tire

Abstract

To improve life performance by suppressing wear on a slippery road surface, and additionally to suppress heat generation on a tread portion.SOLUTION: A tire 1 is provided, comprising a tread rubber forming a tread surface 2a and a lateral groove 3. The tread rubber has a loss tangent tanδ of 0.13 to 0.17. The lateral groove 3 includes a pair of outer groove portions 7 and 7 extending inward in a tire axial direction from a tread end Te and an inner groove portion 8 extending between the outer groove portions 7. The inner groove portion 8 inclines in a second direction which is an opposite direction of the outer groove part 7. A first angle of a first groove wall of the outer groove part 7 is larger than a second angle of a second groove wall of the inner groove portion 8.SELECTED DRAWING: Figure 2

Description

Technical Field

[0006] , , ,

[0001] The present invention relates to a tire.

Background Art

[0002] The following Patent Document 1 describes a pneumatic tire in which a plurality of lug main grooves extending in the tire width direction on both sides of the tire equator and opening at the tread ends are formed in the tread portion, and center inclined grooves connecting the lug main grooves located on both sides of the tire equator are formed.

Prior Art Document

Patent Document

[0007] By adopting the above configuration, the tire of the present invention can suppress wear on slippery road surfaces, improve lifespan, and suppress heat generation in the tread area. [Brief explanation of the drawing]

[0008] [Figure 1] This is a cross-sectional view of the tread portion showing one embodiment of the present invention. [Figure 2] Figure 1 is a plan view of the tire tread. [Figure 3] (A) is a cross-sectional view along line AA in Figure 2, and (B) is a cross-sectional view along line BB in Figure 2. [Figure 4] Figure 2 is a cross-sectional view along the DD line. [Figure 5] This is a perspective view of the land area, including the tread edge. [Modes for carrying out the invention]

[0009] One embodiment of the present invention will be described below with reference to the drawings. Figure 1 is a cross-sectional view of the tread portion 2 of a tire 1 showing one embodiment of the present invention. Figure 2 is a plan view of the tread portion 2 of the tire 1 shown in Figure 1. The present invention is applicable, for example, to pneumatic tires for heavy loads that are frequently driven on rough roads such as roads adjacent to agricultural work areas. However, the present invention can also be applied to pneumatic tires for passenger cars and light trucks, or to non-pneumatic tires that are not filled with compressed air.

[0010] As shown in Figures 1 and 2, the tread portion 2 of the tire 1 is provided with a pair of tread ends Te, a tread rubber 2G that forms a tread surface 2a between the pair of tread ends Te, and a plurality of lateral grooves 3 that extend from one of the pair of tread ends Te to the other. The tread portion 2 is also provided with a flat portion 4 that forms a tread surface 2a.

[0011] In this specification, "tread edge Te" refers to the outermost contact point in the tire's axial direction when a tire 1 in its normal state is subjected to a normal load and contacts a flat surface with a camber angle of 0 degrees. The distance between the two tread edges Te in the tire's axial direction is the tread width TW.

[0012] "Normal condition" refers to a state in which, in the case of pneumatic tires conforming to various standards, the tire is mounted on a normal rim (not shown), filled to the normal internal pressure, and is unloaded. In this specification, unless otherwise specified, the dimensions of each part of the tire are values ​​measured in the aforementioned normal condition.

[0013] A "standard rim" is the rim defined for each tire within the standards system that the tire is based on. For example, it is the "standard rim" for JATMA, the "Design Rim" for TRA, and the "Measuring Rim" for ETRTO.

[0014] "Normal internal pressure" is the air pressure defined for each tire in the standard system including the standards on which the tire is based. In the case of JATMA, it is the "maximum air pressure"; in the case of TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; and in the case of ETRTO, it is the "INFLATION PRESSURE".

[0015] "Normal load" is the load defined for each tire in the standard system including the standards on which the tire is based, in the case of pneumatic tires for which various standards are defined. In the case of JATMA, it is the "maximum load capacity"; in the case of TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; and in the case of ETRTO, it is the "LOAD CAPACITY".

