JP2908468B2 - Radial tires for motorcycles - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a radial tire for a motorcycle, and more particularly, to a belt layer comprising a cord spirally wound around the outer periphery of a carcass and extending in the tire width direction. The present invention relates to a radial tire for a motorcycle provided.

(Prior Art) On the outer periphery of a carcass composed of plies of organic fiber cords arranged in an angle range of 75 to 90 ° with respect to the equatorial plane of the tire,
Radial tire for motorcycles having a belt layer composed of a cord having a large elastic modulus, for example, a cord made of high modulus polyester, polyvinyl alcohol, rayon, or an aromatic polyamide fiber, spirally wound, and extending in the tire width direction. In, the movement of the tread rubber in the ground contact surface is small, based on the so-called `` taga '' effect of the belt layer, the heat generation and rolling resistance are small compared to the bias tire, and the wear resistance is excellent, and Even when a large centrifugal force acts on the tread during high-speed running, the tread has a number of features such as a small contact area and a light weight due to the protrusion of the tread in the tire radial direction.

In addition, the tread is generally provided with a circumferential main groove extending substantially in the circumferential direction of the tire in order to meet the requirements for straight running stability, high speed performance and wet performance of the tire.

(Problems to be Solved by the Invention) However, in the above-mentioned tire, in which the extending direction of the main groove arranged substantially in the circumferential direction substantially coincides with the extending direction of the cord forming the belt layer, the tire shaping is performed. On the occasion,
Since the protrusion formed on the inner surface of the mold and corresponding to the circumferential main groove is pressed against the portion where the circumferential main groove is formed, the tire radius is larger than the groove bottom of the circumferential main groove formed thereby. The belt layer cord located on the inner side in the direction is pushed inward in the tire radial direction, and is pushed and expanded in the width direction.

In other words, in the product tire, the cord of the belt layer is
In the tire width direction, it is not uniformly and spirally wound without being densely and densely, so the tension applied to the wound cord differs in the tire width direction. Because the ratio becomes large, the cord is damaged in a relatively short time at the portion corresponding to the circumferential main groove position, and also, the predetermined strength as the belt layer cannot be exhibited, and the durability of the tire is low. There was a problem to say.

This problem is particularly remarkable in a tire using a fiber having a high elastic modulus as a cord constituting the belt layer, and since tension of the cord is small, it is difficult for the tension to be distributed almost uniformly throughout the belt layer. doing.

The present invention has been made in view of such a problem, and an object thereof is to provide a radial tire for a motorcycle that enables more uniform casting of a belt layer cord than conventional product tires. Is what you do.

(Means for Solving the Problems) In order to achieve this object, according to the present invention, a pair of sidewalls and a tread are connected in a toroidal manner, and these parts are separated by 75 to 90 with respect to the equatorial plane of the tire. Reinforce with a carcass consisting of at least one ply in which organic fiber cords are arranged in an angle range of °, and from both sides around the bead ring embedded at the radially inner ends of both sidewalls, the both ends of the carcass ply A belt made of a cord wound outward and having at least one circumferential main groove extending substantially in the tire circumferential direction in a tread, and spirally wound around the outer periphery of the carcass and extending in the tire width direction. In a radial tire for a motorcycle having at least one layer, each circumferential main groove is constituted by a plurality of main groove portions located at intervals in the tire circumferential direction, and The sum S of the projection length of the main groove portion in the tire circumferential direction and the diameter d of the tread portion where the circumferential main groove is located are S / (πd) ≦
0.4 (however, π is a circle ratio).

(Operation) In the radial tire for a motorcycle satisfying the above-described relationship, the cord of the belt layer in the product tire is spirally and uniformly wound even though the circumferential main groove is formed in the tread. , It is possible to effectively remove the denseness in the tire width direction, so that the durability of the tire is reduced due to the inward displacement and deformation of the cord in the tire width direction and the radial direction. It can be sufficiently prevented.

Hereinafter, preferred embodiments of the radial tire for a motorcycle according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a cross-sectional view in the width direction of a tire showing one embodiment of the present invention. A carcass 12 having both ends wound up from a pair of annular bead cores 10 from the inside to the outside is a tire. It consists of two plies 12a and 12b in which organic fiber cords, for example, 66 nylon having a thickness of 1260d / 2 are arranged in an angle range of 75 to 90 ° with respect to the equatorial plane.

The tread 16 in which the circumferential main groove 14 is formed, which extends in the tire circumferential direction, here, is formed to be continuous with the sidewall 18 toroidally, and between the tread 16 and the carcass 12. A fiber having a large modulus of elasticity, such as high modulus polyester, polyvinyl alcohol, rayon or an aromatic polyamide fiber;
A belt layer 20 formed by spirally winding a cord of 600 kg / mm ² or more in the tire width direction is provided.
This contributes to improving the rigidity of the carcass 12 in the tire circumferential direction.

In the present embodiment, each circumferential main groove 14 disposed substantially in the circumferential direction has a tire circumferential portion as shown in FIG. 1B showing a part of a tire half with respect to the tire equatorial plane P. Direction, that is, a component that extends substantially in the tire circumferential direction, but does not extend continuously over the entire circumference, but is formed at a distance from each other in the tire circumferential direction and has a tread. A plurality of main groove portions L ₁ , L ₂ ,..., Each defined by a land portion 22 having a height equal to the surface of 16
L _n (where n is an integer).

