JP3849997B2 - Heavy duty pneumatic tire - Google Patents

Description

【００２２】
【発明の効果】
以上説明してきたように、本発明の重荷重用空気入りタイヤにおいては、各リブにおけるサイプ角度を最適化したことにより、ウエット性能における発進・制動および旋回の３性能がバランス良くすべて向上すると同時に、耐偏摩耗性をも向上し、さらにサイプ間隔をも最適化することにより、より一層これら性能を向上させることができ、総合性能において一層優れたものとなる。
【図面の簡単な説明】
【図１】本発明の一例重荷重用空気入りタイヤのトレッドパターンの平面図である。
【図２】サイプ角度示す説明図である。
【図３】本発明の他の一例重荷重用空気入りタイヤのトレッドパターンの平面図である。
【図４】ショルダーサイプ角と耐偏摩耗性との関係を示すグラフである。
【図５】サイプ間隔と耐偏摩耗性およびウエット性能との関係を示すグラフである。
【図６】センターサイプ角と制動性および旋回性との関係を示すグラフである。
【図７】セカンドサイプ角と制動性および旋回性との関係を示すグラフである。
【図８】ショルダーサイプ角と制動性および旋回性との関係を示すグラフである。
【符号の説明】
１ トレッドパターン
２ａ センターリブ
２ｂ セカンドリブ
２ｃ ショルダーリブ
３ａ センターリブのサイプ
３ｂ セカンドリブのサイプ
３ｃ ショルダーリブのサイプ
４ 副溝
Ｍ トレッドの周方向中央線
ＴＷ トレッド幅[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heavy-duty pneumatic tire. More specifically, the present invention improves all of the starting, braking and turning performances (hereinafter sometimes referred to as “wet performance” generically) on a wet road in a well-balanced manner, and at the same time The present invention relates to a heavy-duty pneumatic tire with improved wear characteristics and excellent overall performance.
[0002]
[Prior art]
In heavy duty pneumatic tires, four circumferential grooves extending in the tire circumferential direction on the tread surface, center ribs located in the circumferential direction at the center of the tread width, second ribs located on both sides thereof, and further located on both sides thereof A tire having a rib pattern that forms a shoulder rib is particularly common as a tire for traveling on a good road. In addition, in order to improve the wet performance of such a tire, it is also a commonly applied technique to insert sipes into each rib.
[0003]
[Problems to be solved by the invention]
However, in the conventional sipe application technology, it has not been possible to improve all the three performances of start, braking and turning in the wet performance in a well-balanced manner. The reason is that the difference between the start / braking performance and the turning performance in the wet performance is due to the difference in the input direction of the tire, that is, the input from the traveling direction or the input from the lateral direction. That is, if the sipe placed in the rib approaches the circumferential direction (if the angle formed by the sipe and the center line in the circumferential direction of the tread becomes small), the edge component for the lateral input increases, so that the turning performance is improved. In addition, since the edge component with respect to the input from the circumferential direction decreases, the start / braking performance deteriorates. Conversely, if the sipe approaches the width direction (if the angle increases), the start / braking performance is improved, but the turning performance is reduced. However, when sipe is applied, each performance is generally improved as compared to the case without sipe.
[0004]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a heavy-duty pneumatic tire that improves all the three performances of start, braking, and turning in a well-balanced manner while improving uneven wear resistance and excellent overall performance. It is in.
[0005]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present inventor noted that the sipe angle in each rib has a different contribution rate to the start / braking performance and the turning performance of the wet performance, and is also related to the uneven wear of the tread. As a result of intensive studies, the present inventors have found an optimal sipe condition that can achieve the above-described object and have completed the present invention.
[0006]
That is, the heavy-duty pneumatic tire of the present invention includes four circumferential grooves extending in the tire circumferential direction on the tread surface, center ribs located in the circumferential direction at the center of the tread width, and second ribs located on both sides thereof. Furthermore, in a heavy duty pneumatic tire having a rib pattern that forms shoulder ribs located on both sides thereof,
The center rib and the second rib have sipes with both openings extending over the entire width of these ribs, the shoulder rib has a sipe opened only in the groove wall on the center rib side, and the sipe of the center rib has a straight shape. Present,
When the center sipe angle, the second sipe angle, and the shoulder sipe angle are the angles formed by the line connecting the ends of each sipe in the center rib, the second rib, and the shoulder rib and the tread circumferential center line, respectively,
Shoulder sipe angle ≧ 55 °
The relationship expressed by the center sipe angle> the shoulder sipe angle> the second sipe angle is satisfied.
