JP2004009999A - Pneumatic tire - Google Patents

Abstract

A pneumatic tire capable of improving wandering performance is provided.
A shoulder groove 4B located radially outward from the tire equatorial plane CO in the tire axial direction and at the tread end TE in a tire meridian section in a normal state with no load and a normal rim assembled to a normal rim and filled with a normal internal pressure. The tread surface up to a first point P1 located outward in the tire axial direction is a main tread portion 2A formed by an arc, and from the first point P1 to a second point P2 outward in the tire axial direction. The tread surface is a first tapered portion 2T1 formed by a substantially straight line, and the tread surface from the second point P2 to the tread end TE is formed by a second tapered portion 2T2 formed by a substantially straight line. At the same time, the angle α1 at the point P1 is 5 ° to 25 °, and the tangent SP2 to the virtual circle at the second point P2 is the straight line of the second tapered portion 2T2. The angle α2 to 20 ° to 40 °.
[Selection diagram] Fig. 1

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]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a pneumatic tire that can improve wandering performance.
[0002]
[Prior art]
In vehicles running on uneven terrain where concave parts such as ruts and uneven parts such as slopes are formed, a phenomenon called wandering, in which tires are caught on these uneven parts and the steering wheel is picked up and fluctuates. It is easy to occur, especially in a small truck with a loading capacity of 4 tons, the tire tread width is narrow and the frequency of wandering caused by getting stuck in the rut of a large truck increases the difficulty of getting out of the rut (wandering phenomenon) Here, the performance of a tire that can suppress the occurrence of wandering is referred to as wandering performance).
[0003]
Regarding such wandering performance, in a meridional section of the tire, a tire having a so-called square shoulder having a tread edge where a tread surface contour line and a buttress surface contour line intersect as an edge has a straight running property and an uneven wear resistance. On the other hand, the cornering characteristics are excellent, but the interference between the tread edge and the uneven surface, that is, the side surface of the rut is large, and the wandering performance tends to be poor.
[0004]
Note that tires having the square shoulder are often used for large and small truck tires, but truck tires often use a belt layer comprising a plurality of belt plies using a metal cord. As a result, the rigidity of the tread portion 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 portion, a large reaction force acts on the handle, and the handle is easily taken off. It is desired that tires for tires have improved wandering performance.
[0005]
In order to improve such wandering performance, it is desirable to increase the camber thrust (which is a force capable of riding when the road surface is oblique), and for this purpose, the tread edge is provided by an arc having a relatively small radius of curvature. And a tapered shoulder having a tapered slope with a large angle with the tread edge cut off (for example, Japanese Patent Application Laid-Open No. 5-286310). Provision of a groove (for example, JP-A-1-95911) has been proposed.
[0006]
However, when using a round shoulder or a tapered shoulder, when moving the load to the tread edge that occurs during cornering, the grip in the lateral direction is insufficient, and the cornering characteristics are likely to be reduced, and slip on the road surface near the tread edge There is a problem that the amount is large and uneven wear such as shoulder drop wear is likely to occur. A tire having a narrow groove in the tread shoulder portion has a weak appearance, especially in the case of a round shoulder, and is inferior in customer attraction.
[0007]
For this reason, the present applicant has proposed a tire in which a two-step inclined portion is provided in a tread shoulder portion according to Japanese Patent Application Laid-Open No. 2000-185524. However, in this case, a two-stage tapered portion is formed from the outer edge in the tire axial direction of the vertical main groove near the tread edge, and the difference between the second-stage taper angle and the first-stage taper angle is 10 ° or less. .
[0008]
[Problems to be solved by the invention]
This tire has improved wandering performance, but further improvement in wandering performance is desired. An object of the present invention is to provide a pneumatic tire that can increase camber thrust while suppressing uneven wear and a decrease in cornering characteristics, and can further improve wandering performance.
