JP3389500B2 - Pneumatic tire - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire which is lightweight and can maintain durability and steering stability.

[0002]

2. Description of the Related Art In recent years, there has been a strong demand for resource saving as a problem related to the global environment, and it is an urgent need to reduce the weight of tires in order to contribute to low fuel consumption. Has become. In particular, for pneumatic tires for light trucks, and particularly for pneumatic tires having a load of 1 ton or more per tire, the weight of the tire is relatively large, and therefore it is strongly desired to reduce the weight of the tire. .

Since a tire of this type is required to have sufficient durability and tire strength, a carcass is usually formed by using three carcass plies extending from the tread portion to the bead core of the bead portion through the sidewall portion. is necessary.

The carcass ply is reinforced by a carcass cord made of an organic fiber cord. Generally, when the carcass cords have the same thickness, the number of the carcass cords per 5 cm width of the carcass ply is equal to the number of ends. The smaller the weight, the lighter the weight of the tire. However, there is a problem that the reduction of the end causes a decrease in tire rigidity and a decrease in steering stability. That is, the weight reduction of the tire and the tire strength or steering stability are in a trade-off relationship.

The inventors of the present invention have conducted various studies on such a pneumatic tire. As a result, an organic fiber cord having a specific thickness is used for the carcass cord, and the carcass ply has a low-ends ply with a low end. On the basis of using a high-end ply having a larger number of ends than this, it has been found that such a trade-off, that is, weight reduction of a tire and tire strength or steering stability can be achieved at the same time.

As described above, an object of the present invention is to provide a pneumatic tire which is lightweight and can maintain durability and steering stability.

[0007]

The invention according to claim 1 of the present invention is a pneumatic in which a carcass is formed by using three carcass plies extending from the tread portion to the bead core of the bead portion through the sidewall portion. A tire, wherein the carcass comprises two low-end plies having an end number of 40 to 60, which is the number of carcass cords per 5 cm width of the carcass ply, and one end having the end number of 45 to 65. The end of the high-end ply is increased by 5 or more as compared with the end of the low-end ply, and the carcass cord has a thickness of 1000 dtex / 2 or more and 1800.
It is composed of an organic fiber cord of dtex / 2 or less, and
Lowends ply is from tread to sidewall
Through the bead core of the bead part from the inside to the outside in the tire axial direction.
It is folded back to the side and locked, and the high ends
The ply is beaded through the tread and sidewalls.
It is characterized by terminating at the bead core of the cable part .

Further, in the invention according to claim 2, the pneumatic tire according to claim 1, wherein the carcass comprises the high-end ply on the outermost side of the tire.

Further, in the invention according to claim 3, the bead
Part extends outward from the bead core in the radial direction of the tire.
With a bead apex made of hard rubber
Fold back the low-end ply inside the tire in the radial direction.
Height h1 from the bead base line of the
Of the folded part of the low-end ply on the outside in the radial direction of the ear
The folding back height h2 from the bead baseline and the bead height
Height from bead baseline of Doapex h3
Means h1>h2> h3, and the tire cross-sectional height is 7 respectively.
Characterized by being formed with different heights of about 12%
It

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, the pneumatic tire according to the present embodiment includes a carcass 6 that extends from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4 and is composed of three carcass plies, and the tread portion 2
And a belt layer 7 disposed on the inner side of the carcass 6 and on the outer side in the tire radial direction of the carcass 6, a radial tire suitable for a light truck having a load of 1 ton or more per tire is illustrated.

The carcass 6 is composed of the three radial structure plies in which the carcass cords are arranged at an angle of 70 to 90 ° with respect to the tire equator C.

The carcass cord has a thickness of 1000d.
It is composed of an organic fiber cord of tex / 2 or more and 1800 dtex / 2 or less. As a result of various experiments by the present inventors, in this type of pneumatic tire including three carcass plies, the thickness of the carcass cord is 1800 dt.
If the size is much thicker than ex / 2, the rigidity or steering stability of the tire may be improved, but this high rigidity may damage the carcass cord near the bead where the bend is severe and the durability may be reduced. . On the contrary, when the thickness of the carcass cord is smaller than 1000 dtex / 2, the weight can be easily reduced, but it is difficult to secure the rigidity or steering stability of the tire. Examples of the material for the carcass cord of low-ends and high-ends plies include polyester, nylon, rayon, etc., and cords of the same material and the same thickness are preferably used.

