JP2010208424A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire improved in on-snow performance and drainage performance in addition to a significant improvement in on-ice performance by optimizing a tread pattern. <P>SOLUTION: This pneumatic tire includes a plurality of block lines L in a tread part 1, that have blocks 4 arranged side by side in the tire circumferential direction and demarcated by a plurality of vertical grooves 2 extended in the tire circumferential direction and a plurality of lateral grooves 3 extended in the tire width direction while mutually connecting the vertical grooves 2 adjacent to each other in the tire width direction. Moreover, a block number density D of an area with arrangement of the blocks 4 is 0.003-0.04 (pieces/mm<SP>2</SP>). Furthermore, this pneumatic tire includes a plurality of inclined grooves 5 arranged in the tire circumferential direction in the tread part 1, that have groove length longer than the width W<SB>L</SB>of the block line L, and inclined and extended both in the tire circumferential direction and the tire width direction. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a pneumatic tire provided with a number of blocks formed by grooves in a tread portion. More specifically, in addition to a dramatic improvement in performance on ice, improvement in performance on snow and drainage performance on a wet road surface. The technology that brings

  Conventionally, in a pneumatic tire, for the purpose of improving the performance on ice by enhancing the edge effect, as shown in FIG. 6, the tread portion 100 has a longitudinal groove 101 extending in the tire circumferential direction and a tire width direction. In general, it is widely performed that the block 103 is partitioned by the extending lateral groove 102 and a plurality of sipes 104 are added to the formed block 103. In such a conventional pneumatic tire, a large number of sipes 104 are arranged in the block 103 under the requirements of higher driving, braking and turning performance, and in particular, on-ice performance is ensured for a large ground contact area. Therefore, the number of block rows in the tread surface is reduced to 3 to 9 rows, and each block 103 has a vertically long shape in the tire circumferential direction (see, for example, Patent Document 1).

JP 2002-192914 A

  However, in the conventional pneumatic tire as described above, the divided block portion 103a partitioned by the sipe 104 becomes horizontally long and the rigidity becomes too low, and the divided block portion 103a falls down at the time of ground contact, and the grounding property is deteriorated. Therefore, it is difficult to obtain sufficient on-ice performance commensurate with recent improvements in vehicle performance. Also, the size of each block 103 is large, and in the central area of the block 103, the formation of the sipe 104 alone can sufficiently remove the water film between the ice surface and the tire during braking on ice. In view of this, it has been difficult to dramatically improve the performance on ice. In addition, to improve the performance on ice, it is effective to increase the contact surface area of the tread and lower the negative rate (the ratio of the contact surface area to the total area of the contact surface including the groove). For this purpose, it is effective to increase the negative area by increasing the groove area, and these two performances are in a trade-off relationship.

  Therefore, the object of the present invention is to solve these problems, and its purpose is to improve the performance on ice in addition to the dramatic improvement in performance on ice by optimizing the tread pattern. And it is providing the pneumatic tire which can improve the drainage performance on a wet road surface.

In order to achieve the above object, the pneumatic tire according to the present invention has a tire width direction while connecting a plurality of vertical grooves extending in the tire circumferential direction and adjacent vertical grooves in the tire width direction to the tread portion. In a pneumatic tire provided with a plurality of block rows in which blocks divided by a plurality of horizontal grooves extending in the tire circumferential direction are provided, the minimum repeat length of the blocks in the tire circumferential direction is PL (mm), The length in the tire width direction of the range in which the blocks are arranged is W (mm), and the number of the blocks existing in the reference area defined by the minimum repeat length PL and the tire width direction length W is a ( Number of blocks per unit actual ground area in the reference area, given by a / {PL × W × (1−N / 100)}, where N (%) is the negative rate in the reference area. Dense The D, and in the range of 0.003 (pieces ^/ mm 2) to 0.04 (pieces / mm ^2), the tread portion has a longer groove length than the width of the block row, and A plurality of inclined grooves extending in an inclined manner with respect to both the tire circumferential direction and the tire width direction are arranged in the tire circumferential direction.