[0009]
[Means for Solving the Problems]
The invention according to claim 1 of the present application is characterized in that, in a tire meridian section in a no-load normal state where no rim is assembled to a normal rim and is filled with a normal internal pressure, a tire axial direction outward from the tire equatorial plane CO and the tread end TE The tread surface up to the first point P1, which is located further outward in the tire axial direction than the near shoulder groove 4B, is a main tread portion 2A formed by an arc,
And a tread surface from the first point P1 to a second point P2 outward in the tire axial direction is a first tapered portion 2T1 formed by a substantially straight line,
Moreover, the surface of the tread from the second point P2 to the tread end TE is a second tapered portion 2T2 formed by a substantially straight line,
An angle α1 between the first tangent 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 °,
The tangent SP2 to the virtual arc line at the intersection of the virtual arc line extending the arc forming the main tread portion 2A outward in the tire axial direction and the tire radial direction line passing through the second point P2 is the second. While the angle α2 between the tapered portion 2T2 and the straight line is 20 ° to 40 ° and the angle difference (α2−α1) is larger than 10 ° and 30 ° or less,
A plurality of sipes 10 extending outward in the tire axial direction from the tread surface in the main tread portion 2A as a starting point P3 and extending to the opening end P4 of the buttress portion are circumferentially spaced, and
The angle α3 formed by the straight line L34 connecting the starting point P3 of the siping 10, the groove bottom at the opening end P4, and the third tangent SP3 to the main tread portion 2A at the starting point P3 is 5 ° to 35 °. Pneumatic tire.
[0010]
The invention according to claim 2 is characterized in that the siping has a depth gradually increasing portion that increases the groove depth from the starting point P3 toward the opening end P4, and that the angle α3 of the straight line L34 is the same as that 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 in a direction perpendicular to the groove bottom is 3 to 20 mm.
[0011]
In the invention according to claim 3, the first point P1 is defined as a distance LP1 from the tire equatorial plane CO to the tread end TE that is 0.1 to 0.3 times a half tread half width tw in the tire axial direction. The second point P2 is located within a range that separates a distance LT2 of 0.03 to 0.20 times the tread half width tw from the tread end TE, and the first point 2T1 The ratio LT1 / LT2 of the length LT1 in the tire axial direction to the length LT2 in the tire axial direction of the second tapered portion 2T2 is set to 1.5 to 3.5, and according to claim 4, The invention includes a carcass layer composed of a carcass ply and a belt layer composed of a plurality of belt plies, wherein the carcass ply and the belt ply are composed 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 defined for each tire in a standard system including the standard on which the tire is based. , TRA, “Design Rim”, or ETRTO, “Measuring Rim”. The "normal internal pressure" is the air pressure that is defined for each tire in the standard system including the standard on which the tire is based. The maximum air pressure is JATMA, and the table "TIRE LOAD LIMITS" is TRA. The maximum value described in AT VARIOUS COLD INFLATION PRESSURES is set to "INFLASION PRESSURE" for ETRTO, and 180 kPa when the tire is for a passenger car. Further, in the present invention, the “regular load” is a load defined for each tire in the standard system including the standard on which the tire is based. The maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURESRES” is used, and in the case of ETRTO, “LOAD CAPACITY” is used.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a pneumatic tire of the present invention will be described with reference to the drawings. FIG. 1 is a meridian cross-sectional view including a tire shaft in a no-load normal state in which a pneumatic tire 1 is rim-assembled on a normal rim (not shown) and filled with a normal internal pressure. 2 shows a radially outer portion of the axial line H indicating the maximum width position in the tire radial direction, FIG. 2 shows an enlarged view of a tread shoulder portion, which is a main portion, and FIG. FIG. 2 is a plan view in which tires are developed in a region between E and E, and shows a case where the pneumatic tire 1 is a pneumatic radial tire for trucks having a tire size of 225 / 80R17.5.
[0015]
The pneumatic tire 1 is provided with a carcass 6 extending from the tread portion 2 to the bead core (not shown) of the bead portion via the sidewall portion 3, and inside the tread portion 2 and outside the carcass 6 in the tire radial direction. As shown in FIG. 1, the carcass 6 is composed of one carcass ply, and the carcass ply is made of a ply in which steel cords are arranged in parallel. Has a radial structure arranged at an angle of 85 ° to 90 °. The carcass cord may be an organic fiber cord such as polyester, nylon, rayon, or the like, and the number of carcass plies may be increased.
