JPH07108805A - Pneumatic tire for motorcycle of spiral belt structure - Google Patents

Abstract

PURPOSE:To increase turning performance without impairing other performances by reducing the JIS hardness of a tread part at a center district divided in axial direction of a tire and the ratio of loss tangent to dynamic complex modulus of elasticity more than those at districts on both sides. CONSTITUTION:A tread rubber 5 at a crown part 3 is divided into three parts of a center district and districts on both sides by setting an angle formed by a boundary line 6 extended from a 1/4 point on a tread surface toward the inside of a tire and a tire equator surface at a tire meridian section at 45 deg.. Also the JIS (A) hardness of the tread rubber after vulcanization is set so that the hardness at the district on both sides is larger by at least 3 points or more than that at the center district, and the ratio of loss tangent to the dynamic complex modulus of elasticity of the tread rubber 5 of tan delta/E' is set so that it is larger at the district on both sides than that at the center district. Thus turning performance can be improved without impairing straight forward traveling performance and high-speed travel performance, and steering stability also can be increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a single wire or a plurality of cords coated with rubber which exhibits excellent turning and steering performance without damaging expected performance such as straight running performance, high speed performance and uniformity performance. The present invention relates to a pneumatic radial tire for a motorcycle having a spiral belt structure, which is embedded in the tire and wound in the circumferential direction of the tire.

[0002]

2. Description of the Related Art One or more belt layers are formed by spirally winding a material composed of a single wire or a plurality of parallel cords embedded in a coated rubber in an axial direction of a tire in a tire axial direction. If a so-called spiral belt structure with a belt structure is adopted for a radial tire for motorcycles,
While improving the high-speed durability, straight running stability, uniformity performance, etc. of the tire, the cornering force, which is important when the vehicle is turning, and the camber thrust at large camber angles, compared to the conventional cross belt structure. Since it tends to become smaller, various attempts have been made to improve this point. For example, there is a tire having the structure described in the conventional technique and the example of JP-A-4-197805. That is, a technique for increasing the elastic modulus of a case (ply) rubber to improve the case rigidity as described in the prior art of the publication and a technique for using a hard rubber as a base rubber of a cap base structure are known. However, it is said that the former cannot be put to practical use because the side rigidity becomes high and the grounding property is deteriorated, resulting in deterioration of grip performance, and the latter impairs the initial grounding property. Furthermore, in the invention described in the embodiments of the above publications, in a pneumatic radial tire for a motorcycle having a belt structure in which reinforcing cords are arranged in a substantially circumferential direction, the lateral force at the time of a large camber is significantly increased. As a tread structure that can be improved, a part of the tread on both sides of the tread part divided into three areas is formed into two layers of inner layer rubber and outer layer rubber, and the JIS hardness of the inner layer rubber is better than that of the outer layer rubber. A tire designed to be at least 5 degrees larger is proposed.

[0003]

However, when the invention of the above publication is applied to a radial tire having a so-called spiral belt structure to which the present invention is applied, a tread and a belt that are parallel to the ground contact surface at the tire ground contact surface. , Pliers
Rigidity against deformation of bending a tire member in which dust and the like are laminated within the plane (that is, when the tire is subjected to frictional force against the centrifugal force at the ground contact surface, the tire is subjected to such bending deformation within the plane. (It is referred to as bending rigidity) is not sufficiently large, and it is not possible to recover the deterioration of the steering performance at the time of turning, which is a defect of the spiral belt structure. Furthermore, a part of the tread in the both side areas is made of inner rubber and outer rubber. Since it is formed in two layers, there is a problem in that the complexity of tire manufacturing is inevitable.

The present invention relates to the steering performance of a radial tire having a spirally wound belt structure having a code angle in the circumferential direction, particularly a cornering force and a camber at the time of a large camber.
It is an object of the present invention to provide a two-wheeled vehicle tire in which the turning performance represented by thrust is improved without impairing the performance of other tires.

[0005]

In order to achieve the above object, in a pneumatic radial tire for a motorcycle according to the present invention, in claim 1, a plurality of cords arranged in a single line or in parallel are provided in a coated rubber. In a pneumatic radial tire for a motorcycle having a belt structure having one or more belt layers in which a material formed by embedding is spirally wound in the tire axial direction at an angle approximately in the circumferential direction of the tire, the tread portion is the axis of the tire. In three directions, a central area and side areas, and the JIS hardness of the tread rubber in the side areas is at least 3 points greater than the JIS hardness of the tread rubber in the central area.
At the same time, the ratio of the loss tangent to the dynamic complex modulus of the bilateral zone tread rubber tan δ / E ′ is greater than that of the central zone tread rubber, and
In the second aspect, the JIS hardness of both side areas in the first aspect is 55 to 65, and the ratio of the loss tangent to the dynamic complex elastic modulus tan δ / E 'is 3.5 × 10 ^{-9 to} 7 × 10 ^-9.
It is characterized by being in the range of cm ² / dyne.

