STEERING ANGLE SENSOR AND ELECTRIC POWER STEERING DEVICE EMPLOYING THE SAME

摘要

A steering angle sensor 17 is provided which can minimize a detection error even when a steering shaft 6 is inclined. In an annular clearance t1 defined between the steering shaft 6 and an inner cylindrical wall of a first gear 24, there is compressed an elastic O-ring 23. Due to provision of the elastic O-ring 23, inclination of the steering shaft 6, which tends to occur during handling of a steering wheel 1, is suitably absorbed by the elastic O-ring 23, and thus, generation of detection error caused by inclination of the first gear 24, which would follow the inclination of the steering shaft 6, is suppressed or at least minimized.

主权项

1. A steering angle sensor comprising:
a steering shaft rotating together with a steering wheel; a sensor housing arranged to enclose the steering shaft; a first gear rotatably received in the sensor housing, the first gear including an annular body portion disposed about a given part of the steering shaft leaving a given annular clearance therebetween and an annular toothed portion formed on an outer periphery of the annular body portion; a second gear rotatably received in the sensor housing, the second gear having a magnetic member at a center portion thereof and an annular toothed portion meshed with the annular toothed portion of the first gear; a third gear rotatably received in the sensor housing, the third gear having another magnetic member at a center portion thereof and an annular toothed portion meshed with the annular toothed portion of the second gear, the numbers of respective teeth of the second and third gears being mutually indivisible to provide a unit of the second and third gears with a given speed reduction ratio; a first MR element detecting a change of a magnetic field produced by the magnetic member of the second gear for obtaining a first rotation angle of the second gear; a second MR element detecting a change of a magnetic field produced by the magnetic member of the third gear for obtaining a second rotation angle of the third gear; an elastic member compressed in the given annular clearance between the steering shaft and the first gear, a thickness of the elastic member in a non-compressed condition being larger than a thickness of the given annular clearance; and a control unit that obtains an absolute steering angle of the steering wheel based on the first and second rotation angles of the second and third gears.