tire

Abstract

To improve weight reduction and reduce rolling resistance. [Solution] In a pneumatic tire, the belt layer 7 comprises a pair of intersecting belts 71 and 72 on which belt cords intersect, and a circumferential reinforcing layer 73 positioned between the intersecting belts 71 and 72, the width W1 in the tire width direction being smaller than that of the intersecting belts 71 and 72 and being 90% or less of the unfolded width TDW of the tread portion 1, and the cord angle of the belt cords with respect to the tire circumferential direction being 5° or less in absolute value. Furthermore, in this pneumatic tire, the outer surface of the tire, located radially outward from the winding end 4c of the carcass layer 4 of the sidewall portion 2 and radially inward from the tire's maximum width position, is provided with a recess 20 that is continuous in the tire circumferential direction and whose contour line in the meridional section is composed of a plurality of arcs with different radii of curvature.

Description

[Technical Field]

[0001] This invention relates to tires. [Background technology]

[0002] For example, Patent Document 1 describes a pneumatic tire having a belt consisting of at least three belt layers on the radially outer side of the carcass.

[0003] For example, Patent Document 2 describes a pneumatic tire in which continuous recesses in the circumferential direction are formed on the outer surface of the tire in the sidewall portion in order to reduce weight while maintaining the durability of the bead portion. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2018-020746 [Patent Document 2] Japanese Patent Publication No. 2023-146035 [Overview of the project] [Problems that the invention aims to solve]

[0005] To comply with environmental regulations, fuel-efficient tires are becoming mainstream, and reducing rolling resistance is becoming necessary. As a method for reducing rolling resistance, a zero-degree belt structure has been proposed, which is expected to suppress outer diameter growth and reduce strain in the cross belts. However, typical heavy-duty tires have a four-belt structure, and inserting a zero-degree belt into this four-belt structure would increase weight, potentially negating the effect of reducing rolling resistance.

[0006] The purpose of this invention is to provide a tire that can improve weight reduction and rolling resistance. [Means for solving the problem]

[0007] To achieve the above objective, a tire according to one aspect of the present invention includes a tread portion, a pair of sidewall portions arranged on both sides of the tread portion, a pair of bead portions arranged radially inward of each sidewall portion, at least one carcass layer stretched between the pair of bead portions, and a belt layer arranged radially outward of the carcass layer, wherein the belt layer has a pair of cross belts on which belt cords intersect, and a circumferential reinforcing layer arranged between the cross belts, having a width in the tire width direction smaller than the cross belts and 90% or less of the unfolded width of the tread portion, and the cord angle of the belt cords with respect to the tire circumferential direction is 5° or less in absolute value, and each bead portion has a bead core and a bead filler arranged radially outward of the bead core, and the carcass layer is wound up from the inside to the outside of the tire around the bead core and the bead filler between the pair of bead portions The tire comprises a main body located at the front, and a winding portion wound up on the outer side in the tire width direction of the bead core and the bead filler, and the sidewall portion has a recess that is continuous in the tire circumferential direction on the outer surface of the tire, which is radially outward from the winding end of the carcass layer of the sidewall portion and radially inward from the maximum tire width position, and the contour line in the meridional section is composed of a plurality of arcs with different radii of curvature, and when the width between the pair of bead portions is set to a specified rim width in the non-rim assembled state, the line drawn so as to be tangent to the outer contour of the sidewall portion in the meridional section is defined as tangent line L1, the point where tangent line L1 and the outer contour of the recess in the sidewall portion on the radially outward side of the tire is defined as tangency P1, the line passing through the winding end of the carcass layer and intersecting the main body portion perpendicularly is defined as perpendicular line L2, and the line passing through tangency P1 and intersecting the main body portion perpendicularly is defined as perpendicular line L3, and the area A [mm²] of the region enclosed by the outer contour of the sidewall portion and tangent line L1 is defined as 2 The area S[mm²] of the region enclosed by the outer contour of the sidewall portion, the main body portion, the perpendicular line L2, and the perpendicular line L3. 2 The relationship between ] and the thickness G1 [mm] of the bead filler measured along the perpendicular L2 satisfies the relationship 0.10 × (G1 - 17) ≤ A / (S + A) ≤ 0.05 × (G1 - 10). [Effects of the Invention]

[0008] According to this invention, weight reduction and reduction of rolling resistance can be improved.

Brief Description of the Drawings

[0009] [Figure 1] FIG. 1 is a meridian cross-sectional view of a pneumatic tire according to an embodiment. [Figure 2] FIG. 2 is an enlarged meridian cross-sectional view of a bead portion of a pneumatic tire according to an embodiment. [Figure 3] FIG. 3 is a developed view of a belt layer of a pneumatic tire according to an embodiment. [Figure 4] FIG. 4 is an enlarged meridian cross-sectional view of a bead portion of a pneumatic tire according to an embodiment. [Figure 5] FIG. 5 is an enlarged meridian cross-sectional view of a bead portion of a pneumatic tire according to an embodiment. [Figure 6] FIG. 6 is an enlarged meridian cross-sectional view of a bead portion of a pneumatic tire according to an embodiment. <L [Figure 7] FIG. 7 is a chart showing the results of a performance test of a pneumatic tire according to an embodiment. [Figure 8] FIG. 8 is a chart showing the results of a performance test of a pneumatic tire according to an embodiment. [Figure 9] FIG. 9 is a chart showing the results of a performance test of a pneumatic tire according to an embodiment. [Figure 10] FIG. 10 is a chart showing the results of a performance test of a pneumatic tire according to an embodiment.

Mode for Carrying Out the Invention

[0010] Hereinafter, embodiments according to the present invention will be described in detail based on the drawings. Note that the present invention is not limited by this embodiment. In addition, the components of this embodiment include those that are replaceable and self-evidently replaceable while maintaining the identity of the invention. Further, a plurality of modifications described in this embodiment can be arbitrarily combined within the scope self-evident to those skilled in the art.

