Steering apparatus

1. A steering apparatus, comprising:

an axle housing rotatably supporting a wheel hub on which a steered road wheel is installed;

a lower arm adapted to be oscillatingly supported at one end on a vehicle body and having a turning portion provided at the other end for pivotably supporting the axle housing by the turning portion;

an electric motor installed on the lower arm for turning the axle housing by a driving force produced by the motor; and

a speed reducer configured to reduce rotation of the motor and installed on the lower arm and located between a rotation axis of the motor and the turning portion;

wherein the rotation axis of the motor and a pivot of the axle housing are arranged to be offset from each other, and

wherein the rotation axis of the motor is laterally spaced apart from the turning portion and arranged closer to the vehicle body rather than the turning portion.

2. The steering apparatus as claimed in claim 1 , wherein:

the turning portion is mechanically linked via a universal joint to the axle housing.

3. The steering apparatus as claimed in claim 1 , wherein:

the rotation axis of the motor is arranged along a pivot that oscillatingly supports the lower arm; and

the speed reducer comprises a worm gear and a worm wheel.

4. The steering apparatus as claimed in claim 3 , wherein:

the motor is installed on an upside of the lower arm.

5. The steering apparatus as claimed in claim 4 , wherein:

the lower arm is pivotally supported on the vehicle body between two lower-arm supporting portions attached to the vehicle body and spaced apart from each other; and

the motor is located between the two lower-arm supporting portions.

6. The steering apparatus as claimed in claim 4 , further comprising:

a tie rod displaceable in a vehicle lateral direction responsively to rotary motion of the motor; and

a knuckle arm integrally connected to the axle housing and mechanically linked to the tie rod,

wherein a straight line, passing through a rotation center of a turning pair of the tie rod and the knuckle arm and a rotation center of a turning pair of the lower arm and the axle housing, is arranged substantially parallel to the pivot of the lower arm.

7. The steering apparatus as claimed in claim 3 , wherein:

the speed reducer is accommodated in a speed-reducer casing and has a sector gear; and

the speed-reducer casing has a stopper mechanism formed in the casing for restricting anticlockwise and clockwise angular displacements of the sector gear exceeding predetermined angular-displacement limits by way of abutment with the sector gear.

8. The steering apparatus as claimed in claim 1 , wherein:

the motor and the speed reducer are provided for each individual steered road wheel.

9. A steering apparatus, comprising:

an axle housing rotatably supporting a wheel hub on which a steered road wheel is installed;

a lower arm adapted to be oscillatingly supported at one end on a vehicle body and having a turning portion provided at the other end for pivotably supporting the axle housing by the turning portion;

an electric motor installed on the lower arm for turning the axle housing by a driving force produced by the motor; and

a harmonic-drive speed reducer configured to reduce rotation of the motor,

wherein a rotation axis of the motor and a pivot of the axle housing are arranged to be offset from each other, and

wherein the rotation axis of the motor is laterally spaced apart from the turning portion and arranged closer to the vehicle body rather than the turning portion.

10. A steering apparatus, comprising:

an axle housing rotatably supporting a wheel hub on which a steered road wheel is installed;

a lower arm adapted to be oscillatingly supported at one end on a vehicle body and having a turning portion provided at the other end for pivotably supporting the axle housing by the turning portion;

an electric motor installed on the lower arm for turning the axle housing by a driving force produced by the motor; and

a speed reducer configured to reduce rotation of the motor and installed on the lower arm and located between the motor and the turning portion,

wherein the motor is arranged closer to the vehicle body rather than a steering axis serving as a pivot of the axle.

11. The steering apparatus as claimed in claim 10 , wherein:

the motor is installed on an upside of the lower arm.

12. The steering apparatus as claimed in claim 11 , further comprising:

a steering controller configured to control the motor, the steering controller installed on the lower arm.

13. The steering apparatus as claimed in claim 10 , wherein:

the motor and the speed reducer are provided for each individual steered road wheel.

14. A steering apparatus, comprising:

an axle housing rotatably supporting a wheel hub on which a steered road wheel is installed;

a lower arm adapted to be oscillatingly supported at one end on a vehicle body and having a turning portion provided at the other end for pivotably supporting the axle housing by the turning portion;

an electric motor installed on the lower arm for turning the axle housing by a driving force produced by the motor; and

a harmonic-drive speed reducer configured to reduce rotation of the motor,

wherein the motor is arranged closer to the vehicle body rather than a steering axis serving as a pivot of the axle housing.

15. A steering apparatus, comprising:

an axle housing rotatably supporting a wheel hub on which a steered road wheel is installed;

a lower arm adapted to be oscillatingly supported at one end on a vehicle body and pivotably supporting the axle housing at the other end;

an electric motor installed on the lower arm for turning the axle housing by a driving force produced by the motor; and

a speed reducer configured to reduce rotation of the motor,

wherein the motor and the speed reducer are arranged from the vehicle body in that order.

16. The steering apparatus as claimed in claim 15 , wherein:

the motor is installed on an upside of the lower arm.