Heavy duty tire

Abstract

To provide a heavy load tire 2 capable of improving abrasion resistance while suppressing deterioration of wet performance.SOLUTION: The tire 2 includes a tread 4. The tread 4 includes a plurality of land portions 16 separated by the circumferential main grooves 10. The at least one land portion 16 includes a first narrow land portion 28a and a second narrow land portion 28b separated by the circumferential narrow groove 26. The top 32 of the first narrow land portion 28a includes a serration 46 having irregularities and a land 48 having no irregularities. The serration 46 is located between the widthwise center of the first narrow land portion 28a and the first edge 30a of the first narrow land portion 28a. Serration 46 includes a plurality of ridges 50. Two adjacent ridges 50 are separated by a narrow shallow groove 56.SELECTED DRAWING: Figure 8

Description

[Technical Field]

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

[0002] The tread has multiple land areas separated by circumferential main grooves. To improve driving performance on wet roads (hereinafter referred to as wet performance), sipes and narrow grooves are carved into the land areas. Sipes and narrow grooves reduce the rigidity of the land areas. Reduced rigidity can lead to reduced wear resistance. Various studies are being conducted to achieve both wet performance and wear resistance. Patent Document 1 below proposes providing crown lateral grooves that cross the crown land portion in order to improve the uneven wear resistance of the crown land portion while maintaining wet performance. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2021-054294 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a heavy-duty tire that can achieve improved wear resistance while suppressing deterioration in wet performance. [Means for solving the problem]

[0005] The heavy-duty tire according to the present invention has a tread located at the radially outermost position and extending in the circumferential direction. The tread has a plurality of land portions separated by circumferential main grooves. At least one land portion has a first narrow land portion and a second narrow land portion separated by a circumferential sub-groove. Of the two edges of each of the first narrow land portion and the second narrow land portion, the edge on the circumferential sub-groove side is a first edge, and the edge on the other side is a second edge. The top of the first narrow land portion has an uneven serration and a flat land. The serration is located between the width center of the first narrow land portion and the first edge of the first narrow land portion. The serration has a plurality of ridges. A narrow shallow groove is formed between two adjacent ridges. [Effects of the Invention]

[0006] According to the present invention, a heavy-duty tire can be obtained that can achieve improved wear resistance while suppressing deterioration in wet performance. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a development view showing a portion of a tread of a heavy duty tire according to one embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Figure 3] FIG. 2 is a cross-sectional view taken along line III-III in FIG. [Figure 4] FIG. 2 is a development view showing a part of FIG. [Figure 5] FIG. 5 is a cross-sectional view taken along line VV in FIG. [Figure 6] FIG. 10 is a development view showing a modified example of the serrations. [Figure 7] FIG. 10 is a development view showing a modified example of a land portion provided with serrations. [Figure 8] FIG. 10 is a development view showing another modified example of a land portion provided with serrations. [Figure 9] FIG. 9 is a cross-sectional view taken along line IX-IX in FIG. 8. [Figure 10] FIG. 10 is a cross-sectional view showing a modified example of a widthwise sipe. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, the present invention will be described in detail based on preferred embodiments, with appropriate reference to the drawings.

[0009] The tire of the present invention is mounted on a rim. The inside of the tire is filled with air, and the internal pressure of the tire is adjusted. A tire mounted on a rim is also called a tire-rim assembly. A tire-rim assembly includes a rim and a tire mounted on the rim.

[0010] In the present invention, a state in which a tire is mounted on a standard rim, the internal pressure of the tire is adjusted to a standard internal pressure, and no load is applied to the tire is referred to as a standard state.

[0011] In the present invention, unless otherwise specified, the dimensions and angles of each part of the tire are measured in a normal state. The dimensions and angles of each part of the tire's meridian cross section, which cannot be measured when the tire is mounted on a regular rim, are measured on a cut surface of the tire obtained by cutting the tire along a plane including the rotation axis. In this measurement, the tire is set so that the distance between the left and right beads matches the distance between the beads of the tire mounted on a regular rim. Note that the tire configuration, which cannot be confirmed when the tire is mounted on a regular rim, is confirmed on the cut surface.

[0012] A genuine rim is a rim specified in the standard on which the tire is based. The "standard rim" in the JATMA standard, the "design rim" in the TRA standard, and the "measuring rim" in the ETRTO standard are all genuine rims.

[0013] Normal tire pressure refers to the pressure specified in the standard on which the tire is based. The "maximum tire pressure" in the JATMA standard, the "maximum tire pressure" listed in the TRA standard's "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURE" and the "INFLATION PRESSURE" in the ETRTO standard are normal tire pressures.

[0014] Normal load refers to the load specified in the standard on which the tire is based. The "maximum load capacity" in the JATMA standard, the "maximum value" listed in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "LOAD CAPACITY" in the ETRTO standard are normal loads.

[0015] In the present invention, the tread portion of a tire is the portion of the tire that comes into contact with the road surface. The bead portion is the portion of the tire that fits onto the rim. The sidewall portion is the portion of the tire that bridges between the tread portion and the bead portion. A tire has the following portions: a tread portion, a pair of bead portions, and a pair of sidewall portions.

[0016] [Findings that form the basis of the present invention] As mentioned above, the tread has multiple land portions separated by circumferential main grooves. Reducing the number of circumferential main grooves in the tread and thus the number of land portions that make up the tread increases the volume per land portion. In this case, the tire's land portion rigidity can be increased. Increasing the rigidity of the land portion contributes to improved wear resistance. Reducing the number of circumferential main grooves cut into the tread reduces the tire's drainage performance. To improve wet performance while suppressing a decrease in the rigidity of the land portions, for example, circumferential narrow grooves are provided in the land portions.

[0017] The contact pressure of a tire tends to be low near the center of the land portion and high near the edge of the land portion. This contact pressure distribution has a detrimental effect on wet performance and wear resistance. Increasing the rigidity of the land portion and providing circumferential narrow grooves in the land portion may not sufficiently contribute to achieving both wet performance and wear resistance. In other words, if the contact pressure distribution of the land portion can be configured to be uniform without bias, it is expected that the wet performance and wear resistance of the tire can be further improved.

[0018] Therefore, the present inventors have conducted extensive research to establish a technology that can achieve improved wear resistance while suppressing deterioration in wet performance, and have completed the present invention, which will be described below.

[0019] [Outline of the embodiment of the present invention] The present invention provides a heavy-duty tire having a tread located at the radially outermost position and extending in the circumferential direction, the tread having a plurality of land portions separated by circumferential main grooves, at least one of the land portions having a first narrow land portion and a second narrow land portion separated by a circumferential sub-groove, the first narrow land portion and the second narrow land portion each having two edges, the edge on the circumferential sub-groove side being a first edge and the edge on the other side being a second edge, the top of the first narrow land portion having uneven serrations and a flat land, the serrations being located between the width center of the first narrow land portion and the first edge of the first narrow land portion, the serrations having a plurality of ridges, and a narrow shallow groove being formed between two adjacent ridges.

[0020] The heavy duty tire of the present invention can achieve improved wear resistance while suppressing deterioration of wet performance. The mechanism by which this effect is achieved has not been clarified, but is presumed to be as follows.

[0021] At least one of two narrow land portions separated by a circumferential sub-groove has a serration at its top. The serration reduces the contact area. The serration is located near the circumferential sub-groove. Because the contact area near the center of the land portion is reduced, the contact pressure near the center of the land portion increases and the contact pressure near the edge of the land portion decreases relatively. This results in a uniform contact pressure distribution without bias. In this tire, increasing the volume of the land portion increases the rigidity, and providing the circumferential sub-groove in the land portion effectively contributes to achieving both wet performance and wear resistance. This tire can improve wear resistance while suppressing a decrease in wet performance.

[0022] Preferably, the serration includes a plurality of serration portions arranged in a circumferential direction, Each of the plurality of serration portions includes a plurality of the ridges. In this case, the serrations can effectively contribute to forming a uniform contact pressure distribution on the land portion without bias. This tire can improve wear resistance while suppressing deterioration of wet performance.

[0023] Preferably, the tops of the first and second narrow land portions each include the serration and the land, the serration in the first narrow land portion being located between the width center of the first narrow land portion and the first edge of the first narrow land portion, the serration in the second narrow land portion being located between the width center of the second narrow land portion and the first edge of the second narrow land portion, and the serration in each of the first and second narrow land portions each include a plurality of the ridges. In this case, the tops of the two narrow land portions separated by the circumferential sub-groove each include a serration. Ground pressure near the center of the land portion increases, while ground pressure near the edge of the land portion decreases relatively. This results in a uniform ground pressure distribution without bias. This tire can improve wear resistance while suppressing deterioration in wet performance.

[0024] Preferably, the serrations of each of the first and second narrow land portions include a plurality of serration portions arranged in the circumferential direction, each of the plurality of serration portions including a plurality of ridges, and the serration portions of the first and second narrow land portions are arranged alternately in the circumferential direction. In this case, the serrations can effectively contribute to forming a uniform ground pressure distribution in the land portions without bias. This tire can improve wear resistance while suppressing deterioration of wet performance.

[0025] Preferably, the serrations of each of the first and second narrow land portions include a plurality of serration portions arranged in the circumferential direction, each of the plurality of serration portions including a plurality of ridges, and each of the first and second narrow land portions includes a plurality of widthwise sipes extending from the second edge of each of the first and second narrow land portions toward the first edge of each of the first and second narrow land portions. In each of the first and second narrow land portions, a block is formed between two adjacent widthwise sipes, and each block includes one of the serration portions. In this case, the widthwise sipes function as edge components, thereby improving the tire's wet performance. While the widthwise sipes affect the rigidity of the land portions, the serrations contribute to creating a uniform contact pressure distribution without bias, allowing the tire to maintain good wear resistance. This tire can achieve improved wear resistance while suppressing a deterioration in wet performance.

