Tire

Abstract

Provided is a tire capable of reducing pitch noise. 【Solution means】 A tire 1 having a tread portion 2 including a plurality of circumferential grooves 5 and a plurality of land portions 6. In each of the plurality of land portions 6, a plurality of groove-like portions 20 are formed, which have a first end on one side in the tire circumferential direction and a second end on the other side in the tire circumferential direction. In the arrangement rule of the plurality of groove-like portions 20, for each of all pairs of groove-like portions 20 adjacent in the tire circumferential direction, the first end of one groove-like portion 20 in the pair and the second end of the other groove-like portion 20 in the pair are formed at the same position in the tire circumferential direction, and are formed on the same land portion 6 or on different land portions 6 from each other. In at least one land portion 6 in a 70% load-bearing state, the absolute value of the difference between the angle θa of the ground contact edge on both sides in the tire circumferential direction with respect to the tire axial direction and the angle θb of the groove-like portion 20 with respect to the tire axial direction is 5 degrees or more.

Description

Technical Field

[0001] The present invention relates to a tire.

Background Art

[0002] Patent Document 1 below describes a tire having a tread portion including a plurality of circumferential grooves continuously extending in the tire circumferential direction and a plurality of land portions divided by the circumferential grooves. In the plurality of land portions, a plurality of transverse groove-like elements inclined with respect to the tire axial direction and the tire circumferential direction are formed respectively.

[0003] Each of the transverse groove-like elements has a first end on the first side in the tire circumferential direction and a second end on the second side in the tire circumferential direction. The plurality of transverse groove-like elements are arranged according to a first arrangement over one circumference in the tire circumferential direction. In this first arrangement, for each of all pairs of adjacent transverse groove-like elements in the tire circumferential direction, the first end of one transverse groove-like element in the pair is formed at the same position in the tire circumferential direction as the second end of the other transverse groove-like element in the pair.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the above tire, although pitch noise is reduced by continuously grounding the transverse groove-like elements constantly when the tire is running, there is still room for further improvement.

[0006] The present invention has been devised in view of the above actual situation, and the main object is to provide a tire capable of reducing pitch noise.

Means for Solving the Problems

[0007] The present invention relates to a tire having a tread portion, wherein the tread portion includes a plurality of circumferential grooves continuously extending in the tire circumferential direction and a plurality of land portions separated by the plurality of circumferential grooves. In each of the plurality of land portions, a plurality of groove-like portions inclined with respect to the tire axial direction are formed. Each of the plurality of groove-like portions has a first end on one side in the tire circumferential direction and a second end on the other side in the tire circumferential direction. The plurality of groove-like portions are arranged based on a predetermined arrangement rule over one circumference in the tire circumferential direction. In the arrangement rule, for each pair of all the groove-like portions adjacent in the tire circumferential direction among the plurality of groove-like portions, the first end of one groove-like portion of the pair and the second end of the other groove-like portion of the pair are formed at the same position in the tire circumferential direction. The groove-like portions constituting the pair are formed in the same land portion or in different land portions from each other. In a 70% load-bearing state where the tire is mounted on a standard rim at a standard internal pressure and a camber angle is set to 0 degrees while a 70% of the standard load is applied and the tire is grounded on a flat surface, the ground contact edge portions on both sides in the tire circumferential direction of at least one of the plurality of land portions have an angle θa with respect to the tire axial direction, and an absolute value of a difference between the angle θa and an angle θb of the groove-like portion formed in the at least one land portion with respect to the tire axial direction is 5 degrees or more.

Advantages of the Invention

[0008] By adopting the above configuration, the tire of the present invention can reduce pitch noise.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be understood that the drawings include exaggerated expressions and expressions different from the actual structural dimensional ratios in order to assist in understanding the content of the invention. Also, throughout each embodiment, the same or common elements are denoted by the same reference numerals, and redundant descriptions are omitted. Furthermore, the specific configurations shown in the embodiments and the drawings are for the purpose of understanding the content of the present invention, and the present invention is not limited to the specific configurations shown.

[0011] [Tire] FIG. 1 is a developed view showing an example of the tread portion 2 of the tire 1. In FIG. 1, the protrusion 41 (shown in FIG. 5) described later is omitted.

[0012] The tire 1 of the present embodiment is exemplified as a pneumatic tire. Note that the tire 1 may be a non-pneumatic tire (airless tire). Also, as the tire of the present embodiment, for example, a passenger car tire is suitable. Note that the tire 1 may be a motorcycle tire or a heavy-duty tire.

[0013] [Tread Portion] The tire 1 of the present embodiment has a tread portion 2. The tread portion 2 of the present embodiment has a specified mounting direction on the vehicle, but is not limited to such a mode. For example, the mounting direction may not be specified. The mounting direction on the vehicle is indicated by characters or marks (not shown) on, for example, the sidewall portion (not shown) of the tire 1. In FIG. 1, the right side corresponds to the vehicle inner side Vi, and the left side corresponds to the vehicle outer side Vo.

[0014] The tread portion 2 of the present embodiment includes a pair of tread edges 3 and a tread surface 4 therebetween. The tread surface 4 is a portion intended to contact the ground (road surface) when the tire is running, and is formed of tread rubber. When the mounting direction on the vehicle is specified as in the tread portion 2 of the present embodiment, the pair of tread edges 3 includes an inner tread edge 3i provided on the vehicle inner side Vi and an outer tread edge 3o provided on the vehicle outer side Vo.

[0015] The pair of tread edges 3 (in this example, the inner tread edge 3i and the outer tread edge 3o) are specified at the most axially outer grounding positions in the 70% load condition when the tire 1 is a pneumatic tire. Here, the "70% load condition" is a state in which the normal tire 1 is loaded with 70% of the normal load and grounded on a plane with a camber angle of 0 degrees.

[0016] The normal state is a non-loaded state in which the tire 1 is rim-mounted on a normal rim (not shown) at the normal internal pressure. In this specification, unless otherwise specified, the dimensions and the like of each part of the tire are shown as values measured in the normal state. Note that the dimensions and the like are allowed to have normal dimensional errors (tolerances) that are inevitable in manufacturing.

[0017] The "normal rim" is a rim defined for each tire in a standard system including the standard on which the tire 1 is based. Therefore, the normal rim is, for example, the "Standard Rim" in JATMA, the "Design Rim" in TRA, and the "Measuring Rim" in ETRTO.

[0018] The "standard internal pressure" is the air pressure defined for each tire in a standard system including the standards on which the tire 1 is based. Therefore, the standard internal pressure is, for example, "maximum air pressure" in the case of JATMA, the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and "INFLATION PRESSURE" in the case of ETRTO.

[0019] The "standard load" is the load defined for each tire in a standard system including the standards on which the tire 1 is based. Therefore, the standard load is, for example, "maximum load capacity" in the case of JATMA, the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and "LOAD CAPACITY" in the case of ETRTO.

[0020] The tread portion 2 of the present embodiment has a tread pattern 2P in which 1-pitch regions P constituting a pattern configuration unit are arranged in the tire circumferential direction. The 1-pitch regions P may be arranged in plurality, for example, if they have a common pattern, even if a plurality of regions having the same tire circumferential length are arranged, or a plurality of types of regions having different tire circumferential lengths may be arranged randomly. The tire circumferential length L1 of the 1-pitch region P is set to, for example, 19 to 36 mm.

[0021] It is preferable that the tread pattern 2P includes a plurality of 1-pitch regions P having different tire circumferential lengths L1 arranged in the tire circumferential direction. Thereby, the natural frequency between the 1-pitch regions P is changed, and the noise performance is improved. In order to effectively enhance such an effect, it is preferable that the number of types of the 1-pitch regions P is 2 to 10.

[0022] The tread portion 2 (tread pattern 2P) of the present embodiment includes a plurality of circumferential grooves 5 continuously extending in the tire circumferential direction and a plurality of land portions 6 divided by the plurality of circumferential grooves 5.

[0023] [Circumferential groove] The plurality of circumferential grooves 5 extend continuously in the tire circumferential direction on the tread surface 4 between a pair of tread ends 3 (between the inner tread end 3i and the outer tread end 3o). Due to such circumferential grooves 5, when driving on wet roads, the water between the tread portion 2 and the road surface (not shown) is discharged, improving the wet performance.

[0024] The plurality of circumferential grooves 5 of the present embodiment extend linearly along the tire circumferential direction, but are not limited to such a form. The plurality of circumferential grooves 5 may extend, for example, in a wave shape or a zigzag shape.

[0025] The groove width W1 and the groove depth (not shown) of each circumferential groove 5 can be set as appropriate. The groove width W1 is set, for example, to 2.0% to 8.0% of the maximum ground contact width W in the tire axial direction of the ground contact surface in a 70% load-bearing state. The groove depth is set, for example, to 4.0 to 10.0 mm. The maximum ground contact width W is specified as the distance in the tire axial direction between a pair of tread ends 3 (in this example, between the inner tread end 3i and the outer tread end 3o). The groove width is specified as the distance between two adjacent groove edges in a direction perpendicular to the groove center line.

