tire

Abstract

The tire of the present invention can improve off-road performance and noise performance. The tire (1) has a tread portion (2). The tread portion (2) has a shoulder land portion (3) provided with a first shoulder lateral groove (5). The first shoulder lateral groove (5) includes an inner groove portion (6) and an outer groove portion (7). In each first shoulder lateral groove (5) in the tread unfolded top view, the groove area Sb from the tread end (Te) of the outer groove portion (7) to the position of 125% of the tread width (TW) is formed to be larger than the groove area (Sa) of the inner groove portion (6).

Description

Technical Field

[0001] The present invention relates to tires. Background Art

[0002] Patent Document 1 below describes a pneumatic tire that aims to achieve both muddy performance and noise performance. The pneumatic tire proposes providing a plurality of inner center lug grooves and outer center lug grooves in a central land portion and defining their number.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2014-162388

[0004] The inventors have attempted to improve off-road performance and noise performance by a method different from that of the above-mentioned Patent Document 1. Specifically, they have focused on the fact that the shoulder lateral grooves extending across the tread ends have a significant impact on the noise performance on roads and the traction on off-road roads. Furthermore, the groove area of ​​the shoulder lateral grooves is specified based on the tread ends, thereby solving the above-mentioned problems. Summary of the invention

[0005] The present invention is made in view of the above actual situation, and its main purpose is to provide a pneumatic tire that can improve off-road performance and noise performance.

[0006] The present invention is a tire having a tread portion, wherein the tread portion has at least one shoulder land portion including a tread end, and a plurality of first shoulder lateral grooves are arranged in the shoulder land portion, wherein the first shoulder lateral grooves respectively include: an inner groove portion extending axially inward of the tread end, and an outer groove portion extending axially outward of the tread end, and in each of the first shoulder lateral grooves in a top view of the tread, a groove area Sb from the tread end of the outer groove portion to a position of 125% of the tread width is formed to be larger than a groove area Sa of the inner groove portion.

[0007] In the tire of the present invention, it is preferable that the outer groove portion includes a gradually increasing width portion in which the groove width continuously increases from the tread end toward the outer side in the tire axial direction.

[0008] In the tire of the present invention, it is preferable that the inner groove portion includes a uniform width portion having a groove width that becomes uniform from an inner end in the tire axial direction toward an outer side in the tire axial direction.

[0009] In the tire of the present invention, preferably, a ratio Sa / Sb of the groove area Sa of the inner groove portion to the groove area Sb of the outer groove portion is 0.15 to 0.40.

[0010] In the tire of the present invention, preferably, the tread portion includes a shoulder longitudinal groove adjacent to the shoulder land portion, the shoulder longitudinal groove includes a curved portion protruding in the tire axial direction, and the first shoulder lateral groove extends from the curved portion.

[0011] The tire of the present invention is preferably configured such that the outer groove portion includes an inner position, an outer position separated from the inner position axially outward by 5% to 20% of the tread width, and an intermediate position axially disposed in the middle of the tire between the inner position and the outer position, and a ratio Hb / Ha of the groove width Hb in the tire circumferential direction at the intermediate position to the groove width Ha in the tire circumferential direction at the inner position is smaller than a ratio Hc / Hb of the groove width Hc in the tire circumferential direction at the outer position to the groove width Hb at the intermediate position.

[0012] In the tire of the present invention, it is preferable that the ratio Hc / Hb is 4.0 or less, and the ratio Hb / Ha is 1.0 or more.

[0013] The tire of the present invention is preferably provided in the shoulder land portion with: a second shoulder lateral groove arranged between the first shoulder lateral grooves adjacent to each other in the tire circumferential direction, and a third shoulder lateral groove arranged between the first shoulder lateral groove and the second shoulder lateral groove from the tread end toward the outside in the tire axial direction.

[0014] The tire of the present invention is preferably configured such that the third shoulder lateral groove includes an axial portion extending axially from the inner end of the tire, and a bent portion connected to the axial portion and bent toward the first shoulder lateral groove between a position of 117% and a position of 120% of the tread width.

