tire

Abstract

To provide a tire that can reduce pitch noise. [Solution] A tire 1 having a tread portion 2 including a plurality of circumferential grooves 5 and a plurality of land portions 6. Each of the plurality of land portions 6 has a plurality of groove-shaped portions 20 formed thereon, having 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 rules for the plurality of groove-shaped portions 20, for each pair of adjacent groove-shaped portions 20 in the tire circumferential direction, the first end of one groove-shaped portion 20 of the pair and the second end of the other groove-shaped portion 20 of 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. In at least one land portion 6 under a 70% load condition, the absolute value of the difference between the angle θa of the contact edge on both sides in the tire circumferential direction with respect to the tire axis and the angle θb of the groove-shaped portion 20 with respect to the tire axis 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 pair of all 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, during tire running, by continuously grounding the transverse groove-like elements constantly, reduction of pitch noise is attempted, but 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 extending continuously in the circumferential direction of the tire, and a plurality of land portions separated by the plurality of circumferential grooves, each of the plurality of land portions having a plurality of groove-like portions inclined with respect to the tire axis, each of the plurality of groove-like portions having a first end on one side in the circumferential direction of the tire and a second end on the other side in the circumferential direction of the tire, and the plurality of groove-like portions are arranged over one circumference in the circumferential direction of the tire according to a predetermined arrangement rule, wherein for each pair of adjacent groove-like portions in the circumferential direction of the tire, one groove-like portion of the pair The first end and the second end of the other groove-shaped portion of the pair are formed at the same position in the tire circumferential direction, the groove-shaped portions constituting the pair are formed on the same land area or on different land areas, and in a 70% load state where the tire is mounted on a regular rim with regular internal pressure and 70% of the regular load is applied and the camber angle is 0 degrees and the tire is in contact with a plane, at least one of the land areas has a contact edge on both sides in the tire circumferential direction with respect to the tire axis, and the absolute value of the difference between the angle θa and the angle θb of the groove-shaped portion formed on the at least one land area with respect to the tire axis is 5 degrees or more. [Effects of the Invention]

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

[0009] [Figure 1] This is an exploded view showing an example of a tire tread. [Figure 2] Figure 1 shows enlarged sections of the central, inner middle, and outer middle land areas. [Figure 3] This figure shows an example of the footprint of the tread under a 70% load condition. [Figure 4]This figure shows the maximum contact length L and contact length Lm at the footprint of the tread under a 70% load condition. [Figure 5] This is an enlarged perspective view showing an example of a projection provided in the inner shoulder circumferential groove. [Figure 6] This is a cross-sectional view AA in Figure 2. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described below with reference to the drawings. It should be understood that the drawings contain exaggerations and representations that differ from the actual dimensional ratios of the structures in order to aid in understanding the content of the invention. Furthermore, the same or common elements are denoted by the same reference numerals throughout each embodiment, and redundant explanations are omitted. Moreover, the specific configurations shown in the embodiments and 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 in the drawings.

[0011] [tire] Figure 1 is an exploded view showing an example of the tread portion 2 of tire 1. In Figure 1, the protrusion 41 (shown in Figure 5), which will be described later, is omitted.

[0012] In this embodiment, the tire 1 is exemplified as a pneumatic tire. However, the tire 1 may also be a non-pneumatic tire (airless tire). Furthermore, a passenger car tire is preferred as the tire in this embodiment. However, the tire 1 may also be a motorcycle tire or a heavy-duty tire.

[0013] [Tread area] The tire 1 of this embodiment has a tread portion 2. In this embodiment, the orientation of the tread portion 2 when mounted on the vehicle is specified, but the embodiment is not limited to this configuration, and for example, the mounting orientation may not be specified. The mounting orientation on the vehicle is indicated, for example, by letters or marks (not shown) on the sidewall portion (not shown) of the tire 1. In Figure 1, the right side corresponds to the inside Vi of the vehicle, and the left side corresponds to the outside Vo of the vehicle.

[0014] The tread portion 2 of this embodiment includes a pair of tread ends 3 and a tread surface 4 between them. The tread surface 4 is the portion intended to come into contact with the ground (road surface) when the tire is running, and is formed of tread rubber. When the orientation of mounting to the vehicle is specified, as in the tread portion 2 of this embodiment, the pair of tread ends 3 include an inner tread end 3i provided on the inner side Vi of the vehicle and an outer tread end 3o provided on the outer side Vo of the vehicle.

[0015] A pair of tread ends 3 (in this example, the inner tread end 3i and the outer tread end 3o) are identified as the outermost contact point in the tire axial direction when tire 1 is a pneumatic tire. Here, "70% load condition" refers to the state in which tire 1 in its normal state is subjected to 70% of its normal load and made contact with a plane with a camber angle of 0 degrees.

[0016] The "normal state" refers to the unloaded state in which tire 1 is mounted on a normal rim (not shown) with normal internal pressure. Unless otherwise specified, the dimensions of each part of the tire are given as values ​​measured in the normal state. However, it is assumed that normal dimensional errors (tolerances) that are unavoidable in manufacturing are permissible.

[0017] A "regular rim" is the rim specified for each tire in the standard system that includes the standard on which the tire is based. Therefore, a regular rim is, for example, a "standard rim" for JATMA, a "design rim" for TRA, or a "measuring rim" for ETRTO.

[0018] The "standard internal pressure" is the air pressure defined for each tire in the 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 the 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 one pitch region P constituting the pattern unit is arranged in the tire circumferential direction. The one pitch region P may be, for example, a plurality of regions having the same tire circumferential length arranged in the tire circumferential direction as long as they have a common pattern, or a plurality of types of regions having different tire circumferential lengths may be arranged randomly. The length L1 of the one pitch region P in the tire circumferential direction is set to, for example, 19 to 36 mm.

[0021] The tread pattern 2P preferably has a plurality of types of one pitch regions P having different lengths L1 in the tire circumferential direction arranged in the tire circumferential direction. Thereby, the natural frequency between the one pitch regions P is changed, and the noise performance is improved. In order to effectively enhance such an effect, the one pitch region P is preferably set to 2 to 10 types.

[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] Multiple circumferential grooves 5 extend continuously in the circumferential direction of the tire on the tread surface 4 between a pair of tread ends 3 (between the inner tread end 3i and the outer tread end 3o). These circumferential grooves 5 allow water to be discharged between the tread portion 2 and the road surface (not shown) during wet driving, thereby improving wet performance.

[0024] The multiple circumferential grooves 5 in this embodiment extend linearly along the tire's circumferential direction, but the invention is not limited to this configuration. The multiple circumferential grooves 5 may, for example, extend in a wavy or zigzag pattern.

[0025] The groove width W1 and 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 contact width W in the axial direction of the contact surface under a 70% load condition. The groove depth is set, for example, to 4.0 to 10.0 mm. The maximum contact width W is defined as the distance in the axial direction of the tire 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 defined as the distance between two adjacent groove edges in a direction perpendicular to the groove centerline.

