JP6015249B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire in which a large number of sipes are provided in a tread portion, and more particularly to a pneumatic tire that can improve performance on ice and uneven wear resistance.

  In a pneumatic tire for winter typified by a studless tire, a plurality of circumferential grooves extending in the tire circumferential direction and a plurality of lateral grooves extending in the tire width direction are formed in the tread portion, and these circumferential grooves and lateral grooves are formed. Thus, a plurality of blocks are partitioned, and a plurality of sipes extending in the tire width direction are formed in each block. As described above, there is known a technique for improving the performance on ice by removing a water film on the ice surface by arranging a large number of sipes in the tread portion. In general, when the number of sipes is increased to increase the sipe density in order to further improve the performance on ice, the block rigidity is lowered and the steering stability on the dry road surface tends to be lowered.

  On the other hand, a convex portion is formed on one of the pair of wall surfaces facing each other within each sipe, and a concave portion that engages with the convex portion is formed on the other of the pair of wall surfaces. It has been proposed to regulate the collapse (see, for example, Patent Document 1). In this case, it is possible to suppress the falling of the block and exhibit excellent performance on ice.

  In addition, the rigidity of each block varies depending on the size of the block and the length of the sipe formed on the block. If the rigidity is greatly different between the blocks, this causes uneven wear. . In particular, in winter pneumatic tires, since a relatively soft cap compound is used, uneven wear tends to be noticeable. Therefore, in a pneumatic tire for winter in which a plurality of sipes are provided in each block, it is required not only to improve the performance on ice but also to improve uneven wear resistance.

JP-A-5-58118

  An object of the present invention is to provide a pneumatic tire capable of improving performance on ice and uneven wear resistance.

In order to achieve the above object, the pneumatic tire of the present invention is provided with a plurality of circumferential grooves extending in the tire circumferential direction and a plurality of lateral grooves extending in the tire width direction in the tread portion. In a pneumatic tire that divides a plurality of blocks and has each block provided with a plurality of sipes extending in the tire width direction, a convex portion is formed on one of a pair of wall surfaces facing each other in each sipe, and the pair of wall surfaces On the other hand, a concave portion that meshes with the convex portion is formed, and the height of the convex portion is made relatively small in a block having a relatively large block stiffness index E calculated based on the following formula (1). In a block having a relatively small stiffness index E, the height of the convex portion is made relatively large , the maximum depth of the sipe is set to 50% or more of the depth of the circumferential groove, and the convex portion is set to its maximum height. The position is It is characterized in that it has arranged to be included in the tread side region having the maximum depth of less than 50% of the serial sipes.
E = S / (Σ (Ls) × Ds ² ) (1)
However, S: Ground contact area of each block (mm ² )
Ls: Sipe arrangement length on the block tread (mm)
Ds: Average depth of sipe (mm)

  In the present invention, a convex portion is formed on one of a pair of wall surfaces facing each other within each sipe, and a concave portion that meshes with the convex portion is formed on the other of the pair of wall surfaces. It can regulate the fall and improve the performance on ice. In addition, by making the height of the convex portion relatively small in a block having a relatively large block stiffness index E, and by making the height of the convex portion relatively large in a block having a relatively small block stiffness index E, It is possible to make the block rigidity uniform and suppress the occurrence of uneven wear. As described above, according to the present invention, not only the performance on ice but also the uneven wear resistance can be improved by effectively using the concave and convex portions formed on the wall surface of the sipe.

  In the present invention, the maximum depth of the sipe is 50% or more of the depth of the circumferential groove, and the convex portion is included in the tread side region where the maximum height position is less than 50% of the maximum depth of the sipe. It is preferable to arrange. Thereby, the improvement effect of on-ice performance and uneven wear resistance can be enhanced.

  The maximum height of the convex portion is preferably 0.5 mm to 2.5 mm. Thereby, on-ice performance and uneven wear resistance can be improved without impairing the mold releasability. In particular, it is preferable to make the maximum height of the highest convex portion of the convex portions larger than the groove width of the sipe, and further make the maximum height of the lowest convex portion larger than the groove width of the sipe. Thereby, the meshing of the convex portion and the concave portion can be promoted, and the effect of improving the performance on ice and the uneven wear resistance can be enhanced.

