JP3990599B2 - Pneumatic tire - Google Patents

Description

【００４３】
【発明の効果】
このように、本発明の空気入りタイヤは、操縦安定性等の性能を維持しつつキャンバースラスト値を増大させ、ワンダリング性能を向上しうる。
【図面の簡単な説明】
【図１】本発明の実施の一形態を示す空気入りタイヤの子午線断面図である。
【図２】そのトレッドショルダー部を拡大した部分拡大図である。
【図３】本発明を適用したトレッドパターンの一例を示す展開図である。
【図４】サイピングの他の例を示す断面図である。
【符号の説明】
２ トレッド
２Ａ 主トレッド部
２Ｔ１ 第１のテーパー部
２Ｔ２ 第２のテーパー部
３ サイドウォール
４ 縦主溝
４Ａ 中央溝
４Ｂ ショルダー溝
６ カーカス
７ ベルト層
８ 横溝
９ ブレーカークッション
１０ サイピング
ＣＯ タイヤ赤道面
Ｄ 溝深さ
Ｄｍ 最大溝深さＤｍ
ＬＴ１ 第１のテーパー部２Ｔ１のタイヤ軸方向の長さ
ＬＴ２ 第２のテーパー部２Ｔ２のタイヤ軸方向の長さ
Ｐ１ 第１の点
Ｐ２ 第２の点
Ｐ３ 起点
Ｐ４ 開口端
ＴＥ トレッド端
ｔｗ トレッド半巾[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire that can improve wandering performance.
[0002]
[Prior art]
In vehicles traveling on rough road surfaces where concave parts such as ridges and non-flat parts such as slant sides are formed, a phenomenon called wandering where a tire gets caught in this non-flat part and the handle is taken and wobbles. In particular, in small trucks with a load capacity of 4 tons, wandering occurs more frequently due to the narrow tread width of tires and getting stuck in large trucks. The tire performance that can suppress the occurrence of this is called wandering performance here).
[0003]
With regard to such wandering performance, a tire having a so-called square shoulder having a tread edge where the tread surface contour line and the buttress surface contour line intersect with each other in the meridian section of the tire has a straight traveling property and uneven wear resistance. The cornering characteristics are excellent, but the interference between the tread edge and the non-flat surface, that is, the side surface of the heel is large, and the wandering performance tends to be inferior.
[0004]
The tires having the square shoulder are often used for large and small truck tires. In many cases, the tires for trucks use a belt layer composed of a plurality of belt plies using metal cords. Therefore, the rigidity of the tread part is higher than that of passenger car tires. As a result, when the tread end of the tire comes into contact with the non-flat part, a large reaction force acts on the handle, making it easier to remove the handle. Improvement of wandering performance is desired in industrial tires.
[0005]
In order to improve such wandering performance, it is desirable to increase the camber thrust (which is a force that can be climbed when the road surface is slanted). For this purpose, the tread end is formed with an arc having a relatively small radius of curvature. A so-called round shoulder, a tapered shoulder having a tapered slope with a large angle with the tread edge cut off (for example, Japanese Patent Laid-Open No. 5-286310), and a shoulder portion with a narrow width extending in the tire circumferential direction. Providing grooves (for example, JP-A-1-95911) has been proposed.
[0006]
However, round shoulders and tapered shoulders mean that the cornering characteristics are likely to deteriorate due to insufficient grip in the lateral direction when the load is transferred to the tread edge, which occurs during cornering. There is a problem that the amount is large and uneven wear such as shoulder wear is likely to occur. In addition, the tire which provided the narrow groove in the tread shoulder part becomes weak appearance especially in the case of a round shoulder, and will be inferior to customer attraction.
[0007]
For this reason, the present applicant has proposed a tire in which a two-step inclined portion is provided in the tread shoulder portion according to Japanese Patent Laid-Open No. 2000-185524. However, in this case, a two-step tapered portion is formed from the tire axial direction outer edge of the longitudinal main groove near the tread edge, and the difference between the second step taper angle and the first step is set to 10 ° or less. .
[0008]
[Problems to be solved by the invention]
Although this tire has improved the wandering performance, further improvement is desired for improving the wandering performance. An object of the present invention is to provide a pneumatic tire capable of improving camber thrust and further improving wandering performance while suppressing occurrence of uneven wear and reduction in cornering characteristics.
