JPH0446766B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention provides a vehicle for a passenger car that improves the durability of a bead reinforcing layer and also improves handling stability and high-speed durability without impairing ride comfort. Regarding pneumatic radial tires.

[Prior art]

In recent years, tire performance requirements have become more sophisticated and diversified, with no end in sight, due to improvements in expressway networks and higher performance of passenger cars.

For example, it is possible to drive at higher speeds than SR tires.
HR tires make it possible to run at higher speeds
Examples include the demand for VR tires and the emergence of flat tires with better handling stability.

However, from the vehicle perspective, there is also a demand for tires that have the same flatness as conventional tires that can be driven at high speeds and have excellent handling stability due to tire housing issues.

Generally, a radial tire consists of a pair of left and right bead parts, a pair of left and right sidewall parts connected to the bead parts, and a tread part located between the sidewall parts. Cord angle to direction is 70~90°
A carcass layer is folded back from the inside of the tire to the outside of the tire, and a plurality of belt layers are arranged on the carcass layer in the tread portion.

As described above, in a radial tire, since the reinforcing cords of the carcass layer are arranged at substantially 90 degrees with respect to the circumferential direction of the tire, the sidewall portion of the radial tire easily deforms during running. Therefore, while good riding comfort in the vertical direction can be obtained, excessive deformation tends to cause delays in steering response and poor stability in the longitudinal and lateral directions.

In the past, tire manufacturers have attempted to improve this problem by placing reinforcing sheets made of organic fiber cords on the outside or inside of the tire in the bead filler at the bead to increase the rigidity of the bead. . However, since this reinforcing sheet is made of the same material as the conventional carcass layer constituent material, its reinforcing properties are insufficient, and it does not meet the above-mentioned requirements, i.e., it is possible to drive at high speeds with the same aspect ratio as before, and it also has handling stability. This did not meet the demand for a tire with excellent performance.

Afterwards, it was proposed that a reinforcing sheet made of steel cord be used as the bead reinforcing layer, based on the realization that a material similar to that of the carcass layer constituent material was insufficient. However, in this case, although effects such as improved high-speed performance and handling stability were observed,
Riding comfort deteriorates due to the high bending rigidity of the steel cord, so it was necessary to improve this. Therefore, the present inventors considered using an aromatic polyamide fiber cord called Kevlar, which has significantly lower bending rigidity than steel cord, for the bead portion reinforcing layer. However, because aromatic polyamide has the property of being extremely strong in tension but weak in compression due to its crystal structure, this aromatic polyamide fiber cord reinforcing layer is simply used as a bead filler in the tire, similar to the conventional bead reinforcing layer. If the bead is placed only on the outside or inside, it will break due to the compressive strain generated within the bead, and its strong tensile strength characteristics cannot be utilized.

[Purpose of the invention]

The present invention improves durability by properly arranging an aromatic polyamide fiber cord layer in the bead portion, thereby improving handling stability and high-speed durability without compromising ride comfort. The purpose is to provide radial tires.

[Structure of the invention]

The present invention that achieves this object consists of a pair of left and right bead portions in which a bead filler is arranged on the bead wire, a pair of left and right sidewall portions connected to the bead portions, and a tread portion located between the sidewall portions. The cord angle between the pair of left and right bead portions with respect to the tire circumferential direction is 70~
In a pneumatic radial tire for a passenger car, the pneumatic radial tire is equipped with a carcass layer made of an organic fiber cord having an angle of 90 degrees, and a plurality of belt layers are arranged on the carcass layer in the tread portion, and the bead filler is attached to the outer upper part of the tire. It is composed of an upper bead filler and a lower bead filler that are divided in a diagonal curve from the inner side to the lower part of the tire, and from the inside of the tire of the lower bead filler on the upper surface of the bead wire to the outside of the tire of the upper bead filler through the dividing surface of this bead filler. , a reinforcing layer made of aromatic polyamide fiber cord is arranged around the entire circumference of the tire so that the cord angle intersects with the carcass layer; Height H from the bead toe to the midpoint of the tire's rotational axial length
is higher than the flange height G and of the height G.
The gist of the present invention is a pneumatic radial tire characterized in that the reinforcement layer is lower than 2.5 times, so that the reinforcing layer is disposed in a tensile stress region when a load is applied.

Hereinafter, the configuration of the present invention will be explained in detail.

FIG. 1 is a half-sectional explanatory diagram of an example of a pneumatic radial tire of the present invention.