[0015] In the tire of the present invention, it is preferable that the third shoulder lateral groove is connected to the first shoulder lateral groove between a position of 122% and a position of 125% of the tread width.

[0016] The present invention can improve off-road performance and noise performance by adopting the above structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a plan view of a tread portion according to an embodiment of the present invention.

[0018] Figure 2 It is a schematic cross-sectional view of the right half of the tread portion of the present embodiment.

[0019] Figure 3 This is an enlarged top view of the tread.

[0020] Figure 4 This is an enlarged top view of the tread.

[0021] Figure 5 It is a top view of the tread portion.

[0022] Description of reference numerals: 1 ... tire; 2 ... tread portion; 3 ... shoulder land portion; 5 ... first shoulder lateral groove; 6 ... inner groove portion; 7 ... outer groove portion; TW ... tread width; Te ... tread end. DETAILED DESCRIPTION

[0023] Hereinafter, one embodiment of the present invention will be described based on the drawings.

[0024] Figure 1 It is a plan view of the tread portion 2 of the tire 1 according to the present embodiment when it is developed. Figure 1 2 shows a tread portion 2 of a pneumatic tire for a passenger car. In addition, the present invention can also be applied to, for example, pneumatic tires for load-carrying and tires of other categories.

[0025] like Figure 1 As shown, the tread portion 2 of the tire 1 of this embodiment includes at least one shoulder land portion 3 including a tread end Te. In this embodiment, the shoulder land portion 3 is provided on both sides of the tread portion 2 in the tire axial direction.

[0026] The above-mentioned "tread end Te", in the case of a pneumatic tire, is the axially outermost ground contact position of the tire when the tire 1 is assembled into a regular rim (not shown), filled with a regular internal pressure, and in a normal state without a load, and the ground contact is made flat with a 0° camber angle. In this specification, the axial distance between the tread end Te and the tire equator C is the tread width TW. In this specification, the dimensions of each part of the tire 1 are the values ​​in the normal state unless otherwise specified.

[0027] A "regular rim" is a rim that has specifications specified for each tire in a specification system that includes the specifications that the tire complies with, such as a "standard rim" for JATMA, a "design rim" for TRA, and a "measuring rim" for ETRTO.

[0028] "Normal internal pressure" is the air pressure specified for each tire in the specification system that includes the specifications on which the tire is based. If it is JATMA, it is the "maximum air pressure". If it is TRA, it is the maximum value recorded in the table "TIRE LOADLIMITS AT VARIOUSCOLD INFLATION PRESSURES". If it is ETRTO, it is "INFLATION PRESSURE".

[0029] "Normal load" is the load specified for each tire in the specification system including the specifications on which the tire is based. If it is JATMA, it is the "maximum load capacity". If it is TRA, it is the maximum value recorded in the table "TIRE LOAD LIMITS ATVARIOUS COLD INFLATION PRESSURES". If it is ETRTO, it is "LOADCAPACITY".

[0030] The shoulder land portion 3 of the present embodiment is provided with a plurality of first shoulder lateral grooves 5. Such first shoulder lateral grooves 5 provide greater traction on off-road surfaces such as muddy ground, thereby improving off-road performance. The plurality of first shoulder lateral grooves 5 are arranged in the tire circumferential direction.

[0031] Each of the first shoulder lateral grooves 5 includes an inner groove portion 6 extending axially inward of the tread end Te and an outer groove portion 7 extending axially outward of the tread end Te.

[0032] Noise generated when driving on the road includes pumping noise generated by discharge from the tread end Te of the lateral groove to the outside of the tire. This noise can be reduced by reducing the volume of the area axially inward of the tire than the tread end Te. In addition, when driving off-road, the area axially outward of the tire than the tread end Te contacts the ground such as muddy ground. According to the results of a large number of experiments, its range is about 125% of the tread width TW in the tread development diagram. That is, if the groove volume between the tread end Te and the position E1 that is 125% of the tread width TW (hereinafter, sometimes simply referred to as "125% position E1") is increased, it will not affect the pumping noise, but will improve the traction during off-road driving. Therefore, in the present embodiment, in each first shoulder lateral groove 5, the groove area Sb of the outer groove portion 7 between the tread end Te and the 125% position E1 is formed to be larger than the groove area Sa of the inner groove portion 6. This improves off-road performance and noise performance. Figure 1 For convenience, the groove areas Sa and Sb are shown by hatching.

