[YesAuto Technology] Tires are no stranger to everyone. Kindergarten children can draw a wheel with their eyes closed, but many drivers who have driven cars for a lifetime do not understand the mystery of tires. You must be curious about the secret of tires, aren’t they round and inflated? It should be understood that tires, as the only medium for the vehicle to contact the road, have a direct impact on the performance of the vehicle. Look, how can there be no secret for such an important thing? Let's explore it.
● Tire history
Just like the beginning of storytelling, if we want to know the secrets of tires, we must first understand its life experience. Due to space limitations, we will only look at passenger car tires, and commercial vehicle tires and listen to the next breakdown. Okay, let’s get back to business. The first hollow tire was invented by the Englishman Robert Thomson in 1845. He proposed to inflate the elastic bag with compressed air to alleviate the impact during exercise. Although the tires at that time were made of leather and rubberized canvas, this type of tire already showed the advantage of low rolling resistance. Robert Thomson agreed The title of “Improvement of Wheels of Horse-drawn Carriage and Other Vehicles” was awarded a patent by the British government. The first pneumatic tire was born on December 10 of the same year. The first person to buy a pneumatic tire was a nobleman named Luo Lie. The price of the four tires totaled 44 pounds and two shillings. You must know that one pound can be exchanged for silver at that time. Three and two, while the British GDP was only more than 10 million pounds.
In 1868, the American Charles Goodyear (Charles Goodyear) invented a method of vulcanizing rubber to enable rubber to be used in tires. Although Mr. Goodyear obtained a patent, he did not become rich (a newly established tire company in the United States in 1898). To commemorate his contribution, the company named the company Goodyear Tire Company).
In December 1887, British veterinarian John Dunlop saw his son riding a tricycle in a stone courtyard, thinking about how to make the wheels softer to absorb the shock, so he invented the use of inflatable rubber tubes to cover the wooden spokes. The prototype of modern tires was born. In 1903, Mr. J. F. Palmer invented the twill textile. The invention of this twill textile led to the development of bias tires. In 1930, Michelin applied for tube tires (the predecessor of tubeless tires); in 1946 it became world-famous. Patent for radial tires. Look, many big tire factories have arrived.
● Why the tires are black
Everyone knows that tires are mainly composed of rubber. You have never seen rubber but you probably know the color. But have you ever wondered why tires made of rubber are black? In fact, this is mainly determined by the additives used in tire production. As early as the nineteenth century, the color of rubber tires was not fixed due to different additives. By 1915, due to the addition of carbon black, also known as carbon black, during tire manufacturing, the rubber appeared pure black like an ink, and its wear resistance reached an unprecedented level. Since then, rubber tires have entered a long period of black dominating the world.
In the 1950s, many foreign car owners, in order to show their wealth and social status, painted white paint on the outer sidewalls of their tires to distinguish them from others and reflect their individuality. But the biggest disadvantage of this tire beauty method is that the paint will gradually peel off after using the tire for a period of time, which is very unsightly. This method is gradually neglected. By the 1960s, white rubber tires using white rubber had seen a resurgence, but this type of tires had poor strength and tear resistance, poor aging resistance, and more expensive costs. The longer the use time, the rubber will slow down. Slowly turn yellow to brown, losing the original decorative effect. In the 1980s, developed countries such as Japan, Germany, and the United States had reproduced and put in tires with white lettering or ring belts on the sidewalls. Goodyear even designed a fully transparent tire that could be illuminated at night.
In the 1990s, Michelin cooperated with a French chemical group to replace carbon with silica and achieved good results. Since the inherent color of silica is white, any different coloring agents can be added, so that the color of the tire can be selected arbitrarily. In recent years, with the emergence of new rubber anti-aging agents and white and light-colored rubber reinforcing agents, the development of tire color has been further promoted.
After you understand why tires are black, you must be curious about the rubber used in tires. Are the rubber used in tires and the chewing gum in our mouths now “half-brothers”?
The main component of most automobile tire materials is natural rubber or synthetic rubber. Natural rubber is mainly derived from the Hevea rubber tree. When the skin of this rubber tree is cut, milky white juice will flow out, called latex. The latex is coagulated, washed, molded, and dried to obtain natural rubber. The main ingredient of the chewing gum we eat is the gum base. The precise ingredient of the gum base is usually a trade secret. The main ingredient can be gelatin (Japanese gum) or natural rubber (styrene-butadiene rubber, butyl rubber, polyisobutylene). ) So the gum and tire rubber we eat is not a raw material.
