JP4422622B2 - Heavy duty tire - Google Patents

Description

  The present invention relates to a heavy-duty tire that is suitable as a winter tire and enables both on-ice performance and uneven wear resistance.

  For example, in winter tires such as studless tires for heavy-duty vehicles, 5 to 6 rows including a shoulder block row along the tread edge and an inner block row adjacent to the tread edge in order to ensure running performance on icy and snowy roads. The block pattern is frequently used. In tires, a larger load tends to be applied to the shoulder block when turning. Therefore, in order to support this large load and exhibit good steering stability, the shoulder block is more than the other blocks. The block rigidity has been relatively increased by increasing the size, such as making it wider.

  However, at this time, there is a problem that a difference in rigidity between the shoulder block and the middle block becomes large, and uneven wear such as punching wear occurs in which the middle block wears earlier than the shoulder block.

  Therefore, conventionally, in order to suppress this punching wear and improve the performance on ice, the shoulder block is provided with a plurality of horizontal sipings extending in the tire axial direction, and the shoulder block is subdivided into horizontally long block pieces.

  However, in this case, although it is effective in reducing punching wear, the circumferential rigidity of the shoulder block becomes too small, and heel and toe wear is newly generated on the block piece. It was.

  Therefore, the present invention is based on the fact that the shoulder block is divided into four block pieces by vertical siping and horizontal siping in a cross shape, while exhibiting high on-ice performance, such as punching wear and heel & toe wear. It aims at providing the tire for heavy loads which can suppress wear.

JP 2003-118320 A

In order to achieve the above object, the invention of claim 1 of the present application is directed to an outer longitudinal main groove extending continuously in the tire circumferential direction near the tread edge on the tread surface, and the tread edge from the outer longitudinal main groove. By forming a plurality of lateral grooves extending up to, a shoulder block row formed of shoulder blocks surrounded by the outer longitudinal main grooves, lateral grooves, and tread edges and spaced apart in the tire circumferential direction along the tread edges is formed. A heavy duty tire,
The shoulder block is provided with a vertical siping that crosses between the horizontal grooves, and a horizontal siping that crosses between the outer vertical main groove and a tread edge and intersects the vertical siping at an intersection point P. The shoulder block includes a first inner block piece on one side in the tire circumferential direction and on the inner side in the tire axial direction, a first outer block piece on one side in the tire circumferential direction and on the outer side in the tire axial direction, the other side in the tire circumferential direction and the tire axis. Divided into a second inner block piece on the inner side in the direction and a second outer block piece on the other side in the tire circumferential direction and on the outer side in the tire axial direction,
The sipe depth hi of the inner siping portion is 0.4 to 0.7 times the groove depth Hg of the vertical main groove, and the sipe depth ho of the outer siping portion 6o is the groove depth of the vertical main groove. The sipe depth hc of the vertical sipe is 0.2 to 0.4 times Hg, and is equal to or less than the sipe depth ho.
The sipe bottom of the outer sipe part extends outward in the tire radial direction from the sipe bottom of the inner sipe part, and the lateral sipe has a sipe depth ho of the outer sipe part on the outer side in the tire axial direction from the intersection. Is smaller than the sipe depth hi of the inner siping portion on the inner side in the tire axial direction than the intersection.

In the invention of claim 2, the difference (hi-ho) between the sipe depth ho of the outer siping part and the sipe depth hi of the inner siping part is 4.0 to 7.0. In the third aspect of the invention, the vertical siping has a sipe depth hc of 5 mm or more. In the fourth aspect of the invention, the lateral groove protrudes from the groove bottom at a small height and extends in the tire circumferential direction. An inner tie bar that connects the first inner block piece and the second inner block piece that are adjacent to each other in the tire circumferential direction via the lateral groove, and an outer that connects the first outer block piece and the second outer block piece. And includes a first lateral groove having a cross-sectional area So of the outer tie bar larger than a cross-sectional area Si of the inner tie bar, and in the invention of claim 5, One transverse groove and a second transverse groove with only the tie bar inside Becomes, and the first lateral grooves and the second lateral grooves, and characterized in that arranged alternately in the tire circumferential direction.

  Since the present invention is configured as described above, uneven wear such as punching wear and heel & toe wear can be suppressed while exhibiting high performance on ice.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a development view of a tread pattern when the heavy duty tire of the present invention is a studless tire for trucks and buses.

