Heavy-duty tires

Abstract

To provide a heavy load tire which is improved in life performance by enhancing center wear resistance.SOLUTION: In a tire meridian cross section in a 5% inner-pressure state, curvature radii R of respective grounding-face profiles P of a center land part 3, an inside region 4a of a first middle block 4R, an outside region 4b of the first middle block 4R, and a first shoulder block 5R are stipulated. Also, a ratio (Wa / Da) of a groove depth Da and a groove width Wa of a center peripheral groove 8 is equal to or smaller than 0.25. Furthermore, a ratio (Lb / La) of a maximum length La of the first middle block 4R in a tire peripheral direction and a maximum length Lb in a tire axial direction is stipulated.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to heavy duty tires. [Background technology]

[0002] Patent Document 1 listed below describes a heavy-duty tire whose tread is divided into a center land portion, a middle land portion, and a shoulder land portion. When the heavy-duty tire is in a 5% internal pressure state, the contour line of the surface of the tread portion is formed by an arc portion with a curvature radius R1 and an arc portion with an arc center at the tire equator and a curvature radius R2 that intersects with this arc portion at an inflection point P and is smaller than the curvature radius R1. The inflection point P is set at a predetermined position on the middle land portion. This is said to improve the center wear resistance of the heavy-duty tire under light-load specifications. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-127199 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, there has been a demand for further improving center wear resistance and extending the life of heavy duty tires (hereinafter referred to as "life performance").

[0005] The present disclosure has been devised in view of the above problems, and has as its object to provide a heavy-duty tire that can improve center wear resistance and life performance. [Means for solving the problem]

[0006] The present disclosure relates to a heavy-duty tire having a tread portion, the tread portion including: a center land portion located closest to the tire equator; a first middle land portion adjacent to the center land portion via a center circumferential groove; a first shoulder land portion adjacent to the first middle land portion via a shoulder circumferential groove and having a first tread edge; and a first middle lateral groove and a first shoulder lateral groove that divide the first middle land portion and the first shoulder land portion into a first middle block and a first shoulder block, respectively. When the tire is mounted on a regular rim and in a 5% internal pressure state adjusted to 5% of the regular internal pressure, the radius of curvature R1 of the contact patch profile P1 of the center land portion, the radius of curvature R2 of the first middle block, and the radius of curvature R3 of the first middle block are determined. a radius of curvature R2 of a contact patch profile P2 of the axially inner region of each of the first middle blocks, a radius of curvature R3 of a contact patch profile P3 of the axially outer region of each of the first middle blocks, and a radius of curvature R4 of a contact patch profile P4 of each of the first shoulder blocks satisfy the following formulas (1) to (3); the groove depths of the center circumferential groove and the shoulder circumferential groove are 21 mm or more; the ratio (Wa / Da) of the groove depth Da of the center circumferential groove to the groove width Wa of the center circumferential groove is 0.25 or less; and the ratio (Lb / La) of the maximum circumferential length La of each of the first middle blocks to the maximum axial length Lb of each of the first middle blocks is greater than 0.75. 0.95≦(R1 / R2)≦1.05 …(1) 0.95≦(R3 / R4)≦1.05 …(2) R1>R3 …(3) [Effects of the Invention]

[0007] By employing the above-described configuration, the heavy duty tire of the present disclosure can improve center wear resistance and life performance. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a tire meridian cross-sectional view showing an embodiment of a heavy-duty tire of the present disclosure. [Figure 2] FIG. 2 is a development view of the tread portion of the tire of FIG. 1. [Figure 3] FIG. 1 is a diagram showing the contact patch profile at 5% internal pressure. [Figure 4] FIG. 2 is a perspective view conceptually showing a three-dimensional sipe. [Figure 5] FIG. 10 is a plan view of a tread portion of another embodiment. [Figure 6] FIG. 6 is a cross-sectional view taken along line AA in FIG. 5. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. 1 is a cross-sectional view of a heavy-duty tire (hereinafter sometimes simply referred to as "tire") 1 of this embodiment, taken along the tire meridian including the tire rotation axis (not shown), in a normal state. The present disclosure is applied to tire 1 having an aspect ratio of 70% to 90%, for example.

