JP5873765B2 - Sipe blade and pneumatic tire - Google Patents

Description

  The present invention relates to a sipe blade for forming a sipe on a tread surface of a tire, and a pneumatic tire having a sipe formed on a tread surface, and particularly useful for a studless tire.

  Conventionally, in a studless tire, a cut called a sipe is formed in a land portion of a tread surface, and the running performance on an icy and snowy road surface (hereinafter referred to as ice performance) is enhanced by the edge effect and water removal effect of the sipe. ing. In recent years, in order to better express the edge effect, the so-called three-dimensional sipe that changes the shape of the inner wall surface of the sipe in the depth direction and can suppress the collapse of the land portion by the engagement of the inner wall surface has been developed. It has been put into practical use.

  FIG. 7 is a schematic diagram of a three-dimensional sipe previously invented by the present inventor. The inner wall surface of the sipe 9 is provided with a concavo-convex row having a transverse cross section. The sipe 9 has an inner wall portion 91 extending inward in the tire radial direction IN while the wave shape is displaced to one side in the length direction (right side in FIG. 7), and the other side in the length direction in the wave direction (left side in FIG. 7). And an inner wall portion 92 extending inward in the tire radial direction IN while being displaced, and these are alternately connected. Such a sipe structure is described in Patent Document 1.

  Usually, a sipe is formed by a thin sipe blade mounted on a tire mold, and the shape of the outer wall surface of the sipe blade is transferred to the inner wall surface of the sipe. Therefore, in the sipe blade for forming the sipe 9 of FIG. 7, the outer wall surface is provided with a concavo-convex row having a corrugated cross section, and the shape of the outer wall surface corresponds to the inner wall surface of the sipe 9. Become.

  By the way, when the tire is vulcanized using the sipe blade, the sipe blade is bent in the process of repeating the vulcanization process, which may hinder subsequent use. Although this kind of blade bending can be reduced by increasing the thickness of the sipe blade, increasing the thickness of the sipe causes a decrease in the rigidity of the land portion, which in turn promotes the collapse of the land portion. It was not desirable for ensuring the performance.

Japanese Patent No. 3504632

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a sipe blade and a pneumatic tire capable of preventing blade bending during vulcanization while ensuring ice performance.

  In order to achieve the above object, the present inventor has conducted research on blade bending at the time of vulcanization. As a result, a crease in the blade bending is formed along the length direction at a depth position where the uneven row is bent. In addition, the present inventors have found that the rigidity of the sipe blade is lowered at the depth position where the convex top portions where the distortion tends to concentrate are aligned in the length direction, and the blade is bent as a crease. The present invention has been made on the basis of such knowledge, and can achieve the above-described object with the following configuration.

  That is, the sipe blade of the present invention is provided with an uneven wall having a corrugated cross section on the outer wall surface, and the sipe blade is attached to a tire mold and forms a sipe on the tread surface of the tire. A first outer wall portion extending inward in the tire radial direction while displacing to one side in the length direction, and a tire diameter connected to the inner side in the tire radial direction of the first outer wall portion while the wave shape is displaced to the other side in the length direction And a convex top portion facing to one side in the length direction at a depth position where the first outer wall portion and the second outer wall portion are connected to bend the concave-convex row. Are arranged in the longitudinal direction, and the convex apexes located at both ends in the longitudinal direction have a smaller sharpness than the convex apexes located between them.

  In this sipe blade, since the degree of sharpness of the convex crests located at both ends in the length direction is small at the depth position where the concavo-convex row is bent, distortion acting on these can be suppressed. The convex tops at both ends are the parts where large strains act when pulling out the sipe blade from the tire, and by suppressing these distortions, the decrease in rigidity at the depth where the convex tops are lined is reduced, and during vulcanization Blade bending can be prevented. Moreover, by setting the convex crests having a high degree of sharpness between the convex crests at both ends, it is possible to maintain the engaging force of the inner wall surface of the sipe and suppress the falling of the land portion and ensure the ice performance.

  In the sipe blade of the present invention, it is preferable that the convex apex portions located at both ends in the length direction have a larger curvature radius at the tip than the convex apex portions located therebetween. With such a configuration, it is possible to effectively suppress distortion acting on the convex tops at both ends.

  In the sipe blade of the present invention, it is preferable that the convex apex located at one end in the length direction is extended to one side in the length direction and reaches the blade end. With this configuration, it is possible to effectively suppress the distortion that acts on the convex top portion at the one end. In addition, in the formed sipe, the engaging force of the inner wall surface can be increased to effectively suppress the falling of the land portion, and the ice performance can be improved satisfactorily.