  In FIG. 1, the heavy duty tire extends on the tread surface 2S from the outer vertical main groove 3o extending continuously near the tread edge Te in the tire circumferential direction, and from the outer vertical main groove 3o to the tread edge Te. A plurality of lateral grooves 4o are provided. Thereby, the tread surface 2S includes at least a shoulder block row Ro in which a shoulder block Bo surrounded by the outer vertical main groove 3o, the lateral groove 4o, and the tread edge Te is spaced in the tire circumferential direction, Alternatively, a block-rib type tread pattern is formed.

  In this example, the case where the tread pattern is a block pattern composed of five block rows is illustrated.

  Specifically, the four vertical main grooves 3 including the outer vertical main groove 3o and the inner vertical main groove 3m inside the tire axial direction are arranged on the tread surface 2S. The vertical main grooves 3o and 3m are divided by an inner block row Rm consisting of the inner blocks Bm divided by the inner horizontal grooves 4m, and the inner horizontal grooves 4i are divided between the vertical main grooves 3m and 3m. Each block row Ri including the blocks Bi is formed.

  The longitudinal main groove 3 is a groove body having a straight line shape or a zigzag shape and a groove width Wg continuously extending in the tire circumferential direction of 7.0 mm or more, preferably 8.0 mm or more, and a groove depth Hg ( As shown in FIG. 4, a range of 16.0 to 24.0 mm is employed in the case of winter tires. The lateral grooves 4 extend at an angle of 20 ° or less, preferably 15 ° or less with respect to the tire axial direction in order to ensure traction on ice and snow. The lateral groove 4 has a groove width Wy of 1.5 mm or more, and a groove depth Hy (shown in FIG. 4) is about 0.7 to 1.0 times the groove depth Hg of the longitudinal main groove 3. It is formed.

  Further, the number of blocks formed in each block row Ri, Rm, Ro is the same, and therefore the lengths in the tire circumferential direction of the blocks Bi, Bm, Bo are substantially equal. Therefore, in order to increase the cornering force and ensure excellent steering stability (including turning performance), the width Jo of the shoulder block row Ro in the tire axial direction is, for example, compared with the width Jm of the middle block row Rm. The shoulder block Bo is increased in size by 1.1 to 1.4 times. The width Ji of the inner block row Ri is set substantially equal to 100 ± 5% of the width Jm.

  In the present invention, in such a block pattern, in order to suppress uneven wear such as punching wear and heel & toe wear while ensuring high performance on ice, as shown in an enlarged view in FIG. In the block Bo, a vertical siping 5 that crosses between the horizontal grooves 4o and 4o, and a horizontal pipe that crosses between the outer vertical main groove 3o and the tread edge Te and intersects the vertical siping 5 at an intersection P. The siping 6 is formed.

  Thus, the shoulder block Bo is divided into a first inner block piece B1i on the tire circumferential direction one side and the tire axial direction inner side, a tire circumferential direction one side and the tire axial direction outer side first outer block piece B1o, and the tire circumference. A second inner block piece B2i on the other side in the tire direction and on the inner side in the tire axial direction, and a second outer block piece B2o on the other side in the tire circumferential direction and on the outer side in the tire axial direction are divided into four in a cross shape.

  In this example, the vertical siping 5 extends in the tire circumferential direction, and the horizontal siping 6 is formed substantially in parallel with the lateral groove 4o.

  The block pieces B1i to B2o do not need to be equally divided, but the block piece width Wi in the tire axial direction of the block pieces B1i and B2i is in a range of 100 ± 20% of the block piece width Wo of the block pieces B1o and B2o. The block piece length L1 in the tire circumferential direction of the block pieces B1i and B1o is preferably in the range of 100 ± 30% of the block piece length L2 of the block pieces B2i and B2o.

  Thus, by dividing the shoulder block Bo into four crosses, the block rigidity can be reduced in a balanced and appropriate manner. As a result, the rigidity difference from the inner block Bm can be reduced, and punching wear in the inner block Bm can be suppressed. Further, since the rigidity in the circumferential direction of each of the block pieces B1i to B2o is ensured to some extent, heel and toe wear can be suppressed at the same time. If the widths Wi and Wo and the lengths L1 and L2 of the block pieces are out of the above range, the rigidity difference between the block pieces B1i to B2o becomes excessive, and it becomes difficult to suppress uneven wear.

