JP2020100193A - Pneumatic tire - Google Patents

Abstract

To provide a pneumatic tire improved in traction performance and steering stability performance on an ice/snow road surface while optimizing rigidity of blocks and securing steering stability performance on a dry road surface.SOLUTION: The pneumatic tire comprises a tread part 100 including a plurality of blocks. The tread part 100 includes blocks 5 in which are formed first sipes 51 and second sipes 52 which are smaller in width than grooves partitioning the blocks. The second sipe 52 has a width varying in an extending direction of the second sipe 52, and comprises a non-meshing region where the maximum value of the width of the second sipe 52 is larger than a width of the first sipe 51. In the non-meshing region, there is a phase difference between a wave-shape part of a first sipe wall included in the second sipe 52 and a wave-shape part of a second sipe wall. The second sipe 52 is arranged at a center area, being a range corresponding 50% of a length in a tire circumferential direction of the block 5 with a center line of the block 5 in the tire circumferential direction as a center.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a pneumatic tire including a tread portion in which a large number of blocks are arranged.

BACKGROUND ART Conventionally, in a pneumatic tire having a tread portion in which a large number of blocks are arranged, a pneumatic tire having a large number of cuts called sipe formed in each block to enhance the edge effect and improve the performance on snow and snow is known ( See Patent Document 1).

In recent years, it has been required to secure both steering stability performance on dry roads and improvement of performance on ice and snow (Patent Document 2). Increasing the number of sipes in a block is effective for improving the performance on ice and snow. However, if you increase the number of sipes in the block and reduce the rigidity of the block excessively, the sipes tend to close easily, and the edge effect etc. tends to decrease, and the performance on ice and snow, specifically the traction performance on ice and snow road surface The steering stability performance deteriorates. Further, an excessive decrease in block rigidity tends to result in a decrease in steering stability performance on a dry road surface. Although increasing the size of the block suppresses the decrease in block rigidity, it also increases the local variation in block rigidity between the central area of the block and the peripheral area of the block, ensuring stable driving performance on dry roads. It is difficult to contribute to improving both performance on ice and snow.

Patent Documents 3 to 5 each describe a tread portion having a sipe having a partially wide portion in the extending direction of the sipe in order to solve various problems relating to tire performance by devising the shape of the sipe. However, it does not suggest a solution to the above-mentioned excessive decrease or variation in block rigidity.

JP, 2017-190123, A JP 2012-180007 A Special table 2011-506198 gazette JP 2012-101783 A Japanese Patent Publication No. 2013-505874

An object of the present invention is to provide a pneumatic tire in which the block rigidity is optimized and the steering stability performance on a dry road surface is secured while the traction performance and the steering stability performance on an ice/snow road surface are improved.

A pneumatic tire having a tread portion including a plurality of blocks,
The tread portion includes a block in which a sipe group including a plurality of sipes having a width smaller than the groove that divides the block is formed,
The sipe group has a first sipe and a second sipe,
The second sipe has a non-meshing region having a width that changes in the extending direction of the second sipe and having a maximum width value of the second sipe larger than the width of the first sipe,
The second sipe includes a first sipe wall and a second sipe wall that are arranged to face each other,
Each of the first sipe wall and the second sipe wall includes a corrugated portion, and is located between the corrugated portion of the first sipe wall and the corrugated portion of the second sipe wall in the non-meshing region. There is a phase difference,
The second sipe is arranged in a central region within a range of 50% of the tire circumferential direction length of the block centered on the center line of the block in the tire circumferential direction.

Regarding the effect of the pneumatic tire having such a configuration, there is a phase difference between the corrugated portion of the first sipe wall and the corrugated portion of the second sipe wall. The corrugated portion of the sipe wall does not mesh, and the second sipe has a non-meshing region. The non-meshing region includes a wide portion having a wide interval between the first sipe wall and the second sipe wall. This makes it difficult for the second sipe to close and enhances the edge effect of the second sipe. When the edge effect is increased, the traction performance and the steering stability performance on the snow and snow road surface are improved.

Further, the block including the second sipe including the wide portion tends to be divided into a plurality of small blocks having the second sipe as a boundary. The division into small blocks reduces the block rigidity. At this time, since the width of the second sipe is narrower than the width of the groove that divides the block, the block rigidity does not excessively decrease. That is, by optimizing the block rigidity, the edge effect and the like on the ice and snow road surface are enhanced, and the road surface followability of the block is improved. Therefore, it is possible to improve the traction performance and the steering stability performance on the ice and snowy road surface while ensuring the steering stability performance on the dry road surface.

