pneumatic tires

Abstract

Pneumatic tires, including: in a running surface section (1) a plurality of main grooves (9) running in a circumferential direction of the tire; a plurality of ribs (10) defined by the plurality of main grooves (9); wherein at least one rib (10) of the plurality of ribs (10) comprises a plurality of sipes (11) extending in a transverse direction of the tire; wherein the majority of lamellae (11) comprise a beveled lamella (12) with a beveled section (14) provided at least at one edge (12a, 12b) and a non-beveled lamella (13) without a beveled section (14) provided at one edge; wherein the beveled lamella (12) comprises an end section (12c) which terminates blindly in the at least one rib (10) and another end section (12d) which is connected to one of the plurality of principal grooves (9) arranged on each side of the at least one rib (10); wherein a plurality of the beveled sipes (12) which are connected to one of the plurality of main grooves (9) on each side of the at least one rib (10) are arranged alternately in the circumferential direction of the tire; wherein the non-beveled lamella (13) is arranged on at least one side in the circumferential direction of the tire close to the beveled lamella (12), and where a depth Cd of the beveled lamella and a depth Nd of the non-beveled lamella satisfy the ratio 1 < Nd / Cd ≤ 1.5.

Description

Technical field

[0001] The present invention relates to a pneumatic tire and in particular to a pneumatic tire with improved wet performance by developing shapes of sipes provided in its tread section. State of the art

[0002] Generally, a pneumatic tire includes a tread section equipped with numerous grooves and sipes to achieve wet grip. To improve braking performance, which is an indicator of tire performance on a wet road surface, the water drainage capacity of the grooves and sipes must be enhanced.

[0003] As a method for improving drainage performance, the provision of a chamfered section in the edge of a sipe provided in a tread section has been proposed (e.g., JP 2016-88469 A). In this case, the chamfered section acts as a drainage channel to improve the drainage performance of a ground contact area, thus improving the tire's wet performance. Unfortunately, in a configuration where a chamfered section is simply added to a sipe, the chamfered section is compressed due to the deformation of a tread section upon contact with the ground, rendering the chamfered section ineffective as a drainage channel. Therefore, adequate drainage performance may not be ensured.

[0004] US 2016 / 0236517 A1 discloses a pneumatic tire having a tread section provided with a plurality of circumferentially and continuously extending main grooves to separate a plurality of rib sections. The first crown section and the second crown section have a plurality of first crown sipes and second crown sipes, respectively. Each crown sipe comprises a sipe main body and a chamfered section extending radially outside the sipe main body. The chamfered section may extend laterally along one or both sides of the sipe. JP 2015 134 581 A discloses a pneumatic tire comprising a plurality of circumferential main grooves, which define a first rib section on the outermost side in the width direction of the tire and a second rib section on the inner side of the width direction of the tire relative to the first rib section. The second rib section comprises a plurality of chamfered and non-chamfered sipes extending from the circumferential main grooves and terminating within the second rib section. The chamfered sipes comprise a chamfered portion and a sipe portion and have a large rib area outside the respective tire circumference directions, while the non-chamfered sipes have a small rib area. DE 35 31 047 A1 also discloses a pneumatic tire with tread sections that are provided with grooves and beveled sipes. Summary of the invention: Technical problem

[0005] One object of the present invention is to provide a pneumatic tire with improved wet performance by developing shapes of sipes provided in its tread section. Solution to the problem

[0006] To fulfill the above-described objective, a pneumatic tire according to one embodiment of the present invention includes the following: in a tread section a plurality of main grooves running in a circumferential direction of the tire; a plurality of ribs, determined by the plurality of main grooves; wherein at least one rib of the plurality of ribs comprises a plurality of sipes running in a tire transverse direction; wherein the majority of lamellae include a beveled lamella with a beveled section provided at least at one edge and a non-beveled lamella without a beveled section provided at one edge; wherein the beveled lamella includes an end section which terminates blindly in the at least one rib, and another end section which is connected to one of the plurality of main grooves arranged on each side of the at least one rib; wherein a majority of the beveled sipes, which are connected to a majority of main grooves on each side of the at least one rib, are arranged alternately in the circumferential direction of the tire; and wherein the non-beveled sipe is arranged close to the beveled sipe on at least one side in the tire circumferential direction. A depth Cd of the beveled lamella and a depth Nd of the non-beveled lamella satisfy the ratio 1 < Nd / Cd ≤ 1.5. Advantageous effects of the invention

