JP2015089796A - Tire for heavy load - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire for heavy load capable of achieving wear resistance and uneven wear resistance, and wet performance by high level.SOLUTION: A tread part 2 comprises: a pair of center main grooves 3; a pair of shoulder main grooves 4; plural center lateral grooves 51; plural middle lateral grooves 61; and plural shoulder lateral grooves 71, therefore the tread part 2 is divided into a center block 52, a middle block 62, and a shoulder block 72. The center main groove has long side parts 3a, and short side parts 3b inclined in an opposite direction of the long side parts 3a alternately. The center lateral groove 51 couples a space between the long side parts 3a, 3a of the pair of center main grooves 3, and the middle lateral groove 61 couples an outside zigzag apex 3o of the center main groove 3 and an inside zigzag apex 4i of the shoulder main groove 4. The middle block 62 has an inclination slot 64 whose depth gradually increase toward the center main groove 3 on a position sandwiching the center main groove 3 and facing the center lateral groove 51.

Description

  The present invention relates to a heavy duty tire that has both wear resistance, uneven wear resistance, and wet performance.

  Conventionally, in heavy-duty tires used for trucks and buses, for example, as shown in Patent Document 1 below, a plurality of main grooves extending continuously in the tire circumferential direction, and between the main grooves and the main grooves There has been proposed a tread pattern in which a plurality of blocks are formed by a lateral groove that connects a tire and a ground contact end.

  Heavy duty tires are required to have excellent wear resistance and uneven wear resistance from the viewpoints of economy and maintenance saving. In general, in order to increase the wear resistance and uneven wear resistance, it is effective to secure the rubber volume of the tread portion and increase the rigidity of the tread portion by reducing the groove volume of the tread portion.

JP 2011-195045 A

  However, when the groove volume of the tread portion is reduced, drainage performance is lowered and wet performance may be deteriorated.

  The present invention has been devised in view of the above circumstances, and its main object is to provide a heavy duty tire capable of achieving both wear resistance performance, uneven wear resistance performance and wet performance at a high level.

  The present invention provides a tread portion having a pair of center main grooves extending zigzag continuously on both sides of the tire equator in the tire circumferential direction, and zigzag between the center main groove and the ground contact end in the tire circumferential direction. A pair of shoulder main grooves extending, a plurality of center lateral grooves connecting between the pair of center main grooves, a plurality of middle lateral grooves connecting between the center main grooves and the shoulder main grooves, and the shoulder main grooves A center block row in which center blocks separated by the center main groove and the center lateral groove are provided in the tire circumferential direction by providing a plurality of shoulder lateral grooves that connect between the groove and the ground contact end, A pair of middle block rows in which the middle blocks divided by the middle main groove, the shoulder main groove, and the middle lateral groove are separated in the tire circumferential direction, and the front A heavy duty tire having a pair of shoulder block rows in which a shoulder block divided by a shoulder main groove, the ground contact end and the shoulder lateral groove is spaced in the tire circumferential direction, the center main groove and the shoulder main groove Are alternately provided with long side portions and short side portions that are inclined in a direction opposite to the long side portions and have a tire circumferential length smaller than the long side portions, and the center lateral grooves The middle side groove is connected between the outer zigzag top portion protruding toward the grounding end side of the center main groove and the inner zigzag top portion protruding toward the tire equator side of the shoulder main groove. The middle block has an inclined slot whose depth gradually increases toward the center main groove at a position facing the center lateral groove across the center main groove. The features.

  In the heavy load tire according to the present invention, the inclined slot and the center lateral groove facing the inclined slot are 25% of a tire circumferential direction length of the center lateral groove in an opening length of the center main groove. It is desirable to overlap in an area of ~ 50%.

  In the heavy duty tire according to the present invention, the inclined slot extends from the center main groove toward the crown main groove, and terminates in the middle block without communicating with the crown main groove. The length from the opening in the center main groove to the end of the inclined slot is preferably 55% to 65% of the groove width of the center main groove.

