JP2016022807A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire that can secure sufficiently dry performance and enhance on-snow performance.SOLUTION: In a pneumatic tire, in which at least five rows of land parts are partitioned by four main grooves that are provided at a tread part 1 and extended in a tire circumferential direction, the main grooves include a pair of first main grooves 11A closest to a tire equator CL and a pair of second main grooves 11B provided outermost in a tire width direction. On a center land part 20, a pair of intermediate land parts 30 and a pair of shoulder land parts 40 partitioned at the tread part are respectively provided a plurality of lateral grooves extending in a tire width direction and a plurality of sipes, which extend in a tire width direction. Sipes 23 and 43 provided on the center land part and the shoulder land parts comprise first wall-face structures whose wall faces are extended in a sipe depth direction while having amplitude in a sipe thickness direction. The sipes 33 of the intermediate land parts comprise second wall-face structures whose wall faces are extended linearly along a sipe depth direction, and sipe density of the intermediate land parts is larger than sipe density of the center land part and shoulder land parts.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a pneumatic tire in which a large number of sipes are provided in a tread portion, and more particularly to a pneumatic tire that can sufficiently ensure dry performance and enhance snow performance.

  In winter pneumatic tires typified by studless tires, a plurality of main grooves extending in the tire circumferential direction and a plurality of horizontal grooves extending in the tire width direction are formed in the tread portion. These blocks are partitioned, and a plurality of sipes extending in the tire width direction are formed in each block. Thus, by dividing a large number of blocks in the tread portion and providing sipes in each block, the performance on ice and the snow performance are improved, and good tire performance is exhibited as a winter tire.

  However, if the number of sipes is increased to increase the sipe density in order to further improve the performance on ice and snow, the block rigidity tends to decrease and the steering stability on the dry road surface tends to deteriorate. Therefore, it is very difficult to achieve both dry performance and snow performance in winter tires. In addition, it has been proposed that both the tire performances which are contradictory to each other by making the sipe structures different between the center region and the shoulder region of the tread portion (see, for example, Patent Documents 1 and 2). At present, the dry performance and the snow performance cannot be sufficiently improved only by changing the sipe structure between the center region and the shoulder region of the tread portion.

JP 2007-186053 A International Publication No. WO2006 / 022120

  An object of the present invention is to provide a pneumatic tire that can ensure sufficient dry performance and enhance snow performance.

In order to achieve the above object, a pneumatic tire according to the present invention includes a tread portion that extends in the tire circumferential direction to form an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and the sidewall portions. A pair of bead portions arranged on the inner side in the tire radial direction of the tire, and provided with at least four main grooves extending in the tire circumferential direction in the tread portion, and at least five rows of land portions defined by the main grooves. In the tire,
The main groove is a pair of first main grooves disposed at positions closest to the tire equator on both sides of the tire equator and a pair of second main grooves disposed on the outermost side in the tire width direction on both sides of the tire equator. A center land portion including a groove, wherein the land portion is positioned between the pair of first main grooves, a pair of intermediate land portions positioned between the first main groove and the second main groove, and each second A pair of shoulder land portions located outside the main groove, and a plurality of lateral grooves extending in the tire width direction and a plurality of sipes extending in the tire width direction in each of the center land portion, the intermediate land portion, and the shoulder land portion. The sipe disposed in the center land portion and the shoulder land portion is configured to have a first wall surface structure whose wall surface extends in the sipe depth direction while having an amplitude in the sipe thickness direction, and the intermediate The sipe placed on the land is its wall It is configured to have a second wall surface structure extending linearly along the sipe depth direction, and the sipe density of the intermediate land portion is made larger than the sipe density of the center land portion and the shoulder land portion. It is a feature.

