JP2015009775A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire improved in snow performance and steering stability.SOLUTION: In a pneumatic tire comprising a tread 1, a sidewall 2 and bead 3, a main groove unit 10 has a branch structure comprising one circumferential groove 11 extending to a tire circumferential direction in the central area of the tread 1 and a plurality of width directional grooves 12 extending from at least two places of the groove 11 toward a tire width directional outside, and multiple main groove units 10 are disposed at a distance in the tire circumferential direction. The inclination angle α of the circumferential groove 11 to the tire circumferential direction is made to be 0°≤α≤25°, and that angle β of each width directional groove 12 to the groove 11 is made to be 90°+α≤β<180°. Further, a plurality of sipes 13 extending to the tire width direction, and at least one auxiliary groove 14, 15 extending to the tire circumferential direction and shallower than the groove 12 are disposed to a block 21 partitioned to the inside of each unit 10.

Description

  The present invention relates to a pneumatic tire suitable for all seasons, and more particularly to a pneumatic tire that can improve steering stability as well as snow performance.

  Normally, pneumatic tires for all seasons have a tread pattern for the purpose of demonstrating good wet performance and good snow performance, but excellent handling stability is required even in seasons other than the snowfall season. It has been. In this type of pneumatic tire, a plurality of main grooves extending in the tire circumferential direction and a plurality of lug grooves extending in the tire width direction are formed in the tread portion, and a number of blocks are partitioned by these main grooves and lug grooves. In each block, a plurality of sipes are formed (see, for example, Patent Documents 1 and 2).

  In the pneumatic tire having the tread pattern as described above, the snow performance can be improved by increasing the groove components such as the main groove and the lug groove, but the steering stability is lowered accordingly. There is. Therefore, in the all-season pneumatic tire, it is required to improve the snow performance without deteriorating the steering stability.

JP 2010-208507 A JP 2012-76603 A

  An object of the present invention is to provide a pneumatic tire that can improve steering stability as well as 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. In the pneumatic tire provided with a pair of bead portions arranged on the inner side in the tire radial direction of the tire, at least two portions of the circumferential groove portion and one circumferential groove portion extending in the tire circumferential direction in the central region of the tread portion. A plurality of main groove units having a branch structure composed of a plurality of widthwise groove portions extending outward in the tire width direction are arranged at intervals in the tire circumferential direction, and the inclination angle α of the circumferential groove portion with respect to the tire circumferential direction is Is in the range of 0 ° ≦ α ≦ 25 °, and the inclination angle β of each widthwise groove with respect to the circumferential groove is in the range of 90 ° + α ≦ β <180 °, and is partitioned inside each main groove unit. In which it characterized in that a shallow least one auxiliary groove than the width direction groove that the block portion extends sipe and the tire circumferential direction of the plurality of which extends in the tire width direction.

  In the present invention, the tread portion is provided with a plurality of main groove units having a branch structure composed of one circumferential groove portion and a plurality of width direction groove portions, and the plurality of width direction groove portions constituting the main groove unit are tread. By extending toward the outside in the tire width direction from the central region of the portion, a large snow column shearing force can be obtained based on these width direction groove portions, so that excellent snow performance can be exhibited. Further, the plurality of widthwise groove portions constituting the main groove unit extend from the circumferential groove portion located in the central area of the tread portion toward the outer side in the tire width direction, and these widthwise groove portions form the tread portion in the tire. Since it does not cross in the width direction, it is possible to sufficiently secure the rigidity of the central region of the tread portion and exhibit excellent steering stability. Furthermore, by providing at least one auxiliary groove shallower than the width direction groove part in addition to a plurality of sipes in the block section defined inside each main groove unit, the auxiliary groove increases the edge effect and snow performance. In addition, the shallow auxiliary groove does not significantly reduce the rigidity of the tread portion, so that good steering stability can be maintained. Therefore, according to the present invention, the use of the main groove unit having a branch structure can improve the steering stability as well as the snow performance.

  In the present invention, the groove depth of the auxiliary groove is preferably 25% to 85% of the groove depth of the width direction groove portion of the main groove unit. Thereby, both snow performance and steering stability can be achieved at a higher level.

  It is preferable that the width direction groove part of the main groove unit is bent or curved at least at one place in the longitudinal direction. Thereby, the snow column shearing force based on the width direction groove can be increased, and the snow braking performance can be improved.

