JP2002036812A - Tire for motorcycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress chunking of a tread rubber generated in association with high speed revolutions while the straight running stability in high speed range is well secured. SOLUTION: The tread surface 2S is formed from a central region TC having a radius of curvature R1 and a shoulder region TS having a radius of curvature R2, wherein the ratio R2/R1 should range between 0.3 and 0.8. The width W1 of the central region should be 50-97% of the tread width WT, while the angle θof the camber line X tying the tire equator point P to the tread edge TE with respect to the axial line of the tire N should range between 30 and 35 degs.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire for a motorcycle in which tread rubber chunking accompanying high-speed turning is suppressed while ensuring high straight running stability in a high-speed range.

[0002]

2. Description of the Related Art Conventionally, a tread surface of a motorcycle tire has a single radius formed from a tire equator to a tread edge with a single radius of curvature, or FIG. As schematically shown, the radius of curvature r2 of the shoulder region ts on the tread edge side
Is larger (r1 <r2) than the radius of curvature r1 of the central region tc on the tire equator side.

[0003] On the other hand, motorcycle tires have a speed of 200 km / h due to a higher displacement and higher performance of the motorcycle.
The straight running stability in the high-speed range described above is particularly important.
Therefore, in the radial structure, the tread portion tends to be widened and flattened, and as shown in the figure, the tire axis passing through the tire equatorial point P of the camber line X connecting the tire equatorial point P and the tread edge TE. Tires in which the angle θ with respect to the direction line N is set smaller than 30 ° are becoming mainstream.

However, when such a tire is banked so as to be in contact with the shoulder region ts so as to be in contact with the ground, and the vehicle is turned in a high speed region of 200 km / h or more, rubber heat generation in the shoulder region tends to be excessive. Turned out to be strong. As a result, there is a problem in that bubbles are generated in the rubber, and this causes the tread rubber to be peeled and damaged, which is called so-called chunking.

[0005] Accordingly, the present invention provides a method for controlling the angle θ from 30 to 35.
゜, and the radius of curvature of the shoulder area,
Conversely, based on setting it smaller than the radius of curvature of the central area, while ensuring high straight running stability in the high speed area,
It is an object of the present invention to provide a motorcycle tire capable of suppressing chunking of the tread rubber due to high-speed turning and improving high-speed durability.

[0006]

In order to achieve the above object, a motorcycle tire according to claim 1 of the present invention has a tire meridional section in a standard state in which the tire is assembled to a regular rim and filled with a regular internal pressure. , The tread surface has a central region consisting of a first circular arc having a radius of curvature R1 passing through the tire equatorial point, and smoothly extending from the first circular arc to the tread edge and having a radius of curvature of 30% to 80% of the radius of curvature R1. A shoulder region consisting of a second arc of R2,
And the central region width W1 in the tire axial direction of the central region is:
The tread width WT in the tire axial direction between the tread edges is 5
0% to 97%, and the angle θ of the camber line connecting the tire equatorial point and the tread edge to the tire axial line passing through the tire equatorial point is 30 to 35 °.

[0007] In this specification, the "regular rim" is a rim which is defined for each tire in a standard system including the standard on which the tire is based.
Standard rim for ATMA, "Design R for TRA"
im ", or" Measuring Rim "for ETRTO." Normal internal pressure "is the air pressure specified for each tire in the standard, JATMA is the maximum air pressure, and TRA is the table air pressure. TIRE LOAD LIMITS AT VARIOUS
Maximum value in "COLD INFLATION PRESSURES", ETRT
O means "INFLATION PRESSURE".

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a meridional section of a motorcycle tire according to the present invention, which is a rear wheel tire of a large motorcycle and is mounted on a regular rim and filled with a regular internal pressure in a standard state.

In FIG. 1, the motorcycle tire 1
Has a tread portion 2, a pair of sidewall portions 3 extending inward in the tire radial direction from both ends thereof, and a bead portion 4 located at an inner end of each sidewall portion 3. A carcass 6 is bridged between the bead portions 4, and a breaker layer 7 is disposed outside the carcass 6 in the tire radial direction and inside the tread portion 2.

The carcass 6 is folded on both sides of a main body 6a extending from the tread portion 2 to the bead core 5 of the bead portion 4 through the sidewall portion 3 to turn the bead core 5 around from the inside in the tire axial direction to the outside. The folded portion 6b is provided. A bead apex 9 made of a hard rubber extending radially outward from the bead core 5 is provided between the main body portion 6a and the folded portion 6b. The bead apex 9 extends from the bead portion 4 to the sidewall portion 3 and is reinforced. are doing.

The carcass 6 is composed of at least one carcass cord 6A, 6B in the present embodiment in which carcass cords are arranged at an angle of 70 to 90 degrees with respect to the tire circumferential direction. As the carcass cord, an organic fiber cord such as nylon, polyester, or rayon is preferably used.

The breaker layer 7 is formed of at least one breaker ply 7 using a breaker cord having a higher elasticity than a carcass cord, for example, an aromatic polyamide fiber cord.
A in this example, the breaker cord is spirally wound at an angle of 5 ° or less with respect to the tire circumferential direction.
An example formed from a single breaker ply 7A is shown.

In this embodiment, as shown in FIG. 2, the tread surface 2S of the tread portion 2 has a first arc 11 having a radius of curvature R1 passing through a tire equator point P in a meridional section of the tire in the standard state. Central area TC consisting of
And the tread edge TE smoothly connected to the first arc 11
And a shoulder region TS composed of the second circular arc 12 having a radius of curvature R2 of 30% to 80% of the radius of curvature R1.