[0033] Figure 2 FIG. 1 is a schematic cross-sectional view of the right half of the tire 1 in a normal state. Figure 2 As shown, in this specification, the 125% position E1 is a position where 125% of the tread width TW is separated from the tire equator C toward the outer side of the tire axial direction. When driving on a road such as an asphalt road, the 125% position E1 becomes a portion that does not contact the road surface. The profile P of the tread portion 2 of the tire 1 of this embodiment is inclined in a manner that the height in the tire radial direction decreases toward the outer side of the tire axial direction.

[0034] In order to improve off-road performance and noise performance, the ratio Sa / Sb of the groove area Sa of the inner groove portion 6 to the groove area Sb of the outer groove portion 7 is preferably 0.15 or more, more preferably 0.20 or more, and further preferably 0.25 or more. In addition, the ratio Sa / Sb is preferably 0.40 or less, more preferably 0.35 or less, and further preferably 0.30 or less.

[0035] like Figure 1 As shown, the tread portion 2 of this embodiment is provided with a pair of shoulder longitudinal grooves 8 adjacent to the shoulder land portion 3, and a pair of crown longitudinal grooves 9 arranged between the shoulder longitudinal grooves 8 and the tire equator C. Thus, in this embodiment, the tread portion 2 includes: a pair of central land portions 10 divided between the shoulder longitudinal grooves 8 and the crown longitudinal grooves 9, and a crown land portion 11 divided between the pair of crown longitudinal grooves 9, 9. In addition, the tread portion 2 is not limited to such a form.

[0036] In the present embodiment, the shoulder longitudinal grooves 8 and the crown longitudinal grooves 9 extend continuously in the tire circumferential direction. The shoulder longitudinal grooves 8 extend in a zigzag shape in the tire circumferential direction, for example. The crown longitudinal grooves 9 extend in a straight line shape in the tire circumferential direction, for example.

[0037] In the present embodiment, the shoulder longitudinal groove 8 includes: a first inclined portion 8A inclined to one side relative to the tire circumferential direction (toward the lower right in the figure), and a second inclined portion 8B inclined in the opposite direction to the first inclined portion 8A relative to the tire circumferential direction (toward the lower left in the figure). The first inclined portion 8A and the second inclined portion 8B are arranged alternately along the tire circumferential direction, for example.

[0038] In the present embodiment, the shoulder longitudinal groove 8 is connected by the first inclined portion 8A and the second inclined portion 8B to form a curved portion 12 protruding along the tire axial direction. The curved portion 12 includes, for example: an outer curved portion 12A protruding to the outer side of the tire axial direction, and an inner curved portion 12B protruding to the inner side of the tire axial direction. The bending angle θ1 of the outer curved portion 12A is preferably greater than 140 degrees, more preferably greater than 150 degrees, and preferably less than 175 degrees, more preferably less than 170 degrees. Such a shoulder longitudinal groove 8 improves traction during off-road driving and reduces the air column resonance in the groove 8. The bending angle θ1 is the angle at which the groove centerline d1 of the first inclined portion 8A intersects the groove centerline d2 of the second inclined portion 8B.

[0039] The groove width WA of the shoulder longitudinal groove 8 and the crown longitudinal groove 9 is preferably 5% to 15% of the tread width TW, for example. The groove depth DA of the shoulder longitudinal groove 8 and the crown longitudinal groove 9 is preferably 5% to 15% of the tread width TW. Figure 2The axial distance L1 between the swing groove centerline C1 of the shoulder longitudinal groove 8 and the tire equator C is preferably 50% to 70% of the tread width TW. The axial distance L2 between the groove centerline C2 of the crown longitudinal groove 9 and the tire equator C is preferably 5% to 25% of the tread width TW. The groove width WA of the shoulder longitudinal groove 8 is the average of the maximum groove width and the minimum groove width.