[0011] In the following description, the tire radial direction refers to the direction orthogonal to the tire rotation axis (not shown) which is the rotation axis of the pneumatic tire of the embodiment, the inner side in the tire radial direction refers to the side facing the tire rotation axis in the tire radial direction, and the outer side in the tire radial direction refers to the side away from the tire rotation axis in the tire radial direction. Also, the tire circumferential direction refers to the circumferential direction around the tire rotation axis as the central axis. Further, the tire width direction refers to the direction parallel to the tire rotation axis, the inner side in the tire width direction refers to the side facing the tire equatorial plane (tire equator line) CL in the tire width direction, and the outer side in the tire width direction refers to the side away from the tire equatorial plane CL in the tire width direction. The tire equatorial plane CL is a plane that is orthogonal to the tire rotation axis and passes through the center of the tire width of the pneumatic tire, and the tire equatorial plane CL coincides with the tire width direction center line which is the central position in the tire width direction of the pneumatic tire. The tire equator line refers to a line on the tire equatorial plane CL and along the tire circumferential direction of the pneumatic tire. Also, the cross-section in the tire meridian direction (meridian cross-sectional view) refers to the cross-section when the tire is cut by a plane including the tire rotation axis.

[0012] In this embodiment, as an example, a pneumatic radial tire for heavy loads mounted on heavy-duty vehicles such as trucks and buses will be described.

[0013] The pneumatic tire of the embodiment has an annular structure centered on the tire rotation axis. As shown in FIG. 1, the pneumatic tire includes a pair of bead cores 5, a pair of bead fillers 6, a carcass layer 4, a belt layer 7, a tread rubber 11, a pair of sidewall rubbers 12, and a pair of rim cushion rubbers 13.

[0014] [[ID= fourteen]]A pair of bead cores 5 is formed by winding one or a plurality of bead wires made of steel in an annular and multiple manner, and is embedded in the bead portion 3 to constitute the cores of the bead portions 3 on both sides in the tire width direction.

[0015] A pair of bead fillers 6 are respectively arranged on the outer side in the tire radial direction of the pair of bead cores 5 to reinforce the bead portion 3.

[0016] The carcass layer 4 has a single-layer structure consisting of one carcass ply or a multi-layer structure consisting of multiple carcass plies stacked together. The carcass layer 4 is stretched toroidally between the two bead cores 5 to form the framework of the tire. The ends of the carcass layer 4 are also wound back outward in the tire width direction and secured so as to enclose the bead cores 5 and the bead filler 6. The carcass layer 4 is constructed by rolling a plurality of steel carcass cords covered with a coating rubber, and has a cord angle (defined as the longitudinal inclination angle of the carcass cords with respect to the circumferential direction of the tire) of 80 degrees to 90 degrees in absolute value for radial tires, and 30 degrees to 45 degrees for bias tires. As shown in Figure 2, the carcass layer 4 has a main body portion 4a and a winding portion 4b at both ends stretched between the two bead cores 5. The main body portion 4a is the part located mainly on the inside in the tire width direction of the bead core 5 and bead filler 6, and is wound up from the inside to the outside of the tire around the bead core 5 and bead filler 6, and is located between the pair of bead portions 3. The winding portion 4b is continuous with the main body portion 4a and is mainly located on the outside in the tire width direction of the bead core 5 and bead filler 6, and the ends of the bead core 5 and bead filler 6 that are wound up on the outside in the tire width direction form the winding ends 4c of the carcass layer 4.

[0017] The belt layer 7 is a three-layer structure consisting of three belt plies (belts) 71-73 stacked sequentially from the inside in the radial direction of the tire, and is arranged around the outer circumference of the carcass layer 4. These belt plies 71-73 include a pair of cross belts 71, 72 and a circumferential reinforcing layer 73. As shown in Figure 3, the pair of cross belts 71, 72 are constructed by covering multiple belt cords 71a, 72a made of steel with a rubber coating and then rolling them. The pair of cross belts 71, 72 have a cord angle a (defined as the longitudinal inclination angle of the belt cords 71a, 72a with respect to the circumferential direction of the tire) of 10 degrees or more and 45 degrees or less in absolute value. Furthermore, the pair of cross belts 71, 72 have cord angles of opposite signs, and the longitudinal directions of the belt cords 71a, 72a are stacked so as to intersect each other (having a so-called cross-ply structure). As shown in Figure 3, the circumferential reinforcement layer 73 is constructed by covering multiple steel belt cords 73a with a coating rubber and then rolling them. The circumferential reinforcement layer 73 has belt cords 73a with a cord angle b (defined as the longitudinal inclination angle of the belt cords 73a with respect to the tire circumferential direction) of 5 degrees or less in absolute value. As shown in Figures 1 and 3, the circumferential reinforcement layer 73 is laminated between the cross belts 71 and 72 in the tire radial direction. The width W1 of the circumferential reinforcement layer 73 in the tire width direction is smaller than that of the cross belts 71 and 72 and is 90% or less of the unfolded width TDW of the tread portion 1. The circumferential reinforcement layer 73 is laminated with the belt cords 73a intersecting the longitudinal direction of the belt cords 71a and 72a of the cross belts 71 and 72.

[0018] The tread rubber 11 is positioned radially outward of the carcass layer 4 and belt layer 7 to form the tread portion 1 of the pneumatic tire. The tread rubber 11 has a tread surface (tread tread) 1a on its outer circumference that contacts the road surface during driving. The outer end of the tread surface 1a in the tire width direction becomes the contact end T (see Figure 1). The straight distance in the tire width direction when the tread surface 1a is unfolded between each contact end T is defined as the unfolded width TDW.

[0019] Here, the contact end T is defined as the position of the maximum width in the tire width direction at the contact surface between the tread surface 1a and the flat plate when the tire is mounted on a specified rim, filled with a specified internal pressure, and with the tire's equatorial plane CL perpendicular to the flat plate and a load corresponding to the specified load is applied.

[0020] A specified rim refers to a "standard rim" as defined by JATMA, a "design rim" as defined by TRA, or a "measuring rim" as defined by ETRTO. Furthermore, specified internal pressure refers to the "maximum air pressure" as defined by JATMA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" as defined by TRA, or "INFLATION PRESSURES" as defined by ETRTO. Finally, specified load refers to the "maximum load capacity" as defined by JATMA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" as defined by TRA, or "LOAD CAPACITY" as defined by ETRTO.

[0021] A pair of sidewall rubbers 12 are positioned on the outer side of the carcass layer 4 in the tire width direction, forming the sidewall portions 2 on both sides in the tire width direction.