[0026] The plurality of circumferential grooves 5 include at least one center circumferential groove 7 disposed on the tire equator C side. In the present embodiment, a pair of center circumferential grooves 7 and a pair of shoulder circumferential grooves 8 are included. Due to these center circumferential grooves 7 and shoulder circumferential grooves 8, water between the tread portion 2 and the road surface is discharged over a wide range in the tire axial direction, improving the wet performance. Note that the circumferential grooves 5 are not necessarily limited to an embodiment including a pair of center circumferential grooves 7 and a pair of shoulder circumferential grooves 8, and may be configured, for example, by one center circumferential groove 7 and a pair of shoulder circumferential grooves 8.

[0027] A pair of center circumferential grooves 7 are arranged on both sides in the tire axial direction with respect to the tire equator C. When the mounting direction on the vehicle is specified as in the tread portion 2 of the present embodiment, the pair of center circumferential grooves 7 includes an inner center circumferential groove 7i arranged on the vehicle inner side Vi and an outer center circumferential groove 7o arranged on the vehicle outer side Vo. The groove center lines (not shown) of these pair of center circumferential grooves 7 may be provided at positions separated from the tire equator C by a distance of 6% to 15% of the maximum ground contact width W in the outer direction in the tire axial direction from the viewpoint of improving the above wet performance.

[0028] A pair of shoulder circumferential grooves 8 are arranged between the center circumferential groove 7 and the tread end 3 (in this example, either the inner tread end 3i or the outer tread end 3o). When the mounting direction on the vehicle is specified as in the tread portion 2 of the present embodiment, the pair of shoulder circumferential grooves 8 includes an inner shoulder circumferential groove 8i arranged on the vehicle inner side Vi and an outer shoulder circumferential groove 8o arranged on the vehicle outer side Vo. The groove center lines (not shown) of these pair of shoulder circumferential grooves 8 are preferably provided at positions separated from the tire equator C by a distance of 25% to 35% of the maximum ground contact width W in the outer direction in the tire axial direction from the viewpoint of improving the above wet performance. Further, the groove width W1 of the outer shoulder circumferential groove 8o may be set smaller than the groove width W1 of the inner shoulder circumferential groove 8i. Thereby, the tread rigidity on the vehicle outer side where the ground contact pressure becomes relatively large during turning travel increases, and the handling stability performance is improved.

[0029] [Lug portion] The plurality of lug portions 6 are divided by the plurality of circumferential grooves 5. The plurality of lug portions 6 in the present embodiment are configured to include a center lug portion 11, a pair of middle lug portions 12, and a pair of shoulder lug portions 13. Note that the plurality of lug portions 6 are not necessarily limited to such a mode. For example, depending on the running performance required for the tire 1, etc., it may be configured to include a pair of center lug portions 11 and a pair of shoulder lug portions 13.

[0030] The center land portion 11 is divided by a pair of center circumferential grooves 7 (an inner center circumferential groove 7i and an outer center circumferential groove 7o). Thereby, the center land portion 11 is disposed on the tire equator C.

[0031] The pair of middle land portions 12 are divided between the pair of center circumferential grooves 7 and the pair of shoulder circumferential grooves 8. When the mounting direction on the vehicle is specified as in the tread portion 2 of the present embodiment, the pair of middle land portions 12 include an inner middle land portion 12i disposed on the vehicle inner side Vi and an outer middle land portion 12o disposed on the vehicle outer side Vo.

[0032] The inner middle land portion 12i is divided between the inner center circumferential groove 7i and the inner shoulder circumferential groove 8i. On the other hand, the outer middle land portion 12o is divided between the outer center circumferential groove 7o and the outer shoulder circumferential groove 8o.

[0033] The pair of shoulder land portions 13 are divided outside in the tire axial direction of the pair of shoulder circumferential grooves 8. When the mounting direction on the vehicle is specified as in the tread portion 2 of the present embodiment, the pair of shoulder land portions 13 include an inner shoulder land portion 13i disposed on the vehicle inner side Vi and an outer shoulder land portion 13o disposed on the vehicle outer side Vo.

[0034] The inner shoulder land portion 13i is divided outside in the tire axial direction of the inner shoulder circumferential groove 8i (on the vehicle inner side Vi) and includes the inner tread end 3i. On the other hand, the outer shoulder land portion 13o is divided outside in the tire axial direction of the outer shoulder circumferential groove 8o (on the vehicle outer side Vo) and includes the outer tread end 3o.

[0035] Of the above-mentioned land portions 6, the sum of the widths W2a, W2b, and W2c in the tire axial direction of the center land portion 11, the inner middle land portion 12i, and the outer middle land portion 12o may be set to 35% to 60% of the maximum ground contact width W in the tire axial direction in the 70% load-bearing state. By setting the sum to 35% or more of the maximum ground contact width W, the lateral rigidity and the ground contact area of each land portion 6 are ensured, and the handling stability is improved. On the other hand, by setting the sum to 60% or less of the maximum ground contact width W, the groove width W1 (groove volume) of the circumferential groove 5 is ensured, and the drainage performance is improved. From such a viewpoint, the sum is preferably 40% or more of the maximum ground contact width W, and preferably 55% or less of the maximum ground contact width W.

[0036] [Plural groove-shaped portions] In each of the plurality of land portions 6 of the present embodiment, a plurality of groove-shaped portions 20 inclined with respect to the tire axial direction are formed. By these plurality of groove-shaped portions 20, the wet performance is improved. FIG. 2 is a partially enlarged view of the center land portion 11, the inner middle land portion 12i, and the outer middle land portion 12o of FIG. 1.

[0037] As shown in FIG. 2, each of the plurality of groove-shaped portions 20 has a first end 20a on one side S1 in the tire circumferential direction and a second end 20b on the other side S2 in the tire circumferential direction. In the present embodiment, the first end 20a and the second end 20b are specified at the ends of the groove center line 20c along the longitudinal direction of the groove-shaped portion 20. When a chamfered portion 29 is provided as in the groove-shaped portion 20 of the present embodiment, the first end 20a and the second end 20b are specified excluding the chamfered portion 29 (in this example, based only on the sipe main body portion 28).

[0038] The plurality of groove-shaped portions 20 (in this example, the groove-shaped portions provided in the center land portion 11, the inner middle land portion 12i, and the outer middle land portion 12o) of the present embodiment include a sipe main body portion 28 having a width (that is, the width orthogonal to its longitudinal direction) of 2 mm or less. The sipe main body portion 28 of the present embodiment is formed in a slit shape. By these plurality of groove-shaped portions 20 (sipe main body portion 28), while forming an edge component in the tread portion 2, it is possible to suppress a decrease in the rigidity of the land portion 6 when contacting the road surface, and it is possible to improve the handling stability performance.

[0039] The groove-shaped portion 20 is not necessarily limited to the aspect including the sipe main body portion 28. For example, it may include a groove main body portion (not shown) having a width (that is, the width orthogonal to its longitudinal direction) greater than 2 mm. Such a groove main body portion improves wet performance. Further, the depth of the groove-shaped portion 20 (not shown) is set to, for example, 2 to 8 mm.

[0040] As shown in FIG. 1, the plurality of groove-shaped portions 20 of the present embodiment include a plurality of first groove-shaped portions 21, a plurality of second groove-shaped portions 22, a plurality of third groove-shaped portions 23, a plurality of fourth groove-shaped portions 24, a plurality of fifth groove-shaped portions 25, a plurality of sixth groove-shaped portions 26, and a plurality of seventh groove-shaped portions 27. Note that the plurality of groove-shaped portions 20 are not necessarily limited to the aspect including all of these first groove-shaped portions 21 to seventh groove-shaped portions 27. For example, depending on the performance required for the tire 1, etc., some of these may be omitted, or other groove-shaped portions (not shown) may be included.

[0041] The plurality of first groove-shaped portions 21 and the plurality of second groove-shaped portions 22 are provided in the center land portion 11. In the present embodiment, the plurality of first groove-shaped portions 21 are arranged on the vehicle inner side Vi of the center land portion 11. On the other hand, the plurality of second groove-shaped portions 22 are arranged on the vehicle outer side Vo of the center land portion 11. Note that the center land portion 11 is not necessarily limited to the aspect where these first groove-shaped portions 21 and second groove-shaped portions 22 are provided. For example, some of these may be omitted, or other groove-shaped portions (not shown) may be included.

[0042] The plurality of third groove-shaped portions 23 are provided on the inner middle land portion 12i. Note that the inner middle land portion 12i is not limited to the mode in which only the third groove-shaped portion 23 is provided, and for example, other groove-shaped portions (not shown) may be included.

