JP5168803B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire in which a rotation direction is specified. More specifically, even when the ground contact width is large, the air that makes it possible to achieve both drainability and handling stability under wet conditions. Related to tires.

  For tires with a large contact width such as racing tires, it is desired to more reliably prevent hydroplaning and exhibit excellent handling stability when running on a circuit under wet conditions. . In order to prevent the occurrence of the hydroplaning phenomenon, the groove area ratio of the tread portion may be increased. However, if the groove area ratio is increased, the steering stability is deteriorated. Therefore, in tires with a large contact width, it has always been a challenge to achieve both drainability and handling stability under wet conditions.

By the way, in the pneumatic tire, while specifying the rotation direction, the tread portion has a main groove extending in the tire circumferential direction at the tread center position, and is inclined in a direction opposite to the rotation direction from the tread center side toward both shoulder sides. Some of them are provided with a plurality of slant grooves. Such a pneumatic tire can exhibit good drainage performance when traveling straight and turning (see, for example, Patent Document 1).

However, even with a pneumatic tire having a tread pattern as described above, if the ground contact width is large, it is difficult to achieve both high drainage and handling stability under wet conditions. It is desired.
JP 2003-175705 A

  An object of the present invention is to provide a pneumatic tire that can achieve both drainage performance and handling stability under wet conditions even when the contact width is large.

In order to achieve the above object, a pneumatic tire according to the present invention is a pneumatic tire in which a rotational direction is specified. A main groove extending in a tire circumferential direction at a tread center position in a tread portion, and both shoulder sides from the tread center side. A plurality of first slant grooves that are inclined in the direction opposite to the rotation direction toward the main groove and communicate with the main groove, and the same direction as the first slant groove while traversing 6 to 8 first slant grooves Are provided with a plurality of second slant grooves that are not communicated with the main groove, and an average inclination angle of the first slant groove with respect to the tire circumferential direction in the center region corresponding to 50% of the contact width was a 25 ° to 40 °, the average inclination angle with respect to the tire circumferential direction of the second slant grooves and 5 ° to 25 °, and any tire meridian 4-6 present the first scan of at the center region A groove disposed so as to traverse the cement grooves and 7-9 pieces of the second slant groove simultaneously, and characterized in that the contact width not less than 200 mm, and the groove area ratio in the ground contact width is 25% to 45% To do.

In the present invention, based on the inclination angle with respect to the main groove and the tire circumferential direction and extending in the tire circumferential direction in a tread portion is provided with two different slant grooves, drainage capacity of these main grooves and two slant grooves wet The drainage property under the conditions can be improved, and the occurrence of hydroplaning phenomenon during straight running and turning can be prevented. In addition, the average inclination angle in the center region of the first slant groove and the second slant groove is defined in the above range, and any tire meridian has at least four first slant grooves and at least seven second slant grooves. By arranging the grooves so as to cross the two at the same time, it is possible to ensure a uniform grounding property in the tread portion, and as a result, it is possible to maintain high steering stability and uniform wear characteristics. As a result, even when the ground contact width is large, it is possible to achieve both drainage performance and handling stability under wet conditions.

In the present invention, at least one of the first slant groove and the second slant groove may be curved so that the inclination angle with respect to the tire circumferential direction increases as the distance from the tread center position increases. In this case, it is possible to improve the steering stability by increasing the block rigidity on the shoulder side. Further, in order to achieve both drainage performance and handling stability under wet conditions, the groove area ratio within the contact width is set to 25% to 45% . The tread pattern is particularly effective in a pneumatic tire having a contact width of 200 mm or more.

  In the present invention, the contact width is the portion of the tire that comes into contact with the plane when the tread portion of the tire is brought into contact with the plane under the measurement condition of the static load radius determined by the standards such as JATMA, TRA, ETRTO Axial width. However, in the case of racing tires, the contact width is determined when the tire is mounted on a rim and grounded under conditions of an air pressure of 180 kPa and a load of 4 kN.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows a pneumatic tire according to an embodiment of the present invention, and FIG. 2 shows an enlarged tread pattern thereof. In the pneumatic tire of the present embodiment, the rotation direction R at the time of forward movement is designated.

