JPH05116507A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To provide a pneumatic tire having a belt structure which can enhance all of the control stability, the high speed durability, and the comfortability and as well to reduce the weight thereof without lowering the productivity. CONSTITUTION:In a pneumatic tire in which two belt layers B are laid between a carcass and a tread, of two belt layers B, a carcass side first belt layer B1 is formed of a belt made of high strength, synthetic fiber cords such as, aramido fibers and having widthwise opposite end parts which are folded toward the tread side and polymerized, and a second belt B2 is superposed on the first belt layer B2 between both folded and polymerized end parts thereof. A belt reinforcing layer 5 is laid so that at least the folded end parts (b1) of the first belt layer B1 and the boundary parts 4 of the second belt B2 are covered therewith. The belt reinforcing layer 5 is composed of edge plies 5a with which the folded end parts (b) of the belt layer B1 is covered, and a cap ply 5b with which the belt layers are covered over its entire area, the edge ply 5b having a width (b) which is larger than the width (a) of the folded end part (b1).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire mainly for passenger cars traveling at high speed, and more particularly to a pneumatic tire having a belt structure which achieves both light weight and high speed performance without lowering productivity. It is a thing.

[0002]

2. Description of the Related Art Conventionally, as a belt structure of a radial tire for a passenger car, for example, in a high performance tire having a speed symbol H or higher defined by JIS, as shown in FIG. , A belt (B1 ') (B2') consisting of two layers of steel cords is arranged on the outside of the carcass (not shown), and in order to prevent the shoulder from rising due to centrifugal force at high speed, The edge ply (5) that covers the end of the belt is the outermost layer of the belt layer.
a) and a belt reinforcing layer (5 ') made of a synthetic fiber cord such as a cap ply (5b') covering substantially the entire area of the belt layer are generally covered (conventional example 1).

Such a belt structure has good high-speed durability and steering stability, especially at high speeds, but is inferior in riding comfort and lightness, and it is difficult to combine these characteristics.

As shown in FIG. 5, the first belt (B1 ') on the carcass side is a belt made of steel cord, and the first belt (B1') is made of steel cord. There is also a belt structure in which the second belt (B2 ') is made of an aramid fiber cord having high strength, and both ends of the second belt (B2') are bent outward and overlapped with each other (conventional). Example 2).

However, in the case of this belt structure, as compared with the case of the conventional example 1 using the above-mentioned steel cord belt, it has an advantage that the weight and the riding comfort can be improved.
Since different materials of steel cord and aramid fiber cord are combined, it is difficult to balance the rigidity, and the both ends of the belt layer are three layers, and the step (t ') outside the bending end is In order to prevent the air from being mixed into this portion, it is necessary to insert a pad rubber having a relatively large thickness and a large volume at the outside of the bent end during molding. When the volume of the pad rubber is increased, the weight of the tire is increased, the heat generated during high-speed traveling is increased, and the high-speed durability is reduced as compared with the case of the steel belt.

Further, as a solution to the above problem, as shown in FIG. 6, both ends of the first belt (B1 ') made of an aramid fiber cord are bent outward to form a second cord made of the same cord. There is also a structure in which both ends of the belt (B2 ') are wrapped with the first belt (B1') (conventional example 3).

However, even in the case of this belt structure, although the lightness and the riding comfort can be improved, the folding of both ends of the first belt (B1) is performed on the forming drum in order to wrap the above-mentioned end portions of the belt. Therefore, the molding equipment and the molding process are complicated, and the productivity is significantly reduced. Moreover, as in the case of the above-mentioned conventional example 2, since the both ends of the belt layer are three layers and the step (t ') on the outer side of the bent end becomes large, a pad rubber having a volume is required, and high speed durability is achieved. There is a problem in terms of sex.

[0008] The present invention has been made in view of the above, and is a pneumatic structure having a belt structure capable of achieving both steering stability and high-speed durability as well as light weight and riding comfort performance without reducing productivity. It is intended to provide tires.

[0009]

The present invention which solves the above-mentioned problems is a pneumatic tire in which two belt layers are arranged between a carcass and a tread, and of the two belt layers. The first belt on the carcass side is a belt made of a high-strength synthetic fiber cord such as aramid fiber, and both widthwise end portions are bent and polymerized to the tread side, and the second belt on the tread side is the above-mentioned first belt. 1 between both folding parts of 1 belt
The belt reinforcement is arranged so as to be overlapped with the layer portion, and further outside the two belt layers, at least the folding portion of the first belt and the boundary portion between the folding portion and the second belt layer are covered. It is characterized in that the layers are arranged.

The belt reinforcing layer is composed of an edge ply covering the bent portion of the first belt and a cap ply covering the entire belt layer on the outer side thereof, and the width of the cap ply is larger than the width of the bent portion. It is particularly preferable that the cap ply is large and is arranged so as to cover the boundary portion between the bent portion and the second belt.