  Moreover, it is preferable to provide a convex part and a recessed part in 70% or more of the sipe formed in the tread part. That is, it is not necessary to provide the convex part and the concave part in all the sipes formed in the tread part. However, by arranging the convex parts and the concave parts in 70% or more of the sipes, it is possible to enhance the improvement effect on ice and uneven wear resistance. .

In the present invention, the ground contact area S (mm ² ) of each block means the area of an area defined by the contour of the block tread (including the area of the sipe portion), and the sipe arrangement length Ls ( mm) means the distance between the ends of the sipe. Further, Σ (Ls) is the total sum of sipe arrangement lengths Ls in each block. The average sipe depth Ds (mm) is an average depth calculated from the depth of each part of the sipe and the length of each part.

It is meridian sectional drawing which shows the pneumatic tire which consists of embodiment of this invention. It is an expanded view which shows an example of the tread pattern of the pneumatic tire of this invention. FIG. 3 is a side view showing a block having a relatively small block stiffness index E in the tread pattern of FIG. 2. FIG. 4 is a cross-sectional view taken along the line IV-IV in FIG. 3. It is principal part sectional drawing of the block of FIG. FIG. 3 is a side view showing a block having a relatively large block stiffness index E in the tread pattern of FIG. 2. FIG. 7 is a cross-sectional view taken along arrow VII-VII in FIG. 6. It is principal part sectional drawing of the block of FIG. It is a top view which shows the modification of the block in the pneumatic tire of this invention. FIG. 10 is a side view showing the block of FIG. 9. It is XI-XI arrow sectional drawing of FIG. It is principal part sectional drawing of the block of FIG. It is sectional drawing which shows the block which changed the depth of the sipe.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. FIGS. 1 and 2 show a pneumatic tire according to an embodiment of the present invention, and FIGS. 3 to 8 show an essential part thereof.

  As shown in FIG. 1, the pneumatic tire of this embodiment includes a tread portion 1 that extends in the tire circumferential direction and has an annular shape, and a pair of sidewall portions 2 that are disposed on both sides of the tread portion 1. A pair of bead portions 3 are provided inside the sidewall portions 2 in the tire radial direction.

  A carcass layer 4 is mounted between the pair of bead portions 3 and 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is wound up around the bead core 5 disposed in each bead portion 3 from the tire inner side to the outer side. As a reinforcing cord for the carcass layer 4, an organic fiber cord is generally used, but a steel cord may be used. A bead filler 6 made of a rubber composition having a triangular cross-section is disposed on the outer periphery of the bead core 5.

  On the other hand, a plurality of belt layers 7 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 7 include a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and are arranged so that the reinforcing cords cross each other between the layers. In the belt layer 7, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set in a range of, for example, 10 ° to 40 °. A steel cord is preferably used as the reinforcing cord of the belt layer 7. On the outer peripheral side of the belt layer 7, at least one belt cover layer 8 in which reinforcing cords are arranged at an angle of 5 ° or less with respect to the tire circumferential direction is disposed for the purpose of improving high-speed durability. . It is desirable that the belt cover layer 8 has a jointless structure in which a strip material formed by aligning at least one reinforcing cord and covering with rubber is continuously wound in the tire circumferential direction. Further, the belt cover layer 8 may be disposed so as to cover the entire width direction of the belt layer 7, or may be disposed so as to cover only the outer edge portion of the belt layer 7 in the width direction. As the reinforcing cord of the belt cover layer 8, an organic fiber cord such as nylon or aramid is preferably used.

  In addition, although the tire internal structure mentioned above shows the typical example in a pneumatic tire, it is not limited to this.

  As shown in FIG. 2, a plurality of circumferential grooves 11 extending in the tire circumferential direction and a plurality of lateral grooves 12 extending in the tire width direction are formed in the tread portion 1 at intervals in the tire circumferential direction. A plurality of blocks 13 are defined in the tread portion 1 by the circumferential grooves 11 and the lateral grooves 12. Each block 13 is formed with a plurality of sipes 20 extending in the tire width direction. In FIG. 2, E is the tire equator.

