JP2011143898A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire which improves noise performance while enhancing a water removing effect and a scratching effect on a road surface by a novel method different from conventional methods. <P>SOLUTION: The pneumatic tire includes a plurality of recessed portions 10 dispersed in rib-like land portions 3, 4, 5 extending in a tire circumferential direction and opened toward a tread contact surface, and first grooves 12 and second grooves 13 connecting the recessed portions 10 and partitioning a plurality of separated blocks 11 in the rib-like land portions 3, 4, 5. A groove width w12 of the first groove 12 and a groove width w13 of the second groove 13 are set to have a distance such that the blocks 11 spaced away from each other via the first groove 12 and the second groove 13 are at least partially brought into contact with each other in a tire grounding state. The second groove 13 includes a widened portion 14 widening partially in a second groove depth direction. At least one of the second grooves 13 is connected to the recessed portions 10. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a pneumatic tire in which a block is defined by a groove in a rib-like land portion extending along the tire circumferential direction, and in particular, a water removal effect and a road surface scratching effect by a novel method that has not been conventionally used. The present invention relates to a pneumatic tire that is improved and improved in noise performance.

  Various methods have been proposed in the past to improve the water removal effect to remove the water film on ice and wet road surfaces and the scratching effect by the edge, and some of them have been put to practical use. One of the typical ones is that a relatively large block is partitioned and formed with vertical and horizontal grooves in the tread part, and thousands of fine grooves (sipes) are carved per tire on the surface of the formed block. There is a tire (see Patent Document 1).

  However, in the above method, the water removal performance is improved by increasing the number of narrow grooves, and it can be expected that the scratching effect is increased. However, the fall of the block due to the decrease in the rigidity of the block occurs, and the contact area decreases. There was a problem to do. On the other hand, in order to prevent the reduction of the ground contact area at the time of shear input, a so-called three-dimensional sipe or narrow groove formed by bending the narrow groove in the depth direction is formed in a wave shape or zigzag shape in the extending direction. However, since the narrow groove is formed in the block, for example (see Patent Document 2), this problem has not been solved fundamentally.

Japanese Patent Laid-Open No. 06-320917 JP 2007-015510 A

  Therefore, the inventors have made researches to solve the above problems, and as a result, a large number of blocks are formed by forming narrow grooves such as sipes in a mesh shape in the rib-like land portion extending along the tire circumferential direction. It is found that the same edge length (scratch effect) can be obtained while suppressing a decrease in the rigidity of the block, compared to the case where a narrow groove is cut into the block itself as in the prior art, It has also been found that a desired water removal effect can be obtained by providing a recess opening in the tread ground surface in the rib-like land portion.

  However, in a pneumatic tire adopting such a block pattern, when the rib-like land portion contacts the road surface, the recess functions as a so-called air pocket and is sandwiched between the recess and the road surface to escape. It was newly found that the air that lost the air was compressed and expanded, generating noise called pumping noise.

  Therefore, an object of the present invention is to provide a pneumatic tire that improves the water removal effect and the scratching effect on the road surface and improves the noise performance by a novel method that has not been conventionally used.

  In order to solve the above-described problems, a pneumatic tire according to the present invention is arranged in a distributed manner in a rib-like land portion extending along the tire circumferential direction, and a plurality of recesses that open to a tread ground surface and a space between the recesses. A first groove and a second groove, which are connected to each other and define a plurality of independent blocks in the rib-like land portion, and the groove widths of the first groove and the second groove are respectively The block separated by the first groove and the second groove is set to a distance at least partially contacting each other in a tire ground contact state, and the second groove is the second groove. And having a widened portion whose width locally expands in the depth direction, and at least one of the second grooves is connected to the concave portion. The “tire contact state” as used herein means that a tire is mounted on an applicable rim described in JATMA or a standard equivalent thereto, the highest air pressure specified in the standard is applied to the tire, and the tire is stationary. A state in which a load corresponding to 80% of the maximum load capacity is applied is set perpendicular to the flat plate.

