tire

Abstract

Provided is a tire that has improved noise performance while retaining snow performance.　At least two bent grooves 26 (28) which each have at least one tire width-directional end connected to a circumferential main groove and which each have at least two bent sections are provided. Groove parts of at least one set, among groove parts adjacent to each other in the tire circumferential direction, have different groove widths. PTA1 (%) is not less than 0% but less than 50%, and the relationships of PTB2(%)>PTB1(%) and PTB2(%)>PTB3(%) are satisfied.

Description

tire

[0001] The present invention relates to a tire that maintains snow performance while improving noise performance.

[0002] For the purpose of improving snow performance without degrading noise and vibration performance, a tire is known in which at least one of a plurality of center sipes includes a chamfered portion on at least one of the edges in the tire circumferential direction, and these chamfered portions are arranged alternately on each side of the tire equatorial plane in the tire circumferential direction (see Patent Document 1).

[0003] JP 2022-088310 A

[0004] However, in the tire disclosed in Patent Document 1, there is a possibility that the timing of fluctuations in the opening and closing of the grooves (chamfers and sipes) may overlap between circumferentially adjacent chamfers and / or center sipes during tire rotation. In such cases, the sound generated when the tire comes into contact with the road surface is emphasized by a horn effect, increasing so-called pass-by noise (PBN), and there is a risk of deteriorating noise performance.

[0005] To address this issue, reducing the groove area ratio could be considered to improve noise performance, but reducing the groove area ratio could lead to a deterioration in drainage performance and ultimately a deterioration in snow performance. For this reason, there has been a demand in recent years for the development of technology that improves noise performance while maintaining snow performance without reducing the groove area ratio.

[0006] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a tire that has improved noise performance while maintaining snow performance without reducing the groove area ratio.

[0007] In the tire of the present invention, at least three land portions are defined by at least two circumferential main grooves, and on each side of the tire width direction of the tire equatorial plane, with the groove width centerline of the outermost circumferential main groove in the tire width direction as the boundary, a center region is defined as the area inward in the tire width direction of the groove width centerline, and shoulder regions are defined as areas outward in the tire width direction of the groove width centerline, at least one of the land portions formed in the center region is provided with at least two bent grooves, at least one end of which in the tire width direction is connected to the circumferential main groove and which have at least two bent portions, and the groove width of a first portion from one end of the bent groove to just before the first bent portion and the groove width of a second portion from the other end of the bent groove to just before the first bent portion are each different between at least one pair of groove portions among groove portions adjacent in the tire circumferential direction, and the number of bent grooves present in the same land portion is defined as N, The lengths of a first interval, which is the distance between two adjacent bent grooves in the tire circumferential direction, measured over the entire tire circumference are designated Ai (1≦i≦N), and the lengths of a second interval between the first portion and the second portion, measured over the entire tire circumference are designated Bi (1≦i≦N), The tire circumference is designated J (mm), the range of attention length due to transfer characteristics is designated S1 (mm), and the ranges of attention length due to sound source are designated S2 (mm) and S3 (mm), 12.4≦S1(mm)≦19.5, and In the ranges of S1 (mm) and S2 (mm) that satisfy J / (N×1.25×1)≦S2(mm)≦J / (N×0.75×1), the larger of the lower limit values ​​of the two inequalities is designated LFL1 and the smaller of the upper limit values ​​of the two inequalities is designated HFL1, 12.4≦S1(mm)≦19.5, and In the range of S1 (mm) and S3 (mm) that satisfies J / (N×1.25×2)≦S3 (mm)≦J / (N×0.75×2), the larger of the lower limit values ​​of the two inequalities is defined as LFL2, and the smaller of the upper limit values ​​of the two inequalities is defined as HFL2; Condition TA1 defined by LFL1×1<Ai (mm)<HFL1×1, or LFL2×1<Ai (mm)<HFL2×1; Condition TB1 defined by LFL1×1<Bi (mm)<HFL1×1, or LFL2×1<Bi (mm)<HFL2×1; Conditions other than condition TB1, andA condition TB2 is defined as LFL1×0.5<Bi (mm)<HFL1×0.5, or LFL2×0.5<Bi (mm)<HFL2×0.5, and a condition TB3 is defined as a condition other than condition TB1 and other than condition TB2. When the proportion of intervals Ai that satisfy condition TA1 is PTA1 (%), the proportion of intervals Bi that satisfy condition TB1 is PTB1 (%), the proportion of intervals Bi that satisfy condition TB2 is PTB2 (%), and the proportion of intervals Bi that satisfy condition TB3 is PTB3 (%), PTA1 (%) is equal to or greater than 0% and less than 50%, and PTB2 (%) > PTB1 (%) and PTB2 (%) > PTB3 (%) are satisfied.

[0008] In the tire according to the present invention, instead of reducing the groove area ratio, overlapping of the timing of fluctuations in the opening and closing of groove portions between adjacent groove portions during tire rotation is reduced in the tire widthwise central region of the tread, where the sound generated when the tire contacts the road surface is likely to be emphasized due to the horn effect. Specifically, for bent grooves provided in the land portion of the tire widthwise central region, assuming that the groove widths of adjacent grooves in the tire widthwise direction are different, PTA1 (%) is set to 0% or more and less than 50%, and PTB2 (%) > PTB1 (%) and PTB2 (%) > PTB3 (%) are satisfied. This allows intentional staggering of the timing of fluctuations in the opening and closing of groove portions between adjacent groove portions during tire rotation without degrading drainage performance, thereby reducing pass-by noise between these groove portions. Therefore, according to the present invention, noise performance can be improved while maintaining snow performance.

[0009] Fig. 1 is a plan view showing the tread surface of a tire of this embodiment. Fig. 2 is a plan view showing the groove width of the bent groove shown in Fig. 1. Fig. 3 is a plan view showing the interval between groove portions of the bent groove shown in Fig. 1. Fig. 4 is a plan view showing two types of circumferential lengths of the bent groove shown in Fig. 1.

[0010] In the following description, the tire radial direction refers to the direction perpendicular to the tire's rotational axis, the tire radially inner side refers to the side toward the rotational axis in the tire radial direction, and the tire radially outer side refers to the side away from the rotational axis in the tire radial direction. The tire circumferential direction refers to the direction around the rotational axis as the central axis. The tire width direction refers to the direction parallel to the rotational axis, the tire widthwise inner side refers to the side toward the tire equatorial plane (tire equator line) in the tire width direction, and the tire widthwise outer side refers to the side away from the tire equatorial plane in the tire width direction. The tire equatorial plane is a plane perpendicular to the tire's rotational axis and passing through the center of the tire width.

