JP4059592B2 - Pneumatic tire - Google Patents

Description

【００２６】
この表１から判るように、本発明タイヤは従来タイヤ１〜３に比べて偏摩耗の発生が少なく、しかも従来タイヤ１と同等の操縦安定性を確保していた。また、本発明タイヤでは従来タイヤ１に比べて耐ハイドロプレーニング性能も大幅に向上していた。
【００２７】
【発明の効果】
以上説明したように本発明によれば、トレッドのショルダー部にブロック列を設け、その内側に主溝を介して他のブロック列を設けた空気入りタイヤにおいて、ショルダー部のブロック列を最大で接地端からトレッド接地幅の２５％の位置まで延在させると共に、ブロックの主溝に隣接する鈍角部と鋭角部を該主溝の両側で互いに反対側に設け、該主溝を挟んで向かい合うブロックの側壁にそれぞれトレッド法線方向に対する傾斜角度を鋭角部側のブロック端から鈍角部側のブロック端へ向けて徐々に大きくしたテーパ部を設けたことにより、ブロック全長にわたってヒールアンドトウ摩耗等の偏摩耗の発生を効果的に抑制することができ、しかも捩じれ状のテーパ部を形成するためブロック剛性の低下を最小限に留めて操縦安定性の低下を抑制することができる。
【図面の簡単な説明】
【図１】本発明の実施形態からなる空気入りタイヤのトレッドパターンを示す展開図である。
【図２】図１の空気入りタイヤのショルダー部を拡大して示す平面図である。
【図３】図１の空気入りタイヤのショルダー部のブロックを拡大して示す斜視図である。
【図４】従来の空気入りタイヤのトレッドパターンを示す展開図である。
【図５】図４の空気入りタイヤのショルダー部のブロックを拡大して示す斜視図である。
【図６】従来の他の空気入りタイヤのトレッドパターンを示す展開図である。
【図７】図６の空気入りタイヤのショルダー部のブロックを拡大して示す斜視図である。
【符号の説明】
１ トレッド
２，３ 主溝
４ 副溝
５，６ ブロック列
５ａ，６ａ ブロック
５Ａ，６Ａ 鈍角部
５Ｂ，６Ｂ 鋭角部
５Ｃ，６Ｃ テーパ部
５Ｄ，６Ｄ 面取り部
ＴＷ トレッド接地幅
ＣＬ センターライン[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire suitable for RV (Recreational Vehicle), and more particularly to a pneumatic tire that can suppress the occurrence of uneven wear without reducing steering stability.
[0002]
[Prior art]
Large tires such as those for RVs that have straight grooves in the tire circumferential direction tend to cause uneven wear such as heel and toe wear due to uneven rigidity balance in the block. As a result, the tire life itself was shortened.
[0003]
Therefore, conventionally, as a countermeasure, the occurrence of uneven wear has been suppressed by chamfering the sharp edge of the block. For example, in JP-A-1-204805, the inclination angle with respect to the tread normal direction is gradually increased from the obtuse angle side to the acute angle side of the block on the side walls of the block facing each other across the main groove.
[0004]
However, the occurrence of uneven wear could not be effectively suppressed only by chamfering or tapering the sharp edge of the block as described above. Further, if the chamfered portion or the tapered portion is made larger than necessary in order to enhance the effect of preventing uneven wear, there is a problem that the steering stability is lowered.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide a pneumatic tire that can suppress the occurrence of uneven wear without deteriorating steering stability.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the pneumatic tire according to the present invention has a row of blocks each including a plurality of blocks in the shoulder portions on both the left and right sides of the tread, and a plurality of inner rows in the tire width direction of the block rows of the shoulder portions. In a pneumatic tire in which another block row consisting of blocks is arranged and a main groove extending in the tire circumferential direction is interposed between both block rows, the shoulder row block row is located at the maximum inward in the tire width direction from the ground contact end. The block is extended to a position corresponding to 25% of the tread contact width, and an obtuse angle portion and an acute angle portion adjacent to the main groove of the block are provided on both sides of the main groove on opposite sides, and the blocks face each other across the main groove. Tapered on the side walls of the taper gradually increasing the inclination angle with respect to the normal direction of the tread from the block end on the acute angle side toward the block end on the obtuse angle side The is characterized in that provided.
[0007]
Thus, in the pneumatic tire in which a block row is provided in the shoulder portion of the tread and another block row is provided on the inner side through the main groove, a tread normal direction is provided on each side wall of the block facing the main groove. By providing a taper that gradually increases the angle of inclination relative to the block end on the acute angle side toward the block end on the obtuse angle side, the occurrence of uneven wear such as heel and toe wear is effectively suppressed over the entire length of the block can do. That is, instead of increasing the inclination angle of the block side wall near the sharp edge as in the past, in the present invention, by increasing the inclination angle of the block side wall near the obtuse edge, the uneven wear resistance is greatly improved. It becomes possible to do.
[0008]
In addition, the inclination angle is changed so that the tapered portion provided on the side wall of the block constituting the shoulder block row and the tapered portion provided on the side wall of the block constituting the other block row are twisted with each other. By doing so, a decrease in block rigidity can be minimized and a decrease in steering stability can be suppressed.
In the present invention, the tread contact width is a contact width when a tire is filled with an air pressure of 200 kPa and a load of 75% of the maximum load capacity of JATMA is applied.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.
[0010]
FIG. 1 illustrates a tread pattern of a pneumatic tire according to an embodiment of the present invention. In the figure, CL is a tread center line, and TW is a tread ground contact width.
[0011]
The tread 1 includes a pair of left and right main grooves 2, 2 extending straight in the tire circumferential direction at the center portion, a pair of left and right main grooves 3, 3 extending straight in the tire circumferential direction at the shoulder portion, and the tire circumferential direction. A plurality of sub-grooves 4 extending in the tire width direction while being inclined relative to the tire are provided. Thereby, the block row 5 composed of a plurality of blocks 5a is divided and formed on the shoulder portions on both the left and right sides, and the block row 6 composed of a plurality of blocks 6a is divided and formed inside the block row 5 in the tire width direction, Ribs 7 are dividedly formed at the center portion in the tire width direction of the block row 6. In the center portion, a block row composed of a plurality of blocks may be arranged instead of the ribs 7.
[0012]
Extending from the block row 5 is at least a ground end of the shoulder portion extends to 10% of the positions of the tread width to inner side in the tire width direction, and up to 25% of the positions of the tread width from the ground contact end to the inner side in the tire width direction at the maximum It is set to exist. In a large tire for RV or the like having the block row 5 having the above dimensions in the shoulder portion, uneven wear such as heel and toe wear tends to occur particularly in the vicinity of the shoulder portion.
