JP2016203747A - Heavy load tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simultaneously restrict shoulder fall wear in a shoulder area and a step wear.SOLUTION: A tread part 2 has a shoulder area Ys having a contour shape formed from an arc such that the shoulder area is greater in curvature radius R2 than a center area Yc. A distance L from the center of a shoulder main groove 3 to a tire equator Co is 0.45 to 0.55 times as long as a ground half width TW. The shoulder area Ys comprises a shoulder longitudinal narrow groove 5 near a tread ground end Te, and a shoulder lateral groove 9 extending from the shoulder longitudinal narrow groove 5 to a shoulder main groove 3. The depth of the shoulder lateral groove 9 is less than that of the shoulder main groove 3.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a heavy duty tire that simultaneously suppresses shoulder drop wear and step wear in the shoulder region.

  In heavy-duty tires in which the tread portion is divided into an inner center region and an outer shoulder region by a shoulder main groove, the shoulder region gradually wears from the outer side toward the inner side in the tire axial direction due to running. Wear (so-called shoulder wear) is likely to occur. This shoulder drop wear is caused by the fact that the contact pressure acting on the shoulder region decreases as it approaches the tread contact end side, and as the contact pressure decreases, the slip between the tire and the road surface increases in the shoulder region. This is thought to be due to wear.

  In order to suppress this shoulder drop wear, for example, the following Patent Document 1 proposes adjusting the contact length in the shoulder region to improve the tire contact surface shape.

  However, in the proposed tire in which the contact length in the shoulder region is large, so-called step wear in which the vicinity of the tread contact end is worn in a stepped shape tends to occur. This step wear is thought to be due to the fact that the load is concentrated near the tread ground end and the ground pressure near the tread ground end is increased by increasing the ground contact length in the shoulder region.

  That is, shoulder wear and shoulder wear in the shoulder region have a trade-off relationship in the cause of occurrence, and it is a difficult problem to suppress these two uneven wears simultaneously.

JP 2007-182099 A

  Therefore, an object of the present invention is to provide a heavy duty tire capable of simultaneously suppressing shoulder drop wear and step wear in the shoulder region.

In the present invention, by providing a shoulder main groove extending in the tire circumferential direction on both sides of the tire equator in the tread portion, the tread portion is divided into a center region on the inner side and an outer shoulder region on the shoulder main groove. A heavy duty tire,
The contour shape of the surface of the tread portion includes a first arc having a curvature radius R1 in the center region, and a second arc having a curvature radius R2 larger than the curvature radius R1 in the shoulder region.
The distance L from the groove center of the shoulder main groove to the tire equator is 0.45 to 0.55 times the ground contact half width TW, which is the distance from the tread ground contact edge to the tire equator,
The shoulder region comprises a shoulder vertical narrow groove extending in the tire circumferential direction at a position in the vicinity of the tread contact edge, and a plurality of shoulder lateral grooves extending from the shoulder vertical groove to the shoulder main groove,
Moreover, the shoulder vertical groove is inclined inward in the tire axial direction toward the groove bottom,
In addition, the groove depth of the shoulder lateral groove is smaller than the groove depth of the shoulder main groove.

  In the heavy-duty tire according to the present invention, the center region has one or more center vertical grooves having a groove width smaller than that of the shoulder main groove and extending in the tire circumferential direction, and a direction intersecting the center vertical grooves. The plurality of center sipes are preferably divided into a plurality of center blocks.

  In the heavy duty tire according to the present invention, it is preferable that the shoulder main groove extends in a zigzag shape in the tire circumferential direction.

  In the heavy load tire according to the present invention, the shoulder lateral groove includes an inner lateral groove portion that extends from the shoulder main groove at an angle θ with respect to a tire axial direction, and a tire shaft extending from the inner lateral groove portion to a shoulder vertical narrow groove. It is preferable that the outer lateral groove portion extends in the direction.

  In the heavy duty tire according to the present invention, the curvature radius R1 is preferably 600 to 900 mm, and the curvature radius R2 is preferably 1.3 to 3.0 times the curvature radius R1.

  In the heavy load tire according to the present invention, a groove center line of the shoulder vertical groove is orthogonal to the second arc, and a groove depth of the shoulder vertical groove is equal to a groove depth of the shoulder main groove. It is preferably 0.6 to 1.0 times.

