So far, automobile steering systems have gone through four development stages: traditional mechanical steering systems, hydraulic power steering systems, electro-hydraulic power steering systems, and electric power steering systems. In the future, they may develop into wire-controlled power steering systems. At present, automobile steering systems are in the transition stage from hydraulic power steering systems and electro-hydraulic power steering systems to electric power steering systems.
PART.1: Mechanical steering system
The mechanical steering system uses the driver's physical strength as the steering energy, and all components that transmit force are mechanical. It is mainly composed of three parts: steering control mechanism, steering gear, and steering transmission mechanism. The traditional mechanical steering system (MS) is mainly composed of three parts: steering control mechanism, steering gear, and steering transmission mechanism. The steering control mechanism is the mechanism for the driver to operate the steering gear, including components from the steering wheel to the input end of the steering gear. The steering gear is a force-enhancing device that amplifies and outputs the torque transmitted from the steering wheel according to a certain transmission ratio. The earliest steering gear used a worm gear type, and later there were screw nut type, gear rack type, recirculating ball type, etc.
PART.2: Power Steering System
The power steering system is a steering system that uses both the driver's physical strength and the power of the engine (or electric motor) as steering energy. The power steering system is formed by adding a steering booster device to the mechanical steering system.
PART.3: Hydraulic Power Steering System
The hydraulic power steering system (HPS) is an additional hydraulic power system installed on the traditional mechanical steering system. It is generally composed of an oil pump, a V-belt pulley, an oil pipe, an oil supply device, a power assist device and a control valve. It uses hydraulic oil as power and drives the mechanical steering gear to work through the power generated by the hydraulic pump.
PART.4: Electro-hydraulic Power Steering System
The electro-hydraulic power steering system can adjust the steering assist characteristics. There are mainly electronically controlled hydraulic power steering systems (ECHPS) and electric hydraulic power steering systems (EHPS). Among them, EHPS is the most widely used. Electronically controlled hydraulic power steering system (ECHPS)
On the basis of the traditional hydraulic system, electromagnetic valves, sensors, etc. are added, which can provide power according to the vehicle speed, but it has high energy consumption, occupies a large space, is prone to leakage and noise, and has a high cost. It is mostly used in luxury cars and sports passenger cars. Electric hydraulic power steering system (EHPS)
The hydraulic pump is driven by an electric motor and integrated with an electronic control device, which saves fuel and improves economy, but there are still problems such as oil leakage and difficulty in maintenance. It is a technology for the transition from traditional systems to electric power steering systems, and there is still a prospect of application in the future.
PART.5: Electric power steering system
The electric power steering system is based on the traditional mechanical steering system, and sensor devices, electronic control devices and steering power mechanisms are added. Its characteristic is that it uses electric actuators to provide the driver with appropriate power under different driving conditions. The system is mainly composed of an electronic control unit ECU, a torque sensor, a vehicle speed sensor, a motor, a clutch and a steering column assembly.
