JP2002178724A - Tire for heavy load - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce rolling resistance. SOLUTION: This tire has a carcass ply 6A comprising a return section 6b, which turns around a bead core 5 and returns, provided in a body section 6a, which is laid across the bead core 5 of a bead section 4, integrally. The bead section 4 includes a bead apex rubber 9, which extends between the body section 6a and the return section 6b in a tapered form outward in a radial direction from the bead core 5, a packing rubber 10 whose inner end in a radial direction is connected to the outside face 90 of the bead apex rubber 9 and whose outer end 10e extends outward in a radial direction in a tapered form along the body section 6a, and an outer side wall rubber 11, which is arranged outside a packing rubber 10 in the axial direction and forms the outer surface of the tire, and limits the loss tangent tan δand the complex modulus of elasticity E* in a fixed range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heavy duty tire capable of reducing rolling resistance without impairing durability.

[0002]

2. Description of the Related Art In order to protect the global environment, fuel consumption of automobiles has been reduced. For this reason, also for automobile tires, tires with low rolling resistance are desired, and particularly for heavy-duty tires used for heavy vehicles such as trucks and buses with large displacement and heavy fuel consumption, reduction of rolling resistance is desired. ing.

[0003] The rolling resistance of a tire is largely caused by energy loss due to repeated deformation during running. Therefore, in order to reduce the rolling resistance, for example, the rubber of the tread portion having the highest contribution ratio (about 34%) is made into two layers, the compounded rubber having small energy loss is provided on the inside, and the compounded rubber having excellent grip properties is provided on the outside. Have been proposed.

However, the tread portion has a large contribution to the reduction of rolling resistance, but also a large contribution to wear resistance, snow performance, wet performance and the like. In particular, low rolling resistance performance and these various running performances are often in a trade-off relationship in general. Accordingly, there is a problem that the above-described running performance is easily impaired by reducing the rolling resistance.

The present invention has been devised in view of the above-mentioned problems, and focuses on a bead portion that contributes relatively little to abrasion resistance and grip performance, and a rubber disposed on the bead portion. Based on improving the physical properties of the material, it aims to provide a tire for heavy load that can reduce the running resistance without impairing the running performance such as abrasion resistance, snow performance, wet performance, and the durability of the bead part And

[0006]

According to a first aspect of the present invention, there is provided a main body extending from a tread portion to a bead core of a bead portion via a sidewall portion, from the inside in the tire axial direction to the outside around the bead core. A heavy-duty tire provided with a carcass having a carcass ply integrally provided with a turn-back portion, wherein the bead portion is disposed between a main body portion of the carcass ply and a turn-up portion from an outer surface of the bead core to a tire radial outside. A bead apex rubber having a tapered inner surface facing the body portion side and an outer surface facing outward in the tire axial direction, an inner end side in the tire radial direction being connected to the outer surface of the bead apex rubber, and A packing rubber having an outer end tapering outward in the tire radial direction along the main body portion, and a tire axial direction of the packing rubber; Together provided that and includes an outer sidewall rubber that forms the outer surface of the tire to the outside, the loss tangent tanδ of the bead apex rubber 0.1
0 to 0.20 and a complex elastic modulus E * of 45 to 65 MPa,
And the loss tangent tan δ of the packing rubber is 0.03
0.09 and the complex elastic modulus E * is 3.4 to 3.8MP.
a, the loss tangent tan δ of the outer sidewall rubber is 0.065 to 0.125, and the complex elastic modulus E *
Is set to 3.0 to 3.4 MPa.

The complex elastic modulus and the loss tangent tan δ were both determined by preparing a strip sample of 4 mm width × 30 mm length × 1.5 mm thickness and using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd. Temperature 70 ° C, frequency 10Hz, dynamic strain ± 2
It is a value measured under the condition of%.

According to a second aspect of the present invention, the bead portion is disposed between the packing rubber and the outer sidewall rubber on an inner side in the tire axial direction and covers an outer end of a folded portion of the carcass ply. An edge cover rubber and an inner sidewall rubber disposed outside the edge cover rubber, and each loss tangent tanδ of the outer sidewall rubber, the inner sidewall rubber, and the packing rubber is determined by the loss of the ply edge cover rubber. The heavy load tire according to claim 1, wherein the tangent is smaller than tan δ.