In Fig. 1, the cord angle between the pair of left and right bead portions 1, 1 with respect to the tire circumferential direction is 70° to
A carcass layer 4 is arranged which is 90°. Also,
On the carcass layer 4 in the tread section 3, two belt layers 5 are arranged in an annular manner over almost the entire area of the tread section 3. A bead wire 2 is provided in an annular shape in the bead portion 1, and a lower bead filler 6 and an upper bead filler 7, which are divided into upper and lower parts, are arranged thereon. The dividing surface between the lower bead filler 6 and the upper bead filler 7 is diagonally curved from the upper part of the outside of the tire to the lower part of the inside of the tire, and the aromatic polyamide fiber cord 8 as a reinforcing layer is spread throughout the tire along the dividing surface. It is inserted all the way around. The lower bead filler 6 and the upper bead filler 7 comply with JIS K 6361.
The tire has a hardness of 70 to 97 according to JIS K 6361, a 50% modulus of elasticity of 20 to 100 Kg/cm ² according to JIS K 6361, and is located at a position of 60% or less of the tire cross-sectional height T. The carcass layer 4 is provided with two layers, an inner layer and an outer layer, and the end portion of the inner carcass layer 4 is folded back around the bead wire 2 from the inside of the tire to the outside of the tire on the outer surface of the lower bead filler 6. The folded end of this carcass layer 4 is arranged at a position higher than at least the rim flange height G. Further, the outer carcass layer 4 covers the outer sides of the upper bead filler 7 and the lower bead filler 6, and is rolled down to the lower side of the bead wire 2.

It is sufficient that at least one carcass layer 4 is disposed, and as its cord, chemical fibers such as nylon, polyester, and aromatic polyamide fibers are generally used.

As the cord constituting the belt layer 5, cords normally used for tires may be used, and cords of steel, aromatic polyamide fiber, rayon, etc. are preferable, and cords of nylon, polyester, etc. can be used. .

Furthermore, a belt cover layer (not shown) may be provided on the belt layer 5 to improve high-speed durability. Nylon cord is generally used as the cord for this belt cover layer. Its cord angle is virtually 0° with respect to the tire circumferential direction.
(parallel).

Note that the above configuration is intended to exhibit performance comparable to that using steel cords in terms of high-speed running performance and steering stability.

(1) In the present invention, as shown in FIG. 1, the bead filler is divided into an upper bead filler 7 and a lower bead filler 6 in an oblique curve from the upper outer side of the tire to the lower inner side of the tire, and aromatic The polyamide fiber cord layer 8 is arranged from the inside of the tire on the upper surface of the bead wire 2, through the inside of the tire on the lower bead filler 6, and to the outside of the tire on the upper bead filler 7. This is for the following reasons.

Conventionally, in order to reinforce the area around the bead, a cord layer of organic fibers such as nylon or a steel cord layer has been arranged at the bead, as described above. However, in the organic fiber cord layer,
Its reinforcing effect is not sufficient. This is because the rigidity (tensile rigidity, bending rigidity, etc.) of the organic fiber is not sufficiently high. On the other hand, although the steel cord layer has sufficient rigidity, the rigidity (particularly the bending rigidity) is too high, so if the steel cord layer is used as a bead reinforcing layer, riding comfort will deteriorate. Further, when a steel cord layer is used, there is a problem in that the tire weight becomes large.

On the other hand, aromatic polyamide fibers have sufficient rigidity compared to conventional organic fibers, and because their rigidity is lower than the rigidity of steel cords, especially the bending rigidity, they have the effect of reinforcing the bead without impairing riding comfort. can be accomplished. In addition, in terms of weight, the aromatic polyamide fiber cord is much lighter than the steel cord and is comparable to organic fiber, so there is little increase in the weight of the tire.

By reinforcing the area around the bead in this way, it is possible to suppress the movement of the bead of the tire during running and to increase the rigidity around the bead. Therefore, it is possible to sufficiently suppress the movement near the bead portion during high-speed driving, thereby delaying the generation of standing waves, and it is also possible to sufficiently increase lateral rigidity, thereby sufficiently improving steering stability. becomes possible.

By the way, aromatic polyamide fibers are known to be extremely strong in tension but weak in compression due to their crystal structure. Therefore, when an aromatic polyamide fiber cord layer is placed on the outside of the tire as in the conventional bead reinforcement structure, when the bead is subjected to bending deformation using the rim flange as a fulcrum, the compressive force is It is not preferable because it joins the polyamide fiber cord and reduces durability. Therefore, in the present invention, as described above, the aromatic polyamide fiber cord layer 8 is arranged from the vicinity of the bead wire 2 on the inside of the tire, passing between the upper bead filler 7 and the lower bead filler 6, and extending to the sidewall portion 10. In this way, the high modulus function of aromatic polyamide fibers can be effectively utilized.