  In the heavy duty tire according to the present invention, it is desirable that the depth of the deepest portion of the inclined slot is 50% to 100% of the depth of the center main groove.

  In the heavy duty tire according to the present invention, it is desirable that a length of the middle block in the tire axial direction is 95% to 105% of a length of the center block in the tire axial direction.

  In the heavy duty tire according to the present invention, it is desirable that the length of the shoulder block in the tire axial direction is 95% to 105% of the length of the center block in the tire axial direction.

  In the heavy duty tire according to the present invention, it is desirable that a land ratio of the tread portion is 65% to 75%.

  In the heavy load tire according to the present invention, the inclined slot has an inclined surface inclined inward in the tire radial direction from the tread surface of the middle block, and an angle formed by the inclined surface and the tread surface of the middle block is 50 It is desirable to be in the range of 0 ° to 70 °.

  In the heavy load tire of the present invention, the middle lateral groove connects between the outer zigzag top on the ground contact end side of the center main groove and the inner zigzag top on the tire equator side of the shoulder main groove. Such a middle lateral groove has excellent drainage between the center main groove and shoulder main groove and the middle lateral groove.

  Further, the center lateral groove connects between the long sides of the pair of center main grooves, and the middle block has an inclined slot at a position facing the center lateral groove with the center main groove interposed therebetween. Since such an inclined slot gradually increases in depth toward the center main groove, the flow of water from the middle block toward the center lateral groove is promoted, and the drainage of the middle block is enhanced. Thereby, it becomes possible to improve drainage without increasing the groove volume, and it becomes possible to achieve both wear resistance, uneven wear resistance and wet performance at a high level.

It is an expanded view of the tread part which shows one embodiment of the tire for heavy loads of the present invention. It is an AA line sectional view of the tread part of Drawing 1. FIG. 2 is an enlarged development view of a crown land portion of FIG. 1. FIG. 2 is an enlarged development view of a middle land portion of FIG. 1. It is the perspective view which expanded a part of tread part of FIG. It is the perspective view which expanded the middle block of FIG. FIG. 2 is an enlarged development view of a shoulder land portion of FIG. 1.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a development view of the tread portion 2 of the heavy duty tire (not shown) of the present embodiment. FIG. 2 shows a cross section taken along line AA of the tread portion 2. As shown in FIG. 1, a pair of center main grooves 3 that are arranged on both sides of the tire equator C and extend in a zigzag manner continuously in the tire circumferential direction in the tread portion 2, and the tire axial direction of the center main grooves 3 A pair of shoulder main grooves 4 extending outwardly in a tire circumferential direction and extending in a zigzag shape are formed.

  The center main groove 3 is alternately provided with long side portions 3a and short side portions 3b whose length in the tire circumferential direction is smaller than the long side portion 3a. A zigzag center main groove 3 is formed by inclining the short side portion 3b in the direction opposite to the long side portion 3a with respect to the tire circumferential direction.

  Similarly, the shoulder main groove 4 is provided with alternating long side portions 4a and short side portions 4b whose length in the tire circumferential direction is smaller than the long side portion 4a. A zigzag shoulder main groove 4 is formed by inclining the short side portion 4b in the direction opposite to the long side portion 4a with respect to the tire circumferential direction.

  The center main groove 3 has an inner zigzag top portion 3i that protrudes most toward the tire equator C side, that is, the inner side in the tire axial direction, and an outer zigzag top portion 4o that protrudes most toward the ground contact end Te side, that is, the outer side in the tire axial direction. Similarly, the shoulder main groove 4 has an inner zigzag top 4i that protrudes most toward the tire equator C side, that is, the inner side in the tire axial direction, and an outer zigzag top 4o that protrudes most toward the ground contact end Te side, that is, the outer side in the tire axial direction. Yes.

