JPH0585362B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a radial tire for a passenger car that has improved steering stability, ride comfort, and high-speed durability by improving the tire bead area.

[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 can run 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.

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 effects such as improved high-speed performance and handling stability were observed,
The deterioration in riding comfort caused by the high bending rigidity of the steel cord was unbearable, and further improvements were necessary.

[Purpose of the invention]

The present invention was conceived in view of the above-mentioned circumstances, and makes it possible to use carbon fiber cords for the bead reinforcement layer, thereby improving handling stability and high-speed durability without impairing ride comfort. The purpose of this invention is to provide a radial tire for passenger cars.

[Structure of the invention]

For this reason, the present invention provides a tire having a bead portion in which a bead filler is arranged on a bead wire and a carcass layer is folded back from the inside of the tire to the outside of the tire so as to wrap the bead filler around the bead wire. A carbon fiber cord layer is arranged between the carcass layer and the inner liner over the entire circumference of the tire, and the height of the carbon fiber cord layer from the bead heel to the upper end is greater than the height of the bead filler from the bead heel to the upper end. In addition, the carbon fiber cord has a tensile strength of 100 kg/mm ² or more and a tensile modulus of 5000.
Kg/mm ² or more carbon fiber has twist coefficient K value of 0≦K≦
The 100% modulus of the coated rubber is 30 to 70.
The gist of the present invention is a pneumatic radial tire for a passenger car, characterized in that the pneumatic radial tire has a weight of 1 kg/cm ² and is arranged so as to intersect the cords of the carcass layer at an angle of 20° to 70°.

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

FIG. 1 is a half-sectional explanatory view of an example of a pneumatic radial tire for a passenger car according to the present invention, and FIG. 2 is an enlarged explanatory view of a bead portion thereof.

In these figures, a pair of left and right bead portions 1,
Between 1 and 2, the cord angle with respect to the tire circumferential direction is
A carcass layer 4 is arranged which is between 70° and 90°.
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 tread portion 3. A bead wire 2 is provided in an annular shape in the bead portion 1, and a bead filler 6 is arranged on the bead wire 2. The carcass layer 4 is folded back from the inside of the tire to the outside of the tire so as to wrap the bead filler 6 around the bead wire 2 to form a folded part 4a. Further, an inner liner 7 is provided on the inner surface of the tire.

It is sufficient that at least one carcass layer 4 is arranged, and the cord thereof is generally made of chemical fiber such as nylon, polyester, or aramid (aromatic polyamide fiber).

The cords constituting the belt layer 5 may be those commonly used for tires, and cords of steel, aramid, rayon, etc. are preferred, 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).

(1) In the present invention, in the tires shown in FIGS. 1 and 2, a carbon fiber cord layer 8 is arranged between the carcass layer 4 on the inner liner 7 side and the inner liner 7 over the entire circumference of the tire. It is. 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 disadvantage in terms of weight that the tire weight becomes large.

On the other hand, carbon fiber has sufficient rigidity compared to conventional organic fibers, and its rigidity is lower than the rigidity of steel cord, especially the bending rigidity, so it can achieve the effect of reinforcing the bead without impairing riding comfort. be able to. Also, in terms of weight, carbon fiber cords are much lighter than steel cords and are comparable to organic fibers.

(2) In the present invention, as described above, the height h from the bead heel 9 to the upper end of the carbon fiber cord layer 8 arranged in the bead portion 1 is greater than or equal to the height t from the bead heel 9 to the upper end of the bead filler 6. (that is, h is equal to or greater than t).

That is, by arranging the carbon fiber cord layer 8 on the bead portion 1 and reinforcing the area around the bead as described above, it is possible to suppress the movement of the bead portion of the tire while driving and increase the rigidity around the bead portion. Furthermore, by setting the height h to be greater than or equal to t, it is possible to sufficiently suppress the movement near the bead portion during high-speed running and eliminate the generation of standing waves, and it is also possible to sufficiently increase the lateral rigidity. This is because it becomes possible to sufficiently improve steering stability.

Additionally, carbon fiber is known to be extremely strong in tension but weak in compression due to its crystal structure. Therefore, when a carbon fiber cord layer is placed on the outside of the tire as in the conventional bead reinforcement structure, compressive force is applied to the carbon fiber cord when the bead undergoes bending deformation using the rim flange as a fulcrum. This is not preferable because it increases the durability and reduces the durability. Therefore, in the present invention, as described above, a carbon fiber cord layer 8 is provided between the carcass layer 4 on the inner liner 7 side and the inner liner 7.
Moreover, the height h thereof is set to be greater than the height t, thereby making it possible to effectively exhibit the high modulus function of the carbon fiber.