In addition, the carcass 6 is premised on the adoption of a carcass cord having such a thickness and a material as described above. Two low-ends having an end number of 40 to 60, which is the number of carcass cords to be driven per 5 cm width of the carcass ply, are used. The low-end ply 6L is composed of a high-end ply 6L1 and 6L2 and a single high-end ply 6H having 45 to 65 ends.
It shows the number of ends increased by 5 or more as compared with the ends of 1, 6L2.

Each end of the carcass ply is measured along the width direction of the ply orthogonal to the longitudinal direction of the carcass cord. Further, in the case of a radial tire, since the carcass cords radially widen from the bead portion 4 toward the tread portion 2 after vulcanization molding, the vicinity of the bead core 5 which is considered to be closest to the state of the carcass ply before tire molding. It is preferable to measure the ends at the location.

The two low end plies 6L1 and 6L
No. 2 has a smaller end than the high-ends ply 6H, so that the ply weight can be made relatively lighter than the high-ends ply 6H, which in turn helps reduce the weight of the tire. If the ends of the low-ends plies 6L1 and 6L2 are less than 40, the tire strength and the like are greatly reduced, and if the ends are more than 60, the weight of the tire cannot be reduced.

The high-end ply 6H has a larger end than the low-end ply 6L1 and 6L2.
By combining with the low-end plies 6L1 and 6L2, the strength of the tire can be optimally supplemented, and steering stability and the like can be maintained. From this point of view, if the number of ends of the high-end ply 6H is less than 45, the effect of reinforcing the tire strength is small, and if it exceeds 65, the effect of reducing the weight of the tire is impaired.

Furthermore, unless the number of ends of the high-ends ply 6H is increased by 5 or more as compared with the ends of the low-ends plies 6L1 and 6L2, the high-ends ply 6H is obtained.
The effect of reinforcing the strength of the tire is reduced. From this viewpoint, it is particularly desirable that the number of ends of the high-end ply 6H is 7 or more, more preferably 9 or more, and further preferably 12 or more, as compared with the ends of the low-end plies 6L1 and 6L2.

In the present embodiment, the low-end ply 6
L1 and 6L2 indicate those sequentially arranged as two inner sides in the tire radial direction. Also, low-end ply 6L1, 6
L2 is formed, for example, as a so-called folded ply, which is folded and locked from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4 from the inner side to the outer side in the tire axial direction.

On the other hand, the high-end ply 6H is disposed as the outermost portion of the tire and is formed as a so-called unwinding ply which is terminated, for example, from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4. It is illustrated. As a result, the carcass 6 of this example has a so-called (2-1) structure.

As described above, the high-end ply 6H having a relatively large number of ends is arranged on the outermost side of the tire to provide the carcass 6
By configuring the above, the tire strength can be effectively increased, and steering stability and riding comfort can be effectively balanced. The high-ends ply 6H can be used practically as the innermost position in the tire radial direction or as an intermediate layer, or may be a folded ply.

The carcass 6 is a low end ply 6L.
It is desirable that at least one end of the folded-back portions 6b1 and 6b2 of 1 and 6L2 is located on the outer side in the tire radial direction with respect to the tire total width position M that is the outermost side in the tire axial direction. As a result, the carcass 6 has a so-called high turn-up structure, and the lateral rigidity of the tire can be effectively enhanced.

Preferably, the turn-back height h1 from the bead base line BL (the tire axial line passing through the rim radial position) of the turn-back portion 6b1 of the low-end ply 6L1 on the tire radial inner side is 0 of the tire cross-section height H. .45-0.6
Double, and low-end ply 6L2 on the outside in the radial direction of the tire
The height h2 of turning back from the bead baseline BL of
It is desirable that the height H is 0.3 to 0.5 times the sectional height of the tire and less than the folding height h1.

A bead apex 8 extending from the bead core 5 to the outer side in the tire radial direction and made of hard rubber is arranged in the bead portion 4 to reinforce the bead portion 4. The height h3 of the bead apex from the bead baseline is 0.30 to 0.40 of the tire sectional height H.
It is desirable that the length is double and smaller than the folding height h2. In this example, the heights h 1, h 2, h 3 are
Each of them is formed with different heights at substantially equal intervals of about 7 to 12% of the tire cross-section height, whereby the bead portion 4 is effectively reinforced without impairing the riding comfort. Further, the belt layer 7 has a steel cord 15 with respect to the tire equator.
At least two belt plies 7A and 7B, in this example, two inner and outer belt plies 7A and 7B, which are inclined and arranged at a small angle of ˜45 °, are stacked in a direction in which the cords intersect each other.

