JP4281863B2 - Pneumatic tire - Google Patents

Description

表１から、本発明タイヤは、ウェット路面でのパターン要素間における制動距離のバラツキが小さく、ウェット制動性を改善できることがわかる。
【００３２】
【発明の効果】
上述したように本発明は、最大ピッチ長さを有するパターン要素を上記のように規定することにより、ウェット路面での制動距離のバラツキを低減し、ウェット制動性を改善することが可能になる。
【図面の簡単な説明】
【図１】 本発明を説明するための空気入りタイヤの一例（参考例）を示すトレッド面の要部展開図である。
【図２】 本発明の空気入りタイヤの一例を示すトレッド面の要部展開図である。
【符号の説明】
１ トレッド面
１Ｃ センター部
１Ｘ ショルダー部
２ 周方向溝
２Ｌ，２Ｍ，２Ｓ 周方向溝部
３，３Ｌ，３Ｍ，３Ｓ ラグ溝
５ ブロック
６，６Ｌ，６Ｍ，６Ｓ パターン要素
８ ブロック列（陸部列）
ＣＬ タイヤセンターライン
Ｌ，Ｍ，Ｓ ピッチ長さ
Ｔ タイヤ周方向[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire in which wet braking performance is improved in a pneumatic tire in which pattern elements are arranged at a variable pitch.
[0002]
[Prior art]
In general, a pneumatic tire employs a tread pattern in which pattern elements having different pitch lengths are continuously provided on the tread surface in the tire circumferential direction in order to improve tire noise due to the tread pattern (for example, Patent Document 1). reference).
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 4-201610
[Problems to be solved by the invention]
However, the pneumatic tire in which the pattern elements are arranged at a variable pitch in this way has a problem that when braking is applied on a wet road surface during high speed running, the braking distance varies and is not constant.
[0005]
An object of the present invention is to provide a pneumatic tire in which variation in braking distance on a wet road surface can be reduced and wet braking performance can be improved in a pneumatic tire in which pattern elements are arranged at a variable pitch. .
[0006]
[Means for Solving the Problems]
The pneumatic tire of the present invention that achieves the above object is a pneumatic tire in which pattern elements having grooves on the tread surface are provided at variable pitches in the tire circumferential direction, and grooves per unit area in the pattern elements having the maximum pitch length. A pneumatic tire having an area larger than a groove area per unit area in a pattern element having a minimum pitch length , wherein one or more circumferential grooves extending in a tire circumferential direction are provided on the tread surface, In at least one circumferential groove of the directional grooves, the groove width of the circumferential groove portion included in the pattern element having the maximum pitch length is the groove width of the circumferential groove portion included in the pattern element having the minimum pitch length. A width of the tread surface is increased by a plurality of lug grooves extending in the tire width direction on the tread surface and the at least one circumferential groove. Block was formed Yoruda unit, characterized in that the maximum pitch length groove width of the circumferential groove portion included in the pattern element having been widely toward the inside of the tire.
[0007]
Thus, by increasing the groove area of the pattern element having the maximum pitch length, the drainage performance of the pattern element having the maximum pitch length can be enhanced. As a result, the braking effect on the pattern elements having the maximum pitch length when traveling on a wet road is increased, so that variations in the braking distance between the pattern elements can be reduced and wet braking performance can be improved.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.
[0009]
FIG. 1 shows an example (reference example) of a pneumatic tire for explaining the present invention, and a tread surface 1 is provided with a plurality of main grooves 2 extending along a tire circumferential direction T. The lug grooves 3 extending along the tire width direction are arranged at variable pitches along the tire circumferential direction T between the main grooves 2 and from the outermost main groove 2 toward the tire outer side. The pattern elements 6 having blocks 5 having different circumferential lengths divided by 3 are formed in a variable pitch in the tire circumferential direction T by the lug grooves 3. CL is a tire center line.
[0010]
In the illustrated example, pattern elements 6L, 6M, and 6S having three types of pitch lengths L, M, and S are provided, and two pattern elements 6L, 6M, and 6S are connected in series. In addition, the pitch length in the block pattern said here is the tire circumferential direction length between the tire circumferential direction one side ends located in the block surface between the blocks 5 adjacent to the tire circumferential direction T, and each pattern element 6 is The block 5 and the lug groove 3 adjacent to the other side in the tire circumferential direction of the block 5 and the main groove portion 2X in the range of the pitch length are provided.
[0011]
In the present invention, in the pneumatic tire in which the pattern elements 6 having grooves as described above are provided at variable pitches along the tire circumferential direction T, the groove area per unit area in the pattern elements 6L having the maximum pitch length L is as follows. The groove area per unit area in the pattern element 6S having the minimum pitch length S is larger .
[0012]
FIG. 1 shows the width of the lug groove 3L included in the pattern element 6L having the maximum pitch length L in each block row (land portion row) 8 divided by the main groove 2, and the minimum pitch length S. The groove area per unit area in the pattern element 6L having the maximum pitch length L is made larger than the groove width of the lug groove 3S included in the pattern element 6S having the pattern element having the minimum pitch length S. It is made larger than the groove area per unit area in 6S.
[0013]
FIG. 2 shows that the groove width of the circumferential groove 2L included in the pattern element 6L having the maximum pitch length L in the circumferential groove 2 is included in the pattern element 6S having the minimum pitch length S instead of the lug groove described above. The groove area per unit area in the pattern element 6S having the minimum pitch length S is set to be larger than the groove width of the circumferential groove portion 2S to be changed to the groove area per unit area in the pattern element 6S having the minimum pitch length S. It is a larger one.
[0014]
In FIG. 2 , the groove width of the circumferential groove 2 </ b> L included in the pattern element 6 </ b> L having the maximum pitch length L is widened in the outer circumferential grooves 2 that divide the center portion 1 </ b > C and the shoulder portions 1 </ b> X. In at least one circumferential groove 2, the groove width of the circumferential groove 2L of the pattern element 6L having the maximum pitch length L is wider than the groove width of the circumferential groove 2S of the pattern element 6S having the minimum pitch length S. I am doing so. The groove width of the circumferential groove 2M included in the pattern element 6M having the intermediate pitch length M is the same as that of the circumferential groove 2S of the pattern element 6S having the minimum pitch length S.