The aromatic polyamide fiber cord constituting the aromatic polyamide fiber cord layer 8 is not particularly limited as long as it is a cord obtained from aromatic polyamide fiber. However, the following code is preferable.

That is, an aromatic polyamide fiber having a tensile strength of 150 Kg/mm ² or more and a tensile modulus of 3000 Kg/mm ² or more has a weight of 10 to 10% of the weight per unit length of the fiber.
After applying 50% adhesive, twisting was applied so that the twist coefficient K value expressed by the following formula was in the range of 1500≦K≦3500. In addition, especially 2800≦K
When it is ≦3400, the bending fatigue resistance of the cord is improved and the durability of the aromatic polyamide fiber cord layer 8 is improved, which is more preferable.

K=T√ K: Twist coefficient T: Number of twists of the cord (twists/10cm) D: Total denier number of the cord As the adhesive, a mixture of resorcinol/formalin initial condensate and rubber latex (hereinafter referred to as
(abbreviated as RFL) may be used. A cord can be produced by impregnating aromatic polyamide fibers with this RFL, drying and heat-treating the fibers, and then twisting the fibers to a predetermined degree.

The amount of RFL attached to aromatic polyamide fiber is
Preferably it is 10-50%. If it is less than 10%, not only will the adhesion between the obtained aromatic polyamide fiber cord and the coated rubber (covering rubber) be insufficient, but also the bending fatigue resistance of the aromatic polyamide fiber cannot be improved. If it exceeds %, not only will the adhesive layer be insufficiently dried during drying heat treatment due to its thickness, but also air bubbles will occur in the adhesive layer.
This is because it is difficult to obtain a uniform code. A more preferable amount of RFL attached to aromatic polyamide fiber is
It is 20-40%.

Furthermore, when applying RFL to aromatic polyamide fibers, it is important to sufficiently impregnate RFL into the aromatic polyamide fiber filaments in order to improve the bending fatigue properties of the aromatic polyamide fibers. For this purpose, it is preferable that the aromatic polyamide fiber filament is impregnated with RFL in an open state.

The twisted structure may be a so-called double-twisted structure in which several aromatic polyamide fibers are first twisted, and then those several fibers are combined and final twisted. A single-twist structure that simply adds twist to the fiber threads may also be used.

The aromatic polyamide fiber cord layer 8 is made by embedding the above-mentioned aromatic polyamide fiber cord in 100% coated rubber (covering rubber) with a modulus of 30 to 70 kg/cm ² . Cord densities containing 20 to 60 (parallel) aromatic polyamide fiber cords are preferred.

If the 100% modulus of the coated rubber is less than 30 kg/cm ² , the elasticity of the bead reinforcing layer decreases and the reinforcing effect cannot be exerted, resulting in a decrease in handling stability.
If it exceeds 70 kg/cm ² , the coating rubber becomes too hard and productivity deteriorates, and for example, heat is generated during coating, resulting in a scorch phenomenon, so-called burning, which is not preferable.

Therefore, it is preferable that the coated rubber has a 100% modulus of 30 to 70 kg/cm ² .

Furthermore, if the number of cords to be driven exceeds 60, the penetration of the coated rubber between the cords will be inhibited, leading to a decrease in adhesive strength, so it is not preferable;
If the thickness is less than 100 mm, the reinforcing effect will be insufficient.

The cord of the aromatic polyamide fiber cord layer 8 is:
It is preferable that the cord intersects the cord of the carcass layer 4 at an angle of 30° to 80°. By intersecting in this way, each carcass cord is tightly bound,
The reinforcing effect of the bead reinforcement layer is significantly demonstrated, making it possible to improve high-speed durability and handling stability. Furthermore, if this intersection angle exceeds 80°, it is not preferable because it not only deteriorates workability and makes it difficult to cut, but also tends to cause "wrinkles" during the molding operation. If it is less than 30°, the binding force of each carcass cord will decrease, which is not preferable.

(2) In addition, in the present invention, in the tire shown in FIG. 1, the aromatic polyamide fiber cord layer 8
The bead toe 1 to the part sandwiched between the upper bead filler 7 and the lower bead filler 6, that is, the midpoint of the length in the tire rotational axis direction of the pinching area N
The height H from 1 is higher than the flange height G of the rim flange 9 and 2.5 of the flange height G.
It was lower than double that.

As a result, the aromatic polyamide fiber cord layer 8
selectively placed in areas subject to tensile loads,
This is because it is possible to place the device in the best possible position so as not to place it in an area where a compressive load is applied.

