| 摘要 |
PURPOSE:To change mechanical rigidity and reduce the vibrating sound produced by magnetic induction action in a device of detecting revolutions by magnetic induction action, by subjecting a plate body constituting a magnetic circuit to beading, piercing, etc. CONSTITUTION:Slender convex parts 8b by beading are provided radially at several places to a disc 8 of a soft magnetic material formed with a tooth profile part 8a on the outside circumferential part. A coil bobbin 5 and an annular permanent magnet 6 are placed between this disc 8 and a disc 7 of a soft magnetic material and are fixed to a substrate 1. When a rotor 14 revolves and the magnetic resistance of the magnetic circuit formed by the tooth profile part 14a of the rotor 14 and the tooth profile part 8a of the disc 8 changes, the signal corresponding to revolutions is obtained from the coil 13. |