Further, the loss tangent tan δ of the outer sidewall rubber, the inner sidewall rubber, and the packing rubber is as follows:
85 of loss tangent tan δ of the ply edge cover rubber
% Or less.

[0010]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view schematically showing a normal state in which a heavy-duty tire 1 used for heavy vehicles such as trucks (including light-duty trucks) and buses is assembled to a regular rim J and filled with a regular internal pressure and has no load. FIGS. 2A and 2B are partial enlarged views of the bead portion 4, respectively.

The "regular rim" is a rim defined for each tire in a standard system including the standard on which the tire is based, and is a standard rim for JATMA, and a "Design" for TRA. Rim "or" Measuring Rim "for ETRTO. "Normal internal pressure" is the air pressure specified for each tire in the standard system including the standard on which the tire is based. For JATMA, the maximum air pressure is used. For TRA, the table "TIRE LOAD LIMI
The maximum value described in "TS AT VARIOUS COLD INFLATION PRESSURES", or "INFLATION PRESSURE" for ETRTO.

In FIG. 1, a heavy load tire 1 includes a toroidal carcass 6 extending from a tread portion 2 to a bead core 5 of a bead portion 4 through a sidewall portion 3 and a radius of the carcass 6 inside the tread portion 2. A belt layer 7 that can firmly tighten the carcass 6 to increase the rigidity of the tread portion 2 and maintain the tire shape, and a tubeless type that is mounted on a 15-degree deep bottom rim in this example. An example is shown. The heavy load tire 1 of the present embodiment
The rubber material provided in the tread portion 2 is not particularly limited, and a composition that can maximize running performance can be used in consideration of wear resistance, wet performance, snow performance, and the like.

In the present embodiment, the carcass 6 is a single carcass ply 6A having a radial structure in which steel cords are arranged at an angle of 80 to 90 ° with respect to the tire equator C.
It consists of. The carcass ply 6A has a tread portion 2
A main body 6a extending from the first through the sidewall portion 3 to the bead core 5 of the bead portion 4;
Is integrally formed with a folded portion 6b which is turned around from the inside to the outside in the tire axial direction.

As shown in FIG. 3, the height h1 of the folded portion 6b from the bead base line BL is, for example, 2.2 to 3.5 times, more preferably 2 to 3.5 times the flange height hf of the regular rim J. It is desirable to set it to 0.6 to 3.1 times.
If the height h1 is less than 2.2 times the flange height hf, the outer end 6be of the folded portion 6B tends to be close to the rim flange Jf, and the outer end 6be is likely to be separated from the rubber at the outer end 6be. The folded portion 6b is easily pulled out toward the main body 6a. On the other hand, when the height h1 exceeds 3.5 times the flange height hf, not only is the tire weight increased, which is disadvantageous for rolling resistance, but also the outer end 6be of the folded portion 6b is strongly bent at the side wall. It approaches the part 3 side, and the rubber exfoliation easily occurs at the outer end 6be. The flange height hf of the 15 ° deep bottom rim is usually 12.
It is set to 7 mm. The bead base line BL is a tire axial line passing through the rim diameter position of the regular rim J.

In the present embodiment, the belt layer 7 includes an innermost belt ply 7A in which a steel cord is inclined at an angle of, for example, about 60 ± 10 ° with respect to the tire equator C;
5 shows a structure in which a total of four layers of belt plies 7B, 7C, and 7D in which steel cords are inclined at a small angle of 15 to 30 ° are overlapped. However, it is not limited to such a configuration.

As shown in FIG. 2 in an enlarged manner, a cord reinforcing layer 20 is arranged in the bead portion 4 so as to surround the carcass 6 in this embodiment. The cord reinforcing layer 20 includes
In this example, a base 20A extending inward in the tire radial direction of the bead core 5, an inner piece 20B extending from the inner end of the base 20A in the tire axial direction and extending outward in the tire radial direction along the inside of the main body 6a, and the base 20A And an outer piece 20C extending outward in the tire radial direction along the outside of the folded portion 6b. The outer piece 20C is formed in a substantially U-shaped cross section.

In the present embodiment, the cord reinforcing layer 20 is composed of one reinforcing ply in which steel cords arranged in parallel are covered with topping rubber. The steel cords are preferably arranged at an angle of about 15 to 60 ° with respect to the tire circumferential direction, and in this example, are inclined at an angle of about 25 °. As a result, the cord reinforcing layer 20 can fall down without excessive bending deformation of the cord in the tire axial direction and the tire circumferential direction, and can easily follow the deformation of the bead portion 4 during running. This is useful for improving the rigidity of the bead portion 4 while preventing the adhesive from being broken.

