JP4565710B2 - Pneumatic tire - Google Patents

Description

【００２６】
【表２】

【００２７】
【表３】

【００２８】
表３によれば、リブ隅部に面取りだけを施した従来タイヤ２および、リブの側部部分に細溝だけを設けた従来タイヤ３においても転がり抵抗、偏摩耗およびウェット横力のそれぞれに効果があるが、二つの技術を併用した実施例タイヤは、偏摩耗比を悪化させることなく、転がり抵抗およびウェット性能に一層有効であることが解かる。
【００２９】
これに対して比較タイヤ１〜８を用いて細溝の長さ、開口幅、深さおよび配設間隔について検討した結果、それらの値が請求項で特定する範囲を外れた場合には、上記効果が相対的に低下することがわかる。
【００３０】
【発明の効果】
かくして、この発明によれば、陸部隅部の面取りと、陸部の側部部分に設けた細溝とにより、面取り部分の早期の摩耗なしに、操縦安定性およびウェット性能を向上させるとともに、転がり抵抗の増加を有利に防止することができる。
【図面の簡単な説明】
【図１】 この発明の実施の形態を、トレッド半部について示す幅方向断面図である。
【図２】 一のリブの斜視図である。
【図３】 細溝の拡大断面図である。
【図４】 細溝を示す斜視図である。
【符号の説明】
１ トレッド踏面
２，３ 主溝
４，５，６ リブ
５ａ リブ側壁
７，８，９，１０ 隅部
７ａ，８ａ，９ａ，１０ａ 面取り表面
１１，１２ 細溝
Ｑ１，Ｑ２，Ｑ３，Ｑ４ リブ縁
Ｌ１，Ｌ２，Ｌ３，Ｌ４ 幅
Ｈ１，Ｈ２，Ｈ３，Ｈ４ 深さ
Ｌ 延在長さ
Ｈ 主溝深さ
Ｄ 深さ
ｗ 開口幅
Ｐ 配設ピッチ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire applied to a vehicle such as a passenger car, a bus, and a truck having a tread pattern based on a land portion, for example, a rib, which is divided by a circumferential groove provided on a tread surface. Especially, the cross-sectional shape of the rib is changed from the conventional shape according to the contact area shape of the tread surface, and excellent wear is achieved by providing a narrow groove in the rib side part in the width direction of the rib. Under the characteristics, the driving stability for the dry and wet treads is improved, and the rolling resistance is improved.
[0002]
[Prior art]
When a tire with a circumferential groove on the tread surface rolls while touching the road surface and supporting a load, the land portion separated by the circumferential groove, for example, the side portion of the rib, is the center of the rib. It is known that it is subjected to a large shear strain in the width direction compared to the part, and such strain concentration on the side part of the rib results in an increase in rolling resistance, a decrease in wet performance, a decrease in steering stability, etc. In addition, it is also known that the strain concentration portion causes abnormal wear that wears out particularly quickly.
[0003]
For this reason, a proposal has been made to solve the above problem by forming the side part of the rib into a convex curved surface and suppressing the concentration of distortion thereto, On the contrary, depending on the specific method, there is a problem that the side portion of the rib is more rapidly worn, and as a result, steering stability, rolling resistance and the like are deteriorated.
[0004]
Therefore, when the cause of this early wear was investigated, the uneven wear that occurs when the rib side portions are formed in a convex curved surface is caused by the difference in the ground contact length of the rib side portions due to the difference in diameter. Since it becomes shorter than the contact length of the portion, it has been clarified that the side portion is caused by dragging with respect to the road surface and large circumferential shear deformation.
[0005]
[Problems to be solved by the invention]
In consideration of this, the applicant firstly made the shape of the side portion mainly for the purpose of preventing premature wear of the side portion of the rib against the tire input when the vehicle is traveling straight ahead. Japanese Patent Application No. 2000-105467 has proposed a pneumatic tire determined based on the relationship with the opposite side portion of the same rib, the relationship with the side portion of the rib separating the grooves, and the relationship with the ground contact shape.
[0006]
By the way, considering the steering stability when the vehicle turns on a curved road or the like, a larger shearing strain in the width direction due to the turning lateral force is concentrated on the side portion of the rib when turning. Therefore, if the distortion is to be reduced only by the applicant's previously proposed technique, it is necessary to make the side portion of the rib have a more rounded cross-sectional shape, and hence the above-mentioned diameter difference. There was a problem that early wear of the side portions of the ribs was unavoidable.
[0007]
The present invention has been made in view of such problems, and effectively prevents early abnormal wear of the side portion of the land portion for both straight traveling and turning traveling of the vehicle, and also stabilizes steering. The present invention provides a pneumatic tire capable of greatly improving performance and wet performance and effectively suppressing an increase in rolling resistance.
[0008]
[Means for Solving the Problems]
