JPS62265003A - Flat tire - Google Patents

Abstract

PURPOSE:To improve the driving stability of a racing car when it travels at a high speed, by specifying a ratio of flatness and the ratio of the radiuses of curvature of a tread portion and a shoulder portion, respectively. CONSTITUTION:A ratio of flatness H/W, which is defined by a ratio of a tire cross-sectional height H to a tire maximum width W is set to 0.25-0.6. When a tire is regularly pressurized, a radius of curvature R2 of a shoulder width W2 within a range of 12-20% of a tread width W1 is set to 0.12-0.2 of the radius of curvature of a tread crown portion TC. A tread shoulder portion TC is connected to a side wall portion by an arc of small radius of curvature. With this arrangement, a distribution of static pressure made contact with the ground is entirely uniform and a kicking phenomenon is eased, whereby a cornering limit property and a driving property at a high speed are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a flat tire, particularly to a flat tire that is mounted on a racing car and has improved handling stability during high-speed running.

[Conventional technology]

In general, ultra-flat tires for passenger cars with an aspect ratio of 0.25 to 0.6, especially flat tires for high-speed running mounted on racing cars, have a cross-sectional shape of the tread portion as shown in Figure 2.
The intersection portion with the tire side portion is connected by a curve R8 with a small radius of curvature, but the other tread portions are combined to have a curve RC with a single curvature.

[Problem that the invention seeks to solve]

However, as a characteristic of a tire, normally, as the aspect ratio decreases, the tire's lateral rigidity increases and deformation of the trend portion and sidewall portion decreases. Therefore, when cornering, the force of lateral deformation of the tire due to the increase in the positive camber angle due to vehicle roll, etc. and the lateral force received from the road surface due to the slip angle is concentrated on the tire tread shoulder area, rather than the entire tread, and the shoulder area is It tends to float up as a fulcrum for a lever, and the contact area on the inside of the tire suddenly decreases, causing a sudden change in cornering limit characteristics. Furthermore, as shown in Figure 3 (a) and (b), compressive stress is generated in the direction of the tire's rotational axis on the tread surface that receives lateral force, especially from the outer tread shoulders to the center of the tire, which causes damage to the inner carcass and belt layer. This causes a buckling phenomenon and impairs ground contact, resulting in uneven wear and a sudden drop in cornering force.

The present invention aims to provide a flat tire that exhibits excellent handling stability even under high-speed running conditions by optimizing the profile of the surface of the tread portion.

[Means for solving problems]

The present invention has an aspect ratio of 0.25 to 0.6, the surfaces of the tread crown part TC and the tread shoulder part TS are configured with curvature radii R1 and R2, respectively, and the ratio R2/R1 of the two is 0.12. This is a flat tire characterized by having a particle diameter in the range of 0.20 to 0.20.

In FIG. 1, a flat tire T includes a carcass 2 that is folded back around a bead core 1 from the inside to the outside, and a bead apex that extends from the upper side of the bead core 1 toward the sidewall between the carcass 2 and the folded part 2a. 3, and two braai belts N4 arranged at a shallow cord angle in the tire circumferential direction at the crown part of the carcass 2.
It is equipped with

In addition, the tire T has an oblateness ratio H defined by the ratio of the tire maximum medium W to the tire cross-sectional height H of 0.25 to 0.6.

Furthermore, the radius of curvature R2 of the shoulder width W2 in the range of 12 to 20% of the tread width W1 is set to a range of 0.12 to 0.degree.2 of the radius of curvature R1 of the tread crown portion TC. Here, the radii of curvature R1 and R2 are values when the tire is filled with a specified internal pressure. Note that the tread shoulder portion TS and the sidewall portion are connected by an arc with a small radius of curvature.

By configuring the radius of curvature of the tread portion in this manner, the static ground pressure distribution of the tread portion can be made uniform over the entire surface.

