With the continuous improvement of vehicle safety requirements, developers use electronic science and technology to develop a variety of automotive intelligent control technology (automobile braking system), so as to more effectively protect people's safety in travel. In the previous article, Xiaobian gave a brief introduction to the advantages of the anti-lock brake system. In this article, let us continue to understand other electronic technologies in car safety: anti-lock brake system installation Knowledge of its control methods.
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First of all, we must know that the anti-lock brake system is a car safety control system with the advantages of anti-skid and anti-lock. It is an improved technology based on conventional brakes and can be generally divided into mechanical and electronic. By collecting and collating data, Xiaobian's knowledge of the installation of anti-lock braking system comes down to the following points. Let's learn about it.
Anti-lock brake system installation points
Four
(1) Always keep your foot on the brake pedal and do not relax. This will ensure sufficient and continuous braking force to enable ABS to function effectively.
(2) To maintain a sufficient braking distance. When driving on a good road, at least 3 seconds of braking time from the vehicle in front should be guaranteed; when driving on a bad road, it should be left longer for braking.
(3) It is necessary to practice using ABS in advance so that you can prepare and adapt to the brake pedal vibration when ABS is working.
(4) Read the driver's manual in advance. This will allow you to further understand the various operations.
Four don't
(1) Don't be more casual when driving a car with ABS than a car without ABS. Some car owners think that after the car is equipped with ABS, the safety is increased, so the mind will relax during driving and lay a hidden danger for the accident.
(2) Do not step on the brake pedal repeatedly. When driving a car with ABS, repeatedly pressing the brake pedal will cause the ABS to work intermittently, resulting in reduced braking performance and increased braking distance. In fact, ABS itself automatically increases and decreases braking force at a higher rate and provides effective directional control.
(3) Don't forget to control the steering wheel. When braking, the ABS system provides the driver with reliable direction control, but it does not automatically complete the steering operation of the car. In the event of an unexpected situation, someone needs to complete the steering control.
(4) Do not be intimidated by the normal hydraulic working noise of the ABS and the vibration of the brake pedal during the braking process. This sound and vibration are normal and allow the driver to perceive ABS to work.
Two ways of controlling ABS
The anti-lock brake system calculates the vehicle speed, the wheel angle deceleration, and the wheel slip ratio according to the angular velocity signals of the wheels. According to the above information, the anti-lock brake system reduces the braking force when the wheels tend to lock, and the wheel angle deceleration or When the slip ratio is within a certain range, the braking force is maintained, and the braking force is restored after the wheel speed is increased. Because the action is very fast, it seems to put the brakes on.
Anti-lock brake system structure
1, two-parameter control
The two-parameter controlled ABS consists of a vehicle speed sensor (speed radar), a wheel speed sensor, a control unit (computer) and an actuator. The working principle is the vehicle speed sensor and the wheel speed sensor. The vehicle speed and the wheel speed signal are input into the computer respectively, and the actual slip ratio is calculated by the computer, and compared with the ideal slip ratio of 15% to 20%, and then increased or decreased by the solenoid valve. Brake force of the brake. This type of drag sensor is commonly used in Doppler speed radar. When the car is driving, the Doppler radar antenna continuously emits electromagnetic waves to the ground at a certain frequency, and at the same time receives the reflected electromagnetic waves, and measures the difference between the emission and reception of the car radar, so that the vehicle speed can be accurately calculated. The wheel speed sensor is mounted on the transmission housing and is driven by the transmission output shaft. It is a pulse motor and produces a frequency proportional to the wheel speed. The actuator consists of a solenoid valve and a relay. The solenoid valve adjusts the braking force to maintain the desired slip ratio.
This kind of ABS can guarantee the ideal control of the slip ratio, and the anti-lock braking performance is good. However, due to the addition of a speed measuring radar, the structure is complicated and the cost is high.
2, single parameter control
It controls the wheel's angular deceleration and controls the braking force of the wheel to achieve anti-lock braking. Its structure is mainly composed of wheel speed sensor, controller (computer) and solenoid valve. In order to accurately measure the wheel speed, there should be a 1 mm gap between the sensor head and the wheel ring gear. To avoid the effects of water, mud and dust on the sensor, the sensor should be greased before installation. Solenoid valves are used for pressure regulation of wheel brakes.
For a four-channel brake system, one wheel has one solenoid valve; a three-channel brake system has one for each front wheel and one for the two rear wheels. The solenoid valve has three hydraulic holes, which are respectively connected with the brake master cylinder and the wheel brake cylinder, and can realize the pressure regulation function of pressure increase, pressure maintenance and pressure reduction.
The working principle is as follows:
1) Boost When the solenoid valve is not working, the brake master cylinder interface and each brake cylinder interface are directly connected. Due to the high strength of the main spring, the inlet valve is opened and the brake pressure is increased.
2) Pressure maintenance When the pressure in the brake cylinder of the wheel increases to a certain value, the inlet valve is cut off. The bracket is kept in the middle and the three holes are sealed to each other to maintain the brake pressure. 3) Step-down When the solenoid valve is working, the bracket overcomes the spring force of the two springs, and opens the unloading meat to lower the pressure of the brake cylinder. Once the pressure is reduced, the solenoid valve switches to a pressure hold state, or a boosted ready state. The main task of the control unit ECU is to calculate, analyze, amplify and discriminate the signals transmitted from the sensors of the respective wheels, and then output the command signals to the solenoid valves by the output stage to perform the brake pressure adjustment task.
The electronic control device consists of four parts, input stage A, controller B, output stage C, voltage regulation and protection device D. The electronic controller drives the solenoid valve at a frequency of 4 to 101 tz, which the driver cannot do. This single-parameter control mode ABS is widely used due to its simple structure and low cost. Most of the Chrysler sedans in the United States are equipped with this single-parameter control ABS. It is equipped with wheel speed sensors on all four wheels of the car. A 45- or 100-tooth ring gear is mounted on the wheel axle, and the sensor head of the wheel speed sensor is mounted on the top of the ring gear. When the wheel rotates, the sensor continuously generates a voltage signal, and inputs it into the computer, compares the ideal speed in the RoM, and calculates the speed increase or deceleration of the wheel, and sends a command to boost or depressurize the solenoid valve to control the brake cylinder system. power.
to sum up
We know that the anti-lock brake system not only has the braking function of the ordinary braking system, but also prevents the wheel from being locked, so that the car can still steer under the braking state, ensuring the stability of the braking direction of the car and preventing the side slip. And the deviation is the most advanced braking device with the best braking effect. This paper mainly introduces the main points of anti-lock braking system installation and its two-parameter control and single-parameter control.
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