JP5809672B2 - Heavy duty tire - Google Patents

Description

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

  In addition to paved roads, heavy-duty tires such as gravel roads with a lot of pebbles and trucks that often run on rough terrain, etc. intersect with main grooves extending in the circumferential direction of the tire to ensure traction. A block pattern in which a tread portion is divided into a plurality of blocks by a tread groove including a lateral groove in the direction is employed. However, in such a block pattern in which the lateral grooves on both sides of the main groove are shifted by 1/2 pitch in the tire circumferential direction, the stone bites at the groove intersection where the main groove and the lateral groove intersect in a T shape. There is a problem that is likely to occur.

  Stone biting is a phenomenon in which a stone slightly larger than the groove width is first caught in the tread groove, and while the tire repeats rolling, the caught stone gets into the groove bottom while deforming the block. As the wear of the tire progresses, the bite stones strongly hit the groove bottom, eventually damaging the rubber and belt layers inside the groove bottom, leading to problems such as reducing tread durability and tire regeneration rate. .

  Therefore, Patent Document 1 discloses a heavy-duty tire in which a tie bar for connecting blocks adjacent to each other in the circumferential direction is provided at the bottom of the lateral groove in order to suppress damage to the belt layer.

JP 2011-230643 A

  However, in the heavy-duty tire disclosed in Patent Document 1, the tie bar is insufficient in the depth of the lateral groove after the middle stage of wear, and the traction performance on rough terrain may be deteriorated.

  The present invention has been devised in view of the above-described actual situation, and has as its main object to provide a heavy duty tire having improved stone biting performance at a groove intersection where a main groove and a transverse groove intersect.

The present invention has a main groove extending continuously in a zigzag shape in the tire circumferential direction on the tread portion, and land portions provided on both sides thereof, and the land portions on both sides include a plurality of lateral grooves. A heavy-duty tire divided into blocks, wherein the lateral grooves on both sides of the main groove are arranged shifted in the tire circumferential direction, and the main groove has a long side portion and a direction opposite to the long side portion. Inclined and alternately provided with short side portions having a length in the tire circumferential direction smaller than the long side portion, the lateral groove communicates with the main groove in a region including the short side portion, and one of the lateral grooves The first extension line extending the groove edge to the main groove side intersects with the groove edge of the long side portion of the main groove at the first intersection, and the other groove edge of the lateral groove extends to the main groove side. The second extension line intersects the groove edge of the long side portion of the main groove at a second intersection point, and the tire circumferential direction between the first intersection point and the second intersection point And the distance L1, the ratio L2 / L1 of the tire circumferential direction length L2 of the shorter sides is equal to or is 0.08 to 0.25.

  In the heavy load tire according to the present invention, a ratio L3 / a distance L3 between the second intersection and the short side portion in a tire circumferential direction and a distance L1 between the first intersection and the second intersection in the tire circumferential direction. When L1 exceeds 0.25, a ratio L4 / L1 between a distance L4 in the tire circumferential direction between the first intersection and the short side portion and a distance L1 in the tire circumferential direction between the first intersection and the second intersection. Is preferably 0.25 to 0.50.

  In the heavy load tire according to the present invention, a ratio L3 / a distance L3 between the second intersection and the short side portion in a tire circumferential direction and a distance L1 between the first intersection and the second intersection in the tire circumferential direction. When L1 is 0.25 or less, the ratio L4 / the distance L4 in the tire circumferential direction between the first intersection and the short side portion and the distance L1 in the tire circumferential direction between the first intersection and the second intersection. It is desirable that L1 is 0.50 to 0.75.

  In the heavy load tire according to the present invention, a ratio L3 / a distance L3 between the second intersection and the short side portion in a tire circumferential direction and a distance L1 between the first intersection and the second intersection in the tire circumferential direction. When L1 exceeds 0.25, a ratio L4 / L1 between a distance L4 in the tire circumferential direction between the first intersection and the short side portion and a distance L1 in the tire circumferential direction between the first intersection and the second intersection. Is preferably 0.33 or more.

  In the heavy load tire according to the present invention, a ratio L3 / a distance L3 between the second intersection and the short side portion in a tire circumferential direction and a distance L1 between the first intersection and the second intersection in the tire circumferential direction. When L1 is 0.25 or less, the ratio L4 / the distance L4 in the tire circumferential direction between the first intersection and the short side portion and the distance L1 in the tire circumferential direction between the first intersection and the second intersection. It is desirable that L1 is 0.66 or less.

  In the heavy-duty tire according to the present invention, the groove intersecting portion between the main groove and the lateral groove has a first block apex formed by a corner of the first block, and a second adjacent to the first block in the tire circumferential direction. The second block vertex formed by the corner of the block, and the groove edge of the main groove of the third block adjacent to the first block and the second block via the main groove are located closest to the groove center line side of the main groove. It is preferable that a protruding third vertex is provided, and the second block vertex is provided outside a maximum circle that passes through the first block vertex and the third vertex and is within the groove intersection.

According to the heavy duty tire of the present invention, the lateral groove communicates with the main groove in the region including the short side portion, and the first extension line extending one groove edge of the lateral groove toward the main groove side is the length of the main groove. A second extension line that intersects the groove edge of the side portion at the first intersection and extends the other groove edge of the lateral groove to the main groove side intersects the groove edge of the long side portion of the main groove at the second intersection point. And since ratio L2 / L1 of the distance L1 of the tire circumferential direction of the 1st intersection and the 2nd intersection and the length L2 of the tire circumferential direction of a short side part is 0.08 or more, it is the traction performance in rough terrain. Is sufficiently secured. On the other hand, since the ratio L2 / L1 is 0.25 or less, the short side portion facing the pair of block vertices divided by the lateral grooves becomes small. Thereby, it is suppressed that the stone caught in the intersection of the main groove and the transverse groove is supported by the side wall of the short side portion, and the holding force of the stone by the block is reduced. Therefore, the stone once bitten is easily discharged when coming into contact with the road surface, and the stone biting performance is improved. Furthermore, since the horizontal groove communicates with the main groove in a region including the short side portion of the main groove, water in the main groove is guided to the horizontal groove by the short side portion when traveling on a wet road surface, and drainage performance is improved.