[0040] Figure 3 yes Figure 1 An enlarged view of the shoulder land portion 3 of the tire. Figure 3 As shown, the outer groove portion 7 of this embodiment includes a width increasing portion 7A whose groove width (tire circumferential direction) increases continuously from the tread end Te toward the outer side in the tire axial direction. Such an outer groove portion 7 has a high soil discharge performance and can exert a large traction performance. The outer groove portion 7 is formed by the width increasing portion 7A from the tread end Te to the position E1 of 125%, so that the above-mentioned function is effectively exerted. The length L3 of the width increasing portion 7A in the tire axial direction is preferably 15% or more of the tread width TW, more preferably 20% or more, and further preferably 22% or more.

[0041] In the present embodiment, the outer groove portion 7 includes an inner position 15, an outer position 16, and a middle position 17. The outer position 16 is separated from the inner position 15 by a tire axial distance La of 5% to 20% of the tread width TW toward the outer side of the tire axial direction. The middle position 17 is arranged in the middle of the inner position 15 and the outer position 16 in the tire axial direction.

[0042] The outer groove portion 7 is formed, for example, so that the ratio Hb / Ha of the groove width Hb in the tire circumferential direction at the middle position 17 to the groove width Ha in the tire circumferential direction at the inner position 15 is smaller than the ratio Hc / Hb of the groove width Hc in the tire circumferential direction at the outer position 16 to the groove width Hb in the middle position 17. In other words, the change in the groove width from the middle position 17 to the outer position 16 is greater than the change in the groove width from the inner position 15 to the middle position 17. As a result, the mud discharge property in the outer groove portion 7 can be improved, thereby improving the off-road performance. When driving off-road, the inner position 15 contacts a deeper position of the ground than the outer position 16. Therefore, by making the ratio Hb / Ha smaller than the ratio Hc / Hb, the inner position 15 increases the shear force by clamping mud, etc., thereby improving the traction.

[0043] If the ratio Hc / Hb is too large, the rigidity of the shoulder land portion 3 decreases, which may reduce the traction during off-road running. From this point of view, the ratio Hc / Hb is preferably 4.0 or less, more preferably 3.0 or less, and even more preferably 2.0 or less. In addition, in order to improve soil discharge performance, the ratio Hb / Ha is preferably 1.0 or more, more preferably 1.2 or more, and even more preferably 1.3 or more.

[0044] The inner position 15 is separated from the tire equator C by a tire axial distance Lb ( Lb) of 102% to 112% of the tread width TW, for example. Figure 1 ). The outer position 16 is separated from the tire equator C by a tire axial distance Lc of 117% to 122% of the tread width TW, for example. In the present embodiment, the inner position 15 is a position that sometimes contacts the road surface during road driving when a large lateral force is applied to a turn. The outer position 16 is a position that does not contact the road surface during road driving.

[0045] Although not particularly limited, the groove width W1 in the tire circumferential direction at the 125% position E1 of the outer groove portion 7 is preferably 2.5 times or more, and preferably 4.0 times or less, of the groove width W2 in the tire circumferential direction at the tread end Te of the outer groove portion 7. The groove width W2 at the tread end Te of the outer groove portion 7 is, for example, preferably 45% or more, and preferably 65% ​​or less, of the groove width WA of the shoulder longitudinal groove 8.

[0046] The outer groove portion 7 has: a first edge 7e extending in the tire axial direction, and a second edge 7i separated from the first edge 7e in the tire circumferential direction and extending in the tire axial direction. The first edge 7e and the second edge 7i of this embodiment are both composed of a convex portion 18 protruding to one side of the tire circumferential direction (the upper side in the figure) and a concave portion 19 recessed to one side of the tire circumferential direction. The convex portion 18 and the concave portion 19 are both formed in a smooth arc shape, for example. In this embodiment, the first edge 7e and the second edge 7i are connected in a manner that the convex portion 18 and the concave portion 19 form a smooth arc. Such an outer groove portion 7 has a small resistance to mud and the like, so mud and the like can be easily discharged from the 125% position E1.

