pneumatic tires

Abstract

We provide pneumatic tires with staggered shoulders that improve separation resistance without compromising handling stability. [Solution] The shoulder block 350 of the tire 1 comprises a first shoulder block 310 having a first end 310a that is on the outer side in the tire axial direction, and a second shoulder block 320 having a second end 320a that is on the outer side in the tire axial direction, which is further outward in the tire axial direction than the first end 310a, and the first shoulder block 310 and the second shoulder block 320 are arranged alternately in the tire circumferential direction, and a cushion rubber layer 41 is provided which is located in a region sandwiched between the carcass ply 50 and the belt end 31c in the half cross section in the tire axial direction, and the position of the maximum thickness of the cushion rubber layer 41 is on the outer side in the tire axial direction than the belt end 31c and is located between the first end 310a and the second end 320a.

Description

Technical Field

[0001] The present disclosure relates to pneumatic tires.

Background Art

[0002] Conventionally, increasing the rigidity of a tire is known as a method for improving the handling stability of the tire. By widening the belt, the bending rigidity of the tread can be improved, and the handling stability is also improved as the cornering force is increased. On the other hand, when the belt is widened, as the belt moves away from the tire equator plane toward the outside, the position of the belt is arranged closer to the inner side in the tire radial direction according to the tire profile. That is, the position of the belt in the tire radial direction near the belt end is closer to the inner side in the tire radial direction than the position of the belt in the tire radial direction near the tire equator. Therefore, in the tire axial half-section, the belt is arranged in a curved shape as it approaches the belt end. If the curvature of the belt in the tire axial half-section is large, the shear stress generated between the belt and the carcass ply becomes large in the vicinity of the curved portion of the belt, and there has been a risk of separation between the belt and the carcass ply.

[0003] In order to reduce the curvature of the belt in the tire axial half-section, a rubber member (hereinafter also referred to as a cushion rubber layer) having a substantially triangular cross-sectional shape in the tire axial half-section may be arranged between the belt and the carcass ply (see, for example, Patent Document 1).

[0004] Incidentally, so-called staggered shoulders are sometimes adopted, particularly for the purpose of improving off-road performance (see, for example, Patent Document 2). In a staggered shoulder, a first shoulder block and a second shoulder block, whose end is located further outward in the tire axial direction than the end of the first shoulder block, are arranged alternately in the circumferential direction of the tire. This alternating arrangement of the first and second shoulder blocks improves grip on stones and rocks off-road, thereby improving traction and off-road performance. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2024-36222 [Patent Document 2] Japanese Patent Publication No. 2017-213926 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, with a staggered shoulder design, the first and second shoulder blocks repeatedly make contact with the ground alternately during driving, which can lead to large fluctuations in stress near the edges of the tread. Therefore, if there is curvature in the belt near the edges of the first and second shoulder blocks, separation may occur.

[0007] The problem addressed by this disclosure is to provide a pneumatic tire that features a staggered shoulder and can improve separation resistance without compromising handling stability. [Means for solving the problem]

[0008] The pneumatic tire of the present disclosure comprises a pair of beads, a pair of sidewalls extending radially outward from each of the pair of beads, a tread disposed between the pair of sidewalls, and a carcass ply stretched between the pair of beads, wherein the tread has a belt disposed on the outer surface side of the tire than the carcass ply, and shoulder blocks provided at the ends of the tread surface in the axial direction of the tire, the shoulder block having a first shoulder block having a first end on the outer side in the axial direction of the tire, and a tapered tapered tape relatively more tapered than the first shoulder block. The tire comprises a second shoulder block having a second end on the tire axial side, which is on the tire axial side, and the first and second shoulder blocks are arranged alternately in the tire circumferential direction, and a cushion rubber layer is provided in a region sandwiched at least between the carcass ply and the belt end 31c, which is the tire axial end of the belt, in the tire axial half cross section, wherein the maximum thickness position of the cushion rubber layer, which is the position on the tire radial side of the cushion rubber layer corresponding to the position where the thickness of the cushion rubber layer is maximum, is located in the tire axial direction, further out in the tire axial direction than the belt end, and between the first end and the second end. [Effects of the Invention]

[0009] According to this disclosure, it is possible to provide a pneumatic tire that has a staggered shoulder and can improve separation resistance without impairing handling stability. [Brief explanation of the drawing]

[0010] [Figure 1] This figure shows the internal structure of a tire 1, which is a pneumatic tire according to an embodiment, and is a cross-sectional view showing a half-section in the axial direction of the tire. [Figure 2] Figure 1 shows an enlarged view of the area A indicated by the dashed line. [Figure 3]This is a partial unfolded view showing the tread pattern 300 by unfolding the tread surface 37 near the shoulder 40 of tire 1 into a flat plane. [Modes for carrying out the invention]

