Tire

Abstract

To provide a tire that can be improved in wear resistance performance and steering stability performance while maintaining wet performance.SOLUTION: The tire includes a crown circumferential groove 3 and a shoulder circumferential groove. An inside groove wall 9A of the crown circumferential groove 3 has a first part 11 extending linearly without bending. An outside groove wall 8A of the crown circumferential groove 3 has a second part 12 which includes a bending portion 16 protruding to the outside in a groove width direction, an outside portion 17 extending between the bending portion 16 and a tread face 2a, and an inside portion 18 extending from the bending portion 16 to the inside in a tire radial direction. An angle β of the inside portion 18 with respect to a tread normal line n1 is larger than an angle α of the outside portion 17 with respect to the tread normal line n1. The outside groove wall and the inside groove wall of the shoulder circumferential groove have third parts extending linearly without bending.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a tire. [Background technology]

[0002] The following Patent Document 1 describes a tire having at least one main groove in the tread portion. The groove wall of the main groove is provided with a recess that is recessed outward in the groove width direction from the groove edge of the main groove that appears on the ground contact surface. The ground contact surface also has a protrusion in an area where the recess is projected outward in the tire radial direction. This tire is said to exhibit excellent wet performance for a long period of time and suppress uneven wear. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-127228 A Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, there has been a demand for improving wear resistance and steering stability while maintaining wet performance.

[0005] The present invention has been devised in view of the above circumstances, and an object of the present invention is to provide a tire that can improve wear resistance and steering stability while maintaining wet performance. [Means for solving the problem]

[0006] The present invention relates to a tire having a tread portion, the tread portion having a specified orientation for installation on a vehicle, the tread portion including an outer tread edge located on the outer side of the vehicle when installed on the vehicle, an inner tread edge located on the inner side of the vehicle when installed on the vehicle, and a plurality of circumferential grooves extending continuously in a tire circumferential direction between the outer tread edge and the inner tread edge, each of the plurality of circumferential grooves including an outer groove wall on the outer tread edge side, an inner groove wall on the inner tread edge side, and a groove bottom defining a maximum groove depth, the plurality of circumferential grooves including a pair of crown circumferential grooves adjacent to each other across a tire equator, and a pair of shoulder circumferential grooves located axially outboard of each of the pair of crown circumferential grooves, and in a cross section perpendicular to a groove length direction of each of the pair of crown circumferential grooves, the inner groove wall is spaced apart from the tread surface of the tread portion in a radial direction of the tire. the outer groove wall includes a second portion extending radially inward from the tread surface of the tread portion and having the first groove depth, the second portion including a bent portion convex outward in the groove width direction, an outer portion extending between the bent portion and the tread surface, and an inner portion extending radially inward from the bent portion, the inner portion being greater than the angle of the outer portion relative to the tread normal, the outer groove wall and the inner groove wall including a third portion extending radially inward from the tread surface of the tread portion and having the first groove depth, the third portion extending linearly without bending. Effect of the Invention

[0007] By employing the above-mentioned configuration, the tire of the present invention can improve wear resistance and steering stability while maintaining wet performance. [Brief description of the drawings]

[0008] [Figure 1]1 is a plan view of a tread portion of a tire of the present invention. [Diagram 2] FIG. 4 is a cross-sectional view of a crown circumferential groove. [Diagram 3] FIG. 4 is a cross-sectional view of a shoulder circumferential groove. [Figure 4] FIG. 4 is a cross-sectional view of a crown circumferential groove. [Diagram 5] FIG. [Figure 6] FIG. 4 is a cross-sectional view of a crown circumferential groove for explaining the effect of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In order to facilitate understanding of the present invention, the drawings may include exaggerated representations and representations different from the dimensional ratios of the actual structures. In addition, when there are multiple embodiments, the same or common elements are designated by the same reference numerals throughout the specification, and duplicated explanations are omitted.

[0010] Fig. 1 is a plan view of a tread portion 2 of a tire 1 showing one embodiment of the present invention. The present invention is used, for example, in pneumatic tires for passenger cars. However, the present invention may also be used in pneumatic tires for heavy loads and non-pneumatic tires that are not filled with compressed air.

[0011] The orientation of the tread portion 2 when mounted on a vehicle is specified, and as shown in Fig. 1, the tread portion 2 has an outer tread end To located on the outer side of the vehicle when mounted on the vehicle, and an inner tread end Ti located on the inner side of the vehicle.

