JP2002178715A - Tire for heavy load - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve durability while restraining a weight increase by relatively enhancing belt rigidity in an outside area. SOLUTION: This tire has a belt layer 7 including first, second and third belt plies 7A to 7C, and in the second and third belt plies 7B and 7C, an inter- cord distance Ys of the belt ply of the outside area YS is set smaller than an inter-code distance Yc of a central area YC.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention suppresses an increase in weight by making the distance between cords in a belt ply different between an outer region and a central region in the tire axial direction and relatively increasing rigidity in the outer region. The present invention relates to a heavy duty tire with improved durability.

[0002]

2. Description of the Related Art In recent years, maintenance of road networks, speeding up of vehicles,
With the increase in performance, for example, radial, tubeless, and flattening of heavy duty tires for trucks and buses has been promoted. Further, in such a heavy-load radial tire, it is necessary to sufficiently enhance the hoop effect of the belt layer in order to support a high internal pressure and a high load. Conventionally, such a belt layer includes at least three steel sheets. A cord ply is used.

On the other hand, radial tires for heavy loads are usually used by filling them with a high internal pressure of about 700 to 800 kPa. Due to this internal pressure, the carcass ply composed of cords arranged at approximately 90 ° tends to expand so that its cross-sectional shape becomes circular, but the swelling of the carcass ply is suppressed by the highly rigid belt layer. The shape is kept constant.

However, in the case of a low-flat tire having a flatness of, for example, 70% or less, a force for shifting to a circular cross section becomes strong. However, in the outer region on the belt end side, the belt rigidity is insufficient, and the growth in the tread shoulder portion increases. As a result, the contact pressure and distortion at the tread shoulder increases, resulting in mechanical fatigue,
Thermal fatigue causes peeling damage (separation) from the belt edge, and is a cause of deterioration in durability performance.

[0005]

For this purpose, conventionally, the rigidity of the entire belt layer has been increased by increasing the thickness of the belt cord or reducing the distance between the cords, but this is unnecessary. This causes an increase in weight and hinders weight reduction.

Accordingly, the present invention is to set the inter-cord distance Ks in the outer region of the second and third belt plies of the three belt plies to be at least smaller than the inter-cord distance Kc in the central region. It is an object of the present invention to provide a heavy duty tire capable of improving the durability while relatively increasing the belt rigidity in the outer region and suppressing the increase in weight.

[0007]

In order to achieve the above object, the invention of claim 1 of the present application is directed to a carcass extending from a tread portion to a bead portion through a sidewall portion, and a carcass inside the tread portion and the carcass. A heavy-duty tire comprising an outer belt layer, wherein the belt layer has first, second, and third belts having belt cords arranged and arranged in order from radially inside to outside. The second belt ply and the third belt ply include a ply from the ply end of the largest width belt ply among the first to third belt plies to a position 30 mm inward in the tire axial direction from the ply end. In the outer region and the central region from the tire equator to a position separated by 30 mm on both sides in the tire axial direction, the cord-to-cord distance Ks of the belt ply in the outer region is set to Is characterized in that a smaller than the distance Kc.

According to the second aspect of the present invention, the inter-cord distance Ks in the outer region is in the range of 0.5 to 0.85 mm,
And the cord thickness D of the belt cord in the central region.
c2 and Dc3 are equal to each other, and the cord thicknesses Ds2 and Ds3 in the outer regions of the second and third belt plies.
Is the cord thickness D of the belt cord in the central region.
It is characterized by being larger than c2 and Dc3.

According to the third aspect of the present invention, each of the second belt ply and the third belt ply extends continuously from one ply end to the other ply end without interruption. It is characterized in that the inter-code distance Ks in the outer region is in the range of 0.5 to 0.80 mm, and the inter-code distance Kc in the center region is in the range of 0.85 to 1.20 mm.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of the present invention will be described.
This will be described together with the illustrated example. FIG. 1 is a meridional section when the heavy duty tire of the present invention is a truck / bus tire having an aspect ratio of 70% or less.

In FIG. 1, a heavy-duty tire 1 (hereinafter referred to as a tire 1) has a 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 belt layer 7 disposed inside the tread portion 2 and outside the carcass 6.

The carcass 6 has one or more ply folded portions 6b provided at both ends of a ply body portion 6a extending between the bead cores 5 and 5 to bend around the bead core 5 from the inside to the outside in the tire axial direction. In the example, a case where the carcass ply 6A is formed is shown. The carcass ply 6A has a carcass cord 75-
They are arranged at an angle of 90 degrees, and in this example, a steel cord is used as a carcass cord.

The carcass 6 may be composed of one or more plies using an organic fiber cord such as aromatic polyamide, nylon, rayon or polyester, in addition to the steel cord. The ply turn-up portion 6b is interrupted above the bead core 5 and below the maximum width position of the tire. Between the ply turn-up portion 6b and the ply body portion 6a, bead apex rubber 8 is filled, and the bead portion 4 is Reinforced and increased tire lateral rigidity.