[0007] In one embodiment of the present invention, at least one rib of the plurality of ribs encloses the plurality of sipes extending in the transverse direction of the tire, and the sipes include the chamfered sipe with the chamfered section provided at least at one edge and the non-chamfered sipe without a chamfered section provided at one edge. This structure allows for improved drainage performance upon contact with the ground due to the chamfered sipe provided with a chamfered section, resulting in improved wet performance. Meanwhile, the non-chamfered sipe, which is not provided with a chamfered section, is located together in the same rib as the chamfered sipe, close to the chamfered sipe in the circumferential direction of the tire, so that the non-chamfered sipe carries a deformation of the tread section upon contact with the ground.This helps suppress crushing of a chamfered section of the beveled sipe. Furthermore, the beveled sipe includes an end section that terminates blindly in the rib, and the other end section, which connects to one of the main grooves located on each side of the rib. The beveled sipes connected to both of the main grooves located on each side of the rib are arranged alternately around the tire's circumference. This structure ensures a largely consistent ground contact area around the beveled sipe, effectively suppressing crushing of the chamfered section. This results in improved wet performance.

[0008] In one embodiment of the present invention, the distance L1 between the non-chamfered lamella closest to the chamfered lamella and the chamfered lamella in the circumferential direction of the tire is preferably from 2 mm to 15 mm. This effectively prevents crushing of a chamfered section of the chamfered lamella.

[0009] According to the invention, the depth Cd of the beveled lamella and the depth Nd of the non-beveled lamella preferably satisfy the ratio 1 < Nd / Cd ≤ 1.5. This effectively suppresses crushing of a beveled section of the beveled lamella.

[0010] In one embodiment of the present invention, an inclination angle θ fulfills C the beveled slat in relation to the tire circumference direction and an inclination angle θ N The ratio θ of the non-beveled lamella with respect to the tire circumference direction is preferably θC -30° ≤ θ N ≤ θ C + 30°. This effectively prevents crushing of a chamfered section of the beveled lamella.

[0011] In one embodiment of the present invention, the non-chamfered sipe is preferably arranged in the circumferential direction of the tire on each side of the chamfered sipe. This effectively prevents crushing of a chamfered section of the chamfered sipe.

[0012] In one embodiment of the present invention, the non-beveled lamella preferably increases gradually in width from a lower section towards an opening. This allows a crushing of a beveled section of the beveled lamella to be effectively supported.

[0013] In one embodiment of the present invention, an opening in the beveled lamella in a ground contact surface preferably has a width Cw of 1.6 mm to 4.8 mm. This ensures adequate drainage upon contact with the ground.

[0014] In one embodiment of the present invention, the chamfered section preferably has a rectangular cross-sectional shape in a cross-sectional view perpendicular to a direction of travel of the chamfered lamella. This allows a groove volume to be sufficiently protected against deformation of the running surface section upon contact with the ground, thus improving drainage performance.

[0015] In one embodiment of the present invention, the non-chamfered sipe preferably extends through the at least one rib in the transverse direction of the tire. This effectively prevents crushing of a chamfered section of the chamfered sipe.

[0016] In one embodiment of the present invention, the radius of curvature TR of an arc forming a tread profile and the radius of curvature RR of an outer outline of the at least one rib enclosing the chamfered lamella preferably satisfy the ratio TR > RR. This enables an improvement in the drainage performance of the rib upon contact with the ground, thus effectively improving wet performance.

