JP2000185531A - Radial tire for motorcycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control falling of a tire during turning without deteriorating straight line stability. SOLUTION: This tire is provided with a carcass having inner and outer carcass plies. A folded height HP1 of a ply folded portion of the inner carcass ply is greater than a folded height HP2 of the ply folded portion of the outer carcass ply, and the folded height HP1 is 0.7 to 1.0 times a tread end height Hh. The tire is further provided with an insulation rubber layer extending in a radially outward direction, passing through the ply folded portions. A thickness Ti of the insulation rubber layer is 0.1 to 1.0 mm, a tangent loss (tan δ) is 0.05 to 0.50, and an insulation height Hit is 0.4 to 1.0 times the folded height HP1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is particularly suitable as a tire for a front wheel of a large vehicle, and is an automatic tire capable of suppressing a fall of a tire at the time of turning without impairing a straight running stability while minimizing weight increase. The present invention relates to a radial tire for a motorcycle.

[0002]

2. Description of the Related Art In recent years, motorcycle tires having a radial structure in which the outside of a radially arranged carcass is loosely fastened with a belt layer in order to enhance high-speed running performance have been frequently used. .

[0003] However, when a motorcycle equipped with such a radial tire is turned in a medium to low speed range, the motorcycle may fall down during the turn. Conventionally, in order to suppress this falling during turning, for example, means for reducing the rubber thickness of the side wall portion, reducing the folding height of the carcass, and reducing the volume of the bead apex rubber to reduce the size are used. Have been taken.

[0004] However, such means has a problem that the rigidity at the sidewall portion is insufficient, and the stability of straight running is reduced, such as impairment of disturbance convergence.

[0005] As described above, the fall of the tire and the stability of the straight running are in a trade-off relationship, and it has been difficult in the past to improve both of them.

Accordingly, the present invention basically provides an insulation rubber layer having a predetermined tangent loss (tan δ) at a predetermined height between the folded portions of two carcass plies. It is an object of the present invention to provide a motorcycle radial tire capable of suppressing a fall without impairing straight running stability.

[0007]

In order to achieve the above object, the invention of claim 1 of the present application is directed to a ply body portion which extends from a tread portion to a sidewall portion to a bead core of a bead portion and overlaps inside and outside. A radial tire for a motorcycle, comprising: a carcass comprising inner and outer carcass plies; and a belt layer disposed inside the tread portion and outside the carcass, wherein the ply body portion of the inner carcass ply is provided. The turn-up height HP1 of the ply turn-up portion from the bead base line of the ply turn-up portion turned from the inside to the outside in the tire axial direction with the bead core is the turn-up height of the ply turn-up portion of the outer carcass ply from the bead base line. The height of the tread edge from the bead baseline at the tread end is larger than HP2 and is 0.7 to 1.0 times the height Hh. The insulation portion includes an insulation rubber layer extending radially outward between the ply turn-over portions of the inner and outer carcass plies, and the insulation rubber layer has a thickness Ti of 0.1 to 1.0 mm and The insulation height Hit from the bead base line at the outer end of the insulation rubber layer is equal to the fold height HP1 of the inner part, which is made of rubber having a tangent loss (tan δ) of 0.05 to 0.50. It is characterized by being 4 to 1.0 times.

Further, in the radial tire for a motorcycle according to the present invention, the tread edge height Hh is 0.4 to 0.6 times the tire sectional height H0.

In the radial tire for a motorcycle according to a third aspect of the present invention, the outer turning height HP2 is 0.5 to 0.7 times the tread end height Hh.

In the radial tire for a motorcycle according to a fourth aspect of the present invention, the insulation height Hit is set to be 0.6 to 1.0 times the folded height HP1.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIGS. 1 and 2 illustrate a case where a radial tire 1 for a motorcycle (hereinafter referred to as a tire 1) of the present invention is formed as a front wheel tire of a large vehicle having a tire size of 120 / 70ZR17, for example.

In the figure, a tire 1 has a tread 2
And sidewall portions 3 extending inward in the tire radial direction from both ends thereof, and bead portions 4 located at radially inward ends of the respective sidewall portions 3 in the tire radial direction. The carcass 6 is bridged, and a belt layer 7 is provided radially outside the carcass 6 and inside the tread portion 2.

The tread portion 2 has tread ends Te, T
The tire extends from the tire equator C to the tread end Te in a convex arc shape with a small radius of curvature such that the tread width between the tires e becomes the maximum width of the tire. At this time, the tread edge height Hh of the tread edge Te from the bead base line BL is 0.4 to 0.6 times the tire cross-section height H0, and thereby the camber amount of the tread portion 2 is sufficiently secured. This makes it possible to make a turn at a large bank angle.

