JPH09202118A - Pneumatic tire - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To provide a lightweight and simple bead structure of a radial tire for a motorcycle, which improves riding comfort while improving steering stability and cornering performance. A carcass ply including a pair of left and right annular beads, at least one cord layer having a folded portion extending in a toroidal shape between the beads and folding back the bead from the inner side to the outer side, and a bead portion In a pneumatic tire having a carcass ply body and / or a bead reinforcing layer 8 at a folded-back portion, the bead reinforcing layer 8 is a composite member of a nonwoven fabric and a rubber in which at least one layer of fibers has a cross-type multidirectional arrangement. Consists of.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, and more particularly to a bead structure for a radial tire for a motorcycle, which improves cornering performance and steering stability while improving riding comfort.

[0002]

2. Description of the Related Art Conventionally, in order to improve cornering performance of a pneumatic tire, in particular, as shown in FIG. 5, a bead filler 6 is increased from a bead portion to a side portion and / or a twist coated with rubber is used. A general method is to arrange a high-rigidity cord reinforcing layer 7 in which a large number of cords are aligned to increase the rigidity of this portion.

However, although the cornering performance is improved by the above method, there is a problem that the rigidity of the tire / side portion becomes too high and the vibration absorbing action in the side bending region is hindered, and the riding comfort performance deteriorates. Further, when the bead filler is increased, the tire weight increases, which is not preferable. In particular, a large tire diameter such as a tire for a motorcycle causes an increase in rotational moment, and its influence on cornering performance and stability cannot be ignored. Furthermore, in the cord reinforcing layer, the rigidity in the longitudinal direction of the cord is significantly different from the rigidity in other directions, so that the cornering with unsteady circular turning such as acceleration, deceleration or turning of the steering wheel lacks stability. There was a problem. Then, there is a problem in that it is structurally complicated and requires much labor for manufacturing.

[0004]

DISCLOSURE OF THE INVENTION An object of the present invention is to solve the above problems and improve the riding comfort and steering stability and cornering performance, and particularly to a radial tire for a motorcycle. It is to provide a lightweight and simple bead structure.

[0005]

The present invention adopts the following constitution in order to achieve the above object. That is,
A carcass consisting of a pair of left and right annular beads and at least one cord layer having a toroidal portion that extends in a toroidal shape between the beads and is folded back from the inside to the outside.
In a pneumatic tire having a ply and a bead reinforcing layer at a carcass ply main body portion and / or a folded portion of the bead portion, the bead reinforcing layer comprises at least one layer of non-woven fabric and rubber in a cross-type multidirectional arrangement. The structure is composed of a composite member of. Due to the above configuration,
The non-woven fabric with a cross-type multi-directional arrangement of fibers has a rigidity distribution.
Unlike the cord reinforcing layer in which a large number of twisted cords covered with rubber are aligned, the bead portion can be uniformly reinforced in all directions because it is constant without being biased in a specific direction. Therefore, stable cornering performance can be secured in cornering traveling accompanied by unsteady circle turning.

If the composite member has a thick portion having a convex shape on at least one surface side, the bead reinforcing layer can be arranged only in a necessary portion, so that weight reduction is facilitated and it is more preferable.

Further, at least the carcass
The thick-walled portion of the composite member is disposed adjacent to the axially outer side of the ply turn-back portion, and the surface of the thick-walled portion in contact with the turn-back portion is formed into a smooth convex curve toward the turn-back portion. For example, the conventional high bead filler can be used without arranging both the conventional relatively high bead filler and the cord reinforcing layer.
It is preferable because the reinforcing effect is increased with a simple structure without filler.

Further, the thick portion of the composite member is disposed adjacent to the inner side of the carcass ply body portion of the bead portion, and the surface of the thick portion which is in contact with the carcass ply body portion is the carcass.・ If a smooth convex curve is formed toward the main body of the ply, the reinforcing effect can be improved with a simple structure without the conventional bead filler without arranging both the conventional bead filler and the cord reinforcing layer. It is preferable because it increases.

If the bead reinforcing layer is composed of a composite member of a non-woven fabric in which fibers are crossed in a multi-directional arrangement and hard rubber and soft rubber, and the hard rubber is arranged on the side facing the carcass ply. It is preferable because the reinforcing effect is further increased. Then, J of hard rubber forming a composite member of the non-woven fabric and the hard rubber 9 on the side of the bead reinforcing layer facing the carcass ply.
It is preferable that the ISA hardness is 75 to 100 degrees. At this time, if it is less than 75 degrees, the reinforcing effect cannot be expected, and
If it is more than 100 degrees, the riding comfort performance is deteriorated and the bead portion is easily broken, which is not preferable.

Further, if a bead filler 6 is provided which is sandwiched between the carcass ply body and the carcass ply turnback portion and extends within 8% of the tire height from the bead core toward the radial outside, the bead filler 6 is provided. -Since the height of the filler is small, it is possible to improve steering stability and cornering performance without deteriorating riding comfort performance. At this time, if it is 8% or more, the riding comfort performance is excessively deteriorated, and the cornering performance and the steering stability may be deteriorated due to an increase in the rotation moment, which is not preferable.

Furthermore, if the carcass ply turn-up portion contacts the carcass ply body directly above the bead core and extends outward in the radial direction, the bead.
Since there is no filler at all, the simplification can be further facilitated, and the vibration absorbing action of the side portion is further enhanced to improve the riding comfort.