[0011] The embodiments will now be described with reference to the drawings. Figure 1 is a diagram showing the internal structure of tire 1, which is a pneumatic tire according to the embodiment, and is a cross-sectional view showing a half-section in the tire axial direction. Figure 2 is an enlarged view of the area A shown by the dashed line in Figure 1. In Figure 2, hatching has been omitted to clearly show the cross-sectional structure, boundaries, auxiliary lines, etc. of the constituent members. Tire 1 according to the embodiment is, for example, a pneumatic tire for a passenger car. The configuration of tire 1 in this embodiment can be used as a tire for various vehicles other than passenger cars, such as light trucks, trucks, and buses.

[0012] The cross-sectional view in Figure 1 is a half-section view of the tire in the axial direction (tire meridian half-section view) under no-load conditions, with tire 1 mounted on a standard rim (not shown) and filled to the standard internal pressure. The standard rim is the rim specified for each tire in the standard system that includes the standard on which the tire is based. For example, it is the standard rim for JATMA, and the "Measuring Rim" for TRA and ETRTO. The standard internal pressure is the air pressure specified for each tire in the standard system that includes the standard on which the tire is based. For truck and bus tires and light truck tires, it is the maximum air pressure for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and the "INFLATION PRESSURE" for ETRTO. For passenger car tires, it is usually 180 kPa, but for tires marked "Extra Load" or "Reinforced," it is 220 kPa.

[0013] In Figure 1, the symbol S1 represents the tire equatorial plane. The tire equatorial plane S1 is a plane perpendicular to the tire rotation axis (tire meridian) and located at the center of the tire axial direction. The basic internal structure of tire 1 is symmetrical in the cross-section along the tire axial direction with respect to the tire equatorial plane S1. Figure 1 shows a half-cross-section of the right half of tire 1, and the left half, which is not shown, has the same structure.

[0014] Here, the tire axis direction is the direction parallel to the tire rotation axis, and in the cross-sectional view of Figure 1, it is the left-right direction on the paper. In Figure 1, it is shown as the tire axis direction X. The inner direction in the tire axis direction is the direction approaching the tire equatorial plane S1, and in Figure 1, it is the left side of the paper. The outer direction in the tire axis direction is the direction away from the tire equatorial plane S1, and in Figure 1, it is the right side of the paper. The tire radial direction is the direction perpendicular to the tire rotation axis, and in Figure 1, it is the up-down direction on the paper. In Figure 1, it is shown as the tire radial direction Y. The outer direction in the tire radial direction is the direction away from the tire rotation axis, and in Figure 1, it is the upper side of the paper. The inner direction in the tire radial direction is the direction approaching the tire rotation axis, and in Figure 1, it is the lower side of the paper. Note that the tire radial direction is the same direction as the tire cross-sectional height direction.

[0015] As shown in Figure 1, the tire 1 according to this embodiment includes a pair of beads 10 provided on both sides of the tire axial direction, a pair of sidewalls 20 extending radially outward from each of the pair of beads 10, a tread 30 disposed between the pair of sidewalls 20, a pair of shoulders 40 which are the portions that transition from each of the pair of sidewalls 20 to the tread 30, a carcass ply 50 arranged across the pair of beads 10, and an inner liner 60 disposed on the inner side of the carcass ply 50.

[0016] The bead 10 includes a bead core 11 and a bead filler 12 extending radially outward from the bead core 11.

[0017] The bead core 11 is an annular member in which a metal bead wire coated with rubber is wound multiple 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 radial direction to the outer side in the tire radial 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 bead 10 is surrounded by a rim strip rubber 13 with the carcass ply 50 interposed therebetween. The rim strip rubber 13 is disposed at the inner end in the tire radial direction of the tire 1 in a manner that wraps around from the inner side in the tire axial direction of the bead 10 through the inner end in the tire radial direction to the outer side in the tire axial direction.

[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 sidewall surface of the tire 1. The inner end 21b in the tire radial direction of the sidewall rubber 21 extends inward in the tire radial direction and covers the outer end 13a in the tire radial direction of the rim strip rubber 13. The sidewall rubber 21 is the portion that flexes the most when the tire 1 acts as a cushion, and usually, a flexible rubber having fatigue resistance is adopted.

[0020] A rim line 15 is formed at the tip of the inner end 21b in the tire radial direction of the sidewall rubber 21. The rim line 15 is an annular protrusion along the tire circumferential direction.

