JP6228468B2 - Heavy duty tire - Google Patents

Description

  The present invention relates to a heavy duty tire with improved noise performance.

  Conventionally, in order to obtain excellent wet traction performance, a tread pattern having a shoulder lateral groove that forms a block in a shoulder portion has been adopted for a heavy duty tire mounted on a large vehicle traveling on a rough road. In such a pattern, wear resistance performance is regarded as important as well as excellent wet performance.

  Under such a background, for example, in Patent Document 1, in order to achieve both wet performance and wear resistance performance, two rubber compositions having glass transition points in different temperature ranges are mixed, and rubber in the tread portion is mixed. Has been proposed.

Japanese Patent No. 3089435

  By the way, in the heavy duty tire market in recent years, reduction of tire noise is required as part of efforts for environmental protection. However, even if the rubber described in Patent Document 1 is used, it is difficult to sufficiently reduce tire noise, and further reduction of tire noise is required from the tread pattern surface.

  The present invention has been devised in view of the actual situation as described above, and has as its main purpose to provide a heavy-duty tire having both excellent wet performance and wear resistance while also having excellent noise performance. Yes.

  The present invention includes a pair of circumferential grooves that are arranged on both sides of the tire equator in the tread portion and continuously extend in a zigzag shape in the tire circumferential direction, and divide the tread portion into a center land portion and a pair of shoulder land portions. The center land portion is inclined with respect to the tire axial direction, the center land portion is divided into a plurality of center blocks, the shoulder land portion is extended in the tire axial direction, and the shoulder land is extended. A heavy duty tire having a plurality of shoulder lateral grooves that divide the portion into a plurality of shoulder blocks, wherein the center inclined groove communicates the inner zigzag tops that protrude inward in the tire axial direction of the circumferential grooves. The shoulder lateral groove extends from the outer zigzag top portion, which protrudes outward in the tire axial direction of each circumferential groove, toward the tread grounding end. The center lateral shallow groove has a depth smaller than that of the center inclined groove and communicates between the pair of circumferential grooves, and the center lateral shallow groove includes the inner zigzag top and the outer zigzag top. The intermediate portion communicates with the circumferential groove.

  In the heavy duty tire according to the present invention, the center lateral shallow groove communicates between a pair of first shallow groove portions communicating with the pair of circumferential grooves and a pair of first shallow groove portions across the tire equator. It is desirable to have a second shallow groove portion.

  In the heavy duty tire according to the present invention, it is desirable that the pair of first shallow groove portions and the second shallow groove portions are inclined in opposite directions.

  In the heavy duty tire according to the present invention, it is preferable that a width of the second shallow groove portion is larger than a width of the first shallow groove portion.

  In the heavy duty tire according to the present invention, it is preferable that a depth of the second shallow groove portion is larger than a depth of the first shallow groove portion.

  In the heavy duty tire according to the present invention, it is desirable that the center inclined groove extends linearly.

  In the heavy duty tire according to the present invention, it is preferable that an inclination angle of the center inclined groove with respect to a tire axial direction is 15 ° to 35 °.

  In the heavy duty tire according to the present invention, it is desirable that an angle of the circumferential groove with respect to the tire circumferential direction is 10 ° to 30 °.

  In the heavy duty tire according to the present invention, it is desirable that the depth of the center lateral shallow groove is 50% or less of the depth of the circumferential groove.

  In the heavy duty tire according to the present invention, it is preferable that the tread of the center block has a substantially hexagonal shape.

  In the heavy duty tire of the present invention, the tread portion is partitioned into a plurality of center blocks and a plurality of shoulder blocks by a pair of circumferential grooves, a plurality of center inclined grooves, and a plurality of shoulder lateral grooves. Each circumferential groove extends continuously in a zigzag shape in the tire circumferential direction, and each center inclined groove communicates the inner zigzag tops of each circumferential groove.

