GB7258-2017 "Safety Technical Conditions for Motor Vehicle Operation" stipulates that all wheels of automobiles (excluding three-wheeled vehicles), motorcycles (except for three-wheeled motorcycles), and trailers (except for trailers with a total mass of not more than 750 kg) shall be equipped with brakes. . Among them, the front wheels of all special school buses and dangerous goods transport trucks and the front wheels of other passenger cars with a length of more than 9m, as well as all the wheels of dangerous goods transport semi-trailers, three-axis fences and warehouse-type semi-trailers, should be equipped with discs. Brake. All discs for dangerous goods transport semi-trailers shall be equipped with disc brakes, which shall be implemented from January 1, 2019; all wheels for three-axis fence and warehouse-mounted semi-trailers shall be equipped with disc brakes, It will be implemented on January 1, 2020.
First, the structure and current status of the trailer brake system
The main structural form of the trailer axle brake is divided into a drum brake and a disc brake. The drum brake is the main structural form of the trailer axle brake system, which has a simple structure and low cost. The drum brake is mainly composed of brake base plate, brake drum, brake shoe and brake pad, brake cylinder, return spring, camshaft, adjusting arm and other components. The brake base plate is welded to the axle shaft body, and the brake shoe and the brake pad assembly are mounted on the brake base plate through the positioning pins. When braking, the brake cylinder pushes the adjustment arm to rotate the camshaft, so that the brake shoe is opened to form a frictional force with the inside of the brake drum, and the brake drum is decelerated by friction, forcing the wheel to stop rotating.
Safir Lander drum brake
Disc brakes are also known as disc brakes. The main components are brake discs, brake pads, brake cylinders, brake calipers, etc. The brake disc is locked with the hub by bolts, and the brake cylinder is fixed on the brake base plate, and the two brake pads on the brake caliper are respectively mounted on both sides of the brake disc. When braking, the sub-pump pushes the brake pad to squeeze the brake disc to form a friction brake under the action of the brake air pressure. The disc brakes are light in weight, simple in construction and easy to maintain.
Safran Lander disc brake
Second, different brake system comparison
The braking process is to convert the kinetic energy of the car through the brake absorption into heat energy, and the high temperature will cause the brake to have thermal decay. Therefore, the heat dissipation performance of the brake is very important.
Drum brakes have poor heat dissipation and drainage performance during braking, which may easily lead to a decrease in braking efficiency. Especially during long downhill braking, the brake drum high temperature may cause brake failure and tire ignition.
The disc brake has fast heat dissipation, good high temperature resistance during braking and stable braking effect. It can effectively avoid high temperature brake failure, stable braking force input and ensure brake safety. At present, the disc brakes of European trailer axles account for more than 90%.
The vehicle should be frequently braked during driving. The braking performance is directly related to the vehicle and personal safety. Usually we define the advantages and disadvantages of the brake through the following three indicators.
1. Braking performance. That is, the braking distance and the braking deceleration, when the braking distance of the disc brake is at the same speed braking, the braking distance is significantly better than the drum brake. When the vehicle equipped with the drum brake starts to brake at the initial braking speed of 80km/h, the maximum braking distance is about 70m; the same effective mass of the vehicle is equipped with the disc brake, the maximum effective braking distance is about 47m. Dynamic security has been greatly improved.
Brake distance comparison between disc brake and drum brake
2. The stability of braking performance. That is, it is resistant to thermal decay. When the disc brake is braked, the brake disc has good thermal stability, uniform heat, and no overheated area.
Brake disc heat distribution map
3. The directional stability of the car during braking. The brake force distribution during the brake process of the disc brake is reasonable and the stability is good. When the drum brake is braked, there will be some fluctuations in the braking force, and since the brake drum is a closed structure, once the brake shoe is detached or the brake pad is broken, the entire brake system may be locked and a tail phenomenon occurs.
Third, the disc brake brake pad and the drum brake pad friction performance
GB5763-2008 "Brake linings for automobiles", the brake pads are divided into four categories according to their purposes. Among them, the first category is for parking brakes; the second category is for miniature and light-duty vehicle drum brakes; the third category is for medium-duty truck drum brakes; and the fourth category is for disc brakes. Its friction performance is shown in the following table:
Friction performance of automotive brake friction lining
It can be seen from the above table that when the braking temperature exceeds 300 ° C, the friction coefficient performance of the drum brake pad tends to zero, and the friction coefficient of the disc brake tends to be stable.
In summary, the disc brake has the following advantages over the drum brake:
1, good thermal stability
2, water stability is good
3, good braking stability
4. Braking torque is independent of driving state such as forward and reverse of the car.
5. Under the condition of outputting the same braking torque, the structural size and quality of the disc brake are smaller than those of the drum brake.
6. The brake pads of the disc brake are easier to replace than the brake pads of the drum brake, and the structure is relatively simple, easy to repair and maintain.
7. The gap between the brake disc and the brake pad is small, and the braking response is faster.
8. The thermal expansion of the brake disc does not cause the brake pedal stroke loss like the thermal expansion of the brake drum, which also makes the design of the automatic gap adjustment mechanism simple.
9. Brake reliability and safety are good. All wheels can be smoothly and evenly and uniformly braked at different speeds.
10, can install brake wear alarm, can prompt users to replace the friction lining
As a manufacturer of the world's top commercial vehicle parts with a history of nearly 140 years, Safran Lander has accumulated a wealth of experience in disc brakes to ensure that customers are provided with quality and reliable products and services. In the future, Safran Lander will continue to adhere to technological innovation, continuously improve product quality and service quality, always guide the development direction of the industry, and continue to lead customers to the road to success.
Reading volume: Source: SAF HOLLAND Group Author: Cold autumnBike Brake Pads,Bicycle Brake Pads,Bike Disc Brake Pads,Bicycle Disc Brake Pads
Wenzhou Tuxing Automobile and Motorcycle Parts Co., Ltd. , https://www.tuxingbrakes.com