JP2010184552A - Pneumatic tire for heavy load - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire having a superior peripheral rigidity and a durability while reducing its weight. <P>SOLUTION: A pneumatic tire for heavy load is constituted in such a way that inclination directions of cords with respect to a tire equatorial plane are made opposite to each other in a first ply 6 and a second ply 7 and made same in the second ply 7 and a third ply 8, inclination angles of cords in these plies with respect to the tire equatorial plane are 10 to 25° for a first ply α and a second ply β, and 45 to 90° for a third ply γ, and the first ply 6 and the second ply 7 are formed by arranging a plurality of steel cords 11 having a plurality of filaments 13 twisted side by side under their bundle form, and a short diameter (height) A (mm) and a bundle width B (mm) of the bundle 12 of steel cords of the first ply 6 and the second ply 7 satisfy a relation indicated by an equation (1): B/A≥2.0, and a value of S=B/(B+D) satisfies a relation indicated by an equation (2): 0.60≤S≤0.80, respectively. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a heavy-duty pneumatic tire (hereinafter also simply referred to as “tire”) used for trucks, buses, and the like, and more particularly to a heavy-duty pneumatic tire excellent in circumferential rigidity and durability.

  Steel cords are usually embedded at equal intervals in steel belts of heavy duty pneumatic tires. Regarding the improvement of the steel cord applied to such a belt, for example, Patent Document 1 discloses that a steel cord of a belt layer is formed by aligning N strands obtained by twisting a plurality of steel strands in a substantially non-twisted manner. A pneumatic radial tire formed as a converging cord having an outer shape is disclosed.

  Further, for example, in Patent Document 2, the reinforcing elements of the belt layer are divided into several bundles within a few, and a dispersion interval between the bundle and the reinforcing elements adjacent thereto is widened and arranged side by side. A pneumatic radial tire is disclosed in which the width d of the bundle in the direction orthogonal to the distance and the ratio d / l of the interval l between the bundle and the reinforcing element adjacent thereto are defined within a predetermined range.

  Furthermore, conventionally, it has three belt layers with steel cords arranged. Of these belt layers, two layers (referred to as the first layer and the second layer from the inside) in the tire radial direction are cords. Inclined in opposite directions with respect to the tire equator plane and arranged at a relatively small angle with respect to the tire equator plane, and the cord of the outermost layer (referred to as the third layer) in the tire radial direction is the second layer There is known a pneumatic tire that is inclined in the same direction as the cord of No. 1 and arranged at a relatively large angle with respect to the tire equatorial plane.

  For example, Patent Document 3 discloses a vehicle for heavy loads that can suppress the shear strain of rubber between the first layer and the second layer constituting the cross layer pair without impairing the tagging effect of the cross layer pair. A tire is disclosed. Patent Document 4 discloses a heavy-duty pneumatic radial tire in which a belt is composed of three cord layers for weight reduction, and a highly extensible cord is arranged in the outermost cord layer. ing.

  In such a tire, the first layer and the second layer form a crossing layer, exhibiting a strong circumferential rigidity, suppressing the diameter growth against a high internal pressure, and the third layer stepping on rocks and foreign objects on the road. It has the feature of receiving the impact from the outside of the tire when it passes and preventing the failure of the crossing layer. In general, in heavy-duty pneumatic tires used for trucks and buses, etc., four belt layers are used. Therefore, the tire having the three belt layers is lightweight, and the mass of the tire This is advantageous. Furthermore, the steel cord itself has a tensile force acting in the tire circumferential direction, that is, it has a large shrinking force and is easy to spread when cut, but the third layer is at a large angle (low angle) with respect to the equator plane. By comprising, it has cut resistance and can prevent shrinkage in the width direction when a tensile force is applied in the circumferential direction.

JP 2004-217158 A (Claims etc.) JP-A-5-213007 (Claims etc.) JP 2007-283867 A (Claims etc.) JP 2000-85313 A (claims, etc.)

  In recent years, with the increasing needs for environmental performance, weight reduction of tires leading to resource saving and low fuel consumption has been demanded, and this is not an exception even in the heavy duty tire having the three belt layers. In response to this demand for reducing the weight of tires, as a conventional technique for reducing the weight of a belt, it is known to reduce the thickness of a belt using a thin wire diameter cord. However, in this case, since it is necessary to increase the number of drivings in order to maintain the tire strength, the cord interval becomes dense, and the so-called belt end separation (BES) property relating to the occurrence of cracks from the belt end is deteriorated. There was a problem.

