JPH01240304A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To balance high speed durability, control stability and riding comfort ableness at a high level by specifying the modulas of each of coat rubbers of a carcass layer and each of belt layers on the carcass and belt layers, where in each of all layers is a single layer. CONSTITUTION:At a tread part 7 of a tire, a single-layered carcass layer 5, and respective signal-layered belt layers 3, 4 on the carcass and tread sides and respectively laminated. In this case, the layer 5 is formed by burying an aromatic polyamide fiber cord in a coat rubber having 300 modulas equivalent to 100-170kg/cm<2>. The layer 3 is formed by burying a steel cord in a coat rubber having 300% modulas equivalent to that less than 170kg/cm<2>. The layer on the tread 7 side is formed by burying a steel cord or an aromatic polyamide fiber cord in a rubber coat having 300% modulas equivalent to 180-240kg/cm<2>.

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention has a carcass layer made of an aromatic polyamide fiber cord (hereinafter referred to as an aramid fiber cord), and a separation between the carcass layer and a belt layer. This relates to a pneumatic radial tire that exhibits excellent high-speed durability, good handling stability, and excellent ride comfort.

[Conventional technology]

Conventionally, with the spread of automobiles and the expansion of expressways, the radialization of tires has reached approximately 90x for passenger cars and approximately 60x for trunks and buses.

This high ratio of radial tires is due to the unique radial structure of radial tires, which provides superior high speed performance, handling stability, and wear resistance compared to bias tires.

However, conventional radial tires do not necessarily meet the diversified demands of recent automobiles, such as higher performance and more sophisticated tires. In other words, as is well known, the structure of a conventional radial tire consists of a tread portion, a pair of side portions connected to the shoulders of the tread, and a pair of bead portions formed on the inner periphery of the side portions. A device comprising a carcass in which cords are arranged in the radial direction of the tire and a heald layer surrounding the carcass, and a belt layer with a width of 10 to 30 inches in the circumferential direction of the tire.
The carcass layer consists of at least two ply layers in which two or more layers of steel cords are embedded at an angle of 90 degrees, and the carcass layer is a rayon fiber cord, a polyester fiber cord, a nylon fiber cord, etc., which are arranged at an angle of approximately 900 degrees with respect to the circumferential direction. It is formed from one or two ply layers.

Conventional tires with this type of structure use steel cords in the heald part of the tire, so the belt weight is large, and the centrifugal force generated by the rotation of the tire during high-speed driving is large, resulting in shoulder unevenness. This can easily cause belt separation.

Therefore, such conventional radial tires have not been able to satisfy the advanced high-speed durability and handling stability required by recent improvements in performance.

In addition, the conventional organic fibers used as the cords forming the carcass layer have a low tensile modulus and a high creep property, so they are less effective in suppressing the phenomenon of rising of a part of the tire shoulder. I couldn't expect a dramatic improvement in my sexuality. Furthermore, since the tensile modulus is small, responsiveness is poor, especially in high-speed turns, and there is a limit to the improvement in handling stability.

To address these problems, in recent years, a folded structure that combines steel cord and aramid fiber cord has been adopted for the tire belt layer, increasing the tire's high speed and improving ride comfort. An attempt to do so has been proposed. In addition, from the aspect of the carcass, we use aramid fiber, which has an extremely high tensile modulus among organic fibers,
Attempts to improve steering stability have also been proposed. However, in the former case, compared to a tire with only a belt layer made of steel cord, the belt portion is lighter, and although the reduction in belt rigidity certainly improves ride comfort, the decrease in heald rigidity This also reduces the overall casing rigidity of conventional tires using organic fibers as the carcass layer, making it difficult to improve handling stability. In order to increase the casing rigidity, it is necessary to increase the number of carcass cords and create at least two carcass layers. However, this not only increases the weight of the tire but also increases the bead strength from the side of the tire. There is a problem in that the thickness increases as the tire approaches the end, reducing the durability of the tire. On the other hand, in the latter case, sufficient tire strength and tensile modulus can be achieved with just one ply by using aramid fibers, which have about twice the strength and five times the tensile modulus compared to conventional organic fibers. can be ensured,
Higher speeds can be expected by increasing the rigidity of the tire casing.