  It is preferable that at least one of the auxiliary grooves extends continuously in the tire circumferential direction. In this way, by dividing the portion on the center region side and the portion on the shoulder region side of the tread portion by the auxiliary groove continuously extending in the tire circumferential direction, the behavior of the tread portion with respect to the steering becomes smooth, so that the steering stability Can be improved. Moreover, the snow performance improvement effect can be obtained by continuously extending at least one auxiliary groove in the tire circumferential direction.

It is meridian sectional drawing which shows the pneumatic tire which consists of embodiment of this invention. It is an expanded view which shows the tread pattern of the pneumatic tire which consists of embodiment of this invention. It is sectional drawing which extracts and shows the main groove unit of the tread pattern of FIG. It is a top view which extracts and shows the main groove unit of the tread pattern of FIG. It is an expanded view which shows the modification of the tread pattern of the pneumatic tire of this invention. It is an expanded view which shows the other modification of the tread pattern of the pneumatic tire of this invention. It is an expanded view which shows the other modification of the tread pattern of the pneumatic tire of this invention. It is an expanded view which shows the tread pattern of the conventional pneumatic tire. It is an expanded view which shows the comparative example of the tread pattern of the pneumatic tire of this invention. It is an expanded view which shows the other comparative example of the tread pattern of the pneumatic tire of this invention. It is an expanded view which shows the other comparative example of the tread pattern of the pneumatic tire of this invention. It is an expanded view which shows the other comparative example of the tread pattern of the pneumatic tire of this invention.

  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 two-layer 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, in the tread portion 1, a plurality of main groove units 10 having a branch structure are arranged at predetermined intervals in the tire circumferential direction on both sides of the tire equator E. Each main groove unit 10 includes one circumferential groove 11 extending in the tire circumferential direction in the central region of the tread portion 1 and a plurality of widths extending from at least two locations of the circumferential groove 11 toward the outer side in the tire width direction. It is comprised from the direction groove part 12. As shown in FIG. In particular, as shown in FIG. 2, the main groove unit 10 includes three widthwise groove portions 12 that extend from the three circumferential groove portions 11 (both ends and the center portion in the longitudinal direction) toward the outer side in the tire width direction. It is preferable to have a trifurcated branched structure. The main groove unit 10 is arranged so that the main groove units 10 and 10 adjacent in the tire circumferential direction and the tire width direction do not cross each other. The circumferential direction groove part 11 and the width direction groove part 12 which comprise the main groove unit 10 may be linear form, or may be curvilinear form.

  Inside each main groove unit 10, a block portion 21 is defined by a circumferential groove portion 11 and a width direction groove portion 12. In each block portion 21, a plurality of sipes 13 extending in the tire width direction and a plurality of auxiliary grooves 14 and 15 extending in the tire circumferential direction and shallower than the width direction groove portion 12 are formed. As shown in FIG. 3, the block portion 21 defined inside the main groove unit 10 has shallow auxiliary grooves 14 and 15, but has a lump shape that exhibits an integral behavior regardless of the shallow auxiliary grooves 14 and 15. ing. The auxiliary grooves 14 located on the tire equator side remain inside the main groove unit 10, but the auxiliary grooves 15 located on the shoulder side continuously extend in the tire circumferential direction and have a plurality of rows arranged in the tire circumferential direction. The main groove unit 10 is penetrated.

  On the other hand, on the outside of the main groove unit 10, land portions 22 are partitioned so as to surround each main groove unit 10. Similar to the main groove unit 10, a plurality of sipes 13 extending in the tire width direction and auxiliary grooves 15 extending in the tire circumferential direction and shallower than the width direction groove 12 are formed in the land portion 22.

  The main groove unit 10 is the deepest groove in the tread portion 1, and the groove depths of the circumferential groove portion 11 and the width direction groove portion 12 are set in a range of, for example, 5.0 mm to 12.0 mm. Although the groove width of the circumferential direction groove part 11 and the width direction groove part 12 which comprises the main groove unit 10 is not specifically limited, For example, it is set to the range of 3.0 mm-15.0 mm. On the other hand, the auxiliary grooves 14 and 15 are shallower than the main groove unit 10, and the depth of the grooves is set in a range of, for example, 4.0 mm to 9.0 mm. Although the groove width of the auxiliary grooves 14 and 15 is not specifically limited, For example, it is set to the range of 2.0 mm-10.0 mm. Further, the groove width of the sipe 15 is not particularly limited, but is set in a range of 0.4 mm to 1.2 mm, for example.