  On the other hand, the vertical and horizontal sipings 5 and 6 ensure edge components in the tire axial direction and the circumferential direction, so that the performance on ice can be improved. In addition, when only a plurality of horizontal sipings are formed as in the prior art, the edge component in the circumferential direction is insufficient and a tendency to skid is caused in addition to causing heel and toe wear. For this reason, it is necessary to increase the number of block rows to, for example, 6 rows to compensate for edge components in the circumferential direction, but this causes a disadvantage in wear resistance performance of each block row, such as relatively reducing the width of each block row.

Next, as shown in FIG. 3, in the horizontal sipe 6, the sipe bottom of the outer sipe part 6o extends outside the sipe bottom of the inner sipe part 6i in the tire radial direction, so that the tire from the intersection P The sipe depth ho of the outer siping portion 6o on the outer side in the axial direction is smaller than the sipe depth hi of the inner siping portion 6i on the inner side in the tire axial direction than the intersection P (ho <hi).

  The sipe depth hi is in the range of 0.4 to 0.7 times the groove depth Hg of the vertical main groove 3o, and in this example, the case of 11.0 to 13.0 mm is illustrated. The sipe depth ho is in the range of 0.2 to 0.4 times the groove depth Hg, and in this example, the case of 5.0 to 7.0 mm is illustrated. The difference (hi-ho) in the sipe depth at this time is 4.0 to 7.0 mm. The vertical sipe 5 has a constant sipe depth hc, preferably 5 mm or more and not more than the sipe depth ho.

  By setting in this way, the above-mentioned high performance on ice and uneven wear resistance can be exhibited in the early stage of wear. Further, in the middle of wear, the vertical siping 5 and the outer siping portion 6o are worn away, and the block pieces B1i to B2o are combined and enlarged to increase the block rigidity, while the inner siping portion 6i remains. Similarly, it is possible to achieve both on-ice performance and uneven wear resistance. Note that if the sipe depths hi and ho are out of the above ranges, the above-described effect is not exhibited effectively.

  In particular, in order to prevent uneven wear, rib-shaped tie bars 7 that protrude from the bottom of the groove at a small height and extend in the tire circumferential direction are provided in the lateral groove 4o, and shoulders adjacent to each other in the tire circumferential direction through the lateral groove 4o. It is preferable to connect the blocks Bo and Bo to each other.

  In this example, the lateral groove 4o includes an inner tie bar 7i that connects the first inner block piece B1i and the second inner block piece B2i that are adjacent to each other in the tire circumferential direction through the lateral groove 4o, and the first outer block 7i. The first lateral groove 4o1 includes an outer tie bar 7o that connects the block piece B1o and the second outer block piece B2o, and the second lateral groove 4o2 includes only the inner tie bar 7i.

In the first lateral groove 4o1, as shown in FIG. 4, the sectional area So of the outer tie bar 7o is larger than the sectional area Si of the inner tie bar 7i. This is because the outer block pieces B1o and B2o form the outer surface of the tire and thus are more easily moved. By increasing the cross-sectional area So, the block rigidity can be made uniform. In particular, when the sipe depths ho and hi of the horizontal siping 6 are in the above ranges, the cross-sectional area ratio Si / So is preferably set to 0.25 to 0.45 for uniform block rigidity. Specifically, the sectional area So at this time is preferably in the range of 220 to 280 mm ² , and the sectional area Si is preferably in the range of 80 to 90 mm ² .

  The tie bar depth Dt from the tread surface 2S of each tie bar 7i, 7o is 0.4 to 0.6 times the groove depth Hg of the longitudinal main groove 3o from the viewpoint of the reinforcing effect and drainage, and It is smaller than the sipe depth hc.

  When each lateral groove 4o is formed by only the first lateral groove 4o1, there is a tendency to reduce drainage. Therefore, in this example, the first lateral groove 4o1 and the second lateral groove 4o2 are alternately arranged in the tire circumferential direction. Arranged to suppress the deterioration of drainage performance.

  Next, in this example, the inner block Bm and the inner block Bi extend in substantially parallel to the lateral grooves 4m and 4i as shown in FIG. 1, and the horizontal siping divides each block Bm and Bi into two block pieces. 10 is formed.

  The horizontal sipe 10 has a sipe depth that is substantially the same as 100 ± 10% of the sipe depth hi of the inner siping portion 6i. Like the inner siping portion 6i, the sipe depth extends from the initial stage of wear to the middle stage and has a performance on ice. Improve. A plurality of (preferably two) tie bars 8 are formed in each of the lateral grooves 4m, 4i, respectively, and the rigidity of the blocks Bm, Bi is increased to improve the wear resistance. The tie bar 8 has the same depth as the inner tie bar 7i, and its cross-sectional area is set to be approximately equal to 100 ± 10% of the cross-sectional area Si of the inner tie bar 7i in this example.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

  A tire for heavy load having a tire size of 11R22.5 using the tread pattern shown in FIG. 1 as a basic pattern was prototyped based on the specifications in Table 1. Then, the performance on ice and uneven wear resistance of each sample tire were tested and compared. Each tire has substantially the same specifications except for the siping and tie bar in the shoulder block.