[0016] The loss tangent tanδ of the tread rubber 2G is in the range of 0.13 to 0.17. This is the tread rubber 2G considering wear performance. On the other hand, the tread rubber 2G with such a loss tangent tanδ has relatively high heat generation. In order to balance suppressing wear and reducing heat generation, the loss tangent tanδ of the tread rubber 2G is preferably 0.14 or more and preferably 0.16 or less. The loss tangent tanδ is a value measured using a "viscoelastic spectrometer" under the following conditions in accordance with the provisions of JIS-K6394. · Initial strain: 10% · Amplitude: ±1% · Frequency: 10 Hz · Deformation mode: Tension · Measurement temperature: 70 °C

[0017] Each of the plurality of lateral grooves 3 includes a pair of outer groove portions 7, 7 extending inward in the tire axial direction from the tread ends Te on both sides, and an inner groove portion 8 extending between the pair of outer groove portions 7, 7.

[0018] The pair of outer groove portions 7, 7 are inclined in a first direction (in FIG. 2, diagonally upward to the right) with respect to the tire axial direction. Further, the inner groove portion 8 is inclined in a second direction (in FIG. 2, diagonally upward to the left) opposite to the pair of outer groove portions 7, 7 with respect to the tire axial direction. Such a lateral groove 3 has a relatively large groove surface area compared to a lateral groove (not shown) extending in the tire axial direction, and can increase the heat dissipation area of the tread rubber 2G. Note that the first direction is not limited to being inclined diagonally upward to the right, and may be diagonally upward to the left. Further, the second direction may be opposite to the first direction with respect to the tire axial direction.

[0019] FIG. 3(a) is a cross-sectional view taken along line A-A of FIG. 2 and is a cross-sectional view of the outer groove portion 7. FIG. 3(b) is a cross-sectional view taken along line B-B of FIG. 2 and is a cross-sectional view of the inner groove portion 8. As shown in FIG. 3, each of the pair of outer groove portions 7 includes a pair of first groove walls 7a, 7a, and the pair of first groove walls 7a, 7a are inclined at a first angle θ1 with respect to the normal 2n of the tread surface 2a. The inner groove portion 8 includes a pair of second groove walls 8a, 8a, and the pair of second groove walls 8a, 8a are inclined at a second angle θ2 with respect to the normal 2n of the tread surface 2a.

[0020] In the tire 1 of the present invention, the first angle θ1 is formed larger than the second angle θ2. Such an outer groove portion 7 has an excellent heat dissipation effect and smooths the flow of air from the outer groove portion 7 to the inner groove portion 8. Thus, the lateral groove 3 of the present invention exhibits a high heat dissipation effect. Further, for example, in a tire 1 for heavy loads, generally, the volume of the tread portion 2 (tread rubber 2G) on the tread edge Te side is larger than the volume of the tread portion 2 on the tire equator C side, so heat generation of the tread rubber 2G is relatively large on the tread edge Te side. However, since the first angle θ1 is made larger than the second angle θ2, the tread portion 2 on the tread edge Te side is effectively heat-dissipated. Therefore, in the present invention, it is possible to suppress wear of the tread rubber 2G on a slippery road surface and improve the life performance while suppressing heat generation of the tread portion 2.

[0021] If the first angle θ1 is small, it may be difficult to effectively exert the above-mentioned effects. If the first angle θ1 is excessively large, the tread rigidity may decrease, and the tread portion 2 may wear down quickly. For this reason, the first angle θ1 is preferably 10 degrees or more, more preferably 15 degrees or more, preferably 25 degrees or less, and even more preferably 20 degrees or less. If the difference (θ1-θ2) between the first angle θ1 and the second angle θ2 is small, the heat dissipation effect of the outer groove portion 7 may decrease, and the smooth flow of air from the outer groove portion 7 to the inner groove portion 8 may be hindered. If the difference (θ1-θ2) is excessively large, the tread rigidity may decrease. For this reason, the difference (θ1-θ2) is preferably 5 degrees or more, more preferably 7 degrees or more, preferably 15 degrees or less, and even more preferably 13 degrees or less.

[0022] Each first groove wall 7a and each second groove wall 8a extends, for example, in a straight line. Each first groove wall 7a or each second groove wall 8a may extend in an arc shape. If the first groove wall 7a or the second groove wall 8a extends in an arc shape, the first angle θ1 or the second angle θ2 is defined by the tangent (not shown) of each groove wall 7a, 8a at a position 25% of the groove depth, radially inward from the tread surface 2a.