[0026] More preferably, the plurality of widthwise sipes of the first narrow land portion and the plurality of widthwise sipes of the second narrow land portion are arranged in a staggered pattern in the circumferential direction. In this case, the serration portion and the widthwise sipes can effectively contribute to suppressing a deterioration in wet performance and improving wear resistance. This tire can effectively improve wear resistance while effectively suppressing a deterioration in wet performance.

[0027] Preferably, the ratio of the groove depth of the lateral sipes to the groove depth of the circumferential main grooves is 70% or more and 90% or less. In this case, the lateral sipes can fully perform their functions until the tire reaches a terminal wear state requiring replacement. This tire can maintain good wet performance. Since the reduction in rigidity of the land portions due to the lateral sipes is suppressed, this tire can also maintain good wear resistance.

[0028] Preferably, the widthwise sipes extend in a zigzag pattern in the lengthwise and depthwise directions. In this case, a pair of wall surfaces of the widthwise sipes effectively mesh with each other. Deformation of the narrow land portions is effectively suppressed. This widthwise sipe can effectively contribute to improving wear resistance.

[0029] Preferably, the circumferential sub-groove is located at the center of the land portion. In this case, the ground contact pressure near the center of the land portion is increased, and the ground contact pressure near the edge of the land portion is relatively decreased. This results in a uniform ground contact pressure distribution without bias. This tire can improve wear resistance while suppressing deterioration of wet performance.

[0030] Preferably, the ratio of the groove depth of the circumferential sub-groove to the groove depth of the circumferential main groove is 70% or more and 90% or less. In this case, the circumferential sub-groove can fully perform its function until the tire reaches a terminal wear state requiring replacement. This tire can maintain good wet performance. Since the reduction in rigidity of the land portion due to the circumferential sub-groove is suppressed, this tire can also maintain good wear resistance.

[0031] Preferably, the narrow shallow groove is connected to the circumferential sub-groove at its end on the circumferential sub-groove side. In this case, the narrow shallow groove promotes the drainage of water present between the tire and the road surface. The serrations can effectively contribute to improving the tire's drainage performance. This tire can achieve improved wet performance.

[0032] Preferably, the top of the ridge is positioned radially inward of the land, or the top of the ridge is positioned radially inward of the land. In this case, excessive ground pressure at the serrations is suppressed. The ground pressure distribution in the land portion is uniform and not biased. This tire can improve wear resistance while suppressing deterioration of wet performance.

[0033] In heavy-duty tires, the area between the two shoulder land portions, in other words, the crown portion, tends to have high ground contact pressure and is prone to wear. The crown portion has a long contact length, and water tends to accumulate in the crown portion. Therefore, in this heavy-duty tire, in order to achieve both wet performance and wear resistance, the main land portion located between the two shoulder land portions is preferably tuned as follows.

[0034] Preferably, among the plurality of land portions, the two land portions located axially outermost are shoulder land portions, and the land portion located between the two shoulder land portions is a main land portion, and at least one of the main land portions includes the first narrow land portion and the second narrow land portion separated by the circumferential sub-groove. In this case, the ground pressure near the center of the main land portion is increased, and the ground pressure near the edge of the main land portion is relatively decreased. This results in a uniform ground pressure distribution without bias. This tire can improve wear resistance while suppressing deterioration of wet performance.

[0035] As described above, according to the present invention, a heavy-duty tire can be obtained that can achieve improved wear resistance while suppressing deterioration of wet performance. This will be explained in detail below using a heavy-duty tire 2 (hereinafter referred to as tire 2) shown in Figure 1 as an example.

[0036] [Details of the embodiment of the present invention] 1 is a plan view showing a part of a tread 4 of a tire 2 according to one embodiment of the present invention in a developed form. The tire 2 is mounted on vehicles such as trucks and buses.

[0037] The direction indicated by the double arrow AD is the axial direction of the tire 2. The axial direction of the tire 2 means the direction parallel to the axis of rotation of the tire 2. The direction indicated by the double arrow CD is the circumferential direction of the tire 2. The circumferential direction of the tire 2 coincides with the direction of rotation of the tire 2. The direction perpendicular to the plane of the paper in Figure 1 is the radial direction of the tire 2. The dashed dotted line EL extending in the circumferential direction represents the equatorial plane of the tire 2.

[0038] In the axial direction, the direction away from the equatorial plane is the axially outer side of the tire 2, and the direction approaching the equatorial plane is the axially inner side of the tire 2. The direction indicated by arrow CD1 is the first circumferential side of the tire 2, and the direction indicated by arrow CD2 is the second circumferential side of the tire 2.

[0039] The tire 2 has a tread 4. The tread 4 is one of the elements that constitute the internal structure of the tire 2. In the present invention, the internal structure of the tire 2 is not particularly important. Although not described in detail, the tire 2 has a general internal structure as the internal structure of a heavy-duty tire.

[0040] The tread 4 is made of cross-linked rubber. The tread 4 is located at the radially outermost part of the tire 2. The tread 4 extends in the circumferential direction. The tread 4 has a tread surface 6. The tire 2 comes into contact with the road surface at the tread surface 6. Grooves 8 are cut into the tread 4. This forms a tread pattern.

[0041] The tread pattern shown in Figure 1 is one example of a tread pattern configured in the tread 4 of the tire 2 of the present invention. The tread pattern shown in Figure 1 is the tread pattern of a new tire 2 that is not worn.

[0042] The intersection of the tread surface 6 and the equatorial plane is the equator. When the grooves 8 are located on the equatorial plane, the equator is identified based on a virtual tread surface obtained by assuming that the grooves 8 are not on the equatorial plane.

[0043] A solid line TE extending in the circumferential direction represents the edge of the tread surface 6. In a tire, if the edge of the tread surface cannot be identified visually, the position on the outer surface of the tire corresponding to the axially outer edge of the contact patch obtained by applying a normal load to a normal tire in a normal state, setting the camber angle to 0°, and bringing the tire into contact with a flat surface is used as the edge of the tread surface.

[0044] 1, the length indicated by the double arrow TW is the width of the tread 4. The width TW of the tread 4 is the axial distance from one end TE to the other end TE of the tread surface 6. The width TW of the tread 4 is measured along the tread surface 6.

[0045] 2 shows a cross section of a groove 8. The direction indicated by the double arrow RD is the radial direction of the tire 2. The side indicated by the arrow RD1 is the radially outer side of the tire 2, and the side indicated by the arrow RD2 is the radially inner side of the tire 2. In the present invention, the cross section of the groove 8 is represented by a cross section along a plane perpendicular to the longitudinal direction of the groove 8. 2 is a cross section of a center circumferential main groove, which will be described later. The main configuration of the groove 8 will be described based on the cross section of the center circumferential main groove.

[0046] The groove 8 has a pair of wall surfaces 8S including a groove mouth 8M, and a bottom surface 8B including a groove bottom 8T. Unless otherwise specified, the groove bottom 8T is represented by the position where the distance from the reference plane RP to the bottom surface 8B is greatest, measured along the normal to the reference plane RP, which is a plane including the pair of edges 8E that form the groove opening 8M. If the bottom surface 8B is flat, the groove bottom 8T is represented by the center position of the bottom surface 8B. If a protrusion is provided on the bottom surface 8B, the groove bottom 8T is determined based on a virtual bottom surface obtained assuming that the protrusion is not present. The normal line of the reference plane RP that connects the reference plane RP and the groove bottom 8T is the reference normal line RN, and the direction of this reference normal line RN is the depth direction of the groove 8. The groove width of a groove 8 is expressed as the shortest distance between one wall surface 8S and the other wall surface 8S (hereinafter referred to as the wall-to-wall distance). Unless otherwise specified, the wall-to-wall distance is measured along a line perpendicular to the reference normal line RN. When the profile of the tread surface 6 can be confirmed, the groove bottom 8T and groove width may be specified using the profile of the tread surface 6 as the reference surface RP.

[0047] In FIG. 2, the length indicated by the double-headed arrow WG is the groove width of the groove 8 at the groove mouth 8M. If the groove mouth 8M of the groove 8 is tapered, the groove width of the groove 8 at the groove mouth 8M is expressed based on a virtual edge obtained by assuming that the groove is not tapered. The length indicated by the double-headed arrow DG is the groove depth of the groove 8. Unless otherwise specified, the groove depth DG of the groove 8 is expressed as the distance from the reference plane RP to the groove bottom 8T of the groove 8, measured along the reference normal line RN. The position, groove width WG, and groove depth DG of the groove 8 are determined appropriately according to the specifications of the tire 2.

[0048] A groove 8 having a groove width WG of less than 1.0 mm at its groove mouth 8M is called a sipe. A groove 8 other than a sipe is called a normal groove. A normal groove has a groove width WG of 1.0 mm or more at its groove mouth 8M. The sipe may include a portion having a groove width of 1.0 mm or more between the groove mouth 8M and the groove bottom 8T (hereinafter referred to as a portion equivalent to a normal groove). In this case, as the tread 4 wears and the portion equivalent to a normal groove becomes exposed, the sipe changes into a normal groove. The normal groove may include a portion (a portion corresponding to a sipe) having a groove width of less than 1.0 mm between the groove mouth 8M and the groove bottom 8T. In this case, the normal groove changes into a sipe when the tread 4 wears and the portion corresponding to the sipe becomes exposed. Even among ordinary grooves, those with a narrow groove width and a pair of wall surfaces that can come into contact with each other when the tire comes into contact with the road surface are also called narrow grooves, while ordinary grooves with a wide groove width and a pair of wall surfaces that do not come into contact with each other when the tire comes into contact with the road surface are also called main grooves.