  When the center inclined groove is inclined with respect to the tire axial direction, the first-side edge of the center block is gradually grounded from one side to the other side in the tire axial direction. Thereby, the ground contact timing of the first arrival side edge of the center block is dispersed, and the pitch sound is reduced. On the other hand, each shoulder lateral groove extends from the outer zigzag top of the circumferential groove toward the tread grounding end. As a result, the center inclined grooves and the shoulder lateral grooves are arranged alternately shifted in the tire circumferential direction, so that the superposition of pitch sounds is prevented and the noise performance is improved.

  The center block is provided with a center lateral shallow groove having a depth smaller than that of the center inclined groove and communicating between the pair of circumferential grooves. Such a center lateral shallow groove enhances wet performance without impairing wear resistance. Further, the center lateral shallow groove communicates with the circumferential groove at an intermediate portion between the inner zigzag top and the outer zigzag top, whereby the shoulder lateral groove and the center lateral shallow groove are arranged shifted in the tire circumferential direction. The superposition of pitch sound is prevented and the noise performance is improved.

It is an expanded view of the tread part of one embodiment of the heavy duty tire of the present invention. 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. FIG. 2 is a cross-sectional view of the tread portion 2 of FIG. As shown in FIG. 1, the heavy duty tire of the present embodiment has a pair of circumferential grooves 9, 9 that are arranged on both sides of the tire equator C in the tread portion 2 and extend continuously in a zigzag manner in the tire circumferential direction. And a plurality of center inclined grooves 10 which are inclined with respect to the tire axial direction and linearly extend to communicate between the pair of circumferential grooves 9 and 9, and from each circumferential groove 9 toward the tread ground contact Te. And a plurality of shoulder lateral grooves 11 extending in the tire axial direction.

  The tread ground contact Te means the ground contact end on the outermost side in the tire axial direction when a normal load is loaded on a normal tire and grounded on a flat surface with a camber angle of 0 °. Here, the normal state is a no-load state in which a 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.

  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.

  The tread portion 2 is partitioned into a center land portion 12 and a shoulder land portion 13 by a pair of circumferential grooves 9 and 9 arranged on both sides of the tire equator C. The center land portion 12 is a region sandwiched between a pair of circumferential grooves 9 and 9. The center land portion 12 is partitioned into a plurality of center blocks 14 by a plurality of center inclined grooves 10. The shoulder land portion 13 is a region on the outer side in the tire axial direction of the circumferential grooves 9 and 9. The shoulder land portion 13 is partitioned into a plurality of shoulder blocks 15 by a plurality of shoulder lateral grooves 11.

  Since the circumferential groove 9 is disposed so as to be shifted in the tire axial direction from the tire equator C having a high contact pressure, the flow of air in the circumferential groove 9 at the time of contact is suppressed. Thereby, noise performance improves. Furthermore, since the highly rigid center block 14 is disposed on the tire equator C having a high contact pressure, the movement of the entire tread portion 2 is suppressed. Thereby, abrasion resistance performance improves.

  The groove width of the circumferential groove 9 is preferably 10 to 14 mm, for example. When the groove width of the circumferential groove 9 is less than 10 mm, the drainage performance decreases. On the other hand, when the groove width of the circumferential groove 9 exceeds 14 mm, the ground contact areas of the center land portion 12 and the shoulder land portion 13 are reduced, and steering stability and wear resistance are reduced. The groove depth of the circumferential groove 9 is preferably 16 to 20 mm, for example. When the groove depth of the circumferential groove 9 is less than 16 mm, the drainage performance decreases. On the other hand, when the groove depth of the circumferential groove 9 exceeds 20 mm, the rigidity of the center land portion 12 and the shoulder land portion 13 is lowered, and the steering stability is deteriorated.