Since the cord reinforcing layer 20 has the base portion 20A located inside the bead core 5 in the tire radial direction, the cord reinforcing layer 20 is firmly fastened between the bead core 5 and the rim J, and the position is stabilized. The carcass ply 6
The carcass ply 6A can be reinforced because it has the inner piece 20B and the outer piece 20C extending outward in the tire radial direction along the main body portion 6a and the folded portion 6b of A. The cord reinforcing layer 20
Can be formed by two or more plies, or a ply using an organic fiber cord can be mixed or used alone.

In the cord reinforcing layer 20, as shown in FIG. 3, the heights h2 and h3 of the inner piece 20B and the outer piece 20C from the bead base line BL are, for example, 1.5 to 1.5 of the flange height hf. 2.8 times, more preferably 1.8 times
It is desirable to set it to 2.4 times. The height h2 or h
3 is less than 1.5 times the flange height hf, there is a tendency that the reinforcing effect on the carcass 6 by the inner piece 20B and the outer piece 20C tends not to be obtained. In addition to the increase in weight, the rolling resistance tends to be deteriorated, and the outer end of the inner piece 20B or the outer piece 20C tends to approach a severely bent region when the tire is loaded with a load, thereby reducing durability.

As shown in the enlarged view of FIG. 2, the bead portion 4 has a tapered portion between the main body portion 6a and the folded portion 6b of the carcass ply 6A from the outer surface of the bead core 5 outward in the tire radial direction. A bead apex rubber 9 that extends is provided. The complex elastic modulus E * of the bead apex rubber 9 is 45 to 65 MPa, more preferably 48 to 62 MPa, and still more preferably 50 to 57 M.
It is desirable to set it to Pa. The bead apex rubber 9
If the complex elastic modulus E * is less than 45 MPa, it is difficult to impart sufficient bending stiffness or the like that can withstand a high load to the bead portion 4 and the rolling resistance tends to deteriorate.
When the pressure exceeds 5 MPa, the rigidity of the bead portion 4 tends to be excessively increased, and a rigidity step is easily generated between the bead portion 4 and the sidewall portion 3 and the like, and the riding comfort tends to be significantly deteriorated. By limiting the complex elastic modulus E * of the bead apex 9 to a certain range in this way, the bending rigidity of the bead portion 4 is increased, and it is useful to maintain or improve the steering stability.

The bead apex rubber 9 has an inner side surface 9i facing the main body 6a of the carcass ply 6a,
An outer surface 9o having a slope facing outward in the axial direction of the tire is provided, and by connecting the inner surface 9i and the outer end of the outer surface 9o, the tire becomes sharper outward in the tire radial direction. FIG.
As shown in the figure, the outer end 9e of the bead apex rubber 9 is
The height h4 from the bead base line BL is set to, for example, about 2.8 to 4.3 times, more preferably about 3.0 to 4.0 times the flange height hf.

When the height h4 is less than 2.5 times,
Even if the complex elastic modulus E * is limited, the rigidity of the bead portion 4 required to withstand a high load cannot be obtained, so that the durability is remarkably reduced, causing damage, impairing the steering stability, and turning. There is a tendency for performance to deteriorate, and conversely 4.5
Even if it exceeds twice, the rigidity of the bead portion 4 is unnecessarily increased, which tends to deteriorate the riding comfort, and also causes a problem that the balance of hardness with the surrounding rubber is lost and durability performance is easily lowered.

The bead portion 4 includes a packing rubber 10.
Is arranged. The packing rubber 10 is configured such that an inner end 10i side in the tire radial direction is connected to the outer side surface 9o of the bead apex rubber 9 and an outer end 10e in the tire radial direction extends in a tapered shape along the main body 6a. Have been. The packing rubber 10 of the present example has a maximum thickness Tm in the tire axial direction at the position of the outer end 9e of the bead apex rubber 9, from which the tire radially inward and outward in the tire radial direction. The figure shows a structure formed by gradually reducing the thickness in the axial direction. The inner end 10i side of the packing rubber 10 in the tire radial direction is
The bead apex rubber 9 is connected to the outer surface 9o, and the inner end 10i reaches the bead core 5 and terminates.