  In the pneumatic tire having such a configuration, the first groove and the second groove are at least partially closed in the tire contact state, and the blocks separated by the first groove and the second groove are mutually connected. Because of contact, due to the support effect between adjacent blocks, the rigidity of the block with the same edge length is increased compared to the case where the edge length is ensured by engraving a narrow groove in the block itself as in the past. It is possible to effectively prevent a reduction in the ground contact area at the time of shear input. Further, water that has entered the tread ground plane can be efficiently discharged out of the ground plane through the recess. On the other hand, by connecting at least one second groove to the recess, the recess always communicates with at least one of the other recesses via the widened portion of the second groove even in the tire ground contact state. . Thereby, since the volume (total volume) of the air pocket formed by the recess and the road surface is increased, the compression / expansion rate of air in the recess is reduced, and the pumping noise can be reduced.

  Therefore, according to the pneumatic tire of the present invention, the water removal effect and the road surface scratching effect can be improved, and the noise performance can be improved by increasing the apparent volume of the recess.

  In the pneumatic tire of the present invention, it is preferable that the widened portion is disposed closer to the groove bottom in the depth direction of the second groove.

  In the pneumatic tire according to the present invention, at least one second groove extending across the tread grounding end in the tire width direction is connected to a recess located on the outermost side in the tire width direction among the recesses. It is preferable.

  Furthermore, in the pneumatic tire according to the present invention, the range in which the recesses and the second grooves are alternately and continuously connected, and the recesses and the second grooves are alternately and continuously connected. The tire circumferential linear distance is preferably larger than the contact length. Here, the “contact length” means that a tire is mounted on an applicable rim described in JATMA or a standard equivalent thereto, the highest air pressure specified in the standard is applied in the tire, and the plate is stationary with respect to the flat plate. The maximum circumferential distance in the tire circumferential direction at the contact surface with the flat plate when a load equivalent to 80% of the maximum load capacity is applied is assumed.

Moreover, in the pneumatic tire of the present invention, the width of the rib-like land portion is W (mm), the reference pitch length of the block in the rib-like land portion is PL (mm), When the number of blocks existing in the reference area defined by the width W and the reference pitch length PL is a (number) and the negative rate in the reference area is N (%), S = a / { PL × W × (1−N / 100)} The block number density S (pieces / mm ² ) per unit actual contact area of the rib-like land portion is within a range of 0.003 to 0.04. Preferably there is. Here, “the width of the rib-like land portion” refers to the length of the rib-like land portion along the tire width direction. The “reference pitch length of the block” means the minimum unit or a plurality of units of the repeating pattern in the tire circumferential direction formed by the rib-like land block, for example, one block and this block. When the repeated pattern of the pattern of a tire circumferential direction is prescribed | regulated by the recessed part adjacent to the tire circumferential direction of this, it points to what added each tire circumferential direction length of these blocks and recessed parts. Furthermore, the “block number density” represents the number of blocks existing as a density per actual ground contact area in the reference area (total surface area of all blocks in the reference area).

  According to the present invention, it is possible to provide a pneumatic tire with improved noise performance and improved water removal effect and road surface scratching effect by a novel method that has not existed before.

(A) is the partial expanded view which showed the tread pattern of the tire of one Embodiment (tyre of Example 1) according to this invention, (b) is the cross section in alignment with the AA in FIG. 1 (a). It is a figure, (c) is sectional drawing which follows the BB line in Fig.1 (a). (A) is the partial expanded view which showed the tread pattern of the tire of other embodiment (tire of Example 2) according to this invention, (b) follows the AA line in FIG. 2 (a). It is sectional drawing, (c) is sectional drawing which follows the BB line in Fig.2 (a), (d) is sectional drawing which follows the CC line in Fig.2 (a). (A) is the partial expanded view which showed the tread pattern of the tire of other embodiment (tire of Example 3) according to this invention, (b) follows the AA line in Fig.3 (a). It is sectional drawing, (c) is sectional drawing which follows the BB line in Fig.3 (a). (A) is the partial expanded view which showed the tread pattern of the tire of other embodiment according to this invention, (b) is sectional drawing which follows the AA line in Fig.4 (a), (c) ) Is a cross-sectional view taken along the line BB in FIG. 4A, and FIG. 4D is a cross-sectional view taken along the line CC in FIG. 4A. (A)-(c) is the figure which illustrated other block shapes applicable to this invention, respectively. (A)-(d) is sectional drawing which illustrated the other 2nd groove | channel applicable to this invention, respectively. It is the partial expanded view which showed the tread pattern of the pneumatic tire for comparison (tire of the comparative example 1).

