JP2006131097A - Pneumatic tire for winter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire for winter enhancing on-ice braking performance and on-snow braking performance at good balance until it results from a time of a new article to abrasion middle time and enhancing eccentric wearing-resistance. <P>SOLUTION: In the pneumatic tire for winter, a plurality of block rows 4a-4e arranged with a large number of blocks 4 are formed on a tread surface 1, a plurality of sipes 5 extending in a tire width direction are provided on the respective blocks 4 and the blocks 4 are divided to a plurality of small blocks 4s adjacent in a tire circumferential direction. Tire circumferential direction length Le of the small block 4s at front and rear end sides in the tire circumferential direction of the block 4 at the block row 4c at a central area of at least tread surface 1 is made larger than tire circumferential direction length Lc of the small block 4s at an intermediate position in the tire circumferential direction of the block 4. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a winter pneumatic tire, and more particularly to a winter pneumatic tire that improves on-ice braking performance and on-snow braking performance in a well-balanced manner and has improved uneven wear resistance performance.

  The winter pneumatic tire is provided with a plurality of vertical grooves extending in the tire circumferential direction and a plurality of horizontal grooves extending in the tire width direction on the tread surface in order to ensure braking / driving performance on a snowy road surface. Thus, a tread pattern in which a plurality of block rows are partitioned is employed. Furthermore, in order to ensure braking / driving performance on the road surface on ice, a notch called a sipe extending in the tire width direction is provided on the surface of each block, and the grounding property (grip force) is improved by reducing the rigidity of the tread portion. The edge effect by capillary action and water film destruction is improved.

  Conventionally, sipes formed on the surface of a block have been generally formed at equal intervals and the same depth in the tire circumferential direction. However, recently, in order to further improve the braking / driving performance on the road surface on ice by changing the rigidity distribution of each block, the block rigidity on the kicking side is increased by changing the sipe interval in the tire circumferential direction. There is a proposal (for example, refer to Patent Document 2). For example, refer to Patent Document 2).

However, in the former case, the effect of either braking / driving is accompanied by directionality, and in the latter case, on-ice braking / driving is accompanied by a change in the shape of the block surface due to the disappearance of sipe after the middle stage of wear. A decline in performance was inevitable, and all of them left room for improvement as measures to improve the performance of winter tires.
JP-A-10-81114 JP-A-9-76711

  The object of the present invention is to solve the above-mentioned conventional problems, improve the braking performance on ice and braking performance on snow from a new article to after the middle stage of wear in a well-balanced manner, and improve the uneven wear resistance. The purpose is to provide tires.

  In order to achieve the above object, a winter pneumatic tire of the present invention is provided with a plurality of longitudinal grooves extending in the tire circumferential direction on the tread surface and a plurality of transverse grooves intersecting the longitudinal grooves. Forming a plurality of block rows in which a large number of blocks are arranged in the circumferential direction, and providing each block with a plurality of sipes extending in the tire width direction to partition the blocks into a plurality of small blocks adjacent in the tire circumferential direction. In the pneumatic tire, at least the tire circumferential direction length Le of the small block on the front and rear end sides in the tire circumferential direction of the block in the block row in the central region of the tread surface is set to the small block at the intermediate position in the tire circumferential direction of the block. It is characterized by being larger than the tire circumferential direction length Lc.

  The pneumatic tire according to the present invention is a small block on the front and rear end sides in the circumferential direction of a block in a block row in at least a central region of a tire having a block row in which a block is partitioned into a plurality of small blocks adjacent in the circumferential direction by a plurality of sipes Since the circumferential length Le is larger than the circumferential length Lc of the small block at the circumferential intermediate position, the rigidity of the front and rear ends of the circumferential direction of the block can be ensured from the time of the new article to the middle stage of wear. By preventing the block from falling down due to the sipe opening during braking / driving on the road surface, and suppressing the changes in the contact area and contact pressure, the braking / driving performance on the icy and snowy road surface can be improved and the occurrence of uneven wear can be prevented.