It is sectional drawing which shows one Embodiment of the tire for heavy loads of this invention. FIG. 2 is a development view of the tread portion of FIG. 1. FIG. 3 is an enlarged development view of the center land portion of FIG. 2. FIG. 3 is an enlarged development view of a middle land portion of FIG. 2. FIG. 3 is an enlarged development view of a shoulder land portion of FIG. 2. FIG. 3 is an enlarged development view of a groove intersection portion where a shoulder main groove and a shoulder lateral groove of FIG. 2 intersect. FIG. 3 is an enlarged development view of a groove intersecting portion where a middle main groove and a center lateral groove of FIG. 2 intersect. It is a figure which shows the relationship between the groove crossing part of FIG. 7, and the stone which was bitten.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a tire meridian cross-sectional view including a tire rotation axis in a normal state of the heavy duty tire 1 of the present embodiment. 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 If so, it is "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.

  As shown in FIG. 1, a heavy load tire 1 of the present invention includes a toroidal carcass 6 extending from a tread portion 2 through a sidewall portion 3 to a bead core 5 of the bead portion 4, and the outer side of the carcass 6 in the tire radial direction. In addition, a belt layer 7 or the like disposed inside the tread portion 2 is provided. In the present embodiment, a case where the heavy load tire 1 is a tubeless tire attached to a 15 ° taper rim RM is shown.

  The carcass 6 includes a carcass ply 6A in which carcass cords are arranged at an angle of, for example, 80 to 90 ° with respect to the tire equator C. The carcass ply 6A includes a series of ply folded portions 6b that are folded around the bead core 5 from the inner side to the outer side in the tire axial direction at both ends of the ply main body portion 6a straddling the bead cores 5 and 5. Between the ply body portion 6a and the ply turn-up portion 6b, a bead apex rubber 8 having a triangular cross section extending from the bead core 5 to the outer side in the tire radial direction is disposed.

  The belt layer 7 is disposed radially outside the carcass 6 and inside the tread portion 2. The belt layer 7 is constituted by a plurality of belt plies using steel belt cords. The belt layer 7 of the present embodiment includes an innermost belt ply 7A in which belt cords are arranged at an angle of, for example, about 60 ± 10 ° with respect to the tire equator C, and the belt cord 7 is sequentially arranged on the outer side and the belt cords are connected to the tire equator C. 4 layers of belt plies 7B, 7C and 7D arranged at a small angle of about 15 to 35 °. The belt layer 7 is provided with one or more places where the belt cords cross each other between the plies, thereby increasing belt rigidity and strongly reinforcing almost the entire width of the tread portion 2.

  The bead core 5 has a flat and horizontally long hexagonal cross section, and its inner surface in the tire radial direction is inclined at an angle of 12 to 18 ° with respect to the tire axial direction, thereby providing a wide range of fitting force with the rim RM. It is increasing over time.

  FIG. 2 is a development view of the tread portion 2 of the heavy duty tire 1 of the present embodiment. As shown in FIG. 2, the heavy duty tire 1 of the present embodiment has a directional pattern in which the rotation direction R of the tire is designated on the tread portion 2. The tread portion 2 includes a center main groove 10 extending continuously in the tire circumferential direction on the tire equator C, and a pair of middle main grooves disposed on both sides of the tire equator C and extending continuously in a zigzag shape in the tire circumferential direction. 11 and a pair of shoulder main grooves 12 extending continuously in a zigzag manner in the tire circumferential direction on the outer side in the tire axial direction of the middle main groove 11 and on the inner side of the tread grounding end Te.

  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 the tire in a normal state and contacted to a flat surface with a camber angle of 0 °. “Regular load” is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. “JATMA” is “maximum load capacity”, and TRA is “TIRE LOAD”. The maximum value described in “LIMITS AT VARIOUS COLD INFLATION PRESSURES”, or “LOAD CAPACITY” in the case of ETRTO.

  The middle main groove 11 has a long side portion 11a that is inclined with respect to the tire circumferential direction, and a short side portion 11b that is inclined in a direction opposite to the long side portion 11a and whose length in the tire circumferential direction is smaller than the long side portion 11a. And have. The long side portions 11 a and the short side portions 11 b are provided alternately in the tire circumferential direction, and constitute a zigzag middle main groove 11.

  The shoulder main groove 12 has a long side portion 12a that is inclined with respect to the tire circumferential direction, and a short side portion 12b that is inclined in a direction opposite to the long side portion 12a and whose length in the tire circumferential direction is smaller than that of the long side portion 12a. And have. The long side portions 12 a and the short side portions 12 b are alternately provided in the tire circumferential direction, and constitute a zigzag shoulder main groove 12. The zigzag pitch of the middle main groove 11 is equivalent to the zigzag pitch of the shoulder main groove 12.

  The tread portion 2 is divided into a plurality of regions by the center main groove 10, the middle main groove 11, and the shoulder main groove 12. The tread portion 2 includes a pair of center land portions 13 between the center main groove 10 and the middle main groove 11, a pair of middle land portions 14 between the middle main groove 11 and the shoulder main groove 12, and a shoulder main groove. 12 has a pair of shoulder land portions 15 located on the outer side in the tire axial direction. That is, the center land portion 13 and the middle land portion 14 are provided on both sides of the middle main groove 11, and the middle land portion 14 and the shoulder land portion 15 are provided on both sides of the shoulder main groove 12.