Further, since the second sipe is arranged in the central region of the block, it is possible to reduce the block rigidity by aiming at the central region of the block having particularly high block rigidity among the blocks. Therefore, it is possible to reduce local variations in block rigidity between the central region of the block and the peripheral region of the block. As a result, the block rigidity can be further optimized. Therefore, the blocking of sipes is suppressed, the edge effect on the snow and snow road surface is enhanced, and the road followability of the block is improved. Therefore, it is possible to improve the traction performance and the steering stability performance on the ice and snowy road surface while ensuring the steering stability performance on the dry road surface.

It is preferable that each of the first sipe wall and the second sipe wall has a corrugated portion at a central portion in the extending direction and straight-shaped portions at both end portions in the extending direction.

There may be a period difference between the corrugated portion of the first sipe wall and the corrugated portion of the second sipe wall.

The block in which the sipe group including the second sipe is provided corresponds to either one of the center block and the quarter block, or both blocks,
The center block is provided at a position overlapping the tire equator, or provided adjacent to a groove arranged at a position overlapping the tire equator,
The quarter block may be provided between the center block and a shoulder block or a shoulder rib provided on the outermost side in the tire width direction.

Since the center block is closer to the tire equator CL than the other blocks, it contributes particularly to the traction performance. Therefore, for the center block, the pneumatic tire having the above-mentioned configuration is effective for improving the traction performance on the snowy and snowy road surface while ensuring the steering stability performance on the dry road surface. Further, since the quarter block is located at a position away from the tire equator CL, it greatly contributes to turning. Therefore, for the quarter block, the pneumatic tire having the above configuration is effective in improving the steering stability performance.

The pneumatic tire may be an ice and snow road tire.

Development view showing a tread portion in an embodiment of a pneumatic tire according to the present invention Enlarged view of the center block in Figure 1. Enlarged view of the quarter block in Figure 1. Enlarged view of the shoulder block in Figure 1. An enlarged view of a part of the tread portion of the second embodiment. An enlarged view of a part of the tread portion of the third embodiment. An enlarged view of a part of the tread portion of the comparative example

Hereinafter, an embodiment of a pneumatic tire according to the present invention will be described with reference to the drawings. In each drawing, the dimensional ratios of the drawings do not necessarily match the actual dimensional ratios, and the dimensional ratios of the drawings do not necessarily match.

<First Embodiment>
FIG. 1 is a development view showing a tread portion in a first embodiment of a pneumatic tire according to the present invention. The tread portion 100 includes a plurality of blocks that come into contact with the road surface. The block is partitioned by the first groove and the second groove, or the first groove, the second groove, and the tread portion by the ground contact end TE which is the tire width direction end contacting the road surface. The inclined groove 1 corresponding to the first groove is inclined from the center side toward the shoulder side in the tire width direction and extends in a gentle curve. The intersecting groove 2 corresponding to the second groove intersects the plurality of inclined grooves 1 and connects the two inclined grooves 1. The inclined groove 1 and the intersecting groove 2 are repeatedly arranged at intervals in the tire circumferential direction.

In the present embodiment, an example in which the tread pattern formed on the tread portion 100 is a block pattern based on blocks is shown. However, the block pattern of the tread portion 100 shown in FIG. 1 is an example, and various block patterns can be adopted by changing the shapes, widths, and lengths of the first groove and the second groove. For example, the first groove may extend parallel to the tire width direction, or may extend obliquely to the tire width direction but in a straight line. The first grooves may all have the same length or may have different lengths. The same applies to the second groove.

In the present embodiment, the plurality of blocks include center blocks 4 and 5 provided at positions overlapping the tire equator CL. The centers of gravity of the center blocks 4 and 5 are located on opposite sides of the tire equator CL. The shapes of the center blocks 4 and 5 are different from each other. The center blocks 4 and 5 are repeatedly arranged in the tire circumferential direction.

When the tire equator CL does not overlap with the center block but only overlaps with the groove, the block provided adjacent to the groove arranged at a position overlapping with the tire equator CL is the center block. Further, the center blocks may be arranged so as not to overlap in the tire width direction. The shapes of the center blocks are not limited to the shapes different from each other, and may have three or more different shapes. Further, the center blocks having one type of shape may be arranged at positions overlapping the tire equator CL with a space provided along the tire circumferential direction.

