JP2018016129A - Heavy-duty radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heavy-duty radial tire exerting both low heat generation property and crack progress resistance while achieving the former property.SOLUTION: There is provided a heavy-duty radial tire in which a radial carcass and 4 layers of the belt covering a reinforcement with a coating rubber are provided outside the crown part of the radial carcass in a tire radial direction. An inner layer belt 5a, inside belt 5b, outside belt 5c and outermost belt 5d are disposed in this order from the inside of the radial tire in the radial direction. The radial tire is configured by combination of coating rubbers of respective belts satisfying the following expression: Σ{(tanδ(n)index)×V(n)}<93 ... (1) when defining the tanδ index of each coating rubber of the inner layer, inside and outermost belts 5a, 5b and 5d when assuming tanδ of the coating rubber of the outside belt 5c as 100 as tanδ(n)index, and the ratios of the volume of respective coating rubbers from the inner layer belt 5a to the outermost belt 5d occupying in total volume of the coating rubber as V(n) (n=1, 2, 3 or 4), respectively.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a heavy duty radial tire.

In recent years, there has been an increasing demand for lower fuel consumption of automobiles in connection with the movement of global carbon dioxide emission regulations due to increasing interest in environmental problems. In order to meet such demands, reduction of rolling resistance is also demanded for tire performance. In order to reduce the rolling resistance of the tire, improvement of the blending of the tread rubber composition is mainly performed (for example, Patent Document 1).
On the other hand, in heavy-duty pneumatic tires mounted on trucks, buses, industrial vehicles, construction vehicles, aircraft, etc., tires are being rehabilitated, so it is even more important to reduce the fuel consumption of the tire frame members. . Conventionally, it is effective to use a low heat-generating rubber composition having a low loss tangent (tan δ) by means of a tire frame member as a method for realizing low fuel consumption of the tire frame member.
One means of reducing heat generation is to reduce the loss tangent of the belt coating rubber. However, reducing the loss tangent of the belt coating rubber reduces the crack resistance of the rubber. On the other hand, since heavy load radial tires generally tend to concentrate strain at the end of the belt, high resistance to crack propagation is required.

International Publication No. 2012/057355

  The present invention provides a heavy-duty radial tire that achieves both low cracking resistance and high crack resistance by optimizing the combination of a plurality of belt coating rubbers used in a heavy-duty radial tire. This is a problem.

  As a result of intensive studies to solve the above problems, the present inventor has optimized the combination of a plurality of belt coating rubbers used in heavy-duty radial tires, and has a contradictory low heat generation and crack resistance. It has been found that progress can be made compatible. The invention has been completed based on this finding.

That is, the present invention
[1] In a heavy duty radial tire in which four layers of a radial carcass and a belt in which a reinforcing material is coated with a coating rubber are provided on the outer side in the tire radial direction of the crown portion of the radial carcass,
Arranged in the order of 1 belt, 2 belts, 3 belts and 4 belts from the radial inside of the heavy duty radial tire,
When the tan δ of the 3-belt coating rubber is 100, the tan δ index of each of the 1-belt, 2-belt, and 4-belt coating rubbers is “tan δ (n) index”. Occupying the total volume of the coating rubber as V (n), n is n = 1 to 4 according to each belt, and the following formula (1):
Σ {(tan δ (n) index) × V (n)} <93 (1)
A heavy duty radial tire consisting of a combination of coating rubber for each belt,
Is to provide.

  According to the present invention, it is possible to provide a heavy-duty radial tire that realizes low heat build-up while achieving both crack resistance.

It is a cross-sectional schematic diagram which shows an example of the radial tire for heavy loads of this invention. It is a partial section schematic diagram showing a belt part of an example of a radial tire for heavy loads of the present invention.