[0043] The plurality of fourth groove-shaped portions 24 and the plurality of fifth groove-shaped portions 25 are provided on the outer middle land portion 12o. In the present embodiment, the plurality of fourth groove-shaped portions 24 are arranged on the vehicle inner side Vi of the outer middle land portion 12o. On the other hand, the plurality of fifth groove-shaped portions 25 are arranged on the vehicle outer side Vo of the outer middle land portion 12o. Note that the outer middle land portion 12o is not limited to the mode in which these fourth groove-shaped portions 24 and fifth groove-shaped portions 25 are provided, and for example, a part of these may be omitted, or other groove-shaped portions (not shown) may be included.

[0044] The plurality of sixth groove-shaped portions 26 are formed on the inner shoulder land portion 13i. Note that the inner shoulder land portion 13i is not limited to the mode in which only the sixth groove-shaped portion 26 is provided, and for example, other groove-shaped portions (not shown) may be included.

[0045] The plurality of seventh groove-shaped portions 27 are formed on the outer shoulder land portion 13o. Note that the outer shoulder land portion 13o is not limited to the mode in which only the seventh groove-shaped portion 27 is provided, and for example, other groove-shaped portions (not shown) may be included.

[0046] [Arrangement rule] Then, as shown in FIG. 2, the plurality of groove-shaped portions 20 of the present embodiment are arranged based on a predetermined arrangement rule 30 over one circumference in the tire circumferential direction. The arrangement rule 30 of the present embodiment targets the center land portion 11 and the plurality of groove-shaped portions 20 arranged on the pair of middle land portions 12 (inner middle land portion 12i and outer middle land portion 12o), but is not limited to such a mode. For example, only a part of these land portions 6 may be targeted by the arrangement rule 30, or the other land portions 6 (the pair of shoulder land portions 13 shown in FIG. 1) may be targeted by the arrangement rule 30.

[0047] In the array rule 30, for each of all pairs 31 of the plurality of groove-shaped portions 20 that are adjacent to each other in the tire circumferential direction, the first end 20a of one groove-shaped portion 20 of the pair 31 and the second end 20b of the other groove-shaped portion 20 of the pair 31 are formed at the same position in the tire circumferential direction. Further, the groove-shaped portions 20 constituting the pair 31 are formed on the same land portion 6 or on different land portions 6 from each other.

[0048] Here, whether the first end 20a of one groove-shaped portion 20 of the pair 31 and the second end 20b of the other groove-shaped portion 20 of the pair 31 are at the same position in the tire circumferential direction is determined using their groove center lines 20c. That is, the first end 20a of one groove-shaped portion 20 of the pair 31 and the second end 20b of the other groove-shaped portion 20 of the pair 31 are each specified by the ends of the groove center line 20c. However, in view of allowing manufacturing tolerances in consideration of the characteristics of the vulcanized rubber product that is the tire 1, the "same position" includes a mode in which the first end 20a and the second end 20b are displaced by a slight distance in the tire circumferential direction. In this case, the distance in the tire circumferential direction between the first end 20a and the second end 20b is set to 5% or less, preferably 3% or less, and more preferably 1% or less of the total length in the tire circumferential direction of the two groove-shaped portions 20 constituting the pair 31. It should be noted that it is most preferable that the first end 20a and the second end 20b are not displaced in the tire circumferential direction (for example, less than 0.1%).

[0049] The pair 31 of the present embodiment includes a first pair 31a, a second pair 31b, a third pair 31c, a fourth pair 31d, and a fifth pair 31e. Note that some of these pairs 31 may be omitted, or other pairs may be included. The groove-shaped portions 20 constituting the pair 31 of the present embodiment are formed on different land portions 6 from each other.

[0050] The first pair 31a is composed of the fourth groove-shaped portion 24 and the second groove-shaped portion 22 that is adjacent to the fourth groove-shaped portion 24 on the other side S2 in the tire circumferential direction. In the present embodiment, the fourth groove-shaped portion 24 is formed in the outer middle land portion 12o, and the second groove-shaped portion 22 is formed in the center land portion 11. Therefore, the groove-shaped portions 20 that constitute the first pair 31a are formed in different land portions 6 from each other. Also, in the first pair 31a, the first end 20a of the second groove-shaped portion 22 and the second end 20b of the fourth groove-shaped portion 24 are formed at the same position in the tire circumferential direction.

[0051] The second pair 31b is composed of the second groove-shaped portion 22 and the third groove-shaped portion 23 that is adjacent to the second groove-shaped portion 22 on the other side S2 in the tire circumferential direction. In the present embodiment, the second groove-shaped portion 22 is formed in the center land portion 11, and the third groove-shaped portion 23 is formed in the inner middle land portion 12i. Therefore, the groove-shaped portions 20 that constitute the second pair 31b are formed in different land portions 6 from each other, similar to the first pair 31a. Also, in the second pair 31b, the first end 20a of the third groove-shaped portion 23 and the second end 20b of the second groove-shaped portion 22 are formed at the same position in the tire circumferential direction.

[0052] The third pair 31c is composed of the third groove-shaped portion 23 and the fifth groove-shaped portion 25 that is adjacent to the third groove-shaped portion 23 on the other side S2 in the tire circumferential direction. In the present embodiment, the third groove-shaped portion 23 is formed in the inner middle land portion 12i, and the fifth groove-shaped portion 25 is formed in the outer middle land portion 12o. Therefore, the groove-shaped portions 20 that constitute the third pair 31c are formed in different land portions 6 from each other, similar to the first pair 31a and the second pair 31b. Also, in the third pair 31c, the first end 20a of the fifth groove-shaped portion 25 and the second end 20b of the third groove-shaped portion 23 are formed at the same position in the tire circumferential direction.

[0053] The fourth pair 31d is composed of a fifth groove portion 25 and a first groove portion 21 that is adjacent to the fifth groove portion 25 on the other side S2 in the tire circumferential direction. In the present embodiment, the fifth groove portion 25 is formed in the outer middle land portion 12o, and the first groove portion 21 is formed in the center land portion 11. Therefore, the groove portions 20 constituting the fourth pair 31d are formed in different land portions 6 from each other, similarly to the first pair 31a to the third pair 31c. Further, in the fourth pair 31d, the first end 20a of the first groove portion 21 and the second end 20b of the fifth groove portion 25 are formed at the same position in the tire circumferential direction.

[0054] The fifth pair 31e is composed of a first groove portion 21 and a fourth groove portion 24 that is adjacent to the first groove portion 21 on the other side S2 in the tire circumferential direction. In the present embodiment, the first groove portion 21 is formed in the center land portion 11, and the fourth groove portion 24 is formed in the outer middle land portion 12o. Therefore, the groove portions 20 constituting the fifth pair 31e are formed in different land portions 6 from each other, similarly to the first pair 31a to the fourth pair 31d. Further, in the fifth pair 31e, the first end 20a of the fourth groove portion 24 and the second end 20b of the first groove portion 21 are formed at the same position in the tire circumferential direction.

[0055] In the present embodiment, the first pair 31a to the fifth pair 31e constitute one pitch region P shown in FIG. 1, and these first pair 31a to the fifth pair 31e are repeated in order. Thereby, in the arrangement rule 30 of the present embodiment, the groove portions 20 constituting each pair 31 (the first pair 31a to the fifth pair 31e) are formed in different land portions 6 from each other.

[0056] Generally, a pitch sound is known as a noise during tire running. For example, an impact force is generated each time the region 32 (tread surface 4) divided by the first groove portion 21 to the fifth groove portion 25 contacts the road surface. This impact force tends to generate a pitch noise (pitch sound) by periodically vibrating the tread portion 2 and the sidewall portion (not shown).

[0057] In this embodiment, according to the above-described array rule 30, when the tire is running, the first groove-shaped portions 21 to the fifth groove-shaped portions 25 alternately and continuously contact the ground from one side S1 to the other side S2 (or from the other side S2 to the one side S1) in the tire circumferential direction. As a result, the fluctuation of the impact force is reduced. Therefore, the tire 1 of this embodiment can reduce the pitch noise (pitch sound) generated from the land portion 6 (region 32), and the noise performance can be improved.

[0058] In the array rule 30 of this embodiment, the groove-shaped portions 20 constituting each pair 31 are formed in different land portions 6 from each other. As a result, in this embodiment, in each of the land portions 6, the groove-shaped portions 20 constituting each pair 31 are not continuously formed. For this reason, in order to form the first end 20a and the second end 20b at the same position, for example, it is not necessary to increase the angle θb of the groove-shaped portion 20 with respect to the tire axial direction or increase the number of groove-shaped portions 20 formed in each land portion 6. Therefore, it is possible to prevent the rigidity in the tire axial direction of each land portion 6 from decreasing more than necessary, and it is possible to achieve both steering stability and noise performance (quietness).

