| 摘要 |
<p>The invention provides a lightweight, space-saving rotational-speed sensor (220) that is easy to manufacture and easy to mount on an object. The rotational-speed sensor (220) for detecting the rotational speed of an object (gear 210) comprises a sheetlike ring magnet (200) including a substantially flat surface rotatable substantially coaxially with the gear; a Hall element (212) for detecting magnetic field in a fixed position adjacent to the surface of the ring magnet; and a controller (14) for detecting the rotational speed of the gear based on a magnetic field signal. The substantially flat surface of the ring magnet (200) includes a plurality of magnet sections (202, 204). The magnet sections are alternately reversed in polarity (N- and S-poles) along the periphery.</p> |
