JP4170487B2 - Racing cart tires - Google Patents

Description

【００２７】
表１の如く、実施例のタイヤは、路面追従性を損ねることなく、旋回時の横力に対抗するに充分な横剛性を確保することが可能となり、旋回速度が向上し、ラップタイムを短縮することができた。又実施例のタイヤは、３周目と６周目との間でのラップタイムの悪化が少なく、性能を安定して維持できるのが確認できる。
【００２８】
【発明の効果】
本発明は叙上の如く構成しているため、ビードコアの回転を抑制してカーカスの張力を高く維持することができ、これにより縦剛性を増加することなく横剛性を効果的に高め、ラップタイムを向上できる。
【図面の簡単な説明】
【図１】本発明の一実施例のタイヤの断面図である。
【図２】そのビード部を拡大して示す部分断面図である。
【図３】インシュレーションゴム層の他の例を示す断面図である。
【図４】インシュレーションゴム層のさらに他の例を示す断面図である。
【図５】インシュレーションゴム層のさらに他の例を示す断面図である。
【図６】従来タイヤの問題点を説明する線図である。
【符号の説明】
２ トレッド部
３ サイドウォール部
４ ビード部
５ ビードコア
６ カーカス
６Ａ、６Ｂ カーカスプライ
７ インシュレーションゴム層
７Ａ コア覆い部分[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a racing cart tire that can effectively increase lateral stiffness without causing an increase in longitudinal stiffness and can contribute to an improvement in lap time.
[0002]
[Prior art]
In recent years, racing carts have become popular as motor sports. This racing cart has a low center of gravity and is light because a small tire having an outer diameter of 300 mm or less and an aspect ratio of 0.5 or less is attached to a frame-like vehicle body provided with an engine and a single-seat seat. For this reason, the turning speed is also increased, and for example, there is a case where the vehicle runs on one wheel during turning, and the lateral load applied to one tire is considerable. Therefore, high lateral rigidity is required for this type of tire.
[0003]
[Problems to be solved by the invention]
However, when the tire rigidity is increased by using a conventional means such as providing a reinforcing cord layer on the side wall or increasing the folding height of the carcass, the lateral rigidity and the longitudinal rigidity are increased. End up. As a result, the road surface followability is impaired, and the lap time is reduced.
[0004]
In view of such a situation, as a result of a study by the present inventor, as shown in FIG. 6, when a large lateral force acts on the tire during turning, the carcass a is strongly pulled outward by the tension f. At that time, it has been found that the bead core b rotates while being dragged by the carcass a, and the lateral rigidity is not properly exhibited due to the loosening of the tension f of the carcass a caused thereby.
[0005]
Therefore, the present invention is based on the provision of a high-elasticity and high-hardness insulation rubber layer that passes under the core of the bead core between the two carcass plies, thereby suppressing the rotation of the bead core and maintaining a high carcass tension. Accordingly, it is an object of the present invention to provide a tire for a racing cart that can effectively increase the lateral rigidity and increase the lap time without increasing the longitudinal rigidity.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a racing cart tire having an outer diameter of 300 mm or less and an aspect ratio of 0.5 or less,
A carcass composed of two carcass plies which are folded and locked around the bead core of the bead portion from the tread portion to the sidewall portion and the carcass cords are arranged at an angle of 25 to 38 degrees with respect to the tire circumferential direction; An insulation rubber layer disposed between the carcass plies,
The insulation rubber layer includes a core covering portion having a thickness of 0.2 to 1.0 mm and continuous along the inner and outer surfaces in the tire axial direction and the lower surface in the radial direction of the bead core,
The 100% modulus Mi of the insulation rubber layer is 150 to 300% of the 100% modulus Mc of the carcass ply topping rubber, and the JISA rubber hardness HSi of the insulation rubber layer is the JISA rubber hardness HSc of the carcass ply topping rubber. It is characterized by setting it as 115-150%.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In FIG. 1, a racing cart tire 1 (hereinafter referred to as a tire 1) has an outer diameter D of the tire 1 of 300 mm or less and an aspect ratio H / W that is a ratio of a tire cross-sectional height H to a tire width W of 0.5. A small flat tubeless tire as described below, including a tread portion 2, a pair of side wall portions 3 extending inward in the tire radial direction from both ends thereof, and a bead core 5 positioned at an inner end of each side wall portion 3. And a bead portion 4 having.
[0008]
Further, the tire 1 is provided with a carcass 6 including two carcass plies 6A and 6B extending between the bead portions 4 and 4, and at least the carcass plies 6A and 6B between the two carcass plies 6A and 6B. An insulation rubber layer 7 passing under the core of the bead core 5 is provided.
[0009]
The carcass 6 includes a ply body portion 6a extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and the ply body portion 6a connected to the ply body portion 6a from the inner side to the outer side in the tire axial direction. It is composed of two carcass plies 6A and 6B that integrally have the folded ply folding portion 6b.
[0010]
The carcass plies 6A and 6B have a bias structure in which carcass cords arranged at an angle of 25 to 38 degrees with respect to the tire circumferential direction are covered with a topping rubber, and the carcass cords cross each other between the plies. As shown, the direction of the code is different. As the carcass cord, an organic fiber cord such as nylon, polyester, rayon, aromatic polyamide or the like is preferably used.
[0011]
Further, a bead apex rubber 8 having a tapered cross section extending radially outward from the bead core 5 is provided between the ply main body portion 6a and the ply folding portion 6b. The bead apex rubber 8 is made of a hard rubber having a JISA rubber hardness HSa of 65 to 95 °. The bead apex rubber 8 imparts rigidity to the bead portion 4 and is reinforced over the sidewall portion 3.
[0012]
