JP4449647B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that secures traction performance on an icy and snowy road surface and has improved skid resistance.

  Generally, winter pneumatic tires are provided with a plurality of vertical grooves extending in the tire circumferential direction on the tread surface and a plurality of horizontal grooves extending in the tire width direction in order to ensure braking / driving performance on an icy and snowy road surface. Along with the formation of a large number of blocks by these vertical and horizontal grooves, a large number of sipes extending in the tire width direction are formed on the surface of each block to reduce the rigidity of the tread surface and improve the ground contact, as well as capillary action and It has been attempted to obtain higher braking performance on the road surface on ice by utilizing the edge effect caused by water film destruction.

  However, if many sipes in the tire width direction are provided on the block, uneven wear of heel and toe is likely to occur in the divided small blocks, and steering stability on icy and snowy road surfaces and wet road surfaces due to a decrease in block rigidity Problems occur.

As a countermeasure for such a problem, instead of the sipe in the tire width direction, a closed sipe in a loop shape and a branch sipe extending in the tire width direction connected to the block are formed in the block, and thereby the block is divided into a plurality of small blocks. There is a proposal to improve the steering stability on an icy / snow road surface or a wet road surface while reducing uneven wear by partitioning (see, for example, Patent Documents 1 and 2). However, although these proposals improve uneven wear and the like, the skid resistance on ice and snow road surfaces is not sufficient, and there is still room for improvement.
JP-A-6-171321 JP 2000-233612 A

  An object of the present invention is to solve such a conventional problem, and to provide a pneumatic tire that ensures traction performance on an icy and snowy road surface and has improved skid resistance.

  In order to achieve the above object, the 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, and these longitudinal grooves and transverse grooves provide A number of blocks are formed, and a closed sipe in a loop shape is formed inside the block, and a branch sipe extending from each side of the block in the tire width direction and extending into the longitudinal groove is formed on the block surface side of the branch sib. A chamfer is formed at the end of the block in the section.

  The pneumatic tire of the present invention forms a loop-shaped closed sipe and a branch sipe extending in the tire width direction connected to the inside of the block, and chamfers the block end portion at the opening on the block surface side of the branch sipe. Since it is formed, in addition to ensuring the traction performance by forming the closed sipe and the branched sipe, the side skid performance of the tire on the icy and snowy road can be improved particularly by the side wall of the small block corresponding to the chamfered portion.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

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

  In FIG. 1, the pneumatic tire is provided with a plurality of vertical grooves 2 extending in the tire circumferential direction T and a plurality of horizontal grooves 3 extending in the tire width direction intersecting with the tread surface 1. Thus, a large number of blocks 4 are formed.

  Inside each block 4 constituting the four block rows on the central side excluding the block rows on both shoulder sides, a loop-shaped closed sipe 5 extends from the both sides to the longitudinal groove 2 and extends in the tire width direction. A branch sipe 6 is formed. As a result, each block 4 is divided into three small blocks 4 a, 4 b, 4 c by the closed sipes 5 and the branch sipes 6.

  The ends of the small blocks 4b and 4c at the opening on the block surface side of the branch sipe 6 are chamfered at an angle α with respect to the surfaces of the small blocks 4b and 4c, as shown in FIG. The upper end portion of the branch sipe 6 is formed in a V shape in a side view.

  As described above, the block 4 is divided into the three small blocks 4a, 4b, and 4c by the loop-shaped closed sipe 5 and the branch sipe 6, thereby improving the traction on the ice and snow road surface and opening the branch sipe 6. By forming chamfers at the ends of the small blocks 4b and 4c, the chamfered portions of the small blocks 4b and 4c and the closed sipes 5 are partitioned when the tire receives lateral force or rotational torque on the icy and snowy road surface. In a space surrounded by the side wall 4aw (see FIG. 3) of the small block 4a, a snow column shearing force is generated by the ice and snow intervening in the space. This improves the skid resistance of the tire.

  In the embodiment described above, the case where the planar shape of the loop-shaped closed sipe 5 formed in the block 4 is a rectangle is illustrated, but the shape of the closed sipe 5 is not limited to this, and the circumferential direction and the width direction of the tire As long as it has a shape having the above component, it may be oval or other shapes. Further, the number and arrangement of the blocks 4 forming the closed sipes 5 and the branch sipes 6 are not limited to the above-described embodiment.

  In the present invention, the closed sipe 5 and the branch sipe 6 are constituted by narrow grooves having a groove width of 0.3 to 1.0 mm and a depth equal to or less than the height of the block 4. Further, the angle α formed with the chamfered block surfaces formed at the ends of the small blocks 4b and 4c in the opening of the branch sipe 6 is preferably 20 to 70 °. When the chamfering angle α is out of this range, it becomes difficult to obtain a sufficient snow column shear force due to ice and snow intervening in the chamfered portion, and the effect of improving the skid resistance on an icy and snowy road surface cannot be obtained. Furthermore, from the viewpoint of securing the adhesive frictional force on the icy and snowy road, the circumferential width Lk of the chamfered portion may be set to (0.1 to 0.5) × Ls (see FIG. 5).

