JP2000158910A - Pneumatic tire for motorcycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain the improvement in high-speed durability and steering performance relative to a light two wheeler and the prevention of shimmy and improvement in straight traveling stability relative to a heavy two wheeler by differing the modulus at room temperature of the grounding surface-side tread rubber between the central area and shoulder area of the tread part. SOLUTION: A tread part 4 is formed out of a central area 4a having a lateral center (h) coincided with the center of the tread width W of a tire, and a shoulder area 4b nipping it from both sides. In each area 4a, 4b, the modulus in 100% expansion at room temperature of at least the grounding surface-side tread rubber is differed to each other. For the central area 4a, particularly, it is set to a length 0.2-0.4 times the extended length of the tread width W. In a heavy vehicle, low modulus rubber excellent in enveloping property is arranged in the central area 4a to improve the high-speed durability and prevent the shimmy. In a light vehicle, on the other hand, high modulus rubber is arranged in the central area 4a to improve the high-speed durability and steering property.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention is particularly applicable to a motorcycle having a relatively heavy weight, which can achieve straight running stability by preventing shimming, and a motorcycle having a relatively lightweight cornering performance. More particularly, the present invention relates to a pneumatic tire for a motorcycle that can improve high-speed durability and steering performance.

[0002]

2. Description of the Related Art As motorcycles have been improved in performance, the use of circumferential belts has been promoted mainly for the purpose of improving the high-speed durability of rear tires, but the steering characteristics such as handling of front tires have been improved. Because of the emphasis, the conventional cross belt structure was applied.

[0003]

In recent years, there has been a tendency for motorcycles to have higher performance and lighter weight. In particular, in vehicles having a relatively heavy vehicle body, the vehicle has to ride over small unevenness on the road surface. Small vibrations, so-called shimmies, occur, causing a decrease in stability in straight running.On the other hand, for vehicles with relatively light weight, further improvement in steering performance in addition to high-speed durability is required. It has become.

An object of the present invention is to provide high-speed durability and high steering performance when applied to a relatively light motorcycle, and to prevent shimmy when applied to a relatively heavy motorcycle so as to achieve straight running stability. The present invention is to propose a new pneumatic tire having a good performance.

[0005]

According to the present invention, there is provided a bead core embedded in a pair of right and left beads, a toroid extending from one bead to the other bead, and being wound around the bead core to form a bead. In a pneumatic tire including a moored carcass, a circumferential belt layer and a tread portion disposed radially outside a crown portion of the carcass, the circumferential belt layer of the pneumatic tire includes one or more circumferential belt layers. It is formed by winding a long cord or belt-like ply in which a belt cord is covered with rubber in a spiral shape substantially along the circumference of a tire, and the tread portion has a width of 0. A central region having a length of 2 to 0.4 times, the center of which corresponds to the center of the tire tread width;
A pneumatic tire for a motorcycle, comprising a shoulder region sandwiching the central region on both sides, and each region has a different modulus at least when the tread rubber on the contact surface side is stretched by 100% at room temperature. It is.

The present invention is characterized in that the tread rubber in the central region has a modulus lower than that of the shoulder region, or the tread rubber in the central region has a modulus higher than that of the shoulder region. This applies particularly to the front wheels of motorcycles. Here, in the present invention, a relatively heavy vehicle refers to a motorcycle having a displacement of about 900 to 1300 cc,
A relatively light vehicle has a displacement of 400-90.
It refers to a motorcycle that is about 0 cc.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a pneumatic tire which is useful particularly for a front wheel of a motorcycle, and has a belt layer spirally wound around the tire to provide high-speed durability. In accordance with the weight of the motorcycle, the modulus of the tread rubber in the central region of the tread at least at room temperature at the time of 100% elongation at the room temperature and the room temperature of the tread rubber in the shoulder region sandwiching the central region are improved. Because the modulus at the time of 100% extension is changed, the improvement in high-speed durability and steering performance is improved especially for a vehicle having a relatively light weight, and the prevention of shimmy is performed for a vehicle having a relatively heavy weight. Straight running stability can be ensured. In this case, there is an advantage that productivity can be improved because the case of the tire excluding the tread can be shared by all tires.

A circumferential belt layer (spiral belt layer) spirally wound along the circumferential direction of the tire is arranged to improve high-speed durability, and has a more advantageous structural flexibility than a conventional cross belt. Is used to improve the vibration absorption. In this case, since the flexibility in the central region of the tread of the tire is not sufficient, a rubber having a low modulus having excellent envelope properties is arranged in the central region. In this way, it is possible to further prevent the occurrence of shimmy for a relatively heavy vehicle by further absorbing the minute vibration from the road surface.

[0009] In a vehicle that is relatively light and requires stricter high-speed durability, a belt layer is spirally formed to improve high-speed durability in a vehicle where steering performance such as handling is more important in general running than in shimmy. At the same time, a disadvantage to the flexibility of the tire structure due to the use of a spiral belt layer in which rubber having a higher modulus is arranged in the central region of the tread than in the shoulder region is compensated for.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described more specifically with reference to the drawings. FIG. 1 shows a configuration of a motorcycle pneumatic tire according to the present invention. In FIG. 1, reference numeral 1 denotes a bead core embedded in each of right and left bead portions, and reference numeral 2 denotes a bead portion from one bead portion to the other bead portion. The carcass 3, which extends in a toroidal shape and is wound around the bead core 1 and anchored at the bead portion, is a circumferential belt layer disposed radially outside the crown portion of the carcass 2, and the belt layer 3 is It is formed by spirally winding a long cord or belt-like ply in which one or more belt cords are covered with rubber, substantially along the circumference of the tire.