  Further, in the pneumatic tire, as shown in FIG. 4, the inclination angle α of the circumferential groove 11 with respect to the tire circumferential direction is set in a range of 0 ° ≦ α ≦ 25 °, and each widthwise groove with respect to the circumferential groove 11. The inclination angle β of 12 is set in a range of 90 ° + α ≦ β <180 °.

  In the pneumatic tire described above, a plurality of main groove units 10 having a branch structure composed of one circumferential groove portion 11 and a plurality of width direction groove portions 12 are provided in the tread portion 1 to constitute the main groove unit 10. By extending the plurality of widthwise groove portions 12 from the central region of the tread portion 1 toward the outer side in the tire width direction, a large snow column shearing force can be obtained based on these widthwise groove portions 12, so that excellent snow performance is achieved. It becomes possible to demonstrate. Note that the width direction groove portion 12 of the main groove unit 10 has a larger groove volume and better snow removal than a conventional lug groove, which also contributes to an improvement in snow performance.

  A plurality of widthwise groove portions 12 constituting the main groove unit 10 extend from the circumferential groove portion 11 located in the central area of the tread portion 1 toward the outer side in the tire width direction. Does not cross the tread portion 1 in the tire width direction. That is, the land portion 22 is disposed in the central region of the tread portion 1 so as to surround the main groove unit 10. Therefore, it is possible to sufficiently ensure the rigidity of the central region of the tread portion 1 and exhibit excellent steering stability.

  Furthermore, since at least one auxiliary groove 14, 15 shallower than the width direction groove 12 is provided in the block portion 21 partitioned inside each main groove unit 10 in addition to the plurality of sipes 13. 14 and 15 contribute to the improvement of snow performance by increasing the edge effect, and the auxiliary grooves 14 and 15 do not significantly reduce the rigidity of the tread portion 1, so that good steering stability can be maintained. .

  As a result, in the pneumatic tire, by adopting the main groove unit 10 having a branch structure, it is possible to improve steering stability as well as snow performance.

  In the pneumatic tire described above, the inclination angle α of the circumferential groove portion 11 with respect to the tire circumferential direction is in the range of 0 ° ≦ α ≦ 25 °. By reducing the inclination angle α of the circumferential groove portion 11 in this way, the tire Snow performance can be improved by securing a circumferential edge component. When the inclination angle α exceeds 25 °, it is difficult to suppress the side slip on the snow.

  The inclination angle β of each widthwise groove 12 with respect to the circumferential groove 11 is in the range of 90 ° + α ≦ β <180 °, and more preferably in the range of 90 ° + α ≦ β ≦ 140 °. Thereby, it is possible to sufficiently ensure the braking performance and driving performance on snow. When the inclination angle β is out of the above range, good snow performance cannot be obtained.

  In the pneumatic tire, the groove depths of the auxiliary grooves 14 and 15 are preferably 25% to 85% of the groove depth of the width direction groove portion 12 of the main groove unit 10. Thereby, both snow performance and steering stability can be achieved at a higher level. If the groove depth of the auxiliary grooves 14 and 15 is less than 25% of the groove depth of the widthwise groove portion 12, snow clogging is liable to occur, so that snow performance deteriorates. Conversely, if the groove depth exceeds 85%, the rigidity of the tread portion 1 is reduced. Decreases and steering stability decreases.

  In addition, when at least one auxiliary groove 15 is continuously extended in the tire circumferential direction, the central region side portion and the shoulder region side portion of the tread portion 1 continuously extend in the tire circumferential direction. Since it is divided by the auxiliary groove 15, the behavior of the tread portion 1 with respect to steering becomes smooth, and steering stability can be improved. Furthermore, the snow performance improvement effect can be obtained by continuously extending at least one auxiliary groove 15 in the tire circumferential direction.

  FIG. 5 shows a modification of the tread pattern of the pneumatic tire of the present invention. 5, the same components as those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof is omitted. In the embodiment of FIG. 2 described above, a part of the main groove unit 10 is arranged so as to cross the tire equator E. However, in the embodiment of FIG. The main groove unit 10 is arranged on the outer side in the direction so as not to cross the tire equator E. Thereby, the part extended on the tire equator E of the land part 22 is ensured widely, and it is trying to ensure favorable steering stability.

