JP5765025B2 - Pneumatic tire - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a pneumatic tire suitable as a rally tire, and more particularly to a pneumatic tire capable of exhibiting excellent running performance on a tarmac road surface (paved road) and a gravel road surface (unpaved road). .

  As pneumatic tires for running on rough terrain used for dirt racing, there are those that arrange a large number of blocks partitioned by deep grooves in the tread part and ensure traction performance based on these blocks (for example, , See Patent Document 1).

  On the other hand, in a pneumatic tire used in a rally performed on a course in which a tarmac road surface and a gravel road surface are mixed, a tread pattern provided with a plurality of both-end closed grooves with both ends closed in the tread portion has a tread pattern. The rigidity of the tread portion is secured by minimizing the groove area of the tread portion while receiving the edge effect based on the both-end closed grooves.

  FIG. 5 illustrates a tread pattern of a conventional pneumatic tire for rally. As shown in FIG. 5, the tread portion 11 is formed with a plurality of both-end closed grooves 12 extending linearly while being inclined with respect to the tire width direction and closed at both ends. These both-end closed grooves 12 are arranged at predetermined intervals in the tire circumferential direction to form six rows of grooves. Further, the rotational direction of the pneumatic tire is specified, and the both end closing grooves 12 are inclined toward one side in the tire circumferential direction (opposite to the tire rotational direction) from the tire equator E side toward the outer side in the tire width direction. doing.

  The conventional pneumatic tire for rally described above has been well evaluated for traction performance, braking performance, and cornering performance. However, although further improvement in running performance is demanded as the performance of the vehicle increases, the present situation is that the above tread pattern cannot sufficiently cope with it.

JP 2010-155503 A

  An object of the present invention is to provide a pneumatic tire that can exhibit excellent running performance on a tarmac road surface and a gravel road surface.

In order to achieve the above object, a pneumatic tire of the present invention is formed by arranging a plurality of both-end closed grooves extending in the tire circumferential direction and closed at both ends while being bent at a tread portion at a predetermined interval in the tire circumferential direction. At least three rows of groove rows are provided, straight portions are provided on both sides of the bent portions of the both ends closed grooves, and one row of groove rows including the both ends closed grooves is arranged on the tire equator, and the groove rows on the tire equator At least one row of the both-end closed grooves is disposed on each side of the tire, and in the groove row on the tire equator, the both-end closed grooves are alternately reversed along the tire circumferential direction. In the groove rows located on both sides of the groove row on the tire equator, the both-end closed grooves are arranged so that the widening side thereof faces outward in the tire width direction.

  As a result of earnest research on the running performance on the tarmac road surface and the gravel road surface, the present inventor has sufficiently secured the rigidity of the tread portion by defining the arrangement of the both end closing grooves in the tread portion and the shape of the both end closing grooves. However, the present inventors have found that it is possible to effectively increase the edge components of the both-end closed grooves that contribute to traction performance, braking performance, and cornering performance, and have reached the present invention.

That is, in the present invention, there are provided at least three rows of grooves formed by arranging a plurality of both-end closed grooves extending in the tire circumferential direction and closed at both ends while being bent at the tread portion at predetermined intervals in the tire circumferential direction, A straight portion is provided on both sides of the bent portion of each end closed groove, one row of groove rows made of both ends closed grooves is arranged on the tire equator, and at least one row of groove rows made of both ends closed grooves is arranged on both sides thereof. In addition, the groove rows on the tire equator are arranged so that the both ends closing grooves are alternately opposite in the circumferential direction of the tire, and both ends of the groove rows located on both sides of the groove row on the tire equator are By arranging the closing groove so that the widening side faces the outer side in the tire width direction, the edge component of the both-end closing groove contributing to traction performance, braking performance and cornering performance is effectively increased, and the tread portion Sex can be sufficiently secured. Thereby, the traveling performance on the tarmac road surface and the gravel road surface can be improved as compared with the prior art.

  In this invention, it is preferable to arrange | position the both-ends closed groove contained in a pair of groove row | line | column adjacent to a tire width direction in the position which mutually shifted | deviated to the tire circumferential direction. Thereby, the rigidity of a tread part can be improved and the running performance on a tarmac road surface can be improved.

  It is preferable that the angle formed by the straight portions located on both sides of the bent portion of each both-end closed groove is 75 degrees to 100 degrees. Thereby, the traction performance, braking performance, and cornering performance on the tarmac road surface and the gravel road surface can be improved in a well-balanced manner.

  It is preferable that the radius of curvature of the bent portion of each both-end closed groove is not more than twice the width of the both-end closed groove. Thereby, the edge component of both ends closing groove can be increased effectively, and the running performance on the tarmac road surface and the gravel road surface can be improved.