In this embodiment, an example is shown in which the tire is configured as a directional tire having a designated rotation direction, and the rotation direction is indicated by an arrow RD. The front side (the lower side in FIG. 1) of the rotation direction RD is the stepping side of the block, and the rear side (the upper side of FIG. 1) of the rotation direction RD is the kicking side of the block. The rotation direction is designated by, for example, displaying an arrow or the like indicating the rotation direction on the surface of the sidewall portion of the pneumatic tire.

FIG. 2A shows an enlarged view of the center block 5 in FIG. In the center block 5, a sipe group including a plurality of sipes having a width smaller than that of the groove (that is, the inclined groove 1 and the intersecting groove 2) that divides the center block 5 is formed. The groove defining the block has a width of 1.5 mm or more, while each of the sipes forming the sipe group has a width of less than 1.5 mm.

The sipe group includes a first sipe 51 and a second sipe 52. The first sipe 51 is composed of two sipe walls that are arranged opposite to each other with a space therebetween, but in each of FIGS. 2A and 2B, the first sipe 51 is simply represented by one line. The first sipe 51 has a constant width in the extending direction of the first sipe 51. That is, the distance between the two sipe walls arranged to face each other is constant in the extending direction of the first sipe 51. The second sipe 52 has a width that changes in the extending direction of the second sipe 52. That is, the distance between the two sipe walls arranged to face each other changes in the extending direction of the second sipe 52. The second sipe 52 has a non-meshing region, and the maximum width of the second sipe 52 is larger than the width of the first sipe 51 in the non-meshing region.

FIG. 2B is an enlarged view of the second sipe 52 shown in FIG. The second sipe 52 includes a first sipe wall 52a and a second sipe wall 52b that are arranged to face each other. The first sipe wall 52a has a corrugated portion 52aw at the center thereof and straight-shaped portions 52as at both ends thereof. The second sipe wall 52b has a corrugated portion 52bw at the center thereof and straight-shaped portions 52bs at both ends thereof. Then, in the non-meshing region of the second sipe 52, there is a phase difference between the corrugated portion 52aw of the first sipe wall 52a and the corrugated portion 52bw of the second sipe wall 52b. The phase difference means that the wave shape of the first sipe wall 52a and the wave shape of the second sipe wall 52b are deviated in the extending direction of the sipe.

If there is a phase difference between the first sipe wall 52a and the second sipe wall 52b, the corrugated portion 52aw of the first sipe wall 52a and the corrugated portion 52bw of the second sipe wall 52b do not mesh with each other, resulting in a non-meshing region. Will have. In the non-meshing region, the wide portion 521 in which the distance between the first sipe wall 52a and the second sipe wall 52b is relatively large, and the narrow portion in which the distance between the first sipe wall 52a and the second sipe wall 52b is relatively small. And site 522. If there is the wide portion 521, for example, even if a force in the sipe width direction acts on the second sipe 52, the wide portion 521 is difficult to close. If the sipe becomes difficult to close, the edge effect can be enhanced. Further, when the narrow portion 522 is closed, the first sipe wall 52a and the second sipe wall 52b support each other to prevent further deformation of the block 5, making it more difficult to close the second sipe 52. In the non-meshing region, the wide portion 521 and the narrow portion 522 appear periodically, which makes it more difficult to close the second sipe 52.

In addition, since the corrugated portions 52aw and 52bw are composed of curves without corners, the edge effect is exerted not only in the width direction of the sipe but also in multiple directions, and the steering stability performance including turning is improved. To be

Further, due to the existence of the wide portion 521, the center block 5 tends to be divided into the small blocks 53 and 54 having the appropriate size and having the second sipe 52 as a boundary. By being divided into the small blocks 53 and 54, the block rigidity is reduced. However, since the width of the second sipe 52 is narrower than the width of the groove that divides the block, the block rigidity does not excessively decrease.

As shown in FIG. 2A, the second sipe 52 is arranged in the central region Cr ₅ . On the other hand, the second sipe 52 is not arranged outside the central region Cr ₅ . Central region Cr ₅ is a tire circumferential direction length of the center block 5 and _{L 5,} when the center line of the center blocks 5 in the tire circumferential direction _{C 5,} to within ± 0.25 L ₅ from the center line _{C 5} Represents. That is, the second sipe 52 is arranged in the central region Cr ₅ that is within the range of 50% of the tire circumferential direction length L ₅ of the center block 5 with the center line C ₅ of the center block 5 in the tire circumferential direction as the center. ing. The center line C ₅ is an imaginary line extending in the tire width direction.

