JP2702770B2 - Pneumatic tire - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pneumatic tire capable of improving cut resistance without impairing other performances.

[Conventional technology]

2. Description of the Related Art Pneumatic tires, especially high-speed heavy-load radial tires used at high speeds and heavy loads, such as aircraft tires, have increased in use speed and use load with the recent increase in size and flight speed of aircraft. In order to effectively reduce the impact when taking off and landing on the runway, the amount of deflection under tire load is, for example, 28 to
38%, which is extremely large, so that it can withstand large repeated deformation.

As the speed of airplanes increases, the speed of take-off and landing increases, so it must withstand high-speed rotation under heavy loads and large deformations.

To reduce the weight of the airplane,
A load of approximately 130 to 360 times (approximately 50 times for a normal tire) is applied, and for this reason, extremely high pressure air such as 10 to 16 kg / cm ² must be filled.

In addition, it is necessary to withstand taxi conditions in which a large load acts for a relatively long time at a low speed when traveling between the runway and the gate.

In addition, the airplane often makes a turn for changing the direction of the airplane when traveling between the runway and the gate. It is necessary to increase cornering power. Such a steering stability structure is also useful for preventing roll and swing at takeoff and landing.

In addition, particularly in such aircraft tires, the tread portion is easily damaged by foreign substances that tend to be scattered on the road surface due to the heavy load and high speed, and when the tire is damaged, the scratch is relatively easily damaged. The tread portion is damaged, for example, the belt layer is damaged by the foreign material itself that has reached the surface of the layer or has penetrated, and durability is reduced. Therefore, it is necessary to improve the resistance of the tread portion to damage, that is, the cut resistance.

In addition, such damage to the belt layer and the like may make it difficult to correct the tire by replacing the tread rubber.

On the other hand, as an aircraft tire, a tire having a cross-ply structure in which carcass cords are arranged so as to cross each other between plies is frequently used. However, since the carcass cords intersect at a relatively large angle, the rigidity of the tread portion is small and the weight is large although the lateral rigidity is large and the steering characteristics are relatively excellent. In combination with the above, other characteristics such as abrasion resistance and heat generation are not preferable, and the use of the cross-ply structure is being restricted due to the remarkable improvement in performance of recent large jet aircraft.

Accordingly, in recent years, a so-called radial, in which carcass cords are arranged at substantially right angles to the tire equator, and a radially outer side of the carcass having a semi-radial structure, a belt layer made of a highly elastic belt cord inclined at a small angle with respect to the tire equator is arranged. Radial tires are being used.

However, in such radial aircraft tires, the belt cords are arranged in the tire equator direction, and a large hoop effect can be provided in the circumferential direction of the tread portion, and the out-of-plane bending stiffness of the tread portion is reduced. Although it is possible to improve the wear resistance, rolling characteristics, etc., and improve the durability of the tire, the intersection angle of the belt cord of each belt ply is small, and it intersects the carcass cord substantially at a right angle, and the cord is Because they intersect each other in a rectangular shape, conventional radial tires have slightly lower in-plane bending rigidity of the tread,
As a result, the cornering force during turning decreases,
It did not have sufficient structural durability performance, for example, tended to cause run-out and impair steering stability.

Therefore, for example, Japanese Patent Application Laid-Open No. 61-196804 proposes an aircraft tire having a band layer provided outside a belt layer.

Furthermore, Japanese Patent Application Laid-Open No. 57-201704 proposes a tire employing a band layer using a corrugated steel cord.

[Problems to be solved by the invention]

However, aircraft tires according to the former proposal are:
Although it is possible to improve the cornering force by improving the cut resistance and improving the in-plane bending stiffness to some extent by the band layer, in this tire, an organic fiber cord is used as the cord of the band layer. Because
The cut resistance cannot be sufficiently improved.

In the latter, even though the cord is corrugated, the steel cord is used as a band layer, so it is inferior in extensibility, due to a large tagging effect, the inflated shape due to the internal pressure filling of the tire is distorted, Sometimes, the ribs formed on the tread portion meander.

In the conventional tire, it has been found that the durability of the bead portion is relatively lower than the durability of the entire tire. It was also found that standing waves were relatively likely to occur.

