JP3838462B2 - Pneumatic tires for motorcycles - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire for a two-wheeled vehicle, and more particularly to a radial ply tire in which a carcass ply cord is arranged at an angle of 65 to 85 ° with respect to the tire equator plane, and in particular, ensuring excellent straight running stability. And a two-wheeled vehicle that improves the separation resistance of the carcass ply from the point of the tread (1/4 of the length of the arc in the width direction of the tread to the end of the tread) to the end of the tread. The present invention relates to pneumatic tires.
[0002]
[Prior art]
Since the pneumatic tire for a two-wheeled vehicle needs to generate a camber thrust necessary for turning the two-wheeled vehicle by attaching a large camber angle, the crown radius of the tread is compared with the crown radius of the pneumatic tire tire for a passenger vehicle. Make it extremely small. As a result, the pneumatic tire for a two-wheeled vehicle has a narrower tread ground contact width during rolling than the pneumatic tire for a passenger car, and thus tends to impair the straight running stability. In the case of tires, extra care is required.
[0003]
[Problems to be solved by the invention]
Therefore, in order to improve the straight running stability with a pneumatic radial ply tire for a two-wheeled vehicle, basically, it is avoided that the carcass has two or more plies and the cord arrangement of the ply is 90 ° with respect to the tire equatorial plane. A configuration in which the angle is within a range of ˜85 ° and the adjacent ply cords intersect with each other across the tire equatorial plane is widely adopted.
[0004]
Even so, measures such as reducing the gauge of the tread rubber and reducing the number of cord layers constituting the belt have been taken. However, a decrease in the tread rubber gauge reduces the groove depth, leading to a decrease in the wear life of the tread rubber, and a decrease in the number of belt cord layers results in an increase in shear strain between multiple carcass plies. Impairs the separation resistance.
[0005]
Even if the number of belt cord layers is reduced, if the gauge of each carcass ply is made thicker, the necessary separation resistance of the carcass ply can be secured, but in order to do so, the ply gauge must be increased considerably. The rigidity of the carcass is remarkably lowered, leading to a decrease in straight running stability, and a decrease in the number of bent belt cord layers is meaningless.
[0006]
Therefore, the inventions according to claims 1 to 3 of the present invention satisfy both of excellent straight running stability and sufficient separation resistance of the carcass ply at the same time while sufficiently maintaining the wear life of the tread rubber. The object is to provide a pneumatic tire for a two-wheeled vehicle.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the invention described in claim 1 of the present invention is a two-ply or more radial that reinforces a pair of sidewall portions and a tread portion connected to the bead cores embedded in the pair of bead portions. In a pneumatic tire for a two-wheeled vehicle, comprising: a carcass that becomes a rubber coating of an arrayed organic fiber cord; and a belt that becomes a rubber coating of one or more layers of organic fiber cords that reinforce a tread portion on the outer periphery of the carcass.
A gauge (T ₁ ) between each cord center curve of two adjacent plies of the carcass, with respect to a cord center curve connecting the center of gravity of the cross sectional figure of each of the two adjacent plies of the carcass in the radial section of the tire, and a gauge A gauge (T ₂ ) measured from the cord center curve of one of the plies forming (T ₁ ) to the surface of the cord-coated rubber in the opposite direction to the gauge (T ₁ ),
In the region between the tire equator surface and the conical surface including the normal line from the ¼ point of the tread tread surface to the outermost carcass ply surface, the relationship of T ₁ = 2T ₂ is satisfied,
T ₁ > 2T ₂ is satisfied in a region between the conical surface including the normal line and the conical surface or cylindrical surface including the normal line lowered from the tire maximum width position to the outermost carcass ply surface. This is a pneumatic tire for a two-wheeled vehicle.
[0008]
In carrying out the invention described in claim 1, preferably, as in the invention described in claim 2, the tread width extending from one end to the other end of the tread parallel to the tire rotation axis has the maximum tire width. The ratio (T ₁ / 2T ₂ ) of the gauge (T ₁ ) to twice the gauge (T ₂ ) is 1.3 to 4 as a tire, and as in the invention described in claim 3. Within the range of .0.
