JP6545581B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire having sipes formed on land portions of a tread surface, and is particularly useful as a studless tire.

  Conventionally, in a studless tire, notches called sipes are formed on land portions such as blocks and ribs. Due to the edge effect of the sipe and the water removal effect, traveling on an ice road surface with a low coefficient of friction can be stabilized, and so-called ice performance can be enhanced. As such a sipe, a two-dimensional sipe formed in a two-dimensional shape whose shape does not change in the depth direction is known, and a planar sipe or a wavy sipe is put to practical use.

  Also, as described in Patent Documents 1 to 6, a three-dimensional sipes formed in a three-dimensional shape whose shape changes in the depth direction is also known. In the three-dimensional sipe, excessive deformation of the land portion is suppressed because the wall surfaces of the sipe are engaged with each other at the time of braking or turning, so that edge effects and water removal effects can be reliably exhibited. However, if the three-dimensional shape is uniformly formed, only deformation in a certain direction (for example, the front-rear direction) may be suppressed, and deformation in the other direction (for example, the lateral direction) is sufficiently suppressed. As a result, wear resistance and uneven wear resistance may be reduced.

  On the other hand, it has been found that there is room for improvement in ice performance and the like simply by adopting a three-dimensional shape that can suppress deformation in a plurality of directions (for example, the front and back direction and the lateral direction). According to the study of the present inventor, the reason is that the ease of deformation of the land varies depending on the site of the sipes and also depending on the wear stage of the land, and a concrete that takes these into consideration Sipe structure is not known.

Unexamined-Japanese-Patent No. 2004-314758 Unexamined-Japanese-Patent No. 2006-27558 JP 2002-321509 A JP 2005-104188 A International Publication No. 2006/001446 Unexamined-Japanese-Patent No. 2007-22361

  The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to provide a pneumatic tire which can exhibit excellent wear resistance performance and uneven wear resistance performance while securing ice performance.

The above object can be achieved by the present invention as described below. That is, in the pneumatic tire according to the present invention, the sipe formed on the land portion of the tread surface is located on the center sipe bottom side in the length direction, and has a two-dimensional shape whose shape does not change along the depth direction. The formed 2D center portion, the tread surface side of the center in the length direction, the 3D center portion formed in a three-dimensional shape whose shape changes along the depth direction, and the both ends in the length direction And 3D side portions formed in a three-dimensional shape whose shape changes along the depth direction, wherein the 3D center portion and the 3D side portion are respectively opened by the tread surface, and the opening of the 3D center portion is The three-dimensional shape of the 3D center portion is formed in a wave shape and extends in the depth direction while being bent with the center convex portion which is a convex shape in the length direction, and the three-dimensional shape of the 3D side portion is in the width direction Rhino that becomes convex shape Extending in the depth direction while bending with a convex portion, in which longitudinally extending ridge of the side projections as a starting point the center convex portion.

  In the land portion where such sipes are formed, deformation in the length direction is mainly suppressed by the 3D center portion, and deformation in the width direction is mainly suppressed by the 3D side portion. Both the tread side of the sipe where the 3D center portion is located and both ends of the sipe where the 3D side portion is located are portions where the deformation of the land portion is relatively large, and such portions are formed in a three-dimensional shape And excessive deformation of land can be effectively suppressed. A 2D center portion is located on the bottom side of the central sipe in the length direction, which is a portion where deformation of the land portion is relatively small.

  In the early and middle stages of wear, deformation is increased due to the relatively low rigidity of the land area, but according to this tire, excessive deformation of the land area is caused by the 3D center area and the 3D side area as described above Can be suppressed. In addition, at the stage after the middle stage of wear, deformation is small because the rigidity of the land is relatively high, but with this tire, the rigidity of the land is high because the 3D center portion is decreasing or disappearing. And the edge effect of sipes is well exhibited. In addition, even after the middle stage of wear, the rigidity of the land portion is not excessively reduced because the 3D side portions are positioned at both ends of the sipe.

