JP2010285040A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of improving steering stability during cornering, in particular, and improving straight advancing stability, in a block pattern. <P>SOLUTION: This pneumatic tire includes a plurality of block rows in a tire peripheral direction by a plurality of blocks 3 sectioned by grooves 2 in a tread part 1. Each of the block rows includes a symmetry block row constituted of blocks 3 having line-symmetrical shapes in the tire peripheral direction and an asymmetry block row located at the tire width direction outside of the symmetry block row and constituted of the blocks 3 having asymmetrical shapes in the tire peripheral direction. In the block 3 of the asymmetry block row, a maximum kick-out side apex of the tire peripheral direction is located at the tire width direction inside in relation to the maximum step-in side apex of the tire peripheral direction, and an angle formed by a straight line for connecting the maximum kick-out side apex and the maximum step-in side apex and the tire peripheral direction becomes larger toward the tire width direction outside from the symmetry block row. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  According to the present invention, a block group in which a plurality of independent blocks partitioned by grooves are densely arranged mutually is provided in at least a part of the tread portion, and a plurality of block rows extending in the tire circumferential direction by the blocks of the block group More specifically, an object of the present invention is to propose a pneumatic tire that can achieve both improvement in steering stability and improvement in straight running stability.

  A tire having a block pattern is suitable for icy and snowy roads and off-road driving because of excellent driving and braking force on a slippery road surface. In addition, it has the advantages of excellent ride comfort and less road noise. For these reasons, the block pattern is widely used as a basic pattern for studless tires and off-road tires. Conventionally, in these tires, blocks having the same shape, such as those described in Patent Document 1, are often repeatedly arranged.

JP-A-5-169922

  However, in a tire having a conventional block pattern, during cornering, these blocks are likely to be deformed by a lateral force applied to the blocks located on the outer side in the tire width direction, and steering stability may be impaired. On the other hand, it is conceivable to form each block as a horizontally long shape and increase the lateral rigidity of the block to increase the resistance to the above lateral force. A new problem of lowering will arise.

  Therefore, an object of the present invention is to provide a pneumatic tire that can improve the steering stability particularly in cornering and can also improve the straight running stability in the block pattern.

  In order to achieve the above object, the pneumatic tire according to the present invention is a pneumatic tire in which a plurality of block rows are formed in the tire circumferential direction by a plurality of independent blocks partitioned by grooves, An asymmetric block consisting of at least one symmetrical block row consisting of blocks having a line-symmetric shape with respect to the tire circumferential direction, and a block having an asymmetric shape with respect to the tire circumferential direction, located outside the symmetrical block row in the tire width direction. A block row, and in the block of the asymmetric block row, the most kicked-out vertex in the tire circumferential direction is located on the inner side in the tire width direction with respect to the most depressed side vertex in the tire circumferential direction, and the tire circumferential direction The most stepped-side apex of the tire is positioned on the outer side in the tire width direction with respect to the most kicked-out vertex in the tire circumferential direction, and the most kicked-out vertex and the most stepped-on side And the straight line connecting the point, in which the angle between the tire circumferential direction, characterized in that, and increases toward its outer side in the tire width direction than the symmetric block row.

  According to the pneumatic tire of the present invention, in the blocks of the asymmetric block row, the most kicked side apex in the tire circumferential direction is positioned on the inner side in the tire width direction with respect to the most stepped side apex, and the most kicked side apex and Since the angle formed by the straight line connecting the topmost apex and the tire circumferential direction is increased toward the outer side in the tire width direction, the lateral force is counteracted toward the outer side in the tire width direction from the symmetrical block row. The force can be increased, and even when there is an input in the tire circumferential direction by traction, the deformation of the block can be directed to the center side, so that the straight running stability can be improved.