[0047] The inner groove portion 6 of the present embodiment includes a uniform width portion 6A in which the groove width W3 in the tire circumferential direction is uniform from the inner end 6i in the tire axial direction toward the outer side in the tire axial direction. Such a uniform width portion 6A helps to maintain the vibration of the air in the inner groove portion 6 to be small. In this specification, the uniform width portion 6A refers to not only the portion where the groove width is uniform in the dictionary, but also the portion where the minimum value of the groove width W3 is more than 90% of the maximum value of the groove width W3 at more than 50% of the tire axial length L4 of the inner groove portion 6.

[0048] The inner groove portion 6 also includes, for example, an inner width increasing portion 6B connected to the equal width portion 6A and whose groove width W3 increases continuously toward the outer side in the tire axial direction. The inner width increasing portion 6B is formed to be smaller in length in the tire axial direction than the equal width portion 6A, thereby suppressing the reduction of noise performance.

[0049] The maximum groove width W3m of the inner groove portion 6 (equivalent to the groove width W2) is preferably 120% to 140% of the groove width W3 of the equal width portion 6A. The maximum groove width W3m of the inner groove portion 6 is 120% or more of the groove width W3 of the equal width portion 6A, so that mud in the inner gradually increasing width portion 6B can be smoothly discharged to the outside of the tread end Te. The maximum groove width W3m of the inner groove portion 6 is 140% or less of the groove width W3 of the equal width portion 6A, so that the noise performance is maintained at a high level.

[0050] The groove depth D1 of the inner groove portion 6 ( Figure 2 The groove depth D2 of the outer groove portion 7 is preferably 80% to 90% of the groove depth DA of the shoulder longitudinal groove 8. The groove depth D2 of the outer groove portion 7 is preferably 10% to 15% of the groove depth DA of the shoulder longitudinal groove 8.

[0051] The angle θ2 of the equal width portion 6A of the inner groove portion 6 with respect to the tire axial direction is preferably 20 degrees or more, more preferably 25 degrees or more. The angle θ2 is preferably 40 degrees or less, more preferably 30 degrees or less.

[0052] In the present embodiment, the first shoulder lateral groove 5 extends from the shoulder longitudinal groove 8. Such first shoulder lateral groove 5 can discharge mud and the like in the inner groove portion 6 also toward the shoulder longitudinal groove 8, and thus has a high soil discharge performance.

[0053] The first shoulder lateral groove 5 extends from the curved portion 12, for example. In the present embodiment, the first shoulder lateral groove 5 extends from the outer curved portion 12A. Such a first shoulder lateral groove 5 easily allows the air column resonance flowing in the shoulder longitudinal groove 8 to flow in, thereby reducing the air column resonance sound of the shoulder longitudinal groove 8.

[0054] Figure 4 yes Figure 1 An enlarged view of the shoulder land portion 3 of the tire. Figure 4 As shown, the shoulder land portion 3 is further provided with, for example, a second shoulder lateral groove 20 and a third shoulder lateral groove 21. In this embodiment, the second shoulder lateral groove 20 is arranged between the first shoulder lateral grooves 5, 5 adjacent in the tire circumferential direction. The third shoulder lateral groove 21 is arranged between the second shoulder lateral groove 20 and the first shoulder lateral groove 5 from the tread end Te toward the outer side in the tire axial direction. Such second shoulder lateral groove 20 and third shoulder lateral groove 21 improve traction during off-road driving.

[0055] The second shoulder lateral groove 20 of the present embodiment extends beyond the position E1 of 125% of the shoulder longitudinal groove 8. The second shoulder lateral groove 20 is connected to, for example, the middle position of the second inclined portion 8B in the tire circumferential direction.

[0056] The second shoulder lateral groove 20 includes: a second inner groove portion 22 extending on the inner side of the tire axial direction than the tread end Te, and a second outer groove portion 23 extending on the outer side of the tire axial direction than the tread end Te. In the second shoulder lateral groove 20, the groove area Sc of the second outer groove portion 23 between the tread end Te and the position E1 of 125% of the tread width TW is formed to be larger than the groove area Sd of the second inner groove portion 22. As a result, off-road performance and noise performance are further improved. Figure 4 For convenience, the groove areas Sc and Sd are shown by hatching.

