JPH06115326A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To realize light weight by reducing or omitting each rubber filler by using as the major portion of each bead filler a cord reinforcement layer made twofold. CONSTITUTION:A carcass layer 2 extends to the bead core 4 of a bead portion 3 from a tread portion 1 via a side wall portion 7 and is wound up around the core 4 from the tire inside to the outside, and the terminal 2e of its turned-up portion 2B is coupled to a main body side at the sphere of the side wall portion 7. Between the main body portion of the carcass layer 2 and the turned-up portion 2B, a cord reinforcement layer 6 that is made twofold is arranged as a bead filler. As for this cord reinforcement layer 6, its turned-up portion 6s is located on the side wall portion 7 side and both terminal portions 6e, 6e' are located on the bead core 4 side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire in which the weight of a bead portion is reduced without impairing steering stability and durability is improved.

[0002]

2. Description of the Related Art Generally, a bead portion of a pneumatic tire is filled with a rubber filler having an elongated triangular cross section made of hard rubber as a bead filler on the outer peripheral side of a bead core, thereby enhancing the rigidity of the bead portion and improving steering stability. Trying to improve. However, with the recent demand for low fuel consumption of vehicles, as the weight reduction of pneumatic tires is strongly demanded, as a countermeasure, the rubber filler occupying the largest volume in the bead portion is reduced or A proposal has been made in which a plurality of high-rigidity cord reinforcing layers are superposed and arranged instead of removing them (see JP-A-4-66310).

However, in the above cord reinforcing layer, a plurality of free ends thereof are located in the flex region above the tire radial direction, and stress concentration is caused by bending, compression, shearing, etc. during tire load rolling, resulting in separation from the rubber layer. Therefore, there is a problem that durability is lowered. Further, when the number of the cord reinforcing layers is two or less, the lateral rigidity becomes extremely low, which makes it difficult to secure steering stability equivalent to that of the conventional bead filler made of high hardness rubber.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to secure good steering stability while reducing weight by using a cord reinforcing layer to form a bead filler substantially without using a rubber filler. And to provide a pneumatic tire capable of improving durability.

[0005]

SUMMARY OF THE INVENTION The present invention to achieve such an object is to form a main part of a bead filler arranged on the outer peripheral side of a bead core from a cord reinforcing layer folded in two, The bent portion of the cord reinforcing layer is arranged on the side wall portion side, and the terminal portion is arranged on the bead core side.

Thus, by using the cord-reinforcing layer folded in two as the main part of the bead filler, it is possible to reduce the weight, and the folded portion of the bi-fold cord reinforcing layer is located on the side wall side. Since it is arranged, peeling due to stress concentration during tire load rolling can be reduced and durability can be improved. Moreover, since the cord reinforcing layer has a two-fold structure and the bent portion side is arranged on the sidewall portion side, the lateral rigidity of the bead portion can be made equal to that of a high hardness rubber filler to ensure steering stability. it can.

The present invention will be described in detail below with reference to the drawings. FIG. 1 shows an embodiment of a pneumatic tire of the present invention, 1 is a tread portion, 2 is a carcass layer, 3 is a bead portion,
Reference numeral 7 is a sidewall portion. The carcass layer 2 is wound up from the tire inside to the outside around the bead core 4 of the bead portion 3 from the tread portion 1 through the sidewall portion 7,
The terminal 2e of the folded portion 2B is joined to the main body side in the region of the sidewall portion 7. Between the main body portion of the carcass layer 2 and the folded-back portion 2B, the cord reinforcing layer 6 folded in two is arranged as a bead filler.
Further, two belt layers 8 are arranged on the outer peripheral side of the carcass layer 2 corresponding to the tread portion 1 so as to intersect each other at a cord angle of 5 to 35 ° with respect to the tire circumferential direction.

The cord-reinforcing layer 6 folded in two forms a main component of the bead filler, and the bead filler is not substantially filled with the rubber filler. Further, the cord reinforcing layer 6 is arranged such that its bent portion 6s is located on the side wall portion 7 side and both end portions 6e, 6e 'are located on the bead core 4 side. For this reason,
It is lighter than the bead filler made of hard rubber filler, and the bent portion 6s side is arranged in the flex zone, so that peeling is less likely to occur. Further, since the cord reinforcing layer 6 is not an independent two layer but is a continuous two layer by bending one sheet, the lateral rigidity is high and the steering stability is not deteriorated.