  In the pneumatic tire according to the present invention, the blocks in the asymmetric block row have an asymmetric shape with respect to the tire width direction, and the innermost vertex of the block in the tire width direction is the outermost vertex in the tire width direction. The outermost vertex in the tire width direction of the block is located on the stepping side in the tire circumferential direction with respect to the innermost vertex in the tire width direction, and the innermost vertex. The angle formed between the straight line connecting the outermost vertices and the tire circumferential direction is preferably smaller toward the outer side in the tire width direction than the symmetrical block row.

  Further, in the pneumatic tire of the present invention, the projected length in the tire circumferential direction of the straight line connecting the most kicked-out side vertex and the most stepped-on vertex is A, and the straight line connecting the innermost vertex and the outermost vertex. Assuming that the projected length in the tire width direction is B, it is preferable that A / B <1 is satisfied, and A / B becomes smaller toward the outer side in the tire width direction than the symmetrical block row.

  Furthermore, in the pneumatic tire of the present invention, it is preferable to have an inclined groove that has an apex in the symmetrical block row and extends inclined from the apex.

  Furthermore, in the pneumatic tire of the present invention, it is preferable that the inclination angle of the inclined groove with respect to the tire circumferential direction gradually increases as it goes outward in the tire width direction.

  Furthermore, in the pneumatic tire of the present invention, it is preferable to include at least one circumferential groove extending in the tire circumferential direction.

  Furthermore, in the pneumatic tire according to the present invention, it is preferable that the side forming the surface contour of the block consists of a straight line and a curve, and the side adjacent to the inclined groove is a curve.

Moreover, in the pneumatic tire according to the present invention, in the block group formed by densely arranging the blocks, the reference pitch length of the block in the block group is PL (mm), and the width of the lock group is _WG. (mm), is defined by the said reference pitch length PL and the width W _G, the number of blocks existing in the reference zone of the block group a (number), the negative ratio in the reference zone N ( %) and the _{time, a / (PL × W G} × (1-N / 100)) block arrangement density D per unit actual ground contact area of the block group given by the 0.003 (pieces / mm ² ) To 0.04 (pieces / mm ² ).

  Here, 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 reference block length is defined by one block and a groove dividing the block. If a pattern repeat pattern is specified, the reference pitch of the block is the sum of the tire circumferential length of one block and the tire circumferential length of one groove adjacent to the block in the tire circumferential direction. It becomes length. The “width of the block group” refers to the length in the tire 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 contact width is indicated. Furthermore, the “actual ground contact area” of the block group means the total surface area of all blocks in the reference area of the block group, in other words, is defined by the product of the reference pitch length PL and the width W. The area obtained by subtracting the area of the grooves defining the individual blocks from the area of the reference area.

  According to the present invention, in the block pattern, it is possible to provide a pneumatic tire that can improve steering stability particularly during cornering and can also improve straight running stability.

It is the partial expanded view which showed the tread pattern of the pneumatic tire (tire of Example 1) of one Embodiment according to this invention. It is the figure which expanded and showed one of the blocks in the tread pattern of FIG. It is a figure for demonstrating the mode of a deformation | transformation of the block in the tread pattern of FIG. 1, (a) shows the block in a pattern center, and the block of a tire width direction outer side, (b) is the deformation | transformation direction of the block in the whole pattern. Is schematically shown by an arrow. It is the partial expanded view which showed the tread pattern of the pneumatic tire of other embodiment according to this invention. It is the partial expanded view which showed the tread pattern of the pneumatic tire of other embodiment according to this invention. It is the partial expanded view which showed the tread pattern of the pneumatic tire (tire of Example 2) of other embodiment according to this invention. It is the partial expanded view which showed the tread pattern of the pneumatic tire (tire of Example 3) of other embodiment according to this invention. It is the partial expanded view which showed the tread pattern of the pneumatic tire (tire of Example 4) of other embodiment according to this invention. It is the partial expanded view which showed the tread pattern of the pneumatic tire (tire of Example 5) of other embodiment according to this invention. It is the partial expanded view which showed the tread pattern of the pneumatic tire of other embodiment according to this invention. It is the partial expanded view which showed the tread pattern of the pneumatic tire (tire of the prior art example 1) of a prior art. It is the partial expanded view which showed the tread pattern of the pneumatic tire (tire of the comparative example 1) as a comparison. It is the partial expanded view which showed the tread pattern of the pneumatic tire (tire of the comparative example 2) as a comparison.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a pattern diagram of a tread portion of a pneumatic tire (hereinafter referred to as “tire”) according to an embodiment of the present invention. In the drawing, the vertical direction indicates the tire circumferential direction, and the horizontal direction (direction orthogonal to the equatorial plane E) indicates the tire width direction.

