JP2007302071A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of reducing the pattern noise while the off-road running performance is well maintained. <P>SOLUTION: The pneumatic tire is equipped with rows 60 of blocks having lands 2 in the central position of the tread part 1 in such a manner as extending continuously in the tire circumferential direction and consisting of two main grooves 3 and 4 located on both sides of each land 2 in such a fashion as stretching zigzag in the tire circumferential direction and a plurality of blocks 6 partitioned by a plurality of lug grooves 5 coupling the main grooves 3 and 4 with each other, wherein each block 6 of the block row is divided into a central block portion 6a and an outer block portion 6b by a thin groove 9 whose inclination angle α to the tire circumferential direction ranges between 5-12° and groove width W is 2-4% of the grounding width CW, and these block portions 6a and 6b are arranged in dislocation relatively along the stretching direction of the thin groove 9 toward the shorter block edge facing the lug groove 5. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic tire suitable for off-road driving, and more particularly to a pneumatic tire that can reduce pattern noise while maintaining off-road driving performance.

  Conventionally, pneumatic tires mounted on a four-wheel drive vehicle are required to have good off-road driving performance represented by mud driving performance, snow driving performance, and sand driving performance. ing. Such pneumatic tires ensure the mud running performance and snow running performance by setting the groove area ratio of the tread portion large, and ensure the sand running performance by increasing the block length in the tire circumferential direction. However, increasing the groove area ratio causes a deterioration in noise performance, particularly pattern noise (see, for example, Patent Document 1).

In other words, when the groove area ratio is increased, the impact sound when the block contacts the ground increases, and the pumping sound generated when the air compressed between the tread portion and the road surface flows out through the lug groove As a result, the air column resonance sound in the main groove excited is increased. Therefore, it is extremely difficult to reduce pattern noise while maintaining off-road driving performance.
Japanese Patent Laid-Open No. 11-245625

  An object of the present invention is to provide a pneumatic tire capable of reducing pattern noise while maintaining off-road running performance.

  In order to achieve the above object, a pneumatic tire according to the present invention has a land portion that continuously extends in the tire circumferential direction at the center position of the tread portion, and has zigzag shapes on both sides of the land portion. In a pneumatic tire having a block row composed of two main grooves extending in the circumferential direction and a plurality of blocks partitioned by a plurality of lug grooves connecting between the main grooves, each block of the block row is a tire. The central block portion and the outer block portion are divided by a narrow groove having an inclination angle with respect to the circumferential direction of 5 ° to 12 ° and a groove width of 2% to 4% of the ground contact width. The block portion is arranged so as to be relatively shifted along the extending direction of the narrow groove toward the shorter block side facing the lug groove.

  In the present invention, each block of the row of blocks located on both sides of the land portion at the center of the tread portion where vibrations easily occur is separated from the central block portion by the narrow groove slightly inclined with respect to the tire circumferential direction. Generated when the central block portion and the outer block portion are grounded by dividing the block portion into the block portion and arranging the central block portion and the outer block portion relatively displaced along the extending direction of the narrow groove. Since the impact sound generated is reduced and the timing of the impact sound generation is varied, the noise caused by the impact sound can be reduced. In particular, when a pair of the central block portion and the outer block portion are grounded, the portion that is grounded first has a smaller block side length than the portion that is grounded later, so that the impact sound is effectively reduced. be able to. On the other hand, when the groove area ratio of the tread portion is set to be sufficiently large by the main groove having the zigzag shape, the lug groove and the narrow groove, it is possible to exhibit good off-road running performance.

  In the present invention, the relative shift amount between the central block portion and the outer block portion is preferably 20% to 40% of the length of the block side facing the narrow groove. Thereby, the noise reduction effect by dispersion | distribution of an impact sound can be acquired, suppressing generation | occurrence | production of uneven wear.

  The length Ls of the shorter block side facing the lug groove in the central block portion and the outer block portion is preferably 65% to 85% of the length Ll of the longer block side facing the lug groove. Thereby, the noise reduction effect by reduction of impact sound can be acquired, suppressing generation | occurrence | production of uneven wear.

  Moreover, it is preferable to provide at least three sipes in each of the central block portion and the outer block portion. By adding sipes, snow driving performance and ice driving performance can be improved.

  Furthermore, it is preferable that the central block portion and the outer block portion have a shape that is symmetrical with respect to each other around the intermediate point in the narrow groove. Thus, when a point-symmetric shape is adopted for the central block portion and the outer block portion, an effect of improving noise performance can be obtained regardless of the tire rotation direction.

  In the present invention, the groove width of the narrow groove is 2% to 4% of the grounding width, but the groove width of the main groove is 4.5% to 8.0% of the grounding width, and the groove width of the lug groove is the grounding width. 4.0% to 10.0%, and the groove width of the sipe is preferably 1.5 mm or less. Here, the ground contact width means that when the tread portion of the tire is grounded on a flat surface under the measurement conditions of the static load radius determined by standards such as JATMA, TRA, or ETRTO, the tire is grounded on the flat surface. It means the width in the tire axial direction of the part to be.

