JP2012171484A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire with a divided block group formed by narrow grooves and wide grooves, which suppresses falling down of the block and which improves drainage.SOLUTION: A plurality of circumferential main grooves 2 are arranged in a tread face, and a land part is divided each between adjoining two circumferential main grooves 2, and between each circumferential main groove and a tread side edge. A circumferential sub-groove 5 with a narrower groove width than that of the circumferential main groove is arranged in the land part, while an independent plurality of blocks of a polygon with more vertices than a pentagon, which is divided by the linealy extended narrow grooves and wide grooves, is provided at least in a portion, and a block number density S per a unit grounded area of a block group composed of the plurality of polygon blocks is within a range of 0.003 to 0.04 pieces/mm.

Description

  The present invention proposes a technique for improving the drainage of a pneumatic tire, in particular, a pneumatic tire provided with a block group.

  In the conventional pneumatic tire, for example, as described in Patent Document 1, a block is defined by a circumferential groove or an inclined groove on the tread surface, and a sipe is formed in the formed block, thereby providing an edge effect. In general, it is widely practiced to improve driving, braking, and turning performance on wet road surfaces, on-ice road surfaces, and the like.

  However, such tires generally improve the edge effect, but the rigidity of the sub-block partitioned by the sipe is too low, and the sub-block collapses at the time of ground contact, resulting in poor ground contact. It has been difficult to obtain desired wet braking performance due to a decrease in the on-ice performance commensurate with the improvement in vehicle performance and the ground contact area in the tread surface.

  Also, in the conventional pneumatic tire as described above, each block is often formed relatively large for the purpose of improving the performance on ice by securing a large contact area, and in particular, the central area of the block. As a result, the water film could not be removed efficiently, which could also hinder the improvement of performance on ice.

JP 2001-191739 A

  Therefore, the present invention is to provide a pneumatic tire having a block group partitioned by a narrow groove and a large groove, in which the block is prevented from falling and the drainage is improved.

で与えられる、ブロック群の単位実接地面積当たりのブロック個数密度Ｓを０．００３〜０．０４個／ｍｍ^２の範囲内としてなることを特徴とするものである。 In the pneumatic tire of the present invention, a plurality of circumferential main grooves are disposed on the tread surface, and each of two circumferential main grooves adjacent to each other and between each circumferential main groove and the tread side edge. In the land portion, a circumferential sub-groove narrower than the circumferential main groove continuous in the tread circumferential direction is arranged in the land portion, and a thin line extending linearly. A plurality of mutually independent polygonal blocks each having a number of pentagons or more divided by grooves and thick grooves are provided at least in part, and a reference pitch length of a block group consisting of a plurality of polygonal blocks is set to P (Mm), when the width of the block group is W (mm), the number of blocks existing in the reference area of the block group divided by the reference pitch length P and the width W is a (piece), N (%) is the negative rate in the reference area,

The block number density S per unit actual ground contact area of the block group is within the range of 0.003 to 0.04 / mm ² .

Here, the “circumferential main groove” can be extended not only in a linear shape but also in a main groove shape such as a zigzag shape, a wavy line shape, a curved shape, or a crank shape.
The “reference pitch length of the block” refers to the minimum unit of the repeated pattern of the block in one block row constituting the block group. For example, the repeated pattern of the pattern is formed by one block and a groove defining the block. In the case where it is defined, the reference pitch length of the block is obtained by adding the tread circumferential length for one block and the tread circumferential length for one groove adjacent to the block in the tread circumferential direction.
Note that “the number of blocks a in the reference area of the block group” is the number of blocks remaining in the reference area with respect to the surface area of the block, when the block exists inside and outside the reference area and cannot be counted as one. For example, in the case of a block straddling the inside and outside of the reference area and having only half of the reference area, it is counted as 1/2.

The “width W of the block group” refers to the length in the tread width direction of the block group formed by densely arranging the blocks. For example, when the block group exists in the entire tread, the tread ground width is assumed.
“Actual contact area” of a block group refers to the total surface area of all blocks in the reference area of the block group, that is, the reference area defined by the product of the reference pitch length P and the width W. The area obtained by subtracting the area of the groove that divides each block from the area of.

The above lengths, etc. are industrial standards effective in the area where tires are produced and used. In Japan, JATMA (Japan Automobile Tire Association) YEAR BOOK, in Europe ETRTO (European Tire and Rim Technical Organization) STANDARDS MANUAL, In the United States, TRA (THE TIRE and RIM ASSOCIATION INC.) Measured in a state where tires are assembled to rims specified in YEAR BOOK, etc., and the maximum air pressure specified according to the tire size in the standards of JATMA, etc. is filled. Shall be.
The “thin groove” refers to a groove in which the opposed groove walls come into contact with each other within the ground contact surface during tire rolling.

