JP2006298055A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire which improves the sipe shape provided on a block of the tread surface and ensures a high level of compatibility between acceleration and deceleration performance on icy and snowy road surfaces and acceleration and deceleration performance on dry and wet road surfaces. <P>SOLUTION: The plurality of sipes substantially extending to a tread width direction are provided on the block, and each sipe is formed from first straight line parts 10a, 11a extending from the tread surface to the inward of the tire radial direction, inclined parts 10b, 11b extending from the terminating end of the first straight line part to the inward of the tire radial direction at the acute angles α, β and second straight line parts 10c, 11c extending from the terminating end of the inclined part. The inclined part 10b is inclined further at the stepping-in side of the block than the first straight line part 10a to the inward of the tire radial direction on a tread central area (a), and the inclined part 11b is inclined further at the kicking-out side of the block than the first straight line part 11a on a tread side part area (b). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pneumatic tire having a designated rotational direction, and more particularly to a pneumatic tire that achieves both acceleration performance and deceleration performance at a high level on both icy and snowy road surfaces and dry and wet road surfaces.

  In so-called studless pneumatic tires, the tread is divided into a plurality of blocks to increase the grip force on snow, and in order to further increase the grip force on the road surface on ice, the blocks are provided with a plurality of sipes to subdivide the blocks. The frictional resistance on ice has been increased by the edge effect of a large number of block corners formed by subdivision. In such a tire, when the block part subdivided by sipe is brought into contact with the road surface and accelerated or decelerated on a normal dry or wet road surface, the block part falls more than necessary, and the block part There is a problem that the contact area is reduced and the desired acceleration / deceleration performance cannot be obtained. Therefore, as a measure for preventing the block portion from falling more than necessary on dry and wet road surfaces, for example, as described in JP-A-10-21804, the sipe is disposed with an inclination with respect to the tread circumferential direction. Thus, there has been proposed a structure that prevents the subdivided block portion from falling more than necessary.

Further, as described in European Patent Application Publication No. 10735621, a measure in which a sipe is uneven in the tread depth direction, European Patent No. 515349 and Japanese Patent Application Laid-Open No. 11-310012. As described in JP-A-8-244419 and JP-A-11-78432, a method for making the sipe three-dimensional in the tread depth direction as described in JP-A-8-244419 or JP-A-11-78432 Measures to incline a part of the tire toward the stepping-in side or the kicking-out side with respect to the tire radial direction have been proposed, all of which aim to prevent the block part subdivided by sipe from falling more than necessary. To do.
Japanese Patent Laid-Open No. 10-21804 European Patent Application No. 10735621 European Patent No. 515349 Japanese Patent Laid-Open No. 11-310012 JP-A-8-244419 Japanese Patent Laid-Open No. 11-78432

  However, it is clear from recent research that the direction in which the block section subdivided by sipe is easy to fall is different especially during acceleration and deceleration, and that the contact area of the tread is different between acceleration and deceleration. It has become. As a result, there has been a problem that the above measures alone are not perfect for further achieving both acceleration and deceleration performance on icy and snowy road surfaces and acceleration and deceleration performance on dry and wet road surfaces.

  The present invention has been made to solve such problems of the prior art, and its purpose is to improve the shape of the sipe provided on the tread tread block, and to accelerate and decelerate performance on icy and snowy road surfaces. Another object of the present invention is to provide a pneumatic tire that achieves higher levels of acceleration and deceleration performance on dry and wet road surfaces.

  According to the present invention, a plurality of circumferential grooves continuously extending in the tread circumferential direction are provided on the tread surface, and a plurality of horizontal grooves or inclined grooves extending across the circumferential grooves are provided to partition a plurality of block rows. Each of the blocks is provided with a plurality of sipes extending substantially in the tread width direction. A first straight portion extending inward in the direction, an inclined portion extending from the end of the first straight portion at an acute angle with respect to the inner side in the tire radial direction, and a second extending inward in the tire radial direction from the end of the inclined portion In the center region of the tread, the inclined portion is inclined from the first straight portion to the stepping side of the block in the tire radial direction, and in the tread side region, the inclined portion of the block is Is inclined to the exit side, characterized by comprising.

