JP5790199B2 - studless tire - Google Patents

Description

  The present invention relates to a studless tire, and more particularly to a studless tire that improves snow braking performance and ice braking performance in a well-balanced manner.

  In general, in a studless tire that runs on an icy and snowy road surface, a low-hardness rubber is used for the tread rubber, and a large number of blocks are formed on the tread surface. The surface of these blocks is illustrated in FIG. 8 (a). In addition, a plurality of sipes 10 extending substantially in parallel to the lateral grooves defining the blocks 9 are formed, and good motion performance is ensured by the edge effect of these sipes 10.

  However, with this type of tire, there is a problem in that when traveling on a snowy road surface, the sipe 10 is clogged with snow and the braking performance on snow is reduced. As a countermeasure against this, as illustrated in FIG. 8B, a plurality of protrusions 11 are formed on both wall surfaces of the sipe 10 so as to be opposed to each other, and by securing the volume of the protrusions 11, Preventing snow clogging has been done. However, if the large protrusion 11 is formed on the wall surface of the sipe 10, the gap between the both wall surfaces of the sipe 10 is reduced, so that the effect of sucking and removing the water film on the road surface on ice is reduced, especially on the ice near 0 ° C. There was a problem that the braking performance deteriorated.

  Conventionally, in order to suppress the falling of the block and improve the friction performance on ice, a plurality of protrusions that protrude from each other are formed on both wall surfaces of the sipe, and the protrusions formed on both wall surfaces are combined with each other. (For example, refer to Patent Document 1), there is a proposal that the height of the protrusions formed on both wall surfaces of the sipe is high on the side close to the tread surface and is lowered toward the bottom surface side of the sipe (for example, Patent Document 2).

  However, in these proposals, although the braking performance on ice can be improved to some extent, depending on how the cross-sectional shape of the protrusion is set, the braking performance on ice is reduced or the braking performance on the road surface on snow is secured. As a studless tire traveling on an icy and snowy road surface, there is still room for improvement in how to set the cross-sectional shape of the protrusions formed on both wall surfaces of the sipe.

JP 2000-177330 A JP 2009-126293 A

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and to improve the snow braking performance and the ice braking performance in a well-balanced manner by improving the cross-sectional form of the protrusions formed on both wall surfaces of the sipe. Is to provide.

In order to achieve the above object, a studless tire of the present invention forms a plurality of blocks on a surface of a tread portion by a plurality of longitudinal grooves extending in the tire circumferential direction and a plurality of lateral grooves intersecting the longitudinal grooves, and the blocks A studless structure in which a plurality of sipes extending substantially parallel to a transverse groove defining the block is formed on the surface of the sipe and extending substantially in parallel to the transverse grooves, and a plurality of protrusions protruding opposite to each other are formed on both wall surfaces of the sipe In the tire, the protrusion has a maximum cross-sectional height from the sipe wall surface in the cross-section in the width direction of the sipe of 50% or more of the sipe width, and the vertex position of the protrusion is more than the midpoint of the bottom surface of the protrusion Is formed such that the height of the cross section of the protrusion decreases from the apex of the protrusion toward the bottom of the sipe ,
The total number of the protrusions is larger in the front and rear end side regions corresponding to 30% of the tire circumferential length of the block than in the other regions .

Furthermore, in the structure mentioned above, it is preferable to comprise as described in (1)- (6) below.
(1) The apex position of the protrusion is positioned closer to the surface of the block than the bottom surface of the protrusion.
(2) The projected area of the projection as viewed from the surface of the tread portion occupies 70% or more of the projected area of the sipe.
(3) The total number of protrusions is formed more on the surface side of the block based on 50% of the sipe depth, or the total volume of the protrusions is blocked based on 50% of the sipe depth. The surface side of the sipe is 1.3 to 5.0 times that of the bottom of the sipe.
(4) The total number of the protrusions is increased in the central region in the width direction corresponding to 50% of the block width, or the total volume of the protrusions in the width direction in the central region in the width direction corresponding to 50% of the block width. Set to 1.3 to 5.0 times the both end regions.
(5) The planar shape of the sipe is formed in a zigzag shape or a wave shape.
(6) The sipe is formed in a three-dimensional structure having a bent portion in the depth direction.

  According to the present invention, a plurality of protrusions protruding opposite to each other are formed on both wall surfaces of the sipe formed on the surface of the block, and these protrusions have a maximum sectional height from the sipe wall surface of 50% or more of the sipe width. In addition, since the apex position of the protrusion is formed so as to be located on the surface side of the block with respect to the midpoint of the bottom surface of the protrusion, the snow on the snow road surface is pressed on the block surface side of the protrusion and moves to the bottom surface side of the sipe. Therefore, the braking performance on snow can be improved along with the suppression of snow clogging.