  FIG. 3 shows an enlarged view of the center land portion 13. The center land portion 13 is provided with a plurality of center lateral grooves 21. The center lateral groove 21 extends in the tire axial direction, and communicates the center main groove 10 and the middle main groove 11 on both sides of the center land portion 13. Thereby, the center land portion 13 is a block row in which a plurality of center blocks 22 are arranged. Since the center lateral groove 21 is inclined with respect to the tire axial direction, the tread 22s of the center block 22 of the present embodiment has a substantially parallelogram shape.

  The middle main groove 11 has a groove edge 11d on the center land portion 13 side and a groove edge 11e on the middle land portion 14 side. In the middle main groove 11, the vertex 11f of the groove edge 11d closest to the groove center line 11c is closer to the center land portion 13 than the vertex 11g of the groove edge 11e closest to the groove center line 11c. Thereby, in the zigzag middle main groove 11, a region communicating linearly in the circumferential direction is formed, so that the drainage performance of the tread portion 2 is improved.

  In the relationship between the middle main groove 11 and the center land portion 13, the tire axial distance WCm between the vertex 11f of the groove edge 11d closest to the groove center line 11c and the vertex 11g of the groove edge 11e closest to the groove center line 11c. Is 0.07 to 0.13 times the maximum width WDc of the center block 22 in the tire axial direction. When the tire axial direction distance WCm between the apex 11f and the apex 11g is less than 0.07 times the maximum width WDc of the center block 22 in the tire axial direction, the drainage performance may not be sufficiently improved. When the tire axial distance WCm between the vertex 11f and the vertex 11g exceeds 0.13 times the maximum width WDc of the center block 22 in the tire axial direction, the wear resistance of the center land portion 13 may be reduced.

  As shown in FIG. 3, the center lateral groove 21 communicates with the short side portion 11 b of the middle main groove 11. Here, “the center lateral groove 21 is communicated with the short side portion 11 b of the middle main groove 11” means that the groove center line 21 c of the center lateral groove 21 is communicated with the short side portion 11 b of the middle main groove 11. (Hereinafter, the same applies to the middle lateral groove 31 and the shoulder lateral groove 41).

  The center lateral groove 21 extends incline in the tire axial direction, the first portion 21a, the second portion 21b that is displaced in the tire circumferential direction from the first portion 21a and extends in parallel with the first portion 21a, and the first portion 21a. And a third portion 21c that connects the second portion 21b. For example, the depth of the center lateral groove 21 is preferably equal to or less than the depth of the middle main groove 11.

  The pitch of the center lateral groove 21 is twice the zigzag pitch of the middle main groove 11. In other words, the zigzag pitch of the middle main groove 11 is ½ times the pitch of the center lateral groove 21. Accordingly, the center block 22 has a zigzag apex 22a that faces the middle main groove 11 and protrudes outward in the tire axial direction at the center in the tire circumferential direction of the tread surface 22s.

  Chamfered portions 24a and 24b are formed at block vertices where the center main groove 10 and the center lateral groove 21 intersect. Chamfered portions 25a and 25b are formed at block vertices where the middle main groove 11 and the center lateral groove 21 intersect. Such chamfered portions 24a, 24b, 25a and 25b alleviate stress concentration at the block apexes and suppress damage such as chipping. Instead of the chamfered portions 24a, 24b, 25a and 25b, rounded corner portions may be formed.

  The center block 22 is provided with a plurality of center lateral shallow grooves 23. The center lateral shallow groove 23 has one end communicating with the center main groove 10 and the other end communicating with the short side portion 11 b of the middle main groove 11. Similarly to the center lateral groove 21, the center lateral shallow groove 23 extends incline in the tire axial direction, and the first lateral portion 23a is displaced in the tire circumferential direction and extends in parallel with the first portion 23a. It is a zigzag groove having a second portion 23b and a third portion 23c that connects the first portion 23a and the second portion 23b. The depth of the center lateral shallow groove 23 is smaller than the depth of the center lateral groove 21, and the width of the center lateral shallow groove 23 is smaller than the width of the center lateral groove 21. The center lateral shallow groove 23 improves the drainage of the center land portion 13 and optimizes the rigidity distribution of the center block 22.

  FIG. 4 shows an enlarged view of the middle land portion 14. The middle land portion 14 is provided with a plurality of middle lateral grooves 31. The middle lateral groove 31 extends in the tire axial direction, and one end communicates with the middle main groove 11 and the other end communicates with the shoulder main groove 12. Thus, the middle land portion 14 is a block row in which a plurality of middle blocks 32 are arranged. As shown in FIG. 2, the center lateral groove 21 and the middle lateral groove 31 located on both sides of the middle main groove 11 are arranged with a 1/2 pitch shift in the tire circumferential direction. Accordingly, the center block 22 and the middle block 32 located on both sides of the middle main groove 11 are arranged with a 1/2 pitch shift in the tire circumferential direction. Since the middle lateral groove 31 is inclined with respect to the tire axial direction, the tread 32s of the middle block 32 of the present embodiment has a substantially parallelogram shape.

  As shown in FIG. 4, the shoulder main groove 12 has a groove edge 12d on the middle land portion 14 side and a groove edge 12e on the shoulder land portion 15 side. In the shoulder main groove 12, the vertex 12f of the groove edge 12d closest to the groove center line 12c is closer to the middle land portion 14 than the vertex 12g of the groove edge 12e closest to the groove center line 12c. Thereby, in the zigzag middle main groove 12, a region communicating linearly in the circumferential direction is formed, so that the drainage performance of the tread portion 2 is improved.

