Understanding of Friction Performance of Brake pads
The quality of brake pads is directly related to the reliability of vehicle braking. In addition to 100% safety, the owner also expects at all times to have the best brake comfort, sensitivity, noise and smoothness. For the brake pads, the most important thing is the choice of friction material, which basically determines the braking performance of the brake. Friction material from the basic material can be divided into asbestos, NAO type (ie, non-asbestos organic type), semi-metallic and special fiber 4 kinds.
The performance of the friction plate should have four basic requirements:
First, the appropriate coefficient of friction and stability.
Friction coefficient is a friction material of the most important technical indicators, which determines the basic brake pad braking torque. Usually it is not a constant, subject to temperature, pressure, speed or surface state, the friction environment changes. When these factors affect the friction coefficient of change is small, is the ideal coefficient of friction. GB strict requirements on the manufacturer must be marked on the packaging friction coefficient. Friction coefficient must be appropriate, too high will cause the braking process of the wheel lock, out of control and burning, too low braking distance is too long. Such as Bosch safety brake friction coefficient is 0.39.
Second, the reliable security.
Brake in the brake will produce instantaneous high temperature, especially in high-speed driving or emergency braking. At high temperatures, the friction coefficient of the friction plate will decline, known as thermal decay. High thermal decay of high-temperature state and determine the safety of emergency braking. The friction plate maintains its stability and recovery performance under various working conditions, ie it requires good heat resistance, and it can maintain stable performance under high temperature. It has low sensitivity after different humidity and soaking. performance. At the same time have a better physical and mechanical properties, both to meet the requirements of the process, but also to maintain good performance.
Third, the satisfaction of comfort.
Comfort is a direct manifestation of friction performance, including brake feel, noise, dust, smoke, odor and so on. With the increase in private cars and people's living standards improve, to meet the basic premise of safety, comfort has become an important indicator of friction. In the comfort indicators, the owner is often the most concerned about is the noise of the brake pads, in fact, all the noise is the most difficult to solve the problem of friction material manufacturers. Noise is caused by the friction between the friction plate and the friction plate, the causes are very complex, braking force, brake disc temperature, vehicle speed and weather conditions are likely to cause noise. In addition the noise in the brake start, brake and brake release three different stages of the reasons are not the same. If the noise frequency between 0-500Hz, the car will not feel, but if more than 1500Hz, the owner can clearly feel the brake noise.
Fourth, good abrasion resistance, reliability and durability.
This is a measure of the life of friction material is an important indicator, but also the user generally concerned about the product targets. Maintaining sufficient mechanical strength at room temperature and high temperature is an important factor affecting the reliability of the friction plate, but at the same time it is desirable not to scratch the brake disc or the brake drum. The wear resistance is the main factor affecting the durability, the main factors affecting the use of wear pressure, speed and temperature, which led to the temperature. Front brake pads usually guarantee a service life of 3-5 million kilometers. Rear brake pads usually guarantee a service life of 6 to 80,000 kilometers. The large particles of graphite and brass used in the brake pad material also reduce wear on the brake discs. Especially when the noise is reduced to a minimum, to ensure that the environment does not pollute. Braking does not produce noise, high temperature does not emit odor.
As a result of friction, the friction block will gradually wear, in general, the lower the cost of the brakes wear faster. After the friction material used to replace the brake pads, or the plate will be in direct contact with the brakes, the final loss of braking effects and damage to the brake disc.
The friction coefficient of brake pads: Passenger cars Brake Pad,Bus & Truck Brake Pad
EE grade: 0.25-0.35 for Europe and America cars, brake pads are relatively large, relatively low friction coefficient.
FF grade: 0.35-0.45 international standard friction coefficient.
GG grade: 0.45-0.55 for European cars, especially the German cars. Because the speed limit in Germany, so the friction coefficient to be higher.
HH grade: 0.55-0.65 for Special racing brakes in the case of high temperature, allowing a change in coefficient of friction, generally at 100 degrees Hou, the friction coefficient of 0.08 addition and subtraction at 350 degrees Hou 0.14.
The above is a high standard of friction material requirements, it is difficult to fully achieve. Therefore, different models, different conditions put forward different requirements.
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