The pneumatic tire according to the present invention includes at least one main groove formed on the tread surface and continuously extending in the circumferential direction, and a land portion partitioned by the main groove. Chamfering is performed on each of the opposite corners of each land portion according to the contact length of each land edge at the tread surface contact area. The product of the width in the section width direction and the depth in the tire radial direction is a magnitude relationship corresponding to each of the contact lengths. For example, when the contact lengths are equal, the products are also made equal. On the other hand, when the ground contact length on one side is longer than that on the other side, the product on one side is made larger than the product on the other side, and further, the chamfered side portion of the land portion Open in the land side wall facing the width direction of the land part Both the thin groove extending in the main groove bottom direction, spaced in the tread circumferential direction, the opening width of the thin groove is made as a 0.5 to 2.5 mm.
[0009]
The tread surface contact area here refers to the contact area when the maximum load capacity is applied under the maximum air pressure specified in the JATMA YEAR BOOK.
[0010]
In this pneumatic tire, the technology disclosed in Japanese Patent Application No. 2000-105467 according to the applicant's previous proposal, that is, more specifically, at the corners facing each other of the land portions separating the main grooves. Based on the technology of chamfering the size relationship of the contact length at each land edge, by matching the size relationship of the product of the width in the land portion width direction of the chamfer and the height in the radial direction of the tire, In the place where chamfering was performed so that the width direction shear strain can be effectively reduced while removing the rubber in the portion that causes the width direction shear strain by the straight state input and suppressing the early wear due to the diameter difference in the straight state. A narrow groove that opens in the land side wall is cut in the land side wall, and a larger width is generated by lateral force during turning without changing the ground contact length by removing the rubber in the land. Absorbs directional shear strain As a result, the lateral force is effectively suppressed while suppressing the generation of the circumferential shear force due to the difference in the contact length, which occurs when the large width direction shear strain due to the lateral force is absorbed only by chamfering. It reduces the shear strain in the width direction at the time, ensures high wear performance regardless of whether it goes straight or turning, and can effectively improve each of rolling resistance, wet performance, and steering stability.
[0011]
Wherein preferably, the narrow groove, the extending length in the tire radial direction, shall be the 0.6 to 0.9 times the main groove depth.
[0012]
If the extension length of the narrow groove is less than 0.6 times, the amount of rubber to be removed is small, the distortion cannot be reduced sufficiently, and the narrow groove is relatively early as the wear of the land portion progresses. Will disappear. On the other hand, if it exceeds 0.9 times, the rigidity in the circumferential direction of the land portion will be insufficient, and early wear will occur in the portion of the land portion where the narrow groove is provided.
[0013]
The opening width of the narrow groove is 0.5 to 2.5 mm. If the narrow groove opening width is less than 0.5 mm, the amount of rubber to be removed is too small, and if it exceeds 2.5 mm, the ground contact area at the side part of the land will decrease and the contact pressure will increase. This will cause premature wear.
[0014]
And it is preferable to make the depth of such a narrow groove in the land part width direction into the range of 1-2 mm. If it is less than 1 mm, the amount of rubber to be removed is too small, and if it exceeds 2 mm, the ground contact area of the land side portion will be too small.
[0015]
Furthermore, it is preferable that the arrangement pitch of the narrow grooves is in the range of 5 to 30 times the narrow groove opening width. That is, if it is less than 5 times, the ground contact area is too small, and if it exceeds 30 times, the amount of rubber to be removed is too small, and it is difficult to ensure the effectiveness of providing the narrow groove.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a cross-sectional view in the tread width direction showing an embodiment of the present invention with respect to a half portion of the tread.