[0057] Although not particularly limited, the ratio Sd / Sc of the groove area Sd of the second inner groove portion 22 to the groove area Sc of the second outer groove portion 23 is preferably 0.20 or more, more preferably 0.25 or more. Also, the ratio Sd / Sc is preferably 0.35 or less, more preferably 0.30 or less.

[0058] The second inner groove portion 22 includes, for example, a second equal width portion 22A in which the groove width W5 in the tire circumferential direction is the same from the shoulder longitudinal groove 8 toward the outer side in the tire axial direction, and a second inner width increasing portion 22B in which the groove width W5 increases continuously toward the outer side in the tire axial direction. The second inner width increasing portion 22B is connected to the second equal width portion 22A, and is formed to have a smaller length in the tire axial direction than the second equal width portion 22A. Such a second inner groove portion 22 maintains the vibration of the air to be small, and it is easy to discharge mud and the like in the second inner groove portion 22 to the second outer groove portion 23. In this specification, the second equal width portion 22A refers to a portion in which the groove width is the same in the dictionary, and also refers to a portion in which the minimum value of the groove width W5 is more than 90% of the maximum value of the groove width W5 at more than 50% of the length L6 of the second inner groove portion 22 in the tire axial direction.

[0059] In this embodiment, the second outer groove portion 23 includes: a second gradually increasing width portion 23A whose groove width W6 increases continuously toward the outer side in the tire axial direction, and a second gradually decreasing width portion 23B whose groove width W6 decreases continuously toward the outer side in the tire axial direction. The second gradually increasing width portion 23A and the second gradually decreasing width portion 23B are smoothly connected.

[0060] The second outer groove portion 23 includes, for example, a third edge 23e extending in the tire axial direction, and a fourth edge 23i separated from the third edge 23e in the tire circumferential direction and extending in the tire axial direction. The third edge 23e is, for example, formed by a convex portion 18 protruding toward one side of the tire circumferential direction (the upper side in the figure). The fourth edge 23i is, for example, formed by a convex portion 18 and a concave portion 19 recessed toward one side of the tire circumferential direction. In the present embodiment, the fourth edge 23i is formed by smoothly connecting the convex portion 18 and the concave portion 19.

[0061] The maximum groove width W5m of the second inner groove portion 22 is preferably, for example, 120% or more of the groove width W5 of the second equal width portion 22A, and preferably 160% or less. The maximum groove width W6m of the second outer groove portion 23 in the tire circumferential direction is, for example, preferably 2.5 times or more of the groove width W5 of the second equal width portion 22A, and preferably 4.0 times or less. The groove depth (not shown) of the second inner groove portion 22 is preferably 90% to 110% of the groove depth D1 of the inner groove portion 6. The groove depth (not shown) of the second outer groove portion 23 is preferably 90% to 110% of the groove depth D2 of the outer groove portion 7.

[0062] In this embodiment, the third shoulder lateral groove 21 includes an axial portion 25 extending from the inner end 21d in the tire axial direction in the tire axial direction, and a bent portion 26 connected to the axial portion 25 and bent toward the first shoulder lateral groove 5. The distance L7 between the inner end 21d of the third shoulder lateral groove 21 and the tread end Te in the tire axial direction is preferably arranged in a range of 5% or less of the tread width TW. Such a third shoulder lateral groove 21 reduces pumping noise during road driving and improves traction during off-road driving.

[0063] The bent portion 26 is bent, for example, between the position E2 of 117% and the position E3 of 120% of the tread width TW. Such a third shoulder lateral groove 21 can ensure a larger length of the axial portion 25 in the tire axial direction, thereby improving traction during off-road driving. In this specification, the position of the bend is determined by the position where the curvature radius r of the edge 26e of the bent portion 26 is the smallest.

[0064] The third shoulder lateral groove 21 is connected to the first shoulder lateral groove 5, for example, between the position E4 of 122% and the position E1 of 125% of the tread width TW. Such a third shoulder lateral groove 21 can ensure a large length in the tire axial direction, thereby improving traction. In this specification, the position where the third shoulder lateral groove 21 is connected to the first shoulder lateral groove 5 is determined by the position where the groove center line 21c of the third shoulder lateral groove 21 intersects the second edge 7i of the outer groove portion 7.