In this way, by making the radius of curvature R2 of the tread shoulder portion TS smaller than that of the conventional one, the ground contact pressure of the tread shoulder portion TS increases due to the (positive) ground camber angle and slip angle during cornering. Accordingly, it is possible to prevent stress from concentrating on the trend shoulder part TS, to make the static ground pressure distribution of the trend part uniform over the entire surface, and to reduce the tendency to get stuck, improving the cornering limit performance. can.

EXAMPLE Tires of tire size 310/620R13 with specifications shown in Table 1 were prototyped, mounted on a 14-inch rim, filled with an internal pressure of 2.0 kg/-, and subjected to simulation using FEM calculations.

Initial conditions Contact area, static ground pressure 5 kI! / crl, lateral force % x static ground force 1st Table Note that the FEM calculation is performed by dividing the elements shown in Figure 4, and Figure 5 shows the cord tensile run calculation results for the second belt layer, and the tire deformation. The state is shown in FIG.

As can be seen from the figure, in the embodiment of the present invention, the cord tension of the belt layer is high and the amount of deformation in the vicinity of the shoulders of the tread portion is small, so buckling reduction can be reduced and improvement in steering stability can be expected.

〔Effect of the invention〕

In the flat tire of the present invention, like a ridge, the ratio R2/R1 of the radius of curvature of the surface of the tread part and the crown part is set to 0.12 to 0.20 in a tire with a low flatness ratio, so that the ground pressure distribution is uniform, It becomes possible to improve steering stability during high-speed driving.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the right half of an embodiment of the present invention, and FIG.
The figure is a diagram showing a conventional tire, Figure 3 (a> (b)
is a graph showing the relationship between tire cross-sectional shape and ground pressure;
The figure is an element division diagram, FIG. 5 is a cord tensilon distribution diagram of the belt layer, and FIG. 6 is a tire deformation state under load. 1--bead core, 2--carcass, 3-bead apex, 4-belt layer. Patent Applicant Sumitomo Rubber Industries Co., Ltd. Agent Patent Attorney Tadashi Nae Figure 2 Figure 3 (a) Procedural Amendment (transfer) August 22, 1988 Special I'l'ml No. 11374 2. Name of the invention Flat tire 3. Connection with the case of the person making the amendment Patent applicant address: 1-1-4 Tsutsui-cho, Kamishikachuo-ku, agent address: 4-chome Nishinakajima, Yodoyou-ku, Osaka City No. 2, No. 26, No. 7, Subject of amendment (1) "Brief explanation of drawings" column 8 of the specification, Contents of amendment + 11 State of "graph shown - tire membrane" on page 7, lines 14-16 of the specification It is. ” is a graph showing [. ” he corrected. The above is related to the November 7, 1986, case of the person making the amendment Patent applicant address: 1-1-1 Tsutsui-cho, Chuo-ku, Kobe City Name: Residence: Rubber Industry Iusei (Katsura Katsura 1) Shizuo 4. Address of agent: 4-2-26 Nishinakajima, Yodoyo-ku, Osaka 6. Subject of amendment 7. Contents of amendment 111. ``Figure 4'' on page 7, lines 14 to 16 of the specification.
----It is in a deformed state. '' was corrected to ``Figure 4 is a diagram showing element division, Figure 5 is a graph showing the distribution of cord tension in the belt layer, and Figure 6 is a cross-sectional view showing the deformation state of the tire under load.'' do. (2) Figure 4.5.6 of the drawings shall be supplemented as attached. 8. List of attached documents

Claims (2)

[Claims] (1) Has an aspect ratio of 0.25 to 0.6, and has a radius of curvature R of the surfaces of the tread crown and tread shoulder, respectively.
1, R2, and the ratio R2/R1 of both is 0.12 to 0.
．． A flat tire characterized by having a diameter in the range of 20. (2) Shoulder width W2 is 12~12 of tread width W1
A tire according to claim 1, wherein the range is 20%.