By disposing the second sipe 52 in the central region Cr ₅ , the block rigidity can be reduced by aiming at the central region Cr _{5 of the} block having particularly high block rigidity among the center blocks 5. Therefore, it is possible to reduce the local variation in block rigidity between the central region Cr ₅ of the block and the peripheral region of the block.

In this embodiment, there is a phase difference between the corrugated portion 52aw of the first sipe wall 52a and the corrugated portion 52bw of the second sipe wall 52b, but there is no period difference. If the cycle is the same between the corrugated portion 52aw of the first sipe wall 52a and the corrugated portion 52bw of the second sipe wall 52b, it is unlikely that the tread portion will look strange.

By the way, in a sipe having a straight shape in a plan view of the tread portion 100, uneven wear in the block, particularly heel and toe wear occurring in the tire circumferential direction is likely to increase. On the other hand, the sipe having a wavy shape in plan view of the tread portion 100 suppresses heel and toe wear. In addition, since the sipe having a wavy shape in a plan view of the tread portion can obtain an edge effect in multiple directions, the steering stability performance including when turning can be improved. Further, since the corrugated portion is composed of a curved line having no corners, uneven wear due to stress concentration is less likely to occur when a force is applied from multiple directions.

If it has a wavy shape to the sipe end, the sharp angle of the corner formed by the extension direction of the sipe and the block outer edge at the sipe end increases, the rigidity at the corner locally decreases, and in the tire width direction. The uneven wear that occurs tends to increase. However, in the present embodiment, in the first sipe wall 52a and the second sipe wall 52b, the central portion of the sipe wall has corrugated portions 52aw and 52bw, and the end portion of the sipe wall has straight-shaped portions 52as and 52bs. Have. Therefore, the uneven wear resistance performance can be improved.

Since the center block 5 is closer to the tire equator CL than the other blocks, it contributes particularly to the traction performance. Then, the pneumatic tire having the above-mentioned configuration for the center block 5 is effective in enhancing the edge effect on the ice and snow road surface and improving the traction performance.

It is preferable that only one second sipe 52 is arranged in the central region Cr ₅ of the center block 5 as in the present embodiment. As a result, the center block 5 is divided into two small blocks 53 and 54 having an appropriate size, and the block rigidity does not excessively decrease. However, a plurality of second sipes 52 may be included in the central region Cr ₅ in order to obtain appropriate block rigidity. Further, when a plurality of second sipes 52 are included, the first sipes 51 may be arranged so as to be sandwiched between the second sipes 52.

The width of the sipe is represented by the distance between two opposing sipe walls in the direction orthogonal to the sipe extension direction. The width _{T 52} of the second sipe 52 shown in FIG. 2 (b). The width T ₅₁ of the first sipe 51 is preferably 0.3 mm or more. Furthermore, the width T ₅₁ of the first sipe 51 is preferably less than 0.8 mm. The width T ₅₂ of the second sipe 52 is preferably 0.5 mm or more. The width T ₅₂ of the second sipe 52 is preferably less than 1.5 mm. The depth of each sipe is preferably shallower than the depth of the groove that defines the block, and may be the same depth.

FIG. 2C shows an enlarged view of the same center block 5 as that in FIG. As shown in FIG. 2 (c), the extending direction D ₅₁ of the first sipe 51 and the extending direction D ₅₂ of the second sipe 52, either, a straight line passing through the center of the sipe width at both ends of the sipe Shown. Extending direction _{D 51} of the first sipe 51 at an angle of _{A 51} with respect to the tire width direction WL, the extending direction _{D 52} of the second sipe 52, the angle of _{A 52} with respect to the tire width direction WL Eggplant In FIG. 2C, the extending direction D ₅₁ and the extending direction D ₅₂ are upward to the right with respect to the tire width direction WL, but the extending direction D ₅₁ and the extending direction D ₅₂ are in the tire width direction WL. On the other hand, the direction may be downward to the right. Both the angle A ₅₁ and the angle A ₅₂ are preferably within 5 degrees. That is, the first sipe 51 and the second sipe 52 may extend within ±5 degrees with respect to the tire width direction. As a result, the edge effect of the sipe group formed on the center block 5 contributes to the improvement of the traction (driving/braking) performance particularly on an ice/snowy road surface. Further, the extending direction D ₅₁ and the extending direction D ₅₂ may be the same direction as the tire width direction WL (that is, the angle A ₅₁ and the angle A ₅₂ are each 0 degrees). When the extending directions D ₅₁ and D ₅₂ of the first sipe 51 and the second sipe 52 in the center block 5 are downward rightward, the sipe of the center block 4 located on the opposite side with the tire equator CL interposed therebetween. The extending direction may be a right upward direction. At that time, the absolute values of the angles of the center blocks 4 and 5 with respect to the tire width direction may be set to be equal. The angle A ₅₁ and the angle A ₅₂ may have the same value or different values.

