JP2008044441A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance driving stability performance by enhancing handling performance and traveling performance on respective road surfaces while ensuring the sufficient noise performance and drainage performance of a pneumatic tire. <P>SOLUTION: A pair of main grooves 11 arranged so as to clamp a tire equator surface CL and extending in a tire circumferential direction are formed on a tread 2 to form a central land row 31 on an tire equator surface CL. First to fourth lug grooves 21-24 inclined and extending from one end communicating with one main groove 11 in a tire width direction are successively repeatedly arranged on the central land row 31 in the tire circumferential direction to be divided into a plurality of blocks 31B. The first lug groove 21 and the second lug groove 22 are inclined from each one end in the same direction relative to the tire width direction and merged at a terminal end at the tire equator surface CL side. The third lug groove 23 and the fourth lug groove 24 are inclined from each one end in an opposite direction relative to the tire width direction and merged at the terminal end at the tire equator surface CL side. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic tire in which a tread pattern composed of a plurality of blocks is formed in a tread portion, and more particularly, a pneumatic tire such as a tire for a passenger car or a four-wheel drive vehicle that improves a plurality of tire performances in a well-balanced manner. About.

  Pneumatic tires generally have a tread that increases the coefficient of friction between the tire and the road surface to ensure effective driving / braking performance and steering stability performance, or improve drainage performance to improve wet performance, etc. Therefore, a tread pattern composed of various grooves, sipes and the like is formed. As a typical example of this tread pattern, conventionally, a block pattern in which a plurality of blocks are formed by dividing a plurality of main grooves extending in the tire circumferential direction and a plurality of lug grooves extending in a direction intersecting the main grooves is widely used. It is known (see Patent Document 1).

FIG. 3 is a plan view showing an example of a tread pattern of such a conventional pneumatic tire, which is not described in the patent literature.
This pneumatic tire 100 has a tread pattern 110 that is point-symmetric with respect to a point on the tire equatorial plane CL, and as shown in the drawing, a tire circumferential direction that is disposed on the tread portion 101 with the tire equatorial plane CL interposed therebetween. In the tire circumferential direction by two main grooves 111 extending substantially linearly and two main grooves 112 extending zigzag in the tire circumferential direction disposed between the main grooves 111 and the tread ends TE. A plurality (5 in the figure) of land portion rows 113 extending in the direction are formed.

  The pneumatic tire 100 has a plurality of lug grooves 114 that intersect with the main grooves 111 and 112 and extend substantially in the tire width direction, and have the same inclination angle, direction, shape, and the like. Each lug groove 114 is arranged at a predetermined interval in the tire circumferential direction, and each land portion row 113 is partitioned into a plurality of blocks 115. Further, a plurality of sipes 116 are formed in each block 115, and one or two notches 117 are respectively formed on the edges facing the main grooves 111, 112 or lug grooves 114 of each block 115. It is cut out in a predetermined shape to the vicinity of the groove bottom inward.

  In this conventional pneumatic tire 100, a plurality of blocks 115 are formed by a pair of main grooves 111 extending linearly and lug grooves 114 arranged in the tire circumferential direction, and are arranged on both outer sides in the tire width direction. The main groove 112 is formed in a zigzag shape, and the edge component of the block 115 that exhibits the edge effect is increased. As a result, traction performance, braking performance, etc., which greatly affect traveling on off-roads and on snow, etc., are enhanced, and traveling performance on each road surface is improved. In the pneumatic tire 100, the ratio of the groove area to the apparent total ground contact area of the tread portion 101 (negative rate) is set to 45% or less to secure the actual ground contact area, and each block 115 is made relatively large. The block rigidity is increased to ensure on-road driving performance.

  However, in this conventional pneumatic tire 100, as each block 115 is formed to be relatively large, the hitting sound (so-called pattern noise) generated when each block 115 contacts the ground when the vehicle travels increases, and the noise performance. Tend to be low. The pneumatic tire 100 exhibits relatively high braking performance, traction performance, and the like when traveling on off-road or on snow, but other tire performance is achieved by the lug grooves 114 arranged in the tread portion 101. May be relatively affected.

