JP2009234362A - Pneumatic tire for heavy load - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire for a heavy load can certainly suppress uneven wear such as heel-and-toe wear and prolong a tire life by enhancing wear resistance of a whole of a tread part. <P>SOLUTION: The pneumatic tire for heavy load is provided with a circumferential division groove 9 for dividing a block row comprising a plurality of blocks 7 positioned between circumferential main grooves 3 and adjacent in a tire circumferential direction to two parts in a tread width direction and extending in the tire circumferential direction in the zig-zag form. Width (W1) in the circumferential main groove 3 is set wider than width (W2) of the circumferential division groove 9, and a zig-zag direction of the circumferential main groove 3 and a zig-zag direction of the circumferential division groove 9 are opposed to each other, and therefore, the block 7 is formed to the hexagonal shape in plan view. Length (l) of the block satisfies a range of 1.25-2.50% relative to the whole length (L) of the tire. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a heavy duty pneumatic tire, and more particularly to a heavy duty pneumatic tire having a tread width of 300 mm or less and a flatness ratio of 55% or less.

  Conventionally, in heavy-duty pneumatic tires mounted on construction vehicles (for example, dump trucks, claders, tractors, trailers), trucks and buses, a plurality of circumferential main grooves extending in the tire circumferential direction, and tread widths A block pattern in which a plurality of blocks partitioned by a plurality of width direction grooves (lag grooves) extending in the direction is provided is often used.

As such a block pattern, for example, the zigzag direction of the circumferential main groove extending zigzag in the tire circumferential direction and the zigzag direction of the adjacent circumferential main groove face each other, so that the block is viewed in plan view. A heavy duty pneumatic tire that reduces the unevenness of slipping in the tire circumferential direction and tread width direction by forming it in a hexagonal shape and suppresses beer and toe wear in which wear differences occur at both ends of the tire circumferential direction of the block. Is disclosed (for example, see Patent Document 1).
JP 2007-145209 (2nd page-3rd page, Fig. 1)

  However, in the above-described conventional heavy-duty tire, although it is possible to reduce the unevenness of the slip in the tire circumferential direction and the tread width direction and suppress the heel and toe wear, it is desired to further suppress the heel and toe wear. The current situation is.

  In particular, in flat tires having a low flatness ratio, which is becoming widespread, it is considered that the tire outer diameter is small, so that the amount of rubber worn with the thickness of the tread portion is small, and the tire life is shortened. Therefore, there is a demand for improving the wear resistance of the entire tread portion as well as suppressing uneven wear such as heel and toe wear.

  Therefore, the present invention has been made in view of such a situation, and can reliably suppress uneven wear such as heel and toe wear, thereby improving the wear resistance of the entire tread portion and extending the tire life. A heavy-duty pneumatic tire capable of

  The amount of wear of the block is correlated with the wear energy, which is the product of the slip generated between the block and the road surface, and the shearing force (product of ground pressure and friction coefficient μ) acting on the block from the road surface. Are known. Here, the shearing force is larger at the kicking end than at the stepping end. There are two types of slip: slip due to belt bending deformation (relative displacement of belt and tread), and slip due to recovery of block compression deformation (crushing, crushing). Slip occurs outward in the direction perpendicular to the wall.

  As a result of the inventor's analysis of the slip under the conditions assuming the market running, it was confirmed that the slip is concentrated on the kicking end outside the block. This is due to the concentration of ground pressure. In heavy duty pneumatic tires, it is common to increase the thickness of the tread (gauge thickness) in order to improve cut resistance. As a result of extensive analysis of tread deformation, the gauge thickness is increased. As a result, we found that slippage in the same direction as the rotation direction of the tire was large due to the influence of belt bending deformation (relative displacement of belt and tread) during kicking.

  Thus, since the wear amount of the block has a correlation with the slip, it has been found that in order to reduce the uneven wear of the block, it is only necessary to reduce the unevenness of the slip in the tire circumferential direction and the width direction. Further, in the case of a heavy-duty pneumatic tire, since slip in the same direction as the tire rotation direction is large, it has been found that reducing the non-uniformity is effective in improving uneven wear.