[0010] The "normal state" refers to a state in which the tire 1 is mounted on a normal rim (not shown), inflated to a normal internal pressure, and no load is applied. In this specification, unless otherwise specified, the dimensions of each part of the tire 1 are values ​​measured in this normal state.

[0011] A "genuine rim" is a rim that is defined for each tire by a standard system that includes the standard on which tire 1 is based, such as a "standard rim" for JATMA, a "design rim" for TRA, or a "measuring rim" for ETRTO.

[0012] "Normal internal pressure" is the air pressure specified for each tire by each standard in the standard system, including the standard on which tire 1 is based. In the case of JATMA, it is the "maximum air pressure," in the case of TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS SAT VARIOUSCOLD INFLATION PRESSURES," and in the case of ETRTO, it is the "INFLATION PRESSURE."

[0013] Ties and components such as a carcass Ca and a belt layer Ba are disposed inside the tire 1 of this embodiment. The carcass Ca and the belt layer Ba are, for example, embedded in the tread portion 2. Known embodiments are appropriately adopted for these tire components.

[0014] Fig. 2 is a plan view of the tread portion 2. As shown in Fig. 2, in this embodiment, the tread portion 2 includes a center land portion 3 located closest to the tire equator C, a first middle land portion 4 adjacent to the center land portion 3, and a first shoulder land portion 5 adjacent to the first middle land portion 4 and having a first tread edge T1. The center land portion 3 in this embodiment is located on the tire equator C. The first tread edge T1 is marked at the right end of the tread portion 2 in Fig. 2.

[0015] The first tread edge T1 and the second tread edge T2 (described later) are defined as the outermost contact points in the tire axial direction when the tire 1 in a normal state is placed on a flat surface with a normal load and a camber angle of 0 degrees. The axial distance from the tire equator C to the first tread edge T1 is the tread half width Wt (shown in FIG. 1).

[0016] The "normal load" is the load specified for each tire by the standard, and is the maximum load capacity in the case of JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and "LOAD CAPACITY" in the case of ETRTO.

[0017] The tread portion 2 of this embodiment includes a center circumferential groove 8 arranged between the center land portion 3 and the first middle land portion 4, and a shoulder circumferential groove 9 arranged between the first middle land portion 4 and the first shoulder land portion 5. In this embodiment, the tread portion 2 includes a first middle lateral groove 10 connecting the center circumferential groove 8 and the shoulder circumferential groove 9, and a first shoulder lateral groove 11 connecting the shoulder circumferential groove 9 and the first tread edge T1.

[0018] As shown in Fig. 1, the groove depths Da and Db of the center circumferential groove 8 and the shoulder circumferential groove 9 are 21 mm or more. A tire 1 having such center circumferential groove 8 and shoulder circumferential groove 9 has basic life performance that maintains wet performance for a long period of time and enables long-distance driving (e.g., 400,000 km). The groove depths Da and Db of the center circumferential groove 8 and the shoulder circumferential groove 9 are preferably, for example, 25 mm or less.

[0019] The ratio (Wa / Da) of the groove depth Da of the center circumferential groove 8 to the groove width Wa of the center circumferential groove 8 is 0.25 or less. In other words, the center circumferential groove 8 extends elongatedly in the tire radial direction. Such center circumferential groove 8 ensures the land ratio of the center land portion 3 and the first middle land portion 4, thereby helping to improve tire life performance. If the ratio (Wa / Da) is excessively small, the first middle land portion 4 will collapse toward the center land portion 3, concentrating ground contact pressure near the tire equator C, which may result in a deterioration in center wear resistance. From this perspective, the ratio (Wa / Da) is preferably 0.18 or more, more preferably 0.20 or more, and is preferably 0.25 or less.

[0020] As shown in Fig. 2, the first middle land portion 4 is divided into first middle blocks 4R by first middle lateral grooves 10. The first shoulder land portion 5 is divided into first shoulder blocks 5R by first shoulder lateral grooves 11. Each first middle block 4R includes an axially inner region 4a and an axially outer region 4b that is located axially outward of the inner region 4a.