[0026] The multiple circumferential grooves 5 include at least one center circumferential groove 7 located on the tire equator C side. In this embodiment, a pair of center circumferential grooves 7 and a pair of shoulder circumferential grooves 8 are included. These center circumferential grooves 7 and shoulder circumferential grooves 8 allow water to be discharged from the road surface over a wide area in the tire axial direction of the tread portion 2, improving wet performance. Note that the circumferential grooves 5 are not limited to an embodiment that includes a pair of center circumferential grooves 7 and a pair of shoulder circumferential grooves 8; for example, they may consist of one center circumferential groove 7 and a pair of shoulder circumferential grooves 8.

[0027] A pair of center circumferential grooves 7 are positioned on both sides in the tire axial direction with respect to the tire equator C. When the orientation of mounting to the vehicle is specified, as in the tread portion 2 of this embodiment, the pair of center circumferential grooves 7 include an inner center circumferential groove 7i positioned on the inner side Vi of the vehicle and an outer center circumferential groove 7o positioned on the outer side Vo of the vehicle. From the viewpoint of improving the wet performance described above, the groove centerlines (not shown) of this pair of center circumferential grooves 7 may be positioned at a distance of 6% to 15% of the maximum contact width W, in the tire axial direction outward from the tire equator C.

[0028] A pair of shoulder circumferential grooves 8 are positioned 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 orientation of mounting to the vehicle is specified, as in the tread portion 2 of this embodiment, the pair of shoulder circumferential grooves 8 include an inner shoulder circumferential groove 8i positioned on the inner side Vi of the vehicle and an outer shoulder circumferential groove 8o positioned on the outer side Vo of the vehicle. From the viewpoint of improving the wet performance described above, the groove centerlines (not shown) of these shoulder circumferential grooves 8 are preferably positioned at a distance of 25% to 35% of the maximum contact width W, outward in the tire axial direction from the tire equator C. Furthermore, 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. This increases the tread rigidity on the outer side of the vehicle where the contact pressure is relatively higher during cornering, improving steering stability.

[0029] [Rikube] Multiple land sections 6 are separated by multiple circumferential grooves 5. In this embodiment, the multiple land sections 6 consist of a center land section 11, a pair of middle land sections 12, and a pair of shoulder land sections 13. However, the multiple land sections 6 are not limited to this configuration, and may, for example, consist of a pair of center land sections 11 and a pair of shoulder land sections 13, depending on the driving performance required for the tire 1.

[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). As a result, the center land portion 11 is positioned on the tire equator C.

[0031] The pair of middle tread sections 12 are separated between a pair of center circumferential grooves 7 and a pair of shoulder circumferential grooves 8. When the orientation of mounting to the vehicle is specified, as in the tread section 2 of this embodiment, the pair of middle tread sections 12 include an inner middle tread section 12i located on the inner side Vi of the vehicle and an outer middle tread section 12o located on the outer side Vo of the vehicle.

[0032] The inner middle land area 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 area 12o is divided between the outer center circumferential groove 7o and the outer shoulder circumferential groove 8o.

[0033] The pair of shoulder sections 13 are located on the outer side of the pair of shoulder circumferential grooves 8 in the tire axial direction. When the orientation of mounting to the vehicle is specified, as in the tread section 2 of this embodiment, the pair of shoulder sections 13 include an inner shoulder section 13i located on the inner side Vi of the vehicle and an outer shoulder section 13o located on the outer side Vo of the vehicle.

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

[0035] Of the above-mentioned land sections 6, the sum of the tire axial widths W2a, W2b, and W2c of the center land section 11, inner middle land section 12i, and outer middle land section 12o may be set to 35% to 60% of the maximum axial contact width W of the contact surface under a 70% load. Setting the sum to 35% or more of the maximum contact width W ensures the lateral rigidity and contact area of ​​each land section 6, improving handling stability. On the other hand, setting the sum to 60% or less of the maximum contact width W ensures the groove width W1 (groove volume) of the circumferential groove 5, improving drainage performance. From this viewpoint, the sum is preferably 40% or more of the maximum contact width W, and also preferably 55% or less of the maximum contact width W.

[0036] [Multiple groove-like sections] Each of the multiple land sections 6 in this embodiment has multiple groove-like sections 20 that are inclined with respect to the tire axis. These multiple groove-like sections 20 improve wet performance. Figure 2 is a partially enlarged view of the center land section 11, inner middle land section 12i, and outer middle land section 12o of Figure 1.

[0037] As shown in Figure 2, each of the multiple 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 this embodiment, the first end 20a and the second end 20b are identified by the ends of the groove centerline 20c along the longitudinal direction of the groove-shaped portion 20. Note that if a chamfered portion 29 is provided, as in the groove-shaped portion 20 of this embodiment, the first end 20a and the second end 20b are identified excluding the chamfered portion 29 (in this example, based only on the sipe body portion 28).

[0038] The multiple groove-shaped portions 20 of this embodiment (in this example, groove-shaped portions provided in the center land portion 11, the inner middle land portion 12i, and the outer middle land portion 12o) 20 include a sipe body portion 28 with a width (i.e., a width perpendicular to its longitudinal direction) of 2 mm or less. The sipe body portion 28 of this embodiment is formed in a slit shape. These multiple groove-shaped portions 20 (sipe body portion 28) make it possible to form an edge component in the tread portion 2 while suppressing the reduction in rigidity of the land portion 6 when it comes into contact with the road surface, thereby improving steering stability.

[0039] The groove-shaped portion 20 is not limited to an embodiment that includes the sipe body portion 28, and may, for example, include a groove body portion (not shown) with a width (i.e., a width perpendicular to its longitudinal direction) greater than 2 mm. Such a groove body portion improves wet performance. The depth of the groove-shaped portion 20 (not shown) is set to, for example, 2 to 8 mm.

[0040] As shown in Figure 1, the plurality of groove-shaped portions 20 in this 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. However, the plurality of groove-shaped portions 20 is not limited to an embodiment that includes all of these first groove-shaped portions 21 to seventh groove-shaped portions 27. For example, depending on the performance required of the tire 1, some of these may be omitted, or other groove-shaped portions (not shown) may be included.

[0041] Multiple first groove-shaped portions 21 and multiple second groove-shaped portions 22 are provided on the center base 11. In this embodiment, the multiple first groove-shaped portions 21 are arranged on the vehicle-side Vi of the center base 11. On the other hand, the multiple second groove-shaped portions 22 are arranged on the vehicle-side Vo of the center base 11. Note that the center base 11 is not limited to the configuration in which these first groove-shaped portions 21 and second groove-shaped portions 22 are provided; for example, some of them may be omitted, or other groove-shaped portions (not shown) may be included.