Reference numeral 4 denotes a tread portion. The tread portion 4 includes a central region 4a whose center in the width direction coincides with the center of the tread width W of the tire, and shoulder regions 4b sandwiching the central region 4a on both sides. The central region 4a and the shoulder region 4b are different from each other in at least the modulus of the tread rubber on the contact surface side at the time of 100% elongation at room temperature. It has a length of up to 0.4 times.

In the present invention, the length L of the central region 4a of the tread portion 4 along the tread is defined to be in the range of 0.2 to 0.4 times the developed length of the tread width W. This is because the width is such that the motorcycle comes into contact with the ground when traveling straight.

In a vehicle having a relatively heavy weight, the modulus at the time of 100% extension at room temperature is about ²⁰ kgf / cm ² , whereas the tread rubber in the shoulder area 4b has a low modulus having excellent envelope properties in the central area 4a. , For example, a rubber having a modulus of about 10 to 17 kgf / cm ² . By adopting such a configuration, high-speed durability is improved, and at the same time, the occurrence of shimmy is prevented by absorbing minute vibrations from the road surface.

For a relatively light vehicle, for example, the modulus at 100% extension at room temperature is 15 kgf /
The central region 4a has a higher modulus than the tread rubber of the shoulder region 4b which is about ² cm2,
For example, rubber having a modulus of about 18 to 23 kgf / cm ² is provided. By adopting such a configuration, steering performance such as handling is improved in addition to improvement of high-speed durability.

In the present invention, the difference between the modulus of the rubber in the central region 4a of the tread portion 4 and the modulus of the rubber in the shoulder region 4b is 5 kgf / cm ^{2 for} a relatively heavy vehicle.
About 6kg for vehicles with relatively light weight
It is preferable to set the range to about f / cm ² .

A tire (internal pressure: 250 kPa) having one layer of a Kevlar spiral belt and a size of 120/70 ZR17 and having a sectional structure as shown in FIG. 1 was mounted on the front wheel of a vehicle, and the performance of the tire was investigated. . The vehicle used was a 600cc sports car as a light car and a 1200cc tourer car as a heavy car. Each car had a single layer of Kevlar spiral belt and a tire with a size of 180 / 55ZR17 as a rear tire (internal pressure). : 290 kPa).

In a lightweight vehicle, the center area of the tire tread has a modulus of 20 kg at 100% elongation at room temperature.
f / cm ² rubber (length is tread width development length (1
The shoulder region was made of a rubber having a modulus of 15 kgf / cm ² . As a result, the high-speed durability was 100 and the steering performance was 100 when tires having the same structure were used except that the rubber of the tread portion had the same modulus (modulus 17 kgf / cm ² ) in the entire region. In this case (indicated by an index based on actual vehicle feeling evaluation, the larger the index, the better), the high-speed durability of the pneumatic tire according to the present invention is 100, and the high-speed steering is 1
It was about 20 and it was confirmed that the steering performance was remarkably improved.

On the other hand, in a heavy vehicle, the center area of the tread portion of the tire is rubber having a modulus of 15 kgf / cm ² (the length is 0.33 of the developed length (150 mm) of the tread width).
And the shoulder region has a modulus of 17 kgf / cm ^2.
The one provided with a rubber that becomes As a result, high-speed durability was 10% when a tire having the same structure was used except that the rubber of the tread portion had the same modulus (modulus 17 kgf / cm ² ) in the entire region.
0, when the degree of occurrence of shimming is set to 100 (the higher the index, the better), the pneumatic tire according to the present invention has a high-speed durability of about 100 and a degree of occurrence of shimming of about 120. In particular, it was confirmed that the occurrence of shimmy was significantly reduced.

[0019]

According to the present invention, when applied to a motorcycle having a relatively light weight, it is possible to secure high steering performance while maintaining high-speed durability. In application, the occurrence of shimmy can be avoided as much as possible to improve the stability in straight running. In particular, in the present invention, the tire case can be used irrespective of the weight of the vehicle, which is useful for improving productivity.

[Brief description of the drawings]

FIG. 1 is a diagram showing a cross-sectional structure of a motorcycle pneumatic tire according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 bead core 2 carcass 3 circumferential belt layer 4 tread portion 4a central region 4b shoulder region L central region length W tread width

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) B60C 9/22 B60C 9/22 B

Claims (4)

[Claims] A bead core buried in a pair of left and right bead portions; a carcass extending from one bead portion to the other bead portion in a toroidal shape and wound around the bead core and moored to the bead portion; In a pneumatic tire provided with a circumferential belt layer and a tread portion disposed radially outward of a crown portion, the circumferential belt layer of the pneumatic tire includes one or a plurality of belt cords made of rubber. The tread portion is formed by spirally winding a long cord or band-like ply covered substantially spirally around the tire. The tread portion has a tread width of 0.2 to 0.1 mm.
A central region having a length four times the center of which coincides with the center of the tread width of the tire, and a shoulder region sandwiching the central region on both sides, and each region has at least the tread rubber at room temperature of the tread rubber on the tread side. A pneumatic tire for a motorcycle, wherein the modulus at the time of 100% extension is different from each other. 2. The pneumatic tire for a motorcycle according to claim 1, wherein the tread rubber in the central region has a modulus lower than that of the shoulder region. 3. The pneumatic motorcycle tire according to claim 1, wherein the tread rubber in the central region has a higher modulus than that in the shoulder region. 4. The pneumatic tire for a motorcycle according to claim 1, wherein the pneumatic tire is applied to a front wheel of a motorcycle.