Further, in this example, the bead core 5 has a rectangular cross-sectional shape and is arranged such that its lower surface 5c in the radial direction (shown in FIG. 2) follows the inclination of the rim seat surface JS. The bead core 5 is preferably formed by, for example, a so-called single wind structure in which one bead wire is spirally wound, but a tape bead structure in which a tape-like body in which a plurality of bead wires are arranged horizontally is wound in a plurality of layers. Can also be formed.
[0013]
The bead core 5 can be formed in a substantially circular or hexagonal cross section by the single wind structure. However, from the viewpoint of suppressing the rotation of the bead core 5 which is the main purpose of the present application, the bead core 5 has a rectangular cross section as in this example. Those are preferred.
[0014]
Next, as shown in FIG. 2, the insulation rubber layer 7 is made of rubber having higher elasticity and hardness than the topping rubber of the carcass 6 and has a thickness T of 0.2 to 1.0 mm. And arranged between the two carcass plies 6A, 6B.
[0015]
The insulation rubber layer 7 includes at least a U-shaped core covering portion 7A continuous along the inner and outer surfaces 5a and 5b in the tire axial direction of the bead core 5 and the lower surface 5c in the radial direction. In this example, the insulation rubber layer 7 includes the core cover portion 7A, and inner and outer extensions 7Bi extending to the core cover portion 7A and extending radially outward from the upper surface 5d of the bead core 5 at a small height. The case where 7Bo is provided is illustrated. In this example, the heights hi and ho from the bead base line BL of the extension portions 7Bi and 7Bo are equal to or less than the height ha from the bead base line BL of the bead apex rubber 8, and thereby the longitudinal rigidity is increased. The increase is definitely prevented.
[0016]
Such an insulation rubber layer 7 can increase the compression (compression force) between the bead core 5 and the rim seat surface JS by the core cover portion 7A, and can hold the bead core 5 firmly. As a result, the rotation of the bead core 5 is suppressed and the tension of the carcass 6 can be maintained high, thereby effectively increasing the lateral rigidity. In addition, since there is no increase in longitudinal rigidity, road surface followability is not impaired, and an improvement in lap time can be achieved.
[0017]
For that purpose, the 100% modulus Mi of the insulation rubber layer 7 is 150 to 300% of the 100% modulus Mc of the topping rubber of the carcass 6, and the JISA rubber hardness HSi of the insulation rubber layer is the topping rubber of the carcass 6. The JIS rubber hardness HSc must be 115 to 150%.
[0018]
If the 100% modulus Mi is less than 150% of the 100% modulus Mc and the rubber hardness HSi is less than 115% of the rubber hardness HSc, the compression cannot be increased sufficiently, and the required bead core 5 The rotation deterrent effect cannot be obtained. Conversely, when the 100% modulus Mi is greater than 300% of the 100% modulus Mc and the rubber hardness HSi is greater than 150% of the rubber hardness HSc, there is a difference in rigidity between the topping rubber and the insulation rubber layer 7. It becomes excessive and causes a failure such as separation.
[0019]
If the thickness T is less than 0.2 mm, the effect of suppressing the rotation of the bead core 5 is not exhibited. If the thickness T exceeds 1.0 mm, the amount of compressive deformation of the rubber increases, thereby loosening the tension of the carcass 6. Will bring.
[0020]
Next, other examples of the insulation rubber layer 7 are shown in FIGS.
[0021]
In FIG. 3, the insulation rubber layer 7 exemplifies a case where the inner extension portion 7Bi terminates the sidewall portion 3 in the vicinity of the tread end TE of the tread portion 2. In this case, the rigidity of the sidewall portion 3 is enhanced by the extension portion 7Bi, and both the lateral stiffness and the longitudinal stiffness are improved. However, as a whole tire, the effect of improving the lateral rigidity is increased by the action of the core covering portion 7A, and the decrease in road surface followability can be suppressed to a low level.
[0022]
In FIG. 4, the insulation rubber layer 7 shows a case where the inner extension portion 7Bi is interposed in the tread portion 2 through the side wall portion 3, and particularly in this example, the inner extension portions 7Bi, The extension portion 7Bi is illustrated as being continuous at the tire equator CO. In this case, the rigidity of both the sidewall portion 3 and the tread portion 2 can be simultaneously increased by the extension portion 7Bi. However, as a whole tire, the effect of improving the lateral rigidity is increased by the action of the core covering portion 7A, and the decrease in road surface followability can be suppressed to a low level.
[0023]
In FIG. 5, the insulation rubber layer 7 includes a case in which the extension portion 7Bi of the inside is interrupted by the tire shoulder portion between the side interposed portion 7Bi1 interposed in the sidewall portion 3 and the tread interposed portion 7Bi2 interposed in the tread portion 2. Illustrated. In this case, the longitudinal rigidity can be suppressed lower than that in the case of FIG. 4 by the amount of interruption between the side interposed portion 7Bi1 and the tread interposed portion 7Bi2.
[0024]
【Example】
A slick tire having a tire size of 11 × 7.10-5 was made on the basis of the specifications shown in Table 1, and the lap time at that time was compared using each sample tire.
[0025]
In the test, a sample tire was mounted on a racing cart under the same conditions, and the lap time of the 3rd lap and the 6th lap was compared at the lap time of 10 laps in the cart course (Suzuka Circuit South Course) with a course length of 1264m.
[0026]
[Table 1]