[0065] Figure 5 2 is a top view of the unfolded tread portion 2. Figure 5 As shown, the third shoulder lateral groove 21 has, for example, a fifth edge 21e extending in the tire axial direction, and a sixth edge 21i separated from the fifth edge 21e in the tire circumferential direction and extending in the tire axial direction. The fifth edge 21e and the sixth edge 21i of this embodiment are both composed of a convex portion 18 protruding to one side of the tire circumferential direction (the upper side in the figure) and a concave portion 19 recessed to one side of the tire circumferential direction. The fifth edge 21e and the sixth edge 21i are both formed by smoothly connecting the convex portion 18 and the concave portion 19.

[0066] The groove width W7 of the third shoulder lateral groove 21 is preferably 80% or more and 125% or less of the groove width W3 of the inner groove 6. The groove depth (not shown) of the third shoulder lateral groove 21 is preferably 90% to 110% of the groove depth D2 of the outer groove 7.

[0067] In this embodiment, the shoulder land portion 3 is provided with a fourth shoulder lateral groove 28 between the second shoulder lateral groove 20 and the first shoulder lateral groove 5. The shoulder land portion 3 is provided with the fourth shoulder lateral groove 28 or the third shoulder lateral groove 21 between the second shoulder lateral groove 20 and the first shoulder lateral groove 5, for example.

[0068] In this embodiment, the fourth shoulder lateral groove 28 extends in the tire axial direction between the tread end Te and the 125% position E1. The fourth shoulder lateral groove 28 is formed, for example, not to contact the tread end Te and the 125% position E1. Such a fourth shoulder lateral groove 28 reduces pumping noise and improves off-road performance.

[0069] The groove width W8 of the fourth shoulder lateral groove 28 is preferably 80% or more and 125% or less of the groove width W7 of the third shoulder lateral groove 21. The groove depth (not shown) of the fourth shoulder lateral groove 28 is preferably 90% to 110% of the groove depth D2 of the outer groove portion 7.

[0070] The central land portion 10 of the present embodiment is provided with a plurality of central lateral grooves 30 connecting the shoulder longitudinal grooves 8 and the crown longitudinal grooves 9. The central lateral grooves 30 are connected, for example, to the inner curved portions 12B of the shoulder longitudinal grooves 8. In the present embodiment, the central land portion 10 includes a plurality of central blocks 10A divided by the central lateral grooves 30 adjacent to each other in the tire circumferential direction.

[0071] The central lateral groove 30 includes a central inner groove portion 30A connected to the crown longitudinal groove 9, a central outer groove portion 30B connected to the shoulder longitudinal groove 8, and a central middle groove portion 30C connecting the central inner groove portion 30A and the central outer groove portion 30B. The central inner groove portion 30A and the central outer groove portion 30B are continuously inclined to one side (toward the lower right in the figure) relative to the tire axial direction. The central middle groove portion 30C is inclined in the opposite direction to the central inner groove portion 30A relative to the tire axial direction. Such a zigzag central lateral groove 30 can reduce pumping noise.

[0072] In this embodiment, the crown land portion 11 is formed as a flat land portion without grooves. Such a flat land portion contributes to improving noise performance.

[0073] The shoulder land portion 3, the center land portion 10, and the crown land portion 11 are provided with sipes S. Such sipes S reduce the rigidity of each land portion 3, 10, 11, thereby reducing the hitting sound caused by contact with the road surface as the tire rotates. In this specification, the sipe S is a groove-shaped body with a width of not less than 1.5 mm, and is clearly distinguished from a groove with a groove width of 1.5 mm or more.

[0074] As mentioned above, although the tire which concerns on one embodiment of this invention was demonstrated in detail, this invention is not limited to the said specific embodiment, but can be implemented by changing into various aspects.

[0075] Example

[0076] Based on the specifications in Table 1, a prototype with Figure 3 The pneumatic tires for passenger cars with a basic pattern size of 195 / 80R15 were used. The off-road performance and noise performance of each test tire were then tested. The common specifications and test methods of each test tire are shown below.

