I. Introduction ABS anti-lock braking system has become the standard safety configuration of many cars. The earliest mechanical anti-lock braking system (ABS) in the world was invented by Swedish engineer Weiner in 1930, which became a luxury in automobile equipment at that time. Using ABS can effectively shorten the braking distance, reduce vehicle sideslip, prevent wheels from locking and bouncing, improve directional stability and reduce tire wear, ensure smooth braking, and be beneficial to driving safety. After 80 years of hard work, the research on ABS has made a breakthrough, from two-wheel ABS to four-wheel ABS, from mechanical ABS to electronic ABS, which has gradually popularized ABS in the global automobile industry. ABS can prevent any wheel from locking in emergency braking, maintain good adhesion and steering performance, and improve the safety of automobile braking.

Second, the basic composition of the ABS system ABS anti-lock braking system is widely used in automobiles. The purpose is to control the angular deceleration of the wheels, control the braking force of the wheels, and realize anti-lock braking. It is mainly composed of wheel speed sensor, controller (computer) and solenoid valve.

Third, the working principle and adjustment process of ABS

(The working principle of ABS is to collect the rotational speed signals of four wheels through the rotational speed sensors installed on the wheels, and send them to the electronic control unit to calculate the rotational speed of each wheel, and then calculate the deceleration of the vehicle and the slip rate of the wheels. According to the calculated parameters, the ABS electronic control unit adjusts the braking pressure in the braking process through the hydraulic control unit to prevent the wheel from locking. When ABS doesn't work, the electronic braking force distribution system can still adjust the braking force of the rear wheel to ensure that the rear wheel will not lock up before the front wheel and ensure the safety of the vehicle.

(II) Adjustment Process of ABS The control process of wheel brake pressure adjustment is as follows:

1. When braking in the pressure establishment stage, the braking pressure is established by the booster and the master cylinder. At this time, the normally open valve is opened, the normally closed valve is closed, the braking pressure enters the wheel brake, and the wheel speed drops rapidly until the ABS electronic control unit recognizes that the wheel has a locking tendency through the speed sensor.

2. In the pressure maintaining stage, when the ABS electronic control unit receives a signal from the vehicle speed sensor and recognizes that the wheel has a tendency to lock, the ABS electronic control unit closes the normally open valve and the normally closed valve remains closed.

3. In the depressurization stage, if the wheel still tends to lock up during the pressure maintaining stage, the ABS system will enter the depressurization stage. At this time, the ECU commands the normally closed valve to open, the normally open valve to close, the hydraulic pump starts to work, and the brake fluid is sent back to the brake master cylinder from the wheel cylinder through the low-pressure accumulator, so that the brake pressure decreases, the brake pedal shakes, the wheel locking degree decreases, and the wheel speed starts to increase.

4. In order to achieve the best braking effect in the power-assisted stage, when the wheel reaches a certain speed, the ABS electronic control unit commands the normally open valve to open again and the normally closed valve to close. With the increase of braking pressure, the wheels are braked and decelerated again.

Four. Proper use and maintenance of ABS ABS is called "anti-lock braking" system rather than "anti-skid" system. Although the modern ABS system can maximize the stability of the braking system, it can't prevent the wheel from slipping in all cases. When driving on snowy, icy or slippery roads, the stability of the car is still poor. At this time, you should slow down and drive carefully.

ABS can't reduce the time for the driver to step on the brake pedal. Therefore, speeding, especially in corners, wet places with water or too close to the car, may also lead to car accidents, and should be avoided as much as possible.

Don't increase the braking force by stepping on the brake pedal more. In the conventional braking system, stepping on the brake pedal several times can make more brake fluid flow to the cylinder and enhance the braking effect. But for a car equipped with ABS, as long as you step on the brake pedal, the car will automatically brake the anti-lock brake without manual intervention. Stepping on the brake pedal several times will make the ABS computer not get the correct braking signal, which will lead to poor braking effect.

You can't increase the tire diameter at will, but you can increase the tire width while keeping the original tire diameter unchanged. Because the speed signal of ABS is obtained from the wheel, if this regulation is not followed, the data of wheel speed will be inaccurate, and in serious cases, ABS will make a wrong judgment and even cause an accident.

When the ignition switch is in the "on" position, the "ABS" indicator on the instrument panel will light up. Most cars turn off within a few seconds after the engine starts. When the battery voltage is lower than10v, ABS will resume normal operation. If the ABS indicator light is on and does not go out, it means that the system is faulty. At this time, the system can still guarantee the general braking function, but it has no anti-lock braking ability, so it should be carefully driven to the repair shop for maintenance as soon as possible.

When braking, you can feel the jitter of the brake pedal, indicating that ABS works normally. At the same time, drivers are also reminded to slow down when driving on bad roads. Only brake fluid specified by the factory can be used.

When the vehicle is equipped with an airbag (SRS) for ABS maintenance, the function of SRS should be temporarily removed (it should be noted that some vehicles need special instruments to delete the instructions in the SRS computer).

This can prevent SRS from accidentally exploding and injuring people, so special attention should be paid when testing the performance of ABS at high speed. Because the speed sensor is magnetic, it is easy to absorb iron filings, so pay attention to it when maintaining. In addition, when installing the speed sensor, tighten it according to the specified torque, apply the specified antirust agent (butter is not allowed), and pay attention to the gap between the sensor and the gear ring.

If there is air in the brake line, it must be removed. Generally speaking, manual exhaust can solve the problem. If necessary, please refer to the maintenance manual of the original car.