JP4831723B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire provided with a tread pattern having land portions such as blocks or ribs in which a plurality of sipes are formed, and is particularly useful as a studless tire.

  Conventionally, in order to improve the ice performance of a studless tire, a tire pattern in which a plurality of sipes are arranged in each part (center part, mediate part, shoulder part) is known. As a shape of such a sipe, a flat or corrugated sipe whose shape does not change in the depth direction of the sipe has been generally used. By forming such sipes in blocks, the edge effect, water removal effect, and adhesion effect on the ice road surface are improved, so the number of sipes tended to increase in recent years.

  However, increasing the number of sipe and increasing the sipe density increases the number of edges, but the rigidity of the entire block decreases and the sipe collapses excessively, conversely the edge effect decreases and ice performance also decreases Problem arises. For this reason, attention has recently been paid to so-called three-dimensional sipe, in which the shape of the sipe is changed in the depth direction to suppress the sipe collapse.

  Various types of three-dimensional sipe shapes have been proposed so far and can be divided into several types. One of them is a convex portion and a concave portion meshing with the convex portion on both sides of the sipe inner wall. A dimple is known (for example, see Patent Document 1). In this structure, when the block and the sipe fall down, the fall of the sipe inner wall surface is suppressed by the engagement between the convex part and the concave part of the inner wall surface of the sipe.

  However, in order to ensure dewatering on the ice road surface, it is necessary to make the gap of the sipe a certain level or more. Therefore, the rigidity of the entire block is lowered, and the ground pressure distribution is non-uniform, so that There has been a problem that heel wear tends to occur.

On the other hand, in Patent Document 2, when forming a sipe, a columnar space extending in the sipe depth direction is used by using a sipe-formed bone (type blade) provided with at least one reinforcing column. A sipe having is disclosed. However, in this structure, since the columnar space of the sipe continues to the surface, the rigidity of the peripheral portion thereof is locally reduced, and uneven wear tends to occur. Further, since the columnar space continues to the surface, the effect of retaining water is insufficient, and there is room for improvement from the viewpoint of water removal.
JP-A-5-58118 Japanese Patent Laid-Open No. 11-42913

  Therefore, the object of the present invention is to prevent water on the ice road surface by increasing the rigidity of the entire block because the columnar space of the sipe is not continuous in the depth direction while ensuring water removal in the space provided inside the sipe. The object is to provide a pneumatic tire with good performance and uneven wear resistance.

  The above object can be achieved by the present invention as described below.

That is, the pneumatic tire of the present invention is a pneumatic tire having a tread pattern having a block in which a plurality of sipes are formed in the tire width direction, and the gap between the sipes is set to 0.2 to 0.5 mm. A plurality of spaces are formed by disposing the sipe in a plurality of locations on the inner wall surface and having hemispherical recesses having a width in the sipe depth direction of 1.0 to 5.0 mm facing the flat inner wall surface. It is characterized by being.

  According to the pneumatic tire of the present invention, the columnar space of the sipe is not continuous in the depth direction, and the rigidity of the entire block can be increased. Therefore, the influence of uneven contact pressure is reduced, and uneven wear resistance performance is improved. can do. Further, water removal can be secured in the space provided inside the sipe, and the braking performance on the ice road surface is also improved. At this time, since the width of the space portion in the sipe depth direction is small, the rigidity is not easily lowered locally, and since the continuity is not continuous in the depth direction, water removal is also improved.

  In the above, it is preferable that the depth of the recess is not more than half of the thickness of the block piece on which the recess is formed and is not less than the gap of the sipe. As a result, the rigidity of the entire block can be sufficiently maintained while ensuring sufficient water removal.

Moreover, it is preferable that some recessed parts are exposed to the surface of the said block among these recessed parts. Thereby, a space part is also formed on the surface of the block, and the effect of removing the water film on the surface part on the ice road surface can be improved.

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

  As shown in FIG. 1, the pneumatic tire of the present invention includes a tread pattern T having a land portion such as a block 1 in which a plurality of sipes 10 are formed. In the present embodiment, an example is shown in which blocks 1 divided by circumferential grooves 2, lateral grooves 3, 5 and oblique grooves 4 are formed, and six rows of blocks 1 are arranged in the tire width direction.

  Each block 1 is formed with a plurality of rows of sipes 10 in the tire width direction, and both ends of each of the sipes 10 are open in grooves adjacent to the block 1, but are not limited thereto. Instead, it can be properly used depending on the pattern configuration, for example, it is not exposed from the side wall of the block 1 but is fastened inside the side wall of the block 1 or only one side is fastened.