[0009]
[Means for Solving the Problems]
In the invention according to claim 1 of the present invention, in a tire meridian cross section in a no-load normal state in which a normal rim is assembled and a normal internal pressure is filled, the tire equatorial plane CO is the most outward in the tire axial direction and the tread end TE. The tread surface up to the first point P1 located outward in the tire axial direction from the near shoulder groove 4B is a main tread portion 2A formed by an arc,
And the tread surface from the 1st point P1 to the 2nd point P2 of the tire axial direction outside is made into the 1st taper part 2T1 formed in the straight line substantially,
Moreover, the tread surface from the second point P2 to the tread end TE is a second tapered portion 2T2 formed substantially by a straight line, and
An angle α1 formed by the first tangent line SP1 at the first point P1 of the main tread portion 2A and the straight line of the first tapered portion 2T1 is 5 ° to 25 °,
A tangent SP2 to the virtual arc line at the intersection of a virtual arc line obtained by extending an arc forming the main tread portion 2A outward in the tire axial direction and a tire radial direction line passing through the second point P2 is a second value. While the angle α2 formed with the straight line of the tapered portion 2T2 is set to 20 ° to 40 ° and the angle difference (α2−α1) is set to be larger than 10 ° and not larger than 30 °,
A plurality of sipings 10 extending outward in the tire axial direction from the tread surface in the main tread portion 2A to the starting point P3 and extending to the opening end P4 of the buttress portion are spaced apart in the circumferential direction.
An angle α3 formed by a straight line L34 connecting the starting point P3 of the siping 10 and the groove bottom at the opening end P4 and a third tangent SP3 with respect to the main tread portion 2A at the starting point P3 is 5 ° to 35 °. A pneumatic tire.
[0010]
In the invention according to claim 2, the siping has a gradually increasing portion that increases the groove depth from the starting point P3 toward the opening end P4, and the angle α3 of the straight line L34 is set to the value of the first tapered portion 2T1. It is characterized in that it is larger than the angle α1 and smaller than the angle α2 of the second tapered portion 2T2, and the maximum groove depth Dm of the groove depth D perpendicular to the groove bottom is 3 to 20 mm.
[0011]
In the invention according to claim 3, the first point P1 has a distance LP1 that is 0.1 to 0.3 times the tread half width tw in the tire axial direction from the tire equatorial plane CO to the tread end TE. The second point P2 is located within a range separated from the tread end TE by a distance LT2 that is 0.03 to 0.20 times the tread half width tw, and is separated from the first tapered portion 2T1. The ratio LT1 / LT2 between the length LT1 in the tire axial direction and the length LT2 in the tire axial direction of the second tapered portion 2T2 is 1.5 to 3.5, and according to claim 4 The invention includes a carcass layer made of a carcass ply and a belt layer made of a plurality of belt plies, wherein the carcass ply and the belt ply are made of an array of steel cords.
[0012]
The invention according to claim 5 is characterized in that the tread rubber forming the tread surface has a complex elastic modulus E * of 5.0 to 7.2 and a loss tangent tan δ of 0.1 to 0.17. And
[0013]
Here, the “regular rim” for setting the no-load normal state is a rim determined for each tire in the standard system including the standard on which the tire is based. For TRA, “Design Rim”, or for ETRTO, “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. The maximum air pressure is for JATMA, and the table is “TIRE LOAD LIMITS” for TRA. The maximum value described in “AT VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” for ETRTO, and 180 kPa for tires for passenger cars. Further, in the present invention, the “regular load” is a load determined by each standard for each tire in a standard system including a standard on which the tire is based. The maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES”. If ETRTO, “LOAD CAPACITY”.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, one embodiment of a pneumatic tire of the present invention is described based on a drawing. FIG. 1 is a meridian cross-sectional view including a tire shaft in a normal state in which a pneumatic tire 1 is assembled on a normal rim (not shown) and filled with a normal internal pressure, and includes a tire shaft in a normal state with no load. 2 shows an outer portion in the tire radial direction of the axial line H indicating the maximum width position, FIG. 2 shows an enlarged view of a tread shoulder portion which is a main portion, and FIG. FIG. 2 is a plan view of a tire developed in a region between E and E, and shows an example in which the pneumatic tire 1 is a truck pneumatic radial tire having a tire size of 225 / 80R17.5.
