pneumatic tires

Abstract

To provide a pneumatic tire which can easily reduce air resistance and easily increase vehicle's forward propulsion force.SOLUTION: A tire 1 includes: a tread 10 having a ground contact surface; a first rib 51a provided at an outer periphery side between a first ground contact end at a vehicle inner side of the tread 10 and a first maximum width position at the vehicle inner side; and a second rib 51b provided at an outer periphery side between a second ground contact end at a vehicle outer side of the tread 10 and a second maximum width position at the vehicle outer side. A first height Hi of the first rib 51a is higher than a second height Ho of the second rib 51b.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a pneumatic tire. [Background technology]

[0002] Conventionally, a pneumatic tire is described in Patent Document 1. This tire achieves both good handling stability and reduced rolling resistance by making the radius of curvature of the curved portion of the buttress on the outer side in the tire width direction larger than the radius of curvature of the curved portion of the buttress on the inner side in the tire width direction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-171433 Summary of the Invention [Problem to be solved by the invention]

[0004] If it were possible to reduce the air resistance of a tire and increase the vehicle's propulsive force while the vehicle is running, the combined effect would significantly improve fuel efficiency. However, even if you refer to the above-mentioned Patent Document 1, you cannot gain any knowledge regarding reducing air resistance or increasing vehicle propulsive force. Therefore, an object of the present invention is to provide a pneumatic tire that can easily reduce air resistance and easily increase forward vehicle propulsive force. [Means for solving the problem]

[0005] In order to solve the above problems, the pneumatic tire of the present invention includes a tread having a contact surface, a first rib provided on the outer circumferential side between a first contact edge on the vehicle inner side of the tread and a first maximum width position on the vehicle inner side, and a second rib provided on the outer circumferential side between a second contact edge on the vehicle outer side of the tread and a second maximum width position on the vehicle outer side, wherein a first height of the first rib is higher than a second height of the second rib. Note that the above-mentioned inner side and outer side of the vehicle refer to a state in which the pneumatic tire is properly mounted on a vehicle. [Effects of the Invention]

[0006] In the pneumatic tire according to the present invention, the first rib provided on the vehicle inner side is high, so the first rib can act as an obstacle to the airflow from the front. This allows the first rib to disrupt the airflow, generating turbulent airflow between the vehicle and the tire inner side. This turbulent airflow can then be used to generate a propulsive force that propels the vehicle forward. Meanwhile, the second rib on the vehicle outer side is low, so the air from the front side is prevented from receiving force from the second rib. This allows the airflow to be smooth on the tire outer side, making it easier to reduce air resistance. This combined effect makes it easier to significantly improve fuel efficiency. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a half cross-sectional view including the width direction and the radial direction of a pneumatic tire according to one embodiment of the present invention. [Figure 2] 1 is a diagram illustrating vulcanization molding of a pneumatic tire. FIG. [Figure 3] FIG. 2 is a schematic cross-sectional view showing the shape of the outer edge of a pneumatic tire, the cross-sectional view including the radial direction and the width direction. [Figure 4] FIG. 4 is an enlarged cross-sectional view of the periphery of a first rib in FIG. 3. [Figure 5] FIG. 2 is a schematic cross-sectional view including the radial and width directions of a pneumatic tire, with the difference in shape between a first rib and a second rib exaggerated. [Figure 6]2 is an enlarged cross-sectional view showing the periphery of a first buttress located on the anti-serial side in the width direction of the pneumatic tire in the cross section of FIG. 1. FIG. [Figure 7] FIG. 2 is an enlarged cross-sectional view showing the peripheral portion of a second buttress located on the serial side in the width direction of the pneumatic tire in the cross section of FIG. 1. [Figure 8] FIG. 1 is a diagram illustrating the outer edge shapes of two pneumatic tires for which an air resistance simulation test was performed, in a cross section including the radial and width directions. [Figure 9] FIG. 4 is a diagram showing the distribution of air resistance in a first tire for which a simulation test was conducted. [Figure 10] FIG. 10 is a diagram showing the distribution of air resistance in a second tire for which a simulation test was conducted. [Figure 11] 1 is a diagram illustrating the direction of vehicle movement and the direction of wind flow. FIG. [Figure 12] 1 is a diagram illustrating forces that a normal tire receives from wind and a vehicle body when a vehicle is moving. [Figure 13] 1 is a diagram illustrating forces that a tire of the present disclosure receives from wind and a vehicle body when the vehicle is moving. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. It should be noted that, when multiple embodiments or variations are included below, it is assumed from the outset that new embodiments can be constructed by appropriately combining their characteristic features. In the following examples, the same components are designated by the same reference numerals in the drawings, and redundant explanations will be omitted. The drawings include schematic diagrams, and the dimensional ratios of the width, diameter, circumferential length, etc. of each component do not necessarily match between different drawings.

