JP2011098601A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire which improves dry performance by equalizing the ground contact pressure of a land section while ensuring the rigidity of the land section. <P>SOLUTION: In the pneumatic tire, a plurality of blocks 10, which are divided by a circumferential groove extended in the tire circumferential direction, and a lateral groove extended across the circumferential groove, are formed on a tread surface. Each block 10 has corner sections 11 and 13 sharpened at least in one direction of the tire circumferential direction PD. A plurality of small holes 6 formed inwardly from wall surfaces 10a, 10b, 10c, and 10d are arranged at the corner sections 11 and 13. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a pneumatic tire in which a plurality of groove portions and a plurality of land portions divided by the groove portions are formed on a tread surface.

  Usually, the tread surface of a pneumatic tire is divided into a plurality of land portions (blocks, ribs, and the like) by groove portions such as circumferential grooves extending along the tire circumferential direction and transverse grooves extending across the circumferential groove. Various tread patterns according to required tire performance and use conditions are formed.

  Of these, the present inventor conducted research on tread patterns having blocks, and when a force in the front-rear direction acts on the block, the contact pressure at the corners of the block locally increases, and the ground contact on the block surface occurs. It has been found that pressure non-uniformity is caused, and this causes a decrease in steering stability performance on a dry road surface (hereinafter referred to as “dry performance”).

  That is, as shown in FIG. 9, when a braking force is applied to the block 50 rotating in the R direction on the dry road surface, the contact pressure is locally applied in the peripheral region of the block corner portion 51 sharpened in the tire circumferential direction. The contact pressure rises and decreases as the distance from the block corner 51 increases. On the other hand, when a driving force is applied to the block 50, the ground pressure is locally increased in the peripheral region of the block corner portion facing the block corner portion 51 of FIG. It has been found that such uneven contact pressure distribution can deteriorate the dry performance, so that there is a possibility of improving the performance by improving this.

  In Patent Document 1 below, the obtuse angle on the kicking side of the block having a substantially rhombus is formed for the purpose of lowering the rigidity of the kicking side edge of the block to lower the contact pressure and suppressing the wear of the obtuse angle part on the kicking side. A pneumatic radial tire having a concave portion formed in a corner portion toward the center of the block at an intermediate portion in the depth direction is described. By forming the recess in the obtuse angle portion on the kicking side in this way, the block rigidity can be lowered and the contact pressure can be lowered. As a result, it is possible to suppress wear of the obtuse angle portion on the kick-out side and to suppress heel and toe wear.

  However, since the corners of the block are susceptible to distortion, if such recesses are formed in the corners of the block, the rigidity of the corners will decrease too much, resulting in poor grounding of the block, and contact pressure on the block surface. Tends to be non-uniform and the dry performance decreases. In addition, it is not restricted to a block that the corner | angular part is easily distorted in this way, but can be said to the land part generally divided by the groove part.

Japanese Patent Application Laid-Open No. 2008-126887

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a pneumatic tire that can improve dry performance by uniformizing the contact pressure of the land portion while ensuring the rigidity of the land portion. It is to provide.

In order to solve the above problems, a pneumatic tire according to the present invention is
In the pneumatic tire in which the plurality of groove portions and the plurality of land portions divided by the groove portions are formed on the tread surface,
The land portion has a corner portion sharpened toward at least one of the tire circumferential directions, and a plurality of small holes formed from the wall surface to the inside are arranged at the corner portion.

  The effects of the pneumatic tire having such a configuration will be described. In the pneumatic tire according to the present invention, a plurality of groove portions and a plurality of land portions divided by the groove portions are formed on the tread surface, and the land portions are sharpened toward at least one of the tire circumferential directions. A plurality of small holes formed from the wall surface to the inside are arranged at the corners. In other words, by providing a plurality of small holes at the corners sharp in the tire circumferential direction where the contact pressure tends to increase particularly when a longitudinal force acts on the land part, the rigidity of the corner part is reduced and bent. It becomes easy and the ground contact pressure of the land part can be equalized. In addition, in the recessed part with slits as in sipe or the above-mentioned Patent Document 1, the effect of reducing the rigidity is localized, but by forming small holes in the wall surface as in the present invention, the distribution of rigidity is too concentrated on the local part. A spongy effect is obtained, and the ground contact pressure in the land can be made highly uniform. Nevertheless, the small holes arranged at the corners of the land are formed inward from the wall of the land, and no small holes are formed at the tip of the corner where the adjacent wall and the wall intersect. There is no significant decrease in rigidity. As a result, it is possible to improve the dry performance by making the contact pressure of the land portion uniform while securing the rigidity of the land portion.

