JPH06227209A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To provide a pneumatic radial tire for motor race, etc., which is equipped with an improved maneuverability, safety, and driving characteristic and also with a good enhanced high speed durability. CONSTITUTION:At least two carcass layers 4, 4' are installed between a left and a right bead core 5, and belt layers 2, 3 formed from steel cords are arranged on the periphery of the tread part 1. The carcass layers 4, 4' are arranged at a cord angle of 56-86 deg. to the tire circumference and in such a way as intersecting each other, and the steel cords are shaped in spiral form, wherein the conditions 0.01<=F<=0.05, 0.15<=d (in mm) <=0.40, and 2.0<=P (in mm) <=8.0 should be met, where (d) is diameter of unit wire 40, D is spiral diameter, P is pitch length of spiral, and parameter F to specify the spiral shape which is expressed by F=(D-d)/P.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire for competitions, and more specifically, to improve steering, stability and drivability, and particularly high speed durability which is the most important characteristic of this type of tire. Relates to a pneumatic radial tire for competition which is improved.

[0002]

2. Description of the Prior Art Unlike a pneumatic tire for a passenger car, which is used for a long period of time under mild conditions, a racing tire is subjected to a short period of use under extremely severe conditions.
For example, steering wheel operation during high-speed running, sudden braking from high speed, and conversely rapid acceleration from low speed are performed. Therefore, high-speed durability during high-speed running is the most important required characteristic for competition tires.

On the other hand, a radial tire has a problem that it is difficult to control maneuverability and stability because the ground contact area of the tread surface greatly changes during cornering during high speed running as compared with a bias tire. For this reason, in the case of radial tires used for competition, in order to ensure maneuverability, stability and drivability by increasing the contact area and reducing the change in contact area during cornering, the belt layer A steel wire with a smaller wire diameter than the steel cord used for general radial tires (0.0
(6 to 0.10 mm), a flexible steel cord formed by twisting a plurality of strands together is used to reduce the rigidity of the tread surface (tread portion).

However, as described above, the racing tires are used under extremely severe conditions. Therefore, if the twisted wire cord formed by bundling the ultrafine wires as described above is rubbed against each other, Due to the occurrence of wire breakage and the increase in the number of exposed wire ends at the end of the belt layer, problems such as induction of separation occur. Therefore, when trying to improve maneuverability, stability and driveability,
There was a problem that the most important high-speed durability for a racing tire was sacrificed, and it was difficult to achieve both at the same time.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to improve steerability, stability and driveability by constructing a steel cord of a belt layer from a single wire, and wire breakage caused by rubbing between wire strands. It is intended to provide a pneumatic radial tire for competition, in which the high speed durability is remarkably improved.

[0006]

According to the present invention, which achieves such an object, at least two bead cores are provided between a pair of left and right bead cores.
In a pneumatic radial tire for competition in which a carcass layer is mounted, and a belt layer made of steel cord is arranged on the outer peripheral side of the tread portion of the carcass layer, the carcass layer is at 56 to 86 ° with respect to the tire circumferential direction. At code angle,
And arranged so as to intersect with each other, the steel cord is composed of a single wire formed in a spiral shape, and the diameter F of the single wire, the spiral diameter D, the pitch length P of the spiral, and the parameter F for specifying the spiral shape.
= (D−d) / P is 0.01 ≦ F ≦ 0.05 0.15 (mm) ≦ d ≦ 0.40 (mm) 2.0 (mm) ≦ P ≦ 8.0 (mm) It is characterized by being set to.

Thus, the steel cord of the belt layer is composed of a single wire, and the single wire is shaped in a spiral shape, and the parameter F specified by the single wire diameter d, its spiral diameter D, and the spiral pitch length P is set. By keeping the range within a certain range, the rigidity of the single wire is softened, and the fatigue resistance (durability) against repeated bending load and compression load during high speed running is improved. In addition, since it is a single wire, it prevents wire breakage due to rubbing between bare wires like stranded cords, and it can be completely covered with coat rubber to prevent exposure at the edge of the belt layer. Prevents and improves separation resistance. Therefore, high-speed durability can be remarkably improved. In addition, the cord diameter when the wire cross-sectional area is the same as that of the stranded wire can be made smaller, and the coat rubber can be reduced to reduce the weight, and further, the gauge a between cords constituting the belt layer (the spiral diameter D of the single wire D Of the carcass layer of the two carcass layers, which are combined with the belt layer structure, and are inclined at a specific angle with respect to the tire circumferential direction. Therefore, the cornering power is increased, and the maneuverability, stability and drivability can be improved.