Moreover, since the cross-sectional height from the sipe wall surface is formed so as to become lower from the top of the protrusion toward the sipe bottom side, the gap between both wall surfaces of the sipe is appropriately secured, so that the water film on the road surface on ice is The suction effect is promoted, and the braking performance on ice can be improved efficiently.
Furthermore, in the present invention, the total number of the protrusions described above is formed in the front and rear end side regions corresponding to 30% of the tire circumferential length of the block more than the other regions. Therefore, the braking / driving performance on the road surface on ice and snow can be improved efficiently.

It is sectional drawing which shows the structure of the studless tire by embodiment of this invention. It is a partial top view which illustrates an example of the block pattern formed in the surface of the tread part of the tire of FIG. (A) And (b) is a top view which takes out and shows a block from the surface of the tread part of FIG. 2, respectively. FIG. 3A is a partial cross-sectional view taken along the line AA in FIGS. 3A and 3B, and FIG. 4B is a perspective view illustrating the shape of a protrusion formed on the wall surface of the sipe. (A) And (b) is a partial sectional view equivalent to Drawing 4 (a) by other embodiments of the present invention, respectively. FIG. 5 is a partial cross-sectional view corresponding to FIG. 4A according to still another embodiment of the present invention. (A) And (b) is a top view equivalent to Drawing 3 (a) by another embodiment of the present invention, respectively. It is explanatory drawing which shows the form of the sipe in the conventional studless tire, (a) is a top view of a block, (b) is BB arrow partial sectional drawing of (a).

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a cross-sectional view showing the structure of a studless tire according to an embodiment of the present invention, and FIG. 2 is a partial plan view illustrating an example of a block pattern formed on the surface of the tread portion of the tire of FIG.

  In FIG. 1, a studless tire 1 according to the present invention includes a bead filler 4 and 4 disposed on the outer periphery of a bead core 3 and 3 around a bead core 3 and 3 embedded in a pair of left and right bead portions 2 and 2. 2 and a plurality of vertical grooves 7 extending in the tire circumferential direction and these vertical grooves on the surface of the tread portion 6 connected to the bead portions 2 and 2, as shown in FIG. 2. A plurality of blocks 9 are formed by a plurality of lateral grooves 8 intersecting with the blocks 7, and the blocks 9 are spaced on the surface of the blocks 9 at intervals in the tire circumferential direction as shown in FIGS. 3 (a) and 3 (b). A plurality of sipes 10 extending substantially in parallel to the transverse grooves 8 that define the sipe 10 are formed, and as shown in FIGS. 4A and 4B, in the depth direction and the longitudinal direction on both wall surfaces of the sipe 10, respectively. Opposed to form a plurality of projections 11 to be raised.

  And in the studless tire 1 of this invention, as shown to Fig.4 (a), as for the protrusion 11 mentioned above, the maximum cross-sectional height h from the sipe wall surface in the width direction cross section of the sipe 10 is 50% or more of the sipe width w. And the positions of the vertices 11t of the protrusions 11 are located on the surface side of the block 9 with respect to the middle point 11c of the bottom surface of the protrusions 11, and the cross-sectional height of the protrusions 11 is directed from the vertex 11t of the protrusions 11 toward the sipe bottom. It is formed to be low.

  In this way, the protrusion 11 is configured such that the maximum cross-sectional height h from the sipe wall surface is 50% or more of the sipe width w, and the position of the vertex 11t of the protrusion 11 is higher than the intermediate point 11c of the bottom surface of the protrusion 11. In order to effectively prevent the snow on the road surface of the snow 11 from being pushed down on the block surface side of the protrusion 11 and moving to the bottom surface side of the sipe 10, braking on the snow in accordance with the suppression of snow clogging. Performance can be improved.

  Moreover, since the cross-sectional height from the sipe wall surface is formed so as to decrease from the apex 11t of the protrusion 11 toward the sipe bottom, the gap between both wall surfaces of the sipe 10 is appropriately secured, so that the The effect of sucking up the water film is promoted, and the braking performance on ice can be improved efficiently.

  Here, when the maximum cross-sectional height h of the protrusion 11 is less than 50% of the sipe width w, snow clogging into the sipe 11 cannot be sufficiently prevented, and the effect of improving the braking performance on snow is insufficient. . The length x (see FIG. 4B) of the protrusion 11 in the longitudinal direction of the sipe 10 is not particularly limited, and is appropriately set according to the type of tire and the form and size of the block 9.