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a partial development view showing a tread pattern of a pneumatic tire (hereinafter simply referred to as “tire”) according to an embodiment of the present invention.

  Although not shown in the drawings, the tire of this embodiment includes a tread portion that forms a tread surface of the tire, a pair of sidewall portions that are connected to the outer side in the width direction of the tread portion via a shoulder portion, and tires of these sidewall portions. Conventionally provided with a pair of bead portions disposed radially inside, a carcass extending in a toroidal shape between the pair of bead portions inside the tire, and a belt layer disposed on the outer side in the tire radial direction of the crown region of the carcass The tire has a tire structure according to the above.

  As shown in FIG. 1, the tire includes at least one, in this case, three rib-like land portions 3, 4, and 5 extending in the tire circumferential direction in the tread portion 1, and the rib-like land portions 3, Between four and five, two circumferential grooves 7 and 8 extending in the tire circumferential direction are provided. The circumferential grooves 7 and 8 are preferably arranged at positions corresponding to within 35% of the tread contact width (the length in the tire width direction between the tread contact ends TW) with the tire equatorial plane E as the center. This is because if the block row width between the ground contact TE and the circumferential grooves 7 and 8 is reduced, the wear performance may be reduced. The groove widths of the circumferential grooves 7 and 8 are preferably 10 to 40% of the tread ground contact width in order to ensure sufficient drainage. Here, for convenience, both regions outside the circumferential grooves 7 and 8 are shoulder regions, and when three or more circumferential grooves are provided, the tire width direction outermost of the plurality of circumferential grooves is provided. Both regions on the outer side in the tire width direction than the circumferential groove located on the outer side are defined as shoulder regions.

In each of the rib-like land portions 3, 4, and 5, a plurality of concave portions 10 that are open to the tread ground contact surface (surface that contacts the road surface) are distributed. The concave portion 10 takes in water, ice, and snow that are interposed between the tread contact surface and the road surface, and the water, ice, and snow that are taken into the concave portion 10 are discharged to the outside by centrifugal force accompanying rotation of the tire. Is done. The depth, volume, number, shape, arrangement position, etc. of the recess 10 can be appropriately set according to the water removal capability required for the tire, for example, the depth of the recess 10 is about 3 mm to about 8 mm. The volume is preferably about 30 mm ² to about 400 mm ² .

  The rib-like land portions 3, 4, 5 are connected to each other between the adjacent recesses 10, and a plurality of independent blocks 11 are defined in the rib-like land portions 3, 4, 5. The groove 12 and the second groove 13 are provided. That is, the block 11 is formed by arranging the first groove 12 and the second groove 13 in a mesh pattern. At least in the shoulder region, rib-like land portions 3, 4, and 5 in which a plurality of blocks 11 are defined are arranged. For the sake of convenience, the second groove 13 is indicated by a thicker line than the first groove 12 so that the first groove 12 and the second groove 13 can be distinguished on the drawing.

  Further, the blocks 11 in the rib-like land portions 3, 4 and 5 are arranged in a staggered manner. That is, the blocks 11 are arranged side by side in the tire circumferential direction to form a plurality of block rows, and the blocks 11 in one block row and the blocks 11 in another block row adjacent to the block row in the tire width direction. Is arranged so that the phase is different in the tire circumferential direction. Here, “the phases are different in the tire circumferential direction” means, for example, in the example of FIG. 1, a state in which each block 11 is shifted by half a pitch in the tire circumferential direction between adjacent block rows. . By adopting such a staggered arrangement, the ground contact timing of the recess 10 can be shifted, which is advantageous in reducing pattern noise. Further, pattern noise can be further reduced by shifting the positions of the recesses 10 in the tire circumferential direction between all the block rows.