[0049] The tread 4 has a circumferential main groove 10. The circumferential main groove 10 extends continuously in the circumferential direction. The circumferential main groove 10 is the main groove described above. The circumferential main groove 10 has a wide groove width. A pair of wall surfaces 10S of the circumferential main groove 10 do not come into contact with each other even when the tire 2 comes into contact with the road surface.

[0050] The groove depth DGm of the circumferential main groove 10 is, for example, 8 mm or more and 21 mm or less. From the viewpoint of enabling the tire 2 to exhibit good wet performance, the groove depth DGm is preferably 13 mm or more and 18 mm or less. The groove width WGm of the circumferential main groove 10 is preferably 4.0% or more and 10% or less of the width TW of the tread 4.

[0051] 1, a plurality of circumferential main grooves 10 aligned in the axial direction are formed in the tread 4 of this tire 2. The tread 4 includes a plurality of circumferential main grooves 10 aligned in the axial direction.

[0052] In the present invention, when the tread has multiple circumferential main grooves aligned in the axial direction, the two circumferential main grooves located at the outermost positions in the axial direction are shoulder circumferential main grooves. The circumferential main groove located on the equatorial plane is the center circumferential main groove. When there is no circumferential main groove on the equatorial plane, the circumferential main groove located in the zone between the equatorial plane and the edge of the tread surface and closest to the equatorial plane is the center circumferential main groove. When a circumferential main groove is located between the center circumferential main groove and the shoulder circumferential main groove, the circumferential main groove located between the center circumferential main groove and the shoulder circumferential main groove is the middle circumferential main groove.

[0053] The tread 4 of this tire 2 has three circumferential main grooves 10. Of the three circumferential main grooves 10, the axially outermost circumferential main groove 12 is a shoulder circumferential main groove. The circumferential main groove 14 located on the equatorial plane is a center circumferential main groove. This tread 4 has a center circumferential main groove 14 and a pair of shoulder circumferential main grooves 12. In the tread portion T of the tire 2, a portion between the two shoulder circumferential main grooves 12 is also called a crown portion, and portions axially outward of each shoulder circumferential main groove 12 are also called shoulder portions.

[0054] In the present invention, when the groove depth of the center circumferential main groove 14 and the groove depth of the shoulder circumferential main grooves 12 are different, the groove depth of the center circumferential main groove 14 is used as the groove depth DGm of the circumferential main groove 10 .

[0055] As described above, the tread 4 includes a plurality of circumferential main grooves 10. The plurality of circumferential main grooves 10 define a plurality of land portions 16 in the tread 4. The tread 4 includes a plurality of land portions 16 separated by the circumferential main grooves 10.

[0056] In the present invention, among the multiple land portions configured in the tread, the two land portions located at the outermost positions in the axial direction are shoulder land portions. The land portion located between the two shoulder land portions is a main land portion. The tread of the present invention comprises two shoulder land portions and at least one main land portion. When there is one main land portion located between two shoulder land portions, this one main land portion is the crown land portion. When there are multiple main land portions between two shoulder land portions and the multiple main land portions include a main land portion located on the equatorial plane, the main land portion located on the equatorial plane is the crown land portion. When there are no main land portions located on the equatorial plane, the main land portion located between the equatorial plane and the shoulder land portion that is closest to the equatorial plane is the crown land portion. When a main land portion is located adjacent to a crown land portion, the main land portion located adjacent to the crown land portion is a middle land portion.

[0057] The tread 4 of this tire 2 has four land portions 16. The four land portions 16 are arranged symmetrically with respect to the equatorial plane. Of the four land portions 16, two land portions 18 located axially outermost are shoulder land portions. The shoulder land portions 18 include the edge TE of the tread surface 6. The two land portions 20 located between the two shoulder land portions 18 are main land portions. In the case of this tire 2, each of the two main land portions 20 is the main land portion 20 closest to the equatorial plane among the main land portions 20 located between the equatorial plane and the shoulder land portions 18, and is therefore also referred to as a crown land portion 22. The tread 4 includes two shoulder land portions 18 and two main land portions 20 located between the two shoulder land portions 18.

[0058] The width of the land portion 16 formed in the tread 4 is represented by the axial distance from one edge 16E of the land portion 16 to the other edge 16E, and is equal to the axial width of the top 24 of the land portion 16. When the width of the land portion 16 varies in the circumferential direction, the width of the land portion 16 is represented by the average of the maximum and minimum width values. The width of the land portion 16 formed in the tread 4 is determined appropriately taking into consideration the specifications of the tire 2.

[0059] As described above, the tread 4 includes a plurality of land portions 16. At least one of the plurality of land portions 16 includes a circumferential sub-groove . In the tread 4 shown in Fig. 1, two main land portions 20 located between two shoulder land portions 18 each have one circumferential sub-groove 26. Only one of the main land portions 20 may have the circumferential sub-groove 26, or the shoulder land portion 18 may have the circumferential sub-groove 26 rather than the main land portion 20. All four land portions 16 provided in the tread 4 may have the circumferential sub-groove 26.

[0060] Fig. 3 shows a cross section of the circumferential sub-groove 26. Fig. 3 shows a cross section of the circumferential sub-groove 26 provided in the main land portion 20 (specifically, the crown land portion 22). The circumferential sub-groove 26 extends straight in the depth direction thereof. The circumferential sub-groove 26 has a pair of wall surfaces 26S including a groove mouth 26M, and a bottom surface 26B including a groove bottom 26T. 3, the double-headed arrow WGs indicates the groove width at the groove mouth 26M of the circumferential sub-groove 26. The double-headed arrow DGs indicates the groove depth of the circumferential sub-groove 26. The double-headed arrow WL indicates the width of the land portion 16 (i.e., the crown land portion 22) having the circumferential sub-groove 26.

[0061] The circumferential sub-groove 26 has a groove width WGs that is narrower than the groove width WGm of the circumferential main groove 10. The groove width WGs of the circumferential sub-groove 26 in FIG. 3 is 2.0 mm or less. This circumferential sub-groove 26 may be the aforementioned sipe or the aforementioned narrow groove. The pair of wall surfaces 26S of this circumferential sub-groove 26 come into contact with each other when the land portion 16 comes into contact with the road surface and deforms. This allows the two narrow land portions, which will be described later, to support each other.

[0062] The ratio WGs / WL of the groove width WGs of the circumferential sub-groove 26 to the width WL of the land portion 16 is preferably 5% or less. This reduces the effect of the circumferential sub-groove 26 on the rigidity of the land portion 16. Since the land portion 16 has appropriate rigidity, the tire 2 can have improved wear resistance. From this perspective, the ratio WGs / WL is more preferably 4% or less. The ratio WGs / WL is preferably equal to or greater than 2%, which allows the circumferential sub grooves 26 to contribute to drainage and maintain good wet performance of the tire 2. From this viewpoint, the ratio WGs / WL is more preferably equal to or greater than 3%.

[0063] The ratio DGs / DGm of the groove depth DGs of the circumferential sub groove 26 to the groove depth DGm of the circumferential main groove 10 is preferably 70% or more and 90% or less. By setting the ratio DGs / DGm to 70% or more, the circumferential sub grooves 26 can fully demonstrate their functions until the tire reaches a final stage of wear, which requires replacement with a new tire 2. This tire 2 can suppress deterioration in wet performance. From this viewpoint, it is more preferable that the ratio DGs / DGm be 75% or more. Setting the ratio DGs / DGm to 90% or less suppresses the effect of the circumferential sub grooves 26 on the rigidity of the land portion 16. Since the land portion 16 has appropriate rigidity, the wear resistance of the tire 2 can be improved. From this viewpoint, it is more preferable that the ratio DGs / DGm be 80% or less.

[0064] 3, the dashed dotted line LH is the center line of the circumferential sub-groove 26. The double-headed arrow WH indicates the axial distance from the edge 16E of the land portion 16 to the center line LH of the circumferential sub-groove 26.

[0065] The ratio WH / WL of the axial distance WH from the edge 16E of the land portion 16 to the center line LH of the circumferential sub-groove 26 to the width WL of the land portion 16 is preferably 40% or more and 60% or less. This appropriately maintains the difference in rigidity between the first narrow land portion 28a located on one side of the circumferential sub-groove 26 and the second narrow land portion 28b located on the other side. Since abnormal deformation in the land portion 16 is suppressed, the occurrence of uneven wear is suppressed. The tire 2 can improve drainage performance and wear resistance by providing the circumferential sub-groove 26. From this perspective, the ratio WH / WL is more preferably 45% or more and 55% or less. It is particularly preferable that the ratio WH / WL is 50%, that is, the circumferential sub-groove 26 is located at the center of the land portion 16.

[0066] The circumferential sub-groove 26 defines two narrow land portions 28 in the land portion 16. The land portion 16 includes two narrow land portions 28 separated by the circumferential sub-groove 26. In this specification, for ease of explanation, the narrow land portion 28a on the equatorial plane side is referred to as a first narrow land portion, and the narrow land portion 28b on the other side is referred to as a second narrow land portion. The first narrow land portion refers to one of the two narrow land portions defined in the land portion, and the second narrow land portion refers to the other narrow land portion. Therefore, the narrow land portion 28a on the equatorial plane side may be referred to as the second narrow land portion, and the narrow land portion 28b on the other side may be referred to as the first narrow land portion.