  The groove width W1 of the center main groove 3 and the groove width W2 of the shoulder main groove 4 are set according to, for example, the ground contact width TW of the tread portion 2. Here, the contact width TW of the tread portion 2 is the length in the tire axial direction between the tread contact ends Te and 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 °. Here, the normal state is a no-load state in which the tire is assembled on a normal rim (not shown) and filled with a normal internal pressure. Hereinafter, unless otherwise specified, dimensions and the like of each part of the tire are values measured in the 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, use "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". If ETRTO, "INFLATION PRESSURE".

  “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 groove width W1 of the center main groove 3 is preferably 1.5% to 5% of the ground contact width TW of the tread portion 2, for example. When the groove width W1 is less than 1.5% of the ground contact width TW, the drainability of the tread portion 2 may be deteriorated. When the groove width W1 exceeds 5% of the ground contact width TW, the rubber volume is insufficient, and the wear resistance and uneven wear resistance may be deteriorated.

  As shown in FIG. 2, the groove depth D1 of the center main groove 3 is preferably, for example, 10 mm to 20 mm. When the said groove depth D1 is less than 10 mm, there exists a possibility that the drainage of the tread part 2 may fall. When the groove depth D1 exceeds 20 mm, the rigidity of the tread portion 2 is insufficient, and the wear resistance and uneven wear resistance may be deteriorated.

  Similarly, the groove width W2 of the shoulder main groove 4 is desirably 1.5% to 5% of the ground contact width TW of the tread portion 2, for example, and the groove depth D2 of the shoulder main groove 4 is, for example, 10 mm to 20 mm. desirable.

  The center main groove 3 and the shoulder main groove 4 divide the tread portion 2 into a plurality of land portions. That is, the tread portion 2 includes a tire shaft of a pair of middle land portions 6 and a shoulder main groove 4 sandwiched between a center land portion 5 sandwiched between a pair of center main grooves 3 and 3, a crown main groove 3 and a shoulder main groove 4. The region is divided into a pair of shoulder land portions 7 located on the outer side in the direction.

  FIG. 3 shows an enlarged view of the pair of center main grooves 3 and 3 and the center land portion 5. The center land portion 5 is provided with a plurality of center lateral grooves 51 that connect between the pair of center main grooves 3 and 3. The center lateral groove 51 connects the long side portions 3a, 3a of the pair of center main grooves 3, 3. The center land portion 5 is divided into a plurality of center blocks 52 by a plurality of center lateral grooves 51. Thereby, the center land portion 5 is a center block row 53 in which a plurality of center blocks 52 are spaced apart in the tire circumferential direction.

  A pair of chamfered portions 54 are formed at the acute block top located diagonally to the center block 52 among the block tops where the center main groove 3 and the center lateral groove 51 intersect. The chamfered portion 54 promotes the flow of water between the center main groove 3 and the center lateral groove 51. Furthermore, the chamfered portion 54 relaxes stress concentration at the top of the block and suppresses damage such as chipping. Instead of the chamfered portion 54, a rounded corner portion may be formed at the block vertex.

  FIG. 4 shows an enlarged view of the center main groove 3, the shoulder main groove 4, and the middle land portion 6. The middle land portion 6 is provided with a plurality of middle lateral grooves 61 that connect between the center main groove 3 and the shoulder main groove 4. The middle lateral groove 61 connects the outer zigzag top 3o of the center main groove 3 and the inner zigzag top 4i of the shoulder main groove 4. The middle land portion 6 is divided into a plurality of middle blocks 62 by a plurality of middle lateral grooves 61. Accordingly, the middle land portion 6 is a middle block row 63 in which a plurality of middle blocks 62 are spaced apart in the tire circumferential direction.

  FIG. 5 shows an enlarged part of the tread portion 2 viewed from the side of the ground contact Te. In FIG. 6, the middle block 62 viewed from the tire equator C side is shown enlarged. As shown in FIG. 4 to FIG. 6, an inclined slot 64 whose depth gradually increases toward the center main groove 3 is provided on the center main groove 3 side of the middle block 62.

  The inclined slot 64 is provided at a position facing the center lateral groove 51 across the center main groove 3. Such an inclined slot 64 promotes the flow of water from the middle block 62 toward the center lateral groove 51 and improves the drainage of the middle block 62.