  Therefore, the present invention has the following features. First, the invention according to the first feature includes a plurality of blocks defined by a plurality of circumferential main grooves extending zigzag in the tire circumferential direction and a plurality of widthwise grooves extending in the tread width direction on the tread surface. A heavy-duty pneumatic tire having a tread width of 300 mm or less and a flatness ratio of 55% or less, and is a block row comprising a plurality of blocks located between the circumferential main grooves and adjacent in the tire circumferential direction Is divided into two in the tread width direction, and further provided with a circumferential division groove extending zigzag in the tire circumferential direction, and the width (W1) of the circumferential main groove is set wider than the width (W2) of the circumferential division groove The block is formed in a hexagonal shape in plan view by the zigzag direction of the circumferential main groove and the zigzag direction of the circumferential dividing groove facing each other. Tsu length is block length of the click (l) is the gist that satisfies a range of 1.25 to 2.50% with respect to the tire total length (L) is the length in the tire circumferential direction.

  According to such a feature, the block is formed in a hexagonal shape in plan view, and the block length (l) satisfies the range of 1.25 to 2.50% with respect to the tire total length (L), whereby the rigidity of the block is increased. Further, uneven wear such as heel and toe wear generated in the tread center portion can be reliably suppressed while keeping the size constant.

  In addition, since the circumferential dividing grooves are provided between the circumferential main grooves and the width (W1) of the circumferential main grooves is set wider than the width (W2) of the circumferential dividing grooves, the edge component is reduced. While maintaining the rigidity of the block, the heel and toe wear can be more reliably suppressed without degrading the wet performance.

  As described above, even with a flat tire having a low flatness ratio, uneven wear such as heel and toe wear that occurs in the tread center portion can be reliably suppressed, and the wear resistance of the entire tread portion is improved, thereby increasing the tire life. It can be extended.

  The invention according to another feature is summarized in that the shoulder block row located on the outer side in the tread width direction than the circumferential main groove located on the outermost side in the tread width direction is formed in a rib shape continuous in the tire circumferential direction. And

  According to this feature, the shoulder block row is formed in a rib shape, so that the rigidity of the shoulder block row is improved against lateral force, and the shoulder drop wear generated in the tread shoulder portion is also suppressed. It becomes possible.

  In other words, in addition to the heel and toe wear that occurs at the tread center part, uneven wear such as shoulder drop wear that occurs at the tread shoulder part can also be reliably suppressed, improving the wear resistance of the entire tread part and extending the tire life. It becomes possible to extend it reliably.

  The gist of the invention relating to other features is that adjacent circumferential main grooves are arranged with a shift of 0.4 to 0.6 wavelengths with respect to the tire circumferential direction.

  The invention according to other features includes a main groove inclination angle (α) that is an inclination angle of the circumferential main groove with respect to the tire circumferential direction, and a division groove inclination angle (β that is an inclination angle of the circumferential division groove with respect to the tire circumferential direction. ) Is set to 20 to 30 degrees.

  The invention according to another feature satisfies the relationship of 0.5 × d1 ≦ d2 ≦ d1, where “d1” is the depth of the circumferential main groove and “d2” is the depth of the circumferential dividing groove. The gist.

  The gist of the invention relating to other features is that the width (W1) of the circumferential main groove is set to 8 mm or more, and the width (W2) of the circumferential division groove is set to 4 mm or less.

  According to the present invention, it is possible to provide a heavy-duty pneumatic tire capable of reliably suppressing uneven wear such as heel and toe wear and improving the wear resistance of the entire tread portion and extending the tire life. it can.

  Next, an example of a heavy duty pneumatic tire according to the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and ratios of dimensions are different from actual ones. Accordingly, specific dimensions and the like should be determined in consideration of the following description. Moreover, the part from which the relationship and ratio of a mutual dimension differ also in between drawings is contained.

(Configuration of tread pattern)
First, the configuration of the tread pattern of the heavy duty pneumatic tire according to the present embodiment will be described with reference to FIG. FIG. 1 is a developed view showing a tread surface (tread pattern) of a heavy duty pneumatic tire according to the present embodiment, and FIG. 2 is a perspective view showing one block of the heavy duty pneumatic tire according to the present embodiment. FIG. 3 (a) is a tread sectional view (a sectional view taken along line AA in FIG. 1) showing one block of the heavy duty pneumatic tire according to the present embodiment, and FIG. It is a top view which shows one block of the heavy duty pneumatic tire which concerns on this Embodiment.

