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At present, the dominant factor in the purchase of heavy trucks in China is price. In order to ensure sales volume and market share, no manufacturer is willing to vigorously promote the value of its products in the name of safety.
Due to problems in braking technology, the proportion of major traffic accidents caused by heavy trucks is gradually increasing.
According to the latest statistics from the Traffic Management Bureau of the Ministry of Public Security, there were more than 378,781 traffic accidents in the country in 2006. In the analysis of the causes of traffic accidents on trucks, the number one priority was driving violations, followed by mechanical breakdown of vehicles. In the mechanical breakdown of various vehicles, brake failure occupies a very high proportion.
"China's heavy-duty trucks generally use drum brakes, which have poor heat dissipation and are prone to brake failure due to overheating," said Du Fangci, an automotive expert.
Braking failure Frequent accidents
The most recent major accident involving the failure of heavy truck brakes occurred in the Golden Week just past.
On the morning of May 4th, the civilian Sun Xianjun of Baixi Village in Tuoyang Tujia Miao Autonomous County of Chongqing City drove the “BG5084†large truck from Jiande Town of Zunhua City, Hebei Province, to Chongqing from Yongde County. Around 8:30, when the dealership was at the K183+870M line, the "S20475" driven by Wu Yurong, the villager of Yunfu County, Yunxiang County, drove in the same direction, liberating the light truck, and at the same time with the Yunxian Passenger Transport. The company's "cloud S10827" car wiped, causing "cloud S20475" to get out of control and out of the road, waiting outside the rolling road for the people to ride, resulting in 14 dead and 50 injured.
After comprehensive and in-depth investigation by the relevant departments, the cause of the accident has been ascertained: The continuous use of brakes on the 6 km downhill road by the large truck driven by Sun Xianjun caused the slipping time of the brake shoe and the brake drum to be increased. The temperature of the brake drum rises, causing a thermal decay, resulting in brake failure.
In China, the most widely traffic accident concerning the failure of the heavy truck brake system, I am afraid, was not the Badaling accident in 2005. On December 4th of that year, a large truck loaded with calcium carbide collided with a bus carrying 29 people. , Then the two cars turned into the deep trench about 20 meters to the left of the road and burned. The accident caused a total of 24 deaths and 9 injuries. The investigation results of the traffic control department showed that the cause of the accident was the failure of the brakes on the trucks carrying calcium carbide, which caused the major traffic accident.
“The Badaling high-speed driver is most impressed by the cushions in the sharp corners. These buffers are all prepared for the failure of the heavy-duty trucks.†A person involved in the Badaling high-speed accident investigation revealed after the accident.
Car analyst Guo Yu believes that the Badaling high-speed design seems to have fully taken into account the current design flaws of China's heavy-duty trucks. As a result, buffers have been used very visibly and universally on various road sections.
In the accident that took place in Chongqing, the accidental truck driven by Sun Xianjun was a Steyr heavy-duty truck produced by China National Heavy Duty Truck. China National Heavy Duty Truck Group is already a leading domestic manufacturer of heavy-duty trucks, and the quality of its products still appears to be hidden. In the first nine months of 2006, the data released by Sinotruk showed that its heavy-duty trucks have sold 39,365 vehicles, and the market share has approached 20%. The market share is very close to that of FAW Group and Dongfeng Automobile. China National Heavy Duty Truck is about to list on the H-share market. This news may have some negative factors on its listing. "As the major manufacturer of heavy-duty trucks in China, the quality of products that China Heavy-duty Trucks may face illustrates the universality of related issues." Guo Yu Say.
Song Jian, executive vice president of the Institute of Automotive Engineering Development at Tsinghua University, analyzed the problem of brake failure in truck accidents. Song believes that from the braking principle, the brake is to convert the kinetic energy of the vehicle into heat during braking. In general, brakes have three main performance indicators.
One is the braking performance, that is, the ability to brake within a short distance; the other is the stability of the braking, which is the ability of the vehicle to control the direction of the braking process. Whether the vehicle will slide or deviate during the braking process depends on the stability of the brakes; the third one is the thermal recession, which can also be called the constant of the braking performance. He believes that the main reason for the failure of brakes on long-distance slopes is that the thermal decay of the brakes cannot meet the requirements.