Regarding the durability of the bead portion, since the amount of deflection in the tire radial direction under load is as large as about 28 to 38% as described above, the carcass cord of the bead portion falls into the carcass cord by falling down to the rim flange. Compressive stress acts on a portion turned around the bead core, and the carcass cord is cut by fatigue due to repetition of compressive strain due to the compressive stress, resulting in damage to the bead portion.

Further, the standing wave is a waving phenomenon that occurs in the tread portion during running of the tire, such waving of the tread portion impairs tire durability,
In particular, excite the bead portion through the sidewall portion,
Decreases its durability.

As is well known, a standing wave in a radial tire is obtained by the following equation (1).

Here, Vc: critical speed of standing wave generation m: mass of unit length of tread portion EI: bending stiffness in the tire plane of tread portion T: belt tension k: spring constant of carcass

Equation (1) is obtained by assuming that the belt layer is an infinite beam elastically supported by a carcass. In order to increase the critical velocity Vc at which a standing wave is generated, the mass m is reduced. On the other hand, it is understood that the rigidity E1, the belt tension T, and the carcass spring constant k may be increased.

Here, in order to increase the natural frequency of the belt without reducing the mass m and to increase the critical velocity Vc at which a standing wave is generated, a large tension T is applied to the belt by filling the inner pressure, and thereby the tread is increased. It has been proved that the apparent in-plane bending stiffness EI of the portion can also be increased to increase the critical speed Vc. For this reason, by using an elastic cord having high extensibility as a carcass cord, the apparent bending rigidity is increased, thereby increasing the critical generation speed of the standing wave and improving the durability of the bead portion. However, it has been found that when such an elastic cord is used as the carcass cord, the cornering force tends to decrease.

The present invention is based on the use of a cut protector using a composite cord obtained by winding a metallic wire around an organic fiber cord, improving cut resistance without impairing other performances, and increasing knurling force. It aims to provide pneumatic tires that are also useful.

The pneumatic tire of the present invention can be suitably used as a high-speed heavy-load tire, particularly an aircraft tire, and can also be generally used as a passenger car tire, a truck tire, and the like.

[Means for solving the problem]

In the present invention, the tire is folded back from the tread portion to the sidewall portion with the bead core at the bead portion and the tire equator is 75
A carcass made of one or more carcass plies of a carcass cord using an organic fiber inclined at an angle of up to 90 degrees, and a carcass located radially outside of the carcass and inside a tread portion and not more than 5 degrees with respect to the tire equator. A belt layer comprising at least one belt ply of a belt cord using organic fibers arranged at an angle, and a cut protector comprising a ply which is disposed radially outside the belt layer and uses a protective cord, The protection cord includes an inner steel wire spirally wound around a parent cord using organic fibers, and an outer steel wire wound around the outer wire of the inner wire and in a direction opposite to the inner wire. This is a pneumatic tire made of a composite cord wound with a metallic wire including the following.

[Action]

By inclining the belt cord at an angle of 5 degrees or less with respect to the tire equator, the belt layer gives the carcass a stagger effect and increases the rigidity of the tread portion.

The cut protector disposed outside the belt layer prevents the tread from being damaged by the foreign matter on the road surface when the tread is damaged. Further, as a protection cord of the cut protector, a composite cord in which a metallic cord is wound around a parent cord using organic fibers is used. As a result, the metallic strand functions as a protective body against foreign matter, and prevents damage to the belt. For this purpose, it is preferable that the child wire is subjected to a rust-preventive treatment and a plating treatment for enhancing the compatibility with rubber. In addition, the protection cord can be provided with a suitable elongation by using a parent cord made of organic fibers, and by reducing the rigidity step when the belt layer and the tread rubber come into direct contact with each other, damage to the tread portion and The expansion can be prevented. In addition, since the cut protector is arranged outside the belt layer, the in-plane bending stiffness of the tread portion can be increased to some extent, which can contribute to an improvement in cornering force.

When an extensible elastic cord having a large elongation due to a load is used as a carcass cord, the carcass cord can be given a high elongation in advance together with the internal pressure filling to apply a tensile force. Such a tensile force reduces the compressive stress acting on the carcass cord at the portion where the bead falls down to the rim flange side. Therefore, it is possible to prevent the occurrence of local stress due to deformation due to compression and the like, and further to prevent the fertilizer from being cut, thereby reducing the occurrence of repeated stress concentration of the bead portion and improving the durability of the bead portion.