[0009] Furthermore, among the components described below, components that are not recited in the independent claims that represent the highest concepts are optional components and are not essential components. Furthermore, the present disclosure is not limited to the following embodiments and their modifications, and various improvements and modifications are possible within the scope of the claims of this application and their equivalents.

[0010] In the following description, the width direction refers to the width direction of the pneumatic tire 1, the radial direction refers to the radial direction of the pneumatic tire 1, and the circumferential direction refers to the circumferential direction of the pneumatic tire 1. The width direction, radial direction, and circumferential direction are perpendicular to one another. In the following description, when the terms "inside of a vehicle" and "outside of a vehicle" are used, this refers to a state in which the pneumatic tire 1 is properly mounted on a vehicle.

[0011] Fig. 1 is a half cross-sectional view including the width direction and the radial direction of a pneumatic tire 1 according to one embodiment of the present invention. The pneumatic tire (hereinafter simply referred to as tire) 1 has a shape on one side in the width direction that is different from the shape on the other side in the width direction. The tire 1 is mounted on a vehicle so that the left side of the paper surface of Fig. 1 is located on the inside of the vehicle.

[0012] As shown in FIG. 1, the tire 1 includes a tread 10, a pair of buttresses (a pair of shoulders) 11a, 11b, a pair of sidewalls 12a, 12b, and a pair of beads 13a, 13b. The tread 10 is disposed at the center in the width direction and includes a contact surface 10a that comes into contact with the road surface. The tread 10 is made of, for example, cross-linked rubber. A plurality of grooves 24 is provided on the outer peripheral surface of the tread 10. As is well known, the plurality of grooves 24 serve to drain rainwater that has entered between the road surface and the tire 1, thereby ensuring a contact area between the road surface and the tire 1.

[0013] The first buttress 11a, the first sidewall 12a, and the first bead 13a are portions that form the side surface of the tire 1 on the anti-serial side (the side facing the vehicle when the tire 1 is mounted on the vehicle). The second buttress 11b, the second sidewall 12b, and the second bead 13b are portions that form the side surface of the tire 1 on the serial side (the side facing the vehicle when the tire 1 is mounted on the vehicle).

[0014] The first buttress 11a, first sidewall 12a, and first bead 13a extend radially inward from the end of the tread 10 on the anti-serial side (tire inner side) in the width direction. The second buttress 11b, second sidewall 12b, and second bead 13b extend radially inward from the end of the tread 10 on the serial side (tire outer side) in the width direction. The outer peripheral surface of the tire 1 is formed by bonding together an annular tread rubber 61, an annular first sidewall rubber 62, an annular first buttress rubber 63, an annular second sidewall rubber 64, and an annular second buttress rubber 65. The tread rubber 61 includes the contact surface 10a, and the first sidewall rubber 62 includes a first maximum width position 66 on the vehicle inner side. The first buttress rubber 63 is located between a widthwise center 67 and the first maximum width position 66. The second sidewall rubber 64 includes a second maximum width position 68 on the vehicle outer side, and the second buttress rubber 65 is located between the widthwise center 67 and the second maximum width position 68. In this embodiment, the first ground contact edge E1 on the inner side in the width direction of the tire 1 is defined as the boundary position between the tread 10 and the first buttress 11a on the outer peripheral surface of the tire 1, and the second ground contact edge E2 on the outer side in the width direction of the tire 1 is defined as the boundary position between the tread 10 and the second buttress 11b on the outer peripheral surface of the tire 1. The boundary position between the first sidewall rubber 62 and the first buttress rubber 63 on the outer peripheral surface of the tire 1 is defined as the boundary position between the first buttress 11a and the first sidewall 12a on the outer peripheral surface of the tire 1. The boundary position between the second sidewall rubber 64 and the second buttress rubber 65 on the outer peripheral surface of the tire 1 is defined as the boundary position between the second buttress 11b and the second sidewall 12b on the outer peripheral surface of the tire 1. The sidewalls 12a, 12b are rubber layers between the buttresses 11a, 11b and the beads 13a, 13b, and are the most flexible parts of the tire 1. The sidewalls 12a, 12b protect the carcass 15 and prevent it from stretching. The ground contact edges E1, E2 refer to both widthwise ends of the part that comes into contact with the ground when the tire 1 is mounted on a standard rim, the internal pressure is adjusted to the standard internal pressure, and a standard load is applied (regarding standard rims, etc., the same as described in JP 2020-131965 A).