[0021] 3 is a diagram of the contact patch profile (outline of the tread portion 2) of the tire 1 at 5% internal pressure. The 5% internal pressure state refers to the state of the tire 1 mounted on a standard rim and adjusted to 5% of the standard internal pressure. The radii of curvature R1 to R4 of the contact patch profiles P1 to P4 of the center land zone 3, inner region 4a, outer region 4b, and first shoulder block 5R, respectively, are specified to satisfy the following formulas (1) to (3): 0.95≦(R1 / R2)≦1.05 …(1) 0.95≦(R3 / R4)≦1.05 …(2) R1>R3 …(3)

[0022] By setting the ratio (R1 / R2) to 0.95 or greater and 1.05 or less, the contact patch profile P1 of the center land portion 3 and the contact patch profile P2 of the inner region 4a are smoothly connected, thereby suppressing the concentration of ground pressure in this area. This improves center wear resistance. By setting the ratio (R3 / R4) to 0.95 or greater and 1.05 or less, the contact patch profile P3 of the outer region 4b and the contact patch profile P4 of the first shoulder block 5R are smoothly connected, thereby suppressing the concentration of ground pressure in this area. This improves uneven wear resistance, particularly in the first shoulder block 5R. Furthermore, by making the radius of curvature R1 of the contact patch profile P1 of the center land portion 3 greater than the radius of curvature R3 of the contact patch profile P3 of the outer region 4b, wear in the center land portion 3 and the first middle land portion 4 is uniform during straight driving and cornering.

[0023] If the radius of curvature R3 is excessively smaller than the radius of curvature R1, the uneven wear resistance of the first middle block 4R may deteriorate. Therefore, the ratio of the radius of curvature R3 to the radius of curvature R1 (R3 / R1) is preferably 0.14 or more, more preferably 0.16 or more, and preferably 0.20 or less, and even more preferably 0.18 or less. Furthermore, the radius of curvature R1 is preferably 2500 mm or more, more preferably 2700 mm or more, and preferably 3500 mm or less, and even more preferably 3300 mm or less.

[0024] To ensure uniform wear among the center land portion 3, first middle block 4R, and first shoulder block 5R, the radius of curvature R2 is preferably smaller than the radius of curvature R1, and the radius of curvature R4 is preferably smaller than the radius of curvature R3. This maintains the flattening of the circumferential contour of the contact shape from the center land portion 3 to the first shoulder block 5R under varying loads. This flattening of the circumferential contour reduces the number of areas where contact pressure is concentrated across the entire tread portion 2, resulting in uniform wear and improved tire life. The flattening refers to the contour extending parallel to the tire axial direction from both axial ends of the tire.

[0025] The contact patch profile P2 and the contact patch profile P3 intersect at an inflection point J, which is located on the first middle block 4R. Because the inflection point J is located on the first middle block 4R, not at the position of each circumferential groove 8, 9, the connection between the contact patch profile P2 and the contact patch profile P3 is maintained smoothly even after inflation, and changes in the contact patch profiles P2, P3 are suppressed. As a result, the circumferential contour of the contact shape is maintained flat from the center land portion 3 to the first middle block 4R under load fluctuations.

[0026] In this embodiment, each of the contact patch profiles P1 to P4 is formed by an arc having a single radius of curvature R1 to R4, although each of the contact patch profiles P1 to P4 may also be formed by an arc formed by combining multiple arcs.

[0027] The axial distance Lp from the tire equator C to the inflection point J is preferably 0.35 or more times the tread half width Wt, more preferably 0.40 or more times, more preferably 0.50 or less times, and even more preferably 0.45 or less times. This maintains the flattening of the circumferential contour of the contact patch shape from the center land portion 3 to the first middle block 4R, even under varying loads. As a result, it is possible to improve center wear resistance while suppressing shoulder wear in the first middle land portion 4, especially under light loads. In the tread portion 2 of this embodiment, the inflection point J is not formed on the center land portion 3 or the first shoulder block 5R. In this specification, the inflection point J is the point where the radius of curvature of the contact patch profile changes, except at both axial ends of the first middle land portion 4.

[0028] As shown in FIG. 2, each of the first middle blocks 4R is formed so that the ratio (Lb / La) of the maximum circumferential length La to the maximum axial length Lb is greater than 0.75. This ensures the axial rigidity (lateral rigidity) of the first middle blocks 4R, preventing the first middle blocks 4R from collapsing axially inward. This prevents the concentration of ground pressure on the center land zone 3, improving center wear resistance. If the ratio (Lb / La) is too large, the longitudinal rigidity of the first middle blocks 4R may decrease. From this perspective, the ratio (Lb / La) is preferably 0.78 or greater, more preferably 0.85 or less, and even more preferably 0.82 or less.

