Tire tread structure

Abstract

The utility model provides a tire tread structure. A plurality of longitudinal grooves of the tire tread structure are arranged at intervals in the width direction of the tire, so that the tire tread of the tire is divided into a plurality of circumferential pattern parts; the communicating grooves formed in the tire shoulder pattern part are used for communicating the longitudinal grooves with the side part of the tire, and the communicating grooves formed in the tire crown pattern part are used for communicating two adjacent longitudinal grooves; the transverse cutter grooves are provided with bent sections which are arranged in a wave shape or a broken line shape, and transverse cutter grooves are formed in the circumferential pattern part; the reinforcing structure is arranged in the communicating groove and is connected with two groove walls of the communicating groove; wherein the reinforcing structure is provided with a first inclined surface, and the first inclined surface is used for limiting and stopping foreign matters entering the communicating groove. The utility model solves the problem that the tire in the prior art cannot stably run under special road conditions in summer and winter.

Description

Technical Field

[0001] This utility model relates to the field of tire technology, and more specifically, to a tire tread structure. Background Technology

[0002] Currently, the tread pattern structure of traditional tires is often designed specifically for road conditions in a particular season. For example, summer tires often focus on grip on dry and wet surfaces, with wide and shallow grooves to cope with rainy weather in summer. However, in low-temperature environments, the tread blocks cannot embed into ice and snow, resulting in a significant decrease in the grip performance of summer tires. Winter tires, on the other hand, focus on anti-skid on icy and snowy roads, with narrow and deep grooves, high density, and smaller tread blocks to ensure that the tread blocks can embed into ice and snow. However, winter tires have disadvantages such as faster wear, susceptibility to stone trapping, and easy damage on dry roads in summer.

[0003] However, current technology lacks an all-season tire tread design that can take into account the special road conditions in summer and winter. In areas with distinct seasons, users often need to purchase two sets of tires (summer tires and winter tires) and replace them according to the seasonal characteristics of the road surface. If the replacement is not timely, it will lead to increased tire usage costs for users and even safety hazards. Utility Model Content

[0004] The main objective of this invention is to provide a tire tread structure to solve the problem that existing tires cannot maintain stable driving under special road conditions in both summer and winter.

[0005] To achieve the above objectives, this utility model provides a tire tread structure, comprising: longitudinal grooves extending circumferentially along the tire, wherein there are multiple longitudinal grooves spaced apart along the width direction of the tire to divide the tire tread into multiple circumferential tread portions, the multiple circumferential tread portions including two shoulder tread portions and a crown tread portion located between the two shoulder tread portions; connecting grooves, wherein the connecting grooves on the shoulder tread portions are used to connect the longitudinal grooves and the side of the tire, and the connecting grooves on the crown tread portions are used to connect two adjacent longitudinal grooves; lateral sipes having curved sections arranged in a wavy or zigzag shape, and lateral sipes being provided on the circumferential tread portions; and a reinforcing structure disposed within the connecting grooves and connected to the two groove walls of the connecting grooves; wherein the reinforcing structure has a first inclined surface, the first inclined surface being used to limit and stop foreign objects entering the connecting grooves.

[0006] Furthermore, the tread pattern includes a central tread pattern, at least a portion of which coincides with the center surface S of the tire; the connecting groove provided on the central tread pattern includes a central connecting groove, which includes interconnected groove segments and sipe segments, with the groove segments positioned closer to the outer side of the tire than the sipe segments; wherein, along the direction from the groove segment to the sipe segment, the width of the groove segment gradually decreases, and the depth of the groove segment gradually decreases.

[0007] Furthermore, the tire tread structure also includes: a sipe group, including a first sipe and a first strip chamfer. The two ends of the first sipe are respectively connected to two adjacent longitudinal grooves. The first strip chamfer is disposed on the groove wall of the first sipe and is consistent with the extension direction of the first sipe. Along the direction from the tread to the bottom of the first sipe, the width of the first strip chamfer gradually decreases. Along the direction from the outer side of the tire to the inner side of the tire, the width of the first strip chamfer gradually decreases, and the depth of the first strip chamfer gradually decreases, so as to form a second inclined surface on the inner wall of the first strip chamfer. The sipe group is disposed on the central tread portion.

[0008] Furthermore, the transverse sipes provided on the central tread portion include a central transverse sipe, the extension direction of which is set at a first angle A1 with respect to the width direction of the tire, the first angle A1 satisfying: 25°≤A1≤35°; the extension direction of the central connecting groove is set at a second angle A2 with respect to the width direction of the tire, the second angle A2 satisfying: 25°≤A2≤35°; the sipe group provided on the central tread portion includes a central sipe group, the extension direction of the first sipe of the central sipe group is set at a third angle A3 with respect to the width direction of the tire, the third angle A3 satisfying: 25°≤A3≤35°; wherein, the first angle A1, the second angle A2, and the third angle A3 satisfy: A1>A3>A2.

[0009] Furthermore, the tread pattern also includes an inner tread pattern located between the central tread pattern and the shoulder tread pattern. The inner tread pattern is positioned closer to the inner side of the tire than the central surface S. The connecting grooves on the inner tread pattern include an inner connecting groove, which includes a first sub-groove and a second sub-groove that are interconnected. The first sub-groove is positioned closer to the central surface S than the second sub-groove. The first sub-groove is positioned at a fourth angle A4 with respect to the width direction of the tire, and the second sub-groove is positioned at a fifth angle A5 with respect to the width direction of the tire. The fourth angle A4 and the fifth angle A5 satisfy the following conditions: 3°≤A4≤7°, 32°≤A5≤38°.

[0010] Furthermore, the reinforcing structure disposed within the inner connecting groove includes an inner reinforcing structure, which is disposed at the bottom of the second sub-groove, with the first inclined surface of the inner reinforcing structure facing the opening of the second sub-groove; wherein, along the circumference of the tire, the width of the first inclined surface of the inner reinforcing structure gradually decreases.