Further, the amount of expansion of the tread portion, particularly the crown portion, becomes large, and the tension of the belt layer in the portion increases, and the apparent rigidity EI of the tread portion increases, thereby increasing the generation critical speed of the standing wave. It can also contribute to suppressing the occurrence.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings, taking an example of an aircraft tire having a tire size of 46 × 17R20.

In FIG. 1 showing a state where the tire is mounted on a regular rim R and filled with a regular internal pressure, the radial tire 1 includes a beat core 2
The tire includes a bead portion 3 through which the tire passes, a side wall portion 4 which is continuous with the bead portion 3 and extends outward in the tire radial direction, and a tread portion 5 which connects an outer end of the side wall portion 4.

Further, the tire 1 is provided with a plurality of, for example, four carcass ply folds of a bead core 2 folded from the inside to the outside of the tire.
A carcass 7 having an inner layer 7A composed of 7a... And an outer layer 7B composed of a plurality of, for example, two carcass plies 7b, 7b surrounding the folded portion of the inner layer 7A and being folded inward from the outside of the tire.
Is provided. The carcass cords of the carcass plies 7a and 7b are arranged in a radial direction having an inclination of 75 to 90 degrees with respect to the tire equator CO. In this example, the carcass 7 is located between adjacent carcass plies. The lateral rigidity of the tire is improved by the carcass cords being alternately crossed and inclined with respect to the tire radial direction.

Above the bead core 2, a bead apex 9 made of tapered rubber extending in the tire radial direction is provided to increase rigidity and to disperse stress caused by bending of the folded portion of the carcass 7. Further, a chain (not shown) for preventing the rim from shifting can be provided on the outer surface of the bead portion 3.

Further, the tread portion 5 is provided therein with a belt layer 10 having a belt cord located at a radial angle outside of the carcass 7 and arranged at a cord angle of 5 degrees or less with respect to the tire equatorial plane. A cut protector 16 using a protection cord is arranged outside the box. In this example, a cut breaker 14 having an auxiliary cord inclined at a cord angle of 0 to 70 degrees with respect to the tire equatorial plane is interposed between the belt layer 10 and the carcass 7.

The belt layer 10 is composed of a plurality of, for example 6 to 10, belt plies 10a having the belt cords, and the belt plies 10a are gradually narrowed outward in the radial direction. Numeral 10 is trapezoidal in a cross section including the tire axis, and the side surface 10b is a slope having substantially the same thickness as the outer surface SB of the tire buttress portion. The maximum width W10 of the belt layer 10, in this example, the width of the innermost wide ply 10a is in the range of about 75 to 85% of the total width W of the tire. In addition, the belt cords are alternately inclined in reverse for each belt ply 16a.

The cut protector 16 is arranged outside the belt layer 10 and includes one or more plies 16a, 16a using the protection cord, in this example, two plies 16a, 16a.
In addition to improving the cut resistance, the rigidity step between the belt layer 10 and the rubber of the tread portion 5 is alleviated, and the shear stress therebetween is reduced, so that the tread portion 5 is not damaged.
And its expanding growth.

For this purpose, the cut protector 16 preferably has two plies 16a, 16a disposed on the entire surface of the belt layer 10.

Further, the cut protector 16 can be formed of three or more layers in addition to the case where only one layer of plies is used. Further, as shown in FIG.
19 may be provided. This rubber layer 19 facilitates removal of the cut protector 16 without damaging the belt layer 10 during tire rehabilitation.

While the cut breaker 14 uses, for example, two layers of cut breaker plies 14a, 14a using the auxiliary cord, the cut breaker 14 is gradually separated from the carcass 7 at a portion outside the shoulder portion 21 in the tire axial direction. Then, the outer end is terminated inside the outer end of the belt layer 10. The outer end of the cut breaker 14 can be aligned with the outer end of the belt layer 10 or slightly protrude.

