JP2008296859A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire having improved pattern noise without worsening steering stability and road noises. <P>SOLUTION: Lug grooves 3 are arranged in a tread surface 1 at variable pitches in a tire peripheral direction T to form a plurality of types of pattern elements A, B, C, D. Small holes 6 are arrayed in the tread surface 1 in one line at predetermined spaces in the tire peripheral direction T. In the small holes 6 in one line, the ratio La/L is different of a pitch length L of each of the pattern elements A, B, C of a land portion 4Aa in which the small holes 6 are arranged, to a tire peripheral distance La between the width center of one lug groove 3X out of both front and rear lug grooves 3X, 3Y in the tire peripheral direction, adjacent to the land portion 4Aa having the pattern elements A, B, C, and an opening center 6x of the small hole 6. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire in which pattern noise is improved without deteriorating steering stability and road noise.

  Generally, a pneumatic tire has a tread surface in which lug grooves extending in the tire width direction are arranged at variable pitches in the tire circumferential direction, and a plurality of types of pattern elements having different pitch lengths are arranged in the tire circumferential direction by the lug grooves. The pattern is adopted. Thus, by varying the length of the pattern elements constituting the tread pattern, there is an effect of dispersing the noise frequency and reducing the tire noise.

Conventionally, in the pneumatic tire as described above, a technique is known in which small holes are arranged in the tire circumferential direction on a ground contact surface of a land portion such as a block of pattern elements (see, for example, Patent Document 1). As a result, the vertical rigidity can be lowered while securing the lateral rigidity of the land portion, so that there is an advantage that road noise (sound of the land portion hitting the road surface) and the like can be improved while maintaining the steering stability. . However, when the small holes are provided in this way, there is a problem that an air pumping sound is generated by the small holes, and the pattern noise in the 500 Hz band due to the arrangement of the small holes is deteriorated.
JP 2006-76338 A

  An object of the present invention is to provide a pneumatic tire capable of improving pattern noise without deteriorating steering stability and road noise.

  The pneumatic tire of the present invention that achieves the above-mentioned object has a land portion that is divided by the lug grooves and has a land portion that is divided by the lug grooves, and that has lug grooves that extend in the tire width direction on the tread surface. A plurality of types of pattern elements having different L are arranged in the tire circumferential direction, and at least one row of small holes are arranged in the tire circumferential direction at predetermined intervals on the tread surface, and the small holes are arranged at least in the plurality of types of pattern elements. The center of the width of one lug groove and the center of the opening of the small hole are arranged in the land part of some pattern elements and adjacent to the land part of the pattern element in which the small holes are arranged. The ratio La / L of the tire circumferential distance La between the two and the pitch length L of the pattern element in which the small holes are arranged is different in the small holes in the same row.

  According to the above-described present invention, since the relative positions of the small holes are made different in the pattern element in which the small holes are arranged, the frequency generated by the small holes is dispersed due to the pitch variation effect of the small holes, and the small holes are arranged. The resulting pattern noise in the 500 Hz band can be suppressed.

  On the other hand, since the position of the small hole only needs to be changed in the tire circumferential direction, the lateral rigidity and the vertical rigidity of the land portion of the pattern element are not greatly affected. Therefore, the same level of steering stability and road noise performance as in the prior art can be ensured, and pattern noise can be improved without deteriorating steering stability and road noise.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows an embodiment of a pneumatic tire according to the present invention, where 1 is a tread surface and CL is a tire equator surface. A rib 4 and a block 5 are formed on the tread surface 1 by a plurality of circumferential grooves 2 extending in the tire circumferential direction T and lug grooves 3 extending in the tire width direction. The lug grooves 3 are arranged at variable pitches in the tire circumferential direction T, and a plurality of types of pattern elements A, B, and C having different pitch lengths L are formed on the tread surface 1 by the lug grooves 3. The pitch length L of the pattern element A is the longest, the pitch length L of the pattern element B is then long, and the pitch length L of the pattern element C is the shortest.

  Each pattern element A, B, C is a rib portion (land) separated by a lug groove 3 provided on the ground contact surface 4a of the rib 4A located in the shoulder region 1S between the circumferential groove 2A and one tread end 1X. Part) 4Aa has one circular small hole 6 respectively. The small holes 6 are arranged in a row at a predetermined interval in the tire circumferential direction T on the tread surface 1. The arrangement of the small holes 6 in a line means a state in which each small hole 6 is in contact with the virtual line k when the virtual line k is drawn in parallel with the tire equatorial plane CL. It is not always necessary to pass through the opening center of the hole 6.