  In the present invention, a sipe having a first wall surface structure is provided in a center land portion having a large influence on steering stability when traveling straight on a dry road surface and a shoulder land portion having a large influence on steering stability when turning on a dry road surface, By relatively increasing the rigidity of the center land portion and the shoulder land portion based on the first wall surface structure, it is possible to improve the driving stability at the time of straight traveling and turning on the dry road surface, and to improve the dry performance. . On the other hand, the intermediate land portion is provided with a sipe having a second wall surface structure, and the rigidity of the intermediate land portion is relatively lowered based on the second wall surface structure, thereby improving the followability to the snow surface. At the same time, since the sipe density of the intermediate land portion is relatively increased and the edge effect on the snow surface is increased, good snow performance can be ensured. As a result, it is possible to achieve both dry performance and snow performance at a higher level than before.

  The ratio of the sipe density of the intermediate land portion to the sipe density of the center land portion and the shoulder land portion is preferably 1.2 to 2.5. Thereby, dry performance and snow performance can be improved effectively.

  The distance between the center line of the first main groove and the tire equator is 5% to 10% of the tread contact width, and the distance between the center line of the second main groove and the tire equator is 25% to 35% of the tread contact width. It is preferable. Thereby, dry performance and snow performance can be improved effectively.

  It is preferable that the maximum width of the lateral groove disposed in the intermediate land portion is larger than the maximum width of the lateral groove disposed in the center land portion and the shoulder land portion, and the difference in the maximum width is 0.5 mm to 2.0 mm. . Thereby, dry performance and snow performance can be improved effectively.

  The maximum depth of the horizontal groove arranged in the middle land portion is made larger than the maximum depth of the horizontal groove arranged in the center land portion and the shoulder land portion, and the difference in the maximum depth is 0.5 mm to 3.0 mm. Is preferred. Thereby, dry performance and snow performance can be improved effectively.

  In the present invention, the sipe having the first wall surface structure needs to extend in the sipe depth direction while the wall surface has an amplitude in the sipe thickness direction, but the wall surface has an amplitude in the sipe thickness direction. However, it may be extended in the sipe length direction. On the other hand, the sipe having the second wall surface structure needs to extend linearly along the sipe depth direction, but the wall surface has a sipe thickness direction amplitude in the sipe length direction. It may be extended.

The sipe density of each land portion is the sipe density in the contact area of the tread portion, and the contact area (mm ² ) of each land portion divided by the groove is A1, and the tire circumferential direction of the sipe included in the land portion When the total length (mm) of projection lengths on A is A2, it is obtained by A2 / A1 (mm / mm ² ). A sipe is a narrow groove having a groove width of 1 mm or less, but a groove that divides each land portion is a groove having a groove width exceeding 1 mm.

  In the present invention, the contact area of the tread portion is the tread contact in the tire axial direction measured when the tire is assembled on the normal rim and the normal internal pressure is filled and the load is placed vertically on the plane and the normal load is applied. Identified based on width. The ground contact edge is the outermost position in the tire axial direction of the ground contact region. The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based, for example, a standard rim for JATMA, “Design Rim” for TRA, or ETRTO. Then, “Measuring Rim” is set. “Regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. The maximum air pressure is JATMA, and the table “TIRE ROAD LIMITS AT VARIOUS” is TRA. The maximum value described in “COLD INFRATION PRESURES”, “INFLATION PRESURE” for ETRTO, but 180 kPa when the tire is a passenger car. “Regular load” is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. The maximum load capacity is JATMA, and the table “TIRE ROAD LIMITS AT VARIOUS” The maximum value described in “COLD INFORATION PRESSURES” is “LOAD CAPACITY” if it is ETRTO, but if the tire is a passenger car, the load is equivalent to 88% of the load.

It is meridian sectional drawing which shows the pneumatic tire which consists of embodiment of this invention. FIG. 2 is a development view showing a tread pattern of the pneumatic tire of FIG. 1. It is a notch perspective view which shows the land part containing the sipe provided with the 1st wall surface structure. It is a notch perspective view which shows the land part containing the sipe provided with the 2nd wall surface structure.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. 1 to 4 show a pneumatic tire according to an embodiment of the present invention.

