JPS62163807A - Pneumatic radial tire for bicycle - Google Patents

Abstract

PURPOSE:To moderate stress and to prevent generation of a crack from a tread end, by arranging the maximum width end position of a belt to a center side from a position, where a normal is erected from the tread end, so that a distance in the axial direction to a tread external surface is ensured. CONSTITUTION:A tread is constituted of a central part with large wearing resistance and both side parts with rich weather resistance, further the both side parts are formed into the physical property and composition substantially equal to a side tread. While a boundary, formed between the central part and the both side parts as viewed from a cross section of the tread, is arranged to the inner in a radial direction from a tread width end in the external surface of a tire, further means directional extension lines of a boundary surface in the both sides are divided in a range intersecting each other in the tire. Further an outer end part in the radial direction of the side tread interposes between a belt end part and a carcass so that a contact amount of the outer end part with the belt end part obtains at least 5% or more a tread width. while an outer end in the axial direction of a belt is arranged to the inner or the like in the axial direction, further a specific distance in the axial direction is set to 5% or more the tire tread width.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a relatively durable belt end structure of a pneumatic radial tire for two-wheeled vehicles.

Conventional technology Conventionally, in the production of pneumatic radial tires for motorcycles, a top tread having side treads at both ends of the top tread is first extruded, side treads on both sides are first attached during two-stage molding, and then the top tread is attached. It was manufactured by

However, since tires manufactured using this method have a wide belt, which is characteristic of motorcycle tires, the axial distance from the belt end to the tire surface is small, as shown in Figure 1, and the radial distance of the side tread is small. The amount of contact between the outer end portion and the belt end is small, and the outer end of the belt in the axial direction is not on the normal line passing through the tread width edge and perpendicular to the carcass, or inward in the axial direction, and the belt outer surface curve progresses. axial distance becomes smaller.

Problems to be Solved by the Invention As mentioned above, the axial distance from the belt end to the outer surface of the tire is small, and the overlap distance between the belt and the side tread is small, so cracks occur from the belt end and growth is promoted from the cracks. This resulted in a significant loss of durability, resulting in a problem of reduced durability.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a pneumatic radial tire for two-wheeled vehicles, in which the tread is composed of a central portion with relatively high wear resistance and both side portions with relatively high weather resistance. , the both side portions have substantially the same physical properties and composition as the side tread, and when viewed from the cross section of the tread, the boundary between the center portion and both side portions is located radially inward from the tread width edge of the tire on the outer surface of the tire. , and the side tread is divided in a range in which the average direction extension lines of the boundary surfaces on both sides intersect with each other within the tire, and the radially outer end portion of the side tread has a contact amount with the belt end that is smaller than that of the tire tread. (The axially outer end of the belt is interposed between the belt end and the carcass so that the width of the belt is 5% or more, and the axially outer end of the belt is on the normal line passing through the tread width end and perpendicularly to the carcass, or on the axially inner The axial distance from the belt end to the tire outer surface curve is at least 5% of the tire tread width.
It is characterized by the above.

Incidentally, when manufacturing this tire, the tire of the present invention can be manufactured by using the shape of the tread shown in FIG. 2.

Function In the present invention, by locating the belt maximum width end position closer to the center than the normal line position from the tread edge, the axial distance of the tread outer surface curvature is ensured, thereby reducing stress. It is possible to prevent cracks from occurring from the edges. The belt herein includes all interlaced layers or reinforcing layers arranged substantially parallel to the circumferential direction.

As shown in FIG. 3, tires manufactured using a method in which the tread is attached from above the belt and the side treads have a risk of cracking and peeling at the interface between the tread and the side treads starting from the tread ends. By inserting the side tread at the end of the belt and arranging the belt so that it overlaps the side tread, the axial distance to the outer surface of the tire is ensured at a certain level or more, which alleviates stress and prevents cracks from occurring. do.

By using the same type of rubber as the side tread for the rubber on both sides of the tread, cracking and peeling at the interface between the tread and the side tread starting from the tread ends can be prevented.

Examples Pneumatic radial tires for two-wheeled vehicles having the structures shown in Table 1 and tires of Example 1 and Comparative Examples 1.2 of tire size 140/80-17 were prepared.

Table 1 to [- effect Tests were conducted on the prototype tires shown in Examples under the following conditions.

The test conditions are JATMA high speed A condition and JATMA durability condition as shown in Table 2.

Table 2 (1) A high speed A condition for JAT (2) JATMA
Chukyu condition pressure resistance: 2, 25KG/cm2 load 21
4kg Internal pressure: 2.25KG/c++2.
The test results are shown in Table 3 at a speed of 80 kl/h.

Table 3 As in Example 1 above, a radial tire for motorcycles according to the present invention was obtained in which the productivity was significantly improved without impairing the tire's high-speed durability.

[Brief explanation of drawings]

FIG. 1 is a radial cross-sectional half-sectional view of a conventional pneumatic radial tire for two-wheeled vehicles. FIG. 2 is a radial cross-sectional half-sectional view of a manufacturing tire for pneumatic radial tires for two-wheeled vehicles manufactured by Kopu Myokoto. FIGS. 4 and 5 are radial cross-sectional half-sectional views of a conventional pneumatic radial tire for a two-wheeled vehicle as a comparative example.

Claims (1)

[Scope of Claims] A carcass consisting of at least one sheet in which cords are arranged substantially in a radial direction, and a side tread substantially outside the carcass; A pneumatic radial tire for two-wheeled vehicles in which two belts are arranged and a tread is arranged on the outside of the belt, and the tread is composed of a central portion that is relatively highly wear resistant and both side portions that are relatively weather resistant. The both side portions have substantially the same physical properties and composition as the site tread, and when viewed from the cross section of the tread, the boundary between the center circumference and the both side portions is in the radial direction from the tread width edge of the tire on the outer surface of the tire. The side tread is located inwardly and is divided in a range where the average direction extension lines of the boundary surfaces on both sides intersect with each other within the tire, and the radially outer end portion of the side tread has a contact amount with the belt end that is equal to the tire tread. It is interposed between the belt end and the carcass so that the width is at least 5% or more, and the axially outer end of the belt is on a normal line passing through the tread width end and perpendicularly to the carcass, or in the axial direction. A pneumatic radial tire for a two-wheeled vehicle, characterized in that the axial distance from the belt end to the outer surface of the tire is at least 5% of the tire tread width.