[0059] In the array rule 30 of this embodiment, the groove-shaped portions 20 constituting each pair 31 are formed in the center land portion 11 and the pair of middle land portions 12 (inner middle land portion 12i and outer middle land portion 12o). Since these center land portion 11 and the pair of middle land portions 12 tend to have a relatively large contact pressure during straight running, the pitch noise (pitch sound) can be effectively reduced. Further, since the groove-shaped portions 20 constituting each pair 31 are formed in three or more different land portions 6 from each other, a decrease in the rigidity in the tire axial direction of the land portion 6 is prevented, and the steering stability is further improved.

[0060] The array rule 30 of the present embodiment is not limited to such a mode in which the groove-shaped portions 20 constituting each pair 31 are formed on different land portions 6. For example, the groove-shaped portions 20 constituting each pair 31 may be formed on the same land portion 6. In this case, in each land portion 6, since the groove-shaped portions 20 constituting the pair 31 are alternately and continuously grounded without interruption, the variation of the impact force is further reduced. Further, in order to form the first end 20a and the second end 20b at the same position, for example, when the number of groove-shaped portions 20 increases, the edge component increases, so that the wet performance and the like are improved.

[0061] FIG. 3 is a diagram showing an example of the footprint 34 of the tread portion 2 in a 70% load state. In the footprint 34 of FIG. 3, a tread pattern in which one side S1 and the other side S2 in the tire circumferential direction are inverted is shown.

[0062] In the present embodiment, in the 70% load state, the ground contact edge 33 on both sides in the tire circumferential direction of at least one land portion 6 among the plurality of land portions 6 has an angle θa with respect to the tire axial direction. And in the present embodiment, the absolute value of the difference between the angle θa and the angle θb of the groove-shaped portion 20 formed in at least one land portion 6 with respect to the tire axial direction is set to 5 degrees or more. Note that the angle θb used for the calculation of the absolute value is specified in the 70% load state, similarly to the angle θa. Further, the angle θa and the angle θb may be obtained from the footprint 34 obtained by a known procedure, or may be obtained from the calculation result of the ground contact simulation using a computer.

[0063] The angle θa is specified by a straight line 36 passing through both ends 35, 35 in the width direction of the land portion 6 at the grounding edge 33 of each land portion 6. Further, the angle θa of the present embodiment is specified in the land portions 6 (in this example, the center land portion 11, the inner middle land portion 12i, and the outer middle land portion 12o) where the groove-shaped portion 20 that is the object of the arrangement rule 30 shown in FIG. 2 is formed. For this reason, the angle θa includes the angle θa1 of the grounding edge 33 on one side S1 in the tire circumferential direction of the center land portion 11 and the angle θa2 of the grounding edge 33 on the other side S2 in the tire circumferential direction of the center land portion 11. Further, the angle θa includes the angle θa3 of the grounding edge 33 on one side S1 in the tire circumferential direction of the inner middle land portion 12i and the angle θa4 of the grounding edge 33 on the other side S2 in the tire circumferential direction of the inner middle land portion 12i. Further, the angle θa includes the angle θa5 of the grounding edge 33 on one side S1 in the tire circumferential direction of the outer middle land portion 12o and the angle θa6 of the grounding edge 33 on the other side S2 in the tire circumferential direction of the outer middle land portion 12o.

[0064] The angles θa1 to θa6 of the grounding edge 33 of each land portion 6 are specified such that the angle inclined from one side S1 to the other side S2 in the tire circumferential direction is positive when going from the vehicle inner side Vi to the vehicle outer side Vo, and the angle inclined from the other side S2 to one side S1 in the tire circumferential direction is negative. In this case, in the inner middle land portion 12i, the angle θa3 of the grounding edge 33 on one side S1 is negative, and the angle θa4 of the grounding edge 33 on the other side S2 is positive. Also, in the outer middle land portion 12o, the angle θa5 of the grounding edge 33 on one side S1 is positive, and the angle θa6 of the grounding edge 33 on the other side S2 is negative.

[0065] The angle θa of the grounding edge 33 and the shape of the grounding surface (footprint) 37 can be adjusted as appropriate. As an example of the adjustment, for example, changing the thickness of the tread rubber having a well-known structure arranged in the tread portion 2, or changing the tire constituent members having well-known structures such as the carcass arranged inside the tread portion 2, etc. can be mentioned.

[0066] The angle θb is specified at the position 39 (the first end 20a or the second end 20b) where the groove center line 20c along the longitudinal direction of the groove-shaped portion 20 (the sipe main body portion 28 described later) shown in FIG. 2 intersects with the edge 38 extending in the tire circumferential direction on both sides of each land portion 6 in the tire axial direction in the 70% load state. Further, the angle θb of the present embodiment is specified by the groove-shaped portion 20 that is the target of the arrangement rule 30 shown in FIG. 2. For this reason, the angle θb includes the angle θb1 of the first groove-shaped portion 21, the angle θb2 of the second groove-shaped portion 22, the angle θb3 of the third groove-shaped portion 23, the angle θb4 of the fourth groove-shaped portion 24, and the angle θb5 of the fifth groove-shaped portion 25.

[0067] Similar to the angle θa of the ground contact edge 33 of each land portion 6, the angles θb1 to θb5 of each groove-shaped portion 20 are specified such that the angle inclined from one side S1 to the other side S2 in the tire circumferential direction is positive when going from the vehicle inner side Vi to the vehicle outer side Vo. Further, the angles θb1 to θb5 of each groove-shaped portion 20 are specified such that the angle inclined from the other side S2 to the one side S1 in the tire circumferential direction is negative. For this reason, the angle θb1 of the first groove-shaped portion 21, the angle θb2 of the second groove-shaped portion 22, and the angle θb4 of the fourth groove-shaped portion 24 are negative. On the other hand, the angle θb3 of the third groove-shaped portion 23 and the angle θb5 of the fifth groove-shaped portion 25 are positive.

[0068] In the present embodiment, the absolute value of the difference (θa1 - θb1) between the angle θa1 of the ground contact edge 33 on one side S1 of the center land portion 11 and the angle θb1 of the first groove-shaped portion 21 formed in the center land portion 11 is set to be 5 degrees or more. Further, the absolute value of the difference (θa2 - θb1) between the angle θa2 of the ground contact edge 33 on the other side S2 of the center land portion 11 and the angle θb1 of the first groove-shaped portion 21 is set to be 5 degrees or more.

[0069] In the present embodiment, the absolute value of the difference (θa1 - θb2) between the angle θa1 of the ground contact edge 33 on one side S1 of the center land portion 11 and the angle θb2 of the second groove-shaped portion 22 formed in the center land portion 11 is set to be 5 degrees or more. Further, the absolute value of the difference (θa2 - θb2) between the angle θa2 of the ground contact edge 33 on the other side S2 of the center land portion 11 and the angle θb2 of the second groove-shaped portion 22 is set to be 5 degrees or more.

[0070] In this embodiment, the absolute value of the difference (θa3 - θb3) between the angle θa3 of the grounding edge 33 on one side S1 of the inner middle land portion 12i and the angle θb3 of the third groove-shaped portion 23 formed in the inner middle land portion 12i is set to 5 degrees or more. Further, the absolute value of the difference (θa4 - θb3) between the angle θa4 of the grounding edge 33 on the other side S2 of the inner middle land portion 12i and the angle θb3 of the third groove-shaped portion 23 is set to 5 degrees or more.

[0071] In this embodiment, the absolute value of the difference (θa5 - θb4) between the angle θa5 of the grounding edge 33 on one side S1 of the outer middle land portion 12o and the angle θb4 of the fourth groove-shaped portion 24 formed in the outer middle land portion 12o is set to 5 degrees or more. Further, the absolute value of the difference (θa6 - θb4) between the angle θa6 of the grounding edge 33 on the other side S2 of the outer middle land portion 12o and the angle θb4 of the fourth groove-shaped portion 24 is set to 5 degrees or more.

[0072] In this embodiment, the absolute value of the difference (θa5 - θb5) between the angle θa5 of the grounding edge 33 on one side S1 of the outer middle land portion 12o and the angle θb5 of the fifth groove-shaped portion 25 formed in the outer middle land portion 12o is set to 5 degrees or more. Further, the absolute value of the difference (θa6 - θb5) between the angle θa6 of the grounding edge 33 on the other side S2 of the outer middle land portion 12o and the angle θb5 of the fifth groove-shaped portion 25 is set to 5 degrees or more.

[0073] Thus, in this embodiment, by setting the absolute value of the difference between the angle θa and the angle θb to 5 degrees or more, it is possible to suppress the inclination directions of the grounding edge 33 and the groove-shaped portion 20 from matching each other. Thereby, when the tire is running, the groove-shaped portion 20 can be gradually brought into contact with the ground or taken out of contact with the ground with respect to the grounding edge 33. Therefore, when the tire comes into contact with the ground or leaves the ground at the grounding edge 33, it is possible to prevent the air inside the groove-shaped portion 20 from being compressed or released all at once, so that the amplification of the pitch noise volume can be suppressed.