  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. As shown in FIG. 1, a rib-like land portion 2 that extends continuously in the tire circumferential direction is disposed at the center position CL of the tread portion 1. An inner main groove 3 and an outer main groove 4 are provided on both sides of the land portion 2 in a zigzag shape and extending in the tire circumferential direction. Between the main grooves 3 and 4, a plurality of lug grooves 5 communicating with both are provided. A block row 60 composed of a plurality of blocks 6 is defined by the main grooves 3 and 4 and the lug grooves 5. In addition, a plurality of lug grooves 7 are provided in a region on the shoulder side of the outer main groove 4. A block row 80 composed of a plurality of blocks 8 is defined by the main grooves 4 and the lug grooves 7. The lug grooves 5 are inclined in one direction with respect to the tire circumferential direction on both sides of the land portion 2, and the lug grooves 7 are inclined in the other direction with respect to the tire circumferential direction on both sides of the land portion 2. That is, this pneumatic tire constitutes an asymmetric pattern whose mounting direction is not specified.

  Each block 6 of the block row 60 has a central block portion 6a and a narrow groove 9 having an inclination angle α with respect to the tire circumferential direction of 5 ° to 12 ° and a groove width W of 2% to 4% of the ground contact width TCW. The outer block portion 6b is divided (see FIG. 2).

  FIG. 2 shows an enlarged block row between the main grooves. As shown in FIG. 2, in the central block portion 6a and the outer block portion 6b, one of the two block sides facing the lug groove 5 is longer than the other because the narrow groove 9 has an inclination angle α. It has become. That is, the length Ls of the shorter block side is shorter than the longer block side Ll. And the center side block part 6a and the outer side block part 6b are relatively shifted and arranged along the extension direction of the narrow groove 9 toward the shorter block side.

  According to the pneumatic tire described above, the central block portion 6a and the outer block portion 6b are formed by the narrow grooves 9 that slightly incline each block 6 of the block row 60 located in a portion where vibration is likely to occur with respect to the tire circumferential direction. When the central block portion 6a and the outer block portion 6b are grounded, the central block portion 6a and the outer block portion 6b are relatively shifted along the extending direction of the narrow groove 9. Since the impact sound generated at the same time is reduced and the timing of the impact sound generation is made different, the noise due to the impact sound can be reduced. In particular, when the pair of the central block portion 6a and the outer block portion 6b are grounded, the block side length Ll of the portion to be grounded later is relatively large, but the length of the block side of the portion to be grounded first is set. Since Ls is relatively small, the impact sound can be effectively reduced.

  On the other hand, by setting the groove area ratio of the tread portion 1 sufficiently large by the main grooves 3, 4 having the zigzag shape, the lug grooves 5, 7, and the narrow grooves 9, it is possible to exhibit good off-road running performance. It is.

  Here, if the inclination angle α of the narrow groove 9 is less than 5 °, the difference between the block side lengths Ls and Li becomes small, so that an effective noise reduction effect cannot be obtained. Performance decreases. Further, if the groove width W of the narrow groove 9 is less than 2% of the ground contact width TCW, mud clogging or the like is liable to occur in the narrow groove 9, so that good off-road running performance cannot be obtained. Exceeding% will adversely affect the noise performance.

  As shown in FIG. 2, the relative shift amount S between the central block portion 6 a and the outer block portion 6 b is preferably 20% to 40% of the length L of the block side facing the narrow groove 9. If the deviation S is less than 20% of the length L of the block side, the noise reduction effect due to the dispersion of impact sound is reduced. Conversely, if it exceeds 40%, uneven wear tends to occur.

  The length Ls of the shorter block side facing the lug groove 5 of the central block portion 6a and the outer block portion 6b is preferably 65% to 85% of the length Ll of the longer block side. If the length Ls is less than 65% of the length Ll, heel and toe wear tends to occur, and conversely if it exceeds 85%, the noise reduction effect decreases.

  It is desirable to provide at least three sipes 10 in each of the central block portion 6a and the outer block portion 6b. The addition of the sipe 10 can improve snow running performance and on-ice running performance. In particular, at least three sipes 10 preferably include a sipe that opens in the main groove 3 or the main groove 4, a sipe that opens in the lug groove 5, and a sipe that opens in the narrow groove 9. Thus, by providing the sipe 10 so that it may open to each groove | channel surrounding the center side block part 6a and the outer side block part 6b, it becomes difficult to produce mud clogging, snow clogging, etc. to each groove | channel. In addition, it is desirable to provide a plurality of sipes 11 in each block 8 of the block array 80 on the shoulder side.