Further, another heavy-load pneumatic tire of the present invention includes a center rib located in the circumferential direction at the center of the tread width and second ribs located on both sides thereof by four circumferential grooves extending in the tire circumferential direction on the tread surface. In addition, in a heavy duty pneumatic tire having a rib pattern that forms shoulder ribs located on both sides thereof,
The center rib and the second rib have sipes with both openings extending over the entire width of these ribs, and the shoulder rib has a sipe opened only in the groove wall on the center rib side,
Each sipe in the center rib, second rib and shoulder rib is inclined in the same direction with respect to the tread circumferential center line, and the angle between the line connecting both ends of each sipe and the tread circumferential center line is the center sipe angle. When the second sipe angle and shoulder sipe angle are
Shoulder sipe angle ≧ 55 °
The relationship expressed by the center sipe angle> the shoulder sipe angle> the second sipe angle is satisfied.
[0007]
The heavy duty pneumatic tire of the present invention preferably has the following formula:
Center sipe angle ≧ 70 °
50 ° ≦ second sipe angle ≦ 60 °
55 ° ≦ Shoulder sipe angle ≦ 65 °
Further, preferably, the circumferential interval between the sipe of each rib is in the range of 10 to 20% of the total width of the tread.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be specifically described with reference to the drawings.
In the tread pattern 1 of the heavy-duty pneumatic tire which is a preferred example of the present invention shown in FIG. 1, sipes 3a, 3b and 3c are applied to the center rib 2a, the second rib 2b and the shoulder rib 2c, respectively. Yes.
[0009]
The angle α (hereinafter abbreviated as “sipe angle”) formed by a line connecting both ends of the sipe (including a case where the sipe is a curve) and the circumferential center line M of the tread shown in FIG. Greatly affects uneven wear. That is, uneven wear is likely to occur particularly in the shoulder rib 2c having a relatively small contact pressure, and depending on the running (use) conditions, the shoulder sipe angle is extremely easy to be worn when the shoulder sipe angle is less than 55 °. The sipe angle needs to be 55 ° or more in consideration of uneven wear.
[0010]
Further, the center rib 2a, the second rib 2b and the shoulder rib 2c have different contribution ratios to the start / braking performance and the turning performance in the wet performance, respectively, which can be understood from the change in the ground contact shape due to the difference in the tire input direction, The order of the contribution ratio is in the order of center rib 2a> second rib 2b> shoulder rib 2c with respect to start / braking performance, and the order of shoulder rib 2c> second rib 2b> center rib 2a with respect to turning performance. This was confirmed in a wet performance test (turning and braking) on a test course using a tire in which a sipe was added to each of the center rib 2a, the second rib 2b, and the shoulder rib 2c on a rib tire without sipe.
[0011]
Therefore, in the present invention, the center rib 2a has a large sipe angle so that the center rib 2a is mainly responsible for starting and braking performance, and the shoulder rib 2c is responsible for turning performance. Although the rib 2c is set to be small, the sipe angle of the shoulder rib 2c needs to be 55 ° or more in consideration of uneven wear resistance as described above. Can not. Therefore, in the present invention, the second sipe angle is set smaller than the shoulder sipe angle with emphasis on turning performance as a function of the second rib 2b.
The relationship expressed by the center sipe angle> the shoulder sipe angle> the second sipe angle should be satisfied.
[0012]
In consideration of the wet performance, it is necessary to insert the sipe as densely as possible, and design elements for densely installing the sipe include the width of the sipe and the number of the entire tire (circumferential density).
