JPS6234806A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To improve the duration of a reinforcing layer to a bead section by configurating a device in such a way that a bead filler is divided into an upper and a lower section, and a cord layer made of aromatic polyamide fibers is provided from the inside of a tire to a side wall section passing through between the said divided bead fillers. CONSTITUTION:A radial carcass layer 4 is provided in a radial tire in such a way that it is turned up around a bead wire 2 from the inside to the outside, and a bead filler is arranged just above the bead wire 2. In this case, the bead filler is divided into an upper and a lower bead filler 6 and 7. In addition, a cord layer 8 made of aromatic polyamide fibers i provided as a reinforcing layer along the entire circumference of the tire passing through between the said upper and lower bead fillers 7 and 6 toward a sidewall section 10. And the height H of a point which is held by both the bead fillers 7 and 6 of the cord layer 8, and is equivalent to a middle point of the length of the bead fillers in the direction of a tire rotating shaft, is specified to be higher that the height G of a flange 9, but is lower than 2.5 times of the height G.

Description

[Detailed Description of the Invention] [Technical Part of the Invention] The present invention improves the durability of the bead reinforcing layer and provides an air-conditioning system that improves handling stability and high-speed durability without impairing ride comfort. Regarding 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, there is a demand for HR tires that can run at higher speeds than SR tires, a demand for VR tires that can run even faster, and a demand for flat tires that have 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.

Therefore, tire manufacturers have conventionally attempted to address various demands by adding a reinforcing sheet made of organic fiber cords called a bead reinforcing layer to the tire 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 the effects of improving high-speed performance and handling stability were recognized, the deterioration in ride comfort caused by the high bending rigidity of the steel cord was unbearable, and further improvements were needed. It was necessary.

Therefore, consideration was given to using an aromatic polyamide fiber cord called Kevlar, which has significantly lower bending rigidity than steel cord, for the bead reinforcement layer. However, when this aromatic polyamide fiber cord layer is arranged in the same way as in the conventional bead reinforcement layer, the aromatic polyamide fiber cord is extremely strong in tension due to its crystal structure but weak in compression, so the durability is reduced. It had the disadvantage of being inferior.

[Purpose of the invention]

The present invention improves the durability of the bead reinforcing layer by appropriately arranging the aromatic polyamide fiber cord layer as the bead reinforcing layer, and further improves handling stability and high speed without impairing riding comfort. The purpose is to provide a pneumatic radial tire with improved durability.

[Structure of the invention]

For this reason, the present invention provides a tire in which a bead filler is arranged on a bead wire, and a carcass layer has a bead portion folded back from the inside of the tire to the outside of the tire around the bead wire. and a side bead filler, and an aromatic polyamide fiber cord layer is arranged around the entire circumference of the tire from near the bead wire inside the tire, passing between the upper bead filler and the lower bead filler to the sidewall part, The height H from the bead toe to the midpoint of the length in the tire rotation axis direction of the portion of the aromatic polyamide fiber cord layer sandwiched between the upper bead filler and the lower bead filler is calculated as the flange height G ( In other words, JIS D
0 dimension according to 4102) and 2.
The gist of the present invention is a pneumatic radial tire characterized by having a lower height than 5 times.

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, a pair of left and right bead portions 1. In one hour,
A carcass layer 4 having a cord angle of 70° to 90° with respect to the tire circumferential direction is arranged.

Further, on the carcass layer 4 in the tread portion 3, two belt layers 5 are arranged in an annular manner over almost the entire area of the trend portion 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 are arranged on the bead wire 2. The carcass layer 4 is folded around the bead wire 2 from the inside of the tire to the outside of the tire.

It is sufficient that the carcass layer 4 has at least an IFi arrangement, 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, in order to improve high-speed durability, a belt cover layer (not shown) may be provided on the belt layer 5. Nylon cord is generally used as the cord for this belt cover layer.

The cord angle is substantially O” with respect to the tire circumferential direction.
(parallel).

(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, and the upper bead filler 7 and the lower bead filler The aromatic polyamide fiber cord layer 8 is disposed as a reinforcing layer over the entire circumference of the tire, passing between the tire and the sidewall portion 10. 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, the reinforcing effect of the organic fiber cord layer is not sufficient. This is the stiffness (tensile stiffness,
This is because the bending rigidity, etc.) is not sufficiently high. On the other hand, although the steel cord layer has sufficient rigidity, its rigidity (especially bending rigidity) is too high, so if the steel cord layer is used as a partial reinforcing layer, ride comfort will deteriorate. . In addition, when using a steel cord layer,
In terms of weight, there is also the disadvantage that the weight of the tires 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 when driving at high speeds, thereby preventing the occurrence of standing waves, and it is also possible to sufficiently increase lateral rigidity, thereby sufficiently improving steering stability. It becomes possible to do so.

