McPherson suspension is one of the most widely used car front suspension in the world. McPherson suspension is composed of coil spring, shock absorber and triangular lower swing arm. Most models will also add lateral stabilizer bar. The main structure is simple, that is, the coil spring is sleeved on the shock absorber. The shock absorber can avoid the forward, rear, left and right offset of the coil spring when it is stressed, limit the spring to vibrate up and down, and use the stroke length and tightness of the shock absorber to set the soft, hard and performance of the suspension.
The McPherson suspension has a simple structure, so it is light-weight and fast response. Under the geometric structure of a lower rocker arm and strut, it can automatically adjust the camber of the wheel, so that it can adapt to the road when cornering, and maximize the grounding area of the tire. Although the McPherson suspension is not a suspension structure with high technical content, the performance of McPherson suspension in driving comfort is still satisfactory. However, due to its straight barrel structure, it lacks blocking force for the impact in the left and right directions, has poor anti braking nodding effect, weak suspension stiffness, poor stability and obvious turning and roll.
Take the MacPherson front independent suspension of Jetta as an example.
The cylindrical shock absorber 7 is a sliding column, the inner end of the yaw arm 12 is connected with the vehicle body through the hinge 10, and its outer end is connected with the steering knuckle 8 through the ball hinge 15. The upper end of the shock absorber is connected with the vehicle body through the vibration isolation block assembly 2 with bearing (which can be regarded as the upper hinge point of the shock absorber), and the lower end of the shock absorber is connected with the steering knuckle. Most of the lateral force on the wheel is borne by the yaw arm through the steering knuckle, and the rest is borne by the shock absorber piston and piston rod. Therefore, compared with candle suspension, this structure reduces sliding friction and wear to a certain extent.
The connecting line between the center of the upper hinge of the cylindrical shock absorber and the center of the ball hinge at the outer end of the yaw arm is the main pin axis. This structure is also a kingpin free structure. When the wheel jumps up and down, the angle of the kingpin axis changes because the lower fulcrum of the shock absorber swings with the yaw arm. This indicates that the wheel moves along the oscillating kingpin axis. Therefore, when the suspension is deformed, the positioning angle and track width of the main pin will change. However, if the arrangement of the linkage is properly adjusted, these positioning parameters of the wheel can change very little.