First, with respect to the center rib 2a and the second rib 2b, the sipe width is a double opening type over the entire rib width to ensure the length as much as possible, and the shoulder rib 2c has 50% or more, preferably 55% of the rib width. A width of -90%, more preferably 60-80% is ensured. When this value is less than 50%, it can be expected that there is almost no influence on the movement of the ribs at the shoulder end, which is the core of the uneven wear from the shoulder end, and there is substantially no influence on the uneven wear. However, when the sipe of the shoulder rib 2c is full width, the shape of uneven wear differs depending on the running and use conditions, but the sipe opened in the shoulder may be the starting point of uneven wear from the shoulder, and the shoulder end (tread end) May not be applicable to sipe.
[0013]
Next, regarding the sipe density in the circumferential direction, the sipe interval is preferably in the range of 10 to 20% with respect to the total tread width TW. It is obvious that considering the wet performance, it is obvious that the smaller the sipe interval is, the more the number of sipes increases. However, reducing (narrowing) the sipe interval makes the ribs into smaller blocks, This leads to a decrease in tread rigidity. As a result, the deformation of the block at the time of contact is increased, and the uneven wear resistance is deteriorated. That is, if the sipe interval is too small (narrow), a design that takes into account the block rigidity is required. Specifically, if the rigidity is simplified, it is represented by a width (block width) and a length (sipe interval). It is necessary to design based on a function that takes into account the tread width as a determinant of length.
[0014]
From a specific sipe interval study, a sipe interval of less than 10% of the total tread width TW induces heel-and-toe wear that is serrated in the circumferential direction in addition to the aforementioned uneven wear from the shoulder end. As a result, uneven wear is extremely deteriorated. On the other hand, when the sipe interval exceeds 20% of the tread width TW, the number of sipes included in the contact length is reduced, and the effect of improving the wet performance is generally not recognized.
[0015]
In another preferred embodiment of the present invention, as shown in FIG. 3, the sub-groove 4 having a width of 3% or less of the tread width and a depth of 30% or more of the adjacent main groove in the shoulder rib. Is provided. As disclosed in Japanese Patent Application Laid-Open No. 61-143205, the sub-groove 4 has at least one piece extending in the circumferential direction of the tire at a position where the distance from the tread end is less than 50% of the width of the shoulder rib. When the sub-groove 4 is divided into at least two small ribs, the shoulder rib has a width from the circumferential groove to the sub-groove 4, and the sipe is in the sub-groove 4. Do not open.
[0016]
The heavy-duty pneumatic tire of the present invention relates to the improvement of the rib pattern, and other structures and the like are not particularly limited, and conventional ones can be used.
[0017]
【Example】
The following tests were conducted on a tread (tread width: 248 mm) of a heavy duty pneumatic tire of size 315 / 80R225 with four circumferential straight grooves as shown in FIG. 1 and various types of sipes in each rib. Went.
[0018]
(1) Relationship between shoulder sipe angle and uneven wear resistance The sipe angle was varied only on the shoulder ribs and sipe processing was performed, and the relationship between the amount of uneven wear and the shoulder sipe angle due to actual vehicle running was investigated. The obtained results are shown in FIG.
(2) Relationship between sipe interval and uneven wear resistance and wet performance Sipe processing is performed with the sipe angle constant and the sipe interval (%) with respect to the tread width being varied. The relationship with the interval was examined. The obtained results are shown in FIG.
(3) Relationship between sipe angle and start / brake performance and turning performance in wet performance Only the sipe angle of the rib to be tested is changed and sipe processing is performed, and the start / brake performance and turning performance and sipe angle by actual vehicle running I investigated the relationship. The results obtained are shown in FIG. 6 for the center rib, FIG. 7 for the second rib, and FIG. 8 for the shoulder rib.
[0019]
The following can be understood from the test results.
That is, FIG. 4 shows that the shoulder sipe angle needs to be 55 ° or more in order to improve the uneven wear resistance. Further, it can be seen from FIG. 5 that the sipe circumferential interval is preferably in the range of 10 to 20% of the total tread width from the standpoint of achieving both uneven wear resistance and wet performance. Furthermore, it can be seen from FIGS. 6 to 8 that the sipe angles of the respective ribs have different optimum ranges from the viewpoint of achieving both start / braking performance and turning performance in the wet performance.
