JP4325874B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire having a tread pattern having a block 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 the shape of the sipe, a sipe having a straight or corrugated cross section is generally used. By forming such sipes in blocks, the edge effect, the water removal effect, and the adhesion effect are improved, and therefore the number of sipes tends to increase in recent years.

  However, if the number of sipes is increased to increase the sipe density, the number of edges increases, but the rigidity of the entire block decreases and the sipe collapses excessively. It becomes small and the problem that ice performance falls will arise.

  In particular, when a large number of open sipes on both sides extending in the tire width direction are provided in the block, since the sipes are connected to the circumferential groove, the block piece easily falls down, the ground contact area is reduced, the ice performance is reduced, and the block rigidity is reduced. Uneven wear due to lowering is also likely to occur.

  On the other hand, there is a method of providing both sides closed sipes to the block, but in that case, since the block is difficult to fall down, although it is possible to prevent uneven wear, it is difficult to obtain an appropriate deflection for improving ice performance, Ice performance is reduced.

  Therefore, there is a technology that achieves both improvement of sipe density and suppression of block collapse. For example, Patent Document 1 below proposes a pneumatic tire provided with an annular sipe (closed sipe) that forms a micro block at the center of the block, and a sipe that is connected to the sipe and extends to the end of the block. Has been.

  However, in this tire, it is a small annular sipe, and because it is connected to the sipe on both sides, there is almost no effect of suppressing the collapse of the block, the ground contact area becomes smaller due to the collapse of the block, the ice performance also decreases, Uneven wear due to a decrease in block rigidity is also likely to occur.

  Further, in Patent Document 2 below, a pneumatic tire is proposed in which a sipe extending from one end is branched in the middle and is alternately arranged with a sipe extending from the other end for the purpose of improving the sipe density near the center of the block. ing.

  However, in this tire, the sipe extending from one end of the block is branched and extends to the vicinity of the other end. Uniform collapse tends to occur. Moreover, since the sipe density on both sides of the block is small, the edge effect and the water removal effect are insufficient, and the effect of improving the ice performance cannot be said to be sufficient.

Japanese Patent No. 3584079 JP-A-8-332811

  Therefore, the object of the present invention is to improve the ice performance by easily obtaining an appropriate deflection of the block piece for improving the ice performance, good wear resistance performance, and maintaining the edge effect and water removal effect sufficiently. An object of the present invention is to provide a pneumatic tire that can be made to operate.

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, and the block extends from the center of the block to both sides along the tire width direction and has both ends. A central sipe arranged in the block, a sipe provided on both sides of the central sipe with a gap between them, and a sipe opened on each side of the block, and provided with a gap so as to surround the closed ends of the sipe on both sides. An enclosure sipe is provided. Here, the block center refers to the center of the block width with respect to the tire width direction, and the position in the tire circumferential direction may be any.

  According to the pneumatic tire of the present invention, since the central sipe and the both-side sipe do not communicate with each other, the block piece is prevented from falling compared to a normal open sipe. Further, by providing the surrounding sipe with an interval so as to surround the closed ends of the both-side sipes, it is possible to improve the sipe density while improving the block rigidity. Moreover, since the surrounding sipes are provided on both sides of the block, it is possible to make the collapse of the block pieces uniform. As a result, it is easy to obtain an appropriate deflection of the block piece for improving the ice performance, the wear resistance performance is good, and the edge effect and the water removal effect are sufficiently maintained to improve the ice performance.

  In the above, the surrounding sipe is a branch sipe branched from the central sipe, and the branch positions of the branch sipe are all within 1/3 of the block width based on the tire width direction from both side edges of the block. It is preferable to be provided in the region. According to this structure, since the enclosure sipe communicates with the central sipe, the drainage property is improved, and the sipe density can be increased by the amount that the length can be extended. In addition, since the branch sipes are provided in the above-described region, the front-rear rigidity of the block is increased particularly at the end of the block where the load is increased when a front-rear force is generated during braking or the like. Step wear (uneven wear) can be prevented.

  Moreover, it is preferable that the surrounding sipe is formed in a C shape, a U shape, or a V shape. When the surrounding sipe has such a shape, the balance between maintaining the rigidity of the block and the effect of improving the sipe density is good, and it is preferable from the viewpoint of workability and durability.

  Further, it is preferable that the central sipe is a wave sipe and the both-side sipe is a straight sipe. When the center sipe is a waved sipe, the sipe density can be increased even near the center of the block, and the edge effect and the water removal effect can be further improved. Further, if the both-side sipes are straight sipes, the distance from the surrounding sipes can be increased, and chipping of block pieces is less likely to occur.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an enlarged view of a main part showing an example of a tread pattern block in the pneumatic tire of the present invention. FIG. 2 is an enlarged view of a main part of the block shown in FIG.