[0021] The tread 30 has an endless belt 31 and a belt reinforcing layer 34 in the tire circumferential direction, and a tread rubber 36. The belt 31 is disposed on the outer side in the tire radial direction of the carcass ply 50. The belt reinforcing layer 34 is disposed on the outer side in the tire radial direction of the belt 31.

[0022] The belt 31 is a member that reinforces the tread 30. The belt 31 of the embodiment has a two-layer structure including an inner belt 311 disposed on the outer side in the tire diameter direction of the inner liner 60 and an outer belt 312 disposed on the outer side in the tire diameter direction of the inner belt 311. Both the inner belt 311 and the outer belt 312 have a structure in which a plurality of belt cords such as steel cords are covered with rubber. The inner belt 311 is wider than the outer belt 312. That is, the width of the inner belt 311 is the maximum width of the belt 31. The outer end of the inner belt 311 in the tire axial direction constitutes the belt end 31c of the belt 31. 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.

[0023] The belt reinforcing layer 34 is a member that reinforces the tread 30 together with the belt 31. The belt reinforcing layer 34 of the embodiment has an inner belt reinforcing layer 341 and an outer belt reinforcing layer 342 laminated on the tire outer surface side of the inner belt reinforcing layer 341. Each of the belt reinforcing layers 341 and 342 has a structure in which a plurality of insulating organic fiber cords such as polyamide fibers are covered with rubber.

[0024] The belt reinforcing layer end 34a on the outer side in the tire axial direction of the belt reinforcing layer 34 is disposed in the region of the shoulder 40. At the belt reinforcing layer end 34a, the outer ends of the inner belt reinforcing layer 341 and the outer belt reinforcing layer 342 in the tire axial direction are aligned in the thickness direction of the shoulder 40. The belt reinforcing layer 34 covers the entire belt 31 from the tire outer surface side. That is, the belt reinforcing layer end 34a on the outer side in the tire axial direction of the belt reinforcing layer 34 is located slightly outside in the tire axial direction than the belt end 31c of the belt 31. By providing the belt reinforcing layer 34, improvement in durability and reduction of road noise during driving can be achieved. Note that the belt reinforcing layer 34 of the embodiment has a two-layer structure in which the inner belt reinforcing layer 341 and the outer belt reinforcing layer 342 are laminated, but it may be a single layer or a three-layer or more structure.

[0025] The tread rubber 36 is positioned radially outward of the belt reinforcement layer 34. The tread rubber 36 is a component that makes up the tread surface 37, which is the outer surface of the tread 30. The tread pattern 300, which will be described later, is formed on the tread surface 37.

[0026] The outer axial end 36a of the tread rubber 36 covers the outer axial end 34a of the belt reinforcement layer 34. The outer radial end 21a of the sidewall rubber 21 is located on the outer axial side of the outer axial end 36a of the tread rubber 36.

[0027] A cushion rubber layer 41 is positioned between the carcass ply 50 and the outer axial end 36a of the tread rubber 36. In the inner axial portion of the cushion rubber layer 41, a belt 31 and a belt reinforcement layer 34 are positioned on the radially outer side of the cushion rubber layer 41. Details of the cushion rubber layer 41 will be described later.

[0028] The shoulder 40 includes the axial outer end 36a of the tread rubber 36, the radial outer end 21a of the sidewall rubber 21, and the cushion rubber layer 41.

[0029] The carcass ply 50 is stretched between a pair of beads 10. The carcass ply 50 has a structure in which multiple parallel ply cords are covered with rubber. The ply cords are made of steel cords or insulating organic fiber cords such as polyester or polyamide, and function as the skeleton of the tire 1. The carcass ply 50 is embedded in the tire 1 in such a manner that it passes between the pair of beads 10, through a pair of sidewalls 20, a pair of shoulders 40, and the inner side of the tread 30. In the tread 30, a belt 31 is positioned on the radially outer side of the carcass ply 50.

[0030] The carcass ply 50 has a ply body portion 50A, a winding portion 50B, and a bent portion 50C. The ply body portion 50A is the portion that extends from the inner side of one bead core 11 in the tire axial direction, through one sidewall 20, one shoulder 40, tread 30, the other shoulder 40 and the other sidewall 20, to the inner side of the other bead core 11 in the tire axial direction. The ply body portion 50A is positioned on the inner side of the tire radially inward of the bead core 11 and the bead filler 12 in the tire axial direction.

[0031] The winding portion 50B is the part that extends radially outward on the tire axial side of the bead filler 12, by being folded back around the bead core 11 from the inner end of the ply body portion 50A in the tire radial direction. The winding portion 50B is positioned on the tire axial side of the bead core 11 and the bead filler 12.

