JP2016088343A - Heavy load duty tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve drainage performance while maintaining wear resistance.SOLUTION: A heavy load duty tire has, at a tread part 2, a pair of circumferential direction grooves 3, 3 which are provided on both sides of a tire equator C and are continuously extended in a zigzag form in a tire circumferential direction, and plural center inclined grooves 4 which are so provided between the pair of circumferential direction grooves 3, 3 as to partition plural center blocks 6 having a hexagonal shape in a plan view. Each center block 6 is provided with an auxiliary groove 10 which traverses the center block 6. The auxiliary groove 10 includes a first part 11 which is inclined in a direction opposite to the center inclined groove 4, and a second part 12 which is inclined in a direction same as the center inclined groove 4. A groove depth of the first part 11 is smaller than a groove depth of the second part 12.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a heavy duty tire having a center block in a tread portion, and more particularly to a heavy duty tire capable of providing high drainage performance while suppressing center wear.

  Generally, large traction performance is required for heavy duty tires used for large vehicles traveling on rough roads. For this reason, there is a tendency that a pattern provided with a center block is employed in the tread portion of this type of heavy duty tire. On the other hand, when such a tire is mounted on the drive shaft, a large shearing force acts on the center block when it is stepped on and kicked out, and as a result, wear tends to concentrate on the center block (center wear). It was.

  In order to suppress center wear, it has been proposed to enlarge the center block. However, although such a large center block improves wear resistance due to high rigidity, there is a problem that the drainage performance on the tire equator side is remarkably deteriorated.

JP 2014-164429 A

  The present invention has been devised in view of the above circumstances, and has as its main object to provide a heavy duty tire that can provide high drainage performance while suppressing center wear.

  The present invention provides a tread portion having a pair of circumferential grooves arranged on both sides of the tire equator and extending continuously in a zigzag manner in the tire circumferential direction, and a plurality of hexagonal center blocks in plan view between the pair of circumferential grooves. Tires for heavy loads having a plurality of center inclined grooves arranged so as to divide each of the center blocks, and each center block is provided with an auxiliary groove that crosses the center block. A first portion inclined in the opposite direction to the inclined groove, and a second portion inclined in the same direction as the center inclined groove, wherein the groove depth of the first portion is smaller than the groove depth of the second portion. It is characterized by that.

  In another aspect of the present invention, the maximum width of the center block in the tire axial direction may be 20% to 50% of the tread contact width.

  In another aspect of the invention, the second portion of the auxiliary groove may cross the tire equator.

  In another aspect of the present invention, the auxiliary groove may have a zigzag shape in which the first portion is connected to both sides of the second portion.

  In another aspect of the invention, the groove width of the second portion may be larger than the groove width of the first portion.

  In another aspect of the present invention, the groove depth of the first portion may be in the range of 10% to 40% of the groove depth of the circumferential groove.

  In another aspect of the present invention, the groove depth of the first portion may be in the range of 40% to 60% of the groove depth of the second portion.

  In another aspect of the present invention, each side of the center block tread that is divided into left and right by the tire equator includes a first region and a second region having a tread area smaller than the first region by the auxiliary groove. The tread area of the first region may be 1.5 times or more than the tread area of the second region.

The heavy duty tire of the present invention includes a plurality of hexagonal center blocks in plan view. The hexagonal center block in plan view generally has a rigidity balance such that the overall deformation amount is small even when a load is applied, and the difference in deformation amount of each part is also small. Therefore, such a center block is excellent in wear resistance. In particular, the effect is further enhanced by increasing the size of the center block.

  Each center block is provided with an auxiliary groove that crosses the center block. The auxiliary groove includes a first portion inclined in the opposite direction to the center inclined groove and a second portion inclined in the same direction as the center inclined groove. Even when the center block is enlarged, the auxiliary groove facilitates drainage in the vicinity of the tire equator, and thus can suppress a decrease in drainage performance.

  Further, since the auxiliary groove includes the first portion and the second portion having different inclination directions, the water film near the tire equator can be removed in a wider range. In addition, the groove depth of the first portion inclined in the opposite direction to the center inclined groove is smaller than the groove depth of the second portion inclined in the same direction as the center inclined groove. Since the first portion is inclined in the opposite direction to the center inclined groove, the rubber portion sandwiched between the first portion and the center inclined groove tends to give a large rigidity change. By reducing the relative height, drainage performance is improved while minimizing such a change in rigidity.

