JPH03239601A - Pneumatic radial tire for motor bicycle - Google Patents

Abstract

PURPOSE:To improve durability of a pneumatic radial tire by forming a main groove through connections main groove portions alternately crossing each other at a given angle relative to the equator surface in a pneumatic radial tire having a belt layer of spirally wound organic fiber cord in parallel to the equator surface and a main circumferential groove. CONSTITUTION:There is provided a carcass 12 consisting of one or more carcass plys of organic fiber cord such as nylon disposed at a uniform angle within a range from 75 deg. to 90 deg. relative to the equator surface S of a tire. A belt layer 22 made of spirally wound organic fiber cord such as high modulus polyester, etc. having 600kg/mm<2> or more of modulus of elasticity is interposed between a tread 14 and the carcass 12 within a ranges from 70 to 110% of the width of the tread. A main zigzag circumferential groove 20 made by connecting together main groove parts 20a, 20b alternately crossing each other obliquely at a uniform angle is formed within a range from 10 deg. to 45 deg. relative to the equator surface S. According to this constitution, durability can be improved.

Description

Detailed Description of the Invention (Field of Industrial Application) This invention consists of a belt layer of organic fiber cords spirally wound substantially parallel to the equatorial plane of the tire over substantially the tread width of the tire. The present invention relates to a pneumatic radial tire for two-wheeled vehicles having a belt.

(Prior Art) A tire with a so-called radial structure has a carcass made of carcass plies of organic fiber cords arranged at a constant angle within a range of 75° to 90° with respect to the tire equatorial plane. a belt consisting of a belt layer of belt cords arranged in one direction over substantially the tread width at a small angle in the range of 10' to 25 degrees with respect to the tire equatorial plane; The carcass is tightened from the circumferential direction to suppress tread movement.
Due to their low heat generation, excellent wear resistance, and high grip performance, they are being applied to motorcycle tires as expressway networks develop and engines become more powerful.

Furthermore, as the cord forming the belt layer, fibers with a large elastic modulus, such as high modulus polyester with an elastic modulus of 600 kg/lnm2 or more, polyvinyl alcohol,
A radial tire for two-wheeled vehicles has also been proposed, which has a belt consisting of at least one belt layer in which cords of rayon or aromatic polyamide fiber are spirally wound substantially parallel to the tire's equatorial plane. This belt with a high ratio sufficiently suppresses the tread from protruding outward in the radial direction of the tire during running, so there is little reduction in the ground contact area, and it exhibits much better high-speed running performance than conventional Unlike the radial structure tires, there is no need to use multiple belt layers and arrange the belt layer cords obliquely with respect to the tire equatorial plane, which has many advantages such as reducing tire weight. have. In addition, regardless of the structure of the radial tire, the tread that forms the tread surface is provided with a main groove extending in the circumferential direction of the tire, taking into account the tire's straight-line stability, high-speed performance, and wet performance. is common.

(Problem to be Solved by the Invention) However, in a tire having the above-mentioned radial structure in which the extending direction of the main groove formed in the tread and the winding direction of the cord forming the belt are almost the same, the tire When shaving, a protrusion formed on the inner surface of the mold and having a shape corresponding to the circumferential main groove is pressed against the bottom of the main groove extending in the circumferential direction. A so-called "cord opening" occurs in which each cord is pushed out in the tire width direction, and the belt section cords are also curved inward in the tire radial direction, and the spirally wound cords forming the belt layer are stretched across the tire width. They will not be uniformly arranged in the direction and radial direction.

Therefore, during use, the tension that acts on the cords that make up the belt portion corresponding to the bottom of the main groove of the tire is different from the tension that acts on the cords that make up the remaining belt portion. There was a problem in that the belt cord corresponding to the groove bottom part was damaged in a relatively short period of time, and the belt was unable to exhibit the specified strength, resulting in low tire durability. This problem is particularly noticeable when fibers with a high modulus of elasticity are used as belt cords. Cords made of fibers with a high modulus of elasticity have a small elongation, so the tension applied to them is almost uniform throughout the belt. This is due to the fact that it is difficult to disperse.

In order to deal with this problem, by using extremely thick rubber, for example, 3.5M or more, as the rubber located below the main groove extending in the circumferential direction, the inconvenience with belt cord arrangement during shaving can be avoided. Although a method of eliminating it is conceivable, since the unsprung weight increases, this would have a negative effect on the tire's maneuverability, so it cannot be said to be a preferable solution.

The present invention was made in view of such problems,
The object of the present invention is to provide a pneumatic radial tire for two-wheeled vehicles that solves the above problems without impairing wet performance and motion performance.