[0012] In the case of a pneumatic tire, the outer tread edge To and the inner tread edge Ti correspond to the axially outermost ground contact positions in a normal load state where the tire 1 in a normal state is loaded and grounded on a flat surface with a camber angle of 0°. In the case of a pneumatic tire 1 for which various standards are established, the "normal state" refers to a state in which the tire 1 is assembled to a normal rim (not shown), filled to a normal internal pressure, and no load is applied. In the case of a tire for which various standards are not established or a non-pneumatic tire, the normal state refers to a standard use state according to the intended use of the tire and a state in which no load is applied. In this specification, unless otherwise specified, the dimensions of each part of the tire 1 are values ​​measured in the normal state. In addition, the axial distance between the outer tread edge To and the inner tread edge Ti is the tread width TW. Furthermore, in the normal load state, the part that contacts the flat surface is the tread surface 2a of the tread portion 2.

[0013] The "genuine rim" is a rim that is defined for each tire by a standard system that includes the standard on which tire 1 is based, such as a "standard rim" in the case of JATMA, a "Design Rim" in the case of TRA, and a "Measuring Rim" in the case of ETRTO.

[0014] The "normal internal pressure" is the air pressure determined for each tire by each standard in a standard system including the standard on which tire 1 is based, and is the "maximum air pressure" in the case of JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and the "INFLATION PRESSURE" in the case of ETRTO.

[0015] The "normal load" is a load determined for each tire by each standard in the standard system including the standard on which the tire 1 is based, and is the "maximum load capacity" for JATMA, the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "LOAD CAPACITY" for ETRTO. In addition, in the case of tires for which no standards are determined or non-pneumatic tires, the "normal load" refers to the load acting on one tire in the standard mounting state of the tire. The "standard mounting state" refers to a state in which the tire is mounted on a standard vehicle according to the intended use of the tire, and the vehicle is stationary on a flat road surface in a drivable state.

[0016] The tread portion 2 includes a plurality of circumferential grooves G that extend continuously in the tire circumferential direction between the outer tread edge To and the inner tread edge Ti. The plurality of circumferential grooves G include a pair of crown circumferential grooves 3, 3 adjacent to each other across the tire equator C, and a pair of shoulder circumferential grooves 4, 4 located axially outboard of the pair of crown circumferential grooves 3, 3. The pair of shoulder circumferential grooves 4, 4 include an outer shoulder circumferential groove 4A located on the outer tread edge To side, and an inner shoulder circumferential groove 4B located on the inner tread edge Ti side.

[0017] Each of the plurality of circumferential grooves G includes an outer groove wall 8 on the outer tread end To side, an inner groove wall 9 on the inner tread end Ti side, and a groove bottom 10 that defines the maximum depth.

[0018] 2 is a cross section taken along line AA in FIG. 1, which is a cross section perpendicular to the groove length direction of the crown circumferential groove 3. As shown in FIG. 2, each inner groove wall 9A of the crown circumferential groove 3 extends radially inward from the tread surface 2a and includes a first portion 11 having a first groove depth. The first portion 11 extends linearly without bending. Such an inner groove wall 9A ensures a large groove volume, thereby maintaining high wet performance. In this specification, the term "extending linearly" includes not only extending linearly in the cross section, but also extending in an arc with a curvature radius of 100 mm or more.

[0019] In addition, each outer groove wall 8A of the crown circumferential groove 3 extends from the tread 2a to the inside in the tire radial direction and includes a second portion 12 having a first groove depth. The second portion 12 includes a bent portion 16 that is convex outward in the groove width direction, an outer portion 17 that extends between the bent portion 16 and the tread 2a, and an inner portion 18 that extends from the bent portion 16 to the inside in the tire radial direction. Such a second portion 12 can suppress deformation of the land portion 5s connected to the outer groove wall 8A, which is subjected to a relatively large ground pressure and lateral force during running, and can improve wear resistance and steering stability.