[Radial tires for heavy loads]
The radial heavy-duty tire according to the present invention is a radial heavy-duty tire in which four layers of a belt in which a reinforcing material is coated with a coating rubber are provided on the outer side in the radial direction of a radial carcass and a crown portion of the radial carcass,
Arranged in the order of 1 belt, 2 belts, 3 belts and 4 belts from the radial inside of the heavy duty radial tire,
When the tan δ of the 3-belt coating rubber is 100, the tan δ index of each of the 1-belt, 2-belt, and 4-belt coating rubbers is “tan δ (n) index”. Is the ratio of the total volume of the coating rubber to V (n), n is n = 1 to 4 according to each belt, and the following formula (1): Σ {(tan δ (n) index) × V ( n)} <93 ... It is comprised by the combination of the coating rubber of each belt which satisfy | fills (1).
In the heavy duty radial tire of the present invention, preferably, the coating rubber of each belt satisfying the following formula (2): Σ {(tan δ (n) index) × V (n)} <86 (2) It is comprised by combination, More preferably, it is comprised by the combination of the coating rubber of each belt which satisfy | fills following formula (3) :( SIGMA) {(tan (delta) (n) index) * V (n)} <79 ... (3). Is done.
Provided a heavy-duty radial tire satisfying the above formula (1): Σ {(tan δ (n) index) × V (n)} <93 while realizing low heat buildup and achieving both crack growth resistance. can do.

Here, Σ {(tan δ (n) index) × V (n)} in the formula (1) is used as an index because the product of the exothermic property tan δ of the rubber itself and the total volume of the rubber is an index of the exothermic property of the tire. It is because it becomes.
That is, according to the present invention, in the belt structure shown in FIG. 1 to be described later, the most severe distortion is applied particularly to the 3 belt ends, and the distortion of the other belt ends, particularly the 4 belt ends, is relatively small. Therefore, by changing the composition of the coating rubber of the other belts with respect to the coating rubber of the three belts, the fuel efficiency (that is, crack resistance) is reduced without reducing the tire durability (particularly, crack resistance). The 1 belt, 2 belt, 3 belt and 4 belt have different composition and volume of the coating rubber coating the belt, and the sum of the products was used as an index.

The volume ratio of 1 belt, 2 belts, 3 belts, and 4 belts is expressed as V (1), V (2), V (3), and V (4). That is, in the present invention, “V (n)” represents the volume ratio of each belt, and n is an integer of 1 to 4.
V (1), V (2), V (3), and V (4) may be different or the same, and the maximum allowable value from the minimum value of the coating rubber thickness and the reinforcing material of each belt. It is determined taking into account the total surface area.
Specifically, V (1) + V (2) + V (3) + V (4) = 1, and the volume ratio of each belt from 1 belt to 4 belts is V1 (1) is 0.1 or more, 0 .30 or less, V (2) is 0.25 or more and 0.40 or less, V (3) is 0.2 or more and 0.4 or less, and V (4) is 0.1 or more. It is preferable that it is 0.25 or less.