The structure of the present invention will be specifically described below with reference to the drawings. In FIG. 1, 1 is a tread portion,
Reference numerals 4 and 4'denominate two inner and outer carcass layers mounted between the pair of left and right bead doors 5 straddling the tread portion 1 and having a cord angle of 56 to 86 ° with respect to the tire circumferential directions E and E '. And are arranged so as to intersect with each other. The end portion of the inner carcass layer 4 is folded back from the inside of the tire so as to wrap around the bead filler 6 and rolled up, while the end portion of the outer carcass layer 4 ′ is located outside the folded portion of the inner carcass layer 4 to be the bead portion. It has been rolled down to the heel.

On the outer peripheral side of the outer carcass layer 4'of the tread portion 1, two inner belt layers 2 and an outer (outermost) belt layer 3 are respectively 10 to 40 in the tire circumferential directions E and E '.
They are arranged around the entire circumference of the tire so as to intersect each other at a cord angle of °. These belt layers 2 and 3 are
As shown in FIG. 2, a spiral single wire 40 is embedded as a reinforcing cord. The single wire 40 is shaped in a spiral shape as shown in FIG. That is, the single wire 40 having the diameter d
However, it is modeled with a spiral diameter D and a spiral pitch length P larger than the diameter d. The spiral diameter D corresponds to a spiral-shaped outer circumferential circle projected on a plane orthogonal to the wire longitudinal direction, as shown by a broken line in FIG.

In the tire of the present invention having such a structure, the at least two carcass layers 4 and 4'have a semi-radial structure having a cord angle of 56 to 86 ° to ensure proper side rigidity. Therefore, we try to improve the maneuverability and stability during high-speed driving. If the cord angle is less than 56 °, the straight running stability of the radial tire is impaired, and if it exceeds 86 °, the steering stability during high-speed cornering deteriorates.

On the other hand, at least two belt layers 2,
In No. 3, since the reinforcing cord is composed of the single wire 40, and the single wire 40 is shaped in a spiral shape, the tensile elastic modulus is lower than that of the straight single wire, so that the rigidity is relaxed. Therefore, even with a single wire, the fatigue resistance against repeated bending load and compression load can be improved, and the durability of the belt layer can be improved to the same level as that of the twisted wire cord or more. However, if the degree of patterning of this single wire is too large, the decrease in tensile elastic modulus becomes remarkable,
Lateral rigidity of the belt layer is reduced. As a result, the cornering power is reduced, and it becomes difficult to maintain the steering stability equivalent to that of the twisted wire cord.

The spiral shape imprinted on a single wire is the amount by which the space is formed within the spiral circle (D-
It can be characterized by two factors, d) and the pitch length P of the spiral. As in the present invention, the above (D-d)
When expressed by the parameter F = (D−d) / P which is a ratio of P and P, the correlation between the fatigue resistance and the tensile elastic modulus of the above-mentioned single wire can be made more clear, and Indicates the correlation with the durability of the belt layer and the cornering power (steering stability). In the present invention, this parameter F is in the range of 0.01 ≦ F ≦ 0.05.

Table 1 shows the relationship between the spiral-shaped parameter F of the single wire and the fatigue resistance against repeated bending loads carried out under the following measurement conditions. From the results of this Table 1, the parameter F for single wire
It can be seen that the effect of fatigue resistance can be improved as compared with the case of a straight single wire (F = 0) if a spiral-shaped die of = 0.01 is used. Further, it can be seen that if F is made larger than 0.04, almost no wire breakage is observed.

Fatigue resistance measuring method : As shown in FIG. 5, one single wire 40 was connected to 12.5 mm × 12.5 mm × 2.
It is embedded in a rubber block 60 having a size of 0.0 mm, and brass supporting blocks 70 of 12.5 mm × 12.5 mm × 15.0 mm are attached to both ends thereof so that both ends of the single wire 40 are connected to the supporting blocks 70. A sample S for measurement is prepared by adhering to the. As shown in FIG. 6, ten samples S were prepared, mounted between a pair of rotary plates T and T ′, and set so that extension lines of both rotary shafts U and U ′ form an angle θ. A maximum of 1.5% elongation and a maximum of 1.5% compression strain are applied to the rubber block 60 for each rotation. Both rotating plates T and T'set in this way are
After being rotated 0,000 times, the single wire 40 in each sample S
The presence or absence of breakage was checked, and the number of breaks was displayed at a rate of 100 minutes.