  Here, the “minimum repeat length of a block” refers to the minimum unit of a repeat pattern in the tire circumferential direction of a block in an arbitrary block row. For example, a pattern repeats by one block and a lateral groove that partitions the block. When the pattern is defined, the minimum repeating length of the block is obtained by adding the tire circumferential length of one block and the width of the lateral groove adjacent to the block in the tire circumferential direction. In addition, “the length in the tire width direction of the range in which the blocks are arranged” refers to a distance measured along the tire width direction in the range in which the blocks are arranged. For example, when the blocks exist in the entire tread , Refers to the tread contact width. Furthermore, the “actual ground contact area” in the reference area means the total surface area of all blocks in the reference area, in other words, the area obtained by subtracting the area of the groove that divides the block from the area of the reference area. It points to. The “width of the block row” refers to a distance measured along the tire width direction of the block row where the inclined grooves are present. Furthermore, the “groove length” of the inclined groove refers to the extended length of the inclined groove. Further, the longitudinal groove includes not only a groove extending linearly along the tire circumferential direction but also a groove extending in a zigzag shape or a wave shape.

In the pneumatic tire according to the present invention, the number of blocks per unit actual ground contact area in the reference area is set to 0.003 to 0.04 (pieces / mm ² ), so that the blocks can be densely arranged. As a result, the entire peripheral distance (total edge) of the block can be increased, so there are more effective edges when driving on ice than conventional sipe-type winter tires without reducing block rigidity. Obtainable. In addition, since the surface area of each block can be made sufficiently smaller than before, the grounding performance of each block can be improved, and the distance from the center area to the block periphery on the block surface can be reduced to reduce the center area of the block surface. It is possible to efficiently remove the water film at the time of block grounding. Furthermore, the block edge effect and drainage effect by the inclined groove can be obtained, and it is possible to achieve both improvement in performance on ice and improvement in performance on snow and drainage performance.

  Therefore, according to the pneumatic tire of the present invention, the above-mentioned action is combined, ensuring excellent grounding performance and edge effect, efficient water film removal by the block, and effective drainage effect by the inclined groove, block edge By realizing the effect, in addition to the dramatic improvement in performance on ice, the performance on snow and the drainage performance on wet road surfaces can be improved.

  In the pneumatic tire of the present invention, it is preferable that the inclined groove extends in the extending direction while being bent linearly or zigzag.

  And in the pneumatic tire of this invention, it is preferable to provide the circumferential main groove | channel which has the see-through groove part extended linearly along a tire circumferential direction in a tread part.

  According to the present invention, it is possible to provide a pneumatic tire with improved performance on snow and drainage performance on wet road surfaces in addition to dramatic improvement in performance on ice.

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 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 (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 partial development view showing a tread pattern 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 toroid 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 tread pattern shown in FIG. 1 in the tread portion.

As shown in FIG. 1, the tire extends in the tire width direction while mutually connecting a plurality of longitudinal grooves 2 extending in the tire circumferential direction and adjacent longitudinal grooves 2 in the tire width direction to the tread portion 1. A plurality of block rows L in which small blocks 4 divided by a plurality of lateral grooves 3 are arranged in the tire circumferential direction are provided. That is, in the tire, a small block group G _B (a range in which the small blocks 4 are arranged) in which a plurality of independent small blocks 4 partitioned by the vertical grooves 2 and the horizontal grooves 3 are densely arranged in the tread portion 1 is formed. Point). In this embodiment, the small block group G _B extends across the tread portion 1. The small blocks 4 are arranged in a staggered manner in the tire circumferential direction while overlapping with each other as seen in the tire circumferential direction. That is, the small block 4 in one block row L and the small block 4 in another block row L adjacent to this block row L overlap each other when viewed in the tire circumferential direction.

  Each small block 4 has, in its surface contour, a circumferential edge e1 (circumferential edge component) extending along the tire circumferential direction or a widthwise edge e2 (widthwise edge component) extending along the tire width direction, and the tire width. It forms an octagon in which inclined direction edges e3 (inclined direction edge components) extending in an inclined manner in both the tire direction and the tire circumferential direction are formed. In this embodiment, the small block 4 is formed in a horizontally long shape in which the tire width direction length BW is larger than the tire circumferential direction length BL.