  In the sipe blade of the present invention, the sipe blade further includes another first outer wall portion connected to the inner side in the tire radial direction of the second outer wall portion, and the second outer wall portion and the other first outer wall portion are connected to form the uneven row. At least three convex crests facing the other side in the length direction are arranged in the length direction, and the convex crests located at both ends in the length direction are located between them. What has a small sharpness compared with a convex top part is preferable. In this case, even at a depth position where the second outer wall portion and the first outer wall portion on the inner side in the tire radial direction are continuous and the uneven row is bent, the rigidity reduction is reduced in the same manner as described above, and the blade is bent during vulcanization. Can be prevented.

  The pneumatic tire according to the present invention is a pneumatic tire in which a concavo-convex row having a wavy cross section is provided on an inner wall surface of a sipe formed on a tread surface. A first inner wall portion extending inward in the tire radial direction while displacing to the side, and a first inner wall portion extending inward in the tire radial direction of the first inner wall portion, and a wave shape extending inward in the tire radial direction while displacing to the other side in the length direction. 2 at the depth position where the first and second inner wall portions and the second inner wall portion are connected to bend the concavo-convex row, and the concave apex portion directed to one side in the length direction is in the length direction. At least three of the concave apexes arranged at both ends in the length direction have a smaller sharpness than the concave apexes located between them.

  In this sipe of a pneumatic tire, since the degree of sharpness of the concave crests located at both ends in the length direction is small at the depth position where the concavo-convex row of the inner wall surface is bent, the distortion acting on the convex crests of the corresponding sipe blades Is suppressed. For this reason, the rigidity fall in the depth position where a convex top part forms in a sipe blade can be reduced, and the bending of the blade at the time of vulcanization can be prevented. Moreover, since the concave peak part with a large sharpness degree is set between the concave peak parts of both ends, the engagement force of the inner wall surface can be maintained, the falling of the land part can be suppressed, and the ice performance can be ensured.

  In the pneumatic tire of the present invention, it is preferable that the concave apex portions located at both ends in the length direction have a larger curvature radius at the tip than the concave apex portions located therebetween. With such a configuration, it is possible to effectively suppress distortion acting on the convex top portions of the sipe blades corresponding to the concave top portions at both ends.

  In the pneumatic tire of the present invention, it is preferable that the concave apex portion located at one end in the length direction extends to one side in the length direction and reaches the sipe end. With such a configuration, it is possible to effectively suppress the distortion that acts on the convex top portion of the sipe blade corresponding to the concave top portion at one end. In addition, by increasing the engagement force of the inner wall surface of the sipe, the ice performance can be improved satisfactorily by effectively suppressing the collapse of the land portion.

Sectional view showing the tread mold of the tire mold A plan view showing an example of a tread pattern (A) Front view of sipe blade and (B) Cross section along AA arrow Front view of a sipe blade according to another embodiment (A) Top view and (B) Front view showing the inner wall surface of the sipe Front view showing the inner wall surface of a sipe according to another embodiment (A) Plan view and (B) Front view showing the inner wall surface of a conventional sipe

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

  FIG. 1 is a cross-sectional view of a tread mold 6 constituting a tire mold. The tread molding die 6 has an annular tread molding surface 7 and is pressed against the tread surface of the tire to form a tread pattern as shown in FIG. The tread molding surface 7 is provided with a protrusion 8 that forms a main groove 4 extending along the tire circumferential direction and a protrusion (not shown) that forms a lateral groove 5 extending in a direction intersecting the main groove 4. A sipe blade 1 for forming the sipe 2 is mounted.

  The sipe blade 1 is a thin plate-like member that is mounted on a tire mold and forms a sipe 2 on a tread surface of the tire, and an uneven row having a corrugated cross section as shown in FIG. 3 is provided on the outer wall surface. . The sipe blade 1 has a first outer wall portion 11a extending inward in the tire radial direction IN while the wave shape is displaced in one length LDL (left side in FIG. 3), and on the inner side in the tire radial direction of the first outer wall portion 11a. The second outer wall portion 12 extends inward in the tire radial direction IN while being waved and displaced to the other side LDR (right side in FIG. 3) in the length direction. The length direction LD is the length direction of the sipe 2, and is a direction along the tire width direction in the present embodiment.

  The sipe blade 1 further includes a base end portion 10 that is continuous to the outer side in the tire radial direction of the first outer wall portion 11a, and another first outer wall portion 11b that is continuous to the inner side IN of the second outer wall portion 12 in the tire radial direction. Since the base end portion 10 is embedded in the tread molding surface 7, the portion other than the base end portion 10 is used for forming the sipe 2. The first outer wall portion 11b has basically the same configuration as the first outer wall portion 11a except that the depth position is different. In the following description, these may be collectively referred to as the first outer wall portion 11.