[0015] On the other hand, FIG. 4 shows the relationship between the spiral-shaped parameter F of a single wire and the tensile elastic modulus.
From this FIG. 4, it can be seen that the tensile modulus decreases as the parameter F increases. The tensile elastic modulus that the single wire should have is at least 1.5 × 10 ⁴ kgf from the relationship with the cornering power based on the belt layer.
/ Mm ² is necessary, so the parameter F = 0.05
It turns out that should be the upper limit.

Further, in the present invention, the diameter d of the single wire and the pitch length P of the spiral are 0.15 (mm) ≦ d ≦ 0.40 (mm) 2.0 (mm) ≦ P ≦ 8.0 ( mm) range. The diameter d of the single wire is 0.1
5mm or more, spiral pitch length P is 8.0mm
By suppressing the decrease in the tensile elastic modulus E of the single wire by setting the following, it is possible to further improve the fatigue resistance of the single wire by setting the diameter d to 0.40 mm or less and the pitch length P to 2.0 mm or more. I am trying to do it.

[0017]

【Example】

Example 1 The following items (1) to (4) are common to each other, and as shown in Table 2,
Thirteen types of radial tires of the present invention tires 1 to 7 and comparative tires 1 to 6 having different diameters d of the single wire used for the steel cord of the belt layer, the pitch length P of the spiral, the parameter F, and the number of ends were prepared. I made it.

For comparison, a steel cord obtained by twisting two strand wires having a diameter d = 0.10 mm into a stranded wire having a cord structure of 3 × 3 was used as a belt layer with an end number of 60 wires / 50 mm width. Manufactured a conventional tire having the same structure as the comparative tire 1. Tire size: 210 / 640R18 Carcass: Inner / outer two layers Carcass cord: Nylon fiber cord 1260D / 2 Cord angle: 24 ° (intersection between layers) Belt layer: Inner / outer two layers Inner belt layer width: 220 mm Outer belt layer width: 210 mm Gauge between cords a: 0.56 mm Cord angle: 24 ° (intersection between layers) These 14 types of radial tires were evaluated for high-speed durability, cornering power (hereinafter abbreviated as CP) and weight reduction index by the following methods. . The results are shown in Table 2.

High Speed Durability : Test tire pressure 1.5 k
The rim was assembled to a rim of 18 × 8-J at gf / cm ² , and a load of 400 kgf was loaded on a drum having a diameter of 1707.6 mm to run at 200 km / h for 10 minutes. Thereafter, every 10 minutes, 20 km / h. When the vehicle continued to travel with increasing speed, the running speed at the time of failure of the tire and the running time (minutes) at that time were evaluated.

Cornering power : A test tire was assembled on a rim of 18 × 8-J at an air pressure of 1.5 kgf / cm ² and 400 kgf on a drum having a diameter of 1707.6 mm.
Was run at a speed of 10 km / hr, and the average of absolute values of the lateral force when the slip angle was 1 ° right and the lateral force when the slip angle was 1 ° was measured. It is indicated by an index with the measured value of the conventional tire as a reference (100). The larger the index value, the larger the CP and the more excellent the steering stability.

Weight-reduction index : It is expressed as an index when the tire weight of a conventional tire is used as a reference (100). The smaller the index value, the lighter the weight.

[0022]

From Table 2, the comparative tire 1 in which the parameter F is smaller than the specification of the present invention has the same C as the conventional tire.
Although it has P and is lightened, high-speed durability is deteriorated. Further, although the comparative tire 2 in which the parameter F is larger than the regulation of the present invention has good high-speed durability,
Weight is increasing and CP is decreasing. On the other hand, each of the tires 1 and 2 of the present invention satisfying the range of the parameter F has CP and high-speed durability equivalent to those of conventional tires, and is lightweight. Although the tire 3 of the present invention has a slightly lower CP, it has a weight reduction index and high-speed durability that are higher than those of conventional tires.

The comparative tire 3 having a spiral pitch length P smaller than the lower limit of the present invention has the CP equal to that of the conventional tire, but the high-speed durability is slightly deteriorated. The comparative tire 4 in which the pitch length P is larger than the upper limit of the present invention has a remarkable decrease in high-speed durability and a large weight reduction index. On the other hand, the tire 4 of the present invention having the spiral pitch length P as the lower limit of the present invention has CP and high-speed durability equivalent to those of the conventional tire, and has a small weight reduction index. Further, the tire 5 of the present invention in which the pitch length P is the upper limit of the present invention
Has slightly lower high-speed durability, but has better CP and lighter weight index than conventional tires.