  The pneumatic tire of the present invention includes a tread pattern having a block in which a plurality of sipes are formed. In the present embodiment, as shown in FIG. 1, an example is shown in which sipes 10 are formed in a block 1 divided by main grooves extending in the tire circumferential direction PD and the tire width direction WD. The portion other than the block 1 of the tread pattern may be any pattern. For example, a portion in which similar blocks are provided on the left and right of the block 1 may be mentioned.

  As shown in FIG. 1, the block 1 includes a central sipe 11 that extends from the block center BC to both sides along the tire width direction WD and has both ends arranged in the block. In the present embodiment, an example is shown in which a plurality of wavy central sipes 11 are formed in a direction parallel to the tire width direction WD.

  The central sipe 11 may be a straight sipe, but is preferably a wave sipe. The wavy sipe in the present invention includes a zigzag sipe, and its cross-sectional shape is not limited to that close to a sine wave, but is similar to a wavy line or a rectangular wave in which straight lines and curves are alternately combined, etc. Any shape is acceptable. Further, the wavy center sipe 11 may be linear at both ends.

  When the central sipe 11 is a wavy sipe, the amplitude (the sum of the heights of the tops on both sides) is preferably 1 to 2 mm in order to appropriately express the characteristics of a so-called wave sipe, and the period of the central sipe 11 ( For example, the distance between the convex and convex apex portions is preferably 2 to 5 mm.

  The length of the central sipe 11 (the linear distance between the closed ends on both sides) is 30 to 50% of the block width BW based on the tire width direction WD of the block 1 in relation to the position where the surrounding sipe is provided. Is preferable, and it is more preferable that it is 35 to 45%. Note that the closed end of the central sipe 11 does not need to coincide with the branch position BP of the branch sipe 13 that is the surrounding sipe, and may be disposed inside or outside the surrounding sipe.

  In addition, as shown in FIG. 1, the block 1 is provided with both-side sipes 12 that are provided on both sides of the central sipe 11 at intervals and open to the block end sides 1 a and 1 b, respectively. In the present embodiment, an example in which a plurality of linear both-side sipes 12 are formed in parallel to the tire width direction WD is shown, but a wavy both-side sipes 12 may be used.

  The sipe 12 on both sides has a closed end 12a. The distance between the closed end 12a and the closed end of the central sipe 11 is preferably 0.5 to 4 mm, and more preferably 1 to 2 mm. If this distance is less than 0.5 mm, it is too narrow and block breakage occurs, and the rigidity tends to decrease. If it exceeds 4 mm, the sipe density tends to decrease and the ice performance tends to decrease.

  Further, as shown in FIG. 1, the block 1 is provided with an enclosing sipe provided to be spaced from the both-side sipe 12 so as to enclose the closed end 12 a of the both-side sipe 12. In the present embodiment, an example in which the surrounding sipe is a C-shaped branch sipe 13 branched from the central sipe 11 is shown.

  Here, “so as to surround the closed end 12 a” means that the positional relationship between the closed end 13 a of the surrounding sipe (branch sipe 13) and the closed ends 12 a of both side sipes 12 is as shown in FIG. And the angle θ is 200 ° or more. At this time, the positions of both closed ends 13a of the surrounding sipe do not need to be symmetric with respect to the both-side sipe 12, but when both are symmetric, the closed ends 13a of the enclosed sipe are arranged in the region of the arrow A1. It will be.

  The length L1 of the enclosing sipe in the tire width direction WD is preferably 1.5 to 3.5 mm, and more preferably 2 to 3 mm in order to balance the improvement of the sipe density and the maintenance of block rigidity. The length L2 of the encircling sipe in the tire circumferential direction PD is preferably 2 to 4 mm and more preferably 2.5 to 3.5 mm in order to balance the improvement of the sipe density and the maintenance of block rigidity.

  In the present invention, the innermost ends on both sides of the enclosure sipe or the branch positions BP on both sides of the branch sipe 13 both have the block width BW based on the tire width direction WD from the side edges 1a and 1b on both sides of the block 1. It is preferable to be provided in a region within 1/3. When the branching position BP or the like is located on the inner side of this region, when a longitudinal force occurs during braking or the like, the longitudinal rigidity of the block tends to decrease, particularly at the end of the block where the load becomes large, and step wear tends to occur. is there. Further, it is preferable that the branch positions BP and the like are provided in an area of 1/6 or more of the block width BW with respect to the tire width direction WD from the side edges 1a and 1b on both sides of the block 1. If the branch position BP is located outside this region, the effect of improving the sipe density tends to be small even if the surrounding sipe is formed.