  Furthermore, in the groove row on the tire equator, the distance from the intersection where the extension lines of the straight portions located on both sides of the bent portions of the both ends closed grooves intersect each other to the both ends of the both ends closed grooves is made different from each other, and the shorter one The distance is preferably 50% to 75% of the longer distance. Thereby, arrangement | positioning of the both-ends closed groove contained in the groove | channel row | line | column on a tire equator can be optimized, and the travel performance on a tarmac road surface and a gravel road surface can be improved.

  In the present invention, it is preferable that the both-end closed grooves are arranged at the same pitch number and the same interval in all the groove rows composed of the both-end closed grooves, and that the number of arrays in the tread portion of the groove row composed of both-end closed grooves is five. . By adopting such a tread pattern, good running performance can be exhibited on the tarmac road surface and the gravel road surface.

It is an expanded view which shows the tread pattern of the pneumatic tire which consists of embodiment of this invention. It is a top view which expands and shows the principal part of the tread pattern of the pneumatic tire of FIG. It is XX arrow sectional drawing of FIG. Various forms of the both-end closed grooves are shown, and (a) to (d) are plan views each showing an end of the both-end closed grooves. It is an expanded view which shows the tread pattern of the conventional pneumatic tire.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a tread pattern of a pneumatic tire according to an embodiment of the present invention, and FIGS. This pneumatic tire is a rally tire.

  As shown in FIG. 1, the tread portion 1 is formed with a plurality of both-end closed grooves 2 extending in the tire circumferential direction while being bent and closed at both ends. These both-end closed grooves 2 are arranged at predetermined intervals in the tire circumferential direction to form five rows of grooves 21, 22, 23, 24, 25. More specifically, on the tire equator E, one row of groove rows 23 composed of a plurality of both-end closed grooves 2 arranged in the tire circumferential direction is arranged, and on the one side in the tire width direction from the groove row 23. Two rows of groove rows 21 and 22 each including a plurality of both-end closed grooves 2 arranged in the tire circumferential direction are arranged, and a plurality of both ends arranged in the tire circumferential direction on the other side in the tire width direction from the groove row 23. Two rows of groove rows 24 and 25 made up of the closing grooves 2 are arranged.

  Each of the both-end closing grooves 2 includes a pair of linear portions 2a extending linearly, and a bent portion 2b that is located between the linear portions 2a and is bent with respect to the linear portion 2a. Therefore, as shown in FIG. 1, each both-ends closed groove 2 has a shape in which the side opposite to the bent portion 2b is expanded in the tire width direction. In the groove row 23 on the tire equator E, the both-end closed grooves 2 are arranged such that the spreading side thereof is alternately reversed along the tire circumferential direction. On the other hand, in the groove rows 21, 22, 24, and 25 located on both sides of the groove row 23 on the tire equator E, all the both-end closed grooves 2 are arranged so that the spreading side faces the outer side in the tire width direction. The groove rows 21, 22, 24, and 25 located on both sides of the groove row 23 on the tire equator E can be mixed with the both-end closed grooves 2 such that the spreading side is directed inward in the tire width direction. In addition, 90% or more of the both-end closed grooves 2 included in these groove rows 21, 22, 24, and 25 need to be arranged so that the widening side faces outward in the tire width direction.

  As shown in FIG. 3, the groove width W of the both ends closed groove 2 is set to 5 mm to 10 mm, and the groove depth D is set to 3 mm to 8 mm. Further, the inclination angle θ of the inner wall surface of the both-end closed groove 2 with respect to the normal direction of the tread surface is set to 15 degrees to 45 degrees. The groove width W, the groove depth D, and the inclination angle θ of the inner wall surface are preferably within the above ranges, but are not limited thereto.

  In the pneumatic tire configured as described above, a groove array in which a plurality of both-end closed grooves 2 extending in the tire circumferential direction and closed at both ends are bent at the tread portion 1 and arranged at predetermined intervals in the tire circumferential direction. 21 to 25 are provided, one row of groove rows 23 made of both ends closed grooves 2 is arranged on the tire equator E, and groove rows 21, 22, 24, 25 made of both ends closed grooves 2 are arranged on both sides thereof, and In the groove row 23 on the tire equator E, the both-end closed grooves 2 are arranged so that the spreading sides thereof are alternately reversed along the tire circumferential direction, and the groove rows located on both sides of the groove row 23 on the tire equator E 21, 22, 24, and 25, the edge component of the both ends closed groove 2 that contributes to the traction performance, the braking performance, and the cornering performance can be obtained by arranging the both ends closed groove 2 so that the widening side thereof faces outward in the tire width direction. Increase effectively It is allowed, moreover it is possible to sufficiently secure the rigidity based on the pattern of the tread portion 1. That is, when the both-end closed grooves 2 having a bent shape are arranged as described above, it is possible to increase the strut force of the tread portion 1 while effectively functioning the edge component of the both-end closed grooves 2. Thereby, the traveling performance on the tarmac road surface and the gravel road surface can be improved as compared with the prior art.