  The heavy duty pneumatic tire according to the present embodiment (hereinafter referred to as “heavy duty tire 1”) has a tread width of 300 mm or less and a flatness of 55% or less.

  As shown in FIGS. 1 to 3, the heavy-duty tire 1 is a block defined by a plurality of circumferential main grooves 3 extending zigzag in the tire circumferential direction and a plurality of widthwise grooves 5 extending in the tread width direction. 7 is provided.

  Further, between the circumferential main grooves 3, circumferential dividing grooves 9 extending in a zigzag shape in the tire circumferential direction are provided. The circumferential dividing groove 9 divides a block row composed of a plurality of blocks 7 located between the circumferential main grooves 3 and adjacent in the tire circumferential direction into two in the tread width direction.

  The block 7 is formed in a hexagonal shape in plan view because the zigzag direction of the circumferential main groove 3 and the zigzag direction of the circumferential dividing groove 9 are opposed to each other. That is, the block 7 has a shape that increases in width from both side ends to the center in the tire circumferential direction in plan view.

  As shown in FIGS. 2 and 3, the block 7 includes the most protruding upper surface 7a, the front surface 7b positioned on the front side in the rotational direction, the rear surface 7c positioned on the rear side in the rotational direction, the front surface 7b and the rear surface. It is comprised by the side surfaces 7d-7g which connect the direction surface 7c.

  The block length (l), which is the length of the block with respect to the tire circumferential direction, preferably satisfies the range of 1.25 to 2.50% with respect to the total tire length (L), which is the length in the tire circumferential direction (see FIG. 1).

  If the block length (l) is smaller than 1.25% with respect to the total tire length (L) (that is, the block 7 is too short), the deformation when the block 7 steps into the ground contact surface becomes large, The stepping end of the block 7 is worn more than the kicking end, and heel and toe wear may not be suppressed.

  On the other hand, if the block length (l) is greater than 2.50% with respect to the total tire length (L) (that is, the block 7 is too long), the deformation when the block 7 is stepped on the contact surface is reduced. 7, the compression rigidity of the block 7 becomes high, the edge pressure at the end of the block rises, the kicking end of the block 7 tends to wear, and heel and toe wear may not be suppressed.

  The crossing angle (γ) formed by the side surface 7d and the side surface 7e of the block 7 is preferably set to 120 to 150 degrees as shown in FIG.

  If the crossing angle (γ) is smaller than 120 degrees, the rigidity of the region sandwiched between the two side surfaces decreases, the deformation degree of the block 7 increases, and the tire circumferential direction of the block 7 The effect of making the slip in the tread width direction uniform may be reduced.

  On the other hand, when the crossing angle (γ) is greater than 150 degrees, the direction of the slip vector near the wall surface is close to the tire circumferential direction, and the effect of making the block 7 slip in the tire circumferential direction and tread width direction uniform is achieved. May fall.

  The shoulder block row 11 located on the outer side in the tread width direction than the circumferential main groove 3 located on the outermost side in the tread width direction is formed in a rib shape continuous in the tire circumferential direction.

(Configuration of circumferential main groove, width direction groove and circumferential direction division groove)
Next, the structure of the circumferential main groove 3, the width direction groove 5, and the circumferential division groove 9 described above will be described with reference to FIGS.

  As shown in FIG. 1, adjacent circumferential main grooves 3 and circumferential division grooves 9 are arranged with a shift of 0.4 to 0.6 wavelengths with respect to the tire circumferential direction.

  If the adjacent circumferential main grooves 3 circumferential dividing grooves 9 are shifted smaller than 0.4 wavelength or greatly shifted with respect to the tire circumferential direction, a block 7 having a hexagonal shape in plan view is formed. It may be difficult.

  The width (W1) of the circumferential main groove 3 is set wider than the width (W2) of the circumferential division groove 9 as shown in FIG. In particular, the width (W1) of the circumferential main groove 3 is preferably set to 8 mm or more. The width (W2) of the circumferential dividing groove 9 is preferably set to 4 mm or less.