  From the viewpoint of improving the edge effect, the water removal effect, and the adhesion effect, the center sipe 11, the side sipe 12, and the surrounding sipe preferably have a groove width of 0.1 to 0.5 mm.

In the present embodiment, an example in which the combination of the central sipe 11, the both-side sipe 12, and the surrounding sipe is provided substantially in parallel with the entire block 1 is shown. In the present invention, it is preferable that the sipe density in the total of the sipe 10 is 0.05 to 0.20 mm / mm ^2, more preferably 0.1~0.18mm / mm ^2.

  Further, the groove depth of the sipe 10 is preferably 30 to 80% of the main groove depth. The sipe 10 is generally formed so as to be perpendicular to the block surface, but the sipe 10 may be slightly inclined (for example, 15 ° or less) with respect to the normal line of the block surface.

  The pneumatic tire of the present invention is the same as a normal pneumatic tire except that it includes the tread pattern 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 easy to obtain an appropriate deflection of the block piece for improving the ice performance, has good wear resistance performance, and sufficiently maintains the edge effect and water removal effect to improve the ice performance. In particular, it is useful as a studless tire.

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

  (1) In the above-described embodiment, an example in which a sipe is formed in a substantially square block is shown. However, the block 1 is not limited to this shape, and is a parallelogram, a V-shape, a pentagon, or a curve base tone. It may be a block. Moreover, the rib extended linearly in a tire circumferential direction with the block, and the rib extended zigzag in a tire circumferential direction may be formed.

  (2) In the above-described embodiment, an example in which a central sipe or the like is provided in the entire block and a C-shaped branch sipe is provided has been described. However, in the present invention, FIGS. Various forms are possible as shown in FIG.

  In the example shown in FIG. 3A, one combination of the central sipe 11, the double sipe 12, and the surrounding sipe is provided at both ends of the block 1 in the tire circumferential direction PD. Three conventional wavy sipes 14 are provided. In the present invention, as in this example, it is only necessary to have a combination of at least one set of the central sipe 11, the two-side sipe 12, and the surrounding sipe. However, in order to improve the wear resistance and ice performance most effectively, it is preferable that the above combination is provided in the entire block 1.

  In the example shown in FIG. 3B, a V-shaped branch sipe 13 is provided. In the present invention, as shown in FIG. 2, the positional relationship between the closed end 13a of the enclosure sipe and the closed ends 12a of the both-side sipes 12 is an enclosure sipe whose angle θ is 200 ° or more with the closed end 12a as the center. In addition to the C shape, the U shape, or the V shape, a shape in which a part of a polygon such as a circle, an ellipse, a triangle, a quadrangle, or a pentagon is opened may be used. Among them, a C-shaped, U-shaped, or V-shaped enclosure sipe is preferable.

  In the example shown in FIG. 3C, a U-shaped enclosure sipe that is slightly inclined with respect to the tire width direction WD and does not communicate with the central sipe 11 is provided. In the present invention, the enclosure sipe may not communicate with the central sipe 11 as described above. With such a structure, the block rigidity can be further improved and the effect of preventing uneven wear can be further enhanced.

  Moreover, although the center sipe 11 is provided on the straight line which connects between the both-side sipe 12, in this invention, the both-side sipe 12 and the center sipe 11 do not need to be the same linear shape, and tire circumferential direction PD It may be misaligned. Moreover, the center sipe 11 and the both-side sipe 12 may incline with respect to the tire width direction WD, and each inclination angle may differ. When the center sipe 11 and the both-side sipe 12 are inclined, the angle is preferably within ± 15 ° with respect to the tire width direction WD.

  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 performance Tires are mounted on a real vehicle (domestic 3000cc class FR sedan), run on a frozen road under the load condition of one passenger, and ABS is applied by applying braking force at a speed of 40km / h. The braking distance was evaluated with 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) Wear resistance performance When wearing tires on a real vehicle (domestic 3000cc class FR sedan) and traveling on a dry paved road for 8000km under the load conditions of one passenger, the amount of wear on the step (the sipe and sipe due to wear) Step) 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.