  That is, in this pneumatic tire 100, the inclination direction of each lug groove 114 with respect to the tire width direction is formed in substantially the same direction as the entire tread portion 101, and therefore the force in the same direction acts during tire rolling. Thus, there may be a so-called single flow of the vehicle in which the vehicle in a straight traveling state gradually shifts to one side in the traveling direction and flows laterally. In addition, the force also acts on the steering wheel, which easily affects the steering operation, and there is a risk that the handling performance on off-road or on snow may deteriorate. At the same time, since each lug groove 114 is formed at a relatively small angle with respect to the tire width direction, it is also disadvantageous for drainage performance on the wet road surface, for example, for improvement in hydroplaning performance, There is also a problem that the lug groove 114 cannot sufficiently contribute.

  As described above, this conventional pneumatic tire 100 is sufficiently effective in improving the steering stability performance on each road surface by ensuring the running performance, handling performance, drainage performance, etc. on off road, on snow or on road. In addition, it is difficult to achieve a balance between these tire performances including the noise performance described above.

JP 2002-29224 A

  The present invention has been made in view of the above-described conventional problems, and its purpose is to improve handling performance and running performance on each road surface while ensuring sufficient noise performance and drainage performance of a pneumatic tire, thereby stabilizing the operation. It is to improve the performance and to improve the balance between these tire performances.

The invention of claim 1 is provided with a pair of main grooves extending in the tire circumferential direction disposed at least on the tire equatorial plane in the tread portion, and a central land portion row partitioned by the pair of main grooves, A pneumatic tire partitioned into a plurality of blocks by a plurality of lug grooves extending in a direction in which the central land portion row intersects with the main groove, and one end communicating with one of the main grooves in the plurality of lug grooves Including first to fourth lug grooves that are inclined and extended in the tire width direction from the portion, and are repeatedly arranged in the tire circumferential direction. The first lug groove and the second lug groove are tires from the respective one end portions. Inclined in the same direction with respect to the width direction and merged at the other end side of the other main groove side, the third lug groove and the fourth lug groove extend in the tire width direction from the respective one end portions. In contrast, they incline in opposite directions and merge at the other end of the other main groove. And wherein the door.
According to a second aspect of the present invention, in the pneumatic tire according to the first aspect, the first lug groove and the second lug groove, and the third lug groove and the fourth lug groove are respectively the other The end portions terminate in the central land portion row and merge with each other at the end portions.
According to a third aspect of the present invention, in the pneumatic tire according to the first or second aspect, the block defined by the first lug groove and the second lug groove, the third lug groove, and the fourth lug groove. The blocks defined by the lug grooves have overlapping portions.
According to a fourth aspect of the present invention, in the pneumatic tire according to any one of the first to third aspects, the first lug groove has a larger inclination angle with respect to a tire width direction than the second lug groove, and The third lug groove has a larger inclination angle with respect to the tire width direction than the fourth lug groove.
According to a fifth aspect of the present invention, in the pneumatic tire according to the fourth aspect, the third lug groove is in the same direction as the first lug groove and the second lug groove with respect to the tire width direction. It is characterized by being inclined.
A sixth aspect of the present invention is the pneumatic tire according to any one of the first to fifth aspects, wherein the central land portion row is formed point-symmetrically with respect to a point on the tire equatorial plane. The first to fourth lug grooves are provided on both sides sandwiched.

  According to the present invention, while ensuring sufficient noise performance and drainage performance of a pneumatic tire, it is possible to improve handling stability and driving performance on each road surface and improve steering stability performance. Can be improved in a balanced manner.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
The pneumatic tire according to the present embodiment is a pneumatic tire used for, for example, a passenger car, a four-wheel drive vehicle, and the like, and includes at least one pair of bead cores disposed in a tire bead portion and a toroidal shape extending therebetween. It has a known pneumatic tire structure, including a carcass layer made of a carcass ply and a belt layer and a tread disposed on the outer peripheral side of the carcass layer of the tread portion.

FIG. 1 is a plan view showing a developed tread pattern 10 formed on the tread portion 2 of the pneumatic tire 1 of the present embodiment.
The pneumatic tire 1 has a tread pattern 10 that is point-symmetric with respect to a point on the tire equatorial plane CL, and as shown in the drawing, a plurality (here, two) main grooves 11 extending in the tire circumferential direction, And a plurality of lug grooves 20 to 25 extending in a direction intersecting with the main groove 11. In the pneumatic tire 1, the tread portion 2 has a plurality (three in this case) of land portion rows 30 and 31 extending in the tire circumferential direction and defined by the main grooves 11 and the tread ends TE. Moreover, each land part row | line | column 30,31 is divided | segmented by several lug grooves 20-25, and is divided into several block 30B, 31B.