[0015] The buttresses 11a, 11b are shoulder portions of the tire 1, and protrude outward in the width direction from both widthwise ends of the tread 10 and extend radially inward. Similar to the tread 10, the buttresses 11a, 11b are provided in an annular shape along the circumferential direction. The sidewalls 12a, 12b extend radially inward from the buttresses 11a, 11b on both widthwise sides and are also provided in an annular shape along the circumferential direction. The sidewalls 12a, 12b include portions that protrude most outward in the width direction of the tire 1 (portions located at maximum width positions 66, 68), and are gently curved so as to convex outward.

[0016] The beads 13a, 13b extend radially inward from the sidewalls 12a, 12b on both sides in the width direction and are formed in an annular shape along the circumferential direction. The beads 13a, 13b are portions fixed to the rim of a wheel and constitute the inner circumferential portion of the tire 1. The beads 13a, 13b are gently curved so as to convex inward, and are located more inward in the width direction than the sidewalls 12a, 12b.

[0017] The tire 1 includes bead cores 26a, 26b and bead fillers 27a, 27b. The first bead core 26a and the first bead filler 27a are provided in the first bead 13a on the anti-serial side of the tire 1. The second bead core 26b and the second bead filler 27b are provided in the second bead 13b on the serial side of the tire 1. The bead cores 26a, 26b are ring-shaped members made of bundled steel wires covered with rubber. The bead fillers 27a, 27b are made of hard rubber and function to increase the rigidity of the beads 13a, 13b. The bead fillers 27a, 27b are arranged radially outward of the bead cores 26a, 26b.

[0018] FIG. 2 is a diagram illustrating the vulcanization molding of a tire 1. As shown in FIG. 2, the tire 1 is manufactured using a tire vulcanization mold (hereinafter simply referred to as a "mold") 30. The mold 30 has a circular ring shape. The mold 30 molds the outer surface of the tire 1. In FIG. 2, the mold 30 is illustrated together with the tire 1 that has been vulcanized.

[0019] The left side of the mold 30 in Fig. 2 is a portion for vulcanizing and molding the anti-serial side in the width direction of the tire 1. The right side of the mold 30 in Fig. 2 is a portion for vulcanizing and molding the serial side in the width direction of the tire 1.

[0020] The mold 30 includes a cylindrical sector mold 31 and a pair of annular side molds 32a, 32b located radially inward of the sector mold 31. The pair of side molds 32a, 32b are spaced apart in the width direction. The first side mold 32a is used to vulcanize and mold the anti-serial side of the tire 1 in the width direction, and includes an annular first side plate 36a and an annular first bead ring 38a. The second side mold 32b is used to vulcanize and mold the serial side of the tire 1 in the width direction, and includes an annular second side plate 36b and an annular second bead ring 38b.

[0021] The sector mold 31 and the side molds 32a, 32b have approximately the same axis A extending in the width direction. The internal space defined by the sector mold 31 and the pair of side molds 32a, 32b forms a cavity 33 in which a green tire before vulcanization that constitutes the tire 1 is set. After the green tire is set in the cavity 33, high-temperature gas, for example, high-temperature steam, is supplied to the cavity 33 through a supply pipe (not shown). In this manner, the green tire is subjected to a vulcanization process.

[0022] The sector mold 31 is movable in the radial direction indicated by the arrow α around the axis A. The inner peripheral surface of the sector mold 31 includes a tread molding surface 35 that molds the outer peripheral surface of the tread 10. A pair of side plates 36a, 36b are disposed radially inside the sector mold 31 so as to be able to come into contact with the sector mold 31. The first side plate 36a is fixed and immovable. The second side plate 36b is movable in the width direction indicated by the arrow β by a drive mechanism (not shown). The inner surface of the first side plate 36a includes a first sidewall molding surface 37a that molds the outer surface of the first sidewall 12a on the anti-serial side, and the inner surface of the second side plate 36b includes a second sidewall molding surface 37b that molds the outer surface of the second sidewall 12b on the serial side.

