JP4275257B2 - Pneumatic tire - Google Patents

Description

【００５８】
【表２】

【００５９】
（試験方法）
上記各供試タイヤをJATMA で規定する標準リムに装着し、タイヤ内圧：2.3kgf／cm² 、タイヤ負荷荷重：実車２名乗車相当の条件下で、濡れた路面での排水性能、乾いた路面での操縦安定性能及びパターンノイズを評価するための試験を行なった。
【００６０】
濡れた路面での排水性能は、直進走行時の排水性能と、旋回走行時の排水性能のに双方によって評価した。
【００６１】
直進走行時の排水性能は、水深５ｍｍの濡れた路面を走行させ、速度をステップ的に増加させていき、ハイドロプレーニング現象が発生したときの速度を測定し、これによって評価した。
【００６２】
旋回走行時の排水性能は、水深５ｍｍの半径８０ｍの濡れた旋回路面を走行させ、速度をステップ的に増加させていき、ハイドロプレーニング現象が発生したときの速度を測定し、これによって評価した。
【００６３】
乾いた路面での操縦安定性能は、乾いた路面状態にあるサーキットコースを各種走行モードにてスポーツ走行したときのテストドライバーによるフィーリングによって評価した。
【００６４】
パターンノイズは、平滑な路面上を走行させ、100km ／ｈから惰行させたときの車内音をテストドライバーによるフィーリングによって評価した。
【００６５】
これらの評価結果を表３に示す。尚、表３中の数値はいずれも、従来例を100とした指数比で示してあり、数値が大きいほど優れている。
【００６６】
【表３】

【００６７】
表３の結果から、実施例１は、従来例に比べて、濡れた路面での排水性能及び乾いた路面での操縦安定性能に優れており、パターンノイズについては差がなかった。
【００６８】
【発明の効果】
この発明によって、パターンノイズ等の他の性能を犠牲にすることなく排水性能及び操縦安定性能を有効に高めることができる空気入りタイヤ、特に高性能タイヤを提供することが可能になった。
【図面の簡単な説明】
【図１】 この発明に従う空気入りタイヤのトレッド部の一部を展開した図である。
【図２】 (a),(b) はそれぞれ図１のＡ−Ａ、Ｂ−Ｂ線上の断面図であり、(c)は第２面取り部の他の実施形態であり、(d),(e) はそれぞれ図１のＤ−Ｄ及びＥ−Ｅ線上の断面図である。
【図３】 従来タイヤ (従来例) のトレッド部の一部を展開した図である。
【符号の説明】
１ トレッド部踏面
2,3 トレッド部踏面１の略半区域
４ 中央域
5a,5b 周方向溝
6a,6b トレッド接地端
7a,7a₁,7a₂,7b,7b₁,7b₂ 傾斜溝
8a,8b 傾斜陸部
９ 分断溝
10a,10b 傾斜陸部8a,8b の中央側陸部
11a,11b 傾斜陸部8a,8b の側方側陸部
12a,12b 分断溝９の短溝部
13 分断溝９の長溝部
14 側方側陸部の側壁部分
15 第１面取り部
16a,16b トレッド端
17 短溝部12a,12b と長溝部13の連結位置
18 中央側陸部10a,10b の側壁部分
19 中央側陸部10a,10b の角部分
20 角部分19の頂点
21 第２面取り部
22 リブ状陸部
23a,23b リブ状陸部22の側壁
24 擬似陸部
25 先端部
26 先端部25の頂点
27 第３面取り部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire, particularly a high performance tire, that can effectively improve drainage performance and steering stability performance without sacrificing other performance.
[0002]
[Prior art]
Conventional pneumatic tires, especially so-called high-performance tires with a reduced flatness for the purpose of improving steering stability, extend along the tire circumferential direction on the tread surface to ensure drainage. In general, a circumferential groove and a plurality of inclined grooves extending obliquely from the circumferential groove toward the tread grounding end are disposed, and a plurality of land sections are formed by these grooves.
