Automobile system electric power steering system structure technology

1. Overview

The steering system has been evolving step by step since the birth of the automobile. Compared with other chassis components, the steering system has undergone the most iterations and is still continuing. Compared with the models of thirty years ago, the models of twenty years ago have a significant difference in one function. The hydraulic steering system has been transformed into an electric motor drive. In the past decade, another such transformation has occurred. EPS has undergone several developments and has become a part of ADAS. It is not only a factor in vehicle steering, but also related to control, comfort, safety and steering feel. The steering system is very important for the entire vehicle and affects driving safety and driving control to a large extent. In addition to power and chassis, the more direct first feeling of feeling the control performance of a car often comes from "road feel", that is, the steering system of the vehicle. Whether the steering system is good or not, in addition to affecting the vehicle's control performance, is more related to the driving safety of the vehicle. Today, there are various commonly used forms. The steering system of the car has gone through the development process of mechanical steering system, mechanical hydraulic power steering system, electronically controlled hydraulic power steering system, and electric power steering system. The traditional pure mechanical steering system has been almost replaced by the mechanical hydraulic power steering system (HPS), upgraded to the electronic hydraulic power steering system (EHPS), and then the electrically driven electric power steering system (EPS) has gradually become the mainstream.

With the trend of electrification of modern automobile systems and modules, the penetration rate of electronic steering systems is accelerating, electronic control execution system technologies are constantly emerging, and electric power steering is gradually becoming the mainstream.

Second Definition

When the car is driving, the driver manipulates the steering wheel, which, through a set of transmission mechanisms, deflects the steering wheel on the road at a certain angle to change its driving direction, ensuring the normal and stable driving of the car. The whole set of mechanisms (devices) that can deflect the steering wheel to achieve the steering of the car and change or maintain the driving or reverse direction of the car is called the car steering system. The function of the car steering system is to control the driving direction of the car according to the driver's wishes. The function is to change the driving direction of the car as needed by the driver turning the steering wheel.

The car steering system allows the car to change its direction according to the driver's wishes. It also allows the driver to use this mechanism to deflect the steering wheel in the opposite direction when the car's steering wheel is automatically deflected by the road interference and changes the driving direction, so that the car can return to its original driving direction. Undoubtedly, the car steering system is crucial to the driving safety of the car. The car steering system and the braking system introduced earlier are both important systems to ensure the driving safety of the car.

1. Basic requirements of steering system

(1) Good maneuverability

(2) Appropriate steering force and position sense

(3) With return function

(4) Proper road feel

(5) Reliable operation

(6) Energy saving

(7) Low noise

Three components (taking mechanical steering system as an example)

The mechanical steering system uses the driver's physical strength as the steering energy, also known as the human steering system. When the car turns, the force exerted by the driver on the steering wheel is transmitted to the steering gear through the steering shaft (steering column). The steering gear amplifies the steering force and then transmits it through the steering transmission mechanism to push the steering wheel to deflect, causing the car to change its direction. The steering of the car is completely achieved by the driver's operating force. The operation is laborious and labor-intensive, and it cannot meet the requirements of light steering and sensitive steering at the same time. However, it has the advantages of simple structure, reliable operation, good road feel, and easy maintenance. It is mostly used in small and medium-sized trucks or cars.

Automobile mechanical steering system refers to a system that does not rely on external power, but relies on the driver's operation, using the driver's physical strength as the source of steering power, and all mechanical transmission structures are mechanical. The mechanical steering system consists of three major parts: steering control mechanism, steering gear and steering transmission mechanism. Its main structure includes steering wheel, steering shaft, cross universal joint, intermediate shaft, steering gear, etc., as shown in the figure below.

Mechanical steering system structure diagram

When the car turns, the driver turns the steering wheel, and the torque is transmitted to the steering gear through the steering shaft. After the steering gear reduces speed and increases torque, it is transmitted to the steering knuckle arm through the steering rocker arm and the steering straight tie rod, so that the left steering knuckle and the left steering wheel fixed to it deflect around the kingpin. At the same time, the deflection of the left steering knuckle and the left steering wheel mounted thereon will transmit the movement to the right steering knuckle through the left steering trapezoidal arm, the steering tie rod and the right steering trapezoidal arm, so that the right steering knuckle and the right steering wheel fixed thereto produce the same deflection movement, thereby realizing the steering function of the vehicle. As a mechanical steering system that relies entirely on manpower, the coordination of the dual actions of manpower and machinery during the driving process of the vehicle plays a key role in ensuring the flexibility and stability of the car.

1. Steering control mechanism

A general term for all parts between the steering wheel and the steering gear. The steering mechanism consists of the steering wheel, steering column, steering shaft, steering drive shaft, steering universal joint, quick release, quick release shaft, bearing seat, etc. Its function is to transmit the force of the driver turning the steering wheel to the steering gear.

(1) Steering wheel

In ancient times, driving a carriage required controlling the reins, and now driving a car requires controlling the steering wheel. The earliest car steering control was controlled by a tiller, which was a control stick connected to the rudder. Today's car steering wheels are combined with airbags and various control switches. The fashionable ring shape, plus the speaker in the middle, also has switches for controlling the fixed speed and other functions.

The steering wheel is a very important part of the car. It is an essential component of the car's steering system. It is very familiar to everyone and is what we master and control when we drive. Because it ensures safer driving by giving you maximum control over the wheel, your hands are always on the steering wheel, except for the gear lever that you manipulate from time to time. In short, the steering wheel allows you to control the direction your car is going on the road. In the past, the steering wheel was relatively large in diameter, relatively thin, and made mainly of hard plastic. Today's steering wheel design is very comfortable. After the designer's design, the steering wheel can be designed to be very "light", which is convenient for the driver to use and can hold the steering wheel well.

▲ Audi steering wheel

The size of a steering wheel is important in driving because the size is inversely proportional to the force required to turn the steering wheel. This means that the larger the diameter of the steering wheel, the less force is required to turn the steering wheel. Conversely, the smaller the diameter of the steering wheel, the more force is required to turn the steering wheel.

The steering wheel includes a rim, a spoke, and a hub, and the hub has fine-tooth internal splines connected to the steering shaft.

There is a horn button on the steering wheel, and some cars also have speed control switches and airbags on the steering wheel.

Steering wheel collector ring

Steering wheel cable drum

(2) Steering shaft and steering column The steering column tube is fixed to the vehicle body and supports the steering wheel; the steering shaft is the transmission connecting the steering wheel and the steering gear; the steering shaft passes through the steering column tube and is supported on bearings and bushings inside the column tube. The steering shaft and steering column are collectively called the steering column, which connects the steering wheel to the rest of the steering system near or in the wheel. Most modern cars are equipped with a telescopic steering shaft consisting of two steel tubes, one of which is solid and the other is hollow.

1) Function of universal joint (steering joint and steering drive shaft):

① Convenient layout

② Eliminate the adverse effects caused by installation errors and deformation of the mounting bracket

③It is easy to realize the standardization and serialization of components such as steering wheels and steering gears.

2) Energy absorption mechanism: curved bracket type, ball type, bellows type, etc. The most commonly used is the curved bracket type.

①Bent bracket type

②Steel ball rolling deformation steering column

③Corrugated energy-absorbing steering column