Patent ID: 6894484

Claim:
A wheel rotation detecting device, comprising: a rolling bearing unit including: a stationary ring supported on a suspension and being unrotatable in use; a rotary ring supporting a wheel thereon and being rotatable with said wheel; and a plurality of rolling elements respectively rollably interposed between a stationary side raceway formed in a peripheral surface of said stationary ring and a rotary side raceway formed in a peripheral surface of said rotary ring; an encoder supported on said rotary ring or on a part mounted on said rotary ring and being rotatable with said rotary ring; a first sensor supported on said stationary ring or a part mounted on said stationary ring in such a manner as to be opposed to said encoder, for detecting the rotation of said rotary ring; and at least one second sensor disposed within a holder holding said first sensor, for detecting the condition of said rolling bearing unit; wherein said holder is retained within a case of non-magnetic metal holding said first and second sensors and is made of synthetic resin, wherein said sensor outputs a signal used to detect when an abnormality is present in said rolling bearing unit or a portion adjoining said rolling bearing unit, and wherein said wheel rotation detecting device further comprises: a threshold value setting circuit that sets a threshold value in accordance with the rotation speed of said rotary ring detected by said rotation detecting sensor so as to increase said threshold value as said detected rotation speed increases; a comparator for comparing said threshold value with the detect signal of said second sensor; and an abnormality judge circuit for judging the presence or absence of said abnormality in accordance with an output of said comparator.