JP4202824B2 - Pneumatic tire - Google Patents

Description

【００４０】
また図４には、走行速度を変化させて上記と同様に音圧レベルを測定した結果を示す。実施例１では従来例に比べて全体的になだらかであり、ピークが少ないことが分かる。また図５、図６には、ラテラル・ハイドロプレーニングテストの結果を示す。これらのテストの結果、実施例１のタイヤは、従来例に比べて排水性、ノイズ性能ともに向上していることが確認できる。
【００４１】
【発明の効果】
以上説明したように、本発明の空気入りタイヤは、排水性を損ねることなく走行ノイズを低減しうる。
【図面の簡単な説明】
【図１】本発明の一実施形態を示すトレッドパターンの展開図である。
【図２】その部分拡大図である。
【図３】従来例のトレッドパターンを示す展開図である。
【図４】実施例１と従来例との騒音レベルを比較したグラフである。
【図５】フロント横Ｇと旋回走行速度との関係を示すグラフである。
【図６】リア横Ｇと旋回走行速度との関係を示すグラフである。
【図７】実施例１〜３のパターン図である。
【図８】実施例４のパターン図である。
【図９】比較例１のパターン図である。
【図１０】比較例２のパターン図である。
【図１１】比較例３のパターン図である。
【図１２】比較例４のパターン図である。
【符号の説明】
２ トレッド面
３ａ 内の縦溝
３ｂ 内の縦溝
４ａ 第１の内の横溝
４ｂ 第２の内の横溝
５ａ 第１の外の横溝
５ｂ 第２の外の横溝
９ 縦細溝
１２ 小巾横溝
１２ａ サイプ状部
１２ｂ 広巾溝部
Ｂ１ ブロック
Ｂ２ ブロック
Ｃｒ クラウン領域
Ｓｈ ショルダー領域
Ｒｃ クラウン陸部
Ｒｍ ミドル陸部
Ｒｍ 各陸部
ＴＷ トレッド接地巾[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire that can reduce tire noise without impairing drainage.
[0002]
[Prior art and problems to be solved by the invention]
On the tread surface of the tire, a longitudinal groove extending in the tire circumferential direction and a transverse groove extending in a direction crossing the tire are formed. These grooves are important for draining the water film between the tread surface and the road surface to the outside. However, on the other hand, the groove formed on the tread surface repeatedly compresses and releases air during travel, and causes so-called pattern noise. In particular, in a tread pattern in which a block is used in a land portion to increase drainage and the groove volume is increased, there is a tendency to significantly increase pattern noise. Conventionally, various studies have been made in order to achieve both the drainage performance and the noise performance which conflict with each other, and the following prior art has been proposed.
[0003]
[Patent Document 1]
JP-A-6-55912 [Patent Document 2]
Japanese Patent Laid-Open No. 7-30005 [Patent Document 3]
Japanese Patent Laid-Open No. 2001-163011
Patent Document 1 discloses that an enlarged portion having a large groove width is provided in the middle of a sipe. Patent Document 2 teaches that the width of the lateral groove is alternately increased and decreased. Furthermore, Patent Document 3 discloses that wide lugs and narrow lugs are alternately provided in the circumferential direction.
[0005]
The inventors have conducted extensive research and found that pattern noise and drainage are greatly affected by the shape of the lateral groove that divides the shoulder land along the tread grounding edge, and the shoulder land is axially displaced. It has been found that if two types of horizontal grooves whose groove widths change as they extend are divided into blocks, the pattern noise can be dispersed in frequency without lowering the drainage performance, and the feeling noise can be reduced.
[0006]
As described above, an object of the present invention is to provide a pneumatic tire that can reduce tire noise without impairing drainage.
[0007]
[Means for Solving the Problems]
The invention according to claim 1 of the present invention is characterized in that one or two of the tread surfaces are provided in a crown region which is a region of 30% of the tread contact width centered on the tire equator and extend continuously in the tire circumferential direction. An inner vertical groove, one outer vertical groove provided in a shoulder region on both sides, which is a region between the crown region and the tread grounding end, and continuously extending in the tire circumferential direction, and the inner vertical groove A lateral groove formed between the outer vertical groove and the tread grounding end, which traverses the middle land portion formed between the groove and the outer vertical groove, and divides the middle land portion into blocks. An outer lateral groove that crosses the land portion and divides the shoulder land portion into blocks, and the outer lateral groove is a first outer lateral groove whose groove width gradually increases from the outer longitudinal groove toward the outside in the axial direction. The groove width gradually increases from the outer vertical groove toward the outside in the axial direction. And a second outer lateral groove that gradually decreases and has a maximum groove width located approximately in the middle of the axial width of the shoulder land portion, and the first outer lateral groove and the second outer lateral groove are It is a pneumatic tire provided alternately in the tire circumferential direction.