As for an example of the configuration of a heavy-duty radial tire (hereinafter also referred to as “tire”) of the present invention, as shown in FIG. 1, the tire 1 includes stiffeners 3 and 3 respectively outward from the pair of bead cores 2 and 2 ′ in the tire radial direction. Of the carcass ply 4 which extends and is folded from the outside of the stiffener 3 by the bead core 2 to form a horseshoe-shaped tire case shape, folded by the bead core 2 'on the opposite side and locked on the outside of the stiffener 3'. A belt portion 5 composed of four layers of a plurality of belt layers 5a to 5d is disposed on the outer side in the tire radial direction. A tread portion 8 is disposed outside the belt portion 5 in the tire radial direction.
Further, a sidewall rubber 9 is disposed outside the carcass ply 4 and between the tread portion 8 and the stiffener 3. A portion where the sidewall rubber 9 is disposed is referred to as a side portion M, and an inner side in the tire radial direction of the side portion M is referred to as a bead portion N. In the bead portion N, bead cores 2 and 2 ′, stiffeners 3 and 3 ′, and the like are disposed. An inner liner 10 is disposed inside the carcass ply 4 as an air permeation preventive layer.
The belt portion 5 will be further described in detail. As shown in FIG. 2, in the belt layers 5a to 5d (the innermost belt layer 5a, the inner belt layer 5b that forms the crossing layer, the outer belt layer 5c that forms the crossing layer, and the outermost belt layer 5d), A belt wedge rubber 6 is usually disposed between the vicinity of the end of the inner belt layer 5b to be formed and the vicinity of the end of the outer belt layer 5c forming the crossing layer, and each layer end of each of the belt layers 5a to 5d has an end of each layer. A belt end cover rubber 7 (7a to 7d) for covering the portion is disposed, and the belt wedge rubber 6 and the belt end cover rubber 7 are also included in the belt portion 5.
Although an example in which the belt portion 5 includes the belt wedge rubber 6 and the belt end cover rubber 7 has been described based on FIG. 2, the belt wedge rubber 6 and the belt end cover rubber 7 are not limited thereto. It is an optional component and not an essential component.
Each of the belt layers 5a to 5d of the belt portion 5 shown in FIGS. 1 and 2 is composed of a reinforcing material (particularly, a steel cord) and a coating rubber covering the reinforcing material.
As the reinforcing material, a fiber cord such as a steel cord or an aramid cord is used. In a heavy duty radial tire, a steel cord is preferable. In some cases, a fiber cord such as an aramid cord may be used for the four belts. Good.

Furthermore, the innermost belt layer 5a, the inner belt layer 5b that forms the crossing layer, the outer belt layer 5c that forms the crossing layer, and the outermost belt layer 5d shown in FIGS. It corresponds to a belt, 3 belts, and 4 belts.
Hereinafter, the innermost belt layer 5a is also referred to as “1 belt”, the inner belt layer 5b that forms the crossing layer is also referred to as “two belts”, and the outer belt layer 5c that forms the crossing layer is also referred to as “three belts”. The outer belt layer 5d is also referred to as “four belts”.

  In the heavy load radial tire of the present invention, from the viewpoint of resistance to crack propagation, the same belt may be used for the first belt, the second belt, and the third belt, and the same coating rubber may be used for the second belt and the third belt. Good.

  Further, in the radial tire for heavy loads of the present invention, the value of tan δ of the coating rubber of each belt is “4 belts ≦ 1 belt ≦ 2 belts <3 belts” from the viewpoint of satisfying both low heat generation and anticracking resistance. It is preferable that the condition “4 belt ≦ 1 belt <2 belt ≦ 3 belt” may be satisfied, and further, “4 belt ≦ 1 belt <2 belt <3 belt”. The condition of may be satisfied.

Furthermore, the value of tan δ of the three-belt coating rubber to which the largest strain is applied at the end is preferably 0.10 to 0.35, and more preferably 0.15 to 0.30. When the value of tan δ of the three-belt coating rubber exceeds 0.35, the low heat build-up property is inferior. When it is less than 0.10, the crack resistance of the rubber deteriorates and the durability of the tire decreases.
In addition, the value of tan δ of the four-belt coating rubber that is the outermost layer is preferably 0.05 to 0.30, more preferably 0.08 to 0.28, and even more preferably 0.10 to 0.22. When the value of tan δ of the 4-belt coating rubber exceeds 0.30, the low heat build-up property is inferior, and when it is less than 0.05, the crack resistance of the rubber deteriorates and the durability of the tire decreases.