として表される、基準区域Ｚ内における単位実接地面積当りの小ブロック４の個数（ブロック個数密度Ｄ）は、０．００３（個／ｍｍ^２）以上０．０４（個／ｍｍ^２）以下である。ブロック個数密度Ｄは、小ブロック４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）当りに何個の小ブロック４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内に在る小ブロック４の個数ａをカウントするに際して、小ブロック４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、小ブロック４の表面積に対する、基準区域内に残った小ブロック４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の場合は、１／２個と数えることができる。 The individual sizes of the small blocks 4 are set smaller than the conventional pattern shown in FIG. 6, and the density of the small blocks 4 is set higher than that of the conventional pattern shown in FIG. The smaller the size of the small blocks 4 and the higher the density, the higher the edge effect and the water removal effect. The ranges are as follows. In other words, the minimal repeating length of the small blocks 4 and PL (mm), the tire width direction length of the range in which the small blocks 4 are arranged (the width of the small block group G _B) W (mm) (this embodiment In this case, since the small block 4 is arranged on the entire tread portion 1, it is equal to the tread ground contact width TW.), And the tire is in a range where the small repeating length PL of the small block 4 and the small block 4 are arranged. The number of small blocks 4 existing in the reference area Z (area shown by hatching in the figure) divided by the width direction length W is a (number), and the negative rate in the reference area Z is N (%). When

The number of small blocks 4 (block number density D) per unit actual ground contact area in the reference zone Z is 0.003 (pieces / mm ² ) or more and 0.04 (pieces / mm ² ) or less. is there. The block number density D is defined as the number of small blocks 4 per unit area (mm ² ) in the actual ground contact area (area excluding the groove) where the small blocks 4 are arranged. It is a representation. 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 small blocks 4 in the reference area Z, the surface area of the small block 4 is present when the small blocks 4 exist across the reference area Z and cannot be counted as one. And the ratio of the remaining area of the small block 4 remaining in the reference area. For example, in the case of a block straddling the inside and outside of the reference area Z and only half of the block exists in the reference area Z, it can be counted as 1/2.

If the block number density D in the small block group _{G B} is less than 0.003 (pieces / mm ^2), without the formation of sipes, it is difficult to realize a high edge effect, whereas, the block number density D 0.04 If it exceeds (pieces / mm ² ), the small block 4 becomes too small and it is difficult to achieve the required block rigidity. Further, the block number density D in the small block group _{G B,} if within the range of 0.0035 to 0.03 piece / mm ^2, can be achieved a higher level of compatibility between the block rigidity and the edge effect .

In this tire, a plurality of inclined grooves 5 extending in an inclined manner with respect to both the tire circumferential direction and the tire width direction are formed in the tread portion 1 in the tire circumferential direction. Diagonal groove 5 has a width W long groove length than _L of the block row L of the inclined groove 5 is provided, namely the inclined grooves 5 extends across the block row L of the at least two rows. Each inclined groove 5 extends linearly. In this embodiment, the inclined groove 5 extends from one end of the tread portion 1 to the other end, and has a substantially V-shape bent in the opposite direction with the tire equator plane as a boundary. The groove width W ₅ of the inclined grooves 5 is greater than the smallest distance D _m of the distance between the small block 4 in the block row L which it is provided.

  In the tire according to this embodiment, the small blocks 4 are densely arranged in the tread portion 1 to improve the ground contact performance of the tread, and in particular, the brake and traction performance on the road surface on ice. In conventional tires, performance on ice has been improved by forming a large number of sipes in a relatively large block, but in this method, the blocks fall down at the divided blocks between sipes and the blocks are grounded uniformly. However, there was a certain limit to improving the performance on ice. On the other hand, in the present invention, the block number density D is within a predetermined range and a large number of small blocks 4 are densely arranged, so that the total edge component can be made longer than a sipe type winter tire and a high edge effect can be obtained.