[0011] Furthermore, the tread pattern also includes an outer tread pattern located between the central tread pattern and the shoulder tread pattern. The outer tread pattern is positioned closer to the outer side of the tire than the central surface S. The connecting grooves on the outer tread pattern include an outer connecting groove, which includes a third sub-groove and a fourth sub-groove that are interconnected. The third sub-groove is positioned closer to the central surface S than the fourth sub-groove. The third sub-groove forms a sixth angle A6 with the width direction of the tire, and the fourth sub-groove forms a seventh angle A7 with the width direction of the tire. The sixth angle A6 and the seventh angle A7 satisfy: 35°≤A6≤45°, 17°≤A7≤23°. A set of sipes is provided on the outer tread pattern.

[0012] Furthermore, the reinforcing structure provided in the outer connecting groove includes an outer reinforcing structure, which is located at the bottom of the outer connecting groove. A portion of the outer reinforcing structure is located in the third sub-groove, and the other end of the outer reinforcing structure is located in the fourth sub-groove. The first inclined surface of the outer reinforcing structure is positioned opposite to the opening of the outer connecting groove. The width of the first inclined surface of the outer reinforcing structure gradually decreases along the circumference of the tire.

[0013] Furthermore, a shoulder tread portion is provided near the outer side of the tire relative to the center surface S of the tire, which is called the outer shoulder tread portion. The connecting groove provided on the outer shoulder tread portion includes an outer shoulder connecting groove, which includes a fifth sub-groove and a sixth sub-groove that are interconnected. The fifth sub-groove is located near the center surface S relative to the sixth sub-groove. The fifth sub-groove is set at an eighth angle A8 with the width direction of the tire, and the sixth sub-groove is set at a ninth angle A9 with the width direction of the tire. The eighth angle A8 and the ninth angle A9 satisfy: 17°≤A8≤23°, 3°≤A9≤7°. Among them, the fifth sub-groove includes a first groove segment and a second groove segment that are interconnected. The first groove segment is located near the center surface S relative to the second groove segment. The depth of the first groove segment is less than the depth of the second groove segment, so that a first structural reinforcement is formed at the bottom of the first groove segment.

[0014] Furthermore, the shoulder tread portion located near the inner side of the tire relative to the center surface S of the tire is called the inner shoulder tread portion. The connecting grooves on the inner shoulder tread portion include the inner shoulder connecting groove, which includes a seventh sub-groove and an eighth sub-groove that are interconnected. The seventh sub-groove is located near the center surface S relative to the eighth sub-groove. The seventh sub-groove is set at a tenth angle A10 with the width direction of the tire, and the eighth sub-groove is set at an eleventh angle A11 with the width direction of the tire. The tenth angle A10 and the eleventh angle A11 satisfy: 22°≤A10≤28°, 5°≤A11≤9°. Among them, the seventh sub-groove includes a third segment, a fourth segment, and a fifth segment that are interconnected. The fourth segment is located between the third segment and the fifth segment. The depth of the third segment and the depth of the fifth segment are both greater than the depth of the fourth segment, so that a second structural reinforcement is formed at the bottom of the fourth segment.

[0015] Applying the technical solution of this utility model, the longitudinal grooves of the tire tread structure extend along the circumference of the tire, and multiple longitudinal grooves are spaced apart along the width direction of the tire to divide the tire tread into multiple circumferential tread portions. These multiple circumferential tread portions include two shoulder tread portions and a crown tread portion located between the two shoulder tread portions. A connecting groove on the shoulder tread portion connects the longitudinal grooves and the side of the tire, and a connecting groove on the crown tread portion connects two adjacent longitudinal grooves. The transverse sipes have wavy or zigzag curved sections. A reinforcing structure is disposed within the connecting grooves and connected to the two groove walls of the connecting grooves. The reinforcing structure has a first inclined surface, which is used to limit and stop foreign objects entering the connecting grooves. In this way, the tire tread structure in this application actually forms a "snow and water network" through a large number of interconnected grooves arranged on the circumferential tread portion (the interconnected grooves set on the shoulder tread portion and the crown tread portion can respectively connect the longitudinal grooves and the side of the tire, and two adjacent longitudinal grooves), which greatly improves the tire's snow and water removal performance, thereby ensuring that the tire has high driving stability on wet and icy roads (reducing the probability of slippage). The large number of lateral grooves arranged on the circumferential tread portion can not only improve the tire's ability to cut water film, but also increase the overall friction of the tread to further adapt to wet or icy roads; on the other hand, it can balance the rigidity of the circumferential tread portion and increase the flexibility of the circumferential tread portion, ensuring that the tread can generate a sufficiently large interaction force (mainly friction) with the summer or winter road surface (winter road surface is icy and uneven). Building upon this, this application further incorporates a reinforcing structure within the connecting groove. This reinforcing structure connects the two groove walls, providing localized structural reinforcement to the weaker parts surrounding the connecting groove, enhancing structural strength and stability. While ensuring stable embedding of ice and snow at the edge of the connecting groove, it also provides stone removal and self-cleaning effects through the first inclined surface, extending tire lifespan. Therefore, the tire tread structure in this application not only possesses extremely high snow and water removal performance and generates sufficiently large interaction forces with the driving surface (initially adapting to straight-line driving on wet and slippery roads in summer and icy and snowy roads in winter), but also effectively compresses accumulated snow during cornering, improving vehicle steering stability on icy and snowy roads. This solves the problem of existing tires being unable to maintain stable driving under special road conditions in both summer and winter, reducing tire usage costs for users. Attached Figure Description

[0016] The accompanying drawings, which form part of this application, are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an undue limitation of the present invention. In the drawings:

[0017] Figure 1 A partial front view of an embodiment of the tire tread structure according to the present invention is shown;

[0018] Figure 2 It shows Figure 1 A partially enlarged schematic diagram of the inner connecting grooves of the tire tread structure;

[0019] Figure 3 It shows Figure 1 A partially enlarged schematic diagram of the outer connecting grooves of the tire tread structure;

[0020] Figure 4 It shows Figure 1 A cross-sectional view of the tire tread structure at point AA;

[0021] Figure 5 It shows Figure 1 A cross-sectional view of the tire tread structure at the BB section;

[0022] Figure 6 It shows Figure 1 A cross-sectional view of the tire tread structure at point CC.