The tread rubber 12 constituting the tread portion 2 is a rubber having a JIS Shore A hardness Hs in the range of 55 to 70 degrees, usually about 58 degrees, which is excellent in wear resistance. The sidewall rubber 13 forming the sidewall portion 3 has a JIS Shore A hardness Hs in the range of 40 to 70 degrees, and a hardness 50 which is usually softer than the tread rubber 12.
Rubber having a degree of flexibility is used. In this example,
The sidewall rubber 13 rises from the bead portion 4 and has its upper end extending into the gap G between the outer end portion of the belt layer 7 and the carcass 6.

The belt layer 7 is composed of one or more belt cords having belt cords arranged at an angle of 15 to 30 degrees with respect to the tire equator C. In this embodiment, two belt plies 7A and 7 overlapping inside and outside are provided.
B, and an organic fiber cord such as nylon, rayon, polyester, or aromatic polyamide is used as the belt cord.

Next, the carcass 6 is transferred from the tread portion 2 to the side wall portion 3 through the bead core 5 of the bead portion 4.
And the inner and outer carcass plies 6A, 6B having the ply body portions 9A, 9B overlapping inside and outside.

The carcass plies 6A and 6B are formed by applying a carcass cord made of an organic fiber cord such as nylon, rayon or polyester to the tire equator C by 70%.
Are arranged at an angle of up to 90 degrees, and each ply body 9
A and 9B are provided with ply folded portions 10A and 10B which are folded from the inside in the tire axial direction to the outside around the bead core 5 from both ends thereof.

Here, the folded height HP1 of the inner carcass ply 6A from the bead base line BL of the ply folded portion 10A is determined from the bead base line BL of the ply folded portion 10B of the outer carcass ply 6B. It is larger than the outer turning height HP2, and is 0.7 to 1.0 times the tread edge height Hh. in this way,
By making one ply turn-up portion 10A a high turn-up, necessary tire rigidity is secured while covering the end of the other ply turn-up portion 10B and suppressing the cord looseness. In addition, from the viewpoint of straight running stability, the outer turning height HP2 is 0.5 to 0.5 of the tread end height Hh.
0.7 times, and the difference (HP1-HP
2) may be set to about 10 ± 2 mm.

A bead apex rubber 8 made of hard rubber having a JIS Shore A hardness Hs of 50 to 95 degrees and extending radially outward from the bead core 5 is disposed between the ply body 9B and the ply turn-up portion 10B. Reinforced bead portion 4. This bead apex rubber 8
The height HA of the apex from the bead base line BL at the radially outer end of the tread end height Hh is 0.2 to
The range is 0.8 times.

In the present invention, in order to prevent the tire from falling down during turning without impairing the straight running stability,
An insulation rubber layer 11 having different rubber properties from the topping rubber of the carcass 6 is provided on the sidewall portion 3 of the tire 1 having the above-described structure.

More specifically, the insulation rubber layer 11
Is a tangent loss (tan δ) of 0.05 to 0.50,
As shown in FIG. 2, it is made of rubber having a large energy loss, and extends radially outward between the ply folded portions 10A and 10B.

The insulation rubber layer 11 is in the form of a sheet having a thickness Ti of 0.1 to 1.0 mm, the inner end of which is located more inward than the radially outer surface 5E of the bead core 5, and The insulation height Hit from the bead base line BL at the end is 0.4 to 1.0 times the folded height HP1.

Such an insulating rubber layer 1
1 appropriately reinforces the sidewall portion 3 to compensate for the lack of rigidity at the sidewall portion and to improve the straight running stability.
On the other hand, since the loss tangent (tan δ) is large, the shock absorption is excellent, and the fall of the tire can be effectively suppressed while enhancing the disturbance convergence.

Here, the loss tangent (tan δ) is 0.0
If it is less than 5, the shock absorbing property is insufficient and the effect of preventing falling down is not exerted. Conversely, if it exceeds 0.5, the heat generation becomes large and the durability of the tire may be impaired. Therefore, the loss tangent (tan δ) is preferably in the range of 0.3 to 0.4.
The value of the loss tangent (tan δ) was measured using a viscoelastic spectrometer at a frequency of 10 Hz, a temperature of 70 ° C., and a dynamic strain of 2%. The loss tangent (tan δ) of the topping rubber of the carcass 6 is usually 0.05 to 0.2.
And smaller than the insulation rubber layer 11.

When the thickness Ti is less than 0.1 mm, and when the insulation height Hit is 0.4 × HP
When it is less than 1, the reinforcing effect becomes too small, and the straight running stability decreases. Conversely, when the thickness Ti is greater than 1.0 mm, and when the insulation height Hit is greater than 1.0 × HP1, the rigidity at the sidewall portion becomes excessive and the effect of preventing falling down is not exhibited. .

Therefore, the thickness Ti is preferably set to 0.1.
3-0.7mm, insulation height Hit
Is preferably in the range of 0.6 × HP1 to 1.0 × HP1.

