JP4316452B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire provided with a plurality of sipes in a block, and more specifically, based on the sipe shape, it is possible to increase not only block rigidity during braking / driving but also block rigidity during cornering, thereby The present invention relates to a pneumatic tire that simultaneously improves tire performance during braking and driving and cornering.

  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 to make the sipe a three-dimensional shape in order to prevent the block from falling down.

  As a sipe having a three-dimensional shape, there has been proposed a sipe having a zigzag shape on the tread surface and a zigzag shape amplitude changing inside the block (see, for example, Patent Document 1). In this case, although it is possible to increase the block rigidity at the time of braking / driving, there is a disadvantage that the effect of increasing the block rigidity at the time of cornering is hardly obtained.

  Further, a sipe has been proposed in which the tread surface has a zigzag shape and triangular pyramids and inverted triangular pyramids are alternately arranged inside the block (see, for example, Patent Document 2). In this case, although the effect of increasing the block rigidity at the time of cornering can be expected, there is a drawback that the location of the sipe is limited due to the directionality of the sipe.

Further, there has been proposed a sipe 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 3). In this case as well, there is a drawback that the block rigidity during cornering is lower than the block rigidity during braking / driving.
JP 2000-6619 A JP 2002-301910 A JP 2002-321509 A

  An object of the present invention is to enable not only block rigidity during braking / driving but also block rigidity during cornering based on the sipe shape, thereby simultaneously improving tire performance during braking and tire performance during cornering. An object of the present invention is to provide a pneumatic tire that makes it possible.

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. Form a zigzag shape with amplitude ,
While making the amplitude in the tire circumferential direction of the sipe constant, the inclination angle of the sipe in the tire circumferential direction with respect to the normal direction of the tread surface is made smaller at the site on the sipe bottom side than the site on the tread surface side, The amplitude of the bent portion in the tire radial direction is larger at the sipe bottom side than at the tread surface side .

  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, the small blocks on both sides of the sipe mesh with each other even during cornering 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. Further, since the sipe has substantially no directivity, the arrangement location thereof is not limited. Furthermore, the above sipe has an advantage that the difference between the edge length at the time of a new article and the edge length after the middle stage of wear is small.

  In the present invention, in order to sufficiently obtain the improvement effect of the tire performance at the time of braking and the tire performance at the cornering without impairing the releasability, the inclination angle of the sipe in the tire circumferential direction with respect to the normal direction of the tread surface is set. The angle in the tire radial direction of the sipe bend is preferably 0.5 to 5.0 mm.

  According to the present invention, it is possible to suppress the deterioration of releasability by optimizing the inclination angle of the sipe in the tire circumferential direction with respect to the normal direction of the tread surface and the amplitude in the tire radial direction of the bent portion of the sipe. However, in some cases, failure such as block chipping due to the sipe forming blade may occur during mold release.

  Therefore, in order to more surely avoid failures such as chipped blocks, in the above pneumatic tire, while keeping the amplitude of the sipe in the tire circumferential direction constant, the sipe in the tire circumferential direction with respect to the normal direction of the tread surface. It is desirable to make the inclination angle smaller at the sipe bottom side than the tread surface side and to increase the amplitude of the bent portion in the tire radial direction at the sipe bottom side than the tread surface side.

  In other words, even when the amplitude of the sipe in the tire circumferential direction is constant, by reducing the inclination angle of the sipe in the tire circumferential direction with respect to the normal direction of the tread surface from the mold, It is possible to improve the mold release property. Moreover, even when the inclination angle of the sipe in the tire circumferential direction is changed as described above, the block rigidity at the time of braking / driving can be increased by increasing the amplitude of the bent portion in the tire radial direction toward the sipe bottom side. Decrease can be suppressed, and the block rigidity during cornering can be increased.

  In this case, the inclination angle of the sipe in the tire circumferential direction with respect to the normal direction of the tread surface is 30 ° or more and 45 ° or less at the most tread surface portion, and 15 ° or more and less than 30 ° at the most sipe bottom portion. It is preferable to do. Further, it is preferable that the amplitude of the bent portion in the tire radial direction is 0.5 mm or more at the most tread surface portion and 3.5 mm or less at the most sipe bottom side portion.

  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 for explaining the present invention, and FIG. 2 shows a block (reference example) . FIG. 3 shows the side of the block, and FIG. 4 shows the sipe inner wall surface of 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 inclination angle θ of the sipe 5 in the tire circumferential direction with respect to the normal direction of the tread surface S is preferably set to 10 to 45 °. If the angle θ is less than 10 °, the effect of supporting the block 4 to fall down during braking / driving becomes insufficient. Conversely, if the angle θ exceeds 45 °, the removal from the mold becomes worse.