From the viewpoint of the durability of the tire, when the value of tan δ of the coating rubber of the three belts is 100, the value of the tan δ index of the coating rubber of the one belt is preferably 40 or more and 80 or less, more preferably 40 or more and 75 or less. Preferably, 45 or more and 70 or less are more preferable.
Similarly, from the viewpoint of tire durability, when the tan δ value of the coating rubber of the three belts is 100, the value of the tan δ index of the coating rubber of the two belts is preferably 70 or more and 100 or less, more preferably 70 or more, 90 The following is more preferable, and 75 or more and 90 or less are more preferable.
Similarly, from the viewpoint of the durability of the tire, when the value of tan δ of the coating rubber of 3 belts is 100, the value of the tan δ index of the coating rubber of 4 belts is preferably 40 or more and 80 or less, more preferably 40 or more, 75 The following is more preferable, and 40 or more and 70 or less are more preferable.
Furthermore, in order to obtain a desired belt performance (for example, low heat generation property), a desired tire can be manufactured by determining tan δ of the coating rubber of the three belts.
In addition, as shown in FIG. 2, although the crack progress resistance is further suppressed by the belt wedge rubber 6, the volume of the rubber of the belt wedge rubber 6 is 1/2 in the belts 2 and 3 in the present invention. It will be added one by one.

In the belt coating rubber, if the amount of carbon black described later is increased, the value of tam δ is increased, and if the amount of carbon black is decreased, the value of tan δ is decreased. The same applies to silica.
On the other hand, in the belt coating rubber, if the amount of sulfur to be added is increased, the value of tam δ is decreased, and if the amount of sulfur is decreased, the value of tan δ is increased.
Accordingly, carbon black or the like and sulfur are added as appropriate to produce the four-layer belt so as to satisfy the above-mentioned conditions.

Below, the coating rubber of each belt is demonstrated. In addition, the description "-" means the range including the value before and behind that.
(Carbon black)
Examples of the carbon black used for the coating rubber for coating the reinforcing material of each belt of the present invention include HAF (nitrogen adsorption specific surface area: 75 to 80 m ² / g), HS-HAF (nitrogen adsorption specific surface area: 78 to 83 m ^2). / G), LS-HAF (nitrogen adsorption specific surface area: 80 to 85 m ² / g), FEF (nitrogen adsorption specific surface area: 40 to 42 m ² / g), GPF (nitrogen adsorption specific surface area: 26 to 28 m ² / g) , SRF (nitrogen adsorption specific surface area: 25-28 m ² / g), N339 (nitrogen adsorption specific surface area: 88-96 m ² / g), LI-HAF (nitrogen adsorption specific surface area: 73-75 m ² / g), IISAF ( Nitrogen adsorption specific surface area: 97 to 98 m ² / g), HS-IISAF (nitrogen adsorption specific surface area: 98 to 99 m ² / g), and the like. Of these, HAF, HS-HAF, LS-HAF, FEF, LI-HAF and GPF are preferred.

(silica)
In addition to the carbon black used for the coating rubber for coating the reinforcing material of each belt of the present invention, silica may be blended if desired. It is preferable to blend 10 parts by mass or less of silica with respect to 100 parts by mass of the rubber component of the coating rubber.
Any commercially available silica can be used, among which wet silica, dry silica, and colloidal silica are preferably used, and wet silica is particularly preferably used. Although there is no restriction | limiting in particular in the compounding quantity of a silica, For example, it is preferable that the BET specific surface area (measured based on ISO 5794/1) of silica is 40-350 m < ² > / g. Silica having a BET specific surface area within this range has an advantage that both rubber reinforcement and dispersibility in a rubber component can be achieved. From this viewpoint, more preferably silica in the range BET specific surface area of 80~350m ² / g, silica BET specific surface area in the range of 120~350m ² / g is particularly preferred. Examples of such silica include Tosoh Silica Co., Ltd., trade name “Nip Seal AQ” (BET specific surface area = 205 m ² / g), “Nip Seal KQ”, and Degussa product name “Ultra Gil VN 3” (BET specific surface area = 175 m ² / g) can be used.

  Moreover, it is preferable that the total compounding quantity of carbon black and silica used for the coating rubber which coats the reinforcing material of each belt of the present invention is 30 to 65 parts by mass. When the amount is less than 30 parts by mass, the strength of the coating rubber cannot be ensured. When the amount exceeds 65 parts by mass, the low heat buildup and fatigue resistance of the coating rubber are reduced. That is, if it is in the said range, the low heat buildup and durability of a tire can be improved. From these viewpoints, the total amount of carbon black and silica is more preferably 40 to 60 parts by mass.