[0017] In the embodiments of the present invention, a “regular rim” is a rim defined by a standard for each tire according to a system of standards that includes standards on which tires are based, and refers to a “standard rim” in the case of JATMA, a “design rim” in the case of TRA, and a “measuring rim” in the case of ETRTO. “Regular internal pressure” is an air pressure defined by standards for each tire according to a system of standards that includes standards on which tires are based, and refers to a “maximum air pressure” in the case of JATMA, to the maximum value in the “TIRE ROAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” table in the case of TRA, and to the “INFLATION PRESSURE” in the case of ETRTO.The "regular internal pressure" is 180 kPa for a tire on a passenger car. Brief description of the drawings Fig. Figure 1 is a cross-sectional meridian view showing an air tire according to an embodiment of the present invention. Fig. Figure 2 is a perspective view illustrating part of a tread section of a pneumatic tire according to an embodiment of the present invention. Fig. Figure 3 is a top view illustrating part of a tread section of a pneumatic tire according to an embodiment of the present invention. Fig. Figure 4 is a cross-sectional view along line XX of Fig. 3. Fig.Figure 5 is a cross-sectional view illustrating a modified example of a non-chamfered lamella formed in a tread section of a pneumatic tire according to an embodiment of the present invention. Fig. Figure 6 is a top view illustrating another modified example of a chamfered lamella and a non-chamfered lamella formed in a tread section of a pneumatic tire according to an embodiment of the present invention. Fig. Figure 7 is a cross-sectional view illustrating another modified example of a tread section of a pneumatic tire according to an embodiment of the present invention. Fig. Figures 8A to 8D each illustrate a different modified example of a chamfered lamella formed in a tread section of a pneumatic tire according to an embodiment of the present invention, and Fig. Figures 8A to 8D are each a cross-sectional view of each modified example. Fig. Figures 9A to 9F each illustrate a different modified example of a chamfered lamella and a non-chamfered lamella formed in a tread section of a pneumatic tire according to an embodiment of the present invention, and Fig. Figures 9A to 9F are each a top view of each modified example. Description of embodiments

[0018] Configurations of embodiments of the present invention are described in detail below with reference to the accompanying drawings. Fig. Figure 1 illustrates a pneumatic tire according to an embodiment of the present invention, and Fig. Figures 2 to 4 each illustrate a section of the tread of a pneumatic tire. Fig. 1 denotes CL a tire equator line. In Fig. 2 and Fig.3 denotes Tc a tire circumferential direction, and Tw denotes a tire lateral direction.

[0019] As in Fig. As illustrated in Figure 1, a pneumatic tire according to an embodiment of the present invention includes a tread section 1 extending in the circumferential direction of the tire in an annular shape, a pair of sidewall sections 2, 2 which are arranged on both sides of the tread section 1, and a pair of bead sections 3, 3 which are arranged inwards from the sidewall sections 2 in the radial direction of the tire.

[0020] A carcass layer 4 is arranged between the pair of bead sections 3, 3. The carcass layer 4 encloses a plurality of reinforcing cords running radially in the tire direction and is folded back from the inside of the tire to the outside of the tire around bead cores 5 arranged in the bead sections 3. A bead filler 6 with a triangular cross-sectional shape, formed from a rubber compound, is arranged on the outer circumference of the bead core 5.

[0021] A plurality of belt layers 7 are embedded on an outer circumferential side of the carcass layer 4 in the tread section 1. The belt layers 7 enclose a plurality of reinforcing cords inclined with respect to the tire's circumferential direction, the reinforcing cords of the different layers being arranged crosswise. The angle of inclination of the reinforcing cords in the belt layers 7 with respect to the tire's circumferential direction is in a range of, for example, 10° to 40°. Steel cords are preferably used as the reinforcing cords of the belt layers 7. To improve high-speed durability, at least one belt cover layer 8, formed by arranging reinforcing cords at an angle of, for example, no more than 5° with respect to the tire's circumferential direction, is arranged on an outer circumferential side of the belt layers 7.Preferably, nylon, aramid or similar organic glass fiber threads are used as the reinforcing cords of the belt cover layer 8.

[0022] The tread section 1 is also provided with a plurality of main grooves 9 extending in the direction of the tire's circumference. The main grooves 9 define a plurality of ribs 10 in the tread section 1. Fig. Figure 1 illustrates an example in which the tread section 1 is provided with three main grooves 9. The tread section 1 is preferably provided with three to five main grooves 9 to achieve drainage performance and ensure a ground contact area.

[0023] It should be noted that the tire internal structure described above is a typical example of a pneumatic tire and that pneumatic tires are not limited to this.