  In the heavy load tire according to the present invention, the shoulder region includes a thin rib portion extending continuously in a tire circumferential direction outside the shoulder vertical groove, and a narrow portion at a groove bottom of the shoulder vertical groove. The rib width Wa of the rib portion is preferably 5 to 8 times the rib width Wb of the thin rib portion on the surface of the tread portion.

In the heavy load tire according to the present invention, in the contact pressure distribution when a normal load is applied to a tire in a normal state in which a rim is assembled to a normal rim and filled with a normal internal pressure,
The contact pressure gradually decreases from the tire equator toward the tread contact end, and the difference (Pc-Pe) between the contact pressure Pc at the tire equator and the contact pressure Pe at the tread contact end is 0.25 MPa or more. It is preferable that the difference ΔP between the contact pressures at any two positions separated by 5 cm in the tire axial direction is 0.05 MPa or less.

  In the present invention, the dimension of each part of the tire is a value specified in a 5% internal pressure state in which a rim is assembled on a normal rim and 5% of the normal internal pressure is filled. The tire in the 5% internal pressure state substantially matches the shape when the tire is vulcanized with a vulcanization mold. The groove width of each groove including the shoulder main groove is a value measured on the surface of the tread portion.

  In the present invention, the tread grounding end means the position of the outermost end in the tire axial direction of the tread grounding surface that contacts the tire in a normal load state in which a normal load is applied to a tire that is assembled with a normal rim and filled with a normal internal pressure To do.

  The “regular rim” is a rim determined for each tire in a standard system including a standard on which a tire is based. For example, JAMMA is a standard rim, TRA is “Design Rim”, or ETRTO. Then means "Measuring Rim". The “regular internal pressure” is the air pressure defined by the standard for each tire. The maximum air pressure for JATMA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” for ETRA, If so, it means "INFLATION PRESSURE". The “regular load” is a load determined by the standard for each tire, and if it is JATMA, the maximum load capacity, and if it is TRA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” If it is ETRTO, it is "LOAD CAPACITY".

  As described above, in the present invention, in the contour shape of the tread portion, the curvature radius R2 in the shoulder region is larger than the curvature radius R1 in the center region. Therefore, it is possible to suppress the contact pressure in the shoulder region from decreasing toward the tread contact end side, and to relatively reduce the tire circumferential length difference between the shoulder region and the center region. As a result, it is possible to reduce the slipping between the tire and the road surface in the shoulder region and suppress the shoulder drop wear.

  Further, the step wear that tends to occur due to the setting of the curvature radii R1 and R2 is suppressed by the shoulder vertical narrow groove. The shoulder vertical narrow groove divides the shoulder region into a shoulder main portion on the inner side in the tire axial direction and a narrow rib portion on the outer side in the tire axial direction than the shoulder vertical thin groove.

  The thin rib portion exhibits a function A for suppressing an excessive increase in the contact pressure at the tread contact end and a function B as a wear sacrifice component. Specifically, the thin rib portion buffers the force received from the outer side in the tire axial direction, and suppresses a significant increase in the contact pressure at the tread contact end. Further, since the thin rib portion is low in rigidity and easily deformed, the ground pressure is lower than that of the shoulder main portion, and slippage is likely to occur. Therefore, this thin rib part functions as a wear sacrificial component that concentrates wear on itself, and by protecting the shoulder main part from uneven wear, step wear can be suppressed in combination with the function A.

It is the partial expanded view which expand | deployed the tread pattern of the tire for heavy loads of this invention on the plane. It is meridional sectional drawing of a tread part. FIG. 3 is a partially enlarged view of FIG. 2. (A) is a contact surface in a normal load state, (b) is a graph showing a contact pressure distribution.

Hereinafter, embodiments of the present invention will be described in detail.
As shown in FIG. 1, the heavy load tire 1 of the present embodiment includes a shoulder main groove 3 extending in the tire circumferential direction on both sides of the tire equator Co in the tread portion 2. As a result, the tread portion 2 is divided into a center region Yc on the inner side in the tire axial direction from the shoulder main groove 3 and a shoulder region Ys on the outer side in the tire axial direction from the shoulder main groove 3.

  As shown in FIG. 2, in the 5% internal pressure state, the surface S of the tread portion 2 (hereinafter sometimes referred to as “tread surface S”) has the center region Yc formed of the first arc 4c and the shoulder. The region Ys has a double radius contour shape composed of the second arc 4s. The first arc 4c and the second arc 4s each have an arc center on the tire equator Co. The curvature radius R2 of the second arc 4s is larger than the curvature radius R1 of the first arc 4c.