In such a tire, the groove width of the circumferential sub-groove is more preferably in the range of 2.0 to 3.5 mm.
Preferably, the extending form of the circumferential sub-groove is a zigzag shape.
And preferably, the said circumferential subgroove is arrange | positioned in a tread center.

  By the way, it is preferable to arrange the polygonal blocks in a zigzag shape in the tread circumferential direction.

In the pneumatic tire of the present invention, by forming the block number density S (unit / mm ² ) per unit actual ground contact area of the block group in the range of 0.003 to 0.04 piece / mm ² , for example, Compared to the density of studless tires of s = 0.002 pieces / mm ² or less, the density S has increased. Therefore, while securing a sufficient groove area in the block group, the total edge length and edge direction of each block ( The number of edges facing in different directions) can be increased, and excellent edge effects can be exerted, and the adjacent blocks can support each other and improve the grounding performance of each block while securing the ground contact area High performance on ice can be exhibited. In addition, by reducing the size of each block, the distance from the central area of the block to the periphery of the block can be reduced, so that the water film removal effect by the block can be improved.

  That is, when S is less than 0.003, the surface area of the block is increased, and there is a possibility that the grounding property of the tread surface cannot be improved. On the other hand, when S exceeds 0.04, Even if the sipe is not provided, it is difficult to achieve a desired block rigidity.

  In addition, in the present invention, the removal of the water film in the ground contact surface is made efficient by having the circumferential main groove, and the groove area is greatly increased (the ground contact area is lowered) by providing the circumferential sub groove in the land portion. Without this, drainage in the block group in the land can be promoted and the thick water film can be efficiently removed. As a result, not only wet braking performance but also hydroplaning performance can be dramatically improved.

  According to such a tire, excellent grounding performance and edge effect are ensured, and efficient water film removal by the block is achieved to improve performance on ice, and wet braking performance and hydroplaning performance. Can be improved.

It is a partial development view of a tread pattern showing one embodiment of a pneumatic tire of the present invention. It is a partial expanded view of the tread pattern which shows other embodiment of the pneumatic tire of this invention. It is a partial expanded view of the tread pattern of the conventional pneumatic tire. It is a partial expanded view of the tread pattern of the conventional pneumatic tire.

Hereinafter, the pneumatic tire of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a partial development view of a tread pattern showing one embodiment of the pneumatic tire of the present invention.
Since the reinforcing structure inside the tire is the same as that of a general radial tire or bias tire, illustration is omitted.

In the figure, reference numeral 1 denotes a tread tread. The tread tread 1 has a plurality of circumferential main grooves extending in the tread circumferential direction, and two circumferential main grooves 2 in the figure.
A center land portion 3 is defined between two circumferential grooves adjacent to each other, in the drawing, in the vicinity of the tire equator line, and each shoulder land portion 4 is defined between the main groove 2 and the tread side edge.

In the vicinity of the tread center of the center land portion 3, a circumferential sub-groove 5 extending in a zigzag shape in the tread circumferential direction, and a thick groove 6 extending from the circumferential sub-groove 5 in the tread width direction, Two rows of block rows are defined by the narrow grooves 7 extending from the thick grooves 6 so as to be inclined in the tread circumferential direction, and the block rows are formed by a plurality of octagonal first center blocks 8. In the vicinity of the region adjacent to the circumferential main groove of the center land portion 3, a lateral groove 9 extending in the tread width direction from the circumferential main groove 2, and the circumferential main groove 2, the thick groove 6, and the narrow groove 7, A block row is defined, and the block row is formed by a plurality of second center blocks 10 having a substantially octagonal shape.
Here, the first center blocks 8 are arranged in a zigzag pattern in the tread circumferential direction.

  Further, in the vicinity of the center of each shoulder land portion 4, there is a row of blocks by a thick groove 11 extending in the tread width direction and a narrow groove 12 extending from the thick groove 11 in an inclined direction in the tread circumferential direction. A row is defined, and this block row is formed by a plurality of octagonal first shoulder blocks 13. In the vicinity of the area adjacent to the circumferential main groove 2, a block row is defined by a lateral groove 14 extending from the circumferential main groove 2 in the tread width direction, and the circumferential main groove 2, the thick groove 11, and the narrow groove 12. The block row is formed by a plurality of second shoulder blocks 15 having a substantially octagonal shape. In the vicinity of the tread side edge, a block row is defined by a lateral groove 16 extending from the tread side edge in the tread width direction, a thick groove 11 and a narrow groove 12, and this block row is composed of a plurality of third shoulder blocks 17. Form. The third shoulder block 17 is provided with a lateral groove 18 extending from the narrow groove 12 in the tread width direction and ending in the third block.