[0023] The above figures include the following reference numerals:

[0024] 10. Longitudinal trench; 11. First longitudinal trench; 12. Second longitudinal trench; 13. Third longitudinal trench; 14. Fourth longitudinal trench;

[0025] 20. Tire shoulder tread pattern; 21. Outer tire shoulder tread pattern; 22. Inner tire shoulder tread pattern;

[0026] 30. Tread pattern area; 31. Central tread pattern area; 32. Inner tread pattern area; 33. Outer tread pattern area;

[0027] 40. Connecting groove; 41. Central connecting groove; 411. Groove segment; 412. Sipe segment; 42. Inner connecting groove; 421. First sub-groove; 422. Second sub-groove; 43. Outer connecting groove; 431. Third sub-groove; 432. Fourth sub-groove; 44. Outer shoulder connecting groove; 441. Fifth sub-groove; 4411. First groove segment; 4412. Second groove segment; 442. Sixth sub-groove; 45. Inner shoulder connecting groove; 451. Seventh sub-groove; 4511. Third groove segment; 4512. Fourth groove segment; 4513. Fifth groove segment; 452. Eighth sub-groove;

[0028] 50. Lateral sipe; 51. Central lateral sipe; 52. Inner lateral sipe; 53. Outer lateral sipe; 54. Inner shoulder lateral sipe; 55. Outer shoulder lateral sipe;

[0029] 60. Reinforcing structure; 61. Inner reinforcing structure; 62. Outer reinforcing structure; 63. First inclined surface;

[0030] 70. Tool groove group; 71. First tool groove; 72. First strip chamfer; 73. Central tool groove group; 74. Outer tool groove group;

[0031] 81. First structural reinforcement; 82. Second structural reinforcement;

[0032] 90° longitudinal chamfer; 100° transverse chamfer. Detailed Implementation

[0033] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0034] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0035] To address the problem that existing tires cannot maintain stable driving under special road conditions in both summer and winter, this application provides a tire tread structure.

[0036] like Figures 1 to 6 As shown, the tire tread structure includes longitudinal grooves 10, connecting grooves 40, lateral sipes 50, and a reinforcing structure 60. The longitudinal grooves 10 extend circumferentially along the tire, and there are multiple longitudinal grooves 10. These multiple longitudinal grooves 10 are spaced apart along the width direction of the tire to divide the tire tread into multiple circumferential tread portions. The multiple circumferential tread portions include two shoulder tread portions 20 and a crown tread portion 30 located between the two shoulder tread portions 20. The connecting grooves 40, located on the shoulder tread portions 20, connect the longitudinal grooves 10 and the sidewalls of the tire. The connecting grooves 40, located on the crown tread portions 30, connect two adjacent longitudinal grooves 10. The lateral sipes 50 have curved sections arranged in a wavy or zigzag shape. The reinforcing structure 60 is disposed within the connecting grooves 40 and connected to the two groove walls of the connecting grooves 40. The reinforcing structure 60 has a first inclined surface 63, which is used to limit and stop foreign objects entering the communicating trench 40.

[0037] Applying the technical solution of this embodiment, the longitudinal grooves 10 of the tire tread structure extend along the circumference of the tire, and multiple longitudinal grooves 10 are spaced apart along the width direction of the tire to divide the tire tread into multiple circumferential tread portions. These multiple circumferential tread portions include two shoulder tread portions 20 and a crown tread portion 30 located between the two shoulder tread portions 20. A connecting groove 40 provided on the shoulder tread portion 20 connects the longitudinal grooves 10 and the side of the tire, and a connecting groove 40 provided on the crown tread portion 30 connects two adjacent longitudinal grooves 10. A transverse sipe 50 has a wavy or zigzag curved section. A reinforcing structure 60 is provided on the circumferential tread portion. A reinforcing structure 60 is disposed within the connecting groove 40 and connected to the two groove walls of the connecting groove 40. The reinforcing structure 60 has a first inclined surface, which is used to limit and stop foreign objects entering the connecting groove 40. In this embodiment, the tire tread structure actually forms a "snow and water network" through a large number of interconnected grooves 40 arranged on the circumferential tread portion (the interconnected grooves 40 arranged on the shoulder tread portion 20 and the crown tread portion 30 can respectively connect the longitudinal grooves 10 and the side of the tire, and two adjacent longitudinal grooves 10), which greatly improves the tire's snow and water removal performance, thereby ensuring that the tire has high driving stability on wet and icy roads (reducing the probability of slippage). The large number of transverse sipes 50 arranged on the circumferential tread portion can not only improve the tire's ability to cut water film, but also increase the overall friction of the tread to further adapt to wet or icy roads; on the other hand, they can balance the rigidity of the circumferential tread portion and increase the flexibility of the circumferential tread portion, ensuring that the tread can generate a sufficiently large interaction force (mainly friction) with the summer or winter road surface (winter road surface is icy and uneven). Building upon this, this embodiment further incorporates a reinforcing structure 60 within the connecting groove 40. This reinforcing structure 60 connects the two groove walls, providing localized structural reinforcement to the weaker parts surrounding the connecting groove 40, enhancing structural strength and stability. While ensuring stable embedding of ice and snow at the edge of the connecting groove 40, it also achieves stone removal and self-cleaning effects through the first inclined surface 63, extending tire lifespan. Therefore, the tire tread structure in this application not only possesses extremely high snow and water removal performance and generates sufficiently large interaction forces with the driving surface (initially adapting to straight-line driving on wet and slippery roads in summer and icy and snowy roads in winter), but also effectively compresses accumulated snow during cornering, improving vehicle steering stability on icy and snowy roads. This solves the problem in existing technologies where tires cannot maintain stable driving under special road conditions in both summer and winter, reducing tire usage costs for users.

[0038] In this embodiment, the curved section is arranged in a wavy shape.

[0039] Specifically, the transversely arranged transverse sipes 50 can actually balance the rigidity of the circumferential tread portion in the tire circumferential direction (ensuring that the circumferential tread portion can undergo sufficiently large elastic deformation along the tire circumferential direction to generate frictional force in the tire circumferential direction), while the curved section can simultaneously balance the rigidity of the circumferential tread portion in the tire width direction (ensuring that the circumferential tread portion can undergo sufficiently large elastic deformation along the tire width direction to generate frictional force in the tire width direction), thus improving the rigidity balancing capability of the transverse sipes 50.