  Pitch length L of each pattern element A, B, C in which the small holes 6 are arranged (distance in the tire circumferential direction between the width centers of both lug grooves 3X, 3Y before and after the tire circumferential direction dividing the pattern elements A, B, C) ), The opening center 6x (the center of the opening on the tread surface 1) of the small hole 6 arranged in the rib portion 4Aa of the pattern elements A, B, and C and one of the lug grooves 3X of the lug grooves 3X and 3Y. The ratio La / L to the tire circumferential direction distance La to the width center is different in the small holes 6 in one row (same row).

  The present inventor examined the noise generated in the tire of the tread pattern in which the small holes are arranged in the tire circumferential direction. The noise of the 125 Hz band, that is, the road noise can be reduced, but on the other hand, the noise of the frequency of 500 Hz is reduced. I found it to be higher. This is a deterioration of the primary pitch component in the pattern noise.

  Therefore, attention was paid to the positions of the small holes provided in the pattern elements. When the pattern noise was measured by shifting the positions of the arranged small holes in the tire circumferential direction in the pattern element, when the relative position in the pattern element was changed, the pitch variation effect of the small holes caused the small holes. It was found that the generated frequency was dispersed and the noise in the 500 Hz band was reduced.

  Therefore, in the present invention, as described above, the values of the ratio La / L are made different in the row of small holes 6 without making them the same. In addition, since it is only necessary to change the position of the small hole 6 in the tire circumferential direction T, the lateral rigidity and vertical rigidity of the rib portion 4Aa are not greatly affected. Accordingly, it is possible to ensure the same level of steering stability and road noise performance as before, and to improve the 500 Hz band pattern noise caused by the arrangement of the small holes 6 without deteriorating the steering stability and road noise. it can.

  In the above embodiment, the number of types of values having different ratios La / L can be the same as the number of types of pattern elements A, B, and C. In the above example, there are three types of pattern elements A, B, and C, and therefore the number of types of values having different ratios La / L is three.

  In this case, the value of the ratio La / L is maximized in the pattern element A having the largest pitch length L, and then the ratio La / L in the pattern element B having the longest pitch length L is increased. The ratio La / L in the short pattern element C can be minimized, and the value of the ratio La / L can be decreased as the pattern element has a shorter pitch length L. Note that La is a tire circumferential distance between the opening center 6x of the small hole 6 and the width center of the one lug groove 3X as described above. Here, one lug groove 3X has a pitch length. In the small hole 6 of the pattern element A having the maximum L, the lug groove is the one having the longer tire circumferential distance La. In the example illustrated in FIG. 1, the lug groove 3 adjacent to the upper side of the pattern element A is one lug groove 3 </ b> X as illustrated.

  Alternatively, instead of the above configuration, the number of types of values having different ratios La / L may be different from the number of types of pattern elements A, B, and C. In the example of the three types of pattern elements A, B, and C described above, the number of types of values having different ratios La / L can be set to a number other than 3, for example, 4 or 5, 2 or the like. In this case, the small holes 6 are arranged so that the values of the ratio La / L are randomly arranged in the tire circumferential direction T.

  The difference between the maximum value and the minimum value of the ratio La / L is set to 0.2 or more in order to effectively suppress pattern noise. The upper limit of the difference between the maximum value and the minimum value of the ratio La / L is any range as long as the distance in the tire circumferential direction from the lug grooves 3X, 3Y before and after the tire circumferential direction to the small hole 6 can be secured at least 4 mm. It may be a value. When the tire circumferential direction distance is less than 4 mm, the distance between the small holes 6 and the lug grooves 3 becomes too close, so that the primary pitch component is not dispersed and the effect of suppressing pattern noise cannot be obtained. Also, uneven wear tends to occur.

  FIG. 2 shows another embodiment of the pneumatic tire according to the present invention. The pattern element A having the maximum pitch length L without the small holes 6 being arranged in the pattern elements A, B and C, and It is arranged on the rib portion 4Aa of the pattern element B having the long pitch length L and not arranged on the pattern element C having the shortest pitch length L. Other configurations are the same as those of the tire shown in FIG. Even when the small holes 6 are arranged in the rib portions 4Aa of at least some of the pattern elements A, B, and C, the small holes 6 are configured as described above. The same effect can be obtained.

  When the small holes 6 are arranged in at least some of the pattern elements A and B in this way, in order to make the rigidity uniform, when the pitch length L is different by three or more types, at least the pattern having the maximum pitch length L is used. The small holes 6 can be arranged in the element A and then the pattern element B having the longest pitch length L. Preferably, a small hole 6 is provided in each pattern element except the pattern element having the shortest pitch length L.