Further, the tires 6 and 7 of the present invention and the comparative tires 5 and 6 are tires in which the number of ends is adjusted by using single wire having different diameters d. The comparative tire 5 in which the diameter of the single wire d is smaller than the regulation of the present invention has a small weight reduction index, but the CP and high speed durability are deteriorated.
Further, the comparative tire 6 in which the diameter of the single wire d is thicker than the regulation of the present invention also has low high-speed durability.

On the other hand, the tire 6 of the present invention in which the diameter d of the single wire is set to the lower limit specified in the present invention has the same CP and high speed durability as the conventional tire, and the weight reduction index is small.
The tire 7 of the present invention in which the diameter d of the single wire is close to the upper limit specified in the present invention has the same high-speed durability as the conventional tire, the CP is improved, and the weight reduction index is also small. Example 2 With respect to the conventional tire of Example 1, the tires 2, 6 and 7 of the present invention and the comparative tire 6, handleability, stability, and
The drivability and the braking property were evaluated, and the results shown in Table 3 were obtained.

Maneuverability, stability, drivability, braking performance : best time (average value) when three professional drivers run on a circuit with test tires mounted on a racing car
In addition, the steering performance, stability, drivability, and braking performance were evaluated as a feeling. The value of the feeling evaluation is represented by an index with the measured value of the conventional tire as a reference (100). The larger this index value, the better the maneuverability, stability, driveability and braking performance.

[0028] From Table 3, all of the tires 3 and 6 of the present invention have shorter best times and improved maneuverability, stability, braking performance, and drivability as compared with the conventional tires. Further, the tire 7 of the present invention
Has the same braking performance and drivability as conventional tires,
Best time is short and maneuverability and stability are improved.
On the other hand, the comparative tire 6 has a longer best time than that of the conventional tire, and has poor steering performance, braking performance, and drivability except stability.

[0029]

According to the present invention, since the steel cord of the belt layer provided with at least two layers is composed of the single wire, it is possible to prevent the rubbing between the wire wires, which is a problem in the conventional twisted cord of the extra fine wire. A parameter F that can prevent the occurrence of wire breakage due to that, and shape the single wire into a spiral shape and specify the spiral shape.
By keeping the range to a certain range, the rigidity of the single wire is relaxed, the fatigue resistance against repeated bending load and compressive load is improved, and the surrounding area can be completely covered with the coat rubber, which enables high-speed durability. Remarkably improve the sex.

Further, at least two carcass layers have a semi-radial structure to increase the ground contact area of the tread surface by inclining the cord angle, and the cord of the belt layer is composed of the short fiber wire as described above. However, compared to the stranded wire cord, the cord diameter when the wire cross-sectional area was the same was made smaller, reducing the amount of coat rubber and making it lighter,
In addition, since the inter-cord gauge a is reduced to increase the interlaminar shearing force, maneuverability, stability and drivability can be improved.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional perspective view showing a pneumatic pneumatic tire for competition according to an embodiment of the present invention with a part cut away.

FIG. 2 is an enlarged cross-sectional view showing a main part of the tire of FIG.

FIG. 3 is a side view showing an example of a spirally shaped single wire used in the present invention.

FIG. 4 is a graph showing the relationship between the parameter F of a single wire and the tensile elastic modulus.

FIG. 5 is a perspective view showing the shape of a sample for measuring the fatigue resistance of a single wire.

FIG. 6 is a diagram illustrating an outline of a fatigue resistance measuring device for a single wire.

[Explanation of Codes] 1 tread portion 2 inner belt layer 3 outer belt layer 4, 4'carcass layer 40 single wire d single wire diameter D spiral diameter P spiral pitch length

Claims (1)

[Claims] 1. A pneumatic radial tire for competition, wherein at least two carcass layers are mounted between a pair of left and right bead cores, and a belt layer made of steel cord is arranged on the outer peripheral side of the tread portion of the carcass layers, The carcass layer is arranged at a cord angle of 56 to 86 ° with respect to the tire circumferential direction and is arranged so as to intersect with each other, and the steel cord is composed of a single wire formed in a spiral shape. The single wire has a diameter d and a spiral. The diameter D, the pitch length P of the spiral, and the parameter F = (D−d) / P that specifies the spiral shape are respectively 0.01 ≦ F ≦ 0.05 0.15 (mm) ≦ d ≦ 0.40 (mm ) Pneumatic radial tire for competition set to 2.0 (mm) ≤ P ≤ 8.0 (mm).