The carbon fiber cord layer 8 may have two or more layers. Further, the carbon fiber cord constituting the carbon fiber cord layer 8 has a tensile strength of 100 Kg/mm ² or more, a tensile modulus of 5000 Kg/mm ^{2 or more, and preferably a tensile strength of 200 Kg/mm 2} or more.
After applying an adhesive in an amount of 10 to 50% of the weight per unit length of carbon fiber to carbon fiber having properties of Kg/mm ² or more and tensile modulus of 15000 Kg/mm ² or more, the twist expressed by the following formula is applied. Twisting is added so that the coefficient K value falls within the range of 0≦K≦1800.

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

The amount of RFL attached to the carbon fiber is preferably 10 to 50%. If it is less than 10%, not only will the adhesion between the obtained carbon fiber cord and the coated rubber (covering rubber) be insufficient, but also the bending fatigue resistance of the carbon fiber will not be improved, while if it exceeds 50%, This is because not only is the adhesive layer insufficiently dried during drying heat treatment because the adhesive layer is thick, but also air bubbles are generated in the adhesive layer, making it difficult to obtain a uniform cord. More preferably, the amount of RFL attached to carbon fiber is 20~
It is 40%.

Also, when applying RFL to carbon fiber,
It is important to sufficiently impregnate RFL into carbon fiber filaments to improve the bending fatigue properties of carbon fibers. For this purpose, it is preferable to impregnate the carbon fiber filament with RFL in an open state.

In this way, RFL-treated carbon fibers are
Since the fibers are sufficiently attached, the convergence of the fibers can be maintained even without twisting, but it is preferable to add some twist because the convergence will be better. When twisting is applied, if the twist is too large, the high strength and high modulus properties of carbon fiber will be significantly impaired. Therefore, when twisting, the twist coefficient K is 1800 or less,
It is preferable that 300≦K≦1500.

The twisted structure may be a so-called twisted structure in which several carbon fibers are first twisted individually, and then those several carbon fibers are put together and a final twist is added. A single-twist structure that simply adds twist may also be used.

The carbon fiber cord layer 8 is made by embedding the above-mentioned carbon fiber cord in 100% cord rubber (covering rubber) with a modulus of 30 to 70 Kg/cm ² , and the carbon fiber cord has a modulus of 20 to 5 cm per 5 cm in the cord rubber in the direction perpendicular to the cord. A cord density containing 60 (parallel) carbon fiber cords is preferred.

If the 100% modulus of the cord 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 steering 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, the coated rubber should have 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 cords of the carbon fiber cord layer 8 are connected to the carcass layer 4.
Place it so that it intersects the cord at 20° to 70° (θ in Figure 2). By intersecting in this way, each carcass cord is firmly bound, so the reinforcing effect of the bead reinforcing layer is significantly exhibited, and it is possible to improve high-speed durability and handling stability. Furthermore, if the intersection angle θ exceeds 70°, the workability will deteriorate and it will not only be difficult to cut, but also "wrinkles" will easily occur during the molding operation, which is not preferable. If it is less than 20°, the binding force of each carcass cord will decrease, which is not preferable.

〔Effect of the invention〕

As explained above, in the tire of the present invention, a carbon fiber cord layer is arranged between the carcass layer on the inner liner side and the inner liner over the entire circumference of the tire, and the height from the bead heel to the upper end of the carbon fiber cord layer is The carbon fiber cord has a tensile strength of 100 kg/mm ² or more and a tensile modulus of 5000 kg/mm ² or more, and the twist coefficient K value is 0.
It has a twisted structure with twists in the range of ≦K≦1800, and the 100% modulus of the cord rubber is
Since the weight is 30 to 70 Kg/cm ² and the cords are arranged to intersect at 20° to 70° with respect to the cords of the carcass layer, the following effects (a), (b), and (c) can be achieved.

(a) By arranging the above carbon fiber cord layer between the carcass layer on the inner liner side and the inner liner, it overcomes the weakness of the carbon fiber cord to compression and improves durability. By making it possible to use carbon fiber cord, the following (b) and (c) are possible.

(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 excellent high-speed performance and 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 A tire of the present invention, Comparative Tire 1, and Comparative Tire 2 having the following specifications were respectively produced.

(1) Tire of the present invention: Tire size 175/70HR 13. The position of the carbon fiber cord layer is as shown in Fig. 1. The carbon fiber cord layer is made of 40 carbon fiber cords per 5 cm perpendicular to the cord in a rubber having a 100% modulus of 45 Kg/ ^cm2. , 10 ^S × 10 ^Z (T/10cm),
Adhesive adhesion amount: 30%] is embedded, placed at an angle of 30° to the carcass cord, width 50mm, thickness 1.5
mm. The carcass layer has one layer of 1500d/2 polyester cord arranged in a radial carcass shape. The belt layer is made of 1×5 (0.25) steel cords that intersect with each other at 20 degrees to the tire circumferential direction.
Layered structure. h=50mm, t=40mm.

