Patent ID: 7717225

Claim:
A motor-driven steering assist apparatus, comprising: an input shaft to which a steering wheel is connected; an output shaft to which a tire wheel side steering member is connected; a torque sensor disposed between the input shaft and the output shaft; an electric, motor which is driven in correspondence to a detected torque of a torque sensor; a worm gear which is coupled to a rotating shaft of the electric motor; a worm wheel which is coupled to the output shaft, and is engaged with the worm gear; the input shaft, the output shaft, the torque sensor, the electric motor, the worm gear and the worm wheel being installed within a single unit covered by first to third housings, wherein an upper end portion of the input shaft and the torque sensor are supported by three or fewer points of support between the input shaft, the output shaft, and the housing, to the first housing by a first support disposed at an upper point in the first housing; an upper end portion of the output shaft, the electric motor, the worm gear and the worm wheel are supported to the second housing by a second support disposed at an interface between said first and second housings; and a lower end portion of the output shaft is supported to the third housing by a third support disposed at a lower point at an interface between said second and third housings, at least a portion of said third support extending below a lowest point of said second housing, the second housing being disposed between the first housing and the third housing, the lower point being disposed between the upper point and an area of the output shaft connectable to the tire wheel side steering member, a terminal end of the output shaft extending beyond a lowermost point of said third housing, wherein the output shaft is structured such that an upper end portion is supported by an upper bearing provided in the second housing, and a lower end portion is supported by a lower bearing provided in the third housing, and the worm wheel is fixed to the output shaft just below the bearing provided in the second housing in the output shaft, in an inner portion of the second housing.