[0020]
Examples 1 and 2 and comparative example A tread (tread width: 248 mm) of a heavy duty pneumatic tire of size 315 / 80R225 is provided with four circumferential straight grooves as shown in FIG. Each test tire was manufactured by applying sipe to each rib and setting each sipe angle and sipe interval as shown in Table 1 below. The shoulder ribs were siped up to 72% of the rib width. Each of the obtained test tires was tested for wet performance (braking performance, turning performance) by actual vehicle running. The obtained results are also shown in Table 1 below. The evaluation was expressed as an index with Comparative Example 1 as 100. Further, the feeling during running of the wet performance was also evaluated with a perfect score of 10 based on the comparative example.
[0021]
[Table 1]

[0022]
【The invention's effect】
As described above, in the heavy duty pneumatic tire of the present invention, by optimizing the sipe angle in each rib, all three performances of start / brake and turning in the wet performance are improved in a well-balanced manner and at the same time, By improving uneven wear and optimizing the sipe interval, these performances can be further improved, and the overall performance is further improved.
[Brief description of the drawings]
FIG. 1 is a plan view of a tread pattern of an example heavy duty pneumatic tire of the present invention.
FIG. 2 is an explanatory diagram showing a sipe angle.
FIG. 3 is a plan view of a tread pattern of another example heavy duty pneumatic tire of the present invention.
FIG. 4 is a graph showing a relationship between a shoulder sipe angle and uneven wear resistance.
FIG. 5 is a graph showing a relationship between a sipe interval, uneven wear resistance, and wet performance.
FIG. 6 is a graph showing a relationship between a center sipe angle, braking performance, and turning performance.
FIG. 7 is a graph showing the relationship between the second sipe angle, braking performance, and turning performance.
FIG. 8 is a graph showing a relationship between a shoulder sipe angle, braking performance, and turning performance.
[Explanation of symbols]
1 tread pattern 2a center rib 2b second rib 2c shoulder rib 3a center rib sipe 3b second rib sipe 3c shoulder rib sipe 4 minor groove M tread circumferential center line TW tread width

Claims (4)

Four circumferential grooves extending in the tire circumferential direction on the tread surface form a center rib located in the circumferential direction at the center of the tread width, second ribs located on both sides thereof, and shoulder ribs located on both sides thereof. In a heavy duty pneumatic tire having a rib pattern,
The center rib and the second rib have sipes with both openings extending over the entire width of these ribs, the shoulder rib has a sipe opened only in the groove wall on the center rib side, and the sipe of the center rib has a straight shape. Present,
When the center sipe angle, the second sipe angle and the shoulder sipe angle are respectively defined as the angle formed between the line connecting both ends of each sipe in the center rib, the second rib and the shoulder rib and the tread circumferential center line,
Shoulder sipe angle ≧ 55 °
A heavy-duty pneumatic tire characterized by satisfying a relationship expressed by center sipe angle> shoulder sipe angle> second sipe angle. Four circumferential grooves extending in the tire circumferential direction on the tread surface form a center rib located in the circumferential direction at the center of the tread width, second ribs located on both sides thereof, and shoulder ribs located on both sides thereof. In a heavy duty pneumatic tire having a rib pattern,
The center rib and the second rib have sipes with both openings extending over the entire width of these ribs, and the shoulder rib has a sipe opened only in the groove wall on the center rib side,
Each sipe in the center rib, second rib and shoulder rib is inclined in the same direction with respect to the tread circumferential center line, and the angle between the line connecting both ends of each sipe and the tread circumferential center line is the center sipe angle. When the second sipe angle and shoulder sipe angle are
Shoulder sipe angle ≧ 55 °
A heavy-duty pneumatic tire characterized by satisfying a relationship expressed by center sipe angle> shoulder sipe angle> second sipe angle. The following formula,
Center sipe angle ≧ 70 °
50 ° ≦ second sipe angle ≦ 60 °
55 ° ≦ Shoulder sipe angle ≦ 65 °
The heavy duty pneumatic tire according to claim 1 or 2, which satisfies a relationship represented by: The heavy-duty pneumatic tire according to any one of claims 1 to 3, wherein a circumferential interval between the sipe of each rib is within a range of 10 to 20% of a total width of the tread.

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