[0016]
In the present embodiment, the belt layer 7 has 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. The belt cord is formed of three belt plies 72, 73, and the angle and direction of the belt cord with the tire equatorial plane CO are as follows. Has a triangle structure that is excellent in rigidity by being set to 16 ° rising to the left.
[0017]
As shown in FIG. 3, in the tread surface 2a of the pneumatic tire 1, in the present embodiment, a central groove 4A extending in the tire circumferential direction on the tire equatorial plane CO and shoulder grooves 4B, 4B on both sides thereof. The zigzag vertical main grooves 4 are provided. 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. In the corners on both sides, the shoulder grooves 4B, triangular small recesses 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 4c extending in the tire circumferential direction is provided at the outer corner and the inner corner where the small recess 4b is not provided, and the zigzag groove projecting ends at the inner corner and the outer corner have a length of 0 in the tire axial direction. It is removed in a range of 0.5 to 3.0 mm (about 1 mm in this embodiment).
[0018]
Further, in the present embodiment, a main groove siping 4d having a small length extending in the tire axial direction is formed at the tip of each small concave portion 4b. The small recesses 4b and the joints 4c prevent the tread from being chipped at the protruding ends of the groove at the entering corner and the protruding corner, and uneven wear originating from the protruding end of the groove, and the main groove siping 4d improves wet grip performance. At the same time, it is possible to prevent chipping at the protruding end of the small concave portion 4b and prevent occurrence of uneven wear, and to reduce the amount of slip on the road surface at this portion 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 mm. About 0.0 mm and the depth is about 70 to 100% of the depth of the vertical main groove 4, so that the above-mentioned action is effective.
[0019]
Further, a lateral groove 8 is provided on the tread surface 2a. The lateral groove 8 forms a lug groove that is provided independently without being connected to the vertical main groove 4, thereby securing a contact area of the tread shoulder portion to increase a wear life and preventing an excessive decrease in rigidity of the tread shoulder portion. Thus, a decrease in steering stability due to the lateral groove 8 is suppressed. The lateral groove 8 extends beyond the tread end TE and opens at a buttress portion 31 that is an outer portion of the sidewall 3 in the tire radial direction to enhance drainage and maintain wet grip and wet traction of the tire. The lateral groove 8 extends toward each corner of the zigzag shoulder groove 4B.
[0020]
As shown in detail in FIG. 2, the lateral groove 8 forms a deep part 8B from the shallow part 8A in the tire axial direction through the inclined part 8C, and the shallow part 8A prevents a sudden change in tread rigidity. 8 is suppressed. In addition, a distance L8a from the tire equatorial plane CO to the inner end 8a of the lateral groove 8 in the tire axial direction and a distance L8b from the tire 8A to a boundary point 8b of the shallow portion 8A with the inclined portion 8C, the tread from the tire equatorial plane CO. The ratios L8a / tw and L8b / tw to the tread half width tw in the tire axial direction up to the end TE are set in the following ranges.
0.65 ≦ L8a / tw ≦ 0.85
0.75 ≦ L8b / tw ≦ 0.96
And Naturally, L8b / tw is larger than L8a / tw, and (L8b / tw)-(L8a / tw) is about 0.04 to 0.20.
More preferably, L8a / tw is 0.70 to 0.80, and L8b / tw is 0.85 to 0.95. When L8a / tw is less than 0.65, the contact area decreases and the tire life is adversely affected. At the same time, uneven wear is apt to occur, and when it exceeds 0.85, the effect of the lateral groove is difficult to exert. When L8b / tw is less than 0.75, the effect of the shallow portion is hardly exhibited, and when L8b / tw exceeds 0.96, the effect of the lateral groove decreases.
[0021]
Further, the tread surface 2a has a main tread portion 2A centered on the tire equatorial plane CO and a tire axial direction in a tire meridian section in a normal rim assembled in a normal rim, filled with a normal internal pressure, and has no load and no load. It has a bent surface composed of an outer first tapered portion 2T1 and an outer second tapered portion 2T2. Further, the main tread portion 2A extends from the tire equatorial plane CO to a first point P1 located outside 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 is formed in an arc shape, in this embodiment, substantially a single arc. In this specification, “substantially” means that the difference is within a range of about 5% even when considered as such. In the above case, the radius of curvature fluctuates only within 5%, and Means that it can be regarded as a circular arc. The arc has a center on the tire equatorial plane CO and has a relatively large radius TR of 2.5 to 8 times the tread half width tw.