The complex elastic modulus E * of the packing rubber 10
Is set to 3.4 to 3.8 MPa, more preferably 3.45 to 3.75 MPa, and still more preferably 3.5 to 3.8 MPa.
It is set to 3.7 MPa. If the complex elastic modulus E * of the packing rubber 10 is less than 3.4 MPa, a rigid step is likely to occur at the connection surface with the bead apex rubber 9, and the concentration of stress at the connection surface causes rubber peeling and the like, thereby lowering durability. In addition, the deformation of the bead portion 4 is increased, and the energy loss due to the deformation is increased, so that the rolling resistance is increased. On the other hand, if the complex elastic modulus E * of the packing rubber 10 exceeds 3.8 MPa, there are problems such as an increase in the longitudinal spring constant, deteriorating riding comfort, and damage to cargo.

In this embodiment, as shown in FIG. 3, the thickness ta of the bead apex rubber 9 in the tire axial direction at each height position in the tire radial direction and the packing rubber 10 are shown.
(Ta + tb) gradually decreases from the outer surface of the bead core 5 outward in the tire radial direction, and the outer end 9 e of the bead apex rubber 9.
This shows a preferred embodiment in which the thickness tb of the packing rubber 10 gradually decreases even outside the tire radial direction. As a result, the rigidity at the connection surface between the bead apex rubber 9 and the packing rubber 10 changes more smoothly, so that local deformation is prevented from being concentrated on the carcass 6 when the bead portion 4 is deformed during running under load. The durability of the bead portion 4 can be more effectively increased. The height h8 of the outer end 10e of the packing rubber 10
Is desirably set to, for example, about 5 to 8 times the flange height hf.

In the present embodiment, an outer sidewall rubber 11 forming an outer surface of the tire is disposed outside the packing rubber 10 in the tire axial direction. In the present embodiment, the outer sidewall rubber 11 is illustrated as one in which the bead portion 4 extends to near the outermost point Q in contact with the rim flange Jf of the normal rim J in the normal state. Although not shown, the outer end of the outer sidewall rubber 11 in the tire radial direction extends to a tread rubber disposed on the tread portion 2.

Such an outer sidewall rubber 1
1 is required to cover the side portion of the tire over a wide range, thereby protecting the tire from external damage, and being capable of flexibly bending and deforming following deformation due to running of the tire. For this reason, the outer sidewall rubber 11
Is set to be 3.0 to 3.4 MPa, more preferably 3.05 to 3.35 MPa, and still more preferably 3.1 to 3.3 MPa. If the complex elastic modulus E * of the outer sidewall rubber 11 is less than 3.0 MPa, there is a problem that the cut resistance is greatly reduced. Conversely, if it exceeds 3.4 MPa, the tire is repeatedly deformed by the load running. There are problems such as cracks and the like being easily generated in the rubber and ozone resistance being reduced.

A clinch rubber 19 is arranged on the inner end 11i side of the outer sidewall rubber 11 in the tire radial direction. The clinch rubber 19 has, for example, a JIS durometer hardness of 74 to 84 degrees, more preferably 76 to 84 degrees.
It is made of a relatively hard rubber set at 82 degrees, and extends to the bead sheet 4A, so that the bead portion 4 surrounds and forms a portion in contact with the rim J, and the bead portion 4 is preferably formed from the contact friction with the rim. To protect. Clinch rubber 1
It is desirable that the height h5 of the outer end of No. 9 be, for example, about 4.2 to 5.3 times the flange height hf.

In this embodiment, the bead portion 4 is disposed between the outer sidewall rubber 11 and the packing rubber 10 on the inner side in the tire axial direction and the outer end 6be of the folded portion 6a of the carcass ply 6A. And a ply edge cover rubber 12 that covers the rubber and an inner sidewall rubber 13 disposed outside the ply edge cover rubber 12.