[0022] The pair of rim cushion rubbers 13 extend from the inside in the tire radial direction to the outside in the tire width direction of the bead core 5 and the carcass layer 4's reversed portion, respectively, forming the rim fitting surface of the bead portion 3.

[0023] Furthermore, as shown in Figure 1, the pneumatic tire of the embodiment includes a tread surface 1a with a plurality (five in Figure 1) of circumferential main grooves 1b provided with the tire equatorial plane CL as the boundary, and six rows of land areas 1c partitioned by the circumferential main grooves 1b.

[0024] The circumferential main groove 1b is provided extending along the circumferential direction of the tire and has an annular structure that extends continuously around the entire circumference of the tire. The circumferential main groove 1b is defined as a groove that is required to display a wear indicator as specified by JATMA.

[0025] In the pneumatic tire of this embodiment, as shown in Figures 1 and 2, recesses 20 are provided on the outer surface of each sidewall portion 2, continuous in the circumferential direction of the tire. The configuration of the recesses 20 will be described below.

[0026] When the width between the pair of bead portions 3 is set to the specified rim width in the non-rim-assembled state, the recess 20 is positioned radially outward from the winding end 4c of the carcass layer 4 and radially inward from the tire's maximum width position P, as shown in Figure 2. In other words, the contact point P1 of the recess 20, described later, is located radially inward from the tire's maximum width position P, and the contact point P2, described later, is located radially outward from the winding end 4c of the carcass layer 4. By providing such a recess 20, the amount of rubber near the bead portion 3 can be suppressed, thereby reducing the tire weight.

[0027] The specified rim width (Wr) is the width of the specified rim (the "applicable rim" as defined by JATMA, the "Design Rim" as defined by TRA, or the "Measuring Rim" as defined by ETRTO).

[0028] The contour of the recess 20 in the meridional section is composed of multiple arcs with different radii of curvature and is smoothly curved. For example, the contour of the recess 20 is formed by a combination of multiple arcs, one convex outward in the tire width direction and the other convex inward in the tire width direction. In particular, among the multiple arcs that constitute the contour of the recess 20, it is preferable that the innermost arc and the outermost arc in the tire radial direction are convex outward in the tire width direction, so that they smoothly continue with the arcs that are convex outward in the tire width direction on the outer contour of the sidewall portion 2.

[0029] Furthermore, in the embodiment, when the width between the pair of bead portions 3 is set to the specified rim width in the non-rim-assembled state, as shown in Figure 2, a straight line drawn so as to straddle the recess 20 in the meridional cross-section and be tangent to the outer contour of the sidewall portion 2 is defined as tangent line L1, and the point where tangent line L1 and the outer contour of the sidewall portion 2 are tangent (the point on the outer side of the recess 20 in the tire radial direction) is defined as contact point P1. Also, in the pneumatic tire, a straight line passing through the winding end 4c of the carcass layer 4 and intersecting the main body portion 4a perpendicularly is defined as perpendicular line L2. Also, in the pneumatic tire, a straight line passing through contact point P1 and intersecting the main body portion 4a perpendicularly is defined as perpendicular line L3. At this time, the area A [mm²] of the region of the recess 20 enclosed by the outer contour of the sidewall portion 2 and tangent line L1 (the shaded area in Figure 2) is defined as the area of ​​the pneumatic tire. 2 The area S [mm²] of the region enclosed by the outer contour of the sidewall portion 2, the main body portion 4a of the carcass layer 4, and perpendiculars L2 and L3 (the shaded area in Figure 2) 2 The relationship between the thickness G1 [mm] of the bead filler 6 measured along the perpendicular L2 satisfies 0.10 × (G1 - 17) ≤ A / (S + A) ≤ 0.05 × (G1 - 10).

[0030] The pneumatic tire of the above-described embodiment has the following features. The pneumatic tire includes a tread portion 1, a pair of sidewall portions 2 arranged on both sides of the tread portion 1, a pair of bead portions 3 arranged radially inward of each sidewall portion 2, at least one carcass layer 4 stretched between the pair of bead portions 3, and a belt layer 7 arranged radially outward of the carcass layer 4. In this pneumatic tire, the belt layer 7 includes a pair of cross belts 71, 72 on which belt cords 71a, 72a intersect, and a circumferential reinforcing layer 73 arranged between the cross belts 71, 72, the width W1 in the tire width direction being smaller than the cross belts 71, 72 and 90% or less of the unfolded width TDW of the tread portion 1, and the cord angle b of the belt cord 73a with respect to the tire circumferential direction being 5° or less in absolute value. In this pneumatic tire, each bead portion 3 includes a bead core 5 and a bead filler 6 arranged radially outward of the bead core 5. In this pneumatic tire, the carcass layer 4 has a main body portion 4a that is wound up from the inside to the outside of the tire around the bead core 5 and bead filler 6 and is located between the pair of bead portions 3, and a wound portion 4b that is wound up on the outside in the tire width direction of the bead core 5 and bead filler 6. In this pneumatic tire, when the width between the pair of bead portions 3 is set to a specified rim width in the non-rim assembled state, the outer surface of the tire, which is radially outside the wound end 4c of the carcass layer 4 of the sidewall portion 2 and radially inside the tire's maximum width position, has a recess 20 that is continuous in the tire circumferential direction and whose meridional contour is composed of multiple arcs with different radii of curvature. In this pneumatic tire, as described above, the area A [mm²] of the region enclosed by the outer contour of the sidewall portion 2 and the tangent L1 is 2 The area S[mm²] of the region enclosed by the outer contour of the sidewall portion 2, the main body portion 4a, the perpendicular line L2, and the perpendicular line L3. 2 The relationship between ] and the thickness G1 [mm] of the bead filler 6 measured along the perpendicular L2 satisfies the relationship 0.10 × (G1 - 17) ≤ A / (S + A) ≤ 0.05 × (G1 - 10).

