JP4567180B2 - Heavy duty tire - Google Patents

Description

【００５２】
【表２】

【００５３】
【発明の効果】
以上のように、本発明の重荷重用タイヤは、ビード部の耐久性や走行性能を損ねることなく転がり抵抗を低減しうる。
【図面の簡単な説明】
【図１】本発明の一実施形態を示すタイヤの子午断面図（右半分）である。
【図２】ビード部の拡大図である。
【図３】ビード部の拡大図である。
【符号の説明】
２ トレッド部
３ サイドウォール部
４ ビード部
５ ビードコア
６ カーカス
６ａ カーカスプライの本体部
６Ｂ カーカスプライの折返し部
７ ベルト層
９ ビードエーペックスゴム
１０ パッキングゴム
１１ アウターサイドウォールゴム
１２ プライエッジカバーゴム
１３ インナーサイドウォールゴム
２０ コード補強層[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heavy duty tire that can reduce rolling resistance without impairing durability.
[0002]
[Prior art and problems to be solved by the invention]
In order to protect the global environment, the fuel efficiency of automobiles is being reduced. For this reason, tires with low rolling resistance are also desired for automobile tires, and in particular, reduction of rolling resistance is desired for heavy-duty tires used in heavy vehicles such as trucks and buses with large displacement and high fuel consumption. ing.
[0003]
The rolling resistance of the tire is largely attributed to energy loss accompanying repeated deformation during traveling. Therefore, in order to reduce rolling resistance, for example, the rubber of the tread portion having the highest contribution ratio (approximately 34%) is made into two layers, the compounded rubber having a small energy loss on the inside, and the compounded rubber having excellent grip on the outside. The structure etc. which arranged each is proposed.
[0004]
However, the tread portion has a large contribution ratio to the reduction of rolling resistance, but also has a large contribution ratio to wear resistance performance, snow performance, wet performance, and the like. In particular, the low rolling resistance performance and these various performances are generally in a trade-off relationship. Therefore, there has been a problem that the above-mentioned running performance is liable to be impaired by reducing the rolling resistance.
[0005]
The present invention has been devised in view of the above problems, and pays attention to a bead portion that contributes relatively little to wear resistance, grip performance, etc., and the physical properties of the rubber material disposed in this bead portion. It is an object of the present invention to provide a heavy-duty tire capable of reducing rolling resistance without impairing running performance such as wear resistance, snow performance, wet performance, and durability of the bead portion.
[0006]
[Means for Solving the Problems]
The invention according to claim 1 of the present invention is a carcass in which a body portion that extends from a tread portion to a bead core of a bead portion to a bead core is integrally provided with a folded portion that folds around the bead core from the inner side to the outer side in the tire axial direction. A heavy-duty tire having a carcass having a ply, wherein the bead portion tapers from the outer surface of the bead core to the outer side in the tire radial direction between the main body portion and the folded portion of the carcass ply and the main body portion. A bead apex rubber having an inner surface facing the outer side and an outer surface facing the outer side in the tire axial direction, an inner end side in the tire radial direction is connected to the outer surface of the bead apex rubber, and an outer end along the main body portion Packing rubber extending in the tire radial direction outside, and the outer surface of the tire arranged outside the packing rubber in the tire axial direction The bead apex rubber has a loss tangent tan δ of 0.10 to 0.20, a complex elastic modulus E * of 45 to 65 MPa, and the packing rubber has a loss tangent tan δ of 0.03. To 0.09, the complex elastic modulus E * is 3.4 to 3.8 MPa, the loss tangent tan δ of the outer sidewall rubber is 0.065 to 0.125, and the complex elastic modulus E * is 3.0 to 3. It is characterized by being 4 MPa.
[0007]
The complex elastic modulus and loss tangent tan δ are both 4 mm wide × 30 mm long × 1.5 mm thick strip samples, and a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co. is used at a temperature of 70 ° C. , Values measured under conditions of a frequency of 10 Hz and a dynamic strain of ± 2%.
[0008]
According to a second aspect of the present invention, there is provided a ply edge cover rubber in which the bead portion is disposed between the packing rubber and the outer sidewall rubber on the inner side in the tire axial direction and covers an outer end of the folded portion of the carcass ply. Each of the loss tangents tan δ of the outer sidewall rubber, the inner sidewall rubber, and the packing rubber from the loss tangent tan δ of the ply edge cover rubber. The heavy duty tire according to claim 1, wherein the tire is also small.