This is provided with two main grooves 2 and 3 extending continuously in a straight line in the tread circumferential direction in each half of the tread tread surface 1, respectively. The ribs 4, 5, 6 are divided into land portions, for example, and the corners 7, 8, 9, 10 of these ribs 4, 5, 6 facing each other across the main grooves 2, 3 are chamfered. Thus, each of the chamfered surfaces 7a, 8a, 9a, and 10a is a curved surface that is convex outward.
[0017]
In carrying out such chamfering, here, the ribs 4, 5, 6 before chamfering are grounded in the tread tread surface contact area of the rib edges Q1, Q2, Q3, Q4 located across the main groove. The lengths, that is, the respective contact lengths Q1L, Q2L, Q3L, and Q4L when the maximum load capacity is loaded are obtained in advance. , Widths L1, L2, L3, and L4 measured in the land width direction, and the lengths to the rib edges Q1, Q2, Q3, and Q4 in the figure and depths H1, H2, H3, and H4 measured in the radial direction. In the figure, the respective widths L1, L2, L2 × H1, L2 × H2, L3 × H3, L4 × H4 are equal to each other so that the products L1 × H1, L2 × H2, L3 × H3, L4 × H4 are equal to each other. L3, L4 and depth H1 H2, H3, H4 to select.
Here, when there is a difference in the ground contact lengths Q1L, Q2L, Q3L, and Q4L, the dimensions are determined so that the respective products described above become large and small according to the length of each ground contact length. .
[0018]
In addition, here, as shown in FIG. 2 by taking a single rib 5 as an example, the rib 5 is cut into a chamfered side portion in the width direction of the rib 5 and opened to the rib side wall 5a. The grooves 11 and 12 are provided so as to extend in the groove bottom direction of the main grooves 2 and 3. Preferably, as shown in a partially enlarged cross-sectional view in FIG. 3, these narrow grooves 11 and 12 are arranged in the tire radial direction. The extension length L is set to a range of 0.6 to 0.9 times the main groove depth H. And preferably, the depth D of the narrow grooves 11 and 12 in the rib width direction is set to 1 to 2 mm.
[0019]
As shown in FIG. 4, the narrow grooves 11 and 12 are formed so that the opening width w is in the range of 0.5 to 2.5 mm . Moreover, it is preferable to form so that the arrangement pitch P of the narrow grooves 11 and 12 is in the range of 5 to 30 times the opening width w.
[0020]
According to the tire configured as described above, as described above, the chamfered portion is caused by the difference in diameter of the chamfered portion even though the original function of reducing the shear stress in the width direction is sufficiently exhibited. Effectively prevent premature wear based on the function of reducing the shear strain in the width direction due to the narrow groove, advantageously improving the steering stability and wet function, and also effectively preventing the increase in rolling resistance. Can do.
[0022]
【Example】
In a truck tire having a size of 11R22.5 in which four circumferential main grooves are formed symmetrically on the tread surface,
Conventional tire 1 shall be such that the rib contour line coincides with the tread tread surface contour line, no chamfering and no narrow groove,
The conventional tire 2 is configured so that L1 × H1 <L2 × H2 <L3 × H3 <L4 × H4 under the relationship of Q1L <Q2L <Q3L <Q4L of the ground contact length of each rib edge, respectively. Chamfered at the rib corner of
The conventional tire 3 is provided with a narrow groove in the side portion of each rib of the conventional tire 1.
Specific numerical values of the conventional tire 2 are shown in Table 1.
[0023]
With respect to these tires, second tires (ribs 5 in FIG. 1) were constructed according to the present invention, and each of the example tires and comparative tires had the structure shown in Table 2.
The structure of the chamfered portion was the same as that of the conventional tire 2.
Each of these tires is mounted on a rim of 7.5 × 22.5, the filling air pressure is set to 700 kPa, the load is set to 25.0 kPa, and the rolling resistance test, the uneven wear drum test, and the wet lateral force test are performed. Each of them.
The results are shown in Table 3.
[0024]
The value displayed as an index in Table 3 is 100 for the conventional tire 1. The smaller the rolling resistance value, the smaller the resistance value, which is advantageous for fuel saving. The uneven wear ratio is a ratio of the rib side partial wear amount (larger side) to the wear amount of the rib center of the second rib. The closer this value is to 1.0, the more uniform wear is represented.
[0025]
[Table 1]