[0067] In the tire 2, at least one land portion 16 among the multiple land portions 16 formed in the tread 4 includes a first narrow land portion 28a and a second narrow land portion 28b separated by a circumferential sub-groove 26. Of the two edges 30 that each of the first narrow land portion 28a and the second narrow land portion 28b has, the edge 30a on the circumferential sub-groove 26 side is a first edge, and the edge 30b on the other side is a second edge. The edge 30 of the narrow land portion 28 is also the end of the top 32 of the narrow land portion 28. The second edge 30b of the first narrow land portion 28a is the edge 16E on the equatorial plane side of the land portion 16, and the second edge 30b of the second narrow land portion 28b is the edge 16E on the other side of the land portion 16. The second edge 30b of the first narrow land portion 28a is also the edge 14E of the center circumferential main groove 14, and the second edge 30b of the second narrow land portion 28b is also the edge 12E of the shoulder circumferential main groove 12.

[0068] 1 , the shoulder land portion 18 of the tire 2 is provided with a circumferential shallow groove 34. Although not described in detail, the groove width of the circumferential shallow groove 34 is wider than the groove width of the circumferential sub-groove 26 and narrower than the groove width of the circumferential main groove 10. The circumferential shallow groove 34 is shallower than the circumferential sub-groove 26 and the circumferential main groove 10. The circumferential shallow grooves 34 extend continuously in the circumferential direction. The circumferential shallow grooves 34 form two shoulder narrow land portions 36 in the shoulder land portion 18. For ease of explanation, of the two shoulder narrow land portions 36, the shoulder narrow land portion 36a on the equator plane side will be referred to as the first shoulder narrow land portion, and the shoulder narrow land portion 36b on the other side will be referred to as the second shoulder narrow land portion. Of the two edges 38 that each of the first shoulder narrow land portion 36a and the second shoulder narrow land portion 36b has, the edge 38a on the circumferential shallow groove 34 side is a first edge, and the edge 38b on the other side is a second edge. The edge 38 of the shoulder narrow land portion 36 is also the end of the top 40 of the shoulder narrow land portion 36. The second edge 38b of the first shoulder narrow land portion 36a is the edge 18E on the equatorial plane side of the shoulder land portion 18, and is also the edge 12E of the shoulder circumferential main groove 12. The second edge 38b of the second shoulder narrow land portion 36b is the edge 18E on the other side of the shoulder land portion 18, and is also the edge TE of the tread surface 6.

[0069] Each of the first shoulder narrow land portion 36a and the second shoulder narrow land portion 36b has a plurality of widthwise shallow grooves 42 aligned in the circumferential direction. The widthwise shallow grooves 42 have a groove width and groove depth that are approximately the same as those of the circumferential shallow grooves 34. The widthwise shallow groove 42 of the first shoulder narrow land portion 36a bridges between the circumferential shallow groove 34 and the shoulder circumferential main groove 12. The widthwise shallow groove 42 of the second shoulder narrow land portion 36b bridges between the circumferential shallow groove 34 and the edge TE of the tread surface 6.

[0070] The widthwise shallow grooves 42 define a plurality of shoulder blocks 44 arranged in the circumferential direction in each of the first shoulder narrow land portion 36a and the second shoulder narrow land portion 36b. As shown in FIG. 1, the shoulder blocks 44 in the first shoulder narrow land portion 36a and the shoulder blocks 44 in the second shoulder narrow land portion 36b are arranged alternately in the circumferential direction.

[0071] 1, the top 32 of the first narrow land portion 28a includes serrations 46 and lands 48. The top 32 of the second narrow land portion 28b includes the lands 48. The top 32 of the second narrow land portion 28b is composed of the lands 48.

[0072] As will be described later, the serrations 46 are provided with a plurality of ridges. The serrations 46 are configured with an undulating surface. In contrast, the lands 48 are configured with flat surfaces. Although not described in detail, in a cross section of the tire 2 taken along a plane including the rotation axis of the tire 2 (also called a meridian cross section), the contour of the lands 48 coincides with the contour of the tread surface 6.

[0073] The top 32 of the first narrow land portion 28a includes serrations 46 with irregularities and lands 48 with no irregularities. In the tire 2, it is sufficient that the top 32 of one of the two narrow land portions 28 configured in the land portion 16 is provided with the serrations 46. The top 32 of the second narrow land portion 28b, rather than the top 32 of the first narrow land portion 28a, may be provided with the serrations 46 and the land 48. The top 32 of each of the first narrow land portion 28a and the second narrow land portion 28b may be provided with the serrations 46 and the land 48.

[0074] Fig. 4 shows a part of the development view of Fig. 1. In Fig. 4, a dashed line CL indicates the width center of the narrow land portion 28. The serrations 46 extend in the circumferential direction. The serrations 46 have a uniform width in the circumferential direction. As shown in Figure 4, the serrations 46 of the narrow land portion 28 are located between the width center CL of the narrow land portion 28 and the first edge 30a of the narrow land portion 28.

[0075] FIG. 5 shows a cross section of the serration 46. The serrations 46 include a plurality of ridges 50. The ridges 50 are protrusions that protrude from the reference plane SB of the serrations 46 and have a certain length. The ridges 50 extend in the length direction. The cross section of the serrations 46 shown in FIG. 5 is a cross section of the serrations 46 taken along a plane perpendicular to the length direction of the ridges 50.

[0076] The ridge 50 tapers from the reference plane SB toward a top 52 of the ridge 50. The ridge 50 has a top 52 and a pair of side surfaces 54 that bridge between the top 52 and the reference plane SB. The thick solid line drawn on the serration 46 in Figure 4 represents the top 52 of the ridge 50. The ridge 50 extends straight.

[0077] The serration 46 has a plurality of ridges 50 arranged at predetermined intervals. As shown in FIG. 5 , a groove is formed between two adjacent ridges 50. In this tire 2, the groove formed between two adjacent ridges 50 is called a narrow shallow groove. In the serration 46, the space between two adjacent ridges 50 is a narrow shallow groove 56. Since the serration 46 has a plurality of parallel ridges 50, the serration 46 has a plurality of narrow shallow grooves 56. The aforementioned reference plane SB is the bottom surface of the narrow shallow groove 56. The side surface 54 of the ridge 50 is the wall surface of the narrow shallow groove 56. The end of the narrow shallow groove 56 on the circumferential sub groove 26 side is called a first end 56e1 of the narrow shallow groove 56, and the other end of the narrow shallow groove 56 is called a second end 56e2 of the narrow shallow groove 56. The narrow shallow groove 56 extends straight from its first end 56e1 to its second end 56e2.

[0078] In this tire 2, the top 32 of at least one of two narrow land portions 28 separated by a circumferential sub-groove 26 is provided with a serration 46. The serration 46 includes a plurality of parallel narrow shallow grooves 56. The serration 46 is configured with an uneven surface. The bottom surface SB of the narrow shallow grooves 56 does not come into contact with the road surface. The serration 46 reduces the contact area of ​​the narrow land portion 28. As described above, the serrations 46 are located between the width center CL of the narrow land portion 28 and the first edge 30a of the narrow land portion 28. The serrations 46 are located near the circumferential sub-groove 26. By providing the serrations 46, the contact area near the center of the land portion 16 is reduced. The contact pressure near the center of the land portion 16 is increased, and the contact pressure near the edge 16E of the land portion 16 is relatively reduced. This results in a uniform contact pressure distribution in the land portion 16. Increasing the volume of the land portion 16 to increase the rigidity of the land portion 16 for improved wear resistance, and providing the circumferential sub-groove 26 in the land portion 16 for improved wet performance, which is reduced by increasing the volume of the land portion 16, can effectively contribute to achieving both wet performance and wear resistance of the tire 2. This tire 2 can improve wear resistance while suppressing a decrease in wet performance.

[0079] As described above, the serrations 46 are located between the width center CL of the narrow land portion 28 and the first edge 30a of the narrow land portion 28. Of the first end 56e1 and second end 56e2 of the narrow shallow groove 56, the second end 56e2 located closer to the width center CL is located within the narrow land portion 28. In contrast, the first end 56e1 located closer to the first edge 30a (in other words, the position of the end 56e1 of the narrow shallow groove 56 on the circumferential sub-groove 26 side) coincides with the position of the edge 26E of the circumferential sub-groove 26. In other words, the narrow shallow groove 56 connects to the circumferential sub-groove 26 at its end on the circumferential sub-groove 26 side. This allows the narrow shallow groove 56 to promote the discharge of water present between the tire 2 and the road surface. The serrations 46 can effectively contribute to improving the drainage performance of the tire 2. This tire 2 can achieve improved wet performance. From this viewpoint, it is preferable that the narrow shallow groove 56 be connected to the circumferential sub-groove 26 at its end on the circumferential sub-groove 26 side.

[0080] In Figure 4, the dashed-dotted line LR is the center line of the ridge 50 and represents the direction in which the ridge 50 extends. The ridge 50 intersects with the equatorial plane. In other words, the ridge 50 is inclined with respect to the circumferential direction. The angle α is the angle between the center line LR of the ridge 50 and the dashed-dotted line EL representing the equatorial plane. The angle α is the angle the ridge 50 forms with respect to the circumferential direction. The angle α is also called the inclination angle of the ridge 50.

[0081] The inclination angle α of the ridge 50 is preferably 30 degrees or more and 90 degrees or less. This allows the narrow shallow grooves 56 formed in the serrations 46 by providing multiple ridges 50 to effectively contribute to improving the drainage performance of the tire 2. The ridges 50 can effectively function as edge components. This tire 2 can improve wet performance. From this perspective, the inclination angle α of the ridges 50 is more preferably 45 degrees or more and 90 degrees or less.