[0011] Similarly, in the following description, a regular rim refers to an "application rim" defined by JATMA, a "design rim" defined by TRA, or a "measuring rim" defined by ETRTO.

[0012] Similarly, in the following description, "normal internal pressure" refers to the "maximum air pressure" specified by JATMA, the maximum value specified in "Tire Load Limits at Various Cold Inflation Pressures" specified by TRA, or the "Inflation Pressures" specified by ETRTO. Also, "normal load" refers to the "maximum load capacity" specified by JATMA, the maximum value specified in "Tire Load Limits at Various Cold Inflation Pressures" specified by TRA, or the "Load Capacity" specified by ETRTO.

[0013] FIG. 1 is a plan view showing the tread surface of a tire of this embodiment, in an unloaded state (non-contact state) with the tire mounted on a standard rim and given a standard internal pressure. In FIG. 1, only one of several identical components is designated by a reference numeral. The tread portion of the tire 10 shown in the figure is made of a rubber material (tread rubber). The surface of the tread portion (tread surface 12) located at the outermost part in the tire's radial direction comes into contact with the road surface when the vehicle is traveling. As shown in FIG. 1, a predetermined tread pattern is formed on the tread surface. In the tread pattern shown in FIG. 1, the left side is the inside of the tire mounted on the vehicle.

[0014] In the example shown in FIG. 1 , four circumferential main grooves 14 (14a, 14b, 14c, 14d) are provided on the tread surface 12, symmetrically arranged in the tire width direction across the tire equatorial plane CL. The circumferential main grooves 14 have a groove width of 6 mm or more and 14 mm or less. Here, groove width refers to the groove dimension (maximum value) measured in a direction perpendicular to the groove extension direction (the same applies hereinafter to other grooves). The circumferential main grooves 14 also have a groove depth of 5 mm or more and 10 mm or less. Here, groove depth refers to the groove dimension (maximum value) measured in the tire radial direction from a profile line in the absence of the groove (the same applies hereinafter to other grooves).

[0015] These circumferential main grooves 14 define five land portions 16, 18, 20, 22, and 24. The center land portion 16 includes the tire equatorial plane CL, and second land portions 18 and 20 are defined on each side of the center land portion 16 in the tire width direction, and shoulder land portions 22 and 24 are defined on the outer sides of those in the tire width direction. In this embodiment, the land portions defined by the four circumferential main grooves 14a to 14d include not only ribs as shown in FIG. 1 but also block rows.

[0016] On each side of the tire equatorial plane CL in the tire width direction, the groove width center lines (not shown) of the circumferential main grooves 14c, 14d that are outermost in the tire width direction are used as the boundary, and the area inward in the tire width direction from these groove width center lines is defined as a center region CR, and the areas outward in the tire width direction from the groove width center lines are defined as shoulder regions SR, SR.

[0017] The center land portion 16 formed in the center region CR is provided with a plurality of bent grooves, each of which has two bent portions and whose both ends in the tire width direction are connected to the circumferential main grooves 14 a, 14 b. In the example shown in Fig. 1, two types of bent grooves 26, 28 with different groove widths are provided alternately in the tire circumferential direction.

[0018] The bent grooves 26 (28) have a groove width of more than 1.5 mm to ensure excellent snow performance. The upper limit of the groove width is preferably 5 mm. The bent grooves 26 (28) also have a depth of 40% or more of the groove depth of the circumferential main grooves 14 to ensure excellent snow performance. The upper limit of the groove depth is preferably 90% or less of the groove depth of the circumferential main grooves 14.

[0019] 1, the second land portion 18 formed in the center region CR on the outer side fitted to the vehicle is provided with first lug grooves 30 that communicate with both of the circumferential main grooves 14a, 14c on both sides in the tire width direction and whose inclination direction with respect to the tire width direction reverses midway as they extend from the inner side to the outer side in the tire width direction. The first lug grooves 30 are provided on the outer side fitted to the vehicle to improve snow performance, and by reversing the inclination direction with respect to the tire width direction midway as they extend, pass-by noise can be reduced compared to grooves whose inclination direction is not reversed.

[0020] In the second land portion 18, sipes 32 are formed between adjacent first lug grooves 30 in the tire circumferential direction, extending substantially parallel to the first lug grooves 30. In this specification, a sipe means a groove having a groove width of 0.5 mm or more and 1.5 mm or less and a groove depth of 20% or more and 80% or less of the groove depth of the circumferential main groove 14.

[0021] To improve snow performance, the second land portion 20 on the vehicle mounting inner side formed in the center region CR is provided with second lug grooves 34 that extend inward in the tire width direction from the circumferential main groove 14d on the outer side in the tire width direction and terminate within the land portion 20. The second land portion 20 also has sipes 36 that extend from the inner end of the second lug groove 34 in the tire width direction and communicate with the circumferential main groove 14b on the inner side in the tire width direction. Furthermore, the second land portion 20 has sipes 38 formed between the second lug grooves 34, 34 adjacent in the tire circumferential direction, extending approximately parallel to the second lug grooves 34 and communicating with both of the circumferential main grooves 14b, 14d on both sides in the tire width direction.

[0022] The shoulder land portion 22 formed in the shoulder region SR on the vehicle-mounted outer side is provided with third lug grooves 40 that extend inward in the tire width direction across a ground contact edge (not shown) and terminate within the land portion 22. Additionally, the shoulder land portion 22 is provided with sipes 42 extending outward in the tire width direction from the circumferential main groove 14c between adjacent third lug grooves 40 in the tire circumferential direction, and the sipes 42 communicate with small grooves 44 near the ground contact edge. Note that, in this specification, a small groove refers to a groove having a groove width of 0.5 mm to 3.0 mm and a groove depth of 0.3 mm to 2.0 mm. Furthermore, triangular grooves 46 are provided at a constant pitch in the tire circumferential direction on the tire widthwise outer side of the ground contact edge.

[0023] An auxiliary groove 48 is provided in the inner region of the shoulder land portion 22 in the tire width direction, parallel to the circumferential main groove 14c. Generally, the shoulder land portion 22 on the outer side of the vehicle contributes greatly to snow performance, particularly to cornering performance. Therefore, by providing the auxiliary groove 48 in the shoulder land portion 22, the rigidity of the shoulder land portion 22 can be suitably adjusted, and cornering performance can be efficiently improved. The groove depth of the auxiliary groove 48 can be 0.3 to 0.8 times the groove depth of the circumferential main groove 14c.