[0042] Multiple third groove-shaped portions 23 are provided in the inner middle land portion 12i. However, the inner middle land portion 12i is not limited to being provided only with the third groove-shaped portions 23; for example, it may also include other groove-shaped portions (not shown).

[0043] Multiple fourth groove-shaped portions 24 and multiple fifth groove-shaped portions 25 are provided on the outer middle land portion 12o. In this embodiment, the multiple fourth groove-shaped portions 24 are located on the inner side Vi of the outer middle land portion 12o. On the other hand, the multiple fifth groove-shaped portions 25 are located on the outer side Vo of the outer middle land portion 12o. Note that the outer middle land portion 12o is not limited to the configuration in which these fourth groove-shaped portions 24 and fifth groove-shaped portions 25 are provided; for example, some of them may be omitted, or other groove-shaped portions (not shown) may be included.

[0044] Multiple sixth groove-like portions 26 are formed in the inner shoulder land portion 13i. However, the inner shoulder land portion 13i is not limited to being provided only with the sixth groove-like portions 26; for example, it may also include other groove-like portions (not shown).

[0045] Multiple seventh groove-like portions 27 are formed in the outer shoulder land portion 13o. Note that the outer shoulder land portion 13o is not limited to being provided only with the seventh groove-like portions 27; for example, it may also include other groove-like portions (not shown).

[0046] [Arrangement rules] As shown in Figure 2, the multiple groove-shaped portions 20 of this embodiment are arranged around the entire circumference of the tire in the circumferential direction, based on a predetermined arrangement rule 30. The arrangement rule 30 of this embodiment applies to the multiple groove-shaped portions 20 arranged on the center land portion 11 and the pair of middle land portions 12 (inner middle land portion 12i and outer middle land portion 12o), but is not limited to this configuration. For example, only some of these land portions 6 may be subject to the arrangement rule 30, or other land portions 6 (the pair of shoulder land portions 13 shown in Figure 1) may be subject to the arrangement rule 30.

[0047] In the arrangement rule 30, for each pair 31 of adjacent groove-shaped portions 20 in the tire circumferential direction, the first end 20a of one groove-shaped portion 20 in the pair 31 and the second end 20b of the other groove-shaped portion 20 in the pair 31 are formed at the same position in the tire circumferential direction. Furthermore, the groove-shaped portions 20 constituting a pair 31 are formed on the same land area 6 or on different land areas 6.

[0048] Here, whether the first end 20a of one grooved portion 20 of pair 31 and the second end 20b of the other grooved portion 20 of pair 31 are in the same position in the tire circumferential direction is determined using their groove centerlines 20c. That is, the first end 20a of one grooved portion 20 of pair 31 and the second end 20b of the other grooved portion 20 of pair 31 are identified by the ends of the groove centerlines 20c. However, in consideration of the characteristics of the vulcanized rubber product, tire 1, and from the viewpoint of allowing manufacturing tolerances, the "same position" includes a configuration in which the first end 20a and the second end 20b are offset by a small distance in the tire circumferential direction. In this case, the distance between the first end 20a and the second end 20b in the tire circumferential direction is 5% or less, preferably 3% or less, and more preferably 1% or less, of the sum of the lengths of the two grooved portions 20 constituting pair 31 in the tire circumferential direction. Furthermore, it is most preferable that the first end 20a and the second end 20b are not misaligned in the circumferential direction of the tire (for example, less than 0.1%).

[0049] The pair 31 of this 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 may be omitted, or other pairs may be included. The groove-shaped portions 20 constituting the pair 31 of this embodiment are formed on different land portions 6.

[0050] The first pair 31a consists of a fourth groove-shaped portion 24 and a second groove-shaped portion 22 adjacent to the fourth groove-shaped portion 24 on the other side S2 in the tire circumferential direction. In this embodiment, the fourth groove-shaped portion 24 is formed on the outer middle land portion 12o, and the second groove-shaped portion 22 is formed on the center land portion 11. Therefore, the groove-shaped portions 20 constituting the first pair 31a are formed on different land portions 6. In addition, 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 consists of a second groove-shaped portion 22 and a third groove-shaped portion 23 adjacent to the second groove-shaped portion 22 on the other side S2 in the tire circumferential direction. In this 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 constituting the second pair 31b are formed in different land portions 6, similar to the first pair 31a. In addition, 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 consists of a third groove-shaped portion 23 and a fifth groove-shaped portion 25 adjacent to the third groove-shaped portion 23 on the other side S2 in the tire circumferential direction. In this 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 constituting the third pair 31c are formed in different land portions 6, similar to the first pair 31a and the second pair 31b. In addition, 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 consists of a fifth groove-shaped portion 25 and a first groove-shaped portion 21 adjacent to the fifth groove-shaped portion 25 on the other side S2 in the tire circumferential direction. In this embodiment, the fifth groove-shaped portion 25 is formed on the outer middle land portion 12o, and the first groove-shaped portion 21 is formed on the center land portion 11. Therefore, the groove-shaped portions 20 constituting the fourth pair 31d are formed on different land portions 6, similar to the first pair 31a to the third pair 31c. In addition, in the fourth pair 31d, the first end 20a of the first groove-shaped portion 21 and the second end 20b of the fifth groove-shaped portion 25 are formed at the same position in the tire circumferential direction.

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

[0055] In this embodiment, the first pair 31a to the fifth pair 31e constitute the 1-pitch region P shown in Figure 1, and these first pair 31a to the fifth pair 31e are repeated in order. As a result, the arrangement rule 30 of this embodiment ensures that the groove-shaped portions 20 constituting each pair 31 (first pair 31a to fifth pair 31e) are formed on different land areas 6.

[0056] Generally, pitch noise is known as a type of noise produced when tires are in motion. For example, an impact force is generated each time the region 32 (tread surface 4) divided by the first groove section 21 to the fifth groove section 25 makes contact with the road surface. This impact force tends to cause the tread section 2 and the sidewall section (not shown) to vibrate periodically, thereby generating pitch noise (pitch sound).

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

[0058] In this embodiment, the arrangement rule 30 is such that the groove-shaped portions 20 constituting each pair 31 are formed on different land portions 6. As a result, in this embodiment, the groove-shaped portions 20 constituting each pair 31 are not formed continuously on each land portion 6. Therefore, in order to form the first end 20a and the second end 20b at the same position, it is not necessary to increase the angle θb of the groove-shaped portion 20 with respect to the tire axis direction, or to increase the number of groove-shaped portions 20 formed on each land portion 6. Consequently, the rigidity of each land portion 6 in the tire axis direction is prevented from decreasing more than necessary, making it possible to achieve both handling stability and noise performance (quietness).