[0029] The tread portion 2 further includes, for example, a second middle land portion 6 adjacent to the center land portion 3 on the axially opposite side of the first middle land portion 4, and a second shoulder land portion 7 adjacent to the second middle land portion 6 and having a second tread edge T2. In this embodiment, the tread portion 2 also includes a center circumferential groove 8 arranged between the center land portion 3 and the second middle land portion 6, and a shoulder circumferential groove 9 arranged between the second middle land portion 6 and the second shoulder land portion 7. The tread portion 2 further includes, for example, a plurality of center lateral grooves 12 connecting the center circumferential grooves 8. As a result, the center land portion 3 is formed with center blocks 3R divided by the center lateral grooves 12.

[0030] The second middle land portion 6 is formed with the same shape and configuration as the first middle land portion 4. The second shoulder land portion 7 is formed with the same shape and configuration as the first shoulder land portion 5. The center circumferential groove 8 arranged between the center land portion 3 and the first middle land portion 4 and the center circumferential groove 8 arranged between the center land portion 3 and the second middle land portion 6 are formed with the same shape and configuration. The shoulder circumferential groove 9 arranged between the first middle land portion 4 and the first shoulder land portion 5 and the shoulder circumferential groove 9 arranged between the second middle land portion 6 and the second shoulder land portion 7 are formed with the same shape and configuration. Therefore, descriptions of the second middle land portion 6, the second shoulder land portion 7, the center circumferential groove 8 arranged between the center land portion 3 and the second middle land portion 6, and the shoulder circumferential groove 9 arranged between the second middle land portion 6 and the second shoulder land portion 7 will be omitted.

[0031] Although not particularly limited, the axial distance Wc between the amplitude center line 8c of the center circumferential groove 8 and the tire equator C is preferably 10% or more of the tread half width Wt, more preferably 15% or more, and more preferably 30% or less, and even more preferably 25% or less. The axial distance Ws between the amplitude center line 9c of the shoulder circumferential groove 9 and the tire equator C is preferably 55% or more of the tread half width Wt, more preferably 60% or more, and more preferably 75% or less, and even more preferably 70% or less.

[0032] Each of the center circumferential groove 8 and the shoulder circumferential grooves 9 has a zigzag apex K and extends in a zigzag shape along the tire circumferential direction. The zigzag apex K includes an outward apex K1 that protrudes outward in the tire axial direction and an inward apex K2 that protrudes inward in the tire axial direction.

[0033] The outward apex K1 of the center circumferential groove 8 is adjacent in the tire circumferential direction to the inward apex K2 of the shoulder circumferential groove 9. Also, the inward apex K2 of the center circumferential groove 8 is adjacent in the tire circumferential direction to the outward apex K1 of the shoulder circumferential groove 9.

[0034] The first middle lateral grooves 10 connect the outward apexes K1 of the center circumferential groove 8 and the inward apexes K2 of the shoulder circumferential grooves 9. As a result, the first middle blocks 4R of this embodiment are formed in a barrel-like hexagonal shape with the circumferential center bulging outward in the axial direction in a tread plan view. Such first middle blocks 4R have high lateral rigidity, which prevents the tire from collapsing in the axial direction.

[0035] The first shoulder lateral grooves 11 extend axially outward from the outward apexes K1 of the shoulder circumferential grooves 9. As a result, the first shoulder blocks 5R of this embodiment are formed in a pentagonal shape with the circumferential center portion bulging axially inward in a tread plan view.

[0036] The center lateral groove 12 connects the inward apexes K2 of the center circumferential grooves 8 on both sides. As a result, the center block 3R of this embodiment is formed into a barrel-shaped hexagon with the circumferential center bulging outward on both sides in the axial direction in a tread plan view. Such a center block 3R has high lateral and vertical rigidity and exhibits excellent center wear resistance.