[0077] The shape and the groove area Sa of the inner groove portion of the embodiment and the comparative example are formed to be the same.

[0078] Lb: 104% of tread width TW

[0079] Lc: 120% of tread width TW

[0080] <Off-road performance>

[0081] Each test tire was mounted on all wheels of the following vehicle. The test driver used the vehicle to drive on a test route on an off-road surface. The handling stability and traction at this time were evaluated by the test driver's senses. The results were expressed as a score with Comparative Example 1 being 100. The larger the value, the better.

[0082] Vehicle: 660cc passenger car (4-wheel drive)

[0083] Rim: 5.5J

[0084] Internal pressure: 180kPa

[0085] <Noise performance>

[0086] The test driver drove the vehicle on a test route on a dry asphalt road. Then, the test driver evaluated the noise generated by the tire during driving through his senses. The results were expressed as a score with Comparative Example 1 being 100. The larger the value, the better.

[0087] The test results are shown in Table 1.

[0088]

Table 1

[0089]

[0090] From the test results, it can be understood that the tire of the embodiment is excellent in off-road performance and noise performance.

Claims

1. A tire having a tread portion, characterized in that: The tread portion includes at least one shoulder land portion including a tread end. A plurality of first shoulder lateral grooves are provided in the shoulder land portion. The first shoulder lateral grooves include an inner groove portion extending inwardly of the tread end in the tire axial direction, and an outer groove portion extending outwardly of the tread end in the tire axial direction. In each of the first shoulder lateral grooves in the tread development plan view, a groove area Sb from the tread end of the outer groove portion to a position of 125% of the tread width is formed to be larger than a groove area Sa of the inner groove portion, The shoulder land portion is further provided with: a second shoulder lateral groove arranged between the first shoulder lateral grooves adjacent to each other in the tire circumferential direction, a third shoulder lateral groove arranged between the first shoulder lateral groove and the second shoulder lateral groove from the tread end to the outer side in the tire axial direction, and a fourth shoulder lateral groove extending in the tire axial direction between the first shoulder lateral groove and the second shoulder lateral groove and between the tread end and the 125% position, The fourth shoulder lateral groove is formed so as not to contact the tread end and the 125% position and not to communicate with other grooves.

2. The tire according to claim 1, characterized in that The outer groove portion includes a gradually increasing width portion in which the groove width continuously increases from the tread end toward the outer side in the tire axial direction.

3. The tire according to claim 1 or 2, characterized in that: The inner groove portion includes a uniform width portion whose groove width becomes the same from the inner end in the tire axial direction toward the outer side in the tire axial direction.

4. The tire according to claim 1 or 2, characterized in that: A ratio Sa / Sb of the groove area Sa of the inner groove portion to the groove area Sb of the outer groove portion is 0.15 to 0.

40.

5. The tire according to claim 1 or 2, characterized in that: The tread portion has a shoulder longitudinal groove adjacent to the shoulder land portion, The shoulder longitudinal groove includes a curved portion protruding along the tire axial direction. The first shoulder lateral groove extends from the curved portion.

6. The tire according to claim 1 or 2, characterized in that: The outer groove portion includes an inner position, an outer position that is 5% to 20% of the tread width away from the inner position in the tire axial direction, and an intermediate position that is arranged in the middle of the tire axial direction between the inner position and the outer position. A ratio Hb / Ha of the groove width Hb in the tire circumferential direction at the middle position to the groove width Ha in the tire circumferential direction at the inner position is smaller than a ratio Hc / Hb of the groove width Hc in the tire circumferential direction at the outer position to the groove width Hb in the middle position.

7. The tire according to claim 6, characterized in that The ratio Hc / Hb is 4.0 or less, The ratio Hb / Ha is 1.0 or more.

8. The tire according to claim 1, characterized in that The third shoulder lateral groove includes an axial portion extending from an axially inner end of the tire along the tire axial direction, and a bent portion connected to the axial portion and bent toward the first shoulder lateral groove side between a position of 117% and a position of 120% of the tread width.

9. The tire according to claim 1 or 8, characterized in that The third shoulder lateral groove is connected to the first shoulder lateral groove between a position of 122% and a position of 125% of the tread width.

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