JP3583537B2 - Pneumatic radial tire - Google Patents

Description

【００２３】
表１に示すところから明らかなように、発明タイヤはいずれも、空荷時および積荷時のそれぞれにおいて、従来タイヤに比して直進安定性を大きく向上させることができ、なかでも、積荷時の直進安定性は、トレッド部に側方張出し部を設けることによって顕著に改善されることになる。
【００２４】
【発明の効果】
かくしてこの発明によれば、空荷時、積荷時の別なく、ワンダリング現象の発生を有効に抑制して直進安定性を大きく向上させることができる。
【図面の簡単な説明】
【図１】この発明の実施形態を示すトレッド外輪郭線図である。
【図２】キャバースラストの発生態様を例示するタイヤ幅方向断面図である。
【図３】トレッド外輪郭線の曲率半径が小さい場合を示すタイヤ幅方向断面図である。
【図４】ワンダリング現象の発生状況を示す略線正面図である。
【符号の説明】
ＣＲ_１ 第１の円弧
ＣＲ_２ 第２の円弧
ＣＲ_３ 第３の円弧
Ｒ_１ ，Ｒ_２ ，Ｒ_３ 曲率半径
ＴＤ トレッド部
Ｗ トレッド幅
Ｇ 周方向溝
ＳＩ 側方張出し部
ａ 第１の円弧の仮想延長線
Ｘ−Ｘ 対称軸[0001]
TECHNICAL FIELD OF THE INVENTION
This invention, for example, when the vehicle travels on an inclined surface of a road having irregularities such as a rut, the occurrence of a so-called wandering phenomenon, which is a complicated movement of tires that cannot be predicted by the driver, when the vehicle is unloaded, TECHNICAL FIELD The present invention relates to a pneumatic radial tire having a significantly improved straight-running stability by suppressing the load at all times, and particularly to a tire suitable for use in a light truck, a small truck / bus, and a truck / bus.
[0002]
[Prior art]
Radial tires in which the carcass cords extend in a direction substantially perpendicular to the tire equatorial plane are arranged, and are excellent in wear resistance and steering stability. Radial tires have been used more frequently than bias tires not only in passenger cars but also in vehicles such as small trucks, trucks and buses.
[0003]
[Problems to be solved by the invention]
However, in recent years when vehicles are running at high speeds daily due to the expansion and maintenance of the road network, the occurrence of particularly severe wandering phenomena in radial tires has been sufficiently suppressed to improve straight running stability and further improve safety. Is strongly required.
[0004]
Here, as to the occurrence of the wandering phenomenon in the radial tire, as shown in FIG. 4, when the tire T rolls on an inclined road surface S such as a rut, the load load W, each of the reaction force F _R and the camber thrust F _c from the road acts, and, so that the lateral force F _Y as resultant force of horizontal component force of each of these forces acts. By the way, when the tire has a radial structure, the rigidity of the tread portion is increased, and the camber thrust _Fc is smaller than that of the tire having the bias structure. F _Y is the only relatively large corresponding to the decrease in the camber thrust F _c, thus, the tire T, is strongly slides down trend towards the inclined surface downwardly, ruts riding past wandering to be difficult The phenomenon occurs.
[0005]
Accordingly, the present invention increases the camber thrust of the radial tire to sufficiently reduce the occurrence of wandering on an inclined surface such as a rutted road regardless of the magnitude of the applied load, in other words, regardless of the size of the tread contact width. It is an object of the present invention to provide a pneumatic radial tire in which the straight running stability is greatly improved by suppressing the above.
[0006]
[Means for Solving the Problems]
The pneumatic radial tire of the present invention includes a pair of beads and sidewalls, and a toroidal tread portion continuous to both sidewall portions, and a radial carcass for reinforcing the respective portions, and A belt that reinforces the tread portion on the outer peripheral side of the crown portion of the radial carcass,
The outer contour of the tread in the cross section in the tire width direction under the filling of the prescribed internal pressure, the first arc overlapping the tire equatorial plane and centered on the axis of symmetry of the tire cross section, and adjacent to the first arc At least three types of arcs are defined as a second arc and a third arc continuous with the second arc in the tire width direction, and each of the second and third arcs is defined by the first arc. And a radius of curvature of the second circular arc is larger than that of the third circular arc while being disposed outside the virtual extension line of the circular arc in the tire radial direction.
[0007]
Here, preferably, the radius of curvature of the second arc is larger than that of the first arc, and preferably, a circumferential groove is provided at a joint position between the first arc and the second arc.
[0008]
And, more preferably, the first arc and the second arc are joined at a position 0.15 to 0.28 times the tread width from the center axis of the tire cross section, and still more preferably, A lateral overhanging part is provided that contacts only when rolling on an inclined surface.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows the outer contour of the tread in the cross section in the tire width direction under a state where the tire is filled with a specified internal pressure. Tire components other than those shown are the same as those of a conventional general radial tire. It has a structure of
[0010]
Here, the first arc CR ₁ having a center on the axis of symmetry X-X of the tire section overlapping the tire equatorial plane, adjacent to the arc CR ₁ of the first, 0-0 from the symmetry axis X-X. position of 28W, the second arc CR ₂ centered at a line parallel with X-X, of the second circular arc CR _2, on the outer side of the tire width direction, the third arc preferably continuous smooth CR ₃ and three types of arcs, and both the second and third arcs CR ₂ and CR ₃ are located outside the virtual extension line a of the first arc CR ₁ in the radial direction of the tire. with a radius of curvature _{R 2} of the second circular arc CR _2, larger than the radius of curvature _{R 3} of the third circular arc CR _3.
Under such outer contour shape, many would recesses are formed at the junction of the first arc CR ₁ and the second circular arc CR _2.
In this case, the number of types of arcs may be four or more.
[0011]