[0022]
Further, the first tapered portion 2T1 is located in a region 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 dovetail tread surface 2a is formed substantially by a straight line x1. Substantially means that only about 5% of the length of the straight line in the entire length is displaced in a direction perpendicular to the straight line. 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 the two-stage tapered portions 2T1 and 2T2 on the tread shoulder portion, the land portion of the shoulder can soften its rigidity and can appropriately absorb an impact at the time of collision with an inclined surface such as a rut. Can be reduced, wandering can be suppressed, straight running and cornering characteristics can be maintained, and occurrence of uneven wear can be prevented.
[0024]
The 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 °), A tangent SP2 to the virtual arc line Cr at an 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 between the straight line x2 of the second tapered portion 2T2 and the straight line x2 is set to 20 ° to 40 °, and the angle difference (α2−α1) is set to more than 10 ° and 30 ° or less.
[0025]
In such first and second tapered portions 2T1 and 2T2, the first tapered portion 2T1 has the α1 inclined at 5 ° to 25 °, so that this portion can also be grounded. The contact pressure can be reduced as compared with the portion, and the ability to ride over the rut is improved, while, for example, dragging with a road surface is suppressed, and uneven wear is prevented. In addition, by setting the angle α2 of the second tapered portion 2T2 to 20 ° to 40 ° and setting the angle difference (α2−α1) to more than 10 °, an excessive angle between the second tapered portion 2T2 and the first tapered portion 2T2 is obtained. The camber amount, which is the distance in the tire radial direction between the equator point Cq and the tread end TE of the second tapered portion 2T2, is increased without causing a large change in the rigidity of the shoulder. The value can be smoothly increased, and the escape property of the rut can be improved to improve the wandering property.
[0026]
When the angles α1 and α2 of the first and second tapered portions 2T1 and 2T2 are less than 5 ° and less than 20 °, respectively, an effective increase in the camber thrust value cannot be expected, and the wandering performance is improved. 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. However, the shoulder pressure is significantly reduced and the shoulder contact with the road surface is reduced. It tends to cause uneven wear in which the part is worn early.
[0027]
In FIG. 1, the first point P1 is located further outward in the tire axial direction than the shoulder groove 4B closest to the tread end TE, and has a tread half width in the tire axial direction from the tire equatorial plane CO to the tread end TE. Within a range that separates a distance of 0.1 to 0.3 times tw from the tread edge TE, the second point P2 separates a distance of 0.03 to 0.20 times the tread half width tw from the tread edge. 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 2.0. 3.5.
[0028]
Further, each ratio LT1 / tw, LT2 / tw of the tire axial width LT1 of the first taper portion 2T1 and the tire axial width LT2 of the second taper 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 be 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 degraded. When LT1 / tw exceeds 0.25, the steering stability is deteriorated, and more preferably, LT1 / tw is 0.08. ０．２0.25.
[0029]
LT2 / tw is about 0.02 to 0.15. If LT2 / tw is less than 0.02, the wandering performance is reduced, and even if it exceeds 0.15, the wandering performance is reduced. More preferably, LT2 / tw is about 0.02 to 0.15. Further, it is preferable that LT1 / tw−LT2 / tw be in the range of 0.06 to 0.15.
[0030]
The length LT1 is smaller than the tire axial distance L4B from the tire equatorial plane CO to the outermost position of the shoulder groove 4B in the tire axial direction. If LT1> L4B, the contact pressure at the land portion outward from the shoulder groove 4B in the axial direction of the tire 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 near the tread end TE and is continuous with an arc having a radius SR having a center outside the tire.