  FIG. 2A is a perspective view schematically showing the block 1. In FIG. 2A, a part of the block piece 1a is deformed to expose the inner wall surface 13 of the sipe 10 so that the uneven shape of the inner wall surface 13 can be easily understood. Moreover, the example of the linear sipe is shown instead of the wave type sipe.

  In the sipe 10 according to the present invention, as shown in FIGS. 2A to 2C, a plurality of space portions 11 are formed by recesses 13 a provided on the inner wall surface 13 of the sipe 10. In the present embodiment, an example is shown in which substantially the same number of space portions 11 (that is, recesses 13a) are provided for each sipe 10, and the arrangement of the space portions 11 is also distributed substantially uniformly.

The shape of the recess 13a may be hemispherical, semi-elliptical, partial spherical, triangular pyramid, quadrangular pyramid, etc., but in the present invention, a hemispherical shape is adopted, and the sipe blade is easily manufactured and its durability. Therefore, a shape having a substantially spherical surface is preferable.

  The width W of the concave portion 13a in the sipe depth direction is 1.0 to 5.0 mm, and preferably 1.0 to 3.0 mm. If the width W exceeds 5.0 mm, the rigidity of the surrounding land portion is locally reduced, and uneven wear tends to occur. Further, when the width W is less than 1.0 mm, it is difficult to ensure sufficient water removal.

  The depth D of the recess 13a is preferably less than or equal to half the thickness T of the block piece 1a in which the recess 13a is formed and greater than or equal to the gap t of the sipe 10. When the depth D exceeds half of the thickness T, the rigidity of the surrounding land portion is locally reduced, and uneven wear tends to occur. Further, when the depth D is less than the gap t of the sipe 10, there is a tendency that sufficient water removal cannot be ensured.

In the present invention, the gap t of the sipe 10 is 0.2 to 0.5 mm . If the gap t exceeds 1.0 mm, the rigidity of the entire block cannot be increased, and uneven wear due to uneven contact pressure tends to occur. Moreover, if it is less than 0.2 mm, the durability of the sipe blade when forming the sipe tends to be a problem.

  Further, the thickness T of the block piece 1a divided by the sipe 10 is preferably 2 to 10 mm.

  In this invention, as shown to Fig.2 (a), it is preferable that some recessed parts 13a are exposed to the surface of a land part among these recessed parts 13a. Even if the recess 13a is not exposed on the surface of the land immediately after manufacture, the same effect can be obtained even if the recess 13a is exposed on the surface due to wear during use of the tire.

  Further, in the present invention, when the sipe 10 is divided vertically by the center line of the sipe depth, it is preferable that the volume density of the formed recesses 13a is larger on the lower side than on the upper side. This makes it possible to maintain good water removal in the second half of wear. In the case where the recesses 13a having the same volume are formed, it is preferable that the density of the number thereof is larger on the lower side than on the upper side.

  In order to form the sipe 10 as described above, a sipe blade corresponding to its shape may be used, but it is preferable to use a sipe blade 15 as shown in FIGS. In other words, the sipe blade 15 has one blade 15a that is flat, and the other blade 15b is formed with a recess 15c by press molding or the like, and the two are joined by spot welding or the like. It can be a blade 15.

  The pneumatic tire of the present invention is the same as a normal pneumatic tire except that it includes the tread pattern T as described above, and any conventionally known material, shape, structure, manufacturing method, and the like can be employed in the present invention.

  The pneumatic tire of the present invention is particularly useful as a studless tire because it exhibits the effects as described above and is excellent in ice performance.

[Other Embodiments]
Hereinafter, other embodiments of the present invention will be described.

  (1) In the above-described embodiment, an example in which a space portion is provided for a linear sipe has been shown. However, in the present invention, as shown in FIG. 4A, a wave-shaped sipe 10 formed in a block 1 is used. A space portion 11 may be provided. In this case, the cross-sectional shape perpendicular to the sipe depth is not limited to a shape close to a sine wave, and may be any shape such as a wavy line obtained by alternately combining a straight line and a curve, a rectangular wave, or a shape close to a zigzag shape. The period of the unevenness in this cross-sectional shape (for example, the distance between the convex and convex tops) is preferably 1.5 to 5 mm for suitably expressing the characteristics of the so-called corrugated sipe, and the amplitude (the sum of the heights of both side tops). Is preferably 1.5 to 5 mm.