In such a tire, and more preferably, the radius of curvature _{R 1} of the first arc CR _1, second smaller than the radius of curvature _{R 2} of the circular arc CR _2, and preferably, the first arc CR ₁ and second the bonding position of the circular arc CR ₂ provided circumferential grooves G.
[0012]
More preferably, the first arc CR ₁ and the second circular arc CR _2, is bonded within the 0.15 to 0.28 times the tread width W from the symmetry axis X-X, more preferably, the tread The portion TD is provided with a lateral overhang portion SI that contacts the ground only when the tire rolls on an inclined road surface.
[0013]
The operation of the tire configured as described above will be described below based on the example illustrated in FIG.
Camber thrust F _C of the tire rolling on the inclined road surface S, when the tread portion TD is deflected tread portion TD is grounded to the inclined road surface S, in a tire width direction cross-section, the original tread TD specific curved contour due to be extended in a straight line, the bending deformation bs of the tread portion TD, _{b C} shear deformation _{S S} of the tread portion TD, led to _{S C,} the shear deformation _{S S, S C} Generated as a result of the shear stresses f _CS and f _{CC in} the direction of climbing the slope. Therefore, in order to increase the camber thrust F _C , it is effective to reduce the radius of curvature of the curved contour line of the tread portion TD and increase the amount of shear deformation, and further, the shear stresses f _CS and f _CC .
[0014]
Here, in particular, in the case of tires for light trucks, trucks, buses, etc., the load applied when empty and when loading is greatly different, so the tread contact width also changes greatly, and when loading, tire to almost entirely to the ground of the tread width, the ground width in unloaded, since the almost half of the tread width, without separate and when unloaded during a cargo, which always generate a large camber thrust F _C Therefore, the appearance of the outer contour shape of the tread portion TD is strongly desired.
[0015]
Meanwhile, in order to generate a large camber thrust F _C when unloaded is reduced tread central region to be grounded during an unloaded, that is, the radius of curvature R ₁ of the tread portion defined by a first circular arc CR ₁ also it is effective, when defining in arc based the entire tread portion in a radius of curvature R _1, as illustrated in FIG. 3, the tread portion TD _1, on the axis of symmetry X-X the height in the tire radial direction, too large a difference H between the radial height of the tread edge, still, will not be able to ground the tread end portion during cargo, therefore, decreases the camber thrust F _C is reversed at the time of shipment There are inconveniences.
[0016]
Therefore, in the tire is still in a first radius of curvature of the circular arc CR ₁ small enough, so that the difference H does not become excessive, a first adjacent circular arc CR _1, the virtual extension line a of the arc CR ₁ a second arc CR ₂ positioned outside in the tire radial direction are provided. Here, the joint between the two arcs CR ₁ and CR ₂ often becomes a valley, but the arcs CR ₁ and CR ₂ can be smoothly continued so that no valley is formed. The first arc CR ₁ and when the valleys occurs at the junction of the second circular arc CR _2, because it is easy there is the generation nucleus of uneven wear, preferably, forms a circumferential groove G therein By doing so, the occurrence of uneven wear is prevented.
[0017]
The reason why to reduce the radius of curvature R ₁ of the first arc CR _1, since in order to increase the camber thrust F _C during solani as described above, the tread region to be grounded during an unloaded only the may be applied to the first arc CR _1, Therefore, the first arc CR ₁ and the bonding position of the second circular arc CR _2, it is preferable that the ground near edge when unladen. Therefore, the joining position is generally 0.15 to 0.28 times the tread width W from the axis of symmetry XX, although it differs somewhat depending on the vehicle on which the tire is mounted, the tire size, and the like. It is preferable to be located within the range.
[0018]
And further, the second arc CR _2, the third arc CR ₃ that is continuous with the outside of the tire width direction is provided, the arc CR ₃ also radially outwardly from the imaginary extension a circular arc CR ₁ And radii of curvature R ₂ , R ₃ of the respective arcs CR ₂ , CR ₃
R ₂ > R ₃
With, to increase the shear stress f _CS in the tread end portion region to be grounded during cargo occupies become sufficiently large camber thrust F _C at the time of shipment.
[0019]
Incidentally, the tread portion TD of such tires, the lateral overhang SI to ground only when rolling on the inclined road surface, especially can effectively contribute to the increase of camber thrust F _C during cargo.
[0020]
【Example】
Hereinafter, embodiments of the present invention will be described.
A tire having a maximum load capacity of 1180 kgf (JATMA) for a small truck having a size of 195/85 R16 114/112 LT and an invention tire having an outer contour of a tread indicated by a solid line in FIG. 1 and a broken line in the same figure Table 1 shows the comparison between the conventional tire having the outer contour shape indicated by the mark and the comparative tire indicated by the dashed line and the straight running stability under the unloaded state and the loaded state.
[0021]
The evaluation was conducted by filling each tire with a specified internal pressure (6.0 kgf / cm ² ), mounting it on a 2t-stacked small truck (two-wheel type with rear wheels), and checking the unloaded state and the specified maximum load. In each of the loaded states, the test was performed on a paved road having a rut by a test driver, and the straight running stability was evaluated by sensory evaluation.
In the index values in the table, a conventional tire was used as a control, and the larger the numerical value, the better the result.
[0022]
[Table 1]