2 to 7 show another embodiment of the double-folded cord reinforcing layer constituting the above-mentioned bead filler. In the example of FIG. 2, both end portions 6e of the cord reinforcement layer 6,
6e 'is filled with a small amount of rubber filler 5 inside,
In FIG. 3, a small amount of rubber filler 5 is filled on the outside of both end portions 6e and 6e 'of the cord reinforcing layer 6 and on the outer peripheral side of the bent portion 6s. The size of these rubber fillers 5 is only required to adjust the shape of the bead portion, and is made as small as possible in order to reduce the weight.

In FIG. 4, the cord reinforcing layer 6 is folded in two by shifting both end portions 6e, 6e 'of the cord reinforcing layer 6 from each other, and the end portion 6e having the higher tire radial height is the rubber filler on the bead core 4. It is arranged on the 5th. In addition, in FIG. 5, the cord-reinforcing layer 6 having the two-fold structure is disposed inside the tire of the carcass layer 2, and the winding end portion 2 of the carcass layer 2 is disposed.
e is arranged at a position lower than the bent portion 6s of the cord reinforcing layer 6. Also in this practical mode, a small rubber filler 5 is inserted as an auxiliary.

In FIG. 6, contrary to FIG. 5, the cord reinforcing layer 6
Is arranged on the outer side of the folded portion 2B of the carcass layer 2 outside the tire so as to cover the winding end portion 2e of the carcass layer 2. Further, in FIG. 7, the cord reinforcing layer 6 is arranged so that one end portion 6e ′ is folded back from the inside of the tire to the outside around the bead core 4 and faces the other end portion 6e. In this case as well, the auxiliary small rubber filler 5 is inserted.

The cord reinforcing layer 6 constructed as described above.
Can appropriately improve the effect of the present invention by appropriately selecting the positions of the bent portion 6s on the upper side and the terminal portion 6e at the higher position among the terminal portions on the lower side. That is, for the bent portion 6s, the tire radial height Ho from the bead base line L is set to the tire cross-section height SH.
It is better to make it 0.25 to 0.70 times. By setting the tire cross-section height SH to be 0.25 times or more, the bead portion rigidity can be increased and steering stability can be ensured. Further, by setting the ratio to 0.70 times or less, it is possible to prevent deterioration of durability. Further, the bent portion 6s is preferably arranged at a position lower than the winding end portion 2e of the carcass layer 2 as shown in FIGS. 2, 3, 4 and 7.

Further, the height He of the higher end portion 6e from the bead base line L is preferably set to be equal to or less than the height Hr of the rim flange. By maintaining this relationship, it is possible to reduce the stress concentration on the upper end portion 6e due to the deformation of the bead portion and improve the durability, and
The rigidity of the bead portion can be maintained and a decrease in steering stability can be suppressed.

In the present invention, the cord reinforcing layer is composed of a rubberized sheet in which a plurality of cords are aligned in one direction and embedded in coat rubber. As the material of the cord, nylon, aromatic polyamide (aramid), organic fiber cord such as polyester, steel cord and the like can be used. From the viewpoint of weight reduction, organic fiber cords are preferable, and aromatic polyamide fiber cords having a high elastic modulus are particularly excellent. Further, as the coat rubber, a rubber having a high hardness is preferable, and JIS-A hardness (room temperature) 60 is preferable.
More preferably, 65 or more rubber is used.

In the present invention, the cord reinforcing layer is preferably arranged such that the cords are at a cord angle of 20 ° to 70 ° with respect to the tire radial direction and intersect each other. By setting the cord angle to 70 ° or less, steering stability can be improved. Further, by setting the angle to 20 ° or more, the durability can be further improved.