[0082] 5, the double-headed arrow HR indicates the height of the ridge 50. The height HR of the ridge 50 is also the groove depth of the narrow shallow grooves 56. The double-headed arrow DR indicates the interval between adjacent ridges 50. The interval DR is also called the pitch of the ridges 50.

[0083] The height HR of the ridge 50 is preferably 0.1 mm or more and 2.5 mm or less. By setting the height HR of the ridge 50 to 0.1 mm or more, the serrations 46 can contribute to forming a uniform distribution of contact pressure in the land portion 16 without bias and to improving the drainage performance of the tire 2. This tire 2 can maintain good wet performance. From this viewpoint, the height HR is more preferably 0.3 mm or more, and even more preferably 0.5 mm or more. By setting the height HR of the ridge 50 to 2.5 mm or less, the rigidity of the ridge 50 is appropriately maintained. The serrations 46 are prevented from becoming the starting point of wear. The tire 2 can have improved wear resistance. From this viewpoint, the height HR is more preferably 2.0 mm or less, and even more preferably 1.5 mm or less.

[0084] The distance DR between adjacent ridges 50 is preferably 0.5 mm or more and 1.5 mm or less. By setting the distance DR to 0.5 mm or more, the serrations 46 can contribute to forming a uniform distribution of contact pressure in the land portion 16 without bias and to improving the drainage performance of the tire 2. This tire 2 can maintain good wet performance. From this viewpoint, it is more preferable that the distance DR be 0.8 mm or more. By setting the distance DR to 1.5 mm or less, stress concentration on the ridge 50 is suppressed. The serrations 46 are suppressed from becoming a starting point for wear. This tire 2 can have improved wear resistance. From this viewpoint, the distance DR is more preferably 1.3 mm or less.

[0085] 5, the solid line LS represents the height direction of the ridge 50. The height direction of the ridge 50 coincides with the depth direction of the narrow shallow grooves 56. The angle β is the angle between the side surface 54 of the ridge 50 and the solid line LS. The angle β is the angle that the side surface 54 of the ridge 50 forms with respect to the height direction of the ridge 50, and is also called the inclination angle of the side surface 54.

[0086] The inclination angle β of the side surface 54 is preferably 15 degrees or more and 50 degrees or less. By setting the inclination angle β of the side surface 54 to 15 degrees or more, the rigidity of the ridge 50 is maintained. The serrations 46 are prevented from becoming a starting point for wear. This tire 2 can have improved wear resistance. From this viewpoint, it is more preferable that the inclination angle β be 30 degrees or more. By setting the inclination angle β of the side surface 54 to 50 degrees or less, the narrow shallow grooves 56 formed by the multiple ridges 50 can effectively contribute to improving the drainage performance of the tire 2. This tire 2 can effectively improve wet performance. From this perspective, it is more preferable that the inclination angle β be 40 degrees or less.

[0087] As shown in FIG. 5 , the top 52 of the ridge 50 is located radially inward of the land 48. Although not shown, the position of the top 52 of the ridge 50 may coincide with the position of the land 48 in the radial direction. In the tire 2, the position of the top 52 of the ridge 50 coincides with the position of the land 48 in the radial direction, or the top 52 of the ridge 50 is located radially inward of the land 48. This prevents the ground contact pressure from increasing excessively in the serrations 46. The ground contact pressure distribution of the land portion 16 is uniform and not biased. The tire 2 can improve wear resistance while preventing a decrease in wet performance. From this perspective, it is preferable that the position of the top 52 of the ridge 50 coincides with the position of the land 48 in the radial direction, or the top 52 of the ridge 50 is located radially inward of the land 48.

[0088] 5, the double-headed arrow TL indicates the distance from the land 48 to the top 52 of the ridge 50. This distance TL is measured along the normal to the land 48. As described above, it is preferable that the position of the top 52 of the ridge 50 coincides with the position of the land 48 in the radial direction, or that the top 52 of the ridge 50 be located radially inward of the land 48. In other words, it is preferable that the distance TL from the land 48 to the top 52 of the ridge 50 be 0 mm or more. From the viewpoint of achieving both wet performance and wear resistance of the tire 2, the distance TL is preferably 2.0 mm or less, more preferably 1.5 mm or less, and even more preferably 1.0 mm or less.

[0089] 6 shows a modified example of the serration 46. This serration 46 has a plurality of serration portions 58 arranged in the circumferential direction. The plurality of serration portions 58 are arranged at predetermined intervals in the circumferential direction. This serration 46 extends intermittently in the circumferential direction.

[0090] The serration portion 58 has a shape that is long in the circumferential direction and short in the axial direction. The shape of the serration portion 58 shown in Figure 6 is an isosceles trapezoid, but the shape of the serration portion 58 may also be a parallelogram or a rectangle.

[0091] In the serration 46 of FIG. 6, each of the multiple serration portions 58 constituting the serration 46 includes the multiple ridges 50 described above. In other words, each of the multiple serration portions 58 includes multiple parallel narrow shallow grooves 56. The serration portions 58 are configured with an uneven surface. The serration portions 58 reduce the contact area of ​​the narrow land portions 28. The serrations 46 shown in FIG. 6 are also located between the width center CL of the narrow land portion 28 and the first edge 30a of the narrow land portion 28. The serrations 46 are located near the circumferential sub-groove 26. By providing the serrations 46, the contact area near the center of the land portion 16 is reduced. The contact pressure near the center of the land portion 16 increases, and the contact pressure near the edge 16E of the land portion 16 decreases relatively. This results in a uniform contact pressure distribution in the land portion 16. The serration 46 in FIG. 6 can effectively adjust the contact pressure distribution of the land portion 16 by changing the length of the serration portion 58. The serration 46 can effectively contribute to forming a uniform contact pressure distribution of the land portion 16 without bias. The tire 2 can improve wear resistance while suppressing a decrease in wet performance. From this perspective, it is preferable that the serration 46 has a plurality of serration portions 58 arranged in the circumferential direction, and that each of the plurality of serration portions 58 has a plurality of ridges 50. From the viewpoint of effectively adjusting the ground pressure distribution of the land portion 16, the serrations 46 provided on the top 32 of the narrow land portion 28 are preferably serrations 46 that extend intermittently in the circumferential direction rather than serrations 46 that extend continuously in the circumferential direction.

[0092] Fig. 7 shows a modified example of the land portion 16 provided with serrations 46. In Fig. 7, a dashed line CL1 indicates the width center of the first narrow land portion 28a, and a dashed line CL2 indicates the width center of the second narrow land portion 28b. 7, the top 32 of each of the first narrow land portion 28a and the second narrow land portion 28b includes serrations 46 and lands 48. The serrations 46 include the above-mentioned multiple ridges 50. The serrations 46 of the first narrow land portion 28a reduce the ground contact area of ​​the first narrow land portion 28a, and the serrations 46 of the second narrow land portion 28b reduce the ground contact area of ​​the second narrow land portion 28b.

[0093] As shown in FIG. 7 , the serrations 46 in the first narrow land portion 28a are located between the width center CL1 of the first narrow land portion 28a and the first edge 30a of the first narrow land portion 28a. The serrations 46 in the second narrow land portion 28b are located between the width center CL2 of the second narrow land portion 28b and the first edge 30a of the second narrow land portion 28b. The serrations 46 in the first narrow land portion 28a and the serrations 46 in the second narrow land portion 28b are located near the circumferential sub-groove 26. By providing the serrations 46 in each of the first narrow land portion 28a and the second narrow land portion 28b, the contact area near the center of the land portion 16 is effectively reduced. The contact pressure near the center of the land portion 16 is increased, and the contact pressure near the edge 16E of the land portion 16 is relatively reduced. This results in a uniform contact pressure distribution in the land portion 16. Increasing the volume of the land portion 16 to increase the rigidity of the land portion 16 in order to improve wear resistance, and providing the circumferential sub grooves 26 in the land portion 16 in order to improve wet performance that would otherwise be reduced due to the increased volume of the land portion 16, can effectively contribute to achieving both wet performance and wear resistance of the tire 2. The tire 2 can improve wear resistance while suppressing a reduction in wet performance. From this perspective, it is preferable that the tops 32 of each of the first narrow land portion 28a and the second narrow land portion 28b include serrations 46 and lands 48, that the serrations 46 in the first narrow land portion 28a are located between a width center CL1 of the first narrow land portion 28a and a first edge 30a of the first narrow land portion 28a, and that the serrations 46 in the second narrow land portion 28b are located between a width center CL2 of the second narrow land portion 28b and the first edge 30a of the second narrow land portion 28b, and that the serrations 46 in each of the first narrow land portion 28a and the second narrow land portion 28b include a plurality of ridges 50.

[0094] In particular, when the top 32 of both the first thin land portion 28a and the second thin land portion 28b are provided with the serrations 46 and the lands 48, the ground contact pressure distribution of the land portion 16 can be configured to be more uniform and without bias, compared to when the top 32 of either one of the thin land portions 28, the first thin land portion 28a or the second thin land portion 28b, is provided with the serrations 46 and the lands 48. From this perspective, it is more preferable that the top 32 of both the first thin land portion 28a and the second thin land portion 28b be provided with the serrations 46 and the lands 48, rather than when the top 32 of either one of the thin land portions 28, the first thin land portion 28a or the second thin land portion 28b, is provided with the serrations 46 and the lands 48. When the tops 32 of both the first thin land portion 28a and the second thin land portion 28b have serrations 46, it is preferable that the orientation of the ridges 50 in the serrations 46 of the first thin land portion 28a is opposite to the orientation of the ridges 50 in the serrations 46 of the second thin land portion 28b, as shown in Figure 7.