Although the embodiment of the present invention has been described above, the ends and carcass cords of the two low-end plies 6L1 and 6L2 may have the same or different thicknesses. Further, the bead portion 4 may be provided with an appropriate reinforcing layer or the like.

[0025]

EXAMPLES A pneumatic tire of the present invention having a tire size of 195 / 85R16 and shown in FIG. 1 and Table 1 was manufactured (Examples 1 to 3), and the tire strength, steering stability,
Tested on riding comfort, tire weight, durability, etc. For comparison, tires containing no low-end ply (conventional example, comparative example 4, comparative example 5), tires containing one low-end ply (comparative examples 1 and 2), tires not containing high-end ply For (Comparative Example 3), a prototype was also prepared and the same test was performed. For the carcass cord, the same cord (polyester cord 1100 dtex / 2, tensile strength 148) for both high-end ply and low-end ply is used.
N, intermediate elongation 4.3% @ 44N). The test conditions are as follows.

<Tire Strength> A test tire was used as a rim (16 ×
A plunger breaking test according to JIS D4230 was carried out under the condition that the rim was assembled to 5.1 / 2 K) and the internal pressure (600 KPa) was filled. The breaking energy at that time was compared by an index with the conventional example being 100. The higher the number, the better.

<Driving Stability> Test tires were mounted on a small truck, and on the dry asphalt road surface of the tire test course, characteristics such as steering wheel responsiveness, rigidity and grip were evaluated by a driver's sensory evaluation and Comparative Example 1 was 100.
It is displayed with an index. The larger the index, the better.

<Riding comfort> As in the above, the driver's sensory evaluation was performed on the dry asphalt road surface for rugged feel, thrust, and damping.
It is displayed with the index. The larger the value, the better.

<Tire Weight> The weight per tire was measured and indicated by an index with the conventional example being 100. The larger the value, the lighter the tire weight.

<Durability> A test tire was loaded vertically with a load of 1850 kg.
The drum was run on the drum tester at f, and the running time until the visually recognizable damage to the bead portion was measured, and displayed as an index with the conventional example being 100. The larger the value, the better. Table 1 shows the test results and the like.

[0031]

[Table 1]

As a result of the test, it was confirmed that the tires of the examples maintained the tire strength and steering stability while reducing the tire weight. In order to secure the tire strength, Comparative Example 4 in which the tread rubber gauge is thick and Comparative Example 5 in which the number of belt plies are increased can improve the tire strength and the like, but are accompanied by a trade-off of an increase in tire weight. Was also confirmed.

[0033]

As described above, the pneumatic tire of the present invention can reduce tire weight and maintain tire strength and steering stability.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a pneumatic tire showing an embodiment of the present invention.

[Explanation of symbols]

2 tread section 3 Side wall part 4 bead section 5 bead core 6 carcass 6L1, 6L2 Lowends ply 6H Hiens Ply

─────────────────────────────────────────────────── --Continued from the front page (56) References JP-A-8-175105 (JP, A) JP-A-8-175122 (JP, A) JP-A-4-163206 (JP, A) JP-A-8- 108704 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) B60C 1/00-19/12

Claims (3)

(57) [Claims] 1. A pneumatic tire in which a carcass is formed by using three carcass plies extending from a tread portion to a bead core of a bead portion through a sidewall portion, wherein the carcass has a width of 5 cm of the carcass ply. The carcass cord consists of two low-end plies having an end number of 40 to 60 and one high-end ply having an end number of 45 to 65, and the end of the high-end ply is the aforesaid The carcass cord is made of an organic fiber cord having a thickness of 1000 dtex / 2 or more and 1800 dtex / 2 or less, while the carcass cord is increased in number by 5 or more as compared to the end of the low-end ply , and the low-end ply is formed from a tread portion. Sidewalk
Inside the tire axial direction with the bead core of the bead part
The high-end ply is folded back from the side to the outside and locked, and the high-end ply is attached to the side war
Pneumatic tire characterized by terminating at the bead core of the bead portion after passing through the joint part . 2. The pneumatic tire according to claim 1, wherein the carcass includes the high-end ply on the outermost side of the tire. 3. The bead portion is a tie from the bead core.
A bead a that extends outward in the radial direction and is made of hard rubber
In addition to having a peck,
From the bead baseline of the end part of the end ply
Folding height h1 and low ends on the outside in the tire radial direction
Fold the ply back from the bead baseline
Return height h2 and the bead ape of the bead apex
The height h3 from the spline is h1>h2> h3, and
Each has a different height of 7 to 12% of the tire cross-section height.
The air inlet according to claim 1 or 2, characterized in that
Tires.