[0032]
Further, in the present invention, as shown in FIGS. 1 to 3, a plurality of sipes 10 extending from the tread surface 2a in the main tread portion 2A to the opening end P4 of the buttress portion 31 are formed as shoulders between the lateral grooves 8. Part is circumferentially spaced. In the present 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 outside in the tire axial direction on at least the point P3 side. A groove bottom is formed by a straight line L34 connecting P3 and the opening end P4 which is the groove bottom of the siping 10. The angle α3 formed by the straight line L34 and the tangent SP3 on the tread surface 2a of the main tread portion 2A at the starting point P3 is 5 ° to 35 °. If the angle is less than 5 °, the effect of siping cannot be exhibited, and if it exceeds 35 °, the rigidity of the tread shoulder portion is excessively reduced, and problems such as chipping tend to occur.
[0033]
Further, in the siping 10, the angle α3 of the straight line L34 is larger than the angle α1 of the first tapered portion 2T1 and smaller than the angle α2 of the second tapered portion 2T2.
[0034]
A large number of sipings 10 arranged over the entire shoulder portion reduce the rigidity of the tread end TE to further reduce the occurrence of wandering, reduce the amount of slip of the tread shoulder portion with the road surface, and reduce shoulder slippage wear. Called uneven wear can be suppressed and tire life can be improved. 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. At the starting point P3, an arc shape or a portion that suddenly becomes deeper at an angle of about 0 to 45 ° with respect to the radial direction can be used.
[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 set on the main tread portion 2A, that is, the first point P1 Of the tire in the axial direction. Further, the fourth point P4 is located outward of the tread end TE in the tire radial direction. The ratio LP3 / tw between the tire axial distance LP3 from the tread end TE to the third point P3 and the tread half width tw is 0.1 to 0.4 (preferably 0.15 to 0.30). Set to range. If it is less than 0.1, the effect of siping is hardly exhibited, and if it exceeds 0.4, the width of the siping becomes too large relative to the tread width, and problems such as a decrease in steering stability tend to occur.
[0036]
It is preferable that the maximum groove depth Dm of the groove depth D in the direction perpendicular to the groove bottom of the siping 10 from the tread surface 2a be set in the range of 0.5 to 5.0 mm. If it is less than 0.05 mm, the effect of siping is hardly exhibited, and if it exceeds 5.0 mm, problems such as chipping and reduced steering stability, as described above, and new uneven wear starting from the siping tend to occur (preferably more preferably). , 1.0 to 3.0 mm). The distance LP4 between the tread end TE and the fourth point P4 (the groove bottom at the opening end of the siping 10) is set to about 0 to 2.0 mm, so that the rigidity at the tread edge during wandering is reduced. Adjusted to improve wandering.
[0037]
As shown in FIG. 1, in this embodiment, the tread structure employs a so-called SOT (Sidewall Over Thread) 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 In addition, the base layer 2B made of a low heat-generating rubber is covered to suppress heat generation near the belt end, thereby improving durability. The cap layer 2C made of rubber having high wear resistance is exposed on the tread surface 2a. In addition, the groove bottoms of the central groove 4A, the shoulder groove 4B, and the lateral groove 8 expose the cap layer. Further, a gap between the end of the belt layer 7 and the carcass 6 is filled with a breaker cushion rubber 9 to maintain the shape of the belt layer 7 and to prevent peeling due to shear force generated between the carcass layer and the belt layer near the belt end. Prevention and improved durability performance.
[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. I have. In the present specification, the loss elastic modulus E ″ and the loss tangent tan δ are measured at a temperature of 70 ° C., a frequency of 10 Hz, an initial strain of 0%, a strain% at the time of measurement, and a sample size by a viscoelastic spectrum meter manufactured by Iwamoto Seisakusho. It is a numerical value measured as heat 2 mm, length 50 mm, 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 and the steering stability deteriorate, 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 reduced.
[0040]
Although the 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 prototyped, and each performance of the tire was evaluated. Table 1 shows the results. The evaluation method is as follows. In Table 1, the loss modulus E ″ and the loss tangent tan δ are measured by the above-described methods.
<Camber thrust>
The test tire was mounted on a regular rim of JATMA, and the thrust force at a camber angle of 1 ° and 5 ° was measured under the conditions of a regular internal pressure and a regular load of JATMA.