The center block 5 has been described above, but the same applies to the center block 4 and other center blocks arranged at intervals in the tire circumferential direction.

Returning to FIG. 1, in the present embodiment, the plurality of blocks include shoulder blocks 8 and 9 provided on the outermost side in the tire width direction. The shoulder blocks 8 and 9 are defined by the inclined groove 1, the intersecting groove 2, and the ground contact TE.

The ground contact end TE is an outermost position in the tire width direction when the tire, which is assembled to the regular rim and is loaded with the regular internal pressure and the regular load, is grounded on a flat road surface. A regular rim is a rim that is defined for each tire in the standard system including the standard on which the tire is based. For example, a standard rim defined by JATMA, “Design Rim” defined by TRA, or ETRTO. It is a defined "Measuring Rim". The normal internal pressure is the air pressure that each standard defines for each tire in a standard system including the standard on which the tire is based. It is the maximum value described in “INFLATION PRESSSURES” or “INFLATION PRES SURE” specified in ETRTO. The normal load is a load that each standard defines for each tire in a standard system including standards on which the tire is based. For example, the maximum load capacity specified in JATMA and the maximum value described in the above table of TRA. , Or "LOAD CAPACITY" defined in ETRTO.

Although the tread portion 100 includes the shoulder blocks 8 and 9 in FIG. 1, the tread portion 100 may include shoulder ribs instead of the shoulder blocks 8 and 9. Quarter blocks 6 and 7 are arranged between center blocks 4 and 5 and shoulder blocks 8 and 9, respectively. The quarter blocks 6 and 7 are not essential blocks, and the blocks included in the tread portion 100 may be composed of the center blocks 4 and 5 and the shoulder blocks 8 and 9.

FIG. 3A shows an enlarged view of the quarter block 7 in FIG. The quarter block 7 is formed with a sipe group including a plurality of sipes each having a width smaller than that of the groove (that is, the inclined groove 1 and the intersecting groove 2) that divides the quarter block 7.

The sipe group includes a first sipe 71 and a second sipe 72. The first sipe 71 is composed of two sipe walls that are arranged to face each other, but in each of FIGS. 3A and 3B, the first sipe 71 is simply represented by one line. The first sipe 71 has a constant width in the extending direction of the first sipe 71. That is, it means that the interval between the two sipe walls arranged to face each other is constant in the extending direction of the first sipe 71. The second sipe 72 has a width that changes in the extending direction of the second sipe 72. That is, it means that the distance between the two sipe walls arranged to face each other changes in the extending direction of the second sipe 72. The second sipe 72 has a non-meshing region, and the maximum width of the second sipe 72 is larger than the width of the first sipe 71 in the non-meshing region.

FIG. 3B is an enlarged view of the second sipe 72 shown in FIG. The second sipe 72 includes a first sipe wall 72a and a second sipe wall 72b that are arranged to face each other. The first sipe wall 72a has a corrugated portion 72aw at the center thereof and straight-shaped portions 72as at both ends thereof. The second sipe wall 72b has a corrugated portion 72bw at the center thereof and straight-shaped portions 72bs at both ends thereof. Then, in the non-meshing region of the second sipe 72, there is a phase difference between the corrugated portion 72aw of the first sipe wall 72a and the corrugated portion 72bw of the second sipe wall 72b.

The second sipe 72 in the quarter block 7 has a non-meshing region, and in the non-meshing region, the effect of causing the wide portion 721 and the narrow portion 722 is that the second sipe 52 in the center block 5 has a non-meshing region. According to the effect of having. In addition, the corrugated portions 72aw and 72bw are formed by a curve having no corners, and the quarter block 7 is divided into small blocks 73 and 74 having an appropriate size with the second sipe 72 as a boundary. As a result, the second sipe 72 is arranged in the central region Cr ₇ within a range of 50% of the tire circumferential direction length L ₇ of the quarter block 7 with the central line C ₇ of the quarter block 7 in the tire circumferential direction as the center. The effect that the second sipe 72 is not arranged outside the central region Cr ₇ is that the central portions of the sipe walls 72a and 72b have corrugated portions 72aw and 72bw, and the end portions of the sipe walls are straight portions. Similarly, the effect of having 72as and 72bs and the effect related to the number of the second sipes 72 are similar to the effect applied to the second sipes 52 in the center block 5.