  Although the tire of this embodiment is not illustrated, a carcass extending in a toroidal shape between a pair of left and right bead cores, a belt disposed on the outer side in the tire radial direction of the crown portion of the carcass, and an outer side in the tire radial direction of the belt It has a tire structure in accordance with the conventional practice including a tread portion arranged, and has the block pattern shown in FIG. 1 in the tread portion.

As shown in FIG. 1, the tire, the tread portion 1 is formed independently plurality of blocks 3 by the grooves 2, further block group G _B in which the plurality of blocks 3 formed by densely arranged mutually Is formed. In block group G _B, the block 3 is arranged along the tire circumferential direction, block row multi-column L1 to L7 _R, L7 _L are formed side by side in the tire width direction.

  The block 3 has a vertex Q in the symmetric block row L1, and has a V-shape comprising a pair of inclined grooves 4a and 4b extending from the vertex Q in the opposite direction across the tire circumferential direction and extending toward the tread width end. A plurality of grooves 4 and a plurality of intersecting grooves 5 extending across the V-shaped grooves 4 are defined. Further, a substantially rectangular rectangular groove 6 in plan view is provided at the intersection of the V-shaped groove 4 and the intersecting groove 5, where each block 3 finally has a substantially octagonal ground surface shape. Is formed. The inclined grooves 4a and 4b are formed in a curved shape with an inclination angle with respect to the tire circumferential direction gradually increasing toward the tire width direction. As a result, the surface contour shape of the block 3 has a straight side adjacent to the linear crossing groove and a curved side adjacent to the curved inclined groove.

The block rows L1 to L7 _R and L7 _L are composed of at least one row (here, one row) of symmetric block rows L1 made up of blocks 3 having a line-symmetric shape with respect to the tire circumferential direction, and the tires than the symmetric block row L1. It has asymmetric block rows L2 _R , L2 _{L to} L7 _R , L7 _L , which are located outside in the width direction and are made up of blocks 3 having an asymmetric shape with respect to the tire circumferential direction.

Here, the block 3 of the asymmetric block row L7 _R will be described with reference to FIG. 2 as an example. In the blocks of the asymmetric block rows L2 _R , L2 _{L to} L7 _R , L7 _L , the most kick-out vertex P _{K in the} tire circumferential direction the tire with respect to the tire located in the inner side in the tire width direction relative to the circumferential direction of the top leading side vertex P _F, most leading side apex P _F in the tire circumferential direction, most trailing side apex P _K in the tire circumferential direction located outward in the width direction, and, outermost trailing side apex P _K and a straight line S ₁ connecting the outermost leading side vertex P _F, the tire width than the angle theta ₁ is symmetrical block row L1 formed between the tire circumferential direction It gets bigger as you go outward. That is, asymmetric block row _{L2 R, L2 L ~L7 R,} L7 L block 3 is set to top depression vertex _{P F} is displaced in the tire width direction outside him to toward the shoulder side.