[0008]
Here, the “tread grounding width” is the distance in the tire axial direction between the tread grounding ends when the tire is assembled on a regular rim and filled with regular internal pressure, and a regular load is applied and grounded on a flat surface. . The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based. For example, a standard rim for JATMA, “Design Rim” for TRA, or ETRTO If so, use "Measuring Rim". In addition, “regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. It is the maximum air pressure for JATMA and the table “TIRE LOAD LIMITS” for TRA. The maximum value described in “AT VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” if it is ETRTO, but if the tire is for passenger cars, it is uniformly 180 kPa. Furthermore, “regular load” is the load that each standard defines for each tire in the standard system including the standard on which the tire is based. The maximum load capacity is specified for JATMA, and the table “TIRE LOAD LIMITS” for TRA. If the maximum value described in "AT VARIOUS COLD INFLATION PRESSURES", ETRTO is "LOAD CAPACITY", if the tire is for a passenger car, the load is equivalent to 88% of the load.
[0009]
According to a second aspect of the present invention, the inner transverse groove includes a first inner transverse groove having a larger groove width, and a second inner transverse groove having a groove width smaller than the first inner transverse groove, 2. The pneumatic tire according to claim 1, wherein the first inner lateral groove and the second inner lateral groove are alternately provided in a tire circumferential direction.
[0010]
According to a third aspect of the present invention, the first inner lateral groove is provided at a position that is smoothly connected to the first outer lateral groove via the outer vertical groove, and the second inner lateral groove. The pneumatic tire according to claim 2, wherein the pneumatic tire is provided at a position smoothly connected to the second outer lateral groove via the outer vertical groove.
[0011]
According to a fourth aspect of the present invention, the outer lateral groove is formed in a substantially square shape by being composed of two portions having different inclination directions with respect to the tire circumferential direction between the outer vertical groove and the tread ground contact end. A pneumatic tire according to any one of claims 1 to 3.
[0012]
Further, in the invention according to claim 5, the middle land portion or the shoulder land portion has a small-width lateral groove whose one end communicates with the outer longitudinal groove and extends in a direction intersecting with the outer longitudinal groove. The lateral groove is characterized by comprising a sipe-shaped portion having a groove width of 1.0 mm or less, and a wide groove portion that is continuous with the sipe-shaped portion and communicates with an outer vertical groove and has a groove width larger than 1.0 mm. The pneumatic tire according to any one of claims 1 to 4.
[0013]
According to a sixth aspect of the present invention, in the middle land portion, the middle land portion is divided in the tire axial direction by vertical narrow grooves extending in the tire circumferential direction and having a groove width of 1.0 to 2.0 mm. The pneumatic tire according to any one of the above.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a development view of the tread surface 2 of the pneumatic tire of the present embodiment, and FIG. 2 is a partially enlarged view thereof. Although the internal structure of the tire is not shown, various structures such as a radial structure and a bias structure can be used in accordance with conventional practice, and the present invention can be suitably implemented as a pneumatic radial tire for passenger cars.
[0015]
In the figure, the tread surface 2 is provided in a crown region Cr which is a region of 30% of the tread ground contact width TW with the tire equator C as the center, and in the present example extends continuously in the tire circumferential direction. Longitudinal grooves 3a and 3a and one outer longitudinal groove 3b provided in shoulder regions Sh and Sh on both sides, which are regions between the crown region Cr and the tread ground contact E, and continuously extending in the tire circumferential direction. 3b. Thereby, the tread surface 2 includes the crown land portion Rc between the inner vertical grooves 3a and 3a, the middle land portion Rm between the inner vertical groove 3a and the outer vertical groove 3b, and the outer vertical groove 3b. It is divided into a shoulder land portion Rs between the tread ground contact E.