(Rubber component)
The rubber component used in the coating rubber for coating the reinforcing material of each belt of the present invention is preferably natural rubber and / or synthetic polyisoprene rubber (IR), more preferably natural rubber. Even in the case of combined use with other synthetic rubbers, the natural rubber in the rubber component is preferably 60% by mass or more, more preferably 70% by mass or more, and 80% by mass or more. Further preferred is natural rubber alone.
Examples of other synthetic rubbers include polybutadiene rubber (BR), styrene-butadiene copolymer (SBR), and styrene-isoprene copolymer (SIR).

(Adhesion promoter)
The coating rubber for coating the reinforcing material of each belt of the present invention preferably contains 0.4 parts by mass or less of an organic acid cobalt salt as a cobalt amount with respect to 100 parts by mass of the rubber component. 4 parts by mass is more preferable, and 0.02 to 0.3 parts by mass is more preferable. When the organic acid cobalt salt is added in an amount of 0.4 parts by mass or less as the amount of cobalt, it is possible to suitably prevent a decrease in the aging resistance of the coating rubber. Moreover, it is more preferable that the organic acid cobalt salt is blended in an amount of 0.01 parts by mass or more in terms of the amount of cobalt since the initial adhesiveness is improved.
Examples of the organic acid cobalt salt include cobalt naphthenate, cobalt rosinate, cobalt stearate, and other linear or branched monocarboxylic acid cobalt salt having about 5 to 20 carbon atoms (for example, trade name “Manobond”). C ”series, manufactured by OM Group Inc.) and the like.

(Vulcanizing agent)
As a vulcanizing agent used in the coating rubber for coating the reinforcing material of each belt of the present invention, it is preferable to blend 7.0 parts by mass or less of sulfur with respect to 100 parts by mass of the rubber component. In particular, it is the range of 3.0-7.0 mass parts, More preferably, it is the range of 4.0-6.0 mass parts. If sulfur is blended in an amount of 7.0 parts by mass or less, a decrease in the aging resistance of the coating rubber can be suitably prevented. Moreover, it is more preferable to add 3.0 parts by mass or more of sulfur because the initial adhesiveness is improved.

(Other ingredients)
The coating rubber for coating the reinforcing material of each belt of the present invention is not limited to the above-mentioned compounding agents, but other compounding agents, for example, vulcanization activators such as zinc white and organic acids (stearic acid, etc.), vulcanization acceleration An inorganic filler other than silica, an anti-aging agent, an ozone deterioration preventing agent, a softening agent and the like can be added.
Examples of the vulcanization accelerator include N, N′-dicyclohexyl-2-benzothiazolylsulfenamide, N-cyclohexyl-2-benzothiazolylsulfenamide, N-tert-butyl-2-benzothiazolylsulfenamide. Sulfenamide accelerators such as phenamide and N-oxydiethylene-2-benzothiazolylsulfenamide are preferably used. If desired, thiazole accelerators such as 2-mercaptobenzothiazol and di-2-benzothiazolyl disulfide, tetrabenzylthiuram disulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrakis (2-ethylhexyl). ) Thiuram accelerators such as thiuram disulfide and tetramethylthiuram monosulfide may be used.

  As a kneading apparatus used for producing the coating rubber according to the present invention, a Banbury mixer, a roll, an intensive mixer or the like is used.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples. In the following description, unless otherwise specified, “%” and “parts” indicate “% by mass” and “parts by mass”. Moreover, the description of the addition amount in the table is “part by mass”. Various measurements and evaluation methods were performed based on the following methods.

(1) Tensile stress ( _M200 )
A vulcanized rubber obtained by vulcanizing the rubber composition at 145 ° C. for 45 minutes was subjected to a tensile test at room temperature (23 ° C.) in accordance with JIS K6251: 2010, and a tensile stress at 200% elongation (M ₂₀₀ ) Was measured.