However, like conventional organic fibers, aramid fibers also have low bending rigidity, so when a one-brie carcass layer made of aramid fiber cords is formed, the bending rigidity of the tire side part is insufficient, resulting in insufficient handling stability. could not be secured.

Furthermore, when aramid fibers, which have a higher tensile modulus than conventional organic fibers, are used as a carcass layer, they exhibit good damping properties against the impact from the tire tread, but the impact force itself is not alleviated. Because of its large size, it can cause "columns" or "lumps" when passing over joints or small protrusions in the pavement.
This has the drawback of deteriorating the ride comfort, such as the vibration that is felt, which worsens the so-called harshness of the tire.

[Purpose of the invention]

It is an object of the present invention to have good high-speed durability and handling stability, which have been considered to be the limits of the recent high-performance pneumatic radial tires mentioned above, and to have excellent ride comfort without the above-mentioned harshness. and to provide a pneumatic radial tire with highly balanced performance.

[Structure of the Invention] The object of the present invention is to
A single carcass layer embedded in a coated rubber with a 0% modulus of 10 (1 to 170 Kg/am2), a 30oz steel cord as a heald layer adjacent to the carcass layer.
A single-layer belt layer embedded in coated rubber with a modulus of 170 Kg/cm or less and a belt layer provided on the tire tread surface are made of 300% steel cord or aramid fiber cord with a modulus of 180 to 240 Kg/cm.
This can be achieved by constructing a single belt layer embedded in a coated rubber.

That is, the pneumatic radial tire of the present invention (hereinafter simply referred to as a tire) has a carcass layer composed of one ply of aramid fiber cord, and a belt portion composed of a belt layer composed of two plies of a specific cord, Furthermore, by using rubber having a modulus within a certain range as the coating rubber for these carcass layers and the belt layer, high-speed durability and handling stability are improved or stabilized.
It is lightweight and has succeeded in satisfying good riding comfort.

Tires targeted by the present invention include passenger car tires of 14 inches or more and light trunk radial tires, which are relatively large and flat radial tires with an aspect ratio of 75 or less, preferably 65 or less. desirable.

FIG. 1 is a partially cutaway, semi-perspective sectional view showing an example of the tire of the present invention. As shown in the figure, the tire trend section 7 includes a single-layer carcass layer 5 made of aramid fiber cord,
A single-layer side belt reinforcing layer (No. 1 belt layer) 3 made of steel cords provided in contact with the carcass layer 5; and a single-layer tread side belt layer (No. 2 belt layer) 4 made of steel cords or aramid fiber cords. are sequentially laminated, and the tread 7 is formed thereon. Above tread side belt layer 4
One end is bent at the shoulder part, and the bent part 4
° is formed. Note that 1 is a bead wire and 2 is a side wall.

Moreover, FIG. 2 is a schematic cross-sectional view showing the laminated structure of the carcass layer and belt layer of FIG. 1.

Here, the carcass layer of a tire is usually provided with two or more layers from the viewpoint of tire strength, handling stability, etc., but the carcass layer 5 of the present invention is formed of a single layer made of aramid fiber cord. There are characteristics. In other words, if the carcass layer 5 is made of two or more layers, it is not preferable because it not only increases the weight of the tire but also significantly deteriorates the ride comfort.

In addition, aramid fibers have high crystallinity, and if the cut surface is placed in a shoulder part where the movement of the tire is relatively large, failures from the break surface are likely to occur during running. Therefore, it is preferable that the belt layer made of aramid fiber cords has a so-called folded structure by folding the ends in the width direction, and that the cord cut surface is located close to the center of the tread where movement is relatively small.