  In the present embodiment, a chamfered portion 54 is formed at the top of the center block 52 that faces the inclined slot 64 across the center main groove 3, so that water flows from the middle block 62 toward the center lateral groove 51. It is further promoted.

  As shown in FIG. 4, the center lateral groove 51 and the inclined slot 64 facing each other across the center main groove 3 overlap in a region 65 indicated by hatching in the tire circumferential direction. The tire circumferential direction length L1 of the region 65 is desirably 25% to 50% of the tire circumferential direction length L2 of the center lateral groove 51, for example. That is, the inclined slot 64 and the center lateral groove 51 opposed to the inclined slot 64 are in the region of 25% to 50% of the tire circumferential direction length L2 of the center lateral groove 51 in the opening length in the center main groove 3. It is desirable to overlap.

  When the length L1 is less than 25% of the length L2, the effect of promoting the flow of water from the middle block 62 toward the center lateral groove 51 by the inclined slot 64 may be reduced. On the other hand, when the length L1 exceeds 50% of the length L2, the flow of water from the middle block 62 on one side to the center lateral groove 51 across the tire equator C becomes excessively strong, and the middle block on the other side The flow of water from 62 toward the center lateral groove 51 is obstructed, and the drainage performance of the tread portion 2 as a whole may be reduced.

  As shown in FIG. 4, the inclined slot 64 extends from the center main groove 3 toward the crown main groove 4 and terminates in the middle block 62 without communicating with the crown main groove 4. The length L3 from the opening 64a in the center main groove 3 of the inclined slot 64 to the end 64b of the inclined slot 64 is preferably, for example, 55% to 65% of the groove width W1 of the center main groove 3.

  When the length L3 is less than 55% of the groove width W1, the volume of the inclined slot 64 is insufficient, and the effect of promoting the flow of water from the middle block 62 toward the center lateral groove 51 may be reduced. On the other hand, when the length L3 exceeds 65% of the groove width W1, the rubber volume of the middle block 62 is insufficient, and the wear resistance may be deteriorated. Furthermore, the rigidity of the middle block 62 may be reduced, and the uneven wear resistance performance may be reduced.

  As shown in FIGS. 2B and 6, the depth D3 of the inclined slot 64 in the opening 64a, that is, the depth of the deepest portion of the inclined slot 64 is, for example, the groove depth D1 of the center main groove 3. It is desirable to be 50% to 100%.

  When the depth D3 is less than 50% of the groove depth D1, the effect of promoting the flow of water from the middle block 62 to the center lateral groove 51 by the inclined slot 64 may be reduced.

  As shown in FIGS. 2B and 6, the inclined slot 64 has an inclined surface 64 c that is inclined inward in the tire radial direction from the tread surface 62 s of the middle block 62 at the bottom. The angle θ formed by the inclined surface 64c and the tread surface 62s of the middle block 62 is preferably 50 ° to 70 °, for example.

  When the angle θ is less than 50 °, the volume of the inclined slot 64 is insufficient, and the effect of promoting the flow of water from the middle block 62 toward the center lateral groove 51 may be reduced. On the other hand, when the angle θ exceeds 70 °, the rubber volume of the middle block 62 is insufficient, and the wear resistance may be lowered. Furthermore, the rigidity of the middle block 62 may be reduced, and the uneven wear resistance performance may be reduced.

  As shown in FIGS. 4 to 6, among the block tops at which the center main groove 3 and the shoulder main groove 4 intersect with the middle lateral groove 61, the acute block tops located diagonally to the middle block 62 have a pair of A chamfered portion 66 is formed. The chamfered portion 66 promotes the flow of water between the center main groove 3 and the shoulder main groove 4 and the middle lateral groove 61. Further, the chamfered portion 66 relaxes stress concentration at the block top and suppresses damage such as chipping. Instead of the chamfer 66, a rounded corner may be formed at the top of the block.