  As shown in FIGS. 1 and 2, the tread portion 1 has one straight main groove 2 and a plurality of slant grooves 3 (first slant grooves) arranged at a predetermined pitch in the tire circumferential direction. And a plurality of slant grooves 4 (second slant grooves) arranged at a predetermined pitch in the tire circumferential direction, and a large number of blocks 5 are divided by the main grooves 1 and the slant grooves 3 and 4. . The block 5 may be cut with a kerf or the like as necessary.

  The main groove 2 extends continuously in the tire circumferential direction at the tread center position TC. The main groove 2 may extend in the tire circumferential direction while maintaining a constant width, but may be refracted as illustrated based on the arrangement of the blocks 4 adjacent to the main groove 2. However, it is desirable to form a see-through structure in which a groove space having a width of 1 mm or more is continuous in the tire circumferential direction when the main groove 2 is projected in the tire circumferential direction in order to ensure drainage during straight traveling. The groove width of the main groove 2 is 8 mm to 18 mm, and the groove depth is 4.5 mm to 6.5 mm.

The slant groove 3 is inclined in the direction opposite to the rotational direction R from the tread center side toward both shoulder sides, the end on the tread center side communicates with the main groove 2, and the end on the shoulder side extends to the non-grounding region. It is extended. The slant groove 3 may be linear or curved. When an area corresponding to 50% of the contact width TCW centered on the tread center position TC is defined as the center area C, the average inclination angle α of the slant groove 3 in the center area C with respect to the tire circumferential direction is in the range of 25 ° to 40 °. More preferably, it is set in the range of 30 ° to 35 °. The average inclination angle α is defined by a straight line connecting the groove width center position of the end of the slant groove 3 on the tread center side and the groove width center position of the slant groove 3 at the outer edge of the center region C with respect to the tire circumferential direction. Is an angle. If the average inclination angle α is too small, the block rigidity is insufficient and the steering stability is lowered. Conversely, if the average inclination angle α is too large, the drainage performance is lowered. The slant groove 3 has a groove width of 4 mm to 10 mm and a groove depth of 4.5 mm to 6.5 mm.

The slant groove 4 is inclined in a direction opposite to the rotational direction R from the tread center side toward both shoulders while traversing at least six slant grooves 3, and the end on the tread center side is not the main groove 2. It terminates in the block 5 positioned closest to the tread center so as to communicate, and the end on the shoulder side terminates in the block 5 positioned closest to the shoulder. The slant groove 4 may be linear or curved. The average inclination angle β of the slant groove 4 in the center region C with respect to the tire circumferential direction is set in a range of 5 ° to 25 °, more preferably in a range of 10 ° to 20 °. The average inclination angle β is defined by a straight line connecting the groove width center position of the end portion on the tread center side of the slant groove 4 and the groove width center position of the slant groove 4 at the outer edge of the center region C with respect to the tire circumferential direction. Is an angle. If the average inclination angle β is too small, the block rigidity is insufficient and the steering stability is lowered. Conversely, if the average inclination angle β is too large, the drainage performance is lowered. The slant groove 4 has a groove width of 4 mm to 10 mm and a groove depth of 4.5 mm to 6.5 mm.

When an arbitrary tire meridian M (cutting line when the tire is cut in the radial direction) is drawn on the tread portion 1, the tire meridian M simultaneously includes at least four slant grooves 3 and at least seven slant grooves 4. It has a groove arrangement that crosses. That is, the slant grooves 3 and 4 subdivide the tread portion 1 into a large number of blocks 5 having an appropriate size, and contribute to uniform grounding.

