1. Field of the Invention
The present invention relates to a bearing assembly equipped with a rotation sensor capable of detecting the home position, which may be used in, for example, controlling a motor.
2. Description of the Prior Art
A revolution sensor for detecting the number of revolutions of, for example, a wheel is known, which includes a magnetic encoder fitted to a rotating element and having a plurality of opposite magnetic poles N and S defined therein so as to alternate with each other in a direction circumferentially thereof, and a magnetic sensor for detecting alternate passage of the opposite magnetic poles N and S of the magnetic encoder. The conventional rolling bearing assembly having such a revolution sensor built therein is shown in FIG. 13. Referring to FIG. 13, the rolling bearing assembly 31 includes an inner race 32 defining a rotatable member, an outer race 33 defining a stationary member and a plurality of rolling elements 34 operatively retained in position by a retainer or cage 35 and operatively interposed between the inner race 32 and the outer race 33. A magnetic encoder 36 of an annular configuration is fixed to the inner race 32, and a magnetic sensor 37 constructed of, for example, a Hall element is fixed to the outer race 33 and positioned radially outwardly of the magnetic encoder 36 so as to confront the latter. The magnetic sensor 37 is housed and resin-molded within a resin casing 38, and the resin casing 38 housing the magnetic sensor 37 is in turn mounted on the outer race 33 through a metallic casing 39 to thereby fix the magnetic sensor 37 to the outer race 33.
By so constructing the conventional rolling bearing assembly, as the inner race 32 rotates, the magnetic sensor 37 detects change in polarity of the magnetic encoder 36 to thereby provide an incremental rotation pulse signal descriptive of the number of revolutions of the inner race 32.
However, it has been found that with the conventional rotation sensor, even though the incremental rotation pulse signal can be obtained, no home position signal descriptive of the point of origin of revolution can be obtained. Because of this, an extra sensor dedicated to detect the home position is required for effectively accomplishing an initializing operation. The use of the extra sensor renders assemblage to be complicated, accompanied by complication of the structure. It is to be noted that although an absolute type has been suggested as a rotation detecting device, even this type has a problem in that the structure is complicated.