Pneumatic tire

Abstract

To provide a pneumatic tire which can improve drainability, for example, in a case of a high load typed vehicle.SOLUTION: A pneumatic tire includes a tread 30. The tread 30 includes: a tread rubber 37; a contact area 38 where the tread rubber 37 contacts with a road surface; a pair of ground contact ends which are ends of the contact area 38 at outer sides in a tire axial direction; and a belt 31 which is arranged at an inner side of the tread rubber 37 in a tire radial direction. In a half cross section in the axial direction, the end 32b of the belt 31 at the outer side in the tire axial direction is arranged at the outer side in the tire axial direction relative to a contact end 38b at 130% load of the maximum load based on the tire standard ETRTO.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] A pneumatic tire mounted on a vehicle generally has a structure in which sidewalls extend radially outward of the tire from each of a pair of beads, which are portions mounted on a rim of a tire wheel, and a tread that contacts the road surface is disposed between outer ends in the radial direction of the tire of these sidewalls. Although a pneumatic tire is mainly formed of rubber, in order to ensure rigidity and durability, a carcass ply is embedded between a pair of beads inside the tire, and a belt is embedded in the tread (see Patent Document 1, etc.).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] One of the performances of a pneumatic tire is drainage performance. By the way, vehicle types such as hybrid vehicles and EVs (Electric Vehicles) that have been increasingly popular in recent years are heavier than conventional engine-driven passenger cars. Therefore, in such high-load vehicles, for example, even when a load exceeding 100% of the maximum load is assumed, an improvement in drainage performance is required. The tread pattern including a large number of grooves formed on the ground contact surface of the tread and the profile of the tread in the tire axial direction cross section are factors greatly related to drainage performance. Since the belt in the tread affects the profile of the tread, it is a member that affects drainage performance.

[0005] The object of the present invention is to provide a pneumatic tire in which drainage performance is improved, even in the case of, for example, a high load vehicle.

Means for Solving the Problems

[0006] The pneumatic tire of the present invention is a pneumatic tire provided with a tread, and the tread includes tread rubber, a ground contact surface where the tread rubber contacts the road surface, a pair of ground contact ends that are the outer ends of the ground contact surface in the tire axial direction, and a belt disposed on the inner side of the tread rubber in the tire radial direction. In the tire axial direction half cross section, the outer end of the belt in the tire axial direction at the maximum width of the belt is disposed on the outer side in the tire axial direction with respect to the ground contact end when the load is 130% of the maximum load in the tire standard ETRTO.

Effects of the Invention

[0007] According to the present invention, it is possible to provide a pneumatic tire in which drainage performance is improved, even in the case of, for example, a high load vehicle.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Mode for Carrying Out the Invention

[0009] Hereinafter, embodiments will be described with reference to the drawings. FIG. 1 is a view showing the internal structure of a tire 1 which is a pneumatic tire for a vehicle according to an embodiment, and shows a half cross section in the tire axial direction. This tire 1 is suitable as a tire for a passenger car, and among them, it is more suitable as a tire for a relatively high load passenger car such as an EV.

[0010] The cross-sectional view of FIG. 1 is a cross-sectional view in the tire axial direction of the tire 1 in a no-load state where the tire 1 is mounted on a regular rim (not shown) and filled with a regular internal pressure.

[0011] A regular rim is a rim defined by tire specifications. In the case of ETRTO, it is the "Measuring Rim". The regular internal pressure is the air pressure defined by tire specifications. In the case of truck and light truck tires, if it is ETRTO, it is "INFLATION PRESSURE". In the case of passenger car tires, it is usually 180 kPa, but in the case of tires marked with Extra Load or Reinforced, it is 220 kPa.

[0012] The internal structure of Tire 1 is basically symmetric about the tire axial cross-section. Figure 1 shows a half cross-section of the right half of Tire 1, and the left half (not shown) has the same structure. In Figure 1, reference symbol S1 is the tire equatorial plane. The tire equatorial plane S1 is a plane perpendicular to the tire rotation axis and located at the center in the tire axial direction.

[0013] Here, the tire axial direction is the direction parallel to the tire rotation axis, which is the left-right direction of the paper in Figure 1. In Figure 1, it is shown as the tire axial direction X. The inner side in the tire axial direction is the direction approaching the tire equatorial plane S1, which is the left side of the paper in Figure 1. The outer side in the tire axial direction is the direction away from the tire equatorial plane S1, which is the right side of the paper in Figure 1.

