JP4830695B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire in which a plurality of sipes are provided in a block, and more particularly to a pneumatic tire in which braking performance on ice and uneven wear resistance are improved based on the shape and arrangement of sipes.

  In a pneumatic tire for snowy and snowy roads, as a measure for improving the performance on ice, it is generally performed to increase the edge amount of a sipe provided on a block or to reduce the hardness of a tread rubber. However, when the hardness of the tread rubber is reduced, the block rigidity is lowered, so that the block collapses at the time of braking / driving and cornering, the contact area is reduced, and the tire performance in summer and winter is lowered. Therefore, it has been proposed that the sipe has a three-dimensional structure in order to prevent the block from falling down.

  As a sipe having a three-dimensional structure, a sipe having a zigzag shape on the tread surface and a zigzag amplitude changing inside the block has been proposed (see, for example, Patent Document 1). In this case, although it is possible to increase the block rigidity in the front-rear direction, there is a drawback that the effect of increasing the block rigidity in the horizontal direction is hardly obtained.

  Further, a sipe has been proposed in which a tread surface has a zigzag shape, and a bent portion continuous in the tire radial direction is bent in the tire width direction inside the block (see, for example, Patent Document 2). Also in this case, there is a drawback that the block rigidity in the lateral direction is lower than the block rigidity in the front-rear direction.

On the other hand, the tread surface has a zigzag shape and is bent in the tire circumferential direction at two or more locations in the tire radial direction inside the block to form a bent portion continuous in the tire width direction, and in the tire radial direction at the bent portion There has been proposed a sipe in which a zigzag shape having an amplitude is formed on the sipe (see, for example, Patent Document 3). In this case, the block rigidity in the front-rear direction and the block rigidity in the lateral direction can be increased at the same time. However, even with a sipe having such a three-dimensional structure, when the tread rubber having a low hardness is used, the block end tends to fall down. Snow clogging occurs, and as a result, there is a problem that the ground contact area is reduced and braking performance on ice is lowered. There is also a problem that uneven wear resistance is deteriorated when the block end portion easily falls.
JP 2000-6619 A JP 2002-321509 A Japanese Patent Laid-Open No. 2005-126055

  An object of the present invention is to provide a pneumatic tire that can improve braking on ice and uneven wear resistance based on the shape and arrangement of a sipe.

In order to achieve the above object, the pneumatic tire of the present invention 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 in the tread portion. In a pneumatic tire which divides a plurality of blocks and has a plurality of sipes extending in the tire width direction in the blocks,
The sipe has a zigzag shape on the tread surface, and bends in the tire circumferential direction at two or more locations in the tire radial direction inside the block to form a bent portion continuous in the tire width direction, and in the tire radial direction at the bent portion. It has a three-dimensional structure that has a zigzag shape with amplitude,
In the sipe where the distance between two points between the apex on the tread surface side of the bent part of the sipe and the apex on the sipe bottom side is arranged at the end of the block rather than the sipes arranged at the center of the block A plurality of types of sipes having different distances between the two points are mixed in a single block so as to increase.

  In the present invention, since the sipe is bent in the tire circumferential direction at two or more locations in the tire radial direction and is provided with a bent portion continuous in the tire width direction, the small blocks on both sides of the sipe mesh with each other during braking / driving and the block deformation Can be suppressed, and the tire performance during braking / driving can be improved. In addition, since the sipe has a zigzag shape having an amplitude in the tire radial direction at the bent portion, even during cornering, the small blocks on both sides of the sipe mesh with each other to suppress block deformation, and the tire during cornering The performance can be improved. Therefore, even when the hardness of the tread rubber is reduced, it is possible to simultaneously improve the tire performance during braking and driving and the tire performance during cornering.

  Moreover, the distance between the two points between the apex on the tread surface side and the apex on the sipe bottom side of the bent part of the sipe is larger in the sipe disposed at the end of the block than the sipe disposed in the center of the block. As described above, since a plurality of types of sipes having different distances between the two points are mixed in a single block, the total length of edges where adjacent small blocks mesh with each other increases toward the block end side, Insufficient rigidity can be compensated. Therefore, since the falling of the block end can be suppressed, the braking performance on ice and the uneven wear resistance can be improved.