[0024] The shoulder land portion 24 formed in the shoulder region SR on the vehicle-mounted inner side is provided with a fourth lug groove 50 that extends inward in the tire width direction across a ground contact edge (not shown) and terminates within the land portion 24. The shoulder land portion 24 also has a sipe 52 formed between adjacent fourth lug grooves 50 in the tire circumferential direction, extending from the circumferential main groove 14d outward in the tire width direction, and the sipe 52 communicates with a small groove 54 near the ground contact edge. Furthermore, an auxiliary groove 56 is provided in the inner region in the tire width direction within the shoulder land portion 24, extending parallel to the circumferential main groove 14d. The groove depth of the auxiliary groove 56 may be 0.3 to 0.8 times the groove depth of the circumferential main groove 14d.

[0025] FIG. 2 is a plan view showing the groove width of the bent groove shown in FIG. 1 . Below, only two bent grooves 26, 28 adjacent in the tire circumferential direction will be described among the multiple bent grooves provided in the tire circumferential direction. As shown in FIG. 2 , the bent groove 26 (28) has a groove width W1 (W2) of a first portion 26a (28a) extending from one end to just before the first bend, and a groove width W3 (W4) of a second portion 26b (28b) extending from the other end of the bent groove 26 (28) to just before the first bend. These groove widths differ between at least one pair of groove portions adjacent in the tire circumferential direction. That is, in FIG. 2 , the groove width W1 and the groove width W2 are different, and the groove width W3 and the groove width W4 are different. The relationship between the groove width W1 and the groove width W3 is not particularly limited and may be different or the same. The relationship between the groove width W2 and the groove width W4 is also not particularly limited and may be different or the same.

[0026] The groove width W1 (W2) of the first portion 26a (28a) is determined by dividing the first portion 26a (28a) into five equal sections in the extension direction, calculating the dimension of the center of each section in the extension direction in the direction perpendicular to the extension direction, and averaging the calculated values ​​for the five sections. The same applies to the groove width W3 (W4) of the second portion 26b (28b).

[0027] The first portion 26a (28a) and the second portion 26b (28b) may be linear or curved in the extension direction. The bent portion refers to a portion connected to the first portion 26a (28a) and / or the second portion 26b (28b), extending from a point where the curvature of the groove width center line changes relative to the first portion 26a (28a) or the second portion 26b (28b) to a point where the curvature changes again.

[0028] As described above, groove width W1 and groove width W2, or groove width W3 and groove width W4, are different. However, in this embodiment, as long as the groove widths are different between at least one pair of groove portions adjacent to each other in the tire circumferential direction, the groove widths of the other groove portions may be different or the same. When three types of bent grooves A, B, and C with different groove widths are provided in the center land zone 16, the following examples can be given as examples of bent groove units that serve as repeating units. In this paragraph, bent groove A will be referred to as A, bent groove B as B, and bent groove C as C. The examples shown below are merely illustrative, and other examples (when four or more types of bent grooves are provided) are also within the scope of this embodiment.・ABC ・ABBCC ・ABBCCCC ・ABAC ・ABBACC ・ABBACCC ・AABC ・AABBCC ・AABBBCCC ・AABAAC ・AABBAACC ・AABBBAACCC ・AAABC ・AAABBCC・AAABBBCCC ・AAABAAAC ・AAABBAAACC

[0029] When multiple types of curved grooves with different groove widths are provided in the center land zone 16, the widths of the groove portions of the multiple types of curved grooves are set so that the ratio of the standard deviation calculated from each portion to the average value calculated from each portion (standard deviation / average value) is in the range of 0 to 0.1. For example, in the example shown in Figure 2, the ratio of the standard deviation calculated from each portion to the average value calculated from each portion (standard deviation / average value) is set to be in the range of 0 to 0.1 for portions 26a and 28a (portions 26b and 28b).

[0030] The groove widths W1 and W3 of the groove portions included in the bent groove 26 may be the same or different. Similarly, the groove widths W2 and W4 of the groove portions included in the bent groove 28 may be the same or different. In the example shown in FIG. 2 , the groove widths W1 and W3 are the same, and the groove widths W2 and W4 are the same. However, if the groove widths W1 and W3 (or the groove widths W2 and W4) are different, the difference in groove width itself between these groove portions (e.g., between the first portion 26 a and the second portion 26 b) is likely to cause different fluctuation times regarding the opening and closing of the groove portions. For this reason, it is more preferable for the groove widths W1 and W3 (or the groove widths W2 and W4) to be different than if they were the same, because this enhances the pass-by noise reduction effect.

[0031] Fig. 3 is a plan view showing the spacing between groove portions of the bent grooves shown in Fig. 1. Of the multiple bent grooves provided in the tire circumferential direction, only two bent grooves 26, 28 that are adjacent in the tire circumferential direction will be described in Fig. 3. Here, the number of bent grooves present in the center land portion 16 shown in Fig. 1 is defined as N.

[0032] The first distance D1, which is the distance between two adjacent bent grooves 26, 28 in the tire circumferential direction, has a length measured around the entire tire circumference that is designated Ai (1≦i≦N), and the second distance D2 between the first portion 26a and the second portion 26b and the second distance D3 between the first portion 28a and the second portion 28b have lengths measured around the entire tire circumference that are designated Bi (1≦i≦N).

[0033] For example, if only two bent grooves are provided in the central land portion 16 (only bent groove 26 and bent groove 28), one first distance D1 shown in Fig. 3 is defined, and two second distances D2 and D3 are defined in total. In contrast, if 30 bent grooves are provided in the central land portion 16, one first distance D1 shown in Fig. 3 exists for each bent groove, so a total of 30 first distances D1 are defined, and the same number of second distances D2 and D3 as the number of bent grooves are also defined, so a total of 30 second distances D2 and D3 are defined.

[0034] When groove portions of two circumferentially adjacent bent grooves (for example, the first portion 26a and the first portion 28a) are parallel to each other, the first distance D1 between the bent grooves 26, 28 is determined as the shortest distance between an imaginary line drawn based on the groove width center points (not shown) of each of the five equal sections used when determining the groove width W1 shown in Fig. 2, and an imaginary line drawn based on the groove width center points (not shown) of each of the five equal sections used when determining the groove width W2 shown in Fig. 2. Each imaginary line is set so that the five groove width center points are as close as possible to each other.