  Here, the groove width w12 of the first groove 12 is set to a distance at which the blocks 11 separated via the first groove 12 are at least partially in contact with each other in the tire ground contact state. The groove width w13 of the groove 13 is also set to a distance at which the blocks 11 separated via the second groove 13 are at least partially in contact with each other in the tire ground contact state. Here, the adjacent blocks “partially contact” means that the block 11 is deformed by being pressed against the road surface, and the side wall surfaces 11 a of the adjacent blocks 11 are partially in contact with each other. In this embodiment, the groove width w12 of the first groove 12 is constant in the depth direction. However, the groove width w12 may be gradually increased or decreased in the depth direction.

  Further, as shown in FIG. 1C, the second groove 13 has a widened portion 14 whose width is locally expanded in the depth direction (the radial direction of the tire). Therefore, the wide groove portion 14 and the narrow width portion 15 having a groove width smaller than that of the wide width portion 14 are formed in the second groove 13. Here, the widened portion 14 is formed by locally denting the side wall surfaces 11a of both blocks 11 separated by the second groove 13 into a dome shape, whereby the widened portion 14 has a substantially spherical shape. The widened portion 14 does not close even in the tire ground contact state. That is, the side wall portion of the block 11 provided with the widened portion 14 is held in a state of being separated from the side wall portion of the block 11 opposed to the side wall portion across the widened portion 14 even in the tire ground contact state. The widened portion 14 is disposed closer to the groove bottom in the depth direction of the second groove 13, more specifically, in contact with the groove bottom. Here, “close to the groove bottom” means that the widened portion 14 is disposed below the central position in the depth direction of the second groove 13.

  At least one second groove 13 is connected to each recess 10, that is, one end of the second groove 13 opens into one recess 10 and the other end of the second groove 13 is the other. Thus, the recesses 10 adjacent to each other are reliably communicated with each other via the widened portion 14 of the second groove 13. Thereby, in the tire ground contact state, the blocks 11 separated by the first groove 12 and the second groove 13 come into contact with each other to increase rigidity, and the recesses 10 adjacent to each other are widened portions of the second groove 13. 14 to communicate with each other.

  The groove width w12 of the first groove 12 and the groove width w13 of the second groove 13 (groove width in the narrow width portion 15) are preferably less than 0.7 mm. When the groove width w12 of the first groove 12 and the groove width w13 of the second groove 13 are 0.7 mm or more, they are separated via the first groove 12 and the second groove 13 in the tire ground contact state. This is because the blocks 11 may not contact each other. In addition, when changing the groove widths w12 and w13 of the first and second grooves 12 and 13, it can be easily realized by adjusting the thickness of the blade applied to the tire vulcanization mold. Is possible. The groove width w14 (maximum value) in the widened portion 14 of the second groove 13 is preferably 0.7 mm or more and 3 mm or less. This is because if the groove width w14 in the widened portion 14 of the second groove 13 is less than 0.7 mm, the widened portion 14 may be closed in the tire ground contact state, while if it exceeds 3 mm, the widened portion 14 is exceeded. This is because the volume of the block 11 is reduced by a small amount, and sufficient block rigidity may not be ensured.

  According to the tire adopting such a configuration, the first groove 12 and the second groove 13 are at least partially closed in the tire ground contact state, and are blocks separated by the first groove 12 and the second groove 13. Since the blocks 11 are in contact with each other, the blocks having the same edge length as compared with the conventional case where the edge length is ensured by engraving the narrow groove in the block itself due to the support effect between the adjacent blocks 11. 11 can be increased, and a reduction in the contact area at the time of shear input can be effectively prevented. Further, water that has entered the tread ground plane can be efficiently discharged out of the ground plane through the recess 10. On the other hand, the second groove 13 is connected to the concave portion 10, so that the concave portion 10 always passes through at least one of the other concave portions 10 and the widened portion 14 of the second groove 13 even in the tire ground contact state. Communicated. As a result, the volume of the air pocket formed by the recess 10 and the road surface (the total volume of the recess 10 communicated by the second groove 13) increases, and the compression / expansion rate of air in each recess 10 decreases. The pumping sound can be reduced.