[0016]

[Examples] The following tire specifications are common, and the type of cord of the cord reinforcing layer that constitutes the bead filler, the tire radial height Ho (mm) of the bent portion of the cord reinforcing layer, and the ratio to the tire cross-section height SH (%) And the heights He (mm) of the upper end portions of both end portions were made different as shown in Table 1, and tires 1 to 5 of the present invention were manufactured. Also, for comparison,
The following two types of conventional tires and comparative tires were manufactured respectively. Tire specifications : Tire size: 185 / 65R14 Rim: 14 x 6JJ Flange height Hr = 18mm Cord reinforcement layer: Cord angle = 55 ° to tire radial direction Coat rubber: Hardness (JIS hardness) = 70 Height of rubber filler = 25 mm Conventional tire: tire of the present invention 1 having the same configuration except that a rubber filler having a JIS hardness of 85 was filled as a bead filler up to a height of 62 mm from the bead baseline. Comparative tire: The same tire as the bead filler in the tire 1 of the present invention. Tires having the same structure except that two cord reinforcing layers having mutually independent dimensions were used in a laminated manner. These seven types of tires were evaluated for steering stability, durability and lightweight under the following conditions. . The results are shown in Table 1. Steering stability : 20x20mm tires assembled on 14x6JJ rim
It was filled with 0 kPa of air, a load of 3430 N (Newton) was applied, and the magnitude of the lateral spring constant obtained from the magnitude of the lateral force when the lateral force was applied and the deformation amount of the tire was measured and evaluated.

Evaluation was made with an index based on the measured value of a conventional tire. The larger this index, the better the steering stability. Durability : The tire is assembled into a rim of 14 × 6JJ, 250k
The drum diameter is 17 after filling with Pa (maximum allowable air pressure) air.
When mounted on a 00 mm drum and traveling at 81 km / hr, the vehicle traveled until the tire broke while changing the load as described below, and the traveling distance at that time was measured. It is shown as an index with the mileage when the conventional tire is broken as the standard (100). The larger this index is, the more excellent the durability is. Driving conditions: Start at 88% of maximum load, 140
The load is increased by 13% every 2 hours until
The load is increased by 13% every 4 hours up to 270%, and when there is no failure, the finish distance is up to 4050 km. Lightness : The weight of each tire alone was measured, and the weight was expressed as an index based on the weight of conventional tires (100). The smaller this index is, the lighter the weight is.

[0018] Note) ^{* 1} : For the comparative tire, the height of the upper end of the reinforcing layer is used. From Table 1, each of the tires 1 to 4 of the present invention is lighter in weight than the conventional tire, and has substantially the same or more durability and steering stability.

When the cord reinforcing layer is made of a nylon cord as in the tire 5 of the present invention, the effect of weight saving is improved although the effect of improving the steering stability is smaller than that of the aramid fiber cord. On the other hand, although the comparative tire is lighter in weight, the durability is reduced, and moreover,
Due to the low rigidity of the bead portion, steering stability is deteriorated.

[0020]

According to the present invention, by using the cord reinforcing layer folded in two as the main part of the bead filler, the rubber filler can be reduced or omitted, and the weight can be reduced. In addition, since the bent portion of the folded cord reinforcing layer is arranged on the side of the sidewall portion, peeling due to stress concentration during tire load rolling can be reduced and durability can be improved. Moreover, since the cord reinforcing layer has a two-fold structure and the bent portion side is arranged on the sidewall portion side, the lateral rigidity of the bead portion can be made equal to that of a high hardness rubber filler to ensure steering stability. it can.

[Brief description of drawings]

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

FIG. 2 is a sectional view showing an example of a bead portion structure of the present invention.

FIG. 3 is a cross-sectional view showing another example of the bead portion structure of the present invention.

FIG. 4 is a cross-sectional view showing another example of the bead portion structure of the present invention.

FIG. 5 is a sectional view showing still another example of the bead portion structure of the present invention.

FIG. 6 is a cross-sectional view showing another example of the bead portion structure of the present invention.

FIG. 7 is a sectional view showing still another example of the bead portion structure of the present invention.

[Explanation of symbols]

3 Bead part 6 Cord reinforcement layer 6s Bent part 6e, 6e 'Terminal part 7 Sidewall part Ho Height of bent part He Height of higher terminal part 6e Hr Rim flange height L Bead base line SH Tire section height

Claims (1)

[Claims] 1. A main constituent part of a bead filler arranged on the outer peripheral side of a bead core is composed of a cord reinforcing layer folded in two, and a bent part of the cord reinforcing layer folded in two is arranged on the side wall side. Together with the pneumatic tire, the end portion is arranged on the bead core side.