(2) Crack growth resistance (durability)
The molded and vulcanized test tire was subjected to a drum test for 2 days at a speed of 60 km / h under a normal internal pressure and a normal load under a 40 ° C. atmosphere and a constant side force (15 kN). After completion of the drum test, a belt cord layer having belt end rubber at both ends was taken out, and the crack length on the end of the belt cord layer was measured.
In Tables 1 and 2, the reciprocal of the crack length was taken and expressed as an index. The larger the index value, the better the crack growth resistance and the better the durability.

(3) tan δ (25 ° C)
Loss tangent to vulcanized rubber obtained by vulcanizing rubber compositions of Formulations A to F at a frequency of 52 Hz, initial load of 160 g, measurement temperature of 25 ° C. and strain of 2% using a spectrometer manufactured by Toyo Seiki Co., Ltd. (Tan δ) was measured. The results are shown in Table 1.
In Table 2, loss tangent (tan δ) was measured under the same conditions as described above. In Examples and Comparative Examples 2 to 4, the reciprocal number of tan δ of Comparative Example 1 was set to 100 and indicated by the following formula. A smaller index value indicates a lower exothermic property and a smaller hysteresis loss.
Low exothermic index = {(tan δ of coating rubber after test vulcanization in Examples 1 to 10 and Comparative Examples 2 to 5) / (tan δ of coating rubber after vulcanization in Comparative Example 1)} × 100

  The composition and physical properties of the coating rubber are shown in Table 1.

[note]
* 1: HAF (N-330), manufactured by Asahi Carbon Co., Ltd., trade name “Asahi # 70” (nitrogen adsorption specific surface area: 77 m ² / g)
* 2: FEF (N-550), manufactured by Asahi Carbon Co., Ltd., trade name “Asahi # 60” (nitrogen adsorption specific surface area: 40 m ² / g)
* 3: GPF (N-660), manufactured by Asahi Carbon Co., Ltd., trade name “Asahi # 55” (nitrogen adsorption specific surface area: 26 m ² / g)
* 4: Silica: Tosoh Silica Corporation: “AQ”
* 5: Silane coupling agent: “Si69” manufactured by Degussa
* 6: Anti-aging agent 6C: N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine, manufactured by Ouchi Shinsei Chemical Co., Ltd., trade name “NOCRACK 6C”
* 7: OM Group Inc. Product name “Manobond C225” (registered trademark) (cobalt content 22.5%)
* 8: Vulcanization accelerator: N, N′-dicyclohexyl-2-benzothiazolylsulfenamide, manufactured by Ouchi Shinsei Chemical Co., Ltd., trade name “Noxeller DZ”

Examples 1-11 and Comparative Examples 1-5
A heavy-duty radial tire was manufactured based on the following coating rubber manufacturing method and tire manufacturing method.

<Manufacturing method of coating rubber>
Each component of the blends A to D shown in Table 1 was kneaded by a conventional method, and heated and extruded to obtain a rubber composition. These rubber compositions were applied as belt coating rubbers to belt cord layers of heavy duty pneumatic tires as shown in Table 2.

<Tire manufacturing method>
Next, the tire size is made common in 11R22.5, and 16 kinds of coating rubbers of Examples 1 to 11 and Comparative Examples 1 to 5 and the coating rubbers of the above-mentioned combinations A to F are used, and 1 to 4 belts are not added. A sulfur case was prepared. As shown in FIG. 2, the belt part consisted of 4 belt layers. These case parts are vulcanized by a method in which the case part is surrounded from the outside by a vulcanization mold and pressurized and heated with a vulcanization bladder from the inside (pressurized with high-pressure steam at 150 ° C) to produce a heavy load radial. Tires were manufactured.