Here, the tread side area refers to an area defined between the circumferential groove located at approximately 1/4 of the tread tread width from the tire equator line and the tread tread edge, and the tread central area refers to the tread side area. An area excluding a division.
Further, substantially extending in the tread width direction means that the sipe extends in the tire width direction, extends slightly inclined with respect to the tire width direction, or extends along the lateral groove or the inclined groove. Is also included.

The tread tread width means the contact width when a tire is mounted on an applicable rim, a specified air pressure is filled, and a mass corresponding to the maximum load capacity is loaded thereon. The applicable rim here refers to the rim specified in the following standards, the maximum load capacity refers to the maximum mass allowed to be applied to the tire according to the following standards, and the specified air pressure refers to the following standards: Means the air pressure defined corresponding to the maximum load capacity.
The standard is determined by an industrial standard effective in the region where the tire is produced or used. For example, “THE TIRE AND RIM ASSOCIATION INC. YEAR BOOK” in the United States, “The European Tire and Rim Technical Organization STANDARDS MANUAL” in Europe, and “JATMA YEAR BOOK” of the Japan Automobile Tire Association in Japan. .

  In the present invention, during acceleration, the tire rotation speed is relatively high with respect to the vehicle speed, and the action of the centrifugal force causes the tread central area to protrude, so that the ground contact pressure in the tread central area is relative to the shoulder portion. On the other hand, at the time of deceleration, the tire rotation speed is relatively low with respect to the vehicle speed, and the sidewall portion acts to exert a force opposite to the traveling direction on the road surface. Therefore, considering that the ground contact pressure of the shoulder is relatively higher than the center area of the tread, and that the input from the road surface to the tire tread is in the opposite direction during acceleration and deceleration. It was made.

  According to this, in the tread central region where the contact pressure increases during acceleration, the slope of the sipe located closest to the kicking side of the block subdivided by the sipe is inclined by inclining the inclined portion toward the stepping side in the tire rotation direction. In order to increase the tire circumferential thickness of the kicking block part formed between the straight line part and the kicking side end of the block and increase the rigidity in the tread circumferential direction of the kicking block part during acceleration, , Against the block from the road surface, against the force acting from the stepping side to the kicking side, each block part subdivided by sipe, the kicking side block part supports its rigidity and falls down Can be difficult. In addition, the stepped part defined by the sipe slope of each block part supports the moment acting in the direction of falling from the stepping side to the kicking side on the block part adjacent to the stepping side of the block part. Therefore, it is possible to prevent the block portion subdivided by sipe from collapsing. As a result, it is possible to secure the rigidity of the block and the ground contact area necessary for acceleration, and improve the acceleration performance.