(Means for Achieving the Object) In order to achieve this object, in the present invention, a pair of sidewalls and a tread are connected in a toroidal manner, and these parts are arranged in a range of 750 to 90 degrees with respect to the tire equatorial plane. The carcass is reinforced with a carcass consisting of at least one carcass ply of organic fiber cords arranged at a constant angle within the tire, and both ends of the carcass ply are wrapped around bead rings embedded in the radially inner ends of both sidewalls. The elastic modulus 6 is wound outward in the rotational axis direction and spirally wound substantially parallel to the tire equatorial plane between the tread rubber and the carcass over a range of approximately 70% to 110% of the tread width.
A pneumatic radial tire for two-wheeled vehicles, provided with a belt having at least one belt layer made of organic fiber cord of 00 kg/mm2 or more, and provided with a main groove extending substantially in the circumferential direction of the tire at least in the center of the tire tread. In,
The main groove has main groove portions that alternately obliquely intersect the tire equatorial plane at a constant angle within a range of 10° to 45° with respect to the tire equatorial plane.

(Function) Even in a structure using a belt consisting of belt layers in which organic fiber cords are spirally wound substantially parallel to the tire equatorial plane, organic fiber cords are wound alternately at a constant angle within a predetermined range with respect to the tire equatorial plane. The oblique upper groove portions restrain the cords corresponding to the main groove portions from moving inward in the tire width direction and radial direction when shaving the tire, and the cords forming the belt layer are arranged uniformly in the tire width direction. Therefore, the durability of the tire can be improved without causing the cord to open or bending inward in the radial direction of the tire. Furthermore, since there is no increase in tire weight, there is no loss of maneuverability.

(Example) Hereinafter, preferred examples of the pneumatic tire for two-wheeled vehicles of the present invention will be described in detail with reference to the drawings.

FIG. 1(a) shows a tire 10 showing one embodiment of the present invention.
It is a diagram showing a half part in cross section, and the tires are arranged at a constant angle within a range of 75° to 90° with respect to the tire equatorial plane S.
For example, a carcass 1 consisting of at least one carcass ply of organic fiber cord such as nylon or polyester
2 reinforces the tread 14 and sidewall 16 that are connected in a toroidal manner, and both ends of the tread 14 and the sidewall 16 are reinforced.
6 is wound up toward the outside in the tire rotation axis direction around a bead ring 18 embedded in the radially inner end of the tire.

The tread 14 forming the tire tread surface is provided with a main groove 20 extending in the tire circumferential direction, and between the tread 14 and the carcass 12, for example, high modulus polyester, polyvinyl alcohol, rayon, or A cord made of an organic fiber having an elastic modulus of 600 kg/mm2 or more, such as aromatic polyamide fiber R Kevlar (trade name), is stretched substantially parallel to the tire equatorial plane to
At least one belt 22 made of a belt layer spirally wound over a range of 0% to 110% is disposed, and acts as a "hoop" to tighten the carcass 12 from the outside in the tire circumferential direction. It is possible to increase the rigidity and suppress the radially outward expansion of the tread 14 during high-speed running.

Reference numeral 24 is a rubber filler that maintains the rolled up portion of the carcass wound around the bead ring 18 in a predetermined relative positional relationship with the carcass 12, and relieves a portion of the internal pressure acting on the sidewall 16. On the other hand, the elastic modulus of a cord is calculated by extending the slope of the rising part of the load-elongation diagram when a tensile load is applied to the cord, and calculating the load corresponding to 10% cord elongation. This is the value obtained according to the following formula.

Cord elastic modulus = L x 10/A However, A=cord cross-sectional area.

The main groove 20 extending substantially in the circumferential direction at the center of the tire tread is formed at a constant angle within the range of 10' to 45° with respect to the tire equatorial plane S, as shown in FIG. 1(b). (θ), a plurality of main groove portions 20a and 20b are provided which alternately intersect obliquely with the equatorial plane S and are continuous with each other. These main groove portions 20a and 20b greatly contribute to the drainage performance of the tire, and considering that approximately 80% or more of the time when a two-wheeled vehicle is driven in a general city area is in a straight line, at least the tire The central part of the tread, preferably
Width in the range of 30% to 60% of the tread width W (2w,
), thereby ensuring the desired drainage performance of the tire.

Moreover, those main groove portions 20a and 2 forming the main groove 20
The angle (
The reason why θ) is set to a value within the range of 10° to 45° is that the angle (θ) between the main groove portion and the tire equatorial plane S is smaller than 10°, as shown in Figure 2 (a). value, that is, a value close to the equatorial plane S, the interval between adjacent cords at the groove bottom of the main groove 20 spirally wound in the circumferential direction of the tire forming the belt 22 becomes large, as described above. This is because the tension acting on the cord differs greatly between the groove bottom and other parts.On the other hand, the reason why the angle (θ) is set to 45° or less is because the angle (θ) is 4
When the angle exceeds 5°, the residual strength of the cord forming the belt, in this example, the cord made of aromatic polyamide fibers, decreases rapidly, and on the other hand, the angle of the main groove portion of the main groove with respect to the tire equatorial plane S decreases. This is because as the size increases, the drainage performance of the main groove tends to be impaired.