[0009]
Here, the cords of the carcass ply are arranged so as to be inclined within a range of 65 to 85 ° with respect to the tire equatorial plane.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to FIGS.
FIG. 1 is a diagrammatic right half of a radial cross section of a pneumatic tire for a two-wheeled vehicle,
2 is an enlarged explanatory view of a carcass ply portion in a tread portion of a tire cross section shown in FIG.
FIG. 3 is a diagrammatic right half of a radial cross section of another embodiment of the tire shown in FIG.
[0011]
In FIG. 1, a pneumatic tire for a two-wheeled vehicle (hereinafter referred to as a tire) includes a pair of bead portions 1, a pair of sidewall portions 2, and a tread portion 3, and extends between the bead cores 4 embedded in the bead portion 1. A carcass 5 that reinforces the respective parts 1, 2, and 3, a belt 6 that reinforces the tread part 3 on the outer periphery of the carcass 5, and a tread rubber 7 on the outer side of the belt 6. Reference numeral 8 denotes a reinforcing rubber filler of the bead portion 1.
[0012]
The carcass 5 is composed of two or more plies of an organic fiber cord, for example, a nylon 66 cord rubber-coated ply arranged at an inclination angle of 65 to 85 ° with respect to the tire equatorial plane E. And the cords are arranged so as to cross each other with the tire equatorial plane E sandwiched between adjacent plies. The belt 6 has one or more layers, and the illustrated example has a rubber coating layer of two layers of organic fiber cords, for example, Kevlar cords. Desirably, all are inclined with respect to the tire equatorial plane E within a range of 10 to 35 °.
[0013]
FIG. 1 shows a tire having a tire tread width TW having a maximum tire width parallel to a tire rotation axis (not shown) extending from one end Te of the tread surface 3t to the other end Te (not shown) as a tire suitable for the present invention. However, the tire in which the sidewall portion 2 has the maximum width may be used without being particular about this.
[0014]
In the cross section of FIG. 1, a point Q that is ½ of the length of the curve from the intersection Tc of the tread 3t with the tire equatorial plane E to the tread edge Te is generally called a ¼ point. The outer ply of the carcass 5 from the conical surface including the normal Vq and the conical surface including the normal Vq and the tread surface end Te between the conical surface including the normal Vq and the tire equator plane E, which is lowered on the surface of the outer ply 5-2 of the carcass 5. The carcass ply cross section in both side regions surrounded by the conical surface or the cylindrical surface including the normal line Ve lowered to the 5-2 surface has the following configuration.
[0015]
The cross section of the adjacent carcass plies 5-1 and 5-2 shown in FIG. 2 actually shows a curved surface, but this is represented by a straight surface for convenience. Based on the code center curve L _1, L ₂ that contiguous with the center of gravity (centroid) g of the cross-section shape of the organic fiber cord C of the carcass plies 5-1, 5-2 in each ply, center curve L ₁ and the center curve L gauge T ₁ of the between _2, gauge T ₂ or carcass ply 5-2 from the center the curve L ₁ per carcass ply 5-1 until coating rubber R surface 5-1s code C, measured in opposite directions gauge T ₁ Then, the following relationship is satisfied for the gauge T ₂ from the central curve L ₁ to the covering rubber R surface 5-2s of the cord C measured in the direction opposite to the gauge T ₁ .
[0016]
That is, first, the above-described central region satisfies the relationship of T ₁ = 2T ₂ , and next, both side regions satisfy the relationship of T ₁ > 2T ₂ . In other words, the relationship of T ₁ = 2T ₂ and T ₁ > 2T ₂ means that if the cords C of the carcass plies 5-1 and 5-2 have the same diameter, the gauge of the inter-cord covering rubber R of each ply Means double the rubber gauge from the cord C of each ply to the coated rubber R surface 5-1s, 5-2s and thicker than twice.