  Thus, by making the tread surface S have a double radius contour shape with a radius of curvature R2 larger than the radius of curvature R1, the contact pressure in the shoulder region Ys is reduced compared to a tire with a single radius contour shape. It is possible to suppress an excessive decrease toward the ground end Te. In addition, the tire circumferential length difference between the shoulder region Ys and the center region Yc can be reduced as compared with a tire having a single radius contour shape. As a result, slippage between the tire and the road surface in the shoulder region Ys can be reduced, which is advantageous in suppressing shoulder drop wear.

  The curvature radius R1 is preferably in the range of 600 to 900 mm, and the curvature radius R2 is preferably in the range of 1.3 to 3.0 times the curvature radius R1. If the curvature radius R2 is less than 1.3 times the curvature radius R1, it will be difficult to sufficiently suppress the shoulder wear. On the contrary, if it exceeds 3.0 times, it becomes difficult to sufficiently suppress the step wear even by adopting a shoulder narrow groove 5 described later.

  Here, in the heavy load tire 1, various conventional internal structures (not shown) can be suitably employed. As an example, the internal structure includes a toroid-like carcass straddling between the bead portions, and a belt layer disposed outside the carcass in the radial direction and inside the tread portion 2. The carcass can be formed of, for example, one or more carcass plies in which steel carcass cords are arranged at an angle of, for example, 70 to 90 ° with respect to the tire circumferential direction. The belt layer can be formed of, for example, a plurality of, for example, 3 to 4 belt plies in which steel belt cords are arranged at an angle of, for example, 10 to 70 ° with respect to the tire circumferential direction. The belt layer terminates on the outer side in the tire axial direction from the shoulder main groove 3. Accordingly, the tread portion 2 is reinforced including the groove bottom of the shoulder main groove 3, and bending deformation of the tread portion 2 starting from the groove bottom, uneven wear due to the bending deformation, and the like are reduced.

  The shoulder main groove 3 has a ground contact half width TW of 0.45 to .0 .0 in which the distance L in the tire axial direction from the groove center to the tire equator Co is the tire axial distance from the tread ground contact end Te to the tire equator Co. 55 times. The “groove center” means the center of the groove width in the opening portion on the tread surface S of the shoulder main groove 3.

  When the distance L exceeds 0.55 times the ground contact half width TW, the rigidity of the shoulder region Ys becomes excessively low, and the turning performance tends to decrease, and the shoulder region Ys wears earlier than the center region Yc. Tend to. On the other hand, when the ratio is less than 0.45 times, the rigidity of the center region Yc becomes excessively low, and the straightness tends to decrease, and the center region Yc tends to wear earlier than the shoulder region Ys.

  The shoulder main groove 3 is a drainage groove for ensuring wet performance, and is preferably a wide groove having a groove width 3W of 5 mm or more. The groove depth 3D is preferably 8 mm or more. The shoulder main groove 3 can be formed in a straight line shape or a zigzag shape. However, in order to suppress bending deformation of the tread portion 2 starting from the groove bottom, the shoulder main groove 3 is formed in a zigzag shape as shown in FIG. Is preferred. When the shoulder main groove 3 has a zigzag shape, the center of the zigzag amplitude is applied as the groove center.

  In order to suppress the step wear caused by the double radius, as shown in an enlarged view in FIG. 3, the shoulder region Ys includes a shoulder vertical narrow groove 5 extending in the tire circumferential direction at a position near the tread ground contact Te. Yeah. Thus, the shoulder region Ys is divided into a shoulder main portion 6 on the inner side in the tire axial direction than the shoulder vertical groove 5 and a thin rib portion 7 on the outer side in the tire axial direction. The “near position” of the tread ground end Te means a region range whose distance from the tread ground end Te is 5 mm or less, and at least a part of the opening of the shoulder vertical narrow groove 5 is interposed in the region range of this near position. To do. That is, the rib width Wb on the tread surface S of the thin rib portion 7 is 5 mm or less.

  The shoulder vertical narrow groove 5 is a narrow groove whose groove width 5W is smaller than the groove width 3W of the shoulder main groove 3, for example, 30% or less of the groove width 3W, and continues linearly in the tire circumferential direction. . The shoulder vertical groove 5 is inclined inward in the tire axial direction toward the groove bottom. In the present example, the groove center line 5i of the shoulder vertical groove 5 is orthogonal to the second arc 4s. The groove depth 5D of the shoulder vertical groove 5 is preferably in the range of 0.6 to 1.0 times the groove depth 3D of the shoulder main groove 3.