[0003]
In such a tire, as a means for improving drainage performance, it is useful to increase the groove area ratio (negative rate) by increasing the groove width of the circumferential groove or the inclined groove.
[0004]
That is, in the tire having the tread pattern, the circumferential groove mainly plays a role of draining in the front-rear direction of the tire, and the inclined groove mainly plays a role of draining to the side of the tire. As a result, the drainage efficiency in the front-rear direction and the side of the tire is increased, and as a result, improvement in drainage performance of the entire tire can be expected.
[0005]
Further, as other means for improving drainage performance, the inclined groove is a so-called high angle groove that is inclined at a relatively small angle with respect to the tire circumferential direction, and the inclined groove is formed from the pattern center side. It is useful to form the directional pattern in the tread portion by arranging the tread portions so as to enter the contact area sequentially toward the respective tread ground contact ends.
[0006]
Further, considering the case where the same number of circumferential grooves are arranged on the tread portion tread, the drainage performance is better as the number of circumferential grooves arranged on the pattern center side, i.e., in the tread central area, is larger. It is clear from the inventors' experiments and the like.
[0007]
However, any means for improving the drainage performance has its own limitations in terms of securing other performance.
[0008]
Further, when considering a tire (see FIG. 1) having an inclined land portion that is defined by only one circumferential groove and two inclined grooves provided on the center pattern side in a substantially half area of the tread portion tread surface, Since the land area of one inclined land portion is widened and the rigidity of the land portion is increased, the steering stability performance including handling characteristics in the case where lateral force acts, for example, during circuit running, is advantageous. However, when the surface of the sloping land is in contact with the road surface, the contact pressure distribution in the sloping land is non-uniform and uneven wear tends to occur, and there is a puddle on the tread of the sloping land when rolling tires. When stepping on the road surface, the distance from the stepped water to the inclined groove becomes longer, and therefore, there is a problem that such water cannot be quickly discharged to the side of the tire through the inclined groove. It was.
[0009]
Therefore, in the tire having the inclined land portion, the contact pressure distribution in each inclined land portion is made uniform to suppress uneven wear, and the water treaded by the inclined land portion tread is promptly passed to the tire side through the inclined groove. It is necessary to take measures to discharge.
[0010]
As such means, for example, by arranging a dividing groove that opens in two inclined grooves that divide the inclined land portion, the inclined land portion is further divided into a side land portion and a central land portion. It is useful to subdivide.
[0011]
Then, the inventor conducted various studies to further improve the drainage performance and the steering stability performance by changing the arrangement shape of the dividing grooves and the like.
[0012]
As a result, the dividing groove usually has a straight arrangement shape, and the intersection angle with the inclined groove is generally relatively large.In the case of a tire provided with this dividing groove, The discharge direction of the water flowing in the inclined groove and the dividing groove is greatly different, and at the intersection of these grooves, the water flow along the inclined groove and the water flow along the dividing groove collide when they merge or branch. The flow of air is turbulent, and air is easily trapped and bubbles are likely to be generated. The smooth flow in both grooves is obstructed, which causes a decrease in drainage efficiency. There was found.
[0013]
In addition, since the straight dividing groove is relatively low in rigidity against the lateral force of the groove wall, buckling phenomenon is likely to occur at the groove bottom of the dividing groove. It has also been found that the stability tends to decrease.
[0014]
[Problems to be solved by the invention]
The object of the present invention is to improve drainage performance and steering stability performance without sacrificing other performance, particularly by optimizing the arrangement shape of the dividing groove and the shape of the side wall portion of the land portion facing this. The object is to provide a pneumatic tire, particularly a high-performance tire, which can be effectively increased.