  In the present invention, the distance between the two points between the apex on the tread surface side and the apex on the sipe bottom side of the bent part of the sipe is gradually increased from the sipe disposed at the center of the block to the sipe disposed at the end of the block. Preferably, at least three types of sipes having different distances between the two points are mixed in a single block. Thereby, block rigidity can be made uniform over the whole block, and ice braking performance and uneven wear resistance can be further improved.

  The distance between the two points of the sipe disposed at the end of the block is preferably 1.1 times or more and 1.5 times or less the distance between the two points of the sipe disposed at the center of the block. Thereby, the effect of improving the braking performance on ice and the uneven wear resistance can be sufficiently obtained.

  The present invention can provide a remarkable effect when applied to a pneumatic tire for icy and snowy roads represented by a studless tire, but can also be applied to a pneumatic tire for all seasons.

Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows a tread pattern of a pneumatic tire for icy and snowy roads according to an embodiment of the present invention, and FIG. 2 shows a basic structure of the block. FIG. 3 shows a sipe inner wall surface in the block.

  As shown in FIG. 1, the tread portion 1 is formed with a plurality of vertical grooves 2 extending in the tire circumferential direction and a plurality of horizontal grooves 3 extending in the tire width direction. Block 4 is partitioned. Each block 4 is formed with a plurality of sipes 5 extending in the tire width direction. The shape of the block 4 and the number of sipes 5 are not particularly limited.

  As shown in FIG. 2, the sipe 5 has a zigzag shape on the tread surface S, and is bent in the tire circumferential direction (Tc) at two or more locations in the tire radial direction (Tr) inside the block to be tire width direction (Tw). A plurality of bent portions 6 are formed. These bent portions 6 have convex bent portions 6a and concave bent portions 6b. On one wall surface of the sipe 5, convex bent portions 6a and concave bent portions 6b are alternately arranged. On the other wall surface (not shown) facing each other, the positional relationship between the convex bent portion 6a and the concave bent portion 6b is reversed. When the sipe 5 is provided with the bent portion 6 that bends in the tire circumferential direction, the small blocks on both sides of the sipe 5 mesh with each other during braking / driving to suppress the deformation of the block 4 and to prevent the block 4 from falling in the tire circumferential direction. can do. In addition, by providing two or more bent portions 6 in each sipe 5, it is possible to avoid a difference in block rigidity due to normal rotation and reverse rotation of the tire.

  As shown in FIG. 3, the sipe 5 forms a zigzag shape having an amplitude in the tire radial direction (Tr) at the bent portion 6. When the sipe 5 has a zigzag shape with an amplitude in the tire radial direction (Tr) at the bent portion 6, the small blocks on both sides of the sipe 5 mesh with each other during cornering to suppress deformation of the block 4, and the tire width of the block 4 Falling in the direction can be suppressed.

  The rubber composition constituting the tread portion 1 has a JIS-A hardness (0 ° C.) of 40 to 60, preferably 45 to 55. If the JIS-A hardness of the tread rubber is less than 40, the block 4 is liable to fall, and conversely if it exceeds 60, the frictional force on ice decreases.

  According to the pneumatic tire for snowy and snowy roads, the sipe 5 includes the bent portions 6 that are bent in the tire circumferential direction (Tc) at two or more locations in the tire radial direction (Tr) and continuous in the tire width direction (Tw). Therefore, the small blocks on both sides of the sipe 5 are engaged with each other at the time of braking / driving to suppress the deformation of the blocks, and the tire performance at the time of braking / driving can be improved. Further, since the sipe 5 has a zigzag shape having an amplitude in the tire radial direction (Tr) at the bent portion 6, the small blocks on both sides of the sipe 5 are engaged with each other even during cornering to suppress deformation of the block. The tire performance during cornering can be improved.

  Here, the block 4 is divided into a plurality of small blocks by a plurality of sipes 5, but the small block located at the center of the block 4 is supported from both sides by other small blocks, while the block 4 Small blocks located at the end are only supported from one side by other small blocks. Therefore, even when the sipe 5 has a three-dimensional structure as described above, the end of the block 4 is relatively easy to fall down, so that the sipe 5 positioned at the end of the block 4 when traveling on an icy and snowy road surface. Snow clogging easily occurs. And if snow clogging to the sipe 5 occurs, the contact area will decrease and the braking performance on ice will fall. In addition, if the end portion of the block 4 is likely to fall, uneven wear resistance also deteriorates. Therefore, the following sipe structure is adopted for the block 4.

