| 摘要 |
PURPOSE: To realize a structure in which even a compact sensor can obtain a large output. CONSTITUTION: A plurality of holes 17a and 17b are respectively formed on a tone wheel 13 rotating together with a hub 1 with a constant distance in a circumferential direction. A sensor 20a is provided with a permanent magnet 22a, stator 23 and coil 24. The magnet 22a is magnetized in a diameter direction. In addition, a gear-shaped irregularity is formed on the inner periphery of the magnet 22a at the same pitch as that of the hole 17a. Furthermore, a plurality of notches 28 are formed in the stator 23 at the same pitch as that between the holes 17a and 17b. The concentration of magnetic flux flowing and interlinking the coil 24 is changed according to the phase change between the irregularities and holes 17a and 17b. Then the voltage which are changed by the frequency proportional to the rotational speed is generated in the coil 24 by the change in concentration.
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