[0020] In addition, the tire circumferential length of the tread surface 2a is larger on the tire equator C side than on the tread ends To and Ti sides. Therefore, in order to maintain wet performance, it is desirable to suppress the reduction in the groove volume of the crown circumferential groove 3 in order to ensure the drainage performance on the tire equator C side. From this viewpoint, the angle β of the inner part 18 with respect to the tread normal n1 is formed larger than the angle α of the outer part 17 with respect to the tread normal n1. As a result, the outer groove wall 8A can maintain a larger groove volume than the groove wall Gm having a groove width W1 as shown in FIG. 6, for example, in which the angle β of the inner part 18 is smaller than the angle α of the outer part 17. As a result, the outer groove wall 8A of this embodiment maintains high wet performance. The circumferential groove G1 has the same groove width as the groove width W1 of the crown circumferential groove 3 of this embodiment. The tread normal n1 is a line segment passing through the intersection K between the tread surface 2a and each of the groove walls 8 and 9. Furthermore, in the case where each groove wall 8, 9 is provided with a chamfer (not shown) by cutting off the tread surface 2a obliquely, the tread surface 2a is specified as not having the chamfer.

[0021] FIG. 3 is a cross section taken along line BB in FIG. 1, and is a cross section perpendicular to the groove length direction of the shoulder circumferential groove 4. As shown in FIG. 3, the outer groove wall 8B and the inner groove wall 9B of the shoulder circumferential groove 4 extend radially inward from the tread surface 2a and include a third portion 13 having a first groove depth. During cornering, a larger lateral force acts on the sides of both tread ends To and Ti than on the tire equator C (shown in FIG. 1) side, and the shoulder circumferential groove 4 is required to make strong contact with the road surface. In order to maintain high wet performance during cornering, it is necessary to ensure the groove volume of the shoulder circumferential groove 4 located on the sides of both tread ends To and Ti. For this reason, the third portion 13 is formed to extend linearly without bending. As a result, the outer groove wall 8B and the inner groove wall 9B ensure a large groove volume, and therefore maintain high wet performance during cornering. In this way, a pair of third portions 13 is formed in the shoulder circumferential groove 4.

[0022] 1, each of the crown circumferential groove 3 and the shoulder circumferential groove 4 extends, for example, parallel to the tire circumferential direction and linearly. Each of the crown circumferential groove 3 and the shoulder circumferential groove 4 may extend in a zigzag or wavy shape.

[0023] The axial distance La between the groove center line 3c of each crown circumferential groove 3 and the tire equator C is preferably 5% or more of the tread width TW, more preferably 7% or more, more preferably 13% or less, and even more preferably 11% or less. The axial distance Lb between the groove center line 4c of each shoulder circumferential groove 4 and the tire equator C is preferably 21% or more of the tread width TW, more preferably 23% or more, more preferably 32% or less, and even more preferably 30% or less.

[0024] The groove width W1 of each of the pair of crown circumferential grooves 3 is preferably larger than the groove width W2 of each of the pair of shoulder circumferential grooves 4. This allows the water film on the tread surface 2a on the tire equator C side, which is difficult to drain, to be smoothly discharged. In order to effectively exert such an effect, the groove width W1 of the crown circumferential groove 3 is preferably 1.2 times or more, more preferably 1.3 times or more, more preferably 1.8 times or less, and even more preferably 1.6 times or less than the groove width W2 of the shoulder circumferential groove 4. The groove width W1 of the crown circumferential groove 3 is preferably 3% or more of the tread width TW, more preferably 4% or more, more preferably 9% or less, and even more preferably 8% or less.

[0025] In order to effectively exert the above-mentioned action, it is preferable that the groove depth (maximum groove depth) D1 (shown in FIG. 2) of the crown circumferential groove 3 is greater than the groove depth D2 (shown in FIG. 3) of the shoulder circumferential groove 4. Although not particularly limited, the groove depth D1 of the crown circumferential groove 3 is preferably greater than 6.0 mm, more preferably 6.5 mm or more, more preferably 9.0 mm or less, and more preferably 8.5 mm or less. The groove depth D2 of the shoulder circumferential groove 4 is preferably 6.0 mm or more, more preferably 6.5 mm or more, more preferably less than 9.0 mm, and more preferably 8.5 mm or less.

[0026] As shown in FIG. 2, the angle α of the outer portion 17 of the crown circumferential groove 3 and the angle γ of the intersection K between the inner groove wall 9A of the first portion 11 and the tread surface 2a with respect to the tread normal n1 are preferably 0 degrees or more, more preferably 2 degrees or more, more preferably 9 degrees or less, and even more preferably 7 degrees or less. Since the angles α and γ are 0 degrees or more, the rigidity of the land portion adjacent to the crown circumferential groove 3 can be ensured to be high. Since the angles α and γ are 9 degrees or less, the reduction in the groove volume of the crown circumferential groove 3 is suppressed. In this specification, the "angle with respect to the tread normal" is defined as positive (+) in the direction in which each groove wall 8, 9 inclines outward in the groove width direction toward the outer side in the tire radial direction, and negative (-) in the direction in which each groove wall 8, 9 inclines inward in the groove width direction toward the outer side in the tire radial direction.

