JPH01317812A - Radial tire - Google Patents

Abstract

PURPOSE:To obtain both comfort and driving stability by forming the area of an outer sidewall part using a gum material with the specific dynamic modulus of elasticity and the area of an inner sidewall part using a gum material of the greater dynamic modulus of elasticity respectively. CONSTITUTION:On the side part of a tire, plural sidewall parts 2, 2' are placed in the proximity of a carcass layer 4, and respective lower ends are extended to plural rim cushion parts 3, 3'. In installing the tire to a vehicle, the sidewall part 2 facing inside is formed of a gum material with the normal modulus of elasticity of 5-8 pascal. On the other hand, the sidewall part 2' facing outside is divided into plural areas 2t, 2b, that is, the tread part side and the bead part side, and the areas 2t, 2b are formed of the gum materials of dynamic modulus of elasticity of 1-4.3 and 5-9 mega pascal respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a radial tire that improves handling stability without deteriorating ride comfort performance.

[Conventional technology]

Conventionally, rubber materials with excellent cut resistance and crack resistance have been used for the sidewall portions of pneumatic tires to protect the carcass portion, which forms the skeleton of the tire as a pressure vessel, from external damage. In order to prevent cranks from occurring near the outer wall of the sidewall portion due to stress concentration caused by bending during running, rubber with a low dynamic elastic modulus E' is generally used.

Therefore, the sidewall portion of the conventional radial tire did not have a function as a rigid member of the tire.

In addition to the above-mentioned functions such as protection from trauma, the present inventors have discovered that
We discovered that this sidewall part can be an important rigidity member for radial tires, and by increasing the dynamic elastic modulus E of the sidewall rubber, we significantly improved the tire's lateral rigidity and improved handling stability. I suggested tires.

However, despite exhibiting excellent handling stability, this tire inevitably suffers from a decrease in ride comfort, and today's tires are required to have both handling stability and ride comfort at a high level. It turned out that there was a problem with radial tires.

[Problem to be solved by the invention]

The object of the present invention is to increase the dynamic elastic modulus E of the rubber constituting the sidewall portion of the tire, and to suppress as much as possible a decrease in the handling stability of the above-mentioned radial tire, which has improved handling stability.
The goal is to improve riding comfort.

[Means to solve the problem]

A feature of the present invention is that when mounted on a vehicle, the sidewall portion facing the outside is divided into two regions with different dynamic moduli of elasticity E゛, that is, the dynamic modulus of elasticity E° is 1 to 4.3 megapascals (MPa).
) and a region on the bead side made of a rubber material with a dynamic elastic modulus E' of 5 to 8 megapascals (MPa). The entire facing sidewall portion is made of a rubber material having a dynamic elastic modulus E' of 5 to 8 megapascals (MPa).

Here, the dynamic elastic modulus E in the present invention is determined using a viscoelastic spectrometer (for example, manufactured by Iwamoto Seisakusho ■) at a frequency of 20H2, an initial strain of 10χ, a dynamic strain of ±2χ, and a temperature of 20°C.
This value was measured under the following conditions.

Furthermore, a radial tire consists of a pair of bead parts, a pair of sidewall parts continuous between these bead parts, and a tread part located between the sidewall parts, and a carcass is arranged between the bead parts in parallel with the cross-sectional direction of the tire. This tire has a plurality of belt layers intersecting at an angle of 10° to 35° with respect to the tire circumferential direction between the carcass layer and the tread portion.

The figure is a cross-sectional view of a tire showing one embodiment of the tire of the present invention. In the figure, the tread 1 has two belt layers 7u.
, 7d are provided, and a bead filler 6.6' is provided on the bead portion where the beat wires 5, 5' are provided in an annular shape. Then, the carcass layer 4 is turned up around the beat wires 5, 5'' and folded back so as to wrap around the bead filler 6.6''. Further, the tire side portion is located close to the carcass layer 4 and has sidewall portions 2, 2.
The lower end of the rim 3.3 is provided outside the turn-up portion of the carcass layer 4.

The sidewall portion of the tire of the present invention is the “portion between the tread and the bead” specified in the JATMA Automobile Tire Safety Standards, and the sidewall rubber is the rubber material that makes up this sidewall portion. However, the 3.3° rim compression portion shown in the figure is not included.

When the sidewall rubber 2, 2゛ is installed on a vehicle, the sidewall rubber 2, which faces inside, and the sidewall rubber 2°, which faces outside, have different structures. It must be made of a rubber material with a specific elastic modulus E'.