By the way, due to its crystal structure, aromatic polyamide fiber has
It is known to be extremely strong in tension but weak in compression. 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 section undergoes bending deformation using the rim flange as a fulcrum, the compressive force is transferred to the aromatic polyamide fiber cord layer. This is not desirable because it adds to the cord and reduces durability. Therefore, in the present invention, as described above, the aromatic polyamide fiber cord layer 8 is disposed from near the bead wire 2 inside the tire, passes between the upper bead filler 7 and the lower bead filler 6, and extends to the sidewall portion 10. This enabled the aromatic polyamide fiber to effectively exhibit its high modulus function.

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, but the following cords are preferred.

That is, an aromatic polyamide fiber having a tensile strength of 150 kg/ml/iml/ and a tensile modulus of 3000 kg/m#i or more is coated with an adhesive in an amount of 10 to 50% of the weight per unit length of the fiber. After that, twist is added to the twist coefficient expressed by the following formula so that the value falls within the range of 1501≦3500. In addition, especially when it is set to 2800≦≦3400, the bending fatigue resistance of the cord improves,
This is further preferred because the durability of the aromatic polyamide fiber cord layer 8 is improved.

K=T, /""75" K: Twist coefficient T: Number of twists of the cord (twists/10c) D: Total denier number of the cord As the adhesive, a mixture of resorcinol/formalin initial condensate and rubber latex is used. (hereinafter abbreviated as RFL)
You can use 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 10 to 5.
Preferably it is 0%. If it is less than 10%, not only will the adhesion between the obtained aromatic polyamide fiber cord and the coated rubber (covering rubber) become insufficient, but also the bending fatigue resistance of the aromatic polyamide fiber cannot be improved;
This is because if it exceeds 0%, not only will the adhesive layer be insufficiently dried during the heat treatment for drying the adhesive, but also air bubbles will be generated in the adhesive layer, making it difficult to obtain a uniform cord. More preferably, the amount of RFL attached to the aromatic polyamide fiber is 20
~40%.

Furthermore, when applying RFL to aromatic polyamide fibers, it is important to sufficiently impregnate the aromatic polyamide fiber filaments with RFL in order to improve the bending fatigue properties of the aromatic polyamide fibers. For this purpose, it is preferred that the aromatic polyamide fiber filaments are 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 of the above-mentioned aromatic polyamide fiber cord with a 100% modulus of 30 to 70.
It is preferable to have a cord density of 20 to 60 (parallel) aromatic polyamide fiber cords per 5 cm in the direction perpendicular to the cord in the coat rubber.

The 100% modulus of coated rubber is 30kg/cn! If it is less than this, the elasticity of the bead reinforcing layer decreases and the reinforcing effect cannot be exerted, leading to a decrease in steering stability. 70kg/
If it exceeds cal, 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 undesirable.

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

Further, it is preferable that the number of cords is more than 60, since the penetration of the coated rubber between the cords will be inhibited, leading to a decrease in adhesive strength, while if it is less than 20, the reinforcing effect will be insufficient.

Preferably, the cords of the aromatic polyamide fiber cord layer 8 intersect the cords of the carcass WI4 at an angle of 20° to 70°. By intersecting in this way, each carcass cord is firmly bound, so the reinforcing effect of the bead portion reinforcing layer is significantly exhibited, and it is possible to improve high-speed durability and handling stability. Also, if this intersection angle exceeds 70°,
This 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. 20°
If it is less than this, the binding force of each carcass cord will decrease, which is not preferable.

(2) In the present invention, in the tire shown in FIG. 1, the portion sandwiched between the upper bead filler 7 and the lower bead filler 6 of the aromatic polyamide fiber cord N8,
That is, the height H from the bead toe 11 to the midpoint of the length of the pincer area N in the tire rotational axis direction 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.

This is because it becomes possible to place the aromatic polyamide fiber cord layer 8 in the most favorable arrangement state against external forces.

In the bead portion 1, one end of the aromatic polyamide fiber cord layer 8 is disposed in a portion away from the rim flange 9, which is the fulcrum of bending, that is, in the tensile region caused by bending, while in the sidewall portion 10, one end is placed on the tire surface side, that is, in the tensile area caused by bending. The other end of the aromatic polyamide fiber cord layer 8 is arranged in the tension region generated by 1 and side wall part 10
This is because it can be located near the inflection point of bending deformation. Therefore, even if an extreme overload is applied, sufficient load durability can be exhibited.

Note that it is preferable that the height H is 1.50≦H≦2.25G because this provides the best durability.

In addition, the height H is the bead toe 1 of the lower bead filler 6.
Less than the height F from 1 to the top edge, but 80% of the height F
It is preferable that it is below.

The height C from the bead toe 11 to the upper end of the aromatic polyamide fiber cord layer 8 is 75% or less of the tire cross-sectional height T,
Preferably, it is 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, as the height increases, the upper end of the aromatic polyamide fiber cord layer 8 comes closer to a portion of the tire shoulder, that is, an area where bending deformation is large during running, and the durability is significantly reduced.

〔Effect of the invention〕

As explained above, in the tire of the present invention, the aromatic polyamide fiber cord layer of a predetermined height is provided at a predetermined position in the bead portion, so that the following effect (a) can be achieved.

(bl, (C) can be played.