The cut breaker 14 is for increasing the in-plane bending stiffness of the tread portion 5 and increasing the cornering force. For this purpose, the cut breaker 14 is preferably arranged so as to have a triangle structure with a carcass cord and a belt cord. Accordingly, since the carcass cord is inclined at an angle of 75 to 90 degrees with respect to the tire equator and the belt cord is inclined at an angle of 5 degrees or less, the auxiliary cord is inclined at an angle of 10 to 45 degrees, preferably 10 to 30 degrees, with respect to the tire equator. Tilt. When the carcass cord has an angle of 75 to 80 degrees, the inclination of the auxiliary cord with respect to the tire equator can be set near 0 degrees. For this reason, the auxiliary cord is inclined at 0 to 70 degrees.

Next, the protection cord used for the cut protector 16, the carcass cord used for the carcass 7, the belt cord used for the belt layer 10, and the auxiliary cord used for the cut breaker 14 will be described.

As shown in FIG. 3, the protection cord 20 is a composite cord in which a metallic cord 22 is wound around a parent cord 21 using organic fibers. This child wire 22 is for improving the cut resistance of the tread portion 5, and therefore, for example, steel having excellent strength is preferably used.

Parent code 21 is rayon, polyester, vinylon,
Aliphatic polyamides such as nylon 66, aromatic polyamides,
Flexibility and elongation are enhanced by using a twisted cord obtained by twisting a large number of organic fiber filaments 21A, 21A using organic fibers such as polyvinyl alcohol fiber. The parent cord 21 has a relatively small diameter of about 300d / 2 to 1350d / 3.

The parent cord 21 may be a monofilament having a large diameter, a twisted cord in which a plurality of monofilaments are twisted, or a single strand.

As shown in FIG. 3, the slave wire 22 includes a steel wire 22b spirally wound around the parent cord 21 and a steel wire 22b outside and inside the steel wire 22b. It can be formed from a steel wire 22c outside the winding with a reverse spiral.

In the case where the parent cord 21 is a twisted cord, the steel strand 22b in the inside prevents the untwisting of the parent cord 21 by forming a spiral in a direction opposite to the direction of the twisted spiral.

Furthermore, the diameter of the steel strands 22b and 22c is about 0.05 to 0.3m.
It is preferable to apply a brass plating having a thickness of about 2 μm or more, if necessary, in order to prevent rust and adaptation to rubber.

Further, the strand 22 is a spiral pitch P of the steel strand 22b inside.
b is about 0.3 to 1.2 mm, and the spiral pitch Pc of the outer steel strand 22c is about 1.0 to 2.0 mm, and the spiral pitch Pc of the outer steel strand 22c is the spiral pitch Pb of the inner steel strand 22b.
Greater than

By setting the helical pitch Pb of the steel strands 22b within the above range, the flexibility of the protection cord 20 is maintained while protecting the parent cord 21 made of organic fibers. For this purpose, the minimum gap between the steel wires 22b wound around the spiral is set to a distance larger than 50% of the wire diameter in the above range. When the helical pitch Pb is larger than 1.2 mm, the gap between the steel wires 22b becomes excessively large, and the function as the cut protector 16 is reduced.

The outer steel wire 22c also enhances the protection function while maintaining the flexibility of the protection cord 20, and is preferably wound more loosely than the inner steel wire 22b. .

In FIG. 4, a steel wire 22b having a diameter of 0.15 mm is helically pitched at 0.88 mm in a Z-twist and a Z-twisted steel wire is attached to a parent cord 21 made of a 1260d / 2 S-twisted cord made of nylon 66. Helical pitch P with outer steel strand 22c of the same diameter
The elongation curves of the protection cords 20 each having a c of 1.39 mm and wound in an S-twist are illustrated by solid lines.

In addition, the elongation curve of the twisted cord A consisting of only 1260d / 2 nylon 66 cord is shown by a broken line in FIG.

As can be seen from the figure, the protection cord 20 having the steel strands 22b and 22c shows a larger elongation at the same load as compared to the twisted cord A having no steel strand. Further, it was found that the breaking load (kgf) of the protection cord 20 was reduced by about 20% as compared with the twisted cord A.

This is because the diameter of the parent cord 21 has been reduced in advance by winding the steel wires 22b and 22c,
It is considered that the length is reduced due to the spring back after the winding of 2c.