[0035] In contrast, when groove portions of two circumferentially adjacent bent grooves (for example, the first portion 26a and the first portion 28a) are not parallel to each other, the first distance D1 between the bent grooves 26, 28 is determined as follows. Specifically, first, the groove width center points (not shown) of the five equal sections used when determining the groove width W1 shown in FIG. 2 are designated as points a1, b1, c1, d1, and e1, respectively, from one vehicle mounting side. The groove width center points (not shown) of the five equal sections used when determining the groove width W2 shown in FIG. 2 are designated as points a2, b2, c2, d2, and e2, respectively, from one vehicle mounting side. Next, the distance between points a1 and a2 is designated as Sa, the distance between points b1 and b2 as Sb, the distance between points c1 and c2 as Sc, the distance between points d1 and d2 as Sd, and the distance between points e1 and e2 as Se. Then, the average value from the distance Sa to the distance Se is calculated and set as the first interval D1.

[0036] When the groove portions of one bent groove (e.g., the first portion 26a and the second portion 26b) are parallel to each other, the second distance D2 for the bent groove 26 is determined as the shortest distance between a virtual line drawn based on the center points (not shown) of the groove widths of each of the five equal sections used to determine the groove width W1 shown in FIG. 2 and a virtual line drawn based on the center points (not shown) of the groove widths of each of the five equal sections used to determine the groove width W3 shown in FIG. 2. Each virtual line is set so that the five groove width center points are as close as possible to each other. The second distance D3 for the bent groove 28 shown in FIG. 3 is determined in the same manner as the second distance D2 (based on the groove widths W2 and W4).

[0037] In contrast, when the groove portions of one bent groove (e.g., the first portion 26a and the second portion 26b) are not parallel to each other, the second distance D2 for the bent groove 26 is determined as follows. First, the groove width center points (not shown) of the five equal sections used to determine the groove width W1 shown in FIG. 2 are designated as points a1, b1, c1, d1, and e1, respectively, from one vehicle mounting side. The groove width center points (not shown) of the five equal sections used to determine the groove width W3 shown in FIG. 2 are designated as points a3, b3, c3, d3, and e3, respectively, from one vehicle mounting side. Next, the distance between points a1 and a3 is designated as sa, the distance between points b1 and b3 as sb, the distance between points c1 and c3 as sc, the distance between points d1 and d3 as sd, and the distance between points e1 and e3 as se. The average value of the distances sa and se is calculated as the first distance D1. The second distance D3 for the bent groove 28 shown in FIG. 3 is also determined in the same manner as the second distance D2 (based on the groove widths W2 and W4).

[0038] Next, the tire circumference is defined as J (mm), the range of attention length due to the transfer characteristic is defined as S1 (mm), and the range of attention length due to the sound source is defined as S2 (mm) and S3 (mm).

[0039] Here, the range S1 (mm) of the length of attention caused by the transfer characteristics means the range sandwiched between the lower limit value and the upper limit value calculated by dividing the representative speed of the pass-by noise by the upper limit and the lower limit, respectively, of the frequency range that is emphasized in the center region due to the horn effect when the acoustic characteristics of the space around the tire are measured.

[0040] In addition, the range of attention length S2 (mm) due to the sound source means a range of ±25% of the first order of the pitch order that occurs when the block formed by the curved groove comes into contact with the road surface, and the range of attention length S3 (mm) due to the sound source means a range of ±25% of the second order of the pitch order that occurs when the block formed by the curved groove comes into contact with the road surface.

[0041] Next, the range of the length S1 (mm) to be considered due to the transfer characteristics, in which the sound generated from the curved grooves 26, 28 provided in the center land portion 16 is emphasized by the horn effect, is as follows: 12.4<S1 (mm)<19.5

[0042] The ranges of the caution lengths S2 (mm) and S3 (mm) due to the sound source, in which the curved grooves 26, 28 provided in the center land portion 16 cause pass-by noise, are as follows: J / (N×1.25×1)<S2(mm)<J / (N×0.75×1) J / (N×1.25×2)<S3(mm)<J / (N×0.75×2)

[0043] Based on the above ranges of S1 (mm), S2 (mm), and S3 (mm), in the range of S1 (mm) and S2 (mm) that satisfies S1 (mm) ≦ 19.5 and J / (N × 1.25 × 1) ≦ S2 (mm) ≦ J / (N × 0.75 × 1), the larger of the lower limit values ​​of these two inequalities is defined as LFL1, and the smaller of the upper limit values ​​of the two inequalities is defined as HFL1.

[0044] Similarly, in the range of S1 (mm) and S3 (mm) that satisfies 12.4≦S1 (mm)≦19.5 and J / (N×1.25×2)≦S3 (mm)≦J / (N×0.75×2), the larger of the lower limit values ​​of these two inequalities is defined as LFL2, and the smaller of the upper limit values ​​of the two inequalities is defined as HFL2.

[0045] Furthermore, based on the above findings, the condition defined by LFL1×1<Ai (mm)<HFL1×1 or LFL2×1<Ai (mm)<HFL2×1 is defined as condition TA1.

[0046] The condition defined by LFL1×1<Bi (mm)<HFL1×1 or LFL2×1<Bi (mm)<HFL2×1 is defined as condition TB1.

[0047] A condition other than condition TB1 and defined as LFL1×0.5<Bi (mm)<HFL1×0.5 or LFL2×0.5<Bi (mm)<HFL2×0.5 is defined as condition TB2.

[0048] A condition defined as a condition other than condition TB1 and condition TB2 is defined as condition TB3.

[0049] The proportion of intervals Ai that satisfy condition TA1 is PTA1 (%), the proportion of intervals Bi that satisfy condition TB1 is PTB1 (%), the proportion of intervals Bi that satisfy condition TB2 is PTB2 (%), and the proportion of intervals Bi that satisfy condition TB3 is PTB3 (%).

[0050] When condition TA1 is satisfied or when condition TB1 is satisfied, it means that there is a high possibility that the fluctuation times regarding the opening and closing of the groove portions will overlap between adjacent groove portions in the circumferential direction of the tire when the tire is rolling, resulting in large and undesirable pass-by noise.

[0051] Satisfying condition TB2 means that the timing of fluctuations in the opening and closing of groove portions is unlikely to overlap between adjacent groove portions in the tire circumferential direction when the tire is rolling, resulting in small, desirable pass-by noise.

[0052] The case where condition TB3 is satisfied (the case where neither condition TB1 nor condition TB2 is satisfied) means that there is a moderate possibility that the timing of fluctuations in the opening and closing of groove portions will overlap between adjacent groove portions in the tire circumferential direction when the tire is rolling, and therefore pass-by noise is moderate and neither undesirable nor desirable.