[0009]
The invention according to claim 3 is characterized in that each loss tangent tan δ of the outer side wall rubber, the inner side wall rubber, and the packing rubber is 85% or less of the loss tangent tan δ of the ply edge cover rubber. The heavy-duty tire according to claim 2.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view schematically showing a normal state in which a heavy load tire 1 used for heavy vehicles such as trucks (including small trucks) and buses is assembled on a normal rim J and filled with a normal internal pressure and is not loaded. FIG. 2 and FIG. 2 show partially enlarged views of the bead portion 4.
[0011]
The “regular rim” is a rim that each standard defines for each tire in the standard system including the standard on which the tire is based, and is a standard rim for JATMA, “Design Rim” for TRA, For ETRTO, use “Measuring Rim”. In addition, “regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. The maximum air pressure for JATMA and the table “TIRE LOAD LIMITS AT for TRA” The maximum value described in “VARIOUS COLD INFLATION PRESSURES”. If ETRTO, “INFLATION PRESSURE”.
[0012]
In the figure, a heavy load tire 1 includes a toroidal carcass 6 extending from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4, an inner side of the tread portion 2 and a radially outer side of the carcass 6. And 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. In this example, a tubeless type that is mounted on a 15-degree deep rim is illustrated. Yes. In the heavy load tire 1 of the present embodiment, the rubber material disposed in the tread portion 2 is not particularly limited, and the traveling performance can be maximized in consideration of wear resistance, wet performance, snow performance, and the like. Formulation or the like can be used.
[0013]
In this example, the carcass 6 is composed of a single carcass ply 6A having a radial structure in which steel cords are inclined with respect to the tire equator C at an angle of 80 to 90 °. The carcass ply 6A includes a main body portion 6a that extends from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and a folded portion that is folded around the bead core 5 from the inner side in the tire axial direction to the main body portion 6a. 6b is formed integrally.
[0014]
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 the flange height hf of the regular rim J, more preferably 2.6 to 3.1 Desirable to be 1 time. When 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. The folded portion 6b is easily pulled out toward the main body portion 6a. On the other hand, if the height h1 exceeds 3.5 times the flange height hf, not only will the tire weight increase and the rolling resistance will be disadvantageous, but the outer end 6be of the turned-up portion 6b will have a highly bent side wall. It approaches to the part 3 side, and rubber peeling easily occurs at the outer end 6be. The flange height hf of the 15 ° deep bottom rim is normally set to 12.7 mm. The bead base line BL is a tire axial line passing through the rim diameter position of the regular rim J.
[0015]
In this example, the belt layer 7 includes the innermost belt ply 7A in which the steel cord is inclined at an angle of, for example, about 60 ± 10 ° with respect to the tire equator C, and the steel cord 15 to 30 ° with respect to the tire equator C The belt plies 7B, 7C, and 7D that are arranged at an inclination of a small angle are stacked to form a total of four layers. However, it is not limited to such a configuration.
[0016]
Further, as shown in an enlarged view in FIG. 2, the bead portion 4 is provided with a cord reinforcing layer 20 so as to wrap the carcass 6 in this example. In this example, the cord reinforcing layer 20 includes a base portion 20A extending inward in the tire radial direction of the bead core 5 and an inner portion extending inward of the tire radial direction along the inner side of the main body portion 6a. It has a piece 20B and an outer piece 20C that continues to the outer end of the base portion 20A and extends outward in the tire radial direction along the outer side of the turned-up portion 6b, and has a substantially U-shaped cross section.
[0017]
In this example, the cord reinforcing layer 20 is composed of one reinforcing ply in which parallel steel cords are covered with a topping rubber. The steel cords are preferably arranged at an angle of, for example, about 15 to 60 ° with respect to the tire circumferential direction, and are inclined at an angle of about 25 ° in this example. Thereby, the cord reinforcing layer 20 can fall down without causing 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 helps to improve the rigidity of the bead portion 4 while preventing adhesive breakage.
[0018]
Further, the cord reinforcing layer 20 has the base portion 20A located on the inner side in the tire radial direction of the bead core 5, so that the cord reinforcing layer 20 is firmly tightened between the bead core 5 and the rim J, and the position is stabilized. Further, the carcass ply 6A can be reinforced because the carcass ply 6A 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 turned-up portion 6b. The cord reinforcing layer 20 can be formed of two or more plies, and a ply using an organic fiber cord can be mixed or used alone.