[0015]
The pneumatic tire 1 is disposed on the inner side of the tread portion 2 and on the outer side in the tire radial direction of the carcass 6 from the tread portion 2 through the sidewall portion 3 to the bead core (not shown) of the bead portion. As shown in FIG. 1, the carcass 6 includes a single carcass ply, and the carcass ply includes a ply in which steel cords are arranged in parallel, and the carcass cord is a tire equatorial plane CO. And a radial structure arranged at an angle of 85 ° to 90 °. As the carcass cord, for example, an organic fiber cord such as polyester, nylon, rayon or the like can be adopted, and the number of carcass plies can be increased.
[0016]
In the present embodiment, the belt layer 7 includes at least two belt cords made of steel cords arranged at an angle of, for example, 10 ° to 70 ° with respect to the tire equator, and in this embodiment, 71 from the inner side in the tire radial direction. The belt ply 71 has a right angle of 50 ° and the belt ply 72 has a right angle of 16 °. The belt ply 73 has three belt plies 72 and 73. A triangle structure with excellent rigidity is achieved by setting the angle 16 ° to the left.
[0017]
Further, as shown in FIG. 3, the tread surface 2a of the pneumatic tire 1 has three central grooves 4A extending in the tire circumferential direction on the tire equatorial plane CO and shoulder grooves 4B and 4B on both sides thereof. A zigzag vertical main groove 4 is provided, and each vertical main groove 4 has a main portion 4a of the same shape in which the circumferential period of the zigzag is aligned in the tire axial direction, and the central groove 4A has a tire axial direction. In the corners on both sides, the shoulder grooves 4B, triangular corners 4b having a shape obtained by inverting the corners are provided at the corners facing inward in the tire axial direction. In addition, a joint portion 4c extending in the tire circumferential direction is provided in the entrance corner portion where the exit corner portion and the small concave portion 4b are not provided, and the zigzag groove protruding ends of the entrance corner and the exit corner have a length of 0 in the tire axial direction. It is removed in the range of 5 to 3.0 mm (in this embodiment, about 1 mm).
[0018]
Further, in the present embodiment, a small-length main groove siping 4d extending in the tire axial direction is formed at the tip of each small recess 4b. The small concave portion 4b and the joint portion 4c prevent the wear of the tread portion at the groove protruding end at the entrance corner and the exit corner, and uneven wear starting from the groove protruding end, and the main groove siping 4d improves the wet grip property. In addition, the occurrence of chipping and uneven wear at the tip of the small concave portion 4b can be prevented, and the amount of slippage with the road surface at this portion can be reduced to suppress uneven wear. The main groove siping 4d has a groove width of about 0.1 to 2.0 mm, preferably about 0.3 to 1.0 mm, and a length of about 1.0 to 7.0 mm, preferably 2.0 to 4. About 0.0 mm, and the depth is set to about 70 to 100% of the depth of the vertical main groove 4, so that the above action is effective.
[0019]
Further, a lateral groove 8 is provided on the tread surface 2a. The lateral groove 8 is a lug groove provided independently of the longitudinal main groove 4 so as to secure a ground contact area of the tread shoulder portion and increase a wear life, and excessively lower the rigidity of the tread shoulder portion. This prevents and prevents a decrease in steering stability due to the lateral grooves 8. The lateral groove 8 extends beyond the tread end TE and opens at a buttress portion 31 that is an outer portion in the tire radial direction of the sidewall 3 to improve drainage and maintain the wet grip and wet traction of the tire. Further, the lateral groove 8 extends toward each corner of the zigzag shoulder groove 4B.
[0020]
Further, as shown in detail in FIG. 2, the lateral groove 8 forms a deep portion 8B from the shallow portion 8A in the tire axial direction through the inclined portion 8C, and this shallow portion 8A prevents a rapid change in the tread rigidity. Uneven wear caused by 8 is suppressed. It should be noted that a distance L8a from the tire equatorial plane CO to the tire axial direction inner end 8a of the lateral groove 8 and a distance L8b from the tire 8A to the boundary point 8b between the inclined portion 8C and the tread 8A to the tread. The ratios L8a / tw and L8b / tw to the tread half width tw in the tire axial direction to the end TE are set as the following ranges.