  In addition, the ridgeline of the side convex portion included in the three-dimensional shape of the 3D side portion extends in the length direction starting from the central convex portion included in the three-dimensional shape of the 3D center portion. It is possible to prevent the side portion from being connected smoothly and the portion becoming irregularly shaped. As a result, when the wall surfaces of the sipe are engaged, local concentration of stress on the connection between the 3D center portion and the 3D side portion can be prevented, and the occurrence of cracks or defects in the sipe can be prevented. .

  It is preferable that ridge lines of two of the side convex portions adjacent in the depth direction extend in the length direction starting from the same center convex portion. As a result, it is possible to effectively suppress the deformation of the land portion at both ends of the sipe where the side convex portions are densely arranged and the deformation of the land portion tends to be larger than the center of the sipe. When the sipes open on the side of the land, the effect is more remarkable.

  The three-dimensional shape of the 3D center portion may be a laterally V-shaped bent at one point in the depth direction. According to the 3D center portion formed in such a three-dimensional shape, excessive deformation of the land portion in the length direction can be favorably suppressed. Moreover, compared with the shape bent in multiple places of the depth direction, the resistance at the time of the demolding in the vulcanization process of a tire can be made small.

  It is preferable that the distance from the tread surface to the boundary between the 2D center portion and the 3D center portion is 20 to 70% of the sipe depth. Moreover, it is preferable that the distance from the sipe end to the boundary between the 2D center portion and the 3D side portion is 10 to 40% of the sipe length.

A plan view showing an example of a tread surface of a pneumatic tire according to the present invention Perspective view of block Three views of sipes A perspective view showing the wall of a sipe The figure which shows typically the field of 2D center part, 3D center part and 3D side part Front view of sipe in tire of comparative example

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

  The tread surface Tr shown in FIG. 1 is provided with a block 1 as a land portion. Each block 1 is divided by a main groove 2 and a lateral groove 3. The main groove 2 extends continuously in the tire circumferential direction, and the lateral groove 3 extends in a direction intersecting the main groove 2. The block 1 is formed in a rectangular shape in plan view, but is not limited thereto. Instead of or in addition to such blocks, ribs extending continuously in the circumferential direction of the tire may be provided as land portions.

  As shown enlarged in FIG. 2, a sipe 4 is formed in the block 1. The sipe 4 extends in the tire width direction which is the lateral direction in FIG. In order to improve the ice performance, particularly the starting performance and braking performance on an ice road surface, it is preferable that the sipes 4 extend in the direction intersecting the tire circumferential direction as described above. At least one sipe may be formed in the block 1. Therefore, for example, a plurality of sipes 4 arranged at intervals in the tire circumferential direction may be provided in one block 1.

  The longitudinal direction LD is the longitudinal direction of the sipe 4 and in the present embodiment is the same direction as the tire width direction. The sipe length L4 is measured as the linear distance between the ends of the sipe 4. The depth direction DD is the depth direction of the sipe 4. The sipe depth D4 is measured as a linear distance from the tread surface to the sipe bottom. The sipe depth D4 is set to, for example, 40 to 80% of the depth of the main groove 2. The width direction WD is the width direction of the sipe 4, and in the present embodiment, is the same direction as the tire circumferential direction. The sipe width W4 is set to, for example, 0.3 to 2.0 mm in order to develop a sufficient edge effect.

  FIG. 3 is a trihedral view including (a) plan view, (b) side view and (c) front view of the sipe 4. FIG. 4 is a perspective view showing the wall surface of the sipe 4. As shown in FIGS. 3 and 4, the sipe 4 formed in the block 1 of the tread surface Tr has a 2D center portion 5 located on the bottom of the central sipe in the longitudinal direction LD and a tread surface of the central in the longitudinal direction LD. It has a 3D center portion 6 located on the side and 3D side portions 7 located on both ends in the length direction LD. FIG. 5 schematically shows those regions.

  The 2D center portion 5 is formed in a two-dimensional shape in which the shape does not change along the depth direction DD. The 3D center portion 6 and the 3D side portion 7 are each formed in a three-dimensional shape whose shape changes along the depth direction DD. However, they are formed in mutually different three-dimensional shapes. Further, the 3D center portion 6 and the 3D side portion 7 are respectively opened at the tread surface. The opening of the 3D center portion 6 extends along the length direction LD while bending in the width direction WD, and is formed in a wave shape in which short sides and long sides are alternately repeated.