[0053] The above inequalities used to derive any of condition TA1, condition TB1, condition TB2, and condition TB3 were obtained by the inventors through extensive research and numerous experiments. Although the inventors have not found a clear technical basis for these inequalities, they have found that they are supported by a large amount of experimental data and are ultimately useful inequalities for improving noise performance.

[0054] Under the above assumptions, in this embodiment, assuming that the groove widths of adjacent grooves in the tire circumferential direction are different as described above, PTA1 (%) is greater than or equal to 0% and less than 50%, and PTB2 (%) > PTB1 (%) and PTB2 (%) > PTB3 (%) are satisfied.

[0055] In the tire 10 of this embodiment, the groove widths of at least one pair of groove portions adjacent to each other in the tire circumferential direction can be made different, thereby intentionally shifting the timing of fluctuations in the opening and closing of the groove portions to some extent when the tire is rolling (effect 1).

[0056] Then, the proportion PTA1 of undesired spacing between adjacent bent grooves is set to less than half of the total, and the proportion PTB2 of desired spacing between groove portions included in each bent groove, the proportion PTB1 of undesired spacing, and the proportion PTC3 of neither undesired nor undesired spacing are compared, and of these three proportions, the proportion PTB2 of desired spacing is made higher than either the proportions PTB1 or PTB3 of other cases, thereby further shifting the timing of fluctuations in the opening and closing of the groove portions as the tire rolls (effect 2).

[0057] The tire 10 of this embodiment, by combining the above-described effects 1 and 2, can reliably shift the timing of fluctuations related to the opening and closing of the groove portions during tire rotation, thereby reducing pass-by noise and improving noise performance.

[0058] The tire 10 of this embodiment does not reduce the groove area ratio compared to conventional tires, but focuses on specific land portions (specifically, the center land portion 16 included in the center region in the tire width direction) to reduce pass-by noise through the above-mentioned effects 1 and 2. Therefore, the tire 10 of this embodiment can achieve the above-mentioned improvement in noise performance while maintaining snow performance (a combination of drainage performance, handling stability, cornering performance, traction performance, etc.; the same applies below) at a conventional level. Note that, in the example shown in FIG. 1 , in particular, by providing four circumferential main grooves, the width of the center land portion 16, which contributes most to pass-by noise reduction, is relatively small, thereby reducing the rigidity of the land portion 16, thereby efficiently reducing pass-by noise.

[0059] In the example shown in FIG. 1, the curved grooves 26 are provided only in the center land portion 16, but this embodiment is not limited to this case. The curved grooves can be provided in any of the land portions (land portions 16, 18, 20) defined and formed in the center region CR, and the same effect as that achieved by the tread pattern shown in FIG. 1 can be obtained.

[0060] For example, although not shown, if curved grooves are provided in the center land portion 16 and the second land portion 20, the groove widths W1 to W4 shown in Figure 2 and the intervals D1 to D3 shown in Figure 3 are calculated for each land portion, and the above-mentioned ratios PTA1, as well as PTB1, PTB2 and PTB3, are calculated for the entire tire.

[0061] In the example shown in Fig. 1, by setting PTA1 (%) to less than 40%, the timing of fluctuations in the opening and closing of the groove portions during tire rotation can be further shifted, resulting in a further reduction in pass-by noise. Furthermore, by setting PTA1 (%) to less than 30%, the timing of fluctuations in the opening and closing of the groove portions during tire rotation can be further shifted, resulting in a significant reduction in pass-by noise.

[0062] 1 , it is preferable that the difference between the percentage PTB2 and the percentage PTB1 be 20% or more, and that the difference between the percentage PTB2 and the percentage PTB3 be 10% or more. When these conditions are met, the percentage PTB1 of undesired cases described above is lower than the percentage PTB3 of undesired and undesired cases, so that the percentage PTB1 of undesired cases as a whole can be further reduced. As a result, the timing of fluctuations in the opening and closing of groove portions adjacent to each other in the tire circumferential direction during tire rotation can be intentionally shifted by a larger amount, thereby further reducing pass-by noise between these groove portions.

[0063] In the tire 10 shown in Figure 1, the proportion PTB1 is preferably 30% or less. When this condition is satisfied, the proportion PTB1 of undesirable cases relative to the total can be further reduced. As a result, the timing of fluctuations in the opening and closing of groove portions adjacent to each other in the tire circumferential direction can be intentionally shifted by a larger amount during tire rotation, thereby further reducing pass-by noise between these groove portions.

[0064] When the ratio PTB1 is 30% or less and the ratio PTB2 > ratio PTB3 > ratio PTB1 is satisfied, the timing of fluctuations in the opening and closing of the groove portions during tire rotation can be intentionally shifted to an even greater extent, thereby further reducing pass-by noise between these groove portions.

[0065] 4 is a plan view showing two types of circumferential lengths of the bent groove shown in FIG. 1. As shown in FIG. 4, it is preferable that the tire circumferential length DG1 (DG2) between one end and the other end of the bent groove 26 (28) is equal to or greater than the tire circumferential length DB1 (DB2) of the third portion 26c (28c) of the bent groove 26 (28) (a portion other than the first portion and the second portion in each bent groove). Here, the tire circumferential lengths DG1 and DG2 may be the same or different. Furthermore, the tire circumferential lengths DB1 and DB2 may be the same or different.

[0066] 4 (FIG. 1), the longitudinal portion (the tire widthwise centerline) excluding the bent portion is located on the tire equatorial plane CL, and therefore extends in the tire circumferential direction. However, when the longitudinal portion (the tire widthwise centerline) is located offset to either side in the tire width direction from the tire equatorial plane CL, it is preferable to provide the longitudinal portion so that it extends from the inner side to the outer side in the tire width direction, from the leading side to the trailing side of the tire, in consideration of drainage performance.

[0067] By making the tire circumferential length DG1 (DG2) equal to or greater than the tire circumferential length DB1 (DB2), the first portion 26a (28a) and the second portion 26b (28b) of the bent groove 26 (28) become more easily deformed when the tire 10 comes into contact with the road surface, thereby further reducing pass-by noise and further improving noise performance.