  3A and 3B exemplify the case where the plane shape of the sipe 10 is linear, but the studless tire 1 of the present invention is not limited to this and will be described later. Thus, the planar shape of the sipe 10 may be formed in a zigzag shape or a wave shape. In addition, in order to secure rigidity at the front and rear ends of the block 9, both ends of the sipes 10 and 10 located at the front and rear ends of the block 9 may be terminated in the block 9.

  5 (a) and 5 (b) are partial cross-sectional views corresponding to FIG. 4 (a) according to another embodiment of the present invention. FIG. 5 (a) shows the position of the apex 11t of the protrusion 11 as a protrusion. FIG. 5B shows a case where the height of the cross section from the sipe wall surface is lowered stepwise from the vertex 11t of the protrusion 11 toward the sipe bottom. Shows the case. In addition, about the ratio which changes a cross-sectional height toward a sipe bottom part side in steps, it is not restricted to this.

  FIG. 6 is a partial cross-sectional view corresponding to FIG. 4A according to still another embodiment of the present invention. In this embodiment, the apex 11t of the protrusion 11 is located closer to the surface of the block than the bottom surface of the protrusion 11. It is located. As a result, the snow on the road surface during running on the snow surface can be efficiently pressed down on the block surface side of the protrusion 11, so that the on-snow braking performance can be improved more reliably.

  In the studless tire 1 of the present invention, the number and arrangement of protrusions formed on both wall surfaces of the sipe 10 are not particularly limited, but preferably, the projected area of the protrusions 11 as viewed from the surface of the tread portion 6 is It may be adjusted so as to occupy 70% or more, preferably 90% or less of the projected area of 10. Here, if the projected area of the projection 11 is less than 70% of the projected area of the sipe 10, it becomes difficult to prevent snow from entering the sipe 10, and the effect of improving the braking performance on snow is insufficient. If it exceeds 90%, the gap between both wall surfaces of the sipe 10 is excessively reduced, so that it is impossible to obtain the effect of sucking up the water film during running on the ice, resulting in insufficient braking performance on ice.

  More preferably, the total number of protrusions 11 formed on both wall surfaces of the sipe 10 is increased on the surface side of the block 9 on the basis of 50% of the sipe depth, or the total volume of the protrusions 11 is determined as the sipe depth. With reference to 50% of the height, the surface side of the block 9 is adjusted to be 1.3 to 5.0 times, preferably 1.7 to 3.3 times that of the bottom side of the sipe 10. Thereby, the braking performance on snow and the braking performance on ice can be improved with good balance.

  More preferably, the total number of protrusions 11 formed on both wall surfaces of the sipe 10 is increased in the central region in the width direction corresponding to 50% of the block width, or the total volume of the protrusions 11 is set to 50% of the block width. It is good to adjust so that it may become 1.3 to 5.0 times of the width direction both ends area | region in a corresponding width direction center area | region, Preferably it is 1.7 to 3.3 times. Thereby, the braking performance on snow and the braking performance on ice can be improved in a more balanced manner.

In the studless tire 1 of the present invention, it is necessary to form a large number of the above-described protrusions 11 in the sipe 10 located on the front and rear end sides of the block 9. In this case, it is further necessary to form more in the front and rear end regions corresponding to 30% of the tire circumferential length of the block 9 than in the other regions. As a result, the block rigidity on the stepping-in side and the kicking-out side is appropriately ensured, so that the braking / driving performance on the road surface on ice and snow can be improved efficiently.

  In the studless tire 1 of the present invention, the planar shape of the sipe 10 is not particularly limited, but the planar shape of the sipe 10 is shown in FIG. 7A from the viewpoint of ensuring good steering stability on the road surface on ice. And it is good to form in zigzag shape or a wave shape so that it may illustrate in (b). More preferably, the sipe 10 may be formed in a three-dimensional structure having a bent portion in the depth direction. Thereby, since the rigidity with respect to the tire peripheral direction of the block 9 can be improved, the exercise | movement performance on a snowy road surface can further be improved.

  Note that the three-dimensional structure described above refers to the depth direction of the sipe 10 that is formed in a curved surface having two or more different inclination angles, and the concave and convex portions in which both side surfaces of the sipe 10 are engaged with each other are pointed in the depth direction. A structure that is made to exist.

  As described above, when the studless tire of the present invention forms a plurality of protrusions facing each other on both wall surfaces of the sipe formed on the surface of the block, the cross-sectional shape of the protrusions is determined so that the maximum cross-sectional height from the sipe wall surface is the same. 50% or more of the sipe width, the apex position of the protrusion is located on the surface side of the block with respect to the midpoint of the bottom surface of the protrusion, and the cross-sectional height from the sipe wall surface is lowered from the apex of the protrusion toward the sipe bottom side By forming as described above, the braking performance on snow and the braking performance on ice are improved in a well-balanced manner, and can be widely applied to vehicles traveling on icy and snowy road surfaces.