  In the pneumatic tire according to the present invention, the plurality of small holes are arranged in the height direction and the left-right direction of the wall surface, and the total volume of the small holes arranged in the height direction is centered from the side end of the wall surface. It is preferable that it becomes small toward.

  As described above, when a force in the front-rear direction acts on the land portion, the contact pressure at the corner portion of the land portion increases locally, but the contact pressure at the tip portion of the corner portion is particularly high, and the corner portion of the land portion The ground pressure decreases as the distance from the distance increases. By reducing the total volume of the small holes arranged in the height direction of the wall surface from the side edge of the wall surface toward the center, the ease of bending of the land portion from the side edge of the wall surface toward the center can be reduced. It is possible to make the ground contact pressure more uniform. Note that the total volume of the small holes arranged in the height direction of the wall surface can be appropriately set by changing the cross-sectional area, depth, cross-sectional shape, and the like of each small hole.

  In the pneumatic tire according to the present invention, it is preferable that the number of the small holes arranged in the height direction of the wall surface decreases from the side end of the wall surface toward the center.

  By reducing the number of small holes arranged in the height direction of the wall surface from the side edge of the wall surface toward the center, the total volume of the small holes arranged in the height direction is reduced from the side edge of the wall surface to the center. It can be made smaller. Thereby, the easiness of bending toward the center from the side end of the wall surface can be reduced, and the contact pressure of the land portion can be made more uniform.

  In the pneumatic tire according to the present invention, it is preferable that the small hole row height of the small holes arranged in the height direction of the wall surface decreases from the side end of the wall surface toward the center.

  The number of small holes arranged in the height direction of the wall surface is decreased from the side edge of the wall surface toward the center, and the height of the small hole array arranged in the height direction of the wall surface is reduced to the side edge of the wall surface. Since the ground pressure is lowered from the center to the center, the ground contact pressure can be made uniform, and even if land wear continues, the decrease in the number of small holes is suppressed. The effect of equalization can be achieved for a long time.

  As an embodiment of the present invention, the land portion may be a block divided by a circumferential groove extending along the tire circumferential direction and a lateral groove extending across the circumferential groove. In such a corner pointed toward the tire circumferential direction, the contact pressure rises locally in the peripheral region, so that the contact pressure of the block is made uniform while ensuring the rigidity of the block as described above. It is effective.

The top view which shows an example of the tread surface of the pneumatic tire which concerns on this invention Three views of the block provided on the tread surface Three views of a block according to another embodiment of the present invention Perspective view of blocks with different depths of circumferential and transverse grooves The perspective view of the block concerning another embodiment of the present invention. The perspective view of the block concerning another embodiment of the present invention. The perspective view and top view of the block which concern on another embodiment of this invention Front view of blocks according to comparative example and example Conceptual diagram showing the distribution of contact pressure when braking force is applied to the block The top view which shows an example of the tread surface of the pneumatic tire which concerns on other embodiment

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a plan view showing an example of a tread surface of a pneumatic tire according to the present invention. The tread surface is provided with a circumferential groove 2 extending in the tire circumferential direction PD and a lateral groove 3 extending in the tire width direction WD. The direction in which the circumferential groove 2 extends does not have to completely coincide with the tire circumferential direction PD. Further, the lateral groove 3 only needs to extend so as to intersect the circumferential groove 2, and the angle inclined with respect to the circumferential groove 3 is not particularly limited.

  The tread surface is divided into a center rib 5 and a plurality of blocks 10 by a circumferential groove 2 and a lateral groove 3. The center rib 5 extends along the tire equator line CL, and two rows of parallelogram blocks 10 are arranged on both sides thereof. The block 10 is divided in the tire width direction WD by the circumferential groove 2 and divided in the tire circumferential direction PD by the lateral groove 3. In the present invention, the shape of the block is not particularly limited, and may be a rectangular shape, a rhombus shape, or the like.

  FIG. 2 is a three-view diagram of the block 10. A front view of the wall surface 10 b facing the circumferential groove 2 is shown below the plan view, and a front view of the wall surface 10 a facing the lateral groove 3 is shown on the left side. . The block 10 is configured to be surrounded by four wall surfaces 10a, 10b, 10c, and 10d. The corner portion 11 is composed of the wall surface 10a and the wall surface 10b, the corner portion 12 is composed of the wall surface 10b and the wall surface 10c, the corner portion 13 is composed of the wall surface 10c and the wall surface 10d, and the corner portion 14 is composed of the wall surface 10d and the wall surface 10a. .