Comparative example 1 (conventional product)
A radial tire having a size of 205 / 65R15 was manufactured by forming a sipe with the following size in a tread pattern including the entire surface (5 rows) of blocks (28 mm long and 28 mm wide) shown in FIG. Table 1 shows the results of each performance evaluation described above using this tire. The sipe depth was 7 mm, the sipe groove width was 0.3 mm, the period was 4 mm, the amplitude was 1.2 mm, the straight portion length was 6 mm × 2, and the sipe interval was 4 mm.

Example 1
A radial tire having a size of 205 / 65R15 was manufactured by forming a sipe with the following size in a tread pattern (the same as Comparative Example 1 except for the sipe) having the block shown in FIG. Table 1 shows the results of each performance evaluation described above using this tire. Three wavy sipes 14 are made the same as in comparative example 1, the other two sets of sipes have a common depth of 7 mm and a sipe groove width of 0.3 mm, the distance between branch positions on both sides of the central sipe is 16 mm, the period The length of the sipe 12 on both sides was 4.5 mm, the size of the circular enclosure sipe was 3.0 mm in diameter, and the distance between the closed ends was 1.5 mm.

Example 2
A radial tire having a size of 205 / 65R15 was manufactured by forming a sipe with the following size in a tread pattern having the entire block shown in FIG. Table 1 shows the results of each performance evaluation described above using this tire. The five sets of sipe have a common depth of 7 mm and a sipe groove width of 0.3 mm. The distance between the branch positions on both sides of the central sipe is 16 mm, the period is 4 mm, the amplitude is 1.2 mm, and the length of both sipe 12 is 4. The size of the circular enclosure sipe was 5 mm, the diameter was 3.0 mm, and the distance between the closed ends was 1.5 mm.

Example 3
In the second embodiment, the distance between the branch positions of the central sipe is shortened by 0.8 mm on both sides to form a sipe in which the central sipe and the surrounding sipe do not communicate with each other. A radial tire was manufactured. Table 1 shows the results of each performance evaluation described above using this tire.

Comparative Example 2
A radial tire was manufactured in the same manner as in Example 1 except that the sipe shown in FIG. 4B was formed by making the surrounding sipe into an annular sipe and communicating with both side sipe in Example 1. Table 1 shows the results of each performance evaluation described above using this tire.

Comparative Example 3
A radial tire having a size of 205 / 65R15 was manufactured by forming a sipe with the following size in a tread pattern (except for the sipe, the same as in Comparative Example 1) having the block shown in FIG. Table 1 shows the results of each performance evaluation described above using this tire. The sipe 16, 17 has a depth of 7 mm, a sipe groove width of 0.3 mm, a wavy portion period of 4 mm, and an amplitude of 1.2 mm, a straight portion length of 4.5 mm, a sipe tip (closed end) and a block end. The distance to the side was 1.5 mm.

  As the results in Table 1 show, the ice braking performance and wear resistance performance of the examples were significantly improved over the conventional products. On the other hand, in Comparative Example 2 in which the annular enclosure sipe was formed, the effect of improving the ice performance and the wear resistance performance was insufficient due to the large fall of the block pieces and the reduction of the ground contact area. Moreover, in the comparative example 3 in which the sipe extending from one end of the block branches and extends to the vicinity of the other end, the fall of the block piece is large and the ground contact area is reduced. The improvement effect of was insufficient.

The principal part enlarged view which shows an example of the block in the pneumatic tire of this invention FIG. 1 is an enlarged view of the main part showing the main part of the block shown in FIG. The principal part enlarged view which shows the other example of the block in the pneumatic tire of this invention Main part enlarged view showing the shape of the sipe used in the comparative example

Explanation of symbols

1 block 1a, 1b block edge 10 sipe 11 central sipe 12 both sides sipe 12a closed end of both sides sipe 13 branch sipe (enclosure sipe)
BC Block center BP Branch position WD Tire width direction PD Tire circumferential direction

Claims (4)

In a pneumatic tire having a tread pattern having a block in which a plurality of sipes are formed,
The block has a central sipe extending from the center of the block to both sides along the tire width direction and having both ends arranged in the block, and both sides provided at intervals on both sides of the central sipe and open to the end of the block. A pneumatic tire comprising: a sipe; and an enclosing sipe provided at an interval so as to enclose the closed ends of both side sipes.   The enclosure sipe is a branch sipe branched from the central sipe, and the branch positions of the branch sipe are all provided in a region within 1/3 of the block width with respect to the tire width direction from both side edges of the block. The pneumatic tire according to claim 1.   The pneumatic tire according to claim 1 or 2, wherein the surrounding sipe is formed in a C shape, a U shape, or a V shape. The pneumatic tire according to any one of claims 1 to 3, wherein the central sipe is a wave sipe, and the both-side sipe is a straight sipe.

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