[0037] Each first middle block 4R is provided with a first middle sipe 20 that crosses the first middle block 4R. The first middle sipe 20 extends in a zigzag pattern along the longitudinal direction and the tire radial direction. Thus, the first middle sipe 20 of this embodiment is formed as a so-called three-dimensional sipe. FIG. 4 is a perspective view conceptually illustrating a three-dimensional sipe. As shown in FIG. 4, this type of sipe has two wall surfaces S formed with repeated concave and convex portions, which tightly mesh with each other when the tire 1 rolls. This increases the apparent rigidity of the first middle block 4R, suppressing the first middle block 4R from collapsing in the tire axial direction, thereby improving center wear resistance. In this specification, the term "sipe" refers to a notch-like body with a width of less than 1.5 mm and is clearly distinguished from grooves (including circumferential grooves and lateral grooves) with a groove width of 1.5 mm or more.

[0038] Although not particularly limited, the ratio (Ds / Da) of the depth Ds of the first middle sipes 20 to the groove depth Da of the center circumferential groove 8 is preferably 0.6 or more, more preferably 0.7 or more, and more preferably 0.9 or less, and even more preferably 0.8 or less. The ratio (Ya / Yb) of the amplitude Ya (shown in FIG. 2) of the first middle sipes 20 in the longitudinal direction to the amplitude Yb of the first middle sipes 20 in the tire radial direction is preferably 1.0 or more, more preferably 1.1 or more, and even more preferably 1.3 or less, and even more preferably 1.2 or less.

[0039] As shown in FIG. 2, the center block 3R is provided with a center sipe 21 that crosses the center block 3R. In this embodiment, the center sipe 21 extends in a zigzag pattern along the longitudinal direction. Such a center sipe 21 also increases the apparent rigidity of the center block 3R. Note that the center sipe 21 may extend in a zigzag pattern or linearly in the tire radial direction, for example.

[0040] Figure 5 is a plan view of a tread portion 2 of another embodiment. The same components as those of this embodiment are denoted by the same reference numerals, and a description thereof will be omitted. As shown in Figure 5, the tread portion 2 of this embodiment is provided with a center land portion 3, a first middle land portion 4, a first shoulder land portion 5, a second middle land portion 6, and a second shoulder land portion 7. The tread portion 2 also includes, for example, a center circumferential groove 8, a shoulder circumferential groove 9, a first middle lateral groove 10, a first shoulder lateral groove 11, and a center lateral groove 12.

[0041] The first middle lateral grooves 10 of this embodiment connect the first middle blocks 4R adjacent to the first middle lateral grooves 10 and have groove bottom protrusions 25 formed at the groove bottoms 10s. Such groove bottom protrusions 25 further prevent the first middle blocks 4R from collapsing.

[0042] FIG. 6 is a cross-sectional view taken along line AA in FIG. 5. As shown in FIG. 6, the depth Dg of the groove bottom ridge 25 is preferably 40% or more, more preferably 45% or more, and more preferably 60% or less, and even more preferably 55% or less of the groove depth Da (shown in FIG. 1) of the center circumferential groove 8. Since the depth Dg of the groove bottom ridge 25 is 40% or more of the groove depth Da of the center circumferential groove 8, basic wet performance is maintained at a high level. Since the depth Dg of the groove bottom ridge 25 is 60% or less of the groove depth Da of the center circumferential groove 8, collapse of the first middle block 4R is effectively suppressed. The groove depth Dc of the first middle lateral groove 10 is preferably 80% to 120% of the groove depth Da of the center circumferential groove 8. In this embodiment, the groove depth Dc of the first middle lateral groove 10 is the same as the groove depth Da of the center circumferential groove 8.

[0043] 5, the axial length Lg of the groove bottom ridge 25 is preferably 40% or more, more preferably 45% or more, and more preferably 60% or less, and even more preferably 55% or less of the axial length Lc of the first middle lateral grooves 10. This makes the above-mentioned effects more effective.

[0044] The groove bottom ridge 25 is provided, for example, at the axial center 10c of the first middle lateral groove 10. The groove bottom ridge 25 is provided at a position spaced apart from both axial ends 10e, 10e of the first middle lateral groove 10. The axial separation distance Ld between one end 10e of the first middle lateral groove 10 and one end 25e of the groove bottom ridge 25 is preferably 15% or more of the axial length Lc of the first middle lateral groove 10, more preferably 20% or more, and more preferably 35% or less, and even more preferably 30% or less.

[0045] The center lateral groove 12 of this embodiment also has a groove bottom raised portion 26 that connects the center blocks 3R adjacent to the center lateral groove 12 and raises the groove bottom 12s.