[0013]
As shown in FIG. 2, the block 5a which comprises the block row 5 of a shoulder part has the obtuse angle part 5A and the acute angle part 5B in the center side edge. On the other hand, the block 6a constituting the block row 6 has a shape approximating a rhombus having a pair of obtuse angle portions 6A and 6A and a pair of acute angle portions 6B and 6B in plan view. The block 6a has an obtuse angle portion 6A formed on the shoulder side edge thereof on the opposite side of the tire circumferential direction to the obtuse angle portion 5A of the block 5a, and on the opposite side of the tire circumferential direction to the acute angle portion 5B of the block 5a. An acute angle portion 6B is formed. The acute angle portion of the block may have an angle in the range of 25 to 85 °, and the obtuse angle portion may have an angle in the range of 95 to 160 °.
[0014]
As shown in FIG. 3, in the block 5a constituting the block row 5 of the shoulder portion, the inclination angle of the side wall adjacent to the main groove 3 with respect to the normal direction of the tread is from the block end on the acute angle portion 5B side to the block on the obtuse angle portion 5A side. The side wall gradually increases toward the end, and this side wall forms a tapered portion 5C. Further, a chamfered portion 5D is provided at the acute angle portion 5B of the block 5a.
[0015]
On the other hand, in the block 6a constituting the block row 6, the inclination angle of the side wall adjacent to the main groove 3 with respect to the normal direction of the tread gradually increases from the block end on the acute angle portion 6B side toward the block end on the obtuse angle portion 6A side. This side wall forms a tapered portion 6C. Further, a chamfered portion 6D is provided at the acute angle portion 6B of the block 6a.
[0016]
The maximum width a of the tapered portions 5C and 6C is preferably 5 to 15% of the block circumferential length b. If the maximum width a of the taper portions 5C and 6C is less than 5% of the block circumferential length b, the uneven wear resistance is insufficient, and conversely if it exceeds 15%, the steering stability is lowered. In addition, although the inclination angle with respect to the tread normal line direction of the taper portions 5C and 6C gradually changes in the tire circumferential direction, the groove width at the groove bottom of the main groove 2 is substantially constant in the tire circumferential direction.
[0017]
The inclination angles of the taper portions 5C and 6C are 0 to 10 ° at the block ends on the acute angle portions 5B and 6B side, and 5 to 30 ° at the block ends on the obtuse angle portions 5A and 6A side. The difference is preferably 5 to 20 °. By setting such an inclination angle, it is possible to achieve both uneven wear resistance and steering stability.
[0018]
As described above, in the block 5a constituting the block row 5 of the shoulder portion and the block 6a constituting the block row 6 located inside thereof, not only chamfered portions 5D and 6D are provided for sharp edges, By providing tapered portions 5C and 6C in which the inclination angle of the side wall adjacent to the groove 3 is gradually increased from the block end on the acute angle portions 5B and 6B side toward the block end on the obtuse angle portions 5A and 6A side, The occurrence of uneven wear such as heel and toe wear can be effectively suppressed over the entire length of the block while minimizing the decrease in block rigidity.
[0019]
Further, by providing the tapered portions 5C and 6C so as to be twisted with respect to the side wall of the block 5a and the side wall of the inner block 6a in the shoulder portion, a decrease in block rigidity can be minimized, Thereby, it is possible to suppress a decrease in steering stability.
[0020]
【Example】
The tire of the present invention in which the tire size is common to 235 / 75R15, and the inclination angle of the taper portion is gradually increased from the block end on the acute angle side toward the block end on the obtuse angle side in the tread pattern of FIG. In the tread pattern, the conventional tires 1 and 2 in which the side wall of the block is not provided with a taper portion, and in the tread pattern of FIG. 1, the inclination angle of the taper portion is gradually increased from the block end on the obtuse angle side toward the block end on the acute angle side. Each of the conventional tires 3 was manufactured. The tread pattern of the conventional tire 1 and its block shape are as shown in FIGS. 4 and 5, respectively. The tread pattern and the block shape of the conventional tire 2 are as shown in FIGS. 6 and 7, respectively. In the tires of the present invention and the conventional tires 1 to 3, the block row of the shoulder portion was extended from the contact end to a position of 18% of the tread contact width.
[0021]
These test tires were evaluated for uneven wear level, steering stability, and resistance to hydroplaning by the following test methods, and the results are shown in Table 1.
[0022]
Uneven wear level:
The test tire was mounted on a passenger car with a displacement of 2500 cc, and after running for 8000 km at an air pressure of 220 kPa, the amount of step (mm) in the block near the shoulder was measured, and this was defined as the uneven wear level.
[0023]
Steering stability:
The test tire was mounted on a passenger car with a displacement of 2500 cc, and a feeling test was conducted with five panelists at an air pressure of 220 kPa. The evaluation results are indicated by an index with the conventional tire 1 as 100. The larger the index value, the better the steering stability.
[0024]
Hydroplaning resistance:
The test tire was mounted on a passenger car with a displacement of 2500 cc, entered into a pool with a water depth of 8 mm on a straight road with an air pressure of 220 kPa, and the critical speed until the hydroplaning phenomenon occurred was measured by gradually increasing the approach speed. The evaluation results are indicated by an index with the conventional tire 1 as 100. The larger the index value, the better the hydroplaning performance.
[0025]
[Table 1]