  In such a case, the number of types having different values of the ratio La / L can be the same as the number of types of pattern elements A and B in which the small holes 6 are arranged. In the above example, since the number of types of pattern elements A and B in which the small holes 6 are arranged is 2, the number of types of values having different ratios La / L is 2. Similarly, the number of types having different values of the ratio La / L can be made different from the number of types of pattern elements A and B in which the small holes 6 are arranged.

  3 and 4 show still another embodiment of the pneumatic tire of the present invention. In both the embodiments, the small holes 6 arranged in one row along the tire circumferential direction T are further arranged in a plurality of rows in the tire width direction.

  In the pneumatic tire shown in FIG. 3, small holes 6 are arranged in the blocks 5 of both shoulder regions 1S and the ribs 4 in the center region, and the small holes 6 are arranged in four rows in the tire circumferential direction T at predetermined intervals. Further, in the tire shown in FIG. 3, five types of pattern elements A, B, C, D, and E having different pitch lengths are formed by the lug grooves 3 arranged at a variable pitch in the tire circumferential direction T.

  When a plurality of rows of small holes 6 are arranged in this manner, it is preferable to configure the small holes 6 in each row as described above, but the effect can also be obtained by making at least one row of small holes 6 as described above. be able to.

  In the pneumatic tire shown in FIG. 4, two rows of small holes 6 are arranged on the ground contact surface 4a of the same rib 4A. Of the two rows of small holes 6, the small holes 6a arranged on the tire center side are not arranged in the pattern elements A, B, C, but are arranged in the rib portions 4Aa of every other pattern element. Yes. Even when the small holes 6a are arranged in this way, the effect of suppressing pattern noise caused by the arrangement of the small holes 6a can be obtained by configuring the small holes 6a in the same row as described above.

  Further, as shown in FIG. 4, the plurality of small holes 6 arranged in the same pattern element do not overlap when viewed from the tire width direction, but are arranged at positions shifted in the tire circumferential direction T. The pattern noise due to the arrangement of the holes 6 may be further improved.

  In the present invention, the small holes 6 are preferably circular as shown in the figure, but are not limited thereto, and may be oval or polygonal. In that case, the opening center 6x of the small hole 6 is the position of the center of gravity in the small hole opening shape.

The size of the small hole 6 is preferably such that the area at the opening is in the range of 3 to 40 mm ² . If the opening area of the small hole 6 is smaller than 3 mm ² , the vertical rigidity of the land portion cannot be effectively reduced by the small hole 6, so that the road noise reduction effect by the small hole 6 cannot be obtained. When the opening area of the small hole 6 exceeds 40 mm ² , the lateral rigidity of the land portion is lowered, and the steering stability is lowered. Also, the problem of stone biting is likely to occur.

  The depth of the small hole 6 is set to 40% or more of the maximum groove depth of the circumferential groove and the lug groove, while ensuring the lateral rigidity of the land portion provided with the small hole 6 while maintaining the lateral rigidity. It is good in lowering. The upper limit value is preferably 100% or less of the maximum groove depth because there is a possibility of interference with the structural member disposed inside.

  As the types of pattern elements having different pitch lengths L, 2 to 5 types are preferable from the viewpoint of the pitch variation effect.

  In the said embodiment, although the example which provided the small hole 6 in rib part 4Aa was shown, the tire which provided the small hole 6 in the land part which consists of the block 5 may be sufficient.

  Although this invention can be preferably used especially for the pneumatic tire for passenger cars, it is not limited to it.

  The tire size is 215 / 60R16, the tread pattern is the same in FIG. 1, two kinds of pattern elements having different pitch lengths L are alternately arranged, small holes are provided in the rib portions of each pattern element, and the ratio La / L is set. Invention tire 1 and comparative tire 1 as shown in Table 1 were prepared as test tires, respectively.

  Each of these test tires was mounted on a standard rim, the air pressure was set to 220 kPa, and road noise, pattern noise, and steering stability were evaluated by the following method. The results shown in Table 1 were obtained.

Road noise Each test tire is mounted on a test vehicle (FR vehicle) with a displacement of 2500 cc, and in a test course with rough roads, the noise inside the test vehicle is set at the right window of the driver's seat when the test vehicle runs straight at 60 km / h. The result was shown as an index value with the comparative tire as 100. The smaller this value, the lower the road noise.