  The sipes 4 are formed as open-sided sipes open at both ends at the sides of the block 1. However, the sipe 4 may be formed as a single-sided open sipe with only one end open or as a double-sided closed sipe with both ends closed in a block. The deformation of the block tends to be large at both ends of the sipe 4, particularly around the open sipe end, but since the 3D side portions 7 are positioned at both ends of the sipe 4, the excess of the block 1 is excessive as described later. Can be suppressed. 30% or more of block width in length direction LD is preferable, and 50% or more of sipe length L4 is more preferable.

  The two-dimensional shape of the 2D center portion 5 is formed in a wave shape, and the wall surface is provided with an uneven row extending in the depth direction DD. The cross section in the XX arrow view has substantially the same shape as that in FIG. 3A, and in the 2D center portion 5, such a wave shape continues in the depth direction DD. Although this 2D center portion 5 is formed in a so-called corrugated sipe, it may be a flat sipe whose wall surface is formed flat. In a planar sipe, the cross section has a linear shape, and the linear shape is continuous in the depth direction. By having the 2D center portion 5 of the sipe 4, the resistance during demolding in the tire vulcanization process is reduced as compared to the case where the sipe 4 does not.

  The three-dimensional shape of the 3D center portion 6 extends in the depth direction DD while bending with the center convex portion 61 having a convex shape in the length direction LD. This three-dimensional shape has a structure in which the wall surfaces can be engaged in the longitudinal direction LD. On the wall surface, a concavo-convex row having amplitude in the length direction LD and extending in the depth direction DD is provided. The concavo-convex row includes a portion inclined in one of the length direction LD and a portion inclined in the opposite direction, and they are continuous in the depth direction DD via the center convex portion 61. The concavo-convex row of the 3D center portion 6 is smoothly connected to the concavo-convex row of the 2D center portion 5.

  The three-dimensional shape of the 3D side portion 7 extends in the depth direction DD while bending with the side convex portion 71 having a convex shape in the width direction WD. This three-dimensional shape has a structure in which the wall surfaces can be engaged in the depth direction DD. Both ends of the sipe 4 at which the 3D side portion 7 is positioned have a wave shape having an amplitude in the width direction WD and extending in the depth direction DD as shown in FIG. 3B. In the present embodiment, the wave shape appears on the side surface of the block 1. On the wall surface, ridge lines 71a to 71j of the side convex part 71 extend along the length direction LD, and among them, ridge lines 71a and 71b and ridge lines 71f and 71g respectively extend from the center convex part 61 as a starting point. It extends to the LD.

  In the block 1, deformation in the length direction LD is mainly suppressed by the 3D center portion 6, and deformation in the width direction WD is mainly suppressed by the 3D side portion 7. Both the tread side of the sipe 4 where the 3D center portion 6 is located and both ends of the sipe 4 where the 3D side portion 7 is located are portions where the deformation of the block 1 is relatively large, and such portions are formed in a three-dimensional shape As a result, excessive deformation of the block 1 at the time of braking or turning can be effectively suppressed. The 2D center portion 5 is located on the bottom of the central sipe in the longitudinal direction LD, which is a portion where the deformation of the block 1 is relatively small.

  Although the rigidity of the block 1 is relatively low at the stage from the initial stage to the middle stage of the wear, the deformation becomes large, but according to this tire, as described above, the 3D center portion 6 and the 3D side portion 7 cause excessiveness of the block 1 Can suppress the deformation of Moreover, in the stage after the middle stage of wear, deformation is small because the rigidity of the block 1 is relatively high. However, with this tire, the rigidity of the block 1 is small because the 3D center portion 6 decreases or disappears. The edge effect of the sipe 4 is well exhibited without becoming too high. Moreover, even after the middle stage of the wear, the rigidity of the block 1 is not excessively reduced because the 3D side portions 7 are positioned at both ends of the sipe 4.