The decrease in the breaking strength is considered to be due to the notch effect due to the winding of the steel strands 22b and 22c. However, as the protection cord 20 in which the cut resistance is particularly important, such a decrease does not pose a problem.

This protection code 20 is 0 to 90 with respect to the tire equator CO.
The ply 16a of the cut protector 16 is formed by being arranged at an arbitrary inclination. When the cut protector 16 functions as a reinforcing layer that increases the in-plane bending stiffness of the tread portion 5 and increases the cornering force, in addition to the cut resistance, the cut protector 16 is preferably arranged so as to intersect with the belt layer 10. Incline in the range of 20 to 55 degrees, more preferably 30 to 45 degrees.

In addition, the protection cord 20 has 20 to 60
~ 60E / 5cm). When the number is less than 20, the cut resistance is inferior. When the number exceeds 60, the tire weight increases and the tire becomes expensive.

 Therefore, the number is preferably about 30 to 50 per 5 cm.

As described above, the cut protector 16 may use one ply 16a or two plies 16a, 16a, and preferably, at least one ply 16a is attached over the entire width of the grounding surface. Alternatively, the ply 16a may be formed by a cord winding method in which one or a plurality of the protection cords 20 are spirally wound at a small angle.

A highly extensible elastic cord is used for the carcass cord.

The elastic cord has an elongation S ₅ (%) under a load of 5 kg of 5 or more and 10 or less (preferably 5 to 8). 10kg more
Elongation under load S ₁₀ (%) is 9 or more and 15 or less (preferably 10
12), the elongation S ₂₀ (%) under a load of 20 kg is set to 14 to 20.

In yet another embodiment, the carcass cord, the value D ₅ obtained by dividing the elongation S ₅ of 5kg load in denier number of codes and 7.35 × 10 ^-4 or more and 14.7 kg × 10 ^-4 or less. Elongation at 10kg load S
_The value D ₁₀ obtained by dividing ₁₀ by the number of cord deniers, the value D ₂₀ obtained by dividing the elongation S ₂₀ under a load of 20 kg by the number of deniers of the cord, respectively,
13.2 × 10 ^{-4 to} 22.1 × 10 ^-4 and 20.5 × 10 ^{-4 to} 29.4 × 10 ^-4 .

Such an elastic cord has a characteristic of a region sandwiching the lower limit curves a1 and a2 and the upper limit curves b1 and b2 in FIGS. 5 (A) and 5 (B). The elastic cords are represented by curves a and b (curve a
1, a2 together, a, b1, b2 together, b)
As shown in Fig. 5, the elongation is large when the load is small, and the elongation rate decreases as the load increases.

By using the elastic cord having such characteristics, in the initial stage of the internal pressure filling, the carcass cord undergoes large elongation together with the internal pressure filling.

When the load further increases to 10 kg or 20 kg, the carcass cord elongates as the load increases, but the elongation rate gradually decreases.

As shown by the curve c, the conventional cord has a larger rise and a substantially linear shape as compared with the curve a. When such a conventional cord is used, the carcass cord has a small elongation even when the internal pressure is charged. Yes, it is inferior in the ability to relieve the compressive stress acting upon deformation.

On the other hand, the elastic cord has characteristics in the region between the curves a and b, so that the durability of the tire can be improved.

In addition, 5 kg of carcass cord, preferably 10 kg, 20 kg
The provisions for each of the elongations S ₅ , S ₁₀ , and S ₂₀ at the time of loading determine the value itself of the elongation of the cord due to the load, irrespective of the denier of the carcass cord used. On the other hand, the other rule is the value obtained by dividing the elongation S ₅ under a load of 5 kg by the number of deniers, that is, 5 kg per denier of the cord.
It means the elongation rate under load, and the carcass cord is mainly grasped in terms of the characteristics of the cord. Is specified. The former defines values that can be preferably used mainly as tires for aircraft and tires for large jet aircraft.

Further, the initial elastic modulus Es (kg / mm ² ) of the elastic cord is 130 or more (preferably 140 or more) and 200 or less.