  In addition to the auxiliary groove 15, the block part 21 and the land part 22 are formed with a plurality of auxiliary grooves 16 that are shallower than the circumferential groove part 11 and the widthwise groove part 12 constituting the main groove unit 10. These auxiliary grooves 16 are provided with an inclination angle with respect to the tire circumferential direction, and a large number of auxiliary grooves 16 are provided so that the edge amount is larger than in the case of FIG. Therefore, good snow performance can be ensured.

  6 and 7 each show a modification of the tread pattern of the pneumatic tire of the present invention. 6 and 7, the same components as those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof is omitted. 6 and FIG. 7, the depiction of sipes is omitted, but these tread patterns have sipes (not shown). 6 and 7, each main groove unit 10 has a tire width from one circumferential groove 11 extending in the tire circumferential direction in the central region of the tread portion 1 and two locations (both ends) of the circumferential groove 11. It is comprised from the two width direction groove parts 12 extended toward the direction outer side.

  In FIG. 6, the width direction groove portion 12 of the main groove unit 10 is bent at one place in the longitudinal direction. In FIG. 7, the width direction groove portion 12 of the main groove unit 10 is bent at one place in the longitudinal direction. doing. In this way, by bending or curving the widthwise groove portion 12 of the main groove unit 10 at least at one place in the longitudinal direction, the snow column shear force based on the widthwise groove portion 12 is increased, and snow braking performance can be improved. it can.

  FIG. 8 shows a tread pattern of a conventional pneumatic tire. In FIG. 8, a plurality of main grooves 31 extending in the tire circumferential direction and a plurality of auxiliary grooves 32 extending in the tire width direction are formed in the tread portion 1, and a plurality of blocks are formed by the main grooves 31 and the auxiliary grooves 32. The part 33 is partitioned. Each block 33 is formed with a plurality of sipes 34 extending in the tire width direction.

  In the conventional pneumatic tire configured as described above, good snow performance can be obtained based on the main groove 31 and the auxiliary groove 32, but the rigidity of the tread portion 1 becomes insufficient due to the subdivision of the block portion 33. Good steering stability cannot be obtained.

  9 to 11 show comparative examples of the tread pattern of the pneumatic tire of the present invention. In addition, although the depiction of sipes is omitted in FIGS. 9 to 11, these tread patterns are provided with sipes (not shown). In FIG. 9, the main groove 41 has two circumferential grooves extending in the tire width direction and branching in the vicinity of the tire equator E without having a circumferential groove and is shallower than the main groove 41. 42 is arranged so as to connect the two widthwise grooves of the main groove 41 to each other. In this case, since the main groove 41 does not include the circumferential groove portion, the snow performance cannot be sufficiently ensured.

  10 and 11, the main groove 41 includes a circumferential groove portion extending in the tire circumferential direction in the vicinity of the tire equator E, and two widthwise groove portions extending outward from the both ends of the circumferential groove portion in the tire width direction. I have. In this case, since the auxiliary groove which connects the two width direction groove parts of the main groove 41 is not provided, snow performance cannot fully be ensured.

  In FIG. 12, the auxiliary groove 42 includes a circumferential groove portion extending in the tire circumferential direction in the vicinity of the tire equator E, and two width direction groove portions extending outward from the both ends of the circumferential groove portion in the tire width direction. The main groove 41 deeper than the groove 42 is disposed so as to connect the two width direction groove portions of the auxiliary groove 42 to each other. In this case, since the positional relationship between the main groove 41 and the auxiliary groove 42 is opposite to that of the present invention, sufficient snow performance cannot be ensured.