  Further, in the conventional configuration in which the sipe is formed on a relatively large block, there is a problem that it is difficult to remove the water film on the ice surface corresponding to the central area of the block surface, but the small block 4 having a small block surface area is used. Thus, the distance from the central area of the block surface to the peripheral edge can be shortened, and the water removal efficiency can be increased efficiently.

By the way, although the on-ice performance can be drastically improved by a large increase in the actual ground contact area due to the dense arrangement of the small blocks 4, with such a configuration, the tread surface becomes close to a smooth tire. It was difficult to expect improvement in performance on snow and drainage when wet. Therefore, the invention in further in the tread portion 1, and more small block group G in _B in particular, the inclined grooves 5 extending inclined in both the tire circumferential direction and the tire width direction is provided, the performance on snow by block edge effect The improvement of drainage by the drainage effect and the improvement of the drainage effect, and succeeded in balancing the performance on ice.

  In addition, by changing the inclination angle α of the inclined groove 5, the contribution of the traction / brake performance on snow and the cornering performance can be changed. For example, if the inclination angle α of the inclined groove 5 with respect to the tire width direction is increased, the effect of catching in the lateral direction is increased, so that the contribution ratio to cornering performance (handling performance) is increased, while the tire width of the inclined groove 5 is increased. If the inclination angle α with respect to the direction is reduced, the effect of catching in the circumferential direction increases, and the contribution ratio to the traction / brake performance increases. Furthermore, increasing the inclination angle α of the inclined groove 5 with respect to the tire width direction contributes to the improvement of the hydroplaning performance. Further, the number of the inclined grooves 5 on the circumference and the extension length can be changed according to the target performance on snow. For example, when the performance on snow is important, the number of the inclined grooves 5 and the extension length thereof can be increased.

  Therefore, according to the tire of this embodiment, combined with the above-described actions, the small blocks 4 arranged densely achieve excellent grounding property and edge effect and efficient water film removal, while the inclined grooves 5 are more efficient. Since effective drainage and effective snow column shear force can be obtained, performance on snow and drainage performance on wet road surfaces can be improved in addition to dramatic improvement in performance on ice.

  Furthermore, according to the tire of this embodiment, since the small blocks 4 are arranged in a staggered manner in the tire circumferential direction, each edge is caused to act sequentially while forming a larger number of small blocks 4 during tire rolling. Therefore, the edge effect can be exhibited more effectively. Further, by arranging the small blocks 4 in a zigzag pattern in the tire circumferential direction, the contact timing to the road surface can be shifted between the small blocks 4 adjacent in the tire width direction, and pattern noise can also be reduced. it can. Furthermore, by arranging the small blocks 4 in a staggered manner in this way, a high density arrangement of the small blocks 4 can be easily realized. Further, the small blocks 4 are arranged in a zigzag pattern in the tire circumferential direction, and the block number density D is set high so that the small blocks 4 are supported by the adjacent small blocks 4 when a high load is applied to the small blocks 4. According to this, the rigidity of the small block 4 can be further increased to further improve the performance on ice.

  Moreover, according to this embodiment, since the inclined groove 5 extends linearly, the water flowing in the inclined groove 5 can be smoothly flowed, and the drainage performance can be further improved.

  Next, another embodiment of the present invention will be described. FIG. 2 is a partially developed view showing a tread pattern of a tire according to another embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the member same as the tire of FIG. 1, and the description is abbreviate | omitted.

  In the tire of this embodiment, the inclination angle α of the inclined groove 5 with respect to the tire width direction is set larger than that of the tire of FIG. Further, the inclination angle β of the inclination direction edge e3 of each small block 4 with respect to the tire width direction is also set larger than that of the tire of FIG. In this embodiment, the small block 4 is formed in a vertically long shape in which the tire circumferential direction length BL is larger than the tire width direction length BW.

  Therefore, according to the tire of this embodiment, the edge effect in the lateral direction and the snow column shear force can be increased, and the cornering performance and handling performance on ice and snow can be further improved. Further, bringing the inclined groove 5 closer to the tire circumferential direction is also advantageous in terms of drainage performance.