[0015]
[Means for Solving the Problems]
To achieve the above object, according to the present invention, there is provided a circumferential groove extending along the tire circumferential direction at a pattern center side position in at least approximately a half area of the tread surface, and from the circumferential groove toward the tread ground contact end. A plurality of inclined grooves are provided by extending a plurality of inclined grooves extending at an inclination and having a relatively small inclination angle with respect to the tire circumferential direction on the pattern center side and a relatively large inclination angle on the tread ground end side. The inclined land portion is further divided into a center side land portion and a side side land portion by disposing a dividing groove that opens into two inclined grooves that form the section. In the pneumatic tire, the dividing groove includes a pair of short groove portions extending from each inclined groove toward the pattern center and a long groove portion connecting the short groove portions, and faces the long groove portion of the dividing groove. That on the side walls of the lateral side land portion, a pneumatic tire and forming a first chamfered portion where the land portion height decreases towards the long groove.
[0016]
The "substantially half area of the tread part tread" here means one tread area when the tread part tread is divided into two at the pattern center. For example, the half area when the pattern center does not coincide with the tire equator. Is also included.
[0017]
Moreover, it is preferable that the land part height reduction rate of a 1st chamfer part is larger than that of the side wall part of the center side land part which faces the long groove part of a dividing groove.
[0018]
Furthermore, the angle formed by the first chamfered portion and the tread surface of the lateral side land portion is preferably in the range of 120 to 160 °, more preferably 130 to 150 °.
[0019]
Furthermore, the corner portion of the central land portion divided by the inclined groove and the short groove portion of the dividing groove has an acute plane shape, and the land portion height toward the apex and the short groove portion is formed at the corner portion. It is preferable to form a second chamfered portion that decreases.
[0020]
In addition, it is preferable that at least one groove portion of the dividing groove is located in the vicinity of a substantially equally divided position of the tread width as measured from the tread end. It is preferable to extend in a parallel direction, or an angle of 45 ° or less with respect to the parallel direction, and in a direction inclined in the direction opposite to the inclined groove. Preferably, the groove width of the dividing groove is equal to or narrower than that of the inclined groove and preferably narrower than that of the circumferential groove. Moreover, the groove width of the dividing groove is more preferably 2 to 10 mm.
[0021]
In addition, a large number of inclined grooves that extend from the circumferential groove located on the pattern center side toward the tread grounding end are disposed in both areas of the tread surface to form a pair of inclined land portions. Then, it is preferable that the inclined land portions are arranged in such a manner that the inclined land portions are sequentially grounded from the pattern center side portion toward the tread grounding end side portion, and the directional pattern is formed on the tread portion.
[0022]
Furthermore, it is preferable to arrange a pair of circumferential grooves in the central region of the tread and form a rib-like land portion therebetween. The “tread central area” here refers to an area of 50% of the tread grounding width centered on the pattern center.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Next, an example of an embodiment of the present invention will be described below.
FIG. 1 shows a tread pattern of a pneumatic tire according to the present invention. In the figure, 1 is a tread portion tread surface, 2 and 3 are substantially half areas of the tread portion tread surface 1, 4 is a central region, 5a and 5b are Circumferential grooves, 6a and 6b are tread grounding ends, 7a and 7b are inclined grooves, 8a and 8b are inclined land portions, 9 is a dividing groove, 10a and 10b are central land portions, and 11a and 11b are lateral land portions. It is.
[0024]
A pneumatic tire having a tread part tread 1 shown in FIG. 1 is located at least approximately half of the tread part tread (both areas 2 and 3 in FIG. 1) at its pattern center CL side position (in FIG. 1, the pattern center and the tire). The equator and the equator coincide with each other.) More specifically, the circumferential grooves 5a and 5b extending along the tire circumferential direction at positions in the central region 4 and the circumferential grooves 5a and 5b respectively A plurality of inclined land portions 8a and 8b are defined by arranging a plurality of inclined grooves 7a and 7b extending inclined toward the tread grounding ends 6a and 6b.
[0025]
The inclined grooves 7a and 7b have a relatively small inclination angle with respect to the tire circumferential direction on the pattern center CL side (preferably 10 to 40 °), and the inclination angle on the tread ground contact ends 6a and 6b side is relatively large (preferably Is a so-called high angle groove.