  In the present embodiment, the two main grooves 11 are formed to have two groove widths of a narrow width portion and a wide width portion by changing the groove wall position on the inner side in the tire width direction, and sandwiching the tire equatorial plane CL. It arrange | positions between both tread ends TE. As a result, the shoulder land portion row 30 positioned on both outermost sides (shoulder side) in the tire width direction between the main groove 11 and the tread end TE, and the tire equatorial plane CL divided into both the main grooves 11 A wide central land row 31 located above is formed. Further, the lug grooves 20 to 25 are constituted by a shoulder lug groove 20 formed in the shoulder land portion row 30 and first to fifth lug grooves 21 to 25 formed in the central land portion row 31. They are arranged at predetermined intervals in the tire circumferential direction.

  Each shoulder lug groove 20 of the shoulder land portion row 30 extends substantially in the tire width direction from the tread end TE toward the main groove 11 on the inner side in the tire width direction, and opens to the main groove 11 across the shoulder land portion row 30. is doing. Both shoulder land portion rows 30 on the outer side in the tire width direction have a plurality of the one type of shoulder lug grooves 20 at regular intervals in the tire circumferential direction, and are formed point-symmetrically with respect to points on the tire equatorial plane CL. Yes. Hereinafter, the shoulder land portion row 30 and the shoulder lug groove 20 will be specifically described by taking one side (left side in FIG. 1) sandwiching the tire equatorial plane CL as an example.

FIG. 2 is an enlarged plan view of a region indicated by X in FIG.
As shown in the figure, the width of each shoulder lug groove 20 is widest on the tread end TE side, gradually narrowing from there toward the main groove 11 on the inner side in the tire width direction, and slightly at the opening end to the main groove 11. It is formed to spread. As a result, the shoulder land portion row 30 is divided by the shoulder lug grooves 20 and partitioned into a plurality of blocks 30B, and the schematic shape of each block 30B gradually increases in width from the main groove 11 side toward the tread end TE side. Is formed in a trapezoidal shape in plan view. In other words, the block 30B has both edge portions so that the distance in the tire circumferential direction between both edge portions facing the shoulder lug groove 20 side gradually decreases as viewed from the tire radial direction outside. Are formed in a substantially trapezoidal shape (tread surface shape) inclined in opposite directions and at the same angle with respect to the tire width direction, with one of the substantially parallel long sides on the main groove 11 side and the other short side on the tread end. It is arranged at a predetermined interval in the tire circumferential direction toward the TE side.

  Further, in this pneumatic tire 1, in each block 30B of the shoulder land portion row 30, a narrow groove 27 extending in a substantially V shape from the inside of the block 30B toward the outside of the tread end TE and a main groove 11 of the block 30B. A notch 40 is provided by cutting in a predetermined shape from the facing edge into the block 30B. The notch 40 is a recess locally formed at the edge of the block 30B, one end opening in the main groove 11 and the other end ending inside the block 30B. Here, both shoulder land rows A notch 40 is formed at one location of each of the 30 blocks 30B.

  The notch 40 has a trapezoidal shape in a plan view in which the width gradually decreases from the edge of the block 30B toward the inside of the block 30B on the edge (long side) of the trapezoidal block 30B on the main groove 11 side. Is formed. That is, the notch 40 has a cut end (short side) in the block 30B and an open end (long side) in the main groove 11 as seen from the outer side in the tire radial direction, like the block 30B. Are formed in a substantially trapezoidal shape (tread notch shape) in which the notch width in the tire circumferential direction gradually increases from the inside of the block 30B toward the main groove 11, and the main groove of the block 30B is formed. It is arrange | positioned in the approximate center of 11 side edge parts. Here, the notch 40 and the block 30B are substantially similar to each other, and are substantially line symmetrical with respect to the center line S in the substantially tire width direction.

  Further, in order to ensure the rigidity of the block 30B, the notch 40 extends from the surface in the block 30B toward the groove bottom on the edge side of the block 30B (the groove bottom of the main groove 11), and is predetermined. An inclined surface (hereinafter referred to as an inclined stepped portion) 41 having a stepped portion having a cross-sectional shape is integrally provided with the block 30B. The inclined step portion 41 is provided over the entire cutout portion 40, and from the surface of the cut end portion (short side portion) block 30 </ b> B located in the block 30 </ b> B of the cutout portion 40 on the main groove 11 side. It is formed so as to be gradually inclined to the vicinity of the groove bottom of the opening end (long side). In addition, the inclined step portion 41 is formed in a step shape from the surface of the block 30B toward the groove bottom, and has a plurality of concave curved surfaces and at least two tip portions provided between them (here, 3). ).

