JPS6171202A - Radial tire for car - Google Patents

Abstract

PURPOSE:To improve steering stability and reduce nose by specifying the complex modulus of elasticity of tread rubber and side rubber and suing a polyester cord carcass to specify the height and complex modulus of elasticity of a bead apex. CONSTITUTION:Tread rubber 5 uses the rubber whose complex modulus of elasticity ranges from 5okg/cm<2>-150kg/cm<2> and side rubber 6 uses the rubber whose complex modulus of elasticity ranges from 30kg/cm<2>-50kg/cm<2>. In addi tion, a carcass 2 uses a polyester cord. Furthermore, a belt layer in which a comparatively high modulus of elasticity cord such as a steel cord is arranged is arranged outside the crown section of the carcass 2 in the circumferential direction of a tire at an angle of 5-35 deg.. Besides, the complex modulus of elastic ity of a bead apex 4 is set to 200kg/cm<2> and the height hb exceeds the height hw of the maximum tire width or is set not so as to exceed the rim flange height hf. As a result, steering stability can be improved with low noise.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) This invention relates to a radial tire for military use with improved handling stability and reduced noise.

(Prior Art) Recently, as highways are being paved, tires are required to have high-speed performance, and therefore tires with a radial structure are often used. Radial structure tires have carcass cords arranged in the tire radial direction, and a belt layer with a relatively shallow cord angle in the tire circumferential direction is arranged in the tire crown, ensuring stable handling under high-speed driving conditions. Excellent in sex. However, the road noise of this type of tire at medium and low speeds is also an important problem.

(Problem to be Solved) Tire noise is generally said to be greatly affected by the tread pattern, but it is also related to the natural frequency caused by the tire structure. The purpose of this invention is to propose a radial tire for passenger cars that achieves improved handling stability, which is an important characteristic of high-speed performance, and reduced noise during medium- to low-speed driving.

(Means for solving the problem) This invention has a complex modulus of elasticity (E”) of 50 kg/cnl~
tread rubber in the range of 150 kg/cnl, a carcass of polyester cords folded back at the angle of ξ of a pair of left and right bead cores and arranged substantially in the radial direction;
A heald layer having a relatively shallow angle in the tire circumferential direction on the outside of the crown portion of the carcass and a complex modulus of elasticity (E) of 3
Between the side rubber in the range of 0kr/c to 50ksr/a+f, the carcass, and its folded part, the area exceeding the tire maximum width from the top of the bead core or the rim flange h
The complex modulus of elasticity ('E
This is a passenger Honkawa radial tire characterized by having a bead apex of 200 kg/(ze or more).

Embodiments of the present invention will be described in detail below with reference to the drawings. No. 1111 shows the right half of the cross-sectional view of the radial tire of the present invention. In the figure, the radial tire T consists of a carcass 2 that is folded around a bead core 1 from the inside to the outside and locked, a belt layer 3 that has relatively shallow cords arranged in the tire circumferential direction on the outside of the crown of the carcass, and the carcass 2. A bead apex 4 extending from the upper side of the bead core toward the sidewall between the folded portions 2a, a tread rubber 5 in which the belt layer 3 is buried, and side rubber 6 extending from both ends of the tread rubber 5 toward the bead portion. ing.

First, the present invention provides a radial tire using a specific rubber material and cord material, in which steering stability and noise reduction are achieved by making the height of the bead apex extremely high or low. That is, the upper end of the bead apex 4 is extended to a position higher than the tire maximum width hw as shown in the figure, or is kept at a position lower than the upper end height hf of the rim flange 7. In conventional radial structure tires, the height of the bead apex is generally higher than the height of the upper end of the rim flange and lower than the maximum width of the tire, but the present invention has the above-described configuration. By making the flexibility of the side part larger or smaller than before,
The natural frequency of the tire itself is removed from the noise frequency range, reducing the noise level.

Here, in the present invention, the complex elastic modulus (E14) of the bead portion direction and socks is 200 kg/cm2 or more ζ Preferably 5
It ranges from 00 kg/Cl11 to 1500 kg/ad.

Note that the above-mentioned noise can be reduced only when the following tire structure and material are used, and if these conditions are not met, the above-mentioned objective cannot be achieved.

