here is an analysis of the function of tire tread pattern and the factors that affect the function of tread pattern.
first, the function of tire tread pattern
in short, the main function of tire tread pattern is to increase the friction between tread and road surface, so as to prevent the wheel from slipping, which is exactly the same as the function of sole tread pattern. Tire tread pattern improves the ground contact elasticity of the tread, and under the action of tangential forces (such as driving force, braking force and lateral force) between the tread and the road surface, the tread block can produce large tangential elastic deformation. With the increase of tangential force, the tangential deformation will increase, and the "friction effect" of the contact surface will also increase, thus inhibiting the slipping or slipping trend between the tread and the road surface. To a great extent, this eliminates the disadvantage that the tread (smooth tread) tire is easy to slip, and ensures the normal performance of the automobile related to the friction between the tire and the road surface, such as power, braking, steering maneuverability and driving safety. Studies have shown that the friction between the tread and the road surface is also caused by adhesion between the two surfaces, molecular attraction and micro-cutting effect of small-scale rain asperities on the road surface, but the elastic deformation of the pattern blocks is still the main factor.
second, there are many factors that affect the function of patterns, but the main factors related to automobile use are the pattern type and depth.
1. Influence of tread pattern
There are various tread patterns, but in summary, there are three main types: ordinary tread, cross-country tread and mixed tread.
(1) common patterns
common patterns are suitable for use on hard roads. It is divided into longitudinal patterns, transverse patterns and both longitudinal and transverse patterns.
a) longitudinal pattern
The same feature of longitudinal pattern is that the tread is continuous in the longitudinal direction and disconnected in the transverse direction (Figure 1a), so the longitudinal stiffness of the tread is large, but the lateral stiffness is small, and the tire skid resistance is strong in the transverse direction and weak in the longitudinal direction. This tread tire has small rolling resistance and good heat dissipation performance, but the tread groove is easy to be embedded in gravel. Taken together, this pattern is suitable for driving on relatively clean and good hard roads. For example, cars, light and minivans choose this pattern.
b) transverse pattern The transverse pattern * * * is characterized in that the tread is continuous in the transverse direction and disconnected in the longitudinal direction (Figure 1b), so the tread has high transverse stiffness and low longitudinal stiffness. Therefore, the anti-skid ability of the tire is strong in the longitudinal direction and weak in the transverse direction, and it is easy to slip when the car turns at a high speed; Tire rolling resistance is also relatively large, and tread wear is relatively serious. This pattern is suitable for medium-sized or heavy trucks with large traction on general hard roads.
c) both vertical and horizontal patterns
This pattern is between the vertical pattern and the horizontal pattern (Figure 1c). There are generally zigzag longitudinal patterns in the middle of the tread, while transverse patterns are made on both sides near the shoulder. In this way, the vertical and horizontal anti-sliding ability of the table top is better. Therefore, this type of tire has strong adaptability and a wide range of applications. It is suitable for different hard roads as well as cars and trucks.
(2) Cross-country pattern
The common feature of cross-country pattern is that the groove is wide and deep, and the grounding area of the block is relatively small (about 4%~6%). When driving on a soft road, a part of soil will be embedded in the pattern groove, and the tire may slip only after this part of soil embedded in the pattern groove is sheared, so the grip when entering the pattern is great. According to the root test, on the muddy road, the traction of the same type of vehicle using cross-country pattern wheel swelling can reach 1.5 times that of ordinary pattern.
cross-country patterns can be divided into undirected patterns and directional patterns (as shown in Figure 2). Directional patterns are directional when used. Cross-country tread tires are suitable for use on rugged roads, soft dirt roads and roadless areas. Because of the large contact pressure and rolling resistance of the block, it is not suitable for driving on good hard road for a long time. Otherwise, tire wear will be aggravated, fuel consumption will be increased, and vehicle vibration will be severe.
