Heavy truck brake failure is an old topic in China.
Let's take a look at a few dangerous roads that are widely spread: Badaling in Beijing was once called “Valley of Deathâ€, and the Central TV Station of Beijing-Zhuhai Expressway in the northern part of Guangdong has recorded the “Walk into Science†section on brake failure—“ "Death high", in the Asia's largest cross-country waterfall Guangxi Detian has the "risk zone" of the 18th bend. In western Sichuan, Yunnan-Guizhou Plateau, and southern Xinjiang, such dangerous mountainous roads are too numerous to mention.
The most recent major accident concerning the failure of truck brakes occurred. On the early morning of May 4, 2009, the Sun Xianjun of Boxi Village in Tuoyang Tujia Miao Autonomous County, Chongqing, drove the “BG5084†large truck from Jianming Town of Zunhua City, Hebei Province from Yongde. The county headed for Chongqing. When the car was traveling to the line at K183+870M, the “cloud S20475†that was driving in the same direction was used to liberate the light-duty trucks and at the same time collided with the oncoming Yunxian passenger transport company “cloud S10827â€, resulting in “cloud S20475. "Out of control, driving out of the road, waiting for the people on the road outside the rolling highway, resulting in 14 dead and 50 injured." After a thorough and in-depth investigation by relevant departments, the cause of the accident was ascertained: The continuous use of brakes on the 6 km downhill road of the large truck driven by Sun Xianjun caused the slipping time of the brake shoe and the brake drum, resulting in braking. The temperature of the drum rises, causing a thermal recession that eventually leads to brake failure.
Entering "Accident brake failure" on Google results in 62,000 results. In order to alleviate the problem of brake failure or insufficient braking force, a new industry has emerged, namely the construction of highway buffers. In various well-known long downhills, sharp bends and frequent accident areas in the country, various types of emergency buffers built on the basis of sand, rocks, and mud are commonly used. The drivers dedicated to braking disabled vehicles actively “hit†on these sands. Stone heap to achieve the purpose of deceleration. Other yellow belt-shaped speed bumps on the highway are everywhere. Even though the highway department has exerted great efforts, it has set up striking signboards in dangerous areas of the country and has built countless buffers. The safety situation of road vehicles remains severe. In recent years, the number of people who died of road-trafficking each year in China is about 6-8 million, ranking still ranking first in the world.
According to the latest statistics from the Ministry of Transportation and Security, in the analysis of the causes of traffic accidents on trucks, illegal driving is the first priority, followed by mechanical breakdown of vehicles. Many illegal driving situations are accompanied by vehicle failures. In various vehicle fault statistics, brake failure occupies a very high proportion.
We can't help but torture: Should the failure of the brakes only be blamed on the driver's non-standard operation and dangerous road conditions? Is there any other way to improve? The answer is obviously yes.
First analyze the vehicle's braking system. There are usually three indicators for measuring the braking capacity of a vehicle. One is the braking performance, that is, the ability to brake within a short distance (commonly known as the shortest braking distance); the second is the braking stability, which is the vehicle's ability to control the direction of the body during braking, that is, the amount of side slip; It is thermal decay (also called braking constancy), that is, the ability to maintain the braking torque at high temperatures after prolonged braking.
China's most authoritative safety regulation, GB7258, has qualitative descriptions and requirements for the first two indicators, that is, the braking distance, deceleration, and brake force distribution under emergency brake and parking brake conditions must meet certain requirements. Only qualified vehicles can be delivered. However, there is no corresponding regulations and performance test requirements in China for the recession of braking heat.
According to measurements, the brake drum's temperature can reach 700°C or so after a typical truck load drops 3% downhill on a 7% slope. At this time, the brake friction coefficient is drastically reduced to about 1/3 of the normal value. Emergency braking, in this case, even if the driver of the standard operation can not accurately and predictably brake the vehicle within the safety distance from the vehicle or the obstacle in front, if there is overload and slippery road surface The danger will come unexpectedly. For this reason, drivers in the mountainous area have already installed water tanks on the roof of the car. They are specifically designed to maintain a certain braking force by cooling the brake drum during long-distance operations. However, long-term application, its effectiveness and reliability are doubtful, and it is not a permanent solution.
