JP2006062468A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of improving ice performance efficiently. <P>SOLUTION: This pneumatic tire has sipes 34 in lateral direction in a plurality of blocks 26 partitioned by a channel in the peripheral direction and a lateral channel. A plurality of small holes 35 extending in the direction of depth of the block 26 from a bottom of the sipe 34 in the lateral direction are formed in this block 26. Consequently, water drain property is improved while maintaining edge effect by the sipe 34 in the lateral direction to improve ice performance effectively. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pneumatic tire including a plurality of tread blocks partitioned by a circumferential groove and a lateral groove, and more particularly to a pneumatic tire excellent in performance on ice.

  Conventionally, in a pneumatic tire for winter, a lateral sipe has been added to a block portion of a tire tread pattern in order to improve acceleration and braking performance when starting on ice.

  However, as the number of lateral sipes increases, the sipe edge part scratches the road surface (hereinafter referred to as the edge effect) and the sipe part sucks up the water film on the ice surface (that is, the drainage effect) increases. As the rigidity decreases and the contact area on ice decreases, there is a problem that the frictional force between the tire and the icy road surface (hereinafter referred to as surface frictional force) decreases. In addition, if the decrease in the surface friction force exceeds the increase in the edge effect and drainage effect, the performance on ice will not improve, so there is a limit to improving the performance on ice by adding sipes, and the required performance on ice can be realized. There was also a problem that it was not possible.

  As countermeasures, tread rubber has been improved for improving drainage, and pneumatic tires having a foam rubber layer on the tread have been developed (see, for example, Patent Documents 1 to 3). . Furthermore, it has been proposed to provide a small hole in the block portion (see, for example, Patent Documents 4 to 6). Further, improvement of the sipe shape has been studied so that the reduction of the contact area can be suppressed and the surface friction force can be secured even if the number of sipe is increased, and a three-dimensional sipe shape has been developed (for example, Patent Document 7). reference).

However, further improvement in performance on ice is required.
Japanese Patent No. 2510533 Japanese Patent No. 002518870 Japanese Patent No. 002564760 JP-A-5-77613 Japanese Patent Laid-Open No. 10-272905 JP 2001-71712 A Japanese Patent Application No. 11-113321

  In view of the above facts, an object of the present invention is to provide a pneumatic tire in which the performance on ice is efficiently improved.

  The present inventor has examined the edge effect caused by lateral sipes. And when the conventional pneumatic tire rolled on the ice road surface, it paid attention to that an edge effect generate | occur | produces because an edge part scratches an ice surface according to edge pressure. Further, as shown in FIG. 10C, attention is also paid to the fact that the ground pressure at the edge portion 89 (hereinafter referred to as edge pressure) increases when the small block 88 partitioned by the horizontal sipe 84 collapses. did.

  And it has been found that improving the drainage effect while maintaining the edge effect is a proposal for improving the performance on ice.

  Then, this inventor earnestly examined the tread structure which improves a drainage effect, maintaining the edge effect, and came to complete this invention.

  The invention according to claim 1 is a pneumatic tire including a plurality of tread blocks partitioned by a circumferential groove and a lateral groove, wherein the tread block has at least one sipe, and at least one of the sipe One has a plurality of small holes extending from the sipe bottom in the depth direction of the tread block.

  The circumferential groove is a groove that extends substantially along the tire circumferential direction, and the lateral groove is a groove that intersects the circumferential groove.

  It is known that when the tire load and internal pressure conditions are the same, the average contact pressure in the contact surface is substantially equal. Therefore, in order to increase the edge pressure, it is effective to lower the ground pressure at the center of the block and relatively increase the edge pressure by generating a non-uniform ground pressure distribution in the block surface. The contact pressure of the block depends on the compression rigidity. The part with high compression rigidity has high contact pressure, and the part with low compression rigidity has low contact pressure. It becomes possible to increase the edge pressure at the block peripheral edge.

  According to the first aspect of the present invention, a plurality of small holes extending in a needle shape from the sipe bottom in the block depth direction are formed in order to increase the amount of water film that can be sucked up on the ground surface and improve drainage. is doing. Therefore, the drainage is improved while suppressing a decrease in the compression rigidity of the block as much as possible, that is, while maintaining the edge pressure of the sipe. Accordingly, it is possible to realize a pneumatic tire that effectively improves the performance on ice by improving drainage while maintaining the edge effect by sipe.

  Depending on the tire structure, if the number of small holes is increased too much, the compression rigidity of the entire block will be lowered, and the decrease in ice performance due to the reduction in grounding effect will exceed the improvement in ice performance due to the drainage effect. As a result, the performance on ice may not be improved. In such a case, it is effective to devise variations such as variation in the depth and formation position of the small holes.