  In the pneumatic tire, a convex portion 23 is formed on one of the pair of wall surfaces 21 and 22 facing each other in each sipe 20, and a concave portion 24 that meshes with the convex portion 23 is formed on the other of the pair of wall surfaces 21 and 22. (See FIGS. 3 to 8). Although the shape of the convex part 23 and the recessed part 24 is not specifically limited, For example, it is preferable to make it a hemispherical shape. Moreover, the direction of the convex part 23 is not specifically limited, The convex part 23 can be orientated to the one side of a tire circumferential direction, or the convex part 23 from which an orientation direction differs can be mixed.

Here, in the block 13 having a relatively large block stiffness index E calculated based on the following equation (1), the height of the convex portion 23 is set to be relatively small, and the block stiffness index E is relatively In the small block 13, the height of the convex portion 23 is set to be relatively large.
E = S / (Σ (Ls) × Ds ² ) (1)
However, S: Ground contact area of each block (mm ² )
Ls: Sipe arrangement length on the block tread (mm)
Ds: Average depth of sipe (mm)

When the depth of the sipe 20 is constant, the maximum depth d coincides with the average depth Ds. For example, when the depth of the sipe 20 changes (see FIG. 13), the average depth Ds is The depth Ds1, Ds2, Ds3 of each part of the sipe 20 and the lengths Ls1, Ls2, Ls3 of each part are calculated based on the following equation (2).
Ds = (Ds1 × Ls1 + Ds2 × Ls2 + Ds3 × Ls3) / (Ls1 + Ls2 + Ls3) (2)

  3 to 5 show a block 13a having a relatively small block stiffness index E, and FIGS. 6 to 8 show a block 13b having a relatively large block stiffness index E. Here, while the ground contact area of the block 13 is made substantially constant, the number of sipes 20 arranged in each block 13, that is, the total sum of the arrangement lengths Ls of the sipes 20 on the treads of the block 13 is changed. Although the rigidity index E is changing, the block rigidity index E may be changing by changing the contact area of the block 13 based on the pitch variation on the tire circumference.

  As shown in FIGS. 3 to 5, in the block 13 a having a relatively small block stiffness index E (E1), the height h <b> 1 of the convex portion 23 is set to be relatively large. On the other hand, as shown in FIGS. 6 to 8, in the block 13b having a relatively small block stiffness index E (E2), the height h2 of the convex portion 23 is set to be relatively small. That is, when E1 <E2, the relationship h1> h2 is established. When n types of blocks 13 having different block stiffness indices E are arranged in the tread portion 1, when E1 <E2... <En, the relationship of h1> h2. desirable. However, it is not necessary that the block stiffness index E and the height of the convex portion 23 have a strict inverse proportional relationship. For example, even when three or more types of blocks 13 having different block stiffness indices E are arranged in the tread portion 1, two types of convex portions 23 having different heights can be employed. In any case, it is preferable to make the height of the convex portion 23 different from the others in 10% or more of the sipe 20 having the convex portion 23.

  In the pneumatic tire configured as described above, a convex portion 23 is formed on one of the pair of wall surfaces 21 and 22 facing each other within each sipe 20, and the concave portion meshing with the convex portion 23 on the other of the pair of wall surfaces 21 and 22. 24 is formed, the fall of the block 13 is regulated by the engagement of the convex portion 23 and the concave portion 24, and the performance on ice can be improved.

  In addition, in the block 13b having a relatively large block stiffness index E, the height h2 of the convex portion 23 is made relatively small, and in the block 13a having a relatively small block stiffness index E, the height h1 of the convex portion 23 is made relatively. By increasing the width, the rigidity of the block 13 can be made uniform in the tread portion 1 and the occurrence of uneven wear can be suppressed. As described above, by effectively using the concave portion 23 and the convex portion 24 formed on the wall surfaces 21 and 22 of the sipe 20, the performance on ice and the uneven wear resistance can be improved at the same time.