[0016]
In the present embodiment, the inner longitudinal grooves 3a and 3a are provided at symmetrical positions around the tire equator C on both sides of the tire equator C. Similarly, the outer vertical grooves 3b and 3b are also provided at symmetrical positions around the tire equator C. The inner and outer vertical grooves 3a and 3b have, for example, groove widths W1 and W2 set to 2 to 10%, more preferably 3 to 6% of the tread ground contact width TW, and the groove depth is preferably 6.0. It is desirable that the thickness is set to ˜8.5 mm, more preferably 7.0 to 8.5 mm. The groove width and groove depth are not limited to the above numerical range, but when the groove width is less than 2% of the tread ground contact width TW, or when the groove depth is less than 6.0 mm, the groove volume is There is a tendency for drainage to fall short. Conversely, when the groove width exceeds 10% of the tread ground contact width TW, or when the groove depth exceeds 8.5 mm, the groove volume increases more than necessary, and the pattern noise tends to deteriorate. The groove width is a width perpendicular to the groove center.
[0017]
The inner and outer longitudinal grooves 3a and 3b preferably extend linearly along the tire circumferential direction as in the present embodiment, but can also be formed in a wave shape or a zigzag shape. The crown region Cr is provided with two longitudinal grooves 3a, but may be reduced to one. However, if three or more longitudinal grooves 3a are provided in the crown region Cr, the pattern rigidity of the crown region Cr is not preferable. From the same viewpoint, it is desirable to arrange one outer longitudinal groove 3b in the shoulder region Sh.
[0018]
In the present embodiment, the crown land portion Rc is formed as a rib extending continuously without interruption in the tire circumferential direction. The ribs are appropriately provided with cuts 11 that terminate in the land portion on both sides thereof. This is useful for moderately reducing the rigidity of the rib in the tire circumferential direction and suppressing uneven wear. If the width of the crown land portion Rc constituting the rib is too small in the tire axial direction, there is a tendency that the pattern rigidity is insufficient and the steering stability is impaired, and conversely, the drainage performance near the tire equator is too large. It is easy to deteriorate, and there is a risk of causing the hydroplaning phenomenon at an early stage. From such a viewpoint, the width WRc of the crown land portion Rc is preferably set to 5 to 20%, more preferably 10 to 15% of the tread ground contact width TW.
[0019]
The middle land portion Rm is provided with a large number of transverse grooves 4 across the middle land portion Rm. Thus, the middle land portion Rm forms a block row in which the blocks B1... Are arranged in the tire circumferential direction. The inner lateral groove 4 includes first and second inner lateral grooves 4a and 4b having different groove widths in this embodiment. The first inner lateral grooves 4a are formed with a larger groove width than the second inner lateral grooves 4b, and these are alternately arranged in the tire circumferential direction.
[0020]
The inner lateral grooves 4a and 4b guide and discharge the water film in the crown region Cr having a high contact pressure to the inner longitudinal groove 3a or the outer longitudinal groove 3b as the tire rotates. For this reason, it is preferable to form with a comparatively large groove width. However, an increase in the groove width tends to increase the pattern noise. Therefore, in the pneumatic tire of the present embodiment, the groove width of the first inner lateral groove 4a is increased, while the groove width of the second inner lateral groove 4b is decreased (the groove volume is decreased), and these By alternately arranging in the tire circumferential direction, an increase in pattern noise is prevented without impairing drainage. When horizontal grooves having the same groove volume are continuously arranged, substantially the same frequency noise is superimposed at a constant cycle during running, and a large pattern noise is generated. On the other hand, as in the present embodiment, the first and second lateral grooves 4a and 4b having different groove widths are alternately arranged in the tire circumferential direction, thereby preventing the above-described superposition of the same frequency noise. Thus, frequency dispersion can be achieved, and the noise reduction effect is increased.
[0021]
The groove width Wi1 of the first lateral groove 4a is, for example, 2.0 to 8.0 mm, and more preferably 3.0 to 6.0 mm. The groove depth is preferably 50 to 100%, more preferably about 60 to 90% of the groove depth of the inner vertical groove 3a. On the other hand, it is desirable to reduce the groove volume of the second inner lateral groove 4b in order to suppress an increase in pattern noise as described above, and the groove width Wi2 is equal to the groove width Wi1 of the first inner lateral groove 4a. For example, 30 to 80%, more preferably 40 to 60% is desirable. In this example, the groove depth of the second inner horizontal groove 4b is the same as that of the first inner horizontal groove 4a, but may be different. When the groove width changes, the average groove width is used.
