Patent ID: 7537388

Claim:
A bearing assembly having an absolute encoder built therein, comprising: a rolling bearing including a rotatable raceway member, a stationary raceway member enclosing the rotatable raceway member with a cylindrical bearing space defined between it and the rotatable raceway member, and a circumferential row of rolling elements rollingly housed within the cylindrical bearing space and interposed between the rotatable and stationary raceway members; a to-be-detected member carried by the rotatable raceway member and having a magnetic characteristic cyclically varying in a direction circumferentially thereof, the magnetic characteristic, relative to the magnetic sensor unit, having a cycle matching with one complete rotation of the rotatable raceway member; a magnetic sensor unit carried by the stationary raceway member in face-to-face relation with the to-be-detected member; and a magnetic detecting circuit to supply an electric power to the magnetic sensor unit and to process an output signal from the magnetic sensor unit to provide an output to an external circuit, wherein the to-be-detected member is magnetized to have its magnetic flux partially saturated on both a north-pole side and a south-pole side, whereby the to-be-detected member shows the waveform of the magnetic flux having the slope steeper around a zero-crossing point than that of a complete sinusoidal waveform which does not show such saturation and having a cycle matching with one complete rotation of the rotatable raceway member.