  In the pneumatic tire, the maximum depth d of the sipe 20 is set to 50% or more of the depth D of the circumferential groove 11, and more preferably in the range of 50% to 100%. On the other hand, at least some of the convex portions 23 are arranged so that the maximum height position is included in the tread side region A in which the maximum height position is less than 50% of the maximum depth d of the sipe 20. By arranging the convex portion 23 in the tread surface region A in this way, the fall of the block 13 can be effectively suppressed, and the improvement effect on ice performance and uneven wear resistance can be enhanced.

  In the pneumatic tire, the maximum heights h1 and h2 of the convex portions 23 are set in a range of 0.5 mm to 2.5 mm, more preferably in a range of 0.5 mm to 1.5 mm. Thereby, on-ice performance and uneven wear resistance can be improved without impairing the mold releasability. If the maximum heights h1 and h2 of the convex portions 23 are less than 0.5 mm, the effect of improving the performance on ice and uneven wear resistance is lowered, and conversely, if it exceeds 2.5 mm, the releasability is inhibited. In particular, the maximum height h1 of the highest convex portion 23 is preferably larger than the groove width g of the sipe 20, and more preferably, the maximum height h2 of the lowest convex portion 23 is larger than the groove width g of the sipe 20. It is good to enlarge. Thereby, the meshing of the convex part 23 and the concave part 24 can be promoted, and the effect of improving the performance on ice and the uneven wear resistance can be enhanced. The groove width g of the sipe 20 is preferably 0.3 mm to 1.5 mm in order to make the edge effect work effectively.

  Further, the convex portion 23 and the concave portion 24 are formed in 70% or more, preferably 90%, of the sipe 20 formed in the tread portion 1. As described above, by disposing the convex portions 23 and the concave portions 24 in 70% or more of the sipe 20 formed in the tread portion 1, it is possible to enhance the effect of improving the performance on ice and the uneven wear resistance.

  FIGS. 9-12 shows the modification of the block in the pneumatic tire of this invention. 9 to 12, the same components as those in FIGS. 1 to 8 are denoted by the same reference numerals, and detailed description thereof is omitted.

  9 to 12, a plurality of sipes 20 having a zigzag shape extending in the tire width direction are formed in the block 13. A convex portion 23 is formed on one of the pair of wall surfaces 21, 22 facing each other within each sipe 20, and a concave portion 24 that meshes with the convex portion 23 is formed on the other of the pair of wall surfaces 21, 22.

  Even when the convex portions 23 and the concave portions 24 are provided on the wall surfaces 21 and 22 of the sipe 20 having such a zigzag shape, the height of the convex portion 23 is increased in the block 13 having a relatively large block stiffness index E as described above. In the block 13 having a relatively small block rigidity index E, the height of the convex portion 23 is relatively increased, thereby improving the uneven wear resistance in addition to improving the performance on ice. Can be obtained.

  In the present embodiment, a plurality of convex portions 23 are arranged along the depth direction of the sipe 20, and the maximum height position of the convex portion 23 on the tread surface side is less than 50% of the maximum depth d of the sipe 20. The sipe bottom-side convex part 23 is arranged so as to be included in the tread surface side area A, and the maximum height position is included in the bottom side area B where the maximum depth d of the sipe 20 is 50% or more. Has been placed. Thus, the convex part 23 can be arranged not only in the tread side area A but also in the bottom area B.

  Moreover, in this embodiment, although the convex part 23 contained in the tread side area | region A and the convex part 23 contained in the bottom side area | region B are arrange | positioned so that it may protrude in a mutually different direction, the direction of the convex part 23 is required. It can be appropriately selected depending on the tire characteristics.

  In the tire size 195 / 65R15, the tread portion is provided with a plurality of circumferential grooves extending in the tire circumferential direction and a plurality of lateral grooves extending in the tire width direction, and a plurality of blocks are defined by the circumferential grooves and the lateral grooves, In a pneumatic tire in which each block is provided with a plurality of sipes extending in the tire width direction, a plurality of convex portions are formed on one of a pair of wall surfaces facing in each sipe, and a convex portion is formed on the other of the pair of wall surfaces. A plurality of concave portions that mesh with each other, and a height h1 of the convex portion in a block having a relatively small block stiffness index E (E1 = 0.1) and a block having a relatively large block stiffness index E (E2 = 0.15) Example 1 to 3 and Comparative Examples 1 to 2 in which the height h2 of the convex part in) and the ratio of sipes having convex parts and concave parts among the sipes formed in the tread part are set as shown in Table 1 It was manufactured tire.