  Each circumferential groove 9 is inclined in the same direction as the center inclined groove 10 with respect to the tire circumferential direction and linearly extends in a direction opposite to the center inclined groove 10 and a plurality of first inclined portions 9a extending linearly. And a plurality of second inclined portions 9b extending in a shape. The first inclined portions 9a and the second inclined portions 9b are alternately formed in the tire circumferential direction, whereby the zigzag circumferential groove 9 is configured. The so-called pattern edge effect is enhanced by the zigzag-shaped circumferential grooves 9, and the braking performance and traction performance of the heavy duty tire are enhanced. The first inclined portion 9a and the second inclined portion 9b may be formed to be curved.

  An angle α1 with respect to the tire circumferential direction of the first inclined portion 9a of each circumferential groove 9 is preferably 10 ° to 30 °, for example. Similarly, the angle α2 of the second inclined portion 9b of each circumferential groove 9 with respect to the tire circumferential direction is preferably 10 ° to 30 °, for example.

  If the angles α1 and α2 are less than 10 °, the pattern edge effect cannot be sufficiently obtained, and the braking performance and traction performance may not be improved. On the other hand, when the angles α1 and α2 exceed 30 °, drainage of the circumferential groove 9 may be deteriorated.

  The angle α1 and the angle α2 do not need to be fixed to a constant value, and may vary in the tire circumferential direction. In this case, the length of the first inclined portion 9a and the second inclined portion 9b varies in the tire circumferential direction. Furthermore, the angle α1 or the angle α2 may be different between the one circumferential groove 9 and the other circumferential groove 9.

  The zigzag circumferential groove 9 has an inner zigzag apex portion 9c that protrudes inward in the tire axial direction and an outer zigzag apex portion 9d that protrudes outward in the tire axial direction. Here, the inner zigzag top portion 9c is a portion where the groove center line of the first inclined portion 9a and the groove center line of the second inclined portion 9b intersect on the inner side in the tire axial direction, and the outer zigzag top portion 9d The groove center line of the first inclined portion 9a and the groove center line of the second inclined portion 9b intersect with each other on the outer side in the tire axial direction. When the groove center line of the first inclined portion 9a and the groove center line of the second inclined portion 9b are connected via an arc, the inner zigzag top portion 9c and the outer zigzag top portion 9d are formed on the groove center line of the first inclined portion 9a. The extension line and the extension line of the groove center line of the second inclined portion 9b intersect at the tire axial direction inner side and the tire axial direction outer side, respectively.

  The pair of circumferential grooves 9 and 9 are arranged such that their zigzag phases are shifted in the tire circumferential direction. Accordingly, the inner zigzag top portion 9c and the outer zigzag top portion 9d in each circumferential groove 9 are arranged so as to be shifted in the tire circumferential direction. Accordingly, the center inclined groove 10 communicating with the inner zigzag top portions 9c, 9c on both sides of the tire equator C is inclined with respect to the tire axial direction, and the drainage performance in the vicinity of the tire equator C is enhanced.

  The center inclined groove 10 is inclined with respect to the tire axial direction. Thereby, the first-arrival edge of the center block 14 is gradually grounded from one side to the other side in the tire axial direction. Thereby, the grounding timing of the first-side edge of the center block 14 having a high grounding pressure is dispersed, and the pitch sound is reduced.

  The inclination angle β of the center inclined groove 10 with respect to the tire axial direction is preferably 15 ° to 35 °, for example. When the inclination angle β of the center inclined groove 10 is less than 15 °, the first-side edge 14a of the center block 14 is grounded substantially simultaneously from one side to the other side in the tire axial direction, and the pitch sound increases. Further, the pair of shoulder blocks 15 located on both sides of the center block 14 in the tire axial direction are also grounded at the same time, increasing the pitch sound.

  On the other hand, when the inclination angle β of the center inclined groove 10 exceeds 35 °, the tire circumferential rigidity of the center block 14 is lowered. For this reason, the deformation of the center block 14 becomes excessive, and there is a possibility that the wear resistance performance and the rolling resistance performance are lowered.