[0046] The groove bottom ridges 26 of the center lateral grooves 12 are provided with sipes 27. Such sipes 27 suppress the deterioration of wet performance caused by the groove bottom ridges 26.

[0047] Although particularly preferred embodiments of the present disclosure have been described in detail above, the present disclosure is not limited to the illustrated embodiments and can be modified and implemented in various forms. [Example]

[0048] A heavy-duty tire prototype with the basic structure shown in Figure 1 was manufactured and tested for center wear resistance. The test method and common specifications are as follows: Tire size: 295 / 75R22.5 Rim: 8.25 x 22.5 Internal pressure: 750kPa Da, Db: 25 mm R1 / R2:1.00 R3 / R4:1.00

[0049] <Center wear resistance> The test tire was mounted on the first drive axle of a trailer head. A test driver then drove the vehicle, and the groove depths of the center lateral grooves and center circumferential grooves were measured after the run. The results were expressed as an index, with the average groove depth of Comparative Example 1 set to 100. The larger the index, the better the center wear resistance. Vehicle: 10-ton truck (50% of standard load) Mileage: 50,000 km The test results are shown in Table 1.

[0050] [Table 1]

[0051] As shown in Table 1, it can be seen that the tires of the examples are superior in center wear resistance compared to the tires of the comparative examples. Therefore, it can be said that the tires of the examples have high life performance.

[0052] [Note] The present disclosure includes the following aspects.

[0053] [Disclosure 1] A heavy-duty tire having a tread portion, The tread portion includes a center land portion located closest to the tire equator, a first middle land portion adjacent to the center land portion via a center circumferential groove, a first shoulder land portion adjacent to the first middle land portion via a shoulder circumferential groove and having a first tread edge, and first middle lateral grooves and first shoulder lateral grooves that divide the first middle land portion and the first shoulder land portion into first middle blocks and first shoulder blocks, respectively. When the tire is mounted on a regular rim and the internal pressure is adjusted to 5% of the regular internal pressure, the radius of curvature R1 of the contact patch profile P1 of the center land portion, the radius of curvature R2 of the contact patch profile P2 of the axially inner region of the first middle block, the radius of curvature R3 of the contact patch profile P3 of the axially outer region of the first middle block, and the radius of curvature R4 of the contact patch profile P4 of the first shoulder block satisfy the following formulas (1) to (3): The groove depth of the center circumferential groove and the shoulder circumferential groove is 21 mm or more, a ratio (Wa / Da) of a groove depth Da of the center circumferential groove to a groove width Wa of the center circumferential groove is 0.25 or less, Each of the first middle blocks has a ratio (Lb / La) of a maximum length La in the tire circumferential direction to a maximum length Lb in the tire axial direction that is greater than 0.75. Heavy duty tires. 0.95≦(R1 / R2)≦1.05 …(1) 0.95≦(R3 / R4)≦1.05 …(2) R1>R3 …(3) [Disclosure 2] The contact surface profile P2 and the contact surface profile P3 intersect at an inflection point, The heavy-duty tire according to Disclosure 1, wherein the distance in the tire axial direction from the tire equator to the inflection point is 0.35 to 0.50 times the tread half width Wt, which is the distance in the tire axial direction from the tire equator to the first tread end. [Disclosure 3] The heavy-duty tire according to Disclosure 1 or 2, wherein the ratio R3 / R1 of the radius of curvature R1 of the contact patch profile P1 of the center land portion to the radius of curvature R3 of the contact patch profile P3 of the first middle block is 0.14 to 0.20. [Disclosure 4] The first middle block is provided with a first middle sipe that crosses the first middle block, The heavy-duty tire according to any one of Disclosures 1 to 3, wherein the first middle sipe extends in a zigzag pattern along the longitudinal direction and the tire radial direction. [Disclosure 5] The heavy-duty tire according to any one of Disclosures 1 to 4, wherein the first middle lateral grooves connect the first middle blocks adjacent to the first middle lateral grooves and have groove bottom raised portions where the groove bottoms are raised. [Disclosure 6] The heavy-duty tire according to Disclosure 5, wherein the depth of the groove bottom raised portion is 40% to 60% of the groove depth of the central circumferential groove. [Explanation of symbols]

