Patent ID: 8174257

Claim:
A rotation detector equipped wheel support bearing assembly to rotatably support a vehicle wheel relative to a vehicle body structure, comprising: an outer member that serves as a stationary member and having an inner periphery rolling surfaces; an inner member that serves as a rotating member having an outer periphery formed with rolling surfaces opposed to the respective rolling surfaces in the outer member; a plurality of rolling elements interposed between those opposed rolling surfaces; a magnetic encoder fitted to the outer peripheral surface of the inner member at a location adjacent one end thereof; an annular sensor holder made of a resin and fitted to the outer member through a core metal provided in the outer periphery, the annular sensor holder having a magnetic sensor built therein and confronting the magnetic encoder with an axial gap intervening therebetween; and a sealing unit arranged at an outer position axially outwardly, relative to the bearing assembly, of the magnetic encoder and the magnetic sensor to seal a space delimited between the sensor holder and the inner member; wherein the magnetic encoder is in the form of a plastic magnetic encoder that includes a magnet defining a to-be-detected portion is in the form of a plastic magnet, wherein the sealing unit includes a first sealing plate mounted on an outer peripheral surface of the inner member, a second sealing plate mounted on an inner peripheral surface of the sensor holder and a sealing member made of an elastic material, and wherein the plastic magnetic encoder includes the plastic magnet in the form of a multipolar magnet having magnetic poles arranged in a direction circumferentially thereof, and the multipolar magnet is made of a thermoplastic resin containing a powdery magnetic material, which resin has a melting viscosity within the range of 30 to 1500 Pa·s.