  The tire size is 255 / 40R18 99H and extends in the tire circumferential direction to form an annular tread portion, a pair of sidewall portions disposed on both sides of the tread portion, and the tire portion radially inward of the sidewall portions In the pneumatic tire provided with a pair of bead portions disposed on the tire, as shown in FIG. 2, from one circumferential groove portion extending in the tire circumferential direction in the central region of the tread portion and three locations of the circumferential groove portion. A plurality of main groove units having a branch structure composed of a plurality of width direction groove portions extending outward in the tire width direction are arranged at intervals in the tire circumferential direction, and block portions partitioned inside the main groove units Are provided with a plurality of sipes extending in the tire width direction and two auxiliary grooves extending in the tire circumferential direction and shallower than the width direction groove portion. The inclination angle β of each width direction groove with respect to the direction groove, the ratio of the groove depth of the auxiliary groove to the groove depth of the width direction groove, the shape of the width direction groove, the auxiliary groove tire formed in the block portion in the main groove unit Tires of Examples 1 to 7 having different circumferential extension structures (continuous or discontinuous) as shown in Table 1 were produced. In Examples 1 to 7, the groove depths of the circumferential groove portion and the width direction groove portion of the main groove unit were set to 7.5 mm.

  For comparison, as shown in FIG. 8, a plurality of main grooves extending in the tire circumferential direction and a plurality of auxiliary grooves extending in the tire width direction are provided in the tread portion, and a plurality of block portions are formed by these main grooves and auxiliary grooves. The tire of Conventional Example 1 was prepared in which a plurality of sipes extending in the tire width direction were provided in each block portion. In Conventional Example 1, the groove depth of the main groove was 7.5 mm, and the groove depth of the auxiliary groove was 5.8 mm. In addition, a tire of Comparative Example 1 was prepared in which the relationship between the groove depth of the main groove and the groove depth of the auxiliary groove was reversed in the same tread pattern as in Conventional Example 1. That is, in the conventional example 1, the main groove is oriented in the tire circumferential direction while the auxiliary groove shallower than the main groove is oriented in the tire width direction, and in the comparative example 1, the main groove is oriented in the tire width direction while being larger than the main groove. The shallow auxiliary grooves are oriented in the tire circumferential direction.

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

Snow performance:
Each test tire is mounted on a wheel with a rim size of 18 x 8.5 JJ, mounted on a test vehicle (front-wheel drive vehicle) with a displacement of 3500 cc with a pneumatic pressure of 230 kPa, and running at a speed of 40 km / h on a test course consisting of a snowy road. The braking distance from when the vehicle was stopped to when the vehicle stopped was measured. The evaluation results are shown as index values with the conventional example 1 being 100, using the reciprocal of the measured value. A larger index value means a shorter braking distance and better snow performance.

Steering stability:
Each test tire was mounted on a wheel with a rim size of 18 × 8.5 JJ and mounted on a test vehicle (front-wheel drive vehicle) with a displacement of 3500 cc with an air pressure of 230 kPa, and a sensory evaluation was performed by a test driver on a test course consisting of a dry road surface. . The evaluation results are shown as index values with the conventional example 1 as 100. The larger the index value, the better the steering stability.

  As is clear from Table 1, in all the tires of Examples 1 to 7, the snow performance and the steering stability were improved in a well-balanced manner in comparison with Conventional Example 1. On the other hand, although the tire of Comparative Example 1 has the main grooves oriented in the tire width direction, the effect of improving the snow performance is recognized, but the steering stability is lowered accordingly.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 10 Main groove unit 11 Circumferential direction groove part 12 Width direction groove part 13 Sipe 14, 15, 16 Auxiliary groove 21 Block part 22 Land part

Claims (4)

  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. In the pneumatic tire provided, one circumferential groove extending in the tire circumferential direction in the central region of the tread portion, and a plurality of widthwise grooves extending outward in the tire width direction from at least two locations of the circumferential groove. A plurality of main groove units having a branch structure consisting of the following are arranged at intervals in the tire circumferential direction, and the inclination angle α of the circumferential groove portion with respect to the tire circumferential direction is in a range of 0 ° ≦ α ≦ 25 °, while A plurality of sipes extending in the tire width direction in block portions defined on the inner side of each main groove unit, with an inclination angle β of each width direction groove portion with respect to the circumferential groove portion in a range of 90 ° + α ≦ β <180 ° A pneumatic tire characterized in that a shallow least one auxiliary groove than the width direction groove extending in the tire circumferential direction.   The pneumatic tire according to claim 1, wherein a groove depth of the auxiliary groove is 25% to 85% of a groove depth of a width direction groove portion of the main groove unit.   3. The pneumatic tire according to claim 1, wherein a width direction groove portion of the main groove unit is bent or curved at at least one position in a longitudinal direction thereof.   The pneumatic tire according to claim 1, wherein at least one of the auxiliary grooves extends continuously in the tire circumferential direction.

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