| 摘要 |
PROBLEM TO BE SOLVED: To achieve a structure for securing the reliability of detecting a rotational speed inexpensively by improving the distribution of magnetic flux density at the detection section position of a sensor opposite to the axial direction on a surface 28 to be detected in an encoder 15b. SOLUTION: The thickness in the axial direction of a permanent magnet 17b for composing an encoder 15b is changed gradually in the direction of diameter in a direction so that the thickness increases at an outer-diameter side and decreases at an inner-diameter side. Accordingly, even at an inner diameter side section, the amount of magnetic flux toward the detection section of the sensor from a surface 28 to be detected is increased. Reliability in the detection precision of the rotational speed can be improved by the encoder and the rolling bearing unit having the encoder. COPYRIGHT: (C)2005,JPO&NCIPI
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