  In contrast to the shoulder land portion row 30 in which one kind of lug groove 20 is formed, in the central land portion row 31, a plurality of types of lug grooves 21 to 25 are repeatedly arranged at predetermined intervals in the tire circumferential direction. ing.

  The first to fifth lug grooves 21 to 25 (see FIG. 1) of the central land portion row 31 extend from the one end communicating with the one main groove 11 in an inclined manner in the tire width direction. The lug grooves 21 to 24 and the fifth lug groove 25 disposed on the tire equatorial plane CL in the central land portion row 31 are formed symmetrically with respect to a point on the tire equatorial plane CL. . The first to fourth lug grooves 21 to 24 are provided on both sides of the tire equatorial plane CL, and are inclined at a predetermined angle in the opposite direction to the tire width direction with the tire equatorial plane CL interposed therebetween. ing. Further, on the left and right sides of the central land portion row 31 across the tire equatorial plane CL, the first to third lug grooves 21 to 23 are inclined in the same direction with respect to the tire width direction, and the fourth lug groove The 24 and fifth lug grooves 25 are formed to be inclined in the opposite direction to the first to third lug grooves 21 to 23 and the tire width direction.

  Among these lug grooves 21 to 25, the first lug groove 21 and the second lug groove 22, and the third lug groove 23 and the fourth lug groove 24 are in pairs, respectively. The lug groove 21 and the second lug groove 22 are inclined in the same direction with respect to the tire width direction from the respective one end portions communicating with the one main groove 11, and the other main groove 11 side (here, the vicinity of the equator plane CL) ) At the other end side. On the other hand, the third lug groove 23 and the fourth lug groove 24 incline in opposite directions with respect to the tire width direction from the respective one end portions communicating with the one main groove 11, and the other main groove 11 side (here Then, it is formed so as to merge at the other end side of the equatorial plane CL).

  In addition, the angle of inclination with respect to the tire width direction is different between each pair of lug grooves, and the angle of inclination with respect to the tire width direction of one (here, the first lug groove 21 and the third lug groove 23) is the other (here). Then, it is larger than that of the second lug groove 22 and the fourth lug groove 24). Hereinafter, the lug grooves 21 to 25 will be described more specifically by taking one side (left side in FIG. 1) of the central land portion row 31 across the tire equatorial plane CL as an example.

  The first lug groove 21 (see FIG. 2) is inclined at a steep angle with a relatively small angle with respect to the tire circumferential direction from one end portion (outer portion in the tire width direction) opening in the main groove 11 toward the tire equatorial plane CL. The other end portion (the tire center side portion) terminates in the vicinity of the tire equatorial plane CL in the central land portion row 31. The second lug groove 22 has one end opened to the main groove 11 arranged at a predetermined distance from the one end of the first lug groove 21 in the tire circumferential direction, from which the first lug It is formed to be inclined at a gentle angle closer to the tire width direction than the groove 21 and terminates at the same position as the other end of the first lug groove 21. Accordingly, the lug grooves 21 and 22 join (connect) to each other at the end portions near the tire equatorial plane CL, and as a whole, the block 31B (1) having a substantially triangular shape in plan view in which one side is arranged on the main groove 11 side. ).

  The third lug groove 23 is formed so as to be inclined from a substantially intermediate position in the tire width direction of the second lug groove 22 toward the tire equatorial plane CL at a steep angle substantially equal to that of the first lug groove 21. ing. The fourth lug groove 24 is provided at one end opened to the main groove 11 between the first lug groove 21 and the second lug groove 22 (here, the second lug groove 22 side). From there, the second lug groove 22 and the tire width direction are inclined in the opposite direction and at the same angle, intersecting with the first lug groove 21 and formed toward the tire equatorial plane CL. In the third lug groove 23 and the fourth lug groove 24, the other end portion on the tire equatorial plane CL side terminates in the central land portion row 31 and curves in the vicinity of the end portion to join (connect) to each other. As a whole, a block 31B (2) having a substantially triangular shape in plan view in which one side is arranged on the main groove 11 side is defined.

  Here, the first lug groove 21, the second lug groove 22, and the fourth lug groove 24 open to the main groove 11 and communicate directly with the main groove 11, whereas the third lug The groove 23 is formed so as to branch from the middle of the second lug groove 22, and one end portion on the main groove 11 side communicates with the main groove 11 via the second lug groove 22. Thus, in the present invention, when one end portion of the lug groove communicating with the main groove 11 is referred to, one end portion of the lug groove opens to the main groove 11 and directly communicates with the other lug groove. In other words, for example, when the lug groove is branched into a plurality of parts in the middle, one end portion on the main groove 11 side opens to the other lug groove and indirectly communicates with the main groove 11. Including cases.