[0026]
Further, the inclined land portions 8a and 8b are further divided into central land portions 10a and 10b by disposing the dividing grooves 9 communicating with the _two inclined grooves 7a ₁ and 7a ₂ , 7b ₁ and 7b ₂ that define the inclined land portions 8a and 8b. And side land portions 11a and 11b.
[0027]
The main structural feature of the present invention is that the arrangement shape of the dividing grooves 9 arranged in the inclined land portions 8a and 8b and the shape of the side wall portion of the land portion facing this are made more appropriate. Specifically, the dividing groove 9 includes a pair of short groove portions 12a and 12b extending obliquely from the inclined grooves 7a ₁ or 7a ₂ , 7b ₁ or 7b ₂ toward the pattern center 3, and the short groove portions 12a and 12b. The first chamfer is formed on the side wall portions 14 of the side land portions 11a and 11b facing the long groove portion 13 of the dividing groove 9 and the land portion height decreases toward the long groove portion 13. The purpose is to form part 15.
[0028]
Hereinafter, the background to the adoption of the above configuration will be described together with the operation of the present invention. In the case of conventional tires, the dividing groove has a straight planar shape and is generally arranged so as to intersect the inclined groove at a large angle. When driving on the road, water on the road that has been stepped on the inclined land surface can be taken into the dividing groove, but the intersection angle at the intersection of the dividing groove and the inclined groove is large. When the water taken in collides with the water flowing in the inclined groove when it merges with the inclined groove, the flow of these waters is disturbed, and it is easy to generate bubbles by entraining air. As a result of the hindered smooth flow of water in the groove, sufficient drainage performance to the side of the tire through the inclined groove could not be obtained.
[0029]
In addition, since the straight dividing groove is relatively low in rigidity against the lateral force of the groove wall, buckling phenomenon is likely to occur at the groove bottom of the dividing groove. Stability was reduced.
[0030]
Accordingly, the inventor first arranged the dividing grooves so that when the water taken into the dividing grooves 9 flows into the inclined grooves, the flowing water smoothly merges with the water flowing through the inclined grooves. The design was changed in various ways.
[0031]
As a result, at least both end groove portions (that is, short groove portions) of the dividing groove that open (intersect) the inclined groove are as close as possible to the extending direction of the inclined groove and in the direction toward the tread end. It has been found that if the groove is arranged so as to open to the inclined groove, the water flow is less likely to be disturbed when the water in the dividing groove joins the inclined groove.
[0032]
Therefore, in the present invention, the dividing grooves are formed in the direction from the inclined grooves 7a ₁ and 7a ₂ or 7b ₁ and 7b ₂ to the pattern center CL, that is, from the reverse, the inclined grooves 7a toward the tread grounding ends 6a and 6b. ₁ and 7a ₂ , 7b ₁ and 7b ₂ , a pair of short groove portions 12a and 12b extending obliquely in the opening direction, and a long groove portion 13 connecting the short groove portions 12a and 12b, are formed in a substantially “U” shape. Therefore, when the water flowing in the dividing groove 9 merges into the inclined groove, the water flow is less likely to be disturbed, and the buckling at the groove bottom of the dividing groove is less likely to occur. Occurrence can be considerably suppressed as compared with a conventional tire having a straight dividing groove.
[0033]
In addition, since the dividing groove 9 is arranged in such a manner that the inclined land portions 8a and 8b are subdivided into the side land portions 11a and 11b and the central land portions 10a and 10b, the inside of the inclined land portions 8a and 8b. The contact pressure distribution at the center can be made uniform, the contact property of the tread is improved, and the occurrence of uneven wear is also suppressed.
[0034]
Specifically, the disposing position of the dividing groove 9 is preferably such that at least a part of the groove portion is located in the vicinity of the substantially equally divided position of the tread width as measured from the tread ends 16a and 16b. This is because the 1/4 position is suitable as a place to absorb the deformation of the tread during cornering.