The blocks 3 of the asymmetric block rows L2 _R , L2 _{L to} L7 _R , L7 _L have an asymmetric shape with respect to the tire width direction, and the innermost vertex P _I of the block 3 in the tire width direction is the tire width direction The outermost vertex P _O of the block 3 in the tire circumferential direction is positioned on the kicking side in the tire circumferential direction, and the outermost vertex P _O in the tire width direction of the block 3 is stepped on in the tire circumferential direction with respect to the innermost vertex in the tire width direction. The angle θ ₂ formed between the straight line S ₂ that is located on the side and connects the innermost vertex P _I and the outermost vertex P _O and the tire circumferential direction becomes smaller from the symmetric block row L 1 toward the outer side in the tire width direction. Become.

Furthermore, in the tire, the tire circumferential direction of the projected length of the straight line S ₁ connecting the outermost trailing side apex P _K and the most leading side vertex P _F and A, and the innermost vertex P _I in the tire width direction when the outermost vertex projected length of the P _O and the tire width direction of the linear S ₂ connecting the tire width direction is B, meets the a / B <1 relationship, and the tire width direction outside than the symmetric block rows L1 A / B becomes smaller as heading toward.

Therefore, the widths W _{L1 to} W _L7R and W _L7L of the block rows _{L1 to} L7 _R and L7 _L increase from the inner block row in the tire width direction toward the outer block row (that is, the right side of the pattern). In the half, W _L1 <W _L2R <W _L3R <W _L4R <W _L5R <W _L6R <W _L7R , and in the left half, W _L1 <W _L2L <W _L3L <W _L4L <W _L5L <W _L6L <W _L7L .)

として表すことができ、この実施形態において、ブロック個数密度Ｄは、０．００３（個／ｍｍ^２）〜０．０４（個／ｍｍ^２）の範囲内にある。ブロック個数密度Ｄは、ブロック３が配置された部分の実接地面積（溝分を除いた面積）中の単位面積（ｍｍ^２）当りに何個のブロック３があるかということを密度として表現したものである。ちなみに、通常のスタッドレスタイヤの場合には、この密度Ｄは概ね０．００２以下となる。なお、基準区域Ｚ内に在るブロック３の個数ａをカウントするに際して、ブロック３が基準区域Ｚの内外に跨って存在し、１個として数えることができない場合は、ブロック３の表面積に対する、基準区域内に残ったブロック３の残存面積の比率を用いて数えることとする。例えば、基準区域Ｚの内外に跨り、基準区域Ｚ内にその半分しか存在しないブロック３の場合は、１／２個と数えることができる。 Here, in the block group G _B, the density of the block 3 (Block number density), the reference pitch length PL of the block 3 (mm), the width (this embodiment of the block group G _B, the entire tread portion 1 since block is arranged, tread width TW) of W _{B (mm),} the reference pitch within the length PL and a block group W _B with the reference zone Z being defined by (area shown in FIG hatching) When the number of blocks existing in a is a (pieces) and the negative rate in the reference zone Z is N (%),

In this embodiment, the block number density D is in the range of 0.003 (pieces / mm ² ) to 0.04 (pieces / mm ² ). The block number density D represents the number of blocks 3 per unit area (mm ² ) in the actual ground contact area (area excluding the groove portion) where the blocks 3 are arranged. Is. Incidentally, in the case of a normal studless tire, this density D is approximately 0.002 or less. When counting the number a of the blocks 3 in the reference zone Z, if the block 3 exists between the inside and outside of the reference zone Z and cannot be counted as one, the reference to the surface area of the block 3 It is counted using the ratio of the remaining area of the block 3 remaining in the area. For example, in the case of the block 3 straddling the inside and outside of the reference zone Z and only half of the block 3 exists in the reference zone Z, it can be counted as 1/2.

In the tire of this embodiment, the asymmetric block row _{L2 R, L2 L ~L7 R,} L7 L block 3, the most trailing side apex _{P K} in the tire circumferential direction with respect to the most leading side vertex _{P F} is located inside the tire width direction, and the directed angle theta ₁ formed by the straight line S ₁ and the tire circumferential direction formed by connecting the outermost trailing side apex P _K and the most leading side apex P _F to the outer side in the tire width direction The widths W _{L1 to} W _L7R and W _L7L of the block rows _{L1 to} L7 _R and L7 _L increase toward the outer side in the tire width direction, so that the lateral force increases toward the shoulder when cornering. Since the block rigidity in the lateral direction can be increased, the steering stability during cornering can be improved.