  Here, when the depth of the circumferential main groove 3 is “d1” and the depth of the circumferential dividing groove 9 is “d2”, it is preferable that the relationship of 0.5 × d1 ≦ d2 ≦ d1 is satisfied. That is, the depth (d2) of the circumferential dividing groove 9 is equal to or less than the depth (d1) of the circumferential main groove 3 and is half the depth (d1) of the circumferential main groove 3. That's it.

  If the depth (d2) of the circumferential dividing groove 9 is deeper than the depth (d1) of the circumferential main groove 3, the wet performance can be improved, but the rigidity of each block 7 can be maintained. As a result, heel and toe wear may not be suppressed.

  On the other hand, if the depth (d2) of the circumferential dividing groove 9 is shallower than half the depth (d1) of the circumferential main groove 3, the rigidity of each block 7 can be maintained. It may be difficult to absorb rainwater or the like by the direction dividing groove 9, and the wet performance may be deteriorated.

  As shown in FIG. 3B, the main groove inclination angle (α) that is the inclination angle of the circumferential main groove 3 with respect to the tire circumferential direction, and the division groove that is the inclination angle of the circumferential division groove 9 with respect to the tire circumferential direction. The inclination angle (β) is preferably set to 20 to 30 degrees. The main groove inclination angle (α) and the division groove inclination angle (β) are provided in opposite directions. That is, the side surface 7d and the side surface 7e of the block 7 are provided opposite to the tire circumferential direction.

  Here, the slip of the block 7 will be described. The slip of the side surface 7d that comes into contact with the ground earlier includes a slip S1 in the tire circumferential direction due to the influence of belt bending deformation, and a slip S2 in the vertical outward direction of the wall surface due to the deformation recovery of the tread rubber. The slip S5 on the side surface 7d is a vector sum of the slip S1 and the slip S2.

  Similarly, the slip of the side surface 7e to be grounded later includes a slip S3 in the tire circumferential direction due to the influence of the belt bending deformation, and a slip S4 in the vertical direction outward of the wall surface due to the deformation recovery of the tread rubber. S6 is a vector sum of the slip S3 and the slip S4.

  Hereinafter, the slip of the block 7 having a hexagonal shape in plan view and the slip of the rectangular block (block 207 shown in FIG. 5) will be compared. In the case of the slip S5 of the side surface 7d of the block 7 having a hexagonal shape in plan view, the slip S2 facing outward in the vertical direction of the wall surface due to the deformation recovery of the tread rubber is the same tire rotation direction component as the circumferential slip S1 due to the influence of belt bending deformation have. On the other hand, in the case of a rectangular block, the slip at the step-in end has a hexagonal shape in plan view because the two types of slip directions are perpendicular (corresponding to α = 0 degrees in FIG. 3B). The sliding of the side surface 7d of the block 7 is larger.

  On the other hand, in the case of the slip S6 of the side surface 7e of the block 7 having a hexagonal shape in plan view, the slip S4 directed outward in the vertical direction of the wall surface due to the deformation recovery of the tread rubber is opposite to the slip S3 in the tire circumferential direction due to the influence of belt bending deformation. With ingredients. On the other hand, in the case of a rectangular block, the slip at the step-in end has a hexagonal shape in plan view because the two types of slip directions are perpendicular (corresponding to β = 0 ° in FIG. 3B). The sliding of the side surface 7d of the block 7 is smaller. Although the side surfaces 7d and 7e of the block 7 have been described, the same applies to the side surfaces 7f and 7g of the block.

  For this reason, the main groove inclination angle (α) and the division groove inclination angle (β) are set in the above ranges, so that the block 7 having a hexagonal shape in a plan view is less slipping on the stepping end side than the rectangular block. Is relatively increased, and the slip on the kicking end side is relatively reduced, so that the degree of unevenness of the wear energy in the circumferential direction, which is the product of the slip amount and the shearing force, is reduced.

  Further, when slipping to the outside of the block 7 occurs due to the slip angle, the direction of the slip due to the deformation recovery of the block 7 and the direction of the slip due to the deformation recovery near the wall surface at the outer edge of the block 7 are the same. In this embodiment, the wall surface has an angle with respect to the circumferential direction, so that the wall surface has no angle with respect to the circumferential direction (the above rectangular block). In comparison, since the amount of slip on the outside of the block is reduced, the amount of wear on the outside of the block is also improved.