  FIG. 4 shows a block to which the sipe structure of the present invention is applied. In FIG. 4, the block 4 includes a first sipe 51 located at the center in the block longitudinal direction, a second sipe 52 located closer to the end in the block longitudinal direction than the sipe 51, and the block longitudinal direction. A third sipe 53 located at the end of the sipe 53 is formed. The positional relationship between the sipes 51 to 53 is relative. That is, among the plurality of sipes arranged in the block longitudinal direction, the one closest to the central portion in the block longitudinal direction is the central sipe, and the one closest to the end portion in the block longitudinal direction is the end sipe.

  Each of the sipes 51 to 53 has the basic structure described above, but the distance between two points between the apex on the tread surface side of the bent portion 6 and the apex on the sipe bottom side is arranged in the center of the block 4. The third sipe 53 disposed at the end of the block 4 is larger than the first sipe 51. More preferably, the distance between the two points between the apex on the tread surface side of the bent portion 6 and the apex on the sipe bottom side is arranged from the first sipe 51 arranged at the center of the block 4 to the end of the block 4. The third sipe 53 is gradually increased.

  5A to 5C show the inner wall surface of the second sipe formed in the block of FIG. 4, wherein FIG. 5A is a side view, FIG. 5B is a cross-sectional view taken along the line XX, and FIG. Is a cross-sectional view taken along arrow YY. Here, in FIG. 5A, with respect to the bent portion 62 (solid line) of the second sipe 52, the bent portion 61 (broken line) of the first sipe 51 and the bent portion 63 ( A dot-dash line) is shown superimposed.

  As shown in FIGS. 5A to 5C, the distance L1 between two points between the apex A1 on the tread surface side and the apex B1 on the sipe bottom side of the bent portion 61 (broken line) of the first sipe 51, The distance L2 between the two points between the apex A2 on the tread surface side of the bent part 62 (solid line) of the second sipe 52 and the apex B2 on the sipe bottom side, and the bent part 63 (one-dot chain line) of the third sipe 53 ), The distance L3 between the two points between the vertex A3 on the tread surface side and the vertex B3 on the sipe bottom side satisfies the relationship of L1 <L3, preferably L1 <L2 <L3. ing. Thus, the distance between the two points L1 to L3 is increased so as to increase sequentially from the first sipe 51 disposed at the center of the block 4 to the third sipe 53 disposed at the end of the block 4. By mixing three types of sipes 51 to 53 having different distances L1 to L3 between the two points in the block 4, the lack of rigidity at the end of the block 4 can be compensated. As a result, the falling of the end of the block 4 can be suppressed, and in particular, the reduction of the contact area due to snow clogging on the sipe 53 can be avoided, so that the braking performance on ice can be improved. Further, by compensating for the lack of rigidity at the end of the block 4, uneven wear resistance can be improved.

  The distance L3 between the two points of the third sipe 53 arranged at the end of the block 4 is 1.1 times or more the distance L1 between the two points of the first sipe 51 arranged at the center of the block 4. It is preferable to make it less than twice. Thereby, the effect of improving the braking performance on ice and the uneven wear resistance can be sufficiently obtained. If the distance L3 between the two points is less than 1.1 times the distance L1 between the two points, it is not possible to obtain sufficient rigidity to suppress the falling of the block end. On the other hand, when the distance L3 between the two points exceeds 1.5 times the distance L1 between the two points, the angle θ with respect to the tire radial direction of the bent portion decreases accordingly, and the effect of suppressing the block end portion from falling is reduced. Similarly, when the sipe disposed at the block end is nth from the block center, the distance Ln between the two points of the nth sipe is the two points of the first sipe disposed at the block center. The distance L1 is preferably 1.1 to 1.5 times the distance L1.

  In the above-described embodiment, the case where three types of sipes having different distances between two points are provided in a single block has been described. However, in the present invention, a plurality of types having different distances between two points are provided in a single block. More preferably, the same effect as described above can be obtained when three to five types of sipes having different distances between two points are provided in a single block.