[0027] It is desirable that the angle α of the outer portion 17 is the same as the angle γ of the first portion 11. This reduces the difference in rigidity between the land portion adjacent to the outer portion 17 and the land portion adjacent to the first portion 11, thereby making it possible to suppress the occurrence of uneven wear during straight driving.

[0028] The angle β of the inner portion 18 is preferably 20 degrees or more, more preferably 30 degrees or more, more preferably 70 degrees or less, and even more preferably 60 degrees or less. Since the angle β of the inner portion 18 is 20 degrees or more, deformation of the second portion 12 can be suppressed. Since the angle β of the inner portion 18 is 70 degrees or less, the rigidity of the land portion near the bend 16 can be maintained high.

[0029] FIG. 4 is a cross-sectional view (cross-section along line AA in FIG. 1) of the crown circumferential groove 3 in the groove length direction. As shown in FIG. 4, the inner groove wall 9A further includes a first arc portion 20 connecting the first portion 11 and the groove bottom 10A. The outer groove wall 8A further includes a second arc portion 21 connecting the second portion 12 and the groove bottom 10A. The first arc portion 20 and the second arc portion 21 further suppress the decrease in rigidity of the land portion adjacent to the crown circumferential groove 3, thereby improving the steering stability performance and the wear resistance performance. In this embodiment, each of the first arc portion 20 and the second arc portion 21 has a second groove depth. The sum of the first groove depth of the first portion 11 and the second groove depth of the first arc portion 20, and the sum of the first groove depth of the second portion 12 and the second groove depth of the second arc portion 21 each form the maximum groove depth D1 of the crown circumferential groove 3.

[0030] The radius of curvature r1 of the first arc portion 20 and the radius of curvature r2 of the second arc portion 21 are preferably greater than 1.0 mm, more preferably greater than 1.5 mm, more preferably less than 3.0 mm, and even more preferably less than 2.5 mm. Since the radius of curvature r1 of the first arc portion 20 and the radius of curvature r2 of the second arc portion 21 are greater than 1.0 mm, damage such as cracks in the land portion is suppressed. Since the radius of curvature r1 of the first arc portion 20 and the radius of curvature r2 of the second arc portion 21 are 3.0 mm or less, reduction in groove volume can be suppressed.

[0031] The bent portion 16 is formed of an arc having a radius of curvature r3 smaller than those of the first arc portion 20 and the second arc portion 21. Such a bent portion 16 can further suppress a reduction in the groove volume. From this viewpoint, the radius of curvature r3 of the bent portion 16 is preferably 1.0 mm or more, more preferably 1.2 mm or more, preferably less than 3.0 mm, and even more preferably 2.0 mm or less.

[0032] The height H1 of the bent portion 16 from the groove bottom 10A is preferably 15% or more of the maximum groove depth D1 (shown in FIG. 2), more preferably 20% or more, more preferably 45% or less, and even more preferably 40% or less. Since the height H1 is 15% or more of the maximum groove depth D1, deformation of the land portion during running can be suppressed. Since the height H1 is 45% or less of the maximum groove depth D1, reduction in groove volume can be suppressed. The height H1 of the bent portion 16 is determined at the outer end of the bent portion 16 in the tire radial direction.

[0033] As shown in Fig. 3, in the shoulder circumferential groove 4, the outer groove wall 8B further includes an outer third arc portion 23A connecting the third portion 13 and the groove bottom 10B. The inner groove wall 9B further includes an inner third arc portion 23B connecting the third portion 13 and the groove bottom 10B. Each of the outer third arc portion 23A and the inner third arc portion 23B has a second groove depth. In this embodiment, the sum of the second groove depth of the outer third arc portion 23A or the inner third arc portion 23B and the first groove depth of the third portion 13 each forms the maximum groove depth of the shoulder circumferential groove 4.

[0034] The pair of third portions 13 of the shoulder circumferential groove 4 includes an outer third portion 13A (shown in FIG. 1) located on the outer side in the tire axial direction, and an inner third portion 13B located closer to the tire equator C than the outer third portion 13A. More specifically, in the outer shoulder circumferential groove 4A, the outer third portion 13A is formed on the outer groove wall 8B. In addition, in the inner shoulder circumferential groove 4B, the outer third portion 13A is formed on the inner groove wall 9B (shown in FIG. 1). The angle ω1 of the outer third portion 13A with respect to the tread normal n1 is formed larger than the angle ω2 of the inner third portion 13B with respect to the tread normal n1. Such a shoulder circumferential groove 4 can suppress deformation of the groove wall located on the outer side in the tire axial direction where a large lateral force acts during cornering.

