I. Core Definitions and Functions
The automotive steering system is a specially designed mechanism used to change or maintain the driving direction of a vehicle. It is a key part of the vehicle's chassis system that directly affects driving safety. Its fundamental purpose is to control the direction of the car's travel according to the driver's will. It is crucial to the performance of the car and needs to be guaranteed
Precise directivity: There is a definite correspondence between the steering wheel Angle and the wheel Angle.
High sensitivity: Quick response and easy operation.
Appropriate feedback sense (road feel) : It can feed back the information of the parts where the wheels come into contact with the road surface to the driver.
Driving stability: It can automatically return to the center and maintain the stability of the vehicle when driving in a straight line.
Ii. Core Components of the System
Although the structures of different types of steering systems vary, they are basically composed of the following core components:
Steering control mechanism
Steering wheel: The component directly operated by the driver.
Steering column: The drive shaft that connects the steering wheel and the steering gear. It is usually designed with a buffer and energy-absorbing structure that can fold and contract in the event of a collision to protect the driver.
Steering gear (steering gear
This is the core component for power enhancement and motion conversion in the steering system. Its function is to convert the rotational motion of the steering wheel into the reciprocating swing of the steering rocker arm, and to achieve the effect of deceleration and torque increase, enabling the driver to turn the heavy wheels with less force.
Main types
Rack and pinion type: The most mainstream type of modern passenger cars. The structure is simple and compact, with high transmission efficiency and a direct and clear road feel.
Recirculating ball type: Commonly used in SUVs, pickup trucks and large commercial vehicles. Using steel balls as the transmission medium, it is easy to operate and durable, but the road feel is not as clear as that of the rack and pinion type.
Steering transmission mechanism
This is a bar system that transmits the force and motion output by the steering gear to the left and right steering wheels and causes them to deflects in a certain relationship.
The main components include: steering rocker arm, steering straight tie rod, steering knuckle arm, steering tie rod, steering knuckle, etc.
Power steering device (an essential part of a non-pure mechanical system)
It is used to assist the driver in applying steering force, making the steering operation more convenient and comfortable.
Main types
Hydraulic power steering: It is composed of a hydraulic pump driven by the engine, control valves and power cylinders.
Electronic hydraulic power steering: It replaces the engine-driven hydraulic pump with an electric pump, making it more energy-efficient.
Electric power steering: The current mainstream technology. It is assisted by a motor that directly drives the steering column or the steering rack. Compact in structure, highly efficient, and capable of easily achieving advanced driver assistance functions.
Iii. Classification of Steering Systems
According to whether there is assistance and the way of assistance, it can be classified as:
Mechanical steering system: It relies entirely on the driver's physical strength as the power source for steering without any assistance. It is now rarely used in passenger cars.
Power steering system: It uses the power from the engine or motor as an auxiliary energy source to assist the driver in steering. The above-mentioned HPS, EHPS and EPS all fall into this category.
According to the different energy sources being turned, power steering systems can be further classified as:
Hydraulic power steering system
Electric power steering system
Iv. Key Technologies and Characteristics
Ackermann steering geometry: A geometric design that enables the steering Angle of the inner wheels to be greater than that of the outer wheels when a car turns. This ensures that all wheels roll around a common instantaneous center, reducing tire wear and enhancing cornering stability.
Variable steering ratio: Also known as "active steering system". It can make the transmission ratio between the steering wheel Angle and the wheel Angle change with the vehicle speed or the steering wheel Angle. For instance, when parking, the steering is more sensitive (with a smaller transmission ratio); When driving at high speed, the steering is more stable (with a larger transmission ratio).
Four-wheel steering system: An advanced technology that enables the rear wheels to make small-angle steering according to the vehicle speed.
At low speeds: The rear wheels rotate in opposite directions to the front wheels, significantly reducing the turning radius and enhancing flexibility.
At high speeds: The rear wheels rotate in the same direction as the front wheels, enhancing the vehicle's stability when changing lanes and cornering.