Next, the belt layer 7 includes first to third belt plies 7A to 7C which are sequentially arranged from the inner side to the outer side in the radial direction, and in the present embodiment, the belt layers 7 have a narrow width which is arranged outside. It has a four-layer structure including a fourth belt ply 7D, and each of the belt plies 7A to 7D is formed using a steel cord as a belt cord.

The belt layer 7 is formed of the belt ply 7A.
7D, the ply width of the fourth belt ply 7D is the minimum, the ply width of the second belt ply 7B is the maximum, and the first and third belt plies 7A are formed to have substantially the same width. I have. As shown in FIG. 2, the cord angle α1 of the belt cord with respect to the tire equator C in the first belt ply 7A is 50 ° ± 10 °, and the cord angles α2, α3 in the second to fourth belt plies 7B to 7D. α4
Are in the range of 18 ° ± 10 °, respectively. Further, by making the inclination direction of the cord of the second belt ply 7B different from the inclination direction of the cord of the third belt ply 7C, a strong truss structure is formed, and the hoop effect is enhanced.

In this embodiment, as conceptually shown in FIG. 3, the belt layer 7 is formed in the outer region YS on the belt end side.
And a middle area YM on the tire equator side and an intermediate area YM therebetween, the second and third belt plies 7B and 7C respectively determine the inter-cord distance Ks in the outer area YS. , Is set to be smaller than the inter-code distance Kc in the central area YC.

That is, in the second belt ply 7B,
The inter-code distance in the outer area YS is Ks2, and the center area YC
Ks2 <Kc2, where Kc2 is the inter-code distance at
It is. Similarly, in the third belt ply 7C, when the distance between cords in the outer region YS is Ks3 and the distance between cords in the central region YC is Kc3, Ks3 <Kc3.

Here, the "outer area YS" is defined as a first area.
A region from the ply end 7e of the belt ply having the maximum width (corresponding to the second belt ply 7B in this example) among the third belt plies 7A to 7C to a position separated by 30 mm inward in the tire axial direction. I do. The "center area YC" means an area from the tire equator C to a position separated by 30 mm on both sides in the tire axial direction. Further, the "inter-cord distance" means the size of the gap between adjacent belt cords in the ply. In each area YS, YC,
If the inter-code distance changes, the average value is used.

As described above, by adjusting the inter-cord distance in the ply so that Ks2 <Kc2 and Ks3 <Kc3, the belt rigidity in the outer region YS can be relatively increased, and the weight increases. And durability can be improved.

At this time, in order to ensure the effect of improving the durability, the distance Ks between the cords in the outer region YS is determined.
2, Ks3 is preferably in the range of 0.5 to 0.85 mm, respectively. If the thickness exceeds 0.85 mm, sufficient rigidity cannot be attained. If the thickness is less than 0.5 mm, the cords are too close to each other, and cord looseness tends to occur. The ratios Ks2 / Kc2 and Ks3 / Kc3 of the inter-code distances are not particularly limited in the present invention, but are preferably in the range of 0.5 to 0.85, respectively.

In this embodiment, in order to further enhance the effect of improving the durability, the second and third belt plies 7B, 7C
, The code thickness Ds in the outer region YS, respectively.
2, Ds3 is the code thickness D in the central area YC.
larger than c2 and Dc3, that is, Ds2> Dc2, Ds3>
Dc3 is exemplified. Each area YS, Y
When two types of codes having different thicknesses are arranged in C, the average value is used. Also the ratio of cord thickness D
s2 / Dc2 and Ds3 / Dc3 are not particularly limited in the present application, but are preferably in the range of 1.1 to 1.4, respectively.

In implementing this method, in this example,
The second and third belt plies 7B and 7C are divided into ply division pieces 7Bi and 7Ci, respectively, which are divided in the tire axial direction.
The outer ply split pieces 7Bo and 7Co are formed. At this time, the distances L2, L3 of each of the division positions P2, P3 from the ply end 7e may be 30 mm or more, but the difference |
L2−L3 | is preferably 5 mm or more, more preferably 9 mm or more.

The outer ply split pieces 7Bo, 7Co
In the ply division pieces 7Bi, 7Ci in the inner cords Ki2, Ki3.
By setting smaller, Ks2 <Kc2, and K
It is assumed that s3 <Kc3. Similarly, the code thicknesses Do2 and Do3 of the outer ply split pieces 7Bo and 7Co are changed to the code thickness Di of the inner ply split pieces 7Bi and 7Ci.
2. By setting it larger than Di3, Ds2> Dc
2, and Ds3> Dc3.

In the present embodiment, the division positions P2 and P3 are respectively disposed in the intermediate area YM, so that Ko2 = Ks
2, Ko3 = Ks3, Ki2 = Kc2, Ki3 = Kc
3, Do2 = Ds2, Do3 = Ds3, Di2 = Dc
2, Di3 = Dc3.

Here, in order to suppress cord breakage from concentrating on a specific ply and reducing the plunger strength,
Code thickness Dc2, D at least in central area YC
It is preferable to set c3 equal to each other.
It is preferable that the cord thicknesses D1 and D4 of the first and fourth belt plies 7A and 7D are set to be equal to the cord thicknesses Dc2 and Dc3 for plunger strength.