[0023] The first bead ring 38a is disposed radially and widthwise inward of the first side plate 36a so as to be able to come into contact with the first side plate 36a in the width direction. The second bead ring 38b is disposed radially and widthwise inward of the second side plate 36b so as to be able to come into contact with the second side plate 36b in the width direction. The first bead ring 38a is integrated with the first side plate 36a and immovably fixed thereto. The second bead ring 38b is integrated with the second side plate 36b and is movable in the width direction together with the second side plate 36b. The inner surface of the first bead ring 38a includes a first bead molding surface 39a that molds the outer surface of the first bead 13a. The inner surface of the second bead ring 38b includes a second bead molding surface 39b that molds the outer surface of the second bead 13b.

[0024] As shown in FIG. 2, the shape of the inner peripheral surface of the sector mold 31 is asymmetric on both sides in the width direction. The shape of the inner molding surface located on the inner side in the width direction of the first side plate 36a is also different from the shape of the outer molding surface located on the inner side in the width direction of the second side plate 36b. Specifically, a first annular recess 41a with a beak-shaped (triangular cross section) cross section is present inside the mating portion between the sector mold 31 and the first side plate 36a. A second annular recess 41b with a beak-shaped (triangular cross section) cross section is also present inside the mating portion between the sector mold 31 and the second side plate 36b. In this context, the depth of the first annular recess 41a is greater than the depth of the second annular recess 41b.

[0025] 2, the depth of the first annular recess 41a is greater than the depth of the second annular recess 41b. When the tire center B is located on the axis A and is positioned at a position that coincides with the widthwise center of the tire 1, the distance from the tip of the first annular recess 41a to the tire center B is approximately the same as the distance from the tip of the second annular recess 41b to the tire center B.

[0026] FIG. 3 is a schematic cross-sectional view showing the shape of an outer edge 51 of the tire 1, and is a schematic cross-sectional view including the radial direction and the width direction. Note that grooves 24 are not shown in FIG. 3. As shown in FIG. 3, the tire 1 has an annular first rib 51a corresponding to the first annular recessed portion 41a on the first buttress 11a on the anti-serial side (inner side of the tire). The first rib 51a has a beak shape (triangular shape) in the cross section of FIG. 3 and protrudes radially outward and widthwise outward of the tire 1 (toward the vehicle center in the width direction). The tire 1 also has an annular second rib 51b corresponding to the second annular recessed portion 41b on the second buttress 11b on the anti-serial side (outer side of the tire). The second rib 51b has a beak shape (triangular shape) in the cross section of FIG. 3 and protrudes radially outward and widthwise outward of the tire 1 (toward the vehicle center in the width direction). The first height Hi of the first rib 51a is greater than the second height Ho of the second rib 51b.

[0027] The height of a rib may be defined, for example, as follows. The definition of the height of a rib will be explained below using the first rib 51a. FIG. 4 is an enlarged cross-sectional view of the periphery of the first rib 51a in FIG. 3. In the cross-section shown in FIG. 4, let M1 be the point where the curve 53a drawn by the outer edge of the first buttress 11a connects to the bottom of the first rib 51a. When a tangent to the curve 53a approaches point M1 from the radially inner side, let N1 be the innermost tangent. Also, let N2 be a straight line that is parallel to this tangent N1 and passes through the tip M2 of the first rib 51a. In this case, the distance l1 between the tangent N1 and the straight line N2 may be defined as the height of the first rib 51a. Alternatively, when the first rib 51a has a triangular shape as shown in Figure 4 in a cross section including the radial and width directions of the tire 1, and two bases M1 and M3 can be determined in the cross section, the height of the first rib 51a may be defined as the distance l2 between the line segment N3 connecting one base M1 and the other base M3 and the tip M2 of the first rib 51a.