  The center inclined groove 10 is formed linearly. Such a center inclined groove 10 increases the rigidity of the center block 14. Therefore, the movement of the center block 14 at the time of grounding is suppressed, and wear resistance performance is improved.

  The groove width WA of the center inclined groove 10 is preferably 5 to 12 mm, for example. When the groove width WA of the center inclined groove 10 is less than 5 mm, the drainage performance of the center land portion 12 is deteriorated. On the other hand, when the groove width WA of the center inclined groove 10 exceeds 12 mm, the ground contact area of the center land portion 12 is reduced, and steering stability and wear resistance are reduced. From such a viewpoint, the more desirable groove width WA of the center inclined groove 10 is, for example, 7 to 9 mm.

  The groove depth of the center inclined groove 10 is preferably 16 to 20 mm, for example. When the groove depth of the center inclined groove 10 is less than 16 mm, the drainage performance of the center land portion 12 is lowered and the wear resistance performance is lowered. On the other hand, when the groove depth of the center inclined groove 10 exceeds 20 mm, the rigidity of the center block 14 is lowered, the rolling resistance is increased, and the steering stability may be deteriorated. In this embodiment, the groove depth of the center inclined groove 10 is equal to the groove depth of the second inclined portion 9b of the circumferential groove 9, for example.

  The shoulder lateral groove 11 extends from the outer zigzag top portion 9d of each circumferential groove 9, 9 to the tread grounding end. The shoulder lateral groove 11 communicates with the circumferential groove 9 at an outer zigzag top portion 9d where the circumferential groove 9 and the center inclined groove 10 do not communicate with each other. That is, since the center inclined groove 10 and the shoulder lateral groove 11 adjacent to each other with the circumferential groove 9 interposed therebetween are alternately shifted in the tire circumferential direction, the superposition of pitch sound is prevented and the noise performance is improved. In addition, since the air flow from the center inclined groove 10 to the shoulder lateral groove 11 at the time of grounding is suppressed, the noise performance is further improved.

  For example, the shoulder lateral groove 11 is formed by curving the inner end on the tire equator C side, and the angle with respect to the tire axial direction gradually decreases toward the outer side in the tire axial direction. For example, the inner end of the shoulder lateral groove 11 is inclined in the same direction as the center inclined groove 10. As described above, since the center inclined groove 10 and the first inclined portion 9a are inclined in the same direction with respect to the tire circumferential direction, the center inclined groove 10, the first inclined portion 9a, and the shoulder lateral groove 11 are continuous. Thus, the tires are inclined in the same direction with respect to the tire circumferential direction, and drainage performance is improved.

  The groove width WB of the shoulder lateral groove 11 is preferably 22 to 30 mm, for example. When the width WB of the shoulder lateral groove 11 is less than 22 mm, the traction performance on a rough road is deteriorated. On the other hand, when the groove width WB of the shoulder lateral groove 11 exceeds 30 mm, the ground contact area of the shoulder land portion 13 decreases, and steering stability and wear resistance particularly during cornering decrease. From such a viewpoint, the more desirable groove width WB of the shoulder lateral groove 11 is, for example, 24 to 28 mm.

  The groove depth of the shoulder lateral groove 11 is preferably 20 to 24 mm, for example. When the groove depth of the shoulder lateral groove 11 is less than 20 mm, the drainage performance of the shoulder land portion 13 is deteriorated. On the other hand, when the groove depth of the shoulder lateral groove 11 exceeds 24 mm, the rigidity of the shoulder block 15 is lowered, the rolling resistance is increased, and the steering stability particularly during cornering may be deteriorated. In this embodiment, the groove depth of the shoulder lateral groove 11 is larger than the groove depths of the center inclined groove 10 and the second inclined portion 9 b of the circumferential groove 9, for example.