  In each of the lug grooves 21 to 24 described above, the groove wall of one of the third lug grooves 23 (left side in the drawing) is formed in a zigzag shape, and the groove width of the second lug groove 22 is the third lug groove 23. The third lug groove 23 as a whole has the largest groove width, the fourth lug groove 24 has the smallest groove width, and the first lug groove 21 and the second lug groove 21 The lug groove 22 is formed to have an intermediate groove width. In addition, the first lug grooves 21 and the third lug grooves 23 on both sides (see FIG. 1) sandwiching the tire equatorial plane CL are bent and extend near the ends on the tire equatorial plane CL side. The five lug grooves 25 are connected to each other.

  These lug grooves 21 to 25 communicate with each other through the junctions and intersections, cross the central land portion row 31 as a whole, and divide the central land portion row 31 to form a substantially triangular shape or rectangular shape in plan view. It is partitioned into a plurality of blocks 31B such as a shape. Here, since the first lug groove 21 and the fourth lug groove 24 intersect each other, the block 31B defined by the first lug groove 21 and the second lug groove 22 ( 1) and a block 31B (2) defined by the third lug groove 23 and the fourth lug groove 24 have a portion that overlaps and overlaps with each other, and is a small block 31B having a substantially triangular shape in plan view ( 3) is shared.

  In the pneumatic tire 1 of the present embodiment, a plurality of sipes 29 (see FIG. 1) are traversed in these blocks 30B and 31B, or one end is terminated in the blocks 30B and 31B. Forming. In addition, predetermined portions (respective portions indicated by grid-like hatching in the figure) facing the main grooves 11 and the lug grooves 20 to 25 such as corners of the blocks 30B and 31B are inclined from the block surface toward the groove bottom direction. Chamfered chamfered portions 50 are provided at a plurality of locations in each land portion row 30, 31.

  In the pneumatic tire 1 of the present embodiment described above, the pair of main grooves 11 sandwiching the tire equatorial plane CL causes the tire tread surface to be positioned on the shoulder width portion outer row 30 on the outer side in the tire width direction and the center on the tire equatorial plane CL. Since it is divided into the land portion row 31 and divided, different patterns can be formed in each portion of the tire tread surface to have different functions required for each, and the tire performance can be effectively improved. That is, since the shoulder land portion row 30 is a portion having a great influence on the braking performance on snow or the like, in the pneumatic tire 1, the lug groove 20 in the substantially tire width direction is formed in the shoulder land portion row 30. is doing. As a result, the edge component in the front-rear direction (tire circumferential direction) of the block 30B is increased, so that the braking performance on snow and the like can be improved, and the uneven wear resistance of the shoulder land portion row 30 where uneven wear is likely to occur. It can also be improved.

  On the other hand, the central land portion row 31 is less likely to cause uneven wear or the like than the shoulder land portion row 30, and thus can share functions different from the shoulder land portion row 30, and here, in the tire width direction, Each lug groove 21-24 which inclines with respect to a comparatively big angle is formed. The lug grooves 21 to 24 that incline toward the tire circumferential direction can increase the amount of water discharged in the tire circumferential direction when traveling on a wet road surface, and are different in the same direction with respect to the tire width direction. The first lug groove 21 and the second lug groove 22 that are inclined at an angle enable effective drainage of water in each direction even on a deep road surface, thereby improving the drainage performance of the pneumatic tire 1. be able to. In addition, in this pneumatic tire 1, since the third lug groove 23 and the fourth lug groove 24 that are inclined in different directions with respect to the tire width direction are formed in the central land portion row 31, water has multiple directions. The drainage efficiency of the central land portion row 31 can be further increased.

  In addition, since the first lug groove 21 and the second lug groove 22 that are inclined at different angles are merged, a substantially triangular block 31B (1) (see FIG. 2) is formed between the main groove 11 and the first lug groove 21. In addition, block edges that have a large influence on handling performance during off-road driving or on snow can be secured in multiple directions. Thereby, block 31B (1) exhibits an edge effect with respect to each direction, and can improve handling performance at the time of off-road or running on snow.