  On the other hand, as a technique for avoiding a close code interval, a method using a bundle code as disclosed in Patent Document 2 has been proposed. The technique according to Patent Document 2 is mainly intended to ensure durability by improving the belt, but on the other hand, in the heavy-duty pneumatic tire used at high pressure and high load, the diameter growth is suppressed. The need for circumferential rigidity increases. Decreasing the circumferential rigidity in exchange for weight reduction is a fatal defect in the performance of heavy duty pneumatic tires.

  Also, in heavy duty tires having the above three belt layers, when the amount of steel cord used in the belt layer is reduced for the purpose of weight reduction, the distance between adjacent cords becomes large, and the rubber existing therebetween Is freely deformed, the circumferential rigidity as the crossing belt layer may be reduced. In addition, on the other hand, when the amount of rubber used in the belt layer is reduced, the distance in the thickness direction of the two intersecting layers is shortened, and the interlayer strain generated between the belt layers increases, or in the plane of the belt. The distance between adjacent cords is reduced, and the cracks in the rubber generated at the end of the cord at the belt end are easily connected to each other, which may lead to a separation failure of the belt layer, so-called separation between belts. Therefore, a heavy duty tire having three belt layers is required to be a pneumatic tire that is lighter and more excellent in circumferential rigidity and durability with respect to separation between belts.

  Accordingly, an object of the present invention is to provide a pneumatic tire excellent in circumferential rigidity and durability while solving the above-described problems in the prior art and reducing the weight of the tire.

  In the present invention, a mechanism for exerting rigidity when the steel cords are arranged in a bundle shape is examined, and by clarifying this, S (S defined by the bundle width B and the bundle interval D of the steel cord bundles is obtained. = B / (B + D)) The optimum range of values was found.

  That is, in the first place, the steel belt usually exhibits a strong circumferential rigidity by being arranged in two layers so as to intersect each other. In order to exhibit the circumferential rigidity efficiently, it is important to constrain the deformation of the rubber in the belt layer and the deformation of the rubber between the two layers, and the constraining effect is the ratio of steel in the belt (S = B / (B + D)). Therefore, it is considered that the above problem can be solved by designing the arrangement of the steel cord bundle so that the value of S is within the optimum region. From this point of view, as a result of further studies, the present inventor has found that, by adopting the following configuration, it is possible to achieve both weight reduction, durability and circumferential rigidity, and the present invention has been completed.

That is, the heavy-duty pneumatic tire of the present invention has at least one carcass extending in a toroid shape between a pair of left and right bead cores as a skeleton, and three belt layers on the outer side in the tire radial direction of the carcass. A heavy duty pneumatic tire having
The three belt layers are composed of a first layer, a second layer and a third layer in order from the inside in the tire radial direction,
The direction of inclination of the cord with respect to the tire equator plane is opposite in the first layer and the second layer, and in the same direction in the second layer and the third layer. The inclination angle with respect to the equator plane is configured so that the first layer and the second layer are 10 to 25 degrees, and the third layer is 45 to 90 degrees,
The first layer and the second layer are formed by arranging a plurality of steel cords formed by twisting a plurality of filaments in parallel in a bundle,
The short diameter (height) A (mm) and the bundle width B (mm) of the steel cord bundle of the first layer and the second layer are expressed by the following formula (1),
B / A ≧ 2.0 (1)
And the value of S = B / (B + D) defined by the bundle width B (mm) of the steel cord bundle and the distance D (mm) between the steel cord bundles is as follows: Formula (2),
0.60 ≦ S ≦ 0.80 (2)
It is characterized by satisfying the relationship indicated by.

In the heavy duty pneumatic tire of the present invention, the filament diameter F (mm) of the steel cord in the first layer and the second layer is expressed by the following formula (3):
0.20 ≦ F ≦ 0.45 (3)
Is preferably satisfied.

  According to the present invention, the above configuration makes it possible to realize a heavy duty pneumatic tire that achieves both durability and desired circumferential rigidity while reducing the weight of the tire. In particular, if the steel cord bundle that satisfies the formula (3) is satisfied, the effect of reducing the weight can be further improved.

It is a perspective view which shows an example of the structure of the heavy load vehicle tire of this invention. It is the top view which developed the belt in the plane and was seen from the tire radial direction outside. (A) is a schematic sectional drawing which shows the arrangement | sequence state of the steel cord in the 1st layer based on this invention, (b) is sectional drawing which takes out and shows the one steel cord.

DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a perspective view showing an example of the structure of a heavy-duty vehicle tire according to the present invention, and FIG. 2 is a plan view of the belt as seen from the outer side in the tire radial direction. The tire 1 according to the present invention has at least one carcass 2 extending in a toroid shape extending between a pair of left and right bead cores, and a belt 5 is arranged radially outside the carcass 2 and radially inside the tread 4. The belt 5 is composed of three belt layers (belt plies) in which a number of steel cords (hereinafter also referred to as “cords”) are arranged in the circumferential direction. These belt plies are composed of a first layer 6, a second layer 7, and a third layer 8 in order from the inside in the tire radial direction, and the cord 6a of the first layer 6 and the cord 7a of the second layer 7 are: The cord 7a of the second layer 7 and the cord 8a of the third layer 8 are inclined in the same direction with respect to the equator plane E. In the figure, reference numeral 3 denotes an inner liner.

  Further, in the tire 1 of the present invention, the inclination direction of the cord with respect to the tire equatorial plane E is opposite in the first layer 6 and the second layer 7 and in the same direction in the second layer 7 and the third layer 8. In addition, an inclination angle α of the cord 6a of the first layer 6 with respect to the tire equator plane E (hereinafter also referred to as “inclination angle α”), and an inclination angle β of the cord 7a of the second layer 7 with respect to the tire equator plane E (hereinafter referred to as “inclination angle α”). The inclination angle γ (hereinafter also referred to as “inclination angle γ”) of the cord 8a of the third layer 8 with respect to the tire equatorial plane E is 45 to 90 degrees. It is important. In the first layer 6 and the second layer 7, the cords 6 a, 7 a are inclined with respect to the tire equatorial plane E so as to have an angle of 10 to 25 degrees, thereby ensuring desired circumferential rigidity. If the inclination angles α and β are less than 10 degrees, it is difficult to manufacture the belt 5. On the other hand, if the inclination angles α and β exceed 25 degrees, the circumferential rigidity is greatly reduced. In addition, if the inclination angle γ is less than 45 degrees, the third layer 8 also bears the tension generated by the internal pressure, so that it tends to break when stepping over rocks, etc., while the inclination angle γ If γ exceeds 90 degrees, the desired effect of the present invention cannot be obtained.

  FIG. 3A is a schematic cross-sectional view showing an arrangement state of steel cords in the first layer according to the present invention, and FIG. 3B is a cross-sectional view showing one steel cord taken out. Show. As shown in the drawing, the first layer 6 according to the present invention is formed by arranging a plurality of steel cords 11 formed by twisting a plurality of filaments 13 in parallel in a bundle. The second layer 7 has the same configuration.

In the tire of the present invention, the height of the steel cord bundle 12, that is, the short diameter A (mm) of the steel cord and the bundle width B (mm) are expressed by the following formula (1),
B / A ≧ 2.0 (1)
And the value of S = B / (B + D) defined by the bundle width B (mm) of the steel cord bundle 12 and the distance D (mm) between the steel cord bundles 12 is as follows: (2),
0.60 ≦ S ≦ 0.80 (2)
It is important to satisfy the relationship indicated by.

  By making the steel cord bundle 12 satisfy the above formula (1), weight reduction can be secured, and satisfying the above formula (2), the circumferential rigidity and durability Can be compatible. If S is less than 0.60, the distance between the steel cord bundles 2 is increased, and at the same time, the restraint of the interlayer rubber is weakened, so that the circumferential rigidity required for the belt is insufficient. On the other hand, when S is larger than 0.80, the bundle interval is too narrow with respect to the bundle width, and therefore the inter-belt BES property due to crack propagation is deteriorated.

In the present invention, the diameter F (mm) of the filament 13 of the steel cord 11 in the first layer 6 and the second layer 7 is expressed by the following formula (3),
0.20 ≦ F ≦ 0.45 (3)
Is preferably satisfied. If the diameter F of the filament 13 exceeds this range, the wire drawing cost associated with production may be significantly deteriorated, which is not preferable.

  In the tire of the present invention, any tire satisfying the above conditions may be used, and thereby the desired effect of the present invention can be obtained. For example, the steel cord used in the present invention is a flat cord in the illustrated example, but is not limited thereto, and may be a normal circular cross-section cord. The details of the tire structure other than the bundled cord arrangement are not particularly limited, and can be appropriately configured according to a conventional method.