[0023] As shown in Figure 1, the tread portion 2 of this embodiment includes a tread reinforcing layer B disposed on the inside of the tread rubber 2G in the tire radial direction, and a carcass C disposed on the inside of the tread reinforcing layer B in the tire radial direction. The tread reinforcing layer B and the carcass C are formed of a well-known structure. In this embodiment, the tread rubber 2G, having a loss tangent tanδ of 0.13 to 0.17, is disposed between the tread surface 2a and the tread reinforcing layer B. This suppresses wear of the tread portion 2 and improves life performance. The tread portion 2 may also be formed of tread rubber 2G having a loss tangent tanδ of 0.13 to 0.17, and tread rubber (not shown) having a loss tangent tanδ of less than 0.13, disposed between the tread rubber 2G and the tread reinforcing layer B. In this case, it is desirable that the rubber thickness Dt of the tread rubber 2G is greater than, for example, the groove depth D1 of the outer groove portion 7 of the lateral groove 3 (shown in Figure 3(A)).

[0024] As shown in Figure 2, in this embodiment, the outer groove 7 includes a portion in which the groove width W1 continuously increases from the inside to the outside in the tire axial direction. The outer groove 7 extends, for example, to bend closer to the tread edge Te than to an intermediate position between the tire equator C and the tread edge Te.

[0025] The length La of the outer groove 7 in the tire axial direction is preferably 35% to 45% of the tread width TW. This allows for effective heat dissipation of the tread rubber 2G. The length La of the outer groove 7 is the length in the tire axial direction of the groove centerline 7c of the outer groove 7.

[0026] As shown in Figure 3, the groove depth D1 of each of the pair of outer grooves 7 is greater than the groove depth D2 of the inner groove 8. This further enhances the heat dissipation effect of the outer grooves 7. If the groove depth D1 of the outer grooves 7 is excessively larger than the groove depth D2 of the inner grooves 8, the tread rigidity on the tread edge Te side may decrease, potentially reducing the wear suppression effect. For this reason, the groove depth D1 of the outer grooves 7 is preferably 1.15 times or more, more preferably 1.20 times or more, more preferably 1.50 times or less, and more preferably 1.45 times or less than the groove depth D2 of the inner grooves 8. In this embodiment, the groove depth D1 of the outer grooves 7 is the same as the groove depth D1b of the second section 13 (shown in Figure 4), which will be described later. The groove depth D1 of the outer grooves 7 is, for example, 15 to 25 mm.

[0027] As shown in Figure 2, the groove width W1 of each outer groove 7 is larger than, for example, the groove width W2 of the inner groove 8. This further enhances the heat dissipation effect of the outer groove 7. If the groove width W1 of the outer groove 7 is excessively large, the tread rigidity on the tread edge Te side may decrease, potentially reducing the wear suppression effect. Although not particularly limited, it is desirable that the groove width W1 of the outer groove 7 be 8% to 12% of the tread width TW.

[0028] Each of the pair of outer grooves 7 includes a first portion 12 connected to the tread edge Te, and a second portion 13 located inward in the tire axial direction from the first portion 12 and inclined at a larger angle α2 with respect to the tire axial direction than the first portion 12. Such a first portion 12 helps to draw air more smoothly into the groove from both tread edges Te.

[0029] In this embodiment, the first portion 12 is formed with a groove width W1a of the same size along its longitudinal direction. The second portion 13 is formed in a widening shape, for example, between the inner groove portion 8 and the first portion 12, with the groove width W1b continuously increasing toward the outside in the tire axial direction. Alternatively, the first portion 12 may be formed in a widening shape with the groove width W1a continuously increasing toward the outside in the tire axial direction, or the second portion 13 may be formed with a groove width W1b of the same size along its longitudinal direction.

[0030] To effectively exert the above-mentioned effects, the angle α1 of the first part 12 with respect to the tire axis is preferably 10 degrees or less. From the viewpoint of increasing the heat dissipation area of ​​the grooves while suppressing a decrease in tread rigidity, the difference between the angle α2 of the second part 13 and the angle α1 of the first part 12 (α2-α1) is preferably 5 degrees or more, more preferably 10 degrees or more, preferably 30 degrees or less, and even more preferably 25 degrees or less. Although not particularly limited, the angle α2 of the second part 13 is preferably 10 degrees or more, more preferably 15 degrees or more, preferably 30 degrees or less, and even more preferably 25 degrees or less.