[0032] The bent portion 50C is the part that bends in a U-shape in cross-section from the ply body portion 50A around the bead core 11 and connects to the winding portion 50B. The bent portion 50C includes the innermost part in the tire radial direction of the carcass ply 50. The ply body portion 50A and the winding portion 50B are continuous via the bent portion 50C.

[0033] The carcass ply 50 of this embodiment has a two-layer structure in which a first carcass ply 51 and a second carcass ply 52 are stacked on top of each other. In the ply body portion 50A, the first carcass ply 51 is positioned on the inner side of the tire cavity of the second carcass ply 52. ​​In the winding portion 50B, the first carcass ply 51 is positioned on the outer side of the second carcass ply 52 in the tire axial direction. The rim strip rubber 13 described above is provided so as to surround the inner end of the carcass ply 50 in the tire radial direction, including the bent portion 50C. Although the carcass ply 50 of this embodiment has a two-layer structure, the carcass ply 50 may be a single layer or may be three or more layers.

[0034] The inner liner 60 forms the inner surface 1c of the tire between the pair of beads 10. The inner liner 60 is made of air-permeable rubber to prevent air inside the tire cavity from leaking to the outside.

[0035] Furthermore, within the tire of this embodiment, the first rubber layer 70 is positioned between the first carcass ply 51 and the second carcass ply 52, overlapping with the vicinity of the center of the sidewall 20 in the tire radial direction, and extending to a position on the shoulder 40 where it overlaps with the inner belt 311 and the outer belt 312 in the tire radial direction. The first rubber layer 70 extends to the vicinity of the inner end 41b of the cushion rubber layer 41 in the tire radial direction on the shoulder 40, and is positioned further inward than the cushion rubber layer 41 in the tire radial direction. The first rubber layer 70 may be formed from any rubber material that can constitute the tire 1, but it is desirable that the modulus of the first rubber layer 70 be higher than that of the cushion rubber layer 41 in order to suppress kissing of the first carcass ply 51 and the second carcass ply 52.

[0036] In the manufacturing of tire 1, internal pressure is applied during the molding and vulcanization processes. At this time, the first carcass ply 51 and the second carcass ply 52 become excessively tightly bonded, causing the cord fibers to match. This kissing is a manufacturing defect and has adverse effects on tire performance, such as a decrease in the overall rigidity of the tire. To prevent this kissing, a first rubber layer 70 is provided, and it is desirable that the modulus of the first rubber layer 70 be higher than that of the cushion rubber layer 41 in order to accommodate the stretching and bonding of the carcass ply 50.

[0037] Furthermore, within the tire of this embodiment, a second rubber layer 80 is positioned between the inner liner 60 and the ply body portion 50A of the carcass ply 50, from a position overlapping with the outer end 13a of the rim strip rubber 13 in the tire radial direction in the tire axial direction, to a position overlapping with the inner belt 311 and the outer belt 312 in the tire radial direction on the shoulder 40. The second rubber layer 80 extends to the vicinity of the inner end 41b of the cushion rubber layer 41 in the tire radial direction on the shoulder 40, and is positioned further inward than the cushion rubber layer 41 in the tire radial direction. Also, the second rubber layer 80 is positioned further inward than the first rubber layer 70. The second rubber layer 80 may be formed from any rubber material that can constitute the tire 1, but it is desirable that the modulus of the second rubber layer 80 be higher than the modulus of the cushion rubber layer 41. It is also desirable that the modulus of the second rubber layer 80 be higher than the modulus of the inner liner 60.

[0038] As mentioned earlier, in the manufacturing of tire 1, internal pressure is applied during the molding and vulcanization processes. During this process, the inner liner 60 stretches, and in some cases, the inner liner 60 may become thinner than the specified design thickness. If the inner liner 60 becomes too thin, there is a risk of exposing the carcass ply 50. By placing the second rubber layer 80 in a location where the inner liner 60 is prone to stretching, the exposure of the carcass ply 50 can be prevented. For this reason, it is desirable that the modulus of the second rubber layer 80 be higher than that of the cushion rubber layer 41, and also higher than that of the inner liner 60.

[0039] The inner liner 60 covers the inner surface of the ply body 50A of the carcass ply 50, except for the portion at the inner edge in the tire radial direction. In the region where the second rubber layer 80 is present, the inner liner 60 covers the inner surface of the ply body 50A of the carcass ply 50 via the second rubber layer 80. The portion of the inner liner 60 at the inner edge in the tire radial direction covers the portion of the rim strip rubber 13 in the tire axial direction.