[0024] As in Fig.As illustrated in Figure 2, a rib 10 of the plurality of ribs 10 includes a plurality of sipes 11 extending transversely in the tire direction and blocks 20, which are defined by the plurality of sipes 11. The blocks 20 are arranged side by side in the circumferential direction of the tire. Meanwhile, a sipe 11 of the plurality of sipes 11 includes a chamfered sipe 12 and a non-chamfered sipe 13. The sipe 11 is a thin groove with a width of 0.5 mm to 1.6 mm and a depth of 2.0 mm or more when the tire is not mounted on a rim.

[0025] As in Fig. As illustrated in Figure 3, the beveled lamella 12 includes a beveled section 14 at at least one of the edges 12a, 12b. In the Fig. 2 and Fig.In the embodiment illustrated in Figure 3, the chamfer section 14 is provided at the edge 12a on one side along the entire length of the chamfered lamella 12. In other embodiments, the chamfer section 14 can be provided at the edges 12a and 12b on both sides, or it can be provided partially or discontinuously along one direction of the chamfered lamella 12. The chamfered lamella 12 includes an end section 12c that terminates blindly in the rib 10, and another end section 12d that is connected to one of the main grooves 9 and 9 arranged on each side of the rib 10. The beveled sipes 12, 12, which are connected to the corresponding main grooves 9, 9 arranged on each side of the rib 10, are arranged alternately in the circumferential direction of the tire, such that the beveled sipes 12 as a whole are arranged in an offset manner in the circumferential direction of the tire. As shown in Fig. As illustrated in Figure 4, the chamfered section 14 formed on the beveled lamella 12 has the shape of a triangle in a cross-sectional view perpendicular to the direction of the chamfered lamella 12. The section of the chamfered lamella 12 that excludes the chamfered section 14 has a depth of 1 mm or more.

[0026] The non-chamfered sipe 13 is positioned within 50 mm of the chamfered sipe 12 in the circumferential direction of the tire and is not chamfered. The non-chamfered sipe 13 is located close to at least one side of the chamfered sipe 12 in the circumferential direction of the tire. The non-chamfered sipe 13 may be inclined from the transverse direction of the tire or may be bent or curved.

[0027] Rib 10 can be provided with a different groove than the chamfered lamella 12 and the non-chamfered lamella 13. However, the drainage capacity in rib 10 can be adequately ensured by the chamfered lamella 12. Therefore, providing only the chamfered lamella 12 and the non-chamfered lamella 13 is preferable from the perspective of improving braking performance by increasing the ground contact area.

[0028] While a tread rubber with low hardness is advantageous for increasing the ground contact area, a tread rubber with high hardness is advantageous for suppressing the crushing of the chamfered section 14. To fulfill both requirements, the tread rubber preferably has a hardness of 58 to 75 as specified in JIS K6253.

[0029] In the pneumatic tire described above, at least one rib 10 and the majority of ribs 10 have a majority of sipes 11 extending in the transverse direction of the tire. The sipes 11 include the chamfered sipe 12, which is provided with the chamfer section 14 on at least one of its edges 12a, 12b, and the non-chamfered sipe 13, which has no chamfer on any edge. This structure improves the drainage performance when the tire contacts the ground due to the chamfered sipe 12 provided with the chamfer section 14, resulting in improved wet performance.The non-chamfered sipe 13, which has no chamfered section, is located in the same rib 10 as the chamfered sipe 12 and positioned close to the chamfered sipe 12 in the tire's circumferential direction, such that the non-chamfered sipe 13 carries a deformation of the tread section 1 upon contact with the ground. This helps to suppress the crushing of the chamfered section 14 of the chamfered sipe 12.

[0030] Furthermore, the chamfered sipe 12 includes an end section 12c that terminates blindly in the rib 10, and the other end section 12d, which is connected to one of the main grooves 9 arranged on each side of the rib 10. The chamfered sipes 12 connected to the main grooves 9 arranged on each side of the rib 10 are arranged alternately in the circumferential direction of the tire. This structure ensures a largely consistent ground contact area around the chamfered sipe 12, effectively suppressing crushing of the chamfered section 14 of the chamfered sipe 12. This improves wet performance.