The aramid fiber used in the present invention has a tensile strength of at least 250 Kg/mm2 and a tensile modulus of 600.
DuPont's "
There are fibers such as "Kevlar" and Ondai's "Technora", and these fibers are twisted so that the twist coefficient K expressed by the following formula is within the range of 1600 to 2800, and then glued.・This is a heat-treated cord. That is, if the value of the aramid fiber cord is less than 1,600, it is not possible to ensure adequate fatigue resistance as a carcass, and if the value of K(lI!) exceeds 2,800, the tensile strength and elastic modulus of the cord will decrease significantly. undesirable for this reason.

K=T f" (In the above formula, K is the twist coefficient, T is the number of twists, and D is the total denier of the cord.) The carcass layer of the tire of the present invention is composed of the aramid fiber cord. In addition, the 300% modulus of the coated rubber in which the aramid fibers are embedded is 10.
It is important that it is within the range of 0 to 170 kg/cm2. In other words, when the carcass layer is formed from aramid fiber cords, if a coated rubber with a 300% modulus of less than 100 Kg/cm2 is used, the circumferentiality of the carcass layer decreases, resulting in a significant decrease in handling stability. Moreover, the shear strain between the carcass layer and the belt layer increases, and the durability of the tire decreases. In addition, 30% of the rubber
If the 0% modulus becomes thicker than 170 Kg/cm, the above-mentioned circumferential properties will increase, but the ride comfort due to this rigidity will deteriorate, and the heat generation of the carcass layer will increase, which will reduce the durability of the tire. So it's not desirable.

Next, the belt layer of the tire of the present invention is made of steel cord having a modulus of 300% and 1 as the carcass side belt layer.
A single-layer belt layer embedded in a coated rubber of 10 Kg/ctn2 or less; and a single-layer belt layer in which a steel cord or aramid fiber cord is embedded in a coated rubber with a 300% modulus of 180 to 240 Kg/cI112 as the tire tread side belt layer; It is characterized by the fact that it is composed of That is, if the 300% modulus of the coated rubber of the belt layer adjacent to the carcass layer exceeds 170Xg/cm, the impact force from the tire tread side becomes large, the aforementioned harshness is not improved, and the ride comfort is insufficient. In addition, the difference in modulus between the carcass layer and the carcass layer becomes large, and as a result of stress concentration due to the difference in circumferentiality between the carcass layer and the belt layer, separation is likely to occur between the belt layer and the carcass layer. The 300% modulus of the coating rubber of the layer is more preferably 100 Kg/cm" or more. If it is less than 100 g/cm2, there will be discontinuity in rigidity between the carcass layer and the belt layer on the tire tread side, which tends to deteriorate steering response.

and 3 of the coated rubber that constitutes the tire tread side belt layer.
If the 00% modulus is less than 180Kg/cm2,
Belt rigidity becomes too low and steering stability deteriorates, resulting in 24
When it exceeds 0 kg/cm2, the difference in modulus with the carcass side belt layer becomes large, and not only the durability of the heald part decreases, but also the riding comfort deteriorates.

FIG. 3 is a half-sectional view showing another embodiment of the present invention, which is a tire in which the belt layers 3 and 4 are made of steel cord.

〔Example〕

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

Note that high speed performance, ride comfort, and handling stability are values measured as follows.

Student: Measured by indoor high-speed durability test. The test conditions are as follows. □ Tire size: 195/60VR14, rim:
6JJX14 Internal pressure P = 3.0 Kg7cm", load W・-JATM8 maximum weight 80χ (412Kg/
Tire) 1σKm/every 10 minutes from speed V -170Km/hr
Acceleration per hour.

Drum diameter = 1707InlIl: The vehicle is driven under these conditions until the tire breaks.

I. Orthostatic performance: Evaluated by an indoor protrusion climbing test measured under the following conditions.

Rim: 6JJx14 Internal pressure P = JATMA design normal pressure (1.9Kg/c)
m2), load W = JATMA maximum load 80χ (4
12Kg/tire), speed V-60, 80, 100 and 1201f+/hr
average, drum diameter = 2500 mm.