The initial elastic modulus Es (kg / mm ² ) is, as shown in FIG.
Load (kg), elongation (%) using a constant speed elongation type tensile tester
This is a value defined as a gradient of a tangent line X of the curve d at an elongation of 7% in which a curve d is drawn, and the initial elastic modulus Es (kg / mm ² ) is made smaller in the above range as compared with a conventional elastic cord. Thereby, the extensibility of the elastic cord can be enhanced, and the carcass cord can be given elongation.

Further, as the elastic cord, one having a load at break, that is, cord strength of 30 kg or more, preferably about 40 kg or more and about 60 kg or less can be suitably used.

Further, as the elastic cord, a nylon cord, a polyester cord, an aromatic polyamide cord, a carbon cord, or a hybrid cord of one or more cords in a metal cord is used.

Further, such a cord having physical properties, when using an organic fiber cord, makes the tension in so-called dip stretch, in which tension and heat are applied to the cord in advance for a predetermined period of time, wider than the tension used in conventional dip stretch. It is obtained by reducing to In order to enhance this characteristic, for example, when a nylon cord is used, the number of twists per 10 cm is set to 26 to 36 T / 10 cm, which is greater than the number of twists of about 23 T / cm conventionally used. When the load reaches a predetermined value by applying tarumi, such as mixing a cord with a small elongation rate and a cord with a small elongation rate, and winding the small cord in advance with a coil, etc. Can be formed so that a load is applied to the cord and the elongation is reduced as a whole.

The carcass cord is embedded in a base rubber, that is, topping rubber, so that the carcass plies 7a, 7b
To form As the base rubber, a rubber exhibiting the characteristics of the cord in addition to the reinforcing property and the low heat generation property is used.
As such, 50 to 70 parts by weight of carbon is mixed with a base material composed of one or more of natural rubber and synthetic isoprene rubber, and a 100% modulus is 30 to 70 kg / cm ² ,
Those having an elongation at break of 200% or more and 500% or less are suitably used. If the amount of carbon is less than 50 parts by weight, the reinforcing property tends to decrease, and if it exceeds 70 parts by weight, the heat generation tends to increase. If the 100% modulus is less than 30kg / cm ^2,
Heat generation increases, and if it exceeds 70 kg / cm ² , the reinforcing property tends to be low. If the elongation at break is less than 200%, the ability to follow the distortion of the carcass is insufficient and rubber breakage is likely to occur, and if it exceeds 500%, the heat generation tends to increase.

A tire having a carcass cord made of such an elastic cord is given a larger elongation to the carcass 7 in advance than the conventional tire by filling the inner pressure, so that when the bead portion 3 is bent during takeoff and landing, the tire has a rim flange C side. By reducing the generated compressive stress of the carcass cord and reducing the compressive strain, deformation, local bending, and breakage due to fatigue due to the compressive strain are prevented. Further, the compressive stress of the rubber itself of the bead portion 3 can be reduced, and the durability of the bead portion can be improved, for example, by more than 10%.

When such an elastic cord is used for the carcass 7, the distortion due to the internal pressure filling tends to concentrate on the sidewall portion, particularly near the maximum width portion.

In order to prevent this, the belt cord 11 has the same elongation characteristics as the carcass cord together with the cut breaker cord, and the elongation S ₅ (%) under a load of 5 kg is smaller than that of the carcass cord. 6 or elongation S
_The value D ₅ (% / d) obtained by dividing ₅ (%) by the denier number (d) is 3.8
5 × 10 ^{-4 to} 7.69 × 10 ^-4 .

The belt cord 11 and the carcass cord are both relatively thick cards having the same diameter, for example, cords of about 1260d / 2 to 2700d / 3, and the auxiliary cords having the same diameter or smaller diameters are used.

Further, the belt layer 10 may be formed as an endless type by a so-called cord winding method in which one or several cords are spirally wound.

In addition, by using such an elastic cord as the carcass cord and the belt cord 11, the bulging amount of the crown portion 20 can be increased at the time of normal internal pressure filling as compared with at the time of 5% internal pressure filling. Belt cord 11
, The critical speed of the standing wave can be improved.

Example 1 A tire having a tire size of 46 × 17R20 and a structure shown in FIG. 1 was prototyped according to the specifications shown in Table 1. In addition, a tire shown in the comparative example column was experimentally manufactured. In each case, the number of plies is 6 for the carcass, 8 for the belt layer, and 2 for the cut breaker. Each of the carcass winding structures is 4-2. Table 2 shows the code configuration of the carcass code, breaker code, and auxiliary code in the table. Table 3 shows the structure of the protection code.