[0023]
As is evident from Table 1, each of the inventive tires can greatly improve the straight running stability as compared with the conventional tire at the time of unloading and at the time of loading, and especially, at the time of loading. The straight running stability can be significantly improved by providing the tread with lateral overhangs.
[0024]
【The invention's effect】
Thus, according to the present invention, the occurrence of the wandering phenomenon can be effectively suppressed and the straight running stability can be greatly improved regardless of whether the vehicle is unloaded or loaded.
[Brief description of the drawings]
FIG. 1 is a tread outer contour diagram showing an embodiment of the present invention.
FIG. 2 is a cross-sectional view in the tire width direction illustrating a manner in which a caber thrust is generated.
FIG. 3 is a cross-sectional view in the tire width direction showing a case where the radius of curvature of the outer contour line of the tread is small.
FIG. 4 is a schematic front view showing a state of occurrence of a wandering phenomenon.
[Explanation of symbols]
CR ₁ First arc CR ₂ Second arc CR ₃ Third arc R ₁ , R ₂ , R ₃ Radius of curvature TD Tread portion W Tread width G Circumferential groove SI Side overhang portion a Virtual first arc Extension line XX Symmetry axis

Claims (5)

Both include a pair of bead portions and sidewall portions, a toroidal tread portion connected to both sidewall portions, a radial carcass for reinforcing these portions, and a belt for reinforcing the tread portion on the outer peripheral side of the radial carcass. Pneumatic radial tires
Under filling of the prescribed internal pressure, the outer contour of the tread in the tire width direction cross section, a first arc centered on the axis of symmetry of the tire cross section, a second arc adjacent to the first arc, The second arc is defined by at least three types of arcs including a third arc continuing outside in the tire width direction, and each of the second and third arcs is defined by a virtual extension line of the first arc. A pneumatic radial tire that is disposed outside in the tire radial direction and has a radius of curvature of a second arc larger than a radius of curvature of a third arc. The pneumatic radial tire according to claim 1, wherein a radius of curvature of the first arc is smaller than a radius of curvature of the second arc. 3. The pneumatic radial tire according to claim 1, wherein a circumferential groove is provided at a joining position between the first arc and the second arc. The pneumatic pneumatic pump according to any one of claims 1 to 3, wherein the first arc and the second arc are joined at a position 0.15 to 0.28 times the tread width from the symmetry axis of the tire cross section. Radial tire. The pneumatic radial tire according to any one of claims 1 to 4, wherein the tread portion is provided with a lateral overhang portion that comes into contact with the ground only when rolling on an inclined road surface.

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