  The thin rib portion 7 divided by the shoulder vertical narrow groove 5 extends continuously in the tire circumferential direction. The rib width Wa of the thin rib portion 7 at the bottom of the shoulder vertical thin groove 5 is preferably 5 to 8 times the rib width Wb of the tread surface S.

  Such a thin rib portion 7 exhibits a function A for suppressing an excessive increase in the contact pressure at the tread contact end Te and a function B as a wear sacrifice component. That is, the thin rib portion 7 buffers the force received from the outer side in the tire axial direction, and suppresses a significant increase in the contact pressure at the tread contact end Te. Further, since the thin rib portion 7 has low rigidity and is easily deformed, the ground pressure is lower than that of the shoulder main portion 6 and slippage is likely to occur. For this reason, the thin rib portion 7 functions as a wear sacrificial component that concentrates wear on itself, and protects the shoulder main portion 7 from uneven wear, thereby cooperating with the function A (function A for suppressing an increase in ground pressure). Thus, the occurrence of step wear can be suppressed.

  If the rib width Wa of the thin rib portion 7 exceeds 8 times the rib width Wb, the rigidity of the thin rib portion 7 becomes too high and the functions A and B are reduced, and the effect of suppressing step wear is effectively exhibited. Disappear. Further, the flexibility of the thin rib portion 7 is reduced, and the fine rib portion 7 may be lost. On the contrary, when the rib width Wa is less than 5 times the rib width Wb, the rigidity of the thin rib portion 7 is too low and the function A is reduced, and the effect of suppressing the step wear is not effectively exhibited. Further, when the groove depth 5D of the shoulder vertical narrow groove 5 is less than 0.6 of the groove depth 3D, the rigidity of the thin rib portion 7 becomes too high, and the functions A and B are reduced, and the step wear is reduced. The suppression effect is not effectively exhibited. Further, the flexibility of the thin rib portion 7 is reduced, and the fine rib portion 7 may be lost. On the contrary, when the groove depth 5D exceeds 1.0 times the groove depth 3D, the outer end of the belt layer approaches the groove bottom of the shoulder vertical thin groove 5, and the distortion at the outer end increases. It tends to cause belt end peeling.

  The shoulder main portion 6 is provided with a plurality of shoulder lateral grooves 9 that divide the shoulder main portion 6 into a plurality of shoulder blocks 8 by extending from the shoulder vertical narrow groove 5 to the shoulder main groove 3.

  The groove depth 9D of the shoulder lateral groove 9 is smaller than the groove depth 3D of the shoulder main groove 3, and preferably smaller than the groove depth 5D of the shoulder vertical narrow groove 5, in particular, the groove depth. 3D is preferably 50% or less, more preferably 30% or less. As shown in FIG. 1, the shoulder lateral groove 9 in this example includes an inner lateral groove portion 9 i extending from the shoulder main groove 3 at an angle θ with respect to the tire axial direction line, and a shoulder vertical narrow groove extending from the inner lateral groove portion 9 i. 5 and an outer lateral groove portion 9o extending along the tire axial direction line. The angle θ is preferably 30 ° or less, more preferably 20 ° or less. In this example, the inner lateral groove portion 9i and the outer lateral groove portion 9o have substantially the same width, and the tire axial direction length of the inner lateral groove portion 9i is set to be smaller than the tire axial direction length of the outer lateral groove portion 9o. .

  Such a shallow shoulder lateral groove 9 maintains the rigidity of the shoulder block 8 at a high level, and suppresses an excessive decrease in the ground pressure in the shoulder main portion 6. Thereby, the suppression effect of shoulder fall wear can be enhanced in cooperation with the aforementioned double radius and the wear sacrifice function B by the thin rib portion 7. In particular, the shoulder lateral groove 9 forms a bent groove composed of the inner lateral groove portion 9i and the outer lateral groove portion 9o, whereby the rigidity can be improved in a balanced manner in the tire circumferential direction and the tire axial direction.

  Next, as shown in FIG. 1, the center region Yc includes one or more center vertical narrow grooves 10 extending in the tire circumferential direction, and a plurality of center sipes 11 in a direction intersecting with the center vertical thin grooves 10. As a result, the center area Yc is divided into a plurality of center blocks 12.

