At present, the front axle of passenger cars adopts a sliding column swing arm type independent suspension, and the two-way-acting shock absorber is a part of the suspension rod system. The suspension support is connected with the piston rod of the shock absorber with a nut, and the suspension support is fixed on the vehicle body. The coil spring is installed between the dust cover of the shock absorber and the spring seat of the shock absorber. The lower end of the shock absorber is integrated with the steering knuckle. Both ends of the front axle cross beam plate are hingedly connected with the left and right lower swing arms, and the other end of the lower swing arm is connected with the steering knuckle by a ball joint. A swing arm support rod is fixed on the lower swing arm, and the other end of the support rod is elastically connected with the vehicle body through a support bracket.
The shock absorber doubles as the king pin, and its axis is the connection between the upper and lower hinge centers. When the wheel rolls, the up and down jump will inevitably cause the up and down swing of the lower swing arm, and the shock absorber will also swing with the lower swing arm. The swing of the shock absorber causes the angle change of the kingpin axis and the change of the wheel base. Due to the constraints of the independent suspension swing arm support rod, the angle change of the kingpin axis and the change of the front wheel track size are very small under normal conditions, and will not affect the normal matching of the front wheel camber and the front wheel toe. However, when the support rod bracket cushion is worn loose and the restraint on the lower swing arm is relatively reduced, the angle swing of the kingpin axis will increase, and the change of the front wheel track will also increase.
The shock absorber is an important force transmission component in the independent suspension. It not only transmits the driving force that pushes the vehicle forward, but also plays a guiding role to ensure the vehicle travels in a straight line. Frequent starting and stopping of the vehicle will cause the vehicle's center of mass (center of gravity) to change repeatedly, which will cause the shock absorber piston rod to bend, deform or even fail. In severe cases, it will also cause the independent suspension support to be loosely connected to the body. The failure and loosening of the shock absorber will directly destroy the relative position of the kingpin inclination.
The steering knuckle is movably connected with the lower swing arm through the lower swing arm ball head, and most of the lateral force acting on the tire is transmitted to the lower swing arm by the steering knuckle through the swing arm ball head. Therefore, the swing arm ball head is very easy to wear, especially when the dust cover of the swing arm ball head is broken or the grease is aging, which will accelerate the early damage of the swing arm ball head. The looseness of the independent suspension swing arm ball joint will accelerate the looseness and wear of a series of steering transmission rods such as the tie rod ball joint and the intermediate bushing.
The function of the swing arm support rod is to ensure the correct position of the kingpin axis, so as to ensure that the dimensions of each part of the front wheel steering trapezoid do not change, so that the matching of the parameters of the front wheel reaches the best value. If the front support rod is deformed, it will affect the correct position of the kingpin axis, destroy the steering trapezoid, and make the front wheel positioning ineffective.