  In addition, in the pneumatic tire 1, the third lug groove 23 and the fourth lug groove 24 that are inclined in different directions are merged, and the block 31 </ b> B (1) is between the main groove 11. Block 31B (2) having block edges in different directions is formed. As a result, the block edges of these blocks 31B (1) and 31B (2) act in various directions during handling on off-road or on snow, etc., and the edge effect is exhibited in more directions. Handling performance can be improved effectively. In addition, the block edges in various directions can disperse noise generated during tire rolling, and the noise performance of the pneumatic tire 1 can be improved. At the same time, the brake traction on the snow or the like described above is caused by forming the inclination direction of the fourth lug groove 24 in a direction different from the inclination direction of the other lug grooves 21, 22, and 23 and the tire width direction. One-time flow of the vehicle at the time can also be suppressed, and stable handling and running performance can be ensured.

  Furthermore, since one end part of each lug groove 21-24 was connected to the main groove 11, the water, snow, earth, etc. which entered into the lug grooves 21-24 can be smoothly discharged to the main groove 11, and sufficient Drainage, snow removal, and soil removal performance can be ensured. Along with this, it is possible to suppress clogging of the lug grooves 21 to 24 due to snow, soil, or the like, and thus it is possible to suppress the above-described performance from being deteriorated during traveling. On the other hand, the other end portions of the lug grooves 21 to 24 extending toward the tire equatorial plane CL are not communicated with the other main groove 11 but in the central land portion row 31 (here, near the tire equatorial plane CL). Since they are terminated and merged, the block rigidity in the vicinity of the tire equatorial plane CL can be secured. As a result, the overall ability of the tire center in all road surfaces such as on-road (dry road surface, wet road surface, etc.), off-road, and snow can be enhanced, and handling performance and running performance on each road surface can be improved. Each performance can be improved.

  Therefore, according to this embodiment, while ensuring sufficient noise performance and drainage performance of the pneumatic tire 1, it is possible to improve handling stability and driving performance on each road surface and improve steering stability performance. It is possible to improve the performance in a well-balanced manner. Moreover, in this pneumatic tire 1, while forming the several land part row | line | columns 30 and 31 in the tread part 2 with the some main groove 11 extended in a tire circumferential direction, each land part row | line | columns 30 and 31 are made into lug grooves 20-25. Therefore, it is possible to ensure basic performance including the drainage performance required for a comfort-oriented pneumatic tire. Furthermore, in this pneumatic tire 1, the central land portion row 31 is formed point-symmetrically with respect to the tire equator plane CL, and the lug grooves 21 to 24 are arranged on both sides of the tire equator plane CL. Regardless of the rotation direction of 1 or the mounting direction to the vehicle, the tire performances described above can be stably exhibited.

  Here, the inclination angle of the third lug groove 23 and the fourth lug groove 24 that form a pair with respect to the tire width direction is different from the present embodiment, and is formed at the same angle as each other, or the fourth lug The groove 24 may be formed at a larger angle. However, as in this embodiment, the third lug groove 23 is inclined at a steep angle relatively close to the tire circumferential direction, and the first lug groove 21 and the second lug groove 22 and the tire width direction. It is desirable to incline in the same direction. By doing so, water discharge becomes smoother and high drainage performance can be ensured. However, the inclination angle of the third lug groove 23 is the same as that of the first lug groove 21 inclined at a steep angle similar to the tire circumferential direction. It is more desirable to form the same angle as the inclination angle and arrange them substantially in parallel, since more effective drainage becomes possible.

  Further, by changing the groove width (thickness) and length of the first lug groove 21 and the third lug groove 23, the tire performance can be adjusted according to the purpose. For example, when each groove width is narrow, the drainage performance is slightly reduced, but the lug groove is closed when the tire rolls (at the time of ground contact) and the groove walls of the block 31B sandwiching the lug groove come into contact with each other. The blocks 31B support each other and deformation is suppressed. Thereby, the block rigidity of the center land part row | line | column 31 can be improved, and the running performance and handling performance on a dry or wet road surface can be improved. Also, the block rigidity can be increased by adjusting the length of the lug groove to make the shape of the block 31B larger or appropriate, and the same effect as described above can be obtained. In addition, by narrowing only one groove width and widening the other groove width, it is possible to impose block rigidity in the narrow lug groove part, drainage performance in the wide lug groove part, etc. Pattern design according to the purpose is possible.