  In this example, the center vertical narrow groove 10 is composed of a center center vertical thin groove 10c passing over the tire equator Co and center vertical narrow grooves 10m arranged on both sides thereof. As a result, the center region Yc has a center region Yci between the center center vertical groove 10c and the side center vertical groove 10m, and between the side center vertical groove 10m and the shoulder main groove 3. It is divided into a center area portion Yco outside of. The center sipe 11 includes an inner center sipe 11i that divides an inner center region portion Yci into an inner center block 12i, and an outer center sipe 11o that divides an outer center region portion Yco into an outer center block 12o. .

  The center vertical groove 10 has a groove width W10 smaller than the groove width 3W of the shoulder main groove 3, for example, 30% or less of the groove width 3W, and preferably the groove width 5W of the shoulder vertical groove 5 Is set larger than In this example, the center vertical narrow groove 10 extends linearly in the tire circumferential direction.

  Further, the center sipe 11 has a cut shape that closes the groove width at the time of ground contact, and in this example, the center sipe 11 is inclined at an angle α of 45 ° or less with respect to the tire axial line. In this example, the inner center sipe 11i and the outer center sipe 11o have different inclination directions, and the outer ends of the center sipe 11 are approximately 1/2 in the tire circumferential direction between the adjacent center sipe 11 in the tire axial direction. The position is shifted by 2 pitches. Thereby, uniform rigidity can be achieved over the entire center region Yc. Further, a chamfered portion 15 is formed at a corner portion of the center block 12 adjacent in the tire axial direction across the center vertical groove 10m. The chamfered portion 15 formed in one center block 12 adjacent in the tire axial direction and the chamfered portion 15 formed in the other center block 12 are arranged facing each other across the center vertical groove 10m. That is, at least a part of one chamfered portion 15 and the other chamfered portion 15 overlaps in the tire axial direction.

  And the rigidity of the tread portion 2 can be adjusted by appropriately setting the number of the center vertical narrow grooves 10, the center sipes 11, and the shoulder lateral grooves 9, the groove depth, the angle α, etc. The contact pressure distribution is controlled as follows to achieve both shoulder fall wear and step wear at a higher level.

  The “normal load state” means a state in which a normal load is applied to a tire assembled with a normal rim and filled with a normal internal pressure. Strictly speaking, the “ground pressure distribution” is defined as follows. As shown in FIG. 4 (a), in the ground contact surface F when the tire is grounded in the normal load state, the tire axial direction with the ground contact center of the ground contact surface F as the origin 0 is the X axis, the tire The circumferential direction is defined as the Y axis. A distribution in the X-axis direction of the average value of the contact pressure in the range of the tire circumferential width of 5 cm centering on Y = 0 is indicated as a contact pressure distribution J.

  In the tire 1 of this example, as shown in FIG. 4B, in the contact pressure distribution J, the contact pressure P gradually decreases from the tire equator Co toward the tread contact end Te, and the contact pressure at the tire equator Co. The difference (Pc−Pe) between Pc and the ground pressure Pe at the tread ground end Te is set to 0.25 MPa or more. Further, the contact pressure difference ΔP at any two positions Qa and Qb separated by 5 cm in the tire axial direction (X-axis direction) is set to 0.05 MPa or less. By using such a contact pressure distribution J, both shoulder wear and step wear can be achieved at a higher level.

  When the difference (Pc−Pe) is less than 0.25 MPa, the contact pressure in the shoulder region Ys increases, which is disadvantageous for step wear. On the other hand, if the difference (Pc−Pe) is too large, the contact pressure in the shoulder region Ys is lowered, which is disadvantageous for shoulder wear. Therefore, the upper limit of the difference (Pc−Pe) is preferably 0.45 MPa or less. When the difference ΔP exceeds 0.05 MPa, a portion with a large contact pressure difference becomes a starting point for uneven wear.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

A heavy-duty tire of size 295 / 80R22.5 using the tread pattern of FIG. 1 as a basic pattern was prototyped based on the specifications in Table 1 and evaluated for the presence or absence of shoulder drop wear, step wear, and thin ribs on each tire. It was done. Except as described in Table 1, the specifications are substantially the same.
The common specifications are as follows.
・ Shoulder main groove:
Groove width 3W (9.0mm),
Groove depth 3D (17.0mm),
-Radius of curvature R1 (635mm) of the first arc,
・ Shoulder vertical narrow groove:
Groove width 3W (0.5mm),
Groove depth 3D (17.0mm),
・ Width of thin rib part Wb (2.0mm),
・ Shoulder lateral groove angle θ (15 °),
Groove depth 9D (4.0mm),
・ Grounding half width TW (126mm)

<Shoulder drop wear resistance, step wear resistance>
Each sample tire is mounted on the front wheel of a 10t truck under the conditions of a rim (8.25 × 22.5) and internal pressure (800kPa), and is run until the shoulder main groove is worn 30% with 10t loaded. It was. Then, the occurrence of shoulder drop wear and step wear in the shoulder region after running was visually observed and evaluated in five stages.