  Among the corner portions 11, 12, 13, and 14 of the block 10, a plurality of small holes 6 are arranged in the corner portions 11 and 13 that are pointed toward the tire circumferential direction PD. Hereinafter, the corner portion 11 will be described as an example, but the corner portion 13 has the same configuration and operational effects.

  The plurality of small holes 6 are formed from the wall surfaces 10 a and 10 b of the block 10 toward the inside of the block 10. Although not shown in FIG. 2, the small hole 6 is formed to be inclined toward the inner periphery of the tire toward the inside of the block 10.

  As shown in FIG. 2, the small hole 6 is formed away from the tip end portion 11a of the corner portion 11 where the wall surface 10a and the wall surface 10b intersect. Thus, since the small hole 6 is not formed in the front-end | tip part 11a of the corner | angular part 11, block rigidity is not reduced significantly. The small hole 6 is preferably formed at a distance of 0.5 mm or more from the distal end portion 11a in consideration of a decrease in block rigidity.

  The plurality of small holes 6 are arranged in the height direction and the left-right direction of the wall surfaces 10a, 10b, and the plurality of small holes 6 arranged in the height direction constitute small hole rows 60a, 60b, 60c. A plurality of small hole rows 60a, 60b, 60c are arranged in the left-right direction of the wall surface, thereby configuring the small hole region 60 as a whole. In this embodiment, an example in which there are three small hole rows is shown, but the present invention is not limited to this.

  In the present embodiment, the number of the small holes 6 arranged in the height direction is decreased from the lateral side edge of the wall surface toward the center. Along with this, the height of the small hole rows 60a, 60b, 60c decreases from the lateral side edge of the wall surface toward the center.

  When force in the front-rear direction acts on the block 10, the ground contact pressure rises locally at the corner 11 sharpened toward the tire circumferential direction PD, but by providing a plurality of small holes 6 at the corner 11, The corner portion 11 of the block 10 is easily bent, and the ground pressure of the block 10 can be made uniform. Nevertheless, as described above, since the small hole 6 is not formed at the tip end portion 11a of the corner portion 11 where the wall surface 10a and the wall surface 10b intersect, the block rigidity is not greatly reduced. As a result, it is possible to improve the dry performance by making the contact pressure of the block 10 uniform while ensuring the block rigidity.

  In this embodiment, the cross-sectional shape and depth of each small hole 6 are the same, and the volume of each small hole 6 is constant. Thereby, the total volume of the plurality of small holes 6 (small hole rows 60a, 60b, 60c) arranged in the height direction of the wall surfaces 10a, 10b is obtained by multiplying the volume of each small hole 6 by the number of small holes 6. In this embodiment, it becomes small toward the center from the side end of wall surface 10a, 10b.

  When a force in the front-rear direction acts on the block 10, the ground pressure at the corners 11 and 13 of the block 10 locally increases, but in particular, the ground pressure at the tips 11a and 13a of the corners 11 and 13 is the highest, The ground pressure decreases as the distance from the 10 corners 11 and 13 increases. By reducing the total volume of the small holes 6 (small hole rows 60a, 60b, 60c) arranged in the height direction of the wall surfaces 10a, 10b from the side ends of the wall surfaces 10a, 10b toward the center, the wall surfaces 10a, 10b The ease of bending of the block 10 from the side end toward the center can be reduced, and the ground pressure of the block 10 can be made more uniform.

  Further, in the present embodiment, the small hole rows 60a, 60b, 60c are provided so that the lower portions thereof are located in the vicinity of the lower portions of the wall surfaces 10a, 10b, and as far as possible from the surface of the block 10. . Thereby, even if the block wear progresses, the decrease of the small holes 6 is suppressed, and the effect of equalizing the ground pressure by the small holes 6 can be exhibited for a long period of time. In addition, the appearance of the small holes 6 on the tread surface accompanying the wear can be delayed as much as possible to minimize the influence on the uneven wear resistance performance and the traction performance.

  In the present embodiment, the cross-sectional shape of the small hole 6 is formed in a circular shape, and 0.5 to 1 mm is exemplified as the diameter. However, the cross-sectional shape of the small hole 6 is not limited to this, and may be an ellipse, a semicircle, a triangle, a hexagon, a trapezoid, or the like. Further, from the viewpoint of securing the rigidity of the block 10, it is preferable to set the interval between the small holes 6 to 0.5 mm or more.