[0035] In order to improve steering stability and wear resistance while maintaining wet performance, the angle ω2 of the inner third portion 13B is preferably 0 degrees or more, more preferably 2 degrees or more, preferably 9 degrees or less, and more preferably 7 degrees or less. The difference (ω1-ω2) between the angle ω1 of the outer third portion 13A and the angle ω2 of the inner third portion 13B is preferably 2 degrees or more, more preferably 3 degrees or more, preferably 7 degrees or less, and more preferably 6 degrees or less.

[0036] FIG. 5 is a plan view of the tread portion 2. As shown in FIG. 5, the tread portion 2 of this embodiment is divided into a plurality of land portions 5 by a plurality of circumferential grooves G. In this embodiment, the land portions 5 are divided into a crown land portion 5A, an outer middle land portion 5B, an inner middle land portion 5C, an outer shoulder land portion 5D, and an inner shoulder land portion 5E. The crown land portion 5A is located between a pair of crown circumferential grooves 3, 3. The outer middle land portion 5B is located closer to the outer tread edge To than the crown land portion 5A. The inner middle land portion 5C is located closer to the inner tread edge Ti than the crown land portion 5A. The outer shoulder land portion 5D is connected to the outer tread edge To. The inner shoulder land portion 5E is connected to the inner tread edge Ti.

[0037] In the present embodiment, the land portion 5 is provided with a lateral groove 6 extending in the tire axial direction, or a sipe 7 extending in the tire axial direction. The sipe 7 includes a pair of sipe walls 7h extending inward in the tire radial direction from the tread surface 2a (as shown in FIG. 1). In this specification, the sipe is a notched recess having a width of less than 1.5 mm, and is clearly distinguished from the circumferential groove G and the lateral groove 6, which have a groove width of 1.5 mm or more.

[0038] The lateral groove 6 includes a plurality of first lateral grooves 6A arranged in the outer shoulder land portion 5D and a plurality of second lateral grooves 6B arranged in the inner shoulder land portion 5E. The first lateral groove 6A crosses the outer shoulder land portion 5D. The first lateral groove 6A includes a first widened portion 25A in which the groove width W3 increases continuously from the outer tread edge To toward the tire equator C, and a first narrowed portion 26A connected to the first widened portion 25A in which the groove width W3 decreases continuously toward the tire equator C. The axial length of the first widened portion 25A is formed to be greater than the axial length of the first narrowed portion 26A. The second lateral groove 6B extends from the inner tread edge Ti toward the tire equator C and is interrupted within the inner shoulder land portion 5E. The second lateral groove 6B has an end e1 that terminates within the inner shoulder land portion 5E. The second lateral groove 6B includes a second widened portion 25B in which the groove width W4 increases continuously from the inner tread edge Ti toward the tire equator C, and a second narrowed portion 26B in which the groove width W4 increases continuously toward the tire equator C and is connected to the second widened portion 25B. The axial length of the second widened portion 25B is greater than the axial length of the second narrowed portion 26B.

[0039] The sipes 7 include a first sipe 7A, a second sipe 7B, a third sipe 7C, and a fourth sipe 7D. The first sipe 7A crosses the crown land portion 5A. The second sipe 7B crosses the outer middle land portion 5B. The third sipe 7C crosses the inner middle land portion 5C. The fourth sipe 7D is provided in the inner shoulder land portion 5E and is connected to the inner shoulder circumferential groove 4B. The fourth sipe 7D has an end e2 that terminates within the inner shoulder land portion 5E.

[0040] In this embodiment, each sipe 7 is provided with a chamfer 29 that is cut diagonally between the tread surface 2a and the sipe wall 7h. Each sipe 7 includes, for example, a chamfered portion 7a where the chamfer 29 is formed, and a plain portion 7b where the chamfer 29 is not formed. The first sipe 7A, the third sipe 7C, and the fourth sipe 7D are formed, for example, with one chamfered portion 7a and one plain portion 7b. The second sipe 7B is formed, for example, with a pair of chamfered portions 7a located at both ends, and one plain portion 7b sandwiched between the double-sided chamfered portions 7a. In this way, only the multiple sipes 7 and the chamfer 29 are provided in the crown land portion 5A, the outer middle land portion 5B, and the inner middle land portion 5C, and no lateral grooves are provided.