  Next, another embodiment of the present invention will be described. FIG. 3 is a partially developed view showing a tread pattern of a tire according to another embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the member same as the tire of FIG. 1, and the description is abbreviate | omitted.

  In the tire of this embodiment, the inclination angle α of the inclined groove 5 with respect to the tire width direction is set smaller than that of the tire of FIG. Further, the inclination angle β of the inclination direction edge e3 of each small block 4 with respect to the tire width direction is also set smaller than that of the tire of FIG. In this embodiment, the small block 4 is formed in a horizontally long shape in which the tire width direction length BW is larger than the tire circumferential direction length BL.

  Therefore, according to the tire of this embodiment, the edge effect in the tire circumferential direction and the snow column shear force can be increased, and the braking performance and traction performance on ice and snow can be further improved.

  Next, another embodiment of the present invention will be described. FIG. 4 is a partial development view showing a tread pattern of a tire according to another embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the member same as the tire of FIG. 1, and the description is abbreviate | omitted.

  In this embodiment, each small block 4 forms a hexagon in which a circumferential edge e1 and an inclined edge e3 are formed on the surface contour. And although the inclination | tilt angle (alpha) with respect to the tire width direction of the inclination groove | channel 5 is set substantially the same as that of the tire of FIG. 1, the inclination groove | channel 5 is bent into a zigzag, and the tire circumferential direction and a tire width direction as a whole. It extends in the direction inclined with respect to it.

  According to this, it is possible to increase the effective block edge in the lateral direction by bending the inclined groove 5, and handling on snow even if the inclination angle α of the inclined groove 5 is substantially the same as the inclination angle α of FIG. Performance can be improved.

  Next, another embodiment of the present invention will be described. FIG. 5 is a partially developed view showing a tread pattern of a tire according to another embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the member same as the tire of FIG. 1, and the description is abbreviate | omitted.

In this embodiment, each small block 4 forms a hexagon in which a circumferential edge e1 and an inclined edge e3 are formed on the surface contour. Further, the tread portion 1 is formed with two circumferential main grooves 7 having a see-through portion extending linearly along the tire circumferential direction, whereby the tread portion 1 is sandwiched between the two circumferential main grooves 7. The tread central area is divided into a tread outer area located outside the two circumferential main grooves 7 in the tire width direction. Then, the tread outer zone, the width W diagonal groove 5 to the tire circumferential direction extending direction inclined with respect to both the tire circumferential direction and the tire width direction have a longer groove length than _L of the block row L Several are arranged.

  According to this, in addition to the effects of the above embodiment, the hydroplaning performance is improved by increasing the drainage effect in the circumferential main groove 7, and the cornering performance on snow is improved by increasing the lateral edges. Can be realized. This can further improve the performance on ice due to a synergistic effect with the small block 4. Furthermore, in this embodiment, since the inclined groove 5 is provided in the tread outer area, the braking performance on snow can be particularly improved. The inclined groove 5 may be provided in the tread central region, and according to this, the traction performance on snow can be particularly improved. Therefore, according to this embodiment, the inclined groove 5 can be set according to the target performance.

Above has been described in conjunction with the present invention embodiment, in the present invention, negative ratio N of the small block group G _B is preferably 5% to 50%. If negative ratio N is less than 5% in the small block group G _B, the groove area is too small, other also becomes insufficient drainage as were provided with circumferential main grooves 7, the small blocks 4 one by one Since the size becomes too large, it is difficult to realize the edge effect that the present invention aims at. On the other hand, when it exceeds 50%, the ground contact area becomes too small and it becomes difficult to achieve the desired performance on ice. This is because the steering stability may be reduced.

Further, the above description shows only a part of the embodiment of the present invention, and these configurations can be combined with each other or various modifications can be made without departing from the gist of the present invention. For example, in the present invention, the surface contour shape of the small block 4 is not limited to an octagon, but may be a circle, an ellipse, another polygon, or an irregular closed shape. Further, the circumferential main groove 7 is not particularly limited as long as it has a see-through groove portion extending linearly in the tire circumferential direction. For example, the entire groove 7 can be extended while being curved in a wave shape. Although small block group G _B is more effective for the on-ice performance when providing the entire tread portion, possible to balance with other performance such as steering stability and uneven wear resistance by applying a limited area Can do.