[0014] Also, the tire radial direction is the direction perpendicular to the tire rotation axis, which is the up-down direction of the paper in Figure 1. In Figure 1, it is shown as the tire radial direction Y. The outer side in the tire radial direction is the direction away from the tire rotation axis, which is the upper side of the paper in Figure 1. The inner side in the tire radial direction is the direction approaching the tire rotation axis, which is the lower side of the paper in Figure 1.

[0015] As shown in FIG. 1, the tire 1 includes a pair of beads 10, a pair of sidewalls 20 extending radially outward in the tire diameter direction from each of the pair of beads 10, a tread 30 disposed between the pair of sidewalls 20, a shoulder 40 which is a portion where the sidewall 20 transitions to the tread 30, a carcass ply 50 spanned and disposed between the pair of beads 10, and an inner liner 60 disposed on the tire inner cavity side of the carcass ply 50.

[0016] The pair of beads 10 are disposed at both axial ends of the tire and at the inner ends in the tire diameter direction. The bead 10 has a bead core 11, a bead filler 12 extending radially outward in the tire diameter direction from the bead core 11, and a rim strip rubber 13.

[0017] The bead core 11 is an annular member in which a metal bead wire coated with rubber is wound a plurality of times in the tire circumferential direction. The bead core 11 is a member that serves to fix the air-filled tire 1 to the rim. The bead filler 12 has a tapered shape with a decreasing thickness as it extends from the inner side in the tire diameter direction to the outer side in the tire diameter direction. The bead filler 12 is provided to increase the rigidity of the peripheral portion of the bead 10 and ensure high maneuverability and stability. The bead filler 12 is composed of, for example, a rubber having a higher hardness than the surrounding rubber members.

[0018] The rim strip rubber 13 further surrounds the outside of the carcass ply 50 provided to surround the bead core 11 and the bead filler 12. The rim strip rubber 13 contacts the inner surface of the rim on which the tire 1 is mounted.

[0019] The sidewall 20 includes a sidewall rubber 21 disposed on the outer side in the tire axial direction of the carcass ply 50. The sidewall rubber 21 constitutes the outer side surface of the tire 1 in the tire circumferential direction. The sidewall rubber 21 is the most deflected portion when the tire 1 acts as a cushion, and usually, a flexible rubber having fatigue resistance is adopted.

[0020] At the inner end 21a of the sidewall rubber 21 in the tire radial direction, a rim line 21c protruding outward in the tire axial direction is formed. The rim line 21c is an annular line along the tire circumferential direction.

[0021] The tread 30 includes an endless belt 31 and a cap ply 34, and tread rubber 37. The belt 31 is disposed outside the carcass ply 50 in the tire radial direction. The cap ply 34 is disposed outside the belt 31 in the tire radial direction. The tread rubber 37 is disposed outside the cap ply 34 in the tire radial direction.

[0022] The belt 31 is a member for reinforcing the tread 30. The belt 31 of the embodiment has a two-layer structure including an inner belt 32 disposed outside the inner liner 60 in the tire radial direction and an outer belt 33 disposed outside the inner belt 32 in the tire radial direction. Both the inner belt 32 and the outer belt 33 have a structure in which a plurality of belt cords such as steel cords are covered with rubber. The inner belt 32 is wider than the outer belt 33. Therefore, the width of the belt 31 can be said to be the width of the inner belt 32, and the outer end in the tire axial direction of the belt 31 is the outer end 32b in the tire axial direction of the inner belt 32.

[0023] As shown in FIG. 1, in the tire 1 of the embodiment, the ratio of the maximum width (maximum belt width) 31W of the belt 31 to the total tire width W1 is preferably 78% or more and 90% or less. The total tire width W1 here is the design center value in the tire standard ETRTO, and the maximum width of the belt 31 is the tire axial dimension between the left and right outer ends 32b in the tire axial direction of the widest inner belt 32.

[0024] By providing the belt 31, the rigidity of the tire 1 is ensured and the grounding property of the tread 30 with respect to the road surface is improved. Note that the belt 31 is not limited to a two-layer structure and may have a single-layer or three-layer or more structure.