[0026]
[Table 2]

[0027]
[Table 3]

[0028]
According to Table 3, in the conventional tire 2 in which only the chamfered corners of the ribs and the conventional tire 3 in which only the narrow grooves are provided in the side portions of the ribs, the rolling resistance, the partial wear, and the wet lateral force are effective. However, it can be seen that the example tire using the two techniques in combination is more effective in rolling resistance and wet performance without deteriorating the uneven wear ratio.
[0029]
On the other hand, as a result of examining the length, opening width, depth and arrangement interval of the narrow grooves using the comparative tires 1 to 8, when those values are outside the range specified in the claims, the above It turns out that an effect falls relatively.
[0030]
【The invention's effect】
Thus, according to the present invention, the chamfering at the corner of the land portion and the narrow groove provided in the side portion of the land portion improve the steering stability and the wet performance without the early wear of the chamfered portion, An increase in rolling resistance can be advantageously prevented.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view in the width direction showing a tread half according to an embodiment of the present invention.
FIG. 2 is a perspective view of one rib.
FIG. 3 is an enlarged sectional view of a narrow groove.
FIG. 4 is a perspective view showing a narrow groove.
[Explanation of symbols]
1 tread surface 2, 3 main groove 4, 5, 6 rib 5a rib side wall 7, 8, 9, 10 corner 7a, 8a, 9a, 10a chamfer surface 11, 12 narrow groove Q1, Q2, Q3, Q4 rib edge L1 , L2, L3, L4 Width H1, H2, H3, H4 Depth L Extension length H Main groove depth D Depth w Opening width P Arrangement pitch

Claims (4)

A main groove formed on the tread surface and continuously extending in the circumferential direction, and a land portion divided by the main groove,
Depending on the contact length of each land edge that is located across the main groove in the treading area, chamfering is performed on the opposite corners of each land area, and the land area of each chamfer is The product of the width in the width direction and the depth in the tire radial direction has a magnitude relationship corresponding to each of the contact lengths, and the width of the land portion is chamfered on the side portion of the land portion. A narrow groove that opens in the side wall of the land and extends in the bottom direction of the main groove is provided at intervals in the tread circumferential direction, and the opening width of the narrow groove is 0.5 to 2.5 mm. tire.  The pneumatic tire according to claim 1, wherein the extending length of the narrow groove in the tire radial direction is 0.6 to 0.9 times the depth of the main groove. The pneumatic tire according to claim 1 or 2 , wherein the depth of the narrow groove in the land portion width direction is 1 to 2 mm. The pneumatic tire according to any one of claims 1 to 3 , wherein the arrangement pitch of the narrow grooves is 5 to 30 times the opening width of the narrow grooves.

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