[0040] Specifically, the rigid balance results in a greater interaction force between the tire tread and the driving surface, generating greater driving force, braking force, and other corresponding forces, which can comprehensively (with beneficial effects in both summer and winter) improve the tire's driving stability.

[0041] Specifically, in this embodiment, the width of the transverse sipe 50 is actually much smaller than the width of the connecting groove 40 (actually between 1 and 3 mm), meaning that the drainage capacity of the transverse sipe 50 is relatively weak. Its main function is to balance the rigidity of the circumferential tread portion. In addition, the transverse sipe 50 causes each circumferential tread portion to form an edge (the edge of the transverse sipe 50 away from its bottom). These edges can cut the water film between the tread and the driving surface during the pressing of the road surface, so as to avoid the formation of a complete water film between the tread and the driving surface, which would reduce the coefficient of friction of the tread, thereby increasing the interaction force between the tread and the driving surface.

[0042] Specifically, the increased flexibility of the lateral sipes 50 in the circumferential tread pattern can also improve the tire's cushioning performance, thereby enhancing the driving comfort of passengers.

[0043] In this embodiment, the ratio between the total crown arc length (TDW) and the nominal section width (NSW) of the tire is 0.80 ≤ TDW / NSW ≤ 0.88. This ratio optimizes the tread's contact patch and pressure distribution. On dry surfaces, a suitable contact patch ensures sufficient contact between the tire and the road surface, increasing friction, improving handling stability, and enhancing acceleration and braking performance. Specifically, during high-speed emergency braking, a reasonable contact patch allows the tire to quickly transfer braking force to the road surface, shortening the braking distance. On snow and ice, an appropriate contact patch helps the tire better embed itself into the surface, enhancing grip.

[0044] In this embodiment, there are four longitudinal grooves 10, including a first longitudinal groove 11, a second longitudinal groove 12, a third longitudinal groove 13, and a fourth longitudinal groove 14. The width of the first longitudinal groove 11 is (4.9±0.2)%TDW, the width of the second longitudinal groove 12 is (5.5±0.2)%TDW, the width of the third longitudinal groove 13 is (5.5±0.2)%TDW, and the width of the fourth longitudinal groove 14 is (4.9±0.2)%TDW. This width setting ensures that when the tire is driving on wet ground, it can quickly drain water accumulated between the tire tread and the driving surface, preventing hydroplaning and improving driving safety; while when driving on snow, it can accommodate snow accumulation, increasing the friction between the tire tread and the snow.

[0045] In this embodiment, both walls of the fourth longitudinal groove 14 are provided with longitudinal chamfers 90, the inner walls of which are triangular (similar to the structure of the first strip chamfer 72). The longitudinal chamfers 90 on the two groove walls are provided in a one-to-one correspondence, and their widths decrease in opposite directions. In this way, when driving on wet surfaces, the triangular inner walls of the longitudinal chamfers 90 can increase the opening area of ​​the groove, improve drainage efficiency, and increase the ground contact area; while when driving on ice, the triangular inner walls can also form a tiny "serrated" structure to increase the friction between the tire tread and the icy and snowy road surface.

[0046] like Figure 1 As shown, the tread pattern 30 includes a central tread pattern 31, at least a portion of which coincides with the center surface S of the tire. A connecting groove 40 disposed on the central tread pattern 31 includes a central connecting groove 41, which comprises interconnected groove segments 411 and sipe segments 412. The groove segment 411 is disposed closer to the outer side of the tire than the sipe segment 412. Along the direction from the groove segment 411 to the sipe segment 412, the width and depth of the groove segment 411 gradually decrease. In this way, when the vehicle is driving on dry ground, the groove section 411 with gradually varying depth can increase the local rigidity of the tire (the rigidity is relatively greater at the shallower depth) to resist the sudden shear force generated when the vehicle is turning, and avoid tread chipping and damage caused by insufficient rigidity, thereby improving the tire's handling stability. When the vehicle is driving on wet ground, the connection of the central connecting groove 41 can allow water to flow and drain, reducing the risk of hydroplaning. When driving on snow, the deeper part of the groove section 411 can hold more snow, thereby reducing the amount of snow accumulation between the tread and the driving surface, and improving the tire's driving stability on snow.

[0047] like Figure 1As shown, the tire tread structure also includes a sipe assembly 70, which includes a first sipe 71 and a first chamfer 72. The two ends of the first sipe 71 are connected to two adjacent longitudinal grooves 10. The first chamfer 72 is disposed on the groove wall of the first sipe 71 and is aligned with the extending direction of the first sipe 71. Along the direction from the tread to the bottom of the first sipe 71, the width of the first chamfer 72 gradually decreases; along the direction from the outer side of the tire to the inner side of the tire, the width and depth of the first chamfer 72 gradually decrease, forming a second inclined surface on the inner wall of the first chamfer 72. The sipe assembly 70 is disposed on the central tread portion 31. In this way, the sipe assembly 70, while assisting in drainage and cutting the water film through the first sipe 71 to improve the tire's wet-weather driving ability, can also further balance the rigidity of the center tread portion 31, thereby increasing the contact area between the tread and the driving surface (i.e., during the process of the tread pressing and contacting the driving surface, the inner wall of the first chamfer 72 will come into contact with the driving surface), improving the flexibility of the center tread portion 31, ensuring that the center tread portion 31 can adapt to uneven icy and snowy road surfaces, and thus increasing the grip at the center tread portion 31. At the same time, the area of ​​the second inclined surface gradually decreases along the direction from the outer side of the tire to the inner side of the tire, that is, the part of the second inclined surface closer to the outer side of the tire has a relatively larger contact area with the driving surface, and the grip performance is relatively stronger, in order to adapt to the steering force of the outer part of the tread (relative to the tread closer to the outer side of the tire on the center surface S) (when steering, under the action of centrifugal force, the outer part of the tread is subjected to greater force), thereby helping to improve the tire's handling performance.

[0048] In this embodiment, the first chamfer 72 is a chamfered angle of the second inclined surface being a triangle.

[0049] In this embodiment, a first strip chamfer 72 is provided on both walls of the first groove 71, so as to... Figure 1 The inner sipes 70 are combined to form an approximately isosceles triangle shape, which helps to improve the overall aesthetics of the tire tread.