[0031] The axial length Lb of the first part 12 is preferably 5% or more of the tread width TW, more preferably 7% or more, preferably 20% or less, and more preferably 15% or less. Since the length Lb of the first part 12 is 5% or more of the tread width TW, the heat dissipation effect of the tread rubber 2G at the tread edge Te side is enhanced. Since the length Lb of the first part 12 is 20% or less of the tread width TW, high tread rigidity can be maintained.

[0032] Figure 4 is a cross-sectional view of the DD line in Figure 2, and is a longitudinal cross-sectional view of the transverse groove 3. As shown in Figure 4, the groove bottom 12s of the first part 12 and the groove bottom 13s of the second part 13 are smoothly connected. In this embodiment, the groove bottom 12s of the first part 12 and the groove bottom 13s of the second part 13 are connected in a straight line. This reduces the change in tread stiffness, thus delaying the onset of wear. When the groove depth D1a of the first part 12 is greater than the groove depth D1b of the second part 13, heat can be dissipated more effectively from the tread portion 2 on the tread edge Te side. When the groove depth D1a of the first part 12 is the same as the groove depth D1b of the second part 13, the change in tread stiffness can be reduced.

[0033] In this embodiment, the first part 12 includes a base 15 connected to the second part 13 and a deep bottom 16 with a groove depth D7 greater than that of the base 15. The deep bottom 16 includes, for example, the tread edge Te. The groove depth of the deep bottom 16 increases continuously from the outer end 15e of the base 15 in the tire axial direction, beyond the tread edge Te. Since the groove depth D7 of the deep bottom 16 is formed to be 1.0 to 3.0 mm greater than the groove depth D6 of the base 15, the effect of suppressing the decrease in tread rigidity and the effect of improving heat dissipation by the deep bottom 16 are enhanced in a well-balanced manner.

[0034] The groove depth D6 of the base portion 15 is preferably greater than or equal to the groove depth D1b of the second portion 13. This allows for smoother air intake into the lateral groove 3 and effectively dissipates heat from the tread portion 2 on the tread edge Te side. In this embodiment, the groove depth D6 of the base portion 15 is the same as the groove depth D1b of the second portion 13.

[0035] The inner groove 8 is positioned, for example, on the tire equator C. As shown in Figure 2, the inner groove 8 is formed, for example, with the same groove width W2 along the longitudinal direction.

[0036] The angle α3 of the inner groove 8 with respect to the tire axis is preferably greater than the angle α2 of the second portion 13. Such an inner groove 8 helps to increase the heat dissipation area of ​​the tread rubber 2G near the tire equator C, thereby improving life performance. In order to enhance the heat dissipation effect and maintain tread rigidity, the angle α3 of the inner groove 8 is preferably 20 degrees or more, more preferably 30 degrees or more, preferably 50 degrees or less, and more preferably 40 degrees or less.

[0037] In order to achieve a good balance between tread rigidity and heat dissipation, the groove width W2 of the inner groove 8 is preferably 60% or more, more preferably 65% ​​or more, more preferably 80% or less, and more preferably 75% or less of the groove width W1 of the outer groove 7. In this specification, in the case of grooves where the groove width is variable, the groove width is determined by the average of the minimum groove widths.

[0038] Figure 5 is a perspective view of the tread portion 2 as seen from the tread end Te side. As shown in Figures 4 and 5, the tread portion 2 includes a pair of buttress surfaces 20 that extend radially inward from a pair of tread ends Te. The buttress surfaces 20 are formed on the land portion 4. As a result, in this embodiment, the outer groove portion 7 has a pair of corner portions 21 where each of the pair of first groove walls 7a intersects with the buttress surface 20. In this embodiment, the buttress surface 20 includes a convex surface 24 that protrudes in the tire axial direction and extends continuously in the tire circumferential direction.