In the tire of the present invention, when mounted on a vehicle, the sidewall rubber 2 facing inward must be entirely composed of a rubber material having a dynamic elastic modulus E° of 5 to 8 megapascals (MPa).

In other words, when tires are attached to a vehicle and the vehicle turns, the tires on the outside of the turn will be placed in a significantly harsher condition than the tires on the inside. Forces in completely opposite directions are applied to the inner sidewall portion when mounted on a vehicle, and to the outer sidewall portion when mounted on a vehicle, with the equatorial plane as the boundary. Then, the sidewall part (hereinafter referred to as the "inner side part") that becomes the inner side when mounted on the vehicle is deformed so that the inner side part swells diagonally upward, and the sidewall part (hereinafter referred to as the "outer side part") that becomes the inner side when installed in the vehicle deforms so that it bulges diagonally upward. ) is deformed so that this outer side portion is rolled diagonally downward. Therefore, although the outer side portion is pulled in the circumferential direction, deformation due to this pulling is suppressed by the tensile force of the carcass cord, and therefore has sufficient resistance to the circumferential tensile force. On the other hand, since the inner side part is compressed in the circumferential direction, the inner side part cannot take advantage of the apparent rigidity due to the tensile force of the carcass cord.
The so-called hip fracture will cause a sensation.

The present invention uses a rubber material with a large dynamic elastic modulus E' as the rubber material constituting the inner side portion, and increases the compression rigidity of the inner side wall rubber, thereby preventing the above-mentioned lumbar fracture from causing the feeling. , which improves handling stability, but similarly to the dynamic elastic modulus E° of the outer sidewall rubber, increasing the dynamic elastic modulus E' of the inner sidewall rubber significantly reduces ride comfort. It is.

Therefore, in the present invention, the outer sidewall rubber, which contributes less to handling stability, is configured with sidewall rubber that has a different structure and dynamic elastic modulus E' from the inner sidewall rubber, thereby preventing a decrease in ride comfort. .

That is, in the tire of the present invention, when mounted on a vehicle, the tread portion side region 2't of the sidewall rubber 2'' facing outward is the bead portion side region 2'b.
It is necessary that the rubber material has a lower dynamic elastic modulus E' than the rubber constituting the rubber material. This tread side area 2
When the rubber material forming 't is larger than the dynamic elastic modulus E' of the rubber material forming the bead side region 2''b,
Although the overall stiffness of the outer sidewall of the tire increases, the ratio of the horizontal spring constant to the vertical spring constant (lateral spring constant/longitudinal spring constant) (hereinafter referred to as spring ratio) decreases, making it difficult to maneuver. This results in unsatisfactory levels of stability and ride comfort.

If the dynamic elastic modulus E' of the rubber constituting the tread side region 2''t becomes lower than I MPa, the rubber becomes too soft and it becomes difficult to mold an unvulcanized tire. , 3 MPa, the deterioration of ride comfort cannot be suppressed and the advantage of dividing the outer sidewall portion 2'' cannot be utilized.
If the dynamic elastic modulus E of the rubber constituting "b" is lower than 5 MPa, the increase in the lateral spring constant will be insufficient and the improvement in handling stability will not be sufficient. On the other hand, if it exceeds 8 MPa, the ride comfort will be This is not preferable because the decrease in

Further, in the tire of the present invention, the outer sidewall portion 2
It is desirable that the bead side region 2'b constituting the outer sidewall rubber 2'' has a cross-sectional area corresponding to 30χ to 70χ of the total cross-sectional area of the outer sidewall rubber 2''. If the cross-sectional area of region 2°b becomes smaller than 30χ of the total cross-sectional area of the outer sidewall rubber 2', a sufficient increase in the lateral spring constant cannot be expected, and steering stability cannot be sufficiently improved. , 70χ, the ride comfort deteriorates extremely and it becomes difficult to achieve both high standards of handling stability and ride comfort.

Examples of the rubber material forming the sidewall portion of the present invention include natural rubber, isoprene rubber, butadiene rubber (BR), and styrene-butadiene copolymer rubber (BR).
There are rubber compositions that are made by blending various compounding agents such as carbon black and vulcanization accelerators with synthetic rubber such as SBR).
It is possible to obtain a rubber having a dynamic elastic modulus E° defined in the present invention.

In addition, in order to improve adhesion (durability), weather resistance, etc., the sidewall portion made of a rubber layer that satisfies the physical properties specified in the present invention has a rubber layer having different characteristics either above or below it. It goes without saying that there is no problem in forming and laminating them.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

The handling stability and riding comfort of the tires were evaluated by the following slalom running test and bump-over test.