  The tire size is 195 / 65R15, the tire structure is shown in FIG. 1, the tread pattern is shown in FIG. 2, and each block in the five block rows sandwiching the tire equator line in FIG. 2 has a width of 1.0 mm and a depth. A sipe of 7.0 mm is formed, and protrusions are formed on both wall surfaces of all of these sipes. The conventional tires (conventional example 1) are different from each other in the total volume ratio, the ratio of the projected area of the projection viewed from the tread surface to the projected area of the sipe, and whether or not the three-dimensional sipe is adopted as shown in Table 1. 2) and tires of the present invention (Examples 1 to 9).

  In Table 1, regarding the total volume ratio of the protrusions in the sipe depth direction, the ratio between the tread surface side (sipe opening side) and the sipe bottom side is defined as “50% of the sipe depth”. “Open side / bottom side”, and the total volume ratio of the protrusions in the width direction of the sipe is the ratio of the center region corresponding to 50% of the sipe width to the end regions on both sides thereof. Is displayed. Further, the ratio of the projected area of the projection viewed from the tread surface to the projected area of the sipe was expressed as “ratio of the projected area of the projection”.

  About these 11 types of studless tires, the braking performance on snow and braking performance on ice were evaluated by the following test methods. The larger the value, the better.

[Evaluation of braking performance on snow]
A test course with an average snow depth of 50 mm after each tire is mounted on a rim (size: 15 x 6 JJ), filled with air pressure of 230 kPa and mounted on the front and rear wheels of a domestically produced FF vehicle (displacement of 1500 cc). A braking test was performed at an initial speed of 40 km / hr, and the braking performance on snow was evaluated using the reciprocal of the braking distance obtained thereby.

[Evaluation of braking performance on ice]
The above vehicle was subjected to a braking test from an initial speed of 40 km / hr on a test course consisting of an icing road surface with a road surface temperature of −2 to 0 ° C., and the braking performance on ice was evaluated using the reciprocal of the braking distance obtained thereby. It was.

  From the results in Table 1, it can be seen that the tire according to the present invention has a better balance between the braking performance on snow and the braking performance on ice than the conventional tire.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Bead part 3 Bead core 4 Bead filler 5 Carcass layer 6 Tread part 7 Longitudinal groove 8 Horizontal groove 9 Block 10 Sipe 11 Protrusion 11t Apex point of protrusion 11c Midpoint of bottom face of protrusion w Sipe width h Maximum cross section height of protrusion The

Claims (9)

A plurality of blocks are formed on the surface of the tread portion by a plurality of vertical grooves extending in the tire circumferential direction and a plurality of horizontal grooves intersecting the vertical grooves, and the blocks are spaced on the surface of the block at intervals in the tire circumferential direction. In a studless tire in which a plurality of sipes extending substantially parallel to a partitioning lateral groove are formed, and a plurality of protrusions protruding opposite to each other are formed on both wall surfaces of the sipe,
The maximum height of the protrusion from the sipe wall surface in the widthwise cross section of the sipe is 50% or more of the sipe width, and the vertex position of the protrusion is positioned closer to the block surface than the midpoint of the bottom surface of the protrusion. And formed such that the height of the cross section of the protrusion decreases from the apex of the protrusion toward the sipe bottom .
A studless tire in which the total number of protrusions is larger in the front and rear end side regions corresponding to 30% of the tire circumferential length of the block than in other regions .   The studless tire according to claim 1, wherein the top position of the protrusion is positioned closer to the surface of the block than the bottom surface of the protrusion.   The studless tire according to claim 1 or 2, wherein a projected area of the protrusion viewed from the surface of the tread portion occupies 70% or more of a projected area of the sipe.   4. The studless tire according to claim 1, wherein the total number of the protrusions is large on the surface side of the block on the basis of 50% of the sipe depth.   4. The studless tire according to claim 1, wherein the total volume of the protrusions is 1.3 to 5.0 times that of the bottom part of the sipe on the surface side of the block on the basis of 50% of the sipe depth. .   The studless tire according to any one of claims 1 to 5, wherein a total number of the protrusions is formed in a central region in a width direction corresponding to 50% of a block width.   The studless tire according to any one of claims 1 to 5, wherein the total volume of the protrusions is 1.3 to 5.0 times that of both end regions in the width direction in a center region in the width direction corresponding to 50% of the block width. . The studless tire according to any one of claims 1 to 7 , wherein a planar shape of the sipe is formed in a zigzag shape or a wave shape. The studless tire according to any one of claims 1 to 8 , wherein the sipe is formed in a three-dimensional structure having a bent portion in a depth direction.

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