  As shown in FIG. 4, the sipe 5 forms a zigzag shape having an amplitude T in the tire radial direction (Tr) at the bent portion 6. When the sipe 5 has a zigzag shape with an amplitude T 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 the deformation of the block 4, and the tire of the block 4 The falling down in the width direction can be suppressed. The amplitude T of the bent portion 6 is preferably set to 0.5 to 5.0 mm. If the amplitude T is less than 0.5 mm, the effect of supporting the falling of the block 4 during cornering becomes insufficient. Conversely, if the amplitude T exceeds 5.0 mm, the removal from the mold becomes worse.

  In the pneumatic tire for snowy and snowy roads, the JIS-A hardness (0 ° C.) of the rubber composition constituting the tread portion is 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 deformation of the blocks, and the tire performance at the time of braking / driving can be improved. In addition, since the sipe 5 has a zigzag shape with an amplitude T 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 even during cornering to suppress block deformation. In addition, tire performance during cornering 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. In particular, it is possible to increase the number of sipes per block and to use a low-hardness rubber for the tread rubber, so that the tire performance in summer can be maintained while improving the performance on ice.

FIG. 5 shows a block of a pneumatic tire for icy and snowy roads according to an embodiment of the present invention. 6 shows a part of the inner wall surface of the sipe in the block, and FIG. 7 is a cross-sectional view taken along arrow VII-VII in FIG.

  In FIG. 5, 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 and is continuous in the tire width direction (Tw). The bent portion 6 is 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. 6, the sipe 5 forms a zigzag shape having amplitudes A, B, C, and D in the tire radial direction (Tr) at the bent portion 6. When the sipe 5 has a zigzag shape with amplitudes A to D 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 the deformation of the block 4, and the block 4 Can be suppressed in the tire width direction.

  In FIG. 6, the amplitudes A to D in the tire radial direction of the bent portion 6 are larger at the sipe bottom side than at the tread surface side. By increasing the amplitudes A to D in the tire radial direction of the bent portion 6 toward the sipe bottom side, it is possible to suppress a decrease in block rigidity during braking / driving and to increase block rigidity during cornering.

  More specifically, the amplitude A of the bent portion 6 at the most tread surface portion is set to 0.5 mm or more, and the amplitude D of the bent portion 6 at the most sipe bottom side portion is set to 3.5 mm or less. Good. When the amplitude A of the bent portion 6 at the most tread surface side is less than 0.5 mm, the block rigidity is significantly reduced. Further, when the amplitude D of the bent portion 6 at the most sipe bottom side portion is more than 3.5 mm, it is difficult to release the mold. By forming the sipe 5 so that the amplitudes A to D of the bent portion 6 gradually increase from the tread surface side toward the sipe bottom side, both the maintenance of block rigidity and the releasability from the mold are balanced. be able to.

  As shown in FIG. 7, the amplitude X of the sipe 5 in the tire circumferential direction is constant over the entire length of the sipe 5 in the depth direction. The inclination angles a, b, c, d of the sipe 5 in the tire circumferential direction with respect to the normal direction of the tread surface S are smaller at the site on the sipe bottom side than the site on the tread surface side. By reducing the inclination angles a to d of the sipe 5 in the tire circumferential direction with respect to the normal direction of the tread surface S, the releasability from the mold can be improved.

  More specifically, the inclination angle a at the most tread surface portion is set to 30 ° to 45 °, and the inclination angle d at the most sipe bottom portion is set to 15 ° to less than 30 °. . When the inclination angle a at the most tread surface side is less than 30 °, the block rigidity is remarkably lowered. On the other hand, when the inclination angle a exceeds 45 °, release becomes difficult. Further, when the inclination angle d at the most sipe bottom portion is less than 15 °, the block rigidity is remarkably lowered. By forming the sipe 5 so that the inclination angles a to d gradually decrease from the tread surface side toward the sipe bottom side, a smoother mold release becomes possible.

According to the above-mentioned pneumatic tire for snowy and snowy roads, the tire performance during braking and cornering can be improved at the same time even when the hardness of the tread rubber is reduced as in the above-described reference example. Is possible. In addition, according to the present embodiment, the releasability from the mold is improved, so that a failure such as a chipped block can be avoided more reliably.