[0059] In this embodiment, the arrangement rule 30 is such that the groove-shaped portions 20 constituting each pair 31 are formed on the center land portion 11 and a pair of middle land portions 12 (inner middle land portion 12i and outer middle land portion 12o). Since the ground pressure on these center land portions 11 and the pair of middle land portions 12 tends to be relatively high during straight-line driving, pitch noise (pitch sound) can be effectively reduced. Furthermore, since the groove-shaped portions 20 constituting each pair 31 are formed on three or more different land portions 6, a decrease in the rigidity of the land portions 6 in the tire axial direction is prevented, and steering stability is further improved.

[0060] In this embodiment, the arrangement rule 30 is such that the groove-shaped portions 20 constituting each pair 31 are formed on different land areas 6, but the embodiment is not limited to this configuration. For example, the groove-shaped portions 20 constituting each pair 31 may be formed on the same land area 6. In this case, since the groove-shaped portions 20 constituting each pair 31 make contact with the land area 6 alternately and continuously, the fluctuation in the impact force is further reduced. Also, if the number of groove-shaped portions 20 is increased in order to form the first end 20a and the second end 20b at the same position, for example, the edge component increases, which improves wet performance and the like.

[0061] Figure 3 shows an example of the footprint 34 of the tread section 2 under a 70% load condition. In the footprint 34 of Figure 3, a tread pattern is shown in which one side S1 and the other side S2 in the circumferential direction of the tire are reversed.

[0062] In this embodiment, under a 70% load condition, the contact edges 33 on both sides in the tire circumferential direction of at least one of the multiple contact areas 6 have an angle θa with respect to the tire axis. In this embodiment, the absolute value of the difference between angle θa and angle θb of the groove-shaped portion 20 formed on at least one contact area 6 with respect to the tire axis is set to 5 degrees or more. The angle θb used in calculating the absolute value is determined under a 70% load condition, similar to angle θa. Furthermore, angles θa and θb may be obtained from a footprint 34 acquired by a known procedure, or from the calculation results of a contact simulation using a computer.

[0063] The angle θa is defined at the contact edge 33 of each land portion 6 by a straight line 36 passing through both ends 35, 35 in the width direction of the land portion 6. Furthermore, the angle θa in this embodiment is defined at 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 subject to the arrangement rule 30 shown in Figure 2 is formed. Therefore, the angle θa includes the angle θa1 of the contact edge 33 on one side S1 in the tire circumferential direction of the center land portion 11 and the angle θa2 of the contact edge 33 on the other side S2 in the tire circumferential direction of the center land portion 11. In addition, the angle θa includes the angle θa3 of the contact edge 33 on one side S1 in the tire circumferential direction of the inner middle land portion 12i and the angle θa4 of the contact edge 33 on the other side S2 in the tire circumferential direction of the inner middle land portion 12i. Furthermore, the angle θa includes the angle θa5 of the contact edge 33 on one side S1 of the outer middle land portion 12o in the tire circumferential direction, and the angle θa6 of the contact edge 33 on the other side S2 of the outer middle land portion 12o in the tire circumferential direction.

[0064] The angles θa1 to θa6 of the contact edge 33 of each ground portion 6 are defined as follows: the angle of inclination from one side S1 to the other side S2 in the tire circumferential direction is positive, and the angle of inclination from the other side S2 to the one side S1 in the tire circumferential direction is negative, when moving from the inside Vi of the vehicle to the outside Vo of the vehicle. In this case, at the inner middle ground portion 12i, the angle θa3 of the contact edge 33 on one side S1 is negative, and the angle θa4 of the contact edge 33 on the other side S2 is positive. Also, at the outer middle ground portion 12o, the angle θa5 of the contact edge 33 on one side S1 is positive, and the angle θa6 of the contact edge 33 on the other side S2 is negative.

[0065] The angle θa of the contact edge 33 and the shape of the contact surface (footprint) 37 can be adjusted as appropriate. Examples of adjustments include changing the thickness of the tread rubber of a well-known structure arranged in the tread portion 2, or changing the tire components of a well-known structure such as the carcass arranged inside the tread portion 2.

[0066] The angle θb is determined at the position 39 (first end 20a or second end 20b) where, under a 70% load condition, the groove centerline 20c along the longitudinal direction of the groove-shaped portion 20 (sipe body portion 28 described later) shown in Figure 2 intersects with the edges 38 extending in the circumferential direction of the tire on both sides of the tire axis direction of each land portion 6. Furthermore, the angle θb in this embodiment is determined by the groove-shaped portion 20 subject to the arrangement rule 30 shown in Figure 2. Therefore, 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] The angles θb1 to θb5 of each groove-shaped portion 20 are defined as positive when they inclinate from one side S1 to the other side S2 in the tire circumferential direction, from the inside Vi of the vehicle to the outside Vo of the vehicle, similar to the angle θa of the contact edge 33 of each land portion 6. Also, the angles θb1 to θb5 of each groove-shaped portion 20 are defined as negative when they inclinate from the other side S2 to the one side S1 in the tire circumferential direction. Therefore, the angles θb1 of the first groove-shaped portion 21, θb2 of the second groove-shaped portion 22, and θb4 of the fourth groove-shaped portion 24 are negative. On the other hand, the angles θb3 of the third groove-shaped portion 23 and θb5 of the fifth groove-shaped portion 25 are positive.

[0068] In this embodiment, the absolute value of the difference (θa1-θb1) between the angle θa1 of the ground-contacting 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 5 degrees or more. Furthermore, the absolute value of the difference (θa2-θb1) between the angle θa2 of the ground-contacting 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 5 degrees or more.

[0069] In this embodiment, the absolute value of the difference (θa1-θb2) between the angle θa1 of the ground-contacting 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 5 degrees or more. Furthermore, the absolute value of the difference (θa2-θb2) between the angle θa2 of the ground-contacting 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 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. Furthermore, 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 ground-contacting 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 on the outer middle land portion 12o is set to 5 degrees or more. Furthermore, the absolute value of the difference (θa6-θb4) between the angle θa6 of the ground-contacting 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. Furthermore, 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 angles θa and θb to 5 degrees or more, the direction of inclination between the contact edge 33 and the groove-shaped portion 20 is suppressed from coinciding. As a result, during tire travel, the groove-shaped portion 20 can be gradually brought into or out of contact with the contact edge 33. Therefore, since the air inside the groove-shaped portion 20 is not suddenly compressed or released when the contact edge 33 is brought into or out of contact, the amplification of pitch noise volume can be suppressed.

[0074] In the tire 1 of this embodiment, as shown in Figure 2, pitch noise can be reduced by forming 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 at the same position in the circumferential direction of the tire. Furthermore, in the tire 1 of this embodiment, as shown in Figure 3, the absolute value of the difference (θa-θb) between the angle θa of the contact edge 33 and the angle θb of the groove-shaped portion 20 at each ground portion 6 is set to 5 degrees or more, thereby suppressing the amplification of the pitch noise volume. Therefore, the tire 1 of this embodiment can reduce pitch noise, and consequently, its noise performance is improved.