  In the pneumatic tire, since the tread portion 1 is provided with the main groove 2 extending in the tire circumferential direction and the two types of slant grooves 3 and 4 having different inclination angles with respect to the tire, the drainage performance under wet conditions is improved. It is possible to prevent the occurrence of a hydroplaning phenomenon when going straight and turning. Moreover, since the average inclination angles α and β in the center region C of the slant grooves 3 and 4 are defined, and the arbitrary tire meridian M is arranged so as to cross a large number of the slant grooves 3 and 4 at the same time, the tread A uniform grounding property can be ensured at least in the center region C of the part 1, and as a result, high steering stability and uniform wear characteristics can be maintained. As a result, even if the ground contact width is 200 mm or more, or 300 mm or more, it is possible to achieve both drainage performance and handling stability under wet conditions. Further, in the above-described tread pattern, it is possible to reduce the damage to the block even when the vehicle travels with a small amount of rainfall.

  The slant grooves 3 and 4 may be curved so that the inclination angle with respect to the tire circumferential direction increases as the distance from the tread center position TC increases. In this case, it is possible to improve the steering stability by increasing the block rigidity on the shoulder side.

  Moreover, in order to make the drainage property and steering stability under wet conditions compatible, the groove area ratio in the ground contact width TCW is preferably 25% to 45%. The groove area ratio is the ratio of the groove area to the sum of the land area and the groove area within the ground contact width. When the groove area ratio is less than 25%, the drainage performance decreases, and when it exceeds 45%, the steering stability decreases.

In the racing tire of tire size 330 / 710R18, tires of Examples 1 to 10 and Comparative Examples 1 to 3 in which the tread pattern of FIG. 1 is formed and only the dimensional requirements are varied as shown in Table 1 are produced. did. For comparison, as a conventional example, a tire employing a tread pattern described in Japanese Patent Laid-Open No. 2003-175705 was prepared as shown in FIG.

A circuit running test was conducted on these test tires. In other words, each test tire was assembled on a wheel with a rim size of 18 × 13 JJ, mounted on a 3800cc rear-wheel drive vehicle with an air pressure of 180 kPa, and 10 laps by a test driver under wet conditions on a circuit with a lap distance of 5.6 km. The test run was conducted and the average lap time was measured. The results are shown in Table 1.

As can be seen from Table 1, the tires of Examples 1 to 10 had an average lap time shorter than that of the conventional example, and were excellent in drainage and handling stability under wet conditions.

1 is a perspective view showing a pneumatic tire according to an embodiment of the present invention. It is an expanded view which expands and shows the tread pattern of the pneumatic tire which consists of embodiment of this invention. It is an expanded view which shows an example of the tread pattern of the conventional pneumatic tire.

Explanation of symbols

1 Tread part 2 Main groove 3 Slant groove (first slant groove)
4 Slant groove (second slant groove)
5 Block C Center area M Tire meridian R Rotation direction TC Tread center position TCW Ground contact width

Claims (3)

In a pneumatic tire having a designated rotation direction, the tread portion has a main groove extending in the tire circumferential direction at the tread center position, and is inclined in a direction opposite to the rotation direction from the tread center side toward both shoulder sides. A plurality of first slant grooves communicating with the main groove, and a plurality of first slant grooves which are inclined in the same direction as the first slant groove while crossing the 6 to 8 first slant grooves and are not communicated with the main groove. And an average inclination angle of the first slant groove with respect to the tire circumferential direction in the center region corresponding to 50% of the contact width is set to 25 ° to 40 °, and the second slant groove in the center region is the average inclination angle with respect to the tire circumferential direction of the two slant grooves and 5 ° to 25 °, and to cross any of the tire meridian and 4-6 present the first slant groove and 7-9 pieces of the second slant groove simultaneously Such a groove disposed, the contact width not less than 200 mm, the pneumatic tire groove area ratio in the ground contact width is 25% to 45%.   2. The pneumatic tire according to claim 1, wherein at least one of the first slant groove and the second slant groove is curved so that an inclination angle with respect to a tire circumferential direction increases as the distance from the tread center position increases.   The pneumatic tire according to claim 1 or 2, wherein an end portion of the first slant groove on the outer side in the tire width direction is bent outwardly of the contact width in a direction opposite to the rotation direction to be tapered. .

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