  In the relationship between the middle main groove 11 and the middle land portion 14, the tire axial direction distance WCm between the vertex 11f of the groove edge 11d closest to the groove center line 11c and the vertex 11g of the groove edge 11e closest to the groove center line 11c. Is 0.07 to 0.13 times the maximum width WDm of the middle block 32 in the tire axial direction. If the tire axial distance WCm between the apex 11f and the apex 11g is less than 0.07 times the maximum width WDm of the middle block 32 in the tire axial direction, the drainage performance may not be sufficiently improved. When the tire axial distance WCm between the apex 11f and the apex 11g exceeds 0.13 times the maximum width WDm of the middle block 32 in the tire axial direction, the wear resistance of the middle land portion 14 may be deteriorated.

  In the relationship between the shoulder main groove 12 and the middle land portion 14, the tire axial distance WCs between the apex 12f of the groove edge 12d closest to the groove center line 12c and the apex 12g of the groove edge 12e closest to the groove center line 12c. Is 0.07 to 0.13 times the maximum width WDm of the middle block 32 in the tire axial direction. When the tire axial distance WCs between the apex 12f and the apex 12g is less than 0.07 times the maximum width WDm of the middle block 32 in the tire axial direction, the drainage performance may not be sufficiently improved. When the tire axial distance WCs between the apex 12f and the apex 12g exceeds 0.13 times the maximum width WDm of the middle block 32 in the tire axial direction, the wear resistance of the middle land portion 14 may be deteriorated.

  The middle lateral groove 31 includes a first portion 31a extending in the tire axial direction, a second portion 31b displaced in the tire circumferential direction from the first portion 31a and extending in parallel with the first portion 31a, and a first portion 31a. And a third portion 31c that connects the second portion 31b. The depth of the middle lateral groove 31 is preferably equal to or less than the depth of the middle main groove 11 and the shoulder main groove 12, for example.

  The pitch of the middle lateral groove 31 is twice the zigzag pitch of the middle main groove 11 and the shoulder main groove 12. In other words, the zigzag pitch of the middle main groove 11 and the shoulder main groove 12 is ½ times the pitch of the middle lateral groove 31. Accordingly, the middle block 32 has a zigzag apex 32a that protrudes inward in the tire axial direction facing the middle main groove 11 and a shoulder main groove 12 at the center of the tread surface portion 32s in the tire circumferential direction. And a zigzag apex 32b protruding outward in the axial direction.

  Chamfered portions 34a and 34b are formed at block vertices where the middle main groove 11 and the middle lateral groove 31 intersect. Chamfered portions 35a and 35b are formed at block vertices where the shoulder main groove 12 and the middle lateral groove 31 intersect. Such chamfers 34a, 34b, 35a and 35b alleviate stress concentration at the block apexes and suppress damage such as chipping. Instead of the chamfered portions 34a, 34b, 35a and 35b, a rounded corner portion may be formed.

  The middle block 32 is provided with a plurality of middle lateral shallow grooves 33. The middle lateral shallow groove 33 has one end communicating with the short side portion 11 b of the middle main groove 11 and the other end communicating with the short side portion 12 b of the shoulder main groove 12. Similar to the middle lateral groove 31, the middle lateral shallow groove 33 extends in a direction inclined to the tire axial direction, and the first lateral portion 33a is displaced in the tire circumferential direction and extends in parallel with the first portion 33a. It is a zigzag groove having a second portion 33b and a third portion 33c that connects the first portion 33a and the second portion 33b. The depth of the middle lateral shallow groove 33 is smaller than the depth of the middle lateral groove 31, and the width of the middle lateral shallow groove 33 is smaller than the width of the middle lateral groove 31. The middle lateral shallow groove 33 enhances the drainage of the middle land portion 14 and optimizes the rigidity distribution of the middle block 32.

  FIG. 5 shows an enlarged view of the shoulder land portion 15. The shoulder land portion 15 is provided with a plurality of shoulder lateral grooves 41. The shoulder lateral groove 41 extends in the tire axial direction, and one end communicates with the shoulder main groove 12 and the other end communicates with the tread grounding end Te. Thereby, the shoulder land portion 15 is a block row in which a plurality of shoulder blocks 42 are arranged. As shown in FIG. 2, the middle lateral grooves 31 and the shoulder lateral grooves 41 located on both sides of the shoulder main groove 12 are arranged with a 1/2 pitch shift in the tire circumferential direction. Accordingly, the middle block 32 and the shoulder block 42 located on both sides of the shoulder main groove 12 are arranged with a 1/2 pitch shift in the tire circumferential direction.

  In the relationship between the shoulder main groove 12 and the shoulder land portion 15, the tire axial distance WCs between the apex 12f of the groove edge 12d closest to the groove center line 12c and the apex 12g of the groove edge 12e closest to the groove center line 12c. Is 0.07 to 0.13 times the maximum width WDs of the shoulder block 42 in the tire axial direction. If the tire axial distance WCs between the apex 12f and the apex 12g is less than 0.07 times the maximum width WDs of the shoulder block 42 in the tire axial direction, the drainage performance may not be sufficiently improved. When the tire axial distance WCs between the apex 12f and the apex 12g exceeds 0.13 times the maximum width WDs of the shoulder block 42 in the tire axial direction, the wear resistance of the shoulder land portion 15 may be deteriorated.

  As shown in FIG. 5, the shoulder lateral groove 41 communicates with the short side portion 12 b of the shoulder main groove 12. The shoulder lateral groove 41 includes a first portion 41a extending in an inclined manner in the tire axial direction, a second portion 41b that is displaced in the tire circumferential direction from the first portion 41a and extends in parallel with the first portion 41a, and a first portion 41a. And a third portion 41c that connects the second portion 41b. For example, the depth of the shoulder lateral groove 41 is preferably equal to or less than the depth of the shoulder main groove 12.