  In the pneumatic tire, the both-end closed grooves 2 included in a pair of groove rows adjacent to each other in the tire width direction among the groove rows 21 to 25 are arranged at positions shifted from each other in the tire circumferential direction. More specifically, the both-end closed grooves 2 included in any groove row among the groove rows 21 to 25 are disposed between the both-end closed grooves 2 included in the adjacent groove row. By dispersing the both-end closed grooves 2 in this way, it is possible to increase the rigidity of the tread portion 1 and improve the running performance particularly on the tarmac road surface.

  In the pneumatic tire, as shown in FIG. 2, the angle α formed by the straight portions 2a, 2a located on both sides of the bent portion 2b of each end closing groove 2 is set to 75 ° to 100 °. Thereby, the traction performance, braking performance, and cornering performance on the tarmac road surface and the gravel road surface can be improved in a well-balanced manner. If the angle α is less than 75 degrees, the edge component for the lateral force is insufficient, and conversely if it exceeds 100 degrees, the edge component for the longitudinal force is insufficient.

  The radius of curvature R of the bent portion 2b of each end closing groove 2 is set to be not more than twice the groove width W of the both ends closing groove 2, more preferably not less than 1 and not more than twice. Thereby, the edge component of the both-ends closed groove | channel 2 can be increased effectively, and the travel performance on a tarmac road surface and a gravel road surface can be improved. When the radius of curvature R of the bent portion 2b becomes larger than twice the groove width W of the both-end closed groove 2, the edge component is insufficient, and the effect of improving the running performance is lowered.

  In particular, in the groove row 23 on the tire equator E, as shown in FIG. 2, the both ends are closed from the intersection P0 where the extended lines of the straight portions 2a located on both sides of the bent portions 2b of the both ends closed grooves 2 intersect each other. The distances L1, L2 to both ends P1, P2 of the groove 2 are different from each other, and the shorter distance L1 is set to 50% to 75% of the longer distance L2. Thereby, arrangement | positioning of the both-ends closed groove | channel 2 contained in the groove | channel row | line | column 23 on the tire equator E can be optimized, and the travel performance on a tarmac road surface and a gravel road surface can be improved. If the ratio of L1 / L2 is less than 50%, the edge component is insufficient and the effect of improving the running performance is lowered. Conversely, if the ratio exceeds 75%, the rigidity of the tread portion is lowered and the effect of improving the running performance is lowered. To do.

  In the pneumatic tire, the both-end closed grooves 2 are arranged at the same pitch number and the same interval in all the groove rows 21 to 25. By adopting such an arrangement, the tread portion 1 is provided with optimal rigidity, so that the effect of improving the running performance can be enhanced. However, if necessary, the pitch numbers and intervals of the both-end closed grooves 2 in the groove rows 21 to 25 can be varied.

  4A to 4D show various forms of the both-end closing grooves. Various shapes can be adopted for the ends of the both-end closing grooves 2. For example, in FIG. 4A, the end of the both ends closing groove 2 is formed in an arc shape, in FIG. 4B, the end of both ends closing groove 2 is formed in a straight line, and in FIG. 4C, both ends closing groove 2 is formed. In FIG. 4 (d), the ends of the both-end closed grooves 2 are formed in a straight line that is bent. If the rigidity of the tread portion 1 is sufficiently ensured, an arbitrary shape can be selected as the end shape of the both-end closed groove 2.

  In the preferred embodiment described above, the number of arrangements in the tread portion 1 of the groove row composed of the both ends closed grooves 2 is described as five. However, in the present invention, the number of arrangement in the tread portion 1 of the groove row composed of the both ends closed grooves 2 is described. Can be arranged in 3 rows, 7 rows, or the like as required. In particular, when one groove row is arranged on the tire equator and the number of groove rows on both sides is equal, the tread pattern in which the rotation direction and mounting direction of the tire are not limited as shown in FIG. There is an advantage that the handling property at the site becomes good.

  Further, in the preferred embodiment described above, the case where only the both-end closed groove 2 having a bent shape is provided in the tread portion 1 has been described, but in the present invention, the tread portion 1 has a linear shape in addition to the both-end closed grooves 2. A ditch having a groove or a dimple having a circular shape may be added.