Since the quarter block 7 is located away from the tire equator CL, it particularly contributes greatly to turning. Then, the pneumatic tire having the above-mentioned configuration for the quarter block 7 is effective for improving the steering stability performance.

The width _{T 72} of the second sipe 72 shown in FIG. 3 (b). The width T ₇₁ of the first sipe 71 is preferably 0.3 mm or more. Further, the width T ₇₁ of the first sipe 71 is preferably less than 0.8 mm. The width T ₇₂ of the second sipe 72 is preferably 0.5 mm or more. The width T ₇₂ of the second sipe 72 is preferably less than 1.5 mm. The depth of each sipe is preferably shallower than the depth of the groove that defines the block, and may be the same depth.

FIG. 3C shows an enlarged view of the same quarter block 7 as that in FIG. As shown in FIG. 3 (c), the extending direction D ₇₁ of the first sipe 71 and the extending direction D ₇₂ of the second sipe 72, either, a straight line passing through the center of the sipe width at both ends of the sipe Shown. Extending direction _{D 71} of the first sipe 71 at an angle of _{A 71} with respect to the tire width direction WL, the extending direction _{D 72} of the second sipe 72, the angle of _{A 72} with respect to the tire width direction WL Eggplant In FIG. 3C, the extending direction D ₇₁ and the extending direction D ₇₂ are downward rightward with respect to the tire width direction WL, but the extending direction D ₇₁ and the extending direction D ₇₂ are the tire width direction WL. On the other hand, you may take the direction of rising to the right. The angle A ₇₁ and the angle A ₇₂ are each preferably 10 degrees or more and 30 degrees or less. Thereby, the edge effect of the sipe group particularly contributes to turning traveling. When the extending direction of the first sipe 71 and the second sipe 72 in the quarter block 7 is downward right, the extending direction of the sipe of the quarter block 6 located on the opposite side of the tire equator CL is right. You may take the upward direction. At this time, the absolute values of the angles of the quarter blocks 6 and 7 with respect to the tire width direction may be set to be equal. The angle A ₇₁ and the angle A ₇₂ may have the same value or different values.

Although the quarter block 7 has been described above, the same applies to the quarter block 6 and other quarter blocks arranged at intervals in the tire circumferential direction.

FIG. 4 shows an enlarged view of the shoulder block 9 in FIG. The shoulder block 9 has a plurality of sipes 91. The width of the sipe 91 is smaller than the width of the groove that defines the shoulder block. The width of the sipe 91 is preferably 0.3 mm or more and 0.8 mm or less. Extending direction _{D 91} of the sipe 91 is at an angle of _{A 91} with respect to the tire width direction WL. The angle A ₉₁ is preferably 10 degrees or more and 15 degrees or less. The extending direction D ₉₁ is an upwardly rightward direction with respect to the tire width direction WL, but the extending direction D ₉₁ may be an obliquely rightward direction with respect to the tire width direction WL.

Regarding the sipe shape of the sipe 91 of the shoulder block 9, it is preferable that the sipe 91 includes both a wavy portion and a straight portion in the plan view of the tread portion 100. Furthermore, it is more preferable that the sipe 91 has a corrugated portion at the center of the sipe wall forming the sipe 91 and straight portions at both ends of the sipe wall. For the shoulder block 9, a sipe having a constant width may be used. A sipe having a constant width is effective in maintaining high block rigidity and ensuring braking performance on a dry road surface where a large force is applied to the shoulder block 9. The same applies to the shoulder block 8 and other shoulder blocks arranged at intervals in the tire circumferential direction.

Common to the center blocks 4, 5, quarter blocks 6, 7 and shoulder blocks 8, 9, the sipe group is a double-sided open type in which both ends of the sipe are connected to the outer edge of the block, and one end of the sipe is attached to the outer edge of the block. It may be either a one-side open type in which one end is connected and the other end is not connected to the outer edge of the block, or a both-side closed type in which both ends of the sipes are not connected to the outer edge of the block. As the number of open-sided sipes increases, the effect of lowering the block rigidity increases.

<Second Embodiment>
The second embodiment has the same configuration as that of the first embodiment except for the configuration described below, and therefore the common points will be omitted and the different points will be mainly described. The same members as the members described in the first embodiment are designated by the same reference numerals, and duplicate description will be omitted. In addition, the plurality of modified examples described above can be combined and used without particular limitation. The same applies to the third embodiment.