In this embodiment, the ply edge cover rubber 12 covers the folded portion 6b of the carcass ply 6A and the outer end 20Ce of the outer piece 20C of the cord reinforcing layer 20. That is, the outer edge 12e of the ply edge cover rubber 12 in the tire radial direction is located outside the outer end 6be of the folded portion 6b in the tire radial direction (h6> h1). Preferably, the height h6 of the outer end 12e of the ply edge cover rubber 12 from the bead base line BL is, for example, 1.4 to 1.8 times, more preferably 1.6 to 1, times the height h1 of the folded portion 6b. It is desirable to set it to 0.8 times. If the height h6 is less than 1.4 times the height h1 of the folded portion 6b, rubber disposed radially outside the ply edge cover rubber 12 and the folded portion 6b
This is because a large elastic difference tends to occur between the outer end 6be and the outer end 6be, and ply loose tends to occur.

The inner end 1 of the ply edge cover rubber 12
2i is set at least inside the outer end 6be of the folded portion 6b in the tire radial direction. Particularly preferably,
In order to prevent a large rigidity step, the inner end of the ply edge cover rubber 12 is not more than 80% of the height h3 of the folded portion 6b, more preferably the inner piece 20 of the cord reinforcing layer 20.
It is preferable that the end be further terminated radially inward of the outer end 20Ce of C in the tire radial direction.

Such a ply edge cover rubber 12
Is made of a rubber material having excellent adhesiveness, which can effectively adhere to the end of a carcass cord having low adhesive strength. Specifically, a rubber material containing natural rubber or a natural rubber as a main component and, for example, carbon black, silica, a vulcanization aid, an adhesive such as a cobalt salt, sulfur, a vulcanizing agent such as a vulcanization accelerator, etc. Is preferably used.

The ply edge cover rubber 12 flexibly follows the movement of each of the outer ends 6be and 20Ce caused by the bending deformation of the tire, suppresses the adhesive breakage with each of the outer ends for a long period of time, and reduces the durability of the bead portion 4. Help to improve. In addition, the ply edge cover rubber 12 substantially covers the outer surface of the outer piece 20C of the cord reinforcing layer 20 in the tire axial direction, so that the strain between the outer piece 20C of the cord reinforcing layer 20 and the hard crimp rubber 19 is increased. Can be reduced, and the durability of the bead portion 4 can be improved. Further, the ply edge cover rubber 12 is provided with the outer piece 20 of the cord reinforcing layer 20.
It is also interposed between the outer end 20C of C and the folded portion 6b, and effectively relaxes and absorbs the shear strain between the cords.

From such a viewpoint, the complex elastic modulus E * of the ply edge cover rubber 12 is, for example, 6.5 to 10.5.
MPa, more preferably 7.5 to 9.5 MPa. When the complex elastic modulus E * is less than 6.5 MPa, there is a problem that deformation is large and heat generation is large, thereby impairing durability performance. Conversely, when the complex elastic modulus E * exceeds 10.5 MPa, the outer ends 6be and 20Ce have a problem. And the effect of improving the durability of the bead portion 4 is reduced.

The inner side wall rubber 13
Is arranged outside the ply edge cover rubber 12,
It mainly serves to reduce and absorb the difference in rigidity between the ply edge cover rubber 12 and the clinch rubber 13 or the outer sidewall rubber 11. That is, since the ply edge cover rubber 12 is softer and lower in elasticity than the clinch rubber 13, when it is directly connected to the clinch rubber 13, stress concentration occurs at the boundary surface thereof, and the durability is reduced due to adhesive failure. That's why. From such a viewpoint, the complex elastic modulus E of the inner sidewall rubber 13 is
* Is, for example, preferably from 3.4 to 3.9 MPa, more preferably from 3.55 to 3.75 MPa. The outer end height h7 of the inner sidewall rubber 13 is set to, for example, about 1.6 to 1.9 times the flange height hf.

The outer sidewall rubber 11, the inner sidewall rubber 13, and the packing rubber 10
Is 10% or less of the complex elastic modulus E * of the bead apex rubber 9, more preferably 5.0 to 5.0.
It is desirable to set about 7.5%. This allows
There is an advantage that the steering stability and the riding comfort can be maintained and the rolling resistance of the tire can be reduced without impairing the durability performance. The complex elastic modulus E * of the outer sidewall rubber 11, the inner sidewall rubber 13, and the packing rubber 10 is the complex elastic modulus E * of the bead apex rubber 9.
If it exceeds 10%, the balance of each rubber member is lost, the durability performance is reduced, and the rolling resistance tends to be deteriorated.

As described above, the bead portion 4 of the present embodiment is
By using various types of rubber materials, and by limiting the complex elastic modulus E * of each rubber optimally, the durability of the bead portion 4 can be improved, and driving stability and riding comfort can be improved. Performance can be maintained or improved.