[0031] As in Fig.As illustrated in Figure 3, in the case of the pneumatic tire, a distance in the circumferential direction between a recessed area of ​​the chamfered sipe 12, which encloses the chamfered section 14, and a recessed area of ​​the non-chamfered sipe 13 at a position closest to the chamfered sipe 12 is specified as a distance L1. The distance L1 is preferably from 2 mm to 15 mm and more preferably from 4 mm to 11 mm. If the distance L1 is appropriately determined as described above, crushing of the chamfered section 14 of the chamfered sipe 12 due to the non-chamfered sipe 13 can be effectively suppressed. If the distance L1 is less than 2 mm, the stiffness of the rib 10 decreases in a region between the chamfered sipe 12 and the non-chamfered sipe 13.This makes it difficult to ensure contact with the ground, which can lead to a decrease in wet performance.

[0032] In Fig. 3. The non-chamfered sipe 13 extends transversely through the rib 10 in the tire direction. If the non-chamfered sipe 13 is designed as an open sipe extending transversely through the rib 10, as described above, the non-chamfered sipe 13 can withstand more deformation of the tread section 1, thus effectively suppressing crushing of the chamfered section 14 of the chamfered sipe 12. Alternatively, the non-chamfered sipe 13 can be designed as a closed sipe with opposite ends that terminate blindly in the rib 10, or as a semi-closed sipe with only one end terminating blindly in the rib 10.

[0033] As in Fig.As illustrated in Figure 4, the depths of the chamfered lamella 12 and the non-chamfered lamella 13 from a ground contact surface to their groove bottoms are specified as a depth Cd and a depth Nd, respectively. According to the invention, the depth Cd of the chamfered lamella 12 and the depth Nd of the non-chamfered lamella 13 satisfy the ratio 1 < Nd / Cd ≤ 1.5. The ratio 1.1 < Nd / Cd ≤ 1.4 is more preferred. If the depth Nd of the non-chamfered lamella 13 is suitably determined with respect to the depth Cd of the chamfered lamella 12, as described above, crushing of the chamfered section 14 of the chamfered lamella 12 can be effectively suppressed.

[0034] As in Fig.As illustrated in Figure 4, the width of an opening in the beveled lamella 12 in the ground contact area is specified as a width Cw. The width Cw of the opening is measured along a direction perpendicular to the orientation of the beveled lamella 12. At this point, the width Cw of the opening is preferably between 1.6 mm and 4.8 mm. If the beveled lamella 12 is designed as described above, drainage performance upon contact with the ground can be ensured. If the width Cw of the opening in the beveled lamella 12 in the ground contact area is less than 1.6 mm, the improvement in drainage performance is minimal. If the width Cw is greater than 4.8 mm, the ground contact area is reduced, which tends to worsen braking performance on wet road surfaces.

[0035] Fig.Figure 5 illustrates a modified example of the non-chamfered sipe formed in the tread section of the pneumatic tire according to an embodiment of the present invention. As shown in Fig. As illustrated in Figure 5, the width of an opening in the non-beveled lamella 13 in the ground contact surface is given as a width Nw. The width Nw of the opening is measured along a direction perpendicular to the orientation of the non-beveled lamella 13. Fig. 5. The width Nw of the non-chamfered lamella 13 gradually increases from its lower section towards its opening. If the non-chamfered lamella 13 is designed as described above, it can withstand more deformation of the running surface section 1, thus effectively supporting compression of the chamfered section 14 of the chamfered lamella 12.

[0036] Fig.Figure 6 illustrates another modified example of the chamfered sipe and the non-chamfered sipe formed in the tread section of the pneumatic tire according to an embodiment of the present invention. As in Fig. As illustrated in Figure 6, the chamfered sipe 12 and the non-chamfered sipe 13 are inclined with respect to the tire's circumferential direction. The inclination angles of the chamfered sipe 12 and the non-chamfered sipe 13 with respect to the tire's circumferential direction are given as the inclination angle θ. C or as an angle of inclination θ N The angle of inclination θ is specified. C the beveled lamella 12 and the angle of inclination θ N The non-beveled lamella 13 fulfills the ratio θ C -30° ≤ θ N ≤ θ C +30°. If the inclination angles θ C and θ NAs described above, crushing of the chamfered section 14 of the chamfered lamella 12 can be effectively suppressed. The angle of inclination θ N The non-chamfered lamella 13 is specified in an area corresponding to a length of the chamfered lamella 12 in the tire transverse direction.