  In particular, since the sipe density in the block central region is increased, the drainage effect in the block central region where a water film is likely to remain can be enhanced, and the braking / driving performance on the ice road surface can be improved.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a partial plan view showing an example of a tread surface of a winter pneumatic tire according to the present invention, and FIG. 2 is a cross-sectional view taken along line AA in FIG.

  The tread surface 1 of the pneumatic tire is provided with a plurality of longitudinal grooves 2 extending in the tire circumferential direction T and a plurality of transverse grooves 3 intersecting with the plurality of longitudinal grooves 2. A plurality of (5 in the figure) block rows 4a, 4b, 4c, 4d, and 4e in which the blocks 4 are arranged are partitioned. In each block 4 of each block row 4a, 4b, 4c, 4d, 4e, a plurality of (six in the figure) sipes 5 extending in the tire width direction are formed.

  Each block 4 in each block row 4a, 4b, 4c, 4d, 4e is partitioned into a plurality (eight in the figure) of small blocks 4s by sipes 5 that open in the main groove 2. Among the block rows 4a, 4b, 4c, 4d, and 4e, in the block region 4c in the central region, the spacing of the sipe 5 in each block 4 with respect to the tire circumferential direction is sparse on the front and rear end sides of the block 4, and on the central region side. It is dense. That is, as shown in FIG. 2, the tire circumferential direction length Le of the small block 4s on the tire circumferential direction front and rear end side of the block 4 is equal to the tire circumferential direction of the four small blocks 4s at the intermediate position in the tire circumferential direction of the block 4. It is larger than the direction length Lc.

  In this way, at least the circumferential interval of the sipe 5 in the block 4 of the block row 4c in the central area is sparse at the front and rear end sides and dense at the central area side, thereby increasing the rigidity of the block 4 in the circumferential front and rear end side. It is possible to prevent the block from collapsing due to the sipe opening during braking / driving on the snowy / snowy road surface, and to improve the braking / driving performance and uneven wear resistance on the snowy / snowy road surface by suppressing changes in the contact area and contact pressure. Can do. In particular, by increasing the density of the sipes 5 on the side of the central region of the block 4, the drainage effect in the central region of the block 4 where a water film is likely to remain can be enhanced, and the braking / driving performance on the ice road surface can be improved.

  The tire circumferential direction length of the small block 4s described above is gradually increased from the small block 4s at the intermediate position in the tire circumferential direction of the block 4 toward the small block 4s on the front and rear end side, as shown in FIG. It is preferable to gradually increase the thickness. That is, the circumferential length is sequentially changed from d, c, b, a toward the small block 4 s located in the middle of the block 4 toward the small block 4 s on the front and rear end sides, so that d <c <b <a. . More preferably, the circumferential length Lc (= d) of the small block 4s at the middle position in the circumferential direction of the block 4 is set to 3.0 mm or more, and the circumferential length Le (= a) of the small block 4s on the front and rear end side. Is preferably 1.2 times or more of the length Lc (= d). Thereby, the balance of the rigidity of the circumferential direction of the block 4 is maintained, and the braking / driving performance and the uneven wear resistance on the icy and snowy road surface can be improved in a balanced manner.

  In the present invention, the depth of the sipe 5 formed in each block 4 is such that the sipe 5 disappears with the progress of wear and does not affect the braking / driving performance and uneven wear resistance on the icy and snowy road surface. In general, it is preferable that they are substantially the same. However, from the viewpoint of minimizing these effects, the ratio De between the depth De of the sipe 5 on the circumferential front and rear end sides of the block 4 and the depth Dc of the sipe 5 closest to the circumferential intermediate point. / Dc can be set to 0.7 to 1.0. If De / Dc is less than 0.7, the sipe 5 on the front and rear end sides of the block 4 disappears at the end of wear, so that the performance change becomes large, and if it exceeds 1.0, the rigidity on the front and rear end sides of the block 4 decreases. Since the sipe 5 is difficult to open and the block 4 is likely to fall down, the snow and snow braking performance is lowered and uneven wear is likely to occur. Here, the sipe 5 at the position closest to the circumferential intermediate point of the block 4 is formed closest to the intermediate point when the sipe 5 is not formed at the circumferential intermediate point of the block 4. Says Sipe 5.