  Therefore, according to the present invention, it is possible to provide high drainage performance while suppressing center wear.

It is an expanded view of the tread part of the tire for heavy loads of this embodiment. It is an AA line sectional view of the tread part of Drawing 1. It is an expanded development view of the center block of the tread part. It is an expansion development view of the shoulder block of a tread part.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a development view of the tread portion 2 of the heavy duty tire of the present embodiment. As shown in FIG. 1, the tread portion 2 of the heavy duty tire of the present embodiment has a pair of circumferential grooves 3 and 3 that are arranged on both sides of the tire equator C and extend continuously in the tire circumferential direction, and a pair of A plurality of center inclined grooves 4 communicating between the circumferential grooves 3 and 3 and a plurality of shoulder lateral grooves 5 extending in the tire axial direction from the respective circumferential grooves 3 toward the tread ground contact Te are provided. Thus, a plurality of center blocks 6 are partitioned between the pair of circumferential grooves 3 and 3. A plurality of shoulder blocks 7 are divided outside the circumferential grooves 3 and 3.

  The tread contact end Te means the contact end on the outermost side in the tire axial direction when a normal load is applied to a normal tire and contacted with a flat surface with a camber angle of 0 degrees. Here, the normal state is a no-load state in which the tire is assembled on a normal rim (not shown) and filled with a normal internal pressure. Hereinafter, unless otherwise specified, the dimensions and the like of each part of the tire are values measured in this normal state. In the normal state, the distance in the tire axial direction between the tread ground contact Te and Te is defined as the tread ground contact width TW.

  The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based. For example, “Standard Rim” for JATMA, “Design Rim” for TRA, ETRTO Then "Measuring Rim".

  “Regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. “JAMATA” is the “maximum air pressure”, TRA is the table “TIRE LOAD LIMITS” The maximum value described in “AT VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” in the case of ETRTO.

  “Regular load” is the load that each standard defines for each tire in the standard system including the standard on which the tire is based. “JATMA” is the “maximum load capacity”, TRA is the table “TIRE LOAD” The maximum value described in “LIMITS AT VARIOUS COLD INFLATION PRESSURES”, or “LOAD CAPACITY” in the case of ETRTO.

  Each circumferential groove 3 has a zigzag shape in which first inclined portions 3a and second inclined portions 3b inclined in the opposite direction to the first inclined portions 3a are alternately provided in the tire circumferential direction. The zigzag shape includes an inner apex 8 that protrudes toward the tire equator and an outer apex 9 that protrudes toward the tread ground contact Te. Since the zigzag circumferential groove 3 has a so-called pattern edge effect, the traction performance and braking performance of the tire are enhanced.

  In order to enhance the pattern edge effect and the drainage performance with a good balance, the angle of the first inclined portion 3a and the second inclined portion 3b with respect to the tire circumferential direction is preferably 10 to 30 degrees, for example. In a preferred mode, as in the present embodiment, the pair of circumferential grooves 3 and 3 are arranged such that their zigzag phases are slightly shifted in the tire circumferential direction. Thereby, a pattern edge effect is obtained with good balance in the tire circumferential direction. In the present embodiment, the first inclined portion 3a and the second inclined portion 3b extend substantially linearly, but may be curved.

  In order to prevent a decrease in the contact area of the tread portion 2 while maintaining sufficient drainage performance, the groove width W1 of the circumferential groove 3 is preferably 10 to 14 mm, for example. FIG. 2 shows a cross-sectional view taken along line AA of FIG. In order to prevent a decrease in pattern rigidity of the tread portion 2 while maintaining sufficient drainage performance, the groove depth D1 of the circumferential groove 3 is preferably 10 to 20 mm, for example.

  Returning to FIG. 1, the center inclined groove 4 is arranged between the pair of circumferential grooves 3 and 3 so as to partition a plurality of hexagonal center blocks 6 in plan view. Specifically, the center inclined groove 4 extends linearly, and both ends thereof are connected to the inner top portion 8 of the circumferential groove 3. Since the zigzag phases of the pair of circumferential grooves 3 and 3 are arranged slightly shifted in the tire circumferential direction, the center inclined groove 4 is inclined with respect to the tire axial direction. In order to prevent the tire circumferential direction rigidity of the center block 6 from being lowered while enhancing the drainage performance, the angle of the center inclined groove 4 with respect to the tire axial direction is preferably, for example, 15 to 35 degrees.