The second embodiment will be described with reference to FIG. FIG. 5A is an enlarged view of the tread portion showing only the center block 5, the quarter block 7, and the shoulder block 9. A second sipe 57 is provided in the central region of the center block 5, and a second sipe 77 is provided in the central region of the quarter block 7.

FIG. 5B is an enlarged view of the second sipe 57 shown in FIG. The second sipe 57 is composed of a first sipe wall 57a and a second sipe wall 57b which are arranged to face each other. The first sipe wall 57a has a corrugated portion 57aw at the center thereof and straight-shaped portions 57as at both ends thereof. The second sipe wall 57b has a corrugated portion 57bw at the center thereof and straight-shaped portions 57bs at both ends thereof.

Further, there is a phase difference of 180 degrees between the corrugated portion 57aw of the first sipe wall 57a and the corrugated portion 57bw of the second sipe wall 57b. The width T ₅₇ of the second sipe 57 in the second embodiment is larger than the width T ₅₂ of the second sipe 52 in the first embodiment, and the wide portion 571 can be enlarged while maintaining the narrow portion 572. This makes it more difficult for the sipes to close and enhances the edge effect. In addition, the adjustment range for optimizing the block rigidity can be expanded. Similarly, the second sipe 77 of the quarter block 7 may have a phase difference of 180 degrees between both sipe walls. Thereby, the wide portion can be enlarged while maintaining the narrow portion of the second sipe 77.

<Third Embodiment>
The third embodiment will be described with reference to FIG. FIG. 6A is an enlarged view of the tread portion showing only the center block 5, the quarter block 7, and the shoulder block 9. A second sipe 58 is provided in the central region of the center block 5, and a second sipe 78 is provided in the central region of the quarter block 7.

FIG. 6B is an enlarged view of the vicinity of the second sipe 58 shown in FIG. The second sipe 58 includes a first sipe wall 58a and a second sipe wall 58b that are arranged to face each other. The first sipe wall 58a has a corrugated portion 58aw at the center thereof and straight-shaped portions 58as at both ends thereof. The second sipe wall 58b has a corrugated portion 58bw at the center thereof and straight-shaped portions 58bs at both ends thereof.

In addition to the phase difference, there is a cycle difference between the corrugated portion 58aw of the first sipe wall 58a and the corrugated portion 58bw of the second sipe wall 58b. By arranging the sipe walls having different periods so as to face each other, it is possible to diversify the adjustment method for optimizing the block rigidity. The same applies to the second sipe 78 of the quarter block 7, and there is a period difference in addition to the phase difference between the two sipe walls forming the second sipe 78.

As a modification of the first and second embodiments, the wave-shaped portions of both sipe walls may have a difference in the magnitude of the wave amplitude in addition to the phase difference. As a modified example of the third embodiment, the wave-shaped portions of both sipe walls may have a difference in the amplitude of the wave in addition to the phase difference and the period difference. By providing a difference in the amplitude of the wave, it is possible to diversify the adjustment method for optimizing the block rigidity.

The pneumatic tire may be a so-called all-season tire that is used on both an ice-snow road in the winter and a dry road in the summer, but an ice-snow road tire that is mainly used in the ice-snow road and the dry road in the winter (so-called Winter tires). The tire for ice and snow roads has a rubber hardness in the tread portion in the range of 60 to 75 degrees, and has a lower rubber hardness in the tread portion as compared with a normal tire including an all-season tire. The rubber hardness is a value (durometer hardness) measured using a type A durometer in an atmosphere of 23° C. according to JIS K6253.

The pneumatic tire according to the present invention can be configured in the same manner as a normal pneumatic tire except that the tread portion is configured as described above, and any conventionally known material, shape, structure, manufacturing method, etc. can be adopted. To manufacture a pneumatic tire having a tread portion having the above-mentioned sipe shape, a sipe blade for molding a second sipe among a plurality of sipe blades inserted into the surface of the tread portion during vulcanization molding of the pneumatic tire. On the other hand, the surface shape corresponding to the first and second sipe walls may be modified to such an extent. Others can be manufactured in the same manner as the conventional tire manufacturing process. Although illustration is omitted, the pneumatic tire of the present embodiment has a pair of bead portions, a sidewall portion extending from each of the bead portions to a tire radial direction outer side, and a tire radial direction outer end of each of the sidewall portions. And a tread portion continuous with.