[0028] FIG. 5 is a schematic cross-sectional view of the tire 1, including the radial direction and width direction, in which the difference in shape between the first rib 51a and the second rib 51b is exaggerated. As shown in FIGS. 3 and 5, the first height Hi of the first rib 51a is greater than the second height Ho of the second rib 51b. This corresponds to the fact that the depth of the first annular recess 41a is greater than the depth of the second annular recess 41b in FIG. 2. In this embodiment, the relationship 1.0 mm≦(Hi−Ho)≦3.0 mm is set. This condition can be achieved, for example, by setting Ho to 0.8 mm and Hi to 1.8 to 3.8 mm, or by setting Ho to 0.5 to 1.1 mm and Hi to 1.5 to 4.1 mm. Note that the relationship 1.0 mm≦(Hi−Ho)≦3.0 mm is preferred, although it may be outside the range of 1.0 mm≦(Hi−Ho)≦3.0 mm. The reason why it is preferable to satisfy 1.0 mm≦(Hi−Ho)≦3.0 mm will be explained later.

[0029] Fig. 6 is an enlarged cross-sectional view showing the periphery of a first buttress 11a located on the anti-serial side in the width direction of the tire 1 in the cross section of Fig. 1. Fig. 7 is an enlarged cross-sectional view showing the periphery of a second buttress 11b located on the serial side in the width direction of the tire 1 in the cross section of Fig. 1. As shown in Figs. 6 and 7, the tire 1 includes a carcass 15, a belt 16, a belt reinforcing material 17, and an inner liner 18.

[0030] The carcass 15 is a cord layer covered with rubber. The carcass 15 includes carcass plies and forms a tire framework that can withstand loads, impacts, air pressure, etc. The carcass 15 has a radial structure in which carcass cords are arranged extending in a direction perpendicular to the circumferential direction. The carcass 15 is covered and protected by the five rubber materials 61 to 65 described above.

[0031] The carcass plies 15a and 15b constituting the carcass 15 are laid across a pair of bead cores 26a and 26b from the inner side in the width direction and are folded back toward the sidewalls 12a and 12b so as to envelop the bead cores 26a and 26b and the bead fillers 27a and 27b. In the example shown in FIGS. 6 and 7, the carcass 15 includes two carcass plies 15a and 15b. As shown in FIG. 1, the ply end 24a of the first carcass ply 15a closer to the bead cores 26a and 26b is located at the beads 13a and 13b, and the ply end 24b of the second carcass ply 15b is located at the sidewalls 12a and 12b. Note that the carcass may have only one carcass ply, but in this case, the ply end of the carcass ply is generally located at the sidewall.

[0032] The belt 16 is disposed between the tread 10 and the carcass 15. In the width direction, the belt 16 is installed over the entire area where the belt 16 radially overlaps the tread 10 and over some areas of the buttresses 11a and 11b. The belt 16 is a reinforcing band stretched in the circumferential direction, and it tightens the carcass 15 to increase the rigidity of the tread 10. The belt 16 has a two-layer structure, for example, made of a steel belt including a steel cord, and includes two steel belts 16a and 16b. However, the number of belts to be stacked is not limited to two. In addition, a belt including a tire cord using aramid fiber may be used instead of the steel belt. Alternatively, the belt may be configured with only one layer. By providing the belt 16, the rigidity of the tire 1 can be ensured, and the contact state between the tread 10 and the road surface can be improved.

[0033] The belt reinforcement 17 is disposed between the belt 16 and the tread 10. The belt reinforcement 17 has, for example, a two-layer structure and includes two cap plies 17a and 17b. The cap plies 17a and 17b are formed of insulating organic fiber layers such as polyamide fiber and are covered with a topping rubber. The belt reinforcement 17 is installed for purposes such as improving durability and reducing road noise during driving. The number of layered cap plies is not limited to two. The belt reinforcement 17 is disposed over the entire area of ​​the position radially overlapping the tread 10 and over a portion of the buttresses 11a and 11b in the width direction. The outer end 22 of the belt reinforcement 17 extends outward in the width direction beyond the belt 16. The inner liner 18 is a rubber layer for maintaining air pressure and is attached to the inner surface of the carcass 15. The inner liner 18 is formed of, for example, air-resistant rubber and prevents air from leaking from the tire cavity to the outside.