[0074] In the tire 1 of the present embodiment, as shown in FIG. 2, the first end 20a of one groove-shaped portion 20 of the pair 31 and the second end 20b of the other groove-shaped portion 20 of the pair 31 are formed at the same position in the tire circumferential direction, so that pitch noise can be reduced. Further, in the tire 1 of the present embodiment, as shown in FIG. 3, in each land portion 6, the absolute value of the difference (θa - θb) between the angle θa of the ground contact edge 33 and the angle θb of the groove-shaped portion 20 is set to 5 degrees or more, so that the amplification of the volume of pitch noise can be suppressed. Therefore, the tire 1 of the present embodiment can reduce pitch noise, and thus the noise performance is improved.

[0075] In the present embodiment, it is preferable that the absolute value of the difference (θa - θb) between the angle θa of the ground contact edge 33 and the angle θb of the groove-shaped portion 20 is 5 degrees or more in all of the center land portion 11 and the pair of middle land portions (inner middle land portion 12i and outer middle land portion 12o). Since these land portions 6 mainly come into contact with the ground both during straight running and turning, by setting the absolute value to 5 degrees or more, the amplification of the volume of pitch noise is effectively suppressed, and further improvement in noise performance becomes possible.

[0076] On the other hand, when the absolute value of the difference (θa - θb) between the angle θa of the ground contact edge 33 and the angle θb of the groove-shaped portion 20 becomes larger than necessary, the angle θb of the groove-shaped portion 20 becomes larger and the tread rigidity becomes smaller, so there is a possibility that the handling stability may decrease. For this reason, the absolute value of the difference (θa - θb) is preferably 50 degrees or less.

[0077] The absolute value of the difference between the angle θa of the inner middle land portion 12i and the angle θb of the groove-shaped portion 20 formed in the inner middle land portion 12i may be greater than or equal to the absolute value of the difference between the angle θa of the outer middle land portion 12o and the angle θb of the groove-shaped portion 20 formed in the outer middle land portion 12o. As described above, the differences in the angles of the inner middle land portion 12i include the differences (θa3 - θb3) and (θa4 - θb3). Also, the differences in the angles of the outer middle land portion 12o include the differences (θa5 - θb4), (θa6 - θb4), (θa5 - θb5), and (θa6 - θb5).

[0078] By setting the absolute value of the difference in angles at the inner middle land portion 12i to be equal to or greater than the absolute value of the difference in angles at the outer middle land portion 12o, a large edge component can be formed at the inner middle land portion 12i where the ground contact pressure during turning is relatively small compared to the outer middle land portion 12o. Thereby, while maintaining the handling stability, the wet performance is improved. In order to effectively exhibit such an effect, it is more preferable that the absolute value of the difference in angles at the inner middle land portion 12i is greater than the absolute value of the difference in angles at the outer middle land portion 12o.

[0079] Also, the absolute value of the difference between the angle θa of the inner middle land portion 12i and the angle θb of the groove portion 20 formed in the inner middle land portion 12i may be set to be equal to or greater than the absolute value of the difference between the angle θa of the center land portion 11 and the angle θb of the groove portion 20 formed in the center land portion 11. Further, the absolute value of the difference between the angle θa of the center land portion 11 and the angle θb of the groove portion 20 formed in the center land portion 11 may be set to be equal to or greater than the absolute value of the difference between the angle θa of the outer middle land portion 12o and the angle θb of the groove portion 20 formed in the outer middle land portion 12o. As described above, the difference in angles of the center land portion 11 includes the differences (θa1 - θb1), (θa2 - θb1), (θa1 - θb2), and (θa2 - θb2).

[0080] By setting the absolute value of the difference in angles at the inner middle land portion 12i to be equal to or greater than the absolute value of the difference in angles at the center land portion 11, and the absolute value of the difference in angles at the center land portion 11 to be equal to or greater than the absolute value of the difference in angles at the outer middle land portion 12o, the edge component gradually increases toward the inner side of the vehicle where the ground contact pressure during turning is relatively small. Thereby, while maintaining the wet performance, the transient characteristics (handling stability performance) during turning are improved. In order to effectively exhibit such an effect, it is more preferable that the absolute value of the difference in angles at the inner middle land portion 12i is greater than the absolute value of the difference in angles at the center land portion 11, and similarly, it is more preferable that the absolute value of the difference in angles at the center land portion 11 is greater than the absolute value of the difference in angles at the outer middle land portion 12o.

[0081] FIG. 4 is a diagram showing the maximum contact length L and the contact length Lm in the footprint 34 of the tread portion 2 in a 70% load condition. The contact surface 37 of the tread portion 2 in the 70% load condition preferably satisfies the following formula (1) for the ratio L / Lm of the maximum contact length L in the tire circumferential direction to the contact length Lm in the tire circumferential direction. The contact length Lm is specified within a range W60 that is centered on the tire equator C and is 60% or less of the maximum contact width W in the tire axial direction. 1.00 < L / Lm < 1.10 …(1)

[0082] By the ratio L / Lm satisfying the above formula (1), in the region where the contact pressure increases during straight running (that is, the range W60 that is 60% or less of the maximum contact width W) of the contact surface 37, the contact edge 33 of each land portion 6 has a flat shape along the tire axial direction. As a result, the absolute value of the angle θa (shown in FIG. 3) of the contact edge 33 of each land portion 6 (in this example, the center land portion 11, the inner middle land portion 12i, and the outer middle land portion 12o) becomes smaller. For this reason, the absolute value of the above difference (θa - θb) becomes 5 degrees or more, and it becomes possible to easily suppress the amplification of the pitch noise volume. Furthermore, in the above range W60 (the center land portion 11, the inner middle land portion 12i, and the outer middle land portion 12o), since the contact length Lm is maintained large, the handling stability is improved. In order to effectively exhibit such an action, the ratio L / Lm is preferably 1.08 or less, and more preferably 1.06 or less. Similarly, the absolute value of the angle θa of the contact edge 33 shown in FIG. 3 is preferably 0 to 15 degrees.

[0083] Furthermore, the contact surface 37 of the tread portion 2 in the 70% load condition preferably satisfies the following formula (2) for the ratio L / Ln of the maximum contact length L in the tire circumferential direction to the contact length Ln in the tire circumferential direction. The contact length Ln is specified at a position that is 80% of the maximum contact width W in the tire axial direction and is centered on the tire equator C. 1.15 < L / Ln < 1.50 …(2)

[0084] By satisfying the above formula (2) for the ratio L / Ln, the grounding ends on both sides in the tire axial direction become round, and when a high load is applied, the grounding width gradually expands smoothly. As a result, the cushioning performance during launching is enhanced, and the riding comfort is improved. Further, the resistance to water on the road surface is reduced, and the wet performance (hydroplaning performance) is enhanced. Also, even when the lateral force increases during turning, the grounding width smoothly expands, so that the suppression of the local increase in the grounding pressure is achieved. Thereby, the handling stability performance is enhanced. In order to effectively exhibit such an action, the ratio L / Ln is preferably 1.20 or more, and the ratio L / Ln is preferably 1.40 or less.

[0085] Noise during running occurs not only in the groove-shaped portion 20 shown in FIG. 1 but also in the circumferential groove 5. In the circumferential groove 5, mainly column resonance noise is generated. In order to reduce such column resonance noise, at least one protrusion protruding in the tire radial direction may be formed at the groove bottom of the circumferential groove 5. FIG. 5 is an enlarged perspective view showing an example of the protrusion 41 provided in the inner shoulder circumferential groove 8i.

[0086] The protrusion 41 can disturb the air passing through the circumferential groove 5 during tire running by protruding outward in the tire radial direction from the groove bottom 40. Thereby, the column resonance noise likely to occur in the circumferential groove 5 can be reduced.

[0087] The protrusion 41 of the present embodiment is configured to include a first protrusion 41A and a second protrusion 41B. The first protrusion 41A and the second protrusion 41B are adjacent to each other in the tire axial direction in the circumferential groove 5.

[0088] Each of the first protrusion 41A and the second protrusion 41B is configured to include a first surface 43 and a second surface 44. The first surface 43 extends in the tire radial direction. The second surface 44 is arranged on the opposite side of the tire circumferential direction with respect to the first surface 43 and extends at an angle larger than that of the first surface 43 with respect to the tire radial direction.