  FIG. 7 shows an enlarged view of the shoulder main groove 4 and the shoulder land portion 7. The shoulder land portion 7 is provided with a plurality of shoulder lateral grooves 71 that connect between the shoulder main groove 4 and the ground contact Te. The shoulder lateral groove 71 connects between the long side part 4a of the shoulder main groove 4 and the ground contact Te. The shoulder land portion 7 is divided into a plurality of shoulder blocks 72 by a plurality of shoulder lateral grooves 71. Thus, the shoulder land portion 7 is a shoulder block row 73 in which a plurality of shoulder blocks 72 are spaced apart in the tire circumferential direction.

  The shoulder land portion 7 is provided with a plurality of shoulder lateral sipes 74 that connect between the shoulder main groove 4 and the ground contact Te. The shoulder lateral sipe 74 connects between the outer zigzag top 4o of the shoulder main groove 4 and the ground contact Te. Due to the edge effect generated by the shoulder lateral sipe 74, the wet performance of the heavy duty tire is enhanced.

  As shown in FIGS. 3 and 4, the tire axis direction length WB of the middle block 62 is desirably 95% to 105% of the tire axis direction length WA of the center block 52, for example.

  When the length WB is less than 95% of the length WA, the rubber volume of the middle block 62 is insufficient, and there is a possibility that uneven wear occurs in the middle block 62. On the other hand, when the length WB exceeds 105% of the length WA, the rubber volume of the center block 52 is insufficient, so that there is a possibility that uneven wear occurs in the center block 52.

  Similarly, as shown in FIGS. 3 and 7, the length WC of the shoulder block 72 in the tire axial direction is desirably 95% to 105% of the length WA of the center block 52 in the tire axial direction, for example.

  When the length WC is less than 95% of the length WA, the rubber volume of the shoulder block 72 is insufficient, so that there is a possibility that uneven wear occurs in the shoulder block 72. On the other hand, when the length WC exceeds 105% of the length WA, the rubber volume of the center block 52 is insufficient, so that there is a possibility that uneven wear occurs in the center block 52.

  The land ratio of the tread portion 2 on which the above-described pattern is formed is desirably 65% to 75%, for example.

  When the land ratio of the tread part 2 is less than 65%, the rubber volume of the tread part 2 is insufficient, the rigidity of the tread part 2 is lowered, and the wear resistance and uneven wear resistance may be lowered. Furthermore, the center block 52, the middle block 62, and the shoulder block 72 may be damaged due to a decrease in rigidity of the tread portion 2. On the other hand, when the land ratio of the tread portion 2 exceeds 75%, the groove volume of the tread portion 2 is insufficient, and the drainage performance may be deteriorated.

  According to the heavy duty tire of the present embodiment having the above-described configuration, the middle lateral groove 61 connects the outer zigzag top 3o of the center main groove 3 and the inner zigzag top 4i of the shoulder main groove 4, The drainage performance is improved between the center main groove 3 and the shoulder main groove 4 and the middle lateral groove 61.

  Further, the center lateral groove 51 connects the long side portions 3a and 3a of the pair of center main grooves 3 and 3, and the middle block 62 faces the center lateral groove 51 with the center main groove 3 therebetween. 64. Since the depth of the inclined slot 64 gradually increases toward the center main groove 3, the flow of water from the middle block 62 toward the center lateral groove 51 is promoted, and the drainage of the middle block 62 is enhanced. Thereby, it becomes possible to improve drainage without increasing the groove volume of the tread portion 2 so that the wear resistance performance and the uneven wear resistance performance and the wet performance of the heavy duty tire can be compatible at a high level. Become.

  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 215 / 75R17.5 having the basic structure shown in FIG. 1 was prototyped based on the specifications shown in Table 1 and tested for wet performance and uneven wear resistance. The test method is as follows.