“For heavy-duty vehicles, due to the large amount of kinetic energy, the temperature of the brakes during long-distance downhill sections is also relatively high, usually reaching 500-600°C or even higher. In this case, the friction coefficient of the brake is relatively reduced. Sometimes the driver overloads for pulling goods, which increases the chance of the vehicle experiencing brake failure.†Song Jian said.
The lack of national standards for braking technology
A person in charge of the China Machinery Industry Federation stated that the most effective way to alleviate this problem is to use EVB devices. The so-called EVB refers to engine exhaust brake technology. At present, most truck manufacturers in China do not use EVB technology. However, from the perspective of safety, EVB is a very important auxiliary brake equipment for trucks.
According to this person, heavy trucks using the EVB technology do not need to step on the brakes when driving downhill. The engine exhaust system will automatically provide braking force to the vehicle, which will absorb a large amount of energy and convert it into resistance release. The braking force is increased by 70%, which effectively eliminates brake failure. In developed countries in Europe and the United States, EVB has become a safety-enforced technology that is assembled on every heavy truck to ensure its safety in use.
Liu Wei, Weichai Power Markets Division, said that Weichai Power Co., Ltd. has invested heavily in the exclusive purchase of its heavy truck safety brake patented technology, the EVB technology, from MAN Company, a heavy truck arm of Germany, and has formed a unique domestic WEVB plan after digestion and absorption. Since 2006, all heavy truck engines produced by Weichai Power have been equipped with WEVB, so heavy trucks such as Shaanxi Heavy Duty Truck, Foton Motor, Hongyan Auto, and North Benz are currently equipped with this technology.
According to Liu Xie, the accident of Steyr heavy-duty trucks may be due to the failure to use WEVB. In March 2006, Weichai and China National Heavy Industries ended its cooperation with CNHTC using its own engine, but the “5.4 accident†investigation department did not give the date of production of the truck, and it could not confirm whether the truck used EVB technology. Guo Yu believes that from another perspective, even if the EVB assisted braking system is equipped, this accident may not be eliminated because the EVB is an auxiliary braking system.
In addition to EVBs, auxiliary brake systems commonly used in heavy trucks include brake anti-lock braking (ABS) and drive wheel anti-skid control (ASR) systems. Guo Yu believes that compared to the function of the auxiliary braking system, the main brake system uses the drum type or the disc type is the fundamental difference between the brakes. The performance of the disc brakes is much better than that of the drums. However, at present domestic multi-card brands do not use disc brakes. In the final analysis, it is still a matter of cost. At present, the dominant factor in the purchase of heavy trucks in China is the price, the price rises, and the corresponding sales volume is affected. In order to ensure sales volume and market share, no manufacturer is willing to vigorously promote the value of its products in the name of security. This situation has resulted in the obstruction of large-scale implementation of the auxiliary security system.
Brake and braking technology lags behind and increases the probability of accidents in relatively imperfect road systems in China. At present, there are still more than 1.2 million kilometers of highways in the fourth- and fourth-level highways in China, accounting for about 70% of the total traffic mileage of 1.83 million kilometers. In addition, due to various terrain conditions, the road conditions in China are also more complicated. In western and southwestern regions, mountains and mountains are relatively steep. The roads in these areas are often built upside down. Sharp bends, steep slopes, continuous downhill slopes, and downhill slopes are common. These sections are often accident-prone areas. Heavy truck transport is often accompanied by the occurrence of overload conditions, which also lays a hidden danger for brake failure.
“In this context, if we want to effectively solve the problem of increasing traffic accidents caused by large trucks year after year, it is obviously necessary for the state to issue relevant heavy truck manufacturing standards as soon as possible to impose regulations on companies to improve manufacturing standards in order to reduce the occurrence of related accidents. Chance." Guo Yu said.
National standards for frequent braking technology for major traffic accidents are urgently needed