(a) Since the aromatic polyamide fiber cord layer is arranged so as to successfully avoid compressive loads, which are the weak point of aromatic polyamide fiber cords, the load durability of the tire can be significantly improved. - (bl) Comparing to conventional tires in which a one-bead reinforcing layer is placed in the bead, organic fiber cords have a greater reinforcing effect and are superior in high-speed performance and handling stability.

(Q) Compared to conventional tires that use steel cord for the bead reinforcement layer, the bending rigidity is significantly lower, so the ride comfort is excellent.

Therefore, according to the present invention, steering stability and high-speed durability can be sufficiently improved without deteriorating ride comfort.

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

EXAMPLE Tire A of the present invention, comparative tire B, and comparative tire C having the following specifications were respectively produced.

(11 Tire A of the present invention: Tire size 195/701 (R14°) The position of the aromatic polyamide fiber cord layer is the same as in FIG. 1. The aromatic polyamide fiber cord layer has a 100% modulus of 45k.
5c + 4 per a in the direction perpendicular to the cord in g/aa rubber
0 aromatic polyamide fiber cords (1500d/2
') is embedded, and the intersection angle to the carcass cord is 30°
Placed with thickness 1. (1++n+ *Height C - 4 of height T
0%. Length of pincer area N = 40% of height F.

Flange height G = 18mm (5!4JJX14).

Height H: 1.5 G.

The carcass layer is a 1500d/2 polyester layer arranged in a radial carcass shape.

The belt layer is steel cord I x 5 (0,25)
2 which intersect with each other at 20° to the tire circumferential direction.
Layered structure.

(2) Comparative Tire B: Tire size 195/70HR14° The aromatic polyamide fiber cord layer was located inside the lower bead filler as shown in FIG. 2(a). 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
．． 47. The rest is the same as the tire A of the present invention described above.

(3) Comparative Tire C: Tire size: 195/7011R14° The aromatic polyamide fiber cord layer is located outside the lower bead filler as shown in FIG. 2(b). 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, and the others are the same as the above-mentioned invention tire A.

The following tests were conducted on the above-mentioned present invention tire A1 comparative tire B1 comparative tire C.

1. Testing was carried out using an indoor drum testing machine (diameter 1,707 mm).

As for the test conditions, Rim 5! AJJx14, air pressure P
= 2.5 kg/aJ, constant speed 81 km/hr.

The load increased from 520 kg to 70 kg every 4 hours until it failed.

These results are expressed as an index in FIG. 3, with the indoor load durability performance of the 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 tire of the present invention having the structure shown in FIG. 2(c) with a single carcass layer also exhibited good indoor load durability.

In addition, tests were conducted to determine how the ratio H/G between the height H and 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 N terminal on the rim flange side is large, while when H / G = 3, the destruction of the aromatic polyamide fiber cord layer terminal on the sidewall side is comparatively large. It was huge. Therefore, when H/G is greater than 1, it is 2.5
I have found that the smaller size is best.

Riding Engineering 111 Xiongbinyan; As a ride comfort performance test, a test was conducted using an indoor protrusion testing machine.

The indoor protrusion tester is a drum with a diameter of 2,500 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.

As for the test conditions, Rim 5! z[Jx14, air pressure P=
1.9kg/d, load W=520kg, speed V=60
The average speed was 80°, 100.120km/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.

J&K: As a handling stability test, we conducted a test using an indoor cornering test machine.

The indoor cornering tester uses the value obtained by dividing the cornering force generated when a slip angle of 2° is applied to a tire on a drum with a diameter of 2.500 mm divided by 2 as a substitute value for steering stability.

The test conditions were: rim 5% JJ x 14, air pressure P.
=1.9kg/cffl, load W=520kg,
The speed V=20 km/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 a pneumatic radial tire of the present invention, and FIGS. 2(a) to (c) are enlarged explanatory diagrams of tire bead defects. Figure 3 is an explanatory diagram showing the indoor load durability of tires as a graph, Figure 4 is a diagram of the relationship between tire performance and H/C ratio, and Figure 5 is a diagram showing the relationship between tire performance and H/C ratio.
The figure is an explanatory diagram showing the riding comfort of the tire in a graph, and FIG. 6 is an explanatory diagram showing the steering stability of the tire in a graph. DESCRIPTION OF SYMBOLS 1... Bead part, 2... Bead wire, 3... Tread part, 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 0

Claims (1)

[Claims] In a tire in which a bead filler is arranged on a bead wire, and a carcass layer has a bead portion folded around the bead wire from the inside of the tire to the outside of the tire, the bead filler is divided into an upper bead filler and a lower bead filler. , an aromatic polyamide fiber cord layer is disposed around the entire tire circumference from near the bead wire inside the tire to the sidewall portion through between the upper bead filler and the lower bead filler, and the aromatic polyamide fiber cord layer is arranged around the entire tire circumference. The height H from the bead toe to the midpoint of the tire rotational axis direction length of the portion sandwiched between the upper bead filler and the lower bead filler is higher than the height G of the flange, and the height G A pneumatic radial tire characterized by being lower than 2.5 times.