[0068] 1, only the above-mentioned bent grooves 26, 28 are provided in the center land portion 16, but this embodiment is not limited to this example, and other grooves may be provided in the center land portion 16. However, if grooves other than the bent grooves are provided in the center land portion 16, the effect of providing the bent grooves (which allows the timing of fluctuations regarding the opening and closing of the groove portions during tire rotation to be intentionally shifted, and thus reduces pass-by noise between these groove portions) may be weakened by the presence of the other grooves, and therefore, from the perspective of pass-by noise reduction, it is not preferable to provide grooves other than the bent grooves in the center land portion 16.

[0069] As a modification of the example shown in Figure 1, three circumferential main grooves can be provided to define two land portions in the center region without changing the groove area ratio. By providing two or more (preferably three or more) circumferential main grooves, it is possible to obtain excellent noise performance while maintaining the desired drainage performance and, therefore, snow performance in this embodiment.

[0070] 1 , it is preferable that the position where the extension direction of the first lug groove 30 becomes the tire width direction (inclination direction change position) is present in the tire width direction outer region of the second land portion 18. Here, the tire width direction outer region of the second land portion 18 means a region from a position of 50% or more to a position less than 100% (preferably 90% or less) when the tire width direction inner end of the second land portion 18 is set as the 0% position and the tire width direction outer end is set as the 100% position.

[0071] By positioning the inclination direction change position in the outer region in the tire width direction within the second land portion 18, the length of the portion (inner groove portion) of the first lug groove 30 that extends from the circumferential main groove 14a on the inner side in the tire width direction to the inclination direction change position can be made longer than the length of the portion (outer groove portion) that extends from the circumferential main groove 14c on the outer side in the tire width direction to the inclination direction change position.

[0072] When a tire rolls in snowy conditions, the closer to the tire equatorial plane CL, the more likely it is to come into contact with snow or a water film accumulated on the road surface. Therefore, even for the same groove, particularly excellent drainage performance is required in the inner groove portion in the tire width direction. For this reason, even for the first lug groove 30, drainage performance is more important in the inner groove portion than in the outer groove portion. Considering that water flows from the inner side to the outer side in the tire width direction during drainage, adopting the above-mentioned configuration (making the length of the inner groove portion longer than the length of the outer groove portion) allows for drainage in the same direction to a certain extent in the inner groove portion, which is more likely to come into contact with a water film, and then changes the direction of the water flow to continuously drain water in the outer groove portion, thereby further improving snow performance.

[0073] 1 , the second lug grooves 34 preferably terminate in an inner region in the tire width direction within the second land portion 20. Here, the inner region in the tire width direction within the second land portion 20 refers to a region from a position of 50% or more to a position less than 100% (preferably 90% or less), where the outer end portion in the tire width direction of the second land portion 20 is defined as the 0% position and the inner end portion in the tire width direction is defined as the 100% position.

[0074] The second lug grooves 34 extend to the inner region in the tire width direction within the second land portion 20, thereby further improving drainage performance and, in turn, snow performance. In addition, the second lug grooves 34 terminate within the second land portion 20, thereby suppressing the generation of noise in the inner portion in the tire width direction of the second lug grooves 34 and further reducing pass-by noise.

[0075] In the example shown in FIG. 1 , as described above, the second land portion 20 is formed with a sipe 36 that extends from the tire widthwise inner end of the second lug groove 34 and communicates with the circumferential main groove 14b on the tire widthwise inner side. In addition to the example shown in FIG. 1 , this embodiment also includes an example in which the second lug groove 34 does not terminate within the land portion 20 but also communicates with the circumferential main groove 14b. However, if the second lug groove 34 communicates with the circumferential main groove 14b on the tire widthwise inner side, the noise generated at the tire widthwise inner portion of the second lug groove 34 is relatively loud, making it difficult to reduce pass-by noise. In contrast, as shown in FIG. 1 , by terminating the second lug groove 34 within the land portion and forming a sipe 36 that is narrower than the second lug groove 34 on its extension, the noise generated at the tire widthwise inner portion of the sipe 36 can be relatively quiet, and pass-by noise can be efficiently reduced without degrading drainage performance.

[0076] In the tire 10 shown in Fig. 1, the third lug groove 40 extends from the ground contact edge on the vehicle-mounted outer side (or the outer position of the ground contact edge in the tire width direction), crosses the auxiliary groove 48, and terminates in the land portion 22, and the fourth lug groove 50 extends from the ground contact edge on the vehicle-mounted inner side (or the outer position of the ground contact edge in the tire width direction), crosses the auxiliary groove 56, and terminates in the land portion 24. Here, "the lug groove 40 (50) crosses the auxiliary groove 48 (56)" means that the inner end portion in the tire width direction of the lug groove 40 (50) is located more inward in the tire width direction than the inner end portion in the tire width direction of the auxiliary groove 48 (56), and the outer end portion in the tire width direction of the lug groove 40 (50) is located more outward in the tire width direction than the outer end portion in the tire width direction of the auxiliary groove 48 (56).

[0077] The lug grooves 40 (50) extend from the ground contact edge (or the outer position of the ground contact edge in the tire width direction) on the vehicle mounting outer side (vehicle mounting inner side), which reduces the rigidity of the land portion near each ground contact edge to a certain extent, thereby improving traction performance. On the other hand, the lug grooves 40 (50) cross the auxiliary grooves 48 (56) and terminate within the land portion 22 (24), which ensures a certain length of the lug grooves 40 (50) in the tire width direction, further improving drainage performance, and by not communicating the lug grooves 40 (50) with the circumferential main grooves 14 c (14 d), it is possible to suppress the generation of noise at the inner portion of the lug grooves 40 (50) in the tire width direction, thereby further reducing pass-by noise.

[0078] In the example shown in FIG. 1, the lug groove 40 (50) crosses the auxiliary groove 48 (56) and terminates within the land portion 22 (24), but this embodiment is not limited to such an example and also includes an example in which the lug groove crosses the auxiliary groove and terminates within the land portion only on either the outer or inner side of the vehicle mounting surface.

[0079] In the tire 10 shown in Fig. 1 , the tire width direction outer portion of the first lug groove 30 and the tire width direction inner portion of the third lug groove 40 are both inclined toward the same side in the tire width direction, and the tire width direction outer portion of the second lug groove 34 and the tire width direction inner portion of the fourth lug groove 50 are both inclined toward the same side in the tire width direction. With this configuration, the point at the ground contact end of the extension line of the first lug groove 30 extended outward in the tire width direction and the point at the ground contact end of the third lug groove 40 can be separated on the ground contact edge line on the outer side of the vehicle as mounted, thereby further reducing pass-by noise. In addition, the point at the ground contact end of the extension line of the second lug groove 34 extended outward in the tire width direction and the point at the ground contact end of the fourth lug groove 50 can be separated on the ground contact edge line on the inner side of the vehicle as mounted, thereby further reducing pass-by noise.

