Passenger car disc brakes popular in the imperative bus is the main force

"For buses with a length of more than 9 meters, all wheels should be equipped with disc brakes. This is the request for discussion in the draft of the GB7258 "Technical Conditions for the Safe Operation of Motor Vehicles" submitted in May 2010. If nothing unexpected happens, 2011 may be Will be enforced." A bus company official told reporters.

Disc brakes are brakes that were gradually used in buses and trucks in Europe in the 1970s. They have been applied in large quantities since the 1990s. At present, European passenger cars are almost standard with disc brakes. Then, how do the domestic passenger cars use disc brakes?

Performance is better than drum brakes, the advantages of disc brakes have been widely recognized. Drum brakes have poor braking force stability, and the braking force varies greatly on different road surfaces and is not easily controlled. The disc brake has great braking force under the condition of hydraulic power, more comfort and stable performance. It has better braking performance than drum brakes on various road surfaces, especially when it takes a long time for a long downhill to brake. Road section.

European brake system manufacturers and automobile companies have conducted comparative tests of two types of brakes in mountainous areas: When a vehicle is driving at a constant speed on a hillside road that is 11 kilometers long and has a gap of more than 1,000 meters and an average slope of nearly 10%. Disc brakes require only a constant 2.4 bar (1 bar = 100000 Pascals) brake pressure to maintain the required speed. Drum brakes require a gradual increase in pressure. When reaching the foot of the mountain, the brake pressure has risen to 4.3 bar. .

The brakes also generate a lot of heat during the braking of long downhill sections of the vehicle. If the heat does not dissipate well, it will greatly affect the braking performance of the vehicle. "A lot of passenger cars are prone to brake failure when they are on a long slope. The main reason is that the drum brakes have experienced a thermal decline. In the disc brakes, air can flow directly through the brake discs, resulting in good heat dissipation and no thermal degradation. It also reduced the chance of a blowout,” said Mr. Liu, a service manager for Haig Bus Shandong.

Disc brakes also bring service convenience. Mr. Liu introduced: “In general, the 20,000-kilometer friction plate of the drum brake needs to be replaced once. The disk brake's friction plate is replaced about 50,000 kilometers.”

At present, disc brakes are widely used in medium and high-end intercity buses in China. Li Dongmei, chief engineer of the Youth Automotive Group Co., Ltd., introduced: “Young cars started using disc brakes on passenger cars many years ago, but the front plate rear drum brakes are usually used as standard.”

Bus is the main force Although disc brakes have been used on more and more passenger cars, there is still a big gap compared with the level of popularization abroad.

In Europe, passenger cars have basically realized the form of the front disk and rear disk. “The domestic passenger cars mainly use the front disc rear drum form. The disc brakes used by Haig Bus are mainly imported products, of which ZF products account for the largest share. The domestic disc brakes are selected by Liuzhou Fangsheng products, ten meters in Guangxi. The following models use Wuhan Yuanfeng products,” Mr. Liu told reporters.

About half of the Yutong buses use disc brakes. Wu Xiaoguang, deputy chief engineer of Zhengzhou Yutong Bus Co., Ltd., told the reporter: “In the models using disc brakes, there are a considerable number of buses. Low-floor, low-entry buses are chassis-equipped disc brakes. Except for this, there are not many vehicles that choose to use disc brakes."

Obstacles, but imperative The biggest obstacle to the promotion of disc brakes in the country comes from cost. The structure of the disc brake is more complex than the drum brake, and the requirements for the brake caliper and the piping system are also higher, so the cost is higher than that of the drum brake.

According to a survey by the reporter, the cost of a single domestic disc brake is 800 to 1,000 yuan higher than that of a drum brake, and a set of front axle brakes alone will cost 1,500 to 2,000 yuan more.

"Europe and the United States and other developed countries basically do not have users to use drum brakes, because they are not sensitive to price, domestic companies pay more attention to vehicle prices, disc brakes are twice as expensive as drum brakes, and all drum brakes are replaced with discs. With brakes and other accessories, the cost of each car has to be increased by 10,000 to 20,000 yuan. Therefore, it is difficult to popularize it," said Liu.

In fact, even if the implementation of mandatory standards, the promotion of disc brakes is not difficult. Wu Xiaoguang thinks: “At present, the domestic disc brake technology needs to be improved, and there is no mature parts supply system. The service maintenance system cannot keep up with the market demand. In addition, users are not familiar with disc brakes and have not fully grasped the operation essentials. Therefore, misoperations happen from time to time. Only by completing these basic tasks and reducing the price, disc brakes can be fully promoted. This is not a short-term process."

There is also a shortage of domestic disc brakes. "In addition to good braking effect, disc brakes can also effectively reduce noise. We started to use disc brakes in large quantities in 2006. New cars purchased since 2007 have all used disc brakes. Overall, Domestic products are less reliable than foreign products,” said the person in charge of the Beijing Public Transport Corporation.

Mr. Liu, Hirag's Shandong after-sales service manager, believes that although the disc brake has many advantages, due to the relatively complicated technology, the failure rate is higher when used in some areas with complex road conditions, causing trouble to users.

Disc brake fault reverse drum type Mr. Liu told reporters: "Our company's service vehicles, disc brakes are mostly concentrated in domestic brands. The main reason is that the material is poor, such as the friction plate material can not reach the foreign In addition, there is still a gap between domestic disc brakes and foreign brands in terms of details and processing accuracy, such as the relatively poor concentricity of domestic disc brakes, which may result in poor disc brake stability.”

Lack of system technology research on the above issues, Long Xu Holdings Group Chairman Chen Xufeng does not recognize: "The poor reputation of domestic disc brakes is an objective problem in the past two years, mainly due to the fact that some products are too hasty to market and have not been fully verified. After more than two years of improvement and debugging, the quality of many products has now reached the standard. From the point of view of the product itself, disc brakes produced by local companies are not much different from similar foreign products."

Even so, Chen continued to admit that there are still some problems in the disc brake industry. “China’s passenger car disc brakes have been developing since the beginning of 2000 and have achieved certain results to date, but there is a lack of systematic technology research. For example, the matching problem of disc brakes has not attracted the attention of the industry. Domestic companies rarely connect disc brakes to air chambers. The matching test is performed together, if the air chamber outside the disc brake is not sealed properly, it will cause the brake to rust, affect the braking performance of the disc brake, and shorten the service life.At present, the price gap between foreign disc brakes and domestic enterprises is not Large, but the price gap between the air chamber is very large, the price of the imported disc brake supporting air chamber is at least 3 times that of the domestic air chamber, more than 1,000 yuan more expensive.”

According to Chen Xunfeng, the 2011 disc brake industry was suitable for the industry. “After nearly a decade of development, the disc brake industry has been relatively complete, and the forced use of disc brakes will bring market guarantees. I expect at least 30,000 passenger cars in the matching market this year. Therefore, we are already doing a good job in terms of production capacity and resources. Fully prepared, other disc brake companies have also prepared, and the current top ranking companies in the industry have monthly production capacity of more than 10,000 units, to meet the market's demand this year, said Chen Xuanfeng.