[0035]
Further, the long groove portion 13 of the dividing groove 9 has a direction parallel to the tire circumferential direction, or an angle of 45 ° or less (more preferably 5 to 30 °) with respect to the tire circumferential direction, and is opposite to the inclined grooves 7a and 7b. It preferably extends in a direction inclined in the direction. This is because by making the long groove portion 13 of the dividing groove 9 into the above-described arrangement shape, a substantially uniform land portion rigidity (block rigidity) can be obtained, which advantageously affects the steering stability. If the angle exceeds 45 °, the crossing angle at the connecting position 17 between the short groove portions 12a, 12b and the long groove portion 13 becomes too large, and it is easy to be damaged, and it also has an adverse effect on drainage performance. is there.
[0036]
Further, the short groove portions 12a and 12b of the dividing groove 9 have a relatively small angle with respect to the extending direction of the inclined groove 7a ₁ or 7b ₁ , 7a ₂ or 7b ₂ in which it opens, specifically 10 to 40 °. In order to obtain a smooth merge, it is preferable to extend in a direction inclined at an angle of. That is, if the angle is less than 10 °, the effect is small, while if it exceeds 40 °, it is difficult to obtain a smooth merging effect.
[0037]
The groove width of the dividing groove 9 is preferably in the range of 2 to 10 mm, more preferably 5 to 8 mm. That is, if the groove width of the dividing groove 9 is within the above range, it is possible to ensure the radius of curvature R of the groove bottom that can effectively prevent cracks at the groove bottom, ensure the effective grounding area (improve steering stability), and ground This is because it is possible to achieve a good balance between ensuring sex.
[0038]
As described above, in the present invention, the arrangement shape of the dividing groove 9 is required to be the above-mentioned configuration, but the invention is an indispensable matter for the invention. However, the buckling generated at the groove bottom of the dividing groove only by adopting the above configuration. It was difficult to sufficiently suppress
[0039]
Therefore, in the present invention, in addition to the above configuration, the shape of the land portion facing the long groove portion 13 of the dividing groove 9, particularly the side wall portions 14 of the side land portions 11a and 11b is made more appropriate. As shown in FIG. 2 (a), the land portion height decreases toward the long groove portion 13 on the side wall portions 14 of the side land portions 11a and 11b facing the long groove portion 13 of the dividing groove 9. Since the first chamfered portion 15 is formed and the rigidity of the land portion of the side wall portion 14 can be effectively increased thereby, even when a large lateral force acts like during circuit running, The occurrence of buckling at the groove bottom of the dividing groove 9 can be sufficiently suppressed, and as a result, the steering stability can be improved.
[0040]
In addition, since the formation of the first chamfered portion 15 can substantially increase the groove volume of the dividing groove 9, the sloped land portions 8a and 8b, particularly the center side land portions 10a and 10b, on the road surface with puddles. Even if it is stepped on, the water can be easily taken into the dividing groove 9, which is advantageous in terms of drainage performance.
[0041]
The decrease ratio R of the land height H of the first chamfered portion 15 is preferably larger than that of the side wall portions 18 of the central land portions 10a and 10b facing the long groove portion 13 of the dividing groove 9. This is to ensure advantageous block rigidity against lateral input during cornering.
[0042]
In addition, the angle α formed by the first chamfered portion 15 and the tread surface of the side land portions 11a and 11b is preferably in the range of 120 to 160 °. This is because if it is smaller than the above range, it tends to be difficult to achieve both the groove width and the groove depth. If it is larger than the above range, the rigidity of the side wall portion is improved by forming the first chamfered portion 15. This is because the effect is not noticeable.
[0043]
Further, the corner portion 19 of the central land portion 10a defined by the inclined groove 7a ₁ or 7a ₂ and the short groove portion 12a or 12b of the dividing groove 9 has an acute plane shape, and the corner portion 19 has its apex. It is preferable to form the second chamfered portion 21 in which the land height H decreases toward 20 and the short groove portion 12a or 12b. That is, by forming the corner portion 19, buckling at the groove bottom of the dividing groove can be suppressed, and by making the planar shape of the corner portion 19 an acute angle, it flows in the dividing groove 9. Water can be smoothly merged into the inclined grooves 7a and 7b. In addition, the second chamfered portion 21 formed in the corner portion 19 reinforces the rigidity of the corner portion 19, and particularly the center side land portion. There is also an action as an introduction path through which water existing between the treads 10a and 10b and the road surface smoothly flows into the inclined grooves 7a and 7b.
