teeth (24), separated by slots (26), angularly positioned along its periphery is comprised of an elongated core (12) interposed between two permanent magnets (14) and (16) which generate additive magnetic flux passing longitudinally through the elongated core. This additive flux is, however, opposed by a longitudinal flux developed by the opposing ends of the permanent magnets. In the absence of surrounding ferromagnetic material, the magnitudes of the opposing longitudinal flux components are essentially equal, resulting in no net longitudinal component of magnetic flux. The elongated core and permanent magnets are encircled by a multi-turn electrical coil (18) which is wound transversely about a longitudinal dimension. A portion of the elongated core and permanent magnets (30) extending beyond the electrical coil are positioned adjacent the periphery of the target wheel and define an air gap (32) therebetween. As the target wheel rotates, the air gap varies, which in turn varies the magnitudes of the opposing longitudinal components of magnetic flux with respect to one another. An output voltage is generated in the electrical coil having a frequency proportional to the rate of change of the net longitudinal flux magnitude, which is similarly proportional to the rotational speed of the target wheel.</p> |