  Furthermore, the first or second lug groove 21, 22 and the third or fourth lug groove 23, 24 intersect at least at one place and are partitioned by the lug grooves 21 to 24 ( It is desirable to form overlapping portions (small blocks 31B (3)) in 1) and 31B (2). As a result, a plurality (three in this case) of blocks 31B having different shapes are formed, and the central land portion row 31 has block edges in various directions and block rigidity suitable for off-road and snow travel. And the handling performance on each road surface can be effectively improved. At this time, the groove widths of the lug grooves intersecting with each other may be changed in the same manner as described above. For example, when formed so as to close at the time of ground contact, the supporting effect of the block 31B is the effect of the blocks 31B (1), 31B ( 2) It can be demonstrated within and can improve running performance and handling performance on dry or wet road surfaces.

  In the present embodiment, the fourth lug groove 24 inclined in the opposite direction intersects the first lug groove 21. For example, the fourth lug groove 24 is replaced with the first lug groove 21 and the second lug. Each of the lug grooves 21 to 24 intersects with both grooves of the groove 22 and each of the lug grooves 21 to 24 forms four blocks 31B including an overlapping portion. Aspect) may be formed. Moreover, in this pneumatic tire 1, although each lug groove 21-24 was mutually joined by the terminal part, each lug groove 21-24 is formed so that it may extend in the tire equatorial plane CL direction beyond a joining part. That is, you may form so that it may mutually cross | intersect in the terminal part side in the central land part row | line 31. FIG.

  Furthermore, in the pneumatic tire 1 of the present embodiment, the tread portion 2 has at least a pair of main grooves 11 extending in the tire circumferential direction, with the tire equatorial plane CL interposed therebetween, and a central land portion row 31 partitioned by the tire groove. In addition, for example, a main groove extending in the tire circumferential direction is formed between the main grooves 11 and the tread end TE, and each shoulder land portion row 30 is divided into two or more, etc. Three or more main grooves may be formed. The shape of each main groove may be formed in other shapes extending in the tire circumferential direction, such as a zigzag shape, in addition to the linear shape. In the pneumatic tire 1, the tread pattern 10 that is point-symmetric with respect to a point on the tire equatorial plane CL is formed. For example, the tread pattern 10 that is line-symmetric with respect to the tire equatorial plane CL or the asymmetric tread pattern 10. Etc. may be formed in the tread portion 2, and the first to fourth lug grooves 21 to 24 of the present embodiment may be formed in the central land portion row 31 thereof.

(Tire test)
In order to confirm the effect of the present invention, the tire 1 (hereinafter referred to as an implementation product) of the example in which the tread pattern 10 (see FIG. 1) having the structure described above is formed, and the conventional tread pattern 110 (see FIG. 3) described above. ) And a tire 100 (hereinafter referred to as a comparative product) of a comparative example (conventional example) formed with the following test. Each of these tires is a pneumatic radial tire for a passenger car having a tire size of 265 / 70R17 defined by JATMA YEAR BOOK (2006, Japan Automobile Tire Association Standard), and the groove depth of each groove is 10.5 mm.

  As described above, the implemented product is a tread pattern 10 that is point-symmetric with respect to a point on the equator plane CL, and the width of the two main grooves 11 is 8 mm at the narrow portion and 11 mm at the wide portion. did. In addition, each lug groove of the central land portion row 31 of the implemented product has a first lug groove 21 having a groove width of 5 mm, an angle of 20 degrees with respect to the tire circumferential direction, a second lug groove 22 having a groove width of 4 to 8 mm, and a tire. The third lug groove 23 was formed at an angle of 65 degrees with respect to the circumferential direction and a groove width of 6 to 15 mm and an angle of 25 degrees with respect to the tire circumferential direction. On the other hand, the fourth lug groove 24 has a groove width of 3 mm and an angle with respect to the tire circumferential direction is formed at 60 degrees opposite to the lug grooves 21, 22, and 23. The central land portion row 31 was divided by the lug grooves 21 to 24 and partitioned into blocks 31B having a width of 17 to 40 mm, and a plurality of sipes 29 having a width of 0.7 mm were formed in the blocks 31B. On the other hand, in the comparative product, each lug groove 114 arranged at a predetermined interval in the tire circumferential direction is formed in a single shape.

In the tire test, each of the tires described above was mounted on an actual vehicle at an internal pressure of 230 kPa, and each performance was evaluated by applying a load equivalent to that two people got on.
Table 1 shows the test results of the implemented product and the comparative product as indices with the result of the comparative product as 100. For each index in the table, the larger the value, the better the result.