● Talk about tire rubber and additives
The raw materials for tire production include natural rubber and synthetic rubber. Synthetic rubber is made by artificial synthesis. Different types of rubber can be synthesized by using different raw materials (monomers). Among synthetic rubbers, it is the most commonly used general-purpose rubber. General-purpose rubber refers to rubber species that partially or completely replace natural rubber, such as styrene-butadiene rubber, butadiene rubber, isoprene rubber, isopropyl rubber, and neoprene.
It is made by copolymerization of butadiene and styrene. It is the largest general-purpose synthetic rubber produced. There are emulsion polystyrene butadiene rubber, solution polystyrene butadiene rubber and thermoplastic rubber (sbs).
It is produced by solution polymerization of butadiene. Butadiene rubber has particularly excellent cold resistance, abrasion resistance and elasticity, as well as good aging resistance. Butadiene rubber is mostly used in the production of tires, and a small part is used in the manufacture of cold-resistant products, cushioning materials, tapes, and rubber shoes. The disadvantages of butadiene rubber are poor tear resistance and poor wet skid resistance.
It is the abbreviation of polyisoprene rubber, produced by solution polymerization method. Isoprene rubber, like natural rubber, has good elasticity and abrasion resistance, excellent heat resistance and better chemical stability. The strength of raw isoprene rubber (before processing) is significantly lower than that of natural rubber, but its quality uniformity and processing performance are better than natural rubber. Isoprene rubber can replace natural rubber to make truck tires and off-road tires, and it can also be used to produce various rubber products.
Synthesized with ethylene and propylene as the main raw materials, it has outstanding aging resistance, electrical insulation properties and ozone resistance. Ethylene-propylene rubber can be filled with large amounts of oil and carbon black, and the product price is low. Ethylene-propylene rubber has good chemical stability, and its wear resistance, elasticity and oil resistance are close to those of styrene butadiene rubber. Ethylene-propylene rubber has a wide range of uses. It can be used as tire sidewalls, rubber strips, inner tubes, and automotive parts, as well as wire, cable sheathing, and high-voltage and ultra-high-voltage insulation materials. It can also manufacture light-colored products such as rubber shoes and sanitary products.
It is made of chloroprene as the main raw material through homopolymerization or copolymerization of a small amount of other monomers. Such as high tensile strength, excellent heat resistance, light resistance, aging resistance, and oil resistance are better than natural rubber, styrene butadiene rubber and butadiene rubber. It has strong flame resistance and excellent flame retardancy, high chemical stability, and good water resistance. The shortcomings of neoprene are electrical insulation, poor cold resistance, and raw rubber is unstable during storage. Neoprene has a wide range of uses, such as making transportation belts and transmission belts, covering materials for wires and cables, making oil-resistant hoses, gaskets, and chemical-resistant equipment linings.
Although synthetic rubber has many advantages, the overall performance of natural rubber is superior to synthetic rubber, so natural rubber is mostly used in high-end tires. In order to make rubber have the properties required for tire manufacturing, for example, to make the tire have good elasticity, low rolling resistance, low fuel consumption, low heat generation, abrasion resistance, puncture resistance, high load capacity, and ride comfort, it must be in rubber Infiltrate different chemical materials, namely chemical additives.
Polybutadiene rubber and solution polymerized styrene butadiene rubber can be used together as fuel-saving tire tread rubber. Tires with this type of tread rubber have the best overall balance of grip and wear, as well as lower rolling resistance. Can save fuel by 5%.
It is a rubber with many tiny independent bubbles. When the foaming rate is 20% to 30%, the friction coefficient on ice can be increased by 3 to 4 times. In this way, the tire braking distance can be shortened by 10% to 15% by increasing the coefficient of friction on ice. Although the friction on ice of studless tires made of foam rubber is not as good as that of studded tires, the friction is very close.
It has the advantages of high wear resistance, coloring, high cutting resistance, excellent oil resistance and chemical resistance, and it is non-toxic to the human body and can be completely biodegradable. It does not need to add carbon black and aromatic oil. It is used to make tire treads. The ideal material.
BoTred is a new filler based on starch. Firstly, corn starch derivatives are extracted from corn, which are transformed into microdroplets and then converted into biopolymer fillers after treatment. BloTred is spherical particles, which is convenient for minimizing mechanical energy and reducing rolling resistance.