  From the results of Examples 1 to 4 and Comparative Example 1, the results of Examples 5 and 6 and Comparative Examples 2 and 3, the results of Examples 7 and 8 and Comparative Example 4, the results of Examples 9 to 11 and Comparative Example 5 , Σ {(tan δ (n) index) × V (n)} <93 clearly shows that the low heat buildup of the tire is clearly improved.

  The heavy-duty radial tire of the present invention is a tire with improved low heat generation and improved crack resistance, and various pneumatic tires, particularly truck / bus tires, light truck tires, off-the-road tires (mine) It is preferably used as a pneumatic radial tire such as a construction tire or a construction vehicle tire.

DESCRIPTION OF SYMBOLS 1 Tire, 2, 2 'bead core, 3, 3' stiffener, 4 carcass ply, 5 belt part, 5a innermost belt layer (1 belt), 5b inner belt layer (2 belts) which forms a crossing layer, 5c crossing layer Outer belt layer (3 belts), 5d outermost belt layer (4 belts), 6 belt wedge rubber, 7 belt end cover rubber, 7a, 7b, 7c, 7d belt end cover rubber for each belt layer, 8 tread Part, 9, 9 'sidewall rubber, 10 inner liner, M side part, N bead part, CL crown center.

Claims (11)

In the radial tire for heavy loads, the radial carcass and the radial carcass crown portion on the outer side in the tire radial direction are provided with four layers of belts in which a reinforcing material is coated with a coating rubber.
Arranged in the order of 1 belt, 2 belts, 3 belts and 4 belts from the radial inside of the heavy duty radial tire,
When the tan δ of the 3-belt coating rubber is 100, the tan δ index of each of the 1-belt, 2-belt, and 4-belt coating rubbers is “tan δ (n) index”. Occupying the total volume of the coating rubber as V (n), n is n = 1 to 4 according to each belt, and the following formula (1):
Σ {(tan δ (n) index) × V (n)} <93 (1)
A heavy-duty radial tire consisting of a combination of coating rubbers for each belt. Following formula (2):
Σ {(tan δ (n) index) × V (n)} <86 (2)
The radial tire for heavy loads according to claim 1, wherein the radial tire is configured by a combination of coating rubbers of the belts satisfying the conditions. Following formula (3):
Σ {(tan δ (n) index) × V (n)} <79 (3)
The radial tire for heavy loads according to claim 1, wherein the radial tire is configured by a combination of coating rubbers of the belts satisfying the conditions.   The radial tire for heavy loads according to any one of claims 1 to 3, wherein the two belts and the three belts are made of the same coating rubber.   The radial tire for heavy loads according to any one of claims 1 to 4, wherein the first belt, the second belt, and the third belt are made of the same coating rubber. The value of tan δ of the coating rubber of each belt is
The heavy-duty radial tire according to any one of claims 1 to 3, wherein a condition of 4 belts ≤ 1 belt ≤ 2 belts <3 belts is satisfied. The value of tan δ of the coating rubber of each belt is
The heavy-duty radial tire according to any one of claims 1 to 3, wherein a condition of 4 belts ≤ 1 belt <2 belts ≤ 3 belts is satisfied. The value of tan δ of the coating rubber of each belt is
The heavy-duty radial tire according to any one of claims 1 to 3, wherein a condition of 4 belts ≤ 1 belt <2 belts <3 belts is satisfied.   The heavy load according to any one of claims 1 to 3, wherein when the value of tan δ of the coating rubber of the three belts is 100, the value of the tan δ index of the coating rubber of the one belt is 40 or more and 80 or less. Heavy duty radial tire.   The heavy load according to any one of claims 1 to 3, wherein when the value of tan δ of the coating rubber of the three belts is 100, the value of the tan δ index of the coating rubber of the two belts is 70 or more and 100 or less. Heavy duty radial tire.   4. The heavy load according to claim 1, wherein the value of the tan δ index of the four-belt coating rubber is 40 or more and 80 or less when the value of tan δ of the three-belt coating rubber is 100. 5. Heavy duty radial tire.