[0050] like Figure 1As shown, the transverse sipes 50 provided on the central tread portion 31 include a central transverse sipe 51. The extension direction of the central transverse sipe 51 forms a first angle A1 with the width direction of the tire, and the first angle A1 satisfies: 25°≤A1≤35°. The extension direction of the central connecting groove 41 forms a second angle A2 with the width direction of the tire, and the second angle A2 satisfies: 25°≤A2≤35°. The sipe group 70 provided on the central tread portion 31 includes a central sipe group 73. The extension direction of the first sipe 71 of the central sipe group 73 forms a third angle A3 with the width direction of the tire, and the third angle A3 satisfies: 25°≤A3≤35°. The first angle A1, the second angle A2, and the third angle A3 satisfy: A1>A3>A2. In this way, the above-mentioned arrangement causes the central lateral sipe 51, the central connecting groove 41 and the central sipe group 73 located on the central tread portion 31 to present different tilt angles, so as to further present different rigidity balance capabilities. This allows the central tread portion 31 to present different rigidity distributions in the circumferential direction of the tire, thereby further improving the tire's driving stability in complex road conditions (such as uneven surfaces on snowy roads).

[0051] In this embodiment, the central connecting groove 41 and the central sipe group 73 are arranged alternately in the circumferential direction of the tire, and the central transverse sipe 51 is located between the adjacent central connecting groove 41 and the central sipe group 73. The three are evenly distributed on the central tread portion 31.

[0052] In this embodiment, the first included angle A1 is 30°.

[0053] In this embodiment, the second included angle A2 is 28°.

[0054] In this embodiment, the third included angle A3 is 26°.

[0055] like Figure 1 As shown, the tread pattern 30 also includes an inner tread pattern 32 located between the central tread pattern 31 and the shoulder tread pattern 20. The inner tread pattern 32 is positioned closer to the inner side of the tire than the center surface S. A connecting groove 40 on the inner tread pattern 32 includes an inner connecting groove 42, which includes a first sub-groove 421 and a second sub-groove 422 that are interconnected. The first sub-groove 421 is positioned closer to the center surface S than the second sub-groove 422. The first sub-groove 421 forms a fourth angle A4 with the width direction of the tire, and the second sub-groove 422 forms a fifth angle A5 with the width direction of the tire. The fourth angle A4 and the fifth angle A5 satisfy: 3°≤A4≤7°, 32°≤A5≤38°. This configuration allows the inner connecting groove 42 to better guide water flow on wet and slippery surfaces, improving the tire's water drainage performance.

[0056] In this embodiment, the fourth included angle A4 is 5°.

[0057] In this embodiment, the fifth included angle A5 is 35°.

[0058] like Figure 1 , Figure 2 and Figure 4 As shown, the reinforcing structure 60 disposed within the inner connecting groove 42 includes an inner reinforcing structure 61, which is located at the bottom of the second sub-groove 422. The first inclined surface 63 of the inner reinforcing structure 61 is positioned opposite to the opening of the second sub-groove 422. The width of the first inclined surface 63 of the inner reinforcing structure 61 gradually decreases along the tire's circumference. This arrangement of the inner reinforcing structure 61 provides local compensation for the structural strength and stability of the inner tread pattern 32 at the second sub-groove 422, reducing abrupt deformation (such as abrupt shear force generated during tire steering) and abnormal wear at this location. This not only extends tire life but also improves driving safety.

[0059] like Figure 4 As shown, the depth H1 of the first sub-groove 421 is 3.5±0.5mm, and the depth H2 of the second sub-groove 422 and the depth H14 of the fourth longitudinal groove 14 satisfy the following condition: H14-1.8mm≤H2≤H14-1.5mm. Thus, the unequal depths of the first sub-groove 421 and the second sub-groove 422, along with their corresponding tilt angles, increase the contact area and friction between the tire tread and ice and snow (balancing rigidity and accommodating snow accumulation).

[0060] like Figure 2 As shown, the top view of the inner reinforcing structure 61 presents a triangle (first inclined surface 63), with vertices b and c having the same depth, while the depth of vertex a is less than the depths of vertices b and c, thus forming a triangular inclined surface whose height gradually decreases from vertex a to side bc. Simultaneously, the inclined surface also assists the groove in removing stones, extending the tire's service life.

[0061] In this embodiment, the transverse sipes 50 on the inner tread pattern are set as inner transverse sipes 52. The inner transverse sipes 52 and the second sub-groove 422 are arranged intersectingly to further separate the inner tread pattern 32. The inner transverse sipes 52 can increase the elasticity and deformation capacity of the inner tread pattern 32, and can better fit the ice and snow surface when driving on snow and ice, thus improving grip.

[0062] like Figure 1As shown, the tread pattern 30 also includes an outer tread pattern 33 located between the central tread pattern 31 and the shoulder tread pattern 20. The outer tread pattern 33 is positioned closer to the outer side of the tire than the central surface S. The connecting groove 40 provided on the outer tread pattern 33 includes the outer connecting groove 43. The outer connecting groove 43 includes a third sub-groove 431 and a fourth sub-groove 432 that are interconnected. The third sub-groove 431 is positioned closer to the central surface S than the fourth sub-groove 432. The third sub-groove 431 is positioned at a sixth angle A6 with the width direction of the tire, and the fourth sub-groove 432 is positioned at a seventh angle A7 with the width direction of the tire. The sixth angle A6 and the seventh angle A7 satisfy: 35°≤A6≤45°, 17°≤A7≤23°. The outer tread pattern 33 is provided with a sipe group 70. Thus, the larger included angle A6 of the sixth groove results in a greater inclination angle for the third sub-groove 431 near the center plane S. When turning on dry ground, this zigzag groove provides better lateral support, improving handling performance. It also aids in drainage.

[0063] In this embodiment, the sipes 70 provided on the outer tread pattern 33 are the outer sipes 74, and the outer sipes 74, the outer connecting groove 43 and the outer transverse sipes 53 are arranged alternately.

[0064] In this embodiment, the sixth included angle A6 is 40°.

[0065] In this embodiment, the seventh included angle A7 is 20°.