The addition of short fibers can improve the rigidity of the tire, so that the sinking amount of the tire under the same load during driving is significantly reduced, that is, the deformation of the tire is reduced, so the rolling resistance is also reduced; when short fibers are used in the tire tread, not only The rigidity of the tread can be improved, and the friction coefficient of the tread can be reduced, the rolling resistance coefficient is reduced, and the rolling resistance is also reduced accordingly. When short fibers are applied to the tire tread and other parts, the properties of the rubber compound can be changed through the modulus and anisotropy of the short fibers to reduce the noise during the tire driving process, and also improve the durability of the tire.
Silicon-containing tires produce less energy loss while having excellent grip, thereby reducing rolling resistance and abrasion force, achieving better fuel-saving effects than ordinary tires, and extending tire life as much as possible.
● Manufacture of tires
After understanding the history and material of tires, let's take a look at how tires are made. In fact, the manufacture of tires is like the process from kneading noodles to boiling noodles. The previous processes such as mixing, extruding and calendering are like “kneading noodles”-“rolling noodles”-“cutting into noodles” and other steps. When the bead is formed, it is equivalent to preparing the noodles for the pan.
Vulcanization is the last process in rubber processing, which is equivalent to “cooking noodles in a pot”-that is, the final shape, and you can get a shape of rubber products with practical value. “Vulcanization” is named after the original natural rubber products used sulfur as a crosslinking agent for crosslinking. With the development of the rubber industry, a variety of non-sulfur crosslinking agents can now be used for crosslinking. Therefore, the more scientific meaning of vulcanization should be “cross-linking” or “bridging”, that is, the process of forming a network polymer through cross-linking of linear polymers. The process in which rubber macromolecules react chemically with the crosslinking agent sulfur under heating to form a three-dimensional network structure. After vulcanization, the rubber is called vulcanized rubber.
After the curing process is completed, there is a final inspection and tire testing process. In the final inspection area, the tire must first undergo visual appearance inspection, and then uniformity inspection. The uniformity inspection is completed by the “uniformity testing machine”. of. The uniformity testing machine mainly measures radial force, lateral force, cone force and fluctuation. After the uniformity test is completed, a dynamic balance test is required. The dynamic balance test is completed on the “dynamic balance test machine”. Finally, the tire has to undergo X-ray inspection, and during the tire testing process, the tire also needs to be considered for high-speed and durability experiments.
Tips for remixing rubber
Speaking of this, some people may think of Kumho’s “re-mixing” incident. Many people have not figured out what anti-mixing is until now. In fact, refining refers to the leftovers and non-compliant rubber materials produced after the “extrusion” and “calendering” processes. These leftovers are taken back to the initial mixing process-that is, the “kneading” stage, and kneaded again. “Dough”. These scraps and non-compliant rubber materials are the so-called remixed rubber. Therefore, remixing rubber does not mean “recycling of used tires”. Once the rubber is vulcanized, the process is irreversible. Refining is a normal process in the tire manufacturing process. However, the proportion of re-mixed rubber needs to be strictly controlled. A large amount of re-mixed rubber will cause uneven and unstable tire quality, and it cannot be used in the inner liner. The previous domestic industry requirement was that “the uniform mixing ratio of return glue should not exceed 20%”.
The durability of tires with excessive remixed rubber will be significantly affected, and they are prone to aging and cracking, which has great hidden dangers to tire quality and safety performance.
● Tire structure:
The crown is the entire part between the two shoulders of the tire, including the tread, buffer layer (or belt), etc. The crown is the main part of the tire in contact with the ground.
The carcass layer of the tire is a composite shell composed of cords and rubber. The cord materials generally include rayon cords, glass fiber cords, aramid cords, steel fiber cords, and so on.
● Tyre category
There are many types of tires. Here, the tires are divided into bias tires and radial tires only according to the arrangement of the carcass ply cords. The carcass of the bias tire is a ply that crosses diagonally; while the carcass of the radial tire is a polymer multi-layer cross material, and the top layer is a steel belt cord woven by steel wires, which can reduce the tire punctured by foreign bodies. The odds.
The cords of bias tires are arranged diagonally across, hence the name. Its characteristic is that the strength of the tread and the sidewall is large, but the sidewall rigidity is large, and the comfort is poor. Due to the large movement and friction between the plies at high speed, it is not suitable for high-speed driving. With the continuous improvement of radial tires, bias tires will basically be eliminated.