[0034] 6 and 7, the tire 1 has buttresses 11a, 11b with different rubber thicknesses on the serial side (outside of the tire) and the anti-serial side (inside of the tire). The rubber thickness of the first buttress 11a on the anti-serial side, without considering the first rib 51a, is thinner than the rubber thickness of the second buttress 11b on the serial side, without considering the second rib 51b. Therefore, the value Hbi [mm] (see FIG. 6) obtained by subtracting the first height Hi (the value obtained by subtracting FIG. 5) from the shortest distance between the tip of the first rib 51a and the carcass 15 is smaller than the value Hbo [mm] (see FIG. 7) obtained by subtracting the second height Ho (the value obtained by subtracting FIG. 5) from the shortest distance between the tip of the second rib 51b and the carcass 15.

[0035] <Tire air resistance simulation test> An air resistance simulation test was conducted using two different tires. A tire having a cross-sectional shape shown by the solid line in FIG. 8 and an annular rib 72 on the serial side (outer side of the tire) buttress 71 was used as the first tire 70. The height of the annular rib 72 was 0.8 mm. A tire having a cross-sectional shape shown by the dotted line in FIG. 8 and no rib on the serial side (outer side of the tire) buttress 81 was used as the second tire 80.

[0036] Fig. 9 is a diagram showing the distribution of air resistance in the first tire 70, and Fig. 10 is a diagram showing the distribution of air resistance in the second tire 80. In Figs. 9 and 10, the region R L is the area of ​​low air resistance, and the area R is shown as a high density dot area. H 9 and 10, the first tire 70 having a rib has high air resistance on the outer side of the vehicle except for the lateral underside of the tire. In contrast, the second tire 80 having no rib has low lateral air resistance over the entire tire area, and the area R K The air resistance on the upper side of the tire, indicated by , has been significantly reduced.

[0037] This confirmed that increasing the height of the buttress rib causes the rib to obstruct the airflow from the front, disrupting the airflow and making it easier for turbulence to occur, resulting in increased air resistance. Conversely, decreasing the height of the buttress rib reduces the force exerted by the second rib on the air from the front, resulting in smoother airflow and reduced air resistance. Furthermore, it was confirmed that a rib height of 0.8 mm can cause the rib to act as a significant obstruction to the airflow, effectively disrupting the airflow and generating turbulence. It was also confirmed that a 0.8 mm difference in rib height between the outer and inner sides of the tire significantly reduces air resistance on the outer side of the tire.

[0038] <Configuration of the tire disclosed herein and its effects> [Essential Configurations of the Tire of the Present Disclosure and Their Functions and Effects] As shown in Fig. 1, the tire 1 includes a tread 10 having a contact surface 10a, a first rib 51a provided on the outer circumferential side between a first contact edge E1 on the vehicle inner side of the tread 10 and a first maximum width position 66 on the vehicle inner side, and a second rib 51b provided on the outer circumferential side between a second contact edge E2 on the vehicle outer side of the tread 10 and a second maximum width position 68 on the vehicle outer side. Also, as shown in Fig. 3, a first height of the first rib 51a is higher than a second height of the second rib 51b.

[0039] As shown in FIG. 11, assume that vehicles 90a, 90b are moving in the direction of arrow C, and tires 91, 1 are subjected to a wind flow that flows in the opposite direction to the direction of movement of the vehicles 90a, 90b, as indicated by arrow D. If tire 91 is a normal tire with the same shape on both the serial and anti-serial sides, as shown in FIG. 12, when turbulence occurs on the vehicle 90a side (IN side) of tire 91, this turbulence receives force from below vehicle 90a, generating a vortex indicated by arrow E. This vortex then flows in the same direction as the tire's traveling direction on the tire side, pushing tire 91 in the traveling direction, resulting in the generation of a propulsive force. On the other hand, on the outside (OUT side) where vehicle 90a is not present, there is no object that applies force to the turbulent flow, so the vortex indicated by arrow F becomes smaller, resulting in a smaller propulsive force and increased air resistance.

[0040] In contrast, suppose tire 1 is a tire according to the present disclosure, in which the height of first rib 51a on the anti-serial side is higher than the height of second rib 51b on the serial side. Then, as shown in FIG. 13 , on the anti-serial side, the tall first rib 51a effectively blocks the smooth flow of wind, making turbulence more likely to occur. The resulting vortexes can generate a large propulsive force. Furthermore, on the serial side, the height of second rib 51b is low, allowing it to deflect the wind and smooth the wind flow, resulting in a significant reduction in air resistance. Therefore, both an increase in the propulsive force of vehicle 90b and a reduction in air resistance of tire 91 can be achieved during vehicle travel, resulting in a synergistic effect that significantly improves fuel efficiency.