  Examples of the depth of the small hole 6 include 0.5 to 1.5 mm. If the depth is less than 0.5 mm, sufficient ease of bending tends to be difficult due to insufficient volume of the small hole 6. When a sipe is set on the block 10, the depth is preferably 1.5 mm or less in order to avoid interference between the sipe and the small hole 6.

The volume of each small hole 6 is preferably 0.09 to 1.2 mm ³ . Moreover, it is preferable that the area of the small hole 6 formed in the wall surface of the block 10 shall be 0.1S-0.5S with respect to the area S of the whole wall surface. If it is smaller than these ranges, the effect of facilitating the bending of the block 10 by the small holes 6 is difficult to occur, and conversely if it is larger than these ranges, the rigidity of the block 10 is excessively lowered.

  The pneumatic tire of the present invention is manufactured in the same manner as the conventional tire manufacturing process, except that the groove for forming the groove provided in the tire mold is provided with a protrusion corresponding to the small hole 6. Can do. In this embodiment, although not shown in FIG. 2, the small holes 6 are inclined toward the inner periphery of the tire toward the inside of the block 10, so that protrusions can be easily removed from the tread surface when removing the tire. The small holes 6 can be formed smoothly. As an inclination angle of the small hole 6, 10-20 degrees is illustrated with respect to the direction perpendicular | vertical to a wall surface.

  In the present invention, the small holes as described above can be formed for all the blocks 10 in the tread surface, but may be formed only for a part of the blocks 10 in the tread surface.

  The pneumatic tire of the present invention is the same as a normal pneumatic tire except that the small holes as described above are provided in the block, and any conventionally known material, shape, structure, etc. can be adopted in the present invention. In addition, the block provided with the small hole is not limited to the block completely surrounded by the groove portion, but is substantially formed as a block, such as blocks partially adjacent to each other in the tire circumferential direction. If so, the present invention is applicable.

[Other Embodiments]
(1) In the above-described embodiment, an example in which the shapes of the plurality of small holes 6 are all the same is shown. However, in the present invention, the plurality of small holes 6 (small hole rows 60a and 60b) arranged in the height direction of the wall surface. , 60c) as long as the total volume of the wall surface decreases from the side edge toward the center, the present invention is not limited to this. For example, as shown in FIG. 3, by changing the diameter of the small holes 6, the volume of each small hole 6 can be changed even if the depth is the same, and they are arranged in the height direction of the wall surface. The total volume of the small holes 6 (small hole rows 60a, 60b, 60c) can be reduced from the side end of the wall surface toward the center. In FIG. 3, the diameters of the small holes 6 belonging to the same small hole row 60a, 60b, 60c are all the same, but the small holes 6 having various diameters may be mixed. In addition, by changing the depth of the small holes 6, it is naturally possible to change the volume of each small hole 6 even if the diameters are the same.

  (2) In the above-described embodiment, the volume of each small hole 6 formed in the wall surfaces 10b and 10d facing the circumferential groove 2 and the volume of each small hole 6 formed in the wall surfaces 10a and 10c opposed to the lateral groove 3 are as follows. An example that is the same is shown. This is an example when the groove depth of the circumferential groove 2 and the lateral groove 3 is the same, and when the groove depth of the circumferential groove 2 as shown in FIG. 4 is deeper than the groove depth of the lateral groove 3. As shown in FIG. 5, the total volume of the small holes 6 formed in the wall surfaces 10b and 10d may be smaller than the total volume of the small holes 6 formed in the wall surfaces 10a and 10c. That is, the rigidity of the wall surfaces 10b and 10d facing the circumferential groove 2 having a deep groove depth is lower than the rigidity of the wall surfaces 10a and 10c facing the lateral groove 3 having a shallow groove depth. There is no need. Here, an example is shown in which the number of small holes 6 formed in the wall surfaces 10b and 10d and the wall surfaces 10a and 10c is changed.

  (3) Further, when the groove depth of the circumferential groove 2 as shown in FIG. 4 is deeper than the groove depth of the lateral groove 3, as shown in FIG. Reinforcing pillars 15 may be further provided on the wall surfaces 10 b and 10 d that are corner portions 12 and 14 other than 13 and that face the circumferential groove 2. By providing this reinforcing column 15, the unevenness between the rigidity of the wall surfaces 10b, 10d facing the circumferential groove 2 and the rigidity of the wall surfaces 10a, 10c facing the lateral groove 3 is eliminated, and the corner portions 12, 14 are eliminated. The grounding becomes uniform. Thereby, in combination with the effect of the small holes 6, the ground pressure of the entire block can be made more uniform. The size of the reinforcing column 15 is preferably 3 mm or more in the tire circumferential direction PD and 1 mm or more in the tire width direction WD. The height of the reinforcing column 15 is such that the upper surface of the reinforcing column 15 is equal to or more than the bottom surface of the lateral groove 3. It is preferable to do so.