[0044]
The first chamfered portion 15 and the second chamfered portion 21 are shown in FIGS. 1 and 2 (a) and 2 (b) when a flat chamfer is applied, but a curved chamfer is applied. Also good.
[0045]
Furthermore, in the present invention, the above-described configuration may be employed in any one half area 2 or 3 of the tread portion tread 1, but particularly in the case of a high-performance tire that emphasizes drainage, FIG. As shown in the figure, a plurality of inclined grooves 7a, 7b extending from the central area 4 toward the respective tread grounding ends 6a, 6b are disposed in both areas 2, 3 of the tread portion tread 1, The inclined land portions 8a and 8b are formed, and the inclined land portions 8a and 8b are arranged in such a manner that they are sequentially grounded from the central region 4 side toward the tread grounding end 6a, 6b side, and are directed to the tread portion 1. It is preferable to form a sex pattern.
[0046]
Further, in FIG. 1, in order to further improve drainage and improve driving stability, a pair of circumferential grooves 5a and 5b extending in the tire circumferential direction are disposed in the central region 4 and between them, Although the rib-like land 22 is formed and the inclined grooves 7a and 7b are opened to the circumferential grooves 5a and 5b, this structure can be appropriately selected as necessary. If the rib-like land portion is provided, by increasing the rigidity of the land portion located in the central region 4, it is possible to improve the micro rudder angle responsiveness and further improve the steering stability on the dry road surface. .
[0047]
If the tread pattern is a combination of a plurality of inclined grooves 7a, 7b and a pair of circumferential grooves 5a, 5b as shown in FIG. 1, not only the drainage action to the side of the tire by the inclined grooves 7a, 7b is achieved. Furthermore, since drainage in the tire front-rear direction by the circumferential grooves 5a and 5b can be performed effectively, drainage performance can be further improved.
[0048]
In addition, the inventor also examined the drainage mechanism at the time of tire load rolling for the tire having the above tread pattern, and studied to further improve drainage efficiency. The drainage mechanism changes over time. More specifically, the drainage to the front of the tire by the circumferential grooves 5a and 5b is mainly performed immediately before the tire touches the ground, and the circumferential grooves 5a and 5b immediately after the ground contact (including during the ground contact). It was found that the drainage to the side of the tire by the inclined grooves 7a, 7b was mainly rather than the drainage to the tire front-rear direction due to.
[0049]
In addition to adopting the above configuration, as shown in FIG. 1, portions corresponding to the positions where the inclined grooves 7 a or 7 b are opened in the circumferential grooves 5 a or 5 b of the side walls 23 a and 23 b of the rib-like land portion 22. In addition, a pseudo land portion 24 protruding into the circumferential grooves 5a and 5b adjacent thereto is fixed, and the land height H of the pseudo land portion 24 is determined from the side walls 23a and 23b of the rib-like land portion 22. It was found that the drainage performance was further improved if it was formed with an inclined surface that gradually decreased with increasing distance. FIGS. 2 (d) and 2 (e) are those cut along DD and EE in FIG. 1 in order to clarify the cross-sectional shape of the pseudo land portion 24. FIG.
[0050]
That is, by providing the pseudo land portion 24, the water flowing in the circumferential grooves 5a, 5b immediately after the grounding can smoothly flow into the inclined grooves 7a, 7b having different arrangement angles. The drainage efficiency toward the tire side due to the inclined grooves 7a and 7b in the tire is remarkably increased, whereby the drainage performance of the tire can be further improved.