[0037] In Fig. 6. The non-chamfered sipes 13 are arranged in the circumferential direction of the tire on each side of the chamfered sipe 12. When the non-chamfered sipes 13 are arranged as described above, the non-chamfered sipe 13 can withstand more deformation of the tread section 1 of the non-chamfered sipe 13, so that crushing of the chamfered section 14 of the chamfered sipe 12 can be effectively suppressed.

[0038] Fig.Figure 7 illustrates another modified example of the tread section of the pneumatic tire according to an embodiment of the present invention. Fig.7 Each rib 10 is provided with a chamfered sipe 12 and a non-chamfered sipe 13 as described above. An outer outline, defining a road contact surface for each of the ribs 10, projects outward in the tire radial direction from an arc R. In a tire meridian cross-sectional view, the arc R passes through opposite endpoints E1 and E2 and E3 and E4 of two respective main grooves 9 arranged transversely in a tire center section. That is, the radius of curvature TR of the arc R, which forms a tread profile, and the radius of curvature RR of the outer outline of each of the ribs 10 with the chamfered sipe 12 satisfy the ratio TR > RR. This allows for an improvement in the drainage performance of the rib 10 upon contact with the road, thus effectively improving wet performance.The radius of curvature TR and the radius of curvature RR are measured when the tire is mounted on a regular rim and inflated to the regular internal pressure.

[0039] Fig. Figures 8A to 8D each illustrate a different modified example of the chamfered sipe formed in the tread section of the pneumatic tire according to an embodiment of the present invention. As shown in Fig.As illustrated in Figure 8A, in a cross-sectional view perpendicular to the direction of the chamfered lamella 12, the chamfered lamella 12 is provided on one side with a chamfer section 14, and the chamfer section 14 has a rectangular cross-sectional shape. If the chamfer section 14 is formed in a rectangular cross-sectional shape, as described above, the groove volume can be sufficiently protected against deformation of the running surface section 1 upon contact with the ground, thus improving drainage performance. Furthermore, other examples of a cross-sectional shape for the chamfer section 14 of the chamfered lamella 12 than those shown in each of the above figures are possible. Fig. 4 and Fig. Figure 8A illustrates a chamfered section that has an outline with an inwardly projecting curvature in the tire radial direction, as shown in Fig.Figure 8B illustrates a chamfer section having an outline with an outward curvature projecting in the tire radial direction, as shown in Fig. 8C illustrates, and a chamfered section with a triangular shape, as in Fig. 8D illustrated, include.

[0040] Fig. Figures 9A to 9F each illustrate a different modified example of chamfered and non-chamfered sipes formed in the tread section of the pneumatic tire according to an embodiment of the present invention. Other examples of shapes of chamfered sipes 12 and non-chamfered sipes 13 than those shown in each of the Fig. 2, Fig. 3 and Fig.Figure 6 illustrates a structure in which the non-beveled sipes 13 each have a length in the tire transverse direction corresponding to that of each of the beveled sipes 12, and the non-beveled sipes 13 each have an end that terminates blindly in the rib 10, as shown in Fig. Figure 9A illustrates a structure in which the non-beveled sipes 13 each have a length in the tire transverse direction corresponding to that of each of the beveled sipes 12, and two non-beveled sipes, each provided such that one end of theirs terminates blindly in the rib 10, are arranged facing each other, as in Fig. 9B illustrates a structure in which the non-chamfered sipes 13 are each inclined with respect to a tire transverse direction and each extend through the rib 10 in the tire transverse direction, as shown in Fig.9C illustrates this. The examples can also include a structure where the non-chamfered sipes 13 each enclose a curved section and extend transversely through the rib 10 in the tire direction, as shown in Fig. Figure 9D illustrates a structure in which the non-chamfered sipes 13 each have a curved shape and extend transversely through the rib 10 in the tire direction, as shown in Fig. Figure 9E illustrates a structure in which the non-chamfered sipes 13 each extend through the rib 10 in the tire transverse direction and the chamfered sipes 12 each enclose discontinuously provided chamfers 14, as shown in Fig. 9F illustrates. Examples