The area occupied by the tread rubber in both lateral areas of the tire meridian is preferably 50 to 80% of the total area of the tread rubber, and on the outer surface of the tread between the central area and the lateral areas. The dividing position is that the width of the central area is 20 arcs of the tread width with the arc length across the tire equatorial plane.
It is preferable to appropriately select it so as to fall within the range of 50% to 50%.
Furthermore, it is preferable that the boundaries between the central area and the lateral areas in the tire meridian section intersect inside the tire.

[0007]

A belt in which at least one belt layer is formed by spirally winding a material in which a single wire or a plurality of parallel cords are buried in a coated rubber in a spiral shape at an angle toward the tire circumferential direction. In the structure, since the cord is oriented substantially in the tire circumferential direction, the rigidity against expansion and contraction in the tire circumferential direction is high, but on the other hand, in the case where the spiral belt layer is bent in the plane in which the code is arranged, The rigidity (the in-plane bending rigidity) becomes very small. Therefore, since the frictional force of the contact surface against the centrifugal force when the two-wheeled vehicle is turning is linked to the in-plane rigidity, the radial tire of the spiral belt layer has a cornering force and a cornering force based on the frictional force of the contact surface. Camber thrust is reduced.

According to the present invention, in order to remedy this drawback of the radial tire having a spiral belt structure, a tire tread, a belt and a pliers-cass are provided by arranging a tread rubber having high hardness in both side areas of a tire tread in a considerably large volume. While increasing the in-plane bending rigidity of the member in which the etc. are laminated to increase the resistance to the force received from the road surface,
The ratio of the loss tangent to the dynamic complex elastic modulus of the tread rubber on both sides tan δ / E 'is set to a large value to improve the adhesion to the road surface (ability to wrap the unevenness of the road surface), and at the same time, to prevent external input Since the amount of energy absorbed inside is increased to increase the generation of frictional force on the ground contact surface, the cornering force and camber thrust of the tire become high, which is the so-called waist when the vehicle actually runs, especially when turning. It is possible to obtain a tire with a strong grip that works well on the road and has a strong grip.

Incidentally, the hardness of the tread rubber on both sides is set to 3 points or more based on the experimental result described later on the difference in hardness from the tread rubber on the central area. If it is less than 3 points, a rubber having a high hardness is used up to the central area of the tire tread portion, so that heat generation in the central area of the tread increases and high speed performance is deteriorated. Further, as the hardness value selected for the tread rubber on both sides, when the hardness exceeds 65 degrees, stress concentration between the belt end or the tread-belt greatly increases due to external input, and fatigue peeling failure easily occurs at these parts. On the other hand, if the hardness is set to less than 55 degrees, the effect of improving the in-plane bending rigidity cannot be sufficiently obtained.

Next, the value of the ratio tan δ / E 'of the loss tangent to the dynamic complex elastic modulus of the tread rubber on both sides is greater than that of 7 × 10 ^-9 cm ² / dyne. There is a sharp increase in the risk of reducing heat generation performance and promoting thermal fatigue failure between the belt end or tread and belt. The value of the above ratio is 3.5 × 10 ^-9 cm ² /
If the value is less than dyne, the adhesion to the road surface and the friction coefficient are not improved, and the desired grip performance cannot be obtained.

[0011]