  The invention according to claim 2 is characterized in that the sipe is a lateral sipe.

  Thereby, the edge effect by a horizontal sipe can be show | played similarly to the past.

  The lateral sipe may be parallel to the tire width direction or may be inclined to some extent with respect to the tire width direction. When the vehicle is inclined, the inclination angle with respect to the tire width direction is preferably within 40 degrees, and more preferably within 20 degrees.

  The invention according to claim 3 is characterized in that both ends of the sipe are open to a block side wall.

  Thereby, the water sucked into the sipe from the ground surface flows out from the opening of the block side wall, so that the drainage effect is greatly improved.

  Since this invention was set as the said structure, the drainage effect can be improved especially and the drainage performance can be improved, and the pneumatic tire which improved the on-ice performance efficiently can be implement | achieved.

  Hereinafter, embodiments will be described and embodiments of the present invention will be described. In the second and subsequent embodiments, the same components as those already described are denoted by the same reference numerals and description thereof is omitted.

[First Embodiment]
First, the first embodiment will be described. As shown in FIG. 1, a pneumatic tire 10 according to the present embodiment is a studless tire, and includes a carcass 12 that includes a cord that extends substantially in a radial direction and whose both ends are folded back by bead cores 11. The carcass 12 is composed of one layer or a plurality of layers.

  On the outer side in the tire radial direction of the crown portion 12C of the carcass 12, a belt layer 14 in which a plurality of (for example, two) belt plies are stacked is embedded. Each belt ply is embedded so that the cords constituting the belt ply cross in the tire circumferential direction and face each other.

  A tread portion 18 having grooves is formed on the outer side of the belt layer 14 in the tire radial direction. In the tread portion 18, a plurality of circumferential grooves (main grooves) 22 along the circumferential direction and a plurality of lateral grooves 24 (see FIG. 2) intersecting with the circumferential direction are formed on both sides of the tire equatorial plane CL. Has been. Both end portions of each lateral groove 24 communicate with the circumferential groove 22 or extend so as to be drained to the outside in the tire width direction beyond the tread end.

  Here, the tread end means that a pneumatic tire is mounted on a standard rim prescribed in JATMA YEAR BOOK (2004 edition, Japan Automobile Tire Association Standard), and the maximum load in the applicable size and ply rating in JATMA YEAR BOOK. Fills 100% of the air pressure (maximum air pressure) corresponding to the capacity (internal pressure-load capacity correspondence table) as the internal pressure, and indicates the outermost contact portion in the tire width direction when the maximum load capacity is applied. In addition, when TRA standard and ETRTO standard are applied in a use place or a manufacturing place, it follows each standard.

  As shown in FIG. 2, a large number of blocks 26 are formed in the tread portion 18 by the circumferential grooves 22 and the lateral grooves 24.

  As shown in FIG. 3, each block 26 is formed with a plurality of lateral sipes 34 along the lateral grooves 24. Both ends of each lateral sipe 34 are open to the block side wall 26X. In the present embodiment, there are a plurality of (for example, four) horizontal sipes 34.

  The lateral sipes 34 are arranged so as to divide the block 26 at equal intervals a in the block circumferential direction. Thereby, the ground pressure becomes uniform. Therefore, local wear caused by uneven distribution of the ground pressure can be prevented (see FIG. 5).

  With such a configuration, the block 26 has a plurality of small blocks 28 divided by the lateral sipes 34 in an arrayed state on the tread portion of the block 26.

  Here, each lateral sipe 34 is provided with a plurality of small holes 35 extending from the sipe bottom in the block depth direction (see FIGS. 3 and 4). In the present embodiment, the small holes 35 are formed at equal intervals. The diameter and length of the small hole 35 are set so as not to adversely affect the compression rigidity of the block 26 according to the dimension of the lateral sipe 34 and the like. The small hole 35 may be a cylindrical hole or a prismatic hole, and the shape is not particularly limited.

  As a result, the water film between the tread portion and the road surface is sucked into the lateral sipe 34 and further accommodated in the small hole 35. The water accommodated in the small hole 35 flows out from the openings 34M at both ends of the lateral sipe 34 to the circumferential groove 22 and is drained. Therefore, the pneumatic tire 10 having improved performance on ice can be obtained by improving the drainage performance while maintaining the edge pressure of each small block 28, that is, maintaining the edge effect of the lateral sipe 34.

  If the small holes 35 are provided in this way, when the compression rigidity of the block 26 is low and the decrease in performance on ice due to the reduction of the grounding effect is large, the depth of the small holes 35 and the formation position are varied. It is effective to do.