Furthermore, since the increased take toward its outermost depression vertex P _F and the inclination angle theta ₁ tire width direction outer side with respect to the tire circumferential direction of the straight line S ₁ connecting the vertex P _K kick-most block 3, FIG. 3 When there is an input F in the tire circumferential direction by traction, the deformation direction of the block 3 can be directed to the center side (the directions of arrows I and II in FIGS. 3A and 3B), The straight running performance can be improved. Further, since the inclination angle of the inclined grooves 4a and 4b with respect to the tire circumferential direction is gradually increased toward the outer side in the tire width direction, the grooves can be formed along the streamline of water in the tread surface. It can drain more efficiently. Furthermore, since the sides of the block 3 adjacent to the inclined grooves 4a and 4b are curved, the flow of water flowing through the inclined grooves 4a and 4b can be made smooth, and the drainage can be further improved.

  Furthermore, according to the tire of this embodiment, since the blocks 3 partitioned by the grooves 2 are densely arranged with each other, the total edge length of the land portion is increased, and an edge effect higher than that of the sipe is obtained. Moreover, since the surface area per block 3 is small, the grounding property of the block 3 is improved. Further, since the distance from the central area of the block 3 to the peripheral edge of the block is small, the water film in the central area of the block 3 is efficiently removed when the block is grounded.

  Therefore, according to the tire of this embodiment, in the block pattern, it is possible to improve the steering stability and the straight running stability, as well as excellent steering stability on any of a dry road surface, a wet road surface, and an icy and snow road surface, and traction. And drainage can be improved.

It is to be noted that the block number density D in the block group _{G B,} as described above, from 0.003 to 0.04 (pieces / mm ²⁾ and was, but because the block number density D is 0.003 (pieces / mm ^In the case of less than ² ), it is difficult to realize a high edge effect without forming a sipe. On the other hand, if the block number density D exceeds 0.04 (pieces / mm ² ), the block becomes too small and a required block is obtained. This is because it is difficult to achieve rigidity. Therefore, from the viewpoint of achieving both the block rigidity and the edge effect, the block number density D is preferably set in the range of 0.0035 to 0.03 / mm ² .

Further, in the present invention, negative ratio N of the block group _{G B} is preferably 5% to 50%. If negative ratio N of the block group G _B is less than 5%, except that there is a risk that drainage is insufficient, too large the size of each one block have thinner risk of edge effects, whereas If it exceeds 50%, the contact area becomes too small and the steering stability may be lowered.

Furthermore, in the above description, the case symmetric block row is a row in the example, symmetrical block column may be a plurality of rows, three rows as shown in FIG. 4 (block row L1, L2 _L, L2 _R ). Further, the symmetrical block row may be arranged at the center of the tread portion (tire equator position) as shown in FIG. 1, or may be arranged near the shoulder as shown in FIG. 5 (that is, L3 _L is Symmetric block sequence). In the tire shown in FIG. 5, by arranging the symmetrical block row L3 _L on the inner side in the state of being mounted on the vehicle, the tread pattern is made an asymmetrical pattern, and the block rigidity of the shoulder region on the outer side of the vehicle that receives a large lateral force particularly during cornering. Since it can raise, steering stability can be improved more effectively.

  Next, a tread pattern according to another preferred embodiment of the present invention will be described with reference to the drawings.

In the example shown in FIG. 6, the groove width W ₄ of at least a part of the V-shaped grooves 4 is set larger than the groove width W ₅ of the intersecting grooves 5 extending so as to intersect therewith. According to this, it becomes possible to discharge more water to the outside of the tread tread efficiently through the V-shaped groove 4 along the flow line of water in the tread tread and having an increased groove width. The drainage during wet running can be further improved.