[0051]
Moreover, the circumferential groove | channel should just be a shape extended along a tire circumferential direction, and is not limited only to linear form as shown in FIG. 1, It can be made into various shapes.
[0052]
In addition, it is possible to form the third chamfered portion 27 in which the land height H decreases toward the apex 26 at the tip portion 25 that enters the contact area first of the inclined land portions 8a and 8b. It is preferable in terms of securing the water pressure and obtaining the effect of reducing the water pressure at the groove branch point.
[0053]
In order to satisfy both the securing of the block rigidity and the water pressure reduction effect at the groove branching point in a more balanced manner, the reduction ratio R of the land height H of the third chamfer 27 is set to the apex 26 of the tip 25. More preferably, the surface is gradually increased or the surface of the third chamfered portion 27 is formed in a substantially curved shape.
[0054]
The above description only shows an example of the embodiment of the present invention, and various modifications can be made within the scope of the claims. For example, in the above-described tires, only the case where one dividing groove 9 is provided in one inclined land portion 8a, 8b has been described. However, if necessary, two or more dividing grooves are provided. May be.
[0055]
【Example】
Next, a pneumatic tire according to the present invention was prototyped and its performance was evaluated, which will be described below.
Example 1
The tire of Example 1 has the tread pattern shown in FIG. 1 and the first and second chamfered portions having the cross-sectional shapes shown in FIGS. 2A and 2B, and the tire size is PSR205 / 55R16 (tread width: 170). mm), circumferential grooves 5a, 5b, inclined grooves 7a, 7b, dividing grooves 9, first chamfered portion 15, second chamfered portion 21, third chamfered portion 27, simulated land portion 24, and rib-shaped land portion The dimensions of 22 are summarized in Table 1. The tire structure other than the tread portion 1 was substantially the same as the structure of a conventional passenger car pneumatic tire.
[0056]
Conventional Example The tire of the conventional example has the tread pattern shown in FIG. 3, the tire size is PSR205 / 55R16 (tread width: 170 mm), the dimensions of the circumferential grooves 101 to 103 and the inclined grooves 104 to 106, etc. Are shown in Table 2.
[0057]
[Table 1]

[0058]
[Table 2]

[0059]
(Test method)
Each of the above test tires is mounted on a standard rim specified by JATMA, tire pressure: 2.3kgf / cm ² , tire load load: drainage performance on wet road surface, dry road surface under conditions equivalent to two passengers Tests were conducted to evaluate steering stability performance and pattern noise.
[0060]
The drainage performance on wet roads was evaluated by both drainage performance during straight running and drainage performance during turning.
[0061]
The drainage performance during straight running was evaluated by measuring the speed when hydroplaning phenomenon occurred by running on a wet road surface with a water depth of 5 mm and increasing the speed stepwise.
[0062]
The drainage performance during the turning was evaluated by measuring the speed when the hydroplaning phenomenon occurred by running on a wet turning surface with a water depth of 5 mm and a radius of 80 m and increasing the speed stepwise.
[0063]
Steering performance on dry roads was evaluated by feelings by test drivers when driving on circuit courses on dry roads in various driving modes.
[0064]
The pattern noise was evaluated by feeling by the test driver when driving on a smooth road surface and coasting from 100km / h.
[0065]
These evaluation results are shown in Table 3. In addition, all the numerical values in Table 3 are shown as index ratios with the conventional example being 100, and the larger the numerical value, the better.
[0066]
[Table 3]

[0067]
From the results in Table 3, Example 1 was superior in drainage performance on wet road surfaces and steering stability performance on dry road surfaces as compared to the conventional example, and there was no difference in pattern noise.
[0068]
【The invention's effect】
According to the present invention, it is possible to provide a pneumatic tire, particularly a high performance tire, which can effectively improve drainage performance and steering stability performance without sacrificing other performance such as pattern noise.
[Brief description of the drawings]
FIG. 1 is a developed view of a part of a tread portion of a pneumatic tire according to the present invention.