[0080] In the tire 10 shown in Fig. 1, the average inclination angle of the second lug grooves 34 with respect to the tire width direction (average angle of the second lug grooves) is preferably larger than the average inclination angle of the fourth lug grooves 50 with respect to the tire width direction (average angle of the fourth lug grooves). Here, the average angle of the second lug grooves refers to the angle formed with the tire width direction by a line segment connecting the innermost position and the outermost position of the second lug grooves 34 in the tire width direction. Also, the average angle of the fourth lug grooves refers to the angle formed with the tire width direction by a line segment connecting the innermost position and the ground contact edge position of the fourth lug grooves 34 in the tire width direction.

[0081] By making the average angle of the second lug grooves larger than the average angle of the fourth lug grooves, it is possible to disperse the point at the ground contact edge on the extension line of the second lug grooves 34 extending outward in the tire width direction in Figure 1 (the point at the ground contact edge of the series of curves connecting the second lug grooves 34, sipes 52, and small grooves 54 from the inner side to the outer side in the tire width direction) and the point at the ground contact edge of the fourth lug groove 50 on the ground contact edge line, thereby further reducing pass-by noise.

[0082] Test tires (comparative tire and invention examples 1 to 11) were manufactured with a tire size of 245 / 70R17 110T (specified by JATMA), four circumferential main grooves, and meeting the conditions shown in Table 1. Note that all terms in Table 1 are equivalent to the terms explained in this embodiment. Furthermore, among the components of each test tire, components not shown in Table 1 are equivalent to the tire components shown in FIG. 1.

[0083] Next, each test tire was mounted on a 17x7J rim, and the air pressure was adjusted to 230 kPa, and the tires were mounted on a 4WD vehicle with an engine displacement of 3500 cc. All test tires were evaluated for noise performance (related to pass-by noise) and snow performance (related to lateral acceleration performance and braking performance) according to the following procedures.

[0084] (Method of Evaluating Noise Performance) On a test course, the noise level (dB) of passing noise was measured for each test tire when the vehicle was running at a speed of 50 km / h, with the transmission in neutral and the engine stopped. The difference in noise level between each example tire and the comparative tire was determined, and this difference itself was used as a rating. The lower the rating, the better the noise performance. The results are also shown in Table 1.

[0085] (Method for Evaluating Snow Performance) Each test tire was evaluated for lateral acceleration performance (snow performance 1) and braking performance (snow performance 2) when traveling on a snowy road surface on a test course. For snow performance 1, a vehicle was driven around a snowy road test course with a radius of 7 m at various speeds five times, and the lateral acceleration was calculated from the lap time for each lap. The lateral acceleration was evaluated using an index with the result for the comparative tire set at 100. For snow performance 2, a vehicle was driven on a snowy road surface, and the braking distance was measured when braking force was applied at 30 km / h to activate the ABS. The reciprocal of this value was calculated, and the result for the comparative tire was evaluated using an index with the result for the comparative tire set at 100. A higher score indicates better snow performance 1 and 2. These results are also shown in Table 1.

[0086]

[0087] According to Table 1, it can be seen that all of the tires of Invention Examples 1 to 12, which fall within the technical scope of the present invention (i.e., assuming that the groove widths of adjacent grooves in the tire circumferential direction are different, PTA1 (%) is 0% or more and less than 50%, and PTB2 (%) > PTB1 (%) and PTB2 (%) > PTB3 (%) are satisfied), maintain snow performance while improving noise performance compared to the comparative tire, which does not fall within the technical scope of the present invention.

[0088] REFERENCE SIGNS LIST 10 Tire 12 Tread surface 14, 14a, 14b, 14c, 14d Circumferential main groove 16 Center land portion 18, 20 Second land portion 22, 24 Shoulder land portion 26, 28 Bend groove 26a, 28a First portion 26b, 28b Second portion 26c, 28c Third portion 30 First lug groove 32, 36, 38, 42, 52 Sipe 34 Second lug groove 40 Third lug groove 44, 54 Small groove 46 Triangular groove 48, 56 Auxiliary groove 50 Fourth lug groove CL Tire equatorial plane CR Center region D1 First interval D2, D3 Second interval DB1 Circumferential length of third portion 26c of bent groove 26 DB2 Circumferential length of third portion 28c of bent groove 28 DG1: Length in the tire circumferential direction between one end and the other end of the bent groove 26 DG2: Length in the tire circumferential direction between one end and the other end of the bent groove 28 SR: Shoulder region W1, W2, W3, W4: Groove width

Claims

1. At least three land portions are defined by at least two circumferential main grooves, and on each side of the tire width direction of the tire equatorial plane, the groove width centerline of the circumferential main groove that is the outermost in the tire width direction is defined as a center region, and the groove width centerline is defined as a shoulder region, the center region being a region inside the tire width direction of the groove width centerline, and the shoulder region being a region outside the groove width centerline. At least one of the land portions formed in the center region is provided with at least two bent grooves, at least one end of which in the tire width direction is connected to the circumferential main groove and which has at least two bent portions, and the groove width of a first portion from one end of the bent groove to just before the first bent portion and the groove width of a second portion from the other end of the bent groove to just before the first bent portion are different between at least one pair of groove portions among groove portions adjacent in the tire circumferential direction, and the number of bent grooves present in the same land portion is defined as N. a first interval, which is a distance between two bent grooves adjacent in the tire circumferential direction, is defined as Ai (1≦i≦N) in order when measured around the entire tire circumference, and a second interval, which is between the first portion and the second portion is defined as Bi (1≦i≦N) in order when measured around the entire tire circumference, the tire circumference is defined as J (mm), the range of attention length caused by transfer characteristics is defined as S1 (mm), and the range of attention length caused by sound source is defined as S2 (mm) and S3 (mm), and within the range of S1 (mm) and S2 (mm) that satisfies 12.4≦S1 (mm)≦19.5, and J / (N×1.25×1)≦S2 (mm)≦J / (N×0.75×1), the larger of the lower limit values ​​of the two inequalities is defined as LFL1 and the smaller of the upper limit values ​​of the two inequalities is defined as HFL1, and 12.4≦S1 (mm)≦19.5, and Within the range of S1 (mm) and S3 (mm) which satisfies J / (N x 1.25 x 2) ≦ S3 (mm) ≦ J / (N x 0.75 x 2), the larger of the lower limit values ​​of the two inequalities is defined as LFL2 and the smaller of the upper limit values ​​of the two inequalities is defined as HFL2; condition TA1 defined by LFL1 x 1 < Ai (mm) < HFL1 x 1, or LFL2 x 1 < Ai (mm) < HFL2 x 1; condition TB1 defined by LFL1 x 1 < Bi (mm) < HFL1 x 1, or LFL2 x 1 < Bi (mm) < HFL2 x 1; conditions other than condition TB1, anda tire characterized in that: a condition TB2 defined as LFL1 x 0.5 < Bi (mm) < HFL1 x 0.5, or LFL2 x 0.5 < Bi (mm) < HFL2 x 0.5; and a condition TB3 defined as a condition other than condition TB1 and other than condition TB2; wherein, assuming that the proportion of intervals Ai that satisfy condition TA1 is PTA1 (%), the proportion of intervals Bi that satisfy condition TB1 is PTB1 (%), the proportion of intervals Bi that satisfy condition TB2 is PTB2 (%), and the proportion of intervals Bi that satisfy condition TB3 is PTB3 (%), PTA1 (%) is 0% or more and less than 50%, and PTB2 (%) > PTB1 (%) and PTB2 (%) > PTB3 (%) are satisfied.