[0040] Figure 3 is a partial unfolded view showing the tread pattern 300 by unfolding the tread surface 37 near the shoulder 40 of tire 1 into a planar shape. Figure 3 shows the tread surface 37 as viewed from the position and orientation of arrow B in Figure 2. In Figure 3, the direction corresponding to the tire circumferential direction C is indicated by an arrow. The tread pattern 300 near the shoulder 40 includes a shoulder main groove 331, lug grooves 332, a first shoulder block 310, a second shoulder block 320, etc. In addition, there are multiple lug grooves and blocks arranged in the inner region 360 of the tread pattern 300 that is inward from the shoulder main groove 331 in the tire axial direction, but the details are omitted.

[0041] The shoulder main groove 331 is located on the outermost side of the tire axial direction among the multiple main grooves and extends along the tire circumferential direction while repeatedly bending. The lug groove 332 extends roughly along the tire axial direction, and its inner side in the tire axial direction connects to the shoulder main groove 331.

[0042] The first shoulder block 310 and the second shoulder block 320 are blocks positioned at the outer ends of the tread surface 37 in the tread pattern 300, specifically at the ends axially outward of the tire surface. The first shoulder block 310 has a first end 310a, which is its outer end axially outward of the tire surface. The second shoulder block 320 has a second end 320a, which is its outer end axially outward of the tire surface, relatively further outward than the first end 310a compared to the first shoulder block 310. The first shoulder block 310 and the second shoulder block 320 are arranged alternately in the circumferential direction of the tire, forming a shoulder block 350 in the form of a so-called staggered shoulder. By having a staggered shoulder in the shoulder block 350, the tire 1 of this embodiment can improve traction and off-road capability by enhancing its grip on stones, rocks, etc., in off-road conditions. In addition, the first shoulder block 310 and the second shoulder block 320 are provided with a plurality of sipes 351. The specific shapes of the tread pattern 300, including the shapes of the first shoulder block 310 and the second shoulder block 320, are merely examples, and their specific shapes can be changed as appropriate. For example, the specific shape of the sipes 351 may be changed as appropriate, and some or all of them may be omitted.

[0043] As described above, in the tire 1 of this embodiment, a cushion rubber layer 41 is placed between the carcass ply 50 and the outer end 36a of the tread rubber 36 in the tire axial direction. While placing the belt 31 over a wider area is an effective method for improving handling stability, if the width of the belt 31 in the tire axial direction becomes wider, there is a concern that the belt may separate due to the curvature of the belt 31. In the tire 1 of this embodiment, the cushion rubber layer 41 is provided with the purpose of reducing the curvature of the belt 31 in the half cross-section in the tire axial direction.

[0044] The cross-sectional shape of the cushion rubber layer 41 in the axial half of the tire is approximately triangular, and the thickness of the cushion rubber layer 41 in the axial half of the tire is maximum at its vertex 41a (see thickness H in Figure 3). The position on the outer side of the cushion rubber layer 41 in the tire radial direction, corresponding to the position where the thickness of the cushion rubber layer 41 is maximum (in this embodiment, the position of vertex 41a), will be called the maximum thickness position. The position where the thickness of the cushion rubber layer 41 is maximum is the position where the thickness of the cross-sectional shape of the cushion rubber layer 41 is maximum in the axial half of the tire. Furthermore, the thickness of the cushion rubber layer 41 is the distance from the inner surface of the cushion rubber layer 41 in the tire radial direction until the normal reaches the outer surface of the cushion rubber layer 41 in the tire radial direction. In addition, it is conceivable that the vertex 41a is not clearly defined, as in this embodiment, and that there are multiple maximum thickness positions that can be defined. In such cases, the position that is in the center among the multiple possible maximum thickness positions on the outer surface of the cushion rubber layer in the tire radial direction will be called the maximum thickness position.

[0045] In the range from the inner end 41b on the axial side of the tire to the point of maximum thickness (peak 41a), the cushion rubber layer 41 has its outer-facing surface extending substantially along the outer surface of the tread surface 37. This prevents the belt 31 from curving along the carcass ply 50. On the other hand, in the range from the point of maximum thickness (peak 41a) to the outer end 41c on the axial side of the tire, the cushion rubber layer 41 has its outer-facing surface gradually approaching the profile of the carcass ply 50. Therefore, in this range from the point of maximum thickness (peak 41a) to the outer end 41c on the axial side of the tire, the effect of preventing the curvature of the belt 31 gradually decreases.

[0046] Therefore, determining the position of the maximum thickness (vertex 41a) of the cushion rubber layer 41 is important for improving separation resistance. Conventionally, the cushion rubber layer 41 was provided to suppress the separation of the belt 31. On the other hand, in cases where a staggered shoulder is provided, as in the tire 1 of this embodiment, the positional relationship between the staggered shoulder and the cushion rubber layer 41 was not considered.