で与えられる、ブロック群の単位実接地面積当たりのブロック個数密度Ｓを０．００３〜０．０４個／ｍｍ^２の範囲、好ましくは０．００３〜０．０３５個／ｍｍ^２の範囲で形成する。 In this pneumatic tire, the first center block 8 and the first shoulder block 13 are densely arranged by arranging a plurality of mutually independent polygonal blocks each having a pentagonal number or more and octagonal in the figure. A block group is formed. When the reference pitch length of the polygonal block in this block group is P (mm) and the width of the block group is W (mm), the block group is divided by the reference pitch length P and the width W. The number of blocks existing in the reference area of the block group is a (pieces), the negative rate in the reference area is N (%),

The block number density S per unit actual ground contact area of the block group is given in the range of 0.003 to 0.04 / mm ² , preferably 0.003 to 0.035 / mm ^2. .

  In such a tire, water in the ground contact surface can be efficiently drained mainly through the circumferential main groove, and water in the land can be drained efficiently through the circumferential sub-groove. It is possible to increase the total edge length and edge direction (number of edges facing different directions) of each block by arranging the blocks densely while securing a sufficient groove area in the block group. The edge effect can be exhibited. In addition, since the block size has been reduced, the contact performance of each block can be improved, improving braking performance and handling stability on road surfaces with a low friction coefficient μ such as on ice surfaces and wet surfaces. can do. In addition, by reducing the size of each block, the distance from the central area of the block to the peripheral edge of the block can be reduced, and the water film removal effect by the block can also be improved.

Preferably, the negative rate N of the block group is 5% to 50%, and by setting this range, the steering stability can be improved.
That is, when the negative rate N is less than 5%, the groove area is too small and the drainage performance is insufficient, and the size of each block may be too large, making it difficult to achieve the required edge effect. On the other hand, if it exceeds 50%, the ground contact area becomes too small, and the steering stability tends to decrease.

Here, the circumferential main groove 2 has, for example, a groove width of 5 to 20 mm and a groove depth of 4 to 11 mm, and the circumferential sub groove 5 has, for example, a groove width of 2.0 to 3.5 mm, The groove depth is in the range of 1 to 11 mm.
Each of the thick grooves 6 and 11 and the lateral grooves 16 and 18 has a groove width of 1.2 to 10 mm and a groove depth of 2 to 11 mm, and the narrow grooves 7 and 12 and the lateral grooves 9 and 14 have, for example, a groove width. 0.1 to 1.2 mm, the groove depth is 1 to 10 mm, and the extended length of the groove is 1 to 15 mm.
Further, the tread circumferential length of the blocks 8 and 15 is 5 to 25 mm, the tread width direction length is 5 to 25 mm, the surface area is 25 to 330 mm ² , and the distance between adjacent blocks in the tread width direction is 2.5. It can be in the range of -10 mm.

In such a pneumatic tire, preferably, in the figure, the center blocks 8 are arranged in a zigzag shape in the tread circumferential direction, so that a high density arrangement of the blocks 8 can be easily realized, and the grounding property of the tread is improved. In addition to increasing the contact area, the tires are further improved by cutting the water film by causing each edge to act sequentially and generating a high edge pressure under the formation of more blocks 8 during rolling of the tire. The edge effect can be exerted, the decrease in the friction coefficient between the tire and the road surface due to the fluid lubrication effect can be suppressed, and the contact timing to the road surface can be shifted between the blocks 8 adjacent in the tread width direction. Can also be reduced.
In addition, the blocks 8 can be arranged in a zigzag pattern in the tread circumferential direction, and the block number density D can be set high so that adjacent blocks can be supported when a high load is applied to the block 8. According to this, it becomes possible to further increase the rigidity of the block 8 and further improve the wear resistance.

FIG. 2 is a partial development view of a tread pattern showing another embodiment of the pneumatic tire of the present invention. In addition, the same code | symbol is attached | subjected to the element similar to the tire shown in the previous figure, and the description is abbreviate | omitted.
In this embodiment, one circumferential sub-groove 25 that extends linearly in the tread circumferential direction is disposed near the center land portion 3 tread center.
According to this configuration, in particular, the drainage near the tread center can be improved, and as a result, the hydroplaning performance can be improved.

