JPH07102761B2 - Radial tires for motorcycles - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a radial tire for a motorcycle, which can reduce a curvature step and a rigidity step of a tire tread and can improve riding comfort and steering stability.

[Conventional technology]

For example, in radial tires for high-speed motorcycles with a running speed of up to 200 km / h, the ply peeling of the belt layer occurs due to centrifugal force due to high-speed rotation and shear strain due to repeated deformation of ground contact opening. In many cases, as shown in FIG. 3, for example, a band layer B for suppressing the lifting of the belt layer A and the flattening of the tire crown portion at the time of contact with the ground is provided at the center of the crown portion and outside the belt layer A.

[Problems to be Solved by the Invention]

However, since such a band layer B conventionally has a multi-layer structure in which both side edges are aligned, a large rigidity step is likely to occur at the both side edges, and the tread surface shape at the time of internal pressure filling also has this rigidity step. Due to the above, the surface tends to be a curved surface having a plurality of curvatures that are bent at both side edges of the band layer B.

As a result, it becomes difficult to lean the vehicle body when shifting from straight running to cornering, and to smoothly raise the vehicle from cornering to straight running, and to induce vibration of the body and steering wheel. This is a major cause of deterioration in stability and riding comfort.

The present invention is based on spirally winding a band having a band cord, and can effectively alleviate a rigidity step generated on both side edges of the band layer, and can solve the above-mentioned problems. The purpose is to provide tires.

[Means for Solving the Problems]

In order to achieve the above-mentioned object, the radial tire for a motorcycle of the present invention has a belt layer inside the tread and outside in the radial direction of the carcass, and the maximum width around the tire equator is the maximum width of the tread. A reinforcing band layer having a width of 0.2 to 0.6 times the width of the tread along the outer surface is provided, and the band layer has a length of 5 to 20 mm in which band cords are arranged in parallel and continuous with each other with the same width. And the width of the long strip is set to a width obtained by subtracting twice the spiral pitch to be wound from the maximum width. An inner layer having the maximum width outside of the inner layer, an intermediate layer disposed outside the inner layer and having a spiral pitch twice the maximum width, and an outer layer having a spiral pitch four times the outer maximum width. Is characterized by.

[Action]

As described above, the band layer formed by winding the long strip having a width obtained by subtracting twice the spiral pitch to be wound from the maximum width of the band layer 3 times at the spiral pitch is the inner layer having the maximum width, The inner layer, which is arranged on the outside on the outside of which the spiral pitch is doubled from the maximum width, and the outer layer, which is arranged on the outside of which the spiral pitch is reduced by 4 times from the maximum width, are formed. It is possible to gradually decrease toward the edge, and it is possible to effectively mitigate the rigidity step generated at the both side edges. In addition, this also makes the tread surface shape an arc surface shape with a smooth single curvature without inflection points, and in combination with the relaxation of the rigidity step, the collapse of the vehicle body,
It is possible to smoothly go up without feeling uncomfortable and without causing vibration, and it is possible to greatly improve steering stability and riding comfort. Further, the band layer is formed by winding a long strip continuously in a spiral shape three times, so that the shape thereof is extremely easy and the workability in manufacturing can be improved.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of a radial tire for a motorcycle (hereinafter referred to as a tire) of the present invention.

In the figure, a tire 1 is a tread 2 and side walls 3 extending inward from the both ends of the tire 3 in the radial direction of the tire.
And a bead 4 located at the inner radial end of the tire of the side wall 3, and a toroidal carcass 6 is laid between the bead cores 5 and 5 provided on the bead 4 and its radius. The belt layer 7 is arranged on the outer side in the direction. Here, the tread 2 extends on the crown of the carcass 6 from the center of the crown in a direction substantially parallel to the contour of the tread 2 and has a cross-sectional shape whose linear width exceeds the maximum width of the sidewall 3 to maintain the camber thrust during cornering. It

Next, the carcass 6 in this example is composed of two plies whose cords are inclined at an angle of about 70 to 90 degrees with respect to the tire equator, and both ends of the bead core 5 that are folded back from the inside to the outside are as described above. Terminate at Sidewall 3. Here, the folded end 6a of the carcass 6 located outside the bead 4 extends to a position higher than the folded end 6b of the carcass 6 inside the bead 4, and the inner folded end 6b is completely covered by the end. Alleviate stress concentration at.

In this example, in order to reinforce the tire lateral rigidity that is reduced by forming a radial structure, the inner and outer folded ends 6b,
The height Hb from the bead base of 6a, Ha is the tire cross-section height H
15 to 30% and 20 to 40% of that of the bead core 5 in the portion surrounded by the carcass 6 and its folded ends 6a and 6b.
The bead apex 9 made of hard rubber is arranged so that the thickness gradually decreases in the direction from the side wall to the side wall.
The side wall 3 itself is also made of relatively hard rubber. The ply cord of the carcass 6 is an organic fiber cord having an initial elastic modulus of 850 kg / mm ² or less, such as rayon,
Polyester, nylon, etc. are used.

