A wheel bearing having an external, rotating, magnetic encoder which
registers rotational speed of the bearing, and a magnetic particle
trapping device spaced from the magnetic encoder to protect it against
contamination. The trapping device includes a permanent magnet and a
cooperating soft iron member which together form an L-shaped configuration
relative to each other, with the magnet extending axially relative to the
rotation of the wheel and the soft iron member extending radially, or vice
versa. Contaminants are collected in a space between the soft iron member
and the magnet. A magnetically non-conductive element may be provided to
separate the trapping device from the metallic housing of the constant
velocity joint on which the trapping device is mounted. A wiping finger
may be provided to dislodge accumulated contaminant particles, which may
then fall to the roadway.