[0019]
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 2.8 of the flange height hf. It is desirable to make it twice, more preferably 1.8 to 2.4 times. When the height h2 or h3 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 cannot be obtained, and conversely, 2.8 times. If it exceeds 1, there is a tendency to deteriorate the rolling resistance due to an increase in the tire weight, and the outer end of the inner piece 20B or the outer piece 20C approaches a region where bending is severe when the tire is loaded with load, resulting in a decrease in durability. There is a tendency to make it.
[0020]
Further, as shown in an enlarged view in FIG. 2, the bead portion 4 has a bead extending in a tapered manner from the outer surface of the bead core 5 to the outer side in the tire radial direction between the main body portion 6a and the folded portion 6b of the carcass ply 6A. Apex rubber 9 is arranged. 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 MPa. When the complex elastic modulus E * of the bead apex rubber 9 is less than 45 MPa, it is difficult to give the bead portion 4 sufficient bending rigidity that can withstand a high load, and the rolling resistance tends to deteriorate. If it exceeds 65 MPa, the rigidity of the bead part 4 tends to be excessively increased, and a rigidity step is likely to occur between the side wall part 3 and the like, and the riding comfort tends to be remarkably 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, which helps to maintain or improve the steering stability.
[0021]
The bead apex rubber 9 has an inner surface 9i facing the main body portion 6a of the carcass ply 6a, and an outer surface 9o formed of a slope facing the outer side in the tire axial direction. The bead apex rubber 9 has an outer surface 9o outside the inner surface 9i and the outer surface 9o. By connecting the ends, the tires are sharpened outward in the tire radial direction. As shown in FIG. 3, the outer end 9e of the bead apex rubber 9 has a height h4 from the bead base line BL of, for example, 2.8 to 4.3 times the flange height hf, more preferably 3.0 to It is set to about 4.0 times.
[0022]
If 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 necessary to withstand a high load cannot be obtained. May occur, steering stability may be impaired, turning performance may deteriorate, and conversely, even if it exceeds 4.5 times, the rigidity of the bead part 4 is unnecessarily increased and the ride comfort is deteriorated. In addition to being easily invited, there is a problem that the balance of hardness with the surrounding rubber is lost, and the durability performance is likely to deteriorate.
[0023]
A packing rubber 10 is disposed on the bead portion 4. The packing rubber 10 is configured such that the inner end 10i side in the tire radial direction is connected to the outer side surface 9o of the bead apex rubber 9 and the outer end 10e in the tire radial direction extends in a tapered shape along the main body 6a. Has been. In the packing rubber 10 of this example, the thickness in the tire axial direction is the maximum thickness Tm at the position of the outer end 9e of the bead apex rubber 9. It shows what was formed by gradually reducing the thickness in the axial direction. Further, the inner end 10 i side of the packing rubber 10 in the tire radial direction is connected to the outer surface 9 o of the bead apex rubber 9, and the inner end 10 i reaches the bead core 5 and terminates.
[0024]
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 3.7 MPa. When the complex elastic modulus E * of the packing rubber 10 is less than 3.4 MPa, a rigidity step is likely to occur on the connection surface with the bead apex rubber 9, and rubber peeling or the like occurs due to stress concentration on the connection surface, resulting in a decrease in durability. In addition, there is a problem that 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, when the complex elastic modulus E * of the packing rubber 10 exceeds 3.8 MPa, the longitudinal spring constant becomes large and the riding comfort is deteriorated, or the load is damaged.
[0025]
Further, in this example, as shown in FIG. 3, the sum of the thickness ta of the bead apex rubber 9 in the tire axial direction and the thickness tb of the packing rubber 10 in the tire axial direction at each height position in the tire radial direction ( (ta + tb) is preferable in which the thickness tb of the packing rubber 10 gradually decreases gradually from the outer surface of the bead core 5 toward the outer side in the tire radial direction and smoothly from the outer end 9e of the bead apex rubber 9 toward the outer side in the tire radial direction. Is shown. As a result, the rigidity of the connecting surface between the bead apex rubber 9 and the packing rubber 10 changes more smoothly, so that local distortion is not concentrated on the carcass 6 when the bead portion 4 is deformed during load loading. The durability of the bead portion 4 can be increased more effectively. The height h8 of the outer end 10e of the packing rubber 10 is preferably about 5 to 8 times the flange height hf, for example.