  In addition, the ridge lines 71 a and 71 b and ridge lines 71 f and 71 g of the side convex part 71 included in the three-dimensional shape of the 3D side part 7 are long starting from the central convex part 61 included in the three-dimensional shape of the 3D center part 6 By extending in the longitudinal direction LD, the 3D center portion 6 and the 3D side portion 7 are smoothly connected, and it is possible to prevent the portion from being distorted. As a result, when the wall surfaces of the sipe 4 are engaged with each other, stress is prevented from locally concentrating on the connection portion between the 3D center portion 6 and the 3D side portion 7. It can prevent the outbreak.

  In the present embodiment, when the block 1 is deformed in the front-rear direction at the time of starting or braking, the wall surfaces formed in a three-dimensional shape are engaged, and the deformation is mainly suppressed by the 3D side portion 7. Further, when the block 1 is to be deformed in the lateral direction at the time of turning, wall surfaces formed in a three-dimensional shape are engaged, and the deformation is mainly suppressed by the 3D center portion 6. In addition, it is possible to exhibit excellent wear resistance performance and uneven wear resistance performance while responding to the change in the rigidity of the block 1 due to wear and ensuring ice performance. Furthermore, by carefully combining different three-dimensional shapes, it is possible to prevent the occurrence of cracks or defects in the sipe 4.

  The amplitude in the width direction WD in the 3D side portion 7 decreases toward the center in the length direction LD, and the boundary between the 2D center portion 5 and the 3D side portion 7 and the 3D center portion 6 and the 3D side portion 7 At the boundary, they converge substantially linearly as viewed in the longitudinal direction LD. Therefore, the ridgeline of the side convex part 71 inclines so that the center of width direction WD of the sipe 4 may be approached, as it separates from the sipe end, respectively. As a result, the connection at the boundary becomes smooth and it is possible to avoid the irregular shape. As a result, when the wall surfaces of the sipe 4 are engaged with each other, it is possible to prevent the stress from being concentrated locally on the boundary, and to prevent the occurrence of a crack or a defect in the sipe 4.

  In the present embodiment, ridge lines 71 a and 71 b of two side convex portions 71 adjacent in the depth direction DD extend in the length direction starting from the same center convex portion 61. As shown in FIG. 3C, the ridge lines 71a and 71b extend along the length direction LD while inclining in the depth direction DD. The ridge lines 71f and 71g are similarly configured. Accordingly, the deformation of the block 1 can be effectively suppressed at both ends of the sipe 4 in which the side convex portions 71 are densely arranged and the deformation of the block 1 tends to be larger than the center. Since this sipe 4 is opened on both sides of the block 1, its effect can be obtained more remarkably.

  In the present embodiment, as shown in FIG. 3C, the three-dimensional shape of the 3D center portion 6 is in the form of a laterally V-shape bent at one point in the depth direction DD. According to the 3D center portion 6 formed in such a three-dimensional shape, excessive deformation of the block 1 in the longitudinal direction LD can be favorably suppressed. Although the shape bent at a plurality of locations in the depth direction DD may be used, the resistance at the time of demolding in the vulcanization process of the tire can be reduced according to this embodiment as compared to such a shape.

  The distance K1 (see FIG. 5) from the tread surface to the boundary between the 2D center portion 5 and the 3D center portion 6 is preferably 20 to 70% of the sipe depth D4. Thereby, the size in the depth direction DD of 2D center part 5 and 3D center part 6 is secured appropriately. The distance K1 is more preferably 30% or more of the sipe depth D4, and still more preferably 40% or more. The distance K1 is more preferably 60% or less of the sipe depth D4.

  The distance K2 (see FIG. 5) from the sipe end to the boundary between the 2D center portion 5 and the 3D side portion 7 is preferably 10 to 40% of the sipe length L4. Thereby, they are appropriately secured including the size in the length direction LD of the 2D center part 5 and the 3D side part 7 and further the size in the length direction LD of the 3D center part 6. The distance K2 is more preferably 15% or more of the sipe length L4. The distance K2 is more preferably 30% or less of the sipe length L4, and still more preferably 20% or more.