Internationally accepted truck active safety technologies include:
Disc brakes Disc Brake
Anti-Blocking System (ABS)
Hydraulic retarder brake Hydraulic Retarder Brakes (Retarder)
Acceleration Skid Control (ASR)
Electronic Brake System (Integrated Retarder) EBS
CAN bus control CAN bus network
Active Brake Assist (ABA)
Electronic Stability Program (ESP)
Lane Departure Warning System Lane Assistant (SPA)
Continuous Braking Limiter Continuous Braking Limiter (DBL)
Tyre Pressure Control System
Reverse Driving Assistant
Engine Brake
Attention Warning System Attention Warning System
Internationally accepted truck passive safety technologies include:
ECE-R 66 Manufacturing Standard ECE-R 66 certification
Energy Absorbing Backrest Energy-absorbing backrests
Front Collision Fence Front Collision Guard
Integrated 2-point seat belts
On the other hand, in China, the current truck brake technology basically stays at the level of price competition. Although seatbelt technology is fully applied, disc brakes, ABS, engine brakes, etc. are only used in very small quantities of high-end vehicles. In addition, other technologies are not currently introduced. Most trucks still rely on simple drum braking to ensure the safety of the vehicle.
Internationally, the simple and effective way to improve the failure of trucks after prolonged braking is to install a hydraulic retarder (Hydraulic Retarder) that can provide a constant auxiliary braking force.
At present, the hydraulic retarder from the Voith Group in Germany has entered China and enjoys a good reputation in the domestic passenger car industry. It can provide up to 4000NM braking torque, fully meet and exceed the EU ECER13 regulations on continuous braking (> 12T full load trucks work only with a retarder at a gradient of 7%, maintaining the speed of the vehicle at 30KM/H Continuous downhill 6KM can not produce any fault). In the Yunnan-Guizhou Plateau, buses often shuttle back and forth between dangerous areas such as the Quincy, Kunli and Kunpu lines. Passengers equipped with Voith Hydro Retarder have never experienced any accidents, making them comfortable. .
The hydraulic retarder uses the cooling water of the engine to cool down the temperature-increasing slow-medium oil at a proper time to ensure the output of the continuous braking torque, and the revolutionary improvement of the vehicle's braking thermal decay performance is most suitable for the needs of the Continuously braking conditions of the vehicle.
If the auxiliary engine brake device (JACOB or EVB) is additionally assisted, the braking safety level of the entire vehicle will be further improved because the performance of the engine braking is clearly manifested in the low speed region where the hydraulic retarder is weak. . From the 1970s until now, almost all heavy trucks in Europe have been equipped with hydraulic retarders and engine brakes. The gradual application of these safety technologies has resulted in a 80% reduction in the number of fatal calamities in European truck transport over the past 30 years.
Under current conditions, if the vehicle's configuration can be upgraded to disc brakes and ASR, ESP and other systems, it will obviously be more powerful to improve the safety equipment of the entire truck.
It should be noted that at present, there are still more than 1.2 million kilometers of highways in China's fourth-level and below-grade highways, accounting for 70% of the total mileage of China's highways. In areas such as the west and southwest, where mountains, roads are narrow, and squats are acute, long-distance ranges are common. If no hydraulic retarder is installed, truck safety problems will often be tortured.
We urge that, in the context of market economy and the fierce competition of manufacturers to win customers with price competition, it is urgently necessary for the state to issue mandatory ECER13-related issues in order to quickly and effectively solve the problem of traffic accidents caused by truck brake failure. Continually braking safety standards and restricting manufacturers and car owners in the form of laws and regulations with a view to reducing the occurrence of accidents involving heavy trucks and providing more safety guarantees for passengers and drivers.
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