  The groove width W2 of the center inclined groove 4 can be set to, for example, 5 to 12 mm, more preferably 7 to 9 mm in order to obtain a sufficient contact area of the tread portion 2 while improving drainage performance in the vicinity of the tire equator C. . As shown in FIG. 2, the groove depth D2 of the center inclined groove 4 is preferably 16 to 20 mm, for example, from the same viewpoint as described above. In the present embodiment, as a preferred aspect, the groove depth D2 of the center inclined groove 4 is set to be the same as the groove depth D1 of the second inclined portion 3b of the circumferential groove 3, for example. Thereby, it can drain smoothly from the center inclined groove 4 to the circumferential groove 3.

  FIG. 3 is an enlargement of the center block 6 of FIG. The center block 6 is a hexagon defined by a pair of first inclined portions 3a, 3a parallel to each other, a pair of second inclined portions 3b, 3b parallel to each other, and a pair of center inclined grooves 4, 4 parallel to each other. It has a tread shape. The center block 6 having a hexagonal shape on the tread surface in plan view has an excellent rigidity balance so that the overall deformation amount is small even when a load is applied, and the difference in deformation amount between the respective parts is also small. Therefore, such a center block 6 is excellent in wear resistance.

  Here, the “hexagonal shape” does not mean a complete regular hexagonal shape, but may be a hexagonal shape with different lengths on each side. In a preferable aspect, in order to eliminate the anisotropic rigidity as much as possible, it is desirable that the opposite sides are parallel to each other as in the present embodiment as a hexagonal shape. In addition, the “hexagonal shape” may include, for example, a shape in which each apex is smoothly chamfered with an arc as in the present embodiment.

  By increasing the size of the center block 6, the effect of suppressing center wear is further enhanced. In the preferred embodiment, as shown in FIG. 1, the maximum width BW of the center block 6 in the tire axial direction can be set to 20% or more of the tread contact width TW. Thereby, the wear resistance of the center block 6 is more reliably improved. On the other hand, since the excessively large center block 6 may cause deterioration of drainage performance, it is desirable that the maximum width BW of the center block 6 be 50% or less of the tread ground contact width TW. From the same viewpoint, it is desirable that the maximum length BL of the center block 6 in the tire circumferential direction is determined in a range of 110% to 120% of the maximum width BW of the center block 6, for example.

  Returning to FIG. 3, the center block 6 has six interior angles θ. Each internal angle θ is preferably 80 degrees or more. Since the portion where the inner angle θ is less than 80 degrees has small rigidity, the deformation of the center block 6 concentrates there, and there is a possibility that the wear resistance performance and the rolling resistance performance are deteriorated. Each inner angle θ of the center block 6 is appropriately changed by changing the angle of the first inclined portion 3a and the second inclined portion 3b of the circumferential groove 3, the angle of the center inclined groove 4, or the zigzag phase shift, etc. Can be adjusted.

  As shown in FIG. 3, each center block 6 is provided with an auxiliary groove 10 that crosses the center block 6 in half.

  The auxiliary groove 10 includes a first portion 11 inclined in the opposite direction to the center inclined groove 4 and a second portion 12 inclined in the same direction as the center inclined groove 4. In the present embodiment, the second portion 12 is provided in the central region of the center block 6 so as to cross the tire equator C. On the other hand, the first portion 11 is connected to both sides of the second portion 12. Thereby, the auxiliary groove 10 crosses the center block 6 in a zigzag shape.

  The outer end of each first portion 11 in the tire axial direction communicates with the first inclined portion 3 a of the circumferential groove 3. In a particularly preferable aspect, the first portions 11 extend in parallel with each other, and the outer ends in the tire axial direction communicate with the central portion in the length direction of the first inclined portion 3 a of the circumferential groove 3.

  Even when the center block 6 is increased in size, the auxiliary groove 10 can promote sufficient drainage in the vicinity of the tire equator C, and thus suppress a decrease in drainage performance. Further, since the auxiliary groove 10 includes the first portion 11 and the second portion 12 having different inclination directions, the pattern edge effect can be further enhanced while removing the water film near the tire equator C in a wider range. . Accordingly, the drainage performance is further improved.