The bead reinforcing layer may include a composite member of at least one layer of non-woven fabric in which fibers are crossed in a multi-directional arrangement and rubber, and the composite member and other reinforcing material (chafer or flipper). May be combined with. Further, the composite member may be arranged not only around the carcass ply but also between the carcass ply body and the carcass ply turnback portion.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a main part of a bead portion of a radial tire for a motorcycle according to the present invention, in which a tire size is 120 / 70ZR17 and a rim size is MT3.
50. This motorcycle tire has the same structure as that of the conventional tire shown in FIG. 4 except for the bead portion. Carcass 3 and 2 in which two layers of nylon carcass ply having a cord angle of 75 degrees are crossed in the tire circumferential direction. Kevlar code
It has a belt 5.

In the structure of the bead portion, as shown in FIG. 1, the bead reinforcing layer 8 is arranged along the inner side of the carcass ply body in the axial direction and the outer side of the carcass ply turnback portion. The structure of the bead reinforcing layer 8 is as shown in FIG.
The nonwoven fabric 12 is covered with the soft rubbers 10 and 11, and the hard rubber 9 is arranged in the thick portion. In this embodiment, the hard rubber 9 is arranged along the outer side of the carcass ply turnback portion.

FIG. 2 is a cross-sectional view of an essential part of a bead portion showing another embodiment of the present invention, which is characterized in that the hard rubber 9 is arranged inside the carcass ply body in the axial direction. FIG. 3 is a sectional view of a main part of a bead portion showing still another embodiment,
This embodiment is characterized in that the thick portion is not arranged.

In FIGS. 1, 2 and 3, the bead filler 6 is arranged so low as to extend from the bead core 2 toward the outer side in the radial direction by about 5 mm which corresponds to about 6% of the tire height. The bead filler 6 may be omitted if no cavity is formed in the portion.

Next, in order to confirm the effects of the present invention, six types of tires were made as prototypes with the specifications shown in Table 1. These tires have the same structure except for the bead structure. The test shows that for the cornering force, the drum tester has an MT3.5 rim with an internal pressure of 2.5 kgf / cm.
² was built in, and the average of the cornering forces when the camber angles of 10, 20, 30, 40 and 45 degrees were applied at a speed of 50 km / h and a load of 150 kgf were compared. 400 tests for driving stability and ride comfort
It was mounted on the front wheel of a cc motorcycle and a feeling test was conducted. The results are also shown in Table 1.

[0018]

[Table 1]

[0019]

As is apparent from Table 1, according to the radial tire for a motorcycle of the present invention, a cornering force equal to or higher than that of a tire having a conventional structure can be obtained regardless of the simplified structure. In addition, favorable improvement effects were obtained with respect to steering stability and riding comfort performance of the actual vehicle.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part of a bead portion showing an embodiment of the present invention.

FIG. 2 is a sectional view of an essential part of a bead portion showing another embodiment of the present invention.

FIG. 3 is a sectional view of a main part of a bead portion showing still another embodiment of the present invention.

FIG. 4 is a cross-sectional shape including a tire rotation axis showing an example of a bead reinforcing layer of the present invention.

FIG. 5 is a sectional view in the tire width direction showing a conventional example.

[Explanation of symbols]

 T tire 1 bead part 2 bead core 3 carcass ply 4 tread 5 belt 6 bead filler 7 cord reinforcing layer 8 bead reinforcing layer (composite member) 9 thick part (hard rubber) 10, 11 soft rubber 12 non-woven fabric 13 carcass・ Ply body side 14 Carcass ・ Ply turnup side

Claims (8)

[Claims] 1. A carcass ply consisting of a pair of left and right annular beads, at least one cord layer having a toroidal portion extending between the beads in a toroidal shape and folding the bead from the inside toward the outside, and a bead portion. Of a carcass ply body and / or a bead reinforcing layer at a folded-back portion, the bead reinforcing layer is composed of at least one layer of a non-woven fabric-rubber composite member having a cross-type multidirectional arrangement of fibers. Pneumatic tire characterized by being. 2. The pneumatic tire according to claim 1, wherein the composite member has a thick portion having a convex shape on at least one surface side. 3. The thick portion of the composite member is disposed adjacent to at least the axially outer side of the carcass ply turn-back portion of the bead portion, and the surface of the thick portion that is in contact with the carcass ply turn-back portion is 3. A smooth convex curve is formed toward the folded portion.
The pneumatic tire as described. 4. The thick portion of the composite member is disposed adjacent to the inner side of the carcass ply body portion of the bead portion in the axial direction, and the surface of the thick portion that is in contact with the carcass ply body portion is The pneumatic tire according to claim 2, wherein the pneumatic tire is formed into a smooth convex curve toward the carcass ply body. 5. The bead reinforcing layer is made of a composite member of a non-woven fabric in which fibers are crossed in a multi-directional arrangement and hard rubber and soft rubber, and the hard rubber is arranged on the side facing the carcass ply. The pneumatic tire according to any one of claims 1 to 4, wherein: 6. The JIS A hardness of the hard rubber forming the composite member of the non-woven fabric on the side of the bead reinforcing layer facing the carcass ply and the hard rubber is 75 to 100 degrees. Item 5. The pneumatic tire according to item 5. 7. A bead filler that is sandwiched between the carcass ply body and the carcass ply turnback portion and extends within 8% of the tire height from the bead core toward the outer side in the radial direction. The pneumatic tire according to any one of claims 1 to 6, wherein. 8. The carcass ply folded-back portion is in contact with the carcass ply body directly above the bead core and extends outward in the radial direction. Pneumatic tires.