  (4) When the block 10 is provided with the tapered portion 16 as shown in FIG. 7, the small hole 6 may be formed on the wall surface adjacent to the wall surface provided with the tapered portion 16. FIG. 7A is a perspective view of the block 10 provided with the tapered portion 16, and FIG. 7B is a plan view of the block 10. Such a tapered portion 16 may be formed for improving the design and performance. FIG. 7 shows an example in which the tapered portion 16 is formed so that the upper portion of the corner portion 12 is cut obliquely. Since the rigidity of the wall surfaces 10b and 10c constituting the corner portion 12 is reduced by the tapered portion 16, the tapered portion is formed by forming the small holes 6 in the wall surface 10a adjacent to the wall surface 10b and the wall surface 10d adjacent to the wall surface 10c. The rigidity nonuniformity between the wall surfaces 10b, 10c provided with 16 and the wall surfaces 10a, 10d not provided with the tapered portion 16 is eliminated, and the grounding of the corner portions 11, 13 becomes uniform.

  (5) In the above-described embodiment, an example in which the land portion is a block divided by a circumferential groove extending along the tire circumferential direction and a lateral groove extending across the circumferential groove is shown. However, the land portion is not limited to such a so-called block pattern block, and may be one that is divided by a plurality of groove portions. FIG. 10 is a plan view illustrating an example of a tread surface of a pneumatic tire according to another embodiment. That is, the land portion may be a block having a complicated shape as shown in FIG. 10A, or may be a non-block portion or a shoulder block of the center portion as shown in FIG. In FIG. 10, the corner where the ground pressure is locally increased is surrounded by a broken-line circle.

  Hereinafter, the dry performance was evaluated in order to specifically show the configuration and effects of the present invention. The dry performance was evaluated by a driver's sensory test after running on a dry road surface with tires attached to the vehicle, running straight, turning and braking. The dry performance was evaluated when the tire was new and during the middle stage of wear where the wear progressed to some extent. The result of the comparative example is shown as an index with the value of 100, and the larger the index, the better the dry performance.

Comparative Example and Example In a tire of size 195 / 65R15 having a tread pattern as shown in FIG. 1, a small hole is not provided on the wall surface of the block as a comparative example, and small holes are arranged as shown in FIG. Were taken as Examples 1 to 3. The width of the wall of the block is 30 mm, the height is 8 mm, the diameter of each small hole is 1 mm, and the depth is 0.5 mm. The evaluation results are shown in Table 1.

  From Table 1, it can be seen that in Examples 1 to 3, the dry performance is superior to the comparative example in both the new state and the middle stage of wear. This is considered to be because the ground pressure of the block was made uniform by providing the small holes as described above on the wall surface of the block.

  Further, in Example 1, there is no difference in the dry performance between the new product and the middle period of wear, but in Examples 2 and 3, the dry performance is deteriorated in the middle period of wear compared to the new product. This is thought to be because the number of small holes decreases with the progress of wear.

2 circumferential grooves 3 transverse grooves 5 center ribs 6 small holes 10 blocks 10a to 10d wall surfaces 11 to 14 corners 11a and 13a corner tips 15 reinforcing columns 16 taper portions 50 blocks 51 block corner portions 60 small hole regions 60a to 60c small hole rows

Claims (5)

In the pneumatic tire in which the plurality of groove portions and the plurality of land portions divided by the groove portions are formed on the tread surface,
The land portion has a corner portion sharpened toward at least one of the tire circumferential direction, and a plurality of small holes formed from the wall surface to the inside are arranged in the corner portion. tire.   The plurality of small holes are arranged in the height direction and the left-right direction of the wall surface, and the total volume of the small holes arranged in the height direction decreases from the side edge of the wall surface toward the center. The pneumatic tire according to claim 1.   The pneumatic tire according to claim 2, wherein the number of the small holes arranged in the height direction of the wall surface decreases from a side end of the wall surface toward the center.   The pneumatic tire according to claim 3, wherein a small hole row height of the small holes arranged in the height direction of the wall surface decreases from a side end of the wall surface toward the center. 5. The block according to claim 1, wherein the land portion is a block divided by a circumferential groove extending along a tire circumferential direction and a lateral groove extending intersecting the circumferential groove. Pneumatic tire.

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