[0089] The first protrusion 41A has the first surface 43 facing the other side S2 in the tire circumferential direction and the second surface 44 facing the one side S1 in the tire circumferential direction. On the other hand, the second protrusion 41B has the first surface 43 facing the one side S1 in the tire circumferential direction and the second surface 44 facing the other side S2 in the tire circumferential direction. In this way, since the tire circumferential directions of the first surface 41a and the second surface 41b of the first protrusion 41A and the second protrusion 41B are different from each other, the air in the circumferential groove 5 can be effectively disturbed, and the column resonance noise can be reduced. Such a protrusion 41 can be formed, for example, based on the description in Patent Document (Japanese Unexamined Patent Application Publication No. 2020-196281).

[0090] The column resonance sound tends to be large in the center circumferential groove 7 among the plurality of circumferential grooves 5 shown in FIG. 1. For this reason, the protrusion 41 is preferably formed at least in the center circumferential groove 7. The protrusion 41 of the present embodiment is formed not only in the center circumferential groove 7 but also in the shoulder circumferential groove 8. Thereby, the column resonance noise can be effectively reduced.

[0091] In each of the plurality of land portions 6 shown in FIG. 1, the total of the tire axial lengths L2 (shown in FIG. 2) of the groove-shaped portions 20 formed in the one pitch region P is preferably set to 60% to 120% of the tire axial width W2 of the land portion 6. As shown in FIG. 2, the length L2 is specified as the tire axial distance between the first end 20a and the second end 20b of the groove-shaped portion 20 (the sipe main body portion 28).

[0092] In each land portion 6, by setting the total length L2 of the groove-shaped portions 20 to be 60% or more of the width W2 of the land portion 6, even without increasing the absolute value of the angle θb of the groove-shaped portions 20, the first end 20a of one groove-shaped portion 20 of the pair 31 and the second end 20b of the other groove-shaped portion 20 can be formed at the same position. Thereby, a decrease in the lateral rigidity of the land portion 6 associated with an increase in the absolute value of the angle θb is suppressed, and the handling stability is improved. Also, by setting the total length L2 to be 120% or less of the width W2 of the land portion 6, an excessive increase in the number of groove-shaped portions 20 formed in one pitch region P is suppressed, and the handling stability is maintained. From such a viewpoint, the total length L2 is preferably 70% or more of the width W2 of the land portion 6, and is preferably 110% or less.

[0093] The average angle of all the groove-shaped portions 20 with respect to the tire axis direction (the average angle of the absolute values of the angles θb1 to θb5) is preferably 10 to 50 degrees. By setting the average angle to be 10 degrees or more, due to the inclination of the groove-shaped portions 20 of each land portion 6, it becomes possible to form the first end 20a of one groove-shaped portion 20 of the pair 31 and the second end 20b of the other groove-shaped portion 20 at the same position in the tire circumferential direction. On the other hand, by setting the average angle to be 50 degrees or less, a decrease in the lateral rigidity of the land portion 6 associated with an increase in the angle θb of the groove-shaped portions 20 is suppressed, and the handling stability is improved. From such a viewpoint, the average angle is preferably 15 degrees or more and is preferably 45 degrees or less.

[0094] In each of the center land portion 11 and the outer middle land portion 12o, at least one of the plurality of groove-shaped portions 20 may have at least one of the first end 20a and the second end 20b terminating within the land portion 6. Thereby, a decrease in rigidity of the center land portion 11 and the outer middle land portion 12o where the ground pressure becomes relatively large during turning travel is minimized, and the handling stability performance and the braking performance are improved.

[0095] As described above, a plurality of first groove-shaped portions 21 and a plurality of second groove-shaped portions 22 are formed in the center land portion 11. For the plurality of first groove-shaped portions 21, the first end 20a terminates within the center land portion 11, and the second end 20b communicates with the inner center circumferential groove 7i (shown in FIG. 1). On the other hand, for the plurality of second groove-shaped portions 22, the first end 20a communicates with the outer center circumferential groove 7o (shown in FIG. 1), and the second end 20b terminates within the center land portion 11. Thus, in the first groove-shaped portion 21 and the second groove-shaped portion 22, at least one of the first end 20a and the second end 20b terminates within the center land portion 11, so that a decrease in the rigidity of the center land portion 11 where the ground pressure becomes relatively large during turning and straight running is minimized. Therefore, the handling stability performance and the braking performance are improved.

[0096] The length L2b in the tire axial direction of each second groove-shaped portion 22 is smaller than the length L2a in the tire axial direction of each first groove-shaped portion 21. Thereby, in the center land portion 11, the rigidity of the portion on the outer side Vo of the vehicle where the ground pressure becomes relatively large during turning is relatively increased, and the handling stability performance is improved. On the other hand, on the inner side Vi of the vehicle of the center land portion 11, a large edge component is formed, so the wet performance is improved. In order to effectively exhibit such an effect, the length L2b of the second groove-shaped portion 22 is preferably set to 30% to 75% of the length L2a of the first groove-shaped portion 21.

[0097] The first groove-shaped portions 21 and the second groove-shaped portions 22 may be alternately arranged in the tire circumferential direction in the center land portion 11. Thereby, on both sides in the tire axial direction of the center land portion 11, the edge components by the first groove-shaped portions 21 and the second groove-shaped portions 22 are evenly formed in the tire circumferential direction, so the wet performance is improved.

[0098] Each of the plurality of first groove-shaped portions 21 and the plurality of second groove-shaped portions 22 is inclined from the first end 20a to the second end 20b from the outer side Vo of the vehicle to the inner side Vi of the vehicle. Therefore, the plurality of first groove-shaped portions 21 and the plurality of second groove-shaped portions 22 are inclined in the same direction as each other.

[0099] The absolute value of the angle θb1 of the first groove-shaped portion 21 with respect to the tire axis direction and the absolute value of the angle θb2 of the second groove-shaped portion 22 with respect to the tire axis direction are preferably set to 10 to 30°. Note that whether the absolute values of the angles θb1 and θb2 are 10 to 30° shall be specified in the normal state. By setting the absolute values of these angles θb1 and θb2 to 30° or less, the rigidity of the center land portion 11 is maintained, and the handling stability performance and braking performance are improved. On the other hand, by setting the absolute values of the angles θb1 and θb2 to 10° or more, a large edge component is formed, and the wet performance is improved. From such a viewpoint, the absolute values of the angles θb1 and θb2 are preferably 25° or less, and are preferably 15° or more.

[0100] As described above, a plurality of fourth groove-shaped portions 24 and a plurality of fifth groove-shaped portions 25 are formed in the outer middle land portion 12o. The first end 20a of the plurality of fourth groove-shaped portions 24 terminates at the outer middle land portion 12o, and the second end 20b communicates with the outer center circumferential groove 7o (shown in FIG. 1). On the other hand, the first end 20a of the plurality of fifth groove-shaped portions 25 terminates at the outer middle land portion 12o, and the second end 20b communicates with the outer shoulder circumferential groove 8o (shown in FIG. 1). In this way, at least one of the first end 20a and the second end 20b of the fourth groove-shaped portion 24 and the fifth groove-shaped portion 25 terminates within the outer middle land portion 12o, so that a decrease in the rigidity of the outer middle land portion 12o where the ground pressure becomes relatively high during turning travel is minimized. Therefore, the handling stability performance is improved.

[0101] Preferably, the first end 20a of each fourth groove-shaped portion 24 and the first end 20a of each fifth groove-shaped portion 25 are separated from each other in the tire axial direction. Thereby, since the reduction in rigidity of the outer middle land portion 12o where the ground pressure becomes relatively large during turning running is suppressed, the handling stability performance is improved. Further, the length L2d of each fourth groove-shaped portion 24 in the tire axial direction and the length L2e of each fifth groove-shaped portion 25 in the tire axial direction may be the same. Thereby, on both sides in the tire axial direction of the outer middle land portion 12o where the ground pressure becomes relatively large during turning running, edge components of the same length by the fourth groove-shaped portion 24 and the fifth groove-shaped portion 25 are uniformly formed in the tire circumferential direction, so that the wet performance is improved.

[0102] The fourth groove-shaped portion 24 and the fifth groove-shaped portion 25 may be alternately arranged in the tire circumferential direction in the outer middle land portion 12o. Thereby, on both sides in the tire axial direction of the outer middle land portion 12o, edge components are uniformly formed in the tire circumferential direction, so that the wet performance is improved.

[0103] Each of the plurality of fourth groove-shaped portions 24 is inclined from the first end 20a to the second end 20b from the vehicle outer side Vo to the vehicle inner side Vi. Therefore, the plurality of fourth groove-shaped portions 24 are inclined in the same direction as the plurality of first groove-shaped portions 21 and the plurality of second groove-shaped portions 22. On the other hand, each of the plurality of fifth groove-shaped portions 25 is inclined from the first end 20a to the second end 20b from the vehicle inner side Vi to the vehicle outer side Vo. Therefore, the plurality of fourth groove-shaped portions 24 and the plurality of fifth groove-shaped portions 25 are inclined in opposite directions to each other. Due to these fourth groove-shaped portions 24 and fifth groove-shaped portions 25, edge components in different directions are formed on both sides in the tire axial direction of the outer middle land portion 12o, so that the wet performance is improved.