  In the above-described embodiment, the case where the above-described configuration is applied to the sipe 5 formed in each block 4 in the block row 4c among the block rows 4a, 4b, 4c, 4d, and 4e has been described. By applying the above-described configuration to 4a, 4b, 4d, and 4e, the effect of the present invention is further enhanced.

  Further, the pattern configuration of the tread surface 1 of the winter pneumatic tire of the present invention is not limited to the embodiment of FIG. Further, the shape of the kerf 5 formed in each block 4 is not limited to the embodiment of FIG. 1, and may be a zigzag shape, and may include a sipe that does not penetrate in the width direction of the block 4.

  Table 1 shows the ratio Le / Lc of the lengths in the circumferential direction of the small blocks 4s partitioned into the blocks in the block rows 4b, 4c, and 4d with the tire size 265 / 70R16 and the tread pattern in common with FIG. A conventional tire (conventional example), a tire of the present invention (Examples 1 to 3) and a comparative tire (Comparative Example) were produced. In addition, the depth of the sipe was made the same as 7 mm.

  For these five types of tires, the braking performance on ice, braking performance on snow and anti-uneven wear performance are evaluated by the following methods. The performance is shown in Table 1 according to the amount of uneven wear (mm) at 50% wear. About ice braking performance and snow braking performance, it shows that it is so excellent that a numerical value is large.

[Evaluation of braking performance on ice]
Each tire was mounted on a domestic RV 4WD class vehicle, and the braking distance was measured by lock braking at a braking speed of 40 km / h on the road surface on ice.

[Snow braking performance evaluation]
In the same manner as described above, each tire was mounted on a domestic RV 4WD class vehicle, the braking distance was measured by lock braking at a braking speed of 40 km / h on a snowy road surface, and evaluation was performed based on the result.

[Uneven wear resistance]
After mounting each tire on a domestic RV 4WD class vehicle and running on the asphalt road surface until the groove depth of the main groove is halved, the amount of uneven wear on the tread surface is measured at multiple locations on the tire circumference. The average value was displayed as the amount of uneven wear (mm).

  From Table 1, it can be seen that the tire according to the present invention has a better balance between the braking performance on ice and the braking performance on snow than the conventional tire and the comparative tire, and is excellent in uneven wear resistance until the middle stage of wear.

It is a partial top view which shows an example of the tread surface of the winter pneumatic tire by embodiment of this invention. It is AA arrow sectional drawing of FIG. It is sectional drawing of the block corresponded in FIG. 1 by other embodiment of this invention.

Explanation of symbols

1 Tread surface 2 Vertical groove 3 Horizontal groove 4 Block 4s Small block 5 Sipe

Claims (4)

A plurality of vertical grooves extending in the tire circumferential direction and a plurality of horizontal grooves intersecting the vertical grooves are provided on the tread surface, and a plurality of block rows in which a large number of blocks are arranged in the circumferential direction are formed by the vertical grooves and the horizontal grooves. In addition, in a pneumatic tire in which each block is provided with a plurality of sipes extending in the tire width direction and the block is partitioned into a plurality of small blocks,
At least the tire circumferential direction length Le of the small block on the tire circumferential direction front and rear end side of the block in the block row in the central region of the tread surface is the tire circumferential length of the small block at the intermediate position in the tire circumferential direction of the block. Winter pneumatic tire larger than Lc.   2. The winter pneumatic tire according to claim 1, wherein the tire circumferential length of the small block gradually increases gradually from a small block at an intermediate position in the tire circumferential direction of the block toward the small block on the front and rear end side.   The tire circumferential direction length Le of the small block is 1.2 times or more of the tire circumferential direction length Lc of the small block, and the tire circumferential direction length Lc of the small block is 3.0 mm or more. The pneumatic tire for winter according to 1 or 2. The ratio De / Dc of the sipe depth De on the tire circumferential front and rear end side of the block to the sipe depth Dc at a position closest to the tire circumferential intermediate point of the block is 0.7 to 1. The winter pneumatic tire according to claim 1, which is 0.

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