[0095] 7, the serrations 46 of the first thin land portion 28a and the second thin land portion 28b each include a plurality of serration portions 58 arranged in the circumferential direction. The serrations 46 of the first thin land portion 28a and the second thin land portion 28b each extend discontinuously in the circumferential direction. The plurality of serration portions 58 constituting the serrations 46 of the first narrow land portion 28a and the second narrow land portion 28b each include the plurality of ridges 50 described above. The serration portions 58 of the first narrow land portion 28a and the serration portions 58 of the second narrow land portion 28b can contribute to reducing the ground contact area. The serrations 46 of the first narrow land portion 28a and the serrations 46 of the second narrow land portion 28b are located near the circumferential sub-grooves 26, and therefore can effectively contribute to increasing the ground contact pressure near the center of the land portion 16 and relatively reducing the ground contact pressure near the edge 16E of the land portion 16. Moreover, by changing the length of the serration portions 58, the ground contact pressure distribution of the land portion 16 can be effectively adjusted. In this tire 2, the serrations 46 provided in each of the first narrow land portion 28a and the second narrow land portion 28b can effectively contribute to uniformly distributing the ground contact pressure of the land portion 16. This tire 2 can improve wear resistance while suppressing deterioration of wet performance. From this viewpoint, when the first thin land portion 28a and the second thin land portion 28b each have serrations 46, it is preferable that the serrations 46 of the first thin land portion 28a and the second thin land portion 28b each have a plurality of serration portions 58 arranged in the circumferential direction, and that each of the plurality of serration portions 58 has a plurality of ridges 50.

[0096] In the land portion 16 shown in FIG. 7, the serration portions 58 of the first narrow land portion 28a and the serration portions 58 of the second narrow land portion 28b are arranged alternately in the circumferential direction. This land portion 16 can effectively adjust the ground contact pressure distribution. In this tire 2, the serrations 46 provided in each of the first narrow land portion 28a and the second narrow land portion 28b can effectively contribute to forming a uniform ground contact pressure distribution in the land portion 16 without bias. This tire 2 can improve wear resistance while suppressing deterioration of wet performance. From this perspective, when the serrations 46 of each of the first narrow land portion 28a and the second narrow land portion 28b include a plurality of serration portions 58 arranged in the circumferential direction, it is preferable that the serration portions 58 of the first narrow land portion 28a and the serration portions 58 of the second narrow land portion 28b be arranged alternately in the circumferential direction.

[0097] Fig. 8 shows a modified example of the land portion 16 in Fig. 7. In the land portion 16 in Fig. 8, the top 32 of each of the first narrow land portion 28a and the second narrow land portion 28b has serrations 46 and lands 48, and each of the first narrow land portion 28a and the second narrow land portion 28b has a plurality of widthwise sipes 60.

[0098] The widthwise sipes 60 of the first narrow land portion 28a extend straight from the second edge 30b of the first narrow land portion 28a toward the first edge 30a. The widthwise sipes 60 of the second narrow land portion 28b extend straight from the second edge 30b of the second narrow land portion 28b toward the first edge 30a. In the tire 2, the widthwise sipes 60 of the first narrow land portion 28a and the second narrow land portion 28b are inclined with respect to the circumferential direction. The widthwise sipes 60 of the first narrow land portion 28a and the second narrow land portion 28b may extend in the axial direction. 8, the direction of inclination of the widthwise sipes 60 of the second narrow land portion 28b is opposite to the direction of inclination of the widthwise sipes 60 of the first narrow land portion 28a. The direction of inclination of the widthwise sipes 60 of the second narrow land portion 28b may be the same as the direction of inclination of the widthwise sipes 60 of the first narrow land portion 28a.

[0099] In FIG. 8 , the widthwise sipe 60 of the first narrow land portion 28a bridges between the second edge 30b and the first edge 30a of the first narrow land portion 28a. In other words, this widthwise sipe 60 is connected to both the center circumferential main groove 14 and the circumferential sub-groove 26. The widthwise sipe 60 of the second narrow land portion 28b bridges between the second edge 30b and the first edge 30a of the second narrow land portion 28b. In other words, this widthwise sipe 60 is connected to both the shoulder circumferential main groove 14 and the circumferential sub-groove 26. From the viewpoint of drainage performance, it is sufficient for this widthwise sipe 60 to be connected to the second edge 30b of the narrow land portion 28, but it does not have to be connected to the first edge 30a, i.e., the circumferential sub-groove 26. In this case, from the viewpoint of allowing the widthwise sipe 60 to effectively perform its function, the distance from the widthwise sipe 60 to the circumferential sub-groove 26 is preferably 3.2 mm or less.

[0100] In the tire 2, the end of the widthwise sipe 60 on the second edge 30b side of the narrow land portion 28 is located on the second circumferential side of the end of the widthwise sipe 60 on the first edge 30a side of the narrow land portion 28 in the circumferential direction. The end of the widthwise sipe 60 on the second edge 30b side of the narrow land portion 28 may be located on the first circumferential side of the end of the widthwise sipe 60 on the first edge 30a side of the narrow land portion 28 in the circumferential direction.

[0101] 9 shows a cross section of the widthwise sipes 60 of the first narrow land portion 28a. Although not shown, the widthwise sipes 60 of the second narrow land portion 28b have the same cross-sectional shape as the cross-sectional shape of the widthwise sipes 60 of the first narrow land portion 28a. The main configuration of the widthwise sipes 60 will be described based on the cross section of the widthwise sipes 60 of the first narrow land portion 28a shown in FIG.

[0102] The lateral sipes 60 extend straight in the length and depth directions. The lateral sipes 60 are two-dimensional sipes. The lateral sipes 60 have a pair of wall surfaces 60S including groove mouths 60M and a bottom surface 60B including a groove bottom 60T. 9, the double-headed arrow WGH indicates the groove width at the groove mouth 60M of the lateral sipe 60. The double-headed arrow DGh indicates the groove depth of the lateral sipe 60. The groove width WGH of the lateral sipe 60 is less than 1.0 mm. The lateral sipe 60 is the sipe described above.

[0103] In each of the first narrow land portion 28a and the second narrow land portion 28b, the multiple widthwise sipes 60 are arranged at predetermined intervals in the circumferential direction. As a result, multiple blocks 62 are formed in each of the first narrow land portion 28a and the second narrow land portion 28b. In other words, a block 62 is formed between two adjacent widthwise sipes 60. In the land portion 16 of FIG. 8, one block 62 has one serration portion 58.

[0104] In the land portion 16 of FIG. 8 , the serrations 46 provided in each of the first narrow land portion 28a and the second narrow land portion 28b also effectively contribute to forming a uniform ground contact pressure distribution in the land portion 16 without bias. Furthermore, since the widthwise sipes 60 function as edge components, the tire 2 can maintain good wet performance even when the tread 4 wears. As described above, the widthwise sipes 60 are sipes. When the narrow land portion 28 comes into contact with the road surface and deforms, a pair of wall surfaces 60S of the widthwise sipe 60 come into contact with each other. This allows adjacent blocks 62 to support each other. Since a decrease in rigidity of the narrow land portion 28 is suppressed, the tire 2 can maintain good wear resistance. The tire 2 can improve wear resistance while suppressing a decrease in wet performance. From this viewpoint, it is preferable that the serrations 46 of each of the first thin land portion 28a and the second thin land portion 28b have a plurality of serration portions 58 arranged in the circumferential direction, each of the plurality of serration portions 58 have a plurality of ridges 50, each of the first thin land portion 28a and the second thin land portion 28b have a plurality of width-direction sipes 60 extending from the second edge 30b of each of the first thin land portion 28a and the second thin land portion 28b toward the first edge 30a of each of the first thin land portion 28a and the second thin land portion 28b, and that in each of the first thin land portion 28a and the second thin land portion 28b, there is a block 62 between two adjacent width-direction sipes 60, and that this block 62 has one serration portion 58.

[0105] Although not shown, in the tire 2, of the first narrow land portion 28a and the second narrow land portion 28b, the top 32 of the first narrow land portion 28a may include serrations 46 and lands 48, and the first narrow land portion 28a may include a plurality of widthwise sipes 60. Of the first narrow land portion 28a and the second narrow land portion 28b, the top 32 of the second narrow land portion 28b may include serrations 46 and lands 48, and the second narrow land portion 28b may include a plurality of widthwise sipes 60. From the viewpoint of being able to effectively improve wear resistance while effectively suppressing a decrease in wet performance, it is preferable that the top 32 of each of the first narrow land portion 28a and the second narrow land portion 28b include serrations 46 and lands 48, and that each of the first narrow land portion 28a and the second narrow land portion 28b include a plurality of widthwise sipes 60.

[0106] As shown in FIG. 8 , the multiple width-direction sipes 60 of the first narrow land portion 28a and the multiple width-direction sipes 60 of the second narrow land portion 28b are arranged in a staggered pattern in the circumferential direction. This allows the serration portion 58 and the width-direction sipes 60 to effectively contribute to suppressing a decrease in wet performance and improving wear resistance. This tire 2 can effectively improve wear resistance while effectively suppressing a decrease in wet performance. From this perspective, when each of the first narrow land portion 28a and the second narrow land portion 28b has multiple width-direction sipes 60, it is preferable that the multiple width-direction sipes 60 of the first narrow land portion 28a and the multiple width-direction sipes 60 of the second narrow land portion 28b be arranged in a staggered pattern in the circumferential direction.