[0104] The absolute value of the angle θb4 of the fourth groove portion 24 with respect to the tire axis direction is preferably set to 10 to 30°. Note that whether the absolute value of the angle θb4 is 10 to 30° is specified in the normal state. By setting the absolute value of the angle θb4 to 30° or less, the rigidity of the outer middle land portion 12o where the ground pressure increases during both straight running and turning is maintained, and the handling stability performance is improved. On the other hand, by setting the angle θb4 to 10° or more, a large edge component is formed, and the wet performance is improved. From such a viewpoint, the absolute value of the angle θb4 is preferably 25° or less, and is preferably 15° or more.

[0105] The absolute value of the angle θb5 of the fifth groove portion 25 with respect to the tire axis direction is preferably smaller than the absolute value of the angle θb4 of the fourth groove portion 24. Note that the absolute value of the angle θb5 is specified in the normal state. By making the absolute value of the angle θb5 smaller than the absolute value of the angle θb4, the rigidity of the portion Vo on the outer side of the vehicle where the ground pressure during turning is relatively large increases in the outer middle land portion 12o, so that the handling stability performance is improved while maintaining the wet performance. In order to effectively exhibit such an action, the absolute value of the angle θb5 of the fifth groove portion 25 is preferably set to 5 to 25°.

[0106] In the inner middle land portion 12i, at least one of the plurality of groove portions 20 (in this example, the third groove portion 23) may have both the first end 20a and the second end 20b communicating with any of the circumferential grooves 5 shown in FIG. 1 (the inner center circumferential groove 7i and the inner shoulder circumferential groove 8i). Thereby, since a continuous edge component crossing the inner middle land portion 12i in the tire axis direction is formed, the wet performance is improved. Further, the inner middle land portion 12i tends to have a relatively small ground pressure during turning compared to the center land portion 11 and the outer middle land portion 12o. Even if a plurality of groove portions 20 communicating with the circumferential groove 5 are provided in such an inner middle land portion 12i, the handling stability performance can be maintained.

[0107] The third groove portion 23 may be alternately arranged with the first groove portion 21 in the tire circumferential direction. Thereby, in the inner middle land portion 12i and the center land portion 11 adjacent to each other with the inner center circumferential groove 7i (shown in FIG. 1) interposed therebetween, the edge components by the third groove portion 23 and the first groove portion 21 are uniformly formed in the tire circumferential direction, so that the wet performance is improved.

[0108] The plurality of third groove portions 23 are inclined from the first end 20a to the second end 20b from the vehicle inner side Vi to the vehicle outer side Vo. Therefore, the plurality of third groove portions 23 are inclined in a direction opposite to the plurality of first groove portions 21 and the plurality of second groove portions 22. With such a plurality of third groove portions 23, in the inner middle land portion 12i, an edge component in a direction different from that of the center land portion 11 is formed, so that the wet performance is improved.

[0109] The absolute value of the angle θb3 of the third groove portion 23 with respect to the tire axis direction is preferably set to 20 to 40°. Note that the absolute value of the angle θb3 is specified in the normal state. By setting the absolute value of the angle θb3 to 20° or more, a large edge component can be formed in the inner middle land portion 12i where the ground contact pressure during turning travel is relatively small compared to the center land portion 11. Thereby, while maintaining the handling stability, the wet performance is improved. On the other hand, by setting the angle θb3 to 40° or less, it is possible to suppress the rigidity of the inner middle land portion 12i from becoming smaller than necessary, so that the handling stability performance is improved. From such a viewpoint, the absolute value of the angle θb3 is preferably 25° or more and preferably 35° or less.

[0110] Further, at least one of the plurality of groove portions 20 may have a chamfered portion 29. FIG. 6 is a cross-sectional view taken along line A-A of FIG. 2. The chamfered portion 29 is formed as an inclined surface from which the ridge angle 42 (indicated by a two-dot chain line) formed by the tread surface (ground contact surface) 4 and the wall surface 20w of the groove portion 20 is removed. The chamfered portion 29 can be set, for example, based on the description of Patent Document (Japanese Patent Application Laid-Open No. 2023-134124).

[0111] When the chamfered portion 29 is under turning travel (when lateral force is applied) or straight running (when longitudinal force is applied), when a large load acts on the land portion 6, it is possible to suppress the concentration of the ground pressure on the edge of the groove-shaped portion 20. Thereby, the ground pressure acting on the land portion 6 is equalized, and the steering stability performance and the braking performance are improved.

[0112] As shown in FIG. 2, the chamfered portion 29 of the present embodiment is provided in the second groove-shaped portion 22. By such a chamfered portion 29, during turning travel, the concentration of the ground pressure on the edge of the second groove-shaped portion 22 is suppressed, and the steering stability performance is improved. Further, the width of the chamfered portion 29 orthogonal to the longitudinal direction of the second groove-shaped portion 22 may gradually decrease from the first end 20a to the second end 20b of the second groove-shaped portion 22. By such a chamfered portion 29, uneven wear of the center land portion 11 can be suppressed.

[0113] The chamfered portion 29 of the present embodiment is provided in the third groove-shaped portion 23. By such a chamfered portion 29, at the edge of the third groove-shaped portion 23 that completely crosses the inner middle land portion 12i in the tire axial direction, the concentration of the ground pressure is suppressed. Thereby, the steering stability performance and the braking performance are improved.

[0114] Furthermore, the chamfered portion 29 is formed over the entire longitudinal range of the third groove-shaped portion 23, and preferably, the width orthogonal to the longitudinal direction (groove center line 20c) of the third groove-shaped portion 23 gradually increases toward the first end 20a and the second end 20b of the third groove-shaped portion 23. By such a chamfered portion 29, the concentration of the ground pressure on the first end 20a and the second end 20b sides is suppressed, and uneven wear of the inner middle land portion 12i can be suppressed.

[0115] The chamfered portion 29 of the present embodiment is provided in the fourth groove-shaped portion 24. By such a chamfered portion 29, during straight running, the concentration of the ground pressure on the edge of the fourth groove-shaped portion 24 is suppressed, and the braking performance is improved. Further, the width of the chamfered portion 29 orthogonal to the longitudinal direction of the fourth groove-shaped portion 24 may gradually decrease from the second end 20b to the first end 20a of the fourth groove-shaped portion 24. By such a chamfered portion 29, uneven wear of the outer middle land portion 12o can be suppressed.

[0116] As shown in Fig. 1, a plurality of sixth groove-shaped portions 26 are formed in the inner shoulder land portion 13i of the present embodiment. The first end 20a of the sixth groove-shaped portion 26 communicates with the inner tread end 3i, and the second end 20b communicates with the inner shoulder circumferential groove 8i. Thereby, a continuous edge component is formed over a wide range of the inner shoulder land portion 13i, and the wet performance is improved.

[0117] The plurality of sixth groove-shaped portions 26 are inclined from the first end 20a to the second end 20b from the vehicle inner side Vi to the vehicle outer side Vo, and the absolute value of the angle θb6 with respect to the tire axis direction is gradually increasing. Thereby, the change in rigidity in the tire axis direction of the inner shoulder land portion 13i is moderated, and the handling stability is improved. In order to effectively exhibit such an effect, the absolute value of the angle θb6 is preferably set to 0 to 15°.

[0118] A plurality of seventh groove-shaped portions 27 are formed in the outer shoulder land portion 13o of the present embodiment. The first end 20a of the seventh groove-shaped portion 27 communicates with the outer shoulder circumferential groove 8o, and the second end 20b communicates with the outer tread end 3o. Thereby, a continuous edge component is formed over a wide range of the outer shoulder land portion 13o, and the wet performance is improved.

[0119] The plurality of seventh groove-shaped portions 27 are inclined from the first end 20a to the second end 20b from the vehicle inner side Vi to the vehicle outer side Vo, and the absolute value of the angle θb7 with respect to the tire axis direction is gradually increasing. Thereby, the change in rigidity in the tire axis direction of the outer shoulder land portion 13o is moderated, and the handling stability is improved. In order to effectively exhibit such an effect, the absolute value of the angle θb7 is preferably set to 0 to 15°.

[0120] As described above, the particularly preferred embodiments of the present invention have been described in detail. However, the present invention is not limited to the illustrated embodiments and can be implemented in various forms.

[0121] [Appendix] The present invention includes the following aspects.