0.65 ≦ L8a / tw ≦ 0.85
0.75 ≦ L8b / tw ≦ 0.96
It is said. Of course, L8b / tw is larger than L8a / tw, and (L8b / tw) − (L8a / tw) is set to about 0.04 to 0.20.
More preferably, L8a / tw is 0.70 to 0.80, L8b / tw is 0.85 to 0.95, and if L8a / tw is less than 0.65, the ground contact area is reduced and the tire life is adversely affected. At the same time, uneven wear tends to occur, and if it exceeds 0.85, the effect of the lateral groove is hardly exhibited. If L8b / tw is less than 0.75, the effect of the shallow portion is difficult to exert, and if it exceeds 0.96, the effect of the lateral groove is reduced.
[0021]
Further, the tread surface 2a includes a main tread portion 2A centered on the tire equatorial plane CO and a tire axial direction in a tire meridian cross section of a normal rim assembled with a rim and filled with a normal internal pressure and in an unloaded normal state of no load. It forms a bent surface composed of an outer first tapered portion 2T1 and an outer second tapered portion 2T2. The main tread portion 2A extends from the tire equatorial plane CO to a first point P1 positioned outward in the tire axial direction beyond the shoulder groove 4B closest to the tread end TE, and the main tread portion 2A The tread surface 2a has an arc shape, and in the present embodiment, is substantially a single arc. In this specification, “substantial” means that the difference is within a range of about 5% even in such a case. In the above case, the radius of curvature varies only within 5%, and the single It can be considered as a circular arc. The arc has a center on the tire equatorial plane CO and a relatively large radius TR that is 2.5 to 8 times the tread half width tw.
[0022]
The first tapered portion 2T1 is an area from a first point P1 provided at a position beyond the shoulder groove 4B near the tread end TE to a second point P2 located outward in the tire axial direction. The tread surface 2a is formed substantially by a straight line x1. Further, substantially means that only about 5% of the length of the straight line is displaced in the direction perpendicular to the straight line in the entire length. The second tapered portion 2T2 is formed by a substantially straight line x2 from the second point P2 to the tread end TE.
[0023]
By providing these two-step tapered portions 2T1 and 2T2 on the tread shoulder portion, the shoulder land portion can be flexibly rigid, and can suitably absorb shock when colliding with an inclined surface such as a bag, to the handlebar. Can be reduced, wandering can be suppressed, and straight wear and cornering characteristics can be maintained, while the occurrence of uneven wear can be prevented.
[0024]
An angle α1 formed by the first tangent SP1 at the first point P1 of the main tread portion 2A and the straight line x1 of the first tapered portion 2T1 is 5 ° to 25 ° (preferably 6 to 20 °), and A tangent line SP2 to the virtual arc line Cr at the intersection of a virtual arc line Cr obtained by extending an arc forming the main tread portion 2A outward in the tire axial direction and a tire radial direction line passing through the second point P2, The angle α2 formed by the straight line x2 of the second tapered portion 2T2 is set to 20 ° to 40 °, and the angle difference (α2−α1) is set to be greater than 10 ° and 30 ° or less.
[0025]
In the first and second taper portions 2T1 and 2T2, the first taper portion 2T1 is inclined at the angle of 5 ° to 25 °, so that this portion can be grounded. Compared with the portion, the contact pressure can be reduced, and the saddle riding between the road surface and the like can be suppressed and uneven wear can be prevented while improving the overriding ability of the kite. In addition, by setting the angle α2 of the second tapered portion 2T2 to 20 ° to 40 ° and the angle difference (α2−α1) to be larger than 10 °, an excessive amount is formed between the second tapered portion 2T2 and the first tapered portion 2T2. The camber-thrust is prevented by preventing the change in rigidity, and increasing the camber amount, which is the distance in the tire radial direction between the equator point Cq and the second tapered portion 2T2 tread end TE, without causing a large change in rigidity of the shoulder. The value can be increased smoothly, and the wandering property can be improved by improving the escape property of the soot.
[0026]
When the angles α1, α2 of the first and second tapered portions 2T1, 2T2 are less than 5 ° and less than 20 °, respectively, the camber thrust value cannot be effectively increased, and the wandering performance is improved. I can not expect. Conversely, when the angles α1 and α2 exceed 25 ° and 40 °, respectively, an increase in the camber thrust value can be expected, but the shoulder pressure on the shoulder side is significantly reduced, and the contact property with the road surface is lowered. It tends to cause uneven wear in which the portion wears early.