In the example shown in FIG. 7, the tire circumferential direction of the inclined grooves 4 a and 4 b constituting the V-shaped groove 4 in addition to the structure for increasing the groove width W ₄ of at least a part of the V-shaped groove 4 shown in FIG. 6. 6 is smaller than that shown in the example of FIG. 6 (more along the tire circumferential direction). Specifically, the inclination angle with respect to the tire circumferential direction is 45 degrees or less near the tire equator. It is a thing. According to this, since the groove extending direction of the V-shaped groove 4 can be made more along the water flow line in the tread surface, the drainage can be improved more effectively.

  The example shown in FIG. 8 is provided with a circumferential groove 7 extending along the tire circumferential direction at the position of the tire equatorial plane E. The circumferential groove 7 includes a see-through groove portion extending linearly along the tire circumferential direction. According to this, drainage can be improved by the circumferential groove 7, and the cornering performance on snow can be improved by increasing the edge component in the lateral direction. The circumferential groove 7 may extend in a zigzag shape in the tire circumferential direction as the entire groove bottom. The term “zigzag extending” means that the groove portions that are inclined with respect to the extending direction of the circumferential grooves are extended so that the inclined directions are alternated.

  In the example shown in FIG. 9, the tire equatorial plane E is sandwiched between the two positions (preferably, within the range of 20% to 80% of the tread contact width TW from the tire equatorial plane E) in the tire circumferential direction. A circumferential groove 7 extending along the surface is provided. According to this, the drainage performance can be further improved by the circumferential groove 7, and the cornering performance on snow can be further improved by increasing the edge component in the lateral direction. The circumferential grooves 7 may be three as shown in FIG. According to this, drainage and cornering performance can be further improved.

  As described above, the present invention has been described together with the embodiment, but the above description only shows a part of the embodiment of the present invention, and these configurations may be combined with each other without departing from the gist of the present invention. Various changes can be made. For example, in the present invention, the surface shape of the block 3 is not limited to an octagon, but may be a circle, an ellipse, another polygon, or an irregular closed shape. Further, the inclined grooves 4a and 4b may not be inclined in the opposite direction across the tire circumferential direction, may be inclined only in one direction, and may be provided in a part of the tread portion. For example, snow braking performance can be particularly improved by providing inclined grooves in the tread end areas, and snow traction performance can be particularly improved by providing inclined grooves in the central area.

  Next, the tires of Examples 1 to 5 according to the present invention, the tire of Conventional Example 1 according to the prior art, and the tires of Comparative Examples 1 and 2 were respectively prototyped and subjected to various performance evaluations. Each tire is a radial tire for a passenger car having a size of 205 / 55R16, and the tread contact width TW is 190 mm.

  The tire of Example 1 has the tread pattern shown in FIG. In the tire of Example 1, the width of the block row increases as it goes from the block row on the inner side in the tire width direction to the block row on the outer side in the tire width direction, except for the blocks located on the pattern center, It has an asymmetric shape with respect to the tire radial direction and the tire width direction, and further has a V-shaped groove with the pattern center at the apex. Detailed specifications of the tire of Example 1 are as shown in Table 1.

  The tire of Example 2 has the tread pattern shown in FIG. In this tire, a part of the V-shaped groove is wider than the intersecting groove intersecting the V-shaped groove. Detailed specifications of the tire of Example 2 are as shown in Table 1.

  The tire of Example 3 has the tread pattern shown in FIG. In this tire, the inclination angle of the inclined groove constituting the V-shaped groove with respect to the tire circumferential direction is made smaller than that in Example 2. Detailed specifications of the tire of Example 3 are as shown in Table 1.

  The tires of Examples 4 and 5 have the tread pattern shown in FIGS. This tire has circumferential grooves extending along the tire circumferential direction in the tread portion. Detailed specifications of the tires of Examples 4 and 5 are as shown in Table 1.