[0017]
Here, the tread width direction grounding region which is deeply involved in the straight running stability is the central region between the quarter point Q and the quarter point Q of the tread 3t described above, while the initial ply of the carcass 5 is It was clarified that the separation generation area is a both-side area, particularly an area near the tread edge Te.
[0018]
Therefore, in the central region where the cords of the adjacent plies 5-1 and 5-2 intersect at a small angle, the rubber gauges between the cords of the adjacent plies 5-1 and 5-2 are thinner than the rubber gauges in the same region on both sides. As a result of the shear rigidity between the adjacent plies 5-1 and 5-2 in the region being higher than the shear stiffness in the both side regions, it is possible to improve the straight running stability while turning the two-wheeled vehicle. Adjacent plies 5-1 and 5-2 in both side regions where a greater shear strain acts than in the central region during straight running as well as when providing a large camber angle are similar to those in the central region. By being thicker than the rubber gauge, the shear stress generated in each ply cord is greatly relieved, resulting in suppression of separation. It will be. In this way, the tread rubber 7 can maintain the wear life of the tread rubber 7 by securing the conventional gauge, and at the same time, improve the straight running stability and the separation resistance of the carcass 5 at the same time. It becomes possible.
[0019]
In the both side regions of the tread 3t, the relationship of T ₁ > 2T ₂ is that the ratio T ₁ / 2T ₂ of the gauge T _{1 to} the gauge T ₂ is actually in the range of 1.3 to 4.0. The ratio T ₁ / 2T ₂ is less than 1.3 when the value of the ratio T ₁ / 2T ₂ is less than 1.3, and if it exceeds 4.0, the degree of separation resistance is saturated and the tire weight increases. Since there are disadvantages, neither is possible.
[0020]
The tire of the modified example shown in FIG. 3 has the same basic components as the tire shown in FIG. 1 except for the so-called hollow carcass ply 9 that omits the arrangement of the carcass ply in the central region of the tread 3t. The same reference numerals as those in FIG. The hollow carcass ply 9 in the tire of this modified example is handled in the same manner as the plies 5-1 and 5-2 of the carcass 5, and the hollow carcass ply 9 in the illustrated example exists only on both sides of the tread surface 3t. Since the adjacent plies are formed with 5-2, the relationship of T ₁ > 2T ₂ is satisfied, and the value of the actual ratio T ₁ / 2T ₂ is also in the range of 1.3 to 4.0.
[0021]
A tire having the above-described hollow carcass ply 9 has a large camber angle, so that the rigidity from the both sides of the tread surface 3t to the bead portion 1 is effectively increased and exhibits excellent turning performance. If this invention is applied to the tire, it is possible to add the merits of improving the straight running stability and improving the separation resistance of the carcass plies 5 and 9 in the both side regions of the tread surface 3t even to a tire that also considers turning performance.
[0022]
【Example】
It is a tire for a two-wheeled vehicle, the size is 160 / 80R16 (the tire size described in 1997, ETRTO STANDARDDS), and the configuration is in accordance with FIG. 1 (FIG. 2), and the width TW of the tread 3t is 155 mm and the maximum tire width Have The carcass 5 has two plies and has rubber-coated plies 5-1 and 5-2 in which 1890D / 2 nylon 66 cords intersect with each other at an inclination angle of 75 ° with respect to the tire equatorial plane E. And a rubber-coated cord layer in which 1500 D / 2 Kevlar cords are crossed and arranged at an inclination angle of 25 ° with respect to the tire equator plane E.
[0023]
The gauge T _1, T ₂ in the carcass ply 5-1 and 5-2 located in the center region of the tread surface 3t T ₁ = 1.0mm, and T ₂ = 0.5 mm, the carcass ply 5-1 located in side regions The gauges T ₁ and T ₂ in 5-2 were set to T ₁ = 1.5 mm and T ₂ = 0.5 mm, and T ₁ / 2T ₂ = 1.5 in the latter region. On the other hand, conventional tires were prepared in accordance with the example tires except that T ₁ = 1.0 mm and T ₂ = 0.5 mm in all regions of the central region and both side regions.