[0041] [Configurations and Effects Preferable to be Adopted in Tires of the Present Disclosure] It is preferable that 1.0 mm≦(Hi−Ho)≦3.0 mm be satisfied.

[0042] If the first height Hi of the first rib 51a and the second height Ho of the second rib 51b are significantly different, the difference in rigidity between the inner and outer sides of the tire will be greater, resulting in a greater difference in tire flex between the inner and outer sides of the tire when the vehicle corners, making it difficult to corner smoothly and affecting ride comfort. This also increases the likelihood of uneven wear and a deterioration in tire uniformity. On the other hand, if the difference between the first height Hi of the first rib 51a and the second height Ho of the second rib 51b is small, it will be difficult to achieve the effects of the present disclosure.

[0043] In contrast, with this configuration, (Hi-Ho)≦3.0 mm, the difference in stiffness between the inner and outer sides of the tire is not excessively large, and the difference in tire flex between the inner and outer sides of the tire during cornering is suppressed. This facilitates smooth cornering and improves ride comfort. It also reduces uneven wear and improves tire uniformity.

[0044] Furthermore, since 1.0 mm≦(Hi-Ho) and (Hi-Ho) is greater than 0.8 mm, which was effective in reducing air pressure in simulation tests, it is possible to effectively increase the vehicle's propulsive force while the vehicle is running and reduce the tire's air resistance, making it easier to significantly reduce fuel consumption.

[0045] The tire 1 includes a pair of bead cores 26a, 26b spaced apart in the width direction, and a carcass 15 stretched across the pair of bead cores 26a, 26b. It is preferable that a value Hbi obtained by subtracting the first height Hi from the shortest distance between the tip of the first rib 51a and the carcass 15 is smaller than a value Hbo obtained by subtracting the second height Ho from the shortest distance between the tip of the second rib 51b and the carcass 15.

[0046] This configuration makes it possible to balance the thickness of the first buttress 11a on the vehicle inner side and the thickness of the second buttress 11b on the vehicle outer side, making them closer to uniform thickness. This makes it possible to improve the response continuity (linearity) in handling stability when the load on the tire shifts or a slip angle occurs, such as when cornering or changing lanes. [Explanation of symbols]

[0047] 1 tire, 10 tread, 10a contact surface, 11a first buttress, 11b second buttress, 12a first sidewall, 12b second sidewall, 13a first bead, 13b second bead, 15 carcass, 15a first carcass ply, 15b second carcass ply, 16 belt, 16a, 16b steel belt, 17 belt reinforcement, 17a, 17b cap ply, 18 inner liner, 26a first bead core, 26b second bead core, 27a first bead filler, 27b second bead filler, 30 mold, 31 sector mold, 32a first side mold, 32b second side mold, 33 cavity, 36a first side plate, 36b Second side plate, 38a first bead ring, 38b second bead ring, 41a first annular recess, 41b second annular recess, 51a first rib, 51b second rib, 66 first maximum width position, 68 second maximum width position, 70 first tire, 71 buttress, 72 annular rib, 80 second tire, 81 buttress, 90a, 90b vehicle, E1 first ground contact edge, E2 second ground contact edge, Hbi value obtained by subtracting the first height of the first rib from the shortest distance between the tip of the first rib and the carcass, Hbo value obtained by subtracting the second height of the second rib from the shortest distance between the tip of the second rib and the carcass, Hi first height of the first rib, Ho second height of the second rib.

Claims

1. a tread having a contact surface; a first rib provided on an outer circumferential side between a first ground contact end on a vehicle inner side of the tread and a first maximum width position on the vehicle inner side; a second rib provided on an outer peripheral side between a second ground contact end on a vehicle outer side of the tread and a second maximum width position on the vehicle outer side, A pneumatic tire, wherein a first height of the first rib is greater than a second height of the second rib.

2. The pneumatic tire according to claim 1, wherein 1.0 mm≦(the first height−the second height)≦3.0 mm is satisfied.

3. a pair of bead cores spaced apart in the width direction; a carcass that is stretched over the pair of bead cores, 3. The pneumatic tire according to claim 1, wherein a value obtained by subtracting the first height from the shortest distance between the tip of the first rib and the carcass is smaller than a value obtained by subtracting the second height from the shortest distance between the tip of the second rib and the carcass.

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