  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 evaluated on ice performance, snow performance and drainage performance. This will be described below.

The tire of Example 1 is a 205 / 55R16 size passenger car radial tire having the tread pattern shown in FIG. 1 in the tread portion. In this tire, blocks separated by a longitudinal groove extending in the tire circumferential direction and a lateral groove extending in the tire width direction while mutually connecting longitudinal grooves adjacent to each other in the tire width direction are densely arranged in the tread portion. A small block group. In the tire according to the first embodiment, in the small block group, an inclined groove that extends linearly in a direction inclined with respect to both the tire circumferential direction and the tire width direction and has an inclined groove that is bent in the opposite direction with respect to the tire equatorial plane is circumferential 50 are arranged in the above. Each inclined groove, the groove width _{W 5} is 4.4 mm, groove depth 8.5 mm, the inclination angle α is 37.7 °. Other specifications of the tire of Example 1 are as shown in Table 1.

The tire of Example 2 is a 205 / 55R16 size passenger car radial tire having the tread pattern shown in FIG. 2 in the tread portion. In the tire of Example 2, 41 inclined grooves that extend in a straight line and bend in the opposite direction with respect to the tire equatorial plane are arranged in the circumferential direction. Each inclined groove, the groove width _{W 5} is 4.3 mm, groove depth 8.5 mm, the inclination angle α is 49.2 °. Other specifications of the tire of Example 2 are as shown in Table 1.

The tire of Example 3 is a 205 / 55R16 size radial tire for passenger cars having the tread pattern shown in FIG. 3 in the tread portion. In the tire according to the third embodiment, 71 inclined grooves extending in a straight line and bending in the opposite direction with respect to the tire equatorial plane are arranged in the circumferential direction. Each inclined groove, the groove width _{W 5} is 3.6 mm, groove depth 8.5 mm, the inclination angle α is 21.1 °. Other specifications of the tire of Example 3 are as shown in Table 1.

The tire of Example 4 is a 205 / 55R16 size radial tire for passenger cars having the tread pattern shown in FIG. 4 in the tread portion. In the tire of the fourth embodiment, 54 inclined grooves extending in a zigzag shape and bending in the opposite direction with respect to the tire equatorial plane are arranged in the circumferential direction. Each inclined groove, the groove width _{W 5} is 4.3 mm, groove depth 8.5 mm, the apparent tilt angle α is 37.7 °. The inclination angle β of the inclination direction edge of the small block is 20 °. Other specifications of the tire of Example 4 are as shown in Table 1.

The tire of Example 5 is a 205 / 55R16 size radial tire for passenger cars having the tread pattern shown in FIG. 5 in the tread portion. In the tire of this Example 5, the tread portion is a tread central region between the two circumferential main grooves by two circumferential main grooves formed of see-through groove portions extending linearly along the tire circumferential direction, It is divided into a tread outer region outside the circumferential main groove in the width direction. Each circumferential main groove has a groove width of 10.7 mm and a groove depth of 8.5 mm. In the tread outer region, 54 inclined grooves extending in a zigzag shape in a direction inclined with respect to both the tire circumferential direction and the tire width direction are arranged in the circumferential direction. Each inclined groove, the groove width _{W 5} is 4.3 mm, groove depth 8.5 mm, the apparent tilt angle α is 37.7 °. The inclination angle β of the inclination direction edge of the small block is 20 °. The groove width _{W 3} of the lateral grooves in the tread central region is 7.0 mm, the groove width _{W 3} of the lateral grooves in the tread lateral segment is 5.0 mm. The groove width _{W 2} of the longitudinal grooves in the tread central region is 10.7 mm, the groove width _{W 2} of the longitudinal grooves in the tread lateral segment is 0.6 mm. Other specifications of the tire of Example 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. 6 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 are defined in the tread portion by vertical grooves extending in the tire circumferential direction and horizontal grooves extending orthogonally to the vertical grooves. The longitudinal groove has a width of 3 mm and a depth of 8.5 mm, and the transverse groove has a width of 7.9 mm and a depth of 8.5 mm. Each block has three sipes extending linearly. In the tire of Comparative Example 1, a plurality of rectangular blocks are partitioned and formed in the tread portion by vertical grooves extending in the tire circumferential direction and horizontal grooves extending orthogonally to the vertical grooves. The longitudinal groove has a width of 1.2 mm and a depth of 8.5 mm, and the transverse groove has a width of 4.5 mm and a depth of 8.5 mm. Each block has two sipes extending linearly. Other specifications are shown in Table 1.