[0026]
As can be seen from Table 1, the tires of the present invention produced less uneven wear than the conventional tires 1 to 3, and also secured the steering stability equivalent to that of the conventional tire 1. Also, the tire of the present invention has significantly improved anti-hydroplaning performance as compared with the conventional tire 1.
[0027]
【The invention's effect】
As described above, according to the present invention, in a pneumatic tire in which a block row is provided in the shoulder portion of the tread and another block row is provided on the inner side through the main groove, the block row of the shoulder portion is grounded at the maximum. An obtuse angle part and an acute angle part adjacent to the main groove of the block are provided on both sides of the main groove opposite to each other, extending from the end to a position of 25% of the tread ground contact width, and the blocks facing each other across the main groove Each side wall is provided with a taper that gradually increases the inclination angle with respect to the tread normal direction from the block end on the acute angle side toward the block end on the obtuse angle side, thereby providing uneven wear such as heel and toe wear over the entire block length. Can be effectively suppressed, and a twisted taper is formed to minimize the decrease in block rigidity, thereby reducing steering stability. It is possible to win.
[Brief description of the drawings]
FIG. 1 is a development view showing a tread pattern of a pneumatic tire according to an embodiment of the present invention.
2 is an enlarged plan view showing a shoulder portion of the pneumatic tire of FIG. 1. FIG.
3 is an enlarged perspective view showing a block of a shoulder portion of the pneumatic tire of FIG. 1. FIG.
FIG. 4 is a development view showing a tread pattern of a conventional pneumatic tire.
5 is an enlarged perspective view showing a block of a shoulder portion of the pneumatic tire of FIG. 4. FIG.
FIG. 6 is a development view showing a tread pattern of another conventional pneumatic tire.
7 is an enlarged perspective view showing a shoulder block of the pneumatic tire of FIG. 6;
[Explanation of symbols]
1 tread 2, 3 main groove 4 sub groove 5, 6 block row 5a, 6a block 5A, 6A obtuse angle part 5B, 6B acute angle part 5C, 6C taper part 5D, 6D chamfered part TW tread grounding width CL center line

Claims (2)

A block row composed of a plurality of blocks is disposed on the shoulder portions on both the left and right sides of the tread, and another block row composed of a plurality of blocks is disposed on the inner side in the tire width direction of the block row of the shoulder portion. In a pneumatic tire having a main groove extending in the tire circumferential direction therebetween, the block row of the shoulder portion extends from the grounding end to the inner side in the tire width direction up to a position of 25% of the tread grounding width, An obtuse angle portion and an acute angle portion adjacent to the main groove of the block are provided on opposite sides on both sides of the main groove, and an inclination angle with respect to the normal direction of the tread is respectively set on the side wall of the block facing the main groove. The pneumatic tire which provided the taper part which became gradually large toward the block end of the obtuse angle part side from the block end of this. The pneumatic tire according to claim 1, wherein a maximum width of the tapered portion is 5 to 15% of a length in a block circumferential direction.

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