  For example, as shown in FIG. 6, the number of small holes 35 is increased at the central portion of the horizontal sipe 34, or the small holes 37 having a deeper depth are formed at the central portion of the horizontal sipe 34 as shown in FIG. Etc. are effective.

  In the above description, the circumferential groove 22 extends along the tire circumferential direction and the lateral groove 24 extends along the tire axial direction. However, the circumferential groove 22 is inclined with respect to the tire circumferential direction. The lateral grooves 24 may be inclined with respect to the tire axial direction. In addition, the rectangular block 26 has been described, but the shape of the block when the tread portion 18 is viewed in plan is a rhombus, hexagonal shape by adding the direction of the circumferential groove 22 and the lateral groove 24, chamfering, notch, etc. It may have a polygonal shape such as an octagon or a substantially U shape, and may be a circle, an ellipse, or the like.

  Furthermore, the blocks 26 may be arranged so that the circumferential grooves 22 extend in a zigzag manner in the tire circumferential direction, or the circumferential grooves 22 may be arranged so as to extend in a zigzag manner in the tire circumferential direction. . Note that extending in a zigzag manner in the tire circumferential direction means that a groove portion extending in the same direction as the tire circumferential direction and a groove portion extending obliquely with respect to the tire circumferential direction are alternated and extend in the tire circumferential direction. It means that the groove portions extending in the same direction as the circumferential direction are arranged in a staggered manner. The phrase “zigzag extending in the tire circumferential direction” means that the groove portions that are inclined with respect to the tire circumferential direction extend in the tire circumferential direction while turning back so that the inclination directions are alternate.

  Further, the lateral sipe 34 may be parallel to the tire width direction or may be inclined to some extent with respect to the tire width direction. When the vehicle is inclined, the inclination angle with respect to the tire width direction is preferably within 40 degrees, and more preferably within 20 degrees.

[Second Embodiment]
Next, a second embodiment will be described. As shown in FIG. 8, in the present embodiment, the configuration of the horizontal sipe 44 is different from that of the first embodiment. The horizontal sipe 44 has a deep sipe depth at the center and a shallow sipe depth at both ends. As in the first embodiment, a plurality of small holes 45 extending in the block depth direction from the sipe bottom of the horizontal sipe 44 are formed at equal intervals.

  As a result, the shape of the block is not rectangular, that is, the contact pressure of the entire block is changed to a sipe shape as shown in FIG. Becomes uniform. Therefore, it is possible to prevent local wear caused by uneven distribution of the contact pressure.

[Third Embodiment]
Next, a third embodiment will be described. As shown in FIG. 9, contrary to the second embodiment, in the present embodiment, the lateral sipe 54 has a shallow sipe depth at the center and a deep sipe depth at both ends as compared with the first embodiment. . As in the first embodiment, a plurality of small holes 55 extending in the block depth direction from the sipe bottom of the horizontal sipe 54 are formed at equal intervals.

  As a result, when the block shape is not rectangular, that is, the block formed so that the rigidity at the center of the block is particularly small, the sipe shape as shown in FIG. Becomes uniform. Therefore, it is possible to prevent local wear caused by uneven distribution of the contact pressure.

<Test example>
In order to confirm the effect of the present invention, the present inventor made an example of the pneumatic tire 10 of the first embodiment (hereinafter referred to as the pneumatic tire of the example), the pneumatic tire of the conventional example, and the lateral sipe. A pneumatic tire having a depth greater than that of the conventional example (hereinafter, referred to as a pneumatic tire of a comparative example) was prepared, and the performance on ice was evaluated by running the vehicle.

  The tire size was 195 / 65R15 and the vehicle was driven with an internal pressure of 200 kPa.

  As shown in FIG. 10, in the pneumatic tire of the conventional example, the dimensions of the block 87 formed in the tread portion are such that the block circumferential direction (tire circumferential direction) length L is 40 mm, the block width direction length B is 30 mm, The height H is 9 mm, the depth Z of the horizontal sipe 84 is 5.5 mm, and the distance a between the horizontal sipe 84 is 8 mm. In this conventional pneumatic tire, the lateral sipes 84 are arranged at equal intervals, and the contact pressure is uniform. Therefore, local wear is prevented from occurring due to uneven distribution of the ground pressure (see FIG. 10). Note that both ends of the lateral sipe 84 are open at the block wall surface. The small block 28 defined by the horizontal sipe 84 is rectangular when viewed from the sipe surface side.