Also, in the tread side area where the contact pressure increases during deceleration, the sipe second straight line located closest to the stepping side of the block subdivided by the sipe by inclining the inclined part toward the tire rotation direction kicking side In order to increase the rigidity in the tread circumferential direction of the tread side block part of the tread side block part formed between the step part and the step side end of the block, the tread from the road surface during deceleration On the other hand, against the force acting from the kicking side to the stepping side, each block part subdivided by sipe is supported by the stepping side block part with its rigidity, making it difficult to fall down it can. In addition, the stepped part of each block part, which is partitioned by the sipe slope part, exerts a moment acting on the block part adjacent to the kicking side of the block part in the direction of falling from the kicking side to the stepping side. Since it supports, the fall of the block part subdivided by the sipe can be prevented. By these things, the rigidity of the block and the ground contact area required at the time of deceleration can be ensured, and deceleration performance can be improved.
As a result, on dry and wet road surfaces, the necessary rigidity and ground contact area can be secured in the tread center area during acceleration, and the necessary rigidity and ground contact area can be secured in the tread side area during deceleration, thereby accelerating performance and deceleration. Both performances can be achieved at a high level.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a development view of a tread pattern showing an embodiment of the present invention in a front view of a mounting posture on a vehicle. In the figure, the outer side of the mounting is the right side, the inner side of the mounting is the left side, and the arrow indicates the direction of rotation.
Here, the tread tread portion 1 is provided with a circumferential groove 2 extending continuously in the tread circumferential direction linearly on the tire equator line C, and the tire equator line C is symmetrically separated by about 1/4 of the tread tread width W. A pair of circumferential grooves 3 and 4 that are positioned and extend linearly and continuously in the tread circumferential direction, and that extend from the circumferential groove 2 toward the tread tread edge while increasing the angle with respect to the tread circumferential direction. 5 is provided. These circumferential grooves 2, 3, 4 and the inclined groove 5 define a center block 6, a center block 7, a shoulder block 8, and a shoulder block 9. The center block 6 and the center block 7 are provided with a narrow groove 9 that communicates the inclined groove 5 on the kicking side and the inclined groove 5 on the stepping side, respectively, and the center blocks 6a and 7a on the tire equator line side and the tread It is divided into center blocks 6b and 7b on the tread edge side.
The inclined groove 5 may be a lateral groove extending in the tire width direction.

  Since the pattern in FIG. 1 employs a variable pitch, each center block has a different tread circumferential length depending on a portion in the tread circumferential direction. For this reason, each center block 6a, 6b, 7a, 7b has a sipe 10 having a tire width direction component at equal intervals in the tread circumferential direction, and a center block having a short tread circumferential length, respectively. Three are provided at approximately equal intervals, and four are provided at approximately equal intervals in the center block of the long part.

  As shown in FIG. 2A, the shape of the sipe in the AA cross section of FIG. 1 extends from the tread tread surface inward in the tire radial direction and is approximately １ ／ of the depth ds of the entire sipe 10 from the block surface. A first linear portion 10a ending at the position of, and an inclined portion 10b extending from the ending end of the first linear portion 10a toward the inner side in the tire radial direction with an acute angle α toward the tire radial step-in side and ending inside the block And a second linear portion 10c extending inward in the tire radial direction from the end of the inclined portion and ending inside the block.

  According to this, in the center blocks 6a, 6b, 7a, and 7b in the tread central area where the contact pressure becomes high during acceleration, the second straight portion of the sipe that is located closest to the kicking side of the block that is subdivided by the sipe 10 The tire circumferential direction thickness L1 of the kicking side block portion 12 formed between the block 10c and the kicking side end of the block is made thicker than the other block portions 13, and the tread circumference of the kicking side block portion 12 is increased. In order to increase the rigidity in the direction, when accelerating, the force F1 acting from the stepping side to the kicking side as shown by the arrow in FIG. Each of the block portions 13 thus formed can be supported by the kick-out block portion 12 with its rigidity, so that the block portions 13 are not easily collapsed. Further, the stepped portion defined by the sipe inclined portion 10b of each block portion 13 acts on the block portion 13 adjacent to the stepping side of the block portion in a direction of falling from the stepping side to the kicking side. Since the force F1 is supported, the block portion 13 subdivided by sipe can be prevented from falling down. By these things, the rigidity of the center blocks 6 and 7 required at the time of acceleration and a ground contact area can be ensured, and acceleration performance can be improved.