[0025] The cap ply 34 is a member that reinforces the tread 30 together with the belt 31. The cap ply 34 has a structure in which a plurality of organic fiber cords having insulation properties, such as polyamide fibers, are covered with rubber. The cap ply 34 is wider than the belt 31 and covers the entire belt 31 from the outer surface side of the tire. The outer end 34a of the cap ply 34 in the tire axial direction is folded inward on the tire inner cavity side to be double-layered. The portion of the end 34a of this cap ply 34 covers the outer portions of the ends of the inner belt 32 and the outer belt 33 in the tire axial direction from the outer surface side of the tire. By providing the cap ply 34, it is possible to improve the durability of the tire 1 and reduce the road noise during driving. Note that the cap ply 34 is not limited to a single-layer structure as in the embodiment, and may have a two-layer or three-layer or more structure.

[0026] The tread rubber 37 is disposed on the outer side in the tire radial direction of the cap ply 34. The tread rubber 37 includes a ground contact surface 38 that contacts the road surface. A tread pattern 39 is provided on the ground contact surface 38. The tread pattern 39 has a plurality of main grooves 80 extending over the entire circumference in the tire circumferential direction. The main grooves 80 include a first main groove 81 and a second main groove 82 arranged at intervals in the tire axial direction. The outer end 37a of the tread rubber 37 in the tire axial direction covers the outer end 21b of the sidewall rubber in the tire radial direction. The outer end 37a of the tread rubber 37 in the tire axial direction has a buttress 25 that protrudes outward in the tire axial direction.

[0027] The tread 30 includes a central land 71 between the left and right first main grooves 81 sandwiching the tire equatorial plane S1, a pair of intermediate lands 72 between the first main groove 81 and the second main groove 82, and a pair of shoulder lands 73 on the shoulder 40 side of the second main groove 82. The ground contact surface 38 includes the outer surfaces of the central land 71, the intermediate lands 72, and the shoulder lands 73.

[0028] FIG. 1 shows the contact width 100W of the contact surface 38 at 100% of the maximum load according to the tire standard ETRTO and the contact width 130W of the contact surface 38 at 130% of the maximum load according to the tire standard ETRTO in the tire axial direction semi-cross section. Each of the contact widths 100W and 130W indicates the tire axial direction length of the portion where the contact surface 38 contacts the road surface when the corresponding load is applied to the tire 1. FIG. 1 shows the contact end 38a of the contact surface 38 at the contact width 100W and the contact end 38b of the contact surface 38 at the contact width 130W, respectively. That is, the contact width 100W is the tire axial direction length between the tire equatorial plane S1 and the contact end 38a, and the contact width 130W is the tire axial direction length between the tire equatorial plane S1 and the contact end 38b.

[0029] As shown in FIG. 1, in the tire axial direction semi-cross section, the outer end of the belt 31 in the tire axial direction (the outer end of the inner belt 32 in the tire axial direction) 32b is arranged on the outer side in the tire axial direction than the contact end 38b at 130% of the maximum load according to the tire standard ETRTO.

[0030] As shown in FIG. 1, the shoulder 40 is the portion where it transitions from the sidewall 20 to the tread 30. The shoulder 40 includes the outer end 37a of the tread rubber 37 in the tire axial direction.

[0031] The carcass ply 50 is spanned between the pair of beads 10. The carcass ply 50 is embedded inside the tire 1 in a manner of passing through the inner tire cavity sides of the pair of sidewalls 20, the pair of shoulders 40, and the tread 30 between the pair of beads 10. In the tread 30, the belt 31 is arranged on the outer side in the tire radial direction of the carcass ply 50.

[0032] The carcass ply 50 includes a plurality of ply cords (not shown) that form the framework of the tire 1. The plurality of ply cords extend, for example, along a plane in the tire axial direction and are arranged side by side in the tire circumferential direction. The ply cords are composed of insulating organic fiber cords such as polyester or polyamide cords. The plurality of ply cords are coated with rubber to form the carcass ply 50.

[0033] The carcass ply 50 includes a ply main body portion 50A and a pair of turned-up portions 50B. The ply main body portion 50A is a portion that extends from the tread 30 through each of the pair of shoulders 40 and each of the pair of sidewalls 20 to the inside in the tire axial direction of each of the pair of beads 10. The pair of turned-up portions 50B are portions that are folded back radially outward of the tire by being wound around each of the pair of bead cores 11 from the ply main body portion 50A and extend along the sidewall 20.