  At a depth position DP1 where the first outer wall portion 11a and the second outer wall portion 12 are connected to bend the concavo-convex row, the convex top portions 13 facing the one side LDL in the length direction are arranged. The convex top portion 13 is a top portion of a convex row having a horizontal V shape. The convex row and the concave row are determined based on the center CL of the amplitude of the waveform. In the outer wall surface shown in FIG. 3 (A), three convex top portions 13a, 13b, 13c are arranged at the depth position DP1, and the number thereof may be four or more. It is sufficient that at least one of the outer wall surfaces is aligned so that three or more convex apexes are arranged at the depth position DP1, and in the outer wall surface on the back side of the outer wall surface shown in FIG. The number of convex tops arranged in DP1 is two.

  In the convex top portions 13a and 13c located at both ends of the length direction LD, the degree of sharpness is smaller than that of the convex top portions 13b located between them. Although the convex top portions 13a and 13c are pointed toward the one side LDL, the degree thereof is gentler than that of the convex top portion 13b. The convex top portions 13a and 13c in the present embodiment are set to have larger curvature radii at the tips than the convex top portions 13b. For example, the radius of curvature of the tip of the convex top portion 13b is in the range of 0.3 to 0.5 mm, and the radius of curvature of the tip of the convex top portions 13a and 13c is in the range of 0.5 to 1.5 mm.

  Since the convex top portion 13 is a portion where distortion tends to concentrate, in the process of repeating the vulcanization process, the rigidity tends to decrease at the depth position DP1 where they are arranged. However, in this sipe blade 1, since the sharpness is set small at the convex top portions 13a and 13c at both ends where large strain is likely to act, such a decrease in rigidity can be reduced and bending of the blade during vulcanization can be prevented. This is particularly useful when the material of the sipe blade 1 is a low-cost material such as SUS304, but the strength is a concern.

  Further, in the sipe 2 formed by the sipe blade 1, the ridge shape of the convex top portion 13b is large, so that the engagement force of the inner wall surface of the sipe 2 is maintained to prevent the land portion from falling down and to ensure ice performance. be able to. On the other hand, when the sharpness of all the convex crests 13 arranged at the depth position DP1 is set small, the engaging force of the inner wall surface of the sipe 2 is lowered, which may lead to deterioration of ice performance. .

  In the present embodiment in which the first outer wall portion 11 and the second outer wall portion 12 are alternately connected, the depth position DP2 where the second outer wall portion 12 and the first outer wall portion 11b are continuous to bend the concavo-convex row, Convex apexes 14 facing the other side LDR in the length direction are arranged. The convex top portion 14 is on the outer wall surface on the back side of the outer wall surface shown in FIG. 3A, and coincides with the position of the concave top portion at the depth position DP2 in FIG. The convex crests 14a and 14c located at both ends have a smaller sharpness than the convex crest 14b located between them, and have the same configuration as the convex crest 13 at the depth position DP1.

  In FIG. 4, the convex top portion 13a located at the end of the one side LDL in the length direction is extended to the one side LDL to reach the blade end 15. In this manner, the sharpness of the convex top portion 13a is less than the convex top portion 13b. Is also small. The thickness T13 of the convex top portion 13a at the blade end 15 is, for example, 1.5 to 3 mm. Similarly, at the depth position DP2, the convex apex portion 14c positioned at the end of the other side LDR in the length direction extends to the other side LDR and reaches the blade end 15. The remaining convex tops have the same configuration as in FIG.

  Next, a pneumatic tire molded using a tire mold equipped with the sipe blade 1 will be described. The tire has the tread pattern shown in FIG. 2, and a sipe 2 formed by the sipe blade 1 is formed on a plurality of blocks 3 (an example of a land portion) partitioned by a main groove 4 and a lateral groove 5. Yes. The opening of the sipe 2 formed on the tread surface has a wave shape on the surface of the block 3, and this corresponds to the cross section of the sipe blade 1 shown in FIG.

  As shown in FIG. 5, the inner wall surface of the sipe 2 is provided with a concavo-convex row in which the cross section when it is cut along a plane parallel to the land surface is a wave shape. This inner wall surface is a transfer of the shape of the outer wall surface shown in FIG. 3A, and the left and right sides are reversed, so the relationship in the length direction in FIG. 5 (one side LDL and the other side LDR). Is the reverse of FIG. Both ends of the sipe 2 are opened on the side surface of the block 3, but the present invention is not limited to this, and one end or both ends may be closed.