[0122] [Invention 1] A tire having a tread portion, wherein the tread portion includes a plurality of circumferential grooves continuously extending in the tire circumferential direction and a plurality of land portions divided by the plurality of circumferential grooves, a plurality of groove-like portions inclined with respect to the tire axial direction are formed in each of the plurality of land portions, each of the plurality of groove-like portions has a first end on one side in the tire circumferential direction and a second end on the other side in the tire circumferential direction, the plurality of groove-like portions are arranged based on a predetermined arrangement rule over one circumference in the tire circumferential direction, in the arrangement rule, for each of all pairs of adjacent groove-like portions in the tire circumferential direction among the plurality of groove-like portions, the first end of one groove-like portion of the pair and the second end of the other groove-like portion of the pair are formed at the same position in the tire circumferential direction, the groove-like portions constituting the pair are formed in the same land portion or in different land portions from each other, in a 70% load state where the tire is mounted on a regular rim at a regular internal pressure and loaded with 70% of the regular load with the camber angle set to 0 degrees and grounded on a plane, the ground contact edge ends on both sides in the tire circumferential direction of at least one of the plurality of land portions have an angle θa with respect to the tire axial direction, the absolute value of the difference between the angle θa and the angle θb with respect to the tire axial direction of the groove-like portion formed in the at least one land portion is 5 degrees or more, Tire. [Invention 2] The tire according to Invention 1, wherein the groove-like portions constituting the pair are formed in different land portions from each other. [Invention 3] The tire according to Invention 1 or 2, wherein the plurality of land portions include a center land portion and a pair of middle land portions, and in all of these land portions, the absolute value is 5 degrees or more. [Invention 4] The grounding surface of the tread portion in the 70% load state is such that the ratio L / Lm of the maximum grounding length L in the tire circumferential direction to the grounding length Lm in the tire circumferential direction within a range of 60% or less of the maximum grounding width W in the tire axial direction centered on the tire equator satisfies the following formula (1). The tire according to any one of Inventions 1 to 3 of the present invention. 1.00 < L / Lm < 1.10 …(1) [Invention 5] In the tire according to any one of Inventions 1 to 4 of the present invention, the average angle of all the groove-like portions with respect to the tire axial direction is 10 to 50 degrees. [Invention 6] The tread portion has a tread pattern in which one pitch region constituting a pattern unit is arranged in the tire circumferential direction. In each of the plurality of land portions, the total length in the tire axial direction of the groove-like portions formed in the one pitch region is 60% to 120% of the width in the tire axial direction of the land portion. The tire according to any one of Inventions 1 to 5 of the present invention. [Invention 7] The tread portion has a specified mounting direction on the vehicle. The plurality of land portions include a center land portion arranged on the tire equator and an outer middle land portion arranged on the outer side of the vehicle with respect to the center land portion when mounted on the vehicle. In each of the center land portion and the outer middle land portion, at least one of the plurality of groove-like portions has at least one of the first end and the second end terminating within the land portion. The tire according to any one of Inventions 1 to 6 of the present invention. [Invention 8] The plurality of land portions further include an inner middle land portion arranged on the inner side of the vehicle with respect to the center land portion when mounted on the vehicle. In the inner middle land portion, at least one of the plurality of groove-like portions has both the first end and the second end communicating with any of the circumferential grooves. The tire according to Invention 7 of the present invention. [Invention 9] The sum of the widths in the tire axial direction of the center land portion, the outer middle land portion, and the inner middle land portion is 35% to 60% of the maximum ground contact width in the tire axial direction of the ground contact surface in the 70% load-bearing state, the tire according to Invention 8 of the present invention. [Invention 10] The plurality of groove-shaped portions include a sipe main body portion having a width of 2 mm or less, the tire according to any one of Inventions 1 to 9 of the present invention. [Invention 11] At least one of the plurality of groove-shaped portions has a chamfered portion, the tire according to any one of Inventions 1 to 10 of the present invention. [Invention 12] The plurality of circumferential grooves include at least one center circumferential groove disposed on the tire equator side, At least one protrusion protruding in the tire radial direction is formed at the groove bottom of the center circumferential groove, the tire according to any one of Inventions 1 to 11 of the present invention. [Invention 13] The tread portion has a specified mounting direction on the vehicle, The plurality of land portions include a center land portion disposed on the tire equator, an outer middle land portion disposed outside the vehicle with respect to the center land portion when mounted on the vehicle, and an inner middle land portion disposed inside the vehicle with respect to the center land portion when mounted on the vehicle, The absolute value of the difference between the angle θa of the inner middle land portion and the angle θb of the groove-shaped portion formed in the inner middle land portion is greater than or equal to the absolute value of the difference between the angle θa of the outer middle land portion and the angle θb of the groove-shaped portion formed in the outer middle land portion, the tire according to any one of Inventions 1 to 12 of the present invention.

Explanation of Reference Numerals

[0123] 1 Tire 2 Tread portion 5 Circumferential groove 6 Land portion 20 Groove-shaped portion

Claims

1. A tire having a tread portion, The tread portion includes a plurality of circumferential grooves extending continuously in a tire circumferential direction and a plurality of land portions separated by the plurality of circumferential grooves, A plurality of groove portions inclined with respect to the tire axial direction are formed in each of the plurality of land portions, Each of the plurality of groove portions has a first end on one side in the tire circumferential direction and a second end on the other side in the tire circumferential direction, The plurality of groove portions are arranged around one circumference in the tire circumferential direction based on a predetermined arrangement rule, the arrangement rule is such that, for each pair of groove portions adjacent to each other in the tire circumferential direction among the plurality of groove portions, the first end of one groove portion of the pair and the second end of the other groove portion of the pair are formed at the same position in the tire circumferential direction, The groove portions constituting the pair are formed in the same land portion or different land portions, when the tire is mounted on a normal rim at a normal internal pressure and is placed on a flat surface under a 70% load condition with a camber angle of 0 degrees and a load of 70% of a normal load, at least one of the plurality of land portions has an angle θa with respect to the tire axial direction, an absolute value of a difference between the angle θa and an angle θb of the groove portion formed in the at least one land portion with respect to the tire axial direction is 5 degrees or more; tire.

2. The tire according to claim 1 , wherein the pair of grooves are formed in different land portions.

3. The tire according to claim 1 , wherein the plurality of land portions include a center land portion and a pair of middle land portions, and the absolute value is 5 degrees or more in all of the land portions.

4. 2. The tire according to claim 1, wherein a ratio L / Lm of a maximum contact length L in the tire circumferential direction to a contact length Lm in the tire circumferential direction within a range of 60% or less of a maximum contact width W in the tire axial direction centered on the tire equator, in the contact surface of the tread portion under the 70% load condition satisfies the following formula (1): 1.00<L / Lm<1.10...(1)

5. 2. The tire according to claim 1, wherein an average angle of all of the groove portions with respect to the tire axial direction is 10 to 50 degrees.

6. The tread portion has a tread pattern in which one-pitch regions constituting pattern constituent units are arranged in the tire circumferential direction, 2. The tire according to claim 1, wherein in each of the plurality of land portions, a total axial length of the groove portions formed in the one pitch region is 60% to 120% of an axial width of the land portion.

7. The tread portion has a specified orientation for installation on a vehicle, the plurality of land portions include a center land portion disposed on a tire equator and an outer middle land portion disposed on an outer side of the vehicle relative to the center land portion when the tire is mounted on the vehicle; The tire according to claim 1 , wherein in each of the center land portion and the outer middle land portion, at least one of the first end and the second end of at least one of the plurality of groove portions terminates within the land portion.

8. The plurality of land portions further include an inner middle land portion that is disposed on an inner side of the vehicle relative to the center land portion when the tire is mounted on the vehicle, The tire according to claim 7 , wherein in the inner middle land portion, at least one of the plurality of groove portions has both the first end and the second end communicating with any one of the circumferential grooves.

9. The tire according to claim 8, wherein a total of the axial widths of the center land portion, the outer middle land portion, and the inner middle land portion is 35% to 60% of a maximum axial contact width of the contact surface under a 70% load condition.

10. 2. The tire of claim 1, wherein the plurality of grooves includes a sipe body having a width of 2 mm or less.

11. The tire of claim 1 , wherein at least one of said plurality of grooves includes a chamfer.

12. the plurality of circumferential grooves include at least one center circumferential groove disposed on a tire equator side, The tire according to claim 1 , wherein at least one protrusion protruding in a radial direction of the tire is formed at a groove bottom of the central circumferential groove.

13. The tread portion has a specified orientation for installation on a vehicle, the plurality of land portions include a center land portion disposed on the tire equator, an outer middle land portion disposed on the vehicle outer side with respect to the center land portion when mounted on the vehicle, and an inner middle land portion disposed on the vehicle inner side with respect to the center land portion when mounted on the vehicle, 2. The tire according to claim 1, wherein an absolute value of a difference between the angle θa of the inner middle land portion and the angle θb of the groove portion formed in the inner middle land portion is equal to or greater than an absolute value of a difference between the angle θa of the outer middle land portion and the angle θb of the groove portion formed in the outer middle land portion.

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