[0039] A chamfered portion 22 is provided on at least one of the pair of corner portions 21. In this embodiment, the chamfered portion 22 is provided on both of the pair of corner portions 21, 21. In this embodiment, the chamfered portion 22 is also provided on each of the pair of outer groove portions 7, 7. The chamfered portion 22 may also be provided on only one of the pair of outer groove portions 7, 7, for example. In this embodiment, the chamfered portion 22 is formed as a surface that is chamfered including the first groove wall 7a and the buttress surface 20, extending inward from the tread surface 2a in the tire radial direction.

[0040] The chamfer width Wt of the chamfered portion 22, measured parallel to the tread surface 2a, increases, for example, toward the inside in the tire radial direction. Such a chamfered portion 22 suppresses the reduction in tread rigidity of the ground portion 4.

[0041] The chamfered portion 22 is formed as a torsion surface T in which the direction of the normal 22n of the chamfered portion 22 continuously changes, such that the groove width W1a (shown in Figure 2) of the lateral groove 3 (outer groove portion 7) increases toward the inner side in the tire radial direction. In this embodiment, the torsion surface T is formed such that the angle β of the normal 22n of the chamfered portion 22 is larger for normals 22n located toward the inner side in the tire radial direction. The angle β is between the direction perpendicular to the normal 22n and the groove centerline 3c of the lateral groove 3, and is an angle parallel to the tread surface 2a. Furthermore, the torsion surface T is formed such that the groove width W1a increases toward the outer side in the tire axial direction.

[0042] The inner end 22i of the chamfered portion 22 in the tire axial direction is preferably located within 5% of the tread width TW in the tire axial direction from the tread edge Te. Since the axial separation distance Lc between the inner end 22i of the chamfered portion 22 and the tread edge Te is 5% or less of the tread width TW, the reduction in tread rigidity is suppressed.

[0043] In this embodiment, the groove depth D1 of the pair of outer grooves 7 increases outward in the tire axial direction from the inner end 22i of the chamfered portion 22. In this embodiment, the groove bottom of the outer groove 7 (the groove bottom of the deep bottom portion 16) is connected to the convex surface 24.

[0044] As shown in Figures 2 and 4, the tread portion 2 is provided with connecting grooves 9 (sometimes referred to as the first connecting groove 9 in this specification) that connect the inner groove portions 8 of adjacent lateral grooves 3 in the circumferential direction of the tire. In this embodiment, the first connecting groove 9 is located on the tire equator C. The first connecting groove 9 promotes heat dissipation of the tread rubber 2G on the tire equator C side.

[0045] The first joint groove 9 includes a pair of narrowed-width sections 9A in which the groove width continuously decreases from the inner groove sections 8 on both sides toward the tire equator C, and an equal-width section 9B that connects the pair of narrowed-width sections 9A and extends with the same width. Such a first joint groove 9 suppresses the decrease in tread rigidity on the tire equator C side.

[0046] The angle α4 of the first joint groove 9 with respect to the tire axis is preferably 45 degrees or less. The angle α4 of the first joint groove 9 is preferably 10 degrees or more, more preferably 20 degrees or more, and even more preferably 35 degrees or less. Since such a first joint groove 9 has a larger heat dissipation area compared to grooves extending along the tire axis, it further enhances the heat dissipation effect of the tread rubber 2G on the tire equator C side.

[0047] The groove depth D3 of the first joint groove 9 is preferably smaller than the groove depth D2 of the inner groove 8. Such a first joint groove 9 suppresses the decrease in tread rigidity on the tire equator C side. In order to enhance the heat dissipation effect of the tread rubber 2G on the tire equator C side while suppressing the decrease in tread rigidity, the groove depth D3 of the first joint groove 9 is preferably 0.60 times or more, more preferably 0.65 times or more, more preferably 0.80 times or less, and more preferably 0.75 times or less than the groove depth D2 of the inner groove 8.

[0048] In this embodiment, the tread portion 2 is provided with a second connecting groove 10 that connects second portions 13 that are spaced apart in the circumferential direction of the tire. The second connecting groove 10 is inclined at an angle α4 that is larger than the angle α2 of the inner groove portion 8. Furthermore, the second connecting groove 10 is formed with a groove width W3 that is smaller than the groove width W2 of the inner groove portion 8. It is desirable that the groove depth D4 of the second connecting groove 10 is smaller than the groove depth D2 of the inner groove portion 8. For example, the groove depth D4 of the second connecting groove 10 is the same as the groove depth D3 of the first connecting groove 9.