In the bead part 1, one end of the aromatic polyamide fiber cord layer 8 is arranged in a part away from the rim flange 9, which is the fulcrum of bending, that is, in the tensile area caused by bending, while in the sidewall part 10, one end of the aromatic polyamide fiber cord layer 8 is arranged on the tire surface side, That is, the other end of the aromatic polyamide fiber cord layer 8 is arranged in the tensile region caused by bending, and the length of the pinching region N, which is the inflection point of the aromatic polyamide fiber cord layer 8, in the tire rotational axis direction. This is because the midpoint can be located near the inflection point of bending deformation of the bead portion 1 and the sidewall portion 10. Therefore, since the aromatic polyamide fiber cord layer 8 is arranged over its entire length only in the tensile region, the presence of this aromatic polyamide fiber cord layer 8 with extremely high tensile strength makes it possible to resist even extreme overloads. It can exhibit sufficient load durability even when the load is applied. Note that the height H is preferably 1.5G≦H≦2.25G because this provides the best durability.

Further, the height H is smaller than the height F from the bead toe 11 to the upper end of the lower bead filler 6,
It is preferably 80% or less of the height F.

The height C from the bead toe 11 to the upper end of the aromatic polyamide fiber cord layer 8 is the tire cross-sectional height T
75% or less, preferably lower than the tire maximum width position. This is because if it is too high, the upper end of the aromatic polyamide fiber cord layer 8 will easily break. That is, the higher the height, the closer the upper end of the aromatic polyamide fiber cord layer 8 is to the tire shoulder, that is, the area where bending deformation is large during running, and the durability is significantly reduced.

〔Effect of the invention〕

As explained above, the tire of the present invention has the following effects (a), (b), and (c) because the aromatic polyamide fiber cord layer of a predetermined height is provided as a reinforcing layer at a predetermined position of the bead part. can play.

(a) Since the aromatic polyamide fiber cord layer is selectively placed in areas where tensile loads are applied, avoiding areas where compressive loads are applied, the load durability of the tire can be significantly improved.

(b) Compared to conventional tires in which a bead reinforcing layer made of organic fiber cord is placed in the bead, the reinforcing effect is greater and the tire has excellent high-speed performance and handling stability.

(c) Compared to conventional tires that use steel cord for the bead reinforcement layer, the bending rigidity is significantly lower, resulting in superior ride comfort.

Therefore, according to the present invention, it is possible to sufficiently improve handling stability and high-speed durability without causing deterioration of ride comfort.

EXAMPLES The effects of the present invention will be specifically explained below with reference to Examples.

Example Inventive tire A, comparative tire B, and comparative tire C having the following specifications were each produced.

(1) Invention tire A: Tire size 195/70HR14. The position of the aromatic polyamide fiber cord layer is the same as in FIG. Aromatic polyamide fiber cord layer has 100% modulus
5cm perpendicular to the cord in 45Kg/ ^cm2 rubber
40 aromatic polyamide fiber cords (1500d/
2) and the intersection angle to the carcass cord.
Placed at 60°, thickness 1.0mm. Height C = 40% of height T.
Length of clamping area N = 40% of height F. Flange height G = 18mm (51/2JJ x 14). Height H = 1.5G.

The carcass layer consists of two 1000d/2 polyester layers arranged in a radial carcass shape.

The belt layer has a two-layer structure consisting of 1x5 (0.25) steel cords that intersect with each other at 20 degrees to the tire circumferential direction.

(2) Comparison tire B: Tire size 195/70HR14. The aromatic polyamide fiber cord layer is located inside the lower bead filler as shown in Figure 2a. The height of the lower bead filler is the same as the height of the upper bead filler in the tire A of the present invention (however, there is no upper bead filler). C=0.4T. The rest is the same as the tire A of the present invention described above.

(3) Comparison tire C: Tire size 195/70HR14. The aromatic polyamide fiber cord layer is located outside the lower bead filler as shown in Figure 2b. The height of the lower bead filler is the same as the height of the upper bead filler in the tire A of the present invention (however, there is no upper bead filler). C=0.4T. The rest is the same as the tire A of the present invention described above.

The following tests were conducted on the above-mentioned invention tire A, comparative tire B, and comparative tire C.

Indoor load durability test: Conducted using an indoor drum testing machine (diameter 1707 mm).

The test conditions were: rim 51/2JJ x 14, air pressure P = 2.5Kg/cm ² , and constant speed 81Km/hr. The load increased from 520Kg to 70Kg every 4 hours until it failed.

These results are expressed as an index in FIG. 3, with the indoor load durability of tire A of the present invention being set as 100. The larger the number, the better the indoor load durability performance.