The cord thicknesses Do2 and Do3 of the outer ply split pieces 7Bo and 7Co may be different from each other. However, in order to form a well-balanced truss structure and further to use a common material, etc. This code thickness Do
2, Do3 is preferably set equal to each other.

Next, FIG. 4 shows an example in which the inter-code distance Ks in the outer area YS is set to be smaller than the inter-code distance Kc in the central area YC without using the ply split pieces.

In this embodiment, the belt layer 7 during vulcanization molding is used.
Is different between the outer area YS and the central area YC, thereby setting the inter-code distance to Ks <Kc. That is, the stretch amount in the central area YC is set higher than before, and the belt layer 7 is curved in a convex arc shape, so that the inter-cord distance Kc in the central area YC.
Is relatively high.

Therefore, in this embodiment, each of the second and third belt plies 7B and 7C is formed of one ply which extends continuously from one ply end to the other ply end without interruption. be able to. On the other hand,
The code thickness Ds, Dc between the outer area YS and the central area YC
Are inevitably the same. Therefore, in such a case, in order to sufficiently increase the belt rigidity in the outer region YS, the inter-cord distance Ks in the outer region YS is set in the range of 0.5 to 0.80 mm, while the inter-cord distance Kc in the central region YC is set.
Is preferably in the range of 0.85 to 1.20 mm,
At this time, the ratio Ks / Kc of the inter-code distance is set to 0.55 to
Preferably, it is 0.95.

In this embodiment, the cord thicknesses D1 to D4 of the first to fourth belt plies 7A to 7D are set to be equal to each other.

Although the preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the illustrated embodiment, but may be implemented in various forms.

[0032]

EXAMPLE A tire for heavy load having the structure of FIG. 1 and having a belt layer shown in FIG. 3 and having a tire size of 245 / 70R19.5 was prototyped based on the specifications in Table 1, and the durability and durability of each sample tire were measured. The tire weight was measured, and the results are shown in Table 1. Table 2 shows other specifications of the belt layer used.

(1) Durability: Using a drum tester, internal pressure (850 kPa), load (26.15 KN), speed (8
0 to 140 km / h), and the running distance (complete running is 1540 km) until tire damage occurs was determined by Comparative Example 1.
Is shown as an index with 100 as the index. The larger the value, the better the durability.

(2) Weight The weight per tire was measured and is indicated by an index with Comparative Example 1 being 100. The smaller the value, the lighter the weight.

[0035]

[Table 1]

[0036]

[Table 2]

A heavy-duty tire having a belt layer shown in FIG. 4 and having a tire size of 245 / 70R19.5 was prototyped based on the specifications in Table 2, and the measurement results of the durability and tire weight of each test tire are shown in Table 3. Described. Table 4 shows other specifications of the belt layer used.

[0038]

[Table 3]

[0039]

[Table 4]

[0040]

Since the present invention is configured as described above,
The belt rigidity in the outer area can be relatively increased,
Durability can be improved while suppressing weight increase.

[Brief description of the drawings]

FIG. 1 is a sectional view of a tire according to an embodiment of the present invention.

FIG. 2 is a plan view showing a code arrangement of a belt layer.

FIG. 3 is a sectional view conceptually showing an example of a cord arrangement of a belt layer.

FIG. 4 is a sectional view conceptually showing another example of a cord arrangement of a belt layer.

[Explanation of symbols]

 Reference Signs List 2 tread portion 3 sidewall portion 4 bead portion 6 carcass 7 belt layer 7A to 7D first, second, and third belt plies 7e ply end C tire equator YC central region YS outer region

Claims (3)

[Claims] 1. A heavy-duty tire comprising a carcass extending from a tread portion to a bead portion through a sidewall portion and a belt layer disposed inside the tread portion and outside the carcass, The layer includes first, second, and third belt plies having belt cords arranged and arranged in order from the radially inner side to the outer side, and the second belt ply and the third belt ply include:
The outer region from the ply end of the widest belt ply of the first to third belt plies to a position separated by 30 mm inward in the tire axial direction, and the center from the tire equator to a position separated by 30 mm on both sides in the tire axial direction from the tire equator. A heavy-duty tire characterized in that, in the region, the inter-cord distance Ks of the belt ply in the outer region is smaller than the inter-cord distance Kc in the central region. 2. The inter-code distance Ks in the outer region is 0.5.
0.85 mm, and the cord thicknesses Dc2 and Dc3 of the belt cords in the central region are equal to each other, and the cord thicknesses Ds2 and Ds3 in the outer regions of the second and third belt plies are equal to each other. The heavy duty tire according to claim 1, wherein the thickness of the belt cord in the region is larger than the cord thicknesses Dc2 and Dc3. 3. The second belt ply and the third belt ply, wherein each belt cord extends continuously from one ply end to the other ply end without interruption, and a cord-to-cord distance in the outer region. Ks is 0.5-0.8
In the range of 0 mm and the central area, the inter-cord distance Kc
2. The heavy duty tire according to claim 1, wherein the diameter is in the range of 0.85 to 1.20 mm.