[0041] Using a pneumatic tire of size 195 / 65R15, which in a tread section includes a plurality of circumferential main grooves and a plurality of ribs defined by an adjacent pair of the plurality of main grooves, tires of a prior art example, comparative examples 1, 2 and examples 1 to 10 (examples 1 and 2 not according to the invention) were manufactured according to Tables 1 and 2, which show the following: whether a chamfered sipe is provided; whether a non-chamfered sipe is provided; a distance L1 (mm) between a chamfered sipe and a non-chamfered sipe; a ratio (Nd / Cd) of a depth of a non-chamfered sipe to a depth of a chamfered sipe; a difference (θ C - θ N) between the angles of inclination of a chamfered sipe and a non-chamfered sipe; the arrangement of a non-chamfered sipe (on one side or both sides); a width of a non-chamfered sipe (uniform or gradual increase); a width Cw (mm) of an opening of a chamfered sipe in a ground contact area; a cross-sectional shape of a chamfered section; whether a non-chamfered sipe is connected to a main groove; and whether a rib projects outwards in the tire radial direction.

[0042] These test tires were evaluated for braking performance on wet road surfaces according to the following evaluation procedure. The results are shown in Tables 1 and 2. Braking performance on wet road surfaces:

[0043] Each of the test tires, mounted on a wheel with a rim size of 15 × 6J, was tested on a front-wheel-drive passenger car with an engine displacement of 1500 cc.3 The tires were mounted, and the braking distance of the passenger car from an initial speed of 80 km / h to a complete stop was measured on a wet road surface with a water depth of 2 mm, using each of the test tires at an air pressure of 230 kPa. The evaluation results were expressed as index values ​​using the reciprocals of the measured values, with the prior art example set at 100. Higher index values ​​indicate superior braking performance on a wet road surface. [Table 1] Example of the state of the art Comparative example 1 Comparative example 2 Example 1 Example 2 Example 3 Example 4 Beveled slat provided Yes No No Yes Yes Yes Yes Non-beveled slat provided No No Yes Yes Yes Yes Yes Distance L1 (mm) between beveled lamella and non-beveled lamella - - - 20 10 10 10 Ratio of the depth of the non-beveled lamella to the depth of the beveled lamella (Nd / Cd) - - - 1,0 1,0 1,3 1,3 Difference between the inclination angles of the beveled lamella and the non-beveled lamella (θ) C - θ N ) - - - 50° 50° 50° 20° Arrangement of the non-beveled slat (on one side or both sides) - - - On one page On one page On one page On one page Width of the non-beveled lamella (uniform or gradual increase) Uniform Uniform Uniform Uniform Uniform Width Cw (mm) of the opening of the beveled lamella in the ground contact area 1,5 - - 1,5 1,5 1,5 1,5 Cross-sectional shape of the chamfered section triangle - - triangle triangle triangle triangle Runs through the non-beveled lamella to the main groove - - No No No No No Rib protrusion outwards in tire radial direction No No No No No No No Braking performance on wet road surfaces 100 95 96 103 104 105 106 [Table 2] Example 5 Example 6 Example 7 Example 8 Example 9 Example 10 Beveled slat provided Yes Yes Yes Yes Yes Yes Non-beveled slat provided Yes Yes Yes Yes Yes Yes Distance L1 (mm) between beveled lamella and non-beveled lamella 10 10 10 10 10 10 Ratio of the depth of the non-beveled lamella to the depth of the beveled lamella (Nd / Cd) 1,3 1,3 1,3 1,3 1,3 1,3 Difference between the inclination angles of the beveled lamella and the non-beveled lamella (θ) C - θ N ) 20° 20° 20° 20° 20° 20° Arrangement of the non-beveled slat (on one side or both sides) Both sides Both sides Both sides Both sides Both sides Both sides Width of the non-beveled lamella (uniform or gradual increase) Uniform Gradual increase Gradual increase Gradual increase Gradual increase Gradual increase Width Cw (mm) of the opening of the beveled lamella in the ground contact area 1,5 1,5 2,0 2,0 2,0 2,0 Cross-sectional shape of the chamfered section triangle triangle triangle rectangle rectangle rectangle Runs through the non-beveled lamella to the main groove No No No No Yes Yes Rib protrusion outwards in tire radial direction No No No No No Yes Braking performance on wet road surfaces 107 108 110 111 112 113