  Further, as shown in FIG. 2, the auxiliary groove 10 is inclined in the same direction as the center inclined groove 4 in the groove depth D <b> 3 of the first portion 11 inclined in the opposite direction to the center inclined groove 4. The second portion 12 is formed smaller than the groove depth D4. Since the first portion 11 is inclined in the opposite direction to the center inclined groove 4, the rigidity change of the rubber portion sandwiched between the first portion 11 and the center inclined groove 4 tends to be increased. However, the drainage performance can be improved while minimizing the rigidity change as described above by relatively reducing the groove depth D3 of the first portion 11 as in the present embodiment. Thereby, the tire of the present embodiment can provide high drainage performance while suppressing center wear.

  In a preferred embodiment, the angle of the first portion 11 with respect to the tire axial direction is 10 to 45 degrees, more preferably 1 to 30 degrees. On the other hand, it is desirable that the angle of the second portion 12 with respect to the tire axial direction is formed larger than that of the first portion 11. This is particularly effective in preventing a decrease in circumferential rigidity at the center portion of the center block 6 and suppressing center wear. In a particularly preferable aspect, the angle of the second portion 12 with respect to the tire axial direction is 35 to 60 degrees, more preferably 40 to 50 degrees. In particular, since the length of the second portion 12 along the groove is set to be smaller than the length of the first portion along the groove, the circumferential rigidity of the center portion of the center block 6 is more reliably reduced. Can be prevented.

  The groove depth D4 of the deepest second portion 12 in the auxiliary groove 10 is desirably in the range of 10% to 40% of the maximum groove depth D1 of the circumferential groove 3. When the groove depth D4 of the second portion 12 is less than 10% of the groove depth D1 of the circumferential groove 3, the drainage performance near the tire equator may not be sufficiently improved. On the contrary, when the groove depth D4 of the second portion 12 exceeds 60% of the groove depth D1 of the circumferential groove 3, there is a tendency that the effect of improving the wear resistance by the center block 6 is not obtained.

  Similarly, the groove depth D3 of the first portion 11 is desirably in the range of 40% to 60% of the groove depth D4 of the second portion 12. When the groove depth D3 of the first portion 11 is less than 40% of the groove depth D4 of the second portion 12, there is a possibility that the drainage performance cannot be sufficiently improved. Conversely, if the groove depth D3 of the first portion 11 exceeds 60% of the groove depth D4 of the second portion 12, the rigidity of the center block 6 tends to decrease near the first portion 11, and consequently the center block 6 There is a possibility that the wear resistance of the steel deteriorates.

  Returning to FIG. 3, a large shear force in the tire circumferential direction acts on the end portion 6 </ b> A or 6 </ b> B in the tire circumferential direction of the center block 6 when stepping on the road surface. Since the first portion 11 having a relatively small groove depth is disposed behind the end 6A or 6B of the center block 6 in the present embodiment in the tire circumferential direction, the end 6A or 6B of the center block 6 is disposed. The local shear deformation in the vicinity can be suppressed, and as a result, the entire center block 6 can bear the shearing force firmly. Thereby, uneven wear such as heel and toe wear on the center block 6 can also be suppressed. In order to further enhance such an action, the groove width W3 of the first portion 11 is preferably smaller than the groove width W4 of the second portion 12. Thereby, the partial wear of the center block 6 can be suppressed while expecting more drainage in the second portion 12.

  Further, as shown in FIG. 4, each side of the tread of the center block 6 divided into the left and right by the tire equator C has a first area A1 and a tread area smaller than the first area A1 due to the auxiliary groove 10. It is partitioned into a second area A2. The first region A1 is also a region in which the end 6A or 6B of the center block 6 in the tire circumferential direction is included. Therefore, the tread area of the first area A1 is formed larger than that of the second area A2, and in particular, the tread area of the first area A1 is 1.5 times or more than the tread area of the second area A2. By setting as described above, uneven wear on the center block 6 is more effectively prevented. On the other hand, although the second area A2 has a small tread surface area, it is supported by the first area A1 via the first portion 11 having a small depth, so that a decrease in rigidity can be further suppressed.

  As shown in FIG. 1, the shoulder lateral groove 5 extends from the outer top portion 9 of each circumferential groove 3, 3 to the tread grounding end Te. As a result, the center inclined grooves 4 and the shoulder lateral grooves 5 that are adjacent to each other via the circumferential grooves 3 are arranged alternately shifted in the tire circumferential direction. Superimposition of sound is prevented and noise performance is improved. In a preferred embodiment, the shoulder lateral grooves 5 are smoothly curved so that the angle with respect to the tire axial direction gradually decreases toward the outer side in the tire axial direction.