[0075] In this embodiment, it is preferable that the absolute value of the difference (θa-θb) between the angle θa of the grounding edge 33 and the angle θb of the groove-shaped portion 20 is 5 degrees or more for all of the center ground portion 11 and the pair of middle ground portions (inner middle ground portion 12i and outer middle ground portion 12o). Since these ground portions 6 mainly make contact with the ground during both straight-line and turning travel, setting the absolute value to 5 degrees or more effectively suppresses the amplification of pitch noise volume, enabling further improvement of noise performance.

[0076] On the other hand, if the absolute value of the difference (θa-θb) between the angle θa of the contact edge 33 and the angle θb of the groove-shaped portion 20 becomes excessively large, the angle θb of the groove-shaped portion 20 will increase, reducing the tread rigidity, which may lead to a decrease in handling stability. 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 on 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 on the outer middle land portion 12o. As described above, the angle difference of the inner middle land portion 12i includes the differences (θa3-θb3) and (θa4-θb3). Also, the angle difference of the outer middle land portion 12o includes the differences (θa5-θb4), (θa6-θb4), (θa5-θb5), and (θa6-θb5).

[0078] By making the absolute value of the angle difference at the inner middle land area 12i greater than or equal to the absolute value of the angle difference at the outer middle land area 12o, a large edge component can be formed at the inner middle land area 12i, where the ground pressure during cornering is relatively smaller compared to the outer middle land area 12o. This improves wet performance while maintaining handling stability. To effectively exert this effect, it is more preferable that the absolute value of the angle difference at the inner middle land area 12i is greater than the absolute value of the angle difference at the outer middle land area 12o.

[0079] Furthermore, 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 on 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 center land portion 11 and the angle θb of the groove-shaped portion 20 formed on the center land portion 11. Moreover, the absolute value of the difference between the angle θa of the center land portion 11 and the angle θb of the groove-shaped portion 20 formed on the center land portion 11 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 on the outer middle land portion 12o. As described above, the angle differences of the center land portion 11 include differences (θa1-θb1), differences (θa2-θb1), differences (θa1-θb2), and differences (θa2-θb2).

[0080] When the absolute value of the angle difference at the inner middle ground section 12i is greater than or equal to the absolute value of the angle difference at the center ground section 11, and the absolute value of the angle difference at the center ground section 11 is greater than or equal to the absolute value of the angle difference at the outer middle ground section 12o, the edge component gradually increases toward the inner side of the vehicle where the ground pressure during cornering is relatively smaller. This improves transient characteristics (handling stability) during cornering while maintaining wet performance. To effectively exert this effect, it is more preferable that the absolute value of the angle difference at the inner middle ground section 12i is greater than the absolute value of the angle difference at the center ground section 11, and similarly, it is more preferable that the absolute value of the angle difference at the center ground section 11 is greater than the absolute value of the angle difference at the outer middle ground section 12o.

[0081] Figure 4 shows the maximum contact length L and contact length Lm at the footprint 34 of the tread portion 2 under a 70% load condition. It is preferable that the contact surface 37 of the tread portion 2 under a 70% load condition satisfies the following equation (1): The contact length Lm is determined within a range W60 centered on the tire equator C and less than or equal to 60% of the maximum contact width W in the tire axial direction. 1.00 <L / Lm<1.10 …(1)

[0082] When the ratio L / Lm satisfies equation (1) above, in the region of the contact surface 37 where the contact pressure is high during straight-line driving (i.e., the range W60 of 60% or less of the maximum contact width W), the contact edge 33 of each contact area 6 becomes flat along the tire axis. As a result, the absolute value of the angle θa (shown in Figure 3) of the contact edge 33 of each contact area 6 (in this example, the center contact area 11, the inner middle contact area 12i, and the outer middle contact area 12o) becomes small. Therefore, the absolute value of the above difference (θa-θb) becomes 5 degrees or more, making it possible to easily suppress the amplification of pitch noise volume. Furthermore, since the contact length Lm is maintained at a large level in the above range W60 (center contact area 11, inner middle contact area 12i, and outer middle contact area 12o), steering stability is improved. In order to effectively exert these effects, 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 ground edge 33 shown in Figure 3 is preferably between 0 and 15 degrees.

[0083] Furthermore, under a 70% load condition, it is preferable that the contact surface 37 of the tread portion 2 satisfies the following equation (2): 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 determined at a position centered on the tire equator C and at 80% of the maximum contact width W in the tire axial direction. 1.15 <L / Ln<1.50 …(2)

[0084] When the ratio L / Ln satisfies equation (2) above, the contact edges on both sides of the tire's axial direction become rounded, and the contact width gradually widens when a high load is applied. This improves cushioning when bumping and enhances ride comfort. Furthermore, it reduces resistance to water on the road surface, improving wet performance (hydroplaning performance). Also, even when lateral forces are large during cornering, the contact width widens gradually, suppressing localized increases in contact pressure. This improves handling stability. To effectively exert these effects, the ratio L / Ln is preferably 1.20 or higher, and preferably 1.40 or lower.

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

[0086] The projection 41 protrudes radially outward from the groove bottom 40, thereby disturbing the air passing through the circumferential groove 5 during tire operation. This can reduce air column resonance noise that tends to occur in the circumferential groove 5.

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

[0088] Each of the first projection 41A and the second projection 41B is composed of a first surface 43 and a second surface 44. The first surface 43 extends in the radial direction of the tire. The second surface 44 is positioned on the opposite side of the tire circumferential direction from the first surface 43 and extends at a larger angle than the first surface 43 with respect to the radial direction of the tire.

[0089] The first projection 41A has a first surface 43 facing the other side S2 in the tire circumferential direction, and a second surface 44 facing one side S1 in the tire circumferential direction. On the other hand, the second projection 41B has a first surface 43 facing one side S1 in the tire circumferential direction, and a second surface 44 facing the other side S2 in the tire circumferential direction. In this way, the first projection 41A and the second projection 41B have different orientations in the tire circumferential direction of the first surface 41a and the second surface 41b, which can effectively disturb the air in the circumferential groove 5 and reduce air column resonance noise. Such projections 41 can be formed, for example, based on the description in the patent document (Japanese Patent Application Publication No. 2020-196281).

[0090] The air column resonance noise tends to be louder in the center circumferential groove 7 among the multiple circumferential grooves 5 shown in Figure 1. For this reason, it is preferable that the projection 41 be formed in at least the center circumferential groove 7. In this embodiment, the projection 41 is formed not only in the center circumferential groove 7 but also in the shoulder circumferential groove 8. This can effectively reduce air column resonance noise.

[0091] In each of the multiple land sections 6 shown in Figure 1, the sum of the tire axial lengths L2 (shown in Figure 2) of the groove-shaped sections 20 formed in a 1-pitch region P is preferably set to 60% to 120% of the tire axial width W2 of the land section 6. As shown in Figure 2, the length L2 is defined as the distance in the tire axial direction between the first end 20a and the second end 20b of the groove-shaped section 20 (sipe body 28).