  (2) In the above-described embodiment, an example in which a space portion is provided for a two-dimensional sipe has been shown. However, in the present invention, as shown in FIG. The space portion 11 may be provided for the three-dimensional shaped sipe 10 that is changed to prevent the sipe 10 from falling down.

  (3) In the above-described embodiment, an example in which substantially the same number of space portions are provided for each sipe has been shown. However, in the present invention, as shown in FIG. The space portion 11 may be provided with respect to the sipe 10 so as to increase in front of the tire rotation direction.

  In this case, the rigidity of the block piece located in the front of the tire rotation direction where the ground pressure increases during braking is lower than that of the block piece located behind, so that the ground pressure can be made uniform and toe-heel wear can be reduced. It can be effectively suppressed.

(4) In the above-mentioned embodiment, the example which provides a space part with respect to the sipe extended in a tire width direction was shown . FIG 5 (a) ~ (b) , show provided spatial portion 11 with respect to the sipe 10 extending in the tire circumferential direction, it not included in the present invention.

(5) In the above-described embodiment, the example in which the concave portion is formed on only one of the inner wall surfaces of one sipe has been shown. However, in the present invention, as shown in FIG. You may form the recessed part 13a in both. At this time, although not included in the present invention, as shown in FIG. 6B, the recesses 13a may overlap each other, and in this case, one space portion 11 is formed by the two recesses 13a. It will be.

Although not included in the present invention, as shown in FIG. 6 (c), a convex portion 13b may be formed on the opposing inner wall surface 13 so as to overlap the concave portion 13a of the inner wall surface 13, and in that case Thus, one recess 11 is formed by the recess 13a and the protrusion 13b. According to this configuration, when the block collapses, the concave portion 13a and the convex portion 13b are engaged with each other. Therefore, it is possible to effectively prevent the adverse effect (reduction of the edge effect) due to the block falling.

  (6) In the above-described embodiment, the example of the block pattern as shown in FIG. 1 has been shown. However, the block pattern is not limited to this shape, and may be a parallelogram, V-shaped, pentagonal, or curved block. . Further, a block in which grooves are formed near the center or near the end, or a part of the land that is continuous in the circumferential direction, or a rib-based pattern may be used.

  (7) In the above-described embodiment, as shown in FIG. 2, an example in which the sipe is formed so as to be perpendicular to the block surface has been described. It may be slightly inclined (for example, 15 ° or less).

  Examples and the like specifically showing the configuration and effects of the present invention will be described below. In addition, each performance evaluation of the tire was performed as follows.

(1) Ice braking distance Tires are mounted on a real vehicle (domestic 2000cc class FF sedan), run on ice at a speed of 30 km / h under the load conditions of two passengers with the air pressure specified by the vehicle, and stop the vehicle from the start of braking The distance to was measured and evaluated by an index. In addition, evaluation is shown by an index display when the conventional product (Comparative Example 1) is set to 100, and a larger value indicates a better result.

(2) Ice turning speed A tire is mounted on an actual vehicle (domestic 2000cc class FF sedan), and it turns 10 times on the ice with a radius of 25m under the load conditions of two passengers at the specified air pressure. The applied turning speed was measured and evaluated by an index. In addition, evaluation is shown by an index display when the conventional product (Comparative Example 1) is set to 100, and a larger value indicates a better result.

(3) Wear resistance performance The amount of tire toe and heel wear when traveling 10,000 km on a paved road was measured and evaluated by an index. The to-and-heel wear amount indicates the difference in the wear amount in the tire circumferential direction for one block, and the difference between the step-side wear amount and the kick-out wear amount was measured. In addition, evaluation is shown by an index display when the conventional product (Comparative Example 1) is set to 100, and a larger value indicates a better result.

Comparative example 1 (conventional product)
Each block has a test pattern in which rectangular blocks with a width of 25 mm, a circumferential length of 35 mm, and a height of 9.0 mm are formed in six rows in the tire width direction. Each block has the following size: A radial tire of size 205 / 65R15 94H in which five straight open sipes (no spaces) were formed in the tire width direction was manufactured, and each of the above performance evaluations was performed. The results are shown in Table 1.

  The depth of the sipe was 7.0 mm and the gap was 0.5 mm.

