What is a rear steering knuckle
The rear steering knuckle is a key component in the vehicle suspension system. Its main function is to connect the wheels with the vehicle body, ensuring that the wheels can rotate flexibly when the vehicle turns, while also bearing the weight of the vehicle body and transmitting motion force.
Core function
Youdaoplaceholder0 Connection and support : The wheels are fixed to the suspension system through the wheel bracket structure, allowing the wheels to freely rotate around the main pin.
Youdaoplaceholder0 Load transmission : Bears the weight of the vehicle body and the impact loads during driving, and transmits these forces to the frame or vehicle body.
Youdaoplaceholder0 Steering control : Working in coordination with the front steering knuckle, it achieves vehicle steering by adjusting the steering Angle of the wheels.
Youdaoplaceholder0 Shock absorption protection : Some designs incorporate shock absorption elements that can absorb road vibrations and enhance driving comfort.
Structural features
It is usually made of forged steel or cast iron and is divided into two types: independent steering knuckles for independent suspension systems and rigid steering knuckles for non-independent suspension systems.
Steering Knuckle, also known as "sheep's horn", is one of the important parts in the steering axle of a car, which can enable the car to drive stably and sensitively transmit the driving direction.
The function of the steering knuckle is to transfer and bear the load at the front of the vehicle, support and drive the front wheels to rotate around the main pin, thereby steering the vehicle. When a car is in motion, it is subjected to variable impact loads, so it is required to have very high strength
The steering knuckle is a hinge for the wheel to turn, usually in a fork shape. There are two coaxial holes for installing the main pin on the upper and lower forks, and the steering knuckle journal is used for installing the wheels. The two ears of the pin holes on the steering knuckle are connected to the punch-shaped parts at both ends of the front axle through the main pin, allowing the front wheels to deflate at a certain Angle around the main pin to steer the car. To reduce wear, a bronze bushing is pressed into the pin hole of the steering knuckle. The lubrication of the bushing is achieved by injecting grease into the oil nozzle installed on the steering knuckle. To ensure smooth steering, a bearing is installed between the lower ear of the steering knuckle and the punch-shaped part of the front axle. An adjusting gasket is also installed between the upper ear of the steering knuckle and the punch-shaped part to adjust the gap between them.
To maintain the stability of a car during straight-line driving, the ease of steering, and reduce wear between tires and components, the steering wheels, steering knuckles, and front axles must maintain a certain relative position with the frame. This installation with a certain relative position is called steering wheel alignment, also known as front wheel alignment. The correct front wheel positioning should ensure that the car can travel stably in a straight line without swaying. The force on the steering wheel is not significant when turning. The steering wheel has an automatic self-centering function after turning. The tires do not slip against the ground to reduce fuel consumption and extend the service life of the tires. The front wheel positioning includes the main pin tilting backward, the main pin tilting inward, the front wheel tilting outward and the front wheel towing forward.
The backward-inclined Angle γ of the main pin can form a stabilizing moment of self-centering. When the main pin has a backward-inclined Angle γ, the intersection point of the main pin axis and the road surface will be in front of the contact point between the wheel and the road surface. When a car is traveling in a straight line, if the steering wheels are accidentally subjected to an external force and slightly deflect (deflect to the right as indicated by the arrow in the figure), it will cause the car's driving direction to deviate to the right. At this point, due to the centrifugal force of the vehicle itself, at the contact point b between the wheel and the road surface, the road surface exerts a lateral reaction force on the wheel. The reaction force exerts a moment L on the wheel that acts around the main pin axis, and its direction is exactly opposite to the wheel's deflection direction. Under the action of this torque, the wheels will return to their original middle position, thus ensuring the car travels stably in a straight line. Therefore, this torque is called the centering torque.
However, this torque should not be too large either; otherwise, when steering, in order to overcome this stabilizing torque, the driver will have to apply a relatively large force on the steering wheel (that is, the so-called heavy steering). The magnitude of the stabilizing torque depends on the size of the force arm L, and the size of the force arm L depends on the size of the backward tilt Angle γ.
The commonly used γ Angle nowadays does not exceed 2 to 3 degrees. Modern high-speed cars experience an increase in stabilizing torque due to reduced tire pressure and increased elasticity. Therefore, the γ Angle can be reduced to be close to zero, or even negative.
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