<Deficit of thin rib>
After running the test vehicle under the above conditions, the presence or absence of the thin rib portion was judged visually.

  As shown in the table, it can be confirmed that the tires of the examples can increase shoulder wear and step wear in the shoulder region.

DESCRIPTION OF SYMBOLS 1 Heavy load tire 2 Tread part 3 Shoulder main groove 4c 1st circular arc 4s 2nd circular arc 5 Shoulder vertical fine groove 5i Groove centerline 7 Fine rib part 9 Shoulder horizontal groove 9i Inner horizontal groove part 9o Outer horizontal groove part 10 Center vertical fine groove 11 Center sipe 12 Center block 13 Intersection 15 Chamfered portion Co Tire equator Te Tread ground contact end Yc Center region Ys Shoulder region

Claims (8)

By providing shoulder main grooves extending in the tire circumferential direction on both sides of the tire equator in the tread portion, the heavy load tire in which the tread portion is divided into an inner center region and an outer shoulder region from the shoulder main groove. Because
The contour shape of the surface of the tread portion includes a first arc having a curvature radius R1 in the center region, and a second arc having a curvature radius R2 larger than the curvature radius R1 in the shoulder region.
The distance L from the groove center of the shoulder main groove to the tire equator is 0.45 to 0.55 times the ground contact half width TW, which is the distance from the tread ground contact edge to the tire equator,
The shoulder region comprises a shoulder vertical narrow groove extending in the tire circumferential direction at a position in the vicinity of the tread contact edge, and a plurality of shoulder lateral grooves extending from the shoulder vertical groove to the shoulder main groove,
Moreover, the shoulder vertical groove is inclined inward in the tire axial direction toward the groove bottom,
In addition, a heavy duty tire characterized in that a groove depth of the shoulder lateral groove is smaller than a groove depth of the shoulder main groove.   The center region includes a plurality of center blocks each including one or more center vertical grooves having a groove width smaller than that of the shoulder main groove and extending in the tire circumferential direction, and a plurality of center sipes in directions intersecting with the center vertical grooves. The heavy-duty tire according to claim 1, wherein the tire is heavy-duty.   The heavy load tire according to claim 1, wherein the shoulder main groove extends in a zigzag shape in a tire circumferential direction.   The shoulder lateral groove includes an inner lateral groove portion that extends at an angle θ from the shoulder main groove with respect to the tire axial direction, and an outer lateral groove portion that extends from the inner lateral groove portion to the shoulder vertical groove in the tire axial direction. The heavy duty tire according to claim 2, wherein the tire is for heavy loads.   The heavy duty tire according to any one of claims 1 to 4, wherein the curvature radius R1 is 600 to 900 mm, and the curvature radius R2 is 1.3 to 3.0 times the curvature radius R1.   The groove vertical line of the shoulder vertical groove is orthogonal to the second arc, and the groove depth of the shoulder vertical groove is 0.6 to 1.0 times the groove depth of the shoulder main groove. The heavy-duty tire according to any one of claims 1 to 5, wherein:   The shoulder region includes a thin rib portion extending continuously in the tire circumferential direction outside the shoulder vertical groove, and a rib width Wa of the thin rib portion at the groove bottom of the shoulder vertical groove is a tread portion. The heavy-duty tire according to any one of claims 1 to 6, wherein the tire is 5 to 8 times the rib width Wb of the thin rib portion on the surface of the tire. In the contact pressure distribution in a normal load state where a normal load is applied to a tire that is assembled with a normal rim and filled with a normal internal pressure,
The contact pressure gradually decreases from the tire equator toward the tread contact end, and the difference (Pc-Pe) between the contact pressure Pc at the tire equator and the contact pressure Pe at the tread contact end is 0.25 MPa or more. The heavy-duty tire according to any one of claims 1 to 7, wherein a difference ΔP in contact pressure between two arbitrary positions separated by an interval of 5 cm in the tire axial direction is 0.05 MPa or less.

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