[0022]
The first and second lateral grooves 4a and 4b are inclined grooves inclined with respect to the tire circumferential direction, and preferably have angles α1 and α2 with respect to the tire circumferential direction of 30 to 60 °, more preferably 40 to 40 °. Set to 50 °. When the angles α1 and α2 are increased, the pattern noise is likely to increase sharply, and the drainage performance is likely to be deteriorated because the resistance when draining into the vertical groove using the rotation of the tire is increased. The first and second lateral grooves 4a and 4b in the present embodiment are parallel to each other and extend substantially linearly. However, the groove shape may be a curved shape or a zigzag shape. In this case, the angles α1 and α2 can be determined by straight angles connecting both ends of the groove.
[0023]
Further, the corner portion on the obtuse angle side of the communicating portion where the first and second inner lateral grooves 4b and the inner longitudinal grooves 3a intersect is formed as arc portions e1 and e2 chamfered in an arc shape. The arc portions e1 and e2 reduce resistance when drainage flows from the inner vertical groove 3a, and improve drainage performance better. Particularly preferably, the radius of curvature R2 of the arc portion e2 of the second inner lateral groove 4b having a small groove width is larger than the radius of curvature R1 of the arc portion e1 of the first inner lateral groove 4a having a larger groove width. It is desirable. This helps to reduce the difference in drainage performance due to the difference in groove width.
[0024]
Further, in the present embodiment, the middle land portion Rm is divided into two in the tire axial direction by a vertical narrow groove 9 extending in the tire circumferential direction and having a groove width of 1.0 to 2.0 mm. Such vertical narrow grooves 9 increase the lateral edge component in the middle land portion Rm. The edge component in the lateral direction is useful for preventing drastic reduction in lateral G caused by the decrease in lateral hydroplaning that occurs particularly during turning, and greatly improving wet steering stability. If the groove width of the vertical narrow groove 9 is less than 1.0 mm, it is difficult to effectively exhibit the edge component. Conversely, if it exceeds 2 mm, the rigidity of the middle land portion Rm is lowered, which is not preferable. Further, the vertical narrow groove 9 may be not only a straight line but also a curved line or a zigzag shape. Further, the arrangement position of the vertical narrow groove 9 is not particularly limited, but it is desirable to dispose it at the center of the middle land Rm in the tire axial direction. The width WRm in the tire axial direction of the middle land portion Rm is, for example, about 10 to 25%, more preferably 15 to 20% of the tread ground contact width TW from the viewpoint of handling stability.
[0025]
Further, in the shoulder region Rs, outer vertical grooves 5 that cross the shoulder land portion Rs are provided. Thus, the shoulder region Rs is formed as a block row in which the blocks B2 are arranged in the tire circumferential direction.
[0026]
The outer lateral groove 5 includes a first outer lateral groove 5a and a second outer lateral groove 5b whose groove width changes. In this embodiment, each of the first and second outer lateral grooves 5a and 5b has two portions having different inclination directions with respect to the tire circumferential direction between the outer longitudinal groove 3b and the tread ground contact end E, that is, in FIG. In the right half, a groove portion A that is inclined at an angle β1 that rises to the right and a groove portion B that is inclined at an angle β2 that is lowered to the right are shown. β1 is preferably 45 to 80 °, and β2 is 45 to 85 °. Note that the substantially square shape includes a reverse “H” shape such as the lateral groove 5 outside the left half of FIG. 1. The first outer lateral groove 5a gradually increases in groove width from the outer longitudinal groove 3b toward the outer side in the axial direction. The first outer horizontal groove 5a of this example has a groove width that smoothly increases from the communicating portion with the outer vertical groove 3b forming the groove width Wo1a to the tread grounding end E forming the groove width Wo1b. Further, the second outer lateral groove 5b has a groove width gradually increasing from the communicating portion with the outer vertical groove 3b forming the groove width Wo2a, and the maximum groove width Wmax approximately in the middle of the axial width of the shoulder land portion Rs. The groove width is smoothly reduced from there to the tread grounding end E that forms the groove width Wo2b. The first and second outer lateral grooves 5a and 5b are alternately arranged in the tire circumferential direction.