[0031] With this pneumatic tire, the circumferential reinforcing layer 73 maintains the shape of the tread portion 1 when new and over time, resulting in reduced rolling resistance. With this pneumatic tire, by making the circumferential reinforcing layer 73 narrower than the cross belts 71 and 72 and placing it between the cross belts 71 and 72, fluctuations in the rigidity of the tread portion 1 in the tire width direction are mitigated, reducing energy loss near the groove bottoms of the grooves on the tread surface 1a and the edges of the belt layer 7, resulting in reduced rolling resistance. With this pneumatic tire, weight reduction is achieved by providing recesses 20 in the sidewall portion 2. With this pneumatic tire, by increasing the thickness G1 of the bead filler 6 in proportion to the area A of the recesses 20, strain near the winding end 4c of the carcass layer 4 can be dispersed, enabling reduced rolling resistance.

[0032] In pneumatic tires, the durability of the bead portion 3, which is a concern when a recess 20 is provided near the bead portion 3 to reduce the weight of the tire, can be maintained in good condition. Specifically, in pneumatic tires, the recess 20 is located radially outward from the rolled-up end 4c of the carcass layer 4 in the sidewall portion 2 and radially inward from the tire's maximum width position P. The area of ​​the recess 20 (area A), the amount of rubber radially outward from the rolled-up end 4c (area S), and the thickness G1 of the bead filler 6 are set in the above-mentioned relationship. As a result, the thickness G1 of the bead filler 6 can be increased in proportion to the area of ​​the recess 20, dispersing the strain near the rolled-up end 4c caused by the provision of the recess 20, and ensuring good durability of the bead portion 3.

[0033] In a pneumatic tire, if the area A, area S, and thickness G1 of the bead filler 6 are in the relationship 0.10 × (G1-17) ≤ A / (S+A), a sufficient amount of rubber to distribute the strain can be secured, and a significant improvement in the durability of the bead portion 3 can be expected. Furthermore, if the area A, area S, and thickness G1 of the bead filler 6 are in the relationship A / (S+A) ≤ 0.05 × (G1-10), a sufficient area of ​​the recess 20 can be secured, and a significant reduction in tire weight can be expected. In addition, in order to significantly obtain the above effects, it is preferable that the area A, area S, and thickness G1 of the bead filler 6 satisfy the relationship 0.10 × (G1-16) ≤ A / (S+A) ≤ 0.05 × (G1-12) in the pneumatic tire of the embodiment. The value of the ratio A / (S+A) is not particularly limited, but it is preferably between 0.05 and 0.25.

[0034] Furthermore, in the pneumatic tire of the embodiment, when the width between the pair of bead portions 3 is set to the specified rim width in the non-rim assembled state, as shown in Figure 1, in the meridional section, the minimum width W2 in the tire width direction between each recess 20 and the width W1 of the circumferential reinforcing layer 73 satisfy the relationship 0.45 ≤ W1 / W2 ≤ 0.85.

[0035] With this pneumatic tire, if W1 / W2 is less than 0.45, the width of the circumferential reinforcing layer 73 becomes relatively large, resulting in excessive rigidity and a tendency for reduced rolling resistance. If W1 / W2 exceeds 0.85, the spacing between the recesses 20 widens and the recesses 20 become shallower, resulting in a tendency for reduced weight. Therefore, by setting W1 / W2 within the above range, this pneumatic tire achieves weight reduction by reducing the rubber volume of the recesses 20, and reduces rolling resistance by ensuring the rigidity of the tread portion 1 through the appropriate placement of the circumferential reinforcing layer 73. To significantly obtain the above effects, it is preferable that this pneumatic tire satisfies the range of 0.50 ≤ W1 / W2 ≤ 0.80.

[0036] Furthermore, in the pneumatic tire of the embodiment, when the width between the pair of bead portions 3 is set to the specified rim width in the non-rim assembled state, as shown in Figure 1, in the meridional section, the width W3 is half of the minimum width W2 in the tire width direction between each recess 20 minus the width W1 of the circumferential reinforcing layer 73, and position B is a position that is 1 / 3 of the width W3 away inward in the tire width direction from the end of width W2 in one direction of the tire width, then position B is positioned outside in the tire width direction compared to the end of the unfolded width TDW (contact end T).

[0037] With this pneumatic tire, by setting the minimum width W2 between the width W1 of the circumferential reinforcing layer 73 and the recess 20 within a specified range, the appropriate width W1 of the circumferential reinforcing layer 73 is achieved, ensuring the rigidity of the tread portion 1. With this pneumatic tire, by setting the minimum width W2 between the width W1 of the circumferential reinforcing layer 73 and the recess 20 within a specified range, it is possible to prevent the localized placement of recesses 20 while ensuring the area A of the recess 20. This minimizes the deflection caused by the recess 20, and a good balance can be achieved between weight reduction due to the recess 20 and reduced rolling resistance by suppressing deflection and ensuring the rigidity of the tread portion 1.

[0038] Furthermore, in the pneumatic tire of the embodiment, the belt cord 73a of the circumferential reinforcing layer 73 is made of steel wire and has 15 [wires / 50mm] to 30 [wires / 50mm] ends.

[0039] The number of ends is the number of belt cords 73a per 50 mm in the circumferential direction of a tire under no-load conditions when a pneumatic tire is mounted on a standard rim and filled to the standard internal pressure, and the unit is [belts / 50 mm].

[0040] With this pneumatic tire, by setting the number of ends of the circumferential reinforcing layer 73 within a specified range, the rigidity of the tread section 1 is optimized, and strain near the groove bottoms of the grooves on the tread surface 1a and the edges of the belt layer 7 is reduced, resulting in lower rolling resistance.

[0041] Furthermore, in the pneumatic tire of the embodiment, as shown in Figure 2, in the meridional section, the minimum distance G2 from the main body portion 4a of the carcass layer 4 to the outer contour of the recess 20 satisfies the range of 2.5 [mm] ≤ G2 ≤ ​​7.5 [mm].

[0042] With this pneumatic tire, by setting the minimum distance G2 from the carcass layer 4 to the outer contour of the recess 20 within a specified range, the rigidity of the sidewall portion 2 is maintained, deflection due to the reduction in rubber volume of the recess 20 can be suppressed, and both weight reduction and low rolling resistance can be achieved. In order to significantly obtain the above effects, it is preferable that this pneumatic tire satisfies the range of 3.0 [mm] ≤ G2 ≤ ​​6.0 [mm].