[0047] (Relationship between staggered shoulder and cushion rubber layer 41) As described above, the tire 1 of this embodiment is equipped with a staggered shoulder. Therefore, the position of the second end 320a of the second shoulder block 320 is set further outward in the tire axial direction than the position of the first end 310a of the first shoulder block 310, and the first shoulder block 310 and the second shoulder block 320 are arranged alternately in the circumferential direction. Since both the first end 310a and the second end 320a are also the ends of the tread surface 37, the width of the tread surface 37 that contacts the road during driving alternately changes between a wide state and a narrow state. As a result, it is expected that the stress fluctuations near the ends of the tread will be large. Therefore, belt separation near the ends of the first shoulder block 310 and the second shoulder block 320 is a concern.

[0048] Therefore, in the tire 1 of this embodiment, the separation resistance of the belt 31 is improved by optimizing the positional relationship between the staggered shoulder and the cushion rubber layer 41. Specifically, in the tire 1 of this embodiment, the position of the maximum thickness of the cushion rubber layer 41 is located in the tire axial direction, outward in the tire axial direction from the belt end 31c of the belt 31 in the tire axial direction, and is located between the first end 310a and the second end 320a.

[0049] Here, the position of the belt end 31c of the belt 31 in the tire axial direction is defined as the edge portion located on the inner side of the belt 31 in the tire radial direction.

[0050] (Relationship between belt reinforcement layer 34 and cushion rubber layer 41) As described above, the tire 1 of this embodiment is equipped with a belt reinforcement layer 34. Since the belt reinforcement layer 34 has a wider width in the tire axial direction than the belt 31, the end 34a of the belt reinforcement layer 34 is located further outward in the tire axial direction than the end 31c of the belt. Therefore, if the cushion rubber layer 41 is not positioned appropriately, the belt reinforcement layer 34 will curve more than the belt 31 as it approaches the end 34a of the belt reinforcement layer, and in that case, separation of the belt reinforcement layer 34 will be a concern. Therefore, when a belt reinforcement layer is provided, improvement in the separation resistance of not only the belt but also the belt reinforcement layer is required.

[0051] Therefore, in the tire 1 of this embodiment, by optimizing the positional relationship between the belt reinforcing layer 34 and the cushion rubber layer 41, the separation resistance of the belt 31 is improved, as is the separation resistance of the belt reinforcing layer 34. Specifically, in the tire 1 of this embodiment, the position of the maximum thickness of the cushion rubber layer 41 is located in the tire axial direction, outward from the belt end 31c of the belt 31, and inward from the belt reinforcing layer end 34a of the belt reinforcing layer 34.

[0052] Here, as mentioned earlier, the position of the belt end 31c of the belt 31 in the tire axial direction is the edge portion located on the inner side in the tire radial direction of the belt 31. Similarly, the position of the belt reinforcement layer end 34a of the belt reinforcement layer 34 in the tire axial direction is the edge portion located on the inner side in the tire radial direction of the belt reinforcement layer 34. Note that in the figure, the tips of the inner belt 311 and the outer belt 312 are shown as having a roughly triangular cross-sectional shape. This portion is a topping rubber covering the fibers and cords of the inner belt 311 and the outer belt 312, and does not possess the original strength of the belt 31. Therefore, this topping rubber region is not considered the tip of the belt 31.

[0053] To facilitate understanding of the above positional relationships, auxiliary lines are shown in Figure 2. In Figure 2, auxiliary line L41 is a line segment that passes through the position of the maximum thickness of the cushion rubber layer 41 (corresponding to the vertex 41a in this embodiment) and extends in the tire radial direction. Auxiliary line L31 is a line segment that passes through the belt end 31c in the tire axial direction of the belt 31 and extends in the tire radial direction. Auxiliary line L310 is a line segment that passes through the first end 310a of the first shoulder block 310 and extends in the tire radial direction. Auxiliary line L320 is a line segment that passes through the second end 320a of the second shoulder block 320 and extends in the tire radial direction. Auxiliary line L34 is a line segment that passes through the belt reinforcement layer end 34a of the belt reinforcement layer 34 and extends in the tire radial direction. As is clear from these auxiliary lines, auxiliary line L41 is located further outward in the tire axial direction than auxiliary line L31, and is situated between auxiliary lines L310 and L320. Furthermore, auxiliary line L41 is located further outward in the tire axial direction than auxiliary line L31, and further inward in the tire axial direction than auxiliary line L34.