Further, the belt layer 7 in this example is a two-layer belt that is provided with cords inclined at an angle of about 30 degrees or less with respect to the tire equator and has a width extending over substantially the entire width of the tread 2. It consists of plies 7a and 7b, and the ply cord has an initial elastic modulus of 25.
A high modulus fiber cord having a modulus of about 00 kg / mm ² or more, for example, aromatic polyamide fiber, steel fiber, glass fiber, carbon fiber, etc., improves high-speed running performance. The number of plies and the material of the ply cords of the carcass 6 and the belt layer 7 can be appropriately changed depending on the use conditions.

Further, in the tire 1 of the present invention, a band layer 10 is formed outside the belt layer 7 centering on the tire equator.

The band layer 10 has a maximum width W1 centered on the tire equator on the outer side of the band layer and a tread width W of 0.2 along the outer surface of the tread.
It has a width of ~ 0.6 times. Further, the band layer 10 has a three-layer structure formed by spirally winding a long narrow strip 12 in a spiral pitch d in the range of 5 to 20 mm. As shown in FIG. 1, the width W2 of the strip 12 is the maximum width W1 minus twice the spiral pitch d. By setting the width of the band member 12 in this manner, the band layer 10 is arranged on the outer side of the belt layer 7 and has the maximum width W1 and the inner layer S1 arranged outside the inner layer S1 and having the maximum width W1. An intermediate layer S2 having a doubled spiral pitch d is formed, and an outer layer S3 arranged outside the intermediate layer S2 and having a 4-fold spiral pitch d reduced from the maximum width W1.

Due to its rigidity, the band layer 10 prevents the tread crown portion from flattening at the time of contact with the ground, reduces the shear strain of the shoulder portion at the time of contact with the ground, and prevents lifting of the belt layer 7 due to centrifugal force. For this purpose, the band cord used in the band layer 10 is particularly preferably a fiber having a low mass and a high modulus, that is, an aromatic polyamide fiber or a carbon fiber, and the cord angle is 15 with respect to the tire equator. It must be less than or equal to °. As the band cord, other organic fiber cords such as nylon, polyester and rayon can be used as required.

The band 12 may be a continuous fabric of the same width in which the band cords are arranged in parallel in the width direction and covered with topping rubber, and the band 12 may be spirally wound. Thus, the cord angle can be easily set within the above range of 15 degrees or less.

Incidentally, the band layer 10 is preferably smaller from the viewpoint of steering stability and the like within a range of rigidity capable of preventing the flattening of the crown portion. Therefore, the number of loading layers of the band layer 10 also has workability in tire manufacturing. Since it can be improved, it is formed by spirally winding the strip 12 having a width dimension of four times the spiral pitch d or more. Since it gradually decreases toward the spiral pitch interval, it is possible to effectively alleviate the rigidity step generated at the both ends.

If the spiral pitch d is less than 5 mm, the effect of alleviating the rigidity step is insufficient, and if it exceeds 20 mm, the flattening of the crown portion cannot be prevented. Similarly, when the maximum width W1 of the band layer 10 is less than 0.2 times the tread width W, it is difficult to prevent the flattening of the crown portion, and when it exceeds 0.6 times, the rubber peeling of the band layer 10 itself due to shear strain occurs. Is likely to occur.

〔The invention's effect〕

As described above, the radial tire for a motorcycle of the present invention is
Since the band layer is formed by spirally winding the band body, the number of stacked layers of the band layer can be gradually reduced toward the both ends with a spiral pitch width, and a rigidity step generated on both side edges of the band layer can be achieved. Can be effectively mitigated.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG. 2 is a partial sectional view showing a conventional technique. 2 ... Tread, 6 ... Carcass, 7 ... Belt layer, 10
…… Band layer, d …… Spiral pitch, W …… Tread width.

Claims (2)

[Claims] 1. A belt layer is arranged inside the tread and outside in the radial direction of the carcass, and the maximum width around the tire equator is 0.2 to 0.6 times the width of the tread along the outer surface of the tread outside the belt layer. And a band band for reinforcement having a band cord is formed by winding a long band body in which band cords are arranged in parallel with each other and continuous with the same width three times at a spiral pitch of 5 to 20 mm. And the width of the long strip is a width obtained by subtracting twice the spiral pitch for winding from the maximum width, whereby the band layer is the inner layer of the maximum width outside the belt layer and the inner layer. A radial tire for a motorcycle, comprising: an intermediate layer, which is arranged on the outer side of the outermost layer and has a maximum width and a doubled spiral pitch reduced, and an outer layer, which has a outermost width and a fourfold spiral pitch reduced. 2. The radial tire for a motorcycle according to claim 1, wherein the band cord of the band layer is inclined at an angle of 15 ° or less with respect to the tire equator.