[0043] Furthermore, in the pneumatic tire of the embodiment, as shown in Figure 2, in the meridional section, the minimum distance G3 from the winding end 4c of the carcass layer 4 to the outer contour of the tire satisfies the range of 7.0 [mm] ≤ G3 ≤ 14.0 [mm].

[0044] With this pneumatic tire, by ensuring the minimum distance G3 from the rolled-up end 4c of the carcass layer 4 to the outer contour of the tire, the rigidity of the rubber around the carcass layer 4 is maintained, and deflection due to the reduction in rubber volume of the recess 20 can be suppressed, thereby achieving both weight reduction and low rolling resistance. In order to significantly obtain the above effects, it is preferable that this pneumatic tire satisfies the range of 8.0 [mm] ≤ G3 ≤ 13.0 [mm].

[0045] In addition, for the pneumatic tire, as shown in FIG. 5, when the distance between the turned-up end 4c measured on the extension line of the turned-up portion 4b and the outer surface of the recess 20 in the meridian cross section is defined as G4, the distance G4 is preferably 10.0 [mm] or more and 40.0 [mm] or less, more preferably 15.0 [mm] or more and 37.0 [mm] or less. Thereby, in combination with the definition of the distance G3, the distance from the turned-up end 4c to the outer contour of the tire can be sufficiently ensured, the strain between the turned-up end 4c and the outer contour of the tire can be dispersed, which is advantageous for improving the durability of the bead portion 3. When the distances G3 and G4 are smaller than the above ranges respectively, the rubber amount cannot be sufficiently ensured, the strain of the turned-up end 4c cannot be sufficiently dispersed, and the effect of improving the durability cannot be sufficiently expected. When the distances G3 and G4 are larger than the above ranges respectively, the effect of reducing the tire weight cannot be sufficiently expected.

[0046] Further, in the pneumatic tire of the embodiment, for the sidewall rubber 12 forming the sidewall portion 2, the elongation at break ε side [%] and the elastic modulus E' side [MPa] at 60 [°C] satisfy the range of 450 ≤ ε side , 2.5 ≤ E' side ≤ 5.5.

[0047] The elongation at break is a value [%] measured at room temperature (23 [°C]) in accordance with JIS K6251. The elastic modulus at 60 [°C] is a value [MPa] measured under the conditions of an initial strain of 10 [%], an amplitude of ±2 [%], a frequency of 20 [Hz], and 60 [°C] using a viscoelastic spectrometer in accordance with JIS K6394.

[0048] With this pneumatic tire, if a crack-suppressing rubber with high elongation at break is used, the fracture near the winding end 4c of the carcass layer 4 due to repeated strain during tire rolling is suppressed, improving durability. Furthermore, with this pneumatic tire, by increasing the elastic modulus of the sidewall rubber 12, the rigidity of the sidewall portion 2 reduced by the recess 20 can be compensated for, and the strain of the bead portion 3 is reduced, resulting in lower rolling resistance. In order to significantly obtain the above effects, this pneumatic tire has a value of 500 ≤ ε side , 3.5≦E' side It is preferable that the range ≤ 5.0 is satisfied. The upper limit of the elongation at break of the sidewall rubber 12 is not particularly limited, but it is preferable to set it to 800% or less, for example. If the elastic modulus of the rubber constituting the sidewall rubber 12 at 60°C is 2.5 MPa or more, the rigidity of the sidewall portion 2 can be sufficiently ensured, and if it is 5.5 MPa or less, the elongation at break of the sidewall rubber 12 can be kept good, and a sufficient effect of improving durability performance can be expected.

[0049] Furthermore, in the pneumatic tire of the embodiment, as shown in Figure 4, it is preferable that the bead filler 6 is composed of a two-layer structure consisting of an upper bead filler 6a on the radially outer side of the tire and a lower bead filler 6b on the radially inner side of the tire.

[0050] The upper bead filler 6a preferably has a breaking elongation of 400% or more, more preferably 450% or more. In pneumatic tires, using a bead filler 6 with a high breaking elongation suppresses rupture near the edges of the carcass layer 4 due to repeated strain during rolling, which is advantageous in improving the durability of the bead portion 3. Furthermore, the upper bead filler 6a preferably has a breaking elongation of 800% or less. The lower bead filler 6b preferably has a breaking elongation of 50% or more and 250% or less.

[0051] Furthermore, the modulus of elasticity of the upper bead filler 6a at 60°C is preferably 4.0 MPa to 8.0 MPa, more preferably 4.5 MPa to 7.5 MPa. Similarly, the modulus of elasticity of the lower bead filler 6b at 60°C is preferably 14.0 MPa to 20.0 MPa, more preferably 15.0 MPa to 19.0 MPa. This results in a pneumatic tire with good physical properties of the upper bead filler 6a and lower bead filler 6b when the bead filler 6 has a two-layer structure, which is advantageous in improving the durability of the bead portion 3. When the modulus of elasticity of the upper bead filler 6a and lower bead filler 6b at 60°C is within the above range, the deformation of the bead portion 3 under load is reduced, and the strain of the winding end 4c of the carcass layer 4 is also reduced, thus providing a significant improvement in durability. In pneumatic tires, if the modulus of elasticity at 60°C of the upper bead filler 6a and the lower bead filler 6b is within the range described above, the elongation at break of the bead filler 6 can be improved, and a significant improvement in durability can be expected.

[0052] Furthermore, in the embodiment, the pneumatic tire satisfies the relationship 0.20 ≤ S3 / S2 ≤ 0.80 between the area S2 of the upper bead filler 6a and the area S3 of the lower bead filler 6b in the meridional cross-section.

[0053] With this pneumatic tire, by setting S3 / S2 within the specified range, the strain at the winding end 4c of the carcass layer 4 is dispersed by the upper bead filler 6a, which has a relatively large elongation at break, and the deflection suppression effect is obtained by reducing the rubber volume of the recess 20 by the lower bead filler 6b, which has a relatively large modulus of elasticity, resulting in reduced weight and reduced rolling resistance. In order to significantly obtain the above effects, it is preferable that this pneumatic tire satisfies the range of 0.30 ≤ S3 / S2 ≤ 0.70.