(2) Comparison 1: Tire size 175/70HR 13. The bead portion reinforcing layer is located outside the carcass layer folded portion 4a as shown in FIG. Note that 8a in FIG. 3 indicates a bead portion reinforcing layer made of nylon cord. The bead reinforcement layer is made of rubber with a 100% modulus of 27 kg/cm ² and is 5 cm perpendicular to the cord.
40 840d/2 nylon cords are arranged at an angle of 30° to the carcass cord, width 50mm,
Thickness: 1.0mm. The rest is the same as the above-mentioned tire of the present invention.

(3) Comparison tire 2: Tire size 175/70HR 13. The bead portion reinforcing layer is located outside the carcass layer folded portion 4a, as shown in FIG. Note that 8 in Figure 4
b shows a bead reinforcement layer made of steel cord. The bead reinforcement layer has 100% modulus.
40 steel cords [1 x 5 (0.225)] are placed per 5cm in the 45Kg/cm ² rubber in the direction perpendicular to the cord at an angle of 30° to the carcass cord, width 50
mm, thickness 1.5mm. The rest is the same as the above-mentioned tire of the present invention.

The following tests were conducted on the above-mentioned present invention tire, Comparative Tire 1, and Comparative Tire 2.

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 proxy for steering stability.

Test conditions are rim 5-J x 13, air pressure P = 1.9
Kg/cm ² , load W=405Kg, and speed 20Km/hr.
The results are expressed as an index in FIG. The larger the number, the better the steering stability performance.

Figure 5 shows the handling stability of a tire using nylon cord as the bead reinforcement layer (comparative tire 1).
Expressed as an index of 100. It can be seen from FIG. 5 that the tire of the present invention is superior in handling stability by about 7% compared to Comparative Tire 1.

High-speed performance test: As a high-speed performance test, an indoor drum testing machine (diameter
1707mm).

The test conditions were: rim 5-J x 13, air pressure P
= 3.0Kg/cm ² , load W = 405Kg, speed 170Km/
The vehicle was run at a rate of 10 km/hr every 10 minutes until it broke down. The results are expressed as an index in FIG. The larger the number, the better the high-speed performance.

In FIG. 6, the high-speed performance of Comparative Tire 1 is set as 100 and expressed as an index. From FIG. 6, it can be seen that the tire of the present invention is superior in high-speed performance by about 3% compared to Comparative Tire 1.

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 are: rim 5-J x 13, air pressure P 1.9Kg/cm ² , load W = 405Kg, speed V = 60, 80,
I ran at an average speed of 100, 120Km/hr. This result is the seventh
The figure shows the index. The higher the number, the better the ride comfort performance.

Figure 7 shows the ride comfort performance of a tire using nylon cord as the bead reinforcement layer (comparative tire 1).
Expressed as an index of 100. From FIG. 7, it can be seen that the tire of the present invention is comparable to Comparative Tire 1 and superior to Comparative Tire 2.

[Brief explanation of the drawing]

FIG. 1 is a half-sectional explanatory view of an example of a pneumatic radial tire for a passenger car according to the present invention, and FIG. 2 is an enlarged explanatory view of its bead portion. FIGS. 3 and 4 are explanatory half-sectional views of an example of a conventional pneumatic radial tire for a passenger car, respectively. FIG. 5 is an explanatory diagram showing the handling stability of the tire in a graph, FIG. 6 is an explanatory diagram showing the high-speed performance of the tire in a graph, and FIG. 7 is an explanatory diagram showing the riding comfort of the tire in a graph. 1...Bead part, 2...Bead wire, 3...
Treaded portion, 4... Carcass layer, 5... Belt layer, 6... Bead filler, 7... Inner liner, 8... Carbon fiber cord layer.

Claims (1)

[Claims] 1. In a tire having a bead portion in which a bead filler is arranged on a bead wire and the carcass layer is folded back from the inside of the tire to the outside of the tire so as to wrap the bead filler around the bead wire, the carcass layer on the inner liner side and the inner liner A carbon fiber cord layer is arranged around the entire circumference of the tire between the carbon fiber cord layer, and the height from the bead heel to the upper end of the carbon fiber cord layer is greater than the height from the bead heel to the upper end of the bead filler, and the carbon fiber cord Tensile strength 100Kg/
It has a twisted structure in which carbon fibers with a tensile modulus of 5,000 Kg/mm ² or more and a tensile modulus of 5,000 Kg/mm ² or more are twisted so that the twist coefficient K value is in the range of 0≦K≦1,800.
A pneumatic radial tire for a passenger car, characterized in that the tire has a 100% modulus of 30 to 70 kg/cm ² and is arranged so as to intersect the cords of the carcass layer at 20° to 70°.