Each of them is filled with the normal internal pressure,
The durability was tested based on a taxi simulation test based on O-C62c. The results are shown in the table according to the number of times of destruction. 61 indicates that the race was completed. After the test, those that withstood takeoff at 200% load are indicated by a circle.

The cornering force was measured using a flat belt type laboratory tester, and Comparative Example 3 was set to 100. It is shown in exponential notation. A higher value indicates a better result.

The cut resistance is 5mm high, as shown in Fig. 7.
The time until the tire breaks is shown by exponential notation, where 100 is taken as Comparative Example 3 while the wedge pieces having a tip radius of 0.5R are scattered and rotated at a load of 150%. The larger the index, the better the result. An index of 120 or more is a passing criterion.

〔The invention's effect〕

Such a tire of the present invention can improve cut resistance without impairing other performances. In addition, the protection cord of the cut protector is wrapped around the inner strand of steel that is spirally wound around the parent cord that uses organic fibers, and the outer spiral of the inner strand of steel and the opposite spiral to the inner strand of steel. It is composed of a composite cord including an outer steel strand. For example, in the case of a cord in which two steel strands are spirally wound around a parent cord in the same direction, if the twist pitch is not the same,
The interval between the outer steel strands fluctuates periodically, and sometimes the inner and outer steel strands overlap in almost the same direction. . Furthermore, cords that are spirally wound in the same direction tend to twist and impair uniformity of rigidity in the direction of bending. In contrast, in the present application, as described above, by turning the inner and outer steel strands in opposite directions, the outer strand is always wound over the inner steel strand, so that the outer strands overlap in the same direction. There is no overlapping portion, and the protection function for the parent cord, the rigidity of the cord in the twisting and bending directions can be made uniform, and the cut resistance by the cut protector using this protection cord can be further improved.

[Brief description of the drawings]

1 is a sectional view showing an embodiment of the present invention, FIG. 2 is a sectional view showing another embodiment, FIG. 3 is a diagram illustrating a protection cord, and FIG. 4 is a diagram illustrating characteristics of the protection cord. FIGS. 5A and 5B are diagrams showing characteristics of the carcass cord, and FIGS.
FIG. 7 is a diagram illustrating an initial elastic modulus, and FIG. 7 is a perspective view illustrating a drum in a cut resistance test. 2 ... bead core, 3 ... bead part, 4 ... side wall part, 5 ... tread part, 7 ... carcass, 10 ... belt layer, 10a ... belt ply, 16 ... cut protector, 20 ... Protection code, 21: Parent code, 22: Child wire, 22b: Steel wire inside, 22c: Steel wire outside.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-51-106906 (JP, A) JP-A-59-15587 (JP, A) JP-A-61-196804 (JP, A) JP-A 57-106 143535 (JP, A) JP-A-61-166706 (JP, A) JP-A-58-180705 (JP, U) JP-A-56-53798 (JP, U)

Claims (4)

(57) [Claims] The tire is folded back from the tread section to the side wall section at the bead core of the bead section and is positioned at 75% with respect to the tire equator.
A carcass made of one or more carcass plies of a carcass cord using an organic fiber inclined at an angle of up to 90 degrees, and a carcass located radially outside of the carcass and inside a tread portion and not more than 5 degrees with respect to the tire equator. A belt layer comprising at least one belt ply of a belt cord using organic fibers arranged at an angle, and a cut protector comprising a ply which is disposed radially outside the belt layer and uses a protective cord, The protection cord includes an inner steel wire spirally wound around a parent cord using organic fibers, and an outer steel wire wound around the outer wire of the inner wire and in a direction opposite to the inner wire. A pneumatic tire consisting of a composite cord wound with a metallic strand including: 2. The pneumatic tire according to claim 1, wherein said child wire is made of steel. 3. The pneumatic tire according to claim 1, wherein the helical pitch of the outer steel wire is greater than the helical pitch of the inner steel wire. 4. The pneumatic tire according to claim 1, wherein the parent cord is a twisted cord obtained by twisting a plurality of strands using a plurality of organic fiber filaments.