[0054] Thus, in the tire 1 of this embodiment, the position of the maximum thickness of the cushion rubber layer 41 is located in the tire axial direction, outward from the belt end 31c of the belt 31 in the tire axial direction, and between the first end 310a and the second end 320a. By satisfying this relationship, the maximum thickness position of the cushion rubber layer 41 is positioned to a point where the curvature of the belt 31 can be sufficiently suppressed. Furthermore, the position of the maximum thickness of the cushion rubber layer 41 is provided at a position corresponding to the staggered shoulder, which effectively suppresses belt separation caused by the presence of the staggered shoulder.

[0055] Furthermore, in the tire 1 of this embodiment, the position of the maximum thickness of the cushion rubber layer 41 is located in the tire axial direction, outward from the belt end 31c of the belt 31 and inward from the belt reinforcing layer end 34a of the belt reinforcing layer 34. By satisfying this relationship, the maximum thickness of the cushion rubber layer 41 is positioned to a location that sufficiently suppresses the curvature of the belt 31 and the belt reinforcing layer 34 when the belt reinforcing layer 34 is provided. Therefore, separation of the belt and the belt reinforcing layer 34 can be effectively suppressed.

[0056] Furthermore, it is desirable that the volume of the cushion rubber layer 41 on the inner side of the tire axial direction is greater than the volume on the outer side of the tire axial direction, with respect to the maximum thickness position. For example, if the volume of the cushion rubber layer 41 on the inner side of the tire axial direction is VI and the volume on the outer side of the tire axial direction is VO, then in this embodiment, VI:VO = 100:87. Note that the above ratio can be changed as appropriate, for example, VI:VO = 100:90. This ensures that a sufficient volume of the cushion rubber layer 41 is secured in the portion on the inner side of the tire axial direction from the maximum thickness position, which contributes to supporting the belt 31, staggered shoulder, belt reinforcement layer 34, etc. Also, on the outer side of the cushion rubber layer 41 in the tire axial direction from the maximum thickness position, the volume of the cushion rubber layer 41 is relatively reduced, which allows for a higher proportion occupied by the tread rubber 36, thereby suppressing the influence of the cushion rubber layer 41 on the original function of the tread 30. For example, when the modulus of the cushion rubber layer 41 is lower than the modulus of the tread rubber 36, it is possible to suppress the excessive reduction in rigidity near the shoulder 40 due to the presence of the cushion rubber layer 41.

[0057] Furthermore, it is desirable that the modulus of the cushion rubber layer 41 be less than or equal to the modulus of the tread rubber 36. For example, if the modulus of the tread rubber 36 is 10.5 ± 1.5 MPa, the modulus of the cushion rubber layer 41 can be 7.5 ± 1.5 MPa. By having the modulus of the cushion rubber layer 41 be less than or equal to the modulus of the tread rubber 36, the cushion rubber layer 41 is soft against deformation and suitable for absorbing vibrations, thereby improving separation resistance. Note that the modulus refers to the 300% elongation modulus (M300) measured in an atmosphere of 23°C in accordance with "3.7 Stress at a given elongation, S" of JIS K6251:2010.

[0058] The tire 1 according to the embodiment described above provides the following effects.

[0059] (1) The tire 1 according to this embodiment is a pneumatic tire comprising: a pair of beads 10; a pair of sidewalls 20 extending radially outward from each of the pair of beads 10; a tread 30 disposed between the pair of sidewalls 20; and a carcass ply 50 spanning across the pair of beads 10, wherein the tread 30 has a belt 31 disposed on the outer surface side of the tire than the carcass ply 50, and a shoulder block 350 provided at the end of the tread surface 37 in the axial direction of the tire, wherein the shoulder block 350 has a first shoulder block 310 having a first end 310a on the outer side in the axial direction of the tire, and the first end 31 The first shoulder block 310 and the second shoulder block 320 are arranged alternately in the tire circumferential direction, and the cushion rubber layer 41 is located in a region sandwiched between at least the carcass ply 50 and the belt end 31c, which is the tire axial end of the belt 31, in the tire axial half cross section, and the maximum thickness position of the cushion rubber layer 41, which is the tire radially outward position of the cushion rubber layer 41, is located in the tire axial direction, further outward than the belt end 31c, and between the first end 310a and the second end 320a.

[0060] As a result, the maximum thickness position of the cushion rubber layer 41 is positioned to correspond to the staggered shoulder, effectively suppressing belt separation caused by the presence of the staggered shoulder. Therefore, it is possible to provide a pneumatic tire that has a staggered shoulder and can improve separation resistance without impairing handling stability.