2. The tire according to claim 1, wherein the PTB1(%) is 30% or less.

3. A tire as described in claim 1 or 2, wherein a tire circumferential length DG between one end and the other end of the bent groove is equal to or greater than a tire circumferential length DB of a third portion of the bent groove other than the first portion and the second portion.

4. The tire according to claim 1 or 2, wherein only the bent grooves are provided in the land portion in the center region.

5. A tire according to claim 1 or 2, wherein at least four land portions are defined by at least three circumferential main grooves.

6. A tire as described in claim 1 or 2, wherein, among the second land portions adjacent to each side in the tire width direction of the center land portion including the tire equatorial plane, the second land portion on the vehicle-mounted outer side is provided with a first lug groove that is connected to both of the circumferential main grooves on both sides in the tire width direction and whose inclination direction with respect to the tire width direction is reversed midway as it extends from the inner side to the outer side in the tire width direction, and the position where the extension direction of the first lug groove becomes the tire width direction is present in the outer region in the tire width direction within the second land portion.

7. A tire as described in claim 1 or 2, wherein, of the second land portions adjacent to each side in the tire width direction of the center land portion including the tire equatorial plane, the second land portion on the vehicle-mounted inner side is provided with a second lug groove that communicates with the circumferential main groove on the outer side in the tire width direction, extends from the outer side in the tire width direction to the inner side, and terminates in an inner region in the tire width direction of the second land portion.

8. A tire as described in claim 7, wherein a sipe is formed in the second land portion on the vehicle mounting inner side, the sipe communicating with the second lug groove and communicating with the circumferential main groove on the inner side in the tire width direction.

9. The tire according to claim 1 or 2, wherein an auxiliary groove is provided in the shoulder region on the outer side when mounted on a vehicle, the auxiliary groove extending in the tire circumferential direction and having a groove width of 5% to 40% of the groove width of the circumferential main groove at the outermost side in the tire width direction, and a third lug groove is provided extending from at least the ground contact edge toward the circumferential main groove, the third lug groove crossing the auxiliary groove and terminating within a land portion; and / or wherein an auxiliary groove is provided in the shoulder region on the inner side when mounted on a vehicle, the auxiliary groove extending in the tire circumferential direction and having a groove width of 5% to 40% of the groove width of the circumferential main groove at the outermost side in the tire width direction, and a fourth lug groove is provided extending from at least the ground contact edge toward the circumferential main groove, the fourth lug groove crossing the auxiliary groove and terminating within a land portion.

10. Among the second land portions adjacent to each side of the center land portion including the tire equatorial plane in the tire width direction, the second land portion on the outer side of the vehicle mounting is provided with a first lug groove that is connected to both of the circumferential main grooves on both sides in the tire width direction and whose inclination direction with respect to the tire width direction is reversed halfway as it extends from the inner side to the outer side in the tire width direction, and the point at which the extension direction of the first lug groove becomes the tire width direction is present in the outer region of the second land portion in the tire width direction; Among the second land portions adjacent to each side of the center land portion including the tire equatorial plane in the tire width direction, the second land portion on the inner side of the vehicle mounting is provided with a second lug groove that is connected to the circumferential main groove on the outer side in the tire width direction, extends from the outer side in the tire width direction to the inner side and terminates in the inner region of the second land portion in the tire width direction; In the shoulder regions on each side of the vehicle mounting, auxiliary grooves are provided that extend in the tire circumferential direction and have a groove width that is 5% to 40% of the groove width of the circumferential main groove on the outermost side in the tire width direction; 3. The tire according to claim 1 or 2, wherein a third lug groove is provided on an outer side mounted on a vehicle, extending from a ground contact edge toward the circumferential main groove, the third lug groove crossing the auxiliary groove and terminating within a land portion, and / or a fourth lug groove is provided on an inner side mounted on a vehicle, extending from a ground contact edge toward the circumferential main groove, the fourth lug groove crossing the auxiliary groove and terminating within a land portion, an outer portion of the first lug groove in the tire width direction and an inner portion of the third lug groove in the tire width direction are both inclined toward the same side with respect to the tire width direction, and an outer portion of the second lug groove in the tire width direction and an inner portion of the fourth lug groove in the tire width direction are both inclined toward the same side with respect to the tire width direction.

11. A tire as claimed in claim 1 or 2, wherein, of second land portions adjacent to each side in the tire width direction of a center land portion including the tire equatorial plane, the second land portion on the inner side when fitted to the vehicle has a second lug groove that communicates with the circumferential main groove on the outer side in the tire width direction, extends from the outer side in the tire width direction to the inner side and terminates in the inner region in the tire width direction of the second land portion, and an auxiliary groove is provided in the shoulder region on each side when fitted to the vehicle, extending in the tire circumferential direction and having a groove width that is 5% to 40% of the groove width of the circumferential main groove on the outermost side in the tire width direction, and a fourth lug groove is provided on the inner side when fitted to the vehicle, extending from the ground contact edge toward the circumferential main groove, and the fourth lug groove crosses the auxiliary groove and terminates within the land portion, and an average inclination angle of the second lug groove with respect to the tire width direction is greater than an average inclination angle of the fourth lug groove with respect to the tire width direction.

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