  In addition, the rigidity of the block 11 increases as the widened portion 14 is closer to the groove bottom in the depth direction of the second groove 13. In this embodiment, the widened portion 14 is disposed closer to the groove bottom. Since the rigidity is high, the steering stability is excellent, and even if the block 11 is worn away by wear, the widened portion 14 can remain, and the noise reduction effect can be maintained for a long period of time.

  Further, according to the tire of this embodiment, the tread portion 1 is provided with the circumferential grooves 7, 8 extending in the tire circumferential direction between the rib-like land portions 3, 4, 5 adjacent to each other in the tire width direction. From the above, it is possible to obtain a good water removal effect and a scratching effect on the road surface in the rib-like land portions 3, 4, and 5 and to improve the noise performance, while in other regions, it is possible to ensure drainage performance. The adverse effect on drainage due to the dense arrangement of the blocks 11 in the rib-like land portions 3, 4, 5 can be solved.

として表される、各リブ状陸部３、４、５の単位実接地面積当りのブロック個数密度Ｓ（Ｓ１、Ｓ２、Ｓ３）はそれぞれ、０．００３（個／ｍｍ^２）以上０．０４（個／ｍｍ^２）以下である。ここで、リブ状陸部３、４、５の幅Ｗは、タイヤ幅方向の一側縁及び他側縁間のタイヤ幅方向距離を指し、一側縁又は他側縁がトレッド接地端ＴＷを越える場合には、一側縁又は他側縁とトレッド接地端ＴＷとの相互間のタイヤ幅方向距離を指すものとする。ブロック個数密度Ｓは、各リブ状陸部の実接地面積（溝分を除いた面積）の単位面積当りに何個のブロック１１が存在す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、例えば通常のスタッドレスタイヤの場合には、この密度Ｓは概ね０．００２以下となる。なお、基準区域Ｚ内のブロックの個数ａをカウントするに際して、ブロック１１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、基準区域Ｚを跨るブロックの表面積に対する、基準区域内に残った同ブロック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１１の場合は、１／２個と数えることができる。 By the way, in order to increase the total edge length of the block 11 (the total length of the peripheral edges of each block 11), it is necessary to reduce the size of each block to form more blocks 11. However, the proper range is as follows. That is, the width W (W3, W4, W5) (mm) of each rib-shaped land portion 3, 4, 5 and the reference pitch length of the block 11 in the rib-shaped land portions 3, 4, 5 are set to PL (PL3, PL4, PL5) (mm), a reference zone Z (Z3, Z4, Z5) defined by the width W of the rib-like land portions 3, 4, 5 and the reference pitch length PL (shown by hatching in the figure) ) Is the number of blocks 11 existing in a) (a3, a4, a5) (pieces), and the negative rate in the reference zone Z is N (N3, N4, N5) (%),

The block number density S (S1, S2, S3) per unit actual ground contact area of each of the rib-like land portions 3, 4, 5 represented as 0.003 (pieces / mm ² ) or more and 0.04 ( Pieces / mm ² ) or less. Here, the width W of the rib-like land portions 3, 4 and 5 indicates the distance in the tire width direction between the one side edge and the other side edge in the tire width direction, and the one side edge or the other side edge defines the tread grounding end TW. When exceeding, it shall refer to the distance in the tire width direction between the one side edge or the other side edge and the tread ground contact edge TW. The block number density S represents the number of blocks 11 per unit area of the actual ground contact area (area excluding the groove) of each rib-like land portion as a density. Incidentally, for example, in the case of a normal studless tire, this density S is approximately 0.002 or less. In counting the number of blocks a in the reference zone Z, if the block 11 exists across the reference zone Z and cannot be counted as one, the surface area of the block across the reference zone Z is It is counted using the ratio of the remaining area of the block remaining in the reference area. For example, in the case of the block 11 straddling the inside and outside of the reference zone Z and having only half of the block in the reference zone Z, it can be counted as 1/2.