[0027]
As a result of experiments by the inventors, the communication portion between the vertical groove 3b and the horizontal groove 5 in the shoulder region Sh has a large influence on the pitch noise. It has been found that it can be made. Since the first and second outer lateral grooves 5a and 5b as in the present embodiment have relatively small groove widths Wo1a and Wo2a at the communicating portion with the outer vertical groove 3b, they are useful for reducing pitch noise. . Further, the groove width of the first outer lateral groove 5a is gradually increased toward the tread grounding width TW, and the second outer lateral groove 5b has a maximum groove width Wmax in the shoulder land portion Rs. However, since it becomes possible to secure a sufficient groove volume on the outside in the axial direction, it is possible to prevent the drainage performance from deteriorating. Further, while maintaining such a noise frequency dispersion effect, the shoulder land portion Rs has a substantially uniform lateral groove by the sum of the first and second outer lateral grooves 5a and 5b adjacent to each other in any position in the tire axial direction. Since the width can be secured, particularly the hydroplaning generation speed during cornering can be effectively increased, and a rapid decrease in the lateral G can be prevented.
[0028]
Thus, the pneumatic tire of the present invention can improve the hydroplaning performance and the like. Also, by arranging two types of horizontal grooves 5a and 5b that change in different groove widths in the tire circumferential direction, the noise frequency generated in each of the horizontal grooves 5a and 5b is made different as in the middle land portion Rm, and the pattern noise The generation of large peak noise due to the superimposition of can be suppressed.
[0029]
The groove width Wo1a at the communicating portion of the first outer lateral groove 5a to the outer vertical groove 3b is, for example, substantially the same as the groove width Wi1 of the first inner lateral groove 4a, specifically, 80 to 120 of the groove width Wi1. It is preferable to set it at about%. If the groove width Wo1a is too small, the flowing water in the outer vertical groove 3b cannot be taken in smoothly and discharged from the tread grounding end E side. On the contrary, if it is too large, pitch noise is likely to increase. Further, the groove width Wo1b at the tread ground end E of the first outer lateral groove 5a is preferably 1.2 to 2.0 times, more preferably 1.3 to 1.5 times the groove width Wo1a. desirable. If it is less than 1.2 times, the groove volume tends to decrease. Conversely, if it exceeds 2.0 times, large pitch noise tends to occur at the tread ground contact E.
[0030]
Further, the groove width Wo2a at the communicating portion of the second outer lateral groove 5b to the outer vertical groove 3b is, for example, substantially the same as the groove width Wi2 of the inner second lateral groove 4b, specifically, 80 to 80 of the groove width Wi2. It is preferable to set it at about 120%. The maximum groove width Wmax of the second outer lateral groove 5b is preferably 1.2 to 2.0 times, more preferably 1.3 to 1.5 times the groove width Wo2a. If it is less than 1.2 times, the groove volume tends to decrease. Conversely, if it exceeds 2.0 times, large pitch noise tends to occur near the maximum groove width Wmax. The groove width Wo2b at the tread grounding end E of the second outer lateral groove 5b is preferably 100 to 130%, more preferably 110 to 120% of the groove width Wo2a. Note that the maximum groove width Wmax is approximately the intermediate position of the axial width of the shoulder land portion Sh, that is, the intermediate position P of the shoulder land portion Sh in this specification, which is 20 times the axial width WRs of the shoulder land portion Sh. % Area.
[0031]
Further, the first outer lateral groove 5a and the first inner lateral groove 4a are arranged at a position where they are smoothly connected via the outer longitudinal groove 3b. Similarly, the second outer lateral groove 5b and the second inner lateral groove 4b are arranged so as to be smoothly connected via the outer longitudinal groove 3b. The inner and outer lateral grooves 4 and 5 can also be provided by being displaced in the tire circumferential direction, but in this case, since the lateral grooves are interrupted via the longitudinal grooves, the drainage efficiency to the outside in the axial direction is likely to decrease. . On the other hand, in the present embodiment, a substantially continuous drainage channel that is long in the axial direction can be formed by using the inner and outer lateral grooves 4 and 5, and this is used to the outside in the axial direction. The drainage efficiency can be further increased. The width WRs in the tire axial direction of the shoulder land portion Rs is, for example, about 10 to 20% of the tread ground contact width TW, more preferably 13 to 18%, from the viewpoint of wear resistance and steering stability. .