  In a pneumatic tire for ice and snowy road having a tire size of 195 / 65R15 and having a block pattern, tires of a conventional example and Examples 1 and 2 in which only the shapes of sipes provided on the blocks were varied were manufactured. In the conventional example and Examples 1-2, the sipe has a zigzag shape on the tread surface, and is bent in the tire circumferential direction at two or more locations in the tire radial direction inside the block to form a bent portion continuous in the tire width direction. The bent portion has a three-dimensional structure having a zigzag shape with amplitude in the tire radial direction. Then, the distance L1 between the two points of the bent part of the first sipe located in the central part in the block longitudinal direction, and 2 of the bent part of the second sipe located on the end side in the block longitudinal direction from the first sipe. The distance L2 between the points and the distance L3 between the two points of the bent part of the third sipe located at the end in the block longitudinal direction were set as shown in Table 1.

  These test tires were evaluated for braking properties on ice and uneven wear resistance by the following test methods, and the results are also shown in Table 1.

Ice braking performance:
The test tire was mounted on an FR vehicle with a displacement of 2000 cc under the conditions of a rim size of 15 × 6.5 JJ and an air pressure of 200 kPa, and braking was performed on a frozen road surface from a traveling state at a speed of 40 km / h, and the braking distance was measured. The evaluation results are shown as an index with the conventional example being 100, using the reciprocal of the measured value. The larger the index value, the better the braking performance on ice.

Uneven wear resistance:
The test tire was mounted on a FR vehicle with a displacement of 2000 cc under the conditions of a rim size of 15 × 6.5 JJ and an air pressure of 200 kPa. After running 8000 km, the heel and toe wear amount in each block of the test tire was measured. The evaluation results are shown as an index with the conventional example being 100, using the reciprocal of the measured value. The larger the index value, the better the uneven wear resistance.

  As can be seen from Table 1, the tires of Examples 1 and 2 were excellent in braking on ice and uneven wear resistance as compared with the conventional example.

It is a top view which shows the tread pattern of the pneumatic tire for snowy and icy roads which consists of embodiment of this invention. FIG. 2 is a partially cutaway perspective view showing a basic structure of a block in the pneumatic tire for an icy and snowy road of FIG. 1. It is a side view which shows the sipe inner wall surface in the block of FIG. It is a top view which shows the block to which the sipe structure of this invention is applied. The inner wall surface of the 2nd sipe formed in the block of FIG. 4 is shown, (a) is a side view, (b) is XX arrow sectional drawing, (c) is YY arrow sectional drawing. .

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Vertical groove 3 Horizontal groove 4 Block 5,51,52,53 Sipe 6,61,62,63 Bending part A1, A2, A3 Tread surface side vertex B1, B2, B3 Sipe bottom side vertex S Tread surface

Claims (3)

A plurality of longitudinal grooves extending in the tire circumferential direction and a plurality of lateral grooves extending in the tire width direction are provided in the tread portion, and a plurality of blocks are defined by the longitudinal grooves and the lateral grooves, and the blocks extend in the tire width direction. In pneumatic tires with multiple sipes,
The sipe has a zigzag shape on the tread surface, and bends in the tire circumferential direction at two or more locations in the tire radial direction inside the block to form a bent portion continuous in the tire width direction, and in the tire radial direction at the bent portion. It has a three-dimensional structure that has a zigzag shape with amplitude,
In the sipe where the distance between two points between the apex on the tread surface side of the bent part of the sipe and the apex on the sipe bottom side is arranged at the end of the block rather than the sipes arranged at the center of the block A pneumatic tire, wherein a plurality of types of sipes having different distances between the two points are mixed in a single block so as to increase.   At least three different distances between the two points in a single block so that the distance between the two points gradually increases from the sipe disposed at the center of the block to the sipe disposed at the end of the block. The pneumatic tire according to claim 1, wherein sipe is mixed. The distance between two sipe points arranged at the end of the block is 1.1 times or more and 1.5 times or less the distance between two sipe points arranged at the center of the block. The pneumatic tire according to claim 1 or claim 2.

Images