  FIG. 3 is an enlarged development view of the center block 14 of the tread portion 2. The center block 14 is partitioned by a pair of first inclined portions 9a, 9a of the circumferential groove 9, a pair of second inclined portions 9b, 9b, and a pair of adjacent center inclined grooves 10, 10, and a tread 16 thereof. Is composed of a substantially hexagonal shape. That is, the tread surface 16 of the center block 14 has six top portions 16a, 16a, 16b, 16b, 16c, and 16c. Such a hexagonal center block 14 has high rigidity and little deformation at the time of tire rolling, so that it is possible to simultaneously improve wear resistance performance and rolling resistance performance.

  The tread surface 16 of the center block 14 may not be configured with a complete hexagon. For example, in the present embodiment, the corners of the tips of the top portions 16a, 16b, and 16c are appropriately rounded or chamfered to reduce stress concentration and suppress damage such as chipping.

  The internal angle θ1 of the top portion 16a is an angle formed by the first inclined portion 9a and the second inclined portion 9b of the circumferential groove 9. The inner angle θ <b> 2 of the top portion 16 b is an angle formed by the second inclined portion 9 b of the circumferential groove 9 and the center inclined groove 10. The inner angle θ3 of the top portion 16c is an angle formed by the first inclined portion 9a of the circumferential groove 9 and the center inclined groove 10.

  The center inclined groove 10 communicates the inner zigzag crests 9c, 9c of the pair of circumferential grooves 9, 9, so that, in the tread surface 16 of each center block 14, the inner angle θ1 of the crest 16a, the inner angle θ2 of the crest 16b, and the crest 16c. Neither of the interior angles θ3 of these becomes excessively small.

  The internal angles θ1, θ2, and θ3 of all the top portions 16a, 16b, and 16c are preferably 80 ° or more, for example. If the inner angle of any top is less than 80 °, the rigidity of the center block 14 decreases near the top. For this reason, the deformation of the center block 14 is partially excessive, and the wear resistance performance and the rolling resistance performance may be deteriorated.

  In the present embodiment, the inner angle θ2 of the top portion 16b is the smallest, for example, about 87 °. Therefore, the rigidity of the center block 14 is sufficiently secured, and deformation of the center block 14 is suppressed. Thereby, it becomes possible to improve wear resistance performance and rolling resistance performance simultaneously. In FIG. 3, the internal angles θ1, θ2, and θ3 are angles α1 and α2 of the first inclined portion 9a and the second inclined portion 9b of the circumferential groove 9 with respect to the tire circumferential direction, and the inclination of the center inclined groove 10 with respect to the tire axial direction. Adjustment can be made by appropriately changing the angle β and the shift of the zigzag phase.

  In FIG. 1, the maximum width La of the center block 14 in the tire axial direction is preferably 30% to 40% of the tread ground contact width TW, for example. When the maximum width La of the center block 14 is less than 30% of the tread contact width TW, the rubber volume of the center land portion 12 is insufficient, and the wear resistance may be deteriorated. On the other hand, when the maximum width La of the center block 14 exceeds 40% of the tread ground contact width TW, the rubber volume of the shoulder land portion 13 is insufficient, and there is a possibility that uneven wear called shoulder drop wear may occur.

  The maximum length Lb of the center block 14 in the tire circumferential direction is preferably 110% to 120% of the maximum width La of the center block 14, for example. When the maximum length Lb of the center block 14 is less than 110% of the maximum width La, the rigidity of the center block 14 in the tire circumferential direction decreases, the deformation of the center block 14 becomes excessive, and the wear resistance performance and rolling resistance performance decrease. There is a risk. On the other hand, when the maximum length Lb of the center block 14 exceeds 120% of the maximum width La, the drainage performance of the center land portion 12 may be deteriorated.

  As shown in FIG. 3, the center block 14 is provided with a center lateral shallow groove 19 that communicates between the pair of circumferential grooves 9. The center lateral shallow groove 19 bisects the center block 14. The depth of the center lateral shallow groove 19 is smaller than the depth of the center inclined groove 10. Such a center lateral shallow groove 19 improves the drainage performance of the tread 16 of the center block 14 without impairing the wear resistance.