[0027]
In FIG. 1, the first point P1 is located on the outer side in the tire axial direction than the shoulder groove 4B closest to the tread end TE, and the tread half width in the tire axial direction from the tire equatorial plane CO to the tread end TE. The second point P2 is separated from the tread edge by a distance 0.03 to 0.20 times the tread half width tw within a range in which a distance of 0.1 to 0.3 times tw is separated from the tread edge TE. The ratio LT1 / LT2 between the length LT1 of the first tapered portion 2T1 in the tire axial direction and the length LT2 of the second tapered portion 2T2 in the tire axial direction is 1.2 to 3.5.
[0028]
Furthermore, the ratios LT1 / tw, LT2 / tw of the tire axial width LT1 of the first tapered portion 2T1 and the tire axial width LT2 of the second tapered portion 2T2 with respect to the tire half width tw from the tire equatorial plane CO to the tread end TE, It is preferable that the relationship is H or less.
0.08 ≦ LT1 / tw ≦ 0.25
0.02 ≦ LT2 / tw ≦ 0.15
When LT1 / tw is less than 0.08, the wandering performance is deteriorated. When LT1 / tw exceeds 0.25, the steering stability is deteriorated. More preferably, LT1 / tw is 0.08. ~ 0.25.
[0029]
LT2 / tw is about 0.02 to 0.15. When LT2 / tw is less than 0.02, the wandering performance is degraded, and even when it exceeds 0.15, the wandering performance is degraded. More preferably, LT2 / tw is about 0.02 to 0.15. Moreover, it is good to make LT1 / tw-LT2 / tw into the range of 0.06-0.15.
[0030]
The length LT1 is set to be smaller than the tire axial distance L4B from the tire equatorial plane CO to the outermost position in the tire axial direction of the shoulder groove 4B. If LT1> L4B, the ground contact pressure from the shoulder groove 4B outward in the tire axial direction becomes too low, which adversely affects cornering performance and uneven wear resistance.
[0031]
In FIG. 2, the surface of the buttress portion 31 connected to the tread end TE is in contact with the tire radial direction line at the tread end TE in the vicinity of the tread end TE and continues to an arc having a radius SR centered on the outer side of the tire.
[0032]
Further, in the present invention, as shown in FIGS. 1 to 3, a plurality of sipings 10 extending from the tread surface 2 a in the main tread portion 2 </ b> A to the opening end P <b> 4 of the buttress portion 31 as a starting point P <b> 3 are The part is spaced apart in the circumferential direction. In this embodiment, the siping 10 has a depth increasing portion 10a that gradually increases the groove depth from the starting point P3 having a depth of 0 mm toward the outer side in the tire axial direction on at least the point P3 side, and the starting point of the siping 10 A groove bottom is formed by a straight line L34 that connects P3 and the opening end P4 that is the groove bottom of the siping 10. An angle α3 formed by the straight line L34 and a tangent line SP3 on the tread surface 2a of the main tread portion 2A at the starting point P3 is set to 5 ° to 35 °. If the angle is less than 5 °, the siping effect cannot be exhibited. If the angle exceeds 35 °, the rigidity of the tread shoulder portion is excessively lowered, and problems such as chipping tend to occur.
[0033]
Further, the siping 10 sets the angle α3 of the straight line L34 to be larger than the angle α1 of the first taper portion 2T1 and smaller than the angle α2 of the second taper portion 2T2.
[0034]
A large number of sipings 10 arranged over the entire shoulder portion reduce the rigidity of the tread end TE, further reduce the occurrence of wandering, and reduce the amount of slippage with the road surface of the tread shoulder portion, thereby reducing shoulder wear. It is possible to suppress uneven wear and improve tire life. In addition to the straight line, the groove bottom shape of the siping 10 may be formed from a plurality of straight lines 10a, 10b, 10c, etc. as shown in FIG. 4, or a curved shape or a curved shape portion may be added. The starting point P3 may be a circular arc shape or a portion that suddenly deepens at an angle of, for example, about 0 to 45 ° with respect to the radial direction.