Slalom Driving Test A domestically produced FP vehicle was driven on a slalom test road with pylons set up at regular intervals, and the driving stability was evaluated based on the time required.

The rims used are 6 JJ x 14, and the air pressure is 2.0 kg/
c+m".

Protrusion crossing test: 20I in diameter at one place on the circumference of a drum with a diameter of 2500+am
A protrusion riding test machine equipped with IIIll's semicircular protrusions detects the longitudinal axial force (longitudinal impact force) when the test tire passes over the protrusions, and determines ride comfort based on its magnitude. evaluated.

The rims used are 6 JJ x 14, and the air pressure is 2.0 kg/
cm", load was 350 kg, and speed was 80 + m/hr.

Examples, Conventional Examples, and Comparative Examples 1.2 Two types of rubber compositions A and B having different dynamic elastic moduli E shown in Table 1 were used as tire sidewall rubber, and as shown in Table 2, the sidewall Four types of tires (size 195
/60R14) was created.

The conventional example (conventional tire) is a tire whose sidewall part is not divided into the tread side and the bead side and is made of rubber with a low dynamic elastic modulus E", and the comparative example 2 (comparative tire 2) is a tire made of rubber with a low dynamic elastic modulus E". The invention tire (Example) is a tire in which the rubber constituting the sidewall part is arranged oppositely, and in Comparative Example 1 (Comparative Tire 1), the sidewall part is not divided like the conventional tire, but it is different from the conventional tire. This tire is made of rubber with a higher dynamic elastic modulus E' than that of tires.

These tires were subjected to a slalom running test and a bump-over test.

In addition, the belt layer, carcass layer,
The bead structure and sidewall rubber are as follows.

Belt layer: 40 pieces of 1 x 5 (0,25) steel cord per 50+no+, bias laminated at 24″ in the tire circumferential direction, Carcass layer: 55 pieces of 15000/2 polyester cord per 50 m− in the tire circumferential direction actually 900 against
As shown in Figure 2, the bead structure is as shown in Figure 2. Sidewall rubber 2 Sidewall rubber with a dynamic modulus of elasticity E shown in Table 1 is placed in the combinations shown in Table 2 on the inner and outer sides, respectively.

Ratio of bead side area: 5 of total cross-sectional area of sidewall rubber
Cross-sectional area corresponding to 0χ.

Table 1 Note) 1) BR-1 is butadiene rubber (NIPOL-1220) manufactured by Zeon Corporation, and BR-2 is butadiene rubber manufactured by Ube Industries (UBEPOL-VCR412).

Table 2 From the results of the slalom running test shown in Table 2, the tire of the present invention has significantly improved handling stability compared to the conventional tire and Comparative Tire 2 (Comparative Example 2), and is more effective when riding over bumps than Comparative Tire 1. It can be seen that the protrusion impact force in the test was small and the ride comfort was excellent.

〔Effect of the invention〕

The present invention takes advantage of the fact that the sidewall rubber functions as a rigid member of the tire.The present invention utilizes the fact that the sidewall rubber functions as a rigid member of the tire.The sidewall rubber of the tire located on the inside when mounted on a vehicle is constructed using rubber with a specific high dynamic elastic modulus. By doing so, the compression rigidity of that part is increased, and on the other hand, the outer side part, which contributes less to the rigidity of the tire side part than the inner side part, is divided into two parts: the tread part side and the bead part side, upper and lower. ,
By composing them with two types of rubber materials having a specific dynamic modulus of elasticity E, the handling stability of radial tires has been significantly improved without impairing the ride comfort of the tires. It is a radial tire that satisfies today's demands by simultaneously maintaining a high level of comfort and handling stability.

[Brief explanation of the drawing]

The figure is a sectional view showing the ILQ aspect of the pneumatic tire of the present invention. 1... Tread part, 2.2'... Side wall rubber, 2u+2'u... Tread part side area, 2d, 2'
d...Bead portion side region, 3,3''...Limitation, 4...Carcass layer, 5.5''...Bead wire, 7u, 7d...Belt layer. Agent Patent Attorney Nobuo Ogawa −

Claims (1)

[Claims] When mounted on a vehicle, the sidewall portion facing the outside consists of two areas, one on the tread side and the other on the bead side.
It is composed of a rubber material with a dynamic elastic modulus E' of 4.3 megapascals (MPa) and 5 to 8 megapascals (MPa). A radial tire constructed from a rubber material having a dynamic modulus E' of 8 megapascals (MPa).