JPH01145205A - Radial tyre - Google Patents

Abstract

PURPOSE:To secure both excellent operating stable performance and riding comfort by forming a tread by means of using tread rubber whose ratio of a complex elastic modulus in the tyre axial direction to a complex elastic modulus in the tyre radial direction is specified. CONSTITUTION:A tyre 1 has a carcass 3, bead portions 5 with a pair of bead cores 4 made of metal wire, an annular treated 6 arranged radially outside the carcass 3 and side walls 7 connecting the bead portions 5 with both sides of the tread 6. In this structure, the tread 6 is made of reinforced rubber which is formed by means of combining rubber base material 11 with staple 12. The staple 12 is arranged in the tyre axial direction so that the ratio of a complex elastic modulus in the tyre axial direction to a complex elastic modulus in the tyre radial direction is set to be more than 1.5. With this arrangement, the lateral rigidity of the tyre 1 is larger than the longitudinal rigidity so as to secure both excellent operating stable performance and excellent riding comfort.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention makes it possible to achieve both steering stability and ride comfort by using tread rubber with different complex moduli of elasticity in the tire axial direction and in the tire radial direction. Regarding radial tires.

[Prior art]

Radial tires, especially radial tires for passenger cars, require not only stable handling performance such as cornering performance that allows safe turns, but also ride comfort performance that reduces impact from the road surface and enables comfortable driving. be done.

However, when reducing the aspect ratio and increasing the rigidity of the entire tire in order to improve steering stability, the impact mitigation performance from the road surface is reduced, resulting in a decrease in ride comfort.
Steering stability and ride comfort are antithetical performances.
Therefore, in the past, rubber etc. have been selected based on these compromises.

[Problem that the invention seeks to solve]

Therefore, such a tire cannot be a tire that satisfies both handling stability performance and ride comfort performance. However, handling stability performance during cornering is achieved by increasing the tire's axial rigidity, that is, lateral rigidity. By this,
The driver's sense of control can be improved, and ride comfort performance can be judged especially when driving straight at a constant speed, and in order to improve ride comfort, it is possible to reduce the impact when passing over uneven road surfaces. It is better to improve the envelope performance as much as possible, and to do this, it is better to reduce the longitudinal stiffness, that is, the stiffness in the tire radial direction. They realized that they could achieve both handling stability and ride comfort by using rubber with different directional properties, which increases the tire's axial rigidity while simultaneously decreasing the tire's radial rigidity.

Furthermore, they have also discovered that by arranging short fibers in a predetermined direction, the stiffness of the rubber can be made to vary depending on the direction.

Therefore, the present invention aims to provide a radial tire that can achieve both handling stability performance and ride comfort performance by using a tread rubber with different directions that can increase the rigidity in the tire axial direction and reduce the rigidity in the tire radial direction. The purpose is

Means for Solving Problem c] The present invention calculates the trend using the complex modulus of elasticity Ea in the tire axial direction.
Ratio of ``and complex modulus of elasticity in the tire radial direction Eb''Ea''/E
This is a radial tire formed using tread rubber with b'' greater than 1.5.

An embodiment of the present invention will be described below based on the drawings.

In FIG. 1, which shows the tire 1 assembled on a regular rim R and filled with a regular internal pressure, the tire 1 includes a carcass 3, a bead portion 5.5 having a pair of bead cores 4.4 made of metal wire, and a carcass. It has an annular trend 6 disposed outward in the radial direction, and sidewalls 7.7 connecting the bead portion 5 and both sides of the tread 6, and a belt 9 is provided on the outside of the carcass 3 in the tire radial direction. A bead apex 10.10 is arranged in the section 5 and extends radially outward from the bead core 4.4.

Furthermore, in this example, the tire 1 has a maximum weight W and a tire cross-sectional height H.
It is formed as a flat tire with a ratio H/W of 0.7 or less.

The carcass 3 is made up of a few cord layers (all 1 braid) in which organic fiber cords such as synthetic resin or inorganic fiber cords such as metal are arranged in the radial direction. By being rewound by the bead core 4 of the bead portion 5, the body portion 3A and the rewound portion 3 are
The bead apex 10 is arranged between the main body portion 3A and the turned-up portion 3B.

In this example, the belt 9 has an inner ply 9a located on the carcass 3 side and an outer ply 9b disposed outside of the inner ply 9a, and each ply 9a, 9b is parallel and has a diameter of 10 to 35 It is formed by a cord layer in which belt cords 11 are arranged inclined at an angle of .degree. The belt cords 11 of the inner ply 9a and the belt cords 11 of the outer ply 9b are arranged in a direction that intersects with each other, and the belt cord 11 is made of a twisted body of wires 12- made of a metal material such as steel.

The sidewall 7 is formed using ordinary isotropic rubber, and the tread 6 is made of rubber as described above.
, using unidirectional tread rubber.