  In a pneumatic tire having a tire size of 210 / 625R17, as shown in FIG. 1, a plurality of both-end closed grooves, which are bent in the tread portion and extend in the tire circumferential direction and closed at both ends, are arranged at predetermined intervals in the tire circumferential direction. Are arranged on the tire equator, one groove row is arranged on both sides of the tire equator, and two rows are formed on both sides of the groove equator on the tire equator. A groove row is arranged, and in the groove row on the tire equator, the both-end closed grooves are arranged so that the spreading side is alternately opposite along the tire circumferential direction, and the grooves are located on both sides of the groove row on the tire equator. In the row, the both-end closed grooves are arranged so that the widened side faces the outer side in the tire width direction, the angle α (degree) formed by the straight portions of the both-end closed grooves, and the curvature radius R of the bent portion with respect to the groove width W of the both-end closed grooves Ratio (R / W x 100%), on the tire equator Table 1 shows various ratios (L1 / L2 × 100%) of distances L1 and L2 from the intersection where the extended lines of the straight portions of the both ends closed grooves included in the groove row intersect each other. Different tires of Examples 1 to 11 were produced.

  For comparison, as shown in FIG. 5, a plurality of both-end closed grooves extending linearly at the tread portion while being inclined with respect to the tire width direction and closed at both ends are arranged at predetermined intervals in the tire circumferential direction. A tire of Conventional Example 1 having 6 rows of groove rows was prepared.

  In Conventional Example 1 and Examples 1 to 11, the groove width W of the both ends closed groove is 7.62 mm, the groove depth D is 5.5 mm, and the inner wall surface of the both ends closed groove is inclined with respect to the normal direction of the tread surface. The angle θ was 30 degrees, and the groove area ratio of the tread portion was 17%.

  About these test tires, the running performance on the tarmac road surface and the gravel road surface was evaluated by the following evaluation method, and the results are also shown in Table 1.

Driving performance on tarmac surfaces:
Each test tire is mounted on a wheel with a rim size of 17 × 8.0J and mounted on a four-wheel drive vehicle with a displacement of 2.0 liters with an air pressure of 230 kPa (after warm-up). Then, a running test was conducted by a test driver, and the average value of the measured lap times of 5 laps was obtained. The evaluation results are shown as an index using the reciprocal of the average value of the lap times, with the conventional example 1 being 100. The larger the index value, the better the running performance on the tarmac road surface.

Driving performance on gravel road:
Each test tire is mounted on a wheel with a rim size of 17 x 8.0 J and is mounted on a 4-wheel drive vehicle with a displacement of 2.0 liters with an air pressure of 230 kPa (after warm-up). In a test course of 2 km per lap consisting of these parts, a running test was conducted by a test driver, and the average value of the measured lap times of 5 laps was obtained. The evaluation results are shown as an index using the reciprocal of the average value of the lap times, with the conventional example 1 being 100. The larger the index value, the better the running performance on the gravel road surface.

  As is clear from Table 1, the tires of Examples 1 to 11 were significantly improved in running performance on the tarmac road surface and the gravel road surface as compared with Conventional Example 1.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Both-ends closed groove 2a Straight line part 2b Bending part 21-25 Groove row E Tire equator

Claims (7)

Provided with at least three groove rows in which a plurality of both-end closed grooves extending in the tire circumferential direction and closed at both ends are arranged at predetermined intervals in the tire circumferential direction while bending at the tread portion, and bending at each end closed groove A straight line portion is provided on both sides of the tire portion, one row of groove rows composed of the both ends closed grooves is arranged on the tire equator, and at least one row of grooves formed on both ends of the groove row on the tire equator is formed of the both ends closed grooves In the groove row on the tire equator, the both-end closed grooves are arranged in such a manner that the widening sides thereof are alternately reversed along the tire circumferential direction, on both sides of the groove row on the tire equator. The pneumatic tire according to claim 1, wherein in the groove row positioned, the both-end closed grooves are arranged such that a widening side thereof faces outward in the tire width direction.   The pneumatic tire according to claim 1, wherein the both-end closed grooves included in a pair of groove rows adjacent in the tire width direction are arranged at positions shifted from each other in the tire circumferential direction.   The pneumatic tire according to claim 1 or 2, wherein an angle formed by straight portions positioned on both sides of the bent portion of each both-end closed groove is 75 degrees to 100 degrees.   The pneumatic tire according to any one of claims 1 to 3, wherein a radius of curvature of a bent portion of each both-end closed groove is set to be twice or less of a groove width of each both-end closed groove.   In the groove row on the tire equator, the distance from the intersection where the extension lines of the straight portions located on both sides of the bent portion of each end closing groove intersect each other to both ends of the both end closing groove are different from each other, and the shorter distance The pneumatic tire according to any one of claims 1 to 4, wherein the tire is 50% to 75% of the longer distance.   The pneumatic tire according to any one of claims 1 to 5, wherein the both-end closed grooves are arranged at the same pitch number and the same interval in all the groove rows including the both-end closed grooves.   The pneumatic tire according to any one of claims 1 to 6, wherein the number of arrangements in the tread portion of the groove row composed of the both-end closed grooves is five.

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