A radial tire is a new type of tire in which the carcass cords are arranged in the radial direction, and the cords are arranged in the circumferential direction or close to the circumferential direction and the buffer layer is tightly hooped on the carcass. It is composed of six main parts: tread, carcass, sidewall, buffer layer (or belt), bead, inner liner (or inner liner). According to the different cord materials used in the carcass and belt layer, radial tires can be divided into three types: all-steel radial tires, semi-steel radial tires and all-fiber radial tires.
The cord arrangement direction of a radial tire is consistent with the tire meridian section, and its ply is equivalent to the basic skeleton of the tire. Because the tires have to withstand greater tangential force during driving, in order to ensure the stability of the cord, there are several layers of belts (also called tightening layers) made of high-strength, non-stretchable materials on the outside. , The cord direction and the meridian section are at a larger angle. Compared with bias tires, radial tires have greater elasticity, good abrasion resistance, low rolling resistance, good adhesion, good cushioning performance, large load-bearing capacity, and are not easy to puncture; the disadvantage is that the sidewall is easy to crack, due to large lateral deformation, As a result, the lateral stability of the car is slightly worse, the manufacturing technology requirements are high, and the cost is higher.
Tips for the cause of tire bulge phenomenon
I believe everyone must still remember the Kumho Tire bulge incident. Here we will not discuss the manufacturer's handling methods, but only discuss the reasons for the tire bulge. There are many reasons for the bulging phenomenon. Generally speaking, the bulging phenomenon of tires is mostly due to unexpected strong impacts during use, which leads to serious squeezing between the impact objects and the rim flanges of the tires. Deformed.
For radial tires, the sidewall is the weakest place. Without the protection of the belt, the sidewall cords will break once severe deformation occurs. At this time, the air inside the tire will escape from the break. Jack up to form a bulge. Incorrect air pressure, bad road conditions, accidental impacts and negligent driving style are the main factors that cause tire bulge. In addition, frequent traffic jams and tires scratching against obstacles when parking may also cause damage to the sidewall and “bulge”. However, if tires are bulging in large quantities, it is largely caused by quality problems. In the tire manufacturing process, the cord is not dried enough to be glued, or the glue itself is too high in water content. According to relevant industry regulations, the normal trial period of ordinary tires is 3-5 years from the date of leaving the factory. If the bulge is not caused by special reasons such as collision within this period, then the quality of the tire may be problematic.
Tips for blowouts and run-flat tires
There are many factors that cause a puncture. If the tire pressure is too high, the pressure per unit area of the tire increases, the tread wears unevenly, and the sidewall becomes thinner due to the high pressure. Therefore, if you encounter bumps during driving, Tire puncture is easy to happen when there is a bump or pothole; when the tire pressure is too low, the tire will deform significantly, and the shoulder will contact the ground. This deformation makes the tire rotate unevenly, especially the steel wire inside the tire. There will be friction between it and the cord layer to generate a lot of heat, which will accelerate the aging of the tire and cause a puncture. Another cause of the puncture is foreign body puncture. When the car is driving at high speed, it will be punctured by an object, which will cause a puncture. It's not uncommon. So another type of tire came into our field of vision, this is the run-flat protection tire.
First of all, we need to clarify that this kind of “run-flat tire” we often say, its official name should be called-run-flat tire, from the literal meaning you can know that this kind of tire is under pressure or leaks. It helps the vehicle to drive normally within a certain distance and speed, and the name “run-flat tire” is also an exaggerated publicity for this type of tire by tire manufacturers and car manufacturers that use this type of tire.
When a normal tire loses tire pressure, the tire can be separated from the wheel hub like mud in the blink of an eye, relying only on the rim to contact the ground. The biggest difference between run-flat tires and general tires is that they have very tough and supportive sidewalls. Such a design can help ensure that the tire and the rim can be combined and provide certain support to the vehicle when the tire blows out or suddenly deflates, thereby ensuring the safety of the vehicle. Of course, due to the design of special materials and thicker sidewalls, this type of tire will reduce comfort and increase tire noise. The weight of tires is also heavier than ordinary tires, which will cause the unsprung mass to become heavier, which will affect the handling performance of the vehicle to a certain extent. However, considering the design of the sidewall with better support performance, it is suitable for vehicles running on general roads. That said, run-flat tires still have more advantages than disadvantages.