[0054] In a pneumatic tire, as shown in Figure 5, when the point where the tangent line L1 and the outer contour of the sidewall portion 2 meet (the point on the inner side of the recess 20 in the tire radial direction) is defined as the contact point P2, it is preferable that the outer contour of the sidewall portion 2 located between the contact point P2 and point P3 is located outward in the tire width direction, rather than being aligned with the straight line L4 connecting the contact point P2 and point P3, which is 10 mm away from the contact point P2 along the outer contour of the sidewall portion 2 in the tire radial direction outward. As a result, in a pneumatic tire, the outer contour between point P3 and contact point P2 is convex outward in the tire width direction, and the shape (outer contour) of the recess 20 is obtained, which allows for securing the amount of rubber near the winding end 4c and is advantageous in improving the durability of the bead portion 3.

[0055] Furthermore, as shown in Figure 5, it is preferable that the outer contours of the sidewall portion 2 and bead portion 3 located between the contact point P2 and point P4 are positioned outward in the tire width direction, rather than being aligned with the straight line L5 connecting point P2 and point P4, which is 15 mm away from the contact point P2 along the outer contours of the sidewall portion 2 and bead portion 3 in the tire radial direction outward. As a result, the outer contour between point P4 and contact point P2 of the pneumatic tire is also convex outward in the tire width direction, and the shape (outer contour) of the recess 20 is obtained, which allows for securing the amount of rubber near the winding end 4c and is advantageous in improving the durability of the bead portion 3.

[0056] Furthermore, as shown in Figure 6, when the thickness of the bead filler 6 measured on a straight line passing through the contact point P2 and perpendicular to the main body portion 4a is G5 [mm], the ratio of thickness G5 to thickness G1, G5 / G1, satisfies the relationship 0.55 ≤ G5 / G1 ≤ 0.90, and more preferably 0.60 ≤ G5 / G1 ≤ 0.85. This allows the pneumatic tire to secure a volume of bead filler 6 with excellent bending fatigue resistance and fracture characteristics, which is advantageous for improving the durability of the bead portion 3. When G5 / G1 is 0.55 or higher in the pneumatic tire, insufficient rubber volume can be avoided and distortion near the winding end 4c can be sufficiently suppressed, which is expected to have a significant effect on improving durability. Also, when G5 / G1 is 0.90 or lower in the pneumatic tire, insufficient rubber volume in the sidewall portion 2 can be avoided, making it less likely for failures such as ozone cracks to occur.

[0057] As shown in Figure 2, in a pneumatic tire, the area occupied by the bead filler 6 out of the total area S is Sf[mm²]. 2 When this is the case, the ratio Sf / S of area Sf to area S satisfies the relationship 0.25 ≤ Sf / S ≤ 0.50, and more preferably 0.30 ≤ Sf / S ≤ 0.45. This allows the pneumatic tire to secure a volume of bead filler 6 which has excellent bending fatigue resistance and fracture characteristics, which is advantageous for improving the durability of the bead portion 3. When Sf / S is 0.25 or higher in a pneumatic tire, it is possible to avoid a shortage of rubber and sufficiently suppress strain near the edges of the carcass layer 4, and a significant improvement in durability can be expected. Furthermore, when Sf / S is 0.50 or lower in a pneumatic tire, a shortage of rubber in the sidewall portion 2 is avoided, making it less likely for failures such as ozone cracks to occur.

[0058] In a pneumatic tire, as shown in Figure 6, when H1 is the distance along the tire's radial direction from the innermost point of the bead portion 3 in the tire's radial direction (the tip of the bead toe) 3a to the winding end 4c, and H2 is the distance along the tire's radial direction from the innermost point of the bead portion 3 in the tire's radial direction (the tip of the bead toe) 3a to the contact point P2, the ratio H2 / H1 is preferably between 1.1 and 1.5. This results in a better shape for each part of the bead portion 3, which is advantageous for improving the durability of the bead portion 3.

[0059] In the pneumatic tire of this embodiment, as shown in Figure 5, the crack-suppressing rubber layer 14 can also be positioned to cover the rolled-up end 4c of the carcass layer 4. The crack-suppressing rubber layer 14 should be positioned to be in contact with both the sidewall rubber 12 and the rim cushion rubber 13. Furthermore, in the pneumatic tire of this embodiment, as shown in Figure 6, if the steel reinforcement layer 21 described later is provided, it is preferable to position the crack-suppressing rubber layer 14 to cover not only the rolled-up end 4c of the carcass layer 4 but also the end of the steel reinforcement layer 21. Similarly, in the pneumatic tire of this embodiment, as shown in Figure 6, if the organic fiber reinforcement layer 22 described later is provided, it is preferable to position the crack-suppressing rubber layer 14 to cover not only the rolled-up end 4c of the carcass layer 4 but also the end of the organic fiber reinforcement layer 22. When such a crack-suppressing rubber layer 14 is provided in a pneumatic tire, its elongation at break should be set to 400% or more, more preferably 450% or more. By increasing the elongation at break of the crack-suppressing rubber layer 14 in a pneumatic tire, it is possible to suppress breakage near the winding end 4c due to repeated strain during rolling, which is advantageous for improving the durability of the bead. While there is no particular upper limit to the elongation at break of the crack-suppressing rubber layer 14 in a pneumatic tire, it is preferable to set it to, for example, 800% or less.

[0060] In the pneumatic tire of the embodiment, as shown in Figure 6, a steel reinforcement layer 21 can also be arranged along the outer surfaces of the main body portion 4a and the winding portion 4b of the carcass layer 4. The steel reinforcement layer 21 is made of steel cords covered with coated rubber. When a steel reinforcement layer 21 is provided in a pneumatic tire, the end portion 21a on the winding portion 4b side should be set away from the position of the winding end 4c in the radial direction of the tire. The distance between the end portion 21a of the steel reinforcement layer 21 on the winding portion 4b side and the winding end 4c in the radial direction of the tire is preferably 5 mm to 25 mm, more preferably 7 mm to 20 mm. Furthermore, the end 21b of the steel reinforcement layer 21 on the main body portion 4a side is preferably positioned away from the winding end 4c in the radial direction of the tire. The distance between the end 21b of the steel reinforcement layer 21 on the main body portion 4a side and the winding end 4c in the radial direction of the tire should be 5 mm or more and 25 mm or less, more preferably 7 mm or more and 20 mm or less. In this way, by providing a steel reinforcement layer 21 in a pneumatic tire and setting its arrangement as described above, the rigidity of the bead portion 3 can be improved, deformation of the bead portion 3 due to bending can be suppressed, and this is advantageous in improving the durability of the bead portion 3.