When the block number density S in the rib-like land portions 3, 4 and 5 is less than 0.003 (pieces / mm ² ), the total edge length should be increased without forming sipes in the block 11. On the other hand, if the block number density S exceeds 0.04 (pieces / mm ² ), the size of the block 11 becomes too small and it becomes difficult to achieve the required block rigidity. Further, if the block number density S in the rib-like land portions 3, 4 and 5 is within the range of 0.0035 to 0.03 / mm ² , both ensuring block rigidity and increasing the total edge length are achieved. Can be achieved in higher dimensions.

  The negative rate N in the rib-like land portions 3, 4, 5 is preferably 5% to 50%. When the negative rate N in the rib-like land portions 3, 4 and 5 is less than 5%, the groove area is too small and the drainage is insufficient, and the size of each block is too large and the present invention is aimed. This is because it is difficult to increase the edge length. On the other hand, if it exceeds 50%, the contact area becomes too small and the steering stability may be lowered.

  Next, another embodiment of the present invention will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the component same as the component in the tire demonstrated in FIG. 1, and the description is abbreviate | omitted.

  In the tire illustrated in FIG. 2, each of the rib-shaped land portions 3, 5 at the outermost side in the tire width direction is positioned on the outermost side in the tire width direction among the recesses 10 formed in the rib-shaped land portions 3, 5. At least one, here, one second groove 13 extending across the tread grounding end TE in the tire width direction is connected to each recess 10. As shown in FIG. 2 (d), the second groove 13 connected to each concave portion 10 located on the outermost side in the tire width direction in the rib-like land portions 3 and 5 opens the widened portion 14 in the tread ground contact surface. It is configured as follows. According to this, the concave portion 10 located on the outermost side in the tire width direction is opened outside the ground contact surface even in the tire ground contact state via the widened portion 14 of the second groove 13 extending across the tread ground contact end TE. No air pocket (sealed space) is formed, and the generation of noise due to the recess 10 can be further reduced.

  In the tire illustrated in FIG. 3, the recesses 10 and the second grooves 13 are alternately and continuously connected in the tire circumferential direction, and the recesses 10 and the second grooves 13 are alternately and continuously connected. The tire circumferential direction linear distance is configured to be larger than the contact length TL. According to this, since the concave portion 10 is opened to the outside of the ground contact surface even in the tire ground contact state via the widened portion 14 of the second groove 13, an air pocket (sealed space) is not formed, and FIG. As with the tire shown in FIG. 4, the generation of noise due to the recess 10 can be further reduced.

  Furthermore, as shown in FIG. 4, in the rib-shaped land portions 3, 5 at the outermost side in the tire width direction, each of the concave portions 10 formed in the rib-shaped land portions 3, 5 is positioned at the outermost side in the tire width direction. A second groove 13 extending across the tread grounding end TE in the tire width direction is connected to the concave portion 10, and the rib-like land portion 4 sandwiched between the circumferential grooves 7 and 8 has the concave portion 10 and the second groove. 13 can be connected alternately in the tire circumferential direction.

  The present invention has been described based on the illustrated examples. However, the present invention is not limited to the above-described embodiment, and can be appropriately changed within the scope of the claims. For example, the first and first embodiments The shape of the block 11 defined by the two grooves 12 and 13 may be a quadrangle, a pentagon, or a hexagon as illustrated in FIGS. 5A to 5C, and a recess surrounded by these blocks 11. The shape of 10 may be various shapes other than a rectangle, such as a triangle or a circle (not shown). Further, the arrangement position of the widened portion 14 in the depth direction of the second groove 13 is not limited to the above-described embodiment, and the widened portion 14 is tread-contacted as shown in FIGS. 6A and 6B, for example. It can be provided so as to open to the ground or can be provided at a central position in the depth direction. Further, the shape of the widened portion 14 is not limited to the above-described embodiment. For example, as shown in FIGS. 6C and 6D, the maximum width is taken at the groove bottom and the width from the narrow portion 15 toward the narrowed portion 15 is increased. Is gradually reduced, or only the side wall surface 11a of one block 11 of the opposing blocks 11 separated by the second groove 13 is locally recessed into a dome shape to have a substantially half-moon shape. Can be. Moreover, two or more widened portions 14 may be provided for each second groove 13.