Here, the angle α of the inclined portion 10b with respect to the tire radial direction shown in FIG. 2A is 20 to 70 degrees, and the offset amount S1 between the first straight portion 10a and the second straight portion 10c is 0.1 to 3 mm. Is preferred. When the numerical value range is smaller than the lower limit value, the rigidity of the block portion 12 in the tire circumferential direction cannot be sufficiently increased, and the effect of supporting the stepped portion F1 of the block portion 13 becomes too small. When it becomes larger than the upper limit value, the tire circumferential rigidity of the block portion 13 located on the most step side becomes too small.
The sipe depth ds is preferably 70 to 100% of the inclined groove depth d. If the sipe depth ds is less than 70% of the inclined groove depth d, the edge effect on the road surface on ice is reduced, and if it is more than 100%, the rigidity of the block portion subdivided by the sipe becomes too small, which is not preferable.

  Each of the shoulder blocks 8 and 9 is provided with three sipes 11 each having a tire width direction component at equal intervals in the tread circumferential direction. As shown in FIG. 2 (b), the shape in the BB cross section of FIG. 1 is a position that extends inward in the tire radial direction from the tread surface and is approximately 1/3 of the depth ds of the entire sipe 11 from the block surface. A first linear portion 11a that ends at the end, and an inclined portion 11b that extends from the end of the first linear portion toward the tire radial direction inner side in the tire radial direction at an acute angle β and ends inside the block, The second linear portion 11c extends inward in the tire radial direction from the end of the inclined portion 11b and ends inside the block.

  As a result, in the shoulder blocks 8 and 9 in the tread side area where the contact pressure increases during deceleration, the second straight portion of the sipe located closest to the stepping side of the block subdivided by the sipe 11 and the stepping side end of the block In order to increase the rigidity in the tread circumferential direction of the tread side block portion 14 by increasing the tire circumferential direction thickness L2 of the step side block portion 14 formed between and the other block portions 15, As shown by the arrow in FIG. 2B, each block portion 15 subdivided by sipe with respect to the force F2 acting on the tread from the road surface to the tread from the road surface, The portion 14 is supported with its rigidity and can be prevented from falling down. Further, the stepped portion defined by the sipe inclined portion 11b of each block portion 15 acts on the block portion 15 adjacent to the stepping side of the block portion in a direction of falling from the stepping side to the kicking side. Since the force F2 is supported, the block portion 15 subdivided by sipe can be prevented from falling down. By these things, the rigidity of the shoulder blocks 8 and 9 required at the time of deceleration and a ground contact area can be ensured, and deceleration performance can be improved.

Here, the angle β of the inclined portion 11b with respect to the tire radial direction shown in FIG. 2B is set to 20 to 70 degrees, and the offset amount S2 between the first straight portion 11a and the second straight portion 11c is set to 0.1 to 3 mm. Is preferred. If the numerical range is smaller than the lower limit value, the rigidity of the block portion 14 in the tire circumferential direction cannot be sufficiently increased, and the function of supporting the stepped portion F2 of the block portion 15 becomes too small. When it becomes larger than the upper limit value, the rigidity in the tire circumferential direction of the block portion 15 positioned closest to the kicking side becomes too small.
The sipe depth ds is preferably 70 to 100% of the inclined groove depth d. If the sipe depth ds is less than 70% of the inclined groove depth d, the edge effect on the road surface on ice is reduced, and if it is more than 100%, the rigidity of the block portion subdivided by the sipe becomes too small, which is not preferable.

  Further, here, a circumferential sipe 16 that communicates between the sipes 10 and between the sipe 10 and the inclined groove 9 in the tire circumferential direction, and between each sipe 11 and between the sipes 11 and the inclined groove 9 in the tire circumferential direction. By providing the circumferential sipe 17 that communicates with each other, the rigidity of each block is reduced, and the ground contact property and uneven wear resistance are improved.