[0041] In such a tire 1, it is desirable that the difference (CW-RW) between the clip width CW (not shown) and the rim width RW (not shown) is 0 inch or more and 1.0 inch or less. This can improve the performance of suppressing cracks occurring at the groove bottom of the circumferential groove G (TGC resistance performance). In this specification, the rim width RW is the rim width of the regular rim (see JATMA, etc.). In this specification, the clip width CW is the axial distance between a pair of bead molding surfaces that mold the outer surfaces (not shown) of the bead portions of the tire 1 in a vulcanization mold for manufacturing the tire 1, as described in JP 2014-240171 A.

[0042] Although a particularly preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the illustrated embodiment and can be modified and carried out in various forms. EXAMPLES

[0043] Pneumatic tires having the basic pattern shown in Fig. 1 were prototyped. Each test tire was then tested for wet performance, steering stability, and wear resistance. The specifications and test methods were as follows: Tire size: 205 / 55R16 Rim: 16×7.0 Internal pressure: 250kPa W1 is the same in the comparative example and each of the examples. Test vehicle: 2000cc front-wheel drive passenger car

[0044] <Wet performance, steering stability, wear resistance, TGC resistance> The test tires were fitted to all wheels of a test vehicle. For wet performance and steering stability, a test driver ran the tires on a test course on a wet road surface and a test course on a dry asphalt road surface, and evaluated the characteristics related to running stability and cornering performance by sensory evaluation. For wear resistance and TGC resistance, the test driver sensorily evaluated the degree of wear of the tread portion and the degree of cracks occurring in the circumferential grooves after running 16,000 km on the above-mentioned dry asphalt road surface. The results were all shown as a score with Comparative Example 1 being 100, and the higher the value, the better the performance. The test results are shown in Tables 1 and 2. "A" in Table 2 means that the first lateral groove does not cross the outer shoulder land portion, and the second lateral groove crosses the inner shoulder land portion.

[0045] [Table 1]

[0046] [Table 2]

[0047] As a result of the test, it is understood that the tires of the examples maintain wet performance in comparison with the tires of the comparative examples. In addition, the tires of the examples are excellent in steering stability and wear resistance.

[0048] [Note] The present invention includes the following aspects.