In the present invention, the loss tangent tan of the bead apex rubber 9 is reduced in order to reduce the rolling resistance.
δ is 0.10 to 0.20, and the loss tangent tan δ of the packing rubber 10 is 0.03 to 0.09, and the loss tangent tan δ of the outer sidewall rubber 11 is 0.065 to 0.125. Is one of the features.

Since the bead apex rubber 9 is formed of a rubber material having a relatively high elasticity, the amount of bending and compression deformation during load running of the tire is relatively small. Therefore,
The bead apex rubber 9 also generates a relatively small amount of heat due to the deformation history, and thus limits the loss tangent tan δ as described above. Especially preferably, it is good to be 0.10 to 0.16.

The packing rubber 10 has a smaller complex elastic modulus E * than that of the bead apex rubber 9, and the area where the packing rubber 10 is disposed has a relatively large amount of bending deformation and generates a large amount of heat. Easily.
Therefore, in the present embodiment, by setting the loss tangent tan δ of the packing rubber 10 to a value smaller than that of the bead apex rubber 9 as described above, energy loss in the region is reduced, and rolling resistance is reduced. ing.
From such a viewpoint, the packing rubber 1 is particularly preferable.
It is desirable to set the loss tangent tan δ of 0 to 0.03 to 0.07, more preferably 0.03 to 0.06.

The outer sidewall rubber 11 is also
Since the loss tangent tan δ is set to be smaller than that of the bead apex rubber 9 as described above, the energy loss is reduced and the rolling resistance is reduced. From such a viewpoint, the loss tangent tan δ of the outer sidewall rubber 11 is particularly preferably 0.065 to 0.110, more preferably 0.065 to 0.165.
It is desirable to set it to 0.090.

By limiting the loss tangent tan δ of each rubber as described above, the loss of energy (heat generation) in the bead portion 4 is greatly reduced as compared with the conventional one without impairing the running performance and durability, and the rolling of the tire is reduced. Resistance can be improved.
Also preferably, the loss tangent tan δ of the ply edge cover rubber 12 is set to 0.135 to 0.150, more preferably 0.135 to 0.145. This allows
The durability can be improved without impairing the adhesiveness to the steel cord at the ply edge. More preferably, the loss tangent tan δ of the inner sidewall rubber 13 is set to 0.050 to 0.100, more preferably 0.050 to 0.090. Thereby, the durability performance of the bead portion 4 can be further improved.

The folded portion 6 of the carcass ply 6A
In b, damage due to heat generation during running is likely to occur. In order to prevent such damage, it is most effective to surround the ply edge cover rubber 12 covering the folded portion 6b with rubber having a smaller heat generation (smaller loss tangent tan δ) than the ply edge cover rubber 12. Become. Therefore, in this embodiment, the loss tangent tan δ of the outer sidewall rubber 11, the inner sidewall rubber 13, and the packing rubber 10 is smaller than the loss tangent tan δ of the ply edge cover rubber, preferably 85%. By setting the following, the rolling resistance is reduced and, at the same time, the damage of the folded portion 6b is effectively prevented.

More specifically, each of the loss tangents tan δ of the outer sidewall rubber 11 and the inner sidewall rubber 13 is determined by the ply edge cover rubber 12
50 to 70% of the loss tangent tan δ of
5 to 65%. The loss tangent tan δ of the packing rubber 10 is 30 to 50% of the loss tangent tan δ of the ply edge cover rubber 12, and more preferably 35 to 50%.
45%. Thereby, the rolling resistance of the tire can be further reduced, and the durability performance can be improved.

[0045]

EXAMPLE The tire size was 11R22.5 14P.
R. A radial tire for heavy load having the basic configuration shown in FIGS. 1 and 2 was prototyped according to the specifications shown in Tables 1 and 2, and tested for rolling resistance and durability of the bead portion. The common structure of the tire and the contents of the test are as follows