[0107] When the circumferential sub-grooves 26 correspond to sipes, it is preferable that the groove width WGh of the widthwise sipes 60 is the same as or narrower than the groove width WGs of the circumferential sub-groove 26. In other words, it is preferable that the ratio WGh / WGs of the groove width WGh of the widthwise sipes 60 to the groove width WGs of the circumferential sub-groove 26 is 100% or less. This suppresses the influence of the widthwise sipes 60 on the rigidity of the narrow land portions 28. Since the rigidity of the narrow land portions 28 is appropriately maintained, the tire 2 can maintain good wear resistance. From this viewpoint, it is more preferable that the ratio WGh / WGs is 95% or less. From the viewpoint that the widthwise sipes 60 can contribute to improving drainage performance, it is preferable that the ratio WGh / WGs is 75% or more, and more preferably 80% or more.

[0108] The ratio DGh / DGm of the groove depth DGh of the lateral sipes 60 to the groove depth DGm of the circumferential main groove 10 is preferably 70% or greater and 90% or less. By setting the ratio DGh / DGm to 70% or more, the widthwise sipes 60 can fully exert their function until the tire reaches a final stage of wear, which requires replacement with a new tire 2. This tire 2 can suppress deterioration of wet performance. From this viewpoint, it is more preferable that the ratio DGh / DGm be 75% or more. Setting the ratio DGh / DGm to 90% or less suppresses the effect of the widthwise sipes 60 on the rigidity of the narrow land portions 28. Since the narrow land portions 28 have appropriate rigidity, the tire 2 can have improved wear resistance. From this viewpoint, it is more preferable that the ratio DGh / DGm be 80% or less.

[0109] In FIG. 8, the dashed dotted line LW is the center line of the widthwise sipe 60 and represents the direction in which the widthwise sipe 60 extends. The center line LW of the widthwise sipe 60 intersects with the equatorial plane. In other words, the widthwise sipe 60 is inclined relative to the circumferential direction. The angle γ is the angle between the center line LW of the widthwise sipe 60 and the dashed dotted line EL representing the equatorial plane. The angle γ is the angle that the widthwise sipe 60 forms with the circumferential direction. The angle γ is also called the inclination angle of the widthwise sipe 60.

[0110] The inclination angle γ of the widthwise sipes 60 is preferably 30 degrees or greater and 90 degrees or less. This allows the widthwise sipes 60 to effectively contribute to improving the drainage performance of the tire 2 and function effectively as edge components. This tire 2 can achieve improved wet performance. From this viewpoint, the inclination angle γ of the widthwise sipes 60 is more preferably 45 degrees or greater and 90 degrees or less.

[0111] FIG. 10 shows a modified example of the widthwise sipe 60. This widthwise sipe 60 extends in a zigzag pattern in its depth direction. Although not shown, this widthwise sipe 60 also extends in a zigzag pattern in its length direction. This widthwise sipe 60 extends in a zigzag pattern in both its length direction and depth direction. The widthwise sipe 60 shown in FIG. 10 is a three-dimensional sipe. A pair of wall surfaces 60 of a three-dimensional type widthwise sipe 60 meshes more effectively with each other than a pair of wall surfaces 60 of a two-dimensional type widthwise sipe 60 shown in FIG. 9. Deformation of the narrow land portion 28 is effectively suppressed. The three-dimensional type widthwise sipe 60 can effectively contribute to improving wear resistance. From this viewpoint, it is preferable that the widthwise sipe 60 extend in a zigzag pattern in the length direction and depth direction. In other words, it is preferable that the widthwise sipe 60 is a three-dimensional sipe.

[0112] In Figure 8, the length indicated by the double-headed arrow LB is the length of the serration portion 58. The length LB is represented by the circumferential distance from the end of the serration portion 58 on the first circumferential side to the end on the second circumferential side. The length indicated by the double-headed circumferential arrow WB is the width of the serration portion 58. The width of the serration portion 58 is represented by the axial distance from the end of the serration portion 58 on the first edge 30a side of the narrow land portion 28 to the end of the serration portion 58 on the second edge 30b side of the narrow land portion 28. The width of the serration portion 58 is also the width of the serration 46.

[0113] The ratio WB / WL of the width WB of the serration portion 58 to the width WL of the land portion 16 is preferably 10% or more. This allows the serration portion 58 to form a uniform ground contact pressure distribution in the land portion 16 without bias, and effectively contributes to improving drainage. This tire 2 can maintain good wet performance. From this perspective, the ratio WB / WL is more preferably 13% or more. The ratio WB / WL is preferably 25% or less. In this case, too, the serration portion 58 can contribute to forming a uniform contact pressure distribution in the land portion 16 without bias. Since the end of the serration portion 58 on the second edge 30b side of the narrow land portion 28 is positioned away from the second edge 30b of the narrow land portion 28, an increase in contact pressure at the second edge 30b of the narrow land portion 28 is suppressed. This tire 2 can suppress the occurrence of uneven wear. From this viewpoint, the ratio WB / WL is more preferably 23% or less.

[0114] The tread pattern of this tire 2 is formed by repeating unit patterns in the circumferential direction. The unit patterns of the tread pattern are also called pitch patterns. The tread pattern is formed by combining multiple pitch patterns. The length indicated by the double-headed arrow LP in FIG. 8 is the length of this pitch pattern. The dotted lines PB indicate the boundaries of the pitch patterns.

[0115] The ratio LB / LP of the length LB of the serration portion 58 to the length LP of the pitch pattern is preferably 30% or more. This allows the serration portion 58 to form a uniform ground contact pressure distribution in the land portion 16 without bias, and effectively contributes to improving drainage. This tire 2 can maintain good wet performance. From this perspective, the ratio LB / LP is more preferably 35% or more. The ratio LB / LP is preferably 55% or less. In this case, too, the serration portion 58 can effectively contribute to forming a uniform distribution of contact pressure in the land portion 16 without bias. This suppresses the occurrence of uneven wear. This tire 2 can maintain good wear resistance. From this perspective, the ratio LB / LP is more preferably 50% or less.

[0116] 8, the serration portion 58 is located between two widthwise sipes 60 that are aligned in the circumferential direction. In the present invention, of the two widthwise sipes 60 that are aligned in the circumferential direction, the widthwise sipe 60a that is located on a first circumferential side of the serration portion 58 is also referred to as a first widthwise sipe. The widthwise sipe 60b that is located on a second circumferential side of the serration portion 58 is also referred to as a second widthwise sipe.

[0117] The serration portion 58 is connected to the first widthwise sipe 60a at its first circumferential end. The second circumferential end of the serration portion 58 is disposed away from the second widthwise sipe 60b. The first circumferential end of the serration portion 58 may be disposed away from the first widthwise sipe 60a. In this case, the serration portion 58 may be connected to the second widthwise sipe 60b at its second circumferential end. From the viewpoint that providing the serration portion 58 and the widthwise sipe 60 in each of the first narrow land portion 28a and the second narrow land portion 28a can effectively contribute to achieving both wet performance and wear resistance, it is preferable that the serration portion 58 is connected to the first widthwise sipe 60a at its first circumferential end and that the second circumferential end of the serration portion 58 is disposed away from the second widthwise sipe 60b. In this case, it is preferable that the serration portion 58 of the first narrow land portion 28a is located circumferentially between the widthwise sipes 60 of the first narrow land portion 28a and the widthwise sipes 60 of the second narrow land portion 28b, and that the serration portion 58 of the second narrow land portion 28b is located circumferentially between the widthwise sipes 60 of the second narrow land portion 28b and the widthwise sipes 60 of the first narrow land portion 28a.

[0118] As described above, the serration portion 58 in FIG. 8 is connected to the widthwise sipes 60 located on the first circumferential side thereof. In this tire 2, the orientation of the ridges 50 provided in the serration portion 58 matches the orientation of the widthwise sipes 60 to which the serration portion 58 is connected. The ridges 50 may be provided in the serration portion 58 so that the orientation of the ridges 50 intersects with the orientation of the widthwise sipes 60. The orientation of the widthwise sipes 60 to which the serration portion 58 is connected and the orientation of the ridges 50 provided in this serration portion 58 are determined appropriately depending on the specifications of the tire 2.

[0119] In heavy-duty tires, the contact pressure at the crown tends to be higher than that at the shoulder, making the crown more susceptible to wear. Because the contact length of the crown is longer than that of the shoulder, water tends to accumulate in the crown. The crown is at a disadvantage compared to the shoulder in terms of drainage.

[0120] However, in this tire 2, for example, as shown in FIG. 1 , the main land portion 20 located between two shoulder land portions 18—in other words, the main land portion 20 located in the crown portion—has a first narrow land portion 28a and a second narrow land portion 28b separated by a circumferential sub-groove 26, and the top 32 of the first narrow land portion 28a has the above-mentioned serrations 46. Therefore, the ground pressure near the center of the main land portion 20 is increased, while the ground pressure near the edge of the main land portion 20 is relatively decreased. This results in a uniform ground pressure distribution in the main land portion 20. This main land portion 20 contributes to improving the wear resistance of the crown portion. Moreover, the circumferential sub-groove 26 provided in the main land portion 20 can fully demonstrate its function. This tire 2 can improve wear resistance while suppressing a deterioration in wet performance. From this viewpoint, it is preferable that the tread 4 of the tire 2 includes at least one main land portion 20 between the two shoulder land portions 18, and that this main land portion 20 includes the first narrow land portion 28a and the second narrow land portion 28b. When multiple main land portions 20 are located between the two shoulder land portions 18, it is more preferable that, of the multiple main land portions 20 located between the two shoulder land portions 18, the main land portion 20 located on the equatorial plane or the main land portion 20 closest to the equatorial plane includes the first narrow land portion 28a and the second narrow land portion 28b, and it is even more preferable that all of the main land portions 20 located between the two shoulder land portions 18 include the first narrow land portion 28a and the second narrow land portion 28b. When the main land portion 20 has the above-mentioned first narrow land portion 28a and second narrow land portion 28b, it is preferable that the main land portion 20 be provided with serrations 46 and lands 48 as in the land portion 16 shown in Figure 4, Figure 6, Figure 7, or Figure 8, and it is more preferable that the main land portion 20 be provided with serrations 46 and lands 48 as in the land portion 16 shown in Figure 8.