  For comparison, a tire according to a conventional example in which a convex portion and a concave portion are not provided on the wall surface of the sipe was prepared. In the conventional example, Examples 1 to 3 and Comparative Examples 1 and 2, the depth of the circumferential groove was 9 mm, while the maximum depth of the sipe was 7 mm. The groove width of the sipe was set to 0.4 mm. In Examples 1 to 3 and Comparative Examples 1 to 2, the convex portions were arranged so that the maximum height position was included in the tread side region where the maximum height position was less than 50% of the maximum depth of the sipe. Further, among sipes having convex portions, sipes having a convex portion height of h1 were set to 15%, and sipes having a convex portion height of h2 were set to 85%.

  For these test tires, braking performance on ice and uneven wear resistance were evaluated by the following evaluation methods, and the results are also shown in Table 1.

Ice braking performance:
Each test tire is assembled to a wheel with a rim size of 15 x 6 JJ and mounted on a test vehicle. Under a condition of air pressure of 210 kPa, the braking distance from the running state of 40 km / h on ice to braking and complete stop is measured. did. The evaluation results are shown as an index with the conventional example being 100, using the reciprocal of the measured value. The larger the index value, the better the braking performance on ice.

Uneven wear resistance:
Each test tire is mounted on a wheel with a rim size of 15 x 6 JJ and mounted on a test vehicle. A running test of 20,000 km on an asphalt road surface is performed under conditions of air pressure of 210 kPa. Was measured. The evaluation results are shown as an index with the conventional example being 100, using the reciprocal of the measured value. The larger the index value, the better the uneven wear resistance.

  As can be seen from Table 1, since the tires of Examples 1 to 3 are set to satisfy h1> h2 with respect to E1 <E2, the braking performance on ice is improved in comparison with the conventional example, and Uneven wear resistance was improved. On the other hand, the tires of Comparative Examples 1 and 2 showed no improvement in uneven wear resistance.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core 6 Bead filler 7 Belt layer 8 Belt cover layer 11 Circumferential groove 12 Lateral groove 13,13a, 13b Block 20 Sipe 21,22 Wall surface 23 Convex part 24 Concave part

Claims (5)

The tread portion is provided with a plurality of circumferential grooves extending in the tire circumferential direction and a plurality of lateral grooves extending in the tire width direction. The circumferential grooves and the lateral grooves define a plurality of blocks, and each block extends in the tire width direction. In a pneumatic tire provided with a plurality of sipes, a convex portion is formed on one of a pair of wall surfaces facing in each sipe, and a concave portion that meshes with the convex portion is formed on the other of the pair of wall surfaces. 1) The height of the convex portion is relatively small in a block having a relatively large block stiffness index E calculated based on the equation, and the height of the convex portion is in a block having a relatively small block stiffness index E. The maximum depth of the sipe is 50% or more of the depth of the circumferential groove, and the maximum height position of the convex portion is less than 50% of the maximum depth of the sipe. In the tread area A pneumatic tire characterized by being arranged to Murrell so.
E = S / (Σ (Ls) × Ds ² ) (1)
However, S: Ground contact area of each block (mm ² )
Ls: Sipe arrangement length on the block tread (mm)
Ds: Average depth of sipe (mm) The pneumatic tire according to claim 1 , wherein the maximum height of the convex portion is set to 0.5 mm to 2.5 mm. The highest pneumatic tire according to any one of claims 1 to 2, the maximum height of the convex portion, characterized in that larger than the groove width of the sipes of said convex portion. The pneumatic tire according to claim 3 , wherein a maximum height of the lowest convex portion among the convex portions is larger than a groove width of the sipe. The pneumatic tire according to any one of claims 1 to 4, characterized in that a said convex portion and the concave portion to 70% or more of the sipes formed in the tread portion.

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