[0024]
Using the tires of the above examples and conventional examples as test tires, first, a comparative test was performed on the separation durability between the carcass plies 5-1 and 5-2 using a drum testing machine. In the durability test, a tire filled with an internal pressure of 2.8 kgf / cm ² was pressed against a drum rotating at a speed of 81 km / h with a load of 450 kgf under a camber angle of 0 °, and between the carcass plies 5-1 and 5-2. The vehicle was run until a separation failure occurred. As a result of the test, the distance traveled until the failure occurred was expressed as an index with the conventional tire as 100, and the tire of the example was 130, demonstrating a significant improvement in separation resistance.
[0025]
Next, in order to evaluate the straight running stability, an actual vehicle test using a two-wheeled vehicle with a displacement of 1500 cc was performed on a test course. A conventional radial tire of size 130 / 70R18 is mounted on the front tire, and the test tire is mounted on the rear tire with an internal pressure of 2.8 kgf / cm ^2. Went. The score of the test result is expressed by an index with the conventional tire as 100. The tire of the example is 115, and the straight running stability is remarkably improved. From the above test results, it can be seen that the tire of the example has markedly improved both the separation resistance of the carcass ply in the straight running and the stability in the straight running.
[0026]
【The invention's effect】
According to the first to third aspects of the present invention, while maintaining a sufficient wear life of the tread rubber, the characteristics of both the separation resistance of the carcass ply and the stability during straight running are simultaneously obtained. An improved pneumatic tire for a two-wheeled vehicle can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic right half sectional view of a tire according to an embodiment of the present invention.
FIG. 2 is a development view of a partial cross section of the carcass ply.
FIG. 3 is a schematic right half sectional view of a tire according to another embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Bead part 2 Side wall part 3 Tread part 3t Tread surface 4 Bead core 5 Carcass 5-1, 5-2 Carcass ply 6 Belt 7 Tread rubber 8 Rubber filler 9 Hollow carcass ply E Tire equatorial surface Tc Tread surface Te tread on tire equatorial surface End Q 1/4 point Vg on the tread surface Normal to the outer carcass ply surface passing through the point Q Ve Normal to the outer carcass ply surface passing through the tread edge R Carcass ply cord coating rubber C Carcass ply cord g Carcass ply cord Center of gravity L ₁ , L ₂ carcass ply cord center curve T ₁ center curve L ₁ , L ₂ gauge between T ₂ center curve and carcass ply surface

Claims (3)

A carcass that is rubber-coated with a two or more ply radial array organic fiber cord that reinforces the pair of sidewall portions and the tread portion that extends between the bead cores embedded in the pair of bead portions, and the tread portion on the outer periphery of the carcass In a pneumatic tire for a two-wheeled vehicle, comprising a belt that is made of a rubber coating of one or more organic fiber cords that reinforce
A gauge (T ₁ ) between each cord center curve of two adjacent plies of the carcass, with respect to a cord center curve connecting the center of gravity of the cross sectional figure of each of the two adjacent plies of the carcass in the radial section of the tire, and a gauge A gauge (T ₂ ) measured from the cord center curve of one of the plies forming (T ₁ ) to the surface of the cord-coated rubber in the opposite direction to the gauge (T ₁ ),
In the region between the tire equator surface and the conical surface including the normal line from the ¼ point of the tread tread surface to the outermost carcass ply surface, the relationship of T ₁ = 2T ₂ is satisfied,
T ₁ > 2T ₂ is satisfied in a region between the conical surface including the normal line and the conical surface or cylindrical surface including the normal line lowered from the tire maximum width position to the outermost carcass ply surface. A pneumatic tire for two-wheeled vehicles. The tire according to claim 1, wherein a tread width extending from one end of the tread to the other end and parallel to the tire rotation axis has a maximum tire width. The tire according to claim 1 or 2, wherein a value of a ratio (T ₁ / 2T ₂ ) of the gauge (T ₁ ) to a double of the gauge (T ₂ ) is in a range of 1.3 to 4.0.

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