[0121] As is clear from the above description, the present invention provides a heavy-duty tire that can achieve improved wear resistance while suppressing deterioration in wet performance. [Industrial Applicability]

[0122] The above-described technology that can achieve improved wear resistance while suppressing deterioration in wet performance can be applied to various tires.

[0123] [Note] The present invention includes the following aspects.

[0124] [1] A heavy-duty tire having a tread located at the radially outermost position and extending in the circumferential direction, the tread having a plurality of land portions separated by circumferential main grooves, at least one land portion having a first narrow land portion and a second narrow land portion separated by a circumferential sub-groove, the first narrow land portion and the second narrow land portion each having two edges, the edge on the circumferential sub-groove side being a first edge and the edge on the other side being a second edge, the top of the first narrow land portion having uneven serrations and a flat land, the serrations being located between the width center of the first narrow land portion and the first edge of the first narrow land portion, the serrations having a plurality of ridges, and a narrow shallow groove being formed between two adjacent ridges. [2] The heavy-duty tire according to [1] above, wherein the serration has a plurality of serration portions arranged in the circumferential direction, and each of the plurality of serration portions has a plurality of the ridges. [3] A heavy-duty tire according to the above-mentioned [2], wherein the first narrow land portion has a plurality of widthwise sipes extending from the second edge of the first narrow land portion toward the first edge of the first narrow land portion, the plurality of widthwise sipes are arranged in a circumferential direction, a block is formed between two adjacent widthwise sipes, and the block has one of the serration portions. [4] A heavy-duty tire as described in [1] above, wherein the tops of the first narrow land portion and the second narrow land portion each have the serration and the land, the serration in the first narrow land portion is located between the width center of the first narrow land portion and the first edge of the first narrow land portion, and the serration in the second narrow land portion is located between the width center of the second narrow land portion and the first edge of the second narrow land portion, and the serration in each of the first narrow land portion and the second narrow land portion has a plurality of the ridges. [5] A heavy-duty tire as described in [4] above, wherein the serrations of each of the first narrow land portion and the second narrow land portion have a plurality of serration portions arranged in the circumferential direction, each of the plurality of serration portions has a plurality of the ridges, and the serration portions of the first narrow land portion and the serration portions of the second narrow land portion are arranged alternately in the circumferential direction. [6] A heavy-duty tire as described in [4] above, wherein the serrations of each of the first narrow land portion and the second narrow land portion have a plurality of serration portions arranged in the circumferential direction, each of the plurality of serration portions has a plurality of the ridges, each of the first narrow land portion and the second narrow land portion has a plurality of widthwise sipes extending from the second edge of each of the first narrow land portion and the second narrow land portion toward the first edge of each of the first narrow land portion and the second narrow land portion, each of the first narrow land portion and the second narrow land portion has a block between two adjacent widthwise sipes, and each of the first narrow land portion and the second narrow land portion has one of the serration portions. [7] A heavy-duty tire according to the above-mentioned [6], wherein the plurality of widthwise sipes of the first narrow land portion and the plurality of widthwise sipes of the second narrow land portion are arranged in a staggered pattern in the circumferential direction. [8] A heavy-duty tire according to the above-mentioned [3], [6] or [7], wherein the ratio of the groove depth of the widthwise sipes to the groove depth of the circumferential main grooves is 70% or more and 90% or less. [9] The heavy-duty tire according to any one of [3] or [6] to [8] above, wherein the widthwise sipes extend in a zigzag pattern in the lengthwise and depthwise directions.

[10] The heavy-duty tire according to any one of the above-mentioned [1] to [9], wherein the circumferential sub-groove is located at the center of the land portion.

[11] The heavy-duty tire according to any one of the above [1] to

[10] , wherein the ratio of the groove depth of the circumferential sub-groove to the groove depth of the circumferential main groove is 70% or more and 90% or less.

[12] The heavy-duty tire according to any one of the above-mentioned [1] to

[11] , wherein the narrow shallow groove is connected to the circumferential sub-groove at its end on the circumferential sub-groove side.

[13] A heavy-duty tire according to any one of [1] to

[12] above, wherein the position of the top of the ridge coincides with the position of the land in the radial direction, or the top of the ridge is located radially inward of the land.

[14] A heavy-duty tire according to any one of the above-mentioned [1] to

[13] , wherein, among the plurality of land portions, the two land portions located at the axially outermost positions are shoulder land portions, the land portion located between the two shoulder land portions is a main land portion, and at least one of the main land portions has the first narrow land portion and the second narrow land portion separated by the circumferential auxiliary groove. [Explanation of symbols]

[0125] 2. Tires 4. Tread 10...Circumferential main groove 16... Rikubu 20. Main Land Area 22 Crown Land Division 26... Circumferential minor groove 28, 28a, 28b...Hokkaido 30, 30a, 30b... Edge of the landform 32. Top of the Narrow Land Area 46 serrations 48···Rand 50 Ridge 52···Top 56...Shallow groove 58 Serration section 60···Width sipes

Claims

1. The tire has a radially outermost tread extending in the circumferential direction, the tread comprises a plurality of land portions separated by circumferential main grooves, At least one land portion includes a first narrow land portion and a second narrow land portion separated by a circumferential sub-groove, of two edges that each of the first narrow land portion and the second narrow land portion has, the edge on the circumferential sub-groove side is a first edge, and the edge on the other side is a second edge, the top of the first narrow land portion has uneven serrations and a flat land, the serration is located between a width center of the first narrow land portion and the first edge of the first narrow land portion, the serrations comprise a plurality of ridges; A narrow shallow groove is formed between two adjacent ridges. Heavy duty tires.

2. The serration includes a plurality of serration portions arranged in a circumferential direction, Each of the plurality of serration portions includes a plurality of the ridges.

2. The heavy duty tire according to claim 1.

3. the first narrow land portion includes a plurality of widthwise sipes extending from the second edge of the first narrow land portion toward the first edge of the first narrow land portion, A plurality of the widthwise sipes are arranged in a circumferential direction, The space between two adjacent widthwise sipes is a block. The block includes one of the serration portions.

3. A heavy duty tire according to claim 2.

4. a top of each of the first narrow land portion and the second narrow land portion includes the serration and the land, In the first narrow land portion, the serration is located between a width center of the first narrow land portion and the first edge of the first narrow land portion, In the second narrow land portion, the serration is located between a width center of the second narrow land portion and the first edge of the second narrow land portion, the serrations of each of the first thin land portion and the second thin land portion include a plurality of the ridges; 2. The heavy duty tire according to claim 1.

5. the serrations of the first thin land portion and the second thin land portion each include a plurality of serration portions arranged in a circumferential direction, each of the plurality of serration portions includes a plurality of the ridges; the serration portions of the first thin land portion and the serration portions of the second thin land portion are alternately arranged in the circumferential direction, 5. A heavy duty tire according to claim 4.

6. the serrations of the first thin land portion and the second thin land portion each include a plurality of serration portions arranged in a circumferential direction, each of the plurality of serration portions includes a plurality of the ridges; each of the first narrow land portion and the second narrow land portion includes a plurality of widthwise sipes extending from the second edge of each of the first narrow land portion and the second narrow land portion toward the first edge of each of the first narrow land portion and the second narrow land portion; In each of the first narrow land portion and the second narrow land portion, a block is formed between two adjacent widthwise sipes, The block includes one of the serration portions.

5. A heavy duty tire according to claim 4.

7. the plurality of widthwise sipes of the first narrow land portion and the plurality of widthwise sipes of the second narrow land portion are arranged in a staggered pattern in the circumferential direction; 7. A heavy duty tire according to claim 6.

8. A ratio of the groove depth of the widthwise sipe to the groove depth of the circumferential main groove is 70% or more and 90% or less.

7. A heavy duty tire according to claim 3 or 6.

9. The widthwise sipes extend in a zigzag pattern in the lengthwise and depthwise directions.

7. A heavy duty tire according to claim 3 or 6.

10. The circumferential sub-groove is located at the center of the land portion.

2. The heavy duty tire according to claim 1.

11. a ratio of the groove depth of the circumferential sub-groove to the groove depth of the circumferential main groove is 70% or more and 90% or less; 2. The heavy duty tire according to claim 1.

12. The narrow shallow groove is connected to the circumferential sub-groove at an end thereof on the circumferential sub-groove side.

2. The heavy duty tire according to claim 1.

13. a position of a top of the ridge coincides with a position of the land in the radial direction, or a position of the top of the ridge is located radially inside the land; 2. The heavy duty tire according to claim 1.

14. Among the plurality of land portions, two land portions located at the outermost positions in the axial direction are shoulder land portions, and a land portion located between the two shoulder land portions is a main land portion, At least one of the main land portions includes the first narrow land portion and the second narrow land portion separated by the circumferential sub-groove.

2. The heavy duty tire according to claim 1.

Images