  The sipe 2 is connected to a first inner wall portion 21a extending inward in the tire radial direction IN while the wave shape is displaced to one side LDL in the length direction, and the tire shape inward in the tire radial direction IN of the first inner wall portion 21a. A second inner wall portion 22 extending inward in the tire radial direction IN while being displaced to the other side LDR in the vertical direction, and further, another first inner wall portion 21b connected to the tire radial direction inner side IN of the second inner wall portion 22 is provided. Have. The inner wall portions 21a, 22 and 21b correspond to the outer wall portions 11a, 12 and 11b of the sipe blade 1, respectively.

  At a depth position DP1 where the first inner wall portion 21a and the second inner wall portion 22 are connected to bend the concavo-convex row, the concave crest portions 23 facing the one side LDL in the length direction are arranged. The concave top portion 23 is a top portion of a concave row having a horizontal V shape. In the inner wall surface shown in FIG. 5, three concave top portions 23a, 23b, and 23c are arranged at the depth position DP1, and the number thereof may be four or more. It is sufficient that at least one inner wall surface is suitable for the three or more concave peaks at the depth position DP1. On the inner wall facing the inner wall shown in FIG. 5, the concave peaks aligned at the depth position DP1. The number of is two.

  In the concave crests 23a and 23c located at both ends of the length direction LD, the degree of sharpness is smaller than that of the concave crests 23b located between them. The concave top portion 23 corresponds to the convex top portion 13 of the sipe blade 1 in FIG. 3, and the concave top portions 23a and 23c are set to have a radius of curvature larger at the tip than the concave top portion 23b. For example, the radius of curvature of the tip of the concave top portion 23b is in the range of 0.3 to 0.5 mm, and the radius of curvature of the tip of the concave top portions 23a and 23c is in the range of 0.5 to 1.5 mm.

  At the depth position DP2 where the second inner wall portion 22 and the first inner wall portion 21b are connected to bend the concavo-convex row, the concave apex portion 24 facing the other side LDR in the length direction is arranged. The concave crest 24 is on the inner wall facing the inner wall shown in FIG. 5, and coincides with the position of the convex crest at the depth position DP2 in FIG. The concave crests 24a and 24c located at both ends have a smaller sharpness than the concave crest 24b located between them, and have the same configuration as the concave crest 23 at the depth position DP1.

  The inner wall surface of the sipe 2 shown in FIG. 6 is obtained by transferring the shape of the outer wall surface of the sipe blade 1 shown in FIG. In this example, the concave crest 23a located at the end of the one side LDL in the length direction is extended to the one side LDL to reach the sipe end 25. With this aspect, the sharpness of the concave crest 23a is more than the concave crest 23b. Is also small. The thickness T23 of the concave crest 23a at the sipe end 25 is, for example, 1.5 to 3 mm. Similarly, at the depth position DP2, the concave apex portion 24c located at the end of the other side LDR in the length direction extends to the other side LDR and reaches the sipe end 25. The remaining concave tops have the same configuration as in FIG.

  From the viewpoint of improving braking performance and traction on icy and snowy road surfaces, the inclination angle of the length direction LD with respect to the tire width direction is preferably 45 ° or less, and more preferably 30 ° or less. The depth D2 of the sipe 2 (depth D1 of the sipe blade 1) is preferably 30 to 80% of the depth of the main groove 4 in order to sufficiently exhibit the edge effect by the sipe 2. The groove width W2 of the sipe 2 (thickness T1 of the sipe blade 1) is preferably 0.2 to 0.8 mm in order to suppress a decrease in rigidity of the block 3 while exhibiting an edge effect.

  The wave shape in the cross section of the sipe blade 1 or the sipe 2 is not limited to a curve formed by connecting arcs, but may be formed from a bent line that is bent in a zigzag manner, or may be other shapes. Moreover, the land part in which a sipe is formed is not restricted to a block, The rib extended continuously in a tire circumferential direction may be sufficient.

  The relationship of the sharpness of the convex top part or the concave top part described above may be adapted only by the depth position DP1. However, in order to enhance the improvement effect, it is more convenient to match the depth position DP2 as in the present embodiment, and it is preferable to apply to all the depth positions where the concave and convex rows are bent. On the other hand, in the above-described embodiment, the above-described convex peak portion or the degree of sharpness of the concave peak portion may be adapted only at the depth position DP2, and in that case, the outer wall portion 12 is regarded as the first outer wall portion. The inner wall portion 22 is regarded as the first inner wall portion.