[0092] In each land section 6, by ensuring that the total length L2 of the groove-shaped sections 20 is 60% or more of the width W2 of the land section 6, the first end 20a of one groove-shaped section 20 of a pair 31 and the second end 20b of the other groove-shaped section 20 can be formed at the same position without increasing the absolute value of the angle θb of the groove-shaped section 20. This suppresses the decrease in lateral rigidity of the land section 6 that occurs with an increase in the absolute value of the angle θb, thereby improving steering stability. Furthermore, by ensuring that the total length L2 is 120% or less of the width W2 of the land section 6, the formation of an excessive number of groove-shaped sections 20 in a single-pitch region P is suppressed, and steering stability is maintained. From this viewpoint, the total length L2 is preferably 70% or more of the width W2 of the land section 6, and more preferably 110% or less.

[0093] It is preferable that the average angle of all groove-shaped portions 20 with respect to the tire axis (the average angle of the absolute values ​​of angles θb1 to θb5) is between 10 and 50 degrees. By setting the average angle to 10 degrees or more, the inclination of the groove-shaped portions 20 of each land portion 6 makes it possible to form the first end 20a of one groove-shaped portion 20 of a 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 50 degrees or less, the decrease in lateral rigidity of the land portion 6 that occurs with increasing angle θb of the groove-shaped portion 20 is suppressed, and steering stability is improved. From this viewpoint, the average angle is preferably 15 degrees or more, and also preferably 45 degrees or less.

[0094] In each of the center land section 11 and the outer middle land section 12o, at least one of the multiple groove-shaped sections 20 may have at least one of its first end 20a and second end 20b terminate within the land section 6. This minimizes the reduction in rigidity of the center land section 11 and the outer middle land section 12o, where the ground pressure is relatively high during turning, thereby improving steering stability and braking performance.

[0095] As described above, the center base 11 has a plurality of first groove-like portions 21 and a plurality of second groove-like portions 22. The first groove-like portions 21 have a first end 20a that terminates within the center base 11, and a second end 20b that communicates with the inner center circumferential groove 7i (shown in Figure 1). On the other hand, the second groove-like portions 22 have a first end 20a that communicates with the outer center circumferential groove 7o (shown in Figure 1), and a second end 20b that terminates within the center base 11. In this way, by having at least one of the first end 20a and the second end 20b of the first groove-like portions 21 and the second groove-like portions 22 terminate within the center base 11, the reduction in rigidity of the center base 11, where the ground pressure is relatively high during turning and straight-line driving, is minimized. Therefore, steering stability and braking performance are improved.

[0096] The length L2b of each second groove 22 in the tire axial direction is smaller than the length L2a of each first groove 21 in the tire axial direction. As a result, the rigidity of the outer part Vo of the vehicle, where the ground pressure during cornering is relatively high, is relatively increased in the center ground area 11, improving handling stability. On the other hand, a large edge component is formed on the inner part Vi of the center ground area 11, improving wet grip. To effectively exert these effects, it is preferable that the length L2b of the second groove 22 be set to 30% to 75% of the length L2a of the first groove 21.

[0097] The first grooved portion 21 and the second grooved portion 22 may be arranged alternately in the tire circumferential direction on the center land portion 11. This ensures that edge components formed by the first grooved portion 21 and the second grooved portion 22 are evenly distributed in the tire circumferential direction on both sides of the center land portion 11 in the tire axial direction, thereby improving wet performance.

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

[0099] The absolute value of the angle θb1 of the first groove 21 with respect to the tire axis and the absolute value of the angle θb2 of the second groove 22 with respect to the tire axis are preferably set to 10 to 30°. Whether the absolute values ​​of angles θb1 and θb2 are between 10 and 30° is determined in the normal state. Setting the absolute values ​​of these angles θb1 and θb2 to 30° or less maintains the rigidity of the center landing section 11, improving handling stability and braking performance. On the other hand, setting the absolute values ​​of angles θb1 and θb2 to 10° or more creates a larger edge component, improving wet performance. From this viewpoint, the absolute values ​​of angles θb1 and θb2 are preferably 25° or less, and preferably 15° or more.

[0100] As described above, the outer middle land portion 12o has a plurality of fourth groove-like portions 24 and a plurality of fifth groove-like portions 25. The plurality of fourth groove-like portions 24 have their first end 20a terminate in the outer middle land portion 12o and their second end 20b communicate with the outer center circumferential groove 7o (shown in Figure 1). On the other hand, the plurality of fifth groove-like portions 25 have their first end 20a terminate in the outer middle land portion 12o and their second end 20b communicate with the outer shoulder circumferential groove 8o (shown in Figure 1). In this way, at least one of the first end 20a and the second end 20b of the fourth groove-like portions 24 and the fifth groove-like portions 25 terminates within the outer middle land portion 12o, thereby minimizing the reduction in rigidity of the outer middle land portion 12o, where the ground pressure is relatively high during turning. Therefore, steering stability performance is improved.

[0101] Preferably, the first end 20a of each fourth groove 24 and the first end 20a of each fifth groove 25 are spaced apart in the tire axial direction. This suppresses the reduction in rigidity of the outer middle ground portion 12o, where the ground pressure is relatively high during cornering, thereby improving steering stability. Alternatively, the length L2d of each fourth groove 24 in the tire axial direction and the length L2e of each fifth groove 25 in the tire axial direction may be the same. This ensures that edge components of the same length are evenly formed in the tire circumferential direction by the fourth groove 24 and fifth groove 25 on both sides of the outer middle ground portion 12o in the tire axial direction, where the ground pressure is relatively high during cornering, thereby improving wet performance.

[0102] The fourth groove portion 24 and the fifth groove portion 25 may be arranged alternately in the tire circumferential direction on the outer middle land portion 12o. This ensures that edge components are evenly formed in the tire circumferential direction on both sides of the outer middle land portion 12o in the tire axial direction, thereby improving wet performance.

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

[0104] The absolute value of the angle θb4 of the fourth groove-shaped portion 24 with respect to the tire axis is preferably set to 10 to 30°. Whether or not the absolute value of the angle θb4 is between 10 and 30° is determined in the normal state. Setting the absolute value of the angle θb4 to 30° or less maintains the rigidity of the outer middle ground portion 12o, where the ground pressure is high during both straight-line driving and turning, thereby improving handling stability. On the other hand, setting the angle θb4 to 10° or more creates a larger edge component, improving wet performance. From this viewpoint, the absolute value of the angle θb4 is preferably 25° or less, and preferably 15° or more.

[0105] The absolute value of the angle θb5 of the fifth groove 25 with respect to the tire axis is preferably smaller than the absolute value of the angle θb4 of the fourth groove 24. The absolute value of angle θb5 is assumed to be determined in the normal state. By making the absolute value of angle θb5 smaller than the absolute value of angle θb4, the rigidity of the outer part Vo of the vehicle where the ground pressure during cornering is relatively large in the outer middle ground portion 12o is increased, thereby improving handling stability while maintaining wet performance. In order to effectively exert this effect, the absolute value of the angle θb5 of the fifth groove 25 is preferably set to 5 to 25°.