  The pitch of the shoulder lateral grooves 41 is twice the zigzag pitch of the shoulder main grooves 12. In other words, the zigzag pitch of the shoulder main grooves 12 is ½ times the pitch of the shoulder lateral grooves 41. Accordingly, the shoulder block 42 has a zigzag apex 42a that faces the shoulder main groove 12 and protrudes inward in the tire axial direction at the center portion in the tire circumferential direction of the tread surface portion 42s.

  Chamfered portions 44a and 44b are formed at the top of the block where the shoulder main groove 12 and the shoulder lateral groove 41 intersect. Such chamfered portions 44a and 44b alleviate stress concentration at the block apexes and suppress damage such as chipping. Instead of the chamfered portions 44a and 44b, a rounded corner portion may be formed.

  The shoulder block 42 is provided with a plurality of shoulder lateral shallow grooves 43. One side of the shoulder lateral shallow groove 43 communicates with the short side portion 12b of the shoulder main groove 12, and the other end communicates with the tread grounding end Te. Similar to the shoulder lateral groove 41, the shoulder lateral shallow groove 43 extends in a direction inclined with respect to the tire axial direction, and the first lateral portion 43a is displaced in the tire circumferential direction and extends in parallel with the first portion 43a. It is a zigzag groove having a second portion 43b and a third portion 43c that connects the first portion 43a and the second portion 43b. The depth of the shoulder lateral shallow groove 43 is smaller than the depth of the shoulder lateral groove 41, and the width of the shoulder lateral shallow groove 43 is smaller than the width of the shoulder lateral groove 41. The shoulder lateral shallow groove 43 enhances the drainage of the shoulder land portion 15 and optimizes the rigidity distribution of the shoulder block 42.

FIG. 6 shows an enlarged groove crossing 50 between the shoulder main groove 12 and the shoulder lateral groove 41. The shoulder lateral groove 41 communicates with the shoulder main groove 12 in a region including the short side portion 12b. In the present embodiment having such a relationship between the short side portion 12b and the shoulder lateral groove 41, water in the shoulder main groove 12 is guided to the shoulder lateral groove 41 by the short side portion 12b when traveling on a wet road surface. , Drainage performance is enhanced.

A first extended line 41e obtained by extending a groove edge passing through the first block apex P1 of the shoulder lateral groove 41 to the shoulder main groove 12 side intersects the groove edge 12d of the long side portion 12a of the shoulder main groove 12 at the first intersection CP1. Similarly, a second extension line 41f obtained by extending a groove edge passing through the second block apex P2 of the shoulder lateral groove 41 toward the shoulder main groove 12 is a second intersection point CP2 with the groove edge 12d of the long side portion 12a of the shoulder main groove 12. Intersect. As described above, since the shoulder lateral groove 41 communicates with the shoulder main groove 12 in the region including the short side portion 12b, the short side portion 12b is positioned between the first extension line 41e and the second extension line 41f. ing.

  The ratio L2 / L1 between the distance L1 in the tire circumferential direction between the first intersection CP1 and the second intersection CP2 and the length L2 in the tire circumferential direction of the short side portion 12b is preferably 0.08 to 0.25.

  When the ratio L2 / L1 between the distance L1 in the tire circumferential direction between the first intersection CP1 and the second intersection CP2 and the length L2 in the tire circumferential direction of the short side portion 12b is less than 0.08, the rough terrain and the wet road surface There is a risk that sufficient traction performance cannot be secured.

  On the other hand, when the ratio L2 / L1 between the distance L1 in the tire circumferential direction between the first intersection CP1 and the second intersection CP2 and the length L2 in the tire circumferential direction of the short side portion 12b exceeds 0.25, the shoulder lateral groove 41 The short side portion 12b facing the first block vertex P1 and the second block vertex P2 divided by the length becomes longer, and the stones biting into the groove crossing portion 50 are easily supported by the side wall and the surface of the short side portion 12b. Become. Therefore, the holding power of the stone by a block becomes high, a stone becomes difficult to discharge | emit, and there exists a possibility that a stone biting resistance may fall.

  The distance L3 in the tire circumferential direction between the second intersection CP2 and the short side portion 12b and the distance L4 in the tire circumferential direction between the first intersection CP1 and the short side portion 12b desirably satisfy the following relationship. Here, (i) the ratio L3 / L1 between the distance L3 in the tire circumferential direction between the second intersection CP2 and the short side portion 12b and the distance L1 in the tire circumferential direction between the first intersection CP1 and the second intersection CP2 is 0. When it exceeds .25, or (ii) when the ratio L3 / L1 is 0.25 or more, the case will be described separately.

  First, (i) the ratio L3 / L1 between the distance L3 in the tire circumferential direction between the second intersection CP2 and the short side portion 12b and the distance L1 in the tire circumferential direction between the first intersection CP1 and the second intersection CP2 is 0. The case of exceeding 25 will be described. In this case, the ratio L4 / L1 between the distance L4 in the tire circumferential direction between the first intersection CP1 and the short side portion 12b and the distance L1 in the tire circumferential direction between the first intersection CP1 and the second intersection CP2 is preferably 0. .25 or more, more preferably 0.33 or more, and preferably 0.50 or less.