Hereinafter, the present invention will be described in more detail with reference to examples.
A heavy-duty pneumatic tire having a tire size of 11R22.5 was manufactured by applying a bundle-like cord arrangement in accordance with the conditions shown in Tables 1 to 4 below to each layer of a three-layer or four-layer belt. In Tables 1-3, the angle of the cord of each belt ply constituting the belt with respect to the tire equator plane is shown for each belt structure of the tire. The belt ply has a first layer on the inner side in the tire radial direction and a second layer, a third layer, and a fourth layer in order on the outer side. In addition, in the values of inclination angles (for example, R18, L52, etc.) in the table, “R” is inclined upward as viewed from the outside in the tire radial direction, and “L” is also viewed in the same manner. It indicates that the vehicle is tilted to the left, and the numerical value after that indicates the tilt angle with respect to the tire equatorial plane.

<Belt mass>
The obtained tire was dissected, a belt (a belt composed of three layers or four layers) was cut out, and a mass at a width of 50 mm and a length of 300 mm was measured. In comparison with the conventional example, a case where it is 5% or more lighter is marked with ◯, and a case where it is heavier than that is marked with ×.

<Circumferential rigidity>
The tire obtained above was attached to a rim of size 8.25, and the growth amount of the tire outer peripheral length when the internal pressure was filled from 50 kPa to 750 kPa was measured. Compared with the conventional example, the case where the growth amount was less than 10% was marked as ◯, and the case where the growth amount was larger than 10% was marked as x.

<BES properties>
The tire assembled on the rim was attached to a drum durability tester, and the durability test was performed under the conditions of an internal pressure of 750 kPa, a load of 2750 kgf, and a lateral force of 0.3 G. After running for 1,000 kilometers, the tire was dissected and the separation length generated at the belt end was measured. In comparison with the conventional example, the case where the separation length is excellent or similar is indicated as ◯, and the case where the separation length is inferior is indicated as ×.

<Belt cut test>
An iron sphere was fitted into a rib groove close to the crown center portion of the obtained tire to make a so-called “stone-engaged state” and traveled 10,000 km on a drum tester under conditions of an internal pressure of 750 kPa and a load of 2750 kgf. . After running, the tire was dissected, and compared with the conventional example, the case where there was no breakage of the cord at the portion where the stone was bitten was evaluated as ◯, and the case where there was breakage was evaluated as ×.

  Based on the above evaluation results, comprehensive evaluation was performed, and compared with the conventional example, the case where it was excellent was marked with ◎, and the case where it was inferior was marked with ×. These results are also shown in Tables 1 to 4 below.

  As shown in Tables 1 to 4, Examples 1 to 4 are lighter in weight, while exhibiting performance equal to or higher than that of the conventional example in circumferential rigidity, separation between belts (BES property) and belt cut property. It has become possible. On the other hand, in Comparative Examples 1 to 10, a decrease in circumferential rigidity and occurrence of separation between belts due to the design of S being out of the preferred range, or because the design of the belt angle is not in the preferred range, The cord was broken, and compatibility with the weight reduction of the belt was not achieved. Moreover, since the comparative example 11 had B / A smaller than 2.0, weight reduction was not able to be ensured.

DESCRIPTION OF SYMBOLS 1 Tire 2 Carcass 3 Inner liner 4 Tread 5 Belt 6 First layer 6a First layer cord 7 Second layer 7a Second layer cord 8 Third layer 8a Third layer cord 9 Cross layer pair 11 Steel cord 12 Steel Cord bundle 13 Filament E Tire equator

Claims (2)

A heavy-duty pneumatic tire having at least one carcass extending in a toroidal shape across a pair of left and right bead cores and having three belt layers on the outer side in the tire radial direction of the carcass,
The three belt layers are composed of a first layer, a second layer and a third layer in order from the inside in the tire radial direction,
The direction of inclination of the cord with respect to the tire equator plane is opposite in the first layer and the second layer, and in the same direction in the second layer and the third layer. The inclination angle with respect to the equator plane is configured so that the first layer and the second layer are 10 to 25 degrees, and the third layer is 45 to 90 degrees,
The first layer and the second layer are formed by arranging a plurality of steel cords formed by twisting a plurality of filaments in parallel in a bundle,
The short diameter (height) A (mm) and the bundle width B (mm) of the steel cord bundle of the first layer and the second layer are expressed by the following formula (1),
B / A ≧ 2.0 (1)
And the value of S = B / (B + D) defined by the bundle width B (mm) of the steel cord bundle and the distance D (mm) between the steel cord bundles is as follows: Formula (2),
0.60 ≦ S ≦ 0.80 (2)
A heavy-duty pneumatic tire characterized by satisfying the relationship represented by: The filament diameter F (mm) of the steel cord in the first layer and the second layer is expressed by the following formula (3),
0.20 ≦ F ≦ 0.45 (3)
The heavy-duty pneumatic tire according to claim 1, satisfying a relationship represented by:

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