[0011]

The radial tire of the present invention constructed as described above has a two-layer structure formed by bending polymerization of the first belt at both widthwise end portions of the belt layer. Compared to the eggplant, the step outside the bending end is small, the volume of the pad rubber arranged on the outside of the bending end is small, and in combination with the fact that the first belt is made of fiber cord, the tire weight is reduced. It can be made much lighter than before. Further, since the volume of the pad rubber can be reduced, heat generation during high-speed traveling is reduced and high-speed durability is improved.

Further, the insufficient bending rigidity at the end portion of the second belt, the end portion of the bent portion, and the boundary portion between the both,
It can be supplemented by a belt reinforcement layer covering this part,
It is possible to suppress deterioration of durability. Particularly, according to the belt reinforcing layer composed of the edge ply and the cap ply as in claim 2, since the belt reinforcing layers at the both end portions of the belt layer and the boundary portion are doubled, the bending rigidity of this portion is increased,
High-speed durability does not decrease.

[0013]

Embodiments Next, embodiments of the present invention will be described with reference to FIGS.

FIG. 1 shows a schematic sectional structure of a tire (T) according to the present invention, and FIGS. 2 and 3 show the belt structure thereof.

In the figure, (1) is a carcass, and 2 is provided between the carcass (1) and the outer tread portion (2).
A belt layer (B) of layers is arranged.

Of the two belt layers (B), the first belt (B1) on the carcass (1) side is a belt of synthetic fiber cord of high strength such as aramid fiber (aromatic polyamide fiber), Both ends in the width direction are formed by a folding belt that is bent outward and overlapped. (B1) shows the bent piece, (b2) shows the bent end, and (3) shows the folded overlapped portion.

The second belt on the tread side (B2)
Is a flat belt made of the same synthetic fiber cord as that of the first belt (B1) and having no bent portion. The flat belt between the bent portions (b1) and (b1) of the first belt (B1) is 1 The belt layers (B) are arranged in two layers so as to be superposed on the layer portions and arranged between the bent pieces (b1) and (b1). Therefore, the width of this second belt (B2) (W2
) Is a bent part (b1) (b1) of the first belt (B1).
The width (W1) is substantially the same as or slightly smaller than the interval (W1).

In particular, the smaller the gap between the boundary portion (4) between the second belt (B2) and the bent portion (b1), the better the high-speed performance is. The width (W
Even if 2) is the same as or slightly larger than the interval (W1), no overlap occurs in the state after molding and vulcanization. Usually, the gap of the boundary portion (4) is set to be in the range of 0 to 5 mm.

At the outermost layer of the above-mentioned two belt layers (B), a belt reinforcing layer (5) made of a synthetic fiber cord such as nylon fiber is at least the first belt (B1).
) Bending part (b1) and the bending part (b1)
Is arranged so as to cover the boundary portion (4) between the second belt (B2) and the second belt (B2).

The belt reinforcing layer (5) is substantially 0 ° with respect to the tire circumferential direction as in the illustrated embodiment.
An edge ply (5a) covering the bent portion (b1) of the first belt (B1) and a cap ply (5b) covering the entire belt layer (B) on the outside thereof. , The width (b) of the edge ply (5b) is larger than the width (a) of the folded overlapping portion (3),
The edge ply (5a) is set to satisfy the equation of b = α · a (where α> 1), and the second belt (B
The edge ply (5) is arranged so as to straddle both (2) and the bent part (b1) and cover the boundary part (4).
2 layers of a) and the cap ply (5b) on the outside,
It is preferable that the both end portions of the belt layer and the boundary portion (4) have a structure that compensates for insufficient bending rigidity.

The value of α in the above formula is appropriately adjusted depending on the mold shape, pattern, and the like.

The belt-reinforcing layer (5) may be formed by spirally winding a tape-shaped material in which a synthetic fiber cord is formed into a narrow tape shape. You can make up for the shortage. Further, the step (t) outside the bending end (b2) is adjusted to the belt reinforcing layer (5) by adjusting the feeding amount of the tape-shaped material at the time of winding.
It can be easily solved with.

According to the belt structure having the above structure, the first belt (B1) on the carcass side is bent at the end portion of the belt before the tire molding process, and is formed into a cylindrical molding drum. The second belt (B2) separately formed between the folded parts (b1) and (b1) of the first belt (B1) can be easily wound to be molded.
In other words, the first belt (B1) made of a folding belt and the second belt (B2) made of a flat belt can be separately formed and prepared, and the molding equipment can be easily used and the existing equipment can be used as it is, thus reducing the productivity. There is no fear of causing it.