  When the ratio L4 / L1 is less than 0.25, the distance L3 in the tire circumferential direction between the second intersection CP2 and the short side portion 12b and the length L2 in the tire circumferential direction of the short side portion 12b are compared with L4. Relatively long. Therefore, the length from the second intersection point CP2 to the third block vertex P3, that is, the region of the side wall of the shoulder main groove 12 that is recessed with respect to the first block vertex P1 and the second block vertex P2 becomes long. Stone chewing is likely to occur in the area. Stones bitten in such areas are supported by the surface. As a result, the holding power of the stone by the block is increased, and it is difficult for the stone to be discharged, and the stone biting resistance may be reduced.

  On the other hand, when the ratio L4 / L1 exceeds 0.50, the length L2 in the tire circumferential direction of the short side portion 12b becomes excessively small, and there is a possibility that the traction performance on rough terrain or on a wet road surface cannot be secured sufficiently.

  Next, (ii) the ratio L3 / L1 between the tire circumferential direction distance L3 between the second intersection point CP2 and the short side portion 12b and the tire circumferential direction distance L1 between the first intersection point CP1 and the second intersection point CP2 is 0. The case when it is .25 or less will be described. In this case, the ratio L4 / L1 between the distance L4 in the tire circumferential direction between the first intersection CP1 and the short side portion 12b and the distance L1 in the tire circumferential direction between the first intersection CP1 and the second intersection CP2 is preferably 0. .50 or more, preferably 0.75 or less, more preferably 0.66 or less.

  When the ratio L4 / L1 is less than 0.50, the length L2 in the tire circumferential direction of the short side portion 12b is relatively longer than L4, and stone biting occurs in the region of the short side portion 12b. It becomes easy. The stone bitten in the region of the short side portion 12b is supported by the surface of the side wall of the short side portion 12b. As a result, the holding power of the stone by the block is increased, and it is difficult for the stone to be discharged, and the stone biting resistance may be reduced.

  On the other hand, when the ratio L4 / L1 exceeds 0.75, the length from the first intersection CP1 to the third block vertex P3, that is, the first block vertex P1 and the second block vertex P2 among the side walls of the shoulder main groove 12 The region protruding with respect to the length becomes longer, and stone biting is likely to occur in this region. Stones bitten in such areas are supported by the surface. As a result, the holding power of the stone by the block is increased, and it is difficult for the stone to be discharged, and the stone biting resistance may be reduced. Further, in this case, the length L2 of the short side portion 12b in the tire circumferential direction becomes excessively small, and there is a possibility that the traction performance on rough terrain or a wet road surface cannot be sufficiently ensured.

In the heavy duty tire 1 of the present embodiment, the ratio L2 / L1 between the distance L1 in the tire circumferential direction between the first intersection CP1 and the second intersection CP2 and the length L2 in the tire circumferential direction of the short side portion 12b. Is 0.08 or more, the traction performance on rough terrain is sufficiently ensured. On the other hand, since the ratio L2 / L1 is 0.25 or less, the short side portion 12b facing the pair of block vertices P1 and P2 divided by the shoulder lateral groove 41 becomes small. Thereby, it is suppressed that the stone bited into the groove crossing portion 50 of the shoulder main groove 12 and the shoulder lateral groove 41 is supported by the side wall of the short side portion 12b, and the holding force of the stone by the side wall of the block is reduced. To do. Therefore, the stone once bitten is easily discharged when coming into contact with the road surface, and the stone biting performance is improved. Further, since the shoulder lateral groove 41 communicates with the shoulder main groove 12 in the region including the short side portion 12b, the water in the shoulder main groove 12 is guided to the shoulder lateral groove 41 by the short side portion 12b when running on a wet road surface. Performance is enhanced.

  Such a relationship between the shoulder main groove 12 and the shoulder lateral groove 41 can also be applied to the relationship between the shoulder main groove 12 and the middle lateral groove 31, and the relationship between the middle main groove 11 and the center lateral groove 21 and the middle main groove 11. And the middle lateral groove 31 can be applied.

  FIG. 7 shows an enlarged groove intersection 51 between the middle main groove 11 and the center lateral groove 21. At the groove intersection 51, the center block 22 (first block B 1) and the center block 22 (second block B 2) are adjacent to each other via the center lateral groove 21, and the first block B 1 and the second block are interposed via the middle main groove 11. The block B2 and the middle block 32 (third block B3) are adjacent to each other.

  The tread B1s of the first block B1 has a first block vertex P1 that forms a corner of the first block B1s. The tread B2s of the second block B2 has a second block vertex P2 that forms a corner of the second block B2. The first block vertex P1 and the second block vertex P2 are adjacent to each other through the center lateral groove 21. The tread surface B3s of the third block B3 has a third block vertex P3 that protrudes most toward the groove center line 11c at the groove edge 11e of the middle main groove 11. The third block vertex P3 is a zigzag vertex 11g at which the long side portion 11a and the short side portion 11b of the middle main groove 11 intersect on the tread B3s of the third block B3, and the first block vertex via the middle main groove 11 Adjacent to P1 and the second block vertex P2.

  In the heavy load tire 1 of the present embodiment, the center lateral groove 21 is communicated with the short side portion 11 b of the middle main groove 11 at the groove intersection 51. Therefore, the triangle 53 (indicated by hatching in FIG. 7) composed of the first block vertex P1, the second block vertex P2, and the third block vertex P3 tends to deviate from the regular triangle, in other words, the triangle 53 Symmetry tends to be disturbed. Therefore, when stones are caught in the groove intersection 51, the forces acting on the stones from the side walls of the first block B1, the second block B2, and the third block B3 are disperse away from the center of the stones, The stone holding power by each block is reduced. As a result, the stone once bitten is easily discharged when it comes into contact with the road surface, and the stone biting performance is improved.