(3) Mixed pattern
Mixed pattern is a transitional pattern between ordinary pattern and cross-country pattern (as shown in Figure 3). It is characterized in that the middle part of the tread has narrow grooves with different directions or mainly in the longitudinal direction, while the two sides have wide grooves with different directions or mainly in the transverse direction. This pattern collocation makes the mixed pattern have good comprehensive performance and strong adaptability. It is not only suitable for good hard pavement, but also suitable for gravel pavement, slush pavement and soft pavement. Its adhesion performance is better than that of ordinary patterns, but its wear resistance is slightly worse. At present, some trucks and four-wheel drive passenger cars mostly use this type of tread tires.
2. Influence of tread depth
The deeper the tread pattern, the greater the elastic deformation of the tread block, and the rolling resistance caused by the elastic hysteresis loss of the tire will also increase. Deep patterns are not conducive to tire heat dissipation, so that tire temperature rises faster, and the root of the pattern is easy to tear and fall off due to severe stress. The shallow pattern not only affects its water storage and drainage capacity, but also easily produces harmful "water skiing phenomenon", and highlights the disadvantages of smooth tread tires that are easy to slip, thus making the aforementioned automobile performance worse.
therefore, it is not good for the pattern to be too deep and too shallow. The objective law of surface is that the pattern will become smaller and smaller in use. In order to ensure the effectiveness of tread pattern, countries all over the world have formulated clear laws and regulations on the wear limit of tire tread pattern (see Table 1). The tire wear limit warning mark ""or (and) "TWI" in English is engraved on several equal parts of the tire shoulder along the circumference (as shown in Figure 4). When the wear distance of the convex surface of the block is about 1.6mm(1/16 inch) to the bottom of the groove, the pattern at the mark has been ground flat, so a narrow horizontal strip of smooth tread is exposed to warn the driver that it is time to replace the tire.
Table 1 Depth wear limit of tread pattern (mm)
National cars, trucks and buses
USA ≥1.6 ≥2.
Western Europe ≥1. ≥2.
Japan ≥1.6 ≥3.2
China ≥1.6 ≥2.
III. Tire pattern. For vehicles running at medium speed on general hard roads, trucks and buses should choose tires with transverse patterns or both longitudinal and transverse patterns; For vehicles that often drive on expressways and good hard roads, it is advisable to choose longitudinal tread tires and both longitudinal and transverse tread tires with good heat dissipation and strong lateral stability.
2. With the increase of vehicle speed, water film will be formed between the tread and the road before it can be removed, which will slowly lift the tire and even leave the road completely under certain conditions, making the car completely lose maneuverability. This phenomenon is called tire "water skiing". There are many factors that affect the critical speed of water skiing, but the tire pattern and Shenxin Ba are one of the main factors. Cars that often drive on the highway should try to choose anti-skid tires (as shown in Figure 5) when conditions permit. The main feature of this pattern is that a wide drainage ditch (main ditch) is designed in the middle of the tread, forming a large drainage space between the tire and the road surface. There are two side ditches leading to the side of the tire in the main ditch, so the drainage distance is short and the drainage efficiency is high, thus feeding the "water skiing phenomenon" that may occur when the tire runs at high speed on wet road surface to the maximum extent and improving the driving safety.
It is worth noting that this pattern is directional, so it should not be careless when installing.
3. The rotating direction of directional tire is usually indicated by an "arrow" and a mark molded on the sidewall. If the tire rotates in the direction of the arrow, that is, the tip of the herringbone pattern touches the ground first, it is said that it is placed in the forward direction, but it is said that it rotates in the reverse direction.
All water-skiing tires are placed in the forward direction to improve the drainage efficiency.
If the cross-country directional tread tire is installed on the drive axle, it should rotate in the right direction. The tip of the herringbone tread is embedded in the snow mud like a chain, which has strong grip ability, and the snow mud embedded in the groove of the tread can be squeezed out from both sides, so the tread is self-cleaning. If the cross-country directional tread tire installed on the driven axle does not output traction, it should rotate in the opposite direction in order to reduce rolling resistance and wear.
to sum up, tire tread is an important link to improve automobile performance and ensure driving safety. Therefore, it is very important to choose, install and use tire patterns correctly.