  The pneumatic tire according to the present invention can be configured in the same manner as a normal pneumatic tire except that the above-described sipes are formed on land portions such as blocks and ribs. Therefore, any of the conventionally known materials and manufacturing methods can be employed.

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

  The present invention is not limited to the embodiment described above, and various improvements and modifications can be made without departing from the spirit of the present invention.

  Hereinafter, the example which shows concretely the composition and effect of the present invention is described. The performance evaluations of the tires were carried out as follows.

(1) Wear resistance A tire of size 11R22.5 mounted on a rim of 22.5 × 7.50 is mounted on a vehicle with a fixed loading capacity of 10 t, filled with internal pressure 700 kPa, and worn after traveling 20000 km The quantity was measured and the reciprocal was indexed. The larger the index, the smaller the amount of wear and the better the wear resistance.

(2) Uneven Wear Resistance The uneven wear amount (heel and toe wear amount, center wear amount, and shoulder wear amount) of the above tire after traveling 20000 km was measured, and the inverse number was indexed. The larger the index, the smaller the amount of uneven wear, and the better the resistance to uneven wear.

(3) Ice performance A tire of size 11R22.5 mounted on a rim of 22.5 × 7.50 is mounted on a vehicle with a fixed loading capacity of 10 t and filled with an internal pressure of 700 kPa, and the starting performance and braking performance on an ice road surface The evaluation results were integrated and indexed. The starting performance was scored by measuring the time required for the vehicle to travel a distance of 30 m from the stop condition. The braking performance was scored by measuring the braking distance from a traveling state of 30 km / hr to stopping of the vehicle. The larger the index, the higher the score and the better the ice performance.

  The tires of the example and the comparative example subjected to the performance evaluation have the same structure except for the shape of the sipes. In the embodiment and the comparative example, the sipes shown in FIGS. 3 and 6 are formed in all the blocks of the tread surface. The sipe 40 of FIG. 6 has only a three-dimensional shape corresponding to the 3D center portion shown in FIG. 3, and on its wall surface, a concavo-convex row bent at two places in the depth direction of the sipe is provided. The evaluation results are shown in Table 1.

  As shown in Table 1, in the example, excellent wear resistance performance and uneven wear resistance performance can be exhibited while securing the ice performance, and the improvement effect can be confirmed.

1 block (example of land section)
4 sipe 5 2D center portion 6 3D center portion 7 3D side portion 61 center convex portion 71 side convex portion Tr tread surface

Claims (5)

The sipe formed on the land of the tread surface is
A 2D center portion located at the bottom of the central sipe in the longitudinal direction and having a two-dimensional shape whose shape does not change along the depth direction;
A 3D center portion which is located on the central tread surface side in the length direction and formed in a three-dimensional shape whose shape changes along the depth direction;
3D side portions formed in a three-dimensional shape which are located at both ends in the length direction and whose shape changes along the depth direction,
The 3D center portion and the 3D side portion are respectively opened on the tread surface, and the opening of the 3D center portion is formed in a wave shape,
The three-dimensional shape of the 3D center portion extends in the depth direction while bending with a center convex portion which is a convex shape in the length direction,
The three-dimensional shape of the 3D side portion extends in the depth direction while bending with the side convex portions that are convex in the width direction, and the ridges of the side convex portions extend in the length direction starting from the center convex portion Pneumatic tire.
  The pneumatic tire according to claim 1, wherein ridge lines of two side convex portions adjacent in the depth direction extend in the length direction starting from the same center convex portion.   The pneumatic tire according to claim 1 or 2, wherein the three-dimensional shape of the 3D center portion has a laterally-oriented V-shape bent at one point in the depth direction.   The pneumatic tire according to any one of claims 1 to 3, wherein a distance from a tread surface to a boundary between the 2D center portion and the 3D center portion is 20 to 70% of a sipe depth.   The pneumatic tire according to any one of claims 1 to 4, wherein a distance from a sipe end to a boundary between the 2D center portion and the 3D side portion is 10 to 40% of a sipe length.

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