  In order to maintain the ground contact area of the shoulder block 7 while improving the traction performance on a rough road, the groove width W5 of the shoulder lateral groove 5 is, for example, 22 to 30 mm, preferably 24 to 28 mm. Similarly, as shown in FIG. 2, the groove depth D5 of the shoulder lateral groove 5 is preferably 20 to 24 mm, for example. In particular, the groove depth D5 of the shoulder lateral groove 5 is formed to be larger than the groove depths D1 and D2 of the center inclined groove 4 and the second inclined portion 3b of the circumferential groove 3 to reduce traction on rough roads. It is desirable also for raising.

  While the heavy duty tire of the present invention has been described in detail above, the present invention is not limited to the specific embodiment described above, and can be implemented in various forms.

   A heavy duty tire of size 325 / 95R24 having the basic tread pattern of FIG. 1 was prototyped based on the specifications in Table 1 and tested for wet performance and uneven wear resistance. The test method is as follows.

<Abrasion resistance>
Each sample tire was mounted on all wheels of a truck (2-D car) having a maximum loading capacity of 10 tons under the conditions of a rim 24 × 8.50 and an internal pressure of 850 kPa. After traveling 50000 km with the above vehicle, the difference in wear between the center block and the shoulder block was measured evenly at 6 locations in the tire circumferential direction, and the average value thereof was calculated. The result is the reciprocal of the average value, and is displayed as an index with the value of Comparative Example 1 being 100. The larger the value, the less uneven wear and the better.

<Drainage performance>
Each sample tire worn by 75% was mounted on all wheels of a truck (2-D car) having a maximum loading capacity of 10 tons under conditions of a rim of 24 × 8.50 and an internal pressure of 850 kPa. The vehicle is brought into a wet asphalt road surface with a 5mm thick water film, and the passing time of 10m from the moment when the clutch is engaged with the transmission gear fixed at 2nd speed and the engine speed fixed at 1500rpm is measured, It was indexed. The result is the reciprocal of each passing time, and is displayed as an index with the value of Comparative Example 1 being 100. The evaluation shows that the larger the value, the better the drainage performance.

  As is clear from Table 1, the heavy-duty tire of the example should improve drainage performance by about 5% while maintaining almost the same level of wear resistance as compared with Comparative Example 1 without an auxiliary groove. Was confirmed. On the other hand, in Comparative Example 2 and Comparative Example 3 in which the first portion and the second portion are formed with the same groove depth, although there are auxiliary grooves, the wear resistance is reduced by about 3% compared to Comparative Example 1. The wear resistance was not able to be maintained.

2 Tread portion 3 Circumferential groove 4 Center inclined groove 5 Shoulder lateral groove 6 Center block 7 Shoulder block 10 Auxiliary groove 11 First portion 12 Second portion A1 First region A2 First region

Claims (8)

In the tread portion, a pair of circumferential grooves arranged on both sides of the tire equator and continuously extending in a zigzag shape in the tire circumferential direction, and a plurality of hexagonal center blocks in a plan view are divided between the pair of circumferential grooves. A heavy duty tire having a plurality of center inclined grooves arranged in
Each center block is provided with an auxiliary groove across the center block,
The auxiliary groove includes a first portion inclined in the opposite direction to the center inclined groove, and a second portion inclined in the same direction as the center inclined groove,
The heavy load tire, wherein a groove depth of the first portion is smaller than a groove depth of the second portion.   The heavy duty tire according to claim 1, wherein a maximum width of the center block in a tire axial direction is 20% to 50% of a tread contact width.   The heavy duty tire according to claim 1, wherein the second portion of the auxiliary groove crosses the tire equator.   The heavy load tire according to claim 3, wherein the auxiliary groove has a zigzag shape in which the first portion is connected to both sides of the second portion.   The heavy duty tire according to any one of claims 1 to 4, wherein a groove width of the second portion is larger than a groove width of the first portion.   The heavy duty tire according to any one of claims 1 to 5, wherein a groove depth of the first portion is in a range of 10% to 40% of a groove depth of the circumferential groove.   The heavy duty tire according to any one of claims 1 to 5, wherein a groove depth of the first portion is in a range of 40% to 60% of a groove depth of the second portion. Each side divided right and left by the tire equator of the tread of the center block is divided into a first region and a second region having a tread area smaller than the first region by the auxiliary groove,
The heavy duty tire according to any one of claims 1 to 6, wherein a tread area of the first region is 1.5 times or more than a tread area of the second region.

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