[0049] Although particularly preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the illustrated embodiments and can be implemented in various modified forms. [Examples]

[0050] A prototype tire having the basic structure shown in Figure 1 and the basic pattern shown in Figure 2 was manufactured based on the specifications in Table 1, and tested for lifespan and heat dissipation performance. The test method was as follows:

[0051] <Lifespan performance and heat dissipation performance> The test tires were mounted on each of the eight wheels (drive wheels and driven wheels) of a two-axle trailer towed by a 2DD vehicle under the following conditions, and driven on a dirt road scattered with sugarcane debris. Afterwards, the amount of wear (wear length) of the lateral grooves and the difference in surface temperature of the tread before and after driving were measured. The life performance results were expressed as an index with the reciprocal of the wear length in Example 1 set to 100. The heat dissipation performance results were expressed as an index with the reciprocal of the difference in surface temperature in Example 1 set to 100. Heat dissipation performance was measured near the tire equator and near the tread edge, and evaluations were made at both locations. A total score of 270 or higher for all tests was considered a passing grade. Tire size: 295 / 75R22.5 Rim: 22.5 x 8.25 Internal pressure: 850kPa Load: 10.44kN (Distance traveled: 5000km) Load: 34.81kN (Distance traveled: 5000km) Traveling speed: 20~50km / h Total distance traveled: 10,000 km The test results are shown in Table 1.

[0052] [Table 1]

[0053] The test results show that the tire in the example has improved lifespan and suppressed heat generation in the tread area compared to the tire in the comparative example.

[0054] [Note] The present invention includes the following embodiments.

[0055] [Invention 1] A tire having a tread portion, The tread portion is provided with a pair of tread ends, a tread rubber forming a tread surface between the pair of tread ends, and a plurality of lateral grooves extending from one of the pair of tread ends to the other. The loss tangent tanδ of the tread rubber is 0.13 to 0.17. Each of the plurality of lateral grooves includes a pair of outer grooves extending inward in the tire axial direction from the tread ends on both sides, and an inner groove extending between the pair of outer grooves. The pair of outer grooves are inclined in a first direction with respect to the tire axis, The inner groove portion is inclined in a second direction opposite to that of the pair of outer groove portions with respect to the tire axis. Each of the pair of outer grooves is provided with a pair of first groove walls, and the pair of first groove walls are inclined at a first angle θ1 with respect to the normal of the tread surface. The inner groove portion is provided with a pair of second groove walls, and the pair of second groove walls are inclined at a second angle θ2 with respect to the normal of the tread surface. The first angle θ1 is greater than the second angle θ2. tire. [2nd Invention] The tire according to the present invention 1, wherein the difference (θ1-θ2) between the first angle θ1 and the second angle θ2 is 5 to 15 degrees. [Invention 3] The tire according to invention 1 or 2, wherein the first angle θ1 is 10 to 25 degrees. [4th Invention] The tread portion is provided with connecting grooves that connect the inner groove portions of adjacent lateral grooves in the circumferential direction of the tire. The tire according to any one of claims 1 to 3 of the present invention, wherein the groove depth of the joint groove is smaller than the groove depth of the inner groove. [5th ​​Invention] The tire according to any one of claims 1 to 4 of the present invention, wherein the groove depth of each of the pair of outer grooves is greater than the groove depth of the inner groove. [Invention 6] The tire according to any one of claims 1 to 5 of the present invention, wherein each of the pair of outer grooves includes a first portion connected to the tread end and a second portion located inward in the tire axial direction from the first portion and inclined at a larger angle with respect to the tire axial direction than the first portion. [7th Invention] The tire according to the sixth invention, wherein the groove depth of the first portion is greater than the groove depth of the second portion. [8th Invention] The tread portion includes a pair of buttress surfaces extending radially inward from the pair of tread ends, A tire according to any one of claims 1 to 7 of the present invention, wherein a chamfered portion is provided on at least one of a pair of corner portions where the pair of first groove walls of the pair of outer groove portions intersect with the buttress surface. [Invention 9] The chamfer width of the chamfered portion, measured parallel to the tread surface, increases toward the inside in the tire radial direction, as described in the 8th invention. [Invention 10] The tire according to the present invention, wherein the chamfered portion is provided on both of the pair of corner portions. [Invention 11] The tire according to any one of claims 8 to 10 of the present invention, wherein the chamfered portion is a torsional surface in which the direction of the normal to the chamfered portion changes continuously so that the groove width increases toward the radially inward direction of the tire. [Invention 12] The tire according to any one of claims 8 to 11 of the present invention, wherein the inner end of the chamfered portion in the tire axial direction is located within 5% of the tread width in the tire axial direction from the tread edge. [Invention 13] The tire according to the present invention 12, wherein the groove depth of the pair of outer grooves increases outward in the tire axial direction from the inner end of the chamfered portion. [Invention 14] A heavy-duty pneumatic tire, as described in any one of claims 1 to 13 of the present invention. [Explanation of Symbols]