[0032]
In the present embodiment, the middle land portion Rm and the shoulder land portion Rs are each provided with a narrow lateral groove 12 that has one end communicating with the outer vertical groove 3b and extending in a direction intersecting with the outer vertical groove 3b. . The narrow lateral groove 12 includes a sipe-like portion 12a having a groove width of 1.0 mm or less, and a wide groove portion that is continuous with the sipe-like portion 12a and communicates with the outer vertical groove 3b and has a groove width larger than 1.0 mm. 12b.
[0033]
The wide groove portion 12b extends from the outer vertical groove 3b in substantially parallel to the first and second inner horizontal grooves 4a and 4b or the first and second outer horizontal grooves 5a and 5b. It ends at almost the middle position of the land width. In the middle land portion Rm, one end side of the sipe-like portion 12a communicates with the wide groove portion 12b and the other end smoothly curves and communicates with the first and second inner lateral grooves 4a and 4b instead of the inner longitudinal groove 3a. is doing. Further, in the shoulder land portion Rs, the sipe-shaped portion 12a communicates with the wide groove portion 12b at one end side and extends to the tread grounding end E at the other end.
[0034]
Such a small lateral groove 12 can effectively take in the water film in the vicinity of the outer vertical groove 3b that greatly contributes to hydroplaning during cornering by the wide groove part 12b and discharge it to the outer vertical groove 3b. This results in a significant improvement in hydroplaning performance, especially during turning.
[0035]
Further, since the narrow lateral groove 12 includes the sipe-shaped portion 12a, it can be softened without excessively reducing the rigidity of the block B2, and the noise performance, riding comfort and even anti-wear performance can be improved in a balanced manner. it can. Moreover, the narrow lateral groove 12 of the present embodiment has a sipe shape as a result of the sipe-shaped portion 12a communicating with the first or second lateral groove 4a or 4b instead of the longitudinal groove 3a. The block area between the portions 12a can be configured in a vertically long shape that is long in the tire circumferential direction. Thereby, in the block B1, the rigidity in the tire circumferential direction of the block region near the tire equator C having a high contact pressure can be increased, and the stability during straight traveling can be reliably improved.
[0036]
【Example】
A pneumatic radial tire (Example) for a passenger car having a tread pattern of FIGS. 1 and 2 and having a tire size of 205 / 65R15 was prototyped and tested for pattern noise and drainage. For comparison, a conventional tire (conventional example) having the conventional pattern shown in FIG. 3 and a tire (comparative example) based on the pattern shown in FIG. Each tire has the same internal structure with a carcass made by folding a one-ply carcass of polyester around a bead core and a belt layer consisting of two belt plies using steel cords, and only the tread pattern is different. It is a thing. Also, the groove width and groove depth are set so that the land ratio is substantially the same as that of the conventional tire. For the conventional example, the groove width is shown in FIG. The test method is as follows.
[0037]
<Drainage (Lateral Hydroplaning Test)>
Each sample tire is mounted on 4 wheels of a domestic FF vehicle with a displacement of 2000cm ^{3 and} is on a course with a puddle with a depth of 5mm and a length of 20m on an asphalt road surface with a radius of 100m, with only one driver on board. It was made to enter while gradually increasing. Then, the lateral acceleration (lateral G) was measured, and the average lateral G of the front wheels at a speed of 50 to 80 km / h was calculated. The rim size was 15 × 6.0JJ, and the internal pressure was 210 kPa (same before and after). The results were expressed as an index with Comparative Example 1 as 100. The larger the value, the better.
[0038]
<Noise performance>
Drive on a smooth dry road surface at a speed of 50 km / h under the same vehicle conditions as above, and measure the overall noise level dB (A) at the driver's left ear position and the ear height position at the center of the rear seat. The average value of both noise levels was calculated. The evaluation was expressed as an index with the conventional example being 100. The larger the numerical value, the better the noise level of the pattern noise. The test results are shown in Table 1.