  The width groove inclination angle (δ) of the width direction groove 5 with respect to the tire circumferential direction is preferably set to 70 to 85 degrees.

  If the width groove inclination angle (δ) is smaller than 70 degrees, the impact when the block 7 is stepped on the ground surface is not sufficiently reduced, and noise may be generated.

  On the other hand, when the width groove inclination angle (δ) is larger than 85 degrees, the block 7 may be missing because the rigidity of the end portion of the block 7 is lowered. When heel and toe wear occurs, the kicking end of the block 7 is worn more than the stepping end, and the impact at the stepping end increases, so setting the width groove inclination angle (δ) within the above range is: It is also effective after heel and toe wear has occurred.

(Action / Effect)
It has been found that heel-and-toe wear occurring at the tread center portion is effective in suppressing slippage of the kicking end of the block 7. Therefore, although the fundamental countermeasure is to make the rigidity of the block 7 appropriate, it is necessary to return the size of the block 7 in order to change the rigidity of the block 7. However, in reality, the necessary rigidity and size of the block 7 are determined from the wet performance and the steering performance required for each heavy-duty tire 1, and it is difficult to design in consideration of only heel and toe wear.

  If the block 7 has a triangular shape or a quadrangular shape in plan view, the kicking end becomes obtuse in plan view, which is not preferable. The block 7 is formed in a hexagonal shape in plan view, and the block length (l) Satisfying the range of 1.25 to 2.50% with respect to the total tire length (L), the rigidity and size of the block 7 are kept constant, and the heel and toe wear generated in the tread center portion is surely suppressed. Can do.

  Further, the circumferential dividing groove 9 is provided between the circumferential main grooves 3 and the width (W1) of the circumferential main groove 3 is set wider than the width (W2) of the circumferential dividing groove 9. The rigidity of the block 7 can be maintained while maintaining the edge component, and uneven wear such as heel and toe wear and shoulder drop wear can be reliably suppressed without degrading the wet performance.

  As described above, even with a flat tire having a low flatness ratio, uneven wear such as heel and toe wear that occurs in the tread center portion can be reliably suppressed, and the wear resistance of the entire tread portion is improved, thereby increasing the tire life. It can be extended.

  By the way, conventionally, the uneven wear caused by the running of the vehicle was mainly said to beer and toe wear. However, the inventor is a shoulder located on the outer side in the tread width direction that is more influenced by the lateral force. Attention was paid to the occurrence of shoulder drop wear in the block row 11.

  And if shoulder fall wear occurs in the shoulder block row 11, the tire life may be reduced as a result. Therefore, by forming the shoulder block row 11 in a rib shape, On the other hand, it has been found that the rigidity of the shoulder block row 11 is improved, and the shoulder drop wear generated in the tread shoulder portion can be suppressed.

  In other words, in addition to the heel and toe wear that occurs at the tread center part, uneven wear such as shoulder drop wear that occurs at the tread shoulder part can also be reliably suppressed, improving the wear resistance of the entire tread part and extending the tire life. It becomes possible to extend it reliably.

  Further, the adjacent circumferential main grooves 3 (circumferential division grooves 9) are arranged with a shift of 0.4 to 0.6 wavelengths with respect to the tire circumferential direction, so that the block 7 having a hexagonal shape in plan view is formed. It can be formed easily.

  Further, by setting the main groove inclination angle (α) and the division groove inclination angle (β) to 20 to 30 degrees, the block 7 having a hexagonal shape in a plan view is more slippery on the stepping end side than the rectangular block. Is relatively large, and the slip on the kicking end side is relatively small, so that the degree of unevenness in the circumferential direction of the wear energy, which is the product of the slip amount and the shearing force, is reduced. Can be reduced.

  Further, when the depth of the circumferential main groove is “d1” and the depth of the circumferential dividing groove is “d2”, the wet performance is maintained by satisfying the relationship of 0.5 × d1 ≦ d2 ≦ d1. However, the rigidity of each block 7 can be maintained, and uneven wear, particularly heel and toe wear, can be suppressed.

