The wheel alignment angle is the relative angle between the suspension system and each moving part. Maintaining the correct wheel alignment angle ensures the vehicle runs straight, improves the steering performance of the vehicle, ensures the steering system automatically returns, and avoids the bearing due to improper force. Damage and loss of precision can also ensure that the tires are tightly coupled to the ground, reducing tire wear, suspension system wear and fuel consumption.
The main positioning angles of the car suspension system include: wheel camber, wheel toe, king pin back tilt, king pin tilt, thrust angle, etc.
1.Wheel camber :
In a plane that passes the wheel axis and is perpendicular to the vehicle support plane, an acute angle is formed between the wheel axis and the horizontal line. As shown in Figure A, the angle between the centerline of the tire and the vertical line is seen from the front of the car. It is positive outward and negative inward.
The difference in angle can change the contact point between the tire and the ground, directly affecting the wear condition of the tire. And the force distribution of the vehicle weight on the axle is changed to avoid abnormal wear of the bearing. In addition, the presence of the camber angle can be used to offset the angular change caused by the deformation of the suspension system after the body load. The presence of the camber angle also affects the direction of travel of the car. Therefore, the camber angles of the left and right wheels must be equal. When the forces are balanced with each other, the vehicle does not affect the straight line of the vehicle, and then cooperate with the toe of the wheel to make the wheel run straight and avoid the tire. Uneven wear. The four wheel aligner measures the wheel camber to a range of ±10°.
The end points of the horizontal diameter of the inner contour of the wheel rim at both ends of the same shaft are the apexes of the isosceles trapezoid, and the difference between the lengths of the front and rear sides of the isosceles trapezoid is the toe. When the front edge of the trapezoid is smaller than the bottom edge, the toe is positive, otherwise it is negative. The angle between the horizontal diameter of the wheel and the longitudinal plane of symmetry of the vehicle is the toe angle. Due to the camber and road surface resistance, the front wheel has a tendency to open to the sides to make the roller cone movement, but it is restrained by the axle, and cannot roll
outward, causing the wheel to roll and slip, which increases the wear and tear. The instantaneous rolling direction is close to the front, reducing the pressure on the outer bearing of the hub and the wear of the tire. The four-wheel aligner measures the range of the toe angle of the wheel to ±6°.
3.Tilt after the main pin:
The acute angle of the vertical line passing through the center of the wheel and the true or imaginary steering kingpin axis on the longitudinal symmetry plane of the vehicle is the main pin caster angle, the forward is negative, and the backward is positive. The presence of the caster back rake angle allows the intersection of the steering axis of the wheel and the ground to be in front of the grounding point of the tire. The resistance of the ground to the tire can be used to generate a positive return torque about the axis of the kingpin, which is exactly opposite to the direction of deflection of the wheel. To keep the vehicle in a straight line. The greater the back inclination
angle, the better the straightness of the vehicle, and the better the resilience of the steering wheel after steering. However, the caster has a backward tilt angle that makes the steering heavy, and the driver is prone to fatigue. The caster is too small, when the car is straight. When driving, the front wheel is prone to vibration, the steering wheel is swaying, and the steering wheel’s automatic returning ability is weakened after steering, and the driver will lose the sense of road; when the left and right wheel kingpins are not inclined, the vehicle will cause a straight line when driving. When the deviation is over, the driver does not dare to relax the steering wheel, which is difficult to manipulate or can easily cause driver fatigue. The four-wheel aligner measures the caster angle of ±15°.
4.Slant inside the main pin:
Defined as the acute angle formed by the projection of the axis of the true or imaginary steering kingpin on the plane and the perpendicular to the plane of the vehicle support plane in a plane that is perpendicular to both the longitudinal symmetry plane of the vehicle and the vehicle support plane. The function of the inner pin inclination angle is to make the front wheel automatically return to the positive force under the action of gravity when the wheel is driven away from the straight line by external force. In addition, the kingpin inclination angle can also reduce the impact of the front wheel transmission to the steering mechanism, and make the steering light, but the camber angle should not be too large, otherwise the tire wear will be accelerated when turning. Car maintenance master WeChat: 30839790801 The greater the internal steering angle of the main pin, the stronger the positive effect of the front wheel, but the more laborious the steering, the more the tire wears. On the contrary, the smaller the angle, the weaker the positive effect of the front wheel. . The four-wheel aligner measures the range of the kingpin inclination angle to ±20°.
The longitudinal axis of the vehicle in the plan view and the thrust line (which is an imaginary line extending forward from the center of the rear axle and the rear axle travel direction line determined by the two rear wheels). The thrust line is skewed to the left with respect to the longitudinal axis and negative to the right. A car that is in good condition should not have a thrust angle. However, due to the wear of the rear axle rubber sleeve, etc., the rear axle thrust line is deflected, and the rear wheel generates a moment along the center of mass of the car along the thrust line, so that the car runs off. The existence of the thrust angle is an important reason for the deviation of the
car. The four-wheel aligner measures the thrust angle in the range of ±6°.