EXAMPLES Examples of the present invention will be described below. FIG. 1 is a meridional cross-sectional view of a radial tire for a motorcycle having a spiral belt structure according to the present invention, in which a tire size is 170 /
It is 60ZR17. The belt (1) which constitutes the skeleton of the tire has three vulcanized aromatic polyamide fibers (trade name; Kevlar) cords arranged at an angle of 0 degree with respect to the equatorial plane of the tire after vulcanization. ) A one-layer belt in which a ribbon-shaped material (2) embedded in rubber having a hardness of about 70 degrees is spirally wound over almost the entire width of the tire crown portion (3), while a carcass ply is used. (4) is made of a single layer of radial ply in which nylon cords are arranged in a direction of 90 degrees with respect to the equatorial plane and embedded in rubber having a JIS (A) hardness of about 60 degrees after vulcanization. . The tread rubber (5) occupying the crown portion is a boundary line (inwardly extending from the 1/4 point (a point obtained by dividing the tread width measured by the arc length into four equal parts) of the tread surface inward in the tire meridian section. 6) divides the tread into 3 areas with an angle of 45 degrees with the equatorial plane of the tire, and JIS (A) hardness of the tread rubber in the lateral areas and JIS (A) after the vulcanization of the tread rubber in the central area. ) By taking a difference of 3 points or more from the hardness,
Further, the ratio tan δ / E 'of the lost tangent to the dynamic complex elastic modulus of the tread rubber in both side areas was set to be larger than that value in the central area. Moreover, the above-mentioned physical property values of the tread rubber in both side areas are 55 to 65, respectively.
It was selected from the range of 3.5 × 10 ^{−9 to} 7 × 10 ⁻⁹ cm ² / dyne. On the other hand, the tire of the comparative example has the same tire size, the same belt and the same carcass structural material as the tire of the above-mentioned example, but the selection of the above-mentioned physical property values of the tread rubber in both side areas and the central area is the same as that of the present invention. It is out of the specified condition or range.

Incidentally, the JIS (A) hardness after vulcanization is JISK.
6301 Vulcanized Rubber Physical Testing Spring Hardness Test A
It was measured based on the shape. Moreover, the dynamic complex elastic modulus and the viscoelasticity value of the Lost tangent were measured by using Rheograph Solid manufactured by Toyo Seiki Co., Ltd., and the width, thickness and length of the rubber sample were 5 ×
2 × 20 mm, initial tension 2 kg / cm ² , vibration strain ± 1
%, The vibration frequency was 50 Hz, and the measurement temperature was 25 degrees.

Next, in order to confirm the performance improving effect of the radial tire for a two-wheeled vehicle of the present invention, the tires of Examples and Comparative Examples were actually prototyped and the results of comparison of steering performance will be described.
Table 1 shows the tread rubbers having various compounding prescriptions, in which the rubber physical property values were measured. Table 2 shows the tire maneuvering performance of four types of tires of Examples and three types of tires of Comparative Examples, which were produced by combining these tread rubbers so as to meet the selection conditions of the tread rubber physical property values in the above respective areas. The results of measuring the camber thrust and the cornering force, which are expressed by using an indoor maneuverability tester for motorcycles, under the tire internal pressure load condition of JIS standard 100% are shown. The values in Table 2 are camber.
The maximum value of the cornering force with respect to the camber thrust value and the slip angle at an angle of 30 degrees is shown as an index when Comparative Example 1 is set to 100.

[0014]

[Table 1]

[0015]

[Table 2]

From the results shown in Table 2, the camber thrust value and the maximum cornering force of the tires of the examples are 105% to 114% and 105% to 110% of those of the comparative example tires.
It can be seen that the improvement of the steering performance has been achieved since the improvement of 10% has been obtained. Although detailed actual data was omitted, the durability test by the indoor drum test and the actual vehicle steering stability test were separately conducted on the tires of the examples, and the results were originally expected for the radial tire having the spiral belt structure. It was confirmed that excellent high speed durability, straight running stability, etc. were sufficiently maintained.

[0017]

In the radial tire for a motorcycle according to the present invention, the drawback of the in-plane rigidity reduction associated with the spiral belt structure having the circumferential code angle is that stable straight running which is originally expected of the spiral belt structure. Provide high-performance tires with excellent steering stability by improving performance and high-speed performance without deteriorating.

[Brief description of drawings]

1 is a tire meridian sectional view of a radial tire for a motorcycle according to the present invention.

[Explanation of symbols]

 1 Belt 2 Material 3 Crown 4 Carcass ply 5 Tread rubber 6 Boundary line

Claims (2)

[Claims] 1. A belt layer in which a material formed by embedding a single cord or a plurality of parallel cords in a coated rubber is spirally wound in an axial direction of the tire at an angle substantially in the circumferential direction of the tire. In a pneumatic radial tire for a motorcycle having a belt structure having the above, the tread portion is divided into a central region and two side regions in the axial direction of the tire, and the JIS hardness of the tread rubber in the both side regions is that of the tread rubber in the central region. The spiral belt structure is characterized in that it has a ratio of tan δ / E ′ of the loss tangent to the dynamic complex elastic modulus of the tread rubber on both sides greater than that of the central region tread rubber by at least 3 points or more. Pneumatic tires for motorcycles. 2. The JIS hardness of both side areas is 55 to 65,
Ratio of loss tangent to dynamic complex elastic modulus tan δ
/ E 'is 3.5 × 10 ^{-9 to} 7 × 10 ^-9 cm ² / dyne
The tire according to claim 1, which is in the range.