  Although this pneumatic tire can be applied to so-called summer tires and all-season tires, it is particularly useful as a studless tire (winter tire) because it is advantageous in securing ice performance.

  Examples that specifically show the structure and effects of the present invention will be described below.

(1) Blade Bending After vulcanizing 10,000 tires, the presence or absence of sipe blade bending was evaluated.

(2) Ice braking performance (an example of ice performance)
The tire was mounted on a real vehicle and traveled on an icy and snowy road surface. The braking distance when the vehicle was fully locked with a braking force applied at a speed of 40 km / h was measured, and the reciprocal thereof was calculated. The result of Comparative Example 1 is evaluated as an index with the value of 100, and the larger the index, the better the ice braking performance.

Comparative Examples 1 and 2
In the tire having the tread pattern shown in FIG. 2 (tire size: 195 / 65R15), the radius of curvature of the tip of the concave top portion of the sipe (the convex top portion of the sipe blade) is uniformly set to 0.3 mm. Comparative Example 1 Similarly, Comparative Example 2 was set to 0.5 mm uniformly.

Examples 1 and 2
The same configuration as in Comparative Example 1 except that the radius of curvature of the tip of the concave top portion of the sipe (the convex top portion of the sipe blade) is 1.3 mm at the concave top portions at both ends and 0.5 mm at the concave top portion between them. Some were designated Example 1. Further, as shown in FIGS. 4 and 6, the second embodiment is the same as the first embodiment except that the concave top portion of the sipe (the convex top portion of the sipe blade) is extended to reach the sipe end (blade end). It was. The evaluation results are shown in Table 1.

  As shown in Table 1, blade bending was observed in Comparative Example 1 and ice braking performance was reduced in Comparative Example 2, whereas Examples 1 and 2 were able to ensure ice braking performance. Blade bending can be prevented. In particular, in Example 2, the ice braking performance is improved by increasing the engaging force of the inner wall surface of the sipe.

1 Sipe Blade 2 Sipe 3 Block (an example of land)
11 1st outer wall part 12 2nd outer wall part 13 convex top part 14 convex top part 15 blade end 21 first inner wall part 22 second inner wall part 23 concave top part 24 concave top part 25 sipe end DP1 depth position DP2 depth position

Claims (7)

In the sipe blade that is provided on the outer wall surface with a corrugated row having a corrugated cross section and is attached to a tire mold to form a sipe on the tread surface of the tire,
The first outer wall portion extending inward in the tire radial direction while the wave shape is displaced to one side in the length direction, and the inner side in the tire radial direction of the first outer wall portion, the wave shape is displaced to the other side in the length direction. A second outer wall extending inward in the tire radial direction,
At a depth position where the first outer wall portion and the second outer wall portion are connected to bend the concave-convex row, at least three convex top portions facing one side in the length direction are arranged in the length direction, and the length thereof The sipe blade characterized in that the convex top portions located at both ends in the direction have a smaller sharpness than the convex top portions located between them.   2. The sipe blade according to claim 1, wherein the convex top portions located at both ends in the length direction have a larger curvature radius at the tip than the convex top portions located therebetween.   The sipe blade according to claim 1 or 2, wherein the convex apex located at one end in the length direction extends to one side in the length direction and reaches the blade end.   It has another 1st outer wall part which continues in the tire radial direction inside of the 2nd outer wall part, and is the depth position where the 2nd outer wall part and the other 1st outer wall part continue, and the unevenness row is bent. , At least three convex crests facing the other side in the length direction are arranged in the length direction, and the convex crests located at both ends in the length direction have a sharpness degree compared to the convex crests located between them. The sipe blade according to any one of claims 1 to 3. In the pneumatic tire in which the inner wall surface of the sipe formed on the tread surface is provided with a concavo-convex row having a corrugated cross section,
The sipe is connected to the first inner wall portion extending inward in the tire radial direction while the wave shape is displaced to one side in the length direction, and the other side in the tire radial direction of the first inner wall portion. A second inner wall portion extending inward in the tire radial direction while being displaced to the side,
At a depth position where the first inner wall portion and the second inner wall portion are connected to bend the concave-convex row, at least three concave apex portions directed to one side in the length direction are arranged in the length direction, and the length thereof A pneumatic tire characterized in that the degree of sharpness is smaller at the concave tops located at both ends in the direction than the concave tops located between them.   The pneumatic tire according to claim 5, wherein a radius of curvature of the tip is larger in the concave top portions located at both ends in the length direction than in the concave top portions located therebetween.   The pneumatic tire according to claim 5 or 6, wherein the concave top portion located at one end in the length direction extends to one side in the length direction and reaches the sipe end.

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