[0035]
In order to exhibit the effect of the siping 10 more effectively from the interaction with the first taper portion 2T1 and the second taper portion 2T2, the third point P3 is used as the main tread portion 2A, that is, the first point P1. The tire is positioned inward in the tire axial direction. The fourth point P4 is located on the outer side in the tire radial direction of the tread end TE. Further, the ratio LP3 / tw of the tire axial distance LP3 from the tread end TE to the third point P3 and the tread half width tw is set to 0.1 to 0.4 (preferably 0.15 to 0.30). Set to range. If the ratio is less than 0.1, the siping effect is hardly exhibited. If the ratio exceeds 0.4, the siping width with respect to the tread width becomes too large, and problems such as a decrease in steering stability tend to occur.
[0036]
The maximum groove depth Dm of the groove depth D perpendicular to the groove bottom of the siping 10 from the tread surface 2a is preferably set in the range of 0.5 to 5.0 mm. If it is less than 0.05 mm, the effect of siping is difficult to be exhibited, and if it exceeds 5.0 mm, problems such as chipping and poor steering stability are likely to occur, and new uneven wear starting from siping is more likely to occur (more preferably 1.0 to 3.0 mm). The distance LP4 between the tread end TE and the fourth point P4 (groove bottom at the opening end of the siping 10) is set to about 0 to 2.0 mm, thereby increasing the rigidity at the tread edge during wandering. Adjusted to improve wandering performance.
[0037]
As shown in FIG. 1, in this embodiment, the tread structure employs a so-called SOT (Sidewall Over Tread) structure in which the sidewall rubber layer 3S covers the tread rubber 2S in the buttress portion 31, and the belt end of the tread shoulder portion is The base layer 2B made of low heat-generating rubber covers and suppresses heat generation near the belt end, thereby improving durability. On the tread surface 2a, a cap layer 2C made of rubber having high wear resistance is exposed. The groove bottoms of the center groove 4A, the shoulder groove 4B, and the lateral groove 8 expose the cap layer. Further, a breaker cushion rubber 9 is filled between the end of the belt layer 7 and the carcass 6 to maintain the shape of the belt layer 7 and to peel off due to shearing force generated between the carcass layer and the belt layer near the belt end. To prevent and improve durability.
[0038]
Further, the tread rubber 2S forming the tread surface 2a, in this embodiment, the rubber of the cap layer 2C has a complex elastic modulus E * of 5.0 to 7.2 and a loss tangent tan δ of 0.1 to 0.17. Yes. In this specification, the loss elastic modulus E ″ and the loss tangent tan δ are obtained by measuring the temperature at 70 ° C., the frequency of 10 Hz, the initial strain of 0%, the strain at the time of measurement, and the size of the sample using a viscoelastic spectrum meter manufactured by Iwamoto Seisakusho. It is a numerical value measured as heat 2 mm, length 50 mm, and width 4 mm.
[0039]
When the loss elastic modulus E ″ is less than 5 or the loss tangent tan δ is greater than 0.17, the wear resistance performance and the steering stability performance are degraded, and the loss elastic modulus E ″ is greater than 7.2, or It has been found that when the loss tangent tan δ is less than 0.1, the wandering performance is degraded.
[0040]
Although one embodiment of the present invention has been described above, the present invention is not limited to the illustrated embodiment, and various modifications are possible.
[0041]
【Example】
A pneumatic radial tire for trucks having a tire size of 225 / 80R17.5 was made as a prototype, and each performance of the tire was evaluated. The results are shown in Table 1. The evaluation method is as follows. In Table 1, the loss elastic modulus E ″ and the loss tangent tan δ are measured by the methods described above.
<Camber thrust>
A sample tire was mounted on a regular JATMA rim, and the thrust force at a camber angle of 1 ° and 5 ° was measured under the conditions of a normal internal pressure and a normal load of JATMA.
<Cornering Force>
A sample tire was mounted on a regular MATMA rim, and the cone ring force was measured at a slip angle of 1 ° and 5 ° at a speed of 4 km / h under the conditions of a regular internal pressure and a regular load of JATMA.
<Steering stability>
A test tire fitted with a regular JATMA rim and filled with a regular JATMA internal pressure was fitted to a domestic 4 ton dump truck. The vehicle was taken, the handle of the vehicle was taken, and the overall evaluation of the vehicle's wobbling and heel escape performance etc. was evaluated by a 10-point method based on the driver's sensuality. The larger the value, the better.