[0066] like Figure 1 and Figure 3 As shown, the reinforcing structure 60 disposed within the outer connecting groove 43 includes an outer reinforcing structure 62. The outer reinforcing structure 62 is disposed at the bottom of the outer connecting groove 43, with a portion of the outer reinforcing structure 62 located within a third sub-groove 431 and the other end located within a fourth sub-groove 432. The first inclined surface 63 of the outer reinforcing structure 62 is positioned opposite to the opening of the outer connecting groove 43. The width of the first inclined surface 63 of the outer reinforcing structure 62 gradually decreases along the circumference of the tire. The outer reinforcing structure 62 also structurally reinforces the outer tread pattern 33 at the outer connecting groove 43, preventing damage to the outer tread pattern 33 during tire cornering or under significant stress, thereby improving tire durability and driving safety.

[0067] like Figure 3As shown, the top view of the outer reinforcing structure 62 is approximately triangular, with vertices e and f having the same depth (1.5–2 mm from the bottom of the outer connecting groove 43), and vertex g having a depth of 3–5 mm from the tread. This means that the first inclined surface 63, from edge ef to vertex g, gradually increases in height. Simultaneously, the first inclined surface 63 of the triangle also helps to remove stones and extend tire life.

[0068] In this embodiment, the fourth sub-groove 432 has a transverse chamfer 100 on its groove wall (the inner wall has a triangular chamfer structure, consistent with the structure of the first strip chamfer 72). This chamfer design helps with drainage, cutting water film, and increasing the contact surface, thereby improving driving comfort and safety.

[0069] In this embodiment, the transverse slit 50 on the outer tread pattern portion 33 is designated as the outer transverse slit 53.

[0070] like Figure 1 and Figure 6 As shown, a shoulder tread portion 20 is provided near the outer side of the tire relative to the center surface S of the tire, which is called the outer shoulder tread portion 21. The connecting groove 40 provided on the outer shoulder tread portion 21 includes the outer shoulder connecting groove 44. The outer shoulder connecting groove 44 includes a fifth sub-groove 441 and a sixth sub-groove 442 that are connected to each other. The fifth sub-groove 441 is provided near the center surface S relative to the sixth sub-groove 442. The fifth sub-groove 441 is set at an eighth angle A8 with the width direction of the tire, and the sixth sub-groove 442 is set at a ninth angle A9 with the width direction of the tire. The eighth angle A8 and the ninth angle A9 satisfy: 17°≤A8≤23°, 3°≤A9≤7°. The fifth sub-groove 441 includes a first groove segment 4411 and a second groove segment 4412 that are interconnected. The first groove segment 4411 is positioned closer to the center surface S than the second groove segment 4412. The depth of the first groove segment 4411 is less than the depth of the second groove segment 4412, so that a first structural reinforcement 81 is formed at the bottom of the first groove segment 4411. Thus, when driving on snow and ice, the bent groove structure can increase the sharpness of the tire edge, enhance the ability to cut through ice and snow, and improve grip; while when driving on dry ground, it can also provide a certain degree of lateral support. At the same time, the first structural reinforcement 81 can locally reinforce the connecting points to better resist sudden shear forces, prevent tread blocks from falling off, and improve the tire's handling performance.

[0071] In this embodiment, the eighth included angle A8 is 20°.

[0072] In this embodiment, the ninth included angle A9 is 5°.

[0073] In this embodiment, the transverse slit 50 provided on the outer shoulder tread portion 21 is the outer shoulder transverse slit 55.

[0074] In this embodiment, the portion of the sixth sub-groove 442 within the total length TDW of the tire crown arc has a length L1 along the width direction of the tire, and the length L1 is 10 to 15 mm.

[0075] In this embodiment, the first groove segment 4411 has a length L2 in the width direction of the tire, L2 is 6 to 10 mm (the length of the first structural reinforcement 81), and the height H4 of the first structural reinforcement 81 is 3.5 to 4.5 mm.

[0076] In this embodiment, the shoulder tread portion 20, which is located near the inner side of the tire relative to the center surface S of the tire, is the inner shoulder tread portion 22. The connecting groove 40 provided on the inner shoulder tread portion 22 includes the inner shoulder connecting groove 45. The inner shoulder connecting groove 45 includes a seventh sub-groove 451 and an eighth sub-groove 452 that are connected to each other. The seventh sub-groove 451 is located near the center surface S relative to the eighth sub-groove 452. The seventh sub-groove 451 is set at a tenth angle A10 with the width direction of the tire, and the eighth sub-groove 452 is set at an eleventh angle A11 with the width direction of the tire. The tenth angle A10 and the eleventh angle A11 satisfy: 22°≤A10≤28°, 5°≤A11≤9°. The seventh sub-groove 451 includes interconnected third groove segment 4511, fourth groove segment 4512, and fifth groove segment 4513. The fourth groove segment 4512 is located between the third groove segment 4511 and the fifth groove segment 4513. The depths of the third groove segment 4511 and the fifth groove segment 4513 are both greater than the depth of the fourth groove segment 4512, forming a second structural reinforcement 82 at the bottom of the fourth groove segment 4512. Thus, when driving on snow and ice, the curved groove structure increases the sharpness of the tire edges, enhancing its ability to cut through ice and snow and improving grip; while when driving on dry ground, it also provides some lateral support. Simultaneously, the second structural reinforcement 82 can locally reinforce the connecting points to better resist sudden shear forces, prevent tread block breakage, and improve tire handling performance.

[0077] In this embodiment, the tenth included angle A10 is 25°.

[0078] In this embodiment, the eleventh included angle A11 is 7°.

[0079] In this embodiment, the transverse slit 50 provided on the inner shoulder tread pattern 22 is the inner shoulder transverse slit 54.

[0080] In this embodiment, the portion of the eighth sub-groove 452 within the total length TDW of the tire crown arc has a length L3 along the width direction of the tire, and the length L3 is 8 to 15 mm.

[0081] In this embodiment, the fourth groove segment 4512 has a length L4 in the width direction of the tire, L4 is 5 to 11 mm (the length of the second structural reinforcement 82), and the height H3 of the first structural reinforcement 81 is 3.5 to 4.5 mm.