[0034] The ply main body portion 50A is disposed radially inside the belt 31 in the tread 30 and is disposed axially inside the sidewall rubber 21 in the sidewall 20. The turned-up portion 50B is wound from the inside to the outside in the tire axial direction of the bead core 11, then extends radially outward of the tire along the sidewall 20, and further reaches the outer end in the tire axial direction of the tread 30. The portion of the turned-up portion 50B that is radially outside the bead filler 12 is overlapped with the ply main body portion 50A axially outside. The end of the turned-up portion 50B is sandwiched between the outer end in the tire axial direction of the belt 31 and the ply main body portion 50A, and its tip 50b is located axially inside the tip 33b in the tire axial direction of the outer belt 33.

[0035] The rim strip rubber 13 of the bead 10 described above surrounds the end of the carcass ply 50 on the radially inner side that winds around the bead core 11.

[0036] The carcass ply 50 of the embodiment has a single-layer structure, but the carcass ply 50 may have two layers or three or more layers. When the carcass ply 50 has a single-layer structure, it is preferable in terms of achieving weight reduction of the tire 1.

[0037] The inner liner 60 covers the inner surface of the ply main body portion 50A of the carcass ply 50 between the pair of beads 10 to form the tire inner cavity surface. The inner liner 60 is in contact with the inner surface of the carcass ply 50. The inner liner 60 of the embodiment has a two-layer structure including a first inner liner 61 on the tire inner cavity side and a second inner liner 62 laminated on the tire outer surface side of the first inner liner 61. Each of the inner liners 61 and 62 is made of air-permeability-resistant rubber. The inner liner 60 prevents air in the tire inner cavity from leaking to the outside. Note that the inner liner 60 may have a single-layer structure instead of a two-layer structure. Note that, on the inner side in the tire axial direction of the portion of the bead 10 on the inner side in the tire radial direction, the rim strip rubber 13 covers the inner liner 60 to form a part of the tire inner cavity surface.

[0038] In the tire 1 of the embodiment, a reinforcing rubber layer 65 is provided from the portion of the sidewall 20 on the outer side in the tire radial direction through the shoulder 40 to the portion of the tread 30 on the outer side in the tire axial direction. This reinforcing rubber layer 65 is sandwiched between the second inner liner 62 and the ply main body portion 50A of the carcass ply 50.

[0039] Here, as the rubber used for the bead filler 12, at least rubber having a higher hardness than the sidewall rubber 21 and the inner liner 60 is used. The hardness of the rubber is the hardness measured by the "durometer hardness type A of JIS K6253-3:2012".

[0040] For example, when the hardness of the sidewall rubber 21 is taken as a reference, the hardness of the bead filler 12 is preferably about 1.2 times or more and 2.3 times or less the hardness of the sidewall rubber 21. The hardness of the rim strip rubber 13 is more preferably about 1 time or more and 1.6 times or less the hardness of the sidewall rubber 21. By setting the hardness in this way, it is possible to ensure a balance between the flexibility of the tire and the rigidity near the bead 10.

[0041] The tire 1 according to the embodiment has the above internal structure. FIG. 2 is a diagram schematically showing the ground contact shape (the shape of the footprint) of this tire 1. The ground contact shape shown in FIG. 2 is the ground contact shape at 100% load of the maximum load in the tire standard ETRTO. This ground contact shape can also be said to be the tire mark remaining on the ground contact surface in the vehicle stopped state. In FIG. 2, the same reference numerals are given to the marks corresponding to the central land 71, the intermediate land 72, the shoulder land 73, the first main groove 81, and the second main groove 82. That is, in FIG. 2, for example, the reference numeral 71 is the mark of the central land 71 of the tire 1 remaining on the ground contact surface.

[0042] In FIG. 2, the tire circumferential direction length at the center in the tire axial direction is indicated by CeL, and the tire circumferential direction length at a position 10 mm inward from the ground contact ends Ge on both sides in the tire axial direction of the ground contact shape is indicated by ShL. Here, the rectangularity of the tire 1 is "(ShL / CeL)×100" (%). Note that since the actual ShL often differs between the left and right, the average of both is taken.

[0043] Further, FIG. 2 schematically shows a part of a plurality of belt cords 31A provided in the belt 31. The belt cord 31A extends linearly in a direction intersecting the tire circumferential direction C (the vertical direction in FIG. 2). The inclination angle θ1 on the acute angle side of the belt cord 31A with respect to the tire circumferential direction is preferably 24° or more and 32° or less. The belt cord 31A shown in FIG. 2 is the belt cord of the outer belt 33, and the belt cord of the inner belt 32 is not shown. The belt cord of the inner belt 32 is inclined in the opposite direction to the belt cord 31A of the outer belt 33, and the inclination angle on the acute angle side thereof with respect to the tire circumferential direction is substantially the same as that of the belt cord of the outer belt 33.