  Further, for comparison, a tire of Comparative Example 2 which is a 205 / 55R16 size passenger car radial tire and has a tread pattern shown in FIG. In this tire, neither an inclined groove nor a circumferential main groove is provided in the tread portion. Other specifications are shown in Table 2.

(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) Brake performance evaluation test on ice Brake performance on ice was evaluated from the measured distance by measuring the braking distance when fully braking from 20 km / h on an ice plate 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 braking performance on ice. Indicates that

(2) Feeling evaluation test on snow Feeling evaluation on snow is based on the comprehensive braking performance, startability, straightness, and cornering performance of the test driver when driving on a test track on a snowy road surface in various driving modes. This was done by evaluating the feeling. 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

(3) Brake performance evaluation test on snow Brake performance on snow was evaluated by measuring the braking distance when full braking was performed from a speed of 40 km / h on a test course on a snowy 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 braking performance on snow. Indicates that

(4) Trunk performance evaluation test on snow The traction performance on snow is evaluated from the measured time by measuring the section time when accelerating from the initial speed of 10 km / h to 45 km / h on a test course on a snowy road surface. did. 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) Drainage performance evaluation test The drainage performance was evaluated by measuring the limit speed at which a hydroplaning phenomenon occurred on a wet road surface having a water depth of 5 mm and measuring the limit speed. The evaluation results are shown in Table 2. 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. The larger the value, the better the drainage performance. Show.

  From the evaluation results shown in Table 2, it can be seen that application of the present invention can improve performance on snow and drainage performance in addition to dramatic improvement in performance on ice. Moreover, it turns out that drainage performance can be improved further by providing a circumferential direction main groove.

  According to the present invention, it is possible to provide a pneumatic tire having improved performance on snow and drainage performance in addition to dramatic improvement in performance on ice.

1 tread portion 2 longitudinal grooves 3 transverse grooves 4 small blocks 5 inclined groove 7 circumferential-direction main grooves G _B small block group PL block minimal repeating length (reference pitch length)
W Width of small block group Z Reference area

Claims (4)

A block divided by a plurality of vertical grooves extending in the tire circumferential direction and a plurality of horizontal grooves extending in the tire width direction while mutually connecting vertical grooves adjacent to each other in the tire width direction is formed on the tread portion. In the pneumatic tire provided with a plurality of block rows arranged in the direction,
PL (mm) is the minimum repeat length of the block in the tire circumferential direction, W (mm) is the length in the tire width direction in the range where the block is disposed, and these minimum repeat length PL and tire width direction length W A / {PL × W × (1−N / 100) where a is the number of blocks existing in the reference area and N is the negative rate in the reference area. )}, The block number density D per unit actual ground contact area in the reference area is set within a range of 0.003 (pieces / mm ² ) to 0.04 (pieces / mm ² ),
In the tread portion, a plurality of inclined grooves having a groove length longer than the width of the block row and extending inclined with respect to both the tire circumferential direction and the tire width direction are arranged in the tire circumferential direction. A pneumatic tire characterized by that.   The pneumatic tire according to claim 1, wherein the inclined groove extends linearly.   The pneumatic tire according to claim 1, wherein the inclined groove extends in an extending direction while being bent zigzag.   The pneumatic tire according to any one of claims 1 to 3, wherein a circumferential main groove having a see-through groove portion extending linearly along the tire circumferential direction is provided in the tread portion.

Images