[0049] [Invention 1] A tire having a tread portion, The tread portion has a specified orientation for installation on a vehicle, the tread portion includes an outer tread edge located on the outer side of the vehicle when the tire is mounted on the vehicle, an inner tread edge located on the inner side of the vehicle when the tire is mounted on the vehicle, and a plurality of circumferential grooves extending continuously in the tire circumferential direction between the outer tread edge and the inner tread edge, Each of the plurality of circumferential grooves includes an outer groove wall at an outer tread end side, an inner groove wall at an inner tread end side, and a groove bottom defining a maximum groove depth, the plurality of circumferential grooves include a pair of crown circumferential grooves adjacent to each other across the tire equator, and a pair of shoulder circumferential grooves located axially outward of each of the pair of crown circumferential grooves, In a cross section perpendicular to the groove length direction of each of the pair of crown circumferential grooves, the inner groove wall includes a first portion extending radially inward from a tread surface of the tread portion and having a first groove depth, the first portion extending linearly without bending, the outer groove wall includes a second portion extending radially inward from the tread surface of the tread portion and having the first groove depth, the second portion including a bent portion that protrudes outward in the groove width direction, an outer portion that extends between the bent portion and the tread surface, and an inner portion that extends radially inward from the bent portion, an angle of the inner portion with respect to a tread normal at an intersection between the outer groove wall and the tread surface is larger than an angle of the outer portion with respect to the tread normal; In a cross section perpendicular to the groove length direction of each of the pair of shoulder circumferential grooves, The outer groove wall and the inner groove wall extend radially inward from the tread surface of the tread portion and include a third portion having the first groove depth, and the third portion extends linearly without bending. tire. [Invention 2] The tire according to claim 1, wherein an angle of the outer portion with respect to the tread normal and an angle of the first portion with respect to the tread normal at an intersection between the inner groove wall and the tread surface are 0 to 9 degrees. [Invention 3] 3. A tire according to claim 2, wherein the angle of the outer portion is the same as the angle of the first portion. [Invention 4] The tire according to any one of Inventions 1 to 3, wherein the angle of the inner portion is 20 to 70 degrees. [Invention 5] The tire according to any one of claims 1 to 4, wherein the height of the bent portion from the groove bottom is 15% to 45% of the maximum groove depth. [Invention 6] The tire according to any one of claims 1 to 5, wherein the groove width of each of the pair of crown circumferential grooves is larger than the groove width of each of the pair of shoulder circumferential grooves. [Invention 7] In a cross section perpendicular to the groove length direction of each of the pair of crown circumferential grooves, The inner groove wall further includes a first arc portion connecting the first portion and the groove bottom, The tire according to any one of claims 1 to 6, wherein the outer groove wall further includes a second arc portion connecting the second portion and the groove bottom. [Invention 8] The tire according to invention 7, wherein the radius of curvature of the first arc portion and the radius of curvature of the second arc portion are greater than 1.0 mm and equal to or less than 3.0 mm. [The present invention 9] In a cross section perpendicular to the groove length direction of each of the pair of crown circumferential grooves, The tire according to invention 7, wherein the curved portion is an arc having a smaller radius of curvature than the first arc portion and the second arc portion. [The present invention 10] 10. The tire according to claim 9, wherein the radius of curvature of the bent portion is 1.0 mm or more and less than 3.0 mm. [The present invention 11] The tread portion is divided into a plurality of land portions by the plurality of circumferential grooves, the plurality of land portions include a crown land portion located between the pair of crown circumferential grooves, an outer middle land portion located closer to the outer tread end than the crown land portion, and an inner middle land portion located closer to the inner tread end than the crown land portion, The tire according to any one of claims 1 to 10, wherein each of the crown land portion, the outer middle land portion and the inner middle land portion is provided with a plurality of sipes and only chamfers that are obliquely cut off between the tread surface of the tread portion and the sipe walls of the sipes. [The present invention 12] The tread portion is divided into a plurality of land portions by the plurality of circumferential grooves, The plurality of land portions include an outer shoulder land portion connected to the outer tread edge and an inner shoulder land portion connected to the inner tread edge, The outer shoulder land portion includes a plurality of first lateral grooves that cross the outer shoulder land portion, The tire according to any one of claims 1 to 11, wherein the inner shoulder land portion includes a plurality of second lateral grooves extending from the inner tread edge toward the tire equator and terminated within the inner shoulder land portion. [The present invention 13] the pair of shoulder circumferential grooves includes an inner shoulder circumferential groove located on the inner tread end side, 13. The tire according to claim 12, wherein the inner shoulder land portion is provided with a plurality of sipes connected to the inner shoulder circumferential groove. [Invention 14] The tire according to any one of claims 1 to 13, wherein the groove width of each of the pair of crown circumferential grooves is 1.2 to 1.8 times the groove width of each of the pair of shoulder circumferential grooves and is 3 to 9% of the tread width. [The present invention 15] A distance in the tire axial direction between each groove center line of the pair of crown circumferential grooves and the tire equator is 5% to 13% of a tread width, The tire according to any one of claims 1 to 14, wherein a distance in the tire axial direction between each groove center line of the pair of shoulder circumferential grooves and the tire equator is 21% to 32% of the tread width. [The present invention 16] 16. The tire according to any one of claims 1 to 15, wherein the difference between the clip width CW and the rim width RW (CW-RW) is 1.0 inch or less. [Explanation of symbols]

[0050] 1 Tire 2a Tread 3 Crown circumferential groove 4 Shoulder circumferential groove 8A Outer groove wall 8B Inner groove wall 9A Outer groove wall 9B Inner groove wall α, β angles n1 tread normal 11 Part 1 12 Part 2 13 Part 3 16 Bend 17 Outer part 18 Inner part