Cliff j0■: Based on an indoor cornering test measured under the following test conditions.

Rim: 6JJx14 Internal pressure P = substituted with JATMA design normal pressure (1.9Kg/
cm2), load W = 80χ of JATMA maximum load (
412Kg/tire), speed V = 20 Km/1hr.

5A=2.0 Drum diameter -2500nv+.

Example 1, Comparative Examples 1 to 7 1000 D/2, number of twists 50 x 50 concave/10CI
11. 1-ply carcass layer with 50 Kevlar cords with a twist coefficient (K) of 2236 and 15cm length, 1-ply with 2+7 (0,22) steel cords with 35 ends and 15cm length. Carcass layer side belt layer (No. 1 belt layer), 1500 D/2, number of twists: 30
It consists of a 1-ply tread side heald layer (No. 2 belt layer) in which "Kevlar" cords with a twist coefficient (K) of 1643 and 50 ends of 15 cm are inserted, and the above carcass layer, No. 1 and Six types (Example 1,
Comparative Examples 1 to 5) were prepared, and the high-speed performance, riding comfort, and handling stability of these tires were evaluated, and the results are shown in Table 1.

The bending width 4'' was set to 20x of the total width of the belt 4.

(Hereinafter, blank space) In Comparative Examples 6 and 7, the carcass layer of the tire was 1000 D/2, number of twists 50 x 50 times/10 cm
This tire has the same structure as the above except that the carcass layer is made of two-ply polyester fibers in which 50 cords of 15 cm are inserted.

Here, the evaluation results were expressed as an index based on Comparative Example 5.

From Table 1, it can be seen that when the carcass modulus is low, the steering stability deteriorates due to a decrease in the roundness of the carcass, and when the modulus difference between the coated rubbers constituting the carcass layer and the No. 1 belt layer is large, the carcass layer The durability of the belt decreases due to stress concentration between the eyebrows of the belt. Furthermore, it can be seen that if the modulus of the coated rubber of the No. 1 belt layer is too high, the ride comfort is reduced, and if the modulus of the coated rubber of the No. 2 belt layer is too low, the steering stability is reduced.

〔Effect of the invention〕

According to the present invention, a single carcass layer is formed using aramid fibers that have significantly higher strength, higher initial elastic modulus, and lower leap than conventional tire cords, improving high-speed performance. In promising tires, the problem of reduced casing rigidity (decreased handling stability), increased shear between the carcass and belt layer (decreased high speed), and poor adhesion (decreased durability) due to the use of a single-ply carcass layer has been improved. By specifying the modulus of each coating rubber in the belt layer, this problem was resolved and the excellent fiber performance of aramid fibers was reflected in the tire performance, and its technical effects are extremely large.

[Brief explanation of the drawing]

FIG. 1 is a partially cut away semi-perspective cross-sectional view showing one embodiment of the tire of the present invention, FIG. 2 is a schematic cross-sectional view showing an aspect of the laminated structure of the belt layer of the tire of FIG. FIG. 7 is a half-sectional view showing another embodiment of the invention. 3... Carcass side belt layer (first heald layer), 4...
・・Trend side belt layer, 4″・・Helt[?/J bending part, 5・・Carcass layer, 6・orthogonal layer, 7・・・・・
tread.

Claims (1)

[Claims] Aromatic polyamide fiber cord with 300% modulus of 1
A single carcass layer embedded in a coated rubber of 00 to 170 kg/cm^2, a belt layer adjacent to the carcass layer, a steel cord with a 300% modulus of 170
30 kg/cm^2 or less of steel cord or aromatic polyamide fiber cord is used as a single-layer belt layer embedded in coated rubber of 2 kg/cm^2 or less and as a belt layer provided on the tire tread side.
A pneumatic radial tire consisting of a single belt layer embedded in coated rubber with a 0% modulus of 180 to 240 Kg/cm^2.