[0026]
Moreover, in this embodiment, the outer side wall rubber 11 which forms a tire outer surface is distribute | arranged to the tire axial direction outer side of the said packing rubber 10. FIG. In the present embodiment, the outer side wall rubber 11 exemplifies that the bead portion 4 extends to the vicinity of the outermost point Q contacting 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 the tread rubber disposed in the tread portion 2.
[0027]
Such outer side wall rubber 11 needs to be able to flexibly deform flexibly following the deformation caused by running of the tire while protecting the tire from trauma by covering the side portion of the tire over a wide range. Is done. For this reason, the complex elastic modulus E * of the outer sidewall rubber 11 is set to 3.0 to 3.4 MPa, more preferably 3.05 to 3.35 MPa, and still more preferably 3.1 to 3.3 MPa. It is desirable to do. When the complex elastic modulus E * of the outer side wall rubber 11 is less than 3.0 MPa, there is a problem that the cut resistance is greatly reduced. On the contrary, when it exceeds 3.4 MPa, the tire is repeatedly deformed due to load running. As a result, there is a problem that the rubber tends to crack or the ozone resistance is lowered.
[0028]
A clinch rubber 19 is disposed on the inner end 11 i side in the tire radial direction of the outer side wall rubber 11. The clinch rubber 19 is made of a relatively hard rubber having a JIS durometer hardness of 74 to 84 degrees, more preferably 76 to 82 degrees, for example, and the bead portion 4 becomes rim J by extending to the bead sheet 4A. The bead portion 4 is suitably protected from contact friction with the rim. The height h5 of the outer end of the clinch rubber 19 is preferably about 4.2 to 5.3 times the flange height hf, for example.
[0029]
Further, in this embodiment, the bead portion 4 is a ply that is disposed between the outer side wall rubber 11 and the packing rubber 10 on the inner side in the tire axial direction and covers the outer end 6be of the folded portion 6a of the carcass ply 6A. The thing provided with the edge cover rubber | gum 12 and the inner side wall rubber | gum 13 distribute | arranged to the outer side is illustrated.
[0030]
In this example, the ply edge cover rubber 12 exemplifies the one that covers both 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 ply edge cover rubber 12 has an outer end 12e in the tire radial direction positioned 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 the height h1 of the folded portion 6b, more preferably 1.6 to 1. .8 times is desirable. When the height h6 is less than 1.4 times the height h1 of the folded portion 6b, the height h6 is large between the rubber disposed on the radially outer side of the ply edge cover rubber 12 and the outer end 6be of the folded portion 6b. This is because an elastic difference tends to occur and ply loose is likely to occur.
[0031]
The inner end 12i of the ply edge cover rubber 12 is set at least on the inner side in the tire radial direction than the outer end 6be of the folded portion 6b. Particularly preferably, the inner end of the ply edge cover rubber 12 is 80% or less of the height h3 of the folded portion 6b, more preferably outside the inner piece 20C of the cord reinforcing layer 20 in order to prevent a large rigidity step. It is preferable to terminate the inner side in the tire radial direction further than the end 20Ce.
[0032]
Such ply edge cover rubber 12 is made of a rubber material having excellent adhesiveness that can be effectively bonded to the end of a carcass cord having low adhesive strength. Specifically, a rubber material containing natural rubber or natural rubber as a main component, for example, an adhesive such as carbon black, silica, a vulcanization aid, a cobalt salt, or a vulcanizing agent such as sulfur or a vulcanization accelerator. Are preferably used.
[0033]
Further, the ply edge cover rubber 12 flexibly follows the movement of the outer ends 6be and 20Ce accompanying the bending deformation of the tire, and suppresses adhesion failure with the outer ends for a long time, thereby improving the durability of the bead portion 4. To help. The ply edge cover rubber 12 substantially covers the outer side surface in the tire axial direction of the outer piece 20C of the cord reinforcing layer 20, so that the strain between the outer piece 20C of the cord reinforcing layer 20 and the hard clinker rubber 19 is increased. It is possible to alleviate the above and further improve the durability of the bead portion 4. The ply edge cover rubber 12 is also interposed between the outer end 20Ce of the outer piece 20C of the cord reinforcement layer 20 and the folded portion 6b, and effectively relaxes and absorbs the exclusive strain between the cords.
[0034]
From such a viewpoint, it is desirable that 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 the deformation is large and heat generation is large and the durability performance is impaired. Conversely, when the complex elastic modulus E * exceeds 10.5 MPa, the outer ends 6be and 20Ce It is inferior to the ability to relieve the distortion, and the effect of improving the durability of the bead portion 4 is reduced.