  As shown in FIG. 1, the pneumatic tire of the present embodiment includes a tread portion 1 that extends in the tire circumferential direction and has an annular shape, and a pair of sidewall portions 2, 2 disposed on both sides of the tread portion 1. And a pair of bead portions 3 and 3 disposed inside the sidewall portion 2 in the tire radial direction.

  A carcass layer 4 is mounted between the pair of bead portions 3 and 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded from the inside of the tire to the outside around the bead core 5 disposed in each bead portion 3. A bead filler 6 made of a rubber composition having a triangular cross-section is disposed on the outer periphery of the bead core 5.

  On the other hand, a plurality of belt layers 7 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 7 include a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and are arranged so that the reinforcing cords cross each other between the layers. In the belt layer 7, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set in a range of, for example, 10 ° to 40 °. A steel cord is preferably used as the reinforcing cord of the belt layer 7. For the purpose of improving high-speed durability, at least one belt cover layer 8 in which reinforcing cords are arranged at an angle of, for example, 5 ° or less with respect to the tire circumferential direction is disposed on the outer peripheral side of the belt layer 7. Yes. As the reinforcing cord of the belt cover layer 8, an organic fiber cord such as nylon or aramid is preferably used.

  In addition, although the tire internal structure mentioned above shows the typical example in a pneumatic tire, it is not limited to this.

  As shown in FIG. 2, at least four main grooves 11 extending in the tire circumferential direction are formed in the tread portion 1. These main grooves 11 are grooves having a groove width of 3 mm or more, more preferably 7 mm to 12 mm, and a groove depth of 6 mm or more, more preferably 7 mm to 9 mm. The main groove 11 is disposed at a position on the outermost side in the tire width direction on both sides of the tire equator CL, and a pair of first main grooves 11A disposed at positions closest to the tire equator CL on both sides of the tire equator CL. A pair of second main grooves 11B is included. Accordingly, the tread portion 1 includes a center land portion 20 positioned between the pair of first main grooves 11A and a pair of intermediate land portions positioned between the first main groove 11A and the second main groove 11B. 30 and a pair of shoulder land portions 40 located outside the second main grooves 11B.

  The center land portion 20 extends in the tire width direction and has one end communicating with the inner main groove 11A, while the other end is closed in the center land portion 20 and extends in the tire width direction. A plurality of lateral grooves 22 crossing the center land portion 20 are formed at intervals in the tire circumferential direction. These lateral grooves 21 and lateral grooves 22 are alternately arranged along the tire circumferential direction. In the center land portion 20, a plurality of sipes 23 extending in the tire width direction are formed at intervals in the tire circumferential direction.

  The intermediate land portion 30 is formed with a circumferential auxiliary groove 35 that extends in a zigzag shape along the tire circumferential direction and is narrower than the main groove 11. Further, the intermediate land portion 30 includes a plurality of lateral grooves 31 that extend in the tire width direction and cross the intermediate land portion 30, and a second main groove 11 </ b> B and a circumferential auxiliary groove 35 that extend in the tire width direction. The lateral grooves 32 that communicate with each other are formed at intervals in the tire circumferential direction. The lateral grooves 31 and the lateral grooves 32 are alternately arranged along the tire circumferential direction. Further, a plurality of sipes 33 extending in the tire width direction are formed in the intermediate land portion 30 at intervals in the tire circumferential direction.

  In the shoulder land portion 40, a plurality of lateral grooves 41 extending in the tire width direction so as to cross the ground contact edge E and communicating with the second main groove 11B are formed at intervals in the tire circumferential direction. The shoulder land portion 40 is formed with a plurality of sipes 43 extending in the tire width direction at intervals in the tire circumferential direction.