(1) Performance on ice;
Sample tires are mounted on all wheels of a 2-D type truck (loading load 8 tons) under the conditions of rim (7.50 × 22.5) and internal pressure (800 Kpa). The braking distance from h to sudden braking with all-wheel lock applied until the vehicle stopped was measured, and the reciprocal thereof was displayed as an index with Example 4 as 100. The larger the index, the shorter the braking distance and the better the performance on ice.

(2) Uneven wear resistance performance;
Using the vehicle, the general asphalt road traveled for a distance of 45,000 km (corresponding to a wear rate of 30%), and after running, at four positions in the tire circumferential direction, between the inner block pieces of the shoulder block and between the outer block pieces The amount of heel & toe wear was measured and the average was compared. The smaller the value, the better the uneven wear resistance.

It is an expanded view which shows one Example of the tread pattern of the tire for heavy loads of this invention. It is a top view which expands and shows a shoulder block. It is sectional drawing which shows horizontal siping. It is sectional drawing which shows a tie bar.

Explanation of symbols

2S Tread surface 3o Vertical main groove 4o Horizontal groove 4o1 First horizontal groove 4o2 Second horizontal groove 5 Vertical siping 6 Horizontal siping 6i Inner siping part 6o Outer tie bar 7o Outer tie bar B1i, B1o, B2i , B2o Block piece Bo Shoulder block Ro Shoulder block row Te Tread end

Claims (5)

By providing an outer vertical main groove extending continuously near the tread edge in the tire circumferential direction on the tread surface and a plurality of horizontal grooves extending from the outer vertical main groove to the tread edge, the outer vertical main groove is provided. A heavy-duty tire having a shoulder block row formed of shoulder blocks surrounded by grooves, lateral grooves, and tread edges and spaced in the tire circumferential direction along the tread edges,
The shoulder block is provided with a vertical siping that crosses between the horizontal grooves, and a horizontal siping that crosses between the outer vertical main groove and a tread edge and intersects the vertical siping at an intersection point P. The shoulder block includes a first inner block piece on one side in the tire circumferential direction and on the inner side in the tire axial direction, a first outer block piece on one side in the tire circumferential direction and on the outer side in the tire axial direction, the other side in the tire circumferential direction and the tire axis. Divided into a second inner block piece on the inner side in the direction and a second outer block piece on the other side in the tire circumferential direction and on the outer side in the tire axial direction,
The sipe depth hi of the inner siping portion is 0.4 to 0.7 times the groove depth Hg of the vertical main groove, and the sipe depth ho of the outer siping portion 6o is the groove depth of the vertical main groove. The sipe depth hc of the vertical sipe is 0.2 to 0.4 times Hg, and is equal to or less than the sipe depth ho.
The sipe bottom of the outer sipe part extends outward in the tire radial direction from the sipe bottom of the inner sipe part, and the lateral sipe has a sipe depth ho of the outer sipe part outside the intersection in the tire axial direction. However, it is smaller than the sipe depth hi of the inner siping portion on the inner side in the tire axial direction than the intersection.   The heavy load according to claim 1, wherein a difference (hi-ho) between a sipe depth ho of the outer sipe part and a sipe depth hi of the inner sipe part is 4.0 to 7.0 mm. tire. The heavy duty tire according to claim 1 or 2, wherein the vertical siping has a sipe depth hc of 5 mm or more .   The lateral groove is a tie bar inside the first inner block piece and the second inner block piece, which protrudes from the groove bottom at a small height, extends in the tire circumferential direction, and is adjacent to the tire circumferential direction via the lateral groove. And an outer tie bar that connects the first outer block piece and the second outer block piece, and the cross-sectional area So of the outer tie bar is larger than the cross-sectional area Si of the inner tie bar. The heavy duty tire according to any one of claims 1 to 3, further comprising a lateral groove.   The lateral groove includes the first lateral groove and the second lateral groove having only the inner tie bar, and the first lateral groove and the second lateral groove are alternately arranged in the tire circumferential direction. The heavy duty tire according to claim 4, wherein the tire is heavy duty.

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