The remaining strength of the cord is defined as a tire filled with the normal internal pressure on a spot cleat drum, which is made up of a plurality of cylindrical bodies with a height of 12 mm and a diameter of 18 mm arranged around the outer periphery of a cylindrical body with a diameter of 1.7 m. Press with a load equivalent to 100% of the load, at a speed of 6 per hour.
This shows the strength of the cord after running the equivalent of 10,000km at 0km, and by using this drum, it is possible to reveal the conditions when running on a general road with pebbles or steps.

Next, in order to investigate the durability and wet performance of the tire according to the present invention, a comparative tire was used in which the angle that the main groove extending in the tire circumferential direction makes with respect to the tire equatorial plane S was different from that of the tire according to the present invention. A comparative test was conducted as shown below.

The size of the tires used in the test was MCR17.
It is 0/60 R17, and its carcass is 126 in thickness.
The belt has one layer of carcass ply in which cords made of 66 nylon with a thickness of 0d/2 are arranged at an angle of 90° to the tire equatorial plane, while the belt is made of aromatic polyamide fiber cords with a thickness of 1500d/2. It has one belt layer spirally wound substantially parallel to the equatorial plane.

◎Test tire: - Invention tire As shown in FIG. 1(b), a tire in which the angle (θ) of the main groove portion forming the main groove with respect to the tire equatorial plane S is 30°.

Comparative Tire 1 A tire in which the main groove extends substantially linearly in the circumferential direction of the tire, and therefore the angle (θ) formed by the upper groove with respect to the tire equatorial plane S is 0°.

- Comparison Tire 2 A tire in which the main groove portion forming the main groove makes an angle [θ] of 60° with respect to the tire equatorial plane S.

◎Test method: ・Durability Compatibility: Pressure is applied to each tire assembled on a rim. Filled with water to increase the destructive strength of each We investigated and evaluated the index.

- Wet performance: Each tire was mounted alternately on an actual vehicle, a straight slalom test was conducted on a test road with a water depth of 3 mm, and an index evaluation was performed using a feeling test.

◎Test results: Table As is clear from this table, by selecting the angle (θ) formed by the main groove with respect to the tire equatorial plane S from an appropriate range, tire durability can be improved without impairing wet performance. It can be seen that it can improve the

In addition, in this embodiment, as shown in FIG. 2 (b3), the main groove portions 20a and 20b forming the main groove 20 are
Although the configuration is such that they communicate with each other in the tire circumferential direction, the main groove portions 20a and 20 are not limited to this embodiment.
It is also possible to make b discontinuous in the tire circumferential direction, and to make these main groove portions curved and continuous or discontinuous.

(Effects of the Invention) Thus, according to the present invention, a radial tire is provided that includes a belt made of a belt layer of organic fiber cords spirally wound substantially parallel to the tire equatorial plane and a main groove extending in the circumferential direction of the tire. To obtain a pneumatic radial tire for a two-wheeled vehicle with improved tire durability without impairing the advantages of the above.

[Brief explanation of drawings]

FIG. 1(a) is a cross-sectional view of half of the pneumatic radial tire for a motorcycle according to the present invention; FIG. 1(b) is an explanatory diagram showing a tread of the pneumatic radial tire for a motorcycle according to the present invention; FIG. Figure 2 (a) is an explanatory diagram showing the opening of the spirally wound cord forming the belt layer with respect to the angle formed between the main groove portion and the tire equatorial plane, and Figure 2 (b) is an explanatory diagram showing the difference between the main groove portion and the tire equatorial plane. FIG. 3 is a diagram showing the relationship between the residual strength of the spirally wound coat forming the belt layer and the angle between the portion and the tire equatorial plane.

Claims (1)

[Claims] 1. A pair of sidewalls and a tread are connected in a toroidal manner, and these parts are aligned at an angle of 75 degrees to 9 degrees with respect to the tire's equatorial plane.
A bead ring reinforced with a carcass consisting of at least one carcass ply of organic fiber cords arranged at a constant angle within the range of 0°, with both ends of the carcass ply buried in the radially inner ends of both sidewalls. 70% to 110% of the tread width between the tread rubber and the carcass.
A belt having at least one belt layer made of an organic fiber cord having an elastic modulus of 600 kg/mm^2 or more is provided, which is spirally wound substantially parallel to the tire equatorial plane over a range of In a pneumatic radial tire for two-wheeled vehicles, the main groove is provided with a main groove extending substantially in the circumferential direction of the tire.
A pneumatic radial tire for a two-wheeled vehicle, characterized in that it has main groove portions that alternately obliquely intersect the tire equatorial plane at a constant angle within a range of 45° to 45°.