  In the pneumatic tire, the sipe 23, 43 disposed in the center land portion 20 and the shoulder land portion 40 has a first wall surface extending in the sipe depth direction while the wall surfaces 23A, 43A have amplitude in the sipe thickness direction. It has a structure. More specifically, as shown in FIG. 3, the sipe 23, 43 has a wall surface 23A, 43A having an amplitude W1 in the sipe thickness direction (tire circumferential direction Tc) and a sipe depth direction (tire radial direction Tr). ) Along the sipe length direction (tire width direction Tw) while the wall surfaces 23A and 43A have an amplitude W2 in the sipe thickness direction (tire circumferential direction Tc). doing. Thus, when the sipe 23 and 43 provided with the 1st wall surface structure where wall surface 23A, 43A has the amplitude of a sipe thickness direction and extends in a sipe depth direction is provided, the center land part 20 and the shoulder land part 40 are tires. It becomes difficult to produce a fall in the circumferential direction. Note that the sipes 23 and 43 arranged in the center land portion 20 and the shoulder land portion 40 do not necessarily have the first wall surface structure, and the sipes 23 in the center land portion 20 and the shoulder land portion 40 respectively. , 43 may be provided with at least 90% of the first wall surface structure.

  On the other hand, the sipe 33 disposed in the intermediate land portion 30 has a second wall surface structure in which the wall surface 33A extends linearly along the sipe depth direction. More specifically, as shown in FIG. 4, the sipe 33 has a wall surface 33A extending linearly along the sipe depth direction (tire radial direction Tr), while the wall surface 33A is sipe thickness direction. It extends in a zigzag shape along the sipe length direction (tire width direction Tw) while having an amplitude W3 in the (tire circumferential direction Tc). The sipe 33 disposed in the intermediate land portion 30 does not necessarily have the second wall surface structure, and at least 90% of the number of the sipe 33 disposed in the intermediate land portion 30 includes the second wall surface structure. It should be.

Further, in the pneumatic tire, the sipe density of the intermediate land portion 30 is set to be larger than the sipe density of the center land portion 20 and the sipe density of the shoulder land portion 40. Here, the sipe density of the center land portion 20, the intermediate land portion 30, and the shoulder land portion 40 is the sipe density (mm / mm) specified in the ground contact area defined between the pair of ground contact ends E of the tread portion 1. ² ).

  In the pneumatic tire described above, sipes 23 and 43 having a first wall surface structure are provided in the center land portion 20 and the shoulder land portion 40, respectively, and the rigidity of the center land portion 20 and the shoulder land portion 40 is based on the first wall surface structure. By relatively increasing the value, it is possible to improve the steering stability during straight traveling and turning on the dry road surface, and to improve the dry performance. On the other hand, the intermediate land portion 30 is provided with a sipe 33 having a second wall surface structure, and the rigidity of the intermediate land portion 30 is relatively lowered based on the second wall surface structure. Since the sipe density of the intermediate land portion 30 is relatively increased and the edge effect on the snow surface is increased, good snow performance can be ensured. As a result, it is possible to achieve both dry performance and snow performance at a higher level than before.

In making the sipe density of the intermediate land portion 30 larger than the sipe density of the center land portion 20 and the shoulder land portion 40, the ratio of the sipe density of the intermediate land portion 30 to the sipe density of the center land portion 20 and the shoulder land portion 40 is 1 .2 to 2.5. Thereby, dry performance and snow performance can be improved effectively. Here, when the ratio of the sipe density is smaller than 1.2, the effect of improving the snow performance is lowered, and conversely, when the ratio is larger than 2.5, the effect of improving the dry performance is lowered. In particular, the ratio of the sipe density is preferably 1.5 to 2.0. In order to ensure snow performance and dry performance at the same time, the sipe density of the intermediate land portion 30 is set to a range of 0.1 mm / mm ^{2 to} 0.25 mm / mm ² , and the center land portion 20 and the shoulder land portion 40 are set. sipe density is preferably set in a range of ^{0.05mm / mm 2 ~0.2mm / mm 2} .