  For comparison, a 205 / 55R16 size radial tire for passenger cars, the negative rate of the tread portion shown in FIG. 11 having a negative rate of 31.9% for the entire tread portion, and the negative rate of the entire tread portion of FIG. A tire of Comparative Example 1 having a tread pattern shown in FIG. In the tire of Conventional Example 1, a plurality of rectangular blocks 103 are defined in the tread portion 100 by vertical grooves 101 extending in the tire circumferential direction and horizontal grooves 102 extending perpendicular to the vertical grooves 101. The vertical groove 101 has a width of 3 mm and a depth of 8.5 mm, and the horizontal groove 102 has a width of 7.9 mm and a depth of 8.5 mm. Each block 103 has three sipes 104 extending linearly. In the tire of Comparative Example 1, a plurality of rectangular blocks 103 are defined in the tread portion 100 by vertical grooves 101 extending in the tire circumferential direction and horizontal grooves 102 extending orthogonally to the vertical grooves 101. The vertical groove 101 has a width of 1.2 mm and a depth of 8.5 mm, and the horizontal groove 102 has a width of 4.5 mm and a depth of 8.5 mm. Each block 103 has two sipes 104 extending linearly. Other specifications are shown in Table 1.

For comparison, a tire of Comparative Example 2 having a tread pattern shown in FIG. The tire is a block number density D in the tread portion 1 is obtained by placing the block group _{G B} in the range of 0.003 to 0.04 piece / mm @ 2. The shape of each block 3 is a regular octagon. Other specifications are shown in Table 1.

(Performance evaluation)
About each said test tire, it assembled | attached to the rim of size 6.5Jx16, it mounted on the vehicle as internal pressure 220kPa (relative pressure), the following test was done, and the performance was evaluated.

(1) Steering stability on a dry road The circuit course in a dry state was run on sports in various driving modes and evaluated by the feeling of a test driver. The evaluation results are shown in Table 2. The evaluation in Table 2 is the index of the tires of Examples 1 to 5 and the tires of Comparative Examples 1 and 2 with the result of Conventional Example 1 being 100, and the larger the value, the better the steering stability when dry. Shows good.

(2) Steering stability on a wet road surface Wet sports on a circuit course in a wet state in various driving modes, and evaluated by feeling of a test driver. The evaluation results are shown in Table 2. The evaluation in Table 2 is the index of the tires of Examples 1 to 5 and the tires of Comparative Examples 1 and 2 with the result of Conventional Example 1 being 100. The larger the value, the better the steering stability when wet. Shows good.

(3) Steering stability on snow Steering stability on snow comprehensively reflects the braking performance, starting performance, straight running performance and cornering performance of the test driver when traveling on various test modes on a snowy road surface. This was done by evaluating the ring. The evaluation results are shown in Table 2. The evaluation in Table 2 is the index of the tires of Examples 1 to 5 and the tires of Comparative Examples 1 and 2 with the result of Conventional Example 1 being 100. The larger the value, the better the feeling on the snow. Indicates that

(4) Traction performance on snow The traction performance on snow was evaluated by measuring the section time when accelerating from an initial speed of 10 km / h to 45 km / h on a test course on a snow-capped road surface. The evaluation results are shown in Table 2. The evaluation in Table 2 is the index of the tires of Examples 1 to 5 and the tires of Comparative Examples 1 and 2 with the result of Conventional Example 1 being 100. The larger the value, the better the traction performance on snow. Indicates that

(5) Hydroplaning performance The hydroplaning performance was evaluated by measuring the limit speed at which a hydroplaning phenomenon occurred by running straight on a wet road surface with a water depth of 5 mm and measuring the limit speed. The evaluation results are shown in Table 2. The evaluation in Table 2 is the index of the tires of Examples 1 to 5 and the tires of Comparative Examples 1 and 2 with the result of Conventional Example 1 being 100, and the larger the value, the better the hydroplaning performance. It shows that.