Example 1
In the same red pattern as in Comparative Example 1, ten hemispherical recesses having a depth of 0.7 mm and a diameter of 2 mm were uniformly formed for each sipe (gap is 0.3 mm), and size 205 / 65R15 94H A radial tire was manufactured. The number of recesses exposed on the surface was 7 per block. Table 1 shows the results of each performance evaluation described above using this tire.

Example 2
In the same red pattern as in Comparative Example 1, 5 to 15 hemispherical concave portions each having a depth of 0.7 mm and a diameter of 2 mm are formed for each sipe (gap is 0.3 mm) to obtain a size of 205 / 65R15. A 94H radial tire was produced. At that time, the formation density of the recesses was changed so that the number of recesses was maximized in the front in the tire rotation direction, and the number was decreased in the rear sipes. The number of recesses exposed on the surface was 7 per block. Table 1 shows the results of each performance evaluation described above using this tire.

Example 3
In the same red pattern as in Comparative Example 1, as shown in FIG. 4 (b), the sipe is divided at the center to form a sipe extending in the circumferential direction at that portion, and each sipe (gap is 0.3 mm). A radial tire having a size of 205 / 65R15 94H was manufactured by uniformly forming ten hemispherical concave portions each having a depth of 0.7 mm and a diameter of 2 mm. The number of recesses exposed on the surface was 7 per block. Table 1 shows the results of each performance evaluation described above using this tire.

Comparative Example 2
In Comparative Example 1, a radial tire having a size of 205 / 65R15 94H was manufactured in the same manner as in Example 1 except that four columnar grooves having a cross-sectional shape of 1 mm × 2 mm were provided for each sipe. Each of the above performance evaluations was performed. The results are shown in Table 1.

表１の結果が示すように、実施例ではブロック全体の剛性を高めつつ、サイプ内部に設けた空間部で除水性を確保することで、アイス路面での制動性能や耐偏摩耗性能が、従来品より良好であった。特に、タイヤ回転方向の前方ほど凹部の個数が多い実施例２では、アイス制動性と偏摩耗性により優れていた。また、タイヤ周方向のサイプに凹部を形成した実施例３では、特にアイス旋回性能に優れていた。

As shown in the results of Table 1, in the embodiment, while improving the rigidity of the entire block, ensuring water removal in the space provided inside the sipe, braking performance and uneven wear resistance performance on the ice road surface are conventionally improved. It was better than the product. In particular, in Example 2 in which the number of concave portions is larger toward the front in the tire rotation direction, the ice braking performance and uneven wear performance were superior. Moreover, in Example 3 which formed the recessed part in the sipe of the tire circumferential direction, it was especially excellent in ice turning performance.

  On the other hand, in Comparative Example 2 in which the sipe was provided with the columnar recesses, the ice braking performance was insufficient, and the problem of toe heel wear during running on the dry road also occurred.

The top view which shows the tread surface of an example of the pneumatic tire of this invention It is a figure which shows the principal part of the pneumatic tire of this invention, (a) is the perspective view which deform | transformed some blocks, (b) is the II arrow sectional drawing, (c) is dimension explanatory drawing. It is a figure which shows an example of the sipe braid for forming the sipe in this invention, (a) is an assembly perspective view, (b) is sectional drawing. The perspective view which shows the other example of the sipe in this invention The perspective view which shows the example of the sipe which is not included in this invention The perspective view which shows the other example of the sipe in this invention (however, (b) and (c) are not included in this invention).

Explanation of symbols

1 block (land)
DESCRIPTION OF SYMBOLS 1a Block piece 10 Sipe 11 Space part 13 Inner wall surface of Sipe 13a Concave part T Tread pattern

Claims (4)

In a pneumatic tire provided with a tread pattern having a block in which a plurality of sipes are formed in the tire width direction ,
The sipe gap is set to 0.2 to 0.5 mm , and hemispherical recesses having a sipe depth direction width of 1.0 to 5.0 mm arranged in a distributed manner at a plurality of locations on the inner wall surface of the sipe. A pneumatic tire characterized in that a plurality of spaces are formed facing a flat inner wall surface.   2. The pneumatic tire according to claim 1, wherein when the sipe is divided vertically by a center line of a sipe depth, the volume density of the recesses is larger on the lower side than on the upper side.   3. The pneumatic tire according to claim 1, wherein a depth of the recess is not more than half of a thickness of a block piece in which the recess is formed and is not less than a gap of the sipe. The pneumatic tire according to any one of claims 1 to 3, wherein some of the plurality of recesses are exposed on a surface of the block .

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