In addition, in the folding overlapped portion (3) of the first belt (B1), another belt is not overlapped or wrapped, so that the thickness does not become so large (2 / in the case of the wrapped structure, etc.). 3), and hence the step (t) outside the bending end (b2) is small, and the volume (thickness) of the pad rubber arranged on the outside of the bending end is small accordingly, thus reducing the weight and speed of the tire. The durability can be improved.

Further, a belt reinforcing layer (5) is provided on the outside of the belt layer (B), and a bent portion piece (b1) of the first belt (B1) is provided.
Also, since the boundary portion (4) between this and the second belt (B2) is layered so as to cover it, the bending rigidity of this portion can be reinforced, and insufficient rigidity does not occur, high speed durability and general Compensate for the decrease in durability.

Particularly, in the case of the belt reinforcing layer (5) in which the edge ply (5a) and the cap ply (5b) are combined,
It is further excellent in maintaining the rigidity of the folded overlapped portion (3) and the boundary portion (4) at both ends of the belt, and can prevent the phenomenon of the tire shoulder from rising and improve the high-speed durability.

In order to confirm the above effects, high speed durability, belt weight, etc. were compared as follows. However, regarding the embodiment, the belt structure of FIG.
An aramid fiber cord belt was used for both the belt (B1) and the second belt (B2). In the comparative example, a steel cord belt was used as the two-layer belt having the belt structure shown in FIG. In each case, the belt width was set to the same size, and the belt reinforcing cord layer was set to the same constitution condition.

The tire sizes used in the tests were all 225 / 50R1692V. Further, in the high-speed durability test, the drum was run in increments of 10 km / h every 10 minutes until failure, in accordance with the conditions defined in the European Safety Standards Rule 30. The results of this test are shown in Table 1 below.
As shown in.

The driving stability and the riding comfort were evaluated by the driver's sensory evaluation, and the standard was shown as 6. Further, the tire weight is shown as an index with the conventional example being 100.

[0030]

[Table 1]

According to Table 1 above, in the case of the comparative example, the high-speed durability and the steering stability at the high speed are good, but the weight of the tire is large and the riding comfort is not so good. It is lighter than the example and has good riding comfort, and the high-speed durability and driving stability at high speed are not so much compared with those of the comparative example, and both characteristics are compatible. Became.

[0032]

As described above, in the radial tire of the present invention, although the first belt on the carcass side has a folded belt structure in which both ends are bent, the entire belt layer is two layers. Therefore, the step outside the folding end of the belt is small, and the volume of the pad rubber arranged on the outside of the folding end is small, and it may be the first belt on the carcass side or the synthetic fiber cord. The weight of the tire can be reduced, and the heat generated during high-speed running is small, improving high-speed durability.

Further, deterioration of high-speed durability and general durability due to insufficient bending rigidity of the end portion of the second belt on the tread side, the end portion of the bent portion of the first belt and the boundary portion thereof, It can be supplemented by the belt reinforcing layer arranged on the outer side, and there is no fear of deterioration of the durability of these.

Since the first belt made of the folding belt and the second belt made of the flat belt can be separately formed and prepared, the molding equipment can be easily and easily molded, and the existing equipment can be used as it is. Therefore, without reducing productivity, steering stability and high-speed endurance,
It is possible to provide a tire having both riding comfort and lightness.

[Brief description of drawings]

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

FIG. 2 is a schematic cross-sectional view of the above belt structure.

FIG. 3 is a partial schematic plan view showing the above belt structure.

FIG. 4 is a schematic sectional view showing an example of a conventional belt structure.

FIG. 5 is a schematic sectional view showing an example of a conventional folding belt structure.

FIG. 6 is a schematic sectional view showing another example of a conventional folding belt structure.

[Explanation of symbols]

 (1) Carcass (2) Tread part (B) Belt layer (B1) First belt (B2) Second belt (3) Bending overlapping part (b1) Bending part piece (b2) Bending end (4) Boundary Part (5) Belt reinforcement layer

Claims (2)

[Claims] 1. A pneumatic tire having two belt layers disposed between a carcass and a tread, wherein the first belt on the carcass side of the two belt layers is made of aramid fiber or the like. A belt made of a strong synthetic fiber cord, both widthwise end portions of which are folded and polymerized on the tread side, and the second belt on the tread side is a one-layer portion between the both folding portion pieces of the first belt. Arranged so that they overlap
Further, a belt reinforcing layer is arranged outside the two belt layers so as to cover at least the folded portion of the first belt and a boundary portion between the folded portion and the second belt. Pneumatic tire to do. 2. The belt reinforcing layer comprises an edge ply covering the bent portion of the first belt and a cap ply covering the entire belt layer on the outer side thereof, and the width of the cap ply is larger than the width of the bent portion. The pneumatic tire according to claim 1, wherein the cap ply is arranged so as to cover a boundary portion between the bent portion and the second belt in a large size.