  The center lateral shallow groove 19 includes an intermediate portion 9e between the inner zigzag top portion 9c and the outer zigzag top portion 9d in one circumferential groove 9, and an intermediate portion between the inner zigzag top portion 9c and the outer zigzag top portion 9d in the other circumferential groove 9. The portion 9e communicates with the circumferential grooves 9, 9. Here, each intermediate portion 9e is a portion located substantially in the middle between the inner zigzag top portion 9c and the outer zigzag top portion 9d in the first inclined portions 9a, 9a of the respective circumferential grooves 9, 9.

  In the present embodiment, since the center lateral shallow groove 19 communicates with the circumferential groove at the intermediate portion 9e in the one circumferential groove 9 and the intermediate portion 9e in the other circumferential groove 9, the circumferential groove The shoulder lateral grooves 11 and the center lateral shallow grooves 19 that are adjacent to each other with the 9 interposed therebetween are shifted in the tire circumferential direction. Thereby, the superposition of the pitch sound generated in the shoulder lateral groove 11 and the center lateral shallow groove 19 is prevented, and the noise performance is improved.

  As shown in FIG. 2, the groove depth Dc of the center lateral shallow groove 19 is smaller than the groove depth Db of the circumferential groove 9 and the center inclined groove 10, for example, the groove depth Db of the circumferential groove 9. 50% or less is desirable. When the groove depth Dc of the center lateral shallow groove 19 exceeds 50% of the groove depth Db of the circumferential groove 9, the rigidity of the center block 14 is lowered, the wear resistance performance is deteriorated, and the noise performance is lowered. There is a fear.

  The center lateral shallow groove 19 includes a pair of first shallow groove portions 19a, 19a that communicate with the first inclined portions 9a, 9a of the pair of circumferential grooves 9, 9, and a pair of first shallow groove portions 19a that cross the tire equator C. And a second shallow groove portion 19b communicating with each other. In the present embodiment, the groove depth Db is the depth of the second shallow groove portion 19b.

  The first shallow groove portion 19a is inclined in the direction opposite to the center inclined groove 10 with respect to the tire axial direction. The second shallow groove portion 19b is inclined in the same direction as the center inclined groove 10 with respect to the tire axial direction. Thereby, the center lateral shallow groove 19 extends in a zigzag shape in the tire axial direction. Such a zigzag center lateral shallow groove 19 suppresses the flow of air in the center lateral shallow groove 19 at the time of grounding, and improves noise performance.

  The groove width WD of the second shallow groove portion 19b is preferably larger than the groove width WC of the first shallow groove portion 19a. Thereby, the distribution of rigidity in the center block 14 is optimized. This also increases the rigidity of the region closer to the circumferential groove 9 than the central region of the center block 14, thereby suppressing a decrease in the groove width of the circumferential groove 9 at the time of ground contact.

  Furthermore, the groove depth of the second shallow groove portion 19b is preferably larger than the groove depth of the first shallow groove portion 19a. Thereby, similarly to the above, the distribution of rigidity in the center block 14 is optimized, and the decrease in the groove width of the circumferential groove 9 at the time of ground contact is suppressed.

  FIG. 4 is an enlarged development view of the shoulder block 15 of the tread portion 2. The shoulder block 15 is partitioned by the first inclined portion 9a and the second inclined portion 9b of the circumferential groove 9, the adjacent shoulder lateral grooves 11, 11 and the tread grounding end Te, and the tread surface 17 is configured by a substantially pentagon. Yes. That is, the tread 17 of the shoulder block 15 has five top portions 17a, 17b, 17c, 17d, and 17e. Such a pentagonal shoulder block 15 has high rigidity and little deformation at the time of tire rolling, so that it is possible to simultaneously improve the wear resistance performance and rolling resistance performance.