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

As Example 1, a pneumatic tire having a tread portion including the block pattern shown in FIG. 1 and the sipe shape (FIG. 2-4) of the first embodiment was evaluated. As Example 2, a pneumatic tire having a tread portion including the sipe shape (FIG. 5) of the second embodiment was evaluated. The block pattern is the same as in the first embodiment. As Example 3, a pneumatic tire having a tread portion including the sipe shape (FIG. 6) of the third embodiment was evaluated. The block pattern is the same as in the first embodiment.

As a comparative example, a pneumatic tire having a tread portion including the sipe shape of FIG. 7 was evaluated. The block pattern is the same as in the first embodiment. In FIG. 7, the width of the sipe does not include the second sipe whose extension direction changes. That is, all the sipes in the center block 5 and the quarter block 7 are composed of sipes having a constant width. The sipes in the shoulder block 9 are the same as in the first embodiment.

<Evaluation>
The pneumatic tires of Examples and Comparative Examples were attached to a test vehicle, and snow driving performance, snow steering stability performance, and dry steering stability performance were evaluated. The evaluation conditions and evaluation items are shown below.

<Evaluation conditions>
Tire size: 225/50R17
Rim: 17X7.5J
Tire pressure: 220kPa
Test vehicle: Passenger car with displacement of 1984cc

<Evaluation of snow driving performance>
The tire was attached to a test vehicle, an acceleration test was performed on a snowy road, and the time from the stopped state to running 20 m was measured. The evaluation conditions used were those described above. The evaluation result was shown by an index with the result of the comparative example being 100, using the reciprocal of the measured value. The larger the index value, the better the snow driving performance.

<Evaluation of snow handling stability>
Each tire was mounted on a test vehicle, and the vehicle was accelerated, braked, turned and changed lanes on a snow-covered road surface. A relative evaluation was made by a professional driver, and the result of the comparative example was set as 100 and displayed as an index. The larger this index value, the better the snow steering stability performance.

<Evaluation of dry steering stability>
The tires were mounted on the vehicle, and the vehicle was driven on the asphalt-paved dry road surface for acceleration, braking, turning, and lane change. The evaluation conditions used were those described above. A professional driver relatively evaluated the result, and the result of the comparative example was shown as an index with 100. The larger the index value, the better the steering stability performance on a dry road surface.

Table 1 shows the evaluation results. From this, it is shown that Examples 1 to 3 can improve the driving performance on snow and the steering stability on snow while ensuring the steering stability on a dry road surface, as compared with the Comparative Example.

1... Inclined groove 2... Intersection groove 4, 5... Center block 6, 7... Quarter block 8, 9... Shoulder block 51, 71... First sipes 52, 72, 77, 78... Second sipes 53, 54, 73, 74...Small block 91...Sipe 100...Tread part

Claims (5)

A pneumatic tire having a tread portion including a plurality of blocks,
The tread portion includes a block in which a sipe group including a plurality of sipes having a width smaller than the groove that divides the block is formed,
The sipe group has a first sipe and a second sipe,
The second sipe has a non-meshing region having a width that changes in the extending direction of the second sipe and having a maximum width value of the second sipe larger than the width of the first sipe,
The second sipe includes a first sipe wall and a second sipe wall that are arranged to face each other,
Each of the first sipe wall and the second sipe wall includes a corrugated portion, and is located between the corrugated portion of the first sipe wall and the corrugated portion of the second sipe wall in the non-meshing region. There is a phase difference,
The second sipe is arranged in a central region that is within a range of 50% of a tire circumferential direction length of the block centering on a center line of the block in the tire circumferential direction. .. The pneumatic container according to claim 1, wherein each of the first sipe wall and the second sipe wall has a corrugated portion at a central portion in the extending direction and straight-shaped portions at both end portions in the extending direction. tire. The pneumatic tire according to claim 1 or 2, wherein there is a cycle difference between the corrugated portion of the first sipe wall and the corrugated portion of the second sipe wall. The block in which the sipe group including the second sipe is provided corresponds to either one of the center block and the quarter block, or both blocks,
The center block is provided at a position overlapping the tire equator, or provided adjacent to a groove arranged at a position overlapping the tire equator,
The pneumatic tire according to any one of claims 1 to 3, wherein the quarter block is provided between the center block and a shoulder block or a shoulder rib provided on the outermost side in the tire width direction. .. The pneumatic tire according to any one of claims 1 to 4, wherein the pneumatic tire is an ice and snow road tire.

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