[0082] In this embodiment, the width of the outer tread pattern 33 is (13.0±0.2)%TDW, the width of the center tread pattern 31 is (14.0±0.2)%TDW, and the width of the inner tread pattern 32 is (13.0±0.2)%TDW. This allows the wider center tread pattern 31 to provide stable straight-line guidance when the tire is traveling on a dry surface, resulting in a smoother ride. The width settings of the outer and inner tread patterns 33 and 32 help balance the forces acting on the tire during cornering, improving handling performance on wet and snowy surfaces. This effectively reduces the risk of sideslip when cornering on wet surfaces.

[0083] Within the total crown arc length (TDW) of the tire, the widths of the inner shoulder tread portion 22 and the outer shoulder tread portion 21 are equal and both are (9.3±0.2)% TDW. The wider shoulder tread portion 20 provides better lateral support when the tire is traveling at high speeds on dry surfaces, improving the vehicle's handling limits. On snow and ice, it increases the tire's contact area with the road surface, enhancing driving and braking capabilities.

[0084] To verify the effectiveness of this design, a tire using the tire tread structure in this embodiment and the original tire were subjected to performance tests. The test evaluation results are as follows:

[0085] Evaluation Project Original design tire Tire using the tire tread structure of this embodiment comfort 100 108 Wetland controllability 100 106 Dry handling 100 100 wet braking 100 107 Dry braking 100 102 Snow braking 100 120 Snow handling 100 115

[0086] Specifically, the results are compared by setting each performance metric of the original tire design to 100; a higher score indicates better performance. The actual testing involves evaluating the performance of identical test vehicles equipped with the aforementioned tires at test speeds on simulated urban roads within a professional test track.

[0087] This application also provides a tire (not shown) that employs the above-described tire tread structure.

[0088] As can be seen from the above description, the embodiments of this utility model achieve the following technical effects:

[0089] The longitudinal grooves of the tire tread structure extend circumferentially along the tire, and multiple longitudinal grooves are spaced apart along the width direction of the tire to divide the tire tread into multiple circumferential tread sections. These multiple circumferential tread sections include two shoulder tread sections and a crown tread section located between the two shoulder tread sections. Connecting grooves on the shoulder tread sections connect the longitudinal grooves and the sidewalls of the tire, and connecting grooves on the crown tread sections connect two adjacent longitudinal grooves. Lateral sipes have wavy or zigzag curved sections. A reinforcing structure is disposed within the connecting grooves and connected to the two groove walls of the connecting grooves. The reinforcing structure has a first inclined surface, which is used to limit and stop foreign objects entering the connecting grooves. In this way, the tire tread structure in this application actually forms a "snow and water network" through a large number of interconnected grooves arranged on the circumferential tread portion (the interconnected grooves set on the shoulder tread portion and the crown tread portion can respectively connect the longitudinal grooves and the side of the tire, and two adjacent longitudinal grooves), which greatly improves the tire's snow and water removal performance, thereby ensuring that the tire has high driving stability on wet and icy roads (reducing the probability of slippage). The large number of lateral grooves arranged on the circumferential tread portion can not only improve the tire's ability to cut water film, but also increase the overall friction of the tread to further adapt to wet or icy roads; on the other hand, it can balance the rigidity of the circumferential tread portion and increase the flexibility of the circumferential tread portion, ensuring that the tread can generate a sufficiently large interaction force (mainly friction) with the summer or winter road surface (winter road surface is icy and uneven). Building upon this, this application further incorporates a reinforcing structure within the connecting groove. This reinforcing structure connects the two groove walls, providing localized structural reinforcement to the weaker parts surrounding the connecting groove, enhancing structural strength and stability. While ensuring stable embedding of ice and snow at the edge of the connecting groove, it also provides stone removal and self-cleaning effects through the first inclined surface, extending tire lifespan. Therefore, the tire tread structure in this application not only possesses extremely high snow and water removal performance and generates sufficiently large interaction forces with the driving surface (initially adapting to straight-line driving on wet and slippery roads in summer and icy and snowy roads in winter), but also effectively compresses accumulated snow during cornering, improving vehicle steering stability on icy and snowy roads. This solves the problem of existing tires being unable to maintain stable driving under special road conditions in both summer and winter, reducing tire usage costs for users.

[0090] Obviously, the embodiments described above are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of this utility model.

[0091] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0092] It should be noted that the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in sequences other than those illustrated or described herein.

[0093] The above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A tire tread structure, characterized in that, include: Longitudinal grooves (10) extend along the circumference of the tire. There are multiple longitudinal grooves (10). The multiple longitudinal grooves (10) are spaced apart along the width direction of the tire to divide the tire tread into multiple circumferential tread portions. The multiple circumferential tread portions include two shoulder tread portions (20) and a crown tread portion (30) located between the two shoulder tread portions (20). The connecting groove (40) provided on the shoulder tread portion (20) is used to connect the longitudinal groove (10) and the side of the tire. The connecting groove (40) provided on the crown tread portion (30) is used to connect two adjacent longitudinal grooves (10). The transverse groove (50) has a curved section arranged in a wave-like or zigzag shape, and the transverse groove (50) is provided on the circumferential patterned part; A reinforcing structure (60) is disposed within the communicating groove (40) and connected to the two groove walls of the communicating groove (40); wherein the reinforcing structure (60) has a first inclined surface (63), the first inclined surface (63) being used to limit and stop foreign objects entering the communicating groove (40).

2. The tire tread structure according to claim 1, characterized in that, The tread pattern (30) includes a central tread pattern (31), at least a portion of which coincides with the center surface S of the tire. The connecting groove (40) provided on the central tread portion (31) includes a central connecting groove (41), which includes a groove segment (411) and a sipe segment (412) that are connected to each other. The groove segment (411) is provided closer to the outer side of the tire than the sipe segment (412). In the direction from the groove section (411) to the knife groove section (412), the width of the groove section (411) gradually decreases, and the depth of the groove section (411) gradually decreases.

3. The tire tread structure of claim 2, wherein, The tire tread structure also includes: The grooving assembly (70) includes a first grooving (71) and a first chamfer (72). The two ends of the first grooving (71) are respectively connected to two adjacent longitudinal grooves (10). The first chamfer (72) is disposed on the groove wall of the first grooving (71) and is consistent with the extension direction of the first grooving (71). Along the direction from the tread to the bottom of the first grooving (71), the width of the first chamfer (72) gradually decreases. Along the direction from the outer side of the tire to the inner side of the tire, the width of the first chamfer (72) gradually decreases and the depth of the first chamfer (72) gradually decreases to form a second inclined surface on the inner wall of the first chamfer (72). The central patterned part (31) is provided with the knife groove group (70).