[Other embodiments]
As described above, the contents of the present invention have been disclosed through the embodiments of the present invention. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention.

  Specifically, as the internal structure of the heavy-duty tire 1, a general well-known one can be adopted, and since the mounting target shaft of the heavy-duty tire 1 is a drive shaft, It is preferable to provide a character string indicating the above.

  From this disclosure, various alternative embodiments, examples, and operational techniques will be apparent to those skilled in the art. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

  Next, in order to further clarify the effects of the present invention, the results of tests conducted using the heavy duty tires according to the following comparative examples and Examples 1 and 2 will be described. In addition, this invention is not limited at all by these examples.

  Data on each heavy-duty tire was measured under the following conditions.

・ Tire size: 445 / 50R22.5
・ Rim size: 14.00
・ Internal pressure condition: 690 kPa
-Test vehicle: 2-DD tractor-Test course: North American paved road structure The configuration of each heavy-duty tire and the wear test (heel and toe wear test and shoulder drop wear test) will be described using Table 1. In each heavy-duty tire, all conditions except for the tread pattern are the same.

  As shown in FIG. 5, the heavy-duty tire 100 according to the comparative example includes a plurality of circumferential main grooves 103 extending linearly in the tire circumferential direction and a plurality of widthwise grooves 105 extending linearly in the tread width direction. A plurality of partitioned blocks 107 are provided. As shown in Table 1, the heavy-duty tire 100 according to this comparative example is formed in a square shape in plan view. In the heavy duty tire 100 according to the comparative example, the shoulder block row 111 is formed in a block shape.

  In the heavy-duty tire 200 according to the first embodiment, as shown in FIG. 6, the heavy-duty tire 200 is partitioned by a plurality of circumferential main grooves 203 extending zigzag in the tire circumferential direction and a plurality of width-direction grooves 205 extending in the tread width direction. A plurality of blocks 207 are provided. As shown in Table 1, the heavy load tire 200 according to Example 1 is formed in a hexagonal shape in plan view. In the heavy duty tire 200 according to the first embodiment, the shoulder block row 211 is formed in a block shape.

  The heavy-duty tire 1 according to the second embodiment includes a plurality of blocks 7 defined by a plurality of circumferential main grooves 3 extending zigzag in the tire circumferential direction and a plurality of widthwise grooves 5 extending in the tread width direction. (See FIG. 1). As shown in Table 1, the heavy-duty tire 1 according to Example 2 is formed in a hexagonal shape in plan view. In the heavy load tire 1 according to the second embodiment, the shoulder block row 11 is formed in a rib shape.

<Heal and toe wear test>
Each heavy-duty tire was mounted on a test drum, and after traveling 30000 km at a speed of 80 km / h, the step of heel and toe wear was measured. In addition, this level | step difference shows the difference (D) of the height (T1) of the stepping end of each block, and the height (T2) of a kicking end, as shown in FIG. That is, as the level difference is smaller, heel and toe wear can be suppressed.

  As a result, the heavy-duty tire according to Examples 1 and 2 has a smaller step of heel and toe wear and can suppress the heel and toe wear compared to the heavy-duty tire according to the comparative example, which is effective for improving uneven wear. It turns out that. In other words, a heavy-duty tire whose block length (l) satisfies the range of 1.25 to 2.50% with respect to the total tire length (L) can suppress heel and toe wear, and is therefore effective in improving uneven wear. It turns out that.

<Shoulder fall wear test>
Each heavy-duty tire was mounted on a test drum, and after running 30000 km at a speed of 80 km / h, a shoulder wear step was measured. In addition, this level | step difference shows the difference of the height of the most projecting part of each block, and the height of the part shaved most by abrasion. That is, as the level difference is smaller, shoulder wear can be suppressed.

  As a result, the heavy load tire according to Example 2 has a smaller shoulder drop wear step than the heavy load tire according to the comparative example and Example 1, and can suppress the shoulder drop wear. It was found to be effective in improving That is, it has been found that the heavy load tire in which the shoulder block row is formed in a rib shape can suppress the shoulder wear and is effective in improving uneven wear.