  The tread surface 17 of the shoulder block 15 may not be formed of a complete pentagon. For example, in the present embodiment, the corners of the tips of the tops 17a, 17b, 17c, 17d, and 17e are appropriately rounded or chamfered to reduce stress concentration and suppress damage such as chipping.

  The inner angle φ1 of the top portion 17a is an angle formed by the first inclined portion 9a and the second inclined portion 9b of the circumferential groove 9. The inner angle φ2 of the top portion 17b is an angle formed by the second inclined portion 9b of the circumferential groove 9 and the shoulder lateral groove 11. The inner angle φ3 of the top portion 17c is an angle formed by the first inclined portion 9a of the circumferential groove 9 and the shoulder lateral groove 11. An inner angle φ4 of the top portion 17d and an inner angle φ5 of the top portion 17e are angles formed by the shoulder lateral groove 11 and the tread grounding end Te, and are approximately 90 °, for example.

  The shoulder lateral groove 11 extends from the outer zigzag top portion 9d that protrudes outward in the tire axial direction of the circumferential groove 9 to the tread ground contact Te, and extends along the tire axial direction at the tread ground contact Te. Therefore, on the tread surface 17 of each shoulder block 15, the inner angle φ1 of the apex portion 17a, the inner angle φ2 of the apex portion 17b, the inner angle φ3 of the apex portion 17c, the inner angle φ4 of the apex portion 17d, and the inner angle φ5 of the apex portion 17e do not become excessively small.

  The inner angles φ1, φ2, φ3, φ4, and φ5 of all the top portions 17a, 17b, 17c, 17d, and 17e are preferably 75 ° or more, for example. If the inner angle of any top is less than 75 °, the rigidity of the shoulder block 15 decreases in the vicinity of the top. For this reason, the deformation of the shoulder block 15 is partially excessive, and the wear resistance performance and the rolling resistance performance may be deteriorated.

  In the present embodiment, the inner angle θ2 of the top portion 16b is the smallest and is about 77 °. Therefore, the rigidity of the shoulder block 15 is sufficiently ensured, and deformation of the shoulder block 15 is suppressed. Thereby, it becomes possible to improve wear resistance performance and rolling resistance performance simultaneously. In FIG. 4, the inner angles φ1, φ2, φ3, φ4, and φ5 are the inclination of the shoulder lateral groove 11 with respect to the tire axial direction, the curvature of the curved portion of the shoulder lateral groove 11, the first inclined portion 9a of the circumferential groove 9, and the second. It can be adjusted by appropriately changing the angles α1, α2, etc. of the inclined portion 9b with respect to the tire circumferential direction.

  As shown in FIGS. 3 and 4, in the present embodiment, the first inclined portion 9a of the circumferential groove 9 is provided with a tie bar 18 extending along the longitudinal direction of the first inclined portion 9a. The tie bar 18 is a portion where the groove bottom is raised, and connects the adjacent center block 14 and shoulder block 15 with the first inclined portion 9a interposed therebetween. The tie bar 18 increases the rigidity of the center block 14 and the shoulder block 15.

  As shown in FIG. 2, the height Ha of the tie bar 18 is desirably 25% to 45% of the maximum groove depth Db of the circumferential groove 9, for example. In the present embodiment, the height Ha of the tie bar 18 is set to 25% to 45% of the groove depth Db of the second inclined portion 9b, for example. When the height Ha of the tie bar 18 is less than 25% of the maximum groove depth Db of the circumferential groove 9, the center block 14 and the shoulder block 15 have insufficient rigidity, and block deformation that reduces the groove width of the circumferential groove at the time of ground contact. Becomes larger. As a result, the wear resistance and rolling resistance performance may be reduced. On the other hand, when the height Ha of the tie bar 18 exceeds 45% of the maximum groove depth Db of the circumferential groove 9, the cross-sectional area of the circumferential groove 9 decreases, and the drainage performance decreases.