Moreover, on the tread surface 2S, a camber line X connecting the tire equator point P and the tread edge TE is formed.
The angle θ with respect to the tire axial line N passing through the tire equatorial point P is increased to 30 to 35 °. The tire equatorial point P is a point where the tread surface 2S intersects with the tire equatorial surface C, and the first arc 11 has its center point located on the tire equatorial surface C.

That is, the ratio R2 / R1 of the radii of curvature R1 and R2 of the first and second arcs 11 and 12 is 1.0 or more in the conventional tire, whereas in the present embodiment, the ratio R2 / R1 is 0.1.
It is greatly reduced to the range of 3 to 0.8. Furthermore, the angle θ between the camber line X and the tire axial direction line N is smaller than 30 ° in the conventional tire, but is increased to 30 to 35 ° in the present embodiment.

By adopting such a structure,
200 km / h grounded to the shoulder region TS
In the turning traveling in the high-speed region described above, the contact pressure in the shoulder region TS can be reduced, and the temperature rise and the occurrence of chunking due to the temperature rise can be effectively suppressed.

When the ratio R2 / R1 is in the above range (0.3 to
0.8) and the angle θ is within the above range (30 ° to 3).
At times other than 5 ゜), the effect of suppressing chunking cannot be sufficiently ensured. In particular, when the ratio R2 / R1 is within the above range (0.3 to 0.8) and the angle θ is larger than 35 °, the tread profile becomes extremely shoulder-dropped, so that the steering stability itself decreases, It becomes difficult to drive in the high speed range.

Therefore, preferably, the ratio R2 / R1 is set to 0.1.
It is desirable that the angle θ be in the range of 31 ° to 34 °.

In the motorcycle tire 1, it is also important to ensure a sufficiently high straight running stability in the high-speed range.
For this purpose, the width W1 of the central region TC in the tire axial direction is set to 50% to 97% of the tread width WT in the tire axial direction between the tread edges TE. If it is less than 50%, the central area TC is too small, and excellent straight running stability cannot be exhibited. 97%
On the contrary, the shoulder region becomes too small, and the effect of suppressing the chunking cannot be achieved.

Although the radius of curvature R1 is not particularly limited in the present invention, it is usually preferable to set the radius of curvature R1 in a range of 50% or more of the tread width WT. The tread width WT is the maximum width of the tire.
m can be particularly preferably adopted.

Although the preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the illustrated embodiment, but can be implemented in various forms.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A tire having the structure shown in FIG.
A 50ZR17 tire was prototyped according to the specifications shown in Table 1, and the durability and straight running stability of the test tire during turning in a high-speed range were tested. The results are shown in Table 1.

(1) Durability during turning in a high-speed range: The tire is mounted on a rim (17 × MT6.00) and an internal pressure (290 k
Pa), mounted on the rear wheel of a large motorcycle (1300 cc) under the condition of (1300 cc), traveled on a real vehicle on a high-speed circuit (high-speed circuit of Japan Automobile Research Institute), and turned at a curve with a radius of 400 m at a speed of 200 km / h. The vehicle was turned at an increased speed of 20 km / h every 5 minutes, and the running speed when chunking occurred in the tires was compared. Turning speed is 260k
m / h is the upper limit.

(2) Straight running stability in a high-speed range: The high-speed circuit travels on a straight road at a speed of 260 km / h (220 km / h on the curve), and is subjected to a five-point method according to a sensory evaluation of a test driver. evaluated. The higher the score, the better.

The details of the internal structure of the front and rear wheels will be described below. Rear wheel carcass: 2-ply nylon cord, cord fineness 1260d / 2, cord angle 88 ° with respect to tire equator, breaker: 1-ply spiral wound aromatic polyamide, cord angle substantially 0 ° with respect to tire circumferential direction , Cord fineness 1500d / 2 Front wheel Carcass: Nylon cord 2-ply, Cord fineness 1260d / 2, Cord angle 88 ° to tire equator Breaker: 2-ply aromatic polyamide Cord angle 17 ° to tire circumferential direction ( Cross each other) Cord fineness 1500d / 2

[0026]

[Table 1]

As shown in the table, it can be confirmed that the tread rubber of the example can suppress chunking of the tread rubber due to high-speed turning while securing high straight running stability in a high-speed range.

[0028]

Since the present invention is configured as described above,
It is possible to suppress chunking of the tread rubber due to high-speed turning while securing high straight running stability in a high-speed range,
High-speed durability can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a tire according to an embodiment of the present invention.

FIG. 2 is a diagram showing the tread contour shape.

FIG. 3 is a cross-sectional view of a tire illustrating a conventional technique.

[Explanation of symbols]

 2S Tread surface 11 First arc 12 Second arc N Tire axial line P Tire equatorial point TC Central area TE Tread edge TS Shoulder area X Camber line

Claims (1)

[Claims] In a tire meridional section in a standard state where a tire is assembled to a regular rim and filled with a regular internal pressure, a tread surface has a first radius of curvature R1 passing through a tire equator point.
A central region consisting of a circular arc, smoothly connecting to the first circular arc, extending to the tread edge, and having a radius of curvature R1 of 3;
A shoulder region composed of a second arc having a curvature radius R2 of 0% to 80%, and a central region width W1 in the tire axial direction of the central region is:
The tread width WT in the tire axial direction between the tread edges is 5
A motorcycle characterized in that the angle θ between the camber line connecting the tire equatorial point and the tread edge is 30 to 35 ° with respect to a tire axial direction line passing through the tire equatorial point. For tires.