[0027]
As shown in Table 1, the tires of the examples can ensure sufficient lateral rigidity to resist lateral force during turning without impairing road surface followability, improving the turning speed and shortening the lap time. I was able to. In addition, it can be confirmed that the tires of the examples have little deterioration in the lap time between the third and sixth laps, and the performance can be stably maintained.
[0028]
【The invention's effect】
Since the present invention is configured as described above, the rotation of the bead core can be suppressed and the carcass tension can be maintained high, thereby effectively increasing the lateral rigidity without increasing the longitudinal rigidity and reducing the lap time. It can be improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a tire according to an embodiment of the present invention.
FIG. 2 is an enlarged partial sectional view showing the bead portion.
FIG. 3 is a cross-sectional view showing another example of an insulation rubber layer.
FIG. 4 is a cross-sectional view showing still another example of the insulation rubber layer.
FIG. 5 is a cross-sectional view showing still another example of an insulation rubber layer.
FIG. 6 is a diagram for explaining a problem of a conventional tire.
[Explanation of symbols]
2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 6A, 6B Carcass ply 7 Insulation rubber layer 7A Core covering part

Claims (1)

A racing cart tire having an outer diameter of 300 mm or less and an aspect ratio of 0.5 or less,
A carcass composed of two carcass plies in which a carcass cord is arranged at an angle of 25 to 38 degrees with respect to the tire circumferential direction and is folded and locked around the bead core of the bead portion from the tread portion to the sidewall portion; An insulation rubber layer disposed between the carcass plies,
The insulation rubber layer includes a core covering portion having a thickness of 0.2 to 1.0 mm and continuous along the inner and outer surfaces in the tire axial direction and the lower surface in the radial direction of the bead core,
The 100% modulus Mi of the insulation rubber layer is 150 to 300% of the 100% modulus Mc of the carcass ply topping rubber, and the JISA rubber hardness HSi of the insulation rubber layer is the JISA rubber hardness HSc of the carcass ply topping rubber. 115 to 150% of a racing cart tire.

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