  In the pneumatic tire, the distance D1 between the center line LA of the first main groove 11A and the tire equator CL is 5% to 10% of the tread ground contact width TDW, and the center line LB of the second main groove 11B and the tire equator CL are The distance D2 is preferably 25% to 35% of the tread ground contact width TDW. Thereby, dry performance and snow performance can be improved effectively. As a result of the distances D1 and D2 being out of the above range, if the width of the intermediate land portion 30 becomes excessively small, the effect of improving snow performance decreases. Conversely, if the width of the intermediate land portion 30 becomes excessively large, the effect of improving dry performance is reduced. Decreases.

  The maximum width of the horizontal grooves 31 and 32 (the maximum value of the groove width on the tread surface) arranged in the intermediate land portion 30 is the same as that of the horizontal grooves 21 and 22 arranged in the center land portion 20 and the horizontal grooves 41 arranged in the shoulder land portion 40. It is preferable to make it larger than the maximum width (the maximum value of the groove width on the tread surface) and set the difference in the maximum width to 0.5 mm to 2.0 mm. Thereby, dry performance and snow performance can be improved effectively. If the difference in the maximum width is smaller than 0.5 mm, the effect of improving snow performance is lowered, and conversely if it is larger than 2.0 mm, the effect of improving dry performance is lowered. Moreover, in order to ensure snow performance and dry performance at the same time, the maximum width of the lateral grooves 31 and 32 disposed in the intermediate land portion 30 is set in a range of 5 mm to 10 mm, and the lateral grooves 21 and 32 disposed in the center land portion 20 are 22 and the maximum width of the lateral groove 41 arranged in the shoulder land portion 40 are preferably set in a range of 4 mm to 9 mm.

  The maximum depth of the lateral grooves 31 and 32 disposed in the intermediate land portion 30 is larger than the maximum depth of the lateral grooves 21 and 22 disposed in the center land portion 20 and the lateral grooves 41 disposed in the shoulder land portion 40, The difference in maximum depth is preferably 0.5 mm to 3.0 mm. Thereby, dry performance and snow performance can be improved effectively. If the difference in the maximum depth is smaller than 0.5 mm, the effect of improving snow performance is lowered, and conversely if it is larger than 3.0 mm, the effect of improving dry performance is lowered. Moreover, in order to ensure snow performance and dry performance at the same time, the maximum depth of the lateral grooves 31 and 32 disposed in the intermediate land portion 30 is set in the range of 6 mm to 9 mm, and the lateral groove 21 disposed in the center land portion 20. , 22 and the shoulder groove 40 are preferably set to have a maximum depth of 5 mm to 8 mm.

  In a pneumatic tire having a tread portion, a pair of sidewall portions, and a pair of bead portions with a tire size of 205 / 55R16, four main grooves extending in the tire circumferential direction are provided in the tread portion, and the center land is formed in the tread portion. A plurality of lateral grooves extending in the tire width direction and a plurality of lateral grooves extending in the tire width direction on each of the center land portion, the intermediate land portion, and the shoulder land portion. The sipe wall structure, the ratio of the sipe density of the middle land portion to the sipe density of the center land portion and the shoulder land portion (sipe density ratio), and the first main to the tread ground contact width TDW The ratio of the distance D1 between the center line of the groove and the tire equator (D1 / TDW × 100%), the center line of the second main groove with respect to the tread contact width TDW, and the tire equator Conventional example, comparative examples 1 and 2 and examples in which the ratio of distance D2 (D2 / TDW × 100%), the maximum width of the horizontal groove in each land portion, and the maximum depth of the horizontal groove in each land portion are set as shown in Table 1 1-7 tires were produced.

  Regarding the wall surface structure of the sipe, the case where the first wall surface structure (FIG. 3) is adopted is indicated by “A”, and the case where the second wall surface structure (FIG. 4) is adopted is indicated by “B”.

  These test tires were evaluated for dry performance and snow performance by the following test methods, and the results are also shown in Table 1.