FIGS. 2A and 2B are cross-sectional views taken along lines AA and BB in FIG. 1, respectively, FIG. 2C is another embodiment of the second chamfered portion, and FIGS. (e) is sectional drawing on the DD and EE line | wire of FIG. 1, respectively.
FIG. 3 is a developed view of a part of a tread portion of a conventional tire (conventional example).
[Explanation of symbols]
1 Tread tread
2,3 Approximate half zone 4 of tread part 1 Central zone
5a, 5b Circumferential groove
6a, 6b Tread grounding end
7a, 7a ₁ , 7a ₂ , 7b, 7b ₁ , 7b ₂ inclined groove
8a, 8b Inclined land 9 dividing groove
10a, 10b Central land part of inclined land part 8a, 8b
11a, 11b Inclined land 8a, 8b lateral side land
12a, 12b Short groove part of dividing groove 9
13 Long groove of dividing groove 9
14 Side wall of side land
15 First chamfer
16a, 16b tread edge
17 Connection position of short groove 12a, 12b and long groove 13
18 Side walls of the central land 10a, 10b
19 Corner of central land 10a, 10b
20 Vertex 19
21 Second chamfer
22 Rib-shaped land
23a, 23b Side wall of rib-like land portion 22
24 Simulated land
25 Tip
26 Apex of tip 25
27 Third chamfer

Claims (10)

A circumferential groove extending along the tire circumferential direction at the pattern center side position at least in a substantially half area of the tread portion tread surface, and extending obliquely from the circumferential groove toward the tread grounding end, and on the pattern center side A plurality of inclined grooves with a relatively small inclination angle with respect to the tire circumferential direction and a plurality of inclined grooves with a relatively large inclination angle on the tread ground end side are partitioned to form a plurality of inclined land portions. In the pneumatic tire which is further subdivided into a center side land portion and a side side land portion by the arrangement of the dividing grooves opening to the two inclined grooves that form a partition,
The dividing groove is composed of a pair of short groove portions extending from each inclined groove toward the pattern center, and a long groove portion connecting these short groove portions,
A pneumatic tire characterized in that a first chamfered portion whose land portion height decreases toward the long groove portion is formed on a side wall portion of the side side land portion facing the long groove portion of the dividing groove. The pneumatic tire according to claim 1, wherein the land portion height reduction ratio of the first chamfered portion is larger than that of the side wall portion of the central land portion facing the long groove portion of the dividing groove. The pneumatic tire according to claim 1 or 2, wherein an angle formed by the first chamfered portion and the tread surface of the lateral side land portion is in a range of 120 to 160 °. The corner portion of the central land portion divided by the inclined groove and the short groove portion of the dividing groove has an acute plane shape, and the land portion height decreases toward the apex and the short groove portion at the corner portion. The pneumatic tire according to claim 1, 2 or 3, which forms a two-chamfered portion. The pneumatic tire according to any one of claims 1 to 4, wherein at least one groove portion of the dividing groove is in the vicinity of a substantially equally divided position of the tread width as measured from the tread end. The long groove portion of the dividing groove extends in a direction parallel to the tire circumferential direction or a direction inclined at an angle of 45 ° or less and opposite to the inclined groove. The pneumatic tire according to item. The pneumatic tire according to any one of claims 1 to 6, wherein the short groove portion of the dividing groove extends at a relatively small angle with respect to the inclined groove that opens. The pneumatic tire according to any one of claims 1 to 7, wherein a groove width of the dividing groove is equal to or narrower than that of the inclined groove and narrower than that of the circumferential groove. The pneumatic tire according to any one of claims 1 to 8, wherein the dividing groove has a groove width of 2 to 10 mm. In both areas of the tread surface, a large number of inclined grooves extending from the circumferential grooves located on the pattern center side toward the respective tread grounding ends are arranged to form a pair of inclined land portions. The pneumatic land according to any one of claims 1 to 9, wherein the inclined land portions are arranged so as to be sequentially grounded from the pattern center side portion toward the tread grounding end side portion, and a directional pattern is formed in the tread portion. tire.

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