JPH05238204A - Pneumatic tire for two wheeler - Google Patents

Abstract

PURPOSE:To give a tire excellent grounding property and sufficiently increase lateral force generated at turning run. CONSTITUTION:In this pneumatic tire for two wheeler, a radial carcass 4 is provided, and a belt containing one or more belt layers 7, 8 constituted of cords actually extending in the circumferential direction of the tire is arranged on the outer circumferential side of the crown part of the carcass 4 so as to have its width nearly equal to the width of a tread part 1. The width Wo of the bead part 3 is formed narrower than the width W of the bead part 3 in its posture formed by assembling a rim therein, and the width ratio W/Wo is set in the range of 1.08<W/Wo <1.35.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire for a two-wheeled vehicle, and more particularly to ensuring the generation of high lateral force during turning.

[0002]

2. Description of the Related Art A pneumatic tire for a two-wheeled vehicle in which a belt layer made of cords extending substantially in the tire circumferential direction is disposed on the outer peripheral side of a crown portion of a carcass is conventionally known. The ground contact property of the tire is improved based on the low bending rigidity in the widthwise cross section of the tire, which is derived from the structure (1), and as a result, the road grip force during turning is also improved.

[0003]

By the way, in recent years, as the performance of vehicles has improved, the turning speed has also increased.
Since the tires have become higher in height, it has become difficult to generate a lateral force sufficient to counter the centrifugal force only by the grounding property of the conventional tire based on the action of the belt layer as described above.

The present invention has been made as a result of studies aimed at solving such problems of the prior art, and the object of the present invention is to improve the ground contact property of a tire.
It is to provide a pneumatic tire for a two-wheeled vehicle that can maintain a high lateral force of the tire while maintaining the same high value as that of a conventional tire.

[0005]

SUMMARY OF THE INVENTION According to the present invention, in order to increase the lateral force generated by a tire, the shear rigidity in a tire widthwise cross section, in other words, the rigidity against a tangential external force in the cross section is increased. Is based on the finding that is effective.

Therefore, the pneumatic tire for a motorcycle according to the present invention comprises a tread portion, a pair of sidewall portions connected to the tread portion, and a bead portion which is continuous with each sidewall portion, and is arranged in the tire circumferential direction. A carcass formed by at least one ply of cords extending at an angle in the range of 25 to 90 °, and on the outer peripheral side of the crown portion of this carcass, a belt layer made of cords extending substantially in the tire circumferential direction. In a tire in which a belt including at least one layer is arranged with a width substantially equal to the width of a tread portion, the axial distance W ₀ between the rim flange contact surfaces of the bead portion during vulcanization molding is determined by the bead in the rim assembled posture. parts, similar shorter than the axial distance W, the ratio of their two distance W / W ₀ (hereinafter referred foot width change ratio), to a value in the range of 1.08 <W / W ₀ <1.35 .

[0007]

With this pneumatic tire for a motorcycle, when the tire rim is assembled, the axial distance between the contact surfaces of the rim flange of the bead portion is made wider than that during vulcanization molding of the tire, so that the tread of the tire The outer diameter of the shoulder portion becomes larger than the outer diameter during vulcanization molding, and as a result, the tension of the belt layer consisting of the cords extending in the tire circumferential direction becomes particularly large at the enlarged diameter portion, so that the lateral force generated during turning is increased. It is possible to effectively increase the shear rigidity of the tread shoulder portion in which the increase in force is particularly required, within the tire width direction cross section.

Therefore, in this tire, it is possible to sufficiently generate the lateral force required when the vehicle is turning at a high speed, while maintaining a high ground contact property of the tire.

Here, the foot width change ratio exceeds 1.08
Values less than 1.35 are based on the fact that below 1.08 it is not possible to provide a sufficient increase in lateral force and above 1.35 it reduces road grip due to poor ground contact.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view in the tire width direction showing an embodiment of the present invention, in which 1 is a tread portion, 2 is a pair of sidewall portions continuous with the tread portion, and 3 is a sidewall portion. The bead portions are shown respectively.

Here, the angle is 25 to 90 ° with respect to the tire circumferential direction.
The carcass 4 is formed by two plies of cords extending at an angle in the range of, and the side end portion of the carcass 4 is wound around the bead core 5 from the inside to the outside and arranged. Further, a first belt layer 6 made of a cord extending to intersect with the tire circumferential direction is arranged on the outer peripheral side of the crown portion of the carcass 4, and substantially further on the outer peripheral side of the first belt layer 6. Second consisting of a cord that extends in the tire circumferential direction
And the third belt layers 7 and 8 are respectively arranged.