[0056] 1 tire 2 Tread section 2G Tread Rubber 2a Tread 3 Yokomizo 7 Outer groove 7a 1st groove wall 8. Inner groove 8a Second trench wall θ1 1st angle θ2 2nd angle Te tread edge

Claims

1. A tire having a tread portion, The tread portion is provided with a pair of tread ends, a tread rubber forming a tread surface between the pair of tread ends, and a plurality of lateral grooves extending from one of the pair of tread ends to the other. The loss tangent tanδ of the tread rubber is 0.13 to 0.

17. Each of the plurality of lateral grooves includes a pair of outer grooves extending inward in the tire axial direction from the tread ends on both sides, and an inner groove extending between the pair of outer grooves. The pair of outer grooves are inclined in a first direction with respect to the tire axis, The inner groove portion is inclined in a second direction opposite to that of the pair of outer groove portions with respect to the tire axis. Each of the pair of outer grooves is provided with a pair of first groove walls, and the pair of first groove walls are inclined at a first angle θ1 with respect to the normal to the tread surface. The inner groove portion is provided with a pair of second groove walls, and the pair of second groove walls are inclined at a second angle θ2 with respect to the normal of the tread surface. The first angle θ1 is greater than the second angle θ2. tire.

2. The tire according to claim 1, wherein the difference between the first angle θ1 and the second angle θ2 (θ1 - θ2) is 5 to 15 degrees.

3. The tire according to claim 1 or 2, wherein the first angle θ1 is 10 to 25 degrees.

4. The tread portion is provided with connecting grooves that connect the inner groove portions of adjacent lateral grooves in the circumferential direction of the tire. The tire according to claim 1 or 2, wherein the groove depth of the joint groove is smaller than the groove depth of the inner groove.

5. The tire according to claim 1 or 2, wherein the groove depth of each of the pair of outer grooves is greater than the groove depth of the inner groove.

6. The tire according to claim 1 or 2, wherein each of the pair of outer grooves includes a first portion connected to the tread end and a second portion located inward in the tire axial direction from the first portion and inclined at a larger angle with respect to the tire axial direction than the first portion.

7. The tire according to claim 6, wherein the groove depth of the first portion is greater than the groove depth of the second portion.

8. The tread portion includes a pair of buttress surfaces extending radially inward from the pair of tread ends, The tire according to claim 1, wherein a chamfered portion is provided on at least one of the pair of corner portions where the pair of first groove walls of the pair of outer groove portions intersect with the buttress surface.

9. The tire according to claim 8, wherein the chamfer width of the chamfered portion, measured parallel to the tread surface, increases toward the inside in the tire radial direction.

10. The tire according to claim 8 or 9, wherein the chamfered portion is provided on both of the pair of corner portions.

11. The tire according to claim 8 or 9, wherein the chamfered portion is a torsion surface in which the direction of the normal to the chamfered portion changes continuously so that the groove width increases toward the radially inward direction of the tire.

12. The tire according to claim 8 or 9, wherein the inner end of the chamfered portion in the tire axial direction is located within 5% of the tread width in the tire axial direction from the tread end.

13. The tire according to claim 12, wherein the groove depth of the pair of outer grooves increases outward in the tire axial direction from the inner end of the chamfered portion.

14. The tire according to claim 1 or 2, which is a pneumatic tire for heavy loads.

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