[0015]
As shown in FIG. 2 , when the groove width of the circumferential groove 2L of the pattern element 6L is increased in the circumferential grooves 2 on both outer sides, as shown in the figure, the block 5 facing the tire inside of the circumferential groove 2L By narrowing the width, the groove width of the circumferential groove 2L is increased toward the inside of the tire, so that the falling of the block 5 due to the decrease in the block rigidity of the shoulder portion 1X is suppressed during turning, and the deterioration of the steering stability is avoided. It is good from the point to do.
[0016]
In FIG. 2 , the entire groove width of the circumferential groove 2L of the pattern element 6L having the maximum pitch length L is widened, but instead , the groove width of the circumferential groove 2L may be partially widened. .
[0017]
The groove width of the circumferential groove portion 2L having a wider groove width as described above is preferably 1.1 to 2.5 times the groove width of the circumferential groove portion 2S included in the pattern element 6S having the minimum pitch length S. It should be wide. If the groove width of the circumferential groove 2L is narrower than 1.1 times, it becomes difficult to effectively improve the variation of the braking distance on the wet road surface. Conversely, if the groove width exceeds 2.5 times, the block rigidity becomes uneven. This is not preferable because it causes a decrease in uniformity. Desirably, 1.1 to 1.5 times is good. In the case of partially widely circumferential groove 2L is the value Q / L obtained by dividing the area Q of the circumferential groove portion 2L of the tread surface 1 at the pitch length L and the groove width of the circumferential groove portion 2L.
[0018]
When the circumferential groove 2 is widened as described above, preferably, the circumferential groove portions 2L and 2M of the pattern elements 6L and 6M other than the circumferential groove portion 2S included in the pattern element 6S having the minimum pitch length S are widened. At the same time, the groove widths of the circumferential grooves 2L, 2M, and 2S of the pattern elements 6L, 6M, and 6S are made to have widths corresponding to the pitch lengths L, M, and S of the pattern elements 6L, 6M, and 6S. It is good.
[0019]
Further, when the groove width of the circumferential groove is changed as described above, the total groove volume of the pattern element 6L between the pattern elements 6L and 6M and between the pattern elements 6M and 6S (in the illustrated example, the total groove volume in the pattern element 6L). The total volume of the circumferential groove 2L and all the lug grooves 3L) is made 3% or less larger than the total element groove volume of the pattern element 6M, and the total element groove volume of the pattern element 6M is 3% higher than the total element groove volume of the pattern element 6S. It is preferable that the difference is made to be 3% or less by increasing the total groove volume between adjacent pattern elements having a pitch length of 3% or less.
[0020]
When the difference exceeds 3%, the uniformity is deteriorated due to non-uniform block rigidity. Preferably, it should be 1% or less.
[0021]
As a method of making the groove volume different in this way, the groove wall angle of the circumferential groove 2 is increased or decreased, the depth of the lug groove 3 is decreased, and the length of the lug groove 3 is decreased. It can be easily handled by adjusting the
[0022]
As a result of intensive studies on the cause of uneven braking distance on the wet road surface during high-speed running in the pneumatic tire in which the pattern elements are arranged at a variable pitch, the present inventors have found the following.
[0023]
When braking is applied to a tire having a pattern element having a large pitch length when driving at high speed on a wet road surface, the braking distance is increased, and conversely, if braking is applied to a tire having a pattern element having a small pitch length, the braking distance is shortened. .
[0024]
Therefore, in a pneumatic tire in which pattern elements are arranged at a variable pitch, if braking is applied while a pattern element with a small pitch length is mainly in contact with the ground, a braking distance is shortened, and conversely a pattern with a large pitch length. If braking is applied when the element is mainly grounded, the braking distance becomes longer.
[0025]
That is, in a pneumatic tire in which pattern elements are arranged at a variable pitch, the variation in the braking distance largely depends on which pattern element is in contact with the ground at the start of braking.
[0026]
Based on such knowledge, as described above, the groove area per unit area in the pattern element 6L having the maximum pitch length L is made larger than the groove area per unit area in the pattern element having the minimum pitch length L. . Thereby, in the pattern element 6L having the maximum pitch length L, drainage can be improved, so that the braking effect in the pattern element 6L is increased during high-speed driving on a wet road, and therefore the braking distance between the pattern elements 6 is increased. Variations can be reduced and wet braking performance can be improved.
[0027]
The present invention can be preferably used particularly for passenger car pneumatic tires, but is not limited thereto, and can also be applied to heavy duty pneumatic tires.
[0028]
【Example】
And a common tire size 205 / 65R15, 1.5 times the maximum pitch groove width of the circumferential groove included the groove width of the circumferential groove portion included in the pattern element having a length in the pattern element having a minimum pitch length The tire of the present invention configured as shown in FIG. 2 and the conventional tire in which the groove width of the circumferential groove in the tire of the present invention is not widened were produced.
[0029]
Each of these test tires is mounted on a rim with a rim size of 15 x 6.5 JJ, mounted on a passenger car (with ABS device) with a pneumatic pressure of 190 kPa and a displacement of 3 liters. As a result, the results shown in Table 1 were obtained.
[0030]
Wet braking performance On a wet road surface with an average depth of 1 mm, an ABS braking test (according to the actual vehicle test method for passenger cars with JASO-C465 ABS) is performed at an initial speed of 100 km / h, and the braking distance is an index value with the conventional tire as 100 evaluated. The larger this value, the smaller the variation in the braking distance between pattern elements on the wet road surface, and the more stable the wet braking performance is.
[0031]
[Table 1]