  Next, the tires of Examples 1 to 3 according to the present invention and the tire of Comparative Example 1 for comparison were respectively prototyped and subjected to various performance evaluations. Each of these tires is a radial tire for passenger cars having a tire size of 195 / 65R15, and the tread contact width is 140 mm.

The tire of Example 1 has the tread pattern shown in FIG. The circumferential groove 7 is disposed at a position corresponding to 20% of the tread contact width centered on the tire equatorial plane E, and the circumferential groove 8 corresponds to 20% of the tread contact width centered on the tire equatorial plane E. Placed in position. The groove width of the circumferential groove 7 is 14 mm, and the groove depth is 8.3 mm. The groove width of the circumferential groove 8 is 17 mm, and the groove depth is 8.3 mm. The volume of the recess 10 is 145 mm ³ , and 236 are provided in each rib-like land portion around the tire. The groove width w12 of the first groove 12 is 0.5 mm, and the groove depth is 6.0 mm. The groove width (groove width of the narrow portion) w13 of the second groove 13 is 0.5 mm, and the groove depth is 6.0 mm. The widened portion 14 is provided at a position 4 mm to 6 mm from the tread ground plane (that is, the upper end of the widened section 14 is located 4 mm from the tread ground plane, and the lower end of the widened section 14 is located 6 mm from the tread ground plane. The width (maximum value) of the widened portion 14 is 2.0 mm. The negative rate of the entire tread portion 1 including the circumferential grooves 7 and 8 is 28%. Other specifications are shown in Table 1.

  The tire of Example 2 has the tread pattern shown in FIG. In the tire of Example 2, the rib-shaped land portions 3 and 5 on the outermost side in the tire width direction are recessed portions located on the outermost side in the tire width direction among the recessed portions 10 formed in the rib-shaped land portions 3 and 5. 10 is different from the tire of the first embodiment in that one second groove 13 extending across the tread grounding end TE in the tire width direction is connected to the tire 10 in the tire width direction. It is. Other specifications are shown in Table 1.

  The tire of Example 3 has the tread pattern shown in FIG. 3 in the tread portion. The tire of Example 3 is a tire in a range in which the recesses 10 and the second grooves 13 are alternately and continuously connected in the tire circumferential direction, and the recesses 10 and the second grooves 13 are alternately and continuously connected. Unlike the tire of Example 1 in that the circumferential linear distance is configured to be greater than the contact length TL, the other configuration is substantially the same as the tire of Example 1. Other specifications are shown in Table 1.

  The tire of Comparative Example 1 has the tread pattern shown in FIG. 6 in the tread portion, and all the grooves that define the block 11 in the rib-like land portions 3, 4, and 5 are configured by the first grooves 12. Except for the above, the tire has substantially the same configuration as that of the tire of Example 1. The groove width w12 of the first groove 12 is 0.5 mm, and the groove depth is 6.4 mm. The negative rate of the entire tread portion including the circumferential grooves 7 and 8 is 28%. Other specifications are shown in Table 1.

  Regarding the noise reduction effect, after mounting the tire on a rim of size 6J × 15 and applying air pressure of 210 kPa (relative pressure) inside, an indoor noise tester (drum: speed 60 km / hour) was used. Measured by placing a microphone at a position 50 cm away from the tire, and compared with the overall value of all bands. The measured value of noise is an overall value, and the greater the negative value with reference to the tire of Comparative Example 1, the greater the noise reduction effect. The measurement results are shown in Table 2.