[0035]
The inner side wall rubber 13 is arranged outside the ply edge cover rubber 12 and mainly serves to relax and absorb the rigidity difference between the ply edge cover rubber 12 and the clinch rubber 13 or the outer side wall rubber 11. That is, since the ply edge cover rubber 12 is softer and less elastic than the clinch rubber 13, if it is directly connected to the clinch rubber 13, stress concentration occurs at the boundary surface, resulting in a decrease in durability due to adhesive failure. Because. From such a viewpoint, it is desirable that the complex elastic modulus E * of the inner sidewall rubber 13 is, for example, 3.4 to 3.9 MPa, more preferably 3.55 to 3.75 MPa. The outer end height h7 of the inner sidewall rubber 13 is set to about 1.6 to 1.9 times the flange height hf, for example.
[0036]
The complex elastic modulus E * of the outer side wall rubber 11, the inner side wall 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 7.5. It is desirable to set to about%. Thereby, there is an advantage that the rolling stability of the tire can be reduced while maintaining the steering stability and the riding comfort performance without impairing the durability performance. When the complex elastic modulus E * of the outer side wall rubber 11, the inner side wall rubber 13 and the packing rubber 10 exceeds 10% of the complex elastic modulus E * of the bead apex rubber 9, the balance of each rubber member is lost. There is a tendency for durability performance to deteriorate and rolling resistance to deteriorate.
[0037]
As described above, the bead portion 4 of the present embodiment is configured using many types of rubber materials, and the durability of the bead portion 4 is optimally limited by limiting the complex elastic modulus E * of each rubber. As well as driving performance such as handling stability and riding comfort can be maintained or improved.
[0038]
In the present invention, in order to reduce rolling resistance, the loss tangent tan δ of the bead apex rubber 9 is set to 0.10 to 0.20, and the loss tangent tan δ of the packing rubber 10 is set to 0.03 to 0.09. In addition, the loss tangent tan δ of the outer side wall rubber 11 is set to 0.065 to 0.125 as one of the characteristic matters.
[0039]
Since the bead apex rubber 9 is formed of a rubber material having a relatively high elasticity, the amount of deformation during bending and compression when the tire is loaded is relatively small. Accordingly, the bead apex rubber 9 has a relatively small amount of heat generated by the deformation history, and thus limits the loss tangent tan δ as described above. Especially preferably, it is good to set it as 0.10-0.16.
[0040]
The packing rubber 10 has a complex elastic modulus E * set smaller than that of the bead apex rubber 9, and the region where the packing rubber 10 is disposed has a relatively large amount of bending deformation and tends to generate heat. For this reason, in the present embodiment, the loss tangent tan δ of the packing rubber 10 is set to a smaller value as compared with the bead apex rubber 9 as described above, thereby reducing the energy loss in the region and reducing the rolling resistance. ing. From this viewpoint, it is particularly preferable that the loss tangent tan δ of the packing rubber 10 is 0.03 to 0.07, and more preferably 0.03 to 0.06.
[0041]
Since the outer side wall rubber 11 is also arranged in a region where deformation is large as described above, by setting the loss tangent tan δ smaller than that of the bead apex rubber 9, energy loss is reduced and rolling resistance is reduced. . From such a viewpoint, it is particularly preferable that the loss tangent tan δ of the outer sidewall rubber 11 is 0.065 to 0.110, more preferably 0.065 to 0.090.
[0042]
By limiting the loss tangent tan δ of each rubber in this way, energy loss (heat generation) in the bead portion 4 is greatly reduced as compared with the conventional one without impairing running performance and durability, and tire rolling resistance is improved. Yes. 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. Thereby, durability can be improved, without impairing the adhesiveness with the steel cord in a ply edge. Still more preferably, the loss tangent tan δ of the inner side wall rubber 13 is set to 0.050 to 0.100, more preferably 0.050 to 0.090. Thereby, the durability performance of the bead part 4 can further be improved.
[0043]
Further, the folded portion 6b of the carcass ply 6A is likely to be damaged due to heat generation during traveling. 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 lower heat generation property (small loss tangent tan δ) than the ply edge cover rubber 12. Become. Therefore, in this embodiment, each 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%. The following setting is made to effectively prevent the folded portion 6b from being damaged simultaneously with the reduction of the rolling resistance.