<Cornering Force>
The test tire was mounted on a regular JATMA rim, and the cone ring force at a slip angle of 1 ° and 5 ° was measured at a speed of 4 km / h under conditions of a regular internal pressure and a regular load of JATMA.
<Driving stability>
Attach to a JATMA regular rim, attach a trial tire filled with JATMA regular internal pressure to a domestic 4 ton dump truck, and on a test course under the condition of full loading of 4 tons, rutted road surface, normal road surface, speed 60 km / h The vehicle was picked up, the handle of the vehicle was taken, the vehicle was wobbling, and the rut escape performance was evaluated by the ten-point method based on the driver's sensuality. The higher the value, the better.
<Wear resistance>
Installed on a regular JATMA rim, mounted with a trial tire filled with JATMA regular internal pressure on a 4-ton dump truck manufactured in Japan, and under a condition of full loading of 4 tons, a total of 3000 km of a general road type and highway type test course on a test course After running, the abrasion resistance performance and the estimated tire life were evaluated.
[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 performance such as steering stability and improve wandering performance.
[Brief description of the drawings]
FIG. 1 is a meridional section of a pneumatic tire according to an embodiment of the present invention.
FIG. 2 is a partial enlarged view of the tread shoulder portion.
FIG. 3 is a development view showing an example of a tread pattern to which the present invention is applied.
FIG. 4 is a sectional view showing another example of siping.
[Explanation of symbols]
2 tread
2A main tread
2T1 First taper section
2T2 2nd taper part
3 Sidewall
4 vertical main groove
4A center 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 The second point
P3 Starting point
P4 Open end
TE tread edge
tw tread half width

Claims (5)

In a tire meridian section in a no-load and no-load normal state where the tire is assembled to a regular rim and filled with a regular internal pressure, in the tire axial direction, the shoulder groove 4B is located outward from the tire equatorial plane CO in the tire axial direction and closest to the tread end TE. The tread surface up to the first point P1 located on the outside is defined as a main tread portion 2A formed by an arc,
And a tread surface from the first point P1 to a second point P2 outward in the tire axial direction is a first tapered portion 2T1 formed by a substantially straight line,
Moreover, the surface of the tread from the second point P2 to the tread end TE is a second tapered portion 2T2 formed by a substantially straight line,
An angle α1 between the first tangent 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 °,
The tangent SP2 to the virtual arc line at the intersection of the virtual arc line extending the arc forming the main tread portion 2A outward in the tire axial direction and the tire radial direction line passing through the second point P2 is the second. While the angle α2 between the tapered portion 2T2 and the straight line is 20 ° to 40 ° and the angle difference (α2−α1) is larger than 10 ° and 30 ° or less,
A plurality of sipes 10 extending outward in the tire axial direction from the tread surface in the main tread portion 2A as a starting point P3 and extending to the opening end P4 of the buttress portion are circumferentially spaced, and
The angle α3 formed by the straight line L34 connecting the starting point P3 of the siping 10, the groove bottom at the opening end P4, and the third tangent SP3 to the main tread portion 2A at the starting point P3 is 5 ° to 35 °. Pneumatic tire. 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 larger than the angle α1 of the first tapered portion 2T1, and 2. The pneumatic pneumatic pump according to claim 1, wherein the maximum groove depth Dm of the groove depth D in a direction perpendicular to the groove bottom is 0.5 to 5 mm. tire. The first point P1 is within a range that separates the distance LP1 from the tire equatorial plane CO to the tread end TE by a distance LP1 of 0.1 to 0.3 times the tread half width tw in the tire axial direction from the tread end. The point P2 is located within a distance LT2 of 0.03 to 0.20 times the half width tw of the tread from the tread end TE, and the length LT1 of the first taper portion 2T1 in the tire axial direction; The pneumatic tire according to claim 1 or 2, wherein a ratio LT1 / LT2 of the second taper portion 2T2 to a length LT2 in the tire axial direction is set to 1.5 to 3.5. A carcass ply comprising a carcass ply and a belt layer comprising a plurality of belt plies, wherein the carcass ply and the belt ply comprise an array of steel cords. Pneumatic tires. 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. A pneumatic tire according to any one of the above.

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