<Comprehensive evaluation>
When either heel and toe wear or shoulder drop wear becomes larger than the remaining groove amount of each groove located in the tread center portion, the user often determines that the use limit is reached. Therefore, as shown in FIG. 8, when the remaining groove amount and the progress of each uneven wear step are plotted against the travel distance, the travel distance at which the curve of the remaining groove amount and each uneven wear step intersects is the actual tire. Life is reached.

  That is, as shown in FIG. 8, the heavy load tire according to the comparative example has a tire life of 70000 km, and the heavy load tire according to the example 2 has 85000 km. For this reason, as shown in Table 1, it can be seen that the heavy-duty tire according to Example 2 has about 20% longer tire life than the heavy-duty tire according to the comparative example. In addition, although the heavy load tire which concerns on Example 1 is not shown by Table 8, it can be said from a said tendency that a tire life improves compared with the heavy load tire which concerns on a comparative example.

It is an expanded view which shows the tread surface (tread pattern) of the heavy duty pneumatic tire which concerns on this Embodiment. It is a perspective view which shows one block of the heavy duty pneumatic tire which concerns on this Embodiment. It is a tread sectional view and a top view showing one block of a heavy-duty pneumatic tire concerning this embodiment. It is an enlarged plan view showing one block of the heavy duty pneumatic tire according to the present embodiment. It is a development view showing a tread surface (tread pattern) of a heavy duty pneumatic tire according to a comparative example. 1 is a development view showing a tread surface (tread pattern) of a heavy duty pneumatic tire according to Embodiment 1. FIG. It is a figure which shows the level | step difference of the heel and toe abrasion which generate | occur | produces in each block of the heavy duty tire which concerns on a comparative example and Example 1,2. It is a graph which shows the tire life of the heavy duty tire which concerns on a comparative example and Examples 1,2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Heavy load tire 3 ... Circumferential main groove 5 ... Width direction groove 7 ... Block 7a ... Upper surface 7b ... Front surface 7c ... Rear surface 7d-7g ... Side surface 9 ... Circumferential division groove

Claims (6)

The tread surface includes a plurality of blocks defined by a plurality of circumferential main grooves extending zigzag in the tire circumferential direction and a plurality of width direction grooves extending in the tread width direction, the tread width is 300 mm or less, and A heavy duty pneumatic tire having an aspect ratio of 55% or less,
A circumferentially-divided groove extending in a zigzag manner in the tire circumferential direction, and being divided into two in the tread width direction, a block row composed of a plurality of the blocks adjacent to the circumferential direction of the tire located between the circumferential main grooves In addition,
The width (W1) of the circumferential main groove is set wider than the width (W2) of the circumferential division groove,
The block is formed in a hexagonal shape in plan view, with the zigzag direction of the circumferential main groove and the zigzag direction of the circumferential division groove facing each other.
The block length (l) which is the length of the block with respect to the tire circumferential direction satisfies a range of 1.25 to 2.50% with respect to the total tire length (L) which is the length in the tire circumferential direction. A heavy duty pneumatic tire.   The shoulder block row located on the outer side in the tread width direction than the circumferential main groove located on the outermost side in the tread width direction is formed in a rib shape continuous in the tire circumferential direction. Heavy duty pneumatic tires.   The adjacent circumferential main grooves are arranged so as to be shifted by 0.4 to 0.6 wavelengths with respect to the tire circumferential direction. The heavy load pneumatic according to claim 1 or 2, tire.   A main groove inclination angle (α) that is an inclination angle of the circumferential main groove with respect to the tire circumferential direction, and a division groove inclination angle (β) that is an inclination angle of the circumferential division groove with respect to the tire circumferential direction is 20 The heavy-duty pneumatic tire according to any one of claims 1 to 3, wherein the pneumatic tire is set to -30 degrees.   2. The relationship of 0.5 × d1 ≦ d2 ≦ d1 is satisfied, where “d1” is the depth of the circumferential main groove and “d2” is the depth of the circumferential dividing groove. The heavy-duty pneumatic tire according to any one of claims 4 to 4. The width (W1) of the circumferential main groove is set to 8 mm or more,
The heavy tire for a heavy load according to any one of claims 1 to 5, wherein a width (W2) of the circumferential division groove is set to 4 mm or less.

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