  In the present embodiment, the middle horizontal groove 31 communicates with the short side portion 11 b of the middle main groove 11 and the short side portion 12 b of the shoulder main groove 12, so the groove between the middle main groove 11 and the middle horizontal groove 31. The above-described effects can also be obtained in the intersection and the groove intersection between the shoulder main groove 12 and the middle lateral groove 31. Further, since the shoulder lateral groove 41 communicates with the short side portion 12b of the shoulder main groove 12, the above-mentioned effects can be obtained in the same manner at the groove intersection portion between the shoulder main groove 12 and the shoulder lateral groove 41.

  In the heavy load tire 1 of the present embodiment, the angle α1 of the long side portion 11a of the middle main groove 11 with respect to the tire circumferential direction is preferably 2 to 10 °. When the angle α1 is less than 2 °, the triangle 53 constituted by the vertex P1, the vertex P2, and the vertex P3 is close to an equilateral triangle, so that the holding power of the stone by the block is increased and the bite stone is not easily discharged. . If the angle α1 exceeds 10 °, the drainage performance of the tire may not be sufficiently improved. The angle α2 (see FIG. 4) of the long side portion 12a of the shoulder main groove 12 with respect to the tire circumferential direction is the same as described above.

  FIG. 8 shows the details of the groove intersection 51 and the relationship between the groove intersection 51 and the stone 61 bitten by the groove intersection 51. As shown in FIG. 8A, in the heavy duty tire 1 of the present embodiment, the second block vertex P2 of the second block B2 is the same as the first block vertex P1 and the third block of the first block B1. It passes through the third block vertex P3 of B3 and is provided outside the maximum circle Cmax that fits within the groove intersection 51. That is, the second block vertex P2 is provided at a position that retreats relative to the first block vertex P1 and the third block vertex P3.

  Accordingly, as shown in FIG. 8B, a gap G is likely to be generated between the stone 61 bitten in the groove intersection 51 and the second block vertex P2, and at this time, the stone 61 is It will be supported at two points, block vertex P1 and third block vertex P3. Thereby, the holding force of the stone 61 by each block falls, and it will become easy to discharge | emit when the stone 61 once bit | engaged contacts a road surface, and a stone biting performance improves.

In this embodiment, the angle θ1 (°) of the center lateral groove 21 shown in FIGS. 3 to 5 with respect to the tire circumferential direction, the angle θ2 (°) of the middle lateral groove 31 with respect to the tire circumferential direction, and the angle θ3 of the shoulder lateral groove 41 with respect to the tire circumferential direction. (°) preferably satisfies the following relationship.
θ1 <θ2 <θ3 (1)
60 ≦ θ1 <80 (2)
80 <θ3 ≦ 90 (3)

  The angle θ1 of the center lateral groove 21 is an angle with respect to the tire circumferential direction of the groove edge of the center lateral groove 21 at the apex 26 of the center block 22 in FIG. The angle θ2 of the middle lateral groove 31 is an angle with respect to the tire circumferential direction of the groove edge of the middle lateral groove 31 at the apex 36 of the middle block 32 in FIG. The shoulder lateral groove angle θ3 is an angle with respect to the tire circumferential direction of the groove edge of the shoulder lateral groove 41 at the apex 46 of the shoulder block 42 in FIG. 5. When the corner of each block is chamfered or rounded, the intersection of the extension line of the groove edge of each main groove and the extension line of the groove edge of each lateral groove is the apex.

  By satisfying the relationship of the mathematical formula (1), water smoothly flows from the center land portion 13 having a high ground pressure to the shoulder land portion 12 having a low ground pressure through the center lateral groove 21, the middle lateral groove 31 and the shoulder lateral groove 41. Is discharged, and the drainage performance of the tire is enhanced.

  When the angle θ1 of the center lateral groove 21 is less than 60 °, the block apex 26 of the center block 22 becomes an excessively acute angle, which may be a starting point for uneven wear. On the other hand, when the angle θ1 of the center lateral groove 21 is 60 ° or more, the drainage performance in the center land portion 13 may be deteriorated.

  When the angle θ3 of the shoulder lateral groove 41 is less than 80 °, the block vertex 46 of the shoulder block 42 becomes an excessively acute angle, which may become a starting point for uneven wear. On the other hand, when the angle θ3 of the shoulder lateral groove 41 exceeds 90 °, the inclination of the shoulder lateral groove 41 with respect to the tire axial direction is reversed, and the drainage performance in the shoulder land portion 15 may be deteriorated.

In this embodiment, it is desirable that the groove width WE of the center lateral groove 21, the groove width WF of the middle lateral groove 31, and the groove width WG of the shoulder lateral groove 41 shown in FIGS.
WE ≦ WF <WG (4)
1.5 ≦ WG / WE ≦ 2.5 (5)
1.5 ≦ WG / WF ≦ 2.5 (6)

  By satisfying the relationship of the mathematical formula (4), water smoothly flows from the center land portion 13 having a high ground pressure to the shoulder land portion 12 having a low ground pressure through the center lateral groove 21, the middle lateral groove 31 and the shoulder lateral groove 41. Is discharged, and the drainage performance of the tire is enhanced.

  When the groove width ratio WG / WE of Expression (5) is less than 1.5, the groove width WG of the shoulder lateral groove 41 is relatively insufficient with respect to the groove width WE of the center lateral groove 21. There is a risk that water will not be discharged smoothly over the shoulder land portion 15 and the drainage performance of the tire may not be sufficiently improved. On the other hand, when the ratio WG / WE exceeds 2.5, the land ratio of the shoulder land portion 15 is lowered, and the shoulder land portion 15 may be unevenly worn.