(6) Straight-running stability Straight-running stability was determined by evaluating the straight-running stability of a test course consisting of a long straight line in a speed range from low speed to about 120 km / h using a test driver. . The evaluation of Table 2 is the index of the tires of Examples 1 to 5 and the tires of Comparative Examples 1 and 2 with the result of Conventional Example 1 being 100, and the greater the numerical value, the better the straight running stability. Indicates.

  From the evaluation results shown in Table 2, the application of the present invention is excellent in steering stability and straight running stability on any of dry road surfaces, wet road surfaces, and icy and snow road surfaces, and has improved traction and drainage properties. I understand that.

  Thus, according to the present invention, it is possible to provide a pneumatic tire that is excellent in straight running stability in addition to improved steering stability in the block pattern.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Groove 3 Block 4 V-shaped groove 5 Crossing groove 6 Rectangular groove part 7 Circumferential groove

Claims (8)

A pneumatic tire in which a plurality of block rows are formed in the tire circumferential direction by a plurality of independent blocks partitioned by grooves,
The block row is at least one symmetrical block row composed of blocks having a line-symmetric shape with respect to the tire circumferential direction, and is located on the outer side in the tire width direction with respect to the symmetrical block row, and has an asymmetric shape with respect to the tire circumferential direction. An asymmetric block sequence comprising blocks having
In the block of the asymmetric block row, the most kicked-out side vertex in the tire circumferential direction is located on the inner side in the tire width direction with respect to the most depressed side vertex in the tire circumferential direction, and the most depressed side vertex in the tire circumferential direction is the tire The angle formed between the straight line connecting the most kicked-out side vertex and the most stepped-on side vertex with respect to the most kicked-out side vertex in the circumferential direction and the tire circumferential direction is the symmetrical block. A pneumatic tire characterized by becoming larger from the row toward the outside in the tire width direction. The blocks of the asymmetric block row have an asymmetric shape with respect to the tire width direction,
The innermost vertex in the tire width direction of the block is located on the kicking side in the tire circumferential direction with respect to the outermost vertex in the tire width direction,
The outermost vertex in the tire width direction of the block is located on the stepping side in the tire circumferential direction with respect to the innermost vertex in the tire width direction,
The angle formed between the straight line connecting the innermost vertex and the outermost vertex and the tire circumferential direction becomes smaller as it goes outward in the tire width direction than the symmetric block row. The described pneumatic tire.   A projected length in the tire circumferential direction of a straight line connecting the most kicked-out vertex and the most depressed vertex is A, and a projected length in the tire width direction of a straight line connecting the innermost vertex and the outermost vertex is B. The A / B satisfies the relationship of A / B <1, and the A / B becomes smaller toward the outer side in the tire width direction than the symmetric block row, according to claim 1 or 2. Pneumatic tire.   The pneumatic tire according to any one of claims 1 to 3, wherein the symmetric block row has an apex, and has an inclined groove extending inclined from the apex.   5. The pneumatic tire according to claim 4, wherein an inclination angle of the inclined groove with respect to the tire circumferential direction gradually increases toward the outer side in the tire width direction.   The pneumatic tire according to any one of claims 1 to 5, comprising at least one circumferential groove extending in a tire circumferential direction.   5. The pneumatic tire according to claim 4, wherein the side forming the surface contour of the block is formed of a straight line and a curved line, and the side adjacent to the inclined groove is a curved line. In a block group formed by densely arranging the blocks, the reference pitch length of the block in the block group is PL (mm), the width of the lock group is W _G (mm), the reference pitch length PL and the block When the number of the blocks existing in the reference area of the block group divided by the width W _G is a (number) and the negative rate in the reference area is N (%), a / (PL × The block arrangement density D per unit actual contact area of the block group given by W _G × (1-N / 100)) is 0.003 (pieces / mm ² ) to 0.04 (pieces / mm ² ). The pneumatic tire according to any one of claims 1 to 7, wherein the pneumatic tire is within a range of.

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