From Table 1, it can be seen that the tire of the present invention has little variation in the braking distance between the pattern elements on the wet road surface and can improve wet braking performance.
[0032]
【The invention's effect】
As described above, in the present invention, by defining the pattern element having the maximum pitch length as described above, it is possible to reduce the variation in the braking distance on the wet road surface and to improve the wet braking performance.
[Brief description of the drawings]
FIG. 1 is a development of a main part of a tread surface showing an example (reference example) of a pneumatic tire for explaining the present invention.
FIG. 2 is a development of a main part of a tread surface showing an example of a pneumatic tire according to the present invention.
[Explanation of symbols]
1 tread surface 1C center portion 1X shoulder second circumferential grooves 2L, 2M, 2 S circumferential groove portion 3,3L, 3M, 3S lug groove 5 blocks 6,6L, 6M, 6S pattern elements
8 block train (Land part train)
CL Tire center line L, M, S Pitch length T Tire circumferential direction

Claims (4)

In a pneumatic tire in which pattern elements having grooves on the tread surface are provided at a variable pitch in the tire circumferential direction,
A pneumatic tire in which the groove area per unit area in the pattern element having the maximum pitch length is larger than the groove area per unit area in the pattern element having the minimum pitch length ,
One or more circumferential grooves extending in the tire circumferential direction are provided on the tread surface, and the circumference included in the pattern element having the maximum pitch length in at least one circumferential groove of the circumferential grooves. The groove width of the direction groove portion is wider than the groove width of the circumferential groove portion included in the pattern element having the minimum pitch length,
In addition, the at least one circumferential groove and a plurality of lug grooves extending in the tire width direction on the tread surface form a block on a shoulder portion of the tread surface, and are included in the pattern element having the maximum pitch length. A pneumatic tire in which the groove width of the circumferential groove is increased toward the inside of the tire. The groove width of the circumferential groove portion included in the pattern element having the maximum pitch length is 1.1 to 2.5 times wider than the groove width of the circumferential groove portion included in the pattern element having the minimum pitch length. the pneumatic tire according to 1. The pneumatic tire according to claim 1 or 2 , wherein a groove width of a circumferential groove portion included in each pattern element is widened according to a pitch length of each pattern element. The pneumatic tire according to claim 1 , 2 or 3 , wherein a difference in element total groove volume between adjacent pattern elements having a pitch length is 3% or less.

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