Abstract: as the vehicle speed is more and more high, the vehicle handling stability of automobile safety is becoming more and more important, they not only
have four wheel alignment, some high speed passenger cars and limousines also has a rear wheel camber angle and front wheel forward and other parameters, the wheel alignment parameters change will make the vehicle handling and stability deterioration.
1 wheel alignment parameters and the effect of main
Four wheel alignment factors mainly include the camber, caster angle, steering axis angle ( steering kingpin inclination angle ), wheels ( toe ).
(1) the camber
(2) the caster
(3) kingpin inclination
(4) the wheel before the beam
2 wheel alignment is not accurate on vehicle performance
(1) the effect of wheel camber.
Whether the positive or negative camber angle, because the wheel of medial and lateral rotation radius is not consistent and wheel speed and in the same cause necessarily inside the wheel, the outer uneven wear. Caster angle is too large, heavy steering driver fatigue; caster after hours, in the car is on a straight road, prone to front wheel shimmy, steering wheel to swing, automatic steering wheel returnability is weaker, the driver did not dare to relax the steering wheel, difficult to manipulate or extremely easy to cause fatigue of the driver.
In modern cars, due to suspension and axles than past sturdy, coupled with flat surface. Therefore, the inclination of the vehicle is less and less. And the use of zero inclination of the vehicle or negative camber car more and more. In order to improve cornering stability and running smoothness. In the negative camber when turning the vehicle lateral angle decreases, the vehicle inclination is correspondingly reduced. Car steering at a high speed, the centrifugal force is increased, the body inclines outwards to increase, produce more positive camber, the lateral suspension overload exacerbates the lateral deformation of the tire.
Outside of the tire in contact with the ground s internal and external rolling radius less than the medial, lateral, this not only increased tire wear, also can make the steering performance reduction. So the modern car front end wheel aligner decreases or even negative can make the inner side and the outer side of the tire rolling radius approximately equal to the inner and outer side wear uniform but also improve the vehicle lateral stability.
(2) the effect of caster.
After dip angle is bigger, the higher the front wheel speed, stability is better, but after the dip of the steering wheel is heavy, modern high-speed car due to low tire pressure, high elasticity, running as the tire and the ground contact surface movement caused by stable center back torque increases, the tilt angle can be small to close to zero, even is negative (i.e., kingpin anteversion). After the dip angle will not influence of tyre wear, it is used to stabilize the driving direction and steering can automatically return. If the vehicle is equipped with the traditional manual steering wheel, the latter inclination angles is very small and even tends to negative after inclination, allows easy turning. If a vehicle equipped with power steering, the latter angle usually set a larger positive rake angle, so that the drivers steering more sensation, increased after dip angle will increase the turning force, but can increase the stability of the vehicle straight line.
(3) the influence of kingpin inclination.
Kingpin inclination of front wheel turning angle larger or greater is the front of the car, raised taller, front wheel automatic alignment effect is more apparent, but when turning the steering wheel steering wheel effort, the increased wear on the tires. Caster and kingpin inclination has made the car steering self-righting, straight line position effect. But the caster s return effect and speed, and kingpin inclination back is almost irrelevant with speed. Therefore, high speed caster back positive interaction plays a dominant position, and low speed mainly depends on the kingpin inclination back positive role. In addition, straight wheel are occasionally encountered in shock and deflection, the kingpin inclination back positive role.
(4) the influence of front beam.
The front beam is too large, the outer side of the tire wear will have positive camber angle is formed by the wear patterns, tread wear form of feather. When a hand from the lateral to the medial touch, tread edge has a sharp thorn in hand feeling. Negative front beam is too large, the inner side of the tire wear will have negative camber is formed by the wear morphology, tread wear form of feather.
When a hand from the outside to the inside to touch, tread edge has a sharp thorn in hand feeling. Automobile wheel alignment parameters, not only can influence the running performance, but also influences the traffic safety. Therefore, regular car wheel alignment inspection and adjustment, can reduce the wear of tires and suspension system, reduce fuel consumption, is the safety guarantee.