[0044] According to the tire 1 according to the embodiment described above, the following effects are achieved.

[0045] (1) The tire 1 according to the embodiment is a pneumatic tire including a tread 30. The tread 30 includes a tread rubber 37, a ground contact surface 38 where the tread rubber 37 contacts the road surface, a pair of ground contact ends which are the outer ends of the ground contact surface 38 in the tire axial direction, and a belt 31 disposed on the inner side of the tread rubber 37 in the tire radial direction. In the tire axial half cross section, the outer end 32b of the belt 31 in the tire axial direction is disposed more outside in the tire axial direction than the ground contact end 38b under a load of 130% of the maximum load according to the tire standard ETRTO.

[0046] As a result, since the outer end 32b of the belt 31 in the tire axial direction is close to the shoulder 40, the profile in the tire axial cross section near the shoulder 40 has a shape following the belt 31, and the deflection deformation is easily suppressed by the belt 31. Therefore, the round shape of the profile in the tire axial cross section near the shoulder 40 is easily maintained, the crushing is suppressed, and it is difficult to become a square shape. By rounding the ground contact surface shape in this way, the drainage performance is improved.

[0047] (2) In the tire 1 of (1) according to the embodiment, it is preferable that the ratio of the maximum width 31W of the belt 31 to the total tire width W1 is 78% or more and 90% or less.

[0048] As a result, the maximum width of the belt 31 becomes relatively large, and the outer end 32b of the belt 31 in the tire axial direction is close to the shoulder 40. Therefore, the ground contact surface shape easily becomes a round shape, and the drainage performance is improved.

[0049] (3) In the tire 1 of (1) and (2) according to the embodiment, the belt 31 includes a belt cord 31A extending in a direction intersecting the tire circumferential direction, and it is preferable that the inclination angle of the belt cord 31A on the acute angle side with respect to the tire circumferential direction is 24° or more and 32° or less.

[0050] As described with reference to FIG. 2, the rectangularity is such that the shorter the tire circumferential length ShL near the ground contact end Ge is with respect to the tire circumferential length CeL, the smaller the rectangularity becomes, and the ground contact surface shape becomes a round shape. This rectangularity is affected by the inclination angle of the belt cord 31A with respect to the tire circumferential direction. When the inclination angle θ1 is 24° or more and 32° or less as described above in the embodiment, the tire circumferential length CeL extends, and the tire circumferential length ShL becomes shorter, and the rectangularity tends to become smaller. Therefore, when the inclination angle on the acute angle side of the belt cord 31A with respect to the tire circumferential direction is 24° or more and 32° or less, the ground contact surface shape tends to become a round shape, and the drainage performance is improved.

[0051] As described above, the specific embodiments of the present invention have been described. However, the present invention is not limited to the above embodiments, and even if modifications, improvements, etc. are made within the range that can achieve the object of the present invention, they are included in the scope of the present invention.

[0052] The tire 1 of the above embodiment is for a passenger car, but the configuration of this tire 1 can be adopted for high-load passenger car tires such as SUVs and EVs, or for various vehicles such as trucks and buses in addition to passenger cars.

Explanation of reference numerals

[0053] 1... Tire (pneumatic tire) 30... Tread 31... Belt 31A... Belt cord 31W... Maximum width of the belt 32b... Outer end of the belt in the tire axial direction 37... Tread rubber 38... Ground contact surface 38b... Ground contact end W1... Total tire width

Claims

Claim 1 A pneumatic tire having a tread, wherein the tread includes tread rubber, a ground contact surface where the tread rubber contacts the road surface, a pair of ground contact ends that are the outer ends of the ground contact surface in the tire axial direction, and a belt disposed on the inner side of the tread rubber in the tire radial direction; In a half cross section in the tire axial direction, the outer end of the belt at its maximum width is disposed on the outer side in the tire axial direction of the ground contact end when the load is 130% of the maximum load according to the tire standard ETRTO. The pneumatic tire. Claim 2 The pneumatic tire according to claim 1, wherein the ratio of the maximum width of the belt to the total width of the tire is 78% or more and 90% or less. Claim 3 The pneumatic tire according to claim 1 or 2, wherein the belt includes belt cords extending in a direction intersecting the tire circumferential direction, and the inclination angle of the belt cords on the acute angle side with respect to the tire circumferential direction is 24° or more and 32° or less.

Images