  In the pneumatic tire of the example, a plurality of small holes 35 extending in the block depth direction from the sipe bottom of the lateral sipe 34 were formed as shown in FIGS. 3 to 5 in comparison with the conventional pneumatic tire. . The dimensions of the lateral sipe 34 are the same as the lateral sipe 84. Therefore, the number of the lateral sipe 34 is not reduced as compared with the conventional pneumatic tire, and the edge pressure by the lateral sipe 34 is maintained at the same level as that of the conventional pneumatic tire.

  In the present embodiment, the length (depth) U of the small hole 35 is 2 mm, and the depth from the sipe surface to the bottom of the small hole 35 is 7.5 mm. Moreover, the small hole 35 was a prismatic small hole having a square cross section with a side of 0.4 mm. Moreover, when arrange | positioning the small hole 35, it has arrange | positioned so that it may become equal intervals, and the space | interval of the adjacent small holes 35 was 5 mm.

  In the pneumatic tire of the comparative example, a lateral sipe having a sipe depth of 7.5 mm was formed as compared with the pneumatic tire of the conventional example. The number and arrangement position of the horizontal sipes are the same as those of the conventional pneumatic tire.

  Table 1 shows conditions such as dimensions of each pneumatic tire.

  For performance evaluation, these pneumatic tires were mounted on a passenger car, and a start test and a braking test were performed on an icy road.

  In the start test, the accelerator is fully opened from the running state at the initial speed of 10 km / h, the time (acceleration time) until the final speed reaches 45 km / h is measured, and the average calculated from the initial speed, the final speed and the acceleration time The acceleration was calculated. And the evaluation in the pneumatic tire of a prior art example was set to 100, and the index used as relative evaluation was computed about the other pneumatic tire.

  In the braking test, the braking distance from the initial speed of 40 km / h until full braking was applied to the stationary state was measured, and the average deceleration calculated from the initial speed and the braking distance was calculated. And the evaluation in the pneumatic tire of a prior art example was set to 100, and the index used as relative evaluation was computed about the other pneumatic tire.

  The evaluation results are also shown in Table 1. Table 1 shows that the larger the index, the higher the performance.

  As can be seen from Table 1, in the pneumatic tire of the example, both the acceleration on ice and the deceleration on ice were markedly better than those of the conventional pneumatic tire. Further, in the pneumatic tire of the comparative example, evaluation on both the deceleration on ice and the acceleration on ice was lower than that of the conventional pneumatic tire.

  The embodiments of the present invention have been described above with reference to the embodiments. However, these embodiments are merely examples, and various modifications can be made without departing from the scope of the invention. Needless to say, the scope of rights of the present invention is not limited to the above embodiment.

It is tire radial direction sectional drawing of the pneumatic tire which concerns on 1st Embodiment. It is a fragmentary top view which shows the tread part of the pneumatic tire which concerns on 1st Embodiment. It is a perspective view of a block which constitutes a tread part of a pneumatic tire concerning a 1st embodiment. It is a perspective view which shows the shape of the sipe currently formed in the block of the pneumatic tire which concerns on 1st Embodiment. FIGS. 5A to 5D are a bottom view, a side view taken from the side of the block contact surface of the pneumatic tire according to the first embodiment, a side view of arrows 5B-5B, and a friction force acting on the block surface, respectively. 5B is a side view of arrow 5B-5B, and a graph showing the relationship between the small block circumferential direction position and the contact pressure when a frictional force acts on the block surface. It is a perspective view which shows the modification of a sipe in 1st Embodiment. It is a perspective view which shows the modification of a sipe in 1st Embodiment. It is a perspective view which shows the shape of the sipe currently formed in the block of the pneumatic tire which concerns on 2nd Embodiment. It is a perspective view which shows the shape of the sipe currently formed in the block of the pneumatic tire which concerns on 3rd Embodiment. 10 (A) to 10 (D) are a bottom view, a side view of arrows 10B-10B, as viewed from the block contact surface side of a conventional pneumatic tire, and an arrow when a frictional force acts on the block surface, respectively. FIG. 10B is a side view of the view 10B-10B and a graph showing the relationship between the position in the circumferential direction of the small block and the contact pressure when a frictional force acts on the block surface.

Explanation of symbols

10 Pneumatic tire 22 Circumferential groove 24 Horizontal groove 26 Block (tread block)
26Y Block side wall 34 Lateral sipe 84 Lateral sipe 87 Block (tread block)

Claims (3)

In a pneumatic tire having a plurality of tread blocks partitioned by a circumferential groove and a lateral groove,
The tread block has at least one sipe;
The pneumatic tire according to claim 1, wherein at least one of the sipes has a plurality of small holes extending from a sipe bottom in a depth direction of the tread block.   The pneumatic tire according to claim 1, wherein the sipe is a lateral sipe.   3. The pneumatic tire according to claim 1, wherein both ends of the sipe are open to a block side wall.

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