  In the present invention, the closed sipes 5 formed on the block 4 can be formed in plural (2 in the figure) in the tire width direction of the block 4 as illustrated in FIG. When a plurality of closed sipes 5 are formed in the tire width direction as described above, the branches extending in the tire width direction are connected between the small blocks 4a and 4a defined by the closed sipes 5 by connecting the sides of the closed sipes 5 and 5 to each other. A sipe 6 may be formed and the small blocks 4 a and 4 a may be connected by the branch sipe 6. Thereby, the skid-proof performance in an icy and snowy road surface can be improved further.

  Moreover, the closed sipes 5 formed in the block 4 can also be formed in plural (2 in the figure) in the tire circumferential direction of the block 4 as illustrated in FIG. 4B. Furthermore, depending on the form and size of the block 4, a plurality of closed sipes 5 formed on the block 4 can be formed in the tire width direction and the circumferential direction, respectively.

  As described above, the pneumatic tire of the present invention divides the block into a plurality of small blocks by the closed sipe 5 and the branch sipe 6 and forms a chamfer at the end of the block at the opening of the branch sipe 6. In particular, it is characterized by ensuring skid resistance on icy and snowy road surfaces according to the lateral force or rotational torque applied to the tire, especially for heavy loads used under heavy loads such as trucks and buses It is suitable as a tire.

  All specifications except for the tire size (11R22.5), block pattern (FIG. 1) and closed sipe and branch sipe formed in each block are the same, and the form of the closed sipe and branch sipe is shown in FIG. 5 (Ws = 16 mm, Ls = 13 mm) and a chamfer as shown in FIG. 3 (Lk = 3 mm, Hk = 1.5 mm) at the end of a small block corresponding to the upper end of the branch sipe of the conventional tire (conventional example) The tire of the present invention (Example 1) with an inclination angle α = 45 °, and the tire of the present invention (Example 2) in which two closed sipes are formed in the width direction as shown in FIG. 4A (Ws = 5 mm). , Respectively.

  These three types of tires were evaluated in terms of traction performance and skid resistance on icy and snowy road surfaces by the following methods, and are listed in Table 1 with an index display with the conventional example being 100. The larger the value, the better.

The main specifications common to each tire are as follows.
・ Tread deployment width: 232 mm, vertical groove depth: 20 mm
-Block height: 20 mm, block circumferential length: 30 mm, block width: 26 mm

[Traction performance evaluation]
Each tire is assembled on a rim of size 22.5 "x 7.5", filled with 700 kPa air pressure, and mounted on a heavy load vehicle (6 x 2) with a total vehicle weight of 20 tons. The vehicle was subjected to lock braking from an initial speed of 40 km / h, the vehicle braking distance was measured, and the reciprocal of the value was evaluated.

[Evaluation of skid resistance]
Each tire is assembled on a rim of size 22.5 ”× 7.5”, filled with 700 kPa of air pressure, mounted on a heavy load vehicle (6 × 2) with a total vehicle weight of 20 t, and an angle of 3 in the width direction. Lock braking was performed at an initial speed of 10.0 km / h on an ice surface and a snow surface inclined at 0 °, and the slip distance in the lateral direction of the vehicle was measured and evaluated by the reciprocal of the value.

  As a result, it can be seen that the tire of the present invention has improved skid resistance while maintaining the same traction performance on the snowy and snowy road surface as compared with the conventional tire.

It is a partial top view which shows an example of the tread surface of the pneumatic tire of this invention. It is AA arrow sectional drawing of FIG. It is a perspective view which takes out and shows a block in a pneumatic tire of the present invention. (A) And (b) is a perspective view which illustrates the other form of the sipe formed in a block, respectively. It is a perspective view which shows the form of the sipe formed in the block of the conventional tire employ | adopted in order to confirm the effect of this invention.

Explanation of symbols

1 Tread surface 2 Vertical groove 3 Horizontal groove 4 Block 4a, 4b, 4C Small block 5 Closed sipe 6 Branched sive

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 blocks are formed by the vertical grooves and the horizontal grooves, and a loop shape is formed inside the block. A pneumatic tire in which a closed sipe and a branched sipe extending in the tire width direction from both sides of the sipe and passing through the longitudinal groove are formed, and a chamfer is formed at an end of the block in an opening on the block surface side of the branched sipe. The pneumatic tire according to claim 1, wherein an angle formed with the chamfered block surface is 20 to 70 °. The plurality of small blocks partitioned by the closed sipes are arranged in the tire width direction, and branch sipes extending in the tire width direction are formed by connecting the sides of the closed sipes between the small blocks. Pneumatic tire. The pneumatic tire according to claim 1, 2 or 3, wherein a plurality of small blocks partitioned by the closed sipes are arranged in the tire circumferential direction.

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