[0054] 1 Heavy duty tires 3 Center Land Division 4R 1st Middle Block 4a Inner area 4b Outer area Round 5: 1st shoulder block 8 Center circumferential groove P Ground Profile R radius of curvature

Claims

1. A heavy-duty tire having a tread portion, the tread portion includes a center land portion located closest to the tire equator, a first middle land portion adjacent to the center land portion via a center circumferential groove, a first shoulder land portion adjacent to the first middle land portion via a shoulder circumferential groove and having a first tread edge, and first middle lateral grooves and first shoulder lateral grooves that divide the first middle land portion and the first shoulder land portion into first middle blocks and first shoulder blocks, respectively; When the tire is mounted on a regular rim and the internal pressure is adjusted to 5% of the regular internal pressure, the radius of curvature R1 of the contact patch profile P1 of the center land portion, the radius of curvature R2 of the contact patch profile P2 of the axially inner region of the first middle block, the radius of curvature R3 of the contact patch profile P3 of the axially outer region of the first middle block, and the radius of curvature R4 of the contact patch profile P4 of the first shoulder block satisfy the following formulas (1) to (3): The center circumferential groove and the shoulder circumferential groove have a groove depth of 21 mm or more, a ratio (Wa / Da) of a groove depth Da of the center circumferential groove to a groove width Wa of the center circumferential groove is 0.25 or less, Each of the first middle blocks has a ratio (Lb / La) of a maximum circumferential length La to a maximum axial length Lb of the tire that is greater than 0.

75. Heavy duty tires. 1<(R1 / R2)≦1.05…(1) 0.95≦(R3 / R4)≦1.05…(2) R1>R3 ... (3)

2. A heavy-duty tire having a tread portion, the tread portion includes a center land portion located closest to the tire equator, a first middle land portion adjacent to the center land portion via a center circumferential groove, a first shoulder land portion adjacent to the first middle land portion via a shoulder circumferential groove and having a first tread edge, and first middle lateral grooves and first shoulder lateral grooves that divide the first middle land portion and the first shoulder land portion into first middle blocks and first shoulder blocks, respectively; When the tire is mounted on a regular rim and the internal pressure is adjusted to 5% of the regular internal pressure, the radius of curvature R1 of the contact patch profile P1 of the center land portion, the radius of curvature R2 of the contact patch profile P2 of the axially inner region of the first middle block, the radius of curvature R3 of the contact patch profile P3 of the axially outer region of the first middle block, and the radius of curvature R4 of the contact patch profile P4 of the first shoulder block satisfy the following formulas (1) to (3): The center circumferential groove and the shoulder circumferential groove have a groove depth of 21 mm or more, a ratio (Wa / Da) of a groove depth Da of the center circumferential groove to a groove width Wa of the center circumferential groove is 0.25 or less, Each of the first middle blocks has a ratio (Lb / La) of a maximum circumferential length La to a maximum axial length Lb of the tire that is greater than 0.

75. Heavy duty tires. 1<(R1 / R2)≦1.05…(1) 1<(R3 / R4)≦1.05…(2) R1>R3 ... (3)

3. The contact surface profile P2 and the contact surface profile P3 intersect at an inflection point, 3. The heavy-duty tire according to claim 1, wherein the distance in the tire axial direction from the tire equator to the inflection point is 0.35 to 0.50 times a tread half width Wt, which is the distance in the tire axial direction from the tire equator to the first tread end.

4. A heavy-duty tire as described in any one of claims 1 to 3, wherein the ratio R3 / R1 of the radius of curvature R1 of the contact patch profile P1 of the center land portion to the radius of curvature R3 of the contact patch profile P3 of the first middle block is 0.14 to 0.

20.

5. The first middle block is provided with a first middle sipe that crosses the first middle block, 5. The heavy duty tire according to claim 1, wherein the first middle sipe extends in a zigzag pattern along the longitudinal direction and the tire radial direction.

6. A heavy-duty tire as described in any one of claims 1 to 5, wherein the first middle lateral groove connects the first middle blocks adjacent to the first middle lateral groove, and has a groove bottom raised portion where the groove bottom is raised.

7. A heavy-duty tire as described in claim 6, wherein the depth of the groove bottom raised portion is 40% to 60% of the groove depth of the center circumferential groove.

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