From FIG. 3, it can be seen that the tire A of the present invention exhibits good indoor load durability.

In addition, in FIG. 3, in the tire A of the present invention, the entire aromatic polyamide fiber cord layer is destroyed, whereas in the comparative tire B, the end of the aromatic polyamide fiber cord layer on the sidewall side is destroyed, and in the comparative tire C, the aromatic polyamide fiber cord layer is destroyed. The end of the aromatic polyamide fiber cord layer on the rim flange side was destroyed.

Furthermore, subsequent tests revealed that the carcass layer was
It has been found that the layered tire of the invention having the structure shown in FIG. 2c also exhibits good indoor load endurance performance.

Further, tests were conducted to determine how the ratio H/G of the height H to the flange height G affects tire performance. The results are expressed as an index in FIG. In addition, when H/G = 1, the destruction of the aromatic polyamide fiber cord layer end on the rim flange side is large;
On the other hand, when H/G=3, the destruction of the ends of the aromatic polyamide fiber cord layer on the sidewall side was relatively large. Therefore, if H/G is greater than 1, it is 2.5.
I have found that the smaller size is best.

Ride comfort performance test: As a ride comfort performance test, a test was conducted using an indoor protrusion tester.

The indoor protrusion tester is a drum with a diameter of 2500 mm and a semicircular protrusion with a diameter of 20 mm attached to one location on the circumference. The magnitude of the axial force is measured by detecting the axial force in the longitudinal direction when the test tire rides over this protrusion, and this is taken as a representative value of ride comfort performance.

The test conditions were: rim 51/2JJ x 14, air pressure P = 1.9Kg/cm ² , load W = 520Kg, speed V = 60,
I ran at an average speed of 80, 100, and 120Km/hr. The results are expressed as an index in FIG. The smaller the value, the better the ride comfort performance.

From FIG. 5, it can be seen that the tire A of the present invention is excellent in ride comfort performance.

Maneuvering stability test: As a maneuvering stability test, a test was conducted using an indoor cornering test machine.

The indoor cornering tester uses the value obtained by dividing the cornering force generated when a tire is given a slip angle of 2° on a drum with a diameter of 2500 mm by 2 as a substitute value for handling stability.

The test conditions were: rim 51/2JJ x 14, air pressure P = 1.9Kg/cm ² , load W = 520Kg, speed V = 20Km/
It is hr. The results are expressed as an index in FIG. The larger the number, the better the steering stability.

From FIG. 6, it can be seen that the tire A of the present invention is excellent in handling stability.

[Brief explanation of the drawing]

FIG. 1 is a half-sectional explanatory diagram of an example of the pneumatic radial tire of the present invention, and FIGS. 2 a to 2 c are, respectively,
It is an enlarged explanatory view of a tire bead part. Fig. 3 is an explanatory diagram showing the indoor load durability of tires as a graph, Fig. 4 is an explanatory diagram showing the relationship between tire performance and H/G ratio, Fig. 5 is an explanatory diagram showing the ride comfort of tires as a graph, 6
The figure is an explanatory diagram showing the steering stability of the tire in a graph. 1...Bead part, 2...Bead wire, 3...
Tread section, 4...Carcass layer, 5...Belt layer, 6...Lower bead filler, 7...Upper bead filler, 8...Aromatic polyamide fiber cord layer, 9...Rim flange, 10...Side wall part , 11...Bead toe.

Claims (1)

[Scope of Claims] 1. Consisting of a pair of left and right bead portions in which a bead filler is arranged on the bead wire, a pair of left and right sidewall portions connected to the bead portions, and a tread portion located between the sidewall portions, A carcass layer made of an organic fiber cord having a cord angle of 70 to 90 degrees with respect to the tire circumferential direction is installed between the pair of left and right bead parts, and a plurality of belt layers are arranged on the carcass layer in the tread part. In the pneumatic radial tire for passenger cars, the bead filler is composed of an upper bead filler and a lower bead filler that are divided into an obliquely curved shape from the upper outer side of the tire to the lower inner side of the tire, and the A reinforcing layer made of an aromatic polyamide fiber cord is arranged over the entire circumference of the tire from the inside of the tire of the lower bead filler on the upper surface of the bead wire to the outside of the tire of the upper bead filler so as to intersect the cord angle with the carcass layer. Height H from the bead toe to the midpoint of the length in the tire rotational axis direction of the portion of the reinforcing layer sandwiched between the upper bead filler and the lower bead filler
is higher than the flange height G and of the height G.
2. A pneumatic radial tire, characterized in that the reinforcing layer is placed in a tensile stress region when a load is applied.