First, the tread rubber 4 has a complex modulus of elasticity (EI4) of 50.
'kg/c4・-150kg/cn! range, preferably 60 kg/'- to 100 kg/cm2, and more preferably a loss coefficient (tan δ) of 0.200 to 0.
A range of 350 is preferred. If the complex elastic modulus (EX) of the tread rubber is less than 50 kg/cm2, handling stability will be impaired, while if it exceeds 1'50 kg/cr+I, the noise level will increase, which is undesirable.

Next, the complex modulus of elasticity C'E"') of the side rubber 6 is 30.
kg'/cnl to 50 kg'/'c-. The side rubber 6 needs to be made of a rubber material that can cushion the impact transmitted from the tread rubber 6 and can sufficiently withstand repeated bending deformation during running. It is essential that there be.

Further, in the present invention, polyester is selected as the cord used for the carcass. The material of the carcass cord is related to the natural frequency of the tire, and is important for reducing noise, effectively mitigating shock during driving, and improving riding comfort and handling stability. The dynamic characteristics of the tread rubber, side rubber, and bead apex rubber work synergistically to reduce noise and improve handling stability.

The belt layer of the present invention is constructed using cords having a relatively high elastic modulus, such as steel cords, rayon, aramid, etc., arranged at an angle of 5° to 35° in the tire circumferential direction.

Next, in order to confirm the effects of the present invention, the following experiment was conducted.

Tire size 185/70SR14c Examples B, C, E
, F, Comparative Example H), 185/70SR13 (Example A
, D, and Comparative Example G), tires with various specifications shown in Table 1 were prototyped, and the noise level and steering stability were evaluated. The complex modulus of elasticity (E) in the table was measured by cutting a test piece from the tire and using a mucosal spectrometer manufactured by Iwamoto Manufacturing Co., Ltd. at a temperature of 70°C and a frequency of 10Hz.
This is a value measured under the condition of an amplitude of 2%.

In addition, road noise is measured by installing the driver's seat on the vehicle and driving at a speed of 50-/h on a road surface that is prone to road noise.
These are the measurement results from the left ear. Further, the steering stability is a five-point evaluation of the driver's feeling during driving with the actual vehicle, and the higher the score, the better.

In Table 1, comparing Sample A (Example), Sample D (Example), and Sample G (Comparative Example), which differ only in bead apex height with one carcass ply, Sample A (Example) and Sample D (Example). It was observed that road noise was significantly reduced, and that handling stability was improved.

Furthermore, the height of the bead apex with two carcass plies is less than the rim flange, that is, sample B (cold l&
2 Examples> Comparison of sample C (example), sample E (example) that is higher than the tire maximum width, sample F (example), and sample H (comparative example) that has a conventional bead apex height. As a result, it is recognized that all of the embodiments of the present invention reduce road noise and improve steering stability.

(Effects of the Invention) As described above, the present invention provides a radial tire for passenger cars in which the complex modulus of elasticity of the tread rubber and side rubber is set within a specific range, and the carcass cord is made of polyester. By setting it at a lower or higher position, it is possible to improve steering stability and reduce noise.

4. Explanation of drawings FIG. 1 is the right half of a cross-sectional view of the tire of the present invention.

1- bead core, 2- carcass, 3- belt layer, 4-
・Bead apex, 5-) Red part, 6... Side part rubber, 7- Rim flange.

Claims (1)

[Claims] (1) Complex modulus of elasticity (E*) is 50kg/cm^2~1
50 kg/cm^2 of tread rubber, a carcass of polyester cords folded around a pair of left and right bead cores and arranged substantially in the radial direction, and a carcass of polyester cords wrapped around a pair of left and right bead cores and arranged substantially in the radial direction. Belt layer with shallow angle cords and complex modulus (E*)
However, the side rubber is in the range of 30 kg/cm^2 to 50 kg/cm^2, and the complex rubber that extends between the carcass and its folded part from the top of the bead core to an area exceeding the maximum width of the tire or a position lower than the height of the top of the rim flange. A radial tire for a passenger car, characterized by having a bead apex with an elastic modulus (E*) of 200 kg/cm^2 or more.