  From the results shown in Table 2, it can be seen that the application of the present invention improved the noise performance as compared with the prior art. Moreover, it turns out that noise performance improves markedly by opening the 2nd groove | channel connected to a recessed part out of a ground-contact plane.

  Next, the tires of Examples 4 and 5 were further prototyped and evaluated together with the tire of Example 2 above on the influence of the arrangement position of the widened portion 14 in the depth direction on the handling stability and the sustainability of the noise reduction effect. This will be explained below.

  In the tire of Example 4, the second groove is configured as shown in FIG. 6B, and the widened portion 14 is provided at a position of 2 mm to 4 mm from the tread ground surface (that is, the upper end of the widened portion 14). Is located 2 mm from the tread contact surface, and the lower end of the widened portion 14 is located 4 mm from the tread contact surface). Other configurations are the same as those of the tire of the second embodiment.

  In the tire of Example 5, the second groove is configured as shown in FIG. 6A, and the widened portion 14 is provided at a position of 0 mm to 2 mm from the tread ground surface (that is, the upper end of the widened portion 14). Open to the tread ground surface, and the lower end of the widened portion 14 is located 2 mm from the tread ground surface). Other configurations are the same as those of the tire of the second embodiment.

  Regarding steering stability, the tires of Examples 2, 4 and 5 were attached to the standard rim 6J × 15, mounted on the passenger car at an air pressure of 210 kPa (relative pressure), and the circuit course in a dry state was sported in various driving modes. Then, it was evaluated by the feeling of the test driver. The evaluation results are shown in Table 3. The evaluation in Table 3 indicates that the larger the numerical value, the better the steering stability.

  Further, regarding the sustainability of the noise reduction effect, the noise at the time of a new article, 40% wear, and 70% wear was measured by the above-described noise test, and evaluated based on Comparative Example 1 in which the widened portion 14 was not provided. . The evaluation results are shown in Table 3.

  As is clear from this result, it can be seen that by arranging the widened portion closer to the bottom of the second groove, the steering stability is excellent and the noise reduction effect is sustained.

  Thus, according to the present invention, the water removal effect and the scratching effect on the road surface can be improved, and the noise performance can be improved by increasing the apparent volume of the recess.

DESCRIPTION OF SYMBOLS 1 Tread part 3, 4, 5 Rib-like land part 7, 8 Circumferential groove | channel 10 Recessed part 11 Block 12 1st groove | channel 13 2nd groove | channel 14 Wide part 15 Wide part

Claims (5)

A plurality of recesses disposed in a distributed manner in a rib-like land extending along the tire circumferential direction, and opening in the tread ground surface;
A first groove and a second groove for connecting the recesses to each other and defining a plurality of independent blocks in the rib-like land portion,
The groove widths of the first groove and the second groove are at least partially in contact with each other when the blocks separated via the first groove and the second groove are in contact with the tire. Set to distance,
The second groove has a widened portion whose width locally expands in the depth direction of the second groove,
The pneumatic tire according to claim 1, wherein at least one second groove is connected to the recess.   2. The pneumatic tire according to claim 1, wherein the widened portion is disposed closer to a groove bottom in a depth direction of the second groove.   The pneumatic according to claim 1 or 2, wherein at least one of the second grooves extending across the tread ground contact edge in the tire width direction is connected to a recess located on the outermost side in the tire width direction among the recesses. tire.   A tire circumferential direction linear distance in a range in which the recesses and the second grooves are alternately and continuously connected, and the recesses and the second grooves are alternately and continuously connected is greater than a contact length. The pneumatic tire according to any one of claims 1 to 3. The rib-shaped land portion has a width W (mm), a reference pitch length of a block in the rib-shaped land portion is PL (mm), and the rib-shaped land portion width W and the reference pitch length PL are partitioned. S = 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 S (units / mm ² ) per unit actual ground contact area of the rib-like land portion to be given is within a range of 0.003 to 0.04. The described pneumatic tire.

Images