| 摘要 |
PURPOSE:To reduce the size and weight of a detector, improve its dust protection and responsibility, and also improve the reliability by utilizing an annular magnet as part of labyrinth structure. CONSTITUTION:A shaft 13 running in the center of a fan body 11 having a blade 12 is supported pivotally by a bearing 14 formed in a casing 15. A magnetic detecting element 17 such as a Hall element or magnetoresistance effect element is provided to the casing 15 opposite the annular magnet 16 fitted to the fan body 11. An annular rib 18 provided to the outer circumference of the fan body 11, an annular rib 19 stood in the casing 5, and the magnet 16 overlap one another to form the labyrinth structure. |
