Rolling bearing unit with rotational speed detection device having a tone wheel and a sensor

摘要

A rolling bearing unit has a rotational speed detection device which is comprised of a sensor having a yoke, a pair of permanent magnets and coil, and a tone wheal which is made by press-forming a magnetic metal plate so as to comprise a cylindrical support base secured onto an end portion of the bearing unit, a ring-shaped first detecting part which is bent radially outward from the inner rim of the cylindrical support base, and a cylindrical shaped second detecting part which extends axially from the outer peripheral rim of the first detecting part the first and second detecting parts having a ferro-magnetic first portion and a non-magnetic second portion, and the yoke having opposite ends to be faced to the first and second portions, and the permanent magnets being faced to each other so that magnetic fluxes flow alternatively through the yoke corresponding the rotation of the tone wheel.