Suspension joining structure

1. A suspension joining structure comprising:

a lower arm having one end fastened to a vehicle body;

an assist knuckle having a strut thereon;

a fastening unit configured to connect one end of the lower arm and a lower end of the assist knuckle to each other;

a suspension fastened to the assist knuckle and rotating independently of the assist knuckle to assist steering of a wheel;

a steering input part connected to the assist knuckle, and configured such that a steering force is applied to the suspension upon steering; and

a rotation transfer unit arranged between the suspension and the steering input part,

wherein the steering input part comprises at least one mounting part fastened to the assist knuckle, and

wherein the assist knuckle comprises a fastener at one end thereof, the fastener arranged to correspond to the at least one mounting part.

2. The suspension joining structure of claim 1 , wherein the fastening unit includes a universal joint.

3. The suspension joining structure of claim 1 , wherein the assist knuckle comprises:

an upper hole on an upper end of the assist knuckle so that an upper end of the suspension extends through the upper hole; and

a lower hole on the lower end of the assist knuckle so that a lower end of the suspension extends through the lower hole,

wherein the suspension is configured to rotate with respect to the upper hole and the lower hole.

4. The suspension joining structure of claim 1 , wherein the fastening unit comprises:

a yoke arranged on the lower arm;

a ball stud fastened to the assist knuckle; and

a cross shaft arranged on the yoke and the ball stud so that the yoke and the ball stud have center axes different from each other.

5. The suspension joining structure of claim 1 , wherein the rotation transfer unit comprises a spline rod arranged at a center axis of the steering input part, and

wherein the suspension comprises an inlet so that the spline rod is configured to be seated into the inlet.

6. The suspension joining structure of claim 1 , wherein the steering input part is arranged on an upper end of the assist knuckle in parallel to the strut.

7. The suspension joining structure of claim 1 , further comprising a fixing part into which the steering input part is fitted at an upper end of the assist knuckle.

8. The suspension joining structure of claim 7 , wherein the fixing part comprises grooves defined in a direction into which the steering input part is inserted, and

wherein the steering input part and the assist knuckle are connected to each other through a pinch bolt fastened between the grooves.