Claims

1. A tire having a tread portion, The tread portion has a specified orientation for installation on a vehicle, the tread portion includes an outer tread edge located on the outer side of the vehicle when the tire is mounted on the vehicle, an inner tread edge located on the inner side of the vehicle when the tire is mounted on the vehicle, and a plurality of circumferential grooves extending continuously in the tire circumferential direction between the outer tread edge and the inner tread edge, Each of the plurality of circumferential grooves includes an outer groove wall at an outer tread end side, an inner groove wall at an inner tread end side, and a groove bottom defining a maximum groove depth, the plurality of circumferential grooves include a pair of crown circumferential grooves adjacent to each other across the tire equator, and a pair of shoulder circumferential grooves located axially outward of each of the pair of crown circumferential grooves, In a cross section perpendicular to the groove length direction of each of the pair of crown circumferential grooves, the inner groove wall includes a first portion extending inward in a tire radial direction from a tread surface of the tread portion and having a first groove depth, the first portion extending linearly without bending, the outer groove wall includes a second portion extending radially inward from the tread surface of the tread portion and having the first groove depth, the second portion including a bent portion convex outward in the groove width direction, an outer portion extending between the bent portion and the tread surface, and an inner portion extending radially inward from the bent portion, an angle of the inner portion with respect to a tread normal at an intersection between the outer groove wall and the tread surface is larger than an angle of the outer portion with respect to the tread normal; In a cross section perpendicular to the groove length direction of each of the pair of shoulder circumferential grooves, the outer groove wall and the inner groove wall include a third portion extending inward in a tire radial direction from a tread surface of the tread portion and having the first groove depth, the third portion extending linearly without bending. tire.

2. 2. The tire according to claim 1, wherein an angle of the outer portion with respect to the tread normal and an angle of the first portion with respect to a tread normal at an intersection of the inner groove wall and the tread surface are between 0 and 9 degrees.

3. The tire of claim 2 wherein said angle of said outer side is the same as said angle of said first portion.

4. A tire according to any one of claims 1 to 3, wherein the angle of the inner side is between 20 and 70 degrees.

5. 4. The tire according to claim 1, wherein a height of the bent portion from the groove bottom is 15% to 45% of the maximum groove depth.

6. The tire according to claim 1 , wherein a groove width of each of the pair of crown circumferential grooves is larger than a groove width of each of the pair of shoulder circumferential grooves.

7. In a cross section perpendicular to the groove length direction of each of the pair of crown circumferential grooves, the inner groove wall further includes a first arc portion connecting the first portion and the groove bottom, The tire according to claim 1 , wherein the outer groove wall further includes a second arc portion connecting the second portion and the groove bottom.

8. 8. The tire of claim 7, wherein the radius of curvature of said first arcuate portion and said second arcuate portion is greater than 1.0 mm and less than or equal to 3.0 mm.

9. In a cross section perpendicular to the groove length direction of each of the pair of crown circumferential grooves, The tire according to claim 7 , wherein the bent portion is an arc having a smaller radius of curvature than the first arc portion and the second arc portion.

10. 10. The tire according to claim 9, wherein the radius of curvature of the bent portion is equal to or greater than 1.0 mm and less than 3.0 mm.

11. The tread portion is divided into a plurality of land portions by the plurality of circumferential grooves, the plurality of land portions include a crown land portion located between the pair of crown circumferential grooves, an outer middle land portion located closer to the outer tread end than the crown land portion, and an inner middle land portion located closer to the inner tread end than the crown land portion, 4. The tire according to claim 1, wherein each of the crown land portion, the outer middle land portion, and the inner middle land portion is provided with a plurality of sipes and only chamfers that are obliquely cut off between a tread surface of the tread portion and a sipe wall of the sipe.

12. The tread portion is divided into a plurality of land portions by the plurality of circumferential grooves, The plurality of land portions include an outer shoulder land portion connected to the outer tread edge and an inner shoulder land portion connected to the inner tread edge, The outer shoulder land portion includes a plurality of first lateral grooves that cross the outer shoulder land portion, The tire according to claim 1 , wherein the inner shoulder land portion includes a plurality of second lateral grooves extending from the inner tread edge toward the tire equator and terminated within the inner shoulder land portion.

13. the pair of shoulder circumferential grooves includes an inner shoulder circumferential groove located on the inner tread end side, The tire according to claim 12 , wherein the inner shoulder land portion is provided with a plurality of sipes that are connected to the inner shoulder circumferential groove.

14. The tire according to claim 11, wherein the groove width of each of the pair of crown circumferential grooves is 1.2 to 1.8 times the groove width of each of the pair of shoulder circumferential grooves and is 3 to 9% of the tread width.

15. a distance in the tire axial direction between each groove center line of the pair of crown circumferential grooves and the tire equator is 5% to 13% of a tread width, The tire according to claim 11, wherein a distance in the tire axial direction between each groove centerline of the pair of shoulder circumferential grooves and the tire equator is 21% to 32% of the tread width.

16. 4. The tire according to claim 1, wherein the difference between the clip width CW and the rim width RW (CW-RW) is 1.0 inch or less.

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