  When the ratio WG / WF of the groove width in Expression (6) is less than 1.5, the groove width WG of the shoulder lateral groove 41 is relatively insufficient with respect to the groove width WF of the middle lateral groove 31. There is a possibility that water is not smoothly discharged to the shoulder land portion 15 and the drainage performance of the tire cannot be sufficiently improved. On the other hand, when the ratio WG / WF exceeds 2.5, the land ratio of the shoulder land portion 15 is lowered, and the shoulder land portion 15 may be unevenly worn.

  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 11.00R20 having the basic structure shown in FIG. 1 was prototyped based on the specifications shown in Table 1 and tested for stone biting performance, wet performance, wear resistance performance and uneven wear resistance performance. The test method is as follows.

<Stone-resistant performance>
Each sample tire was mounted on the rear wheel of a truck (2-D car) having a maximum loading capacity of 10 tons under the conditions of a rim of 20 × 8.00 and an internal pressure of 780 kPa. The tire of the specification of Example 1 was mounted on one rear wheel, and the tire of each specification was mounted on the other rear wheel. The vehicle was run until any of the rear wheel tires was worn 50%, and the number of stones caught in the tire of each specification at the end of the run was measured. The result is the reciprocal of the number of stones caught in the tire of Example 1, 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 stone biting performance.

<Traction performance>
Each of the 75% worn tires was mounted on all wheels of a truck (2-D car) with a maximum loading capacity of 10 tons under the conditions of a rim of 20 × 8.00 and an internal pressure of 780 kPa. The vehicle was brought into a wet asphalt road surface with a water film with a thickness of 5 mm, and the passing time of 10 m from the moment the clutch was engaged with the transmission gear fixed at 2nd speed and the engine speed fixed at 1500 rpm was measured. . The result is the reciprocal of each passing time, and is represented by an index with the value of Example 1 being 100. The evaluation shows that the larger the value, the better the traction performance on the wet road surface.

  As is clear from Table 1, it was confirmed that the heavy load tires of the examples had significantly improved stone biting performance and traction performance as compared with the comparative examples.

DESCRIPTION OF SYMBOLS 1 Heavy duty tire 2 Tread part 11 Middle main groove 11a Long side part 11b Short side part 11c Groove center line 12 Shoulder main groove 12a Long side part 12b Short side part 13 Center land part 14 Middle land part 15 Shoulder land part 21 Center lateral groove 22 Center block 31 Middle lateral groove 32 Middle block 41 Shoulder lateral groove 41e First extension line 41f Second extension line CP1 First intersection point CP2 Second intersection point

Claims (6)

The tread portion has a main groove extending continuously in a zigzag shape in the tire circumferential direction, and land portions provided on both sides thereof, and the land portions on both sides are divided into a plurality of blocks by a plurality of lateral grooves. A heavy duty tire,
The lateral grooves on both sides of the main groove are arranged shifted in the tire circumferential direction,
The main groove is alternately provided with a long side portion and a short side portion that is inclined in the opposite direction to the long side portion and whose length in the tire circumferential direction is smaller than the long side portion,
The lateral groove communicates with the main groove in a region including the short side part,
A first extension line obtained by extending one groove edge of the horizontal groove toward the main groove intersects with the groove edge of the long side portion of the main groove at a first intersection, and the other groove edge of the horizontal groove is connected to the main groove. The second extension line extended to the side intersects the groove edge of the long side portion of the main groove at a second intersection point,
A ratio L2 / L1 between a distance L1 in the tire circumferential direction between the first intersection and the second intersection and a length L2 in the tire circumferential direction of the short side portion is 0.08 to 0.25. Heavy duty tires.
When the ratio L3 / L1 between the distance L3 in the tire circumferential direction between the second intersection and the short side portion and the distance L1 in the tire circumferential direction between the first intersection and the second intersection exceeds 0.25,
A ratio L4 / L1 between a distance L4 in the tire circumferential direction between the first intersection and the short side portion and a distance L1 in the tire circumferential direction between the first intersection and the second intersection is 0.25 to 0.50. The heavy duty tire according to claim 1. When the ratio L3 / L1 between the distance L3 in the tire circumferential direction between the second intersection and the short side portion and the distance L1 in the tire circumferential direction between the first intersection and the second intersection is 0.25 or less,
A ratio L4 / L1 between a distance L4 in the tire circumferential direction between the first intersection and the short side portion and a distance L1 in the tire circumferential direction between the first intersection and the second intersection is 0.50 to 0.75. The heavy duty tire according to claim 1. When the ratio L3 / L1 between the distance L3 in the tire circumferential direction between the second intersection and the short side portion and the distance L1 in the tire circumferential direction between the first intersection and the second intersection exceeds 0.25,
A ratio L4 / L1 between a distance L4 in the tire circumferential direction between the first intersection and the short side portion and a distance L1 in the tire circumferential direction between the first intersection and the second intersection is 0.33 or more. 2. Heavy duty tire according to 2. When the ratio L3 / L1 between the distance L3 in the tire circumferential direction between the second intersection and the short side portion and the distance L1 in the tire circumferential direction between the first intersection and the second intersection is 0.25 or less,
A ratio L4 / L1 between a distance L4 in the tire circumferential direction between the first intersection and the short side portion and a distance L1 in the tire circumferential direction between the first intersection and the second intersection is 0.66 or less. 3. Heavy duty tire according to 3. A first block apex formed by a corner of a first block and a second block apex formed by a corner of a second block adjacent to the first block in the tire circumferential direction at a groove intersection of the main groove and the lateral groove. A third vertex that protrudes most toward the groove center line side of the main groove at the groove edge of the main groove of the third block adjacent to the first block and the second block via the main groove is provided,
The heavy duty tire according to any one of claims 1 to 5, wherein the second block vertex is provided outside a maximum circle that passes through the first block vertex and the third vertex and falls within the groove intersection.

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