Foreword
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In order to improve the safety of vehicle driving, automotive engineers from all over the world are committed to research work on automotive brake systems. The anti-lock brake system is one of the most outstanding applications of automotive brake technology in automobiles. The anti-lock braking system allows the car to maintain directional stability and shorten the braking distance while braking, effectively improving the safety of driving. Let's take a look at the classification and performance characteristics of the anti-lock brake system.
First, the classification of anti-lock braking system
First, according to the manufacturer, and second, according to the control channel. The following mainly introduces the method of classification by channel.
In the anti-lock braking system, a brake line capable of independently adjusting the brake pressure is referred to as a control passage. The control channels of the ABS system (ABS control mode) are divided into four channels, three channels, two channels and one channel.
(1) Four-channel type
The four-channel ABS has four wheel speed sensors. In the pipeline leading to the four wheel brake cylinders, a brake pressure regulator device is provided for independent control to form a four-channel control mode. Guangzhou Honda is using a four-channel ABS device. Performance characteristics: Since the four-channel ABS is independently controlled for each wheel according to the signals input by the wheel speed sensors of each wheel, the utilization factor of the adhesion coefficient is high, and the maximum adhesion of each wheel can be utilized to the maximum extent during braking. The four-channel control mode is especially suitable for the road surface with the adhesion coefficient of the left and right sides of the car, which not only can obtain good directional stability and direction control ability, but also can obtain the shortest braking distance. However, if the adhesion coefficient of the left and right wheels of the car is quite different (such as water or ice on the road surface), the ground braking force of the two wheels will be different when braking, so the yaw moment will be generated and the body will be made. The side with greater power is out of the way, and it is impossible to keep the car running in the predetermined direction, which will affect the stability of the braking direction of the car. Therefore, when driving on a wet road surface such as freezing or standing water, the driver should reduce the speed of the vehicle and do not blindly believe in the ABS device.
(2) three-channel type
The three-channel ABS is independent control of the two front wheels, and the two rear wheels are controlled together according to the principle of low selection (that is, the two wheels are controlled by one channel to ensure that the wheels with less adhesion are not locked), also called mixing. control. Santana 2000GSi is the ABS device used.
Performance characteristics: When the two rear wheels are controlled together according to the principle of low selection, it can ensure that the braking force of the left and right rear wheels is equal under various conditions, even if the adhesion coefficients of the two wheels are different, the braking force of the two wheels is Restricted to a level of low adhesion, the braking force of the two rear wheels is always balanced, ensuring good directional stability when the car is braked under various conditions. Of course, when the two rear wheels are controlled together according to the principle of low selection, there may be a problem that the adhesion of the rear wheel on the side with a large adhesion coefficient cannot be fully utilized, so that the total braking force of the automobile is reduced. However, it should be noted that in the case of emergency braking, due to the axial load forward, the proportion of the rear wheel braking force is reduced in the total braking force of the car, especially for the front-wheel-drive car, the front wheel The force is much stronger than the adhesion of the rear wheel. Usually, the rear wheel braking force only accounts for about 30% of the total braking force. The loss of insufficient utilization of the rear wheel adhesion has little effect on the total braking force of the car. In the 60 km/h emergency braking comparison test conducted on Santana 2000, the ABS model is only one meter shorter than the ABS-free model, but the ABS models always have directions and will not lose direction. control.
Independent control of the two front wheels, mainly considering small cars, especially front-wheel-drive cars, the braking force of the front wheels accounts for a large proportion of the total braking of the car (up to 70%), which can make full use of the two The adhesion of the front wheels. On the one hand, the car obtains the largest possible total braking force, which is beneficial to shorten the braking distance. On the other hand, the two front wheels in the brake can always maintain a large lateral adhesion, so that the car maintains good steering ability. Although the independent control of the two front wheels may cause the braking force imbalance of the two front wheels, the braking force imbalance of the two front wheels has a relatively small influence on the running direction stability of the vehicle, and the influence of the steering operation of the driver can be exerted. Make corrections. Therefore, three-channel ABS is commonly used in cars.
(3) Two-channel type
The two-channel ABS is difficult to achieve in terms of directional stability, steering control, and braking performance, and is currently rarely used. (4) One-channel one-channel ABS is often called single-channel ABS. It is equipped with a brake pressure regulator in the rear brake master and a wheel speed sensor on the rear axle final drive (also on the rear wheel). Install one each).
Second, the performance characteristics of anti-lock brake system
The single-channel anti-lock braking system generally controls the two rear wheels in accordance with the principle of low selection. The single-channel anti-lock brake system cannot fully utilize the adhesion of the two rear wheels, so the braking distance is not necessarily significantly shortened. In addition, the front wheel brake is not controlled, and the front wheel will still brake and lock when the brake is applied, so the steering ability is not improved, but the brake can be significantly improved due to the fact that the two rear wheels will not lock when braking. The directional stability of the time is a great advantage in terms of safety, and has the advantages of simple structure and low cost, so it is widely used in light trucks.
In summary, although the anti-lock braking system has the characteristics of shortening the braking distance, maintaining the optimal braking effect of the wheel, maintaining the braking direction stability and maneuverability, different types of ABS devices are generated in the emergency braking. The effect is not the same, so the driver should not be misled by excessive publicity. It should be understood that the ABS system is only a device that assists safe driving, and is not a panacea. Only superb driving skills are a lifetime benefit. In addition, different types of ABS devices have different prices due to their composition and structure. Therefore, when purchasing a car, you should not only see the price, but you should also see which type of ABS device is installed.
Third, the advantages of anti-lock brake system
When the wheel is about to reach the next lock point, the pressure of the brake oil makes the airbag repeat, so that it can act 60~120 times in one second, which is equivalent to constantly braking and relaxing, which is similar to the mechanical "point brake". Therefore, the ABS anti-lock brake system can avoid out-of-control and wheel side slip during emergency braking, so that the wheel is not locked when braking, and the tire is not allowed to rub against the ground at one point, thereby increasing friction. It can achieve braking efficiency of more than 90%, while reducing brake consumption and extending the service life of brake drums, discs and tires. The anti-skid performance of vehicles equipped with ABS on dry asphalt roads, rainy days, snow days, etc. It reaches 80%-90%, 30%-10%, 15%-20%.
Conclusion
The application of brake anti-lock braking technology in the development of auto workers is not smooth in the development process, and there are many hardships and setbacks. Thanks to the rapid advancement of electronic control technology, the anti-lock brake system is more responsive, less costly, easier to install, easier to maintain, and more affordable for small and medium-sized family cars. Brake anti-lock devices are now standard on cars.
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