ROTATIONAL SPEED DETECTOR AND BEARING FOR WHEEL HAVING THE SAME

摘要

PROBLEM TO BE SOLVED: To provide a rotational speed detector in which a detecting accuracy can be improved without lowering an output of a sensor without obstructing a reduction in size of the detector and to provide a bearing for a wheel having the same. SOLUTION: This rotational speed detector 26 comprises a magnetic encoder 20 multi-pole magnetized circumferentially and the sensor 15 opposed to the encoder 20 to detect a rotational speed. When a sensor gapδis 0.5 to 2.0 mm if the circumferential pole width W of the encoder 20 is 2 mm or less, an encoder one side piece sectional height (e) is set to a larger value of the about 2 mm and the height (e) of a formula e=d+0.4δ+0.55 (mm) is one side eight of the encoder 20 perpendicular to the circumferential pole width W of the encoder 20 from a center of the sensor 15.