[0044] As can be seen from Tables 1 and 2, the tires of examples 1 to 10 have improved braking performance on wet road surfaces compared to the prior art example due to the shape of the sipes provided in the tread section.

[0045] In comparison example 1, a sufficient improvement in braking performance on a wet road surface could not be achieved due to the rib lacking any lamellae. In comparison example 2, a sufficient improvement in braking performance on a wet road surface could not be achieved due to the rib only featuring lamellae without chamfering. List of reference symbols 1 tread section 2 Side wall section 3 bead section 9 Main groove 10th rib 11 lamella 12 Beveled slat 12a, 12b Margin 12c, 12d Final section 13 Non-beveled lamella 14 Bevel section

Claims

[1] Pneumatic tyres comprising: in a tread section (1) a plurality of main grooves (9) extending in a tire circumferential direction; a plurality of ribs (10) defined by the plurality of main grooves (9); wherein at least one rib (10) of the plurality of ribs (10) comprises a plurality of sipes (11) extending in a tire transverse direction; wherein the plurality of slats (11) comprise a beveled slat (12) having a bevel portion (14) provided on at least one edge (12a, 12b) and a non-beveled slat (13) without a bevel portion (14) provided on an edge; wherein the beveled slat (12) comprises an end portion (12c) which blindly terminates in the at least one rib (10) and another end portion (12d) which is connected to one of the plurality of main grooves (9) arranged on each side of the at least one rib (10); wherein a plurality of the chamfered sipes (12) connected to one of the plurality of main grooves (9) on each side of the at least one rib (10) are arranged alternately in the tire circumferential direction; wherein the non-bevelled sipe (13) is arranged close to the bevelled sipe (12) on at least one side in the tire circumferential direction, and where a depth Cd of the bevelled slat and a depth Nd of the non-bevelled slat satisfy the relationship 1 < Nd / Cd ≤ 1.

5. [2] A pneumatic tire according to claim 1, wherein a distance L1 between the non-chamfered sipe (13) closest to the chamfered sipe (12) and the chamfered sipe (12) in the tire circumferential direction is from 2 mm to 15 mm. [3] A pneumatic tire according to claim 1 or 2, wherein an inclination angle θ C of the beveled sipe (12) with respect to the tire circumferential direction and an inclination angle θ N of the non-bevelled sipe (13) with respect to the tire circumferential direction, the ratio θ C - 30° ≤ θ N ≤ θ C + 30°. [4] A pneumatic tire according to any one of claims 1 to 3, wherein the non-chamfered sipe (13) is arranged on each side of the chamfered sipe (12) in the tire circumferential direction. [5] A pneumatic tire according to any one of claims 1 to 4, wherein the non-chamfered sipe (13) gradually increases in width from a lower portion toward an opening. [6] A pneumatic tire according to any one of claims 1 to 5, wherein an opening of the chamfered sipe (12) in a ground contact surface has a width Cw of 1.6 mm to 4.8 mm. [7] A pneumatic tire according to any one of claims 1 to 6, wherein the chamfer portion (14) has a rectangular cross-sectional shape in a cross-sectional view perpendicular to an extending direction of the chamfered sipe (12). [8] A pneumatic tire according to any one of claims 1 to 7, wherein the non-chamfered sipe (13) extends through the at least one rib (10) in the tire transverse direction. [9] A pneumatic tire according to any one of claims 1 to 8, wherein a radius of curvature TR of an arc constituting a tread pattern and a radius of curvature RR of an outer contour of the at least one rib (10) comprising the chamfered sipe (12) satisfy the relationship TR > RR.

Images