[0106] In the inner middle land area 12i, at least one of the multiple groove-shaped portions 20 (in this example, the third groove-shaped portion 23) may have both its first end 20a and second end 20b communicating with one of the circumferential grooves 5 shown in Figure 1 (the inner center circumferential groove 7i and the inner shoulder circumferential groove 8i). This creates a continuous edge component that traverses the inner middle land area 12i in the tire axial direction, thereby improving wet performance. Furthermore, the inner middle land area 12i tends to have relatively lower ground pressure during cornering compared to the center land area 11 and the outer middle land area 12o. Even if multiple groove-shaped portions 20 communicating with the circumferential grooves 5 are provided in such an inner middle land area 12i, steering stability can be maintained.

[0107] The third groove-shaped portion 23 may be arranged alternately with the first groove-shaped portion 21 in the circumferential direction of the tire. As a result, edge components formed by the third groove-shaped portion 23 and the first groove-shaped portion 21 are evenly distributed in the circumferential direction of the tire in the inner middle land portion 12i and the center land portion 11 adjacent to each other across the inner center circumferential groove 7i (shown in Figure 1), thereby improving wet performance.

[0108] The multiple third groove-shaped portions 23 are inclined from the inside Vi of the vehicle to the outside Vo of the vehicle, from the first end 20a to the second end 20b. Therefore, the multiple third groove-shaped portions 23 are inclined in the opposite direction to the multiple first groove-shaped portions 21 and the multiple second groove-shaped portions 22. Due to these multiple third groove-shaped portions 23, edge components are formed in the inner middle land area 12i in a different direction from the center land area 11, thereby improving wet performance.

[0109] The absolute value of the angle θb3 of the third groove-shaped portion 23 with respect to the tire axis is preferably set to 20 to 40°. The absolute value of the angle θb3 is assumed to be determined in the normal state. Setting the absolute value of the angle θb3 to 20° or more allows a large edge component to be formed in the inner middle land portion 12i, where the ground pressure during cornering is relatively smaller compared to the center land portion 11. This improves wet performance while maintaining handling stability. On the other hand, setting the angle θb3 to 40° or less prevents the rigidity of the inner middle land portion 12i from becoming unnecessarily small, thus improving handling stability. From this viewpoint, the absolute value of the angle θb3 is preferably 25° or more, and preferably 35° or less.

[0110] Furthermore, at least one of the multiple groove-shaped portions 20 may have a chamfered portion 29. Figure 6 is a cross-sectional view of AA in Figure 2. The chamfered portion 29 is formed as an inclined surface from which the ridge angle 42 (shown by the dashed line) formed by the tread (contact surface) 4 and the wall surface 20w of the groove-shaped portion 20 has been cut away. The chamfered portion 29 can be set, for example, based on the description in the Patent Document (Japanese Patent Application Publication No. 2023-134124).

[0111] The chamfered portion 29 can suppress the concentration of ground pressure on the edge of the groove-shaped portion 20 when a large load is applied to the ground portion 6 during turning (when lateral force is applied) or straight-line driving (when longitudinal force is applied). As a result, the ground pressure acting on the ground portion 6 is made more uniform, improving steering stability and braking performance.

[0112] As shown in Figure 2, the chamfered portion 29 in this embodiment is provided on the second groove-shaped portion 22. Such a chamfered portion 29 suppresses the concentration of ground pressure on the edge of the second groove-shaped portion 22 during turning, thereby improving steering stability. Furthermore, the width of the chamfered portion 29 perpendicular 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. Such a chamfered portion 29 can suppress uneven wear of the center landing portion 11.

[0113] In this embodiment, the chamfered portion 29 is provided on the third groove-shaped portion 23. This chamfered portion 29 suppresses the concentration of ground pressure at the edge of the third groove-shaped portion 23 that completely traverses the inner middle ground portion 12i in the tire axial direction. As a result, steering stability and 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 it is preferable that the width perpendicular to the longitudinal direction (groove centerline 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. Such a chamfered portion 29 can suppress the concentration of ground pressure on the first end 20a and the second end 20b side, thereby suppressing uneven wear of the inner middle land portion 12i.

[0115] In this embodiment, the chamfered portion 29 is provided on the fourth groove-shaped portion 24. Such a chamfered portion 29 suppresses the concentration of ground pressure on the edge of the fourth groove-shaped portion 24 during straight-line driving, thereby improving braking performance. Furthermore, the width of the chamfered portion 29 perpendicular 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. Such a chamfered portion 29 can suppress uneven wear of the outer middle land portion 12o.

[0116] As shown in Figure 1, the inner shoulder land portion 13i of this embodiment has a plurality of sixth groove-like portions 26 formed therein. The first end 20a of each sixth groove-like portion 26 communicates with the inner tread end 3i, and the second end 20b communicates with the inner shoulder circumferential groove 8i. As a result, the sixth groove-like portion 26 forms a continuous edge component over a wide area of ​​the inner shoulder land portion 13i, improving wet performance.

[0117] The multiple sixth groove-shaped portions 26 are inclined from the inner side Vi to the outer side Vo of the vehicle from the first end 20a to the second end 20b, and the absolute value of the angle θb6 with respect to the tire axis gradually increases. This makes the change in stiffness of the inner shoulder portion 13i in the tire axis direction more gradual, improving handling stability. To effectively exert this effect, it is preferable to set the absolute value of the angle θb6 to 0 to 15°.

[0118] In this embodiment, multiple seventh groove-like portions 27 are formed on the outer shoulder land portion 13o. The first end 20a of each seventh groove-like portion 27 communicates with the outer shoulder circumferential groove 8o, and the second end 20b communicates with the outer tread end 3o. As a result, the seventh groove-like portion 27 forms a continuous edge component over a wide area of ​​the outer shoulder land portion 13o, improving wet performance.

[0119] The multiple seventh groove-shaped portions 27 are inclined from the inside Vi of the vehicle to the outside Vo of the vehicle from the first end 20a to the second end 20b, and the absolute value of the angle θb7 with respect to the tire axis gradually increases. This makes the change in stiffness of the outer shoulder land portion 13o in the tire axis direction more gradual, improving handling stability. To effectively exert this effect, it is preferable to set the absolute value of the angle θb7 to 0 to 15°.

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

[0121] [Note] The present invention includes the following embodiments.