[0061] (2) In the tire 1 described in (1), the volume of the cushion rubber layer 41 on the inner side of the tire axial direction is greater than the volume on the outer side of the tire axial direction, with respect to the position of the maximum thickness.

[0062] This ensures that a sufficient volume of cushioning rubber layer 41 is secured in the portion axially inward of the tire, beyond the point of maximum thickness that contributes to supporting the belt 31, staggered shoulder, belt reinforcement layer 34, etc. Furthermore, it suppresses the influence of the cushioning rubber layer 41 on the original function of the tread 30.

[0063] (3) In the pneumatic tire described in (1) or (2), the modulus of the cushion rubber layer 41 is less than or equal to the modulus of the tread rubber 36 that constitutes the tread 30.

[0064] As a result, the cushion rubber layer 41 is soft against deformation and suitable for absorbing vibrations, thereby improving resistance to separation.

[0065] (Transformed form) The embodiments described above are not limited to those described above, and various modifications and changes are possible, which are also within the scope of this disclosure.

[0066] In the (modified form 1) embodiment, the maximum thickness position of the cushion rubber layer 41 is described as being located outward in the tire axial direction from the belt end 31c of the belt 31 and inward in the tire axial direction from the belt reinforcing layer end 34a of the belt reinforcing layer 34. However, the description is not limited to this, and for example, the maximum thickness position of the cushion rubber layer 41 may be located outward in the tire axial direction from the belt reinforcing layer end 34a of the belt reinforcing layer 34.

[0067] (Modified form 2) In the embodiment described, an example with a belt reinforcing layer 34 was given. However, the invention is not limited to this, and for example, a pneumatic tire without a belt reinforcing layer 34 may also be used.

[0068] The embodiments and variations may be used in combination as appropriate, but a detailed explanation is omitted. Furthermore, this disclosure is not limited to the embodiments described above. [Explanation of Symbols]

[0069] 1 tire 1c inner surface of tire 10 beads 11 Bead core 12 Bead Fillers 13 Rim strip rubber 13a Rim strip rubber outer edge in the tire radial direction 15 Rimline 20 Sidewall 21 Sidewall rubber 21a The outer edge of the tire in the radial direction of the sidewall rubber 21b Sidewall rubber, inner edge in the tire's radial direction 30 tread 31 belt 31c belt end 34 Belt reinforcement layer 34a Belt reinforcement layer end 36 Tread Rubber 36a Tread rubber tire axial outer edge 37 Tread surface 40 Shoulder 41 Cushion rubber layer 41a The apex of the cushion rubber layer 41b Edge of the cushion rubber layer 41c Edge of the cushion rubber layer 50 Carcass Ply 50A Ply Body 50B Winding section 50C bent part 51 First Carcass Spry 52. Second Carcass Spry 60 Inner Liner 70 First rubber layer 80 Second rubber layer 300 Tread Pattern 310 First shoulder block 310a 1st end 311 Inner belt 312 Outer belt 320 Second Shoulder Block 320a 2nd end 331 Shoulder main groove 332 lug grooves 341 Inner belt reinforcement layer 342 Outer belt reinforcement layer 350 Shoulder Block 351 Sipe 360 tread pattern 300 inner area

Claims

1. A pneumatic tire comprising: a pair of beads; a pair of sidewalls extending radially outward from each of the pair of beads; a tread positioned between the pair of sidewalls; and a carcass ply spanning across the pair of beads, The tread comprises a belt positioned on the outer surface side of the tire than the carcass ply, and shoulder blocks provided at the ends of the tread surface in the tire axial direction. The shoulder block comprises a first shoulder block having a first end on the outer side in the axial direction of the tire, A second shoulder block having a second end that is relatively outward in the tire axial direction compared to the first end, Equipped with, The first shoulder block and the second shoulder block are arranged alternately in the circumferential direction of the tire. In the axial half-section of the tire, The belt comprises a cushion rubber layer positioned in a region sandwiched between at least the carcass ply and the belt end, which is the end of the belt in the tire axial direction, A pneumatic tire in which the position of maximum thickness of the cushion rubber layer, which corresponds to the position where the thickness of the cushion rubber layer is maximum and is located radially outward of the cushion rubber layer in the tire axial direction, is located radially outward of the belt end and between the first end and the second end.

2. In the pneumatic tire described in claim 1, The cushion rubber layer is a pneumatic tire in which the volume on the inner side of the tire axial direction is greater than the volume on the outer side of the tire axial direction, with respect to the position of the maximum thickness.

3. In the pneumatic tire according to claim 1 or claim 2, A pneumatic tire wherein the modulus of the cushion rubber layer is less than or equal to the modulus of the tread rubber constituting the tread.

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