  In addition, preferably, by setting the groove width of the circumferential sub-grooves 5 and 25 in the range of 2.0 to 3.5 mm, the drainage performance is reduced without reducing the rigidity of the block located in the vicinity of the circumferential sub-groove 5. Can be improved.

  The extending form of the circumferential sub-groove may be a main groove form such as a straight line, a zigzag shape, a wavy line shape, a curved shape, a crank shape, etc., but it is preferably a zigzag shape. The strength of the block located in the vicinity thereof can be ensured without deteriorating the drainage of the direction sub-groove.

  And preferably, by disposing the circumferential sub-grooves 5 and 25 at the tread center, the compression rigidity near the tread center is reduced without causing uneven wear on the blocks near the circumferential sub-grooves 5 and 25. The drainage of the tread center can be improved.

  By the way, it is preferable to arrange two circumferential main grooves 2 on the tread surface, and it is possible to dispose continuous grooves in the tread circumferential direction without hindering the block group provided on the tread surface 1. It is possible to efficiently remove a thick water hung from the circumferential main groove 2.

Next, tires having a structure as shown in the figure and having a size of 195 / 65R15 were manufactured as prototypes. For each of 1 and 2, the braking performance and hydroplaning performance of the wet road surface were measured.
In addition, since the comparative example tire does not require modification about structures other than the tread portion, it was assumed to be in conformity with the example tire.

(Wet road surface braking performance)
Example tires 1 and 2 and comparative tires 1 and 2 are assembled on a rim of size 195 / 65R156J, mounted on a vehicle with an internal pressure of 200 kPa, and a wet asphalt road test course with a depth of 0.6 mm. Was performed by measuring and evaluating the braking distance when fully braking from 60 km / h. The evaluation results are shown in Table 2.
In addition, the index value in a table | surface is calculated | required as a control the value of the comparative example tire 1, and shows that the braking performance of a wet road surface is excellent, so that an index is large.

(Hydroplaning performance)
Example tires 1 and 2 and comparative tires 1 and 2 were assembled on a rim having a size of 195 / 65R15 6J, the inner pressure was 200 kPa, and the hydroplaning limit speed when passing through a wet wet surface with a water depth of 6 mm. The feeling was evaluated and the results are shown in Table 2.
In addition, the index value in a table | surface is calculated | required using the value of the comparative example tire 1 as control, and shows that hydroplaning performance is excellent, so that an index | exponent is large.

  From the results of Table 2, the tires 1 and 2 of the examples were able to improve the braking performance and the hydroplaning performance of the wet road surface compared to the comparative tires 1 and 2.

DESCRIPTION OF SYMBOLS 1 Tread tread 2 Circumferential main groove 3 Center land part 4 Shoulder land part 5,25 Circumferential subgroove 6,11 Thick groove 7,12 Narrow groove 8 First center block 9, 14, 16, 18 Horizontal groove 10 Second center Block 13 First shoulder block 15 Second shoulder block 17 Third shoulder block

Claims (5)

A plurality of circumferential main grooves are arranged on the tread surface, and a land portion is defined between two adjacent circumferential main grooves and between each circumferential main groove and the tread side edge. In pneumatic tires,
In the land portion, a circumferential sub-groove narrower than the circumferential main groove that is continuous in the tread circumferential direction is disposed, and a corner of a pentagon or more is defined by a narrow groove and a large groove that extend linearly. A plurality of mutually independent polygon blocks are provided at least in part,
A block defined by the reference pitch length P and the width W, where P (mm) is the reference pitch length of the block group composed of a plurality of polygonal blocks and W (mm) is the width of the block group. The number of blocks present in the reference area of the group is a (pieces), the negative rate in the reference area is N (%),

A pneumatic tire characterized in that the block number density S per unit actual ground contact area of the block group is within a range of 0.003 to 0.04 / mm ² .   The pneumatic tire according to claim 1, wherein a groove width of the circumferential auxiliary groove is in a range of 2.0 to 3.5 mm.   The pneumatic tire according to claim 1 or 2, wherein the circumferential auxiliary groove extends in a zigzag shape.   The pneumatic tire according to claim 1, wherein the circumferential sub-groove is disposed in a tread center. The pneumatic tire according to any one of claims 1 to 4, wherein the polygonal blocks are arranged in a zigzag shape in the tread circumferential direction.

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