  Further, the central block portion 6a and the outer block portion 6b may be shaped so as to be symmetrical with respect to each other around the intermediate point A in the narrow groove 9. In this way, when the point-symmetric shape is adopted for the central block portion 6a and the outer block portion 6b, the effect of improving the noise performance can be obtained regardless of the rotation direction of the tire. Of course, the arrangement of the sipes 10 in the central block portion 6a and the outer block portion 6b may be point-symmetric with respect to each other around the intermediate point A in the narrow groove 9.

  Two tires having a tire size of 285 / 60R18, having a land portion continuously extending in the tire circumferential direction at the center position of the tread portion, and extending in the tire circumferential direction in a zigzag shape on both sides of the land portion, respectively. In a pneumatic tire having a block row composed of a plurality of blocks partitioned by main grooves and a plurality of lug grooves connecting the main grooves, each block of the block row is a narrow groove extending in the tire circumferential direction. Divided into a central block part and an outer block part, these central block part and outer block part are relatively shifted and arranged along the extending direction of the narrow groove toward the shorter block side facing the lug groove. The ratio (%) of the deviation amount S to the length L of the block side, the inclination angle α (°) of the narrow groove, the ratio (%) of the groove width W of the narrow groove to the grounding width TCW, The tires of Comparative Examples 1 to 3 and Examples 1 to 7 having different ratios (%) of the length Ls of the block side to the length Li as shown in Table 1 were produced. The central block portion and the outer block portion have a shape that is symmetrical with respect to each other around an intermediate point in the narrow groove. As a conventional example, a tire was prepared in which the block rows between the main grooves were not divided by narrow grooves.

  These test tires were evaluated for off-road running performance, noise performance, and uneven wear by the following test methods, and the results are also shown in Table 1.

Off-road driving performance:
The test tire was mounted on a wheel with a rim size of 18 × 8 JJ, mounted on a four-wheel drive vehicle with an air pressure of 230 kPa, and an off-road running sensory test was performed by a test driver. The evaluation results are shown as an index with the conventional example being 100. A larger index value means better off-road driving performance.

Noise performance:
The test tire is mounted on a wheel with a rim size of 18 x 8 JJ, mounted on a four-wheel drive vehicle with an air pressure of 230 kPa, and after adjusting the load (2 passengers + measuring instrument + vehicle weight), the speed of the paved road is 100 km / h. The vehicle noise was measured by pattern noise using a microphone installed on the driver's seat window side. 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 less pattern noise and better noise performance.

Uneven wear:
The test tire is mounted on a wheel with a rim size of 18 x 8 JJ, mounted on a four-wheel drive vehicle with an air pressure of 230 kPa, and after traveling a distance of 8000 km (mountain road: 59%, paved road: 41%), between the main grooves The heel and toe wear amount (mm) in the block row was measured.

  As can be seen from Table 1, the tires of Examples 1 to 7 can improve the noise performance related to the pattern noise while maintaining the off-road running performance in comparison with the conventional example, and the occurrence of uneven wear. Was hardly recognized.

  On the other hand, in the tire of Comparative Example 1, since the inclination angle α of the narrow groove was 0 ° and the block shift amount S was 0% of the block side length L, the noise performance improvement effect could not be obtained. In the tire of Comparative Example 2, the off-road running performance was degraded because the inclination angle α of the narrow groove was too large. In the tire of Comparative Example 3, the off-road running performance was degraded because the groove width W of the narrow groove was too narrow.

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 block row | line between the main grooves in the tread pattern of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Land part 3,4 Main groove 5,7 Lug groove 6,8 Block 60,80 Block row 6a Center side block part 6b Outer block part 9 Narrow groove 10,11 Sipe

Claims (5)

  It has a land portion that continuously extends in the tire circumferential direction at the center position of the tread portion, and has two main grooves that extend in the tire circumferential direction in zigzag shapes on both sides of the land portion, and between these main grooves. In a pneumatic tire having a block row composed of a plurality of blocks partitioned by a plurality of connecting lug grooves, each block of the block row has an inclination angle of 5 ° to 12 ° with respect to the tire circumferential direction. It is divided into a central block portion and an outer block portion by a narrow groove whose width is 2% to 4% of the ground contact width, and the central block portion and the outer block portion are formed on the shorter block side facing the lug groove. A pneumatic tire disposed relatively shifted along the extending direction of the narrow groove.   The pneumatic tire according to claim 1, wherein a relative shift amount between the central block portion and the outer block portion is 20% to 40% of a length of a block side facing the narrow groove.   The length Ls of the shorter block side facing the lug groove of the central block part and the outer block part is set to 65% to 85% of the length Ll of the longer block side facing the lug groove. The pneumatic tire according to claim 1 or claim 2.   The pneumatic tire according to any one of claims 1 to 3, wherein at least three sipes are provided in each of the central block portion and the outer block portion. The pneumatic tire according to any one of claims 1 to 4, wherein the central block portion and the outer block portion are shaped symmetrical with respect to each other around an intermediate point in the narrow groove.

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