  In Table 1, the hydroplaning performance index is a performance when a wet road surface with a water depth of 5 mm is straightly driven at a normal hydroplaning generation limit speed, and was evaluated based on the feeling of a test driver. As a result, it was found that the actual product was 110 higher than the comparative product 100, and the drainage performance was improved and the hydroplaning performance was improved.

  The dry maneuvering stability index is an evaluation of maneuvering stability on dry roads, and was evaluated based on the feeling of test drivers when driving on dry circuit courses in various driving modes. As a result, it was found that the actual product was 113 higher than the comparative product 100, and the steering stability performance on the dry road surface was improved.

  The wet maneuverability stability index is an evaluation of maneuverability stability on a wet road surface, and was evaluated based on the feeling of a test driver when driving on a wet circuit course in various driving modes. As a result, it was found that the actual product was 111 higher than the comparative product 100, and the steering stability performance on the wet road surface was improved.

  The tire noise performance index is an evaluation of noise (pattern noise) generated during rolling of the tire, and was evaluated based on the feeling of a test driver when driving on a general road in a dry state in various driving modes. As a result, it was found that the actual product was higher than 112 for the comparative product, and the noise performance was improved.

  The feeling feeling on snow is a comprehensive evaluation of braking performance, starting performance, straight running performance, and cornering performance on a test course of a snowy road surface, and was evaluated based on the feeling of a test driver. As a result, it was found that the value of the comparison product was as high as 110 with respect to the comparison product of 100, and the overall evaluation on snow was improved.

  The off-road feeling index is a comprehensive evaluation of braking performance, starting performance, straight running performance, and cornering performance on a test track on an unpaved road, and was evaluated based on the feeling of a test driver. As a result, it was found that the value of the comparative product was higher than that of the comparative product, which was 108, and the overall evaluation in off-road was improved.

  From the above results, according to the present invention, while ensuring sufficient noise performance and drainage performance of the pneumatic tire 1, it is possible to improve handling performance and driving performance on each road surface and improve steering stability performance. It has been proved that the performance can be balanced and improved in a balanced manner.

It is a top view which expands and shows a tread pattern formed in a tread part of a pneumatic tire of this embodiment. It is the top view to which the area | region shown by X of FIG. 1 was expanded. It is a top view which expands and shows an example of the tread pattern of the conventional pneumatic tire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Pneumatic tire, 2 ... Tread part, 10 ... Tread pattern, 11 ... Main groove, 20-25 ... Lug groove, 27 ... Fine groove, 29 ... Sipe 30 ... Shoulder land row, 30B ... Block, 31 ... Central land row, 31B ... Block, 40 ... Notch, 41 ... Inclined surface, 50 ... Chamfered portion, CL: tire equator surface, TE: tread edge.

Claims (6)

The tread portion includes a pair of main grooves extending in the tire circumferential direction disposed at least across the tire equatorial plane, and a central land portion row defined by the pair of main grooves, the central land portion row being the main land row. A pneumatic tire partitioned into a plurality of blocks by a plurality of lug grooves extending in a direction intersecting the groove,
In the plurality of lug grooves, including first to fourth lug grooves that are inclined and extended in the tire width direction from one end communicating with one of the main grooves, and are repeatedly arranged in the tire circumferential direction,
The first lug groove and the second lug groove are inclined in the same direction with respect to the tire width direction from the respective one end portions, and merge at the other end portion side on the other main groove side,
The third lug groove and the fourth lug groove are inclined in opposite directions to the tire width direction from the respective one end portions and merge at the other end portion side on the other main groove side. Pneumatic tires. In the pneumatic tire according to claim 1,
The first lug groove and the second lug groove, and the third lug groove and the fourth lug groove respectively end at the other end portion in the central land portion row, and merge at the end portions. A pneumatic tire characterized by that. In the pneumatic tire according to claim 1 or 2,
The block defined by the first lug groove and the second lug groove and the block defined by the third lug groove and the fourth lug groove have overlapping portions. And pneumatic tires. In the pneumatic tire according to any one of claims 1 to 3,
The first lug groove has a larger inclination angle with respect to the tire width direction than the second lug groove, and the third lug groove has a larger inclination angle with respect to the tire width direction than the fourth lug groove. And pneumatic tires. In the pneumatic tire according to claim 4,
The pneumatic tire is characterized in that the third lug groove is inclined in the same direction with respect to the tire width direction as the first lug groove and the second lug groove. In the pneumatic tire according to any one of claims 1 to 5,
The central land portion row is formed point-symmetrically with respect to a point on the tire equator plane, and has the first to fourth lug grooves on both sides of the tire equator plane.

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