  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, wear resistance performance and noise performance. Each tire is formed with a tread pattern having a center inclined groove that communicates the inner zigzag peaks of the circumferential grooves shown in FIG. 1 and a shoulder lateral groove that communicates the outer zigzag peaks of the circumferential grooves and the tread grounding end. Yes. The test method is as follows.

<Wet 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 represented by an index with the value of Example 1 being 100. In the evaluation, the larger the numerical value, the better the wet performance.

<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. The groove depth of each tire after running 50000 km with the vehicle was measured. A result is displayed by the index | exponent which sets the value of Example 1 to 100, and evaluation is so favorable that there is so little abrasion that a numerical value is large.

<Noise performance>
External noise was measured when the vehicle passed through a dry paved road surface at a speed of 70 km / h. The result is displayed as an index using the reciprocal of the measured value and the value of Example 1 as 100. The larger the index, the better the outside noise and the better.

  As is clear from Table 1, it was confirmed that the heavy load tire of the example had significantly improved noise performance while achieving both wet performance and wear resistance performance as compared with the comparative example.

1 Heavy load tire 2 Tread portion 9 Circumferential groove 9c Inner zigzag top portion 9d Outer zigzag top portion 9e Intermediate portion 10 Center inclined groove 11 Shoulder lateral groove 14 Center block 15 Shoulder block 19 Center lateral shallow groove 19a First shallow groove portion 19b Second shallow groove portion

Claims (9)

In the tread part,
A pair of circumferential grooves that are arranged on both sides of the tire equator and extend continuously in a zigzag manner in the tire circumferential direction, and divide the tread portion into a center land portion and a pair of shoulder land portions;
A plurality of center inclined grooves that incline the center land portion with respect to the tire axial direction and partition the center land portion into a plurality of center blocks,
A heavy duty tire having a plurality of shoulder lateral grooves extending in the tire axial direction of the shoulder land portion and dividing the shoulder land portion into a plurality of shoulder blocks,
The center inclined groove communicates the inner zigzag tops that are convex inward in the tire axial direction of each circumferential groove,
The shoulder lateral groove extends from the outer zigzag top that protrudes outward in the tire axial direction of each circumferential groove toward the tread grounding end,
The center block is provided with a center lateral shallow groove that is smaller in depth than the center inclined groove and communicates between the pair of circumferential grooves,
The center lateral shallow groove communicates with the circumferential groove at an intermediate portion between the inner zigzag top and the outer zigzag top. The center lateral shallow groove is
A pair of first shallow groove portions including one first shallow groove portion communicating with the one circumferential groove and the other first shallow groove portion communicating with the other circumferential groove, and a pair of first shallow groove portions traversing the tire equator, A first shallow groove portion that communicates between the first shallow groove portions;
The heavy duty tire according to claim 1, wherein the pair of first shallow groove portions and the second shallow groove portions are inclined in directions opposite to each other with respect to a tire axial direction . The heavy duty tire according to claim 2 , wherein a width of the second shallow groove portion is larger than a width of the first shallow groove portion . The heavy duty tire according to claim 2 or 3 , wherein a depth of the second shallow groove portion is larger than a depth of the first shallow groove portion . The heavy duty tire according to any one of claims 1 to 4, wherein the center inclined groove extends linearly . The heavy duty tire according to any one of claims 1 to 5, wherein an inclination angle of the center inclined groove with respect to a tire axial direction is 15 ° to 35 ° . The heavy load tire according to any one of claims 1 to 6, wherein an angle of the circumferential groove with respect to a tire circumferential direction is 10 ° to 30 ° . The heavy duty tire according to any one of claims 1 to 7 , wherein a depth of the center lateral shallow groove is 50% or less of a depth of the circumferential groove . The heavy duty tire according to any one of claims 1 to 8, wherein the tread of the center block has a substantially hexagonal shape .

Images