[0122] [Invention 1] A tire having a tread portion, The tread portion includes a plurality of circumferential grooves extending continuously in the circumferential direction of the tire, and a plurality of land portions separated by the plurality of circumferential grooves. Each of the aforementioned land areas has a plurality of groove-like sections formed therein, which are inclined with respect to the tire axis. Each of the aforementioned groove-shaped 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 aforementioned plurality of groove-shaped portions are arranged around the entire circumference of the tire according to a predetermined arrangement rule. In the arrangement rule described above, for each pair of adjacent grooves in the tire circumferential direction, the first end of one groove in the pair and the second end of the other groove in the pair are formed at the same position in the tire circumferential direction. The groove-shaped portions constituting the pair are formed on the same land area or on different land areas. When the tire is mounted on a regular rim with regular internal pressure and subjected to a 70% load condition with 70% of the regular load applied and the camber angle set to 0 degrees, the contact edges on both sides in the tire circumferential direction of at least one of the multiple contact areas have an angle θa with respect to the tire axis. The absolute value of the difference between the angle θa and the angle θb of the groove-shaped portion formed on the land portion with respect to the tire axis is 5 degrees or more. tire. [Invention 2] The tire according to the present invention 1, wherein the groove-shaped portions constituting the pair are formed on different land areas. [Invention 3] The tire according to invention 1 or 2, wherein the plurality of land sections consist of a center land section and a pair of middle land sections, and in all of these land sections the absolute value is 5 degrees or more. [4th Invention] The tire according to any one of inventions 1 to 3, wherein, under the 70% load condition, the contact surface of the tread portion has a ratio L / Lm of the contact length Lm in the circumferential direction of the tire, which is 60% or less of the maximum contact width W in the axial direction of the tire, centered on the tire equator, and satisfying the following formula (1). 1.00 <L / Lm<1.10 …(1) [5th ​​Invention] A tire according to any one of inventions 1 to 4, wherein the average angle of all the groove-shaped portions with respect to the tire axis is 10 to 50 degrees. [Invention 6] The tread portion has a tread pattern in which one-pitch regions constituting pattern constituent units are arranged in the circumferential direction of the tire. The tire according to any one of inventions 1 to 5, wherein in each of the plurality of land portions, the sum of the lengths in the tire axial direction of the groove-shaped portions formed in the 1-pitch region is 60% to 120% of the width of the land portion in the tire axial direction. [7th Invention] The tread portion has a specified orientation for mounting on the vehicle. The aforementioned plurality of land portions include a center land portion positioned on the tire equator and an outer middle land portion positioned on the outside of the vehicle relative to the center land portion when mounted on the vehicle. The tire according to any one of inventions 1 to 6, wherein in each of the center land portion and the outer middle land portion, at least one of the plurality of groove-shaped portions has at least one of the first end and second end terminated within the land portion. [8th Invention] The aforementioned plurality of land portions further include an inner middle land portion which is positioned on the inside of the vehicle relative to the center land portion when mounted on the vehicle. The tire according to the present invention, wherein in the inner middle land portion, at least one of the plurality of groove-shaped portions has both its first and second ends communicating with one of the circumferential grooves. [Invention 9] The tire according to the present invention, wherein the sum of the widths in the 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 contact width in the axial direction of the contact surface under a 70% load. [Invention 10] The tire according to any one of inventions 1 to 9, wherein the plurality of groove-shaped portions include sipe body portions with a width of 2 mm or less. [Invention 11] The tire according to any one of inventions 1 to 10, wherein at least one of the plurality of groove-shaped portions has a chamfered portion. [Invention 12] The plurality of circumferential grooves include at least one center circumferential groove located on the tire equator side, The tire according to any one of inventions 1 to 11, wherein at least one projection protruding in the radial direction of the tire is formed at the bottom of the center circumferential groove. [Invention 13] The tread portion has a specified orientation for mounting on the vehicle. The aforementioned plurality of land portions include a center land portion positioned on the tire equator, an outer middle land portion positioned on the outside of the vehicle relative to the center land portion when mounted on the vehicle, and an inner middle land portion positioned on the inside of the vehicle relative to the center land portion when mounted on the vehicle. The tire according to any one of inventions 1 to 12, wherein 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. [Explanation of Symbols]

[0123] 1 tire 2 Tread section 5 Circumferential groove 6 Land 20 Groove

Claims

1. A tire having a tread portion, The tread portion includes a plurality of circumferential grooves extending continuously in the circumferential direction of the tire, and a plurality of land portions separated by the plurality of circumferential grooves. Each of the aforementioned land areas has a plurality of groove-like sections formed therein, which are inclined with respect to the tire axis. Each of the plurality of groove-shaped 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 aforementioned plurality of groove-shaped portions are arranged around the entire circumference of the tire according to a predetermined arrangement rule. In the arrangement rule described above, for each pair of adjacent groove-shaped portions in the tire circumferential direction, the first end of one groove-shaped portion of the pair and the second end of the other groove-shaped portion of the pair are formed at the same position in the tire circumferential direction. The groove-shaped portions constituting the pair are formed on the same land area or on different land areas. When the tire is mounted on a regular rim with regular internal pressure and subjected to a 70% load condition with 70% of the regular load applied and the camber angle set to 0 degrees, the contact edges on both sides in the tire circumferential direction of at least one of the multiple contact areas have an angle θa with respect to the tire axis. The absolute value of the difference between the angle θa and the angle θb of the groove-shaped portion formed on the land portion with respect to the tire axis is 5 degrees or more. tire.

2. The tire according to claim 1, wherein the groove-shaped portions constituting the pair are formed on different land areas.

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

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

5. The tire according to claim 1, wherein the average angle of all the groove-shaped portions with respect to the tire axis 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 circumferential direction of the tire. The tire according to claim 1, wherein in each of the plurality of land portions, the sum of the lengths in the tire axial direction of the groove-shaped portions formed in the 1-pitch region is 60% to 120% of the width of the land portion in the tire axial direction.

7. The tread portion has a specified orientation for mounting on the vehicle. The aforementioned plurality of land portions include a center land portion positioned on the tire equator and an outer middle land portion positioned on the outside of the vehicle relative to the center land portion when 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 plurality of groove-shaped portions has at least one of the first end and second end terminated within the land portion.

8. The aforementioned plurality of land portions further include an inner middle land portion which is positioned on the inside of the vehicle relative to the center land portion when 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-shaped portions has both its first and second ends communicating with one of the circumferential grooves.

9. The tire according to claim 8, wherein 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 contact width in the tire axial direction of the contact surface under a 70% load.

10. The tire according to claim 1, wherein the plurality of groove-shaped portions include sipe body portions with a width of 2 mm or less.

11. The tire according to claim 1, wherein at least one of the plurality of groove-shaped portions has a chamfered portion.

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

13. The tread portion has a specified orientation for mounting on the vehicle. The aforementioned plurality of land portions include a center land portion positioned on the tire equator, an outer middle land portion positioned on the outside of the vehicle relative to the center land portion when mounted on the vehicle, and an inner middle land portion positioned on the inside of the vehicle relative to the center land portion when mounted on the vehicle. The tire according to claim 1, wherein 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.

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