Tire structure Carcass) Number of plies: 1, cord material: steel Cord construction: 3 / 0.20 + 7 / 0.23 Angle: 90 ° at the tire equator Belt layer) Number of plies: 4, cord material: steel cord construction 1 × 3 / 0.20 + 6 / 0.35 Angle: 51 ° R, 19 ° R, 19 ° R at the tire equator
19 ° L cord reinforcing layer) Number of plies: 1, cord material: steel Cord configuration: 1 × 9 / 0.20 + W Angle: 25 ° at the tire equator Height of each part hf = 12.7 mm h1 / hf = 2.8 h2 / hf = 2.0 h3 / hf = 2.0 h4 / hf = 3.5 h5 / hf = 4.7 h6 / hf = 4.5 h7 / hf = 4.6 h8 / hf = 6.7

Test method (1) Rolling resistance index Using a rolling resistance tester, each tire was subjected to a regular rim (22.
5 × 8.25 15 ° deep bottom rim)
The rolling resistance was measured at kPa, a speed of 80 km / h, and a load of 24.52 KN, and was indicated by an index when the tire of Comparative Example 1 was set to 100. The smaller the value, the smaller the rolling resistance and the better.

(2) Bead endurance index The test tire was mounted on a regular rim (22.5 × 8.25 at 15 °).
The drum test machine is run under the conditions of test load (three times the standard maximum load = 88 KN) and test speed (20 km / h) while assembling the rim with the regular internal pressure (784 KPa) on the deep bottom rim. The running distance at which damage that was visually observable occurred was measured. The higher the value, the better.

(3) Running Performance The test tires were mounted on the front wheels of a 2-D-4 10-ton constant load test vehicle, and the characteristics related to ride comfort, steering wheel responsiveness, rigidity, grip, etc. were measured by the driver's sensuality. According to the evaluation, the evaluation was made according to a 10-point method with the comparative example being 6. The larger the value, the better the running performance.

The results of the test are shown in Tables 1 and 2, and it was confirmed that the tires of the examples reduced the rolling resistance while improving the durability of the bead portions. Also, it was confirmed that there was no decrease in running performance.

[0051]

[Table 1]

[0052]

[Table 2]

[0053]

As described above, the heavy duty tire of the present invention can reduce the rolling resistance without impairing the durability and running performance of the bead portion.

[Brief description of the drawings]

FIG. 1 is a meridional sectional view (right half) of a tire showing one embodiment of the present invention.

FIG. 2 is an enlarged view of a bead portion.

FIG. 3 is an enlarged view of a bead portion.

[Explanation of symbols]

 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 6a Body part of carcass ply 6B Carcass ply turnback part 7 Belt layer 9 Bead apex rubber 10 Packing rubber 11 Outer side wall rubber 12 Ply edge cover rubber 13 Inner side wall Rubber 20 Cord reinforcement layer

Claims (3)

[Claims] 1. A carcass having a carcass ply in which a bend portion is provided integrally with a body portion extending from a tread portion to a bead core of a bead portion through a sidewall portion to bend around the bead core from inside to outside in the tire axial direction. A tire for heavy load, wherein the bead portion extends between the main body portion and the folded portion of the carcass ply from the outer surface of the bead core to a radially outer side in the tire radial direction and an inner surface facing the main body portion side. A bead apex rubber having an outer surface facing outward in the tire axial direction, an inner end side in the tire radial direction connected to the outer surface of the bead apex rubber, and an outer end tapering outward in the tire radial direction along the main body. A packing rubber extending outside, and an outer surface disposed outside the packing rubber in the tire axial direction and forming an outer surface of the tire; Together containing Id wall rubber, the loss tangent tanδ of the bead apex rubber 0.
10 to 0.20 and complex elastic modulus E * of 45 to 65MP
a, and the loss tangent tan δ of the packing rubber is 0.03
0.09 and the complex elastic modulus E * is 3.4 to 3.8MP.
a, and the loss tangent ta of the outer sidewall rubber
A heavy duty tire characterized in that nδ is 0.065 to 0.125 and the complex elastic modulus E * is 3.0 to 3.4 MPa. 2. The ply edge cover rubber disposed between the packing rubber and the outer sidewall rubber in the tire axial direction and covering an outer end of a folded portion of the carcass ply. And the loss tangent tan δ of the outer sidewall rubber, the inner sidewall rubber, and the packing rubber is smaller than the loss tangent tan δ of the ply edge cover rubber. The heavy duty tire according to claim 1, wherein: 3. The loss tangent tan δ of the outer sidewall rubber, the inner sidewall rubber, and the packing rubber is not more than 85% of the loss tangent tan δ of the ply edge cover rubber. 2. The heavy duty tire according to 2.