First, tires of Conventional Examples 1 to 3 and Reference Example 1 in which the tire size is 195 / 65R15 91Q and the shape of the sipe provided on the block is varied in the pneumatic tire for ice and snowy roads having a block pattern are manufactured.

As described in Japanese Patent Application Laid-Open No. 2000-6619, Conventional Example 1 employs a sipe in which the tread surface has a zigzag shape and the amplitude of the zigzag shape changes inside the block (FIG. 8). reference). Conventional example 2 employs a sipe that has a zigzag shape on the tread surface and alternately arranges triangular pyramids and inverted triangular pyramids inside the block, as described in JP-A-2002-301910. (See FIG. 9). As described in Japanese Patent Application Laid-Open No. 2002-321509, Conventional Example 3 employs a sipe that has a zigzag shape on the tread surface and a bent portion continuous in the tire radial direction inside the block that is bent in the tire width direction. (See FIG. 10). On the other hand, Reference Example 1 adopts the sipe shown in FIG.

  These test tires were evaluated for ice braking performance, wet braking performance, and wet turning performance by the following test methods, and the results are 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 1 as 100, using the reciprocal of the measured value. The larger the index value, the better the braking performance on ice.

Wet braking performance:
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. The evaluation results are shown as an index with the conventional example 1 as 100, using the reciprocal of the measured value. A larger index value means better wet braking performance.

Wet turning performance:
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. The evaluation results are shown as an index with Conventional Example 1 as 100. The larger the index value, the better the wet turning performance.

この表１から判るように、参考例１のタイヤは氷上制動性能、ウェット制動性能及びウェット旋回性能が従来例１〜３に比べて優れていた。

As can be seen from Table 1, the tire of Reference Example 1 was superior in braking performance on ice, wet braking performance, and wet turning performance to those of Conventional Examples 1-3.

Next, tires of Examples 1 to 7 in which the sipe inclination angles a to d and the amplitudes A to D of the sipe bends were varied based on the tire of Reference Example 1 were produced.

For these test tires, the braking performance on ice was evaluated, the failure occurrence rate during vulcanization was determined, and the results are shown in Table 2. However, the braking performance on ice is indicated by an index with reference example 1 being 100. The failure occurrence rate is a percentage (%) of a failure occurrence tire with respect to the number of tire vulcanizations when the occurrence state of a tread portion chipping or a cut flaw by a sipe forming blade is investigated for a vulcanized tire.

この表２から判るように、実施例１〜７のタイヤは参考例１のタイヤと同等の氷上制動性能を備えながら故障発生率が極めて低いものであった。

As can be seen from Table 2, the tires of Examples 1 to 7 had an on-ice braking performance equivalent to that of the tire of Reference Example 1, while having a very low failure rate.

It is a plan view showing a tread pattern of a pneumatic tire for ice and snow for illustrating the present invention. It is a perspective view showing a block (reference example) of a pneumatic tire for snowy and snowy roads with a part cut away. It is a side view of the block of FIG. It is a side view which shows the sipe inner wall surface in the block of FIG. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a part of a block of a pneumatic tire for an icy and snowy road according to an embodiment of the present invention. It is a side view which shows a part of sipe inner wall surface in the block of FIG. It is a VII-VII arrow cross section of FIG. It is a perspective view which shows the block of the prior art example 1. FIG. It is a perspective view which shows the block of the prior art example 2. FIG. It is a perspective view which shows the block of the prior art example 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Vertical groove 3 Horizontal groove 4 Block 5 Sipe 6 Bending part S Tread surface T Amplitude θ Inclination angle

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. Form a zigzag shape with amplitude,
While making the amplitude in the tire circumferential direction of the sipe constant, the inclination angle of the sipe in the tire circumferential direction with respect to the normal direction of the tread surface is made smaller at the site on the sipe bottom side than the site on the tread surface side, A pneumatic tire characterized in that an amplitude in a tire radial direction of the bent portion is larger at a sipe bottom side than at a tread surface side. The inclination angle of the sipe in the tire circumferential direction with respect to the normal direction of the tread surface is 30 ° or more and 45 ° or less at the most tread surface portion, and 15 ° or more and less than 30 ° at the most sipe bottom portion. The pneumatic tire according to claim 1 . The pneumatic tire according to claim 1 or 2 , wherein an amplitude of the bent portion in a tire radial direction is 0.5 mm or more at a portion closest to the tread surface and 3.5 mm or less at a portion closest to the sipe bottom. .

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