[0061] In the pneumatic tire of this embodiment, as shown in Figure 6, an organic fiber reinforcement layer 22 can also be placed on the outer side in the tire width direction of the winding portion 4b of the carcass layer 4. The organic fiber reinforcement layer 22 is made of organic fiber cords covered with coated rubber. In the pneumatic tire of this embodiment, if the above-mentioned steel reinforcement layer 21 is provided, it is preferable to provide two layers of the organic fiber reinforcement layer 22 on the outer circumference side (outer side in the tire width direction) of the winding portion 4b side of the steel reinforcement layer 21, as shown in the figure. In the pneumatic tire, if an organic fiber reinforcement layer 22 is provided, it is preferable that the outer end 22a in the tire radial direction is located further outward in the tire radial direction than the winding end 4c, and the inner end 22b in the tire radial direction is located further inward in the tire radial direction than the center 5a of the bead core 5. Furthermore, it is preferable that the outer end 22a in the tire radial direction of the organic fiber reinforcement layer 22 is 6 mm or more away from the recess 20. Thus, by providing an organic fiber reinforcement layer 22 in the pneumatic tire and setting its arrangement as described above, deformation due to bending can be suppressed, which is advantageous for suppressing strain near the winding end 4c of the carcass layer 4 and improving durability.

[0062] By the way, in this embodiment, as described above, a pneumatic tire was described as an example of a tire. This pneumatic tire can be filled with air, an inert gas such as nitrogen, or other gases. However, the characteristic configuration of the pneumatic tire described in this embodiment can be arbitrarily applied to other tires within the scope of what is obvious to those skilled in the art. Other tires include, for example, airless tires and solid tires. [Examples]

[0063] Figures 7 to 10 are charts showing the results of performance tests of the pneumatic tire according to the embodiment. Below, we will describe the performance evaluation tests conducted on the conventional pneumatic tire, the comparative pneumatic tire, and the pneumatic tire according to the embodiment. The performance evaluation tests focused on weight reduction and low rolling resistance.

[0064] The weight reduction evaluation test involved measuring the mass of a pneumatic tire (size 11R22.5) in its non-rim-mounted state, and then indexing the reciprocal of that mass. This evaluation was performed using an index based on the previous example as the baseline (100), with a higher value indicating a lighter tire weight and greater weight reduction.

[0065] The evaluation test for reduced rolling resistance involved measuring the rolling resistance of pneumatic tires of the above tire size using a rolling resistance test compliant with ISO-28580, and then indexing the reciprocal of the rolling resistance. This evaluation was performed using an index evaluation with the conventional example as the baseline (100), and a higher value indicates reduced rolling resistance.

[0066] Conventional pneumatic tires have recesses and a four-layer belt structure with intersecting belts, but they do not have circumferential reinforcing layers between the intersecting belts.

[0067] The pneumatic tire of the embodiment has a recess and a circumferential reinforcing layer between the intersecting belts in a three-layer belt structure.

[0068] As the test results show, the pneumatic tire of this embodiment shows improvements in tire weight reduction and rolling resistance compared to conventional examples.

[0069] This disclosure includes the following inventions: [Invention 1] The tread section and A pair of sidewall portions arranged on both sides of the tread portion, A pair of bead portions are arranged on the inner side of each sidewall portion in the radial direction of the tire, A carcass layer of at least one layer is stretched between a pair of bead sections, A belt layer is disposed on the outer side of the carcass layer in the radial direction of the tire, Includes, The belt layer comprises a pair of intersecting belts on which belt cords cross, and a circumferential reinforcing layer positioned between the intersecting belts, having a width smaller than the intersecting belts and being 90% or less of the unfolded width of the tread portion, and having a cord angle of the belt cords with respect to the tire circumferential direction of 5° or less in absolute value. Each bead portion comprises a bead core and a bead filler positioned radially outward of the bead core. The carcass layer has a main body portion that is wound around the bead core and the bead filler from the inside to the outside of the tire and positioned between the pair of bead portions, and a winding portion that is wound around the bead core and the bead filler on the outside in the tire width direction. The sidewall portion has a recess that is continuous in the circumferential direction of the tire on the outer surface of the tire, located radially outward from the winding end of the carcass layer in the tire diameter direction and radially inward from the tire's maximum width position, and whose meridional contour is composed of multiple arcs with different radii of curvature, When the width between the pair of bead portions is set to the specified rim width in a non-rim-assembled state, When a straight line drawn in the meridional section so as to be tangent to the outer contour of the sidewall portion is defined as tangent line L1, the point where tangent line L1 and the outer contour of the recess in the sidewall portion on the radial side of the tire are tangent to each other is defined as tangency point P1, a straight line passing through the winding end of the carcass layer and intersecting the main body portion perpendicularly is defined as perpendicular line L2, and a straight line passing through tangency point P1 and intersecting the main body portion perpendicularly is defined as perpendicular line L3, Area A [mm²] of the region enclosed by the outer contour of the sidewall portion and the tangent line L1. 2 The area S[mm²] of the region enclosed by the outer contour of the sidewall portion, the main body portion, the perpendicular line L2, and the perpendicular line L3. 2 The relationship between ] and the thickness G1 [mm] of the bead filler measured along the perpendicular L2 satisfies the relationship 0.10 × (G1 - 17) ≤ A / (S + A) ≤ 0.05 × (G1 - 10), tire. [Invention 2] When the width between the pair of bead portions is set to the specified rim width in a non-rim-assembled state, In the meridional section, the minimum width W2 in the tire width direction between each of the recesses and the width W1 of the circumferential reinforcing layer satisfy the relationship 0.45 ≤ W1 / W2 ≤ 0.85. The tire described in Invention 1. [Invention 3] When the width between the pair of bead portions is set to the specified rim width in a non-rim-assembled state, In the meridional section, when the width W3 is half of the minimum width W2 in the tire width direction between each of the recesses minus the width W1 of the circumferential reinforcing layer, and position B is defined as a position one-third of the width W3 away from the end of the width W2 in the tire width direction, Position B is located outside the tire width direction of the edge of the unfolded width. A tire according to invention 1 or 2. [Invention 4] The belt cord of the circumferential reinforcing layer is made of steel wire and has 15 [wires / 50mm] or more and 30 [wires / 50mm] or less ends. A tire according to any one of inventions 1 to 3. [Invention 5] In the meridional section, the minimum distance G2 from the main body of the carcass layer to the outer contour of the recess satisfies the range of 2.5 [mm] ≤ G2 ≤ ​​7.5 [mm]. A tire according to any one of inventions 1 to 4. [Invention 6] In the meridional section, the minimum distance G3 from the winding end of the carcass layer to the outer contour of the tire satisfies the range of 7.0 [mm] ≤ G3 ≤ 14.0 [mm]. A tire according to any one of inventions 1 to 5. [Invention 7] Regarding the sidewall rubber forming the aforementioned sidewall portion, the elongation at break ε side [%] and the modulus of elasticity E' at 60[℃] side [MPa] is 450≦ε side , 2.5≦E' side Satisfying the range ≤ 5.5, A tire according to any one of inventions 1 to 6. [Invention 8] The bead filler consists of an upper bead filler on the radially outer side of the tire and a lower bead filler on the radially inner side of the tire. In the meridional section, the area S2 of the upper bead filler and the area S3 of the lower bead filler satisfy the relationship 0.20 ≤ S3 / S2 ≤ 0.80. A tire according to any one of inventions 1 to 7. [Explanation of Symbols]