4. The tire tread structure according to claim 3, characterized in that, The transverse slit (50) provided on the central tread portion (31) includes a central transverse slit (51), the extension direction of the central transverse slit (51) is set at a first angle A1 with the width direction of the tire, and the first angle A1 satisfies: 25°≤A1≤35°; The extension direction of the central connecting groove (41) is set at a second included angle A2 with the width direction of the tire, and the second included angle A2 satisfies: 25°≤A2≤35°; The groove group (70) provided on the central tread portion (31) includes a central groove group (73). The extension direction of the first groove (71) of the central groove group (73) is set at a third included angle A3 with the width direction of the tire. The third included angle A3 satisfies: 25°≤A3≤35°. Among them, the first included angle A1, the second included angle A2 and the third included angle A3 satisfy the following condition: A1 > A3 > A2.

5. The tire tread structure of claim 3 wherein, The tread pattern portion (30) further includes an inner tread pattern portion (32) located between the central tread pattern portion (31) and the shoulder tread pattern portion (20), the inner tread pattern portion (32) being disposed closer to the inner side of the tire relative to the center surface S. The connecting groove (40) provided on the inner crown tread portion (32) includes an inner connecting groove (42), the inner connecting groove (42) includes a first sub-groove (421) and a second sub-groove (422) that are connected to each other, the first sub-groove (421) is provided close to the center surface S relative to the second sub-groove (422); The first sub-groove (421) is set at a fourth angle A4 with respect to the width direction of the tire, and the second sub-groove (422) is set at a fifth angle A5 with respect to the width direction of the tire. The fourth angle A4 and the fifth angle A5 satisfy: 3°≤A4≤7°, 32°≤A5≤38°.

6. The tire tread structure according to claim 5, characterized in that, The reinforcing structure (60) provided in the inner connecting groove (42) includes an inner reinforcing structure (61), which is provided at the bottom of the second sub-groove (422). The first inclined surface (63) of the inner reinforcing structure (61) is provided opposite to the opening of the second sub-groove (422). Along the circumference of the tire, the width of the first inclined surface (63) of the inner reinforcing structure (61) gradually decreases.

7. The tire tread structure according to claim 5, characterized in that, The tread pattern portion (30) further includes an outer tread pattern portion (33) located between the central tread pattern portion (31) and the shoulder tread pattern portion (20), the outer tread pattern portion (33) being disposed closer to the outer side of the tire relative to the central surface S. The connecting groove (40) provided on the outer tread pattern (33) includes an outer connecting groove (43), which includes a third sub-groove (431) and a fourth sub-groove (432) that are interconnected. The third sub-groove (431) is located near the center surface S relative to the fourth sub-groove (432). The third sub-groove (431) is set at a sixth angle A6 with respect to the width direction of the tire, and the fourth sub-groove (432) is set at a seventh angle A7 with respect to the width direction of the tire. The sixth angle A6 and the seventh angle A7 satisfy: 35°≤A6≤45°, 17°≤A7≤23°. The outer tread pattern (33) is provided with the sipe group (70).

8. The tire tread structure according to claim 7, characterized in that, The reinforcing structure (60) disposed in the outer connecting groove (43) includes an outer reinforcing structure (62), which is disposed at the bottom of the outer connecting groove (43). A part of the outer reinforcing structure (62) is located in the third sub-groove (431), and the other end of the outer reinforcing structure (62) is located in the fourth sub-groove (432). The first inclined surface (63) of the outer reinforcing structure (62) is disposed opposite to the opening of the outer connecting groove (43). Along the circumference of the tire, the width of the first inclined surface (63) of the outer reinforcing structure (62) gradually decreases.

9. The tire tread structure according to claim 1, characterized in that, A shoulder tread portion (20) is provided near the outer side of the tire relative to the center surface S of the tire, which is called the outer shoulder tread portion (21). The connecting groove (40) provided on the outer shoulder tread portion (21) includes the outer shoulder connecting groove (44). The outer shoulder connecting groove (44) includes a fifth sub-groove (441) and a sixth sub-groove (442) that are connected to each other. The fifth sub-groove (441) is provided near the center surface S relative to the sixth sub-groove (442). The fifth sub-groove (441) is provided at an eighth angle A8 with the width direction of the tire. The sixth sub-groove (442) is provided at a ninth angle A9 with the width direction of the tire. The eighth angle A8 and the ninth angle A9 satisfy: 17°≤A8≤23°, 3°≤A9≤7°. The fifth sub-groove (441) includes a first groove segment (4411) and a second groove segment (4412) that are interconnected. The first groove segment (4411) is disposed close to the center surface S relative to the second groove segment (4412). The depth of the first groove segment (4411) is less than the depth of the second groove segment (4412) so that a first structural reinforcement (81) is formed at the bottom of the first groove segment (4411).

10. The tire tread structure according to claim 1, characterized in that, The shoulder tread portion (20) located near the inner side of the tire relative to the center surface S of the tire is the inner shoulder tread portion (22). The connecting groove (40) located on the inner shoulder tread portion (22) includes the inner shoulder connecting groove (45). The inner shoulder connecting groove (45) includes a seventh sub-groove (451) and an eighth sub-groove (452) that are connected to each other. The seventh sub-groove (451) is located near the center surface S relative to the eighth sub-groove (452). The seventh sub-groove (451) is located at a tenth angle A10 with the width direction of the tire. The eighth sub-groove (452) is located at an eleventh angle A11 with the width direction of the tire. The tenth angle A10 and the eleventh angle A11 satisfy: 22°≤A10≤28°, 5°≤A11≤9°. The seventh sub-groove (451) includes a third groove segment (4511), a fourth groove segment (4512), and a fifth groove segment (4513) that are interconnected. The fourth groove segment (4512) is located between the third groove segment (4511) and the fifth groove segment (4513). The depth of the third groove segment (4511) and the depth of the fifth groove segment (4513) are both greater than the depth of the fourth groove segment (4512), so that a second structural reinforcement (82) is formed at the bottom of the fourth groove segment (4512).

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