In the present embodiment, the thickness of the rubber on the side wall 3 outside the carcass 6 is regulated as follows in order to effectively exert the effect of the insulation rubber layer 11.

That is, the 1/3 height point J on the tire outer surface
1, the tire thickness TF between the tire outer surface and the carcass 6 is equal to the tire nominal sectional width W (120 m in this example).
m) is 1.6% to 5.9%, and in this example, 2.0% to 5.9%.
The range is 7.0 mm. Also 2/3 on the tire outer surface
The rubber thickness TE between the tire outer surface and the carcass 6 at the height point J2 is 1.6% of the nominal sectional width W of the tire.
To 5.9%, and in this example, the range is 2.0 to 7.0 mm. The rubber thickness TD between the tread end Te and the carcass 6 is 4.1% or more of the tire nominal sectional width W.
10.0%, and in this example, the range is 5.0 to 12.0 mm.

Here, the 1/3 height point J1 and the 2/3 height point J2 are defined as distances 1/3 times and 2/3 times the tread edge height Hh, respectively, from the bead base line BL. Means a point on the outer surface of the tire that is radially separated from. Further, in the present embodiment, in the rubber thicknesses TF, TE and TD, the ratio
D / TE 1.8 to 2.1 and ratio TD / TF 1.8
To 2.1.

When both the ratio TD / TE and the ratio TD / TF exceed 2.1 or are less than 1.8,
This tends to reduce the effect of suppressing the fall and decrease the turning performance. When only one of the ratio TD / TE or the ratio TD / TF exceeds 2.1, the feeling of tire rigidity decreases, and conversely, at least one of the ratio TD / TE or the ratio TD / TF is 1.8. If it falls below, the turning performance will decrease.

[0031]

EXAMPLES A tire having a tire size of 120/70 ZR17 and having the basic structure shown in FIG. 1 was prototyped according to the specifications shown in Table 1, and the durability, falling down of the tire, and straight running stability of each test tire were tested. . The specifications shown in Table 2 are common to each tire.

(1) Durability test: Using a drum test machine, a test tire was mounted on a standard rim (MT 3.50 × 1).
7) Under the standard internal pressure (250 kpa), apply a load 1.3 times the maximum load specified in JIS, run at a speed of 50 km / H, and check for damage when traveling a distance of 15,000 km. Pass / Fail was determined by.

(2) Test of fallability and straight running stability: A test tire was mounted on the front wheel of a large 750 cc motorcycle under a standard rim (MT 3.50 × 17) and a standard internal pressure (250 kpa). Pass / fail was determined by sensory evaluation of the rider when the vehicle was running on dry asphalt road surface.

[0034]

[Table 1]

[0035]

[Table 2]

[0036] It was confirmed that the tires of the examples were improved while achieving both the falling property of the tire and the straight running stability.

[0037]

Since the present invention is configured as described above,
Tilt down during turning can be suppressed without impairing straight running stability, and steering stability can be greatly 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 an enlarged sectional view showing a bead portion.

[Explanation of symbols]

 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 6A, 6B Inside and outside carcass ply 7 Belt layer 9A, 9B Ply main body part 10A, 10B Ply folded part 11 Insulation rubber layer BL Bead base line

Claims (4)

[Claims] 1. A carcass comprising an inner and an outer carcass ply, each having a ply body portion extending from a tread portion to a bead core of a bead portion through a sidewall portion and overlapping inside and outside, and a carcass comprising an inner and an outer carcass ply, and an inside of the tread portion and an outside of the carcass. A radial tire for a motorcycle comprising a belt layer disposed on a ply body portion of a carcass ply extending from the ply main body portion of the inner carcass ply and a bead core and a bead core of a ply fold-back portion that folds from the inside in the tire axial direction to the outside. Height of the inside HP
1 is 0.7 to 1.0 times the tread edge height Hh from the bead base line at the tread end, which is greater than the outer turn height HP2 of the ply turn portion of the outer carcass ply from the bead base line. The bead portion includes an insulation rubber layer extending radially outward between the ply folded portions of the inner and outer carcass plies, and the insulation rubber layer has a thickness Ti of 0.1. ~
1.0 mm and tangent loss (tan δ) of 0.05 to 0.5
0, and the insulation height Hit from the bead base line at the outer end of the insulation rubber layer is 0.4 to 1.0 of the inner folded height HP1.
A radial tire for motorcycles, characterized in that it is doubled. 2. The motorcycle radial tire according to claim 1, wherein the tread end height Hh is 0.4 to 0.6 times the tire section height H0. 3. The radial tire for a motorcycle according to claim 1, wherein the outer turning height HP2 is 0.5 to 0.7 times the tread end height Hh. 4. The radial tire for a motorcycle according to claim 1, wherein the insulation height Hit is 0.6 to 1.0 times the folded height HP1. .