[0044]
More specifically, the loss tangent tan δ of the outer sidewall rubber 11 and the inner sidewall rubber 13 is 50 to 70%, more preferably 55 to 65% of the loss tangent tan δ of the ply edge cover rubber 12. . The loss tangent tan δ of the packing rubber 10 is 30 to 50%, more preferably 35 to 45% of the loss tangent tan δ of the ply edge cover rubber 12. Thereby, the rolling resistance of the tire can be further reduced and the durability performance can be improved.
[0045]
【Example】
Tire size is 11R22.5 14P. R. A heavy-duty radial tire having the basic structure shown in FIGS. 1 and 2 was prototyped according to the specifications shown in Tables 1 and 2, and tested for rolling resistance and bead durability. The tire common structure and test contents are as follows.
[0046]
Tire structure
Carcass)
Number of plies: 1, cord material: steel
Code structure: 3 / 0.20 + 7 / 0.23
Angle: 90 ° on the tire equator
Belt layer)
Number of plies: 4, cord material: steel
Cord configuration: 1 × 3 / 0.20 + 6 / 0.35
Angle: 51 ° R, 19 ° R, 19 ° R, 19 ° L on the tire equator
Cord reinforcement layer)
Number of plies: 1, cord material: steel
Cord configuration: 1 × 9 / 0.20 + W
Angle: 25 ° on the tire equator
Height of each part
hf = 12.7mm
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
[0047]
Test method
(1) Rolling resistance index
Using a rolling resistance tester, each tire was mounted on a regular rim (22.5 × 8.25 15 ° deep bottom rim), and the rolling resistance was measured at an internal pressure of 700 kPa, a speed of 80 km / h, and a load of 24.52 KN. The tires of Comparative Example 1 are shown as an index when the tire is 100.
The smaller the value, the smaller the rolling resistance and the better.
[0048]
(2) Bead durability index
A test tire was assembled on a regular rim (22.5 × 8.25 15 ° deep bottom rim) with a regular internal pressure (784 KPa), and the test load (three times the standard maximum load = 88 KN), test speed (20 km / Under the conditions of h), the drum tester was run, and the running distance at which damage visually visible in the bead portion occurred was measured and displayed as an index with a comparative example of 100. The larger the value, the better.
[0049]
(3) Driving performance
The test tire is mounted on the front wheel of a 2-D-4 10-ton constant load test vehicle, and the characteristics relating to ride comfort, handle response, rigidity, grip, etc. are evaluated by the driver's sensory evaluation as Comparative Example 6 It was evaluated by the 10-point method. The larger the value, the better the running performance.
[0050]
The test results 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 portion. It was also confirmed that there was no decrease in running performance.
[0051]
[Table 1]

[0052]
[Table 2]

[0053]
【The invention's effect】
As described above, the heavy load tire of the present invention can reduce 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 an 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
3 Side wall
4 Bead section
5 Bead core
6 Carcass
6a Carcass ply body
6B Carcass ply turn-up 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)

A heavy duty tire comprising a carcass having a carcass ply in which a body portion extending from a tread portion to a bead core of a bead portion to a bead core of the bead portion is integrally provided with a folded portion that folds around the bead core from the inner side to the outer side in the tire axial direction. And
The bead portion extends between the main body portion and the folded portion of the carcass ply in a tapered manner from the outer surface of the bead core to the outer side in the tire radial direction and is directed to the inner side surface facing the main body portion side and the outer side in the tire axial direction. Bead apex rubber having side and
A packing rubber in which the inner end side in the tire radial direction is connected to the outer surface of the bead apex rubber and the outer end tapers outward in the tire radial direction along the main body portion;
And an outer sidewall rubber that is disposed on the outer side in the tire axial direction of the packing rubber and forms the outer surface of the tire,
The bead apex rubber has a loss tangent tan δ of 0.10 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 to 0.09 and the complex elastic modulus E * is 3.4 to 3.8 MPa,
Moreover, the heavy duty tire is characterized in that the loss tangent tan δ of the outer sidewall rubber is 0.065 to 0.125 and the complex elastic modulus E * is 3.0 to 3.4 MPa. The bead portion is disposed between the packing rubber and the outer sidewall rubber, on the inner side in the tire axial direction and covering the outer end of the folded portion of the carcass ply, and an inner portion disposed on the outer side. With sidewall rubber,
2. The heavy load load according to claim 1, wherein 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. tire. 3. The heavy load according to claim 2, wherein each loss tangent tan δ of the outer sidewall rubber, the inner sidewall rubber, and the packing rubber is 85% or less of a loss tangent tan δ of the ply edge cover rubber. tire.

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