[0039]
[Table 1]

[0040]
FIG. 4 shows the result of measuring the sound pressure level in the same manner as described above while changing the traveling speed. It can be seen that Example 1 is generally smoother and has fewer peaks than the conventional example. 5 and 6 show the results of the lateral hydroplaning test. As a result of these tests, it can be confirmed that the drainage and noise performance of the tire of Example 1 are improved as compared with the conventional example.
[0041]
【The invention's effect】
As described above, the pneumatic tire of the present invention can reduce running noise without impairing drainage.
[Brief description of the drawings]
FIG. 1 is a development view of a tread pattern showing an embodiment of the present invention.
FIG. 2 is a partially enlarged view thereof.
FIG. 3 is a development view showing a tread pattern of a conventional example.
FIG. 4 is a graph comparing noise levels of Example 1 and a conventional example.
FIG. 5 is a graph showing a relationship between a front lateral G and a turning traveling speed.
FIG. 6 is a graph showing a relationship between a rear lateral G and a turning traveling speed.
7 is a pattern diagram of Examples 1 to 3. FIG.
8 is a pattern diagram of Example 4. FIG.
9 is a pattern diagram of Comparative Example 1. FIG.
10 is a pattern diagram of Comparative Example 2. FIG.
11 is a pattern diagram of Comparative Example 3. FIG.
12 is a pattern diagram of Comparative Example 4. FIG.
[Explanation of symbols]
2 Vertical groove 4a in the tread surface 3a Vertical groove 4a in the first First horizontal groove 4b Second inner horizontal groove 5a First outer horizontal groove 5b Second outer horizontal groove 9 Vertical narrow groove 12 Small lateral groove 12a Sipe-shaped part 12b Wide groove part B1 Block B2 Block Cr Crown area Sh Shoulder area Rc Crown land part Rm Middle land part Rm Each land part TW Tread contact width

Claims (6)

One or two longitudinal grooves provided in a crown region that is 30% of the tread contact width centered on the tire equator and continuously extending in the tire circumferential direction on the tread surface;
Each one outer longitudinal groove provided in shoulder regions on both sides, which is a region between the crown region and the tread ground contact edge, and continuously extending in the tire circumferential direction;
An inner lateral groove that crosses the middle land portion formed between the inner longitudinal groove and the outer longitudinal groove and divides the middle land portion into blocks;
An outer lateral groove that crosses a shoulder land portion formed between the outer longitudinal groove and the tread grounding end and divides the shoulder land portion into blocks; and
The outer lateral groove includes a first outer lateral groove whose groove width gradually increases from the outer vertical groove toward the axially outer side,
A second outer lateral groove that gradually decreases after the groove width gradually increases from the outer vertical groove toward the outer side in the axial direction, and whose maximum groove width is located approximately in the middle of the axial width of the shoulder land portion;
A pneumatic tire in which the first outer lateral groove and the second outer lateral groove are alternately provided in the tire circumferential direction. The inner transverse groove includes a first inner transverse groove having a larger groove width and a second inner transverse groove having a groove width smaller than that of the first inner transverse groove,
The pneumatic tire according to claim 1, wherein the first inner lateral groove and the second inner lateral groove are alternately provided in a tire circumferential direction. The first inner lateral groove and the first outer lateral groove are smoothly connected via the outer longitudinal groove,
The pneumatic tire according to claim 2, wherein the second inner lateral groove and the second outer lateral groove are smoothly connected to each other through the outer longitudinal groove. 4. The outer lateral groove is formed in a substantially square shape by being composed of two portions having different inclination directions with respect to the tire circumferential direction between the outer vertical groove and a tread ground contact end. The pneumatic tire according to any one of the above. The middle land portion or the shoulder land portion has a small lateral groove extending in a direction in which one end communicates with the outer vertical groove and intersects the outer vertical groove,
The small-width lateral groove is composed of a sipe-shaped portion having a groove width of 1.0 mm or less, and a wide-width groove portion that is continuous with the sipe-shaped portion and communicates with an outer vertical groove and has a groove width larger than 1.0 mm The pneumatic tire according to any one of claims 1 to 4. The pneumatic tire according to any one of claims 1 to 5, wherein the middle land portion is divided in a tire axial direction by a vertical narrow groove extending in a tire circumferential direction and having a groove width of 1.0 to 2.0 mm.

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