Pattern noise When each test tire is mounted on a drum testing machine and driven on a rotating drum at a speed of 60 km / h, the sound pressure level of 500 Hz is 1 m laterally from the test tire and high from the ground contact surface of the rotating drum and the test tire. The measurement was made with a microphone installed at a position of 0.25 m, and the result was shown as an index value with the comparative tire as 100. The smaller this value, the lower the pattern noise.

Steering stability A sensory test by a test driver is performed on the circuit course, and the evaluation result is shown as an index value with a comparative tire as 100. The larger this value, the better the steering stability.

  From Table 1, it can be seen that the tire 1 of the present invention can improve pattern noise without deteriorating steering stability and road noise.

  The tire size and tread pattern are the same as in Example 1, five types of pattern elements having different pitch lengths L are arranged, and small holes are arranged in the rib portions of the pattern elements other than the pattern elements having the shortest pitch length L. Inventive tire 2 and comparative tire 2 having a ratio La / L as shown in Table 2 were prepared as test tires, respectively.

  When each of these test tires was evaluated for road noise, pattern noise, and steering stability in the same manner as in Example 1, the results shown in Table 2 were obtained.

  From Table 2, it can be seen that the tire 2 of the present invention can improve pattern noise without deteriorating steering stability and road noise.

  The tire size and tread pattern are the same as those in Example 1, five types of pattern elements having different pitch lengths L are arranged, and the ratio La / L is 0.60, 0.50, 0.45, 0.40, 0. The tire 3 of the present invention and the comparative tire 3 in which the values of the ratio La / L were arranged at random were prepared as test tires. In the comparative tire 3, the ratio La / L is constant at 0.50.

  When these test tires were subjected to road noise, pattern noise, and steering stability evaluation tests in the same manner as in Example 1, the results shown in Table 3 were obtained.

  From Table 3, it can be seen that the tire 3 of the present invention can improve pattern noise without deteriorating steering stability and road noise.

It is a principal part expanded view of the tread surface which shows one Embodiment of the pneumatic tire of this invention. It is a principal part expanded view of the tread surface which shows other embodiment of the pneumatic tire of this invention. It is a principal part expanded view of the tread surface which shows other embodiment of the pneumatic tire of this invention. It is the partial expanded view of the tread surface which shows other embodiment of the pneumatic tire of this invention.

Explanation of symbols

1 tread surface 2 circumferential groove 3, 3X, 3Y lug groove 4, 4A rib 4Aa rib portion (land)
5 blocks (Land)
6, 6a Small hole 6x Center of opening A, B, C Pattern element T Tire circumferential direction

Claims (6)

  Lug grooves extending in the tire width direction are arranged on the tread surface at a variable pitch in the tire circumferential direction, and plural types of pattern elements having land portions divided by the lug grooves and having different pitch lengths L are arranged in the tire circumferential direction. On the other hand, at least one row of small holes is arranged in the tire circumferential direction at a predetermined interval on the tread surface, and the small holes are arranged on land portions of at least some pattern elements of the plurality of types of pattern elements. The tire circumferential direction distance La between the center of the width of one lug groove of both the lug grooves before and after the tire circumferential direction adjacent to the land portion of the pattern element in which the hole is disposed, and the small hole A pneumatic tire in which the ratio La / L to the pitch length L of the arranged pattern elements is varied in the small holes in the same row.   If the pitch length L differs by three or more types in the land portion of each pattern element, at least the pattern element having the largest pitch length and then the land portion of the pattern element having the longest pitch length, the small holes The pneumatic tire according to claim 1, wherein:   The number of types of different values of the ratio La / L is the same as the number of types of pattern elements in which the small holes are arranged, and the value of the ratio La / L is maximized in the pattern element having the maximum pitch length, and the short pitch The pneumatic tire according to claim 2, wherein the pattern element having a length has a smaller ratio La / L.   The number of types of different values of the ratio La / L is different from the number of types of pattern elements in which the small holes are arranged, and the small holes are arranged so that the values of the ratio La / L are randomly arranged in the tire circumferential direction. 2. The pneumatic tire according to 2.   The difference between the maximum value and the minimum value of the ratio La / L is 0.2 or more, and the distance in the tire circumferential direction from both lug grooves to the small hole in the tire circumferential direction is at least 4 mm. Or the pneumatic tire of 4.   The pneumatic tire according to any one of claims 1 to 5, wherein the small holes are arranged in a plurality of rows in the tire width direction, and the small holes in the same pattern element are shifted in the tire circumferential direction.

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