As a safety component of automobiles, the state has a strict licensing and access system. But like our food, the existence of the system can not guarantee that the products on the market are good. The phenomenon of imitation, counterfeiting and selling lies in various industries. But just because it is the safety part of the car, the automobile factory dares not carelessly choose the original car parts. Its selection standard is far higher than the national standard. So, as an ordinary consumer, you just need to follow the automobile factory to choose it. When choosing brake pads, automobile factories generally require products to meet some technical specifications:
1. Service life: prolong service life as far as possible and reduce the frequency of replacement.
2. Noise: Neither emergency brake nor normal brake, light brake nor continuous brake can produce harsh noise.
3. Thermal expansion: both continuous brake and emergency brake will cause high temperature. According to the physical principle of thermal expansion and cold contraction, the brake pad will also expand, but in the requirements, its expansion must be kept in a very small range. If the expansion is too large, the gap between the pad and the dual will be too small, so that the pad and the disc are always in the normal driving process. Keeping the brake state will eventually lead to oil leakage and brake failure due to the increase of oil temperature in the brake cylinder.
4. Thermal decay: The friction coefficient of the brake pad is cold, hot, sour and sweet, and the sample is feasible. The material must adapt to a wide temperature range to ensure that it can not reduce its capacity under various conditions.
5. Friction coefficient: The simple understanding of friction coefficient is the braking ability, and its stability is a key index of the brake pad. What is stability? When a car runs, it will encounter various road conditions, such as frozen days, rainy days, long-distance downhill from the mountain, Hill Road uphill and downhill, emergency braking and so on. Whether the brake pads are in cold, wet, high temperature, alternating cold and heat, and high temperature state, the stability of friction coefficient is extremely important.
6. Compressibility: It reflects that when we brake with a certain amount of braking force, the brake pads can not be too soft or too hard, too soft, which will affect the reaction time of the brake pads; too hard, damaged discs and prone to noise. According to the corresponding standard, its compression is between 0.1 mm and 0.2 mm.
7. No disc damage: The social cost of brake pads is much lower than that of brake pads. In western developed countries such as Europe and the United States, high pollution projects such as foundry are not allowed to exist. Therefore, China's brake pads account for 70% of the world's production capacity, and we are complacent. Therefore, in this duality, brake pads are required to be worn rather than brake discs. Ceramic brake pads used in mid and high-end Japanese models are very important in that they do not damage the discs and only wear the brake pads. Therefore, few Japanese Toyota and other brake discs are sold in the aftermarket because they do not wear. Only wear oneself, but also to protect the service life, to solve this contradiction requires very high technology, and the use of more advanced materials, ceramics products are the reason for high prices. Too many brake pads on the market now add enough grinding additives to ensure their service life, but they can not solve the grinding disc and noise, which is the manifestation of immature formulation technology.
8. Environmental protection: Now everyone knows that asbestos is not allowed in European and American countries. Even if you add sepiolite and other trace asbestos-containing materials to your recipe, it will lead to returns and fines. However, asbestos is still used in a large number of trucks in our country. There are proposals in the United States that copper should not be allowed in products step by step. The introduction of these legislation will also promote the progress of the friction material industry, and those factories that do not have R&D capabilities will be phased out.
9. Comfort: How to be comfortable? That is, when you are driving, you plan to brake to what position, with your own feeling to brake, and the brake just arrives at that position according to your wishes, without noise and shaking, so smoothly to that position, my understanding, comfort should be such a feeling. It's a bit arbitrary. It is very difficult to adjust the formula to achieve this feeling. The braking coefficient is too big, too small, too big, and the braking ability is very strong. But the brake will bow, jitter, noise, small, more dangerous, and it feels like it should stop.
You may be a little tired after reading all this. It's so troublesome! Yes, it's troublesome, but the most troublesome thing is the formulation debugging. To satisfy these requirements as much as possible, several or more kinds of raw materials need to be selected from hundreds of raw materials and debugged. This debugging experience is only secondary. Whether a good formula can be found or not, thousands or even tens of thousands of bench experiments should be carried out to simulate brakes on the bench. Think about what kind of material to use, how much to use, we need to use a lot of experimental data analysis to prove that if anyone says he can make a good formula for you to use, it is absolutely boastful! And the formulation is not fixed, the emergence of new materials, you have to try whether it can be used, how to use the performance, but also a lot of experiments.