<Abrasion resistance>
A sample tire fitted with a regular JATMA rim, filled with a regular JATMA internal pressure, is mounted on a domestic 4 ton dump truck, and the test course is 4 km ton full load. It was run and evaluated for wear resistance and estimated tire life.
[0042]
[Table 1]

[0043]
【The invention's effect】
As described above, the pneumatic tire of the present invention can increase the camber thrust value while maintaining the performance such as steering stability, and can improve the wandering performance.
[Brief description of the drawings]
FIG. 1 is a meridian cross-sectional view of a pneumatic tire showing an embodiment of the present invention.
FIG. 2 is a partially enlarged view in which the tread shoulder portion is enlarged.
FIG. 3 is a development view showing an example of a tread pattern to which the present invention is applied.
FIG. 4 is a cross-sectional view showing another example of siping.
[Explanation of symbols]
2 Tread 2A Main tread portion 2T1 First taper portion 2T2 Second taper portion 3 Side wall 4 Vertical main groove 4A Central groove 4B Shoulder groove 6 Carcass 7 Belt layer 8 Horizontal groove 9 Breaker cushion 10 Siping CO Tire equatorial plane D Groove depth Dm Maximum groove depth Dm
LT1 Length of the first tapered portion 2T1 in the tire axial direction LT2 Length of the second tapered portion 2T2 in the tire axial direction P1 First point P2 Second point P3 Starting point P4 Open end TE Tread end tw Tread half width

Claims (5)

A tire rim in the tire meridian section of an unloaded normal state in which the rim is assembled to the regular rim and filled with the regular internal pressure. The tread surface up to the first point P1 located outside is a main tread portion 2A formed by an arc,
And the tread surface from the 1st point P1 to the 2nd point P2 of the tire axial direction outside is made into the 1st taper part 2T1 formed in the straight line substantially,
Moreover, the tread surface from the second point P2 to the tread end TE is a second tapered portion 2T2 formed substantially by a straight line, and
An angle α1 formed by the first tangent line SP1 at the first point P1 of the main tread portion 2A and the straight line of the first tapered portion 2T1 is 5 ° to 25 °,
A tangent SP2 to the virtual arc line at the intersection of a virtual arc line obtained by extending an arc forming the main tread portion 2A outward in the tire axial direction and a tire radial direction line passing through the second point P2 is a second value. While the angle α2 formed with the straight line of the tapered portion 2T2 is set to 20 ° to 40 ° and the angle difference (α2−α1) is set to be larger than 10 ° and not larger than 30 °,
A plurality of sipings 10 extending outward in the tire axial direction from the tread surface in the main tread portion 2A to the starting point P3 and extending to the opening end P4 of the buttress portion are spaced apart in the circumferential direction.
An angle α3 formed by a straight line L34 connecting the starting point P3 of the siping 10 and the groove bottom at the opening end P4 and a third tangent SP3 with respect to the main tread portion 2A at the starting point P3 is 5 ° to 35 °. Pneumatic tire. The siping has a depth increasing portion that increases the groove depth from the starting point P3 toward the opening end P4, and the angle α3 of the straight line L34 is larger than the angle α1 of the first tapered portion 2T1, and the first The pneumatic groove according to claim 1, characterized in that it is smaller than the angle α2 of the tapered portion 2T2 of 2 and the maximum groove depth Dm of the groove depth D perpendicular to the groove bottom is 0.5 to 5 mm. tire. The first point P1 is within a range in which a distance LP1 of 0.1 to 0.3 times the tread half width tw in the tire axial direction from the tire equatorial plane CO to the tread end TE is separated from the tread end. The point P2 is located within a range separating the distance LT2 from 0.03 to 0.20 times the tread half width tw from the tread end TE, and the length LT1 in the tire axial direction of the first tapered portion 2T1; The pneumatic tire according to claim 1 or 2, wherein a ratio LT1 / LT2 to the length LT2 in the tire axial direction of the second tapered portion 2T2 is 1.5 to 3.5. The carcass ply comprising a carcass ply and a belt ply comprising a plurality of belt plies, wherein the carcass ply and the belt ply comprise an array of steel cords. Pneumatic tires. 5. The tread rubber forming the tread surface has a complex elastic modulus E * of 5.0 to 7.2 and a loss tangent tan δ of 0.1 to 0.17. The pneumatic tire according to any one of the above.

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