Here, for ease of explanation, the inclination of each of the main groove portions L ₁ , L ₂ ,..., L _n defined by the land portions 22 with respect to the tire equatorial plane P is constant (α). age,
The projection length of each main groove parts l _1, l _2, ..., when the l _n, the tire circumferential direction component thereof main groove _{portions, l 1 = L 1 COSα,} l 2 = L 2 C
OSα,..., L _n = L _n COSα, the sum S of the circumferential components of the respective main grooves is S = l ₁ + l ₂ +... + L _n .

When the diameter of the surface of the tread portion on which the main groove portions L ₁ , L ₂ ,..., L _n are formed is d, the sum S of the circumferential components of the main groove portions and the diameter d are as follows. It shall be selected to satisfy the relationship. Here, π represents the pi.

S / (πd) ≦ 0.4 Here, the length over the entire circumference of the surface of the tread portion where the circumferential main grooves 14 arranged substantially in the circumferential direction are formed, that is, the circumferential component of each main groove portion with respect to πd The reason why the ratio of the total sum S is 0.4 or less is that if the ratio is larger than 0.4, the cords of the belt layer portion related to the main groove portions are not uniformly arranged in the tire width direction during shaping. This is because the strength per unit width of the belt is greatly reduced.

Incidentally, the ratio (peripheral component ratio) of the total sum S of the peripheral components of the main groove portions arranged substantially in the peripheral direction to the length over the entire circumference of the surface of the tread portion where the peripheral main grooves are formed is shown. The cords of each belt layer portion related to the circumferential main groove are opened, that is, spirally wound and extended in the tire width direction, the magnitude of the distance between adjacent cords, and one cord The following table shows the results of examining the ratio (pulling ratio) of the actual belt strength to the strength per unit number of belt layer cords calculated from the strength per hit.

◎ Tire specifications ・ Tire size: MCR 160/60 R17 ・ Carcass cord: A nylon 1260d / 2 cord made of 66 nylon is arranged at an angle of 90 ° to the tire equatorial plane.

・ Belt layer: made of Kevlar (product name), thickness 1500d /
The cord No. 2 is spirally wound around the tire in a single layer and extends in the tire width direction.

◎ Evaluation method-The product (after vulcanization molding) was examined for the magnitude of the opening of the cords constituting the belt layer and for the alignment rate.

According to this table, the ratio of the circumferential component, that is, the ratio of the sum S of the circumferential components of the main groove portion forming the circumferential main groove to the entire circumference of the tread surface on which the circumferential main groove is formed is 40%. If the ratio exceeds, the opening of the cords increases, while the alignment ratio deteriorates. Therefore, it is understood that the circumferential component ratio is preferably set to 40% or less.

Note that the present invention is not limited to the above-described embodiment, and that the circumferential main groove is constituted by a plurality of main groove portions located at intervals in the tire circumferential direction, and Sum S of projected length of the portion in the tire circumferential direction
And the diameter d of the tread portion where the circumferential main groove is located,
On the condition that the relationship of S / (πd) ≦ 0.4 is satisfied, each main groove portion forming the circumferential main groove is formed in a staggered manner in the tire circumferential direction, that is, as shown in FIG. In the above, the extending directions of the main groove portions may be alternately changed so that the inclination angles of the respective main groove portions are + α and −α every other line. The land part 22 that separates and defines the main groove part of
While slightly stepping down in the tire radial direction from the surface of the tread 16, it can also be located radially outward from the bottom of the main groove portion, and furthermore, the main groove portion in the tire circumferential direction, It can be bent and extended one or more times in a zigzag manner. In addition, a plurality of belt layers may be arranged,
Various modifications are possible within the scope of the claims.

(Effects of the Invention) As described in detail above, according to the present invention, in a belt layer made of a cord spirally wound and extending in the tire width direction, the cord is formed in the product tire in the tire width direction. Since the windings are wound uniformly and the cords adjacent to each other are not opened and almost uniform tension acts on each cord, it is possible to provide a two-wheeled radial tire excellent in durability. it can.

[Brief description of the drawings]

FIG. 1 (a) is a view showing a cross section of the radial tire of the present invention, and FIG. 1 (b) is a schematic perspective view showing a part of the tire shown in FIG. 1 (a). 10 ... bead core, 12 ... carcass 14 ... circumferential main groove, 16 ... tread 18 ... side wall, 20 ... belt layer 22 ... land part

Claims (1)

(57) [Claims] 1. A pair of sidewalls and a tread are formed in a toroidal series, and each of these parts is composed of at least one ply in which organic fiber cords are arranged at an angle of 75 to 90 ° with respect to the equatorial plane of the tire. Reinforced with a carcass, winding both ends of the carcass ply from inside to outside around a bead ring embedded in the radially inner ends of both sidewalls, and extending at least one extending substantially in the tire circumferential direction. The circumferential main groove is formed in the tread, and in the radial tire for a motorcycle including at least one belt layer made of a cord spirally wound around the outer periphery of the carcass and extending in the tire width direction, each circumferential main groove is , A plurality of main groove portions located at intervals in the tire circumferential direction, the total S of the projection length of each main groove portion in the tire circumferential direction, and each circumferential main groove is The diameter d of the tread portion is S / (πd) ≦ 0.4
A radial tire for a motorcycle, wherein the radial tire satisfies the following relationship.