In this example, the treaded rubber has short fibers 12 on a rubber base material 11.
The short fibers 12 are oriented in the axial direction of the tire, thereby increasing the complex modulus of elasticity Ea* in the axial direction of the tire and the complex modulus Eb* in the radial direction of the tire.
The ratio Ea''/Eb''' is set to be greater than 1.5, thereby increasing the lateral stiffness compared to the longitudinal stiffness. The complex modulus of elasticity was measured using a viscoelasticity spectrometer made by Wakagi Seisakusho.A sample with a width of 4fi, a length of 30mm, and a thickness of 2fi was cut out from the tire tread in the tire axial direction and tire radial direction, and the frequency was 10Hz and the temperature was 70°C. , measured at a dynamic strain of 2%.

The rubber base material 11 is made of natural rubber, polyisoprene rubber,
It is a mixture of at least one or more types of styrene-butadiene rubber, polybutadiene rubber, etc. In addition, the rubber base material is mixed with reinforcing materials such as carbon black and silica, as well as appropriate additives such as anti-aging materials. be done.

The short fibers 12 are nylon, rayon, polyester,
Fibers made of organic materials such as aromatic polyamide crystalline polybutadiene carbon fibers, fibers made of inorganic materials such as glass fibers, metal fibers, whiskers, and boron can be used. In addition, various tires with a diameter of about 0°1 μm to 0.1 fl have the complex modulus ratio Ea/Eb larger than 1.5, and the complex modulus Ea in the axial direction of the tire 7
It is blended so that the complex elastic modulus Eb* in the tire radial direction is in the range of 50 to 80 kg/-.

By setting the complex modulus of elasticity Ea" % Eb" to such a ratio, the lateral stiffness of the tire is made larger than the longitudinal stiffness, increasing the resistance to lateral force during cornering and improving steering stability, while at the same time increasing the longitudinal stiffness. By not increasing the profile, the envelope characteristics can be increased and the ride comfort performance can be improved, and this can be particularly effective in tires with an aspect ratio of 0.7 or less, as in this example.

Further, when the ratio Ea''/Eb'' is smaller than 1.5,
Such improvement effect is reduced. Furthermore, by setting the complex modulus of elasticity Ea* in the tire axial direction to 70 kg/- or more, cornering is improved compared to conventional tires, and by setting the complex modulus of elasticity Eb'' in the tire radial direction to 60 kg/a11 or less, ride quality is improved. is improved.

Note that as the crystalline polybutadiene for forming the above-mentioned anisotropic tread rubber, there is, for example, VCR (trade name, manufactured by Ube Industries, Ltd.) and the like.

Furthermore, as shown in FIG. 2, for example, the tread rubber is made by molding with a calender roll or by extrusion, so that the orientation of the short fibers 12 is arranged in the extrusion direction, and the sheet weight 5 is embedded in the rubber base material 11 in the longitudinal direction. By attaching this sheet piece 16 in the circumferential direction of the tire, the tread 6 in which the short fibers 12 are oriented in the axial direction of the tire can be formed.

〔Example〕

Steel radial tires with a tire size of 185/60R14 were manufactured according to the specifications shown in Table 1. Similarly, comparative products shown in Table 1 were produced, both were installed in a passenger car, and a sensory test was conducted by a driver to evaluate them on a five-point scale. Comparative examples and the like are set as standard 3, and higher scores indicate better results. As a result of Table 1, the tire mixed with crystalline polybutadiene (VCR) of Example 1 was particularly excellent in ride comfort, and the tire containing nylon-embedded natural rubber (trade name: FRR, manufactured by Ube Industries, Ltd.) as short fibers was found to be It can be seen that the vehicle used in Example 2 has excellent handling stability and achieves both handling stability performance and ride comfort performance.

In Table 1, all compounding values are shown in parts by weight, and as mentioned above, the VCR of Example 1 was made of crystalline polybutadiene made by Ube Industries, and the FR of Example 2 was made of nylon short fiber composite made by the same company. Nylon short fibers and natural rubber are mixed in advance at a ratio of 1:2.

〔Effect of the invention〕

As described above, the radial tire of the present invention has a complex modulus of elasticity in the tire axial direction of 1.
5, the stiffness in the axial direction of the tire is increased without increasing the rigidity in the tire radial direction. Therefore, it is possible to balance and improve both steering stability performance and ride comfort performance, which are said to be antinomic characteristics. becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of the present invention, and FIG. 2 is a perspective view schematically showing a method for manufacturing tread rubber. 6--Tread, 11--Rubber base material, 12- Short fiber. Patent applicant Sumitomo Rubber Industries Co., Ltd. Agent Patent attorney Tadashi Naemura 2nd wI

Claims (3)

[Claims] (1) The ratio of the tread's complex elastic modulus Ea^* in the tire axial direction to the complex elastic modulus Eb^* in the tire radial direction Ea^*/E
A radial tire formed using treaded rubber with b^* greater than 1.5. (2) The radial tire according to claim 1, wherein the tread rubber contains short fibers. (3) The radial tire according to claim 1, wherein the tread rubber contains crystalline polybutadiene.