In the tire having such a constitution, here, the axial distance W ₀ between the rim flange contact surfaces of the bead portion during vulcanization molding, in other words, the tire foot width in the vulcanization mold is shown in the figure. A similar axial distance W of the bead portion in the assembled state of the rim, which is indicated by an imaginary line, in other words,
It should be narrower than the tire foot width in the rim assembled state, and the foot width change ratio should be in the range of more than 1.08 and less than 1.35.

In such a pneumatic tire for a motorcycle,
Under the action of the belt layer cord extending in the tire circumferential direction, it is possible to sufficiently enhance the ground contact property of the tire, and also based on the diameter expansion deformation of the tread shoulder portion during the rim assembly,
As described above, it is possible to effectively increase the shear rigidity within the tire width direction cross section, and thus the lateral force generated during turning.

(Comparative Example) A comparative test on straight running stability, turning stability and road surface grip force between the invention tire and the comparative tire will be described below.

◎ Test tire The size of the tire is 170/60 R 17. The rim flange width of the mounting rim was 5.5 ″ (140 mm).

Invention tire 1 In the tire having the structure shown in FIG. 1, the ply cord of the carcass 4 extends at 90 ° with respect to the tire circumferential direction.
Made of 1260d / 2 nylon cord, the cord of the first belt layer 6 extends at 75 ° to the tire circumferential direction, 840d / 2
And the respective belt layer cords of the second and third belt layers 7 and 8 are formed of 1260d / 2 nylon cords extending at 0 ° with respect to the tire circumferential direction. Tire width in the vulcanization mold
127 mm.

Invention Tire 2 Same as Invention Tire 1 except that the tire foot width in the vulcanization mold was 114 mm.

Comparative tire 1 Same as the invention tire 1 except that the tire foot width in the vulcanization mold was 140 mm.

Comparative tire 2 The same as the invention tire 1 except that the tire foot width in the vulcanization mold was 102 mm.

◎ Test method Each of the above tires was mounted on an actual vehicle with a displacement of 750cc to run, and straight running stability was evaluated by stability and feeling against external force (disturbance), and turning stability was evaluated. , The grip force during cornering, the feeling of rigidity, and the stability against disturbance were comprehensively evaluated, and regarding the road surface grip force, the slip speed during the cornering and during the steady circular turn and the slip when the limit was exceeded. The behavior was evaluated comprehensively.

◎ Test Results The results of the above tests are shown in Table 1. The numerical values in the table are shown in a 10-point evaluation by feeling, and the larger the numerical value, the better the result.

[0022]

[Table 1]

As shown in Table 1, the performance of each of the invention tires is equal to or higher than that of the comparative tire.
In particular, it is clear that the road grip and turning stability are remarkably improved.

[0024]

As described above, according to the present invention, it is possible to provide the tire with excellent grounding property under the action of the belt layer, and particularly, to improve the tire foot width in the vulcanization mold.
By making the width of the foot narrower than the tire width in the rim assembled state and setting the foot width change rate in the range of more than 8% and less than 35%, it is sufficient to counter the centrifugal force even at high speed turning. It becomes possible to generate a large lateral force.

[Brief description of drawings]

FIG. 1 is a sectional view in the tire width direction showing an embodiment of the present invention.

[Explanation of symbols]

1 tread portion 2 sidewall portion 3 bead portion 4 carcass 6 first belt layer 7 second belt layer 8 third belt layer W ₀ axial distance between rim flange contact surfaces of bead portion during vulcanization molding W rim assembly Axial distance between the rim flange contact surfaces of the bead when

Claims (1)

[Claims] 1. A tread portion, a pair of sidewall portions connected to the tread portion, and a bead portion which is continuous with each sidewall portion, and extends at an angle in the range of 25 to 90 ° with respect to the tire circumferential direction. While disposing a carcass formed by at least one ply of a cord, on the outer peripheral side of the crown portion of this carcass, a belt including at least one belt layer of a cord substantially extending in the tire circumferential direction, A pneumatic tire for a motorcycle, which has a width substantially equal to the width, wherein the axial distance W ₀ between the rim flange contact surfaces of the bead portion during vulcanization molding is the same as that of the bead portion in the rim assembled posture. Of the distance W / W _0.
Is a pneumatic tire for motorcycles with a range of 1.08 <W / W ₀ <1.35.