<Wet performance>
Each sample tire was mounted on all wheels of a truck (2-D car) with a maximum loading capacity of 4 tons. With the above vehicle, the vehicle entered a circular asphalt road surface with a water film of 1.4 to 1.6 mm while gradually increasing the speed, and the average lateral acceleration was measured at a speed of 70 to 90 km / h. It was. A result is displayed by the index | exponent which sets Example 1 to 100, and wet is so favorable that a numerical value is large.

<Uneven wear resistance>
The vehicle travels 10,000 km with a constant load, the groove depth of the center main groove and the shoulder main groove is measured, and the uneven wear amount of the tread portion is calculated based on the groove depth of each main groove. It was. A result is displayed by the index | exponent which sets Example 1 to 100, and uneven wear resistance performance is so favorable that a numerical value is large.

  As is clear from Table 1, it was confirmed that the heavy load tires of the examples had significantly improved wet performance while improving the wear resistance and uneven wear resistance compared to the comparative example.

2 tread portion 3 center main groove 4 shoulder main groove 51 center horizontal groove 52 center block 53 center block row 61 middle horizontal groove 62 middle block 63 middle block row 64 inclined slot 64a opening 64b end 64c inclined surface 71 shoulder horizontal groove 72 shoulder block 73 shoulder block Column

Claims (8)

A pair of center main grooves extending zigzag continuously on the tire equator on both sides of the tire equator on the tread portion, and a pair extending zigzag continuously between the center main groove and the ground contact end in the tire circumferential direction. Shoulder main grooves, a plurality of center lateral grooves connecting between the pair of center main grooves, a plurality of middle lateral grooves connecting between the center main grooves and the shoulder main grooves, the shoulder main grooves and the grounding By providing multiple shoulder lateral grooves that connect between the ends,
A center block row in which center blocks divided by the center main groove and the center horizontal groove are spaced apart in the tire circumferential direction, and a middle block divided by the middle main groove, the shoulder main groove, and the middle horizontal groove is a tire. A pair of middle block rows spaced in the circumferential direction, and a pair of shoulder block rows in which the shoulder blocks partitioned by the shoulder main groove, the ground contact end, and the shoulder lateral groove are spaced in the tire circumferential direction are provided. A heavy duty tire,
The center main groove and the shoulder main groove are alternately provided with a long side portion and a short side portion that is inclined in a direction opposite to the long side portion and whose length in the tire circumferential direction is smaller than the long side portion. ,
The center lateral groove connects between the long side portions of the pair of center main grooves,
The middle lateral groove is connected between the outer zigzag top portion protruding toward the ground contact end of the center main groove and the inner zigzag top portion protruding toward the tire equator of the shoulder main groove,
The heavy load tire, wherein the middle block has an inclined slot whose depth gradually increases toward the center main groove at a position facing the center lateral groove across the center main groove.   The inclined slot and the center lateral groove facing the inclined slot overlap in an area of 25% to 50% of the tire circumferential direction length of the center lateral groove in the opening length of the center main groove. The heavy duty tire according to claim 1. The inclined slot extends from the center main groove toward the crown main groove, and terminates in the middle block without communicating with the crown main groove.
The heavy duty tire according to claim 1 or 2, wherein a length from an opening of the inclined main slot to the end of the inclined slot is 55% to 65% of a groove width of the central main groove.   The heavy duty tire according to any one of claims 1 to 3, wherein a depth of a deepest portion of the inclined slot is 50% to 100% of a depth of the center main groove.   The heavy load tire according to any one of claims 1 to 4, wherein a length of the middle block in the tire axial direction is 95% to 105% of a length of the center block in the tire axial direction.   The tire for heavy loads according to any one of claims 1 to 5, wherein a length of the shoulder block in the tire axial direction is 95% to 105% of a length of the center block in the tire axial direction.   The heavy duty tire according to any one of claims 1 to 6, wherein a land ratio of the tread portion is 65% to 75%.   The inclined slot has an inclined surface inclined inward in the tire radial direction from a tread surface of the middle block, and an angle formed by the inclined surface and the tread surface of the middle block is 50 ° to 70 °. The heavy duty tire according to any one of 7.

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