[0070] 1. Tread section 2 Sidewall section 3. Bead section 4. Carcass layer 4a Main body 4b Winding section 4c winding end 5 Bead core 6. Bead Filler 6a Upper bead filler 6b Lower bead filler 7 Belt layer 71, 72 Cross belt 71a, 72a, 73a Belt cord 73 Circumferential reinforcement layer 12 Sidewall rubber

Claims

1. The tread section and A pair of sidewall portions arranged on both sides of the tread portion, A pair of bead portions are arranged on the inner side of each sidewall portion in the radial direction of the tire, A carcass layer of at least one layer is stretched between a pair of bead sections, A belt layer is disposed on the outer side of the carcass layer in the radial direction of the tire, Includes, The belt layer comprises a pair of intersecting belts on which belt cords cross, and a circumferential reinforcing layer positioned between the intersecting belts, having a width smaller than the intersecting belts and being 90% or less of the unfolded width of the tread portion, and having a cord angle of the belt cords with respect to the tire circumferential direction of 5° or less in absolute value. Each bead portion comprises a bead core and a bead filler positioned radially outward of the bead core. The carcass layer has a main body portion that is wound around the bead core and the bead filler from the inside to the outside of the tire and positioned between the pair of bead portions, and a winding portion that is wound around the bead core and the bead filler on the outside in the tire width direction. The sidewall portion has a recess that is continuous in the circumferential direction of the tire on the outer surface of the tire, located radially outward from the winding end of the carcass layer in the tire diameter direction and radially inward from the tire's maximum width position, and whose meridional contour is composed of multiple arcs with different radii of curvature, When the width between the pair of bead portions is set to the specified rim width in a non-rim-assembled state, When a straight line drawn in the meridional section so as to be tangent to the outer contour of the sidewall portion is defined as tangent line L1, the point where tangent line L1 and the outer contour of the recess in the sidewall portion on the radial side of the tire are tangent to each other is defined as tangency point P1, a straight line passing through the winding end of the carcass layer and intersecting the main body portion perpendicularly is defined as perpendicular line L2, and a straight line passing through tangency point P1 and intersecting the main body portion perpendicularly is defined as perpendicular line L3, Area A [mm²] of the region enclosed by the outer contour of the sidewall portion and the tangent line L1. ２ The area S [mm²] of the region enclosed by the outer contour of the sidewall portion, the main body portion, the perpendicular line L2, and the perpendicular line L3. ２ The relationship between ] and the thickness G1 [mm] of the bead filler measured along the perpendicular L2 satisfies the relationship 0.10 × (G1 - 17) ≤ A / (S + A) ≤ 0.05 × (G1 - 10), tire.

2. When the width between the pair of bead portions is set to the specified rim width in a non-rim-assembled state, In the meridional section, the minimum width W2 in the tire width direction between each of the recesses and the width W1 of the circumferential reinforcing layer satisfy the relationship 0.45 ≤ W1 / W2 ≤ 0.

85. The tire according to claim 1.

3. When the width between the pair of bead portions is set to the specified rim width in a non-rim-assembled state, In the meridional section, when the width W3 is half of the minimum width W2 in the tire width direction between each of the recesses minus the width W1 of the circumferential reinforcing layer, and position B is defined as a position one-third of the width W3 away from the end of the width W2 in the tire width direction, Position B is located outside the tire width direction of the edge of the unfolded width. The tire according to claim 1.

4. The belt cord of the circumferential reinforcing layer is made of steel wire and has 15 [wires / 50 mm] or more and 30 [wires / 50 mm] or less ends. The tire according to claim 1.

5. In the meridional section, the minimum distance G2 from the main body of the carcass layer to the outer contour of the recess satisfies the range of 2.5 [mm] ≤ G2 ≤ ​​7.5 [mm]. The tire according to claim 1.

6. In the meridional section, the minimum distance G3 from the winding end of the carcass layer to the outer contour of the tire satisfies the range of 7.0 [mm] ≤ G3 ≤ 14.0 [mm]. The tire according to claim 1.

7. Regarding the sidewall rubber forming the aforementioned sidewall portion, the elongation at break ε ｓｉｄｅ [%] and the modulus of elasticity E' at 60 [°C] ｓｉｄｅ [MPa] is 450 ≤ ε ｓｉｄｅ , 2.5 ≤ E' ｓｉｄｅ Satisfying the range ≤ 5.5, The tire according to claim 1.

8. The bead filler consists of an upper bead filler on the radially outer side of the tire and a lower bead filler on the radially inner side of the tire. In the meridional section, the area S2 of the upper bead filler and the area S3 of the lower bead filler satisfy the relationship 0.20 ≤ S3 / S2 ≤ 0.

80. The tire according to claim 1.

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