  The pneumatic tire according to the present invention has the tread pattern of FIG. 1 having a size of 195/65 R15 in order to evaluate the effect of enhancing acceleration performance and braking performance on snowy and dry road surfaces and dry road surfaces. Example tire 1 having a sipe shape, comparative tire 1 having the tread pattern shown in FIG. 1 and having the sipe shape shown in FIG. 3, and comparison having the tread pattern shown in FIG. 1 and the sipe shape shown in FIG. Example tire 2 and comparative example tire 3 having the tread pattern shown in FIG. 1 and the sipe shape of FIG. 5 are attached to a 6 J × 15 rim, filled with an internal pressure of 210 kPa, and attached to a test vehicle. The acceleration performance and the deceleration performance were evaluated by using the comparative tire 1 as a control. The results are shown in Table 1.

  Here, the sipe shown in FIG. 3 has a planar shape extending in the tread width direction, and the sipe shown in FIG. 4 has two sipes 10 located on the stepping side with respect to the sipe 10 of the center block from the substantially center in the tread circumferential direction. The sipe 10 is a sipe having an inclined portion 10b inclined toward the stepping side, and the sipe 10 positioned on the kicking side from the center is a sipe having an inclined portion inclined toward the kicking side. Further, for the sipe 11 of the shoulder block, the sipe that is located closest to the kicking side is a sipe that has an inclined portion that is inclined to the kicking side, and the two sipes on the stepping side are inclined portions 11b that are inclined to the stepping side. With a sipe. In addition, the sipe inclined portions 10b and 11b shown in FIG. 5 extend at an acute angle with respect to the inner side in the tire radial direction, and are inclined toward the tire rotation direction kicking side.

  According to the data in Table 1, it can be seen that the example tire 1 can improve the acceleration performance and the deceleration performance on all the icy and snowy road surfaces and especially on the icy road surface, as compared with the comparative tire 1. Further, it can be seen that more excellent acceleration performance and deceleration performance can be exhibited especially on the road surface on ice as compared with the comparative tire 2. Further, even when compared with the comparative example tire 3, it can be seen that acceleration performance and deceleration performance can be improved on all icy and snowy road surfaces and especially on dry road surfaces.

  The present invention is effective when applied to a pneumatic tire in which the rotation direction is specified, in particular, a pneumatic tire having improved acceleration performance and deceleration performance on dry and wet road surfaces, such as a studless tire.

It is an expanded view of the tread pattern which shows one Embodiment of this invention. It is a schematic cross section showing the form of the sipe in the AA cross section of FIG. It is a schematic cross section showing the form as a comparative example of the sipe in the AA cross section of FIG. It is a schematic cross section showing the form as another comparative example of the sipe in the AA cross section of FIG. It is a schematic cross section showing the form as another comparative example of the sipe in the AA cross section of FIG.

Explanation of symbols

1 tread surface 2 circumferential groove 3 circumferential groove 4 circumferential groove 5 inclined groove 6 center block 7 center block 8 shoulder block 9 shoulder block 10 sipe 10a first linear portion 10b inclined portion 10c second linear portion 11 sipe 11a first linear portion 11b inclined portion 11c 2nd straight part 12 Block part 13 located in the most kick-out side Other block part 14 Block part 15 located in the most stepping side 15 Other block part 16 Circumferential sipe 17 Circumferential sipe d Inclined groove depth ds Sipe depth The

Claims (1)

The tread tread surface portion is provided with a plurality of circumferential grooves extending continuously in the tread circumferential direction, and a plurality of lateral grooves or inclined grooves extending across the circumferential grooves to provide a rotation direction in which a plurality of block rows are partitioned. Is a designated pneumatic tire,
Each block is provided with a plurality of sipes extending substantially in the tread width direction, each sipe extending inward in the tire radial direction from the tread surface in the tire circumferential cross section, and the end of the first linear portion An inclined portion extending at an acute angle with respect to the inner side in the tire radial direction from the end, and a second straight portion extending inward in the tire radial direction from the end of the inclined portion. A pneumatic tire that is inclined from the first straight portion to the stepping-in side of the block with respect to the inner side in the tire radial direction, and is inclined from the first straight portion to the kicking side of the block in the tread side region.

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