Dry performance:
Each test tire is mounted on a wheel with a rim size of 16 × 6 1 / 2J and mounted on a front-wheel drive vehicle with a displacement of 2000 cc. The air pressure after warm-up is 220 kPa. The sensory evaluation by the panel was implemented about the dry performance to include. The evaluation results are shown as an index with the conventional example being 100. A larger index value means better dry performance.

Snow performance:
Each test tire is mounted on a wheel with a rim size of 16 × 6 1 / 2J and mounted on a front-wheel drive vehicle with a displacement of 2000 cc. The braking distance until stopping was measured. The evaluation results are shown as an index with the conventional example being 100, using the reciprocal of the measured value. A larger index value means better snow performance.

  As can be seen from Table 1, both the dry performance and the snow performance of the tires of Examples 1 to 7 were improved in comparison with the conventional example. On the other hand, in the tire of Comparative Example 1, the sipe disposed in the center land portion and the shoulder land portion has the first wall surface structure, and the sipe disposed in the intermediate land portion has the second wall surface structure. Since the density was constant, the effect of improving snow performance could not be obtained. In the tire of Comparative Example 2, the sipe density of the intermediate land portion is larger than the sipe density of the center land portion and the shoulder land portion, but the sipe disposed in each land portion has the second wall structure. Therefore, the effect of improving the dry performance could not be obtained.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 11A 1st main groove 11B 2nd main groove 20 Center land part 21,22 Horizontal groove 23 Sipe 30 Middle land part 31,32 Horizontal groove 33 Sipe 40 Shoulder land part 41 Horizontal groove 43 Sipe

Claims (5)

An annular tread portion extending in the tire circumferential direction, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the inner side in the tire radial direction of the sidewall portions. A pneumatic tire in which at least four main grooves extending in the tire circumferential direction are provided in the tread portion, and at least five rows of land portions are partitioned by the main grooves,
The main groove is a pair of first main grooves disposed at positions closest to the tire equator on both sides of the tire equator and a pair of second main grooves disposed on the outermost side in the tire width direction on both sides of the tire equator. A center land portion including a groove, wherein the land portion is positioned between the pair of first main grooves, a pair of intermediate land portions positioned between the first main groove and the second main groove, and each second A pair of shoulder land portions located outside the main groove, and a plurality of lateral grooves extending in the tire width direction and a plurality of sipes extending in the tire width direction in each of the center land portion, the intermediate land portion, and the shoulder land portion. The sipe disposed in the center land portion and the shoulder land portion is configured to have a first wall surface structure whose wall surface extends in the sipe depth direction while having an amplitude in the sipe thickness direction, and the intermediate The sipe placed on the land is its wall It is configured to have a second wall surface structure extending linearly along the sipe depth direction, and the sipe density of the intermediate land portion is made larger than the sipe density of the center land portion and the shoulder land portion. A featured pneumatic tire.   2. The pneumatic tire according to claim 1, wherein a ratio of a sipe density of the intermediate land portion to a sipe density of the center land portion and the shoulder land portion is set to 1.2 to 2.5.   The distance between the center line of the first main groove and the tire equator is 5% to 10% of the tread contact width, and the distance between the center line of the second main groove and the tire equator is 25% to 35% of the tread contact width. The pneumatic tire according to claim 1 or 2, wherein   The maximum width of the horizontal groove arranged in the intermediate land portion is made larger than the maximum width of the horizontal groove arranged in the center land portion and the shoulder land portion, and the difference in the maximum width is set to 0.5 mm to 2.0 mm. The pneumatic tire according to any one of claims 1 to 3.   The maximum depth of the transverse groove arranged in the intermediate land portion is made larger than the maximum depth of the transverse groove arranged in the center land portion and the shoulder land portion, and the difference in the maximum depth is 0.5 mm to 3.0 mm. The pneumatic tire according to any one of claims 1 to 4, wherein:

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